JPH0841851A - Soil improvement method and device thereof - Google Patents

Abstract

PURPOSE:To improve a broad range of ground efficiently by means of a small number of piles. CONSTITUTION:Casing 1 is penetrated into the ground W while giving lateral oscillation thereinto, and during the penetration of the casing 1 into the ground and during the pulling up thereof, water content in the ground W is forcedly discharged from a suction pipe 4. When the casing 1 is pulled out, a ground improvement material S is thrown into the ground W while giving lateral oscillation thereinto to form a ground improvement pile P.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground improvement method and apparatus for compacting soft ground by utilizing vibration.

[0002]

2. Description of the Related Art Conventionally, as a typical ground improvement method for compacting the ground by utilizing vibration, a vibrating body called a vibro flot is vibrated in the ground while simultaneously injecting water around the vibrating body. , A vibro flotation method that creates a pile of compacted sand by pulling up the vibrating body while filling the gap created around the vibrating body with sand, gravel, etc., and adding sand, etc. to the ground while applying vibration. There is a sand compaction pile method of creating sand piles that are pressed and compressed. According to such a construction method, the ground strength is increased due to the strength of the pile itself such as sand and the surrounding consolidation effect of the pile such as sand.

[0003]

However, in all of the above construction methods, since the main purpose is to construct piles, the ground improvement effect does not extend to the very periphery of the pillar, and it is attempted to improve the ground as a whole. In that case, a large number of pillars of sand or the like must be formed at a small pitch, which not only requires a long time for construction when a wide range of ground is targeted, but also has a problem that construction cost rises.

It is an object of the present invention to provide a ground improvement method and an apparatus therefor capable of efficiently improving a wide range of ground with a small number of piles.

[0005]

In order to achieve the above object, the ground improvement method according to claim 1 of the present invention is a ground W
The casing 1 is penetrated while giving a lateral vibration to the inside, and while the casing 1 is being penetrated or pulled up, the water generated in the ground W is forcibly drained from the water absorption pipe 4 provided in the casing 1, and the casing 1 is pulled up. At times, the ground improvement material S is introduced into the ground W from the casing 1 while applying lateral vibration to form the ground improvement pile P.

In the ground improvement method according to claim 2,
It is characterized in that the ground W around the casing 1 is compacted when the casing 1 penetrates by the projections 8 provided on the outer peripheral surface of the casing 1 at appropriate intervals in the longitudinal direction.

Further, in the ground improvement apparatus according to claim 3 of the present invention, the casing 1 is provided with a vibrator 2 for generating a lateral vibration at the tip thereof, and the casing 1 for introducing the ground improvement material S into the ground W from the inside, and the casing. 1 is composed of a strainer 3 attached to the outer peripheral side of the tip end portion, and a water absorption pipe 4 provided on the outer peripheral surface of the casing 1 for forcibly discharging the water that has entered the strainer 3 to the ground.

In the ground improvement device according to claim 4,
The outer peripheral surface of the casing 1 is characterized in that projections 8 for compacting the ground are provided at appropriate intervals in the longitudinal direction.

In the ground improvement device according to claim 5,
The strainer 3 and the vibrator 2 are provided so as to project further downward than the lower end of the casing 1.

In the ground improvement device according to claim 6,
An air supply nozzle 19 for supplying air into the casing 1 and an opening / closing valve 20 for enclosing the air in the casing are provided at the upper end of the casing 1, and the lower end of the casing 1 is provided when the casing penetrates. It is characterized by being provided with an opening / closing bottom plate 21 for preventing intrusion of earth and sand into the inside of the casing 1.

