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为对水力压裂煤体裂缝的起裂判据作定量计算,根据弹性力学理论,分析了注水钻孔周围的应力状态,给出了水平和垂直裂缝产生时注水压力的计算模型;探讨了裂缝扩展的方向以及其扩展所需要的泵注压力;采用自制的高水载荷下煤体裂隙生成及延展模拟装置在实验室模拟了不同围压和轴压加载下条件下煤体起裂的临界注水压力及裂隙生成和延展的方向.实验研究表明:泵注压力克服最小主应力与煤体的抗拉强度之和时,煤体开始破裂;裂隙总是沿着最大主应力的方向发展.实验模拟结果和理论分析相吻合.
In order to quantitatively calculate the initiation and fracture criteria of fractured coal fractures in hydraulic fracturing, according to the theory of elasticity mechanics, the stress state around the water injection borehole was analyzed, and the calculation model of injection pressure during horizontal and vertical fractures was given. The direction of expansion and the pump injection pressure required for its expansion. A self-made coal crack initiation and propagation simulation device under high water load was used to simulate the critical injection of coal under different confining pressure and axial pressure Pressure and the direction of fracture formation and extension.The experimental results show that when the pump pressure is over the sum of the minimum principal stress and the tensile strength of coal, the coal begins to crack, and the fracture always develops along the direction of the maximum principal stress. The result is consistent with the theoretical analysis.