【作者】 姚海波；

【导师】 王梦恕； 张顶立；

【作者基本信息】 北京交通大学 ， 岩土工程， 2005， 博士

【摘要】 大断面隧道(隧道开挖面积在100～140m~2)因其跨度大，形状偏于扁平，而在施工过程中表现出独有的力学特点，主要是：隧道在开挖过程中应力集中程度大，是普通隧道的1.5～2倍；隧道底脚处应力集中过大，要求围岩具有较高的地基承载力；拱顶在施工过程中易坍塌；由于开挖跨度大，围岩塌落拱高度大，要求上覆围岩成拱厚度大，浅埋条件下无法形成承载拱，从而导致很大的围岩松动压力；支护结构提供的承载力相对较小。由于以上特点，施工过程中大断面隧道产生的环境效应要远大于普通隧道。而采用浅埋暗挖法在既有地铁运营线下开挖、修筑大断面隧道无疑是对隧道施工技术的挑战。由于环境对象的特殊性——既有线为动态运营的地下铁路线，决定了新线隧道的施工必须采取“一个中心，两项安全”的原则，即以既有线的正常运营为中心，保证既有结构的安全使用和新线隧道的安全施工。使老线的运行和新线的施工协调一致。将每一步施工引起的既有线变位控制在分步变位控制标准以内，最终实现整体变位的有效控制。论文从既有结构变形、破坏规律、施工方法研究、管棚的作用机理和施工管理控制四个方面深入研究了大断面隧道下穿既有地铁构筑物的施工技术问题：(1)根据施工过程中对既有结构的远程监测资料，归纳出既有结构与整体道床随施工开挖各个步序的变位规律(包括结构的绝对沉降、差异沉降和扭转)，基于此，建立了研究结构间受力的三铰拱力学模型，讨论了三铰拱形成和破坏的条件，并采用弹性地基梁和弹性叠合梁理论对既有结构的受力和结构与道床间脱开情况进行了研究；(2)对地铁车站这类大断面隧道的施工方法进行了全面的研究，以数值模拟为工具，系统地分析、比较了软土大断面隧道施工常用的中洞法、柱洞法和侧洞法，研究不同工法对围岩和既有结构的扰动特点，并对拟采用工法的关键施工步序进行了深入分析，工程量测结果表明，计算结果对指导施工有足够的精度；(3)将弹性地基梁与弹性链杆法相结合，对穿越施工所采用的主要支护手段——水平长管棚的工作机理进行了系统的建模分析，研究了管棚在端部不同约束条件下，以及管径、管间距、土体刚度、工作面开挖效应、掘进速度和初期支护施作质量等各因素对管棚挠度和受力的影响，找出了各因素间所符合的函数关系，并提出了管棚的挠度控制设计方法；(4)根据新线隧道施工步序与既有线结构沉降开展的对应关系，提出了既有线变位分配控制原理，利用数值模拟、1：1模型试验，确定了既有线分步沉降控制标准，借助于远程监测，通过勘测、预测、监测、对策这一系统控制流程，以既有线变位为指针，将新线隧道的施工与既有线的运营紧密地结合起来，使既有线变位控制具有很强的可操作性。以上研究基本阐明了大断面隧道下穿既有地铁构筑物所面临的主要技术问题和工程对策。更多还原

【Abstract】 With large section, shallow overburden, the subway station tunneling under a running Metro proves to be very complicated engineering. The upper existing tunnel demands that the construction of the subway station have to focus on its displacement so as to ascertain the normal running and prevent it from damage caused by settlement of soil mass. A systematic controlling process consisting of exploring, forecasting, monitoring and engineering measures was put forward, in which the total subsidence was divided into every step of the construction. Through controlling the value of settlement caused by its corresponding step, the total settlement standard could be reached.The dissertation includes four main technical problems confronted in crossing tunneling: the displacement style and possible damaging model, construction method, the working principle of long level steel pipe and the construction administration controlling method.The details are as follows:1. Based on the measuring data of the running tunnel during construction, the displacement law was summarized and the diagrams was drawn. Several kinds of possible damaging styles of the existing tunnel was analyzed by means of mechanics models.2. A number of construction method in view of large-section tunnel were researched. The characteristics of environment effects were compared. Further analyses were made on key construction steps of the method that would be adopt.3. The beam model on elastic foundation was used to simulate the behavior of long level steel pipe during excavation on basis of considering all construction contents in detail. The equations expressing the relation between factors were founded. At last a designing method of long level steel pipe based on deflection controlling was put forward.4. The displacement-dividing principle was founded, which associated the construction steps of metro station with the settlement control of the existing subway tunnel tightly and easily operated.The proceeding research work basically made clear the main aspects confronted in crossing tunneling engineering and corresponding measures.更多还原