JP7143067B2 - Pile structure, construction method of pile structure, and excavator and stirrer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pile structure used in buildings such as houses, and more particularly to a pile structure having a columnar improvement body around a foundation pile that is ground improved with a cement-based solidifying agent.

Conventionally, in this type of pile structure, a steel pipe pile is used in which an excavation blade that protrudes laterally and a stirrer that protrudes laterally are provided at the tip of the steel pipe pile. When constructing this pile structure, in the process of driving steel pipe piles into the ground while rotating them, cement milk (cement-based solidifying agent) and earth and sand scraped off by the excavation blade are mixed by a stirring part, While driving the steel pipe pile into the ground, the mixture of cement milk and earth and sand around the pile steel pipe is solidified. As a result, a soil-improved columnar improvement body is formed around the steel pipe pile over the entire length of the steel pipe pile (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2003-105747

By the way, since the columnar improvement body formed by the construction method is formed over the entire length of the steel pipe pile from the ground surface, there is a problem that a large amount of cement-based solidifying agent is used and the construction time of the pile structure is long. rice field.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and it is an object of the present invention to provide a pile structure that is simple in construction and that can be constructed in a short time while reducing the amount of cement-based solidifying agent used.

In order to solve the above problems, a pile structure according to the present invention includes a foundation pile buried in the ground and a columnar improvement body formed around the foundation pile and made by hardening soil and sand with a cement-based solidifying agent. The pile structure is characterized in that the columnar improved body is formed from the ground surface to a depth shorter than the length of the foundation pile. The columnar improved body is formed by mixing the earth and sand around the buried foundation pile with a liquid cement-based solidifying agent such as cement milk, and solidifying the earth and sand with the cement-based solidifying agent to form a cylindrical shape. be.

In the pile structure of the present invention, for example, a long foundation pile that reaches the support layer is formed with a columnar improved body having a short length from the ground surface. Therefore, only the foundation piles are buried in the ground below the columnar improved body, and the amount of cement-based solidifying agent for forming the columnar improved body can be greatly reduced. This can significantly reduce the construction time of the pile structure. In addition, the foundation piles ensure the vertical bearing capacity of the pile structure, and the columnar improvement body reinforces the surface layer of the soil that was stirred when the foundation piles were buried in the ground, so the horizontal resistance of the pile structure is increased. can be greatly improved.

Here, as the foundation pile, an appropriate pile such as a metal pile or a concrete pile can be used. It is a steel pipe pile, and the diameter of the columnar improved body is larger than the diameter of the tip wing.

According to this aspect, the steel pipe pile can be penetrated into the ground by excavating with the tip wing, and the diameter of the columnar improved body becomes larger than the diameter of the earth and sand excavated by the tip wing. Compared to , the pile structure is more rigid, and the horizontal resistance can be further increased.

Further, a method for constructing a pile structure according to the present invention is a method for constructing a pile structure in which a columnar improved body is formed on the ground surface side of a foundation pile buried in the ground, and a depth shorter than the length of the foundation pile from the ground surface is provided. The ground around the foundation pile is excavated up to the ground, and the soil generated by excavation is stirred in the ground, and the cement-based solidification agent is supplied to mix the soil and the cement-based solidification agent, It is characterized in that the columnar improved body is formed around the foundation pile.

According to the pile structure construction method configured in this way, the ground around the foundation pile is excavated from the ground surface to a depth shorter than the length of the foundation pile, and the earth and sand generated by the excavation are stirred in the ground, A cement-based solidifying agent is supplied to this, and earth and sand are mixed with the cement-based solidifying agent. For this reason, by using less cement-based solidifying agent than before, it is possible to harden the soil with the cement-based solidifying agent in a shorter time and form a columnar improved body from the ground surface to a depth shorter than the length of the foundation pile. .

In the method for constructing a pile structure configured as described above, after the foundation pile is buried in the ground, the columnar improved body is formed. According to this configuration, the foundation pile is buried in the ground in advance, and the excavation stirrer described later is rotated and lowered along the axis of the foundation pile to excavate the ground around the foundation pile and excavate. The earth and sand generated from the ground can be agitated in the ground. A cement-based solidifying agent is supplied to the agitated earth and sand, and after they are mixed, the cement-based solidifying agent is solidified. In this way, the improved columnar body can be easily formed on the basis of the pre-embedded foundation pile, so that the pile structure can be easily constructed.

Further, in the method for constructing a pile structure, the foundation pile is a steel pipe pile having a tip wing attached to its lower portion, and the columnar improved body is formed while penetrating the foundation pile into the ground. According to this configuration, the steel pipe pile is penetrated into the ground while excavating the ground with the tip blade attached to the lower part of the steel pipe pile, and when the steel pipe pile reaches a predetermined depth to form the columnar improvement body, While excavating the ground around the steel pipe pile and stirring the surrounding earth and sand, the earth and sand are mixed with the cement-based solidifying agent, and the steel pipe pile can be further penetrated into the ground. In this way, since the penetration of the foundation pile and the formation of the columnar improved body are performed simultaneously, the pile structure can be constructed in a short time.

