Dizhi lixue xuebao (Jun 2023)
Influence of rock inhomogeneity degree on the crustal stress results measured by hydraulic fracturing method
Abstract
Accurate in-situ crustal stress data are essential for excavation support design and long-term stability analysis of underground projects. We tested the main shaft of the Shaling Gold Mine for crustal stress using hydraulic fracturing technology, and the crustal stress state of 20 measurement points was obtained. The Brazilian test, uniaxial compression test, and acoustic emission test of the cores were conducted indoors to obtain the rock’s spatial inhomogeneity and strength distribution. We analyzed the relationship between the inhomogeneity of the rock and the hydraulic fracturing results. The analysis results show that the magnitude of the principal stress increases nearly linearly with the measurement depth, with the maximum horizontal principal stress value ranging from 20.78 to 45.2 MPa and the minimum principal stress value from 14.94 to 35.33 MPa. The average direction of the maximum horizontal principal stress is NW 65°. The inhomogeneity of each layer of the cores varies, and the inhomogeneity coefficient of the metagabbro is from 0.1 to 0.3. The number of acoustic emission signals under each intensity of the rock is basically the same, and the dispersion of the rock is small. The non-homogeneity coefficient of granite is up to 1.0, dominated by the acoustic emission signals generated by the intense-phase rupture at the late loading stage. The non-homogeneity of the rock affects the direction of expansion of the hydraulic fracture, and the angle\begin{document}$\varphi $\end{document}between the expansion direction and the maximum horizontal principal stress affects the measurement results of the horizontal maximum and minimum principal stresses and has a more significant effect on the horizontal minimum principal stress. The relationship between hydraulic fracture measurements and rock properties was analyzed, which is helpful for accurately detecting the distribution of stress fields in inhomogeneous strata.
Keywords
