JP2000120051A - Method for scouring sedimentary sand on bottom and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to smooth convey also gravel having large particle size mixed with sedimentary sand through the inside of a scour pipe when a siphon scour method for reducing energy and cost necessary for scour work is adopted and to enable surely the execution of the scour work capable of corresponding also to the sedimentary sand mixed with gravel. SOLUTION: A method for scouring sedimentary sand in a dam reservoir 5 is so constituted that a suction pipe 3 of one end of a scour pipe 1 used as the bottom is opened to the bottom of a lake of the dam reservoir 5, a discharge pipe 4 of the other end is opened to a diversion channel 6 in the downstream and that water and sedimentary sand 18 in the dam reservoir 5 are sucked up with sipon operation of the scour pipe 1 and are discharged to the diversion channel 6. In that case, an air inlet is provided to the scour pipe 1, a high speed rotational flow is generated inside of the pipe by air blown out along the circumferential wall in the pipe of the scour pipe 1, an air core is formed in the center of the scour pipe 1, and a rotational flow of earth and sand is formed in the circumference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for discharging sediment from a water bottom such as a dam reservoir.

[0002]

2. Description of the Related Art There are various types of dams, such as those for power generation, irrigation, flood control, etc., but all of them generate sediment. The sediment generated in the basin is washed down by the river into the downstream basin, and the sediment is deposited in descending order of the particle size according to the decrease of the river gradient and the decrease of the flow velocity. Large-sized soil particles also move away from the riverbed (floating) and are transported downstream in a stream (moving while rolling on the riverbed).

[0003] That is, when a flood flow accompanied by sediment approaches the dam reservoir, the river cross section sharply increases, so that the flow velocity decreases, and large-grained gravel is deposited near the entrance of the reservoir. Such sedimentation not only causes a decrease in the amount of stored water, but if left unchecked, sedimentation gradually develops upstream, and during floods the water level rises in the upstream area, causing flood damage. There is also.

In the downstream area of the dam, the riverbed of the river is scoured, adversely affecting the foundation of the bridge and the embankment, adversely affecting flora and fauna due to the outflow of fine particles, and furthermore, the supply of sand to the coast. Decrease in the amount will cause loss of sandy beach and destruction of revetment due to retreat of coastline.

[0005] Therefore, it is necessary to discharge the sediment in the dam lake, and various methods have hitherto been used. One of them uses a dredging machine such as a grab-type dredge, a backhoe-type dredge, or a pump-type dredge.The grab-type dredge is a non-navigation type that grabs the sediment at the bottom of the water with a grab bucket and is used for primary transportation. Uses an earth transport ship.

A backhoe-type dredger has a backhoe mounted on a barge. The hull is fixed with spuds to perform dredging, and the primary transport of dredged soil is carried out by pneumatic pumping using a soil carrier or pipeline. A pump-type dredger uses a pump onboard to suck up water and sediment with water from a pumping port, and transports it by a pipeline, or dredges a submersible sand pump from an assembling barge.

As another method, there is a method in which a sand discharge gate is installed in a dam to discharge and discharge sediment. Another method is disclosed in Japanese Patent Application Laid-Open No. 9-21127 which was previously proposed by the applicant.
There is a siphon-type sand discharging method as described in Japanese Patent Application Laid-Open No. H10-260, 1988. In this siphon type, the suction part at one end of the sediment discharge pipe is opened at the bottom of the lake of the dam reservoir, the water discharge part at the other end is opened at the river downstream of the dam, and the water and sediment in the dam reservoir are siphoned. Pumping and flowing down the downstream of the dam, the suction part is installed at a work base composed of a float, and the work base determines the installation position by winch operation using an anchor installed on land.

[0008]

The method using a dredging machine not only requires a large amount of energy to drive the machine, but also increases transportation costs. In addition, the method of installing a gate for sand discharge requires a great deal of cost when it is installed on an existing dam. In this regard, the siphon type can save energy and reduce cost, but if gravel is mixed in sediment, the gravel has a large particle size, so it should be sucked well. Can not.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the disadvantages of the prior art and reduce the energy and cost required for the sand removal operation by using a siphon-type sand removal method when mixing with sand. Gravel can be transported smoothly through the sand drainage pipe, and a transport speed corresponding to the size of the gravel can be obtained. It is an object of the present invention to provide a method and an apparatus for discharging sediment from a dam reservoir, which can efficiently and reliably perform sand.

