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1.
Interaction of longitudinal surface settlements for twin tunnels in shallow and soft soils: the case of Istanbul Metro 总被引：1，自引：1，他引：0
Ibrahim Ocak 《Environmental Earth Sciences》2013,69(5):1673-1683
Increasing demands on infrastructures increases the attention on shallow soft ground tunneling methods in urbanized areas. Especially, in metro tunnel excavations, it is important to control the surface settlements observed before and after excavation, which may cause damage to surface structures. To solve this problem, earth pressure balance machines (EPBMs) have widely been used throughout the world. This study focuses on surface settlement measurements, the interaction of twin tunnel surface settlement, and the relationship between shield parameters and surface settlement for parallel tunnels using EPBM shields in clay and sand soils. In this study, the tunnels were excavated using two EPBMs. The tunnels were 6.5 m in diameter, as twin tubes with a 14 m distance from center to center. The EPBM in the first tube followed about 100 m behind the other tube. Segmental lining with 1.4 m of length was employed as a final support. The results from this study showed that (1) the most important parameters for the maximum surface settlements are the face pressure and backfill; (2) in twin tunnel excavation with EPBM for longitudinal profile, the settlement rate reached its peak value when the shield came to the monitoring section and this peak value continued until the shield passed the monitoring section; (3) every shield affected the other tunnel’s longitudinal surface settlement profile by approximately 35–36.8 %; (4) S A, S B and S C values were found to be 38.0, 35.8 and 26.2 %, respectively for an EPBM, and (5) ensuring good construction quality is a very effective way to control face stability and minimize surface settlement. 相似文献
2.
Environmental effects of tunnel excavation in soft and shallow ground with EPBM: the case of Istanbul 总被引：8，自引：4，他引：4
Ibrahim Ocak 《Environmental Earth Sciences》2009,59(2):347-352
In metro tunnel excavations, it is important to control surface settlements observed before and after excavation, which may
cause damage to surface structures. Otherwise, the metro tunnel cannot perform the task expected, and the advantages of the
tunnel are lost. In this study, short-term surface settlements and their effect on buildings are examined in three zones for
twin tunnels, which have been excavated between the Otogar and Kirazlı 1 stations of the Istanbul Metro line, and are 5.8 km
in length. Geology in the study area is composed of fill, stiff clay, dense sand, very dense sand, and hard clay, respectively,
starting from the surface. Tunnels are excavated by using two Earth Pressure Balance Tunnel Boring Machines (EPBMs) with a
6.5 m diameter as twin tubes with 14 m distance from center to center. The EPBM in the right tube is followed about 100 m
behind the other tube. Segmental lining with 1.4 m of length is currently employed as final support. The results of this study
indicate that, with EPBM excavation method in shallow depths and soft grounds, the damage done to the environment prolonged
project costs up to 15.8% more. In addition, tunnel conditions prolonged the project schedule to 29.3%. 相似文献
3.
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
4.
Calculation of surface settlements caused by EPBM tunneling using artificial neural network, SVM, and Gaussian processes 总被引：2，自引：2，他引：0
Increasing demand on infrastructures increases attention to shallow soft ground tunneling methods in urbanized areas. Especially in metro tunnel excavations, due to their large diameters, it is important to control the surface settlements observed before and after excavation, which may cause damage to surface structures. In order to solve this problem, earth pressure balance machines (EPBM) and slurry balance machines have been widely used throughout the world. There are numerous empirical, analytical, and numerical analysis methods that can be used to predict surface settlements. But substantially fewer approaches have been developed for artificial neural network-based prediction methods especially in EPBM tunneling. In this study, 18 different parameters have been collected by municipal authorities from field studies pertaining to EPBM operation factors, tunnel geometric properties, and ground properties. The data source has a preprocess phase for the selection of the most effective parameters for surface settlement prediction. This paper focuses on surface settlement prediction using three different methods: artificial neural network (ANN), support vector machines (SVM), and Gaussian processes (GP). The success of the study has decreased the error rate to 13, 12.8, and 9, respectively, which is relatively better than contemporary research. 相似文献
5.