The excavation stirring device according to the present invention is used in the construction method described above, and excavates the ground around the foundation pile and excavates for stirring the earth and sand generated from the ground by excavation in the ground. A stirring device, which covers the pile head of the foundation pile and rotates around the axis of the foundation pile during excavation and stirring, and from the outer peripheral surface of the casing, in the radial direction of the casing a digging edge extending and secured to the casing.

According to the excavation stirrer configured in this way, the pile head of the upper end of the foundation pile is inserted into the lower opening of the cylindrical casing to cover the pile head, and the ground is excavated along the foundation pile with the excavating blade. Since the earth and sand generated from the ground can be agitated in the ground while excavating, it is possible to efficiently form a columnar improvement body with a uniform diameter around the foundation pile.

In a more preferred embodiment, the excavation blade includes at least an upper excavation blade and a lower excavation blade fixed to the casing, and the excavation agitator has, between the upper excavation blade and the lower excavation blade, It extends radially longer from the outer peripheral surface of the casing than the upper digging blade and the lower digging blade, is rotatably attached to the casing, and rotates together with the casing during excavation and stirring. Equipped with a co-rotation prevention member that prevents

According to this aspect, during excavation and stirring, the upper excavating blade and the lower excavating blade rotate (revolve) together with the rotation of the casing. On the other hand, the anti-corotation member attached between the upper digging blade and the lower digging blade extends radially from the outer peripheral surface of the casing and is rotatably attached to the casing. , digs into the ground and does not co-rotate with the casing during excavation and agitation. Therefore, the earth and sand between the upper excavating blade and the lower excavating blade are prevented from rotating together with them, and the earth and sand can be efficiently mixed with the cement-based solidifying agent.

According to the pile structure of the present invention, the horizontal bearing capacity of the upper part of the foundation pile can be greatly improved, and the pile structure can be constructed in a short time using a small amount of cement-based solidifying agent. When the foundation pile is a steel pipe pile, the effect of rust on the portion of the steel pipe pile around which the columnar improved body is formed can be reduced.

1 is a cross-sectional view of one embodiment of a pile structure according to the present invention; FIG. (a) is a cross-sectional view of Embodiment 1 of the excavation stirrer for forming a columnar improved body in the pile structure shown in FIG. 1, and (b) is a cross-sectional view of the pile head of the steel pipe pile. FIG. 3 is a cross-sectional view showing the dimensions of the excavator and agitator shown in FIG. 2; 2(a) is a plan view of the excavator and stirrer shown in FIG. 2(a), and FIG. 2(b) is a sectional view taken along the line AA of FIG. 2(a). (a) is a cross-sectional view of Embodiment 2 of the excavation stirring device for forming a columnar improved body in the pile structure shown in FIG. 1, and (b) is a cross-sectional view of the pile head of the steel pipe pile. 5. (a) is a plan view of the excavator and stirrer shown in FIG. 5, and (b) is a cross-sectional view taken along line BB of FIG. FIG. 3 is a cross-sectional view showing steps of Embodiment 1 of a construction method for forming a columnar improved body and constructing a pile structure using the excavation agitator of Embodiment 1; FIG. 8 is a cross-sectional view showing a post-process of the process shown in FIG. 7; FIG. 9 is a cross-sectional view of a pile structure in which a post-process of the process shown in FIG. 8 is shown and a columnar improved body is formed. It is sectional drawing which shows the process of Embodiment 2 of the construction method which forms a column-shaped improved body using the excavation stirrer of Embodiment 2, and construct|builds a pile structure. FIG. 4 is a cross-sectional view showing another embodiment of the pile structure construction method according to the present invention. FIG. 7 is a cross-sectional view of a modification of the rubber ring used in the excavator stirrer shown in FIGS. 5 and 6;

[Pile structure]
Hereinafter, one embodiment of the pile structure according to the present invention will be described in detail based on the drawings. FIG. 1 is a vertical sectional view showing one embodiment of the pile structure according to this embodiment.

In FIG. 1, the pile structure 1 of the present embodiment includes a steel pipe pile 2 as a foundation pile buried in the ground, and a columnar shape formed around the steel pipe pile 2 and solidified with a cement-based solidifying agent such as cement milk. a refinement 3; The steel pipe pile 2 is formed of a steel pipe with a diameter d1 of about 100 to 300 mm, and has a length reaching the support layer 4 from the ground surface. In the case of the deep support layer 4, a steel pipe of about 6 to 10 m is welded. etc. to obtain the required length. The depth L1 of the support layer 4 is generally about 10 to 30 m.

