WO2005040555A1

WO2005040555A1 - Drainage membrane and installation method

Info

Publication number: WO2005040555A1
Application number: PCT/AU2004/001574
Authority: WO
Inventors: Daniel Bosco; Neil Sweeting; John Martin
Original assignee: Parchem Construction Products Pty Ltd
Priority date: 2003-11-24
Filing date: 2004-11-15
Publication date: 2005-05-06
Also published as: WO2005040555A8

Abstract

The invention relates to a dimple sheet drainage membrane construction and method for its installation, for example in a tunnel bore (10) or other excavated substrate surface. The membrane sheet (20) has dimpled portions creating a drainage space on one side of the sheet and non-dimpled edge regions (26) and interior regions (24) for facilitating joining and to form an array of fixing locations (28) for non-penetrative fixing to the underlying substrate. The invention also relates to a fixing method for a drainage sheet using an array of plate-like fixing discs (30) secured to the substrate surface at locations corresponding to the fixing locations of the sheet and non-penetrative fixing means for securing the sheet, and to a fixing pattern for securing the sheet to the tunnel bore.

Description

TITLE OF THE INVENTION DRAINAGE MEMBRANE AND INSTALLATION METHOD

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to waterproofing drainage membranes of the type used in tunnels and other engineering applications. In particular, the invention relates to "dimple sheet" drainage membranes, to tunnels and other structures incorporating such membranes and to methods for their installation.

2. Description of the Art

[0002] Dimple sheet is a type of waterproofing membrane used in civil engineering projects, such as tunnelling, where it is fixed to the substrate of the tunnel bore and an inner layer of concrete is then applied, for example by slipforming. The membrane is formed of polypropylene, polyethylene or other plastic sheeting formed with a regular dimple pattern which in use forms a drainage space between the substrate and the sheet. [0003] In prior art installations, the dimple sheet is attached to the substrate surface by nails shot or drilled through the dimples into the substrate at regular spacings, each nail having a washer sized to fit within the dimple. However the variability of the substrate surface into which the nails are being fired will prevent certain fixing of all nails, and therefore this method may result in some nails coming loose and resultant holes in the dimple sheet. Holes may also be torn in the dimples if the nail and washer combination is misaligned with the dimple. The formation of holes and tears in the sheet is particularly undesirable in installations requiring complete water impermeability, and can be difficult to trace for repair once the membrane and the inner concrete layer are installed. [0004] Joints between adjacent sheets may be formed by overlapping the sheets at their edges and either heat welding or using a butyl sealing tape. [0005] The present invention aims to provide a new dimple sheet configuration which will facilitate joining and fixing of the sheet, and a new method for fixing the sheet to the substrate surface.

