JP2002030646A - Construction method for horizontal drain using biodegradable draining member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate excavation work after improvement of soft soil by decomposing biodegradable draining members in a short time in the construction method for improvement of soft soil by use of the biodegradable draining members. SOLUTION: The water-pervious draining members 4 formed with a biodegradable material are horizontally laid in place and negative pressure is applied to the interior of each draining member 4 by a pressure reducing means, so that soft soil is consolidated by a vacuum pressure. Thereafter, a hose 23 is passed through each draining member 4 to supply air and other decay promoting substances to promote biodegradation of the biodegradable material forming the draining members 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a case where dredged soil such as rivers and dams is improved at an early stage so that it can be transported by land transportation such as dump trucks, or ground excavation such as shield construction is performed after ground improvement. The present invention relates to a horizontal drain construction method using a biodegradable drain material for performing soft ground improvement at a place where excavation work may be performed after the improvement, such as a place where there is a possibility of performing excavation work.

[0002]

2. Description of the Related Art In general, as a method of improving soft ground, a drain material is laid in the ground, and the inside of the drain material is made negative to apply atmospheric pressure to the ground surface to consolidate the drain material. There is known a consolidation dewatering acceleration method (also known as vacuum consolidation method) in which water is drained through a pipe.

As a method of this kind, a large number of drain materials such as plastic board drains are buried in a soft ground horizontally, and a decompression hose is connected to an end of each drain material, and the hose is connected through the hose. There is known a horizontal drain construction method in which a negative pressure is generated by a pressure reducing means such as a vacuum pump to drain the water.

[0004]

In the conventional dewatering-improved ground using the horizontal drain method using a plastic board drain, a large number of drain materials are buried in a multi-stage arrangement in the depth direction. If you need to transport earth and sand later, or if excavation work occurs in the future,
The drain material hinders the excavation by a drilling machine such as a backhoe, and there is a problem that the processing of the drain material after the excavation requires expense.

Further, a biodegradable drain material using a biodegradable material such as an organic material has been developed as a drain material. It is difficult to adjust the degradability of the biodegradable material, as the function may be reduced, and it is considered that the strength of the biodegradable material with slow degradability hardly decreases during excavation after ground improvement There was a problem that is.

In view of the above-mentioned conventional problems, the present invention sufficiently exerts the function as a drain material during a period required for improvement of consolidation, and decomposes rapidly after completion of consolidation. The purpose of this is to make adjustments possible.

[0007]

SUMMARY OF THE INVENTION The features of the present invention for solving the conventional problems as described above and achieving the intended purpose are as follows.
A water-permeable drain material made of synthetic resin or the like is laid horizontally in the soft ground, and the inside of the drain material is set to a negative pressure by a decompression means such as a vacuum pump. Drain in the drain material, in a horizontal drain method to consolidate the soft ground, the drain material is made of a biodegradable material, and connected to a hose made of an air-impermeable material at both ends of the drain material,
The hose or one of the hoses is communicated with the pressure reducing means, and the pressure in the drain material is reduced to a negative pressure by the pressure reducing means,
After the consolidation of the soft ground is completed, a decomposition promoting substance that promotes the biodegradation of the biodegradable material constituting the drain material is supplied through the hose into the drain material.

[0008] The horizontal drain material should be provided with a continuous ventilation / water passage in the longitudinal direction, and a biodegradable material that decomposes in an aerobic environment should be used. However, it is preferable to use air as the biodegradation promoting substance from the viewpoints of the shape and environmental protection.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is used for dewatering a dredged soil of a river or a dam will be described with reference to the drawings.

Prior to dredging, as shown in FIG. 1, a dredged soil storage facility 2 surrounded by a bank 1 is constructed. Then, the dredged soil dredged by using a dredge pump (not shown) is supplied into the facility 2 together with water. The input dredged soil becomes soft ground 3 and settles in the facility 2.

After the soft ground 3 formed by the dredged soil thus introduced reaches a predetermined depth, a large number of drain members 4 are laid horizontally and at predetermined intervals in the vertical and horizontal directions. For laying the drain material 4, a conventionally used drain material horizontal laying device 5 as shown in FIG. 3 can be used.

The laying apparatus 5 includes a barge 7 floating on the supernatant water layer 6 on the soft ground 3, the upper end of which is rotatably supported in the front-rear direction with respect to the barge 7, and which hangs down in the soft ground 3. , And a plurality of drain material reels 10, 10,... For winding and mounting the drain material 4 fed along the mandrel 8.

