Mechanism analysis of rock damage and failure based on the relation between deep chamber axial variation and in situ stress fields

The demands for deep underground mining and construction are increasing with the continuing development of society and the economy. Deep underground chambers function as primary elements in deep underground mining and other subsurface facilities. Therefore, rational designs of such chambers would play a pivotal role in construction safety and economic efficiency. The primary goal of this study is to reveal the relation between the in situ stress field and axes of an elliptical cross section of an underground chamber. Based on the rock deformation and damage, a numerical model is developed to define the heterogeneous damage evolution near the chamber. In this parametric study, we characterized the damage evolution in response to the chamber’s cross-sectional shape, lateral stress coefficient, and tectonic stress azimuth, thus introducing the critical lateral stress coefficient to define the chamber stability. Furthermore, a case study of a −2000 m chamber in the Sanshandao gold mine was conducted using the proposed model to optimize the shape, design, and location analysis of the underground mining chamber. Simulation outcomes show that the damaged area and stress concentration near the chamber are minimized when the axis ratio is equal to the lateral stress coefficient. The damaged area is determined by the in situ stress configuration; a high lateral stress coefficient sees a pronounced increment in the tension stress inside the roof and floor of the chamber, resulting in an exponential enlargement of the damaged area. Compared with the shallow underground chamber, the deep chamber is more sensitive to an increase in the lateral stress coefficient. With an increase in depth, the critical lateral stress coefficient gradually decreased to 1. The larger horizontal tectonic stress in the deep strata causes damage accumulation in the roof and the floor, encouraging rock outbursts in the damaged zones. To conclude, to optimize the design and minimize the outburst hazard for a deep underground chamber, the chamber’s cross-sectional shape, axes ratio, and direction must reasonably reflect the in situ stress field.