JPH08232256A - Foundation improving method for weak ground - Google Patents

Abstract

PURPOSE: To enhance construction properties by forming a columnar improver through the processes of pressing a casing into the ground, discharging a core, injecting a stiffener transversely from an end, and pulling up the casing while taking sludge into the casing. CONSTITUTION: As a casing 1 is pressed into the ground, a core in a casing 1 is discharged by means of an auger or the like to form a cavity 41 inside the casing 1. Next, a stiffener G is injected transversely from an injection nozzle 31 at the end of the casing 1, the ground is drilled, and as the sludge 45 formed is taken into the casing 1 the casing 1 is pulled up to construct a columnar improver 43 in the ground. In this case, the sludge 45 formed is stored in the casing 1 and not discharged onto the ground, so wasting the large amount of stiffener G is prevented and the need for removing the sludge is eliminated. Further, since the sludge 45 is taken into the casing 1 by drilling of a hole in the ground, the pressure decrease of jets is reduced. Thus cost can be reduced, and the large-diameter improver can be formed in a short time.

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 for soft ground.

[0002]

2. Description of the Related Art Conventionally, as a ground improvement method for soft ground,
A jet grout method is known in which a hardening material is injected under pressure into a target ground. This jet grout method is to laterally inject a hardening material such as cement milk from an injection pipe embedded in the ground, and agitate the sand and hardened material cut by this jet jet to pull up the injection pipe, The columnar improvement body will be created in the ground. However, if only the curing material is injected from the injection pipe, the range of the jet jet flow is short and the diameter of the columnar improved body is reduced.

Therefore, in order to increase the effective range of a jet jet to form a columnar improved body having a large diameter, recently,
The JSG method and the C-JG method, in which compressed air and water jet are used together to increase the injection pressure and flow rate, and at the same time, the compressed air and the like are used to discharge sludge, have become widespread.

[0004]

[Problems to be Solved by the Invention] However, these J
In the SG method and the C-JG method, as mentioned above, the compressed air or the like is used together to increase the jet pressure of the jet jet, and the sludge is discharged, so that the injection pipe is pulled up and injected into the ground. It has been pointed out that more than half of the hardened material is mixed with earth and sand, and is discharged as mud to be discharged to the ground, resulting in a large amount of hardened material being wasted.

Moreover, although this sludge is treated as industrial waste, a large amount of cost is conventionally required for this treatment, and 1/3 to 1/2 of the construction cost is usually required for this treatment. Have been spent for. Further, in general, the pressure attenuation of the jet jet injected into the underground mud is remarkable, and the increase in the improved diameter due to the jet jet described above increases the construction time and is inefficient.

[0006] Furthermore, since there are uncertain factors such as hardness and softness of the geology in the ground, the expected improvement diameter may not be obtained, and in the case of bottom improvement in the ground with groundwater, columnar It has been pointed out that the wraps between the improved bodies may be incomplete and may lead to accidents such as flooding. The present invention has been devised in view of such circumstances, solves the above-mentioned conventional drawbacks, and can reliably form a large-diameter columnar improved body in a shorter construction time than the conventional one, and to the ground. It is an object of the present invention to provide a ground improvement method for soft ground, which eliminates the discharge of sludge and does not require sludge treatment.

[0007]

In order to achieve such an object, a ground improvement method for soft ground according to a first aspect of the present invention is such that a casing is pushed into a target ground and a core in the casing is discharged to discharge the inside of the casing. After forming a cavity in the casing, the hardening material is jetted laterally from the tip side of the casing to cut the ground, and the sludge generated by this is taken into the casing and the casing is pulled up to a diameter larger than that of the casing. It is characterized by creating a columnar improved body.

The invention according to claim 2 is based on claim 1.
In the ground improvement method for soft ground according to the above, a hardening material injection device is attached to the tip of the casing, a cavity is formed in the casing, and then the casing is rotated or rocked to remove the hardening material from the injection device. The ground is cut by spraying, the sludge generated by this is taken into the casing, and the rotating or swinging casing is pulled up to form a columnar improved body in the ground. The invention according to claim 3 is
In the ground improvement method for soft ground according to claim 1, after forming a cavity in the casing, an injection pipe having a hardening material injection device attached at its tip is inserted into the casing to make the injection device tip of the casing. The injection pipe is rotated or swung, and then the hardened material is sprayed from the spraying device to cut the ground, and the sludge produced by this is taken into the casing, and then rotated or swung. And the casing are simultaneously pulled up to form a columnar improved body in the ground.

