METHOD FOR BUILDING SHEET PILE WALLS

Abstract: A method for building sheet pile walls comprises the steps of providing a first sheet pile (10), said first sheet pile (10) having a leading sheet pile interlock (14) with an interlock chamber (20); driving said first sheet pile (10) into the ground while protecting said interlock chamber (20) from ground material; providing a second sheet pile (10'), said second sheet pile (10') having a trailing sheet pile interlock (12') with an interlock head (16); engaging said interlock head (16) of said trailing sheet pile interlock (12') in said interlock chamber (20) of said leading sheet pile interlock (14); driving said second sheet pile (10') into the ground. The method further comprises the step of coating said interlock head (16) of said trailing sheet pile interlock (12') with fixing agent prior to engaging said interlock head (16) of said trailing sheet pile interlock (12') in said interlock chamber (20) of said leading sheet pile interlock (14).

Description: Method for building sheet pile walls. Field of the invention The present invention relates to a method for building sheet pile walls. Background of the invention The use of sheet piles for building 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 EN 10248 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 pile interlocks against longitudinal shifting relative to one another. This can be achieved by bonding the interlocked sheet pile interlocks with a fixing agent, like e.g. an adhesive or cement. United States Patent US-4,981 ,540 discloses a method for securing sheet pile interlocks, wherein the interlock chamber of the leading sheet pile interlock is filled with an adhesive, and a caliber piece is applied to the interlock to protect the adhesive and keep soil out of the interlock chamber. Once the sheet pile is driven in, the caliber piece is extracted and a next sheet pile can be driven in. The trailing sheet pile interlock of the next sheet pile is forced into the adhesive filling the interlock chamber in the leading sheet pile interlock of the sheet pile in place in the ground. A major drawback of this method is that the adhesive in the interlock chamber will make the withdrawal of the caliber piece more difficult. Furthermore, an adhesive with a long curing time must be used, as the adhesive must not be allowed to set until the next sheet pile is driven into the ground. According to another method described in US-4,981,540, a caliber piece, having a pipe with nozzles mounted on it, is introduced into the leading sheet pile interlock before the sheet pile is driven in. Once the ramming operation is finished, the caliber piece is withdrawn while an adhesive is simultaneously injected through the pipe nozzles into the interlock chamber. A major drawback of this second method is that a very fluid adhesive must be used, because it has to be injected through a long pipe into the interlock chamber. It is however impossible to warrant a homogeneous distribution of such a fluid adhesive in a vertical interlock chamber, which is subjected to impacts and vibrations during the ramming process of the next sheet pile. In order ensure good bond conditions, it is with both methods important to keep ground material off the contact surfaces of the interlocking sheet pile interlocks. However, when the caliber piece is withdrawn, ground material inevitably mixes with the uncured adhesive, thereby impairing the bond conditions. A further drawback of the above methods is that the interlock head of the trailing sheet pile interlock engaging the interlock chamber of the leading sheet pile interlock progressively acts upon the adhesive in the interlock chamber as a kind of percussive expulsion piston pushing most of the adhesive out of the interlock chamber. In other words, most of the adhesive injected into the interlock chamber is lost in the surrounding ground. Object of the invention The technical problem underlying the present invention is to provide an improved method for building sheet pile walls, which alleviates or remedies the above drawbacks when using a fixing agent for securing two sheet piles. This problem is solved by a method as claimed in claim 1. General description of the invention In accordance with the method of the present invention, a first and a second sheet pile are provided, the first sheet pile having a leading sheet pile interlock with an interlock chamber, the second sheet pile having a trailing sheet pile interlock with an interlock head. The first sheet pile is driven into the ground while protecting the interlock chamber from ground material. The interlock head of the trailing sheet pile interlock is engaged in the interlock chamber of the leading sheet pile interlock before the second sheet pile is driven into the ground. An important feature of the method is that prior to engaging the interlock head of the trailing sheet pile interlock in the interlock chamber of the leading sheet pile interlock, the interlock head of the trailing sheet pile