Analytical stress and displacement due to twin tunneling in an elastic semi‐infinite ground subjected to surcharge loads 
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下载免费PDF全文 The construction of twin tunnels at shallow depth has become increasingly common in urban areas. In general, twin tunnels are usually near each other, in which the interaction between tunnels is too significant to be ignored on their stability. The equivalent arbitrarily distributed loads imposed on ground surface were considered in this study, and a new analytical approach was provided to efficiently predict the elastic stresses and displacements around the twin tunnels. The interaction between 2 tunnels of different radii with various arrangements was taken into account in the analysis. We used the Schwartz alternating method in this study to reduce the twin‐tunnel problem to a series of problems where only 1 tunnel was contained in half‐plane. The convergent and highly accurate analytical solutions were achieved by superposing the solutions of the reduced single‐tunnel problems. The analytical solutions were then verified by the good agreement between analytical and numerical results. Furthermore, by the comparison on initial plastic zone and surface settlement between analytical solution and numerical/measured results of elastoplastic cases, it was proven that the analytical solution can accurately predict the initial plastic zone and its propagation direction and can qualitatively provide the reliable ground settlements. A parametric study was finally performed to investigate the influence of locations of surcharge load and the tunnel arrangement on the ground stresses and displacements. The new solution proposed in this study provides an insight into the interaction of shallow twin tunnels under surcharge loads, and it can be used as an alternative approach for the preliminary design of future shallow tunnels excavated in rock or medium/stiff clay. 相似文献
6.
以上海4条地铁线路道床长期沉降监测资料为基础,分析了地铁隧道的纵向沉降特征;结合该地区地质环境调查资料,深入分析地铁隧道沉降与下卧层地层结构、浅部地下水位变化以及区域地面沉降三个地质环境因素之间的相互作用关系。结果表明,地铁隧道下卧地层结构差异是地铁隧道沉降差异性的重要地质环境因素,深基坑降排水引起降水目的含水层地下水位下降,使得降水目的层以及相邻软黏性土层发生较大的压缩变形,导致以降水目的层上覆软黏性土层为承载体的地铁隧道也随之发生沉降,区域地面沉降也是地铁隧道沉降的重要影响因素。 相似文献
7.
在盾构隧道基础上结合浅埋暗挖法可以有效地解决地铁车站和盾构隧道施工之间的矛盾。北京地铁14号线试验段采用外径为10 m的土压平衡盾构修建,试验段上的车站结合PBA法（洞桩法）扩挖而成。综合运用预测地表沉降的经验公式、相关统计资料和规范,以及数值模拟方法,对大断面盾构隧道结合洞桩法修建地铁车站的施工过程进行地表沉降分析。结合北京地铁车站地表沉降控制基准值和现有地铁车站地表沉降统计数据,提出较为合理的地表沉降控制标准,并按照三级控制的管理方法,分级分步进行地表沉降控制,研究结果对指导工程施工有一定的参考价值。 相似文献
8.
The interaction between twin‐parallel tunnels affects the tunnelling‐induced ground deformation, which may endanger the nearby structures. In this paper, an analytical solution is presented for problems in determining displacements and stresses around deforming twin‐parallel tunnels in an elastic half plane, on the basis of complex variable theory. As an example, a uniform radial displacement was assumed as the boundary condition for each of the two tunnels. Special attention was paid to the effects of tunnel depth and spacing between the two tunnels on the surface movement to gain deep insight into the effect of the interaction between twin‐parallel tunnels using the proposed analytical approach. It is revealed that the influence of twin tunnel interaction on surface movements diminishes with both the increase of the tunnel depth and the spacing between the two tunnels. The presented analytical solution manifests that, similar to most of the existing numerical results, the principle of superposition can be applied to determine ground deformation of twin‐parallel tunnels with a certain large depth and spacing; otherwise, the interaction effect between the two tunnels should be taken into account for predicting reliable ground movement. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
9.
紧邻多孔交叠隧道是随着地铁建设的不断深入发展而出现的一种复杂的隧道空间分布形式。依托武汉地铁2号线和4号线工程,针对4孔紧邻交叠隧道,采用三维有限元方法分析了隧道动态施工过程引起的地表变形规律以及后建隧道对已建隧道受力与变形的影响。计算结果表明：隧道埋深对地表变形影响显著;紧邻4孔交叠隧道施工引起的地表最终变形达到了32 mm,超出了规范的限值;隧道埋深越大,引起的地表变形越小,但影响的范围越大;紧邻4孔交叠隧道施工时的影响范围为：前方约为30 m、后方约25 m、单侧约30 m;隧道的变形主要表现为上下压扁,两拱腰外扩,变成倒鸭蛋形;隧道的变形主要发生在盾构机刀盘通过前后约1D的范围内,随后很快趋于稳定;隧道结构的沉降主要取决于隧道自身以及其上部的垂直隧道的施工,邻近隧道的施工主要影响已建隧道的侧向变形;后建隧道将少量增加已建隧道管片内的内力。研究成果可为武汉地铁建设以及国内今后类似工程的设计与施工提供参考和指导 相似文献
10.
