JPH0359206B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an undulating weir made of a flexible membrane fabric, such as a rubberized fabric.

As shown in Fig. 1, a flexible membrane fabric undulating weir is constructed by attaching a flexible membrane fabric envelope (bag-like body) to at least the river bed in the direction across the river, and forming a weir body. A fluid such as air, water, or both is sent from an inlet/exhaust (water) pipe communicating with the enclosure to cause the enclosure to expand and stand up, or discharge fluid from the inside of the envelope to cause the enclosure to contract and fall down (for example, Japanese Patent Publication No. 11702/1973). Tokuko Akira
44-2371).

That is, in Fig. 1, 1 is a flexible membrane cloth, such as rubber-coated cloth, forming an envelope (bag-like body), 2 is a riverbed, that is, riverbed concrete, 3 is water or air, or water and air, and 4 is a drainage water. pipe or inlet/outlet pipe, 5 is upstream water,
A is the contact point with the riverbed concrete 2 on the upstream side of the rubberized cloth 1 (the joining method is, for example,
2371), B is that of the downstream side.

The design of the current rubber-coated undulating weir (hereinafter referred to as weir) is shown in Figure 1. In other words, the design is such that when the upstream water level rises and reaches the planned collapse water level, the downstream membrane will come into contact with the foundation, that is, the riverbed concrete. Furthermore, the weir is designed taking into consideration the stability and economic efficiency of the weir, considering the material strength against the tension acting on the sheath and the circumferential length (required amount) of the sheath. In this case, the relationship between the upstream water level and the rubberized fabric tension T is approximately expressed as [(ρh)+ρ(h+H)/2]×H=T(1+cosα).

Here, ρ is the specific gravity of water, H is the weir height, h is (upstream water level - weir height), and α is the rising angle of the weir membrane cloth at the contact point A.

For this reason, the ratio of membrane circumference to ground length x ₁ is approximately 10:2.
The rising angle of the membrane without upstream and downstream water levels is approximately 30 degrees. When the weir collapses, the collapse width _Y1 from the downstream contact point B is approximately 1.5 times the weir height.

This results in problems at sites where there are many mudflows.
In other words, if there is sediment accumulation on the downstream side in the expanded state (see Figure A), even if the weir collapses, the state shown in Figure B will not occur, and the rubberized cloth will rest on the sediment, reducing the cross-sectional area of the river to 100% during a flood. I can't take advantage of it. That is, as shown in FIG. 3, the accumulated earth and sand 6 under the rubberized cloth 1 remains.
Note that 7 in Figure 3 is the planned lodging water level.

The present invention has been developed in view of the above problems.

That is, in the present invention, as shown in FIG. 2, even when the upstream water level reaches the planned collapse water level at the point of contact with the riverbed on the downstream side of the flexible membrane fabric, the expanded membrane fabric It has a rising angle β (see Figure a). In this case, the relationship between the upstream water level and the tension T is approximately given by the following equation.

[(ρh)+ρ(h+H)/2]×H=T(cosα+cos
β) The difference from the conventional design is that, as can be seen from the equation, even at the same upstream water level and weir height, the tension T increases and a strong rubberized fabric is required.

In the present invention, by setting the rise angle β on the downstream side as described above, X ₁ <X ₂ and Y ₁ >Y ₂ are satisfied.

If there is no upstream or downstream water level, and the rising angle β of the membrane fabric at the downstream contact point B is approximately 60 to 150 degrees, then at the time of lodging, the lodging width Y ₂ from the downstream side contact B is at least greater than the height when the envelope expands and stands up. (When the rising angle β is 60 degrees, the lodging width Y ₂ is the weir height
When the rising angle β is 150 degrees, the lodging width Y ₂ is 0.18 times the weir height. ) As shown in Figure 4, even if there is sediment downstream, when the upstream reaches the overturned water level, water flows over the overturned weir membrane and the downstream sediment is easily flushed out, so that it does not impede the river flow.

In addition, such a semicircular weir has small fluctuations in weir height with respect to fluctuations in upstream and downstream water levels, and is more effective than conventional weirs in controlling water levels and as an estuary weir.

