JP2015067950A - Drilling blade mounting steel pipe for constructing cast-in-place concrete pile and construction method of cast-in-place concrete pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drilling blade mounting steel pile for constructing a cast-in-place concrete pile capable of constructing a concrete pile for ground reinforcement with stable quality without being affected by a state of soil at a site and reliably constructing the concrete pile while facilitating construction work at the site.SOLUTION: A drilling blade mounting steel pipe 1 has: a steel pipe 10; and a tip drilling blade 20 which is detachably attached to a tip of the steel pipe with a drilling blade body 22 installed on a tip face thereof. The steel pipe 10 also has protrusions 13 which are inwardly protruded from an inner periphery at a tip thereof. The tip drilling blade 20 has: rotation support sections 23a which contact the protrusions 13 and enable the tip drilling blade 20 to rotate together with the steel pile 10 when the same is rotated in a predetermined rotation direction; and separation restriction sections 23b which are installed at the tips of the rotation support sections 23a and restrict the tip blade 20 from being separated from the steel pile 10 in an axial direction by engaging with surfaces of the protrusions 13 at a side opposite to the tip of the steel pile 10.

Description

  The present invention relates to an excavating blade-attached steel pipe for building a cast-in-place concrete pile used for building a concrete-based pile built in-situ in the ground to support the foundation of the building, and a method for building a cast-in-place concrete pile .

  When building a building on soft ground, the ground is reinforced by a columnar improvement method, a method of burying small-diameter steel pipe piles, and the like. The columnar improvement method is a method of constructing a columnar improvement pile in which soil is solidified with a solidifying material by mixing and stirring the solidified material in the excavated soil while excavating a pile hole in the ground.

  As an alternative to the above-described columnar improvement method, Patent Document 1 discloses excavation while excavating a pile hole in the ground with an excavation auger having an excavation claw at the tip, and filling the pile hole with a hydraulic solidified liquid made of cement or the like. A method of constructing a replacement column in which a hydraulic solidifying material liquid is solidified by lifting an auger from the ground has been proposed.

  Further, in Patent Document 2, a tip head having a drilling blade is detachably attached to a lower end of a cylindrical casing made of a steel pipe or the like, and the casing and the tip head are rotated and penetrated into the ground. A method of constructing a concrete pile has been proposed by filling cement milk or the like, and then separating the tip head from the casing and pulling out only the casing from the ground.

JP 2011-106253 A JP 2006-77388 A JP 2010-59603 A JP 2004-124398 A

The conventional columnar improvement method has the following problems.
・ Since the soil and solidified material at the site are mixed and stirred at the site, the quality of the built-up columnar piles varies depending on the soil quality and the stirring method at the site.
-In order to avoid insufficient strength due to poor solidification or poor stirring, it may be necessary to inject a large amount of solidified material slurry, which places a heavy burden on the environment.
-Depending on the soil, harmful substances such as hexavalent chromium may be eluted. Although it is possible to test whether hexavalent chromium or the like is eluted in advance and confirm that there is no dissolution, this requires cost and time.

The method of burying small diameter steel pipe piles has the following problems.
-Since it is necessary to support the front-end | tip of a small diameter steel pipe pile on comparatively hard ground (generally N value> 10), it may not be applied depending on the ground.
・ Deterioration due to corrosion of small diameter steel pipe piles. For this reason, it is designed in advance to allow for corrosion.

  Since the construction method of Patent Document 1 does not mix the soil at the site with the solidification material, each problem of the conventional columnar improvement construction method does not occur. However, in the method of Patent Document 1, when the excavation auger is pulled up from the ground, a part of the inner peripheral surface of the pile hole collapses, and the soil is mixed with the hydraulic solidification liquid, so that a good replacement column may not be formed. There is sex.

  In the construction method of Patent Document 2, since the casing is pulled out from the ground after filling the cylindrical casing with cement milk or the like, there is no fear that the inner peripheral surface of the pile hole collapses. In this construction method, the tip head is detachably attached to the casing. When the casing is pulled out from the ground, the tip head is separated from the casing, and the tip head is left at the bottom of the pile hole. For this reason, it is required that the tip head is easily attached to the casing and that the tip head is reliably separated from the casing.

