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1.
以西安地铁一号线朝阳门站一康复路站区段饱和软黄土地铁隧道为研究对象,通过施工期现场地表沉降变形监测,分析了在饱和软黄土特殊地层条件下隧道浅埋暗挖法施工引起的该区段地表沉降变形规律以及地表沉降槽分布特征。结果表明:在饱和软黄土隧道开挖时,随着掌子面的推进,隧道顶地表沉降可分为沉降微小阶段、沉降显著发展阶段、沉降缓慢阶段和沉降稳定阶段;单线隧道开挖后的最大地表沉降量为18.89mm,双线隧道开挖后的最大地表沉降量为36.4mm;已开挖隧道对围岩土体的扰动作用使得后开挖隧道的地表沉降发展较大;双线隧道的地表沉降槽宽度接近单线隧道沉降槽宽度的2倍,因此可以将其近似为单线隧道地表沉降槽宽度与双线隧道轴线中点距离之和;单线隧道开挖后地表沉降槽宽度为8.4~9.3m,双线隧道开挖后地表沉降槽宽度为16.2~17.5m;隧道开挖施工的沉降槽宽度参数为0.435~0.467,单线隧道开挖后的地层损失率为0.765%~1.324%,双线隧道开挖后的地层损失率为1.231%~2.200%。  相似文献   

2.
针对地表下隧道周围土体变形的观测困难,用熔融石英和溴化钙溶液配置透明土,提出基于透明土的盾构开挖面失稳试验研究方案,获得隧道前方纵断面土体位移矢量、沉降槽曲线和破坏模式等。试验结果表明,隧道开挖面失稳后土体变形以垂直位移为主,浅埋时土体破坏呈现“楔”形,破坏面延伸至地表,埋深增加时扰动范围向开挖面变窄,深埋时出现压力拱,扰动体呈现为筒仓形;隧道纵断面内沉降槽呈现为Weibull分布,最大沉降发生在隧道开挖面前方约(0.3~0.5)D(D为隧道半径)的拱顶处,变形主要发生在隧道开挖面前方的拱顶以上,浅埋时沉降槽从地表往下向深而窄变化,深埋时沉降槽宽度接近相同,从地表往下逐渐变深。  相似文献   

3.
地铁隧道施工引起地层位移规律的探讨   总被引:9,自引:0,他引:9  
韩煊  李宁 《岩土力学》2007,28(3):609-613
目前对城市隧道开挖所引起的地表以下地层的位移规律的认识还很不充分,长期以来只有定性地认识。英国学者Mair等人(1993年)根据在黏土中的有限实测资料,基于预测地表位移的Peck公式,考虑了沉降槽宽度随深度变化,从而提出了地表以下的位移计算公式。他们的研究成果被广泛引用,但是由于其仅适用于黏性土,且假定地表处沉降槽宽度参数为0.5,因此在应用上受到很大的限制。在Mair公式的基础上,着重讨论了沉降槽宽度参数随地层深度的变化趋势,并提出了修正计算公式,不仅可以考虑地表沉降槽宽度参数与0.5相差较大的情况,还适用于砂类土地层,因此比Mair公式具有更广泛的适用性。  相似文献   

4.
孟建宇 《地质与勘探》2020,56(3):597-604
在对地表变形产生的沉降槽的研究中,通常将土性参数看作确定值,并且假定沉降槽是关于隧道轴线对称的,这样往往忽略了土体的非均质性特点,对沉降槽的假定也偏于理想化。为此,借助随机场的计算机模拟方法,在引入曲线偏移量对经典Peck公式改进的基础上,开展Monte-Carlo随机分析,分析土体弹性模量空间变异性对沉降槽曲线的影响。研究结果表明:(1)引入曲线偏移量是可行的,并且可以表现沉降槽在隧道轴线位置的不对称性;(2)土体弹性模量空间变异性对沉降槽的形态影响不明显,但对沉降槽宽度、最大沉降值和最大沉降位置有重要影响。  相似文献   

