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

Recent Landslides

Landslides (2010) 7:503510 DOI 10.1007/s10346-010-0211-2 Received: 21 September 2009 Accepted: 26 March 2010 Published online: 1 May 2010 Springer-Verlag 2010

Ivan Gratchev I Ikuo Towhata

Geotechnical characteristics of volcanic soilfrom seismically induced Aratozawa landslide, Japan

Abstract 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 1,200m long and 800m 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.

Keywords Landslide . Earthquake . Mechanism . Cyclic tests

IntroductionThe Iwate-Miyagi Nairiku earthquake struck the Tohoku region of northeastern Honshu, Japan on June 14, 2008. The epicenter was located about 85 km north of Sendai, and about 385 km north northeast of Tokyo (Fig. 1). The Japan Meteorological Agency estimated the magnitude MJMA at 7.2, while the moment

magnitude (Mw) measured by the United States Geological Survey was 6.9. The earthquake triggered several slope failures, primarily deep-seated rotational slides in weathered rocks, as well as a few shallow translational slides and debris ows. According to Kayen et al. (2008), most of the large landslides that caused considerable damage to highways and bridges were concentrated within an area with a radius of 1520 km from the epicenter.

The Aratozawa landslide located in the vicinity of the Aratozawa Dam was clearly the largest failure caused by the earthquake (Fig. 2). The landslide extended about 1.2 km long and 800 m wide. The total volume...