  In Patent Document 2, a specific example of the structure for attaching and detaching the tip head to the casing is shown in paragraphs 0032 to 0036 and FIGS. 1 to 3 of the document. That is, the front end head is attached to and detached from the casing by inserting and withdrawing the convex portion provided on the main body peripheral wall portion of the front end head in the notch formed on the inner peripheral surface of the lower end of the casing. When the casing is rotated in a predetermined direction with the convex portion inserted into the notch, the convex portion is locked to the notch, and the leading end head is swung around the casing. Even if the rotation of the casing is stopped, since the convex portion is received from below by the hook portion of the notch portion, the tip head is not separated from the casing. When the casing is rotated in the reverse direction, the convex portion is detached from the hook portion of the cutout portion, so that the tip head can be separated from the casing.

  In the mounting structure of the above example, when the tip head is mounted on the casing, the tip head is mounted on the casing in a state where the axial centers of the casing and the tip head are aligned and the circumferential phase of the notch and the convex is aligned. Since the relative movement in the axial direction is required, it is troublesome to mount the tip head. In addition, in order to prevent dirt from entering the casing, in the state where the tip head is mounted on the casing, the entire outer periphery of the main body peripheral wall portion of the tip head is fitted to the inner periphery of the casing. Even if it is rotated, the tip head rotates around the casing due to frictional resistance between the inner peripheral surface of the casing and the outer peripheral surface of the main body peripheral wall of the tip head, and the convex portion does not come off from the hook portion of the notch, Even if it comes off, the main body peripheral wall portion of the tip head may not come off from the inner peripheral surface of the casing, and the tip head may not be separated. If the tip head is not separated, the cement milk or the like filled in the casing will be lifted together with the casing.

The object of the present invention is that it is possible to construct a concrete pile for ground reinforcement with stable quality without being affected by the soil condition at the site, and there is no need for phase alignment at the time of attaching the tip excavating blade. It is an object of the present invention to provide an excavating blade mounting steel pipe for on-site concrete pile construction that can be easily and reliably constructed on site.
Another object of the present invention is that it is possible to construct a concrete pile for ground reinforcement with stable quality without being affected by the soil condition at the site, and no phase alignment or the like is required when the tip excavating blade is attached. It is to provide a construction method for a cast-in-place concrete pile that can be constructed on site easily and reliably.

  An excavating blade mounting steel pipe for building a cast-in-place concrete pile according to the present invention includes a steel pipe and a tip excavating blade which is detachably attached to the tip of the steel pipe and has an excavating blade on the tip surface. A protrusion projecting toward the inner diameter side is provided on the inner peripheral surface of the tip, and the tip excavation blade is integrated with the steel pipe by contacting the protrusion when the tip excavation blade rotates in the rotation direction so as to penetrate the ground. A rotation receiving portion that is rotated in the axial direction protrudes in the axial direction toward the steel pipe.

Construction of a cast-in-place concrete pile using an excavating blade-attached steel pipe for construction of a cast-in-place concrete pile of this configuration is performed as follows.
First, a drilling blade mounting steel pipe is prepared by detachably attaching a tip drilling blade to the tip of the steel pipe. The tip excavating blade is attached to the steel pipe by inserting the tip excavating blade into the steel pipe with the axis of the steel pipe and the tip excavating blade aligned. It is not necessary to match the circumferential position of the steel pipe and the tip excavation blade. For this reason, in order to move the tip head relative to the casing in the axial direction with the axial centers of the casing and the tip head aligned, and with the circumferential phase of the notch and the convex aligned. In comparison, there is no need for phase alignment, and the mounting is easy.

  The excavation blade mounting steel pipe prepared in this way is supported so that the tip excavation blade is on the lower side. Then, the excavating blade mounting steel pipe is pushed down while being rotated in a direction in which the rotation receiving portion comes into contact with the projection, thereby penetrating into the ground while excavating downward by the tip excavating blade. Next, mortar, ready-mixed concrete, or cement milk is filled into the steel pipe of the excavating blade mounting steel pipe that has penetrated into the ground.

  Thereafter, the steel pipe is pulled up while rotating in a direction in which the rotation receiving portion is separated from the protrusion, and the tip excavation blade is separated from the steel pipe. When the excavation of the pile hole is completed, the tip excavation blade can be reliably separated from the steel pipe since the fixation of the steel pipe and the excavation blade by the fixing means or the separation regulating portion described later is released. Then, by pulling out only the steel pipe from the ground, the mortar, ready-mixed concrete, or cement milk in the steel pipe is poured into the pile hole that becomes the trace of the steel pipe. By hardening mortar or ready-mixed concrete or cement milk, concrete piles are built on site.

