Precast tunnel segments with GFRP reinforcement

The possibility of substituting the traditional steel reinforcement with Glass Fiber Reinforced Polymer (GFRP) bars in precast segmental lining tunnels is investigated herein.The use of this kind of reinforcement in tunnel segments allows several advantages mainly related to durability aspects or when provisional lining is forecast. Furthermore, GFRP reinforcement can be used when dielectric joints are necessary.In the presented research, full-scale bending tests have been performed on precast segments in order to compare the structural performance of GFRP reinforced concrete with respect to traditional steel reinforced concrete. Furthermore, peculiar aspects of the design procedure for the proposed solution are remarked and discussed.     

环形预应力盾构管片摩阻损失测试与研究

基于某国内预应力工程,首次对原型预应力盾构管片结构环衬砌进行摩阻损失测试。采用夹片-P锚结合的环锚技术,对预应力管片环施加预应力,以满足其承受内水压和外荷载的要求,较准确地获得了环形预应力盾构管片摩阻损失。同时初步确定摩阻系数,并对试验数据进行处理和分析。结果表明,测试结果与设计理论值比较吻合,可以满足实际试验要求。     

Structural behaviour of precast tunnel segments in fiber reinforced concrete

An experimental research on the possibility of using fiber reinforced concrete precast tunnel segments instead of traditional reinforced concrete (RC) elements is presented herein. This solution allows removing the traditional reinforcement with several advantages in terms of quality and cost reduction.The case of precast elements used with a Tunnel Boring Machine (TBM) in the Brennero Base Tunnel has been considered.Full-scale tests on both traditional reinforced concrete and fiber reinforced elements have been performed. In particular, bending tests were carried out in order to compare the behaviour of the segments under flexural actions, while point load tests were developed with the aim of simulating the thrust force induced by the Tunnel Boring Machine, and then the effect of load concentration and splitting phenomena.The tests results showed that, in this peculiar application, the fiber reinforced concrete can substitute the traditional reinforcement; in particular the segment performance is improved by the fiber presence, mainly in terms of cracking opening control.     

盾构隧道预应力管片接头的模型试验研究

盾构隧道普通混凝土管片接头的抗弯刚度主要是通过现场试验确定,目前尚无现成的公式或者图表可遵循,对于预应力管片这一新型的结构型式则更有必要对其接头的正负转角刚度,为此进行了弯曲的预应力管片接头试验.文章介绍了模型试验的设计及试验过程,通过试验数据分析了影响预应力管片接头刚度的各项因素,如施加预应力的大小、偏心距等,并得出了计算其刚度的经验公式.     

预制混凝土衬砌管片常见质量问题与预防

管片作为地铁隧道的主要受力构件,其质量非常重要,是地铁隧道结构安全性、耐久性的主要保障。为了有效预防和规避管片的质量问题、提高管片质量,对预制混凝土管片在施工过程中常见的质量问题进行了分析,并提出了相应的解决方案和规避措施。     

Assessment the influence of ground stratification,tunnel and surface buildings specifications on shield tunnel lining loads (by FEM)

Urban development and rapid extension of cities have been accompanied by a considerable growth in mechanized shield tunnelling. Commonly precast concrete segments are used as tunnel lining which comprises relatively considerable part of tunnelling cost. The optimum design of lining needs to an accurate evaluation of loads acting on the lining.In this paper, the effects of ground stratification, surface buildings specifications and tunnel depth on lining loads were studied. For this purpose a 3D finite element model was used employing the ABAQUS software (Ver. 6.11). The geometry of tunnel, lining segments, injection grout and the surrounding soil properties were adopted from the under construction Tabriz urban railway line 2 project.The results show that the studied parameters have considerable effects on lining loads. For mentioned case study, surface buildings with 5 and more story have a considerable effect on lining loads, especially for shallow tunnels. The geometry of surface buildings influences the internal forces of the tunnel lining and increase of buildings width and length increases the lining loads. The building width is the most important parameter and with increase of that the influence of other parameters increases. Also by comparison of obtained results in this study with results of 2D analysis, reliability of 2D models was investigated. The comparisons show that 3D analysis is superior to 2D analysis, particularly in the cases of surface buildings presence. The difference between results increases with decrease of building length and increase of tunnel depth and building weight.     

