Physical Modeling Investigation On Failure Mechanism of Layered Surrounding Rock And Deformation Characteristics Based On Digital Speckle Correlation Method

In rock mass engineering such as underground coal mine roadway, underground tunnel and water conservancy and hydropower chamber construction, layered rock mass is a type of surrounding rock mass that is often encountered. Due to the influence of bedding structural plane, its deformation process and failure mode are obviously different from that of intact enclosed rock mass. For the layered rock structure of roadway, the previous studies mainly focused on the situation of no support or single bolt support, but there is still a lack of experimental studies on the mechanical properties and failure laws of surrounding rock under different support methods. In this paper, the deep roadway and surrounding rock environment with a buried depth of 742-877m are taken as the engineering background, which is located in Anhui Province, China. Based on the similarity theorem and similarity criterion, river sand is used as aggregate, gypsum and cement are used as cementing material. According to the test results, 5:0.7:0.3, 6:0.3:0.7 and 4:0.5:0.5 of river sand, gypsum and cement were selected as the similar materials to simulate the surrounding rock of the roadway, and the bedding plane structure of the surrounding rock of the roof and floor near the roadway was designed by using the self-developed similar material physical model test bed. Digital Speckle Correlation Method (DSCM) is used to analyze the deformation evolution process of roadway surrounding rock under three supporting schemes: no-support scheme, bolt support scheme, and synergistic support of bolt and anchor cable. Based on this, the failure mode and instability mechanism of deep layered surrounding rock are further discussed. The results show that the tensile and shear resistance of laminated roof surrounding rock is weak, and the laminated roof is easily separated from each other at the bedding plane without support, resulting in bending deformation and bed separation. After adopting effective support, the laminated roof surrounding rock is transformed into a composite beam bearing structure, and the stability of surrounding rock increases. The research results have certain theoretical guiding significance and engineering application value for practical engineering.