【作者】 富海鹰；

【导师】 关宝树；

【作者基本信息】 西南交通大学 ， 桥梁及隧道工程， 2006， 博士

【摘要】 地面沉降是区域性地面标高降低的一种环境地质现象，具有持续时间长、影响范围广和防治难度大等特点。地面沉降主要由开采地下水资源，工程基础施工及地下空间的开发利用引起。 城市地铁暗挖隧道工程是在岩土体内部进行的，无论其埋深大小，开挖施工将不可避免地会扰动地下岩土体，使其失去原有的平衡状态，而向新的平衡状态转化。在此过程中，隧道开挖使围岩产生卸荷临空面引发收敛变形，进而造成地表下沉；同时，扰动及地下水的流失会使土体重新固结，引起整个地层的固结沉降。这一系列的沉降变形发展到一定的程度，将影响地面建筑物的安全和地下管线的正常使用。因此，长期以来城市地铁隧道施工引起的地表沉降问题一直都是人们关注和研究的重要课题。 关于地表沉降的研究需要解决两个主要问题：提出先进的有效控制沉降的施工方法及计算并预测地铁隧道施工引发的地表沉降量。 采用浅埋暗挖法施工地铁隧道，以往普遍采用全线降水法，此法能保证在地铁隧道施工过程中实现“无水”施工，但是，在我国南方富水软土地层中，再采用这种方法就会在隧道未开挖之前，由于降水井抽水引发大范围的地表沉降，而且这部分沉降在总沉降中所占的比例高达70—80％，因此，在这样的地层施工地铁隧道，控制沉降的关键在于减小隧道开挖对地层的扰动和控制地下水的流失。深圳地铁大～科区间隧道恰在富水软土地层中施工，且地下管线与地面建筑物的存在要求沉降必须得到有效控制，针对这一问题创新性地提出了以控制地下水流失为主要目标的非降水施工方法。本文在此工法实施前采用了三维有限元数值模拟和离心机模型试验方法进行对比研究，证明该法可行。根据实际施工情况及现场监测的数据显示，非降水施工方法科学合理取得了成功。 本论文在研究过程中，采用三维显示有限差分分析软件FLAC^3D，考虑流固耦合效应，建立地铁施工过程的渗流—变形—沉降耦合模型，对渗流、变形，开挖及沉降进行仿真模拟，系统分析研究了降水法施工及非降水法施工全过程对地表下沉的影响，通过对比分析确定在富水软土地区施工地铁隧道，地层失水是造成地表沉降的控制性因素且非降水施工方法控制沉降的高效性。采用离心模型试验重点研究了SK3+355和SK3+395断面的地表沉降规律，通过对非降水施工法及降水施工法对比分析，得出非降水施工法为最佳方法的结论。数值模拟和离心模型实验研究成果与现场监测基本一致，以水平旋喷桩为技术核心的以控制地下水流失为目标的非降水施工法，可减小施工对地层的扰动、减小施工过程中的地下水流失，是在富水软土地层采用浅埋暗挖法施工时的最佳施工方法。 目前的地表沉降计算与预测多采用Peck系列的经验公式，该系列公式认为地表的变形主要取决于土层和地下水位条件，而隧道的埋深、隧道的直径、支更多还原

【Abstract】 Land subsidence, the characteristic of which beng of long duration, in a wide area of influence and hard to take prevention and curation, is an environmental geologic phenomenon which appears as the fall of the elevation of local ground surface. Settlement of ground is mainly induced by exploitation of groundwater, construction of foundation and utilization of underground space.Tunnels in city subway project are constructed in the interior of rockmass. Driving of the tunnel will inevitably disturb the surrounding rock no matter how small the buried depth of the tunnel is. During the process of tunneling, the mechanical equilibrium state of the adjacent formation will change continuously. And also excavation will induce deformation of the adjacent rock towards the free face known as convergence deformation which causes settling of ground simultaneously. On the other hand, disturb of soil and discharge of underwater will induce consolidation settlement of ground as well. The increasing land subsidence will do harm to the building on the ground and the pipeline under the ground unless some measures are taken to restrict it. So, the problem of settlement of ground caused by construction of tunnel in city subway project is always an important research direction.There are two main problem regarding land subsidence that must be solved in this thesis. One is to propose the construction method by which the settlement of ground can be controlled efficiently. The other is to calculate the land subsidence induced by subway tunnel construction.Different construction method brings on different results of land subsidence for metro tunnels which are buried in soft soil with high water level in south of China. The most effective measures to restrict the settlement of ground are reducing disturbance of driving and diminishing the loss of ground water. Drainage method is the most universal techniques in the subway construction with shallow undermining method in our country. This method may provide a favorable condition which may insure the process of subway tunnel construction against water. However, to pump water by wells in drainage method may result in large-area subsidence of ground which may be 70-80 percentage of the total settlement of ground when tunneling in fluent plastic clay formation. Hence, both three dimensional numerical analysis method and centrifuge model test are used to study this problem. Non-drainage method characteristic by controlling the loss of ground water is developed. This method is also verified by the results of practical construction and field monitoring. This thesis adopts the FLAC^3D as compute tool which is a three dimensional更多还原