Geotechnical characteristics of volcanic soil from seismically induced Aratozawa landslide, Japan

This paper seeks to investigate the properties of volcanic soil from the Aratozawa landslide, the largest failure triggered by the 2008 Iwate-Miyagi Nairiku earthquake, Japan. The Aratozawa landslide, which extended about 1,200 m long and 800 m wide, consisted of a complex system of ridges and depressions, including a number of smaller failures that occurred within the slide body. Field investigation was carried out to study the geotechnical properties of pumice that was exposed at the scarp of two smaller slides. The pumice was found to be heavily weathered, having low dry density and high moisture content. Portable cone penetration tests were performed to evaluate the in situ properties of soil as well as to determine the thickness of the weathered zone. Laboratory examination included slake-durability tests, grain-size distribution analysis, and a series of cyclic loading triaxial compression tests conducted on undisturbed and reconstituted samples. Laboratory test data indicated that the soil had a high potential for generation of excess pore-water pressures, suggesting that liquefaction might have occurred in the weathered mass of pumice during the earthquake.