Measurement of in-situ rock stress by hemispherical-ended borehole technique

Abstract

The paper presents a new technique to measure the complete state of in-situ rock stress in a single borehole. The stress tensor is computed from 16 strains on the hemispherical bottom surface of a borehole. An arrangement of strain gauges to determine the stress tensor with high accuracy is described. Details concerning relevant equations to be used in practice, a spherical strain cell to bond the strain gauges directly to the bottom surface at the designated stations and the system for in-situ measurement by the stress relief technique are presented and discussed.