World leaders in the manufacture of laboratory systems for soil & rock

Transcription

1 World leaders in the manufacture of laboratory systems for soil & rock GDS Instruments Product Catalogue 2014

2 About GDS Instruments GDS Instruments (Geotechnical Digital Systems, or simply GDS) designs, develops and manufactures material testing machines and software used for the computer-controlled testing of soils and rocks. This technology is used to evaluate the mechanical properties that are key in geotechnical and earthquake engineering design. Since being founded in 1979, it is estimated that GDS products have been used to help achieve over 1000 PhD s. As well as being the first choice for academic research, GDS products have been used in many world renowned commercial laboratory for projects including the Three Gorges Dam in China, the Millau Viaduct in France, the Vasco da Gama Bridge in Portugal, Terminal Five at Heathrow and the new Crossrail link in London. GDS employs over 35 permanent members of staff at their offices in Hook, Hampshire, UK, as well as working with a network of agents spanning 40 countries. GDS UK based staff include 3 PhD s, 8 qualified civil / geotechnical engineers, 4 software designers, 4 hardware designers and 5 electrical/electronics specialists, allowing GDS the capability to design, build, test and ship their products directly to the customer. In 2011 GDS were awarded the prestigious Queens Award for Enterprise in International Trade. Values at GDS GDS believes in providing the best equipment for the job combined with first class support from engineers who understand the equipment and applications. GDS design and develop all their products in-house using their team of geotechnical engineers, software designers, hardware designers (3D CAD) and electrical/electronics designers and specialists. This allows GDS to have complete control of the design, build, test and shipping process. GDS in-house expertise allows them the capability to design bespoke systems (hardware, electronics and software), which forms a significant part of the GDS business. GDSLAB software supports every GDS computer controlled device manufactured since 1979, as well as devices from other manufacturers that have long since been made obsolete by them. This forms part of our unique commitment to long term customer support. When you receive training from or ask a technical question of GDS, your reply will be from, or via a geotechnical engineer. This is our philosophy for ensuring the best service possible. Great service = repeat customers and we have many repeat customers. GDS production and manufacturing is carried out in the UK to strict quality standards and our management systems are ISO9001 accredited. GDS Customers GDS work closely with Research and Commercial companies. Utilising our network of agents has allowed GDS to work in many countries around the world and become involved with some world renowned organisations / institutes on a variety of different projects. Please Note: Due to continued developments, specifications of products within this brochure may change. 2

3 Product Catalogue Contents Product Code Page Section 1: GDS Software GDSLAB 1 Section 2: Triaxial Testing Apparatus 2 Triaxial Automated System GDSTAS 3 Triaxial Testing System GDSTTS 4 Unsaturated Triaxial Testing of Soil UNSAT 5 Virtual Infinite Stiffness Loading System GDSVIS 6 Triaxial Cells CELLS 7 High Pressure Environmental Triaxial System HPETAS 8 Enterprise Level Dynamic Triaxial Testing System ELDYN 9 Advanced Dynamic Triaxial Testing System DYNTTS 10 Hydraulic Loading Frame GDSHLF 11 Large Diameter Cyclic Triaxial Testing System LDCTTS 12 True Triaxial Apparatus GDSTTA 13 Section 3: Rock Testing Apparatus kN Load Frame VIS kN Static Compression Loadframe HLF1000-S kN Hydraulic Actuator Loadframe HLF1000-H 17 High Pressure Triaxial Cells CELLS-HP 18 High Pressure Back Pressure Shearbox HPBPS 19 Section 4: Shear Testing Apparatus 20 Shearbase System (Direct & Simple Shear) GDSSS 21 Electro-mechanical Dynamic Cyclic Simple Shear EMDCSS 22 Combined Advanced Dynamic Cyclic Simple Shear ADVDCSS 23 Large Automated Direct Shear System (300mm) GDSLADS 24 Back Pressured Shearbox GDSBPS 25 Dynamic Back Pressure Shearbox DYNBPS 26 Interface Shear Tester GDSIST 27 Variable Direction Dynamic Cyclic Simple Shear VDDCSS 28 Section 5: Resonant Column & Hollow Cylinder 29 Resonant Column GDSRCA 30 Small-Strain Hollow Cylinder Apparatus GDSHCA 31 Section 6: Consolidation Systems 32 Consolidation Testing System (Rowe Type) GDSCTS 33 Constant Rate of Strain Cell (In Load Frame) GDSCRS 34 Automatic Oedometer System GDSAOS 35 Section 7: GDS Pressure / Volume Controller Range 36 Enterprise Pressure / Volume Controller up to 1MPa ELDPC Standard Pressure / Volume Controller up to 4MPa STDDPC Advanced Pressure / Volume Controller up to 8MPa ADVDPC High Pressure Volume Controllers 8MPa to 150MPa HPDPC Pneumatic Pressure Controller GDSPPC 40 Infinite Volume Controller GDSIVC 41 Section 8: Transducers & Load Cells 42 Bender Element System GDSBES 43 Hall Effect Local Strain Transducers GDSHE 44 LVDT Local Strain Transducers LVDT 45 Section 9: Field Geophysics 46 Spectral Analysis of Surface Waves SASW 47 Continuous Surface Wave System CSWS 48 Section 10: Bespoke Testing Systems 49 Section 11: Customer Testimonials 50

4 Section 1: GDS Software GDSLAB GDSLAB is the control and data acquisition software for geotechnical laboratory applications. GDSLAB starts with a core application known as the kernel. The GDSLAB kernel allows for data acquisition from your hardware and on screen data presentation but no test control. Simply add the appropriate module or modules to complete the test control functionality you require. Advantages of GDSLAB include: Allows your existing hardware to be upgraded to PC control, Compatible with every GDS product since 1979, One of the main advantages of GDSLAB is that as well as the ability to integrate all existing GDS hardware other manufacturers hardware can also be used. Commercial or research testing is possible with the choice of modules available, see the GDS website for a full list. GDSLAB Reports GDSLAB Reports is a laboratory test results presentation package to National Standards e.g. BS 1377:1990. This program can be used to present data whether saved in a GDSLAB data file, or input by hand. Additionally, it can be used with other manufacturer s dataloggers. GDSLAB Reports combines the simplicity of a Windows user interface, with the power of Microsoft Excel. Data obtained using GDSLAB control and data acquisition software (or directly from your logger s software) may be selected, viewed and manipulated where necessary before being exported directly as an Excel spreadsheet. The GDSLAB Reports user interface is designed to manage your test data files as well as provide a means for essential user input procedures such as locating t90. The Excel template spreadsheet created by GDSLAB REPORTS may then be selected for a particular national standard (e.g. BS 1377). The template spreadsheet can be customised to a specific company format as required. Excel is widely accepted as the most popular spreadsheet program available today, and as such is seen as a simple interface, that many computer users can already easily manipulate. This also allows your reports to be distributed in electronic format without the need for specific software. GDSLAB Reports Screenshots. GDSLAB. 1

5 Section 2: Introduction to GDS Triaxial Testing Apparatus GDS are world leaders in Static, Dynamic and Unsaturated triaxial testing systems. In addition to complete systems, GDS also supply individual components such as pressure controllers, specialist transducers, unsaturated soil testing upgrades and bespoke units supplied to customer s specifications. Static Triaxial Testing Systems: The GDSTAS (Triaxial Automated System) on page 3, is a load frame based system where the axial loading is applied by a load frame. This is one of the most configurable systems in the GDS range. By choosing the load frame range, the pressure controller range and the triaxial cell range, the system can be configured for soft soils right up to a high pressure rock testing system. The lower range is generally the system of choice for commercial laboratories, with the upper range system the choice for rock mechanics laboratories. Based on all the same features of the GDSTAS, the high pressure environmental triaxial automated system (HPETAS) on page 8, can be fitted with a heating or cooling system that is PC controlled. The GDSTTS (Triaxial Testing System) on page 4, is the original automated stress path system created by GDS using a Bishop and Wesley hydraulically actuated cell. Axial stress is applied directly as a stress through a bellofram diaphragm, i.e. is a true stress controlled system. The system can be configured using Enterprise, Standard or Advanced controllers. GDSTTS system in a commercial laboratory. UNSAT (Unsaturated Testing) represents the GDS range of upgrades for performing unsaturated testing. GDS offer four types of unsaturated testing, Method A, B, C, D. See page 5 for more information on these methods. GDSVIS (Virtual Infinite Stiffness) is the premier high range load frame in the GDS range. The VIS is a unique GDS development, as well as being a very stiff design of load frame, it allows the axial loading system to operate as though it has infinite stiffness (zero system compliance). See page 6 for a full explanation. Dynamic Triaxial Testing Systems: The ELDYN (Enterprise Level Dynamic System) on page 9, is the lowest cost GDS dynamic triaxial testing system. Generally considered to be far superior to pneumatically actuated systems, this electromechanically actuated system is designed to compete with low cost pneumatic systems directly on price, whilst being superior on performance. This is the system of choice for teaching establishments and commercial testing. The DYNTTS (Dynamic Triaxial Testing System) on page 10, is the top level device in the GDS dynamic triaxial system range. This advanced dynamic systems contain the most flexibility in configuration and a nocompromise approach in terms of accuracy, stability and features. The system of choice for advanced commercial testing and research. GDSHLF (Hydraulic Load Frame) on page 11, contains a dynamic actuator built into the cross beam of the frame. Load capacities are up to 250kN and +/- 50mm stroke capability based around a stiff loading frame. The LDCTTS, on page 12 is a dynamic cyclic triaxial testing system based on the GDSHLF, using large diameter triaxial cells to enable tests to be performed on large particle sizes such as ballast. GDSTTA sample preparation. The True Triaxial Apparatus (GDSTTA) on page 13, has a defining characteristic that, unlike conventional triaxial apparatus, all three principal stresses can be controlled independently, rather than just two in a conventional triaxial system. This allows a wider range of complex stress paths to be performed. 2

6 Triaxial Automated System (GDSTAS) Overview: The GDS Triaxial Automated System (GDSTAS) is a load frame-based triaxial testing system. The system is configured by choosing from a range of load frames, triaxial cells, pressure controllers and software. The system can be configured as a multi-station commercial testing apparatus right through to high load rock testing at research level. If an existing system requires upgrading, parts of the GDSTAS system can be incorporated with existing equipment (including those from some other manufacturers) to upgrade the system. Standards: ASTM D-4767 ASTM D-5034 Each system may be configured exactly to the customer s specification and budget: Automated software control: Interchangeable range of load cells: Submersible load cells are standard: Standard set-ups available (ELTAS, STDTAS, ADVTAS, HPTAS): Compatible with other manufacturers products: The user can choose the load frame, pressure controllers, triaxial cell or just parts to integrate into existing equipment to build their ideal TAS set-up to match budget to requirement. The software directly controls the cell & back pressure, testing rate, in addition to managing all data acquisition. Automated control allows tests to proceed continuously and increases the throughput of tests. Enables the user to run tests on soils of different stiffness and match the load transducers accordingly, giving greater accuracy of results. Seal friction does not effect load readings. GDS has a range of standard GDSTAS set-ups to help the user identify the correct set-up. The set-ups based on the pressure the systems will run to. See technical specifications below for system information. If a user has existing components they may incorporate them with GDS equipment to create a system, saving capital expenditure. B-check saturation, unconsolidated undrained (UU) triaxial, consolidated drained (CD) triaxial, consolidated undrained (CU) triaxial, consolidation (Triaxial), constant rate of loading (CRL), constant rate of strain (CRS), slow cyclic testing, K0 (K-Zero), multi-stage testing, quasi-static (low speed/creep) tests and stress paths. Please Note - The availability of tests may depend on selected hardware/software. Bender element system (Vertical, Horizontal, S and P waves), hall effect local strain, LVDT local strain, laser sample measurement, very low effective stress testing and unsaturated testing. Enterprise (ELTAS): 50, 100, Standard (STDTAS): 50, 100, 250, 500 Load Range (kn): Advanced (ADVTAS): 50, 100, 250, 500, 1000 High Pressure (HPTAS): 50, 100, 250, 400, 500, 1000, 2000 Enterprise (ELTAS): 1 Standard (STDTAS): 1 to 4 Pressure Range (MPa): Advanced (ADVTAS): 2 to 8 High Pressure (HPTAS): 8 to 128 Sample Sizes (mm): 20 to 300 3