A steel pipe pile 2 as a foundation pile has a tip wing 2A as an excavating blade fixed to its lower portion by welding or the like. The tip blade 2A is made of a steel plate that is inclined when viewed from the side and is formed in a spiral shape, and its diameter d2 is set to about 500 to 800 mm. The tip wing 2A excavates the ground and supports the steel pipe pile 2 with respect to the ground when the steel pipe pile 2 penetrates into the ground. The steel pipe pile 2 is set perpendicular to the ground surface by a pile driver (not shown), and its tip reaches the support layer 4 . At the time of installation, the steel pipe pile 2 is turned, and the steel pipe pile 2 is penetrated into the ground while excavating the earth and sand with the tip wing 2A, and if necessary, the steel pipe pile 2 is added by welding or the like, until the support layer 4 is reached. The tip including the tip wing 2A is reached. The steel pipe piles 2 allow the pile structure 1 to obtain vertical bearing capacity. The perimeter of the steel pipe pile 2 that has reached the support layer 4 is covered with earth and sand 5 excavated by the tip wing 2A. exists in the range of A part of the earth and sand 5 existing at the depth L2 constitutes a part of the columnar improved body 3 hardened with cement milk.

The columnar improved body 3 is cylindrically formed around the steel pipe pile 2, and has a diameter D of about 0.6 to 1.5m and a depth L2 of about 4m. The columnar improvement body 3 excavates the earth and sand around the steel pipe pile 2 with the tip wing 2A, and the part near the ground surface (the part from the ground surface to the depth L2) of the excavated earth and sand 5 has a diameter d2 of the tip wing 2A. In a large area, the ground is further excavated, the excavated soil is mixed with cement milk, and the mixed soil is solidified. Therefore, the columnar improved body 3 is formed from the ground surface to a depth L2 shorter than the length L1 of the steel pipe pile 2 . Further, the diameter D of the improved columnar body 3 is set larger than the diameter d2 of the tip blade 2A. For example, diameter D/diameter d2 is preferably in the range of 1.2 to 2.0.

In the pile structure 1 configured in this way, the steel pipe piles 2 as foundation piles reach the support layer 4, so that the support layer 4 can receive the vertical bearing force through the steel pipe piles 2. , has sufficient strength in the vertical direction. On the other hand, in the pile structure 1 of the present embodiment, a columnar improvement body 3 solidified with cement milk is formed on the ground surface portion of the upper part of the steel pipe pile 2, and is reinforced with a larger outer diameter than the excavated earth and sand 5 portion. Therefore, even if a horizontal force acts on the steel pipe pile 2, the column-shaped improved body 3 can sufficiently resist it. In addition, since the length of the columnar improved body 3 is shorter than the length of the steel pipe pile 2, the configuration is simple, and the amount of cement milk used can be reduced compared to before when constructing the pile structure 1 described later. Therefore, the improved columnar body 3 can be formed in a short period of time, and the cost can be reduced.

[Embodiment 1 of the excavator stirrer]
Next, in order to construct the pile structure 1 shown in FIG. 1, an excavation stirrer 10 suitable for forming the columnar improved body 3 around the steel pipe pile 2 will be described below with reference to FIGS. . FIG. 2(a) is a cross-sectional view of Embodiment 1 of the excavation stirring device 10, FIG. 2(b) is a cross-sectional view of the pile head of the steel pipe pile 2, and FIG. 4(a) is a plan view of the excavator 10 shown in FIG. 2(a), and FIG. 4(b) is a cross-sectional view taken along the line AA of FIG. 2(a). 4(a) and 4(b) are diagrams showing a state in which the co-rotation prevention blade 17 is rotated from the position shown in FIG.

2 to 4, the drilling and agitating device 10 includes a double-tube type embodiment 1 described below and a single-tube type embodiment 2 described later. First, the double-tube type excavation stirring device 10 will be described in detail. This excavation stirring device 10 is installed in accordance with the upper end (pile head) exposed above the ground of a steel pipe pile 2 as a foundation pile buried in the ground, and is turned and lowered along the steel pipe pile 2. , to excavate and agitate the ground around the steel pipe pile 2, supply and mix cement milk with the agitated earth and sand 5, and solidify the earth and sand with the mixed cement milk to form the columnar improvement body 3; device.

The excavation stirrer 10 includes a double-pipe cylindrical casing 11 in which an inner tube 11A and an outer tube 11B are coaxially arranged with a gap therebetween. The inner tube 11A and the outer tube 11B are connected and fixed by connecting tools (not shown) such as bolts and nuts so that the gap between them is constant. The upper end of the inner tube 11A is closed with an upper lid 12, and the lower end is open. The upper end of the outer tube 11B is closed with an upper lid 13 having a through hole 13a, and the lower end is open. A cylindrical joint 14 is fixed to the upper lid 13 of the outer tube 11B so as to communicate with the through hole 13a. The joint 14 is equipped with a drive source such as a pile driver for rotating the excavator and stirrer 10, and is formed with a center hole for supplying cement milk.

