pile spacing effects under lateral loading

ultimate lateral resistance and lateral subgrade modulus within a pile group are known as the key parameters in the soil-pile interaction phenomenon. in this study, experimental investigations were conducted on twelve model pile groups of configuration for embedded length-to-diameter ratio l/d=32 into loose and dense sand, spacing form 3 to 6 pile diameter, in parallel and series arrangement. the ultimate lateral load is increased 53% in increasing of s/d from 3 to 6 owing to effects of sand relative density. an increasing of the number of piles in-group decreases the group efficiency owing to the increasing of overlapped stress zones and active wedges. a ratio of s/d more than 6d is large enough to eliminate the pile-to-pile interaction and the group effects. it may be more in the loose sand.