CAST-IN TUNNEL GASKET AND JOINING METHOD

The present invention relates to an improved “cast-in” tunnel gasket and a method of joining such a tunnel gasket.

Elastomeric (rubber) gaskets are used to seal segmentally formed tunnels; for example, against water ingress. The rubber gaskets are fitted between concrete tunnel segments. Previously, rubber tunnel gaskets were fitted into grooves pre-formed in the tunnel segments and secured with adhesive. However, it has been shown to be advantageous to mould the concrete tunnel segments around a gasket, known as a cast-in tunnel gasket, to form a tunnel segment having an integrated seal.

An example of an existing cast-in tunnel gasket includes that disclosed in patent publication WO2013189491 (Datwyler), wherein a moulded product is produced in a shutter assembly. It is known to provide such anchored/“cast-in” tunnel seals as an alternative to inserting a seal in a pre-cast groove in the concrete using a contact adhesive. A “cast-in” tunnel segment gasket (TSG) has been found to offer advantages in reliability and eliminates the cost and inconvenience of using adhesives. Currently “cast-in” tunnel segment gaskets are manufactured by encasing the segment gasket in concrete during the casting of the segments themselves. It is also known that it is advantageous to provide a gasket profile that allows for the significant forces that the concrete tunnel segments are to be placed under. For example, the tunnel segment gasket (TSG) comprises profiled geometries according to the expected deformation of the gasket under compression; for example including one or more longitudinal channels running therethrough and/or having “anchored” profiles with legs protruding therefrom. It is known that a cast-in tunnel gasket “collapses” into the groove into which it has formed during use, to close the gap between adjacent concrete tunnel segments.

However, it has been found that existing cast-in TSG products are problematic, particularly when they are fitted at a corner, i.e. where two gaskets are joined. This is a significant disadvantage of known cast-in TSGs because the gaskets are commonly provided in the form of a frame to be cast-in adjacent to the perimeter of the concrete tunnel segment. Current joining methods for TSGs create problems because of excessive rubber collecting at the join when gaskets are joined by injecting or “shooting” rubber into the corners. This effectively creates a solid corner joint that restricts significantly the movement which is essential to the performance of the gasket as it “collapses” into the groove into which it is fitted. A solid corner join results from “shooting” rubber in at the corner joint, often termed a “shot-joint”, which then travels along the longitudinal channels in the adjoining gaskets. Such a solid, filled corner joint does not allow for any compression or movement of the joint; for example if the TSGs are not aligned perfectly or if there is ground movement after installation. Thus, existing solid corner TSG joints lead to excessive load building up at the corners, which will eventually lead the concrete segments attached thereto to crack. Furthermore, the gaskets will be not be securely held and leaks are very likely to occur.

This problem has previously been acknowledged with respect to conventional, adhesively fitted gaskets and was solved by allowing for higher arches in the gasket profile at the corners to allow for a more uniform volume of rubber at the joint when compared with the volume of rubber along the length of the gaskets joined thereto. However, the requirements of the profile of a cast-in TSG are quite different from adhesively-held gaskets and the problems associated with excessive rubber at corner joints remain. As previously discussed, the profile of any TSG is configured so that when the solid tunnel segments are joined and bolted together, the relatively “open” profiled of the rubber gasket collapses into the groove in the tunnel segment in which it is held. The cross-section or profile of the gasket is designed to take the strain of the load applied by the adjoining tunnel segments; that is, to minimise the closure forces exerted on the tunnel segments whilst securely sealing the tunnel. Thus, there remains a need for an improved TSG and joining method, which maintains performance of TSG along the full length of the seal, particularly at the corners.

The present invention sets out to alleviate the problems described above by providing an improved tunnel segment gasket and an improved method of joining tunnel segment gaskets.

In one aspect, the invention provides a tunnel segment gasket comprising a shaped profile having at least two anchoring legs for casting in to a tunnel segment; a plurality of longitudinally extending bores; a shot film joint and a strengthening element at the base of the gasket.

