Study on the Bearing Characteristics of Belled Pile Under Combined H-U Load in Loess Soil

To study the influence of inclination angle and expanded diameter ratio of inclined uplift load (H-U) on the pull-out bearing characteristics of belled piles in loess area,pullout tests of 4 load angles θ(0°,15°,30°,60°) and 2 expanded diameter ratios λ(1.5,2.0) were performed.The load displacement curves,strain variation,and distribution of earth pressure under different engineering scenarios were compared according to the tests results.In addition,the relationship between the pull-out bearing performance of belled pile with respect to the load inclination and expanded diameter ratio were explored.Further,the influential factors such as load sequence,length to diameter ratio,and shear strength on the failure envelope under H-U combined loads were investigated.Results indicate that the ultimate bearing capacity T of the belled pile increased by 126% with λ increases from 1.5 to 2.0 when θ= 0°.With the increase of λ,increment of the ultimate bearing capacity of belled pile decreased.The ultimate bearing capacity under H-U combined load increases with the length to diameter ratio L/d and the shear strength of the soil.Soil resistance around the enlarged part contributes to the uplift bearing capacity of the pile.