[0009]

According to the first aspect of the invention, first, the casing is pushed into the target ground, the core in the casing is discharged, and the cavity is formed in the casing. Then, when the planned depth is reached, the hardening material is jetted laterally from the tip side of the casing to cut the ground, and the sludge generated by this is taken into the casing and the casing is pulled up to make the diameter larger than that of the casing. A columnar improvement will be created in the ground.

And, in the invention according to claim 2,
After forming the cavity in the casing as described above, the hardener is laterally jetted from the jetting device mounted on the rotating or swinging casing to cut the ground, and the sludge generated by this is taken into the casing. By pulling up the casing that rotates or swings, a columnar improved body is formed in the ground.

According to the third aspect of the invention, after the cavity is formed in the casing, the injection pipe is inserted into the casing so that the injector is projected from the tip of the casing. Then, the injection pipe is rotated or swung to inject the hardening material from the injection device to cut the ground, and the sludge generated by this is taken into the casing, and the injection pipe and the casing are rotated or swung simultaneously. If it is pulled up, a columnar improved body will be formed in the ground.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a sectional view of a main part of a casing used in an embodiment of the ground improvement method according to claims 1 and 2 and a dresser for connecting the casing to a boring machine.
Is a casing having a double pipe structure composed of an inner pipe 3 and an outer pipe 5,
As shown in FIG. 2, the casing 1 is connected to a rotary head 11 of a boring machine 9 via a dresser 7, and an auger 15 driven by a kerry bar 13 is axially inserted in the center thereof.

Then, as shown in FIG. 1, the dresser 7
A plurality of thin tubes 19 communicating with the swivel 17 mounted on the outer circumference of the casing 1 are inserted in the inner wall of the casing 1. The thin tubes 19 connectable between the inner tubes 3 and the outer tubes 5 of the casing 1 can be connected to the thin tubes 19. 21 are arranged at equal intervals in the axial direction of the casing 1, and each of the thin tubes 19 and 21 is a hardening material G that is pressure-fed from a high-pressure hose 23 connected to a swivel 17 as shown in FIG.
Is designed to function as a passage.

A casing shoe 27 having a plurality of bits 25 mounted thereon is connected to the tip of the casing 1, and the casing shoe 27 also has a plurality of thin tubes 29 connectable to the thin tubes 21. It is inserted in the direction. On the tip side of the casing shoe 27, as shown in FIG. 3, an injection nozzle 31 for injecting the hardening material G pressure-fed from the high-pressure hose 23 through the thin tubes 19, 21, 29 in the lateral direction is provided in each thin tube 29. The ground 33 is cut by the jet jet of the hardening material G jetted from each jet nozzle 31.

As shown in FIG. 2, the rotary head 1
1 is connected to a jack (not shown) attached to the mast 35 via a guide 37 as in the conventional case, and the casing 1 is moved in the vertical direction by the jack,
Then, it is pressed into the ground 33 by the rotating force or swinging force of the rotary head 11 and the pressing force of the jack.

The auger 15 is a rotary head 1.
It is adapted to rotate in the same direction in association with the rotation of the kelly bar 13 which is vertically movable with respect to 1. The casing 1, the dresser 7 and the drilling machine 9 in this embodiment are configured in this way, and the method of the present invention is carried out as follows using these. First, the thin tubes 19, 21, 29
The casing 1 is connected to the hole drilling machine 9 via the dresser 7, and the casing shoe 27 is attached to the tip of the casing 1. Then, the rotary head 11 and the jack are driven to sequentially connect the casings 1 according to the drilling depth as shown in FIGS. 1, 4 and 5, and rotate or swing the casings 1 in the ground 33. The core 33 'in the casing 1 is pushed in and discharged by the auger 15.

