In order to improve the effectiveness of steel sheet-pile method for the countermeasure on soft ground settlement under embankment load, a PFS method was developed under the research group whose chair was Prof. Ochiai of Professor Emeritus at Kyushu University, Japan in 2005. At that moment, a series of in-situ full scale tests for this countermeasure method including PFS method which is the combination of end bearing sheet-pile with those of floating type were conducted in the City of Kumamoto, Japan under the Ministry of Construction (current name of this ministry is Ministry of Land, Infrastructure, Transportation and Tourism).
In this paper, the main objective is to discuss the quantitative evaluation of PFS method using coupling finite element analysis. Because of the geometry of PFS structures, this analysis was conducted in three dimensions. A numerical analysis was done for the cases of the full scale tests at the site in Kumamoto City, in which the field tests with the case of PFS method was conducted. A “tij model” developed by Nakai et al which can be considered the effect of intermediate principal stress was used as a constitutive model for clayey soil. Here, not only displacements in the ground but also the change of excess pore water pressure were compared.
Finally, based on those numerical studies, an effectiveness of PFS method as a countermeasure method was discussed.