JPH08134896A - Stabilization of soft ground - Google Patents

Abstract

PURPOSE: To greatly and economically reduce the manufacturing cost of piles without necessity of costly sand and gravel. CONSTITUTION: A cylindrical easing 2 having a large diameter is buried in a specified depth of the ground by a rotary press-in and pull-out device 1 and a cement solidifying paste is injected from the front end of a hollow rod 7 while vibrating a vibro-float and vertically moving it. The rod 7 is inserted in the soil of the casing 2 and pulled out thereof to mix the soil in the casing with the cement solidifying paste and form a granular paste mixture S. Thereafter, the casing 2 is pulled out by the rotary press-in and pull-out device 1 to form a soil improvement pile P' in the ground.

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 constructing a large-diameter ground improving pile on soft ground by utilizing an apparatus for a whole casing method.

[0002]

2. Description of the Related Art All conventional casing construction methods have a diameter of 1 to
A large-diameter casing of 2 m is pushed into the ground while being rotated by a rotary press-fitting / extracting device installed on the ground, and the excavated soil is discharged to the ground while excavating the inside of the casing with an excavation tool such as a hammer mag. The concrete pile is created in the ground by pouring fresh concrete into the casing and then pulling the casing while rotating it by the rotary press-in / pull-out device. Therefore, sufficient supporting force can be obtained even in soft ground.

[0003]

However, the biggest difficulty of the above-mentioned conventional whole casing construction method is that a large amount of ready-mixed concrete is used, so that the construction cost is very high. Especially, sand and gravel, which are the main materials of ready-mixed concrete, are very expensive, and it is almost impossible to procure them in Japan.
Most of them are currently procured from foreign countries, and even foreign-made ones are quite expensive.

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

[0005]

In the construction method according to claim 1 of the present invention, a large-diameter cylindrical casing 2 is embedded to a predetermined depth in the ground by a casing rotary press-in / pull-out device 1, and then a hollow rod 7 is used. While vibrating and vertically moving the vibro flot 8 which is attached to the tip of the hollow rod and can be moved up and down by the vertical movement means, a paste cementitious solidifying material or cement milk is injected from the tip of the hollow rod 7, By inserting the rod 7 into the soil in the casing 2 to the bottom thereof and pulling it up, the soil in the casing 2 and the paste-like cementitious solidifying material or cement milk are stirred and mixed to obtain a mixed powder paste S.
After that, the casing 2 is inserted into the rotary press-fitting / pulling-out device 1
The ground improvement pile P'is formed in the ground by pulling out by.

In the construction method according to claim 2, the casing 2 is pulled out by the rotary press-fitting / pulling-out device 1, and
Again, while vibrating the vibro flot 8 and moving it up and down, the mixed powder paste S is stirred and mixed to form the ground improvement pile P in the ground.

In the construction method according to claim 3, a butterfly-shaped opening / closing plate 16 is provided at the lower part of the vibro flot 8 to open laterally by earth pressure and to close downward by its own weight. When the casing 2 is pulled out, the butterfly-shaped opening / closing plate 16 is opened / closed as the vibro flot 8 is vertically moved by the vertically moving means.

In the construction method according to claim 4, a hydraulic cylinder 6 is used as the vertical movement means.

In the construction method according to claim 5, 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 claim 1 of the present invention, the cylindrical casing 2 having a large diameter is embedded by the rotary press-in / pull-out device 1 to a predetermined depth in the soft ground, and the soil in the casing 2 is not discharged. Since it is used as it is as earth and sand material for pile formation, excavation and earth removal work like the conventional whole casing method is unnecessary, and expensive sand and gravel are not required, which is extremely economical, The pile construction cost can be significantly reduced.

Further, in the method of the present invention, the paste-like cement-based solidifying material or cement milk is injected from the tip of the hollow rod 7 while vibrating and vertically moving the vibroflot 8, and the hollow rod 7 is soft ground. A mixed powder granule paste S is obtained by stirring and mixing the soil inside the casing 2 and the pasty cement-based solidifying material or cement milk by inserting and pulling up to the bottom inside the casing 2 embedded therein. Since the soil and the paste-like cementitious solidifying material or cement milk are stirred and mixed inside the casing 2 in the soft ground, there is no mixing of earth and sand or water from the surrounding ground or earth pressure of the surrounding ground. , And both are effectively stirred and mixed to form a homogeneous and good mixed powder / grain paste body S.

