A fast mesh model for block generation in tunnels

Abstract

In rock tunnels, the intersection of discontinuities and excavation surfaces tends to generate rock blocks, resulting in disasters. The block generation approach is an important study. The element-assembling approach has advantages in terms of robustness and fine characterization; however, the computational speed is a bottleneck, and efficient subdivision of the rock mass is also urgently needed. In this paper, a fast mesh model for subdividing a tunnel-surrounding rock is proposed using a polyhedron-slicing algorithm, which has obvious advantages in terms of ease of implementation and low requirements for element quality. For the mesh model, a block-generation approach based on an element-assembling idea is presented, and it highlights three innovative measures for improving the computational speed: designing of a new polyhedron data structure for a fast polyhedron-slicing algorithm, the construction and maintenance of the connections between elements, and the use of a composite detection approach for the contact between a discontinuity and an element. The applicability and accuracy of the proposed approach for complex blocks are verified by two cases. Compared with traditional methods, the three measures can improve the computational speed by 45%∼55%, 25%∼35%, and 15% respectively. Combining them can improve the computational speed by about 90%, indicating that the effect is noticeable. Meanwhile, it has a limitation that a fast mesh model with excavation section is only suitable for tunnels, which can be solved by improving the slicing algorithm in the subsequent work.