JP2004270256A - Sand removal method and sand removal device of reservoir - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove sand without a sand removal gate and remove sand extending over the whole of a reservoir. <P>SOLUTION: In this sand removal method, sediment 3 deposited in the reservoir 2 such as a dam lake is sucked by a sand removal pipe 7 and discharged. In the method, a sheet-like member 5 covering the deposited sediment 3 is laid along the surface 4 of the deposited sediment 3, and a suction port 11 of the sand removal pipe 7 is faced to the deposited sediment 3 from the back of the sheet-like member 5 to thereby suck and discharge the sand. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method and apparatus for discharging sand from a reservoir for discharging sediment deposited in a reservoir such as a dam lake.
[0002]
[Prior art]
In recent years, more than half of the medium-sized dams 782 dams with more than 1 million cubic meters of total water storage have been buried in sediment at a faster-than-expected rate, and more than half of the reservoirs are already buried with sediment. Reported by a provincial survey.
[0003]
Therefore, it is an important issue to discharge sediment from reservoirs such as dam lakes to restore the amount of water stored at the time of dam construction.
[0004]
Therefore, conventionally, various sand discharging methods as described below have been adopted.
[0005]
(A) Dredging method using a grab bucket This method is a method in which sediment (sediment) is grabbed by a grab bucket suspended from a barge, and the sediment is transported to another place by a sediment carrier or slurry transport. .
[0006]
(B) Dredging method using suction pipe In this method, the suction pipe is lowered from the barge or dedicated boat to the bottom of the water, the sediment is sucked by the suction pipe, and the sediment is transported to another place by a soil transport ship or slurry transport. Is the way.
[0007]
(C) Sand discharge method using a sand discharge gate In this method, a sand discharge pipe is installed in advance below a planned sedimentation surface of a dam embankment, and a sand discharge gate is provided on the sand discharge pipe, and sedimentation is performed. If the height of the sediment rises above the planned sedimentation level, a sand discharge gate is opened, and the sediment is discharged downstream through a sand discharge pipe together with the drainage water.
[0008]
(D) Bed-loading method This method lowers the water level of the reservoir to create a flow similar to a river in the reservoir, and uses the bed-loading action to remove the sand-discharge pipes that have been installed in the dam embankment in advance. It is a method of transporting sediment downstream through a sand discharge gate.
[0009]
However, the above-mentioned sand removal method has the following problems.
[0010]
In the dredging method using the grab bucket of (A), the sand is discharged while raising and lowering the grab bucket, so that the sand discharging efficiency is poor. In addition, since the sediment is directly grasped and lifted by the grab bucket, a large amount of turbid water is generated. There is a problem that it takes time and labor because it is necessary to dredge while moving the ship.
[0011]
In the dredging method using the suction pipe of (B), the sand can be continuously discharged. Therefore, although the efficiency is higher than the dredging method using the grab bucket of (A), the sediment is directly sucked by the suction pipe. When foreign matter such as driftwood is included, it is inevitable that the suction pipe sucks in the foreign matter, and therefore, there is a problem that the foreign matter is clogged in the suction pipe and the operation is interrupted. Further, in the case of direct suction by the suction pipe, the earth and sand can be sucked only in a narrow range, and dredging is performed while moving the barge like a grab bucket.
[0012]
In the sand discharging method using the sand discharging gate of (C), the sediment flowing into the sand discharging pipe is limited to the sediment near the sand discharging pipe, and there is a problem that sand cannot be discharged in a wide range of the reservoir. At the same time, there is a problem that foreign matter is clogged in the sand discharge pipe. Further, once the sand discharge gate is opened, adverse effects such as sediment biting into the gate may occur and the sand discharge gate may not be able to be closed.
[0013]
In the bedload discharge method of (D), it is necessary to flow the entire amount of water to create the same flow as the river in the reservoir, and the original water storage function of the dam is lost. There was a problem that could not be implemented unless the dam had recovered quickly.
[0014]
[Patent Document 1]
JP-A-8-13453
[Problems to be solved by the invention]
Among the above-mentioned methods (A) to (D), the present applicant pays attention to the sand discharging method using the sand discharging gate of (C), and is capable of discharging the sediment in a wider range, and furthermore, the clogging of foreign matters is prevented. A method of preventing sand from occurring is proposed (Japanese Patent Application No. 2002-062157).
