JPS648135B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for constructing sandbag pillars by tightening sandbags with water when forming sandbag pillars in soft ground such as the seabed.

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, sand breaks during construction, causing the sand pillar to become discontinuous or become thinner, creating problems during construction. Not only did this require 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 into the casing while adjusting the drainage amount to form a sandbag pillar, and then the casing etc. are removed leaving only the sandbag pillar. An invention was made in Japanese Patent Publication No. 53-16604 concerning the construction method and device for forming a block post, and it is put into practical use as one of the effective construction methods of the underwater block drain method.

In this case, the sand bag pillars are created by pouring a slurry of sand and water into the net bag, but the conventional method was to drain the excess water from the sand bag pillars through the mesh of the net bag. Because sand particles with a diameter smaller than the mesh are washed away, the sand column creation efficiency is poor, and the sand yield is poor, which increases the cost of sand and increases the cycle time. There is.

As a countermeasure to this problem, there is a method of using a mesh bag with a fine mesh, but this method has the disadvantage that the cost of the mesh bag increases.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the drawbacks of the conventional construction methods, to increase the yield of sand while using conventional net bags, and to make it possible to construct sand bag pillars at high speed. This is what I did.

That is, in the sand bag pillar construction method of the present invention, a casing is driven into soft ground such as the seabed, and while water filling the casing is discharged through a drain pipe, a slurry of sand and water is poured into a net bag inside the casing. A sandbag filled with sand is lowered into the casing to form a sandbag pillar, and the casing, etc. is removed leaving only the sandbag pillar, and the sandbag pillar is created in soft ground such as the seabed. In the underwater pack drain construction method,
Separate sand and water, install a filter on the outer periphery or inside of the part of the net bag that is not contained in the casing, and have a mesh finer than the sand particles, and drain excess water when tightening the sand bag through the filter. In addition, in order to further improve the drainage efficiency of surplus water during water tightening, suction can be drawn into an outer tube provided on the outer periphery of the device consisting of the above-mentioned net bag and filter as necessary. This is a construction method that applies force.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall layout diagram of a sand bag pillar creation device of an embodiment to which the construction method of the first invention of the present invention is applied, and FIG. FIG. 2 is an enlarged side sectional view of the water tightening portion of the sandbag pillar shown in the figure.

First, in the sand bag pillar creation device shown in Fig.
Water W is present in the casing 2 in the state where it is driven.

A net bag 3 with a bottom is inserted into the casing 2 from a net bag cassette 4, and the sand S supplied via the sand supply hopper 5, belt conveyor 6, and chute 7 is fed through the supply water adjustment valve 8. It is introduced into the sand bag 3 via the sand supply hopper 10 together with the supply water W supplied from the supply water pipe 9.

As described above, the net bag 3 into which the sand S in a slurry state containing the supply water W is poured from the sand supply hopper 10 descends inside the casing 2 as an underwater pack P, but the net bag 3 inside the casing 2 The water W previously filled in the lower part is discharged through the discharge water adjustment valve 1.
The underwater pack 9 is gradually discharged out of the casing 2 through the drain pipe 13 having the sandbag 2, and accordingly the underwater pack 9 becomes a sandbag pillar and descends inside the casing 2.

Further, a cylindrical filter 16 having meshes narrower than the particles of the sand S is provided on the outer periphery of the portion of the net bag 3 that is not inside the casing 2.

In the sand bag column creation device of this embodiment configured as described above, a slurry of sand and water is poured into the net bag 3, and surplus water W ₁ from the sand bag column during water tightening is passed through the filter 16. Drain the excess water W ₁
is collected in the separated water receiver 14 and then discharged from the separated water outlet 15. In addition to placing the filter on the outside of the net bag as described above, the filter may also be placed on the inside of the net bag.

Next, FIG. 3 shows a second embodiment of the present invention, in which the outer periphery of the filter 16 similar to that of the previous embodiment is further covered with outer tubes 17 and 18 made of steel pipes, etc. By flowing high-speed water W ₂ into the filter 18 , a suction force acts on the filter 16 according to Bernoulli's theorem, promoting the effect of sucking out the surplus water W ₁ from inside the filter 16 . The effect of sucking out W ₁ can be changed by controlling the speed of high-speed water W ₂ .

In this way, the outer tubes 17 and 18 may be single tubes instead of double tubes, and the inside thereof may be suctioned by means other than the above embodiments, such as a vacuum pump.

Therefore, if the construction method of the present invention is adopted when tightening the sand bag pillars using the underwater pack drain method, the sand bag pillars can be constructed using conventional net bags, the yield of sand will be high, and the sand bag pillars can be constructed using the conventional net bags. This has the advantage of speeding up the creation of pillars.

In addition, since the present invention provides a filter in the upper part of the net bag that is not in the casing, surplus water can be drained evenly and sufficiently before the sand enters the casing. Water is sufficiently removed and the water content can be made uniform, and as a result, sandbag pillars can be constructed efficiently.

[Brief explanation of drawings]

Fig. 1 is an overall layout diagram of a sand bag pillar creation device according to an embodiment of the first invention to which the construction method of the present invention is applied; 3
The figure is a side sectional view of a water tightening portion of the sand bag pillar creating device according to the second embodiment of the present invention. 1... Soft ground, 2... Casing, 3... Net bag, 13... Drain pipe, 16... Filter, S...
...sand, W...supply water, _W1 ...surplus water, _W2 ...high-velocity water.

Claims (1)

[Scope of Claims] 1. Sand in which a casing is driven into soft ground such as the seabed, and a slurry of sand and water is poured into a net bag inside the casing while draining the water filling the casing through a drain pipe. An underwater pack drain construction method in which a sand bag pillar is created by lowering the bag into the casing, and the casing etc. are removed leaving only the sand bag pillar in place in soft ground such as the seabed. A filter having meshes finer than the sand particles is provided on the outer periphery or inside of the part of the net bag that is not contained in the casing, and excess water during water tightening of the sand bag is discharged through the filter. Sand bag pillar construction method. 2. A casing is driven into soft ground such as the seabed, and while draining the water filling the casing through a drain pipe, a sand bag containing a slurry of sand and water poured into a net bag inside the casing is lowered into the casing. In the underwater pack drain construction method, which creates sand bag pillars in soft ground such as the seabed, the casing etc. are removed leaving only the sand bag pillars. A filter with mesh finer than the sand particles is installed on the outer periphery or inside of the unfilled part, and suction is applied to the outer cylinder provided around the outer periphery of the net bag and the filter. A sandbag pillar construction method that is characterized by draining excess water.