EVALUATION ON TOWADA SHIRASU PUMICE COMPRESSIBILITY AND ABRASIVITY DURING CYCLIC SHEARING

Abstract

 Volcanic sandy soil Shirasu filled ground whose particle is porous, crushable and liquefable had sometimes caused mudflow-type slope failure during earthquake under high water retention condition. In order to investigate the liquefable mechanism, the solid phase of porous soil particle compressibility and abrasivity were quantified by uniaxial compression test and cyclic shear test using small-sized test-piece shaped from Shirasu pumice stone. The solid specimens compression strength was 400-6200kPa, Young's modulus was 30-1100MPa, bulk modulus was 10-370MPa. These were too smaller value than concrete or original stone. Abrasion rate was 0.0027g/cm²/m/kPa. Assuming soil skeleton as face-centred cubic lattice whose particle size is mean diameter of Shirasu sand, the compressibility and mass-exchange due to abrasiveness significantly caused to increase void ratio. The B value was slightly incleased. Increasement of void ratio by abrasion during cyclic liading may be one of liquefable factors of Shirasu soil.