Disaster-causing Mechanism and Control Technology of Strong Rock Pressure in Fully Mechanized Caving Face of Steeply Inclined Coal Seam

摘要

Under the condition of fully mechanized horizontal sublevel caving mining in steeply inclined and extra-thick seam,the problem of disaster caused by strong rock pressure is becoming increasingly prominent,which seriously restricts the safe production of the mine.It is urgent to study its mechanism to provide theoretical basis for the prevention and control of rock pressure.In this study,numerical simulation experiments are carried out to reveal the change characteristics of stress field,displacement field and plastic zone of the whole model after single slice mining in steep seam.Then,combined with the coal seam occurrence characteristics and mining methods,using the knowledge of mine pressure and rock mechanics,the structure model of stope overburden is obtained.The results show that under the complicated geological occurrence conditions of steeply inclined seams,it is difficult for roof strata to collapse in time under the condition of self-weight after mining,and a large area of roof suspension is formed.Under the combined action of transfer stress and bending stress of suspended roof,a triangular stress concentration area(SFC=2.5-3)is formed in the stope rock mass 6m-45m away from the roof roadway along the coal seam inclination,which makes the stress of roadway support system increase sharply and causes the occurrence of floor heave and side heave and other rock pressure phenomena.With the mining level extending to the deep,the stress concentration degree increases,and the rock pressure appearance also increases.When the stress reaches the ultimate tensile strength of roof strata,the roof collapses in a large area instantaneously,forming a strong rock pressure event.According to the structure and stress characteristics of overburden caving,the electromagnetic radiation intensity of coal and rock mass is obviously reduced by adopting multi-level roof blasting weakening technology of surface and underground,which reduces the stress concentration in coal and rock mass of working face,effectively controls the rock pressure problem of working face,and ensures the safety production of working face.