Tunnelling: Unobstructed Flow Path for Mountain Water
In tunnelling, it is essential to provide adequate water drainage
both during and after the construction phase. Depending on
the prevailing mountain and water conditions, both the upper
part of the tunnel arch and the tunnel base are affected
by fissure, stratum, and seepage water. The long-term stability
and permanent usability of a tunnel depend on whether the
inner shell and base are reliably protected against water
ingress and consequent frost damage.
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 It is imperative to collect the surface and seepage water over a wide area between the inner and the outer shell of the tunnel, both in the upper and in the lower parts of the tunnel, and to remove it through carefully designed drainage and seepage layers. This applies particularly for efficient tunnelling methods using water impermeable concrete which must not come into
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Plaster
Lath 
