JP2804898B2 - Improvement method for soft ground - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving soft ground, and more particularly to a method for improving soft ground by placing a ground improvement pile on soft ground.

[0002]

2. Description of the Related Art The mainstream of ground improvement methods is
This is the so-called sand compaction pile method. In this method, the casing is driven into the soft ground to a predetermined depth,
The compacted pile, that is, the compacted pile is extruded by extruding the sand and the like from the tip while pulling up the casing while squeezing the sand and gravel etc. put in this casing with a shaker or a rod, etc. It is created inside. According to the sand compaction pile method, a sufficient supporting force can be obtained for soft ground.

[0003] As a method of forming a ground improvement pile using a cement-based solidification material, a method of excavating the ground to a predetermined depth with an auger screw and kneading the cement-based solidification material into a paste during the excavation is performed in the ground. To form a kind of soil cement pile by directly stirring and mixing with earth and sand in the ground.

[0004]

However, the biggest difficulty of the former sand compaction pile method is that the material, sand and gravel, is very expensive, hardly procurable in Japan, and most of it is from foreign countries. It is currently procured. Even foreign-made ones are quite expensive. In addition, there is also a problem that, for a long period of time, the sand compaction pile is cut off midway due to the flow pressure in the soft ground, particularly in the deep layer, and the bearing capacity is lost.

Further, in the latter soil cement pile method, since the pasty cement-based solidifying material is injected into the ground while excavating the ground, earth and sand or water from the surrounding ground may be mixed during the work, and the surrounding ground may be removed. Under the influence of earth pressure, it is difficult for the excavated soil and the paste-like cement-based solidification material to be mixed uniformly, and the pile may be partially constricted to form a uniform pile with a uniform diameter over the entire length. Therefore, there is a problem that sufficient supporting force cannot be obtained.

An object of the present invention is to solve these difficulties.

[0007]

In order to solve the above-mentioned problems, in the method according to the first aspect of the present invention, an auger machine 1 is used to form a tubular casing 2 and a tremee pipe inserted therein. After the casing 2 is integrally embedded in the ground to a predetermined depth, the casing 2 is separated from the auger machine 1 and left in the ground, and the tremy pipe 3 is removed by the auger machine 1.
, The cement-based solidifying material M or the cement powder is discharged from the tip of the tremy tube 3 into the soil in the casing 2, and then the rod 18 having a vibroflot 17 at the tip and the rod 18 rotatable relative to the rod 18 so as to be able to move vertically. The hollow tube 20 with the stirring blade 19 fitted to the outside is inserted into the soil in the casing 2 to the bottom thereof while vibrating the vibrating flot 17. Thereafter, the vibrating froth 17 is vibrated and the stirring blade 19 is vibrated. The hollow shaft body 6 is rotated
The casing 2 is rotated by the vertical movement means 3 and moved up and down by the vertical movement means. The mixed powder and granules S in the casing 2 are discharged into the ground while being pulled out together with the hollow pipe 20, and the mixed powder and granules S discharged into the ground absorb the moisture of the ground to form the ground improvement pile P. It is something to do.

In the construction method according to the second aspect, the hollow tube 20 with the stirring blade 19 is rotated and moved up and down even when inserted into the soil inside the casing 2.

In the method according to claim 3, the hollow tube 2
A hydraulic cylinder 29 is used as the vertical movement means for vertically moving 0.

In the method according to a fourth aspect, when the rod 18 is pulled out, the rod 18 is moved up and down by a hydraulic cylinder 31 for vertically moving the rod.

[0011] In method according to claim 5, the lower portion of the vibrator Roff lot 17 opens to deploy laterally facing substantially horizontally by earth pressure, equipped with a butterfly closing plate 33 for closing to collapse downwards by its own weight The butterfly-shaped opening / closing plate 33 is opened and closed in accordance with the vertical movement of the vibrofrotto 17 by the rod vertical movement hydraulic cylinder 31.

