Applications of deep mixing technology for mitigating earth-quake disaster in Urban Area

Abstract

Many earthquakes take place every year in Japan, in which the 1995 Hyogoken-Nambu earthquake and the 2011 Tōhoku earthquake induced both a humanitarian crisis and massive economic impacts. As liquefaction, which occurs in a loose and saturated sand layer, induces quite large damages of infrastructures, the importance of liquefaction mitigation has been emphasized to minimize earthquake disasters for many years. Many kinds of ground improvement techniques based on various improvement principles have been developed for earthquake disaster mitigation. Among them, the deep mixing technology has been often applied to liquefaction mitigation. In the techniques, in-situ soil is mixed with binder by several types of methods: mechanical mixing, high pressure injection mixing and combined mixing. The high applicability of the method was confirmed in several earthquakes, including the 1995 Hyogoken-Nambu earthquake and the 2011 Tōhoku earthquake. In this paper, the outline of the deep mixing method and some applications of the deep mixing method to earthquake disaster mitigation are briefly introduced.