Liquefaction-Induced River Levee Failure at Miwa of Inba Along Tone River During 2011 Tohoku Earthquake

A numerous number of river levee failures were observed in Kanto region far from the epicentre during 2011 Tohoku earthquake. In this study, the earthquake reconnaissance investigations were carried out on the liquefaction-induced sliding failure of the river levee located at Miwa of Inba along Tone river. A series of weight sounding tests were conducted at a dozen of locations near the failed river levee. Soil sampling was also carried out at each location of weight sounding, and laboratory sieve and sedimentation analyses were performed to determine the grain size distributions of the soil samples. At this particular site, the outer face of the river levee slid laterally, and the evidence of sand boils was clearly found at the foot of the river levee. The liquefaction resistance of soils was estimated based on the results of weight sounding and soil sampling, by using the empirical formula developed by the authors, which explicitly incorporates the effect of fines. The values of liquefaction resistance of foundation soils at which the river levee failed and did not fail are estimated, and the cause of the sliding failure is discussed in detail.