WO2002035004A1

WO2002035004A1 - A vibration damping system

Info

Publication number: WO2002035004A1
Application number: PCT/DK2001/000691
Authority: WO
Inventors: John Christian Asmussen
Original assignee: Rockwool International A/S
Priority date: 2000-10-27
Filing date: 2001-10-19
Publication date: 2002-05-02
Also published as: AU2002210399A1

Abstract

The invention relates to a vibration damping system, especially for use in the damping of vibrations e.g. from trains and other traffic and damping of vibrations in ground in general. The vibration damping system comprises at least two layers, namely a mineral fibre board having a first and a second major surface and four side surfaces, and a surfactant free geotextile placed onto said first major surface. The invention also relates to a method of applying a vibration damping system and use of a vibration damping system.

Description

A vibration damping system

The invention r.elates to a vibration damping system, especially for use in the damping of vibrations e.g. from trains and other traffic and damping of vibrations in ground in general .

In the prior art, layers of elastic material especially made from rubber and PUR-foams, respectively, have been used for damping vibrations. The need for products which are able to damp vibrations can e.g. be related to railways and roads, particularly in urban areas. One of the preferred materials for the damping of vibrations has so far been plates or mats of vulcanised rubber which has excellent elastic properties for use as vibration damping material. Vibrations damping constructions wherein the vibration damping elements are constituted by rubber have in most situations an acceptable vibration damping efficiency, however, the amount of rubber necessary in such constructions in many situations results in a relatively expensive product. Furthermore, there is a general aim to avoid or reduce the use of rubber materials due to environmental pollution during its production and pollution due to escape of additives e.g. softening additives during use in moist environments. US patent publication No 5,060,856 describes such an elastomeric mat for use e.g. in damping of the sound from trains.

It has also been tried to use a mineral fiber board as sound damping material in railway construction, e.g. as disclosed in DE 35 27 829. This sound damping system has shown to be very good in certain situations. EP patent publication No 922 808 discloses a foundation for railways in the form of a board having an uppermost sheet of rubber granulates glued together and to a lowermost layer of mineral wool. In order to achieve a low dynamic rigidity as well as a high static rigidity, the foundation of EP 922 808 has shown to be effective.

In general, it has been found that the use of mineral fiber mats or boards in vibration damping systems for railway foundations is highly desirable due to adequate performance, easy installation, 100 % recyclability, low pollution effect and a competitive price. However, the mineral fiber board may be relatively fragile when used in applications where it is under high stress such as the stress from ballast gravels during passage of train which in most situations can have a highly destructive effect on the mineral fiber material.

The object of the invention is, thus, to provide a vibration damping system that does not have the drawbacks as described above.

Another object is, thus, to provide a vibration damping system in which a layer of mineral fiber is included and which has a long durability and is effective for use in structural systems, where it could be subjected to point- by-point loading without being destroyed thereby.

The vibration damping system according to the invention is defined in the claims.

The vibration damping system according to the invention has shown to posses a very high vibration damping effect, whereby undesired vibrations from railway traffic and likewise can be reduced to an acceptable level or be substantially eliminated. It has been found that the vibration damping effect of the vibration damping system is only slightly or not at all influenced by the temperature of the surrounding environment, which means that the system works effectively under winter conditions as well as summer conditions. Furthermore, the cost involved in the production of a vibration damping system according to the invention is competitive or even less than the cost involved in the production of vibration damping systems composed of rubber alone. Another desired property of the vibration damping system is its durability which is highly increased due to the construction, because gravel, stone, soil and other covering materials do not result in a destruction of the mineral fiber material, and simultaneously the fiber material is protected from being soaked with water and thus its vibration damping effect is maintained.

The vibration damping system according to the invention comprises at least two layers, namely a mineral fibre board having a first and a second major surface and four side surfaces, and a surfactant free geotextile placed onto said first major surface.

The mineral fiber board is supposed to be placed with the first major surface upwardly in the system.

