• For the 3 by 3 pile group tested, results clearly showed the effect of shadowing, in which the soil
resistance of a pile in a trailing row was greatly reduced because of the presence of the pile ahead
of it. The soil resistance of the piles in the leading row was only slightly less than that of a laterally loaded isolated single pile. The key in the design of pile groups subjected to lateral loads is to
account for the loss of soil resistance for the piles in the trailing rows. One method to account for
this loss of soil resistance is to use a “p-multiplier,” which is a constant used to modify the p-y
curves of a single isolated pile.