JP2023023295A - Rotary penetration steel pipe pile and construction method for rotary penetration steel pipe pile - Google Patents

Rotary penetration steel pipe pile and construction method for rotary penetration steel pipe pile Download PDF

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JP2023023295A
JP2023023295A JP2021128674A JP2021128674A JP2023023295A JP 2023023295 A JP2023023295 A JP 2023023295A JP 2021128674 A JP2021128674 A JP 2021128674A JP 2021128674 A JP2021128674 A JP 2021128674A JP 2023023295 A JP2023023295 A JP 2023023295A
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pile
blade
steel pipe
diameter
lowermost
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真利奈 河合
Marina KAWAI
敏雄 篠原
Toshio Shinohara
利行 深谷
Toshiyuki Fukaya
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JFE Steel Corp
Chiyoda Geotech Co Ltd
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JFE Steel Corp
Chiyoda Geotech Co Ltd
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Priority to JP2021128674A priority Critical patent/JP2023023295A/en
Priority to KR1020247004793A priority patent/KR20240029557A/en
Priority to CN202280052912.6A priority patent/CN117813430A/en
Priority to PCT/JP2022/029408 priority patent/WO2023013563A1/en
Publication of JP2023023295A publication Critical patent/JP2023023295A/en
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/22—Piles
    • E02D5/56—Screw piles
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D2600/00—Miscellaneous
    • E02D2600/20—Miscellaneous comprising details of connection between elements
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D2600/00—Miscellaneous
    • E02D2600/30—Miscellaneous comprising anchoring details

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  • Structural Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
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  • General Engineering & Computer Science (AREA)
  • Piles And Underground Anchors (AREA)

Abstract

To provide a rotary penetration steel pipe pile driven so as to be arranged in an intermediate layer without allowing the tip of the pile to reach the bearing layer, and capable of sufficiently exhibiting bearing capacity and reducing costs, and a construction method for the rotary penetration steel pipe pile.SOLUTION: A rotary penetration steel pipe pile 1 according to the present invention is driven so that the tip of the pile is placed in an intermediate layer without reaching the bearing layer, and comprises a lowermost blade 3 with a substantially helical single turn provided near the tip of the pile, and single-turn upper blades 5 provided in multiple stages above the lowermost blade 3 and at regular intervals within the range of 1.25 to 7.5 times the blade diameter. The outer diameter of the lowermost blade 3 is set to be larger than the outer diameter of the upper blade 5 and 1.5 to 3 times the pile diameter. The outer diameter of the upper blade 5 is smaller than the outer diameter of the lowermost blade 3 and 1.6 times or less than the pile diameter, and the pitch thereof is set to be the same as the pitch of the lowermost blade 3.SELECTED DRAWING: Figure 1

Description

本発明は、地盤中に回転して施工する鋼管杭に関し、特に杭先端を支持層に到達させることなく中間層に配置されるように打設される回転貫入鋼管杭及び該回転貫入鋼管杭の施工方法に関する。 The present invention relates to a steel pipe pile that is rotated and constructed in the ground, and in particular, a rotary penetration steel pipe pile that is driven so that the tip of the pile is placed in the intermediate layer without reaching the bearing layer, and the rotary penetration steel pipe pile. Concerning the construction method.

支持層が地中深く（例えば深度30m以上）に存在し、かつ中間層（例えば、地中10～20mでN値が5～30程度）が存在する場合、杭の材料費や施工費を低減するために、杭体の外周面に作用する地盤からの摩擦抵抗力で支持する機構のいわゆる摩擦杭が用いられることが多い。 If the bearing layer exists deep underground (e.g. 30m or more) and there is an intermediate layer (e.g. 10-20m underground with an N value of 5-30), the material and construction costs for piles can be reduced. In order to do so, so-called friction piles are often used, which are supported by the friction resistance force from the ground acting on the outer peripheral surface of the pile body.

