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Analysis of bearing capacity of reinforced retaining structures

Resumo

Retaining structures are one of the commonly used applications of geogrid reinforced soil. Most design codes such as EBGEO, BS8006 and other international regulations assume a multi-body failure mechanism below a quasi-monolithic reinforced block securing adequate bearing capacity for re-taining walls. Consequently, the flexible behavior of the geogrid reinforcement is not taken into account. Therefore, laboratory model tests have been developed at the Geotechnical Institute of RWTH Aachen University to investigate the bearing capacity behavior of both rigid and flexible retaining structures. The laboratory model tests illustrate the crucial failure kinematics of reinforced retaining structures quali-tatively. A path-controlled punching force is increased on top of the structures until post failure behavior of the specimen is observed. During loading the deformation of the soil is evaluated with the digital im-age correlation (DIC) method. The results visualize the development of shear bands and indicate different failure modes for rigid and flexible retaining walls. Bearing capacity failure occurred in cases of flexible geogrid reinforced walls, whereas a comparable rigid wall failed by sliding and overturning. Moreover, an improved bearing capacity resistance is observed with enlarged geogrid anchorage length. Based on the experimental results a numerical model is set up in order to investigate the influence of wall geometry, soil and geogrid properties on occurring failure modes. First results confirm the capability of the finite el-ement analysis to simulate the mechanisms observed in the laboratory qualitatively.

Conclusão

In this paper, laboratory model tests and numerical simulations of both rigid and geogrid reinforced re-taining structures were presented.
The experimental test results confirmed a considerable increase in bearing capacity with enlarged rein-forcement length resulting in an improved bearing resistance. Moreover, different failure modes were ob-served for rigid and flexible walls. Bearing capacity failure occurred in cases of flexible geogrid rein-forced walls, whereas a comparable rigid wall failed by sliding and overturning. The sliding mechanism was apparently not decisive for reinforced structures due internal resistance and flexibility of the rein-forced soil block. Finally, the load resistance of bearing capacity was considerably higher compared to sliding resistance.
First results of numerical simulations with a finite element model confirm the occurring failure kine-matics and shear bands qualitatively, which were observed in the laboratory.