4.5 Monitoring and evidence-gathering measures for tunnelling beneath buildings and transport infrastructure

9.3 Design and geotechnical requirements for the tendering of mechanised tunnelling as an alternative proposal

Prof. Dr.-Ing. Bernhard Maidl

mtc – Maidl Tunnelconsultants GmbH & Co. KG

Fuldastr. 11

47051 Duisburg

Germany

Dr.-Ing. Ulrich Maidl

mtc – Maidl Tunnelconsultants GmbH & Co. KG

Rupprechtstr. 25

80636 München

Germany

Prof. Dr.-Ing. Markus Thewes

Lehrstuhl für Tunnelbau, Leitungsbau und Baubetrieb

Ruhr Universität Bochum

Universitätsstr. 150

44801 Bochum

Germany

Translated by David Sturge, Kirchbach, Germany
Cover: Mounting of a TBM for innercity tunnelling, photo: Herrenknecht AG, George Tjepkema

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Print ISBN: 978-3-433-03049-3

ePDF ISBN: 978-3-433-60354-3

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Dedicated to My Grandchildren

Maximilian

Leon

Antonia

Frederik

The authors

o. Professor em. Dr.-Ing. Dr. h.c. mult. Bernhard Maidl

Former holder of the Chair of Construction Technology, Tunnelling and Construction Management at the Institute for Structural Engineering of the Ruhr University, Bochum

Univ. Professor Dr. Ing. Markus Thewes

Holder of the Chair of Tunnelling and Construction Management, Ruhr University Bochum

Dr.‑Ing. Ulrich Maidl

Managing Director of Maidl Tunnelconsultants GmbH & Co. KG

With the collaboration of:

Dipl.-Ing. Michael Griese (overall coordination), Maidl Tunnelconsultants GmbH & Co. KG

Dipl.-Ing. Stefan Hintz, Maidl Tunnelconsultans GmbH & Co. KG

Foreword to the English edition

The “black book of tunnelling” has become a standard work in German-speaking countries since its first German edition in 1984. It can be found on every tunnel site and in every design office – whether contractor or consultant. Students at universities and technical colleges use it as a textbook.

For many years, colleagues from abroad have been asking me for an English edition. Now the time has come to publish the two-volume book in English. An important step was that the publisher of the first German edition, VGE, gave their permission for the publishing of the English edition by Ernst & Sohn, Berlin. Special thanks are due to Dr. Richter from Ernst & Sohn for his successful negotiations. However, preparation of the text for the translation showed that the 3rd German edition required updating and extending. In particular, the standards and recommendations have been revised. This will all be included in a 4th German edition, which will be published soon. Changes to the standards and recommendations are given in this edition, with the references stating the latest version.

As with all books, the English edition has also required the collaboration of colleagues. Professor Dr.-Ing. Markus Thewes, who has succeeded me as the holder of my former university chair, and my son Dr.-Ing. Ulrich Maidl, managing director of the consultant MTC, have joined me in the team of authors. Dipl.-Ing. Michael Griese from MTC is the overall coordinator, assisted by Dipl.-Ing. Stefan Hintz from MTC. I thank all those involved, also the translator David Sturge and the employees of the publisher Ernst & Sohn in Berlin.

Bochum, in September 2013

Bernhard Maidl

Writing without violence is impossible.
I constantly put myself under pressure.
Violence is perhaps not the right word.
Daniel Boulanger

Foreword to the 3^rd German edition

The above quotation introduced the complete revision of the second volume for the 3rd German edition. This became necessary after 15 years because not only the tunnelling technology in the first volume has developed enormously but also the standards and regulations have been revised or harmonised in the European Union. Under these premises, all chapters have been reworked and extended, partly based on my other books like shotcrete, steel fibre shotcrete, shield and TBM tunnelling as well as more recent publications.

The chapter “Dewatering during the Construction Phase” has been extended and is now called “Dewatering, Waterproofing and Drainage” in the second volume; this includes detailed information about hardness stabilisers.

As already in Volume 1, my employees have supported me in every way, although I have also received external help. For example, Dr. Heimbecher revised the section about road tunnels in Chapter 1 and Mr Chromy contributed to the section about the EU machinery directive in Chapter 8.

I wish to thank them all, and also the collaborators on my former books, which we have referred to for the revision work. Great thanks are also due to the many helpers from the consultancy Maidl + Maidl and for the contributions of several machine manufacturers and the publishers Glückauf.

Bochum, in January 2004

Bernhard Maidl

Foreword to the 2^nd German edition

The good sales of the “Handbook of Tunnel Engineering” have also accelerated the publication of the second volume. Numerous ongoing and future large tunnel projects lead to a great demand for relevant literature. Reference books about design, tendering and construction are of great importance today, whether for instruction at universities, for practical application in consultancies and on construction sites, but also for the individual engineer interested in gaining further knowledge. So I am personally very satisfied to find the “Handbook of Tunnel Engineering” in use in design offices, on site, and also repeated in the text of university lectures.

