JP6582361B2 - Vacuum-consolidated dredging method, tower-type airtight loading box and dedicated work ship. - Google Patents

Description

  The present invention relates to the reuse of the seabed, riverbed ground vacuum consolidation, dredging, and compacted dredged material to materials such as landfill and seabed embankment in deepening and maintaining the depth of ships' routes and anchorages.

  The sediment deposited in the estuary of large rivers is often soft soil with a high water content. In particular, sediments in the waters of harbors with large cities behind them become super soft soils due to the accumulation of organic matter due to the inflow of domestic wastewater and industrial wastewater. The characteristic of soft soil is that the moisture content is very large. However, when organic matter is contained, the moisture content becomes as high as 200%, and the surface layer reaches 400%. The surface layer is called floating mud and is a fluid mud with a very low density. In general, even in the case of high plastic clay, the water content at the liquid limit is at most about 100%. A soft soil with a water content ratio exceeding the liquid limit is a fluid mud that does not form.

Whether or not a ship can navigate is determined by the water depth. The draft depth of the largest vessel navigating there must always be maintained. For this reason, a permanent maintenance rod is required.
Dredging is the deepening of the bottom sediment. Moved soil is moved to other places and used for landfill. In the civil engineering field of the ocean and harbor, dredging work and landfill work are often a series of works. The purpose of acupuncture varies. There are dredging for creating new routes and anchorages, dredging for widening and deepening existing routes, and dredging for maintaining water depth. In addition, the collection of earth and sand for land reclamation and dredging of removal of water bottom sludge for environmental measures.

Dredgers are selected according to the type of sediment, the scale of the dredger, and where the dredger is disposed. Dredgers are roughly divided into pump dredgers and grab dredgers, and the former is suitable for large-scale dredgers. Pump dredgers are generally pump dredgers with cutters. The bottom sediment is cut with a cutter, sucked with water with a pump, and transported to a landfill or disposal site through a sand pipe. Dredging capacity per hour there is a 2,000 m ^3. Dredgers are generally non-self-propelled that do not sail by themselves, but there are also self-propelled dredgers.
Self-propelled dredgers called trailing suction hopper dredgers (drag suction dredgers in Japan) are active in large-scale dredging and landfill works in Europe and the United States. This dredger uses a dredge pump to suck up sediment and water from the bottom of the water and load them into the hold.

  When dredged soil is used for landfill material, if dredged soil is sandy soil, there are few problems with conventional dredged landfill methods. However, if the dredged soil is a viscous soil, water is mixed during dredging, resulting in a high water content ratio several times the liquid limit. This is an artificially made ultra-soft clay soil. At present, such poor soil mixed with unnecessary water is transported, and artificially defective soil is used as landfill material.

  Current acupuncture technology is definitely progressing. Development of large-capacity dredging technology, ship position measurement technology using GPS, and environmental conservation dredging methods. As an example of this construction method, there is one that uses a sealed grab and discharges excess seawater from the grab to reduce the pollution diffusion and achieve a high mud content dredging. However, even this method has many problems as measures against floating mud. When excess seawater is discharged from the grab, the floating mud itself is discharged. The fundamentally existing dredging technology is that there is no idea of dewatering and improving the dredged soil from the original riverbed and seabed using civil engineering as recycled materials.

  Japan's use of dredged soil has been used in landfills such as harbors and industrial sites. However, it is difficult to secure a landfill site for dredged soil. Therefore, the clay of clay soil has been improved by dehydration and volume reduction at the plant or by mixing solidification material, and then actively used for landfill. However, the cost is high and its utilization rate is small.

  In Japan, the vacuum consolidation method has been widely used as a land improvement method on land, but it is also being used for the submarine ground. The characteristics of the vacuum consolidation method for submarine ground are to maintain the airtightness of the loaded ground surface in some way, and to use the water pressure in addition to atmospheric pressure for the loaded load. The environmental aspect of this method is that it can increase the strength and volume of the submarine ground by consolidation settlement without causing water pollution in situ. If the water depth of the channel is secured only by consolidation settlement, the water depth maintenance method will not cause dredging.

  The method of Patent Document 1 relates to the ground improvement method by vacuum consolidation of the seabed ground, and was developed mainly as a countermeasure for residual settlement of the viscous ground in port facilities. Therefore, there is no dredging process in this method. A major feature of this construction method is that a repeated load that is a dynamic load (about 5% of the static load) is used in combination with an atmospheric pressure and a water pressure that are static loads of vacuum consolidation. As a result, the pressure fluctuation is transmitted to the seabed ground, and the wave of excess pore water pressure is generated to realize the rapid consolidation settlement.

  The construction method of Patent Literature 2 is a development of the ground improvement construction method and the dredge construction method by vacuum consolidation of Patent Literature 1 as a series of construction methods. Hereinafter, this series of construction methods is referred to as a vacuum consolidation method. The vacuum consolidation dredging method is intended for dredging and dredging dredging on the original riverbed and seabed using dredged soil as a civil engineering reclaimed material. In-situ dewatering improvement is required by compaction for ultra-soft soils with a water content ratio that greatly exceeds the water content limit of the liquid limit.

  There are two major features of Patent Document 2. The first is a function that opens and closes the bottom of the tower-type airtight loading box that realizes dredging with a bottom plate shutter. The box is used both as a vacuum-consolidated air-tight loading box and a glove bucket. The second is a mobile spud function that allows a dedicated work ship to move by itself.

  The loading of submarine soil by the method of Patent Document 2 is realized by a bottom plate shutter. The extrusion of the middle-sealed soil, which is the loading and unloading of the seabed soil, is said to press the upper surface of the middle-sealed soil under pressure with compressed air that has passed through a water permeable lid (rigid filter).

  The basic structure of the tower-type airtight loading box of Patent Document 2 is a box-type structure with a bottom opening, a vacuum tank layer on the inner ceiling surface, and an inner space divided by a box partition with a drain function on the lower surface. Forming a compartment. Here, on the upper surface of the compartment, a water-permeable lid that allows drainage but not dirt particles is provided. In Patent Document 2, a bottom plate shutter is installed on the bottom surface of the box. (Patent Document 2 refers to a tower-type loading box. Also, the vacuum tank layer is referred to as a micro-thick space, and the water-permeable lid is referred to as a rigid filter.)