In the method according to the sixth aspect, the cement-based solidifying material contains calcium oxide, silicon dioxide, aluminum oxide and sulfur trioxide as main components.

[0013]

According to the construction method of the first aspect of the present invention, the casing 2 is buried in the soft ground to a predetermined depth by the auger machine 1, and the soil inside the casing 2 is used as it is as a soil material for forming a pile. Therefore, it is extremely economical, and the construction cost can be significantly reduced.

In the method of the present invention, after the tremy tube 3 is embedded in the ground integrally with the casing 2, the casing 2 is cut off and the tremy tube 3 is left in the ground.
The cement-based solidifying material M or the cement powder is discharged into the soil inside the casing 2 from the tip thereof while extracting the soil. 19, the surrounding ground is discharged while the cement-based solidifying material M or cement powder is being discharged into the soil inside the casing 2 or while the soil is mixed with the cement-based solidifying material M or the cement milk. There is no intrusion of earth and sand or water and no influence of the earth pressure on the surrounding ground. Therefore,
The cement-based solidification material M or cement powder does not react unexpectedly with the earth and sand or water in the surrounding ground, and the soil and the cement-based solidification material M or cement milk can be surely stirred and mixed, resulting in good mixed powder and granules. The body S is formed. In this method, the casing 2 is inserted and the tremy tube 3 is inserted and withdrawn by the auger machine 1 which is generally used, so that the equipment is simplified.

In the method of the present invention, when the hollow pipe 20 and the rod 18 are inserted into the soil inside the casing 2 embedded in the ground, the hollow pipe 20 and the rod 18 can be easily and reliably inserted. Further, when the casing 2 is pulled out, the vibrating rod 17 vibrates, and the hollow tube 20 rotates around the rod 18 and the rod 1
8, the agitating blade 19 moves up and down while rotating, and thus the vibrating action of the vibroflot 17 and the swirling and vertical movement of the stirring blade 19 allow
The soil in the casing 2 and the cement-based solidifying material M are effectively stirred and mixed, and the mixed powder S is uniform and highly accurate.
Is formed, and the mixed powder S is discharged into the ground as it is, and a continuous ground improvement pile P is continuously formed up to the deep part of the ground.

Further, since the mixed powder and granules S discharged into the ground absorb moisture in the ground to form the ground improvement pile P, the moisture contained in the soft ground is mixed with the mixed powder and granules. While being absorbed by S, the density of the soft ground is increased, and the mixed granular material S absorbs moisture in the ground and hardens, so that the granular material S swells and consolidates the soft ground. The consolidation of soft ground can be effectively achieved.

According to the construction method of claim 2, the stirring blade 19
By rotating and moving up and down the attached hollow tube 20 even when it is inserted into the soil inside the casing 2, the soil inside the casing 2 and the cement-based solidifying material M are mixed with the stirring blade 19.
The mixture is stirred and mixed due to the swirling action and up and down operation. Therefore, by the stirring and mixing at the time of the insertion and the stirring and mixing at the time of the extraction, the soil in the casing 2 and the cement-based solidified material M or the cement milk are more uniformly stirred and mixed, and the mixed powder and granules with higher accuracy are obtained. S will be formed.

According to the construction method of the third aspect, a sufficient driving force can be obtained by using the hydraulic cylinder 29 as a means for moving the hollow tube 20 up and down.
The structure is compact and installation is easy.

According to the construction method of claim 4, when the rod 18 and the hollow tube 20 are pulled out,
Is moved up and down by a hydraulic cylinder 31 for vertically moving the rod, thereby facilitating the discharge of the mixed powder and granular material S from the lower end of the casing 2 and consolidating the mixed powder and granular material S discharged into the ground. Is done.

