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Tunnelling: Digging for growth

Tunnels have been at the heart of economic growth for over 150 years, and their long-term benefits should be taken into account when planning major infrastructure projects, argues Richard Coakley.

Tunnels have long been a powerful force in driving economic prosperity. In 1845 Joseph Locke created the first Woodhead Tunnel across the Pennines. It was one of the longest tunnels in the world, and helped transform the UK into an industrial powerhouse. More than 150 years later, chancellor George Osborne recently announced his support for a new cross-Pennine rail link, part of a wider plan to maximise economic growth across the North of England.

No doubt tunnelling will play an important role in such a scheme, using a 19th century innovation to solve a very 21st century problem.

A range of new infrastructure schemes is currently being mooted for the UK, with growth not limited to the transport sector. Rising demand for a cleaner, more sustainable supply of energy is driving investment in renewables and transmission schemes, many of which are likely to include tunnelling as a vital component.

Water cooling

Extensive tunnelling will also be required for water cooling systems at the UK’s new nuclear power stations. Add to this the strength of economies in a number of European countries, particularly in Scandinavia, and we look set for significant investment in tunnelled infrastructure over the coming years.

As with the pioneering Woodhead Tunnel, the demand for new infrastructure is often driven by the need for higher capacity and more efficient transport links. But what our 19th century forebears could not have predicted are the additional challenges we now face - such as mitigating the adverse impact of climate change - to which tunnels can often provide a feasible solution.

Tunnelling to protect against flooding in urban areas and tunnels to transfer water from wet to dry locations are just two examples of the important role underground infrastructure can play in tackling the effects of climate change. Large scale water transport from the North to the drought-prone South and East of England are considered by some as the key to securing a resilient and effective supply of water in the UK.

As world’s cities continues to grow, so too does the demand for new infrastructure. And with high land costs and limited available space, building underground is often the only option

A second issue contributing to an increase in investment for tunnelled infrastructure is the rapid rise in the urban population. As the number of people living in the world’s cities continues to grow, so too does the demand for new infrastructure. And with high land costs and limited available space, building underground is often the only option.

Take the East Side Access project in New York City, one of the largest infrastructure schemes currently underway in the US. When completed, the new branch to the Long Island Rail Road will provide a fast and easy commute from Long Island and Queens to the east side of Manhattan for more than 160,000 passengers every day.

The scheme includes extensive new tunnels driven in both soft ground and rock in Queens and Manhattan, a new 10 platform station below the famous Grand Central Terminal, the reconfiguration of Lexington Avenue subway station, a new station in Long Island City and the renovation of existing tunnels between 63rd Street and Queens Boulevard, all within a congested city environment.

The new station under Grand Central Terminal requires two very large underground adjacent arched caverns - each one 18m wide by 23m high - to facilitate the platforms and mezzanine levels. URS is delivering programme and construction management services for the major scheme, which involves more than 70 different design and construction packages.

Large scale underground projects like this are happening all over the world, from new rail networks developing across China’s largest cities to Crossrail in the UK. As well as helping to solve the problem of overcrowded public transport, Crossrail is set to add an estimated £42bn to the UK’s economy.

In addition to stimulating both long-term and immediate economic growth, underground infrastructure can also bring environmental benefits by minimising disturbance at the surface.

There are now more sections of tunnel on the proposed High Speed 2 (HS2) route than originally outlined in order to protect landscape in the Chilterns Area of Outstanding Natural Beauty.

Our Victorian sewers may no longer be fit for purpose, but their performance over the past 150 years is testament to the sustainable legacy that tunnelled infrastructure can provide

Similarly the Thames Tideway Tunnel is urgently needed to tackle overflows from London’s Victorian sewers and protect the River Thames from increasing pollution. This scheme will also help the UK meet European environmental regulatory standards, and there are similar projects proposed for Glasgow and Dublin.

Our Victorian sewers may no longer be fit for purpose, but their performance over the past 150 years is testament to the sustainable legacy that tunnelled infrastructure can provide. Numerous tunnels built by the Victorians are still in use, and present-day modifications are securing their future for many years to come.

The Connaught Tunnel, originally built in 1878 under the Royal Docks in London, is undergoing a refurbishment to deepen, strengthen and widen the structure so that it can be re-used for Crossrail. Planned upgrades to existing tunnels on the UK’s rail network are also adding to the UK’s pipeline of tunnelling work, with Network Rail’s electrification programme requiring the invert of many existing tunnels to be lowered to accommodate overhead line equipment.

Long term benefits

Such examples of long-term benefits help to demonstrate the financial viability of tunnelled infrastructure, which has traditionally been viewed as a costly alternative to above-ground options.

Yet rapid advances in technology and expanded capabilities have helped reduce the cost of tunnelling over the past few decades, making a much more compelling proposition.

Just as the introduction of modern tunnel boring machines (TBMs) transformed construction methods to allow longer stretches of tunnel to be bored much more quickly and with less disturbance, technology such as sprayed concrete lining has added to the efficiency of tunnelling methods and reduced maintenance costs by enhancing the durability of structures.

Such advances have also unlocked opportunities for construction in complex ground conditions, helping projects such as the proposed London

Underground Northern Line Extension to Nine Elms and Battersea become much more viable.

Skilled engineers

The upturn in tunnelled infrastructure investment we are experiencing is welcome news, yet major projects in the pipeline will require a large number of skilled engineers.

Decades of under-investment have contributed to a decrease in the UK’s tunnelling expertise. Given the importance of underground infrastructure to economic growth, closing this skills gap is the single biggest challenge facing our industry.

Initiatives such as the Construction Industry Training Board’s Tunnelling and Underground Construction Academy (TUCA), started by Crossrail in 2011, are helping to address this shortage. TUCA provides specialist training for those pursuing a career in tunnelling, equipping them with the necessary skills to work underground on Crossrail and other planned infrastructure schemes.

Retaining this talent will be key to the future success of the UK’s tunnelling industry. As a country, we can ill afford to repeat the stop-start investment pattern that saw the departure of many highly skilled tunnelling professionals to more buoyant markets overseas in the 1970s.

A long-term pipeline of work will allow the industry to recruit with real confidence that the demand for skills will be sustained.

The advancement of proposed infrastructure schemes designed to drive the UK’s economic prosperity will also help to future-proof the country’s tunnelling industry.

It is therefore welcome news that HS2 Ltd chairman Sir David Higgins’ report in October 2014 on the northern phase of HS2 will also include initial options for the trans-Pennine rail route.

My hope is that this marks further long-term investment in tunnelling and cements the future of the UK’s highly valued tunnellers.

  • Richard Coackley is business lines director at URS

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