[0010]

In order to achieve the above object, the present invention provides, as a method, first, a suction pipe at one end of a sand discharge pipe is opened at the bottom of the water, and a water discharge pipe at the other end is connected to a downstream water discharge channel. A method of discharging sediment at the bottom of a water tank, which pumps up water and sediment in a dam reservoir by a siphon action of a sand discharge pipe and discharges it to a water discharge channel, wherein an air suction port is provided in the sand discharge pipe, and the air suction port is provided. Generating a high-speed rotary flow in the pipe by air blown along the peripheral wall in the pipe of the sand discharge pipe from the above, forming an air core portion at the center of the sand discharge pipe, and forming a rotary flow of sediment therearound. Second, the water bottom should be the lake bottom of the dam reservoir.

[0011] As a device, first, in a submerged sediment discharge device in which a suction pipe at one end of a sand discharge pipe is opened to the water bottom and a water discharge pipe at the other end is opened to a downstream water discharge passage, The gist of the invention is that air suction ports are provided on the peripheral wall at appropriate intervals in the length direction, and the direction of air blowout from the suction port is directed to the circumferential direction of the inner wall of the sand discharge pipe.

Secondly, the air suction port of the sand discharging pipe is provided with an air pipe in the length direction outside the sand discharging pipe, provided at an appropriate interval in the air pipe, and has an opening in the peripheral wall of the sand discharging pipe. The gist is an air outlet formed at the open end of the projecting pipe.

According to the first aspect of the present invention, as a method, when water and sediment at the bottom of the water are pumped up by the siphon action of the sand discharging pipe, the air suction port provided in the sand discharging pipe is used to form a peripheral wall in the pipe. A high-speed rotating flow is generated in the pipe by the air blown out, and an air core is formed at the center of the sand discharge pipe, and a rotating flow of sediment is formed around it. The pipes can be transported smoothly and sand can be efficiently and easily discharged. In this case, since the speed of the rotating flow can be determined by selecting the air blowing speed, an appropriate rotating flow speed corresponding to the particle size of the gravel can be obtained.

According to the second aspect of the present invention, in addition to the above-mentioned effects, not only can a reduction in the amount of water stored in the dam reservoir be prevented, but also a bridge caused by scouring of the riverbed downstream of the dam. Adverse effects on foundations and embankments can be prevented, and fine particles can be prevented from harming flora and fauna. Destruction can be prevented.

According to the third aspect of the present invention, the apparatus has a simple structure in which only an air suction port is provided in the circumferential direction of the peripheral wall of the sand discharge pipe, and the air blown into the pipe from the air suction pipe enters the pipe. A rotating flow can be generated.

According to the fourth aspect of the present invention, in addition to the above-described operation, the air suction port of the sand discharging pipe is provided with an air pipe disposed outside the sand discharging pipe in a length direction. Since it is composed of the formed air outlet, it is sufficient to simply attach an air pipe to the sand discharge pipe, it is simple in structure and applicable to existing equipment, it can secure a large pipe diameter and can secure a large transport volume .

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a front view showing an embodiment of a method and an apparatus for discharging sediment on a water bottom according to the present invention, FIG. 2 is a perspective view of a sand discharging pipe which is a main part of the same, and FIG.
In the drawing, reference numeral 1 denotes a sand discharging pipe, one end of which is formed in a suction pipe 3 and the other end of which is formed in a water discharge pipe 4. The suction pipe 3 is opened to the bottom of a lake of a dam reservoir 5 with the water suction pipe 3 as a water bottom. An opening is provided in the water discharge channel 6 downstream of the dam, and a part thereof is placed along the upper surface of the dam body 2 which is a bank. At the top of the dam body 2, a pump 7 for bleeding air from the inside of the sand discharge pipe 1 is provided. . In the figure, reference numeral 11 denotes a floodgate installed in the water discharge channel 6.

The sand discharge pipe 1 is made of, for example, a flexible spiral pipe, and a float 8 is attached at an appropriate position in the middle to float above the water of the dam reservoir 5. The diameter of the pipe laid in the dam reservoir 5 is thin. The thing laid on the water discharge channel 6 side is formed thick.

Also, an air pipe 12 is disposed outside and parallel to the sand discharging pipe 1 in the length direction, and a projecting pipe 13 is integrally protruded from the air pipe 12 at appropriate intervals in the length direction. The opening end of the projecting pipe 13 was opened in the peripheral wall of the sand discharging pipe 1, and this opening was used as an air suction port 14. In this case, the mounting angle of the protruding pipe 13 to the sand discharging pipe 1 is determined so that the direction of air blowing from the air suction port 14 into the sand discharging pipe 1 is directed to the circumferential direction of the inner wall of the sand discharging pipe 1. I do.

