Study On The Influence Of Normal Faults On Overlying Strata Movement And Stress Evolution In Adjacent Working Face

Fault is a common geological structure in mining.The existence of fault breaks the continuity of strata,and changes the stress distribution of the original rock in the surrounding area,it may induce fault activation and lead to mine dynamic disaster,which will seriously affect the safe and efficient mining of working face.In recent years,many scholars at home and abroad have done a lot of research on the movement and evolution of the surrounding rock when the working face passes through the fault,but little research has been done on the condition that the fault develops along the working face strike.Therefore,it is of great significance to study the influence of faults on strata behaviors of adjacent working faces in order to enrich the control theory of surrounding rock in Stope and guide field engineering practice.In this paper,through rock mechanics experiment,similar material simulation experiment,numerical simulation,theoretical analysis and field monitoring,etc.,the influence of strike normal fault on the movement of overlying strata and the evolution law of mining stress in adjacent working face is systematically analyzed,and the stability control measures are put forward by on-site monitoring:As the working face approaches the fault,the " Inverted trapezoid" overlying rock structure formed by the fault line and coal body between the fault and the working face evolves to the " Inverted wedge",and the structural stability is enhanced,the " Inverted trapezoid" overlying rock structure in the footwall has the tendency of turning to the working face under the action of self-weight stress,along the working face tendency,the roof near the side of the fault is easy to collapse as a whole,while along the direction of the vertical coal seam,under the influence of the dip angle of the fault,the roof of the working face of the footwall is more easily to turn to the working face with the integral overturning cutting and breaking,and the stability is poor.When the distance between the footwall working face and the fault is more than 30 m,the fault has no obvious influence on the working face,and when the distance is less than 30 m,the stress increase amplitude of the coal body between the fault and the working face suddenly increases,the difference of the lead abutment pressure of coal wall and the subsidence of roof at the two ends of working face is gradually enlarged.Compared with the two faces,the influence of the fault on the abutment pressure of the upper face is more obvious,and the influence on the stress concentration degree of the coal body between the lower face fault and the working face is more obvious,at the same time,the subsidence of the roof on the side facing the fault is larger than that on the other side of the working face,indicating that the distribution of the roof stress and displacement along the dip of the working face gradually appears as the working face approaches the fault,the smaller the distance between the fault and the working face,the more intense the roof movement of the two plates.The failure of rock beam in two plates is affected by elastic modulus,thickness,dip length of working face and dip angle of fault,the difference of load transfer capacity between upper and lower wall rock leads to different stress state of roof of two walls.When the maximum tensile stress of rock beam exceeds its allowable stress,it will break and lose stability,and the lower plate roof than the upper plate more vulnerable to instability.Based on the ground pressure monitoring in the face of Linzheng fault strike arrangement in Ruineng coal industry of Huangling County coal mine,the average working resistance of the support along the face inclined to have the characteristics of " Central area>side of boundary coal pillar>side of fault".As the working face is near the fault,the roof of the area near the fault is broken,the working resistance of the support is small and the loading is unstable before and after the coming pressure.In view of the uneven distribution of faults along the strike of the working face and the variation of the distance between the fault and the working face,it is difficult to control the stability of the surrounding rock,the stability control measures of roof and roadway surrounding rock along strike are put forward to ensure the safety mining of the face.