Measurement of induced stress and estimation of rock mass strength in the near-field around an opening

In order to estimate rock mass strength and sliding criterion of discontinuity from the stress state around an opening, methods of measuring induced stress and monitoring stress change are described. Those methods are the Compact Conicalended Borehole Overcoring (CCBO) technique and the Cross-sectional Borehole Deformation Method (CBDM). Firstly the concept of estimation of rock mass strength from the stress state measured by those methods is explained. Then applying the CCBO to measure around underground opening, rock mass strength and sliding criterion of discontinuity from the obtained stress distributions are estimated. Furthermore a case example of the CBDM such that stress change around an opening is monitored under construction is demonstrated. It is shown that the CCBO andCBDMare convenient for estimating not only induced stress and stress change but also rock mass strength and sliding criterion of discontinuity.