On the threshold to the next century, with tunnels becoming ever longer and being constructed under ever more challenging conditions, construction methods are also demanded to comply with ecological, environmental and economic requirements. The necessary development potential covers all construction methods, both in conventional and mechanised tunnelling. The initial requirements, specifically the description of the geology and hydrology with the associated structural verifications and measurements, the environmental requirements, and also the special features of scheduling and cost planning with the associated contractual provisions, are likewise significant factors. This book covers all these subjects.

A complete revision for a new edition would naturally represent the latest state of information, but this is not achievable in the available time. The reader must therefore be asked to consider this when one or other innovation has not yet been included.

I wish to thank the publisher for their processing.

Bochum, in October 1995

Bernhard Maidl

Research and Technology demand ever
more Interdisciplinary Knowledge. It
is almost a characteristic of our Time
that scientific and technical Progress is
increasingly taking place at the Interfaces
of traditional Professions.

Karlheinz Kaske, 1987

Foreword to the 1^st German edition

Four years after the publication of the first volume, work on the second volume is at last complete. This Volume II devotes its first chapters to the fundamentals of design, aspects of engineering geology, structural verifications and instrumentation for monitoring with the intention of providing a clear classification of the known theoretical and practical methods. The composition of the chapter “Structural design verifications, structural analysis of tunnels” proved demanding despite the intensive assistance of Herr Dipl.-Ing. Jens-Detlev Wolter. Although tunnels are engineering structures, their structural analysis and calculation cannot be undertaken like structures above ground. Their load-bearing behaviour is decisively influenced by the construction method, also including for the tunnel engineer the time factor as construction progresses. This factor is at least as significant as the effect of the rock mass around the tunnel considered as a “construction material”.

The construction method is emphasised in the second volume just as in the first. Construction process technology in tunnelling is a prime example of interdisciplinary research: only an engineer who can master the technical basics of all influential factors can work competently. I could not and did not want to offer a qualitative or even quantitative evaluation of calculation procedures. Experienced structural engineers will form their own opinion. However, construction experience and calculation examples from recent rail, road and underground railway tunnels have been included.

This Volume II also deals with auxiliary works such as dewatering, measurement and control technology and scheduling. The control technology for tunnel boring machines is developing rapidly, particularly for shield machines in different soil types.

Similarly to Volume I, Volume II also includes extensive tables and illustrations in order to represent the idea of a handbook. The examples are taken from numerous newer construction projects.

In the production of this Volume II, I have relied heavily on the assistance of my colleagues at the Institute for Tunnelling and Construction Management. I thank Dipl.-Ing. Jens-Detlev Wolter, Dr.-Ing. Dieter Handke, Dipl.-Geophys. Günther Eichweber, Dr.-Ing. Harald Brühl, Professor Dr.-Ing. Dietrich Stein, Dipl.-Ing. Karl-Jürgen Athens and Dipl.-Ing. Jürgen Brenker for their tireless motivation and months of collaboration, and I particularly wish to thank Dipl.-Ing. Uwe von Diecken for the overall leadership of the group. Thanks are also due to Professor Dr.-Ing. Werner Brilon, chair of transport I at the Ruhr University, Bochum, for collaboration on Section I.1 in regard to transport technology. I thank my brother Dipl.-Ing. Reinhold Maidl for his help and the help of the consultancy, particularly for the assistance with the work load at all times.

I thank the ladies at my chair and the consultancy, Frau Agatha Eschner-Wellenkamp and Frau Hildegard Wördehoff, and at the drawing office led by Herr Helmut Schmidt for their industrious help in the production of the work.

The publisher has assisted me greatly with this volume by looking through the manuscript critically, suggesting improvements and have also presented the work excellently.

Let us hope that Volume II “Basics and Auxiliary Works in Design and Construction” can find its way, as Volume I already has, into the hands of the engineers working for contractors, clients and their supervisors, and not least of the students at the various further education establishments.

Bochum, in May 1988

Bernhard Maidl

1 General Principles for the Design of the Cross-section

1.1 General

The shape and size of the design cross-section derive firstly from the purpose of the tunnel (rail tunnel, road tunnel, sewer, water tunnel or pressure tunnel for a hydropower station) and thus the required clearance gauge. Secondly, the dimensions will also be influenced, as is the alignment, by the geotechnical or structural conditions in the ground to be passed through; whether earth or water pressure could occur or whether no external loading is to be expected. Thirdly, the construction process also has an effect on the design of the cross-section; for a given clearance gauge, the most economic cross-section is that which can be constructed with the least excavation and support technology and with the optimal machinery, taking into account the given basic shape.