The mineral fiber board may be any board comprising at least 25 % by weight of mineral fibres e.g. fibres produced from rock, slag, glass and similar vitreous materials. The optimal density of the mineral fiber board may vary in relation to the vibrations it is supposed to damp, but generally the mineral fiber board should have a density of between 40 and 450 kg/m³, preferably between 150 and 300 kg/m³.

Also the thickness depends on the load it is supposed to be subjected to, but in most circumstances the thickness should not be less than 10 mm, and also a thickness of 200 mm should be sufficient. The mineral fiber board may also comprise two or more layers of mineral fibres having different densities and different or equal thickness. The system may also comprise two or more mineral fiber boards placed up on each other where the edge or edges of the boards are placed in distance from each other in order to cover joints. If the boards or the layers of the boards have different densities, the board or layer with the higher density should preferably be placed upon the board or layer with the lower density.

Preferably, the mineral fiber board or at least the exposed surfaces of the board is hydrophobic. The surface tension of the fiber material of the board should preferably not be higher than the surface tension of the natural non-bonded and treated fibres. The board should preferably be sufficient hydrophobic to avoid any substantial entrance of water, when water drops at 20 °C is sprayed onto the board. The mineral fiber board may preferably have a surface tension below 73 dynes/cm, e.g. have a surface tension below 40 or even below 30 dynes/cm.

The mineral fiber boards may be made hydrophobic by using a hydrophobic bonding agent and/or treating the fiber material with a hydrophobic impregnating agent, e.g. oil such as silicone oil. Alternatively, any other method of making the mineral fiber board hydrophobic may be used. The geotextile may in principle be any type of geotextile provided that it is surfactant free. By the term geotextile" is meant any flexible plane structure of fibres.

By the term surfactant free" is meant that the fibres of the geotextile have not been treated with a surfactant, which in this application designates a wetting agent or a tenside (surface tension decreasing agent) .

The surfactant free geotextile should have a thickness of at least 0.1 mm, preferably between 0.4 and 3 mm measured according to EN 964-1 under a load of 2 kN/m². A thickness between 0.5 and 1 mm will in most applications be optimal.

The surfactant free geotextile may preferably be selected from the group consisting of staple fibre, continuous filament non-woven, thread-structure mats and strip mats. Such types of mats and their preparation are generally known to a skilled person. It has been found that a non- woven surfactant free geotextile in general provides the mineral fiber board with an optimal surface protection. The surfactant free geotextile may e.g. be substantially watertight or alternatively it may be permeable for water.

The surfactant free geotextile could in principle be of any kind of material. However in order to obtain a stable and sufficiently strong geotextile, it is preferred that the surfactant free geotextile is made from fibres, threads or filaments of synthetic fibre, more preferably of polymeric materials. The synthetic fibre material may e.g. be selected from the group consisting of polyester, polyamide, polypropylene, polyether, polyethylene, polyetheramide, polyacrylnitrile, glass or a combination thereof. In a preferred embodiment the surfactant free geotextile is made from fibres or filaments comprising or consisting of polyamide coated polyester and/or polypropylene .

The surfactant free geotextile may preferably be fixed to the mineral fiber board e.g. by heat fusing or gluing.

In order to protect the mineral fiber board to an optimal degree, the surfactant free geotextile should preferably have a tensile strength of at least 8 kN/m, preferably at least 20 kN/m measured according to EN ISO 10319. Preferably the surfactant free geotextile should have a tensile strength in all directions of its plane which is above 8 kN/m.

Useful structures of geotextile are e.g. the geotextile marketed under the trade name Typar® SF" by DuPont® Nonwovens .

In the vibration damping system according to the invention the mineral fiber board may be more or less covered by the surfactant free geotextile along one or more of the four side surfaces being covered with the layer of surfactant free geotextile. The mineral fiber board may e.g. be totally coated by the surfactant free geotextile or it may be coated on its first major surface and along all of the four sides. The surfactant free geotextile is however relatively expensive, and since in most embodiment it is not necessary to cover more than the first major surface of the mineral fiber board this will often be avoided.

