NUMERICAL ANALYSIS ON MECHANISM OF DEWATERING AS A MITIGATION METHOD AGAINST LIQUEFACTION

Abstract

In recent years, liquefaction due to major earthquake caused serious damages to many infrastructures and houses around the world. In order to protect people’s daily life and infrastructure from the disaster, development of effective and economical countermeasure against liquefaction that can be applied to existing houses is becoming increasingly important. Although many liquefaction countermeasures have been developed by many researchers, most of them require large construction machines and are costly, which limits their application to existing structures. For this reason, a liquefaction countermeasure, called as groundwaterlevel decreasing method, has been proposed in Japan. This method has already been put into practice and the construction of the countermeasure has finished several years ago. The purpose of this method is to change a liquefied layer to a non-liquefied layer by lowering the groundwater level. Yet the performance of this method has not been fully evaluated quantitatively. Therefore, in this paper, numerical analysis using FEM method was carried out to evaluate the liquefaction damage before and after the lowering of groundwater level. The calculation is conducted with 2D soil-water coupling finite element-finite difference (FE-FD) analysis based on a rotating-hardening elastoplastic constitutive model. From the analyses, it is found that the effective stress of the ground below under-groundwater level increases significantly because of the lowering of groundwaterlevel, resulting in an increase in resistance to liquefaction and mitigating the settlement damage of ground.