Modified sheet pile

Abstract

A modified Z-shaped sheet pile comprising: a central web 102 with a first and second end; a first upper flange 104, a second lower flange 106 having a first and second end, the second lower flange; wh

Description

Field of the Invention This invention relates to an improved sheet pile, for use and installation on a construction site. Background of the Invention A Z-pile is a type of deep foundation used in construction to support structures, particularly when the ground is too weak or unstable to bear the load. It gets its name from its Z-shaped cross-section, which gives it added strength and stability. Z-piles are typically made of steel and are driven into the ground using specialized equipment, much like other types of piles. In engineering, Z-piles are used to transfer the load of a building or structure to deeper, more stable soil or rock layers beneath the surface. This is especially useful in areas with soft or loose soil. The Z-shape helps to resist bending and shearing forces, making them ideal for use in challenging soil conditions. They are often used in projects such as bridges, buildings, and waterfront structures, where deep foundations are required to prevent settling or tilting over time. By the term 'piling' we mean a support which may be used as a deep foundation to transfer and distribute loads through ground material or stratum (e.g. soil) with inadequate bearing, sliding or uplift capacity to more solid ground material located at a depth with a higher bearing, sliding or uplift capacity and more capable of supporting a load. Suitably, a piling may be constructed from steel, concrete, timber and other metals. Preferably, a piling comprises steel, including reinforced steel, or concrete. By the term 'displacement piling' we mean a piling as defined herein which is driven into the ground and ground material is displaced essentially simultaneously. By the term ‘replacement piling’ we mean a piling as defined herein which is inserted (e.g. driven) into a hole in the ground and ground material is not displaced essentially simultaneously. By the term 'sheet piling' we mean a piling which is essentially in the form of sheet material. The sheet material may comprise different shapes, dimensions and configurations. Current manufacturers guidance for operation of the pile pressing machines recommend a maximum pile length, when pressing Z section piles in singles of 12.0m long. FIG 1(a) is an example of two sheet piles 100 connected together, with a close up of the join between two piles shown in FIG 1(b). As illustrated each sheet pile has a web section 102, a first flange 104 extending from one end of the web section, with a clutch 108 at the other end of the first flange, and a second flange 106 extending from the other end of the web section 102, with a clutch 110 at the opposite end of the second flange 106. The clutch 110 is a male clutch, and the clutch 108 is a female clutch. The sheet piles 100 are connected together by securing the male clutch of a sheet pile inside the female clutch 108 of the adjacent sheet pile 100. The z-pile 100 has a height h, and a width w. The web 102 has a thickness tw and the flanges 104, 106 have a thickness tf. FIG 1(b) is a close up of the connection between the two sheets, showing outer section 130 of male clutch 1110, received in the interior 132 of the female clutch 108. The applicant has become aware of issues which exist during installation of long single Z section sheet piles, which result in failure to install the sheet piles within contractual installation tolerances and premature pile refusal (i.e. the sheet pile not reaching the required design pile toe level.) The main issue is a tendency for the leading clutch of the sheet pile being installed tending to rotate inwards or ‘corkscrew’ as a result of the driving process. This rotation is inherently associated with the profiled shape of a Z section pile, the rotation of a pile within the interlocked clutch and the pile behavior during driving. Statements of Invention A modified Z-shaped sheet pile comprising: a central web with a first and second end; a first upper flange having a first and second end, the first upper flange connected at the first end to the first end of the central web, and extending horizontally outwards from the first end of the central web, a second lower flange having a first and second end, the second lower flange connected at the first end to the second end of the central web, and extending horizontally outwards from the second end of the central web, in the opposite direction to the first upper flange; wherein the flanges are arranged to be parallel, and the central web is offset from the vertical with respect to the flanges; wherein the first upper flange has a male clutch at the second end, the second lower flange has a female clutch at the second end, wherein the male clutch of a first sheet pile is received in the female clutch of a second sheet pile, to secure neighbouring sheet piles together; wherein a deflection plate is provided on one of the flanges of the sheet pile, adjacent to the region of the clutch on the flange, so that when clutches of adjacent piles are secured together, the deflection plate will overlap from the flange on which it is secured to the flange of the adjacent sheet pile, to prevent movement of the flange of the pile being secured relative to the flange of the pile provided with the deflection plate. Preferably, the first upper flange is provided with the deflection plate on the outside of the first upper flange, wherein when the female and male clutches of adjacent plates are secured together, the deflection plate on a first sheet pile, overlaps the outside of the second lower flange on a second sheet pile, to prevent rotation of the first sheet pile against the second sheet pile. Further preferably, the deflection plate is welded to the first upper flange of the first sheet pile. In a preferred embodiment, the deflection plate is formed of metal. Further preferably, the metal is carbon steel Preferably, the deflection plate is located no more that 1m from the base of the sheet pile. Further preferably, the deflection plate is located no more than 50cm from the base of the sheet pile In a preferred embodiment, the deflection plate is between 10-30mm thick. Preferably, the deflection plate is between 100-200mm wide, and 75-125mm in length. Other optional and preferred features of the invention are set out in the dependent claims, and the description, below. The features of one aspect of the invention can be combined in any complimentary manner, with one or more features of another aspect of the invention, the dependent claims, and / or with one or more features of the description, where such a combination of features would provide a working embodiment of the invention. Brief Description Of The Drawings The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, which together with the detailed description below are incorporated in and form part of the specification and serve to further illustrate various embodiments of concepts that include the claimed invention, and to explain various