挤压地层双护盾TBM围岩变形及应力场特征研究

为研究挤压地层双护盾隧道掘进机（TBM）作用下围岩变形及应力场特征,采用FLAC3D建立了完整模型,并详细阐述了隧道掘进机（TBM）施工过程中的模拟方法,重点分析了隧洞纵横断面内围岩位移场、应力场、塑性区特征。模拟结果表明,两腰下部范围内的围岩与TBM护盾发生接触并产生挤压,拱顶并未接触;受刀盘与护盾连接处的尺寸高差和前后护盾的锥度影响导致仰拱围岩内出现3次加卸载,仰拱内部环向应力和径向应力均大于拱顶和两腰,而且其主应力方向与径向线斜交,受扰动剧烈,但仰拱下方70°范围内的围岩基本处于弹性状态;横向断面内围岩塑性区自上而下逐渐减小,且距掌子面越远塑性区范围越大,但后盾塑性区范围变化不大。     

The Interaction Between Shield,Ground and Tunnel Support in TBM Tunnelling Through Squeezing Ground

When planning a TBM drive in squeezing ground, the tunnelling engineer faces a complex problem involving a number of conflicting factors. In this respect, numerical analyses represent a helpful decision aid as they provide a quantitative assessment of the effects of key parameters. The present paper investigates the interaction between the shield, ground and tunnel support by means of computational analysis. Emphasis is placed on the boundary condition, which is applied to model the interface between the ground and the shield or tunnel support. The paper also discusses two cases, which illustrate different methodical approaches applied to the assessment of a TBM drive in squeezing ground. The first case history—the Uluabat Tunnel (Turkey)—mainly involves the investigation of TBM design measures aimed at reducing the risk of shield jamming. The second case history—the Faido Section of the Gotthard Base Tunnel (Switzerland)—deals with different types of tunnel support installed behind a gripper TBM.     

The Effect of Consolidation on TBM Shield Loading in Water-Bearing Squeezing Ground

When planning a TBM drive in squeezing ground, the tunnelling engineer faces a complex problem involving a number of conflicting factors. In this respect, numerical analyses represent a helpful decision aid as they provide a quantitative assessment of the effects of key parameters. The present paper investigates the interaction between the shield, ground and tunnel support by means of computational analysis. Emphasis is placed on the boundary condition, which is applied to model the interface between the ground and the shield or tunnel support. The paper also discusses two cases, which illustrate different methodical approaches applied to the assessment of a TBM drive in squeezing ground. The first case history—the Uluabat Tunnel (Turkey)—mainly involves the investigation of TBM design measures aimed at reducing the risk of shield jamming. The second case history—the Faido Section of the Gotthard Base Tunnel (Switzerland)—deals with different types of tunnel support installed behind a gripper TBM.     

富含生物成因气体地层盾构掘进克泥效的密封阻隔效应研究

富含生物成因气体地层盾构隧道施工风险高,气体极易通过开挖舱、泥浆管、盾尾间隙和管片节间渗入盾构和隧道内部,引发燃爆事故威胁施工安全。为了密封阻隔生物成因气体的泄漏通道,克泥效被用于填充中盾和洞壁之间的开挖间隙。本研究针对盾构掘进过程中生物成因气体的密封阻隔问题,提出了一种克泥效密封阻隔生物成因气体试验装置与方法,研究了克泥效注入厚度与气体击穿时间的相关关系,揭示了生物成因气体在克泥效中的渗透扩散机制,并依托苏通GIL综合管廊工程验证了克泥效密封阻隔生物成因气体的作用效果。研究结果表明:气体击穿时间随克泥效注入厚度的增加近似线性增长;当克泥效注入厚度为30 mm时,平均击穿时间为51.5 min,超过单环管片拼装所需最长时间50 min,满足苏通GIL综合管廊工程施工需求。现场气体监测结果表明,相较于注入克泥效填充开挖间隙之前,注入克泥效后CH₄和CO浓度均在允许范围内,克泥效有效阻隔了生物成因气体进入盾构隧道内部。相关研究结果可为类似工程地质条件下生物成因气体防治提供理论依据和技术支撑。     

