CATS-TRX-SOIL Triaxial Software Module

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1 GCTS is committed to designing accurate testing systems by integrating innovative software engineering with advanced hardware. GCTS systems perform at the highest levels of reliability, providing efficient systems that satisfy customer needs and expectations. CATS-TRX-SOIL Triaxial Software Module Static and Dynamic Loading with Stress/Strain path control Adaptive control for precise dynamic waveform application through specimen failure or liquefaction Automatic ram-specimen touch-down with programmed initial contact stress Display and/or control sensor and calculated parameters in any desired unit Procedures for Saturation, Isotropic and Anisotropic Consolidation, Stress/Strain path including Ko Strain Path, Dynamic Loading, Liquefaction, Resilient Modulus, etc. Automatic Mohr-Coulomb model fitting Easy to setup and conduct Triaxial tests DESCRIPTION The GCTS CATS Triaxial module is part of our 32bit Windows software, CATS (Computer Aided Testing System), the most advanced Geotechnical software available today. Conducting Triaxial tests have been greatly simplified in this module by the incorporation of direct user programming of test calculated parameters in the units of interest (stress, strain, etc.) based on the specimen dimensions. These parameters are calculated in real time and are available for display, graph and/or control. Using calculated test parameters directly eliminates complex and lengthy pre-calculations to design test programs. This allows the user to concentrate on the material behavior rather than on the electronics and equipment operation. Data can be readily exported into other Windows programs such as Excel. The software offers a vast unit selection for displaying each parameter even allowing mixing different unit systems. Unit management is completely automatic.

2 2 The Triaxial test module has the ability to automatically control all of the three test axes: Axial Actuator, Cell pressure, Back Pressure. The advanced controls for the loading frame, cell pressure, pore pressure, and chamber temperature offered by CATS testing software provide for a very precise and synchronized execution of the prescribed test commands. In addition to the parameters read directly from the system sensors, the Triaxial test module contains 20 test inputs as listed in table 1. These parameters are calculated in real time and are available for monitoring and/or control. There are user selectable methods to calculate the strains: εa, εr, and εv, which can either be from a direct input, or calculated as a function of the other strains. εa can be measured from the frame axial deformation, or it can be measured using the gauge axial deformation input. εr can be measured from a Radial, Diametric, or Circumferential device or it can be back-calculated as a function of the other strains. εv can be a direct internal (pore) or external (cell volume) measurement, or it can be a function of εa and εr. All the above parameters are automatically calculated from specimen dimensions and test system setup. Just by answering a few questions, this program provides the right calculations for all the field parameters. Table 1. Standard Calculated Inputs 1.- εa - Axial Strain 2.- εr - Radial Strain 3.- εv - Volumetric Strain 4.- εoct - Octahedral Strain 5.- γ- Shear Strain 6.- Ac - Corrected Area 7.- σd - Deviator Stress 8.- σa - Axial Stress 9.- σa' - Axial Effective Stress 10.- σc' - Cell Effective Pressure 11.- p Cambridge Mohr Parameter Stress 12.- p' Cambridge Mohr Parameter Effective Stress 13.- p MIT Mohr Parameter Stress 14.- p' MIT Mohr Parameter Effective Stress 15.- q Mohr Parameter Stress 16.- τoct - Octahedral Shear Stress 17.- Uex Excess Pore Pressure 18.- µ Poisson s Ratio 19.- Et Tangent Young s Modulus 20.- Es Secant Young s Modulus This software module includes a procedure to automatically lower the loading piston until it contacts the specimen by first moving under deformation control until an axial load is detected and then changing to stress control to reach a prescribed seating stress. The software corrects the σd - Deviator Stress for the loading piston uplift forces generated by the confining pressure. Controlling the σd directly prevents the loading piston from loosing contact with the specimen when changing the confining pressure (manually or programmed). The stresses are calculated with respect to the corrected area, not the original area, so the true stresses are calculated and/or controlled in real time. In addition the CATS environment offers complete and automatic management of most common devices used for soil triaxial tests such as volume change devices and pressure/volume controllers. These devices can be programmed to reverse flow direction when approaching the device end via a 4-way valve keeping track of these changes and correcting the volume change data. Pressure volume controllers can be made to automatically recharge when approaching pre-establish limits without introducing measurement errors to total flow volume. The CATS-TRX-SOILS software program provides a default data acquisition procedure but it can be overridden by providing the user selectable acquisition rates. Data can be acquired by time, level crossing, or both. The Triaxial Module is actually made up of 6 independent Stages: Saturation, Consolidation, Static Loading, Dynamic Loading, Resilient Modulus, and Universal. With the ability to define end of

