WO2004035942A1

WO2004035942A1 - Internal excavation method through pile, and foundation pile structure

Info

Publication number: WO2004035942A1
Application number: PCT/JP2003/012522
Authority: WO
Inventors: Yoshinobu Kiya
Original assignee: Mitani Sekisan Co., Ltd.
Priority date: 2002-09-30
Filing date: 2003-09-30
Publication date: 2004-04-29
Also published as: JP2010209678A; CN100510276C; CN1685113A; JP2010031647A; KR101071122B1; JPWO2004035942A1; JP2012207532A; JP5520347B2; JP4625896B2; JP5265500B2; KR20050059183A; JP5114529B2; AU2003266716A1

Abstract

An internal excavation method through a pile, comprising the steps of (a) fitting a tip metal device (13) to an existing concrete pile (1), inserting an excavating rod (15) without a soil discharging mechanism into the existing concrete pile, and excavating by a rotary excavating arm (21) of an excavator head (18) to immerse the existing pile (1), (b, c, d) excavating a ground, while loosening, with a diameter 1.4 times the outer diameter of the existing pile (1) or more and stamping the loosened excavated soil to the outside by the outer face of the exiting pile (1), and filling, agitating, and mixing cement mill in stratums (26A, 26B) designated by design to form solidified mixed layers (29A, 29B) with recovered or improved ground strength, (e) forming a foot protection layer (30) filled with cement mill on a pile hole bottom (31) side, and (f) raising the excavating head (18) to the ground, lowering the existing pile (1), and positioning the tip metal device (13) in the foot protection layer (30), whereby a supporting force of approx. two times that of an existing internal excavation method can be developed, and a soil discharge amount can be remarkably decreased.

Description

Technical field of the invention The present invention relates to a method of excavating a pile hole and burying a ready-made pile, and a foundation pile having a ready-made pile buried in a pile hole formed based on this method. Regarding the structure. Above all, ground

This is particularly effective when the ground contains a relatively soft ground layer and the layer does not provide sufficient bearing capacity.

Background art In a typical pile drilling method, a drilling head formed with a drilling head and an earth removal spiral is inserted into the hollow part of a ready-made pile, and the drilling hole protruding from the tip of the ready-made pile is inserted. At the same time, the existing piles were being laid while excavating the stratum. In this case, the excavation diameter of the excavation head was slightly smaller (about minus 4 Omm) than the inner diameter of the ready-made pile to be buried (Non-Patent Document 1). Then, the ready-made pile was pushed into the pile hole as it was, or cement milk was injected into the gap between the inner wall of the pile hole and the ready-made pile, and the ready-made pile was pushed in (for example, Patent Document 1, 2 to 3 from the upper left of page 5, line 3) ).

In addition, in the case of using the excavation method to increase the diameter of the solidified portion to increase the bearing capacity at the tip, the excavation blade (Patent Literature 1) that swings to the excavating head and excavates can be extended perpendicular to the axis of the excavating rod. The excavation blade protruding in the direction (horizontal direction) was formed, and the excavation of the expanded root compaction was performed.

In addition, prior to burial of ready-made piles, in the method of digging all pile holes with a drilling hole and then burying ready-made piles and burying foundation piles (first digging method), a widening blade is inserted in the middle of the drilling rod. A method has been proposed to excavate the enlarged diameter part in the shaft of a pile hole by forming a hole (Patent Document 2). However, this method cannot be used in soft geological formations and the like, and the range of use has been limited.

In addition, in the borehole method, as described above, a pile hole with a diameter smaller than the outer diameter of the ready-made pile is excavated. Patent Literature 35 discloses an invention aimed at reducing the amount of unloaded soil, since the existing piles were exclusively used because they could not be used.

(Patent Document 1) Japan. JP-A-8-291682

(Patent Document 2) Japan. JP-A-2-108724

(Patent Document 3) Japan. JP-A-57_74534

(Patent Document 4) Japan. JP-A-2002-54135

(Patent Document 5) Japan. Japanese Patent Application Laid-Open No. 2002-81059

(Non-Patent Document 1) Japan. “Study on pile foundations: from design to construction”

(2nd revised edition)

Japan Society of Geotechnical Engineers First edition issued May 25, 1993

425-431 Disclosure of the Invention

1. Problems that the Invention is to Solve

(1) In the so-called pre-drilling method, prior to burying the ready-made piles, after excavating all the pile holes, the ready-made piles can be buried, and the wall of the pile holes can be leveled by the drilling drum and the cement milk can be stirred and filled. However, in the excavation method, generally, most of the excavated soil is discharged by a drill rod, and it is difficult to attach a kneading drum to the drill rod from the structure, so that the pile hole wall cannot be leveled. Therefore, the periphery of the pile between the ready-made pile and the pile hole could not be sufficiently used as the bearing capacity.

In addition, drilling rods for digging have a structural limitation that they must pass through the hollow part of a ready-made pile (usually concrete), and even if the diameter can be expanded relatively easily (Patent Document 2), It must take three positions: the hollow part passing state (minimum diameter), the pile hole shaft excavation state (intermediate diameter), and the pile hole excavation part excavation state (maximum diameter). Was. In addition, in the case of a two-stage switching of the normal excavation diameter, in the case of forming an expanded bottom consolidation part, the excavation diameter of the consolidation part is up to about 1.2 times the shaft diameter of the pile hole. Even if the excavating head was equipped with a swinging arm with an excavating blade, the limit was 1.5 times. In particular, when a large-diameter ready-made pile with an outer diameter of 1000, etc. is used, 1- It was limited to about twice.

In addition, in the Nakahori method, generally, the tip of a ready-made pile is positioned directly above a drilling head, and excavation is performed while sinking the ready-made pile. It was not possible to excavate the enlarged diameter part.

Therefore, in the excavation method, in order to increase the excavation speed, the excavated soil had to be discharged more, and as a result, it was not preferable from the environmental point of view, and the soil to be constructed was limited. That is, various measures were taken to improve the discharge of excavated soil (air blowing in Japan, Japanese Patent Publication No. 5-3353).

(2) In general, in the excavation method for forming the expanded bottom solidified part on the ground such as sandy soil and gravel soil,

Total bearing capacity R _a = lZ3 (R _p + R _f ) (kN / piece)

It is calculated by

Where R _p = aXN _{a ve} XA _p

a: Bearing capacity constant (usually around 250)

N _ave : Pile tip average N value

A _p : Tip cross section of ready-made pile

It is. Here, the cross-sectional area of the tip of the ready-made pile corresponds to the area of adhesion to the soil cement layer that contributes to the propagation of shear force due to the load.

R _f is the frictional resistance of the pile surface. It depends on the use of the fixation solution around the pile. ■ When using the fixation solution around the pile: R _f = CXN _ave XLX <i>

(C = 2-3)

■ When pile circumference fixing fluid is not used: R _f = CXLX φ

(C = l 5)

Use the value of

Also, where

L: The length of the ground that allows for the peripheral frictional force of the pile

Φ: Perimeter of pile

N _ave : Average N value of the section that uses pile circumference fixative

It is.

In general, when the N value is low (for example, 10 or less), a normal cylindrical pile is used as a ready-made pile. When used, R _f (pile surface frictional resistance) was smaller than that of a foundation pile structure using a nodal pile.

Therefore, it was necessary to increase one or both of R _p and R _f to increase the bearing capacity in the excavation method.

An object of the present invention is to improve the outer peripheral portion of a shaft portion of a pile hole in order to increase _Rf, and to improve the ground strength as a whole peripheral surface of a ready-made pile. This will secure and increase the overall frictional resistance of the peripheral surface of the ready-made pile, and increase the stress propagation area so that the stress can be widely relaxed and propagated. That is, in the above-described formula of R _f , N or coefficient C is increased.

(3) In order to enhance the R _p (tip bearing capacity), pile lower end as well as enhance the adhesion area with the widened pile outside table surface of the (tip) Soirusemento, sufficiently stress than deposition surface An object of the present invention is to form a rooted portion having a high solidification strength that can propagate. That is, in the above equation, α and _Ap are increased.

Another object of the present invention is to reduce the amount of soil discharged from the hollow portion of a ready-made pile to the ground when excavating a pile hole in the excavation method.

