DETERMINATION OF FRACTURE TOUGHNESS OF GABBRO BY DOUBLE TORSIONAL METHOD

The stress intensity of Jinan gabbro was measured by using the double torsional method. The crack velocities V were also observed from the load relaxation at constant crosshed displacement under dry and wet conditions. The results obtained are similar to that of Atkinson's.The fracture toughness of gabbro was found to be 2.81 0.03 MNm-3/2 A view different from that of Spetzler and Atkinson on the mechanism of the subcritical crack growth under wet condition has been proposed.The relation between acoustic emission rate and the stress intensity is nearly the same as those of V vs K1 from results of acoustic emission experiment.