Problems and countermeasures in the study of fracture propagation laws of rock mass under induction

The instability observed in most underground engineering projects is typically attributed to the expansion and penetration of fractures in the rock mass due to long-term “induction” effects, which alter the inherent strength characteristics of the rock mass. Consequently, the study of the spatiotemporal evolution patterns of fractures in rock masses is deemed crucial for elucidating the mechanisms and essence of rock instability and failure phenomena. In this paper, the current research status on the expansion of fractures in rock masses is introduced from three aspects: physical experiments, numerical simulations, and mechanical theory. Moreover, the issues present in current fracture propagation research are analyzed in conjunction with the evolution process of underground engineering and its requirements. To address these issues and better align with engineering requirements, a novel research approach has been proposed: methods involving similar materials, 3D printing, and acoustic emission are proposed. The composition and mixing ratio range of similar materials suitable for acoustic emission monitoring are determined through compression experiments on small samples, and then 3D printing techniques are employed to fabricate specimens with intersecting fractures for tensile and shear tests. Creep experiments are conducted to investigate the propagation patterns of fractures and their associated failure precursors through acoustic emission. Additionally, the changes in rock mass strength over time due to creep are analyzed. On this basis, a large-scale similar material model of fractured rock masses is established to investigate predictive models for excavation-induced changes in fracture parameters over time. Furthermore, the relationship between the initiation time of rock mass collapse, fracture parameters, and excavation space is explored. The evolution mechanism of fractured rock mass collapse is aimed to be revealed, along with the prediction of the timing and extent of collapse. The theoretical support provided by these findings is intended to contribute to the long-term stability and collapse control of underground engineering projects.