When building a cast-in-place concrete pile using this excavated blade-attached steel pipe, the soil and solidified material are not mixed and agitated unlike the conventional columnar improvement method. Therefore, it is possible to build concrete piles for ground reinforcement with stable quality at all times. In addition, there is no worry of toxic substances such as hexavalent chromium eluting depending on the soil. Furthermore, the soil around the pile hole is pushed around by the steel pipe and the ground is compacted. For this reason, the pile peripheral surface resistance force of a concrete pile can be taken largely.
Until the tip digging blade comes into contact with the ground, the tip digging blade may be detached from the steel pipe. Therefore, either fix the steel pipe and the tip digging blade with temporary fixing means, or use the separation restricting section as follows. Regulates excavation blades coming off.

In this invention, when the rotation receiving portion is in contact with the protrusion on the tip excavation blade, the steel pipe and the tip excavation blade are engaged with each other on the surface of the protrusion opposite to the steel pipe. A separation restricting portion that restricts separation in the direction may be provided.
With this configuration, when the rotation receiving portion of the tip excavating blade is in contact with the protrusion of the steel pipe, the separation restricting portion of the tip excavating blade is locked to the surface of the protrusion opposite to the steel pipe, and the steel pipe And the tip excavating blade are restricted from separating in the axial direction. When the rotation receiving portion is separated from the protrusion, the separation restricting portion is unlocked from the protrusion, and the tip excavation blade can be separated from the steel pipe. Therefore, if the tip digging blade has a separation restricting portion, there is no need to provide a separate fixing means for fixing the steel pipe and the tip digging blade, the configuration is simplified, and the effort to remove the tip digging blade from the steel pipe is eliminated. Is no longer necessary.

When the tip excavation blade has the separation restricting portion, the surface of the rotation receiving portion that faces the protrusion is parallel to the rotation axis of the tip excavation blade in a state where the tip excavation blade is attached to the steel pipe. In addition, the surface of the separation restricting portion that faces the projection may form an obtuse angle with respect to the surface of the rotation receiving portion that faces the projection.
When the surface facing the protrusion of the rotation receiving portion is parallel to the rotation axis of the tip excavation blade, the rotation of the steel pipe is smoothly transmitted to the tip excavation blade. In addition, when the surface facing the projection of the separation restricting portion forms an obtuse angle with respect to the surface facing the projection of the rotation receiving portion, the steel tube is rotated in a direction in which the rotation receiving portion of the tip excavating blade is separated from the steel pipe projection By doing so, the locking of the separation restricting portion with respect to the surface of the protrusion opposite to the steel pipe is easily released. Therefore, separation of the tip excavation blade from the steel pipe is performed reliably.

In the present invention, the tip excavating blade may be provided with a rising portion that is inserted into the steel pipe in a state where the tip excavating blade is attached to the steel pipe and closes a gap between the steel pipe and the tip excavating blade. .
If the rising portion is provided, it is possible to prevent soil from entering the steel pipe, and it is possible to build a good on-site concrete pile.

In this invention, you may provide the blade for helical groove formation which protruded in the outer peripheral side rather than the outer peripheral surface of this steel pipe in the lower end of the said steel pipe.
When the spiral groove forming blade body is provided, the spiral groove is formed on the outer periphery of the pile hole by excavating the pile hole using the excavating blade-attached steel pipe. By filling the steel pipe with mortar or ready-mixed concrete or cement milk and pulling out only the steel pipe from the ground, the mortar or ready-mixed concrete or cement milk is poured not only into the pile hole but also into the spiral groove. With concrete piles are built. When the concrete pile has a spiral knot, the shear resistance of the pile peripheral surface is large. Therefore, the pile peripheral surface resistance force of the concrete pile can be further increased. Large pile surface resistance has the following advantages.
-It is possible to reduce the pile diameter and reduce material costs.
-Less material is required for concrete piles, and environmental load can be reduced.
-Since the tip of the pile can be supported by the ground having a relatively small N value, the pile length can be shortened.

In the construction method of the in-situ concrete pile according to the present invention, in the state where the excavation blade mounting steel pipe is supported so that the tip excavation blade is on the lower side, the rotation receiving portion is in contact with the protrusion. By pushing down while rotating, the process of inserting into the ground while excavating downward by the tip excavating blade, the process of filling mortar, ready-mixed concrete or cement milk into the steel pipe, and the rotation receiving part being separated from the projection The steel pipe is pulled up while rotating in the direction to separate the tip excavation blade from the steel pipe, and then only the steel pipe is pulled out from the ground, so that a mortar in the steel pipe is formed in a pile hole as a trace of the steel pipe. A process of pouring ready-mixed concrete or cement milk.
In this way, after filling the steel pipe of the excavating blade mounting steel pipe inserted into the ground with mortar, ready-mixed concrete or cement milk, by pulling out only the steel pipe from the ground, the pile hole that becomes the trace of the steel pipe is put in the steel pipe. Pour mortar or ready-mixed concrete or cement milk. By hardening mortar or ready-mixed concrete or cement milk, concrete piles are built on site.

