GB2077825A

GB2077825A - Collapsible Rubber Dam

Info

Publication number: GB2077825A
Application number: GB8107060A
Authority: GB
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 1980-03-06
Filing date: 1981-03-06
Publication date: 1981-12-23
Also published as: IT1137416B; IT8120161A0; GB2077825B

Abstract

A collapsible rubber dam secured to a riverbed (15) and slope portions (16) of both riverbanks is inflated and deflated by supply and discharge of a fluid. A pipe for supply and discharge of fluid communicates with the inside of the rubber dam from the slope portion of at least one riverbank. Preferably, the pipe for supply and discharge of the fluid is located in a region (ABD) defined by the top end (A) of the rubber dam located in the slope portion, substantially the middle position (D) of the deflated width of the rubber dam at the toe of the slope portion, and a securing position (B) of the rubber dam at the toe of the slope portion.

Description

SPECIFICATION Collapsible Rubber Dam This invention relates to a collapsible rubber dam to be used for example as an intake dam for irrigation water, a tide embankment against storm surge, or a barrier for damming seawater near a mouth of a river.

As water-level regulating barriers for taking irrigation water or damming seawater at the mouth of a river, there have recently been developed water-level regulating dams composed of rubbery sheet material, or so-called collapsible rubber dams, which are inflated and deflated by direct supply of a fluid such as air or water and are easy to install and maintain.

Heretofore, the inflation and deflation of such a rubber dam have been performed by using a pipeline for the supply and discharge of the fluid as schematically shown in Figure 1 of the accompanying drawings, which is a schematic view of a conventional rubber dam. This pipeline comprises a horizontal pipe 2 laid in a riverbed and a plurality of conduits 3 communicating between the horizontal pipe 2 and a rubber dam 1. Moreover, a fluid pumping device inclusive of a pump and a discharge port, which is connected to the horizontal pipe 2, is usually arranged in an operating chamber stood on one of the riverbanks.

In the illustrated pipe-line, a fluid such as air is pumped into the inside of the rubber dam 1 through the horizontal pipe 2 and conduits 3 by means of a pump (not shown) to inflate the rubber dam. However, moisture contained in the air is condensed during the pumping and remains in the rubber dam and pipe to form a drain. In particular, when using the conventional pipe-line as shown in Figure 1, the drain remains in the horizontal pipe 2 laid in the riverbed. If it is intended to deflate the rubber dam by the discharge of the enclosed air, a valve V, is first opened to remove the drain from the horizontal pipe 2 and then a valve V2 is opened to discharge the enclosed air from the inside of the rubber dam. Therefore, the deflation operation of the rubber dam is troublesome and inefficient. Also, laying the pipe in the riverbed is complicated and takes a long time.

Further, when the rubber dam is automatically deflated (which is usually performed by the automatic opening of a float valve) in case of an emergency, for example if the water level in the river abnormally increases due to flooding, if the drain produced by condensation remains in the pipe-line, the enclosed air cannot be discharged from the rubber dam. Moreover, the drain may freeze and cause cracking of the pipe.

The present invention provides a collapsible rubber dam secured to a riverbed and to slope portions of both riverbanks at the upstream side of the river and being inflatable and deflatable by supply and discharge of a fluid, wherein an end of a pipe for supply and discharge of fluid communicates with the inside of the rubber dam from the said slope portion of at least one riverbank but not from the riverbed portion to which the rubber dam is secured.

In a preferred embodiment of the invention, the end of the pipe for supply and discharge of fluid is located in a region defined by the top end of the rubber dam located in the slope portion, substantially the middle position of the deflated width of the rubber dam at the toe of the slope portion, and a securing position of the rubber dam at the toe of the slope portion.

The pipe for supply and discharge of fluid preferably communicates with the inside of the rubber dam from the slope portions of both the riverbanks but not from the riverbed portion securing the rubber dam and above an acceptable height of the remaining drain in the rubber dam.

In order to achieve complete deflation of the rubber dam, the rubber dam is preferably provided at its inside with at least one protruding member having a rigidity endurable to water pressure and extending along the longitudinal direction of the rubber dam.

An elastic element capable of deforming in accordance with the inflating shape of the rubber dam is preferably located in at least one part of the rubber dam or the dam height at inflation of the rubber dam is preferably lowered at at least one position along the widthwise direction of the river, in order to shorten the complete deflating time of the rubber dam.

The invention will be further described, by way of example only, with reference to the accompanying drawings, wherein: Figures 2 and 3 are perspective views of embodiments of flexible plate bodies to be used as collapsible rubber dams according to the invention, respectively; Figures 4 and 5 are respectively a partial front view and a side view of one end portion of a collapsible rubber dam according to the invention; Figure 6 is a schematic left-half front view of a collapsible rubber dam according to the invention; Figures 7a, 8a, 9a and 1 0a are schematic sectional views taken along the lines VIl-VIl, VIlI-VIlI, IX-IX and X-X in Figure 6 in a direct flow state, respectively;; Figures 7b, 8b, 9b and 1 orb are schematic sectional views taken along the lines VIl-VIl, VIlI-VIlI, IX-IX and X-X in Figure 6 in a back flow state, respectively; Figures 11 and 12 are respectively a front view partly shown in section and a side view illustrating the fitted state of a pipe for the supply and discharge of a fluid to a collapsible rubber dam according to the invention; Figures 13 and 14 are schematic views illustrating other embodiments of the fitted stateof a pipe for the supply and discharge of a fluid to a collapsible rubber dam according to the invention at the slope portion of the riverbank, respectively;; Figure 1 5 is a schematic view of an embodiment of a pipe-line to be used in the invention; Figures 16 and 1 7 are schematic views of other embodiments of pipe-lines to be used in the invention, respectively; Figure 18 is a sectional view of a collapsible rubber dam according to the invention provided with a drain extracting pipe; Figure 1 9 is a perspective view of another embodiment of a flexible plate body to be used as a collapsible rubber dam according to the invention; Figure 20 is a schematic view of an embodiment of a pipe-line applicable to the collapsible rubber dam of Figure 19; Figure 21 is a sectional view illustrating the deflated state of the collapsible rubber dam of Figure 19;; Figure 22 is a schematic view illustrating the inlet port in a collapsible rubber dam according to the invention and a pipe-line used therefor; Figure 23 is a sectional view illustrating a collapsible rubber dam according to the invention provided with a continuous hollow body as a protruding member and secured to the riverbed; Figure 24 is a schematic front view illustrating the inflated state of the collapsible rubber dam of Figure 23; Figure 25 is a perspective view of another embodiment of a continuous hollow body to be used in the invention; Figures 26-28 are schematic views illustrating three manners of arranging a continuous hollow body in a collapsible rubber dam according to the invention, respectively;; Figure 29 is a schematic view illustrating the arrangement of a continuous hollow body inside a collapsible rubber dam in the slope portion of a riverbank; Figure 30 is a partly sectional view of an embodiment of a fitting means for a continuous hollow body; Figure 31 is a schematic view illustrating a collapsible rubber dam according to the invention provided with an elastic element and secured to the riverbed; Figure 32 is a schematic view illustrating the inflated state of the collapsible rubber dam of Figure 31; Figures 33 and 34 are schematic views illustrating the deflating state of the collapsible rubber dam of Figure 32 with lapse of time, respectively;; Figures 35 45 illustrate various embodiments of collapsible rubber dams according to the invention in which the dam height is lowered in at least one position along the widthwise direction of the river, the different embodiments being shown in Figure 35, Figures 36 and 37 (Figure 37 being a schematic transverse view taken along the line Z-Z in Figure 36), Figure 38, Figure 39, Figures 40 and 41 (Figure 41 illustrating a modified embodiment of Figure 40), Figure 42, Figures 43 and 44 (Figure 44 being a schematic sectional view illustrating the deflated state of the flexible plate body shown in Figure 43), and Figure 45, respectively; Figure 46 is a schematic view of an embodiment of the pipe-line for a collapsible rubber dam according to the invention; Figure 47 is a detailed illustration of the pipe- - line shown in Figure 46;; Figure 48 is an enlarged view of a lever float valve to be used with a collapsible rubber dam according to the invention; and Figures 49-52 are schematic views of other embodiments of pipe-lines for collapsible rubber dams according to the invention, respectively.

Like parts are designated by like numerals and like symbols throughout the drawings.

In Figures 2 and 3 are shown preferred embodiments of flexible plate bodies to be used as rubber dams in the invention. Each flexible plate body is composed of a rubbery elastic material and has at least one split portion formed at a predetermined position in the thickness direction of the body and along the lengthwise direction thereof. In Figure 2, a flexible plate body 10 is opened at its one widthwise end by a split portion 1 Oa. In Figure 3, a flexible plate body 10' is a hollow plate body containing a split portion 1 O'a. A reinforcing material 11 such as canvas or bias cut weave fabric is provided for the reinforcement of each of the flexible plate bodies.

