Analysis of damage and fracture mechanisms in quartzite with different inclination angles under liquid oxygen phase change-induced fracturing

Abstract

To address the unresolved damage mechanisms and unclear fracture propagation laws of jointed rock masses subjected to gas-expansion-induced rock breaking, a series of liquid-oxygen phase-transition fracturing model tests combined with X-ray CT–based three-dimensional reconstruction were conducted. The damage evolution characteristics of rock masses with different structural configurations under high-pressure gas loading were systematically investigated, and the dynamic propagation behavior and three-dimensional spatial distribution of blast-induced fractures were revealed. The results indicate that the joint inclination angle reconstructs the energy distribution pattern by regulating the reflection–refraction behavior of stress waves. With increasing joint inclination, the strain response exhibits alternating tensile–compressive characteristics, manifested by enhanced tensile strain peaks and attenuated compressive strain peaks, which in turn drive the systematic evolution of fracture geometric parameters: the average fracture width increases monotonically, the average fracture orientation angle continuously decreases, while the surface density and crushed-zone area show pronounced nonlinear variations. Fracture network parameters respond in a differentiated manner: the fracture surface area, fracture volume, and fracture ratio reach peak values at specific inclination angles, whereas fracture length, width, and equivalent diameter increase monotonically. Furthermore, a coupled damage–porosity heterogeneity characterization index is proposed, quantitatively revealing the nonlinear decay laws of the volumetric fractal dimension and damage degree under the gradient control of joint inclination. This index effectively characterizes the coupling mechanism between damage propagation and pore structure evolution in jointed rock masses subjected to gas-driven fracturing.