Further, according to the method according to claim 5, during withdrawal of the casing 2, butterfly closing plate 33, the lateral direction substantially horizontal direction by the pressure of the mixed powder or granular material S during downward movement of the vibrator Roff Lot 17 And moves downward in this open state to push the mixed powder and granular material S, and when moving upward, closes downward by its own weight, and smoothly moves upward without receiving the resistance of the mixed powder and granular material S. As the butterfly-shaped opening / closing plate 33 opens and closes with the vertical movement of the vibroflot 17, the discharge of the mixed powder S from the lower end of the casing 2 is promoted and effectively discharged. Then, a pressing force is applied to the mixed powder S discharged into the ground, whereby a sufficiently compacted pile P is formed.

Further, according to the method of the present invention, when a cement-based solidifying material containing calcium oxide, silicon dioxide, aluminum oxide and sulfur trioxide as main components is used, the results of experiments show that ordinary cement is used. 240 kg / m ^{3 of} powder
While the unconfined compressive strength of the cementitious solidified material was ² kgf / cm ² when added, the unconfined compressive strength of 6.4 kgf / cm ² when 240 kg / m ³ was added, It has been found that it exhibits about three times the strength of cement powder. Therefore, according to the cement-based solidifying material, a very good supporting force as a pile can be exhibited.

[0022]

Embodiments will be described with reference to the drawings.
FIGS. 1A and 1B show a pile forming apparatus used to carry out the method according to the present invention. First, in FIG. 1 (A), reference numeral 1 denotes an auger machine which is equipped with a cylindrical casing 2 and a tremy tube 3 which is inserted concentrically therein and drives the casing 2 to rotate. It is supported so as to be able to move up and down, and is suspended from the top of the reader by a lifting wire (not shown). In this auger machine 1, a pair of motors 5 and 5 with a reduction gear are provided on a machine frame 4 and a hollow shaft body 6 for driving a casing is rotatably provided, and a gear fixed to an output shaft 5a of each motor 5 is provided. The rotation of each output shaft 5a is transmitted to the hollow shaft body 6 by the gear 7 and the gear 8 fixed to the hollow shaft body 6, so that the casing 2 is rotated.

The lower end of the casing driving hollow shaft 6 projects downward from the lower surface of the machine frame 4 by an appropriate length, and the upper end 2a of the casing 2 is fitted to the lower projecting end. A through hole 2 provided in the upper end 2a of the casing 2
b, a detachable pin or bolt 9 is inserted into a through hole or a screw hole (not shown) provided at a corresponding position of the hollow shaft body 6.
Is inserted or screwed into the casing 2 so as to be integrally rotatable with the casing 2.

The tremy tube 3 is, for example, a casing 2
And is concentrically arranged in the casing 2 and has an upper end 3a fixed in the machine frame 4 and has an upper end 3a ,
A hopper 11 for supplying cement-based solidification material or cement powder is continuously provided via a large-diameter cylindrical portion 10. As shown in FIG. 1A, the large-diameter cylindrical portion 10 is opened by its own weight as shown by a solid line, and is opened by an air pressure injected from an air nozzle 12 provided in the cylindrical portion 10 as shown by a phantom line. An opening / closing valve 13 is provided. Then
After a required amount of cement-based solidifying material or cement powder is supplied from the hopper 11 into the tremie pipe 3, air is supplied from the air nozzle 12 to close the on-off valve 13, and the supply of the air supplies the tremee. The internal pressure of the pipe 3 is increased, and the internal cement-based solidifying material or cement powder is extruded from the lower end of the tremy pipe 3.

When using the tremy tube 3, FIG.
As shown in (C), a bottom cover 14 is detachably attached to the lower end of the tremy tube by, for example, an adhesive tape 15.