(4) Also, the invention of Patent Document 3 discloses a method in which a steel pipe having a metal fitting which can be screwed into the ground at the tip in advance and which is used as a reinforcement is screwed into the ground as a casing. An invention is disclosed that realizes a reduction in earth removal by a method of inserting a). However, in this method, the ready-made pile is simply placed on the metal fittings, and there is no integration between the ready-made piles and the metal fittings, and the solidification of the soil cement layer, etc., that ensures the stress propagation between the ground and the ready-made piles Due to the lack of consideration for the mixed layer, high bearing capacity cannot be expected. In addition, since this method requires metal fittings, it cannot be applied to the excavation method at all. Also, the invention of Patent Document 4 is a pre-drilling method in which a pile hole having a diameter equal to the outer diameter of a ready-made pile is excavated, and then a ready-made pile having a spiral wing is buried. It is disclosed that the diameter of the shaft of the pile hole is made relatively small to reduce the amount of excavated soil. However, in the invention of Patent Document 4, when screwing the spiral wing, a large twist is generated in the ready-made pile, and when the ground is hard, a huge torsion is generated in the ready-made pile, and it is impossible to perform with a ready-made concrete pile. is there. Also, if the formation contains a soft layer, the pile hole diameter is small, and it is difficult to form a solidified mixed layer with cement milk etc. in the gap between the pile hole wall and the outer surface of the ready-made pile. It is difficult to exert frictional force. Also, the invention of Patent Document 5 discloses that a propulsion head having a spiral wing and an excavating blade is fitted to the lower end of a hollow prefabricated pile, and the propulsion head is rotated by a rotating mouth through the prefabricated pile. A method of rotating and penetrating a ready-made pile without rotation is disclosed. However, in the invention of Patent Document 5, since the integrity of the buried propulsion head and the ready-made pile is uncertain and the excavation cannot be performed, it is possible to use the propulsion head to enhance the supporting force around the effective supporting ground. Absent. In addition, if the formation at the middle depth contains a soft layer, a solidified mixed layer cannot be formed at that part, and the peripheral frictional force cannot be enhanced. Furthermore, the propulsion head with a complicated structure cannot be recovered from the supporting ground, which requires cost. 2. Means to solve the problem

In order to solve the above-mentioned problems, in the present invention, a pile hole including a shaft portion of a pile hole is excavated with a larger excavation diameter than the conventional one (relative to the pile diameter of a ready-made pile), and further excavation of the pile hole is performed. In addition, a configuration was adopted in which a pile hole was excavated while forming a solidified mixed layer at least in an appropriate section within the desired depth range for design.

That is, in the first invention, the excavation head of the excavation hole protrudes from the tip of the hollow part of the prefabricated pile, excavates the ground to lower the prefabricated pile while forming a pile hole, and In the pile excavation method of burying the ready-made pile in the hole,

This is a pile excavation method in which a solidified mixed layer is formed at a predetermined depth range determined by design in the ground, and ordinary pile drilling is performed in depth ranges other than the depth range. .

Further, the second invention is characterized in that a drilling head of a drilling rod protrudes from the tip of the hollow portion of the ready-made pile, excavates the ground, lowers the ready-made pile while forming a pile hole, and places the ready-made pile in a predetermined pile hole. In the pile digging method to bury the pile,

In the ground, a solidified mixed layer is formed at a predetermined depth range determined by design to restore and strengthen the ground strength, and normal pile drilling is performed in depth ranges other than the depth range This is a method of digging piles.

In the third invention, a cement hole is formed with a diameter larger than the outer diameter of a ready-made pile, and when excavating a predetermined depth range determined by design, cement milk is injected into excavated soil. 3. The pile excavation method according to claim 1, wherein said excavated soil is stirred and mixed to form a solidified mixed layer having a predetermined solidification strength. In a fourth aspect, in the first to third aspects, a pile hole is formed with a diameter of 1.4 times or more the outer diameter of the ready-made pile, and a predetermined depth range determined by design is excavated. At this time, a method of excavating soil by injecting cement milk into the excavated soil and stirring and mixing the excavated soil to form a solidified mixed layer having a predetermined solidification strength.

In a fifth aspect of the present invention, the excavation head of the excavation rod is protruded from the tip of the hollow portion of the prefabricated pile, and the prefabricated pile is lowered while excavating the ground to form a pile hole. In the pile digging method to bury ready-made piles,

Pile holes are formed with a diameter of at least 1.4 times the outer diameter of the ready-made pile, and cement milk is injected into the excavated soil in a depth section including a relatively soft stratum on the ground, and the excavated soil is formed. This is a method for excavating piles, characterized by forming a solidified mixed layer with a predetermined solidification strength by stirring and mixing.

In a sixth aspect of the present invention, the drilling head of the drilling rod protrudes from the tip of the hollow portion of the ready-made pile, excavates the ground to lower the ready-made pile while forming a pile hole, and places the ready-made pile in a predetermined pile hole. In the pile digging method to bury the pile,

Using an excavating rod without an unloading mechanism in the middle, excavating the ground with a diameter of at least 1.4 times the outer diameter of the ready-made pile, and excavating the loosened soil on the outer surface of the ready-made pile This is a method of digging a pile, wherein the ready-made pile is laid down while being compacted to the outside.

In a seventh aspect of the present invention, the drilling head of the drilling rod protrudes from the tip of the hollow part of the ready-made pile, excavates the ground, lowers the ready-made pile while forming a pile hole, and moves the ready-made pile into a predetermined pile hole. In the pile digging method to bury the pile,

Excavating the ground with a diameter of at least 1.4 times the outer diameter of the ready-made pile, and submerging the ready-made pile while pressing the loosened excavated soil outward on the outer surface of the ready-made pile. This is a method of digging a pile.

In the eighth invention, the excavation head of the excavation hole protrudes from the tip of the hollow portion of the prefabricated pile, excavates the ground to lower the prefabricated pile while forming a pile hole, and In the pile excavation method of burying the ready-made pile in the hole,

Intermediate portion using the drill rod having no earth unloading mechanism, in the in the ground, a predetermined depth range defined in the design, while loosening the ground 1. More than ^four times the diameter of the outer diameter of the prefabricated pile excavation The loosened excavated soil is pressed outward on the outer surface of the ready-made pile, This is a method of excavating a pile with a feature that a solidified mixed layer with a predetermined solidification strength is formed in a predetermined depth range determined by the total, and ordinary pile hole excavation is performed in a depth range other than the depth range.

According to a ninth invention, in the first to eighth inventions, a tip fitting is connected to a tip of the ready-made pile, and a drilling head is protruded from the tip of the tip fitting to excavate the ground to make a pile hole. The tip fitting is provided with one or more support surfaces on the outer surface of the cylindrical base, which can transmit the shear force upward and downward and can be used as tip support force. This is a method of excavating piles, which is characterized by being formed in a pile.

In a tenth aspect, in the first to eighth aspects, the excavation head is formed from the tip of the prefabricated pile by using a prefabricated pile having an uneven portion formed on the outer surface of the lower end of the pile shaft. And excavate the ground to form a pile hole, and the uneven portion of the ready-made pile propagates upward or downward on the outer surface of the lower end of the ready-made pile, as a tip supporting force. This is a method of excavating piles, characterized by forming one or more support surfaces that can be used.

Also, in the eleventh invention, in the first to eighth inventions, a tip fitting having a lateral projection formed on an outer surface of a cylindrical base is connected to a tip of the ready-made pile, and This is a method of excavating piles by protruding an excavation head from the tip and excavating the ground to form pile holes.

According to a twelfth invention, in the first to eighth inventions, the outer diameter of the solidified mixed layer and the outer diameter of the pile-fixing portion of the pile hole are formed to be substantially the same outer diameter. It is a method of digging a pile.

A thirteenth invention is a foundation pile structure in which a ready-made pile is buried in a pile hole,

The pile hole is constructed by restoring and improving the ground strength at least in a depth range predetermined by design, and the ready-made pile is provided with a tip fitting at a lower end thereof, and the tip fitting is an outer surface of a cylindrical base. A foundation pile structure characterized in that a support surface capable of transmitting a shearing force and being used as a tip supporting force is formed at one or a plurality of locations in an obliquely upward or obliquely downward direction. It is.

