JP2017172328A - Cast-in-place steel pipe concrete pile and steel pipe thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cast-in-place steel pipe concrete pile and a steel pipe thereof, capable of integrating the steel pipe and concrete, and capable of also setting a dimension of a spacer properly in response to an excavation hole diameter, while making a reinforced cage passable in the steel pipe.SOLUTION: In a cast-in-place steel pipe concrete pile composed of a steel pipe 1 installed in an excavation hole upper part, a reinforced cage having a plurality of spacers on the outer periphery and built up in an excavation hole via the inside of the steel pipe 1 and concrete placed in the excavation hole, a plurality of restricting members 2 for restricting axial directional dislocation between the steel pipe and hardened concrete are provided at an interval in the circumferential direction on the inner periphery of the steel pipe 1, and when building up the reinforced cage, the spacers are made passable between the restricting members 2 and 2, and a reinforcement member is provided on the outer periphery of the steel pipe at least just above the restricting members in the axial direction of the steel pipe.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cast-in-place steel pipe concrete pile and its steel pipe.

  For example, the cast-in-place steel pipe concrete pile method known as the KCTB method is a method of installing a steel pipe having a spiral inner surface protrusion around the head of the cast-in-place concrete pile so as to surround it.

  According to this method, the pile head is reinforced with a steel pipe integrated with concrete by spiral protrusions, so the necessary pile strength against large bending moment and shear force can be obtained without increasing the cross-sectional area of the pile head. It is done. At the same time, high deformation performance (toughness) can be obtained, and the earthquake resistance can be further improved. Compared with cast-in-place concrete piles made of ordinary reinforced concrete, the pile head can be made thinner, so when combined with the expanded pile method, the construction period can be shortened and the amount of concrete and excavated soil can be reduced. .

  However, a steel pipe having a spiral inner protrusion is made by a manufacturing method in which a strip-shaped steel plate having a large number of protrusions is formed into a cylindrical shape by rounding it into a spiral shape, which leads to higher delivery problems and costs. There are difficulties.

  Moreover, in the cast-in-place concrete pile construction method, there are a case where the inside of the steel pipe is made of concrete only (SC type) and a case where the steel pipe is made of reinforced concrete (SRC type). In the case of the SRC type, the reinforcing bar is as shown in FIG. It is built in the excavation hole. That is, as shown in FIG. 2A, the casing 50 is built in the upper part of the excavation hole formed in the ground, and the steel pipe 51 is deposited in the casing 50. The rebar bar 52 is generally unitized to a predetermined length, and the rebar bar unit 52 is built into the excavation hole 53 through the inside of the steel pipe 51 while being sequentially connected.

  A plurality of spacers 54 are provided on the outer periphery of the reinforcing bar rod unit 52 to hold the reinforcing bar rod at the axis of the excavation hole 53. However, since the steel pipe 51 has the spiral protrusion 55 on the inner surface as described above (see FIG. 5B), in order to allow the rebar rod unit 52 to pass through the steel pipe 51, the spacer Therefore, it is necessary to reduce the radial projecting dimension of the 54 reinforcing bar rod units 52. As a result, although the spacer 54 has passed through the steel pipe 51, the spacer 54 is greatly separated from the hole wall of the excavation hole 53, and the function as the spacer is not achieved.

  Although it does not mention the said problem, as what is described below as a prior art literature regarding a cast-in-place steel pipe concrete pile, the following can be mentioned, for example.

JP 2002-4271 A JP 2011-74569 A

The present invention has been made based on the technical background as described above, and achieves the following object.
The object of the present invention is to integrate the steel pipe and the concrete without using a steel pipe having spiral projections, which increases the cost, and in addition, allows the reinforcing bar rod to pass through the steel pipe, while the reinforcing bar of the spacer. PROBLEM TO BE SOLVED: To provide a cast-in-place steel pipe concrete pile and its steel pipe, in which the projecting dimension from the ridge can be made appropriate according to the diameter of the digging hole, and thereby the reinforcing bar can be held in the digging hole axis. .

