IUT ’08: Focus on modern Tunnelling and Geothermics

The 5th tunnel fair featuring “Innovation underground”/IUT ‘08 [1] (September 17th/18th, 2008) at the Hagerbach Test Gallery (VSH) close to Sargans provided interested trade visitors with a wide choice of well presented specialised information with the 2 seminars “Modern Tunnel Equipment for Road and Rail” and “Tunnel Geothermics – Possibilities of Utilisation and Potentials” in addition to excursions to construction sites (Uetliberg Tunnel and Saaser Tunnel) [2].

Tunnelling Seminar
Whereas the seminars at previous fairs have largely dealt with tunnel driving methods (IUT ’02) and tunnel linings (IUT ’05) [3], the tunnelling seminar at the IUT ’08 concentrated on “Operational and traffic-technical Tunnel Equipment”. In 3 years the tunnelling seminar at the IUT ’11 will deal with a further, increasingly more topical topic, namely “Maintaining, Developing and Renovating older Tunnels” – given full or restricted services.
Prof. Alfred Haack of the STUVA Inc., who chaired the seminar initially reported on the increasing worldwide significance of underground construction for transport, landscape protection as well as supply and disposal. The contributions by internationally recognised experts were accordingly devoted to topical issues.


The Rail Technology Works Contract for the Gotthard Base Tunnel
The AlpTransit Gotthard AG (ATAG), a subsidiary of the SBB AG, examined the path leading to the works contract for the Gotthard Base Tunnel [4, 5]: from the risk analysis by way of tendering and awarding, dealing with complaints, judicial rulings (no effective delay in the event of public interest in the completion deadline) right up to the works contract from April 29th, 2008 worth 1.69 bill. CHF (1 bill. Euro) with details on the extent of work (slab track, electric installations, power supply, Telecom and safety facilities etc.) as well as setting out the project for execution and the deadlines.


Findings made when installing the rail-technical Equipment
The model of total contractors (TU) independent of each other was chosen for equipping the Lötschberg Base Tunnel, bearing the entire responsibility for planning, executing and operating their system. Following the tendering stage the outcome was an overall total contractor, which led to fewer interfaces and enhanced safety for deadlines [6,  7]. Experiences gained during the installation of the slab track were dealt with at length.

Maintenance and Costs for the Tunnel Equipment
The high safety demands for the Lötschberg Base Tunnel (access control and video units, ventilation as well as doors and gates regarding fire safety) (Fig. 2) and the maintenance costs (without renovation) of 240 CHF (150 Euro) per 1  m of track per year, i.e. 7  % roughwork, 25  % rail technology, 48  % tunnel technology and safety facilities as well as 20.5  % technical operation and logistics were dealt with.

Modern Technology for Train Security
Thanks to the European Train Control System (ETCS) trains travel faster –  this was first of all the case on the new Mattstet-ten–Rothrist route with the Önzberg and Wolfach tunnels and as from 2007 also on the new Lötschberg axis with the Lötschberg Base Tunnel [8]. Thanks to ETCS Level 2, which facilitates speeds in excess of 160  km/h, external signals are eliminated and the train driver operates the train in accordance with a display in the cab (Fig. 3) – with the speed being monitored independent of external visibility conditions. As trains can run more frequently this results in better services. At present the ETCS is being used in Europe for 23 projects on a total of 3,000 route km and some 800 vehicles. It is also intended to equip the Gotthard axis with the Gotthard and Ceneri tunnels with ETCS Level 2.

Road Tunnels:
EU Directives and RABT
Both the EU directives as well as the national guidelines for the furnishing and operating of road tunnels (RABT) [10] provide minimum demands for the constructional and technical installations in road tunnels primarily to ensure the safety of tunnel users in the event of an unforeseen incident right up to a case of fire. However, the requirements contained in the national code of practice actually often exceed the demands found in the EU directives: this applies in particular to highly frequented shorter tunnels as most tunnels are shorter than 1,000  m. Organisational, constructional and technical measures such as safety management, escapeway identification, guidance installations (LED markings), emergency exit design, modes of ventilation in the event of fire given 2-way traffic as well as one-way traffic with a proclivity for tailbacks – especially controllable smoke extraction valves – were dealt with at length.


Layout, Operation and Servicing the Tunnel
Operating Technology for Road Tunnels
In this connection details on the development of operating costs for old and new facilities (development of energy costs), ventilation systems (full cross ventilation taking the size of the cross-passage doors into consideration), video monitoring, lighting systems (white instead of yellow sodium high-pressure vapour lamps), traffic signals (traffic lights, LED blinkers) and the materials used in the tunnel relating to fire resistance and service life (stainless steels) were provided.


Permanently installed Fire Fighting Systems
Prof. A. Haack provided an overview of the development [11, 12] and the current stage reached by research and knowledge. In conjunction with the application of automatic fire fighting systems (Fig. 4) the following aspects have still to be clarified:
– whether investments can partially be compensated through savings for ventilation systems and
– to identify the most favourable point in time for activating the system in order to restrict fire development on the one hand and the changed conditions for evacuation and rescue on the other.

