This chapter gives information on the general principles of maintenance, technical inspections and life cycles. Some information related to complex tunnels, civil works and winter maintenance is also given.
Structural elements and the technical equipment need regular maintenance, the aim of which is to ensure safe driving conditions for the public by keeping the tunnel at its designed safety standard (see page on Maintenance of equipment). General recommendations for maintenance in tunnels are defined as well as the specific features and their facilities.
Life cycle or Life Cycle Cost (LCC) aspects are becoming increasingly important. From an economic point of view, it is important to consider these aspects both in the design and in the operation of tunnel equipment (see page on Life cycle of tunnel equipment).
It is important to verify that the maintenance actions conducted have enabled the pre-defined objectives to be achieved. These verifications take the form of technical inspections, their aim being to make sure that the maintenance actions carried out allow the equipment to function in a satisfactory manner and that the frequency of maintenance actions is adequate (see page on Technical inspections).
The technical report Good Practices in Maintenance and Traffic Operation of Heavily Trafficked Urban Road Tunnels - Collection of Case Studies provides a collection of case studies to gather, evaluate and comment on international expertise related to maintenance and traffic management in highly trafficked urban road tunnels. A large number of cases provided an insight into the implementation of these special requirements for urban road tunnels.
Although maintenance actions on a “Complex underground road network” are essentially similar to those on a typical road tunnel, they are more complex due to:
The special recommendations concerning the maintenance of an "underground road network" are presented on the page "Maintenance of complex tunnels“.
In some countries, and not only in mountainous areas but also in very cold areas, winter maintenance can be quite a challenge in maintaining the tunnel functional and safe or in implementing new electronical and mechanical equipment’s and technologies (see the page on Winter maintenance)
Civil engineering structures within the tunnel also need regular monitoring and inspections. It is necessary to carry out regular maintenance of facilities such as drainage systems, gutters and all secondary structures (premises inside the tunnel, technical rooms, etc.), For further information, please consult the page on “Civil Works”.
Throughout the life of the tunnel, the operator should carry out both the maintenance of civil engineering works and the tunnel equipment. (See Report 05.13BEN "Good Practice for the Opereation and Maintenance of Roads Tunnels"). The maintenance of civil engineering structures is not described in this paragraph.
The maintenance operations on equipment can be classified into two groups:
It is recommended to use preventive maintenance where possible and for those systems that are not redundant and are related to safety. Preventive maintenance allows the joint planning of different maintenance tasks in the event of every closure of the tunnel to traffic. Moreover, it helps maintain 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. However, preventive maintenance will ensure costly corrective maintenance is kept to a minimum.
Usually the operator's staff do not carry out all maintenance tasks; the operator normally entrusts contractors and several options are consequently available:
Chapter 7 of Technical Report 05.06.B entitled "Cost of maintenance", chapter 4 of Technical report 05.13.B entitled "Maintenance and operation" and chapter 6 of Technical Report 2007R04 entitled "Organising operating staff", give more complete information on the subject of maintenance.
If they exceed a few hundred meters in length, road tunnels are to be provided with equipment for ensuring the safety of users under normal conditions or in case of disruptions 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.
The increasing variety of tunnel equipment means that life cycles may vary considerably from one type of equipment to another.
Some equipment may have a lifespan of more than 20 years (power supply, ventilation ...); others will only last a decade or so (notably equipment with a lot of electronics). For some, its lifespan may even be less than 10 years.
It is therefore essential to examine the lifespan of each family of equipment, with particular attention when this lifespan is low (10 years or less). The purpose of this review is to identify the factors that have a strong influence and that can be acted upon to ensure the lifespan of the product, or even improve it.
It is particularly useful to take into account factors such as temperature, humidity, mechanical stress and the environment.
A life cycle analysis can be conducted at different stages of the life of a tunnel (and its equipment):
Technical reports 2016R01 “Best practice for life cycle analysis for tunnel equipment” and 2012R14 “Life cycle aspects of electrical road tunnel equipment” provide further information on this issue.
