JP6497249B2 - Joint pile - Google Patents

Description

  The present disclosure relates to joint piles.

The ready-made piles applied to the pile foundation are roughly classified into support piles and friction piles. The tip (bottom) of the support pile is made to reach the support layer, and the support pile supports the superstructure by an upward force acting on the tip. In the friction pile, the superstructure is supported by the frictional force acting on the peripheral surface of the friction pile.
Conventionally, joint piles have been used as friction piles. The node pile has a main body part (shaft part) and a plurality of annular node parts protruding radially outward from the main body part (see, for example, Patent Document 1).

JP 2012-241500 A

In recent years, the function as a support pile has been required for the joint pile, and the long-term pile material allowable support force is also required for the joint pile. The long-term pile material allowable bearing force depends on the thickness t of the main body of the joint pile and the strength of the concrete constituting the main body.
Here, under the constraint condition that the outer diameter of the node portion is constant, the outer diameter of the main body portion decreases as the protrusion height h of the node portion from the main body portion increases. For this reason, there is a limit to the increase in the wall thickness t of the main body, and there is a limit to the increase in the long-term pile material allowable supporting force of the node pile that depends on the wall thickness t of the main body.

  Under such circumstances, the present inventors have found that in the conventional joint pile, the protrusion height h of the joint is designed to be higher than necessary compared to the necessary joint support pressure. If the protrusion height h of the joint can be reduced, the outer diameter of the main body can be increased, and the wall thickness t of the main body can be increased.

  Therefore, for example, if the outer diameter of the main body is increased so as to surround the base of the conventional node without changing the shape of the node, the protrusion height h of the node can be reduced. However, the stepped surface of the node part usually intersects with the outer peripheral surface of the main body part with an inclination of about 45 °. , Also referred to as the root area Ar). When the root area Ar is reduced, the shear strength of the node is reduced.

  In view of the above circumstances, an object of at least one embodiment of the present invention is to provide a knot pile having improved long-term pile material allowable supporting force while ensuring the shear strength of the knot portion.

(1) The node pile according to at least one embodiment of the present invention is:
A cylindrical body,
And at least one node protruding from the outer peripheral surface of the main body,
The main body portion and the node portion include concrete,
The area occupied by the node on the outer peripheral surface of the main body is defined as a root area Ar, and the area of the node projected in the axial direction of the main body with respect to a surface orthogonal to the main body is defined as a projected area An. In this case, the ratio An / Ar of the projected area An to the root area Ar is 0.069 or more and 0.320 or less.

According to the configuration (1), the ratio An / Ar of the projected area An with respect to the root area Ar is 0.320 or less, which is smaller than the conventional one. The fact that the ratio An / Ar is small means that if the root area Ar is constant, the protrusion height h of the node is small. If the protruding height h of the pile can be reduced, the wall thickness t of the main body portion can be increased instead, and the long-term pile material allowable supporting force can be increased.
On the other hand, the ratio An / Ar of the projected area An to the root area Ar being 0.320 or less means that the root area Ar is large if the protrusion height h of the node is constant. If the root area Ar of the pile can be increased, the shear strength of the node can be ensured.
And according to the said structure (1), the ratio An / Ar of projected area An with respect to root area Ar is 0.069 or more, Therefore Sufficient support pressure by a node part is securable.

(2) In some embodiments, in the configuration (1),
The outer diameter of the main body is more than 400 mm,
The ratio h / t of the protrusion height h to the wall thickness t is 0, where h is the protrusion height of the node portion in the radial direction of the body portion and t is the wall thickness of the body portion. 250 or more and 0.625 or less.

In the joint pile, when the outer diameter of the main body is more than 400 mm, the rate of change of the wall thickness t with respect to the change of the outer diameter of the main body is smaller than when the outer diameter of the main body is 400 mm or less. For this reason, if the ratio h / t of the protrusion height h to the wall thickness t of the main body portion is 0.625 or less in the range where the outer diameter of the main body portion exceeds 400 mm, the wall thickness of the main body portion as compared with the conventional case. It can be said that t is larger than the protrusion height h. Therefore, in the joint pile of the said structure (2), since the outer diameter of a main-body part is over 400 mm and ratio h / t is 0.625 or less, the thickness t of a main-body part is the protrusion height h. Compared with large, long-term pile material allowable bearing force can be increased.
On the other hand, according to the above configuration (2), since the ratio h / t of the protrusion height h to the wall thickness t of the main body portion is 0.25 or more, the supporting pressure by the node portion can be sufficiently ensured. .

  According to at least one embodiment of the present invention, there is provided a node pile having improved long-term pile material allowable support force while ensuring the shear strength of the node portion.

