Numerical study on spalling failure of rock surrounding deep buried tunnel based on DEM

Abstract

Spalling failure is a common phenomenon in hard and brittle rocks surrounding deep buried tunnels. The particle discrete element method and the flat-joint model are useful for describing the characteristics of such rocks. Based on discrete element method (DEM) and Particle Flow Code (PFC3D, version 5.0), this study established a three-dimensional model of brittle rock by using layered modeling to simulate the spalling failure of rock surrounding a deep buried tunnel. The DBSCAN (density-based spatial clustering of application with noise) algorithm was used to process the data and establish a connection between macro- and meso-fractures. Spalling failure occurred mainly at the spandrel and the foot of the arch of the tunnel, and dense zones of intersection of the meso-fractures occurred at the top and bottom of the tunnel. Given that the axis of the tunnel was aligned with the in-situ intermediate principal stress, the magnitudes of the maximum and minimum in-situ principal stress acted as external factors affecting the occurrence of spalling failure. The in-situ intermediate principal stress influenced the depth and range of spalling failure, where this instability depended on the Poisson's ratio of the rock. The post-peak behavior of the rock also influenced the depth of the spalling failure.