Application of Mathematical Modeling Using the Results of Geodetic and Geotechnical Measurements on Reinforced Earth Construction by Armovia System

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1 29 Application of Mathematical Modeling Using the Results of Geodetic and Geotechnical Measurements on Reinforced Earth Construction by Armovia System Cihlá ová, D. and Lahuta, H. VSB - Technical University of Ostrava, Faculty of Civil Engineering, L. Podéšt 1875, Ostrava-Poruba, Czech Republic, Web site: Tel.: , denisa.cihlarova@vsb.cz, hynek.lahuta@vsb.cz Abstract The construction of the highway D47 was needed to ensure connection to the existing road network in Ostrava. These reroutings due to the character of the area consist mainly soil embankment. In cases when it was not possible to implement the classical earth embankment, was used for retaining walls of reinforced soil (system Armovia ). This paper approaches the issue of geotechnical and geodetic monitoring of these structures. There were observed leveling points to the structure, pore pressures in the subsoil of embankment (piezometric measurements), settlement hydrostatic leveling. Interest object is tracked since Analysis of the behavior of the structure was supported by mathematical modeling with the Plaxis software. This was also obtained feedback on the suitability of the chosen measurement method and the efficient distribution of observed points on the structure. Key words: retaining wall, geotechnical and geodetic monitoring, mathematical modeling, measurement method. 1 SUBJECT OF INTERES The structures are located on the D 47 highway between km and situated in the cadastre of Ostrava-Svinov. Mining effects in the territory can be believed to have disappeared. The certified Armovia structures were used there. The face components are large split concrete panels laid on a strip footing. The carrying component is a one-axis geo-mesh, Tensar 120 RE. The mesh starter is anchored into the rear side of the face component. The mesh starter is backfilled with soil and set to a length specified in the project Fig. 1. Crusher-run materials (0-63c) from the Bohu ovice quarry was used for backfilling and the remaining part of the highway embankment was filled by the tailing. The embankment is m high. TS 1 Data Processing INGEO th International Conference on Engineering Surveying Brijuni, Croatia, September 22-24, 2011

2 30 INGEO 2011 Figure 1. Armovia system 2 THE MONITORING STATION 2.1 GEODETIC MEASUREMENT In order to monitor the behaviour of the wall structure, the monitoring station was extended from SO 8246 to SO 7280 Fig. 2 and 3. The monitoring station consists of 19 profiles (in three height levels) that monitor spatial deformations and 11 bench-marks to monitor subsidence. The Baltic vertical system, after adjustment, was used for the height measurements. The topography measures was attached to JTSK- LVS flyover Rudná. Following parameters are monitored in the structures: subsidence, transversal and longitudinal shifts of points referred to the axis of the structure. Below listed surveying methods have been used. 1 st order leveling (PN) with a closed traverse was used for the vertical surveying. Reflecting shields in individual profiles were measured in the method of transition points due to landscape configuration. LEVELLIN G SCREW G2 2.2 GEOTECHNICAL MONITORING Figure 2. Profile points localization Measurement of soil embankment settlement was carried out by hydrostatic apparatus GEOKON. Pprofile length is about 60 m. The measuring instrument works by measuring the

3 Cihlá ová, D. et al.: Application of Mathematical Modeling Using 31 difference of hydrostatic pressure between the probe and a fixed point outside the reference profile. Before the construction of the embankment of the reference is stored in his basement into a horizontal trench guide tube, which is at the very protracted probe measurements and readings take place in a given step. The portable measuring device is then deducted the difference in height between the probe and the reference point. The portable measuring device is then deducted the difference in height between the probe and the reference point. Height reference points are measured by precise leveling. Measurements took place in the period to The location is shown in Fig.3. 3 STABILITY MODEL Figure 3. The Monitoring station For mathematical simulation program was used system of PLAXIS, see (Hrubešova, 2004). The simulation was solved by the basic-mohr Coulomb constitutive model. Model s chronological stages are: Tension-deformation analysis of the background at the start of on-site works. Tension-deformation analysis of the background and in the body of the wall at the end of on-site works. Tension-deformation analysis of the background and in the body of the wall during monitoring. Settlement prediction. For the analysis of these models were created: actual situation in the two profiles according to the method of construction, no element interface (model 1-147,644 km, model 3-147,684 km) real status in both the stationing according to the method of construction, with the interface element. Element interface in this case represents the interaction between the geogrid and soil. It is a strength reduction factor for geogrid soil interface, called Rinter. According to (Hossain et al. 2004), the values for HDPE and soil interaction is about 0.67 (Model 2-147,644 km, model 4-147,684 km). The mathematical models were carried out on the boundary of both objects and is represented by the most significant measured settlement (point G6, G9). In the profile 147, 684 km (G6) is the height 9,4 m and the length of geo-grids is 10 m (from back of wall). And in the profile 147, 644 km (G9) is the height 8,8 m and the length of geo-grids is 7,6 m (from

