Mounting structure for a flexible membrane weir

Abstract: The mounting of an inflatable flexible membrane weir to the crest surface (1a) of a dam (1) extending between banks (2) of a body of water, the crest surface being of arcuate shape in cross-section, is enhanced without there being any need for provision of a pedestal adjacent to the dam and extending the entire width of the body of water by positioning at the respective intersections of crest surface (1a) and bank slope surfaces (2a) on the upstream side of the dam crest (1) of a fillet (3), which is a tetrahedrally shaped body having a curved surface lying on the dam crest, its remaining surfaces being flat and including a top surface (3a) extending between crest and bank and a surface intended to abut the respective bank slope surface (2a), both of which surfaces include a curved side which is common to the curved triangular surface. An upstream toe edge of slope (5a) of an inflatable flexible membrane weir (5) is secured along the upstream side of the crest surface (1a) and extends over the fillet and onto the bank slope surface (2a) to be secured thereto.

Description: This invention relates to a collapsible flexible membrane weir or dam capable of adjusting a water level and which is generally referred to herein as a "rubber weir", and more particularly to the mounting of such rubber weir on the crest of a dam structure extending across a body of water. One example of a heretofore known structure for mounting a rubber weir onto the crest of an existing dam structure is shown in Figure 6 of the accompanying drawings. The rubber weir is to be mounted on a dam crest 02 having a crest surface 02a of arcuate shape in cross section and which is disposed on a river bed, between banks 01 on the respective sides of the river (only one bank shown). Extending immediately adjacent the dam on its upstream side over its entire length, that is right across the width of a river bed, is a pedestal 04 having a flat horizontal top surface 04a extending from a top line t (dash-dot line) of the crest surface 02a. Placed on the top surface 04a of this pedestal 04 is a free end of a folded on itself rubber membrane 03 which is held by nuts (not shown) on anchor bolts 06 which extend into the dam crest 02 to achieve fixing of pedestal 04 to the dam crest 02. The nuts act on a metal clamping strip 05 disposed along the free end of the membrane so as to press the strip 05 onto the rubber membrane. Clamping in this manner takes place on the flat horizontal top surface 04a and, as a result of bending of the strip as shown, at the banks 01. The membrane is sealed at its upstream ends and its lateral margins. The membrane is to form an inflatable bladder as a result of the clamping and usually as a result of heat sealing together of the overlying marginal regions of the rubber membrane. At the banks the rubber may be cut obliquely to achieve a good fit when the weir is being installed. Since the upstream free ends of the rubber membrane 03 are secured to the horizontal top surface 04a of the pedestal 04, the mounting arrangement for the rubber membrane 03 is similar to that used if mounting the rubber membrane directly onto a flat river bed. Should the inflated rubber membrane 03 drop down when acting as a weir, either due to deflation of the bladder or as might occur when a low level of water exists behind it, it can drop without the toe of slope surface 03a of the membrane protruding excessively either on the top surface 04a of the pedestal 04 beyond clamping strip 05 or on the surface of slope 01a of the bank 01 beyond clamping strip 05. Hence, there exists an enhanced fit of rubber membrane 03 and smooth flow of river water over the weir can be achieved. The rubber membrane is not subject to excessive force at any time. However, since the configuration of the crest 02 is now effectively different over the entire length of the dam, i.e. over the width of the river bed, as a result of the provision of the pedestal 04, the coefficient of discharge may be lowered by about 10 %. In addition, since the pedestal 04 extends over the entire length of the dam, that is over the entire width of the river bed, the cost of construction of the dam will generally be high and the period of construction for the dam will generally be long. Another known structure for mounting a rubber weir onto the crest of a dam is shown in EP-A-0 379 327. It is an object of the present invention to provide mounting structure means for a collapsible flexible membrane weir whose use reduces the cost of mounting a such membrane weir onto banks and onto a crest disposed on a river bed between the banks. According to one aspect of the invention, there is provided, at, or for providing at, a location in a body of water at which an arcuate