Energy-based Research On Cyclic Failure Mode And Failure Criterion Of Taiping Tailings

The dynamic characteristics of tailings are closely related to the engineering design of the tailings dam and its stability under seismic loading.Tailings have huge differences in physical characteristics due to different ore crushing methods,sedimentation methods,and mineral composition,which leads to different cyclic response under cyclic loading.On the basis of reexamination of researches on low-plasticity fine-grained tailings,it was found that some low-plasticity fine-grained tailings have distinctive cyclic response.Beyond a critical cycle,the strain of soil sample suddenly increases suddently and sharply.The sudden increase in strain often occurs in sandy soils and cross-graded soils with less clay content.Obviously,the dynamic characteristics and failure modes of this type of tailings soil need to be further studied.This paper takes the tailings soil?Taiping tailings soil,a kind of low-plasticity fine-grained tailings?from Phase III project of Jiangxi Xingang Taiping tailings dam as the research object.A series of monotonic and cyclic triaxial undrained tests are conducted to investigate the mechanical response of Taiping tailings.?1?The viscous energy dissipation ratio is used as a new energy expression method to study the energy dissipation law of Taiping tailings soil.This new energy calculation method can eliminate the influence of different cyclic stress amplitudes and cyclic strain amplitudes of the i^th cycle,and normalize the viscosity energy dissipation level of the i^th cycle.?2?The research on the various dynamic characteristics of Taiping tailings soil shows that after the peak of the viscous energy dissipation ratio,the samples failed rapidly and the dynamic characteristics are significantly different.The viscous energy dissipation ratio is characterized by a sudden drop,the cyclic axial strain amplitude and the residual pore water pressure ratio are characterized by a sudden and sharp increase,and the hysteresis curve is characterized by a failure pattern similar to that of sand liquefaction.The suddent change of dynamic characteristics during the final period of cyclic loading indicates the collapse failure mode of Taiping tailings.?3?On the basis of collapse failure mode,this paper defines the peak of viscous energy dissipation ratio as the failure point of Taiping tailings soil as a new energy-based failure criterion.Combining the critical state line and the cyclic resistance ratio,camparison between the new energy-based failure criterion and traditional strain-based failure criteria indicates that the new energy-based failure criterion considering the collapse mode failure of soil is relatively reasonable and safer.In general,the research will deepen the understanding of the tailings soil exhibiting a collapse failure mode,and the newly proposed failure criterion based on the energy method will provide a more reasonable method for cyclic strength assessment of this type of soil.