Between a rock and a hard place

The challenges engineers face tunnelling through the mountains between RAK and Korfakkan.

BORED OUT: Geological challenges
BORED OUT: Geological challenges

The mountain range between the furthest reaches of Ras al Khaimah and the port of Korfakkan is throwing up a few engineering challenges for those that want to tunnel through it.

There's an old puzzle, developed by a guy named Edward DeBono for management problem solving. It goes 'Tom won't come to the mountain'.

Men in suits then have to think of solutions, but we are guessing that few will say  'Track in several drill Jumbos and dynamite to blast through the Mountain to see Tom,' That, however is exactly the plan for the Diftah-Shis tunnel project, though 'Tom' in this case is the village of Shis.

Although just 11.5 km long, the project is reckoned to be the most difficult road-builds in the Middle East. In short, the problems facing this project can be summarised in to that of geography both political and physical.

Politically, the project needs to skirt around the Oman border, which makes the route harder than it is supposed to be. As a result, the road takes a circuitous route, carving through the punishing terrain of the Masafi hills.

The detour means that the road has to be taken through a series of wadis and straight through a mountain.

Contract

The Government of Sharjah awarded the first phase of the project to Iranian contractor General Mechanic Co. (GMC) under supervision of Halcrow International, while a third company, Gulf Rock acts as a subcontractor.

Some unusual problems are faced by the team. Rain is not often a problem in the UAE, but in the mountains, some 600 metres above sea level, it can be. Flash floods fill the valleys, meaning that there is even more rock to be drilled than usual in order to get the machines.

The new highway in phase I is predominantly routed through wadis and this too is not without problems.

According to the site manager, Mr. Arash Foroozan Yazdani, the contractor is on constant alert throughout the rainy season, even when there is no sign of rain. "It is very difficult" he explained.


In the past, torrents of water have come crashing through the valley, destroying a number of prepared access roads, even though the sun was shining above the site.

A condition of the contract was to keep the wadis wherever possible, which means placing culverts up to 140m long wherever it is necessary to reroute.

Sometimes though, the wadi has to be permanently re-routed. This means no let-up for the machines, which work more than twelve hours a day, seven days a week.

On our visit, the machines had been allowed a brief period of rest, as the noonday sun was beating down and the workers by law had to stop. A Tadano 40-ton all-terrain crane sat in the wadi, while on the trail that is to become the main road, a Cat 16G grader of indeterminable vintage, basked in the heat.

Flooding

Despite the warmth, the risk of flooding constantly hangs over the site manager's heads, so equipment is parked on high ground when not in use. However, when the machines are running, the access roads are prepared with a Komatsu 'dozer.

Often it is necessary to first widen the path with a digger, in this case a Hitachi Zaxis 35 ton machine, fitted with a Sandvik G88 breaker attachment.

Once the pass is sufficiently wide, the 'dozer is re-engaged to clear the access. The breakers continue to provide essential service breaking through the rocky outcrops to permit access for the dozer on steep gradients.

Three hydraulic surface drills, including a new Tamrock CHA560 are operated over the rocky surface.

However, by far the most challenging part of the project so far is carving out two giant tunnels, each 1.2km in length, cleaving straight through the rocky mountain.

The problems have been partly geological, A low Rock Quality Density (RQD) meant progress was never going to fast, but extra safety requirements and red tape have also hindered the blasting.


At the beginning, work was delayed as the explosives store had to be upgraded and an armed guard put in place. In addition, local police have to be on site while the blasting is done, limiting the amount of time that operations can take place.

These factors, coupled with the price of diesel and other materials going up mean that the project is set to cost around double the original estimate.

Drilling

To actually make the tunnel, takes some serious work. So far, both tunnels measure about three hundred metres long. The way of blasting a tunnel takes a little explaining though.

Back in the Victorian days, holes were 'drilled' by men hitting steel piles into walls. The spikes would then be removed and the holes filled with dynamite to blast the rock.

Later, the number of men on site was reduced by the invention of steam drills, which were in turn replaced by electric or pneumatic units.

However, it wasn't until the 1930s when the Hoover Dam project was underway that the concept of the 'drill jumbo' was introduced.

Originally, these were Model-T Fords fitted with an enormous square frame around the pick up bed, where half a dozen men would stand and drill blasting holes in the rock face. Modern machines, however are almost completely automated with giant drills controlled by a junction of hydraulics.

The giant Tamrock machine on site at the time of our visit, looked like something out of a science fiction movie, with its scarred mining-orange paint, nests of pipes and faint smell of heavy oil.

The machine could support three drill heads, though it had just the two when we saw it, both equipped with Sandvic HL510 hydraulic rock drills. Later in the project, this jumbo will be joined by another Sandvic product, a CHA 560 which has recently been ordered.

Blasting

Blasting is of course an exact science, because if the wrong amount of explosives are used at best, the bore of the tunnel will be incorrect and a lot more finishing will be required, and at worst, there could be a collapse.


After each blast, where several hundred tonnes of rock is brought down, a specialist with some gas checking equipment is sent in.

After these checks, and an analysis of the geological conditions are carried out, it is time to send in a Cat 996E wheel loader to remove the rubble, which is then dropped into to one of two waiting Volvo A25E articulated dump trucks.

It is also worth noting that no spark-ignition vehicles are allowed in the tunnels. The power source has to be either diesel or electric.

The next step is to coat the stretch of excavated tunnel with a special wet-mix concrete, applied with a high pressure gun.

This substance is known as 'shotcrete' and was originally invented in the 1920s by a taxidermist who wanted to quickly fill his dead animals with plaster! Today, it is used in building projects all over the world and is applied in this instance on an industrial scale, via a Putzmeister-style concrete pump.

After the nozzleman has done his work, micro-piles have to be hammered in to the tunnel, to further ensure the integrity of the structure. After this, it is then time to do it all again, if the project is going to meet it's 25m per day schedule.

As the tunnel is built, it will be time to think about phase two of the project. Contracts have not been awarded for the stretch, which winds around the Omani border to the busy port of Korfakkan.

Currently under design, the next stage will continue from Shis village to the port covering a further 19 km and feature 5 km long twin tunnels.

Just like phase one, the road will cut through slopes, under mountains and across Wadis, but despite the engineering challenges, the Sharjar government are prepared to bankroll it in order to open up the port and town.

So, next time you take a drive through the northern Emirates, just think what is involved in preparing the road in front of you.

Where is it?

Khorfakkan is actually an exclave of Sharjah, while Diftah on the other hand is in Ras Al Khaimah, while an exclave of Oman prevents the road from going to its final destination directly.

To make matters worse Sharjah has an exclave in the Oman enclave... Confused? We certainly were, but the short of it is that the road is being paid for by the government of Sharjah, but can't be build through the most direct route, due to the Oman border.

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