4 32 INGEO 2011 back of wall). The width of geo-grid stripes is 1,30 m. The spacing between the stripes decreases downwards from 0,80 m to 0,40 m. The input data are defined by geometrical parameters, backfill material properties as well as geotechnical parameters of the substratum Table 1. The total length of models are 100m. The models includes the substratum bed of 28,0m (after levelling). The phreatic surface was reached at 2,60m and stabilised at 1,45m. Construction materials parameters are shown in Table 2. Table 1. Properties of soil Material unsat sat k E def c ef [kn/m 3 ] [kn/m 3 ] [m/day] [-] [kn/m 2 ] [kn/m 2 ] [ ] slag ,64 0, gravel materials ,64 0, F6 Cl a. clay 20,5 23,5 8, , G5 GC gravel ,4 0, F8 CH m clay 20,5 23,5 5,184,10-4 0, Table 2. Properties of geomaterial Material E.A E def w [k N/m] [kn/m 3 ] [kn/m 2 ] [kn/m 2 ] Basetex 800/ Tensar 120RE face component 5, ,96 pavement ,6 4 RESULTS AND SOLUTIONS 4.1 COMPARISON OF EXPERIMENTAL AND GEODESIC ON-SITE DATA The points shown in Fig 4 can be used to compare vertical and horizontal displacements, which points G6, W 6103, S 6203 and S 6303 are 147,684 km of profile points and G9, W 101, W 102 and W 303 to 147,644 km profile. Figure 4. Location comparison points

5 Cihlá ová, D. et al.: Application of Mathematical Modeling Using Vertical movement The Chart 1 shows comparison of in situ measurements with the values of models 3, 4. All models (1, 2, 3, 4) correspond well with measured values. The maximum deviation is + 5 cm. In both cases, the models created with the interface element (model 2 and 4) have values closer to measured values and leads to earlier stabilization process decreases. Chart 1. The measured and calculated values of vertical movements on the profil 147,684 km Horizontal movement Since it was created a 2D model, can be compared only to the horizontal lateral displacements, ie. displacements perpendicular to the axis of communication. Measured transverse horizontal displacements were compared to 147,684 km in profile with models 3, 4, chart 2 and 147,644 km of profile models 1, 2. The measured data in a chart 2 represent the dotted curve. Elevation levels are color coded: blue 0.5 m above the surface, 3.5 meters above the red surface, 6, 5 meters above the green surface. Modeled lateral displacements are full and dashed curves. The dot after the number of the reference point, represents the model (1, 2, 3, 4, etc.). Chart 2. Comparison transversical movements of profil 147, 684 km

6 34 INGEO COMPARISON OF EXPERIMENTAL AND GEOTECHNICAL ON-SITE DATA Settlement was monitored hydrostatic ground leveling. Graphical representation of ground subsidence corresponds to the character of the building. The values observed subsidence modeling in both cases correspond well with the measured reality. Step change (chart 3 blue curve) in the data may be due to an accuracy of reading or local changes in the subsoil. The maximum deviation between two measurement points is about 2 cm, instrument accuracy is ± 1 mm, accuracy depends mainly on the length of the observation, ie. stabilize the probe in surveying position. Chart 3. Curve settlement of subsoil under embankment in profile 147, 684 km 5 CONCLUSION The technology of reinforced retaining walls in the Czech republic is used about 15 years and for this reason the results and findings from the measurements can contribute not only to learning. They can also serve to assess compliance calculation assumptions and facts and for further optimization of the design, or construction. PLAXIS program has proved a suitable tool for modeling structures of this type. Selection of tool elements (interface) but is dependent on how we want to watch alone or mound soil or behavior reinforcement. It can be used as a basis for selection of suitable monitoring (instrumentation, location, timing measurements) and also as a check in the application of observational methods during construction. This outcome has been achieved with the financial support of the Ministry of Education, Youth and Sports of the Czech Republic, project No. 1M0579, within activities of the CIDEAS research centre. REFERENCES HOSSAIN, S., OMELCHENKO, V., MAHMOOD, T., History of GeosyntheticReinforced Segmental Retaining Wall Failure (in english), [online] 2009 [Citace: 21. Dubna 2010.] Dostupné z: < HRUBEŠOVÁ, E., LAHUTA, H., Charakteristika a možnosti vybraných softwarových produkt pro modelování svahových pohyb. Geotechnika, 2004,.1, s , ISSN 121.