Behavior of Disconnected Pile Foundation System

In the design of a foundation, the settlement of the foundation may exceed allowable design criteria even with a competent bearing stratum. In such a case, a pile foundation system may be adopted using piles as a settlement reducing component. In this paper, Disconnected Pile Foundation (DPF) system, which installs disconnected piles underneath the footing and uses the piles as ground reinforcements, is studied as a cost effective design method against the classical pile foundation system. To this end, large size loading tests were carried out on weathered ground, changing area replacement ratio and length of piles. The results indicated that the settlement of the reinforced ground was reduced by 46–85% from that of the unreinforced original ground. The correlating formula between the area replacement ratio and the load bearing ratio of piles was derived from the test results and numerical analysis. From the correlation, a design method determining the size and the quantity of the disconnected piles to enhance the bearing capacity of original ground to the desired value was proposed based on settlement criteria.