Study On Shear Strength Of Unsaturated Copper Tailings Under Multiple Stress Paths

In the process of copper mine mining,the copper tailings after technology screening will be piled on roads in the form of dry storage or piled on the foundation pit,and the copper tailings will be stored in a non-saturated state.In order to use the copper tailings in practical projects,copper tailings which is piled on roads or pits should be excavated or buried in the roadbed.Different excavation conditions will result different stress,the properties of the copper tailings will be changed and deformed under different stress path conditions.Therefore,this paper conducted an indoor triaxial test study on copper tailings which is produced by Sanxin Company,Daye City,Hubei Province.It has studied and tested copper tailing's basic properties and the shear strength of unsaturated copper tailings which is under different stress paths.The specific content are as follows:1)Taking copper tailings as the research object,do basic mechanical testing and judge the basic properties of copper tailings.2)Using filter paper method to test the water characteristic curve for unsaturated copper tailings,design scheme due to different stress path test.Do three kinds of stress path triaxial tests of unsaturated copper tailings: conventional,isobaric and decompression.Study the effects of matrix suction on the shear strength and deformation characteristics of unsaturated copper tailings.Analyze and compare the effects of three different stress paths on the shear strength of unsaturated copper tailings.The specific conclusions are as follows:1)In the conventional triaxial stress path,as the matrix suction increase,its stress-strain curve appears as a strain hardening type.In the conventional stress path,the volumetric strain of the sample is directly proportional to the suction force of the matrix.The bulk strain curves show shear shrinkage under different suction forces.In the isobaric triaxial stress path,its stress-strain curve shows different types due to the increasing matrix suction.With the increasing matric suction,the stress-strain curve shows a transition from strain softening to strain hardening.When the matrix suction is 50 k Pa,the volumetric strain curve shows shear shrinkage then dilatation.In the decompression triaxial stress path,the softening phenomenon occurs after the stress-strain curve reaches the peak strength.Under the decompression triaxial stress path,the volumetric strain curves under different matrix suctions show shear shrinkage to dilation.2)Among the three stress paths,the shear strength value is the largest under the conventional stress path condition,and the shear strength value under the isobaric stress path condition is the second,and the shear strength value under the decompression stress path condition is the smallest.