JP2000001846A - Underwater ground improvement method and improvement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an underwater ground improvement method having no need of disposal by improving the ground in an original position and to make it possible to reduce a construction cost as well as a disposal cost. SOLUTION: An improvement device is equipped with vertical drain members 10, an air-tight box body 12 and a water absorption device 14. The box body 12 is equipped with a main body 12a having the closed upper end and opened lower end, and the main body 12a is made to pass through the underwater ground 16 so as to surround the peripheral surfaces of the drain members 10. The water absorption device 14 is equipped with a vacuum pump 14b, and a pipe 14c linking and connecting one end thereof to a tank 14a is connected to a perforated pipe 12b provided to the inside of the box body 12. When the vacuum pump 14b is driven, the water in the main body 12a is discharged to the outside, and then, water in the underwater ground 16 collected through the drain members 10 is discharged to the outside. When the water is continuously discharged, the pressure in side the box body 12 is drecreased, and this pressure drop and the pressure difference between the hydraulic pressure applied to the box body 12 and the dead load are used to make consolidation settlement of the underwater ground 16 in an original position in part which the drain members 10 are buried.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for improving underwater ground.

[0002]

2. Description of the Related Art Conventionally, as a method for improving the underwater ground such as the sea, lakes, and rivers, it has been general practice to dredge and remove mud accumulated on the bottom of the water to repair a cross section of the underwater ground. .

[0003] In such a ground improvement method, the dredged mud has its water content reduced by dehydration or the like, mixed with a solidified material, etc., and landfilled at a landfill site such as the land. .

[0004] However, such a method of improving the underwater ground has the following problems.

[0005]

That is, when landfilling dredged mud, a large disposal site is required, which not only increases the economic burden but also takes into account environmental issues and land conditions. And it is very difficult to secure land.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a method of improving the underwater ground which does not require disposal by improving the ground in situ. Is to provide.

Another object of the present invention is to provide an apparatus for improving the underwater ground which can be diverted and which is easy to handle.

[0008]

In order to achieve the above object, the present invention comprises a step of placing a vertical drain material in a submarine ground, and a step of placing the vertical drain material on the outer periphery of the vertical drain material placed in the submarine ground. , The airtight box whose upper end is closed,
The method comprises a step of covering the underwater so that an outer peripheral edge thereof penetrates into the underwater ground, and a step of consolidating and sinking the underwater ground in the airtight box by sucking and draining the airtight box. According to the underwater ground improvement method configured as described above, since the underwater ground is consolidated and settled in situ to improve the ground, waste disposal is not required. Further, the apparatus for improving the underwater ground according to the present invention comprises a plurality of vertical drain materials cast in the underwater ground, and an outer periphery of the vertical drain material cast in the underwater ground, an upper end of which is closed, and an outer peripheral edge. Has an airtight box covered so as to penetrate into the underwater ground, and water absorbing means for sucking and draining water in the airtight box. According to the improved device configured in this way, when the water bottom ground in the airtight box is improved by consolidation and sinking by suction and drainage of the water absorbing means, the airtight box is recovered, and the airtight box is recovered. It can be diverted to the improvement of underwater ground. The airtight box is provided along a closed surface, and has a perforated pipe connected to the water absorbing means, and a drain provided below the perforated pipe so as to cover an opening of the box. Filter material, and the perforated tube and the filter material can be integrated with the airtight box. According to this configuration, clogging of the water absorbing means can be prevented, and handling is simplified by integrating the unit (integrally).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 and 2 show an embodiment of a method and an apparatus for improving the underwater ground according to the present invention.

The apparatus for improving the underwater ground shown in FIG. 1 includes a vertical drain material 10, an airtight box 12, and a water absorbing means 14. The vertical drain material 10 penetrates and is buried in the water bottom ground 16 in a substantially vertical state, and the upper end side is exposed on the water bottom ground 16, and has a function of collecting water in the water bottom ground 16.

The vertical drain member 10 is made of, for example, a paper drain member, a PVC drain member, or the like, and is arranged in large numbers at predetermined intervals in the front, rear, left, and right directions. The airtight box 12 has a rectangular box-shaped main body 12a whose upper end is closed and whose lower end is open, and this main body 12a is made of, for example, a steel plate or FRP.

The main body 12a of the airtight box 12 is penetrated into the underwater ground 16 such that the outer peripheral edge on the opening side surrounds the outer periphery of the vertical drain material 10.

The water absorbing means 14 includes a separate tank 14a installed on a work boat (not shown) located on the water surface,
A pipe 14c having a vacuum pump 14b and one end of which is connected to the separate tank 14a is connected to the airtight box 12
At the other end with a perforated pipe 12b provided inside the inside.

