Welding of sheet piles
During the execution of a sheet pile wall structure, welding will be frequently used at the site for joining steel elements together.
Information regarding the following important items is given in this annex :
- butt welding multiple lengths;
- splicing with plates (fish plates);
- junction piles for joining a part wall element to the main wall;
- special corner piles;
- straight web junction piles;
- box piles;
- sealing welds.
B.2 Butt welding multiple lengths
The preparation of normal butt joints is carried out in accordance with 8.4.
- a template piles fixed to bed
- b butt weld
- c lengths to be welded
Manufacturing tolerances mean that piles of the same section size can have several millimetres difference in width and height. Care is necessary to ensure that interlocks are aligned at the joints. Alignment can be achieved by construction of a template into which the ends of piles to be joined can be entered prior to welding. The laying out bed should also be provided with supports to ensure overall straightness of the resulting spliced pile. In figure B.1 the general arrangement and the detail of a butt welding template is shown.
The welds are completed across the full width of the pile except for the interlocks. The pile is then removed from the template so that the welds can be completed. It is important to avoid weld metal being deposited on the inner faces of the interlocks. This should be carefully checked before the piles are used.
B.3 Welding multiple lengths by splicing with plates
When lengthening is carried out by means of plates, which are welded to the ends of both sheet piles, it is important to ensure that the forces that have to be transmitted, are distributed as evenly as possible over the cross section of the sheet piles.
Figure B.2 shows two examples for splicing a double Z-pile and a single U-pile. The use of tapered plates reduces the risk of cracking at sharp edges due to stress concentrations.
The splice plates must be welded around their entire perimeter. It is necessary to check that this is carried out in accordance with the requirements of 8.4.
- a double Z-pile spliced with plates
- b single U-pile spliced with plates
B.4 Junction piles (U and Z-piles) for joining a part wall element to the main wall
Figure B.3 shows a junction pile consisting of a double Z-sheet pile with a sheet pile offcut. The inserted angle section as shown in the figure, may alternatively be omitted.
D1, D2 welds
|a angle section
c double Z-pile
|b offcut clutch
d weld sequence
B.4.2 Type of welding
Welds D.1 and D.2 are intermittent welds with an effective weld thickness aeff of 5 to 6 mm, the total length of the intermittent weld being 30 % of the pile length, meaning 3 welds of 100 mm each per metre.
When there exists a possibility of serious corrosion, a continuous sealing weld may be necessary between the intermittent welds.
B.4.3 Assembly and welding procedure for the junction pile
- prepare and straighten the offcut clutch;
- assemble the offcut clutch and angle section on horizontal supports;
- tack weld over the whole length;
- apply the final welds (100 mm in length), commencing in the centre of the assembly (over a distance of about 1 m), then apply the final welds at both ends of the assembly over a distance of about 1 m;
- apply the final welds (100 mm in length) in the intermediate portions of the assembly in a back step procedure, starting from the centre and moving towards the ends;
- during welding operations welds D.1 and D.2 are applied in a staggered sequence as indicated in figure B.3;
- if the offcut clutch deforms during welding, straighten it prior to subsequent operations with a torch or a press;
- assemble the offcut clutch/angle section connector and the sheet pile on horizontal supports. Generally the welded on section does not extend to the top of the special pile to allow for pile driving using a cap or clamps;
- tack weld over the whole length;
- apply the final welds (100 mm in length) commencing in the centre of the assembly (over a distance of about 1 m), then apply the final welds at both ends over a distance of about 1 m;
- apply the final welds (100 mm in length) in the intermediate portions of the assembly in a back step procedure starting from the centre and moving towards the ends of the pile;
- during the welding operations welds D.1 and D.2 are applied in a staggered sequence as indicated in figure B.3;
- if the pile deforms during welding, straighten it with a torch or a press.
B.4.4 Welding filler materials
In 8.4 the characteristics of the selected filler metals are given.