动载条件下地铁运行时对上跨深基坑开挖的影响研究

发布时间：2018-06-17 15:06

本文选题：深基坑 + 监测　；参考：《合肥工业大学》2014年硕士论文

【摘要】：列车动荷载对邻近基坑围护结构影响的研究已逐渐成为岩土工程领域研究的难点与热点问题之一。本文以上跨地铁2号线的基坑为工程背景，针对基坑开挖时既有地铁隧道的变形情况以及列车动荷载对基坑围护结构的影响进行研究。采用MIDAS/GTS通用有限软件建立模型，全过程模拟基坑的开挖施工。研究分析了下穿基坑的既有地铁隧道变形的原因及控制其变形的措施，并且从地表沉降、基坑围护结构的受力变形与振动及既有地铁隧道稳定等方面，研究分析了列车移动荷载对上部基坑稳定性的影响。本文所做工作与结论如下：（1）以南京城西干道综合改造工程作为工程背景，设计了基坑监测方案并完成现场实际监测工作，通过对监测数据进行分析，得出了基坑围护结构的变形规律。研究表明，围护桩深层水平位移最大值出现在桩顶，围护桩底的水平位移很小（几乎为零）。支撑轴力与围护桩桩顶位移随着开挖深度的增加而变大；在基坑底板浇筑完成后，轴力与桩位移保持稳定。（2）采用MIDAS/GTS建立模型，模拟基坑的开挖施工，数值模拟结果与现场实测数据基本一致。研究分析在基坑开挖过程中影响下穿隧道变形的原因，探讨了控制既有隧道变形的施工措施。通过把监测数据与数值模拟结果相结合分析，得出由于基坑开挖卸载所引起的下穿既有隧道变形规律，如既有隧道纵向隆起曲线呈正态分布，地铁隧道纵向隆起的范围大约为基坑沿隧道方向开挖长度的2到3倍。研究结果表明采用的施工措施可以有效的控制隧道的上抬变形。（3）列车移动荷载对基坑围护结构的作用所产生的影响不能忽视。通过分析表明，当基坑下部既有隧道有列车运行时，列车移动荷载对基坑围护结构产生的内力较小，工程中可以不考虑；列车动荷载对围护结构在Z方向上的振动较为明显，但围护墙的振动依然处于安全可控的范围内。通过有限元计算，预测既有隧道结构在长期地铁移动荷载作用下，，列车动荷载对既有隧道结构的正常使用与耐久性会产生一定的危害。为确保地铁的安全运营，需要采用相应的减震措施来降低列车动荷载对既有隧道的影响。因此，既有隧道需要采取一些抗震措施如在钢轨上添加一些减震性扣件来降低列车动荷载的振动影响。
[Abstract]:The research on the influence of train dynamic load on the surrounding structure of adjacent foundation pit has gradually become one of the difficult and hot problems in geotechnical engineering field. In this paper, the foundation pit which spans Metro Line 2 is the engineering background. The deformation of the existing subway tunnel and the influence of the train dynamic load on the retaining structure of the foundation pit are studied during the excavation of the foundation pit. The model is built by MIDAS-GTS software, and the excavation of foundation pit is simulated in the whole process. This paper studies and analyzes the causes of deformation of existing subway tunnel under foundation pit and the measures to control its deformation, and from the aspects of ground subsidence, mechanical deformation and vibration of foundation pit enclosure structure and the stability of existing subway tunnel, etc. The influence of train moving load on the stability of upper foundation pit is studied and analyzed. The work and conclusions of this paper are as follows: (1) based on the comprehensive reconstruction project of Nanjing West main Road, the monitoring scheme of foundation pit is designed and the actual monitoring work is completed, and the monitoring data are analyzed. The deformation law of foundation pit enclosure structure is obtained. The results show that the maximum horizontal displacement of the retaining pile appears at the top of the pile, and the horizontal displacement at the bottom of the retaining pile is very small (almost zero). The axial force of support and the displacement of the top of retaining pile become larger with the increase of excavation depth, and the axial force and displacement of pile remain stable after the foundation pit floor is cast. (2) MIDAS-GTS is used to establish a model to simulate the excavation of foundation pit. The numerical simulation results are in good agreement with the field measured data. This paper analyzes the causes of tunnel deformation in the process of foundation pit excavation, and discusses the construction measures to control the deformation of existing tunnel. By combining the monitoring data with the numerical simulation results, the deformation law of the existing tunnel caused by excavation and unloading of the foundation pit is obtained, such as the normal distribution of the longitudinal uplift curve of the existing tunnel. The longitudinal uplift of the subway tunnel is about 2 to 3 times the length of the excavation along the tunnel direction. The results show that the construction measures can effectively control the uplift deformation of the tunnel. 3) the effect of the moving load on the foundation pit enclosure structure can not be ignored. The analysis shows that when there is train running in the existing tunnel in the lower part of the foundation pit, the internal force generated by the train moving load on the foundation pit enclosure structure is relatively small, which can be ignored in the engineering, and the vibration of the supporting structure in Z direction is obvious under the train dynamic load. However, the vibration of the retaining wall is still in a safe and controllable range. Through finite element calculation, it is predicted that the train dynamic load will cause certain harm to the normal use and durability of the existing tunnel structure under the action of long term subway moving load. In order to ensure the safe operation of subway, it is necessary to adopt corresponding seismic absorption measures to reduce the influence of train dynamic load on the existing tunnel. Therefore, it is necessary to take some seismic measures such as adding some dampening fasteners to the existing tunnel to reduce the vibration effect of train dynamic load.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U451.3;TU753

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