An experience of tunnelling in mudstone area in southwestern Taiwan

Many tunnels will be constructed in southwestern Taiwan in the upcoming decade to meet the huge demands of transportation, energy and water infrastructure projects. Mudstone strata cover more than a 1000 km² area, consisting mainly of massive mudstone or alternation of mudstone and sandy layer, exhibiting unfavorable geological and hydrological characteristics, making it extremely difficult for tunnelling. This paper presents the lessons learned from three tunnelling projects in the 1990s in a mudstone area. In addition to discussing the rock behavior in the vicinity of tunnel and its failure patterns, the monitoring data during tunnelling are presented as well. Finally, the effective method of design and construction are recommended for tunnelling in mudstone area.     

Construction of underground works in Shanghai, P.R.C.

For nearly thirty years, Shanghai has been constructing underground works designed to improve the city's infrastructure. A number of projects were undertaken using shield tunnelling method in order to determine whether this method could be used successfully in Shanghai's geology, which is characterized by silt and silty or puddly clay. These underground projects have included subway tunnels, sewage and water supply tunnels, road tunnels, and offshore discharge tunnels. This paper describes eight subsurface projects in Shanghai that have used the shield tunnelling method successfully.     

Landtunnel Utrecht at Leidsche Rijn: The conceptualisation of the Dutch multifunctional tunnel

The Landtunnel Utrecht at Leidsche Rijn has become a milestone in Dutch tunnelling because it signifies a remarkable leap forwards in the conceptualisation, awareness and insight into the use of underground space technology and tunnelling for environmental purposes. At the beginning of the 21st century, all motorway tunnels in the Netherlands (with the exception of the Schiphol road tunnel) were subsurface constructions that were built to pass waterways. The Landtunnel Utrecht at Leidsche Rijn is the first aboveground motorway tunnel built to minimise the environmental impact of the road, and it allows development of the largest residential area in the Netherlands: Leidsche Rijn, Utrecht. Implementing the project highlights the difficulties decision makers face when they have to balance safety issues, high costs, multiple environmental issues, complex financing and urban development objectives. With no effective regulation in place and no similar practice to fall back on, the Landtunnel Utrecht (together with Sijtwende and the Green Link A15) breaks ground to allow the use of motorway tunnels for a new and promising application: environmental and spatial integration of motorways in urban areas.     

EPBMs for the North East line project

Fifteen years ago construction started on phase one of the Mass Rapid Transit tunnels in Singapore. Since that time tunnelling technology has advanced considerably. Earth Pressure Balance Machines (EPBMs) are far more commonly used than ever before on tunnelling projects in the Far East, Asia and Europe. For the first time in Singapore full-face tunnelling is being carried out in the Old Alluvium for the construction of North East Line Project (NELP). The TBMs selected for the NELP are, in the main, EPBMs. This paper compares the types of EPBMs chosen for each Contract, highlighting the particular design features of each. The paper also provides an update on the progress of the EPBM tunnelling operations currently being undertaken on the NELP.     

Developments and quality safeguards in immersed tunnel technique

Over the past decade, quality assurance has become increasingly important in immersed tube tunnelling. A guarantee of meeting quality standards has become paramount in obtaining financing for high-risk tunnelling projects. To assist in designing such works to guarantee durability and watertightness, the Dutch Ministry of Public Works has begun a project to inspect thoroughly and record information about various civil engineering projects, including immersed tunnels. A computerized program will describe problems with quality, define repair needs and link this information to repair and maintenance costs. This paper discusses ways to control the concrete-hardening process (a major concern in assuring quality in tunnels) through computer-assisted engineering programs in order to obtain a high-quality product. Advantages of computer-aided design systems are addressed, as are future needs with regard to solving problems associated with tunnel leakage.     

New developments in TBM tunnelling for changing grounds

Mechanized tunnelling has seen substantial growth in the recent years in the construction industry for small to large scale infrastructure works. This development is due to a growing number of large-scale projects that were successfully realized with certainty and reliability in construction, compliance with construction schedules and thus supported the economic success of the projects. Tunnel projects are planned and implemented today in changing grounds that could not be realized without the newest technological progress and innovations in mechanized tunnelling. Today’s demand in tunnelling is to construct tunnels with high safety standards especially in urban areas with sensitive geological and hydrogeological conditions. In the context of this publication, new developments in TBM tunnelling related to changing ground conditions are highlighted. References of major infrastructure projects will be addressed that illustrate also the effect and importance of mechanized tunnelling technology used today to complete infrastructure projects on time and with high quality and technical standards.     

Tunnelling projects in Southern Africa

Until some thirty years ago tunnelling in southern Africa for civil engineering purposes had been on a relatively small scale and of a sporadic nature. The first major tunnel to be built in the region was the 82 km long Orange-Fish Tunnel. Since 1970 more than 175 tunnels with an aggregate length of just over 400 km have been built. Much of the first phase of the Lesotho Highlands Water Project, which will have more than 100 km of tunnels, is about to be completed. The last thirty years represent the busiest period of tunnelling by civil engineers that southern Africa has ever known. The paper starts by summarising the early history of tunnelling in the region, and goes onto describe recent and current tunnelling projects. It also gives an indication of the possible demand for tunnels in the future.     

