Shaft configuration and Bearing Capacity of Pile Foundation.

Abstract

This paper presents the results of recent research on shaft configuration and bearing capacity of pile foundation from both laboratory as well as field experimental investigations. Prototype piles of cylindrical, prismatic and conical sections were tested in the laboratory, with piles of corresponding (chosen) configurations/cross sections used as test piles on the field. Using experimental models and load tests, the study compares the values of bearing capacities of pile of various shape tested on weak soil in Minsk area of Belarus. Prismatic piles yielded lower strength at the early loading than both conical and cylindrical piles. But as the loading increases, it showed higher resistance to load than cylindrical, but still lower than conical piles. The results of test piles in a close test point proximity area, showed that conical piles have the highest bearing capacity, 1.5 – 2 times higher than prismatic piles, and 2 - 3 times higher than cylindrical piles. It further revealed that, for non-homogenous (layered) soil, mostly encountered in construction sites, pile installed by driven or boring have bearing capacity increment of 10 - 14% in bored piles, 18 - 24% hammer driven piles, and 20-30% in vibrated driven piles. For the investigated prototype modeled piles, as well as test piles, the tapering and wedging effects are responsible for increase in normalized skin friction and normalized lateral stresses of tapered conical piles. In all, tapered conical pile offers larger resistance than the cylindrical piles and prismatic piles, and is therefore recommended for use, with other factors being considered.