Patent Description:
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 <CIT> 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 <NUM>° 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 <NUM> 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 <NUM>° with respect to the neutral axis P<NUM> of the metal sheet pile and are extended by an interlock comprising consecutively:.

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

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:.

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 <FIG>, the metal sheet pile <NUM> according to the invention first comprises, in cross-section perpendicular to its length, a central web <NUM> and a first inclined flange <NUM> and a second inclined flange <NUM> 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 <FIG>) or on two different sides so as to form a Z-shaped sheet pile (as illustrated on <FIG>). The angle β between the central web and one inclined flange is generally comprised between <NUM>° and <NUM>°. The sheet pile is preferably a U-shaped sheet pile. Preferably, inclined flanges <NUM> and <NUM> 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 <FIG>, 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 <NUM> and <NUM>%. 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 <FIG>, the inclined flange(s) <NUM>, <NUM> can comprise a shoulder <NUM> located at the junction between the central web <NUM> 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 <NUM>, 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 <NUM> and the inclined flange(s) <NUM>, <NUM> 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 <NUM> 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 <NUM>° with respect to the neutral axis P<NUM> 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-<NUM>:<NUM>. 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 <NUM>° and <NUM>° 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 <FIG>, 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 <FIG>, 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 <FIG>, the metal sheet pile <NUM> according to the invention further comprises a first interlock <NUM> and a second interlock <NUM> extending from the extremity of respectively the first inclined flange <NUM> and the second inclined flange <NUM>. Interlocks <NUM> and <NUM> are designed so that interlock <NUM> of a first metal sheet pile can slot into interlock <NUM> of a second metal sheet pile, as illustrated on <FIG>.

With reference to <FIG>, each of the two interlocks <NUM>, <NUM> comprises a bottom part <NUM> convexly extending outward from the extremity of the inclined flange and a finger <NUM> 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 <NUM>. As illustrated on <FIG>, 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 <NUM> comprises an internal side <NUM> and an external side <NUM> separated by a radial thickness T<NUM>. By internal side, it is meant the side facing the chamber <NUM> 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 <NUM> extends along a first portion of circle <NUM> whose center lies in a plane P<NUM> perpendicular to plane P<NUM> and whose radius of curvature R<NUM> satisfies inequation (i) : <MAT>.

As the thickness of the bottom part can vary along its cross-section, the radial thickness T<NUM> is defined as the thickness measured along the perpendicular bisector of the first portion of circle <NUM>.

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 <NUM> is located above the bottom part.

Thanks to the rounded bottom part, and in particular to the ratio between the radius of curvature R<NUM> and the radial thickness T<NUM>, the chamber <NUM> presents a rounded shape which improves the rotational capacity of the sheet pile. This is illustrated on <FIG> where the illustrated variant allows rotating the interlock by <NUM>° 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 R<NUM> and the radial thickness T<NUM> is comprised between <NUM> and <NUM>. 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 <NUM> is within plane P<NUM>. This symmetry favors the interlocking of two adjacent sheet piles.

Preferably, the first portion of circle <NUM> has an angle of aperture γ comprised between <NUM>° and <NUM>°, depending on the radius of curvature R<NUM>. 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 R<NUM> and the angle of aperture γ satisfy the inequation (iii): <MAT>.

The external side <NUM> extends along a second portion of circle <NUM> whose center lies in plane P<NUM> and whose radius of curvature R<NUM> is at least equal to R<NUM>+T1.

Preferably, the perpendicular bisector of the first portion of circle <NUM> and the perpendicular bisector of the second portion of circle <NUM> are identical. This ensures a symmetrical distribution of the material on both sides of the perpendicular bisector of the first portion of circle <NUM>. This favors a homogeneous behavior of the interlock.

According to one variant of the invention, the second portion of circle <NUM> and the first portion of circle are concentric. In that case, R<NUM> is equal to R<NUM>+T1.

According to another variant of the invention illustrated on <FIG>, R<NUM> is greater than R<NUM>+T1. In other words, this means that the bottom part <NUM> is thicker on its extremities than along the perpendicular bisector of the first portion of circle <NUM>. This material surcharge on the extremities reinforces the mechanical resistance of the interlock and, in particular, its resistance to declutching.

With reference to <FIG>, the finger <NUM> is of substantially triangular cross-section, extending upward from the bottom part, pointing towards the inclined flange. Preferably, the cross-section of finger <NUM> is substantially a rectangular triangle, whose hypotenuse <NUM> is facing the chamber <NUM>, whose lateral side <NUM> is parallel to plane P<NUM> and whose top side <NUM> is parallel to plane P<NUM>. More preferably, the vertex between the lateral side and the top side is rounded. Even more preferably, the radius of curvature R<NUM> of the rounded vertex is equal to the radius of curvature R<NUM> of the internal side <NUM> of the bottom part <NUM>. 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 <NUM> has a projected width W<NUM> which is defined as the distance along a plane parallel to P<NUM> between the fingertip <NUM> and the plane P<NUM>, perpendicular to P<NUM>, which contains the lateral side <NUM>.

The finger <NUM> is separated from the extremity of the inclined flange by the distance W<NUM>, which is defined as the distance along a plane parallel to P<NUM> between the fingertip <NUM> and the inclined flange.

The finger <NUM> is positioned so that W1 and W2 satisfy the inequation (ii): <MAT>.

Thanks to this ratio between the projected width W<NUM> of the finger and the distance W<NUM>, the two interlocks <NUM>, <NUM> 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 <NUM> 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 W<NUM> of the finger and the distance W<NUM> is comprised between <NUM> and <NUM>. This was found to be the best compromise between rotational capacity and resistance to declutching.

Claim 1:
Metal sheet pile (<NUM>) comprising in cross-section a central web (<NUM>) bordered by outwardly inclined flanges (<NUM>, <NUM>), the extremities of which are inclined at an angle α of at least <NUM>° with respect to the neutral axis P<NUM> of the metal sheet pile and are extended by an interlock (<NUM>, <NUM>) comprising consecutively:
- A bottom part (<NUM>), convexly extending outward from the extremity of the inclined flange, comprising an internal side (<NUM>) and an external side (<NUM>) separated by a radial thickness T<NUM>, the internal side extending along a first portion of circle (<NUM>) whose center lies in a plane P<NUM> perpendicular to plane P<NUM> and whose radius of curvature R<NUM> satisfies inequation (i) : <MAT> and the external side extending along a second portion of circle (<NUM>) whose center lies in plane P<NUM> and whose radius of curvature R2 is at least equal to R1+T1,
- A finger (<NUM>) of substantially triangular cross-section, extending upward from the bottom part, pointing towards the inclined flange, having a projected width W<NUM> on plane P<NUM>, the fingertip (<NUM>) being separated from the inclined flange by distance W<NUM>, W<NUM> and W<NUM> satisfying the inequation (ii): <MAT>