Tunnel scan Within a few minutes, a tunnel scanner can record millions of measurement points in the tunnel. This is necessary to check the size of the excavation. If different construction phases are scanned, for example excavation and application of shotcrete, this method can be used to check the thickness of the shotcrete. With this method the contracting authority can monitor the compliance with the structural requirements. Accuracy of the breakthrough For the construction of the exploratory tunnel the largest expected deviation for the breakthrough in the Brenner area is 22 cm. For the construction of the two main tubes the largest expected deviation, 9 cm, is likely to occur during the breakthrough between the construction lots in Mules and the Isarco river underpass. The deviation during the construction of the main tubes will be much lower, because the measurements can be carried out via the shaft connections to the already completed exploratory tunnel. The largest deviation in the Austrian project area was encountered during the breakthrough of the emergency tunnel, with a deviation of 18.2 cm, whereas the smallest one was encountered during the breakthrough of the exploratory tunnel, where the deviation along the tunnel length was 1.7 cm. Surveyor at work with a tachymeter. 27 BRENNER BASE TUNNEL
RkJQdWJsaXNoZXIy Mjc1MzM=