: In order to assess the strength, integrity and stability of a fractured underground excavation subjected to seismic and blast waves, a dynamic analysis of the displacement and stress fields around the excavation is carried out using a boundary integral equation (BIE) approach with a slip model of fracture. This paper outlines the approach and presents results of preliminary parametric studies. The results indicate that an intersecting fracture redistributes and usually amplifies the stress along and around the surface of the cavity. For certain combinations of the parameters, the stress amplification and complication can be very significant. It is found that the strongest stress concentration and deformation do not occur when the traction on the fracture is free but occur when the frequency dependent normalized slip stiffness parameters are of moderate values.
1 INTRODUCTION
An underground excavation such as tunnel, mine opening or permanent geological repository for nuclear wastes in a rock mass has to deal with the presence of prominent joints or joint sets or faults. The strength, integrity and stability of the excavation depend significantly on the characteristics of the fracture pattern as well as its strength and stiffness properties. In particular, the response of an excavation subjected to dynamic events such as earthquakes, underground explosions, blasts, or rock bursts can be critically controlled by nearby fractures in the rock. The dynamic interaction between the cavity wall and fractures will cause increased displacements and stresses in the rock in a complex manner. Thus, a thorough understanding of the dynamic response of fractures intersecting the excavation to incoming waves at various frequency ranges is important for the excavation ’s safety, including preventing rock falls and keeping the excavation stable and usable.
