JP2021177053A - Dredging device, dredging system, and dredging method - Google Patents

Abstract

To provide a dredging device, a dredging system and a dredging method which can achieve efficient dredging without blocking a pump and a pipe when dredging sediment using the pump.SOLUTION: A dredging device 700 has an underwater work machine 300 having an attachment 100 for dredging mounted on the tip of an arm, and a controller 600. An attachment 300 for dredging has a pump 30, a suction pipe 40 and a transport pipe 35 communicating with the pump 30, a screen 60 surrounding a suction port of the suction pipe 40 and having a plurality of openings 65 and a cutting bit 64, and an actuator 50 rotating the screen 60. Change control of the number of rotations of the actuator 50 is executed by the controller 600.SELECTED DRAWING: Figure 1

Description

The present invention relates to a dredging device, a dredging system, and a dredging method.

In a reservoir such as a dam lake, the sediment that has flowed in together with rainwater, river water, etc. accumulates on the bottom of the lake, and the sediment may accumulate on the bottom of the lake, which may reduce the reservoir performance of the reservoir. Therefore, in dam lakes and the like, sediment (sediment) deposited on the bottom of the lake is removed by various methods.
Examples of the method for removing the sediment include onshore excavation and dredging. In onshore excavation, it is necessary to lower the reservoir level of the reservoir when excavating sediment, so it is necessary to limit the operation of the dam. In addition, there is a problem that the excavation range is limited to the upstream area of the reservoir.
On the other hand, methods of dredging from the water include grab dredging and pump dredging. Foreign substances such as giant gravel, drifting trees, sunken trees, and dust are generally mixed in the sediment deposited on the bottom of the lake. Since the maintenance for removing is unavoidable, the efficiency of sediment removal may be significantly reduced. Therefore, when dredging using a pump, it is preferable to separate sediment and foreign matter as a pre-process, but it is practically impossible to separate sediment and foreign matter in water.

Here, when excavating the excavated soil excavated from the bottom of the water by the excavation means, it is possible to prevent impurities such as branches and stones contained in the excavated earth and sand from being clogged in the excavation means. A dredging device capable of efficiently dredging earth and sand has been proposed. Specifically, a cutter for excavating earth and sand on the bottom of the water, a tubular body provided above the cutter, and a chamber formed between the cutter and the partition wall blocking the bottom of the tubular body. It is a dredging device provided with an earth removal means for discharging excavated earth and sand taken into a chamber through an opening provided in a cutter by a sand pump (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-214263

According to the dredging device described in Patent Document 1, when dredging the sediment accumulated on the bottom of the lake with a pump, there is a problem that foreign substances such as boulder, driftwood, sunken trees, and dust that may exist in the sediment block the pump and piping. Can be resolved.
By the way, as a cause of the clogging of the pump and the pipe, in addition to the above-mentioned foreign matter, the sucked muddy water has a high sediment concentration. In order to prevent such suction of muddy water with a high concentration of earth and sand, a method of adjusting the amount of muddy water sucked by a pump by operating, or a collar is provided at the tip rotating part of the dredging attachment to penetrate the dredging attachment into the sediment. There is a way to limit the amount. However, with the operating method, the suction of sediment becomes intermittent, and with the method of limiting the amount of penetration of the dredging attachment into the sediment, the pumping capacity is limited, and the dredging efficiency is reduced by either method. There is a risk of Furthermore, when applying a dredging attachment for deep dredging, the reduction in dredging efficiency can be even more pronounced with the operating method.
Therefore, in addition to being able to eliminate the blockage of the pump and piping due to foreign matter that may exist in the sediment, for example, a dredging device and a dredging system and a dredging method that can eliminate the blockage of the pump and piping due to muddy water having a high sediment concentration. Development is desired.

An object of the present invention is to provide a dredging device, a dredging system, and a dredging method capable of realizing efficient dredging without obstructing a pump or a pipe when dredging sediment using a pump. There is.

In order to achieve the above object, one aspect of the dredging device according to the present invention is
An underwater work machine with a dredging attachment attached to the tip of the arm,
With a controller,
The dredging attachment is
With a pump
A suction pipe and a transport pipe communicating with the pump,
A screen that surrounds the suction port of the suction tube and has a plurality of openings and cutting bits.
It has an actuator that rotates the screen.
The controller executes control of changing the rotation speed of the actuator.

According to this aspect, according to the change control of the rotation speed of the actuator, the change control of the rotation speed of the screen surrounding the suction port of the suction pipe is executed, for example, by lowering the rotation speed of the screen, the sediment concentration is reduced. It can be lowered to suppress pipe blockage. In this action, while the suction amount by the pump is constant, the amount of earth and sand to be cut decreases due to the decrease in the rotation speed of the screen, and the amount of earth and sand sucked into the suction pipe through the opening decreases. This is due to the decrease in sediment concentration. Therefore, the sediment concentration, the sediment amount (sand flow rate), etc. are measured in the suction pipe and the transport pipe, and when the sediment concentration, etc. is too high, the change control for lowering the rotation speed of the actuator is executed based on the measurement result. This makes it possible to suppress blockage of the suction pipe, the transport pipe, and the pump.
In addition, since a screen having a plurality of openings is arranged so as to surround the suction port of the suction tube, foreign substances such as boulders, driftwood, sunken trees, and dust are less likely to be taken into the screen, and suction is performed. It also eliminates the blockage of pipes and pumps by these foreign substances.
Furthermore, since the screen equipped with the cutting bit is rotated by the actuator, when foreign matter approaches the opening of the screen due to the suction force of the pump, the cutting bit can repel or crush the foreign matter. The effect of preventing blockage of the suction pipe and the like is further enhanced.

Examples of the underwater work machine constituting the dredging device of this embodiment include a work machine that runs on the bottom of a lake, a work machine that moves up and down along a shaft hanging from a pontoon, and a work machine that is suspended from a pontoon by a wire. , Various forms of underwater work equipment can be mentioned.
Further, the "soil concentration" is, for example, a volumetric sediment concentration obtained from the volume of the soil particle portion of the soil and the volume of the water (muddy water) mixed with the soil. For the sediment concentration that blocks the pump and suction pipe, perform a test construction using the pump and suction pipe that is actually applied prior to the implementation work, and specify in advance the sediment concentration that can block the pump and suction pipe. , It is desirable to specify the size of the water supply port that can be adjusted to less than this sediment concentration. For example, when the sediment concentration that blocks the suction pipe or the like is specified to be about 20% by this test construction, the target sediment concentration is set to about 15% or 10%, and water is supplied so as to satisfy this target sediment concentration. The size (caliber) of the mouth can be set. In addition, it is preferable to set the diameter of the suction pipe, the opening of the screen (screen opening), etc. in consideration of the suction efficiency of dredged earth and sand, the non-blocking property of foreign substances, and the like.

