M. S. A. Siddiquee

Modeling of Cyclic Plane Strain Response of Toyoura Sand

Test results of Toyoura sand subjected to plane strain cyclic loading illustrates that it has the memory effect i.e., memory about its last load reversal point in the shear stress-strain plane, which produces a closed hysteretic loop. To simulate this response, a novel formulation of kinematic hardening rule is used here by introducing a framework in which the dimensionless kinematic hardening rate is varied according to the instantaneous stress value at that point along the stress path. When the direction of the loading is reversed, the initial rate of hardening is restored and the rate of variation of hardening is scaled according to extended Masing’s law. As a result, a closed hysteretic stress-strain loop is obtained due to cyclic loading. Finally, cyclic plane strain response of Toyoura sand is simulated and compared with available test results.

Numerical Study on the Deformation and Failure of Reinforced Sand Retaining Walls Subjected to the Vertical Load

To gain a better insight into the deformation and failure of reinforced sand retaining walls subjected to the vertical load from the crest and their associated reinforcing mechanisms, the model experimental results from well-controlled fully-instrumented load tests of full-scale reinforced sand retaining wall with sand backfill are simulated by making use of a nonlinear elasto-plastic finite element model considering strain localization. In the finite element method (FEM) analysis, the effects of the following factors for the filled sandy soil are taken into account: (a) the non-linear pre-peak work-hardening and post-peak work-softening; (b) effects of stress history and stress path; (c) the confining pressure dependency and strength anisotropy; (d) the stress-dilatancy characteristics; and (e) strain localization into a shear band(s) with a width proportional to the particle size. The load-settlement relationship obtained from FEM analysis is generally in good agreement with the physical experimental result. It is also found that the progressive failure with a development of shear bands and the horizontal earth pressure on the back of facing and the tensile force in the reinforcement layers can be reasonably simulated by the proposed FEM analysis.

Elasto-Viscoplastic Simulation of Bearing Capacity Characteristics of Strip Footing on Reinforced Sand

A nonlinear FEM analysis incorporating an elasto-viscoplastic constitutive model for sand that has been developed based on results from comprehensive laboratory stress-strain tests including plane strain compression tests is described. A series of plane strain laboratory model tests on the bearing capacity on a model strip footing (10 cm -wide) performed on unreinforced and reinforced level sand grounds were simulated by the FEM. The simulated footing load and settlement relation and failure mechanism in the unreinforced and reinforced sand grounds were compared with the measured ones. It is reported that the proposed FEM analysis method can simulate very well the test results, including the effects of reinforcing. It is one of the characteristic features of the proposed numerical analysis method that the footing and settlement behaviour around the peak footing load state and the one in the post-peak regime can be simulated in a very stable manner. It is shown that this is due largely to that the realistic viscous properties of sand that are properly modeled are incorporated in the FEM analysis.