このような摩擦杭は、杭1本当たりの支持力が小さいために、鋼管によって形成するとその材料強度を十分発揮させることができず、経済性でコンクリート杭に劣ることが多い。
そこで、鋼管の外周面に多数の翼をつけて、支持力（見かけの摩擦力）を増やして鋼材の材料強度を十分に発揮させるようにしているものがある。その代表的な既存技術として、特許文献１と特許文献２に開示がある。 Since such friction piles have a small bearing capacity per pile, if they are made of steel pipes, they cannot fully exert their material strength, and are often inferior to concrete piles in economic efficiency.
Therefore, there is a steel pipe with a large number of wings attached to its outer peripheral surface to increase the supporting force (apparent frictional force) and to fully demonstrate the material strength of the steel material. Patent document 1 and patent document 2 disclose typical existing technologies.

特許文献１に開示された鋼管杭は、杭外周面に少なくとも１周以上螺旋状に形成された螺旋羽根を、杭外周面に断続的に多数配置したものである。
また、特許文献２に開示された鋼管杭は、一巻きの螺旋状の羽根を、断続的に設けたものである。 The steel pipe pile disclosed in Patent Literature 1 has a large number of spiral blades intermittently arranged on the outer peripheral surface of the pile.
In addition, the steel pipe pile disclosed in Patent Document 2 is intermittently provided with one turn of spiral blades.

特開2012-136823号公報JP 2012-136823 A 特開2003-074057号公報JP-A-2003-074057

特許文献１の鋼管杭は、各螺旋羽根が１周以上の螺旋状に形成されたものであるため、支持力は大きくなるが、翼の材料費と取り付け費が高くならざるを得ない。
他方、特許文献２の鋼管杭の螺旋状の羽根は、１周であるため、コスト面では特許文献１よりも低減できるが、滑りを発生しやすいという問題がある。このため、特許文献１と同様の態様で実用化されているものは、設けられる羽根の径（翼径）が鋼管径の2倍程度もあり、断続的であってもコストの高い杭になっている。 In the steel pipe pile of Patent Literature 1, each spiral blade is formed in a spiral shape with one or more turns, so although the bearing capacity is large, the material cost and installation cost of the blade are inevitably high.
On the other hand, the helical blade of the steel pipe pile of Patent Document 2 has one turn, so the cost can be reduced as compared with Patent Document 1, but there is a problem that slippage is likely to occur. For this reason, those that have been put into practical use in the same manner as in Patent Document 1 have blade diameters (blade diameters) that are about twice the diameter of steel pipes, and even if they are intermittent, they are expensive piles. ing.

本発明はかかる課題を解決するためになされたものであり、杭先端を支持層に到達させることなく中間層に配置されるように打設される回転貫入鋼管杭であって、支持力を十分に発揮できると共にコスト低減ができる回転貫入鋼管杭、該回転貫入鋼管杭の施工方法を提供することを目的としている。 The present invention has been made to solve such problems, and is a rotary penetration steel pipe pile that is driven so as to be placed in an intermediate layer without allowing the tip of the pile to reach the support layer, and has sufficient bearing capacity. It is an object of the present invention to provide a rotary penetration steel pipe pile and a construction method of the rotary penetration steel pipe pile that can be exhibited in a high efficiency and at the same time that the cost can be reduced.

（１）本発明に係る回転貫入鋼管杭は、杭先端を支持層に到達させることなく中間層に配置されるように打設されるものであって、
杭先端近傍に設けられた略らせん状の一巻きの最下段翼と、該最下段翼の上方に複数段で、かつ翼径の1.25～7.5倍の範囲内の一定間隔で設けられた一巻きの上段翼とを有し、
前記最下段翼の外径は、前記上段翼の外径より大きく、かつ杭径の1.5～3倍に設定され、
前記上段翼の外径は、前記最下段翼の外径より小さく、かつ杭径の1.6倍以下であり、そのピッチが前記最下段翼のピッチと同一に設定されていることを特徴とするものである。 (1) The rotary penetration steel pipe pile according to the present invention is driven so that the tip of the pile is placed in the intermediate layer without reaching the support layer,
A substantially spiral one-turn bottom wing provided near the tip of the pile, and one turn provided at regular intervals within the range of 1.25 to 7.5 times the blade diameter in multiple stages above the bottom wing. and an upper wing of
The outer diameter of the lowermost blade is set to be larger than the outer diameter of the upper blade and 1.5 to 3 times the pile diameter,
The outer diameter of the upper blade is smaller than the outer diameter of the lowermost blade and 1.6 times or less than the pile diameter, and the pitch thereof is set to be the same as the pitch of the lowermost blade. is.