The common work process of the vacuum consolidation method is to install an airtight loading box into the seabed ground so that the seabed soil is filled in the box. Next, it is divided into the consolidation process, dredging process, and dredging process. The dredging process is subdivided into a process of separating the padded submarine soil from the box, loading the submarine soil held in water or in the air, and unloading it by extrusion.

A verification experiment using a model compartment was conducted on the loading and unloading of subsea soil with an airtight loading box, that is, lifting and extruding the subsea soil in the air. The actual size of the compartment is assumed to be a cube of 1.0m x 1.0m x 1.0m. The scale of the model is 1/5. There is no bottom shutter in the model compartment. The model compartment has an airtight tank layer with the upper part of the inner space separated by a permeable lid. The sample soil of the experiment is a highly plastic reclaimed clay with an initial water content Wo of 100 to 110% and a limit Wl of 85%. The model compartment was installed on the sample soil in the soil layer box, and the sample soil was filled in the model compartment. The interior of the installed model compartment is airtight. The airtight tank layer was evacuated with a vacuum pump, and the packed sample soil was loaded at atmospheric pressure to proceed with consolidation. In the consolidation progress state, the water content W of the filling sample soil is classified by the liquid limit Wl.

For lifting the sample soil in the model compartment in the air, the airtight tank layer is evacuated by a vacuum pump and the upper surface of the sample soil is vacuumed. The results are as follows.
W> Wl: Cannot be lifted. Most of the padded sample soil fell out.
W = Wl: Can be lifted. However, the bottom surface of the filling sample soil is partially removed.
W <Wl: Can be lifted. However, the bottom surface of the filling sample soil is not flat.
The reason why the bottom surface of the filled sample soil was not flat was thought to be that a negative pressure was generated on the bottom surface of the sealed sample soil when the model compartment was lifted from the soil layer box. Therefore, a vent pipe with 8 valves was attached to the side of the model compartment. As a result of the experiment of releasing the airtightness of the bottom surface when lifting the model compartment, the bottom surface was almost flat.

Extruding the sample soil in the model compartment in the air is performed by releasing the vacuum state of the model compartment. The results are as follows.
W = Wl: Extrusion is possible only by releasing the vacuum state.
W <Wl: Extrusion is not possible although the vacuum state is released.
In the model airtight compartment, the solid sample soil was pushed out just by releasing the vacuum state of the airtight tank layer when the water content of the medium sampled soil was near the liquid content limit. However, when the moisture content was clearly small, the method of extruding the padded sample soil with compressed air in Patent Document 2 did not work. Moreover, even if vibration and impact were applied, it did not fall out. The wall adhesion strength of the compartment is a major obstacle.
After all, the construction method of Patent Document 2 can consolidate a soft padded seabed soil only up to the water content ratio of the liquid limit. In other words, the submarine viscous soil having a water content that is clearly smaller than the water content of the liquid limit cannot be dredged by the method of Patent Document 2.

Japanese Patent Application No. 2007-309073 Japanese Patent Application No. 2015-87107

Problem 1 is realized by the function of opening and closing the bottom surface of the airtight loading box with a bottom plate shutter. However, the mechanism of the function is complicated as a working device in the ground, and the risk of failure is high. If a failure occurs during construction, it cannot be handled on site and the construction is interrupted.

The problem 2 is that the loading and unloading of the clay in the construction method of Patent Document 2, that is, the extrusion of the padded seabed soil, is performed by pressing the upper surface of the padded seabed soil with compressed air. However, it does not work when the water content of the middle-sealed soil is clearly smaller than the water content of the liquid limit. Therefore, it is not possible to load and unload dredged soil.

Problem 3 is a method in which the vacuum consolidation dredging method is intended to improve dehydration in situ by the consolidation and to continue dredging. The consolidation method of Patent Document 1 realizes rapid consolidation by generating a wave of excess pore water pressure. In the case of highly plastic clay, the consolidation speed is said to be 2-3 times higher. However, if it becomes super soft soil that greatly exceeds the water content ratio of the liquid limit, a long consolidation time is required even in the consolidation method of Patent Document 2 incorporating the rapid consolidation of Patent Document 1. This greatly impairs the advantages of the vacuum consolidation method.

The present invention is a series of vacuum consolidation method and dredging method, and requires a system in which all means for solving the above-described problems are incorporated. In other words, it is a construction method that enables loading and unloading of seabed soil, which is dredging, in addition to compaction with a tower-type airtight loading box with a bottom opening.
The basic structure of the tower type airtight loading box of the present invention is as follows.
In the vacuum consolidation method for seabed ground, a vacuum tank layer is divided on the inner ceiling surface of the airtight loading box at the bottom opening, and a plurality of compartments are formed by dividing it by a box bulkhead with a drain function directly below it. A tower type airtight loading box having a water permeable lid on the upper surface of the chamber and a box tower having a height exceeding the water depth is used at the center of the outer upper surface of the box.

The working process of the tower type airtight loading box of the present invention is as follows.
In the box installation step, the box body is pushed into the seabed ground so that the seabed soil is filled with the box. In the consolidation process, the vacuum tank layer is evacuated to load atmospheric pressure and water pressure on the padded seabed soil and the seabed ground to advance the consolidation settlement. Increase strength beyond possible strength. The loading of the seabed soil in the dredging process is to release the airtight state of the bottom surface of the box while keeping the box in a vacuum state, and to lift the box to separate the padded seabed soil from the seabed. The loading and unloading of the box stops the vacuum state of the box and pushes it out by using compressed air or vibration as necessary.
In the consolidation process of the present invention, in the consolidation process, the seabed soil is consolidated more than the strength that can be dredged by the box at the bottom opening, and in the dredging process, the air pressure and water pressure of the box are controlled to control the seabed. A major feature is dredging the soil.

The configuration of the main equipment of the tower type airtight loading box is as follows.
An automatic valve in which a vacuum tank chamber communicating with the vacuum tank layer is provided on the outer upper surface of the central part of the box to install a drainage device and a fixed vibration device, and the water pressure on the outer upper surface and the bottom surface of the box communicates. An automatic drainage device with an automatic drainage device and an automatic drainage device with an automatic valve that drains directly from the compartment of the box to the outside are installed, and a vacuum device and a compressor are installed above the tower of the box tower It is.
Here, the vibration device is fixed directly to the vacuum tank chamber. This is to transmit the inherent vibration that causes resonance in the box by the operation of this device, and to transmit this vibration to the subsea soil. In addition, the automatic water flow device is a device for releasing the airtight state of the bottom surface while maintaining the vacuum state of the box when the inside soil of the box is lifted off from the sea floor. Moreover, the automatic drainage device is a device for discharging without passing through the water-permeable lid, such as one having extremely small specific gravity of floating mud in the outermost layer of the seabed soil that is not subject to dredging. This is a measure for avoiding unnecessary clogging of the permeable lid. In addition, the vacuum state of the vacuum tank layer described above refers to a vacuum space state in which no water is accumulated in the vacuum tank layer due to the operation of the vacuum device and the drainage device.

