Numerical Simulation Of Single Shear Test Based On Property-dependent Plastic Potential Theory

The relationship of stress and strain for the sand under different stress conditions such as earthquakes,traffic and wave loads have different degrees of rotation in the main stress axis.It is a spotlight for the stress and strain relation of the sand under this condition in the engineering and academic circles.Most of the constitutive relations for existing sand are established under the framework of continuum mechanics.The theoretical framework adopts the assumption that the material is isotropic.When assumption is true,the principal of stress axis rotates to the material.However this assumption poses a great challenge to describe the stress-strain relationship of the sand under the condition of the main stress axis rotation.In the process of natural formation,the particles will be arranged in a certain direction,showing the original anisotropy under the complex stress conditions,the particle space will evolve,showing a significant stress induced anisotropy,and it’s more difficult to describ the complexity of its stress-strain relationship under this condition.Based on the theory of plasticity potentials proposed by our research group,considering the influence of sand microstructure on its mechanical properties,the sand constitutive model of sand is established.According to the existing single shear,the results show that the stress-strain relationship of single shear is been described,and the stress-strain relationship for the principal stress rotation is described.Finally,the single shear test is simulated by PFC software.The main contents are as follows:1.According to the stress and strain characteristics of single shear test,the constitutive description equation of sand under stress condition is deduced and the experiment is simulated.According to the characteristics of the rotation of the main stress axis of the single shear test,the structural tensor is introduced into the yield equation of the sand to describe the effect of the microstructure on the yield function of the sand under the stress condition.And the newly defined anisotropic state variables are introduced into the critical state equation to describe the influence of the micromorphic structure on its critical state by the material state.The constitutive model of sand is established based on the theory of plastic properties of material properties.Finally,based on the result of single shear test,the stress and strain of the relationship between the stress and the non coaxial horn is simulated under the experiment condition,and the results are compared with the experimental results.2.Based on the theory of plastic properties of material properties,combined with single shear test,the stress dilatation equation of sand is deduced by energy conversion principle.According to the characteristics of the main stress axis during the single shear test,the relationship between the principal strain increment angle and the corresponding principal strain rotation angle is calculated by the plastic deformation potential of the material stress in the rotation process of the stress axis.The parameters are used to describe the influence of the material parameters on the relationship between the dilatancy of the sand under the rotation condition of the principal stress axis.And combined with Rowe’s parameter in the non-coaxial stress dilatancy relation and the theory of material-related properties to analyze the principal stress rotation angle,non-coaxial parameter and shearing property of loose sand,medium sand and sand under the single shear test condition.3.Using the PFC commercial procedure,the stress-strain relationship and the paper-cut relationship under the single shear test were simulated by discrete element.The initial loading conditions of the discrete elements were determined according to the single shear test conditions.The relationship between the stress-strain relationship,the strain and the volume change of the spherical particles under different confining pressures,different porosities and different particle diameters were analyzed.The influence of the spatial arrangement for particles on the stress-strain,shear-off relation and the force chain distribution of the single-shear test under the condition of random arrangement of non-spherical particles is carried out.The influence of the spatial arrangement of non spherical particles on the stress-strain of the main stress axis is explored.