The relatively soft stratum mentioned above is the ground where ready-made piles are to be buried, and one of the pile holes has a strength smaller than the assumed ground strength compared to the assumed ground strength. Refers to ground with only ground strength. For example, if the assumed ground strength is assumed to be "20" in an N value in sandy soil, it has a value significantly lower than the average N value, for example, an N value having a value smaller than "5". It refers to the ground that can hardly be considered as bearing capacity. In this case, the assumed ground strength may be set for each pile hole, or may be set for the entire site.

Further, in the above, cement milks refer to cement milk which solidifies after a lapse of a predetermined time if mixed into excavated soil and a hydraulic material equivalent to cement milk.

In the above, the “predetermined depth range determined by design” means that the normal ground is formed from strata of various ground strengths, and which depth range is set depends on the strength of the entire foundation pile structure. Determine the range to be enhanced. That is, when the soft stratum is defined as the “predetermined depth range”, or when the middle layer having relatively strong ground strength is defined as the “predetermined depth range”, the soft strata are appropriately combined and set as the “predetermined depth range”. Or a certain depth range is defined as a “predetermined depth range” regardless of the ground strength.

In the above, “excavation was performed at least 1.4 times the outer diameter of the ready-made pile”, but there is no upper limit especially for the shaft of the pile hole, and the larger the diameter is, the easier it is to bury the ready-made pile. Yes, and can be expected to increase support capacity. However, a larger diameter requires a larger excavation hole, and lowers the excavation speed, resulting in poor construction efficiency. Therefore, by comparing and adjusting the installation interval of the above and the foundation piles (ready piles), the excavation diameter is usually 1.4 to 1.5 times the same as the excavation diameter at which the high tip support force can be obtained at the foundation. Desired degree,

In addition, the “propagation of shear force” in the above refers to “a ready-made pile with the tip 13 attached” or “a pre-made pile with a convex portion on the outer surface of the lower end” in the solidified cement layer in the pile hole. When buried, means that shear force can be propagated toward the soil cement layer. Also, the “supporting surface that can transmit the shearing force” is a projection (for example, an annular projection) on the “outer surface of the cylindrical base (steel pipe body) 6 of the tip metal fitting” or the “outer surface of the lower end of the prefabricated pile”. When the projections are formed, the lower surface of the projection 10 constitutes a support surface B to which the shear force can be propagated downward, and the upper surface of the projection 10 propagates the shear force upward. Constitute a support surface A that can be Figure (a)). In this case, it is desirable that the upper and lower surfaces of the projection 10 are surfaces slightly inclined with respect to the vertical surface. Also, according to experiments, it has been found that the direction in which the shear force propagates acts obliquely to the vertical plane, so that it is desirable to form the shear force at right angles to the propagation direction.

When the support surface on which the shear force in the vertical direction acts is formed as a concave portion on the outer surface of the cylindrical base 1 in order to increase the protrusion, a side wall surface of the concave portion constitutes each of the support surfaces A and B. (Fig. 4 (b)) _D Further, the supporting surface is not limited to the protrusion or the concave portion, and a step is formed on the outer surface of the cylindrical base 6 to be the supporting surface A or the supporting surface B having the same function. (Fig. 4 (c) (d)), and the shape is arbitrary. In short, the outer surface of the cylindrical base 6 (the lower shaft 36 when the annular projection 37 is formed on the ready-made stake 1; FIG. 2 (a)) is provided on the outer surface with some means effective for transmitting the shear force (for example, a step). Part) is formed, and if it can be used as the tip support force, the support surface can be configured irrespective of the shape of the unevenness.

The cylindrical base 6 (or the lower shaft 36 in FIG. 2 (a)) is desirably cylindrical in view of the balance of stress propagation, but its shape such as a square tube is arbitrary.

Further, in the above, the outer diameter D "is of the tubular base part 6 of the end bracket 1 3, if a diameter smaller than the outer diameter of the prefabricated pile 1 (Du ^ D ^;) , the outer diameter D ₀₁ of the prefabricated pile 1 desirable since it suffices drilling Kuiana corresponding. in this case, the upper end of the tubular base part 6, to form a large diameter portion 7 corresponding to the outer diameter D ₀₁ of the prefabricated pile 1 (FIG. 2 (b )). in this case, the outer diameter D ₁₃ of the annular projection 10 forming a supporting lifting surface, the outer diameter D ₀₁ of the prefabricated pile 1 (i.e., a smaller diameter than the outer diameter) of the large diameter portion 7 (D ₁₃ < D _01), or the outer diameter D ₁₃ can in be a larger diameter than the outer diameter D ₀₁ of the prefabricated pile _{_{1 (D 01 <D 13)}} . in addition, of course, D ₁₃ = D _01, it is also to possible. also, since the outer diameter D ₁₃ is better not greater than D ₀₁ resistance when the input揷prefabricated pile is small, it is effective in the construction of the ground, such as high ground intensity (or density of the soil).

Also, the outer diameter D i of the tubular base 6 is made equal to the outer diameter D ₀₁ of the ready-made pile 1 (Doi ^ Di!), Or the outer diameter D „of the tubular base 1 is changed to the outer diameter of the ready-made pile 1. Can be larger than D ₀₁

These dimensions can be selected depending on the ground strength, soil density, required strength of foundation piles, and so on.

Also, without using the tip metal fittings 13, a small diameter lower shaft portion 36 is formed in the ready-made pile 1. When the annular projections 37, 37 are formed in this portion (FIG. 2 (a)), the outer surface 1 of the cylindrical base 6 corresponds to the outer surface of the lower shaft portion, and is set to have the same configuration.

Further, in the above, Shi desired to the inner diameter ₂ of the tubular base part 6 and ready pile 1 having an inner diameter D _{0 2} equal or les. This is because it becomes easy to pass the excavation head through the section.

3. Effect of the invention

(1) A solidified mixed layer is formed in a predetermined section, and the ground is pressed by the outer peripheral wall of the ready-made pile without discharging excavated soil. As a result, it is possible to demonstrate about twice the bearing capacity.

Regardless of the value of N value, when drilling a pile hole with a large diameter in an appropriate section and injecting cement milk to form a solidified mixed layer, it is possible to further restore and reinforce the pile circumferential friction force Therefore, it is expected that the support capacity will surely be increased.

(2) The conventional excavation method has the disadvantage that a large amount of excavated soil is discharged, but in the present invention, the diameter is larger than the outer diameter of the ready-made pile (for example, about 1.4 times or more the outer diameter of the ready-made pile). By unraveling the pile hole of large diameter, it is possible to settle the existing pile without the need for an earth removal mechanism, especially at the excavation hole. Can be reduced to about the amount of injected material. It is also possible to form a solidified mixed layer by injecting and mixing cement milk into the excavated soil only in the depth section that includes a relatively soft and unbearable formation (poor formation). Furthermore, when excavating a large-diameter pile hole with a diameter of about 1.4 times or more the outer diameter of a ready-made pile, a rooted part that can obtain a high bearing capacity is formed, so it has higher resistance to power. Foundation piles can be built at the same time.

(3) Since the solidified mixed layer is formed in the excavated pile hole, if the solidified mixed layer can adhere to the outer peripheral surface of the ready-made pile integrally, a ready-made pile having a large-diameter annular protrusion on the outer periphery can be constructed, so it is adjacent If the solidified mixed layer is formed at the same depth with the foundation pile and can be constructed before solidification, adjacent solidified mixed layers can be connected to each other, realizing a stronger foundation pile structure as an interconnected group it can.

(4) By making the outer diameter of the solidified mixed layer approximately the same as the diameter of the piled-up part, the drilling work for the pile hole is simplified, the control process is simplified, and the reliability of the drilling head is also improved. improves. Also, the outer diameter of the solidified mixed layer can be more than 1.5 times the outer diameter of the foundation pile. Drilling heads can be easily realized.

In addition, when the construction ground is hard or high in density, even if the construction speed is increased by providing a little soil removal mechanism on the excavation rod, this construction method can significantly reduce The amount of soil can be reduced.

(5) Although it is desirable to use metal fittings at the tip, it is possible to obtain the same high bearing capacity by using a pre-made concrete pile with an uneven portion at the lower end. In this case, the same construction method can be adopted by making the uneven parts the same configuration as the tip metal fittings.Therefore, there is a case where a concrete precast pile with uneven parts formed at the lower end by the conventional excavation method is buried. By forming a similar rooting portion, a high supporting force can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (a) shows a ready-made pile and a drilling rod according to an embodiment of the present invention, and is an enlarged front view of a broken ready-made pile, and FIG. 1 (b) is a basic pile of the present invention. Structure.