  As described above, the spiral protrusions that limit the protruding dimension of the spacer from the reinforcing bar are for increasing the adhesive force between the concrete and the steel pipe and restraining the axial displacement of the hardened concrete. Thus, as a result of extensive studies, the inventors of the present invention have found that the hardened concrete can be sufficiently constrained by simply forming a ring-shaped protrusion on the inner surface of the steel pipe without using a spiral shape. It was. However, since the size of the spacer is still limited, the following solution has been found to solve this.

That is, this invention has a steel pipe installed at the upper part of the excavation hole, a plurality of spacers on the outer periphery, a reinforcing bar to be built into the excavation hole through the steel pipe, and a concrete to be cast into the excavation hole, A cast-in-place steel pipe concrete pile consisting of
A plurality of restraining members for restraining axial displacement between the steel pipe and the hardened concrete are provided at intervals in the circumferential direction on the inner periphery of the steel pipe, and the spacer is used when the reinforcing bar is installed. It is in a cast-in-place steel pipe concrete pile characterized by being able to pass between.

  In the cast-in-place steel pipe concrete pile, a reinforcing member may be provided at least directly above the restraining member and on the outer periphery of the steel pipe. Further, a plurality of bleeding treatment members for preventing the separated water due to the concrete bleeding from rising toward the restraining member below the restraining member and on the inner periphery of the steel pipe, It may be provided with an interval corresponding to.

Further, the present invention is a steel pipe for a cast-in-place steel pipe concrete pile, which is installed in the upper part of the excavation hole, and a reinforcing bar having a plurality of spacers on the outer periphery is built in the excavation hole,
A plurality of restraining members for restraining axial displacement between the steel pipe and the hardened concrete are provided on the inner periphery at intervals in the circumferential direction, and the spacer passes between the restraining members when the reinforcing bar is installed. It is in cast-in-place steel pipe for concrete pile.

  In the cast-in-place concrete pile steel pipe, a reinforcing member may be provided at least directly above the restraining member and on the outer periphery of the steel pipe. Further, a plurality of bleeding treatment members for preventing the separated water due to the concrete bleeding from rising toward the restraining member below the restraining member and on the inner periphery of the steel pipe, It may be provided with an interval corresponding to.

  According to the present invention, since the concrete and the steel pipe are integrated by providing a plurality of restraining members on the inner periphery of the steel pipe, the steel pipe can be obtained by rounding a normal flat steel sheet, The delivery time can be shortened and the cost can be reduced. In addition, since a space is formed between the plurality of restraining members, the spacer can pass between the restraining members when the reinforcing bar is installed. Thereby, the protrusion dimension from the reinforcing bar rod of a spacer can be made into the big thing which the front-end | tip almost reaches the inner periphery of a steel pipe. As a result, the outer peripheral end of the spacer is positioned near the hole wall of the excavation hole, and the spacer exhibits the original function of holding the reinforcing bar rod at the axial center of the excavation hole.

Embodiment of the steel pipe by this invention is shown, (a) is a top view, (b) is an axial sectional view. The other embodiment of a steel pipe is shown, (a) is a top view, (b) is an axial sectional view. It is a top view which shows the example of a form of a restraint member. It is an axial direction sectional view showing other examples of a restraining member. It is a vertical direction sectional view which shows the construction procedure of the cast-in-place steel pipe concrete pile by this invention. FIG. 6 is a vertical sectional view showing a construction procedure subsequent to FIG. 5. It is sectional drawing explaining the expansion pressure which acts on a steel pipe by the force which pushes out the concrete in a steel pipe. It is the schematic diagram (a) for demonstrating the relationship between the expansion pressure which acts on a steel pipe, and the tensile force generate | occur | produced in the steel pipe circumferential direction, and the graph (b) which shows the relationship between a restraint pressure and D / t. It is an axial direction sectional view showing another embodiment of a steel pipe in consideration of restraint pressure. It is a figure which shows the influence (a) on the restraint member by the bleeding of concrete, and a countermeasure (b). It is an axial direction sectional view showing an embodiment which provided a bleeding processing member to a steel pipe. A prior art example is shown, (a) is a sectional view in the vertical direction, and (b) is an enlarged sectional view showing a relationship between the spacer and the spiral protrusion when the reinforcing bar is built.

  Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a plurality of restraining members 2 are provided on the inner periphery of the lower part of the steel pipe 1 at intervals d in the circumferential direction. The restraining member 2 is for restraining the concrete that has been cast and hardened in the steel pipe 1 from shifting in the axial direction with the steel pipe 1 and is made of a steel material having a predetermined thickness and a rectangular cross section. It has been. The restraining member 2 can be rephrased as a protrusion or a protrusion, and the thickness thereof becomes the height of the protrusion or protrusion.

  The number of restraining members 2, that is, the number of intervals d is a number corresponding to the number of spacers provided in the reinforcing bar rod in the circumferential direction, and generally 4 to 8 are provided on the same circumference according to the pile diameter. In the illustrated example, the restraining member 2 is one stage in the axial direction of the steel pipe 1, but it may be arranged in a plurality of stages.

  The circumferential length of the restraining member 2 can be increased or decreased according to the magnitude of the necessary restraining force on the concrete. When the required restraining force may be small, as shown in FIG. 2, the circumferential length can be shortened, and as a result, the distance d can be increased.

  The restraining member 2 is fixed to the inner periphery of the steel pipe 1 by welding, but may be fixed by other means such as bolting. As shown in FIGS. 3 and 4, the restraining member 2 can take various forms. FIG. 6A shows an example in which tapered portions 3 are provided at both ends of the restraining member 2 so that the thickness (projection height) is gradually reduced. By providing such a tapered portion 3, the interval d is widened on the inner side of the steel pipe, so that the spacer easily passes between the restraining members 2 and 2.

  FIG. 2B shows an example in which the weld beads 5 are provided at both ends of the restraining member 2 to partially increase the thickness. Thereby, the adhesive force of concrete and the steel pipe 1 can be increased. FIG. 3C shows an example in which a plurality of restraining members 2 are formed by welding the ring member and then grinding the ring member at a plurality of locations spaced in the circumferential direction.

  FIG. 4 shows an example in which tapered portions 4 are provided at both ends of the restraining member 2 so that the width (dimension in the axial direction of the steel pipe) gradually decreases. By providing such a tapered portion 4, the distance d is widened upward, so that the spacer can easily pass between the restraining members 2, 2 when the spacer is moved downward as indicated by an arrow in the figure. .

  5 and 6 show a schematic construction procedure of a cast-in-place steel pipe concrete pile using the steel pipe 1 described above. As shown in FIG. 5 (a), the hole 11 for the casing 10 is preliminarily excavated by an earth drill machine or the like, and further, the hole 12 for the pile shaft portion having a smaller diameter than the prior excavation hole 11 is excavated further below. Then, the casing 10 is installed in the preceding excavation hole 11, and the steel pipe 1 is deposited in the casing 10 via the support tool 13.

  Next, as shown in FIG. 2B, the reinforcing bar unit 14a manufactured to a predetermined length is built into the shaft excavation hole 12 through the steel pipe 1. The rebar rod unit 14a is provided with a plurality of spacers 15 spaced in the circumferential direction and spaced in the axial direction. The spacer 15 is generally formed in a U shape, and is fixed to the reinforcing bar unit 14a so that both ends on the open side are positioned vertically above and below.

  When the preceding reinforcing bar rod unit 14a is installed, it is temporarily received by the steel pipe 1 through the support 16 and the following reinforcing bar rod unit 14a is suspended as shown in FIG. Is connected to the upper end portion of the preceding reinforcing bar rod unit 14a.

  Thereafter, similarly, the reinforcing bar rod unit 14a is built in the shaft excavation hole 12 while being sequentially connected, thereby forming the reinforcing bar rod 14 having a predetermined length as shown in FIG. The support 16 that temporarily receives the reinforcing bar 14 is fixed to the steel pipe 1, and the reinforcing bar 14 having a predetermined length is fixed to the support 16 by welding. That is, the upper end portion of the reinforcing bar 14 is fixed to the upper end portion of the steel pipe 1 through the support 16.

