Abstract： By using finite element method，the pile group effect coefficient of soil resistance under pile cap is analyzed for the composite pile foundation. The author-developed finite element program is successfully used to analyze the impact of the proportion of pile cap width to pile length，the pile distance，the number of piles and the soil type etc. on the pile group effect coefficient of soil resistance under pile cap，respectively. The results indicate that (1) both the soil resistance and its effect coefficient increase with the proportion of pile cap width (B) to pile length (L)，and the pile distance (S)，while decrease with the number of piles (n)，and (2) the pile group effect coefficient of soil resistance under pile cap is closely related to the soil type.