  The excavation blade mounting steel pipe for building a cast-in-place concrete pile with a node according to the present invention includes a steel pipe and a tip excavation blade which is detachably attached to the tip of the steel pipe and has an excavation blade body on the tip surface, A protrusion projecting toward the inner diameter side is provided on the inner peripheral surface of the tip of the steel pipe, and the tip excavating blade is brought into contact with the protrusion when the steel pipe rotates in a rotation direction penetrating into the ground, and the tip excavating blade is inserted into the steel pipe. Since the rotation receiving part that rotates integrally with the steel pipe is protruded in the axial direction, it is possible to build a concrete pile for ground reinforcement with stable quality without being affected by the state of the soil at the site. In addition, phase alignment or the like at the time of attachment of the tip excavation blade is unnecessary, and construction on the site is easy and a concrete pile can be constructed reliably.

  In the construction method of the in-situ concrete pile according to the present invention, in the state where the excavation blade mounting steel pipe is supported so that the tip excavation blade is on the lower side, the rotation receiving portion is in contact with the protrusion. By pushing down while rotating, the process of inserting into the ground while excavating downward by the tip excavating blade, the process of filling mortar, ready-mixed concrete or cement milk into the steel pipe, and the rotation receiving part being separated from the projection The steel pipe is pulled up while rotating in the direction to separate the tip excavation blade from the steel pipe, and then only the steel pipe is pulled out from the ground, so that a mortar in the steel pipe is formed in a pile hole as a trace of the steel pipe. Including the process of pouring ready-mixed concrete or cement milk, so that the quality of the land is stable without being affected by the soil conditions at the site. The Concrete piles for reinforcement can be construction, and does not need a phase adjustment or the like during mounting of the tip digging edge can construction site in to construction easily and reliably Concrete piles

It is a front view of the excavation blade attachment steel pipe for field casting concrete pile construction concerning one embodiment of this invention. (A) is sectional drawing of the front-end | tip part of the steel pipe of the excavation blade attachment steel pipe, (B) is the side view. (A) is the top view of the front-end | tip excavation blade of the excavation blade attachment steel pipe, (B) is the front view, (C) is the bottom view. It is a perspective view of the tip excavation blade. (A) is VA-VA sectional drawing of FIG. 1, (B) is VB-VB sectional drawing of FIG. 5 (A). It is explanatory drawing of each process of the construction method of the cast-in-place concrete pile performed using the excavation blade attachment steel pipe shown in FIG. 1 thru | or FIG. It is explanatory drawing which shows each process of the initial stage when rotating and penetrating the same excavation blade attachment steel pipe into the ground. It is a perspective view of a different tip excavation blade. (A) is a horizontal sectional view of the excavating blade-attached steel pipe attached to the tip excavating blade, and (B) is an IXB-IXB sectional view thereof.

  An excavating blade mounting steel pipe for building a cast-in-place concrete pile according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the excavating blade-attached steel pipe 1 includes a steel pipe 10 and a distal excavating blade 20 that is detachably attached to the distal end (lower end in FIG. 1) of the steel pipe 10.

  As shown in FIG. 2, a plurality of (for example, two) helical groove forming blades 11 projecting to the outer peripheral side from the outer peripheral surface of the steel pipe 10 are provided at the tip of the steel pipe 10. The spiral groove forming blade 11 is inclined so that the tip side is preceded when the steel pipe 10 rotates around the axis O1 in a predetermined excavation rotation direction (A direction). The excavation rotation direction is the rotation direction of the steel pipe 10 in the process of penetrating the excavation blade-attached steel pipe 1 into the ground. In this example, the excavation rotation direction is the right rotation direction when viewed from above. Block-like projections 13 projecting toward the inner diameter side are provided at a plurality of locations (for example, two locations) in the circumferential direction on the inner circumferential surface of the steel pipe 10. In the illustrated example, the axial position of the block-shaped protrusion 13 is substantially the same as that of the spiral groove forming blade 11.