Problem 1 described above is that the risk of failure of the bottom plate shutter, which is a key point of the bag, is high. The means for solving the problem is in the verification experiment using the model compartment described above. The falling force of the subsea soil in the tower type airtight loading box is its own weight. The fall prevention force against this is the vacuum suction force on the upper surface of the padded seabed soil and the wall adhesion force of the compartment.
Here, consider the balance between the drop force and the prevention force of the middle-sealed submarine soil. The height of the box-body 2m at maximum, sufficient specific weight of Chutsume Sediments advanced the consolidation 16 kN / m ³ approximately, when the vacuum suction force of the unit area by a vacuum pump and 80 kN / m ^2, vacuum Suction force 80kN / m ² > Unit area weight of padded seabed soil 32kN / m ²
Sufficiently lifted by vacuum suction alone. Here, the vacuum suction force is a force that acts on the upper surface of the subsea soil and pulls it up. Therefore, this balance is subject to the integral condition that the padded seabed soil is not divided. From the above-mentioned compartment model experiment, the integrated condition of the middle-filled seabed soil is the water content ratio W of the middle-filled seabed soil <the water content ratio Wl of the liquid limit.

In the case of a vacuum-consolidation method for seabed soil using an airtight loading box with a bottom opening, if the moisture content of the padded seabed soil in the airtight loading box is higher than the water content ratio of the liquid limit, it will be less than this Securing the integrity of the padded seabed soil and holding the padded seabed soil with the vacuum suction force and the wall adhesion of the upper surface of the padded seabed soil.
The loading of dredged soil in the dredging process refers to the retention of the padded seabed soil in the box. It is easy to retain the padded seabed soil that ensures the integration conditions by utilizing the vacuum suction force and the wall adhesion force. A risky bottom plate shutter is not required.

Problem 2 described above is the unloading in the dredging process, that is, the extrusion of the middle seabed soil, and does not function in the method using compressed air in Patent Document 2. The cause of this is the function of the water-permeable lid (rigid filter) that allows water to pass but not soil particles. The water-permeable lid generates a large resistance when passing high compressed air. For this reason, a water-permeable lid will be damaged when trying to pass high compressed air.

The solution of the problem 2 is that the water-permeable lid is an upper and lower movable water-permeable lid in the tower-type airtight loading box used in the vacuum consolidation method. By pushing down the padded submarine soil together with the movable permeable lid, the adhesion strength of the peripheral surface of the padded submarine soil of the box is cut, and the padded submarine soil is pushed out while applying vibration as necessary.

There are two ways to push down the movable permeable lid. One is a method using compressed air, and the other is a method of pushing down with a movable lid driving device. The proper use of these methods depends on the amount of pressing force required. The former is a simple method, but when the pressure of the compressed air increases, the compressed air leaks from the gap between the wall surface of the compartment and the movable water-permeable lid, and the function deteriorates. On the other hand, the latter is a reliable method that requires an upper and lower drive device for the movable permeable lid of each compartment. Here, as an example of the upper and lower movable lid driving devices, there is a double-acting hydraulic cylinder.

Problem 3 described above is that the ultra-soft clay soil having a very high water content has a long consolidation time. The basis for shortening the consolidation time is to shorten the drainage distance. As a typical method, there is a vertical drain method. The drainage distance is about 30 cm at the shortest. In this method, a minimum drainage distance of 1 to 2 cm is set. The ultra-rapid consolidation method is realized by combining with the rapid consolidation method using both static load and dynamic load in Patent Document 1.

The drain material allows water to pass but not soil particles. And the more water that passes through, the more clogging occurs. Also, clay with a higher water content tends to have a longer consolidation time. Suspended mud corresponds to this. In the case of floating mud, clogging occurs in 1 to 2 minutes, and the consolidation speed decreases rapidly. The progress of consolidation on one side of the unit panel drain is from several mm to several tens of mm. The unit panel drain is double-sided, so the progress is doubled on both sides. This is far from rapid consolidation.

A method for realizing the minimum drainage distance is a drain system in which the drain of the tower-type airtight loading box moves intermittently.
When the drain moves intermittently between the compartment and the vacuum tank chamber, consolidation of the padded seabed soil proceeds when the drain is in the compartment. Scraping off the attached subsea soil and cleaning the drain surface in the vacuum tank chamber is repeated according to intermittent movement. This achieves ultra-rapid compaction by always keeping the drainage distance of the confined seabed soil to a minimum distance. There are flexible belt drains and rigid panel drains. The movement of the belt drain is a circuit, and the arrangement of the belt drain is positioned by a fixed pulley. In contrast, the panel drain moves up and down.

As an example of a method for realizing the minimum drainage distance, a unit panel drain device that can move up and down is used. The unit panel drain device includes a unit panel drain, a panel drain holder, a drain vertical drive device, and a panel drain cleaning device. The configuration of this apparatus is as follows.
In a tower-type airtight loading box, a unit panel drain that can move up and down is installed in the compartment, and a fixed permeable lid is fixed to the top of the compartment. The unit panel drain is provided with a plurality of slits through which the unit panel drain is rubbed, and the unit panel drain is a vacuum tank layer, and the upper part thereof is fixed integrally with a drain holder, and the vacuum tank layer is high enough to lift the unit panel drain. The drain holder is a tower-type airtight loading box characterized in that it is linked to the vertical drive device.

