JP2003176532A - Cast-in-place concrete pile structure - Google Patents
Cast-in-place concrete pile structureInfo
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- JP2003176532A JP2003176532A JP2001377594A JP2001377594A JP2003176532A JP 2003176532 A JP2003176532 A JP 2003176532A JP 2001377594 A JP2001377594 A JP 2001377594A JP 2001377594 A JP2001377594 A JP 2001377594A JP 2003176532 A JP2003176532 A JP 2003176532A
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- expanded
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- expanding
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、場所打ちコンクリ
ート杭構造に関し、特に、複数段の拡底部を支持層中に
埋設して、比較的小さい拡底径でも大きな拡底径と同等
の支持力を得ることができる場所打ちコンクリート杭構
造に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast-in-place concrete pile structure, and more particularly, by embedding a plurality of stages of bottom expanding portions in a support layer, a bearing force equivalent to a large bottom expanding diameter can be obtained even with a relatively small bottom expanding diameter. The present invention relates to a cast-in-place concrete pile structure that can be used.
【０００２】[0002]
【従来の技術】例えば、特開平６−４９８４２号公報に
示されるように、杭の支持力を高めるために、杭の埋設
部分に拡幅部を設けた節杭が提案されている。しかし、
この節杭の節部の抵抗力は、節部を直径とした仮想の杭
としての土砂のせん断抵抗力であり、この抵抗力は底部
支持力に比較してそれほど大きな値にはならないため、
底部支持力と同じにするためには、多くの節を付けなけ
ればならず、コストアップになる。また、節杭の掘削工
法は、掘削バケットに取り付けたスクレーパーを油圧装
置によって開閉することにより掘削孔を拡幅するが、油
圧シリンダーの伸縮によってスクレーパーが開閉するた
め、バケットの径により油圧シリンダーの長さに限界が
あり、自ずと、バケットの径と油圧シリンダーの最大長
（扉の最大開き長さ）が決められ、構造的に拡幅径は杭
径の１．８〜１．９倍が限度である。2. Description of the Related Art For example, as disclosed in Japanese Unexamined Patent Publication No. 6-49842, there has been proposed a node pile in which a widened portion is provided in a buried portion of the pile in order to increase the supporting force of the pile. But,
The resistance of the node of this node pile is the shearing resistance of the earth and sand as a virtual pile with the node diameter, and this resistance is not so large compared to the bottom supporting force.
In order to make it the same as the bottom supporting force, many nodes must be added, which increases the cost. In addition, in the method of excavating the piles, the excavation hole is widened by opening and closing the scraper attached to the excavation bucket with a hydraulic device, but since the scraper is opened and closed by expanding and contracting the hydraulic cylinder, the length of the hydraulic cylinder depends on the diameter of the bucket. However, the diameter of the bucket and the maximum length of the hydraulic cylinder (the maximum opening length of the door) are naturally determined, and structurally the widening diameter is limited to 1.8 to 1.9 times the pile diameter.
【０００３】一方、場所打ちコンクリート杭としては、
例えば、特開平５−３３９９４０号公報に示されるよう
に、杭外周部の一部あるいは全部にリング状の連続リブ
を設けた場所打ちコンクリート杭がある。しかし、上記
従来の場所打ちコンクリート杭では、拡底径が大きくな
るに従って、掘削時における応力開放による先端地盤の
ゆるみがより大きくなるため、先端支持力度（ｍ2当り
の支持力）が低減する。実設計においては、拡底径１．
５ｍ以上の杭に対してβ＝１．０−０．３（Ｄ−１．
５）／２．５なる低減係数を用いて支持力を低減してい
る。On the other hand, for cast-in-place concrete piles,
For example, as shown in JP-A-5-339940, there is a cast-in-place concrete pile in which a ring-shaped continuous rib is provided on a part or all of the outer peripheral portion of the pile. However, in the conventional cast-in-place concrete pile, the looseness of the tip ground due to the stress release at the time of excavation becomes larger as the diameter of the expanded bottom becomes larger, so that the tip supporting force (bearing force per m 2 ) is reduced. In the actual design, the expanded bottom diameter is 1.
Β = 1.0-0.3 (D-1.
