Study On Stability Of Water-rich Burnt Rock Slope In Opencast Coal Mine

There are many burning areas in the west of China due to the erosion of coal resources.A large amount of groundwater often exists in the burning area,which threatens the slope stability of open-pit mines.Based on the research background of the South Slope of the No.2Mine of Dananhu Coal Mine,this thesis studies the seepage characteristics of the underground water and the mechanism of slope sliding and instability by using the methods of indoor and field pumping tests and numerical simulation,the size of watertight coal and rock pillar on slope is optimized.Pumping test was carried out to study the water-rich characteristics of the slope.The permeability coefficient varies greatly in different areas of the slope.Statistics of the water level at different locations of the slope shows that the slope hydraulic gradient is between 5.3°and 12.8°.Based on the analysis of the characteristics of groundwater seepage at the interface between the three types of burning area and the original rock area,the seepage velocity of different types of groundwater has a jump phenomenon,and the peak value of velocity jump and the front discharge are the largest under the condition of form 2.With the increase of Slope Mining Depth and dip angle,the seepage path of groundwater changes,and the seepage velocity and flow rate increase.The mechanism of slope instability is studied by means of numerical simulation and mechanical analysis.The results show that the slope stability is affected by both upper and lower weak layers.The effect of groundwater makes the rock mass move along the upper weak layer to the open face,which causes the burnt rock mass at the back edge to break up,and the broken burnt rock mass promotes the slope mass to accelerate the slope deformation,the Rock mass deformation in the lower weak layer control region promotes the activation of the upper weak layer,and finally the slope along the upper weak layer shear deformation instability.Based on the control action of two weak layers on slope stability,the reasonable size of upper weak layer and slope stability dip angle are calculated,and it is determined that the size of upper weak layer is 59 m,and the slope obliquity is 22°,which is the best scheme of coal and rock pillar retaining.