The flexible plate bodies shown in Figures 2 and 3 are preferred embodiments; use may also be made of, for instance, a conventional bag-like body of rubbery sheet material, or a rubber dam body wherein the riverbed constitutes a part of an inflating chamber.

The flexible plate body 10 of Figure 2 is formed by joining two superimposed rubber sheets 12, 1 3 to each other at their one widthwise end along the whole lengthwise direction thereof.

The manufacture of the flexible plate body 10 may be carried out as follows. Two crude rubber sheets corresponding to the rubber sheets 12, 13 are superimposed one upon the other and placed on a heat surface plate of a moulding press. Then, an antitack member is interposed between the crude rubber sheets along the lengthwise direct n thereof to leave only the end portions of the sheets in contact. Thereafter, the crude rubber sheet assembly is pressed at the vulcanizing temperature of the crude rubber sheet to obtain the flexible plate body 10. In this case, a desirable reinforcing layer can be obtained by embedding for example canvas in the crude rubber sheet.

The thus obtained plate bodies 10 are suitable as collapsible rubber dams for rivers, streams and channels which have various different widths, because they can be manufactured in a desired length. Further, the gauge of the rubber sheets 12, 1 3 can be freely selected because the plate body is manufactured by the one-piece press molding of the crude rubber sheets.

The flexible plate body 10 is secured to a riverbed and riverbanks as follows with reference to Figures 4 and 5.

First, the open end portion of the flexible plate body 10 is positioned toward the upstream side of the river (in the drawings, the direction of stream is shown by an arrow F). Then, holes (not shown) pierced in the open end portion receive respective anchor bolts 1 8 previously embedded in a riverbed 1 5 and the slope portion 16 of a riverbank. Thereafter, the open end portion of the flexible plate body 10 is secured to the riverbed 1 5 and the riverbank through an elongate and perforated keep member 17 by means of nuts 19.

A pipe for supply and discharge of a fluid (hereinafter referred to as a fluid entrance pipe) communicates with the inside of the flexible plate body comprising the collapsible rubber dam body from a slope portion of at least one riverbank. The fluid entrance pipe is preferably located in a region of the rubber dam body always contacting the slope portion of the riverbank irrespective of the inflated and deflated states of the rubber dam and the direct and back flows of the river.

In the inflated state of the rubber dam 10 as shown in Fig. 6 the sectional shapes of various parts taken along lines VIl-VIl, VIlI-VIlI, IX-IX and X-X are shown in Figs 7a-1 Ob, wherein Figs. 7a, 8a, 9a and 1 0a represent the case of direct flow, Figs. 7b, 8b, 9b and 1 0b represent the case of back flow, and a dot-dash line Y represents a secured position of the rubber dam body to the riverbed and riverbank.

When the rubber dam body 10 is secured to the riverbed only at the upstream side of the river, if the back flow of the stream is produced by accident, the inflated portion of the rubber dam body located near the center of the width of the riverbed 1 5 falls from backward to forward as apparent from Figs. 1 0a and 1 0b. Further, as apparent from Figs. 7b, 8b and 9b, the back flow of the stream is apt to push up the rubber dam body at its secured position even in the vicinity of the boundary between the riverbed and the slope portion of the riverbank.

Fig. 5 also shows the contact state of the rubber dam body 10 with the slope portion 16 of the riverbank. In Fig. 5, character A represents the top end of the rubber dam body secured to the slope portion of the riverbank, character B a securing position of the rubber dam body at the toe of the slope portion, and character C another end of the rubber dam body opposite to the securing position B at the toe of the slope portvn in the deflated state of the rubber dam body. As apparent from Fig. 5, the contact area of the rubber dam body 10 with the slope portion 16 in the deflated state is a region AABC. Next, when the rubber dam body is inflated by the supply of fluid at the direct flow state, the contact area changes from the region bABC to a region AABD.

If back flow occurs, the contact area reduces somewhat to a shadowed region in the region HARD.

Therefore, the position of a point D at the toe of the slope portion is very significant in the contact area during the inflation of the rubber dam body.

As a result of various experiments, the inventors have found that when the distance BC isBC=l (I substantially corresponds to the width of the rubber dam body), the distance BD isBD-1l.

Thus, when the fluid entrance pipe is attached to the rubber dam body in such a manner that the attached portion of the fluid entrance pipe is located in a region from a line (AD) connecting the top end of the rubber dam body at the slope portion to the middle position of the rubber dam body in its widthwide direction at the toe of the slope portion toward the upstream side of the river, a forcible stress is hardly given to the attached portion of the pipe even in the case of the inflated and deflated states of the rubber dam body or the back flow state.

In Figs. 11 and 12 is shown an embodiment of the attachment of the fluid entrance pipe to the rubber dam body according to the invention. In these figures, numeral 20 is a fluid entrance pipe, one end of which communicates with supply equipment such as a blower and a discharge valve (not shown). The pipe 20 is disposed at substantially an upgrade so as not to leave the drain in the pipe. Moreover, the pipe 20 is somewhat bent near its port opening as shown in Fig. 11, but such a bending degree is insignificant even if the drain remains in the bent portion of the pipe because the drain may be pushed out into the inside of the rubber dam body during the pumping of the fluid. In any case, it can be said that the pipe 20 as shown in Fig. 11 is disposed at substantially an upgrade.

When the pipe 20 is attached to the rubber dam body at the slope portion of at least one riverbank, a portion of the rubber dam body contacting the slope portion 1 6 is first cut out at a position corresponding to the pipe 20 and anchor bolts 21 embedded in the slope portion and then one end of the pipe 20 is fixed to the rubber dam body through a washer 22 by means of nuts 23.

The port opening of the pipe 20 attached to the rubber dam body is, of course, positioned in the contact area as described above at the slope portion of the riverbank. Considering that the drain remains in the inside of the rubber dam body (particularly, the pipe is disposed only in the slope portion of the riverbank without laying in the riverbed), it is preferable that the port opening is positioned above an acceptable height of the remaining drain in the rubber dam (i.e. about 10% of the dam height at the inflated state).

In Figs. 13 and 14 are shown other embodiments of attaching the fluid entrance pipe to the rubber dam body at the slope portion of the riverbank, respectively. In these figures, broken lines indicate the position of the pipe at the slope portion and a shadowed region is a contact area of the rubber dam body with the slope portion at the inflated state. The region capable of attaching the pipe to the rubber dam is substantially trapezoidal in Fig. 13, and in this case the top end of the rubber dam body is considered to be an end at the downstream side. In Fig. 14, the position of the pipe is further shifted toward the upstream side.

According to the invention, the pipe for supply and discharge of the fluid (or fluid entrance pipe) communicates with the inside of the rubber dam body from the slope portion of at least one riverbank as mentioned above, so that it is not necessary to lay the pipe in the riverbed and hence the securing operation of the rubber dam body to the riverbed is simplified considerably.

Also, the drain remaining in the rubber dam body never flows into the pipe. Further, if it is intended to discharge the enclosed fluid from the inside of the rubber dam body, the drain extracting operation becomes unnecessary, and particularly the discharge of the enclosed fluid can be exactly worked even in an emergency such as flooding to achieve the complete deflation of the rubber dam.

Even if the drain remains in the inside of the rubber dam body according to the invention, it serves as a cushioning member for the rubber dam body at the deflated state, which mitigates damage of the rubber dam body due to collision with rolling stones.

Moreover, the drain can be discharged by a forced-drain means at such a stage that the quantity of the remaining drain reaches to a certain height.

When using a rubber dam body manufactured by the one-piece press molding as shown in Figs.

2 and 3, the advantages of not laying the pipe in the riverbed are developed effectively.

Preferably, when the fluid entrance pipe communicates with the rubber dam body from the slope portion of the riverbank, it is located in the contact area of the rubber dam body with the slope portion of the riverbank at the inflated state of the rubber dam, so that a forcible stress is not given to the portion of the rubber dam body surrounding the attached portion of the pipe even if a change of water level or back flow occurs, and consequently premature failure of the rubber dam body is prevented to considerably improve the durability of the rubber dam body. Moreover, the attachment of the pipe from only the slope portion of the riverbank without laying in the riverbed is particularly effective in elimination of stress concentration.

A fluid entrance pipe which communicates with the inside of the rubber dam body from both the riverbanks will be described with reference to Fig. 15.

Referring to Fig. 15, the fluid entrance pipes 20 communicate with the rubber dam body 10 from the slope portions 1 6 of both riverbanks. In this case, each port opening of the pipes 20 is located in the shadowed region AABD shown in Fig. 5 and above the acceptable height of the remaining drain in the rubber dam body. Therefore, no forcible stress is given to the connected portion between the pipe and the rubber dam body during the inflation of the rubber dam body or due to the change of water flow.

Furthermore, the pipes 20 communicate with a discharge valve 25 located upward at the riverbank. In the illustrated embodiment, one of the pipes 20 is connected to a horizontal pipe 26 laid in the riverbed 15 in order to perform the valve operation at only the side of the riverbank.