dam crest surface meets opposite banks of the body of water at respective lines of intersection therebetween, a pair of fillets each of which is a tetrahedrally shaped body having first, second and third flat triangular faces, and a fourth triangular face which is curved to match the curvature of the dam crest surface and has one edge positioned or to be positioned at the line of intersection between the dam crest surface and the respective bank, the first and second flat triangular faces each having one curved edge matched to the curvature of the dam crest surface and having a common straight edge and the second flat triangular face having an inclination to the fourth triangular face to enable it to abut the bank. This invention provides, in a second aspect, a flexible dam structure of variable height which comprises a dam spanning a body of water between a pair of banks and having a crest of arcuate cross-section, there being located on the upstream side of the dam at positions of intersection of the crest surface of the dam and the respective banks a fillet according to the first aspect of the invention, over which is positioned an inflatable flexible membrane weir which extends in a first edge region along the dam crest surface to which it is secured and in second and third edge regions over the slope surfaces of said banks to which it is secured, and including edge regions between the first edge region and the second and third edge regions respectively extending over the first triangular faces of the fillets. In a third aspect, the invention provides a method of providing an inflatable flexible membrane weir on the crest surface of a dam extending between opposite banks of a body of water, the crest surface having an arcuate cross-section, which comprises providing at the line of intersection between the dam crest surface and the slope surface of each bank a fillet according to the first aspect of the invention, positioning on the dam crest surface an inflatable flexible membrane weir formed from rubber sheet material folded over on itself to provide a sheet material open end position on the upstream side of the dam crest and extending over the fillets onto the slope surfaces of the banks and securing the inflatable flexible membrane weir to the dam crest and the respective bank slope surfaces at or adjacent three edges of the inflatable flexible membrane. Since the fillets are only present at the opposite ends of the dam, there is little lowering of the coefficient of discharge at the dam, the cost of construction as well as the period of construction can be reduced and the fitting of the membrane onto the crest surface and onto the surface of the slope of the bank is also improved. For a better understanding of the invention and to show how the same can be carried into effect, reference will now be made by way of example only to the accompanying drawings wherein; Figure 1 is a perspective view of a portion of a dam crest at a position at which it adjoins a river bank, and which is ready for the mounting of a collapsible rubber weir in accordance with this invention; Figure 2 is a like perspective view to that in Figure 1, now showing the disposition of a rubber weir which has been mounted onto the dam crest; Figure 3 is a plan view of the same rubber weir; Figure 4 is a side view, partly in section, of the same rubber weir; Figure 5 is a like view to that shown in Figure 4 of an alternative mounting structure from a rubber weir in accordance with an alternative embodiment of the present invention; Figure 6, to which reference has already been made herein, is a perspective view showing how a rubber weir has previously been mounted on a dam. Referring to Figures 1 to 4 of the drawings, the perspective view of Figure 1 shows the crest 1 of a dam which has been provided on a river bed and which extends across the river from a bank 2. The crest is shown before a rubber membrane to serve as a rubber weir is mounted thereon. The crest 1 has a crest surface 1a of arcuate cross-sectional shape and the bank 2 has an almost vertical slope 2a. Formed on the upstream side of the crest (on the left side in Figure 1 beyond top line t (dash-dot line) of the crest surface 1a is a fillet 3. This is disposed at the position at which crest 1 adjoins the bank 2. The fillet 3 has the shape of a trigonal pyramid, i.e. a tetrahedron-like shape having a curved surface at least where the fillet lies on the crest. In addition, in this particular embodiment, a second trigonal pyramid-shaped fillet 4 is disposed on the downstream side of top line t . In greater detail, fillet 3 has four surfaces consisting of a surface matched to slope 2a of the bank 2, a surface 1a matched to the surface of crest 1, a fillet upper surface 3a and an upstream side vertical