Etihad Rail's mighty mole bores through Hajar mountains to pave way for tracks

The gaping mouth that leads into a vast tunnel deep into the heart of the Hajar Mountains is the beginning of one of the region’s largest and most ambitious engineering projects.

China Civil Engineering Construction Corporation, the construction partner of Etihad Rail, began boring into the mountainside near Fujairah in early 2020.

By the end of 2021, just two years later, the project connecting the eastern seaboard with the rest of the UAE by rail is on course for completion.

Specialist tunnelling teams, using a huge tunnel boring machine called a mega-mole, with giant drill-heads, have been working 24 hours a day to drill, excavate and clear almost 7 kilometres of cavernous shafts.

At 1.8km long, T1 is the largest of nine tunnels carved through this stunning corner of the Emirates.

It took construction crews more than 300,000 man hours to remove about 500,000 tonnes of rock — an amount similar in weight to all the materials used to build the Burj Khalifa.

This slice of the network is known as Package D, and has demanded the most technical construction of the nationwide railway to date because of the soaring Hajar mountain range that stands in its way.

While tunnelling through mountains is far from an engineering first, it has been one of the most challenging construction projects seen in the country to date.

Loose rocks were drilled and blasted by explosives to leave a hole measuring 14m in diameter.

Expert teams then followed with giant tunnelling machinery to secure loose rock, spray concrete scree and fit waterproofing membranes to prevent tunnels from flooding during mountain storms.

Once that was in place, a concrete facade was fitted to the face of the tunnel before electric lines with water pipes and drainage channels were added.

Train tracks will finally be secured to edge the project closer to completion.

A circular scaffold frame can now painstakingly move through the tunnel, allowing workers to operate safely through the walls of the snaking shaft of T1.

Despite the intense 45ºC heat in August, air conditioning and blowers keep the chamber free from dust and the worst of the scorching temperatures outside. Engineers are able to work comfortably in shifts, around the clock.

The tunnel is big enough to carry two-tier trains, for freight and passengers, with a series of emergency escape tunnels bored out alongside each of the main passageways.

Elsewhere in Package D, there are 54 bridges and 20 animal crossings.

Further work towards the completion of the rail network elsewhere in the UAE is likely to continue for years.

Eventually, Etihad Rail will stretch across more than 1,200km of track from Ghuweifat on the Saudi Arabia border, through Abu Dhabi and Dubai, while connecting Sharjah, Ajman and Ras Al Khaimah with Fujairah through the Hajar Mountains.

Universal tracks, infrastructure and tracking systems across the GCC will eventually make the network fully operationally throughout the region.

Crucially, it will connect Abu Dhabi's Khalifa Port and Mussaffah with Jebel Ali port in Dubai and the Port of Fujairah — taking up to 375,000 vehicles off the roads and cutting greenhouse gases by more than 2.2 million tonnes annually.

The Etihad Rail is being built in three phases.

It was established in 2009 and the first phase, a 264km stretch between Al Ruwais and the Shah and Habshan gasfield in Abu Dhabi, became operational in 2016.

In December 2019, Etihad Rail awarded a Dh4.6bn contract to the Chinese joint venture to work on the 145km link alongside the borders of Sharjah, Fujairah and Dubai, which includes building 15 tunnels through the Hajar Mountains with a total length of 16km, as well as the construction of 35 bridges and 32 underpasses.

World's top five tunnels

The 7km network of tunnels through the Hajar Mountains has been an engineering challenge, but it is not the longest or largest of mountainside excavations.

1 Gotthard Base Tunnel, Switzerland

At 57km long and plunging to depths of 2,300m under the Swiss Alps, Gotthard Base is the world’s largest and deepest tunnel.

Connecting the Swiss towns of Erstfield and Bodio in the north and south of the country, train times between Zurich and Milan have been slashed by an hour.

2 Seikan Tunnel, Japan

Another railway tunnel, Seikan is a 53km concrete conduit, with almost half built 140m below sea level spanning the Tsugaru Strait, connecting the islands of Honshu and Hokkaido.

Work began on the 53km tunnel in 1964 and took 24 years to complete.

3 Channel Tunnel, United Kingdom and France

Connecting Folkestone in Kent with Calais in France, the ‘Chunnel’ runs for 50km.

The undersea tunnel brought a viable alternative to ferries and short-haul flights for millions of cross-channel travellers.

4 The Laerdal Tunnel in Norway

At 24.5km the Laerdal is the longest road tunnel in the world and takes about 20 minutes to drive through.

Work began in 1992 and eight years later, the first motorists were cruising between the two largest cities in Norway, Oslo and Bergen. Special lighting along chamber walls helps keep drivers alert at the wheel.

Like the Etihad Rail project, difficult terrain and the high risk of rock falls technically challenged engineers during the construction phase.

5 Tokyo Bay Aqua-Line, Japan

This may look more like a bridge than a tunnel as a 4.4km bridge section dips into a 9.6km subsea tunnel.

The $1.2 billion roadway connects the city of Kawasaki with Kisarazu across Tokyo Bay. It is the world’s fourth-largest underwater tunnel and slashed travel times between the two cities from 90 minutes to just 15 when it opened in 1997.