Research On Influence Of Coal Mining Face Layout On Slope Deformation Characteristics In Loess Valley Area

Compared with the plain area,due to its unique landform and lithological characteristics,a series of geological and environmental problems caused by coal mining in the loess valley area are more complicated.In addition to ground collapse,ground fissures,and soil erosion,it may also induce sudden geological disasters such as collapses and landslides,which pose a serious threat to the safe production of the mining area and the safety of the lives and property of the people.The field investigation found that the layout of the coal mining face has an important influence on the deformation characteristics of the slopes on both sides of the loess valley area.Studying the deformation characteristics and instability and failure mechanism of the slopes on both sides of the loess valley under different coal mining face layouts can provide a reference for the selection of the coal mining face layout and mining methods during coal mining in the loess valley area.And,it can also provide a reference for the evaluation of geological hazards in the loess valley area and the prediction of the deformation and damage of mining slopes and surface protection,so as to reduce the loss of people and property.This article first summarizes and analyzes the stress distribution characteristics and deformation characteristics of overburden rock and slope in mined-out area under the condition of longwall mining in gently inclined coal seam.The failure modes of soil slope instability under the influence of mining in gently inclined coal seam are summarized.Based on the above analysis,Xujiagou and Tielougou in the mining area are selected as the research objects,and the three-dimensional numerical models are established by using the Midas/GTS NX finite element numerical simulation software based on the geological conditions and coal mining conditions in the research area.The reliability of the numerical simulation is verified by comparing the simulation results with the deformation characteristics of the slope surveyed on site.Finally,the Xujiagou area is used as a prototype to establish multiple excavation conditions by changing the layout of the coal mining face,simulating the changes in the displacement,stress,and strain of the slope under differentcoal mining face layouts,and summarizing the deformation characteristics and instability and failure mechanism of the slope under various coal mining face layouts and make a comparative analysis of their deformation degree.The result shows:(1)When the advancing direction of the coal mining face is parallel to the orientation of valley,if the goaf is located behind the slope,the slope is displaced backward by the traction force at the slope.At this time,the stability of the slope is good,and instability is not easy;If the goaf is located below the slope,the instability and failure process of the slope above the goaf is pulling of upper slope body-creep deformation of middle slope body-compression of upper slope body of lower slope body-shear failure of front edge of slope body-crack running through slope body-overall sliding and the failure mode is a thrust-type landslide;if the goaf is located in the middle of the valley,the instability of the slope on both sides of the goaf is rupture of lower slope body-instability and failure of lower slope body-traction of lower slope body to move upper slope body-creep deformation of upper slope body-overall sliding and the failure mode is traction landslide.(2)When the advancing direction of the coal mining face is perpendicular to the orientation of valley,the failure mode of the slope with the same direction as the advancing direction of the working face is thrust-type landslide,and the failure mode of the slope with the opposite direction of the advancing direction is traction landslide.The deformation characteristics of the slopes on both sides of the valley when the advancing direction of the coal mining face is diagonal to the orientation of valley are basically the same as when the advancing direction of the coal mining face is perpendicular to the orientation of valley.(3)When the coal mining face crosses the valley,the maximum deformation value of the mining slope in the direction of the free surface is affected by the angle between the advancing direction of the coal mining face and the orientation of the valley.When the included angle is 0°,that is,the coal mining face advance direction is parallel to the orientation of valley and the working face is in the middle of the valley,the maximum deformation value of the slope in the orientation of the free surface is the largest.As the angle between the advancing direction of the coal mining face and the orientation of the valley increases,the maximum deformation value of the slope in thedirection of the free surface gradually decreases.When the advancing direction of the coal mining face is perpendicular to the orientation of the valley,the maximum deformation value of the slope in the direction of the free surface is the smallest.