JP2004270440A - Construction method for foundation pile, and prefabricated pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain about twice a bearing capacity than before by eliminating earth removal in the burial of a prefabricated pile. <P>SOLUTION: A spiral blade 8 and an auxiliary spiral blade 12 are formed on the outer periphery of the lower end of outer-hull steel pipe concrete so as to serve as the prefabricated pile 16. An excavating rod 18 wherein an earth removing means is not formed is inserted into a hollow part 3 of the prefabricated pile 16 (a). A posthole shaft 24 with a diameter D<SB>21</SB>is excavated by means of an excavating head 20 without the use of excavation liquid or the earth removal so that ground can be unstiffened. The prefabricated pile 16 is concurrently or alternately pushed in while being rotated, and made to penetrate into the ground while being screwed into the ground by means of the spiral blade 12 (b). An expanded foot protection part 25 with a diameter D<SB>22</SB>is formed on the bearing ground (c). After cement milk is injected into excavated soil in the foot protection part 25 so that a soil cement layer 26 can be formed, the excavating rod 18 is pulled up on the ground 29 (d), and the prefabricated pile 16 is screwed for burial in such a manner that the spiral blade 8 and the auxiliarly spiral blade 12 are positioned in the cement layer 26, so that the foundation pile 28 can be constructed (e). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a method of constructing a foundation pile using a prefabricated pile, and more particularly to a method of constructing a foundation pile realizing a higher bearing capacity and a reduction in earth removal during excavation by using a prefabricated pile with spiral blades, and this construction. It relates to ready-made piles used in the method.

  Conventional pile foundation creation method: Pile foundation using precast concrete piles, which mainly use tip bearing capacity, has a certain level of workability, mainly due to the excavation speed, to ensure economic efficiency. However, the excavated soil generated during the construction of pile holes is actually discharged in large quantities as mud, and it has been a long-standing issue to reduce environmentally unloaded soil while maintaining performance and economy. Met.

(1) Conventional excavation method of concrete pile In the excavation method, a rod with an excavation head is inserted into the hollow part of a concrete cylindrical precast pile from above the pile and protrudes from the lower end of the precast pile. And the ground is excavated by rotating the rod through a drilling rod, and the pile is gradually lowered and settled while forming a pile hole having substantially the diameter of the pile, thereby forming a foundation pile. Therefore, it is effective for the ground which is relatively easily excavated or easily collapses.
In such an underground excavation method, it is necessary to improve the excavation property of the excavated soil upward in order to improve the workability (in order to increase the setting speed of the ready-made pile). Therefore, at the time of excavating the pile hole, drilling water or air is poured out through the rod to pulverize the excavated soil, and the rod has a spiral shape to facilitate lifting and carrying out the excavated soil. Various methods have been devised for the earth discharging property so as to reduce the push-in obstacle caused by the intrusion.
In addition, since the excavation rods for excavation have few parts that can contact the inner wall of the pile hole, it is difficult to install a drum for kneading mud.Therefore, the excavated soil can be kneaded on the inner wall of the pile hole to reinforce the ground. Due to the difficulty, the frictional force on the peripheral surface becomes insufficient, and the excavated soil is discharged in proportion to the excavated amount.
That is, from the environmental point of view, it was difficult to reduce the earth removal because it was difficult to lay down the ready-made piles, and the workability was poor.

(2) Conventional excavation method for concrete piles Using a drilling head and a stirring rod, and in some cases, a drilling rod equipped with a kneading drum, excavate the ground while rotating the drilling rod to obtain the maximum outer diameter of the pile. Form suitable pile holes. During the excavation, excavation is performed while injecting excavation water such as water to improve excavation properties. Also, if necessary, after excavated soil and a solidifying material such as cement milk are stirred and mixed to form a soil cement layer having a predetermined solidifying strength, an existing pile is laid to form a foundation pile.
Compared to the middle digging method, the rod can be equipped with a plurality of kneading drums, so that the excavated soil is kneaded to the inner wall of the pile hole, the inner wall is reinforced and the peripheral frictional force is considerably improved, and at the same time, the excavated soil is discharged. Although it has been reduced to some extent, basically excavated soil and solidified material or a large amount of mud mixed with water, etc. are discharged, so it is not only environmentally friendly, but also environmentally friendly. there were.
That is, from the environmental point of view, it is practically impossible to lay concrete stakes on ordinary ground to significantly reduce soil removal.
There is also a blow method, but the level of impact and vibration was so great that daily living was difficult in residential areas.

(3) Construction method of pile foundation for screwing and laying steel pipe pile with spiral wings Since the steel pipe pile with spiral wings is screwed and settled, there is almost no earth removal and the construction method is environmentally friendly. Generally, it is an effective construction method for a weak ground where the reaction force from the ground at the time of screwing is small, that is, the ground strength is not good.
In other words, in order to improve the screwing strength, it is necessary to withstand torsion, and it is necessary to increase the wall thickness of the steel pipe, and it does not match the thickness required for the supporting force, and becomes thicker than necessary. Then, it was not economically viable compared to concrete piles.
Also, without excavation, the pile is screwed down by the spiral wing and the soil is not discharged, so the pile is laid down without disturbing the ground at the shaft of the pile hole, so the so-called peripheral friction force using the spiral wing is efficient. It is available for use.
However, the bearing capacity at the tip of the pile is quite inadequate, and is about half that of the tip support of the pile foundation made of concrete piles. The applications are limited, and furthermore, the applications are limited in terms of economy due to the expensive steel pipe piles compared to concrete piles.
Under such circumstances, proposals have been made for ready-made concrete piles with spiral blades (Patent Documents 1 to 4).
4-14500 Japanese Patent Publication No. 58-54211 JP-A-1-94112 JP-A-60-123620 Tokuho 7-49655 JP-A-2002-61179

  Each of the above prior arts has the following problems.