5) /2.5 is used to reduce the bearing capacity.
【０００４】また、杭の掘削工法として、アースドリル
エ法とリバースサーキュレーション工法の２種類がある
が、アースドリル工法の方が安価なため、ほとんどの拡
底杭はアースドリル工法で施工している。このアースド
リル工法は、掘削バケット内にある油圧ジャッキのシリ
ンダーを上下させることにより、拡幅ビットを連結して
いる連結ロッドを介して拡幅ビットを開閉し、拡底部を
掘削して掘削土をバケット内に取り込む構造になってい
る。しかしながら、拡幅ビットは、基部がヒンジ構造、
先端部が掘削刃になっていることから、連結ロッドを長
くして拡底径を広げようとしても、拡幅ビットの長さ以
上にはならないことや、連結ロッドが拡幅ビットの基部
に当ること等により、拡底径は自ずと制限され、拡底径
はやはり杭径の１．８〜１．９倍が限度である。There are two types of pile excavation methods, the earth drill method and the reverse circulation method, but most of the bottom piles are constructed by the earth drill method because the earth drill method is cheaper. In this earth drill method, the cylinder of the hydraulic jack in the excavation bucket is moved up and down to open and close the widening bit through the connecting rod that connects the widening bit, and the bottom is excavated to excavate the excavated soil in the bucket. It is structured to be taken into. However, the widening bit has a hinge structure at the base,
Since the tip part is an excavating blade, even if you try to lengthen the connecting rod and widen the bottom expanding diameter, the length does not exceed the length of the widening bit, and the connecting rod hits the base of the widening bit. The expanded diameter is naturally limited, and the expanded diameter is limited to 1.8 to 1.9 times the pile diameter.
【０００５】このように、従来の場所打ちコンクリート
杭では、大きな鉛直荷重が作用する場合には、拡底径を
大きくしなければならないが、大きくすればするほど先
端支持力の増加の割合が下がり、また、杭径も大きくし
なければならなくなり、掘削土量及び残土量が増加し不
経済となるという問題を有している。As described above, in the conventional cast-in-place concrete pile, when a large vertical load is applied, it is necessary to increase the diameter of bottom expansion, but the larger the diameter, the lower the rate of increase in the tip supporting force, In addition, the pile diameter must be increased, which increases the amount of excavated soil and the amount of remaining soil, which is uneconomical.
【０００６】[0006]
【発明が解決しようとする課題】本発明は、上記従来の
場所打ちコンクリート杭構造が有する問題点に鑑み、複
数段の拡底部を支持層中に埋設して、比較的小さい拡底
径でも大きな拡底径と同等の支持力を得ることができる
場所打ちコンクリート杭構造を提供することを目的とす
る。SUMMARY OF THE INVENTION In view of the problems of the conventional cast-in-place concrete pile structure, the present invention embeds a plurality of steps of bottom expansion into a support layer to allow a large bottom expansion even with a relatively small bottom expansion diameter. It is an object of the present invention to provide a cast-in-place concrete pile structure capable of obtaining a bearing force equivalent to the diameter.
【０００７】[0007]
【課題を解決するための手段】上記目的を達成するた
め、本発明の場所打ちコンクリート杭構造は、杭の先端
部に２段以上の拡底部を有するとともに、最上段の拡底
部の支持面が、少なくとも支持層上面より下方に位置す
るとともに、次段以下の拡底部が当該支持層中に位置す
ることを特徴とする。In order to achieve the above-mentioned object, the cast-in-place concrete pile structure of the present invention has a bottom expanded portion having two or more steps, and a support surface of the top expanded portion is It is characterized in that it is located at least below the upper surface of the support layer, and that the expanded bottom portion of the next stage and below is located in the support layer.
