The Interaction Mechanism Of "Support-surrounding Rock" In Pitching Oblique Mining Area Of Steeply Dipping Seam

In the mining process of steeply dipping seam,there are still som e problems such as uneven load collection of support,proine to falling down,frequent occurrence of coal wall and flying gangue.The comprehensive mechanized mining method of long wall pitching oblique mining is an effective way to solve the above problems.The research on the interaction mechanism of "support-surrounding rock" in pitching oblique mining area of steeply dipping seam can not only guide the selection of support in actual engineering,It is also of great significance to enrich the theory of longwall mining in steep seam.In this paper,based on the engin eering geological and mining technical conditions of lvshuidong coal mine,the stress,displacement evolution characteristics and support surrounding rock interaction characteristics of th e surrounding rock in the face with large dip angle and long wall pseudo downdip are studied by means of field monitoring methods,physical similarity simulation and numerical simulation.The main conclusions are as follows:lie weighting of steeply dipping seam longwall pitching oblique working face has regionality and time sequence.The results show that the pressure in the middle part of the working face is the first,the upp er part is the second,and the lower part is the last;the duration of weighting is the longest in the lower part,followed by the upper part,and the middle part is the shortest.The roof caving of working face has time sequence,and the filling of gangue to the lower part of working face is a dynamic proc ess which can be divided into four stages.? The results show that the upper boundary of gangue filling is in a straight line along the strike in the area far away from the support.The effect ot the support is "smash,press,push",the lower part of the tilt is the thrust acting on the rear side of the support,and the upper part is the weakest.The difference between the direct roof and the basic roof in the middle of the working fece on the support is that the direct roof has short acting time,low strength and high frequency;the basic roof has a long time,high strength and low frequency.The action form and degree of the broken roof on the support in different areas of pitching oblique mining area of steeply dipping seam are different.The action of the middle falling gangue on the support performance "Shocking,pressing and pushing".The lower part is mainly the thrust acting on the rear side of the support,and the upper part is the weakest.The difference between the direct roof and the basic roof in the middle of the working face is that the direct roof has short acting time,low strength and high frequency,while the basic roof has long acting time,high strength and low frequency.With the increase of mining space,the support effect of the support along the working face inclines to the lower area>the middle area>the upper area.The coal wall has obvious effect on the stability of the support,which leads to the maximum movement speed of the support side plate.The reverse support function of the support inhibits the top plate movement and has obvious effect on the middle and lower part of the working face The movement of the support base is different in different regions due to sliding,and the support is prone to tilt forward and lose stability.As the mining space increases,the stress in the middle area of the support column is the largest,the stress in the lower area of the base is the largest,and the stress in the upper area of the working face of other parts of the support increases obviously,and the upper area>the middle area>the lower area;There are differences in the regional characteristics between the pillar and other parts of the support,the displacement of the column is in the middle region>the upper region>the lower region,and the other parts of the support are in the upper region>the middle region>the lower regiont.The stress in the lower part indicates that the surrounding rock in the middle and upper part of the working face is relatively active,and the support is prone to instability.The support arrangement of the working face is stepped,the area with obvious interaction between supports is in the middle and upper part of the side of the top plate and the side pushing device at the bottom of the support,and has obvious regional characteristics.In the lower area of the working face,the contact surface of the support forms stress concentration and maximum displacement on the side pushing device at the bottom of the support;in the middle area of the working face,the stress concentration area and the maximum displacement area of the contact surface of the support It is easy to change,during which it is easy to topple and swing the tail;in the upper middle area of the working face,the support The stress concentration area and the maximum displacement area of the contact surface are located in the side pushing device at the bottom of the support and the side middle and upper part of the top beam of the support.The instability mode of the support is more complex.The support is prone to fall sideways,swing tail,up and down staggered movement,and there are phenomena of top beam separation between the supports and roof hanging.Through the field engineering practice,the support structure and support parameters are optimized to meet the production requirements of the working face,so that the stability of the"support-surrounding rock" system is better,and good social and economic benefits are achieved.