SUMMARY OF THE INVENTION

[0006] In a first form, the present invention provides a dimpled drainage membrane sheet having a first portion having a dimple pattern formed therein for , creating a drainage space on one side of the sheet and a second portion being an area being formed without said dimple pattern. [0007] Preferably, said second portion area includes a non-dimpled edge region adjacent an edge of the membrane sheet. Preferably, said edge region is a border of at least 100mm, and more preferably at least 150-200mm, wide. Preferably, the sheet is generally rectangular and said border runs along at least two opposite edges, preferably the edges of longest dimension, of the sheet. [0008] Preferably also, said second portion of the membrane sheet further includes a plurality of interior non-dimpled portions, repeating at intervals along the longest dimension of the sheet. [0009] Preferably, said interior non-dimpled portions are formed in regions running across the sheet width transverse to the edges of longest dimension of the sheet, and form an array of non-dimpled fixing locations on said membrane sheet. [0010] In a further form, the invention provides a method of fixing a drainage barrier membrane to a substrate surface, including the steps of fixing an array of fixing elements to the surface, optionally testing fixing of at least some of the fixing elements to the surface and attaching the membrane to the fixing elements by non- penetrative attachment means. [0011] The invention also relates to a structure incorporating the above dimpled drainage membrane, and/or formed by the above method. [0012] Preferably, the membrane is attached to the fixing elements by plastics welding or by adhesion, preferably by double-sided adhesive tape. [0013] Preferably, the fixing elements are plate-like members fixed to the surface by fasteners or adhesion. [0014] Preferably, the fixing strength of the elements is tested by applying a static load. [0015] Preferably, the sheet has non-dimpled regions corresponding to the positions of the fixing elements. [0016] In a further form, the invention provides a method of fixing a drainage barrier membrane to a generally cylindrical tunnel bore surface, including the step of fixing the drainage barrier to the tunnel surface by an array of fixing elements, said array said fixing elements being at a closer spacing in a first zone adjacent a crown of the tunnel and at an increased spacing in a second zone away from the crown of the tunnel. [0017] Preferably, said second zone extends from said first zone to approximately a horizontally widest point of said tunnel bore and the method further includes the step of fixing said array of fixing elements at a further increased spacing in a third zone below said second zone.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Further preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: [0019] Fig. 1. is a schematic cross-section of a tunnel construction of the type in which the present invention may be employed; [0020] Fig. 2 is a schematic plan view of a dimple sheet according to a first embodiment of the invention; [0021] Fig. 3 is a part plan view of detail A of the sheet of Fig. 2, showing the dimple layout in more detail; [0022] Fig. 4 is a detail of portion B of the dimple layout of Fig. 3; [0023] Fig. 5 is a detailed cross-section of a portion of the dimple sheet; [0024] Fig. 6 is a cross-section of a fixing arrangement of a second embodiment of the invention; [0025] Fig. 7 is a cross-section of a fixing arrangement of a third embodiment of the invention; [0026] Fig. 8 is a part plan view of a dimple sheet according to a fourth embodiment of the invention; [0027] Fig. 9 is a detail of portion C of Fig. 8; [0028] Fig. 10 is a plan view of the sheet of Figs 2-5, showing the fixing locations; [0029] Fig. 11 is an axonometric view of the lower portion of the tunnel showing the fixing locations; and [0030] Fig. 12 is a schematic plan view of a dimple sheet according to a fourth embodiment of the invention; and [0031] Fig. 13 is a part plan view of detail A of the sheet of Fig. 12, showing the dimple layout in more detail; [0032] Dimensions, where shown, are in millimetres unless otherwise indicated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Fig. 1 schematically illustrates a tunnel construction of the type used for example for rail or road transport, comprising a circular bore 10 cut through the native rock 12, and a concrete shell 14 which extends around most of the tunnel circumference except for the base which has a pre-cast concrete slab 16 forming a flat base for laying the railway tracks 18 or roadway. [0034] The tunnel may have bends in both the horizontal and vertical planes. [0035] In between the substrate of the bore 10 and the shell 14 is a waterproofing membrane 20 to prevent ingress of ground water into the tunnel. The waterproofing arrangement may be one of two general types: a tanking membrane, which seals out the ground water; or a drainage membrane, which forms barrier against ingress of the water and a drainage path leading to collection points near the sides of the slab 16. The present invention is illustrated with reference to a drainage membrane arrangement, though may also be used as a tanking membrane. [0036] The waterproof drainage membrane 20 is formed as a sheet of polypropylene, polyethylene or other suitable thermoplastics material, into which is formed a pattern of dimples extending outwards toward the rock to form a