Dewatering, waterproofing and drainage - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 225

Table 5-16 continued

Property Testing according to Requirements

standard EAG-EDT

section

polyolefin-
based

PVC-P-based

Long-term resistance
behaviour after heat alteration
(70 d, 80 °C)

DIN EN ISO
11925-2
DIN EN 13501-1

4.12.21 Alteration of the

tension strength
and failure strain
compared to deli-
very state ≤ 20 %
Behaviour when
folded cold
(-20° C): no cracks

Fire behaviour DIN EN ISO

11925-2
DIN EN 13501-1

4.12.23 Class E

Behaviour of joint seam in
shear test
Short-term factor of joint seam
Behaviour of joint seam in peel
resistance test
Peel resistance

DIN EN
12317-2

Tear outside the joint seam

≥ 0.6
Peeling is permissible as long as peel
resistance is achieved
≥ 6.0 N/mm²

DIN EN
12316-2

The above table does not include any reference to the recently developed autoclave tests,
which can give information about the ageing process of plastic membranes and enable a
theoretical lifetime to be determined. More information can be found in the EAG-EDT.
Waterproofing layers. The following sequence of layers is currently usual for water-
proofing with plastic membranes (Fig. 5-20) [143]:
- Shotcrete outer support layer as waterproofing support.
- Geotextile protection layer.
- Plastic waterproofing membrane.
- Inner lining.
Laying the waterproofing. A 204 g/m 2 synthetic fleece is first fixed by shooting to the tun-
nel sides. This serves to protect the waterproofing membrane against mechanical damage, for
example perforation due to the uneven surface of the underlying shotcrete. Due to the danger
of hydrolysis of polyester, geotextiles made of this material should be avoided. The fleece also
prevents any toothing or shear transfer between the tunnel sides and the waterproofing mem-
brane in sections under compression loading, and avoids areas of excessive tension stress in the
membrane due to deformation of the rock mass or shrinkage movement. The fleece layer also
serves as a drainage layer to collect any residual water and drain it down to the invert.

The fleece is fixed at points with steel washers (Fig. 5-21) of 20 mm diameter. The spac-
ing of the nailed fixings reduces towards the crown to ensure that the fleece does not hang
down. When the tunnel vault is uneven, the nails must be shot at the deepest points, as oth-
erwise there would be a danger that fleece and waterproofing membrane could tear when
the inner lining is concreted. The inner lining requires the best possible void-free contact
with the outer support for rock mass structural reasons. The external fleece does not need
welded seams, but should be overlapped.