JPH0941370A - Method of increasing bearing capacity of existing piles with new steel pipe piles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reutilize an existing pile as the bearing pile of a new building by increasing the bearing power of the existing pile at the time of the rebuilding of an existing building by adopting a new steel-pipe pile having a bore. SOLUTION: A new steel-pipe pile 12 having a bore larger than an existing pile 11 and radially having reinforcing ribs 14, 15 in specified depth on the insides of both end sections is driven to the outer circumference of the underground existing pile 11 in building traces. Sections from the pile front end of the existing pile 11 to a pile head section are covered with the new steel-pipe pile 12, and the existing pile 11 is constituted in a new reinforcing pile, in which vertical bearing power and horizontal resistance are increased by the reinforcing ribs 14, 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reusably increasing the bearing capacity of an existing underground pile as a reinforcing pile for a new building when rebuilding an existing building.

[0002]

2. Description of the Related Art As shown in FIG. 11, when an existing building 3 supported by piles 2 placed in the ground 1 is to be removed and replaced with a new building, conventionally, the existing building 3 is dismantled at the same time. It was common to remove existing stakes 2 or bury them.

FIG. 12 shows one example of the existing pile 2
The removal by using the vibro hammer 4 is often adopted, and the method of burying the remaining piles is that after cutting and removing a few meters from the ground surface, the remaining piles are buried.

[0004]

This conventional method has the following problems. Removal costs are relatively high. There is a great deal of waste by not reusing existing piles in order to throw away existing piles that have bearing capacity. The existing piles are left in the ground, which hinders the placement of support piles in the new building. When existing piles are left in the ground, the freedom of construction of the upper building is reduced.

Since all of these problems are caused by leaving the existing piles in the ground, it is possible to solve the problems by reusing the existing piles as reinforcing piles for a new building. When using it, it is necessary to increase the bearing capacity of the piles corresponding to the new building.

An object of the present invention is to increase the bearing capacity of an existing pile by using a steel pipe pile having a large diameter, and reuse the existing pile whose bearing capacity is enhanced by the steel pipe pile as a reinforcing pile for a new building. There is a new way you can. Further, an object of the present invention is to place a new steel pipe pile on the outer periphery of the existing pile, regardless of whether the existing pile is a steel pipe pile or a PHC pile, and to reinforce both ends of the outer peripheral new steel pipe pile. The purpose of the present invention is to provide a new method for increasing the bearing capacity of existing piles by which ribs and reinforcing rings can quickly transfer vertical and horizontal loads generated from a new building to the ground.

[0007]

According to the present invention according to the above-mentioned object, reinforcing ribs having a diameter larger than the existing pile and having a required depth are radially provided on the outer periphery of the existing pile underground of the building trace. A new steel pipe pile is placed, and the new steel pipe pile covers from the pile tip to the pile head of the existing pile, and the existing pile becomes a new reinforcement pile in which the vertical supporting force and horizontal resistance are increased by the reinforcing ribs. It is composed.

The existing piles to which the present invention is applied are steel pipe piles,
New steel pipe piles such as PHC piles that are cast around the outer circumference of these steel pipe piles are preferably up to about 2.0 times the pile diameter of existing steel pipe piles. The unit length of the new steel pipe pile is generally 10 m to 15 m, and a large number of the reinforcing ribs are integrally attached beforehand by welding inside both ends of the unit length, but the range is the tip of the pile. , The pile joint and the pile head are different.

The above-mentioned reinforcing ribs greatly contribute to the improvement of the effect of blocking the tip of the pile, which is a big problem in the new steel pipe pile, and the guide ribs that make the new steel pipe pile reach the pile support layer along the outer periphery of the existing pile. Has a role. For the purpose of this guide effect, it is possible to attach a driving guide to the inner end of the reinforcing rib at the tip end by welding. In this case, the driving guide is a steel pipe having a diameter about 5 cm larger than the diameter of the existing pile, and the length is preferably about the same as the reinforcing rib.

When the existing pile is a steel pipe pile or a PHC pile, whether the area of the reinforcing rib is the same as the area surrounded by the new steel pipe pile and the reinforcing rib and the existing steel pipe pile is the same as the area surrounded by the existing steel pipe pile. However, it is preferable that they are installed so as to be less than that and arranged so that the blocking effect of about 0.8 can be secured.

Further, the tip shape of the reinforcing rib is formed in a tapered shape so that a new steel pipe pile can be smoothly driven and the existing pile is not easily scratched. When the guide is provided, the taper at the tip of the reinforcing rib becomes unnecessary.

The pile head can be reinforced against a horizontal force of the pile head by providing a slightly longer reinforcing rib (depth of about 5 to 10 m). The reinforcement of the new steel pipe pile and the existing steel pipe pile is possible. It is also possible to apply concrete up to the position where the reinforcing ribs are provided, and the construction can be easily performed by cast-in-place or precast concrete.

[0013]

1 to 10 show an embodiment of the present invention. In FIG. 1, reference numeral 10 denotes a reinforcing pile composed of an existing pile 11 and a new steel pipe pile 12 around the existing pile 11. This reinforcement pile 10 has a larger diameter than the existing pile pile 11 on the outer periphery of the existing pile 11 in the basement of the existing building traces that has been laid from the ground GL to the pile support layer 13, and many inside the both ends. Multiple unit steel pipe piles 12 with required length having reinforcing ribs
a, 12b, 12n are sequentially driven, and the new steel pipe pile 12 formed by jointing the unit steel pipe piles covers the existing pile 11 from the pile tip to the pile head.

The length of each of the unit steel pipe piles 12a, 12b, 12n is about 12 m, and the reinforcing ribs 14 inside the tip of the unit steel pipe pile 12a which is the pile tip of the reinforcement pile 10 and the reinforcement pile 10 are provided.
Of the unit steel pipe piles 12n, which are the pile heads, except for the reinforcing ribs 15 inside the rear end of the unit steel pipe piles 12n.
The reinforcing ribs 16 at the ends of 2b and 12n are all formed to have the same depth.

The depth of the reinforcing ribs in this embodiment is about 1 to 2 m for the reinforcing ribs 14 at the tip of the pile, 5 to 10 m for the reinforcing ribs 15 at the pile head, and 0 for each reinforcing rib 16 at the splice part. .5
Although different from m, the protruding lengths are all the same and a required clearance is formed between the existing pile 11 and the side surface.

2 to 4 show the case where the existing pile 11 is a steel pipe pile (hereinafter referred to as the existing steel pipe pile 11), and the number of the reinforcing ribs 14, 15, 16 at each part is the same (8 pieces). The unit steel pipe piles 12a and 12n are radially attached integrally by welding. In addition, the reinforcement rib 14 at the tip of the pile
As shown in FIG. 3B, the tip of the new steel pipe pile 12 is tapered so that the new steel pipe pile 12 can be driven smoothly and the existing steel pipe pile 11 is not easily scratched.

In FIG. 4, a reinforcing ring made of a steel pipe having a diameter 5 cm larger than the diameter of the existing steel pipe pile 11 and the same length as the reinforcing rib is attached inside the reinforcing rib 14 by welding as a driving guide 17. If this is the case, this placing guide 17
As a result, the driving of the new steel pipe pile 12 becomes more reliable than in the case of using the reinforcing ribs 14. However, both the reinforcing ribs 14 and the driving guides 17 have the effect of closing the pile tips as shown in FIG.

FIGS. 5 to 7 show a case where the existing pile 11 is a PHC pile (hereinafter referred to as an existing PHC pile). The structure of the new steel pipe pile 12 for the existing PHC pile is no different from that of the new steel pipe pile 12 described in FIGS. 2 to 4, and the difference is the existing pile 11 for the target.
Since the structure of the reinforcing pile 10 is the same as that of the existing steel pipe pile, the description of the drawings is omitted.

