Research On The Mechanical Behavior Evolution Of Sand Shear Band And Sand-structure Interface Layer Under High And Low Pressure

With the background of the shear band and interface layer problem, a sand model whichcould unify the shear dilatancy softening property and shear contraction hardening property isbuilt in this paper through laboratory experiment and theoretical analysis. Simulation for thegeneration and evolution of sand shear band and sand-structure interface layer is realizedcombined with meshless method, and the description of real damage process on geotechnicalengineering become possible.Mechanical property of sand is systemically analyzed under different pressure throughlaboratory experiment. The fitting curves of isotropic compression and shearing critical state areobtained ase a b exp c ln p. The peak stress ratio of sand is affected by both sand particlesize and confining pressure, while the residual stress ratio would not be affected by particle sizeand confining stress and could meet the classical M-C strength criterion.Combined with the strength and deformation properties of sand under different pressure, asand model which could show the shear dilatancy softening properties and shear contractionhardening properties is built. The new model has two yield surfaces, and they are current yieldsurface and potential yield surface. This model includes10parameters involved with elastic,critical strength, current yield surface and potential yield surface. These parameters have specificphysical significance and all of them could be obtained through conventional triaxial test.The relative scale of sand particle size and shape scale has influence on the shearmechanical property of sand-structure interface, and there are two obvious features which couldbe defined as extreme relative scale Rmaxand critical relative scale Rcrrespectively. Before theextreme relative scale Rmax, the sand-structure contact shear mode is defined as frictional contactmechanism and the corresponding structure surface type is rough surface. After the extremerelative scale Rmax, the sand-structure contact shear mode is defined as shape restrained contactmechanism and the corresponding structure surface type is shape surface.This paper analyzes the calculation difficulties of strain softening and mesh distortionproblems in the simulation of sand shear band and sand-structure interface layer. The meshlessSPH method is used as a second development platform for sand model and a new SPH solver iscompiled, making it possible to simulate the large strain problem for strain softening material.The simulation tests of biaxial compression and sand-structure interface shear are carried outwith the newly generated solver. Simulation result confirms the feasibility of the new solver, andsome important conclusions are obtained.