7 Triaxial Testing System (GDSTTS) Overview: The GDS Triaxial Testing System (GDSTTS) is a fully automated triaxial testing system designed principally for stress path testing. The GDSTTS is based on the classic Bishop & Wesley type stress path triaxial cell which controls stress directly on the sample. The system can be configured using Enterprise, Standard or Advanced level controllers (depending on the required accuracy / maximum pressure). The 38/50mm cell can provide up to 7kN axial force, with the larger 70/100mm cell up to 25kN. Standards: ASTM D-4767 ASTM D-5034 Each system may be configured exactly Users can choose the transducers, pressure controllers, triaxial cell or just to the customer s specification and parts to integrate into existing equipment to build their ideal set-up. budget: Direct actuation of axial stress through The Bishop and Wesley cell is designed specifically for stress path testing. the hydraulically controlled ram in the Direct axial stress application means greater accuracy for stress control. base of each cell: GDSTTS can run advanced tests: Tests such as stress paths, slow cyclic and K0, all under PC control. Standard through to advanced GDS provide advanced (ADVTTS) systems with all the features of the standard configurations: systems but with higher accuracies and resolution. May be upgraded at any time: Additional transducers, software modules, bender element testing and unsaturated testing makes the system future proof. B-check saturation, unconsolidated undrained (UU) triaxial, consolidated drained (CD) triaxial, consolidated undrained (CU) triaxial, consolidation (Triaxial), constant rate of loading (CRL), constant rate of strain (CRS), slow cyclic testing, K0 (K-Zero), multi-stage testing, quasi-static (low speed/creep) tests and stress paths. Please Note - The availability of tests may depend on selected hardware/software. Bender element system (Vertical, Horizontal, S and P waves), hall effect local strain, LVDT local strain and unsaturated testing. A high pressure STDTTS is available for cell pressure up to 10MPa. Accuracy of Pressure Measurement: Standard (STDTTS) <0.15% full range, Advanced (ADVTTS) <0.1% full range Accuracy of Volume Measurement: Standard (STDTTS) 0.25% measured value, Advanced (ADVTTS) <0.1% measured value Load Range (kn): Standard (STDTTS): 7 or 25, Advanced (ADVTTS): 7 or 25, High Pressure (HPTTS): 7 or 25 Pressure Range (MPa): Standard (STDTTS): 1,2,3,4. Advanced (ADVTTS): 1,2,3,4. High Pressure (HPTTS): Up to 10 Resolution of Pressure Measurement: Standard (STDTTS): 1kPa, Advanced (ADVTTS): 0.1kPa Resolution of Volume Measurement: Standard (STDTTS): 1mm 3, Advanced (ADVTTS): 0.1mm 3 Sample Sizes (mm): 38/50 or 70/100, upgrades available up to

8 Unsaturated Testing of Soil (UNSAT) Overview: GDS Unsaturated Triaxial Testing System (UNSAT) is an extension to traditional triaxial testing, in that soils from above the water table may be tested under conditions approaching the in-situ stress state and degree of saturation. All GDS triaxial testing systems (as well as triaxial equipment from other manufacturers*) can be modified to allow for unsaturated triaxial testing. GDS provide 4 methods to perform unsaturated testing. Unsaturated testing can also be added to the following test types, Shear, Hollow Cylinder, Resonant Column, Consolidation and True Triaxial Testing. *Please confirm existing equipment with GDS to check for compatibility. Choice of different methods: Hong Kong University of Science and Technology: Mixed and matched: GDS experience: To suit your testing requirements and budget, see options A, B, C & D below. Method B has been developed in conjunction with HKUST (Hong Kong University of Science and Technology), who are specialists in unsaturated soil testing. Methods may be mixed and matched to create a custom system. GDS has knowledge of many different unsaturated test methods and can objectively advise customers on the best method for their test requirements. GDS are not limited to a single solution and have currently over 100 unsaturated systems in use. Triaxial Unsaturated Testing Methods: Method A: Direct volume change measurement of pore air and water using a GDS pore air pressure/volume controller, water pressure controller and measurement of atmospheric pressure. Method B: HKUST inner cell - Total specimen volume change is measured from the change in water level in an inner cell using a differential pressure transducer. Method C: Double walled cell - A GDS pressure volume controller is used to measure inner cell volume change which is directly related to sample volume change. Due to the outer cell pressurisation, the inner cell wall is considered to be infinitely stiff. Method D: On-sample local strain transducers measure directly on sample to calculate total volume change. Method A: Method B: Method C: Method D: Resolution of measurement: Accuracy of measurement: Resolution of volume change measurement: Accuracy of sample volume change measurement: Resolution of measurement of cell volume: Accuracy of measurement of cell volume: Resolution of displacement: Accuracy: Pressure = 0.2kPa, volume = 1mm 3 Pressure = <0.1% full range, volume = 0.25% <10mm 3 Estimated at 32mm 3 or 0.04% volumetric strain for a triaxial specimen 38mm in diameter, 76mm in height 1mm % <0.1μm Hall Effect = 0.8% FRO, LVDT = 0.1% FRO 5

9 Virtual Infinite Stiffness Loading System (GDSVIS) Overview: The GDS Virtual Infinite Stiffness loading system (GDSVIS) is the premier load frame in the GDS range. The VIS allows the axial loading system to operate as though it has infinite stiffness (zero system compliance). This type of frame is unique to GDS. The VIS functionality is achieved by calibration and correction of system compliance. The GDSVIS is extremely stiff and designed principally for rock testing to allow minimum backlash at the point of sample shearing (other, less stiff load frames do not give analagous results at this critical point in the test due to the recovery of the load frame under fast unload conditions). Load-deformation relationship: Built in feedback: Automatic correction: Column strength: The GDSVIS is calibrated to provide precise data on the load-deformation relationship of the entire load application and load measuring system, which is then automatically used for self compensation. All VIS frames have feedback control and continuous display of axial load and platen displacement to allow simple and confident control of force and displacement. VIS provides automatic correction for system compliance, a common cause of error, which can under-estimate results of sample stiffness. The 500kN load frame has been built with 4 columns for extra strength and rigidity and can hold a cell size with a 700mm outer cell diameter. B-check, consolidated drained (CD) triaxial, consolidated undrained (CU) triaxial, consolidation (Triaxial), constant rate of loading (CRL), constant rate of strain (CRS), slow cyclic testing, K0 (K-Zero), multi-stage testing, quasi-static (low speed/ creep) tests, stress paths and unconsolidated undrained (UU) triaxial. Typical Applications: High Pressure / Load triaxial testing and unconfined testing. Computer Interface: USB Dimensions: Nominal Size: 2.3m x 1.0m x 0.96m Displacement Accuracy: 0.05% of full range Displacement Range (mm): 100 Load Range (kn): 100, 250, 400, 500 Power: v, A.C Hz, 65w maximum, single phase three wire earthed supply, 2A fuse x 2 Weight Approx (kg): 800 to 2000 (depending on model) Resolution of measurement and control: 100kN = 3N, 250kN = 8N, 400kN = 12N, 500kN = 15N 6

10 Triaxial Cells (CELLS) Overview: GDS produce an extensive range of triaxial cells in order to satisfy the complex range of tests required by today s modern geotechnical laboratories. In addition, there are a number of features such as balanced ram, access ports and access rings for internal transducers that are offered. In summary, the cells are grouped in the following categories:- Traditional Passive Triaxial Cells Low Pressure (< 5MPa). High Pressure (> 5MPa with balanced ram). High Pressure (> 5MPa without balanced ram) Active Triaxial Cells (Hydraulically Actuated Triaxial). Pressure ranges: Range of specimen size: Optional balanced ram: Low pressure cell construction: High pressure cell construction: Large range of pressures available up to 100MPa. Large range of standard sample sizes. Custom sample sizes are available upon request 20mm - 500mm diameters. Accurate testing with a Balanced Ram, see full description below. Aluminium with perspex wall making it light weight and easy to handle. Stainless steel for long life with no corrosion. GDS have been designing and making triaxial cells for over 30 years. GDS have learnt not to compromise on materials or surface treatments. As a result GDS manufactures all cells in the UK from top specification Aluminium Alloys and state of the art surface treatment to give our users equipment that lasts. What are the advantages of a Balanced Ram? A balanced ram system compensates for the up thrust on the ram exerted by the cell pressure. GDS system utilises a secondary chamber around the ram that balances the pressure in the cell against a second piston seal such that the pressure load is not exerted onto the loadframe. This system means that a smaller range loadframe can be used to achieve the same deviator loadings on the sample. For example, if a cell has a 50mm diameter ram and a cell pressure of 32MPa this would give an upthrust of over 63kN that would have to be deducted from the maximum achievable deviator loading that a given frame can apply. With a balanced ram, the full load frame capacity may be used to apply axial force on the sample as there is zero ram upthrust. In addition, a balanced ram within a high pressure passive cell eliminates disturbance to constant cell pressure during axial loading. Bender element system (Vertical, Horizontal, S and P waves), hall effect local strain, LVDT local strain, unsaturated testing, transducer access rings and temperature control. Max Sample Size (mm) and Pressure Range (MPa): Low Pressure (<5MPa) Cells: High Pressure (>5MPa) Cells with Balanced Ram: High Pressure (>5MPa) Cells without Balanced ram: Hydraulically Actuated Cells: 50mm/1.7MPa, 70mm/2MPa, 76mm/3.4MPa, 100mm/1.7MPa, 100mm/2MPa, 150mm/1.7MPa, 200mm/1MPa, 250mm/1MPa, 300mm/1MPa 54mm/64MPa, 100mm/64MPa 50mm/14MPa, 50mm/64MPa, 70mm/100MPa, 10mm/14MPa, 10mm/20MPa 50mm/2MPa, 100mm/2MPa, 50mm/10MPa 7

11 High Pressure Environmental Triaxial System (HPETAS) Overview: The High Pressure Environmental Triaxial System (HPETAS) can be fitted with a heating or cooling system that is automatically controlled alongside the whole system via software. Based on the same features as the GDSTAS system, the main difference with the HPETAS system is the triaxial cell and the optional temperature control system. Two options are available, one allows heating only and the other can heat and cool the cell. All of the same features apply for this system as for GDSTAS (stress paths, slow cyclic loading etc). Heating only system (Ambient to 60 o c, optionally to 100 o c): Combined Cooling / Heating System (-20 to 60 o c): PC controlled: Gaseous back pressures: Flexible system set-up The heating system works using thermal pads attached to the outside of the cell then enclosed within an environmental chamber to retain the heat. There are up to 4 temperature sensors relaying back to the control box for enhanced temperature accuracy. The cooling system uses a coiled tube section inside the cell, this is connected through the standard ports within the cell base to a glycol cooling unit, therefore temperature transfer is close to the specimen. Temperature control is added to selected GDSLAB test modules to allow temperatures to be easily set for each configured test stage. Can be adapted for gaseous back pressures such as Air, CO2 or Nitrogen. The HPETAS is made up of several apparatus each of which have a number of options that can be tailored to suit specification and budget. The pressure & samples you will be testing determines the options available. B-check, consolidated drained (CD) triaxial, consolidated undrained (CU) triaxial, consolidation (Triaxial), constant rate of loading (CRL), constant rate of strain (CRS), slow cyclic testing, K0 (K-Zero), multi-stage testing, quasi-static (low speed/ creep) tests, stress paths and unconsolidated undrained (UU) triaxial. Bender elements, unsaturated testing, local strain transducers and gaseous back pressures. Load Range (kn): 50, 100, 250, 400, 500, 1000, 2000 Pressure Range (MPa): 8, 14, 16, 20, 32, 64, 100 Sample Sizes (mm): 38 to 150 Available Temperature Ranges: -20 C to 60 C / ambient to 100 C / -20 C to 100 C 8

12 Enterprise Level Dynamic Triaxial Testing System (ELDYN) Overview: The GDS Enterprise Level Dynamic Triaxial Testing System (ELDYN) is a triaxial system, based on an axially-stiff load frame with a beam mounted electromechanical actuator. The ELDYN has been designed to fulfil the demand within the geotechnical laboratory testing industry for a lower cost, more basic dynamic triaxial testing system, yet still performs to the very advanced standards that customers expect from GDS. Standards: ASTM D-3999 ASTM D-5311 Electro-mechanical system: Cost savings, environmental benefits and safer operation: The ELDYN system supersedes systems using pneumatic actuators in terms of life costs and overall usable performance. Electro-mechanical systems can carry out full load dynamic testing to the stated frequency. Pneumatic systems tend to reduce the available amplitude with load due to the amount of air that needs to be moved from one side of the actuator to the other. Electro-mechanical systems are more environmentally friendly as they only draw the energy required to do the test, resulting in lower life costs. Electromechanical systems are also safer to run due to no high pressure air or hydraulic pipelines being required. No large noisy power packs are required to be running all the time, the ELDYN only requires a standard mains electricity outlet, this reduces the laboratory space required and the installation costs. Consolidated drained (CD), consolidated undrained (CU), consolidation (Triaxial) dynamic, cyclic loading of samples under either load or strain, slow cyclic testing, quasi-static (low speed/creep) tests, stress paths and user defined waveforms. Optional upgrade to user defined waveforms, upgrades from 5kN to 10kN, Bender element system (Vertical, Horizontal, S and P waves), hall effect local strain, LVDT local strain and unsaturated testing. Actuators: Highly accurate dynamic electro-mechanical actuator Axial Displacement Encoder: Yes Axial Load: +/- 5 kn at 5Hz (upgradeable to +/-10kN) Computer Interface: USB Data Acquisition: 16 Bit Load Range (kn): 5 (optional 10) Operating Frequency (Hz): 5 (optional 10) Pressure Range (MPa): Depends on cell chosen (2 standard) Sample Sizes (mm): Depends on cell chosen (38 to 150 standard) 9