FIG. 2 is an enlarged front view of a reinforced portion of the foundation pile structure, and (a) and (b) are embodiments of the present invention.

FIG. 3 is a vertical cross-sectional view for explaining the excavation method of the present invention.

FIGS. 4 (a;) to (d) are schematic longitudinal sectional views for explaining the support surface of the tip fitting and the propagation of shearing force according to the present invention.

FIG. 5 is a front view of another excavating head used for carrying out the present invention.

Fig. 6 is an enlarged front view of the foundation of the foundation pile structure, showing a comparative example excavated by the pre-drilling method.

BEST MODE FOR CARRYING OUT THE INVENTION 1. Basic Embodiment

(1) On the ground where ready-made pile 1 is to be buried, project through hollow part 2 of ready-made pile 1 The excavated head 18 excavates the pile hole 28 and lowers the ready-made pile 1 into the pile hole 28 formed by loosening the ground (Fig. 3 (a) to (c). )). The excavation diameter of the pile hole 28 excavated by the excavation head 18 is larger than the outer diameter of the ready-made pile 1 to be set, for example, about 1.4 to 1.5 times as large as the excavation from the ground 25. Here, since the excavated soil is not discharged during excavation and when the ready-made piles are laid, it is not always necessary to provide a conventional function for discharging soil (such as a spiral) in the middle of the excavated rod.

When excavating ground with high ground strength or ground with very high soil density, if the application speed is to be increased, the drilling rod must be partially connected to the drilling rod in order to reduce the penetration resistance of the ready-made pile. It is also effective to form a normal spiral (discharge function) or to form a small-diameter spiral and to discharge a little amount of soil.

At this time, when excavating the formations 26 A and 26 B corresponding to the ground to be improved, excavation and agitation were performed while pouring the solidification agent into the excavated soil from the excavation head 18 to improve the specified solidification strength. A good ground will be created, and the ready-made pile 1 will be laid down in parallel.

According to the conventional drilling method, the outer periphery of the ready-made pile 1 immediately reaches the ground through a pile fixed liquid layer having a thickness of 1 to 2 cm, but in the present invention, in the solidified mixed layer, the solidified mixed layer is It is formed thick, and the entire outer periphery of the solidified mixed layer (outer diameter) is in contact with the ground.

For example, if the outer diameter of the ready-made pile 1 is 600 mm, the outer diameter of the solidified mixed layer will be about 840 to 90 Omm, and in order to secure a sufficient thickness for transmitting the stress, the solidified mixed layer The thickness (vertical length) is preferably lm or more from the viewpoint of strength.

Here, the large-diameter excavation of the present invention appropriately loosens and loosens the ground, so even though the excavated soil is not discharged, concrete-made pre-fabricated piles with irregularities on the outer surface can also be laid, so almost all The foundation pile without soil can be created. Of course, steel pipe precast piles, which are thinner than concrete precast piles, are easier to settle down, so steel pipe precast piles can also be used. In addition, the excavated soil that has been injected due to the solidification agent is discharged, so it is desirable that the solidified mixed layer be as small as possible.

(2) As a solidifying agent, for example, high-concentration cement milk is used, poured into the excavated soil, and stirred and mixed with the excavating head 18 to form a solidified mixed layer (soil cement layer) 29 A, 29 B To form In this case, the adhesive strength between the inner peripheral surface of the solidified mixed layer (soil cement layer) 29 A and 29 B and the outer peripheral surface of the ready-made pile 1 is equal to the outer peripheral surface of the solidified mixed layer 29 A and 29 B. Greater than the bond strength with the ground surface is necessary to improve stress propagation It is.

The donut-shaped solidified mixed layers 29 A and 29 B attached to the outer periphery of the ready-made pile 1 solidify and act as annular projections of the ready-made pile. That is, a vertical load or pulling force is applied to the ready-made pile 1 and a shear force can be propagated from the upper and lower surfaces of the solidified mixed layer to the upper and lower ground layers, thereby enhancing the vertical supporting force and pulling force (Fig. 1 (b)). (Shown by a chain line arrow).

(3) In the layer that does not form the solidified mixed layer, no solidifying agent is injected into the excavated soil.Therefore, loosened and loosened excavated soil is pressed around the perimeter of the ready-made pile 1 by the outer circumference of the ready-made pile that is settled as it is. It is accumulated in the state where it was done. In other words, in the layer (depth range) between the solidified mixed layer 29A and the solidified mixed layer 29B, a radially pressed excavated soil layer is formed on the outer peripheral side of the ready-made pile.

(4) As described above, if the pile hole 28 was excavated to the predetermined depth while forming the solidified mixed layers 29 A and 29 B at the predetermined depth position (Fig. 3 (a) -(C)), followed by the formation of the root compaction. In other words, in the consolidation section, high-concentration cement milk is injected from the lower end of the excavation head 18 and only the lower end of the pile hole is stirred and mixed. The excavated mud is replaced with cement milk, etc. to form the root consolidation layer 30 (Fig. 3 (d) (e)). The root consolidation layer 30 is filled with cement milk having a solidification strength equal to or higher than the ground strength. Subsequently, the excavating head 18 is closed, and the excavated pile 1 is pulled up to the ground 25 through the hollow part 2 of the pile 1 (Fig. 3 (3)). At the same time, the tip of the ready-made stake 1 is sunk into the stake of the pile hole 28, which is filled with cement milk (exists in the form of soil cement), and the lower surface of the stake 1 is fixed from the bottom of the stake. Leave only the length. As described above, the burying of the ready-made pile 1 is completed, and after the cement milk solidifies, the foundation pile structure 33 is formed (Fig. 1 (b)). In this case, in order to reinforce the foundation, it is also possible to use an excavation port provided with a spiral for excavation and agitation on the body or upper part of the excavation head 18 (shown in the figure). Absent). The purpose is to remove excavated soil as much as possible from the embankment, or to mix and mix cement milk and excavated soil for + minutes to form a high-quality embankment layer 30.

(5) The ready-made pile 1 used in the middle digging method according to the present invention is integrated with the stiffening layer 30 in the stiffening layer 30 made of cement milk formed in the stiffening portion, and has a high vertical bearing capacity. And a projection with a large attachment area (or Prefabricated pile 1 with spiral wings) is desirable. In particular, in order to reduce the push-in resistance when laying the ready-made pile 1 and to easily push it in and to increase the adhesion surface area, the tip fitting 13 with the cylindrical steel pipe main body 6 with a projection as the base is replaced with the ready-made pile 1 It is desirable to mount it on the tip 3.

In the case of adopting this excavation method, a large-diameter projection formed at the lower end of the pre-made pile 1 to be used or formed at the end fitting 13, for example, a structure having relatively small penetration resistance, and By forming a spiral wing with a large diameter, a foundation pile with high bearing capacity can be constructed.

In addition, this tip metal fitting 13 has a cylindrical steel pipe main body 6 that is not larger than the outer diameter of the prefabricated pile 1 in order to increase the adhesion area with the protrusion, and the outer diameter of the protrusion is at the top to reduce the pushing resistance. The outer diameter should be equal to or less than the outer diameter of the ready-made pile 1 to be mounted, and the number of projections should be the number that matches the required area of attachment with the required consolidation layer 30. Appropriate in terms of power balance. Furthermore, when the ready-made pile 1 is laid, it is necessary to prevent the soil and mud from adhering to the protruding surface of the tip fitting 13 and to increase the adhesion in the consolidation layer 30. It is desirable to increase the attachment area by slightly increasing the outer diameter of the prefabricated pile 1 or to taper the upper and lower surfaces of the projection.

Further, by performing a treatment for preventing the adhesion of soil and mud to the projection surface, the initial settlement after the solidification layer 30 is solidified can be prevented.

In addition, in order to increase the heat resistance, it is necessary to increase the surface area of the projection of the end fitting 13. However, in terms of the effectiveness of shear force propagation under load, Conversely, the diameter needs to be small. Therefore, the outer diameter of the steel pipe main body 6 located at the base of the projection should be as small as possible, and the outer diameter of the projection should be set at the upper part so as to minimize penetration resistance when laying the existing pile. It is desirable that the dimensions be approximately the same as the outer diameter of 1 and not too large. In other words, considering the propagation of shear force generated from the projecting surface involved in bearing capacity, at least the outer surface (lower surface or upper surface) of the protrusion has the required size and shape, and the soil cement layer has a higher solidification strength than the ground strength. Is indispensable.