The inner diameter of the inner pipe 11A is set so that the steel pipe pile 2 can be inserted through the opening at the lower end of the inner pipe 11A. That is, the inner diameter d4 of the inner pipe 11A is larger than the diameter d3 of the steel pipe pile 2. Thus, the cylindrical casing 11 opening downward has a shape capable of covering the pile head portion of the steel pipe pile 2 .

In this embodiment, the excavation agitator 10 extends in the radial direction (horizontal direction) of the casing 11 from the outer peripheral surface of the outer tube 11B of the casing 11 and is fixed to the outer tube 11B. A lower digging blade) 15 and a second digging blade (upper digging blade) 16 are further provided. The first digging edge 15 is fixed to the outer peripheral surface of the lower portion of the outer tube 11B of the casing 11 by welding or the like, and the second digging edge 16 is spaced upward from the first digging edge 15 by a distance h1 of 50 cm to 1 m. It is fixed by welding or the like to the outer peripheral surface of the outer tube 11B with a space therebetween.

In this embodiment, a co-rotation prevention wing (co-rotation prevention member) 17 is rotatably attached to the outer tube 11B of the casing 11 at an intermediate position between the first digging edge 15 and the second digging edge 16. there is Specifically, the co-rotation prevention blade 17 is formed with a ring portion 17a so as to be freely rotatable with respect to the outer tube 11B of the casing 11, and the two arms 17c extend horizontally (radially). extends and protrudes.

A stirring blade (stirring portion) 17 b is formed in the co-rotation prevention blade 17 at a position facing the first digging blade 15 and the second digging blade 16 . When the first excavating edge 15 and the second excavating edge 16 rotate, the anti-corotation wing 17 is fixed to the ground. Stirring can be performed by a stirring blade (stirring portion) 17b of the co-rotation prevention blade 17 and blade portions 15b and 16b of the first excavating blade 15 and the second digging blade 16, which will be described later.

The first digging edge 15 is provided with two fixed arms 15a, 15a, which extend in opposite horizontal directions with respect to the casing 11, which are connected to the casing 11. is fixed to the outer tube 11B. A plurality of blade portions 15b, 15b, .

The second digging edge 16 also has two fixed arms 16a, 16a, and the two fixed arms 16a, 16a extend in the same horizontal direction as the fixed arms 15a, 15a of the first digging edge 15 extend. (see, for example, FIG. 4(a)), and these are also fixed to the outer tube 11B of the casing 11. As shown in FIG. A plurality of blade portions 16b, 16b, . The blades 15b and 16b excavate the ground around the steel pipe pile 2 and agitate the earth and sand generated thereby, and are made of metal with high hardness and are tapered.

In this embodiment, the two fixed arms 15a, 15a of the first digging edge 15 and the two fixed arms 16a, 16a of the second digging edge 16 extend in the same direction. These extending directions may be orthogonal to each other, and the angle at which these directions intersect may form a predetermined angle.

The first digging edge 15 and the second digging edge 16 protrude from the center of the casing 11 in a range of about 300 to 750 mm.
. The length is set so that it turns on a circle with a diameter d5 of 5 m. This circumference d5 forms the outer diameter D of the improved columnar body 3 shown in FIG. In the radial direction of the casing 11 , the length of the co-rotation prevention wings 17 positioned between the first digging edge 15 and the second digging edge 16 is longer than the lengths of the first digging edge 15 and the second digging edge 16 . It is long (for example, about 30 to 50 mm long) and is set to a length such that its tip rotates on the circumference of diameter d6. The height h2 of the casing 11 is set to about 4 m, and this height h2 corresponds to the height of the improved columnar body 3. A height h1 of the first digging edge 15 and the second digging edge 16 from the tip of the casing 11 is set to 500 to 1000 mm.

A gap between the inner tube 11A and the outer tube 11B is a passage space 18 set to about 50 to 100 mm so that the cement milk injected from the center hole of the upper joint 14 can pass without resistance. . The lower end opening of the gap (passage space 18) between the inner tube 11A and the outer tube 11B is sealed. A large number of outlets 18a, 18a, . The inner diameter of the discharge port 18a is preferably about 50 to 100 mm. Further, it is preferable that the discharge port 18a is formed between the first digging blade 15 and the second digging blade 16, because the agitated earth and sand and cement milk can be efficiently mixed.

A chuck 19 for fixing the steel pipe pile 2 is attached to the upper inner peripheral surface of the inner pipe 11</b>A that constitutes the casing 11 . The chuck 19 has a T-shaped engagement groove 19a composed of a longitudinal groove 19b and a lateral groove 19c that engages with a projection (not shown) formed on the outer peripheral surface of the pile head of the steel pipe pile 2. formed. When connecting the steel pipe pile 2 and the casing 11, the above-described projection of the steel pipe pile 2 is inserted into the longitudinal groove 19b formed along the vertical direction from below the T-shaped engagement groove 19a, and the steel pipe By rotating the pile 2 and the casing 11 relative to each other, this protrusion is brought into contact with the end of the lateral groove 19c formed in the circumferential direction.