Further, according to the method of the present invention, the casing 2 is pulled out by the rotary press-in / pull-out device 1 to discharge the mixed powder paste S inside the casing 2 into the ground to form a ground improvement pile. Is something that
The mixed powder paste S discharged from the casing 2 into the ground is in a state of being compressed inside the casing 2 until then, and the pasty cement-based solidifying material or cement milk reacts with the soil particles. Since it is on the way, its volume is expanded to form a soil improvement pile P ′ having a diameter larger than that of the casing 2. When the pile volume expands in this way, the ground around it is consolidated, and this consolidation enhances the ground strength.

According to the method of claim 2, when the casing 2 is pulled out by the rotary press-fitting / pulling-out device 1,
While vibrating the vibro flot 8 and moving it up and down,
By inserting the vibroflot 8 into the soil inside the casing 2 to the bottom through the hollow rod 7 and pulling it up from it, the mixed powder paste S discharged into the ground is vibrated by the vibroflot 8. It is sufficiently mixed and stirred for action and vertical movement, which promotes the reaction between the pasty cement-based solidifying material or cement milk and soil particles, and further expands the volume, thereby consolidating and strengthening the soil improvement pile. As P is formed,
The surrounding ground is consolidated, and this consolidation further enhances the ground strength.

Further, according to the construction method of claim 3, the butterfly-shaped opening / closing plate 16 mounted on the lower portion of the vibro flot 8 is opened laterally by earth pressure when the vibro flot 8 is moved downward, and this is opened. In this state, it moves downward to push the earth and sand and the like, and when it moves upward, it can be closed downward by its own weight so that it can move up smoothly without receiving the resistance of earth and sand. Therefore, in the construction method of claim 1, the butterfly-shaped opening / closing plate 16 opens and closes as the vibro flot 8 moves up and down, whereby the soil inside the casing 2 and the paste-like cement-based solidifying material or cement milk are stirred. While the action is promoted, the agitated mixed powder / grain paste body S is consolidated, and in the method of claim 2, in addition to the above action, the mixed powder / grain paste body S discharged into the ground is tightened. It is hardened and consolidated.

According to the construction method of the fourth aspect, by using the hydraulic cylinder 6 as the vertically moving means, a sufficient driving force can be obtained, and the structure is compact and the mounting is easy.

Further, according to the method of claim 5, when the cement-based solidifying material containing calcium oxide, silicon dioxide, aluminum oxide and sulfur trioxide as main components is used, the result of the experiment shows that ordinary cement is used. 240 kg / m ^{3 of} powder
The contrast uniaxial compressive strength upon addition was 2 kgf / cm ^2, in this cement-based solidifying material, uniaxial compressive strength upon addition of 240 kg / m ³ at 6.4kgf / cm ^2, It was found that the strength of the cement powder was about three times that of cement powder. Therefore, according to this cement-based solidifying material, a very good supporting force as a pile can be exhibited.

[0017]

EXAMPLES Examples will be described with reference to the drawings.
FIG. 1 shows a pile forming apparatus used for carrying out the construction method according to the present invention. In FIG. 1, reference numeral 1 denotes a casing rotary press-fitting / pulling-out device for pushing the large-diameter cylindrical casing 2 into the ground while rotating it, or pulling it out of the ground. Reference numeral 3 denotes a rod elevator frame, which is supported so as to be vertically movable along a reader 4 as shown in FIG.
Suspended and supported by a lifting wire 5 from the top of the reader 4.
A hollow rod 7 is suspended from the rod elevator frame 3 via a hydraulic cylinder 6, and a vibro flot 8 is attached to the lower end of the hollow rod 7. In addition, the rod elevator frame 3
If necessary, a drive device may be provided for causing the hollow rod 7 to exert a downward propulsive force when the machine frame 3 descends along the leader 4.

The casing rotary press-fitting / pulling-out device 1 is a well-known device that has been conventionally used. For example, as shown in FIG. 2, a rotary drive shaft 10, a hydraulic motor 11, and a press-fitting device are mounted on a base frame 9 installed on the ground. It is equipped with a pull-out means 12, a chuck device 13 and the like. While the casing 2 is inserted into the rotary drive shaft 10 and gripped by the chuck device 13, the rotary drive shaft 10 is rotated by driving the hydraulic motor 11. Then, the casing 2 is pushed into the ground or pulled out while rotating the casing 2.

As shown in FIG. 3 (A), a hollow rod 7 is coaxially suspended from a hydraulic cylinder 6 suspended from the rod lift frame 3, and a vibro flot 8 is attached to the lower end of the hollow rod 7. It is equipped, and this vibro flot 8 is enlarged and shown in (B) of the same figure. The hydraulic cylinder 6 is an up-and-down moving means for moving the vibro flot 8 up and down by a predetermined stroke through the hollow rod 7. As the up-and-down moving means, instead of the hydraulic cylinder 6, an air spring or the like that moves up and down by a predetermined stroke. However, the hydraulic cylinder 6 has advantages that a stronger driving force can be obtained, and that the structure is compact and the mounting is easy.

The vibro flot 8 is well known, and although its internal structure is not shown, the eccentric shaft is rotated by an electric motor to generate horizontal vibration.
The power supply cable 13 for the electric motor is inserted into the hollow portion 7a of the hollow rod 7, and extends from the upper end of the rod 9 into the rod elevator frame 3 in a coil shape. The coiled portion of the cable 13 is adapted to correspond to the vertical movement of the hollow rod 7 due to the operation of the hydraulic cylinder 6.

Further, as shown in FIGS. 3 (A) and 3 (B), the paste-like cement-based solidifying material or cement milk is pressure-supplied from the upper end portion of the hollow portion 7a of the hollow rod 7 so that the rod is 7 is ejected from the ejection hole 14 at the lower end. A supply hose 15 for supplying a paste-like cement-based solidifying material or cement milk from the outside is connected to the upper end of the hollow rod 7, and the tip end side of the supply hose 15 is connected to the vibrof. Similar to the power supply cable 13 of the lot 8, it is formed in a coil shape so as to cope with the vertical movement of the hollow rod 7 due to the operation of the hydraulic cylinder 6. In addition, this supply hose 1
5 is connected from the inside of the rod elevator frame 3 to an external supply unit (not shown) for the paste-like cement-based solidifying material or cement milk.

Further, the vibro flot 8 is shown in FIG.
As shown in (A) and (B), it is possible to equip the lower part thereof with a butterfly-shaped opening / closing plate 16 that opens laterally by earth pressure and closes downward by its own weight. In that case, a short tubular support tube 17 having a large diameter is attached to the vibro flot 8 via a plurality of attachment pieces 18,
In the lower end portion of this support pipe 17, a horizontal support shaft 1 is diametrically formed.
9 is fixed, and a pair of semicircular plates 16 are attached to the horizontal support shaft 19.
A butterfly-shaped opening / closing plate 16 composed of a and 16a is pivotally attached. The butterfly-shaped opening / closing plate 16 is normally closed so as to be folded downward by its own weight as shown by the solid line in FIG. 3 (A), and is rotated upward by receiving earth pressure from below as shown by the phantom line in FIG. It moves to be deployed in the lateral direction, and is in contact with and supported by the lower end of the support tube 17 at the deployed position.

Next, regarding the method of the present invention for forming a soil improvement pile in soft ground using the pile forming apparatus having the above-mentioned structure, mainly referring to FIG. 4, referring to other drawings as needed. explain. 4 to 4 show the order of construction.

First, as shown in FIG. 4, the casing rotary press-fitting / pulling-out device 1 is used to rotate the large-diameter casing 2 and press-fit it into the soft ground to embed it. in this case,
A plurality of casings 2 each having a unit length are used, and the casings 2 are sequentially added to be embedded in the ground.

After the casing 2 is embedded to a predetermined depth in the ground as shown in FIG. 5, the hollow rod 7 is lowered while the rod elevator frame 3 is lowered along the leader 4.
Is inserted into the soil inside the casing 2 as shown in the same figure, and while the hollow rod 7 is being inserted, the rod 7
The vibro flot 8 at the tip is vibrated and moved up and down by the hydraulic cylinder 6, and the paste-like cement-based solidifying material or cement milk is ejected from the ejection hole 14 at the tip of the rod 7 and injected into the soil inside the casing 2. . When the vibro flot 8 reaches the bottom of the soil inside the casing, the rod elevating frame 3 is raised to pull out the hollow rod 7. During this withdrawal,
Similarly to the insertion, the vibro flot 8 is vibrated and moved up and down, and the paste-like cement-based solidifying material or cement milk is injected into the soil inside the casing 2 through the ejection holes 14 at the tip of the rod 7.

