地铁交叉隧道盾构施工的三维有限元分析

某新建地铁隧道工程近距离垂直上穿既有地铁隧道,采用有限元软件Mi das/GTS模拟了新建双线盾构隧道施工对上部地表和下部既有隧道变形的影响。计算结果给出了新建盾构隧道近距离垂直上穿既有双线地铁隧道时的位移变化规律。     

双线隧道开挖对邻近隧道影响的两阶段分析方法

随着我国很多大城市地铁隧道的兴建,大多数隧道设计施工方案都采用双线平行盾构法或暗挖法施工。在地下空间越来越拥挤的城市地区,最重要的研究问题是新建双线平行隧道对既有隧道产生的影响问题。合理预测双线平行隧道施工穿越既有隧道引起的变形是确保既有隧道结构安全和新建双线平行盾构的顺利掘进的关键。考虑新建双线平行隧道施工中对周边土层和既有隧道产生的叠加效应,提出了预测新建隧道引起的邻近隧道纵向变形的两阶段分析方法。首先,考虑新建双线平行隧道引起地层位移的不对称性,计算新建双线平行隧道开挖作用在既有隧道上引起的广义附加荷载。然后,将既有隧道考虑为Pasternak 地基上的Euler-Bernoulli梁,基于 Galerkin 法求解既有隧道纵向变形影响的基本微分方程。通过与工程沉降实测数据进行对比,验证该文提出的预测方法的合理性和结果的准确性。     

双线盾构隧道近距离下穿城市既有运营双线隧道时空变形规律分析

随着城市轨道交通的快速发展,新建地铁隧道近距离下穿既有运营地铁隧道日渐成为常态。因此,新建盾构隧道近距离下穿既有运营隧道的综合控制技术、施工安全评价及时空变形规律成为当前研究的热点问题。以广州地铁22号线下穿既有地铁3号线为例,采用现场监测、理论分析、数值模拟等方法,重点研究了新建双线盾构隧道分别下穿既有运营双线隧道过程中的时空变形规律,特别是隧道结构、轨顶面等关键位置处的竖向变形规律。首先分析了水平定向钻孔加固范围和土体参数加固影响范围,提出了加固区岩土力学参数增强系数计算方法,确定了加固地层计算参数。然后基于精细化建模,分析了22号线左线下穿3号线时既有运营隧道的时空变形规律及隧道结构内力,并与监测结果进行了对比,对比显示计算结果与监测结果吻合度较高,充分证明了该研究提出的分析方法的可靠性,对下穿既有运营隧道安全评价及施工技术选取具有重要的借鉴意义。     

双线盾构隧道斜交下穿既有市政隧道的变形规律研究

随着城市化进程的推进,城市地铁数量及规模得到空前发展。文章主要针对新建盾构隧道斜交下穿既有市政框架隧道,以杭州地铁五号线浙三区间斜交下穿紫金港路隧道工程为依托,研究双线盾构斜交下穿时,上方既有隧道的竖向位移、扭转与盾构所在的位置及注浆压力的关系,找出下穿不同阶段各项施工技术参数变化对于上部隧道沉降及变形影响的规律,并给出相应的建议,为以后类似的工程提供指导与参考。     

浅埋暗挖隧道近距下穿既有地铁的关键技术

 主要针对越来越多的浅埋暗挖隧道近距下穿既有地铁工程，结合北京地铁5号线崇文门站下穿既有地铁2号线区间隧道工程，介绍新建浅埋暗挖隧道近距下穿既有地铁隧道的关键控制技术。主要包括：对既有地铁的现状进行全面调查评估；根据现状评估结果并结合理论分析和类似工程经验确定既有地铁的变形控制标准；通过有限元分析方法等进行新建隧道施工对既有地铁影响的预测分析；对主要施工方案进行优化，并选取超前大管幕、掌子面注浆、补偿注浆等辅助措施；根据数值分析结果并结合既有工程经验，将主要控制标准按施工步序进行分解，实施控制标准的分阶段控制；通过远程实时监控系统即时监测和分析既有地铁的动态变化，对出现的结构开裂、沉降过大等异常情况及时采取灌浆加固、注浆抬升等处理措施，确保既有地铁的正常安全运营。     

