Abstract: Ground improvement using a joint technology of combined in-situ shadow solidification and pipe-pile-reinforced foundation is one of effective methods used for deep soft clay treatment under infrastructure embankments. Based on the load transfer theory of the composite foundation, this paper analyzes the embankment filling, solidified layer, pile, soil between piles and underlying layer as a whole, and establishes the calculation method of stress and settlement of composite foundation considering the continuity of stress and settlement deformation. The deformations of pipe piles, the surrounding soil, and the overlying solidified layer are compatible by applying the stress continuity and volume deformation continuity at the bottom of the solidified layer. This paper discusses the influence of the in-situ shadow solidification on the pile-soil stress ratio and settlement of the composite foundation. The established method has been verified via comparisons with field tests data about the joint technology and traditional pipe pile-reinforced foundation. It shows that the pile-soil stress ratio in composite foundation increases linearly with the modulus of the solidified layer (with 1.6 MPa?1). The position of the neutral point of pile moves up with the increase of the solidified layer modulus (between 0.12 and 0.45). Considering the performance and reinforcement effect of curing agents, it is more appropriate to select the curing agent with cement content no more than 11%.

Key words: in-situ shallow solidification, pipe pile-reinforced foundation, load transfer, pile-soil stress ratio