Study On The Stability Evolution Mechanism Of Fractured High-steep Rock Slope Under The Coupling Of Heavy Rainfall Infiltration And Mining Unloading

Heavy rainfall infiltration and complex excavation are two key factors that affect the safety and stability of high and steep rock slopes in mines.The deformation evolution characteristics,engineering stability evolution mechanism of high-steep rock slope fractured rock mass under the coupling of heavy rainfall infiltration-mining unloading were systematically studied.Taking the Huangniuqian east mining area of Dexing Copper Mine as the research background,combined with engineering geological survey,indoor rock mechanics test,physical model test of similar materials,Mat DEM numerical simulation,Open CV digital image processing,theoretical analysis and other methods,an in-depth analysis of the slope height of 200 m,the failure evolution law,failure mechanism and slope angle effect of fractured rock mass under slope angle45°,50°and 55°models.The failure mechanism of fractured rock mass on high and steep rock slopes under the coupling of heavy rainfall infiltration and mining unloading was revealed from the engineering scale.(1)A systematic investigation was carried out on the engineering geology,regional geological structure,hydrogeological conditions,engineering geological conditions of the slope and the failure mode of the slope in the study area.In addition,the determination of rock mechanical parameters was carried out through laboratory rock mechanics test.(2)According to the occurrence conditions of ore bodies in Huangniuqian east mining area.Based on the similarity theory,the physical model test of similar materials was used to analyze the rock mass movement and deformation failure,stope cover and slope angle of 45°,50°and55°during the mining process of heavy rainfall infiltration and underground room-and-pillar mining.The results showed that under the combined action of rainfall infiltration and excavation unloading force,the closer to the goaf,the greater the stress unloading degree of the roof of the stope.In addition,the goaf was the movement direction of the open-pit slope and the underground stope,and the maximum horizontal and vertical displacements both occurred at the upper boundary of the gob near the toe of the open-pit slope.Along the excavation tendency of the ore body,the farther away from the underground stope,the smaller the impact of mining stress.On the other hand,along the vertical direction of the ore body inclination,the farther the vertical distance of each measuring point from the stope,the smaller the mining influence range.(3)Based on discrete element theory,Mat DEM numerical simulation method was used to analyze the fracture evolution law of fractured rock mass stress field,displacement field and overlying rock under the coupling of heavy rainfall infiltration and open-pit transferred to underground mining unloading.The numerical simulation results showed that the whole stope had a pressure relief phenomenon,and the stress change was larger at the foot of the slope,which was in the shape of alternating wave crest and wave trough.With the advancement of the stope,the unloading range of the stope moves forward dynamically,and stress concentration occurred at the boundary of the stope.The farther away from the stope,the smaller the influence of rainfall infiltration and mining unloading,and the smaller the unloading degree.The subsidence decreased continuously,and the deformation and damage of the rock layer decreased,which was similar to the similar simulation results.(4)By using the Open CV open-source image library,a region growing segmentation algorithm combining multi-pixel seed points and point cloud coordinates was proposed,which can effectively identify the damaged area of the fractured rock mass.Rainfall infiltration will reduce the strength of the rock mass and cause the rock mass to fall off or slide.Under the time series,with the increased of rainfall intensity,the ability of unsaturated rock mass under the platform to absorb rainwater increased,the water content and pore water pressure increased,and shedding damage occurred.After the underground mining was completed,the toe of the slope and the overlying rock mass reached a saturation state.Under the action of its own weight,collapse and damage in a large area occurred,and the peripheral extension of the overlying rock develops to the waist of the slope.(5)Combined with similar simulation,numerical simulation and image processing technology,the length,width,height and density values of developed fractures,stress and displacement data of stope rock mass,water content and pore water pressure data of rainfall infiltration,deformation area and volume data of rock mass were calculated.Among them,the area and volume values of the models with slope angles of 45°,50°and 55°were 0.2982 m~2,0.02402 m~3,0.279 m~2,0.02366 m~3,0.2705 m~2,and 0.02203 m~3,respectively.Thus,when the slope height was constant and the slope angle increased,the coupling effect between the rainfall infiltration force and the mining unloading force was weakened,the overlying rock was less affected,and the damage scale was reduced.