When the steel pipe pile 2 is engaged with the engagement groove 19a of the chuck 19 and interlocked with the steel pipe pile 2 and the casing 11, the steel pipe pile 2 is rotated and penetrated into the ground, and the excavation stirrer 10 is operated. can be swiveled. Note that the chuck 19 can be omitted when the penetration of the steel pipe pile 2 and the forming of the improved columnar body 3, which will be described later, are not performed at the same time.

[Embodiment 2 of Excavator Stirrer]
Next, a single-tube excavator and stirrer 10A of Embodiment 2 will be described in detail with reference to FIGS. 5 and 6. FIG. Fig. 5(a) is a cross-sectional view of the excavation stirring device 10A of Embodiment 2, Fig. 5(b) is a cross-sectional view of the pile head portion of the steel pipe pile 2, and Fig. 6(a) is a cross-sectional view of Fig. 5(a). A plan view of the excavation stirring device 10A shown in FIG. 6B is a sectional view taken along the line BB in FIG. 6(a) and 6(b) are diagrams showing a state in which the co-rotation prevention blade 17 is rotated from the position shown in FIG. The same reference numerals are given to the same members as those of the excavation stirring device of the first embodiment, and detailed description thereof will be omitted.

The excavation stirrer 10A includes a single-tube cylindrical casing 21 . The casing 21 is made of a pipe such as a steel pipe, and its upper end is closed by an upper lid 13. A through hole 13a is formed in the center of the upper lid 13. A joint communicating with the through hole 13a is provided in the upper lid 13. 14 is installed. Joint 14 is formed with a central hole for feeding cement milk into casing 21 . The lower end of the casing 21 is open, and the inner diameter of the casing 21 is set so that the steel pipe pile 2 can be inserted through the opening of the lower end. That is, the inner diameter d4 of the casing 21 is larger than the diameter d3 of the steel pipe pile 2 . Therefore, the cylindrical casing 21 opening downward has a shape capable of covering the pile head portion of the steel pipe pile 2 .

The casing 21 of the excavation agitator 10A has a first excavation edge (lower excavation edge) 15 and a second excavation edge (upper excavation edge) 16 horizontally arranged on the outer peripheral surface in the same manner as the excavation agitator 10 described above. , and extends in the radial direction of the casing 21 . Between the first digging edge 15 and the second digging edge 16, an anti-corotation wing 17 is rotatably attached to the casing 21. As shown in FIG. The lengths of the first digging edge 15 and the second digging edge 16 are set so that their tips turn on the circumference of the diameter d5, and the anti-co-rotation wing 17 is arranged around the circumference of the diameter d6 larger than the diameter d5. It is set to a length that rotates upward.

A circumferential groove having an arc-shaped cross section is formed in the inner peripheral surface of the lower portion of the casing 21, and a rubber ring 27 such as an O-ring is attached to the circumferential groove. The rubber ring 27 has the function of closing the gap between it and the outer peripheral surface of the steel pipe pile 2 inserted into the lower opening of the casing. The rubber ring 27 prevents cement milk from leaking out from the gap between the inner peripheral surface of the casing 21 and the outer peripheral surface of the steel pipe pile 2 when the cement milk is supplied into the casing 21 .

A chuck 29 for fixing the steel pipe pile 2 is attached to the ceiling of the casing 21 . The chuck 29 has a pair of claw portions 29a, 29a, and is configured such that the pile head portion of the steel pipe pile 2 is fitted between the claw portions 29a, 29a. When rotating the excavation stirrer 10A while rotating the steel pipe pile 2 and penetrating into the ground, the pile head of the steel pipe pile 2 is fitted to the chuck 29, and the steel pipe pile 2 is connected to the casing 21.例文帳に追加Note that the chuck 29 can be omitted when the penetration of the steel pipe pile 2 and the forming of the improved columnar body 3, which will be described later, are not performed at the same time.

A plurality of outlets 11a for discharging the cement milk supplied into the casing 21 to the outside of the casing are formed in the circumferential direction of the casing 21 . The discharge port 11 a is formed above the rubber ring 27 . In the excavation stirrer 10A having a single-tube type casing 21, an upper lid 2B is fixed to the pile head so that when cement milk is supplied into the casing 21, it does not enter the steel pipe pile 2. In addition, in the excavation stirrer 10 provided with the double-pipe casing of Embodiment 1, cement milk does not enter the inside of the steel pipe pile 2 from the pile head. is not provided (see FIG. 2(b)).

[Embodiment 1 of Construction Method of Pile Structure]
Embodiment 1 of the construction method using the excavator 10 for the pile structure 1 of this embodiment configured as described above will be described below with reference to FIGS. 7 to 9. FIG. In this embodiment, since the improved columnar body 3 is formed after the steel pipe pile 2 is buried in the ground, the chuck 19 shown in FIG.