负弯矩作用下钢筋混凝土U型叠合梁受力性能研究

针对一种由预制U型梁、预制板和现浇板组成的新型钢筋混凝土叠合梁,开展了负弯矩作用下钢筋混凝土U型叠合梁与现浇对比梁的足尺模型试验,对其破坏形态、截面承载力、位移延性和滑移等进行了较为系统的研究。研究表明:负弯矩作用下叠合梁和现浇梁均发生了受弯破坏;达到峰值荷载时叠合梁中预制板与现浇层之间、预制梁与预制板之间和预制梁与现浇层之间的最大滑移值均不大于0.5 mm;叠合梁的负弯矩截面抗弯承载力较现浇梁约低1%;叠合梁的位移延性系数为8.16,较现浇梁的位移延性系数高17%。本文研究成果可为这种新型钢筋混凝土U型叠合梁的工程应用提供技术依据和参考。     

The Channel Expressway: Twin-bored road tunnels under the English Channel

The proposal for a fixed link between France and England by means of a submarine tunnel under the English Channel has been examined in its various aspects of layout, tunnelling, ventilation, safety and operation criteria. The choice of the underground solution has been suggested by the low depth (40–60 m) of the Channel sea bottom between Calais and Dover, and by the presence, at an accesible depth, of a quite continuous geologic stratum of chalk marl with a low permeability and fair compressive strength. The submarine road tunnel is 48 km long and is constituted of two tunnels with an external diameter of 12.10 m. The excavation of the two main tunnels will be done with prototypical tunnel boring machines allotted to the various sections, for an average excavation rate of 25 m per day over a five-year period. The lining is made of precast concrete segments laid by two erectors from the machine itself. The suggested longitudinal ventilation system has short supplementary ventilation tunnels for air filtration, external and adjacent to the main two tunnels and of the same diameter. The ventilation is influenced and facilitated by the input of fresh air from two vertical shafts connected with islands on the open sea. Safety equipment is forseen for communication and information inside the tunnel as well as to guide transit in the dangerous zones. A new lighting system has been proposed.     

The inner lining system in Norwegian traffic tunnels

A number of different Water and Frost Protection Systems, or so-called inner linings, have during the years been introduced and tested in Norwegian road tunnels. At present a limited number of such systems have been approved by the Norwegian Public Roads Administration (NPRA). These systems will all be described in brief. A system based on pre-cast concrete segments will be described in details, including the installation procedure. Experience and limitations associated with this system will also be discussed. A basic design concept for using an inner lining as water and frost protection is that there is no interaction between the inner lining and the rock support. The rock support practise in Norwegian traffic tunnels will also be briefly described in this paper. Sprayed concrete and rock bolts are the main support measures. In-situ cast-in-place concrete lining is only used locally to solve severe stability problems.     

Design of FRC tunnel segments considering the ductility requirements of the Model Code 2010

Fibre reinforced concrete (FRC) is used to improve the mechanical response of precast segments for tunnels. The structural use of the material has been regulated by national codes and, recently, by the Model Code 2010 (MC 2010, hereinafter). In this regard, it is necessary to update the philosophy applied to the design of tunnel segments in compliance with the most recent guidelines, evaluating their applicability and repercussion. The objective of this paper is to present a critical analysis of the design of FRC segments according to the ductility requirements from the MC 2010; an alternative approach is proposed that is compatible with the condition found in some tunnels. The repercussions of both approaches are evaluated for the Metro Line 9 from Barcelona using results obtained in an experimental program with full-scale segments. The study suggests that the alternative approach may be applied under certain conditions, leading to a reduction in the fibre consumption.     

无黏结预应力环锚衬砌力学特性原位加载试验研究

新型无黏结环锚衬砌具备预应力损失低、薄弱区小、施工便捷等优势,但因结构复杂致使力学特性不明确,阻碍了其广泛应用。依托引松工程总干线压力隧洞,开展了首次预应力环锚衬砌大型原位加载试验,明确了内水压加载过程中衬砌预应力重分布特征,揭示了环锚拉力、钢筋应力以及锚固应力损失变化规律,并探讨了围岩和环锚衬砌联合承载作用。原位试验表明:环锚衬砌整体预应力分布均匀,高效地利用了锚索高强抗拉性和混凝土抗压性,常规钢筋作用极小,因而整体可不配筋或仅构造配筋;锚具槽背后混凝土预应力稍薄弱,是高内水压作用下结构潜在破坏区域,但内水加载过程中衬砌环向、纵向预应力值趋于一致,将有效减缓预应力薄弱部位开裂倾向;环锚衬砌具备优越的抗拉和抗渗性能,可不依赖于围岩条件而独立承载,也可利用围岩部分承载以降低预应力设计值或增加结构安全裕度,它能为覆盖层薄、地质条件差且内水压力高的大直径压力隧洞长期存在的支护难问题,提供解决新途径。     

Distribution of fibers in SFRC segments for tunnel linings

This paper presents research results regarding the distribution of steel fibers in concrete used to build precast tunnel segments for Line 9 of the Barcelona Metro. The fiber distribution was studied using the actual fiber contents obtained by means of crushed cores drilled from different points of three full-scale tunnel lining segments. A statistical analysis determined that the fiber content in the ends of segments tends to be greater than in the central zone. The way of transporting, pouring and compacting concrete influences the fiber content and the fiber distribution across the thickness of the segment. In addition, cores with a diameter of 150 mm were found to have a lower scatter in the fiber content than smaller diameter specimens. Finally, based on probabilistic approaches, a minimum of 11 cores is proposed to control the fiber content in FRC segments.     

