Characteristics of ground pressure and mechanism of coal burst in the gob side roadway at Xinjie deep mining area

The main mining areas of coal resources are moving to the western China,some western mines reach a deep mining level. The coal burst of gob side roadway occurs frequently,which threatens the safe mine production seriously. In this paper,the characteristics of ground pressure and mechanism of coal burst in the gob side roadway at Xinjie deep mining area is studied by site investigation,theoretical analysis and numerical simulation. The mechanical model of gob side roadway in front of longwall face under the dynamic and static combined loading is established. This model focuses on the initial weighting and full mining stages. The principle of dynamic and static combined loading for the gob side static load,the front abutment pressure and the mining induced dynamic load is proposed by finely describing the static load and mining induced dynamic load in different stages. The stress criterion of coal burst of gob side road- way is provided. The mechanism of coal burst of the gob side roadway is discovered,the high stress and energy will transfer from the roof strata to the rib and floor of roadway,which can result in the stress concentration and energy ac- cumulation. As the stress and energy reaches the threshold value of the coal burst,the coal burst in gob side roadway will occur. Moreover,as far as the coal burst disaster in gob side roadway with thick and hard stratum in the roof,the prevention methods for coal burst are proposed. The method consists of “ cutting off the dynamic load sources”,“ re- ducing the static load stress concentration” and “ using energy absorption bolt anchorage with constant resistance at large deformation”. The results show that the gob roof of adjacent double longwall faces can form asymmetrical T-type structure when the initial weighting stage in gob side longwall face,the sub-key stratum ( SKS) I is broken,but the SKS II is not broken. The roof weighting of longwall face is small,the static load in the surrounding rock of gob side roadway is large,and the mining induced dynamic load is relative small. However,the gob roof of adjacent double long- wall faces can form a symmetrical T-type structure at the periodic weighting (full mining) stage. The double sub-key stratums are broken,the static load and mining induced dynamic load are both larger in the surrounding rock of gob side roadway,which can induce a coal burst in gob side roadway easily.