First, in the present embodiment, the steel pipe pile 2 as a foundation pile is set in a vertical state and rotated by using a pile driver (not shown), and is penetrated into the ground by excavating the ground with the tip wing 2A. . The steel pipe pile 2 is penetrated until it reaches the support layer 4 . Thereby, the vertical bearing force of the pile structure 1 is sufficiently obtained. The steel pipe pile 2 is buried in the ground with the top of the pile protruding from the ground surface.

As shown in FIG. 7, the pile head of the steel pipe pile 2 in this state is covered with a casing 11 of the excavation stirring device 10, and the excavation stirring device 10 is installed vertically to the ground surface. That is, the pile head of the steel pipe pile 2 is inserted into the lower opening of the casing 11 and installed. By rotating and lowering the excavation stirring device 10, the ground around the steel pipe pile 2 is excavated with the first excavation edge 15 and the second excavation edge 16, and the earth and sand generated by the excavation of the ground are stirred.

At this time, the first excavating edge 15 and the second excavating edge 16 that turn together with the casing 11 draw around the surrounding earth and sand, but the co-rotation prevention wings 17 located in the middle bite into the outer earth and sand and do not turn. Therefore, the earth and sand near the first excavating edge 15 and the second excavating edge 16 swirl, and the earth and sand near the anti-corotation wing 17 do not swirl. of earth and sand can be stirred reliably. Further, when the excavator agitating device 10 is lowered while rotating, the agitating range of the earth and sand increases downward, and the pile head approaches the upper lid 12 of the casing 11 as shown in FIG.

During this excavation and stirring, as shown in FIG. 8, cement milk is supplied from the central hole of joint 14 as indicated by arrow Y1. As a result, the cement milk passes through the passage space 18 between the inner pipe 11A and the outer pipe 11B of the casing 11, flows downward, and is discharged outside the casing 11 from the discharge port 18a as indicated by an arrow Y2. The discharged cement milk is mixed with the earth and sand 5 stirred by the first digging edge 15 , the second digging edge 16 and the co-rotation prevention blades 17 . After that, when the excavation stirrer 10 is removed from the pile head of the steel pipe pile 2 while rotating the first excavation blade 15 and the second excavation blade 16, as shown in FIG. A mixture of earth and sand and cement milk to be the columnar improved body 3 is present around the . The mixture that becomes the columnar improved body 3 is formed from the ground surface to a depth shorter than the length of the steel pipe pile 2 .

The excavating agitating device 10 is pulled out from the ground, and the soil mixed with cement milk gradually hardens (hardens) to form a columnar improvement body 3 that improves the ground. The solidified columnar improvement body 3 has a good bite with the ground, and since the upper part of the stirred earth and sand 5 is reinforced by the columnar improvement body 3, the horizontal bearing capacity as well as the vertical bearing capacity is greatly improved. be able to. The upper part of the steel pipe pile 2 is reinforced by the columnar improvement body 3, and the pile structure 1 having strength enough to withstand horizontal force applied to the steel pipe pile 2 is obtained.

[Embodiment 2 of construction method of pile structure]
Next, a method of constructing the pile structure 1 using the excavation stirring device 10A of Embodiment 2 will be described with reference to FIG. FIG. 10 is a cross-sectional view showing a part of the process of forming the improved columnar body 3 and constructing the pile structure 1 using the excavation stirrer 10A of the second embodiment. In this construction method, illustration of the step of installing the excavation stirring device 10A on the pile head of the steel pipe pile 2 and the step of rotating the excavation stirring device 10A is omitted. In this embodiment, since the improved columnar body 3 is formed after the steel pipe pile 2 is buried in the ground, the chuck 29 shown in FIG. 5 is omitted in the excavation stirrer 10A.

Also in this embodiment, although not shown, the steel pipe pile 2 is installed by covering the pile head with the casing 21 of the excavation stirrer 10A. That is, the pile head of the steel pipe pile 2 is inserted into the lower opening of the casing 21, the pile head is inserted into the rubber ring 27 attached to the inner surface of the casing 21, and the pile head of the steel pipe pile 2 is covered with the casing 21. Then, the excavation stirrer 10A is installed vertically with respect to the ground surface. The rubber ring 27 is compressed by the outer peripheral surface of the steel pipe pile 2 . Then, the excavation stirrer 10A is turned and lowered, the ground around the steel pipe pile 2 is excavated with the first excavation blade 15 and the second excavation blade 16, and the earth and sand generated by the excavation are removed together with the co-rotation prevention blade 17. Stir.

