Abstract
There have been very few experimental results on mechanical properties of natural volcanic breccia. A series of triaxial compression tests under undrained condition were performed to elucidate the effects of the percentage of clasts, specimen size and maximum clast size on its strength and deformation behavior. The results suggest that the effect of the percentage of clasts is small, even though the internal friction angle become large and the deformation become inhomogeneous when the percentage of clasts exceed 20%. As to the effect of the specimen size, the mechanical properties are not largely different between specimens of various diameters up to 30cm although the internal friction angle is slightly small for large specimens. Moreover no effect of the maximum clast size is recognized on mechanical properties.