The vacuum-consolidation method for fluidized seabed sediments with ultra-high water content uses a tower-type airtight loading box with a unit panel drain device that can move up and down. These steps are as follows.
In the process of installing the airtight loading box, the airtight loading box is pushed into the seabed ground with the unit panel drain located in the compartment, so that the seabed soil is in the middle of the bottom of the airtight loading box. In the consolidation process, the vacuum tank layer is placed in a vacuum state, and atmospheric pressure and water pressure are loaded on the padded seabed soil to advance the consolidation settlement. When the consolidation speed decreases, the unit panel drain is pulled into the vacuum tank layer. As a result, the consolidation proceeds by the slits of the fixed water-permeable lid, scraping off the padded seabed soil adhering to the unit panel drain, and then lowering the unit panel drain to the original position of the compartment to prevent consolidation. Repeat the process of making a new drainage surface with the progressing paddy subsoil. In this way, rapid consolidation is realized by always keeping the drainage distance for consolidation of the middle-sealed subsoil to a minimum distance.

As described above, the tower-type airtight loading box equipped with the unit panel drain device is used for the vacuum consolidation method of the seabed soil in a fluid state with an ultra-high water content ratio. The panel drain is made of a material that allows water to pass through but does not allow soil particles to pass through. However, this drain becomes clogged while using it and the water permeability becomes worse. The more water that passes through, the higher the percentage of clogging.
This is especially true for submarine soils with a very high water content, and it is necessary to release clogging. The means provides a function of cleaning the unit panel drain within the time in the vacuum tank layer by the vertical movement of the unit panel drain. This is provided with a high-pressure washing device using water in the middle of a slit parallel to the fixed water-permeable lid, and is automatically washed with high-pressure water spray while the unit panel drain moves up and down.

The rapid consolidation method using the dynamic load of the present invention is a further development of the method of Patent Document 1.
When vibration is applied to saturated viscous ground, stress fluctuations (longitudinal and transverse waves) occur in the solid part of the ground and pressure fluctuations (longitudinal wave only) occur in the pore water. Propagation of stress fluctuations in viscous ground is fast and requires a lot of energy to deepen the target ground. On the other hand, since the attenuation of propagation of pressure fluctuation is slow, it is effective for large-scale ground improvement. Propagation of pressure fluctuation becomes a wave of excess pore water pressure because dynamic load of repeated load is combined with static load of atmospheric pressure and water pressure. It is natural that the construction method of Patent Document 1 is a repetitive load limited to pressure fluctuation that does not use huge energy that vibrates the ground. Patent Document 1 specifically refers to a vibration load having only pressure fluctuation as a repeated load. On the other hand, the object of the rapid consolidation of the present invention is a small-scale surface ground, a medium-sealed submarine soil of an airtight loading box. Therefore, both stress fluctuation and pressure fluctuation are effective. Accordingly, the vibration device can be reduced in size.

The process of the rapid vacuum consolidation method using dynamic load according to the present invention comprises loading the atmospheric pressure and water pressure of static load by bringing the vacuum tank layer of the hermetic loading box into a vacuum state, and the hermetic loading box By operating the vibration device in accordance with the natural vibration of the bulkhead or unit panel drain, it is made to resonate, and both fluctuations of stress and pressure due to the dynamic load of vibration are transmitted to the padded submarine soil. It is characterized by performing rapid consolidation. By resonating, the vibration device can be further reduced in size and can be directly fixed to the vacuum tank chamber.

In addition to the static load of the present invention, the combined use of a dynamic load that transmits both fluctuations of stress and pressure is effective not only for rapid compaction but also forcible elution of harmful substances.
In the pollution diffusion prevention method for contaminated seabed sediment, the elution process of harmful substances is carried out by loading the vacuum tank layer of the box into a vacuum state to load atmospheric pressure and water pressure of static load, and the airtight loading box By operating the vibration device in accordance with the natural vibration of the bulkhead or unit panel drain, it is made to resonate, and both fluctuations of stress and pressure due to the dynamic load of vibration are transmitted to the padded submarine soil. Concentrated seabed soil density is increased by forcibly eluting toxic substances and rapid compaction, and then the contaminated water purification process sends the contaminated water collected in the vacuum tank layer to the contaminated water purification device with a drainage device to make it harmless. It is characterized by preventing contamination diffusion.

The tower-type airtight loading box of the present invention is usually installed on a dedicated work ship. The box has a box-type dedicated work ship equipped at the center of the dedicated work ship and a box-front-type dedicated work ship equipped at the front. The box-type dedicated work ship can also carry the dredged material in the box. Since the bottom of the box is open, the dedicated work ship needs a bottom so as not to disperse pollution during long-distance transportation. The box-type dedicated work ship is a general-purpose dedicated work ship that transports dredged soil. This dedicated work ship requires a countermeasure for stability because the center of gravity of the hull is biased forward when dredging. The configuration and functions of these dedicated work vessels are as follows.

A box-type dedicated work ship equipped with a tower-type airtight loading box forms a space in which the box is housed in the center of the carriage, and the guide tower and guide of the box can be removed by surrounding the space. The tower support girder is fixed to the trolley, and the cargo box incorporated in the tower has a function of moving up and down in the guide tower, and opens and closes the bottom of the opening space of the trolley where the box is accommodated. A dedicated work ship equipped with a mobile ship bottom device.

Similarly, a box front type dedicated work ship equipped with a tower type airtight loading box has a hanging rod for fixing the position of the box to the front of the carriage and is fixed to the carriage. The box incorporated in the vertical guide rail has the function of moving up and down in the guide rail, and the vertical support is added to the center of gravity of the dedicated work ship that is biased forward during dredging work. Dedicated work ship, characterized by maintaining stability with a spud device.

In the vacuum consolidation method of the present invention, if the water content of the seabed soil is equal to or higher than the water content of its liquid limit, it is consolidated to at least the following. This enables the loading of seabed soil in dredging processes with the simple equipment and functions of a tower-type airtight loading box with a bottom opening in the vacuum consolidation method.

In the vacuum consolidation method of the present invention, the water-permeable lid of the tower-type airtight loading box is used as a movable water-permeable lid, and the padded seabed soil is pushed down together with the water-permeable lid. For this reason, in the dredging process, it was possible to load and unload the seabed soil with high density by consolidation.

In the rapid consolidation of submarine soil with an ultra-high water content, ultra-rapid consolidation was achieved by minimizing the drainage distance of the padded submarine soil with a unit panel drain device.

The vacuum compaction method of the present invention implements rapid vacuum compaction and scissors as a series of steps by developing the equipment and functions of the vacuum compaction method. As a result, the volume of dredged soil is reduced by consolidation, and it is not a dredged soil in which seawater is mixed by disturbing the submarine soil as in conventional dredging, but the strength and density increase after consolidation is achieved. Produces the effect of becoming dredged as it is.