A perforated pipe 12b provided in the airtight box 12 is connected to a merging pipe provided at the center of the main body 12a and to the left and right sides of the merging pipe as shown by a dotted line in FIG. And is laid along the closed surface of the main body 12a and fixed to the main body 12a.

A drain filter material 12c is provided below the perforated pipe 12b. The drainage filter material 12c is made of a nonwoven fabric having a predetermined thickness with water permeability.
It is made of a woven cloth, a synthetic resin mat, etc., and allows the passage of water and prevents the penetration of earth and sand.

In the case of this embodiment, the drainage filter material 12c is formed to have a size to cover the opening of the main body 12a, and when the main body 12a penetrates into the underwater ground 16,
It comes into close contact with the upper end side of the vertical drain material 10.

The improved device having such a configuration is installed as follows. That is, first, when installing the improvement device, the vertical drain material 10 is cast from a work boat to a predetermined depth of the underwater ground 16.

The vertical drain material 10 is cast in the area of the underwater ground 16 to be improved so as to be positioned at each of the lattice-shaped intersections at predetermined intervals in the front-rear and left-right directions. The upper end side of each drain material 10 is cut while projecting upward from the underwater ground 16.

When the placement of the vertical drain material 10 is completed, the airtight box 12 is installed. In the airtight box 12, a perforated pipe 12b and a drainage filter material 12c are previously integrated inside a main body 12a, and these members are unitized.

The unitized airtight box 12 is suspended and supported by a crane or the like with the opening side of the main body 12a facing downward, and penetrates into the underwater ground 16 by its own weight.

When the installation of the airtight box 12 is completed, the pipe 14c is connected to the perforated pipe 12b.

In the apparatus for improving the underwater ground constructed as described above, when the vacuum pump 14b of the water absorbing means 14 is driven, first, the water in the main body 12a of the airtight box 12 is discharged.
2b, the water in the underwater ground 16 that has been discharged to the outside and then collected through the vertical drain material 10 is
It is discharged to the outside via the filter material 12c.

When such water discharge is continued, the pressure in the hermetic box 12 decreases, and the pressure difference between the pressure drop and the water pressure and the weight applied to the hermetic box 12 is used. Then, the underwater ground 16 in the portion where the vertical drain material 10 is buried is consolidated and settled at the original position, and the ground improvement of the underwater ground 16 is performed.

When the underwater ground 16 is improved as described above, the mud is condensed and settled in situ and treated. Therefore, unlike the conventional method, a disposal site is not required, and construction costs and treatment costs are greatly reduced. It becomes possible to reduce.

In the process of the ground improvement, the airtight box 12 is used to create a pressure difference. When the ground improvement is completed by a predetermined consolidation settlement, only the vertical drain member 10 is removed from the bottom. The remaining members can be collected in the ground 16 and diverted to ground improvement in another place.

At this time, in the case of the present embodiment, the airtight box 12 is provided along the closed surface and the water absorbing means 1 is provided.
4, a perforated pipe 12b connected to the
Since it has a drain filter material 12c provided so as to cover the opening of the box 12 below, the perforated pipe 12b and the filter material 12c are unitized together with the main body 12a of the box 12, Clogging of the water absorbing means 14 can be prevented, and handling is simplified by unitization.

[0027]

As described above in detail in the embodiments,
ADVANTAGE OF THE INVENTION According to the improvement method and apparatus of the undersea ground which concern on this invention, since a disposal site is not required, it becomes possible to reduce construction cost and processing cost greatly.

Further, the required water depth can be secured by sinking the underwater ground.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of a construction state of a method and apparatus for improving underwater ground according to the present invention.

FIG. 2 is an explanatory top view of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vertical drain material 12 Airtight box 12a Main body 12b Perforated pipe 12c Drain filter material 14 Water absorption means 14a Separator 14b Vacuum pump 16 Underwater ground

Claims (3)

[Claims] A step of placing a vertical drain material in the underwater ground; and a step of placing an airtight box having an upper end closed on the outer periphery of the vertical drain material placed in the underwater ground. A water bottom, comprising: a step of penetrating and submerging the water bottom ground; and a step of consolidating and sinking the water bottom ground in the air tight box by sucking and draining the air tight box. How to improve the ground. 2. A plurality of vertical drain materials cast in the underwater ground, and an upper end is closed on an outer periphery of the vertical drain material cast in the underwater ground, and an outer peripheral edge penetrates into the underwater ground. An improved apparatus for improving the underwater ground, comprising: a hermetically sealed box covered in such a manner as described above; and water absorbing means for sucking and discharging water in the hermetically sealed box. 3. The airtight box is provided along a closed surface, and is provided with a perforated pipe connected to the water absorbing means, and an opening of the box below the perforated pipe. The apparatus for improving the underwater ground according to claim 2, further comprising: a drainage filter member provided in the airtight box, wherein the perforated pipe and the filter member are integrated with the airtight box.