interlock is coated with a fixing agent. While driving the first sheet pile into the ground, the interlock chamber of its leading sheet pile interlock is protected from ground material. It follows that when the second sheet pile is interconnected, the coated interlock head of its trailing sheet pile interlock engages in a clean interlock chamber. As the contact surface of the interlock chamber which receives the interlock head is free from ground material, excellent bond conditions are guaranteed. The method according to the present invention hence allows driving sheet piles into the ground wherein the sheet piles are reliably secured against longitudinal shifting relative to one another. The withdrawal of the protection means is made easier, as no fixing means is present in the interlock chamber of the leading sheet pile interlock when the sheet pile is driven into the ground. The withdrawal of the protection means does furthermore not cause ground material to mix with the fixing means, as no fixing means is present in the interlock chamber of the leading sheet pile interlock as the sheet pile is driven into the ground. As the interlock head of the trailing sheet pile interlock can be coated with fixing means just before engaging the interlock chamber of the leading sheet pile interlock of the previous sheet pile, it is now possible to use fixing means with a shorter curing time. It is furthermore possible to guarantee a homogenous distribution of the fixing means on the interlock head by using very viscous fixing means which remain on the interlock head. Finally, the interlock head does no longer act as a percussive expulsion piston, therefore no or little fixing means is lost in the surrounding ground. A spreader can be used for applying the fixing agent onto the interlock head of the trailing sheet pile interlock. The spreader preferably has a spreader chamber that has substantially the same form as the interlock head of a sheet pile interlock, but is slightly bigger than the latter, so that a uniform layer of fixing agent is applied over the whole length of the interlock head of the trailing sheet pile interlock. The fixing agent can be injected into said spreader chamber through an injection opening arranged in said spreader by means of an injection nozzle. As the spreader is moved along the sheet pile interlock, a uniformly thick layer of fixing agent is applied onto the interlock head of the sheet pile interlock. In accordance with a preferred embodiment of the present invention an obturating device comprising an inflatable tube is inserted into the interlock chamber to be protected. Once the obturating device is in place within the interlock chamber, its inflatable tube is inflated, so that the obturating device effectively closes the opening to the interlock chamber. It follows that no ground material can enter the interlock chamber while the sheet pile is being driven into the ground. Once the sheet pile is in place, the inflatable tube is again deflated, and the obturating device can be easily withdrawn from the interlock chamber. In short, while the inflatable tube is inflated, the obturating device ensures excellent protection for the interlock chamber against ground material, and while the inflatable tube is deflated, the obturating device can be easily inserted into or retracted from the interlock chamber. The obturating device can further comprise a flexible tube with an open front end alongside the inflatable tube which has a closed front end. This flexible tube can then be used for filling the interlock chamber with sand or synthetic foam (as e.g. a PU foam) while the obturating device is withdrawn from the interlock chamber. Especially in case the sheet piles are driven into light or muddy ground material, it is advantageous to fill the interlock chamber with sand or synthetic foam material in order to prevent light or muddy ground material to enter the interlock chamber once the obturating device has been withdrawn. It is not excluded to conceive the flexible tube as a separate piece, but it is preferred to firmly attach it to the inflatable tube and, in particular, to form it in one piece with the inflatable tube. In accordance with a preferred embodiment, inflation of the inflatable tube pushes an obturating block into the longitudinal opening of the interlock chamber. This obturating block closes the longitudinal opening of the interlock chamber. It will be appreciated that the obturating block can be made stronger than the inflatable tube and is hence less likely to be damaged during the driving process. It is preferably a semi-rigid body, because such a semi-rigid body may be more easily introduced in and withdrawn from the interlock chamber. Furthermore, it is preferably a wedge shaped body engaging the longitudinal opening of the interlock chamber. The wedge shape ensures that, when the inflatable tube is inflated, the obturating block centres itself in the longitudinal opening of the interlock chamber so as to effectively obturate this opening from the inside of the interlock chamber. It is not excluded to conceive the obturating block as a separate piece, but it is preferred to firmly attach it to the inflatable tube and, in particular, to form it in one piece with the inflatable tube. The fact that the inflatable tube and obturating block are firmly attached together allows for easy manipulation on the building site. In particular, when constructing a sheet pile wall, the obturating device is inserted into the interlock chamber of the leading sheet pile interlock of a first sheet pile. The inflatable tube is inflated, e.g. by means of compressed air, and this first sheet pile is driven into the ground. Once this first sheet pile is in place, the inflatable tube is deflated and the obturating device is withdrawn from the interlock chamber. It will be appreciated that the withdrawn obturating device leaves an interlock chamber in the leading sheet pile interlock that is perfectly clean, i.e. free from any ground material. The obturating device is then inserted into the interlock chamber of the leading sheet pile interlock of a second sheet pile and the inflatable tube is inflated. The interlock head of the trailing sheet pile interlock of the second sheet pile is coated with fixing agent. The bottom end of the trailing sheet pile interlock of the second sheet pile is now intercon- nected with the top end of the leading sheet pile interlock of the first sheet pile. As the second sheet pile is driven into the ground, the coated interlock head of its trailing sheet pile interlock slides down through the clean interlock chamber of the leading sheet pile interlock of the first sheet pile. Once the sheet pile is in place, the inflatable tube is again deflated and the obturating device withdrawn. This process is repeated for the third, fourth, etc sheet piles. Consequently, the trailing sheet pile interlock of a sheet pile is always interconnected with a clean leading sheet pile interlock of the preceding sheet pile. It follows that the sheet piles are reliably secured, as excellent bond conditions are guaranteed through the clean contact surfaces in the leading sheet pile interlocks. Before driving a sheet pile into the ground, it is recommended to insert a front end obturator in the bottom end of the interlock chamber of a leading sheet pile interlock. The front end obturator displaces ground material from under the axial opening of the interlock chamber and prevents ground material from axially entering the interlock chamber. It will be appreciated that the front end obturator can e.g. be a simple bolt. However, in order to be most effective, the front end obturator advantageously has a conical head. The front end obturator is preferably just inserted into the interlock chamber, rather than fixed to the sheet pile, so that the front end obturator can simply be pushed out of the interlock chamber of the leading sheet pile interlock by the trailing sheet pile interlock of the subsequent sheet pile. This is of particular interest in case a sheet pile needs to be driven deeper into the ground than the preceding one. A short cleaning piece is preferably engaged with the leading sheet pile interlock of a first sheet pile before interconnecting this interlock with the trailing sheet pile interlock of a second sheet pile. When the second sheet pile is driven into the ground, its trailing sheet pile interlock pushes the cleaning piece along the leading sheet pile interlock of the first sheet pile. It will be appreciated that the cleaning piece can e.g. be a piece of an interlocking sheet pile interlock, which removes any ground material from the inner walls of the leading sheet pile interlock and preferably wraps the outer walls of the leading sheet pile interlock, so that it also effectively removes any ground material from the outer walls of the leading sheet pile interlock. It follows that all exterior and interior contact surfaces of the leading sheet pile interlock are free of ground material when coming into contact with the corresponding contact surfaces of the trailing sheet pile interlock of the subsequent sheet pile. Usage of the cleaning piece is particularly of advantage if the interlock chamber of the leading sheet pile interlock of the first sheet pile has been filled with sand as the obturating device was withdrawn from the interlock chamber. It will further be appreciated that alternative protection means for protecting the interlock chamber from ground material can be considered. Brief description of the drawings A preferred embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig.1: is a perspective view of two sheet piles being interconnected; Fig.2: is a section through a sheet pile interlock on which fixing agent is being applied; Fig.3: is a perspective view of a sheet pile on which fixing agent is being applied; Fig.4: is a perspective view of a sheet pile in which an obturating device is being inserted; Fig.5: is a section through a deflated obturating device inside a sheet pile