JP2012031667A - Construction method for peg-top type pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a peg-top type pile that facilitates construction and that makes a construction cost and a transportation cost low, and a construction method for the same.SOLUTION: A peg-top type pile includes a peg-top foundation body that has a horizontal plane at an upper end and that is provided with a tapered portion having a diameter reduced downward, and a pivot foot portion that is elongated downward from a lower end of the peg-top foundation body. A construction method for the peg-top type pile comprises: a burying step of burying a pile for forming the pivot foot portion, in the ground; a recess forming step of exposing the pile by removing and/or consolidating an area at a peripheral edge of an upper end of the buried pile and of forming a tapered recess; a reinforcing step of installing a reinforcing member for reinforcing the peg-top foundation body, at the upper end of the pile; and a peg-top foundation body forming step of placing concrete in the tapered recess.

Description

  The present invention relates to a method for constructing a top-type pile in which a top foundation is integrated with the upper end of a normal ready-made pile.

  A frame foundation is known as a pile for stabilizing the ground and reinforcing the foundation (for example, Patent Documents 1 and 2). As shown in FIG. 4, the top of the frame is provided with a body 100 having a horizontal surface at the upper end and a diameter decreasing downward, and a shaft foot 101 is provided downward from the lower end of the body 100. Yes. Since the trunk | drum 100 has spread the taper shape upwards, the frame foundation can disperse | distribute stress diagonally downward and can disperse | distribute a foundation load widely. Further, since the shaft foot 101 is pierced into the ground, the frictional force between the shaft foot and the ground becomes a force that supports the load. For this reason, it is possible to stabilize the ground and strengthen the foundation.

  Further, Patent Document 3 describes an invention in which a cylindrical ready-made pile having a threaded portion at the upper end is driven into the ground, and a piece foundation is screwed into the threaded portion at the upper end to form a piece foundation with a long shaft foot portion. Yes. According to the present invention, the supporting force can be ensured by a large frictional force between the ground and the long shaft foot portion.

JP 51-125905 A JP 61-151315 A Japanese Patent Laid-Open No. 4-14525

  When constructing the top foundation, as shown in FIG. 5, first, a hole 103 is first dug in the ground 102, the shaft leg 101 is pierced vertically, and the hole is filled again. . At this time, if the ground is soft, clogged crushed stone 104 should be applied around the trunk portion 100 to make it hard. For this reason, there was a problem that a lot of labor was required for the construction, and the construction cost was high. In addition, since the shaft foot 101 protrudes downward from the lower end of the body 100 having a large diameter, there is a problem that it is difficult to efficiently stack and load it on a transport vehicle, and the transportation cost is high. Furthermore, if the shaft foot 101 is lengthened, the frictional force between the shaft foot 101 and the ground 102 is increased and the supporting force is increased, but the center of gravity is increased and becomes unstable, so that the construction of the shaft foot 101 becomes difficult. .

  In this regard, if the frame base is a long frame foot part in which the frame foundation is screwed to the upper end of the ready-made pile of Patent Document 3, the frame foundation part and the ready-made pile part are separated before construction. It can be efficiently stacked and loaded on the car, reducing the transportation cost. In addition, the frictional force between the shaft foot and the ground increases and the supporting force increases.

  However, the work of screwing a large and heavy piece foundation to the upper end of the ready-made pile has to be done in the air, and screwing the piece foundation having a large diameter is accompanied by the difficulty of the work.

  The present invention has been made in view of the above-mentioned conventional circumstances, and has a construction method for a top-type pile that has a large supporting force, is easy to construct, has high pile strength, and has low construction costs and transportation costs. Providing is a problem to be solved.

  The method for constructing a top pile according to the present invention includes a top base body having a tapered portion that has a horizontal surface at the upper end and has a diameter reduced downward, and a shaft foot portion that extends downward from the lower end of the top base body. A method of constructing a top-type pile, comprising: an embedding step of embedding a pile for forming the shaft foot portion in the ground; and removing and / or compacting an upper end peripheral region of the embedded pile. A step of forming a concave portion that exposes and forms a tapered concave portion in the ground; a step of reinforcing a reinforcing member for reinforcing the top of the top of the top of the pile; and placing concrete in the tapered concave portion. And a top base body forming step for forming the top base body.

  In the construction method of the top type pile of this invention, the pile for forming a shaft leg part is first embed | buried as an embedding process. This pile is not provided with a trunk which is a feature of the top type pile. The method for burying the pile is not particularly limited. For example, a method using a pile driving machine that drops a large hammer from a known pile such as a PC steel pipe pile, PHC pile, RC pile, or SC pile, or drives it using vibration, or lifts its own weight with a crane. There are a method of press-fitting, a method using the machine weight and the weight of the base machine to which a weight block or a hydraulic cylinder is attached, and a method of press-fitting while rotating a PC pile or a steel pipe pile.

And next, as a recessed part formation process, while removing and / or compacting the upper-end peripheral area | region of this buried pile, this pile is exposed, and a taper-shaped recessed part is formed in the ground. The method using the consolidation of the ground for the formation of the tapered recess is particularly preferable because the strength of the ground is increased by the consolidation and the reinforcement effect of the foundation by the top pile is further improved.
The removal and / or consolidation method and the range of the region are not particularly limited. However, since the shape and size of the tapered recess formed in the recess forming process directly determines the shape and size of the trunk of the top pile, the supporting force required for the top pile, It is determined appropriately considering the hardness of the ground. The removal region can be a conical region or a pyramid region centered on the axis of the pile, but the conical region is particularly preferable. This is because the conical shape can equalize the stress applied to the tapered portion. Moreover, it is preferable that the maximum diameter D of the frame base body is in a range of 2 to 3 times the diameter d of the shaft foot. When the maximum diameter D of the top foundation body is less than twice the diameter d of the shaft foot, the area where the taper portion of the top foundation body contacts the ground is relatively smaller than the area where the shaft foot contacts the ground. The stress that supports the ground by the tapered portion of the top foundation main body becomes small, and the ground supporting force by the tapered portion of the top basic body may be insufficient. In addition, if the maximum diameter D of the top foundation body exceeds three times the diameter d of the shaft foot, the area where the shaft foot and the ground come into contact with each other becomes relatively small, so that the ground support force by the shaft foot is insufficient. There is a risk.
Further, the inclination angle of the tapered recess with respect to the horizontal plane is preferably 20 ° or more and 45 ° or less. If it is like this, the stress concerning a pile can be disperse | distributed diagonally downward, and a foundation load can be widely disperse | distributed.

  After completion of the recess forming process, a reinforcing member for reinforcing the trunk is installed at the upper end of the pile (reinforcing process). The reinforcing member plays a role as a reinforcing material for enhancing the integration of the pile and the top of the pile and increasing the strength of the trunk of the piece-shaped pile, and uses a high-strength reinforcing bar used for reinforced concrete. It is preferable.

  Although there is no particular limitation on the shape of the reinforcing member, it may have an annular reinforcing portion that surrounds the upper peripheral surface of the pile, and an oblique reinforcing portion that extends diagonally downward and radially inward from the annular reinforcing portion. preferable. If it is like this, the contact area of the concrete and the reinforcement member in the trunk | drum of a top-type pile will become large, and the integration and intensity | strength of the trunk | drum of a top-type pile can be made excellent. Moreover, when using a reinforcing bar for a reinforcement member, it is preferable to set it as a deformed reinforcing bar. If it is like this, the contact area of a reinforcing bar and concrete will increase, and the top type pile can be made more excellent in mechanical strength.

  Finally, concrete is placed in the tapered recess as the top foundation main body forming step. Thereby, a taper-shaped recessed part plays the role of a formwork, and a frame | base foundation main body is formed. That is, in the method for constructing a top pile according to the present invention, a top foundation body having a tapered portion, which is a feature of the top pile, is formed on the top of the pile embedded in the embedding process with concrete made in the field. For this reason, unlike the conventional method of constructing a top-type pile, the existing foot-type pile is suspended with a crane and the tip of the top-type pile is driven by its own weight. Since it can be erected, it is easy to embed the shaft foot. Moreover, since it becomes easy to embed the shaft foot part deep into the ground, it becomes easy to reach the shaft foot part to the support ground. Moreover, the supporting force of the ground is significantly improved by a large frictional force between the ground and the shaft foot. In addition, it is possible to work without the need to crush clogged stones around the trunk of the top of the top of the top of the top of the top of the top of the top of the top of the top of the top of the top of the top of the top of the top of the top of the top of the top of the top as well. Therefore, the construction cost can be reduced. Furthermore, since the trunk is made of cast-in-place concrete, the transportation cost is low, unlike the case where the existing top-shaped pile with an unstable shape is transported. In addition, when the pile is hollow and a reinforcing member is also provided in the pile, the adhesion force of the concrete entering the pile is improved, and the pile and the piece foundation are integrated. The strength of the pile is increased.

  Therefore, according to the construction method of the top type pile of this invention, construction is easy, the intensity | strength of a pile becomes high, and construction cost and transportation cost become low.

It is a schematic diagram which shows embedding process S1 and recessed part formation process S2 in an Example. It is a schematic diagram which shows reinforcement process S3 and the top foundation main body formation process S4 in an Example. It is a perspective view of the steel pipe upper end part which mounted the reinforcement member. It is a perspective view of the conventional piece type pile. It is process drawing which shows the construction method of the conventional top type | form pile.

  Hereinafter, the Example of the construction method of the top type | form pile of this invention is described in detail based on drawing.

Example 1
<Embedding process S1>
In the construction method of the top-type pile of Example 1, first, the steel pipe 12 having a diameter of 100 mm is set on a steel pipe pile construction machine (not shown), and the steel pipe 12 is embedded by being rotationally inserted until the upper end of the steel pipe 12 is slightly below the ground line ( FIG. 1 (a) (b)).

<Recess formation step S2>
Next, as shown in FIG.1 (c), the soil of the upper-end peripheral area of the steel pipe 12 is removed with a hydraulic shovel or a scoop so that the inclination angle of the tapered portion with respect to the horizontal plane is 30 ° and the maximum diameter is 300 mm. An inverted conical tapered recess 13 is formed. Instead of removing the soil in the upper edge region, the tapered recess may be formed by compacting using a hydraulic jack or the like, or by using soil removal and compaction together. If this is the case, the strength of the ground will increase due to the compaction of the soil, and the reinforcement effect of the foundation by the top type pile will be further improved.

<Reinforcing step S3>
Further, as shown in FIG. 2 (d), a reinforcing bar 14 as a reinforcing member is installed at the upper end of the steel pipe 12. As shown in FIG. 3, the reinforcing reinforcing bars 14 include a cross reinforcing bar 14 a that is joined in a cross shape and placed on the upper end of the steel pipe 12, and a hairpin type that fixes the cross reinforcing bar 14 a at predetermined four positions on the upper end of the steel pipe 12. A reinforcing bar 14b and an annular reinforcing bar 14c surrounding the upper peripheral surface of the steel pipe 12 and welded to the end of the cross reinforcing bar 14a are provided. In addition, four diagonal reinforcing bars 14d extending from the annular reinforcing bar 14c in a radially inward direction of 30 ° downward are welded to the annular reinforcing bar 14c and the hairpin type reinforcing bar 14b. In addition, a wooden round frame 14e is suspended from the cross rebar 14a by a hanging string 14f at a position slightly lower than the upper end inside the steel pipe 12.

<Frame basic body formation process S4>
And finally, as shown in FIG.2 (e), concrete is cast in the taper-shaped recessed part 13, and an upper surface is finished flush. In this manner, the top-shaped pile 16 in which the inverted conical body portion 15 and the steel pipe 12 are joined is completed.

  As described above, in the method for constructing the top-shaped pile 16, the inverted conical body portion 15 is formed of on-site concrete at the upper end portion of the steel pipe 12 embedded in the embedding step S1. That is, since the trunk portion is not combined with the steel pipe 12 at the time of the embedding step S1, a normal pile driving machine can be used without using a special construction method for embedding. For this reason, the steel pipe 12 can be driven and stood by a conventional pile driving machine, unlike the case where an existing top pile is suspended by a crane and the top of the top pile is driven by its own weight. The construction of 12 burials becomes easy. Moreover, since it becomes easy to embed the steel pipe 12 deeply in the ground, it becomes easy to reach the steel pipe 12 to the support ground. Further, the ground support force is greatly improved by the large frictional force between the ground 10 and the steel pipe 12. Furthermore, it is possible to work without the need to crush and crush clogged stones around the trunk of the top of the top type pile, as with conventional existing top type piles. However, the construction cost can be reduced. Furthermore, since the trunk | drum 15 is formed with cast-in-place concrete, the transportation cost also becomes low unlike conveying the existing top-shaped pile of an unstable shape.

  Therefore, according to the construction method of the top pile according to the embodiment, the construction is easy, and the construction cost and the transportation cost are low.

  The present invention is not limited to the description of the embodiments and examples of the invention described above. Various modifications are also included in the present invention as long as those skilled in the art can easily conceive without departing from the scope of the claims.

10 ... Ground 12 ... Steel pipe (pile)
DESCRIPTION OF SYMBOLS 13 ... Tapered recessed part 14 ... Reinforcing bar 14c ... Annular reinforcing bar 14d ... Diagonal reinforcing bar 15 ... Trunk 16 ... Koma type pile

Claims (5)

It is a construction method of a top-type pile comprising a top base body having a tapered portion that has a horizontal surface at the upper end and has a diameter reduced toward the lower side, and a shaft foot part extending downward from the lower end of the top base body,
A burying step of burying a pile for forming the shaft foot part in the ground;
A recess forming step of removing and / or compacting the upper end peripheral region of the buried pile to expose the pile and forming a tapered recess in the ground;
A reinforcing step of installing a reinforcing member for reinforcing the top foundation body at the upper end of the pile;
A top foundation body forming step for forming the top foundation body by placing concrete in the tapered recess;
A method for constructing a top-type pile characterized by including:   2. The top type of claim 1, wherein the reinforcing member includes an annular reinforcing portion that surrounds the upper peripheral surface of the pile, and an oblique reinforcing portion that extends obliquely downward and radially inward from the annular reinforcing portion. Pile construction method.   The method for constructing a top pile according to claim 1 or 2, wherein the tapered portion of the top base body has a conical shape.   The method for constructing a top pile according to any one of claims 1 to 3, wherein the maximum diameter D of the top foundation body is in a range of 2 to 4 times the diameter d of the shaft foot.   The method for constructing a top-type pile according to any one of claims 1 to 4, wherein an inclination angle of the taper portion with respect to a horizontal plane is 20 ° or more and 45 ° or less.

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