Using the finite element method

the paper is mainly focused on the effect of pile group and its effect coefficient of the composite pile foundation. Some influential factors

such as the pile length (L)

the ratio of the pile spacing to the pile diameter (Sa /d)

the pile number (n) density and soil type etc.

are introduced and their effects on the effect of pile group and its effect coefficient

are analyzed

respectively. The results indicate that: the bearing capacity of the single pile (Qu) and the effect coefficient of pile group both increase with the pile length (L)

and decrease with pile number (n). While the ratio of the pile spacing to the pile diameter (Sa/d) is a fixed quantity

the Qu and theη will achieve maximum. The effect of pile group and its effect coefficient of the composite pile foundation is correlated with the soil type.