surface. The upper surface 3a has one edge which is horizontal and intersects the end of top line t at the point at which the latter reaches the surface of slope 2a of the bank 2. The upper surface 3a then extends obliquely downwardly towards the crest surface 1a at an angle of inclination ϑ with respect to a horizontal plane. There is thus formed an inclined mounting surface for a metal clamping element 6 (see Figure 2) which can undergo transition thereover from the crest surface 1a to the vertical surface of slope 2a as is shown in Figure 2. A rubber membrane 5 is folded on itself and disposed on the crest surface 1a with an open free end directed in the upstream direction. This open free end is secured to a curved surface portion of the crest on the upstream side of the top line t of the crest surface 1a as well as being secured to the upper surface 3a of the fillet 3. The side portions of the folded rubber membrane 5 are secured to the surfaces of slopes 2a of the banks 2. The side portions themselves are generally thermally fused together to assist in forming a collapsible bladder structure from the rubber membrane. This seal is usually produced on site before fitting of the membrane. The metal clamping element 6 for pressing the superposed free ends of the rubber membrane against the surfaces on which they are disposed is laid along the curved surface portion of crest surface 1a on the upstream side thereof to extend parallel to the top line t . Opposite end portions of this metal clamping element 6 are bent upwardly from this position over the inclined upper surface 3 of the fillet 3. Where the metal clamping element 6 reaches the respective vertical face of slope 2a of a bank 2, it extends obliquely upwardly towards the downstream side of the dam. Disposed along the crest surface 1a, fillet upper surfaces 3a and the surfaces of slopes 2a are studded anchor bolts 7 (Figure 4), set at predetermined intervals. The bolts are positioned along lines at which the metal clamping element 6 is to be disposed and have protecting portions able to penetrate through the free end portion of the rubber membrane 5. The anchor bolts 7 also penetrate the metal clamping element 6, passing through preferably pre-formed appropriately sized openings therein. Nuts 8 threadedly engage the exposed head portions of the anchor bolts 7 whereby the free end of the rubber membrane 5 becomes fastened in place on application of the nuts 8 to the anchor bolts 7 (see Figure 4). Since the metal clamping element 6 which is laid on the crest surface 1a and extends therefrom to the vertical surface of slope 2a and acts for securing the free ends of the rubber membrane 5 can be readily bent and secured where it passes over the inclined upper surface 3a of the fillet 3, the toe of slope 5a of the rubber membrane also fits intimately to the crest surface 1a, fillet upper surfaces 3a and slope 2a surfaces. As illustrated, a second fillet 4 is also provided. Fillet 4 is located on the downstream side of the crest surface 1a. This fillet 4 supports the toe part of slope 5a of the membrane on the downstream side of the dam where it will be otherwise unsupported as a result of dropping of the inflated bladder formed from the folded-over membrane and thereby prevents the toe of slope 5a from flowing away from the crest surface 1a and the surfaces of slope 2a. As the fillets 3 are provided only at the positions at which there is transition to slope 2a, that is at the opposite ends of the crest surface, the configuration of the crest surface 1a will not be changed by these fillets 3 except at these end positions and the coefficient of discharge will hardly be lowered. Since most of the crest surface 1a remains unchanged and the metal clamping element 6 is secured along the existing crest surface, the cost of construction can be reduced and construction can be carried out in a reduced time period. As shown in Figure 5, the aforementioned arrangement can be modified. Thus, a groove 10 may be provided at the portion of the crest surface 1a at which metal clamping element 6 is laid. The metal clamping element 6 may then secure the free end of the rubber membrane 5 within the groove 10 as shown in Figure 5. As a result of this modification, overflow at the time the weir falls can be rendered smooth and stones being entrained in the river may be prevented from striking directly against the metal clamping element 6. Figure 5 shows the membrane in its inflated condition including a nipple 11 to which air supply is connected for inflating the membrane structure. While the slope surfaces 2a of the banks 2 are shown to be vertical in the above described embodiments, this will often not be the case. The mounting structure can then be modified to take account of this surface inclination.