The vibration damping system may preferably further comprise a drain-core layer comprising or in form of a three-dimensional matting of looped filaments.

The looped filaments should have a sufficiently high strength to avoid a complete and permanent collapse under the load of the gravel, stones or similar covering materials, which may be covered onto the vibration damping system. It is preferred that the looped filaments are made of polymeric monofilaments welded together where they cross, whereby an open structure with an open volume is provided. The looped filaments of the drain-core layer are preferably made from a material selected from the group consisting of polyamide, polyester, high density polyethylene, polystyrene and combinations thereof. A particularly preferred material for the production of the looped filaments of the drain- core layer is polyamide.

The open volume should constitute 80 % or more of the total volume of the drain-core layer. The drain-core layer should preferably be placed between the first major surface of said mineral fibre board and said covering layer of surfactant free geotextile.

In a preferred embodiment of the vibration damping system according to the invention the vibration damping system further comprises a second layer of geotextile placed between the first major surface of the mineral fibre board and the drain-core layer. This preferred embodiment, thus, includes a layered product comprising a mineral fibre board covered on its first major surface with a draining mat of a drain-core layer sandwiched between two layers of surfactant free geotextile.

The thickness of the drain-core layer may preferably be up to about 100 mm. Drain-core layers thicker than that tend to be too soft for the requirement to static stiffness of the system. Since the price of the drain- core layer is highly dependent on the height of this drain-core layer, it is preferred to use a height as low as possible of this layer, where the effect is optimal or at least satisfactory. It is preferred that the total thickness of the drain-core layer including the looped polyamide filaments, the surfactant free geotextile and the second surfactant free geotextile is at least 3 mm, preferably at least 5 mm. In general it is preferred that the surfactant free geotextile is as thin as possible while still being able to provide a distribution of the forces against the underlying mineral fiber board. The geotextiles of the draining mat may preferably be glued or heat melted to the drain-core layer.

The second surfactant free geotextile may be selected from the same group of materials and be of the same type as the surfactant free geotextile as described above. The strength of the second surfactant free geotextile is not so important, and, thus, the second surfactant free geotextile may be of same thickness as the surfactant free geotextile or it may be thinner.

In a particularly preferred embodiment the draining mat is formed from two layers of surfactant free geotextile of non-woven polyamide coated polyester fibres and a looped polyamide filaments drain-core layer sandwiched between the two surfactant free geotextile.

Useful draining mats of the above type are e.g. described in DE publication Nos . DE 2150590 and DE 4431976. A particularly preferred type of draining mats is marketed by Colbond Geosynthetics, The Netherlands, under the trade name Enkadrain®.

In some high loadable applications the vibration damping system according to the invention should preferably be provided with a layer of elastic material. The elastic material could in principle be any type of material with a Shore A hardness of between 35 and 98 measured according to ASTM D2240. The material should preferably be a rubber material, more preferably a rubber material with a hardness of between 55 and 85 IRHD measured according to DS/ISO 48. The rubber material may preferably have an elastic modulus varying between 17xl0⁵ and 69xl0⁸ Pa, more preferably between 35xl0⁵ and 35xl0⁸.

In order to be able to damp intensive vibration, the layer of elastic material should preferably have a density of 400-1300 kg/m³, preferably between of 800-1200 kg/m³.

The layer of elastic material may preferably comprise natural or synthetic rubbers or mixtures of natural and synthetic rubbers. Particularly preferred materials are butadiene rubber, butyl rubber, isoprene rubber, styrene- butadiene rubber, natural rubber, polyacrylate rubber, ethylene-acrylate rubber, ethylene-propylene rubber, nitrile rubber and mixtures thereof. The layer of elastic material may in principle be placed onto the surfactant free geotextile, but preferably the layer of elastic material is placed against the second major surface of the mineral fiber board, so that the elastic material is placed beneath the mineral fiber board in use. Thereby a more effective and durable vibration damping system is obtained. The layer of elastic material should preferably cover at least the major part and more preferably all of the second major surface of the mineral fiber board.

