解决水平钻孔水压致裂法在地应力测量中计算原理不明确的问题,以天山胜利隧道水平定向钻勘察项目为依托,首先构建基于原生裂隙法与多孔交汇法的水平孔围岩三维应力状态理论模型,并探讨其控制边界条件及计算方法;
然后,通过与室内物理模型试验数据进行对比分析,验证理论模型的合理性; 最后,构建水平孔水压致裂法地应力测量有限元模型,通过对比数值模拟、理论计算和室内试验结果,验证该有限元模型建模方法的可行性。结果表明: 1)理论模型计算结果与室内物理模型试验记录数据接近,最大误差为6.8%,说明结合原生裂隙法与多孔交汇法构建的水平孔围岩应力状态理论模型可以适用于基于水平定向钻勘察的水压致裂法地应力计算; 2)数值模拟结果与试验记录数据接近,最大误差为9.51%,说明采用Abaqus扩展有限元法(XFEM)结合嵌入式Cohesive单元的方法能够合理模拟真实水平孔水压致裂测量地应力的过程; 3)理论模型计算结果与数值模拟结果的一致性较好,最大误差在允许范围内,验证了理论模型与有限元模拟方法的正确性、准确性和可靠性。
The calculation principles
in the measurement of in-situ
stresses using the horizontal drilling hydraulic fracturing method are
undefined. Therefore, a case study is conducted on a horizontal directional
drilling survey project of the Tianshan Shengli tunnel. A theoretical model for
the three-dimensional stress state of the surrounding
rocks in horizontal boreholes is established on the basis of the native fissure
and intersecting porous methods, and its controlling boundary conditions and
computational methodologies are investigated. Subsequently, the rationality of
the theoretical model is validated through comparative analysis with data from
indoor physical model experiments. Finally, a finite element model for stress
measurement using hydraulic fracturing in horizontal boreholes is constructed,
and its feasibility is validated through comparative analyses of numerical
simulations, theoretical calculations, and indoor experimental results. The
findings are as follows: (1) The calculated results of the theoretical model
closely align with the recorded data from the indoor physical model
experiments, with a maximum discrepancy of 6.8%,
indicating that the theoretical model for the stress state of surrounding rocks
in horizontal boreholes, constructed by integrating the native fissure method
and intersecting porous method, is applicable for stress calculations using
hydraulic fracturing in surveys based on horizontal directional drilling. (2)
The results of numerical simulations closely resemble the experimental records,
with a maximum deviation of 9.51%, indicating that the
use of the Abaqus extended finite element method combined with embedded
cohesive elements can effectively simulate the measurement of stress induced by
hydraulic fracturing in real horizontal boreholes. (3) The consistency between
the calculated results of the theoretical model and numerical simulations is
satisfactory, with the maximum error falling within an acceptable range. This
validates the correctness, accuracy, and reliability of both the theoretical
model and finite element simulation method.