Study on regional stress background and prevention of the rock burst accident on October 20th, 2018 in the Longyun Coal Industry area, Shandong, China

Objective The stability of underground chambers such as mine tunnels and transportation tunnels is closely related to the stress environment of the surrounding rock mass and the geological conditions of the area. Analyzing the relationship between deep-seated stress and factors such as the orientation and shape of underground chambers can help to proactively mitigate the risks associated with chamber excavation. Methods This study, set against the background of the rock burst accident on October 20th in the Longyun Coal Industry area in Shandong, reveals the current stress environment of the shallow crustal layers in western Shandong through in-situ stress measurement and monitoring work. Results According to the characteristics of the current ground stress field near the Longyun coal mining area, the study investigates the regional stress background that led to the rock burst accident and proposes corresponding prevention and control suggestions from the perspective of ground stress. The results indicate that the magnitude of the principal stress generally increases linearly with depth within the measurement range, with the maximum horizontal principal stress ranging from 3.48 to 20.76 MPa and a gradient of 0.0182 MPa/m with increasing depth, while the minimum horizontal principal stress ranges from 3.44 to 14.95 MPa with a gradient of 0.0130 MPa/m. The maximum horizontal principal stress azimuth in the area ranges from NE 43°to 89°, with an average azimuth of NE 75°. The tectonic action in the shallow crust is mainly horizontal, but with increasing depth, they gradually transition to vertical. Conclusion The triggering mechanism of the rock burst accident in the Longyun Coal Industry area on 20th October is primarily attributed to the vertical stress exceeding the horizontal principal stress, indicating a current extensional stress environment, especially when the tunnel orientation is parallel to the direction of maximum horizontal principal stress. It is suggested that the angle between the tunnel axis and the direction of maximum horizontal principal stress in the Longyun Coal Industry area should be between 60° and 90°, and that the tunnel roof can be designed as an arch-shaped roof to ensure the stability of the tunnel rock mass.