Microfracturing characteristics in brittle material containing structural defects under biaxial loading

The purpose of this study is to specify the influence of structural defects and confining pressure on microfracturing characteristics in rocklike brittle materials. The stress field and microfracturing events of rock samples containing structural defects under biaxial loading are simulated by the finite element software, Rock Failure Progress Analysis (RFPA2D). The simulated rock samples are compressed by an increasing vertical displacement of 0.001 mm/step and confined with different constant horizontal lateral pressures 0, 5, 10 and 15 MPa, respectively. The characteristics of microfracturing events with stress field evolution in rock failure process are visually represented by damaged elements. The results show that rock failure with great structural effects is greatly dependent on the arrangement of structural defects. As the outer loading increases, the stresses in rock mass are built up gradually. When the stress of an element reaches a certain critical value, a microfracturing event occurs. Two neighboring damaged elements owning one same edge are considered in the same damaged element group. Based on the newly-developed statistic function of RFPA2D on damaged element group, the scales (element number in a group) and counts of damaged groups (micro cracks) are recorded. The distribution of microfracturing events for all rock samples under different lateral pressures represents self-similar fractal features. However, rescaled range analysis indicates that microfracturing events do not exhibit the similar scale-invariant property strictly under higher lateral pressures.