[0011]

In the ground improvement method according to the first aspect of the present invention, excessive pore water pressure is generated in the ground W due to the lateral vibration applied to the ground W during the penetration or the pulling up of the casing 1. Then, the ground W is liquefied and the consolidation is advanced. By forcibly draining this excess pore water pressure to the outside through the water absorption pipe 4, the gap ratio of the ground W is reduced, and the consolidation is further promoted. On the other hand, when the casing 1 is pulled up, the ground improvement material S is loaded from the casing 1 into the ground W while vibrating in the lateral direction, so that the ground improvement material S loaded from the casing 1 receives lateral vibration and tightens. A strong ground improvement pile P that has been solidified and consolidated is formed in the ground W, and the strength of the ground improvement pile P itself and the surrounding consolidation effect of the pile P increase the strength of the ground W. Therefore, it is possible to improve a wide range of ground W with a small number of ground improvement piles P by performing the construction once.

In the ground improvement method according to claim 2,
When the casing 1 penetrates, the projection 8 on the outer peripheral surface of the casing 1
However, the soil W around the casing 1 is scraped off and pushed into the peripheral gap portion of the casing 1, whereby the surrounding soil W of the casing 1 is compacted and consolidated, and the consolidation of the soil W is promoted.

In the ground improvement device according to the third aspect of the present invention, the excessive pore water pressure is generated in the ground W by the lateral vibration from the vibrator 2 at the tip of the casing 1, and the pore water is generated by the excess pore water pressure. , Moves to the tip side of the casing 1, enters the strainer 3, and is discharged to the outside through the water absorption pipe 4 on the outer peripheral surface of the casing 1. On the other hand, the casing 1 can be filled with the ground improvement material S by maximizing the use of its internal space, and forms the required ground improvement pile P when the casing 1 is pulled up.

In the ground improvement device according to claim 4,
When the casing 1 penetrates, the projection 8 on the outer peripheral surface of the casing 1
However, the soil W around the casing 1 is scraped off and pushed into the peripheral gap portion of the casing 1, whereby the surrounding soil W of the casing 1 is compacted and consolidated, and the consolidation of the soil W is promoted.

In the ground improvement device according to claim 5,
Since the strainer 3 and the vibrator 2 are provided so as to project further downward than the lower end portion of the casing 1, the lateral vibration of the vibrator 2 is effectively transmitted to the ground W, and excess pore water pressure causes pore water to reach the strainer 3. It effectively penetrates, and the ground improvement material S is easily discharged from the lower end of the casing 1.

In the ground improvement device according to claim 6,
When the casing 1 is pulled up, the on-off valve 20 is closed, air is supplied from the air supply nozzle 19 into the casing 1 filled with the ground improvement material S to increase the internal pressure, and the lower end of the casing 1 is introduced into the ground. The ground improvement material S is
A strong ground improvement pile that is sufficiently compacted evenly by being pressed by the pressure air in the casing 1 and is subjected to lateral vibration from the vibrator 2 at the lower end of the casing 1 to be densely consolidated. P is continuously formed. In addition, the opening / closing bottom plate 21 at the lower end of the casing 1
Prevents the infiltration of soil and even water when the casing 1 penetrates.

[0017]

EXAMPLES Examples will be described with reference to the drawings.
FIG. 1 shows a ground improvement apparatus according to the present invention. In this figure, reference numeral 1 is a cylindrical casing for introducing a ground improvement material S into a ground W.
A vibrator 2 that generates lateral vibration is provided concentrically with the casing 1, and a plurality of strainers 3 are arranged so as to surround the vibrator 2. Reference numeral 4 denotes a water absorption pipe, and a plurality of water absorption pipes are arranged along the outer peripheral surface of the casing 1. The lower end of each water absorption pipe 4 is connected to each strainer 3, and the upper end of each water absorption pipe 4 is connected to the upper outer peripheral surface of the casing 1. One water collecting pipe 4 provided along the ring
A discharge pipe 4b connected to a and extending from the water collection pipe 4a is connected to a drainage pump (not shown). Reference numeral 5 is a hopper provided at the upper end of the casing 1 for supplying the ground improvement material, 6 is a balance weight for balancing with this hopper, and 7 is a vibro hammer continuously provided at the upper end of the casing 1.

