JP2530615B2 - Airlift dredging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention excavates earth and sand accumulated in a reservoir lake of a dam by injecting high-pressure water from a nozzle of an excavation hood directly connected to a lower end of an air lift pipe. The present invention relates to an air-lift type dredging method for sucking up and removing.

[Conventional technology]

Dams for water storage, irrigation, power generation, etc. are constructed by investing a large amount of money, but the sediment that accumulates in the dam's reservoir lake reduces the amount of water that can be effectively used each year and reduces its function. It is necessary to collect and remove the collected soil one by one.

As means for removing such accumulated sediment, conventionally,
A dredging device that continuously scoops with a bucket conveyor, a dredging device that excavates earth and sand with a rotary excavation bucket and sucks it with a pump, a dredging device that grabs with a grab bucket, and a dredging device with an air lift are used.

[Problems to be solved by the invention]

As for children, the dredging device using the bucket conveyor method has a limited water depth, and the dredging device using the grab bucket method intermittently picks up the water, which is inefficient. The pump dredging device using a rotating bucket is widely used as an effective dredging method, but the ladder that tilts from the barge and descends to the bottom of the water becomes longer as the water depth increases, and the device becomes larger, resulting in a narrow space. Not suitable for the dredging of large dams.

In addition, with the conventional air lift type dredging device, only the soil directly under the air lift pipe can be sucked in, so the lower end of the air lift pipe must be frequently swung, and efficient dredging can be achieved when the water depth becomes large. There wasn't.

This invention is to solve the above-mentioned problems in the conventional dredging method, and it is possible to excavate the sediment in a wider range than the soil directly under the airlift pipe by high-pressure water jet and strongly suck it up. Reduce the frequency of movement,
It is an object of the present invention to provide an air lift type dredging method capable of improving the efficiency of dredging work.

[Means for solving problems]

In order to solve the above problems, the air lift type dredging method of the present invention is an air lift pipe suspended vertically from a barge, and an opening edge portion of a predetermined multiple size larger than the diameter of the air lift pipe. Using a dredging device with a drilling hood having a nozzle and directly connected to the lower end of the air lift pipe,
An air lift pipe is hung while keeping an opening edge portion of the drilling hood at a predetermined distance from the water bottom, and compressed air is supplied to the air lift pipe, and high pressure water is jetted from the nozzle of the drilling hood toward the water bottom. It is a thing.

[Action]

By maintaining the gap between the opening edge of the drilling hood and the water bottom at a predetermined distance, a strong horizontal water flow is generated from the opening edge of the drilling hood to directly below the central air lift pipe, and Since the high-pressure water jetted from the nozzle of the drilling hood toward the bottom of the water excavates the sediment,
Extensive sediment around the drilling hood is excavated in the form of being crushed to a deep part of the layer thickness, transferred to the position just below the air lift pipe by the water flow and sucked up by the air lift pipe, the movement frequency of the air lift pipe decreases, Efficient dredging work is performed.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration explanatory view showing an example of a dredging device used in the airlift type dredging method of the present invention, in which an airlift device 2 is mounted on a barge 1 constituted by a floating body.
The air lift device 2 includes an air lift pipe 3, a crane device 4 that vertically hangs the air lift pipe 3, an air compressor 5 that supplies compressed air to the air lift pipe 3, and a suction device in the middle of the air lift pipe 3 from the air compressor 5. It is composed of a pressure tube 6 connected to the mouth 7.

An excavation hood 10 as shown in FIGS. 2 and 3 is directly connected to the lower end of the air lift pipe 3. Nozzles 11 for injecting high-pressure water are attached to a plurality of locations at the opening edge of the drilling hood 10, and a water supply pipe 13 is connected to the nozzles 11 from a high-pressure water generator 12 installed on the ship 1. .
The size (diameter) of the opening edge of the drilling hood 10 is set to be several times larger than the diameter of the air lift pipe 3. In this embodiment, the shape of the drilling hood 10 is a truncated cone, but it may be a truncated pyramid. The other end of the air lift pipe 3 is connected to a draining device 21 installed on the pier 1,
A draining device 21 and a conveyor line 22 are arranged through a sieving device 23 to a storage place 24. Further, a pump 25 for discharging the sludge discharged from the drainer 21 is installed on the pontoon 1, and a mud pipe 27 is laid from the pump 25 to the settling tank 26. 14
Is the bottom of the reservoir, 15 is the dam body, and 16 is the sediment deposited on the reservoir.