[0016]
In the method of this prior application, the surface of the sediment around the sand discharge pipe is covered with a water-impermeable impervious material, and in that state the sand discharge gate provided on the sand discharge pipe is opened to allow the water to flow to the sand discharge pipe. In this way, the sediment is caused to flow together with the running water from a sand discharging pipe. In this sand removal method, the water pressure directly acts on the water-blocking member and presses down the sediment below it with water pressure, so that the sediment flowing into the sand discharge pipe has a relatively small particle size carried by the water flow toward the sand discharge pipe. Since it is earth and sand, the foreign matter having a large diameter cannot be moved by being pressed by the water shielding member, so that there is an excellent effect that the clogging due to the foreign matter can be solved and the sediment in the area covered by the water shielding member can be discharged.
[0017]
However, in the above-mentioned sand discharging method, the sand discharging pipe is buried in the sediment at the start of the sand discharging, so when the sand discharging gate is opened, the sediment layer in contact with the sand discharging pipe collapses due to its internal pressure, and the sand discharging pipe is extremely collapsed. The highly concentrated sediment flow flows down the sand drain. Therefore, since a very large pressure fluctuation is caused downstream thereof, there is a possibility that facilities such as a sand discharging pipe and a sand discharging gate may be damaged. There is also a problem that a dam without a sand drainage pipe cannot be used.
[0018]
Further, in this sand discharging method, since a sand discharging pipe and a sand discharging gate provided in advance on the dam embankment are used, there is no foreign matter being caught. There is still a risk that the gate will not close, leaving problems in practical implementation.
[0019]
Therefore, the present invention has been devised to solve the above-mentioned problem, and it is an improvement of the invention of the prior application, in which sand can be discharged without using a sand discharge gate, and moreover, the sand is discharged over the entire reservoir. It is an object of the present invention to provide a method and a device for discharging sand from a reservoir.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a sand discharging method of sucking and discharging sediment deposited in a reservoir such as a dam lake by a sand discharging pipe, wherein the surface of the deposited sediment is formed along the surface thereof. This is a sand discharging method for a reservoir in which a sheet-like member covering the sediment is laid, and the suction port of the sand discharging pipe is made to face the sediment from the back surface of the sheet-like member to suck and discharge the sand.
[0021]
According to the above method, a sheet-like member is laid so as to cover the surface of the sediment, and the suction port of the sand discharging pipe is made to face the sediment from the back surface of the sheet-like member so as to suck and discharge the sand. Therefore, a water flow can be created between the sheet-shaped member and the sediment, and the sediment can be effectively sucked from a wide range by the scavenging action. Further, since a sand discharge gate is not required, the present invention can be applied to a dam having no sand discharge gate, and there is no fear that the sand discharge pipe and the sand discharge gate are clogged.
[0022]
Then, the discharge port of the sand discharging pipe is disposed at a position lower than the water level of the reservoir by passing over the embankment of the reservoir, so that the sediment deposited on the back surface of the sheet-shaped member is sucked and discharged by a siphon phenomenon. The preferred method of sand removal from the reservoir is as follows.
[0023]
According to this, the siphon is economical because the water flow can be obtained with zero gravity.
[0024]
Also, the present invention provides a sand discharging device for sucking and discharging sediment deposited in a reservoir such as a dam lake by a sand discharging pipe, wherein the suction port of the sand discharging pipe is expanded radially outward from the suction port. This is a sand discharging device for a reservoir provided with a sheet-like member that covers the surface of the sediment, and configured to suck and discharge the sediment on the back surface of the sheet-like member.
[0025]
Further, it is preferable that a weight is attached to the periphery of the sheet-shaped member to prevent the sheet-shaped member from floating.
[0026]
The weight is preferably provided over the entire periphery of the sheet-like member, and is preferably deformed according to the surface shape of the sediment.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[0028]
As shown in FIG. 1, the reservoir 2 of the dam is formed by damming a river with a dam embankment (embankment) 14.
[0029]
Here, the sediment 3 deposited on the bottom of the reservoir 2 for dredging is the sediment flowing from the upstream, which has been dammed by the dam embankment 14 and accumulated for many years.
[0030]
The sediment 3 is made of sand having various particle diameters, and the sediment 3 contains foreign matter such as driftwood and boulders.
[0031]
When the sediment 3 is discharged, first, a sheet member 5 having a sufficient laying area is laid on the surface 4 of the sediment 3 to be dredged.
[0032]
The sheet-like member 5 is formed of a water-impermeable or water-impermeable cloth, resin, rubber, or the like, and has the flexibility to follow the surface 4 of the sediment 3 and the property of sinking without floating in water. I have. The sheet-like member 5 may be formed by providing a mesh-like reinforcing material on the cloth, resin, rubber, or the like.
