Rock fracturing failure simulation via sub-block element splitting with discontinuous deformation analysis (DDA)

Abstract

Discontinuous deformation analysis (DDA) is a representative numerical method for simulating the deformation and large displacement behaviors of discontinuous media like rock masses. For rock fracturing simulations, the previous sub-block element DDA fracturing modeling method (sub-block DDA method) only allows cracks to develop along artificial joints between sub-blocks, therefore showing high mesh dependency. In the present work, a new sub-block element splitting DDA fracturing modeling method (sub-block splitting DDA method) which allows the self-splitting of sub-blocks is developed. The new method determines the tensile and shear self-splitting of sub-block elements in crack initiation or propagation simulations based on the sub-block stress state. Its algorithm mainly involves the search of discontinuity loops, determination of crack tips, crack initiation and propagation criteria, and split and update of sub-block elements. Tensile failure tests of rectangular rock specimens with pre-existing cracks, radial compression splitting tests of an intact disc and rock discs with pre-existing cracks, and the Hopkinson spalling test of a rock rod are simulated. The simulation results are in good agreement with the corresponding experimental, theoretical, or other numerical simulation results. It is well demonstrated that the new method overcomes the limitations of previous DDA fracturing simulation methods which could only approximate crack paths by crack bands, and greatly reduces the mesh dependency effect. The seismic fracturing and failure of a jointed rock slope are also simulated. The characteristics of the failure process and failure mode of the slope are analyzed, and the seismic surface-oriented effect and elevation amplification effect are revealed. The new sub-block splitting DDA method provides a potential powerful numerical approach for rock mass mechanical behavior simulations involving deformation, fracturing and large displacements.