Study On Stability Analysis And Reinforcemnt Design Of Open Pit Mine Slope Under The Underground Mining

In recent years, with the continuous development of large open pit coal mine in ourcountry, a lot of open pit mine has entered the stage of deep mining and undergroundmining. As the existing open pit has gradually deepened and the exposed slope heightand area are gradually increased, it is very important to make the stability analysis,safety evaluation and treatment of slope. In this paper, the northern slope in Antaibaoopen pit mine of China coal Pingshuo company is taken as a research project, and someresearch on the slope stability and deformation is studied. Then, the impact of the slopeunder the underground mining is evaluated and instability region is strengthened byprestressed anchor cable. This paper provides a scientific basis for safety production ofAntaibao open pit mine, and provides a reference for the subsequent open pit slopestability analysis and reinforcement.1. Based on the practical engineering, the open pit slope engineering landslidesituation is analysed, and potential safety problems in northern slope of the open pitmine are pointed out. Factors influencing the stability of the slope are particularlyresearched, especially in the discontinuous surface in the rock area, physical andmechanical properties of rock and soil area, rainfall effect area, earthquake effect areaand human engineering activities area.2. The three-dimensional model is established by using numerical analysisFLAC3D software, and the deformation and stress distribution in the z-direction of theslope is analysed. The slope safety factor before the underground mining is analyzed.Displacement and stress transformation of slope rock and soil under the exploitation of4thand9thcoal are studied. In the condition of underground mining, the displacement ofrock mass moves to goaf largely, and a certain degree displacement moves to invadingside. The vertical stress concentration phenomenon occurs in goaf sides.3. With the specific examples combined, the influence of the necessary physicaland mechanical parameters of rock and soil as well as the grid size on slope safetyduring slope stability analysis through FLAC3D are researched, and impact factorsensitivity analysis is done. The results show that the influence of the internal friction angle, the density and the cohesion of rock and soil mass are more evident to slopestability, compared with other influencing factors.4. SLIDE software which is based on limit equilibrium method is applied toanalyze the stability under different engineering condition: before and after theunderground mining, groundwater and earthquake. The results show that the safetyfactor when the underground mining slope suffers the earthquake does not meet theregulatory requirements. So the slope should be reinforced.5. The reinforcement mechanism of prestressed anchor cable is studied, and theprestressed anchor cable is designed from four areas: cross section calculation,anchorage section length calculation, free section length evaluation and angleevaluation.