Further, in another aspect of the dredging device according to the present invention, at least one of a sand lifting flow meter, a sediment concentration meter, and a pressure gauge is attached to the suction pipe and the transport pipe.
A load ammeter is attached to the pump.
The controller has a receiving unit, a storage unit, a comparison calculation unit, and a control unit.
The receiving unit receives measurement data measured by at least one of the sand lifting flow meter, the earth and sand concentration meter, the pressure meter, and the load ammeter.
The storage unit stores at least one of a sand flow threshold, a sediment concentration threshold, a pressure threshold, a dredging amount threshold of a dredging amount specified by the sand flow and the sediment concentration, and a load current threshold.
The comparison calculation unit compares the measurement data with the threshold value associated with the measurement data.
When the measurement data exceeds the related threshold value, the control unit executes control to reduce the rotation speed of the actuator.

According to this aspect, the sand flow rate, the sediment concentration, and the pressure are measured in at least one of the suction pipe and the transport pipe, or the load current is measured in the pump, and one of the measurement data and the preset data are set in advance. By executing the control of lowering the rotation speed of the actuator in comparison with the set threshold value, it is possible to suppress the blockage of the suction pipe or the like based on various indexes. In addition, all the instruments such as the sand flow meter, the sediment concentration meter, and the pressure gauge are attached to either or both of the suction pipe and the transport pipe, and all the instruments including the load current meter attached to the pump. The measurement data is received from, and in the comparison calculation unit, all the measurement data are stored in the storage unit, and the dredging amount specified by the sediment flow rate threshold, the sediment concentration threshold, the pressure threshold, the sediment flow rate and the sediment concentration. It may be compared with the dredging amount threshold and the load current threshold of. In this case, control to reduce the rotation speed of the actuator may be executed when even one element exceeds the threshold value (control on the safe side), for example, the rotation speed is maintained if all the elements do not exceed the threshold value. Such control may be executed (control on the dangerous side), and there are various forms of control of the rotation speed of the actuator using a plurality of measurement data.

Further, in another aspect of the dredging device according to the present invention, the screen is
A plurality of annular cross members arranged at intervals in the vertical direction,
It exhibits a substantially hemispherical shape having a plurality of U-shaped vertical members arranged at intervals in the circumferential direction of the plurality of annular cross members and connected to each annular cross member, and the plurality of annular cross members. And the plurality of the vertical members intersect in a grid pattern to form the plurality of the openings.
An inclined plate material whose lower end is inclined in the rotation direction of the screen is connected to the plurality of annular cross members, and among the inclined plate materials, a plurality of cutting bits are attached to the end faces on the front side in the rotation direction of the screen. Ori,
The plan view shape of the screen is circular, and in the plan view of the screen, the end face on the front side in the rotation direction of the inclined plate material is located radially outward from the tangential direction of the circle.

According to this aspect, an inclined plate material whose lower end is inclined in the rotation direction of the screen is provided, and in the plan view of the screen, the end surface (the end surface to which a plurality of cutting bits are attached) on the front side in the rotation direction of the inclined plate material is said to be circular. Since it is located radially outward from the tangential direction of (it is inclined at a rake angle θ with respect to the tangential direction), a dredging device having excellent cutting performance is formed.

Further, in another aspect of the dredging device according to the present invention, the dredging attachment further includes a water supply port at an intermediate position of the suction pipe.
By the operation of the pump, the dredged earth and sand are taken into the suction pipe through the opening of the screen, and the fresh water is taken into the suction pipe through the water supply port, and both the fresh water and the dredged earth and sand are said to be said. It is characterized in that it is sucked into the pump through the suction pipe and transported through the transport pipe.

According to this aspect, since the water supply port is provided in the middle of the suction pipe, when the pump is operated, the dredged earth and sand are taken into the suction pipe through the opening of the screen, and the dredged earth and sand are taken into the suction pipe through the water supply port. Fresh water is taken into the suction pipe, and both the fresh water and the dredged earth and sand are sucked into the pump through the suction pipe, so that the concentration of the dredged earth and sand in the sucked muddy water can be reduced by the fresh water. As a result, it is possible to eliminate the blockage of the pump and the pipe due to the muddy water having a high sediment concentration.
Further, a water supply pipe having an appropriate length may be attached to the water supply port. In addition, a straight pipe or a unit pipe of a straight pipe and a vent pipe can be applied to the suction pipe, and the position where the water supply port is opened in the suction pipe is also the position where the sediment sprinkled during the suction of sediment does not enter the water supply port. It is desirable to set it (a position away from the suction port). Further, the fresh water provided to the suction pipe through the water supply port includes tap water, rainwater, purified water and the like supplied from the ground in addition to lake water.

Further, another aspect of the dredging device according to the present invention is that the suction pipe is a double pipe including an outer pipe and an inner pipe.
The fresh water supplied to the suction pipe through the water supply port flows through the outer flow path between the outer pipe and the inner pipe, goes around the suction port of the inner pipe, and flows inside the inner pipe. It is characterized in that it is introduced into the road and sucked by the pump together with the dredged earth and sand taken into the inner flow path.

According to this aspect, the fresh water supplied through the water supply port flows through the outer flow path of the suction tube composed of the double pipe to the suction port side, goes around the suction port of the inner pipe, and is inside the inner pipe. By being introduced into the flow path, both the dredged earth and sand and the fresh water can be sucked from the suction port of the inner pipe, and the sediment concentration of the drenched earth and sand due to the fresh water can be reduced more effectively. When the suction pipe is made of a single pipe, it is not possible to reduce the sediment concentration by fresh water in the process from the suction port of the suction pipe to the water supply port of fresh water, but when the suction pipe is made of a double pipe, it is inside. This is because it is possible to reduce the sediment concentration by fresh water from the suction port of the pipe.

