Simulations of underground structures subjected to dynamic loading using the distinct element method
We present the preliminary results from a parameter study investigating the stability of underground structures in response to explosion-induced strong ground motions. In practice, even the most sophisticated site characterization may lack key details regarding precise joint properties and orientations within the rock mass. Thus, in order to place bounds upon the predicted behavior of a given facility, an extensive series of simulations representing different realizations may be required. The influence of both construction parameters (reinforcement, rock bolts, liners) and geological parameters (joint stiffness, joint spacing and orientation, and tunnel diameter to block size ratio) must be considered. We discuss the distinct element method (DEM) with particular emphasis on techniques for achieving improved computational efficiency, including the handling of contact detection and approaches to parallelization. We introduce a new approach for simulating deformation of the discrete blocks using the theory of a Cosserat point, which does not require internal discretization of the blocks. We also outline the continuum techniques we employ to obtain boundary conditions for the distinct element simulations. We present results from simulations of dynamic loading of several generic subterranean facilities in hard rock, demonstrating the suitability of the DEM for this application. These results demonstrate the significant role that joint geometry plays in determining the response of a given facility.
simulation dynamic loading geology