Optimal pile arrangement for minimizing differential settlements in piled raft foundations

This paper presents an optimal pile arrangement scheme fur minimizing the d ifferential settlements of piled raft foundations. A raft is modeled as a p late based on the Mindlin theory, and soil and piles are modeled as Winkler and coupled springs, respectively. The stiffness of piles is obtained by t he approximate analytical method proposed by Randolph and Wroth, and the mo dulus of the subgrade reaction is adopted to evaluate the Winkler spring co nstant. The objective function for the optimization is defined as the squar ed L-2 function norm of the gradient vector of the defected surface of the raft for circumventing difficulties in using direct definition of the maxim um differential settlement. The optimization is performed with respect to t he locations of the plies, The recursive quadratic programming is adopted f or optimization. The validity and effectiveness of the proposed method are demonstrated by three numerical examples. (C) 2001 Elsevier Science Ltd. Al l rights reserved.