CA1111780A - Prefabricated subsurface drains - Google Patents
Prefabricated subsurface drainsInfo
- Publication number
- CA1111780A CA1111780A CA316,376A CA316376A CA1111780A CA 1111780 A CA1111780 A CA 1111780A CA 316376 A CA316376 A CA 316376A CA 1111780 A CA1111780 A CA 1111780A
- Authority
- CA
- Canada
- Prior art keywords
- filter
- sheet material
- woven fabric
- bonded
- mesh
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Laminated Bodies (AREA)
- Filtering Materials (AREA)
Abstract
ABSTRACT
The invention conce??s a laminated structure for use in prefabricated subsurface drains comprising a supporting sheet material and a filter sheet material. The filter sheet material has a permeability sufficient to allow the passage of water while retaining soil. The supporting sheet material has a structural configuration such that channels are formed between it and the filter sheet material to allow free flow of water within the plant of the laminated structure. The laminated structure may comprise the supporting sheet material with (a) the filter material on one side only, or (b) the filter material on both sides. or (c) the filter material on one side and an impermeable sheet material on the other side.
The filter material preferably is a synthetic, thermoplastic filamentary, non woven fabric and the supporting material is preferably a thermoplastic plastics net-like material. The materials are preferably joined by a flame-bonding technique.
The invention conce??s a laminated structure for use in prefabricated subsurface drains comprising a supporting sheet material and a filter sheet material. The filter sheet material has a permeability sufficient to allow the passage of water while retaining soil. The supporting sheet material has a structural configuration such that channels are formed between it and the filter sheet material to allow free flow of water within the plant of the laminated structure. The laminated structure may comprise the supporting sheet material with (a) the filter material on one side only, or (b) the filter material on both sides. or (c) the filter material on one side and an impermeable sheet material on the other side.
The filter material preferably is a synthetic, thermoplastic filamentary, non woven fabric and the supporting material is preferably a thermoplastic plastics net-like material. The materials are preferably joined by a flame-bonding technique.
Description
The present invention concerns impro~ements in and relating to prefabricated subsurface drains.
Subsurface drains have been used for many years to remove excess water from the ground to improve crop growth, strengthen pavement foundations, stabilise slopes7 and reduce water pressure against retaining walls. The water is usually carried away from the site by a perforated pipe, and a filter material .nust be provided between the soil and the pipe that will retain the soil while allowing free flow of water into the pipe. Long established methods have uti-lised a filter composed of mineral aggregate graded so as to match the soil, but this type of filter performed satisfac-torily only when designed and constructed with great care.
The present invention seeks to provide a syn-thetic filter medium, comprising a laminated structure for use of prefabricated subsurface drains.
According to the present invention, a synthe-tic filter medium for use in prefabricated subsurface drains comprises a thermoplastic plastics mesh-like material which exhibits high tensile and fle~ibility properties having thermally bonded thereto over at least one surface thereof, a non-woven fabric comprising ~hermoplastic polymerlc bicom-ponent. filaments of fibres, the non-woven fabric being suffi-ciently permeable to allow the passage of water therethrough whilst retaining at least some soil particles.
; The invention also includes prefabricated ; subsurface drains which are formed from or incorporate such synthetic filter medium.
The laminated structure may comprise the sup_ porting sheet material with the non-woven filter fabric bonded ;
. , : : . - .
to one side only. The supporting sheet material may have the non-woven filter fabric bonded to both s:ides thereof, or the non-woven filter fabric bonded to one side and an impermeable sheet material, for example, a synthetic polymer:Lc film, bonded to the other side; in these cases the supporting material acts as a core or spacer.
Preferably, the non-wo~en filter fabric is form-ed from synthetic, polymeric, thermoplastic, bicomponent fila-ments or fibres of sheathlcore or sicle/side configuration in which one of the components has a lower melting point than the other components, and in which the filaments ~re bonded toge-ther at their point of contact by means of ~he lower melting point component Eollowing a heat treatment. A preferred non-woven fabric of this type is sold under the Registered Trade Mark 'TERRAM'.
The non-woven filter Eabric, although being per-meable to water and soil retaining, is desirably constructed to have a mesh si~e capable of initially allowing finer frac-tiDns of soil to pass, thereby creating a natural filter zone in the soil in the immediate proximity to the fabric. Conse-quently, the filter zone then has a higher permeability than the surrounding soil.
The supporting sheet material or core has a structural configuration such that it can inherently form channels for the flow of water from the filter fabric. Prefer-ably, it has an open, net-like structure formed for example of thermoplast~c plastics material. Desirably, a thermoplastic plastics mesh- or n~t-like material is used, such as sold under the Registered Trade Mark 'NETLON'.
