Abstract: The reinforcing and restraining effect of piles embedded in soils is objective existence. However, the correlative research work on pile groups settlement methods is not deep enough and needs to be continued. Based on the shear displacement method, considering the reinforcing and restraining effect, the settlements of the analyzing pile caused by loads on the pile top were calculated, including the reduction effect caused by the existence of the other adjacent piles. And the additional settlements of the adjacent piles arising from the settlement of the loaded pile were obtained as well. Thus a simplified formula of interaction coefficients between any two piles was presented. Meanwhile, the equivalent shear stiffness coefficients of soil around each pile were developed; and an equation of displacements caused by load on top of the analyzing pile imbedded in multi-layered soils was built; so recurrence relations of settlement and axial force of pile shaft between upper and lower of each pile sections were respectively deduced; in the process of deduction, Boussinesq solution was modified to include the effect of different embedded depths, and then used to derive the equivalent stiffness coefficients of the soil under the pile tips. Lastly, the formula was extended to the settlements calculation of high and low cap pile groups. Different methods were compared with two engineering cases. The results show that the load-settlement curve computed by present method agreed well with those measured from real engineering cases; and the calculating interaction coefficients are much less than ones calculated by the elastic theory method.

Key words: reinforcing and restraining effect, interaction coefficient, pile group settlement, shear displacement method, multi-layered soils