1.2 Dependence on intended use

1.2.1 Road tunnels

General. The traffic conditions in a road tunnel should in principle correspond to those in the open air. Road tunnels are, however, special sections of a road and demand stringent requirements for their construction, maintenance and operation. Road tunnels have to meet particular requirements regarding road safety and operational safety. When the needs of traffic management are balanced against economy, it is therefore necessary and justifiable in many cases to limit the speed compared to parts of the road in the open air. The permitted maximum speed is thus normally limited to 80 km/h in road tunnels, which inevitably differentiates the traffic flow in tunnels from roads in the open air.

Tunnel cross-section. Road tunnels with two-way traffic and those with one-way traffic are fundamentally different. Two-way tunnels normally consist of a single tube with one lane in each direction. In one-way tunnels, the traffic in each direction is constructionally separated, for example through the provision of two bores. While in the past each bore was often laid out with two lanes without a hard shoulder, the changing composition of the traffic and ever increasing traffic loading will also demand three lanes without hard shoulder, and in exceptional cases even three lanes with a hard shoulder.

The design of the cross-section of road tunnels has to consider road traffic aspects, operational equipment and the tunnel structure. The design of the cross-section of a cut-and-cover road tunnel is often subject to different constraints from a mined underground tunnel. Some examples of cross-sections of mined road tunnels are shown in Fig. 1-1.

Figure 1-1 Cross-sections of some mined road tunnels.

The starting point of all considerations does, of course, remain the space required for the road intended to run through the tunnel. The required total cross-section can often be twice that of the actual cross-section for traffic, and the cross-sectional area at breakdown bays of autobahn tunnels can be up to 200 m² and more. The space required is also influenced by the horizontal and vertical alignments selected for the project.

The design of tunnel cross-sections in Germany is based on the guidelines for the equipment and operation of road tunnels (RABT) [77], also taking into account the guidelines for road design; cross-sections (RAS-Q) [76] and alignment (RAS-L) [75]. These guidelines include requirements for the standard cross-section, the structure or vehicle gauge to be maintained, the transverse and longitudinal gradients in tunnels and the provision of breakdown bays and emergency exits.

Standard cross-section. The standard cross-section of a road tunnel has to provide dimensions to enable the installation of equipment like lighting, ventilation, traffic management and safety technology, normally outside the clearance gauge. Particularly ventilation and signage equipment may demand an enlargement of the tunnel cross-section. In order to limit the multitude of possible cross-sections – also for economic reasons – the standard cross-sections of roads in the open air are assigned to road cross-section types in tunnels. The selection of road tunnel cross-sections is carried out according to [33] (Fig. 1-2).

In tunnels intended for two-way traffic, the standard cross-section type 10,5 T with 7.50 m paved width between the kerbs is normally provided. This cross-section is also used in open-air sections where wider verges are provided due to high heavy goods traffic volumes. In the course of a road with 2 + 1 RQ 15,5 sections (two lanes with an overtaking lane), sections running through tunnels are also constructed to section 10,5 T. The over-taking lane in this case thus has to be terminated in good time before the tunnel. Special solutions like an additional crawler or climbing lanes in the tunnel are an exception. When in exceptional cases tunnel sections on main roads only provide RQ 9,5 section, crosssection 10,0 T should be used [33].

The normal layout in tunnels with multi-lane carriageways in one direction should be a reduced standard road section without hard shoulders (26 t or 33 t), although it is justifiable under certain economic or traffic conditions to provide hard shoulders. Economic aspects in this case could be the construction and operating costs resulting from the length of the tunnel or the costs resulting from congestion and accidents. The hard shoulders are available for vehicles to swerve to the side or stop in an emergency. They often allow continued multi-lane traffic flow after minor accidents or breakdowns and also simplify maintenance work without serious disruption of traffic flow. The width of hard shoulders varies depending on cross-section type (Fig. 1-2). It is

– for cross-section type	29,5 T	2.50 m.
– for cross-section types	26 T and 33 T	2.00 m.
– for cross-section type	26 Tr	1.50 m.

Figure 1-2 Standard cross-sections for road tunnels [33, 77].

For the layout of hard shoulders in tunnels, reference should be made to [33]. Using this decision-making process, it should be checked whether the additional utility resulting from a hard shoulder exceeds its extra cost. Using the diagrams for use with this process, it can be seen that the decision to provide the cross-sections with hard shoulders (26 T or 33 T) can only be justified under very favourable construction conditions or with a high volume of heavy good vehicle traffic combined with steep gradients. This process applies for multi-lane carriageways in one direction in road tunnel up to 2,000 m long.

The reduced form of special cross-section 26 Tr should only be considered for tunnels to be driven with shield machines. In this case, the reduced hard shoulder replaces the other-wise necessary breakdown bays along the entire length [33].