位移释放率对双护盾TBM护盾压力的影响研究

为了研究隧洞纵向位移（LDP）释放率对双护盾隧洞掘进机（TBM）围岩变形及护盾压力的影响,在FLAC3D中采用应力释放法对LDP曲线实现了较好的控制,并指出采用计算时间步控制的缺陷,在考虑护盾与围岩之间不均匀间隙情况下,详细分析了应力释放率对TBM掘进中围岩LDP曲线变化规律、护盾所受挤压力及围岩塑性区的影响。得出了以下结论：（1）不同岩体力学参数下,LDP曲线受应力释放率的敏感程度不同;（2）随着应力释放率的逐渐增加,围岩LDP曲线特征及与TBM护盾相互接触的部位有所不同,TBM护盾接触挤压力和所受摩擦阻力逐渐增大;（3）护盾外围塑性区的形状与应力释放率和护盾与围岩之间的不均匀间隙有关,当在较大的应力释放率下,塑性区呈现自上而下逐渐减小的特征。     

Ground disturbance caused by shield tunnelling in a stiff, overconsolidated clay

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.     

A Completely 3D Model for the Simulation of Mechanized Tunnel Excavation

For long deep tunnels as currently under construction through the Alps, mechanized excavation using tunnel boring machines (TBMs) contributes significantly to savings in construction time and costs. Questions are, however, posed due to the severe ground conditions which are in cases anticipated or encountered along the main tunnel alignment. A major geological hazard is the squeezing of weak rocks, but also brittle failure can represent a significant problem. For the design of mechanized tunnelling in such conditions, the complex interaction between the rock mass, the tunnel machine, its system components, and the tunnel support need to be analysed in detail and this can be carried out by three-dimensional (3D) models including all these components. However, the state-of-the-art shows that very few fully 3D models for mechanical deep tunnel excavation in rock have been developed so far. A completely three-dimensional simulator of mechanised tunnel excavation is presented in this paper. The TBM of reference is a technologically advanced double shield TBM designed to cope with both conditions. Design analyses with reference to spalling hazard along the Brenner and squeezing along the Lyon–Turin Base Tunnel are discussed.     

A case history of Tunnel Boring Machine jamming in an inter-layer shear zone at the Yellow River Diversion Project in China

This is a case study of a Tunnel Boring Machine (TBM) jamming in a section of the Connection Works No. 7 tunnel of the Yellow River Diversion Project (YRDP) in China. Analysis of tunnel lithology, rock convergence by shearing, rock strength and ground stress, indicates that a high rate of convergence within an inter-layer shear zone in the lower part of an anticline was a dominant factor in the jamming. In addition, the shield encountered unfavorable tunnelling conditions in the form of wet clay, groundwater inflow, and cavities, coincident with tensile stresses in the lower part of an adjacent syncline. Based on these diagnoses, economical and quick measures were adopted, including additional excavation outside of the shield leaving free space to release the TBM. After 9 days of being jammed, the TBM was totally released and resumed normal excavation. This example highlights lessons learned from folding and inter-layer shear zone in TBM tunnelling.     