As described above, in the soil inside the casing 2 embedded in the soft ground, the vibroflot 8 at the tip of the hollow rod 7 is vibrated and moved up and down, and the paste-like cement is applied from the tip of the hollow rod 7. By injecting the system solidifying material or cement milk, the hollow rod 7 is inserted to the bottom and pulled up, so that the casing 2
The soil inside and the paste-like cement-based solidifying material or cement milk are stirred and mixed to form a mixed powder paste S. In this case, since the soil and the pasty cement-based solidifying material or cement milk are stirred and mixed inside the casing 2, neither soil nor water is mixed from the surrounding ground, or the earth pressure of the surrounding ground is not received, and both Is effectively stirred and mixed to form a homogeneous and excellent mixed powder / grain paste body S. At this time, the butterfly-shaped opening / closing plate 16 opens and closes in accordance with the up-and-down movement of the vibro flot 8 to promote the stirring action between the soil inside the casing 2 and the pasty cement-based solidifying material or cement milk. The agitated mixed powder paste S is compacted.

Then, as shown in FIG. 4, the casing 2 embedded in the ground is pulled out while being rotated by the casing rotation press-fitting / pulling device 1, so that the mixed powder paste S inside the casing 2 is removed. Discharge into the ground. The withdrawal of the casing 2 may be performed in the middle of inserting the vibro flot 8 into the soil inside the casing 2 and pulling it up.

A mixed powder paste S which is discharged from the lower end of the casing 2 into the ground by pulling out the casing 2.
4 is in the state of being compressed inside the casing 2 and is still in the process of reacting the pasty cement-based solidifying material or cement milk with the soil particles.
The volume is expanded to form a ground improvement pile P ′ having a diameter larger than that of the casing 2, as shown in FIG. When the pile expands in this manner, the ground around it is consolidated, and the consolidation strengthens the ground. The ground improvement pile P'is a pile formed by the construction method according to claim 1 of the present invention.

After the casing 2 is pulled out by the rotary press-fitting / pulling-out device 1 or during the pulling-out, the rod elevator frame 3 is again lowered and raised as shown in FIG. The vibroflot 8 is inserted into the soil inside the casing 2 through the hollow rod 7 to the bottom of the loft lot 8 while vibrating and vertically moving the loft lot 8, and then the vibroflot 8 is pulled up from the bottom of the vibroflot 8 to remove the mixed powder discharged from the casing 2. The ground paste S is further mixed by stirring, and the ground improvement pile P as shown in FIG.
Is formed. The ground improvement pile P is a pile formed by the construction method according to claim 2 of the present invention.

As described above, according to the construction method in which the steps shown in FIG. 4 and the steps shown in FIG. 4 are added, the mixed powder paste S discharged into the ground by pulling out the casing 2 is , The vibrating flot 8 is vibrated and moved up and down to repeatedly mix and stir,
As a result, the mixed powder granule paste S promotes the reaction between the pasty cement-based solidifying material or cement milk and the soil particles, and further expands in volume, thereby consolidating the surrounding ground, and by this consolidation, the ground strength is increased. Will be further enhanced.

Further, as shown in and of FIG. 4, the mixed powder granule paste S discharged from the casing 2 into the ground.
When inserting the vibro flot 8 and pulling it up, the butterfly-shaped opening / closing plate 16 installed at the bottom of the vibro flot 8
However, when the vibro flot 8 is moved downward by the hydraulic cylinder 6, the mixed powder granule paste S is opened in the lateral direction by the pressure, and in this open state, the mixed powder granule S is moved downward to push the mixed powder granule S upward. When it moves, it closes downward due to its own weight and moves up smoothly without receiving the resistance of the mixed powder S. Then, the butterfly-shaped opening / closing plate 16 opens and closes in accordance with the up-and-down movement of the vibro flot 8 so that the mixed powder and granules S discharged into the ground are pressed and consolidated, and the surrounding ground is also consolidated. As a result, a strong consolidation pile P is formed and the ground strength is further enhanced.

In the construction method of the present invention described above, either the paste-like cement-based solidifying material or the cement milk may be injected into the soil inside the casing 2 embedded in the soft ground, but the paste-like cement-based solidifying material may be injected. That is, when using a paste that is obtained by kneading water and a cement-based solidifying material, as the cement-based solidifying material, those containing calcium oxide, silicon dioxide, aluminum oxide and sulfur trioxide as main components are used. It is good to use, and specifically, the following compounding ratios are suitable.