基坑开挖对近邻运营地铁隧道影响规律研究 总被引：1，自引：0，他引：1
对某邻近基坑开挖的地铁隧道的水平位移和沉降的时空分布做了深入分析。由于软土的蠕变效应,应考虑基坑分块开挖的先后顺序造成的时空效应的影响,以及基坑围护体系的水平支撑结构对土体位移的限制作用。基坑开挖对邻近地铁隧道的影响范围为2.5倍开挖深度,而对于远基坑的右线,影响范围更低,甚至低至1.5倍开挖深度。将基坑和隧道的监测数据联系分析,得到比值与水平距离的关系曲线,将基坑监测数据代入拟合公式,对地铁水平和垂直位移进行估算。隧道水平位移与邻近的同深度土体水平位移的比值（?）,其最大累计位移点的? 较多地处在0.60～0.65范围,在底板浇筑都已完成后,稳定在0.60。隧道沉降与邻近地表沉降的比值（?）,其最大累计沉降点的?,较多地处在0.50～0.60间,底板浇筑完成后,稳定在0.52±0.05水平。 相似文献
11.
12.
以云南平年隧道为工程背景,采用MARC三维非线性有限元法程序,对新奥法修建的偏压、错台、浅埋小间距隧道模拟了先行隧道不同超前距离情况下的动态施工过程。掌子面距离的变化对洞室的横向位移的影响大于竖向位移,且对于左洞更为显著;随着左右洞掌子面距离的增大,洞周位移、中间岩柱位移均减小,但部分范围内地表沉降值有所增大,局部区域受力、变形恶化。 相似文献
13.
14.
地铁隧道穿越角度对地表建筑物的影响分析 总被引：2，自引：0，他引：2
结合深圳地铁隧道下穿某住宅小区建筑群的工程实践,以某框架结构建筑为研究对象,按照隧道-土体-结构共同作用,利用Midas/GTS软件建立三维非线性有限元模型,计算了隧道轴线与地面建筑物成90º、60º、45º和30º夹角4种不同工况,分析隧道轴线与建筑物不同夹角条件下隧道开挖对地表建筑物基础沉降和结构受力变形分布形态的影响。计算结果表明,隧道以不同角度穿越时,地表建筑基础的沉降过程和分布形态差异明显。随着穿越角度? 的减小,基础沉降最大增幅为37.3%,建筑基础沿线沉降由对称分布转为侧向倾斜,相邻柱基沉降差增大;建筑倾斜和扭曲变形增加明显,最大增幅达10倍;由于分析部位不同,相比建筑基础及底部结构变形而言,隧道穿越角度的改变对建筑内力影响较小。 相似文献
15.
我国沿海地区大量的地铁隧道都修建在饱和软土地层,饱和软土地层中地铁列车运行引起的环境振动逐渐成为社会关注的问题。以上海2号线某地铁区间隧道为研究对象,采用循环运动模型本构模型和水土耦合动力分析方法,分析了饱和软土中地铁列车运行引起的地表振动加速度以及振动位移响应规律,采用加速度振级对地表的振动强度进行了评价,分析了单次列车通过时引起的隧道下卧土层超孔隙水压力（EPWP）响应规律。计算结果表明,饱和土的振动响应比干土要小得多,地表水平向与竖向的振动规律明显的不同,超孔隙水压力沿隧道下方沿向是不断减少的,在距离隧道中心的纵断面上是先增加后减少。分析饱和土中地铁运行引起的环境响应规律,可为地铁沿线建筑物减隔振设计及沉降控制提供一定依据。 相似文献
16.
Shuying Wang Junsheng Yang Yuanhong Yang Fangping Zhong 《Geotechnical and Geological Engineering》2014,32(2):453-467
The structure on the ground bears impact from the tunneling-induced settlement, especially when the tunnel is shallow and its span is large. This paper presents the construction of Lijiachong twin tunnels below a high-rise transmission tower and the prevention techniques to avoid the failure of the tower. The span of each tunnel is about 18 m, and the tunnel embedded depth below the tower foundations is only 15.5 m. There was a high risk of influencing the performance of the tower during the tunneling. To reduce the risk of collapse of the transmission tower, the available methods in field to reinforce the tower foundations were proposed. For engineering cost and construction convenience, the separated pile foundations were connected with framed girders, resulting in that the separated foundations worked as a whole. The effectiveness of the reinforcement was evaluated by monitoring deformation and stress in the tower, indicating that the measured values were lower than their respective allowable ones. With reinforcing the tower foundations using the framed girders, the Lijiachong twin tunnels safely passed beneath the transmission tower, and the continuous performance of the transmission tower was ensured. 相似文献
17.
