Study On Mechanical Properties And Slope Stability Of Soil-rock Mixture In Gonchangling Open-pit Mine

As a kind of special rock and soil medium,soil-and-rock mixture is widely distributed in a part of Gongchangling open-pit mine.With the deep concaving mining of open-pit mine,the slope stability problem is increasingly prominent due to the influence of slope conditions and mining disturbance.Therefore,it is very necessary to study the mechanical properties of the soil-rock mixture slope.According to the condition of the soil-rock mixture slope,the mechanical properties of the soil-rock mixture and the sliding characteristics of the slope are studied by means of field investigation,laboratory experiment and numerical simulation.The main contents are as follows:The basic physical properties of the sliding-zone soil were measured by indoor physical tests,which provided a reference for the design of the test scheme and the determination of the macro parameters of numerical simulation.The similarity gradation theory is introduced to establish the relation between field test and laboratory test.The mechanical properties of soil-rock mixture samples under different rock content,particle size distribution and water content were studied by laboratory triaxial tests.Results show that the sample under different factors of the shape variation of stress-strain curve is not obvious,the strength of the specimen under the influence of non-uniform coefficient is small,in the case of grain size distribution is good,the effect of rock content on mechanical properties of samples is much greater than that of particle grading,under the condition of stone content less than 65%,the cohesive force increases with the increase of stone content,internal friction angle of the opposite.The effect of water content on the internal friction angle is obvious,but not on the cohesion.Based on the laboratory test results,a biaxial test model of the soil-rock mixture with a rock content of more than 65% was established by using Particle Flow Code(PFC2D).By analyzing the evolution process of shear zone and the deformation characteristics of the samples,it was concluded that the failure mode of the soil-rock mixture was conjugate shear failure.Based on the analysis of deviatoric stress curve and volumetric strain curve,the relationship between strength,shear characteristics and rock content of soil-rock mixture is studied.Specifically,the strength increases with the increase of rock content,the larger the rock content,the lower the confining pressure and the more obvious the dilatancy phenomenon.Combined with the slope geometry and material composition,Particle Flow Code(PFC2D)was used to construct the bedrock under the overlying deposit-slope calculation model,considering the moisture content change on base-the influence of mechanical properties,analyses the gradual slope sliding process,the calculation results show that the landslide begins with the trailing edge of the landslide mass and thereafter for sliding circular sliding and slope on the front of the whole deformation,suitable landslide types mainly goes on type of compound slide.