It is a figure which shows roughly the state by which the joint pile concerning one Embodiment of this invention was embed | buried in the ground. The left side of FIG. 2 schematically shows the side face of the nodal pile in FIG. 1, and the right side of FIG. 2 schematically shows the cross section of the nodal pile in FIG. FIG. 3 is an enlarged view of a region III in FIG. 2. It is a figure for demonstrating the projection area of a node part. It is a figure for demonstrating the root area Ar of a node part. In the joint piles of Examples 1 to 45, the outer diameter Dn of the node portion, the outer diameter Dp of the main body portion, the thickness t of the main body portion, the ratio An / Ar of the projected area An to the root area Ar of the node portion, It is a table | surface which shows ratio h / t of the protrusion height h of the node part with respect to the thickness t, and ratio of the long-term pile material allowable support force with respect to a node part supporting pressure. It is a table | surface corresponding to FIG. 6 of Comparative Examples 1-18. It is a graph which shows the relationship between ratio An / Ar and the ratio of long-term pile material allowable bearing force with respect to a node support pressure about the case where the outer diameter Dn of a node is 600 mm, 800 mm, and 1200 mm. It is a graph which shows the relationship between ratio h / t and the ratio of the long-term pile material allowable supporting force with respect to a nodal support pressure about the case where the outer diameter Dn of a nodal part is 600 mm, 800 mm, and 1200 mm. It is a figure which shows roughly the structure of the test apparatus for measuring a node part supporting pressure.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent.
For example, expressions expressing relative or absolute arrangements such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” are strictly In addition to such an arrangement, it is also possible to represent a state of relative displacement with an angle or a distance such that tolerance or the same function can be obtained.
For example, an expression indicating that things such as “identical”, “equal”, and “homogeneous” are in an equal state not only represents an exactly equal state, but also has a tolerance or a difference that can provide the same function. It also represents the existing state.
For example, expressions representing shapes such as quadrangular shapes and cylindrical shapes represent not only geometrically strict shapes such as quadrangular shapes and cylindrical shapes, but also irregularities and chamfers as long as the same effects can be obtained. A shape including a part or the like is also expressed.
On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one constituent element are not exclusive expressions for excluding the existence of the other constituent elements.

  Drawing 1 is a figure showing roughly the state where the node pile concerning one embodiment of the present invention was buried in the ground. In FIG. 1, two node piles 2, 4 and one straight pile 6 are shown. The joint piles 2 and 4 and the straight pile 6 are connected in series to form a single pile (connected pile) 8. The pile 8 can support an upper structure (not shown).

  More specifically, the pile 8 is set inside a pile hole 10 excavated in advance. A root-setting liquid is injected into the bottom of the pile hole 10, and a root-setting part 12 surrounding the lower end of the pile 8 is formed by hardening the root-setting liquid. Moreover, a pile peripheral liquid is inject | poured above the bottom part of the pile hole 10, and the pile peripheral part 14 surrounding the pile 8 is formed when a pile peripheral liquid hardens | cures. The pile 8 is supported by the ground via the root hardening part 12 and the pile peripheral part 14. The root consolidation liquid and the pile circumference liquid each contain a cement component, and the cement component is mixed with the earth and sand generated by excavation of the ground and then hardened to form the root consolidation portion 12 and the pile circumference portion 14 respectively. .

The left side of FIG. 2 schematically shows the side of the joint pile 2 in FIG. 1, and the right side of FIG. 2 schematically shows the cross section of the joint pile 2 in FIG. FIG. 3 is an enlarged view of region III in FIG.
As shown in FIGS. 2 and 3, the joint pile 2 has a main body portion (shaft portion) 16 and a node portion 18 formed integrally with the main body portion 16. The main body 16 and the node 18 are made of concrete. The main body portion 16 has a cylindrical shape. An annular end plate 20 may be fixed to each upper and lower end surface of the main body 16, and a PC steel rod 22 may be bridged between the end plates 20 through the main body 16. Further, the outer peripheral surfaces of both end portions of the main body portion 16 may be covered with a metal cylindrical cover 24, and a helical or linear reinforcing bar (not shown) is embedded in the main body portion 16. It may be.

