Study On Regulation Of Rockburst Induced By Faults Under Horizontal Sublevel Mining In Steeply Inclined And Thick Coal

In recent years,the rockburst has become more frequent in steeply inclined and thick coal,and faults and other geological structures often exists at the sites where the rockburst occurs.However,the mechanism of fault-induced rockburst is not clear in steeply inclined and thick coal at present.Therefore,the theoretical analysis,numerical simulation,monitoring and prevention measures are used to study the regulation of faults-induced rockburst and prevention techniques under horizontal sublevel mining conditions of steeply inclined and thick coal seams.The characteristics of strong shock and rockburst nearby faults are statistically analyzed in horizontally mining of steeply inclined and thick coal.In the condition of fault skewing with coal,when the workingface approaches the fault,the mine shock energy and frequency increases sharply;when the workingface passes through the fault,the mine shock energy decreases gradually;in the condition of the fault be parallel coal,the mine shock energy and frequency is little change.According the local positional relationship between the fault and coal,the faults are divided into three categories:faults in the parallel coal on the roof side,faults in parallel coal on the floor side,and faults skewing with coal.This paper analyzes the roof collapse modes and inducing mechanism of steeply inclined and thick coal under three types of faults.A roof instability model was established and it was concluded that when the angle between the fault and the coal is less than 90°,the roof is more likely to destabilize;when the angle between the fault and the coal is greater than 90°,the roof is more stable.The mechanism of fault induced rockburst was analyzed from the perspective of dynamic and static load,and the fault slip criterion under static load stress field was established.It was concluded that when the angle between fault and coal seam is 35°and 70°,the static friction coefficient is 0,and the fault is most likely to slip.Numerical simulation study the induced-rockburst regulation of three types of faults in horizontally mining of steeply inclined and thick coal.Faults parallel to the coal on the roof side:The shear stress and the normal stress of the fault plane change synchronously under the influence of mining depth,which isn't causing fault slip.The faults at the roof 5m distance from the coal seam have little effect on the stress of the roof,and the stress of the roof at 15m away from the coal seam is maximum at the time of back mining to fifteenth delamination,and the influence of the faults at positions of 24m,30m,40m and 50m away from the coal stress increases with depth.faults in parallel coal on the floor side:the shear stress of the fault plane does not change much under the effect of mining depth,the normal stress increases,and the fault does not slip.Distance from coal 5m-35m on the floor side,both the vertical and horizontal stresses of the soleplate increase with depth,stress the 15^th coal reaches the maximum,when mining back to 20^th coal,the floor breaks and the vertical stress decreases.Faults skewing with coal:when the workingface is near the fault,degree of the faults activation from large to small is:30°>15°>75°>60°>45°>105°>90°;When the face passes through the faults,degree of fault activation at different angles is small;When mining the first layer to five layers,the degree of influence of the fault on the stress of the roof from large to small is:30°>15°>45°>60°>75°>105°>90°;When mining back to the 10^th coal,The 60°fault has the greatest effect on the roof;When mining back fifteen coal,coal has been cut seamlessly by fault in the workingface.According the research results,the monitoring and prevention of the fault zone under the condition of horizontal sublevel mining of steeply inclined and thick coal in Yaojie No.3 Mine was determined,and drill cutting,support resistance observation and microseismic method and roof presplit blasting,coal pressure relief blasting and floor blasting was adopted,ensuring the safety of the working face,and achieving good results.