Here, it is desirable that the suction port of the inner tube is located downstream of the suction port of the outer tube in the suction direction. According to this form, since the suction port of the inner pipe is located downstream of the suction port of the outer pipe in the suction direction, fresh water flows through the outer flow path of the suction pipe made of a double pipe and is inside. When it goes around the suction port of the pipe and is introduced into the inner flow path inside the inner pipe, it suppresses the fresh water that flows out without being introduced into the inner flow path, and effectively introduces the fresh water into the inner flow path. can do. The "downstream side in the suction direction" means the pump side to which the suction pipe is attached. The level difference between the suction port of the outer tube and the suction port of the inner tube (the distance from the suction port of the outer tube to the suction port of the inner tube that has entered the inside) also consists of the pump and double tube that are actually applied. It is desirable to carry out a test construction using a suction pipe to effectively identify the level difference at which fresh water is introduced into the inner flow path.

Further, it is desirable that a shielding member for shielding the flow of fresh water in the outer flow path is provided at a position downstream of the water supply port in the outer flow path in the suction direction. According to this form, since the shielding member is provided at a position downstream of the water supply port in the outer flow path in the suction direction, a part of the fresh water supplied to the outer flow path through the water supply port is inside. It is possible to eliminate the fact that the pipe flows to the side opposite to the suction port side and is not introduced into the inner flow path. For example, in a suction pipe made of a double pipe formed of two steel pipes having different diameters, a donut-shaped shielding member obtained by hollowing out a circle having an outer diameter of the inner pipe from a disk having an inner diameter of the outer pipe can be applied. can.

Moreover, one aspect of the dredging system according to the present invention is
A pontoon with an operation room and
A shaft that is held by the pontoon and extends to the bottom of the lake,
It has the underwater work machine constituting the dredging device, which is attached to the shaft so as to be swivelable and ascendable.
The controller is arranged in the operation chamber, and is characterized in that the turning and raising / lowering of the underwater working machine and the change control of the rotation speed of the actuator are executed.

According to this aspect, the underwater work machine constituting the dredging device is attached to the shaft held by the pontoon and extended to the bottom of the lake so as to be able to rotate and move up and down. Dredging can also be performed on the bottom of the lake at a depth using a dredging device. At this time, since the shaft is stably supported at two points, the pontoon and the bottom of the lake, it is possible to stably dred the sediment with the dredging attachment that accompanies the movement of the arm of the underwater work equipment. It is possible to realize efficient dredging of sediment according to the plan.
In this system, the underwater work equipment can be dredged up to the extension range of the arm while turning around the shaft, and by performing the same dredging while moving the pontoons in sequence, even a wide reservoir etc. is possible. It will be possible to dred the sediment in a short construction period.

Moreover, one aspect of the dredging method according to the present invention is
It is a dredging method that uses an underwater work machine with a dredging attachment attached to the tip of the arm.
The dredging attachment is
With a pump
A suction pipe and a transport pipe communicating with the pump,
A screen that surrounds the suction port of the suction tube and has a plurality of openings and cutting bits.
It has an actuator that rotates the screen and
It is characterized in that dredging is performed while adjusting the rotation speed of the actuator so as not to cause obstruction of at least one of the suction pipe and the transport pipe.

According to this aspect, the sediment concentration is reduced by executing the control of changing the rotation speed of the screen surrounding the suction port of the suction pipe according to the change control of the rotation speed of the actuator, for example, by lowering the rotation speed of the screen. It can be lowered to suppress blockage of pipes and pumps.

According to the dredging device, the dredging system, and the dredging method of the present invention, when dredging the sediment using a pump, efficient dredging can be realized without blocking the piping and the pump.

It is an overall block diagram which shows an example of the dredging apparatus and the dredging system which concerns on embodiment. FIG. 5 is an enlarged side view showing a state in which the dredging device according to the embodiment is attached to the shaft so as to be able to move up and down and to be swiveled. It is a figure which shows an example of the hardware composition of the controller in an operation room together with peripheral devices. It is a figure which shows an example of the functional structure of the controller in an operation room. It is a side view of an example of the dredging attachment constituting the dredging apparatus, and is the figure which showed by breaking a part so that the inside can be visually recognized. It is the VI direction arrow view of FIG. 5, and is the front view of an example of the dredging attachment. FIG. 5 is a view taken along the line VII-VII of FIG. 5, which explains the extending direction of the inclined plate material attached to the screen. It is a vertical cross-sectional view of an example of a suction pipe, and is a figure which shows the state which sucks sediment and is supplied with fresh water. It is a view of arrow VIII-VIII of FIG.

Hereinafter, an example of the dredging device, the dredging system, and the dredging method according to the embodiment will be described with reference to the attached drawings. In the present specification and the drawings, substantially the same components may be designated by the same reference numerals to omit duplicate explanations.

[Dredging device and dredging system according to the embodiment, and dredging method]
<Dredging device and dredging system>
First, an example of the dredging device and the dredging system according to the embodiment will be described with reference to FIGS. 1 to 4. Here, FIG. 1 is an overall configuration diagram showing an example of the dredging device and the dredging system according to the embodiment, and FIG. 2 shows the dredging device according to the embodiment attached to the shaft so as to be able to move up and down and to be swivelable. It is a side view which shows the state in an enlarged manner. Further, FIG. 3 is a diagram showing an example of the hardware configuration of the controller in the operation room together with peripheral devices, and FIG. 4 is a diagram showing an example of the functional configuration of the controller in the operation room. If necessary, refer to FIG. FIG. 5 is a side view of an example of a dredging attachment constituting the dredging device, and is a view showing a part of the attachment so that the inside can be visually recognized.

The dredging system 800 is a system for dredging sediment SE accumulated by flowing sediment together with rainwater, river water, etc. in the dam lake DL by using a pump. The dredging system 800 is attached to a pontoon 400 equipped with an operation chamber 550, a shaft 200 held by the pontoon 400 and extending to the bottom of the lake, and a shaft 200 that can be swiveled and moved up and down. It has an underwater working machine 300 and a dredging attachment 100 attached to the tip of an arm 340 included in the underwater working machine 300. The underwater work machine 300 may be mounted on the shaft 200 so as to be rotatable and ascending / descending as shown in the illustrated example, or may be mounted on the bottom of the water or on land, for example.

Further, the dredging device 700 is formed by the underwater work machine 300 provided with the dredging attachment 100 and the controller 600 (operation panel) provided inside the operation room 550. As shown in FIG. 5, the dredging attachment 100 surrounds the pump 30, the suction pipe 40 and the transport pipe 35 communicating with the pump 30, and the suction port of the suction pipe 40, and has a plurality of openings 65 and cutting bits 64. It has a screen 60 provided and an actuator 50 for rotating the screen 60.