  Next, as shown in FIG. 4E, the steel pipe 1 and the reinforcing bar 14 are once pulled up until the lower end of the steel pipe 1 is positioned at an appropriate height above the ground, and the lower end of the steel pipe 1 and the reinforcing bar 14 Are connected by a plurality of connecting reinforcing bars 17, and a reinforcing bar 14 is fixed to the lower end of the steel pipe 1. And as shown to the same figure (f), the steel pipe 1 and the reinforcing bar 14 are lowered | hung to the axial part excavation hole 12, and a pile top end is set. That is, the jig 18 is attached to the casing 10, and the steel pipe 1 is held at a predetermined height position by the suspension bar 19. Thereafter, although not shown, after removing slime from the excavation holes 11 and 12, concrete is placed in the excavation holes 11 and 12, and the casing 10 is pulled out to complete the construction.

  In the construction procedure as described above, when the reinforcing bar unit 14a is allowed to pass through the steel pipe 1 (FIGS. 5B and 5C), since the distance d is formed between the restraining members 2 and 2, the spacer 15 Can pass between the restraining members 2 and 2. Thereby, the protrusion dimension from the reinforcing bar rod unit 14a of the spacer 15 can be made large so that the tip thereof reaches the inner circumference of the steel pipe 1 substantially. As a result, the outer peripheral end of the spacer 15 is positioned near the hole wall of the shaft excavation hole 12, and the spacer 15 exhibits the original function of holding the reinforcing bar 14 at the shaft center of the shaft excavation hole 12.

  By the way, in the concrete pile constructed as described above, when the punching force F acts on the hardened concrete C in the steel pipe 1 as shown in FIG. And resists punching force. However, on the other hand, since the concrete portion immediately above the restraining member 2 is restrained by the bearing pressure by the restraining member 2, an expansion action due to restraint occurs. And since concrete breaks by bearing pressure, as shown in the figure (b), as the final fracture shape, it will be in the state where the upper part of the restraint member 2 swelled, and as a result, the steel pipe 1 will also expand and deform | transform into a lantern state.

The relationship between the expansion pressure acting on the steel pipe 1 and the tensile force generated in the inner circumferential direction of the steel pipe can be expressed as follows with reference to FIG.
T (N) = p (N / mm) x D / 2 (mm) (1)
T: Tensile force generated in steel pipe
p: Expansion load
D: Steel pipe diameter

Here, when the steel pipe thickness is t, the steel pipe circumferential stress σ _sr (N / mm ² ) = T (N) / (t (mm) × 1 (mm)) and the expansion pressure σ _p (N / From mm ² ) = p (N / mm 2) / 1 (mm), equation (1) is as follows.
σ _p = (2 × t) · σ _sr / D (2)

Since the steel pipe circumferential direction stress σ _sr is determined by a design value, as shown in FIG. 8 (b), the expansion pressure that the steel pipe can withstand as the steel pipe diameter D becomes larger at the same steel pipe thickness t, so-called restraint pressure. Will become smaller. The greater the restraining pressure, the more the punching resistance of concrete is improved.

  Therefore, in this invention, in order to reinforce against the stress acting on the upper part of the restraining member 2 by the support pressure restraining effect of the restraining member 2, as shown in FIG. The reinforcing member 21 was provided on the outer periphery of the. The reason why the reinforcing member 21 is provided not only directly above the restraining member 2 but also directly below is to reinforce against the stress generated by the pulling force of the concrete in the direction opposite to the pushing force.

  The reinforcing member 21 is made of a steel material having a quadrangular section and is formed in a ring shape. However, a plurality of reinforcing members 21 may be provided partially at intervals in the circumferential direction. The reinforcing member 21 is also fixed to the steel pipe 1 by welding like the restraining member 2, but other means such as bolting may be used. By providing such a reinforcing member 21, the steel pipe thickness t in the equation (2) is partially increased, so that the restraining performance on concrete can be improved, and the punching and pulling resistance can be improved. The reinforcing member 21 is integrated from the portion directly above the restraining member 2 to the portion directly below, but the outer peripheral portion of the restraining member 2 is not necessarily required, and therefore the portion directly above and the portion directly below may be separated.

