Study on the crack propagation morphology and initiation law of coal rock under the action of underwater electric pulse.

Based on the symmetric initiation mechanism of double-wing cracks in coal rock mass induced by high-pressure electro-recoil water pressure, fracturing experiments have been performed on coal rock mass under different water pressures and discharge conditions using high-voltage electric pulse hydraulic fracturing devices. Combined with CT scans, the crack spatial distribution inside the post-break coal rock mass was analyzed and found that the edge of the water injection hole is prone to produce double-wing cracks along the drilling hole diameter. ABAQUS is used to verify the physical test and extend the test conditions, the geometric parameter change, morphological expansion rule and crack initiation mechanism of double-wing crack in coal rock mass under different discharge conditions and ground stress conditions are studied.

Mechanical properties and damage characterization of cracked granite after cyclic temperature action.

Due to the unique geographical environment of the plateau, large-scale damage and destruction of fractured surrounding rock often occur during geotechnical engineering construction as a result of high-temperature cycles. Therefore, this study aims to investigate the mechanical properties and damage characteristics of fractured granite under the influence of cyclic temperature, uniaxial compression tests were conducted on granite specimens with pre-existing fractures at cyclic temperatures of 30 °C, 50 °C, 70 °C, 100 °C, and 130 °C. The study integrated analyses of characteristic stress, acoustic emission parameters, damage variables, fractal dimensions, and SEM to explore the mechanical properties and damage features of granite.

Experimental research on damage characteristics of red sandstone under the combined action of temperature, water and stress.

In order to study the damage properties of red sandstone under combined action of temperature, water and stress, the uniaxial compression test was carried out for red sandstone after immersing in water for 0.5 h, 1 h and 3 h at 25 ℃, 55 ℃, 85 ℃ and 95 ℃, the mechanical properties, characteristic stress points, acoustic emission RA-AF parameters and failure forms of red sandstone were analyzed, the damage constitutive equation was established, and the damage properties of red sandstone were studied. The results showed: (1) temperature could significantly improve the saturated water content percentage of red sandstone.

Crack Damage Propagation and Morphology Distribution of Hydraulic Electric Pulse Fractured Coal.

This work discusses the damage and failure effect of a hydraulic electric pulse and the law of crack growth on coal. The impact and failure effect of a water shock wave and the mechanism of crack initiation, propagation, and arrest were studied by numerical simulation and the fracturing test of coal, combined with CT scanning, PCAS software, and Mimics 3D reconstruction technology. The results show that a high voltage electric pulse that increases permeability is an effective artificial crack making technology.

Study of mixed mode fracture toughness and fracture trajectories in gypsum interlayers in corrosive environment.

Based on the engineering background of water dissolving mining for hydrocarbon storage in multi-laminated salt stratum, the mixed mode fracture toughness and fracture trajectory of gypsum interlayers soaked in half-saturated brine at various temperatures (20°C, 50°C and 80°C) were studied by using CSNBD (centrally straight-notched Brazilian disc) specimens with required inclination angles (0°, 7°, 15°, 22°, 30°, 45°, 60°, 75°, 90°) and SEM (scanning electron microscopy). The results showed: (i) The fracture load of gypsum specimens first decreased then increased with increasing inclination angle, due to the effect of friction coefficient. When soaked in brine, the fracture toughness of gypsum specimens gradually decreased with increasing brine temperature.