Compacted fill and rammed aggregate piers (RAPs) were separately installed adjacent to a 9-ft by 9-ft by 2.5-ft driven pile foundation founded in soft clay. The compacted fill used to laterally reinforce an area of 11 ft by 5 ft by 6 ft deep adjacent to the pile cap was clean concrete sand. The thirty-inch diameter RAPs were installed in three staggered rows to a depth of 12.5 ft below the ground surface adjacent to the pile cap to test the increase in lateral resistance afforded by their installation. The foundation was laterally loaded and load, displacement, and strain readings were recorded. The results of this testing were compared with similar tests performed with virgin soil conditions. The total lateral capacity of the pile foundation increased by 5 percent or14 kips due to compacted fill placement against the face of the pile cap. The passive force acting only on the pile cap decreased from 54 kips in the virgin case to 30 kips after installation of the compacted fill, a decrease of about 45 percent. The total lateral capacity of the pile foundation that was retrofit with RAPs was increased by 18 percent or 52 kips as compared to an identical pile cap in virgin clay. The passive force acting on the pile cap at 1.5 inches of pile cap displacement was determined to be approximately 50 kips, showing a slight decrease in passive resistance as compared to the tests performed on virgin soil. Both reinforcement techniques reduced pile head rotation and the bending moments in the shallow portions of the piles.



College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering



Date Submitted


Document Type





Nathan Lemme, lateral, pile group, compacted fill, rammed aggregate pier, ground improvement, soil, reinforcement