Mechanism And Prevention Of Rockburst In Out-roadway Induced By The Motion Of Multi-workface Excavation

Rockburst is one of the dynamic hazards in mining engineering. Within the stressconcentrate zone, especially the forehead stress zone, the frequency of rockburst is higher.Therefore, lots of studies have been focusing on this area. However, as the mining actives arestride forward to deep coal seam, some out-roadway which is far away from the mining areabegan show rockburst dynamic hazard. In order to prevent the rockburst disaster in out-roadway,this paper intends to do some research on this issue.After analyzing the structure of surrounding rock, we divided the surrounding rock into foursections along the mining direction and into three sections along the upward direction. In otherwords, the profile of mining workface which across the middle point of workface is dividedhorizontally into remnant stress zone, stress relieve zone, high stress zone and normal stress zoneand vertically into caving zone, fault zone and bend-sink zone. Analysis of the deformation andfracture of overlying strata demonstrate that the steady structure of overlying strata will bere-disturbed by the mining activities. This would cause the rockburst disaster. For multi-seammining, the stress of prepare roadway surrounding rock would increase as the mining activeprocessing. Overlying strata of up-seam is likely to break with the disturbance of miningactivities in low-seam. This kind of break has more serious burst consequence.The key cause of rockburst is the concentration of elastic energy in surrounding rock, whichoutcast suddenly, seriously and dynamically. Stress concentration causing the elastic energy hasthree main resources including stress disturbance of roadway dig, stress disturbance of miningand dynamic disturbance of seism. In the energy view, if the surrounding rock does not haveburst liability, the released energy of roof strata is less than the fracture energy of coal,E1E2.The studies of rockburst under static stress disturbance and dynamic stress disturbance show thatrockburst under dynamic disturbance release more energyp(t)2/2than that under static stressdisturbance.Different kinds of rock fracture activities cause different seism. Based on the GDEMmethod, we analyzed the displacement disturbance of stretch seism, sheer seism andstretch-sheer seism on surrounding rock. The results demonstrate that the displacement directionof seism disturbance vary according to the type of seism center. The closer the point to the seismcenter the more serious the displacement disturbance on the point. The degree of thedisplacement of surrounding rock decreases significantly with the increase of distance betweenthe point and the seism center. The displacement cloud pictures of surrounding rock aresymmetry according to the different type of seism center. The geologic structures have obviouseffect on seismic energy transport. Stretch seism center has the biggest displacement disturbance, followed by stretch-sheer seism center. Displacement disturbance of sheer seism center is thesmallest among the three types of seism centers.The seismic data of-1000m west zone in zhangshuanglou mine demonstrate that mostseismic activities are small energy seism, and the number of large energy seism is smaller. Thereis an apparent intermission of seism activate before rockburst disaster. Based on multi-parameteranalyze method, we determine the prepare roadway coal column and the fault zone of7thcoal ishighest hazardous zone, the cutting roadway of7thcoal and the fault zone of9thcoal is middlehazardous zone. Moreover, the paper introduced the rockburst prevent methods, such as acrossroadway mining, re-dig roadway, as well as the stress release methods, such as big diameterstress release hole, coal burst stress release, cut roof method, et al.