Research on the compressive deformation and re-bearing capacity characteristics of broken rock mass in deep roadway

Under the deep high ground stress conditions, the large deformation roadway is mainly due to the enhanced expansion deformation and shear deformation of the surrounding rock, which leads to an elevated fragmentation degree of surrounding rock. At this time, the support object of the anchor is transformed from the fissured rock mass to the broken rock mass (BRM). Under the action of the anchoring force, BRM and anchor carry the secondary stress after the excavation of the roadway. In this paper, constrained compression tests of BRM at different grain sizes are carried out using indoor tests and numerical simulations. The test results show that the compressive deformation curve of the BRM includes three stages of slip flow deformation, fracture-filling deformation and compacted elastic deformation. As the grain size of the BRM increases, the maximum axial deformation and the sustained compressive time gradually increase, and the porosity and compactness inside specimen gradually decrease. As the freedom degree of the BRM increases, leading to the gradual increase in the number of acoustic emission events and cumulative energy at different stages, the weight proportion of rock mass at each stage of the grain size after compression screening gradually decreases. Based on a set of multi-view 2D images of BRM, the morphological features of the BRM are quickly reconstructed. The cluster model of the BRM is established in PFC^3D software by using the fragment replacement method (FRM) to realize the whole process simulation of the BRM. It is found that the BRM is dominated by tensile failure during the compressive process. As the grain size of the BRM increases, the contact force of the skeleton force chain gradually increases and the number gradually decreases, and the internal structural stability of specimen is weakened. The porosity loss and the coordination number inside specimen gradually increased, and the secondary fragmentation phenomenon is obvious. Therefore, in the deep roadway drilling and blasting excavation process should try to ensure the presence of large-scale BRM in the surrounding rock.