Netting with rhomboid mesh for use in civil engineering in geotechnical applications

Abstract

A netting with rhomboid mesh, in particular for use in civil engineering in geotechnical applications, preferably in the field of protection from natural risks, is composed of elongate elements which are bent in the manner of a flattened spiral and are wound about adjacent elongate elements by half a revolution, that is to say by 180°. At least some of the elongate elements are ropes or strands which are each constructed with at least two metal wires which are helically wound about the same axis, wherein each metal wire has a diameter less than 3 mm.

Description

Field of the invention

[0001] The present invention relates to a netting with rhomboid mesh for use in civil engineering in geotechnical applications, for example, in the field of protection from natural risks.

[0002] The invention has been developed with particular regard, even if not exclusively, for a netting with rhomboid mesh with high resistance, for carrying out civil engineering works, such as protection barriers against rockfalls or avalanches, for covering the surface of rocky walls in order to contain detachments of rocks, for three-dimensional stabilization of earth, scarps, dams, embankments, tunnels and road constructions, for constructing containment walls for embankments, for protecting banks of bodies of water, for constructing weirs and other debris-protection barriers along rivers and streams and water works in general, for constructing gabions and other similar products made of metal nettings or comprising a metal netting, and for any other use of the generally known civil and geotechnical type, in which it is necessary to provide a metal netting which is resistant and durable.Technological background

[0003] The nettings to which the present invention relates are used in the field of civil and geotechnical works mainly for protection from natural risks. For example, using such nettings it is possible to avoid or in any case reduce the risk of rocks, debris, snow or other similar natural elements falling downstream as a result of natural instabilities, such as, for example, landslides, avalanches, flows of debris, river floods, detachments of rocks and other phenomena of the type, reaching and damaging roads, dwellings, bridges, etc., or even putting at risk the safety of people. To this end, these nettings, together with the supports thereof, are configured to withstand great impacts and high pressures, such as the ones brought about by a rockfall, by a flow of debris or by an avalanche which strikes it.

[0004] Typical, even if not limiting, uses of these nettings are the construction of barriers for protection from rockfalls or avalanches, covering rocky walls in order to contain detachments of rocks, three-dimensional stabilization of earth, scarps, dams, embankments, tunnels and road constructions, constructing containment walls for embankments, protecting banks of bodies of water, constructing weirs and other debris-protection barriers along rivers and streams and water works in general, constructing gabions and other similar products made of metal nettings or comprising a metal netting, and for any other use of the generally known civil and geotechnical type which has to use a netting which is resistant and durable, both with respect to impacts and to corrosion.

[0005] In the geotechnical sector, there are generally known, for the objects mentioned above, so-called nettings with rhomboid mesh which are also known as loose-mesh nettings. The geometry of these nettings is produced by bending in the form of a flattened spiral a series of metal wires which are then interlaced with each other by "twisting" them in order to form the rhomboid mesh of the netting.

[0006] US 6279858 describes an example of such a netting with rhomboid mesh, which is constructed using metal wires, each of which is bent in a spirally flattened manner and interlaced with similar adjacent metal wires in order to form the rhomboid meshes. The metal wires which compose this known netting are made from a high-strength steel which has an ultimate tensile strength between 1000 and 2200 N / mm 2< (MPa). The high resistance of these steel wires allows the weave of the netting to maintain the three-dimensional structure thereof which is defined similarly to a mattress, even under conditions with a high force.

[0007] A rhomboid mesh netting which is constructed according to the principle of US 6279858 is known by the commercial name TECCO ®< and is produced by Geobrugg AG. This netting is constructed with metal wires having an ultimate tensile strength of approximately 1770 N / mm 2< and a diameter of 2 mm, 3 mm or 4 mm, with meshes which may have dimensions of the diagonals of the rhomboids of approximately 62 x 95 mm, approximately 83 x 143 mm or approximately 102 x 177 mm, respectively.

[0008] Another rhomboid mesh netting is known by the commercial name 3STUTOR ®< which is produced by 3S Geotecnia y Tecnologia S.L. This netting is constructed with metal wires having an ultimate tensile strength of 900 N / mm 2< and a diameter of 2.7 mm, 3.4 mm, 4.0 mm or 4.5 mm. On the website where the above-mentioned netting 3STUTOR ®< is described, http: / / www.3sgeotech.com / es / productos / mallas-de-alambre-3STUTOR, there are mentioned the patent documents ES237412 and WO2015 / 114177, which describe the construction of a rhomboid mesh (or diamond-like) netting but which are constructed with a single rope rather than metal wires. The rope has a diameter between 12 mm and 18 mm and the meshes of the netting have a size between 500 mm and 700 mm and an acute angle between approximately 50° and approximately 65°.

[0009] A problem with known nettings with rhomboid mesh which are constructed with metal wires, such as the ones mentioned above, is that gradually, if the resistance of the wires increases, the greater is the difficulty of constructing the netting as a result of the substantial force necessary for bending the wires. Although US 6279858 describes the construction of metal wires with wires having a resistance of up to 2200 N / mm 2< , in practice there do not appear to have been constructed any nettings having wires with resistance values of approximately 1770 N / mm 2< .

[0010] Another problem which is encountered when constructing the known nettings with rhomboid mesh is that, with an increase in the resistance of the metal wires, the resilience thereof also increases, which makes it difficult to obtain the desired form of the nettings.

