JP2002138456A - Soft ground improvement method by vacuum consolidation - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a soft ground improvement method by vacuum consolidation in which a vertical drain material can be driven in a short time with a small amount of on-site work, and the soft ground is efficiently improved. The vertical drain material (2) cut into a length corresponding to the insertion depth into the soft ground (1) has water permeability inside at a fixed length from the end at the upper end, and ventilation from the peripheral surface. A vertical drain member 2 having an airtight cap 17 fixed in advance is used at the upper end thereof, and a drainage tubular member 19 is integrally provided at the upper end of each vertical drain member 2. The airtight cap 17 is fixed in advance, and the tip of the drainage tube 18 integrally projecting from the airtight cap is fixed to the lower end of the other vertical drain material 2 to connect many vertical drain materials to one. In addition, at the ground improvement site, drainage cylinder 1
8 is cut and each vertical drain material is sequentially inserted into the soft ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving soft ground by vacuum consolidation for consolidating soft ground such as a landfill with cohesive soil.

[0002]

2. Description of the Related Art Conventionally, a soft ground improvement method by vacuum consolidation (hereinafter referred to as a vacuum consolidation method) also known as an atmospheric pressure method has been known. As an example, as shown in FIG. 7, a large number of vertical drain members 2, 2,.
, And a sand mat 3 is laid on the soft ground 1 to embed the upper end of each vertical drain material 2 in the sand mat 3. The surface of the sand mat 3 is covered with a sealing sheet 4, Inside the permeable sheet 4, the sand mat 3
There is a method of reducing the pressure by a pressure reducing means using a vacuum pump 6 through a sand filter 5 embedded in the inside.

[0003] This conventional method is a soft ground improvement method in which the inside of a drain inserted into the soft ground is depressurized so that the atmospheric pressure is loaded on the ground surface and consolidation and drainage are promoted.

[0004] In such a conventional method using vacuum consolidation, construction costs for laying a sand mat are required and a large amount of cost is required. In addition, as a method of treating dredged soil, the dredged soil is charged and condensed repeatedly. When the ground is formed, the sand mat layer will be formed in several stages in the middle, and the amount of dredged soil that can be charged will decrease by that much, which is due to the dredged soil that occurs regularly in ports etc. This is extremely undesirable in a situation where the number of processing yards is small.

[0005] In addition, a sealing sheet is indispensable, costly and requires high airtightness, and work for ensuring airtightness over a wide range requires great care and labor.

Further, in the construction method using a horizontal drain material, it is necessary to perform a complicated operation for connecting the vertical drain and the horizontal drain and for connecting the horizontal drain and the water collecting pipe.

As a method of solving the above-mentioned problems in the conventional atmospheric pressure method, recently, as shown in FIG. An air-impermeable portion 15 having air-permeability from the peripheral surface is provided, and the lower end of the air-impermeable portion 15 is inserted into the soft ground 1 to a predetermined depth from the surface thereof, A method has been developed in which an airtight cap 17 having a drainage tube 18 connected thereto is fitted to the upper end of the portion 15 while maintaining airtightness, and the drainage tube 18 is connected to a pressure reducing means. ing.

[0008]

The conventional construction method in which the upper end of each of the above-mentioned vertical drain materials is communicated with the drainage cylindrical material through an airtight cap, the continuous long vertical drain material is connected to the reel. After winding into the construction site, a series of operations such as cutting at a predetermined insertion length, forming an impermeable portion at the end, and installing an airtight cap at the construction site are performed every time the vertical drain material is driven. However, there has been a problem that the number of on-site work steps is large, and much labor and time are required.

In view of the above problems, the present invention provides a method for improving soft ground by vacuum consolidation, in which a vertical drain material can be driven in a short time with a small amount of work on site, and the soft ground can be efficiently improved. It was made for the purpose.

[0010]

SUMMARY OF THE INVENTION In order to solve the conventional problems as described above and to achieve the intended object, a feature of the present invention is to insert a permeable vertical drain material into soft ground, By reducing the pressure in the drain material by the pressure reducing means, the soft ground is compacted by vacuum pressure, and the water in the soft ground is allowed to flow into the vertical drain material and drained. An airtight cap integrally provided with a drainage pipe material is previously fixed to the upper end of the vertical drain material cut to a length corresponding to the insertion depth into the soft ground, and the vertical drain material with the airtight cap is attached. It is to carry into a soft ground improvement construction site, place the airtight cap on the upper side, and insert it into the soft ground until the airtight cap reaches a predetermined depth.