[0033]
The shape of the sheet-like member 5 is circular or polygonal, and its diameter is formed to about 100 m in consideration of a range in which a water flow described later and a range in which the sediment 3 by the sheet-like member 5 is pressed down and sealed. However, those having a range of several tens to one hundred and several tens of meters can be used.
[0034]
The shape of the sheet-like member 5 is not limited to a circular or polygonal shape, but may be any shape such as an elliptical shape in which the distance from the center to each peripheral portion does not greatly differ.
[0035]
To lay the sheet-shaped member 5, specifically, first, the sheet-shaped member 5 is placed in a folded state on the barge 15 floating on the reservoir 2, and the target position of the water bottom is kept in the folded state. Submerge it and lay it out at the bottom of the water. Note that the sheet-like member 5 may be spread near the water surface and gradually sink in that state.
[0036]
A weight 9 is attached to the peripheral portion 8 of the sheet-shaped member 5 to prevent the sheet-shaped member 5 from rising due to a water flow or the like. The weight 9 is made of a ring-shaped and flexible material such as a chain provided along the entire periphery 8 of the sheet-shaped member 5, and is deformed according to the surface shape of the sediment 3 when laying. Then, the peripheral portion 8 of the sheet member 5 is preferably pressed against the sediment 3 with the weight 9 of its own weight.
[0037]
As an example of the weight 9, a ring-shaped chain has been described. However, the present invention is not limited to this, and the weight is attached at intervals along the peripheral edge 8 of the sheet member 5. May be configured.
[0038]
A sand discharging hole 6 is formed at the center of the sheet-shaped member 5, and a sand discharging pipe 7 has a suction port 11 passing through the sand discharging hole 6 of the sheet-shaped member 5 from a front surface portion of the sheet-shaped member 5 to a back surface portion. Is connected so as to face the sediment 3.
[0039]
The sand discharging pipe 7 is made of a flexible resin pipe, and its diameter is preferably large in consideration of sand discharging efficiency, but is preferably about 300 mm in consideration of workability. In addition, not only the resin pipe but also a part of steel pipe may be used as the sand discharging pipe 7.
[0040]
The connection of the sand discharging pipe 7 may be made before the sheet-like member 5 is laid, or may be connected after the sheet-like member 5 is laid. The connection between the sheet-like member 5 and the sand discharge pipe 7 is made by forming a flange 16 (see FIG. 5) at the tip of the sand discharge pipe 7 and attaching the flange 16 to the sand discharge hole 6 of the sheet-like member 5 in advance. A seat (not shown) is formed, and the flange 16 is installed above the receiving seat of the sheet-shaped member 5 and connected with bolts and nuts.
[0041]
The length of the sand discharge pipe 7 is the sum of the water depth of the reservoir 2, the distance from the water surface on the dredging position to the dam embankment 14, and the height from the upper surface of the dam embankment 14 to the water surface of the reservoir 2. It is formed sufficiently longer than the length (several hundreds of meters depending on the water depth of the reservoir), and therefore, predetermined lengths are sequentially connected to form the required length.
[0042]
The sand discharge pipe 7 is supported on a barge 15, and is laid so that the discharge port 12 from the barge 15 is located below the water level 17 of the reservoir 2 over the upper part of the dam embankment 14. A valve (not shown) is appropriately connected to the sand discharging pipe 7.
[0043]
If the height h from the water level 17 to the upper part of the dam embankment 14 is 10 m or more, sand discharge by a siphon method described later cannot be performed, and therefore, for example, a pump ( (Not shown), a sand discharge pipe 7 is connected, and the pump sucks and pumps the earth and sand.
[0044]
Conveniently, the barge 15 is provided with a delivery device that supports the sand discharge pipe 7 and sends the sand discharge pipe 7 downward.
[0045]
In the above-described embodiment, the description has been given of the example in which the number of the sand discharging pipes 7 is one. However, a plurality of sand discharging pipes 7 may be connected to the sheet member 5 to discharge the sand.
[0046]
Next, the operation of the present embodiment will be described.
[0047]
As described above, the sheet-like member 5 is laid on the surface 4 of the sediment 3 to be sand-deposited, the sand-exhaust pipe 7 is connected, and the sand-exhaust pipe 7 is passed over the dam bank 14 through the barge 15. And the outlet 12 is located below the water level 17 of the reservoir 2.
