Based on elastic theory and reasonable assumption

the control differential equations have been put forward by adopting the load-transfer function method in order to research the load transfer mechanism of composite foundation of rigid piles with cap

including relations among pile settlement and its axial stress

vertical displacement of soil under pile cap and vertical stress of it

vertical displacement of soil besides pile cap and vertical stress of it

the friction force of pile-side

the soil friction force of the edge of pile cap and load level

depth in rigid pile with cap composite foundation. The corresponding analytical formulas have also been derived by using approximate solution method of differential equation. The calculation results can image basically the mechanical behavior rules of the load transfer for rigid pile with cap composite foundation according to the method proposed

using directly the relation of load-settlement of pile tests as known condition.