Stress-strain Behaviors Of Rockfill Considering Time-effect

Rockfill has been applied widely as filling material in engineering constructions for its excellent engineering properties.As we know,particle crushing,creep and wetting are the three major factors that affect the stress-strain behaviors of rockfill,and they should be considered in the constitutive model for rockfill in order to describe well the deformation of the engineering entity.Nowadays,some test and theory researching achievements for rockfill have been acquired by researchers from home and abroad,but there still be some limitations in engineering calculation.So in this paper,we devote to propose a constitutive model reflecting the influences of particle crushing and time-effect rationally,and obtain the engineering calculation results which more conform to reality through this model.The mechanical characteristics and deformation regularities of rockfill are similar with sand,so the researching achievements of constitutive model for sand can be extended to rockfill.The test results for rockfill show that the shear failure stress ratio M_f and the characteristic point stress ratio M_c are both affected by particle crushing,and they can be both written as the power functions of mean stress p.Taking a new hardening parameter H revised with crushing stress p_c to replace the plastic volumetric strain?_v~p in plastic yield function,a elasto-plastic constitutive model for rockfill crushing was acquired.The influence of loading rate on stress-strain behaviors under isotropic compression condition was analyzed,and the assumption that the plastic deformation is dependent on time while the elastic one is not was proposed.It analyzed that the isotropic compression curve in?_v-(p_m/p_a)~m plane is linear and its slope is related with loading rate.Based on the conclusion above,the time-dependent stress-strain relationship under isotropic compression condition was acquired.According to the model researching achievements for rockfill crushing,the time-dependent constitutive relationship was generalized from isotropic condition to shearing condition,and a Visco-elasto-plastic constitutive model considering particle crushing and time-effect was proposed further.The comparison of predicted and test results indicated that the proposed model can not only consider the influence of particle crushing and time-effect on deformation while loading reasonably,but also describe well the deformation with time increasing during holding the load.