（２）本発明に係る回転貫入鋼管杭の施工方法は、上記（１）に記載の回転貫入鋼管杭の施工方法であって、
1回転当たり貫入量が最下段翼のピッチと同じになるように、杭打機から杭に与える下方向押込み力を調整しながら回転貫入することを特徴とするものである。 (2) A method for constructing a rotary penetration steel pipe pile according to the present invention is the construction method for a rotary penetration steel pipe pile according to (1) above,
It is characterized by rotating penetration while adjusting the downward pushing force applied from the pile driver to the pile so that the amount of penetration per rotation is the same as the pitch of the lowermost wing.

本発明に係る回転貫入鋼管杭は、杭先端に上段翼よりも径の大きい最下段翼を有することにより、中間層に止める杭であるにもかかわらず、大きな鉛直支持力を確保できる。
また、最下段翼の上方に翼径が杭径の1.6倍以下の複数の上段翼を、その径と取付間隔を考慮して配置したことにより、大きな摩擦抵抗力を確保できるとともに、取付コストを抑えられる。
さらに、最下段翼と上段翼のピッチを同じにしたことにより、上段翼周辺の地盤の軟化を抑えることができ、確実な摩擦抵抗力を確保できる。 The rotary penetration steel pipe pile according to the present invention has a lowermost wing with a diameter larger than that of the upper wing at the tip of the pile, so that a large vertical bearing capacity can be secured in spite of being a pile that is stopped in an intermediate layer.
In addition, multiple upper blades with a diameter of 1.6 times or less than the pile diameter are arranged above the lowest blade, taking into consideration the diameter and mounting interval, ensuring a large frictional resistance and reducing the installation cost. suppressed.
Furthermore, by making the pitches of the lowermost blades and the upper blades the same, softening of the ground around the upper blades can be suppressed, and reliable frictional resistance can be ensured.

本発明の一実施の形態に係る回転貫入鋼管杭の説明図である。BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the rotation penetration steel pipe pile which concerns on one embodiment of this invention. 図１に示した回転貫入鋼管杭の作用を説明する説明図である。It is explanatory drawing explaining the effect|action of the rotation penetration steel pipe pile shown in FIG. 本発明の一実施の形態に係る回転貫入鋼管杭における上段翼の翼間隔と翼径との関係の決定するための実験結果を示すグラフである。It is a graph which shows the experimental result for determining the relationship between the wing|blade space|blade distance of the upper stage wing|blade, and the wing|blade diameter in the rotary intrusion steel pipe pile which concerns on one embodiment of this invention.

本実施の形態に係る回転貫入鋼管杭１は、杭先端を支持層に到達させることなく中間層に配置されるように打設されるものであって、杭先端近傍に設けられた略らせん状の一巻きの最下段翼３と、最下段翼３の上方に複数段で設けられた上段翼５とを有している。
以下、各構成を詳細に説明する。 The rotary penetration steel pipe pile 1 according to the present embodiment is driven so that the tip of the pile is placed in the intermediate layer without reaching the support layer. It has a lowermost blade 3 with one turn and upper blades 5 provided in a plurality of stages above the lowermost blade 3. - 特許庁
Each configuration will be described in detail below.

＜用途＞
本実施の形態の回転貫入鋼管杭１は、上述したように、杭先端を支持層に到達させることなく中間層に配置されるように打設される、いわゆる摩擦杭である。
このような摩擦杭は、支持層の深度が深く（例えば深度30m以上）、かつ中間層（例えば、地中10～20mでN値が5～30程度）が存在する地盤に施工される。
なお、杭先端を支持層まで打設して支持層で支持をする先端支持杭は、先端を通常N値が約30以上の地層に止めるのが一般的であり、本発明の回転貫入鋼管杭１とはその用途が異なっている。 <Application>
The rotary penetration steel pipe pile 1 of the present embodiment is, as described above, a so-called friction pile that is driven so as to be placed in the intermediate layer without allowing the tip of the pile to reach the support layer.
Such friction piles are constructed in the ground where the support layer is deep (for example, 30 m or more) and there is an intermediate layer (for example, 10 to 20 m underground with an N value of 5 to 30).
It should be noted that the tip of the tip of the pile that is driven to the support layer and supported by the support layer is generally stopped in a stratum with an N value of about 30 or more, and the rotary penetration steel pipe pile of the present invention 1 is used differently.