13 Advanced Dynamic Triaxial Testing System (DYNTTS) Overview: The Advanced Dynamic Triaxial Testing System (DYNTTS) is a high-end testing apparatus combining a triaxial cell with a dynamic actuator capable of applying load, deformation and stresses at up to 10Hz. The axial axis is screw-driven from an integral base unit housing the motor drive. Axial force and axial deformation are applied through the base of the cell. Standards: ASTM D-3999 ASTM D-5311 High accuracy electro-mechanical control: Interchangeable load cells: In-built balanced ram (up to 5Hz systems): Interchangeable pedestals and triaxial extension top caps: Direct closed loop of axial displacement & axial force: The DYNTTS system is capable of very small strain static tests through to large strain dynamic tests. Allows user to accommodate very soft to very stiff soils with ranges of 1, 2, 4, 8, 10, 16, 25, 40 and 60kN. Keeps cell pressure constant during cycling, meaning a dynamic pressure controller is not required (unless dynamic cycling of cell pressure is required). Allows testing of 38, 50, 70 and 100mm diameter test specimens in the same cell. Accurate control in either axial displacement or axial force mode. Consolidated drained (CD), consolidated undrained (CU), consolidation (Triaxial), dynamic cyclic loading of samples under either load or strain, slow cyclic testing, quasi-satic (low speed/creep) tests, stress paths, K-Zero and user defined waveforms. Dynamic cell pressure, larger sample sizes up to 300mm diameter, higher cell pressure up to 5MPa, Bender element system (Vertical, Horizontal, S and P waves), Hall Effect Local Strain, LVDT local strain, unsaturated testing and temperature controlled testing. Actuators: High accuracy electro-mechanical Axial Force Accuracy: <0.1% Axial Force Resolution: 16bit (i.e. <0.4N for 10kN load cell, <1.5N for 40kN load cell) Axial Load (kn): 10, 25, 40 or 60 Displacement Range (mm): 100 Displacement Resolution: 0.20µm Operating Frequency (Hz): 2 (Standard), 5, 10 Pressure Range (MPa): 2 (Standard), upgradeable to 5 Speed of Measurement and Control: 5 /10kHz Sample Sizes (mm): 38, 50, 70, 100 (other sizes available on request up to 300) 10

14 Hydraulic Axial/Radial Loading Frame (HLF28), (HLF100) and (HLF250) Overview: The GDS Hydraulic Loading Frames (GDSHLF) are load frames with a dynamic hydraulic actuator mounted on the cross beam for axial loading and an optional second actuator for dynamic radial stress loading. The system is capable of dynamically controlling axial displacement or axial force and can be synchronised with an optional dynamic cell pressure actuator (radial stress) to give advanced capability of dynamic stress path testing. The GDSHLF is ideal for performing tests on large particle sizes such as ballast, (see LDCTTS on page 12). Standards: ASTM D-3999 Dynamic control of axial displacement or axial force to 10Hz, sinusoidal waveform: Optional dynamic control of radial stress to 10Hz, sinusoidal waveform: Optional interchangeable load cells: Load frame strength: Direct (dynamic, 10Hz) closed loop control of axial displacement, axial force and cell pressure. The dynamic control of cell pressure means that for those tests where the cell pressure is constant but the axial actuator is moving dynamically, the cell pressure actuator automatically adjusts the volume of oil in the cell to maintain a constant cell pressure. Or it can be used to cycle the cell pressure. To accommodate soft to very stiff soils with ranges of 28, 100 and 250kN. The load frame is supplied with an external load cell to match the model maximum load range as standard. GDS load frames are extremely stiff to allow minimum backlash at the point of sample shearing. Axial compression, axial extension, cyclic loading, cyclic displacement, optional cyclic cell pressure, static load and static displacement. Triaxial testing, bender element system (Vertical, Horizontal, S and P waves), hall effect local strain or LVDT local strain, unsaturated testing and temperature controlled. Axial Force Accuracy: <0.1% of load cell range (i.e. 1N for 10kN load cell) Axial Force Resolution: 16 bit (i.e. <0.4N for 10kN load cell, <1.5N for 40kN load cell) Data Acquisition (Built In): 16bit - 4 channel where load cell is Channel 1 Displacement Accuracy: 0.05% of full range Displacement Range (mm): 50 or 100 Displacement Resolution: <3 µm Load Range (kn): 28, 100, 250 Operating Frequency (Hz): 0-10 Sample Sizes (mm): Dependant on test type / cell selection, up to 300mm diameter Weight Approx (kg): 28kN (200kg), 100kN (1800kg), 250kN (3000kg) 11

15 Large Diameter Cyclic Triaxial Testing System (LDCTTS) Overview: The Large Diameter Cyclic Triaxial Testing System (LDCTTS) is a hydraulically actuated load frame combined with a large diameter triaxial cell suitable for testing samples with large particle sizes such as railway ballast. The system is capable of monotonic (static) and dynamic triaxial tests as well as other advanced triaxial tests. Standards: ASTM D-3999 pren AASHTO t294/t-307 Flexible system capacity: Interchangeable (internal submersible) load cells: GDSDCS (dynamic control system): Direct closed-loop dynamic control of axial displacement or axial force to 10Hz, sinusoidal, triangular or user defined waveform: Specimen size, load and pressures can be selected to suit specification and budget. Load cells to accommodate very soft to very stiff soils with ranges of 8, 16, 25, 32, 64, 128 and 250kN are available. The load frame is supplied with an external load cell to match the model maximum load range as standard (100 or 250kN). For data acquisition and control, 8 channel of expandable accurate high speed acquisition and control. Accurate and flexible control options. Consolidated drained (CD) triaxial, consolidated undrained (CU) triaxial, consolidation (Triaxial) dynamic, cyclic loading of samples under either load or strain, slow cyclic testing, quasi-static (low speed/creep) tests, stress paths, resilient modulus tests and user defined waveforms. Sample volume measurement by HKUST, bender element system (Vertical, Horizontal, S and P waves), LVDT local strain and unsaturated testing. Axial Force Accuracy: <0.1% of load cell range (i.e. 10N for 100kN load cell) Axial Force Resolution: 16bit (i.e. <0.4N for 10kN load cell, <1.5N for 40kN load cell) Displacement Accuracy: <0.15% (i.e. <0.15mm) Displacement Range (mm): 100 Displacement Resolution: 16bit (i.e. <3µm) Load Range (kn): 100, 250 Operating Frequency (Hz): 0 to 10 Sample Sizes (mm): 300 (standard) 12

16 True Triaxial Apparatus (GDSTTA) Overview: The GDS True Triaxial Apparatus (GDSTTA) has the defining characteristic that, unlike conventional triaxial apparatus, all three principal stresses can be controlled independently, rather than just two in a conventional triaxial system. This allows a wider range of complex stress paths to be performed. This dynamic cyclic system is powered by advanced electro-mechanical actuators or optional hydraulic actuators and is an extremely sophisticated research tool. Vertical and one horizontal axis are loaded via the dynamic actuators (axis 1 and 2), stress control is provided for the 2nd horizontal axis, (axis 3) via cell pressure. Stress or strain is applied to a 75mm x 75mm x 150mm sample independently on three axes: Ram specification: Electro-mechanical actuators as standard: Custom designed optional hydraulic actuators: Sample preparation: Two pairs of matched dynamic rams for axes 1 and 2, and a confining fluid provides pressure for the 3 rd axis on load readings. Each ram has its own internal submersible load cell and displacement transducer to ensure friction effects are minimised. Electro-mechanical actuators provide an easier to use and environmentally friendly solution for accurate testing to 5Hz. Electro-mechanical actuators do not require a hydraulic power pack to be present, hence no requirement to service a powerpack or to protect system users from noise generated by a powerpack. The hydraulic actuators have been custom designed by GDS to be seal-less with hydrostatic bearings. This improves the actuator performance (up to 10Hz) and reduces whole-life servicing costs as there are no piston seals to replace. Each actuator pair can be controlled in static-mode with either constant, ramp or slow cyclic targets in terms of load, stress or displacement. Full sample preparation equipment for cohesive and non-cohesive samples is provided with the system including a specially designed soil lathe for producing cuboidal samples. Hydraulic 28kN actuators (10Hz), electro-mechanical 10/20kN actuators (5Hz), bender element system (vertical, horizontal, S and P waves), LVDT local strain and proximitor (axis 3 only), unsaturated testing and dynamic cell pressure (5Hz). Fully independent control of axis 1 and 2 for load, stress, displacement and strain, stress control on axis 3 via cell pressure. Axis 1 and 2 can be controlled at up to 5Hz or 10Hz depending on the model selected (electro-mechanical vs hydraulic). Data Acquisition: 16 Bit, 16 Channel Pressure Range (MPa): 2 Load Range (kn): 5, 10, 20 - Electro-mechanical 28 - Hydraulic 13

17 Section 3: Introduction to GDS Rock Testing Apparatus GDS have manufactured high pressure automated triaxial testing systems for rock mechanics for over 20 years, with systems installed at leading research and commercial institutes around the world. The HPTAS is a load frame based triaxial testing system for accurate testing of rock samples. It is GDS most flexible system whereby components can be chosen by the user to meet their exact requirements. An image of the 500kN VIS load frame is shown below. The HPTAS is made up 3 fundamental components: 1) High stiffness, high capacity load frames up to 2000kN, see pages 15, 16 and 17. 2) Pressure control for cell and back pressure up to 150MPa, see section 7 on pressure / volume controllers. 3) Test cell (either a high pressure triaxial cell or a Hoek cell), see page 18. GDS have a wide range of high pressure triaxial cells, either with or without a balanced ram to complement their rock testing apparatus. Traditional Passive Triaxial Cells up to 64MPa with balanced ram and 100MPa without Balanced Ram. Alongside GDS range of high pressure rock triaxial testing systems is the GDS High Pressure Back Pressure Shearbox (HPBPS), see image below and page 19 for a full description. The HPBPS is a high pressure version of GDS back pressures shearbox, which also has the unique feature of being able to perform direct shear tests with precise back pressure control for the realistic modelling of slope failure. The device can load the sample to 100kN axially and in shear whilst also being capable of maintaining up to 10MPa back pressure. HPBPS - High pressure back pressured shearbox. 500kN VIS Load Frame. 14

18 500kN Load Frame (VIS500) Overview: The 500kN Virtual Infinite Stiffness loading system (VIS500) is the premier load frame in the GDS VIS range. VIS stands for virtual infinite stiffness, it allows the axial loading system to operate as though it has infinite stiffness (zero system compliance). This type of frame is exclusive to GDS. The 500kN version of the VIS has the added advantage that the beam lift can be used to lift the cell top on/off the cell base (extra long columns as an option) as well as options for hydraulic clamps to hold the beam in place. The 500kN VIS is a superstiff version of a standard GDSVIS to minimise system compliance even further. System calibration: Load frame stiffness: 4 column rigidity: Feedback control: USB computer interface: The GDSVIS is calibrated to provide precise data on the load-deformation relationship of the entire load application and load measuring system. GDSVIS load frames are extremely stiff and designed principally for rock testing to allow minimum backlash at the point of sample shearing (other, less stiff load frames do not give good results at this critical point in the test due to the stretch of the load frame under high load). The load frame has been built with 4 columns for extra strength and rigidity and can hold a cell size with a 700mm outer cell diameter. The GDSVIS comes with feedback control and continuous displays of axial load and platen displacement. May be used stand-alone using the keypad supplied or under computer control. Axial compression load, axial displacement, axial extension load and cyclic (slow speed) load or displacement. Extra tall columns allow heavy cell tops to be raised from their boxes using the automatic cross beam raising and lowering mechanism, making sample preparation quick and easy for a single operator. Hydraulic column locks replace the standard torque wrench tightened bolts, allowing the user to quickly and easily exert clamping forces when adjusting the height of the frame. Computer Interface: USB Displacement Accuracy: 0.05% of full range Displacement Range (mm): 100 Load Range (kn): 500 Data Acquisition: 16 Bit 4 Channel Resolution of Measurement and Control: <0.1% full range, displacement = 0.1micrometre 15