In any case, the pipe 20 can be considered to extend toward the discharge valve 25 at substantially an upgrade, so that the drain never remains in the pipe.

The inflation and deflation of the rubber dam body 10 using the pipe-line shown in Fig. 1 5 are performed as follows: The inflation of the rubber dam body is achieved by pumping a fluid such as air into the inside of the rubber dam body 10 by means of a supply equipment 27 such as a blower. When the.

pipe-line shown in Fig. 1 5 acts as a pipe for supply and discharge of the fluid, even if the drain remains somewhat in the horizontal pipe 26 during the pumping, such drain is pushed out from the horizontal pipe 26 into the inside of the rubber dam body by the pumped fluid, so that the fluid-supplying operation is not obstructed even when the drain remains in the horizontal pipe 26.

Moreover, in order to efficiently push out the drain from the horizontal pipe 26 into the inside of the rubber dam body during the pumping of the fluid, it is preferable to use pipe-lines as shown in Figs.

1 6 and 17. In Fig. 16, the diameter of the pipe 20' located on the side of the supply equipment 27 is made smaller than the diameter of the opposite pipe 20 to increase the pressure loss during the supply of the fluid, whereby the pressure in the horizontal pipe 26 is increased to push out the drain into the inside of the rubber dam body. In Fig. 1 7, a check valve 28 is arranged in the pipe 20 located on the side of the supply equipment 27, whereby the fluid is supplied into the inside of the rubber dam body 10 through the horizontal pipe 26 and the opposite pipe 20 during the pumping of the fluid, while the enclosed fluid is removed through both the pipes 20, 20' during the discharge of the fluid.In any case, when the actuation of the supply equipment 27 is stopped after the completion of the inflation, the drain never returns into the horizontal pipe. On the contrary, when using the conventional pipe-line as shown in Fig. 1, even if the drain remaining in the pipe 2 is pushed out into the inside of the rubber dam by pumping the fluid from the supply equipm,nt, the drain always returns into the pipe 2 through the conduits 3.

During the inflation, the enclosed fluid is condensed by the change of air temperature to produce a drain. Almost all the drain is produced by the condensation of the enclosed fluid in the rubber dam from the viewpoint of its volume.

According to the invention, the pipe is not opened in the riverbed portion, so that even if the drain is produced inside the rubber dam, it never flows into the pipe from the inside of the rubber dam.

On the contrary, in the conventional pipe-line as shown in Fig. 1, the drain produced inside the rubber dam always returns to the horizontal pipe 2 through the conduits 3.

The inflated rubber dam body is deflated as follows. In this case, it is possible to conduct suction of the enclosed fluid by the actuation of the blower, but the enclosed fluid is usually discharged into atmosphere by the opening of the discharge valve 25. That is, with the opening of the discharge valve 25 the rubber dam body 10 begins to deflate from approximately the central portion in its lengthwise direction in connection with the water flow, whereby the enclosed fluid is pushed away to the slope portions of both the riverbanks and smoothly discharged through the two pipes 20 and horizontal pipe 26 to the discharge valve 25 into atmosphere. On the contrary, in the conventional pipe-line of Fig. 1, the drain always remains in the horizontal pipe 2, so that the enclosed fluid cannot be discharged from the inside of the rubber dam until the drain is extracted completely.

In Fig. 1 8 is shown an embodiment wherein a drain extracting pipe 29 is arranged in the rubber dam body 10 in order to extract the drain remaining inside the rubber dam body 10. The drain extracting pipe 29 may be disposed in any position of the riverbed 15. Particularly, when using the rubber dam body manufactured by the one-piece press molding as previously mentioned, it is preferable that the drain extracting pipe 29 is located in the riverbed near the toe of the slope portion 16 (shown by point a in Fig.15) in view of the attaching operation.

As a modified embodiment of the flexible plate body as shown in Fig. 3, there is a flexible plate body 10' provided with an auxiliary inflatable chamber 14 having a diameter smaller than that of the main inflatable chamber (or split portion) 1 0'a in order to smoothly perform the discharge of the enclosed fluid as shown in Fig. 19. The flexible plate body 10' is secured at its solid flange portion 1 0'b to the riverbed portion and the slope portions of both the riverbanks in the same manner as mentioned above and then a pipe-line as shown in Fig. 20 is attached near the end portion of the flexible plate body 10' at the slope portion 1 6 of one riverbank.

That is, pipes 20, 30 for supply and discharge of fluid are airtightly connected to port openings 31, 32 for the main inflatable chamber 10'a and auxiliary inflatable chamber 14, respectively. In the illustrated embodiment, the fluid entrance pipe 20 serves as a pipe for supply and discharge of the fluid to the main inflatable chamber 1 0'a, but the pipe 20 may function for only the discharge of the fluid, if necessary, by using another pipe for only the supply of the fluid. In any case, each of the port openings 31 and 32 is located in the shadowed region bABD shown in Fig. 5 and above the acceptable height of the remaining drain.

In Fig. 20, the fluid entrance pipe 20 is connected at its one end to the port opening 31 located in the portion of the flexible plate body 1 0' secured to the slope portion 1 6 at the highest end of the inflation height. The other end of the pipe 20 is extended upward at substantially an upgrade and connected to a blower B through valves1 and b2. Further, between the blower B and the valve b2 is disposed a branch pipe 20' provided with a valve b3 and a discharge port 33.

A branch pipe 20" is connected at its one end to the pipe 20 between the valves b1 and b2 and the other end thereof is connected to the blower B through a valve b4. Furthermore, between the blower B and the valve b4 is disposed a branch pipe 20"' provided with a valve b5 and an intake port 34.

To the branch pipe 20" is connected an end of the fluid entrance pipe 30 for the auxiliary inflatable chamber 14 through a valve be.

Moreover, a branch pipe 35 is connected at its one end to the pipe 20 between the port opening 31 and the valve b, and the other closed end thereof is provided with a float valve 36. This float valve 36 interlocks with a float 38 present in a float chamber 37 arranged just beneath the valve 36 to open and close an opening 35' of the branch pipe 35. The float chamber 37 communicates with a water intake port 39 arranged above the flexible plate body on the upstream side (or downstream side as the case may be) at a position corresponding approximately to a critical water level in order to detect the critical water level upon rising of the river due to flooding.

That is, when water flows into the float chamber 37 through the water intake port 39 upon rising of the river, the float 38 rises with the increase of the water level to push up the float valve 36 upward, whereby the opening 35' of the branch pipe 35 is opened.

There will now be described the working cycle of the pipe-line shown in Fig. 20.

(1) Inflation of flexible plate body 10': First, the valves b3, b4 and be are closed, while the valves b1, b2 and b5 are opened. Then, air is drawn through the intake port 34 by the actuation of the blower B and thereafter pumped into the main inflatable chamber 1 0'a through the valves b5, b2 and1, the pipe 20 and the port opening 31 to inflate the flexible plate body 10'. After the main inflatable chamber 10'a is filled with air, the actuation of the blower B is stopped and the valves5, b2 and b1 are closed.

(2) Deflation of flexible plate body 1 0': (i) Deflation by forced-draining First, the valves b3, b1 and b4 are closed, while thevalvesb5, b2 and be are opened. Then, air is drawn through the intake port 34 by the actuation of the blower B and thereafter pumped into the auxiliary inflatable chamber 14 through the pipe 30 to protrude the chamber 14 on the inner wall of the main inflatable chamber 10'a. Next, the valves5, b2 and b6 are closed, while the valves b1, b4 and b3 are opened. By actuating the blower B, air filled in the main inflatable chamber 1 0'a is discharged from the discharge port 33 through the port opening 31, the pipe 20 and the valves b1, b4 and b3 into atmosphere, whereby the flexible plate body 10' begins to deflate.

Moreover, the auxiliary inflatable chamber 14 is previously inflated as described above, so that even if the flexible plate body 1 0' is deflated at any position, the auxiliary inflatable chamber 14 protrudes inside the main inflatable chamber 1 0'a to form continuous clearance parts 40 as shown in Fig. 21. Therefore, the opposed inner walls of the main inflatable chamber 1 0'a do not adhere to each other owing to the presence of the protruded auxiliary inflatable chamber 14.

Furthermore, the continuous clearance part 40 extends near the port opening 31 along the inflated auxiliary inflatable chamber 14 in the lengthwide direction thereof, so that air remaining in the main inflatable chamber 1 0'a moves to the port opening 31 through the continuous clearnace part 40 and is completely discharged through the above mentioned discharge line. As a result, there is prevented abnormal deflation of the flexible plate body 10' due to the influence of water pressure.

