ABSTRACT
Blasting loads resulting from detonation have been attached great importance to the design and protection of underground structures in these years. In order to analyze the dynamic response and stability of underground structures, a number of numerical approaches such as FEM and BEM have been introduced. However, numerous discontinuities existing in the rock masses in the forms of faults, joints or bedding planes (Goodman, 1976), on the one hand, can dominate the mechanical response of rock masses to blasting loads; on the other hand, the conventional numerical methods employed in the simulation are usually continuum based. As a result, it is not very easy for these methods to give reasonable predictions. Discrete element method (DEM), a discontinuous model for simulating fractured rockmasses (Cundall, 1971), can be an alternative. At the early stage, DEM was mostly employed to simulate static problem. In 1987, Lemos developed a numerical technique to study the dynamic response of a jointed rock mass (modeled as an infinite elastic mediumwith a single discontinuity) subjected to a line source of incident waves (Lemos, 1999). He demonstrated the validity of the numerical technique. Chen S G, et al employed the UDEC and 3DEC to model shock wave propagation in rock masses, and reported that reasonable results were obtained by using the velocity history obtained from another code, AUTODYN. In this study, the shock wave propagation as well as the response of underground structures to farfield detonation in jointed rockmasses are investigated through two case studies by using the fractal theory.
