Qatar's key infrastructure projects
William Skidmore looks at the $20bn of projects underway in Qatar
As Doha’s infrastructure roll-out gathers momentum, the importance of being able to build over- and underground is essential. William Skidmore looks at the estimated $20bn of projects underway in Qatar that focus on bridges, tunnels and interchanges
The most significant tunnelling activity planned in Qatar is for the Doha Metro project, which recently held a groundbreaking ceremony within developer Msheireb Properties’ Downtown Doha scheme. The ceremony took place at the site of a proposed metro station at Msheireb, which will be the hub for Doha’s proposed 85km, $3bn metro system.
Qatar Rail CEO Caad Ahmed al-Muhannadi said: “Phase 1 of the Doha Metro is scheduled to be operational in Q4 2019.” The $79m enabling works on the first phase of the project is being carried out by a JV between Austrian tunnelling specialist Porr Group alongside Qatari firm HBK Contracting and the Saudi Binladin Group.
The Msheireb Station will act as an intersection for all three of the proposed lines on the metro network, namely Green, Red and Golden. All three will be underground at Mshreib, with the Red and Green lines running parallel above the Golden line.
Al-Muhannadi said: “The Msheireb Station will meet the strictest criteria for sustainable design. Being underground will complement Msheireb’s aim to combine advanced technology with building practices that respect our local heritage and cultural traditions.”
A spokesperson for Qatar Rail’s own enabling works team said excavation works had commenced “without any difficulty or delay, mainly due to the meticulous planning and preparation over the past 12 to 18 months.”
The work will involve 60km of tunneling – a 30km route from New Doha International Airport via Msheireb and West Bay to Qatar University, and a tunnel from Msheireb to Education City, in addition to a tunnel running north from Airport City to Al Waab.
The first of a series of tenders to build elevated sections of the lines are expected to be issued before the end of the year, while tenders for the underground lines and stations are expected in Q1 2013.
Paul Groves is director and tunnelling network chair at Atkins, which employs more than 150 tunnel engineers across the world. Groves played a key role in the company’s tunnelling activities as lead designer of the Dubai Metro, which has set the benchmark for metro systems in the region.
“Until relatively recently there was not a track record of tunnelling in the Middle East, with the exception of some fairly large-scale highway cut-and-cover tunnels and small-diameter pipe jacking.
That all changed with the Dubai Metro, followed by Abu Dhabi’s deep sewerage tunnels, and this has provided a great deal of learning which will be fed into the next surge of tunnelling activity in Qatar.
“Cut-and-cover tunnelling is a tried-and-tested technique wthat remains a primary method of tunnelling for many types of projects throughout the world. However, the Dubai Metro saw the first use of tunnel boring machines (TBMs) in the region.
These can provide a number of advantages, particularly in urban areas, including Downtown Doha. TBMs all essentially perform the same task: they cut the ground and remove spoil, while allowing safe building of the tunnel lining rings, and they manage ground movements and control groundwater.
“This is all achieved in a tightly controlled process and at potentially rapid advance rates. Through the use of TBMs in Dubai, we managed to maintain high advance rates, while minimising settlement to just millimetres, including the underpassing of building piles,” explains Groves.
“Also very recently, drill-and-blast methods were used for excavating hard rock for UAE road tunnels – for example, in the Hajar Mountains of Sharjah.
“One of the key characteristics of tunnelling in the Middle East, including Doha, is the fact that the ground conditions are chemically aggressive, and this affects the tunnel linings.
This is an important consideration during the design phase, because you have to tailor the lining design to suit the conditions. Studies will need to be undertaken to understand exactly how aggressive Doha’s ground conditions are.
“There are also significant voids in the ground, and these need to be handled in the design and construction phases as well. While these do pose challenges, they are very much within the normal parameters of modern, international tunneling, and for tunnel engineers it is what makes the job interesting,” says Groves.
He elaborates on the cut-and-cover process: “Traditionally, you start with a temporary retained deep excavation, then build the concrete structure from the bottom up, before installing the roof slab and covering it over again.
Sometimes, however, it makes sense to adopt a top-down approach to building cut-and-cover tunnels. This involves the installation of permanent diaphragm walls from ground level, followed by excavation down to the tunnel-roof slab level, using temporary strut restraints.
The roof slab is then cast before the lower part of the excavation has been dug out down to
base-slab level. In some instances, this approach can simplify construction sequencing, while still providing lateral restraint, which is more supportive of sensitive buildings and structures.”
In terms of mechanised tunnelling, Groves says: “Modern TBMs both support the tunnel face and erect the tunnel lining behind it. The TBM’s shield enables you to build the permanent lining in free air and dry conditions, without the ground and groundwater applying any load to it, until the ring is complete and expelled from the shield as the TBM advances.”
Groves adds that mining methods, also known as NATM (New Austrian Tunnelling Method), can be used in competent soils and rock that can be excavated by hand or mechanical breakers or backhoes, and which typically involve temporary shotcrete, steel arches or other elements and a separate permanent concrete lining.
The main risk revolves around the management of ground movement. Highlighted as one of the most important parts of Qatar’s infrastructure development, bridging, tunnelling and interchange projects have been allocated some $20bn, helping to bring cohesion to the country’s burgeoning rail, road and urban transportation systems.
The necessity of these mega projects, ranging from entire underground networks through to international bridges, is not only important to the development of the region, but also to realising Qatar’s National Vision 2030:
Doha Metro Network
As one of the most high-profile rail-network developments in the world, Qatar Rail recently announced tenders for four tunnelling packages, heralding the beginning of Phase 1A of the Doha Metro. The network, which will eventually span 200km of track, will comprise 110km of tunnelling and elevated tracks, eventually offering a sustainable public transport network for Qatar’s east coast.
While there have been some initial delays, it is estimated that the first TBM will break ground in late 2013, with the aim to deliver the initial 75km of Phase 1a in advance of the FIFA inspection 2020.
Lusail Light Railway Transit Network
Not only offering an efficient transportation system for residents of this hi-tech urban development, the LLRTN will also interconnect with other rail networks in Qatar. The network comprises four tram lines running both over and underground, stretching over 30km and connecting 36 passenger stations.
The tunnelling aspect of the network will be focused in the southern part of the city, where there will be over 5km of underground railway. Estimated to cost $1.8bn, both bridges and tunnels will be essential to the completion of this network.
Doha Bay Crossing
As one of Qatar’s proposed mega projects, the Doha Bay Crossing was conceived in order to alleviate congestion between the New Doha International Airport and the West Bay area which, according to proposed statistics, will be unsustainable for the Corniche and ‘A’ Ring Road to handle. The Doha Bay Crossing will comprise a 5km tunnel running under the city before surfacing onto a 6km bridge crossing over Doha Bay.
Lusail Expressway Project
The Expressway has an estimated cost of $960m. It comprises dual four lanes, and will connect the three significant interchanges of Al Wahda, Onaiza and The Pearl. This mammoth contract is being carried out by Hyundai Engineering & Construction, with CDM Smith providing supervisory services.