【０００８】この場所打ちコンクリート杭構造は、杭の
先端部に２段以上の拡底部を有するとともに、最上段の
拡底部の支持面が、少なくとも支持層上面より下方に位
置するとともに、次段以下の拡底部を当該支持層中に位
置させることにより、複数段の拡底部を同一の支持層中
に埋設して、比較的小さい拡底径でも大きな拡底径と同
等の支持力を得ることができ、また、従来の拡底杭より
杭径を小さくして、掘削土量や残土処分量、生コンクリ
ート量を削減することにより、コストを低減するととも
に地球環境に及ぼす影響を小さくすることができる。This cast-in-place concrete pile structure has two or more expanded bottom portions at the tip of the pile, the support surface of the expanded bottom portion of the uppermost step is located at least below the upper surface of the support layer, and the following steps and below. By locating the expanded bottom portion of the above in the support layer, it is possible to embed a plurality of stages of expanded bottom portion in the same support layer, to obtain a supporting force equivalent to a large expanded diameter even with a relatively small expanded diameter, In addition, the pile diameter can be made smaller than that of the conventional bottom-expanded pile to reduce the amount of excavated soil, the amount of residual soil disposal, and the amount of ready-mixed concrete, thereby reducing the cost and the impact on the global environment.
【０００９】この場合において、拡底部を略裁頭錐体状
に形成するとともに、上下に隣接する拡底部で、上段拡
底部の支持面外周位置をＡ、下段拡底部の上端位置を
Ｂ、上段拡底部の支持面内周位置をＣ、支持層土砂の内
部摩擦角をφとして、ＢＣ≧ＡＣｔａｎ（４５°＋φ／
２）とすることができる。ここで、「ＢＣ」は、上段拡
底部の支持面外周位置Ａと下段拡底部の上端位置Ｂとの
距離、「ＡＣ」は、上段拡底部の支持面外周位置Ａと上
段拡底部の支持面内周位置Ｃとの距離を意味する（本明
細書において、同じ）。In this case, the bottom expanding portion is formed into a substantially truncated pyramid shape, and in the bottom expanding portions vertically adjacent to each other, the outer peripheral position of the support surface of the upper bottom expanding portion is A, the upper end position of the lower bottom expanding portion is B, and the upper bottom position is B. BC ≧ ACtan (45 ° + φ /, where C is the inner circumferential position of the support surface of the expanded bottom and φ is the internal friction angle of the support layer
It can be 2). Here, "BC" is the distance between the support surface outer peripheral position A of the upper bottom expanding portion and the upper end position B of the lower bottom expanding portion, and "AC" is the support surface outer peripheral position A of the upper bottom expanding portion and the support surface of the upper bottom expanding portion. It means the distance from the inner circumferential position C (the same in this specification).
【００１０】これにより、上段拡底部の外径、及び上段
拡底部と下段拡底部との間隔を適正にすることができ
る。Thus, the outer diameter of the upper bottom expanded portion and the distance between the upper bottom expanded portion and the lower bottom expanded portion can be made appropriate.
【００１１】また、下段拡底部の上面傾斜角度βを４５
°−φ／２以下とすることができる。Further, the upper surface inclination angle β of the lower bottom expanded portion is set to 45.
It can be set to ° -φ / 2 or less.
【００１２】これにより、下段拡底部の傾斜面が対数ら
せんのすべり面に交わらないようにすることができる。This makes it possible to prevent the inclined surface of the lower bottom expanded portion from intersecting with the slip surface of the logarithmic spiral.
【００１３】[0013]
【発明の実施の形態】以下、本発明の場所打ちコンクリ
ート杭構造の実施の形態を図面に基づいて説明する。BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a cast-in-place concrete pile structure of the present invention will be described below with reference to the drawings.
【００１４】図１〜図３に、本発明の場所打ちコンクリ
ート杭構造の一実施例を示す。この場所打ちコンクリー
ト杭構造は、杭１の先端部に上下２段の拡底部２、３を
有するとともに、最上段の拡底部２の支持面２１が、少
なくとも支持層４の上面４ａより下方に位置するととも
に、次段以下の拡底部３が当該支持層４中に位置してい
る。1 to 3 show an embodiment of the cast-in-place concrete pile structure of the present invention. This cast-in-place concrete pile structure has upper and lower two-stage expanded portions 2 and 3 at the tip of the pile 1, and the support surface 21 of the uppermost expanded portion 2 is located at least below the upper surface 4a of the support layer 4. At the same time, the expanded bottom portion 3 of the next stage and below is located in the support layer 4.
