First tunnel boring machine checked and accepted
Although it carries the serial number S-544, the tunnel boring machine (TBM) is unique: it was produced specially for the construction of the linear accelerator tunnel and the first two sections of the tunnel “switchyard”. According to the expected make-up of the ground in the Hamburg area, the technique used is the so-called liquid medium-supported mixshield. In this technique, the soil at the tunnel face is loosened by the rotating cutting wheel, mixes with the support liquid in the pressure chamber and is then pumped to the surface outside the tunnel. Under the protection of a cylindrical shield, the tunnel is constructed in 1.50-metre-long sections comprising six annular steel-reinforced concrete segments – called linings – and one key segment that closes and braces the ring. After completion of one such ring, presses are extended that push the TBM forward.
After completion of the TBM, specialists from the ordering party travelled to the manufacturer in southern Germany to check the machine for four days in each and every particular. On the fourth day, they were joined by representatives from European XFEL and DESY wishing to appraise the TBM and have it explained to them. The visitors then witnessed the most impressive features of the machine: the rotation of the blue cutting wheel (see photograph) in both directions, the smashing of a boulder by means of the stone crusher integrated into the machine, the transport and positioning of a lining, the extension and retraction of the presses.
The transfer of the tunnel boring machine to its site of operation at the European XFEL construction site Schenefeld, which will last several days, is due to begin in a few weeks. The 71-metre-long TBM can thus now be disassembled again for the transport.