In addition, the surface area of the protruding part of the tip fitting 13 is designed to be large in order to secure the bonding strength between the surface of each part of the tip fitting 13 and the stiffening layer (soil cement layer) 30 of the stiffening part. However, at the time of construction, mud adheres to the surface of It is necessary to prevent the wearing strength from decreasing. In particular, in the excavation method, unlike the case where the ready-made pile 1 is laid in the pile hole た filled with soil cement as in the excavation method, the height position where the pile hole 28 is excavated to form the soil cement Since the tip 3 of the ready-made pile 1 is located directly above (the position of the excavation head 18), consideration must be given to the attachment between the tip fitting 13 and the rooting layer 30. Therefore, it is desirable that the upper and lower surfaces of the protruding portion are not horizontal but inclined surfaces, so that they are knotted or slightly larger than the outer diameter of the upper pile to prevent soil and mud from being caught on the upper surface when protruding. By devising the shape and dimensions of the tip of the projection, such as a projection with a large outer diameter, reliable and stable expression of the supporting force can be achieved.

(6) In addition, the drilling rod 15 used in the inner digging method of the present invention can excavate a pile hole with an outer diameter of 1.5 to 1.5 times the outer diameter of the ready-made pile 1 when opened. Use a drilling head 18 that can be closed with an outer diameter less than its inner diameter so that it can pass through the hollow part 2 of the ready-made pile 1 by diameter. That is, the excavating head 18 needs a structure having a large ratio between the diameter reduction and the diameter expansion. For example, a digging arm 21 having a digging blade 22 at its tip is swingably attached to both sides of a head body 19 that can be connected to the mouth body 16 (Fig. 1 (a)). . Therefore, if this drilling head 18 is used, the outer diameter of the protrusion of the tip metal fitting of the ready-made pile 1 (or the protrusion formed on the outer periphery of the lower end of the ready-made pile) is larger than the outer diameter of the shaft of the ready-made pile. Even if it does, the ready-made pile 1 can be easily penetrated and buried in the pile hole 28 if it has a shape (for example, a spiral wing, etc.) in consideration of the resistance at the time of penetration.

In addition, in the conventional drilling method using a rocking head that uses a rocking drilling arm, which can realize a large diameter dimension relatively easily, small-diameter drilling at the shaft of a pile hole 28 (for existing piles) (External diameter + 2 cm), large-diameter excavation at the bottom of the pile with pile holes 28 (approximately 1.2 times the external diameter of ready-made piles), when the diameter of the excavation head 18 is reduced when pulled out (Less than the inner diameter of the ready-made pile), three control steps are required. However, this method reduces the number of control steps to two, that is, large-diameter excavation and agitation and extraction of the excavation head 18. The structure of the drilling head 18 can be simplified, and the rigidity can be increased. Therefore, the control of large-diameter excavation is reliable and stable, and the reliability is improved. In addition, the repair and maintenance are stable and economical. The excavation head 18 used in this method is Since a drilling diameter of at least 1.4 to 1.5 times the outer diameter of the ready-made pile 1 is required, The use of two excavating heads 18 with a structure having the excavating arms 21 and a structure having high rigidity and strength was achieved by using two excavating arms.

In addition, the rod body 16 of the excavation rod 15 can omit a spiral mainly used for earth removal as in a conventional drilling hole for a middle excavation. Stabilizer function for aligning the core of pile hole 2 8 and the core of hollow part 2 of ready-made pile 1 with the core of drilling rod 15 and a member with the function of stirring the excavated soil around drill rod 15 (Figure 1 (a)).

(7) In this method, depending on the soil properties, the size of the excavation diameter is adjusted (by adjusting the ratio of the excavation diameter of the excavation head 18 to the outer diameter of the ready-made pile 1). Although the ready-made pile 1 can be sunk quickly and the setting speed of the ready-made pile 1 can be controlled, an excavation head suitable for large-diameter excavation is required in order to further improve the excavation and crushability of the ground. For example, the outer cylinder 41 is attached to the cylindrical head body 19 so as to be able to move up and down, the upper arm 42 at the upper end of the head body 19, and the lower arm at the lower end of the outer cylinder 41. The lower end of 43 can be connected with a pin, and the lower end of the upper arm 42 and the upper end of the lower arm 43 can be connected with a pin to form the excavating head 18 (Fig. 5). In this case, the excavating arm 21 is composed of the upper arm 4 2 and the lower arm 4 3, and the excavating blades 20 and 20 are provided at the lower end of the outer cylinder 4 1, and the excavating blades 2 and 2 are provided on the lower surface side of the upper arm 4 3. 2 is formed.

In this excavation head, the outer cylinder 41 and the head body 19 are moved up and down relatively so that the upper arm 42 and the lower arm 43 of the excavation arm 21 overlap (horizontally). The drilling diameter can be enlarged and the driving range can be extended, so that the diameter of the drilling arm is reduced compared to a normal drilling head (the upper arm 4 2 and the lower arm 4 3 of the drilling arm 21 are arranged vertically). In other words, it is possible to excavate at a large ratio compared to the outer diameter of the already-made pile, and the drilling blades can be formed in multiple stages, so that the grinding performance can be controlled. Therefore, with this excavating head 18, large-diameter excavation and agitation with a pile diameter ratio of at least twice the diameter of an existing pile is possible, and it is possible to exert a greater supporting force.

Further, the excavation head 18 may be provided with a plurality of stoppers in a vertical direction (not shown), and in this case, different excavation diameters can be easily accommodated. Therefore, by using the excavation head 18, the excavator (the rod body 16 of the excavation opening head 15) is mounted with one excavation head 18 while changing the excavation position and changing the diameter. Pile of When drilling holes, continuous excavation is possible only by adjusting the stopper. Also,

Even when one pile hole is used to form a pile hole that has a shaft with a diameter that varies in the depth direction, the drilling diameter can be easily changed only by adjusting the stopper, and a solidified mixed layer with a different diameter is provided. Construction of the foundation pile to be performed becomes easy.

(8) As described above, according to the present invention, a solidified mixed layer can be formed on a predetermined ground by excavating to about 1.4 to 1.5 times the outer diameter of the ready-made pile 1, so that the high-concentration The solidified mixed layer made of the cement also functions as an annular projection formed on the outer periphery of the ready-made pile 1. For example, in the case of a ready-made pile with an outer diameter of 80 O mm, a solidified mixed layer with an outer diameter of about 120 to 1200 mm is formed. That is, the protrusion height (horizontal direction) (Projection distance) An annular projection of 160 to 20 O mm can be formed.

In this case, the ready-made pile 1 and the solidified mixed layer 29 A, 29 B act integrally, so that the outer surface area of the ready-made pile is increased to increase the adhesion to the ground, and the vertical load or When a pull-out force is applied, the upper and lower surfaces of the solidified mixed layers 29A and 29B act as stress propagation surfaces, and the shear force effectively propagates from the upper and lower surfaces to the ground located above and below the soft ground To increase the bearing capacity (Fig. 1 (b)).

In this way, the loosening of the ground reduces the frictional force around the piles of the ready-made piles.However, the frictional forces at the periphery of the piles of the ready-made piles can be restored by appropriately forming a solidified mixed layer, etc. It can be reinforced, and if it is constructed so that the adhesion between the solidified mixed layers 29 A and 29 B and the outer surface of the ready-made pile 1 is sufficiently enhanced, the support exerted on the shaft of the conventional ready-made pile 1 You can get about twice the supporting force.

In addition, the surface area of the ready-made piles is substantially increased, and the stress propagation area of the ready-made piles is widened, so that the transmitted load stress (stress per area) to the surrounding weak ground is reduced and relaxed, Increase load capacity.

At the height of the specified stratum, the area was excavated widely, stirred, and immediately after the solidified mixed layers 29 A and 29 B had been formed and before they were solidified, the ready-made piles 1 were sequentially pushed in, The pushing resistance (penetration resistance) of the ready-made pile 1 is reduced, and the ready-made pile can be easily laid.