Returning to FIG. 1, the pontoon 400 is configured by arranging hollow rectangular parallelepiped floating blocks in parallel to form a substantially rectangular shape in a plan view. The operation room 550 is mounted. Further, a cove 410 for inserting a shaft is provided in a part of the pontoon 400, and a shaft fixing turret 500 is installed so as to surround the cove 410 in a U-shape in a plan view. The shaft fixing turret 500 is provided with an upper and lower keeper and a shaft fixing pin (neither shown), and holds the shaft 200 suspended by the crawler crane 540 mounted on the pontoon 400 with the fixing pin. At the same time, the extension shaft 201 is sequentially added and removed.

The pontoon 400 is towed by a towing vessel (not shown) or travels by driving a traveling propeller (not shown) equipped on the pontoon 400. Further, the dredging system 800 of the illustrated example is mainly composed of a screen on which the dredging attachment 100 rotates and a pump for sucking sediment, but a bucket, a twin header, a ripper, an underwater breaker, a dresser, an ejector, and an air. Other types of attachments, such as drifters, may be applied and a usable attachment may be mounted on the pontoon 400.

The shaft 200 is configured by connecting a plurality of steel pipes, and as shown in FIG. 2, an underwater auger 203 is provided near the tip of the shaft 200 so that the casing at the tip is fixed to the bottom of the lake by the underwater auger 203. It has become. That is, when the sediment SE on the bottom of the lake is dredged, the upper end of the shaft 200 is fixed by the shaft fixing turret 500, and the lower end thereof is fixed to the bottom of the lake, so that the shaft 200 is stably supported at two points.

As shown in FIG. 2, a plurality of racks 202 are attached around the shaft 200 so that the underwater work machine 300 can move up and down in the X1 direction.

The underwater work machine 300 has an elevating mechanism 310 internally provided with a pinion (not shown) that engages with each rack 202 included in the shaft 200, and a swivel that is rotatably provided in the X2 direction around the elevating mechanism 310. A mechanism 320 is provided, and the swivel mechanism 320 constitutes a working machine main body.

A boom 330 is rotatably attached to the work machine main body 320, an arm 340 is attached to the tip of the boom 330, the work machine main body 320 and the boom 330 are connected by a hydraulic cylinder mechanism 350A, and the boom 330 and the arm are connected. The 340 is connected by a separate hydraulic cylinder mechanism 350B. Further, a dredging attachment 100 is attached to the tip of the arm 340, and the arm 340 and the dredging attachment 100 are further connected by a separate hydraulic cylinder mechanism 350C.

The electric power cable 511 extending from the generator 510 on the pontoon 400 is electrically connected to the working machine main body 320, and the underwater working machine 300 is lifted and swiveled, and the hydraulic cylinder mechanisms 350A, 350B, and 350C are slidable. The electric power required for driving the pumps and actuators constituting the dredging attachment 100 is supplied.

The work machine main body 320 turns around the shaft 200 by a predetermined angle and stops, and the boom 330 and the arm 340 are sequentially extended and dredged by the dredging attachment 100, which is repeated over the entire circumference of the shaft 200. , Dredging in the extension range of the boom 330 and the arm 340 is possible in all directions around the shaft 200.

An attachment 100 for dredging is attached to the tip of the arm 340. The dredging attachment 100 includes a transport pipe 35 for transporting the dredged sediment SE. Inside the transport pipe 35, a sand lifting flow meter 36, a soil concentration meter 37, and a pressure meter 38 are provided. Further, the pump 30 provided in the dredging attachment 100 is provided with a load ammeter 31. At least one or two of the sand flow meter 36, the sediment concentration meter 37, and the pressure gauge 38 may be provided, and the sand lift meter 36, the sediment concentration meter 37, and the pressure gauge 38 suck. It may be provided inside the pipe 40.

When the dredged sediment SE flows through the transport pipe 35, the sand pumping flow meter 36, the sediment concentration meter 37, the pressure meter 38, and the load ammeter 31 measure the corresponding physical quantities and are measured by each instrument. The measured data is transmitted to the controller 600 equipped in the operation room 550 at any time. The controller 600 configured by a computer compares each received measurement data with a threshold value for each physical quantity stored inside the controller 600, and controls the rotation speed of the actuator 50 that rotates the screen 60 as necessary ( Control to reduce the number of revolutions) is executed. The details of this control will be described below.

After the dredging of the sediment SE around the fixed shaft 200 is completed, the pontoon 400 is moved and the shaft 200 is similarly suspended and fixed to the bottom of the lake, and the dredging by the underwater work machine 300 and the dredging attachment 100 is the same. By repeating the movement of the pontoon 400 and the dredging of the sediment SE in sequence, the sediment SE deposited on the bottom of the dam lake DL can be dredged.

As shown in FIG. 1, for example, a temporary storage pit 560 is provided at one corner of the bottom of the dam lake DL, and the tip of the transport pipe 35 extending from the dredging attachment 100 is fixed to the temporary storage pit 560. , The sediment SE that has been dredged by the dredging attachment 100 is transported to the temporary storage pit 560. Instead of transporting the dredged sediment SE to the temporary storage pit 560, it may be transported to a mud drainage pit provided on the water or on the ground.

Further, the boom 330 and the arm 340 are equipped with an angle meter (not shown), and the angle data measured by each angle meter is transmitted to the controller 600 in the operation room 550. In addition, the top position of the shaft 200 is measured by GPS (Global Positioning System) or a total station, and transmitted to the controller 600 together with the measurement data from the tilt meter and rotary encoder (neither shown) attached to the shaft 200. It is supposed to be done. Then, from each angle data and each measurement data received by the controller 600, the tip position (attachment position of the dredging attachment 100) of the arm 340 of the underwater work machine 300 can be accurately grasped, and the dredging attachment 100 can be accurately grasped. It is possible to carry out dredging work without omission while specifying the position of each time.

Further, the underwater work machine 300 is equipped with a multi-fan beam and an ultrasonic underwater camera (neither of them is shown), and the multi-fan beam transmits three-dimensional data of the lake bottom to the controller 600 in the operation room 550. , A three-dimensional image of the lake bottom is displayed on the monitor screen of the controller 600. In addition, the image data of the lake bottom by the ultrasonic underwater camera is also transmitted to the controller 600 in the operation room 550, the dark lake bottom is visualized on the monitor screen of the controller 600, and the operator of the underwater work machine 300 can operate. The underwater work machine 300 and the dredging attachment 100 can be remotely controlled while looking at the monitor screen.

Next, an example of the hardware configuration and the functional configuration of the controller 600 in the operation room 550 will be described with reference to FIGS. 3 and 4.

