JP3494727B2 - Liquefaction countermeasures - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquefaction countermeasure method for improving the ground where a liquefaction phenomenon may occur due to an earthquake. More specifically, it is similar to a method called a gravel drain method. The present invention relates to a liquefaction countermeasure construction method for constructing a gravel (solid piece such as crushed stone) drain body for dissipating excess pore water pressure in the ground.

[0002]

2. Description of the Related Art Conventionally, the gravel drain construction method has been known as one of the liquefaction countermeasure construction methods, and this liquefaction countermeasure construction method has many construction results. And this gravel drain method rotates the casing earth auger and penetrates the casing earth auger to a predetermined depth while excavating and discharging the soil, and at this time, the casing earth auger is filled with water or compressed air to form a casing. Prevent the inflow of groundwater from the bottom opening of the earth auger. Then, when the casing earth auger is penetrated to a predetermined depth, crushed stone is put in from the upper part of the casing earth auger, and the casing earth auger is pulled out while compacting or compacting the crushed stone to construct a gravel drain body in the ground. Is.

[0003]

However, in the above-mentioned conventional gravel drain construction method, the casing earth auger placing machine is large, and the weight is as heavy as 80 to 100 tons (including a crushed stone compactor), and the workability is high. Has the problem of being bad.

Further, since the gravel drain pile constructed by the conventional gravel drain method has a structure in which a large number of crushed stones are buried in the ground so as to be piled up in a pillar shape (a ground wall shape is also possible), this gravel drain pile is used. Drain piles have the problem that they may be deformed by external pressure and the porosity may change locally or, in the worst case, collapse. Although various external pressures can be assumed, for example, when ground deformation occurs, the conventional gravel drain pile cannot follow it, the porosity changes locally, or the gravel drain pile is divided in the middle. Sometimes. Further, the same phenomenon occurs in vibration such as an earthquake, and if it is further compacted by the vibration, the porosity does not return to the original value and the drain function may be impaired.

Further, the above-mentioned gravel drain pile constructed by the conventional method has a problem that it may be clogged with fine particles that have invaded after a long period of time and the initial function may not be exhibited.

Therefore, the present invention has been made in view of the above problems, and provides a liquefaction countermeasure method in which solid pieces such as crushed stones are elastically bonded to each other and the porosity does not change even by the external pressure. The purpose is to do.

Another object of the present invention is to provide a liquefaction countermeasure construction method in which the construction machine is compact, prevents the collapse of the excavated hole wall, and consolidates the periphery of the hole to improve the soft ground. It is intended.

[0008]

In order to solve the above-mentioned problems, the structure of the present invention, which has the above-mentioned claims as its gist, meets the above-mentioned object, and as a first step, the ground is excavated to form a hole. In the second step, a solid piece such as crushed stone having an adhesive having rubber-like elasticity adhered to the surface after adhesion is put into the hole, and a large number of solid pieces adhere to each other in the ground. It is a technical measure taken to construct a porous body.

Further, in the invention of "claim 2", as a first step, the ground is excavated to form a hole, and as a second step, the crushed stone or the like having an adhesive having rubber-like elasticity adhered to the surface after adhesion is used. Porous body molded by throwing solid pieces into a mold in advance,
It is a technical measure that is designed to be inserted into the hole.

The invention of claim 3 is, as the first step, an air hammer type boring in which a steel pipe is held as a set and is housed in the steel pipe or an air hammer at the end of the steel pipe presses the steel pipe into the ground by impact. Consolidation excavation of the ground with a machine to provide a hole, and as the second step, after pulling out the air hammer from the steel pipe, a solid piece such as crushed stone to which an adhesive having rubber-like elasticity after adhesion is attached to the surface,
It is a technical means to put in the above-mentioned steel pipe and to draw out the above-mentioned steel pipe as a third step to construct a porous body in which a large number of solid pieces are bonded to each other in the ground.