＜最下段翼＞
最下段翼３は、杭先端近傍に設けられた略らせん状の一巻きの翼である。
最下段翼３の外径は、上段翼の外径より大きく、かつ杭径の1.5～3倍に設定されている。
杭先端近傍とは、杭本体部である鋼管７の先端面または先端近傍の鋼管７の外周を含む。
略らせん状の翼とは、らせん状、または形状が疑似らせん状でらせん状翼と同様にねじ込み作用を有する翼をいう。例えば、2個の半割り円環状平板を直列に繋げて1個のらせんに近い形状に構成した翼などを含む。 <Bottom wing>
The lowermost wing 3 is a substantially helical one-turn wing provided in the vicinity of the tip of the pile.
The outer diameter of the lowermost blade 3 is larger than the outer diameter of the upper blade and is set to 1.5 to 3 times the diameter of the pile.
The vicinity of the tip of the pile includes the tip surface of the steel pipe 7 which is the pile main body or the outer periphery of the steel pipe 7 near the tip.
The term "substantially helical wing" refers to a wing having a helical shape or a quasi-spiral shape and having a screwing action similar to a helical wing. For example, it includes a wing that is formed by connecting two half-circular flat plates in series to form a shape close to a single spiral.

最下段翼３の外径を杭径の1.5～3倍にする理由は、以下の通りである。
発明者がこれまでに経験した回転貫入杭の施工実績から、杭径の1.5倍を下回るといわゆる滑り（1回転当たり貫入量が極端に小さくなる空転現象）が生じやすくなる。また、約3倍を超えると、回転貫入時のトルクが大きくなりすぎて、杭体の許容ねじりトルクやくい打ち機の回転能力を超える。また、3倍を超えると、トルク上昇への対応として、翼の板厚を厚くする必要があり、それにより、応力集中や溶接が困難となることも挙げられる。 The reason why the outer diameter of the lowermost blade 3 is 1.5 to 3 times the pile diameter is as follows.
From the results of the construction of rotary penetration piles that the inventor has experienced so far, so-called slippage (slipping phenomenon in which the amount of penetration per rotation becomes extremely small) tends to occur when the diameter is less than 1.5 times the pile diameter. On the other hand, if it exceeds about 3 times, the torque at the time of rotary penetration becomes too large, exceeding the allowable torsional torque of the pile body and the rotational capacity of the pile driver. In addition, if it exceeds 3 times, it is necessary to increase the plate thickness of the blade in order to cope with the increase in torque, which makes stress concentration and welding difficult.

＜上段翼５＞
上段翼５は、最下段翼３の上方に複数段で設けられた略らせん状の一巻きの翼である。
複数段の上段翼５における翼間の間隔は、翼径の1.25～7.5倍の範囲内の一定間隔に設定されている。
上段翼５の外径は、最下段翼３の外径より小さく、かつ杭径の1.6倍以下であり、そのピッチが最下段翼３のピッチと同一に設定されている。 <Upper wing 5>
The upper stage blade 5 is a substantially spiral single turn blade provided in a plurality of stages above the lowermost stage blade 3 .
The interval between blades in the multiple stages of upper blades 5 is set to a constant interval within the range of 1.25 to 7.5 times the blade diameter.
The outer diameter of the upper blades 5 is smaller than the outer diameter of the lowermost blades 3 and 1.6 times or less than the pile diameter, and the pitch thereof is set to be the same as the pitch of the lowermost blades 3 .

上段翼５は、一巻きの翼を複数段で設けており、断続的な翼となっているが、このようにした理由は取付コストを考慮したためである。
すなわち、連続的に取り付けたほうが、施工時の貫入性能や供用時の支持力が大きくなるが、取り付け費用が数倍多くかかるため、取付コストを重視したものである。 The upper stage blade 5 is provided with single-turn blades in a plurality of stages, and is an intermittent blade.
In other words, the continuous installation increases the penetration performance during construction and the bearing capacity during use, but the installation cost is several times higher, so the installation cost is emphasized.

