WO2017098082A1

WO2017098082A1 - Mesh for mining and subterranean constructions

Info

Publication number: WO2017098082A1
Application number: PCT/FI2016/050853
Authority: WO
Inventors: Ingmar BAARMAN; Stefan KÄLLBERG
Original assignee: Tammet Oy
Priority date: 2015-12-07
Filing date: 2016-12-07
Publication date: 2017-06-15

Abstract

The invention relates to a mesh for mining and subterranean constructions, the mesh comprising a first edge rod and a second edge rod which are parallel to each other and a plurality of straight rods, which arranged between the first edge rod and the second edge rod and at a distance from each other. A third edge rod and a fourth edge rod are parallel to each other and perpendicular to the first and the second edge rods, and a plurality of straight rods are arranged between the third edge rod and the fourth edge rod and at a distance from each other. The distance between the edge rod and an adjacent second rod closest to the edge rod is smaller than the distances between the remaining rods.

Description

MESH FOR MINING AND SUBTERRANEAN CONSTRUCTIONS

The present invention relates to a mesh for mining and subterranean constructions according to the preambles of the enclosed independent claims.

A mesh manufactured from steel wire, a so-called mining mesh, is attached to the walls of mine tunnels and respective subterranean structures to reinforce the tunnel structure and to prevent the falling of loose rocks. These meshes can be used for example in mines, road tunnels, underground parking spaces, or the like. The mesh should be relatively easy to shape as it shaped by mechanical pressing to conform to the walls of the tunnel. Therefore the mesh is manufactured from a rod having an appropriate ductility. However, there are certain strength requirements for the mesh. In conventional mining mesh structures the rods are arranged at constant distance from each other, the distance between the adjacent rods being, for example 75 mm.

There is a need for mining mesh structures that would be cost efficient and easy to use but still fulfil the strength requirements.

An object of this invention is to minimise or possibly even eliminate the disadvantages existing in the prior art. Another object of the present invention is to provide a mesh which is light and easy to use while improving or maintaining the required tensile strength of the whole mesh and, as a consequence, improving or maintaining safety.

Typical mesh according to present invention for mining and subterranean constructions comprises

- a first edge rod and a second edge rod which are parallel to each other, and a plurality of parallel straight rods, arranged between the first edge rod and the second edge rod and at a distance from each other, - a third edge rod and a fourth edge rod which are parallel to each other and perpendicular to the first and the second edge rods, and a plurality of parallel straight rods, arranged between the third edge rod and the fourth edge rod and at a distance from each other,

whereby the distance between the edge rod and an adjacent second rod closest to the edge rod is smaller than the distances between the remaining rods.

Now it has been surprisingly found out that by reducing the distance at least between the rods closest to the edges of the mesh, i.e. the edge rods and the adjacent second rods, it is possible to obtain a mesh structure which has improved properties compared to conventional meshes where the distance between all the rods is constant throughout the whole mesh. The spacing between the edge rods and the adjacent rods is smaller, which means that all the edges of the mesh have an area where the rods are more closely spaced each other. It has been observed that with this arrangement the strength properties of the mesh are at least the same or better as with conventional meshes. Especially, the mesh with closely spaced rods in the edge region is able to resist point-like tension forces caused by falling stone blocks or the like. The distance between the edge rods and the adjacent second rods may be in the range of 45 - 65 mm, preferably 45 - 55 mm. This distance provides improved resistance for tension forces. Furthermore, when the mesh is attached to the roof of a mining tunnel or the like in overlapping fashion, as explained later, the edge regions with closely spaced rods are able to provide improved mounting base for bolts.

In the present context the edge of the mesh is understood as the immediate outer edge of the mesh and the edges of the mesh are defined by the edge rods. The edge rod thus forms the edge of the mesh. The straight rods which are arranged between the edge rods, e.g. between first and second edge rods, are parallel with the edge rods between which they are arranged. All the rods of the mesh, which means the edge rods, adjacent second rods as well as the remaining rods are straight, essentially free from bends, folds, crinkles or the like. Furthermore, the first and second edge rods and all the straight rods parallel with them are arranged on the first side of the third and fourth edge rods and the straight rods parallel with the third and fourth edge rods. The rods are attached to each other at their crossing points by welding. This means that the perpendicular rods are not threaded over or under each other or otherwise interlaced. In the present context the term "remaining rods" encompasses the all other rods of the mesh, except the edge rods and the adjacent second rods closest to the edge rods. The remaining rods are thus situated between and parallel to adjacent second rods of opposite edges of the mesh. In this context two parallel remaining rods, situated next to each other, are called neighbouring rods.

