The stress distribution of coal and rock mass and the risk evaluation of rock burst in the composite structure area

The abnormal concentration of stress in the structure area of the working face is closely related to the rock burst. Based on the good correlation between the wave velocity and stress of the coal and rock mass, the seismic wave CT detection technology is widely used in the evaluation and warning of the risk of rock burst. However, the existing researches are mainly focused on simple conditions or single structure area. The composite structure area formed by multiple geological structures has not been discussed. Taking the 2305 fully mechanized working face of a mine in Shandong as an example, in the context of the concentration of microseismic events in the composite structure area and the occurrence of rock bursts, the seismic wave CT detection technology is used to obtain the stress distribution of coal and rock mass in the structure area and the characteristic index c including speed and speed gradient of seismic wave is introduced to analyze the stress distribution characteristics and the risk of rock burst. The research results show that: ① The concentration of microseismic events is related to adjacent structures. The concentrated areas can be divided into single or composite areas according to the number of structures, and can be divided into strongly or weakly disturbed areas according to the degree of disturbance. ② The strongly disturbed area composite structure area has the highest static stress concentration, and the weakly disturbed single structure area has the lowest stress concentration. The stress increase level of the fault single structure area is positively correlated with the degree of disturbance. The syncline in the weakly disturbed composite structure area has a significantly higher stress than the fault area. ③ The static stress concentration of the surrounding rock in the structure area is the main cause of intense surrounding rock activity. Based on the static load of surrounding rock and the dynamic load increment under the influence of mining, the risk of rock burst in the concentrated area of different microseismic events can be obtained.