黄土地铁隧道盾构开挖面稳定性研究

发布时间：2019-03-02 11:18

【摘要】：随着地下空间的不断开发,盾构施工技术得到了越来越广泛的应用,其中土压平衡式盾构掘进技术以其安全、高效、环保及对周围环境影响较小等优点而广泛应用于隧道工程。盾构施工过程中,由于土层条件和掘进参数的不断变化,使得实际掘进过程中盾构机的支护力不是完全满足开挖面平衡的要求。所以为确保开挖面的稳定性及施工对周围土体较小的影响,需要研究支护力的变化对开挖面稳定性的影响以及对地层、地表变形的影响,进而确定确保开挖面稳定的极限支护力,并对实际工程提供借鉴意义。本文依托西安地铁项目,采用有限元软件ABAQUS进行盾构隧道开挖面支护模拟,研究了支护力不足及过大时开挖面的失稳模式,开挖面周围土体塑性区开展以及地层、地表变形特性,并对在支护力不足情况下影响开挖面稳定性的主要因素如隧道埋深、隧道直径、地层的强度参数c、φ进行影响性分析,给出规律性结论。本文针对以上问题,主要进行了以下研究工作:(1)阐述了土压式盾构法施工的主要技术环节,确定了本文研究的技术环节为开挖面支护力的控制。阐述了盾构施工对周围环境的主要影响,确定了本文数值模拟输出的主要结果。阐述了盾构开挖过程中前方土体的三种应力状态,分析了支护力的大小与土体应力状态的对应关系。阐述了支护压力的设置原则,确定了数值模式时,在不考虑推进阻力和地下水压力时,开挖面支护压力的计算公式。(2)对比常用的土体强度准则,选择较为常用且合理的Mohr-Coulomb强度准则,设计了合理的开挖面稳定性模拟方案,分为地应力平衡,开挖区应力释放,开挖土体及拼装管片,改变开挖面支护压力四个分析步。(3)利用ABAQUS有限元软件,依托西安地铁六号线一期工程岩土勘察报告,选取合理的地层及管片参数,建立黄土地层下的半空间三维隧道模型。分别模拟当支护压力不足和过大时,开挖面的失稳模式,周围土体的应力及变形规律,塑性区发展规律以及地层、地表的变形规律。并给出本文开挖面最小极限支护压力的判别标准。(4)在黄土地层条件下,在支护力不足情况下,选取对开挖面稳定性影响较大的因素即隧道的埋深、直径、土体的c、φ进行影响性分析,研究极限支护压力比随上述参数的变化规律。并研究在极限支护压力作用下,开挖面变形、开挖面塑性区开展、地层及地表沉降随上述参数的变化规律。
[Abstract]:With the continuous development of underground space, shield construction technology has been more and more widely used, in which soil pressure balance shield tunneling technology for its safety, high efficiency, environmental protection and small impact on the surrounding environment and other advantages, widely used in tunnel engineering. In the course of shield construction, the support force of shield machine does not fully meet the requirement of the balance of excavation surface due to the continuous change of soil layer conditions and tunneling parameters. Therefore, in order to ensure the stability of the excavation surface and the small influence of construction on the surrounding soil, it is necessary to study the influence of the change of support force on the stability of the excavation surface, as well as on the formation and surface deformation. Furthermore, the ultimate support force to ensure the stability of excavation surface is determined, and it can be used for reference in practical engineering. Based on Xi'an metro project, this paper uses finite element software ABAQUS to simulate the excavation surface support of shield tunnel, and studies the unstable mode of excavation surface when the support force is insufficient and too large, the development of plastic zone of soil around the excavation surface and the stratum. The main factors affecting the stability of excavation surface, such as tunnel depth, tunnel diameter, strength parameter c and 蠁, are analyzed under the condition of insufficient support force, and the regular conclusions are given. In view of the above problems, this paper mainly carried on the following research work: (1) elaborated the main technical link of the earth pressure shield method construction, determined that the technical link of this paper is the excavation surface support protection force control. This paper expounds the main influence of shield construction on the surrounding environment, and determines the main results of numerical simulation output in this paper. Three kinds of stress states in front of soil during shield excavation are described, and the corresponding relationship between support force and stress state of soil is analyzed. The setting principle of supporting pressure is expounded, and the calculation formula of supporting pressure on excavation surface is determined when the numerical model is not considering propulsion resistance and groundwater pressure. (2) comparing with the common soil strength criterion, Choosing the common and reasonable Mohr-Coulomb strength criterion, the reasonable stability simulation scheme of the excavation surface is designed, which is divided into in-situ stress balance, stress release in the excavation area, excavation soil mass and assembled pipe segments. (3) using the ABAQUS finite element software and relying on the first-phase geotechnical investigation report of Xi'an Metro Line 6, the reasonable stratum and segment parameters are selected, and the supporting pressure of the excavation face is changed four steps. (3) the finite element software ABAQUS is used to select the reasonable stratum and segment parameters. A three-dimensional half-space tunnel model under loess stratum is established. When the support pressure is insufficient and too large, the unstable mode of the excavation surface, the stress and deformation law of the surrounding soil, the development law of the plastic zone and the deformation law of the stratum and the surface are simulated respectively. (4) under the condition of loess stratum, under the condition of insufficient supporting force, the factors influencing the stability of excavated face are selected, namely, the depth of tunnel, the diameter of tunnel, the soil mass c, and so on, which are the main factors that affect the stability of excavated face, such as the depth of tunnel, the diameter of tunnel and the soil mass c, under the condition of loess stratum. The influence of 蠁 is analyzed, and the variation rule of pressure ratio of limit support with the above parameters is studied. Under the action of ultimate support pressure, the deformation of excavation surface, the development of plastic zone of excavation surface, and the variation of stratum and surface settlement with the above parameters are studied.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U455.43;U231.3

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