Lattice modelling of gravity and stress-driven failures of rock tunnels

Abstract

Abstract In this paper, an investigation is performed regarding the applicability of the Rigid Body Spring Network method (RBSN) to the analysis of hard rock tunnels in massive and fractured rock masses. For this objective, the method is enhanced with a new meshing scheme and a Cohesive Zone Model (CZM) formulation based on an exponential softening law. While the new meshing scheme provides for models containing complex Discrete Fracture Networks, the CZM affords realistic representations of fracturing phenomena. In order to demonstrate the robustness of the contributions, a verification model and three study cases are presented. The verification concerns the analysis of an elastic jointed medium with a circular hole, from which stresses and displacements are calculated and checked against Finite Element solution. The study cases are based on the real Monte-Seco and Mine-By tunnels and on a hypothetical tunnel. Simulations are performed, and the results are compared to either observed in situ behavior or Finite Element analyses. In the end, the cases show that the enhanced RBSN can realistically represent both gravity and stress-driven types of failures that are encountered in hard rock tunneling. Additional results highlight the method’s simple material calibration procedure and the practicality of the new meshing scheme.