As shown in FIG. 3, the controller 600 includes a CPU (Central Processing Unit) 611, a RAM (Random Access Memory) 612, a ROM (Read Only Memory) 613, an HDD (Hard Disc Drive) 614, and an NVRAM (Non-Volatile RAM). ) 615 and the like, and they are connected by a system bus so that data communication is possible.

The ROM 613 stores various programs and data used by the programs. The RAM 612 is used as a storage area for loading the program stored in the ROM 613 and as a work area of the loaded program. The CPU 611 realizes various functions by processing the program loaded in the RAM 612. For example, the suction control of the pump 30 is executed according to the optimum pump suction amount stored, and the rotation speed of the screen 60 (the rotation speed at which the sediment SE can be effectively taken into the suction pipe) is adjusted. The rotation control of the actuator 50 is executed. The HDD 614 stores a program and various data used by the program. Various setting information and the like are stored in the NVRAM 615.

When the operator operates various operation levers and the like in the operation room, the controller 600 controls the operation of various devices (hardware) constituting the underwater work machine 300 and the dredging attachment 100. That is, the elevating drive of the elevating mechanism 310 of the underwater work machine 300, the swivel drive of the swivel mechanism 320 of the submersible work machine 300, the sliding drive of the hydraulic cylinder mechanisms 350A, 350B, 350C of the submersible work machine 300, and the dredging attachment 100. The rotational drive of the actuator 50 that rotates the screen 60, the suction drive of the pump 30 of the dredging attachment 100, and the like are controlled.

Further, when the sediment SE dredged by the dredging attachment 100 flows through the transport pipe 35, it was measured by a sand lifting flow meter 36, a sediment concentration meter 37, a pressure gauge 38, and a load ammeter 31. Each measurement data is transmitted to the controller 600 at any time.

As shown in FIG. 4, the controller 600 includes a receiving unit 602, a storage unit 608, a comparison calculation unit 604, and a control unit 606.

The receiving unit 602 receives the measurement data measured by the sand lifting flow meter 36, the earth and sand concentration meter 37, the pressure meter 38, and the load ammeter 31, and stores the measurement data in the storage unit 608 at any time.

The storage unit 608 stores a sand flow threshold, a sediment concentration threshold, a pressure threshold, a dredging amount threshold of the dredging amount specified by the sand flow and the sediment concentration, and a load current threshold. These various threshold values are tested and constructed in advance of the actual work, and various physical quantities when the suction pipe 40, the transport pipe 35, and the pump 30 are blocked are specified in this test construction, and the specified physical quantities are determined. It is stored in the storage unit 608 as a threshold value. The method for specifying the dredging amount (m ³ / h) described above is as follows. For example, when the sand flow rate is 10 (m ³ / min) and the sediment concentration is 10 (%), the volume of dredged sediment is 10 (m ³ / min) x 60 (minutes / hour) x 0.1 (10). (%)) = 60 (m ³ / hour). Assuming that the void ratio of the dredged earth and sand is 40%, the dredged amount (m ³ / h) can be specified as ^{60 (m 3} / hour) ÷ 0.6 = 100 (m ^{3 / hour).}

The comparison calculation unit 604 compares various measurement data with the associated threshold value. Then, when the measurement data exceeds the related threshold value as a result of the calculation in the comparison calculation unit 604, the control unit 606 executes a control for lowering the rotation speed of the actuator 50.

Here, the comparison calculation unit 604 executes a comparison calculation between various measurement data, the specified dredging amount, and the threshold value associated with each of them. At this time, when even one element exceeds the threshold value, A control for lowering the rotation speed of the actuator 50 may be executed, or for example, a control for maintaining the rotation speed may be executed if all the elements do not exceed the threshold value, and these settings are set by the administrator. At discretion. For example, when executing control to reduce the rotation speed of the actuator 50 when even one element exceeds the threshold value, this content is set in the storage unit 608, and the control unit 606 sets the actuator 50 based on the set content. Executes the change control of the rotation speed of.

For example, when the control for lowering the rotation speed of the actuator 50 is executed, the amount of earth and sand sucked by the pump 30 is constant, whereas the amount of earth and sand to be cut decreases due to the decrease in the rotation speed of the screen 60. As a result, the amount of sediment that is sucked into the suction pipe 40 through the opening 65 and transported through the transport pipe 35 is reduced, and the sediment concentration is reduced. By reducing the sediment concentration, it is possible to suppress blockage of the suction pipe 40, the transport pipe 35, and the pump 30.

As described above, the dredging method according to the embodiment is a method including a step of dredging while adjusting the rotation speed of the actuator 50 so as not to cause blockage of at least one of the suction pipe 40 and the transport pipe 35. ..

<Attachment for dredging>
Next, an example of the dredging attachment constituting the dredging device according to the embodiment will be described with reference to FIGS. 5 to 9. Here, FIG. 5 is a side view of an example of the dredging attachment constituting the dredging device, and is a view in which a part of the attachment is broken so that the inside can be visually recognized. Further, FIG. 6 is a view taken along the VI direction of FIG. 5, which is a front view of an example of the dredging attachment, and FIG. 7 is a view taken along the line VII-VII of FIG. 5, which is attached to the screen. It is a figure explaining the extension direction of the inclined plate material. Further, FIG. 8 is a vertical cross-sectional view of an example of a suction pipe, showing a state in which sediment is sucked and fresh water is supplied, and FIG. 9 is a view taken along the line VIII-VIII of FIG. It is a figure.

The dredging attachment 100 includes an attachment body 10, a pump 30 (dredging pump) arranged inside the attachment body 10, and a suction pipe 40 attached to the pump 30 at the lower end of the pump 30 so as to be able to communicate with each other. It has a screen 60 rotatably attached at the lower end of the attachment body 10, an actuator 50 that rotates the screen 60, and a transport pipe 35 that communicates with the pump 30.

The attachment main body 10 is a pair of left and right side plates 11, a horizontal plate 12 horizontally laid on the front and rear of the lower portion of the side plate 11, and a square cylindrical frame member fixed to the lower ends of the side plate 11 and the horizontal plate 12. 13 and all the constituent members are formed of a steel plate, a hard resin plate, or the like.

The side plate 11 has a side surface shape that is bent in the middle, and at the upper end thereof, a mounting plate 20 provided with rotating shafts 21 and 22 that are rotatably attached to the tip of the arm 340 of the underwater work machine 300. Is fixed.