interlock; Fig.6: is a section through an inflated obturating device inside a sheet pile interlock; Fig.7: is a section through an inflated obturating device with flexible tube inside a sheet pile interlock; Fig.8: is a perspective view of a front end obturator; and Fig.9: is a schematic underneath view of the front end obturator of Figure 8 inserted in a sheet pile interlock. Detailed description of a preferred embodiment On Fig.1 , a first sheet pile 10 with its trailing and leading sheet pile interlocks 12, 14 can be seen in place in the ground. A second sheet pile 10' with its trailing and leading sheet pile interlocks 12', 14' is ready to be interlocked with the first sheet pile 10. The trailing sheet pile interlock 12' of the second sheet pile 10' has an interlock head 16 coated with a fixing agent 18. This interlock head 16 engages in an interlock chamber 20 of the leading sheet pile interlock 14 of the first sheet pile 10. The interlock chamber 20 is clean, i.e. it is free from any ground material. The interlock head 16 of the trailing sheet pile interlock 12' of the second sheet pile 10' slides down the clean interlock chamber 20 of the leading sheet pile interlock 14 of the first sheet pile 10 as the second sheet pile 10' is driven into the ground. Fig.2 shows a trailing sheet pile interlock 12' whose interlock head 16 is being coated with a fixing agent 18. The fixing agent 18 is being applied by means of a spreader 22, which has a spreader chamber that has substantially the same form as the interlock head 16 of a sheet pile interlock, but is slightly bigger than the latter, so that a uniform layer of fixing agent 18 can be applied over the whole length of the head 16 of the trailing sheet pile interlock 12'. The fixing agent 18 is injected into the spreader chamber of the spreader 22 through an injection opening 24 by means of an injection nozzle 26. Fig.3 shows a pumping apparatus 28 for applying a fixing agent 18 onto the trailing sheet pile interlock 12' of a sheet pile 10'. By means of the pumping apparatus 28, and via a flexible tube 29, the injection nozzle 26 injects the fixing agent 18 into the spreader chamber of the spreader 22. As the spreader 22 is moved axially along the trailing sheet pile interlock 12', the interlock head 16 is coated with a uniform layer of fixing agent 18 over the whole length of the sheet pile 10'. Fig.4 shows an obturating device 30 being inserted in the leading sheet pile interlock 14 and inflated by compressed air means 32. The obturating device 30 is described in more detail by referring to Fig.5 and 6, in which the obturating device 30 is arranged in an interlock chamber 20 of a leading sheet pile interlock 14. The obturating device 30 comprises an inflatable tube 32 and a wedge shaped obturating block 34. Fig.5 and 6 show the inflatable tube 32 in its deflated and inflated state respectively. When the inflatable tube 32 is inflated, the obturating block 34 is firmly pressed in the longitudinal opening, which gives access to the interlock chamber 20. In other words, it blocks off this longitudinal opening of the interlock chamber 20, thereby preventing ground material from entering into the interlock chamber 20 through this opening. Fig.7 shows an obturating device 30 having a flexible tube 35 running alongside the inflatable tube 32. The flexible tube 35 has an open front end and is used to insert sand into the interlock chamber 20 when the obturating device 30 is being removed from the interlock chamber 20. The longitudinal opening of the interlock chamber 20 is thereby blocked off, whence preventing ground material from entering into the interlock chamber 20 through this opening. It will be noted that the preferred obturating device 30 shown in Fig.5 and 6 and in Fig.7 is a semi-rigid rubber piece. It may include synthetic or metallic reinforcement fibres or fabrics, which increase its tensile strength. Its surfaces coming into contact with the walls of the sheet pile interlock may receive a friction reducing coating. In order to protect the interlock chamber 20 from soil being pushed in axi- ally from below as the sheet pile 10 is being driven, a front end obturator 36 is inserted in the bottom end of the interlock chamber 20. This front end obturator 36, which is shown in Fig.8 and 9, has a cylindrical body 38 and a conical head 40. Before the second sheet pile 10' is interlocked with the first sheet pile 10 and driven into the ground, a short cleaning piece 42 is engaged in the leading sheet pile interlock 14 of the first sheet pile 10 for removing any ground material from the inner walls of the leading sheet pile interlock 14. The short cleaning piece 42 shown in Fig.1 wraps the outer walls of the leading sheet pile interlock 14 and has an acute front end 44. Consequently, when it is pushed down along the leading sheet pile interlock 14 by the trailing sheet pile interlock 12' of the second sheet pile 10', it effectively removes any ground material from the outer walls of the leading sheet pile interlock 14.

