Model tests on bearing behaviors and calculation of multi-stage expanded piles

The bearing capacity-settlement curve (Q - S) of single pile and the side friction resistance of piles are obtained based on the model tests on the compressive static loads on equal-diameter pile, expanded pile and expanded-diameter pile (multi-stage expansion) in the sandy silt of Ningbo, the bearing behavior of three kinds of piles are compared, and the formula for the bearing capacity and settlement of multi-stage expanded piles are deduced for the first time. The results show that expanded-diameter pile can make full use of the bearing capacity of the soil under the expanded head and has the better effect of reducing the settlement and increasing the bearing capacity. The lateral resistance near the middle of the enlarged head cannot be fully exploited because of the expanded head. However, the expansion resistance is an important way of load transfer. The proposed formula for calculating the bearing capacity and settlement of multi-stage expanded piles is reasonable.