Description Of Shear Volumetric Deformation For Sand

A large number of experimental studies have shown that,the stress-strain behavior of sand is dependent on both densities and effective principal stress levels.Based on the mechanics behavior of sands,a constitutive model is established which is simple and practical.The main purpose is to use the constitutive model as a tool for solving engineering problems,another objective is to reflect the underlying physical processes of the mechanics of sands.Especially the parameters describing the sand should have definite physical meaning.Based on the unified hardening parameter,an extended critical state constitutive model has been proposed for sand.One state parameter is used to adjust the hardening parameter and dilatancy equation,thus giving a better description of dilatancy and contraction behavior for sand.The other structural parameter is used to revise the yield function and adjust the shape of yield surface responding to different initial state of sand,thereby predicting the plastic deformation more appropriately.The introduction of the above two parameters into the model emphasizes the dependency on both density and effective principal stress of sand.Linear isotropic consolidation and critical state lines are applied in void ratio versus the power of effective mean stress space,all the ICLs intersect at one point,which can reflect the stress-strain behavior of sand more specifically in a wide range of effective mean stress.The combined effect of density and effective mean stress on sand can be described by the model using a unique set of model parameters in a wide range of density and confining pressure.Based on the SMP(Spatially Mobilized Plane)criterion and the corresponding transformed stress tensors,the proposed model can be applied to the three-dimensional stress space to describe the behavior of sand under different conditions.A comparison between model simulations and experimental results under drained and undrained triaxial compression and extension shows the validity of the proposed model.