Stability Analysis of Shotcrete Lining for a Mine Shaft Using the Finite-Discrete Element Method

This paper aims to provide insights into the effectiveness and failure mechanism of shotcrete lining in mine developments. For this purpose, a two-dimensional numerical program based on the Finite-Discrete Element Method (FDEM) was utilized to simulate an instrumented section of a 10-m diameter mine shaft at a depth of 1.2 km in an average quality rock mass. The shaft wall was supported by shotcrete and concrete liners installed at 3 m and 12 m behind the face, respectively. However, only shotcrete support was considered in the numerical simulations. The shotcrete liner was modelled as a material with a thickness of 50 mm and calibrated based on the mechanical properties of early-age fiber reinforced shotcrete obtained from available laboratory test results and empirical equations. The rock material near the modelled shaft was calibrated against the extensometer measurement data. It was found that the shotcrete liner fails due to bending caused by the shaft wall convergence and local rock mass bulking. Therefore, for the rock mass and in situ stress conditions representative of the mine shaft, it is concluded that the addition of a permanent support element, such as a concrete liner, is necessary for the long-term stability of the shaft.