EP0928850A2

EP0928850A2 - Drainage channels

Info

Publication number: EP0928850A2
Application number: EP98310210A
Authority: EP
Inventors: David William Monks
Original assignee: Hodkin & Jones (sheffield) Ltd
Current assignee: Hodkin & Jones (sheffield) Ltd
Priority date: 1998-01-09
Filing date: 1998-12-11
Publication date: 1999-07-14
Also published as: EP0928850A3; GB2333113B; GB2333113A; GB9800473D0

Abstract

A drainage channel section has an interior flow-confining surface including an elongate planar floor (12) having spaced parallel side edges. Two side walls (14) project outwardly from respective side edges of the floor (12) and each side wall is formed by an upper wall portion (15) and a lower wall portion (16). The lower wall portions (16) extend upwardly and outwardly from the floor (12) at an angle α. The width of the floor (12) may be between W / 1.5 and W / 2.5 where W is the width of the channel between the outer edges of the lower side wall portions (16). The height of these edges above the floor may be W 2 sinα where α is between 45° and 75°. This provides good flow capacity and sediment transportation. It also allows the sections to be free standing and to be stacked in pairs with one section of the pair inverted and the side wall of the inverted section located between the side walls of the other section.

Description

The invention relates to drainage channels.
Drainage channels are formed from drainage channel sections that are laid end-to-end to form a continuous conduit. They are used to drain surface water and may, for example, be located along the lateral edges of roads or across large open areas. The drainage channel is covered by a lid with water draining through the lid and then flowing along the channel.
In many cases, the water will contain suspended solids and it is important that the shape of the channel is such as to maximize the carriage of the suspended solids by the flowing water and minimize their deposit as sediment within the channels.
There are, however, other functional requirements on drainage channels and drainage channel sections. It is beneficial if drainage channel sections can stand in a stable upright position so that they do not have to be held upright while they are being laid end-to-end. It is also desirable that the drainage channel sections can be stacked compactly for transport so minimizing the amount of dead space during transport.
According to the invention, there is provided a drainage channel section including an interior flow-confining surface comprising an elongate planar floor having parallel spaced side edges and two spaced side walls, each side wall projecting upwardly from a respective side edge of the floor and being formed by an upper wall portion and a planar lower wall portion, each lower wall portion having spaced first and second side edges extending generally parallel to the plane of the floor with the first side edge joined to the associated side edge of the floor, each first wall portion being inclined away from the floor at an angle α with a width W between the second side edges of the lower wall portions, the width of the floor being between W/1.5 and W/2.5 and the height of each second side edge above the plane of the floor being W 2 sinα where α is between 45° and 75°.
It has been found that such a drainage channel section produces a flow which discourages the deposition of suspended solids in water carried by the drainage channel. Further, the provision of the planar floor requires the provision of a flat under surface on which the drainage channel section can stand during manufacture, transport and installation. Further, for transport, two such channels can be transported with one inverted and a side wall of the inverted section located between the side walls of the other section. This reduces significantly the volume occupied by the sections during transport and storage.
The following is a more detailed description of an embodiment of the invention, by way of example, reference being made to the accompanying drawings in which:-
Figure 1 is a perspective view of a drainage channel section, parts of the section being removed to reduce the length of the figure, and
Figure 2 is a section through the drainage channel section of Figure 1.
Referring first to Figure 1, the drainage channel section is formed, for example, from fibre reinforced concrete. The drainage channel section comprises a generally U-shaped shell 10 and three reinforcing ribs 11.
As best seen in Figure 2, the shell 10 includes an interior flow-confining surface comprising an elongate planar floor 12 having parallel spaced side edges 13. Two spaced side walls 14 project upwardly from respective side edges 13.
Each side wall 14 is formed by an upper wall portion 15 and a lower wall portion 16. Each lower wall portion 16 is planar and has first and second spaced side edges 17,18 extending generally parallel to the plane of the floor 12. The first side edge 17 of each lower wall portion 16 is continuous with an associated side edge 13 of the floor 12.
Each lower wall portion 16 is inclined away from the floor 12 at an angle α to the plane of the floor 12 which in the illustrated case is 60°. If the width between the second side edges 18 of the lower wall portion 16 is W, the width of the floor 12 and of each lower wall portion 16 is W / 2 and the height of the second side edges 18 above the plane of the floor 12 is W 2 sin60°.
It will be appreciated that these dimensions can be varied. The width of the floor 12 may be between W / 1.5 and W / 2.5 and the height of each second side edge 18 above the plane of the floor 12 may be between W 2 sin45° and W 2 sin75°.
The upper wall portions 15 lie in respective planes normal to the plane of the floor 12. The upper wall portions 15 are thus separated by a constant distance equal to W. Each upper wall portion 16 has an upper edge 19 defining an opening to the drainage channel. Each upper edge 19 is formed by an outwardly projecting flange 20 having an upper surface 21 lying in a plane parallel to the floor 12 and formed with a longitudinally extending groove 22.
As best seen in Figure 2, apart from at the flange 20, the thickness of the shell 10 is constant around its periphery and along its length. The shell 10 thus has an exterior floor 23, exterior lower wall portions 24 and exterior upper wall portions 25. These exterior parts 23,24,25 are dimensioned and shaped in correspondence with the associated interior portions 12,15,16.
The ribs 11 extend around the exterior of the shell 10. One rib 11a is located adjacent to, but not at, a first end of the shell, a second rib 11b is located intermediate the ends of the shell and the third rib 11c is located at a second end of the shell 10. The first rib 11a and the second rib 11b are identical and will be described together.