[0012]

Therefore, since the porous body obtained by the present invention is composed of solid pieces such as crushed stone to which the adhesive having rubber-like elasticity is adhered to the surface after the adhesion, it exhibits the action of being hard to collapse.

In addition, the porous body obtained by the present invention has a gap between the solid pieces which are overlapped with each other, and exhibits a general elasticity and elasticity due to the property of the adhesive. By the way, FIG. 9 is a partially enlarged cross-sectional view of the porous body according to the method of the present invention.
Adhesive 110 is attached around 100, and a gap 12 is formed in the non-contact portion of the solid pieces 100, 100, 100.
0, 120, 120 ... Are secured.

According to the present invention, the porous body having elasticity and elasticity as described above is embedded in the ground, so that the porous body first functions as a drain because it is porous. It is the same as the gravel drain method.

Since the above-mentioned porous body has elasticity, it can be deformed following ground deformation, and can cope with some ground deformation without changing the porosity so much. As a porous body, it remains in the ground and retains the function of dissipating excess pore water pressure.

Since the porous body has elasticity, when the ground is vibrated, it is temporarily deformed by the vibration, but when the vibration subsides, it returns to its original shape.
It acts to prevent the porosity from changing.

When the vibration is applied as described above, the porosity temporarily changes and returns to the original state. Therefore, the fine particles that have entered the gap may be pushed out of the gap due to the amplitude of the porosity. It is possible to expect the self-cleaning action of clogging.

Further, according to the invention of "claim 3", since the ground is compactly excavated by the air hammer type boring machine in which the air hammer presses the steel pipe into the ground when the hole is excavated, the hole wall is prevented from collapsing with the steel pipe. It has a function of reforming the surrounding ground due to peeling and consolidation.

[0018]

EXAMPLES Next, examples of the present invention will be described. First, in the liquefaction countermeasure construction method of the present invention, as the first step, the ground is excavated to form a hole. Various conventionally known excavators and excavation methods can be used for excavating this hole, and the sectional shape of the hole is not limited to a circular shape, and a conventional continuous wall-shaped hole for a continuous underground wall may be used.

Among the various publicly known hole drilling methods known in the prior art, in the invention of "claim 3", a steel pipe is held and housed in this steel pipe, or an air hammer at the end of the steel pipe presses the steel pipe into the ground by impact. The ground is compacted by an air hammer type boring machine.

The air hammer type boring machine is
Generally referred to as "Grundmart", a guide 22 is attached to the vehicle 21 so as to be able to move up and down, and a steel pipe 30 is held by the guide 22 so that the steel pipe 30 can be settled. A machine 23 (hereinafter, referred to as "Grundmart 23") that generates an impact force by the pressure air is housed, and the Grundmart 23 gives an impact force to the tip side reduced diameter portion 31 of the steel pipe 30, 30 is pressed into the ground.

The reason for using the above air hammer type boring machine is that the boring machine itself is compact as compared with the conventional earth auger or the like.
This is because it has good workability, can be easily carried into existing buildings and structures, and can handle a wide range of construction sites.

Further, in this air hammer type boring machine, since the steel pipe 30 is press-fitted into the ground to obtain a hole, there is no generation of excavated soil, and it is not necessary to carry out and process the excavated soil. Unlike the conventional gravel drain method, the soil can be consolidated to improve the soft soil. In addition, as one of the liquefaction countermeasure construction methods, the sand compactor cushion pile construction method, etc. have been proposed.
It is widely accepted that compaction of the ground is effective as a countermeasure against liquefaction.

Then, in the second step of the present invention, a solid piece of crushed stone or the like, to which an adhesive having a rubber-like elasticity is adhered after being adhered, is put into the hole to make a large number of pieces in the ground. The solid pieces are adapted to build up a porous body that adheres to each other.