Also, unlike the conventional excavation method, the excavated rod does not need to have a spoiler-shaped excavated soil discharge mechanism, and the total amount of excavated soil can be reduced. In other words, the excavation diameter is significantly larger than before (for example, 1.4 times or more the diameter of ready-made piles) while loosening and loosening the ground. When excavating and laying a ready-made pile, the excavated soil loosened on the outer surface (peripheral surface) of the ready-made pile is pressed almost radially against the surrounding ground, and the ready-made pile is laid down to construct the foundation pile. As in the past, the ready-made piles can be laid without the need for an excavating mechanism on the drilling rod.

(9) Excavation of a pile hole having a deepened root solidification part 35 by the first excavation method, and making the lower shaft part 36 smaller in the deepened root solidification part 35 filled with soil cement with a solidification strength higher than the ground strength, When the foundation pile structure 38 is formed by burying the prefabricated pile 1 having the annular projections 37, 37 at the lower end including the shaft 36, the shear force can be sufficiently transmitted from the surface of the annular projections 37, 37. With such construction (Fig. 6), it has been confirmed that the bearing capacity can be obtained about twice that of the conventional cylindrical piles. In the basic pile structure 33 of the present invention, the prefabricated pile 1 to which the tip metal fitting 13 is fixed or the prefabricated pile 1 having the annular projection 37 formed therein is buried in the above-described procedure (FIG. 2 (a)).

(b), Fig. 3), it is possible to achieve the same high bearing capacity as this foundation pile structure 38 by the conventional excavation method (Fig. 6).

Therefore, in the present invention, the excavation diameter is made larger than the outer diameter of the ready-made pile (for example, 1.4 times or more of the outer diameter of the ready-made pile) by the inside excavation method, thereby making it possible to reduce the amount of earth removal as a whole At the same time, a high bearing capacity can be realized.

2. Specific Embodiment

[1] ready-made piles 1

As the ready-made pile 1, a cylindrical concrete pile with the following shape and size will be adopted. If the required proof stress is large, steel pipe-coated concrete piles (SC piles) can be selected (Fig. 1 (a), Fig. 2 (b)).

Pile outer diameter D. i = 800 mm

Pile thickness t ₀₁ = 1 1 Omm

Pile inner diameter D. ₂ = 580mm

Pile length 9m

[2] Tip fittings 13

Outer diameter D ", the inner diameter D _12, the upper end portion of the steel pipe pile body (thickness _tll) 6 of the total length Ln, the outer diameter A large-diameter portion 7 of D ₁₃ is formed, and the large-diameter portion 7 serves as a connection portion with the ready-made pile 1. The large-diameter portion 7 forms a partially conical inclined slope in which the upper surface 8 has a horizontal plane shape and the lower surface 9 has a gradually decreasing diameter. The outer diameter of the connecting portion, i.e., the outer diameter D ₁₃ of the large diameter portion 7 is a substantially equal to the outer diameter of the prefabricated pile 1 to be connected (the outer diameter of D ₀₁ lower end). The width (height) of the large-diameter portion 7 is formed by a leaf ₁₃ .

The lower end outer side of the steel pipe body 6, to protrude the annular projection 1 0 discoid (donut shape) of the outer diameter D _13. The upper surface 11 of the annular projection 10 is formed in a horizontal plane, the lower surface 12 forms a partially conical slope, and the lower end of the slope reaches the lower end of the steel pipe body 6. The width of the annular projection 10 (height) is formed by L ₁₃ (FIG. 2 (b)).

The tip fitting 13 is configured as described above (FIG. 2 (b), FIG. 1 (a)). Spacing between the large diameter portion 7 and the annular projection 10 or is formed by L _12, when the protrusion length _{_{L 14 (= (D 13 _Dn}} ) ÷ 2), the propagation of action without failure shear force of the supporting surface To do at least

L ₁₂ > L ₁₄ X tan 6 = L ₁₄ X tan 30 = L ₁₄ X 3

It is formed so as to satisfy.

The dimensions are formed as follows.

Steel pipe body 1 outer diameter D _{1 X} = 610 mm

Steel pipe body

2 mm

Steel pipe length L L ^ 749 mm

Large diameter part 7 width L 9 mm

Distance between large diameter part 7 and annular projection 10 L _12: 430 mm

In the above embodiment, the inner diameter of the steel pipe main body 6 is the inner diameter D of the ready-made pile 1 connected to the upper part. ₂ and the thickness ti of the steel pipe body 6 is about 15 to 40 mm, so that the outer diameter D of the knot-shaped steel material of the annular projection 10! 3 is the outer diameter of the ready-made pile 1 at the top. It can be set as above, and the projection area (the area of adhesion to soil cement) can be large. Therefore, by simply increasing the number of the annular projections 10 to be formed, a bearing force equivalent to the bearing force exerted by the ready-made pile 1 one rank higher in outer diameter than the ready-made pile 1 can be obtained.

[3] Drill port 1 5

Attach the drilling head 18 to the tip of the hollow mouth body 16 Is composed. The excavating head 18 is configured by swingably mounting the upper ends of the excavating arms 21 and 21 on both sides of a head body 19 that can be connected to the mouth head body 16 (FIG. 1 (a)). . The head body 19 has a flat portion that tapers from the middle portion to the lower end portion, and excavation blades 20 and 20 project from the tip of the flat portion.

The excavating arm 21 has an upper end attached to the head body 19 with a rotating shaft 24, and a middle part directed downward so that the head body 1 extends along the flat part of the head body 19. The lower end formed with the digging blades 22 and 22 is bent so as to approach downward and open outward together with the digging blades 22 and 22. With such a shape, the excavating arms 21 and 21 have low rotational resistance, are easy to swing, and the entire excavating head 18 is compact, so that it is easy to penetrate the hollow portion of the ready-made pile. Therefore, large-diameter excavation becomes easier.

The head body 19 is provided with stoppers 23, 23 for limiting the range in which the excavating arms 21, 21 swing in accordance with the excavating diameter of the pile hole 28.

Further, the rod body 16 is provided with horizontal plates 17 and 17 symmetrically in diameter at predetermined heights (for example, 5 m), omitting the spiral for discharging the earth. The horizontal plates 17 and 17 combine the function of a stabilizer for aligning (centering) the axis of the drilling rod 15 with the axis of the pile hole 28 or the axis of the ready-made pile 1, and the function of stirring the excavated soil. Have.

The operation mode of the excavating head 18 is as follows when excavating the pile hole 28 (during excavation of the shaft portion of the pile hole, excavating to form a solidified mixed layer, agitating, excavating the agglomeration section, and agitating) and the hollow space of the ready-made pile 1. It has been simplified to a two-step method when passing through part 2. By moving the excavating arm 21, the outer diameter is about 1.5 times (1200mm) of the outer diameter of the ready-made pile 1, and even if the excavating rod 15 does not have a discharging mechanism, reliable and stable excavation and agitation can be achieved. It was realized. [4] Excavation method

(1) The ground where the ready-made pile 1 is to be buried (mainly sandy soil) is from 25 above the ground, and 6.

5m to 7.51111 thickness 1111 minutes, 13.5m to 14.5 ^ 1 thickness 1111 minutes, Designated two locations (for example, relatively weak N value of about 5) 26 B exists (Fig. 1 (b), Fig. 3).

(2) Connect the upper surface 8 of the large-diameter portion 7 of the tip fitting 1 3 to the tip 3 of the ready-made pile 1 (the lower surface of the lower end plate). And the large diameter part 7 and the lower end plate are fixed together by porting, welding, etc. to form a ready-made pile 1 with the tip fitting 13 (Fig. 2 (b), Fig. 1 (a)) .

(3) At a predetermined excavation position, the excavation hole 15 passes through the hollow part 2 of the pre-made pile 1 with the tip fitting 12 and the hollow part 6 a of the tip fitting 13 and the tip fitting 13 The drilling head 18 protrudes from the tip 14 of the drill.

In this state, when the ready-made pile 1 and the drilling rod 15 are vertically supported and the drilling rod 15 is rotated, the drilling arm 21 swings until it is regulated by the stopper 23, and the swing angle The pile hole 28 can be excavated with the excavating blades 2 2 and 2 2 of the excavating arm and the excavating blades 20 and 20 of the head body 19 while maintaining the same. With the excavation head 18 protruding from the tip 14 of the tip fitting 13, the shaft of the pile hole 28 having a diameter larger than the outer diameter of the ready-made pile 1 is excavated. While excavating, the excavating rod 15 is lowered and the ready-made pile 1 is lowered (Fig. 3 (a)).