[0011] A solution to this last problem is described in EP 2817455 which relates to a method for bending the metal wires so as to form a series of bends in order to make the netting even flatter with respect to the previously known ones. In EP 2817455, the metal wires are flattened at both sides of each bend, forcing them beyond the planar surface over an additional angle, for example, from 10° to 30°, so that the resilient return of the netting when the forcing action is stopped reduces the angle and brings the netting into a flattened condition. This forcing action of the wires of the netting is particularly advantageous when the wires are made from high-strength steel with an ultimate tensile strength between 1000 N / mm 2< and 3200 N / mm 2< .

[0012] However, the solution described in EP 2817455 is not completely satisfactory because it involves additional operations for forcing the bending of the metal wires beyond the desired final configuration. In addition to this, the operation is not readily controllable and can give rise to a netting with a non-homogeneous shape.

[0013] Another example of nettings with rhomboid mesh with a high resistance used for stabilizing earth is described in US 2007 / 210214. In this case, the rhomboid mesh of the netting are not formed by single metal wires, as are the ones previously mentioned in US 6279858 or the netting TECCO ®< , but instead by strands or ropes, each of which is formed by a number of metal wires which are helically wound. At least two of the wires which form each strand or rope are made of steel with a tensile strength between low-strength steels of 100 N / mm 2< and high-strength steels of 2200 N / mm 2< . Within this very wide range of values, US 2007 / 210214 indicates the possibility of using a generic spring steel in accordance with the standard DIN 17223. In the single example described and illustrated expressly in US 2007 / 210214, the strands which form the rhomboid mesh are formed by two metal wires each having a diameter of 3 mm and an ultimate tensile strength of 1770 MPa in accordance with the DIN standard 2078. These characteristics make the netting very rigid so as not to be subjected to virtually any deformation under load and so as not to require any ring-like fixing elements (for example, cross-like clips).

[0014] A netting having the features described in US 2007 / 210214 is produced by Geobrugg AG with the commercial name Spider ®< . It is formed by 1 x 3 helical strands, that is to say, each one is formed by three metal wires wound together in a helical form about the common theoretical axis with a uniform lay length. The nominal diameter of each strand is 6.5 mm while each of the three metal wires which form the strand has a diameter of 3 mm and is made from a steel with a high resistance of 1770 N / mm 2< . The rhomboid meshes of this Spider ®< netting are much wider with respect to the meshes of the TECCO ®< netting mentioned above of the same Geobrugg AG, because they nominally measure 164 mm (smaller diagonal) x 270 mm (larger diagonal).

[0015] The production of rhomboid mesh nettings with such wires or strands from high-strength steel is difficult, if not impossible, as a result of the substantial rigidity of the individual wires which, in the nettings with lower resistance, have to have in any case a diameter of 2 mm in order to achieve a nominal ultimate tensile strength, taking into account the area of the cross-section of the wire, of at least 5.5 kN. As mentioned above, in order to produce these rhomboid mesh nettings with wires with a high resistance, it is necessary to use very robust machines which in any case have an extremely high wear rate. It is further necessary to use special arrangements for bending the metal wires as a result of the fact that the wires or strands made of high-strength steel tend to behave like harmonic steel wires for springs with a substantial resilient return and a very poor tendency to become plastically deformed so as to maintain the form of the helical bending.

[0016] Therefore, the problem of known rhomboid mesh nettings remains unsolved in relation to how to increase the resistance of the nettings themselves without having to substantially increase the dimensions of the meshes, as in the above-mentioned Spider ®< netting of Geobrugg AG, and without using special or complex machines and often additional imprecise operations, such as, for example, the over-bending described in EP 2817455, with respect to the standard operations used for manufacturing the nettings which use metal wires made of steel with low resistance.Statement of invention

[0017] An object of the present invention is to solve the problems of the prior art, providing a netting with rhomboid mesh for use in civil engineering in geotechnical applications which require a high level of resistance of the netting, in addition to a high level of ease of handling and flexibility, with a relatively reduced weight.

[0018] Another object of the invention is to provide a netting with rhomboid mesh with high resistance which can be readily manufactured with existing machines which are normally used for manufacturing nettings with rhomboid mesh which use relatively soft wires.

[0019] Another object of the invention is to provide a netting with rhomboid mesh which is sufficiently flexible to adapt to the irregular shape of the ground of scarps, slopes, banks, etcetera.

[0020] Another object is to provide a netting with rhomboid mesh which is relatively light in terms of weight per unit of measurement in order to be transported and installed readily and with reduced costs, particularly in impassable regions, such as, for example, mountainous zones which are potentially subject to rockfalls, avalanches, landslides, debris flows, etcetera.

[0021] Another object of the invention is to provide a netting with rhomboid mesh which is economical, simple to produce and durable.

[0022] The above-indicated objects are achieved by the invention as defined in the appended claims.

[0023] In the present description, the term "strand" is intended to be understood to be a rope with simple winding which is constituted by wires which are wound helically about the same axis; this rope is also known as a "helical rope". The axis of the strand or helical rope can be virtual, as, for example, in the case of strands with three or four wires, or real, in which case it can be constituted by a metal wire, as, for example, in the case of strands with seven wires or helical ropes with several layers of wires.

