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. (ii) When soaked in brine, the crystal boundaries of gypsum separated and became clearer, and the boundaries became more open between the crystals with increasing brine temperature. Besides, tensile micro-cracks appeared on the gypsum...

本研究以多层盐岩层烃类储库水溶开采工程为背景，采用带有预设倾角（0°、7°、15°、22°、30°、45°、60°、75°、90°）的中心直切口巴西圆盘（centrally straight-notched Brazilian disc，CSNBD）试样，并借助扫描电子显微镜（scanning electron microscopy，SEM），研究了不同温度（20℃、50℃、80℃）下半饱和卤水浸泡环境下石膏夹层的复合型断裂韧性与断裂轨迹。研究结果表明：(i) 受摩擦系数影响，石膏试样的断裂载荷随倾角增大先降低后升高；经卤水浸泡后，石膏试样的断裂韧性随卤水温度升高逐渐降低。(ii) 经卤水浸泡后，石膏的晶界发生分离且愈发清晰，随着卤水温度升高，晶体间的晶界张开程度愈发显著；此外，石膏试样上出现拉伸微裂纹……