Tunnel Geothermics:
Possibilities of Utilisation and Potentials
At the IUT ’08 a seminar on tunnel geothermics (September 18th) was held for the first time staged by the Swiss Geothermic Society (SVG). According to introductory remarks provided by the seminar chairman, Dr. Roland Wyss from the SVG, more than 700 rail and road tunnels in Switzerland can be used for geothermic purposes as a result of the amount of energy produced and the local conditions. Cooling deep-lying sectors of tunnel or the transfer of not excessively hot tunnel water into collectors are numbered among the tasks for tunnellers. In future the geothermic use must be properly taken into consideration at an early stage for each major tunnel project.

Tunnel Heat Utilisation:
Principles and Examples from Switzerland
Tunnel heat, i.e. underground water heat, can be utilised in various ways. Deep-lying tunnels in some cases drain large quantities of hot underground water at temperatures of 20 to 50°  C depending on the rock overburden. The thermal capacity and the outflow temperature at the portal are determining for how the tunnel water is used for energy purposes. As far as direct utilisation is concerned
– economy (heat users close to the portal) and
– environmental aspects (conditions for discharge in keeping with water protection regulations; maximum underground water discharge temperature in winter +1.5°  C for the Reuss, Ticino and Rhône; possibly cooling facilities) have to be taken into account.
Switzerland with its many tunnels provides an interesting potential for the utilisation of hot water from tunnels and galleries (roughly 30  MW without the Base Tunnels; 6–300 l/s, 12–35°  C); a number of examples already exist (Tab. 1), 3 tunnel water applications are being constructed and 6 others are at the planning stage.  

Heat Utilisation from Tunnel Water
There are also heat utilisation projects in conjunction with the Alp transit tunnels. The Lötschberg and  Gotthard Base Tunnels with 2.0 and 2.5  km rock overburden offer hot water source potentials of 2.5 to 6.7  MW with 60 to 120  l/s delivery at 17 to 35°  C. Possibilities of utilisation exist for
– residential areas and public buildings,
– industry and commerce,
– agriculture (greenhouses) and fish cultivation as well as
– leisure time facilities.
Investments of between 7 and 17 mill. CHF (4.2/10 mill. Euro) are required for the application of tunnel heat water from both tunnels. For local heat supply systems heat production costs of 0.10 to 0.15 CHF (6 to 9 ct)/kWh result. If these projects are realised CO2 emissions are cut down by 13,300  t per annum. Consequently utilisation of tunnel water is extremely interesting both in economic and energy political terms.

Using the hot Water from the Lötschberg Base Tunnel
In this connection details pertaining to the origin and properties (chemical composition and physical parameters such as capacity, temperature and ph-value) of the underground water were provided and the conditions for introducing the underground water into the surface waters (Kander and Engstlige) with calculation of the permissible temperature and delivered water quantity provided. In the Base Tunnel there is a discharge pump station, which if need be diverts a part of the underground water into the Rhône via the apex point. The underground water is used for
– the “Tropenhaus Frutigen” project (greenhouse with plants and pools for cultivating fish, operating building and gastronomy) rounded off by
– a local heating supply to heat buildings in the vicinity of Frutigen station.
Depending on the air temperature between 5.22 and 3.13  MW of thermal energy can be obtained from the underground water (Fig. 5). The example shows that a purposeful utilisation of heat from the tunnel water is feasible to arrive at the production of tropical fruit and fish within the local heating supply system.

Ventilation and Air-Conditioning of deep-lying Chamber Systems
As the world’s longest tunnel the Gotthard Base Tunnel places extremely high demands also with respect to ventilation and air-conditioning for the technical facilities in the chambers for the multi-function stations Sedrun and Faido (Fig. 6). Both are connected to a ventilation centre, from which fresh air can be blown in if required and spent air or smoke gases removed to the outside from the station sectors. These facilities need continuous ventilation and air-conditioning to ensure that systems that are essential for operating the tunnel can be run reliably on a permanent basis. The requirements and general conditions were examined in more detail as well as details relating to technical solutions (filtering the external air and spent air, heat recycling, mechanical air-conditioning, electric reheater, vapour moistening, air temperature/air humidity measurement).

Tunnel Heat Utilisation with Absorber Elements
Since the start of the 1990s technologies to exploit major energy potentials from the earth’s natural heat have been developed; this mainly relates to structural parts made of concrete, which are laid in the absorber lines (Fig. 7):
– concrete linings in tunnels created by mining means,
– concrete structures for tunnels produced by cut-and-cover;
– energy piles (in situ bored and rammed piling made of reinforced concrete) for cut-and-cover projects (Lainz Tunnel) and
– diaphragm walls to secure excavation pits including tunnels.
New developments [13] are
– energy tunnels with nonwoven fabric and anchors for tunnels produced by mining means and
– energy wells for groundwater lowering in the case of construction work.
The utilisation of the earth’s heat by exploiting tunnels is advantageous for
– tunnels are usually located at depths with a constant temperature,
– tunnels provide large contact surfaces with the earth for obtaining energy,
– long tunnels possess considerable internal heat sources (exhaust heat from vehicles – also applying to Underground networks).
The exploitation of natural heat can also have advantages (costs and acceptance) during approval proceedings for major tunnels.
Thanks to interesting papers and numerous points of discussion the exchange of views on new recognitions in tunnelling and tunnel geothermics was successfully fostered. Further details are contained in the Proceedings obtainable via Fax ++49.5241.80.9650.
The next tunnel fair, the 6th IUT, will once again be held at the Hagerbach Test Gallery on September 14th and 15th, 2011.        

G. B.