JP2007023602A - Construction method for foundation structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction method for a foundation structure of such type that a foundation of a structure is put on a head part of an existing pile buried into the ground to form a joint condition of the existing pile and the foundation of the structure into a semi-rigid joint condition conforming to prospects in design. <P>SOLUTION: This construction method for the foundation structure comprises a process for burying the existing pile 1 provided with a tool engaging with a rotary press-fitting device in the pile head part protrudedly into the ground by using the rotary press-fitting device, a process for removing the tool, a process for forming a cavity E enlarged toward a downward part between a side face of the pile head part and an inner peripheral face of a form 3 by putting and covering the mold 3 whose inner peripheral face is inclined on the pile head part, a process for placing leveling concrete around the form 3 while preventing flowing-in of concrete into the cavity E, and a process for placing foundation concrete becoming the foundation 2 of the structure on the hardened leveling concrete. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for constructing a foundation structure in which a structure foundation is placed on a pile head of a ready-made pile embedded in the ground.

  As a semi-rigid joint type foundation structure that can reduce the bending moment applied to the pile head while ensuring a high shear force transmission capability, Patent Document 1 discloses a structure foundation on the pile head of an already-made pile embedded in the ground. The basic structure which mounts is disclosed.

  In this foundation structure, by making the pile head of the ready-made pile enter the recess provided in the bottom surface of the structure foundation, a high shearing force transmission capability is ensured, and between the recess and the side of the pile head. The bending moment applied to the pile head is reduced by forming a gap that expands downward and allowing the pile head to rotate.

  In addition, when embedding a ready-made pile in the ground, as disclosed in Patent Document 2, a rotary press-fitting device that press-fits the ready-made pile while rotating is used.

JP 2004-162259 A JP 2002-212952 A

  By the way, as described also in Patent Document 2, in order to prevent the twist generated in the ready-made pile at the time of rotary press-fitting, a jig that engages with the rotary press-fitting device protrudes from the pile head of the ready-made pile. However, when the foundation structure of Patent Document 1 is constructed using such a ready-made pile, the rotation of the pile head is constrained by the jig left on the pile head. In some cases, performance cannot be demonstrated.

  Moreover, when constructing the foundation structure of patent document 1, after forming a predetermined | prescribed space | gap around a pile head by covering the pile head of a ready-made pile with the formwork in which the internal peripheral surface inclined, The foundation concrete that forms the foundation will be placed, but when placing the foundation concrete, the formwork is likely to be displaced or deformed, and in the void around the pile head formed by the formwork. Basic concrete may enter. In such a state, since the rotation of the pile head is constrained, the assumed design performance cannot be exhibited.

  Thus, in the basic structure of Patent Document 1, it is necessary to solve the various problems described above in order to satisfy the joining state as expected in the design.

  From such a viewpoint, the present invention is a method for constructing a foundation structure of a type in which a structure foundation is placed on a pile head of an already-made pile embedded in the ground, and the joint state between the ready-made pile and the structure foundation is It is an object of the present invention to provide a construction method of a foundation structure that can be in a semi-rigid joint state as expected in design.

  This invention which solves such a subject is a construction method of a foundation structure formed by placing a structure foundation on a pile head of an already-made pile embedded in the ground, and a jig that engages with a rotary press-fitting device Is embedded in the ground using the rotary press-fitting device, the jig is removed, and the formwork with an inclined inner peripheral surface is attached to the pile head. Covering, forming a gap between the side surface of the pile head and the inner peripheral surface of the formwork and expanding the space downward, and placing a leveled concrete around the formwork And a step of placing foundation concrete as a structure foundation on the cured leveled concrete.

  If a foundation structure is constructed in such a procedure, the joint state between the ready-made pile and the structure foundation can be made into a semi-rigid joint state as expected in the design. In other words, in the present invention, the jig for the rotary press-fitting device provided on the ready-made pile is removed before the pile head of the ready-made pile is covered, so that the pile head is rotated by the jig. The problem of being restrained can be solved. Further, in the present invention, the formwork can be constrained by the leveled concrete, so that when the foundation concrete is placed, the formwork is not easily displaced or deformed. Further, the pile formed by the formwork The foundation concrete does not enter the gap around the head.

  Before placing the leveling concrete, fix the formwork to the pile head using a fixing tool, and remove the fixing tool before placing the foundation concrete. As a result, it is possible to reliably prevent a minute shift of the formwork that may occur when the metal is placed, so that it is possible to more reliably obtain the joining state as expected in the design.