複数段の上段翼５における翼間の間隔を、翼径の1.25～7.5倍の範囲内の一定間隔に設定した理由を図２に基づいて説明する。
本発明による鉛直支持力は、最下段翼３下面に作用する上向きの地盤反力（ここでは、便宜的に＜先端支持力＞と呼ぶ）と、複数の上段翼５による支持力（ここでは便宜的に＜摩擦抵抗力＞と呼ぶ）の二種の支持力が合成されたものなる。 The reason why the interval between blades in the multiple stages of upper blades 5 is set to a constant interval within the range of 1.25 to 7.5 times the blade diameter will be described with reference to FIG.
The vertical support force according to the present invention consists of an upward ground reaction force acting on the lower surface of the lowest blade 3 (here, for convenience, referred to as <tip support force>), and a support force by the plurality of upper blades 5 (here, for convenience, Generally called <frictional resistance>), it is a combination of two types of bearing forces.

先端支持力の大きさは、地盤の強度（硬さ）に最下段翼３の面積を掛けた値にほぼ比例するため、地盤があまり硬くない地盤に適用する本件発明においては、翼面積は大きいほうがよい。このため、最下段翼３の外径は杭径の1.5倍以上としている。
また、摩擦抵抗力は、図２に示す個々の上段翼５の支圧抵抗力の和と、上段翼５の外径を円周とする円筒体(点線で示す)における地盤のせん断抵抗力のうち、小さいほうの値が摩擦抵抗力になる。 Since the magnitude of the tip support force is approximately proportional to the value obtained by multiplying the strength (hardness) of the ground by the area of the lowermost wing 3, the wing area is large in the present invention applied to the ground that is not very hard. Better. For this reason, the outer diameter of the lowermost blade 3 is set to 1.5 times or more the diameter of the pile.
Frictional resistance is the sum of the bearing pressure resistance of the individual upper blades 5 shown in FIG. Among them, the smaller value is the frictional resistance.

支圧抵抗力の和とせん断抵抗力とのうちどちらが大きくなるかは地盤の土質や硬さにより多少変わるが、発明者の検討によって、上段翼５の翼間隔を上段翼５の翼径で除した（翼間隔/翼径）値が1.25未満になると、上段翼５の支圧抵抗力の和よりも円筒体側面のせん断抵抗力が相当小さくなることがわかった。
したがって、翼間隔/翼径は1.25以上であることが好ましい。
一方、翼間隔/翼径が7.5を超えると、層厚が限られる中間層における翼の取付個数が少なくなるため、支圧抵抗力の和は円筒側面のせん断抵抗力よりも相当小さくなる。
このことから、翼間隔/翼径を1.25～7.5に設定することでバランスがよく、大きな摩擦抵抗力を発現することができる。
なお、翼間隔/翼径は1.25以上が好ましい点については、後述の実施例で実証している。 Which of the sum of the bearing pressure resistance and the shear resistance is greater depends on the soil quality and hardness of the ground. It was found that when the calculated (blade spacing/blade diameter) value is less than 1.25, the shear resistance on the side surface of the cylindrical body becomes considerably smaller than the sum of the bearing pressure resistance of the upper stage blades 5 .
Therefore, the blade spacing/blade diameter is preferably 1.25 or more.
On the other hand, when the blade spacing/blade diameter exceeds 7.5, the number of blades attached to the intermediate layer, which has a limited layer thickness, is reduced, so the sum of the bearing pressure resistance becomes considerably smaller than the shear resistance of the cylindrical side surface.
Based on this, setting the blade spacing/blade diameter between 1.25 and 7.5 provides a good balance and a large frictional resistance.
It should be noted that the fact that the blade spacing/blade diameter is preferably 1.25 or more has been demonstrated in Examples described later.