(1) Patent Document 1: Japanese Utility Model 4-14500
This publication discloses that a small-diameter concrete pile is connected to the top of a tip concrete pile having a large-diameter helical collar, a propulsion case with a spiral collar is engaged with the tip concrete pile, and rotational force is applied to the pile via the propulsion case. A device is disclosed in which a pile is provided, the pile is sunk while being screwed in, and the propulsion case is extracted after the pile is sunk.
In this invention, it is described that the earth removal is reduced, but since the tip of the concrete pile is made of concrete, the strength at the time of screwing is insufficient, and the construction ground is limited to a specific ground with a soft ground, Practical effects are uncertain, and furthermore, consideration is not given to the construction of high strength (structure in which shear propagates efficiently) as the pile foundation structure.

(2) Patent Document 2: Japanese Patent Publication No. 58-54211
In the invention described in this publication, in a concrete pile having a spiral collar, the shape of the spiral collar and the strength of the concrete pile are devised to improve the penetration of the pile by screwing.
According to the invention, when the pile is penetrated, the angle of the upper and lower surfaces of the spiral spiral collar made of concrete is adjusted to adjust the torque of torsion, thereby improving the penetration property of the pile and the discharging property of the excavated soil. However, low-strength concrete piles are limited in the ground that can be constructed even if they are slightly improved, and there is also a lack of consideration for reinforcement of load capacity (structure in which shear propagates efficiently) as the pile foundation structure. I have.

(3) Patent Document 3: JP-A-1-94112
The invention described in this publication discloses that a spiral auger is inserted into a hollow portion of a steel pipe pile having a threaded protrusion formed on an inner wall of the pile tip, and the pile is pressed into the pile while excavating the tip of the pile. When it arrives, the pile is screwed and penetrated, and finally hit to secure the pile and secure the tip support force.
According to the present invention, since the screw-shaped protrusions and the spiral auger on the inner wall of the pile tip are used for discharging the soil, it is easy to push up the excavated soil, the penetration speed of the pile is improved, and the bearing capacity is considerably obtained. However, the amount of excavated soil is large as before, and there is no description of the pile foundation structure as to the enhancement of load-bearing capacity, and there is insufficient consideration (structure for efficient propagation of shear).

(4) Patent Document 4: JP-A-60-123620
In this publication, a square fitting hole is formed in the center of a steel-pipe concrete composite pile provided with a spiral blade at the tip of the pile, and the pile is settled while inserting a rotating shaft of a square block and applying a rotating force. Is disclosed.
In the present invention, since the outer shell material of the pile such as the spiral blade is a steel material, the strength of the spiral blade itself is sufficient with respect to the strength at the time of rotating and pushing, but it is interposed between the rotating shaft and the blade. Due to the torsional strength acting on the concrete part (having a low torsional strength), the construction ground is limited to a specific soil with soft ground, and the overload is also limited.
Furthermore, although it can be applied to various pile materials, in the case of a joint pile, it is necessary to form a fitting portion that gives a similar rotational force to each joint pile, and there is a limit on the length of settlement. In addition, there is a lack of consideration as a foundation pile structure (structure in which shear propagates efficiently) to increase the load bearing capacity.

(5) Patent Document 5: Japanese Patent Publication No. 7-49655
This publication describes an invention of a foundation pile in which a floating ring in which an end of a hollow pile is fitted is fixed to a base portion of a propulsion pile with spiral wings, and the floating ring and an end plate of the hollow pile are welded and joined. Have been.
The foundation pile is submerged by the propulsion action of the spiral wings of the propulsion pile, so the hollow pile connected to the upper part is protected without a torsional moment, but the propulsion pile located at the tip has a torsional moment in the concrete part. Acts, lacks strength, and limits the construction range (construction ground, overlay load, etc.). In addition, there is a lack of consideration as a foundation pile structure (structure in which shear propagates efficiently) with regard to the enhancement of load bearing capacity.

(6) Patent Document 6: JP-A-2002-61179
In the invention described in this publication, the ground is excavated and penetrated by a digging head for medium digging in which the hollow portion of the pile with a spiral wing is inserted, and in the support layer at the tip of the pile, the lower end of the pile is closed with the digging head. Further, the drilling rod is separated from the drilling head part by further screwing, and the drilling head part is left to increase the supporting force.
In the present invention, the hollow pile is a conventional hollow digging method with a lower open end, so that it can easily penetrate. Regarding the tip supporting force, the excavating head is pushed into the ground at the tip of the pile, and the supporting force is higher than that of a normal pile with a spiral wing. However, it is economical loss because the excavation head is left behind, and a large amount of excavated soil is expected to be discharged although the effect is not described. Insufficient considerations (structure in which shear propagates efficiently).

  As described above, as in (1) to (6), various proposals have been made for screwing in concrete piles with spiral wings, but the entire pile required for screwing the spiral wings on construction ground of various strengths. Because of the lack of proof stress and the lack of efficient support on the spiral wing surface, the current situation was that the construction method was not compatible with low soil removal and economic efficiency.

  However, in the present invention, a prefabricated pile is formed by forming spiral blades on the outer periphery of the lower end of a concrete pile body whose outside is covered with a steel pipe, and a pile hole is excavated without using a drilling liquid, or the ground is unraveled. In addition, since the ready-made pile is buried while being screwed into the ground around the pile hole with the spiral blade, each of the above problems is solved.

That is, the invention of this method is:
(1) Spiral blades are formed on the outer periphery of the lower end of a concrete pile body whose outside is covered with a steel pipe to constitute a ready-made pile.
(2) The hollow portion of the ready-made stake is penetrated by a digging rod that does not form a soil discharging means, and the digging head of the digging rod protrudes from the lower end of the ready-made stake.
(3) By rotating the excavation head, with a diameter that allows the ready-made pile to be screwed in accordance with the ground strength, without using a drilling liquid, and while excavating a pile hole without discharging the soil, Form loose ground. At the same time or alternately, the ready-made pile is rotated, and the ready-made pile is penetrated into the ground while being screwed into the ground with the spiral blade.
(4) When the excavation head has formed a solidification portion on a predetermined support ground, the excavation head is accommodated, and the hole is lifted to the ground through the hollow portion of the ready-made pile, and the above-mentioned solidification portion is formed in the solidification portion. The foundation pile is formed by burying the ready-made pile so that the spiral blade is positioned.
(5) A method for forming a foundation pile characterized by burying a ready-made pile as described above.

