JPH0565650B2 - - Google Patents

Description

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

Conventional technology and its problems Conventionally, as a ground improvement method, a jet jet of air is injected horizontally into the ground to cut the ground, and the airlift effect of the air removes the cutting shear to the ground surface as slime. A so-called jet grouting method has been proposed, in which a space is formed underground and 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 of injection filling.
It is said that this can reach up to 30% of the total amount of grout, and not only does this result in a large loss of grout, but the slime also solidifies due to the grout contained in it, requiring complicated steps such as crushing it to remove it from the construction site, and even causing waste to be dumped. In some places, 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 as slime to the ground surface by the air lift effect of the air. In the ground improvement method, which creates a space inside and injects grout into the space, the grout contained in the slime that has been removed to the ground surface is separated and then poured into the grout filling section underground. This relates to a ground improvement method that is characterized by being returned and refilled.

Embodiment An embodiment of the present invention will be described below based on the accompanying drawings.

When implementing the construction method of the present invention, as shown in the diagram,
A guide hole 2 is drilled in the ground 1 to be constructed,
A triple pipe rod 3 is built inside this hall 2.

Next, in the triple pipe rod 3, ultra-high pressure water from the conduit 4, compressed air from the conduit 5, and further conduit 6 are supplied.
A grouting material such as cement milk is supplied individually through the swivel joint section 7, and ultra-high pressure water and compressed air are simultaneously injected into the ground from the high-pressure nozzle section 8 at the bottom of the rod 3. It 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 10 and gradually pulled up by the operation of a crane (not shown), ultra-high pressure water and compressed water are simultaneously injected into the ground from the high pressure nozzle 8. The air cuts the ground within the improved area 1a, and the cutting shear is turned into slime by the air lift effect of the compressed air.
The slime is removed through the guide hole 2 on the outer periphery of the grout into the slime retainer 11 on the ground surface, and the removed portion is injected and filled with grout material 12 from the injection nozzle 9, thereby achieving the purpose of ground improvement. This ground improvement method itself is not substantially different from conventional methods.

In this ground improvement method using jet grouting, the slime removed to the ground surface contains
Contains large amounts of cement milk. The reason for this is that the ground cutting condition is disturbed by the jet water jet accompanied by compressed air, and the cutting part and the cement injection part are in a state of disturbance, and it is inevitable that cement material will be mixed into the cutting slime. Therefore, the amount of cement to be supplied must exceed the amount required for improvement considering the amount mixed in the discharged slime, and 50 to 80% of the supplied amount of cement milk is 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 slime reservoir 1 on the ground surface is
Sand pump 13 the slime that was eliminated in 1.
While pumping up the soil, it is guided to a soil separator, for example, a vibrating sieve 14, through a conduit 22, and the soil and sand are sent to a tank 15, and the liquid components, including cement, are sent to a settling tank 17 via a chute 16, where they are separated and recovered. do.

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 methods 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 added to the tank 10. It is discharged out of the system through the overflow pipe 18. 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 will pollute rivers, etc. even if it is discharged as is. There is no danger. Further, from the bottom of the tank 10, the sedimented and concentrated cement components are pumped in the form of cement milk through the conduit 19 toward the circulation pipe 20 by the operation of the circulation pump 18.

The circulation pipe 20 is inserted into the improvement area 1a, for example, in the peripheral side thereof, and the improvement area 1a is inserted into the improvement area 1a at the lower end.
It has an injection nozzle 21 directed toward the center of a. Although the figure shows a case in which one pipe 20 is provided, a plurality of pipes 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 same ground improvement effect can be achieved with a 20 to 40% lower supply amount than in the conventional method that does not recycle cement milk.

Effects As described above, since the method of the present invention requires quasi-monitoring of the grout material, 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 being thrown away. Since the cement component contained in the slime component can be reduced, the slime will not solidify, and the number of steps involved in transporting and dumping the slime can be reduced.

[Brief explanation of drawings]

The drawing is a schematic explanatory diagram showing one implementation situation of the present invention. 1 is the ground, 2 is a guide hole, 3 is a triple pipe rod, 4, 5 and 6 are conduits, 7 is a swivel joint, 8 is a high pressure nozzle part, 9 is an injection nozzle, 10 is a column machine, 11 is a slime reservoir, 12 is a grout material, 13 is a side pump, 14 is a vibrating sieve, 15 is a tank, 16 is a chute, 17 is a settling tank, 18 is an overflow pipe, 19 is a conduit, 20 is a circulation pump, and 21 is an injection nozzle. .

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. In a ground improvement method in which grout is injected and filled, the grout contained in the slime removed to the ground surface is separated and then returned to the grout filling section underground for refilling. Improved construction method.