Then, the suction pipe 3 at one end of the sand discharge pipe 1 is positioned on a work boat 10 which can move, for example, through the dam reservoir 5 by means of position adjusting means.
Secure through 15. This position adjusting means 15 is, for example, 2
The guide pipes 16a and 16b are respectively perpendicular to the workboat 10,
The two guide tubes 16 are mounted movably in the horizontal direction.
The sheath tube 17 is mounted on a shaft so that the mounting angle can be freely adjusted and the movable member can be moved up and down so as to be bridged between a and 16b.
The suction tube 3 is inserted into 17.

A submersible pump such as a high-pressure turbine pump (not shown) is installed near the mouth of the suction pipe 3, and a screen is installed to prevent suction of driftwood and other obstacles.

Further, if necessary, an air compressor for stirring the sediment is installed on the workbench 10, and
A cutter for breaking down the sediment 18 is attached to the tip of the sand discharge pipe 1.

Next, a method of discharging the sediment 18 of the dam reservoir 5 using such an apparatus will be described. The work boat 10 is moved to the working position, and the position adjusting means 15 is operated to operate the guide pipes 16a,
In addition to adjusting the horizontal and vertical positions of 16b, the mounting angle of the sheath tube 17 with respect to the guide tubes 16a and 16b is adjusted,
The mouth of the suction pipe 3 attached to the tip of the sheath pipe 17 is positioned at an optimum angle with respect to the sediment 18.

The water discharge pipe 4 is closed, and a submersible pump provided near the mouth of the suction pipe 3 is operated to supply water into the sand discharge pipe 1 to fill the inside of the pipe with water. Alternatively, the pump 7 is operated to bleed air from the sand discharge pipe 1. After the air in the pipe is removed in this way, if the side of the water discharge pipe 4 is opened, the water and the sediment 18 of the dam reservoir 5 are sucked up from the suction pipe 3 by the siphon action and pass through the sand discharge pipe 1 from the water discharge pipe 4. Spillway 6
To be released. At this time, since the water discharge pipe 4 has a large diameter, a large drainage capacity can be obtained.

In the case of the sediment 18 having many fine grains, the sediment is often solidified due to a drought in the past and the like, and sediment having a large particle size such as gravel is often mixed. Sand efficiency may be extremely reduced. In response to this, the fixed earth and sand is broken down with a cutter attached to the tip of the suction pipe 3, or the air compressor is operated to blow out compressed air into the water and agitate it to exert an air lift effect, thereby discharging the earth and sand. And reduce the frictional resistance in the pipe.

If the air pipe 12 attached to the outer peripheral surface of the sand discharging pipe 1 is connected to a compressor and air 20 is blown out from the air suction port 14 into the sand discharging pipe 1, the air 20 is discharged from the sand discharging pipe 1.
Flows along the circumferential direction of the inner wall of the, and becomes a rotating flow. As a result, the centrifugal separation action causes the center of the
19 is formed, around which the sand mixed with gravel swirls while rotating, and is transported efficiently and smoothly in the pipe.

The flow velocity required for transporting sediment mixed with gravel having a large particle diameter in a pipe can be obtained from the following formula as the critical tractive force flow velocity. The critical tractive force flow velocity V _c is

(Equation 1) Where V _c : critical tractive force flow velocity (cm / s) β: constant ≒ 0.06 f: friction constant ≒ 0.03 Po: density of earth and sand = 2.60 Pw: density of water = 1.00 g: Gravitational acceleration = 980 (cm / s ² ) d: particle size (cm)

The flow velocity in the vortex tube is as shown in FIG.
Is the flow velocity in the pipe axis direction, v θ in the circumferential direction of the pipe
Assuming the flow velocity,

(Equation 2) Becomes

Here, based on the above equation, the particle diameter d = 10
The flow velocity required to move cm of gravel is determined.

(Equation 3)v (cm / s) v θ (cm / s) 500.9 0 491.8 95 459.2 200 401.1 300 301.5 400 30.0 500 where V_c: Limit sweeping force flow velocity (cm / s) β: Constant ≒ 0.06 f: Friction constant ≒ 0.03 Po: Density of earth and sand = 2.60 Pw: Water density = 1.00 g: Gravitational acceleration = 980 (Cm / s^Two) d: Particle size (cm)

From the above calculation result, v (flow in the pipe axis direction)
In order to reduce the speed, the speed v θ (to eddy current
The flow velocity in the circumferential direction of the pipeline).
v As long as θ can maintain the specified value, even if v is reduced,
It can be understood that large-sized sediment such as
Degree of transportation is possible.