The mandrel 8 has drain material feeding portions 11, 11... At regular intervals in the longitudinal direction, and the drain material 4 drawn from each reel 10 is made to extend along the rear surface of the mandrel 8, and from each feeding portion. Soft ground 3 each
I try to let it go inside. The angle of the mandrel 8 is adjusted by pulling one of the rotating operation wires 12 and 12 stretched back and forth and extending the other.

The laying device 5 is floated on the supernatant water layer 6 and the drain material 4 is drawn out from the mandrel 8 while moving the barge 7 from both sides of the dredged soil accommodating facility 2 through the marine vessel maneuvering wire 9 and moving out. The drain members 4 are laid in a multi-stage arrangement with a depth.

As the drain material 4 to be laid in this way, for example, a material formed entirely of a biodegradable material is used, and as shown in FIG. 4, a large number of grooves extending in the longitudinal direction are integrally formed. Water-permeable sheet 16
And a large number of parallel ventilation passages 17 having a shape in which the grooves are closed by a water-permeable sheet 16 are provided in the longitudinal direction.

Examples of the biodegradable material include cellulose, cellulose acetate resin, starch, polylactic acid, aliphatic polyester resin such as polycaprolactone, polymer material such as resin containing a decomposition accelerating substance, and biodegradable natural material. Can be used alone or in combination of two or more. The biodegradable material may be a composite of a non-biodegradable material, and may be a material that is entirely divided by decomposition of the biodegradable material.

Prior to the installation of the drain material 4, a suction hose 20 made of an air-impermeable material is connected to the tip of the drain material 4 via a cap 21. As shown in FIG. 5, the cap 21 is a main body 21 fitted outside the distal end of the drain material 4.
a, and a hose fitting tube portion 21b having an opening communicating with the top of the main body portion 21. The suction hose 20 is fitted to the outside of the hose fitting tube portion 21b.

In this way, the suction hose 20 is connected to each drain member 4 and the suction hose is connected to two.
3, the mandrel 8 is rotated so as to be suspended in the soft ground 3 as shown in FIG. (Not shown), and the drain material 4 is fed out while being moved to the other end side of the processing facility 2, whereby a plurality of drain materials 4 are simultaneously laid in an upper-lower arrangement.

After the barge 7 is moved to the vicinity of the other end of the processing facility 3, the drain material 4 is cut at a predetermined length, and air is supplied to the tip of the drain material 4 via the cap 21 described above. The drain hose 4 is laid in a state where the other end of the air supply hose 23 is connected to the ground as shown in FIG.

This operation is repeated successively at regular intervals, and the drain members 4 are laid almost uniformly over the entire soft ground 3.

After the drain material is laid in this manner, the surface of the soft ground 3 is covered with the air-impermeable sheet 24 and the suction hose 20 is connected to a pressure reducing device using a vacuum pump 25. And the valve 2
7 is closed to make air supply impossible. In this state, the decompression device is operated to depressurize the inside of the drain material 4 through the suction hose 20 to suck and discharge water in the ground. As a result, the inside of the ground 3 is depressurized below the atmospheric pressure, and the ground is compacted by the atmospheric pressure applied to the surface of the impermeable sheet 24.

After the ground has been improved by vacuum consolidation in this way, the on-off valve 27 is opened to introduce air as a decomposition promoting substance into the drain material 4. At this time, the depressurizing device may be operated at the same time to forcibly suction. As a result, the inside of the drain material 4 becomes an aerobic environmental condition in which oxygen is introduced, the aerobic microorganisms in the soil are activated, and the decomposition of the drain material 4 formed of a biodegradable material is promoted, and the drain material 4 is decomposed at an early stage. You.

The intake from the air supply hose 23 may be performed continuously or intermittently for a predetermined time at regular intervals.

As described above, in addition to using air as a decomposition promoting substance by utilizing the difference in decomposition rate between an anaerobic environment and an aerobic environment, it also promotes the decomposition of microorganisms such as soil bacteria that perform biodegradation. The aqueous solution containing the substance may be forcibly circulated through the circulation path 28 shown in FIG. For example, when a cellulose acetate resin, which is a biodegradable resin, is used for the drain material, it is conceivable to mix soil bacteria with water and aerial circulation while aerating the mixture.