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

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

[0035]

According to the construction method of claim 1 of the present invention,
A large-diameter cylindrical casing can be embedded to a specified depth in soft ground by a rotary press-in / pull-out device, and the soil in this casing can be used as it is as soil material for pile formation without discharging it. This eliminates the need for work and eliminates the need for expensive sand or gravel, which is extremely economical and can significantly reduce pile construction costs.

Further, according to this construction method, the soil and the pasty cement-based solidifying material or cement milk are agitated and mixed inside the casing embedded in the soft ground, so that soil and water are mixed from the surrounding ground. Therefore, the soil and the pasty cement-based solidifying material or cement milk are effectively stirred and mixed without being affected by the soil pressure of the surrounding ground, and a homogeneous and good mixed powder / paste body is formed.

Further, according to this construction method, when the casing is pulled out, the mixed powder and granular paste inside the casing is discharged into the ground to form a ground improvement pile, but the mixed powder discharged into the ground is discharged. The powdery paste body is in the state of being compressed inside the casing and is in the process of reacting the pasty cement-based solidifying material or cement milk with the soil particles, so that the pile volume is expanded, It is possible to consolidate the surrounding ground, thereby increasing the ground strength.

According to the construction method of claim 2, the mixed powdery granular paste discharged into the ground is repeatedly mixed and stirred again by vibrating and vibrating action of the vibro flot, thereby solidifying the pasty cement-based paste. The reaction between the lumber or cement milk and soil particles is promoted to further expand the volume, thereby forming a consolidated and strong ground improvement pile, and at the same time consolidating the surrounding ground to further strengthen the ground strength. can do.

Further, according to the construction method of claim 3, the butterfly-shaped opening / closing plate opens and closes in accordance with the vertical movement of the vibro flot. The solid cementitious solidifying material or cement milk is effectively agitated and mixed, and the agitated and mixed powder particle paste is compacted, and in the method of claim 2, the mixture discharged into the ground is mixed. The powdery paste body is pressed and consolidated, and the surrounding ground is also consolidated, whereby a stronger consolidated pile can be formed, and the ground strength can be further enhanced.

According to the construction method of the fourth aspect, by using the hydraulic cylinder as the vertical moving means, a sufficient driving force can be obtained, and the structure is compact and the mounting is easy.

Furthermore, according to the construction method of the fifth aspect, it is possible to obtain a ground improvement pile having a semi-permanently strong supporting force.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing a casing rotation press-fitting / pulling-out device.

FIG. 3 (A) is a partial cross-sectional side view showing a rod lift frame, a hollow rod suspended from the rod elevator frame via a hydraulic cylinder, and a vibro flot attached to the lower end of the rod; It is an expansion perspective view which shows a vibro flot.

FIG. 4 is an explanatory diagram showing a construction sequence of the method of the present invention.

[Explanation of symbols]

 1 Casing rotary press-in / pull-out device 2 Large-diameter tubular casing 3 Rod lifter frame 6 Hydraulic cylinder (vertical moving means) 7 Hollow rod 8 Vibroflot 14 Jet hole at the lower end of the hollow rod 16 Butterfly opening / closing plate S Mixed powder paste Body P ′ Ground improvement pile P Ground improvement pile

Claims (5)

[Claims] 1. A casing rotary press-fitting / pulling-out device is used to embed a large-diameter cylindrical casing in the ground to a predetermined depth, and then vibrating a vibroflot attached to the tip of a hollow rod and vertically movable by vertical moving means. While moving up and down, inject a paste-like cement solidifying material or cement milk from the tip of the hollow rod, insert the hollow rod into the soil in the casing to its bottom and pull it up, so that the soil inside the casing Mixing paste-solidified cement or cement milk with stirring to form a mixed powder granule paste body, and then improving the soft ground by forming a ground improvement pile in the ground by pulling out the casing with the rotary press-in / pull-out device. Construction method. 2. The rotary press-fitting / pulling-out device pulls out the casing, and again while vibrating and vertically moving the vibroflot, the mixed powder particles are stirred and mixed to form a ground improvement pile in the ground. The method for improving soft ground according to claim 1, wherein 3. A bottom portion of the vibroflot is equipped with a butterfly-shaped opening / closing plate that opens laterally by earth pressure and closes downwardly by its own weight, and the vertical movement means moves the vibroflot up and down. The method for improving soft ground according to claim 1 or 2, wherein the butterfly-shaped opening / closing plate is opened / closed in accordance with the above. 4. The method for improving soft ground according to claim 1, wherein a hydraulic cylinder is used as the vertical movement means. 5. 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.