Cyclic lateral performance of helical tapered piles in silty sand

A novel piling system, spun-cast ductile iron (SCDI) tapered pile fitted with a lower helical plate, is proposed in this study to support solar energy panels. The cyclic lateral performance of the pile is investigated herein. Seven piles were installed using mechanical torque and tested in sand: five SCDI tapered and two steel straight shafts. The cyclic lateral performance of the piles was evaluated and compared to the previously reported monotonic load test results. Effects of prior lateral loading on the piles performance were also assessed. Additionally, three-dimensional finite element simulation of the field tests was carried out to further understand the piles performance characteristics and to evaluate any possible system stiffness change. Straight and tapered shafted helical piles showed a generally satisfactory lateral cyclic performance. Degradation of the system stiffness was observed during testing. The application of prior lateral static tests also had a degrading effect on the cyclic lateral performance of the piles.