JPH0441210B2 - - 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 dense and tightly packed 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 such construction methods, if sand with a small particle size is used, water rises inside the bagged sand pile when the bagged sand pile is settled into the casing while draining the water in the casing. 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 sandbag type inside a casing, water inside the casing infiltrates into the sandbag column. 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 underwater bagged sand pile construction methods of the present invention is that when constructing a packed sand pile in soft underwater ground,
After driving the casing into the soft water-bottomed ground, a cylindrical sand bag with a bottom, the bottom of which is made of a towel-like material and filled with sand from above, is placed into the casing, and sand is poured into the casing. forming a bag pillar,
While an air layer is interposed between the water surface in the casing and the bottom of the sand bag, the water in the casing is discharged and the sand bag column is allowed to settle to the bottom of the casing, and the sand bag column is moved to the bottom of the water. It consists of leaving the pillar in the soft ground and removing only the casing.
Another invention provides that when constructing a bagged sand pile in soft ground with an underwater bottom, after driving a casing into the soft ground with an underwater bottom, at least the bottom of a cylindrical sand bag with a bottom is sealed so that sand does not pass through it, and A bottomed cylindrical sand bag made of an easily extensible material and filled with sand from above is put into the casing to form a sand bag column, and the water surface in the casing and the bottom of the sand bag are connected to each other. An air layer is interposed between the sandbags and the water inside the casing is discharged while supplying air from the lower end of the casing, causing the sandbags to settle to the bottom of the casing, leaving the sandbag pillars in the weak ground at the bottom of the water. , consists of an underwater bagged sand pile construction method characterized by 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 plug that is openable and closable with a hinge or the like.The casing 1 has already been driven into the soft ground 4 at the bottom of the water surface 3, and the casing 1 Water W has entered inside 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 8, a sandbag 9 is sewn in advance into a bottomed cylindrical mesh 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 is made of a material that does not allow sand to pass through and is easily stretchable, such as a towel material 12, and the other cylindrical part is conventionally used as a sand bag. It is made of a mesh material that does not allow sand S 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 the water W that has penetrated into the casing 1 and remains, and an air layer 15 is created in advance between the water surface 16 and the toweling-like material 12 at the bottom of the sand bag column 9'. It is mediated.

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.

Further, in order to replenish the air layer between the water surface in the casing and the bottom of the sand bag when the air layer becomes insufficient, an air pipe 21 is opened at the bottom of the casing 1, and the upper part of the air pipe 21 is opened at the water surface. 3, and a compressor 22 is attached.

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, an air layer 15 having an appropriate distance is interposed between the water surface 16 in the casing 1 and the toweling-like material 12 at the bottom of the sandbag column 9'.

Pressure is applied to the upper surface 16 of the water W inside the casing 1 by the sand bag column 9' through the air layer 15, and the water W is drained into the casing 1 through the drain pipe 18.
By discharging the sandbag pillar 9' to the outside, the sandbag pillar 9' sinks into the casing 1, and finally the casing 1 with the sandbag pillar 9' on the bottom is pulled up (at this time, the bottom plug 2 is released naturally by a hinge etc.). ), the sand bag pillars 9' are left in the soft ground 4 as underwater bag sand piles for ground improvement.

As mentioned above, part of the air in the air layer 15 interposed between the upper surface 16 of the water W and the toweling-like material 12 passes through the toweling-like material 12, so the amount of air may decrease. In such a case, air A is supplied to the air layer 15 from the lower part of the casing 1 through the air pipe 21.

Here, a terry cloth-like material 12 is used for the bottom plug of the sand bag 9, but this is because terry cloth is generally available at a low price, and when it contains water W, it expands and the bottom of the sand bag column 9' This is because the focus is placed on the fact that it comes into close contact with the inner circumferential surface of the casing 1, and as a result, relatively good watertightness can be maintained. Although terry cloth is used here as an example, other materials may be used as long as they do not allow sand to pass through and are easily stretchable.

Furthermore, by interposing the air layer 15, it is possible to prevent the water W in the casing 1 from penetrating into the sand bag column 9', thereby preventing the boiling phenomenon within the sand bag column 9', which has been a problem in the past. become.

〔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.

Further, since the water inside the casing is discharged with an air layer interposed between the water surface inside the casing and the sand bag, and the sand bag columns are allowed to sink to the bottom of the casing, the drain pump 19 and the drain valve By adjusting 20, the speed of descent of the sandbag column can be controlled. As a result, it is possible to prevent the sandbag from falling suddenly and to freely choose the speed of descent.

In addition, by draining the water inside the casing while supplying air from the bottom end of the casing, the lack of air in the air layer is replenished, promoting complete separation of the sand bag and water, and the sand bag is completely removed. It can also act to enhance the rate of descent.

Furthermore, since the water in the casing pipe can be completely drained, the sandbag pillar can be completely lowered to the vicinity of the tip of the casing.

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 the drawing]

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'...Sandbag pillar, 12...Town-like material, 15...
Air layer, 16... Upper surface of water, 21... Air pipe, S
...Sand, W...Water.

Claims (1)

[Scope of Claims] 1. When constructing a bagged sand pile in soft ground with an underwater bottom, after driving a casing into the soft ground with an underwater bottom, at least the bottom of the cylindrical sand bag with a bottom is inserted without allowing sand to pass through, A bottomed cylindrical sand bag made of an easily extensible material and filled with sand from above is put into the casing to form a sand bag column, and the sand bag is placed between the water surface in the casing and the bottom of the sand bag. The sandbag column is allowed to settle to the bottom of the casing while the water inside the casing is freely discharged with an air layer interposed between the sandbag column and the casing, leaving the sandbag column in the soft ground at the bottom of the water. An underwater bagged sand pile construction method that is characterized by the removal of sand piles. 2. When constructing a packed sand pile in soft ground with a water bottom, after driving a casing into the soft ground with a water bottom, at least the bottom of the bottomed cylindrical sand bag is made of a material that does not allow sand to pass through and is easily stretchable. A cylindrical sand bag with a bottom and filled with sand from above is put into the casing to form a sand bag pillar, and an air layer is created between the water surface in the casing and the bottom of the sand bag. The sandbag pillars are allowed to sink to the bottom of the casing while supplying air from the lower end of the casing and discharging the water in the casing in an adjustable manner, leaving the sandbag pillars in the soft ground at the bottom of the water. An underwater bagged sand pile construction method that is characterized by removing sand piles.