By supplying the decomposition promoting substance into the drain material 4 in this manner, the biodegradation of the drain material is promoted, and as the decomposition proceeds, the flow of air and other decomposition promoting substances deteriorates. Supply continues until 4 is closed by decomposition.

[0026]

As described above, in the horizontal drain method using the biodegradable drain material according to the present invention, the drain material is made of a biodegradable material, and both ends of the drain material are made of an impermeable material. The two hoses or one of the hoses are connected to the decompression means, and the pressure in the drain material is reduced to a negative pressure by the decompression means, and after the consolidation of the soft ground is completed, the By supplying a decomposition promoting substance that promotes the biodegradation of the biodegradable material constituting the drain material through a hose, the environment for activating aerobic microorganisms around the drain material after the completion of consolidation of the soft ground is completed. And the biodegradation of the drain material can be promoted. For this reason, an accurate drainage action can be obtained during the consolidation period, and the decomposition rate of the drain material can be controlled such that it is quickly decomposed after the consolidation is completed. This has the effect of eliminating troubles and eliminating the need for drain material disposal.

Further, by using a horizontal drain member having a continuous ventilation / water passage in the longitudinal direction therein, drainage during compaction and supply of a decomposition promoting substance during biodegradation can be accurately performed. You.

It is preferable to use a material that decomposes a biodegradable material in an aerobic environment and use air as a biodegradation promoting substance in terms of cost and environmental protection.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a state during vacuum consolidation in a horizontal drain method using a biodegradable drain material according to the present invention.

FIG. 2 is a cross-sectional view showing a state of supplying a biodegradation promoting substance according to the first embodiment.

FIG. 3 is a side view showing an example of a drain material horizontal laying device used in the method shown in FIG.

FIG. 4 is a partially cutaway perspective view showing an example of a drain material used in the method shown in FIG.

FIG. 5 is a partial plan view showing a state where a hose is connected to the drain material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Embankment 2 Dredged soil accommodation facility 3 Soft ground 4 Drain material 5 Drain material horizontal laying device 6 Superficial water layer 7 Berth boat 8 Mandrel 9 Driving wire 10 Drain material reel 11 Drain material feeding part 12 Mandrel operation wire 15 Drain body 16 Water permeable sheet 17 Ventilation / water passage 20 Suction hose 21 Cap 21a Main body 21b Hose fitting tube 22 Clamping fitting 23 Air supply hose 24 Impermeable sheet 25 Vacuum pump 27 Open / close valve 28 Circulation path

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 10, 2000 (2008.1.
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008] The horizontal drain material is provided with a ventilation / continuous water passage which is continuous in the longitudinal direction inside, and a material which decomposes in an aerobic environment as a biodegradable material is used. It is preferable to use air as a biodegradation promoting substance in terms of cost and environmental protection.

Continuation of the front page (72) Inventor Yoshinori Kurumada 154-1, Yotsuku-cho, Nishinasuno-machi, Nasu-gun, Tochigi Prefecture Goyo Construction Co., Ltd. (72) Inventor Masafumi Yoshikawa 1-4-4, Atobe Kitanomachi, Yao-shi, Osaka No. 25 Inside Kinjo Rubber Co., Ltd. (72) Inventor Masanori Ito 3-2-5 Kasumigaseki Building, Chiyoda-ku, Tokyo 16th floor, Kasumigaseki Building Daicel Chemical Industries, Ltd. F-term (reference) 2D043 CA04 CB08 DA03 DC02 DC11 DC03 DD03 DD20

Claims (3)

[Claims] 1. A water-permeable drain material made of synthetic resin or the like is laid horizontally in a soft ground, and the inside of the drain material is made negative by a pressure reducing means such as a vacuum pump. Drain the water into the drain material,
In the horizontal drain method for consolidating the soft ground, the drain material is made of a biodegradable material, hoses made of an impermeable material are connected to both ends of the drain material, and both or one of the hoses is depressurized. After the consolidation of the soft ground is completed, the hose is passed through the drain material, and the biodegradable material constituting the drain material is biodegraded. A horizontal drain method using a biodegradable drain material, characterized by supplying a decomposition promoting substance for accelerating the decomposition. 2. The horizontal drain method using a biodegradable drain material according to claim 1, wherein the horizontal drain material is provided with a ventilation / water passage continuous in the longitudinal direction inside. 3. A horizontal drain method using a biodegradable drain material according to claim 1, wherein a material which decomposes in an aerobic environment is used as the biodegradable material, and air is used as a biodegradation promoting substance. .