Analysis And Evaluation Of Mining Stability Of Downdip Soft Rock Slope In Shengli Dong No.2 Open-pit Mine

Based on the theory of open-pit mining and slope engineering,this paper makes a comprehensive and detailed study on the south slope structure and landslide evolution law of Shengli east No.2 open-pit coal mine.Based on the research data of the south slope and the supplementary mechanical experiment,the physical and mechanical parameters of the strata in the South slope are determined.Based on the analysis of engineering geological data and site reconnaissance,the distribution of weak strata is clarified.The influencing safety factor of the south composite slope and the weakening mechanism of the soft rock interlayer deformation are analyzed.According to the open-pit mining procedure,the change law of the geometry structure of the south slope during the mining by drop period is deduced.The stability of the south slope is evaluated synthetically and the stability evolution law of the south slope under the control of downdip weak layer is revealed.According to the historical landslide data of the south slope,the key factors affecting the landslide and the deformation mechanism of soft rock interlayer are analyzed.The evolution of weak intercalation to sliding zone is an important way to form landslide.The evolution process can be divided into three stages: primary soft rock zone,interlaminar shear zone and slimy intercalation slide zone.The corresponding mechanical behaviors are stress concentration stage,small deformation stage and large deformation stage.According to the sliding form,the south composite slope is divided into three areas: loose sliding body,landslide area and deformation area.It is determined that the landslide mode of the south side composite slope is shear-bedding slip,multi-stage repose and traction mega landslide.Based on the geotechnical test,the physical and mechanical properties of the rock mass of the southern slope are determined,and the natural strength and residual strength of the weak layer of soft rock are obtained.The limit equilibrium method is used to analyze the stability evolution law of the four typical sections,35#,36#,37# and 39#,and it is concluded that the complexity of rock strata in the slope increases with the increase of mining depth.When the depth reaches the downdip stratum,the slope stability decreases obviously.When a weak layer is exposed on the slope surface in the depth of the descending section,shear failure will occur.The safety factor of slope cannot meet the needs of engineering,and there is a great risk of landslide.Three-dimensional stability analysis in mining process was carried out for four typical sections,35#,36#,37# and 39#.With the increase of the depth of the excavation,the plastic zone of the slope is gradually transferred to the weak layer,coal seam and mudstone layer of the lower excavation bench.The potential sliding surface of the slope is gradually transferred from the initial composite slope through the sliding surface to the local sliding surface of the lower slope of stope.The initial integral sliding of the composite slope gradually evolved into the sliding form of multiple benches at the lower part of the slope.The variation of the stress variables in the slope is concentrated in the soft rocks and distributed in strips along the rocks.The variation of the stress variables is transferred from the soft rocks to the foot of the slope.The safety factor of slope of the overall slope of the south wall shows a tendency of decreasing in the mining by drop period.Section 35 and section 36 appear landslide after excavation of 37 m and 39 m respectively.Section 37 and Section 39 are always in a stable state during the mining by drop period.There are 70 figures,8 tables,85 references in this thesis.