JPH01102122A - Ground improving work - Google Patents

Abstract

PURPOSE:To save trouble in the carrying-out of slime by a method in which while separating grout contained in slime discharged to the ground surface, the grout is returned to the grouting portion under the ground for re-packing. CONSTITUTION:A triple tubular rod 3 is set in the ground 1, and superhigh- pressure water and compressed air jet stream from a high-pressure nozzle 8 are jetted into the ground. While excavating the ground, excavation muck as slime is discharged through a guide hole 2 around the rod 3 to a slime trap on the ground surface by air-lifting effect. The slime is pumped up by a sand pump 13 and directed through a conduit 22 to a vibrating screen 14 to separate soil into a tank 15 and also to separate liquid portion containing cement into a setting concentrating tank 17. The regenerated cement milk on the bottom of the tank 17 is circulated and again jetted from the nozzle 21 of a circulating pipe 20. The construction cost can thus be reduced.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a ground improvement method.

Conventional technology and its problems Traditionally, as a ground improvement method, the ground is cut by injecting a jet stream of air along the sideways underground, and the cutting shear is removed to the ground surface as slime by the air lift effect of the air. A so-called jet grouting method has been proposed, in which a space is formed in the ground using grouting methods, and then grout is injected into the space. However, in this ground improvement method, a large amount of grout material is contained in the slime removed to the ground surface, and the content is 50 to 80% of the amount injected.
It is said that this process not only causes a large loss of grout, but also causes the slime to solidify due to the grout contained in it, requiring complicated steps such as crushing it to remove it from the construction site, and furthermore, the slime has to be removed from the construction site. In some cases, there were problems such as causing pollution.

The present invention has been made with the aim of eliminating such conventional problems.

Means for Solving the Problems The present invention cuts the ground by injecting a jet stream of air along the sideways underground, and removes the cutting shear to the ground surface as slime by the air lift effect of the air. In a ground improvement method in which a space is formed underground and grout is injected into the space, the grout contained in the slime removed to the ground surface is separated and the grout is poured into the grout filling section underground. This relates to a ground improvement method characterized by returning the soil to the soil and refilling it.

EXAMPLE An example of the present invention will be described below with reference to the accompanying drawings.

When carrying out the construction method of the present invention, as shown in the figure, a guide hole (2) is drilled in the ground (1) to be constructed, and a triple pipe rod (3) is installed in this hole (2).

Next, in the triple pipe rod (3), ultra-high pressure water from the pipe (4), compressed air from the pipe (5), and further pipe (6) are added.
) is supplied individually through the swivel joint (7), and ultra-high pressure water and compressed air are simultaneously supplied into the ground from the high-pressure nozzle (8) at the bottom of the rod (3). On the other hand, the grout material is injected into the ground from an injection nozzle (9) provided at the lower end of the rod (3), that is, at a position lower than the high pressure nozzle (8).

When the rod (3) is rotated by the operation of the column machine (1o) and gradually pulled up by the operation of the crane (not shown), the high pressure nozzle (8) simultaneously injects it into the ground. The ultra-high pressure water and compressed air cut the ground within the improved area (1a), and the cutting shear is converted into slime due to the air lift effect of the compressed air and is transferred to the ground surface through the guide hole (2) on the outer periphery of the rod (3). The slime is removed into the retainer (11), and the removed portion is injected and filled with grout (12) from the injection nozzle (9), thereby achieving the purpose of ground improvement in the chord. This ground improvement method itself is not substantially different from conventional construction methods.

In such a ground improvement method using jet grouting, a large amount of cement milk is contained in the slime that is removed to the ground surface. The reason for this is that when the ground is cut by a jet of water accompanied by compressed air, the cutting part and the cement injection part are disturbed, and it is inevitable that cement material will be mixed into the cut slime. Therefore, the amount of cement to be supplied must exceed the amount required for improvement considering the amount that will be mixed into the discharged slime, and 50 to 80% of the cement milk that is supplied will be contained in the slime and removed to the ground surface.

The construction method of the present invention is characterized in that the cement milk contained in the slime and removed to the ground surface is separated and recovered and reused for circulation.

That is, in the construction method of the present invention, the sand pump (13) is operated to pump up the slime that has been removed to the slime reservoir (11) on the ground surface while continuing to improve the ground using the rod (3). The soil is guided through a conduit (22) to a soil separator, such as a vibrating sieve (14), and the soil is transferred to a tank (22).
15), the liquid component containing the cement part is transferred to the chute (1
6) and are separately collected into a sedimentation concentration tank (17).

The earth and sand separated and collected in the tank (15) contains almost no cement component, so it does not solidify, and is carried to a dumping site and dumped by applying conventional means without the need for crushing or the like.

On the other hand, in the settling tank (17), cement with a relatively high specific gravity (specific gravity 3.1) quickly settles and is separated into water in the upper part and cement components in the lower part, and the separated water is
It is discharged out of the system through an overflow pipe (18) attached to the tank (10). Depending on the residence time in the tank (10), this wastewater may contain a small amount of cement components and other suspended matter, but the content is low and even if it is discharged as it is, it will not be used in rivers, etc. There is no risk of contamination. Further, from the bottom of the tank (10), the cement components that have been sedimented and concentrated are in the state of cement milk, and the circulation pump (18) is operated to pump the conduit (1
9) and is fed under pressure towards the circulation pipe (20).

The circulation pipe (20) is inserted into the improvement area (1a), for example, at the peripheral side thereof, and the improvement area (1a) is inserted into the lower end of the improvement area (1a).
It has an injection nozzle (21) directed toward the center of. Although the figure shows a case in which one pipe (20) is provided, a plurality of pipes (20) may be provided at equal intervals in the circumferential direction.

From the injection nozzle (21) at the lower end of the circulation pipe (20), the recycled cement milk that has been pressure-fed into the pipe (20) is injected toward the center and used for circulation. By recycling cement milk in this way, the supply amount can be reduced by 20% compared to the conventional method that does not recycle cement milk.
~b, the same ground improvement effect can be obtained.

Effects As described above, in the construction method of the present invention, the grout material is reused, so it is possible to reduce the consumption of grout material, reduce usage loss, contribute to lower construction costs, and reduce the amount of grout material that is thrown away. Since the cement component contained in the slime component can be reduced, the slime will not solidify, and the labor involved in transporting and dumping the slime can be reduced.

[Brief explanation of the drawing]

The drawing is a schematic explanatory diagram showing one implementation situation of the present invention. (1) is the ground, (2) is the guide hole, (3) is the double pipe rod, (4), (5) and (6) are the conduits, (7) is the swivel joint, and (8) is the high pressure nozzle. part, (9) is injection nozzle, (10) is column machine, (11) is slime reservoir, (12) is grout material, (13) is side pump, (14) is vibrating sieve, ('15) is tank , (1
6) is a chute, (17) is a settling tank, (18) is an overflow pipe, (19) is a conduit, (20) is a circulation pump, (21)
) is the injection nozzle. (or more)

Claims (1)

[Claims] (1) While cutting the ground by injecting a jet stream of air along the sideways underground, the air lift effect of the air removes the cutting shear to the ground surface as slime, creating a space underground. A ground improvement method in which grout is injected and filled into a space, and the feature is that the grout contained in the slime removed to the ground surface is separated and then returned to the grout filling section underground for refilling. Ground improvement method.