19 1000kN (1MN) / 2000kN (2MN) Static Compression Loadframes (HLF1000-S), (HLF2000-S) Overview: The GDS Static Loadframes are actuated from the base by a hydraulic actuator at loads up to 2000kN. To increase efficiency and to reduce whole life costs the actuator is powered by a 200cc / 64MPa GDS advanced pressure controller. This efficiency means that the full load of the frame, can be achieved by drawing less than 1000 Watts from mains electricity in place of a hydraulic power pack which could draw up to 50kW, to achieve similar loads. To increase efficiency and to reduce whole life costs the actuator is powered by a 200cc / 64MPa GDS Advanced pressure controller: The static frame uses low pressure compressed air on the reverse side of the actuator to raise the actuator post compression: Ideal for creep and relaxation testing: Infinite Volume Controller option: This efficiency means that the full load of the frame can be achieved by drawing less than 1000 Watts (1kW) from mains electricity in place of a hydraulic power pack which can draw up to 50kW. Control is carried out by a GDS advanced pressure controller and as such is very stable and accurate. No special requirements are needed to host or service a powerpack or to protect system users from noise generated by a powerpack. This allows a simple manual regulator to be set with a small pressure in the upper chamber of the actuator. This innovation allows lower stress testing to be carried out more efficiently and more accurately without the cost implications of using a second pressure controller for the upper chamber of the actuator. Once the regulator is set it can then be left unattended for all tests, so long as a supply of clean, dry compressed air is available at a pressure greater than 0.5MPa (5Bar). Ideal for use where displacements are very small and loads needs to be very stable and well controlled. For tests where continuous displacement is required to amplitudes greater than 5mm. Load control and axial displacement control. Triaxial, additional 64MPa controller and Infinite Volume Controller for tests where continuous displacement is required, additional data acquisition channels, an extensive range of Triaxial and Hoek cells are available to a complete triaxial testing solution for rocks and temperature control (up to 200 Degrees C). Actuators: Hydraulic Dimensions (mm): Frame footprint 700 x 600 x 1850 Displacement Range (mm): 100 Load Range (kn): 1000 / 2000 Weight (kg):

20 1000kN Dynamic Load Frame with Hydraulic Actuator (HLF1000-H) Overview: The 1000kN Dynamic Loadframe (HLF1000-H) is a servo-hydraulic system that has been designed to be a compact and effective addition to a soil and rock testing laboratory. Hydraulic power is derived from a separate powerpack that can be sited up to 15m from the loadframe. Two versions of the 1MN loadframe are available: 4 Column Moveable Head - where different sized test cells are to be used. Fixed Heads. The HLF1000-H has closed loopfeedback control of force and position as standard: Compact design: Hydraulic power: ELDCS control system: Closed loop-feedback control of force and position as standard: Low friction, bidirectional actuator: This allows the frame to be used for many different test types from soil to rock mechanics and other material test applications where precise control of axial force and displacement are required in a very stiff reaction frame (2GN/mm). Reduces the laboratory floor space required, only 2430mm x 750mm x 700mm. Hydraulic power is derived from a separate powerpack that can be sited up to 15m from the loadframe. This loadframe is controlled by the ELDCS control system which, has 4 channels of high speed data acquisition built in and is connected to the PC via the USB bus. The loadframes have closed loop-feedback control of force and position as standard. This allows the frame to be used for many different test types from soil to rock mechanics and other material test applications where precise control of axial force and displacement are required in a very stiff reaction frame. Full system load is available in compression and tension. Axial compression, axial extension, load control (Static), load control (Dynamic), displacement control (Static) and displacement control (Dynamic). An extensive range of Triaxial and Hoek cells are available to a complete triaxial testing solution for rocks and Temperature control (up to 200 Degrees C). Actuators: Hydraulic Dimensions: Dependant on chosen specifications Displacement Accuracy: 0.2% FRO Displacement Range (mm): 100 Load Range (kn): 1000 Max Loading Frequency (Hz): 2.5 Data Acquisition: 4 Channel 16 Bit 17

21 High Pressure Triaxial Cells (CELLS-HP) Overview: GDS produce cells for 20 to 100mm and from 4 to 100MPa to satisfy the complex range of tests required by today s modern geotechnical laboratories. Cells are available with or without balanced ram. Large pressure range: Large variety of sample sizes: 3rd party frames: Temperature control: Stainless steel design: Balanced ram: GDS triaxial cells are available from 4-100MPa, allowing user to choose the ideal cell for their range of testing needs. GDS range of cells can hold samples up to 100mm at a variety of different pressures. GDS Triaxial cells can be supplied as part of a complete system or for use in pre-existing 3rd party loadframes. Please contact GDS with the make and model of existing frame for fit information. Versions of some cells are available for testing samples at elevated temperatures up to C. All GDS high pressure cells are made from stainless steel and as such they will give many years of use without tarnishing or needing to be replaced due to corrosion. GDS high pressure triaxial cells are available with or without balanced ram. See difference below. What is a Balanced Ram? The balanced ram is a system that compensates for the up thrust on the ram exerted by the cell pressure. Our system utilises a secondary chamber around the ram that balances the pressure in the cell against a second piston seal such that the pressure load is not exerted onto the loadframe. This system usually means that a smaller range loadframe can be used to achieve the same deviator loadings on the sample. For example if a cell has a 50mm diameter ram and a cell pressure of 32MPa the up thrust would be approximately 63kN on the frame. This would have to be deducted from the maximum achievable deviator loading that a given frame can apply. With a balanced ram, the full load frame capacity may be used to apply axial force on the sample as there is zero ram upthrust. In addition, a balanced ram within a high pressure passive cell eliminates disturbance to constant cell pressure during axial loading. Pressure Range (MPa): High Pressure Passive cells with balanced ram; max sample size/pressure range: 54mm/64MPa, 100mm/64MPa High Pressure (>5MPa) Passive cells without balanced ram; max sample size /pressure range: 50mm/14MPa, 50mm/64MPa, 70mm/100MPa, 10mm/14MPa, 10mm/20MPa 18

22 High Pressure Back Pressure Shearbox (HPBPS) Overview: The High Pressure Back Pressure Shearbox (HPBPS) is a high pressure, high load version of GDS standard back pressure shearbox and is able to perform direct shear tests with precise back pressure control, for the direct control and measurement of realistic slope failure. The device can load the sample to 100kN axially and in shear whilst also being capable of applying up to 10MPa back pressure. Realistic slope stability conditions: Highly accurate displacement measurement: Direct shear testing: 10MPa stainless steel cell: Provide accurate results whilst working at high loads: Conditions can be applied by accurately controlling the normal force, shear force and back pressure. For very small yet long term creep movements to be measured. Allow direct shear tests to be performed under closely controlled conditions in terms of axial load and back pressure. For back pressure control and pore pressure measurement. Up to 100kN axial and shear load. Monotonic shear, cyclic (slow speed) shear and creep tests (under load or displacement control). Small strain shear LVDT system. Computer Interface: USB Data Acquisition: 16 bit Load Range (kn): 100 Axial 100 Shear Operating Frequency (Hz): Quasi Static (capable of slow speed cyclic testing, periods around 5 minutes). Pressure Range (MPa): 10 Sample Sizes (mm): 50 diameter or 100 diameter cylindrical, 50 high 219

23 Section 4: Introduction to GDS Shear Testing Apparatus Simple Shear Testing: The GDS Shearbase System (GDSSS) on page 21, is an electromechanical shear testing device that comes with the option to be configured as a simple shear or a direct shear apparatus with interchangeable sample set. The GDS Electro-mechanical Dynamic Cyclic Simple Shear Device (EMDCSS), on page 22, is for simple shear testing only. It is capable of carrying out dynamic cyclic tests from small strain (0.005% shear strain amplitude) to large strain (10% shear strain amplitude), as well as extremely accurate quasi-static testing. This is the choice for a nocompromise simple shear machine with the greatest range of testing capability. The perfect choice for advanced commercial testing or academic research. Combined Advanced Dynamic Cyclic Simple Shear System (ADVDCSS), on page 23, can be used for dynamic cyclic simple shear testing and dynamic triaxial testing. The complete shear actuator of the machine can be moved relative to the top actuator to create a system capable of testing triaxial samples up to 100mm diameter by 200mm high. Simple shear samples are typically 20mm high and up to 100mm diameter. Direct Shear Testing: The GDS Large Automated Direct Shear System (GDSLADS), see page 24, is an electro-mechanical direct shear testing device for large samples, up to 300mm square or round. Back Pressure Shear (GDSBPS). This advanced direct shearbox, see page 25, has the unique feature of being able to perform direct shear tests with precise back pressure control for the modelling of realistic slope failure. The BPS range includes a saturated version (control of pore water pressure) and an unsaturated version (control of pore water and pore air pressure). The Dynamic Back Pressured Shearbox (DYNBPS), on page 26, is for static and dynamic direct shear testing on soil specimens with control of sample pore pressures and loading frequencies up to 5Hz. The Interface Shear Tester (GDSIST), on page 27, is a CRS consolidation cell with the additional capability that the base pedestal may infinitely rotate. The internal load cell measures the axial force on the specimen as well as the torque generated. The system is designed to test the shear interface between the sample and top-caps of varying material roughness/types. GDS EMDCSS, see page 22. The Variable Direction Dynamic Cyclic Simple Shear System (VDDCSS), on page 28, allows simple shear to be performed in two directions, rather than the standard one. This is achieved by having a secondary shear actuator that acts at 90 degrees to the primary shear actuator. The VDDCSS is similar in principle to the EMDCSS machine, except for the additional horizontal axis. All standard simple shear tests can be performed as well as more complex tests involving parameters such as horizontal stress rotation. GDSSS, see page 21. GDSADS stands for Automated Direct Shear, and allows existing shearboxes from other manufacturers to be upgraded to be automated. Many shearboxes from other manufacturers can be controlled by the GDSLAB software and so full automation may be achieved with the addition of GDSLAB, a datalogger and transducers. Please Contact GDS to check the compatibility of existing devices and to discuss options. 20

24 Shearbase System (GDSSS) Overview: The GDS Shearbase System (GDSSS) is an electro-mechanical shear testing device that can be configured as either a simple shear or direct shear. One benefit of this apparatus is that the conversion between simple shear and direct shear is easy and therefore if both options are not supplied at time of build the missing option can be supplied at a later date. The Shearbase system can carry out fully automated simple shear, and direct shear tests (after shear gap settings). Standards: ASTM D-6528 BS CEN ISO/TS :2004/ AC:2005 Desktop apparatus: Runs from mains electricity: No requirements for compressed air or hanging weights: Normal (axial) and shear forces are applied using GDS electro-mechanical force actuators: Topcap fixity: Sample preparation and topcap support apparatus: Closed loop feedback: Fully automated: This desktop apparatus comes with built in controllers, resulting in a small footprint of just H x 660mm, L x 660mm, D x 220mm. The GDSSS comes with an integrated power supply, meaning the only laboratory service required for the system is mains electricity (110Vac 240Vac). The apparatus is a fully self contained, no lifting of heavy hanging weights. The use of GDS force actuators makes the system very flexible, each axis can be controlled in displacement (strain or velocity) mode as well as load control. Topcap fixity is assured through a system of crossed roller linear guides to minimise topcap rocking during shearing. Simple shear sample preparation and insertion into the system is made easy by using the included sample preparation and topcap support apparatus. This ensures that no load is applied to the sample during preparation and insertion. Axial and shear load readings are controlled under closedloop feedback. For direct shear, once the shear gap has been set, the test can complete with no further user intervention. For simple shear, once the top-cap is docked all consolidation and shearing stages can proceed with no further user intervention. Direct shear and simple shear tests. The GDS Shearbase can be upgraded to allow the system to perform both simple and direct shear tests. This is done by swapping the pedestal and top cap for a shear box. Simple Shear Options 10kN axial upgrade and Bender Elements Direct Shear Options 10kN axial upgrade. Data Acquisition: 16 Bit Load Range (kn): 2.5, 5, 10 Sample Sizes (mm): Up to

