Optimal Pile Arrangement for Minimizing Differential Settlements in Piled

             Raft Foundations


K.N. Kim, S.H. Lee, K.S. Kim, C.K. Chung, M.M. Kim, H.S. Lee



 This paper presents an optimal pile arrangement scheme for minimizing the differential settlements of piled raft foundations. A raft is modeled as a plate based on the Mindlin theory, and soil and piles are modeled as Winkler and coupled springs, respectively. The stiffness of piles is obtained by the approximate analytical method proposed by Randolph and Wroth, and the modulus of the subgrade reaction is adopted to evaluate the Winkler spring constant. The objective function for the optimization is defined as the squared L2 function norm of the gradient vector of the deflected surface of the raft for circumventing difficulties in using direct definition of the maximum differential settlement. The optimization is performed with respect to the locations of the piles. The recursive quadratic programming is adopted for optimization. The validity and effectiveness of the proposed method are demonstrated by three numerical examples.

KEY WORDS : differential settlement; piled raft foundation; optimal pile arrangement; optimization; recursive quadratic programming

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