Experimental Study on the Failure Process of Fault Rock Bursts in Tunnels Based on a 3D-Printed Large-Scale Physical Model

Abstract

To investigate the failure process of fault rock burst in tunnels, a large-scale physical model test is conducted. Using the 3D printing technology of the wet-material extrusion deposition molding process, a 2 m × 2 m × 1.5 m model with a rigid closed fault is successfully printed. The mechanical similarities between the printed model and natural rock are quantitatively evaluated based on similarity theory. Based on the printed model, gradual excavation and multistage loading tests under true-triaxial stress conditions are conducted, and the failure process of the Jinping 11.28 rock burst is simulated. The test process is monitored with distributed fiber optical sensing, acoustic emission (AE), and video observation systems. During the excavation process, the surrounding rockmass is stable. The compressive strain concentration of the optical fibers near the fault is obvious. The AE events are mainly distributed along the fault and nucleated near the tunnel face. During the multistage loading process, the left sidewall primarily exhibits surface cracking accompanied by local spalling and slight rock burst, while several local intense rock bursts occur on the right sidewall, indicating the controlling effects of the fault on the failure modes. In the critical period of the intense rock bursts, the monitored stain of the optical fibers penetrating the fault changes from compressive to tensile suddenly, which can be related to the slip and dislocation of the fault. In addition, the AE events increase sharply and concentrate in the footwall of the fault. Failure mechanism analysis of AE events indicates that tensile failure is dominant during the excavation process, and shear failure increases significantly in the following multistage loading process. The research results can provide an important reference for better understanding of the fault rock bursts.