【作者】 曾祥勇；

【导师】 邓安福；

【作者基本信息】 重庆大学 ， 岩土工程， 2001， 硕士

【摘要】 浅基础的地基强度及变形历来是土力学与基础工程学的重要内容之一。我国现行规范GBJ7-89将这两者分开考虑，其计算地基承载力设计值的公式是根据弹性地基中应力分布及土的极限平衡状态理论为依据而得出的，求地基的沉降变形时则视土体为弹性，这些理论对地基及土的假设与浅基础地基的实际工作状态及天然土体的非线性、弹塑性存在一定的偏差。 随着计算技术和土的本构模型理论的发展，有限单元法逐渐成为一种广泛应用于岩土工程分析的数值方法。本文即以有限元-无限元耦合的数值方法用FORTRAN90语言编制了竖向荷载作用下浅基础地基的非线性、弹塑性三维分析程序，分析中采用的土的本构模型有非线性的邓肯-张模型、成都科大K-G模型和弹塑性的修正剑桥模型、殷宗泽双屈服面模型、Drucker-Prager模型。利用该程序，本文对浅基础的地基分均质地基和层状地基两类情况分别进行了分析。对均质地基情况，分析了基底中心点的p～s沉降曲线、不同等级荷载下塑性区开展的不同深度情况及地基的极限承载力。对层状地基情况，通过对六种不同组成的层状地基各自基底中心点的p～s沉降曲线、不同等级荷载下层状地基中塑性区开展的不同情况及层状地基的极限承载力分析结果的比较得到了一些浅基础的层状地基强度变形变化规律。同时文中还用ANSYS有限元软件对这两类地基情况进行了弹塑性分析，分析中地基土采用Drucker－Prager本构模型。另外，对各地基情况还用规范GBJ7-89进行了相应的地基沉降及承载力设计值计算。 在两类地基情况中均对本文程序、ANSYS有限元软件、规范GBJ7-89的计算结果进行了比较，结果表明，本文的有限元数值分析方法可将地基的沉降及承载力分析结合起来，可求得各级荷载下地基的非线性沉降变形、地基土体塑性区的开展情况和地基的极限承载力，能反映竖向荷载作用下浅基础地基的实际工作机理。更多还原

【Abstract】 The bearing capacity and settlement of the shallow foundation on soil is the important subject of the soil mechanics and foundation engineering. The current Chinese foundation design code GBJ7-89 use limit equilibrium theoiy with elastic soil stress distribution to give Out bearing capacity design value calculating fonnula and use elastic soil model to evaluate foundation settlement. According to the above theories, code GBJ7-89 gives the correlative terms. But these do not accord with the practical mechanism of loaded soil below the shallow foundation and the elastoplastic property of natural soil so defects exist. With the development of the compute technology and the soil constitutive model. the finite element method (FEM) gradually becomes a comprehensively used numerical method in geotechnique engineering. The paper uses the coupled numerical method by combine the finite element method (FEM) with the infinite element method (IEM) to analysis the strength and deformation of the soil under the shallow foundation. The corresponding three-dimensional analytical program is devised by FORTRAN9O computer language. In the program. the used soil constitutive models include Duncan-Chang constitutive model, K-G model, modified Cambridge model, Yin Zongze model with two yield surfaces and Drucker-Prager elastoplastic model. With the program, the paper analysis the uniform soil condition and the layered soil condition separately. To uniform soil condition, the p-~s settlement curve of the center point at the bottom of the shallow’ foundation and the different depth of the soil plastic zone in different load grade and the ultimate bearing capacity of the foundation are analyzed. To layered soil condition, by the comparisons of the p-s settlement curve of the center point at the bottom of the shallow foundation and the different style of the soil plastic zone in different load grade and the ultimate bearing capacity of the foundations of the six different layered soil, some conclusions of the layered soil condition are achieved. The ANSYS large finite element soft ware elastoplastic analysis is also used in the above all soil conditions with Drucker-Prager model. And the foundation capacity design value and the settlement of the soil in the above all soil conditions are calculated by Chinese foundation design code GBJ7-89 at the same time. The comparisons of the results in the analysis of theIIdevised program and the ANSYS software and the code GBJ7-89 show that the finite numerical method used in the paper can combine the analyses of the bearing capacity and the settlement of the foundation at the same time and can obtain the nonlinear settlement of the foundation under different load grade and the development of the soil plastic zone and the ultimate bearing capacity of the foundation and can imply the practical mechanism of loaded soil below the shallow foundation under the vertical load.更多还原