The above structure will be described in more detail with reference to FIGS. 2 to 5. On the outer peripheral surface of the casing 1, a large number of cross-shaped projections 8 are provided at appropriate intervals in the longitudinal direction and the circumferential direction. As shown in FIG. 5, the casing 1 includes a vertical member 8a fixed to the outer peripheral surface thereof and a horizontal member 8b fixed orthogonally thereto. As shown in FIG. 2, each strainer 3 has a tubular body 10 made of steel pipe having a large number of water absorption holes 9 and a closed lower end, and a filter material 11 loaded inside the tubular body 10. Consists of
The lower end of the water absorption pipe 4 is connected to the upper end of the tubular body 10. Although not shown in detail, the filter material 11 has, for example, a tubular mesh-like body disposed along the inner peripheral surface of the tubular body 10, and the granular material such as gravel, crushed stone, or nylon is provided in the mesh-like body. It is configured by inserting a fibrous body such as a thread or a net thread.

As shown in FIG. 2, the vibrator 2 is connected to the strainer 3 through a plurality of (same number as the strainer 3) connecting plates 12 at a concentric position with the casing 1 properly separated from the lower end of the casing 1 downward. A rotary shaft 15 having an eccentric body 14 mounted inside a tubular main body 13 and a motor 16 for driving the rotary shaft 15 to rotate are provided. The rotary shaft 15 is rotated by the operation of the motor 16. The eccentric body 14 makes an eccentric rotary motion, and a horizontal vibration is generated in the main body 13 to give a horizontal vibration to the ground W via the connecting plate 12 and the strainer 3. A cabtire cable 17 for supplying electric power to the motor 16 is inserted in a cable guide pipe 18, and the pipe 1
Although not shown, 8 is arranged along the outer peripheral surface of the casing 1 in parallel with the water absorption pipe 4. Further, the lower end 10a of the pipe body 10 of the strainer 3 and the lower end 12a of the connecting plate 12 are formed obliquely, respectively, as shown in FIG.
The casing 1 can be easily penetrated into the ground W.

The vibrator 2 and strainer 3 are
As shown in FIG. 2, since it is provided so as to project further downward than the lower end portion of the casing 1, it is possible to effectively transmit the lateral vibration of the vibrator 2 to the ground W, and at the same time, to prevent the clearance due to excess pore water pressure. Water can be effectively infiltrated into the strainer 3.

At the upper end of the casing 1, the casing 1
An air supply nozzle 19 for supplying air into the inside, and an opening / closing valve 20 for enclosing the air in the casing 1 supplied from the nozzle 19 are provided. This on-off valve 20
1, is normally closed by, for example, a spring, and is opened by the dropping load when the ground improvement material is dropped from the hopper 5 as shown in FIG. Also,
At the lower end of the casing 1, there is provided an opening / closing bottom plate 21 for preventing intrusion of earth and sand into the casing 1 when the casing 1 penetrates, and the opening / closing bottom plate 21 is provided at the lower end of the casing 1 in the diametrical direction. It is composed of a pair of semi-circular plate members 21a that can be opened and closed by a hinge part 21b, and is normally in an open position as shown by the solid line in FIG. 2, which is closed by earth pressure of the ground when the casing 1 penetrates. It can be done automatically. If it is difficult to close the open / close bottom plate 21 due to earth pressure, it may be manually closed before the casing 1 is inserted.

Next, a ground improvement method using the ground improvement device constructed as described above will be described.

