Abstract Hydraulic fracturing is a combined process of mechanical and hydraulic behavior due to in situ stress, well bore pressure, fluid infiltration in the rock mass. The initial state of surrounding well bore prior to hydraulic fracturing can be subject to either dry or saturated condition. We investigated various mechanical properties and hydraulic fracturing behavior of dry and saturated granite specimens containing pre-existing microcracks. After saturation, P-wave velocity increased by 27%–33% and S-wave velocity increased by 13%–15%. Saturation weakened the material, with a 3%–6% decrease in uniaxial compressive strength, a 3%–9% decrease in Brazilian tensile strength, and 5%–6% decrease in mode-I fracture toughness, but the elastic modulus and Poisson’s ratio varied little. The tensile strength estimated from hydraulic fracturing tests on cylinders, showed a negligible decrease (2%–3%) in saturated specimens compared with initially dry specimens. However, acoustic emission (AE) monitoring analysis results show that water saturation influence hydraulic fracturing initiation and propagation. When comparing the initially saturated specimens to the dry specimens, higher AE hit rates were observed right before and at the breakdown, and the percent of tension correlated AE hit was slightly lower. Moreover, computed tomography observations show that fractures tend to propagate in a wider area in the saturated specimens.

中文翻译：

---

含水饱和度对花岗岩力学性能和水力压裂行为的影响评价

摘要 水力压裂是岩体中地应力、井筒压力、流体渗入等作用下力学和水力行为的综合过程。水力压裂前周围井筒的初始状态可以是干燥或饱和状态。我们研究了含有预先存在的微裂纹的干燥和饱和花岗岩试样的各种力学性能和水力压裂行为。饱和后，P波速度增加27%~33%，S波速度增加13%~15%。饱和会削弱材料，单轴抗压强度降低 3%–6%，巴西拉伸强度降低 3%–9%，I 型断裂韧性降低 5%–6%，但弹性模量和泊松比例变化不大。与最初干燥的试样相比，饱和试样的水力压裂试验估计的抗拉强度显示出可忽略不计的下降 (2%–3%)。然而，声发射（AE）监测分析结果表明，含水饱和度会影响水力压裂的起裂和扩展。当将初始饱和试样与干燥试样进行比较时，在断裂之前和断裂时观察到更高的 AE 命中率，并且与张力相关的 AE 命中百分比略低。此外，计算机断层扫描观察表明，在饱和试样中，裂缝倾向于在更广泛的区域内扩展。声发射（AE）监测分析结果表明，含水饱和度影响水力压裂的起裂和扩展。当将初始饱和试样与干燥试样进行比较时，在断裂之前和断裂时观察到更高的 AE 命中率，并且与张力相关的 AE 命中百分比略低。此外，计算机断层扫描观察表明，在饱和试样中，裂缝倾向于在更广泛的区域内扩展。声发射（AE）监测分析结果表明，含水饱和度影响水力压裂的起裂和扩展。当将初始饱和试样与干燥试样进行比较时，在断裂之前和断裂时观察到更高的 AE 命中率，并且与张力相关的 AE 命中百分比略低。此外，计算机断层扫描观察表明，在饱和试样中，裂缝倾向于在更广泛的区域内扩展。