Elevated view of tower type airtight loading box 1A installed on the seabed Elevated view of the airtight loading box 11A Elevated view of the tower type airtight loading box 1A separated from the seabed Elevated view of the state of loading the bottom-packed submarine soil of the same airtight loading box 11A Elevated view of tower-type airtight loading box 1B installed on the seabed Elevated view of airtight loading box 11B Explanatory drawing of drain system of airtight loading box 11B Elevated view of the box-type central workboat 2C equipped with a tower-type airtight loading box 1A Plan view on the upper surface of the carrier 21 of the dedicated work ship 2C Elevated view of the tower-type airtight loading box 1A of the dedicated work ship 2C in the state of consolidation on the sea floor Elevated view of airtight loading box 11A of the dedicated work ship 2C installed on the seabed landfill or embankment and loaded with unsealed seabed soil Side view of box-type front dedicated work ship 2D equipped with tower-type airtight loading box 1A Elevated view of the dedicated workboat 2D Plan view of the upper surface of the carrier 21 of the dedicated work boat 2D Elevation view of the airtight loading box 1A of the dedicated work ship 2D installed on the sea floor and in the state of consolidation

The greatest feature of the vacuum-consolidating method of the present invention is that the vacuum-consolidating and scissors are carried out in a series of steps using the tower-type airtight loading box 1 having a bottom opening. The tower-type airtight loading box 1 of the present invention includes an airtight loading box 11 and a box tower 12. There are two types of tower-type airtight loading boxes 1, an integrated box tower 12 </ b> A and a separate box tower 12 </ b> B composed of a tower base and a tower upper part. The separation type box tower 12B changes the length of the upper part of the tower according to the depth of water. The long box tower 12 is conveniently a separate type when mounted on a work boat. The horizontal cross-sectional area of the box 11 is a square, one side is about 10 to 30 m, and the height is about 1 to 2 m.

The tower-type airtight loading box 1 and the airtight loading box 11 of the present invention have different structures depending on the moisture content of the seabed soil to be dredged. There are a tower type airtight loading box 1A and an airtight loading box 11A for seabed soil with a normal water content ratio, and a tower type airtight loading box 1B and an airtight loading box 11B for seabed soil with an extremely high water content. Further, the vacuum compacting method according to the present invention differs in the work ship to which the tower type airtight loading box 1 is attached depending on the scale of construction. An existing crane ship or two types of dedicated work ships 2. The dedicated work ship 2 is a box-type dedicated work ship 2C equipped with a tower type airtight loading box 1 in the center and a box-front dedicated work ship 2D equipped in the front. The dedicated work ship 2C transports the dredged material to the box 11 in a packed state. Since the bottom surface of the airtight loading box 11 is open, the dedicated work ship 2C is provided with a mobile ship bottom device 24 so as not to disperse pollution during transportation. The work process of the vacuum consolidation method using the tower type airtight loading box 1 of the present invention is the same for all work ships.

Hereinafter, an embodiment of a tower-type airtight loading box 1A for seabed soil having a normal water content ratio according to the present invention will be described with reference to FIGS.
Fig. 1 is an elevation view of the tower type airtight loading box 1A installed on the seabed, or an elevation view of the state of the consolidation process, Fig. 2 is an elevation view of the airtight loading box 11A, and Fig. 3 is a tower type. FIG. 4 is an elevational view of the airtight loading box 1A separated from the seabed ground, and FIG. 4 is an elevational view of the state where the undersea filling soil of the airtight loading box 11A is loaded on the bottom of the sea.

The structure of the tower-type airtight loading box 1 </ b> A includes an airtight loading box 11 </ b> A and a box tower 12. The airtight loading box 11A includes a vacuum tank layer 111, a box partition 112, a compartment 113, a vacuum tank chamber 114, and a movable water-permeable lid 115A. The device configuration of the tower-type airtight loading box 1A includes an automatic water flow pipe 14, a vacuum device 15, a drainage device 16, a compressor 17, a vibration device 18, an automatic drainage device 19, and a movable lid driving device 116. There are two methods for driving the movable water-permeable lid 115A: compressed air (compressor 17) and movable lid driving device 116 (double-acting hydraulic cylinder).

In the vacuum compacting method using the tower-type airtight loading box 1A, first, the drainage device 16 is slightly operated in the installation process, and the seabed soil is filled with the box 11A. At this time, the movable water-permeable lid 115A is at the upper end of the compartment 113. Here, if there is an extremely small specific gravity floating mud that is not subject to dredging in the outermost surface layer of the seabed soil, it is directly discharged out of the box 11A by the automatic drainage device 19. Next, in the consolidation process, the vacuum device 15 and the drainage device 16 are operated, and a static load of atmospheric pressure and water pressure is loaded on the padded seabed soil 6 and the seabed ground 5.
In the rapid consolidation method, the vibration device 18 is operated in parallel with the static load loading to resonate the box bulkhead 112 of the box. It promotes rapid consolidation by transmitting both fluctuations. (Refer to Figs. 1 and 2) If the water content of the padded seabed soil 6 is greater than the water content of the liquid limit, the water content is less than the liquid limit and is not less than the strength that can be dredged by the box 11A. Consolidate to increase strength.

The loading of the seabed soil in the dredging process is to release the airtight state of the bottom surface of the tower-type airtight loading box 1A by opening the automatic water pipe 14 while keeping the vacuum state of the tower-type airtight loading box 1A. Pull up and detach the middle-sealed soil 6 from the seabed 5. (Refer to FIG. 3) The filling of the bottom sea bottom soil stops the vacuum state of the box 1A, and while sending low compressed air, pushes down the movable water permeable lid 115A with the movable lid driving device 116 to Perform loading and unloading. (See Figure 4)

Hereinafter, an embodiment of a tower-type airtight loading box 1B for seabed soil with an ultra-high water content of the present invention will be described with reference to FIGS. Suspended mud is a typical submarine soil with a very high water content. The big problem in vacuum compaction of floating mud is the clogging of drain and the length of compaction time.
5 is an elevation view of the tower-type airtight loading box 1B installed on the seabed, or an elevation view of the compaction process, FIG. 6 is an elevation view of the airtight loading box 11B, and FIG. 7 is an airtight load. It is explanatory drawing of the drain system of the box 11B.