5.
基于Peck公式的双线盾构引起的土体沉降预测   总被引:1,自引:0,他引:1  
陈春来  赵城丽  魏纲  丁智 《岩土力学》2014,35(8):2212-2218
基于Peck公式,对双线水平平行盾构隧道施工中土体损失引起的三维土体沉降计算方法进行研究。考虑先行隧道施工对后行隧道的影响和两条隧道开挖面的不同位置,建立修正的三维Peck公式;通过分别计算先行盾构隧道和后行盾构隧道施工引起的土体沉降,叠加得到双线水平平行盾构施工引起的总的三维土体沉降。算例分析结果表明:预测值与实测值比较吻合;随着两条隧道开挖面前后距离的逼近,地面最大沉降量会逐渐增大;随着土体深度z的增大,沉降略增大、沉降槽宽度则略减小;当两条隧道轴线水平距离L较小时,地面沉降量较大,符合正态分布规律;随着L的增大,最大地面沉降量会逐渐减小,沉降曲线形状慢慢由V型转变成W型。  相似文献   

6.
盾构隧道施工引起地表下土体变位的分析评估   总被引:2,自引:0,他引:2  
王占生  王梦恕  张弥 《岩土力学》2009,30(6):1699-1704
目前对盾构隧道施工引起的地表下土体变位进行预测分析的研究还相对较少,尤其是缺乏简单实用的工程估算方法。在深埋隧道周围土体弹性位移计算方法及盾构间隙参数研究成果的基础上,通过相应的分析和假设提出了一种预测盾构隧道施工引起地表下土体水平变位的简便估算方法。另外,在已有研究成果基础上,提出了一种新的盾构隧道沉降槽的描述方法,并结合Mair等提出的计算公式对盾构隧道施工引起的地表下土体沉降变位进行预测。通过与有限元计算结果及一些典型盾构隧道监测数据的对比分析,证明提出的估算方法能够较好地预测实际工程中盾构隧道施工引起的地表下土体的变位情况。  相似文献   

7.
双线平行盾构隧道施工引起的三维土体变形研究   总被引:4,自引:0,他引:4  
魏纲  庞思远 《岩土力学》2014,35(9):2562-2568
基于双线水平平行盾构施工中土体损失引起的土体变形二维解析解,建立土体变形三维解析解。取不同的纵向位置作为变量,建立土体损失率沿纵向的变化方程;考虑先行隧道施工对后行隧道的影响,分别计算两条盾构隧道施工引起的土体变形,叠加得到双线平行盾构施工引起的土体总变形。其方法能够计算土体深层沉降和水平位移,较精确地反映土体三维变形。算例分析结果表明:预测值与实测值较为吻合;土体沉降随着离开挖面距离的增加而不断增大,最终在x=-40 m左右时趋于稳定;随着先行隧道与后行隧道开挖距离的接近,最大土体总沉降量逐渐增大;土体沉降会随着深度z的增大而略微增加,但沉降槽宽度将略微减小;随着两条隧道轴线水平距离L的增大,最大土体沉降逐渐减小,沉降曲线形状慢慢由V型转变成W型,不再符合正态分布规律。  相似文献   

8.
以厦门吕厝站地铁基坑开挖工程为工程原型,采用分离相似设计方法确定了模型试验所需要关键参数的相似比,制作了异形基坑试验模型,并设计了合理的监测系统。通过模拟基坑实际的开挖过程,根据取得的监测数据,分析了地表沉降、地连墙变形和受力等变化规律。结果表明:与基坑边缘距离越大,地表沉降影响越小,且墙体边长及开挖深度越大沉降越显著;地表沉降曲线形式与沉降数值大小有关,基坑开挖表现出明显的空间效应和角隅效应,地表沉降主要发生在坑内土体开挖阶段;随开挖的进行,土层卸荷对地表沉降影响逐渐减小,地连墙弯矩大小与开挖深度呈正相关,最大弯矩值出现在基坑最深开挖面附近。  相似文献   

