Modeling discrete fractures in continuum analysis and insights for fracture propagation and mechanical behavior of fractured rock

Abstract

This paper presents a procedure for modeling discrete fracture initiation, deformation, and propagation in continuum analysis of rock, and provides numerical simulations to evaluate performance of the procedure against analytical solutions and laboratory data. The procedure is based on aggregating the mechanical behavior of evolving discrete fractures and unfractured rock and provides specific information about fracturing; such as when and where fractures may occur and the type (tensile or shear), geometrical attributes, and aperture of each fracture. By storing fracture geometry as continuum properties that are used internally to generate geometrical parameters needed for analysis, the procedure models the geometry and mechanical behavior of discrete fractures explicitly in continuum analysis without including the fractures in the model grid. Numerical simulations are described for typical laboratory loading conditions such as triaxial compression and extension, and Brazilian testing. The results are compared with laboratory data, analytical solutions, and established concepts to make a case that the procedure performs satisfactorily and can be relied upon for understanding and predicting rock mechanical behavior. Furthermore, the paper discusses insights based on the simulation results for understanding rock fracturing; mechanical behavior of fractured rock; and large-scale behavior such as localization of rock deformation, stress control of fracture mechanisms in failure zones, and conditions for occurrence of multiple parallel fractures.