FRACOD3D: A Three-Dimensional Crack Growth Simulator Code

Abstract

This chapter first outlines the theory and an implementation of a well-established three-dimensional boundary element method, displacement discontinuity method (DDM), for a three-dimensional crack growth simulator, FRACOD3D. A modified crack growth criterion and triangular elements are used in the simulator code. A new developed numerical scheme is used to overcome a difficulty associated with the evaluation of the basic solution for DDM in some special situations and another numerical scheme is used to calculate the stresses on the boundary elements where the stresses obtained from the normal DDM scheme have large errors. The crack growth is implemented incrementally in that new front elements are introduced at the crack front, without re-meshing the old part of the cracks. Effects of neighboring front elements are taken into account in the implementation of the crack front evolution to overcome severe twisting of the new front elements generated from the growth. Numerical results from FRACOD3D of two simple validation examples agree very well with analytical solutions. Propagation configuration of a circular disc crack in an infinite body under shear loading is close to that observed in an experiment and other numerical simulation in literature under similar loading condition. The DDM is then combined with another indirect boundary element method for temperature to investigate the thermal stress effect on rock deformation and fracturing. Finally, coupling between fluid pressure in fractures and rock deformation is considered with an iteration scheme. The fluid pressure is solved with a finite volume method (FVM).