Electric heating – Metal heating – By arc
Reexamination Certificate
2002-09-27
2003-12-16
Elve, M. Alexandra (Department: 1725)
Electric heating
Metal heating
By arc
C219S137200, C405S274000
Reexamination Certificate
active
06664509
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for securing two sheet piles interlocked by means of sheet pile interlocks.
BACKGROUND OF THE INVENTION
The use of sheet piles for constructing retaining walls is well known. The sheet piles used in such walls have sheet pile interlocks along their longitudinal edges, which can be interlocked so as to maintain the longitudinal edges of adjacent sheet piles interconnected with each other. Current sheet pile interlocks of the double-hook interlock type (type 1 according to EN10248 norm), as e.g. LARSSEN type sheet pile interlocks, are hook shaped elements with an internal interlock chamber. A sheet pile wall is formed by driving a first sheet pile into the ground, introducing the bottom end of the trailing sheet pile interlock of a second sheet pile with the top end of the leading sheet pile interlock of the first sheet pile, driving the second sheet pile into the ground, and then repeating the process to insert third, fourth etc sheet piles into the wall.
It is often necessary to secure two interconnected sheet piles against longitudinal shifting relative to one another for example at a harbour, canal, or building-excavation construction site. This is particularly the case for sheet pile walls constructed with U-shaped sheet piles having the sheet pile interlocks aligned along the neutral plane of the sheet pile wall.
It is known to secure two interconnected sheet piles by bonding the interlocked sheet pile interlocks with a curing mass, e.g. an adhesive or cement. However, the shearing strength of an adhesive bond is limited. Furthermore, this bond is often not reliable because of ground material and/or water penetrating the interlock chamber.
According to EP-0 898 021, two interconnected sheet piles can be secured by pressing impressions on the outer connection joint between the two interlocked sheet pile interlocks. The pressing of these impressions are effected by means of a punch adapted to be operated by a hydraulic percussion hammer. The securing of interconnected sheet piles by pressing impressions is e.g. used for combining sheet piles into double or triple sheets, also known as driving units, prior to driving them into the ground. Of course, such an impression can only be made on the sheet pile interlocks which are accessible from at least one side. It follows that driving sheets cannot be secured in this way once they are driven into the ground. After excavation on one side of the sheet pile wall the sheet pile interlocks are again accessible. It is however during excavation that the unsecured sheet pile interlocks tend to shift and the sheet pile wall is deformed. The securing of sheet piles after excavation is hence of little importance. It follows that there is a need for a method for securing sheet piles after they have been driven into the ground, but before excavation takes place. Furthermore, in order to render the interlocked sheet pile interlocks waterproof, a welding seam can be made on the outer connection joint between two interlocked sheet pile interlocks. This welding seam can of course only be made on the interlocks of two adjacent sheet piles which are accessible, i.e. before they are driven into the ground or after excavation. The interlocked sheet pile interlocks between two driving units cannot be rendered waterproof in this way. Even if the welding seam is made after excavation, the welding seam can only be made on the top half, often only the top third of the sheet pile interlocks, as the remaining part of the sheet pile wall is still not accessible. The remaining part of the sheet pile wall can hence not be rendered waterproof.
SUMMARY OF THE INVENTION
The technical problem underlying the present invention is to provide a reliable method for firmly securing sheet pile interlocks against longitudinal shifting relative to one another, even if the sheet pile interlocks are not accessible. This problem is solved by a method as claimed.
GENERAL DESCRIPTION OF THE INVENTION
In accordance with the method of the present invention a welding electrode is axially inserted into an axial groove between the sheet pile interlocks, which are then welded together in the groove. The sheet pile interlocks need not be accessible from the outside in order to make a welding. It follows that sheet piles or driving units can now also be secured after having been driven into the ground. This is of particular advantage in case excavation is to take place as the sheet piles or driving units can be secured beforehand. The sheet pile interlocks can hence not shift and the sheet pile wall cannot deform during the excavation process.
It will be appreciated that a method in accordance with the invention is particularly advantageous if the interlocked sheet pile interlocks are at least partially located below ground level. The welding electrode can then be axially introduced through the axial groove below ground level and the sheet pile interlocks can be welded together below ground level. The method hence allows firmly securing two sheet piles or driving units, after they are driven into the ground. It will be appreciated that the welding operation allows to provide a bond with a higher shearing strength than a bond achieved by injecting a curing mass, and that the welding operation is far less affected by ground material and/or water penetrating the interlock chamber than a curing operation. Furthermore, a continuous welding seam can be made along the whole length of the axial groove, whereby the sheet pile wall can be rendered waterproof along the whole of its height.
The welding electrode is connected to a conductor, which is preferably a semi-rigid conductor, e.g. an electrically insulated copper conductor, so that it can be used to push the welding electrode far down into the axial groove.
According to a first embodiment, the welding electrode is axially introduced into the axial groove up to a first depth, where a first welding is made. The welding electrode is then drawn back to a second depth; where a second welding is made. This discontinuous welding allows for time saving securing operation.
According to a second embodiment, the welding electrode is axially introduced into the axial groove up to a first depth, where the welding electrode is consumed by making a welding. The conductor is then withdrawn from the groove and connected to a new welding electrode, which is then axially introduced into the axial groove up to a second depth, where it is consumed by making another welding. The second depth can for example correspond to the end of the first welding, so that a continuous welding seam is obtained. This continuous welding provides a sealed connection between two sheet piles.
It is advantageous to use a fluxed electrode, as such an electrode facilitates arc ignition and stability during welding. It also allows welding to take place under water and it can be easily used on site with conventional welding generators. The fluxed electrode also has the particular advantage that it allows for a discontinuous welding, i.e. local weldings can be made at different depths in the axial groove.
A straightener can be used for introducing the semi-rigid conductor with the welding electrode into the groove. It straightens the semi-rigid conductor and pushes it down the axial groove. It can further be used to pull the conductor back out of the axial groove.
When constructing a sheet pile wall, the first sheet pile is first driven into the ground. The leading sheet pile interlock of the first sheet pile has an interlock chamber protected from ground material. An interlock head of a trailing sheet pile interlock of a second sheet pile is engaged in the interlock chamber when the second sheet pile is driven into the ground. The interlock head preferably has an axial groove facing a wall of the interlock chamber for receiving the welding electrode.
The interlock chamber can have a substantially right angle corner. The interlock head engaging the interlock chamber preferably has a cross-section that is complementary to
Moulin Jean-Michel
Rix André
Elve M. Alexandra
International Sheet Piling Company Sarl
McCormick Paulding & Huber LLP
Tran Len
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