Waterproofing in Tunnels

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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