In the reinforcement pile 10 composed of the existing pile 11 and the new steel pipe pile 12 cast around the outer periphery thereof, as shown in FIG. 8, the bottom area is the bottom area A ₁ of the existing pile 11 and the new steel pipe pile 12
Since it is formed from both of the bottom areas A ₂ divided by the reinforcing ribs 14 in FIG.

As for the pile head, as shown in FIG. 9, when the concrete 18 is placed up to the depth of the reinforcing ribs 15, it becomes like a steel pipe concrete pile and the horizontal resistance of the pile increases.

FIG. 10 shows an example of the layout of newly constructed reinforcing piles. Existing piles 11 such as steel pipe piles or PHC piles are installed in the new building 19 in the basement after the superstructure is dismantled. If they remain in the arrangement shown in the figure,
Only with respect to the existing piles 11 in the new building 19 where the load of the structure is large, the reinforcing piles 10 are used to increase the bearing capacity, and the other existing piles 11 having the required bearing capacity are not reinforced, and are kept as they are. use. As a result, most of the existing underground piles 11 can be effectively reused.

Next, regarding the method of evaluating the vertical bearing capacity of the reinforcing pile having the above-mentioned structure, the long-term bearing capacity of the pile foundation by the steel pipe pile is expressed by the following formula, but generally depends largely on the bearing capacity of the pile tip. In this formula, the bearing capacity of the pile tip is the first term of {}.

[0023]

[Equation 1]

In the present invention, it is important how to increase the closing effect η of the new steel pipe pile, but as shown in FIG. 8, the new steel pipe pile has reinforcing ribs to make the closed area smaller than that of the existing steel pipe pile. Therefore, the area between the existing steel pipe pile and the new steel pipe pile is considerably small, and the bearing capacity is large. Below is a comparison of the tip bearing capacity of the existing steel pipe pile alone, the new steel pipe pile alone, and the double steel pipe reinforcement pile.

I) In case of existing steel pipe pile Steel pipe pile: 500φ (t = 9mm) Tip support force _Ra = (30 × 0.664 × 50 × 0.1963) /3=65.2t
/ Piece → 65t / piece Area of pile tip A _P ＝ A ₁ ＝ 0.1963m ² Blocking effect η ＝ 0.16 × 4.15 ＝ 0.664 (2 <200 / 48.2
= 4.15 <5)

Ii) In the case of new steel pipe pile New steel pipe pile: 900φ (t = 14 mm) Tip support force R _a = (30 × 0.366 × 50 × 0.6362) /3=116.0
t / piece → 115 t / piece Area of pile tip A _P = 0.06362 m ² Closure effect η = 0.16 × 2.29 = 0.366 (2 <200 / 87.2
= 2.29 <5)

Iii) Double Steel Pipe Reinforced Pile (Existing Steel Pipe Pile + New Steel Pipe Pile) An outline of the double steel pipe reinforced pile is shown in FIG. New steel pipe pile: 900φ (t = 14mm) + Reinforcing rib Rib.PL-2
000 × 160 × 12 (8 sheets) Tip support force 500φ
R _a1 = 65 t / piece Tip support force 900φ R _a2 = 8 × (30 × 0.8 × 50 × 0.0550) /3=176.0 t / piece → 175
t / piece Area of pile tip A _P = A ₂ = 0.0550 m ² → Equivalent circle diameter = 0.
2646cm Blocking effect η = 0.8 (5 <200 / 24.66 = 8.11) Tip support force of double steel pipe reinforced pile _Ra = 65 + 175 = 240t

The tip supporting force of the double steel pipe reinforced pile is 500φ.
It is much larger than the bearing capacity (R _a = 65t, 115t) when the steel pipe piles of 900 mm and 900φ are individually constructed, and the tip bearing capacity obtained by adding both of them.