The equipment of a tunnel is highly varied. From electromechanical equipment (power supply, ventilation, lighting ...), to operating equipment using more recent technologies (video surveillance, SCADA, automatic incident detection...), it requires more or less frequent interventions to maintain functionalities.
Interventions to be performed on equipment can be grouped into three broad categories:
Maintenance can be defined as a set of actions that maintain equipment in a specified state, restore it to this state or ensure that it can provide a specific service. These actions can be preventive in nature (referred to as preventive maintenance) or remedial (corrective maintenance).
Maintenance control, in the broadest sense, aims at ensuring that the maintenance actions carried out allow satisfactory operation of the equipment and that the financial resources allocated are adapted to requirements.
An assessment can be carried out by conducting technical inspections at specified periods:
The initial inspection must be carried out before equipment is put into operation. It aims, on the one hand, to check the quality and performance of the installations and, on the other hand, to ensure that the tunnel and its equipment comply with regulations, in particular with regard to safety.
The initial inspection, which provides a reference on the condition and performance of the tunnel at commissioning, should be followed by further inspections throughout the tunnel’s life. These inspections must be carried out periodically at an interval that may vary from one country to another, but which is, in most cases, of the order of several years.
The results obtained during these various inspections therefore make it possible to verify that maintenance is well adapted and that the expenditure and financial budget makes it possible to achieve the objectives set.
When the equipment approaches the end of its life, these inspections also enable refurbishment or renewal actions to be planned.
Further information on technical inspections can be found in technical report 2012R12EN: Recommendations on management of maintenance and technical inspection of road tunnels.
1. Responsibility of each operator
2. Commitment of each operator in the context of the overall maintenance strategy
3. Coordination between the Operators
Maintenance in complex tunnels is a holistic and interrelated issue where a contribution of one sector must be proactively complemented by the contribution of other sectors. The purpose of maintenance in underground and complex tunnel structures is to improve the serviceability of the infrastructure and to reduce operational costs. When maintenance is performed at the time of the tunnel life cycle it optimises the available equipment, minimises the risk of accidents and largely contributes to public safety. Tunnel operators, particularly those involved in the maintenance of large underground and interconnected infrastructures are reminded of the need to optimise their maintenance strategies and to enhance public confidence in the use of these infrastructures by making them safer, efficient and continuously available for use.
The strategic components related to maintenance in tunnel networks may be divided into four categories:
Each operator is responsible for the safety level of its infrastructure, which contributes to the overall level of safety of the entire complex. Each operator is responsible for informing the lead operator of its maintenance demands and the demands of the others. A global maintenance coordination plan should be established among all operators and adjusted to the individual operators. Focus should be on global benefits and minimizing the time of restricted tunnel operations is essential.
At same time, each operator has responsibilities that may be impacted by actions of other operators. The Lead Operator of the underground tunnel infrastructure is responsible for the overall co-ordination and communication process.
Each operator is responsible for managing and maintaining its own equipment. Each operator must establish the list of equipment under its responsibility and share it with the other operators.
Some equipment could be considered as strategic equipment, necessitating collective responsibilities. The list of this strategic equipment must be established, discussed and shared. It has also to be clearly defined who is in charge of what.
It is crucial to acknowledge that the collective efforts of operators will trigger combined responsibilities for all participants in the process.
The coordination process in the context of the underground interconnected complex tunnels entails the following:
a) Organizational Behaviour
There is a need to develop group work which is only achievable if the organisational behaviour is aligned to the needs of the infrastructure (refer to Operation of complex tunnels).
b) Maintenance of one has implications on the others
Best practices in tunnel maintenance will also require a coherent effort from the key players and stakeholders. This can be achieved by defining a set of principles and procedures set out in the operator’s procedure manual generally known as the inventory manual. Tunnel operators are encouraged to be acquainted with all key components of the inventory manual which are applicable to their functions and have been developed by PIARC over many years.
