Master plan for a sustainable supply and disposal infrastructure of mega cities - Part II
Nov 09, 2006
This is the second part of the technical report series “Master plan for a sustainable supply and disposal infrastructure of mega cities”. It is exclusively about utility tunnels with special emphasis on structural design and commercial aspects.
In recognition of the linkage between line networks and changing user structures, there is a need for sustainable systems that are able to react smoothly or by small adaptations to changing and new requirements whose time, locality, scope and duration cannot be foreseen.
Characteristic features of utility tunnels, as already mentioned, are the installation of all possible supply and discharge lines into a structure situated underground whose traversability or accessibility is possible for personnel without elaborate equipment (Figure 1). These features make demands on the design of this type of structure that impinge on safety and operational matters of the structure as well as construction and installation points of view of the line networks. Further specific requirements emerge from the special conditions of operation. Thus, the following requirements must be taken into account in the structural design of a man-accessible utility tunnel [1, 2, 3]:
- Sufficient size of the cross section for inclusion of the planned lines taking into account the number and sizes of the individual lines, reserve or surfaces for extensions.
- Accessibility by adherence to minimum dimensions for the gangway and access for various purposes (including control, execution of maintenance works);
- Consideration for the mutual compatibility conditions of the individual pipes and cables in the utility tunnel for prevention of pipe damage or reduction of quality of network parameters (e.g. increase in temperature for drinking water);
- Ensuring installation-specific requirements of the individual pipes and cables (including gradient conditions especially for gravity piping in the sewer network, high and low points for ventilating and venting and drainage, support possibilities);
- Ensuring the operation of the individual networks (including expansion requirements for heating pipes, heat insulation of district heating pipes, drinking water temperature in the water supply, branches and connections in the network);
- Ensuring the operational capability of the man-accessible utility tunnel (including climatic conditions, protection against unauthorized entry, safety systems such as gas warning installations, drainage installations, lighting installations, fire warning and protection systems);
- Construction and erection requirements (e.g. sealed and strong structure of the shell, installation possibilities for the different pipes and cables, support design, connection and transfer points from the gangway to the surface network, erection openings).
Many cross-sectional shapes are possible for man-accessible utility tunnels (Figure 2):
- Circular cross sections (e.g. full circles, circular segments)
- Limited curved cross sections (e.g. arched profile)
- Quadratic and rectangular cross sections (the latter in lateral or vertical form)
- Combined cross section (e.g. semicircular arch).
- Prevention of mutual influences of lines,
- Damage limitation in the case of a catastrophe,
- Insufficient space in the underground space,
- Structural reasons.
The clear dimensions of a utility tunnel are determined by the following:
- Accessibility,
- Number and sizes of the lines to be accommodated and crossing the tunnel including the need for reserve space in accordance with the expected development,
- Safety and operational conditioned spacing between the lines,
- Construction and erection requirements for spacing of the lines,
- Dimensions of valves and fittings.
b = max. installed DN/ID + 200 mm.
The literature already contains individual commercial comparisons between the single installation of lines in the form of directly buried installation and multi-installation in man-accessible utility tunnels which have led to the conclusion that man-accessible utility tunnels are the expensive installation alternative for pipe-referenced infrastructure systems. As these cost comparisons are usually limited to the time period of original installation, i.e. the initial investments, the alternative of the utility tunnel usually must be worse than the single installation of various line networks and lead to an incorrect assessment.
- operated and abandoned directly installed line networks compete for space in installation zones in the pavement area and increasingly have to be removed from the road area for future new installations thus usually causing high direct costs;
- besides the replacement of old line-referenced infrastructure, often also later additions, the replacement of existing or the installation of completely new lines systems such as transport piping for goods or waste are necessary and these are possible in the utility tunnel with significantly lower investment;
- in the course of more stringent environmental responsibility laws, the inspection and servicing needs such as the shortening of inspection cycles for sewers, rise and these incur less costs in a utility tunnel or fall away entirely because they take place within the scope of an optical check;
- especially in the field of telecommunication, additional network operators can enter the supply market and contribute, because of the planned reserve space in man-accessible utility tunnels to a reduction of the empty costs, thus the unused capacity of the utility tunnel.
- Influence on retail trade
- Traffic deviation and hindrance
- Noise and pollutant emissions
- Reduction of the remaining life of road surfaces and the loss of value associated with it
- Damage to growth
- Further negative interruptions with reference to the specific limiting conditions of the construction site.
