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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.
A new approach for estimating the transverse surface settlement curve for twin tunnels in shallow and soft soils 总被引：1，自引：1，他引：0
Ibrahim Ocak 《Environmental Earth Sciences》2014,72(7):2357-2367
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
3.
Accurate prediction of ground surface settlement is necessary for effectively controlling the settlement that develops during tunneling. Many models have been established for this purpose by extracting the relationship between the settlement and the factors that influence it. However, most of the models focused on the maximum ground surface settlement and do not involve dynamic and real-time predictions. This paper investigated how tunneling-induced ground surface settlement developed using a smooth relevance vector machine with a wavelet kernel (wsRVM). Various factors that affect this settlement, including geometrical, geological and shield operational parameters were considered. The model was applied to earth pressure balance (EPB) shield-driven tunnels. The results indicate that the prediction model performs well and that the distribution of the predictions can provide a measure of the prediction uncertainty. Unlike conventional methods that requireadditional efforts to determine relevant model parameters, the proposed method can optimize the parameters in the training process. The results of the parametric study conducted show that the model performance can be improved by the optimization and that the method can serve as a simple tool for practitioners to use in estimating ground surface settlement development during tunneling. 相似文献
4.
Chenyang Zhao Arash Alimardani Lavasan Thomas Barciaga Tom Schanz 《国际地质力学数值与分析法杂志》2019,43(4):781-800
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
5.
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
6.
Ebrahim Farrokh Jamal Rostami Chris Laughton 《Rock Mechanics and Rock Engineering》2011,44(4):431-445
Estimation of advance rate and utilization of tunnel boring machines (TBM) are some of the important steps in planning a TBM
tunneling project. Estimation of the utilization factor depends on realistic analysis of downtime components. Among the different
parameters influencing TBM downtime, tunnel support is the most influential factor, which can take up to 50% of the total
excavation time in some cases. Although, there are some rock mass classification systems specifically developed to link ground
conditions with the type and amount of support installed in TBM tunneling, the related downtime for support installation has
not been studied in detail. Unit supporting time (UST) is the time required for the installation of ground support per unit
length of tunnel. Support installation time (SIT) is the time required for installation of a single ground support element.
In this paper, approximate ranges of UST and SIT are discussed and analyzed on the basis of recorded ground SIT from a number
of TBM tunneling projects. The primary goal of this paper is to link UST with rock mass classifications that have been specifically
developed to assess ground support requirements for different tunnel sections using open-type TBM. An accurate estimate of
UST and SIT allows for realistic determination of the related downtime and TBM utilization rate. 相似文献
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9.
This study investigates the behavior of shield tunneling based on a complete case record of an excavation in sandy cobble ground. Both numerical and analytical analyses were conducted to estimate the surface displacement along the tunnel axis and the surface-zone affected by the shield tunneling. This paper presents the performance of the Peck method in forecasting the transversal surface settlement trough caused by the shield tunneling in a sandy cobble layer. In particular, this study has made a comparison with the vertical surface displacement monitored during the advancing excavation to the settlements estimated by using the Peck method and by conducting a three-dimensional finite element analysis. The effective measures to provide the necessary face support pressure and to reduce the formation of sinkholes and ground settlements in sandy cobble ground were also investigated and discussed. 相似文献
10.
盾构穿越砂卵石地层地表沉降特征细宏观分析 总被引：2，自引：0，他引：2
以成都砂卵石地层中地铁1号线的土压平衡盾构掘进施工为研究背景,采用室内试验、PFC2D二维颗粒流程序和 Plaxis 3D有限元软件对盾构穿越砂卵石地层地表沉降特征进行了细宏观数值模拟,揭示了土压盾构穿越砂卵石地层的失稳机制和沉降规律,并结合实际施工参数和实测地表沉降数据进行了对比分析,获得了土压盾构在砂卵石地层中掘进引起的地表横向沉降槽和纵向沉降槽曲线,分析了不同大小的开挖面土仓压力和盾尾注浆压力对地表沉降的影响,给出了砂卵石地层开挖面土仓压力的建议值和盾尾注浆压力参数的合理取值范围。细宏观分析表明,与注浆压力相比较,土仓压力对地表最大沉降曲线的形状影响较小;但必须关注土仓压力的变化,在砂卵石地层中由于土拱效应对开挖面稳定性影响较大,甚至发生突然坍塌破坏。 相似文献
11.
