JPH0469250B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for draining water inside a casing in an underwater pack drain construction method in which sand bag pillars are constructed in soft ground such as the seabed or other soft ground.

[Prior art]

Conventionally, the sand drain method using sand pillars has been widely adopted as a construction method for improving soft ground such as the seabed.

However, as the length of the sand pillar increases, there is a problem in construction as the sand pillar breaks during construction and becomes discontinuous or thin. Not only did it have a large diameter and required a large amount of sand, but the drain effect was unstable and its reliability was questionable.

Therefore, when a casing is driven into soft ground such as the seabed and a sand bag is dropped into the casing, the water below the sand bag inside the casing is discharged through a drain pipe by a pump.
The sandbag is deposited in soft ground such as the seabed, and the sandbag is deposited into the casing while adjusting the drainage amount to form a sandbag column, and then the casing etc. are removed leaving only the sandbag column. A method and device for forming pillars was invented in Japanese Patent Publication No. 53-16604, and is now in practical use as one of the most effective construction methods for underwater pack drain construction.

In the above-mentioned underwater pack drain construction method, while the sand bag column is being formed inside the casing, the sand bag slowly descends inside the casing due to its own weight, while the water that fills the casing is drained from the bottom of the casing. It will be discharged to the outside from the drain pipe connected to the .

However, when lowering the sandbag into the casing during construction of the sandbag pillar, the speed of descent of the sandbag pillar is almost the same as the rate of descent of the water surface, and it takes time for the sandbag pillar to sink to the bottom, which increases the sandbag pillar. There was a problem in that it took a long time to create.

[Purpose of the invention]

Therefore, the present invention solves the above-mentioned conventional problems,
The purpose of this project is to use the underwater pack drain method to increase the speed at which the sand bag pillars sink to the bottom within the casing, thereby shortening the time it takes to construct the sand bag pillars.

[Structure of the invention]

That is, in the casing drainage method of the underwater pack drain construction method of the present invention, a casing is driven into soft ground such as the bottom of the water, and while draining the water filled in the casing, a sand bag is lowered into the casing to form a sand bag column. In the underwater pack drain construction method, in which sand bag pillars are created in soft ground such as the water bottom, the casing etc. are removed leaving only the sand bag pillars. Connect with a drain pipe that has an opening and a drain valve,
When a sandbag column is formed within the casing, the water in the casing is released from the drainage outlet, and after the sandbag column passes through the drainage outlet above the casing, the drainage port is unblocked by the sandbag column. , drainage is discharged from above the sandbag column from the drain port and acts to press the sandbag column downward.

〔Example〕

The details of the present invention will be explained below with reference to the drawings. Fig. 1 is an overall layout diagram of a sand bag column forming device in an embodiment to which the method for draining water in a casing in the underwater pack drain method of the present invention is applied. , FIG. 2 is an enlarged side view showing the joint between the lower part of the hopper section shown in FIG. 1 and the cassette, and FIG. 3 is an enlarged side view of the hopper section shown in FIG. 1.

First, in the apparatus shown in FIG. 1, the casing 2 is filled with water W while the casing 2 is driven into the flexible ground 1 such as the water bottom to be improved.

Next, a water-shielding material 4 is inserted into the casing 2 in advance, and a sand bag 3 is inserted from above the water-shielding material 4, and the sand bag 3 is supplied via a belt conveyor, chute, etc. (not shown). The sand S is supplied from the hopper section 5.

This hopper part 5 has sand S as shown in FIG.
A screw conveyor 6 for supplying a fixed amount of sand S is provided in the feeding direction of the sand S, that is, in the vertical direction, and this screw conveyor 6 is rotated by a motor 7, and is further supplied by a supply water pump 8. Water W is supplied to the lower part of this screw conveyor 6 via a supply water pipe 15 having a flow meter 21, and is injected from a supply water injection nozzle 9 to mix the sand S into the sand column 3. are being introduced.

As mentioned above, the lower part of the hopper section 5 consisting of the screw conveyor 6, the supply water injection nozzle 9, etc.,
A cassette 10 for the sand pillar 3 as shown in FIG.
It is removably connected to the lower end of the cassette joint 12.

Furthermore, a sand bag 3 with a bottom made of a water-permeable net or the like is compressed in the longitudinal direction and attached to the outer periphery of the cassette 10 in a bellows shape. It descends into the casing 2 filled with water W.

Furthermore, when the sand bag 3 supplied with sand S as described above descends into the casing 2, the casing 2
In order to drain the water W filled in the casing 2, as shown in FIG.
The upper and lower parts of the building are arranged so as to communicate with each other.

On the other hand, two upper and lower sand surface detection sensors 18A, 18B are provided in the upper part of the casing 2 shown in FIG.
8B has a plurality of tactile switches that abut on the outside of the sand bag so as to make contact with the sand bag, and when the sand bag is filled with sand, the tactile switches are pressed and sensed.