【００１５】拡底部２、３は、それぞれ裁頭錐体状に形
成されるとともに、上段拡底部２の支持面外周位置を
Ａ、下段拡底部３の上端位置をＢ、上段拡底部の支持面
内周位置をＣ、支持層土砂の内部摩擦角をφとして、Ｂ
Ｃ≧ＡＣｔａｎ（４５°＋φ／２）となるように、上段
拡底部２と下段拡底部３との間隔が設定されている。ま
た、下段拡底部３の上面傾斜角度βは、４５°−φ／２
以下に設定されている。The bottom expanding portions 2 and 3 are each formed in a truncated cone shape, and the outer peripheral position of the supporting surface of the upper expanding portion 2 is A, the upper end position of the lower expanding portion 3 is B, and the supporting surface of the upper expanding portion. The inner circumferential position is C, the internal friction angle of the support layer is φ, and B
The interval between the upper bottom expanded portion 2 and the lower bottom expanded portion 3 is set so that C ≧ ACtan (45 ° + φ / 2). Further, the upper surface inclination angle β of the lower expanded bottom portion 3 is 45 ° −φ / 2.
It is set below.
【００１６】杭の典型的な支持力機構は図４に示す通り
であるが、これを本実施例の場所打ちコンクリート杭構
造の上段拡底部２に応用すると、図１に示すように、上
段拡底部２の支持面外周位置Ａ点からすべり面Ａ−Ｂが
角度４５゜＋φ／２で発生し、このすべり面Ａ−Ｂが杭
１の軸部１１とＢ点で交わる。下段拡底部３はこのＢ点
から始まり、下段拡底部３の傾斜面３１が対数らせんの
すべり面に交わらないように、その角度は４５゜−φ／
２以下とする。よってＢＣ＝ＡＣｔａｎ（４５＋φ／
２）となる。上段拡底部２の支持面２１は、図１では水
平になっているが、支持面２１は水平でなくともよく、
支持力に影響を及ぼさないすべり面Ａ−Ｂまで、つまり
４５゜＋φ／２までは傾けることができる。A typical supporting force mechanism of a pile is as shown in FIG. 4, but when this is applied to the upper bottom expanding part 2 of the cast-in-place concrete pile structure of this embodiment, the upper bottom expanding part as shown in FIG. A slip surface AB is generated at an angle of 45 ° + φ / 2 from the outer peripheral position A of the support surface of the portion 2, and the slip surface AB intersects the shaft portion 11 of the pile 1 at the point B. The lower bottom expanding part 3 starts from this point B, and its angle is 45 ° -φ / so that the inclined surface 31 of the lower bottom expanding part 3 does not intersect the slip surface of the logarithmic spiral.
2 or less. Therefore, BC = ACtan (45 + φ /
2). The support surface 21 of the upper bottom expanded portion 2 is horizontal in FIG. 1, but the support surface 21 does not have to be horizontal,
It is possible to incline up to a slip surface AB that does not affect the supporting force, that is, up to 45 ° + φ / 2.
【００１７】（実施例１）図２（ａ）に示すように、ア
ースドリル機５により軸径１２００ｍｍ、掘削長３１．
０ｍの掘削を行った。支持層４は３．５５ｍ掘削してい
る。同図（ｂ）に示すように、拡底バケット５１を掘削
孔５２に挿入し、上段拡底部２をその外径がφ２１００
ｍｍになるように拡底掘削した。掘削底面は支持層４の
上面４ａとした。その後、同じ拡底バケット５１でもっ
て、同図（ｃ）に示すように下段拡底部３を、その外径
がφ２１００ｍｍになるように拡底掘削した。この場
合、支持層４の内部摩擦角φは４６．６゜であるから、
４５−φ／２＝４５−４６．６／２＝２１．７゜とな
り、この２１．７゜よりも小さい角度である１２゜を上
面傾斜角度βとして、下段拡底部３の上面傾斜面を掘削
した。また、図１に示すように、上段拡底部２の支持面
２１（Ｃ点）から下段拡底部３の上端位置Ｂまでの長さ
は１．１３ｍであり、下段拡底部３の長さは２．１２
ｍ、下段拡底部３の立ち上がり３２の長さは０．３ｍで
ある。(Embodiment 1) As shown in FIG. 2 (a), an earth drill machine 5 was used to form a shaft diameter of 1200 mm and an excavation length of 31.
