Testing and analysis of a laterally loaded bridge caisson foundation in gravel

This paper presents the results of an in situ lateral load test on a caisson-type foundation of the old Niu-Dou Bridge in Ilan County, Taiwan. The caisson was 12 m long and had circular cross-sections whose diameters were 5 m in the upper portion and 4 m in the lower portion. The test site was located on soil with a high gravel content. A site investigation, including laboratory and field tests, was carried out. A six-component Winkler-beam model was applied to simulate the caisson response in the lateral load test. To determine the nonlinear properties of the Winkler springs, a method based on large-scale geotechnical field testing was proposed. With this method, the soil springs could be properly set and the Winkler-beam model could reasonably capture the lateral behavior of the caisson foundation.