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  Tunnelling of Bucharest Metro Line 5: hard-points and performances

  The Bucharest metro system is actually made of four (4) operating metro lines (Line 1 to Line 4), one line under construction (Line 5), and another one in the design stage (Line 6). The Line 5 (Magistrala 5) is made of twenty-four (24) stations, running from Râul Doamnei station tostation, crossing the city centre in the East-South West direction. The stretch of the Line 5 of the metro system of Bucharest going from Raul Doamnei to Eroilor 2 is a 6.2 km long twin-tunnel alignment realized by means of two 6.60m diameter EPBs machines. The tunnelling operations of the stretch started in September 2013 and are still in undergoing. As the line crosses the city centre, several hard-points are detected along the alignment. The tubes being beneath the water level, the axis of twin-tunnels being 11m to 18m deep and 11m to 21 m distant each other, the risk of inducing significant effects at the surface is not to be considered as negligible. Such risk has to be properly controlled and managed. Therefore, the need arises of monitoring the tunnelling operations during the whole construction process. A follow-up procedure has been implemented and the tunnelling operations have been supervised during the whole excavation process of stretch of the line within Academia Militara station and Orizont station, in order to optimize the machines’ performances, the construction time and to minimize the urban impact. The EPBs parameters have been monitored during the excavation process of the tubes: the advancing and the mechanical parameters (face pressure, torque, thrust…), the soil conditioning parameters (foams pressure, density…), the weight of the extracted soil have been continuously checked, elaborated and finally correlated to the EPBs advancing rates and to the effects induced at the ground surface. The analysis of the excavation parameters of the first stretch of the line finally lead to optimize the machines’ performances and to remarkably increase the tunnel production of the further stretches.

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