Research On Influence Of Upper And Lower Wall Mining On Slope Deformation,Failure And Stability Conditions

While coal mining and supply bring great convenience to all mankind,the continuous expansion of coal mining scale and the continuous deepening of mining depth have caused extremely serious damage to the entire ecological environment.In my country,especially in Shanxi,unstable slopes There are many types,great dangers and extremely high frequency.Underground mining leads to instability of mountain slopes,which in turn causes a series of geological disasters such as landslides and collapses,which pose a huge threat to the life safety of people in the mining areas and the development of the local economy.The existence of faults is relatively common in the process of coal mining,and it is also a geological structure with farreaching influence and complex structure.As a weak layer,its strength is far less than that of the surrounding rock layers.The existence of faults will cause the deformation and damage of the slope.And stability becomes more complex,and mining the upper and lower walls separately has different effects on the slope.Therefore,combined with the theory of surface subsidence,it is of great significance to study the influence of the upper and lower walls on the deformation,failure and stability of the slope.In this paper,taking into account the complexity and particularity of the geological environment conditions in Shanxi Province and the actual situation of coal mining,in view of the geological and topographical conditions of Shanxi Province,which are dominated by loess and mountainous areas,the Fengmaoding slope,which is a very typical representative,is selected as the study area.By using the finite element numerical simulation software Midas GTS NX,aiming at a typical fault in the study area and making reasonable modifications,two numerical models are established to simulate the mining of the upper wall and the mining of the lower wall,respectively.Stress,shear stress and stability are comprehensively analyzed,and the similarities and differences between the two laws are explored;and 18 numerical models are established by changing the dip angle,fault thickness,and fault distance of the fault to simulate the change of the geometric properties of the fault.Mining and footwall mining were conducted to explore the influence of the surface movement and deformation of the slope and the stability of the slope.The results are as follows:(1)Under the mining conditions of the hanging wall,the fault divides the slope into two parts,and the displacement of the hanging wall is obviously larger than that of the foot wall.With the activation of the fault,the fault will block the movement and deformation of the overlying rock in the goaf.effect,the displacement of the footwall is relatively reduced,and the position of the maximum subsidence moves from the center of the goaf to the downhill direction;under the footwall mining,the subsidence of the top of the slope is significantly higher than that of the hanging wall,indicating that the fault hanging wall The footwall generates a certain pushing force,and the mining faults in the footwall are easier to activate,while the blocking effect on the slope is relatively small.(2)The fault is a weak layer,and there will be a large shear stress concentration area at the junction of the fault and the coal seam.With the continuous activation of the fault,the shear stress will increase faster,and deformation and damage will occur.On the whole,the footwall mining faults It is easier to activate,and the shear stress at the slope angle is the largest,resulting in cracks,indicating that the upper wall mining has stronger control on the slope toe.(3)The stability coefficient of lower wall mining before and after excavation is greater than that of upper wall mining,indicating that during lower wall mining,the slope is more affected by coal seam excavation,which is not conducive to slope stability.(4)The fault dip angle,fault throw,and fault thickness will all affect the surface movement,deformation and stability of the slope.For hanging wall mining,the increase of fault dip angle and thickness is conducive to fault activation,which will increase slope subsidence,which is not conducive to slope stability;For footwall mining,the increase of fault throw and fault thickness is conducive to fault activation,which will increase slope subsidence,which is not conducive to slope stability.