  In addition, a mark is provided on the outer peripheral surface of the formwork along the lower edge thereof, and before placing the leveled concrete, the ground material is provided on the outer periphery of the lower end of the formwork up to the position of the mark. It is good to arrange. When the ground material is arranged on the outer periphery of the lower end of the formwork, it is possible to prevent the inflow of concrete into the gap formed between the side surface of the pile head and the inner peripheral surface of the formwork. The surrounding gap can be ensured reliably. Here, the ground material is a general term for crushed stones (gravels), sand, clay, on-site generated soil, and the like. In order to dispose the ground material around the formwork, for example, crushed stone or the like may be piled up on the outer periphery of the formwork, or the lower end of the formwork may be embedded in the ground (floored surface).

  According to the construction method of the foundation structure according to the present invention, the joint state between the ready-made pile and the structure foundation can be a semi-rigid joint state as expected in the design.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.

  First, the basic structure according to the present embodiment will be described. The foundation structure according to the present embodiment is a semi-rigid joint type foundation structure that reduces the bending moment applied to the pile head while ensuring shearing force transmission capability, as shown in FIG. The pile cap 2 which is a structure foundation is mounted on the pile head of the ready-made pile 1 embedded in the ground G. The pile head of the ready-made pile 1 is covered with a crested tubular formwork 3 having an inclined inner peripheral surface. Further, a crushed stone layer S and a leveled concrete layer C are laminated between the ground G and the pile cap 2.

  As shown in FIG. 2B, the ready-made pile 1 includes a cylindrical member 11 having a hollow inside, an annular end plate 12 attached to the upper end surface of the cylindrical member 11, and an end plate 12. And a jig 13 projecting from the head.

  The cylindrical member 11 may be made of any material as long as it can obtain a desired strength. For example, the cylindrical member 11 is made of concrete with different diameter reinforcing bars or flat steel, concrete with outer shell steel pipe, steel pipe, or the like. be able to.

  The end plate 12 is made of a steel member. A plurality of female screw holes 12a, 12a,... Are formed in the end plate 12 at intervals in the circumferential direction.

  When the cylindrical member 11 is made of concrete, the end plate 12 is embedded on the end surface of the cylindrical member 11 by embedding an anchor (not shown) protruding from the bottom surface of the end plate 12 in the cylindrical member 11. When the cylindrical member 11 is made of steel, it is fixed by welding. When the cylindrical member 11 is made of steel, the end plate 12 can be omitted.

  The jig 13 is engaged with a drive shaft of a rotary press-fitting device (not shown), and prevents twisting generated in the ready-made pile 1 at the time of rotary press-fitting. In the present embodiment, the jig 13 is made of a steel material having an inverted L shape, and is fixed to the end plate 12 by welding. The jig 13 may be detachably fixed to the end plate 12 using a mechanical joining method. Moreover, when the cylindrical member 11 is formed of concrete with a steel pipe or a shell steel pipe, the jig 13 may be fixed to the side surface of the upper end portion of the cylindrical member 11 by welding or the like.

  A pile cap (structure foundation) 2 shown in FIG. 1A is a reinforced concrete structure, and a recess 21 is formed on the bottom surface thereof. The recessed part 21 is shape | molded by placing the foundation concrete used as the pile cap 2 in the state which covered the formwork 3 on the pile head of the ready-made pile 1. FIG.

  The formwork 3 includes a disk-shaped top 31 that contacts the upper end surface of the ready-made pile 1 (that is, the upper surface of the end plate 12), and a side portion 32 that surrounds the pile head of the ready-made pile 1. As shown in 2 (a), it has a frustoconical appearance.

  The top portion 31 has the same planar shape as the upper end surface of the ready-made pile 1. The top portion 31 is formed with a plurality of through holes 31 a corresponding to the female screw holes 12 a of the end plate 12.

  The side part 32 is formed in the outer periphery of the top part 31, The internal diameter is gradually increasing as it goes below (refer (a) of FIG. 1). Further, on the outer peripheral surface of the side portion 32, a mark 32 a serving as a guide when the side portion 32 is embedded in the crushed stone layer S or the ground G (see FIG. 1A) is written along the lower edge of the mold 3. Has been. The mark 32a may be formed at a position at least 2 cm higher than the lower edge of the mold 3. In addition, although the mark 32a of illustration is continuously described over the perimeter of the side part 32, it is not limited to this and may be described intermittently.

  And according to such a basic structure, as shown in (b) of FIG. 1, since the space | gap E exists around the pile head of the ready-made pile 1, at the time of an earthquake etc., the pile head of Rotation is allowed. That is, even if the horizontal force (shearing force) Q acting on the structure due to an earthquake, wind, or the like acts on the ready-made pile 1, a large bending moment is not generated at the pile head.

