Herrenknecht TBMs Deployed for Drainage Project in Qatar
Two Herrenknecht TBMs are driving a tunnel 20 to 30 m (65 to 100 ft) underground for the Abu Hamour Southern Outfall Project. The EPB Shields with a diameter of 4,470 mm (14.6 ft) are designed for Doha’s soft limestone soil. Muck comprising excavated material serves as the support medium for the shield, providing the requisite pressure balance at the tunnel face. Protected by the shield skin, the tunnel is excavated using ring-shaped reinforced concrete segments. The individual segments are transported through the tunnel as it is completed and connected to form closed rings (segmental lining process) directly behind the TBM with an erector.
Herrenknecht tunnelling technology was also used in designing some of the inlets during an initial construction phase. Using a slurry AVN machine from Herrenknecht, a total of 4 km (2.5 miles) of tunnel with an outer diameter of 3.6 m (11.8 ft) was excavated with the pipe jacking method in 2008. This is a remarkably large diameter for pipe jacking.
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