复合荷载作用下桶形基础的承载力研究

发布时间：2018-10-25 07:24

【摘要】：桶形基础作为一种新型的海洋平台基础,不仅在近海油田开发中有着广阔的应用前景,而且也能较好的应用在港口码头等防波堤工程中。埋置在近海浅滩地区软黏土中的桶形基础不仅受到上部构筑物所引起的竖向荷载(V)作用,还受到风、波浪等引起的水平荷载(H)与力矩荷载(M)的共同作用,在这三种荷载共同作用下的桶形基础承载力特性直接关系到其在实际工程中的推广应用。但是由于桶形基础的特殊性,目前现有的承载力计算方法很难计算出其在三种荷载复合作用下的地基承载力,而地基承载力破坏包络面方法则是研究复合加载模式下桶形基础地基极限状态的一种行之有效的方法。当荷载组合在破坏包络面外时则地基处于失稳状态,而在破坏包络面内时则处于稳定状态。本文以连云港徐圩港区的单桶多隔舱基础防波堤为背景,在将桶形基础简化的基础上,运用ABAQUS大型有限元分析软件,对软件中土体模型进行二次开发,研究了桶形基础在复合荷载情况下的承载力包络线。本文主要研究内容包括如下几个方面:1.介绍南水土体本构模型的基本理论,并基于此理论对大型有限元软件ABAQUS中的土体模型进行二次开发,然后通过与已有研究成果进行对比,验证了南水模型在分析桶形基础承载力时的合理性与适用性,接着确定所研究桶形基础的基本参数,并建立有限元模型。2.对建立好的有限元模型采用位移控制方法进行分析,研究桶形基础在竖向荷载(V)、水平荷载(H)与力矩荷载(M)三种荷载分量单独作用下的失稳破坏模式和极限承载力特性,并变动参数进行研究,得出不同桶体埋深比与不同土层相对位置情况下桶形基础的地基极限承载力的经验计算关系式。3.根据第二章研究得到的在不同荷载分量作用下桶形基础的极限承载力,采用Swipe法和常位移比法进行加载,得到桶形基础在不同荷载组合情况下的地基承载力包络线,同样变动参数进行研究,分析得到不同桶体埋深比与不同土层相对位置情况下桶形基础的破坏包络线,并将其进行归一化分析。4.运用常位移比加载方式,对桶形基础在竖向荷载(V)、水平荷载(H)与力矩荷载(M)复合作用下的承载力包络线进行分析研究,归纳得到在竖向荷载不同的情况下桶体埋深比与土层相对位置比之间的关系曲线,为桶形基础的设计提供参考。
[Abstract]:As a new type of offshore platform foundation, bucket foundation not only has a broad application prospect in offshore oil field development, but also can be used in breakwater engineering such as port and wharf. The bucket foundation buried in soft clay in the coastal shoal area is not only affected by the vertical load (V) caused by the upper structure, but also by the interaction of the horizontal load (H) and the moment load (M) caused by wind, wave and so on. The bearing capacity of bucket foundation under these three loads is directly related to its popularization and application in practical engineering. However, due to the particularity of bucket foundation, it is very difficult for existing methods to calculate the bearing capacity of foundation under the combined action of three kinds of loads. The method of failure envelope surface is an effective method to study the limit state of bucket foundation under composite loading mode. When the load combination is outside the failure envelope plane, the foundation is in a state of instability, while in the failure envelope plane, the foundation is in a stable state. This paper takes the breakwater of single bucket and multi-compartment foundation in Xuwei Port area of Lianyungang as the background. On the basis of simplifying the bucket foundation, using ABAQUS large-scale finite element analysis software, the soil model in the software is redeveloped. The envelope of bearing capacity of bucket foundation under composite load is studied. The main contents of this paper are as follows: 1. This paper introduces the basic theory of the constitutive model of Nanshui soil mass, based on which the soil model in the large-scale finite element software ABAQUS is redeveloped, and then compared with the existing research results. The rationality and applicability of the Nanshui model in analyzing the bearing capacity of bucket foundation are verified. Then the basic parameters of the bucket foundation are determined and the finite element model is established. The displacement control method is used to analyze the established finite element model, and the failure modes and ultimate bearing capacity characteristics of bucket foundation under the three load components of vertical load (V), horizontal load (H) and moment load (M) alone are studied. The empirical formula of ultimate bearing capacity of bucket foundation with different ratio of buried depth of bucket and relative position of soil layer is obtained. According to the second chapter, the ultimate bearing capacity of bucket foundation under different load components is studied. The envelope of bucket foundation bearing capacity under different load combinations is obtained by using Swipe method and constant displacement ratio method. The same variable parameters are studied, and the failure envelope of bucket foundation is obtained under the condition of different ratio of buried depth of bucket and relative position of different soil layer, and the damage envelope of bucket foundation is analyzed by normalization. 4. In this paper, the load envelope of bucket foundation under the combination of vertical load (V), horizontal load (H) and moment load (M) is analyzed and studied by the method of constant displacement ratio loading. The relationship curve between the ratio of buried depth of bucket and the ratio of relative position of soil layer under different vertical loads is obtained, which provides a reference for the design of bucket foundation.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU470

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