The node 18 protrudes from the cylindrical outer peripheral surface 26 of the main body 16 in the radial direction of the main body 16. The node portion 18 has an annular shape so as to surround a part of the outer peripheral surface 26 of the main body portion 16. The node 18 has, for example, a cylindrical outer peripheral surface 28, and the outer peripheral surface 26 of the main body 16 and the outer peripheral surface 28 of the node 18 are arranged concentrically. Further, the node portion 18 has, for example, tapered step surfaces 30 on both sides in the axial direction of the main body portion 16, and the outer peripheral surface 26 of the main body portion 16 and the outer peripheral surface 28 of the node portion 18 form the step surface 30. It is connected through. For example, the angle θ formed by the outer peripheral surface 26 of the main body 16 and the step surface 30 is 45 °.
As shown in FIG. 3, the thickness t of the main body 16 is determined by the difference between the inner diameter Di and the outer diameter Dp of the main body 16 (t = (Dp−Di) / 2). The protruding height h of the node 18 in the radial direction is determined by the difference between the outer diameter Dp of the main body 16 and the outer diameter Dn of the node 18 (h = (Dn−Dp) / 2).

  FIG. 4 is a diagram for explaining the projected area An of the node portion 18, and the node of the node pile 2 in the axial direction of the main body portion 16 with respect to a plane orthogonal to the axial direction of the main body portion 16 of the node pile 2. FIG. 6 is a projection view in which a unit 18 is projected. The projected area An of the node 18 corresponds to the area of the hatched area in FIG. The projected area An is determined by the outer diameter Dn of the node 18 and the outer diameter Dp of the body 16 regardless of the angle θ of the stepped surface 30 of the node 18 with respect to the body 16.

  FIG. 5 is a perspective view schematically showing the joint 18 of the joint pile 2 and its periphery, and is a diagram for explaining the exclusive area (root area Ar) of the joint 18 on the outer peripheral surface 26 of the main body 16. is there. The root area Ar corresponds to the area of the cylindrical region with hatching in FIG. The cylindrical region corresponds to the boundary between the main body 16 and the node 18 and is determined by the circumferential length of the node 18 on the outer peripheral surface 26 of the main body 16 and the axial length La.

Here, in the above-mentioned node pile 2, the ratio An / Ar of the projected area An to the root area Ar is configured to be 0.069 or more and 0.320 or less.
According to the joint pile 2 of the said structure, ratio An / Ar of projected area An with respect to root area Ar is 0.320 or less, and is small compared with the past. The fact that the ratio An / Ar is small means that if the root area Ar is constant, the protruding height h of the node 18 is small. If the protrusion height h of the node portion 18 can be reduced, the wall thickness t of the main body portion 16 can be increased instead. The long-term pile material allowable bearing capacity depends on the thickness t of the main body portion 16 of the joint pile 2 and the strength of the concrete constituting the main body portion 16, so that the long-term pile material can be increased if the thickness t of the main body portion can be increased. The allowable supporting force can be increased.

  On the other hand, the ratio An / Ar of the projected area An to the root area Ar being 0.320 or less means that the root area Ar is large if the protrusion height h of the node 18 is constant. If the root area Ar of the node 18 can be increased, the shear strength of the node 18 can be ensured.

  On the other hand, according to the above configuration, the ratio An / Ar of the projected area An to the root area Ar is 0.069 or more, so that the bearing pressure by the node 18 can be sufficiently ensured.

  In some embodiments, the outer diameter Dp of the main body portion 16 is more than 400 mm, and the ratio h / t of the protrusion height h of the node portion 18 to the thickness t of the main body portion 16 is 0.250 or more and 0.00. 625 or less.

In the joint pile 2, when the outer diameter Dp of the main body portion 16 is more than 400 mm, the rate of change of the wall thickness t with respect to the change of the outer diameter Dp of the main body portion 16 is larger than that when the outer diameter Dp of the main body portion 16 is 400 mm or less. small. For this reason, if the ratio h / t of the protrusion height h of the node portion 18 to the wall thickness t of the main body portion 16 is 0.625 or less in the range where the outer diameter D of the main body portion 16 exceeds 400 mm, compared to the conventional case. Thus, it can be said that the thickness t of the main body portion is larger than the protruding height h of the node portion 18. Therefore, in the joint pile 2, if the outer diameter Dp of the main body portion 16 is more than 400 mm and the ratio h / t is 0.625 or less, the thickness t of the main body portion is larger than the protruding height h. It is possible to increase the long-term pile material allowable bearing force.
On the other hand, if the ratio h / t of the protrusion height h of the node portion 18 to the wall thickness t of the main body portion 16 is set to 0.25 or more, the supporting pressure by the node portion 18 can be sufficiently ensured.

  In some embodiments, the joint pile 2 is a hollow ready-made pile and is a high strength prestressed concrete pile (PHC pile), but is a reinforced concrete pile (RC pile) or a high strength prestressed reinforced concrete pile (PRC pile). There may be.

  In some embodiments, the angle θ of the stepped surface 30 of the node 18 is not less than 45 ° and less than 90 °.

[Examples and Comparative Examples]
FIG. 6 shows the projected area An of the outer diameter Dn of the node portion 18, the outer diameter Dp of the main body portion 16, the wall thickness t of the main body portion 16, and the root area Ar of the node portion 18. It is a table | surface which shows ratio An / Ar, ratio h / t of the protrusion height h of the node part 18 with respect to the thickness t of the main-body part 16, and ratio of the long-term pile material allowable support force with respect to a node part supporting pressure.
FIG. 7 is a table corresponding to FIG. 6 of Comparative Examples 1 to 18.
FIG. 8 is a graph showing the relationship between the ratio An / Ar and the ratio of the long-term pile material allowable bearing force to the nodal support pressure when the outer diameter Dn of the nodal portion 18 is 600 mm, 800 mm, and 1200 mm.

FIG. 9 is a graph showing the relationship between the ratio h / t and the ratio of the long-term pile material allowable bearing force to the node support pressure when the outer diameter Dn of the node 18 is 600 mm, 800 mm, and 1200 mm.
FIG. 10 is a diagram schematically showing the configuration of a test apparatus for measuring the nodal support pressure.
In addition, the angle θ of the step surface 30 of the node portion 18 with respect to the outer peripheral surface 26 of the main body portion 16 is 45 ° in all of Examples 1 to 45 and Comparative Examples 1 to 18.

From FIG. 8, when comparing each outer diameter Dn of the node portion 18, the ratio An / Ar is more than 0.320 when the ratio An / Ar of the projected area An to the root area Ar is 0.320 or less. It can be seen that the ratio of the long-term pile material allowable bearing force to the node support pressure is larger than the case.
Further, from FIG. 9, when the outer diameter Dp of the main body portion 16 is more than 400 mm, when compared with each outer diameter Dn of the node portion 18, the protrusion height h of the node portion 18 with respect to the wall thickness t of the main body portion 16. It can be seen that when the ratio h / t is 0.625 or less, the ratio of the long-term pile allowable bearing force to the nodal support pressure is larger than when the ratio h / t is more than 0.625. .

  The nodal support pressure is a support pressure obtained by each nodal part 18 and can be obtained by, for example, the test apparatus 40 shown in FIG. For the measurement of the nodal support pressure, a part of the nodal pile 2 including the nodal portion 18 is provided. A part of the joint pile 2 is surrounded by a soil cement 42 corresponding to the root consolidation part 12 or the pile peripheral part 14, and further surrounded by a steel restraint pipe 44, whereby a test body 46 is formed. The test apparatus 40 includes a support base 48 that can support the soil cement 42 of the test body 46, a press apparatus 50 that can apply a downward load to a part of the joint pile 2 in the test body 46, and the soil cement 42. And a displacement meter 52 capable of detecting a relative displacement of a part of the joint pile 2. The nodal support pressure is obtained as a load when relative displacement occurs.

  In addition, although this embodiment demonstrated the cylindrical-shaped node pile, it is not limited to this shape, For example, it can apply also to rectangular node piles, such as a triangular cylinder shape and a square cylinder shape.

  Finally, the present invention is not limited to the above-described embodiments, and includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.

2, 4 Node pile 6 Straight pile 8 Pile 10 Pile hole 12 Root consolidation part 14 Pile circumference 16 Body part (shaft part)
18 Node 20 End Plate 22 PC Steel Bar 24 Cover 26 Outer Peripheral Surface (Shaft)
28 Outer peripheral surface (node)
30 Stepped surface 40 Test device 42 Soil cement 44 Restraint tube 46 Specimen 48 Support base 50 Press device 52 Displacement meter Dp Main body outer diameter Dn Nodal outer diameter An Nodal projection area Ar Nodal root area h Nodal Projection height t of the main body Thickness La of the main body Axis length θ of the node on the main body side Step surface angle

Claims (2)

A cylindrical body,
And at least one node protruding from the outer peripheral surface of the main body,
The main body portion and the node portion include concrete,
The area occupied by the node on the outer peripheral surface of the main body is defined as a root area Ar, and the area of the node projected in the axial direction of the main body with respect to a surface orthogonal to the main body is defined as a projected area An. The ratio An / Ar of the projected area An to the root area Ar is 0.069 or more and 0.320 or less. The outer diameter of the main body is more than 400 mm,
The ratio h / t of the protrusion height h to the wall thickness t is 0, where h is the protrusion height of the node portion in the radial direction of the body portion and t is the wall thickness of the body portion. The joint pile according to claim 1, wherein the pile is not less than 250 and not more than 0.625.

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