EP4705619A2

EP4705619A2 - A construction fastener

Info

Publication number: EP4705619A2
Application number: EP24768149.7A
Authority: EP
Inventors: Matthew Link
Original assignee: Valro Manufacturing Ltd
Current assignee: Valro Manufacturing Ltd
Priority date: 2023-06-06
Filing date: 2024-06-06
Publication date: 2026-03-11
Also published as: GB2631681A; WO2024252148A2; WO2024252148A3; GB202308429D0

Abstract

A construction fastener (100) comprises a boss section comprising an elongate main body (101) having a first end and a second end; a disc section (102) connected to the main body (101) at or close to the second end of the elongate main body (101), the (disc 102) extending from the main body (101) substantially perpendicularly to the length of the main body (101); a heat activated adhesive coating applied to substantially the entirety of that face of the disc (102) facing in the same direction as the second end, and; at least the disc section (102) is formed from ferritic stainless steel.

Description

A CONSTRUCTION FASTENER

FIELD

The present invention relates to a construction fastener. More particularly, the present invention relates to a construction fastener for use as part of a construction fastening system for fastening waterproof membranes to the inside of tunnels. The present invention also relates to a method of using a construction fastener.

BACKGROUND

When creating tunnels for roads, railways, or similar, it can be important to waterproof the surface of the tunnel in order to prevent water seepage through the surrounding rock into the tunnel. The New Austrian tunneling method (NATM) - a tunnelling technique developed between 1957 and 1965 in Austria - uses a series of steps where the tunnel is first sequentially excavated and supported with the initial ground support provided by shotcrete in combination with fibre or welded-wire fabric reinforcement or similar, and where the permanent support is typically a cast-in-place concrete lining placed over a waterproofing membrane.

Typically, the waterproof membrane or membranes is/are connected to the wall of the tunnel via fasteners that are anchored into the rock or concrete wall of the tunnel, and which are bonded to the membrane. An example of a typical fastening anchor for this type of bonding system is shown and described in EP0510501 .

Similar typical anchors are sold by BA-Anker Technik GmbH, and shown and described on their website: https://www.ba-anker.ch/.

These anchors are used as part of the ‘Austrian Tunnel Method’, where the anchor is bonded into the rock of the tunnel wall, and holds and seals the waterproofing material against the tunnel wall. It is necessary to first hang the waterproofing material in front of pre-drilled holes in the wall, and align the material with these holes. This can result in loose waterproofing material hanging from the wall, which can be a leakage risk. Further, it is necessary for a user to hand-weld a cover piece to the waterproofing material, and this is time-consuming. A variation of this method and the apparatus used for the method is the ‘Norwegian Tunnel Method’. In this method, holes are first drilled in the tunnel wall, and long steel rods are bonded into these. An anchor is connected to the free end of the rod. Waterproofing material is then hung in front of these, and holes are made that are intended to align with the anchors behind. A second anchor part is then screwed on in order to clamp the waterproof membrane to make a seal.

For both of these methods, the holes in the membrane can present a significant leakage risk both during construction and after.

EP 1696081 shows and describes a device that has a sealing body with a disk-shaped film section, with a central through opening for sealed, material-engaging connection to a continuous sealing layer between the object and the substrate, a sleeve section made in one piece with the disk-shaped film section and aligned with the through opening and a threaded rod connected to the sleeve section in sealed manner and protruding through the sleeve section and the through opening for fixing the object.

EP2806083 shows and describes a device and a method for fixing plastic sheets to components or structures, in particular concrete components or concrete structures, and a mounting kit for fixing plastic sheets and a lining system for lining of components or structures. The device has a base body with a welding element, the base body having a side facing the component or structure and an upper side facing the plastic plate, wherein the base body consists of a thermoplastic material. The welding element is made of an electrically conductive material which is embedded in the base body at its upper side. The penetration-free connection between the plastic plate and the base body is made by generating an alternating electromagnetic field with which the welding element is brought to a temperature which is sufficiently high that the thermoplastic of the base body melts. As a result, plastic plate and base body are thermally welded.

