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水压致裂原地应力测量系统的柔性对最大水平主应力的结果会产生很大的影响,提高最大水平主应力的测量精度对各种地下等工程设计都具有重要意义。通过进行直接拉伸试验、“垫条加载”和“角锥荷载”形式的圆盘劈裂实验、弯曲拉伸实验获得岩石抗拉强度,结合实测破坏压力、孔隙压力数据及相关理论计算出最大水平主应力,并与利用经典水压致裂公式计算得到的最大水平主应力进行数据对比分析。结果表明:通过“角锥荷载”圆盘劈裂实验、直接拉伸试验、“垫条加载”圆盘劈裂实验、三点弯曲实验所获得的最大水平主应力均大于经典水压致裂公式计算得到的最大水平主应力,且偏差依次增大,由此也说明测试系统的柔性会导致利用经典公式计算的最大水平主应力偏小。4种实验中,通过“角锥荷载”圆盘劈裂实验所获得的数据较其他3种方法更接近经典公式计算得到的最大水平主应力,且偏差较小,可以作为估算最大水平主应力的一种替代方法。在未来的工作研究中,可以为避开系统柔性对实测最大水平主应力的影响、提高测量精度提供方法参考。
The flexibility of in-situ stress measurement system of hydraulic fracturing will greatly affect the result of the maximum horizontal principal stress, and improving the measurement accuracy of the maximum horizontal principal stress is of great significance for various underground engineering design. Tensile strength of rock was obtained by direct tensile test, disk splitting test with “pad loading ” and “pyramid load ”, bending tensile test. Combined with measured fracture pressure, pore pressure data and correlation The theoretical maximum principal stress is calculated and compared with the maximum principal stress calculated by the classical hydraulic fracturing formula. The results show that the maximum horizontal principal stress obtained by the “pyramid load” disk splitting experiment, the direct tensile test, the “pad loading” disk splitting experiment and the three-point bending experiment are all larger than the classical water The maximum horizontal principal stress calculated by the pressure fracture formula, and the deviation increases in turn, which also shows that the flexibility of the test system will lead to the use of the classical formula to calculate the maximum horizontal principal stress is too small. Among the four experiments, the data obtained by the “pyramid load ” disk splitting experiment are closer to the maximum level principal stress calculated by the classical formula than the other three methods, and the deviation is small, which can be used as the criterion for estimating the maximum level An alternative to stress. In the future work research, we can provide a method reference for avoiding the influence of system flexibility on the measured maximum horizontal principal stress and improving the measurement accuracy.