In large-span tunneling projects, the mechanical behavior of the rock changes in response to different sequential excavation methods (SEMs) of advancing the tunnel face. The double side drift method (DSDM), which is a development of SEM, was widely used in loess tunnels with large cross sections in China for its ability to limit ground displacement. This paper presents the deformation characteristics of large-span loess tunnels of the high-speed railway line in China. Field monitoring and numerical simulations were conducted to determine the optimal construction approach and reveal the deformation properties of large-span loess tunnels in China. The construction approaches, support measures, ground surface, and subsurface deformation characteristics associated with DSDM are demonstrated. The ground surrounding the loess tunnel underwent vertical settlement at the arch part and at the ground surface because of the metastable structure of the loess. This study provides an in-depth illustration of the influence of face-advancing sequences on ground displacement induced by tunneling, which helps us implement the most effective SEMs. 相似文献
12.
13.
潘涛 《水文地质工程地质》2022,49(1):101-108
研究盾构隧道施工对周围地面以及建筑物沉降造成的影响,是软土地区盾构隧道安全施工和正常运营的基础课题。为了分析宁波轨道交通5号线同德路站—石碶站区间双线盾构隧道施工对周边地表和建筑物的影响,本文在建立盾构隧道动态施工过程三维有限元模型的基础上,基于地表以及建筑物沉降数值模拟结果与现场监测值的对比,分析了隧道开挖对隧道周围地表沉降与建筑物沉降的影响。结果表明,掘进完成时,开挖方向沉降槽往上行线隧道方向偏移、呈现倒梯形形态,横断面影响区域为距离双线隧道轴线中心小于3倍隧道直径;上行线在下行线开挖后并不会增加地表沉降,但增大了沉降槽宽度;下行线到达前产生的沉降占最终累计沉降的67%;当盾构掘进面刚到达建筑物时、建筑物的倾斜方向与盾构掘进方向一致,当盾构掘进面离开建筑物时、建筑物将沿着盾构掘进的反方向倾斜;建筑物两侧沉降值较中部沉降值降低了83%;双线贯通后建筑物沉降呈“U”形分布,最大沉降量发生在远离隧道一侧距建筑物中心0.5 m处。 相似文献
14.
Double shield TBMs are amongst the most technically sophisticated excavation machines in use by tunneling industry. However, using the shielded machine limits access to the walls for observation of ground conditions and presence of shield makes the machine susceptible to entrapment or seizure in weak rocks under high stresses which results in high convergence. To realistically evaluate the possibility of machine seizure in such grounds, the interaction between the rock mass and shields, lining and backfilling need to be understood. This study explains the application of numerical analysis for 3D simulation of mechanized tunneling by using a double shield TBM. For this purpose, a comprehensive numerical simulation is developed to systematically evaluate the potential of excessive ground convergence. Simulation results at five reference points on the tunnel circumference along the tunnel have been examined. The results are including longitudinal displacement profile (LDP) as well as contact force profiles (LFP) on both front and rear shields, frictional forces and required thrust to move the machine, stress history of ground, and estimated loading of the segments. The results also proved that numerical analyses can successfully be used for prediction of loads on the shield during excavation to assess risks of machine entrapment. 相似文献
15.
盾构施工引起的固结沉降分析 总被引：1，自引：0，他引：1
盾构在低渗透性土层中开挖,常常伴随着地表下沉,究其原因为超孔隙水压力消散引起固结沉降的结果。为对盾构施工引起土体的固结沉降进行研究,首先,根据隧道施工前后土体应力的变化值,应用Henkel超孔隙水压力理论,推导了隧道开挖引起的初始超孔隙水压力的计算公式,并采用数值分析方法,考虑了由于土体的固结引起的沉降变形。研究成果应用到上海地铁2号线,根据具体的地质条件进行理论计算分析。结果表明,隧道开挖引起的初始超孔隙水压力最大值位于隧道起拱线处,地表固结沉降预测值与实测值吻合较好。 相似文献
16.
