WO2009144693A1

WO2009144693A1 - Construction of a tidal wall

Info

Publication number: WO2009144693A1
Application number: PCT/IE2009/000030
Authority: WO
Inventors: John Joseph Fleming
Original assignee: Biomedy Limited
Priority date: 2008-05-30
Filing date: 2009-05-28
Publication date: 2009-12-03
Also published as: GB0909188D0; GB2460342B; GB2460342A

Abstract

At least part of the length of a tidal enclosure wall (1) is formed by erecting parallel spaced-apart panels (2) upright in the sea bed (B), capped by cap beams (3). The panels are inter-linked by tie bars (5) extending across the wall and through the panels (2), and being secured by high strength couplers (8) on the outer surfaces of the panels (2). Infill (4) is retained between the panels (2). The wall (1) is topped by a compacted fill (6) and top soil (7), which is planted with a suitable vegetation of a variety for best environmental integration. Rock armour (10) is deposited on the outer sides of the panels (2), for additional wall support and preventing scouring. The panels (2) are of pre-cast reinforced concrete material, and have dimensions of 14m high x 6m long x 0.5m wide in this example. Some sections of the wall may include anchor bars (32) extending down through a panel and into the sea bed to provide an additional lateral restraint. The method of constructing a tidal wall is relatively fast because the panels can be erected with established jetting and excavation practices. It is particularly convenient if dredged material can be used for the infill. The wall can form a tidal enclosure when erected along a shore, thus providing for power generation without need to build a barrage across an estuary.

Description

"Construction of a Tidal Wall"

INTRODUCTION

Field of the Invention

The invention relates to tidal walls for applications such as generation of power from the tide.

Prior Art Discussion

WO2005/026535 describes a system for extracting tidal power from the tide by forming an enclosure. This document gives a background to approaches to construction of tidal barrages, particularly for the Severn estuary in Wales, UK, and proposes constructing a barrage by pile- driving support columns in the sea bed and using them to support panels placed one atop the other. Tongues and grooves along the panel edges are used to interlock them. It appears that this arrangement might lack sufficient structural strength for the forces which arise in this situation. It also appears that difficulties would remain arising from the unevenness of the sea bed.

US4034231 describes an apparatus comprising a V-shaped frame submerged near a beach with its apex pointed away from, the beach. It appears that this arrangement would generate only limited power because of its scale.

US4039847 describes a tidewater power plant in which turbines are moved vertically in response to changing water levels.

Also, in general much work has been done in developing turbines for generating electricity from water flow from dams on channels such as described in US6831373.

The invention is directed towards providing an improved method to construct a tidal wall for uses such as tidal power generation or flood defence. An object is that the wall be simpler to construct, and/or quicker to construct, and/or be more robust and long-lasting, and/or have less impact on the environment. SUMMAHY OF THE INVENTION

According to the invention, there is provided a method of constructing at least part of a tidal wall, the method comprising the steps of: erecting inter-linked panels on a sea, lake or river bed to form spaced-apart wall leaves, and in-filling material into the space between the leaves.

In one embodiment, lower ends of the panels are embedded in the bed, to a depth in the range of 2m to 6m.

In another embodiment, at least some panels are erected by jetting the bed as the panel is being placed to provide n elongate recess into which a panel fits.

In a further embodiment, the jetting is via tubes cast in the panels.

In one embodiment, the panels are of reinforced concrete.

In another embodiment, at least some panels extend for the full height of each leaf of the wall.

In a further embodiment, at least some of the panels are interconnected laterally by infill concrete in a gap between the panels.

In one embodiment, said panels have grooves along their side edges, said grooves mating to provide a void which is in-filled with concrete.

hi another embodiment, rock armour is deposited outside the panels on at least one external side.

hi a further embodiment, the infill between the leaves includes dredged material.

In one embodiment, at least some opposed panels are interconnected by tie bars extending laterally through the wall, including the panels.

In another embodiment, the tie bars are of double corrosion-protected high strength steel. In a further embodiment, the tie bars are connected to the panels by load-spreading plates on the external surfaces of the panels.

In one embodiment, at least some opposed panels are interconnected by concrete braces.

IQ another embodiment, the concrete braces are pre-cast.

In a further embodiment, the method comprises the further steps of forming a section of the length of the wall using caissons, said caissons providing integrated panels and transverse braces, and the space between the panels of the caissons is in-filled.

In one embodiment, at least one section of the wall is anchored additionally by anchor bars which extend through parts of the wall and into the seabed to act as lateral constraints.

