School of Emergency Management,Chengdu University
State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University
School of Resources and Safety Engineering,Chongqing University
State Key Laboratory of Coal Mine Disaster Prevention and Control
CCTEG Chongqing Research Institute

为揭示软煤压裂孔周致裂行为特征,依据时步均等划分方法将压裂过程分为6个阶段,对孔周应力的空间分布、随时间变化规律、水平应力差异系数的演化进行了PFC2D离散元模拟研究。结果表明:水力压裂过程的1~4阶段,最大主应力方向孔周应力增幅较大;5、6阶段最小主应力方向的应力增幅迅速增大。孔周应力集中明显,接近孔周位置应力水平高。在应力集中影响范围内,x方向和y方向孔周应力路径趋势一致,水平应力差异系数相差较小,而在应力集中影响范围以外则恰恰相反。应力差异系数可反映裂隙发育的均匀程度,而应力集中程度影响着裂隙的发育和扩展范围,揭示了软煤水力压裂孔周扩孔致裂—应力外移的行为特征。

In order to reveal the cracking characteristics around borehole of soft coal,the fracturing process was divided into stages according to the time-step equal division method. And spatial distribution of the stress around the borehole,the variation characteristics with time and the evolution of the difference coefficient of the horizontal stress were simulated by PFC discrete element method. The results show that the stress around borehole increases greatly in the direction of the maximum principal stress in the first to fourth stages of hydraulic fracturing simulation. The stress increases rapidly in the direction of minimum principal stress in the and stages. The stress concentration around the borehole is obvious,and the stress level near the borehole is high. In the influence range of stress concentration,the trend of stress path around borehole in x direction and y direction is the same,and the difference coefficient of horizontal stress is small,but the stress paths and horizontal stress difference coefficient outside the influence range of stress concentration is just the opposite. The stress difference coefficient can reflect the uniform degree of crack development,and the degree of stress concentration affects the development and expansion range of crack. Based on this, the behavior characteristics of crack induced by Mining Safety & Environmental borehole enlargement and stress shifts outward around hydraulic borehole of soft coal is revealed.

国家自然科学基金项目(52074049)

张跃兵,胡千庭,李全贵,等.软煤水力压裂孔周应力的时空演化研究[J].矿业安全与环保,2024,51(5):1-7.

ZHANG Yuebing,HU Qianting,LI Quangui,et al. Study on temporal and spatial evolution of stress around borehole in hydraulic fracturing of soft coal[J]. Mining Safety & Environmental Protection,2024,51(5):1-7.