TUNNEL WATERPROOFING

A step further in quality of works.

Hispano Sueca de Ingeniería S.A. (HISISA) was incorporated in 1965 with the purpose of executing special works of high quality and precision in the area of underground construction.

From its beginnings up to the present it has carried out complex and delicate projects such as demolitions of buildings, bridges, concrete plugs in dams, blasting in mining cuts, industrial excavations and quarries, as well as individual excavations requiring the use of contouring and presplitting techniques and control of spraying and vibrations.

As examples of individual excavations, HISISA has executed underwater blasting and large caverns for hydroelectric power plants. The scope of HISISA’s work includes Engineering projects such as designs, technical and economic analyses, forecast and control programmes, supervision and establishment of working methods, as well as viability studies for all kinds of underground projects.

To supplement the work it has been carrying out for over 47 years, HISISA continues to provide solutions that contribute added value to underground projects, now in the field of waterproofing tunnels, galleries, shafts, caverns, etc., analysing the technique best suited to the specific requirements of each case and subsequently carrying out the work with its own resources so as to guarantee the appropriate quality necessary to achieve long-lasting underground infrastructure.
TUNNEL WATERPROOFING WITH SPRAYED CONCRETE SUPPORTS.
Most applications of geotextiles and membranes in tunnel construction comprise waterproofing carried out according to the usual underground methods of working.

In this case the waterproofing involves a geotextile and a membrane, which are put in place during the final phase of the works, after the excavation and supports have been executed, including the preliminary water collection (drainage) and levelling operations, and always before the structural lining.

The waterproofing of a tunnel comprises the membrane as the waterproof element and the geotextile as a protective layer against mechanical damage and also for outflow of seepage water.

The waterproofing of a tunnel consists of:
› A support
› A protective geotextile
› A waterproofing fabric membrane
The geotextile is fixed directly to the sprayed concrete of the support usingsecuring pins with washers, keeping folds to a minimum. As many pins are applied as are necessary to fit it to the shape of the support.

The sheets of geotextile are secured using pins with washers, discs or strips of the same material as the membrane. They are placed transverse to the axis of the tunnel.

After applying the first sheet, the second is placed overlapping the previous one by at least 20 cm.
The membrane is placed transversally, secured to the washers previously installed, and thermoplastically welded (with no perforation) using hot air and/or wedge machines, with a central channel for checking the waterproofing.

The membrane is placed in position by hand, using appropriate scaffolding or platform lifts.

The welding between the sheets has a minimum overlap of 8 cm.
Welding-temperature and -speed adjusted to the climatic conditions on site (welding test prior to work mandatory).


The welding check is carried out by compressed air testing at a pressure of 2 atm for 15 min. A loss of 10% during the test is allowed, due to the flexibility of the waterproofing membrane.
These are used in concrete for sealing of construction or working joints and expansion joints with low or high water pressures. They differ from joint sealers in the respective locations of the two elements. The tapes are placed in their projected position when the concrete is poured into the moulds and their function as seals comes into effect once the concrete has set.
 
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