JP4601339B2 - 浚 渫 Method - Google Patents

Description

  The present invention relates to a dredging method for dredging sediments (sand, mud, sludge, etc.) deposited on the bottom of dam lakes, lakes, rivers, harbors, etc., and more specifically, when dredging sediments by suction. The present invention relates to a dredging method for removing sediment deposited on the bottom of the water while minimizing the diffusion of muddy water.

Since the original function of a reservoir such as a dam lake is impaired when the amount of stored water is reduced, it is necessary to periodically remove sediment from the bottom of the water by dredging. In addition, dredging is conducted in lakes, rivers, and seas for the purpose of removing water-contaminated soil and securing navigation routes by maintaining water depth.
Currently, the sediment at the bottom of the water is removed by suction using a pump or by scooping it up with a bucket attached to a crane ship or the like.
When the slurry (mixture of earth and sand) is sucked from the bottom of the water by a pump, the sucked slurry is separated into earth and sand and water. The sediment is separated by sedimentation, or the sediment and water are forcibly separated by a filter or cyclone method, and the separated water is returned to the original water source.

Here, the dredging method that removes earth and sand with a bucket can remove a large amount of earth and sand at one time, but the dredging device becomes large, and turbid water generated by the dredging work around the target water area. Contamination is a problem.
On the other hand, the method of sucking slurry from the bottom of the water with a pump and precipitating the sediment in the sedimentation basin requires a large space for the sedimentation basin, so a large space such as port reclamation is separated and partitioned from the water area. Therefore, the method is limited only when it can be set, and therefore this method cannot be used in a confined space, and there is also a risk of causing phytotoxicity due to the use of a sedimentation accelerator.

Therefore, in dam lakes and lakes where it is not possible to secure a vast space for setting a sedimentation basin, sediment and water are separated by a filter or cyclone method, and the separated water is returned to the original dam lake or lake. A reflux method is generally used. However, the separated water is turbid water containing earth and sand components, and if this is simply introduced into the original place, the turbidity spreads around the water area.
Therefore, in the “slag type mud recovery device” of Patent Document 1, a means for suppressing the diffusion of muddy water by guiding the separated muddy water to the bottom of the water and discharging it near the suction port is proposed. In the “saddle construction method and apparatus”, means has been proposed in which the earth and sand are spouted with a part of the separated water and the remaining water is spouted toward the suction port.
Japanese Patent Laid-Open No. 01-322030 JP 2002-266369 A

  However, although the devices / construction methods described in Patent Documents 1 and 2 have a certain effect, the circulating water (turbid water) is gradually warmed by kinetic energy or the like, and thus leaks without being sucked from the suction port. The turbid water convected, and the polluted water area eventually spread.

  For these reasons, in dam lakes and lakes, development of technology that can collect earth and sand and buried objects without requiring a large space for installing a sedimentation basin and causing almost no turbidity. Longed for.

  The present invention has been proposed in order to solve the above-mentioned problems, and in the narrow dam lakes and lakes where a sedimentation basin cannot be installed, the removal of earth and sand for the purpose of recovering the amount of stored water and improving the water quality, etc. The purpose is to provide a dredge method for carrying out the process with almost no turbidity.

In order to achieve the above object, the dredging method according to claim 1 is a dredging method for suppressing the diffusion of muddy water when dredging sediment deposited on the bottom of a dam lake, lake, river, harbor or the like. The slurry is sucked from the suction port of the suction pipe opened at the bottom of the water, the sucked slurry is separated into earth and sand and muddy water, the muddy water which is muddy water separated from the slurry is cooled, and the cooled muddy water is opened near the bottom of the water. The turbid component in muddy water is precipitated by slowly discharging from the outlet of the returned water pipe.

The dredging method according to claim 2 is characterized in that a discharge port of the return water pipe is disposed close to a suction port of the suction pipe, and a part of the cooled muddy water is circulated.

The dredging method according to claim 3 is characterized in that the cooling temperature of the muddy water is about 4 degrees Celsius.

