Rock stress determinations from overcoring--an overview.
Denver, CO: U.S. Department of the Interior, Bureau of Mines, Bulletin 694, 1993 Jan; :1-146
This bulletin describes the U.S. Bureau of Mines three-component borehole deformation gage and the overcoring techniques used in rock stress determination. Thirty years of experience with the borehole gage has shown that it is an accurate instrument for measuring deformation of a borehole. The theoretical basis relating the deformation of a borehole to the in situ field stress is presented. Rock anisotropy, variation of topography on the stress field, and nonlinearity of the rock can be accounted for in calculating the in situ state of stress. Drilling equipment, accessories, and instrumentation necessary for the overcoring are presented, as well as the design, fabrication, operation, and calibration of the gage; site selection; and proper overcoring procedures. Biaxial and triaxial testing of the stress-relief core to determine the elastic properties of the rock are discussed. Data reduction, stress calculations, interpretation of results, and computer codes are included to provide a complete working knowledge for determining surface or underground in situ rock stress. A comparison of alternative methods for determining the absolute in situ field stress is also presented.
Underground mining; Rock mechanics; Overburden; Stress concentration; Coring; Computer applications
NTIS Accession No.
Denver, CO: U.S. Department of the Interior, Bureau of Mines, Bulletin 694