【作者】 陈志荣；

【导师】 熊传祥；

【作者基本信息】 福州大学 ， 岩土工程， 2006， 硕士

【摘要】 软土广泛的分布在我国东南沿海和内陆,由于其具有强度低,变形大,透水性差,变形持续时间长等特点,给隧道施工带来了一定的难度。软土的抗剪强度很低,周围土体的自稳能力极差,开挖后易产生坍塌,故需要强大的支护结构; 软土的变形很大,使得软土隧道的开挖变形也很大,地面沉降难以控制,过大沉降易引起路面开裂,甚至坍陷,影响交通安全。在软土地基修建浅埋暗挖隧道,不同于传统方法,而应该通过对传统工艺的改进,达到更有效地控制变形与土体稳定的目的。在软土地基中采用浅埋暗挖法进行隧道施工,研究周围土体变形行为,寻求合理施工工艺具有重要意义。本文主要工作如下: 首先,简单介绍了软土地基隧道的主要施工方法及浅埋暗挖法的发展,总结了目前国内外隧道工程引起地层移动的研究现状; 接着介绍了软土和软土隧道的特点及浅埋暗挖法的优缺点与适用条件,并以福州地层为例,重点介绍了软土地基浅埋暗挖隧道施工方法,并对各工艺特点进行论述; 然后介绍了三维快速拉格朗日分析程序FLAC-3D的计算理论与方法,主要介绍了三维快速拉格朗日法的数学模型描述、数值公式表示及数值计算过程。其次,运用FLAC-3D数值分析软件建立了浅埋隧道的三维模型,研究不同因素对浅埋暗挖隧道性状的影响,重点研究了施工方法、开挖进尺、拱顶加固体强度以及地层条件对隧道开挖后周围土体稳定性的影响,主要从地表沉降及隧道开挖后周围土体的应力分布和塑性区范围进行分析。模型中使用了结构单元,考虑了土和衬砌之间的接触作用,采用Mohr-Coulomb弹塑性本构模型进行计算分析。最后,对具体的工程实例进行分析比较,结果表明,本文研究成果与实测结果的规律基本相似,从而为软土地基中合理设计浅埋暗挖隧道提供了依据。更多还原

【Abstract】 The soft soil is distributed extensivly in the southeast coastal area and inland of our country, which adds difficulty in tunnel construction because of its own characteristics, such as low strength, great deformation, bad water permeability and long time of lasting deformation. The soft soil has low shear strength and the soil around has low stability and it is easy to collapse after excavating, so it needs strong support structure. The soft soil has great deformation, which makes the deformation of soft soil tunnel also great after excavating and ground settlement hard to control. The oversized settlement is easy to cause road surface crack, even collapse, which affects the traffic safety. Using shallow tunnel construction method (STCM) in soft soil foundation is different from the traditional method, so the traditional process should be improved to control the deformation and keep soil stable more effectively. When using STCM in soft soil foundation, it is important to research the deformation behavior of soil around and seek reasonable construction process. The following works are done in the paper: First, the author takes a review on the methods of tunnel construction in soft soil foundation, the development of STCM and computational theories of the ground movement. Second, a brief introduction is made about the characteristics of soft soil and tunnel in soft soil,the characteristics and suitable condition of STCM. Based on the stratum of Fuzhou, the construction technologies of STCM in soft soil foundation are introduced. Then a few words are said about the calculation theory and method of FLAC-3D (Three Dimensional Fast Lagrangian Analysis of Continua), including the mathematical model description, the formula expression and the computation process. Next, the three-dimension model for shallow tunnel is set up by FLAC-3D and some researches are made about the effects of different factors for character of shallow tunnel construction. The stability of soil around after tunnel excavated is focused on in the paper, which considering construction methods, the length of excavation, the strength of reinforcement in vault and the condition of stratum. Ground settlements, stress distribution and plastic zone are analyzed. The contact interaction between soil and lining is taken into account. The constitutive model employed is Mohr-Coulomb plasticity with linear elasticity assumed within the yield strength surface. At last, a case is analyzed in this paper. It showed that the calculated results are similar the measured ones. It provides some useful conclusions for its design.更多还原