The dredging method according to claim 4 , wherein the rake placed on the bottom of the water is operated at an extremely low speed so as to suppress the scattering of the earth and sand and is buried in the bottom of the earth and sand before the suction of the earth and sand from the suction port. It is characterized by scraping and removing objects.

The dredge method according to claim 5 , wherein the rake is vibrated, the buried object caught by the rake is finely vibrated in the vicinity of the bottom of the water, and the buried object is pulled up after shaking off the adhering earth and sand. It is characterized by that.

  According to the first aspect of the present invention, a method is adopted in which earth and sand are sucked together with water from the suction port of the bottom of the water, and the sucked earth and sand is separated from the water by a filter or a cyclone method. Even in narrow dam lakes and lakes that cannot be used, dredging can be carried out by separating sediment and water. In addition, by cooling water (turbid water) separated from the earth and sand to make the specific gravity of muddy water larger than the specific gravity of the water at the bottom, the cooled muddy water is slowly discharged from the outlet near the bottom of the water, so the muddy water is convected. It settles without forming a liquid layer at the bottom of the water, and turbid components in muddy water can be easily precipitated in a short time. This makes it possible to remove earth and sand with almost no turbidity in water.

According to invention of Claim 2, a part of cooled muddy water can be circulated by arrange | positioning the discharge port of muddy water close to the suction port of earth and sand. As a result, it is possible to minimize the diffusion of the muddy water that stagnates by forming a liquid layer on the bottom of the water, and to save energy required for cooling the muddy water.

According to the invention described in claim 3 , by cooling the temperature of the separated turbid water to about 4 degrees Celsius and maximizing the specific gravity of the turbid water, the turbid water settles to the bottom of the water quickly and reliably, and Sediment can be sucked in with minimal diffusion of muddy water.

According to the fourth aspect of the present invention, when removing the buried object that cannot be sucked from the suction port, such as a branch or a rock buried in the sediment at the bottom of the water before the dredging of the sand, the rake is used at a very low speed. By performing the scrubbing operation, it is possible to perform the pretreatment for soot by suction while minimizing the occurrence of turbidity caused by the removal of the buried material.

According to the invention described in claim 5, when pulling this by out off the implant, which is buried in the sea bed sediment by lake, adhering the implant hooked rake by fine vibration at the bottom of the water near By shaking off the earth and sand, it is possible to minimize the diffusion of earth and sand (turbidity) into the water when the buried object is lifted onto the water. In addition, since the turbidity at the time of shaking off occurs near the bottom of the water, it can settle in a short time.

The present invention is a dredging method for removing soil and sand for the purpose of recovering the amount of stored water and improving the water quality in a narrow dam lake or lake swamp that cannot mainly have a sedimentation basin. It is.
Since the flow of water is almost lost in dams, the inflowing water will be stored in the dam lake for a long time, and sediment will easily settle on the bottom of the lake. In particular, most of the fine-grained soil called the wash road accumulates on the bottom of the lake and gradually reduces the amount of water stored in the dam lake. Therefore, it is necessary to remove this periodically.
There are several methods for removing sediment such as sediment deposited on the bottom of the dam lake, such as a method of flowing the sediment from the bypass tunnel downstream by bypassing the dam lake during floods, or using the power of water during floods. There is also a method of flushing sediment accumulated in the river downstream.
However, the present invention adopts a suction method that can gradually dredge throughout the year, not only at the time of flooding, has no influence on the downstream, and can dredge the lake bottom uniformly and over a wide area. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view of a dam lake for explaining an embodiment of a dredging method according to the present invention. The bottom of the dam lake 2 where the soil has been prepared has relatively small sand and mud (sediment) that have been swept away from the upstream and deposited in the same thickness over a wide area. Is relatively flat. Also, all or a part of the buried object 6 such as a tree branch flowing from the upstream is buried in the sediment.

In addition to the engine 11 that generates thrust, the dredger 10 that floats on the surface of the lake sucks the sediment 4 at the bottom of the lake with water from the suction port (suction part) 12a of the suction pipe 12 that is opened at the bottom of the lake and opens it near the bottom of the lake. The suction pump 16 for discharging the water (turbid water 8) separated from the sediment from the outlet 14a of the return water pipe 14 and the centrifugal separation for separating the slurry sucked from the lake bottom into the soil 4 and water (turbid water 8). The separator 18, the cooler 22 for cooling the muddy water separated from the earth and sand, the winding device 28 for winding the wire rope 26 to which the rake 24 is attached, and the centrifugal separator 18 are discharged. An earth and sand tray 32 for receiving the earth and sand 4 from which the moisture to be separated is received, a winch 36 for winding the wire 34 supporting the dredger 10 and the like are provided.
The suction pump 16, the centrifugal separator 18, the cooler 22 (when a compressor is used), the winding device 28, and the winch 36 are configured to be driven using the power of the engine of the dredger 10. Downsizing and downsizing.

  The dredger 10 is connected to one of a plurality of support posts 38 provided at appropriate intervals on the lake shore by a wire 34. The length of the wire is adjusted by a winch 36, and a support post for connecting the dredger is provided. It can be anchored at a desired position on the lake surface by appropriate selection. The wire 34 is for preventing the ship from being pulled and moved by the rake when the rake 24 scrapes the buried object 6 in the earth and sand.

The rake 24 attached to the wire rope 26 of the winding device 28 has a substantially L-shaped comb shape as shown in FIG. 2, and the length of the second wire 34 attached to the teeth at both ends is set. By adjusting from the top of the dredger, the inclination angle of the wire rope 26 can be freely changed. Further, the length of the second wire 34 can be changed in a very small range, whereby the inclination angle of the rake 24 can be changed in a short period to finely vibrate the rake.

The suction pipe 12 and the return water pipe 14 that can be adjusted to extend from the dredger 10 to the bottom of the lake are supported by swingable swing arms 42 that extend obliquely upward from the rear of the dredger 10 and are connected in parallel to form a bottom of the lake. It is hung up to. The suction pipe 12 and the return water pipe 14 are branched in the vicinity of their tips (FIG. 1).
At the tip of the suction pipe 12, a suction part 12 a that is disposed on the bottom of the lake and sucks earth and sand is attached. A suction part suitable for the property of the earth and sand 4 to be sucked is selected. That is, the opening (suction port) itself of the suction tube 12 can be used as the suction part, but when sucking sandy sand 4 having a relatively low viscosity, the side as shown in FIG. It is preferable to use a suction part for sucking earth and sand from above, as shown in FIG.
On the other hand, the return water pipe 14 branched from the suction pipe 12 is (1) in order to reduce the flow velocity of the turbid water 8, the discharge outlet 14 a at the tip thereof is enlarged in a trumpet shape so as to face the lake bottom, and the turbid water 8 is placed in the lake bottom. (2) What slowly circulates the turbid water 8 toward the suction port 12a of the suction part to circulate a part of the turbid water 8 (FIG. 3 (a) and FIG. 4 (a) )) Can be used. (Other than that, in the suction section of FIG. 3, (3) the turbid water 8 ejected from the nozzle 13 provided at the tip of the return pipe 14 is passed through the throat formed on the inner surface on the back side of the suction port 12a. Circulating almost everything and sucking earth and sand from the suction port 12a by the ejector effect (Fig. 3 (b)), and in the suction part of Fig. 4, (4) turbid water is jetted into the sediment at the bottom of the lake inside the suction part Then, what softens the earth and sand (Fig. 4 (b)) is also conceivable.

  The centrifugal separator 18 provided in the dredger 10 separates heavy sediments from water by rotating the slurry dredged by the suction pipe 12 at a high speed. However, since the colloidal fine sediment cannot be separated even by the centrifugal separator 18, the separated water becomes turbid water mixed with sediment colloid.