Drilled 0 m. The support layer 4 is excavated 3.55 m. As shown in FIG. 7B, the bottom expanding bucket 51 is inserted into the excavation hole 52, and the outer diameter of the upper stage bottom expanding part 2 is φ2100.
The bottom was excavated so that it would be mm. The bottom surface of the excavation was the top surface 4a of the support layer 4. Thereafter, with the same bottom expanding bucket 51, bottom expanding was performed on the lower stage bottom expanding part 3 so that the outer diameter thereof was φ2100 mm, as shown in FIG. In this case, since the internal friction angle φ of the support layer 4 is 46.6 °,
45−φ / 2 = 45−46.6 / 2 = 21.7 °, and 12 °, which is an angle smaller than 21.7 °, is used as the upper surface inclination angle β, and the upper surface inclined surface of the lower expanded portion 3 is excavated. did. Further, as shown in FIG. 1, the length from the supporting surface 21 (point C) of the upper bottom expanding portion 2 to the upper end position B of the lower bottom expanding portion 3 is 1.13 m, and the length of the lower bottom expanding portion 3 is 2 .12
m, the length of the rising 32 of the lower bottom expanded portion 3 is 0.3 m.
【００１８】（実施例２）軸径１５００ｍｍ、掘削長４
５．５ｍの杭築造において、図３（ａ）に示すように、
まずアースドリル機５により、支持層４の上面４ａ（深
さ４１．２３ｍ）まで杭１の軸部１１を埋設するための
掘削を行った。同図（ｂ）に示すように、拡底バケット
５１を掘削孔５２に挿入し、上段の拡底部２をその外径
がφ２６００ｍｍになるように拡底掘削した。掘削底面
は支持層上面とした。その後、軸部掘削用のバケット５
３に入れ替えて、同図（ｃ）に示すように、軸部径でも
って支持層４を４．２７ｍ掘削した。そして、同図
（ｄ）に示すように、下段の拡底部３をその外径がφ２
６００ｍｍになるように拡底掘削した。この場合、支持
層４の内部摩擦角φは４６．６゜であるから、４５−φ
／２＝４５−４６．６／２＝２１．７゜となり、この２
１．７゜よりも小さい角度である１２゜でもって下段拡
底部３の上面傾斜面３１を掘削した。なお、上段拡底部
２の支持面２１から下段拡底部３の上端位置までの長さ
は１．３８ｍであり、下段拡底部３の長さは２．５９
ｍ、下段拡底部３の立ち上がり３２の長さは０．３ｍで
ある。(Example 2) Shaft diameter 1500 mm, excavation length 4
In the 5.5m pile construction, as shown in Fig. 3 (a),
First, the earth drill machine 5 was used to dig the shaft 11 of the pile 1 to the upper surface 4a (depth 41.23 m) of the support layer 4. As shown in FIG. 6B, the bottom expanding bucket 51 was inserted into the excavation hole 52, and the bottom expanding part 2 of the upper stage was bottom excavated so that its outer diameter was φ2600 mm. The excavated bottom surface was the top surface of the support layer. After that, bucket 5 for shaft excavation
In place of 3, the support layer 4 was excavated for 4.27 m with the shaft diameter as shown in FIG. Then, as shown in FIG. 3D, the outer diameter of the bottom expanded portion 3 is φ2.
The bottom was excavated to 600 mm. In this case, since the internal friction angle φ of the support layer 4 is 46.6 °, 45-φ
/2=45-46.6/2=21.7°, and this 2
The upper sloping surface 31 of the lower expanded bottom portion 3 was excavated at 12 °, which is smaller than 1.7 °. The length from the supporting surface 21 of the upper bottom expanding portion 2 to the upper end position of the lower bottom expanding portion 3 is 1.38 m, and the length of the lower bottom expanding portion 3 is 2.59.
m, the length of the rising 32 of the lower bottom expanded portion 3 is 0.3 m.
