JPH0429810B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an underwater bagged sand pile construction method for constructing bagged sand piles on soft ground at the bottom of the water.

[Prior art]

Conventionally, in order to improve the soft ground at the bottom of the sea, rivers, lakes, etc., various construction methods have already been proposed for constructing improvement piles in soft ground.

In other words, in a casing that is driven into soft ground, the sand in the sand bag is actively added with water to moisten it, forming a highly dense sand bag column, and then
Special Publication Showa 53-16604 and Special Publication No. 16604, which allow the casing to settle to the bottom and then pull out only the casing.
20,243 inventions are known.

In addition, in this construction method, if sand with a small particle size, such as Asamayama sand, is used, when the bagged sand pile is settled into the casing while draining the water inside the casing, the water will flow into the bagged sand. rise through the pile,
The so-called boiling phenomenon occurs, and the volume of the area where the phenomenon occurs decreases, and lateral pressure is applied there. When the casing is pulled out, thin spots, or constrictions, occur in the bagging sand pile, causing the bagging There was a problem that the quality of the sand piles deteriorated.

Therefore, a flexible bag filled with fluid, such as a balloon, is inserted into a casing that has been driven into soft ground at the bottom of the water, and a sand bag filled with sand is thrown into the casing from above the flexible bag. , relates to an improved method for constructing piles for soft ground under water, which prevents the boiling phenomenon described above by letting the sand bag column settle to the bottom of the casing while draining water below the flexible bag body in the casing. Unexamined Japanese Patent Publication 1983
-47817 has also been made, but in this case, the flexible bag such as a balloon is disposable, so there is a problem that the cost is high and it is not economical.

[Purpose of the invention]

Therefore, the present invention has been made to solve the above-mentioned conventional problems, and when forming a packed sand pile of sand bag pillars in a casing, water in the casing infiltrates into the sand bag pillars. The purpose of the present invention is to provide an inexpensive method for constructing underwater bagged sand piles for improving soft ground, which can improve the quality of bagged sand piles by preventing the occurrence of boiling phenomena.

[Structure of the invention]

That is, one of the methods for constructing underwater bagged sand piles of the present invention is that when constructing bagged sand piles in soft underwater ground,
After driving the casing into the soft ground with a water bottom, at least the bottom and the vicinity of the bottom of the bottomed cylindrical sand bag are made of an impermeable and extensible material, and the sand bag is filled with sand from above. A sand bag with a cylindrical bottom is put into the casing to form a sand bag column, and the sand bag column is allowed to settle to the bottom of the casing while draining water from the bottom surface of the sand bag column in the casing. It is constructed by leaving the column in the soft underwater ground and removing only the casing.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method of the present invention will be described below with reference to the drawings, which are vertical cross-sectional views of essential parts of an underwater bagged sand pile construction apparatus in one embodiment.

First, in the figure, 1 is a casing, and 2 is a bottom cover that is provided on the bottom of the casing so that it can be opened and closed with a hinge, etc. The casing 1 has already been driven into the soft ground 4 at the bottom of the water surface 3, and the casing Water W has entered the interior of the tank and remains. (The casing 1 is placed below the water surface 3 with the bottom plug 2 open, and the bottom plug 2 is automatically closed by a hinge etc. at the same time as landing on the soft ground 4, so water W remains inside the casing 1. ).

Next, a support frame 5 is fixed to the upper end of the casing 1, and the upper end 6 of this support frame 5 is struck in the direction shown by arrow H with a hammer (not shown) or the like installed on a work boat (not shown). By doing so, the casing 1 is driven into the soft ground 4 at the bottom of the water.

An intermediate plate 7 is fixedly installed in the middle of the support frame 5, and a sandbag attachment device 8 is attached below the intermediate plate 7.

On the outer periphery of this sandbag attachment device, a sandbag 9 is sewn in advance into a bottomed cylindrical net bag having a required diameter and length.
is compressed in the longitudinal direction and attached like a bellows.

The portion of the sand bag 9 filled with sand S is stretched in the longitudinal direction by the weight of the sand S to form a sand bag column 9'.

Therefore, the sandbag 9 used in the construction method of the present invention is
It has a cylindrical shape with a bottom, and at least the bottom and the vicinity thereof are made of a water-impermeable and extensible material, for example, a rubber material 12 such as natural rubber or synthetic rubber in this embodiment, or a material equivalent thereto. The other cylindrical portion is made of a mesh material that does not allow the sand S, which is conventionally used as a sand bag, to pass through.

