Enlarged Base (Belled) Piles for Use in Ice or Ice-Rich Permafrost

The influence of enlarging the base of a pile on the total and end bearing capacities of a pile in ice-rich permafrost is evaluated along with the principles used to evaluate the total capacity of uniform diameter and belled piles of the same length in ice-rich soils. Procedures developed by Weaver and Morgenstern in 1981 for predicting the total capacity of straight piles are extended to predict the capacity of belled piles to study the capacity of enlarging the pile base. The total capacity can be substantially improved through the use of belled piles. Techniques to form the bell in different types of permafrost are reviewed with an emphasis on jet cutting. The techniques to allow for installation are described as well as the need for field tests to confirm the proposed installation technique and the predicted increased capacity.