Combination of 3-yield surface model with SMP criterion;

The simulation of the yield surface of natural sand with experimental data;

Theory of yield surface and stress strain relation in generalized plastic mechanics;

The unified macro and micro mechanics constitutive model was used to investigate the influence of micro-structural geometry,such as fiber shape and fiber packing array,on the composite initial yielding surfaces under multi-axial loading.

Standard for the determination of the least favourable direction of ground motion for bridge is established using the yielding surface function proposed by Bresler.

The change of stress states can be described with a loading path on the yield surface.

The main contents of the research are:(1)initial yield surface in the stress space,(2)surface of ultimate stness in the stress sauce,(3)reaction between the initial yield surface and the surface of ultimate stress in the stress space.

At present domestic and foreign has established very many models through the ground class material fundamental research, Revision Cambridge model, the Lade-Duncan model, and so on double yield surface model with the Matsuoka model applied widely.

Afterwards, the multisurface plasticity model is adopted for the analysis of the localization of rocks with crack sets and conditions for both continuous bifurcation and discontinuous bifurcation are formulated.