  The cooler 22 provided on the ship is connected to the centrifuge 18 and cools the muddy water 8 separated from the earth and sand by the centrifuge 18. When the temperature of the turbid water is relatively warm, the cooler 22 cools the turbid water so that the temperature of the turbid water and the water temperature of the lake bottom have a certain temperature difference (for example, about 5 ° C.), and the water temperature of the lake bottom is cold (approximately The temperature of turbid water is cooled to 4 ° C. When the water temperature at the bottom of the lake is colder than 4 ° C, the turbid water is exceptionally warmed to 4 ° C. This is because the specific gravity of water increases as the temperature decreases up to 4 ° C, while the specific gravity decreases at 4 ° C.

Next, the earth and sand dredging method according to this embodiment will be described in order. FIG. 5 is a flowchart showing the flow of the dredge method of the present embodiment.
In the dredging method of the present embodiment, prior to the suction of the earth and sand, an operation is performed in which the buried object 6 in which all or a part of the earth and sand is buried in the lake bottom is removed in advance by the rake 24.
At this stage, first, the rake 24 attached to the tip of the wire rope 26 by the winding device 28 is lowered from the swing arm 42 on the ship so that the rake L-shaped teeth of the rake face in the stern direction. The earth and sand 4 is stirred and slowly settled so as not to generate turbidity. Next, the rake 24 that has been grounded is not moved, the wire 34 that supports the dredger 10 is wound up by the winch 36 while the wire rope 26 is loosened, and the dredger 10 is moved in the bow direction. As a result, the wire rope 26 to which the rake 24 is attached is inclined from the bottom of the lake toward the dredger 10 on the water surface.

  Subsequently, the winding device 28 is driven to draw the rake 24 until it is almost directly below the dredger 10 and scrapes the buried object 6 such as a tree branch buried in the earth and sand 4 on the bottom of the water. At this time, the winder 28 is driven at a sufficiently low speed so that the lake rake 24 moves while scraping the buried material so as not to cause turbidity as much as possible. The speed is, for example, about 1 cm per second. However, this speed is preferably adjusted according to the nature of the earth and sand. That is, when the particle size of the sediment deposited on the bottom of the lake is large, that is, when the sediment rises little even if the rake 24 scrapes the buried object 6, the operating speed of the rake 24 can be increased. When the particle size of the earth and sand is small and the earth and sand soar during the scraping operation is large, it is preferable to slow down the operating speed of the rake 24. By slowly operating the rake 24 in this way to scrape the buried object 6, it is possible to minimize the soaring of the earth and sand (turbidity) into the water for the removal of the buried object 6 as a preparation. Also, the soil that has soared can easily sink to the bottom of the lake again. Further, by softening the earth and sand by scraping, the suction of the earth and sand by the suction pump 16 to be performed later can be facilitated.

  After the rake 24 from which the buried object 6 has been scraped is drawn almost directly below the dredger 10, the buried object 6 is lifted from the earth and sand 4 into the water near the bottom of the lake, and the length of the second wire 34 is shortened within a minute range. The rake 24 is finely vibrated by changing the period. Thereby, the buried object 6 is vibrated and the earth and sand 4 adhering to the buried object 6 is shaken off in the vicinity of the lake bottom. By carrying out the shaking of the earth and sand adhering before the buried object is lifted onto the water, it is possible to minimize the spread of the earth and sand that occurs near the water surface during the lifting. In addition, since the earth and sand adhering to the buried object is shaken off near the bottom of the lake, the turbid component once generated can easily settle to the bottom of the lake, and the turbidity does not spread over a wide range.

