小净距双洞隧道盾构法施工对地层稳定性影响的研究

发布时间：2018-05-01 06:26

本文选题：小净距隧道 + 盾构法施工　；参考：《山东建筑大学》2017年硕士论文

【摘要】：随着城市化建设的不断深化,为解决城市交通拥挤的现象,对地下空间的开发和利用也成为当今城市发展的需求。按照《公路隧道设计规范》(JTG_D70-2004)第4.3.2条对小净距隧道的定义(在软岩地段两隧道净距小于4B为小净距隧道,B表示隧道宽度),而《地铁设计规范》(GB 50157-2013)规定,盾构法施工的并行隧道间的净距,不宜小于隧道外轮廓直径。那么城市地铁大部分都是小净距隧道,但盾构法施工的小净距隧道与新奥法施工的山岭隧道差异较大,且土体与岩体性质也有较大差异,在不同地层条件下,城市地铁小净距隧道盾构法施工过程中仍会引起周围地层位移及引起地表沉降,从而对临近的地下结构以及相邻的地面建筑物产生不利的影响,引发一系列的问题。本文以石家庄地铁一号线谈固站~朝晖桥站区间工程为背景,利用理论分析,数值模拟等方法对小净距双洞隧道盾构法施工过程中,在不同地层,不同净距条件下隧道周围岩土体的稳定性进行研究。利用有限差分模拟软件FLAC~(3D)对不同地层,不同净距条件下,盾构法施工的小净距隧道对周围岩土体的扰动进行分析,对隧道开挖过程利用应力释放法进行模拟,模型中隧道周围土体模型采用Mohr-Coulomb准则的弹塑性模型,混凝土管片采用线弹性模型,盾构管片采用壳单元(Shell),土体的开挖采用空模型(Null)。观察隧道周围岩土体的应力应变、塑性区大小以及变形情况,所得出的结论如下:(1)随着双洞隧道的净距减少,隧道周围岩土体中的应力在不断增加,当净距小于1.0B时,小净距隧道周围岩土体中的应力增加幅度变大,因此,《地铁设计规范》(GB50157-2013)中规定的盾构法施工的隧道间的净距不宜小于隧道外轮廓直径是合理的。(2)随着双洞隧道的净距增加,隧道周围岩土体产生的沉降在不断减小,变化速率也在不断减小,但到净距大于4.5B时有开始增大的趋势。为避免沉降过大,盾构法施工的双线隧道净距应尽可能的接近4.5B,但4.5B的净距会产生大量的地下空间浪费,因此,在考虑节约空间等因素后,建议净距以2.0B左右为宜。(3)不同地层条件下的盾构法施工的小净距隧道的塑性区分布也有些许差别。粘性土中的应力相对较大,而粉土与砂类土相对较小。在应用盾构法施工小净距隧道时,应注意施工对不同岩土体产生的扰动也是不同的。(4)对不同地层,小净距隧道应用盾构法施工所产生的沉降,也不尽相同。其中,粘性土是模拟的四种岩土体中产生沉降最大的,而粘性土在工程上是最常遇到的土层之一,在粘性土地层应用盾构法施工时,要加强对隧道沉降的监控,如若发现有沉降加大的趋势,应提前采取相应措施加固土体。
[Abstract]:With the development of urbanization, in order to solve the problem of urban traffic congestion, the development and utilization of underground space has become the demand of urban development. According to article 4.3.2 of the "Road Tunnel Design Code" / JTGSP / D70-2004), the definition of a small clean distance tunnel (in soft rock areas where the net distance is less than 4B means the width of the tunnel by the small spacing tunnel "B", and the "Subway Design Code" / GB50157-2013), The net distance between the parallel tunnels constructed by shield method should not be smaller than the diameter of the outer profile of the tunnel. Well, most of the urban subway is a small clean distance tunnel, but the difference between the small clear distance tunnel constructed by shield method and the mountain tunnel constructed by New Austrian method is great, and the properties of soil and rock mass are also quite different. Under different stratum conditions, In the course of shield tunneling construction of small distance tunnel of urban subway, the ground displacement and ground subsidence will still be caused, which will have adverse effects on the adjacent underground structure and adjacent ground buildings, thus causing a series of problems. In this paper, based on the project between Shuanggu Station and Chaohui Bridge Station of Shijiazhuang Metro Line 1, using the methods of theoretical analysis and numerical simulation, in the course of shield tunneling with small spacing and double holes, different strata are used. The stability of rock and soil around the tunnel was studied under the condition of different net distance. In this paper, the disturbance of surrounding rock and soil is analyzed by using the finite difference simulation software FLACZ3D, and the stress release method is used to simulate the excavation process of the tunnel. In the model, the soil model around the tunnel adopts the elastic-plastic model of Mohr-Coulomb criterion, the concrete segment adopts the linear elastic model, the shield segment adopts the shell element, and the soil is excavated using the empty model. The stress and strain of surrounding rock and soil mass, the size of plastic zone and the deformation are observed. The conclusions are as follows: 1) with the decrease of the net distance of the tunnel, the stress in the surrounding rock and soil is increasing, when the net distance is less than 1.0 B. Since the stress increases in the surrounding rock and soil mass of the tunnel with small clear distance, the net distance between the tunnels constructed by shield method stipulated in the "Subway Design Code" GB50157-2013) should not be less than the diameter of the outer profile of the tunnel. The net distance between the tunnels should not be less than the diameter of the outer profile of the tunnel. (2) with the increase of the net distance of the double-hole tunnel, The settlement of rock and soil around the tunnel is decreasing and the rate of change is decreasing, but the net distance is larger than 4.5B. In order to avoid excessive settlement, the net distance of double-line tunnel constructed by shield method should be as close to 4.5B as possible, but the net distance of 4.5B will cause a lot of waste of underground space. It is suggested that the appropriate net distance is about 2.0B.) the plastic zone distribution of the small clearance tunnel constructed by shield method under different stratum conditions is also slightly different. The stress in cohesive soil is relatively large, while silt and sandy soil are relatively small. When using shield method to construct small clear distance tunnel, attention should be paid to the disturbance caused by construction to different rock and soil mass, to different strata, and to the settlement produced by shield tunneling construction in small distance tunnel. Among them, clay soil is the largest settlement of the four simulated rock and soil mass, and clay soil is one of the most frequently encountered soil layers in engineering. When the shield method is used in the construction of viscous soil layer, it is necessary to strengthen the monitoring of tunnel settlement. If there is a tendency to increase settlement, corresponding measures should be taken in advance to strengthen the soil.
【学位授予单位】：山东建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U455.43

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