Mitsumasa Furuzumi

The Charpy Impact Test of Rock (2nd Report)-Dynamic Fracture Toughness-

In this study, we investigated dynamic fracture toughness and crack propagation velocity of rocks by using Charpy impact test.The results of the experiments showed that crack propagation velocity of the rocks depends on impact energy applied to it, and Q (impact energy/crack propagation velocity) correlates with static strengths of the rocks. Also, the dynamic fracture toughness of the rocks, which is calculated from the dynamic fracture energy obtained by using Charpy impact test, was found to depend on the impact energy applied with it, and correlates with crack propagation velocity and static compression and tensile strengths of the rocks.

Shear Displacement Behavior of Rocks in Shear Fatigue Process. Experimental study on cyclic fatigue process of rocks under direct shear test (2nd Report).

In this study, the behavior of upper and lower (permanent) shear displacements was investigated with cyclic shear loading tests for two kinds of rocks. The behavior of shear displacement obtained in this study may be classified into two processes. In one process, shear displacement is induced mainly by the closure of pores and cracks, the deformation within grains and sliding. In the other one, it is induced mainly by the growth of cracks. In case of neglecting the effect of normal stress, the slope of the equation expressing the relationship between the minimum rate of upper shear displacement and the number of cyclic loading on log-log graph is -1.02 for Kimachi sandstone and -0.92 for Tohoku marble. It is -1.09 for Kimachi sandstone and -1.00 for Tohoku marble when the rate of lower shear displacement is minimum. Upper shear displacement where the rate of upper shear displacement increases rapidly corresponds to shear displacement at the peak shear stress in the convenient direct shear test. Similarly, lower shear displacement where the rate of lower shear displacement increases rapidly corresponds to the permanent shear displacement at the peak shear stress.