  Next, the construction method of the foundation structure will be described in detail. First, as shown in FIG. 3A, the ready-made pile 1 is embedded in the ground G using a rotary press-fitting device (not shown). At this stage, the jig 13 is left on the pile head of the ready-made pile 1. In addition, when the ready-made pile 1 is rotationally press-fitted, the bolt B1 is screwed into the female screw hole 12a so that earth and sand etc. are not clogged in the female screw hole 12a (see FIG. 2A) of the end plate 12. .

  When the burying of the ready-made pile 1 is completed, as shown in FIG. 3B, the ground G around the ready-made pile 1 is dug down to expose the pile head.

  Next, the jig 13 is removed by an appropriate method, and the upper end surface of the ready-made pile 1 is smoothed as shown in FIG. Specifically, for example, when the jig 13 is fixed to the end plate 12 by welding, the base of the jig 13 may be melted and the cut surface may be polished by a grinder or the like. The bolt B1 screwed into the female screw hole 12a is also removed.

  Further, before and after removing the jig 13, the unevenness of the floored surface G1 is corrected, and then a crushed stone layer S is formed by laying and rolling the crushed stone on the floored surface G1. Note that the crushed stone layer S may be omitted depending on the ground conditions and the like.

  Next, as shown in FIG. 4A, the formwork 3 is covered with the pile head of the ready-made pile 1 in a state where the top 31 of the formwork 3 is in close contact with the upper end surface of the ready-made pile 1. A gap E that expands downward is formed between the side surface 11a of the part and the inner peripheral surface 32b of the mold 3. In addition, when covering the formwork 3 on the pile head (end plate 12), the through hole 31a (see FIG. 2 (a)) of the formwork 3 and the female screw hole 12a (see FIG. 2). The position of b) is adjusted.

  When the formwork 3 is covered with the pile head of the ready-made pile 1, the formwork 3 is attached to the pile head using a bolt (fixing tool) B2 screwed into the female screw hole 12a (see FIG. 2B). Fix it temporarily. In addition, when the female screw hole 12a is not formed in the end plate 12, the formwork 3 is fixed to the pile head by adhesion, welding, or the like with a strength that does not deteriorate the rotational performance of the pile head.

  Once the formwork 3 is temporarily fixed to the pile head of the ready-made pile 1, the bottom edge of the formwork 3 and the crushed stone layer S are formed by depositing ground material S ′ such as crushed stone or earth and sand on the outer periphery of the lower end of the formwork 3. The gap between the upper surface of the substrate is closed. The ground material S ′ may be disposed up to the mark 32 a (see FIG. 2A) marked on the outer peripheral surface of the mold 3.

  In addition, when the lower end part of the formwork 3 is located below the upper surface of the crushed stone layer S, if the lower end part of the formwork 3 is embedded in the crushed stone layer S up to the position of the mark 32a, The ground material is arranged on the outer periphery. Moreover, when the lower end part of the formwork 3 is located below the flooring surface G1, as shown in FIG. 5, after flooring the flooring surface G1, the ground material such as crushed stone or earth and sand is formed on the outer periphery thereof. S 'is arranged or, as shown in FIG. 6 (a), the lower end of the mold 3 is embedded in the ground G, which is the ground material, and the crushed stone layer S is formed on the floored surface G1. do it.

  In addition, in this embodiment, after forming the crushed stone layer S, the formwork 3 was covered on the pile head, but it is not limited to this, and before forming the crushed stone layer S, the formwork 3 is attached to the pile head. It does not matter even if it covers the part. Moreover, in this embodiment, before depositing the ground material S ′ on the outer periphery of the mold 3, the mold 3 was fixed to the pile head using the bolt B 2, but the present invention is not limited to this. It may be fixed after depositing S ′. Moreover, in the case where the mold frame 3 is covered on the pile head before the crushed stone layer S is formed, even if the mold frame 3 is fixed to the pile head using the bolt B2 before the crushed stone layer S is formed. Good.

  When the ground material S ′ is arranged on the outer periphery of the lower end portion of the mold 3, as shown in FIG. 4B, leveled concrete is placed around the mold 3 to form the leveled concrete layer C. Form. In addition, since the space | gap E is sealed by the ground material S 'piled up around the lower end part of the formwork 3, the leveled concrete does not flow into the space | gap E. FIG. The thickness of the leveled concrete layer C is not particularly limited, but preferably it is preferably set so that the height from the upper surface of the leveled concrete layer C to the upper surface of the mold 3 is 5 cm or more.

  When the leveled concrete has hardened, remove the bolt B2. At this time, the top 31 of the formwork 3 is hit with a mallet or the like to confirm again that the top 31 is in close contact with the upper end surface of the ready-made pile 1, and the side 32 is hit with a mallet or the like to obtain a gap. Make sure that no leveling concrete flows into E.