【００１９】表１に、本実施例の拡底杭における上段拡
底部２の支持面２１の支持力と、従来の節杭の抵抗力と
を比較した例を示す。従来の節杭が、本実施例の拡底杭
における上段拡底部２の支持面２１の支持力と同じ抵抗
力を得るためには、節のある部分の長さを拡底径の６倍
以上にする必要がある。この場合、節間隔は拡底径のほ
ぼ２倍であるから、節の数は４個以上になる。これに対
し、本実施例の拡底杭の拡底部２、３は２箇所であり、
この２段拡底杭の拡底の施工手間は、節杭の節の施工に
対して半分以下の手間でよい。Table 1 shows an example in which the supporting force of the supporting surface 21 of the upper bottom expanding part 2 in the bottom expanding pile of this embodiment and the resistance of the conventional node pile are compared. In order for the conventional node pile to obtain the same resistance as the supporting force of the support surface 21 of the upper bottom expanding part 2 in the bottom expanding pile of the present embodiment, the length of the part having the node should be 6 times or more of the bottom expanding diameter. There is a need. In this case, since the node interval is almost twice the expanded diameter, the number of nodes is four or more. On the other hand, there are two bottom expanding portions 2 and 3 of the bottom expanding pile of the present embodiment,
The work for expanding the bottom of the two-stage expanded pile may be less than half the time for constructing the nodes of the node pile.
【００２０】[0020]
【表１】 [Table 1]
【００２１】表２に、本実施例の拡底杭の杭先端部の支
持力と、従来の拡底杭の支持力とを比較した例を示す。
従来の拡底杭は軸径に対して最大の拡底径とし、本実施
例の拡底杭も上下段拡底径ともそれと同じとしている。
支持力度（単位面積当りの支持力）は、上段拡底部２及
び下段拡底部３とも、現在設計に用いている２５００ｋ
Ｎ／ｍ2である。支持層４へ拡底部２、３を余分に２．
２〜２．９ｍ入れることにより、本実施例の２段拡底杭
は、従来の拡底杭より杭径を３００〜４００ｍｍ小さく
することが可能である。これにより、掘削土量や、残土
処分量、生コンクリート量を約３割低減することがで
き、経済的効果や地球環境に及ぼす効果が非常に大きく
なる。Table 2 shows an example in which the supporting force of the pile tip portion of the bottom expanding pile of this embodiment and the supporting force of the conventional bottom expanding pile are compared.
The conventional bottom-expanding pile has a maximum bottom-expanding diameter relative to the shaft diameter, and the bottom-expanding pile according to the present embodiment has the same bottom-bottom bottom-expanding diameter.
The bearing capacity (bearing capacity per unit area) is 2500 k, which is currently used for designing both the upper bottom expanded part 2 and the lower expanded bottom part 3.
N / m 2 . 1. Add extra bottom expansions 2 and 3 to the support layer 4.
By inserting 2 to 2.9 m, the two-stage bottom expanding pile of this embodiment can have a pile diameter smaller than that of the conventional bottom expanding pile by 300 to 400 mm. As a result, the amount of excavated soil, the amount of residual soil disposal, and the amount of ready-mixed concrete can be reduced by about 30%, and the economic effect and the effect on the global environment become extremely large.
【００２２】[0022]
【表２】 [Table 2]
【００２３】表３に、本実施例の拡底杭における上段拡
底部２の支持面２１の支持力と、１つの拡底部を円柱状
に長くした従来の杭の周面摩擦力とを比較した例を示
す。拡底部を長くした従来の杭の杭周面摩擦力が、本実
施例の拡底杭の上段拡底部２の支持面の支持力と同じ抵
抗力を得るためには、拡底部のある長さを拡底径のほぼ
１２倍に設計する必要がある。すなわち、本実施例の２
段拡底杭では拡底部のある長さは拡底径の２倍以下（表
２参照）であるから、従来の拡底杭では、その約６倍の
拡底部長さが必要となり、掘削土量や、残土処分量、生
コンクリート量が多くなり、コストアップとなる。Table 3 shows an example in which the supporting force of the supporting surface 21 of the upper bottom expanding part 2 in the bottom expanding pile of this embodiment and the peripheral frictional force of the conventional pile in which one bottom expanding part is elongated are compared. Indicates. In order to obtain the same resistance as the bearing force of the support surface of the upper-stage bottom expanding part 2 of the bottom expanding pile of the present embodiment, the pile peripheral surface frictional force of the conventional pile having a long bottom expanding part requires a length with a bottom expanding part. It is necessary to design the diameter to be approximately 12 times the expanded diameter. That is, 2 of the present embodiment
Since the length of the stepped bottom pile with the bottom expansion part is less than twice the bottom expansion diameter (see Table 2), the conventional bottom expansion pile requires about 6 times the bottom expansion part length. The amount of disposal and the amount of ready-mixed concrete increase, resulting in higher costs.