[0048]
At this time, the water is flowing into the sand discharge pipe 7 submerged in the reservoir 2 near the water surface, and in this state, a pump (not shown) is connected to the discharge port 12 for suction. Then, the water flows from the barge 15 into the sand discharge pipe 7 straddling the dam embankment 14 and flows. After the stored water once flows into the sand discharge pipe 7 as described above, the stored water is constantly drained from the sand discharge pipe 7 due to the siphon phenomenon even if the pump is removed.
[0049]
After the drainage by the siphon phenomenon is performed as described above, the stored water is constantly sucked from the suction port 11 of the sand discharge pipe 7, and thus, in the sediment 3 on the back surface of the sheet-like member 5, FIG. As shown in FIG. 5, a water flow is generated toward the suction port 11 (sand discharge hole 6). Since the sheet-like member 5 is formed of a water-impermeable material, the water-flow flows through the surface 4 and the inside of the sediment 3 on the back surface of the sheet-like member 5, and the water-and-water flows on the water-flow. The soil comes to the suction port 11 and the sand is discharged through the sand discharge pipe 7.
[0050]
Further, a water head pressure is applied to the front surface of the sheet member 5, and a negative pressure due to suction of the sand discharge pipe 7 is applied to the back surface of the sheet member 5. Therefore, a force for pressing the sheet-like member 5 downward acts by the head pressure and the negative pressure.
[0051]
Thereby, a depression 24 having a volume corresponding to the earth and sand discharged together with the water at the suction port 11 is formed as shown in FIG. The sheet-shaped member 5 is formed of a flexible material, and is deformed according to the shape of the depression 24. Thereby, a water flow as shown by an arrow in FIG. 5 is generated in the sediment 3 under the sheet member 5, particularly between the back surface of the sheet member 5 having a large suction action and the sediment 3. At the same time, the earth and sand is sucked into the sand discharging pipe 7 while moving to the center along the depression 24.
[0052]
Since the depression 24 is pressed down from above by the sheet-like member 5 and the back surface of the sheet-like member 5 is made to have a negative pressure, the sediment on the surface 4 of the depression 24 is always broken by the water flow. A gentle depression 24 is sufficiently smaller than the angle of repose of 3. The depression 24 is formed over substantially the entire sheet-shaped member 5 with the suction port 11 as a center, depending on the particle size of the sediment 3 discharged.
[0053]
Further, since the weight 9 is provided on the peripheral edge 8 of the sheet-shaped member 5, the peripheral edge 8 is pressed by the weight 9, and the sheet-shaped member 5 is turned up by the flow of water in the reservoir 2. It can be prevented from rising.
[0054]
During sand removal, as shown in FIG. 5, there is a foreign matter 25 having a large diameter such as driftwood or boulder in the sediment 3, and when the foreign matter 25 reaches the back surface of the sheet-like member 5 due to sand removal, the foreign matter 25 Since it is pressed down by the sheet-like member 5, unlike the earth and sand, it does not flow to the suction port 11 together with the water flow but descends as the depression 24 sinks. Therefore, the foreign matter 25 does not enter the sand discharging pipe 7 and clog the sand discharging pipe 7 or block the suction port 11.
[0055]
By laying the sheet member 5 in this manner, the depression 24 has a gentle inclination, and the water on the surface side of the depression 24 is prevented from flowing directly to the sand drainage pipe 7 by the sheet member 5. In addition, by causing a sweeping action of the earth and sand by the water flow formed on the back surface of the sheet-like member 5, and by pressing the depression 24 with the sheet-like member 5, the sweeping action of the earth and sand can be promoted. The sediment 3 can be discharged on average over the entire circumference of the sheet member 5.
[0056]
Therefore, the suction range of the sediment 3 from the sand discharge pipe 7 at the same position is widened. Thereby, the number of times of movement of the barge 15, the sand discharge pipe 7, and the sheet-like member 5 can be greatly reduced, and the sand discharge efficiency is improved.
[0057]
In the above-described embodiment, an example has been described in which drainage is performed by the sand discharge pipe 7 by the siphon phenomenon. However, when the water level of the reservoir 2 and the height difference h between the top of the dam embankment 14 are close to 10 m or more, the water flow by the siphon is Can not secure enough or can not use the siphon phenomenon. Therefore, in this case, a pump is connected to the sand discharging pipe 7 and sand is discharged by the driving force of the pump.
