When constructing a pile foundation under the condition that a thin soft layer is present on the support layer, the shaft resistance of the pile is insufficient because the embedded depth is not enough, and as a result, the pile is designed to be deeply put into the support layer and it affects the workability and economy. In particular, when the support layer is a rigid ground such as soft rock or rock, it is very difficult to install the pile deep into the support layer. In order to cope with such a situation, there are cases where a pile construction method is adopted in which a steel pipe pile is inserted deep into the support layer using a high drilling power piling rig with twin coaxial rotary head, and then cement slurry is injected to fix the pile to the support layer (hereinafter referred to as EAC method). This paper introduces the outline of EAC method and the results of loading tests of piles constructed by EAC method.
In loading tests of piles constructed by the EAC method conducted in the Kyushu region, greater axial resistance was exhibited in any of the tests than previously assumed. In the loading tests, it was not possible to load until the stage of confirming the ultimate resistance, so the base resistance of the piles was slightly smaller compared to the estimation formula of other pile construction methods. In contrast, it was confirmed that the shaft resistance per unit area of the range where the piles were cemented was slightly larger than the estimation formula and the measurement results of that of piles constructed by other methods. Although it is difficult to suggest an estimation formula for the axial resistance of a pile constructed by the EAC method only with the test results this time, the details of the construction method and load test results shown in this paper will be helpful for the construction of similar piles in the future.

Key Words: Pile, Axial resistance, Piling rig with twin coaxial rotary head, Cement grouting,Pile load test