Cross-section type 29,5 T is only worth considering for very unusual cases and in any case only for very short tunnels with an exceptionally low-cost construction method.

Clearance gauge, traffic gauge. The clearance gauge denotes the space for the road cross-section, which has to be kept clear of obstructions. It consists of the traffic gauge and the safety margins at the top and the sides. The necessary cross-sectional area of the clearance gauge ensues from the traffic purpose of the tunnel. It is derived from the applicable standard cross-section in the open air; the permissible restriction of the cross-section inside structures also has to be considered (RAS-Q [76]).

The total width of the clearance gauge is the sum of the widths of the side safety margins, the carriageway, the verges and any additional lanes (for example hard shoulders) (Fig. 1-3).

Figure 1-3 Outline of the clearance gauge in road tunnels (standard solution) [77].

The required headroom for road traffic is 4.50 m. For economic reasons, the sides of the outline are normally vertical, demanding a widening of the safety margin when the cross-slope gradient is steep. For circular cross-sections, on the other hand, it can be economic to tilt the clearance gauge with the carriageway. The outline at the sides can then be assumed to be vertical to the carriageway. It is not necessary in such cases to widen the safety margin.

The outline of the clearance gauge includes areas solely reserved for traffic. Emergency pavements are provided on each side of the carriageway, which are 1.00 m wide and have to have clear headroom of 2.25 m. These are separated from the carriageway with kerbs, normally 7 cm high. Part areas are assigned at a height > 2.25 m above the emergency side pavements, in which easily deformable furniture elements particularly traffic signs and notices can be located although these are only permitted to approach within 50 cm of the traffic gauge; jet fans required for ventilation have to be installed in niches or ceiling coves. Easily deformable light fittings are only permitted to approach within 50 cm of the traffic gauge at a height of > 3.75 m. If jet fans are located inside the normal structural dimensions, this results in widenings of the emergency pavements dependent on the diameter of the fans to be installed [77].

It is often practical to locate traffic signs on the end walls of breakdown bays. In exceptional cases, traffic signs can by located down to a minimum of 30 cm from the traffic gauge at a height > 2.25 m above the emergency pavements; but this does not apply where a widening of the emergency pavement has been provided for fans. If traffic signs have to be made with smaller dimensions than stated in the regulations [32], then this has to be agreed with the authority responsible for traffic management.

Light fittings are permitted to approach within 50 cm of the traffic gauge in exceptional cases when it can be ensured that a clear headroom of 4.10 m from the top of the emergency pavement to the underside of the light fitting is maintained at all points. Jet fans with external diameters ≤ 70 cm are permitted in exceptional cases to be located in the safety margin with a minimum distance at the side of ≥ 30 cm to the traffic gauge in the upper corners.

Gradient and cross-slope. According to the RAS-L [75], the gradient in uninhabited areas running through tunnels should be limited to 4 % if possible and a maximum of 2.5 % should be the intention, particularly for longer distances. The chimney effect, which also increases with increasing gradient, normally leads to higher longitudinal flow, which in case of fire can severely impair the rapid and effective removal of smoke by a ventilation system. In order to ensure road safety and due to the chimney effect, gradients steeper than 5 % should be avoided in road tunnels in uninhabited areas.

A minimum cross-slope of 2.5 % is specified for straight stretches in order to drain surface water [76]. Depending on the design speed, the cross-slope may have to be adapted to suit the curve radius [75]. In addition to these conventional requirements, the cross-slope of roads in tunnels has special significance in case of an accident. If a fire breaks out, any leaking flammable liquids have to be drained away as fast as possible, which is ensured by a steep cross-slope and high-capacity drainage. Slot channels with a capacity of 100 l/s should therefore be provided, with firestops spaced at max. 50 m [77].

1.2.2 Constructional measures for road safety in tunnels

Breakdown bays. Breakdown bays should be provided where the provision of hard shoulders is not economically justifiable. They are required in tunnels more than 900 m long, and under special conditions from 600 m (for example ≥ 4,000 HGV · km / bore and day) [77]. The end wall should have an angle of ≤ 1:3 in the travel direction (Fig. 1-4). It can be secured by suitable passive protection according to RPS [78]. Concrete protection walls should have an angle ≤ 1:3. In tunnels with two-way traffic, these requirements apply to both end walls.

Figure 1-4 Dimensions of a breakdown bay next to a carriageway [77].

The spacing of breakdown bays should be ≤ 600 m in each direction. In tunnels with two-way traffic, the breakdown bays should be arranged opposite each other in order to enable vehicles to run in case of emergencies (turning bays).

Emergency exits, escape and rescue routes. Escape and rescue routes, which are to be signed and have lighting, should be provided in tunnels and the escape route in the traffic gauge should lead to the emergency exit and the rescue route from the emergency exit should lead to the open air directly or through safe areas.