3 3 stage conditions and automatically zero deformations to update specimen dimensions, the user is able to perform multi-stage testing using one specimen and one test program. A test program can be composed of up to 100 stages in any order or repeated as many times as required CATS-TRX-SOILS allows the user to configure the computer screen with virtually an infinite number of displays and graphs. The user can select from several different tools to display on real time any of the test sensor outputs or calculated parameters in any desired unit. In addition, user configurable charts and plots can be designed and displayed on real time to graph any test parameter while performing any tests. Screen designs can be saved to be re-used at a later time. SATURATION Consolidation Stress selection, so the consolidation stress can be applied in a ramp format, instead of being instantaneous. The CATS-TRX-SOILS program calculates t50 from consolidation data and recommends the proper strain rate for the static loading stage. Either Casagrande or Taylor's method may be selected to obtain t50. Both procedures may be used with the axial deformation data or the volumetric deformation data. STATIC LOADING The Static Loading stage is an easy to setup static loading stage where control of all of the three test axes can be established, with either the constant or ramp functions. Any test parameter, measured or calculated, can be selected for control allowing for the performance of sophisticated tests. Smooth or bump less control transfers from one parameter to another in the middle of a test are also possible eliminating any sample disturbance during this transfer In this way, a test can be programmed to start with stress control, then switch to axial or radial strain control, to obtain better loading rates as well as to slow down during specimen failure. This control options are available for all three axes, axial actuator, cell pressure, and back pressure. In this fashion, the loading ram can be easily programmed to apply axial strains at a constant rate while the confining pressure is programmed to maintain zero radial strain (Ko test). The Saturation stage features completely automatic saturation (provided that the Back Pressure is also automatically controlled) with B value measurement. If the required B value is not reached in the first Saturation Stage, the software will advance to the next Saturation stage and saturate again. Once the required B value is reached, the software will skip the next Saturation stage(s). CONSOLIDATION This stage also features the ability to manually change the stress/strain rates during testing, for all three axes. The user can leave the Data Acquisition selection to be automatic, whereas the software selects the parameters, or the user can manually prescribe the Data Acquisition parameters. The Consolidation stage features Isotropic and Anisotropic consolidation. The stage also features a Time to Apply The Static Loading stage can be stopped by numerous methods which can be programmed, including by time, by reaching an input limit, or by peak reversal, when the peak drops by a certain amount or the tangent module becomes zero. These options can be selected in any combination. By programming these conditions, a multi-stage test can be automatically conducted.

4 4 CATS software brochure for more information about the Universal test module DYNAMIC LOADING The Dynamic Loading stage is an easy to setup cyclic stage where control of all three axes can be established, with the traditional Sine, Triangular, and Square dynamic waveforms (Constant waveform is available for the Cell Pressure and Back Pressure axes). Controlling the axial stress (as oppose to the axial load) and Peak and Valley compensation ensures the precision of the programmed waveform amplitude even after the specimen undergoes significant deformations or stiffness degradation. This is an important feature in order to maintain cyclic amplitudes throughout the entire test. More advanced waveforms can be applied using the Universal software module. RESILIENT MODULUS The Resilient Modulus stage features built in AASTHO test sequences, and the capability for user defined sequences. Available waveforms include Haversine, Sine, Square and UNIVERSAL The Universal module can be used when the standard modules do not offer the required test program. This Universal module provides the user complete control of all the available hardware (load frame, cell pressure, cell temperature, etc.). This module offers several pre-programmed waveforms such as ramp, sine, triangular, square, random, etc. where the frequencies and amplitudes can be specified as constants or variable from cycle to cycle (amplitude or frequency sweeps). In addition, a play-back feature allows the user to program any user generated profile for any of the control axes. All of the triaxial test calculated parameters are also available for logging and/or control within the Universal module. See the Triangular, along with a user defined waveform selection. Resilient Modulus test specifications require applying cyclic loads with very different amplitudes for a single test. The CATS-TRX- SOIL provides a Peak & Valley Compensation to ensure proper and automatic matching of the load parameters throughout the complete test and without user intervention. This feature is also available during DYNAMIC and UNIVERSAL stages.

5 5 Real-time calculation of the deformation sensors relative difference, Rv, and the Resilient Modulus, Mr, allows the user to ensure the test sensors are working properly. The complete Resilient Modulus test is performed automatically by this module and test results according to AASHTO 307 and NCHRP 1-28 specifications are easily produced from within this software program. In addition, all test data can be exported to a spreadsheet program such as Excel for custom made graphs and reports. REPORT GENERATION The CATS TRX-ROCK program provides the user an easy and fast report generation where individual test results can be plotted in many different formats. It also allows for the combination of test results to calculate the friction and cohesion intercept (for peak and residual values). Graphs and plots can be directly exported to any Windows program such as Word for an easy and fast report preparation. Standard test sequences according to AASHTO, SHRP and NCHRP specifications are pre-programmed into this module. In addition, the user can specify different combinations of cell pressure and cyclic deviator stresses and save them for later use. With this option, the program satisfies today specifications as well as any future modification. Multiple graphs and meters can be displayed within the CATS program environment allowing the user to monitor in real-time all the sensors including all the deformation sensors. During export, curve fitting is done to fit the results to models that predict Mr as a function of σ m, σ d, CP (Cell Pressure), and τoct (octahedral stress). Mr = K1 (σm) K 2 Mr = K1 (σd) K 2 Mr = K1 (σd) K 2 CP K 3 Mr = K1 Pa[(Θ-3K6)/Pa] K 2 [τoct/pa + K7] K 3 Resilient Modulus - Mr vs. Deviator Stress - Sd In addition, all of the saved test data and calculated parameters including Mohr circles can be directly exported into Excel for further analysis and report generation. The friction angle and cohesion intercept are automatically calculated using all available test specimens for a particular sample. The software calculates these parameters from peak and residual conditions as well as for total and effective stresses. The program also allows the user to select which specimens are used in the calculation. Even though, the Mohr circles and other result graphs can be printed or directly imported to programs such as Word, CATS TRX-SOIL allows you to export all the graph data including the Mohr circles (as data vectors) into Excel for a more customized and professional report presentation. Resilient Modulus - Mr (MPa) 250 Confininf pressure (kpa) Deviator Stress - Sd (kpa)