Simulation analyses for in-situ cyclic loading tests in cohesive soil were conducted to indicate that finite element models considering nonlinearity of soil material , pile-soil separation , and a loosened soil layer were valid for evaluating lateral resistance of steel pipe piles with wings driven by rotational penetration. The results of analytical studies demonstrated that pile head load of piles with a loosened soil layer approached that of piles without a loosened soil layer when pile head displacement progressed. Linear finite element models were proposed to evaluate reduction of lateral resistance of piles due to a loosened soil layer.