盾构隧道下穿既有隧道施工影响的三维数值模拟

地铁隧道的交叉穿越是地下工程领域前沿研究课题之一。隧道开挖施工引起地层位移进而会引起附近既有隧道或其他各类结构的变形,甚至造成灾害。结合广州地铁交叉隧道工程实例,利用三维有限元方法对新建隧道盾构施工进行建模分析,研究了交叉隧道盾构施工对既有隧道位移的影响。结果表明,由于既有隧道的存在,新建隧道盾构施工引起既有隧道产生不均匀沉降和水平位移,分布曲线均符合正态分布。     

软土隧道盾构近距离下穿U形公路的数值分析

盾构隧道施工经常会穿越各种既有建筑物,因此,保证既有建筑物的正常使用及隧道施工的安全是盾构隧道施工的重中之重。以宁波地铁双线盾构隧道近距离下穿钢筋混凝土U形公路为例,对盾构掘进过程进行了三维数值模拟计算,以综合判断盾构所引起的软土地层变形规律和对上部U形公路的影响,从而给出施工合理化建议,可为类似的盾构穿越工程提供借鉴。     

软土地区盾构上穿越既有隧道的离心模拟研究

随着地铁网络不断完善,新建盾构隧道近距离穿越既有隧道的现象越来越多。盾构近距离穿越既有隧道的影响问题,比常规盾构施工的研究更为复杂。结合上海外滩通道盾构上穿越地铁 2 号线工程,采用离心模型试验与现场实测相结合的方法对盾构上穿越对周围地层及既有隧道的影响进行了研究。文中选用排液法在离心场中模拟盾构施工,在国内首次实现了在不停机状态下模拟隧道开挖卸载、地层损失和注浆过程,并分析了盾构上穿越施工引起的地层、新建隧道与既有隧道的纵向位移变化规律。通过现场实测数据分析了既有隧道在盾构上穿越过程中纵向变形与时程曲线的变化规律。     

双线隧道盾构穿越建筑物桩筏基础的三维有限元分析

双线隧道情况下盾构施工掘进时,因为受到隧道间距、隧道埋深、穿越桩筏基础的位置等因素影响,其对建筑物桩筏基础的影响比单一隧道情况下的影响更复杂。文章以某地铁区间段双线隧道穿越建筑物桩筏基础盾构施工为背景,基于FLAC3D软件,建立了双线隧道和其穿越建筑物的桩筏基础计算模型,分析双线隧道在穿越桩筏基础时影响范围内的地表沉降规律、隧道周围土体的变形规律以及桩基的水平变位规律。结果表明,双线隧道穿越群桩时,地表沉降曲线与Peck经验公式稍有不同。由于桩基的"挡墙"效应,其对土体变形的阻碍作用较明显。此外,隧道开挖对桩基水平变位的影响范围主要是桩基与隧道同高度处。文章的分析结果对该类工程的设计和施工具有一定的指导意义。     

盾构隧道始发段上跨穿越施工对既有地铁隧道的影响分析

文章以深圳地铁10号线福田口岸站—福民站区间盾构始发段施工工程为依托,研究设计袖阀管注浆加固方案下,新建地铁隧道在盾构始发处正交上跨穿越既有地铁线路施工的力学行为。通过数值分析,得到以下结论:在设计方案下,新建盾构隧道施工对既有隧道管片受力影响有限;新建隧道开挖后的土体卸载作用会引起下方既有隧道产生轻微隆起;在设计方案下进行上跨施工,可以保证既有地铁隧道的受力和变形满足安全运营的要求。     

地铁隧道间大直径桩基础施工技术及隧道监控方法

广州塔裙楼桩基础后期工程部分大直径钻孔灌注桩需在4条地铁隧道之间进行施工,文中介绍其施工过程和地铁隧道监控情况,并分析钻孔灌注桩施工对临近地铁隧道结构及运营的影响程度,供同类施工参考.     

