A Note on Pile Length Optimization of Pile Groups Considering the Non-Linear Behavior of Piles

The use of dissimilar piles below a raft is a relatively innovative concept and can optimize the design of a piled raft. This paper discusses a pile length optimization method. To analyze non-linear behaviour of piles, a "cut-off" method was adopted to limit pile capacity in the integral equation considering linear behaviour of piles. In this method, adjacent non-yielding piles take more loads when some piles start to yield (i.e., reaching their individual ultimate load capacity). A pile-square rigid raft system was analyzed to illustrate the effects of the proposed approach. The analysis showed that the stiffness of the piled raft decreased after considering the load cut-off. The load cut-off procedure could make the distribution of the reactions for short piles more reasonable in terms of their locations and lengths. The optimized design using dissimilar piles would create a more economical solution than the design with uniform piles.