  As shown in FIG. 3 and FIG. 4, the tip excavation blade 20 is composed of an integrally formed product made of steel by casting or forging. The tip digging blade 20 has a digging blade body 21 having an outer diameter dimension substantially the same as that of the steel pipe 10 and having a cylindrical rising portion 21a that can be fitted into the tip portion of the steel pipe 10 on the opposite end side. The height of the rising portion 21a is, for example, about 1 cm. In a state in which the rising portion 21 a is fitted in the distal end portion of the steel pipe 10, the distal end surface 14 of the steel pipe 10 abuts on a step surface 21 b adjacent to the rising portion 21 a of the excavating blade main body 21 as shown in FIG. In this way, the rising portion 21a of the tip excavating blade 20 enters and is connected to the steel pipe 10, and there is almost no gap between the steel pipe 10 and the outer peripheral surface of the rising portion 21a.

  3 (B) and 3 (C), the distal end surface of the excavating blade body 21 is a conical surface 21c, and two excavating blade bodies 22 are provided on the conical surface 21c. The two digging blade bodies 22 are provided in parallel with the diameter line L adjacent to both sides of the diameter line L passing through the axis O2 of the tip excavation blade 20 respectively. Specifically, one excavation blade body 22 extends from a position on one outer peripheral side in the diametric line direction to an intermediate position between the axis O2 and the other outer peripheral position over the axis O2. ing. The other excavation blade body 22 extends from the position on the other outer peripheral side in the diameter line direction to the intermediate position between the axis O2 and the position on the one outer peripheral side over the axis O2. Yes.

  The outer peripheral side end in the diameter line direction of each excavation blade body 22 is an outer blade portion 22a that protrudes toward the distal end side, and the other end is an inner blade portion 22b that protrudes further toward the distal end side than the outer blade portion 22a. The outer diameter 22a of the outer cutter 22a and the outer outer surface 22ba of the inner cutter 22b are both along the axis O2. Therefore, the front-end | tip of the outer blade part 22a and the inner blade part 22b is formed in an acute angle by front view, and it is easy to bite into the ground. Each digging blade 22 has a certain width in the direction perpendicular to the diameter line L, and the height relative to the digging blade body 20 is the same at any location in the direction perpendicular to the diameter line L.

  Further, as shown in FIGS. 3A, 3B, and 4, the excavation blade main body 21 has a plurality of (for example, two) hook-like bodies 23 protruding to the opposite end side from the rising portion 21a. Is provided. The hook-like body 23 rotates from the position on the inner peripheral side with respect to the rising portion 21a of the excavating blade body 21 to the side opposite to the rising portion 21a, that is, when the tip excavating blade 20 is attached to the steel pipe 10, to the steel pipe side. It comprises a receiving portion 23a and a separation restricting portion 23b bent in the circumferential direction from the opposite end of the rotation receiving portion 23a. One surface F1 in the circumferential direction of the rotation receiving portion 23a is a surface facing the side surface of the projection 13 of the steel pipe 10 in a state where the tip excavating blade 20 is attached to the steel pipe 10, and this surface F1 is the tip excavating blade. It is parallel to the 20 axis O2. Further, the front-side surface F2 of the separation restricting portion 23b is a surface facing the opposite end surface of the protrusion 13 of the steel pipe 10 in a state where the front-end excavation blade 20 is attached to the steel pipe 10, and the surface F2 is An obtuse angle is formed with respect to the surface F1. The elevation angle α of the surface F2 with respect to the surface perpendicular to the axis O2 is, for example, about 5 °.

  FIG. 5 is a cross-sectional view of the attachment portion between the steel pipe 10 and the tip excavation blade 20. The tip excavation blade 20 is attached to the steel pipe 10 as follows. That is, the tip excavating blade 20 is relatively moved toward the steel pipe 10 in a state where the tip excavating blade 20 is disposed on the tip side of the steel pipe 10 and the axial centers O1 and O2 of the steel pipe 10 and the tip excavating blade 20 are aligned. Then, the rising portion 21 a of the tip excavation blade 20 is fitted into the tip portion of the steel pipe 10. At this time, the protrusion 13 of the steel pipe 10 and the rotation receiving portion 23a of the hook-like body 23 of the tip excavating blade 20 are in axial alignment with each other. In this state, the tip excavation blade 20 is rotated in the anti-excavation rotation direction (anti-A direction) with respect to the steel pipe 10, so that the surface F1 of the rotation receiving portion 23a comes into contact with the side surface of the projection 13 and the projection 13 is counteracted. The surface F2 of the separation restricting portion 23b is locked to the front end surface. This completes the installation. Since the rising portion 21a of the tip digging blade 20 is fitted into the tip portion of the steel pipe 10, the tip digging blade 20 can be stably attached without wobbling. This attachment operation is easily performed because it is not necessary to align the circumferential phase of the protrusion 13 and the hook-like body 23 when the excavation blade body rising portion 21a of the distal excavation blade 20 is fitted into the distal end portion of the steel pipe 10. be able to.

