Study on crack evolutional behavior of rocks in triaxial compression based on colony growth dynamics model

Abstract

The crack propagation behavior of rock during compression involves complex mechanisms. Describing the growth behavior of a large number of cracks with conventional mechanical models is a major challenge. Therefore, in this work, we propose a new method to describe crack growth behavior by considering crack bodies as free voxels that can expand and coalesce within a rock sample according to certain rules. Specifically, we first propose a crack growth model that quantitatively describes the crack growth ratio and crack growth rate, which are integrally related to the loading rate, internal friction angle, cohesion, initial porosity, and confining stress. Second, to avoid the complex analytical process of the traditional mechanical model in solving the propagation directions of multiple cracks, we introduce a method for determining the crack growth directions of shearing failure based on the colony growth assumption. This method defines the crack propagation direction as a synthetic vector of the inertial direction, the attractive direction, the Coulomb direction, and the edge direction. Moreover, a new mathematical description method of fracture energy and plastic energy is proposed to calculate the crack growth at each time step. The simulation results show that our crack growth model for shearing failure agrees well with the experimental results and explains the fracture behavior and transformation law of cracks to some extent.

Study on Creep Characteristics and Long-Term Strength of Mud-Calcareous Conglomerates in the Three Gorges Reservoir Area

“…In 1967, Bieniawski [9] found that when a rock sample approached fracture, the volume of the rock sample would expand and dilate, and an unstable crack expansion would occur inside the sample. The stress corresponding to the unstable expansion of the fracture is the critical point of the volumetric strain curve transition from negative (compression) to positive (expansion), and it can be considered the long-term strength [10,11]. Above is the basic outline of the volume expansion method, which was also the primary method used to determine the long-term strength of rocks in early phases of this field of research [12].…”