CH683110 describes and shows an anchor for the tight anchoring of an object in a substrate made of stone, with a continuous sealing layer between the object to be anchored and the stone substrate, the anchor comprising a carrier which has an integrally formed plate section and a pin section, the plate section tightly connected to a disk-shaped film part.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

SUMMARY

It is an object of the present invention to provide a construction fastener which goes some way to overcoming the abovementioned disadvantages or which at least provides the public or industry with a useful choice.

It is a further object of the invention to provide a method of using a construction fastener which goes some way to overcoming the abovementioned disadvantages or which at least provides the public or industry with a useful choice.

The term “comprising” as used in this specification and indicative independent claims means “consisting at least in part of’. When interpreting each statement in this specification and indicative independent claims that includes the term “comprising”, features other than that or those prefaced by the term may also be present. Related terms such as “comprise” and “comprises” are to be interpreted in the same manner.

As used herein the term “and/or” means “and” or “or”, or both.

As used herein “(s)” following a noun means the plural and/or singular forms of the noun.

Accordingly, in a first aspect the present invention may broadly be said to consist in a construction fastener, comprising: a boss section comprising an elongate main body having a first end and a second end; a disc section connected to the main body at or close to the second end of the elongate main body, the disc extending from the main body substantially perpendicularly to the length of the main body; a heat activated adhesive coating applied to substantially the entirety of that face of the disc facing in the same direction as the second end, and; at least the disc section is formed from ferritic stainless steel.

In an embodiment, the disc section is further formed from a stainless steel that is corrosion-resistant.

In an embodiment, the ferritic stainless steel comprises stainless steel grade EN 1.4521 (type 444).

In an embodiment, the boss section is formed from austenitic stainless steel.

In an embodiment, the boss section is at least partly formed from stainless steel grade EN 1.4301 (type 304) or grade EN 1 .4401/4 (type 316 or 316L).

In an embodiment, the boss section is formed from plastic.

In an embodiment, two holes are formed at each end of the main body, the holes having a substantially common axis.

In an embodiment, the holes are threaded.

In an embodiment, the disc has a generally flat outer surface.

In an embodiment, the outer edge of the disc is turned inwards.

In an embodiment, the boss section and disc section are crimped together.

In an embodiment, a sealing material is added between the boss and disc when the crimped connection is made.

In an embodiment, the construction fastener further comprises a drill tip attached to the first end of the boss section.

In an embodiment, the drill tip comprises at least one internal passage, the boss section further comprising a passage therethrough between the first and second ends.

In an embodiment, the boss section further comprises a one-way valve located in the passage that allows passage of fluids from the outer end to the inner end. In an embodiment, the boss section further comprises a flange extending from the boss section at or close to the outer end of the main body, the disc connected to the outer edge of the flange at the outer edge of the disc.

In an embodiment, the disc and flange are crimped together at their outer edges.

In an embodiment, the construction fastener further comprises at least one rib extending from the inner face of the flange towards the first end and integrally connected to the main body.

In an embodiment, the boss section further comprises a flange extending from the boss section at or close to the inner end of the main body, the flange extending to form a conical section around and enclosing the inner part of the boss section, the disc connected to the outer edge of the flange at the outer edge of the disc.

In an embodiment, the construction fastener further comprises at least one rib located in the space between the flange and the inner part of the boss section. in a second aspect the present invention may broadly be said to consist in a method of attaching a waterproof lining to a tunnel wall, comprising the steps of: i) drilling a series of holes in the tunnel wall, the holes configured to receive a plurality of construction fasteners at least some of which are as claimed in any one of claims 1 to 20; ii) emplacing the construction fasteners in the holes; iii) positioning a sheet of waterproof membrane over the top of the construction fasteners, the inner face of the sheet in contact with the heat activated adhesive coatings; iv) placing an induction heating tool on the outer surface of the waterproofing membrane over the disc and heating the disc inductively to activate the adhesive coating.

In an embodiment, the method comprises the further step of placing a magnetic clamp on the bond location following heating to ensure the membrane is in contact with the adhesive coated disc. In an embodiment, in the step of drilling holes in the tunnel wall, these are drilled in a grid pattern at approximately 1m spacings.