また、上段翼５の外径が鋼管径の1.6倍以下に設定した理由は以下の通りである。
上段翼５の断面積は径の２乗に比例して増えるため、材料費も２乗に比例して増える。他方、上段翼５による支持力は径の二乗に比例しない。そのため、複数段に設置される上段翼５の径を大きくすることは不経済になる。これらを総合的に判断すると、上段翼５の外径は鋼管径の1.6倍以下が好ましい。 The reason why the outer diameter of the upper blade 5 is set to 1.6 times or less the diameter of the steel pipe is as follows.
Since the cross-sectional area of the upper blade 5 increases in proportion to the square of the diameter, the material cost also increases in proportion to the square. On the other hand, the supporting force by the upper wing 5 is not proportional to the square of the diameter. Therefore, it is uneconomical to increase the diameter of the upper stage blades 5 installed in a plurality of stages. Judging these factors comprehensively, it is preferable that the outer diameter of the upper blade 5 is 1.6 times or less the diameter of the steel pipe.

上段翼５のピッチ（上段翼５が１周して進むらせん直角方向の距離）が、最下段翼３のピッチ（最下段翼３が１周して進むらせん直角方向の距離）と同一に設定されている理由は以下の通りである。
回転貫入鋼管杭１は回転貫入時に、その1回転当たりの貫入量は、外径が大きな最下段翼３のピッチに近い値で貫入しようとする。このとき、上段翼５のピッチが最下段翼３と異なると、回転貫入鋼管杭１の回転に要するトルクをより大きくする必要がある。また、上段翼５周辺の地盤をより多く乱すため、上段翼５周辺の支持力が減少する。換言すると、上段翼５のピッチが最下段翼３と同じであれば、回転貫入鋼管杭１の回転に要するトルクが小さくなり、また、上段翼５周辺の地盤を乱すことが少なくなり、上段翼５周辺の支持力が減少する。 The pitch of the upper blades 5 (the distance in the direction perpendicular to the spiral that the upper blades 5 advance in one round) is set to be the same as the pitch of the lowermost blades 3 (the distance in the direction perpendicular to the spiral that the lower blades 3 advance in one rotation). The reason is as follows.
During rotary penetration, the rotary penetration steel pipe pile 1 attempts to penetrate at a value close to the pitch of the lowermost wing 3 having a large outer diameter. At this time, if the pitch of the upper wing 5 is different from that of the lowermost wing 3, it is necessary to increase the torque required to rotate the rotary penetration steel pipe pile 1 . Further, since the ground around the upper wing 5 is disturbed more, the supporting force around the upper wing 5 is reduced. In other words, if the pitch of the upper blade 5 is the same as that of the lower blade 3, the torque required to rotate the rotary penetration steel pipe pile 1 is reduced, and the ground around the upper blade 5 is less disturbed. 5 Peripheral bearing capacity is reduced.

以上のように構成された本実施の形態の回転貫入鋼管杭１によれば、以下の効果を奏することができる。
杭先端に径の大きい最下段翼３を配置したことにより、中間層に止める杭であるにもかかわらず、大きな鉛直支持力を確保できる。
また、最下段翼３の上方に翼径が杭径の1.6倍以下の複数の上段翼５を、その径と取付間隔を考慮して配置したことにより、大きな摩擦抵抗力を確保できるとともに、取付コストを抑えられる。
さらに、最下段翼３と上段翼５のピッチを同じにしたことにより、上段翼５周辺の地盤の軟化を抑えることができ、確実な摩擦抵抗力を確保できる。 According to the rotary penetration steel pipe pile 1 of the present embodiment configured as described above, the following effects can be obtained.
By arranging the lowermost wing 3 with a large diameter at the tip of the pile, it is possible to secure a large vertical bearing force in spite of the fact that the pile is fixed to the intermediate layer.
In addition, a plurality of upper blades 5 having a blade diameter of 1.6 times or less than the pile diameter are arranged above the lowermost blade 3 in consideration of the diameter and the mounting interval. Reduce costs.
Further, since the lowermost blade 3 and the upper blade 5 have the same pitch, softening of the ground around the upper blade 5 can be suppressed, and reliable frictional resistance can be secured.

なお、本実施の形態に係る回転貫入鋼管杭の施工方法は、1回転当たり貫入量が最下段翼３のピッチと同じになるように、杭打機から杭に与える下方向押込み力を調整しながら回転貫入することが好ましい。この理由は以下の通りである。 In addition, in the construction method of the rotary penetration steel pipe pile according to the present embodiment, the downward pushing force applied from the pile driver to the pile is adjusted so that the penetration amount per rotation is the same as the pitch of the lowermost wing 3. Rotating penetration is preferable. The reason for this is as follows.

