JPS62284831A - Dredging apparatus of air lift system - Google Patents

Abstract

PURPOSE:To improve the efficiency of dredging, by suspending an air lift pipe telescopically from a platform ship, and by providing the lower end of the air lift pipe with a hood. CONSTITUTION:After an air lift pipe 3 is moved upward or downward by a crane device 4 and is kept so that a distance between the edge section of a hood 10 and the bottom 14 of the water may be set to be a specified distance, pneumatic pressure is fed to the inlet 7 of the air lift pipe 3 from a compressor 5. As a result, a great negative pressure is generated in the air lift pipe 3 near the inlet 7, and ascending current is generated in the air lift pipe 3, and sediment 16 is lifted up from the bottom 14 of the water.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an air lift dredging device for removing accumulated earth and sand from a dam.

[Conventional technology]

Dams for water storage, irrigation, power generation, etc. are constructed with great investment, but due to sedimentation on the lakebed of the dam, the effective water storage volume decreases year by year and its function deteriorates. needs to be removed.

Conventionally, means for removing such earth and sand include dredging equipment that continuously scoops up the earth and sand using a packet conveyor, dredging equipment that excavates earth and sand using a rotary excavation packet and sucks it up with a pump,
There are dredging devices that are grabbed by grab buckets and dredging devices that use air lifts.

[Problem that the invention seeks to solve]

However, dredging equipment using a packet conveyor system has a limit to the depth of water, and dredging equipment using a grab bucket method is inefficient because it picks up water intermittently. Pump dredging equipment using rotary packets is widely used as an effective dredging method, but the ladder, which is lowered from a barge to the bottom of the water, becomes longer as the water gets deeper, making the equipment larger and less suitable for dredging narrow dams. Not suitable.

Furthermore, with conventional airlift dredging equipment, only the soil directly below the airlift pipe can be sucked in, so the lower end of the airlift pipe must be swung and moved frequently. could not.

This invention solves the above-mentioned problems in dredging, and is an air lift that can powerfully suck up sediment over a wide range, reduce the frequency of movement of the air lift pipe, and improve the efficiency of dredging work. The purpose is to provide a type dredging device.

Means for Solving Problem C] In order to solve the above problem, the airlift dredging device of the present invention has an airlift pipe telescopically suspended from a barge, and a hood is provided at the lower end of the airlift pipe.

[Effect]

By maintaining a predetermined gap between the edge of the hood and the bottom of the water, a strong horizontal flow is generated from the edge of the hood directly below the central air lift tube. This water flow transports the earth and sand around the hood directly below the airlift pipe and sucks it up by the airlift, reducing the frequency of movement of the airlift pipe and making dredging work more efficient.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory diagram of the configuration of an airlift dredging device according to an embodiment of the present invention, in which an airlift device 2 is mounted on a barge 1 that is a floating body. The air lift device 2 includes an air lift pipe 3, a crane device 4 for suspending the air lift pipe 3, a compressor 5, and a pneumatic air pipe 6 connected from the compressor 5 to a blowing lower part in the middle of the air lift pipe 3. It is configured.

A hood 1O as shown in FIGS. 2 and 3 is provided at the lower end of the air lift tube 3. A nozzle 11 that sprays high-pressure water is attached to the hood 10, and the barge 1
A water pipe 13 from a high-pressure water generator 12 installed in the nozzle is connected to this nozzle. In this embodiment, the hood 10 is shaped like a truncated cone, but it can also be shaped like a polygonal pyramid.

The other end of the air lift pipe 3 is installed on the barge 1 and connected to a drainage device 2.
1, and a conveyor line 22 is arranged from this draining device 21 to a storage area 24 via a sieving device 23. Furthermore, a pump 25 is installed on the barge 1 to discharge mud water from the drainage device 21, and a mud feeding pipe 27 is installed from the pump 25 to the sedimentation tank 26. 14 is the water bottom, 15 is the dam body, and 16 is accumulated earth and sand.

