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Compact and powerful: The FlexiROC T20 R drilling dewatering holes in the confined space of the Green Line tunnel.
The first construction phase of the new Doha Metro is progressing according to plan as three of the four tunnels in the network begin to take shape.
The Green Line, also known as the Education Line, was one of the first projects to get under way. It consists of twin tubes running into Doha from the south before bearing off westwards, through the university district, and on to the Al Rayyan sports stadium.
This is also the line that will transport many thousands of football fans to and from the stadium during the FIFA world Cup in 2022.
Like all of the tunnels in the system, the Green Line has an inner diameter of 6.17 m and a total underground length of 37 km (2 x 18.5 km). It is also being driven at a depth of about 20 m through soft rock – a mix of Simsima limestone, Midra shale and Rus formations.
進捗はスケジュールどおりですが、トンネルは常に大量の地下水の浸水による影響を受けており、エンジニアたちにとって大きな課題となっています。特に、多数の緊急用連絡坑道が集まる接続ポイントでは、常に位置合わせの問題が発生します。 このような坑道は長さが10～15 mで、小型の油圧ショベルを使用して建設しますが、周囲の地中に浸出した地下水を完全に排水するまではメイントンネルに接続できません。この作業には、特殊なさく孔技術と専門知識が要求されます。 困難な作業ではありますが、プロジェクトを請け負っているPSH JVにより、順調に進められています。PSH JVは、Porr Bau GmbH（オーストリア）、Saudi Binladin Group（サウジアラビア）、Hamad Bin Khalid Contracting社（HBK、カタール）による共同企業体です。 プラントマネジャーのフェレンツ・ラヴィクスカ氏は「この作業で重視されるのは、品質と信頼性、安全性、そして持続可能性です。ですから、連絡坑道の掘削時に浸水の問題に対処する方法を模索するうえで、可能な限り優れたソリューションを必要としていたのです」と話しています。
"The equipment is very effective and robust which is necessary for this application. "
One of the FlexiROC T20 R operating crews together with Atlas Copco specialists during a recent training session in Doha.
The FlexiROC T20 R rigs start drilling the dewatering holes immediately after the TBM’s last gantry has passed the cross passage installation points. The holes are 76 mm in diameter and installed mainly in the tunnel walls to a depth of 12–14 m. Up to 10 holes are completed per day in two, 10 hour shifts.
During these essential dewatering operations the rigs have also proved to be very fuel efficient, consuming just 20–25 liters per hour. In addition, all rock drilling tools, including R32 drill rods, shank adapters and drill bits, are proving to be perfectly matched to the application and are long lasting. The service life of the bits, for example, is reported to be 1–1.5 months after continuous use.
"The whole arrangement is working out very well. The equipment is not just getting the job done it is also proving to be very robust which is necessary for this application. We are very satisfied with the progress."