Also, the invention of another method is
(1) Spiral blades are formed on the outer periphery of the lower end of a concrete pile body whose outside is covered with a steel pipe to constitute a ready-made pile.
(2) The excavation head at the tip of the excavation rod has a diameter that allows the ready-made pile to be screwed in accordance with the soil strength, and excavates the ground without using drilling fluid and without discharging the soil. While the ground is loosened, a pile hole having a rooted portion is formed in a predetermined supporting ground.
(3) The prefabricated pile is rotated so that the prefabricated pile is screwed into the ground around the pile hole wall while rotating the prefabricated pile into the pile hole, and the spiral blade is positioned in the root compaction portion. Is buried to create a foundation pile.
(4) A method for forming a foundation pile characterized by burying a ready-made pile as described above.

  In the invention of the above method, the excavating head excavates an enlarged root consolidation portion having a diameter equal to or larger than the outer diameter of the spiral blade, and the spiral blade of the ready-made pile is placed in the soil cement layer formed in the enlarged root consolidation portion. This is the method of constructing the foundation pile to be located. Further, the present invention is a method for forming a foundation pile for forming a pile hole or loosened ground while excavating with a drilling head at a diameter equal to or larger than the outer diameter of the pile body. In addition, a ready-made pile composed of spiral blades formed on the outer periphery of the lower end of a concrete pile body covered with steel pipe on the outside is used as a lower pile, and another concrete pile is used as an upper pile, and an existing pile to be buried is constructed. Then, a lower pile of the casing covering the upper pile is locked to the lower pile, and the upper pile of the casing is rotated to rotate the lower pile.

  Further, the invention of the ready-made pile is a concrete pile main body whose outside is covered with a steel pipe, wherein a spiral blade is formed on an outer periphery of a lower end portion.

  Further, in the above-mentioned, a prefabricated pile, wherein two of the half donut-shaped spiral blade pieces for a half circumference are spirally fixed at rotationally symmetric positions to form a spiral blade. Further, the present invention is a ready-made pile, wherein the lower end of the pile main body is closed and a drilling means is protruded from the lower end of the pile main body. At the lower end of the pile main body, two half donut-shaped spiral blade pieces for a half circumference are spirally fixed at rotationally symmetric positions to form a spiral blade, and a drilling protrusion is protruded from the lower end of the spiral blade. A prefabricated pile, wherein an auxiliary spiral blade having a diameter smaller than the diameter of the spiral blade is formed above the spiral blade in the pile main body. Further, the pile is a ready-made pile in which a spiral strip having a smaller diameter than the auxiliary spiral blade is formed above the spiral blade in the pile main body.

  In the above “loose ground”, the pile hole wall is not clearly formed, and the broken pile hole is filled with loosened excavated soil.

(1) In the present invention, since the foundation pile is constructed by burying the prefabricated pile so that the spiral blade of the prefabricated pile is located at a predetermined depth in the root consolidation part of the pile hole, the prefabricated pile having the large diameter spiral blade is Thus, the upper and lower surfaces of the spiral blade can be used as a supporting force, and there is an effect that the vertical supporting force of the foundation pile can be enhanced. As compared with a conventional pile with a spiral blade used conventionally, it is possible to obtain about twice the supporting force per unit area of the spiral blade.
Also regarding the pull-out force. Similar effects can be obtained.

(2) Drilling of a pile hole using a drilling rod that does not have a means for discharging soil is performed on a ready-made pile having a concrete body. Can be significantly reduced. Even when cement milk is injected and a cement milk layer is formed on the consolidation portion, the amount of soil removal can be limited to the amount corresponding to the injected cement milk.

(3) Previously, the pile buried ground was loosened and a ready-made pile having a spiral bladed concrete body was buried. There is an effect that a foundation pile can be constructed by burying a ready-made pile in ordinary ground without being limited to a specific soft ground. Further, in this case, it is possible to realize the penetration of the ready-made pile without soil removal at a normal practical excavation speed.

(4) By making the excavation diameter of the pile hole shaft part large (for example, up to the maximum diameter of the root consolidation part), the torsion that occurs when screwing a ready-made pile with spiral blades can be controlled to be small. It is possible to design a ready-made pile according to the supporting force required for the construction ground, without being limited to the screw-in strength of the ready-made pile, for example, by reducing the thickness of the spiral blade. Therefore, the present invention can be applied without being limited to the construction ground, and can be economically matched.

(5) In addition, when the ground of the shaft portion of the pile hole is not good, it is possible to obtain a stable and predetermined high supporting force by improving only the ground of the shaft portion.

(6) Depending on the strength of the construction ground, it is possible to make effective use of the frictional resistance of the periphery of the shaft by making the diameter of the shaft excavated by the excavation blade (the range of loosening the ground) smaller than the diameter of the prefabricated pile.

