Study of microstructure effect on the nonlinear mechanical behavior and failure process of rock using an image-based-FDEM model

Rock microstructures, including the mineral heterogeneity and initial microcracks, not only affect its failure process but also influence its nonlinear mechanical behavior. However, in previous studies the rock microstructures especially the width of initial microcracks are usually unreasonably considered, which as a result fail to capture the rock realistic nonlinear mechanical behaviors (such as the gradual crack closure characteristic) and failure process. In this study, an image-based model considering the rock microstructures is developed by an FDEM scheme. The rock microstructures are characterized by a series of image process and then are incorporated into the numerical model. The width of the initial microcracks are considered in the model through inserted cohesive elements with certain thickness. The proposed model is firstly validated, based on which the influences of microcrack density, microcrack width and microcrack orientation on rock mechanical behavior are then discussed. The numerical results indicate that the initial microcrack has a larger influence on the stress distribution than the mineral heterogeneity and its width is a key factor affecting rock crack closure behavior.