The thickness should preferably be in the interval of 2- 20 mm. If the thickness is below 2 mm, the layer of elastic material has virtually no effect, and if the thickness of the layer of elastic material exceeds 20 mm, it may increase the price of the finished product to an undesired level without further increase of its effect.

The layer of elastic material may preferably be adhered to the mineral fibre board with a glue. Thereby the layer of elastic material, particularly if it is relatively thin, may be easier to handle. It is particularly preferred that the layer of elastic material is made from granulates of elastic material which are adhered to each other using the glue. Thereby it is possible to re-use rubber materials e.g. from tyres.

It has been found that using granulates which have an average maximum diameter of up to about 5 mm, results in a very effective layer of elastic material. Even better results may be obtained by using granulates which have a size whereby at least 90 % by weight of the granules can pass a sieve with a mesh size of about 5 mm. Any glue capable of gluing the rubber granulates together may be used. Preferably the glue is a PUR-based glue or a glue made from a 4,4'-MDI isomer prepolymer, preferably the glue is made from a difenylmethan-4, 4' -diisocyanat prepolymer. A prepolymer for such glue may be obtained from UTAB Uretan Teknik AB, Sweden, under the trade name prepolymer 901 MDI .

The invention also relates to a method of applying a vibration damping system as defined in claims 1-15 to a ground subject to vibrations.

The method comprises the steps of

i providing a mineral fiber board with a first and a second major surface and four side surfaces;

ii applying a layer of surfactant free geotextile onto said first major surface;

ii applying the mineral fiber board onto the ground with the first major side upwards prior to or after the application of the surfactant free geotextile onto the first major side; and

iv optionally covering the surfactant free geotextile covered board with concrete, stone, gravel and/or soil .

Prior to the application of the vibration damping system the ground is prepared e.g. by levelling the ground in the depression in the ground where the vibration damping system is to be applied. Prior to the application, the ground may preferably be further stabilised e.g. by covering the ground with a material selected from the group consisting of water pervious foil, granulates of rubber, gravel or mixtures thereof.

If the vibration damping system should include a layer of elastic material, this layer could be applied in the form of panels of elastic material, in the form of loose granulates of elastic material, or in the form of a panel of granulates of elastic material glued to each other. The layer of elastic material may be applied alone or it may be adhered to the mineral fiber board layer and applied with this layer. If the vibration damping system includes a layer of elastic material this layer should preferably be below the mineral fiber board.

The mineral fiber board may further be applied alone or as mentioned with an elastic layer. Alternatively, the major surface of the board is covered with the surfactant free geotextile prior to the application onto the ground. Using this method, it is preferred that the surfactant free geotextile and the mineral fiber board are glued, sewed or heat fused together.

In some applications, however, it could be easier to apply the surfactant free geotextile onto the first major side of the mineral fiber board after this board is applied.

If the vibration damping system further comprise a drain- core layer and/or a second layer of surfactant free geotextile, these layers may be applied one by one onto the mineral fiber board prior to the application of the surfactant free geotextile, or these layers may be applied together with the surfactant free geotextile in the form of a draining mat as defined above.

The draining mat may preferably be applied from a roll of draining mat material directly onto the mineral fiber board or boards. It is preferred that the draining mat material from one roll covers two or more mineral fiber boards. The width of the roll of draining mat material should preferably be at least substantially equal to the width of the mineral fiber boards.

When the vibration damping system has been safely applied, it may preferably be covered with concrete, stone, gravel and/or soil, or similar materials. A railway track may e.g. be applied onto the vibration damping system.

The vibration damping system according to the invention is preferably used for damping the vibrations caused by trains, trolley busses, tramcars and/or other traffic on a railway or roadway, wherein the use comprises incorporation of the vibration damping system in the ground under the railway and/or road.

Examples

Example 1

A vibration damping system according to the system is prepared by digging a hole with a width of about 3 m, length of about 10 m and a depth of about 1 m. The bottom of the hollow is levelled and a layer of mineral fiber boards is applied. The mineral fiber boards are made from rock wool and have a density of about 190 kg/m³, and a thickness about 50 mm. Onto the mineral fiber board is applied a layer of a surfactant free geotextile Typar® SF77 obtained from DuPont Nonwovens . Onto the surfactant free geotextile is applied gravel and a set of railway tracks .