(4) from the ground 6. Where drilled about O m, drilling soil, injecting the head body 1 8 Karase instrument milk (approximately solidified intensity 2 ON / mm ^2), want a stirred mixed with excavated soil Excavation soil and cement milk are excavated for about 2 m while stirring and mixing, and they are compacted to form a soil cement layer 29 A around the ready-made pile 1. The soil cement layer (solidified mixed layer) is formed at the position specified in the design, and the vertical height including the geological layer 26 A is to be formed. If the drilling head 18 is raised and lowered when pouring cement milk, a well-mixed and homogeneous soil cement layer can be formed. The solid cement strength of the soil cement layer (solidified mixed layer) 29 A is about 0.5 N / mm ² .

In addition, since the height position where the solidified mixed layer is formed can be roughly grasped by the N value obtained by a standard penetration test in advance, it is desirable to form the solidified mixed layer at the height position where the N value is applicable. That is, the current value of the motor of the auger that rotates and raises and lowers the excavation hole 15 during excavation is measured, and the integrated current value is calculated for each predetermined height range (for example, 5 Ocm). If this is done, the ground strength can be compared at the same depth as the N value of the standard penetration test, and the height position indicating the integrated current value will be the corresponding ground to be improved. As a result, a solidified mixed layer can be formed at an accurate depth section.

(5) Similarly, on the formed soil cement layer 29A, lower the ready-made pile 1 and then lower the drill hole 15 and drill the pile hole 28 with the drill head 18 Ready-made Lower stake 1.

(6) Cement milk is also discharged from the head body 19 at a height of 13.Om ~ l 5.Om from the ground corresponding to the geological formation 26B specified in the design, and mixed with the excavated soil. Then, a soil cement layer (solidified mixed layer) 29B is formed (Fig. 3 (b)). After that, similarly, the pile hole 28 is excavated without using cement milk (Fig. 3 (c)).

As described above, since the ready-made piles 1 are sequentially laid while the ground is being improved, the outflow of the soil cement can be prevented, and the solidified mixed layers 29A and 29B can be reliably formed.

(7) If a pile hole is excavated to a predetermined depth (approximately 21 m), which is the supporting ground (N value: 30), cement milk (solidification strength: 20 N / mm) can be obtained from the pile hole bottom 31 to a height of about 2 m. ^{(About 2} ) while rotating the excavating head 18 and moving it up and down to form the consolidation layer 30 while stirring and mixing the excavated soil and cement milk (Fig. 3 (d) (e)). If necessary, the excavated soil can be replaced with cement milk by discharging cement milk from the bottom of the consolidation section to push up the excavated soil.

(8) if the roots solidified layer 30 of high solidification strength of about 2 ON / mm ² than ground strength near the form shape, close the drilling arms 21, 21 to reverse the drill rod 15, drilling inlet head 1 rotation of 5 once stopped by drilling arm 21, to drooping state along 21 the head body 1 9 f (in that state, the maximum outer diameter of the drilling head 18 is below the inner diameter D ₀₂ of the prefabricated pile 1 Has become). Subsequently, the drilling rod 15 is slowly rotated while rotating the drilling rod 15 so that the drilling arms 21 and 21 do not swing, and the drilling head 18 is moved together with the drilling rod 15 together with the tip fitting 1 while stirring the consolidation layer 30. Insert the hollow part 6a of No. 3 and the hollow part 2 of the ready-made pile 1 (Fig. 3 (f)) and pull it up to the ground.

In addition, a stopper can be attached to the side of the head body 19 of the excavating head 18 where the excavating arms 21 and 21 swing when the excavating head 15 rotates in the reverse direction. In this case, in this case, if the drilling head 18 is pulled up while rotating in the reverse direction, the inner wall of the hollow part 2 of the ready-made pile 1 is not damaged, and the drilling head can be reliably recovered.

(9) Subsequently, or in parallel with the lifting of the excavating rod 15, the ready-made pile 1 is lowered (FIG. 3 (f)), and the tip fitting 13 is positioned in the consolidation layer 30. the tip (lower end) 14 and Kuianasoko 3 1 and the axial outer diameter D ₀₁ of about the distance L ₂₀ of prefabricated pile 1 (here was about lm. FIG. 2 (b)) at a location spaced , With tip bracket 13 Precast pile 1 is retained in pile hole 2 8.

After the soil cement layers 29 A and 29 B and the root consolidation layer 30 have solidified, the soil cement layers 29 A and 29 B and the root consolidation layer 30 and the ready-made pile 1 are fixed and integrally formed. The constructed foundation pile structure 33 is constructed (Fig. 1 (b), Fig. 2 (b)).

[5] Test results

When constructing this foundation pile structure 33, the excavated soil is hardly discharged with a small amount of soil removal equivalent to the amount of cement milk injected, so the surrounding ground strength is compacted and high in the load test. A bearing capacity of 9300 kN (maximum load) is obtained. In addition, improvement in variation in settlement characteristics can be expected.

In addition, the conventional inner digging method does not use the tip metal fittings 13 of this method, but uses the same diameter as the outer diameter 60 Omm of the tip metal fittings 13 in the consolidation layer of this method. This is compared with the conventional excavation method using a pre-made concrete pile. When a ready-made pile with an outer diameter of 60 O mm was used and the tip of the ready-made pile was similarly anchored in the consolidation layer, the maximum load was about 310 kN on the same ground.

[6] Other embodiments

(1) In the above embodiment, the timing for lowering the ready-made stake 1 is arbitrary as in the conventional digging method. However, in the formed soil cement layers 29 A and 29 B, it is desirable to install the ready-made pile 1 immediately after the formation of the layers.

(2) In the above embodiment, a solidified mixed layer was formed in which two sections of the formations 26A and 26B were improved and replaced with high-concentration soil cement layers 29A and 29B. Regardless of the size, it is possible to appropriately form a high-concentration soil cement layer in other sections to increase the bearing capacity of the shaft (not shown). Further, in the above-described embodiment, the solidified mixed layer is formed only in the section where the N value is particularly small, and a comprehensive solidified mixed layer having a high bearing capacity enhancing effect is created with a small amount of processing. Wataru connexion solidified strength full depth of ² 8 0. 5 NZmm 2 to form a solidified mixture layer below 1 high solidification strength for example in the ground have a better. oN / mm ² approximately Soirusemento layer (the solidified mixture layer ) Can also be formed.

However, the amount of excavated soil is not equal to the amount of newly added cement milk, etc. In order to reduce the amount of excavated soil, etc., it is desirable to minimize the injection of cement milk, etc.

(3) In the above-described embodiment, the ready-made pile 1 having the tip metal fitting 13 fixed at the lower end is buried. However, another ready-made pile 1 without using the tip metal fitting 13 can be used.

As the ready-made pile 1, a lower shaft portion 36 which is thinner than the upper shaft portion 34 is formed at a lower end portion, and a step portion (boundary portion) between the upper shaft portion 34 and the lower shaft portion 36, above the step portion, below the step portion ( Annular protrusions 37, 37 are formed on the lower shaft portion). If the required strength is large, it is also possible to select a connecting pile, a lower pile as the above-mentioned ready-made pile, a steel pipe-coated concrete pile (SC pile) as the upper pile, etc. (Fig. 2 (a)). The upper shaft portion 34 in the above is a portion excluding the lower shaft portion 36 formed at the lower end portion of the shaft portion, and is a shaft portion including an intermediate portion.

■ Pile outer diameter (shaft) D. = 700 mm

■ Pile thickness t ₀₁ = 100 mm

■ Pile inner diameter D. ₂ = 500mm

Outer diameter of lower shaft 0 ^ = 600 mm

■ Outer diameter of annular projection 37 D ₁₃ = 75 Omm

-Drilling diameter of pile hole D ₂₁ = 1 100 mm

• N value of the ground where the tip of the pile is located = 30

In this case, the interval ₂ between the annular projections 37 and 37 and the length L i ₄ of the annular projection 37 from the lower shaft portion 36 are equal to the interval L t ₂ between the large-diameter portion 7 and the annular projection 10 in the embodiment. Make the same settings. The annular projection 37 has an inclined upper surface 37a and an inclined lower surface 37b, and the inclined lower surface 37b has the same function as the lower surface 9 of the large diameter portion of the steel pipe body 6 and the lower surface 12 of the annular projection 10. Set to. The inclined upper surface 37a is similarly formed.