In FIG. 1 (B), reference numeral 16 denotes a hollow rod 18 having a vibro-flot 17 at a tip thereof, and a stirring blade 19 externally fitted to the rod 18 so as to be relatively rotatable and vertically movable. An elevating body equipped with an empty tube 20 and raised and lowered by a leader, a crane, or the like.
At the lower part of the housing, a casing mounting pipe 21 for detachably mounting the casing 2 is provided so as to protrude from the lower surface of the elevating body 16 by an appropriate length and surround the hollow pipe 20. The casing mounting pipe 21 is the same as the casing driving hollow shaft body 6. The upper end 2 a of the casing 2 is fitted to the pipe 21 and the casing 21 is inserted through the through hole 2 b of the casing upper end 2 a. The casing 2 can be mounted by inserting or screwing a detachable pin or bolt 9 into the through hole or screw hole 22 of the tube 21.

Further, as shown in FIG.
A rotation driving means 23 for rotating the hollow tube 20 with the stirring blade 19 and a vertically moving means 24 for vertically moving the hollow tube 20 by a predetermined stroke are provided in the inside of the tube 6.

The rotation driving means 23 includes the rod 18
A pair of motors 26 with a reduction gear provided on a movable frame 25 which can move up and down relative to the motor, a gear 27 fixed to an output shaft 26a of each motor 26, and fixed to the hollow tube 20; Each of the motors 26 rotates the hollow tube 20 via the gears 27, 28. The vertical movement means 24 is provided between a pair of hydraulic cylinders 29, 29 provided on both sides of the hollow tube 20 between the bottom wall 16 a of the elevating body 16 and the movable frame 25. The two hydraulic cylinders 29,
The expansion / contraction operation of 29 causes the hollow tube 20 to move up and down by a predetermined stroke via the movable frame 25.

The movable frame 25 is mounted on the hollow tube 20 via a bearing device 30 so as to be able to move up and down integrally with the hollow tube 20 while allowing the hollow tube 20 to rotate. . In this case, by providing a guide (not shown) for guiding the movable frame 25 that moves up and down in accordance with the expansion and contraction operation of the hydraulic cylinder 29, the movable frame 25 can be moved up and down in a stable state. The empty tube 20 can be reliably moved up and down. A plurality of stirring blades 1 each formed in a rod shape are provided on the outer peripheral surface of the hollow tube 20.
9 are integrally protruded at appropriate intervals in the length direction and the circumferential direction of the hollow tube 20.

Therefore, by operating the rotation driving means 23 and the vertical movement means 24, the hollow tube 20 moves up and down a predetermined stroke along the rod 18 while rotating around the rod 18, thereby making the hollow tube 20 hollow. Each stirring blade 19 protruding from the outer periphery of the pipe 20 moves up and down while turning.

As shown in FIG. 1B, the rod 18 is provided so that the upper end thereof penetrates the inside of the elevating body 16, and the upper end of the rod 18 is installed above the elevating body 16. Connected to a hydraulic cylinder 31 for vertically moving the rod. Therefore, the rod 18 can move up and down by a predetermined stroke by the expansion and contraction operation of the hydraulic cylinder 31. In FIG. 1B, reference numeral 32 denotes a cylindrical guide member for supporting and guiding the hollow tube 20 so as to be rotatable and vertically movable.

FIG. 2 shows a vibroflot 17 mounted on the lower end of the rod 18. The vibroflot 17 is a well-known one, and although not shown, the eccentric shaft is rotated by an electric motor. A horizontal vibration is generated, and a power supply cable K for the electric motor is generated.
Is inserted through the hollow portion of the rod 18 and extends outward from the upper end of the rod 18, and the extended portion
As shown in (B), rod 1 by hydraulic cylinder 31
8 so as to be able to cope with the vertical movement of the coil.

In the lower part of the vibrofrotto 16,
As shown in FIG. 2 and FIG. 1 (B), a butterfly-shaped opening / closing plate 33 that opens to expand laterally by earth pressure and closes to fold downward by its own weight may be provided. In this case, a short-diameter support tube 34 having a large diameter is attached to the vibroflot 17 via a plurality of attachment pieces 35, and a horizontal support shaft 36 is fixed in the lower end portion of the support tube 34 in the diametric direction. A pair of semicircular plates 33a, 33
The butterfly-shaped opening / closing plate 33 is pivotally mounted. The butterfly-shaped opening / closing plate 33 is normally closed so as to be folded downward by its own weight as shown by a solid line in FIG. Under the pressure, as shown by the phantom line in the figure, it rotates upward and expands laterally, and is supported by the lower end of the support tube 34 at the developed position.

To connect the casing 2 to the hollow shaft body 6 for driving the casing of the auger machine 1, as described above, the through hole 2b provided at the upper end portion 2a of the casing 2 and the through hole of the hollow shaft body 6 are formed. Alternatively, a detachable pin or bolt 9 may be inserted or screwed into a screw hole (not shown), but instead of such a connection method using the detachable pin or bolt 9,
A one-touch connection method as shown in FIG. 4 may be adopted. That is, a pair of engaging projections 37 are provided on the outer peripheral surface of the lower end portion of the hollow shaft body 6, and the upper opening portion 38 a is narrow on the inner peripheral surface of the upper end portion of the casing 2, and the lower portion is enlarged in one horizontal direction. Forming a pair of L-shaped grooves 38 formed in the stop portion 38b,
Then, for example, the auger machine 1 is lowered, and each of the engaging projections 37 of the hollow shaft body 6 is inserted into each of the L-shaped concave grooves 38 of the casing 2.
By rotating the hollow shaft body 6 in a direction indicated by an arrow in FIG. 4 (a direction in which the casing 2 rotates when the ground penetrates), each of the engaging protrusions 37 is engaged with the engaging portion 38b. And the casing 2 is connected to the hollow shaft body 6.

Next, the method of the present invention using the pile forming apparatus having the above-described structure will be described with reference to other drawings as needed, centering on FIG. 4 to FIG.
Indicates a construction order.

First, as shown in FIG. 4, the auger machine 1 rotates the casing 2 in the direction of the arrow and embeds it in the soft ground together with the tremy tube 3 inserted in the casing 2. During this embedding, a required amount of cement-based solidifying material (or cement milk) is charged and supplied into the tremy tube 3. During the embedding of the tremy tube 3,
Since the lower end of the pipe 3 is closed by the bottom cover 14, earth and sand and water in the ground do not mix into the cement-based solidified material inside the tremy pipe 3.

If the casing 2 and the tremy tube 3 are buried to a predetermined depth in the ground as shown in FIG.
As shown in FIG. 4A, a detachable pin or bolt 9 connecting the casing driving hollow shaft body 6 of the auger machine 1 and the casing 2 is removed, and the casing 2 is removed from the auger machine 1 as shown in FIG. The auger machine 1 is pulled up while leaving it separated and remaining in the ground, and the tremy tube 3 is pulled out of the soil inside the casing 2.

As the tremy tube 3 is pulled out, the adhesive tape 15 fixing the bottom cover 14 is peeled off by the weight of the cement-based solidifying material supplied into the tremy tube 3, and the bottom cover 14 is removed. As shown in FIG. 4, the cement-based solidified material M inside the casing 2 is discharged from the lower end of the tremy tube 3 into the soil inside the casing 2 (the cavity of the soil after the tremy tube 3 is removed). At this time, FIG.
As shown in (A), air is supplied from the air nozzle 12 to increase the internal pressure on the upper side of the tremie pipe 3 with the on-off valve 13 closed, and the cement-based solidified material M is fed downward by the air pressure. Then, it is discharged from the lower end of the tremy tube 3.

When the tremy tube 3 has been pulled out of the soil inside the casing 2 as shown in FIG. 4, instead of the auger machine 1, the elevating body 16 is placed directly above the casing 2 embedded in the ground. The rod 18 having the vibroflot 17 at the tip and the hollow tube 20 with the stirring blade 19 fitted externally to the rod 18 are placed in the vibrator as shown in FIG. The loft 17 is inserted into the soil inside the casing 2 to the bottom while vibrating. At the time of this insertion, vibroflot 1
Since the vibrating member 7 is easily inserted into the soil inside the casing 2, the vibrating action of the vibroflot 17 mixes the soil inside the casing 2 and the cement-based solidified material M to some extent.

