Study on in-situ stress distribution law of multi-coal seams mining in Wuhai Mining Area

To reveal the distribution patterns of the in-situ stress field and its primary controlling factors in the Wuhai Mining Area, scientifically evaluate the stability of engineering geological conditions, and provide a scientific basis for safe and efficient coal mining as well as disaster prevention and control, this study employs the hydraulic fracturing method to conduct in-situ stress measurements at 19 measurement points across six typical coal mines within the Wuhai Mining Area. The measured stress data are analyzed to thoroughly explore the characteristics of the in-situ stress distribution. The results indicate that the in-situ stress distribution in the Wuhai Mining Area is significantly influenced by tectonic stress. The number of measurement points exhibiting the stress pattern σ_H＞σ_h＞σ_v equals that of points showing σ_H＞σ_v＞σ_h, with nine cases each. Only one measurement point records vertical stress exceeding horizontal stress. The dominant orientation of the maximum horizontal principal stress is NW-trending, with the Gongwusu Mining Area being the sole exception where it displays an NE-trending orientation. The results demonstrate that the majority of the Wuhai Mining Area falls within the low-stress zone, followed by the medium-stress zone, with no high-stress or extremely high-stress zones identified. Furthermore, the results reveal a general linear relationship between principal stress magnitudes and burial depth. As the burial depth increases, the increase in horizontal stress is greater than that of vertical stress. The lateral pressure coefficient predominantly ranges between 1 and 2. While the functional form of the relationship between burial depth and the average lateral pressure coefficient aligns with Hoek-Brown’s proposed formulation, the specific numerical values differ. The maximum shear stress ranges from 0.13 MPa to 2.91 MPa, exhibiting an overall increasing trend with measurement depth. The principal stress difference ratio is primarily concentrated within the 0.3-0.4 range, reflecting the degree of horizontal stress anisotropy. These findings provide crucial empirical evidence for understanding the in-situ stress state and its controlling factors in the Wuhai Mining Area. They offer direct engineering guidance for optimizing coal mine roadway support design and preventing dynamic hazards such as rockburst in this region.