Further, in the above, the length L ₁₄ of the annular projection 37 is configured so that the inclined upper and lower surfaces 37 a and 37 b of the annular projection 37 can be as large as possible without protruding from the outer surface of the upper shaft portion 34. also, set in relation to the L ₁₂ as described above.

In the case of the foundation pile structure 33 formed by the same construction as that of the above-described embodiment using the ready-made pile 1 having the annular projection 37 without using the tip fitting 13 (FIG. 2 (a)), As a result of the same loading test, a high bearing capacity of 7492 kN was obtained at the maximum load. Considering the difference in the diameter of the annular projection 37 and the annular projection 10 in the Comparing the bearing capacity per unit cross-sectional area, in the case of the foundation pile structure 33 using the tip fitting 13 (Fig. 2 (b)), 6 18 kN / m \ for ready-made pile 1 (FIG. 2 (a)) in 5 6 5 k NZm ^2, comparable supporting force can be expected. Further, this prefabricated pile 1 is buried in the pile hole 28 in the same process as the prefabricated pile 1 to which the tip fitting 13 of the above-mentioned embodiment is fixed to form a foundation pile structure 33 (FIG. 2 ( a)). In this case, since the outer circumference of the tip of the annular projection 37 has the largest outer diameter, soil and mud are likely to adhere thereto. Therefore, if the annular projections 37, 37 are covered by an appropriate method (not shown). However, a stable and larger supporting force can be exhibited in the root consolidation layer 30.

In this prefabricated pile 1, instead of the annular projection 37, a projection can be formed from a non-annular projection obtained by cutting the annular projection or a projection that is dispersedly arranged (not shown). In addition, if the ready-made pile 1 has the same function as the inclined upper surface 37a and the inclined lower surface 37b, an annular concave portion can be formed instead of the annular protrusion (convex portion) 37 (see FIG. Not shown).

(4) In the above-described embodiment, it is preferable to use a drilling rod 15 having no spiral for discharging in the rod body 16 from the viewpoint of reducing the discharging. It is also possible to use a drilling rod in which a spiral having a smaller outer diameter is formed in a part or the whole of the mouth body 16 (not shown). This is effective when priority is given to increasing the excavation speed in areas where the ground strength is high, or when priority is given to removing excavated soil as much as possible from the inside of the consolidation.

Therefore, when excavating a pile hole having a diameter larger than the diameter of the pile according to the invention, the drilling rod is provided with a certain amount of earth discharging mechanism to control the earth discharging amount, so that the construction speed and the earth discharging amount (the earth discharging processing amount). It can be seen that the foundation pile can be constructed more economically than in the past, because and can be appropriately combined.

Claims

The scope of the claims

1. Protrude the excavation head of the excavation hole from the tip of the hollow part of the prefabricated pile, lower the prefabricated pile while drilling the ground to form a pile hole, and place the prefabricated pile in the specified pile hole. In the digging method of buried piles,

A method for excavating a pile in a pile, characterized by forming a solidified mixed layer in a predetermined depth range defined by the design in the ground and excavating a normal pile hole in a depth range other than the depth range.

2. Protrude the excavation head of the excavation hole from the tip of the hollow part of the prefabricated pile, lower the prefabricated pile while drilling the ground to form a pile hole, and place the prefabricated pile in the specified pile hole. In the digging method of buried piles,

In the ground, a solidified mixed layer is formed at a predetermined depth range determined by design to restore and strengthen the ground strength, and ordinary pile drilling is performed at depths other than the depth range. Digging method for piles.

3. When a pile hole is formed with a diameter larger than the outer diameter of the ready-made pile, and when excavating within the specified depth range specified by the design, cement milk is injected into the excavated soil and the excavated soil is removed. 3. The method according to claim 1 or 2, wherein a solidified mixed layer having a predetermined solidification strength is formed by stirring and mixing.

4. When a pile hole is formed with a diameter of 1.4 times or more the outer diameter of the ready-made pile, and when excavating a specified depth range specified by design, cement milk is injected into the excavated soil and the excavation is performed. 3. The method according to claim 1, wherein the soil is stirred and mixed to form a solidified mixed layer having a predetermined solidification strength.

5 · Protrude the excavation head of the excavation hole from the tip of the hollow part of the ready-made pile, lower the ready-made pile while drilling the ground to form a pile hole, and place the ready-made pile in the specified pile hole. In the method of digging piles to bury

Pile holes are formed with a diameter of at least 1.4 times the outer diameter of the ready-made pile, and cement milk is injected into the excavated soil in the depth section including the relatively soft stratum on the ground, A method of excavating piles, characterized in that a solidified mixed layer with a predetermined solidification strength is formed by stirring and mixing.

6. Excavate the ground by protruding the drilling head of the drilling rod from the tip of the hollow part of the ready-made pile. In the pile excavation method of lowering the ready-made pile while shaving to form a pile hole and burying the ready-made pile in a predetermined pile hole,

Using a drilling rod without an earth removal mechanism in the middle,

A method of digging a pile, wherein the excavated soil is excavated with a diameter of 1.4 times or more, and the unraveled excavated soil is compacted outward on the outer surface of the prefabricated pile, and the prefabricated pile is laid down.

The excavation head of the excavation port is protruded from the tip of the hollow part of the ready-made pile, and the ready-made pile is lowered while digging the ground to form a pile hole, and the ready-made pile is buried in the specified pile hole. Digging method for piles

Excavating the ground with a diameter of at least 1.4 times the outer diameter of the ready-made pile, excavating the ground, and placing the ready-made pile while squeezing the loosened soil outward on the outer surface of the ready-made pile. Pile digging method.

The excavation head of the excavation hole is protruded from the tip of the hollow part of the prefabricated pile, and the prefabricated pile is lowered while drilling a hole to form a pile hole, and the prefabricated pile is inserted into the specified pile hole. In the digging method for buried piles,

Using a drilling rod without an earth removal mechanism in the middle, excavating in the ground at a specified depth range determined by design with a diameter of 1.4 times or more the outer diameter of the ready-made piles Then, the loosened excavated soil is compacted outward on the outer surface of the ready-made pile, or a solidified mixed layer with a predetermined solidification strength is formed in a predetermined depth range determined by design, and in a depth range other than the depth range, This is a method of excavating piles, which involves drilling a normal pile hole.

A tip fitting is connected to the tip of the ready-made pile, a drilling head is protruded from the tip of the tip fitting, and the ground is excavated to form a pile hole, and the tip fitting is formed on the outer surface of the cylindrical base, upward or downward. 9. A method according to claim 1, wherein a support surface capable of transmitting a shear force downward and being used as a tip support force is formed at one or a plurality of locations downward. Underground construction method of pile described in paragraph 1. Using a prefabricated pile having an uneven portion formed on the outer surface at the lower end of the pile shaft, projecting a drilling head from the tip of the prefabricated pile, excavating the ground to form a pile hole, and forming the uneven portion of the prefabricated pile. One of the support surfaces that can transmit the shear force upward and downward and use it as the tip support force on the outer surface of the lower end of the ready-made pile 9. The method according to claim 1, wherein the pile is formed at a plurality of locations.

1 1. At the tip of the ready-made pile, connect a tip fitting with a lateral projection formed on the outer surface of the tubular base, project the drilling head from the tip of the tip fitting, excavate the ground and drill a pile hole. 9. The method according to any one of claims 1 to 8, wherein the pile is formed.

12. The outer diameter of the solidified mixed layer and the outer diameter of the pile consolidation portion are formed to have substantially the same outer diameter. Underground pile construction method described in the pile.

1 3. A foundation pile structure constructed by burying ready-made piles in pile holes,

The pile hole is constructed by restoring and improving the ground strength at least in a depth range predetermined by design, and the ready-made pile is provided with a tip metal fitting at a lower end thereof, and the tip metal fitting is an outer surface of a cylindrical base. A foundation pile structure characterized in that a support surface capable of transmitting a shear force and being used as a tip support force is formed at one or a plurality of positions obliquely upward or diagonally downward.