Abstract: In order to accurately calculate the settlement of rigid pile composite foundation under embankment load, an analysis method is provided based on vertically linear development model of friction coefficient between the inner and exterior soil columns in the embankment supported by the composite foundation, as well as distribution mode of pile-soil relative displacement and development coefficient of skin friction on the pile. Thus, considering soil arching effect in the embankment and coupling characteristics of vertical load transfer between the embankment and improved zone, pile-soil stress ratio, differential settlement between pile and soil, and settlement of the improved zone are all derived by the principle of static equilibrium of a microelement in the embankment-foundation system. The proposed method can quantitatively reflect the dominant influence factors, such as height of embankment, internal friction angle and cohesion of the filling and soft foundation soil, pile length, pile diameter and pile spacing. Analysis results of examples show that relative error between the calculated and measured values is less than 15%. Pile length has non-linear effect on the settlement of the improved zone, while area replacement ratio, cohesion and internal friction angle of the foundation soil have linearly negative effect on the settlement. Moreover, the settlement is more sensitive to internal friction angle than cohesion.

Key words: embankment, rigid piles, composite foundation, soil arching effect, settlement of improved zone