Applicability of Cross-Sectional Borehole Deformation Method (CBDM) to Measure Rock Stress Changes through Laboratory and In-Situ Experiment

Abstract

The stress state around rock structures, such as underground opening and rock slope, is changed as their construction progresses and the time proceeds. The monitoring of the stress change is important to verify the design, control the construction and estimate the long term stability of rock structures.
In order to measure two dimensional stress changes in a plane perpendicular to a borehole axis, we developed the Cross-sectional Borehole Deformation Method (CBDM) and made clear the influence of factors on estimated stress change theoretically. In this paper, the applicability of CBDM to measure stress change in laboratory and in situ experiment. Firstly, the prototype instrument with a laser displacement sensor is described in detail. Secondly, the instrument is applied to estimate the stress change in a laboratory experiment. Then it is made clear that a non-linear least square method and a non-linear programming for optimization with the technique of golden section search is effective for estimating rock stress change. Finally, applying the CBDM to measure rock stress change within the immediate sidewall of underground opening under its construction, the stress changes for six months can be estimated successfully.
As a result, it is concluded that the CBDM is available for estimating rock stress change in two dimension.