EP4065775B1

EP4065775B1 - Reusable metal sheet pile

Info

Publication number: EP4065775B1
Application number: EP19813945.3A
Authority: EP
Inventors: Aloyse Hermes
Original assignee: ArcelorMittal SA
Current assignee: ArcelorMittal SA
Priority date: 2019-11-25
Filing date: 2019-11-25
Publication date: 2025-03-26
Anticipated expiration: 2039-11-25
Also published as: WO2021105740A1; PL4065775T3; EP4065775A1

Description

The present invention relates to a metal sheet pile, in particular a metal sheet pile for the construction of temporary structures.
It is well known to use metal sheet piles for the construction of earth retaining structure, such as river embankments, quay walls of ports, retaining walls, cut-off walls, basements, underground carparks, abutments for bridges or earthquake strengthening structures, where a differential surface level is to be established. These structures can be either temporary or permanent.
More particularly, the metal sheet piles are driven in the ground, alone or in pairs so that the interlock located on one of their lateral extremities slot into the interlock of a metal sheet pile previously driven in the ground. Once the metal sheet piles have been assembled, the assembly must resist the mechanical constraints imposed by the ground. The metal sheet piles are thus designed to have both a good drivability and a good resistance to declutching.
In the specific case of temporary structures, when the metal sheet piles are removed and reused, the interlock gets damaged which jeopardizes the tightness and weaken the resistance of the structure.
The document CN201386275Y discloses a metal sheet pile comprising in cross-section a central web bordered by outwardly inclined flanges, the extremities of which are inclined at an angle α of at least 97° with respect to the neutral axis of the metal sheet pile and are extended by an interlock comprising: a bottom part, convexly extending outward from the extremity of the inclined flange, comprising an internal side and an external side separated by a radial thickness, the internal side extending along a first portion of circle whose center lies in a plane perpendicular to the plane as defined above by the neutral axis and 1.1 the external side extending along a second portion of circle whose center lies in plane perpendicular to the plane as defined above by the neutral axis and whose radius of curvature is at least equal the radius of curvature of the internal side plus the radial thickness separating said internal and external sides.
The aim of the present invention is therefore to remedy the drawbacks of the metal sheet piles of the prior art by providing a sheet pile whose drivability and reusability have been improved while maintaining a good resistance to declutching.
For this purpose, a first subject of the present invention consists of a metal sheet pile comprising in cross-section a central web bordered by outwardly inclined flanges, the extremities of which are inclined at an angle α of at least 97° with respect to the neutral axis P₁ of the metal sheet pile and are extended by an interlock comprising consecutively:

A bottom part, convexly extending outward from the extremity of the inclined flange, comprising an internal side and an external side separated by a radial thickness T₁, the internal side extending along a first portion of circle whose center lies in a plane P₂ perpendicular to plane P₁ and whose radius of curvature R₁ satisfies inequation (i) : $1.5 \leq R_{1} / T_{1} \leq 5$
and the external side extending along a second portion of circle whose center lies in plane P₂ and whose radius of curvature R2 is at least equal to R1+T1,
A finger of substantially triangular cross-section, extending upward from the bottom part, pointing towards the inclined flange, having a projected width W₁ on plane P₁, the fingertip being separated from the inclined flange by distance W₂, W₁ and W₂ satisfying the inequation (ii): $1.2 \leq W_{1} / W_{2} \leq 1.7$

The metal sheet pile according to the invention may also have the optional features listed below, considered individually or in combination:

angle α is comprised between 97° and 101°,
the ratio between the radius of curvature R₁ and the radial thickness T₁ is comprised between 1.5 and 2.5,
the perpendicular bisector of the first portion of circle is within plane P₂,
the first portion of circle has an angle of aperture γ comprised between 20° and 137°,
the perpendicular bisector of the first portion of circle and the perpendicular bisector of the second portion of circle are identical,
R₂ is equal to R₁+T₁,
the finger comprises a lateral side and a top side, the vertex of which is rounded with a radius of curvature R₃ equal to the radius of curvature R₁ of the internal side of the bottom part,
the ratio between the projected width W₁ of the finger and the distance W₂ is comprised between 1.45 and 1.55,
at least one of the inclined flanges comprise two sides which converge in the direction of the interlock with a convergence rate comprised between 1 and 3%,
at least one of the inclined flanges comprises a shoulder located at the junction between the central web and the at least one of the inclined flanges,
the connections between the central web and the inclined flanges delimit concave corners which are substantially flattened by a material surcharge.