principles and advantages of those embodiments. FIG. 1(a) shows an example top view of z-piles connected together FIG 1(b) is a close up view of the join between 2 adjacent z-piles. FIG. 2 an example top view of a sheet pile with excessive compression; FIG. 3 is an example top view of two connected sheet piles illustrating the corkscrew effect; FIG. 4 is an example front view of four connected sheet piles illustrating showing the distortion due to the corkscrewing effect; FIG. 5 is an top view of an example of two connected sheet piles according to an example embodiment; FIG. 6 is a close up of region A of FIG.5; FIG. 7(a) is a front view of a sheet pile according to an embodiment; FIG. 7(b) is a side view of a sheet pile according to an embodiment. FIG. 8 is a front view of an embodiment of the sheet pile being installed in a foundation. Detailed Description of the invention During the number of years involved with driving Z section sheet piles, the applicant has become aware of the need to devise a solution to prevent the piles from ‘corkscrewing’ and rotating inwards during installation if they were to be in a position to achieve certainty of installation tolerances and ensure the design solution is satisfied. This is illustrated in FIGs 2 to 4. FIG 2 shows a top view of a single z-pile 100, in a regular unstressed configuration, and a superimposed top view of the single z-pile 100, that is corkscrewed, due to excessive compression, and thus leading to the pile web 102, to buckle. Under this compression the leading clutch, in this case, male clutch 110, rotates inwards, towards the web 102. FIG 3 show a top view of 2 connected sheet piles when the two z-piles are fixed together by inserting the male clutch 110, into the female clutch 108 of the adjacent z-pile 100. This figure shows the original unstressed configuration, as well as the distorted configuration due to the compression that occurs when the piles are connected. FIG 4 shows the pile refusal due to the distortion of the leading clutch. A shown, there are four adjacent piles 100, with a distorted leading clutches 110,108, as a result of the corkscrewing that occurs as the piles are joined together. What this figure illustrates is the progressive refusal once the corkscrewing effect of the sheet piles occurs. In essence the largest inward rotation occurs at the bottom of the pile since it is this element which has been driven into the ground the furthest (hence the term corkscrewing). So for the first sheet pile this is installed into the ground with the bottom most section of the leading pile clutch not actually aligned and vertical but rotated inwards. The exact magnitude of this is not known and will be dependent on a number of variable factors (thickness of pile I ground conditions I operator etc). So when the second pile is installed the trailing interlock of no. 2 pile slides vertically down the leading interlock of pile no. 1. Assuming everything is vertical during this process then pile number 2 is driven into the ground. There are sufficient tolerances I clearances within the sheet pile clutches to accommodate standard installation tolerances I minor variations I minor discrepancies. However once the bottom of the second sheet pile encounters the area of the first sheet pile where the leading sheet pile clutch has rotated inwards then it is not possible for the two clutches to continue interlocking in a vertical manner. At this stage the clutches become jammed and the pile is deemed to have ‘refused’. There is not sufficient force from the piling rig available to overcome the jamming effects and even if there was what would happen is the shear force involved which cause the clutch to rip and the sheet piles would de-clutch. The reason for this is the inherent unstable nature of a single Z pile section when it is being pressed into the ground. The following installation issues are known to exist: - • During pressing the Z section piles tend to ‘corkscrew’ into the ground resulting in the leading clutch rotating inwards. • This not only means the clutch is off-line for installation of subsequent clutched piles, but also results in the pile trying to lean backwards resulting in excessive compression and buckling of the pile web Line or Row • Once the above issues are present during installation then installation of the sequential piles becomes more and more difficult, as a result of cumulation of excessive clutch friction • These issues, along with straightness of the leading clutch, are exaggerated with increasing pile lengths. For these reasons, the recommendation is for a 12m maximum pile length. The inventors of this application sought to overcome this problem and develop a solution, which prevented single Z section sheet piles from rotating inwards during driving. The inventors have considered various options which could be incorporated into the drilling process in order to prevent the twisting of the sheet pile. FIGS. 5 and 6 demonstrates embodiments of a sheet pile which addresses these problems. FIGS 5 and 6 illustrate an embodiment of a sheet pile 140 including an ‘Anti Rotation Plate 150.’ FIGs. 7(a) and 7(b) show a front view of the sheet pile 140, and a side view of the sheet pile 140. More specifically, the web section 102, flanges 104 and 106, and clutch sections 108 and 110 are the same as shown in FIGs 1-4. However, these figures also show plate 150, affixed to the outer side of one of the flanges 104,106, adjacent to the clutch section 108, 110, and positioned on the flange 104, 106, so that when the clutches 108, 110 are fixed together, the plate 150 overlaps both of the clutch sections of the adjacent sheet piles 100. As shown the plate 150 is welded at region 152, to the outer section of the flange where it is connected. The free end of the plate 150, will then overlap with the outer section of the flange of the adjacent sheet pile 100. When the plate 150 is welded to flange 104, it will overlap with flange 106, and vice versa. Preferably, the plate 150 is welded to the trailing clutch of the pile which was being installed. The plate 150 prevents corkscrewing / rotation of the pile 100 that is being installed by reacting against the previously installed sheet pile 100. In an embodiment there is provided a modified Z-shaped sheet pile comprising: a central web with a first and second end; a first upper flange having a first and second end, the first upper flange connected at the first end to the first end of the central web, and extending horizontally outwards from the first end of the central web, a second lower flange having a first and second end, the second lower flange connected at the first end to the second end of the central web, and extending horizontally outwards from the second end of the central web, in the opposite direction to the first upper flange; wherein the flanges are arranged to be parallel, and the central web is offset from the vertical with respect to the flanges; wherein the first upper flange has a male clutch at the second end, the second lower flange has a female clutch at the second end, wherein the male clutch of a first sheet pile is received in the female clutch of a