Various techniques may be used to bond together the component materinls of the laminated structure. The prime consideration is to achieve an adequate bond strellgth without
Subsurface drains have been used for many years to remove excess water from the ground to improve crop growth, strengthen pavement foundations, stabilise slopes7 and reduce water pressure against retaining walls. The water is usually carried away from the site by a perforated pipe, and a filter material .nust be provided between the soil and the pipe that will retain the soil while allowing free flow of water into the pipe. Long established methods have uti-lised a filter composed of mineral aggregate graded so as to match the soil, but this type of filter performed satisfac-torily only when designed and constructed with great care.
The present invention seeks to provide a syn-thetic filter medium, comprising a laminated structure for use of prefabricated subsurface drains.
According to the present invention, a synthe-tic filter medium for use in prefabricated subsurface drains comprises a thermoplastic plastics mesh-like material which exhibits high tensile and fle~ibility properties having thermally bonded thereto over at least one surface thereof, a non-woven fabric comprising ~hermoplastic polymerlc bicom-ponent. filaments of fibres, the non-woven fabric being suffi-ciently permeable to allow the passage of water therethrough whilst retaining at least some soil particles.
; The invention also includes prefabricated ; subsurface drains which are formed from or incorporate such synthetic filter medium.
The laminated structure may comprise the sup_ porting sheet material with the non-woven filter fabric bonded ;
. , : : . - .
to one side only. The supporting sheet material may have the non-woven filter fabric bonded to both s:ides thereof, or the non-woven filter fabric bonded to one side and an impermeable sheet material, for example, a synthetic polymer:Lc film, bonded to the other side; in these cases the supporting material acts as a core or spacer.
Preferably, the non-wo~en filter fabric is form-ed from synthetic, polymeric, thermoplastic, bicomponent fila-ments or fibres of sheathlcore or sicle/side configuration in which one of the components has a lower melting point than the other components, and in which the filaments ~re bonded toge-ther at their point of contact by means of ~he lower melting point component Eollowing a heat treatment. A preferred non-woven fabric of this type is sold under the Registered Trade Mark 'TERRAM'.
The non-woven filter Eabric, although being per-meable to water and soil retaining, is desirably constructed to have a mesh si~e capable of initially allowing finer frac-tiDns of soil to pass, thereby creating a natural filter zone in the soil in the immediate proximity to the fabric. Conse-quently, the filter zone then has a higher permeability than the surrounding soil.
The supporting sheet material or core has a structural configuration such that it can inherently form channels for the flow of water from the filter fabric. Prefer-ably, it has an open, net-like structure formed for example of thermoplast~c plastics material. Desirably, a thermoplastic plastics mesh- or n~t-like material is used, such as sold under the Registered Trade Mark 'NETLON'.
Various techniques may be used to bond together the component materinls of the laminated structure. The prime consideration is to achieve an adequate bond strellgth without
- 2 -~ r ~
impairing the filtering action of the non-woven fabric.
Thermal bonding techniques are preferred.
In respect of a laminated structure comprising 'TERRAM' non-woven fabric and 'NETLON' mesh material a parti~
cularly preferred technique i6 flame bonding. In utilising this method~ a surfac2 of the mesh mclterial is softened by a flame and is then brought into contact with the non-woven fabric and pressure applied, eg by passing the mesh material and the non--woven fabric between a pair of nip rolls. The speed of passing the mesh material relative to the flame, the flame temperature, and the distance of the flame from the surface of the mesh material determine the conditions under which the appropriate amount of softening occurs. Desirably, heavier g~ades of lTERRAM' non-woven fabric, eg 'TERRA~' lOQ0, are used with the flame bonding process. The impermeable - sheet material, if present, may also be attached by this method.
The structural configuration of the supporting sheet material is purely to permit water to flow away from the filter fabric. It must also permit the initial flush of fine soil particles to take place. The openness of the sup-porting fabric between the filter fabric support areas are desigDed to be large enough to accept water and fines but small enough to substantially prevent the filter fabr~c being pushed lnto its structure, thus reducing its capacity to transmit water. Furthermore, the tensile strength, and resis-tance to~deformation~ of the supporting sheet miqterial should be capable of withstanding the earth pressures Dormally encountered in use.
A ~ypical example of a subsurface drain ln which an embodiment of the in~ention composed of the support~
impairing the filtering action of the non-woven fabric.
Thermal bonding techniques are preferred.
In respect of a laminated structure comprising 'TERRAM' non-woven fabric and 'NETLON' mesh material a parti~
cularly preferred technique i6 flame bonding. In utilising this method~ a surfac2 of the mesh mclterial is softened by a flame and is then brought into contact with the non-woven fabric and pressure applied, eg by passing the mesh material and the non--woven fabric between a pair of nip rolls. The speed of passing the mesh material relative to the flame, the flame temperature, and the distance of the flame from the surface of the mesh material determine the conditions under which the appropriate amount of softening occurs. Desirably, heavier g~ades of lTERRAM' non-woven fabric, eg 'TERRA~' lOQ0, are used with the flame bonding process. The impermeable - sheet material, if present, may also be attached by this method.