Example 2

A vibration damping system according to the invention is prepared as described in example 1, with the difference that the surfactant free geotextile is replaced by an Enkadrain® TP comprising a geotextile turning away from the mineral fiber board with a thickness of about 0.65 mm measured according to EN 964-1 and a load of 2 kN/m², and a tensile strength of 20 kN/m measured according to EN ISO 10319.

Example 3

A vibration damping system according to the invention is prepared by digging and levelling a hole having the dimension as in examples 1 and 2. A water pervious PE foil is applied to the hollow and onto the foil is applied a 10 mm thick layer of granulated isoprene rubber (IR) obtained from used tyres. The average size of the granulates is about 3.5 mm (maximal diameter). Onto the layer of granulates a layer of mineral fiber boards and a draining mat are applied as described in example 2.

Example 4

A vibration damping system as described in example 3 is prepared with the only difference that the layer of granulated isoprene rubber (IR) is glued together and to the second major side of the mineral fiber boards using a glue prepared from water and prepolymer 901 MDI (UTAB Uretan Teknik) prior to the application onto the ground.

Claims

PATENT CLAIMS:

1. A vibration damping system comprising a mineral fibre board, said board comprising a first and a second major surface and four side surfaces, said first major surface being covered with a layer of surfactant free geotextile, the surfactant free geotextile preferably having a thickness of at least 0.1 mm, more preferably between 0.4 and 3 mm measured according to EN 964-1 under a load of 2 kN/m².

2. A vibration damping system according to claim 1, wherein at least 10 %, preferably substantially all of one or more of the four side surfaces being covered with the layer of surfactant free geotextile.

3. A vibration damping system according to any one of claims 1 and 2, wherein the surfactant free geotextile is selected from the group consisting of staple fibre, continuous filament non-woven, thread-structure mats and strip mats, preferably the surfactant free geotextile is a non-woven textile.

4. A vibration damping system according to any one of claims 1, 2 and 3, wherein the surfactant free geotextile is made from fibres, threads or filaments of a material selected from the group consisting of polyester, polyamide, polypropylene, polyether, polyethylene, polyetheramide, polyacrylnitrile, glass or a combination thereof, preferably said surfactant free geotextile is made from fibres or filaments of polyamide coated polyester or polypropylene.

5. A vibration damping system according to any one of the preceding claims, wherein the surfactant free geotextile has a tensile strength of at least 8 kN/m, preferably at least 20 kN/m measured according to EN ISO 10319.

6. A vibration damping system according to any one of the preceding claims, wherein the vibration damping system further comprises a layer of a drain-core material comprising a three-dimensional matting of looped filaments, preferably made of polymeric monofilaments welded together where they cross, whereby an open structure is provided, wherein the open volume constitutes 80 % or more of the total volume of the drain-core layer, said drain-core layer preferably being placed between said first major surface of said mineral fibre board and said covering layer of surfactant free geotextile .

7. A vibration damping system according to claim 6, wherein the vibration damping system further comprises a second layer of geotextile, preferably placed between said first major surface of said mineral fibre board and said drain-core layer to thereby provide a layered product comprising a mineral fibre board covered on its first major surface with a draining mat of a drain-core layer sandwiched between two layers of surfactant free geotextile.

8. A vibration damping system according to any one of claims 6 and 7, wherein the looped filaments of the drain-core layer are made from a material selected from the group consisting of polyamide, polyester, high density polyethylene, polystyrene and combinations thereof.

9. A vibration damping system according to claim 7 or 8, wherein the draining mat is formed from surfactant free geotextile of non-woven polyamide coated polyester fibres and a looped polyamide filaments drain-core layer, said draining mat preferably having a total thickness of at least 3 mm, preferably at least 5 mm.