Each rib 11a,11b has side faces 26 that converge as they extend away from the shell 10 with the ends of the side faces being interconnected by an outer surface 27. Thus the ribs 11a,11b are thicker at the shell 10 than at their ends remote from the shell 10. As best seen in Figure 2, this outer surface 27 has first portions 27a that overlie respective upper wall portions 18 and are parallel to the upper wall portions 18. This is followed by lower portions 27b that extend downwardly from the level of the second side edges 18 and are angled inwardly. As seen in Figure 2, the angle made by these portions 27b to the plane of the floor 12 is greater than the angle made to the plane of the floor 12 by the associated lower wall portions 16 so that the width of the flange increases in this region. Finally, there is a base portion 27c lying in a plane generally parallel to the plane of the floor 12.
The third rib 11c is similar in many respects to the first and second ribs 11a,11b. Parts common to the third rib 11c, on the one hand, and to the first and second ribs 11a,11b, on the other hand, are given the same reference numerals and are not described in detail. The third rib 11c, as best seen in Figure 1, projects slightly beyond the associated end of the shelf 10. Rather than being angled, the side face 26a of the third rib 11c that is beyond the end of the shell 10 lies in a plane normal to the side edges 13 of the floor 12. There is thus formed between the end face 28 of the shell 10 and the interior edge 29 of the third rib 11c an L-shaped rebate. As will be immediately apparent, this is for accommodating the first end of a second drainage channel section so that the sections laid end-to-end can form a continuous channel.
Each rib 11a,11b,11c includes six holes 30 spaced around the rib 11a,11b,11c. Two holes 30 are adjacent respective upper edges 19 of the upper wall portions 15, two holes are adjacent respective second side edges 18 of the lower wall portion 16 and two holes 30 are adjacent the side edges 13 of the floor 12. Each hole 30 of each rib 11a,11b,11c is in register with a hole in each of the other ribs 11a,11b,11c along a line parallel to the plane of the floor 12. Thus, reinforcing bars (not shown) can be passed through a set of registering holes 30 for a purpose to be described below.
The holes 30 adjacent the side edges 13 of the floor 12 are of larger diameter than the remaining holes 30. These holes can be used to lift a drainage channel section by use of a mechanical lifting device (not shown).
Typical values of W may be between 0.15 metres and 0.6 metres. The upper edge 19 of the upper wall portions 15 may be spaced from the plane of the floor by a height H which is between 0.38 metres and 1.1 metres.
The drainage channel sections described above with reference to the drawings are produced by casting. A number of such drainage channel sections can be transported in pairs with one section of each pair being inverted and a side wall 14 of the inverted section inserted between the side walls 14 of the other section. This is made possible by the interior shape of the sections, as described above. This reduces significantly the volume occupied by such sections during transportation and storage.
In use, a plurality of sections of the kind described above with reference to the drawings are laid end-to-end in a suitably excavated trench. As described above, the first end of one section fits into the rebate at the second end of a succeeding section due to the arrangement of the third rib 11c. The sections are laid at a suitable gradient which, for example, may be 1:1000. Reinforcing rods are inserted through the sets of holes 30. The channels are closed by suitable lids of known kind which rest on the upper surfaces 21 of the flanges 20 and may be located by engaging in the grooves 22.
The installation may be as described in our GB-A-2229212. One form of lid suitable for use with the drainage channel sections described above with reference to the drawings is described in our UK Patent Application No.9621056. The presence of the floor 12 and the correspondingly shaped portion of the ribs 11, provide a flat surface on which the drainage channel section can stand when stored during transport and during installation. The drainage channel section thus has a stable upright position.
Once installed, water enters the drainage channel through holes in the lid (not shown). The water falls into the interior of the channel and then runs away along the channel due to the inclination of the drainage channel sections.
Where the water contains suspended solids, these will be conveyed along the channel by the flowing water. It has been shown that the shape of the lower wall portions 16 and the floor 12 as described above are particularly efficient in providing a water flow that tends to transport such suspended solids rather than allowing them to rest as sediment on the bottom of the channel. This is due to the fact that this shape generates high sheer stresses at the walls that prevent sedimentation.
Further, the drainage channel sections described above with reference to the drawings can accommodate high flow rates.
The mobilization of suspended solids is also assisted by water falling through the lid and into the channel. Since the upper side wall portions 15 are substantially vertical, they have little or no effect in preventing the conversion of the potential energy of the water into kinetic energy. Water reaching the lower wall portions 16 thus has maximum kinetic energy and this can provide a scouring effect to mobilize suspended solid matter for conveyance by the water. This mechanism has maximum effect when flow is subsiding during the falling limb of a storm.
It will be appreciated that there are a number of alterations that can be made to the drainage channel section described above with reference to the drawings. Alterations to the width W and the height of the second side edges 18 above the floor 12 have been discussed above. In addition, the side wall portion 16 need not be of the same length and inclined at the same angle; they could be of different lengths and inclined at different angles. The upper wall portions need not be parallel; they could converge or diverge slightly.
There need not be three ribs; there could be more or less ribs. The ribs need not be shaped as described above; they could have any suitable shape. The shell 10 need not be of constant thickness around the periphery; the thickness could vary.
The lid need not be formed separately from the shell; it could be formed with the shell 10 or fixed firmly to the shell 10 on manufacture.