It is understood that the “base of the gasket” refers to the face of the gasket between the two anchoring legs, which is external to the shot film joint.

Preferably, the strengthening element is shaped and positioned to increase the strength of the tunnel segment gasket at the joint.

Preferably, the strengthening element is a rhombus shape having a centre line parallel to the shot film joint.

Preferably, the strengthening element is integral with the shot film joint.

Preferably, the shot film joint is concealed within the tunnel segment gasket and the strengthening element is exposed at the base of the gasket.

It has been found that the configuration of the present invention provides much improved joint security for tunnel segment gaskets. The strengthening element acts, in use, as a “keying element” and protrudes from the shot film joint at the base of the main body of the shaped profile. When the strengthening element is cast in to a concrete tunnel segment/s the risk of crack propagation is significantly reduced when the gasket is placed under load. The strengthening element of the profile does not affect the load characteristics of the gasket under compression. The strengthening element/“keying element” does not hinder the closure performance of the tunnel segments nor does it affect the load compressing the gasket, but provides a remarkably secure joint. It has been found that the security of the joint is remarkably improved and the risk of the gasket pulling apart at the joint and the joint failing is much reduced.

Optionally, the tunnel segment gasket further comprises at least one curved protrusion on its base.

By providing curved protrusion/s on the base of the tunnel segment gasket, the present invention minimises load build up when joining gaskets at a corner, i.e. so that the joint has substantially the same load characteristics at the corner as the remainder of the gasket. The present invention optionally provides an improved gasket profile whereby one or more curved protrusions on the base of the gasket provide a greater surface area over which a gasket joint can be formed. It has been found that by increasing the surface area of the gasket at the joint, the gasket is less likely to tear or split. Thus, a secure seal for segmentally lined tunnels can be formed whilst using a reduced amount of rubber at the joint. The volume of rubber at the joint is minimised to ensure that the gasket can take the strain of the adjoining tunnel segments and avoid the generation of excess force at the joint. The profile of the TSG of the present invention provides the required energy within the seal and generates a secure seal when the segments have been assembled; for example against water ingress, or for retention in tunnels used for transport of storage.

Preferably, the cross-section of the or each longitudinally extending bore is circular.

By having cylindrical bores (bores with a circular cross-section) it has been found that the TSG performs better when a load is applied, i.e. when multiple tunnel segment gaskets are joined. The relative movement of the TSG under load will be substantially the same regardless of the direction in which the load is acting on the or each longitudinally extending bore. The TSG is better able to withstand the load exerted on it when it collapses into the segment groove in which it is held, when tunnel segments are joined. This ensures that the TSG does not collapse without effectively sealing the segments and minimises the closure forces exerted on the tunnel segments.

Optionally, the cross-section of the or each longitudinally extending bore is semi-circular.

Preferably, the plurality of longitudinally extending bores comprises one or more, preferably a plurality of bores having a circular cross-section and one or more, preferably a plurality of bores having a semi-circular cross-section.

For TSG having a wider base, to be cast-in to a tunnel segment, it has been found that providing one or more longitudinally extending bores having a semi-circular profile ensures that the gasket performs well when put under strain—i.e. when the tunnel segments are joined and the profile of the gasket collapses into the groove in which it is fitted. The ability of the gasket to collapse ensures that tunnel segments can be safely and securely fitted together without any risk of cracking of the segments or leaks.

Optionally, the tunnel segment gasket comprises at least two curved protrusions on its base.

Having two curved protrusions on the base of the TSG provides an increased surface area over which a gasket joint can be formed, whilst ensuring that the gasket is less likely to tear or split.

Optionally, the or each curved protrusion is positioned between the two anchoring legs.

Preferably, the tunnel segment gasket further comprises at least two shaped transverse protrusions.

Having shaped transverse protrusions or shoulders allows for secure casting of the TSG in a concrete tunnel segment, wherein the shoulders lay substantially parallel to the plane of the face of the concrete tunnel segment, in use.