  A method for constructing an in-situ concrete pile using an excavating blade-attached steel pipe for constructing an in-situ concrete pile having this configuration will be described with reference to FIGS.

  First, as shown in FIG. 6 (A), the excavating blade mounting steel pipe 1 is placed on the pile driving device 3 with a rotating mechanism mounted on a work vehicle 2 or the like capable of self-propelling so that the tip excavating blade 20 is on the lower side. Support. The steel pipe 10 of the excavating blade mounting steel pipe 1 may be attached with its upper end fixed to the lifting head 4 of the pile driving device 3. In that case, every time an in-situ concrete pile is built, the tip excavation blade 20 is attached to the tip of the steel pipe 10 in a state of being lifted by the pile driving device 3 by the attaching operation.

  Next, as shown in FIG. 6B, the steel pipe 10 is rotated in the excavation rotation direction (A direction), that is, in the direction in which the rotation receiving portion 23a of the hook-like body 23 (FIG. 5) contacts the protrusion 13 (FIG. 5). Push down while rotating. As a result, the ground 30 is excavated downward by each excavation blade body 22 of the tip excavation blade 20, and the spiral groove 31 is formed in the soil on the outer periphery of the steel pipe 10 by the spiral groove forming blade 11 provided in the steel pipe 10. The excavating blade mounting steel pipe 1 is penetrated into the ground 30 while forming. The rotational force is transmitted from the steel pipe 10 to the tip excavation blade 20 via the projection 13 and the hook-like body 23, but the surface F1 facing the projection 13 of the rotation receiving portion 23 a of the hook-like body 23 is the steel pipe 10 and the tip excavation blade. The rotation of the steel pipe 10 is smoothly transmitted to the tip excavation blade 20 because it is parallel to the 20 rotation axes O1 and O2. Since the rising portion 21 a of the tip excavating blade 20 is fitted into the tip portion of the steel pipe 10 to close the gap between the steel pipe 10 and the tip excavating blade 20, soil does not enter the steel pipe 10.

  When excavating the ground 30 with each excavating blade body 22, the inner blade 22b first bites into the ground 30 as shown in FIGS. 7A and 7B, and then as shown in FIG. 7C. The outer blade 22a bites into the ground 30. Thus, since the inner blade part 22b near the axial center O2 of the tip excavating blade 20 bites into the ground 30 first, the force for swinging the tip part of the excavating blade-attached steel pipe 1 to the side is small. When the outer blade portion 22a bites into the ground 30, a force that swings the tip portion of the excavating blade mounting steel pipe 1 to the side acts, but the diametrical outer surface 22ba along the axis O2 of the inner blade portion 22b has a ground surface. It is firmly engaged with the 30 excavated peripheral surface H1 in the horizontal direction, and this engaging action prevents the swinging movement of the distal end portion of the excavating blade mounting steel pipe 1. Further, since the outer surface 22aa in the diameter line direction of the outer blade portion 22a is also a surface along the axis O2, once the outer blade surface 22a bites into the ground as shown in FIG. 7D, the outer blade portion 22a. The outer surface 22aa in the diametrical direction is engaged with the peripheral surface H2 that has been excavated, and the tip of the excavating blade-attached steel pipe 1 is prevented from swinging sideways. In this way, at the initial stage of rotational penetration of the excavating blade-attached steel pipe 1, the tip of the excavating blade-attached steel pipe 1 is prevented from swinging sideways, and the excavating blade-attached steel pipe 1 can be stably penetrated into the ground 30. it can.

  Moreover, since the said inclination angle is given to the spiral groove forming blade 11, when the spiral groove forming blade 11 rotates, a downward driving force is exerted on the entire excavation blade mounting steel pipe 1. For this reason, it is easy to form a spiral groove 31 having a regular shape with a constant interval.

  Furthermore, in this embodiment, since the front end surface of the excavation blade main body 21 is a conical surface 21c, the excavated soil is guided along the conical surface 21c to the outer peripheral side of the front end excavation blade 20. Thereby, the excavation blade attachment steel pipe 1 is smoothly penetrated into the ground 30 by rotation penetration. Moreover, the soil excavated by the excavating blade body 22 is guided to the outer peripheral side of the tip excavating blade 20 so that the outer peripheral side of the steel pipe 1 with the excavating blade is densely compressed at the outer peripheral portion of the steel pipe 1 with the excavating blade. As a result, the ground 30 is compacted.