According to one embodiment of the invention it is also possible to increase the distance between the remaining rods, when the distance between the edge rod and adjacent second rod is smaller. The distance between the remaining rods can be increased at least by 10 %, preferably at least by 20 %, sometimes even over 30 %. For example, if the distance between the edge rod and adjacent second rod is reduced, the distance between the remaining rods can be increased from 75 mm to 100 mm or to 125 mm. The distance between the remaining rods may be, for example, in the range of 95 - 130 mm, preferably 105 - 130 mm, more preferably 1 10 - 125 mm. This means that a fewer number of rods is needed for making one mining mesh while maintaining or even improving the tensile strength of the mesh. This naturally reduces the manufacturing costs. A further advantage which is obtained is the reduction in weight of one mining mesh, when the number of remaining rods is reduced. It is possible to significantly reduce the weight of the mesh, which makes them easier to transport and install.

According to one embodiment of the invention the mesh, having an area of 4 - 6.5 m², preferably 5 - 6 m², has a weight in a range of 20 - 27 kg, preferably 22 - 25 kg. According to another embodiment of the invention the mesh having an area of 6.5 - 7.5 m², has a weight in a range of 27 - 31 kg, preferably 27 - 30 kg.

When the meshes are fastened to the wall of a mine tunnel or the like, the adjacent meshes are arranged to overlap each other, in order to provide sufficient security against detached loose stones or stone blocks. It has also been observed that the reduced distance between the edge rods and the adjacent second rods reduces the area which the adjacent meshes overlap each other when installed. According to one embodiment of the invention the area covered by one single mesh can be increased by 7%. This means that the sufficient strength can be obtained even if the overlapping area is smaller, whereby the total area covered by a certain number of the meshes increases. When large areas are covered e.g. in mine tunnels, even small increase in total cover area may provide a significant reduction in the total number of meshes required.

Typically the mining mesh according to the invention is used in the walls of mine tunnels and other corresponding structures to reinforce the tunnel/subterranean structure and to prevent the falling of loose rocks. The mesh is typically a planar and ductile steel mesh. The mesh can be attached to the wall of the mine tunnel, road tunnel or corresponding structure, and before or after attaching the mesh the tunnel walls can be shotcreted. The length of edge of the mining mesh is typically 1 .5 - 5 m, preferably 2 - 3 m, more preferably 2 - 2.6 m or 2.2 - 2.9 m. The perpendicular edges of the mesh can be of different length, but the parallel edges are of the same length.

The mesh is formed of cut rods that are arranged parallel and perpendicular to each other at desired distances. The overlapping rods are welded together at locations, where the rods intersect. According to the invention the distance between the edge rod and the adjacent second rod closest to the edge rod in all edges of the mesh is smaller than the distances between the remaining rods. This means that all edges of the mesh show reduced distance between the edge rods and the adjacent second rods closest to the edge rods.

The number of adjacent second rods may be 1 - 5, preferably 1 - 3. This means that the distance between up to five adjacent second rods closest to the edge rod may be smaller than the distances between the remaining rods. Preferably distances between two or three adjacent second rods closest to the edge rod may be smaller than the distances between the remaining rods. If there is more than one adjacent second rod, the distance between the further adjacent second rods is the same as the distance between the edge rod and the first adjacent second rod closest to the edge rod. According to one preferred embodiment the distances between first two or three adjacent second rods closest to the edge rod are the smallest of the distances between neighbouring rods in the whole mesh. According to one embodiment of the invention the distance between the neighbouring rods may increase from the edge of the mesh towards the centre of the mesh until the distance reaches a maximum value. This means that the distance between the neighbouring rods at the centre of the mesh is larger than at the edge regions of the mesh.

According to another embodiment of the invention distance between the neighbouring remaining rods increases from the edge of the mesh towards the centre of the mesh until the distance reaches a maximum value, whereafter the distance between the neighbouring remaining rods again decreases to a local minimum value, which is found near the centre of the mesh. This means that the rods which are located in the centre area of the mesh are arranged closer to each other, i.e. the distance between them is smaller than between the remaining rods, but equal or larger than the distance between the edge rod and the adjacent second rods closest to the edge rods. This embodiment provides denser mesh at locations where the mesh is attached to the underlying rock. This improves the security of the fastening. In one embodiment the distance between the rod closest to the middle point of the mesh and at least one the neighbouring rod is smaller than the distances between the remaining rods, but equal or larger than the distances between the edge rods and adjacent second rods. The middle rod is the rod which is crosses the centre point of the mesh or passes nearest to the centre point of the mesh. This means that at the centre of the mesh there is an area where the distance between the rods may be smaller than in other parts of the mesh, excluding the edges of the mesh. The change in distance, i.e. increase/decrease, between the neighbouring remaining rods may be gradual or stepwise. Gradual change from the edge towards the centre of the mesh means that each distance is larger than the previous distance until the maximum distance at the centre of the mesh is reached. Stepwise change from the edge towards the centre of the mesh means that there may be two or more adjacent distances which are the same before distance is increased.

