Efficient 3D probabilistic stability analysis of rock tunnels using a Lattice Model and cloud computing

Abstract

In this paper, the Classic Lattice Spring Model is developed in order to be applied to probabilistic stability analyses of rock tunnels in low in situ stress environments, where the falling of blocks is the main failure mechanism. For this objective, the method is combined with the Synthetic Rock Mass technique and Barton-Bandis joint constitutive model, giving it a series of advantages: simulations with deformable blocks; possible formation of tension cracks; and an appropriate constitutive model for the mechanical behavior of joints. The use of cloud computing technology is proposed for efficient probabilistic analyses using the Monte Carlo simulation. A case study is presented based on an unsupported section of a shallow rock tunnel excavated in the state of Espírito Santo, Brazil. A 3D probabilistic stability analysis of the tunnel is performed with the proposed methodology. From the results, a positional probability map is elaborated, which indicates the likelihood of block failure around the excavation cross-section. The unstable zones indicated by the map are then compared to the failed region of the real tunnel so as to demonstrate the competence of the methodology.