A Numerical Investigation for In-Situ Measurement of Rock Mass Mechanical Properties with a CCBO Probe and Evaluation of the Method’s Error in Estimating the In-Situ Stresses with the Overcoring Technique
Keywords:In-situ stresses, overcoring, measurement accuracy, numerical methods, CCBO method, COMSOL
Accurate determination of rock stress in great depths has become one of the most critical issues in civil and mining affairs along with the expansion of underground excavation spaces’ scale and deepening of under-excavation areas. The hydraulic fracturing method and coring-based laboratory methods including ASR, DSCA, and AE are main techniques in rock stress measurement in the earth’s depth. Thus far, previous studies have reported repeated samples from the values obtained from the above mentioned techniques. Nonetheless, the “Compact Conical Borehole Overcoring” (CCBO) technique is an example of the stress-relief method and this technique, is one of the most cost-effective and accurate methods for measuring the in-situ stresses simply by digging one borehole either in the tunnels’ wall or in the deep wells’ depth. The current study aims at analyzing the overcoring technique with the CCBO probe to identify errors regarding the number of sensors installed, as well as checking its ability to estimate mechanical parameters of mass rock in-situ. In this study, we have utilized the analytical method based on numerical simulations to determine the accuracy of the method’s dependence on the number of sensors installed on the probe. We performed numerical analysis using COMSOL finite element software, as well as MATLAB software. In addition, we attempted to propose possible relations for estimating mechanical parameters of mass rock using the probe, a method determined by the inventors.