水-动力耦合作用下红砂岩动态强度及破坏机理

为探究水化学损伤下红砂岩的动态强度和破坏机理,通过自然、干燥和饱水红砂岩试样的静态单轴压缩和动态单轴冲击试验,结合岩石碎块的电镜扫描(SEM)图像,分析了不同含水状态和应变率荷载等级下岩石的强度特性,并基于损伤断裂理论分析了含水岩石微裂纹起裂和扩展机理.试验结果表明:红砂岩试样动态抗压强度随含水率的增加而降低,随应变率的增加而增大,饱水试样具有显著的应变率效应;冲击荷载下,饱水试样应力-应变曲线具有显著的体积压缩现象,峰值应变最大,塑性变形明显,而干燥试样弹性变形最大,峰前塑性变形最小;受孔隙水影响,饱水试样颗粒结构疏松多孔,胶结物质被溶蚀而使胶结作用弱化.根据最大周向正应力理论,对含水岩石的微裂纹起裂条件和扩展方向进行了讨论,并对裂尖的动态应力强度因子进行了修正.

Study of Dynamic Strength and Failure Mechanism of Red Sandstone under Condition of Hydrodynamic Coupling Effect

In order to explore the dynamic strength and failure mechanism of red sandstone under condition of hydro chemical damage, the static uniaxial compression and dynamic uniaxial impact tests of natural, dry and water saturated red sandstone samples are carried out. Combined with the SEM images of rock fragments, the strength characteristics of rocks under condition of different water bearing and strain rate loading levels are analysed, and based on the damage fracture theory, the initiation and propagation mechanism of micro cracks in water bearing rock are analysed as well. The test results show that the dynamic compressive strength of red sandstone decreases with the increase of water content and increases with the increase of strain rate, and the saturated sample has significant strain rate effect; under condition of impact load, the stress strain curve of saturated sample has significant volume compression phenomenon, with the maximum peak strain and obvious plastic deformation, while the dry sample has the largest elastic deformation and the smallest plastic deformation before the peak; under the influence of pore water, the grain structure of saturated sample is loose and porous, and the cementation is weakened by dissolution of cementation material. According to the theory of maximum circumferential normal stress, the conditions of initiation and propagation direction of micro cracks in water bearing rock are discussed, and a modification to the dynamic stress intensity factor at crack tip is made.