The structural configuration of the supporting sheet material is purely to permit water to flow away from the filter fabric. It must also permit the initial flush of fine soil particles to take place. The openness of the sup-porting fabric between the filter fabric support areas are desigDed to be large enough to accept water and fines but small enough to substantially prevent the filter fabr~c being pushed lnto its structure, thus reducing its capacity to transmit water. Furthermore, the tensile strength, and resis-tance to~deformation~ of the supporting sheet miqterial should be capable of withstanding the earth pressures Dormally encountered in use.
A ~ypical example of a subsurface drain ln which an embodiment of the in~ention composed of the support~
3 -..
ing sheet material with the non-woven filter fabric on one side only thereof may be used~ is a cylindrical vertical drain. In this case, the laminated material is formed into a cylinder with the filter fabric exposed on the outside.
This is positioned into a cylindrical hole in the ground and the interior of the cylinder filled with sand.
The embodiment ~f the invention which comprises the supporting sheet material, as a core or spacer, with the non-woven filter fabric on both sides thereof is particularly utilisable in a so-called prefabricated 'slot~ drain. The latter consists of a slotted, water impermeable pipe with the laminated structure arranged vertically and inserted into the slot in the pipe. The filter fabric retains the soil and keeps the 'core' channels open, thereby allowing water to drain through the filter fabric, down the channels, and into the pipe. In a modification of this arrangement, a non-slotted, water permeable pipe is used, in which case the vertically arranged laminated structure also encloses the pipe.
The laminated structure with the filter fabric 2~ on both sides may be used as a simple vertical drain when cut or made into strips 9 say 9 inches wide, and the edges sealed to render them water impermeable.
The embodiment of the invention in which the laminated structure comprises a non-woven filter fabric on one side of the supporting material and an impermeable film on the other side may conveniently be used in the construction of a cut-off drain, in which the laminated structure is arranged vertically with the filt~r fabric Eacing the water flow.
; :
ing sheet material with the non-woven filter fabric on one side only thereof may be used~ is a cylindrical vertical drain. In this case, the laminated material is formed into a cylinder with the filter fabric exposed on the outside.
This is positioned into a cylindrical hole in the ground and the interior of the cylinder filled with sand.
The embodiment ~f the invention which comprises the supporting sheet material, as a core or spacer, with the non-woven filter fabric on both sides thereof is particularly utilisable in a so-called prefabricated 'slot~ drain. The latter consists of a slotted, water impermeable pipe with the laminated structure arranged vertically and inserted into the slot in the pipe. The filter fabric retains the soil and keeps the 'core' channels open, thereby allowing water to drain through the filter fabric, down the channels, and into the pipe. In a modification of this arrangement, a non-slotted, water permeable pipe is used, in which case the vertically arranged laminated structure also encloses the pipe.
The laminated structure with the filter fabric 2~ on both sides may be used as a simple vertical drain when cut or made into strips 9 say 9 inches wide, and the edges sealed to render them water impermeable.
The embodiment of the invention in which the laminated structure comprises a non-woven filter fabric on one side of the supporting material and an impermeable film on the other side may conveniently be used in the construction of a cut-off drain, in which the laminated structure is arranged vertically with the filt~r fabric Eacing the water flow.
; :
Claims (5)
1. A prefabricated subsurface drain structure comprising a thermoplastic plastics mesh-like material which exhibits high tensile and flexibility properties having thermally bonded thereto over at least one surface thereof, a non-woven fabric comprising thermoplastic polymeric bicom-ponent filaments or fibres, the non-woven fabric being suffi-ciently permeable to allow the passage of water therethrough whilst retaining at least some soil particles.
2. A structure as claimed in Claim 1 comprising the mesh-like material with the non-woven fabric bonded to both surfaces thereof.
3. A structure as claimed in Claim 1 comprising the mesh-like material with the non-woven fabric bonded to one surface and an impermeable sheet material bonded to the other surface.
4. A structure as claimed in Claim 3 wherein the impermeable sheet material is a synthetic polymeric film.
5. A structure according to claim 1, 2 or 3 wherein the mesh-like material and non-woven fabric have been bonded together by a flame bonding process.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA316,376A CA1111780A (en) | 1978-11-16 | 1978-11-16 | Prefabricated subsurface drains |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA316,376A CA1111780A (en) | 1978-11-16 | 1978-11-16 | Prefabricated subsurface drains |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1111780A true CA1111780A (en) | 1981-11-03 |
Family
ID=4112963
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA316,376A Expired CA1111780A (en) | 1978-11-16 | 1978-11-16 | Prefabricated subsurface drains |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1111780A (en) |
-
1978
- 1978-11-16 CA CA316,376A patent/CA1111780A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |