JP5577528B2 - Synthetic friction pile - Google Patents

Description

  The present invention relates to a synthetic friction pile used for a foundation pile of soft ground.

  In soft ground, etc., in the center of a columnar body such as soil cement or concrete made by stirring cement milk and excavated earth and sand, a prefabricated pile such as a steel pipe pile or a concrete pile is used as the core material before the columnar body is cured. Synthetic friction piles are often used. FIG. 3 is a conceptual diagram showing this synthetic friction pile, wherein G is the ground, S is a soil cement (columnar body), and 1 is a core material (ready-made pile). The head of the core material 1 is connected to a footing of a structure (not shown) to receive a load, and the outer periphery of the columnar body S is in contact with the surrounding ground G to be frictionally supported.

In the synthetic friction pile, adhesion between the core material and the soil cement columnar body, that is, integration is important. Patent Document 1 describes that a protrusion is formed by rolling on the surface of a steel pipe as a core material, or a protrusion is provided by welding a weld bead or a reinforcing bar.
FIG. 4 is a front view showing a steel pipe with protrusions attached to the surface, FIG. 5 is a perspective view of the same, (a) shows a steel pipe 1 with a vertical rebar 2a attached, and (b) shows a steel pipe 1 surface. A spiral rebar 2b attached, (c) with an annular rebar 2c, and if the angle formed with the horizontal plane of the helix is θ, (a) is θ = 90 degrees and (c) is θ = 0 degrees. It corresponds to. The welded portion is indicated by a bold line.

  FIG. 6 is a graph showing the relationship between load and displacement for (a) and (b). The vertical displacement δ is the amount of settlement of the pile head. In the case of a vertical reinforcing bar, the supporting force is exerted immediately with a small load, while the supporting force decreases as the subsidence progresses, so it is used when the allowable amount of subsidence is small. On the other hand, since the helical reinforcing bar exerts a supporting force gently, it is used when the allowable amount of settlement is large. Therefore, the allowable amount of settlement is 10% of the pile diameter, so vertical bars are optimal for small-diameter piles and helical reinforcing bars are optimal for medium-diameter piles.

  In addition, the steel pipe pile which provided the cyclic | annular reinforcement is described in patent document 2. FIG.

Japanese Patent Laid-Open No. 62-268422 JP 2001-323459 A

  An object of this invention is to implement | achieve the synthetic | combination friction pile from which each of the pile body which attached the vertical reinforcing bar to the surface, and the pile body which attached the helical reinforcing bar can obtain a high bearing force over a wide range.

The present invention excavates the ground into a columnar shape, and inserts a core material into the central portion of the soil cement columnar body formed by mixing and stirring the excavated earth and cement milk before the columnar body is cured, and these are integrated. in the synthesis friction piles which is adapted to exert a circumferential surface frictional force becomes, the core material state, and are not the longitudinal reinforcing bars and the spiral reinforcement attached by a composite on the surface of the pile body, seen from the performance of the ground depending on the required supporting force, a synthetic friction piles which allocations of the spiral reinforcement and the longitudinal reinforcing bars is characterized that you have been adjusted, preferably a previous 1-4 present the Kitate rebar, said helix rebar is the synthetic friction piles characterized that you and 30 to 70 ° the angle with respect to the pile vertically.

  According to the present invention, by adjusting the composition ratio of the longitudinal reinforcing bar and the helical reinforcing bar, a synthetic friction pile that can obtain a high bearing force over a wide range can be easily obtained, and an efficient foundation structure in soft ground or the like is realized. It has an excellent effect.

It is a perspective view which shows the synthetic | combination friction pile of this invention Example. It is a graph which shows the supporting force characteristic in the Example shown in FIG. It is a conceptual diagram which shows the synthetic | combination friction pile concerning this invention. It is a front view which shows the steel pipe which attached the processus | protrusion to the surface in the prior art. It is a perspective view which similarly shows the steel pipe which attached the processus | protrusion to the surface in a prior art. It is a graph which shows the relationship between the load and displacement of the steel pipe which attached the processus | protrusion to the surface in the prior art.

  As described above with reference to FIG. 6, the supporting force is exerted immediately with a small load in the vertical rebar, but the supporting force decreases as the subsidence progresses, whereas the amount of subsidence increases in the helical rebar, and as the subsidence proceeds Supportive power is exhibited gently. Therefore, when these are combined, these characteristics are synthesized, and in the pile body of the present invention, a high bearing force is expressed from the smaller subsidence amount region in the action of the longitudinal rebar part, and then the amount of subsidence increases and the action of the helical rebar increases. The characteristic that the supporting force is maintained as it is is obtained, and as a result, a substantially constant high supporting force can be secured regardless of the amount of settlement.

  In the present invention, a steel pipe pile or a ready-made concrete pile can be used as the pile body. Ready-made concrete piles include reinforced concrete piles (RC piles), prestressed concrete piles (PC piles), high-strength prestressed concrete piles (PHC piles), concrete piles with shell steel pipes (SC piles), high-strength concrete expanded piles (ST Stakes) and the like.

As a method for attaching the wire with projections to the surface of the pile body, it is preferable to use welding when the pile body is a steel pipe pile or a concrete pile with an outer shell steel pipe (SC pile). At this time, it is not necessary to weld all the wire lengths of the wire rod with protrusions, and a predetermined pitch may be provided for discrete welding.
In addition, when the pile body is a precast concrete pile such as a reinforced concrete pile (RC pile), a prestressed concrete pile (PC pile), a high strength prestressed concrete pile (PHC pile), a high strength concrete expanded pile (ST pile), When manufacturing these ready-made concrete piles, a plurality of steel slabs, etc. are formed so as to be exposed on the surface (outer peripheral surface), and wire with a projection is attached to these steel slabs by welding, or ready-made using anchors etc. It is possible to use a method in which a plurality of wire rod fittings are provided on the surface (outer peripheral surface) of a concrete pile, and wire rods with protrusions are attached to these wire rod fittings.

As described above, in the present invention, a steel pipe pile or a ready-made concrete pile can be used as the pile body. However, from the viewpoint of easy mounting of the wire with protrusions, a steel pipe pile or a concrete pile with an outer shell steel pipe (SC pile) And steel pipe piles are most preferred.
Below, the case where a steel pipe (steel pipe pile) is used as a pile body is demonstrated as an example, However, The following description is completely the same also in the case of a ready-made concrete pile.

In the case of a friction pile that penetrates into the columnar body of the improved ground, the bearing capacity of the entire composite pile including the columnar body is between the frictional force between the ground and the columnar body, and between the columnar body and the core material (friction pile). This is the sum of No matter how firmly one is connected, if the other slips, total support cannot be obtained.
The bearing capacity of the pile is evaluated as a load value acting on the pile when a displacement occurs in the pile. Generally, the allowable displacement of the pile is δa, and the vertical load W acting at that time is considered as the supporting force of the pile. The allowable displacement δa of the pile is generally set to a displacement amount corresponding to 10% of the pile diameter. For example, if the pile diameter is 1000 mm, the vertical load acting when the displacement is 100 mm (settlement) is the support force, and if the pile diameter is 100 mm, the vertical load when the pile displacement is 10 mm (settlement) is the support force. Therefore, as the pile diameter is smaller, it is necessary to develop a predetermined supporting force with a smaller amount of displacement, and the load to displacement performance necessary for the pile is defined by the pile diameter.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing three embodiments of the core material in the synthetic friction pile, and all are cases where the pile body as the core material is a steel pipe. A vertical rebar 2a and a helical rebar 2b are combined and attached to the surface of the steel pipe 1. FIG. 1 (a) is mainly composed of the vertical rebar 2a, and the helical rebar 2b is sparsely arranged with a large pitch. Yes. Here, as an example, four vertical reinforcing bars 2a and spiral reinforcing bars 2b are attached at an angle of 70 ° with respect to the pile vertical direction. This example is used when it is desired to obtain a large supporting force at the time of initial settlement, but it is not possible to physically arrange only the vertical reinforcing bars with respect to the steel pipe. A longitudinal reinforcing bar alone cannot provide a supporting force of 300,000 N or more exceeding a predetermined supporting force of 100,000 N. In this example, if the helical rebar 2b is sparsely arranged at an angle of 70 ° with respect to the vertical direction of the pile, and an adhesive force is added to the main longitudinal rebar 2a, the bearing force of 300,000 N + α can be demonstrated. Has an effect.

  In FIG. 1 (c), the spiral reinforcing bar 2b is mainly wound tightly, and a small amount of the vertical reinforcing bar 2a is arranged. Here, as an example, an example is shown in which one vertical reinforcing bar 2a and one helical reinforcing bar 2b are attached at an angle of 30 ° with respect to the pile vertical direction. This example only requires a helical reinforcing bar in terms of supporting force, but is used when it is desired to improve the initial rigidity in order to suppress the amount of settlement. In this example, a predetermined bearing force of 100,000 N can be sufficiently secured only by the helical reinforcing bar 2b, but by adding one longitudinal reinforcing bar 2a, the initial rigidity is increased and the amount of settlement is reduced.

  In FIG. 1 (b), the vertical reinforcing bars 2a and the helical reinforcing bars 2b are arranged approximately equally in the middle of both. Here, as an example, two vertical reinforcing bars 2a and spiral reinforcing bars 2b are attached at an angle of 50 ° with respect to the pile vertical direction. This example is used when it is desired to stably exert a predetermined supporting force over a wide range of the amount of settlement. The predetermined supporting force of 100,000 N cannot be exerted in the initial stage only by the helical rebar 2b alone. In this example, by arranging two vertical reinforcing bars 2a and adding an adhesive force, it has an effect of supplementing the initial insufficient support force and maintaining a total support force of 100,000 N or more.

Hereafter, Fig.1 (a)-FIG.1 (c) are set as Examples 1-3, respectively.
FIG. 2 is a graph showing the supporting force characteristics of the pile bodies of Examples 1 to 3 shown in FIG. The bearing capacity characteristic of each example is a combination of the characteristics of the longitudinal reinforcing bar and the helical reinforcing bar. The effect of the longitudinal reinforcing bar is obtained at a small part of the settlement, and the effect of the helical reinforcing bar is produced at a part where the settlement is large. Appears and exhibits a predetermined supporting force over a wide range of sinking amount.

The bearing force characteristics in the present invention can be variously changed by adjusting the ratio of the configuration of the vertical reinforcing bar and the helical reinforcing bar. In FIG. 2, (a) having a high ratio of vertical reinforcing bars can immediately exert a supporting force from a small amount of subsidence, and conversely (c) having a high proportion of helical reinforcing bars provides a high supporting force even if the amount of subsidence increases. continue.
Therefore, the type (a) mainly composed of vertical reinforcing bars is preferably used when it is desired to obtain a large supporting force at the time of initial (minute) settlement, but only the vertical reinforcing bars cannot be physically disposed on the steel pipe. On the other hand, the type (c) mainly composed of the helical reinforcing bars may be only the helical reinforcing bars in terms of the supporting force, but may be used when it is desired to improve the initial rigidity in order to suppress the initial settlement.

The intermediate type (b) is preferably used when it is desired to stably exert a predetermined supporting force over a wide range of settlement.
If the core material provided with the composite protrusion of the present invention is used, it is possible to effectively utilize the bearing capacity characteristics in a building foundation where the amount of settlement is severe, such as a precision machine factory.
Moreover, since the display ratio of each supporting force characteristic can be adjusted with the attachment ratio of a vertical reinforcing bar and a helical reinforcing bar, the supporting force-subsidence amount characteristic as the whole pile can be controlled easily.

  According to the present invention, by adjusting the composition ratio of the vertical reinforcing bar and the helical reinforcing bar, a synthetic friction pile that can obtain a high bearing force over a wide range can be easily obtained, and an efficient foundation structure in soft ground or the like can be realized. Therefore, there is a remarkable effect in the industry.

1 Core material (off-the-shelf pile, steel pipe)
2 Protrusions 2a Vertical bars 2b Helical bars 2c Ring bars G Ground S Soil cement columnar

Claims (2)

The core material is penetrated into the central part of the soil cement columnar body formed by excavating the ground into a columnar shape and mixing and agitating the excavated soil and cement milk, and the columnar body does not harden. In synthetic friction piles that are designed to exert surface friction,
The core material state, and are not the longitudinal reinforcing bars and the spiral reinforcement attached by a composite on the surface of the pile body, depending on the required supporting force as seen from the performance of the ground, the configuration of the spiral reinforcement and the longitudinal reinforcing bars synthesis friction piles ratio is characterized that you have been adjusted. Before the Kitate rebar and 1-4 present the synthesis friction piles of claim 1, wherein the helical reinforcement is characterized that you and 30 to 70 ° the angle with respect to the pile vertically.

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