Elisabetta Cattoni Chiara Miriano Laura Boco Claudio Tamagnini 《Acta Geotechnica》2016,11(6):1385-1399
In this work, the effects of coupled hydromechanical (consolidation) processes associated with shield tunneling excavation in soft clays are investigated with particular attention to the prediction of ground movements at the ground surface. A series of 2d FE analyses have been carried out in parametric form in order to investigate the effects of tunnel excavation velocity relative to the soil consolidation rate and the hydraulic boundary conditions at the tunnel boundary. The shield advancement process has been simulated with a simplified procedure incorporating both volume loss and ovalization of the tunnel section. In order to investigate the relative importance of soil consolidation during the excavation process, different characteristic times for the tunnel face advancement and for the consolidation process around the tunnel have been considered, for the two limiting conditions of fully permeable liner and impervious liner. The potential damage induced by the tunnel excavation on existing structures, based on computed ground surface distortions and horizontal deformations, has been found to vary significantly with time during the consolidation process. The results of the simulations allowed to obtain useful information on the minimum tunnel face advancement speed for which the assumption of fully undrained conditions for the soil during the excavations is acceptable, as well as on the speed range for which solving the fully coupled hydromechanical problem is necessary. 相似文献
17.
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
18.
This paper presents the results of a three-dimensional numerical investigation into the interaction between conventional tunneling and a pile supported bridge. Hypothetical tunneling conditions under an existing pile supported bridge were first developed in consideration of an actual urban tunneling situation. Various components of the bridge, including piers, piles, and pile caps have been replicated from the areas in question within this model. Also included in the model is the pile-ground interface to allow for possible slip between the piles and the ground during tunneling. The results of the analysis indicate that during tunnel driving, piles directly above the tunnel can experience significant losses in their shaft loads due to downward settlements of piles relative to surrounding soils. Piles within the same system, but farther away from the tunnel tend to experience slight increases in the pile loads. Practical implications of the findings are discussed. 相似文献
19.
求水山隧道下穿机荷高速段新奥法施工有限元计算 总被引：5，自引：0，他引：5
结合求水山隧道的暗挖法施工方案,对软土地区浅埋隧道下穿高速公路的施工过程进行了有限元模拟,以用于评价按该施工方案施工时对其上部高速公路的影响。由于该段隧道最小埋深仅4 m,且上部还有高速公路车辆荷载,因此,在设计时采用了新奥法结合管棚工法的方案。有限元建模使用平面应变单元,通过引入应力释放分析步和使用追踪单元等方法充分体现了新奥法的特点,并通过设置耦合和弹簧的方法实现了管棚工法的模拟,在计算中还考虑了开挖顺序和支护顺序的影响。研究结果表明：对于上部有荷载的浅埋暗挖隧道,控制衬砌的水平向变形能改善衬砌环的工作状态,因此,可显著减少开挖引起的隧道顶面沉降,新奥法结合管棚工法可较好地控制该类型隧道开挖引起的地表沉降变形。 相似文献
20.
富水软岩隧道突泥塌方及地层沉降的模型试验 总被引：1，自引：0，他引：1
在富水软岩地层中修建隧道容易出现突泥塌方,对施工及周边环境产生严重影响。北岗隧道围岩强度低且地下水丰富,在施工中多次遇到突泥涌水现象,出现了围岩大面积坍塌、地表开裂、地下水位下降等严重灾害问题。以北岗隧道为原型,开展了室内模型试验,再现了该隧道的破坏现象,研究了隧道突泥塌方的影响因素、破坏规律及影响范围。结果表明:（1）地表未出现裂缝时,隧道开挖导致的地表和地层内部变形可以采用Peck的正态分布曲线描述;（2）涌水是造成隧道围岩发生严重坍塌的根本原因;（3）隧道破坏从拱顶开始,呈拱形破坏型式;（4）地表的两条主裂缝在隧道塌方初期形成,塌方对地表沉降和裂缝的主要影响区域位于两条主裂缝之间。 相似文献