When the ground 33 is a sand layer containing groundwater, etc., the core 33 'in the casing 1 is discharged using a well-known bucket 39 as shown in FIG. 6 instead of the auger 15. Then, as shown in FIG. 3, the casing 1 reaches the planned depth.
The core 3 in the casing 1
3'is discharged by the auger 15 or the bucket 39 to form a cavity 41 in the casing 1, and then the casing 1 which rotates or swings as shown in FIGS. 3, 7 and 8 is jacked up and swiveled. High pressure hose 23 connected to 17
Then, the hardened material G is pressure-fed into the thin tubes 19, 21, and 29, and the hardened material G is laterally jetted from the jet nozzle 31 attached to the casing shoe 27 to cut the ground 33.

Thus, the casing 1 is rotated or swung in this manner and pulled up, and the ground 3 is jetted with the hardening material G.
As the columnar improvement body 43 having a larger diameter than the casing 1 is formed in the ground 33 by cutting 3, the core 33 'in the casing 1 is formed in the casing 1 as described above.
Since the hollow 41 is previously discharged to form the cavity 41 in the casing 1, the sludge 45 of the hardening material G and the cut sand is taken into the casing 1 as shown in FIGS. 7 and 8.

In general, it is considered that the amount of hardened material G and the amount of mud discharged from the earth and sand is approximately equal to the amount of hardened material G injected from the injection nozzle 31 and the total amount of increase in the amount of soil of the ground 33 cut by the jet jet. To be Therefore, if the sludge 45 generated by cutting is contained in the casing 1, the sludge 45 will not be discharged to the ground, so that the casing 1 to be used in constructing the columnar improved body 43 having a predetermined length and a predetermined diameter. Find the drilling depth according to the number and push it into the ground 33,
The core 33 ′ in the casing 1 may be discharged to form the cavity 41 in the casing 1 in advance.

Then, as shown in FIG. 9, when the formation of the columnar improvement body 43 is completed up to the planned depth, the rotating or swinging casing 1 is pulled out from the ground 33, and the drilled hole 47 makes the drainage 4
If not filled with 5, the formation of the columnar improved body 43 is completed by backfilling it with earth and sand 49 as shown in FIG. As described above, in this embodiment, the casing 1 is rotated or swung to be pushed into the target ground 33, and the core 33 ′ in the casing 1 is augered.
Or a bucket 39 to form a cavity 41 in the casing 1 and then the hardening material G is laterally jetted from a jet nozzle 31 attached to the casing shoe 27 at the tip to inject the ground 33.
In this embodiment, the columnar improvement body 43 is formed in the ground 33 by cutting and removing the sludge 45 generated thereby into the casing 1 and pulling up the rotating or swinging casing 1. According to the above, the sludge 45 generated by cutting is not contained in the casing 1 and is not discharged to the ground. As a result, a large amount of the hardened material G is not wasted, and the sludge treatment is unnecessary. Therefore, there is an advantage that the construction cost can be reduced as compared with the conventional one. Further, as already mentioned, the pressure drop of the jet jet injected into the underground mud water has been remarkable in the past, and the increase in the improved diameter due to the jet jet increases the construction time, resulting in poor efficiency. In some cases, the expected improved diameter could not be obtained due to the presence of uncertainties such as hardness and softness of
In order to pre-drill the ground 33 using the auger 15 and the like, and to take the sludge 45 into the casing 1,
As compared with the conventional case, the pressure accumulated in the ground 33 is reduced and the pressure attenuation of the jet jet is reduced.

Therefore, according to this embodiment, the range of jet jet can be extended as compared with the conventional one, and the rotation speed of the casing 1 (the rotation speed of the injection nozzle 31) and the pulling up can be performed at a distance less than the effective range. In order to shorten the construction time by increasing the speed, etc., the columnar improvement body 4 having a diameter not less than that of the casing 1
3 was obtained, and it became possible to reliably wrap the columnar improved bodies 43 with each other.

