Tunnels and structural elements
A railway tunnel build with precast concrete elements was produced through altered and weathered bedrock. The fractured and metamophosed rock did not leave a peferct round hole after drilling. Big parts of the rock fell down in the tunnel cieling leaving up to 6m of cavities between the prefabricated tunnel elements and overlaying rock. To protect the concrete tunnel and prevent further rockfall the empty space above the tunnel needed to be filled out.
Why Expanded Clay:
Expanded clay is a chemically inert natural material produced by clay and was partly chosen because it will not release any harmful substances to the ground water. Expanded clay can also be installed, maybe more so than most other materials, with high capacity in hard to reach places, by blowing.
The installation of the expanded clay up into the overlaying cavities went very well, filling out the voids. Each blowing truck could drive into the tunnel to the right tunnel segment and use several sections of hoses to reach the place of installation.
Blowing, Drainage, and Mechanical protection