State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China.
State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam, Chongqing University, Chongqing 400044, China.
Sci Rep. 2016 Dec 8;6:38810. doi: 10.1038/srep38810.
Fluid injection has been applied in many fields, such as hazardous waste deep well injection, forced circulation in geothermal fields, hydraulic fracturing, and CO geological storage. However, current research mainly focuses on geological data statistics and the dominating effects of pore pressure. There are only a few laboratory-conditioned studies on the role of drilling boreholes and the effect of injection pressure on the borehole wall. Through experimental phenomenology, this study examines the risk of triggering geological disasters by fluid injection under shear stress. We developed a new direct shear test apparatus, coupled Hydro-Mechanical (HM), to investigate mechanical property variations when an intact rock experienced step drilling borehole, fluid injection, and fluid pressure acting on the borehole and fracture wall. We tested the peak shear stress of sandstone under different experimental conditions, which showed that drilling borehole, water injection, and increased pore pressure led to the decrease in peak shear stress. Furthermore, as pore pressure increased, peak shear stress dispersion increased due to crack propagation irregularity. Because the peak shear stress changed during the fluid injection steps, we suggest that the risk of triggering geological disaster with injection under shear stress, pore, borehole, and fluid pressure should be considered.
流体注入已经应用于许多领域，如危险废物深井注入、地热田强制循环、水力压裂和 CO2 地质储存。然而，目前的研究主要集中在地质数据统计和孔隙压力的主导作用上。只有少数实验室条件下的研究涉及钻孔和注入压力对钻孔壁的作用。本研究通过实验现象学研究了在剪切应力下流体注入引发地质灾害的风险。我们开发了一种新的水力-机械（HM）直剪试验装置，研究了完整岩石在经历分步钻孔、注水和作用于钻孔和裂缝壁的孔隙压力时力学性能的变化。我们测试了不同实验条件下砂岩的峰值剪切应力，结果表明钻孔、注水和孔隙压力的增加导致了峰值剪切应力的降低。此外，由于裂纹扩展不规则性，随着孔隙压力的增加，峰值剪切应力的分散度增加。由于在流体注入过程中峰值剪切应力发生变化，我们建议应考虑剪切应力、孔隙、钻孔和流体压力下注入引发地质灾害的风险。
