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.

中文翻译：

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一种新型的大阶梯锥形空心桩及其承载力

介绍了一种用于岩溶地区的新型大阶梯锥形空心桩及其施工方法。为了揭示这种桩的优势，直径为15 m。用Flac ^3D模拟吉安深圳大桥的STH桩软件。通过考虑可变截面的宽度和数量以及桩周围土壤特性的影响来评估竖向承载力。此外，评估了两种不同形式的新型大型STH桩，以扩大此类桩的实际应用。结果表明，对于大直径桩，通过设计空心截面和可变截面可以提高混凝土的利用率和竖向承载力。大型STH桩的锥角的最佳范围为2·68-5·36°，可变截面的最佳数量为2至4个。承载力随着土壤抗剪强度参数的增加而增加，桩被认为适合于刚性地层。