JP2001254368A - Foundation reinforcing method and fixture for reinforcing pile for use therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve reinforcement of an existing foundation easily and at a low cost, in order to increase a supportable load applied thereto by a ground structure such as a steel tower, and in order to increase the strength of the foundation against an earthquake, etc. SOLUTION: A required number of reinforcing piles 5 are driven from a location in proximity to a side surface 2a of a footing 2 of the foundation 1B of the steel tower to the periphery of the existing pile 3 in the ground below the footing 2. Then, a fixture 4 formed of a steel product or the like is attached to a pile head of each reinforcing pile 5, and a substrate 41 of the fixture 4 is anchored to the side surface 2a of the footing 2 by means of an anchor 45.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a construction technique for reinforcing a foundation in a building such as an electric power tower for supporting a high-voltage transmission line on an elevated road.

[0002]

2. Description of the Related Art As shown in FIG.
The foundation 100B of the structure such as 0 is a foundation pile 101 made of a cast-in-place concrete pile or the like cast on the ground G, and a footing 102 made of concrete joined and integrated with the pile head 101a (the illustrated one is a continuous The pedestal 103 of the steel tower 100 is connected to the footing 10.
It is built on two. Usually, one to a plurality of foundation piles 101 are vertically driven per footing 102.

In recent years, in the case of a power tower 100,
With an increase in power demand in recent years, the weight of a transmission line (not shown) increases, and the amount of slack in the transmission line increases (drops). In order to compensate for such drooping, it is necessary to increase the erection height of the transmission line, and thus the height of the steel tower 100 tends to increase. As a result, the weight of the steel tower 100 increases, and it is required to improve the strength of the foundation pile 101 that supports the tower.

On the other hand, a steel tower 10 generated during a large earthquake
Damage such as zero inclination or collapse is caused by breakage of the foundation pile 101. Therefore, from the viewpoint of improving earthquake resistance, it is required to improve the strength of the foundation pile 101.

Conventionally, as a method for reinforcing an existing foundation pile (hereinafter referred to as an existing pile) 101, a construction method as shown in FIG. 8 is known. That is, in the conventional construction method, first, a required number of vertical through holes 102 are provided in the footing 102 adjacent to the vertical projection position of the existing pile 101.
Then, the ground adjacent to the existing pile 101 is bored in the vertical direction through the vertical through hole 102a, and the reinforcing pile 104 is driven. Then, bearing members 105 are attached to the pile heads of the reinforcing piles 104, and these bearing members 1
05, on the upper surface of the footing 102,
The reinforced concrete 106 is joined at the required thickness.

[0006]

However, according to the above-mentioned conventional reinforcing technique of the existing foundation, a number of vertical through holes 10 are formed in the footing 102 made of reinforced concrete.
In order to fix the bearing member 105 after drilling the hole 2a or driving the reinforcing pile 104, a process of assembling a formwork on the footing 102, arranging reinforcing bars, and adding concrete 106 is required. Therefore, there is a problem that not only the construction is complicated and the cost is increased, but also the construction period is lengthened.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and its main technical problems are to increase the supporting load from an overground structure such as a steel tower and the strength of the foundation to withstand an earthquake or the like. An object of the present invention is to provide a construction method that can easily and at low cost reinforce an existing foundation in order to improve the construction.

[0008]

The above technical problems can be effectively solved by the present invention. That is, the method of reinforcing the foundation according to the present invention comprises: placing a required number of reinforcing piles around existing piles in the ground below the footing from a position adjacent to the side surface of the footing in the structure; A fixture is attached to the head and the fixture is fixed to the side surface of the footing.

[0009] A fixture for a reinforcing pile according to the present invention comprises a board made of a required thickness of steel plate or the like having a plurality of connecting holes formed along an edge thereof, and a pile head inserted into the board and projected therefrom. A coupling plate having a hole, a coupling member group for coupling a pile head of a reinforcing pile inserted into the pile head insertion hole to the coupling plate, and being inserted into the coupling hole and driven or screwed into a side surface of a footing. And a plurality of anchors for fixing the substrate.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a foundation reinforcing method according to the present invention will be described below with reference to FIGS.