second sheet pile, to secure neighbouring sheet piles together; wherein a deflection plate is provided on one of the flanges of the sheet pile, adjacent to the region of the clutch on the flange, so that when clutches of adjacent piles are secured together, the deflection plate will overlap from the flange on which it is secured to the flange of the adjacent sheet pile, to prevent movement of the flange of the pile being secured relative to the flange of the pile provided with the deflection plate. The intention of the plate 150 was that as the leading clutch 108, 110 of the pile 100 being installed, tried to twist and rotate inwards; the plate 150 would provide resistance to prevent this rotation occur by virtue of the reaction from the previously installed pile 100. FIG. 8 is a front view of two sheet piles 100, with the plate 150 overlapping the flanges 104, 106 of adjacent piles 100. As shown, the first pile 100 has been inserted into the ground 200, and the second pile 10o is installed adjacent to the first pile, with the plate 150, overlapping the adjoining flanges 104, 106. The pile 100 to be installed is higher above the ground that than the already installed pile, and will be inserted into the ground. It is known in pile pressing that if the pile can be installed straight and plumb during the first 3m of drilling, then the restraint of the ground below this depth will assist with installation of tolerance control. The ‘Anti Rotation Plate’ 150 was therefore located at the bottom of the pile being installed, so it was acting to prevent twisting during the initial penetration of the pile. Preferably, the plate 150 is located within 1.0-0.5m from the base of the sheet pile. The closer the plate 150 is to the toe of the pile 100 on which the plate 150 is installed, the maximum impact it has on preventing any initial rotation of the sheet pile clutch 108, 100 which would (if not prevented) simply become more pronounced as the pile is driven into the ground. Also 0.5m is a reasonably practical distance above ground level for installing the plate since access is required for the welder undertaking the works. The inventors have established that unless the plate was located within the bottom 1.0m of the sheet pile toe it had little I no effect on preventing the rotation of the pile clutch during driving. The plate 150 can be fixed to either the male or the female clutch of the sheet pile 140 depending on which clutch is leading during the driving process. However the plate 150 must always be located on the outside of the flange I clutch since the leading clutch will always want to rotate inwards and it is only by virtue of the tendency of the leading clutch to rotate inwards that the plate will then in fact gain the reaction against the previously installed pile as during the rotation process. If the plate was located on the inside flange I clutch then it would not react with the previously installed pile. The plates were located on the outside of the pile to react with the previous pile to prevent inward rotation. Preferably, the first upper flange is provided with the deflection plate on the outside of the first upper flange, wherein when the female and male clutches of adjacent plates are secured together, the deflection plate on a first sheet pile, overlaps the outside of the second lower flange on a second sheet pile, to prevent rotation of the first sheet pile against the second sheet pile. Further preferably, the deflection plate is welded to the first upper flange of the first sheet pile. The plate material had to be of a sufficient size and thickness to both generate enough resistance to prevent twisting of the pile and also sufficient thickness to not be bent or distorted. Preferably, the plate 150 will be from hot rolled carbon steel plate which can be easily profiled and welded. The steel grade of the plate will be Grade S355. In a preferred embodiment, the deflection plate is formed of metal. Further preferably, the metal is carbon steel Typically, the plate 150 has a size of 150mm x 100mm x 20mm. Preferably, the deflection plate is located no more that 1m from the base of the sheet pile. Further preferably, the deflection plate is located no more than 50cm from the base of the sheet pile In a preferred embodiment, the deflection plate is between 10-30mm thick. Preferably, the deflection plate is between 100-200mm wide, and 75-125mm in length. It has been was established the ‘Anti Rotation Plates’ were indeed beneficial in preventing the twisting I corkscrewing effect of the sheet pile 100 during drilling. The plates 150 clearly managed to generate sufficient resistance against the previously installed pile to prevent the pile being installed tending to twist inwards. Upon extraction of the pile it was found that the ‘plates 150 remained in good condition and there was no bending of the plates during installation. Following these results the plate dimensions were reduced to 150mm x 80mm x 20mm on the basis the smaller depth dimension of the plate would have very little impact on the desired performance. The results achieved with the revised Plates 150 dimensions were similar to the original plate, thus concluding the revised dimensions would be acceptable. During driving of the single Z piles 100 with the plates 150 installed, it was evident from the installation tolerances that by maintaining the leading clutch 108, 110 of the sheet pile 100 straight and plumb during the initial drilling, prevented the rotation I twisting which would otherwise occur and cause significant clutch friction and eventual premature pile refusal when installing long single Z section sheet piles. Therefore, within the procedure for the activity of installing the ‘Plates’ a full profile of 6mm fillet weld was specified to ensure there was no failure of the plates due to insufficient weld. As a result of the success of the ‘z-piles 100 with the plate 100 it has become possible to successfully install 16m long single Z section sheet piles. This has ultimately lead to increased confidence in installing single Z section sheet piles using a pile pressing method. In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the scope of the invention as set forth in the appended claims, and that the claims are not limited to the specific examples described above. Details have not been explained in any greater extent than that considered necessary, for the understanding and appreciation of the underlying concepts of the present invention and in order not to distract from the teachings of the present invention. The word ‘comprising’ does not exclude the presence of other elements or steps then those 5 listed in a claim. Furthermore, the terms ‘a’ or ‘an,’ as used herein, are defined as one or more than one. Also, the use of introductory phrases such as ‘at least one’ in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles ‘a’ or ‘an’ limits any particular claim to embodiments of the invention containing only one such element. The 10 same holds true for the use of definite articles. Unless stated otherwise, terms such as ‘first’ and ‘second’ are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements.

Claims

1. A modified Z-shaped sheet pile comprising:a central web with a first and second end;a first upper flange having a first and second end, the first upper flange connected at the first end to the first end of the central web, and extending horizontally outwards from the first end of the central web,a second lower flange having a first and second end, the second lower flange connected at the first end to the second end of the central web, and extending horizontally outwards from the second end of the central web, in the opposite direction to the first upper flange; wherein the flanges are arranged to be parallel, and the central web is offset from vertical with respect to the flanges;wherein the first upper flange has a male clutch at the second end, the second lower flange has a female clutch at the second end, wherein the male clutch of a first sheet pile is received in the female clutch of a second sheet pile, to secure neighbouring sheet piles together;wherein a deflection plate is provided on one of the flanges of the sheet pile, adjacent to the region of the clutch on the flange, so that when clutches of adjacent piles are secured together, the deflection plate will overlap from the flange on which it is secured to the flange of an adjacent sheet pile, to prevent movement of the flange of the pile being secured relative to the flange of the pile provided with the deflection plate.

2. The sheet pile of claim 1 wherein the first upper flange is provided with the deflection plate on an outside of the first upper flange, wherein when the female and male clutches of adjacent plates are secured together, the deflection plate on a first sheet pile, overlaps the outside of the second lower flange on a second sheet pile, to prevent rotation of the first sheet pile against the second sheet pile.

3. The sheet pile as claimed in claim 1 or claim 2 wherein the deflection plate is welded to the first upper flange of the first sheet pile.

4. The sheet pile as claimed in any preceding claim wherein the deflection plate is formed of metal.

5. The sheet pile as claimed in claim 4 wherein the metal is carbon steel6. The sheet pile as claimed in any preceding claim wherein the deflection plate is located no more that 1 m from the base of the sheet pile.

7. The sheet pile as claimed in claim 6 wherein the deflection plate is located no more than 50cm from the base of the sheet pile8. The sheet pile of any preceding claim wherein the deflection plate is between 10-30mm thick.

9. The sheet pile of any preceding claim wherein the deflection plate is between 100-200mm wide, and 75-125mm in length.

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