Tunnelling on the Doha Metro mega-project is complete following final breakthrough of the last machine on the Red Line South. Sunday’s historic achievement (25 September), witnessed by a host of dignitaries including the Prime Minister and Interior Minister of the State of Qatar, completes 111km of mechanised tunnelling using 21 Herrenknecht EPBMs.

Final breakthrough celebrations at Hamad International Airport

A total of 70,071 tunnel rings, comprising 470,497 individual segments, have been required to line the tunnels of the four new underground lines that make up Phase 1 of the ambitious project. Overall completion now stands at 50% as attention turns to track fit-out, M&E and station construction.

Eng. Abdulla Al Subaie, Managing Director and Chairman of the Executive Committee of project owner Qatar Rail, said: “Qatar Rail’s achievements and its ambitious plans are made possible through the leadership and continuous guidance of His Excellency Sheikh Abdullah bin Nasser bin Khalifa Al Thani, Prime Minister and Minister of the Interior of the State of Qatar and the Chairman of Rail Steering Committee; and His Excellency Jassim Saif Ahmed Al Sulaiti, Minister of Transport and Communications and Vice Chairman of Rail Steering Committee.

“The end of tunnelling marks an impressive milestone in the progress of construction of this important project, and I would like to congratulate all those involved in making this milestone happen. It has been made possible due to the combined efforts of the entire Qatar Rail team and its JV contractors. This is an incredible feat of engineering and I am especially proud that the tunnels have been built to a world-class standard with the very highest standards of quality and safety having been achieved.”

Doha Metro achievement in review

He added: “Tunnelling for the Doha Metro began just over two years ago and has seen a record-breaking 21 TBMs work to achieve this milestone. The Doha Metro project is a vital part of Qatar’s long-term plan to support a growing economy while improving the lives of the country’s residents. The achievement of this significant milestones brings us one step closer to its much anticipated delivery.”

Dr. Eng. Saad Al Muhannadi, Chief Executive Officer of Qatar Rail, said: “Completion of tunnelling on the Doha Metro is yet another major milestone for the project and one we are delighted to have achieved on schedule. As of now 7.5km of viaducts have been installed, and base slab and foundations have been completed on 33 of the 37 stations. Rooves have been completed on eight stations and roof slabs are progressing at 27 others.”

Phase 1 of the Doha Metro is expected to open in 2020, ahead of the country’s hosting of the Soccer World Cup in 2022.

Final breakthrough on the ambitious Doha Metro project in Qatar is just weeks away, with only two of the total 21 Herrenknecht TBMs procured by the owner to complete the twin running tunnels still in operation.

Final Green Line breakthrough at Education City in March 2016

Abdulla Ali Al-Mawlawi, for project owner QRail, told TunnelTalk that a final breakthrough ceremony at Terminal One of Hamad International Airport is planned for the end of September 2016. It will be preceded a few weeks earlier, at the beginning of September, with a penultimate breakthrough ceremony in the same location when the first of the last two operating machines completes its drive.

“Total tunnelling completed as of 1 August 2016, is 110,723m, with just 789.5m remaining to complete all underground excavation on Phase 1 of the Doha Metro project,” said Al-Mawlawi.

When the last machine emerges for completion of the 12km of twin-running tunnels that comprises the Red Line South as the last of four underground lines to be completed as part of Phase 1, some 112km of mechanised excavation will have been accomplished in the 26 months since the first TBM launch on the Red Line North in July 2014.

Fig 1. Four lines of the 72km Doha Metro Phase 1 (56km underground)

Fig 2. Phase 2 of the project, dotted line are underground sections

The 72km-long, 37-station first phase of the project (Fig 1), which set a world record for the number of TBMs working simultaneously on a single project when all 21 machines were in operation in August 2015, concentrates on construction of the central underground infrastructure at the heart of Doha. The project remains on schedule for the four-line system (Red Line North, Red Line South, Green Line and Gold Line) to be open and in service in 2020, a year later than originally scheduled but two years ahead of when the Qatari capital city is due to host the 2022 Soccer World Cup.

The metro network will be extended in Phase 2 with an all-underground circular line, the Blue Line (Fig 2) and an addition of underground, elevated and surface level extensions to all four of the Phase 1 lines that are currently under construction.