From a tunnel length of ≥ 400 m, emergency exits should be provided at a regular spacing of ≤ 300 m [77]. Emergency exits can lead

– into the open air.

– directly into the other tunnel bore.

– through cross-passages into the other tunnel bore.

– to escape and rescue shafts.

– to escape and rescue tunnels.

Cross-passages in this case denote connecting structures between two parallel tunnel bores. They should be closed from each tunnel bore with doors. In two-bore tunnels, every third emergency access to the other bore can be designed to allow passage for fire service and emergency service vehicles in case this is required by the safety and rescue plan.

In escape and rescue shafts, escaping people are led up stairs to the open air. The stairs have to be 1.50 m wide for two-way access. The design of escape and rescue shafts should give reasonable consideration to the limited physical capabilities of disabled and older people.

Escape tunnels normally run parallel to the tunnel and connect various emergency exits from the tunnel to a common exit into the open air. The gradient should not be more than 10 % and they should have a clear passage of 2.25 m × 2.25 m.

In exceptional cases for tunnels with a high traffic volume, it can be practical to make escape tunnels more than 300 m long accessible for emergency service vehicles. This measure should however be verified as part of an overall safety plan.

The equipment of road tunnels with lighting and ventilation for normal operation and in case of fire, with drainage and also communications equipment, fire detector and extinguishing systems all pose additional requirements for the design of the cross-section. These requirements can lead to various solutions depending on the local conditions and should thus be decided for each project.

1.2.3 Rail tunnels

General. The first rail tunnel in Germany was built near Oberau in the years 1837 to 1839 and had a length of 512 m. The oldest tunnel that is still in operation is the 691 m long Busch Tunnel near Aachen, built from 1841 to 1843. Most of the tunnels that are still in operation were built in the years 1860 to 1880. These had to be maintained at greet cost through the 20^th century [118]. The cross-sections of early tunnels were mainly based on the clearance gauge for rolling stock. The clearance gauge encloses the cross-sectional area, into which no part of the train may extend.

For rail tunnels, the horseshoe profile was generally used, in a higher form for single-track tunnels and a flatter form for two-track tunnels. It can also be designed with vertical inner side surfaces. Today an arched profile with or without invert vault is more commonly used for conventionally driven tunnels, and a circular profile for tunnels bored by shield machines. In addition to the cross-sectional areas required for the rolling stock and tracks including signal lamps, contact shoes and any other necessary accessories, rail tunnels require a loading gauge that allows for deviations of the wagons through snaking, for example as a result of broken springs. In addition to the loading gauge determined in this way, space also has to be provided for signals, overhead, cables, lighting, pipes and other equipment required for rail operations and escape routes.

At stations, the tunnel has to be enlarged to house the platforms. It is important for rail operations that the platform is wide and long enough not to obstruct rail traffic, including consideration of traffic peaks. For this reason it is much better to provide sufficient space for platforms in advance than to be forced to undertake rebuilding measures later due to insufficient capacity [93].

Rail tunnel on new high-speed lines (NBS) of German Railways DB AG are designed according to the planned use and the resulting design speed v_E. This is categorised by new regulations (Ril 853) into four categories:

– High-speed traffic	with 230 km/h < v_E < 300 km/h.
– Express traffic	with 160 km/h < v_E < 230 km/h.
– Passenger and goods traffic	with v_E < 160 km/h.
– S-Bahn, urban transit	with v_E < 120 km/h.

The gradient on main lines should be limited to 12.5 ‰ and on urban and side lines 40 ‰. The permissible gradient should be laid down for each individual case and can, like for example in the Irlahüll Tunnel on the NBS Nuremberg – Ingolstadt at 14.5 ‰, also lie outside the ideal value stated above. A lower limit should also be maintained – depending on the planned use – of 2 ‰ (tunnel length l < 1,000 m), or 4 ‰ (l > 1,000 m). Ideally, the vertical alignments of tunnels should be ramps with the gradient in one direction for fire protection reasons.

The permissible curve radii should be limited to

2,000 m < r_A < 30,000 m

and determined more precisely from the design speed within this range.

The size and shape of the excavated cross-section depend on the loading gauge of the train, the lining thickness and the construction process. Depending on the various planned uses, the guideline Ril 853 specifies different track spacings in tunnels and thus various sizes of cross-sections. An enlargement of the cross-section compared to previous regulations is necessary because high pressures are created when two trains pass each other in a tunnel at high speed. The sudden change of pressure can reduce the travel comfort of the passengers in a small tunnel and more seriously can cause stresses in the windows that endanger operations.