Comparison of Squeezing Prediction Methods: A Case Study on Nowsoud Tunnel

According to the International Society of Rock Mechanics, squeezing is a time dependent large deformation occurring during tunnel construction around the tunnel associated with creep caused by exceeding a limiting shear stress (Barla in ISRM News J 2:44–49, 1995). This research is conducted using a case study on the Nowsoud Tunnel, Iran. Being 14 km in length and 4.5 m in diameter, the tunnel is located in the western part of Iran near the Iraq border. Nowsoud tunnel, which was excavated using a double shield TBM, exhibited severe squeezing (with 8919 m) in its critical zone which resulted in excavation termination. In this research, the best approach for predicting squeezing among the recommended methods for reducing the damages caused by squeezing on TBM was determined. In this regard, approaches commonly used to predict squeezing are empirical, semi-empirical, and theoretical–analytical methods. Besides, these methods, numerical modeling is used to estimate convergence generated along the tunnel pathways, which is ultimately used to categorize squeezing. This paper compares squeezing prediction methods in 68 section of Nowsoud Tunnel. These 68 sections indicate that the empirical methods propose a general estimation/overview of squeezing. Among the semi-analytical approaches, the one proposed by Hoek and Marinos (Rock engineering in difficult rock conditions—soft rocks and karst, Taylor & Francis Group, London, pp 49–60, 2000) are compatible with the occurrence of squeezing in the critical zone. However, the degree of predicted squeezing is less than the real degree of squeezing in this zone. Based on the result of Aydan approach, 75 % of the tunnel sections are under squeezing condition. Theoretical–analytical approaches underestimate the possibility of squeezing in the critical zone. Barla?s approach (1995) demonstrated the possibility of squeezing in the critical zone with low intensity. The numerical computations in this paper were performed using Plaxis (version 8.5), a two-dimensional numerical program based on the finite element method. Plaxis results, classified by Hoek and Marinos (2000) method, show that 8800 m of the tunnel length is under the non-squeezing condition. According to all prediction methods, the squeezing zones depend on faulted zones, argillaceous limestone and shale formations such as J₁Kh, J₄Kh, J₅Kh, and Kgr. These formations were identified with a high quantity of shale and argillaceous limestone. Bedding of these geological formations is thin and their geotechnical properties are weaker than those of limestone formations. On the other hand, non-squeezing zones depend on limestone formations such as J₂Kh, J₃Kh, J₆Kh, K^abg, and Kbg. Moreover, all approaches predicted squeezing potential for the critical zone where TBM is jammed.     

盾构法施工过程的有限元模拟

在综合考虑了现有的有限元模拟方法的基础上,对部分仿真模拟细节进行了改进,改进了水平荷载的施加方法,用"等代层"来模拟盾尾建筑空隙,用预设单元的刚度迁移来模拟盾构的推进过程。通过对某地铁隧道盾构施工过程的模拟,分析了盾构推进过程中地表土体的位移与变形,计算得到的隧道横断面和隧道纵向地面沉降分布曲线与实测数据比较接近,结果证明了模拟方法是可行的。     

开敞式TBM过类泥石流不良地质洞段施工处理技术

开敞式TBM在掘进过程中,往往会遇到断层破碎带,目前业界已经有相应的处理方式,但是在遇到类泥石流洞段时,单独依靠目前TBM自身条件及已有的处理方式很难实现顺利通过,需要采取特殊的施工处理措施相互配合才能通过。本文依托吉林引松供水项目三标段类泥石流不良地质洞段的处理,形成了一套完整的开敞式TBM过类泥石流不良地质洞段施工处理技术,即在碎块石夹杂断层泥段采用超前管棚支护,在类泥石流不良地质洞段采用堵水灌浆加固技术并配以喷锚喷网 钢拱 模筑混凝土的联合支护技术。工程实践验证了该技术的可行性。     

Analysis of Unit Supporting Time and Support Installation Time for Open TBMs

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.     

Advance numerical simulation of tunneling by using a double shield TBM

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.     

粉质黏土地层超大直径泥水盾构隧道地表变形与施工参数相关关系研究

本文以粉质黏土地层超大直径泥水盾构隧道为工程背景,分析了地表变形特征随盾构掘进参数的变化规律。并针对粉质黏土地层隧道施工监测数据进行分析,提出了超大直径泥水盾构下穿建构筑物的施工关键控制参数。研究结果表明:不同施工参数对地表变形的影响存在显著差异,注浆量相对最大,刀盘扭矩和贯入度相对次之,刀盘推力、泥水压力、注浆压力和掘进速度相对最小。注浆量对地表变形的影响随隧道埋深的变化而变化,当隧道埋深小于一倍洞径时,注浆量对地表变形影响相对较大;当隧道埋深大于一倍洞径时,注浆量对地表变形影响相对较小。刀盘推力与泥水压力、注浆压力以及水土压力之间存在较好的相关关系。当泥水压力比水土压力约大0.1 MPa,注浆压力比水土压力约大0.3MPa时,盾构下穿建构筑物造成的地表变形相对较小,盾构地质适应性得以显著优化。相关研究成果可为后续粉质黏土地层超大直径盾构隧道地表变形分析和施工参数优化等提供理论依据和技术支撑。     

