A series of triaxial compression tests, plane strain tests and cyclic undrained triaxial tests on several volcanic coarse-grained soils were performed to understand the physics of the mechanical behavior of soils with particle crushing. Volcanic coarse-grained soils were taken from natural deposits, produced by fall deposition in Hokkaido, Japan. Test results showed that anisotropy in mechanical properties of volcanic soils is observed more clearly than that of clean sand. It was also found that the stress-strain-strength properties of granular materials are strongly influenced by their particle breakage, when the test is performed under stress system with the increase of effective mean principal stress.