Study On Deformation And Failure Mechanism Of Mining Slope With Flat And Gentle Inclination Considering The Characteristics Of The Face

Gently dipping inner slopes are widely distributed in Guizhou.Mining-induced slope deformation and instability disasters occur frequently in mountainous areas of Guizhou,and its slope deformation and failure mechanism are complex.Good frontage is a significant feature of the southwest mining slope,so the study of the influence of frontage on the deformation and failure of mining slope is of great significance for the early identification of such slope failure.Based on the basic analysis of a large number of data collection,Four typical examples of deformation and failure of gently dipping inner-mined slopes were selected for field investigation.It is recognized that the characteristics of the frontage(height,slope)are the important factors affecting the deformation and failure law of the mining slope.Therefore,15 working conditions were designed under different combinations of the height and slope of the air front.The physical simulation test and discrete element numerical simulation were used to discuss the deformation and failure law of the gently dipping mining slope,and the following cognition was obtained:(1)Gentle inward slope is relatively stable in the natural state,but under the disturbance of underground mining,the inducement slope deforms and fails,and the good open surface conditions aggravate its deformation.(2)Through field investigation and test,slope deformation lags behind coal seam mining.When the goaf reaches a certain area,the overburden rock of the goaf deforms and develops upward,affecting the slope surface and the slope top,resulting in the subsidence,tension and cracking of the slope surface and the slope top,and finally instability and failure.The evolution process of deformation and failure can be summarized as follows: coal seam mining-deformation and development of overlying strata in goaf-formation and instability evolution of control surface.(3)Combined with the bottom friction test and numerical simulation,it is concluded that when the slope is less than 60°,the lower part of the slope takes the lead in deformation and gradually develops to the top of the slope,and the top deformation lags behind the slope.When the slope ?60°,the deformation occurs first on the surface of the slope and develops downward.As the slope increases,the overall slope deformation decreases,while the top deformation increases first and then decreases,and a turning point occurs when the slope is 75°.(4)The horizontal displacement of the slope surface decreases with the increase of the height of the aerial surface;The crack competition gradually decreases at the top of the slope,which indicates that the influence range on the right side of the goaf becomes larger.When the slope is large,the top subsidence increases first and then decreases with the increase of the height.When the slope is small,the amount of subsidence decreases with the increase of height.(5)Considering the characteristics of goaf surface and underground mining comprehensively,when the slope is less than 60°,the deformation and failure mode is mining-cleavage-shear-shear(slip),and the disaster is mining-induced landslide;When the slope > 60°,the deformation failure mode is as follows: mining-out-tearing-shear-dumping,and the disaster is mining-induced collapse.When the slope is 60°,it is the boundary slope of the slope deformation and failure mode,and both of the above two modes are possible.With the slope increasing,the disaster changes from mining landslide to mining collapse,and the scale decreases gradually.With the increase of the height of the open surface,the deformation and failure modes of the slope are the same,but the scale of the deformed body becomes larger,so does the potential threat.(6)Three notable characteristics of the gently dipping mining slope: steep dip joints,underground mining,and good frontage conditions.Under the same conditions of underground mining,the foregoing slope can distinguish the potential failure mode and disaster type of the slope,the foregoing height can judge the scale of the disaster,and the foregoing slope and height can serve as the deformation development trend of the slope.