That is, when the position of the upper end surface X of the sand column contacts the upper sand surface detection sensor 18A, that is, when the upper end surface X is located above this sand surface detection sensor 18A,
In conjunction with the detection by the sand surface detection sensor 18A, the screw conveyor 6 in the hopper section 5 and the water supply pump 8 are activated.
is stopped, and when the position of the upper end surface X is not in contact with the lower sand surface detection sensor 18B, that is, when the upper end surface X is located below this sand surface detection sensor 18B,
A control device 20 is provided to close the drain valve 13 of the drain pipe 14 for automatic control.

The drain valve 13 is operated by an air cylinder controlled by a solenoid valve, and has two positions: a set opening and a fully closed position.
Opening and closing is smooth.

When applying the underwater pack drain method using the sand column forming device with the above configuration, it is necessary to
Drive casing 2 into the casing 2.
The water W filled in the inside is discharged through the drain pipe 14 due to the downward pressure generated when the sand bag 3 into which the sand S and the supply water W have been introduced descends inside the casing 2, forming a sand bag pillar, and the sand After the formation of the sandbag pillars is completed, the casing 2 is removed leaving only the sandbag pillars.

Therefore, in the present invention, the drain pipe 14 is connected above and below the casing 2 to form a circulation circuit with the drain pipe 14 and the casing 2.
A part of the pipe is made up of a flexible pipe 14A, and a drainage outlet 24 is provided in the middle of the flexible pipe 14A.

Therefore, when a sandbag column is formed within the casing 2, as the sandbag 3 descends, the water W filling the casing 2 passes through the drain port 2A at the bottom of the casing 2 and reaches the top of the drain pipe 14. The water is discharged to the outside from the provided drainage outlet 24. That is drain port 2
This is because B is closed by the sandbag pillar. In addition, after the sandbag pillars are constructed, the upper end surface
Since the circulation circuit is cased by the drain pipe 14 and the drain pipe 14, the drainage water inside the casing 2 helps the sandbag column to descend, and as a result, the weight balance effect can be enhanced, and the sandbag column can be removed from the top. It will be pressed down by the discharged water, and the falling speed will increase.

Here, the reason why at least a part of the drain pipe 14 is made of the flexible pipe 14A is because the drain pipe 14 is integrated with the casing 2 when the casing 2 is installed, but the drain pipe 14 is provided at the top of the drain pipe 14. This is because it is desirable that the drainage opening 24 is always maintained at a constant height, and in this embodiment, the drainage opening 24 is
Only the upper portion having the above structure is the flexible tube 14A.

〔Effect of the invention〕

Therefore, according to the casing drainage method of the underwater pack drain construction method of the present invention, the discharged water from inside the casing is re-injected and circulated into the upper part of the casing during the descending process after sand bag pillar construction. This will have a weight balance effect on the sandbag pillar, which can increase the falling speed of the sandbag pillar.
This has the effect of reducing the time required to create sandbag pillars.

Furthermore, according to the present invention, the lowering of the sandbag pillar, the discharge of water in the casing, and the supply of the discharged water onto the sandbag pillar can be performed without using any pumps, thereby saving costs and power. The amount of drainage inside the casing can be adjusted by opening and closing a drainage valve installed in the drain pipe, and drainage from above to the sandbag pillars is automatically applied when the sandbag pillars pass through the upper drainage port. The major feature lies in the fact that it is carried out in such a way.

[Brief explanation of drawings]

Fig. 1 is an overall layout of a sand column forming device in one embodiment to which the underwater pack drain method of the present invention is applied, and Fig. 2 is an enlarged side view showing the joint between the lower part of the hopper and the cassette in Fig. 1. FIG. 3 is an enlarged side sectional view of the hopper portion of FIG. 1. 1... Soft ground, 2... Casing, 2A...
Bottom drain, 2B...Top drain, 3...Sand bag, 10...Cassette, 14...Drain pipe, 14A
...Flexible pipe, 24...Drainage outlet.

Claims (1)

[Claims] 1. A casing is driven into soft ground such as a water bottom, and while draining the water that has filled the casing, a sand bag is lowered into the casing to form a sand bag pillar, and the sand bag pillar is left behind. In the underwater pack drain construction method, in which sandbag pillars are constructed in soft ground such as the water bottom from which the casing etc. are removed, the upper and lower parts of the casing are connected by a drain pipe that has a drainage outlet and a drainage valve in the middle. When a sandbag is formed in the casing, the water in the casing is released from the drainage outlet, and after the sandbag pillar passes through the drainage opening above the casing, the water is discharged from above the sandbag pillar. A method for draining water inside the casing in the underwater pack drain construction method, which presses down the sandbag pillar.