Stress-strain relationship and strength criterion of geotechnical materials

• 1、Commerial Aircraft corporation of China Ltd

Abstract： In classical elastic-plastic mechanics, the strain in the process of material elastic-plastic deformation is divided into elastic strain and plastic strain. In order to distinguish between elastic strain and plastic strain, researchers put forward the concept of yield surface, which is divided into single yield surface, double yield surface and multiple yield surface. The stress state produces elastic strain within the yield surface while plastic strain outside the yield surface, In fact, in the process of elastic-plastic deformation, elastic strain and plastic strain occur at the same time, so the material constant defined in elasticity is no longer applicable. Based on a variety of material tests, this paper puts forward the continuous deformation elastic-plastic model. The elastic-plastic deformation is continuous deformation. There is no elastic region and plastic region in the P-Q coordinate system. Each stress-strain curve contains all the mechanical information of the material. In conventional triaxial compression experiments, σ 1- σ 3=a1*(arctan(（ ε 1- ε 3）*c1)- e/( 2*c1*c1*( σ m+ σ m0)^n1) *LN((（c1*c1*（ ε 1- ε 3）)^ 2+1)）， ε v= ε vm0+a4*(arctan(（ σ m+ σ m0 ）*c4)-e4*( σ 1- σ 3)^n4 *LN((（c4*（ σ m+ σ m0)) ^ 2 + 1), pressure meridian equation （ σ 1- σ 3)max= a1*(arctan(（ ( σ m+ σ m0)^n1）*c1*c1/e1)- e1/（2*c1*c1*( σ m+ σ m0)^n1）*LN((（c1*c1*（c1*( σ m+ σ m0) ^ n1 / e1) 2 + 1). The experimental data show that the continuous deformation elastic-plastic model can reflect the stress-strain characteristics of geotechnical materials better.

Keywords： Constitutive equation Strength criterion Continuous deformation model Stress-strain relationship