The long-term bearing capacity of the pile foundation when the existing pile is a PHC pile is

[Equation 2]

Below, a comparison is made of the tip supporting forces of the existing PHC pile alone, the new steel pipe pile alone, and the reinforcing pile. i) In case of existing PHC pile Steel pipe pile: 500φ (t = 9mm) Tip support force _Ra = (30 ×× 50 × 0.1963) / 3 = 98.2t / piece → 95t / piece Pile tip area A _P = A ₁ = 0.1963m ²

Ii) In case of new steel pipe pile New steel pipe pile: 1000φ (t = 14mm) Tip support force R _a = (30 × 0.328 × 50 × 0.7854) /3=128.8
t / piece → 125 t / piece Area of pile tip A _P = 0.7854m ² Blocking effect η = 0.16 × 2.05 = 0.328 (2 <200 / 97.2
= 2.05 <5)

Iii) Reinforcement pile (existing PHC pile + new steel pipe pile) Although the outline of the reinforcement pile is not particularly shown, the bottom area A ₁ of the existing PHC pile corresponds to the outer peripheral area of the existing steel pipe pile in FIG. New steel pipe pile: 1000φ (t = 14mm) + Reinforcing rib Rib.PL
-2000 × 190 × 12 (8 sheets) Tip support force 500φ R _a1 = 95t / piece Tip support force 1000φ R _a2 = 8 × (30 × 0.8 × 50 × 0.07364 / 3 = 235.6 t / piece → 235
Area of t / piece pile tip A _P = A ₂ = 0.07364 m ² → Equivalent circle diameter =
0.3062cm Blocking effect η = 0.8 (5 <200 / 30.62 = 6.53) Tip support force of reinforcing pile _Ra = 95 + 235 = 330t

The supporting force at the tip of the reinforcing pile is 500φ for existing P
It is much larger than the bearing capacity (R _a = 95t, 125t) when the HC pile and the new steel pipe pile of 1000φ are individually constructed and the tip bearing strength obtained by adding both of them.

Evaluation method of retained horizontal proof strength Horizontal proof stress can also be obtained by applying the method shown at the tip of the pile to the pile head. The outline is shown in Fig. 9, and the reinforcing rib of the new steel pipe pile is made to have a length of about 5 to 10 m as compared with the tip of the pile so that it can withstand the horizontal resistance during an earthquake. The rigidity of the pile is as shown below in the case of the pile in the previous section.

In the case of existing steel pipe pile i) Steel pipe pile 500φ (t = 9mm), corrosion margin 1.0mm ... I = 36900 cm ⁴ ii) Steel pipe pile 900φ (t = 14mm), corrosion margin 1.0mm ... I = 353000cm ⁴ iii) Double steel pipe reinforcement pile, with 1.0mm corrosion margin ………… I = 400000cm ⁴ or more

In the case of existing PHC pile i) Steel pipe pile 500φ …………………………………………………… I = 246 300cm ⁴ ii) Steel pipe pile 1000φ (t = 14mm) Corrosion margin 1.0mm … I = 353000cm ⁴ iii) Reinforcement pile, corrosion margin 1.0mm …………………… I = 400000cm ⁴ or more

Further, as shown in the figure, concrete is pre-cast into the reinforcing rib portion (at the time of manufacturing the reinforcing pile,
When placed in a factory), it becomes a steel pipe concrete pile, and the horizontal resistance of the pile increases dramatically.

[0038]

Since the present invention is constructed as described above, it has the following effects. When rebuilding an existing building, steel pipe piles or PH
Although the cost of removing existing piles such as C piles is enormous, the effective use of existing piles basically eliminates the need for removal costs. By reducing the number of existing waste piles as much as possible, it is possible to perform a "global environment friendly" building rebuilding work. By adopting the new steel pipe pile provided with the reinforcing ribs, it is possible to construct a pile exhibiting a significantly larger vertical support force and horizontal resistance than the existing pile, the new steel pipe pile, or a combination thereof. The new steel pipe pile is basically concentric with the existing pile and has a diameter that is reasonably larger than the existing pile, and the reinforcing ribs provided inside it serve as a guide when driving the new steel pipe pile. Construction of steel pipe piles is relatively easy, and for those with a steel pipe driving guide inside the reinforcing ribs,
The guide effect is further improved. Buildings can be rebuilt without being dominated by existing piles, and new buildings can be freely designed.