25 Electro-mechanical Dynamic Cyclic Simple Shear (EMDCSS) Overview: The GDS Electro-mechanical Dynamic Cyclic Simple Shear Device (EMDCSS) is for simple shear testing only. It is capable of carrying out dynamic cyclic tests from small strain (0.005% shear strain amplitude) to large strain (10% shear strain amplitude), as well as extremely accurate quasi-static testing. This is the choice for a no-compromise simple shear machine with the greatest range of testing capability. The perfect choice for advanced commercial testing or academic research. Standards: ASTM D-6528 Teflon coated low friction retaining rings: Electro-mechanical actuators that give superior performance, reduce space and provide cost savings: Active height control: Axial & Shear linear guidance provided by super-stiff crossed-roller bearings: GDS shear loadcell: A cylindrical soil specimen is laterally confined by teflon coated low friction retaining rings, ensuring a constant cross sectional area (or K-zero conditions). Electro-mechanical actuators can carry out tests up to +/-1mm at 5Hz, with greater accuracies than comparable pneumatic actuators. Mains powered means no external noisy power pack is required and as opposed to pneumatic systems electro-mechanical systems draw only the power that is required. Therefore constant volume conditions are enforced i.e Simple Shear. No manual intervention between stages plus little or no effects of vertical compliance. 200mm bearing length not only provides stability while ensuring minimal rotation of the topcap during shearing, allowing testing to be simple shear rather than rotational motion, but also provides high load capacity with low friction with accurate linear guidance. Designed so that shear force is measured in front of the linear guides, as such the shear force measurement does not include frictional errors. Cyclic simple shear and quasistatic simple shear. P and S wave measurements with bender element system and small strain measurement system. Data Acquisition: Integrated, with 8 input channels up to ±10v, 16 bit A/D converters Dimensions (mm): 1200 (H) x 500 (L) X 770 Displacement Range: Axial: +/- 25mm, Shear: +/- 15mm: Accuracy = <0.1% FSO (In practice, axial range is +/-50mm to aid sample placement, measured stroke is +/- 25mm) Displacement Resolution: 16 bit (i.e. +/- 20mm = 0.6μm, +/- 15mm = +/- 0.5μm, +/- 2.5mm = <0.1μm) Load Range (kn): 5 or 10 Operating Frequency (Hz): 0 to 5 Power: 240V or 110V 50/60Hz 1 ph Sample Sizes (mm): Up to 100 Weight Approx (kg):

26 Combined Advanced Dynamic Cyclic Simple Shear (ADVDCSS) Overview: The GDS Combined Advanced Dynamic Cyclic Simple Shear (ADVDCSS) is a testing system that can be used for dynamic cyclic simple shear and dynamic triaxial testing. The ADVDCSS allows the principal stress direction to continuously rotate through 90 degrees, giving the ability to simulate the stress states common to many geotechnical problems, including earthquake loading. Then, by moving the machine into triaxial mode and installing the longer cell wall, the device may be used for dynamic and static triaxial tests. Electro-mechanical actuators that give superior performance, reduce space and provide cost savings: Easy sample saturation: Accurate testing: High accuracy results: Teflon coated low friction slip rings: Independent control of axial axis and shear axis: Increased strength and alignment: Electro-mechanical actuators can carry out tests up to +/-1mm at 5Hz, with greater accuracies than comparable pneumatic actuators. Mains powered means no external noisy power pack is required and as opposed to pneumatic systems electro-mechanical systems draw only the power that is required. The ADVDCSS can saturate simple shear samples in a similar way to normal triaxial testing, using cell pressure and back pressure. This cannot be achieved in a normal simple shear system. Direct closed loop control of axial and shear force and direct closed loop of normal and shear displacement control leads to accurate testing with no user tuning / intervention during a test. The ADVDCSS has been designed to be extremely stiff in the axial and shear directions, this leads to very low system compliance and high accuracy results. During simple shear tests constant volume conditions are ensured in the sample by use of teflon coated low friction slip rings around the sample. Allows tests such as out of phase loadings. Preprogrammed sine, havesine, triangular and square waveforms provides ease of use for standard tests. High quality, low friction linear guides are used to ensure strength and alignment in normal and shear directions. Consolidated drained (CD) triaxial, consolidated undrained (CU) triaxial, consolidation (Triaxial), cyclic loading of samples under either load or strain, slow cyclic testing, quasi-static (low speed/creep) tests, stress paths, user defined waveforms, cyclic simple shear, simple shear, K-zero, permeability and simple shear. Bender element testing, unsaturated testing (Method A & D) and to local strain measurement (triaxial). Data Acquisition: 8 Channel Dynamic 16 Bit data logger Load Range (kn): 5, 10 Sample Sizes (mm): 50, 70,

27 Large Automated Direct Shear System (300mm)((GDSLADS) Overview: The GDS Large Automated Direct Shear System (GDSLADS), is a state of the art system that extends the boundaries of traditional shear testing. The GDSLADS automates the loading procedures as well as data acquisition and presentation. Normal and Shear forces are applied by GDS force actuators so they are controllable in terms of stresses and strains in both directions. The system is floor mounted and self-contained. No pneumatic/hydraulic powerpacks are required, only mains electricity. Tests can be controlled from either the keypads and displays associated with the force actuators or via GDSLAB software. Electro-magnetic actuation: Electro-magnetic & normal force application: Automated data logging (multiple stage tests): Cylindrical or square samples can be supplied, as well as multiple sample boxes: Built in loadcells (Standard 100kN, other ranges can be provided): Stiff construction: After setting of shear gap no further user intervention is required: Only mains electricity required (no hydraulics or pneumatics) therefore reducing the space required and providing a more accurate system. No hanging weights, hydraulics or pneumatics. Testing can run unattended over night and at weekends to increase throughput and reduce staff costs. Multiple stage tests can be preprogrammed and saved in GDSLAB. GDSLADS has the flexibility to test different shaped samples allowing the user greater flexibility of use, along with increased throughput of tests via multiple sample boxes. Interchangeable loadcells allow lower range, more accurate loadcells to be used for low stress testing. To reduce equipment compliance and increase accuracy. Automated test control and a greater throughput of samples. Different sample sets can be used to achieve the following types of testing in one system: Standard direct shear up to 300mm x 300mm. Geomembrane shear test. Rock mechanics sample set. Actuators (kn): 100 Shear force actuator, 100 Normal force actuator Data Acquisition: 16-bit data acquisition Load Range (kn): 100 Sample Sizes (mm): Up to 300 x 300 x 150 Weight Approx (kg):

28 Back Pressured Shear Box (GDSBPS) Overview: The Back Pressure Shearbox (GDSBPS) has the ability to performs direct shear tests with precise back pressure control, for the recreation and measurement of realistic slope failures. The BPS range includes a saturated version (control of pore water pressure), an unsaturated version (control of both pore water and pore air pressure) and a dynamic version, see page 26. Developed in conjunction with the University of Durham, UK (saturated version) and Zhejiang University, China (unsaturated version). Internal loadcell: Optional low-cost version: Rigid aluminium cell body: Unsaturated GDSBPS: Real-world situations to be modelled in the laboratory: Internal loadcell for shear and optionally normal force for load measurements as close to the sample as possible for greater accuracy. Low-cost version available which uses hanging weights for axial load. To reduce system compliance. The unsaturated GDSBPS is based on a standard, saturated device but modified to allow the measurement and control of matric suction (the difference between the pore air and water pressures). All versions allow the pore pressures within the sample to be controlled. The control of pore pressure during direct shear testing allows real-world situations to be modelled in the laboratory. The GDSBPS apparatus can be specified with many different options, some are noted below but many more are available. Please contact GDS if the required specification is not listed here or if higher pressures / forces are required. Upgrade to unsaturated back pressured shear box, increase maximum back pressure from 1MPa up to 10MPa, increase maximum axial shear and shear load from 5kN up to 100kN. Upgrades also include normal (axial) load upgrade to electro-mechanical actuator and the addition of bender elements. Data Acquisition: 8 channel, 16 bit with, serial interface and 8 user definable gain ranges from 10mV to 10V input Dimensions (mm): L= 875 x W = 350 Displacement Accuracy: <0.1% FSO Displacement Range: Axial = +/- 15mm, Shear = +/- 25mm Power: 240V or 110V 50/60Hz single phase Resolution of Measurement and Control: 16 bit, ± 25mm = ± 0.7μm (shear), ±10mm = ±0.3μm (axial) Sample Sizes (mm): 75 x 75 (alternative sizes available on request) 25

29 Dynamic Back Pressure Shearbox (DYNBPS) Overview: The Dynamic Back Pressured Shearbox (DYNBPS) is used for static and dynamic direct shear testing on soil specimens with control of sample pore pressures. The control of pore pressure during direct shear testing allows real-world situations to be modelled in the laboratory. This dynamic version of the device allows a landslide to be modelled as it quickly gains velocity after the initial moment of failure. Cyclic direct shear testing is also possible while still controlling and measuring pore pressure. Electro-mechanical actuators: Realistic modelling: Interchangeable internal load cells: Closed-loop control: Shear gap: Balanced rams: Designed for long life and highly accurate position control. Unlike pneumatic actuators this type of actuator is suitable for carrying out small strain testing, long term creep tests and dynamic tests up to 5Hz. The DYNBPS provides a realistic model of many real-world cyclic and seismic geotechnical problems, such as slope stability and earthquake loading. For increasing accuracy and resolution on soft soils. For shear force/displacement and normal force/displacement. Manually set-able from outside the pressure vessel whilst under pressure. Allows cost effective static pressure controllers to be used for back pressure with minimal pressure fluctuations during dynamic tests. Back pressured static direct shear tests, back pressured cyclic shear load tests and back pressured cyclic shear displacement tests. Bender elements and small strain transducers. Axial Force Resolution: 16bit (i.e. <0.4N for 10kN load cell, <1.5N for 40kN load cell) Computer Interface: USB Data Acquisition: 16bit Dimensions (mm): 1200(H) x 500(L) x 770(W) Load Range (kn): Normal force 25, Shear force 10 Operating Frequency (Hz): 5 Power: 3 phase Pressure Range (MPa): 1 Resolution of Measurement and Control (MHz): 10 Sample Sizes (mm): Square: 50, 75 (custom sizes available on request) Sample height: Weight Approx (kg):

30 Interface Shear Tester (GDSIST) Overview: The GDS Interface Shear Tester (GDSIST) has been designed to test the shear interface between the soil specimen and the sample top-cap. Top-cap interfaces of differing roughness can be used to stimulate differing insitu conditions. The GDSIST is a CRS consolidation cell with the ability for the base pedestal to infinitely rotate. The internal load cell measures the axial force on the specimen as well as the applied torque. Interface friction studies: Load cells: Stainless steel: Internal submersible load cell: Compact: GDS force actuators for axial stress: The most common uses for the GDSIST include studies of interface friction, for example between geomembranes, pipline footings and natural materials. Low range load cell for accurate low stress testing of axial load and torque. Available in stainless steel for corrosive sample testing. This allows the user to measure friction between the sample and material without errors being introduced by the seal friction on the ram. Small laboratory footprint. Accurate electro-mechanical control of axial force and displacement with keypad + display for local control. Axial or radial deformation, consolidation undrained, constant rate of strain, oedometer / consolidation, stepping loading, controlled hydraulic gradient, unsaturated tests, consolidation drained, constant rate of loading and saturation ramp. Unsaturated testing. Actuators: 1 off vertical, 1 off torsional Axial Force Accuracy: ±0.2% Axial/Torque Force Range: 1kN/10Nm to 5kN/100Nm Computer Interface: USB Load Range (kn): 1 Power: Table top frame: 240V, Control systems: V~1.6A MAX Pressure Range (MPa): 1, (2MPa cell available upon request) Sample Sizes (mm): 38, 50, 70, 100, other sample sizes available upon request 27

31 Variable Direction Dynamic Cyclic Simple Shear (VDDCSS) Overview: The Variable Direction Cyclic Simple Shear (VDDCSS) allows simple shear to be performed in two directions, rather than the standard single direction. This is achieved by having a secondary shear actuator that acts at 90 degrees to the primary shear actuator. The VDDCSS is similar in principle to the EMDCSS machine, except for the additional horizontal axis. When used as a variable direction machine, the secondary shear axis can be used independently of the other shear axis or in conjunction with it, therefore simple shear may be performed in any horizontal direction. Tests can be carried out with constantly rotating shear vectors. Test control: Direction of shear and pattern of shear rotation from zero degrees can be defined: Teflon coated rings: GDSLAB can also define test stages at different shear stress: Independent axis control: Local strain LVDT s for both shear directions: Test control allows specification of amplitude of shear stress/strain as well as direction. Constant at zero degrees. Ramp from zero degrees to x degrees in n seconds. Cycles from zero degrees plus or minus x degrees with period in seconds. K-zero conditions ensured by use of 1mm high, low-friction, teflon coated rings. Angles relative to zero e.g. 0, 10, 20, 30 etc. Definition of waveform by datum/ common point, amplitude, controlling parameter and frequency. Each axis can be stress / load controlled or strain controlled. Highly accurate strain measurement / control. Local LVDT is used for active height control during constant volume tests. Simple shear and variable direct simple shear. Local strain LVDT s for both shear directions and bender elements. Actuators: Axial Force Accuracy: Typically <0.1% Axial Load (kn): 5 3 x electro-mechanical, high accuracy, encoder controlled actuators Displacement Range: Shear axis +/- 10mm (+/-30% shear strain) Normal axis +/- 25mm (+80% consolidation strain) Displacement Resolution: 0.3µm Load Range (kn): 5 normal force, 2 on each shear measurement (y and z) Operating Frequency (Hz): 1 Sample Size (mm): 50 diameter specimen, height 20 to 30 (other sizes on request) 28