When the rod 18 and the hollow tube 20 are inserted, the vibrator slot 17 is vibrated,
The hollow tube 20 may be rotated by the rotation driving means 23 and moved up and down by the hydraulic cylinder 29, so that the soil inside the casing 2 and the cement-based solidified material M can be swirled by the stirring blade 19 and The mixture is agitated and mixed by the up and down operation, and the mixed powder and granules are formed before the casing 2 is pulled out.

When the rod 18 and the hollow tube 20 reach the bottom of the casing 2 as shown in FIG.
Of the casing 2 projecting from the ground into the upper end portion 2a of the casing 2 protruding from the ground. In this state, the operation of the vibratory flotte 17, the rotation drive means 23 and the hydraulic cylinder 29 is temporarily stopped. After stopping, the upper end portion 2a of the casing 2 and the casing 20 with the casing 2 protruding into the inside thereof are detached with pins or bolts 9.
And the casing 2 is connected to the elevating body 16.

After the casing 2 is connected to the elevating body 19 in this way, the vibrating rod 17 at the tip of the rod 18 is vibrated again, and the hollow tube 20 is rotated by the rotary driving means 23 and moved up and down by the vertical moving means 24. While rotating the stirring blade 19 on the outer periphery of the hollow tube 20 and moving it up and down, thereby stirring and mixing the soil inside the casing 2 and the cement-based solidified material M to form the mixed powder S, While pulling out the casing 2 together with the rod 18 and the hollow tube 20, the mixed powder S inside the casing 2 is discharged from its lower end, and a ground improvement pile P is formed in the ground (see FIG. 4 and).

During the drawing process of the casing 2 as described above, the vibrating action of the vibrating
The soil inside the casing 2 and the cement-based solidified material M are effectively stirred and mixed by the swirling action of the stirring blade 19 protruding from the outer periphery of the and the vertical movement thereof, and the uniform and highly accurate mixed powder particles are obtained. The body S is formed. In this drawing step, the rod 18 is moved up and down by the hydraulic cylinder 31 for vertically moving the rod to move the vibrofrotto 17 at the tip of the rod 18 up and down, thereby discharging the mixed powder and granular material S from the lower end of the casing 2. Is promoted, and the mixed powder S discharged into the ground is compacted and compacted.

When the butterfly-shaped opening / closing plate 33 is provided at the lower part of the vibroflot 17, the butterfly-shaped opening / closing plate 33 is moved when the vibroflot 17 is lowered while the casing 2 is being pulled out. The mixed powder S is opened laterally by the pressure of the mixed powder S, moves downward in this open state to push the mixed powder S, and is closed downward by its own weight at the time of upward movement. As the butterfly-shaped opening / closing plate 33 opens and closes in accordance with the vertical movement of the vibratory flot 17, the mixed powder S is discharged from the lower end of the casing 2. Is further promoted and discharged effectively, and at the same time, a pressing force is applied to the mixed granular material S discharged into the ground, whereby a sufficiently compacted pile P is formed.

The mixed powder and granules S discharged into the ground as described above are formed into a pile and immediately after the formation (about 3
After an hour, curing begins. ), Absorbs pore water between the soil particles in the surrounding ground to lower the water content, and at the same time, absorbs water and expands by reacting with water to increase the volume by 30 to 60% when the pile is formed. As described above, when the ground improvement pile P expands, the surrounding ground is compacted, the ground strength is enhanced by the consolidation, and the ground improvement pile P once expanded itself becomes a cured body by the hardening action. There is no shrinkage, i.e. no reduction in volume, so that this ground improvement pile P will remain compacted in the ground, compacting the surrounding ground and further increasing its strength.

In the method of the present invention as described above, the cement-based solidification material or cement powder may be used as the material to be charged into the soil inside the casing 2 by the tremy tube 3. When used, it is better to use those having calcium oxide, silicon dioxide, aluminum oxide and sulfur trioxide as main components,
Specifically, the following compounding ratio is suitable.

Silicon dioxide 18.6-20.2% Aluminum oxide 6.2-4.6% Ferric oxide 1.8-2.5% Calcium oxide
59.6-63.1% Magnesium oxide About 1.8% Sulfur trioxide 7.
7-6.7% Insoluble residue 0.1-0.2%

[0048] Commercially available cement-based solidifying materials include:
Trade name Heart Keep P-430 (manufactured by Tokuyama Corporation) or trade name Aso Solid Ace (manufactured by Aso Cement Co., Ltd.) is preferred.

[0049]

According to the method of the first aspect of the present invention,
The casing is buried to a certain depth in the soft ground, and the soil inside the casing is used as it is as the soil material for forming the pile, so it is extremely economical and the construction cost can be significantly reduced. it can.

Further, according to this method, after the tremy tube is embedded in the ground integrally with the casing, the casing is cut off and left in the ground, and while the tremy tube is pulled out, the cement-based solidifying material or cement is removed from the tip thereof. The powder is discharged into the soil inside the casing, and the soil and the cement-based solidifying material or cement powder are stirred and mixed by the stirring blade of the hollow tube inside the casing, so that the cement-based solidification into the soil inside the casing is performed. During the discharge of the material M or cement powder, or during the mixing of the soil with the cement-based solidified material M or cement milk, the intrusion of soil and water from the surrounding ground or the influence of the earth pressure on the surrounding ground. No cement-based consolidation material or cement powder will react unexpectedly with soil and water in the surrounding ground, Or stirring and mixing with cement milk is reliably performed, it is possible to form a good mixed powder or granular material.

According to this method, the casing can be embedded and the tremee tube can be inserted and withdrawn by a generally used auger machine. Therefore, the conventional auger machine can be used as it is, and the equipment can be used. It becomes simple.

Further, according to this construction method, when inserting the hollow tube and the rod into the soil inside the casing embedded in the ground, the insertion can be performed easily and reliably by the vibrating action of the vibrofrotto. it can. In addition, when the casing is pulled out, the soil inside the casing and the cement-based solidified material are effectively stirred and mixed by the vibrating action of the vibroflot and the swirling and vertical movement of the stirring blade, so that a uniform and highly accurate mixed powder is obtained. Granules are formed, and the mixed powder and granules are discharged into the ground as it is, so that a continuous ground improvement pile can be formed continuously to the deep part of the ground.

Further, since the mixed powder and granules discharged into the ground absorb moisture in the ground to form a ground improvement pile,
The moisture contained in the soft ground is absorbed by the mixed powder and granular material to increase the density of the soft ground, and the mixed powder and granules absorb the moisture in the ground and harden, whereby the powder and granules swell. This consolidates the soft ground, whereby the solidification of the soft ground can be effectively achieved.

According to the construction method of claim 2, the hollow pipe is
By rotating and moving up and down also when inserting into the soil inside the casing, the soil inside the casing and the cement-based solidifying material can be agitated and mixed by the swirling action of the stirring blade and the up-down operation. Due to the stirring and mixing at the time of mixing and the stirring and mixing at the time of drawing, the soil and cement-based solidifying material or cement milk inside the casing can be more uniformly stirred and mixed, and a more precise mixed powder can be formed. .

According to the construction method of the third aspect, by using a hydraulic cylinder as a means for vertically moving the hollow pipe, a sufficient driving force can be obtained, and the structure is compact and the mounting is easy. There is.

According to the construction method of the fourth aspect, when the rod and the hollow tube are pulled out, the rod is moved up and down, so that the discharge of the mixed powder and granular material from the lower end of the casing is promoted, and the ground is removed. The mixed powder discharged therein is compacted to form a consolidated pile.

According to the construction method of the fifth aspect, while the casing is being pulled out, the butterfly-shaped opening / closing plate opens and closes with the vertical movement of the vibroflot, thereby discharging the mixed powder and granules from the lower end of the casing. Is promoted and discharged effectively, and a pressing force is applied to the mixed powder and granules discharged into the ground, thereby forming a sufficiently compacted pile.

Further, according to the construction method of the sixth aspect, it is possible to obtain a ground improvement pile having a strong supporting force semipermanently.

[Brief description of the drawings]

FIG. 1 (A) is a partial cross-sectional side view showing an auger machine for carrying out the method of the present invention, a casing and a tremee pipe mounted on the auger machine, and FIG. 1 (B) is an elevating body, mounted on the same. FIG. 2 is a cross-sectional side view illustrating a hollow rod with a rod and a stirring blade, and FIG. 2C is an enlarged cross-sectional view illustrating a lower end portion of the tremy tube.

FIG. 2 is a perspective view showing a vibrofrotto.

FIG. 3 is a perspective view showing another example of connecting a casing to a hollow shaft body for driving a casing of an auger machine.

FIG. 4 is an explanatory view showing a construction order of the method of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 auger machine 2 casing 3 tremy pipe 5 prime mover 6 hollow shaft body for driving casing 9 detachable pin or bolt 11 hopper 16 elevating body 17 vibrofrotto 18 rod 19 stirring blade 20 hollow tube 23 rotation driving means 24 vertical movement means 29 Hydraulic cylinder 31 Hydraulic cylinder for rod up / down movement 33 Butterfly opening / closing plate M Cement-based solidifying material S Mixed powder and granule P Ground improvement pile

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) E02D 3/12 102 E02D 3/08

Claims (6)

(57) [Claims] An auger machine integrally embeds a tubular casing and a tremie pipe inserted therein to a predetermined depth in the ground, separates the casing from the auger machine, and leaves the casing in the ground. While pulling out the tremy tube, the cement-based solidifying material or cement powder is discharged from the tip of the tremy tube into the soil in the casing, and then a rod having a vibro-flot at the end and a rotatable relative to the rod so as to be movable up and down relative to the rod. The fitted hollow tube with a stirring blade is inserted into the soil in the casing up to the bottom thereof while vibrating the vibroflot, and then the vibroflot is vibrated and the hollow tube with the stirring blade is rotated by the rotation driving means. Rotate and move up and down by the up and down movement means to separate the soil in the casing from the cement-based solidifying material or cement powder. And if stirring to form a mixed powder granules of both, while pulling the casing together with the rod and the hollow tube, and discharging the mixed powder or granular material in the casing in the ground,
A method of improving soft ground in which mixed powder and granules discharged into the ground absorb moisture in the ground to form a ground improvement pile. 2. The method of improving soft ground according to claim 1, wherein the hollow tube with stirring blades is rotated and moved up and down even when inserted into the soil inside the casing. 3. The method for improving soft ground according to claim 1, wherein a hydraulic cylinder is used as said vertical movement means. 4. The method of improving soft ground according to claim 1, wherein the vibrofrotto is vertically moved by a hydraulic cylinder for vertically moving the rod when the rod is pulled out. The bottom of wherein said vibrator Lof lot, opened to deploy laterally facing substantially horizontally by earth pressure, equipped with a butterfly closing plate closing to collapse downwards by its own weight, the vertical movement of the vibrator Roff Lot 5. The method for improving soft ground according to claim 4, wherein the butterfly-shaped opening / closing plate is opened / closed in conjunction with the above. 6. The method for improving soft ground according to claim 1, wherein said cement-based solidifying material mainly comprises calcium oxide, silicon dioxide, aluminum oxide and sulfur trioxide.