When performing the dredging work, the crane device 4 raises and lowers the air lift pipe 3 to hold the opening edge of the excavation hood 10 and the water bottom 14 at a predetermined distance, and the air compressor 5 lifts the air lift pipe 3 from the air lift pipe 3. The compressed air is sent to the blow-in port 7 of. Due to the compressed air blown from the middle of the air lift pipe 3, the average specific gravity inside the air lift pipe 3 from the blow-in port 7 to the water surface becomes smaller than the specific gravity of the water outside the pipe, and due to the difference in specific gravity, the inside of the pipe near the blow-in port 7 A large negative pressure is generated. Due to this negative pressure, an upflow is generated in the air rephoto tube 3, and the water flow can suck up the earth and sand 16 from the water bottom 14. The flow state in the air lift pipe 3 becomes a solid-liquid two-phase flow of earth and sand and water below the blow-in port 7, and a gas-liquid solid three-phase flow to which air is further added above.
In the solid-liquid two-phase flow part, 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 the gas-solid three-phase flow part, the average flow velocity increases as it approaches the water surface, Since air is present, the liquid specific gravity is smaller than in the solid-liquid two-phase flow section, and the pipe friction loss is also smaller. Air lift device 2
Operates with a balance between these resistances and buoyancy.

In order to horizontally move the sediment 16 accumulated on the water bottom 14 by the air lift device 2 from the opening edge portion of the excavation hood 10 to just below the central air lift pipe 3 and vertically suck it up and convey it, the opening edge of the excavation hood 10 is to be conveyed. Flow velocity V in the section is approximately 3 m
Must be / sec or higher. The flow velocity V is set such that the distance between the opening edge of the truncated cone-shaped drilling hood 10 having the outer diameter D and the water bottom 14 is h. It is represented by. Here, Q is the amount of upward flow of water due to the air lift. Therefore, if the interval h is set so that V = 3 m / sec, the diameter is smaller than that of the air lift pipe 3 having the diameter d alone.
A wide range of D / d times wide soil 16 can be horizontally moved and sucked up.

In addition, high-pressure water is sent from the high-pressure water generator 12 on the pontoon 1 to the nozzle 11 provided on the excavation hood 10 through the water pipe 13 and jetted toward the water bottom 14 to excavate the sediment 16 and improve the dredging capability. . When the excavation hood 10 is rotated or rotated by an angle of π / nozzle or more, the excavation amount can be further increased and the dredging capability can be improved.

If the distance h between the bottom of the drilling hood 10 and the water bottom 14 cannot be maintained due to the magnitude of the negative pressure in the drilling hood 10, an opening is provided in the drilling hood 10 to open or close it, or a high-pressure water jet thrust from the nozzle 11 is provided. To maintain a predetermined interval. Drilling hood 10
Can also be relocated by this thrust.

The slurry made up of the sand 16 and water sucked up in the air lift pipe 3 by the air lift device 2 is separated into the sand and water by the draining device 21, and is transferred to the storage place 24 via the conveyor line 22 and the sieving equipment 23. Sent and deposited. On the other hand, the drained muddy water is discharged by a pump 25 to a sedimentation basin 26 via a mud pipe 27, and after sedimenting mud, the supernatant water is discharged into or out of the dam.

〔The invention's effect〕

According to the present invention, the compressed air is supplied to the air lift pipe while maintaining a predetermined interval between the opening edge of the excavation hood directly connected to the lower end of the air lift pipe and the water bottom. In addition to generating a strong horizontal water flow toward the bottom of the excavation hood, the high-pressure water sprayed from the nozzle provided on the excavation hood to the bottom of the excavation excavates the sediment around the excavation hood, so even if the sediment layer is thick In addition to being dug up to the ground, even hardened soil that has been hardened for a long period of time will be finely crushed and can be transported by a water flow, and suctioned by an air lift pipe for a wide range of deposited sand in the horizontal and depth directions. Since it is possible, the frequency of movement of the air lift pipe will be significantly reduced, and it will be applied regardless of the sedimentation period of soil and the degree of hardening. Bets can be, the effect is obtained that the dredging efficiency is greatly improved.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of an air lift type dredging device used in the present invention, FIG. 2 is an enlarged sectional view of an excavation hood portion, and FIG. 3 is a plan view of the excavation hood portion. In the figure, 1 is a ship, 2 is an air lift device, 3 is an air lift pipe, 10 is an excavation hood, 11 is a nozzle, 12 is a high-pressure water generator, 14 is the bottom of a reservoir lake, and 16 is sediment.

Continuation of the front page (56) References JP-A-54-139256 (JP, A) Actually opened 61-80845 (JP, U) Actually opened 36-1164 (JP, Y1)

Claims (1)

(57) [Claims] 1. An air lift pipe suspended vertically from a barge, and a nozzle at an opening edge portion having a size that is a predetermined multiple of the diameter of the air lift pipe, and at the lower end of the air lift pipe. Using a dredging device with a directly connected drilling hood, the opening edge of the drilling hood is held at a predetermined interval with respect to the water bottom to suspend an air lift pipe, and while supplying compressed air to the air lift pipe, An air-lift dredging method characterized by injecting high-pressure water from the nozzle of the drilling hood toward the bottom of the water.