After removing the lake bottom burial material 6 by the above-mentioned operation, the next operation is performed after a time of about one day in order to sufficiently settle the turbid component of the water bottom.
In this operation, first, the dredger 10 is moved above the bottom of the lake to be dredged (whether or not the dredger 10 is connected to the support post 38 by the wire 34), and the length of the dredger 10 can be adjusted in parallel. The suction pipe 12 and the return water pipe 14 are extended to the bottom of the lake while being supported by the swing arm 42 at the rear of the dredger 10. After the suction portion 12a at the tip of the suction pipe 12 is settled, the suction pump 16 is driven to suck the earth and sand 4 together with water from the lake bottom.
Next, the sand 4 that has been mixed with water to form a slurry is sucked up on a dredger, and this is applied to a centrifugal separator 18 to remove moisture from the sediment component. The earth and sand 4 from which moisture has been removed is discharged to the earth and sand tray 32 on the ship. On the other hand, the water (turbid water 8) removed from the earth and sand is sent to a cooler 22 disposed adjacent to the centrifugal separator 18 and cooled by a certain temperature. As the cooler 22, a cooling device using a compressor, a cooling tower filled with ice or the like made by using nighttime electric power, and the like can be used.

The turbid water 8 after cooling is carried to the bottom of the lake through the return water pipe 14 and discharged from the outlet 14 a disposed near the suction part 12 a of the suction pipe 12. In addition, in order to prevent the temperature rise of the muddy water 8 inside, it is preferable to use what has a heat insulation structure for the return water pipe 14.
The turbid water to be discharged is slowly discharged from the wide area outlet 14a according to the type of the suction unit described above.
Since the discharge port 14a is disposed near the suction part 12a, part of the muddy water discharged from the discharge port is sucked again from the suction port 12a together with the earth and sand 4 and circulates. The turbid water that has not been sucked from the suction port 12a also settles quickly because its temperature is lower than the surrounding water temperature. The fine sediment in the muddy water that has settled settles down to the bottom of the lake over time.

When moving the dredging area, first stop the discharge of muddy water 8 from the outlet 14a, then lift the suction part slightly from the bottom of the lake, move it parallel to the place you want to dredge, and lower the suction part to the bottom of the lake again. After that, perform suction and continue sputum.

  By cooling the turbid water separated from the earth and sand and returning it to the bottom of the lake, the turbid water settles without convection and forms a liquid layer on the bottom of the turbid water. Precipitate. This makes it possible to remove earth and sand by suction with almost no turbidity in the water.

In addition to the above, it is also conceivable to suppress the diffusion of muddy water to the surroundings by separating the certain water area including the lake bottom from other water areas and then dredging the earth and sand.
As shown in FIG. 6, in the vicinity of the tips of the connected suction pipe 12 and return water pipe 14, the number of diameters surrounds the suction port 12a (suction part) and the discharge port 14a with the suction tube 12 as the central axis. A metal frame 44 that defines a cylindrical space of about a meter is attached. The frame 44 moves up and down integrally with the up and down movement of the suction pipe 12 and the return water pipe 14 by the winding device 28 (see FIG. 1).
The frame 44 is covered with a sheet material 46 on the surface other than the bottom surface. The lower end of the sheet material covering the side surface of the frame has a skirt shape, and the water area including the suction port 12a and the discharge port 14a is separated from other water regions on the flat lake bottom with the suction part 12a bottomed. As the sheet material 46, a fine mesh structure having a certain degree of water permeability is used. By using the sheet material 46 having a fine mesh structure, it is possible to reduce the resistance of water when the frame 44 covered with the sheet material 46 is lowered from the dredger 10 to the bottom of the lake, and the like. Diffusion of the released turbid water 8 can be suppressed. It is possible to use a non-water-permeable sheet such as vinyl or rubber as the sheet material 46, but in this case, an opening / closing window 48 that opens to the sheet material 46 covering the cylindrical frame 44 due to water resistance. It is preferable to provide.

  A nozzle 13 is attached to the tip of the return water pipe 14, and the muddy water 8 separated from the nozzle 13 by the centrifugal separator 18 and cooled by the cooler 22 is ejected toward the bottom of the lake near the suction port 12a. . The turbid water ejected softens the sediment at the bottom of the lake and facilitates the suction of the sediment 4 from the suction port 12a. In addition, when muddy water is ejected, the earth and sand will rise, but since the water area is separated by the sheet material 46, the muddy water 8 is less likely to leak to the outside, and the muddy water 8 may leak from the lower surface of the separated water area. Since the muddy water has been cooled in advance, the fine sediment in the muddy water that has settled settles to the lake bottom over time without sinking to the lake bottom and diffusing to the surroundings.

