【作者】 周军；

【导师】 刘国明；

【作者基本信息】 福州大学 ， 水工结构工程， 2003， 硕士

【摘要】 80年代以来，随着我国公路建设的迅猛发展，在软土地区兴建公路日益增多。由于路堤软土地基沉降预估的复杂性，准确地预估路堤软基的沉降量，特别是预估软基沉降与时间的关系便成为公路设计的重要问题。而用常规方法计算的路堤软基沉降值与实测资料相比存在较大的误差，故本文作者引入BIOT固结理论，对路堤软基沉降作非线性有限元分析。 本文首先根据BIOT固结理论与有限元原理，用FORTRAN语言编制了平面应变条件下考虑地基土体BIOT固结的非线性有限元程序BP。该程序包括了土体单元、加筋体单元、接触面单元和桩体单元。其中土体采用了Duncan—chang双曲线本构模型，可以考虑土的应力-应变的非线性特征。该程序可用于加筋堤、桩体复合地基和砂井地基等多种路堤软基的沉降计算，同时又可计算路堤软基在各个时刻的侧向变形和孔隙压力值，并能模拟各种施工加载情况。本文用一维固结问题考题，用程序BP计算的结果与太沙基理论解析解十分吻合，证明此程序是基本可靠的。 本文应用有限元程序BP计算了一个假设的路堤软基的沉降，与常规路堤软基沉降方法进行比较，得出了BIOT固结有限元法更为真实地反映侧向变形对沉降的影响、更为合理地计算各个时刻的沉降量、便于考虑施工分级加载对沉降的影响等结论。 本文应用有限元程序BP计算了砂井地基、二灰土桩复合地基和加筋堤软基等三个工程实例。从前两个工程实例的计算结果来看，路堤软基沉降的有限元计算值与工程现场实测值比较接近，吻合程度较高，孔隙压力的变化也比较令人满意，说明本文编制的BIOT固结有限元程序BP有较高的可靠性和实际应用价值。根据计算结果分析，得出了路堤软基沉降、侧向变形和孔隙压力随时间及荷载的变化规律。本文第三个实例分别采用了Duncan-chang非线性模型和线弹性模型计算，将其计算结果与实测资料进行比较，结果证明用非线性模型比较符合工程实际。更多还原

【Abstract】 Since the 1980’s, with the rapid development of highway construction, there are more and more roads built on the soft soil. Because of the difficulty in estimating the settlement of soft ground, how to estimate the settlement of soft ground well and truly, especially to estimate the relation between settlement and time is becoming an important problem of highway design. However, compared with the measured results, the results calculated by the ordinary method usually can’t meet the demand. So in this thesis, the author introduced the Biot consolidation theory and analyze the settlement of soft ground with the nonlinear Finite Element Method.On the base of the Biot consolidation theory and the principle of Finite Element Method, the author developed a FEM program BP in FORTRAN language. This program includes soil element, reinforcement element, Goodman element and pile element etc. In the program, Duncan-chang model was applied to earth, which can consider the nonlinear relation between the stress and strain. This program can be used to calculate the settlement of various kinds of soft ground under highway embankment, it can also be used to calculate lateral displacement and pore water pressure. In this thesis, the author used this program to calculate one-dimensional consolidation problem, and the results showed that this program was credible.The author used FEM program BP to calculate the settlement of soft foundation under a supposed highway embankment. Comparing Finite Element Method with ordinary method, the author concluded that the Biot FEM can reflect the influence of lateral displacement more truly, calculate the settlement at every moment more suitably, and consider the progress of construction more easily.At last, the author analyzed three engineering cases with FEM program BP. From the results of first two engineering cases, it can be found that the results calculated by BP were very close to the measured results. This proved that the FEM program BP is very credible and practical. On the base of the results, the author concluded the rule of settlement, lateral displacement and pore water pressure along with the load and time. In the third engineering case, the author separately adopted Duncan-chang model and linear elastic model. Compared their results with the measured results, the author found that the Duncan-chang model is more suitable to evaluate the settlement of soft ground.更多还原