Fig 1. Snowstorm at the entrance of the Somport tunnel (Spain)
The considerations that impact the winter serviceability of road tunnels are both numerous and varied. The operator, whose mission is to ensure user safety, must therefore make every effort to counter the adverse effects of winter as well as ensure that users benefit from safe conditions in circumstances that are sometimes very difficult, such as extreme weather events. The operator must adequately coordinate its tunnel de-icing and snow-clearing teams, which can be challenging and slow in busy traffic. Visibility in tunnels further decreases during the winter months, as lighting fixtures become dirty and due to the spray deposits along the walls, which also affect surveillance cameras and air quality sensors. The operator must assure the operational availability of all safety and fire protection equipment, which must also be protected from freezing.
Fig. 2: Snow clearing of the Viger tunnel without traffic disruption – Montreal Quebec (Canada)Operational continuity is of the utmost importance for the operator. However, according to the nature of the problems experienced in winter, any major event forcing a closure or a reduction in operations will inevitably have repercussions on the entire network, resulting in socioeconomic costs related to delays and user complaints. More so than any other season, winter compromises operational continuity. A sound management of the network is therefore essential.
Communications make it possible to transmit information in order to facilitate the management of difficult situations. At all times, the operator must provide useful information to the media in order to quickly inform users of road conditions, closures and snow removal operations. In a transport organisation, efficient communications structured in a well-defined decision-making hierarchy make it possible to effectively manage extreme weather events that require major decisions, such as lane or tunnel closures, whether for safety reasons or de-icing operations.
Table 1 below presents a list of the particular problems inherent to the winter conditions that road tunnel operators must face. It also presents a non-exhaustive list of preventive and corrective actions, in addition to the usual constraints that operators must deal with when conducting operations.
| Problem | Preventive actions | Corrective maintenance | Constraints |
|---|---|---|---|
|
Water infiltration |
- Program to identify and seal leaks and infiltration - Monitor waterproof joints |
- Manage infiltrations - Install heated temporary pipes - Repair waterproof joints
|
- Maintaining traffic flow - Heavy traffic periods - Permit to close lanes temporarily for maintenance (closures usually at night or on weekends) - Difficult work conditions in road tunnels |
|
Formation of icicles or stalactites |
Locate icicles and stalactites and conduct de-icing operations as needed when user safety is compromised |
- Availability of snow removal teams and equipment - Heavy traffic periods - Permit to close lanes temporarily for maintenance - Difficult work conditions in road tunnels |
|
|
Frost or snow on the roadway - Unexpected slippery conditions in road tunnels - Motor vehicles and heavy vehicles have difficulty exiting tunnels during snowstorms, causing traffic slowdowns, traffic jams and accidents - Risk of skidding in sloped accesses, causing motorists to lose control, accidents |
- Inspection of snow removal equipment after use and before storage - Application of de-icing agents when precipitations begin - Installation and use of roadway de-icing systems (heating cables, hydronic heating, etc.) at tunnel - Predictive diagnostics to preheat equipment that is sensitive to extreme cold |
Remove and transport snow and apply de-icing agents (abrasives are to be avoided as they can block drain pipes) |
- Budget - Availability of snow removal teams and equipment (24/7) - Heavy traffic periods - Permit to close lanes temporarily for maintenance - Restrictions on the use of de-icing agents (environmental impact, toxicity, storage and application precautions, recovery, transport and destruction) - Efficiency of de-icing agents relative to temperature - Risk of damage to the concrete structure caused by de-icing agents (e.g. salt). |
|
Debris and formation of ice in drain pipes |
- Periodic inspection program - Clean pipes, bore holes as needed - Verify the operation of heating cables - Monitor low temperature alarms in protected systems |
- Flush pipes - Remove ice in gutters - Bore holes in pipes as needed - Replace defective drainage components |
- Maintaining traffic flow - Heavy traffic periods - Permit to close lanes temporarily for maintenance (closures usually at night or on weekends) - Difficult work conditions in road tunnels |
|
Accumulation of dirt on tunnel walls, ceiling and equipment, such as surveillance cameras, lighting fixtures, air quality sensors, signalling equipment, escape route indicators, etc. |