双护盾TBM施工隧洞综合超前地质预报方法研究

由于受护盾、管片及电磁干扰的影响,地质素描、炸药激振地震法、电磁法等超前地质预报方法在双护盾TBM施工中无法使用。根据双护盾TBM技术特点,以CCS水电站引水隧洞为工程背景,提出了以地质分析法、物探法、和超前钻探等为主的综合超前地质预报方法。综合超前地质预报采用"由粗到细、点面结合"的原则。地质分析法包括隧洞沿线地质分析、施工地质观察、岩渣及掘进参数分析等,不占用TBM掘进时间,成本低,可全洞段采用。物探法包括ISIS地震法和BEAM电法。物探法和超前钻探占用TBM掘进时间,且预报成本较高。因此,应根据预报精度、预报成本及是否占用掘进时间综合权衡后,确定采用何种预报方法。基于综合超前地质预报结果,针对不良地质条件,提出了相应的处理措施。研究结果表明,综合超前地质方法符合双护盾TBM施工特点,能有效识别掌子面前方的不良地质条件,同时可为工程应对措施提供基础支撑,从而有效避免或降低不良地质条件的影响。     

万家寨引黄工程泥灰岩段隧洞岩石掘进机(TBM)卡机事故工程地质分析和事故处理

隧道全断面岩石掘进机 (TBM )的施工对地质条件适应性是一个不断认识和深化的过程 ,其中很多认识是来自已发生的各种各样事故和对事故原因的理性认识。本文是在对某隧洞TBM卡机地段的岩性 (包括工程性质 )、构造、地应力及其在TBM施工条件下的变化等方面进行工程地质力学研究的基础上 ,指出层间剪切带的存在及由此而产生的较大变形速率是导致事故发生的工程地质原因 ,并提出了相应的处理意见和建议。TBM卡机问题的顺利解决和它重新开始快速掘进证明了作者分析和工程处理措施的合理性。本文的分析有助于加深TBM施工对复杂地质条件适应性的认识 ,并可望为避免类似事故的再次发生提供参考和借鉴。     

A case study on the behavior of shield tunneling in sandy cobble ground

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.     

A discrete numerical approach for modeling face stability in slurry shield tunnelling in soft soils

In this paper, a numerical simulation method for evaluating tunnelling-induced ground movement is presented. The method involves discrete element simulation of TBM slurry shield advancement and considers explicitly soil excavation from the face, effects of varying face support pressure, and the influence of tunnel cover depth. For the cases studied, it is found that for tunnel cover depths (C/D) between 0.7 and 2.1, ground deformations inducing by the tunnelling can be controlled within a certain extent and tunnel face stability can ensured, provided the support pressure ratio (N) lies between 0.8 and 1.5. The proposed method is reasonably benefited to modeling the face stability in shield-driven tunnels in soft soils.     

盾构隧道施工引起地表下土体变位的分析评估

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。     

砂土地层中不同支护模式下盾构隧道开挖面稳定性研究

防止盾构隧道开挖面失稳的关键是合理设置不同盾构支护平衡模式下的支护压应力。在改进的筒仓楔形体模型计算方法得出的开挖面松动土体对刀盘压力呈近似呈抛物线分布的基础上,研究了气压支护模式、泥水支护模式和土压支护模式下,盾构隧道开挖面分别在地下水位以上和地下水位以下时开挖面的稳定性,研究结果表明:有效支护应力均匀分布时,除粘土开挖面下部失稳外,其余土体均为开挖面中下部失稳;有效支护压应力呈上小下大的梯形分布时,除软粘土开挖面下部失稳外,其余土体均为开挖面上部失稳;有效支护应力呈上大下小的梯形分布时,所有土体开挖面均为下部失稳;在气压、泥水和土压平衡支护模式下,开挖面在未到达筒仓楔形体模型所假设的开挖面整体失稳前,开挖面已经发生了局部失稳,采用筒仓楔形体模型确定的极限稳定支护力是不安全的。最后给出了开挖面松动土体对刀盘压应力公式中计算参数的无量纲化图,以方便实际工程运用。