In the above embodiment, the casing 1 has a double pipe structure composed of the inner pipe 3 and the outer pipe 5, and the hardening material G is attached to the peripheral wall of the casing shoe 27 on the front end side.
Although it was injected laterally from No. 1, as in one embodiment of the invention according to claim 1 and claim 3 shown in FIG. 11, the casing 51 of the single pipe structure was sequentially connected according to the drilling depth. Ground 3
3 is rotated or oscillated and pushed into the casing 3, and the core in the casing 51 is discharged by an auger or the like.
After forming the cavity 41 in the casing 1, insert the injection pipe 53 having the branch pipes 53a and 53b bifurcated in the direction of the inner wall of the casing 51 into the casing 51, and attach it to the tips of the branch pipes 53a and 53b. The injection nozzle 55 is projected from the casing shoe 57 to inject the hardening material G in the lateral direction, and then the injection pipe 53 is rotated or swung to pull it up at the same time as the casing 51 to form the columnar improvement body 43. Good.

Thus, according to this embodiment, the intended purpose can be achieved as in the case of the above embodiment.

[0024]

As described above, according to the ground improvement method for soft ground according to each claim, since the sludge produced by cutting is not discharged to the ground, the hardening material is wasted. In addition, there is an advantage that the treatment cost of the sludge is not required and the construction cost can be reduced. Furthermore, according to the present invention, there is an effect that it is possible to reliably form a columnar improved body having a large diameter in a shorter construction time than in the past.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a casing used in an embodiment of a ground improvement method according to claims 1 and 2 and a dresser for connecting the casing to a hole drilling machine.

FIG. 2 is a side view of a hole drilling machine used in an embodiment of the ground improvement method according to claim 1 and claim 2.

FIG. 3 is a process diagram of an example of the ground improvement method according to claim 1 and claim 2 showing a cutting state of the ground with a hardening material.

FIG. 4 is a process drawing of an embodiment of the ground improvement method according to claim 1 and claim 2 showing a state where the casing is pushed into the ground.

FIG. 5 is a view showing a state where a core is discharged by an auger.
FIG. 5 is a process chart of an embodiment of the ground improvement method according to claim 2;

FIG. 6 is a view showing a core discharge state by a bucket.
FIG. 5 is a process chart of an embodiment of the ground improvement method according to claim 2;

FIG. 7 is a process drawing of an example of the ground improvement method according to claim 1 and claim 2 showing a raised state of the casing.

FIG. 8 is a process drawing of an example of the ground improvement method according to claim 1 and claim 2 showing a raised state of the casing.

FIG. 9 is a process drawing of an embodiment of the ground improvement method according to claim 1 and claim 2 showing a state where the casing is pulled out from the ground.

FIG. 10 is a cross-sectional view of the formed columnar improved body.

FIG. 11 shows a cutting state of the ground with a hardening material.
FIG. 4 is a process chart of an example of the ground improvement method according to claim 3;

[Explanation of symbols]

 1,51 Casing 3 Inner tube 5 Outer tube 7 Dreeterer 9 Drilling machine 11 Rotary head 13 Kerry bar 15 Auger 17 Swivel 19,21,29 Thin tube 23 High pressure hose 25 Bit 27,57 Casing shoe 31,55 Injection nozzle 33 Ground 33 ' Core 39 Bucket 41 Cavity 43 Columnar improved body 45 Exhaust mud 47 Drilling hole 53 Injection pipe G Hardening material

Claims (3)

[Claims] 1. The casing is pushed into the target ground, the core in the casing is discharged to form a cavity in the casing, and then the hardening material is jetted laterally from the tip side of the casing to cut the ground. , A method for improving ground on soft ground, characterized in that the sludge generated thereby is taken into the casing and the casing is pulled up to form a columnar improved body having a diameter larger than the casing in the ground. 2. A hardening material injection device is attached to the tip of the casing to form a cavity in the casing, and then the casing is rotated or rocked to inject the hardening material from the injection device to cut the ground. The ground improvement method for soft ground according to claim 1, wherein the sludge generated thereby is taken into the casing and the rotating or rocking casing is pulled up to form a columnar improved body in the ground. . 3. After forming a cavity in the casing, an injection pipe equipped with a curing material injection device at its tip is inserted into the casing to cause the injection device to protrude from the tip of the casing, and then the injection pipe is rotated. Or, by rocking and injecting a hardening material from a spraying device to cut the ground and taking in the mud generated by this, the rotating or rocking injection pipe and casing are pulled up at the same time to form a pillar in the ground. The ground improvement method for soft ground according to claim 1, wherein an improved body is created.