  Next, as shown in FIG. 6C, cement milk S is filled into the steel pipe 10 of the excavating blade-attached steel pipe 1 that has penetrated into the ground 30. Instead of cement milk S, mortar or ready concrete may be filled.

  When the filling of the cement milk S is completed, the steel pipe 10 is rotated in the anti-digging rotation direction (anti-A direction), that is, in a direction in which the rotation receiving portion 23a of the hook-like body 23 (FIG. 5) is separated from the protrusion 13 (FIG. 5). The tip excavating blade 20 is separated from the steel pipe 10 by pulling up. Since the surface F2 of the separation restricting portion 23b of the hook-like body 23 forms an obtuse angle with respect to the surface F1 of the rotation receiving portion 23a, by rotating the steel pipe 10 in the anti-excavation rotation direction, the hook to the protrusion 13 The separation restricting portion 23b of the shape body 23 can be easily released. Since the steel pipe 10 and the tip excavation blade 20 are not separated in the axial direction only by the separation restricting portion 23b of the hook-like body 23 being locked to the surface of the protrusion 13 opposite to the steel pipe, the above-mentioned engagement If the stop is released, the tip excavation blade 20 can be reliably separated from the steel pipe 10.

  Then, by rotating only the steel pipe 10 from the ground 30 while rotating the steel pipe 10 in the anti-excavation rotation direction, the pile hole 32 and the spiral groove 31 that become the trace of the steel pipe 10 are formed as shown in FIG. The cement milk S in the steel pipe 10 is poured. The tip excavation blade 20 separated from the steel pipe 10 is left at the bottom of the pile hole 32. The cement milk S in the pile hole 32 may be compacted using a vibrator or the like. If the steel pipe 10 is completely pulled out, the pile head Sa of the cement milk S is smoothed out. This completes the construction. When the cement milk S is hardened, the cast-in-place concrete pile 33 is formed.

  The cast-in-place concrete pile 33 has a spiral node on the outer periphery of the columnar pile body, and the spiral node bites into the ground 30. Further, in the process of penetrating the excavating blade-attached steel pipe 1 into the ground 30, the soil of the portion that becomes the pile hole 43 is pushed around by the steel pipe 10 and the ground 15 is compacted. Therefore, the shear resistance of the pile peripheral surface is large.

When the pile peripheral surface resistance of the in-situ concrete pile 33 is large, the following advantages are obtained.
-It is possible to reduce the pile diameter and reduce material costs.
-The material for the on-site concrete pile 33 can be reduced, and the environmental load can be reduced.
-Since the tip of the pile can be supported by the ground having a relatively small N value, the pile length can be shortened.

  The construction method of the cast-in-place concrete pile using this excavating blade-attached steel pipe 1 does not mix and agitate the soil and solidified material in the field unlike the conventional columnar improvement method. Therefore, it is possible to build concrete piles for ground reinforcement with stable quality at all times. In addition, there is no worry of toxic substances such as hexavalent chromium eluting depending on the soil. Furthermore, since the soil around the pile hole is pushed around by the steel pipe and the ground is compacted, the pile surface resistance force of the concrete pile can be increased.

In summary, the excavating blade-attached steel pipe 1 has the following effects when the tip excavating blade 20 having the above configuration is detachably attached to the tip of the steel pipe 10.
A predetermined pile diameter can be secured by the tip excavation blade 20.
-The tip support force can be secured by the tip excavation blade 20.
The tip excavation blade 20 can be smoothly attached to and detached from the steel pipe 10 by devising the angle of the separation restricting portion 23 b of the hook-like body 23.
-By providing the tip excavating blade 20 with the rising portion 21a fitted to the tip of the steel pipe 10, it is possible to prevent soil from entering the steel pipe 10 during the rotation penetration.
-By providing the rising portion 21a, the tip excavation blade 20 can be stably attached to the steel pipe 10.

  The tip excavating blade 20 of the above embodiment is provided with a hook-like body 23 composed of a rotation receiving portion 23a and a separation restricting portion 23b. Instead of the hook-like body 23, as shown in FIGS. In addition, the separation restricting portion 23b may not be provided and only the rotation receiving portion 23a may be provided. Other configurations are the same as those in the above embodiment. Also in this configuration, similarly to the above-described embodiment, the tip excavation blade 20 can be easily attached to the steel pipe 10, and the tip excavation blade 20 can be reliably separated from the steel pipe 10 when the steel pipe is pulled out.