Claims

A drainage channel section including an interior flow-confining surface comprising an elongate planar floor (12) having parallel spaced side edges (13), and two spaced side walls (14), each side wall (14) projecting upwardly from a respective side edge of the floor and being formed by an upper wall portion (15) and a planar lower wall portion (16), each lower wall portion (16) having spaced first and second side edges (17,18) extending generally parallel to the plane of the floor (12), with the first side (17) edge joined to the associated side edge of the floor (12), each lower wall portion (16) being inclined away from the floor (12) at an angle α to the plane of the floor (12) with a width W between the second side edge (18) of the lower wall portions (16), the width of the floor (12) being between W / 1.5 and W / 2.5 and the height of each second side edge (18) above the plane of the floor being W 2 sinα where α is between 45° and 75°.
A section according to claim 1 wherein the angles of inclination of the lower wall portions (16) are equal.
A section according to claim 2 wherein the width of the floor (12) is W / 2.
A section according to claim 2 or claim 3 wherein α is 60° and each lower wall portion (16) has a width W / 2 between the first and second side edges (17,18) thereof.
A section according to any one of claims 1 to 4 wherein the upper wall portions (15) lie in respective spaced planes normal to the plane of the floor (12), each upper wall portion (15) having an upper edge (19) defining an opening into the drainage channel with the upper edges (19) of the upper wall portions (15) spaced by the distance W.
A section according to any one of claims 1 to 5 wherein the upper wall portions (15) lie in respective planes normal to the plane of the floor (12), each upper wall portion (15) having an upper edge (19), each upper edge (19) being spaced from the plane of the floor (12) by a height H where H is between 0.38 metres and 1.1 metres.
A section according to any one of claims 1 to 6 wherein W is between 0.15 metres and 0.6 metres.
A section according to any one of claims 1 to 7 and having an exterior surface provided with at least one reinforcing rib (11), the rib (11) lying in a plane generally normal to the planes of the side walls (14) and the floor (12), and extending around the exterior surface of the drainage channel from an upper edge (19) of one side wall (14) to an upper edge (19) of the other side wall (14).
A section according to claim 8 wherein the or each rib (11) has an outer surface (27) remote from the exterior surface, the outer surface (27) having a base portion (27c) extending generally parallel to the plane of the floor (12), spaced upper portions (27a) extending generally parallel to the upper portions (18) of the side walls (14) and lower portions (27b) extending between respective upper portions (27a) and the base portion (27c), each lower portion (27b) being inclined away from the base portion (27c).
A section according to claim 9 wherein each lower portion (27c) of the or each rib is inclined at a lesser angle than the inclination of the associated lower wall portion (16) from the floor.
A section according to claim 10 wherein each portion of the or each rib (11) bounded by a lower portion (27b) of the rib outer surface and the base portion (27c) of the rib outer surface includes a lifting hole 30.
A section according to any one of claims 8 to 11 and provided with three ribs (11) spaced apart along the length of the channel.
A section according to claim 12 wherein each rib (11) includes a plurality of holes (30), each hole (30) of each rib (11) being in register with a hole (30) in each of the other ribs (11) along a line parallel to the plane of the floor (12), so that a reinforcing bar is insertable through a set of registering holes.
A section according to any one of claims 1 to 13 wherein each side wall (14) terminates in an upper edge (19), each upper edge (19) including an outwardly projecting flange (20) extending along the length of the upper edge (19).
A section according to any one of claims 1 to 15 and made of fibre-reinforced concrete.