The basic configuration and basic work process of the airtight loading box 11B are substantially the same as those of the airtight loading box 11A, but the main difference is the unit panel drain device 13 that can be moved up and down and the relationship thereof.
At the time when the tower type airtight loading box 1B is installed on the seabed, the unit panel drain 131 is located in the compartment 113. (See FIGS. 5 and 6) A fixed water-permeable lid 115B is provided at the top end of the compartment 113, and a plurality of slits through which the unit panel drain 131 is rubbed are provided. The head of the unit panel drain 131 protrudes from the vacuum tank layer 111, and this head is integrally fixed by a panel drain holder 132, and further linked to the drain vertical drive device 133. Here, the vacuum tank layer 111 has a sufficient height necessary for pulling up the unit panel drain 131. In FIG. 7, reference numeral 134 denotes a drain cleaning device, which is installed at equal intervals in the middle position of the plurality of slit rows.

The rapid consolidation process is started from a state where the tower type airtight loading box 1B of FIG. 5 is installed on the seabed. The basic operation of the consolidation process apparatus is the same as that of the tower-type hermetic loading box 1A. The vacuum tank layer 111 of the box 1B is brought into a vacuum state so that static atmospheric pressure and water pressure are loaded, and the vibration device 18 is operated in accordance with the natural vibration of the unit panel drain 131 to resonate. In addition to the static load, both the stress fluctuation and the pressure fluctuation due to the dynamic load of vibration are transmitted to the middle seabed soil 6 to perform ultra-rapid consolidation.

FIG. 7 is an explanatory view of the drain system of the airtight loading box 11B, and is an elevation view of the unit panel drain device 13 in which the unit panel drain 131 moves intermittently between the compartment 113 and the vacuum tank layer 111. The progress of consolidation of the middle subsea soil 6 is shown in FIG. 7a. When the consolidation speed decreases, the unit panel drain 131 is pulled up to the vacuum tank layer 111. This state is shown in FIG. The unit panel drain 131 moves. That is, it is the state from FIG. 7a to FIG. 7b. During this movement, consolidation progresses through the slits of the fixed water permeable lid 115B and scrapes off the padded seabed soil 6 adhering to the unit panel drain 131. In the vacuum tank layer 111, the unit panel drain is operated by the drain cleaning device 134. 131 is washed. When the unit panel drain 131 is lowered to the position of the compartment 113, a new drainage surface with the unfilled undersea soil 6 is formed, and the consolidation proceeds. By repeating this work process, rapid consolidation is realized by always setting the drainage distance of consolidation of the padded seabed soil 6 to a minimum distance. Here, the cycle time of the vertical movement of the unit panel drain 131 in the consolidation process is several minutes.

The loading of the seabed soil in the dredging process is to release the airtight state of the bottom surface by opening the automatic water pipe 14 while keeping the vacuum state of the box 1B, and pulling up the box 1B. Cut off the middle seabed soil 6 from the seabed. The loading and unloading of the middle-sealed submarine soil 6 stops the vacuum state of the box 1B and raises the unit panel drain 131 to the vacuum tank layer 111. The adhesion strength of the unit panel drain 131 and the undersea filling soil 6 is cut, and if necessary, the intermediate filling soil 6 is pushed out by combined use of vibration.

The configuration of the box central dedicated work boat 2C according to the present invention will be described with reference to FIGS. A series of processes of large-scale vacuum consolidation, dredging, and seabed embankment will be described with reference to FIGS. There are two types of tower-type airtight loading boxes 1, A and B, but here is an example using a tower-type airtight loading box 1 </ b> A.

FIG. 8 is an elevational view when the box-shaped central workboat 2C equipped with the tower-type airtight loading box 1A of the present invention is levitated. FIG. 9 is a plan view on the upper surface of the carriage 21 of the dedicated work ship 2C, and shows an example in which two tower-type airtight loading boxes 1A are arranged in parallel.
The main structure and apparatus constituting the central box-type dedicated work ship 2C of the present invention are two tower type airtight loading boxes 1A, two guide towers 22, two guide tower support girders 23, 4 A ship carrier 21, four mobile spud devices 3, and two sets of mobile bottom devices 24. The four trolleys 21 are joined and integrated to form a space in which two tower-type airtight loading boxes 1A are accommodated.
The dedicated work boat 2C has extremely high stability because the center of gravity of the hull is central even during work. The lifting height of the airtight loading box 11A is up to the position where it is stored in the carriage 21. The ship bottom device 24 in FIG. 8 is in a closed state.

The tower-type airtight loading box 1A moves up and down freely within the guide tower 22. This movement is realized by a rack and pinion system. A pair of racks are fixed to both sides of the box tower 12, and two box vertical drive units 25 are combined. The box vertical drive device 25 converts the rotational motion of the motor with a speed reducer into a linear motion and transmits it to the rack. The two box vertical drive devices 25 are simultaneously operated.

  The mobile spud device 3 of the box-type dedicated work boat 2C of the present invention is equivalent to Patent Document 2, and is a device that freely and accurately moves the dedicated work boat 2C. The mobile spud device 3 is composed of four mobile spuds 31 and a track 32 provided on four sides of the outer periphery of the carriage 21.

The mobile ship bottom device 24 includes a work ship bottom plate 241 and a bottom plate support girder 242. The work ship bottom plate 241 is a thin box type and has a semi-floating structure. For this reason, the weight in water cancels out its own weight and buoyancy and does not cause friction in movement. This movement is operated with a winch. The bottom plate support girder 242 has a structure in which two groove-shaped steel members face each other, and is extended and fixed to both ends of the left and right trolleys 21. A work bottom plate 241 is incorporated in the groove.

FIG. 10 is an elevational view of a state in which the tower-type airtight loading box 1A of the box-type central workboat 2C is installed on the seabed and is being consolidated. The mobile ship bottom device 24 of FIG. 10 is in an open state. The submarine installation process and the consolidation process of the tower type airtight loading box 1A are as shown in paragraph number 0051. The dredge process is as shown in paragraph 0052.

FIG. 11 is an elevational view showing a state in which the airtight loading box 11A is installed on the seabed landfill surface or the embankment surface of the seabed embankment 7. The submarine embankment process by the box central dedicated work boat 2C is as follows.
The means for carrying out the seabed embankment 7 with dredged material transports the dredged soil with a required strength to the work area of the seabed embankment 7 in an airtight loading box 11A. Then, the airtight loading box 11A is lowered to a predetermined position on the seabed embankment 7 and installed. The submarine embankment of the present invention does not drop the padded submarine soil into the sea. This is to prevent material deterioration and seawater pollution of the middle-sealed submarine soil. The extraction (unloading) of the middle seabed soil on the embankment surface of the airtight loading box 11A stops the vacuum state of the vacuum tank layer 111 and pushes the movable water permeable lid 115A by the movable lid driving device 116 to push out the middle seabed soil. . The effect of reusing dredged soil according to the present invention has a strength as a banking material, so that a predetermined banking gradient can be secured. If necessary, slope protection work can be performed later.

In the case of large-scale consolidation, dredging, and submarine embankment construction, it is recommended to secure a temporary storage area for dredging in the vicinity of the consolidation dredging area. A plurality of box-type central work boats 2C are prepared and assigned roles. Consolidation and dredging and reconsolidation, transportation and embankment. The dedicated work vessel 2C for compaction and dredging performs the necessary minimum consolidation that can be dredged with the airtight loading box 11A, that is, the consolidation of the water content of the boxed soil is slightly lower than the liquid limit. In order to shorten the working time of the consolidation zone. The dedicated work vessel 2C for re-consolidation, transportation and embankment ensures a consolidation time in which the padded soil in the box has sufficient strength as a embankment material. This is in order to reduce the time limit for navigation by shortening the consolidation work time when the consolidation dredging zone is a route with severe ship navigation. The latter is large in the proportion of the dedicated work ship 2C for consolidation and dredging and reconsolidation, transportation and embankment. The specific ratio is determined by the latter re-consolidation time and transport distance.

The consolidation dredging process when the water content of the seabed sediments to be dredged is higher than the liquid limit is as follows.
The box-type dedicated work ship 2C immediately precedes the consolidation process for the entire target area without taking the dredging process immediately after the consolidation. The reason is that the seabed sediments are in a fluidized state exceeding the liquid limit, so even if they are drowned, the surrounding seabed sediments flow in and refill the dredged part. For this reason, it is necessary to make the water content ratio of the surrounding seabed soil below the liquid limit. It is preferable that the box-centered dedicated work ship 2C is implemented by a plurality of ships with the consolidation process and the transport process up to the temporary storage area as a division of labor.

When there is a possibility that the seabed sediment may be contaminated and diffused by the harmful substances, the diffusion prevention countermeasure method by the box central type dedicated work ship 2C is as follows.
The countermeasure method is implemented through consolidation, dredging and soil covering processes. The aim is to remove pollutants that are likely to elute from contaminated sediments and to cover them with high quality seabed soil at the current location. The vibration consolidation according to the present invention promotes the elution of harmful substances. In the consolidation process, the interstitial water in the sedimentary soil accumulates in the vacuum tank layer 111 and is drained by the drainage device 16. Since harmful substances are eluted in this waste water, it is rendered harmless via a contaminated water purification device. Contaminants that are likely to elute at this stage are removed.

Normally, contaminated marine sediments are thin and widely distributed. Moreover, the diffused contaminated sediment is fluidized beyond the liquid limit. Therefore, the consolidation process of the entire target area is preceded. When the consolidation of all the target areas and the purification of pore water have been completed, move to the soil covering process. It is convenient if a good quality clay is available for the covering material.

The depth control of the sea floor by dredging is carried out at the level height of the bottom of the tower type airtight loading box 1. The shape dimensions of the tower type airtight loading box 1 are known. The level height of the box tower 12 at the end of the consolidation process may be confirmed. The height of the box tower 12 is measured by leveling. The box tower 12 is preferably marked with a scale from the top.

The box front type dedicated work ship 2D is a general purpose dedicated work ship, and the transport of dredged soil becomes an earth ship. This type of work ship requires a countermeasure against stability because the center of gravity of the hull is biased forward when dredged. The configuration and function of the dedicated work boat 2D will be described with reference to FIGS.

FIG. 12 is a side view showing a state in which the tower-type airtight loading box 1A is levitated in the box front dedicated work ship 2D of the present invention. FIG. 13 is an elevation view of the dedicated work boat 2D. FIG. 14 is a plan view of the dedicated work boat 2D. In the figure, 26 is a steering ridge, 27 is a suspension rod, 28 is a winch, 3 is a mobile spud device, which includes a mobile spud 31 and a track 32.

The box front dedicated work boat 2D of the present invention fixes a suspension rod 27 for making the position of the airtight loading box 1 in front of the base boat 21 to the base boat 21. The airtight loading box 1 is incorporated in the vertical guide rail of the suspension rod 27 and has a function of moving up and down in the guide rail. Further, since the center of gravity of the dedicated work ship 2D during the dredging work is biased forward, the mobile spud device 3 provided with vertical support in addition to horizontal support assists in stability as necessary. 14 is a plan view of a state in which three of the four mobile spud devices 3 are concentrated in front of the carriage 21. FIG. In addition, the mobile spud device 3 of Example 3 is equivalent to Patent Document 2 as a device that freely and accurately moves the dedicated work ship 2C. FIG. 15 is an elevation view of the airtight loading box 1 </ b> A of the dedicated work ship 2 </ b> D installed on the sea bottom in a state of consolidation progress.

The vacuum compaction and dredging work operations and processes by the box front dedicated work ship 2D of the present invention are the same as those of the box central dedicated work ship 2C because the tower type loading box 1 is the same. However, seabed embankment is not suitable. The dedicated work ship 2D can easily be dredged at the quay of a port facility. On the other hand, the box-type dedicated work ship 2C is not suitable for dredging such as on a quay.