In another embodiment, at least some of the anchor bars extend through the panels.

In a further embodiment, the method comprises placing concrete braces extending between the panels and at least some of the anchor bars extend through the braces.

In one embodiment, the method comprises the further steps of forming at least a section of the length of the wall using caissons, said caissons providing integrated panels and transverse braces, and the space between the panels of the caissons is in-filled; and wherein at lest some of the anchor bars extend through concrete stitching interconnecting the caissons.

In another embodiment, the anchor bars comprise a tube of a high strength material filled with a material such as concrete.

hi a further embodiment, the anchor bars further comprise an outer tube of high strength material, the space between the inner and outer tubes being filled with a material such as concrete.

In one embodiment, the width of the wall is in the range of 5m to 20m. In another embodiment, the panels have a thickness in the range of 0.3m to 1.0m.

In a further embodiment, a sustainable covering material is deposited on top of the infill material, and is planted with suitable vegetation.

In one embodiment, the wall is erected to form an enclosure between it and a shore.

In another embodiment, the wall is erected to form a tidal enclosure together with the shore.

In a further embodiment, the wall is erected to form a tidal enclosure along the shore of an estuary, without crossing the estuary.

In one embodiment, the wall is erected so that a shallow area adjoining the shore holds water at high tide.

In another embodiment, the wall further comprises a water inlet for filling the enclosure and a water outlet, and a power plant for power generation during inflow or outflow of water.

In another aspect, there is provided a tidal wall comprising: inter-linked panels on a sea, lake or river bed to form spaced-apart wall leaves, and in-filled material in the space between the leaves.

In another aspect, there is provided a tidal power plant comprising a tidal wall as defined above, a water inlet and a water outlet, and a power plant located in either or both of the inlet and outlet and adapted to generate power from flowing water.

DETAILED DESCRIPTION OF THE INVENTION

Brief Description of the Drawings The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which:-

Fig. 1 is a cross-sectional view through a tidal enclosure wall of the invention for use in tidal power generation;

Fig. 2 is a set of views showing a panel which forms part of the wall and details of tie bars and how they are connected in place;

Fig. 3 is a perspective view of part of the enclosure wall of Fig. 1, before deposit of in-fiU material;

Fig. 4 is a plan view of an alternative wall section, in which panels have embedded vertical anchor bars, Fig. 5 is a cross-sectional elevational view of this wall section, and

Fig. 6 is an end view of an anchor bar of the wall;

Figs. 7 to 10 are diagrammatic perspective, plan and cross-sectional views of an alternative wall section incorporating concrete braces for supporting the panels;

Figs. 11 to 14 are diagrammatic perspective, plan, and cross-sectional views of an alternative wall section, incorporating pre-cast box caissons which provide integral panels and concrete braces;

Figs. 15 and 16 are side views of parts of a tidal enclosure power plant and sluice gates respectively, incorporated in a wall of the invention; and

Fig. 17 is an aerial view of how a power plant incorporating the invention may be installed in the Severn estuary, the seaward side being to the left.

Description of the Embodiments

Referring to Figs. 1 to 3 at least part of the length of a tidal wall 1 is formed by erecting parallel spaced-apart panels 2 upright in the sea bed, capped by cap beams 3. The panels are inter-linked by anchor tie bars 5 extending across the wall and through the panels 2, and being secured by high strength couplers 8 on the outer surfaces of the panels 2.

Infill 4 is retained between the panels 2. The wall 1 is topped by a compacted fill 6 and top soil 7, which is planted with a suitable vegetation of a variety for best environmental integration. Rock armour 10 is deposited on the outer sides of the panels 2, for additional wall support and preventing scouring.

The panels 2 are of pre-cast reinforced concrete material, and have dimensions of 14m high x 6m long x 0.5m wide in this example. The lateral side edges of the panels 2 have grooves 15, which together form a cylindrical space 16 when the panels are abutted. The space 16 is filled with reinforced concrete.

The tie bars 5 are of double corrosion-protected high-strength steel material, 63.5mm in diameter. The spacing of the tie bars 5 is 3m x 3m, as viewed in elevation (see Fig. 2, elevation of panel).

The panels 2 are erected with approximately 4m depth into the sea bed (B), and they extend about 10m above the sea bed, to the high water level, MHWS. They are erected by jetting water and air to create a suitable trough as the panel is being lowered. The depth is chosen for each panel so that the tie bars will be approximately horizontal for maximum effectiveness in providing wall integrity.