The vertical drain material cut into a length corresponding to the depth of insertion into the soft ground has water permeability inside by a certain length from the end at the upper end, and ventilation from the peripheral surface. A vertical drain member having an air-tight cap previously fixed to the upper end of the air-impermeable portion is used, and the lower end of the air-impermeable portion at the upper end of the vertical drain member is connected to the soft ground. Into a predetermined depth from the surface thereof, connect the drainage pipe to the drainage channel communicating with the decompression means, depressurize the inside of the vertical drain material by the decompression means, and insert depth into the soft ground The end of the drainage tube that is integrally protruded from the airtight cap fixed to the upper end of the vertical drain material cut to a length corresponding to the length of the vertical drain material is fixed to the lower end of the other vertical drain material, and a large number of vertical drain materials are It is transported to the ground improvement site in a state where it is connected to Lane material, it is preferred to insert into each soft in the ground separately by cutting the drainage tube material of the upper end.

[0012]

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

FIG. 1 shows a state in which a vertical drain material is inserted into a soft ground in the method of the present invention and communicated with a decompression means. In FIG. 1, 1 shows a soft ground formed by reclamation with dredged soil, for example. Reference numeral 2 denotes a vertical drain material inserted into the soft ground 1 at regular intervals.

As the vertical drain member 2, for example, a plastic board drain as shown in FIG. 2 is used. This vertical drain material 2 is configured by applying a water-permeable covering material 13 made of a nonwoven fabric to both sides of a core material 12 having a corrugated cross section.

Other examples of the vertical drain material 2 include a chemical drain made of a porous material made of synthetic resin fiber, and the like.
A hollow or porous water passage is formed inside, and a vertical drain material having shape retention properties can be used.

The vertical drain material 2 used in this method is cut in advance in a factory to a length corresponding to the insertion depth into the soft ground 1 to be constructed, and a predetermined length of the upper end of each vertical drain material 2 is set. An air-permeable portion 15 is formed by blocking the air permeability from the outer peripheral surface by a length (about 3 m), and an air-tight cap 17 is provided at the tip of the air-permeable portion 15.
Is fixed.

A drainage tube 18 made of a hose is integrally connected to the top of the airtight cap 17 in advance, and the tip of the drainage tube 18 is connected to another end as shown in FIGS. Is fixed to the lower end of the vertical drain member 2 and a number of vertical drain members 2 are connected in a single line.
The reel is taken up on a reel 22 that can be mounted on the reel 3 and is carried into a construction site.

The above-described impervious portion 15 is formed, for example, by applying an impervious synthetic resin coating to the outer surface of the water-permeable covering material 13, and the connection of the air-tight cap 17 to the tip is shown in FIG. As shown in (2), the upper end of the vertical drain material 2 is inserted into the lower end side opening, and the airtightness between the vertical drain material 2 and the airtight cap 17 is provided by, for example, taping or applying an adhesive (not shown). To integrate.

Further, each of the vertical drain members 2 has an air-impermeable portion 1.
5 has an insertion depth H1 of about 1 from the surface of the soft ground 1
m into the ground so that the protruding length H2 from the ground surface is about 2 m.

The driving of the vertical drain 2 is performed, for example, when there is supernatant water on the soft ground surface, as shown in FIG.
The vertical drain material 2 wound in advance on a reel 22 is fed out by using a barge type vertical drain driving device 24 equipped with the vertical drain 3, and the distal end of the drainage tubular material 18 is cut and connected to the vertical drain material 2. , And each is sequentially driven to a desired depth.

If the soft ground 1 has a sufficient supporting force on the upper surface of the soft ground 1 so that a vertical drain material driving device can be carried in, a ground-drainable vertical drain driving device is used.

As shown in FIGS. 1 and 5, the distal end of the drainage pipe member 18 connected to each of the vertical drain members 2 inserted into the soft ground is connected to a water collecting pipe 19, respectively. The water collecting pipe 19 is communicated with a pressure reducing means having the vacuum pump 6, and the inside of the vertical drain is depressurized through the water collecting pipe 19 and the drainage pipe member 18 to drain the flowing water, thereby consolidating the soft ground.

The depth of the impervious portion 15 into the ground is adjusted according to the properties of the soft ground, and when the air is depressurized by the decompression means, the air or water on the ground surface from the permeable portion on the outer periphery of the vertical drain material is reduced. The depth shall not be sucked.

[0024]

As described above, in the soft ground improvement method by vacuum consolidation according to the present invention, the drainage pipe material is attached to the upper end of the vertical drain material cut into a length corresponding to the insertion depth into the soft ground. The airtight cap integrally provided with the airtight cap is fixed in advance, the vertical drain material with the airtight cap is carried into a soft ground improvement construction site, the airtight cap is turned upward, and the airtight cap is brought to a predetermined depth. By inserting into the soft ground until reaching, the work of attaching the airtight cap at the construction site becomes unnecessary, the work at the site is simplified, and the construction period is shortened and the cost is reduced.