(ii) Automatic deflation by atmospheric discharge After the main and auxiliary inflatable chambers 10'a and 1 4 are previously inflated as mentioned above, all of the valves are closed, whereby the flexible plate body 10' is actually worked. If the flow rate of the stream in the river abnormally increases due to flooding, the increased water first flows into the float chamber 37 through the water intake port 39. As a result, the float 38 rises to push up the float valve 36, whereby air filled in the main inflatable chamber 1 0'a is smoothly discharged into atmosphere through the port opening 31, pipe 20, branch pipe 35 and opening 35'. In this case, the complete deflation can be expected by the action of the auxiliary inflatable chamber 14 as mentioned above.

By using the flexible plate body 10' as shown in Fig.19, complete deflation can be achieved, but it is necessary to perform the supply and discharge of the fluid for the auxiliary inflatable chamber 14, so that the pipe-line becomes complicated as shown in Fig. 20.

Therefore, a protruding member endurable to water pressure is extended inside the flexible plate body in its lengthwise direction over at least the riverbed portion instead of the auxiliary inflatable chamber, whereby not only the adhesion between the opposed inner walls of the main inflatable chamber is prevented in the deflation of the flexible plate body, but also the pipe-line for supply and discharge of the fluid can be simplified.

As the protruding member, use may be made of once having a rigidity endurable to water pressure and dead weight of the flexible plate body of any shape, examples of which include hollow bodies, solid bodies and chain bodies each made of rubber, synthetic resin or metal.

Such hollow and solid bodies can take any sectional shape such as a circle, rectangle or polygon.

The protruding member is arranged inside the flexible plate body in its lengthwise direction over at least the riverbed portion when securing the flexible plate body to the riverbed and slope portions of both the riverbanks. In this case, at least one row of the protruding member is extended in the lengthwise direction of the flexible plate body as a continuous body or a discontinuous body (block body). Particularly, it is preferable to extend the protruding member near the port opening for the fluid entrance pipe. If necessary, the protruding member may be adhered and fixed to the inner wall of the main inflatable chamber inside the flexible plate body.

When using a chain body such as a metal chain, a solid rod, a solid body prepared by filling a hollow portion of a flexible hose with a fluidizable material capable of solidifying at room temperature, or a plurality of discontinuous hollow bodies as the protruding member, if such a protruding member is extended inside the main inflatable chamber 1 0a of the flexible plate body 10 as shown in Fig. 2 along its lengthwise direction over approximately the widthwise region of the river, it is sufficient to use a pipe-line for supply and discharge of the fluid as shown in Fig.

22, wherein symbols B1 and B2 are valves, symbol E an ejector, symbol P an air compressor or pump, and numeral 41 a pipe for connecting a safety device S to the inside of the flexible plate body 10. Although the safety device S is not shown in detail, there may be used a device utilizing the water level difference, a device utilizing the mechanical elasticity of rubber or a spring. In the pipe-line of Fig. 22, the fluid entrance pipe for the auxiliary inflatable chamber can be omitted, so that this pipe-line is simplified as compared with the pipe-line shown in Fig. 20.

When the flexible plate body 10 is inflated by using the pipe-line of Fig. 22, the valve B1 is first opened, while the valve B2 is closed. Then, a fluid such as air or water is pumped into the inside of the flexible plate body 10 through the pipe 20 by the actuation of the air compressor or pump P. In this case, even if the internal pressure of the flexible plate body exceeds a proper pressure by mistakenly pumping the excessive amount of the fluid into the flexible plate body, the excessive internal pressure is released by the actuation of the safety device S because the internal pressure of the flexible plate body is exactly transmitted to the safety device S through the pipe 41. That is, breakage of the flexible plate body is prevented by the actuation of the safety device S.

In order to deflate the inflated flexible plate body as mentioned above, the enclosed fluid may be discharged into atmosphere only by opening the valve B2. Preferably, the valves B, and B2 are opened and the pump P is actuated, whereby the fluid filled in the main inflatable chamber is forcedly discharged from the valve B2 by the action of the ejector E. Thus, the inflated flexible plate body 10 begins to promptly deflate from that portion of the main inflatable chamber, unbalancing the relation between the internal pressure of the main inflatable chamber and the water pressure appiied externally.

When the port opening for the fluid entrance pipe is arranged only at one end of the flexible plate body as shown in Fig. 22, if the auxiliary inflatable chamber or the protruding member is not extended inside the flexible plate body as in the conventional rubber dam, there is a fear of causing abnormal deflation because when the middle portion of the flexible plate body begins to deflate, the opposed inner walls of the main inflatable chamber adhere to each other at that deflated portion and hence it is impossible to discharge the fluid in the space between the deflated portion and the other end containing no port opening.

On the other hand, according to the illustrated embodiment, even if the flexible plate body is deflated from any position, the presence of the protruding member extending inside the flexible plate body along its lengthwise direction over approximately the widthwise region of the river prevents the adhesion between the opposed inner walls of the main inflatable chamber to form substantially continuous clearance parts along the protruding member in its lengthwise direction upon deflation of the flexible plate body. As a result, the opposed inner walls of the main inflatable chamber are not closely adhered to each other by the water pressure. Furthermore, the fluid remaining inside the flexible plate body is moved along the clearance parts and discharged through the port opening into atmosphere, whereby the flexible plate body is deflated completely.

However, when a chain body or solid body is used as the protruding member, if the height of the remaining drain becomes higher than the height of the protruding member, the clearance parts extending along the protruding member are filled with the remaining drain during the deflation of the flexible plate body. As a result, it is difficult to smoothly discharge the enclosed fluid and there may be caused incomplete deflation of the flexible plate body.

In the preferred embodiment of the invention, therefore, at least one hollow body having a continuous hollow part in its lengthwise direction (hereinafter referred to as a continuous hollow body) is used as the protruding member, an end of which is opened upward inside the flexible plate body. Such a continuous hollow body can take any sectional shape such as a circle, rectangle or polygon as well as a body of 7-shaped section forming a hollow part together with the inner wall of the flexible plate body. Preferably, the continuous hollow body is made of a flexible material such as rubbery elastomer.

The continuous hollow body may be a wire braided hose 42 as shown in Figs. 23 and 24, but a composite pipe obtained by connecting flexible pipes of rubbery elastomer each extending along the slope portion of the riverbank to both ends of a metal pipe extending along the riverbed or a metal pipe assembly obtained by connecting metal pipes with a flexible pipe at a position near the toe of the slope portion may be used. Also, there may be used a hollow body 43 as shown in Fig. 25, wherein both the lengthwise sides are cut out into a semi-circular sectional shape. In the latter case, the area of the clearance part can further be increased in the lengthwise direction.

In the illustrated embodiment of Fig. 23, two continuous hollow bodies (wire braided hoses) 42 are extended side by side along the lengthwise direction of the flexible plate body 10, but at least one continuous hollow body (or protruding member) may be extended at any position inside the flexible plate body in accordance with the use circumstances of the river to be damned. In any case, it is important that at least one end of the continuous hollow body is opened upward inside the flexible plate body along the slope portion of the riverbank. The opening end of the continuous hollow body must be positioned above the acceptable height of the remaining drain because moisture contained in the fluid such as air to be supplied into the flexible plate body is condensed to form a drain remaining in the bottom of the flexible plate body.

When the wire braided hose 42 is attached as a protruding member to the flexible plate body (or rubber dam body) 10 shown in Fig. 2, the open end portion of the flexible plate body 10 is first positioned on the riverbed 1 5 and slope portions 1 6 of both the riverbanks toward the upstream side of the river. Then, the split portion 1 0a is opened from the open end portion and the wire braided hose 42 is disposed on the upper surface of the bottom side of the split portion 1 0a along the lengthwise direction of the flexible plate body 10. Thereafter, the wire braided hose 42 is fixed to the inner wall of the flexible plate body by an adhesive or a physical fitting means.In this case, a canvas such as rubberized canvas is wound around the hose 42 at proper positions and then fixed to the inner wall of the flexible plate body with an adhesive, but the fixing of the hose may be performed by using fixing members as shown in Figs. 26-28.

A fixing member 44 shown in Fig. 26a is a rubber block body. A plurality of fixing members 44 are fixed to the inner wall of the flexible plate body 10 at predetermined positions with an adhesive and then the hose 42 is fitted into a hollow part 44a of the fixing member 44 as shown in Fig. 26b. A fixing member shown in Fig.

27 is a hollow rubbery block body 45 provided at its one side with a solid flange portion 45a, through a hollow part 45b of which is passed the hose 42. This block body 45 is fixed at the solid flange portion 45a to the flexible plate body 10 by means of bolts or anchor bolts previously embedded in the riverbed and nuts. As a modified embodiment of Fig. 27, there is a hollow rubbery block body having no flange portion 45a, which may be fixed to the inner wall of the flexible plate body with an adhesive in the same manner as described in Fig. 26. A fixing member shown in Fig. 28 is a steel block body 46 of J-shaped section. Since this block body 46 itself is considerably heavier, the hose 42 is merely covered by the block body 46. Moreover, the block body 46 may also be fixed by means of bolts and nuts or an adhesive in the same manner as described above. In any case, these fixing members serve to prevent the floating off of the continuous hollow body when the drain remains in the inside of the flexible plate body. When using a heavy continuous hollow body such as metal pipe, there is not caused the moving or floating off of the continuous hollow body, so that the illustrated fixing members can be omitted.

