Application of the previous semi-empirical bounding surface plasticity model [Aboim et. al. (1982) and Bardet (1983, 1985)] to simulate the nonlinear behavior of loose beach Li-Kang sand subjected to cyclic loading has been investigated. The bounding surface plasticity model describes strain-softening and stressdilatancy with nine material constant calculated for the results of conventional static triaxial tests. The experimental program were performed on local loose beach Li-Kang sand with the initial relative density about 30 %. A series of static triaxial tests and cyclic undrained triaxial tests were performed on test specimens under the effective cell pressure of 50, 100 and 150 kPa as well as the OCR of 1.0, 1.25 and 1.50 to evaluate the liquefaction potential on loose saturated sand deposit subjected to earthquake.
This paper presents the general formation of the sand model which was previously developed (Bardet 1983, 1985). The advantages of boundary surface plasticity over conventional plasticity are investigated for not only cyclic but also monotonic loading. This model takes into account strain-softening, stress-dilatancy and accumulation of irreversible strain during cyclic loading for loose and dense sands.
A typical material response during a triaxial loading-unloading cycle is schematically shown in Fig. 1(a). At the beginning of loading, the response is assumed to be elastic. At removing the elastic strain, it is represented by the vertical line of Fig. 1(b). If the stress is further increased, the stress-strain curve approaches and merges with the bound represented by the straight line XX'. The slope of response curve at any point is taken as a function of the distance AA', denoted by d, between the stress state and the bound XX'.