In the ground improvement, first, this device is suspended together with a vibro hammer 7 by a leader standing on a crawler crane, the vibrator 2 at the lower end of the casing 1 is grounded on the ground W, and the vibro hammer 7 is activated. The penetration of the casing 1 is started. When the penetration of the casing 1 is started, the vibrator 2 is activated, and at the same time, the drainage pump connected to the water absorption pipe 4 is also activated. When the casing 1 penetrates, as shown in FIG. 1, the casing 1 in which the local sand G (that is, high-quality soil collected from the surface of the ground W) is grounded on the ground W
Heaps are piled up so as to surround the lower end. The opening / closing bottom plate 21 is closed by earth pressure when the casing 1 penetrates, but it may be closed on the ground in advance.

Thus, the strainer 3 at the tip of the casing 1 receives the longitudinal vibration of the vibro hammer 7 and gradually penetrates into the ground W, during which the lateral vibration of the vibrator 2 passes through the connecting plate 12 and the strainer 3. Transmitted to the ground W. Due to the transmission of the lateral vibration from the vibrator 2, shear stress acts on the ground W, and excess pore water pressure is generated in the ground W. The generation of this excessive pore water pressure causes the ground to be liquefied and its consolidation to proceed. In addition, due to this excess pore water pressure, pore water moves to the tip side of the casing 1 and enters the inside of the strainer 3 through the water absorption hole 9. The interstitial water that has entered the strainer 3 passes through the filter material 11 so that coarse particles are captured, and water of high purity is absorbed into the water absorption pipe 4
Is discharged to the outside through. On the other hand, the discharge of this pore water reduces the gap ratio of the ground W, and the consolidation of the ground W proceeds.

During the penetration of the casing 1, the projections 8 projecting from the outer peripheral surface of the casing 1 push the ground W soil around the casing 1 into the gaps around the casing 1 while scraping off the ground W soil. At this time, the earth and sand G piled up on the ground W as described above becomes the ground W.
It is pushed into the space around the casing 1 together with the earth and sand. As a result, the ground W around the casing 1 is compacted and consolidated, and the ground W is further consolidated. By thus penetrating the casing 1 to a predetermined depth, the ground W in a wide range around the casing 1 is improved.

When the casing 1 penetrates into the ground W to a predetermined depth, the operation of the vibro hammer 7 is stopped, the vibrator 2 and the drainage pump continue to operate, and the ground of sand, gravel, crushed stone, etc. A predetermined amount of the improvement material S is supplied into the casing 1 from the hopper 5 (this ground improvement material S may be filled during the penetration of the casing 1), and air is supplied into the casing 1 from the air supply nozzle 19. To increase the internal pressure, and in this state the casing 1
To start raising. When the casing 1 is started to be pulled up, the ground improvement material S in the casing 1 is extruded from the lower end of the casing 1 and put into the ground W to form the ground improvement pile P.

Even while the casing 1 is being pulled up, the lateral vibration of the vibrator 2 is transmitted to the ground W via the connecting plate 12 and the strainer 3, and the lateral vibration from the vibrator 2 causes shear stress to the ground W. Acting,
The pore water due to the excessive pore water pressure generated thereby is absorbed from the water absorption hole 9 of the strainer 3 on the tip side of the casing 1, and is discharged to the outside through the water absorption pipe 4. This significantly enhances the consolidation of the ground W.

On the other hand, the ground improvement material S introduced into the ground from the lower end of the 8-thing 1 is subjected to the pressing action of the compressed air in the casing 1 and the lateral vibration from the vibrator 2 at the lower end of the casing 1. As a result, a strong ground improvement pile P that is compacted evenly and densely and densely is formed. As a result, the strength of the ground W can be significantly increased.

In the above embodiment, the forced drainage of water in the ground W by the water absorption pipe 4 is performed both when the casing 1 is inserted and when the casing 1 is pulled up. It may be carried out only or only when pulling up. Further, although the vibro hammer 7 is used for penetrating the casing 1 in the above-mentioned embodiment, the method of penetrating the casing 1 is arbitrary, and for example, a drop hammer may be used.

[0030]

According to the ground improvement method of the first aspect of the present invention, the excessive pore water pressure is positively generated in the ground by utilizing the lateral vibration, and the excessive pore water pressure is reduced by the forced drainage. At the same time, since the ground improvement material was put into the ground from the casing to form the ground improvement pile, it is possible to efficiently improve a wide range of ground with a few ground improvement piles, and the construction efficiency is significantly improved. The work period can be shortened and the construction cost can be significantly reduced.

According to the ground improvement method of the second aspect, when the casing penetrates, the protrusion on the outer peripheral surface of the casing causes
Since the surrounding ground is compacted, consolidation of the ground can be promoted.

According to the ground improvement device of the third aspect, the ground improvement method of the first aspect can be efficiently and effectively implemented.

According to the ground improvement device of the fourth aspect, when the casing penetrates, the protrusion on the outer peripheral surface of the casing causes
Since the surrounding ground is compacted, consolidation of the ground can be promoted.

According to the ground improvement device of the fifth aspect, lateral vibration of the vibrator can be effectively transmitted to the ground, and pore water can be effectively infiltrated into the strainer, and the ground improvement from the lower end of the casing can be performed. The material can be easily discharged.

According to the ground improvement device of the sixth aspect, the ground improvement material charged into the ground from the casing is pressed by the pressure air in the casing, and lateral vibration from the vibrator is generated at the lower end of the casing. Accordingly, it is possible to continuously form a solid ground improvement pile that is sufficiently compacted evenly, and that is densely consolidated. Also, by the opening and closing bottom plate at the lower end of the casing,
It is possible to prevent the infiltration of earth and sand or water when the casing penetrates.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a ground improvement device according to the present invention.

FIG. 2 is an enlarged detailed view showing the structure of the lower end portion of the casing of the ground improvement device of the above.

3 is a cross-sectional view taken along line XX of FIG.

FIG. 4 is an enlarged cross-sectional view taken along line YY of FIG.

FIG. 5 is an enlarged perspective view showing a protrusion provided on the outer peripheral surface of the casing.

[Explanation of symbols]

 1 Casing 2 Vibrator 3 Strainer 4 Water absorption pipe 5 Hopper for supplying ground improvement material 7 Vibro hammer 8 Protrusion 9 Strainer water absorption hole 10 Strainer pipe body 11 Strainer filter material 12 Connecting plate 19 Air supply nozzle 20 Open / close valve 21 Opening / closing bottom plate W Ground S Ground improvement material P Ground improvement pile G Site sand

Claims (6)

[Claims] 1. A casing is pierced while giving lateral vibration to the ground, and during the piercing or raising of the casing, water generated in the ground is forcibly drained from a water absorption pipe provided in the casing to raise the casing. At times, a soil improvement material is introduced from the casing into the soil while applying lateral vibration to form soil improvement piles. 2. The ground improvement method according to claim 1, wherein projections provided on the outer peripheral surface of the casing at appropriate intervals in the longitudinal direction compact the ground around the casing when the casing penetrates. 3. A casing equipped with a vibrator for generating lateral vibration at its tip, for putting the ground improvement material into the ground from the inside, a strainer attached to the outer peripheral side of the casing tip, and forcing moisture entering the strainer. A ground improvement device comprising a water absorption pipe provided on the outer peripheral surface of the casing for the purpose of effectively discharging the ground. 4. The ground improvement apparatus according to claim 3, wherein projections for ground compaction are provided on the outer peripheral surface of the casing at appropriate intervals in the longitudinal direction. 5. The strainer and the vibrator are
The ground improvement device according to claim 3, wherein the ground improvement device is provided so as to project further downward from a lower end portion of the casing. 6. An upper end portion of the casing is provided with an air supply nozzle for supplying air into the casing, and an opening / closing valve for sealing air in the casing, and the lower end portion of the casing is provided when the casing penetrates. The ground improvement device according to claim 3, further comprising an opening / closing bottom plate that prevents intrusion of earth and sand into the inside of the casing.