A second subject of the invention consists of an earth retaining structure comprising at least two metal sheet piles according to the invention interlocked to one another.
Other characteristics and advantages of the invention will be described in greater detail in the following description.
The invention will be better understood by reading the following description, which is provided purely for purposes of explanation and is in no way intended to be restrictive, with reference to:

Figure 1, which is a cross-section of the metal sheet pile according to one variant of the invention,
Figure 2, which is a cross-section of the metal sheet pile according to another variant of the invention,
Figure 3, which is a partial cross-section of the metal sheet pile according to the variant illustrated on Figure 1,
Figure 4, which is a partial cross-section of the interlocking of two adjacent metal sheet piles according to one variant of the invention,
Figure 5, which is a cross-section of the interlock of a metal sheet pile according to one variant of the invention,
Figure 6, which is a cross-section of the interlock of a metal sheet pile according to one variant of the invention,
Figure 7, which is an illustration of the rotational capacity of the metal sheet pile according to one variant of the invention,
Figure 8, which is a cross-section of the interlock of a metal sheet pile according to another variant of the invention,
Figure 9, which is an illustration of the resistance to declutching of the metal sheet pile according to one variant of the invention,
Figure 10, which is an illustration of the resistance to declutching of the metal sheet pile according to another variant of the invention.

It should be noted that the terms "above", "outward", "outwardly", "convexly", "concave" ... as used in this application refer to the positions and orientations of the different constituent elements of the metal sheet pile when the y-y axis of the sheet pile is horizontal.
With reference to Figure 1, the metal sheet pile 1 according to the invention first comprises, in cross-section perpendicular to its length, a central web 2 and a first inclined flange 3 and a second inclined flange 4 both extending outwardly from the lateral edges of the central web.
The metal sheet pile is preferably made of steel and obtained by hot rolling.
The central web is preferably substantially flat and lies in a plane. It is preferably of constant thickness across the cross-section.
The two inclined flanges extend either on the same side of the central web so as to form a U-shaped sheet pile (as illustrated on Figure 1) or on two different sides so as to form a Z-shaped sheet pile (as illustrated on Figure 2). The angle β between the central web and one inclined flange is generally comprised between 110° and 150°. The sheet pile is preferably a U-shaped sheet pile. Preferably, inclined flanges 3 and 4 are symmetrical.
According to one variant of the invention, the inclined flange is of constant thickness across the cross-section. According to the variant illustrated on Figure 3, its thickness decreases towards the extremity of the sheet pile, i.e. towards the interlock. In other words, the inclined flange has a conical cross-section. More preferably, the two sides of the flange converge in the direction of the interlock with a convergence rate comprised between 1 and 3%. The convergence rate is defined as the difference between the thicknesses at two points of the wing divided by the distance between these two points. The conicity of the inclined flange(s) improves the drivability of the metal sheet pile while optimizing its weight.
According to one variant of the invention illustrated on Figure 3, the inclined flange(s) 3, 4 can comprise a shoulder 5 located at the junction between the central web 2 and the inclined flange(s). By "shoulder", it is meant a material extension projecting with respect to the imaginary plane which prolongs the external face of the inclined flange towards the central web. The shoulder increases the resistance modulus and thus the reusability of the metal sheet pile.
Alternatively, or in addition to shoulder 5, the central web can comprise an extension (not illustrated) projecting with respect to the imaginary plane which prolongs the external face of the central web towards the inclined flange.
Similarly, the bending radius at the junction between the central web 2 and the inclined flange(s) 3, 4 can be increased so as to thicken the connection of the central web and the inclined flange(s) from the inside. In other words, the concave corners 6 delimited by the two flange/web connections are substantially flattened by a material surcharge. This increases the mechanical resistance of the metal sheet pile and, thus, improves its reusability.
The extremity of the inclined flanges, defined as the end of the inclined flanges located on the opposite side of the central web, are inclined at an angle α of at least 97° with respect to the neutral axis P₁ of the metal sheet pile. The neutral axis is defined as the axis along which there are no stresses or strains. The neutral axis is always parallel to the y-y axis of the sheet pile as defined in EN1993-5:2007. In the case of a U-shaped sheet pile, the interlocks are on the neutral axis; in other words, the central web is parallel to the neutral axis. In the case of a Z-shaped sheet pile, the neutral axis is parallel to the inclined flanges and cross the central web in its middle. Thanks to this inclination, and in combination with the shape of the interlock (described later on), the rotational capacity of the sheet pile is improved. This improved rotational capacity strongly limits the risk of deforming the interlock when the sheet pile is driven in the ground and/or removed before reuse. More preferably, angle α is comprised between 97° and 101° in order to have the best compromise between rotational capacity and resistance to declutching.
According to one variant of the invention, the flange is straight in that case. According to another preferred variant illustrated on Figure 3, the extremity of the inclined flange is bent so that angles α and β differ. Thanks to this bent at the extremity of the inclined flange, angle β can be adjusted to optimize the tension modulus of the sheet pile while angle α is adjusted differently to optimize the rotational capacity of the sheet pile. According to the variant illustrated on Figure 2, one of the extremities of the inclined flanges is inclined with respect to the neutral axis in the form of a protrusion thickening the extremity in direction of the neutral axis. The other extremity is bent so that the interlocking is possible.
With reference to Figure 1, the metal sheet pile 1 according to the invention further comprises a first interlock 8 and a second interlock 9 extending from the extremity of respectively the first inclined flange 3 and the second inclined flange 4. Interlocks 8 and 9 are designed so that interlock 8 of a first metal sheet pile can slot into interlock 9 of a second metal sheet pile, as illustrated on Figure 4.
With reference to Figures 5 and 6, each of the two interlocks 8, 9 comprises a bottom part 10 convexly extending outward from the extremity of the inclined flange and a finger 11 of substantially triangular cross-section, extending upward from the bottom part. The extremity of the inclined flange, the bottom part and the finger delimit a chamber 12. As illustrated on Figure 4, the finger of a first metal sheet pile can slot into the chamber of a second metal sheet pile so as to connect the two sheet piles.
The bottom part 10 comprises an internal side 13 and an external side 14 separated by a radial thickness T₁. By internal side, it is meant the side facing the chamber 12 and which extends from the external face of the inclined flange. The external side is thus the side at the opposite from the chamber and which extends from the internal face of the inclined flange.
The internal side 13 extends along a first portion of circle 15 whose center lies in a plane P₂ perpendicular to plane P₁ and whose radius of curvature R₁ satisfies inequation (i) : $1.5 \leq R_{1} / T_{1} \leq 5$
As the thickness of the bottom part can vary along its cross-section, the radial thickness T₁ is defined as the thickness measured along the perpendicular bisector of the first portion of circle 15.
As the bottom part extends convexly from the extremity of the inclined flange, the center of the circle corresponding to the first portion of circle 15 is located above the bottom part.
Thanks to the rounded bottom part, and in particular to the ratio between the radius of curvature R₁ and the radial thickness T₁, the chamber 12 presents a rounded shape which improves the rotational capacity of the sheet pile. This is illustrated on Figure 7 where the illustrated variant allows rotating the interlock by 19° both clockwise and counter-clockwise. In combination with the inclination of the extremity of the inclined flange, the rounded bottom part thus strongly limits the risk of deforming the interlock when the sheet pile is driven in the ground and/or removed before reuse.
More preferably the ratio between the radius of curvature R₁ and the radial thickness T₁ is comprised between 1.5 and 2.5. This was found to be the best compromise between rotational capacity and resistance to declutching.
Preferably, the perpendicular bisector of the first portion of circle 15 is within plane P₂. This symmetry favors the interlocking of two adjacent sheet piles.
Preferably, the first portion of circle 15 has an angle of aperture γ comprised between 30° and 140°, depending on the radius of curvature R₁. This favors a smooth transition between the bottom part and, on one side, the finger and, on the other side, the inclined flange. More preferably, the radius of curvature R₁ and the angle of aperture γ satisfy the inequation (iii): $100116 {(R_{1})}^{- 2.499} \leq γ \leq 3044 {(R_{1})}^{- 1.122}$
The external side 14 extends along a second portion of circle 16 whose center lies in plane P₂ and whose radius of curvature R₂ is at least equal to R₁+T1.
Preferably, the perpendicular bisector of the first portion of circle 15 and the perpendicular bisector of the second portion of circle 16 are identical. This ensures a symmetrical distribution of the material on both sides of the perpendicular bisector of the first portion of circle 15. This favors a homogeneous behavior of the interlock.
According to one variant of the invention, the second portion of circle 16 and the first portion of circle are concentric. In that case, R₂ is equal to R₁+T1.
According to another variant of the invention illustrated on Figure 8, R₂ is greater than R₁+T1. In other words, this means that the bottom part 10 is thicker on its extremities than along the perpendicular bisector of the first portion of circle 15. This material surcharge on the extremities reinforces the mechanical resistance of the interlock and, in particular, its resistance to declutching.
With reference to Figures 5 and 6, the finger 11 is of substantially triangular cross-section, extending upward from the bottom part, pointing towards the inclined flange. Preferably, the cross-section of finger 11 is substantially a rectangular triangle, whose hypotenuse 17 is facing the chamber 12, whose lateral side 18 is parallel to plane P₂ and whose top side 19 is parallel to plane P₁. More preferably, the vertex between the lateral side and the top side is rounded. Even more preferably, the radius of curvature R₃ of the rounded vertex is equal to the radius of curvature R₁ of the internal side 13 of the bottom part 10. This favors the interlocking of two interlocks and improves the rotational capacity of the sheet pile.
Preferably, the vertex between the top side and the hypotenuse is rounded too to favors the interlocking of two interlocks.
The finger 11 has a projected width W₁ which is defined as the distance along a plane parallel to P₁ between the fingertip 20 and the plane P₃, perpendicular to P₁, which contains the lateral side 18.
The finger 11 is separated from the extremity of the inclined flange by the distance W₂, which is defined as the distance along a plane parallel to P₁ between the fingertip 20 and the inclined flange.
The finger 11 is positioned so that W1 and W2 satisfy the inequation (ii): $1.2 \leq W_{1} / W_{2} \leq 1.7$
Thanks to this ratio between the projected width W₁ of the finger and the distance W₂, the two interlocks 8, 9 can more easily interlock and rotate while maintaining a good resistance to declutching. Thanks to this ratio, and in combination with the rounded shape of the bottom part 10 and the inclination of the extremity of the inclined flange, the rotational capacity of the sheet pile is improved. This improved rotational capacity strongly limits the risk of deforming the interlock when the sheet pile is driven in the ground and/or removed before reuse.
Preferably, the ratio between the projected width W₁ of the finger and the distance W₂ is comprised between 1.45 and 1.55. This was found to be the best compromise between rotational capacity and resistance to declutching.
Numerical simulations with the Qform metal forming simulation software have been performed on the metal sheet piles according to the invention. The performed simulation is similar to a tensile test where a continuous axial displacement is imposed in the tool direction and the force on the clamp is measured. The results are presented in Figure 9 where X is the time in seconds and Y is the force in MN. They show that, when R₂ is equal to R₁+T₁, the interlock resists a load of 0.085 MN before declutching, which is similar to the performances obtained with the metal sheet pile from the prior art. The results presented in Figure 10 show that increasing the radius of curvature R₂ compared to R₁ (as illustrated on Figure 8) further improves the resistance to declutching.

Claims

Metal sheet pile (1) comprising in cross-section a central web (2) bordered by outwardly inclined flanges (3, 4), the extremities of which are inclined at an angle α of at least 97° with respect to the neutral axis P₁ of the metal sheet pile and are extended by an interlock (8, 9) comprising consecutively:
- A bottom part (10), convexly extending outward from the extremity of the inclined flange, comprising an internal side (13) and an external side (14) separated by a radial thickness T₁, the internal side extending along a first portion of circle (15) whose center lies in a plane P₂ perpendicular to plane P₁ and whose radius of curvature R₁ satisfies inequation (i) : $1.5 \leq R_{1} / T_{1} \leq 5$
and the external side extending along a second portion of circle (16) whose center lies in plane P₂ and whose radius of curvature R2 is at least equal to R1+T1,

- A finger (11) of substantially triangular cross-section, extending upward from the bottom part, pointing towards the inclined flange, having a projected width W₁ on plane P₁, the fingertip (20) being separated from the inclined flange by distance W₂, W₁ and W₂ satisfying the inequation (ii): $1.2 \leq W_{1} / W_{2} \leq 1.7$
Metal sheet pile according to claim 1 wherein angle α is comprised between 97° and 101°.
Metal sheet pile according to any one of claims 1 or 2 wherein the ratio between the radius of curvature R₁ and the radial thickness T₁ is comprised between 1.5 and 2.5.
Metal sheet pile according to any one of the preceding claims wherein the perpendicular bisector of the first portion of circle (15) is within plane P₂.
Metal sheet pile according to any one of the preceding claims wherein the first portion of circle (15) has an angle of aperture γ comprised between 20° and 137°.
Metal sheet pile according to any one of the preceding claims wherein the perpendicular bisector of the first portion of circle (15) and the perpendicular bisector of the second portion of circle (16) are identical.
Metal sheet pile according to any one of the preceding claims wherein R₂ is equal to R₁+T₁.
Metal sheet pile according to any one of the preceding claims wherein the finger (11) comprises a lateral side (18) and a top side (19), the vertex of which is rounded with a radius of curvature R₃ equal to the radius of curvature R₁ of the internal side (13) of the bottom part (10).
Metal sheet pile according to any one of the preceding claims wherein the ratio between the projected width W₁ of the finger and the distance W₂ is comprised between 1.45 and 1.55.
Metal sheet pile according to any one of the preceding claims wherein at least one of the inclined flanges (3, 4) comprises two sides which converge in the direction of the interlock with a convergence rate comprised between 1 and 3%.
Metal sheet pile according to any one of the preceding claims wherein at least one of the inclined flanges (3, 4) comprises a shoulder located at the junction between the central web (2) and the at least one of the inclined flanges (3, 4).
Metal sheet pile according to any one of the preceding claims wherein the connections between the central web and the inclined flanges delimit concave corners (6) which are substantially flattened by a material surcharge.
Earth retaining structure comprising at least two metal sheet piles according to any one of claims 1 to 12 interlocked to one another.