In order to maintain functional safety while adhering to or increasing the capacity. Already the partial renewal of deeply buried lines (especially sewers) can lead to grave interventions into the road cross section and can justify a premature renewal of all lines with re-routing into a utility tunnel. The same applies to the case of increases, new installations or the design of networks.
When installing the utility tunnel in the trenchless method below the existing lines, they can remain in operation up to the completion of the new system.
With specific applications such as airports, exhibition centres, goods traffic centres, harbours, universities, medical centres, etc. which demand a high degree of safety of supply and/or a high degree of supply comfort or an adaptation to utility-referenced and changing line demands with little effort.
New planning of roads, changing the route and re-designing metropolitan rail systems present measures that can trigger the renewal of line networks. Utility tunnels should be provided in this connection at dense node points for a circular interception of crossing main routes and the provision for reserve space for later traffic structures. Utility tunnels can serve as crossing structures, for underpasses of bundled routes under heavily used main roads. Mutual constraint points of traffic and line roads, such as bridges, underpasses or rails or railway lines can be designed with the use of utility tunnels without interruptions. For the widening of streets, re-designing of rail installations and executing of main network improvements, they can be usefully employed for keeping the traffic lanes free from lines and for limited paths and open spaces or with tight time limitations of traffic construction measures.
The new construction of underground traffic installations can force the building of over- or under-crossings or deviating line paths at points of conflict if line rerouting is generally necessary. The integration in existing or planned building structures (e.g. underground garages, underground railroads, street tunnels) is also feasible.
The utility tunnel can be used for main development sections for compact dwellings with corresponding requirements for supply and discharge safety.
Bibliography
[1] Drewniok, P.: Begehbare Sammelkanäle als effektives Erschließungsprinzip Entwicklung und Anwendung in der ehemaligen DDR. Dokumentation "Der begehbare Leitungsgang" Vol. 1: Beiträge zur Kanalisationstechnik (ed. D. Stein), Berlin: Analytica, 1991, 37-55.
[2] Komplexrichtlinie Sammelkanäle, Schriftenreihen der Bauforschung, Reihe Ingenieur- und Tiefbau (special edition 1), Bauakademie der DDR, Institut für Ingenieur- und Tiefbau, Berlin, 1976.
[3] SIA 205: Verlegung von unterirdischen Leitungen. Schweizerischer Ingenieur- und Architektenverein, issue 1984.
[4] visaplan GmbH, Bochum, Germany: www.visaplan.com.
[5] Company information SAKA Sammelkanal- und Service GmbH, Berlin-Marzahn, Germany.
[6] Girnau, G.: Unterirdischer Städtebau. Düsseldorf: Ernst & Sohn, 1970.
[7] Köhler, T. Erneuerung urbaner Ver- und Entsorgungsinfrastruktur mit Hilfe begehbarer Leitungsgänge – eine ökonomische Bewertung. Dissertation Ruhr-Universität Bochum, Fakultät für Wirtschaftswissenschaften, Bochum, 1998.
[8] Stein, D.; Klemmer, P.; Tettinger, P. J.: Studie zur ökologischen Erneuerung innerstädtischer Ver- und Entsorgungsleitungen sowie zur Erschließung kontaminierter Industriebrachen mit Hilfe von begehbaren Leitungsgängen unter besonderer Berücksichtigung des bergmännischen Stollenvortriebs. Unpublished research report Ruhr-Universität Bochum (1997).
[9] Stein, D.: Instandhaltung von Kanalisationen. 3rd edition. Berlin: Ernst & Sohn, 1998.
[10] Grunwald, G.: Wirtschaftlichkeitsuntersuchungen bei Kanalsanierungen: Dissertation Ruhr-Universität Bochum 1996. Published in the paper series of the Institut für Kanalisationstechnik Ruhr-Universität Bochum; Report 97/3 (1997).
[11] Horne, M.: Roads and the Utilities. Department of transport, London, 1985.
[12] Ling, D.; Read, G.; Vickridge, I.: Gebührenerhebung für die Benutzung von Straßenraum. Tiefbau Ingenieurbau Straßenbau (TIS) (1993), H. 12.
[13] Stein, D.: Erneuerung innerstädtischer Ver- und Entsorgungsleitungen durch Leitungsgänge. In: D. Stein (ed.), Der begehbare Leitungsgang, Beiträge zur Kanalisationstechnik, Vol. I, Berlin: Analytika, 1990, 9-24.
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