【作者】 李兴毓；

【导师】 申翃；

【作者基本信息】 武汉理工大学 ， 岩土工程， 2009， 硕士

【摘要】 CFG桩复合地基是竖向增强体复合地基的一种,由于该方法可以掺入工业废料粉煤灰、不配筋以及充分发挥桩间土的承载能力,工程造价一般为桩基的1/3—1/2,经济效益和社会效益非常显著,因此得到越来越广泛的应用。目前比较常用的设计方法主要是先根据复合地基承载力来初选各项参数,再依据变形要求来调整参数,该方法需多次试算,且计算结果不一定经济。因此寻求更合理的设计计算方法变得非常迫切。本文首先详细介绍了复合地基的基本理论,包括复合地基承载力和复合地基变形的计算方法,进而单独介绍了规范对CFG桩复合地基设计计算的要求。在CFG桩复合地基设计计算理论准备充分的情况下,引入了最优化设计理论。着重介绍了最优化问题模型的三要素包括:设计变量、目标函数和约束条件。并对最优化设计流程图做了介绍。然后简要介绍了MATLAB软件的基础知识,对MATLAB软件的流程控制语句做了具体介绍。在此基础上,分析了CFG桩设计参数桩径d、桩长l、置换率m和桩体强度对复合地基加固效果的影响。通过建立60m厚的均质土体模型,运用MATLAB绘图演示了该关系。为CFG桩复合地基优化设计的设计参数选取提供了依据。通过以上理论准备,本文选取了CFG桩复合地基的桩径d、桩长l、置换率m作为设计参数,并对桩体强度做了要求;以满足复合地基的承载力f_spk、控制总变形量s为约束条件;将CFG桩混合料的总用量定为目标函数;以能够实现CFG桩混合料用量最少的设计作为最优化设计。以MATLAB软件为优化计算平台,根据MATLAB流程控制语句的特点,建立了CFG桩复合地基优化设计的流程图。本文选取了具体的工程实例,对其进行优化设计。以与原设计相同的沉降值作为变形控制条件,优化设计后CFG桩混合料的用量可以节约10%,取得了较显著的经济效益。更多还原

【Abstract】 Cement Fly-ash Gravel (CFG) pile composite foundation is a kind of vertical reinforcement composite foundations. As industrial waste fly-ash can be added and no steel is needed in this method, as well as the bearing capacity of soil can be fully used, engineering cost of the CFG piles normally is only 1/3 to 1/2 of that for pile foundations. Due to remarkable economic and social benefits, CFG pile composite foundations are applied into engineering practice more and more widely. In general design each parameter is primarily assumed a value according to the required bearing capacity, and then it is adjusted to satisfy the settlement limitation of subsoils. It may take many trials in the calculation, while the result still may not be economical. Thus it becomes very urgent to look for a more reasonable design method.Firstly, the basic theory of composite foundation is introduced, including the calculation methods about the bearing capacity and settlement of the composite foundation, then the requirements of the design calculation by standardization about CFG piles composite foundation are introduced. Secondly, following the theoretical preparation of CFG piles composite foundation is the optimization design theory. Emphasis is paid on three key elements of the optimization problem model, including design parameters, objective function and constraint conditions, and then is the flow chart of the optimization design. Thirdly, this paper briefly covers the basic knowledge of MATLAB software, and a specific introduction to the flow control statements of MATLAB software is shown.The influence of design parameters which include pile diameter, pile length, area replacement rate and strength of the CFG piles on stabilization effect is analyzed. Through an established homogeneous soil mass model of 60m thick, the relationships between design parameters and bearing capacity and settlement of CFG pile composite foundation are shown by using the graphics of MATLAB. This work provides basis to select the design parameters for the optimization design of CFG piles composite foundation.According to above-mentioned theoretical preparation, the author adopts the pile diameter, pile length, and area replacement rate as the main design parameters, while considering the strength of the piles. The permitted bearing capacity of composite foundation and total controlling settlement are taken as the constraint conditions, and the total volume of the CFG piles mixture is selected as the objective function. The design achieving the least amount of the CFG piles mixture is the optimum one. Using MATLAB as a computing platform, the author sets up a flow chart of the optimization design according to the features of MATLAB’s flow control statements.In the paper, a practical engineering project is taken as an example to carry out optimization analysis. With the same settlement value in original design, it shows the volume of CFG piles mixture in the case can be saved up to 10%.更多还原