JPS6329048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sand pillar construction method for creating sand pillars (sand piles) as drainage channels in soft ground below the water surface.

A sand drain method has long been known in which a large number of sand pillars are formed using tubular casings in soft ground beneath the water surface, and these pillars are used as drainage channels to improve the ground. However, in the conventional sand drain construction method, when sand is poured into the casing to form a sand column inside, the settling of the sand is caused by the water or sludge that entered the casing when it was driven into the ground. There was a problem in that the entire inside of the casing could not be uniformly filled with sand because the sand could be stopped midway and a space without sand could be formed in the lower part of the casing.

The present invention solves the above problems and provides a sand pillar construction method that can compact the sand pillar inside the casing using a vibrohammer and create a uniformly packed sand pillar in soft ground below the water surface. aim at something.

An embodiment of the present invention will be described below with reference to the drawings.

An example of a casing used in the construction method of the present invention is shown in FIGS. 1 to 6. As shown in the figure, a tubular casing 1 has a lid 2 at the bottom that is closed when penetrating into soft ground and opens when pulled out, and a discharge pipe 3 that communicates with the inside of the casing 1 and rises vertically from there at the bottom. have. Casing 3
A sand inlet 4 is provided at the top of the casing 3 in the part that emerges above the water surface when it penetrates into the soft ground, and a compressed air supply port 4 is provided for feeding compressed air flowing in the direction of arrow A in the figure into the casing 3. 5 is provided. A two-axis eccentric vibrohammer 6 that generates vertical vibration is fixed to the upper end of the casing 3.

When the casing 1 having the above configuration is to be cast in soft ground E below the water surface L as shown in the illustrated example, the casing 1 is placed vertically with the wire 7 on a crane on the gunwale side of a drain ship (not shown). It is supported so as to be movable in the vertical direction, and when installed in soft ground on land, it is supported by a crane vehicle with wires 7.

Next, an example of the construction method of the present invention implemented using the casing 1 will be described with reference to FIGS. 1 to 6.

First, the casing 1 held vertically is lowered, and as shown in Fig. 1, the soft ground L below the water surface L is lowered.
The lid 2 is placed on top with the lower end opening closed.
Then, as shown in FIG.
Compressed air is sent in this direction, and foreign matter such as water or sludge that has entered the casing 1 up to the time of penetration of the casing 1 is discharged through the discharge pipe 3.

Next, as shown in FIG. 3, the sand inlet 4 is opened and sand (indicated by dots in the figure) is introduced into the casing 3 using a belt conveyor (not shown) or the like. After a certain period of time has elapsed since the start of sand injection, the vibrohammer 6 is operated again to compact the sand column filled in the casing 1, creating a uniformly packed sand column S as shown in FIG.

Then, by pulling up the casing 1, the lid 2 at the lower end of the casing 1 is opened, and the compacted sand column S is placed vertically on the floor, and as shown in FIG. The casing 1 is pulled up while introducing compressed air from the supply port 5 and pressurizing it from the upper part of the casing 1.

As a result, a sand column S shown in FIG. 6, which is uniformly filled with sand, is created on the soft ground E.

Furthermore, the operation of driving the casing 1 into the next soft ground E and penetrating it is repeated, creating a large number of sand pillars S in the soft ground E to be ground improved, and using these as drainage channels to improve the soft ground E. Ground improvement can be done.

The present invention is a construction method as described above, in order to quickly fill the casing with sand by removing foreign substances such as water or sludge that have entered the casing by the time the casing penetrates into the soft ground beneath the water surface. After forming a space, sand is poured into the casing and the vibrohammer is activated again to create a compacted sand column inside the casing, and the casing is pulled out while compressing the inside, so it is always uniform. Sand pillars filled with water can be created in soft ground beneath the water surface in a short time, and the efficiency of sand pillar creation can be greatly improved. Therefore, the sand column obtained by the method of the present invention can be used to replace the conventional sand column that was created by simply pouring sand into the casing that penetrated into the soft ground below the water surface without removing the water that had entered the casing. Compared to
By improving the vertical consolidation drainage effect, it is possible to improve the soft ground beneath the water surface, and further strengthen the ground.

[Brief explanation of the drawing]

Figures 1 to 6 are front views of the casing part showing the order in which the construction method of the present invention is carried out. Figure 3 shows a state in which the casing has penetrated into soft ground to a certain depth, and Figure 3 shows a state in which the sand column in the casing is compacted by operating the vibrohammer while injecting sand from the sand inlet. Figure 4 shows the state in which a compacted sand column has been created inside the casing, Figure 5 shows the state in which the casing is pulled up while pressurizing the inside of the casing from the top, and Figure 6 shows the state in which a sand column is created in soft ground. This shows the state in which the 1... Casing, 2... Lid, 3... Discharge pipe, 4... Sand input port, 5... Compressed air supply port, 6... Vibrohammer, E... Soft ground, L... Water surface, S... Sand column.

Claims (1)

[Claims] 1. A tubular casing, which has a lid that allows the lower end opening to be opened and closed, and a discharge pipe rising upward, and which has a sand inlet, a compressed air supply port, and a vibrohammer in the upper part, is connected by the lid. With the lower end opening closed, the vibrohammer is operated to penetrate into the soft ground below the water surface to a required depth while keeping the upper part of the casing above the water surface. Foreign matter such as water or sludge that has entered the casing is discharged through the discharge pipe by applying pressure from the compressed air supply port, and then sand is introduced from the sand input port and the vibrohammer is operated again to remove the foreign matter from the casing. The sand column is characterized in that the sand put in the sand is compacted to form a sand column, and then the lid is opened and the casing is pulled out while applying pressure from the upper part of the casing, so that the sand column remains in the soft ground. Construction method.