Optionally, the tunnel segment gasket has a width of between about 20 mm and about 50 mm; preferably, between about 28 mm and about 45 mm.

In a further aspect, the invention provides a method of forming a tunnel segment gasket joint comprising the steps of:

i) extruding a first tunnel segment gasket through a first cutting guide;

ii) extruding a second tunnel segment gasket through a second cutting guide;

iii) cutting an angled end of both the first and second tunnel segment gasket;

iv) providing a thin elastomeric film between the angled ends of the first and second tunnel gasket to form a joint.

Preferably, the method comprises providing a thin elastomeric film between the angled ends of the first and second tunnel segment to form a joint and a strengthening element integral with the joint.

Preferably, the method comprises forming a joint and an integral strengthening element wherein the strengthening element is exposed at the base of the gasket.

The present invention provides a much improved spliced joint for a tunnel segment gasket and also addresses a previously identified problem whereby the diagonal cutting of a profiled TSG was not possible. By using a first and second cutting guide, movement of the shaped flexible profile of the TSG away from the cutting blade is prevented to significantly improve the accuracy of the required diagonal cut at the joint-facing ends of the TSG. The method of the present invention offers an improvement in ensuring that the angle of the TSG can be carefully selected according to the tunnel segments with which the TSGs will be used and also ensures that the TSG is held securely prior and during cutting. Accurate diagonal cutting means that a “spliced” joint can be formed where two TSGs can be secured to each other whilst requiring the addition of only the minimum possible amount of extra elastomeric material at the joint. The method of the present invention avoids elastomeric material travelling along the channels of grooves in the gasket. The method of the present invention ensures that the load generated at the joint is evenly distributed across the corner; the TSG adjacent thereto and along the reminder of the gasket; that is, no excessive load is created. By carefully maintaining the profile of the TSG this ensures that any point stresses will be avoided, which could lead to splitting of the gasket and crack propagation, so that no cracking of the concrete segments will result over time.

Preferably, the elastomeric film is a rubber film.

Preferably, the thin elastomeric film has a thickness of between about 0.2 mm and about 2 mm.

Preferably, the thin elastomeric or rubber film is provided by placing the film between the angled ends of the first and second tunnel gasket to form a joint; more preferably, the thin elastomeric or rubber film is provided by injecting or “shooting” the elastomeric or rubber film between the angled ends of the first and second tunnel gasket to form a joint; optionally, the thin elastomeric or rubber film is provided by placing a rubber film between the mating faces to be joined.

Preferably, the method of forming a tunnel segment gasket joint further comprises the step of clamping at least one end of both the first and second tunnel segment gaskets.

In another aspect, the invention provides a tunnel segment gasket joint produced by a method described herein.

Within this specification, the term “about” is interpreted to mean optionally ±20%, preferably optionally ±10%, more preferably optionally ±5%.

For the purposes of clarity and a concise description, features are described herein as part of the same or separate embodiments; however it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described. For example, it will be appreciated that all preferred features described herein are equally applicable to all aspects of the invention described therein.

The invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which:—

FIG. 1a is a perspective view of a slice through a tunnel segment gasket constructed in accordance with a first embodiment of the present invention;

FIG. 1b is a cross-sectional view across the joint, effectively showing half of a tunnel segment gasket, as shown in FIG. 1a, in accordance with a first embodiment of the present invention;

FIG. 2 is a cross-sectional view of a tunnel segment gasket, as shown in FIG. 1b, cast in to a concrete tunnel segment;

FIG. 3 is a cross-sectional view of a tunnel segment gasket constructed in accordance with a second embodiment of the present invention;

FIG. 4 is a cross-sectional view of a tunnel segment gasket constructed in accordance with a second embodiment of the present invention shown in FIG. 3, which is shown cast-in to a tunnel segment;

FIG. 5 is a cross-sectional view of a tunnel segment gasket constructed in accordance with a further embodiment of the present invention;

FIG. 6 is a cross-sectional view of a tunnel segment gasket constructed in accordance with the further embodiment of the present invention shown in FIG. 5, which is shown cast-in to a tunnel segment;

FIG. 7 is a view from above of a cutting guide for cutting a first (left hand) tunnel segment gasket of the present invention to be joined to form a corner joint, as described with respect to FIG. 15;

FIG. 8 is a view from the side of the cutting guide of FIG. 7, for cutting a first tunnel segment gasket of the present invention to be joined to form a corner joint;

FIG. 9 is a perspective view of the cutting guide of FIGS. 7 and 8 for cutting a first tunnel segment gasket of the present invention to be joined to form a corner joint;

FIG. 10 is a view from above of a cutting guide for cutting a second (right hand) tunnel segment gasket of the present invention to be joined to form a corner joint, as described with respect to FIG. 15;

FIG. 11 is a view from the side of the cutting guide of FIG. 10 for cutting a second tunnel segment gasket of the present invention to be joined to form a corner joint;

FIG. 12 is a perspective view of the cutting guide of FIGS. 10 and 11 for cutting a second tunnel segment gasket of the present invention to be joined to form a corner joint;

FIG. 13 is a perspective view of the left hand and right hand cutting guides;

FIG. 14 is a schematic view of the cutting of the left hand and right hand tunnel segment gaskets according to the present invention;

FIG. 15 is a perspective view of a tunnel segment gasket joint having an obtuse angle, in accordance with the present invention;

FIG. 16 is a view from above of a tunnel segment gasket joint having an obtuse angle;

FIG. 17 is an internal view of the tunnel segment gasket joint of FIG. 16;

FIG. 18 is a perspective view of a tunnel segment joint having an acute angle; and

FIG. 19 is a perspective view of a tunnel segment gasket joint having an acute angle, according to the present invention.

Referring to FIG. 1a and FIG. 1b, showing a slice through the tunnel segment gasket (TSG) 1′, the TSG 1′ comprises an elastomeric (rubber) body 3′ having a shaped profile. The body 3′ comprises anchoring legs 5′, such that the full profile of the gasket 1′, as shown in FIG. 2 comprises two anchoring leg 5′, with one on each side of the TSG 1′. The TSG 1′ further comprises a plurality of longitudinally extending bores 7′.

Referring to FIG. 2, each of the anchoring legs 5′ secures the TSG 1′ in position when cast in to a concrete tunnel segment 6′. In use, the gasket 1′ is compressed under load of the concrete tunnel segments 6′ in which the TSG 1′ is cast. The width of the gasket 1′, excluding the shoulders 13′, in a first embodiment is about 28 mm and the height of the main body of the gasket 1′, excluding the anchoring legs 5′, is about 18 mm. The height of each shoulder 13′ from the base of the gasket 1′ is about 9 mm. The width of the base of the gasket is about 21 mm.

Referring to FIG. 1b, the gasket 1′ further comprises a shot film joint 43′ and a strengthening element 4′ at the base of the gasket 1′. It is understood that the “base of the gasket” refers to the face of the gasket 1′ between the two anchoring legs 5′, which is external to the shot film joint 43′. The strengthening element 4′ is shaped and positioned to increase the strength of the tunnel segment gasket 1′ at the joint 43′ and reduces the risk of crack propagation when the tunnel segment gaskets 1′ are joined and cast in to concrete tunnel segments 6′.

In the embodiment of FIG. 1b, the strengthening element 4′ has four sides forming a rhombus shape wherein a centre line of the strengthening element 4′ is aligned with the centre line of the shot film joint 43′. The strengthening element 4′ is integrally formed with the shot film joint 43′. The shot film joint 43′ is concealed within the tunnel segment gasket 1′ and the strengthening element 4′ is concealed, in use by the concrete tunnel segment 6′ into which it is cast. It is understood that, in alternative embodiments of the present invention the strengthening element 4′ can have a different shape according to user requirements. The shape of the strengthening element 4′ is determined by the method described with respect to FIGS. 15 and 17 and is formed integrally with the shot film joint 43′.