  However, when it does not have the separation restricting portion 23b as shown in FIGS. 8 and 9, the drilling blade mounting steel pipe 1 is installed in the pile driving device 3 (FIG. 6) until the tip drilling blade 20 is grounded during construction. In the meantime, it is necessary to provide a fixing means (not shown) for fixing both ends of the steel pipe 10 so that the tip excavation blade 20 does not come off. The fixing means temporarily fixes the steel pipe 10 and the tip excavation blade 20, and is removed as follows when the steel pipe 10 enters the ground, and does not interfere with the entry into the ground. For example, a simple structure using a magnet, a pin, a belt, or the like may be used. Further, it is desirable that the fixing means can be easily fixed and released manually. If the excavating blade mounting steel pipe 1 is lowered when the concrete pile is constructed and the tip excavating blade 20 comes into contact with the ground surface, the tip excavating blade 20 will not come out of the steel pipe 10, so the steel pipe 10 and the tip excavating by the fixing means The fixing of the blade 20 is released.

DESCRIPTION OF SYMBOLS 1 ... Excavation blade attachment steel pipe 10 ... Steel pipe 11 ... Spiral groove forming blade 13 ... Protrusion 20 ... Tip excavation blade 21a ... Rising part 22 ... Excavation blade 23 ... Hook-like body 23a ... Rotation receiving part 23b ... Separation restriction Part 30 ... Ground 31 ... Spiral groove 32 ... Pile hole 33 ... In-situ concrete pile F1 ... Face F2 facing the protrusion of the rotation receiving part ... Face O1 facing the protrusion of the separation restricting part ... Center axis O2 of the steel pipe ... Axis center of tip drilling blade S ... Cement milk

Claims (6)

  A steel pipe and a tip excavating blade that is detachably attached to the tip of the steel pipe and has an excavating blade on the tip surface, and provided with a protrusion protruding toward the inner diameter side on the inner peripheral surface of the tip of the steel pipe, A rotation receiving portion that abuts on the protrusion and rotates the tip excavating blade integrally with the steel pipe when the steel pipe rotates in a rotation direction in which the steel pipe penetrates into the ground is protruded axially toward the steel pipe side. An excavating blade-attached steel pipe for construction of cast-in-place concrete piles.   2. The excavating blade mounting steel pipe for building a cast-in-place concrete pile according to claim 1, wherein when the rotation receiving portion is in contact with the projection at the tip of the rotation receiving portion, the steel pipe opposite tip of the projection An excavating blade-attached steel pipe for building a concrete pile provided with a separation restricting portion that is locked to a side surface and restricts the steel pipe and the tip excavating blade from separating in the axial direction.   The excavation blade mounting steel pipe for building a cast-in-place concrete pile according to claim 2, wherein a surface of the rotation receiving portion facing the protrusion is the distal excavation blade in a state where the distal excavation blade is attached to the steel pipe. An excavation blade-attached steel pipe for building a concrete pile, in which a surface parallel to the rotation axis of the separation regulating portion and facing the projection of the separation restricting portion forms an obtuse angle with respect to a surface facing the projection of the rotation receiving portion .   The excavating blade-attached steel pipe for building a cast-in-place concrete pile according to any one of claims 1 to 3, wherein the steel pipe is attached to the tip excavating blade and the tip excavating blade is attached to the steel pipe. An excavating blade-attached steel pipe for building a concrete pile provided with a rising portion that is inserted inside the steel pipe and closes a gap between the steel pipe and the tip excavating blade.   The excavating blade-attached steel pipe for building a cast-in-place concrete pile according to any one of claims 1 to 4, wherein a spiral groove projecting outward from the outer peripheral surface of the steel pipe is provided at a lower end of the steel pipe. Excavation blade mounting steel pipe for building concrete piles with forming blades. A method for building a cast-in-place concrete pile using the excavating blade-attached steel pipe for building a concrete pile according to any one of claims 1 to 5,
With the excavating blade mounting steel pipe supported by the tip excavating blade on the lower side, it is pushed down by the tip excavating blade by rotating it down in the direction in which the rotation receiving portion abuts against the projection. The process of inserting into the ground while excavating,
Filling the steel pipe with mortar, ready-mixed concrete or cement milk;
The steel pipe is pulled up while rotating in a direction in which the rotation receiving portion is separated from the protrusion, and after the tip excavation blade is separated from the steel pipe, only the steel pipe is pulled out from the ground, thereby becoming a trace of the steel pipe. The process of pouring mortar or ready-mixed concrete or cement milk in the steel pipe into the pile hole,
On-site concrete piles including

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