Calculation and application of in-situ stress components in hollow inclusion measurement

To improve the in-situ stress calculation method applied in hollow inclusion measurement, the formulas to calculate in-situ stress components are deduced by the least squares fitting method of the linear parameter by considering the installation mode of the hollow inclusion strain cell. We obtained a modified calculation method of six in-situ stress components with standard errors. In Gongchangling underground mine, measurements were performed by using the complete temperature compensation technique, and the improved hollow inclusion strain devices are applied at three points with the levels of -160 m, -220 m and -280 m, respectively. Three sets of borehole wall strain data are measured. The results show that the standard error of in-situ stress components calculated by the modified calculation method is less than that calculated by the traditional method. Therefore, the reliability of calculated results is improved by using the modified calculation method. Based on six obtained in-situ stress components calculated by the modified method, the stress states of Gongchangling underground mine are analyzed. The results show that the in-situ stress is dominated by the horizontal tectonic stress field in the mine area. The maximum horizontal principal stress is oriented in SEE-NWW direction. The maximum horizontal principal stress, the minor horizontal principal stress and the vertical principal stress are increased with the depth.