In the following section, the most important parameters demanded in Ril 853 for the cross-sections of rail tunnels are described, depending on the planned use:

1. Tunnels for high-speed traffic at 230 km/h < v_E ≤ 300 km/h

In new construction and major refurbishments, the standard track spacing in straights and curves should be exactly 4.50 m, with a specified formation width of 12.1 m and a distance of the track centre to edge of formation of 3.8 m. The radius of the cross-sectional area is specified as 6.85 m for two-track tunnels, resulting in a total area above top of rails (TOR) of A = 92 m². The same total area results for the case of a three-centred arch for two-track traffic, for which radii of R₁ = 6.85 and R_² = 4.00 m should be selected (Fig. 1-5). The permanent way can consist of a ballastless track or tracks laid on ballast. This choice then influences further parameters of cross-section design but not the total area of the cross-section. Details of these minor differences can be found in Ril 853.

Figure 1-5 Guideline detail for a two-track high-speed tunnel with three-centred arch section according to Ril 853.

In new construction and major refurbishment of single-track tunnels, a safety space has to be maintained on the side of the cable trough, and in multi-track tunnels outside the danger area on each side. This serves for access to the tunnel and for the evacuation of passengers to an exit in case of emergency. The safety space must be at least 2.20 m high and 0.50 m wide. In all new tunnels, there must be one continuous escape and rescue path leading to the open air for each track. The escape and rescue path should lie on the side of the safety space outside the outline of the clearance gauge. The passage width of the escape and rescue path should be at least 1.20 m, and the clear headroom at least 2.20 m.

The illustration (Fig. 1-5) shows an example of these requirements and the other details of the clearance gauge for a two-track tunnel with three-centred arch section on a high-speed line. The corresponding guideline details for a single-track tunnel with circular or three-centred shape of the cross-section can be found in Ril 853.

2. Tunnels for express traffic at 160 km/h < v_E ≤ 230 km/h

The cross-section of a rail tunnel for express traffic only differs from that for high-speed travel in the specified dimensions according to the guideline detail. The requirements for safety spaces and escape routes are formulated independently of design speed, so the requirements are identical for all design speeds. Ril 853 specifies a track spacing of only 4.00 m for express traffic in two-track tunnels, so the required formation width at u = 0 reduces to 11.60 m. The required spacing of track centreline to edge of formation remains at 3.80 m. The radius of a circular cross-section also reduces to r = 6.10 m, from which an altogether smaller cross-sectional area of A = 79.2 m² above TOR can be calculated. As with tunnels for high-speed traffic, individual parameters can also vary with the selection of as ballastless or conventional permanent way. This is illustrated below with a guideline detail for a two-track tunnel for express traffic with circular cross-section according to Ril 853 (Fig. 1-6).

Figure 1-6 Guideline detail for a two-track express tunnel with circular section according to Ril 853.

3. Passenger and goods traffic at v_E ≤ 160 km/h

For passenger and goods traffic with a design speed of v_E < 160 km/h, the Ril 853 does not provide any guideline details for two-track cross-sections. Because the traffic is mixed, only single-track tunnels should be used in this case according to the guideline for civil protection from the EBA (federal rail authority), so two-way traffic has to run through separate parallel tunnels. Fundamentally, it can be stated that the distance of the track centreline from the edge of formation reduces to 3.30 m in comparison with other layouts and the formation width of open-air sections at u = 0 is thus 10.60 m. The dimensions for escape routes and safety spaces still apply for passenger and goods traffic since they are independent of design speed. This is illustrated below with a guideline detail for a single-track tunnel with circular cross-section (Fig. 1-7).

Figure 1-7 Guideline detail for a single-track tunnel with circular cross-section for passenger and goods traffic according to RiL 853.

4. S-Bahn, urban transit traffic at v_E ≤ 160 km/h

Urban or rapid transit railways (S-Bahn in Germany) are categorised as railways according to the provisions of the general railway law and the railways construction and operation regulations [41] derived from it. In order to take into account developments in tunnelling technology and associated special processes for tunnelling inner-city rapid transit lines, the DB AG guidelines RiL 853, RiL 800.0130 and Ril 997.0101 are applicable, of which the Ril 853 has a chapter dedicated to the special features of urban rail tunnel construction.

In densely built-up urban areas, in hilly terrain or near stations at intermodal hubs, urban rail lines often run underground. S-Bahn lines in the cities of Stuttgart, Munich, Hamburg and Berlin have numerous underground stations. The locomotive-hauled S-Bahn shuttle in the Rhine-Ruhr area also partly runs underground.

S-Bahn tunnels can have either round, vaulted or rectangular cross-sections. With a permissible gradient of 40 ‰ and track radii of R > 250 m, smaller cross-sectional dimensions are possible than at speeds of over 120 km/h due to the lower design speed. The specified track spacing is 3.80 m, the distance from track centreline to edge of formation is 3.20 m and the specified formation width at u = 0 is 10.20 m.

