Estimation of the Shaft Capacity of Single Piles Using the Conventional and Modified β Method

Abstract

The influence of matric suction above the groundwater table towards the load carrying capacity of pile foundations is conventionally ignored in engineering practice. In the present study, the contribution of matric suction on the shaft capacity of a single pile of 20 m in length and 1 m in diameter was estimated for varying groundwater table depths with both positive and negative pore water pressure profile for two coarse and two fine-grained soils. The load carrying capacity was calculated using the conventional and the modified β method that are based on the mechanics of saturated and unsaturated soils, respectively. The influence of only the shaft resistance is considered and the end resistance is neglected in the analyses. The focus of the present study is to highlight how conservative the conventional methods are when they are extended for unsaturated soils.