导　　师： 刘润

学科专业： 081401

授予学位： 硕士

作　　者： ;

机构地区： 天津大学

摘　　要： 大直径筒型基础是为适应我国近海地质条件和风机荷载特点而研发的新型基础形式。作用在风力机上的水平荷载通过塔筒等上部结构传至基础顶面，导致地基基础在承受竖向荷载作用的同时还需承受巨大的水平力和弯矩，传统的承载力计算方法难以确定此种复合荷载作用下大直径筒型基础的地基承载力。地基承载力的破坏包络面法是研究复合加载模式下地基极限状态的有效方法，当荷载组合位于破坏包络面以内时则地基处于稳定状态，反之地基失稳。本文针对复合加载模式下粘性土地基所能达到的极限状态，应用数值计算方法，系统研究了地基的承载力包络面与破坏模式。主要研究内容和结论如下： 1.基于极限分析理论，莫尔库伦强度理论与刚塑性土体的假定，提出了大直径筒型基础地基运动许可可变速度场的构造方法，从而求得了筒型基础地基竖向极限承载力的上限解。 2.研究了土体弹性模量对计算精度与收敛速度的影响，筒型基础筒壁长度对地基承载力的影响。结果表明土体的弹性模量对提高计算精度和收敛速度影响显著，随着筒壁长度的增大，地基承载能力有显著的提高。 3.得到了不同荷载组合下地基承载力包络线，复合荷载作用下饱和不排水软粘土地基承载力包络线和φ≠0粘性土地基承载力包络线有较大的差异：饱和不排水软粘土地基承载力包络面随着竖向荷载的增大向原点收缩，φ≠0粘性土地基破坏包络面随着竖向荷载的增大先向外扩张，而后向原点收缩。 4.系统研究了不同荷载组合作用下地基破坏模式。结果表明：/(1/)竖向荷载的大小决定了地基的破坏模式，主要包括：表层滑动、浅层滑动或深层滑动；/(2/)水平荷载造成了地基破坏模式的非对称性；/(3/)弯矩荷载改变了基础的有效宽度，从而导致了� Large diameter bucket foundation is a new kind of foundation to adapt to China'scoastal geological conditions and environment loads. Upper structures are typicallysubjected to significant horizontal. As a result, combined vertical, horizontal, andmoment loading is a common scenario for their footings. The classical bearingcapacity design approach is difficult to determine the bearing capacity of largediameter bucket foundation. A more accurate approach is to express a footing’sbearing capacity under general loading explicitly in terms of a surface written directlyin combined loading space. Load combinations inside the surface are considered safe,whereas those outside the surface cause footing failure. According to the ultimatebearing capacity of foundation under combined loading mode, the failure pattern andthe ultimate bearing capacity of clay foundation are analyzed and investigated in thispaper. The main results of this study are as follows: 1. Based on the limit analysis principle, and on the assumption of Mohr failuretheory and soil rigid-plasticity model, the kinematic allowing variable velocity fieldare given, and then the upper bound solution of ultimate bearing capacity of largediameter bucket foundations are given. 2. The result of finite element method indicates that the value of soil elasticmodulus has an effect on the value of accuracy of ultimate bearing capacity andconvergence rate. The skirt length of bucket foundation improves the ultimate bearingcapacity of clay ground obviously. 3. The failure envelope under combined loads is investigated by adopting thefinite element method. There is much difference between the failure envelope ofundrained saturated foundation and the clay foundation. The failure envelopes ofundrained saturated foundation contract with the increasing of vertical load. Thefailure envelopes of clay foundation expand and then contract. 4. The failure mechanism of foundation are analyzed in this paper usingnumerical calculation method. The results are as follows:

关 键 词： 大直径筒型基础 粘性土地基 地基极限承载力 极限分析 包络线 破坏模式

领　　域： [建筑科学] [建筑科学]