9.
武汉地铁三号线土层盾构开挖引起的地表沉降研究   总被引:3,自引:3,他引:0       下载免费PDF全文
为分析隧道盾构开挖引起的地表沉降规律,本文以武汉地铁三号线为工程背景,采用现场监测和数值模拟计算相结合的方法,综合分析了土质地层盾构开挖时隧道的纵向、横向地表沉降特征,探讨了不同注浆半径条件下地表沉降变化规律,结果表明:数值计算结果与现场监测数据相吻合;开挖过程中盾首上方地表沉降迅速,盾构穿过后沉降减缓,注浆后回弹,最终趋于平稳;隧道拱顶沉降值最大,平均沉降值约40 mm,离隧道轴线越远沉降值越小,形成沉陷槽,沉陷槽宽度约30 m;注浆半径越大,沉降值越小,施工时可根据技术要求和经济条件选择最优注浆半径。  相似文献   

10.
杨泽飞  魏纲  林磊磊  张世民 《岩土力学》2013,34(Z2):338-343
盾构法隧道施工引起的土体超孔隙水压力消散,会导致工后地表继续沉降。在前人研究基础上,提出了隧道周围土体的初始超孔隙水压力计算方法。采用分层总和法,计算由于扰动区内土体超孔隙水压力消散引起的地表固结沉降量,结合施工阶段地表沉降量,叠加得到总的工后横向地表沉降。提出了固结开始t时刻的地表总沉降量计算方法,研究了地表沉降速率随时间的变化。算例分析结果表明:本文方法计算得到的横向地表沉降曲线符合正态分布规律,与实测值吻合;地表总沉降速率的发展也与实测沉降速率曲线相符。  相似文献   

11.
Nowadays, due to urbanization and population increase, need for metro tunnels, has been considerably increased in urban areas. Common characterization of urban area tunnels is that they are excavated in very shallow depths and soft ground. In such excavations, main challenge for tunneling is low bearing capacity and easy deformation characteristic of the ground. Tunnel face instability and the potential surface settlement are the most hazardous factors that should be considered in all tunneling methods applied in urban areas. Incorrect estimation of the maximum surface settlement value can lead to irreparable damages to the buildings and other nearby structures. There are several published relationships concerned with field measurements and analytical solutions to estimate the amount of the maximum surface settlement value due to tunneling. These relationships are not precise for calculating the aimed values. Therefore, providing accurate equations for estimation of these values is certainly useful. First purpose of this study is to determine the effective parameters such as geotechnical factors (cohesion, internal friction angle, density, Young’s modulus and Poisson’s ratio), and engineering factors (tunnel depth, tunnel diameter and face support pressure) on the maximum surface settlement value. In this study, three metro project constructions namely Istanbul, Tehran, Mashhad in the Middle East were chosen. FLAC3D (Itasca Consulting Group 2002) was used for detailed numerical analysis. The second aim is to present better equations in estimating the maximum surface settlement-based actual data set from several tunnel projects and numerical modeling. The results from the new estimation equation are compared with results of empirical and field observations. The maximum surface settlement values obtained from the new equation have good agreement with the actual results for three different metro case studies.  相似文献   

12.
当盾构隧道平行侧穿建筑物时,大多关注建筑物的横向沉降规律,对其纵向沉降关注较少。为此,针对盾构隧道平行侧穿建筑物引发的空间变形开展研究。首先,对天津地铁6号线平行侧穿四座结构形式相近的砖混建筑的实测数据进行分析,得到建筑物基本变形模式;基于工程实测并考虑土体的小应变硬化特性建立三维有限元数值分析模型,研究了盾构侧穿引发的建筑物纵向挠曲、土体变形与应力变化规律,并分析了不同建筑平面长宽比的影响。结果表明,盾构隧道平行侧穿将诱发平面长宽比较大的建筑出现"下凹式"挠曲变形,纵墙中部沉降最大可为其角点沉降的2倍,平行侧穿并不能简化为平面应变问题进行分析。建筑物修建和盾构开挖将导致隧道上方土体经历较为复杂的应力变化过程,并可划分为6个阶段。沿建筑纵向基础中部的土体与边缘土体相比,其首先经历更大的压缩变形(建筑施工导致),在盾构穿越后又产生了更大的卸荷变形。当建筑平面长宽比小于2时,盾构开挖导致的纵向挠曲变形将显著减小。  相似文献   

