【作者】 余闯；

【导师】 宰金珉； 王旭东；

【作者基本信息】 南京工业大学 ， 岩土工程， 2003， 硕士

【摘要】 传统的桩基础设计理论考虑桩工作在弹性阶段，上部荷载完全由桩来承担。复合桩基设计理论令桩工作在非线性阶段，充分利用了桩和桩间土的承载能力，有效地减少桩的用量，但其沉降和差异沉降都比常规桩基时要大。 本文在阐明桩土共同作用中引入地基土非线性的重要性基础上，利用带接触面的非线性有限元程序，模拟了单桩的非线性工作性状，考虑了复合桩基中以单桩非线性为主的工作状态，得出了复合桩基中桩的刺入变形必然存在的结论，进一步探讨了土的邓肯非线性模型中各参数以及桩和接触面性质对桩工作性状的影响。 本文利用有限单元法，模拟分析了复合桩基和常规桩基地基土中附加应力的分布特征，得出了复合桩基的沉降由桩间土体的压缩和桩端以下土体的压缩两部分组成的规律。并结合现有的简化计算方法，提出了一种新的复合桩基沉降简化计算方法——修正简化应力调整法：将桩间土的附加应力简化为一矩形分布，将桩端以下土体的附加应力简化为三角形分布用于沉降计算，并给出了变形模量的取值方法。利用该方法和其他多种方法对四个复合桩基工程实例进行了计算，计算结果和现场测试数据的对比分析表明：该方法物理概念清楚、计算简便，本文方法得到的结果与实测数据具有良好的一致性，满足工程应用的计算精度，便于在工程上的应用。 本文提出了控制桩筏基础差异沉降的主要措施，通过调整筏板刚度和桩基支承刚度的分布等措施达到减小差异沉降的目的。对方形和圆形筏板桩筏基础的差异沉降进行了数值模拟和分析，得出了中心布桩和单桩变刚度调整法是减小桩筏基础差异沉降的两种有效的布桩方法。 对某油罐桩筏基础的数值模拟和实测结果的对比分析，说明了本文所提出的单桩变刚度调整法是控制桩筏基础差异沉降中的一种切实可行的方法。人为地调整该桩筏基础的桩长和布桩方式后进行数值分析，结果表明差异沉降可得到进一步的减小，甚至产生零差异沉降，使筏板工作在最优状态，从而实现了差异沉降的有效控制。更多还原

【Abstract】 In conventional pile foundation design theory, piles work at the elastic range and upper loads are fully shared by piles. But in composite pile foundation theory, piles work at the nonlinear range and the bearing capacity of piles and soils between piles are fully utilized, so the pile number decreases clearly, at the same time the settlement and differential settlement are larger than those of common pile foundation.The paper puts the emphasis on importing the nonlinear model of foundation soil in the pile-soil interaction and analyses the main working state of single pile in composite pile foundation. The finite element program with interface element simulates single pile’s nonlinear working state, which shows the inevitability and essentiality of penetrated settlement in composite pile foundation. At the same time the influences of soil parameters in Duncan nonlinear model, the pile and interface element properties on pile working states are discussed.The distributions of additional stress of common pile foundation and composite pile foundation are simulated by finite element program. The settlement of composite pile foundation is divided into two parts: the compress of soil between piles and soil under pile bottom. On the base of present simplified calculation method, a new method of calculating the settlement of composite pile foundation is presented. It is Modified Simplified Stress Method. In this method, the distribution of additional stress of soil between piles is simplified as a rectangle and that of soil under pile bottom is simplified as a triangle, at the same time the calculating method for soil’s modulus of deformation is offered. Then the simplified stress is applied to the settlement calculation. The calculated settlements of several practical composite pile foundation engineerings are contrasted with the observed results and other settlement calculation method’s results. The comparisons show that the calculated value by the method not only corresponds with the practical results, but also the method owes clear physical concept, simplified calculation and certain precision, and it is convenient to be applicated in the practical engineering.The paper puts forward the main measures of controlling the differential settlement of piled raft foundation by increasing the rigid of raft and modifying foundation rigid. Through the numerical simulations and analyses of rectangular and circular raft pile foundation, we can draw a conclusion that locating piles in a central area and rigid adjusted method of single pile are two effective ways to reduce the differential settlement of piled raft foundation.The comparison of numerical simulation and measured results of one oil storage tank engineering verifies that rigid adjusted method of single pile is a very good method in controlling differential settlement of piled raft foundation. By the adjusted pile length and pile layout, thedifferential settlement is reduced furthermore, even the differential settlement is completely eliminated, then the raft works at the best situation and the aim of differential settlement control comes into being.更多还原