On the other hand, a sand feed pipe 10 with a hopper is mounted so as to be able to come out, passing through the central opening of the intermediate plate 7 and the sand bag attachment device 8.

A guide cylinder 11 is provided at the lower part of the support frame 5 to serve as a guide when filling the sand bag 9 with sand S.

Next, 16 is the upper surface of water W that has penetrated into the casing 1 and remains, and the water surface 16 and the bottom of the sandbag column 9' form the bottom of the sandbag column 9' and its vicinity. It is blocked by a rubber material 12, and prevents water W inside the casing 1 from entering into the sand bag column 9'.

A drain port 17 is located slightly above the bottom end of the casing 1.
A drain pipe 18 is provided to communicate with the drain port 17 and project above the water surface 3, and a drain pump 19 and a drain valve 20 are connected to the drain pipe 18.
is connected.

The procedure for carrying out the construction method of the present invention using the above-mentioned apparatus will be explained below.

First, after driving the casing 1 into the soft ground 4 at the bottom of the water, a sand bag 9 is inserted from the top of the casing 1, sand S is supplied into the sand bag 9 from a work boat (not shown), and the guide tube 11 is At this point, the sand bag 9 is filled with sand to form a sand bag column 9', but the sand bag column 9' falls into the casing 1 due to its own weight.

At this time, the water surface 16 inside the casing 1 is partitioned off by the bottom rubber material 12 of the sand bag column 9', and the water surface 16 of the water W inside the casing 1 is accessed through this rubber material 12. Pressure is applied by the sandbag column 9', and water W is discharged from the casing 1 through the drain pipe 18, so that the sandbag column 9' sinks into the casing 1, and finally the sandbag column 9' When it reaches the bottom, pull up the casing 1 (at this time, the bottom plug 2 is naturally released by the hinge etc.) and leave the sand bag column 9' in the soft ground 4 as an underwater bag sand pile for ground improvement. become.

In the above embodiment, the rubber material 1 is attached to the bottom of the sand bag 9.
2 is used, but the reason is that the sandbag 9
This is because when sand S is filled inside, the rubber material 12 stretches toward the inner circumferential surface of the bottom casing 1 and adheres tightly, and does not allow water W to pass through.As a result, the water W inside the casing 1 becomes sandy. It is possible to prevent the sand S from entering the sand bag pillar 9', and to prevent the boiling phenomenon of the sand S in the sand bag pillar 9'.

〔Effect of the invention〕

Therefore, by adopting the submerged bagged sand pile construction method of the present invention, it is possible to prevent the water in the casing from penetrating into the sand bag pillars filled with sand, and to prevent the occurrence of the boiling phenomenon in the sand bag pillars. This method has the effect that it is possible to prevent this problem, and to create a high-quality bagged sand pile, and the disposable sand bags are also inexpensive, making it possible to carry out economical work.

In particular, in the construction method of the present invention, water-impermeable material such as rubber is used for the bottom of the sand bag, so watertightness is maintained completely, and a flexible bag-like material is used as in the invention of JP-A-58-47817. Since there is no need to partition the sand bag column, the bottom, and the water surface inside the casing with a body, air space, or other material, the construction of the bagged sand pile can be carried out more easily, and the work cost can be reduced accordingly. I can do it.

Further, if the construction method of the present invention is adopted, there is an advantage that even sand having a relatively small particle size can be used for underwater bagged sand piles.

[Brief explanation of drawings]

The drawing is a longitudinal cross-sectional view of a main part of an embodiment of the underwater bagged sand pile construction apparatus of the present invention. 1...Casing, 4...Soft ground, 9...Sand bag,
9'...Sand bag pillar, 12...Rubber material, 16...Water surface, S...
Sand, W...Water.

Claims (1)

[Claims] 1 When constructing bagged sand piles in soft ground with a water bottom, after driving a casing into the soft ground with a water bottom, at least the bottom and the vicinity of the bottom of the cylindrical sand bag with a bottom should be made impermeable and extensible. A cylindrical sand bag with a bottom and filled with sand from above is placed into the casing to form a sand bag pillar, and the sand bag pillar is placed on the lower surface of the sand bag pillar in the casing. A method for constructing underwater bagged sand piles, which is characterized in that water is allowed to settle to the bottom of the casing while being drained, and only the casing is removed, leaving the sand bagged column in the soft ground at the bottom of the water.