Seismic damage analysis on the river levees reinforced with steel sheet pile by the 2016 Kumamoto earthquake

摘要

In April 2016, earthquakes occurred in Kumamoto prefecture that recorded a maximum magnitude of 7.3, causing the ground subsidence of river reeve caused by the liquefaction of river reeve body and its foundation ground. A steel sheet piling method has been widely used as a reinforcement for river levees in Kumamoto prefecture to reduce the ground settlement and lateral displacement of soft ground. In the steel sheet piling method, there are a conventional method penetrating sheet piles to support layer, a floating steel sheet piling method (called “the FL method”) not penetrating them to support layer, and partial floating steel sheet piling method (called “the PFS method”) that is combined with the FS method and the conventional method. The objective of this study is to investigate the damage of river levee caused by the 2016 Kumamoto earthquake and to evaluate the effectiveness of the steel sheet piling method as a countermeasure against earthquake. The seismic damage of the river levee reinforced with the steel sheet piling methods was analyzed in terms of both liquefactions of foundation ground and river levee body.