13.
This study investigates the ground movements due to mechanized tunnel excavation by applying two-dimensional finite element analyses. To assess the contribution of the compressibility and plasticity of the soil on the ground movements, different constitutive models are employed to describe the soil behavior. The influence of volume loss around the tunnel on the surface volume loss is investigated, and a quadratic correlation between them is proposed. Consequently, the empirical Gaussian distribution curve, which is generally used to determine the tunneling induced settlement trough, is improved by applying the proposed quadratic correlation between surface volume loss and tunnel volume loss. Furthermore, the settlement trough width parameter has been derived by a linear function of tunnel volume loss as well. The proposed equations are validated via a case study of centrifuge tests from the literature. The results show that the proposed modification enhances the empirical solution by having better knowledge on the model parameters. Additionally, tunnel overburden and coefficient of lateral earth pressure at rest (K0) are taken into account to study their influence on the tunneling induced surface settlements. Finally, global sensitivity analysis is applied to evaluate the relative importance of corresponding model parameters in terms of their influence on the ground movements.  相似文献   

14.
A complex variable solution is derived for the ground movements around a tunnel considering the lining at different positions in the drilled hole in a linear elastic half-plane. The soil displacements for three different convergence patterns are presented and compared. It is shown that the surface settlement trough will become flatter and wider when the lining moves upwards; the horizontal displacements are more concentrated in the region below the lining; and the region influenced by displacements is wider. Most calculated settlement troughs can be well represented by Gaussian curves with simple parameters, but the obtained width parameters are larger than the traditional empirical values. The rigorous solution can be used as a simple tool to understand the fundamental mechanism of the lining buoyancy problem and as a benchmark for numerical procedures based on more sophisticated models. The importance of buoyancy effect on the displacement field should be taken into account.  相似文献   

15.
Prediction of settlement trough induced by tunneling in cohesive ground   总被引:1,自引:0,他引:1  
Surface settlements of soil due to tunneling are caused by stress relief and subsidence due to movement of support by excavation. There are significant discrepancies between empirical solutions to predict surface settlement trough because of different interpretations and database collection by different authors. In this paper, the shape of settlement trough caused by tunneling in cohesive ground is investigated by different approaches, namely analytical solutions, empirical solutions, and numerical solutions by the finite element method. The width of settlement trough was obtained by the finite element method through establishing the change in the slope of the computed settlement profile. The finite element elastic-plastic analysis gives better predictions than the linear elastic model with satisfactory estimate for the displacement magnitude and slightly overestimated width of the surface settlement trough. The finite element method overpredicted the settlement trough width i compared with the results of Peck for soft and stiff clay, but there is an excellent agreement with Rankin’s estimation. The results show that there is a good agreement between the complex variable analysis for Z/D = 1.5, while using Z/D = 2 and 3, the curve diverges in the region faraway from the center of the tunnel.  相似文献   

16.
姜晓婷  路平  郑刚  崔玉娇  崔涛 《岩土力学》2014,35(Z2):535-542
以天津地铁2号线下穿多层建筑物的盾构隧道为例,建立了盾构下穿空旷场地以及下穿建筑物的有限元模型,计算结果与现场实测数据进行了对比验证。在此基础上分析了在天津软土地区盾构隧道施工对地表沉降及多层砌体结构建筑物差异沉降的影响,并对采用小应变土体本构模型与硬化土本构模型的计算结果进行比较。结果表明,采用小应变本构模型的地表最大沉降和横向沉降槽宽度与实测数据吻合良好。盾构斜下穿砌体结构房屋时,建筑物有偏向隧道轴线方向的倾斜,采用小应变土体本构模型的计算结果可以更好地反映建筑物的倾斜斜率的变化。因此,研究软土地区盾构掘进对上方建筑物沉降影响的精细化分析时应考虑土体小应变的影响。  相似文献   