drainage space between the membrane and the rock, in the gaps between the dimples. The membrane extends around the majority of the circumference of the tunnel bore, ending at the sides of the bottom concrete slab 16 where drains are located. Thus, for a typical 5- 10m tunnel diameter, the membrane extends over an arc length of approximately 15-30m. [0037] The membrane is applied lengthwise circumferentially about the tunnel, and adjacent sheets joined by heat- welding or taping. If the arc length is greater than the length of the membrane sheet, two of the membrane sheets may be joined end-to-end. [0038] After the circular bore is cut through the rock, the bore is optionally lined with a water-permeable geotextile material and the water-impervious dimple sheet membrane 20 is fixed as will be described later with reference to Figs. 6 and 7. The inner concrete shell is then formed by slipcasting. [0039] Figs. 2 to 5 show, in increasing detail, the dimple arrangement according to a first embodiment of the invention. Dimensions, where shown, are in millimetres. [0040] Fig. 2 illustrates a sheet of the dimpled drainage membrane, approximately 18.8m long and 4.8m wide, with alternating dimpled and non-dimpled regions 22, 24 extending in lines across the width of the sheet, and further non- dimpled edge regions 26 along the long sides of the sheet. [0041] Figs. 3 to 5 show the dimple configuration in greater detail. [0042] With reference to Fig. 5 it may be seen that each dimple is approximately 15mm diameter at its base, 10mm diameter at its peak and about 8mm high, pressed into the approximately 0.5 to 1mm thick membrane sheet. Within each of the dimpled regions, the dimples are spaced at approximately 25mm centres in a regular pattern. [0043] With reference to Figs. 3 and 4, the non-dimpled edge regions 26 are approximately 200mm wide, and the alternating dimpled and non-dimpled regions 22, 24 repeat at approximately 0.5m intervals - the dimpled regions 22 are strips approximately 300mm in width and the non-dimpled interior regions 24 are formed at approximately 1.25 - 1.3m centres across the width of the sheet, in a strip about 200mm across. [0044] The dimple pattern of the sheet is symmetrical about both the longitudinal and transverse axes of the sheet. [0045] Each non-dimpled interior region 24 is formed as a rectangle approximately 200mm by 900mm in dimension, with its major axis extending across the length of the membrane sheet. Approximately halfway along each rectangular non-dimpled region 24 is a generally circular non-dimpled spot 28 of about 300mm diameter, thus forming an array of these non-dimpled spots 28 over the membrane sheet surface for fixing of the sheet to the tunnel bore as will be described later with reference to Figs. 6 and 7. Smaller, non-dimpled fixing areas may be employed, thereby increasing the dimpled area and drainage capacity of the sheet. [0046] It will be appreciated that the non-dimpled regions 24 are significantly greater in dimension than the spacing between the dimples in the dimpled region 22. [0047] Connecting the ends of adjacent non-dimpled regions 24 of each transverse strip, and connecting adjacent non-dimpled spots 28 of adjacent strips, are regions 29 having a dimple pattern with wider dimple spacing. [0048] The repeating dimple configuration may be formed by pressing the sheet material over a heated, contoured drum, or by any other suitable method. [0049] The 200mm non-dimpled edges 26 facilitate joining of adjacent sheets along their edges, by taping or by heat welding, while maintaining the integrity of the joints. Preferably, the sheets are overlapped along their edges and joined by heat welding along two parallel seams approximately 15-20mm apart, with the integrity of the seams being tested before installation by introduction of air under pressure. The excess width of the non-dimpled edge regions of the two adjacent sheets allows the sheets to be overlapped and joined at an angle of up to a few degrees, to facilitate joining of the sheets at bends in the tunnel bore in either the vertical or horizontal plane. [0050] The non-dimpled strips 24 extending across the sheet allow end-to-end joining of sheets at a plurality of positions along the sheet, for example as may be required at recesses and junctions in the tunnel wall. [0051] Fig. 6 illustrates one arrangement for fixing the drainage membrane to the tunnel bore. [0052] In the arrangement of Fig. 6, a plurality of discs 30 - about 70mm to 100mm diameter (preferably 80mm) and of similar height to that of the dimples - are fixed to the tunnel bore after application of the geotextile layer. In one form, the discs 30 are fixed to the bore by nails 32 shot through the discs into the rock, although alternative fixing means such as high strength double-sided adhesive tape may be if used if they will result in sufficient fixing strength. The discs 30 are fixed to the tunnel bore at regular spacing coinciding with the spacing of the circular non-dimpled regions 28 of the sheet. The greater diameter of the non-dimpled spots relative to the discs allows some tolerance in positioning of the discs. [0053] Because of natural variations in the stone to which the discs are fixed, not all of the fixings into the rock may have the required strength. The present embodiment allows for testing of the fixing strength of the discs to the rock before the dimple sheet is installed, thus preventing the situation which may occur in the prior art where failure of a