  As described above, the restraining member 2 is an effective means for resisting the punching force and pulling force of the concrete, but there is a risk that the restraining pressure does not work due to the bleeding phenomenon that occurs after the concrete is placed. That is, as shown in FIG. 10 (a), when the separated water rises as indicated by arrow A due to the bleeding of concrete, it is blocked by the lower portion of the restraining member 2, and a defective portion 22 of concrete such as a cavity is generated in this portion. .

  If it does so, drawing force C will not be transmitted to restraint member 2 among punching force and drawing force shown by arrows B and C, and drawing resistance will become insufficient. In order to cope with such bleeding, a bleeding treatment member 23 for preventing the separated water from rising toward the restraining member 2 may be provided on the inner periphery of the steel pipe 1 below the restraining member. As a result, the defective portion 22 occurs in the lower portion of the bleeding processing member 23, but does not occur in the lower portion of the restraining member 2. Therefore, the restraining member 2 restrains the concrete against both the punching force and the pulling forces B and C. And can resist sufficiently.

  As shown in FIG. 11, the bleeding processing member 23 is a member having a quadrangular cross section like the restraining member 2, and a plurality of bleeding processing members 23 are provided at intervals on the inner periphery of the steel pipe 1. The distance between the bleeding members 23 and 23 corresponds to the distance d between the restraining members 2 and 2 so that the spacer 15 of the reinforcing bar 1 can pass through. Since the treatment effect is reduced when the bleeding processing member 23 is set too far from the restraining member 2, it is desirable that the position of the bleeding processing member 23 be within 30 cm below the restraining member 2.

  Further, it is desirable that the thickness of the bleeding processing member 23 (height as a protrusion or a protrusion) is equal to or greater than the thickness of the restraining member 2. The bleeding treatment member 23 can be made of a light material such as a plastic material without using a steel material from the viewpoint of its function, but by using the steel material, a restraining force on the concrete can be expected together with the restraining member 2.

1: Steel pipe 2: Restraint member 11, 12: Excavation hole 14: Reinforcing bar unit 15: Spacer 21: Reinforcement member 23: Bleeding treatment member d: Interval

Claims (4)

Cast-in-place steel pipe concrete comprising: a steel pipe installed at the upper part of the excavation hole; a plurality of spacers on the outer periphery; a rebar bar built into the excavation hole through the steel pipe; and a concrete cast into the excavation hole A plurality of constraining members for constraining axial displacement between the steel pipe and the hardened concrete on the inner periphery of the steel pipe at intervals in the circumferential direction; A cast-in-place steel pipe concrete pile, characterized in that a spacer can pass between the restraining members, and a reinforcing member is provided at least directly above the restraining member in the axial direction of the steel pipe and on the outer periphery of the steel pipe. A plurality of bleeding treatment members for preventing water separated by concrete bleeding from rising toward the restraining member below the restraining member and on the inner periphery of the steel pipe correspond to the spacing between the restraining members. The cast-in-place concrete pile according to claim 1, wherein the cast-in-place concrete pile is provided at an interval. A steel pipe for a cast-in-place steel pipe concrete pile installed at the upper part of the excavation hole and having a plurality of spacers on the outer periphery through the inside of the excavation hole. A plurality of restraining members for constraining the axial displacement between are provided at intervals in the circumferential direction, and the spacer can pass between the restraining members when the reinforcing bar is installed, and in the axial direction of the steel pipe A cast-in-place steel pipe for concrete piles, wherein a reinforcing member is provided at least directly above the restraining member and on the outer periphery of the steel pipe. A spacing corresponding to the spacing of the restraining members is provided on the inner periphery of the steel pipe below the restraining members, and a bleeding treatment member for preventing separation water due to concrete bleeding from rising toward the restraining members. The cast-in-place steel pipe for concrete according to claim 3, wherein the steel pipe is provided.

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