【作者】 李茂文；

【导师】 陈寿根；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2011， 硕士

【摘要】 本文以深圳地铁5号线翻身～灵芝盾构区间隧道下穿碧海花园小区施工为工程依托,通过采用技术调研、理论分析和数值模拟、施工现场配合和现场管片试验等相结合的方法,对盾构隧道施工引起的地表沉降、建筑物桩基位移、管片衬砌力学特性以及盾构掘进控制技术进行了较深入的研究,以此来减小盾构施工对建筑物的影响,也可为今后的地铁工程提供重要的参考价值,主要研究工作和研究成果为：(1)通过对盾构机下穿建筑物开挖过程进行计算机数值模拟,分析了地表的隆沉规律,研究了盾构施工引起的地表沉降以及影响地表沉降的因素。地表隆沉与盾构掘进参数密切相关,适当加大土仓压力和注浆压力能有效控制地表沉降,但其值也不宜过大,否则可能会造成地表隆起。(2)通过对监控量测的数据分析,地表横断面的沉降曲线与正态分布曲线相近,沉降最大值发生在隧道轴线上方。地表横断面内沉降影响范围约为两倍隧道直径,纵断面内主要影响范围为盾构前后方各三倍隧道直径的距离,地表沉降监测结果与数值模拟结果基本吻合。盾构机开挖施工时,上方建筑物除了会产生竖向位移,同时由于盾构机对地层的不规则扰动及偏载等缘故,使得建筑物桩基也产生水平位移,但相较竖向位移,水平位移一般只有垂直位移的1/3。(3)盾构开挖过后,拱顶沉降,拱底隆起,随着盾构的不断推进,已经拼装上的盾构管片的隆沉变形也越来越明显,在管片脱出盾尾时,地表沉降突然增大,而且沉降速率达到最大,因此,对管片脱出盾尾阶段的变形控制是整个盾构施工中控制地表变形的关键。(4)基于施工资料的处理和分析,总结出了一套盾构隧道下穿建筑物的掘进控制技术参数。在穿越建筑物前对盾构机设备检修,制定应急预案,按照“安全、快速、连续”的原则进行施工。合理控制掘进参数,土仓压力应该在计算的基础上预留0.2bar左右的安全量,严格控制出土量,减小超挖量,合理纠偏,以减小盾构掘进引起的土体扰动、地表位移及地层损失；严格控制同步注浆压力和注浆量,注浆量一般为6.0m3/环：加强渣土改良,使渣土具有良好的流塑性,减轻对刀具的摩损,延长刀具的使用寿命。(5)当地质条件不佳时,为保证建筑物的安全,要对建(构)筑物的桩基、地基等的持力层进行预加固或是跟踪注浆,盾构机进时要增大监控量测的频率,监测结果及时反馈至施工环节,进而调整施工参数,做到边施工,边预报,有效防止地层沉降过大过快。(6)在盾构推进过程中,避免建筑物发生隆沉、倾斜,甚至结构破坏的措施,有主动控制措施和被动控制措施两种。主动控制措施是通过对施工参数的优化,从盾构开挖的源头开始采取有关措施来减少对建筑物的不利影响。被动控制措施是通过诸如隔断、托换、土体加固等工程方法来保护周围建筑物。盾构隧道沿线附近的建筑物保护,应首先把重点放在主动控制措施上。更多还原

【Abstract】 Based on the shield tunneling underpassing Bihai Garden on Shenzhen Subway Line 5, this study investigated the behavior of ground settlement, displacement of building pile foundation, mechanical characteristics of segment linings, as well as control technology of shield driving due to shield tunneling, by using a combined method of literature review, theoretical analysis, numerical simulation, field construction assort and field segment tests. The achievement obtained from the study can be used to reduce the impact of shield tunneling on buildings, and to provide an important reference to the metro projects in the future. The main research work and achievements are as follows:(1) By carrying out numerical modeling of shield tunneling process of underpassing buildings, the study analyzed the pattern of groud settlement and facors affecting the surface settlement. The surface settlement is closely related to tunnling parameters. Appropriately increasing soil storage pressure and grouting pressure can effectively control ground settlement, but the pressure value should not be too large, otherwise it could easily lead to surface uplift.(2) The analysis of monitoring data showed that the surface settlement of cross-section is close to the normal distribution, the maximum subsidence occurs on the tunnel axis. Affected area of cross-sectional settlement and vertical section are respectively about twice and triple the tunnel diameter. Ground settlement monitoring results are consistent with the numerical results. The upside building will produce horizontal displacement except for vertical displacement, by the reason of irregular disturbances and partial load when shield excavating, but compared to the vertical displacement, the value of horizontal displacement is just about one third vertical displacement.(3) After the shield tunneling started, the tunnel arch subsides while the tunnel bottom upsides. With the continuous advance of shield, the deformation of assembled segments becomes more and more obvious. When the segment coming out of the shield tail, the surface settlment increases suddenly and settlement rate reaches its maximum. So the deformation control when the segment coming out of the shield tail is the key to control ground settlement in shield tunneling. (4) Based on the processing and analysis of construction data, a set of control parameters of shield tunneling beneath the buildings were summarized. Before the tunneling, the shield machine equipment must be checked and repaired carefully, and an emergency plan would be made, the construction would be in accordance with the principle of "safe, fast, continuous". It would reasonably control tunneling parameters, an extra 0.2 Bar of earth chamber pressure would be given based on the calculation, it would strictly control the unearth amount, reduce the amount of over excavation and reasonably make deviation rectification in order to reduce disturbance to soil, surface displacement and ground loss; it would strictly control the amount of synchronized grouting and grouting pressure, grouting volume is generally six cubic per ring; it would enhance sediment improving to has a good plastic and to reduce friction loss of the tool furthermore extending tool life.(5) When the geological condition is poor, to ensure the safety of the building, the support layer of pile and foundation must be prereinforced or reinforced. While shield machine is excavating beneath the building, the frequency of monitoring must be increased, the monitoring results must be timely feedbacked to the construction and used to adjust the construction parameters, which can prevent ground from too large or too fast settlement.(6) In the process of shield tunneling, there are two type of measures to avoid occurrence of settlment, tilt, even structural damage, including active control and passive control. The active control is optimizing construction parameters to reduce the adverse effect on buildings through the construction source. The passive control is, however, protecting the surrounding buildings by adopting partition, underpinning, soil stabilization and other methods. The active control should be focused on in the protection of nearby buildings along the tunnel.更多还原