Referring to FIG. 3, the tunnel segment gasket (TSG) 1 comprises an elastomeric (rubber) body 3 having a shaped profile. The profile comprises two anchoring legs 5 and a plurality of longitudinally extending bores 7. The base 9 of the TSG 1 optionally has two curved protrusions 11 that are arranged to increase the surface area of the base 9 of the TSG 1. The embodiment shown in FIG. 1 has a rubber volume for a 1000 mm length of gasket of 302 cc; however, the volume of rubber is given by way of example only. For any given gasket, the volume of rubber is varied according to the requirements of the given gasket; for example depending on the application for which it is to be used. The profile further comprises two shoulders 13 protruding substantially perpendicular to the direction of the anchoring legs 5. The width of the gasket (FIG. 1-A), excluding the shoulders 13, in a first embodiment is about 28 mm and the height of the main body of the gasket (FIG. 1-B), excluding the anchoring legs 5 is about 19 mm. The height of each shoulder 13 from the base of the gasket (FIG. 1-C) is about 8 mm. The width of the base of the gasket (FIG. 1-D) is about 21 mm.

In use, as shown in FIG. 4, the anchoring legs 5 are cast in to a tunnel segment 13. The longitudinally extending bores 7 of the TSG 1 are shown to have a circular cross-section. However, in alternative embodiments the cross-section of the longitudinally extending bores 7 can be configured according to the anticipated load requirements of the TSG 1. That is, it is understood that the number, shape and dimensions of each of the longitudinally extending bores 7 can vary according to the gasket's load requirements. Referring to FIG. 2, when the TSG 1 is cast into the tunnel segment 23, the volume of the groove 15 in which the TSG 1 sits has a volume of about 335 cc; however, the volume of the groove is given by way of example only. For any given gasket, the volume of rubber is varied according to the requirements of the given gasket; for example depending on the application for which it is to be used. The volume of the rubber and the groove 15 is carefully calculated to ensure that it will be possible to close adjacent tunnel segments 23 securely. The shoulders 13 of the TSG 1 are configured to protrude within the tunnel segment in which they are cast, with the shoulders 13 substantially parallel to and along the upper face of the tunnel segment 23.

In the embodiments shown in FIG. 3 (and FIG. 4), the optional protrusions 11 have a substantially semi-circular profile extending along the base 9 of the TSG 1. The curved profile of the curved protrusions 11 prevents any points of stress when the TSGs are joined; thus, avoiding the risk of splitting of the joint or crack propagation when a load is applied to the joint; that is, when the TSG 1 is used in joining two tunnel segments (not shown). It is envisaged that the curved profile of the curved protrusions 11 can take the form of an elongate beading running along the length of the underside of the TSG 1. The cross-section of the curved protrusions 11 is semi-circular or domed. It is also envisaged that it alternative embodiments, a plurality of curved protrusions are provided, however, the preferred embodiment is that shown in FIGS. 1a, 1b and 2, as referred to above. By providing the optional curved protrusions 11, the surface area of the base 9 of the TSG 1 is increased to allow for efficient joining of two TSGs 1 without an excess of elastomeric material being required at the joint.

As shown in FIG. 5 and FIG. 6, in a further embodiment of the present invention, when the TSG 1 is to be cast in to a tunnel segment 23, having groove volume 25 of about 434 cc for a 1000 mm length, the dimensions of the TSG 1 are altered accordingly. The volume of rubber is given by way of example only. For any given gasket, the volume of rubber is varied according to the requirements of the given gasket; for example depending on the application for which it is to be used.

The width of the gasket 1 (FIG. 5-E), excluding the shoulders 13, in this further embodiment is about 32 mm and the height of the main body of the gasket 1 (FIG. 5-F), excluding the anchoring legs 5 is about 20 mm. The height of each shoulder 13 from the base of the gasket (FIG. 5-G) is about 9 mm. The width of the base of the gasket (FIG. 5-H) is about 33 mm. In alternative embodiments, the width of the base of the gasket is about 40 mm or about 45 mm, but all dimensions will vary according to the sealing requirements and the application of the TSG.

