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Waterproofing in Tunnels
http://www.wiskoamerica.com
Proper waterproofing of tunnels, galleries and shafts is one of the most cost effective ways to
enhance safety and function as well as increase useful life of these structures.
Water seeping into the structure endangers block and cast work, especially through
freeze/thaw action. Spalling concrete or block, icicles, and effluorescence or stalactites are all
evidence of a tunnel with either no waterproofing or an inadequately designed system.
A greater feeling of safety is imparted to the user by optimal use of waterproofing,
ventilation, lighting, and emergency stations, which combined offer the greatest degree of
comfort and convenience.
Safety is increased because water seeping through the structure and freezing on the road or
track surfaces is eliminated. Additionally, spilling of poured concrete or concrete block, due
to freeze/thaw action, is avoided, thereby allowing traffic to pass and routine maintenance
work to be performed with greater security. This not only allows road and track beds to
function as designed, but also permits the proper operation of electrical, lighting, and
ventilating systems contained within the structure. The long-term effects of water incursion,
such as leaching of lime and minerals from concrete and mortar and the corrosion of
reinforced elements are likewise avoided.
Waterproofing tunnels then become a matter of economics. Special maintenance due to
untimely deterioration of the structure is virtually eliminated and, more importantly, the
structure is able to function as designed over long periods of time.
PVC waterproofing membranes are preferred because of their particularly high resistance to
aging and to excellent elongation and tensile characteristics. Application and seaming
requirements ensure an installation which is completely secure and leak free.
The most important qualities of PVC tunnel membranes are:
aging and rot resistance, even under the influence of water containing aggressive
elements
high mechanical strength and load resistance
sensible and effective installation
Tunnel Waterproofing Systems
The choice of a waterproofing system depends upon the type and construction of the tunnel as well as the
geological criteria. Tunnels through rock generally deal only with seepage through cracks in the rock, a
condition in which there is no head of water. In these cases, waterproofing is applied only on the vault. This
is called partial or umbrella waterproofing. In the case of tunnels in frable or loose rock, however, one often
encounters springs and water running through the strata. These conditions require the tunnel to be fully
wrapped in waterproofing material designed to withstand the expected hydrostatic pressure.
Application Rock Tunneling / Umbrella System
hydrostatic condition no hydrostatic pressure, ground water level is below tunnel footings
tunnel wall condition uneven
substrate structure shotcrete min 3" thick
waterproofing
geotextile/ drainage layer nailed at intervals onto tunnel wall
using PVC-disk, 2pcs/sq.ya.
membrane 1.5mm, 2.0mm, 2.5mm, 3.0mm welded to pvc-disk.
Joints welded by hot wedge machine or hot air.
inner lining cast in place concrete or shotcrete
> pictures <
Application Soft Ground / Closed System
hydrostatic condition hydrostatic pressure, ground water level is within tunnel area
tunnel wall condition even
substrate structure shotcrete, concrete segments
waterproofing
geotextile/ drainage layer nailed at intervals onto tunnel wall using
PVC-disk, 2pcs/sq.ya.
membrane 1.5mm, 2.0mm, 2.5mm, 3.0mm welded to PVC-disk.
Joints welded by hot wedge machine or hot air.
water barrier welded to membrane as required
inner lining cast in place concrete or shotcrete
> pictures <
Application Cut & Cover / Umbrella or Closed System
hydrostatic condition hydrostatic pressure or no hydrostatic pressure
tunnel wall condition even
substrate structure clean, smooth, cast in place concrete
waterproofing
geotextile/ drainage layer nailed at intervals onto tunnel wall using
PVC-disk, 2pcs/sq.ya.
membrane 1.5mm, 2.0mm, 2.5mm, 3.0mm welded to PVC-disk.
Joints welded by hot wedge machine or hot air.
water barrier welded to membrane as required.
inner lining cast in place concrete
> pictures <
Installation and Welding
PVC membranes are delivered to the job site in rolls or prefabricated panels, the size of
which is determined by the shape and size of the structure. Seams are produced either by hot
air or hot wedge welding, depending on the type of seam specified. The welding equipment
can be adjusted for to allow for temperature and humidity conditions on the site.
Generally, the sheets are loosely laid and do not require the substrate to be dry. This can be
the deciding factor in choosing the type of waterproofing in areas where there is continuous
water seepage through the rock or where open cut construction exposes the lining to weather
for long periods of time.
The leveling layer, composed of non-woven geotextile mat or drainage fabric, is an
indispensable element in the waterproofing system.
All materials used in the system, including concrete, must be compatible to ensure that the
material properties of age resistance, elongation and tensile strength will last for years.
Welding Methods
Hot Wedge Welding Air Pressure Test Hot Air Welding
For use with polyethylene and
PVC waterproofing membranes
to produce long straight seams.
The membranes are overlapped
and the wedge is inserted
between the sheets. The heated
surfaces are pressed between
wheels above and below to
produce a strong double weld
with a space between for air
pressure testing after the
application is complete.
The air pressure test requires that
the channel between the two
welds be sealed at both ends and
inflated to 30 psi (2 bar). Test
results are positive when the
pressure does not fall more than
5 psi (.33 bar) in 10 minutes.
The pressure in the channel
stresses the weld providing
evidence of its integrity.
For use with PVC waterproofing
membranes. Hot air welding
requires controlled heat from a
hot air gun be applied between
the membranes. The hot surfaces
are then pressed together with a
roller to complete the weld. The
weld is made with three passes
with hand-held heat gun . Welds
are mechanically tested for
continuity.
WISKO America, Inc. field technicians are trained in the installation of membranes other than the
PVC referenced in the precedeing text. Each underground project should be evaluated to determine
which membrane best meets the specific project requirements. Material thickness should also be
evaluated when designing an underground waterproofing system. With our many years of project
experience, the management of WISKO America, Inc. is available for consultation on your
waterproofing requirements.
WA-ANCHOR SYSTEM
DESCRIPTION
The WA-ANCHOR consists of a prefabricated PVC-ELEMENT, a PVC MEMBRANE and a
STEEL ANCHOR.
FIELD APPLICATION
The WA-ANCHOR is used in tunnel construction to carry the dead load of the reinforcement
of the final lining.
ADVANTAGES
high load transfer through the PVC-ELEMENT into the shotcrete lining
perfect waterproof around the area of the STEEL ANCHOR
STEEL ANCHOR is corrosion protected quick and simple installation
TECHNICAL DETAILS
PIPE PENETRATION
PVC ATTACHMENT ASSEMBLY
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