With respect to the above description then, it is to be realised that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

BRIEF DESCRIPTION OF THE FIGURES

Further aspects of the invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings which show an embodiment of the device by way of example, and in which:

Figure 1a shows a perspective view from one side and above of a construction fastener according to an embodiment of the invention, the fastener having a boss with a threaded, ribbed or otherwise textured external surface configured to receive a threaded extender rod at the inner end and a threaded extender rod at the outer end, the rod in use inserted into a hole in a tunnel wall, a disc section at the outer end of the main body, the disc extending outwards from the main body perpendicularly to the length of the main body, the disc section formed from ferritic stainless steel, and a heat activated adhesive coating applied to the outer face of the disc.

Figure 1b shows a side view of the construction fastener of figure 1a, showing hidden detail of internal holes at each end of the boss.

Figure 1c shows a cutaway side view of the construction fastener of figures 1 a and 1 b.

Figures 2a - 2c show cutaway side views of a second embodiment and variations of a second embodiment, the second embodiment similar to the first embodiment but having a drill tip screwed onto the inner end of the boss, the drill tip in the variations of figures 2b and 2c having passages to allow epoxy to pass through the boss and drill tip.

Figure 3a shows a perspective view from one side and above of a construction fastener according to a second embodiment of the invention, the fastener having a boss with a smooth external surface configured to receive a threaded extender rod at an inner end and a threaded extender rod at the outer end, a disc section at the outer end of the main body, the disc extending outwards from the main body perpendicularly to the length of the main body, the disc section formed from ferritic stainless steel, and a heat activated adhesive coating applied to the outer face of the disc.

Figure 3b shows a side view of the construction fastener of figure 3a, showing hidden detail of internal holes at each end of the boss.

Figure 3c shows a cutaway side view of the construction fastener of figures 3a and 3b.

Figure 4 shows a further embodiment of a construction fastener, the construction fastener of this embodiment having a boss or body made from plastic, the boss having a flange that extends from the outer end of the boss to support a disc.

Figure 5 shows a further embodiment of a construction fastener, the construction fastener of this embodiment having a boss or body made from plastic, the boss having a flange that extends from the inner end of the boss to support a disc. Figure 6 shows sequential side views of the embodiments of figure 1 and 3, showing how the disc is attached by crimping to the boss.

DETAILED DESCRIPTION

Embodiments of the invention, and variations thereof, will now be described in detail with reference to the figures. Similar numbering will be used for features that are the same or similar in different embodiments - e.g. boss 101 , 201 , 301 , or disc 102, 202, 302, etc.

First Embodiment

A first embodiment of a construction fastener 100 is shown in figures 1 a - 1 c. The construction fastener 100 comprises two main parts: a boss or body 101 and a disc

102.

The boss 101 in this embodiment comprises a cylindrical body having a diameter of 25-40mm and a length of anywhere from 50-150mm, but most preferably in the range 70-95mm. The body 101 in this embodiment is formed from stainless steel, such as for example grade EN 1 .4301 (type 304) or grade EN 1 .4401/4 (type 316 or 316L), and has a threaded, ribbed or otherwise textured exterior. Two blind holes

103, 104 are formed at each end, with their axes congruent with the main axis of the body 101. The holes 103, 104 are threaded. These are sized as M 16 in the most preferred form, but can be any other size as required.

The disc 102 in this embodiment is connected to the boss 101 at an outer or second end, and extends outwards from the main body 101 generally perpendicularly to the main axis or length of the main body 101 . The disc section 102 is formed from a ferritic stainless steel, for example stainless steel grade EN 1 .4521 (type 444) - that is, nickel-free molybdenum-alloyed ferritic stainless steel. As well as being ferritic, this material offers extremely good corrosion resistance. An aperture is formed in the centre of the disc 102 that aligns with hole 104 in the outer or second end of the boss 101 .

It should be noted that ‘inner’ and ‘outer’ as used in this specification refer to the construction fastener in use. The inner end is inserted into the tunnel wall, or is aligned towards the tunnel wall, and the outer end is opposite this in use. The inner end is also referred to as the first end, and the outer end as the second end. This description is used consistently throughout this specification.

The disc 102 is circular in plan view, and has a generally flat outer surface that forms the main bonding surface (as described below). The disc in this embodiment is 80mm in diameter, but can be between 50-150mm as required, or other dimensions outside this range. Although circular in plan view is preferred, other shapes can also be used - for example square or hexagonal or similar.

As shown in figures 1a - 1c, the centre of the disc is formed down or indented outwards to accommodate a connection to the main body 101 . The outside edge of the disc 102 is also turned down in order to keep the edge away from waterproofing material on the outer side during use, as the rim might present a sharp edge that could cut the material. The profiling of the disc gives the disc an overall depth or height of 5mm, although the disc can be constructed so as to have a depth/height of anywhere from 3mm to 10mm, depending on the particular use required. Other depths are also possible.

The disc is formed from stainless steel having a thickness of 0.8mm, but can be formed from material having a thickness of anywhere from 0.5-1.5mm, or more as required. The inner edge of the disc 102 is also turned down in order to accommodate a connection to the boss 101 that must be kept below the flat outer surface of the disc 102.

A heat-activated adhesive coating 105 is applied to the outer face of the disc 102 (that surface facing away from the main body 101 ) - that is, that face of the disc facing in the same direction as the second end, or outwards away from the second end. The coating 105 is applied over substantially the total surface area of the disc 102. The coating is formed from any suitable adhesive that will activate when the disc 102 heats up, as outlined below. The adhesive is normally ‘dry’ or non-sticky when not activated. A hotmelt adhesive is an example of a type of suitable adhesive. The adhesive layer can be applied by any suitable means such as spraying, dipping, or roller. The disc 102 is connected to the body 101 via crimping or similar. As shown in figure 6, a lip 110 extends up from the perimeter of hole 104, and once the disc 102 is positioned on the outer end of the body 101 , the lip 110 is bent down over and around the central aperture of the disc 102 to hold it in place on the outer end of the body 101. The join between the body 101 and disc 102 needs to be made in such a way that it is strong and substantially watertight. The boss 101 and disc 102 must be firmly and permanently connected. This can alternatively be achieved via welding or riveting or similar. An example of the crimping process is shown in figure 6, where the steps are shown sequentially from left to right of a disc being positioned on the boss, and the lip being pressed downwards and outwards in order to make the connection and seal. It is most preferred that a sealing material is added between the boss 101 and disc 102 when the crimp is made, in order to make this connection substantially watertight. This can be a pre-applied liquid seal, or an o-ring, gasket, or sealing washer, or similar. Any suitable material or seal can be used, as long as this will withstand short but high heat exposure during the induction bonding step, and retain its sealing properties for a long service life.

In use, a threaded extender rod 111 can be inserted (via screwing or similar) into hole 103 in the main body or boss 101 . However, the body/boss 101 is formed from steel as outlined above, and therefore in use this is usually strong enough to support the weight of a rod (and any other weight) inserted/connected with hole 104. Therefore, only a shallowly-drilled hole in the rock is required. This can save considerably on installation times and costs. If the installation is taking place in weaker rock where greater embedment strength is required, then an extender rod can be fitted into hole 103, and a deeper hole can be drilled to accommodate this.

In use, a user drills a hole in the rock wall and cleans this out. This is then filled with epoxy resin, and the construction fastener 100 is screwed in (the boss 101 is screwed into the epoxy-filled hole). The hole is drilled so that it is not substantially larger in diameter than the diameter of the main body 101 , and so the inner face of the disc 102 rests against the wall of the tunnel once the main body 101 is inserted. An epoxy resin is used to fill the hole so that the boss or main body 101 is permanently emplaced and firmly held within the hole. The external boss threads, ribs or texture enhance the boss embedment strength within the resin.

A number of the fasteners 100 are emplaced on the wall in a grid pattern, at approximately 1 m spacings.

A sheet of waterproof membrane is placed over the top of the grid, in contact with the adhesive coating 105. Using an induction heating tool that is placed on the surface of the waterproofing membrane, the disc 102 is heated inductively (the type of stainless steel allowing this heating to take place), and this activates the adhesive coating 105. Once activated, the adhesive coating bonds the waterproof membrane to the disc. A magnetic clamp may be positioned on the bond location immediately following heating to ensure the membrane is in contact with the adhesive coated disc. This is then removed once the bond has cooled.

As there are no apertures formed through the waterproof membrane, this is leakproof. A hole can be formed in the membrane to allow access to hole 104 for insertion of a steel rod or similar. However, this will not compromise the seal around the rest of the disc 102, and as there is no path from one end of the boss 101 to the outer end via the holes 103, 104, there is no path for water to pass from one side of the membrane to the other.

Further, longer fasteners can be dis-advantageous if the rock settles, as these then bend and deform with the rock settling, which can lead to breakages if using a longer plastic boss, or can lead to the epoxy material coming loose.

A further advantage is that if the boss is formed from a non-ferritic stainless steel or other non-ferrous material, this will not heat directly when the disc is induction heated, and only via secondary direct contact heating, over a relatively small surface area.

Second Embodiment

A second embodiment of construction fastener 200a is shown in figure 2a. The construction fastener 200a of this embodiment is similar to that of the first embodiment, with the addition of a tungsten carbide drill tip 207 attached (e.g. by screwing) onto the inner end of the boss 201 .

The drill tip 207 allows the fastener 200 itself to ‘self-drill’ or ‘self-tap’ holes into the wall of the tunnel in use. The threads of the boss 201 and drill tip 207 are configured so that the tip 207 will not come loose from the boss 201 during insertion (it will not unscrew).

Variations of this embodiment are shown in figures 2b and 2c. In these embodiments, the drill head comprises a series of internal passages 209 which allow for epoxy or similar to be injected through the boss and drill head and into the cavity. As shown in figures 2b and 2c, the holes 203, 204 are connected to allow this process. A one-way valve such as valve 208 can be fitted to the aperture between the holes 203, 204 to prevent backflow between the holes. That is, fluids can flow from the outer end to the inner end.

Additionally, as shown in figure 2c, a backing plate 210c can be fitted on the inner side of the disc 202c. This acts to hold down any softer geotextile material around the disc 202c so that the disc 202c does not sink below the surface of the geotextile material and prevent bonding with the waterproof membrane from taking place. The back plate can be formed of any suitable material such as for example a rigid plastic.

Third Embodiment

A third embodiment of construction fastener 300 is shown in figures 3a - 3c. The construction fastener 300 of this embodiment is similar to that of the first embodiment, having a boss 301 and a disc 302 formed from the same materials, and having substantially the same dimensions. In this embodiment, the outer surface of the boss 301 is smooth rather than threaded.

In this variation, the boss 301 is formed from austenitic stainless steel grade EN 1 .4401/4 (type 316/316L). This material provides good corrosion resistance while still allowing a good connection with the disc. Carbon steel can also be used, but preferably needs to be coated to prevent corrosion, and this can make it difficult to connect the boss and disc by crimping or welding. In use, a hole is drilled in the tunnel wall and cleaned out. This is then filled with epoxy resin and a long steel rod is inserted so that this extends away from the tunnel wall. The fastener 300 is then screwed onto the free or inner end of the rod using hole 303.

A grid of these holes and fasteners are formed in the tunnel wall. The waterproof membrane or sheet is hung in front of these and, using an induction heating tool placed on the surface of the waterproofing membrane, the disc 302 is heated inductively (the type of stainless steel allowing this heating to take place), and this activates the adhesive coating 305. Once activated, the adhesive coating bonds the waterproof membrane to the disc in the same or a similar manner to that described above.

Fourth Embodiment

A fourth embodiment of construction fastener 400 is shown in figure 4. The construction fastener 400 in this embodiment comprises two main parts: a boss or body 401 and a disc 402.

The boss 401 in this embodiment comprises a cylindrical body having a diameter of 30-60mm and a length of anywhere from 50-150mm, but most preferably in the range 70-95mm.

Two blind holes 403, 404 are formed at each end, with their axes congruent with the main axis of the body 101 . The holes 403, 404 are threaded. These are sized as M16 in the most preferred form, but can be any other size as required.

The boss 401 in this embodiment is formed from a high strength plastic that offers suitable stiffness, strength and heat resistance to withstand the forces involved (e.g. bending forces). In particular, the stiffness and strength need to be sufficient to withstand the bending force in use from two axially aligned steel rods in the holes 403, 404. In particular, the thread in the holes 403, 404 needs to be of sufficient strength so that it will not pull out or ‘strip out’ under load. The plastic needs to be suitable to resist the heating of the disc 402 in use when this is inductively heated. The plastic can, if required, be reinforced with glass fibre or metallic inserts or similar.

A flange 412 extends outwards from at or close to the outer end of the main body 401 , the flange 412 angled slightly outwards from perpendicular to the main body (angled off perpendicular towards the outer end). If required, the flange can be supported by multiple radial webs or ribs 413 that extend from the inner face of the flange 412 towards the inner end, the webs/ribs 413 integrally connected to the main body 401 .

The disc 402 in this embodiment is connected to the flange 412 at the second or outer end, and extends from the edge of the flange 412 (which is congruent with the edge of the disc 402) inwards to cover the flange 412. The connection between the disc 402 and the flange 412 is made at the outer edge of both the disc 402 and flange 412 by crimping the rim or edge of the disc 412 around the edge of the flange 412. The angle of the flange 412 means that aside from the crimped rim, the flange 412 and disc 402 are not in contact.

It is most preferred that a high-temperature seal is included in the crimped joint. The seal could be for example an elastomeric seal, an O-ring, gasket, sealing washer, or similar. The seal must be suitable to provide a watertight seal for the lifetime of the construction fastener 400, as well as being able to withstand high, but short-lived, heat exposure during the induction bonding process when the construction fastener is emplaced.

The disc section 402 is formed from a ferritic stainless steel, for example stainless steel grade EN 1.4521 (type 444) - that is, nickel-free molybdenum-alloyed ferritic stainless steel. As well as being ferritic, this material offers extremely good corrosion resistance. An aperture is formed in the centre of the disc 402 that aligns with hole 404 in the outer or first end of the boss 401. The apertures are sized so that the centre hole of the disc 402 allows at least a steel rod to pass through to the hole 404.

The disc 402 is circular in plan view, and has a generally flat outer surface that forms the main bonding surface (as described below). The disc in this embodiment is 80mm in diameter, but can be between 50-150mm as required, or other dimensions outside this range. Although circular in plan view is preferred, other shapes can also be used - for example square or hexagonal or similar.

As for the first embodiment, the centre of the disc is formed down or indented inwards to accommodate a connection to the main body 401 . The outside edge of the disc 102 is crimped around the flange to make a soft rolled edge. The profiling of the disc gives the disc an overall depth or height of 5mm, although the disc can be constructed so as to have a depth/height of anywhere from 3mm to 10mm, depending on the particular use required. Other depths are also possible.

The disc is formed from stainless steel having a thickness of 0.5mm, but can be formed from material having a thickness of anywhere from 0.25-1 ,5mm. The inner edge of the disc 102 is also turned down in order to accommodate a connection to the boss 101 that must be kept below the flat outer surface of the disc 102.

A heat-activated adhesive coating 105 is applied to the outer face of the disc 102 (that surface facing away from the main body 101 ), over substantially the total surface area of the disc 102. The coating is formed from any suitable adhesive that will activate when the disc 102 heats up, as outlined below. The adhesive is normally ‘dry’ or non-sticky when not activated. A hotmelt adhesive is an example of a type of suitable adhesive. The adhesive layer can be applied by any suitable means such as spraying, dipping, or roller.

Fifth Embodiment

A fifth embodiment of construction fastener 500 is shown in figure 5. The construction fastener 500 of this embodiment is similar to that of the fourth embodiment, except that the flange 512 is integrally formed with the inner end of the main body 501 , the effect being that the main body 501 has an inner part 501 and an outer part 512 (the flange). The flange 512 forms a conical section around and enclosing the inner part, with the narrower end of the conical section at the inner end of the main body 501 . Radial ribs 515 can be positioned in the space between the flange 512 and the main body 501 to stiffen both of these elements.

All other features are substantially as described for the fourth embodiment.