(1) The spiral blade 8 and the auxiliary spiral blade 12 are formed on the outer periphery of the lower end portion of the pile body 1 in which the outside of the concrete body 2 is covered with the outer steel pipe 4 to form a ready-made pile 16 (FIG. 2). The hollow portion 3 of the ready-made pile 16 is open vertically.
(2) The hollow part 3 of the ready-made pile 16 is penetrated by a drilling rod 18 formed by connecting a drilling head 20 to the tip of a rod body 19 that does not form a soil discharging means. (FIG. 4A).
(3) The excavating head 20 is rotated to excavate the pile shaft portion 24 of the D _{21 having} a slightly larger diameter than the pile body without using drilling fluid and without discharging the soil. (FIG. 4 (b)). Simultaneously or alternately, the prefabricated pile 16 is pushed in while rotating, and the prefabricated pile 16 penetrates the ground while being screwed into the ground by the spiral blade 8 (FIG. 4B).
(4) to form an enlarged root consolidated portion 25 of diameter _{D 22} to a predetermined supporting ground drilling head 20 (FIG. 4 (c)).
(5) Cement milk is poured from the lower end of the excavation head 20 into the excavated soil in the enlarged root compaction part 25, and is stirred and mixed to form a soil cement layer 26. Through the hollow part 3, it is raised to the ground. After the soil cement layer 26 is formed, the prefabricated pile is screwed and buried so that the spiral blade 8 and the auxiliary spiral blade 12 are located in the soil cement layer 26 of the expanded root compaction part 25 to form the foundation pile 28 ( FIG. 4 (d) (e)).
(6) The foundation pile 28, by adjusting the drilling diameter D ₂₁ of the excavation head 20, it is possible to reduce the twisting occurring to the ready-made pile 16, the thickness depending on the bearing capacity of the foundation obtained piles of Can be set, and the thickness and the like of the outer steel pipe 4 can be reduced. That is, in this foundation pile, the degree of loosening of the ground, that is, the torsional force generated in the ready-made pile 16 is controlled by adjusting the excavation diameter D21 excavated by the excavation head 20. Can be manufactured. Note that this thickness is slightly different depending on the outer diameter of the ready-made pile, the outer diameter of the spiral blade, and the like.

  An embodiment of the foundation pile of the present invention will be described with reference to FIGS.

[A] Structure of foundation pile

The outer periphery of the concrete body 2 having the hollow portion 3 is covered with an outer steel pipe 4 having an outer diameter D ₁₁ , a thickness t ₁₁ , and a length L ₁₁ to form the pile main body 1.

  Excavation blades (excavation means) 6, 6 protrude from the lower end 1 a of the pile body 1, that is, the lower surface of the end plate 7. The excavation blade 6 is formed by arranging three triangular plate pieces having a high center axis portion of the pile main body 1 at equal intervals. Here, a hollow portion 7 a is formed in the end plate 7 and communicates with the hollow portion 3 of the concrete body 2.

On the outer periphery of the lower end of the pile main body 1, two donut-shaped spiral blade pieces 9 for a half circumference are placed at rotationally symmetric positions in the same rotational direction (at positions shifted by 180 ° in phase or at linearly symmetric positions). Are fixed to form a spiral blade 8. Spiral blade pieces 9, an outer diameter D _12, made of a steel plate having a thickness of t _12, so that the distance L ₁₂ from the upper end 9b to the lower end 9a, and is secured by twisting spirally. The lower end 9a of the spiral blade 8 protrudes slightly below the lower end 1a of the pile main body 1, and excavation projections 10, 10 for excavation protrude from the lower end. The excavating pieces 10, 10 are arranged at different positions in plan view so as to excavate below the excavating blade 8 without fail (FIG. 1 (c)).

At the outer periphery of the lower end portion of the pile main body 1, one round of a donut-shaped steel plate having an outer diameter D ₁₄ and a thickness t ₁₄ is spirally twisted and fixed above the spiral blade 8 to form the auxiliary spiral blade 12. . The auxiliary spiral blade 12 is desirably a spiral shape (spiral shape) having a small earth pressure resistance at the time of screwing in, since the screwing force of the pile at the time of screwing can be reduced. Also formed by a length L ₁₄ to the lower end from an upper end of the auxiliary spiral vane 12. The distance between the spiral blade 8 the auxiliary spiral vane 12 are formed by L _13. Normal distance L ₁₃ is, considering the reliability or the like of the propagation of the shear force at screwing efficiency and roots consolidated layer, it is preferred to the more if possible about pile diameter D _11, short acting load It can be adjusted within a range that satisfies the compressive strength of the solidified expanded bottom rooted portion itself of soil cement that can withstand the above.

  A ready-made pile is constituted as described above (FIG. 1).

[B] Another embodiment

(1) In the above embodiment, a deformed reinforcing bar 14 may be spirally wound and fixed above the auxiliary spiral blade 12 on the outer peripheral portion of the pile main body 1 (shown by a chain line in FIG. 1).

(2) In the above embodiment, the cover 5 may be fixed to the end plate 7 so as to cover the hollow portion 3 and the excavating blades 6 may be fixed to the lower surface of the cover 5 (FIG. 1 (d)). )). Further, the excavating blades 6, 6 can be omitted depending on the ground strength (not shown).

(3) In the above-described embodiment, when the drill is used for the inner digging method, the excavating blades 6 are removed, and the hollow portion 3 is opened up and down without using the lid 5 to form the ready-made pile 16. (FIG. 2).

(4) Further, in the above embodiments, the pile body 1 as the length L ₀ that includes at least the spiral blade 8 and the auxiliary spiral vane 12 (FIG. 1 (a)), can be configured off-the-shelf piles 17 (FIG. 5 (B)). In this case, various other concrete piles 31 (steel pipe-covered concrete piles, concrete piles) are connected above the ready-made piles 17 and used (FIG. 5B).

(5) In the above-described embodiment, the auxiliary spiral blades 12 are also made of two half-circle donut-shaped steel plates in the same rotational direction as the spiral blades 8 in the rotationally symmetric position (in the same rotational direction). 180 ° or a position symmetrical with a straight line, both of which have the same equivalent structure) (not shown). Thereby, the supporting force can be reinforced, the screwing property of the ready-made pile is further improved, and the screwing strength of the spiral blade 8 can be reduced.

(6) In the above embodiment, the auxiliary spiral blade 12 may be omitted. Further, it is sufficient that at least one spiral blade 8 is formed at the lower end, and conversely, a plurality of spiral blades 8 can be additionally provided over the entire length of the pile main body 1 (not shown). That is, in consideration of the adhesive strength to the soil cement and the shear strength, it is appropriately formed so as to be adapted to the required supporting force.