回転貫入鋼管杭１は硬い地盤の上端や土質の変化部で滑りを発生しやすい。本実施の形態の回転貫入鋼管杭１は、先端に大きな径を持つ最下段翼３を有しているため、滑りを発生しにくくしているが、それでも施工条件によっては滑り発生が避けられない。
また、本実施の形態の回転貫入鋼管杭１は、上段翼５を多数有するため、滑りが発生すると翼周辺の地盤をこね返して軟化させ、その結果摩擦抵抗力が大幅に減少して、上段翼５を取り付けている意味がなくなる。
この点、回転貫入鋼管杭１の1回転当たり貫入量が最下段翼３のピッチと同じである場合、最下段翼３が地盤を切るように入るため、地盤の乱れが最小になる。
そこで、杭打機から回転貫入鋼管杭１に伝える下方向押込み力を調整することで、１回転当たり貫入量を翼のピッチに合わせるように貫入をコントロールするとよい。 The rotary penetrating steel pipe pile 1 is likely to slip at the top of hard ground or at a change in soil quality. Since the rotary penetration steel pipe pile 1 of this embodiment has the lowermost wing 3 with a large diameter at the tip, it is difficult to cause slippage, but slippage is still unavoidable depending on the construction conditions. .
In addition, since the rotary penetration steel pipe pile 1 of the present embodiment has a large number of upper blades 5, when slippage occurs, the ground around the blades is kneaded and softened. There is no point in attaching the wings 5 .
In this regard, when the penetration amount per rotation of the rotary penetration steel pipe pile 1 is the same as the pitch of the lowermost blade 3, the lowermost blade 3 cuts the ground, so ground disturbance is minimized.
Therefore, by adjusting the downward pushing force transmitted from the pile driver to the rotary penetration steel pipe pile 1, it is preferable to control the penetration so that the amount of penetration per rotation matches the pitch of the blade.

上段翼５の径と取付間隔の最適範囲を求めるために、実物と同じ比率の縮小モデルを用いた土層実験を行った。縮小モデルとして用いた試験体の杭の鋼管径は76.3mm、鋼管板厚は2.8mm、土層のＮ値=20として表１に示す条件で試験結果を比較した。 In order to determine the optimum range of the diameter of the upper blade 5 and the mounting interval, a soil layer experiment was conducted using a scaled-down model with the same ratio as the real one. The test results were compared under the conditions shown in Table 1, with a steel pipe diameter of 76.3 mm, a steel pipe plate thickness of 2.8 mm, and a soil layer N value of 20.

Figure 2023023295000002
Figure 2023023295000002

試験結果を図３に示す。
図３の横軸は上段翼５の翼間隔を上段翼５の翼径で除した（翼間隔/翼径）値であり、縦軸は翼部の周面摩擦力係数（kN/m2）である。
一般に翼の付いていない鋼管杭の周面摩擦力係数は、鋼管径に関わらず２（kN/m2）が用いられることがあり、これとの比較をすることから、多段翼が付いているものにおいても周面摩擦力係数に相当するものを算出して比較することとした。具体的には、縮小モデルに荷重を負荷して支持力を計測し、その支持力を、翼径を直径とし杭長と同じ長さの円筒の表面積で除算した値を周面摩擦力係数として図中にプロットした。 The test results are shown in FIG.
The horizontal axis in FIG. 3 is the value obtained by dividing the blade interval of the upper blade 5 by the blade diameter of the upper blade 5 (blade interval/blade diameter), and the vertical axis is the circumferential friction coefficient of the blade (kN/m 2 ). is.
In general, 2 (kN/m 2 ) is used for the coefficient of circumferential friction force of steel pipe piles without blades, regardless of the steel pipe diameter. We decided to calculate and compare the coefficient of frictional force on the peripheral surface. Specifically, load is applied to the scaled-down model to measure the bearing capacity, and the value obtained by dividing the bearing capacity by the surface area of a cylinder whose diameter is the blade diameter and whose length is the same as the pile length is taken as the skin friction coefficient. plotted in the figure.