Single-shell In-situ concrete tunnel lining: Experience in the Federal Republic of Germany

Although traffic tunnel construction in West Germany typically has used in-situ concrete as a double-shell lining, this method is both time-consuming and costly to apply. Recent research efforts have focused on the possibilities of single-shell in-situ concrete tunnel lining. This paper describes tests performed recently in West Germany on the use of (1) shotcrete and (2) steel-fibre-reinforced pumped concrete. The discussion deals with problems involved in these types of construction, the site and laboratory tests performed, and recommendations/prospects for application of these types of tunnel linings. The article also reports on two recent research projects, involving: (1) tunnel lining for large cross-sections with steel plate skin and unreinforced backfill concrete; and (2) construction and economic possibilities for creating tunnels in monocoque design.     

Dynamic response of lined circular tunnel to plane harmonic waves

Two dimensional harmonic response of lined circular tunnels in elastic full space medium against plane P–SV waves is investigated. The solution uses hybrid boundary, and finite element methods for modelling of media and lining, respectively. In the proposed ring element used in modelling of lining, the radial and tangential deformations are defined by Fourier series expansion. Therefore, the direct finite element unknowns of the problem are introduced as coefficients of these series. The non-dimensional shear and hoop stresses in the lining, and the same parameters in its interface with surrounding media are presented.     

Developments in immersed tunnelling in Holland

Holland has 22 immersed tunnels (14 road, 5 rail and 3 utilities tunnels). Another three are under construction, and more are foreseen. The tunnels are of the concrete type, i.e., constructed without a steel shell. The paper describes developments in technology and in design philosophy since the first immersed tunnel was completed 52 years ago. These developments include, amongst others: the introduction of the Gina rubber gasket between elements; the division of elements into sections divided by flexible joints; the application (if possible) of longer elements (up to 268 m); the use of precast sections for tunnels that have a small cross-section; the omission of the watertight lining (made possible by cooling the concrete of the walls during the first days after pouring); various foundation methods (e.g., sand flow instead of sand jet system; piled foundations when necessary); the use of the excavation for the open ramps (or the part of the tunnel built on land) as a casting basin for the elements; the changed approach to casting basins now that well pumping is usually forbidden; and the transport of the elements across shallow locations and across the sea. It is emphasized that the current state of immersed tunnel technology is the result of a continuous international exchange of ideas and experiences.     

全预制混凝土结构预应力施工监测研究

以上海旗忠网球中心全预制混凝土看台结构模型为对象,进行全预制混凝土结构预应力施工监测研究。对模型结构环向和径向预应力张拉全过程进行了监测及ANSYS有限元模拟分析。     

Tübbinge aus Stahlfaserbeton: Optimierung der Bewehrung durch experimentelle Untersuchungen

Steel Fibre Concrete for Precast Tunnel Segments The aim of these studies was to evaluate on precast tunnel segments the possibility of partially or totally replacing the usual steel reinforcing bars with steel fibres in a complex static system. In a first step, tests were carried out on connecting joints between precast segments and in a second step on whole tunnel segments coming from the precasting site of the Oenzberg tunnel (Swiss Railways, Berne–Zurich). They are 5.42 m long, have a width of 0.85 m and are 0.30 m thick. The segments were placed horizontally under a double hydraulic jack testing installation in the EIA‐FR structure laboratory. The double hydraulic jack introduced vertical forces while normal forces were produced by two metal pull‐rods simulating an arch‐effect. These experimental studies on connecting joints and on precast tunnel segments show good behaviour on the part of steel fibre reinforced concrete under such combined loads. This study highlights the major impact of compression forces in the bent section. Therefore, fibre reinforced concrete appears particularly well‐adapted for precast tunnel segments subjected to high compression loads. However, these studies also indicate the inadvisability of totally renouncing the use of conventional reinforcement in case of large tunnel segments.     

盾构隧道衬砌结构的壳-接头模型研究

提出了一种新型的盾构隧道衬砌结构计算模型——壳-接头模型。该模型中采用壳单元模拟衬砌管片,管片和管片环之间通过接头联接单元相连。基于对盾构隧道衬砌结构接头力学特性的分析,建立了接头联接单元的刚度矩阵和计算流程,定义了弯曲、剪切和拉压刚度的计算方法,使之能准确模拟接头的力学行为。最后利用壳-接头模型模拟盾构隧道接头原型试验,计算结果与试验较为吻合,验证了壳-接头模型模拟盾构隧道衬砌结构力学行为的准确性和适用性。     

浅谈静压预应力混凝土预制管桩施工

本文介绍了静压预应力混凝土预制管桩施工的工艺流程以及施工成品保护注意事项,为类似工程提供参考.     

30米跨预应力钢筋砼斜交T型梁预制施工技术

本文通过预应力钢筋砼斜交T型梁施工实例,详细介绍预制场地布置、钢模制作、砼浇筑、钢模拆模和张拉施工技术。