Normally the mesh from the centre to the edge is a mirror image of the mesh from the centre to the opposite edge. Preferably the mesh is symmetrical in regard of any straight line drawn through the geometrical centre point of the mesh.

The edge rods, adjacent second rods and the remaining rods are typically identical with each other. The rods are made of steel and their elongation (Aio) may be at least 20%, preferably 25 - 35% and tensile strength R_m may be < 450 N/mm², preferably 370 - 420 N/mm². The wire rod used is a rod manufactured from steel by hot rolling, the diameter of which wire is typically substantially round. The mesh is preferably manufactured from substantially smooth-surface steel rod. The diameter of the rod may be from 3mm to 8 mm, preferably from3 mm to 6 mm. In one embodiment of the invention rod having a diameter of 5.5 mm or 6 mm may be used. Preferably all the rods of the mesh have same diameter.

According to one embodiment of the invention at least one layer of expanded plastic or synthetic polymeric material arranged on one large surface of the mesh. The expanded plastic material, such as expanded polystyrene or expanded polyurethane, can be in form of a sheet and it can be laminated on the large surface of the mesh, preferably a layer of expanded plastic material can be added on both large surfaces of the mesh. According to this embodiment the rods of the mesh are fully embedded into the expanded plastic material. The laminated plastic material provides further improved properties in form of a damp-proofing, waterproofing and/or heat insulation layer.

The mesh is attached to the walls and/or ceiling of the tunnel by using large bolts in each corner of the mesh. Typically attachment is done also in the midpoint of the mesh as well as in the middle of the mesh edges.

According to one embodiment of the invention the mesh comprises attachment areas, which are indicated with colour. When the mesh has been pressed against the tunnel wall/ceiling, it becomes irregularly formed. This makes it demanding to estimate the correct attachment areas, where the bolts should go through the mesh, especially in middle of the mesh/mesh edges. If the bolts are fixed at wrong location, the strength of mesh is not optimal. When the attachment areas are indicated with a differing colour, it is easy to find the correct attachment areas, even if the mesh is in deformed state.

Some embodiments of the invention are shown in the appended non-limiting and schematical Figures, where Figure 1 show one embodiment of the invention, and

Figure 2 show another embodiment of the invention.

Figure 1 shows one embodiment of the invention. The mining mesh 10 comprises a first edge rod 1 and a second edge rod 2, which are parallel to each other. A plurality of straight rods is arranged between the first edge rod 1 and the second edge rod 2. Further, the mesh 10 comprises a third edge rod 3 and a fourth edge rod 4, which are parallel to each other and perpendicular to the first edge rod 1 and the second edge rod 2. A plurality of straight rods is arranged between the third edge rod 3 and the fourth edge rod 4.

It can be seen that in each edge of the mesh 10 the two second rods 5', 6' closest to the edge rods 1 , 2, 3, 4 are arranged closer to each other so that the distance A formed between the edge rods and the adjacent second rods is smaller than the distance B between the remaining rods 5", 6".

Figure 2 shows another embodiment of the invention. Same reference numbers are used for same parts as in Figure 1 .

It can be seen in Figure 2 at that the two adjacent second rods 5', 6' closest to the edge rods 1 , 2, 3, 4 are arranged closer to each other so that the distance A formed between the edge rods and the adjacent second rods 5', 6' is smaller than the distances between the remaining rods of the mesh 10. However, it can be further seen that the distance between the third and the fourth neighbouring remaining rod 5", 6" as well as the distance between the fourth and the fifth neighbouring remaining rod is larger than the distance between the edge rods and adjacent second rods 5', 6'. Thus the distance between the neighbouring rods increases, constantly or stepwise, until it reaches a maximum and is then again reduced in the centre part of the mesh. In Figure 2 the distance A is smaller than distance B; the distance B is smaller than distance C; and the distance C is smaller than distance D. The invention is described more closely in the following non-limiting example.

