新建隧道上穿工程对既有地铁隧道纵向隆起变形影响研究

发布时间：2018-07-08 13:06

本文选题：新建隧道上穿 + 既有地铁隧道　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：随着我国城市地铁的大量建设以及地铁网络的不断完善,新建隧道上穿既有已运营的地铁隧道的工程越来越多。新建隧道的开挖势必会破坏周围地层平衡应力场,从而使既有地铁隧道结构产生附加内力和变形,因此如何有效预测以及控制新建隧道上穿对既有地铁隧道的纵向隆起变形成为了穿越工程中急需解决的难题。为保证既有地铁的安全运营,本文着重研究新建隧道上穿工程对既有地铁隧道的卸荷作用机理、力学响应规律以及既有隧道结构隆起的影响因素,并提出相应的控制措施及建议。本文的主要研究工作及成果如下:建立了新建隧道上穿对既有地铁隧道的卸荷模型,基于Mindlin弹性应力解求解了既有地铁隧道受到的卸荷附加应力。通过求解卸荷附加应力系数,系统地分析了上穿卸荷因素对既有地铁隧道受到的卸荷作用的影响。研究表明:土体平均泊松比以及新建隧道纵坡对既有隧道受到的卸荷作用影响不大。针对新建隧道上穿既有地铁隧道工程,将既有地铁隧道视作搁置在利夫金地基模型上的Euler-Bernoulli梁模型,基于“两阶段分析法”思路,提出了一种新建隧道上穿工程对既有地铁隧道隆起位移的计算方法。通过算例结果与数值解的对比确定了利夫金模型的无量纲参数,改进了传统两阶段分析法中Winkler模型地基不连续的缺陷。基于三个已报道的工程实例验证了本文计算方法的有效性,本文方法可快速有效预测既有隧道隆起位移。以深圳市地铁6号线上穿既有4号线拟建工程为背景,通过MIDAS/GTS NX软件建立了新建隧道上穿既有地铁隧道的三维有限元模型,重点研究了新建隧道上穿卸荷因素对既有地铁隧道纵向隆起变形的影响,并提出了相应的抗浮措施及建议。研究表明:既有隧道隆起位移峰值与开挖断面面积近似成正比,工程中应考虑隧道施工的时空效应,尽量减小一次开挖面积及掘进距离,及时施作支护结构;上穿过程中,隆起值变化较为明显的阶段为穿越前后各1.5倍开挖外径,实际工程中可考虑在新建隧道内部距离既有隧道轴线1.5倍开挖外径的区域及相应的地表区域采取堆载抗浮措施;增大水平投影夹角可以降低既有隧道的隆起量,当水平投影夹角大于45°时,其降低速率变缓;随夹层土体厚度的增大,既有隧道最大隆起位移逐渐减小,且变化速率变缓,工程中应使夹层土体厚度大于1.5倍开挖外径;新建双线隧道对既有隧道的隆起影响可看作两个单线隧道的叠加,随着双线隧道轴线间距变大,既有隧道的隆起峰值变小,实际工程中应尽量增大双线隧道间的距离,消除隧道间的叠加效应。
[Abstract]:With the large number of urban subway construction and the continuous improvement of subway network, there are more and more new tunnels passing through the existing subway tunnels. The excavation of the new tunnel will inevitably destroy the equilibrium stress field of the surrounding strata, thus causing additional internal force and deformation to the existing subway tunnel structure. Therefore, how to effectively predict and control the longitudinal uplift deformation of the existing subway tunnel through the new tunnel has become a difficult problem that needs to be solved in the crossing engineering. In order to ensure the safe operation of the existing subway, the mechanism of unloading, the law of mechanical response and the factors affecting the uplift of the existing tunnel structure are studied in this paper. And put forward the corresponding control measures and suggestions. The main work and results of this paper are as follows: the unloading model of the existing subway tunnel is established, and the additional unloading stress of the existing subway tunnel is solved based on the Mindlin elastic stress solution. By solving the additional stress coefficient of unloading, the influence of unloading factors on the unloading of existing subway tunnels is analyzed systematically. The results show that the average Poisson's ratio of soil and the longitudinal slope of new tunnel have little effect on the unloading of existing tunnel. Aiming at the project of passing through the existing subway tunnel, the existing subway tunnel is regarded as Euler-Bernoulli beam model shelved on the foundation model of Lifkin, based on the idea of "two-stage analysis". In this paper, a method for calculating the uplift displacement of existing subway tunnel is presented. The dimensionless parameters of the Lifkin model are determined by comparing the numerical results with the numerical results, and the defects of the Winkler model foundation discontinuity in the traditional two-stage analysis method are improved. Based on three reported engineering examples, the effectiveness of the proposed method is verified. The proposed method can be used to predict the uplift displacement of existing tunnels quickly and effectively. Based on the proposed construction of Shenzhen Metro Line 6 through existing Line 4, the 3D finite element model of new tunnel through existing subway tunnel is established by Midas / GTS NX software. The influence of unloading factors on the longitudinal uplift deformation of existing subway tunnel is studied, and the corresponding anti-floating measures and suggestions are put forward. The research shows that the peak displacement of the existing tunnel uplift is approximately proportional to the area of the section of the excavation. The space-time effect of tunnel construction should be taken into account in the project, the area of primary excavation and the distance of excavation should be reduced as far as possible, and the supporting structure should be constructed in time. The obvious change of uplift value is 1.5 times outside diameter of excavation before and after crossing. In actual engineering, the anti-floating measures can be taken in the area with 1.5 times outer diameter of existing tunnel axis and the corresponding surface area. Increasing the angle of horizontal projection can reduce the uplift of the existing tunnel. When the angle of horizontal projection is greater than 45 掳, the decrease rate of the tunnel becomes slower, and the maximum uplift displacement of the existing tunnel decreases gradually with the increase of the thickness of the intercalated soil, and the change rate of the tunnel becomes slower. In engineering, the thickness of interlayer soil should be greater than 1.5 times of the outer diameter of excavation, the influence of the new double-line tunnel on the uplift of the existing tunnel can be regarded as the superposition of two single-line tunnels, and the peak value of the uplift of the existing tunnel becomes smaller with the increase of the distance between the axes of the two-line tunnel. In practical engineering, the distance between two-line tunnels should be increased as far as possible to eliminate the superposition effect between tunnels.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U456.3

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