Road Tunnels Manual

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4.8 Maintenance of equipment

Throughout the life of the tunnel, the operator should carry out both the maintenance of civil engineering works and the tunnel equipment. The maintenance of civil engineering structures is not described in this paragraph.

The maintenance operations on equipment can be classified into two groups:

  • The preventive measures that are carried out at fixed intervals with the objective of preserving the equipment in a good operating condition. Preventive maintenance offers the advantage of preventing, as far as possible, unforeseeable failures and, by the way, it is easy to plan in advance. It can however lead to high costs if the interventions are too frequent: therefore, they need to be optimised suitably.
  • The corrective actions that are carried out when a system or a part of a system has failed or been damaged. Corrective maintenance offers the advantage of using a system to the maximum extent of its service life. Its disadvantage however is that it cannot be planned and therefore emergency repairs are normally carried out with a significant surplus cost.

It is recommended to use preventive maintenance where possible and for those systems that are not redundant and are related with safety. Preventive maintenance allows the joint planning of different maintenance tasks in the event of every closure of the tunnel to the traffic. Moreover it helps keep the equipment in a good operating condition. It may be noted however that even when preventive maintenance is carried out very well, the operator cannot avoid corrective interventions.

Usually the operator's staff do not carry out all maintenance tasks; the operator normally entrusts contractors and several options are consequently available:

  • It is possible to contract only those maintenance tasks related to a specific technical level. The operator can thus contract tasks that present no technical complexity (cleaning, washing, ...) or it can contract only very complex tasks (supervision system, radio retransmission equipment, ...)
  • It is possible to contract all tasks of one or more equipment groups (all ventilation systems, all remote surveillance installations, etc.).

More detailed information on the subject of maintenance is provided in Chapter 7 "Cost of maintenance" of Technical Report 05.06.B, in Chapter 4 "Maintenance and operation" of Technical report 05.13.B" and in Chapter 6 "Organising operating staff" of Technical Report 2007R04".

If they exceed a few hundreds of meters in length, road tunnels are to be provided with equipment for ensuring the safety of users under normal conditions or in case of disturbances to normal operation. Because of their involvement in the global safety chain of the tunnel, this equipment must be selected and designed with great care, with regard to maintenance, inspection and refurbishment. Hence a report has been produced to assist the operator or operating body with the issue of maintenance and technical inspection.

The technical report 2012R12EN entitled "Recommendations on management of maintenance and technical inspection of road tunnels" gives recommendations for the management of maintenance, essentially in the domain of equipment. The aspects relating to light civil engineering are listed and described only very briefly.

Life Cycle Cost (LCC) aspects have become an important issue for private tunnel owners, as well as government agencies. Sound knowledge of life cycles helps to optimise investment costs during the early stages of designing a system. It is also helpful in organizing the periodical maintenance of technical equipment. The technical report 2012R14EN entitled "Life cycle aspects of electrical road tunnel equipment" outlines how LCC aspects support the design of equipment as well as maintenance concepts. Bearing in mind that investment decisions are often technology-driven and that equipment costs have risen dramatically in the past years, the report helps to understand the life cycle process and the aging process of material. The report provides background knowledge on LCC aspects, which could be of use for further investigations. Specific focus is given to the surrounding ambient conditions, e.g. temperatures, which have a significant impact on the aging process.

 
Complementary to this report, the technical report 2016R01EN entitled "Best practice for life cycle analysis for tunnel equipment" describes how life cycle analysis in the sense of condition analysis should be performed systematically, how system criteria can be used, how aggregation of different criteria should be done and how risk-based methods for system analysis can be applied. Particular consideration is given to the problematic aggregation of different condition values, evaluated with a set of criteria. The report outlines and clarifies how criteria can be checked with regard to dependencies and how "orthogonality" can be reached. It also explains that "random sampling" methods are seldom appropriate due to the low number of inspected items.
 
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