- Visual inspections - Maintenance operations, including cleaning surveillance cameras, walls and lighting fixtures outside busy traffic hours |
Maintenance operations, including cleaning surveillance cameras, walls and lighting fixtures outside busy traffic hours |
- Low temperatures - Heavy traffic periods - Permit to close lanes temporarily for maintenance - Restrictions on the use of cleaning products (environmental impact, toxicity, storage and application precautions, recovery, transport and destruction) - Efficiency of cleaning products relative to temperature - Difficult work conditions in road tunnels |
|
Corrosion of doors, anchors, equipment, cable and equipment mounts |
- Use of products and materials that are compatible with the aggressive environment in tunnels - Periodic inspection program - Use of stainless steel or composite components where applicable - Inspection and maintenance operations, including lubrification and/or rust protection |
Replace rusted components and equipment as needed |
- Standards applicable to road tunnels - Resistance to fire, water, humid and corrosive environments |
|
Cracking, fragmentation of concrete debris falling on the roadway, heaving of concrete slabs, contamination of concrete |
- Waterproof membranes - Protective coatings - Periodic inspection program with damage and contamination surveys - Surface repairs |
Repair the concrete Seal cracks Rehabilitate the infrastructure |
Budget Permit to close temporarily for inspections Maintaining traffic flow during work Degraded modes of operation Measures to reduce impact on users Difficult work conditions in road tunnels |
|
Increased energy consumption during winter, peak power demand and impact on the electricity network Uneven between seasons and impact on billing |
- Analyse and follow up energy consumption and peak power demand - Intelligent energy management system and measures to reduce demand - Selection of energy-efficient equipment - Use of alternative energy sources where possible and cost-effective - Storage of energy during low consumption periods to balance energy use - Technological watch |
- Budget and cost-effectiveness of performance-enhancing solutions - Availability of space for required equipment (e.g. storage) - Availability of alternative energy sources - Resistance to changing operational and energy consumption habits - Laws, regulations, political pressure, sustainable development |
|
|
Erratic operation of electronic equipment due to cold and humidity |
- Use of products that are compatible with the cold, humid and aggressive environment in tunnels - Monitor alarms - Periodic operational tests and calibration |
- Permit to close temporarily for inspections - Maintaining traffic flow during work - Degraded modes of operation - Measures to reduce impact on users - Difficult work conditions in tunnels |
|
Usually, the construction of roads through mountain ranges may require tunnels at high altitudes. Above 1.000 meters over sea level, special maintenance activities are required to provide acceptable traffic conditions inspite of the risk of snow or ice formation. This situation becomes critical in the proximity of tunnel portals.
At the north of the province of Huesca, in Spain, where several tunnels above 1.100 meters above sea level can be found, several important factors are to be considered to deal with temperatures which can go below -20ºC.
Water is the hardest enemy to fight: causing infiltration due to low temperatures, producing cracks and even spalling in vaults and side walls.
At the tunnel portal, an adequate construction of pavement and good quality of road painting are key factors for their durability. High quality materials are required because snow plough circulation and extreme meteorological conditions can cause their deterioration.
To fulfil the requirements of Rd635/2006, the transposition to the Spanish law of the European Directive 2004/54 on minimum requirements for road tunnels safety, several types of equipment must be installed which can be severely affected by malfunctioning or even breakdowns when needed.
Suspended power supply lines are exposed to ice formation which is the origin of outages which, if regular, can affect the durability of UPS and diesel generators.
Water tanks to supply fire hoses of the tunnel must be carefully constructed to avoid the appearance of cracks. In addition, continuous water circulation is advisable.
Water supply pipes must be protected with thermal protection and, if possible, emptied. Opening elements of fire hydrant and hoses can be also affected and the technical rooms containing pumping machinery should be above 0ºC.
In addition, proper maintenance of the vehicles used for operational and emergency purposes is crucial, including the use of adequate antifreeze products for motor and fuel and water tank protection.
And last but nor least, both the difficulties in the relief of the operation staff and appropriate clothing (not only warming or waterproof aspects but also visibility improvement) must be considered.
