Study Of Mechanical Properties Of Iron Tailing Sands Under Different Stress Paths

In different geotechnical constructions,the stress paths experienced by the soil are different,and the mechanical properties of the soil such as stress-strain and shear expansion are obviously influenced by the stress paths.There are still relatively few studies that combine macro and fine views to explore the mechanical properties of iron tailings sand under different stress path tests,therefore,it is of great theoretical and practical significance to study the effect of considering stress paths on the mechanical properties of soils.In this paper,the mechanical properties of iron ore tailing sand under different stress path conditions are investigated,and the damage process of sand samples under different stress paths is simulated using PFC2 D,with the aim of generalising the deformation and damage characteristics of iron ore tailing sand under different stress paths.Conducting consolidation and drainage tests with different stress paths(CTC,TC,RTC)to investigate the mechanical properties of iron tailings sands.The results show that the strength magnitude of the sand samples under different stress paths is expressed as CTC>TC>RTC.The stress-strain curves show a linear increase for all three stress paths tested at initial loading,with slightly different trends after reaching the peak point.As the strain increases,the partial stress in the CTC stress path remains constant and the curve shows a strain hardening type,while the partial stress in the TC and RTC stress paths shows a slow decline and an accelerated decline,and both curves show a strain softening type,and the strain softening characteristic of the RTC stress path is more significant.In the same stress path,the cohesion and internal friction angle of iron tailing sand decrease with increasing water content,and the decrease in cohesion is greater than the decrease in internal friction angle;while the increase in dry density also leads to a decrease in the cohesion of iron tailing,but the internal friction angle tends to increase.The range of difference in internal friction angles for the different stress paths in iron tailings sands is less than the cohesion,and the cohesion for the TC and RTC stress paths is less than the CTC stress path.Based on the Duncan-Tensor model,the Duncan Tensor model parameters were calculated for different stress paths,and the relationship between Eu and envelope pressure was investigated for the TC and RTC paths,with a higher Eu fit for the RTC path than for the TC path.The concept of unloading ratio was introduced and it was found that the stress path can have a greater effect on the unloading ratio,with the RTC stress path having a greater unloading ratio than the TC stress path.The PFC2 D numerical model was developed to simulate the damage process of iron tailings sand under different stress paths,and the distribution of particle displacement and the evolution of force chains were analysed.The stress paths have obvious effects on the damage morphology of the shear zone,the shear zone of CTC stress path is X-shaped,the shear zone of TC stress path is monoclinic plane,while the shear zone of RTC stress path is two intersecting symmetrical wedge-shaped planes.The influence of the different stress paths on the evolution of the force chains all show that the vertical columnar force chains are predominant before the formation of the shear zone,and after the formation of the shear zone,the vertical force chains in the shear zone decrease and become oblique flexural force chains,which can lead to the generation of microcracks.