(7) In the above embodiment, the spiral blades 8 are two donut-shaped spiral blade pieces 9 for a half circumference, so that the ready-made pile 15 (16) is easily screwed into the ground, which is preferable. Depending on the case, a steel plate for one round of a donut shape may be spirally twisted (not shown), similarly to the auxiliary spiral blade 12.

  Based on FIGS. 2 to 5, a method of forming the foundation pile 28 by the inside digging method using the ready-made pile 16 having the lower end opened in the first embodiment will be described.

[A] Configuration of drill rod 18

  The drilling rod 18 to be used is configured by attaching a drilling head 20 to the lower end of a straight rod body 19 having no spiral for discharging the earth (FIG. 3). The excavating head 20 is configured such that base ends of excavating arms 22, 22 having excavating blades 22a, 22a formed at the tip are swingably attached to a head body 21 having excavated blades 21a, 21a formed at the lower end.

  When the excavating rod 18 is a construction ground having poor soil quality and is difficult to break, a stirring rod or the like may be protruded at an intermediate portion of the rod main body 19 to assist the excavation head 20 to loosen the ground.

  The excavating arm 22 swings to one side (FIG. 3), and can perform excavation corresponding to a normal shaft diameter of the pile hole, and can swing to the other side to perform enlarged excavation corresponding to the enlarged bottom of the pile hole. It can pass through the hollow part of the ready-made pile without swinging and hanging downward.

Here, the drilling diameter D ₂₁ of the excavation head 20, the torsional force generated when pressing the ready-made pile, are adjusted to prefabricated pile 16 to be used to match the torsional strength held.

[B] Construction method of foundation pile

(1) With the drilling rod 18 inserted through the hollow portion 3 of the ready-made stake 16, and with the digging head 20 protruding from the tip 1a of the ready-made stake 16, the ready-made stake 16 and the drilling rod 18 are connected to a pile driver (shown in the figure). (Not shown) (FIG. 4A).

Next, the drill rod 18 rotates in the forward direction, and excavating the Kuiana shaft portion 24 of the outer diameter D ₂₁ loosen the soil. At the same time, the outer steel pipe 4 of the ready-made pile 16 is rotated forwardly above the excavation head 20, and the ready-made pile 16 is rotated forward and screwed in with the spiral blade 8 (FIG. 4B). At this time, since the small-diameter auxiliary spiral blade 12 is rotated above the large-diameter spiral blade 8, it can be easily screwed into the ground and compacted.

  At this time, since the spiral for discharging the earth is not formed in the rod body 19 of the excavating rod 18, the excavated soil loosened by the excavating head 20 is not discharged to the ground 29 but remains in the pile hole.

Also, here, above the drilling head 20, but Kuiana shaft portion 24 of the diameter D ₂₁ Until helical blade 8 of prefabricated pile 16 is formed, the upper helical blade 8, helix ground blade 8 since the screwed in, Kuianakabe diameter D ₂₁ is collapsed, in a state of excavated soil which loosened the outer periphery of the ready-made pile 16 is pushed.

(2) When the excavating head 20 reaches a predetermined supporting ground, the sinking of the ready-made pile 16 is stopped, the rotation of the excavating rod 18 is switched from forward rotation to reverse rotation, and the excavating arms 22 and 22 of the excavating head 20 are rotated. the is swung to the other side, in the drilling head 20, drilling a larger root consolidated portion 25 of the outer diameter _{D 22} (FIG. 4 (c)). The excavated soil is agitated while excavating with the excavating head 20, and furthermore, cement milk having a predetermined solidification strength is discharged from the excavating head 20 through the hollow portion of the excavating rod 18, and a uniform soil cement layer is formed in the expanded root compaction unit 25. 26 is formed.

(3) Subsequently, the rotation of the excavating rod 1 is temporarily stopped, and the excavating arms 22 and 22 are suspended downward, pulled up to the ground 29 through the hollow portion 3 of the ready-made pile 16 (FIG. 4D), and collected. . At the same time, the prefabricated pile 16 is screwed into the soil cement layer 26 having a predetermined solidification strength by rotating the prefabricated pile 16 and the prefabricated pile 16 is settled until the spiral blade 8 is located at a predetermined position at the lower end of the enlarged root compaction part 25.

(4) When the soil cement layer 26 is solidified, the construction of the foundation pile 28 is completed (FIG. 4E).

In the above, Kuiana the total length _{L 23,} Kuiana shank length _{L 21} of the outer diameter _{D 21,} Kuiana拡底portion 25 of the outer diameter _{D 22} is formed with a length _{L 22} (FIG. 4 (e )).

).

[C] Another embodiment

(1) In the above embodiment, a case where a concrete pile (a ready-made pile, which is not covered with an outer steel pipe) 31 is connected to an upper part using a ready-made pile 17 constituted by using a pile body 1 having a length L ₀ . In this case, the outside of the concrete pile 31 is covered with a steel pipe (casing) 33, and the lower end 34 of the steel pipe 33 is engaged with the outer steel pipe 4 of the ready-made pile 17 for construction. The locking is performed, for example, by locking the notch of the steel pipe 31 to the protrusion 36 protruding from the outer surface of the outer steel pipe 4 (FIG. 5A).

That is, the excavation rod 17 is inserted through the hollow portion 3 of the ready-made piles 31 and 17 covered with the steel pipe 33, and the excavation head 22 rotates the pre-made pile 17 via the steel pipe 33 while breaking the ground in the same manner as described above. Then, it sinks while screwing into the ground (FIG. 5 (a)). When rotating the ready-made pile 17 by rotating the upper end portion 34a of the steel pipe 33 with a pile driving machine and applying a rotational propulsive force to the ready-made pile 17, the concrete pile 31 is structurally harmful. This is preferable because twisting is not applied. In addition, In addition, because the _{L 0} is short can be thinner wall thickness _{t 11} of the ready-made pile 17.