In FIG. 10 , when the excavation stirring device 10A descends, a gap is formed around the steel pipe pile 2 within the casing 21 . When cement milk is supplied from the center hole of the joint 14 into the casing 21 as shown by the arrow Y1 in this state, the cement milk enters the gap around the steel pipe pile 2 in the casing 21, flows down through the gap, and is discharged. It is discharged outside the casing 21 from the outlet 11a. In this state, the cement milk is mixed with the earth and sand 5 being agitated by the first digging edge 15, the second digging edge 16 and the co-rotation prevention blades 17. As shown in FIG.

After that, before the cement milk solidifies, the excavation stirring device 10A is pulled out from the ground while rotating the first excavation blade 15 and the second excavation blade 16, and when the cement milk and the earth and sand solidify into cement, the columnar improvement is performed. A body 3 is formed in the surface layer of the ground. Thus, even when the columnar improvement body 3 is formed by the excavation stirring device 10A, the upper part of the stirred earth and sand 5 is reinforced with the columnar improvement body 3, as in the case described above. Therefore, it is possible to greatly improve the horizontal bearing force as well as the vertical bearing force.

[Another embodiment of the pile structure construction method]
Next, as another embodiment of the construction method of the pile structure, a construction method for forming the columnar improvement body 3 while penetrating the steel pipe pile 2 into the ground will be described below with reference to FIG. 11 . FIG. 11 is a cross-sectional view showing another embodiment of the pile structure construction method. In addition, in FIG. 11, the construction method using the excavation agitating device 10 is explained, and the structure for supplying cement milk is omitted.

In FIG. 11, the steel pipe pile 2 has not reached a predetermined depth, for example, the support layer 4, and the steel pipe pile 2 needs to be further penetrated while further excavating the ground with the tip wing 2A. be. Therefore, the excavator 10 does not reach the ground surface.

The steel pipe pile 2 is connected by the chuck 19 as described above, and the steel pipe pile 2 and the casing 11 rotate integrally. Therefore, the turning force of the pile driver is transmitted to the casing 11 of the excavator and agitator 10 via the joint 14 to turn the casing 11 and is transmitted to the steel pipe pile 2 via the chuck 19 . As a result, when the steel pipe pile 2 is lowered while being rotated so that the tip wing 2A excavates the ground, the steel pipe pile 2 is further penetrated into the ground.

In this state, the steel pipe pile 2 and the excavation agitator 10 continue to descend, and when the first excavation blade 15 of the excavation agitation device 10 reaches the ground surface, the excavation agitation device 10 gradually excavates the ground around the steel pipe pile 2. At the beginning, penetration of the steel pipe pile 2 into the ground, excavation of the ground for forming the columnar improved body 3, and stirring of the generated earth and sand are performed simultaneously. Penetration and excavation are continued to a position corresponding to the depth of the columnar improvement body 3 by the excavation stirrer 10, and the penetration of the steel pipe pile 2 and excavation of the ground for forming the columnar improvement body 3 are completed to a predetermined depth.

When cement milk is supplied into the casing 11 from the joint 14 side during such stirring, the cement milk passes through the passage space 18 between the inner pipe 11A and the outer pipe 11B and is discharged out of the casing 11 from the discharge port 18a. be. The protruded cement milk is mixed with the earth and sand 5 stirred by the first excavating edge 15, the second excavating edge 16 and the co-rotation prevention blades 17. After mixing for a predetermined time and the cement milk and the earth and sand are mixed uniformly, the engagement by the chuck 19 is released, the excavation stirring device 10 is removed from the steel pipe pile 2, and the excavation stirring device 10 is pulled up from the ground, and the columnar improvement is performed. A body 3 is formed.

In this pile structure construction method, in addition to the effects shown in the above-described embodiment, the penetration of the steel pipe pile 2 equipped with the tip wing 2A, the excavation of the ground of the columnar improved body 3, the agitation of the earth and sand, the supply of cement milk, and Mixing of earth and sand and cement milk can be carried out in a series of processes, and a pile structure can be constructed efficiently in a short time.

A modified example of the rubber ring used in Embodiment 2 of the excavation stirring device described above will be described with reference to FIG. 12 . Although the rubber ring 27 used in the excavation stirrer 10A has a circular cross-sectional shape, a rubber ring 27A having a trapezoidal cross-sectional shape can be used. The rubber ring 29A is fitted in a circumferential groove of a rectangular concave portion formed on the inner surface of the casing 21 to be mounted. In this rubber ring 29A, the edge portion protruding inwardly contacts the outer peripheral surface of the steel pipe pile 2 to prevent the cement milk from leaking out to the outside. By making contact at the edge, the cement milk can be cut well and leakage can be reliably prevented.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the invention described in the claims. Changes can be made. For example, as the foundation pile, an example of a steel pipe pile having tip wings was shown, but other concrete piles such as PHC piles without tip wings can be used.

As the columnar improver, an example in which cement milk is mixed with soil and solidified is shown, but the columnar improver is not limited to cement milk, and other cement-based solidifying agents can be used to form the columnar improver. In addition, although the foundation pile has a length reaching the support layer, it may be used as a friction pile without reaching the support layer.