In the case of moving the dredging area, the discharge of the muddy water 8 from the outlet 14a is stopped in the same manner as in the first embodiment, and after waiting for the turbidity of the water area surrounded by the frame 44 to settle, the suction part 12a and the frame 44 are moved. Is lifted slightly from the bottom of the lake, moved parallel to the place where the user wants to dredge, and the suction part and the frame 44 are lowered again to the bottom of the lake, and then the dredging is continued.
For example, if a buffer tank capable of temporarily storing a certain amount of aspirated slurry or turbid water 8 separated from the slurry is provided on the dredger 10, the turbid water 8 from the nozzle 13 is stopped after being released. By sucking the muddy water 8 in the water area surrounded by the water and temporarily storing it in the buffer tank, the suction part 12a can be quickly moved to the next dredging point without waiting for the muddy water in the water area surrounded by the frame to settle down. You can continue the trap by moving.

The dredging method of the present invention is to cool the muddy water separated from the slurry and return it to the bottom in order to suppress the diffusion of turbidity that occurs when dredging earth and sand by the suction method, or a certain water area. It is not limited to the embodiment of the invention described above as long as it separates from other water areas and sucks sediment and turbid water in the water areas, and various modifications can be made without departing from the gist of the present invention. Of course.

As described above, according to the present invention, when dredging in a place where a large space for installing a sedimentation basin such as a dam lake cannot be taken, turbid water separated from earth and sand and returned to the bottom of the water is widely used. Diffusion can be prevented.
In addition, even if it is a case where a wide space for installing a sedimentation basin can be taken, when the sedimentation basin is not desired, naturally, the dredging method of the present invention can be used.

It is sectional drawing of the dam lake for demonstrating the dredging method of this invention. It is a perspective view of the rake used for the dredging method of this invention. It is a sectional side view of a suction part. It is a sectional side view of a suction part. It is the flowchart which showed the flow of the dredging method of a present Example. A frame and a sheet material surrounding the suction port and the discharge port.

2 Dam lake 4 Sediment 6 Buried material 8 Turbid water 10 Dredger 12 Suction pipe 12a Suction port 13 Nozzle 14 Return pipe 14a Outlet 16 Suction pump 18 Centrifuge 22 Cooler 24 Rake 26 Wire rope 28 Winding device 32 Sediment tray 34 Wire 36 winch 38 support post 42 swing arm 44 frame 46 sheet material 48 opening and closing window

Claims (5)

A dredging method for suppressing the diffusion of muddy water when dredging sediment deposited on the bottom of dam lakes, lakes, rivers, harbors, etc.
Aspirate the slurry from the suction port of the suction tube opened at the bottom of the water,
The sucked slurry is separated into earth and sand and muddy water,
Cool the muddy water that is muddy water separated from the slurry,
A dredging method characterized in that the turbid water in the turbid water is settled by slowly discharging the cooled turbid water from the outlet of the return pipe opened near the bottom of the water. The dredging method according to claim 1, wherein a discharge port of the return pipe is disposed close to a suction port of the suction pipe, and a part of the cooled muddy water is circulated. The dredging method according to claim 1 or 2 , wherein the cooling temperature of the muddy water is about 4 degrees Celsius. Before sucking the earth and sand from the suction port, the rake placed on the bottom of the water operates at an extremely low speed so as to suppress the scattering of the earth and sand, scraping and removing the buried objects buried in the bottom of the earth and sand. The dredge method according to any one of claims 1 to 3 . The lake by oscillating the, the implant hooked rake is finely vibrating in the sea bed near the adhered performed to raise implant after shaking off the earth and sand are, it claim 4, wherein浚 渫 method.

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