32 Section 5: Introduction to GDS Resonant Column and Hollow Cylinder Apparatus Resonant Column The GDS Resonant Column Apparatus (GDSRCA), on page 30, is used to excite one end of a confined solid or hollow cylindrical soil specimen. From the resonant frequency, small strain stiffness can be found. The GDSRCA is used by advanced commercial laboratories and Universities for performing research. GDSRCA systems are current driven using a transconductance power amplifier. This is an advantage due to the fact that impedance of the RCA system changes with frequency. At higher frequencies, using a constant voltage, the current would be seen to reduce. As the torque is directly proportional to current, the torque would also reduce. This change to using a current driven power amplifier reflects the current thinking in the state-of-the-art resonant column testing throughout the world and ensures constant torque is applied at all frequencies. Options exist for an environmental temperature chamber (-20 degs C to +40 degs C) and an axial loading actuator and frame. GDS can also supply a Hardin Oscillator type RCA which, is suitable for anisotropic loading. GDS Resonant Column set-up with lifting frame. Hollow Cylinder The GDS Small-Strain Hollow Cylinder Apparatus (SS-HCA), on page 31, allows for rotational displacement or torque to be applied to a hollow cylindrical specimen of soil. Using this device it is possible to control the magnitude and direction of the three principal stresses within a soil specimen. The SS-HCA s (static) and SS-HCA d (dynamic) are both designed around the same central core of components. All of these components have been designed to give the machine high levels of axial and torsional stiffness coupled with the minimum amount of backlash and friction. All of these design considerations result in both machines being well suited for small strain testing through to high strain testing. For example studies can be made of the following: The anisotropy of soil samples. The effects of principal stress rotation. The effects of intermediate principal stress. GDS Hollow Cylinder System. 29

33 Resonant Column (GDSRCA) Overview: The GDS Resonant Column Apparatus (GDSRCA) is a true fixed free resonant column where one end of a confined solid or hollow cylindrical soil specimen is excited and the other is fixed. From the resonant frequency, small strain stiffness can be found. GDSRCAs are used by advanced commercial laboratories and Universities for performing research. RCA systems that GDS supplies are current driven using a transconductance power amplifier: Designed to provide maximum rigidity: Simple automated tests: Electro-magnetic drive system: Internally mounted, counter-balanced accelerometer: Internal cell: This is because the impedance of magnet / coil devices change with frequency. At higher frequencies, using a constant voltage amplifier the current would be seen to reduce. As the torque is directly proportional to current, the torque will also reduce and a non-linear torque input would affect results. This effect is removed in the GDSRCA by using a current driven power amplifier. Providing minimum losses and a more consistent frequency response and no rigid support to the top cap so it is completely free vibrating. Low equipment damping. Which incorporates precision wound coils and composite sintered neodymium iron boron (NdFeB) rare-earth magnets. Used to measure vibratory response of the sample. To surround sample with water, to avoid air penetrating the membrane. Damping ratio in flexure, damping ratio in torsion, resonance in flexure, resonance in torsion and optional slow speed (<2Hz) torsional shear. Lifting frame for easy cell top removal, vertical bender elements (S and P wave), unsaturated RCA testing pedestals, torsional shear upgrade using non-contacting proximetor transducer, high pressure upgrades from 1MPa (standard) to 2MPa, 3MPa or 25MPa, anisotropic test upgrade (hanging weights), gas hydrate upgrade option, unsaturated testing (Method A and B), option for environmental temperature chamber (-20 degs C to +40 degs C), an axial loading actuator and frame and a Hardin Oscillator type actuator with axial force actuator. Frequency Range (Hz): 300 Data Acquisition: 16 Bit Pressure Range (MPa): 1 standard, 2, 3 and 25 as options Sample Sizes (mm): 50, 70, optionally

34 Small-Strain Hollow Cylinder Apparatus (SS-HCA) Overview: The GDS Small-Strain Hollow Cylinder Apparatus (SS-HCA) allows for rotational displacement and torque to be applied to a hollow cylindrical specimen of soil. Using this device it is possible to control the magnitude and direction of the three principal stresses. Two version of the system are available, SS-HCA s (static) and SS-HCA d (dynamic). Both systems exhibit high levels of axial and torsional stiffness coupled with the minimum amount of backlash and friction: Flexibility in the capacity of the system: Balanced ram: Submersible, interchangeable combined axial / torque loadcell: Cell top lift frame: Resulting in both machines being well suited for small strain testing right through to high load and strain testing. Specimen size, load, pressures can be chosen to ensure the system is created specifically to suit the testing required and the budget. Allows a static pressure controller to be used for cell pressures with no significant fluctuations of cell pressure during dynamic tests. Measures axial load/torque with no errors introduced due to friction on the loading ram. For ease of use when lifting the cell top, comes as standard. HCA generalised stress path (P, Q, B, α), advanced HCA loading procedures and dynamic HCA loading. Triaxial testing with optional items. Sample sizes, transducers, celltop counter balanced lift, optional large cell for 200mm samples, internal bore LVDT, outside diameter non-contacting proximetors and unsaturated testing. Axial Displacement Encoder: <1μm Axial Load Resolution: 0.3N (for 10kN systems) Axial/Torque Force Range: 10kN/200Nm, 12kN/200Nm, 15kN/400Nm Torque Resolution: 0.06kN (200kN Systems) Dimensions (mm): 700 X 700 X 1000 (cell de-mounted), 1450 (cell mounted), 2350 with cell top lifting frame Load Range (kn): 10, 12 or 15 Operating Frequency (Hz): 0.5, 1, 2 or 5 Pressure Range (MPa): 1, 2 Sample Sizes (mm): 100/60/200 or 200/160/400 (OD, ID, height) Weight Approx (kg):

35 Section 6: Introduction to GDS Consolidation System Apparatus GDS manufacture three consolidation systems, all of which come with a variety of upgrade options. Below is a short overview of each of the systems. The GDS Consolidation Testing System (GDSCTS), on page 33, is a state-of-the-art, fully-automated consolidation testing system designed for soil. GDSCTS can run classic tests such as step loading to more advanced tests such as automated testing rate by controlled hydraulic gradient or cyclic loading, all under PC control. More commonly seen in university laboratories for teaching or research. The GDS Constant Rate of Strain consolidation cell (GDSCRS) on page 34, is designed primarily for advanced testing laboratories who want to reduce the time required to complete a consolidation test. The GDSCRS cell fits neatly into your load frame in place of the Triaxial cell. As shown in the image on the right. The GDS Automatic Oedometer System (GDSAOS) on page 35, is the modern replacement for a traditional hanging weight oedometer. The GDSAOS is a self contained stepper motor driven unit that can be controlled either manually using its Smart Keypad or from a PC using the USB interface. There is no GDSCRS set-up, see page 34 for more information. requirement for compressed air or manually placed weights. When used with the GDSLAB control and data acquisition software, the GDSAOS can be used for a complete array of tests beyond those which a hanging weight oedometer can perform. GDS also manufacture a large diameter consolidation cell for sample sizes up to 500mm. Manufactured from stainless steal, the device is used within a load frame for large scale consolidation or CRS testing. Primarily designed to be used within the GDS 250kN load frame. Please contact us for more information on this cell. Below are images of GDS consolidation products. From left to right, the Consolidation Testing System (GDSCTS), Constant Rate of Strain cell (GDSCRS), Automatic Oedometer System (GDSAOS) and finally the 500mm consolidation cell. 32

36 Consolidation Testing System (Rowe Type) (GDSCTS) Overview: The GDS Consolidation Testing System (GDSCTS) is a state-of-the-art, fully-automated consolidation testing system designed for soil. The system is based on the Rowe and Barden type consolidation cell using GDS pressure/volume controllers from the Advanced, Standard, or Enterprise range. Two of these pressure controllers link to the computer, one for axial stress and axial displacement control and one for setting back pressure. Rowe and Barden type cell: Flexibility in the capacity of the system: Advanced testing (ADVCTS): Standard testing (STDCTS): Direct stress control on specimen via either a flexible or rigid porous disk. Specimen size, load, pressures can be chosen to ensure the system is created specifically to suit the testing required and the budget. Remains the leading Rowe & Barden type consolidation system for research testing throughout the world. All elements of the ADVCTS system are biased towards achieving the greatest resolution and accuracy, for the highest quality tests achievable in a research environment. Provides a low cost alternative with all the features of the ADVCTS system with slightly reduced accuracies by using GDS standard pressure/volume controllers. Stepped loading, constant rate of loading (CRL), constant rate of strain (CRS) and hydraulic gradient controlled tests. Radial drainage, UNSAT (High air entry stone bonded into a specially modified base) and bender elements. The GDS consolidation system can become a GDS stress path triaxial testing system by changing the test cell, adding a further 200cc pressure/volume controller and software. Accuracy of Pressure Measurement: Accuracy of Volume Measurement: Data Acquisition: Resolution of Measurement and Control: Resolution of Volume Measurement: Sample Sizes (mm): 50, 70, 100 Standard set-up (STDCTS): <0.25% measured value Advanced set-up (ADVCTS): <0.1% full range Standard set-up (STDCTS): <0.25% measured value Advanced set-up (ADVCTS): <0.1% measured value 16 Bit Standard set-up (STDCTS): 1kPa Advanced set-up (ADVCTS): 0.5kPa Standard set-up (STDCTS): 1mm 3 Advanced set-up (ADVCTS): 0.5mm 3 33

37 Constant Rate of Strain Cell (Used in a Load Frame) (GDSCRS) Overview: The GDS Constant Rate of Strain Consolidation cell (GDSCRS) is designed primarily for advanced commercial testing laboratories who want to reduce the time required to complete a consolidation test. The CRS cell fits in a load frame in place of a triaxial cell, or in a GDSAOS. The load frame based one dimensional consolidation cell is capable of applying back pressure and measuring pore pressures up to 1MPa (low pressure version) or 20MPa (high pressure version). Stress increments applied gradually: Controlled back pressure (water) is applied to the sample and drainage is allowed through the base of the apparatus: Run the entire test from start to finish: Construction material: Integral cutter / sample ring: The advantage of this method is that the time required to complete a consolidation test can be reduced significantly. Allows excess pore pressure to be monitored so tests can run at maximum speed and hence increase specimen throughput. More efficient testing as no waiting for user inputs. Anodised aluminium with perspex outer cell wall for long life. Disturbance on samples is reduced by having a cutting edge integrated into the sample confinement ring. Constant rate of loading (CRL), constant rate of strain (CRS) and stepped loading. 20MPa version and bender elements. Load Range (kn): Pressure Range (MPa): Sample Sizes (mm): Low Pressure: 50 High Pressure: 100 Low Pressure: up to 1 High Pressure: up to 20 Low Pressure: 38, 50, 70, 100, High Pressure: 38,

38 Automatic Oedometer System (GDSAOS) Overview: The GDS Automatic Oedometer System (GDSAOS) is the modern replacement for a traditional hanging weight oedometer. The GDSAOS is a self-contained stepper motor driven unit that can be controlled either manually using its Smart Keypad or from a PC using the USB interface. There is no requirement for compressed air or manually placed weights. When used with the GDSLAB control and data acquisition software, the GDSAOS can be used for a complete array of tests beyond those of a hanging weight oedometer. Standards: BS-1377/5 ASTM D-2435 ASTM D-3877 ENISO/ TS17892/5 AASHTO- T216 Direct replacement for a hanging weight oedometer system: Automated logging of data (and optionally reporting): Incremental loading stages: Accurate results throughout the load range: Utilise existing equipment: The GDSAOS is a stand-alone unit (with no requirement for compressed air). Having a small footprint significantly reduces the bench space required coupled with the additional advantage that loading weights are not required. Automation saves time recording results and controlling the test. When using GDSLAB the GDSAOS can be preprogrammed to include numerous incremental loading stages which automatically move to the next stage via preprogrammed end of consolidation conditions, thus increasing sample throughput. From 1N to 10kN the GDSAOS electro-mechanical pressure controlled systems provide accurate results, compared to pneumatic consolidation systems that are typically inaccurate at low loads. If upgrading from a PC logged hanging weight system, it may be possible to utilise the current data logger and transducers as many data loggers, even those from other manufacturers, are compatible with the GDSLAB software. Constant rate of loading (CRL), constant rate of strain (CRS) and stepped loading. GDSLAB with the Oedometer module Automated testing (step loading) and data acquisition. An external displacement transducer can be added to increases the accuracy of strain measurements. With the addition of an RFM the device can measure and control from an additional transducer, i.e. axial displacement or pore pressure. The GDSAOS can be arranged in greater numbers connected to a single PC or to multiple PCs. Commonly oedometers are used in groups of 4-6 and these can all be connected to GDSLAB and controlled with tests starting at different times and differing load increments. Axial Force Accuracy: Axial Force Resolution: Displacement Accuracy: Displacement Resolution: 0.1%FRO 0.001kN Load Range (kn): Max Load 10 Power: 0.1% - dependant on selected transducer mm - dependant on selected transducer 110 to 240 AC Volt Input, 60 Watts Sample Sizes (mm): 38, 50, 63.50, 71.40, 75, 100, 101.6,

