Seal for a joint or juncture – Process of static sealing
Reexamination Certificate
1999-04-12
2001-02-20
Melius, Terry Lee (Department: 3628)
Seal for a joint or juncture
Process of static sealing
C277S650000, C277S935000, C405S274000
Reexamination Certificate
active
06189890
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sealing joint for sheet piles.
2. Description of the Prior Art
Sheet piles are metallic sections having geometries of varying complexity (Z-shaped, U-shaped or flat sheet piles, for example, or joined together in a caisson), which are assembled to form continuous structures known as sheet-pile walls. Assemblies of sheet piles are used more particularly during work connected with excavation, with the construction of dams, reservoirs and basins for confinement of sewage etc., in order to retain soil and, to a certain extent, water as well.
On site, the sheet piles, which are often assembled two at a time (twinning) at the factory by what are called threading machines, are driven into the ground by ramming, by vibration or by presses to form a metallic wall by virtue of the mutual interlocking between their gripping elements or claws. A certain amount of play in the region of their gripping elements must be allowed so that the sheet piles can easily be interlocked during their assembly, and this naturally forms a source of leakage.
As soon as there is a requirement for the sheet-pile wall to be impervious, whether the imperviousness is to be perfect or as efficient as possible, additional measures must be provided for sealing the gripping elements.
Attempts have been made to seal the sheet-pile wall after being driven in, either by welding the sheet piles to each other, or by pressurised injection of a sealing mass into the interstices of the gripping elements, as described in the German patent application published under no. DE-OS-21 40 250.
These two methods are, however, applicable only if one of the two faces of the sheet-pile wall remains accessible.
If the sheet-pile wall is inaccessible, it is possible to proceed as described in the German patent application published under no. DE-OS-21 42 957 and inject into a gripping element of the sheet piles, even on site and before pile-driving, a mass which is introduced in the liquid state and which solidifies in the form of a foam with an elastic consistency.
Alternatively, it is possible to conform to the German patent application DE-AS 27 22 978, according to which a joint is formed in the gripping element to be interlinked by injecting into it a suitable product, generally polyurethane, and by smoothing out the product by means of a mobile device to give it the desired shape.
The above-mentioned sealing joints have the disadvantage that they offer little resistance to stresses during the interlocking, particularly to shearing. While the sheet piles are being driven in, the gripping elements rub against each other and the sealing joint may be destroyed, at least locally, by the joint being planed down.
The use of these polyurethane-based joints generally requires an elaborate preparation of the gripping element. In fact, it is often necessary to clean the gripping element by sand-blasting and to introduce a product to improve the adhesion of the joint to the steel. In spite of all these precautions, sheet piles incorporating this type of joint cannot be driven in by vibration, since the joints would suffer too much damage during the pile-driving.
SUMMARY OF THE INVENTION
The aim of the present invention is to propose a product to seal the gripping elements of the sheet piles which is both safe from the environmental point of view and which withstands stresses well during pile-driving.
This aim is achieved through the use of a paraffinic product to seal the joints of the sheet piles.
The use according to the invention of a paraffinic product is advantageous, since this product is inert and does not release harmful compounds into the environment.
Because of its consistency and its good plastic deformability, the joint using a paraffinic product is not liable to be destroyed during the interlocking of the sheet piles. It has a better resistance to shear and to other stresses during pile-driving than polyurethane joints.
The sealing of sheet-pile gripping elements using paraffinic products is simpler than it is with polyurethane, because neither sand-blasting the gripping element nor introducing a product to improve adhesion between the steel and the joint are necessary.
Moreover, joints made of paraffinic products are much cheaper than joints made of polyurethane.
To seal the gripping elements of sheet piles, bitumen-based masses for sealing have long been used. These products generally possess an acceptable resistance to shear. However, one of the disadvantages of these sealing products is that, when used in contact with groundwater, certain harmful compounds may be released into the environment.
The use of paraffinic products in the manufacture of sealing joints for sheet-pile gripping elements offers several advantages over the use of bitumen-based products.
The plasticity and deformability when cold of the paraffinic product are significantly superior to those of bitumen-based products. These properties have been confirmed by tests on interlocking of sheet piles.
Paraffinic products have a lubricating power that is superior to that of bituminous products, i.e. sheet piles incorporating a joint made of paraffinic products are generally easier to interlock: the force required to couple together two sheet piles sealed with a paraffinic product is less than that required to couple together sheet piles sealed with a bituminous product.
Joints made with paraffinic products are not degraded by mineral oils, unlike joints made with bituminous products. The resistance of joints made with paraffinic products to petroleum oil and/or motor spirit is significantly greater than that of joints made of bituminous products.
The temperature at which paraffinic products are applied is significantly lower than that for bituminous products. In fact, it is sufficient to heat paraffinic products to temperatures below 140° C. whereas bituminous products must be heated to about 200° C. At these temperatures, bituminous products have a tendency to give off disagreeable smells and overheating may also produce harmful smoke.
During the interlocking of the sheet piles, a certain amount of the sealing product is ejected from the gripping element and must be removed manually. Paraffinic products are removed by scraping with a tool and the surface is easily finished using a solvent based on aliphatic hydrocarbons, such as “Premium Degreaiser” made by Texaco. The amount of paraffinic product ejected is less and it is distributed more homogeneously in the gripping element. The aesthetic appearance of a sheet-pile wall incorporating joints made of paraffinic products is consequently significantly more attractive than that of a sheet-pile wall incorporating joints made of bituminous products.
If sheet piles are reused, the gripping elements must generally be completely cleaned.
In such a case, joints made of bituminous products must be removed using a blowpipe, whereas joints made of paraffinic products are quite simply removed by scraping and possibly by using a solvent.
Another advantage of paraffinic products is that they remain homogeneous even at high temperatures. With bitumen-based products, a local thickening of the bituminous joints due to inhomogeneities is sometimes observed. These thicker regions may lead to difficulties in interlinking the sheet piles. In such cases, the awkward region must be slightly heated in order to facilitate the twinning of the sheet piles.
Another advantage lies in the fact that the joints of paraffinic products may be coloured en masse by adding a dye or coloured pigments to the molten products.
Joints made of paraffinic products may be introduced at the factory or on site before the sheet piles are interlocked.
REFERENCES:
patent: 3784441 (1974-01-01), Kaempen
patent: 4449713 (1984-05-01), Ishido et al.
patent: 4670089 (1987-06-01), Hanson
patent: 5547318 (1996-08-01), Decker
patent: 5938210 (1999-08-01), Schatzle
patent: 0 264 527 (1988-04-01), None
patent: 0 352 172 (1990-01-01), None
patent: 454306 (1936-09-01), None
patent: 70126
Moulin Jean-Michel
Rix André
Chapman and Cutler
Melius Terry Lee
Miller William L.
Profilarbed S.A.
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