Microstructure and the resistance of rock to tensile fracture

The resistance of rock to tensile fracture may be measured by its fracture energy G I , which is found to range from 40 to 200 J/m 2 in tests on nine types of sedimentary and crystalline rock. Differences in microstructure among the rocks tested are the principal cause of differences in the steady state value of G I , in the distance that a crack must advance before steady state fracturing is attained, and in the amplitude of the fluctuation of...