Asghar Siahmansouri Javad Gholamnejad Mohammad Fatehi Marji 《Arabian Journal of Geosciences》2014,7(3):1059-1066
Twin tunnels can be used for many applications. Interaction between two tunnels is an important problem in tunnel engineering that should be studied specially. Numerical investigations are well adapted to field data and numerical methods can be used in design of rock pillar of twin circular tunnels. So far, no relationship has been provided to estimate the minimum stable rock pillar width. In this paper, the interaction between twin circular tunnels has been studied using 2D finite element analysis. To do this, a great number of twin tunnels were modeled in Phase2 software with different conditions of rock mass (RMR value) and depth of tunnel. Models were analyzed and minimum stable rock pillar width was determined. This process was repeated for three different ratios of K (ratio of horizontal stress to vertical stress, 0.5, 1, and 1.5). Finally, according to the linear and nonlinear regression methods, the best merit function was fitted to result of numerical analysis. Then, new approximate formula was proposed to estimate the minimum rock pillar width according to RMR value and depth of twin circular tunnels with different K values. The formulae are very accurate (coefficient of correlation equals to minimum 0.96) that can be used for estimating the minimum rock pillar width of twin circular tunnels. 相似文献
18.
Attewell, P.B. and Farmer, I.W., 1974. Ground disturbance caused by shield tunnelling in a stiff, overconsolidated clay. Eng. Geol., 8: 361–381.
Some of the factors affecting ground deformation around shield tunnelling excavations in stiff clays are considered. There is particular reference throughout the paper to an analysis and interpretation of measured ground deformation around a 4.146-m diameter, hand-excavated, shield-driven tunnel at a nominal axis depth of 29.3 m in the overconsolidated London Clay. The maximum surface settlement was found, by precise levelling, to be 6.1 mm but the shape of the transverse surface settlement profile conformed to a normal probability curve only up to the time of shield passage. Of the contributory ground losses at the tunnel, yield of the clay at the tunnel face appears to dominate to the extent of generating up to 50% of the eventual surface settlement. Measurement evidence suggests a rate of yield at the face that is 2 to 3 times the radial yield over the shield and implies that up to about one-fifth of the surface settlement could be attributed to radial yield into the grouted sections of the erected tunnel lining. 相似文献
19.
在上跨隧道的基坑工程中基坑开挖常引起下卧隧道发生结构变形,限制隧道的隆起变形成为基坑施工控制的关键。详细介绍了该类工程的特点,包括交叉形式、隧道变形特点、常见控制措施等,对近期国内发生的39例类似工程进行分类总结,分析了隧道纵向最大隆起变形与各影响因素间的关系,并提出了隧道最大隆起变形的预测模型。结果表明,该类工程中工程地质对隧道的隆起变形影响较大,工程地质条件越差隧道的隆起变形越难控制;开挖深度、基坑面积、基坑形状同样是影响隧道隆起变形的重要因素,基坑开挖面积及深度越大,形状越不规则,隧道的隆起变形越大;在软土地区,当基坑开挖面积及深度较大时设置抗拔桩能显著减小隧道的最大隆起变形。 相似文献
20.
根据南京地区的工程地质与水文地质条件和多年隧道结构变形的监测资料,系统分析了不同地貌单元内隧道结构的变形特征,指出影响南京地铁隧道结构变形的主要工程地质因素是盾构隧道的软土问题和矿山法隧道的水文地质问题。结果表明:南京地区发育不同成因类型的软土,特别是长江河谷平原区软土,具有高孔隙比、高含水量、高压缩性、结构性强等特性,易导致隧道结构发生不均匀沉降。同时,穿越丘岗地区的矿山法隧道,一旦上游水源补给量超过正常值时,易导致隧道结构的衬砌逐渐抬升变形甚至引发运营中断事故。这一研究成果为南京地铁运营隧道结构变形分析提供了工程地质方面的理论基础,以便采取针对性的措施及时控制变形,确保安全营运。 相似文献