Study On Mechanical Properties And Slope Stability Of Loose Soil-rock Mixture With Different Rock Content

In the mining process of open-pit mine,a large number of dump sites with different shapes will be formed along with the continuous discharge of stripped materials.The mechanical properties and deformation characteristics of the dump are of great significance to the safe mining.The dump is a loose soil-rock mixture slope formed by the discharge of stripped materials.In the process of discharge,the soil and rock content of the dump slope will change with different mining parameters and discharge methods.The mechanical properties of the loose soil-rock mixture and the change rule of slope stability under different rock content are studied and mastered.It can provide theoretical basis and engineering guidance for safe and efficient mining and disaster prevention of open-pit mine.In this paper,four kinds of soil-rock mixture samples with different stone content were prepared by consolidation test using similar grading method.The mechanical properties of soil-rock mixture with different stone content were studied by triaxial shear test based on GDS triaxial test instrument.The discrete element method numerical simulation software PFC was used.The macro and micro mechanical properties,deformation mechanism and slope stability of soil-rock mixture under different rock content are studied in depth,and the main research results are as follows:(1)By conducting different stone content of soil-rock-mixture indoor compression test and triaxial test,analysis of the factors such as different stone content and confining pressure effect on the mechanical properties of soil-rock-mixture,the experimental results showed that: as the axial pressure gradually increases,the sample by the elastic deformation stage of start soon entered the stage of plastic deformation has a certain degree of strain hardening characteristics.The greater the confining pressure,the greater the transverse binding force of soil and stone particles in the sample.After being forcibly squeezed and occluded,the original loose "block stone" plays a stronger role of skeleton support,and the greater the strength of the sample.(2)Flexible biaxial numerical simulation tests of soil-rock mixture with different gravel content were carried out.A two-dimensional discrete element model of soil-rock mixture was established by using particle flow numerical simulation software.The lateral flexible membrane boundary was used to load the numerical model servomatically.The macro and micro mechanical behavior,mechanical properties and deformation and failure mechanism of soil-rock mixture were further studied by calibrating and verifying the micro mechanical parameters of particles in the model.The results show that the peak strength of the sample increases with the increase of stone content,and the stress-strain curve of the sample fluctuates greatly with the increase of stone content.With the increase of stone content,the internal force of soilrock mixture gradually changes from soil force to soil-rock joint force,and then to the complete force of skeleton structure formed by block stone.Under the condition of high stone content,the soil-rock mixture exhibits obvious bulging deformation failure on both sides.(3)The particle flow software is used to establish the meso-soil-rock mixture slope model with different rock content based on discrete element method.Based on the strength reduction theory,the stability characteristics and meso-failure characteristics of soil-rock mixture slope with different rock content are studied by analyzing the mesoparameters such as displacement,velocity and contact force after instability failure.The results show that the slope stability increases greatly with the increase of stone content,and the maximum displacement of slope model particles and the overall height of slope after landslide decrease with the increase of stone content.After the slope slides,the overall height and stability coefficient of the slope have the largest difference between40% and 60% of the stone content.At this stage,the skeleton structure formed by block stone limits the soil displacement and increases the slope stability.The total contact force,peak area and peak value of contact force in the slope increase with the increase of stone content,and the slope gravity is gradually transferred from soil to soil and block rock,and finally completely borne by the skeleton structure formed by block rock in the slope.There are 39 figures,9 tables and 54 references in this paper.