Finite element analysis of rigid-soft composite pile foundation

A model of 6×6 piles rigid-soft-pile foundation was established to analyze coordinative working performance of composite pile foundation with the three-dimensional FEM. When the ratio of the rigid-soft –pile-number and loading level becomes，the changing rule of loading on the top of the piles and strain-stress in the foundation was researched. If the rigid-soft-piles-number ratio is constant and the piles’ loading is lower than their ultimate loading capacity, under different loading levels, the rigid-soft-pile-loading ratio is nearly invariable. Under the same loading level, there is economical ratio (lower than 40 %) of the rigid-total-piles-number. When the rigid-total-pile-number ratio is lower than it, the stress in superficial layer reduces effectively with the number of rigid piles increased. And the effect of decreased-settlement is also obvious. When the rigid-total-pile-number ratio is higher than it, increased the number of rigid piles reduces the stress and strain in the foundation un-apparently.