fixing nail through the sheet may cause tearing of the sheet. [0054] One preferred testing method is to test the fixing strength by static load, for example by hanging weights from the discs, or from at least a statistically valid sample of the discs, for a predetermined time. The amount of weight applied to the discs, and the time, may be set according to the fixing strength required. [0055] After fixing and testing of the discs 30, the sheets of dimple sheet drainage membrane are then positioned to align the non-dimpled spots 28 with the discs 30 and attached to the discs by heat welding 34. To facilitate this, the discs are preferably formed from the same thermoplastic material - for example polypropylene or polyethylene or compatible thermoplastics materials with similar melting characteristics, so that they can be heat- welded together by means of a heat gun. [0056] After fixing of the drainage membrane to the bore, the inner concrete shell 14 is cast in place, thus providing further support for the drainage membrane layer. [0057] With reference to Fig. 7, the discs 30 are fixed to the rock and tested in similar fashion to the embodiment of Fig. 6, and the sheet attached to the discs by means of an industrial strength double-sided adhesive tape 36 such as 50mm wide Kontabit R, from Isoltema SpA of Italy or similar. [0058] Other forms of non-penetrative fixing, for example a hot-melt or other adhesive, may be used to attach the drainage membrane sheet to the discs. [0059] Figs. 8 and 9 illustrate an alternative dimple layout according to a further embodiment of the invention. [0060] The dimple sheet 120 of Figs. 8 and 9 is generally similar in overall dimension to that of Figs. 2 to 5, e.g. 18m by 4.8m, but may be made of lighter gauge sheet, such as 0.65 mm thickness. [0061] The dimple layout of Figs. 8 and 9 has non-dimpled edge regions 126 and alternating dimpled and non-dimpled strips 122. The dimple layout of sheet 120 also has additional non-dimpled strips 140 perpendicular to the non-dimpled strips 124 and intersecting with the non-dimpled spots 128a, 128b. End strips 140a may be approximately 65-70mm in width and intermediate strips 140b about 80mm wide. The provision of these lengthwise strips 140 facilitates repair of any punctures of the membrane 120 caused on-site, by providing a closed locus of non-dimpled sheet around the puncture site to which a repair patch (not shown) may be attached by heat welding or gluing. [0062] Figs. 10 and 11 show a suitable fixing pattern for the membrane sheet of Figs. 2 to 5, whereby an array of fixing discs is fixed to the tunnel substrate at locations corresponding to the non-dimpled spots 28 of the membrane sheet. Fig. 10 shows the fixing positions relative to the sheet, and Fig. 11 is an axonometric view of the lower part of the tunnel cross-section. The fixing locations are indicated by the black dots 40. [0063] The spacing of the fixing discs varies depending on the distance from the crown (line 42-42 in Fig. 10) of the tunnel. In the region 44 adjacent the crown of the tunnel, the fixing discs are located at each non-dimpled spot 28, at centres of approximately 1250mm longitudinally to the tunnel and at about 500mm centres circumferentially. In intermediate regions 46 extending down to about the widest point (48, Fig. 11) of the tunnel bore, the fixing discs are affixed only at alternate non- dimpled strips, at centres of about 1250mm longitudinally to the tunnel and 1000mm circumferentially. Below the widest point 48, the fixing discs are positioned on alternate strips at only the edgemost non-dimpled spots 28 of the sheets. [0064] The fixing arrangement of the invention thus allows for a very substantial reduction in the number of fixing points required, compared to prior art installations which are fixed at 400mm centres, while providing adequately secure fixing. [0065] Figs. 12 and 13 illustrate an alternative dimple layout according to a fourth embodiment of the invention. [0066] The dimple sheet 220 of Figs. 12 and 13 is generally similar in overall dimension to that of Figs. 2 to 5, e.g. 18m by 4.8m, but is symmetrical along its longitudinal centre line so that it may cut during manufacture to facilitate transport. [0067] The dimple layout of Figs. 12 and 13 has non-dimpled longitudinal edge regions 226a about 200mm wide, and a further longitudinal non-dimpled region 226b of twice that width extending along the longitudinal centre line C-C of the sheet. Cutting the sheet along the longitudinal centre line will thus form two identical sheets of 2.4m width, each with non-dimpled longitudinal edge regions 226a, allowing the sheet material to be transported as 2.4m long rolls. [0068] Non-dimpled spots 228 of 300mm diameter are formed approximately 0.5m from the edge of the sheet and from the centre line C-C, in a repeating pattern at about 0.5m intervals. The small non-dimpled fixing regions 228 provide a large dimpled area and hence high drainage capacity to the sheet. [0069] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing for the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. It will further be understood that any reference herein to known prior art is commonly known by those skilled in the art to which the invention relates. [0070] In the specification, the word "comprising" is understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of. A corresponding meaning is to be attributed to the corresponding words "comprise, comprised and comprises where they appear.

