Investigation of Arching Effect Using Large Scale Model Test for Pile-Supported Embankment

초록

A large-scale model test was carried out to investigate the arching mechanism in pile-supported embankment. 16 square model piles with 400 mm width were arranged in 4 by 4 square array with a center to center pile spacing of 1.2 m. Soft subsoil was simulated with polyurethane foam. Fill soil was compacted on the piles and the foam in 2.55 m height with 12 lifts of about 0.2 m thickness. The load carried by central three piles were measured by the load cells installed on the pile heads. The loads concentrated on the piles by arching effects were analyzed according to fill heights. The pile efficacies that are the fractions of weight of the embankment fill carried by piles linearly increased up to 60% until the fill height of 1.2 m and decreased slightly for the greater fill heights. The pile efficacies and the stress reduction ratio estimated based on the tests results were compared with those calculated by several arching theories. When the fill is higher than the pile spacing, the pile loads, efficacies, and stress reduction ratios calculated by the existing theories were comparable with measured values. However there found some discrepancies between the results of the test and the theory at lower fill height and the peak shear strength of granular soil cannot be taken into account in the theories.