沉箱—垫层—桩复合深水基础竖向承载性能试验研究

发布时间：2018-01-08 05:04

本文关键词：沉箱—垫层—桩复合深水基础竖向承载性能试验研究　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：沉箱-垫层-桩复合基础是跨海桥梁建设中新近出现的一种设置基础,在希腊里翁大桥得到成功应用。本课题以“十二五”交通运输重大科技专项(2011318494160)《水深大于50m特大型桥梁深水基础适宜结构型式及其设计方法研究》为依托,以琼州海峡跨海大桥为工程背景,在室内模型试验的基础上,利用F1ac3D数值模拟作为辅助,探究了沉箱-垫层-桩复合基础在竖向荷载下的承载性能,现将本文的主要工作和成果陈述如下：1、设计并实施了砂土中沉箱-垫层-桩复合基础的模型试验,分析了竖向荷载作用下的土压力分布、钢管桩的受力机理和基础沉降的基本规律,桩土荷载分担比或桩土应力比在加载过程中的动态变化。2、在竖向加载的全过程,复合基础土压力沿基础纵向或横向均呈现中间大、边缘小的近似凸函数曲线分布。3、与沉箱-桩复合基础相比,沉箱-垫层-桩复合基础的桩身出现负摩阻力,最大桩身轴力不在桩顶,中性点位置受着垫层厚度的影响,垫层越厚,此位置越低。4、沉箱-垫层-桩复合基础的沉降曲线均为缓降型,极限承载力根据沉降限值确定。垫层厚度与基础沉降正相关,相应地极限承载力为负相关。5、室内模型的承载力与沉降计算采用了刚性桩复合地基理论,计算结果与试验数据误差较小。同样运用此理论,对琼州海峡大桥的中塔基础设计可行性进行了验算,结果表明基础设计能满足安全性和适用性要求。6、运用FLAC3D有限差分软件对本模型试验进行了数值模拟,重点探究了垫层厚度的改变对基础沉降和承载力的影响。
[Abstract]:Caisson-cushion-pile composite foundation is a newly emerging foundation for bridge construction across the sea. It has been successfully applied in Rion Bridge, Greece. In this paper, a major scientific and technological project for transportation in the 12th Five-Year Plan (2011318494160) is presented. Study on the suitable structural types and Design methods of Deep Water Foundation of Super large Bridge with Water depth more than 50 m based on it. Taking Qiongzhou Strait Crossing Bridge as the engineering background, based on indoor model test, using F1ac3D numerical simulation as an aid, the bearing capacity of caisson, cushion and pile composite foundation under vertical load is explored. In this paper, the main work and results are described as follows: 1. The model test of caisson-cushion-pile composite foundation in sand is designed and implemented, and the distribution of earth pressure under vertical load is analyzed. The stress mechanism of steel pipe pile and the basic law of foundation settlement, the dynamic change of the load-sharing ratio of pile and soil or the stress ratio of pile to soil in the course of loading, are in the whole process of vertical loading. Compared with caisson pile composite foundation, the soil pressure of composite foundation is distributed by approximate convex function curve with large middle and small edge along the longitudinal or lateral direction of foundation. The pile body of caisson cushion pile composite foundation has negative frictional resistance the maximum axial force of pile body is not on the top of pile and the neutral position is affected by the thickness of cushion the thicker the cushion the lower the position of 4. 4. The settlement curves of caisson cushion pile composite foundation are all of the type of slow fall and the ultimate bearing capacity is determined according to the settlement limit value. The thickness of cushion is positively correlated with the foundation settlement and the corresponding ultimate bearing capacity is negatively correlated with that of the foundation. The theory of rigid pile composite foundation is used in the calculation of bearing capacity and settlement of indoor model, and the error between calculation result and test data is relatively small. The feasibility of the mid-tower foundation design of Qiongzhou Strait Bridge is checked and calculated. The results show that the foundation design can meet the safety and applicability requirements of .6. The numerical simulation of the model test is carried out by using FLAC3D finite difference software, and the influence of the thickness of the cushion on the settlement and bearing capacity of the foundation is studied.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U443.1

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