Development of a Stress Relief Method with a Three-Directional Borehole Deformation Gage

摘要

The stress relief method for determining in situ stresses is based on the theoretical relationship of the deformation of a drill hole in an isotropic elastic body to the corresponding change of stress. If a small volume of the body containing the drill hole is cut away from the main body, it may be assumed that all stresses are relieved in the cutaway portion, and the change of stress is numerically equal to the stresses existing in the main body. The development of a stress relief method for determining 3-dimensional in situ stresses using a 3-directional borehole deformation gage is reviewed. Conclusions are that: (1) 3 nonparallel drill holes are required to obtain a 3-dimensional stress solution; (2) the stress-relief method using the borehole gage required complex and precise procedures; and (3) the method is suitable for obtaining stresses in large masses. (Author)