Simple Shear Experimental Study On Monotonic And Cyclic Behavior And Correlations Of Sands

As a kind of natural building material,sand is widely used in embankment,dam,slope and various building infrastructure.Under cyclic loading,especially under seismic loading,the sand can occur liquefaction,which will lead to the instability and damage of buildings on the sand foundation.Based on the simple shear test,this paper studies the influence of initial consolidation stress,relative density,particle gradation,particle shape or material on the monotonic and cyclic behavior.The main contents are as follows:?1?Through the undrained monotonic shear tests of sand,the effects of relative density,particle gradation,particle shape or material on the effective stress path and stress-strain relationship are studied.The friction angle of peak line,phase transformation line and ultimate state line and the normalized stress-strain relationship were investigated under different test conditions.?2?Cyclic shear tests of sand under the same conditions as monotonic tests were carried out,and the relationship between monotonic and cyclic behavior of sand is studied,mainly including the study of instability behavior and backbone curves.The pore pressure growth,double amplitude strain accumulation,stiffness degradation and damping ratio development were analyzed.A feature point of 0.75N/N_ILis found.There are obvious differences in the development of cyclic parameters before and after the feature point.?3?The influence of cyclic stress ratio,initial consolidation stress,relative density,particle shape or material on the liquefaction resistance of sand was investigated.A new index can be used to evaluate uniformly the liquefaction resistance of sand under different test conditions.