Dewatering, waterproofing and drainage - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 229

Finally, voids remaining in the tunnel crown are grouted with cement grout. Special meas-
ures need to be taken for the adequate ventilation and filling of the locking anchors of the
connection strips. The installation of additional slightly tapered concreting pipes in the
crown, as shown in Fig. 5-26, has proved successful. The pipes provide ventilation while
the concrete is poured and are later used to inject cement suspension “wet-in-wet”.
Figure 5-26 Arrangement
of additional concreting
pipes in the crown [193].
Waterproofing support. The loading in the construction state is different from that in the
completed state, which often provides scope for mistakes. The waterproofing support in
the construction state, the temporary support layer, is for economic reasons very depend-
ent on the construction process, which itself depends on the geological conditions and the
constructional requirements. The first purpose of the temporary support is to support the
rock mass and its function as a support for the waterproofing layer is only secondary; this