The sediment SE sucked by the pump 30 is transported to the outside of the pump via the transport pipe 35. Further, the suction pipe 40 attached to the lower end of the pump 30 is a unit pipe of a straight steel pipe and a vent pipe, and the lower end of the suction pipe 40 protrudes below the frame member 13 of the attachment main body 10. ing. The suction pipe may be formed only from a straight pipe, or may be formed from a cast iron pipe, a vinyl chloride pipe, or the like other than a steel pipe.

The screen 60 is formed by welding or the like with a plurality of annular cross members 61 arranged at intervals in the vertical direction and at intervals in the circumferential direction of the plurality of annular cross members 61. It has a substantially hemispherical shape with a U-shaped vertical member 62 to be connected. A plurality of openings 65 are formed by intersecting the plurality of annular cross members 61 and the plurality of vertical members 62 in a grid pattern. The U-shaped vertical member 62 of the illustrated example is connected to the annular cross member 61 in a manner in which the lower portion thereof is inclined in the X3 direction, which is the rotation direction of the screen 60. The screen may have a conical shape, a truncated cone shape, a columnar shape, or the like, in addition to the substantially hemispherical shape. Further, the U-shaped vertical member 62 may be connected to the annular cross member 61 in a vertical manner without being inclined. Further, the vertical member 62 may have a linear or slightly curved substantially linear form in addition to the form shown in the illustrated example which is bent into a U shape.

The annular cross member 61 is formed of an annular flat steel and is arranged so that the wide surface is in the horizontal direction. On the other hand, the U-shaped vertical member 62 is formed of flat steel or a steel rod. By arranging the thick surfaces of the annular cross member 61 and the vertical member 62 made of flat steel so as to face the outer periphery of the screen 60, a desired opening area in each opening 65 is secured.

The shape of the opening 65 is substantially rectangular in the upper and middle stages of the screen 60, and is substantially triangular in the lower stage. The maximum dimension of the opening 65 (the length of the diagonal line of a substantially rectangular shape) is such that the suction pipe 40 and the pump 30 are not blocked by foreign matter (giant gravel, driftwood, sunken wood, dust contained in the sediment SE). The dimensions are set, and can be set to, for example, about 60 mm.

In the screen 60, the inclined plate member 63 whose lower end is inclined in the X3 direction, which is the rotation direction thereof, is connected to the plurality of annular cross members 61 by welding or the like. Here, the inclined plate member 63 may be inclined in a curved shape or may be inclined in a straight line. In this way, a plurality of inclined plate members 63 are attached to the plurality of annular cross members 61 in addition to the plurality of vertical members 62. The inclined plate member 63 is also made of, for example, flat steel, and is processed into a U shape like the vertical member 62. And unlike the vertical member 62, the inclined plate member 63 is arranged so that its wide surface faces the outer periphery of the screen 60.

Among the inclined plate members 63, a plurality of cutting bits 64 are attached to the end faces on the front side in the rotation direction of the screen 60 at intervals in the longitudinal direction of the inclined plate members 63.

Here, as shown in FIG. 7, in the plan view (or cross-sectional view), in the screen 60 having a circular outer shape, the end surface 63a on the front side in the rotation direction is inclined outward in the radial direction from the circular tangential direction (tilt angle). The inclined plate member 63 is attached as described in θ). With this configuration, the machinability by the cutting bit 64 attached to the end face 63a is enhanced.

The dredging of the sediment SE is performed in a state where the screen 60 is rotated around the tip of the suction pipe 40. As a result, when foreign matter such as boulder, driftwood, sunken wood, and dust comes close to the screen 60, the foreign matter can be repelled or crushed by the cutting bit 64, so that the foreign matter can block the opening 65 of the screen 60 or the suction pipe 40. The blockage and further the blockage of the pump 30 are effectively suppressed. In addition, the rotating cutting bit 64 can also cut down the solidified earth and sand at the bottom of the lake.

Further, in the screen 60, an inclined plate member 63 whose lower end is inclined in the X3 direction, which is the rotation direction thereof, is attached, and a plurality of cutting bits 64 are attached to the end surface of the inclined plate material 63 on the front side in the rotation direction of the screen 60. When the screen 60 is inserted into the sediment SE while rotating, the screen 60 comes into contact with the sediment SE in order from the cutting bit 64 located at the lower front in the rotation direction. Therefore, the screen 60 can be inserted into the sedimentation SE with as little load as possible, and the sedimentation SE can be dredged while effectively cutting foreign matter as needed.

Further, since the inclined plate material 63 is arranged so that its wide surface faces the outer periphery of the screen 60, the reaction force acting on the inclined plate material 63 when the plurality of cutting bits 64 cut foreign matter is resisted. , The shear rigidity of the inclined plate member 63 can be ensured (the thickness of the wide surface contributes to the shear rigidity). For example, when the inclined plate member 63 is arranged so that its thick surface faces the outer periphery of the screen 60 like the vertical member 62, the cutting bit 64 is attached to the wide surface of the inclined plate material 63. With respect to the reaction force from the cutting bit 64, the width of the thick surface of the inclined plate member 63 contributes to the shear rigidity, and the shear rigidity is compared with the case where the thickness of the wide surface contributes to the shear rigidity as shown in the illustrated example. Will be low.

The actuator 50 is formed by a motor, and the drive shaft 51 of the motor 50 and the base of the screen 60 are connected by a power transmission belt 52.

As shown in FIG. 5, a water supply port 43 is provided at an intermediate position of the suction pipe 40, and when the pump 30 is operated to suck the sediment SE from the suction port of the suction pipe 40, the water supply port 43 Fresh water such as lake water is sucked from the water, and the sucked fresh water makes it possible to reduce the sediment concentration of the sediment SE. In addition, it may be in the form of supplying purified water or the like as fresh water from the ground or on board.

Here, with reference to FIGS. 8 and 9, the structure of the suction pipe 40 and the reduction of the sediment concentration of the sediment SE sucked will be described.

As shown in FIG. 8, the suction pipe 40 is formed by a double pipe having an outer pipe 41 and an inner pipe 42, and an outer flow path 44 is formed between the outer pipe 41 and the inner pipe 42. An inner flow path 45 is formed inside the pipe 42, and a water supply port 43 is opened at a position in the middle of the outer pipe 41. A water supply pipe having a predetermined length may be connected to the water supply port 43, and the water supply pipe may project from the suction pipe 40.