Further, the inside of the vertical drain material cut into a length corresponding to the insertion depth into the soft ground has water permeability inside by a certain length from an end portion, and ventilation from the peripheral surface is provided. A vertical drain member having an air-tight cap previously fixed to the upper end of the air-impermeable portion is used, and the lower end of the air-impermeable portion at the upper end of the vertical drain member is connected to the soft ground. To a predetermined depth from the surface thereof, connect the drainage pipe to the drainage passage communicating with the pressure reducing means, and reduce the pressure inside the vertical drain material by the pressure reducing means. The need for a sealing sheet covering the surface is eliminated, the number of working steps and materials used are reduced, and a small dredged soil treatment area can be used more effectively in ground improvement in dredged soil treatment.

Further, the tip of the drainage tube material integrally projecting from the airtight cap fixed to the upper end of the vertical drain material cut to a length corresponding to the insertion depth into the soft ground is connected to another vertical drain. A large number of vertical drain materials are fixed to the lower end of the material and are carried to the ground improvement site in a state where they are connected to each other. Each vertical drain material is cut off by cutting the drainage tubular material at the upper end thereof, and is softened. By inserting it into the ground, a large number of texts can be wound onto one reel and carried into the construction site in the same manner as before, and the vertical drain material can be driven using the conventional driving machine Can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the method of the present invention, showing a state in which a vertical drain material is inserted and a water collecting pipe is connected.

FIG. 2 is a partially cutaway perspective view of an example of a vertical drain material used in the present invention.

FIG. 3 is a partially omitted front view showing a connected state of the vertical drain material according to the first embodiment.

FIG. 4 is an enlarged cross-sectional view of a connecting portion according to the first embodiment.

FIG. 5 is a plan view showing an example of an arrangement of a vertical drain member and a drainage channel according to the embodiment.

FIG. 6 is a side view showing an example of the vertical drain material placing device of the above.

FIG. 7 is a sectional view showing an example of a conventional atmospheric pressure method.

FIG. 8 is a cross-sectional view showing another example of the conventional atmospheric pressure method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Soft ground 2 Vertical drain material 6 Vacuum pump 11 Reinforcement material 12 Core material 13 Water-permeable covering material 15 Air impervious part 17 Airtight cap 18 Drainage tube material 19 Water collecting pipe 21 Barge 22 Vertical drain material reel 23 Driving machine 24 barge type vertical drain material placing device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Shinsha 154-1, Yotsuku-cho, Nishinasuno-machi, Nasu-gun, Tochigi Prefecture Within Goyo Construction Co., Ltd. (72) Inventor Satoshi Taguchi Nishiki, Nagoya-shi 3-2-1, Goyo Construction Co., Ltd., Nagoya Branch (72) Inventor Michihiro Kimura 1-4-4, Atobe-Kitanomachi, Yao-shi, Osaka F-term in Kinjo Rubber Co., Ltd. 2D043 CA09 DA09

Claims (3)

[Claims] A vertically permeable permeable drain material is inserted into a soft ground, and the inside of the vertical drain material is decompressed by a pressure reducing means to consolidate the soft ground by vacuum pressure and to remove water in the soft ground from the vertical. In the soft ground improvement method by vacuum consolidation, which drains into the drain material and drains it, a drainage tube is integrated with the upper end of the vertical drain material cut to a length corresponding to the insertion depth into the soft ground The airtight cap provided in advance is fixed in advance, the vertical drain material with the airtight cap is carried into a soft ground improvement construction site, the airtight cap is turned upward, and until the airtight cap reaches a predetermined depth. Soft ground improvement method by vacuum consolidation characterized by being inserted into soft ground. 2. The vertical drain material cut into a length corresponding to the insertion depth into the soft ground has a water permeability inside at a predetermined length from the end at the upper end, and ventilation from the peripheral surface. A vertical drain member having an air-tight cap previously fixed to the upper end of the air-impermeable portion is used, and the lower end of the air-impermeable portion at the upper end of the vertical drain member is connected to the soft ground. The soft ground improvement by vacuum consolidation according to claim 1, wherein the drainage pipe is inserted to a predetermined depth from the surface thereof, a drainage channel communicating with the pressure reducing means is connected to the drainage tubular material, and the pressure in the vertical drain material is reduced by the pressure reducing means. Construction method. 3. A drainage pipe member integrally projecting from an airtight cap fixed to an upper end of a vertical drain material cut to a length corresponding to an insertion depth into soft ground, and being connected to another vertical drain. It is carried to the ground improvement site in a state where many vertical drain materials are connected to one and fixed to the lower end of the material. Claim 1 to be inserted into the ground
Or the soft ground improvement method by vacuum consolidation according to 2.