39 Section 7: Introduction to GDS Pressure/Volume Controllers GDS have been making pressure controllers for over 30 years and have sold in excess of 2,500 units. Pressure controllers are available with pressures from 100kPa up to 150MPa for water/oil, all with accurate measurement of volume change. GDS controller ranges are capable of being logged and controlled by PC. The image on the right of this page shows one of the first controllers ever sold by GDS in Advanced controller sold in The latest edition to the range is the Enterprise Level Pressure/Volume Controller (ELDPC) which, is aimed at commercial testing (max 1MPa). The controller is available to one specification, 1MPa pressure, 200cc volume. The Standard Pressure/Volume Controller (STDDPC) is aimed at medium pressure commercial testing ( 4MPa), undergraduate teaching and research. The standard controller is the mid level controller from GDS, available in 200cc only, but with pressure ranges from 100kPa to 4MPa (standard is 3MPa). GDS ELDPC, see page 37 for more information. The Advanced Pressure/Volume Controller (ADVDPC) and High Pressure/ Volume Controllers (HPDPC) are the premier controllers in the GDS range. Designed to give the highest accuracy in terms of pressure and volume, these controllers are the first choice for research. Available in 200cc or 1000cc (2MPa only) and with pressures ranging from 100kPa to 150,000kPa (150MPa). See pages for controller comparison. The Pneumatic Controller (GDSPPC) on page 40, is an economical source of computer controlled regulated air pressure control. The controller regulates an external pressure source of compressed air from a compressor or compressed air cylinder to provide a controlled output pressure. The control of the valve is via the Serial bus (RS232) from the PC and software. The pneumatic controller is a cost effective route for upgrading manual regulator systems to automated systems. The GDS Infinite Volume Controller (GDSIVC) on page 41, is designed to remove constraints of volume capacity such that a test can continuously flow fluid under pressure or volume control. The GDSIVC allows 2 pressure controllers to be used together with automated switching between them and a reservoir for continuous volumetric supply. Standard controllers undergoing quality assurance check/tests at GDS. 36

40 Enterprise Pressure/Volume Controller (ELDPC) Overview: The GDS Enterprise Level Pressure/Volume Controller (ELDPC) is a general-purpose water pressure source and volume change gauge for the precise regulation and measurement of fluid pressure and volume change. The enterprise level controller is aimed at commercial testing and is available in one configuration, 1MPa pressure, 200cc volume. Standard Pressure/Volume Controller (STDDPC) Overview: The GDS Standard Level Pressure/Volume Controller (STDDPC) is a general-purpose water pressure source and volume change gauge. Aimed at medium pressure commercial testing ( 4MPa), undergraduate teaching and research, the standard controller is the mid level controller from GDS. Available in 200cc only, but with pressure ranges from 1MPa to 4MPa (the standard range is 3MPa). Advanced Pressure/Volume Controller (ADVDPC) Overview: The GDS Advanced Pressure/Volume Controller (ADVDPC) has the highest precision for the regulation and measurement of fluid pressure and volume change. The advanced version offers the highest level of accuracy, resolution and control and is the defacto standard for research devices. The ADVDPC may be used with water, oil or air. Available in pressure ranges from 100kPa to 4000kPa and a volumetric capacity of 200cc, or up to 2000kPa with a volumetric capacity of 1000cc. High Pressure/Volume Controllers 8MPa to 150MPa (HPDPC) Overview: Based on the advanced controllers, the GDS High Pressure/Volume Controllers are a general purpose water pressure source and volume change gauge for the precise regulation and measurement of fluid pressure and volume change at much greater pressures. The advanced version offers the highest level of accuracy, resolution and control and is the defacto standard for research devices. The high pressure range of controllers are available in pressure ranges from 8MPa to 150MPa and a volumetric capacity of 200cc. High pressure controllers can be used with water or oil. 37

41 Key Features of GDS Controllers: Does not require a supply of compressed air to function: Controlled with or without a PC: Accurate measurement: GDS controllers automatically protect themselves from pressure and volume over-ranges: Controllers are an ideal back-pressure source: Controllers can be used with different media: GDS pressure controllers do not rely on lab air supplies. The GDS pressure controllers can be controlled directly from a computer using the USB 2.0 interface and GDSLAB or with the Smart Keypad (optional for ELDPC) the controller can be configured as a completely stand-alone device. Pressure is measured by an integral pressure transducer. Volume change is measured by counting the steps of the incremental motor. All GDS pressure controllers are self-protecting and can also be programmed to protect any attached equipment. Allowing the measurement of change in volume of the test specimen with no requirement for a separate volume change device. The ELDPC, STDDPC and ADVDPC run using water or oil and GDS have an ADVDPC (1000cc) specifically for use with Air. All GDS Digital Pressure Controllers are fully RoHS and CE Compliant. All GDS Pressure Controllers are designed, machined and assembled to the highest quality standards and materials in the UK. Optional: Digital Remote Feedback Module (Digi RFM) - for STDDPC and ADVDPC Controllers Normally, the feedback to the main control circuit board comes from the internal pressure transducer. However, this input could come from a different source, such as a remote transducer. GDS has developed this into an elegantly engineered enhancement, which is the Remote Feedback Module (RFM). The RFM enables the output of an external transducer to be measured and displayed by the controller. It also enables the controller to be controlled from the feedback of the external transducer. The internal pressure transducer and the external transducer readings are displayed and transmitted over the computer interface. Benefits of the Digi RFM include:- Precision when regulating from the external transducer, as it can be positioned closer to the experiment. Can increase the accuracy of the application by choosing a transducer closer to the range of the experiment. Can be used with wet-wet differential pressure transducer to increase the accuracy and measurement, e.g. for precise control between back pressure and cell pressure for accurate measurement and control of very small effective stresses. Legacy Board Many customers have been using GDS advanced pressure controllers for many years with their own software. The software interface has remained unchanged since A legacy interface board is available to allow new USB based controllers to operate on RS232 with the same PC interfaces as advanced controllers sold between 1980 and 2013, to avoid changing existing software. 38

42 The table below is a controller comparison chart for the Enterprise (ELDPC), Standard (STDDPC), and Advanced (ADVDPC/HPDPC) level pressure / volume controllers. Features ELDPC STDDPC v2 ADVDPC / HPDPC Accuracy (pressure and volume): 0.25% FRO 0.15% FRO Better than 0.1% FRO Pressure range (MPa): 1 1, 2, 3, 4 Pressure Display Readable to: Resolution of logging via software: 1kPa 1kPa (1000 device) 0.1kPa on 1MPa range, 1kPa on 2MPa and above ranges. 0.1kPa on 1MPa version, 1kPa on 2MPa and above 0.1, 0.2, 0.4, 0.8, 1, 2, 4, 8, 16, 20, 32, 64, 100, 128 and kPa up to 64MPa range, 0.8kPa for 64MPa and above ranges 0.1kPa up to 4MPa range, 1kPa up to 150MPa Pressure calibration: 2 point calibration (FRO) 2 point calibration (FRO) Multipoint calibration, certified with table. Resolution (volume): 1mm 3 (0.001 cc) 1mm 3 (0.001 cc) 0.5mm 3 Volumetric range: 200cc 200cc Ball screw: Rolled lead error 100 µm in 330mm Rolled lead error 100 µm in 330mm Linear guide: Rolled error unspecified Rolled error unspecified 200cc or 1000cc (2 MPa only) Ground lead error <25 μm in 330mm Ground running parallelism error 20μm in 500mm Gearbox: Class C Class C Class A, precision Volumetric accuracy: 0.4% measured Better than 0.25%, calculated Better than 0.1% Interface options: USB USB RS232 or IEEE Material and finish of pressure cylinder: Brass, painted Brass, painted Size (mm): 500 x 100 x x 100 x 140 Weight (kg): 5.5 (empty) 10.2 (empty) Electrical supply (universal): V AC, 50-60Hz, 0.7A. Max Consumption: 20W. Typical Consumption: <12W V~1.6A MAX, 50-60Hz Brass, bright nickel plated and polished stainless steel 860 x 230 x 220 (2MPa) 860 x 230 x 230 (1000cc) 860 x 230 x 260 (32MPa) 860 x 230 x 330 (64MPa) 85 VAC to 260 VAC; Hz 39

43 Pneumatic Pressure Controller (GDSPPC) Overview: The Pneumatic Pressure Controller (GDSPPC) is an economical source of computer controlled regulated air pressure. The controller regulates an external pressure source of compressed air from a compressor or compressed air cylinder to provide a controlled output pressure. The control of the valves is via the serial bus (RS232) from the PC and software. The pneumatic controller is a cost effective route for upgrading manual regulator systems to automated systems. The GDSPPC is available with one or two channels. Built in pressure transducer measures the air pressure: Pressure measurement from the system is sent via a separate datalogger to the PC: Automated control: The pneumatic controller is available as either a 1 or 2 channel controller: Calibration certificate: Media that can be used with pneumatic controllers: The result is a compact, neat, self-contained unit. 10V output signal can be connected to most existing data loggers. The automated control of the pneumatic controller allows the user to run and log a series of tests without having to be continually monitoring or manually adjusting the pressure. Two channel units are a very efficient way of replacing existing cell and back pressure manual regulators. The pneumatic controller is calibrated at GDS, and is supplied with a certificate. No user adjustment to the hardware is necessary. Nitrogen. Air. Argon. Helium. Most inert gases. Computer Interface: RS232 Dimensions (mm): 600 x 230 x 100 Pressure Range (MPa): 1, 2 or 3 Weight Approx (kg):

44 Infinite Volume Controller (GDSIVC) Overview: The GDS Infinite Volume Controller (GDSIVC) is designed to remove the constraint of volume capacity such that a test can continuously flow fluid under pressure or volume control. By connecting two GDS pressure/volume controllers in parallel, the GDSIVC system automatically switches between them when they run out of volume, thus providing a seamless supply of pressure with unlimited volume capacity. The GDSIVC can be used with any two pressure controllers from the GDS range, i.e. Advanced, Standard or Enterprise. The GDSIVC system automatically switches between controllers when they Infinite Volume! run out of volume: Controller flexibility: Can be used with all types of GDS controller (ELDPC, STDDPC or ADVDPC). The second controller will match the output pressure of the primary controller, Secondary controller follows primary: this feature allows for minimum time switching. Empty controllers are automatically refilled from a reservoir (not supplied). Continuous volume flow: Allows long term (laminar flow) permeability tests to be carried out. Primary controller in control (Master) Primary (Master) and Secondary (Slave) Controllers: The GDSIVC system works by connecting two GDS pressure controllers in parallel, automatically switching between them when they run out of volume. One controller is designated as the primary controller and is used as the main pressure/volume source. While acting as the pressure and volume source this controller is called the master controller. Careful switching sequencing in the software ensures that valves are energized for the minimum period necessary, and remain unenergised for most of the test because soleniod valves generate heat when energised that could affect the downstream experiment. The configuration also ensures any pressure calibration differences between the primary and the secondary controller are compensated for. Secondary controller tracking primary controller pressure (slave) Primary controller runs out of volume With the secondary controller already pre-pressurised, both the primary and secondary controller are put on hold volume and both opened to the experiment to check any calibration offset between the two controllers at pressure. The primary is considered the correct controller, and so any offset found will be applied naturally to the target pressure sent to the secondary controller. This ensures smooth volume hand over. Primary controller closed to experiment and opened to reservoir to refill Secondary controller takes over as the master temporarily while the primary controller is refilling. When primary controller has refilled, it will resume control of the experiment by once again becoming the master controller. Secondary controller will refill as necessary, return to its mid point and pre-pressurise. Dimensions (mm): Panel: 440 x 260 x 100, Control Box: 440 x 260 x 50 Pressure Range (MPa): 3, options available for higher pressures 41

45 Section 8: Introduction to GDS Transducers GDS supply a large range of transducers of various types and ranges to meet all accurate measuring requirements. A sample of the types of transducers that can be supplied is listed below. Bender Elements, (see page 43). Hall Effect local Strain - Displacement, (see page 44). LVDT Local Strain - Displacement, (see page 45). The following transducers are also available but not displayed in this catalogue Linear Potentiometric Displacement. Digital Displacement. Internal Submersible Load cells. Ultra Low range Wet-Wet pressure Transducers. External S-beam Load Cells. Laser line scanners for non-contacting specimen measurement. All transducers can be linked to GDSLAB software so data can be easily managed and recorded. Transducers are a popular upgrade to many existing GDS and other manufacturer systems. This section provides an overview of some of GDS popular transducers. For more information on any of these transducers please visit GDS website or direct on info@gdsinstruments.com. 42