When performing dredging work, the airlift pipe 3 is raised and lowered by the crane device '4 to maintain a predetermined distance between the edge of the hood 10 and the water bottom 14, and the compressor 5 blows air into the airlift pipe 3. Sends pressure to the lower. Because the air is blown in from the middle of the air lift pipe 3, the average specific gravity inside the air lift pipe 3 from the blowing lower to the water surface is smaller than the specific gravity of the water outside the pipe, and this difference in specific gravity creates a large negative load inside the pipe near the blowing lower. Pressure is generated. This negative pressure generates an upward flow within the air lift pipe 3, and the water flow can lift up the earth and sand 16 from the water bottom 14. The flow 1 state inside the air lift pipe 3 is
Below the blowing lower, there is a solid-liquid two-phase flow of earth and sand, and water, and above the blower, a gas-liquid-solid three-phase flow occurs with air added. In a solid-liquid two-phase flow section, the liquid specific gravity increases due to the presence of particles, and the pipe friction loss becomes larger than in the case of water, but in a gas-solid three-phase flow section,
As it gets closer to the water surface, the average flow velocity increases (although the presence of air causes the liquid specific gravity to be smaller than in the solid-liquid two-phase flow section, and the friction loss of the strainer tube to be reduced. It operates in a balanced state.

Earth and sand 16 deposited on the underwater structure 4 by the air lift device 2
In order to move the hood horizontally and convey it vertically, the flow velocity at the end of the hood 10 needs to be approximately 3 m/sec or more. The flow velocity V at the end is determined by the conical hood 10 with the outer diameter.
When the distance between the edge of the water and the water bottom 14 is h, it is expressed as V=-πDh. Here, Q is the upward flow rate due to air lift. Therefore, by setting the interval so that V=3 m/sec, it is possible to horizontally move and suck up a wide range of earth and sand 16 whose diameter is D/d times that of the case where the air lift pipe 3 of diameter d is used alone.

Also, high pressure water is sent from the high pressure water generator 12 on the barge 1 to the nozzle 11 provided in the hood 10 through the water pipe 13,
The water is injected to excavate the underwater bottom 14 and improve dredging ability. If this hood 10 is rotated or rotated by an angle greater than or equal to π/number of nozzles, the amount of excavation can be further increased and the dredging capacity can be improved.

Note that if the spacing cannot be maintained due to negative pressure inside the hood 10, an opening may be provided in the hood 10 and opened and closed, or
The spacing is controlled by the high-pressure water jet thrust from the nozzle 11 to maintain the spacing. The hood 10 can also be relocated using this thrust.

The slurry consisting of the earth and sand 16 and water sucked up by the air lift device 2 is separated into earth and water by the drainer 21, and sent to the storage area 24 via the conveyor line 22 and the sieve membrane [23], where it is deposited. . On the other hand, the drained mud water is discharged by the pump 25 through the mud feed pipe 27 into the settling tank 26, and after the mud and the like are settled, the supernatant water is discharged into or outside the dam.

〔Effect of the invention〕

In this invention, a hood is provided at the lower end of the airlift pipe to generate a strong horizontal flow, enabling dredging over a wide range, reducing the frequency of movement of the airlift pipe, and improving dredging efficiency.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of an air lift type dredging device that is an embodiment of the present invention, FIG. 2 is an enlarged vertical sectional view of the hood portion, and FIG. 3 is a plan view of the hood portion. In the figure, 1 is a barge, 2 is an air lift device, 3 is an air lift pipe, 10 is a hood, and 11 is a nozzle. Patent applicant Yutaka Oyamauchi, Furukawa Mining Co., Ltd.

Claims (2)

[Claims] (1) An airlift dredging device equipped with an airlift device on a barge, characterized in that an airlift pipe is telescopically suspended from the barge and a hood is provided at the lower end of the airlift pipe. (2) The air lift dredging device according to claim 1, wherein the hood is an excavation hood equipped with a nozzle that sprays high-pressure water.