Moreover, when a flexible pipe is extended as a part of the continuous hollow body along the slope portion of the riverbank, it is necessary to fix the flexible pipe at a proper position by means of any fixing member as shown in Figs. 26-28.

In the securing operation of the flexible plate body to the riverbed, if a riverbed portion constitutes a part of the main inflatable chamber of the rubber dam body, the continuous hollow body may be extended on a concrete surface of that riverbed portion.

Furthermore, the fixing of the continuous hollow body may be carried out locally at proper positions or over the whole length of the rubber dam body along its lengthwise direction.

Alternatively, only the end of the continuous hollow body may be fixed to the inner wall of the flexible plate body 10 by using a fixing canvas as shown in Fig. 29 or a fixing member 48 as shown in Fig. 30 and bolts and nuts.

As previously mentioned, at least one end of the continuous hollow body is opened upward from the riverbed along the slope porpon of the riverbank in the rubber dam body. The other end of the continuous hollow body is terminated near the port opening for the fluid entrance pipe 20 as shown in Fig. 24 or may be terminated upward over the port opening as shown in Fig. 29.

Alternatively, the other end of the continuous hollow body may be positioned outside the flexible plate body by passing through the fluid entrance pipe 20 or without passing through the fluid entrance pipe.

In the illustrated embodiments, a separate protruding member is extended in the inside of the flexible plate body 10 along its lengthwise direction, but the protruding member may be integrally formed in the one-piece press molding of the flexible plate body.

After the protruding member is arranged inside the flexible plate body as mentioned above, holes (not shown) pierced in the open end portion of the flexible plate body 10 receive respective anchor bolts 18 previously embedded in the riverbed 15.

Then, the open end portion of the flexible plate body 10 is airtightly secured to the riverbed 1 5 through an elongate and perforated keep member 1 7 by means of nuts 19. In the securing of the flexible plate body to the slope portion of the riverbank, the open end portion at both side ends of the flexible plate body is obliquely cut at a predetermined angle toward the downstream side of the river and then the thus cut open end portion is airtightly secured to each slope portion 1 6 of both riverbanks in the same manner as described above by means of anchor bolts 18, keep member 17 and nuts 19.

In the flexible plate body 10 secured to the riverbed and riverbanks is arranged the fluid entrance pipe 20 in the same manner as described in Figs. 11 and 12.

A dotdash line shown in Fig. 23 shows the inflated state of the flexible plate body 10 by supplying a fluid such as air or water through the fluid entrance pipe 20 (see Fig. 24). In this case, the rubber dam body is hardly subjected to damage by driftwood owing to the thicker gauge of the rubber sheets 12, 13 constituting the rubber dam body. Further, a joint portion 1 Ob of the plate body acts as a throat, so that vibration Qf the rubber dam body and hence fatigue phenomenon accompanied therewith are not caused. As a result, the rubber dam body develops a stable damming effect.

When the rubber dam body is changed from the inflated state shown by the dot-dash lines into the deflated state shown by solid lines in Fig. 23 by the discharge of the enclosed fluid, since the wire braided hose 42 endurable to water pressure and the dead weight of the rubber dam body is extended inside the rubber dam body along its lengthwise direction over its whole length, continuous clearance parts 40 are formed along the hose 42 in its lengthwise direction in addition to the hollow part of the hose 42.Therefore, even when the fluid entrance pipe is attached only to the slope portion of the riverbank, not only is the adhesion between the opposed inner walls of the flexible plate body prevented, but also the fluid filled in the portion of the flexible plate body near the slope portion of the opposite riverbank is rapidly discharged through the hollow part of the hose and the clearance parts extending along the hose. As a result, even if the rubber dam body begins to deflate from any position, the enclosed fluid never remains inside the rubber dam body in the course of the deflation, so that the rubber dam body always becomes flat in the complete deflated state as shown in Fig. 23.Moreover, when the riverbed portion securing the rubber dam body is cut out in accordance with the deflated shape of the rubber dam body as shown in Fig. 23, the upper surface of the rubber dam body is approximately equai to the surface of the riverbed, which serves to prevent damage of the rubber dam body without obstructing the water fiow.

As mentioned above, when the protruding member endurable to water pressure is extended inside the rubber dam body along its lengthwise direction over approximately its whole length, the adhesion between the opposed inner walls of the.

rubber dam body due to water pressure and the dead weight of the dam body is prevented in the deflation operation and also movement of the enclosed fluid is permitted by the continuous clearance parts extending along the protruding member in its lengthwise direction, so that complete deflation of the rubber dam body can always be expected without causing abnormal deflation. Further, the port opening for the fluid entrance pipe need be disposed only at one position in the slope portion of the riverbank without laying the pipe in the riverbed, so that the workability and the inflation and deflation operabilities are excellent.

Particularly, when using a continuous hollow body as the protruding member, even if the continuous clearance parts extending along the protruding member are filled with drain remaining in the inside of the rubber dam body, the enclosed fluid is smoothly discharged through the hollow part of the continuous hollow body because the end of the coninuous hollow body is opened upward above the acceptable height of the remaining drain on the slope portion of the riverbank. As a result, the complete deflation of the rubber dam body can always be achieved.

In the above illustrated embodiments, the deflation of the rubber dam body is performed by discharging the enclosed fluid into atmosphere by the opening of a valve or by forced-draining with a vacuum pump. In any case, the deflation of the rubber dam body results from pushing down by water pressure, so that the time required for the deflation of the rubber dam is fairly long.

In order to shorten the deflating time of the rubber dam body, according to one preferred embodiment of the invention an elastic member 50 as shown in Fig. 31 is arranged inside the rubber dam body.

That is, when the flexible plate body 10 is secured to the riverbed 15 as shown in Fig. 31, the open end portion of the flexible plate body 10 is first positioned on a riverbed 1 5 and slope portions 1 6 of both riverbanks toward the upstream side of the river. Then, an upper split portion 1 Oa of the flexible plate body 10 is opened upward and the elastic member 50 having a length equal to or slightly smaller than the deflated width of the flexible plate body is arranged on the upper surface of the lower split portion. In this case, the elastic member 50 is extended inside the flexible plate body at a suitable position in the widthwise direction of the river, but may be positioned over the whole width of the river, if necessary.

As the elastic element 50, use may be made of any shape having a restoring force without causing plastic deformation, and may be a metal, a spring steel, a plastic, a FRP, or a hard rubber.

A plate body of such material is preferably used, but a plurality of elastic elements having a circular section such as steel cord or piano wire may also be used side by side.

After the elastic element 50 as shown in Fig.

31 is arranged inside the flexible plate body and the split portion 1 0a is closed, the flexible plate body 10 is airtightly secured to the riverbed 1 5. In this case, holes (not shown) pierced in the open end portion of the flexible plate body and the end portion of the elastic element receive respective anchor bolts 1 8 previously embedded in the riverbed 1 5 and thereafter the securing is performed through a keep member 17 by means of nuts 19.

In the securing of the flexible plate body 10 to the slope portion 1 6 of the riverbank, the open end portion at both side ends of the flexible plate body is obliquely cut at a predetermined angle toward the downstream side of the river and then the thus cut open end portion is airtightly secured to the slope portion of the riverbank by using the anchor bolts, keep member and nuts in the same manner as described above.

In the flexible plate body 10 secured to the riverbed 1 5 and the slope portions 1 6 of both riverbanks, the fluid entrance pipe is arranged in the same manner as described in Figs. 11 and 12.

Figs. 32 and 33 show the inflated state of the flexible plate body 10 by the supply of a fluid such as air or water. In this case, the elastic element 50 deforms in compliance with the inflated shape of the flexible plate body. In such an inflated state, the rubber dam body is hardly subjected to damage by driftwood owing to the thicker gauge of the rubber sheets 1 2, 1 3 constituting the rubber dam body. Further, a joint portion 1 Ob between the rubber sheets 12, 13 of the plate body acts as a throat, so that vibration of the rubber dam body and hence fatigue phenomenon accompanied therewith are not caused. As a result, the rubber dam body develops a stable damming effect.

When the fluid filled in the main inflatable chamber 1 0a is discharged in the inflated state of Figs. 32 and 33, the rubber dam body 10 begins to deflate under the influence of water pressure.