With a clear width of 9.16 m and a clear height 5.49 m, a two-track rectangular cross-section on a straight line has an area of 50.3 m². In curves, this area is slightly greater due to the cant. With a clear width of 9.25 m, the Ril 853 specifies a clear height of 5.59 m and thus a total area of 51.7 m². It is also the case here that the selection of permanent way type can change individual parameters of cross-sectional design.

One special detail of S-Bahn tunnels is the layout of the clearance gauge for the overhead. Ril 853.1003 specifies, in contrast to Ril 800.0130, a space to be kept clear for the over-head as shown in Fig. 1-8.

Figure 1-8 Clearance gauge for the overhead in urban rail tunnels.

Figure 1-9 Guideline detail for a two-track S-Bahn tunnel in a curve with rectangular cross-section according to RiL 853.

An exception permit is to be obtained from the BMVBW (federal ministry for transport, building and town development) in each individual case for the application of the height of 5 100* mm above TOR according to Fig. 1-8.

In contrast to the details described until now, the safety space in S-Bahn tunnels has to be at least 80 cm wide. For the height and width of the escape route, the dimensions of 2.20 m · 1.20 still apply.

Fig. 1-9 shows as an example the guideline detail from Ril 853 for a 2-track S-Bahn tunnel with rectangular cross-section.

1.2.4 Construction of rail tunnels

The fire and civil protection requirements for the construction and operation of rail tunnels are laid down in the guideline of the federal railway authority (EBA) with the same name from 15 August 2001. The following section describes some important design principles from this guideline. More detailed information can be found in the guideline.

Fire duration and temperature curve. In order to minimise the depth of concrete spalling that could endanger passengers, a curve of temperature against time is to be assumed for design purposes (Table 1-1).

Table 1-1 Temperature curve depending on fire duration according to EBA.

These data can be used to determine the additional stresses, which have to be resisted by constructional measures (for example additional layers of reinforcement).

Safe areas, escape routes, emergency exits. Each track is provided with its own escape route next to it, as has already been mentioned in the description of the various planned uses. Localised narrowing of the escape route is to be avoided or in exceptional cases limited to a length of 2.0 m and a depth of 0.3 m. Handrails should be provided on all escape routes.

For the design and layout of escape shafts and tunnels, the limited physical capabilities of frail people and those with disabled mobility should be considered. Shafts should not exceed a level difference of 60 m and if the level difference is more than 30 m, should be equipped with a lift with dimensions 1.1 · 2.1 m. Stairs should be suitable for people passing and for the transport of stretchers according to DIN 13024.

Escape tunnels must have a cross-section of at least 2.25 m · 2.25 m, and not exceed a maximum gradient of 10 % and a maximum length of 150 m if they do not reach the open air directly but up a shaft. For lengths of more than 300 m long, rescue shafts must be accessible for ambulances.

Rescue areas and access roads. All exits and portals of the tunnel must be accessible by road. For long tunnels, a rescue area is to be provided at each portal and emergency exit. For shorter tunnels, one rescue area is sufficient.

Access roads and rescue areas must

– have secure planning status,

– have secure property status,

– be covered by an access regulation in traffic law.

In this case DIN 14090 should be complied with.

Access roads to rescue areas should be separate from exits. If this is not possible, two-way traffic with 2.50 m width must be ensured, if unavoidable by providing passing places. If rescue areas are connected to dead-end streets, it must be possible to turn.

Extinguishing water supply. Each tunnel portal must have sufficient water supply available for extinguishing fire (at least 96 m³ at 800 l/min) within a maximum distance of 300 m.

Two-track tunnels are to be provided with a continuous dry fire extinguishing pipeline, which can be supplied from the portals and from the emergency exits.

In single-track tunnels on a two-track line, a continuous dry fire-extinguishing pipeline is to be laid in every running tunnel. In addition to the above provisions, both pipelines must be joined by dry pipes at junction structures.

It must be possible to operate dry extinguishing pipelines in sections and they are to be laid with protection.

1.2.5 Underground railway and underground tram tunnels

General. The cross-sectional dimensions of these tunnels are determined by constraints resulting from vehicle dimensions, dynamic travel properties, alignment elements, layout of safety spaces in the tunnel, location and type of power supply, environmental protection requirements (damping of vibration) and construction.

Guidelines. The following guidelines are applicable for all new design and design revisions for underground railway and underground tramlines:

1. Regulations concerning the construction and operation of tram lines (BOStrab) from 11 December 1987.

2. Guidelines for tunnels in the Regulations concerning the construction and operation of tram lines (Tunnel construction guidelines) from 30 April 1991.

3. Accident prevention regulations (UVV) of the accident insurer for trams, underground railways and railways.

For the design of urban railways, the regulations that have been introduced in the Rhine-Ruhr area [227] are widely regarded as a standard. The Stadtbahngesellschaft Rhine-Ruhr has produced detailed guidelines.

