Model tests on uplift capacity of double-belled pile influenced by distance between bells

To optimize the distance between the bells in pile design, this paper reports a series of small scale tests on the uplift capacity of double belled piles embedded in dry dense sand considering different bell space ratios. Finite element modelling is also performed to evaluate the range of soil failure around the piles during pile uplift displacement. Test results show that when bell space ratio is 6 or 8, the uplift capacity reaches the peak value. The upper bell bears more load than the lower one for the piles with bell space ratio less than 6, while the lower bell bears more load than the upper one for the piles with bell space ratio larger than 8.