  When the ready-made pile 17 is laid down to the predetermined supporting ground, the steel pipe 33 is removed and collected on the ground (FIG. 5B), and a foundation pile in which the ready-made piles 17 and 31 are buried in the pile holes can be formed. . In this case, the steel pipe 33 can be repeatedly used for the ready-made pile 17 in another foundation pile construction.

  In this case, it is desirable that the connecting portion between the ready-made pile 17 and the concrete pile 31 is positioned and embedded in the enlarged root consolidation portion 25 (soil cement layer 26). Thereby, the strength of the connecting portion can be reinforced.

(2) In the above embodiment, when the ground strength of the pile hole shaft portion 24 is lower than that of the support ground, the ground can also be improved with the pile hole shaft portion 24 (not shown). The ground improvement is performed, for example, by injecting cement milk having various solidification strengths into the shaft of the pile hole. However, earth removal occurs only for the injection amount.

(3) In the above-described embodiment, the excavating head 20 has a thin, downwardly tapering head body 21 and a thin, downwardly bent inner side along the head body 21. In addition, a digging blade 22a that is bent outward and is directed outward is provided (not shown, similar to FIG. 6). Therefore, the excavation efficiency is good at the time of excavation, and the shape of the excavation soil is hardly affected by the excavation soil at the time of lifting. However, if the excavation head 40 having the shape structure shown in FIG. 3 are obtained.

  It is also desirable to use drilling heads 20, 40, but it is also possible to use a drilling head for digging in other structures (not shown).

  Next, a case where the present invention is applied to the pre-drilling method will be described with reference to FIGS.

[A] Configuration of drill rod 38

  The drilling rod 38 used in the embodiment of the present invention is also provided with a drilling head at the lower end of a straight rod body 39 to which spiral or other means for promoting earth removal, kneading means, and stirring means are not attached, as in the second embodiment. 40 (FIGS. 6A and 6B).

  The excavating head 40 is formed with excavating blades 21a, 21a fixed to the lower end thereof, and the base end of the excavating arms 22, 22 having excavating blades 22a, 22a formed at the tip thereof, on the head body 21 which can be joined to the rod main body 39. It is configured to be mounted swingably.

The head body 21, to regulate the maximum amplitude of oscillation of the drilling arm 22 during normal rotation stopper 41, 41 defines a shank drill diameter D ₂₁ of Kuiana, also rocking drilling arm 22 during reverse rotation to regulate the maximum amplitude of movement, the stopper 42, 42 defines a拡底portion diameter D ₂₂ of Kuiana are attached respectively. In addition, a stopper 43 for engaging with the back surface of the excavating arm 22 during the reverse rotation and maintaining the maximum amplitude of the swing of the excavating arm 22 is also attached (FIGS. 6B and 6C).

  Here, the shaft portion excavation diameter D21 is adjusted so that the torsion force generated when the ready-made pile 15 is pushed in conforms to the torsional strength of the ready-made pile 15.

  As in the second embodiment, the excavation rod 38 is provided with a stirring rod or the like at an intermediate portion of the rod body 39 so that the excavation head 40 loosens the ground in the case of construction ground having poor soil quality and hard to break. You can also help.

  The drill rod 38 is configured as described above (FIG. 6).

  In the excavating head 40, the head main body 21 has a plate-like rectangular parallelepiped shape in plan view and is tapered downward (FIGS. 6A, 6B, and 6C). The excavating arms 22, 22 are also thin, are bent inward downward along the head main body 21, are further bent outward at the lower end, and are directed outward. 22a is attached (FIG. 6B).

Therefore, when the excavation head 40 excavates, the excavated soil around the excavation blades 22a, 22a is lifted immediately above, so that the resistance of the excavation blades 21a, 22a to be pushed up can be reduced and the excavation speed can be improved. Therefore, excavation efficiency is good. Further, as compared with the drilling diameter D _21, the cross-sectional area excavation head 40 is occupied by a small (FIG. 6 (d)), when pulled, since less susceptible to resistance of excavated soil present in the pile hole, easy pulling It is. Here, the cross-sectional area of the excavation head 40 needs to be 60% or less of the excavation cross-section, and is desirably 1/3 or less. By using this excavation head 40, as a whole, it is easy to excavate and loosen the construction ground without discharging the excavated soil, and to implement the present invention as an economical construction method in which the excavation head 40 can be easily pulled out. It is suitable.

[B] Construction method of foundation pile 28

(1) the drill rod 38 is supported at a predetermined position, and rotates forward, the drilling arm 22 swings to one side (FIG. 6 (c) (d) a chain line shown 22A), pushing, diameter _{D 21,} drilling Kuiana shaft portion 24 of the length _{L 21} (FIG. 7 (a)). At this time, no excavated water is used and no earth discharging is performed.

(2) When the excavating head 40 reaches a predetermined supporting ground, subsidence is stopped, the rotation of the excavating rod 40 is switched from forward rotation to reverse rotation, and the excavating arm 22 is swung to the other side (see FIG. 6 (c) (d) The excavated bottom 25 of the pile hole having a diameter D ₂₂ and a length L ₂₂ is excavated.

  Subsequently, cement milk having a predetermined solidification strength is discharged from the excavating head 40 through the hollow portion of the excavating rod 38 to form a uniform soil cement layer 26 in the enlarged root compaction part 25 (FIG. 7B). 38 is raised to 29 above the ground.

  At this time, since the soil is not discharged to the ground 29, no cavity is formed in the pile hole shaft portion 24, and the loosened excavated soil is packed.

(3) Subsequently, using the ready-made pile 15 having the excavating blades 6, 6 projecting from the lower end (FIGS. 1A to 1C), the spiral blade 8 is rotated while rotating the ready-made pile 15 in the pile hole. Then, descend while screwing into the ground of the pile hole wall. The spiral blade 8 and the auxiliary spiral blade 12 are positioned and held at predetermined positions on the soil cement layer 26.

  When the soil cement layer 26 is solidified, the foundation pile 28 is formed (FIG. 7C).

[C] Another embodiment

(1) In the examples, using the ready-made pile 17 of length L _0, when used in conjunction with other concrete pile 31 (see FIG. 5 (b)), similarly as in Example 2 Next, the outside of the ready-made piles 17, 31 is covered with a steel pipe 33, and the steel pipe 31 whose lower end 34 is locked to the outer steel pipe 4 is rotated (see FIG. 5A).

  In this case, it is desirable that the connecting portion between the ready-made pile 17 and the concrete pile 31 is positioned and embedded in the enlarged root consolidation portion 25 (soil cement layer 26). Thereby, the strength of the connecting portion can be reinforced.

(2) In the above embodiment, the excavating rod 39 (the excavating head 40) is used. However, for example, another excavating rod such as the excavating rod 20 of the second embodiment can be used (not shown). .

(3) In the above embodiment, the ready-made pile 15 was used, but the ready-made pile 15 (FIG. 1 (d)) with the cover 5 covered on the bottom, and the ready-made pile 16 (FIG. ) Can also be used.

  When the hollow portion 3 is opened without providing the lid 5 at the bottom, the excavated soil can be put into the hollow portion 3, so that the required screwing force can be reduced. When the lid 5 is fixed to the bottom and the hollow portion 3 is closed, the cement milk having high solidification strength is formed in the hollow portion 3 of the ready-made pile 15 after or during the embedding of the ready-made pile 15. And fresh concrete can be filled, and a higher strength foundation pile can be constructed (not shown).

(4) Further, in the above embodiment has formed the enlarged root hardened portion 25 may be a root consolidated portion of the shaft portion diameter D ₂₁ (not shown).

(5) In the above-described embodiment, another excavating head 40 to which the stirring blade 45 is attached can be used (FIG. 8). This excavating head 40 has the same structure as the excavating head 40 shown in FIG.

  That is, the excavation rod 38 is configured by attaching the excavation head 40 to the lower end of the rod body 39 (FIG. 8).

  The excavating head 40 swings the base ends of the excavating arms 22, 22 having excavating blades 22 a, 22 a formed at the distal end, on the head body 21 forming excavating blades 21 a, 21 a fixed to the lower end and being connectable to the rod main body 39. It is configured to be mounted movably.

The head main body 21 has an angular enlarged portion 44 formed at a lower portion, and a stirring blade 45 is attached to the upper portion and the enlarged portion 44. Also, the head body 38 is to regulate the maximum amplitude of oscillation of the drilling arm 22 during normal rotation stopper 41, 41 defines a shank drill diameter D ₂₁ of Kuiana, also drilling arm during reverse rotation 22 to regulate the maximum amplitude of the swing stopper 42, 42 defines a拡底portion diameter D ₂₂ of Kuiana are attached respectively. In addition, a stopper 43 is attached to engage with the back surface of the excavating arm 22 during the reverse rotation to maintain the maximum amplitude of the swing of the excavating arm 22 (FIGS. 8B and 8C).

  The drill rod 33 is configured as described above (FIG. 8).

  In the excavation head 40, the head main body 21 has a plate-like rectangular parallelepiped shape in plan view and is tapered downward (FIGS. 8A, 8B, and 8C). The excavating arms 22, 22 are also thin, are bent inward downward along the head main body 21, are further bent outward at the lower end, and are directed outward. 22a is attached (FIG. 8B).

Therefore, when the excavation head 40 excavates, the excavated soil around the excavation blades 21a, 22a is lifted immediately above, so that the resistance of the excavation blades 22a, 22a to be pushed up can be reduced and the excavation speed can be improved. Excavated soil excavation efficiency is good. Further, as compared with the drilling diameter D _21, the cross-sectional area excavation head 40 is occupied by a small (FIG. 8 (d)), when pulled, since less susceptible to resistance of soil cement present in the pile hole, easy pulling It is. Here, the cross-sectional area of the excavation head 40 needs to be 60% or less of the excavation cross-section, and is desirably 1/3 or less.

Test results

  A vertical loading test and the like were performed on the foundation pile 28 formed by burying the ready-made pile 15 by the so-called excavation method of the third embodiment (FIG. 7C).

[A] Construction of foundation pile 28

(1) Construction ground properties Average N value of the tip of the ready-made pile 15: 30
Soil: sandy soil

(2) Specifications of ready-made pile 15 Length L ₁₁ of pile body 1 of ready-made pile 15 = 15 m
Outer diameter D ₁₁ = 600 mm of pile body 1 of ready-made pile 15
Wall thickness t ₁₁ = 12 mm of outer steel pipe 4 of pile body 1 of ready-made pile 15
Outer diameter D ₁₂ of spiral blade 8 = 1200 mm
Plate thickness t ₁₂ of spiral blade 8 = 40 mm
Length L ₁₂ between upper and lower ends 9b and 9a of spiral blade 8 = 200 mm
Outer diameter D ₁₄ of auxiliary spiral blade 12 = 900 mm
The thickness t ₁₄ of the auxiliary spiral blade 12 is 40 mm.
Length L ₁₄ of upper and lower ends of auxiliary spiral blade 12 = 200 mm
The distance L ₁₃ between the spiral blade 8 and the auxiliary spiral blade 12 is 600 mm.

(3) Kuiana specifications Kuiana: drilling enlarged root hardened portion located shank 24 through _D 21 = 600 + 30mm
The excavation length L ₂₁ of the shaft portion 24 = 13.5 m
Diameter D ₂₂ of expanded root compaction part 25 = 1200 mm
Length L ₂₂ of the expanded root compaction part 25 = 2500 mm
Soil cement solidification strength at the expanded root solidification part 25: 20 N / mm ²

[B] Test results

(1) In formula results long tip supporting force R _p in the vertical loading test,
R _p = α × N _p × A _p
N _p: Pile tip average N values pile bottom from below D, the outer diameter of the average value D = ready pile between the upper 4D _{(= D 12)}
A _p : Cross-sectional area including spiral blade 8 of ready-made pile (effective use part)
In the above, a value of the supporting force coefficient α = about 400 was obtained.

