- The downdrag on pile groups was investigated by using a numerical analysis and an analytical study. The emphasis was on quantifying the reduction of downdrag on piles in a group due to the group effect. The case of a single pile and subsequently the response of groups is analyzed by using a three dimensional non-linear finite element approach. An approximate closed form solution is also developed for the case of the single pile. It is shown that the downdrag on piles in a group is much less than the downdrag on a single pile. Based on the results obtained, a simple method is proposed to design groups of 9 to 25 piles with spacing-to-diameter ratios varying from 2.5 to 5.0 for downdrag loads.