Study On Physical And Mechanical Properties And Slope Stability Of Open-pit Argillaceous Limestone Under Dry And Wet Cycle

During the open-pit mining process,the soft rock layer is often exposed,and the strength of the soft rock layer has a very obvious impact on the stability of the slope.Especially when the soft rock layer is also prone to disintegration and expansion,the impact of circulating rainfall on the stability of the slope is exacerbated.In addition,rainfall can cause dramatic changes in the distribution of seepage fields within the slope,which has a direct and indirect impact on slope stability.Therefore,studying the changes of physical and mechanical properties of argillaceous limestone under different dry and wet cycles and the influence of seepage field on the slope instability mechanism has important engineering guiding significance for the efficient and safe mining of open-pit mines.In this thesis,the exposed argillaceous limestone slope of an open-pit mine in southwest China was used as the research background,a reasonable dry-wet cycle scheme was explored,and marlin limestone samples under different dry-wet cycles were prepared by saturator.The macroscopic and microscopic physical and mechanical properties of argillaceous limestone samples under different dry and wet cycles were studied through saturation density test,saturation water absorption test,saturation permeability coefficient test,compressive test,variable angle shear test,SEM analysis and XRD analysis,and the changes of seepage field and slope instability mechanism in argillaceous limestone slopes under different dry and wet cycles were studied by finite difference numerical simulation software FLAC3 D.The results show that the best conditions for the preparation of argillaceous limestone samples by saturator are to select the rock and soil below 1mm particle size and the drying temperature of 50 ° C,while the initial natural density and initial saturation density of the prepared argillaceous limestone samples are 1.594g/cm3 and1.751g/cm3,respectively,and the initial natural moisture content of the sample is5.62%.With the increase of the number of dry and wet cycles,the argillaceous limestone specimens will show a slight increase in saturation density,saturation and water absorption first increase rapidly and then slowly increase,the permeability coefficient first increases rapidly and then remains stable and finally greatly decreases,the compressive and shear strength are slowly reduced without much change in the internal friction angle,and it is also concluded that frequent dry and wet cycles will cause the mud of the marl limestone specimen to undergo seepage filtration.Affected by the dry and wet cycle,the microscopic pores in the argillaceous limestone specimen will become larger and larger,more and more regular,and the pore size distribution will become more and more concentrated.The dry and wet cycle has a certain influence on the proportion of mineral content,and the decrease of mineral content with greater strength leads to a decrease in the strength of argillaceous limestone samples.In the numerical simulation of the dry and wet cycle,it is concluded that the seepage field at the bottom of the slope changes greatly than that at the slope surface and the top of the slope,the transient saturation zone area in the slope continues to increase,the area of the unsaturated zone and the peak of matrix suction continue to decrease,the depth of the infiltration line will slowly increase,and the stability coefficient of the overall slope and the local slope will slowly decrease.Due to the faster decline rate of local slope,the stability of local slope will be lower than that of the overall slope in the third dry and wet cycle,resulting in the transfer of the overall landslide trend to the local landslide trend.Finally,the mechanism of slope landslides under dry-wet cycle is summarized as follows: the dry-wet cycle changes the pores and mineral content in the argillaceous limestone,which affects the physical and mechanical properties of the marlin limestone,and finally causes the deterioration of the argillaceous limestone in the transient saturation zone in the seepage field,the decrease of matrix suction in the unsaturated zone and the increase of gravity near the surface,resulting in slope instability.The thesis has 106 figures,17 tables,and 60 references.