The above-mentioned adhesive can be realized by mixing latex with natural rubber, synthetic rubber, synthetic resin or the like with a vulcanizing agent or a curing agent, and further mixing a plasticizer or a foaming agent as required. The curing time can be adjusted by changing the amount of water added, and the elasticity after curing can be adjusted by selecting the type of molecules suspended in the latex and the amount of plasticizer or blowing agent mixed. is there. By the way,
In this example, Adeka Ultraseal C-50 (trade name) manufactured by Asahi Denka Kogyo Co., Ltd. was dissolved in water and used.

Then, in order to attach the adhesive to the surface of the solid piece, a dipping method or a spraying method can be used. A specific example of the dipping method is to prepare a tank filled with an adhesive, store the solid pieces in a basket, put them in the tank, and pull them up. Adjust by changing. In addition, the example as a spraying method,
The solid piece may be put in a rotary drum, and the adhesive may be sprayed while rotating the drum. In this case, the amount of the adhesive adhered is adjusted by changing the spray amount together with the concentration of the adhesive.

Then, the solid piece to which the above-mentioned adhesive is attached is put into the hole to be cured. When the adhesive hardens, a large number of solid pieces adhere to each other to form a porous body, which exhibits a drain function.

If the adhesive having a high adhesive strength as in the above-mentioned embodiment is used as the adhesive, it is possible to form a porous body on the ground and carry and suspend it.
According to the invention of "Claim 2", instead of the method of charging into the excavated hole, a solid piece having the adhesive adhered to a mold for molding on the ground is charged and a porous body previously molded is molded into the hole. It is designed to be inserted inside.

Next, with reference to the attached drawings, the invention of "Claim 3" will be specifically described. In the figure, reference numeral 20 denotes an air hammer type boring machine. As described above, the air hammer type boring machine 20 has a guide 22 attached to a vehicle 21 so as to be able to move up and down, and is guided by the guide 22 to sink. The steel pipe 30 is held as much as possible, and the Grundmart 23, which generates an impact force by the compressed air for driving from the compressor 26, is housed in the steel pipe 30. The Grundmart 23 impacts the tip end side reduced diameter portion 31 of the steel pipe 30. A force is applied to press the steel pipe 30 into the ground.

The reduced diameter portion 31 at the tip of the steel pipe may be set to have a small inner diameter so that the Grundmart 23 does not come out from the tip of the steel pipe 30, as shown in FIG. The tip end of 30 is formed so that the tip end side is successively reduced in diameter, the tip of the Grundmart 23 is formed as a conical surface, and a part of the tip is projected from the tip of the steel pipe 30, but another embodiment Although not shown in the figure, a flange may be provided on the outer peripheral portion of the Grundmart 23, and an inward protruding ring with which the flange abuts may be provided on the lower inner peripheral surface of the steel pipe 30. Further, a compressor 26 is connected to the Grundmart 23 by a pipe 26a, and a conventionally known hammer mechanism (usually housed in the Grundmart 23), which is not shown in the figure, is supplied by the compressed air for driving sent from the compressor 26. It is designed to work.

First, the above-mentioned vehicle 21 is put into a construction site, and the guide 22 (usually referred to as a "leader") which is in a horizontal position as shown in FIG. The cylinder 24 is operated to stand up. Normally, this guide 22 is used by erecting vertically, but as shown in FIG. 11, in order to obliquely install the porous body 1 obtained by the present invention in the lower part of the existing building A, tilt it at a predetermined angle. Further, although not shown, the standing of the guide 22 may be omitted in order to construct the porous body 1 substantially horizontally from the slope or the like.

When the guide 22 is erected at a predetermined position as shown in FIG. 2, the steel pipe 30 is installed on the guide 22, and the Grundmart 23 is hung from above the steel pipe 30 with the winch 25, and the steel pipe 30 Take it down. Since the Grundmart 23 is configured to generate an impact force by the driving pressure air from the compressor 26,
At the same time as impacting force is applied to the ground at the tip of the Grund Mart 23 to carry out consolidation digging, the steel pipe 30 also has 31
Since it receives an impact force, it is pressed into the ground.