In this case, the deflation is immediately started from the position of the elastic element 50 arranged inside the main inflatable chamber 10a by the restoring force of the elastic element, whereby the time required for the complete deflation is shortened considerably. Particularly, when the elastic member 50 is arranged near the slope portion of the riverbank opposite to the riverbank including the fluid entrance pipe 20 as shown in Fig. 33, the rubber dam body 10 begins to deflate from the position of the elastic element 50 arranged therein at an initial stage of discharging the enclosed fluid.As a result, the fluid filled in the main inflatable chamber 1 0a is gradually pushed away toward the fluid entrance pipe 20, whereby the rubber dam body 10 is successively deflated in a direction as shown by an arrow G in Fig. 34. Moreover, when the restoring force applied to the rubber dam body is successively changed in the lengthwise direction of the dam body, for instance, by sparsely arranging the elastic elements 50 toward the fluid entrance pipe 20, the deflation of the rubber dam body as shown in Fig. 34 is achieved more rapidly.

In any case, when the elastic element 50 is arranged at such a position as shown in Fig. 33, the clogging of the port opening for the fluid entrance pipe 20 is prevented in the deflation of the rubber dam body, so that the rubber dam body is completely deflated without causing abnormal deflation. Furthermore, laying work in the riverbed is unnecessary, so that the installation of the dam becomes easier.

In the illustrated embodiment, a single elastic plate is used as the elastic member 50, but instead a plurality of elastic battens of very narrow width or a plurality of elastic members of a circular section may be used.

Furthermore, the elastic member as shown in Fig. 31 is secured together with the open end portion of the flexible plate body to the riverbed by means of anchor bolts, but the elastic member 50 may be embedded in the rubber sheet 13 in the one-piece press molding of the flexible plate body 10. Alternatively, the elastic member 50 may be adhered to the upper surface of the lower split portion 1 0a or to the outer surface of the split portion facing the riverbed by vulcanization or with an adhesive.

Moreover, the elastic member has a size sufficient to produce an elastic force (or restoring force) upon deflation of the rubber dam body after it is positioned at least partly inside the main inflatable chamber and then deformed in accordance with the inflated state of the main inflatable chamber.

The elastic member may be located at any suitable position in the widthwise direction of the river. When the fluid entrance pipe is disposed on the slope portion of one riverbank as shown in Fig.

33, it is preferable that the elastic element is located near the slope portion of the opposite riverbank so as to lastly deflate the portion of the rubber dam body near the fluid entrance pipe.

When the elastic element is located near the slope portion of the riverbank, however, water flowing over the rubber dam body swirls at the downstream side at the beginning of the deflation, and as a result earth and sand are apt to be accumulated between the rubber dam body and the riverbed at the downstream side.

Considering this fact, it is most preferable that the elastic member is located at substantially the middle position of the rubber dam body in the widthwise direction of the river, whereby the accumulation of earth and sand is prevented at the downstream side and the adjustment of the dam height becomes easy. In any case, the continuous hollow body as shown in Fig. 23 is used in order to prevent abnormal deflation of the rubber dam body.

When the rubber dam body as shown in Fig. 2 is deflated by discharging the enclosed fluid without using an elastic member, the starting position for deflation is not constant, so that there may be caused the following problems.

(1) Since the starting position for deflation is uncertain it is required to lay a pipe for supply and discharge of a fluid in the riverbed securing the rubber dam body. As a result, the laying operation is complicated and takes a long time.

(2) When the rubber dam body is installed in a river apt to cause the accumulation of earth and sand, if the rubber dam body begins to deflate from a position near the slope portion of the riverbank, earth and sand are accumulated at the downstream side of that deflated portion. As a result, the rubber dam body is incompletely deflated even when continuing the discharge of the fluid, so that the function inherent to the rubber dam body or the free inflation-deflation operation is adversely affected.

Therefore, the dam height in the inflated state of the rubber dam body by the supply of fluid is lowered in at least one position along the widthwise direction of the river, which is always a starting position for deflation.

The position of lowering the dam height is properly determined in accordance with use conditions of the rubber dam body. For instance, it is desirable to set the stream lead of the river in the widthwise center thereof, which is achieved by lowering the dam height at the central portion of the rubber dam body in the widthwise direction of the river. Also, it is desirable that the port opening for the fluid entrance pipe is located on the slope portion of at least one riverbank but not the riverbed in view of the difficulty of laying in the riverbed. In the latter case, the dam height is lowered at a position near the slope portion of the opposite riverbank in order to smoothly perform the supply and discharge of the fluid.

Various embodiments for lowering the dam height in at least one position of the rubber dam body along the widthwise direction of the river will be described below.

In a first embodiment as shown in Fig. 35, the middle portion of the riverbed 1 5 in the widthwise direction of the river is previously dug down and thereafter the flexible plate body 10 is secured to the riverbed 15, whereby the middle portion 52 of the flexible plate body 10 is lowered as compared with the remainder of the flexible plate body.

In a second embodiment as shown in Fig. 36, the dam height is lowered by holding down the secured portion of the flexible plate body 10 to the riverbed 1 5 near the widthwise center of the river with a constraining member 54. Fig. 37 is a schematic transverse view taken along a line Z Z in Fig. 36. Moreover, as the constraining member 54, use may also be made of an elongate and perforated keep member used for securing the flexible plate body to the riverbed, provided that the width is increased only at the central portion ; the lengthwise direction.

Fig. 38 is a schematic transverse view of a third embodiment, wherein the dam heigth of the middle portion 52 in the widthwise direction of the river is lowered by pulling and constraining a.

part of the flexible plate body with a chain or rope 55 toward the downstream side of the river. In this case, the use of the flexible plate body 10, 10' as shown in Figs. 2 and 3 is preferable because the chain or rope is easily attached to the joint part 1 Ob of the flexible plate body and there is no problem relating to the leakage of the enclosed fluid as compared with the case of shaping the rubbery sheet material into a closed bag at the working site.

Fig. 39 is a schematic transverse view of a fourth embodiment, wherein the dam height of the middle portion 52 is lowered by disposing the constraining member 54 inside the flexible plate body 10 at the widthwise center of the river.

Moreover, the constraining member 54 is the same as used in Fig. 36.

In a fifth embodiment, the dam height of the middle portion 52 is lowered by the restoring force of the elastic member 50 arranged inside the flexible plate body 10 as shown in Fig. 31.

Thus, the use of the elastic member 50 is particularly preferable because it serves not only to lower the dam height, but also to shorten the deflation time.

Fig. 40 shows a sixth embodiment viewed from the upstream side, wherein the dam height of the middle portion 52 is lowered by protruding a part 53 of the open end portion of the flexible plate body 10 from the keep member 17 at the widthwise center of the river in the securing of the flexible plate body 10 to the riverbed 1 5 in such a manner that the peripheral length of the middle portion is shorter than that of the remainder.

Fig. 41 is a perspective view of a modified embodiment of Fig. 40, wherein a part of the joint portion 1 Ob (the middle portion 52 in the illustrated embodiment) is further extended toward the open end portion of the flexible plate body 10 so as to shorten the peripheral length of that part in the inflated state.

Fig. 42 is a schematic transverse view of a seventh embodiment, wherein a part of the flexible plate body 10 (the middle portion 52 in the illustrated embodiment) is constrained by extending a rope, belt or chain 55' over the rubber dam body and fixing both ends thereof at the upstream and downstream sides.

It makes possible to lower the dam height by attaching a weight to a part of the rubber dam body. In this case, however, it is necessary to use a considerably heavier weight. In an eighth embodiment as shown in Fig. 43, a clip fitting member 56 is used instead of a weight. That is, a part of the main inflatable chamber 1 0a is constrained over the joint portion 1 Ob with the clip fitting member 56 to shorten the peripheral length of the flexible plate body 10 at that constrained portion, whereby the dam height is lowered at the predetermined position. Fig. 44 is a schematic view illustrating the deflated state of the flexible plate body 10 shown in Fig. 43. The longer the constrained length of the main inflated chamber 1 Oa, the shorter the peripheral length of the flexible plate body 10 at that constrained portion.In the attachment of the clip fitting member 56 to the flexible plate body, the use of the flexible plate bodies 10, 10' as shown in Figs.

2 and 3 is preferable because the clip fitting member 56 can be secured to the joint portion 1 Ob by means of bolts and nuts as shown in Fig.

44 and there is no problem reiating to the leakage of the enclosed fluid as compared with the case of shaping the rubbery sheet material into a closed bag at the working site.

Fig. 45 is a ninth embodiment viewed from the downstream side, wherein the dam height is lowered near the slope portion of the riverbank in any one of the same manners as mentioned above. In this case, the complete deflation of the rubber dam body can be achieved only by disposing the fluid entrance pipe 20 at the slope portion of the opposite riverbank as shown in Fig.

45.

As described above, when the dam height in the inflated state of the rubber dam body is lowered in at least one position along the widthwise direction of the river, the inflated rubber dam body begins to deflate from that lowered position during the discharge of the enclosed fluid, so that the starting position for deflation is always determined. Furthermore, there are the following advantages.