図３に示されるように、比較例１、２では周面摩擦力係数が２（kN/m2）よりも小さいが、h/wが本発明範囲内にある発明例１、２の周面摩擦力係数は２（kN/m2）よりも大きく、また比較例１、２よりもはるかに大きな値となっている。
このことから、翼間隔/翼径が本発明の範囲である1.25以上であれば、周面摩擦力係数を大きくできる、換言すれば支持力を大きくできることが分かる。 As shown in FIG. 3, in Comparative Examples 1 and 2, the peripheral surface friction force coefficient is smaller than 2 (kN/m 2 ), but h/w is within the scope of the present invention. The coefficient of frictional force is greater than 2 (kN/m 2 ) and much greater than those of Comparative Examples 1 and 2.
From this, it can be seen that if the blade spacing/blade diameter is 1.25 or more, which is the range of the present invention, the coefficient of circumferential friction force can be increased, in other words, the supporting force can be increased.

なお、上記の模型実験データが実大のものに妥当していることを確認するため実大実験を行った。実大実験は、杭径318.5mm、翼径は杭径の1.5倍=477.75mm、翼間隔hは1200mm、とした。実大実験の結果は図３の×印のプロットで示されており、模型実験データとほぼ同じ4.762ｋN/m2の周面摩擦力係数が得られた。これによって、上記の模型実験が実大のものに妥当していることが実証された。 In addition, a full-scale experiment was conducted to confirm that the above model test data is appropriate for a full-scale model. In the full-scale test, the pile diameter was 318.5 mm, the blade diameter was 1.5 times the pile diameter = 477.75 mm, and the blade interval h was 1200 mm. The results of the full-scale experiment are shown by the plots marked with x in FIG. 3, and a circumferential friction force coefficient of 4.762 kN/m 2 , which is almost the same as the model experiment data, was obtained. This proved that the above model experiment was appropriate for a full-scale model.

１ 回転貫入鋼管杭
３ 最下段翼
５ 上段翼
７ 鋼管 1 rotary intrusion steel pipe pile 3 bottom wing 5 upper wing 7 steel pipe

Claims (2)

杭先端を支持層に到達させることなく中間層に配置されるように打設される回転貫入鋼管杭であって、
杭先端近傍に設けられた略らせん状の一巻きの最下段翼と、該最下段翼の上方に複数段で、かつ翼径の1.25～7.5倍の範囲内の一定間隔で設けられた一巻きの上段翼とを有し、
前記最下段翼の外径は、前記上段翼の外径より大きく、かつ杭径の1.5～3倍に設定され、
前記上段翼の外径は、前記最下段翼の外径より小さく、かつ杭径の1.6倍以下であり、そのピッチが前記最下段翼のピッチと同一に設定されていることを特徴とする回転貫入鋼管杭。 A rotary penetration steel pipe pile that is driven so as to be placed in an intermediate layer without allowing the tip of the pile to reach the bearing layer,
A substantially spiral one-turn bottom wing provided near the tip of the pile, and one turn provided at regular intervals within the range of 1.25 to 7.5 times the blade diameter in multiple stages above the bottom wing. and an upper wing of
The outer diameter of the lowermost blade is set to be larger than the outer diameter of the upper blade and 1.5 to 3 times the pile diameter,
The rotation characterized in that the outer diameter of the upper blade is smaller than the outer diameter of the lowermost blade and is 1.6 times or less than the pile diameter, and the pitch thereof is set to be the same as the pitch of the lowermost blade. Penetrating steel pipe piles. 請求項１に記載の回転貫入鋼管杭の施工方法であって、
1回転当たり貫入量が最下段翼のピッチと同じになるように、杭打機から杭に与える下方向押込み力を調整しながら回転貫入することを特徴とする回転貫入鋼管杭の施工方法。 A construction method for a rotary penetration steel pipe pile according to claim 1,
A construction method for rotary penetration steel pipe piles characterized in that rotary penetration is carried out while adjusting the downward pushing force applied to the pile from a pile driver so that the amount of penetration per rotation is the same as the pitch of the lowermost wing.
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