Post-mining failure characteristics of rock surrounding coal seam roadway and evaluation of rock integrity: a case study

Accurate knowledge of the distribution characteristics of structural planes in rocks is beneficial in the evaluation of rock mass quality and roadway support decision-making. In this study, in situ monitoring results were used to analyse the deformations and failure characteristics of the rock surrounding the main haulage roadway in the Huahong coal mine to establish a deformation and failure model for the surrounding rock affected by mining. According to an analytic hierarchy process, a comprehensive evaluation index for the degree of fracturing in the rock surrounding the coal seam roadways was proposed. Additionally, a classification method based on the comprehensive widths of the structural planes (CWSPs) inside the complete rock mass was proposed to determine the quality of the surrounding rock. The structures of the rocks surrounding the main haulage roadway in the mine before and after coal mining were observed in situ at monitoring station no. 22. Borehole imaging technology was used to classify the surrounding rock quality using the CWSP-based evaluation method. The results indicated that the roof rock was mildly affected by mining; the corner rock had a large degree of fracturing in the central part of the borehole and a small degree of fracturing at both ends; the rib rock was highly fractured. These evaluation results were consistent with the macroscopic characteristics of the surrounding rocks, indicating the reliability of the deformation and failure model for characterizing the surrounding rocks affected by mining.