When the steel pipe 30 is press-fitted to a predetermined depth as described above, that is, when the state of "FIG. 5" is reached through the state of "FIG. 3", the steel pipe 30 is left in the ground and is ground by the winch 25. The mart 23 is pulled up, the Grund mart 23 is taken out of the steel pipe 30, and the state shown in FIG. 6 is obtained.

Next, as a second step of the invention of “claim 3”, the steel pipe 30 is provided with an adhesive having rubber-like elasticity on the surface of a solid piece such as crushed stone in the steel pipe 30. The attached one is thrown in (see "Fig. 7"). At the time of this charging, if necessary, a vibrator is used to complete the charging, or the solid pieces being charged are compacted.
This vibrator may be either a vibrator that applies vibration to a solid piece that is charged by a charging method or a vibrator that applies vibration to the steel pipe 30 to apply vibration to the solid piece from the steel pipe 30. Use the former throw-on vibrator to avoid damaging the wall.

Next, in the third step of the invention of "claim 3", the steel pipe 30 is drawn out to construct the porous body 1 in which a large number of solid pieces are bonded to each other in the ground. The withdrawal of the steel pipe 30 may be performed after all the solid pieces have been charged, but the operation of withdrawing the steel pipe 30 by a predetermined amount may be repeated after a predetermined amount of the solid pieces are charged. In the present embodiment, the former method, that is, the steel pipe 30 is pulled out all at once after the solid pieces have all been charged into the state shown in FIG. 8, so this method is used after the steel pipe 30 is pulled out. Since the amount of solid pieces corresponding to the volume corresponding to the thickness of the steel pipe 30 is insufficient, this was additionally charged.

Of course, when pulling out the steel pipe 30, it is desirable to compact the solid pieces while applying vibration by the vibrator. The method of pulling out the steel pipe 30 at once after all the solid pieces have been charged has an advantage that the upper end of the steel pipe 30 is low and thus the charging is easy, but the solid piece is drawn in the hole where the steel pipe 30 is pulled out. In order to densely fill in the steel pipe 3
It is advantageous to repeat the operation of pulling out a certain amount of 0,
Which one is adopted may be selected depending on the angle of repose of the solid piece.

After pulling out the steel pipe 30, the adhesive is hardened by leaving the steel pipe 30 as it is to construct a porous body 1 in which a large number of solid pieces are bonded to each other in the ground.

The porous body 1 may be constructed at predetermined intervals, and the building A or the like may be constructed on the ground previously constructed at predetermined intervals as shown in FIG. But,
If buildings A, etc. already exist, the ground F around them
Therefore, it is confirmed that if the porous body 1 is constructed so as to surround the underground of the existing building A, the liquefaction countermeasure is hardened. Further, when the existing building A is present, it goes without saying that the obliquely installed porous body 1a may be provided.

In FIG. 4, reference numeral 25a indicates a tow rope.

[0039]

EFFECTS OF THE INVENTION The present invention is as described above, and since the porous bodies 1, 1a constructed in the ground are porous with a gap in the joint portion between solid pieces, the conventional gravel drain construction method is used. Similarly to the above, it is possible to provide a liquefaction countermeasure method capable of coping with the liquefaction phenomenon by exhibiting the drain function.

Further, according to the present invention, since the solid pieces are adhered to each other with an adhesive, it is possible to provide a liquefaction countermeasure method capable of coping with the liquefaction phenomenon for a long period of time because the porous bodies 1 and 1a are hard to collapse. .

The porous body 1 obtained according to the present invention has elasticity and stretchability as a whole due to the properties of the adhesive, can be deformed following ground deformation, and has a porosity for some ground deformation. It is possible to deal with it without much change, and even if it is deformed to some extent, it remains as a continuous pile in the ground and the function of dissipating excess pore water pressure can be maintained for a long time.

Further, in the present invention, since the porous body 1 has elasticity, when the ground is vibrated, it is temporarily deformed by the vibration, but when the vibration subsides, it returns to its original shape and the porosity changes. It is possible to provide a highly reliable liquefaction countermeasure construction method since it is prevented.

Further, according to the present invention, when vibration is applied, the porosity temporarily changes and returns to the original state, so that the fine particles that have entered the gap may be pushed out of the gap due to the amplitude of the porosity. It is possible to provide a liquefaction countermeasure construction method that can be expected to cause a self-cleaning action of clogging.

Further, in the invention of "claim 3", since the air hammer type boring machine is used, it is possible to provide a liquefaction countermeasure method in which the construction apparatus is compact and the construction is easy to construct. Since it is pressed into the ground by impact, the hole wall is prevented from collapsing with a steel pipe,
It is possible to provide an efficient liquefaction countermeasure method in which the surrounding ground is modified by consolidation.

[Brief description of drawings]

FIG. 1 is a side view of an air hammer type boring machine used in an embodiment of the present invention.

FIG. 2 is a side view showing a state during construction preparation of the liquefaction countermeasure construction method of the present invention.

FIG. 3 is a partial cross-sectional side view showing a state during construction.

FIG. 4 is a lower sectional view of a steel pipe used in the present invention.

FIG. 5 is a partial cross-sectional side view showing a state in which the press-fitting of a steel pipe is completed during construction.

FIG. 6 is a partial cross-sectional side view showing a state where the machine is pulled up during construction.

FIG. 7 is a partial cross-sectional side view showing a state where solid pieces are put in during construction.

FIG. 8 is a partial cross-sectional side view showing a state in which a steel pipe is pulled out during construction.

FIG. 9 is a partially enlarged cross-sectional view of a porous body constructed by the method of the present invention.

FIG. 10 is a partial cross-sectional side view of the construction example of the present invention.

FIG. 11 is a partial cross-sectional side view in the middle of another construction example of the present invention.

[Explanation of symbols]

1 Porous body 1a Porous body 20 Air hammer type boring machine 21 vehicles 22 Guide 23 Grund Mart 26 Compressor 30 steel pipe 31 Reduced diameter part

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toru Watanabe Toru Watanabe 2570-4 Shimotsuruma, Yamato City, Kanagawa Nishimatsu Construction Co., Ltd. Technical Research Institute (72) Nobuyuki Oyano 1-34 Konan, Minato-ku, Tokyo Life Line Industrial Co., Ltd. (56) Reference JP-A-4-41811 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) E02D 3/10 E02D 27/34

Claims (3)

(57) [Claims] 1. As a first step, the ground is excavated to form a hole, and as a second step, a solid piece such as crushed stone having an adhesive having rubber-like elasticity adhered to the surface after bonding is put in the hole. A liquefaction countermeasure method in which a solid piece-made porous body in which a large number of solid pieces are adhered to each other is built into the ground by pouring. 2. As a first step, the ground is excavated to form a hole, and as a second step, a solid piece such as crushed stone having an adhesive having rubber-like elasticity adhered to the surface after bonding is put into a mold in advance. A liquefaction countermeasure method that inserts a porous body molded by the above into the hole. 3. As a first step, a set of steel pipes is held and stored in the steel pipes, or the ground is compacted by an air hammer type boring machine in which an air hammer at the end of the steel pipe presses the steel pipes into the ground by impact. A hole is provided, and as a second step, after pulling out the air hammer from the inside of the steel pipe, a solid piece such as crushed stone having an adhesive having rubber-like elasticity adhered to the surface after bonding is put into the steel pipe, A liquefaction countermeasure method in which the above-mentioned steel pipe is drawn out in three steps to construct a porous body in which a large number of solid pieces are bonded to each other in the ground.