In other words, in the case of conventional weirs, as shown in Figure 6, (a) the design conditions are assumed to be zero downstream water depth. (See Figure a) As the downstream water depth increases, the weir height increases, and the overflow depth becomes small, meaning that the weir collapses at a small overflow rate. (See Figure b) In other words, the height of the weir rises and the weir frequently collapses at low overflow depths, making it no longer essential to the weir.

In addition, in severe cases, the river sometimes collapsed without being overflowed.

(b) When the design conditions are assumed to be a case where the downstream water depth is high. (See Figure c) When the downstream water depth becomes 0, the weir height becomes low and the overflow water depth increases, causing weir overflow vibration.
(See Figure d) In other words, the height of the weir decreases, resulting in a high overflow water depth, which causes overflow vibration of the weir body, which in severe cases can lead to destruction, making it unsuitable for estuary weirs where downstream water depth fluctuates. be.

Next, data will be shown to show that the nearly semicircular weir of the present invention has little variation in weir height with respect to fluctuations in upstream and downstream water levels.

FIG. 7 is a diagram showing the relationship between weir height fluctuation and weir shape in the air expansion type, where the horizontal axis represents the rising angle and the vertical axis represents the weir height/basic weir height. In addition, the above is based on the basic condition (upstream water level = weir height) and the upstream water depth is the basic weir height.
This is when the value changes by 1.2 times.

That is, in the conventional case (when the rising angle is smaller than 60 degrees), the variation in the weir height is large, and in the case of the present invention (when the rising angle is larger than 60 degrees), the variation in the weir height is small.

FIG. 8 is a diagram showing the relationship between downstream water depth and weir height in the air expansion type, with the horizontal axis representing downstream water depth/basic weir height and the vertical axis representing weir height/basic weir height.

That is, as the downstream water depth increases, the weir height also increases, and in the conventional case, the fluctuation in the weir height is large, but in the case of the present invention, the fluctuation in the weir height is small.

As described above, the present invention has problems that conventional weirs do not have, such as the fact that the downstream sediment is easily flushed during the overturning and does not impede the flow of the river, and the weir height has small fluctuations in response to fluctuations in upstream and downstream water levels. This pioneered a new field of use in controlling hot water levels and as estuary (tidal) weirs.

[Brief explanation of drawings]

Fig. 1 is a diagram of a conventional undulating weir made of a flexible membrane cut in the river flow direction, where Fig. a is erected, Fig. b is when it is collapsed, and Fig. 2 is a undulating weir made of a flexible membrane of the present invention. Diagrams cut in the direction of river flow: Figure a is upright, Figure b is collapsed, Figure 3 is an illustration of the undulating weir in Figure 1 with sedimentation, and Figure 4 is the undulating weir in Figure 2. FIG. 5, which is an explanatory diagram of the weir in the case where there is sedimentation, illustrates the weir when it is inflated and when it is collapsed, respectively, when there is no upstream or downstream water level. Figure 6 is a diagram (Figures b, d) for explaining the state of collapse when the downstream water depth varies depending on the design conditions (Figures a, c), and Figures 7 and 8 are diagrams for explaining the effects of the present invention. be. DESCRIPTION OF SYMBOLS 1...Flexible membrane fabric forming an envelope, 2...River bed concrete, 3...Water or air, or water and air, 4...Inlet/outlet pipe or inlet/outlet pipe, 5...Upstream water, 6... ...Soil accumulation, 7...Planned overturning water level, A...
...The contact point between 1 and 2 on the upstream side, B...The contact point between 1 and 2 on the downstream side, H...Weir height, h...Overflow water depth, hd...Downstream water depth, W...Upstream water depth, 8...
The state of the weir at the time of its collapse.

Claims (1)

[Claims] 1. Cross a river and fix a flexible membrane cloth to the river bed on the upstream and downstream sides to form an envelope, inject fluid into the interior of the envelope to make it erect, and also pump fluid from inside the envelope. In a weir that can be discharged and collapsed by contraction, the membrane is expanded even when the upstream water level reaches the planned collapse water level at the point of contact with the river bed on the downstream side of the flexible membrane fabric. The fabric is characterized by a rising angle, and when there is no upstream or downstream water level, the rising angle of the membrane fabric at the contact point between the upstream and downstream membranes and the foundation is 60° to 150°. An undulating weir made of flexible membrane characterized by: