JP2713864B2 - 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 forming a large-diameter ground improvement pile on extremely soft ground by using an apparatus for all casing methods.

[0002]

2. Description of the Related Art In the entire casing method, a large-diameter casing having a diameter of 1 to 2 m is excavated by a drilling tool such as a hamag lab while being pushed into the ground while being rotated by a rotary press-in / draw-out device installed on the ground. The excavated soil is discharged to the ground, and fresh concrete is poured into the discharged casing, and then the casing is pulled out while being rotated by the rotary press-in / draw-out device, thereby forming a concrete pile in the ground. Sufficient support force can be obtained even on soft ground.

[0003]

However, the biggest disadvantage of the conventional whole casing method as described above is that the use of a large amount of ready-mixed concrete results in a very high construction cost. In particular, sand and gravel, which are the main materials of ready-mixed concrete, are very expensive and hardly available in Japan.
At present, most of them are procured from foreign countries, and even foreign-made ones are quite expensive.

Further, although the concrete pile in the soft ground by the above-mentioned conventional whole casing method can provide a sufficient ground supporting force, there is no drain effect for discharging extra water from the surrounding ground to the ground, and therefore, there is no drainage effect. Consolidation could not be performed effectively.

[0005] As a ground improvement pile using a cement-based solidifying material, a cement-based solidifying material is kneaded into a paste, poured into the ground, and directly stirred and mixed with the earth and sand in the ground. However, since this soil cement pile mixes the cement-based solidification material and the earth and sand in the ground in the ground with stirring, it is determined whether both are sufficiently and uniformly stirred and mixed. It is impossible to do so, and there is a possibility that the supporting force varies, and the up and down movement and rotation of the stirring rod for stirring and mixing must be performed at a considerable frequency. The work was extremely complicated.

An object of the present invention is to solve the above problems.

[0007]

In the method according to the first aspect of the present invention, a large-diameter cylindrical casing 2 is pushed into the ground by a casing rotary press-in / draw-out device 1, and the casing 2 is placed in the ground. After penetrating to a predetermined depth, the soil in the casing 2 is excavated with an excavating tool 3 such as a hamag rub and the excavated soil is discharged to the ground. The mixed powder S thus formed is put into the casing 2 and the mixed powder S is pressurized by the pressurized air supplied into the casing 2. 1 to discharge the mixed powder S in the casing 2 into the ground, and the mixed powder S discharged into the ground absorbs moisture in the ground to form a ground improvement pile P. In which it was to be formed.

In the construction method according to the second aspect, when the mixed powder S is introduced into the discharged casing 2, a mixing valve having an on-off valve 15 and an air nozzle 16 is provided at the upper end of the casing 2. A hopper 11 for charging the granular material is mounted, and the mixed granular material S
Is supplied into the casing 2 from the air nozzle 16 in a valve-closed state, and the supplied mixed granular material S is pressurized.

[0009] The method according to claim 3 is characterized in that the cement-based solidifying material contains calcium oxide, silicon dioxide, aluminum oxide and sulfur trioxide as main components.

[0010]

According to the construction method of the first aspect, the large-diameter cylindrical casing 2 is pushed into the ground by the rotary press-fitting / pulling-out device 1 and penetrates to a predetermined depth, and the soil in the casing 2 is excavated such as a hamag lab 3 or the like. The excavated soil excavated by the tool and discharged to the ground is used as it is as a soil material for forming a pile, and the excavated soil and the cement-based solidifying material or cement powder are mixed and stirred on the ground to form a mixed powder granule S. Is introduced into the casing 2, so that expensive sand and gravel as in the prior art is not required, and it is extremely economical, and the pile construction cost can be significantly reduced.

Further, according to this construction method, the casing 2 is pulled out by the rotary press-in / draw-out device 1, and the mixed powder and granules S inside the casing 2 are discharged into the ground, and the mixed powder and granules discharged into the ground are discharged. Since S absorbs moisture in the ground to form the ground improvement pile P, the moisture contained in the soft ground is absorbed by the mixed powder and granular material S, thereby increasing the density of the soft ground, The mixed granular material S absorbs moisture in the ground and hardens, so that the mixed granular material S swells and consolidates the soft ground, thereby effectively achieving the consolidation of the soft ground.

The mixed powder S in the casing 2 is pressurized by the pressurized air supplied into the casing 2. In this case, for example, sand or the like in the casing is removed as in a conventional sand compaction method. The soil is not compacted positively by rods, etc., but is only pressed from above by pressurized air. Form P. However, even if the mixed powder S forming the ground improvement pile P absorbs moisture in the soft ground and hardens, it hardens in a rough state. The drain effect due to the phenomenon can be sufficiently exerted, so that excess water in the surrounding ground can be discharged to the ground, and the solidification of the soft ground can be effectively achieved.

According to the construction method of the second aspect, when the mixed powder S is charged into the discharged casing 2, the mixing with the on-off valve 15 and the air nozzle 16 attached to the upper end of the casing 2 is performed. Hopper 11 for powder material input
After the valve 15 is opened and the mixed powder S is charged into the casing 2, the valve 15 is closed, pressure air is supplied from the air nozzle 16 into the casing 2, and the mixed powder S is discharged. Apply pressure. Therefore, by using such a hopper 11, the pressurizing operation of the mixed granular material S inside the casing 2 can be easily and easily performed. Further, since the mixed powder S can be appropriately pressurized in the casing 2, when the mixed powder S is discharged into the ground by the subsequent withdrawal of the casing 2, a continuous good quality with no breaks is provided. A pile can be formed, and a good pile having an appropriate supporting force can be formed.

According to the method of the third aspect, 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.

[0015]

Embodiments will be described with reference to the drawings.
FIG. 1 shows a pile forming apparatus used to carry out the method according to the present invention. In this figure, reference numeral 1 denotes a casing rotary press-in / pull-out device for pushing a large-diameter cylindrical casing 2 into the ground while rotating or pulling the large-diameter tubular casing 2 out of the ground. Reference numeral 3 denotes a leader 4 mounted on a crawler crane, for example. Is a well-known hammer grab (digging tool) which is suspended and supported via a lifting wire 5.

The casing rotary press-in / pull-out device 1 is a well-known device which has been conventionally used. For example, as shown in FIG. 2, a rotary drive shaft 7, a hydraulic motor 8, a press-fit Pull-out means 9, chuck device 1
The casing 2 is rotated by driving the hydraulic motor 8 while driving the hydraulic motor 8 while inserting the casing 2 into the rotary drive shaft 7 and holding the casing 2 by the chuck device 10. While pushing it into the ground or pulling it out.

FIG. 3 shows a hopper 11 for charging mixed powder and granules which is detachably mounted on the upper end 2a of the casing 2, and a base cylinder whose lower end is fitted in the upper end 2a of the casing 2. And a hopper body 13 connected to an upper end of the base cylinder portion 12 and concentrically integrally connected to an outer peripheral side of a lower end portion of the base cylinder portion 13, and externally fitted to an upper end portion 2 a of the casing 2. An opening / closing valve 15 is pivotally attached to the upper end of the base cylinder portion 12, and an air nozzle 16 is provided below the opening / closing valve 15. This hopper 1
To attach 1 to the casing 2, as shown in FIG.
The lower end of the base cylinder 12 is fitted inside the upper end 2a of the casing 2 and the locking cylinder 14 is fitted externally.
The ends of the plurality of fixing bolts 17 screwed into the casing 2 may be locked to the lower end of the upper end 2a (thick portion) of the casing 2.

The on-off valve 15 is normally kept closed by a spring (not shown) as shown by a solid line in FIG. 3, and the mixed powder and granules are put into the hopper body 13 of the hopper 11. In this case, the valve is opened as shown by the phantom line in FIG. Alternatively, the above-mentioned spring is not used, and the valve is normally in a closed state as shown by the phantom line in FIG. A configuration in which the valve is opened may be adopted. The air nozzle 16 is connected to an air compressor (not shown) via an air hose 18.

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 FIGS. 4A and 4B, the large-diameter casing 2 is pushed into the soft ground while being rotated by the casing rotary press-fitting / pulling-out device 1 and penetrates. In this case, a plurality of casings 2 having a unit length are used,
The casings 2 penetrate into the ground while being successively added. As shown in the figure, every time the casing 2 penetrates to a certain depth, the ground soil inside the casing 2 is excavated by the hammer rub 3 and the excavated soil is discharged to the ground. Thus, the casing 2 penetrates into the soft ground to a predetermined depth, and the ground soil inside the casing 2 is entirely discharged to the ground.

The excavated soil discharged from the inside of the casing 2 to the ground as described above is, for example, as shown in FIG. 6, a stirring tank (notch tank) 1 previously installed near the work site.
9, and into the excavated soil carried into the stirring tank 19, an appropriate amount of cement-based solidifying material or cement powder is mixed, and as shown in FIG. Device 2 with device 20 attached
1 can be stirred and mixed. This stirring device 2
As shown in FIG. 5, the rotary pawl 0 has a rotary claw 22 that rotates quickly forward and backward by a hydraulic motor, and replaces this with a shovel of a hydraulic shovel to attach the agitating device 20, for example, Mitsui Co., Ltd. It is recommended that a stirrer manufactured by Miike Seisakusho (trade name, MT twin header) and a stirrer manufactured by Maruzen Construction Co., Ltd. (product side, stabilizer) have extremely good stirring efficiency, and that they be employed in the practice of the present invention. You.

As described above, when stirring and mixing the excavated soil discharged from the inside of the casing 2 to the ground with, for example, a cement-based solidified material, the cement-based solidified material is
It is preferable to use one containing calcium oxide, silicon dioxide, aluminum oxide and sulfur trioxide as main components, and specifically, those having the following compounding ratio are 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 0.8% Sulfur trioxide 7.7 to 6.7% Insoluble residue 0.1 to 0.2%

As a commercially available cement-based solidifying material, Heart Keep P-430 (trade name, manufactured by Tokuyama Corporation) or Aso Solid Ace (trade name, manufactured by Aso Cement Co., Ltd.) is preferable.

The mixing ratio of the cement solidified material and the excavated soil differs depending on the soil quality of the excavated soil. Generally, the compression strength of one sand compaction pile (uniaxial compression strength)
kgf / cm ² ) is ± ² to 3 kg before and after 7 kgf / cm ²
It is said that f / cm ² is necessary and sufficient, but in order to reach these strengths, as a result of experiments by the present inventors, the mixing ratios shown in the following Tables 1 to 3 are suitable. It has been found.

[0026] Remarks The above clayey soil is 80% silt, 40% clay,
Heartkeeping P-430 (manufactured by Tokuyama Corporation) was used as a cement-based solidifying material having a sand content of 60% and a water content of 70%. The above-mentioned compressive strength is the value after 7 days from the casting.

[0027] The above sandy silt has a silt content of 70% and a clay content of 15
%, Sand content 85%, water content 70%, and other conditions are the same as those in Table 1.

[0028] Remarks The above sandy soil is 15% silt, 15% clay,
The conditions are the same as those in Table 1 except that the sand content is 85% and the water content is 70%.

The excavated soil discharged from the inside of the casing 2 and the cement-based solidified material are stirred and mixed on the ground by the above-described apparatus 21 as shown in FIG. The mixed powder S is formed.

The mixed powder S formed as described above
As shown in FIG. 4, the excavated soil inside the casing 2 is introduced into the casing 2 from which the excavated soil is discharged to the ground by the above-described mixed powder / granule introduction hopper 11 having the on-off valve 15 and the air nozzle 16. The mixed powder and granular material S is
When it is charged into the inside, the upper end 2a of the casing 2
The hopper 11 is attached to the
When the mixed powder S is supplied to the hopper main body 13, the on-off valve 15 is automatically opened, and the mixed powder S is introduced into the casing 2 from the base cylinder 12.

In this case, the mixed powder S in the entire volume of the casing 2 embedded in the ground is not charged at once, but may be charged several times. That is, after a certain amount of the mixed powder S is first supplied into the casing 2 by the hopper 11, the on-off valve 15 is closed, pressure air is supplied from the air nozzle 16, and the internal pressure of the casing 2 is increased. The mixed powder S in the casing 2 is pressurized by pressure (see FIG. 4), and then the same operation is repeated, for example, two to three times, so that the required amount of the mixed powder S in the casing 2 is reduced. Finally, the mixed powder S is filled into the entire casing 2 in a pressurized state. of course,
After the total volume of the mixed powder and granules S in the casing 2 has been charged at one time, the on-off valve 15 is closed, and pressurized air is supplied from the air nozzle 16. Pressure may be applied occasionally.

As described above, using the mixed powder and granular material hopper 11 with the on-off valve 15 and the air nozzle 16,
By pressurizing the mixed powder and granular material S charged into the casing 2 by air pressure, a cavity is not formed in the mixed powder and granular material S charged into the casing 2 and the mixed powder and granular material S Since the mixed powder S is discharged into the ground by the subsequent withdrawal of the casing 2 because the casing 2 is appropriately pressurized, it is possible to form a continuous high-quality pile with no breaks, and to have an appropriate support. A pile having power can be formed. This has a great effect when the mixed powder S is charged in the casing 2 while being pressurized in the casing 2 by a required amount in several times.

When the mixing of the mixed powder S into the casing 2 is completed, the hopper 18 is removed from the upper end of the casing 2 and the casing 2 is inserted into the rotary press-in / draw-out device 1 as shown in FIG. To remove the mixed powder and granular material S inside the casing 2 into the ground, and the mixed powder and granular material S discharged into the ground absorbs moisture in the ground to form a ground improvement pile. .

The mixed powder S discharged into the ground forms a pile P. Immediately after the formation, the hardening starts after about 3 hours, and the pore water between the soil particles in the surrounding ground is absorbed. While reducing the water content, it reacts with water during the water absorption to expand, and its volume is reduced to 30% to 60% of the volume when the pile is formed
Increase. As described above, when the soil improvement pile expands, the surrounding ground is compacted, and the strength of the ground is enhanced by the consolidation. The soil improvement pile will therefore remain suspended in the ground, consolidating the surrounding ground and further increasing its strength (see FIG. 4).

Further, in this case, the mixed powder S has not been positively compacted in the casing 2 by that time, but has been just moderately pressurized by pressurized air.
Since the casing 2 is discharged into the ground as it is by being pulled out, the mixed powder S discharged into the ground is:
The ground improvement pile P is formed in a coarse state having a relatively low density. Therefore, even if the mixed powder S forming the ground improvement pile P absorbs moisture in the soft ground and hardens, it hardens in a rough state, so that it has an appropriate ground supporting force.
The drainage effect due to the capillary phenomenon can be sufficiently exerted, whereby excess water in the surrounding ground can be discharged to the ground, and the solidification of the soft ground can be effectively achieved.

[0036]

According to the method of the first aspect of the present invention, the excavated soil excavated from the soil in the casing and discharged to the ground is used as it is as a soil material for forming a pile, and the excavated soil and the cement-based material are used. Because the mixed powder and granules formed by mixing and stirring the solidified material or cement powder on the ground is put into the casing, it does not require expensive sand or gravel as in the past, it is extremely economical, The pile construction cost can be significantly reduced.

In the method of the present invention, the excavated soil inside the casing is discharged to the ground, and the excavated soil and the cement-based solidifying material or cement powder are stirred and mixed on the ground to form a mixed powder and granule. Therefore, the mixture can be uniformly and sufficiently stirred and mixed, and there is no variation in the mixing of the two. In addition, it is necessary to change the mixing ratio of the cement-based solidifying material or the cement powder depending on the soil material, that is, the soil component contained in the excavated soil, but this mixing ratio can be also ensured accurately. As a result, a ground improvement pile having a uniform strength over the entire length can be formed.

Further, according to the method of the present invention, the casing is pulled out, and the mixed powder and granules inside the casing are discharged into the ground, and the mixed powder and particles discharged into the ground remove water in the ground. Absorbs to form a soil improvement pile, so that the density of the soft ground is increased, and the mixed powder and granules absorb moisture in the ground and harden, causing the mixed powder and particles to swell and soft ground. And consolidation of soft ground can be effectively performed.

Further, according to the method of the present invention, the mixed powder and granules are put into the casing left in the ground, and the mixed powder and granules inside the casing are separated into rods as in the conventional sand compaction method. Without positively squeezing it, that is, without positively consolidating inside the casing, just pressurize it with pressurized air and discharge it directly into the ground by pulling out the casing. The mixed powder and granular material forms a ground improvement pile in a relatively low-density coarse state. Then
Even if this mixed powder and granule absorbs moisture in the soft ground and hardens, it hardens in a rough state, so it can exert a sufficient drainage effect while having a certain ground support force, and thereby the surrounding ground The excess water can be discharged to the ground, effectively consolidating the extremely soft ground.

According to the construction method of the second aspect, the use of the open / close valve and the air-nozzle-attached hopper for mixed powder and granules mounted on the upper end of the casing allows the pressurization of the mixed powder and granules inside the casing. Can be easily and easily performed. In addition, since the mixed powder and granular material can be appropriately pressed in the casing, when the mixed powder and granular material is discharged into the ground by subsequent withdrawal of the casing, a continuous high-quality pile without any breaks can be formed. At the same time, a good pile having an appropriate supporting force can be formed.

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

[Brief description of the drawings]

FIG. 1 is a side view showing a pile forming apparatus for carrying out a method of the present invention.

FIG. 2 is a perspective view showing a casing rotary press-in / draw-out device.

FIG. 3 is a partially sectional side view showing a hopper with an on-off valve and an air nozzle attached to an upper end of a casing.

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

FIG. 5 is a perspective view showing an example of a stirring device used in the method of the present invention.

FIG. 6 is a perspective view showing an example of use of the stirring device of FIG. 6; DESCRIPTION OF SYMBOLS 1 Casing rotary press-in / draw-out apparatus 2 Casing 3 Hamamagrub (digging tool) 11 Hopper for charging mixed powder and granular material 15 Open / close valve 16 Air nozzle S Mixed powder and granular material P Ground improvement pile

Claims (3)

(57) [Claims] A large-diameter tubular casing is pushed into the ground by a casing rotary press-in / draw-out device, the casing penetrates to a predetermined depth in the ground, and the soil in the casing is excavated by a drilling tool such as a hammer rub. After discharging the excavated soil to the ground, a mixed powder formed by mixing and stirring the excavated soil and the cement-based solidifying material or cement powder on the ground is put into the inside of the casing, and the mixed powder and granules are discharged. The casing is pressurized by the pressure air supplied into the casing, and then the casing is pulled out by the casing rotary press-in / draw-out device to discharge the mixed powder and granular material inside the casing into the ground, and the mixed powder and granular material discharged into the ground Is a soft ground improvement method that absorbs moisture in the ground to form a ground improvement pile. 2. A mixed hopper with an on-off valve and an air nozzle is mounted on the upper end of the casing when the mixed powder is charged into the discharged casing. The method according to claim 1, wherein after the mixed powder and granules are charged into the casing in a valve state, pressurized air is supplied into the casing from an air nozzle in a closed state to pressurize the input mixed powder and granules. Improvement method for soft ground. 3. The method for improving soft ground according to claim 1, wherein the cement-based solidifying material contains calcium oxide, silicon dioxide, aluminum oxide and sulfur trioxide as main components.