Abstract: Compared with traditional equal section pile, belled wedge pile has advantages of high unit material utilization, large pile side friction and tip resistances. However, there is little research focused on the quantitative model test on its vertical and lateral bearing capacities The bearing capacities of belled wedge pile embedded in sand under vertical load, lateral load, and surcharge load are tested experimentally to measure the pile shaft, tip resistances, lateral earth pressure, down-drag displacement, and drag load. At the same time, the bearing capacities of equal section pile with the same concrete usage are compared. The mechanism and differences of these piles are preliminary discussed. The results show that the vertical compressive bearing capacity of belled wedge pile are nearly 2.33 times that of equal circular pile, the side and tip resistance are higher than circular pile; the lateral bearing capacity of belled wedge pile is nearly 1.48 times that of circular pile, the larger diameter of the upper part of belled wedge pile and the expanded tip improve the lateral bearing capacity. Comparing with circular pile, the wedge angle can effectively reduce the down-drag displacement of pile top. It presents as one effective ways to reduce the negative friction resistance to the pile foundation by converting the traditional pile type into the belled wedge pile.

Key words: belled wedge pile, model test, vertical bearing capacity, lateral bearing capacity, downdrag