METHOD FOR DETERMINATION OF PRINCIPAL NORMAL STRESSES IN ROCK MASS AND DEVICE FOR ITS REALIZATION Russian patent published in 1995 - IPC

FIELD: mining. SUBSTANCE: three clusters of three parallel holes are drilled in rock mass in three orthogonal planes in vertexes of equilateral triangle whose one side is taken as initial zero direction. Installed in holes are radiators and receivers of elastic vibrations. Measured are time of propagation of longitudinal waves in rock samples taken at same distance from drilling machine station. Height of sample equals two hole diameters. Measured also is time of propagation of longitudinal waves in interhole space. Base of measurement-to-hole diameter ratio is taken equal to ten. Determined are stresses in measurement points of each hole cluster. Calculated are normal and tangent stresses of rock mass is planes square to direction of X, Y and Z axes in each of three hole cluster and principal normal stresses under conditions of volumetric stress state of rock mass is determined. Device for method realization includes piezoelectric elements located in cylindrical body with supporting plate suspended from body covers on sound-insulating flexible braces and hold-down member. Piezoelectric elements are turned through 60 deg. relative to one another. EFFECT: higher efficiency. 2 cl, 6 dwg, 4 tbl