Despite its low annual rainfall of less than 100 mm, Doha can still face the prospect of extensive flooding, caused by individual driving rain showers, similar to many of the GCC cities.
Work is underway on a comprehensive drainage system, with two tunnel boring machines supplied by Herrenknecht at work deep below the surface of the city. The two TBMs are driving a tunnel 20 to 30 meters underground for Abu Hamour Southern Outfall Project. The EPB Shields with a diameter of 4,470 mm are designed for Doha’s soft limestone soil. The EPB is the first to drive a tunnel in a segmental lining process in Qatar.
Muck comprising excavated material serves as the support medium for the so-called Earth Pressure Balance Shield (EPB), 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.
Via the main tunnel extending 9.5 kilometers, up to 16.5 cubic meters of water per second will later be conveyed to a central pump station near the New Doha International Airport.
Herrenknecht is also involved in the new Doha Metro System with a total of 21 EPB Shields, many of which have already been delivered.
Apart from the two machines for the Abu Hamour Southern Outfall waste water project, Doha will also be deploying another 21 Herrenknecht EPB Shields during construction of the its much-vaunted metro.