Claims: Claims 1. A method for building sheet pile walls, comprising the steps of: providing a first sheet pile (10), said first sheet pile (10) having a leading sheet pile interlock (14) with an interlock chamber (20); driving said first sheet pile (10) into the ground while protecting said interiock chamber (20) from ground material; providing a second sheet pile (10'), said second sheet pile (10 1 ) having a trailing sheet pile interlock (12') with an interlock head (16); engaging said interlock head (16) of said trailing sheet pile interlock (12') in said interlock chamber (20) of said leading sheet pile interlock (14); driving said second sheet pile (10') into the ground; characterised by coating said interlock head (16) of said trailing sheet pile interlock (12') with a fixing agent (18) prior to engaging said interlock head (16) of said trailing sheet pile interlock (12') in said interlock chamber of said leading sheet pile interlock (14). 2. Method according to claim 1 , characterised in that a spreader (22) is used to apply a layer of fixing agent (18) onto said interlock head (16) of said trailing sheet pile interlock (12'). 3. Method according to claim 2, characterised in that a spreader chamber of said spreader (22) engages said interlock head (16) of said trailing sheet pile interlock (12 1 ), said spreader chamber having a slightly bigger cross- section than said interlock head (16) of said trailing sheet pile interlock (12'). 4. Method according to claim 3, characterised in that an injection nozzle (26) injects said fixing agent (18) into said spreader chamber through an injection opening (24) arranged in said spreader (22). 5. Method according to any of the preceding claims, characterised in that protecting said interlock chamber (20) from ground material comprises the following steps: inserting an obturating device (30) into said interlock chamber (20), said obturating device (30) comprising an inflatable tube (32); inflating said inflatable tube (32); driving said first sheet pile (10) into the ground; deflating said inflatable tube (32); and withdrawing said obturating device (30) from said interlock chamber (20). 6. Method according to claim 5, wherein said obturating device (30) comprises an obturating block (34), wherein inflation of said inflatable tube (32) pushes said obturating block (34) into the longitudinal opening of said interlock chamber (20). 7. Method according to claim 5 or 6, characterised in that said obturating device (30) further comprises a flexible tube (35); and in that while withdrawing said obturating device (30) from said interlock chamber (20), said interlock chamber (20) is filled with sand through said flexible tube (35). 8. Method according to any of claims 5 to 7, further characterised by: inserting a front end obturator (36) in the bottom end of said interlock chamber (20) of said leading sheet pile interlock (14) before driving said sheet pile (10) into the ground. 9. Method according to any of claims 5 to 8, further characterised by inserting a cleaning piece (42) into said leading sheet pile interlock (14) of said first sheet pile (10) before interlocking it with said trailing sheet pile interlock (12') of said second sheet pile (10'). 10. Method according to any of claims 1 to 9, wherein said fixing agent is an adhesive or cement.

Inventors: MOULIN JEAN-MICHEL, RIX ANDRE, MOULIN, JEAN-MICHEL, RIX, ANDRE
Applicants: INTERNAT SHEET PILING COMPANY, MOULIN JEAN MICHEL, RIX ANDRE, INTERNATIONAL SHEET PILING COMPANY SARL, MOULIN, JEAN-MICHEL, RIX, ANDRE
Application year: 2001
Main classification: E02D5
IPC codes: E02D5