暗挖隧道空洞初步普查施工及处理

以北京地铁某暗挖隧道为例,分析了隧道衬砌背后空洞的形成原因,通过人工敲击法和雷达探测法确定了空洞位置,并提出了相应的处理措施,为地铁暗挖隧道空洞普查及处理提供参考。     

拆复建桥桩对软土地层盾构隧道结构影响研究

以大直径桥桩紧邻既有地铁盾构隧道施工为研究背景,基于隧道病害调查和长期变形监测数据,分析典型河漫滩软土地区钻孔桩打、拔近接施工对盾构隧道衬砌环结构影响,并对钢护筒超前加固效果进行量化评估。结果表明:近距离桥桩拆复建工程在原隧道结构较大变形的基础上,进一步对结构病害产生不良影响,使得结构安全性储备降低,需要进行及时必要的修复性处理;淤泥质粉质黏土较其他地层内隧道受施工影响变形量更为显著;采取钢护筒措施可减少隧道62.5%位移变形量、42.9%横断面收敛变形量。     

隧道下穿既有线的案例分析与沉降分析方法

随着城市地铁建设渐入规模,越来越多的地铁建设将面临多次穿越既有地铁线路的问题,这是新线建设中等级最高的风险工程之一。对这类问题引起的工程风险的合理预测和评估具有重大的工程意义,也是领域内研究的难点,迄今尚未提出有针对性的有效预测和评价方法。基于刚度修正法的基本思路和对实测既有线隧道变形特征的分析,从国内外典型的地铁下穿既有线的案例分析着手,着重考虑既有隧道埋深、结构刚度对其变形特征的影响,从而提出适用于预测既有线在新建隧道下穿影响下产生沉降的简便分析方法,为地铁隧道施工对既有线隧道影响的风险预测及评估提出崭新的思路和工程实用的分析途径。     

隧道下穿既有地铁车站施工结构沉降控制案例研究

北京地铁6号线朝阳门站至东大桥站区间隧道采用平顶直墙结构垂直密贴下穿既有2号线朝阳门站。采用FLAC~(3D)模拟分析了密贴下穿施工引起既有地铁车站结构沉降规律,据此提出了下穿施工期间既有地铁车站结构沉降控制方案,并基于现场监测数据对既有地铁车站结构沉降进行了分析与安全性评价,主要取得以下认识:下穿段两沉降缝间的既有地铁车站结构为沉降控制的重点区域;区间隧道下穿施工期间,初支背后回填注浆能够在一定程度上减小既有地铁车站结构沉降,千斤顶顶升则是既有地铁车站结构沉降控制的关键措施;隧道开挖初期既有地铁车站结构沉降显著,根据现场监测数据及时调整千斤顶顶升力并加强注浆质量,确保了下穿施工期间既有地铁车站的结构安全。研究成果可为城市新建隧道密贴下穿既有地下结构等类似工程提供借鉴及参考。     

横跨既有地铁线隧道施工中的关键技术分析

目前下沉式隧道横跨既有地铁及城市管线时对既有结构物的变形控制是一个技术难题。本文以广州市猎德大桥系统工程中的花城大道隧道工程为依托,对隧道施工中的重难点及处理方案进行分析研究,重点对地铁隧道的自动监测进行讨论。研究成果为既有地铁与地下市政管线的安全运营及下沉式隧道的安全施工提供重要的技术保障,可为类似工程的施工提供参考。     

Full 3D modelling for effects of tunnelling on existing support systems in the Sydney region

The assessment of the interaction between a new tunnel and existing structures is an important issue in urban areas. In this study, the effect of tunnelling on the existing support system (i.e. shotcrete lining and rock bolts) of an adjacent tunnel is firstly investigated using ABAQUS and TUNNEL3D through full three-dimensional (3D) finite element calculations coupled with elasto-plastic material models, which takes into account the tunnelling procedure, the interaction between the shotcrete lining and rock mass, the interaction between the rock bolts and rock mass, and the elasto-plastic behaviour of the rock mass, the shotcrete lining and the rock bolts. Then, on the basis of the calculated results, it is concluded that the driving of the new tunnel significantly affects the existing support system when the advancing tunnel face passes the existing support system and is minor when the face is far from it. Moreover, the support system in the side of the existing tunnel closest to the new tunnel is more significantly affected than that on the side opposite to the new tunnel. It is also found that in a region such as Sydney with relatively high horizontal regional stresses, the driving of the new tunnel will not cause considerable adverse effects on the existing support system, if the new tunnel is driven horizontally parallel to the existing tunnel with a sufficient separation, since both the tensile stress in the existing shotcrete lining in the lateral sides of the preceding tunnel and the compressive stress at the crown decrease although noticeable tensile stress increments are observed on some parts of the existing rock bolts. Finally, it is pointed out that the effects of tunnelling on the existing support system strongly depend on the position between the original and new tunnels. In terms of the stress increments on the existing support system, especially the maximum tensile stress increments on the existing shotcrete lining, the driving of the new tunnel causes increasingly adverse effects on the existing support system in a sequence of: (i) horizontally parallel tunnels with a separation of 30 m; (ii) horizontally parallel tunnels with a separation of 20 m; (iii) staggered tunnels with a separation of 30 m; (iv) vertically alignment tunnels; and (v) staggered tunnels with a separation of 20 m in the cases investigated in this study. For the relatively high regional stresses in the Sydney region, the obtained results qualitatively agree with other’s published observations from the construction of closely parallel subway tunnels.     

Bahnsteigerweiterung der U6 unter dem neuen Rathaus in München – Spritzbetonvortrieb mit Vereisung

Platform extension of the subway U6 below the historical town hall in Munich – shotcrete method combined with ground freezing. The construction of the new football stadium in Munich‐Fröttmaning made it necessary to extend the platform of the subway station U6 “Marienplatz” below the historical town hall of Munich. For this, two new tunnels for pedestrians were driven parallel to the existing subway tunnels. They were planned as shotcrete construction and driven under atmospheric conditions. The tunnels have a vertical distance of approx. 10 m to the foundation of the town hall. Artificial ground freezing was used to guarantee the stability and safety of the tunnel roof and to reduce the deformations. The freezing pipes were implemented in a smaller pilot tube lateral above the tunnels. Both the magnitude of the frost heave displacements and the settlements had to be predicted prior to undertake the construction. Therefore frost heave tests and FE‐computations were carried out. During the construction process these results were permanently compared to measurements in order to control and ensure tolerable deformations. In the following contribution the substantial computations and results of measurement relating to the ground deformations and to the lowering of groundwater are described. Furthermore the methods for the reduction of the frost heave are explained. A comparison of the methods of construction and calculation of the old tunnels and the new tunnels illustrates the developments in tunnel construction resulting from the shotcrete method.     

地面堆载对临近既有盾构隧道影响的研究综述

随着我国城市建成和运营的地铁盾构隧道越来越多,地铁沿线突发堆土(地面堆载)现象也越来越频繁。地面堆载会导致下方土体产生附加沉降,使临近既有地铁隧道产生相应的附加变形和受力,严重威胁到隧道结构及地铁运营安全。根据现有研究成果,将地面堆载对临近隧道影响的研究方法归纳为:现场实测法、理论分析法、数值模拟法和模型试验法。对发展概况及研究进展进行综述,提出需进一步研究的课题和研究思路。     

Effects of lateral unloading on the mechanical and deformation performance of shield tunnel segment joints

Unloading during lateral excavation widely occurs in existing subway shield tunnels. Previous studies have focused on the overall stress and deformation of existing tunnels caused by nearby unloading. However, the stress and deformation state of tunnel segment joints have yet to be considered. This study considered the non-continuity of the shield tunnel lining and the interactions among tunnel segment, surrounding rocks and ballast bed. A hybrid model of a shield tunnel was established based on 3D nonlinear contact theory. The mechanical and deformation properties of the segments and joints of an existing shield tunnel under the influence of lateral excavation of the foundation pits were studied. Unloading during lateral excavation caused the cross section of the shield tunnel to generate vertical convergence and shift horizontally towards the foundation pit. An opening and dislocation in the joint, which caused the waterproof ability of the joint to decrease sharply, were observed. Meanwhile, stress at the segment joint increased sharply and caused local cracks in the segment lining. Axial and shearing force on the joint bolt also increased significantly. Based on existing subway regulations, the calculation results were combined to establish a deformation control standard for existing shield tunnels under lateral excavation. The rate of vertical convergence of the lining should be less than 3.68‰, and the rate of horizontal shift of the axis should be less than 0.53‰.