Claims

1. A dimpled drainage membrane sheet having a first portion having a dimple pattern formed therein for creating a drainage space on one side of the sheet and a second portion being an area being formed without said dimple pattern.

2. A dimpled drainage membrane according to claim 1 wherein said second portion area includes a non-dimpled edge region adjacent an edge of the membrane sheet.

3. A dimpled drainage membrane according to claim 1 wherein said edge region is a border of at least 100mm along an edge of said membrane sheet.

4. A dimpled drainage membrane according to claim 3 wherein said border is at least 150mm wide.

5. A dimpled drainage membrane according to claim 3 wherein said membrane sheet is generally rectangular and said border runs along at least two opposite edges of longest dimension of the sheet.

6. A dimpled drainage membrane according to claim 1 wherein said second portion area includes a plurality of interior non-dimpled portions, repeating at intervals along the longest dimension of the sheet.

7. A dimpled drainage membrane according to claim 6 wherein said plurality of interior non-dimpled portions form an array of non-dimpled fixing locations on said membrane sheet.

8. A dimpled drainage membrane according to claim 7 wherein said interior non- dimpled portions are formed in regions extending across a width of said membrane sheet.

9. A dimpled drainage membrane according to claim 7 wherein said array of non- dimpled fixing locations is formed by enlarged non-dimpled fixing areas of said interior non-dimpled portions.

10. A method of fixing a drainage barrier membrane to a substrate surface, including the steps of fixing an array of fixing elements to the surface and attaching the membrane to the fixing elements by non-penetrative attachment means.

11. A method of fixing a drainage barrier membrane according to claim 10 further including the step of testing fixing of at least some of the fixing elements to the surface prior to attaching said membrane.

12. A method of fixing a drainage barrier membrane according to claim 11 wherein the fixing strength of the elements is tested by applying a static load.

13. A method of fixing a drainage barrier membrane according to claim 10 wherein fixing elements are plate-like members fixed to the surface.

14. A method of fixing a drainage barrier membrane according to claim 13 wherein said non-penetrative attachment means comprises plastics welding of said membrane to said fixing elements.

15. A method of fixing a drainage barrier membrane according to claim 13 wherein said non-penetrative attachment means comprises a double-sided adhesive tape.

16. A method of fixing a drainage barrier membrane according to claim 10 wherein said drainage barrier membrane includes at least one dimpled drainage membrane sheet according to claim 7, and wherein said step of fixing said array of fixing elements includes fixing said fixing elements at locations corresponding to at least some of said non-dimpled fixing locations of said membrane sheet.

17. A method of fixing a drainage barrier membrane according to claim 16 wherein said array of non-dimpled fixing locations is formed by enlarged non-dimpled fixing areas of said interior non-dimpled portions.

18. A method of fixing a drainage barrier membrane according to claim 10 wherein said substrate is an excavated surface.

19. A method of fixing a drainage barrier membrane according to claim 18 wherein said substrate is a bore of a tunnel.

20. A method of fixing a drainage barrier membrane according to claim 19 wherein said tunnel bore is generally cylindrical, including the step of locating said fixing elements at a closer spacing in a first zone adjacent a crown of the tunnel and at an increased spacing in a second zone away from the crown of the tunnel.

21. A method of fixing a drainage barrier membrane according to claim 20 wherein said second zone extends from said first zone to approximately a horizontally widest point of said tunnel bore and further including the step of fixing said array of fixing elements at a further increased spacing in a third zone below said second zone.

22. A method of fixing a drainage barrier membrane according to claim 21 wherein said fixing elements are located substantially only along opposed edges of said membrane sheet in said third zone.

23. A method of fixing a drainage barrier membrane to a generally cylindrical tunnel bore surface, including the step of fixing the drainage barrier to the tunnel surface by an array of fixing elements, said array said fixing elements being at a closer spacing in a first zone adjacent a crown of the tunnel and at an increased spacing in a second zone away from the crown of the tunnel.

24. A method of fixing a drainage barrier membrane according to claim 23 wherein said second zone extends from said first zone to approximately a horizontally widest point of said tunnel bore and further including the step of fixing said array of fixing elements at a further increased spacing in a third zone below said second zone.

25. A method of fixing a drainage barrier membrane according to claim 24 wherein said fixing elements are located substantially only along opposed edges of said membrane sheet in said third zone.