Abstract
Triaxial compression test was performed on two set of parallel grading samples, which were composed of crushed rhyolite and granite, respectively and compacted to 90% of relative density. Finer and coarser samples of granite showed same relation of confining pressure and shear strength, however, the finer sample showed higher strength for rhyolite. It would come from the flatter grain shape of finer sample. The nature of decreasing secant moudulus of shear strength with increasing confining pressure was due to the flatness of grain shape, too. On the other hand, crushing of grain during shearing seemed to no influence on shear strength.
