Configurational force driven fracture modelling
A computational framework has been developed for quasi-static brittle fracture in three-dimensional solids. Concept of configurational mechanics, consistent with Griffith’s theory have been used as the theoretical basis for determining the initiation and direction of propagating cracks, and mesh adaptivity method has been used for removing the restriction for predicting crack path in the finite element method. A local mesh improvement procedure is developed to maximise mesh quality in order to improve both accuracy and solution robustness and to remove the influence of the initial mesh on the direction of propagating cracks. An arc-length control technique has been derived to enable the dissipative load path to be traced. A hierarchical hp-refinement strategy is implemented in order to improve both the approximation of displacements and crack geometry.
Shale gas reservoir rocks
The modelling framework is used to reproduce the fracture propagation process in a shale rock sample under standard laboratory Brazilian Disc test. Data collected from the experiment are employed to determine the sample tensile strength and fracture toughness. To incorporate the effects of shale formation heterogeneity in the simulation of crack paths, fracture properties of the sample are defined as spatially random fields. A computational strategy on the basis of stochastic finite element theory is developed that allows to incorporate the effects of heterogeneity of shales on the fracture evolution.