[Brief description of drawings]

FIG. 1 is a schematic elevational view of a reinforcing pile constructed according to the present invention.

FIG. 2 is a schematic vertical sectional elevational view showing an outline of a reinforcing pile composed of an existing steel pipe pile and a new steel pipe pile in the same as above.

FIG. 3 (A) is a plan sectional view of the tip of the reinforcing pile in FIG.
FIG. 3B is a partial vertical sectional view of FIG.

FIG. 4 (A) is a plan sectional view of a tip portion of a reinforcing pile when a driving guide is provided, and FIG. 4 (B) is a partial vertical sectional view of FIG. 4 (A).

FIG. 5 is a schematic vertical sectional elevation view showing an outline of a reinforcing pile formed by an existing PHC pile and a new steel pipe pile.

FIG. 6 (A) is a plane cross-sectional view of the tip of the reinforcing pile in FIG.
FIG. 3B is a partial vertical sectional view of FIG.

FIG. 7 (A) is a plan sectional view of a tip portion of a reinforcing pile when a driving guide is provided, and FIG. 7 (B) is a partial vertical sectional view of FIG. 7 (A).

FIG. 8 is a plan cross-sectional view of a pile head showing a bottom area of an existing steel pipe pile and a divided bottom area of a new steel pipe pile in a reinforcing pile.

FIG. 9 is a partial vertical elevation view of a head portion of a reinforcing pile.

FIG. 10 is a plan view showing an arrangement of existing piles and reinforcing piles and an outline of a new building.

FIG. 11 is an explanatory diagram showing the relationship between existing piles and existing buildings.

FIG. 12 is an explanatory view showing a processing state of a conventional existing pile.

[Explanation of symbols]

 10 Reinforcement Pile 11 Existing Pile 12 New Steel Pipe Pile 13 Support Ground 14 Reinforcement Rib at Tip of Pile 15 Reinforcement Pile at Pile Head 16 Reinforcement Rib at Pile Joint 17 Punching Guide

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuo Murakami 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Kiyoshi Ishii 1-2-2 Shibaura, Minato-ku, Tokyo No. 3 in Shimizu Construction Co., Ltd. (72) Inventor Eiji Wakida 1-2-3 Shibaura, Minato-ku, Tokyo No. 3 In Shimizu Construction Co., Ltd. (72) Inventor Jun Yoshida, 1-2 Shibaura, Minato-ku, Tokyo No. 3 in Shimizu Construction Co., Ltd. (72) Inventor Takeyoshi Fuku, 1-chome, Shibaura, Minato-ku, Tokyo No. 3 In Shimizu Construction Co., Ltd. (72) Inventor Ikuo Takahashi, Shibaura, Minato-ku, Tokyo 2nd-3rd Shimizu Construction Co., Ltd. (72) Inventor Atsushi Onoue 1st-3rd Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Ogisako Eiji Minato-ku, Tokyo Shibaura 1-3-2 Shimizu Construction Co., Ltd. (72) Author Hideyuki Mano 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu construction company (72) Inventor Ryo Kishida 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu construction company (72) Inventor Kazutomo Yokoyama 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Company (72) Inventor Katsuzawa Sakae 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Company

Claims (2)

[Claims] 1. A new steel pipe pile, which has a larger diameter than the existing pile and radially has reinforcing ribs of a required depth radially inside both ends, is placed around the outer periphery of the existing pile of the building trace. A new steel pipe, characterized in that the pile is covered from the pile tip of the existing pile to the head of the pile, and the existing pile is configured as a new reinforcing pile in which the vertical supporting force and horizontal resistance are increased by the reinforcing ribs. Method of increasing bearing capacity of existing piles by piles. 2. The new steel pipe pile according to claim 1, wherein the new steel pipe pile is provided with a guide for placing a steel pipe having a diameter larger than that of the existing pile inside the reinforcing ribs at the tip end. Method to increase bearing capacity of existing piles.