[0024] According to a first aspect, there is described a netting with rhomboid mesh, also called a loose-mesh netting, in particular for use in civil engineering in geotechnical applications, preferably in the field of protection from natural risks. The netting is composed of elongate elements which are bent in the manner of a flattened spiral and are wound about adjacent elongate elements by half a revolution, that is to say by 180°. At least some of the elongate elements are ropes or strands which are each constructed with at least two metal wires which are helically wound about the same axis. Each metal wire has a diameter less than 3 mm, preferably less than or equal to 2.5 mm, very preferably less than or equal to 2 mm, more preferably less than or equal to 1.5 mm, even more preferably less than or equal to 1.1 mm, this also being able to be less than 1 mm.

[0025] A netting which is constructed according to the invention affords a number of advantages, including the fact that it is very resistant and at the same time light and convenient to move, including by hand, facilitating the positioning operations, particularly in locations and in positions which are more impassable. Being light and flexible, the netting is readily rolled for transport and unrolled where applicable at the installation site.

[0026] According to a particular aspect, the metal wires of each elongate element may have the same nominal diameter. This allows a netting to be obtained with a substantially uniform resistance as well as a reduced cost as a result of the intrinsic lower cost of the strands.

[0027] According to a particular aspect, the metal wires which form the strands are made of high-strength steel, with an ultimate tensile strength greater than 770 MPa, preferably greater than or equal to 1500 MPa, for example, of approximately 1550 MPa. The ultimate tensile strength of the metal wires may be even greater, for example, preferably greater than or equal to 1700 MPa, for example, of approximately 1750 MPa, or 1860 MPa. Even more preferably, the resistance of the metal wires may be greater than or equal to 1900 MPa, for example, of approximately 1950 MPa, and, for example, it may reach or even exceed 2160 MPa. The high resistance of the metal wires which form the strands from which the netting is made allows relatively thin wires which, as a result of the helical winding thereof, still ensure a high level of flexibility of the netting, in addition to a substantial lightness thereof, to be produced. Nevertheless the wires which form the strands can be intrinsically resilient as a result of the high level of resistance of the steel, the netting generally has a specific plasticity which allows it to be shaped and to be adapted to the varied configuration of the ground. This effect appears to be a result of the fact that, even if not yet completely confirmed, the metal wires with a relatively small diameter which form the strands can slide slightly with friction on each other in such a manner as to maintain over time the configuration which is imposed thereon but without there being a significant plastic deformation yield of the material.

[0028] According to another particular aspect, the elongate elements which form the netting have a nominal diameter less than or equal to 5 mm, preferably less than or equal to 4 mm, preferably less than or equal to 3 mm, even more preferably less than or equal to 2.50 mm, for example, 2.40 mm.

[0029] Metal elements with these dimensions can readily be processed in the conventional machines used to construct nettings with rhomboid mesh with individual metal wires.

[0030] According to another particular aspect, the strands or ropes of the netting are helical ropes with simple winding with a single layer of wires, each one comprising at least two metal wires, more preferably at least three metal wires, even more preferably at least five metal wires, even more preferably at least seven metal wires. These helical ropes are flexible and are, however, rather compact so as to be also readily usable in conventional weaving machines for hexagonal mesh nettings which are normally used for manufacturing nettings with single metal wires.

[0031] According to another aspect, the elongate elements may have a protection covering. The protection covering may be made of metal, for example, an alloy of zinc and aluminium, or plastics material, for example, polyethylene PE, polyvinyl chloride PVC or polyamide PA, or a combination thereof. The covering may be constructed on each wire which forms the strand or, alternatively or additionally to the covering on each wire, on the entire strand. A particular example of covered strands is the one of so-called sheathed strands, with a sheath made, for example, from HDPE. In a preferable but non-limiting manner, the thickness of the covering may vary from approximately 0.2 mm to approximately 0.5 mm.

[0032] According to another aspect, the rhomboid mesh of the netting can have dimensions equal to those of the rhomboid nettings constructed with single metal wires, that is to say, with dimensions of the diagonals of the rhomboids from approximately 60 x 90 mm to approximately 110 x 180mm, with an acute angle of the rhomboid mesh which can be between 45° and 55°, preferably between 47° and 54°, more preferably between 48° and 52°, even more preferably between 50° and 51°.Brief description of the drawings

[0033] Additional features and advantages will be appreciated from the following detailed description of a preferred embodiment with reference to the appended drawings which are given purely by way of non-limiting example and in which: Figure 1 is a perspective view of an exemplary strand which is constructed with three metal wires and which is used to construct an exemplary netting with rhomboid mesh according to the invention; and Figure 2 is a front view of some of the rhomboid mesh of a netting according to the invention. Detailed description

[0034] Now with reference to Figure 1, there is illustrated by way of example a strand 1 which is also sometimes referred to in the sector as a "cord", "braid" or "helical rope", which is used for constructing a netting with rhomboid mesh according to the invention. The strand 1 is made of steel and can be provided in reels, thereby being able to be used in the same manner in which the single metal wires are used for the manufacture of nettings with rhomboid mesh with the known machines.

[0035] More specifically, the strand 1 which is simply a non-limiting example, given solely for better comprehension of the invention, is constituted by three metal wires 2 which all have the same nominal diameter and which are wound together in helical form about the common axis with a uniform lay length L. The strand can also be of the type in which one of the wires is central and forms a core, about which there are helically wound the remaining wires of the strand. Another example of a strand is, for example, the one referred to as 1x7, which is constituted by seven metal wires. Naturally, the invention is not limited to the use of such a strand or helical rope, but may comprise using other types of ropes, for example, helical ropes with several layers.

[0036] The diameter d of each wire may be less than or equal to 2 mm, preferably less than or equal to 1.5 mm, even more preferably less than or equal to 1.1 mm. In the case of the example illustrated, the 1x3 strand has a diameter of 2.4 mm and each wire 2 has a nominal diameter of approximately 0.9 mm. The ultimate tensile strength is approximately 1770 N / mm 2< . In another example, which is not illustrated, there is advantageously used a 1x7 strand with a diameter of 3 mm, the wires of which have a diameter of 0.9 mm, still with an ultimate tensile strength of approximately 1770 N / mm 2< . Naturally, these values have to be considered to be exemplary but not limiting with respect to the invention, which can be carried out with strands or ropes which are different from those described here in detail.

[0037] The strand 1 has its own nominal diameter D which may be less than or equal to 5 mm, preferably less than or equal to 4 mm, preferably less than or equal to 3 mm, even more preferably less than or equal to 2.50 mm, for example, in the case of Figure 1 of approximately 2.40 mm.

[0038] The wires 1 which form the strand 2 are made of steel having a resistance greater than 770 MPa, preferably greater than or equal to 1500 MPa, for example, of approximately 1550 MPa. The ultimate tensile strength of the metal wires may be even greater, for example, preferably greater than or equal to 1700 MPa, for example, of approximately 1750 MPa, or 1860 MPa. Even more preferably, the resistance of the metal wires may be greater than or equal to 1900 MPa, for example, of approximately 1950 MPa, such as, for example, it may reach or even exceed 2160 MPa. Experiments have been successfully carried out with strands constructed with metal wires having a nominal resistance of 1770 MPa.

[0039] As can be seen in Figure 2, a netting 10 according to the invention is constructed using a series of strands 1 of Figure 1 which are initially bent in a spiral and then wound (or "twisted") with each other in order to form rhomboid mesh 12. In particular, the rhomboid mesh 12 are formed by engaging adjacent strands 12 which alternately form twists of 180° at the locations at which they intersect in such a manner that each strand 1 takes up a zig-zag pattern when the netting 10 is viewed from the front as in Figure 2.

[0040] As a result of the flexibility of the strands 1, it is possible to produce rhomboid meshes which are rather small, reproducing, for example, the dimensions of the meshes commonly used for nettings of this type but constructed with single wires for uses in the geotechnical sector. For example, it is possible to construct rhomboid meshes with dimensions of the diagonals of the rhomboids from approximately 60 x 90 mm to approximately 110 x 180 mm, with an acute angle ε of the rhomboid mesh which may be between 45° and 55°, preferably between 47° and 54°, more preferably between 48° and 52°, even more preferably between 50° and 51°.

[0041] The strands 1 of the netting 10 may have a corrosion protection covering. This covering may be constructed both individually on each wire 2 and - alternatively - on the strand 1 already formed. The protection covering may be of the type which is generally known, for example, made of metal, such as an alloy of zinc and aluminium, such as the one commercially designated Galfan, or plastics material, for example, of polyethylene, polyvinyl chloride or polyamide, or a combination thereof.

[0042] In order to construct the netting 10, the strands 1 are used in the known machines for producing nettings with rhomboid mesh. The dimensions of the strands 1, in particular the nominal diameter D thereof, is compatible with the known machines because it does not exceed the dimension of the metal wires used in the construction of the nettings with rhomboid mesh which are known. It has been found experimentally that the initial flattened spiral winding of the strands 1, which precedes the connection of the various strands in order to form the netting 10, is possible without it being necessary to use over-bending or other special procedures, as otherwise described in the prior art which uses individual metal wires with high resistance.

[0043] Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated, without thereby departing from the scope of the present invention.

Examples

Embodiment Construction

[0034]Now with reference to Figure 1, there is illustrated by way of example a strand 1 which is also sometimes referred to in the sector as a "cord", "braid" or "helical rope", which is used for constructing a netting with rhomboid mesh according to the invention. The strand 1 is made of steel and can be provided in reels, thereby being able to be used in the same manner in which the single metal wires are used for the manufacture of nettings with rhomboid mesh with the known machines.

[0035]More specifically, the strand 1 which is simply a non-limiting example, given solely for better comprehension of the invention, is constituted by three metal wires 2 which all have the same nominal diameter and which are wound together in helical form about the common axis with a uniform lay length L. The strand can also be of the type in which one of the wires is central and forms a core, about which there are helically wound the remaining wires of the strand. Another example of a strand is, fo...

Field of the invention

[0001] The present invention relates to a netting with rhomboid mesh for use in civil engineering in geotechnical applications, for example, in the field of protection from natural risks.

[0002] The invention has been developed with particular regard, even if not exclusively, for a netting with rhomboid mesh with high resistance, for carrying out civil engineering works, such as protection barriers against rockfalls or avalanches, for covering the surface of rocky walls in order to contain detachments of rocks, for three-dimensional stabilization of earth, scarps, dams, embankments, tunnels and road constructions, for constructing containment walls for embankments, for protecting banks of bodies of water, for constructing weirs and other debris-protection barriers along rivers and streams and water works in general, for constructing gabions and other similar products made of metal nettings or comprising a metal netting, and for any other use of the generally known civil and geotechnical type, in which it is necessary to provide a metal netting which is resistant and durable.Technological background

[0003] The nettings to which the present invention relates are used in the field of civil and geotechnical works mainly for protection from natural risks. For example, using such nettings it is possible to avoid or in any case reduce the risk of rocks, debris, snow or other similar natural elements falling downstream as a result of natural instabilities, such as, for example, landslides, avalanches, flows of debris, river floods, detachments of rocks and other phenomena of the type, reaching and damaging roads, dwellings, bridges, etc., or even putting at risk the safety of people. To this end, these nettings, together with the supports thereof, are configured to withstand great impacts and high pressures, such as the ones brought about by a rockfall, by a flow of debris or by an avalanche which strikes it.

[0004] Typical, even if not limiting, uses of these nettings are the construction of barriers for protection from rockfalls or avalanches, covering rocky walls in order to contain detachments of rocks, three-dimensional stabilization of earth, scarps, dams, embankments, tunnels and road constructions, constructing containment walls for embankments, protecting banks of bodies of water, constructing weirs and other debris-protection barriers along rivers and streams and water works in general, constructing gabions and other similar products made of metal nettings or comprising a metal netting, and for any other use of the generally known civil and geotechnical type which has to use a netting which is resistant and durable, both with respect to impacts and to corrosion.

[0005] In the geotechnical sector, there are generally known, for the objects mentioned above, so-called nettings with rhomboid mesh which are also known as loose-mesh nettings. The geometry of these nettings is produced by bending in the form of a flattened spiral a series of metal wires which are then interlaced with each other by "twisting" them in order to form the rhomboid mesh of the netting.

[0006] US 6279858 describes an example of such a netting with rhomboid mesh, which is constructed using metal wires, each of which is bent in a spirally flattened manner and interlaced with similar adjacent metal wires in order to form the rhomboid meshes. The metal wires which compose this known netting are made from a high-strength steel which has an ultimate tensile strength between 1000 and 2200 N / mm 2< (MPa). The high resistance of these steel wires allows the weave of the netting to maintain the three-dimensional structure thereof which is defined similarly to a mattress, even under conditions with a high force.

[0007] A rhomboid mesh netting which is constructed according to the principle of US 6279858 is known by the commercial name TECCO ®< and is produced by Geobrugg AG. This netting is constructed with metal wires having an ultimate tensile strength of approximately 1770 N / mm 2< and a diameter of 2 mm, 3 mm or 4 mm, with meshes which may have dimensions of the diagonals of the rhomboids of approximately 62 x 95 mm, approximately 83 x 143 mm or approximately 102 x 177 mm, respectively.

[0008] Another rhomboid mesh netting is known by the commercial name 3STUTOR ®< which is produced by 3S Geotecnia y Tecnologia S.L. This netting is constructed with metal wires having an ultimate tensile strength of 900 N / mm 2< and a diameter of 2.7 mm, 3.4 mm, 4.0 mm or 4.5 mm. On the website where the above-mentioned netting 3STUTOR ®< is described, http: / / www.3sgeotech.com / es / productos / mallas-de-alambre-3STUTOR, there are mentioned the patent documents ES237412 and WO2015 / 114177, which describe the construction of a rhomboid mesh (or diamond-like) netting but which are constructed with a single rope rather than metal wires. The rope has a diameter between 12 mm and 18 mm and the meshes of the netting have a size between 500 mm and 700 mm and an acute angle between approximately 50° and approximately 65°.

[0009] A problem with known nettings with rhomboid mesh which are constructed with metal wires, such as the ones mentioned above, is that gradually, if the resistance of the wires increases, the greater is the difficulty of constructing the netting as a result of the substantial force necessary for bending the wires. Although US 6279858 describes the construction of metal wires with wires having a resistance of up to 2200 N / mm 2< , in practice there do not appear to have been constructed any nettings having wires with resistance values of approximately 1770 N / mm 2< .

[0010] Another problem which is encountered when constructing the known nettings with rhomboid mesh is that, with an increase in the resistance of the metal wires, the resilience thereof also increases, which makes it difficult to obtain the desired form of the nettings.

[0011] A solution to this last problem is described in EP 2817455 which relates to a method for bending the metal wires so as to form a series of bends in order to make the netting even flatter with respect to the previously known ones. In EP 2817455, the metal wires are flattened at both sides of each bend, forcing them beyond the planar surface over an additional angle, for example, from 10° to 30°, so that the resilient return of the netting when the forcing action is stopped reduces the angle and brings the netting into a flattened condition. This forcing action of the wires of the netting is particularly advantageous when the wires are made from high-strength steel with an ultimate tensile strength between 1000 N / mm 2< and 3200 N / mm 2< .

[0012] However, the solution described in EP 2817455 is not completely satisfactory because it involves additional operations for forcing the bending of the metal wires beyond the desired final configuration. In addition to this, the operation is not readily controllable and can give rise to a netting with a non-homogeneous shape.

[0013] Another example of nettings with rhomboid mesh with a high resistance used for stabilizing earth is described in US 2007 / 210214. In this case, the rhomboid mesh of the netting are not formed by single metal wires, as are the ones previously mentioned in US 6279858 or the netting TECCO ®< , but instead by strands or ropes, each of which is formed by a number of metal wires which are helically wound. At least two of the wires which form each strand or rope are made of steel with a tensile strength between low-strength steels of 100 N / mm 2< and high-strength steels of 2200 N / mm 2< . Within this very wide range of values, US 2007 / 210214 indicates the possibility of using a generic spring steel in accordance with the standard DIN 17223. In the single example described and illustrated expressly in US 2007 / 210214, the strands which form the rhomboid mesh are formed by two metal wires each having a diameter of 3 mm and an ultimate tensile strength of 1770 MPa in accordance with the DIN standard 2078. These characteristics make the netting very rigid so as not to be subjected to virtually any deformation under load and so as not to require any ring-like fixing elements (for example, cross-like clips).

[0014] A netting having the features described in US 2007 / 210214 is produced by Geobrugg AG with the commercial name Spider ®< . It is formed by 1 x 3 helical strands, that is to say, each one is formed by three metal wires wound together in a helical form about the common theoretical axis with a uniform lay length. The nominal diameter of each strand is 6.5 mm while each of the three metal wires which form the strand has a diameter of 3 mm and is made from a steel with a high resistance of 1770 N / mm 2< . The rhomboid meshes of this Spider ®< netting are much wider with respect to the meshes of the TECCO ®< netting mentioned above of the same Geobrugg AG, because they nominally measure 164 mm (smaller diagonal) x 270 mm (larger diagonal).

[0015] The production of rhomboid mesh nettings with such wires or strands from high-strength steel is difficult, if not impossible, as a result of the substantial rigidity of the individual wires which, in the nettings with lower resistance, have to have in any case a diameter of 2 mm in order to achieve a nominal ultimate tensile strength, taking into account the area of the cross-section of the wire, of at least 5.5 kN. As mentioned above, in order to produce these rhomboid mesh nettings with wires with a high resistance, it is necessary to use very robust machines which in any case have an extremely high wear rate. It is further necessary to use special arrangements for bending the metal wires as a result of the fact that the wires or strands made of high-strength steel tend to behave like harmonic steel wires for springs with a substantial resilient return and a very poor tendency to become plastically deformed so as to maintain the form of the helical bending.

[0016] Therefore, the problem of known rhomboid mesh nettings remains unsolved in relation to how to increase the resistance of the nettings themselves without having to substantially increase the dimensions of the meshes, as in the above-mentioned Spider ®< netting of Geobrugg AG, and without using special or complex machines and often additional imprecise operations, such as, for example, the over-bending described in EP 2817455, with respect to the standard operations used for manufacturing the nettings which use metal wires made of steel with low resistance.Statement of invention

[0017] An object of the present invention is to solve the problems of the prior art, providing a netting with rhomboid mesh for use in civil engineering in geotechnical applications which require a high level of resistance of the netting, in addition to a high level of ease of handling and flexibility, with a relatively reduced weight.

[0018] Another object of the invention is to provide a netting with rhomboid mesh with high resistance which can be readily manufactured with existing machines which are normally used for manufacturing nettings with rhomboid mesh which use relatively soft wires.

[0019] Another object of the invention is to provide a netting with rhomboid mesh which is sufficiently flexible to adapt to the irregular shape of the ground of scarps, slopes, banks, etcetera.

[0020] Another object is to provide a netting with rhomboid mesh which is relatively light in terms of weight per unit of measurement in order to be transported and installed readily and with reduced costs, particularly in impassable regions, such as, for example, mountainous zones which are potentially subject to rockfalls, avalanches, landslides, debris flows, etcetera.

[0021] Another object of the invention is to provide a netting with rhomboid mesh which is economical, simple to produce and durable.

[0022] The above-indicated objects are achieved by the invention as defined in the appended claims.

[0023] In the present description, the term "strand" is intended to be understood to be a rope with simple winding which is constituted by wires which are wound helically about the same axis; this rope is also known as a "helical rope". The axis of the strand or helical rope can be virtual, as, for example, in the case of strands with three or four wires, or real, in which case it can be constituted by a metal wire, as, for example, in the case of strands with seven wires or helical ropes with several layers of wires.

[0024] According to a first aspect, there is described a netting with rhomboid mesh, also called a loose-mesh netting, in particular for use in civil engineering in geotechnical applications, preferably in the field of protection from natural risks. The netting is composed of elongate elements which are bent in the manner of a flattened spiral and are wound about adjacent elongate elements by half a revolution, that is to say by 180°. At least some of the elongate elements are ropes or strands which are each constructed with at least two metal wires which are helically wound about the same axis. Each metal wire has a diameter less than 3 mm, preferably less than or equal to 2.5 mm, very preferably less than or equal to 2 mm, more preferably less than or equal to 1.5 mm, even more preferably less than or equal to 1.1 mm, this also being able to be less than 1 mm.

[0025] A netting which is constructed according to the invention affords a number of advantages, including the fact that it is very resistant and at the same time light and convenient to move, including by hand, facilitating the positioning operations, particularly in locations and in positions which are more impassable. Being light and flexible, the netting is readily rolled for transport and unrolled where applicable at the installation site.

[0026] According to a particular aspect, the metal wires of each elongate element may have the same nominal diameter. This allows a netting to be obtained with a substantially uniform resistance as well as a reduced cost as a result of the intrinsic lower cost of the strands.

[0027] According to a particular aspect, the metal wires which form the strands are made of high-strength steel, with an ultimate tensile strength greater than 770 MPa, preferably greater than or equal to 1500 MPa, for example, of approximately 1550 MPa. The ultimate tensile strength of the metal wires may be even greater, for example, preferably greater than or equal to 1700 MPa, for example, of approximately 1750 MPa, or 1860 MPa. Even more preferably, the resistance of the metal wires may be greater than or equal to 1900 MPa, for example, of approximately 1950 MPa, and, for example, it may reach or even exceed 2160 MPa. The high resistance of the metal wires which form the strands from which the netting is made allows relatively thin wires which, as a result of the helical winding thereof, still ensure a high level of flexibility of the netting, in addition to a substantial lightness thereof, to be produced. Nevertheless the wires which form the strands can be intrinsically resilient as a result of the high level of resistance of the steel, the netting generally has a specific plasticity which allows it to be shaped and to be adapted to the varied configuration of the ground. This effect appears to be a result of the fact that, even if not yet completely confirmed, the metal wires with a relatively small diameter which form the strands can slide slightly with friction on each other in such a manner as to maintain over time the configuration which is imposed thereon but without there being a significant plastic deformation yield of the material.

[0028] According to another particular aspect, the elongate elements which form the netting have a nominal diameter less than or equal to 5 mm, preferably less than or equal to 4 mm, preferably less than or equal to 3 mm, even more preferably less than or equal to 2.50 mm, for example, 2.40 mm.

[0029] Metal elements with these dimensions can readily be processed in the conventional machines used to construct nettings with rhomboid mesh with individual metal wires.

[0030] According to another particular aspect, the strands or ropes of the netting are helical ropes with simple winding with a single layer of wires, each one comprising at least two metal wires, more preferably at least three metal wires, even more preferably at least five metal wires, even more preferably at least seven metal wires. These helical ropes are flexible and are, however, rather compact so as to be also readily usable in conventional weaving machines for hexagonal mesh nettings which are normally used for manufacturing nettings with single metal wires.

[0031] According to another aspect, the elongate elements may have a protection covering. The protection covering may be made of metal, for example, an alloy of zinc and aluminium, or plastics material, for example, polyethylene PE, polyvinyl chloride PVC or polyamide PA, or a combination thereof. The covering may be constructed on each wire which forms the strand or, alternatively or additionally to the covering on each wire, on the entire strand. A particular example of covered strands is the one of so-called sheathed strands, with a sheath made, for example, from HDPE. In a preferable but non-limiting manner, the thickness of the covering may vary from approximately 0.2 mm to approximately 0.5 mm.

[0032] According to another aspect, the rhomboid mesh of the netting can have dimensions equal to those of the rhomboid nettings constructed with single metal wires, that is to say, with dimensions of the diagonals of the rhomboids from approximately 60 x 90 mm to approximately 110 x 180mm, with an acute angle of the rhomboid mesh which can be between 45° and 55°, preferably between 47° and 54°, more preferably between 48° and 52°, even more preferably between 50° and 51°.Brief description of the drawings

[0033] Additional features and advantages will be appreciated from the following detailed description of a preferred embodiment with reference to the appended drawings which are given purely by way of non-limiting example and in which: Figure 1 is a perspective view of an exemplary strand which is constructed with three metal wires and which is used to construct an exemplary netting with rhomboid mesh according to the invention; and Figure 2 is a front view of some of the rhomboid mesh of a netting according to the invention. Detailed description

[0034] Now with reference to Figure 1, there is illustrated by way of example a strand 1 which is also sometimes referred to in the sector as a "cord", "braid" or "helical rope", which is used for constructing a netting with rhomboid mesh according to the invention. The strand 1 is made of steel and can be provided in reels, thereby being able to be used in the same manner in which the single metal wires are used for the manufacture of nettings with rhomboid mesh with the known machines.

[0035] More specifically, the strand 1 which is simply a non-limiting example, given solely for better comprehension of the invention, is constituted by three metal wires 2 which all have the same nominal diameter and which are wound together in helical form about the common axis with a uniform lay length L. The strand can also be of the type in which one of the wires is central and forms a core, about which there are helically wound the remaining wires of the strand. Another example of a strand is, for example, the one referred to as 1x7, which is constituted by seven metal wires. Naturally, the invention is not limited to the use of such a strand or helical rope, but may comprise using other types of ropes, for example, helical ropes with several layers.

[0036] The diameter d of each wire may be less than or equal to 2 mm, preferably less than or equal to 1.5 mm, even more preferably less than or equal to 1.1 mm. In the case of the example illustrated, the 1x3 strand has a diameter of 2.4 mm and each wire 2 has a nominal diameter of approximately 0.9 mm. The ultimate tensile strength is approximately 1770 N / mm 2< . In another example, which is not illustrated, there is advantageously used a 1x7 strand with a diameter of 3 mm, the wires of which have a diameter of 0.9 mm, still with an ultimate tensile strength of approximately 1770 N / mm 2< . Naturally, these values have to be considered to be exemplary but not limiting with respect to the invention, which can be carried out with strands or ropes which are different from those described here in detail.

[0037] The strand 1 has its own nominal diameter D which may be less than or equal to 5 mm, preferably less than or equal to 4 mm, preferably less than or equal to 3 mm, even more preferably less than or equal to 2.50 mm, for example, in the case of Figure 1 of approximately 2.40 mm.

[0038] The wires 1 which form the strand 2 are made of steel having a resistance greater than 770 MPa, preferably greater than or equal to 1500 MPa, for example, of approximately 1550 MPa. The ultimate tensile strength of the metal wires may be even greater, for example, preferably greater than or equal to 1700 MPa, for example, of approximately 1750 MPa, or 1860 MPa. Even more preferably, the resistance of the metal wires may be greater than or equal to 1900 MPa, for example, of approximately 1950 MPa, such as, for example, it may reach or even exceed 2160 MPa. Experiments have been successfully carried out with strands constructed with metal wires having a nominal resistance of 1770 MPa.

[0039] As can be seen in Figure 2, a netting 10 according to the invention is constructed using a series of strands 1 of Figure 1 which are initially bent in a spiral and then wound (or "twisted") with each other in order to form rhomboid mesh 12. In particular, the rhomboid mesh 12 are formed by engaging adjacent strands 12 which alternately form twists of 180° at the locations at which they intersect in such a manner that each strand 1 takes up a zig-zag pattern when the netting 10 is viewed from the front as in Figure 2.

[0040] As a result of the flexibility of the strands 1, it is possible to produce rhomboid meshes which are rather small, reproducing, for example, the dimensions of the meshes commonly used for nettings of this type but constructed with single wires for uses in the geotechnical sector. For example, it is possible to construct rhomboid meshes with dimensions of the diagonals of the rhomboids from approximately 60 x 90 mm to approximately 110 x 180 mm, with an acute angle ε of the rhomboid mesh which may be between 45° and 55°, preferably between 47° and 54°, more preferably between 48° and 52°, even more preferably between 50° and 51°.

[0041] The strands 1 of the netting 10 may have a corrosion protection covering. This covering may be constructed both individually on each wire 2 and - alternatively - on the strand 1 already formed. The protection covering may be of the type which is generally known, for example, made of metal, such as an alloy of zinc and aluminium, such as the one commercially designated Galfan, or plastics material, for example, of polyethylene, polyvinyl chloride or polyamide, or a combination thereof.

[0042] In order to construct the netting 10, the strands 1 are used in the known machines for producing nettings with rhomboid mesh. The dimensions of the strands 1, in particular the nominal diameter D thereof, is compatible with the known machines because it does not exceed the dimension of the metal wires used in the construction of the nettings with rhomboid mesh which are known. It has been found experimentally that the initial flattened spiral winding of the strands 1, which precedes the connection of the various strands in order to form the netting 10, is possible without it being necessary to use over-bending or other special procedures, as otherwise described in the prior art which uses individual metal wires with high resistance.

[0043] Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated, without thereby departing from the scope of the present invention.

Examples

Embodiment Construction

[0034]Now with reference to Figure 1, there is illustrated by way of example a strand 1 which is also sometimes referred to in the sector as a "cord", "braid" or "helical rope", which is used for constructing a netting with rhomboid mesh according to the invention. The strand 1 is made of steel and can be provided in reels, thereby being able to be used in the same manner in which the single metal wires are used for the manufacture of nettings with rhomboid mesh with the known machines.

[0035]More specifically, the strand 1 which is simply a non-limiting example, given solely for better comprehension of the invention, is constituted by three metal wires 2 which all have the same nominal diameter and which are wound together in helical form about the common axis with a uniform lay length L. The strand can also be of the type in which one of the wires is central and forms a core, about which there are helically wound the remaining wires of the strand. Another example of a strand is, fo...

Claims

1. A netting with rhomboid mesh, in particular for use in civil engineering in geotechnical applications, preferably in the field of protection from natural risks, the netting being composed of elongate elements which are bent in the manner of a flattened spiral and are wound about adjacent elongate elements by half a revolution, that is to say by 180°, wherein at least some of the elongate elements are ropes or strands which are each constructed with at least two metal wires which are helically wound about the same axis, wherein each metal wire has a diameter less than 3 mm.

2. A netting with rhomboid mesh according to claim 1, wherein each metal wire of the ropes or strands has a diameter less than or equal to 2.5 mm, very preferably less than or equal to 2 mm, more preferably less than or equal to 1.5 mm, even more preferably less than or equal to 1.1 mm, this also being able to be less than 1 mm.

3. A netting with rhomboid mesh according to claim 1 or claim 2, wherein the metal wires of each rope or strand have the same nominal diameter.

4. A netting with rhomboid mesh according to any one of claims 1 to 3, wherein the metal wires of the elongate elements are made of high-strength steel, with an ultimate tensile strength greater than 700 MPa, preferably greater than or equal to 1500 MPa, even more preferably greater than or equal to 1700 MPa, even more preferably greater than or equal to 1900 MPa.

5. A netting with rhomboid mesh according to any one of the preceding claims, wherein the elongate elements have a nominal diameter less than 5 mm, preferably less than or equal to 4 mm, even more preferably less than or equal to 3 mm, even more preferably less than or equal to 2.50 mm.

6. A netting with rhomboid mesh according to any one of the preceding claims, wherein the strands or ropes of the netting are helical ropes with a single layer of wires, each one comprising at least two metal wires, more preferably at least three metal wires, even more preferably at least five metal wires, even more preferably at least seven metal wires.

7. A netting with rhomboid mesh according to any one of the preceding claims, wherein the elongate elements have a protection covering.

8. A netting with rhomboid mesh according to any one of the preceding claims, wherein the metal wires of the elongate elements have a protection covering.

9. A netting with rhomboid mesh according to any one of the preceding claims, wherein the meshes have dimensions of the larger and smaller diagonals of the rhomboids between approximately 60 x 90 mm and approximately 110 x 180 mm.

10. A netting with rhomboid mesh according to any one of the preceding claims, wherein the acute angle of each rhomboid mesh is between 45° and 55°, preferably between 47° and 54°, more preferably between 48° and 52°, even more preferably between 50° and 51°.

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