程健 姜君 王栋

摘 要：當桶基发生平动或转动，其侧壁可能与土体发生脱离，形成空隙，土体破坏模式由“双侧式”变为“单侧式”，承载力降低。建立桶基与黏性土相互作用的三维有限元模型，设置允许脱离和不允许脱离两种接触类型，改变土体强度和桶基长径比，确定桶基与土体发生脱离的条件，探讨脱离对桶基承载力的影响，总结单向与复合加载的承载力公式。结果表明：当允许桶基与土脱离时，土体强度越高，单向与复合承载力降低越严重，但长径比对承载力降低程度影响不大。对于单向承载力，建议通过折减系数量化脱离的影响;对于复合加载，提出了同时适用于允许和不允许脱离的归一化包络面表达式。

关键词：桶基;承载力;脱离;有限元;黏土

中图分类号：TU470   文献标志码：A   文章编号：2096-6717（2020）04-0052-06

收稿日期：2020-10-25

基金项目：国家自然科学基金（41772294、U1806230、42025702）

作者简介：程健（1994- ），男，主要从事海洋岩土工程研究，E-mail：chengjian@stu.ouc.edu.cn。

王栋（通信作者），男，教授，博士生导师，E-mail：dongwang@ouc.edu.cn。

Received：2020-10-25

Foundation items：National Natural Science Foundation of China （No. 41772294， U1806230， 42025702）

Author brief：CHENG Jian （1994- ）， main research interest： offshore geotechnical engineering， E-mail： chengjian@stu.ouc.edu.cn.

WANG Dong （corresponding author）， professor， doctorial supervisor， E-mail： dongwang@ouc.edu.cn.

Capacities of bucket foundation considering the influence of sidewall-soil separation

CHENG Jian， JIANG Jun， WANG Dong

（College of Environmental Science and Engineering， Ocean University of China， Qingdao 266100， Shandong， P. R. China）

Abstract： When the bucket foundation moves laterally or rotates， its sidewall may be separated from the soil to form a gap. The failure mechanism of the soil changes from "double-sided" to "single-sided"， which reduces the bearing capacity. The three-dimensional finite element model was established to simulate the reaction between bucket foundation and cohesive soil. Two different types of contact types were set up， allowing separation or not allowing separation. The soil strength and aspect ratio of the bucket foundation were varied to determine the conditions when separation occurs. The effect of the separation on the bearing capacity of the bucket foundation under different conditions was studied， and the capacity formulas of uniaxial and combined loading have been proposed. The results show that the separation of the bucket foundation from the soil reduces the uniaxial and combined bearing capacity， and the reduction is more significant with the increase of soil strength， while the aspect ratio has little effect on the reduction of bearing capacity. For uniaxial bearing capacity， it is recommended to quantify the impact of separation through the reduction factor. For combined bearing capacity， the normalized envelope surface expression that is suitable for both separation and not separation situations has been proposed.

Keywords：bucket foundation; bearing capacity; separation; finite element method; clay

负压桶基础广泛应用于海洋工业，如作为管道终端的支撑基础、张力腿平台的锚泊基础以及海上风机基础等[1-3]，本质上是一种底端敞开、上端封闭的裙式基础（图1）。安装负压桶时，由桶顶向外抽水，在桶内形成负压，将桶基压入土中。桶形基础根据材料可分为钢质和混凝土桶基，壁厚范围通常在0.012～0.5 m之间[4-5]。与海上风电常用的单桩基础相比，桶形基础具有埋深浅、施工快捷、可回收等优点[6-7]，更适用于基岩上覆土层厚度有限的地层，如中国福建和广东部分海域，这些地区的基岩上仅覆盖了10～30 m厚的软土层。……