1 Tower-type airtight loading box
1A Tower-type airtight loading box for submarine soil with normal water content
1B Tower type airtight loading box for submarine soil with ultra high water content
11 Airtight box
11A Airtight loading box for submarine soil with normal water content
11B Airtight loading box for submarine soil with ultra high water content
111 Vacuum tank layer
112 Box bulkhead
113 compartment
114 Vacuum tank chamber
115 permeable lid
115A movable permeable lid
115B fixed permeable lid
116 Movable lid drive
12 Box tower
12A Integrated box tower
12B Separate box tower
121 exhaust
122 Drainage
123 Air supply
13 Unit panel drain device
131 Unit panel drain
132 Panel drain holder
133 Drain vertical drive
134 Drain cleaning device
14 Automatic water flow device
15 Vacuum equipment
16 Drainage device
17 Compressor
18 Vibration device
19 Automatic drainage device 2 Dedicated work boat 2C Box central type dedicated work boat 2D Box forward type dedicated work boat
21 trolley
22 Guide tower
23 Guide tower support girder
24 Mobile ship bottom equipment
241 Work boat bottom plate
242 Bottom plate support girder
25 Box vertical drive
26 Steering building
27 Hanging rod
28 Winch 3 Mobile spud device
31 Mobile spud
32 Track 4 Sea surface 5 Submarine ground 6 Filled seabed 7 Seabed embankment

Claims (11)

  In the vacuum consolidation method for seabed ground, etc., a vacuum tank layer is formed on the inner ceiling surface of the airtight loading box at the bottom opening, and a plurality of compartments are formed by dividing it by a box partition with a drain function immediately below this. A permeable lid is provided on the upper surface of the compartment, and a tower-type hermetic loading box with a box tower attached to the center of the outer upper surface of the box is used. Consolidation progresses beyond the strength that can be dredged by the box. In the dredging process, the air pressure and water pressure of the box are controlled to dredge the seabed soil, etc. A vacuum-consolidating method, characterized by a series of steps of compaction and scissors.   In the vacuum consolidation method for submarine ground or the like according to claim 1, the floating mud with a very small specific gravity outside the target of dredging of the outermost layer such as the seabed soil in the tower type airtight loading box before the consolidation process. A vacuum-consolidation method characterized by a process of directly discharging the container from the compartment of the box to the outside.   In the vacuum consolidation method for submarine ground according to claim 1, in the consolidation process, the water content of the tower-type airtight loading box is less than the liquid limit of the liquid limit, and in the dredging process, The holding of soil etc. is characterized by utilizing the vacuum suction force and wall adhesion force on the inner upper surface of the box, and releasing the airtight state of the box bottom with an automatic water flow device when separating from the seabed ground etc. The vacuum consolidation method.   In the loading and unloading of middle-sealed submarine soil or the like of the vacuum consolidation method using the tower-type airtight loading box of claim 1, the permeable lid is a movable permeable lid that moves up and down in the compartment, and the movable permeable lid is A vacuum-consolidating method for carrying out loading and unloading by pushing down compressed air or a movable lid driving device to push out the packed seabed soil or the like of the box.   2. The tower-type airtight loading box drain system apparatus according to claim 1, wherein when the drain is intermittently moved between the compartment and the vacuum tank layer, consolidation of the padded seabed soil proceeds. In addition, when the drain is moved, it is equipped with a system device that repeats washing the drained surface in the vacuum tank chamber while the density of the compartment increases due to consolidation in the compartment and scrapes off the padded seabed soil adhering to the drain. A tower type airtight loading box.   In the tower type airtight loading box according to claim 5, a unit panel drain vertically movable in which a plurality of panel drains are integrated is installed in the compartment, and a fixed permeable lid is fixed to the top end of the compartment. The fixed water-permeable lid is provided with a plurality of slits through which the unit panel drain can be worn. The unit panel drain is a vacuum tank layer, and the upper part thereof is fixed integrally with a drain holder. The vacuum tank layer is a unit panel. There is a height required to pull up the drain, the drain holder is linked to the vertical drive device, and when the unit panel drain is in the vacuum tank layer due to the vertical movement of the unit panel drain A tower type airtight loading box having a function of cleaning.   In the vacuum-consolidation dredging method of the seabed soil or the like in a flow state with a super-high water content ratio using the tower-type airtight loading box of claim 6, the unit panel drain is located in the compartment in the installation process of the airtight loading box In the state, the seabed soil is pushed into the bottom of the tower type airtight loading box, and the consolidation process advances the consolidation settlement by bringing the vacuum tank layer into a vacuum state. By pulling up the unit panel drain into the vacuum tank layer, the solid seabed soil adhering to the drain is removed by compaction and density increase by the slits of the fixed water permeable lid, and in parallel in the vacuum tank layer the unit panel drain Next, the unit panel drain is lowered to the position of the compartment, so that it becomes a new drainage surface with unfilled undersea soil etc. And, the vacuum consolidation dredging method, characterized in that in the constantly minimum distance drainage distance compaction such Chutsume marine soil to achieve rapid consolidation. In tower type airtight loading a box body in the vacuum consolidation dredging method according to claim 1 or 6, rapid consolidation step of the hermetic loading a box body provided with a vibration device by the vacuum tank layer of the hermetic loading a box body and a vacuum state A static load of atmospheric pressure and water pressure is loaded, and the vibrating device is resonated by operating the bulkhead of the airtight loading box or the natural vibration of the unit panel drain. Is a vacuum consolidation method characterized by rapid consolidation by transmitting both fluctuations of stress and pressure due to dynamic load of vibration in addition to static load. The tower type airtight loading box in the vacuum consolidation method according to claim 1 or 6 , wherein the step of eluting harmful substances in the airtight loading box provided with the vibration device is performed by setting the vacuum tank layer of the airtight loading box to a vacuum state. By loading the atmospheric pressure and water pressure of static load, and resonating this by operating the vibration device according to the natural vibration of the bulkhead or unit panel drain of the airtight loading box, In addition to static load, in addition to static load, both stress fluctuation and pressure fluctuation due to vibration are transmitted to forcibly elution of harmful substances and densification of padded seabed soil by rapid consolidation. The contaminated water purification process is a vacuum consolidation method characterized in that the contaminated water collected in the vacuum tank layer is sent to the contaminated water purification device by a drainage device to make it harmless and prevent the diffusion of contaminated seabed soil .   A dedicated work ship equipped with the tower-type airtight loading box according to claim 1 or 6, wherein a space for housing the box is formed in the center of the carriage, and the box guide that is removable around the space. The tower and the guide tower support girder are fixed to the carriage, and the box tower of the box incorporated therein has a function of moving up and down in the guide tower, and the opening space of the carriage where the box is accommodated. A dedicated work ship equipped with a mobile ship bottom device that opens and closes the ship bottom.   A dedicated work ship equipped with the tower-type airtight loading box according to claim 1 or 6, wherein a hanging rod for fixing the position of the box to the front of the carriage is fixed to the carriage, The box tower of the box incorporated in the vertical guide rail has the function of moving up and down in the guide rail, and supports the vertical support by adding the center of gravity of the dedicated work ship biased forward during dredging work to the horizontal support. A dedicated work ship that is kept stable by a mobile spud device.