10. A vibration damping system according to any one of the preceding claims, wherein the vibration damping system further comprises a layer of elastic material, said layer of elastic material being placed against the second major surface of the mineral fiber board, whereby at least the major part of the second major surface of the mineral fiber board is being covered with the elastic material, said elastic material having a Shore A hardness of between 35 - 98, and preferably an elastic modulus varying between 17x10^s and 69xl0⁸ Pa, preferably between

35x10° and 35xlO^E

11. A vibration damping system according to claim 10, wherein the layer of elastic material has a density of 400-1300 kg/m³, and preferably a thickness of 2-20 mm.

12. A vibration damping system according to any one of claims 10 and 11, wherein the layer of elastic material comprises natural or synthetic rubbers or mixtures of natural and synthetic rubbers, preferably the layer of elastic material is made from a material selected from the group consisting of butadiene rubber, butyl rubber, isoprene rubber, styrene-butadiene rubber, natural rubber, polyacrylate rubber, ethylene-acrylate rubber, ethylene-propylene rubber, nitrile rubber and mixtures thereof .

13. A vibration damping system according to any one of claims 10, 11 and 12, wherein the layer of elastic material is adhered to the mineral fibre board with a glue, said layer of elastic material preferably being in the form of granulates adhered to each other using the glue .

14. A vibration damping system according to claim 13, wherein the elastic material granulates have an average maximum diameter of up to about 5 mm, preferably the granulates have a size whereby at least 90 % by weight of the granules can pass a sieve with a mesh size of about 5 mm.

15. A vibration damping system according to any one of claims 13 and 14, wherein said glue is a PUR-based glue or a glue made from a 4, '-MDI isomer prepolymer, preferably the glue is made from a difenylmethan-4, 4' - diisocyanat prepolymer.

16. A method of applying a vibration damping system as defined in claims 1-15 to a ground which is subjected to vibrations, said method comprising the steps of

v providing a mineral fiber board with a first and a second major surface and four side surfaces;

vi applying a layer of surfactant free geotextile onto said first major surface;

ii applying the mineral fiber board onto the ground with the first major side upwards prior to or after the application of the surfactant free geotextile onto the first major side;

viii optionally covering the surfactant free geotextile covered board with concrete, stone, gravel and/or soil .

17. A method of applying a vibration damping system according to claim 16, wherein the ground prior to the application is covered with a material selected from the group consisting of water pervious foil, granulates of rubber, gravel or mixtures thereof.

18. A method of applying a vibration damping system according to any one of claims 16 and 17, wherein the major surface of the board is covered with the surfactant free geotextile prior to the application onto the ground, said surfactant free geotextile and said mineral fiber board preferably being glued or heat fused to each other.

19. A method of applying a vibration damping system according to any one of claims 16 and 17, wherein the mineral fiber board is first applied to the ground and thereafter the surfactant free geotextile is applied onto the first major side of the mineral fiber board.

20. A method of applying a vibration damping system according to anyone of claims 16-19, wherein a drain-core layer is applied onto the first major side of the mineral fiber board and the geotextile is applied onto the drain- core layer, preferably a second layer of geotextile is applied onto the first major side of the mineral fiber board prior to the application of the drain-core layer.

21. A method of applying a vibration damping system according to claim 19, wherein the surfactant free geotextile is provided as a part of a draining mat composed of a drain-core layer sandwiched between two layers of surfactant free geotextile, said drain-core layer being in the form of a three-dimensional matting of looped filaments, said draining mat preferably being applied from a roll of the material directly onto the major sides of one or more boards, said roll of draining mat material preferably has a width substantially equal to the width of the mineral fiber boards.

22. A method of applying a vibration damping system according to any one of claims 16 to 21, wherein the surfactant free geotextile covered board is covered with concrete, stone, gravel and/or soil, said method further comprises the step of applying a railway track onto the vibration damping system.

23. Use of a vibration damping system as defined in any one of claims 1-15 for damping the vibrations caused by trains, trolley busses, tramcar and/or other traffic on a railway or roadway, wherein the use comprises incorporation of the vibration damping system in the ground under the railway and/or road.