  After that, reinforcing bars and formwork (not shown) are installed on the leveled concrete layer C, and the foundation concrete to be the pile cap 2 is placed on the leveled concrete layer C as shown in FIG. Once cured, the construction of the foundation structure is complete.

  When the foundation structure is constructed in the above-described procedure, the joint state between the ready-made pile 1 and the pile cap 2 can be a semi-rigid joint state as expected in the design. That is, since the jig 13 for the rotary press-fitting device provided in the ready-made pile 1 is removed before covering the formwork 3 on the pile head of the ready-made pile 1 (see FIG. 3 (c)), the jig The trouble that rotation of a pile head is restrained by 13 can be eliminated. Moreover, since the formwork 3 can be constrained by the leveled concrete layer C (see FIG. 4B), it is difficult for the formwork 3 to be displaced or deformed when the foundation concrete is placed. The foundation concrete does not enter the gap E around the pile head formed by the mold 3.

  Moreover, since the formwork 3 was fixed to the pile head of the ready-made pile 1 using the bolt B2 before placing the leveled concrete (see (a) of FIG. 4), when placing the leveled concrete As a result, it is possible to more reliably obtain the joining state as expected in the design. Since the bolt B2 is removed before placing the foundation concrete (see (c) in FIG. 4), the rotation of the pile head is not restricted.

  In addition, above-described embodiment can be used suitably when drawing-out force does not act on the ready-made pile 1. FIG. When a pulling force acts on the ready-made pile 1, as shown in FIG. 6A, a pull-out resistance rod 14 may be erected on the upper end surface of the ready-made pile 1 and embedded in the pile cap 2. For example, a PC steel bar or a rolled steel bar for construction structure (SNR) can be used as the pulling resistance bar 14, but the number and strength thereof are set to such a degree that a semi-rigid joint state can be maintained. In addition, the pulling-out resistance rod 14 can be attached using the internal thread hole 12a (refer (a) of FIG. 2) formed in the end plate 12 of the ready-made pile 1, for example.

  Even in such a foundation structure, since the gap E exists around the pile head of the ready-made pile 1, the pile head is allowed to rotate as shown in FIG. That is, even if a horizontal force (shearing force) acting on the structure due to an earthquake or wind acts on the ready-made pile 1, a large bending moment does not occur at the pile head.

(A) is sectional drawing which shows the basic structure which concerns on embodiment of this invention, (b) is sectional drawing for demonstrating a semi-rigid joining state. (A) is a perspective view which shows a formwork, (b) is a perspective view which shows a ready-made pile. It is sectional drawing for demonstrating the construction method of the foundation structure which concerns on embodiment of this invention, Comprising: (a) is sectional drawing which shows the state which laid the ready-made pile, (b) is a pile head dug down the ground Sectional drawing which shows the state which exposed, (c) is sectional drawing which shows the state which removed the jig | tool. It is sectional drawing for demonstrating the construction method of the foundation structure which concerns on embodiment of this invention, Comprising: (a) is sectional drawing which shows the state which covered the formwork on the pile head, (b) is leveled concrete Sectional drawing which shows the state which laid, (c) is sectional drawing which shows the state which laid foundation concrete. It is sectional drawing which shows the modification of the basic structure which concerns on embodiment of this invention. (A) is sectional drawing which shows the other modification of the basic structure which concerns on embodiment of this invention, (b) is sectional drawing for demonstrating a semi-rigid joining state.

Explanation of symbols

1 Ready-made pile 13 Jig 2 Pile cap (Structure foundation)
3 Formwork C Leveled concrete layer E Void B2 Bolt (fixing tool)

Claims (3)

A construction method of a foundation structure in which a structure foundation is placed on a pile head of an already-made pile buried in the ground,
A step of burying a ready-made pile in which a jig engaging with the rotary press-fitting device protrudes from the pile head using the rotary press-fitting device;
Removing the jig;
A step of covering the pile head with the formwork having an inclined inner peripheral surface, and forming a gap expanding downward between a side surface of the pile head and the inner peripheral surface of the formwork;
Placing a leveled concrete around the formwork;
And a step of placing foundation concrete as a structure foundation on the hardened leveled concrete.   The fixing tool is fixed to the pile head using a fixing tool before placing the leveling concrete, and the fixing tool is removed before placing the foundation concrete. 1. A method for constructing the basic structure according to 1. On the outer peripheral surface of the mold, a mark is marked along its lower edge,
The foundation structure according to claim 1 or 2, wherein a ground material is arranged up to a position of the mark on an outer periphery of a lower end portion of the formwork before placing the leveled concrete. Method.

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