New Technologies for Soft Ground Improvement in Japan ― Low Improvement Ratio Cement Column Method and Lightweight Banking Method

This paper presents promising new technologies for soft ground improvement which include the low improvement ratio cement column method (LCC) and the lightweight banking method using foam mixed soil (LFS). As a measure to reduce settlement and lateral deformation due to road embankment loading on soft ground, the column type deep mixing method used at a low improvement ratio of around 10-20% throughout the whole bottom surface of embankment has been found to have sufficient performance and to save total costs. LCC is often combined with surface stabilization or geotextile sheeting depending on the situation. This paper reports on the points of the design of LCC based on the case histories in Japan and Thailand. An attempt to use lightweight foam mixed soil (LFS) throughout the entire road embankment cross-section on a soft ground was shown to be applicable, in which cohesive soil taken in situ from the surface of the ground was used to make a high lightweight soil embankment, which means that the in-situ surface soil is expanded to attain the required volume of the embankment and that purchase and carrying of fill materials is unnecessary.