Modelling local failure around hard-rock tunnels based on a linked multiscale mesh strategy

Abstract

Research on local failure around hard-rock tunnels is the basis for revealing the failure mechanism of surrounding rock, predicting the ground excavation response and formulating effective support strategies. However, to characterize the failure morphology at a high resolution, a global uniform fine mesh numerical model may lead to a high computational time and space burdens. This study aims to develop a linked multiscale mesh modelling that establishes a high-resolution square mesh only near the free face around a tunnel instead of a global uniform fine-scale mesh. Then, the linked multiscale mesh strategy is implemented with a meso-damage smear numerical method to model local failure around hard-rock tunnels. The simulation results of laboratory- and engineering-scale examples indicate that the proposed strategy can save considerable computational cost; moreover, the downscaling refinement range and pattern have almost no effect on the surrounding rock failure results. It is shown that the combination of the linked multiscale mesh strategy and damage smear mechanical method presented in this study can be effectively employed for tunnel lightweight modelling, and this approach is very well suited for modelling hard-rock tunnel stability problems.