CYCLIC UNDRAINED TRIAXIAL TESTS FOR LIQUEFACTION STRENGTH AND DEFORMATION PROPERTIES OF SATURATED AND UNSATURATED NINOHE SHIRASU

Abstract

 Mudflow of earthfill composed of volcanic porous sandy soil called Ninohe Shirasu occurred during the 2011 Tohoku earthquake under high water content conditions. After sampling the soil and remolding it, cyclic undrained triaxial tests for liquefaction strength and deformation properties were conducted under saturated and unsaturated conditions. Not only saturated soil but also unsaturated soils were liquefied. The liquefaction resistance of saturated soil was less than that of standard sand. The liquefaction resistance of unsaturated soil was about 1.5 times greater than that of saturated soil, but the safety factor was low value under actual ground condition. The initial equivalent Young's modulus of the soil was about 90 MN/m².