In the process of deep mining, the dynamic disasters of coal and rock occur frequently under the action of high stress and high seepage pressure, the essence of which is energy-driven coal rock failure. In order to explore the energy evolution law and damage mechanism of sandstone with intermittent cracks under the coupling effect of stress and seepage, in this paper, by comparing the differences in mechanical characteristics between fractured rock and intact rock, the energy evolution characteristics, crack propagation, and micro-damage mechanism of fractured rock under different confining pressures and seepage pressures are analyzed. The research shows that: (1) The local stress drop phenomenon occurs in the fractured rock during the loading process, and the stress–strain shape is ‘bimodal’. At the same time, there is stress concentration at both ends of the fracture. (2) The energy conversion of the fractured rock changes in stages during loading. As confining pressure rises, the energy storage limit and the maximum dissipation energy go up. The increase in seepage pressure reduces the energy storage limit, while the dissipation energy shows an upward trend. The energy consumption ratio curve shows ‘concave’ evolution during the loading process. (3) Based on the dissipation energy and residual stress, the damage state of the specimen is analyzed, and the proposed damage variable can reasonably explain the whole process of the damage evolution of intermittent fractured rock under stress and seepage. (4) The increase in confining pressure increases the friction between the particles inside the sample and promotes the transformation of the sample from tensile failure to shear failure. The seepage pressure reduces the friction between the particles in the sample through the air wedge effect to deepen the damage degree, thus promoting the tensile failure of the sample.

Coal and gas outburst disaster seriously restricts the safe development of deep coal resources. This study aimed to elucidate the evolution characteristics of dynamic behavior and two-phase flow migration mechanism throughout the various stages of outburst. The dynamic characteristics of fluids at different outburst stages were analyzed in terms of impact force and static pressure primarily based on physical simulation tests of outbursts. Based on gas dynamics, a complex wave system distribution model of the turning structure was constructed, and a numerical simulation revealed the migration mechanism of outburst fluids within the turning structure. The results show that the shock in the stage1 shows an evolutionary trend of multi-peak oscillations. Coal–gas two-phase flow in the stage2 mainly has strong disaster-causing characteristics at the front end and middle of the straight roadway, and the impact force has a sudden and intermittent steep increase-drop phenomenon. Impact force decline process has a recovery phenomenon, the larger the solid–gas ratio, the faster the impact force attenuation. Coal powder can promote the attenuation of static pressure, and the larger the solid–gas ratio, the greater the attenuation. The fluid in the high-velocity jet region is fast and unevenly distributed, and the static pressure is negatively distributed, with expansion-compression phenomenon. In the turning roadway, there is a steep increase in velocity, and the distribution is strong–weak, which is consistent with the phenomenon of steep increase in impact force in the test. The research results are of crucial guiding significance for accurately assessing the impact range of outburst accidents, optimizing the design of disaster prevention facilities, and formulating emergency rescue plans for accidents.

Coal and gas outburst disasters severely restrict the safe and sustainable development of deep coal resources. Outburst fluid migration is violent and highly nonlinear, posing significant challenges to its mathematical modeling. This paper presents a high-Mach-number compressible flow model for outburst fluid migration. By combining physical and numerical simulation methods, the spatiotemporal evolution characteristics of the outburst two-phase flow were revealed, and the influence of the turning angle on the migration law of the outburst fluid was analyzed. The results show that the impact pressure presents a strong–weak alternating distribution characteristic in the roadway. In the straight roadway, the impact pressure under the non-arc condition is generally higher than that under the arc condition. In the turning roadway, the impact pressure of arc and non-arc roadways increases sharply, especially in the non-arc roadway. The arc turning structures are helpful in promoting the passing ability of pulverized coal when compared with the non-arc turning structures. An arrangement of acute and right angles effectively reduces the disaster intensity of the dynamic pressure of airflow in the straight roadway but increases the disaster intensity after the turning roadway. An obtuse angle arrangement increases the disaster intensity of static pressure in the whole roadway.