[0058]
Further, according to the above-described sand discharging method and the sand discharging device 1, it is possible to perform the sand discharging over the entire reservoir 2 by moving after performing the sand discharging for each part and discharging the sand to another position. it can.
[0059]
Here, a sand discharging test performed using the test device of FIG. 3 will be described.
[0060]
The test apparatus shown in FIG. 3 lays sand (sedimentary sand) 3 having a particle size of 0.3 mm to a thickness of 50 cm in a water tank 21 having a depth of 200 cm, and lays a sheet-like member 5 on the sand. A sand discharge pipe 7 having a diameter of 32 mm is connected to the sand discharge hole 6 to suck the sand 3 and water by a siphon method to discharge the sand. A φ16 mm flange 16 is attached to the suction port 11 of the sand discharge pipe 7. In the drawing, reference numeral 22 denotes a water supply pipe for supplying water to the water tank 21, and its tip is opened in a horizontal direction so as not to create a flow for digging the sand 3. The reason for supplying water here is to keep the water level in the water tank 21 substantially constant. In the drawing, 23 is a water receiving tank for storing the sucked sand 3 and water.
[0061]
FIG. 4 shows the state of sand removal by this test.
[0062]
In FIG. 4, a broken line indicates a hollow shape of the sand 3 when the sand is discharged only by the sand discharge pipe 7 without using the sheet-shaped member 5. This depression is in a state where the sand 3 is held at the angle of repose in water.
[0063]
According to the sand discharge test employing the method of discharging sand from the reservoir according to the present embodiment, a depression 24 is formed around the sand discharge pipe 7 in the sediment 3 along with the sand discharge. The inclination of 24 becomes much smaller and gentler than in the case where suction is performed only by the above-mentioned sand discharge pipe 7. This is because the sheet-like member 5 is laid on the surface 4 of the sediment 3 and the lower part of the sediment 3 is sucked together with the water through the sand discharging pipe 7 to obtain the above-described operation and effect. 3 proves that the sand is discharged efficiently.
[0064]
【The invention's effect】
In short, according to the present invention, an excellent effect such that sand can be discharged without using a sand discharge gate and sand can be discharged over the entire reservoir.
[Brief description of the drawings]
FIG. 1 is an overall sectional view showing a preferred embodiment of a sand discharging device for a reservoir according to the present invention.
FIG. 2 is a plan view showing a sheet-like member of a sand discharging device for a reservoir according to the present invention.
FIG. 3 is a configuration diagram showing a test apparatus for performing a sand discharging test using the sand discharging apparatus for a reservoir according to the present invention.
FIG. 4 is a cross-sectional view showing a state of sand discharge in a sand discharge test.
FIG. 5 is a cross-sectional view showing a state of sand discharge performed by using the sand discharge device of the reservoir according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sand discharging device 2 Reservoir 3 Sediment 4 Sediment 4 Surface 5 Sheet-shaped member 6 Sand discharging hole 7 Sand discharging pipe 8 Peripheral part 9 (of sheet-shaped member) Weight 11 Suction port 12 (of sand discharging pipe) Drainage outlet 14 (dam) Drainage body 15 Barge 17 Water level 24 (Reservoir)

Claims (5)

In a sand discharging method of sucking and discharging sediment deposited in a reservoir such as a dam lake by a sand discharging pipe, a sheet-like member that covers the deposited sediment is laid along the surface of the deposited sediment, A method for discharging sand from a reservoir, wherein the suction port of the sand discharging pipe is made to face the sediment from the back surface of the sheet-shaped member to suck and discharge the sand. The discharge port of the sand discharging pipe was disposed at a position lower than the water level of the reservoir by passing over the embankment of the reservoir, and the sediment deposited on the back surface of the sheet-shaped member was sucked and discharged by a siphon phenomenon. The method for discharging sand from a reservoir according to claim 1. In a sand discharging device for sucking and discharging sediment deposited in a reservoir such as a dam lake by a sand discharging pipe, the suction port of the sand discharging pipe is expanded radially outward to cover the surface of the sediment. A sand discharging device for a reservoir, wherein a sheet-shaped member is provided to suck and discharge sediment deposited on the back surface of the sheet-shaped member. 4. The sand discharging device for a reservoir according to claim 3, wherein a weight for preventing the sheet-shaped member from floating is attached to a peripheral portion of the sheet-shaped member. The sand discharging device for a reservoir according to claim 4, wherein the weight is provided over the entire periphery of the sheet-shaped member, and the weight is deformed according to the surface shape of the sediment.

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