Experimental Study On Mechanical Properties Of Remolded Loess Under True Triaxial Round-Trip Loading And Unloading

Rate effect and cyclic effect are two aspects to describe the dynamic characteristics of soil under dynamic load.At present,cyclic effect is one of the hot spots in the study of dynamic characteristics of loess.Based on the true triaxial apparatus newly developed such as stress amplitude round-trip to reshape the loess and unloading test system to carry out the experimental study,the research considers the confining pressure,moisture content,the influence of the dynamic stress amplitude and complex stress path,the main research contents include dynamic stress strain relations,the dynamic elastic modulus,damping ratio and the cumulative plastic strain.The research conclusions are as follows:(1)The time-history curve of dynamic stress and dynamic strain reflects the change of dynamic stress and dynamic strain with time.Study on backbone curves:The dynamic stress-strain curves of remolded loess conform to hyperbolic model under different initial conditions,and the dynamic strain changes little with the increase of confining pressure,the decrease of water content and the increase of intermediate principal stress parameters.(2)The influence of the number of cycles on the variation of hysteretic curve is analyzed.The results show that with the increase of the number of cycles,the distance between the center points,the area of the hysteretic curve and the degree of non-closure of the hysteretic curve are all affected and all decrease,and the whole hysteretic curve moves to the right.(3)Reshaping is analyzed,the dynamic elastic modulus,damping ratio of loess,the change rule of factors including the confining pressure,moisture content,the principal stress parameters,the results show that the proposed under the influence of dynamic strain increase,decrease,1/Ed～εd curve had good linear relationship,with movement under the strain,the smaller the greater the confining pressure and moisture content,the principal stress in the parameter,the greater the corresponding dynamic elastic modulus is larger;The damping ratio increases with the increase of dynamic strain and presents a zonal distribution.(4)The cumulative plastic strain of the remolded loess under different conditions was analyzed,and it was found that it was significantly affected by dynamic stress amplitude,water content and medium principal stress parameters.The results showed that under the same other conditions,the larger the dynamic stress amplitude,the larger the water content and the smaller the medium principal stress parameters,the larger the cumulative plastic strain was.(5)In the curve of the relationship between cumulative plastic strain and cycle times,the development law of cumulative plastic strain increases nonlinearly,and the appropriate formula is selected to fit the test data points,which provides a reference for the settlement study of remolded loess under cyclic load.