Abstract
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.
