A new large step-tapered hollow pile and its bearing capacity

This paper introduces a new large step-tapered hollow (STH) pile used in a karst area and its construction method. To reveal the advantages of this pile type, a 15 m dia. STH pile in Ji'an Shenzhen Bridge was simulated using Flac^3D software. The vertical bearing capacity was assessed by considering the influences of the width and number of the variable cross-sections and the soil characteristics around the pile. In addition, new large STH piles of two different forms were assessed to expand the practical application of such piles. The results showed that, for a large-diameter pile, the concrete utilisation rate and the vertical bearing capacity of the pile were improved by the design of hollow and variable cross-sections. The optimal range of the taper angle for the large STH pile was found to be 2.68-5.36° and the optimal number of variable cross-sections was found to be between two and four. The bearing capacity increased with an increase in the soil shear strength parameters and the pile was deemed suitable for stiff strata. The results of this work could facilitate design practice for large STH piles.