The method of compression test under high pressures in a cubic press and the strength of granite

Abstract

A cubic press was used for the triaxial test on rocks under very high confining pressures up to 4 GPa. For a specimen of 16 mm length and 8 mm diameter in a silver chloride sleeve with a pressure-medium of pyrophyllite, the axial and the confining pressures were calibrated by means of the phase transitions in bismuth, thallium and barium. The compressive strength of granite was determined up to 3 GPa of confining pressure in the cubic press. The results were compared with those from the ordinary triaxial testing machine with a pressure-medium of oil up to 450 MPa. For the whole pressure range, the compressive strength was expressed by : C/ C 0 = 1 + 4.33 ( P/ C 0) 0.47 where C is the differential compressive strength, P is the confining pressure and 0 is the uniaxial compressive strength which was 180 MPa for the Man-nari granite used in this work.