Comparison and evaluation of overcoring and hydraulic fracturing stress measurements.

The stress measurements determined by both the overcoring (OC) and hydraulic fracturing (HF) methods in the Shuichang iron mine and Sanshandao gold mine were compared and evaluated, respectively. The results indicate that the independent OC and HF data in the two mines reveal the same dominant faulting stress regime. The σH orientations derived from the OC and HF methods in the Shuichang iron mine are dominantly oriented in the N81.1°W-N89.4°W and N77.0°E-N88.0°E, respectively, and the σH orientations yielded from the OC and HF techniques in the Sanshandao gold mine are predominantly in the N30°W-N90°W and N55.5°W-N60.4°W, respectively; hence, the σH orientations obtained by the two different methods in the two mines are comparatively similar. In addition, the shapes of the probability density diagrams using an improved Bayesian regression approach of the three principal stresses measured by the OC and HF methods in the same mine are quite similar, and all the obtained Kolmogorov-Smirnov test p-values are larger than the selected significance level of 0.01, indicating that the stress data interpreted by the two methods approximately follow the same distribution law. Thus, the performance of the two techniques and the reliability of the measured data are satisfactory.