It is envisaged that in other embodiments the panels may include cast-in tubes to allow jetting down through the panels, thus simplifying installation of the wall.

The infill 4 may be of locally dredged material, if possible from environmental and civil engineering perspectives. This has the particular advantage that it does not need to be transported, thus minimising cost, time, and energy. Alternatively, some or all of the infill may be transported to the site if it is not available in the immediate area. Such infill may comprise large stone at the base, followed by smaller grade stone. The anchoring of the panels in the sea bed, the infill, and the tensional strength of the tie bars 5 provide comprehensive strength for the wall 1. It is expected that the life span would be more than 60 years.

Referring to Figs 4 to 6 a wall section 30 has panels 31 with embedded vertical anchor bars 32. As shown particularly in Fig. 6 the anchor bars 32 have inner steel tubing 33 in-filled with concrete 34, an outer tube 35, and in-fill concrete 36 between the inner and outer tubes 33 and 35. The anchor bars 32 provide significant additional reinforcing for the panels and they also protrude downwardly into the sea bed for improved anchoring. The anchor bars 32 provide additional lateral shear restraints, increasing resistance of the wall section 30 to overturning and sliding.

Referring to Figs. 7 to 10 a section of a tidal wall 40 comprises panels 41 separated and supported by pre-cast concrete braces 42 at 6m spacings, and joined to the panels 41 at concrete stitches 43. The stitches are made by pouring concrete in situ into exposed reinforcing bars of the braces 42 and the panels 41. In addition, in this example there are vertical anchor bars 32 in the braces 42 to provide additional lateral shear restraints. The anchor bars 32 may or may not be used, depending on ground conditions.

Referring to Figs. 11 to 14 a wall section 60 comprises pre-cast concrete caissons 61 joined by concrete stitches 62. There are anchor bars 32 embedded in the stitches 62. In this embodiment the caissons 61 provide in an integrated manner both panels and transverse supports.

The full wall may be constructed with sections of different types described above according to sea bed and tidal conditions, thus optimising the wall for strength and cost. For example, the wall may have a section according to Figs. 11 to 14 adjacent a power plant or sluice gates, for better inter-connection. Also, where the sea bed material is too soft for a large depth at certain parts of the wall, the construction of Figs. 11 to 14 and/or of Figs. 7 to 10 maybe used. Also, panels with embedded anchor bars may be selectively used, according to conditions.

Fig. 15 shows part of a power plant incorporated in a wall to form a power plant. These are prefabricated modules 120 incorporating turbines 121 and abutted to adjoining sections of the wall. Other modules may incorporate sluice gates 140 such as rotary sluice gates shown in Fig. 16. As shown in Fig. 17, in one example, an enclosure or lagoon formed by a wall of the invention and the shore is about 25 km by about 4 km wide. Turbines and sluice gates are at the seaward end, and sluice gates only at the opposite end.

It will be appreciated that the method of constructing a tidal wall is relatively fast because the panels can be erected with established jetting and excavation practices and because infill is used to provide a lot of the bulk of the wall. It is particularly convenient if dredged material can be used for the infill. Also, much of the material and resilience of the enclosure comes from the infill, which is inexpensive and may be quickly deposited into the gap between the erected panels. The invention allows feasible construction of a tidal enclosure for a considerable distance of say 25km along a side of the Severn estuary, the shore forming one side of the enclosure. The weight of the infill, the panel penetration into the sea bed, and the tensional strength of the tie bars provide comprehensive dead load and passive pressure to retain some 800 million cubic meters of water for example.

The invention provides a sustainable solution to the problem of harnessing tidal power. A major advantage of the invention is that it provides for harnessing the potential of a huge volume of water without erecting a barrage across an estuary. This is very advantageous as a barrage typically needs to have to a huge height as the sea depth at the centre of some estuaries is very large. It also avoids the problem of blocking passage of shipping, and also the problem of the huge environmental impact of a barrage. In the invention the enclosure would for example occupy the space of a mud fiat, and operation of the plant would leave the mud flats intact for sea life and bird activity in a relatively undisturbed manner.

It is not essential that the tidal wall be part of a tidal power plant. It could alternatively be for flood protection or for part of harbour construction for example.

The invention is not limited to the embodiments described but may be varied in construction and detail. For example, the infill may include stone transported to the site. Also, the depth of sinking of the panels may be different, depending on civil engineering conditions.

Claims

1. A method of constructing at least part of a tidal wall (1), the method comprising the steps of: erecting inter-linked panels (2) on a sea, lake or river bed to form spaced-apart wall leaves, and in-filling material (4) into the space between the leaves.