Immersed tube tunnelling offshore: Execution of immersed tube tunnelling projects under offshore conditions, based on studies for the euroroute fixed channel link proposal

The development of the international road and railroad network has suffered from the worldwide stagnation in economy over the past years. Nevertheless, leading economists consider new, large international infrastracture projects to be a necessity for an upturn in the economy. Among these projects are a number of connections over or under sea straits, such as Gibraltar and the English Channel. With the completion of the Seikan Tunnel, Japan has already executed such a project. The study for Euroroute's fixed Channel link proposal indicated that an immersed tube tunnel is a realistic and, often, favorable solution. Thanks to the development of immersed tube tunnelling technology, the development of the offshore industry, and work on recent large projects (such as the Dutch Eastern Scheldt Storm Surge Barrier), tunnelling techniques have improved considerably. This article provides a brief comparison between bored and immersed tunnelling solutions. The article mainly focuses on hydraulic problems, dredging and immersing the tubes. The following questions are considered: What circumstances and conditions influence the applicable methods such as surveying, dredging, immersing and related equipment? What considerations must be taken into account on immersed tube tunnelling projects?     

Recent large-diameter tunnel construction in Singapore using sprayed concrete linnings

Sprayed Concrete Lining (SCL) or the New Austrian Tunnelling Method (NATM) has had limited exposure in Singapore. Previously this has been restricted to excavations of less than 6 metres inside diameter in the boulder clay and decomposed granite. For the North East Line Project (NELP) a section of SCL tunnel was constructed as part of the tunnelling works on Contract 710. This paper describes the design, planning, and construction issues of twin 8.4-metre inside diameter crossover tunnels spaced less than one diameter apart constructed in the Jurong Formation. In addition, the construction of a SCL tunnel in the Old Alluvium, is also described. This tunnel is an advance tunnel for the future Deep Tunnel Sewage Scheme (DTSS) and is being constructed as part of the NELP Contract 705 Works. Details of the Jurong Formation and Old Alluvium are given together with their geotechnical characteristics, which played a major role in the selection of temporary support methods used and the behaviour of the ground during tunnelling. The planning and design issues concentrate on aspects to ensure overall integrity and stability of both SCL projects. The success of various construction techniques utilised to construct the tunnels safely is discussed and a summary of the ground movements is presented.     

近距离多线叠交盾构施工对既有隧道变形的影响研究

针对上海地铁新建11号线先下后上近距离穿越既有4号线,形成三层隧道四线叠交的特殊工况,采用有限元数值模拟和现场监测相结合的方法,考虑既有隧道周围土压力的分布规律,研究了盾构下穿施工时土仓压力和注浆压力以及上穿施工时压重范围和压重量对既有隧道变形的影响。研究结果表明：下穿施工结束时,既有隧道的沉降量不随土仓压力比的改变而改变,但随注浆压力比的减小而增大;上穿施工应采取压重措施预防既有隧道的上浮和局部隆起变形,宜遵循新建隧道同步压重为主,既有隧道压重为辅的原则。     

Effects of above-crossing tunnelling on the existing shield tunnels

Tunnelling in the dense urban areas frequently results in over-crossing or bypassing the existing tunnels. It is obvious that the over-crossing tunnelling will adversely affect and even damage the existing tunnels if the induced deformation exceeds the capacity of tunnel structures. Increasing concerns have been raised about the interactions between the over-crossing tunnelling and underlying tunnels. In order to obtain a better mechanical understanding of the effects of the over-crossing tunnelling on the existing tunnels and provide a quick but low cost assessment alternative method for evaluating the behavior of underlying tunnels prior to construction, a simplified analytical method is proposed in this study. In this simplified method, the tunnel is simply considered as a continuous Euler-Bernoulli beam with a certain equivalent bending stiffness. The unloading stress at the tunnel location caused by the over-crossing tunnelling is computed through Mindlin’s solution, ignoring the presence of the existing tunnel. Then, the tunnel-soil interaction due to the relief stress is analyzed based on the commonly-accepted Winkler foundation model. The applicability of the presented method is validated by three well-documented case histories. Results of these case studies show a reasonable agreement between the predictions and observations. Finally, a parametric analysis is also preformed to investigate the influences of the different factors on the behavior of the existing tunnels, including clearance distance, advancing distance and multiple tunnels construction.     

Application of precedent type analysis (PTA) in the construction of Ertan hydro-electric station, China

Precedent type analysis (PTA) emerged in China in the 1980s. It is a principle and method used for rapid analysis and prediction of rock stability in tunnelling projects. In this paper, PTA is formally defined and emphasis is placed on the application of PTA to the assessment of designs for diversion tunnels at the Ertan hydro-electric station. It compares PTA with the conventional analysis of rock mechanics; it also contrasts their applications and conclusions.     

城市隧道下穿工程中的安全风险管理

阐述了城市隧道下穿工程中环境风险、变形风险的控制要点,结合工程实践,对风险管理中风险预评估、风险监控、过程控制指标的制订、风险的预控制和控制过程、应急预案五个要素进行了总结,从而完善城市隧道风险管理体系。     

Rock mechanics for design of Brisbane tunnels and implications of recent thinking in relation to rock mass strength

This paper explores the potential implications of recent thinking in relation to rock mass strength for future tunnelling projects in Brisbane, Australia, particularly as they are constructed within deep horizons where the in situ stress magnitudes is larger. Rock mass failure mechanisms for the current tunnels in Brisbane are generally discontinuity controlled and the potential for stress-induced failure is relatively rare. For the road tunnels which have been constructed in Brisbane over the last 12 years, the strength of the more massive rock masses for continuum analysis has been estimated by the application of the Hoek-Brown (H-B) failure criterion using the geological strength index (GSI) to determine the H-B parameters m_b, s and a. Over the last few years, alternative approaches to estimating rock mass strength for ‘massive to moderately jointed hard rock masses’ have been proposed by others, which are built on the work completed by E. Hoek and E.T. Brown in this area over their joint careers. This paper explores one of these alternative approaches to estimating rock mass strength for one of the geological units (the Brisbane Tuff), which is often encountered in tunnelling projects in Brisbane. The potential implications of these strength forecasts for future tunnelling projects are discussed along with the additional work which will need to be undertaken to confirm the applicability of such alternative strength criteria for this rock mass.     

Interesting solutions for the construction of tunnels under waterways in Germany

The soil in the Tertiary and Quarternary formations characterize the constructions methods for underwater tunnels in the Federal Republic of Germany. The floating method and the method of lowering precast tunnel sections have been used for tunnelling below waterways for large ships. The floating sections were up to 140 m long and had a displacement of approx. 46 000 m³. A number of construction methods were available for various construction projects for tunnelling below rivers and inland water canals. Several examples are given.     

A quantitative evaluation of the sustainability or unsustainability of three tunnelling projects

There is a perception that tunnelling is sustainable. This is because it occurs underground, and consequently does not significantly interfere with surface or atmospheric processes unlike other anthropogenic activities. However, the tools and assessments used in tunnelling projects to evaluate sustainability in the construction and operational phases are primarily concerned with the reduction of carbon footprint and environmental performance. This does not provide a suitable approach to determining the sustainability of a tunnelling project directly. Environmental Impact Assessment (EIA) on the other hand does have this potential. However, it requires two things: (1) a suitable quantitative-based method of EIA; and most critically and (2) a means to evaluate sustainability from the EIA results. Based upon the recent work of Namin et al. (2014) concerning a new EIA methodology for tunnelling projects, this paper applies an established mathematical model of sustainability to the results of the EIA to determine the sustainability or unsustainability of tunnelling projects. The model’s application, in the form of an algorithm, evaluates three case studies assessed by Namin et al. (2014). The results are analysed and discussed in respect to the three projects’ construction and operation phases. The broader context of the results is then discussed in respect to the use of underground space as a means to achieve sustainability.     

Future trends in the structural design of tunnels

A design in engineering is based on conceptual models of outer actions (loads), stress-strain behaviour, failure criteria; it tries to predict these phenomena within the projected lifetime of the structure. For underground structures, the design must take into account the actions and reactions of the ground caused by tunnelling; the strength properties of ground and structural supports; and possible failure modes during and after excavation. What are the trends foreseeable at present towards future developments of those items entering into the structural design of tunnels? This paper tries to project developments, e.g. in the fields of extracting ground parameters, computer-aided excavation and computer-aided evaluation of monitoring, defining numerical analysis, etc. A summary lists the most promising fields of work for further developments in the structural design of tunnels and caverns.     

Applications of immersion technologies in underwater construction

The following aspects of immersed tube tunnelling are discussed: (1) geological, hydraulic and meteorological surveying; (2) hydraulic laboratory testing; (3) consideration for immersion of tunnel units; (4) joints; and (5) foundation considerations. These techniques are discussed in relation to their application to the following types of projects: inland road or rail tunnels in sheltered areas; offshore tunnels in areas exposed to wind and waves; and tunnels built in coastal areas affected by surf. The author also describes the Submersible Tunnel Element Position System (STEPS), originally developed for a proposal for the English Channel tunnel, and its possible applications for other tunnel projects.     

Status of tunnelling and underground construction activities and technologies in India

A considerable amount of tunnelling work has been going on in India for hydroelectric, irrigation, roads and railways projects. Most of these projects are located away from urban areas. The use of tunnelling for urban utilities, such as water supply, sewerage disposal and metro rail has recently begun. A few projects have been completed and some are under construction in metropolises such as Mumbai, Calcutta and Delhi. The present status of tunnelling and its future potential in India is highlighted in the paper with emphasis on tunnelling projects for hydro-power developments, as this sector presently has maximum underground construction activity in India. The tunnelling technologies for planning, design and construction have also been presented in this paper.     

Bored tunnels under deep waterways: What lies ahead?

This paper deals with future subaqueous tunnels: first, by describing briefly some of the bored tunnelling opportunities that are being considered at the present; and then by suggesting ways in which technology may need to be developed in order to carry out these projects. The paper also considers the financial implications of such research and development.