(2) The amount of soil dumped on the ground 29 was about the amount of cement milk injected into the consolidation of pile holes.

(3) The existing piles were buried at the same speed as the conventional construction speed.

(A) is a front view, (b) is a side view, (c) is a bottom view, and (d) is a partial longitudinal sectional view of another embodiment of the ready-made pile according to the embodiment of the present invention. FIG. 3A is a front view, FIG. 3B is a side view, and FIG. 3C is a bottom view of another ready-made pile according to the embodiment of the present invention. FIGS. 6A and 6B are front views of a drill rod used in a second embodiment of the present invention, wherein FIG. (A)-(e) is the outline longitudinal cross-sectional view explaining the construction method of Example 2 of this invention. FIG. 4A is a front view of a ready-made pile according to another embodiment of the present invention, in which FIG. 4A is a partially broken front view and FIG. (A) is a non-rotating front view, (b) is a side view, (c) is a rotating front view, and (d) is a bottom view. Represent each. (A)-(c) is the outline longitudinal cross-sectional view explaining the construction method of Example 3 of this invention. Other rods used in Embodiment 3 of the present invention, (a) is a front view when not rotating, (b) is a side view, (c) is a front view when rotating, and (d) is a bottom view. Respectively.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Pile main body 2 Concrete body 3 Hollow part 4 Shell steel pipe 5 Lid 6 Drilling blade (drilling means)
7 End plate 8 Spiral blade 9 Spiral blade piece 10 Drilling protrusion 12 Auxiliary spiral blade 14 Deformed bar (spiral strip)
15 Ready-made pile 16 Ready-made pile 17 Ready-made pile 18 Drilling rod 19 Rod body 20 Drilling head 21 Head body 22 Drilling arm 24 Pile hole shaft part 25 Expanded root compaction part 26 Soil cement layer 28 Foundation pile 29 Ground 31 Concrete pile 33 Steel pipe (casing) )
38 drilling rod 39 rod body 40 drilling head 41 stopper 42 stopper 43 stopper

Claims (10)

(1) Spiral blades are formed on the outer periphery of the lower end of a concrete pile body whose outside is covered with a steel pipe to constitute a ready-made pile.
(2) The hollow portion of the ready-made stake is penetrated by a digging rod that does not form a soil discharging means, and the digging head of the digging rod protrudes from the lower end of the ready-made stake.
(3) By rotating the excavation head, with a diameter that allows the ready-made pile to be screwed in accordance with the ground strength, without using a drilling liquid, and while excavating a pile hole without discharging the soil, Form loose ground. At the same time or alternately, the ready-made pile is rotated, and the ready-made pile is penetrated into the ground while being screwed into the ground with the spiral blade.
(4) When the excavation head has formed a solidification portion on a predetermined support ground, the excavation head is accommodated, and the hole is lifted to the ground through the hollow portion of the ready-made pile, and the above-mentioned solidification portion is formed in the solidification portion. The foundation pile is formed by burying the ready-made pile so that the spiral blade is positioned.
(5) A method for forming a foundation pile, comprising burying a ready-made pile as described above. (1) Spiral blades are formed on the outer periphery of the lower end of a concrete pile body whose outside is covered with a steel pipe to constitute a ready-made pile.
(2) The excavation head at the tip of the excavation rod has a diameter that allows the ready-made pile to be screwed in accordance with the soil strength, and excavates the ground without using drilling fluid and without discharging the soil. While the ground is loosened, a pile hole having a rooted portion is formed in a predetermined supporting ground.
(3) The prefabricated pile is rotated so that the prefabricated pile is screwed into the ground around the pile hole wall while rotating the prefabricated pile into the pile hole, and the spiral blade is positioned in the root compaction portion. Is buried to create a foundation pile.
(4) A method for forming a foundation pile, comprising burying a ready-made pile as described above. The drilling head excavates an enlarged root compaction having a diameter equal to or larger than the outer diameter of the spiral blade, and positions the spiral blade of the ready-made pile in a soil cement layer formed in the enlarged root compaction. 2. The method for creating a foundation pile according to 2. The method for forming a foundation pile according to any one of claims 1 to 3, wherein the excavation head forms a pile hole or a loosened ground while excavating with a diameter equal to or larger than the outer diameter of the pile body. Construct a ready-made pile to be buried, using a pre-made pile formed by forming spiral blades around the lower end of the concrete pile body whose outside is covered with steel pipe as a lower pile, and other concrete piles as an upper pile,
The foundation pile according to any one of claims 1 to 4, wherein a lower end of the casing covering the upper pile is locked to the lower pile, and an upper end of the casing is rotated to rotate the lower pile. Construction method. A ready-made pile comprising a concrete pile body whose outside is covered with a steel pipe, and a spiral blade formed on an outer periphery of a lower end portion. 7. The ready-made pile according to claim 6, wherein two of the half donut-shaped spiral blade pieces for a half circumference are spirally fixed at rotationally symmetric positions to form a spiral blade. The ready-made pile according to claim 6 or 7, wherein a lower end of the pile main body is closed, and a digging means is protruded from a lower end of the pile main body. At the lower end of the pile main body, two half-donut-shaped spiral blade pieces for a half circumference are spirally fixed at rotationally symmetric positions to form a spiral blade, and an excavation protrusion is protruded from the lower end of the spiral blade. The ready-made pile according to any one of claims 6 to 8, wherein an auxiliary spiral blade having a diameter smaller than the diameter of the spiral blade is formed above the spiral blade in the pile main body.   The ready-made pile according to any one of claims 6 to 9, wherein a spiral strip having a smaller diameter than the auxiliary spiral blade is formed above the spiral blade in the pile main body.

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