Y形沉管灌注桩复合地基荷载变形特性

BEARING CAPACITY AND DEFORMATION CHARACTERISTIC OF A COMPOSITE FOUNDATION WITH DRIVEN CAST-IN-PLACE Y PILES

Y形沉管灌注桩是根据国外先进的Y形桩设计理念结合国内传统沉管灌注桩的施工工艺研制出的一种新型沉管灌注桩。结合Y形沉管灌注桩在某高速公路桥头软基加固中的应用,根据理论计算和现场静载试验,得出同等截面积的Y形桩比圆形桩的侧表面积增加了50%左右,证明Y形沉管灌注桩侧摩阻力可以显著提高,从而在等工程量的前提下可以大幅提高桩基的承载能力;根据其工作机制分析,表明Y形桩是一种以摩擦为主的摩擦桩或端承摩擦桩。通过现场监测,对Y形沉管灌注桩复合地基的桩土应力比、表面沉降、土体侧向变形等变化规律进行研究,并分析桥头软基加固效果;监测资料和现场静载试验表明,Y形沉管灌注桩复合地基具有承载特性好、可显著减小地基的沉降量、路基工后沉降小的特点。根据技术经济比较,表明Y形沉管灌注桩比其他复合地基方法有一定的优势,具有施工质量可靠、加固效果显著、经济合理的特点,可以在同类工程中推广应用。

A new driven cast-in-place Y pile, developed according to the innovative design concept of Y pile and the traditional construction technology of driven cast-in-place pile in China, was introduced in this paper. The newly developed piles were used in a ground improvement project for an expressway bridgehead. Based on the theoretical calculation and static load test results, the longitudinal surface area ofa Y pile is about 50% more than that of a circular pile for a given cross-sectional area, from which its side friction and bearing capacity is substantially enhanced. The Y pile is either a friction pile or end bearing friction pile from its working mechanism. Based on the field monitoring results and static load test results, the pile-soil stress ratio, surface settlement, lateral deformation of the driven cast-in-place Y pile composite foundation were discussed. The Y pile composite foundation has better bearing characteristics while the foundation settlement and post-construction settlement of embankment are substantially reduced. From the technical and economical point of view, it has certain advantages over other composite foundation on reliable construction quality, significant reinforcement effect and economical rationality. It can be applied to other projects with similar geological conditions.