The inner diameter of the outer pipe 41 is φ1, the inner diameter of the inner pipe is φ2, the inner diameter of the water supply port 43 provided in the outer pipe 41 is φ3, and the distance from the suction port 41a of the outer pipe 41 to the center of the water supply port 43 is t1. Is. Further, the suction port 42a of the inner tube 42 is located in the L direction, which is downstream of the suction port 41a of the outer tube 41 in the suction direction, and the level difference is t2.

The distance t1 from the suction port 41a of the outer pipe 41 to the center of the water supply port 43 is often set to a distance at which the sprinkled sediment SE does not enter the water supply port 43 when sucking the sediment SE. It is better to set it in the test construction that is carried out prior to the construction work. For example, the distance t1 can be set to about 1 m.

When the pump 30 is driven to suck in the Y1 direction, the fresh water supplied in the Y2 direction through the water supply port 43 flows through the outer flow path 44 toward the suction port 41a and the suction port 42a of the inner pipe 42 in the Y3 direction. It wraps around and is introduced into the inner flow path 45. Then, the dredged earth and sand SE sucked from the suction port 42a of the inner pipe 42 into the inner flow path 45 in the Y4 direction mixes with the fresh water, and at this time, the concentration-reduced earth and sand in which the initial sediment concentration of the dredged earth and sand is reduced by the fresh water is produced. The generated sediment with reduced concentration is sucked into the pump 30 in the Y5 direction.

In this way, the fresh water supplied through the water supply port 43 flows through the outer flow path 44 toward the suction port 41a, goes around the suction port 42a of the inner pipe 42, and is introduced into the inner flow path 45. Both the dredged sediment and fresh water can be sucked from the suction port 42a of the inner pipe 42, and the sediment concentration of the dredged sediment due to the fresh water can be effectively reduced. This makes it possible to eliminate the blockage of the pump 30 and the suction pipe 40 due to muddy water having a high sediment concentration.

Further, since the suction port 42a of the inner pipe 42 is located downstream of the suction port 41a of the outer pipe 41 in the suction direction, fresh water flows through the outer flow path 44, and the suction port 42a of the inner pipe 42 is opened. When it wraps around and is introduced into the inner flow path 45, the fresh water that is not introduced into the inner flow path 45 but flows out to the outside is suppressed, and the fresh water supplied to the double pipe 40 is effectively transferred to the inner flow path 45. Can be introduced. Here, since the amount of fresh water flowing out to the outside changes depending on the level difference t2 between the suction port 42a and the suction port 41a, the optimum combination of the suction force by the pump 30 and the level difference t2 is also set by the test construction. good.

Further, as shown in FIG. 8, a shielding member 46 for shielding the flow of fresh water in the outer flow path 44 is provided at a position downstream of the water supply port 43 in the outer flow path 44 in the suction direction. As shown in FIG. 9, the shielding member 46 has a donut-shaped planar shape and completely shields the hollow annular outer flow path 44.

Since the shielding member 46 is attached to the position downstream of the water supply port 43 in the suction direction, the fresh water supplied through the water supply port 43 as shown in FIG. 8 is supplied to the inner flow path in the outer flow path 44. Even if the flow flows to the downstream side in the suction direction opposite to the 45 side, the flow is blocked by the shielding member 46 and flows in the Y6 direction, which is the flow toward the inner flow path 45 side. As a result, the fresh water supplied through the water supply port 43 can be effectively provided to the inner flow path 45.

The inner diameter of the outer pipe 41 is φ1, the inner diameter of the inner pipe is φ2, and the inner diameter of the water supply port 43 is φ3. It is better to set by test construction. For example, if there is no supply of fresh water, the sediment concentration is about 20%, and if there is a risk that the pump 30 or suction pipe 40 will be blocked at this sediment concentration, the target sediment concentration is, for example, about 10%. Therefore, the inner diameters φ1, φ2, and φ3 are set in relation to the suction force of the pump 30.

For example, as the specifications of the pump 30, when the lift is 28 m, the flow rate is 6 m ³ / min, and the maximum size of the opening 65 of the screen 60 is 60 mm, the inner diameter φ1 of the outer pipe 41 is 200 mm, the inner diameter φ2 of the inner pipe is 150 mm, and the water supply port 43. The inner diameter φ3 of is set to 100 mm.

[Demonstration experiment]
<Experimental outline>
The present inventors filled the test water tank with water and sand, dredged using a dredging device simulating the dredging device 700 according to the embodiment, and performed continuous operation of returning to the water tank via a pipe. A flow meter, a sediment concentration meter, a pressure gauge were installed in the piping, and a current sensor was installed in the pump cable to record the sediment flow rate, pressure (lift), sediment concentration, and current value. Based on these values, the performance test of the dredging device and the verification of the operable range were carried out in order to obtain an appropriate screen opening and screen rotation speed (rpm) as a shape that can obtain an average of 10% of the target sediment concentration.

Capability of dredging attachment: Dredging capacity (m ³ / h) = average flow rate (m ³ / min) x 60 (minutes) x average sediment concentration (%) ÷ 100 ÷ 0.6 (porosity 40%) bottom. Further, it is desirable that the pump be operated below the rated current value (105A), and when the pump exceeds the rated current value, 125% (131A) of the rated current value is set as a threshold value and kept within this range.

<Experimental method>
First, test sand is added, filled with water, and dredged in the water tank. Specifically, the test water tank ^{is filled with 80 m 3} of sand and filled with water. Dredging the inside of the test water tank with a backhoe equipped with a dredging attachment for about 5 to 6 minutes by swirling. The opening degree of the tip of the suction pipe of the dredging attachment is adjusted by the opening degree adjusting plate. The number of rotations of the casing is adjusted to an arbitrary number by controlling the amount of oil in the backhoe piping with the control box at the backhoe operation seat.

Next, the piping is measured. For the dredged earth and sand, each item is measured by the measurement pipe via the suction hose 20 m. Here, each item is a pressure (MPa), a flow rate (m ³ / min), a sediment concentration (%), and a current value (A).

Next, it is transported via a pipe to remove sand. Extend the pipe with STK steel pipe beyond the measurement pipe to give an appropriate resistance load to the pump. Based on the known Darcy formula, the first experimental condition was a total pipe length of 120 m as a pipe length that could secure ^{8 (m 3 / h) when sand was lifted.} Next, the pipe was extended and an experiment was conducted with a pipe length of 150 m. The wastewater passing through the steel pipe section returns to the test tank and is continuously circulated. The drainage part is tied up with a backhoe phase number machine to prevent the hose from swaying. In this experiment, the actual head is 0 m because the drainage part is submerged to the water surface.