【００２４】[0024]
【表３】 [Table 3]
【００２５】以上、本発明の実施例を説明したが、例え
ば拡底部を３段以上設ける等、本発明の場所打ちコンク
リート杭構造は、その要旨を逸脱しない範囲において適
宜に変更することが可能である。Although the embodiments of the present invention have been described above, the cast-in-place concrete pile structure of the present invention can be appropriately modified without departing from the gist thereof, for example, by providing three or more stages of expanded bottom portions. is there.
【００２６】[0026]
【発明の効果】本発明の場所打ちコンクリート杭構造に
よれば、杭の先端部に２段以上の拡底部を有するととも
に、最上段の拡底部の支持面が、少なくとも支持層上面
より下方に位置するとともに、次段以下の拡底部を当該
支持層中に位置させることにより、複数段の拡底部を同
一の支持層中に埋設して、比較的小さい拡底径でも大き
な拡底径と同等の支持力を得ることができ、また、従来
の拡底杭より杭径を小さくして、掘削土量や残土処分
量、生コンクリート量を削減することにより、コストを
低減するとともに地球環境に及ぼす影響を小さくするこ
とができる。EFFECTS OF THE INVENTION According to the cast-in-place concrete pile structure of the present invention, the bottom end of the pile has two or more bottom expansion portions, and the support surface of the top bottom expansion portion is located at least below the upper surface of the support layer. In addition, by arranging the bottom expanded part of the next stage and below in the support layer, the bottom expanded parts of multiple stages are embedded in the same support layer, and a supporting force equivalent to a large bottom expanded diameter is obtained even with a relatively small bottom expanded diameter. In addition, by reducing the pile diameter and the amount of excavated soil, the amount of residual soil disposal, and the amount of ready-mixed concrete to reduce the cost and the impact on the global environment, it is possible to reduce be able to.
【００２７】また、拡底部を略裁頭錐体状に形成すると
ともに、上下に隣接する拡底部で、上段拡底部の支持面
外周位置をＡ、下段拡底部の上端位置をＢ、上段拡底部
の支持面内周位置をＣ、支持層土砂の内部摩擦角をφと
して、ＢＣ≧ＡＣｔａｎ（４５°＋φ／２）とすること
により、上段拡底部の外径、及び上段拡底部と下段拡底
部との間隔を適正にすることができる。In addition, the bottom expanding portion is formed into a substantially truncated cone shape, and the vertically adjacent bottom expanding portions have an outer peripheral position of the support surface of the upper bottom expanding portion A, an upper end position of the lower bottom expanding portion B, and an upper bottom expanding portion. The inner diameter of the support surface is C, the internal friction angle of the support layer is φ, and BC ≧ ACtan (45 ° + φ / 2), so that the outer diameter of the upper bottom expanded portion and the upper bottom expanded portion and the lower expanded bottom portion The interval between and can be made appropriate.
【００２８】さらに、下段拡底部の上面傾斜角度βを４
５°−φ／２以下とすることにより、下段拡底部の傾斜
面が対数らせんのすべり面に交わらないようにすること
ができる。Further, the upper surface inclination angle β of the bottom expanded portion is set to 4
By setting the angle to 5 ° -φ / 2 or less, it is possible to prevent the inclined surface of the lower expanded portion from intersecting with the slip surface of the logarithmic spiral.
【図１】本発明の場所打ちコンクリート杭構造の一実施
例を示す断面図である。FIG. 1 is a sectional view showing an embodiment of a cast-in-place concrete pile structure of the present invention.
【図２】同実施例の場所打ちコンクリート杭構造の掘削
工程を示す工程図である。FIG. 2 is a process drawing showing an excavation process of a cast-in-place concrete pile structure of the same example.
