Pull-out tests on belled piles

The belled pile has been widely applied in foundation engineering for long time. Early, it was mostly used to increase the tip resistance of piles through the enlarged base in hard soil to reduce the cost. The uplift capacity of a single belled pile could be remarkably increased by adding a bit of concrete when the pile was bearing pull-out load. Based on the results of the static uplift load tests in site and laboratory model tests, the uplift capacity of a single belled pile is compared with that of a single constant section pile, and the uplift capacity of belled tension pile is analyzed. The formula for the uplift capacity of a single belled pile in soft soil area is proposed. Moreover, the effect of group belled piles is also discussed.