(1) When the dam height is lowered in the middle portion of the rubber dam body in the widthwise direction of the river, the stream lead of the river always locates in the widthwise center thereof, so that the accumulation of earth and sand is not biased at the downstream side of the rubber dam body and also the adjustment of the dam height is easy. That is, the lowering of the dam height at the middle position in the widthwise direction of the river is favourable in view of hydraulics.

(2) When the dam height is lowered at a position near the slope portion of the riverbank, that position is a starting position for deflation, so that complicated laying work in the riverbed and the use of a protruding member are unnecessary and consequently the working operation is simplified.

Moreover, the position of lowering the dam height in the inflated state is not limited to the middle position in the widthwise direction of the river and the position near the slope portion of the riverbank as described above, but can be properly selected in accordance with the structure of the river or the construction of the riverbed.

When using the pipe-line for supply and discharge of the fluid as shown in Fig. 20, if the water level of the river abnormally rises due to flooding, flood damage can be prevented by opening the float valve 36 to deflate the rubber dam body 10'. However, the deflation of the rubber dam body 10' occurs rapidly, so that there is a risk of producing a step-wave at the downsteam side of the rubber dam body.

Furthermore, all the dammed water flows out toward the downstream side upon complete deflation, so that the reinflation of the rubber dam body for damming water takes a long time.

Therefore, a simple pipe-line as shown in Fig. 46 may be employed to automatically adjust the dam height of the rubber dam body, whereby rapid deflation of the rubber dam body can be prevented.

In Fig. 46, the rubber dam body 10 secured to the riverbed 1 5 and slope portions 1 6 of both the riverbanks by means of anchor bolts, keep member and nuts communicates with supply and discharge means (not shown) through the fluid entrance pipe 20. Numeral 60 is a bored portion in a house built on the riverbank and numeral 61 is a water conduit for connecting the bored portion to the river.

In Fig. 47 is shown in detail the pipe-line shown in Fig. 46. Inside the rubber dam body 10 are arranged two protruding members (or continuous hollow bodies as shown in Fig. 23), serving to uniformly and completely discharge the enclosed fluid, and a drain extracting pipe 29 (see Fig. 18) serving to discharge the remaining drain from the inside of the rubber dam body 10 to the riverbed at the downstream side.

The fluid entrance pipe 20 is connected to a supply means 66 and a discharge means 67 through a supply pipe 64 and a discharge pipe 65, respectively. The supply means 66 comprises a filter 66a, a blower 66b and a prime mover 66c driving the blower 66b, and is connected to the supply pipe 64 through a flexible pipe coupling 68. The discharge means 67 of the illustrated embodiment comprises a manual on-off valve 67a. In this figure, numerals 69 and 70 are a supply valve and a pressure gauge arranged in the supply pipe 64, respectively.

Further, a discharge pipe 71 having preferably a smaller diameter is branched from the fluid entrance pipe 20. A lever float valve 72 acting as a discharge valve is disposed in the middle portion or open end portion of the small discharge pipe 71. The lever float valve 72 is positioned in such a manner that the working water level of the valve 72 is a contemplated water level for the deflation of the rubber dam body.

As shown in Fig. 48, the lever float valve 72 comprises a float 72a, a lever 72c connecting the float 72a to a link mechanism 72b, a valve element 72f actuated by a mid-lever 72c pivoting with respect to a valve body 72d of the link mechanism 72b, and a seat packing 72g secured to the valve element 72f and closing or separating from a valve seat of the valve body 72d.

If the float 72a rises with the rise of water level over the contemplated water level for deflation, the valve element 72f also rises by the acutation of the link mechanism 72b, whereby the seat packing 72g is separated from the valve seat.

Conversely, when the water level drops from the contemplated water level, the seat packing 72g is closed to the valve seat by the descending of the float 72a.

In the lever float valve 72 of the above structure, when the float 72a and the lever 72c are made sufficiently light in weight in connection with a pressure receiving area of the seat packing 72g, the rise of the internal pressure in the rubber dam body can separate the seat packing 72g from the valve seat. In this case, therefore, the lever float valve 72 also acts as a safety valve.

In Fig. 47, numerals 73 and 74 are a check valve and a flexible pipe coupling disposed in the fluid entrance pipe 20, respectively.

The operation of the pipe-line shown in Fig. 47 will be described below.

In order to inflate the rubber dam body 10, the valve of the drain extracting pipe 29 and the manual on-off valve 67a are first closed, while a fluid such as air or water (air in the illustrated embodiment) is supplied into the inside of the rubber dam body 10 from the supply means 66 through the supply pipe 64 and fluid entrance pipe 20. In this case, the fluid entrance pipe 20 acts as a supply pipe. During the supplying of air, the internal pressure of the rubber dam body is monitored by the pressure gauge 70. When the pressure gauge 70 indicates a value corresponding to about the head pressure for the rubber dam, the operation of the supply means 66 is stopped.

The thus inflated rubber dam body dams a predetermined volume of water at its upstream side. If the water level dammed at the upstream side reaches a position L corresponding to the contemplated water level due to the increase of the flowing water, the lever float valve 72 is actuated as a discharge valve to discharge the fluid (air) filled in the rubber dam body from the small discharge pipe 71 into atmosphere. In this case, the fluid entrance pipe 20 acts as a discharge pipe.

The fluid filled in the rubber dam body is gradually discharged through the small discharge pipe 71 based on the actuation of the lever float valve 72, so that the discharge of the dammed water to the downstream side is very gentle and there is no fear of producing a step-wave at the downstream side.

When the water level drops below the contemplated water level by the discharge of the dammed water before the complete discharge of the fluid inside the rubber dam body, the small discharge pipe 71 is closed by the lever float valve 72. As a result, the damming of a particular volume by the rubber dam body is further continued. Therefore, it is very easy for the rubber dam body to be reinflated to the predetermined dam height by supply of the fluid, if necessary.

On the other hand, when the water level abruptly rises due to flooding, if the discharge of the enclosed fluid through the small discharge pipe 71 is not enough, the manual on-off valve 67a is further opened to discharge the enclosed fluid through the large discharge pipe 65. As a result, the rubber dam body 10 is deflated rapidly and corilpletely and hence all of the dammed water flows away toward the downstream side. In this case, the manual on-off valve 67a is opened after the dam height of the rubber dam body 10 is lowered to a certain extent by opening the lever float valve 72, whereby the occurrence of a stepwave can be avoided.

Fig. 49 shows a first modified embodiment of.

the pipe-line shown in Fig. 47, wherein a plurality of lever float valves are arranged at positions corresponding to different contemplated water levels and the discharge means is the same manual on-off valve 67a as used in the previous illustrated embodiment in order to rapidly deflate the rubber dam body in case of emergency.

As apparent from Fig. 49, three small discharge pipes 75a, 75b and 75c are branched from the fluid entrance pipe 20 and provided with respective lever float valves 76a, 76b and 76c, each of which having the same function as described in Fig. 48. Each of these lever float valves 76a, 76b and 76c is positioned so as to operate at different contemplated water levels.

According to the pipe-line of Fig. 49, when the water level rises to a first contemplated water level L3, only the lever float valve 76a is opened to conduct very slow discharge of the enclosed fluid.

As a result, the deflation of the rubber dam body occurs gently. Then, when the water level reaches a second contemplated water level L2, the lever float valves 76a and 76b are opened to advance the deflation of the rubber dam body at a relatively fast rate. If the water level rises to a third comtemplated water level L3, all of the three lever float valves 76a, 76b and 76c are opened to promote the deflation of the rubber dam body at a fairly fast rate. In other words, the higher the rising water level or the more the danger, the faster the deflation rate of the rubber dam body.

In this embodiment, the discharge of the enclosed fluid is performed through the small discharge pipes 75a, 75b and 75c by the successive opening of the lever float valves 76a, 76b and 76c, so that the occurrence of a stepwave due to rapid deflation of the rubber dam body can be prevented satisfactorily. Further, when any of the lever float valves is closed by dropping of water level, the deflation of the rubber dam body is stopped to dam a particular volume of water, so that reinflation of the rubber dam body to the predetermined dam height can easily be achieved in a shorter time.

In the illustrated embodiment of Fig. 49, the contemplated critical water level for deflation is selected at a position L, and the lever float valve 76c functions as a main discharge valve, so that the deflation of the rubber dam body is realized at slow but proper speed.

Fig. 50 is a second modified embodiment of the pipe-line shown in Fig. 47. In this case, the discharge means 67 comprises a main discharge valve 67b, a crank member 67c integrally united with a valve body of the main discharge valve 67b and giving a turning moment to the valve body, a lever 67d engageable with the crank member 67c for maintaining the crank member in a closed position of the valve body, a float 67e pivoting the lever 67d, and a spring 67f.

In the small discharge pipe 71 branched from the fluid entrance pipe 20 is arranged the same lever float valve 72 as described in Fig. 47. The lever float valve 72 is positioned in such a manner that the operating water level L4 is sufficiently lower than the operating water level of the float 67d or the contemplated water level for deflation L5, whereby rapid deflation of the rubber dam body is prevented.

