The excavations of highway tunnels in Stockholm imply serious problems within the area of intersections with the existing tunnels. In the extreme tunnel intersections cases the rock cover or bottom of the existing tunnel is blasted away. The Swedish telecommunication authority Telia accepted encroachments into the prohibited area around the tunnel demanding to sign a contract with the Swedish Road Administration claiming terms of assurance that an undisturbed communication traffic operation in the existing tunnels has to be secured. The concrete tunnels anchored in the bedrock were constructed before the excavation of highway tunnels started in March 1999. The unique automatic computerised stability controlling system has been installed in the cable tunnel to control tunnel stability during the highway tunnelling. Rock blasting detected by accelerometers initiates collecting and transmitting stability parameters measured to the supervising staff that is commissioned to stop the tunnelling if the contracted limit load/stress values are exceeded.
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