<Experimental results>
The change in sediment concentration due to the change in the tip opening of the suction pipe and the number of rotations of the screen was determined. First, continuous dredging was performed at each tip opening degree and screen rotation speed at a pipe length of 120 m, and each item was measured. Each data was calculated by the average value of the section where the sediment concentration is stable. When fresh water was sucked under each condition, the flow rate was about 9.5 (m ³ / min), and it was confirmed that the opening degree of the tip of the suction pipe and the rotation speed of the screen did not affect the pump suction performance. .. The experimental results are shown in Table 1 below.

The following was identified as the tendency of measured values when sand was sucked.
(Tendency 1) When the sediment concentration increases, the pressure and current values increase, and the flow rate decreases.
(Tendency 2) As the opening degree of the tip of the suction pipe increases, the sediment concentration increases.
(Tendency 3) As the casing rotation speed (screen rotation speed) increases, the sediment concentration increases.
(Tendency 4) When the sediment concentration is 10%, the rate of decrease in the flow rate from the fresh water flow rate is 10%.

It was identified that when the casing (screen) surely scrapes the earth and sand up to the suction pipe in the center, and the opening degree of the tip of the suction pipe becomes large, the earth and sand are sucked further and the earth and sand concentration becomes high. In addition, since the casing (screen) rotation speed and the sediment concentration are almost proportional to each other, it was specified that the sediment concentration can be adjusted by the tip opening degree of the suction pipe and the casing rotation speed even under various piping conditions. ..

In this experiment, when the casing rotation speed exceeds 40 rpm, the sediment concentration becomes high and the pump current value becomes 125% or more of the rated current value 105A, and there is a concern that the pump may stop or deteriorate due to overload during on-site work. Results have been obtained.

It should be noted that the configuration or the like described in the above embodiment may be another embodiment in which other components are combined, and the present invention is not limited to the configuration shown here. .. This point can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form thereof.

10: Attachment body 30: Pump 31: Load ammeter 35: Transport pipe 36: Sand lift meter 37: Sediment concentration meter 38: Pressure gauge 40: Suction pipe (double pipe)
41: Outer pipe 41a: Suction port 42: Inner pipe 42a: Suction port 43: Water supply port 44: Outer flow path 45: Inner flow path 46: Shielding member 50: Actuator (motor)
60: Screen 61: Circular cross member 62: Vertical member 63: Inclined plate material 64: Cutting bit 65: Opening 100: Dredging attachment 200: Shaft 300: Underwater work machine 310: Elevating mechanism 320: Swivel mechanism (working machine body)
330: Boom 340: Arm 400: Vessel 550: Operation room 560: Temporary storage pit 600: Controller (operation panel)
602: Receiver 604: Comparison calculation unit 606: Control unit 608: Storage unit 700: Dredging device 800: Dredging system DL: Dam lake SE: Sedimentation

Claims (7)

An underwater work machine with a dredging attachment attached to the tip of the arm,
With a controller,
The dredging attachment is
With a pump
A suction pipe and a transport pipe communicating with the pump,
A screen that surrounds the suction port of the suction tube and has a plurality of openings and cutting bits.
It has an actuator that rotates the screen.
A dredging device, characterized in that the controller executes change control of the rotation speed of the actuator. At least one of a sand flow meter, a sediment concentration meter, and a pressure gauge is attached to the suction pipe and the transport pipe.
A load ammeter is attached to the pump.
The controller has a receiving unit, a storage unit, a comparison calculation unit, and a control unit.
The receiving unit receives measurement data measured by at least one of the sand lifting flow meter, the earth and sand concentration meter, the pressure meter, and the load ammeter.
The storage unit stores at least one of a sand flow threshold, a sediment concentration threshold, a pressure threshold, a dredging amount threshold of a dredging amount specified by the sand flow and the sediment concentration, and a load current threshold.
The comparison calculation unit compares the measurement data with the threshold value associated with the measurement data.
The dredging device according to claim 1, wherein when the measurement data exceeds the related threshold value, the control unit executes a control for lowering the rotation speed of the actuator. The screen is
A plurality of annular cross members arranged at intervals in the vertical direction,
It exhibits a substantially hemispherical shape having a plurality of U-shaped vertical members arranged at intervals in the circumferential direction of the plurality of annular cross members and connected to each annular cross member, and the plurality of annular cross members. And the plurality of the vertical members intersect in a grid pattern to form the plurality of the openings.
An inclined plate material whose lower end is inclined in the rotation direction of the screen is connected to the plurality of annular cross members, and among the inclined plate materials, a plurality of cutting bits are attached to the end faces on the front side in the rotation direction of the screen. Ori,
The plan view shape of the screen is circular, and in the plan view of the screen, the end face on the front side in the rotation direction of the inclined plate material is located radially outward from the tangential direction of the circle. The dredging device according to Item 1 or 2. The dredging attachment is further provided with a water supply port in the middle of the suction pipe.
By the operation of the pump, the dredged earth and sand are taken into the suction pipe through the opening of the screen, and the fresh water is taken into the suction pipe through the water supply port, and both the fresh water and the dredged earth and sand are said to be said. The dredging device according to any one of claims 1 to 3, wherein the dredging device is sucked into the pump via a suction pipe and transported through the transport pipe. The suction pipe is a double pipe having an outer pipe and an inner pipe.
The fresh water supplied to the suction pipe through the water supply port flows through the outer flow path between the outer pipe and the inner pipe, goes around the suction port of the inner pipe, and flows inside the inner pipe. The dredging device according to claim 4, wherein the dredging earth and sand introduced into the road and taken into the inner flow path are sucked by the pump. A pontoon with an operation room and
A shaft that is held by the pontoon and extends to the bottom of the lake,
The underwater working machine constituting the dredging device according to any one of claims 1 to 5, which is attached to the shaft so as to be rotatable and elevating.
A dredging system in which the controller is arranged in the operation chamber, and the turning and raising / lowering of the underwater working machine and the change control of the rotation speed of the actuator are executed. It is a dredging method that uses an underwater work machine with a dredging attachment attached to the tip of the arm.
The dredging attachment is
With a pump
A suction pipe and a transport pipe communicating with the pump,
A screen that surrounds the suction port of the suction tube and has a plurality of openings and cutting bits.
It has an actuator that rotates the screen and
A dredging method comprising dredging while adjusting the rotation speed of the actuator so as not to cause obstruction of at least one of the suction pipe and the transport pipe.

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