In the illustrated embodiment of Fig. 50, when the water level at the upstream side reaches the position L4 due to the rising of water flow, the lever float valve 72 is opened to gradually discharge the fluid (air) filled in the rubber dam body 10 through the small discharge pipe 71 into atmosphere. As a result, the water level drops down below the position L4, during which the lever float valve 72 is closed to dam a particular volume of water. If the rising water level reaches the contemplated water level for deflation L5, the main discharge valve 67b is opened by buoyancy of the float 67e and spring action of the spring 67f in addition to the opening of the lever float valve 72, whereby the discharge of the enclosed fluid is also performed through the large discharge pipe 65.Therefore, the rubber dam body 10 is deflated rapidly and completely to discharge all the dammed water toward the downstream side.

In the pipe-line of Fig. 50, the difference between the positions L4 and L5 is so selected that the main discharge valve 67b is opened after the rubber dam body 10 is deflated to a certain extent by the opening of the lever float valve 72, whereby the occurrence of a step-wave can be avoided.

Fig. 51 shows a third modified embodiment of the pipe-line shown in Fig. 47, which aims at the automatic control of the dam height.

A fluid, particularly air, is mainly supplied from a blower 80 through the fluid entrance pipe 20 into the inside of the rubber dam body 10 extending between both the riverbanks. The internal pressure of the rubber dam body corresponds to about the head pressure for the predetermined dam height in the usual use state, so that it is not economical if microadjustment control of the internal pressure is performed by using a blower 80 of a large capacity. In the microadjustment control, therefore, air accumulated in a tank 81 by a compressor 82 is supplied into the inside of the rubber dam body through an auxiliary supply pipe 83. In the latter case, an on-off valve 84 disposed in the fluid entrance pipe 20 is closed.

The auxiliary supply pipe 83 branched from the pipe 20 is provided at its middle position with a reducing valve 85 for reducing the internal pressure of the tank 81 to a value corresponding to the predetermined internal pressure of the rubber dam body, and a lever float valve 86 acting on a position of a.float or water level. The lever float valve 86 has the same structure as described in Fig. 48 and comprises a float 86a and a closable control portion 86b interlocking with the float 86a to open and close the pipe 83. That is, the lever float valve 86 acts to close the pipe 83 if the water level rises above the predetermined value.

In the illustrated embodiment, a discharge pipe 87 is further branched from the fluid entrance pipe 20. The discharge pipe 87 is provided at its one end with a manual discharge valve 88, and there is branched a small discharge pipe 90 provided at its end or middle portion with a lever float valve 89. This lever float valve 89 has a structure opposite to the mechanism of the lever float valve 86. That is, the lever float valve 89 acts to open the pipe 90 with the rising of water level.

Moreover, when each of the auxiliary supply pipe 83 and small discharge pipe 90 is a flexible tube, the position of the lever float valves 86 and 89 can be changed easily and also the change of the contemplated water level for deflation is easy.

In addition, the manual discharge valve 88 can be replaced by an automatic control valve detecting the contemplated water level to deflate the rubber dam body automatically.

In the operation of the pipe-line shown in Fig.

51, the rubber dam body 10 is mainly inflated by the actuation of the blower 80 and the internal pressure thereof is adjusted by the air supply from the tank 81 to dam water in the riven During the usual water-level regulation, the inflated rubber dam body 10 always dams a constant volume of water.

If the dammed water level rises, however, it is necessary to drop the water level by lowering the dam height. In this case, the lever float valves 86 and 89 are simultaneously actuated at a predetermined water level. That is, the auxiliary supply pipe 83 is closed by the lever float valve 86 to cut off the communication between the tank 81 and the rubber dam body 10, while the small discharge pipe 90 is opened by the lever float valve 89 to communicate the rubber dam body 10 with atmosphere. Thus, the enclosed air is discharged through the discharge pipes 87 and 90 into atmosphere, whereby the dam height is gradually lowered to drop the dammed water level.

When the dammed water level is dropped to a certain value by the actuation of the lever float valves 86, 89, the pipe 83 is then opened by the valve 86, while the pipe 90 is closed by the valve 89. As a result, air sufficient to compensate for the reduced quantity of the internal pressure is supplied from the tank 81 to again inflate the rubber dam body 10 to the original dam height.

Moreover, when the operating water levels of the lever float valves 86 and 89 are different, i.e.

when the operating water level of the valve 86 is somewhat lower than that of the valve 89, there can be obtained a certain region of water level not performing the supply and discharge of air to the rubber dam body and hence the power of the compressor 82 for the microadjustment control can be reduced.

In the illustrated embodiment, the change of the dammed water level is based on the change of the dam height upon discharge of the enclosed fluid, so that it is preferable that the diameter of each of the pipes 83,90 is made sufficiently small in order to prevent excessive supply and discharge of fluid.

Fig. 52 shows a modified embodiment of the pipe-line shown in Fig. 51 using water as a fluid.

In this case, a water tank 91 is used instead of the tank and compressor, a pump 80a is used instead of the blower, and pipes 20a, 83a, 87a and 90a are used as supply and discharge pipes for water.

The inflation of the rubber dam body 10 is performed by the actuation of the pump 80a and the microadjustment control of the dam height is performed by the actuation of the lever float valve 86 communicating with the water tank 91. On the other hand, water is supplied to the tank 91 through a water service pipe 92. In the latter case, the water level in the water tank 91 is constantly maintained by the actuation of a lever float valve 93 permitting the supply of water to the tank 91 when dropping the water level below a predetermined position.

The pipe-line of Fig. 52 develops the same function as described in Fig. 51 for the adjustment of the dam height in accordance with the rise or fall of water.

In the embodiments of Figs. 51 and 52, when the rubber dam body 10 is completely deflated upon abrupt rising of water level, the on-off valve 84 and a valve disposed in the auxiliary pipe 83 or 83a (not shown) are closed, while the manual discharge valve 88 is opened to discharge the dammed water toward the downstream side.

The pipe-lines for supply and discharge of the fluid as illustjted above are simple in structure and can always maintain a constant dammed volume with reliable actuation. Particularly, when using a plurality of lever float valves, the inflated rubber dam body is deflated gently, so that not only is the occurrence of a step-wave prevented, but also adverse action upon a rubber dam body disposed at the downstream side can be removed. Further, the rubber dam body can dam a particular volume of water until the rising water level reaches a contemplated water level for deflation, so that reinflation to the predetermined dam height is easy and consequently the time, fluid supply amount, and consumed power required for the reinflation can be reduced considerably as compared with the prior art.

Claims

1. A collapsible rubber dam secured to a riverbed and to slope portions of both riverbanks at the upstream side of the river and being inflatable and deflatable by supply and discharge of a fluid, wherein an end of a pipe for supply and discharge of fluid communicates with the inside of the rubber dam from the said slope portion of at least one riverbank but not from the riverbed portion to which the rubber dam is secured.

2. A çollapsible rubber dam as claimed in claim 1 , wherein the said end of the pipe for supply and discharge of fluid is located in a region defined by the top end of the rubber dam located in the said slope portion, substantially the middle position Qf the deflated width of the rubber dam at the toe of the slope portion, and a securing position of the rubber dam at the said toe of the slope portion.

3. A collapsible rubber dam as claimed in claim 1 or 2, wherein the said pipe for supply and discharge of fluid communicates with the inside of the rubber dam from the said slope portions of both riverbanks but not from the said riverbed portion securing the rubber dam and above an acceptable height of the remaining drain in the rubber dam.

4. A collapsible rubber dam as claimed in any of claims 1 to 3, wherein the rubber dam is provided at its inside with at least one protruding member having a rigidity endurable to water pressure and extending along the longitudinal direction of the rubber dam.

5. A collapsible rubber dam as claimed in claim 4, wherein the said protruding member is a hollow body having a continuous hollow part in its lengthwise direction, which extends substantially over the whole length of the rubber dam and is open upward at its one end inside the rubber dam.

6. A collapsible rubber dam as claimed in any of claims 1 to 5, wherein the rubber dam is provided at its inside with an elastic member capable of deforming in accordance with the inflating shape of the rubber dam and located in at least one part of the rubber dam along its lengthwise direction.

7. A collapsible rubber dam as claimed in any of claims 1 to 5, wherein the dam height at inflation of the rubber dam is lowered at at least one position along the widthwise direction of the river.

8. A collapsible rubber dam secured to a riverbed portion and slope portions of both riverbanks only at an upstream side of a river and being inflatable and deflatable by supply and discharge of a fluid, wherein an end of a pipe for supply and discharge of fluid communicates with the inside of the rubber dam from the said slope portion of at least one riverbank except the said riverbed portion securing the rubber dam.

9. A collapsible rubber dam according to claim 1, substantially as herein described with reference to, and as shown in, any of the figures of the accompanying drawings.