QRail remains uncommitted about the procurement schedule for Phase 2, which has a planning stage completion set in 2026. Al-Mawlawi confirmed to TunnelTalk that construction of the Blue Line is included in a second phase that will see the addition of 100 more stations and 40 more than previously announced, and adding: “Our focus for now in on Phase 1 so we will answer any Phase 2-related questions at a later stage.”

In addition to the 56km of twin tube underground alignment, Phase 1 construction includes surface and elevated alignments that extend the Red Line North a further 6.5km as far north as the waterfront residential and commercial development of Lusail City for connection with the Lusail LRT which is also under construction. This new tram-based system, comprises four lines with 37 stations and 10km of the 38km network in double-track underground alignment.

Completion of Red Line North, March 2016

Capturing the Red Line North breakthroughs

Further contracts for a 3km surface and elevated extension of the Green Line from Al Riffa westwards to the Al Rayyan Stadium, and for 6.5km of surface and elevated alignment out to Al Wakra at the southern end of the Red Line South, are nearing completion.

TBMs

For completion of the 112km of underground excavations, QRail, as owner of the project, procured all 21 EPBMs from Herrenknecht of Germany, with cutterhead diameters ranging from 7.05m to 7.11m. Selection of EPB technology was based on the expectation of a soft ground geology comprising Simsima Limestone and Midra Shale, with mechanised excavation proceeding at relatively shallow depths of an average 20m, and through a high groundwater table, especially in coastal locations.

Continuous conveyor mucking systems were supplied by H&E to some of the contracts with others, the other using rail-bound mucking systems. VMT provided systems to all TBMs for navigation, monitoring, communication and process data management. Emergency refuge chambers on board the 21 TBMs were supplied by MineARC and the segment moulds and handling equipment in the segmental lining casting yards were installed by Herrenknecht Formwork. For the contracts with continuous conveyor mucking systems, multi-service vehicles by MSD/Techni-Métal Systèmes provided in-tunnel transportation of men, materials and segments to the advancing TBM headings.

Acceptance of Red Line South TBMs in Feb 2014

The first machines leave the Herrenknecht factory in Schwanau, were the five machines for the Red Line South (RLS), and event that with TunnelTalk attended and reported on in February 2014. The original program called for an early start on the Red Line South to facilitate addition of a 3.3km spur tunnel between Al Matar and Airport City within the contract. This spur, however, has not been built as planned, and will now form part of the Phase 2 Blue Line as originally envisaged.

By the time final project breakthrough is achieved, the TBMs used on the project will have recorded 45 intermediate breakthroughs, numerous TBM transfers, and 31 final machine breakthroughs. Al Mawlawi told TunnelTalk that as each machine completes its scheduled drives it is dismantled and all parts returned to the Herrenknecht maintenance facility in Doha for recycling or sale. New machines will therefore need to be procured for excavation of the Blue Line.

Program challenges

Progress across all four lines has been rapid, with the TBMs recording up to 30m/day at peak performance. On the Green Line a best daily rate of 60m was recorded by Porr of Austriawhile on the Red Line North a best daily advance rate of 42m was achieved by Salini Impregilo.­ The best daily rate of 43m and a project-best single machine monthly production rate of 920m was achieved on the Gold Line by tunnelling subcontractor Seli Overseas.

Last Gold Line breakthrough by subcontractor Seli Overseas (May 2016)

In spite of the immense achievements, the project has not been without its challenges. The most serious incident for the tunnelling works occurred in April last 2015 when progress on the Red Line South was stalled for three months following a flood event at al-Bidda Station on the Red Line North contract. The inundation of ground water and material through the screw conveyor when a technical fault prevented closure of the discharge gate, left the TBM completely submerged, and once recovered, repair required complete replacement of all electronic components and delivery of more than 1,000 spare parts from Germany.

As part of the contractual experience, earlier this year, in May, Spanish contractor OHL, as a partner in the Samsung/OHL/Qatar Building Company JV that was awarded the contract to build the two largest stations on the network at Education City and Msheireb, announced to the London Stock Exchange that QRail had terminated its contract on the grounds of “non-compliance of certain contractual obligations.” The contract has since been taken over by the Consolidated Contractors Group, with OHL now involved in a legal dispute with QRail.

TunnelTalk will continue to monitor progress as the project nears its final TBM breakthrough and on towards official opening of services on the network in 2020.