This paper investigates the lateral resistance of a composite foundation of pile with reusing existing piles by cyclic lateral loading tests and simulation analysis. In this foundation, existing piles are not jointed to the raft with shallow soil improvement between a new pile and existing piles. The major findings obtained from tests and simulation analysis are summarized as follows; 1) Existing piles left in the soil have almost no effect on lateral resistance of a new pile. On the other hand, due to shallow soil improvement between a new pile and existing piles, existing piles are displaced together with a new pile and therefore lateral resistance of a new pile increases. 2) The test results, such as lateral resistance of a new pile and stresses in piles, are precisely simulated by 3-D finite element analysis. Furthermore, ultimate stress in improved soil can be approximately predicted.