FIG. 1 schematically shows a state in which a foundation 1B of a power tower is reinforced by the method of the present invention. That is, in this figure, reference numeral 1 denotes a power tower constructed of a steel frame or the like, and its base 1B
Is a footing 2 which is joined to the lower end of the column base 11 of the steel tower 1 and is made of reinforced concrete on the surface layer of the ground G.
And an existing foundation pile (hereinafter, referred to as an existing pile) 3 such as a cast-in-place concrete pile or the like in which a pile head 3a is joined to the footing 2 and is vertically driven into the ground G.

Side surface 2a of footing 2 in foundation 1B
, A plurality of fixing tools 4 are arranged at appropriate intervals in a direction orthogonal to the cross section shown in the figure, and a plurality of reinforcing piles 5 driven from the periphery of the footing 2 in parallel with the existing pile 3 (vertically). Each pile head 5 a is fixed to the side surface 2 a of the footing 2 via the fixing tool 4.

As shown in the perspective view of FIG. 2 and the cross-sectional view of FIG. 3, the fixture 4 includes a substrate 41 made of a required thickness, such as a steel plate, having a plurality of coupling holes 41a formed in an outer peripheral portion thereof. A coupling plate 42 made of a steel plate or the like protruded perpendicularly to the surface of the substrate 41 at the center thereof, and both sides of the coupling plate 42 in the width direction are provided on both the substrates 41 and 42. A pair of reinforcing plates 43 made of a steel plate or the like provided perpendicular to the
The fixing member 4 is firmly fixed by being inserted into the coupling hole 41a of the board 41 and driven or screwed into the side surface 2a of the footing 2, and a coupling member group 44 for coupling the coupling plate 42 and the reinforcing pile 5 to each other. Anchors 4 to settle in
5 is provided. The substrate 41, the coupling plate 42, and the reinforcing plate 43 are integrated with each other by welding or the like, and are rust-proofed by plating or painting or spraying after construction.

As the reinforcing stake 5, a stake having a relatively small diameter (for example, φ300 mm or less) having a known structure and high proof strength is suitably adopted. That is, as shown in FIG.
1 is inserted to the lower end or deeper, and the head is inserted through the inner periphery of the steel pipe 51 whose head is joined to the connecting plate 42 of the fixture 4 via the connecting member group 44, respectively. A lower end 52a extending further downward from the lower opening of the steel pipe 51 reaches into a solid support layer G2 below the soft layer G1, and has a head connected to the connecting plate 42 via the connecting member group 44, respectively. A deformed reinforcing bar 52 as a joined metal core material, and a grout 5 as a consolidated material filled between the steel pipe 51 and the ground G and the deformed reinforcing bar 52
3). The grout 53 is formed in an enlarged pedestal shape below the steel pipe 51 (in the support layer G2), and a part of the grout 53 is formed of the steel pipe 5.
1 and is fixed to the drilled surface of the ground G.

As shown in FIGS. 4 to 6, various connecting structures of the fixing tool 4 and the reinforcing pile 5 are exemplified, and the steel pipe 51 of the reinforcing pile 5 is appropriately attached to the connecting plate 42 of the fixing tool 4. A pile head insertion hole 42a that can be inserted with ample play is provided.

In the example shown in FIG. 4, the connecting member group 44 is arranged so that the reinforcing pile 5
And a lower flange 441 made of steel fixed to the outer periphery near the head of the steel pipe 51 by welding or the like, and the outer periphery of the head of the steel pipe 51 projecting upward from the pile head insertion hole 42a of the coupling plate 42 by welding or the like. A steel upper flange 442 fixed by the above-described method, and a reinforcing pile arranged in a state where the upper flange 442 is sandwiched between the upper plate 442 and the coupling plate 42 by being tightened by the plurality of screw members 443. 5 and a steel support plate 444 for holding the pile head. A screw hole 444a is formed at the center of the support plate 444, and the head of the deformed reinforcing bar 52 in the reinforcing pile 5 is screwed into the screw hole 444a, so that the support plate 44 is formed.
4 is fixed.

