What Is Tunnel Rehabilitation And When Is It An Option?
Tunnels are amongst the greatest, most ambitious and most important pieces of transport infrastructure ever constructed, requiring extensive work not only to bore the tunnel, but also networks of vulcanised conveyor belts to ensure that debris is safely and efficiently moved.
In general, this aspect of construction disproportionately focuses on new tunnels, in part because they are where efficient construction technology is needed the most and where equipment such as tunnel boring machines is used most extensively.
However, it is also important to focus on what happens to older tunnels, particularly if they end up becoming redundant or are otherwise no longer used for their intended purpose.
The question of whether to fix a tunnel, extensively update it or replace it entirely is one that is asked whenever an important tunnel reaches the end of its operating life, or it increasingly strains against the demands and needs of a growing number of users.
However, whilst repairs are often used as a stopgap to buy time, and replacements are often extensive infrastructure projects, rehabilitation is not as commonly discussed as an option as perhaps it should be.
What is tunnel rehabilitation? When can it be considered? And does any rehabilitated tunnel necessarily have to be used purely as a transport link?
What Is Tunnel Rehabilitation?
Historically, there has been an all-or-nothing approach to tunnel construction; tunnels are constructed, used for as long as they can reasonably be repaired, and then they are either left disused or demolished entirely, whilst a brand new tunnel is built in their place.
This can be problematic and can lead to a not-insignificant level of disruption if the repaired tunnel is barely fit for purpose.
The Blackwall Tunnel, originally constructed in 1897, is a prime example of this, as the original tunnel is infamous for its levels of congestion due to the vast numbers of people travelling north across the River Thames, but replacing it entirely is unfeasible for the exact same reason.
Similarly, larger tunnels are years-long projects, sometimes taking a decade or more to be completed, which is often an unacceptable timeframe to spend with diversions or major transport links if the existing tunnel is a vital artery.
Tunnel rehabilitation is a middle-ground approach, consisting of far more extensive repairs, rationalisation and widening of existing tunnels to increase capacity, remove deteriorated sections and allow for less restrictive use, whilst maintaining the fundamental structure and architectural features.
When Is Tunnel Rehabilitation An Option?
Tunnel rehabilitation is typically considered on a case-by-case basis, as it requires an intensive survey of the tunnel’s existing condition, the condition of the surrounding area and a survey of the work necessary to minimise or eliminate the conditions which led to the deterioration of the tunnel in the first place.
Whilst there are cases where a tunnel has become so eroded or is facing such extensive damage that it is either impossible or economically infeasible to rehabilitate it, most tunnels can typically be expanded, regenerated and brought up to modern standards.
Examples Of Successful Tunnel Rehabilitation
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- The Thames Tunnel, originally designed by Marc Brunel (Isambard Kingdom Brunel’s father), was extensively rehabilitated in 2007, improving the lighting, ventilation and foundations whilst keeping its original architectural features intact.
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- The Park Avenue Tunnel in New York City was almost as old as the Thames Tunnel and had been in consistent operation for essentially its entire life. In 2014, it was refurbished extensively, widened and made more structurally sound.
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- The Whiteball Tunnel in Somerset was subject to extensive rehabilitation works to improve its structural stability and drainage to minimise future flood risks and water damage.
Can Tunnel Rehabilitation Revive Disused Tunnels?
When tunnel rehabilitation is discussed, it typically involves tunnels that are actively being used and are featured in transportation and infrastructure plans. However, is that always a necessity when considering rehabilitation?
Tunnels are huge, historically significant and sometimes visually arresting pieces of architectural infrastructure that are important to preserve and maintain for reasons that go beyond transportation.
Sometimes, rehabilitation is necessary to stop them from falling into disrepair and disuse due to the inability to safely preserve them, and this can often prove to be a highly beneficial and financially lucrative course of action.
The Thames Tunnel is a prime example of this; whilst it is no longer necessary to get around London, it has thrived as a historical artefact and pedestrian access route in its own right.
This is similarly the case for when the Paris Catacombs were rehabilitated to better serve as a tourist attraction, as well as the Cu Chi Tunnels in Ho Chi Minh City, Vietnam, which were initially makeshift tunnels used by the Viet Cong and have been preserved as a living museum.