A newly developed composite foundation technique is used in the practical project of soft soil foundation treatment. This kind of composite foundation is made up of two types piles
the rigid one is concrete pile
and the flexible one is mixed-in-place cement pile. The design ideas of the composite foundation are proposed. In order to determine the bearing capacity of composite foundation
the in-site loading tests of an important project were carried out; and the major engineering characteristics of the composite foundation are studied. The stress ratio and the load ratio of pile to soil in the process of loading are analyzed carefully. The results of tests indicate that the rigid pile
the flexible pile and soil can interact on each other very well; and their bearing capacities can be developed reasonably.