Thus, for example, v θ = 4m / sec, v =
Set the air suction speed to 3 m / sec
To obtain high-speed rotating flow for transporting sediment mixed with gravel
And set an appropriate air suction speed corresponding to the particle size.
Of high-speed rotating flow for sediment transport mixed with gravel
Speed can be set, and reliable and efficient transportation is possible.

As the work progresses, the work boat 10 is freely moved to move the drinking mouth at the tip of the suction pipe 3, and the sediment 17 at the lake bottom is sequentially discharged. The sand discharging pipe 1 also moves with the movement of the work boat 10, but since the sand discharging pipe 1 is formed as a flexible spiral pipe, it smoothly follows the movement of the work boat 10.

Driftwood and other obstacles settled on the bottom of the lake are removed by a screen provided on the suction pipe 3 and the sand discharge pipe 1
It will not be sucked inside.

[0034]

As described above, the method and apparatus for discharging sediment from a dam reservoir according to the present invention employ a siphon-type sand discharging method in order to reduce the energy and cost required for sand discharging work. The air is supplied so as to generate a rotating flow in the sand discharge pipe, so that the gravel mixed in the sediment can be moved to the periphery of the pipe by the centrifugal action by the rotating flow in the pipe, and the inside of the sand discharge pipe smoothly In addition to being able to transport, by setting the air suction speed freely, it is possible to obtain an appropriate transport speed corresponding to the particle size of the gravel, It can respond appropriately to sedimentation and can efficiently and reliably discharge sand.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a method and an apparatus for discharging sediment on a water bottom according to the present invention.

FIG. 2 is a perspective view of a sand discharging pipe, which is a main part, of the embodiment of the submerged sediment discharging device of the present invention.

FIG. 3 is a vertical sectional front view of a sand discharging pipe which is a main part of the embodiment of the submerged sediment discharging device of the present invention.

FIG. 4 is an explanatory diagram of a flow rate in a sand discharging pipe, which is a main part, of the embodiment of the submerged sediment discharging apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sand discharge pipe 2 ... Dam main body 3 ... Suction pipe 4 ... Water discharge pipe 5 ... Dam reservoir 6 ... Water discharge channel 7 ... Pump 8 ... Float 10 ... Workboat boat 11 ... Water gate 12 ... Air pipe 13 ... Projection pipe 14 ... Suction Port 15: Position adjusting means 16a, 16b: Guide pipe 17: Sheath pipe 18: Sedimentation 19: Air core 20: Air

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takeshi Ikeya 2-9-1-1, Tobita-Sen, Chofu-shi, Tokyo

Claims (4)

[Claims] 1. A suction pipe at one end of a sand discharging pipe is opened at the bottom of the water,
In the method for discharging sediment at the bottom by opening the water discharge pipe at the other end to the downstream water discharge channel, pumping water and sediment at the bottom by the siphon action of the sand discharge pipe, and discharging the sediment at the water bottom discharged to the water discharge path, sucking air into the sand discharge pipe A high-speed rotating flow is generated in the pipe by the air blown out from the air suction port along the peripheral wall in the pipe of the sand discharge pipe, and an air core portion is formed at the center of the sand discharge pipe, and the surroundings of soil and sand are formed. A method for discharging sediment at the bottom of water, comprising forming a rotating flow. 2. The reservoir according to claim 1, wherein the bottom is a lake bottom of a dam reservoir.
The method of discharging sediment at the bottom of the water described above. 3. A suction pipe at one end of the sand discharging pipe is opened at the bottom of the water,
In a bottom sediment discharging device in which a water discharge pipe at the other end is opened to a downstream water discharge channel, air suction ports are provided at appropriate intervals in a length direction on a peripheral wall of the sand discharge pipe, and a direction in which air is blown from the suction port. A sediment discharge device at the bottom of the water, wherein the sand is directed in a circumferential direction of an inner wall of the sand discharge pipe. 4. An air suction port of the sand discharging pipe is provided with an air pipe disposed outside the sand discharging pipe in a longitudinal direction, provided at an appropriate interval on the air pipe, and formed with a projection opening on a peripheral wall of the sand discharging pipe. 4. The apparatus according to claim 3, wherein the outlet is an air outlet formed at an open end of the pipe.