Considering the different types of vehicle at each location, the provisions regarding crosssections only have the character of a recommendation. The shape of the tunnel cross-section is decisive for the determination of the outline of the loading gauge and the clearance gauge. Tunnels are differentiated into those with rectangular cross-sections and circular or similar cross-sections.

1.2.6 Innovative transport systems

In recent years, the development of guided transport systems for inner city public transport has been advancing in the Federal Republic of Germany.

Bus transport is being further developed, particularly for travel through tunnels, with buses being guided electronically or mechanically in the tunnel. The advantage of this principle is the considerable reduction of the cross-sectional dimensions of the tunnel compared to a manually steered bus (Fig. 1.10), which can greatly cut construction costs. This type of tunnel for buses will mainly be restricted to inner-city areas. Bus tunnels are already being designed and constructed in the cities of Essen and Regensburg. The dimensions of the tunnel cross-section derive from the size of a standard bus. These have a width of 2.50 m plus 0.25 m on each side for the rear-view mirrors and a height of 3.95 m. The mechanical guidance (Fig. 1-11) requires a road trough with a width of 2.95 m.

Figure 1-10 Automatically guided bus. Circular tunnel cross-section (left) and possible cost savings (right) [168].

Figure 1-11 Mechanical guidance for busses. Rectangular cross-section for straight stretches of two-way tunnel [15].

1.2.7 Monorail with magnetic levitation, Transrapid, Metrorapid

A new method of transport, which has already been under development for about 30 years, is the “Transrapid” high-speed monorail with magnetic levitation, which represents an alternative between jet and train with a speed of 400 km/h (Fig. 1-12).

After the construction and testing of the Transprapid in Shanghai, an application in Germany is still in the design phase. The planning of the Metrorapid in the Ruhr area from Dortmund to Düsseldorf and in Munich between the airport and the main station has however been abandoned for financial reasons. This would have required a 4 km long tunnel bored by a shield machine.

Figure 1-12 Standard cross-section for a shield-driven tunnel for a magnetic monorail.

1.2.8 Other underground works

General. In addition to the road and rail tunnels described above, tunnels are also devoted to the needs of pedestrians, skiers, shipping, drinking water supply and drainage and electricity and gas supply.

Pedestrian tunnels. These are of a similar nature to road tunnels, but the small clearance gauge, small curve diameters and the steeper permissible gradients, which can be up to 10 %, and the possibility of joining them into a lift shaft lead to such a decisive simplification of their design and construction that they can be regarded as a different group. Pedestrian tunnels are found almost exclusively in inner cities and only seldom under rural roads.

The best-known pedestrian tunnels are those in Hamburg under the Elbe and in Antwerp under the Schelde. Neither of these has a staircase, but the pedestrians enter and leave the tunnels in lifts, escalators or shafts at the riverbank. The tunnel in Antwerp is a fully independent tunnel only intended for pedestrians, but the tunnel in Hamburg is for mixed traffic since there is a central single-track road with a 1.25 m wide pavement each side, similar to a road bridge [238].

Pedestrian tunnels either have rectangular or circular cross-sections according to whether they are below paving or deeper (including below water).

In order to make the pedestrians feel comfortable, pedestrian tunnels should have generous height and width. The clear headroom should not be less than 2.44 m, better still 2.75 m or more. The width is determined by the number of pedestrians.

Ski tunnels. These are becoming ever more common in many countries [128], [223]. A good example of this new sort of tunnel was opened in Saas Fee, Switzerland in December 1984 for an underground funicular railway to transport skiers. The tunnel, almost 1,600 m long, was driven at rock temperatures of 0 °C, so no water ingress had to be feared. Altogether over 80 % of the tunnel could be driven in excavation class I according to the Swiss SIA standard 198 (see Chapter 2). Fig. 1-13 shows the excavation conditions and the chosen cross-section. The tunnel was bored by a full-face machine with a diameter of 4.20 m.

Figure 1-13 Cross-section of the Metro-Alpin Tunnel in Saas Fee [128].

Shipping tunnels. Historically, shipping tunnels were the forerunner of today’s transport tunnels, as water transport was formerly more significant. These tunnels are not described in further detail here.

Tunnels to transport water under gravity mostly have a horseshoe section. The cross-sections of pressure tunnels tend to a circular form with increasing water pressure.

Utility tunnels. These are mostly in urban areas and serve to house utility supply pipes. The cross-section is normally circular or rectangular according to the chosen construction process. This sector is currently the subject of much research and development, particularly regarding the repair or replacement of old pipes and small cross-sections. The various construction processes and characteristic cross-sections are described in more detail in Chapter 7 of volume 1.

No further details are given here of the cross-sections of shafts, caverns, chambers or other applications.

1.3 The influence of the ground

General.Fig. 1-14