Claims: A pair of fillets (3), provided at locations in a body of water at which an arcuate dam crest surface (1a) meets opposite bank(s) (2) at respective lines of intersection therebetween, each of said pair of fillets (3) is a tetrahedrally shaped body having first, second and third flat triangular faces and a fourth triangular face which is curved to match the curvature of the dam crest surface (1a) and has one edge positioned or to be positioned at the line of intersection between the dam crest surface (1a) and the respective bank (2), the first and second flat triangular faces each having one curved edge matched to the curvature of the dam crest surface and having a common straight edge and the second flat triangular face (3a) having an inclination to the fourth triangular face to enable it to abut the bank. A pair of fillets as claimed in Claim 1, each of which is cast onto the concrete dam crest (1a) or secured thereto so as to abut the respective bank (2). A pair of fillets as claimed in Claim 2, which is provided at said locations and wherein the banks (2) are constituted by preformed walls or pillars each having a vertical surface (2a) which is connected by the respective fillet to the crest surface. A pair of fillets as claimed in Claim 1 or 2, which is provided at said locations and wherein the banks (2) have bank surfaces inclined to the vertical, said first flat triangular face of each fillet being adapted to connect the surface of the respective bank to the crest surface (1a). A pair of fillets as claimed in any preceding claim, which is provided at said locations with said common straight edge of each fillet being horizontal and extending to the top line of the dam crest surface. A flexible dam structure of variable height which comprises a dam (1) spanning a body of water between a pair of banks (2) and having a crest of arcuate cross-section, there being located on the upstream side of the dam at positions of intersection of the crest surface (1a) of the dam (1) and the respective banks a fillet (3) according to any preceding claim, over which is positioned an inflatable flexible membrane weir (5) which extends in a first edge region along the dam crest surface (1a) to which it is secured and in second and third edge regions over the slope surface (2a) of said banks to which it is secured, and including edge regions between the first edge region and the second and third edge regions respectively extending over the first triangular faces of the fillets (3). A flexible dam structure as claimed in Claim 6, wherein a channel (10) is formed in the upper part of the dam crest surface (1a) running lengthwise thereof, and wherein the inflatable flexible membrane weir (5) is secured to the dam crest surface (1a) within the channel. A flexible dam structure as claimed in Claim 6 or 7, wherein securing of the inflatable flexible membrane weir (5) to the dam crest surface (1a) is effected by means of a clamping strip (6) running lengthwise thereof. A method of providing an inflatable flexible membrane weir (5) on the crest surface (1a) of a dam (1) extending between opposite banks (2) of a body of water, the crest surface having an arcuate cross-section, which comprises providing at the line of intersection between the dam crest surface (1a) and the slope surface (2a) of each bank (2) a fillet (3), as defined in any one of Claims 1 to 5, positioning on the dam crest surface an inflatable flexible membrane weir (5) formed from rubber sheet material folded over on itself to provide a sheet material open end position on the upstream side of the dam crest and extending over the fillets (3) onto the surfaces (2a) of the banks (2) and securing the inflatable flexible membrane weir (5) to the dam crest (1a) and the respective bank surfaces (2a) at or adjacent three edges of the inflatable flexible membrane. A method as claimed in Claim 9, wherein additional fillets (4) are positioned at the respective lines of intersection between the dam crest surface (1a) and the bank surfaces (2a) on the downstream side of the dam (1). A method as claimed in Claim 9 or 10, wherein securing of the free edge of the inflatable flexible membrane weir (5) to the dam crest surface (1a) takes place in a groove (10) extending lengthwise of the dam crest surface on the upstream side thereof. A method as claimed in any one of Claims 9 to 11, wherein securing of the inflatable flexible membrane weir (5) to dam crest surface (1a) and bank surfaces (2a) is effected by means of a clamping strip (6) extending lengthwise of the dam crest surface and held to dam crest surface (1a) and bank surfaces (2a) by means of fixing bolts (7) spaced at intervals therealong.

Inventors: FUJISAWA MASAO, SATO YOSHIHIRO, FUJISAWA, MASAO, SATO, YOSHIHIRO
Applicants: BRIDGESTONE CORP, BRIDGESTONE CORPORATION
Application year: 1992
Main classification: E02B7
IPC codes: E02B7