【図３】本発明の他の実施例の場所打ちコンクリート杭
構造の掘削工程を示す工程図である。FIG. 3 is a process drawing showing an excavation process of a cast-in-place concrete pile structure according to another embodiment of the present invention.
【図４】杭の支持力を示す説明図である。FIG. 4 is an explanatory diagram showing a supporting force of a pile.
Ａ 支持面外周位置 Ｂ 下段拡底部の上端位置 Ｃ 支持面内周位置 Ａ−Ｂ すべり面 １ 杭 １１ 軸部 ２ 上段拡底部 ２１ 支持面 ３ 下段拡底部 ３１ 上面傾斜面 ３２ 立ち上がり ４ 支持層 ４ａ 支持層上面 ５ アースドリル機 ５１ 拡底バケット ５２ 掘削孔 ５３ 軸部掘削用バケット A support surface outer peripheral position B Upper end position of bottom expanded part C Support surface inner circumference position AB sliding surface 1 pile 11 Shaft 2 Upper stage bottom part 21 Support surface 3 Lower bottom expanded part 31 Top slope 32 rising 4 Support layer 4a Support layer upper surface 5 Earth drill machine 51 bottom expanding bucket 52 drill holes 53 Shaft excavation bucket
───────────────────────────────────────────────────── フロントページの続き (72)発明者 筒井 通剛 大阪府大阪市阿倍野区松崎町２丁目２番２ 号 株式会社奥村組内 Ｆターム(参考） 2D041 AA01 BA22 CA03 CB04 DA01 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Tsutsui Tsuyoshi 2-2-2 Matsuzaki-cho, Abeno-ku, Osaka-shi, Osaka No. Okumura Gumi Co., Ltd. F-term (reference) 2D041 AA01 BA22 CA03 CB04 DA01
Claims (3)
とともに、最上段の拡底部の支持面が、少なくとも支持
層上面より下方に位置するとともに、次段以下の拡底部
が当該支持層中に位置することを特徴とする場所打ちコ
ンクリート杭構造。1. The pile has a bottom expanded portion having two or more steps, and the support surface of the top expanded portion is located at least below the upper surface of the support layer, and the bottom expanded portions of the next step and below are supported. Cast-in-place concrete pile structure characterized by being located in layers.
に、上下に隣接する拡底部で、上段拡底部の支持面外周
位置をＡ、下段拡底部の上端位置をＢ、上段拡底部の支
持面内周位置をＣ、支持層土砂の内部摩擦角をφとし
て、ＢＣ≧ＡＣｔａｎ（４５°＋φ／２）としたことを
特徴とする請求項１記載の場所打ちコンクリート杭構
造。2. The bottom expanding portion is formed into a substantially truncated cone shape, and the upper and lower adjacent bottom expanding portions have an outer peripheral position of a support surface of the upper bottom expanding portion A, an upper end position of the lower bottom expanding portion B, and an upper bottom expanding portion. 2. The cast-in-place concrete pile structure according to claim 1, wherein BC ≧ ACtan (45 ° + φ / 2), where C is the inner circumferential position of the support surface and φ is the internal friction angle of the support layer earth and sand.
φ／２以下としたことを特徴とする請求項２記載の場所
打ちコンクリート杭構造。3. The inclination angle β of the upper surface of the lower expanded portion is 45 °-
The cast-in-place concrete pile structure according to claim 2, characterized in that it is φ / 2 or less.
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|---|---|---|---|
| JP2001377594A JP3888888B2 (en) | 2001-12-11 | 2001-12-11 | Cast-in-place concrete pile structure |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001377594A JP3888888B2 (en) | 2001-12-11 | 2001-12-11 | Cast-in-place concrete pile structure |
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| Publication Number | Publication Date |
|---|---|
| JP2003176532A true JP2003176532A (en) | 2003-06-24 |
| JP3888888B2 JP3888888B2 (en) | 2007-03-07 |
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ID=19185517
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|---|---|---|---|
| JP2001377594A Expired - Fee Related JP3888888B2 (en) | 2001-12-11 | 2001-12-11 | Cast-in-place concrete pile structure |
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