Claims

Claims:

1 . A construction fastener, comprising: a boss section comprising an elongate main body having a first end and a second end; a disc section connected to the main body at or close to the second end of the elongate main body, the disc extending from the main body substantially perpendicularly to the length of the main body; a heat activated adhesive coating applied to substantially the entirety of that face of the disc facing in the same direction as the second end; characterised in that at least the disc section is formed from ferritic stainless steel.

2. A construction fastener as claimed in claim 1 wherein the disc section is further formed from a stainless steel that is corrosion-resistant.

3. A construction fastener as claimed in claim 1 or claim 2 wherein the ferritic stainless steel comprises stainless steel grade EN 1.4521 (type 444).

4. A construction fastener as claimed in any one of claims 1 to 3 wherein the boss section is formed from austenitic stainless steel.

5. A construction fastener as claimed in claim 4 wherein the boss section is at least partly formed from stainless steel grade EN 1 .4301 (type 304) or grade EN 1 .4401 /4 (type 316 or 316L).

6. A construction fastener as claimed in any one of claims 1 to 3 wherein the boss section is formed from plastic.

7. A construction fastener as claimed in any one of claims 1 to 6 wherein two holes are formed at each end of the main body, the holes having a substantially common axis.

8. A construction fastener as claimed in claim 7 wherein the holes are threaded.

9. A construction fastener as claimed in any one of claims 1 to 8 wherein the disc has a generally flat outer surface.

10. A construction fastener as claimed in claim 9 wherein the outer edge of the disc is turned inwards.

11 . A construction fastener as claimed in any one of claims 1 to 10 wherein the boss section and disc section are crimped together.

12. A construction fastener as claimed in claim 11 wherein a sealing material is added between the boss and disc when the crimped connection is made.

13. A construction fastener as claimed in any one of claims 1 to 12 wherein the boss external surface is threaded, ribbed or otherwise textured to enhance embedment strength of the boss within a substrate.

14. A construction fastener as claimed in any one of claims 1 to 13 further comprising a drill tip attached to the first end of the boss section.

15. A construction fastener as claimed in claim 14 wherein the drill tip comprises at least one internal passage, the boss section further comprising a passage therethrough between the first and second ends.

16. A construction fastener as claimed in claim 15 wherein the boss section further comprises a one-way valve located in the passage that allows passage of fluids from the outer end to the inner end.

17. A construction fastener as claimed in any one of claims 1 to 16 wherein the boss section further comprises a flange extending from the boss section at or close to the outer end of the main body, the disc connected to the outer edge of the flange at the outer edge of the disc.

18. A construction fastener as claimed in claim 17 wherein the disc and flange are crimped together at their outer edges.

19. A construction fastener as claimed in claim 17 or claim 18 further comprising at least one rib extending from the inner face of the flange towards the first end and integrally connected to the main body.

20. A construction fastener as claimed in any one of claims 1 to 16 wherein the boss section further comprises a flange extending from the boss section at or close to the inner end of the main body, the flange extending to form a conical section around and enclosing the inner part of the boss section, the disc connected to the outer edge of the flange at the outer edge of the disc.

21 . A construction fastener as claimed in claim 20 further comprising at least one rib located in the space between the flange and the inner part of the boss section.

22. A method of attaching a waterproof lining to a tunnel wall, comprising the steps of: i) drilling a series of holes in the tunnel wall, the holes configured to receive a plurality of construction fasteners at least some of which are as claimed in any one of claims 1 to 21 ; ii) emplacing the construction fasteners in the holes; iii) positioning a sheet of waterproof membrane over the top of the construction fasteners, the inner face of the sheet in contact with the heat activated adhesive coatings; iv) placing an induction heating tool on the outer surface of the waterproofing membrane over the disc and heating the disc inductively to activate the adhesive coating.

23. A method as claimed in claim 22 comprising the further step of placing a magnetic clamp on the bond location following heating to ensure the membrane is in contact with the adhesive coated disc.

24. A method as claimed in claim 22 or 23 wherein in the step of drilling holes in the tunnel wall, these are drilled in a grid pattern at approximately 1 m spacings.