In the example shown in FIG. 5, the connecting member group 44 is fixed to the outer periphery near the head of the steel pipe 51 in the reinforcing pile 5 by welding or the like so as to be located below the connecting plate 42. Steel lower flange 441 and the steel pipe 5 projecting upward from the pile head insertion hole 42a of the coupling plate 42.
1 and a bearing cap 445 made of steel, which is arranged so as to cover the head portion of the steel pipe 1 and the lower surface of the outer periphery thereof is in contact with the coupling plate 42 and is fixed to the steel pipe 51 by welding or screwing. Rebar insertion hole 44 opened in the upper center of the building
5a, a pair of nuts 446 and 446 for fixing the head of the deformed reinforcing bar 52 of the reinforcing pile 5 in an inserted state is provided.

In the example shown in FIG. 6, the connecting member group 44 is fixed to the outer periphery near the head of the steel pipe 51 in the reinforcing pile 5 by welding or the like so as to be located below the connecting plate 42. Steel lower flange 441 and the steel pipe 5 projecting upward from the pile head insertion hole 42a of the coupling plate 42.
An upper flange 442 made of steel fixed by welding or the like to the outer periphery of the head 1 and disposed on the upper flange 442, and the upper flange 442 is sandwiched between the coupling plate 42 by a plurality of bolts 447. A steel bearing plate 444 for holding the pile head of the reinforcing pile 5 in a worn state, and the bearing plate 444
And a pair of nuts 446 and 446 for fixing the head of the deformed reinforcing bar 52 in the reinforcing pile 5 in the inserted state in the reinforcing bar insertion hole 444b opened in the center of the reinforcing pile 5.

According to the above-mentioned reinforcing method, the load due to the weight of the tower 1 and the transmission line (not shown) installed on the tower 1 is:
The power is transmitted from the column base 11 to the existing pile 3 via the footing 2, and also transmitted from the footing 2 to each reinforcing pile 5 via the fixture 4. For this reason, since the supporting strength of the foundation 1B against the load increases, for example, in response to an increase in power demand, the existing steel tower 1 shown by a solid line in FIG.
It is possible to cope with an increase in the load caused by rebuilding the tower 1 ′ having a large size as indicated by a chain line.

In addition, the reinforcing pile 5 improves the proof strength against the horizontal inertia force when the horizontal acceleration due to the earthquake is applied to the pylon 1 and the proof strength against the moment and the pull-out force due to the shaking of the pylon 1. Therefore, the shear strength of the entire pile is increased, and the existing pile 3 is destroyed when a large earthquake occurs,
Alternatively, it is also useful as a seismic retrofitting method for preventing the steel tower 1 from tilting or collapsing due to the destruction of the joint between the footing 2 and the existing pile 3 or the like.

The construction procedure according to the reinforcing method of this embodiment will be described below. As shown in FIG. 2, first, the ground G around the footing 2 is excavated to a required depth, and the side surface of the footing 2 is excavated. Expose 2a.

Next, the reinforcing pile 5 is driven vertically from a position adjacent to the side surface 2a of the footing 2. The placement position of the reinforcing pile 5 is determined in consideration of the position of the pile head insertion hole 42a in the coupling plate 42 when the fixing tool 4 is fixed to the side surface 2a. The setting interval is appropriately determined in consideration of the intended strength.

As is well known, the operation of placing the reinforcing piles 5 first involves boring (casing excavation) using a tubular casing (not shown) having a diameter larger than the steel pipe 51 of the reinforcing piles 5. And the supporting layer G2 in the ground G
A hole is formed to reach inside. At this time, the steel pipe 51 is inserted together with the casing up to the support layer G2 of the ground G in accordance with the boring. After the hole is formed, the steel pipe 51 is left in the ground G, and only the casing is pulled out. Next, the deformed reinforcing bar 52 is inserted into the steel pipe 51. A device for press-fitting the grout 53 is attached to the deformed reinforcing bar 52 and is inserted together. When the insertion is completed, the grout 53 is press-fitted into the hole by using the press-fitting device, and the steel pipe 51 is pulled up to a predetermined height accordingly. When the grout 53 is sufficiently filled, the steel pipe 51 is inserted again, and at the same time, the grout 53 is press-fitted again. The pressing force at this time causes the grout 53 to diffuse in a pedestal shape below the steel pipe 51.