In addition, in the above-described embodiment, the digging blade is a two-stage digging blade composed of two types of first digging blade and second digging blade, but the number of digging blades may be one or three or more. When three or more are provided above and below, co-rotation prevention wings may be further provided between them.

In addition, when excavating the ground and stirring the earth and sand, cement milk may be supplied to the earth and sand and the cement milk may be mixed. The earth and sand around the steel pipe pile may be agitated while being swirled with the steel pipe pile, and cement milk may be supplied to the agitated earth and sand.

1: Pile structure, 2: Steel pipe pile (foundation pile), 2A: Tip blade (excavation blade), 3: Columnar improvement body, 4: Support layer, 5: Excavated earth and sand, 10: Excavation stirrer, 11, 21 : casing, 11A: inner pipe, 11B: outer pipe, 15: first digging blade (lower digging blade), 16: second digging blade (upper digging blade), 17: co-rotation prevention wing (co-rotation prevention member), D: Diameter of columnar improved body, d2: Diameter of tip wing, L1: Length of foundation pile, L2: Depth of columnar improved body

Claims (6)

A pile structure construction method for forming a columnar improved body on the ground surface side of a foundation pile buried in the ground,
The ground around the foundation pile is excavated from the ground surface to a depth shorter than the length of the foundation pile, and the soil and sand generated by the excavation are stirred in the ground and a cement-based solidification agent is supplied to the soil and sand. The cement-based solidifying agent is mixed to form the columnar improved body around the foundation pile,
The foundation pile is a steel pipe pile with a tip wing attached to the lower part of the steel pipe, and the foundation pile is buried in the ground while penetrating into the ground,
The diameter of the range where the ground to be the columnar improved body is excavated is larger than the diameter of the tip wing,
The tip wing has a diameter larger than the diameter of the steel pipe ,
A method for constructing a pile structure, characterized by forming the improved columnar body after burying the foundation pile in the ground . An excavation stirring device used in a pile structure construction method for forming a columnar improved body on the ground surface side of a foundation pile buried in the ground,
The excavation stirring device excavates the ground around the foundation pile from the ground surface to a depth shorter than the length of the foundation pile, and supplies the cement-based solidification agent while stirring the soil generated by the excavation in the ground. By mixing the earth and sand with the cement-based solidifying agent, the columnar improved body is formed around the foundation pile ,
The excavation stirring device includes a cylindrical casing that covers the pile head of the foundation pile and rotates around the axis of the foundation pile during excavation and stirring;
a digging edge extending radially from the outer peripheral surface of the casing and fixed to the casing ;
The casing is arranged coaxially with the inner pipe so that a gap is formed between the inner pipe covering the pile head of the foundation pile and the inner pipe so that the cement-based solidifying agent flows down. A double-tube cylindrical casing comprising a tube and
A lower end opening of the gap between the inner tube and the outer tube is sealed, and a discharge port for discharging the cement-based solidifying agent flowing down the gap is formed on the outer periphery of the outer tube. and a drilling agitator. An excavation stirring device used in a pile structure construction method for forming a columnar improved body on the ground surface side of a foundation pile buried in the ground,
The excavation stirring device excavates the ground around the foundation pile from the ground surface to a depth shorter than the length of the foundation pile, and supplies the cement-based solidification agent while stirring the soil generated by the excavation in the ground. By mixing the earth and sand with the cement-based solidifying agent, the columnar improved body is formed around the foundation pile ,
The excavation stirring device includes a cylindrical casing that covers the pile head of the foundation pile and rotates around the axis of the foundation pile during excavation and stirring;
a digging edge extending radially from the outer peripheral surface of the casing and fixed to the casing ;
The casing has an inner diameter such that a gap is formed between the casing and the outer peripheral surface of the foundation pile in a state where the pile head of the foundation pile is covered, through which the cement-based solidifying agent flows down,
A ring material is provided on the inner peripheral surface of the lower part of the casing to seal leakage of the cement-based solidifying agent that has flowed down the gap between the outer peripheral surface of the foundation pile and the inner peripheral surface of the casing,
An excavator and agitator according to claim 1, wherein a discharge port for discharging the cement-based solidifying agent flowing down through the gap is formed on the outer circumference of the casing . The excavation blade includes an upper excavation blade and a lower excavation blade fixed to the casing with a space therebetween in the vertical direction,
4. The excavating agitator according to claim 2 , wherein the discharge port is formed between the upper excavating blade and the lower excavating blade. 5. The apparatus according to claim 4 , wherein a co-rotation prevention wing is attached to said casing between said upper excavating edge and said lower excavating edge and is rotatably attached to said casing. drilling agitator. A pile structure construction method for forming the columnar improvement body using the excavation stirrer according to any one of claims 2 to 5,
A method for constructing a pile structure, wherein the columnar improved body is formed while penetrating the foundation pile into the ground.

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