AN IMPROVED DISCRETE ELEMENT METHOD FOR STABILITY ANALYSIS OF TUNNELS IN ROCK MASS*

Abstract – Rock masses supporting a tunnel often have natural cracks and joints which must be detected and analyzed at excavation to assess tunnel stability. Mathematically, these are discontinuities that must be embedded in the finite element model of the excavation to improve reliability. Because direct consideration of cracks as mathematical discontinuities in excavation models presents considerable computational and analytical challenge, a simple discrete element model (DEM) has been used to analyze the stability of tunnels in jointed rocks. This model, which is a member of the DEM group, has the advantage of being able to model large displacements and behavior of highly fractured rock masses. The low volume of numerical computing and high speed in analysis are other advantages of the used model. A new algorithm for detecting contact points between blocks has been used to improve the model. Different examples and case studies have been solved successfully using this modified discrete element model