2. A method as claimed in claim 1, wherein lower ends of the panels are embedded in the bed, to a depth in the range of 2m to 6m.

3. A method as claimed in claim 2, wherein at least some panels (2) are erected by jetting the bed as the panel is being placed to provide n elongate recess into which a panel fits.

4. A method as claimed in claim 3, wherein the jetting is via tubes cast in the panels.

5. A method as claimed in any of claims 1 to 4, wherein the panels (2) are of reinforced concrete.

6. A method as claimed in any preceding claim, wherein at least some panels (2) extend for the full height of each leaf of the wall.

7. A method as claimed in any preceding claim, wherein at least some of the panels (2) are interconnected laterally by infill concrete in a gap (16) between the panels.

8. A method as claimed in claim 7, wherein said panels have grooves (15) along their side edges, said grooves mating to provide a void which is in-filled with concrete.

9. A method as claimed in any preceding claim, wherein rock armour (10) is deposited outside the panels on at least one external side.

10. A method as claimed in any preceding claim, wherein the infill (4) between the leaves includes dredged material.

11. A method as claimed in any preceding claim, wherein at least some opposed panels (2) are interconnected by tie bars (5) extending laterally through the wall, including the panels (2).

12. A method as claimed in claim 11, wherein the tie bars (5) are of double corrosion- protected high strength steel.

13. A method as claimed in either of claims 11 or 12, wherein the tie bars (5) are connected to the panels (2) by load-spreading plates (8) on the external surfaces of the panels.

14. A method as claimed in any preceding claim, wherein at least some opposed panels (41) are interconnected by concrete braces (42).

15. A method as claimed in claim 14, wherein the concrete braces (42) are pre-cast.

16. A method as claimed in any preceding claim, comprising the further steps of forming a section of the length of the wall using caissons (61), said caissons providing integrated panels and transverse braces, and the space between the panels of the caissons is in-filled.

17. A method as claimed in any preceding claim, wherein at least one section of the wall is anchored additionally by anchor bars (32) which extend through parts of the wall and into the sea bed to act as lateral constraints.

18. A method as claimed in claim 17, wherein at least some of the anchor bars (32) extend through the panels (31).

19. A method as claimed in either of claims 17 or 18, comprising placing concrete braces (42) extending between the panels (41) and at least some of the anchor bars (32) extend through the braces (42).

20. A method as claimed in any of claims 17 to 19, comprising the further steps of forming at least a section of the length of the wall using caissons (61), said caissons providing integrated panels and transverse braces, and the space between the panels of the caissons is in-filled; and wherein at lest some of the anchor bars (32) extend through concrete stitching interconnecting the caissons.

21. A method as claimed in any of claims 17 to 20, wherein the anchor bars (32) comprise a tube (33) of a high strength material filled with a material (34) such as concrete.

22. A method as claimed in claim 21, wherein the anchor bars (32) further comprise an outer tube (35) of high strength material, the space between the inner and outer tubes being filled with a material (36) such as concrete.

23. A method as claimed in any preceding claim, wherein the width of the wall is in the range of 5m to 20m.

24. A method as claimed in any preceding claim, wherein the panels have a thickness in the range of 0.3m to 1.0m.

25. A method as claimed in any preceding claim, wherein a sustainable covering material (6, 7) is deposited on top of the infill material (4), and is planted with suitable vegetation.

26. A method as claimed in any preceding claim, wherein the wall is erected to form an enclosure between it and a shore.

27. A method as claimed in claim 26 wherein the wall is erected to form a tidal enclosure together with the shore.

28. A method as claimed in claim 27, wherein the wall is erected to form a tidal enclosure along the shore of an estuary, without crossing the estuary.

29. A method as claimed in claim 28, wherein the wall is erected so that a shallow area adjoining the shore holds water at high tide.

30. A method as claimed in any of claims 26 to 29 wherein the wall further comprises a water inlet (140) for filling the enclosure and a water outlet (140), and a power plant (120) for power generation during inflow or outflow of water.

31. A tidal wall comprising: inter-linked panels (2) on a sea, lake or river bed to form spaced-apart wall leaves, and in-filled material (4) in the space between the leaves.

32. A tidal wall as claimed in claim 32, wherein lower ends of the panels are embedded in the bed, to a depth in the range of 2m to 6m.

33. A tidal power plant comprising a tidal wall of claims 32 or 33, a water inlet and a water outlet, and a power plant located in either or both of the inlet and outlet and adapted to generate power from flowing water.