Penghui Guo

The surrounding rock of deep roadway is in the state of limit stress equilibrium, under the environment of high vertical stress and strong tectonic stress, the dynamic load disturbance is prone to impact damage, which seriously hinders the safe and efficient production of the mine. Aiming at the problem of frequent rock burst in the main roadway of Gaojiapu Coal Mine, based on the analysis of the energy characteristics of microseismic monitoring of coal-rock burst failure in deep roadway, the evolution characteristics of different types of energy when coal-rock burst failure occurs in deep roadway under dynamic load disturbance are studied by means of theoretical analysis, numerical simulation and engineering practice, and the energy criterion of burst failure of surrounding rock in deep roadway is formed. The field microseismic monitoring results show that: when there is no impact danger in the roadway, the total energy of the microseismic day continues to remain at an energy level of less than 10³ J, which is in a state of stable energy release; Weak impact danger, the total energy of microseismic day is 10⁴ J; in the case of medium impact risk, the total energy of a microseismic day during one month is 10⁵ J; strong impact danger, the total energy of two or more microseismic days is 10⁵ J during a month, and the energy fluctuates greatly. The results of numerical simulation show that: at the initial stage of dynamic load disturbance, the plastic zone of roadway surrounding rock roof expands rapidly; in the middle and late stages of dynamic load disturbance, the plastic zone of roadway surrounding rock gradually develops to the floor, which will cause floor heave under the influence of bottom coal. The expansion of the plastic zone consumes the shape change energy stored in the coal and rock mass, if the dynamic failure occurs in the coal and rock mass, the volumetric strain energy stored in the coal and rock mass will be converted into kinetic energy, forming the roadway rock burst. Based on the results of numerical simulation and theoretical analysis, the optimum angle of large diameter drilling construction in a panel roadway is put forward.

With the reduction and depletion of shallow energy, the mining depth of coal around the world is increasing year by year, and the mining depth of some coal mines in China has reached kilometers. The main roadway near the goaf with the deep high static stress is very easy to be damaged after being disturbed by the mine earthquake. Taking the main roadway in the no. 1 mining area of Gaojiapu coal mine in Binchang mining area, Shaanxi Province, China, as the engineering background, the high-energy mine earthquake monitored by the on-site microseism is equivalently simulated through the dynamic module of FLAC^3D, and the spatial-temporal rotation characteristics of the principal stress of roadway surrounding rock under the disturbance of mine earthquake are studied and analyzed and put forward corresponding prevention and control measures. Research shows early stage of mine earthquake disturbance, roadway roof is first affected, and the principal stress of the roof has the trend of deflection to the side of the goaf. In the middle stage of mine earthquake disturbance, the main body of roof principal stress deflects to the side of goaf, and the deflection range is large. In the later stage of mine earthquake disturbance, the principal stress directions in the surrounding rock reverse rotation, and the reverse rotation angle of the principal stress direction in the roof is the largest. Finally, the asymmetric distribution characteristics of principal stress rotation are verified by using the asymmetric deformation phenomenon on both sides of roadway surrounding rock. Based on the rotation characteristics of principal stress under the dual influence of mine earthquake disturbance and goaf, optimize the layout scheme and blasting parameters of blasting pressure relief holes. The transmission direction of principal stress can be changed by blasting pressure relief method; meanwhile, the transmission of principal stress can be blocked; through the comparison of microseismic activity law before and after pressure relief, pressure relief effect is good. The research results can provide a certain reference basis for coal mine roadway pressure relief and reducing disaster conditions.

Deep high static loading roadway is extremely prone to rock burst under dynamic load disturbance. The “force-energy criterion” for the failure of surrounding rock in such deep roadways and the “energy criterion” for the rock burst was established by considering the stress and energy evolution characteristics of rock burst under this circumstance. Under the engineering background of the main roadway in No.1 mining area of Gaojiapu Coal Mine in Binchang Mining Area, Shaanxi Province, China, the partial stress field and distortion energy field of surrounding rock in the main roadway and the spatial-temporal evolution laws under dynamic load disturbance were simulated and analyzed by using a built-in dynamic module of FLAC^3D. Results show that after the dynamic load disturbance, the partial stress and distortion energy are concentrated in the shallow part at two walls of the roadway in the early phase. With the continuous propagation of dynamic load stress wave, the partial stress and distortion energy are transferred to the deep part. The sudden high-energy release occurred in the peak zone of partial stress, leading to the plastic failure of coal and rock mass. Subsequently, the distortion energy was fully accumulated in the original plastic zone and transferred from shallow surrounding rocks to the deep surrounding rocks in the roadway, where the partial stress and distortion energy of coal and rock mass reached the yield conditions. Thus, the original plastic zone was sharply expanded, thereby forming a new plastic zone. The coal and rock mass experienced an approximately static failure when no residual energy (ΔU) was found in it. When ΔU > 0, the rock mass experienced dynamic failure, and ΔU was mainly the volume transformation energy, which is approximately one-half of the total elastic strain energy. ΔU was transformed into the initial kinetic energy of broken coal and rock mass. Thus, the coal and rock mass are burst out. In severe cases, this condition was manifested by the rock burst in the main roadway. An optimization scheme of prevention and control measures for rock burst was proposed on the basis of the above conclusions. The microseismic activity laws before and after the unloading were compared, and a good effect was achieved. The research results can lay a theoretical foundation for predicting and preventing rock bursts in coal mines by actively regulating the disaster-pregnant environment and mitigating the disaster-inducing conditions.