As described above, the reinforcing pile 5 has a diameter of φ
Since a material having a small diameter of 300 mm or less and having a high yield strength is suitably adopted, it can be easily driven from a position close to the side surface 2a of the footing 2, and can be driven by a relatively small heavy machine. is there. In addition, a vertical through hole 102 as shown in FIG.
Since it is not necessary to drill holes a, the construction cost for driving the reinforcing pile 5 is reduced.

In the vicinity of the head of the steel pipe 51 of each of the installed reinforcing piles 5, as shown in FIGS.
The lower flange 441 which is a part of the connecting member group 44 is previously joined by welding or the like. Then, the fixtures 4 are respectively arranged at the pile heads of the reinforcing piles 5 protruding into the excavation space S around the footing 2, and the pile head insertion holes 42 of the coupling plates 42 are provided.
The pile head (the head of the steel pipe 51) is passed through a, and the substrate 41 of the fixture 4 is fixed to the side surface 2a of the footing 2 by a plurality of anchors 45. At this time, it is not necessary to add concrete to the footing 2 and the fixture 4 can be manufactured at low cost by using a steel plate or the like.
Again, construction costs are reduced.

Next, the connecting plate 42 and the pile head of the reinforcing pile 5 are connected by a connecting member group 44 by a method as shown in FIGS. Thereafter, if necessary, rustproofing is performed by painting, spraying, or the like, and then the excavation space S around the footing 2 is backfilled with excavated soil to complete the construction.

In the above embodiment, the reinforcing pile 5
Although a so-called micropile has been described above, the present invention is not limited to this, and any device can be used as long as it can be fixed by the fixture 4 and has a required strength.

[0028]

As described in detail above, the following effects are realized by the method for reinforcing a foundation according to the present invention. First of all, since there is no need to drill holes in the footing or add concrete to the construction, large-scale construction is not required, and construction can be performed in a narrow space around the footing, so it can be performed easily and at low cost. It is.

Further, by reinforcing the existing piles by this method, the bearing capacity of the foundation against vertical loads and the horizontal strength in the event of an earthquake are improved, so that the supporting loads due to the rebuilding of ground structures such as steel towers can be increased. This can be an effective measure for preventing damage such as tilting or collapse of the structure caused by destruction of the foundation pile during a large earthquake.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a foundation of a steel tower reinforced by a foundation reinforcement method according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a state in which a footing and a reinforcing pile are joined by a fixture in the embodiment.

FIG. 3 is a cross-sectional view showing a structure of a reinforcing pile and a fixture in the embodiment, together with a footing and a part of an existing pile.

FIG. 4 is a cross-sectional view of a main part showing an example of a connection structure between a fixture and a reinforcing pile in the embodiment.

FIG. 5 is a cross-sectional view of a main part showing another example of the connection structure between the fixture and the reinforcing pile in the embodiment.

FIG. 6 is a cross-sectional view of a main part showing another example of the connection structure between the fixture and the reinforcing pile in the embodiment.

FIG. 7 shows the basic structure of a power tower, and FIG.
Is a longitudinal sectional view, and (B) is a partial plan view.

FIG. 8 is an explanatory view schematically showing a state in which a foundation of a power tower is reinforced by a conventional reinforcing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel tower (structure) 1B Foundation 2 Footing 3 Existing pile 4 Fixture 41 Board 41a Connection hole 42 Connection plate 42a Pile head insertion hole 44 Connection member group 5 Reinforcement pile

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masahiro Nakamura 4-6-1 Sendagaya, Shibuya-ku, Tokyo F-term in Fujita Co., Ltd. F-term (reference) 2D046 CA01 CA03 DA11

Claims (2)

[Claims] 1. A step of placing a required number of reinforcing piles around existing piles in the ground below the footing from a position adjacent to a side surface of the footing in a structure, and a fixture attached to a pile head of the reinforcing pile. Attaching the fixing device to the side surface of the footing, and reinforcing the foundation. 2. A board made of a required thickness of a steel plate or the like having a plurality of connecting holes formed along an edge, a connecting plate projecting from the board and having a pile head insertion hole formed therein, and the pile A coupling member group that couples the pile head of the reinforcing pile inserted into the head insertion hole to the coupling plate, and a plurality of anchors that are inserted through the coupling hole and are fixed to the substrate by being driven or screwed into the side surface of the footing, A fixing device for a reinforcing pile, comprising: