Eng. Essa Al Maidoor explains microtunnelling

Technique played significant role in development of the country

Eng. Essa Al Maidoor, president of the UAE Society of Engineers.
Eng. Essa Al Maidoor, president of the UAE Society of Engineers.

Microtunnelling will continue to be a technique that allows the UAE’s urban landscape to evolve in a cost-effective and non-evasive manner, Eng. Essa Al Maidoor, president of the UAE Society of Engineers told Construction Week.

Al Maidoor, who is also director-general of Dubai Health Authority and chairman of Noor Dubai, said microtunnelling has played a significant role in the development of the country. He singled out projects like the Dubai Metro that have helped to establish it as a successful method.

“Tunnelling as a technology in the UAE has been deep in our history up to the early 90s, when we used thrust boring and auguring of roads. With the development of the cities and the growth that we have, the development in tunnelling technology has made it possible for us to move forward from those basic techniques.

“We came up with Dubai Metro, which was in part done by microtunnelling, and this saved a lot of headache and disruption to infrastructure, the environment and people’s lives.”

Al Maidoor said that the expansion of Dubai Metro and also the proposed Abu Dhabi Metro would undoubtedly utilise microtunnelling.

“There are major projects going to come up in the UAE like tunnels for sewerage rather than simple piping,” he added. “All the flow goes in one unique pathway under the ground. Nobody sees it, nobody feels it.”

Part of the society’s role is raising awareness about tunnelling, so it is hosting an Abu Dhabi conference in December with the International Tunnelling and Underground Space Association (ITA).

“The event will bring experts from all around the world talking about the potential of microtunnelling: the techniques, the latest developments,” said Al Maidoor.

“As you know, the development in IT and electronics impacts many fields, especially microtunnelling where you can now be extremely precise and faster and cheaper.”

The society is also working with local universities to ensure engineering students are exposed to industry developments.

“So these students in their senior engineering years benefit a lot with the events which we hold,” said Al Maidoor.

“They participate in these seminars and conferences and are exposed to the latest industry issues and trends, and experts.”

There is also the work going on at a regional level through the Gulf Engineering Union and the Federation of Arab Engineers.

“In the GCC we learn from each other because we have a lot of similarities when we talk of engineering: environment, temperature, humidity, rock type etc,” said Al Maidoor. Meanwhile, engineering firm CH2M Hill said it is making steady progress on a major project that involves extensive tunnelling – Qatar’s Inner Doha Resewerage Implementation Strategy (IDRIS).

CH2M Hill has an eight-year contract (2012-19) to lead all project management and engineering solutions of the scheme worth in excess of $2.7bn (QR10bn).

IDRIS is a plan developed by Ashghal, the country’s public works authority, to upgrade and expand Doha’s sewerage infrastructure network and to accommodate projected population growth, with an additional 1mn people or so set to move into Doha’s oldest area – the south catchment.

The IDRIS scheme is comprised of lateral sewers that will be used to intercept flows and relieve an existing overloaded system. The flows will be conveyed by gravity via the main trunk sewer and will travel over 45km south to a terminal pump station located at the downstream end of the tunnel, then lifted to the new Doha South Sewage Treatment Works (STW). The sewage will be reclaimed as treated sewage effluent (TSE) and returned to the Doha metropolitan area, with the treated water recyclable for irrigation purposes.

The major tunnelled interceptor sewer (MTS) and advanced sewage treatment works scheme will meet the long-term demands of the Doha South catchment for the next 50 years, eliminating the hydraulically-overloaded conditions that currently result in surface flooding, and disconnecting foul sewage flows from over 30 pumping stations.

With regards to current progress, the main trunk sewer contract (MTS-01, MTS-02, and MTS-03) was released earlier this year with closing dates for two contracts in July 2014 and the third set for the beginning of September. The award of all three contracts is expected to be announced by end of this year or early 2015.

A total of 10 huge tunnel boring machines (TBMs) will be employed to construct the MTS: six TBMs to build the central and southern segments (MTS-02 and MTS-03) and four TBMs to construct the northern branches (MTS-01).

Other contracts on the project include the work to develop the IDRIS terminal pump station (TPS) and STW; the lateral interceptor sewer contracts (LIS-01, LIS-02, and LIS-03), with the closing dates for these set for the end of Q3; and the post-contract professional consultancy services.

With regards to the lateral interceptor sewer contracts, construction work will involve excavation through microtunnelling and pipe jacking, with varying diameters ranging from 400mm to 2,400mm, and the construction of approximately 280 shafts. The sewers will be located within the public right-of-way, adjacent buffer zones and allocated utility corridors.

As of the end of July 2014, IDRIS had 26 full-time staff in its programme management office and was utilising another 117 reach back resources on a part-time basis from office locations in the region and from around the world. Additional staff will be joining the team over the next few months.

IDRIS’s TBMs will (of course) be burrowing underneath the city at the same time as around 25 other machines working on various lines of the Doha Metro. Delivery of the first 21 of these took place by April, with four more arriving in June. These are currently being assembled, with a view to the first excavation works taking place later this year.

Elsewhere, formwork firm Doka said its new tunnel formwork, DokaCC, has been developed especially for for the open construction method also known as cut and cover method.

Doka said it allows for quick, efficient and safe construction of various traffic tunnels, in particular in initial approach and gathering areas of underground railways. It has been used for station buildings on the Lusail LRT project and the Metro in Algeria.

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