17.
在地下隧道施工中遇到既有桩的情况并不少见,尽管近年来隧道--土--桩相互作用引起了广泛关注,但以往的研究主要集中在小规模隧道开挖引起的桩的反应上。通过三维离心模型试验,研究了双管大型隧道开挖引起的群桩变形机理。由于隧道开挖引起的应力释放,群桩的实测沉降随隧道的推进几乎呈线性增加。监测点距新建隧道较短,导致群桩沉降较大。单隧道开挖完成后,在隧道中心线正上方观测到最大桩群沉降为0.23%D(即隧道直径)。双管开挖后,最大群桩沉降增加到0.32%D,最大群桩沉降位置向两隧道之间的中心线移动。随着开挖面接近监测断面,既有桩群迅速向开挖面倾斜。当隧道工作面通过监测断面时,减少了现有群桩的倾斜。显然,当隧道工作面位于监测断面正下方时,测得的群桩倾斜达到最大值。这清楚地说明了隧道开挖引起群桩的三维变形机理。若将隧道开挖简化为二维问题,则忽略了群桩沿隧道纵向的倾斜,而群桩的倾斜位于非保守侧。  相似文献   

18.
盾构隧道和矿山法隧道的施工,对围岩扰动的形式和程度不同;并行近接情况下,对彼此的扰动也将不同。以南宁轨道交通地铁1号线百佛区间的盾构-矿山法隧道小净距并行施工为研究对象,根据实际施工进度情况建立监测分析系统,分析了盾构-矿山法施工在竖直和水平方向位移的相互扰动。盾构法隧道后行,盾构的挤推作用,导致先行矿山法隧道拱顶上升、净空收缩;盾构弱化围岩和盾构沉降影响区的作用,导致先行矿山法隧道拱顶下沉、净空扩容。矿山法隧道后行,矿山法隧道侧向卸荷作用,导致先行盾构隧道管片产生管片隆起和净空扩容。研究成果揭示了小净距并行施工时,盾构隧道-矿山法隧道相互间的扰动规律;可以为类似小净距并行隧道施工顺序的选择,及相应辅助施工措施的采用,提供技术支撑。  相似文献   

19.
Increasing demand on infrastructures has led to increased attention to shallow soft ground tunneling methods in urbanized areas. Especially in metro tunnel excavations, it is important to control the surface settlements which are observed before and after excavation, which may cause damage to surface structures. Unlike motorway, sewage and other infrastructure tunnels, metro tunnels generally have to be excavated as twin tunnels and must have a larger diameter. Metro tunnels also have shallow depth. Due to their shallow depth, metro tunnels generally have been constructed in weak rocks or weak soils in cities. The construction of twin tunnels will generate ground movements which have the potential to cause damage to existing surface and subsurface structures. To solve this settlement problem, experts have used the Earth pressure balance machine (EPBM) and the slurry balance machine. In such excavations, especially in twin tunnels, the main challenges for constructers are estimating the maximum surface settlement, controlling the interaction of transverse surface settlement and shaping the settlement curve. Incorrect estimation of these parameters can lead to significant problems above the tunnels and in nearby structures. This paper focuses on surface settlement measurements, on the interaction of twin tunnel transverse surface settlement and on the relationship between shield parameters and transverse surface settlement for parallel tunnels using EPBM shields in clay and sand soils in shallow depth. Also, a new equation is proposed for estimating the transverse settlement curve of twin tunnels. The results from this proposed equation are compared with the results of field observations. The transverse settlement curve values obtained from the proposed equation have good agreement with the actual results for the Otogar–Kirazli metro case studies.  相似文献   

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