As shown in FIG. 5, for the further embodiment shown, the profile of the gasket 1 comprises a plurality of longitudinally extending bores 7 having a circular cross-section and also a plurality of longitudinally extending bores 7b having a substantially semi-circular cross section. The profile comprises two anchoring legs 5 and two shoulders 13 protruding substantially perpendicular to the direction of the anchoring legs 5.

As shown in FIG. 6, in use, the anchoring legs 5 are cast in to form a groove 25 in a tunnel segment 23. The shoulders 13 of the TSG 1 are configured to protrude substantially parallel to and along the upper face of the TSG 1.

As shown in FIGS. 7, 8 and 9, a first cutting guide 30 is used to extrude a first tunnel segment gasket (not shown) along a curing line. As shown in FIG. 9, the cutting guide 30 comprises a bottom plate 32 and a top plate 31. The bottom plate 32 comprises a channel 33. As shown in FIG. 8, the cross-section of the channel 33 is shaped according to the gasket profile that is required. The angle of the channel 33 to the outer faces of the cutting guide is also carefully selected according to the required angle of the joint that is to be formed by the TSG.

As shown in FIGS. 10, 11 and 12, a second cutting guide 35 is used to extrude a first tunnel segment gasket (not shown). As shown in FIG. 10, the cutting guide 35 comprises a bottom plate 37 and a top plate 36. The bottom plate 37 comprises a channel 38. As shown in FIG. 9, the cross-section of the channel 33 is shaped according to the gasket profile that is required. The angle of the channel 38 to the outer faces of the cutting guide is also carefully selected according to the required angle of the joint that is to be formed by the TSG.

Referring to FIG. 13, the first and second cutting guides 30, 35 form the left hand and right hand guides for forming the corner joint of two tunnel segment gaskets 41, 42, as shown in FIGS. 15 and 16. To form the corner joint a first tunnel segment gasket 41 is extruded through the channel 33 of the left hand cutting guide 30, shown in FIG. 7. A second tunnel segment gasket 42 is extruded through the channel 38 of the right hand cutting guide 35.

Referring to FIG. 14, two rotating blades 40a, 40b are used to accurately cut the end surface of each of the two extruded tunnel segment gaskets 41, 42 whilst they are held within the respective cutting guides 30, 35.

Referring to FIG. 15, the present invention also provides a method of manufacturing a tunnel segment gasket joint. A first and second tunnel segment gasket 40, 41 are joined together by shooting in a thin film of rubber 43, as shown in FIG. 17. The thin film “shot” joint 43 is applied to the first and second tunnel segment gaskets 40, 41 whilst they are clamped in the required position. The increased accuracy of the cutting of the extruded TSGs together with the increased accuracy of the joining is such that the profile of the gasket 40, 41 is substantially unchanged by the joining method, as shown in FIG. 13. The joining method of the present invention provides a stronger, fully vulcanised joint. The optional curved protrusions, at the base of the gasket ensure that not only is the desired angle achieved at the joint but the joint profile is maintained to allow for secure sealing without the risk of split propagation.

Referring to FIG. 16, the cutting guides allow for the angle 46 at the joint to be obtuse, as shown in FIG. 16 or to be acute, as shown in FIG. 18, or to be a 90-degree angle, if required. The increased accuracy of the angle at the joint improves the performance of the TSGs when positioned to join tunnel segments. This capability to produce any required joint angle also ensures an accurate fit with the segment with which the TSG is to be used.

The above described embodiment has been given by way of example only, and the skilled reader will naturally appreciate that many variations could be made thereto without departing from the scope of the claims.

Number	Date	Country	Kind
1601753.5	Feb 2016	GB	national
1611217.9	Jun 2016	GB	national

CAST-IN TUNNEL GASKET AND JOINING METHOD

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