EXAMPLE

The maximum strength of a mesh is measured by attaching the mesh from its corners into a test rig with four bolts in a square pattern. The distance between bolts is 1 m. The mesh is attached to the test rig by placing it on the bolts and clamping it to the test rig by utilizing rock bolt washers and nuts. In this manner the attachment of the mesh mimics the way the mesh is mounted in a mine. The centre of the mesh is pressed upwards by using a cylindrical shape with a diameter of 200 mm, provided with outwardly tapering flange with maximum diameter of 310 mm. The force of the cylinder is focused to the middle of the mesh i.e. to the crossing point of the diagonals between the bolts. The force and the moving distance of the cylindrical shape that is required for deforming and eventually breakage of the mesh are recorded.

A mining mesh according to the invention with 50 mm spacing between the edge rods and the adjacent second rods and with 100 mm spacing between the remaining rods at the edges achieved a maximum force of 51 kN at 570 mm deformation. The rod diameter was 5.5 mm.

A conventional mining mesh without closely spaced edge regions was used as reference. The reference mesh had constant spacing of 100 mm between all the rods, and achieved a maximum force of 32 kN at a deformation of 510 mm. The rod diameter was 5.5 mm.

From the results it is seen that the mesh according to the invention achieves significantly higher maximum force than the conventional mesh with same spacing between the remaining rods than the reference mesh. In practice the strength improvement corresponds to the strength of a conventional mining mesh with closer 75 mm spacing between all the rods. However, the closer spacing between the rods requires more rods per mesh, which increases the mesh weight. The mesh according to the invention thus achieves the same strength than a heavier conventional mesh, but is much lighter. A mesh according to the invention and having a size of 2.2 χ 2.5 m may provide a weight saving of 15 - 20 %, often 17 - 19 %, when compared to conventional meshes with the same size and same strength properties. The invention is not intended to be limited to the above-presented exemplary embodiments, but the intention is to apply the invention widely within the inventive idea defined by the claims defined below.

Claims

1 . Mesh for mining and subterranean constructions, comprising

- a first edge rod and a second edge rod which are parallel to each other, and a plurality of straight rods, arranged between the first edge rod and the second edge rod and at a distance from each other,

- a third edge rod and a fourth edge rod which are parallel to each other and perpendicular to the first and the second edge rods, and a plurality of straight rods, arranged between the third edge rod and the fourth edge rod and at a distance from each other,

characterised in that

the distances between all the edge rods and adjacent second rods, which are closest to the edge rods, are smaller than the distances between the remaining rods.

2. Mesh according to claim 1 , characterized in that the distances between up to five adjacent second rods closest to the edge rod are smaller than the distances between the remaining rods.

3. Mesh according to claim 1 or 2, characterised in that the distances between two or three adjacent second rods closest to the edge rod are smaller than the distances between the remaining rods

4. Mesh according to claim 3, characterised in that the distances between two or three adjacent second rods closest to the edge rod are the smallest of the distances between succeeding rods in the whole mesh.

5. Mesh according to claim 1 , 2, 3 or 4, characterised in that the distance between the edge rods and the adjacent second rods is in the range of 45 - 65 mm, preferably 45 - 55 mm.

6. Mesh according to any of preceding claims 1 - 5, characterised in that the distance between the remaining rods is in the range of 105 - 130 mm, preferably 1 10 - 125 mm.

7. Mesh according to any of preceding claims 1 - 6, characterised in that the distance between the neighbouring rods increases from the edge of the mesh towards the centre of the mesh until the distance reaches a maximum value.

8. Mesh according to claim any of preceding claims 1 - 7, characterised in that the distance between the neighbouring rods increases from the edge of the mesh towards the centre of the mesh until the distance reaches a maximum value, whereafter the distance between the neighbouring rods again decreases to a local minimum value, which is found near the centre of the mesh.

9. Mesh according to claim 8, characterised in that the distance between the rod closest to the middle point of the mesh and the neighbouring rod is smaller than the distances between the remaining rods, but equal or larger than the distances between the edge rods and adjacent second rods.

10. Mesh according to any of preceding claims 1 - 9, characterised in that all the rods are made of steel and their elongation (Ai₀) is at least 20%, preferably 25 - 35% and tensile strength R_m is < 450 N/mm², preferably 370 - 420 N/mm².

1 1 . Mesh according to any of preceding claims 1 - 10, characterised in that at least one layer of expanded plastic material arranged on one surface of the mesh.

12. Mesh according to claim 1 1 , characterised in that the rods of the mesh are fully embedded into the expanded plastic material.

13. Mesh according to any of preceding claims 1 - 12, characterised in that mesh comprises attachment areas, which are indicated with colour.