46 Bender Element System (GDSBES) Overview: The GDS Bender Element System (GDSBES) enables measurement of the maximum shear modulus of a soil at small strains. The GDS system is unique in that it is a turn-key system that has been designed to make bender element testing reliable and easy to perform. The GDSBES system can be added as an option to most GDS systems, as well as systems from other manufacturers. To date GDS have installed bender elements in triaxial, consolidation, simple shear, resonant column, core holders and many other systems manufactured by GDS and equipment from other manufacturers. USB interface: Titanium element inserts: Utilising existing products: The GDS Bender elements are bonded into a standard insert: 2 Mega Samples/Second Data Acquisition: Elements are manufactured to allow S and P wave testing to be performed: Vertical and horizontal elements are available as standard: Allows the system to be swapped to any PC in the lab with a USB interface. Reduces the weight of the top-cap. Pedestals and top-caps can be made for other manufacturers cells as well as GDS cells. This method of manufacture has 2 advantages, it makes the bender element insert a modular device that can then be easily fitted into a suitably modified pedestal/top-cap. Should an element fail, it is simple and quick to replace the complete insert. High speed data acquisition is essential as the sample interval provides the resolution for determining wave speeds. Determining S & P waves velocities parameters allows more specimens to be determined. Specimen Anisotrophy can be studied. GDS Bender Element Analysis Tool: The subjectivity and lack of satisfactory standards for interpreting shear wave travel times across the industry from bender element test data, has led GDS to develop a bender elements analysis tool. The tool allows the rapid, automated analysis of bender element tests to objectively estimate the shear wave travel time. The analysis tool is available to download from GDS website. The aim is to share the software with the geotechnical community and help the progression towards accepted standards for these tests. Gmax, maximum shear modulus and S & P wave velocities in vertical and horizontal directions. Pedestals for unsaturated testing and bender elements (i.e. with bonded high air entry porous disc) & Horizontal bender elements. Computer Interface: Data Acquisition Speed: Element type: USB 2MH z Single element S and P wave. 43

47 Hall Effect Local Strain Transducers (GDSHE) Overview: The GDS Hall Effect Local Strain Transducers (GDSHE) provide on sample small strain measurements of axial and radial strains for triaxial testing. GDSHE are very light and easy to handle, therefore can be mounted to the sample for small strain measurement with minimal disturbance to the sample. Small strain stiffness values are becoming more commonly required by consultants due to the parameters required for FE models. It has been recognised for many years that small strain measurement is more representative to the operational strain, and that the small strain stiffness curve is required for any advanced modelling of the soil. Axial and radial deformation measured directly on the triaxial test specimen: Light compact semiconductor chip: Accurate determination of soil stiffness: Small strain measurement: Measurement is taken in the middle third of the sample which is less restrained than the end zones: Removes bedding errors or end effects. The Hall Effect semiconductor chip is very light, has compact assembly and is compensated against changes in ambient temperature and changes in DC voltage supply. True soil strains can be masked by deflections which originate in the compliances of the loading system and load measuring system. Such equipment compliance errors add to a variety of sample bedding effects to give a poor definition of the stress strain behaviour of the material under test, particularly over the small strain range. Recent work has demonstrated that soils can be equally as brittle as rocks and that an understanding of their behaviour at levels of shear strain below 0.05% is very important. Therefore, it is highly desirable that radial and axial deformations are measured locally in this region if realistic deformation moduli are to be found. Displacement Range: Pressure Range: Resolution of Measurement: Sample Sizes (mm): Accuracy: Weight Approx (kg): +/-3.0mm Up to 1700kPa <0.1μm 38, 50, 70, 76, 100,150, custom +/-0.2% FRO over 4mm range, +/-0.3% FRO over 5mm range and +/- 0.4% FRO over 6mm range Radial caliper weight: 38mm caliper = 24g, 70mm caliper = 46g. Axial apparatus weight: (1 off) = 16g. Transducer weight: (1 off encapsulated HE Chip) = 5g 44

48 LVDT Local Strain Transducers (LVDT) Overview: The GDS LVDT Local Strain Transducers (LVDT) provide on-sample small strain measurements of axial and radial strain for triaxial testing. Accurate determination of soil stiffness is difficult to achieve in routine laboratory testing. Conventionally, stiffness of a triaxial test specimen is based on external measurements of displacement which, include a number of extraneous movements. True soil strains can be masked by deflections which originate in the compliances of the loading system and load measuring system. Such equipment compliance errors add to a variety of sample bedding effects to give a poor definition of the stress-strain behaviour of the material under test, particularly over the small strain range. Axial and radial deformation measured directly on the triaxial test specimen: Inherently robust LVDT s as they have no physical contact across the sensing element: Submersible low pressure version (pictured above): Vented high pressure version: Temperature limits -20 C to 60 C: Measurement is taken in the middle third of the sample which is less restrained than the end zones: Through bore configurations: Radial sprung aluminium-bronze hinge for no backlash and low friction: Removes bedding errors or end effects. Zero wear ensuring longer life and lower friction effects. Water version can be used up to 3500kPa. High pressure version for use in non-conducting oil up to 200MPa (Pressure relieved). Suitable to use with GDS Environmental Triaxial Testing equipment, see page 8 for more information). Higher temperature versions available. Therefore, it is highly desirable that radial and axial deformations are measured locally in this region if realistic deformation moduli are to be found. Allows test to continue after the LVDT has passed its measurement range. The transducers measure sample effects not those of the measuring calipers. Displacement Range: Data Acquisition: Resolution of Volume Measurement: Sample Sizes (mm): Volume Accuracy: Weight Approx (kg): +/- 2.5mm or +/-5.0mm 16 Bit +/- 2.5mm = <0.1μm, +/- 5.0mm = <0.2μm 50, 70, 76, 100, 150, up to 300 as standard 0.1% FRO Radial caliper weight: (based on a nominal 70mm caliper) = 74g : Axial apparatus weight: (1 off) = 26g : Transducer weight: (1 off LVDT) = 20g 45

49 Section 9: Introduction to GDS Field Geophysics Systems GDS produce two types of surface wave system, the Continuous Surface Wave System (CSWS) see page 48 and the Spectral Analysis of Surface Waves (SASW) see page 47. Each system works on the same fundamental principal, that Rayleigh waves (surface waves) can be generated at a source and the measured on the ground using geophones. The main difference between the systems is that the CSWS system uses a ground vibrator as the source of the energy, and the SASW uses an impact source (usually a sledge hammer). CSWS: Vibrator Source. SASW: Impact Source. The different sources of the two systems generally leads to differences in the depth of penetration that can be achieved. For example, a 6-7Kg hammer should generate frequencies down to 10-15Hz. This should achieve depths up to 8 to 10m penetration in a stiff clay or less for less stiff material (generally SASW depths are quoted to be useful for depths up to 5 to 7m penetration). Because the penetration depth of the surface wave technique depends on the frequency of the waves under test, this is where the ground vibrator comes into its own. It can be specifically set to vibrate at frequencies as low as 5Hz. With significantly lower frequencies being generated, the CSWS system typically measures to penetration depths between 2 and 3 times that of the SASW system. CSWS on test, see page

50 Spectral Analysis of Surface Waves (SASW) Battery or Generator Control Unit USB Connector Overview: SASW provides a portable, quick and nondestructive insitu ground stiffness profiling tool. Typically a test can be carried out in under 15 minutes with initial results available whilst still on site. Sledge Hammer Geophones Can be used in a multitude of ground conditions: Fast Fourier Transform (FFT): Portable design: Set up in 5 minutes, tests performed in 10: Non-invasive testing: Typically used in site investigations for foundation engineering design and settlement prediction. The SASW is also suited for the rapid sub-grade evaluation for roads, tracks and runways. The system performs an on-line Fast Fourier Transform (FFT) on the acquired data with automatic stacking and trigger arming allowing for as many as 15 separate records per minute to be acquired for a single test. The stacked data can be manually or automatically picked to create an on-line stiffness v depth plot. The SASW runs continuously for up to 8 hours with user supplied 12V battery and is supplied with a padded transport case with built in laptop weather hood. Providing stiffness v depth results immediately in field. No samples are required to be obtained from the test site. Non invasive shear wave velocity and shear modulus profiling. Can be upgraded to a CSWS system (Continuous Surface Wave System) with the addition of an amplifier, a ground vibrator and the CSWS software. Computer Interface: USB Connection Data Acquisition: 16 Bit Dimensions (mm): 400 x 380 x 150 Power: 12-24V DC Weight Approx (kg): Source + Battery 47

51 Continuous Surface Wave System (CSWS) Amplifier Power Generator Control Unit USB Connector Overview: CSWS provides the user with the ability to generate a wider and more controlled frequency range for carrying out surface wave testing. This will usually achieve greater penetration depths and resolution than the SASW. Vibrator Geophones Provides depth profile up to 30m: Rapid results through non-invasive test methods: Insitu nondestructive testing: Quick test: Enables the measurement of Gmax: Automated test software: Lightweight & portable design: Provides on-line shear modulus with depth profile to depths of up to 30m depending on the type of soil or rock Enables rapid assessment of ground variability across a site in terms of stiffness via a non-invasive test. Provides stiffness parameters for ground that is difficult or impossible to sample in a representative manner, e.g. granular soils and highly fractured rock. Verifies soil improvement, from dynamic compaction, vibrofloatation and classic consolidation. Enables the measurement of Gmax which can provide a valuable benchmark for stiffness investigations in soils and sample quality. The user enters the required test frequencies and the software runs the complete test automatically. Output can be imported directly into Microsoft Excel. Data output includes time domain, frequency domain (magnitude and phase), coherence and stiffness v depth using the Lambda/3 method. Rugged, robust, smaller and lighter control unit (version III control unit weighs only 5.5kg) and is supplied with a padded transport case with built in laptop weather hood. Non invasive shear wave velocity and shear modulus testing. Standard system for 2-6 geophones, upgradeable to a maximum of 12. Can be used as a Spectral Analysis of Surface Waves (SASW) test system using an impact source. Computer Interface: USB Connection Data Aaquisition: 16 Bit Dimensions (mm): Unit: 400 x 380 x 150 Ground Vibrator: 450 x 350 x 180 Power: 12-24V DC Weight Approx (kg): Ground Vibrator: 70, Control Unit:

52 Section 10: Introduction to GDS Bespoke Testing Systems GDS have been working in the field of geotechnical engineering for over 30 years. During this time GDS have worked with many research and commercial labs on bespoke projects, some with very high levels of input from customers, some based on outline specifications only. GDS have four mechanical design engineers based at our offices in Hook, who design new and adapt existing products to meet the needs of our customers. GDS actively encourage those customers looking for a bespoke product to be involved in the design process and often have customers visiting the design office to review drawings. The production and quality assurance of each product is done onsite at GDS offices in Hook. This helps produce a consistently high level of apparatus and allows the customers the opportunity to see the product working before it is shipped. Examples of bespoke testing equipment: A few examples of bespoke equipment GDS has designed for customers. Adapted a typical Electro-mechanical Dynamic Triaxial Testing System (DYNTTS) to hold a 300mm sample. Typical sample sizes were previously up to 100mm. GDS CO2 absorption cell. A University approached GDS about a particular test they wanted to run. Their ideas and designs were reviewed, suggestions were made and a detailed design was produced. Once the University were happy GDS manufactured and installed the cell. See website for product details. A smaller project recently completes was a soft soil membrane placement jig, see the Accessories section of the website for more information. ENSG & GDS developed a device to monitor the radial profile of the specimen whilst under test using highly accurate laser. See GDS website for case study on this project. Together Politecnico di Torino and GDS Instruments, teamed up to design and develop a new direct shear box to help investigate the effects of the Beauregard Dam in the Aosta Valley in Italy....The shear testing apparatus designed by GDS Instruments and PoliTo has many innovative features for a direct shear device. Its advanced characteristics, in particular its capability to apply high back pressures to the sample and apply 100kN axially and in the shear direction, allow for testing to be conducted in a variety of ways. In particular, the shear behaviour of an intact specimen can be investigated under a change of pore pressure as observed in field conditions. It is shown that the new equipment is working properly and that the accuracy of the measurement system implemented allows one to obtain relevant results during both the shearing and creep stages, says a PoliTo professor. See GDS website for a case study on this project. GDS Design Team GDS have a team of software, electrical, firmware and application engineers who design all of our products at the office in Hook. If you are starting a new project, would like advice on how to change an existing product or would like a product similar to one of GDS products but with a few tweeks, contact them direct. All GDS manufacturing is carried out in the UK to strict quality and material standards. 49