JP2019183496A - Construction method of cast-in-place concrete pile - Google Patents

Construction method of cast-in-place concrete pile Download PDF

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JP2019183496A
JP2019183496A JP2018075063A JP2018075063A JP2019183496A JP 2019183496 A JP2019183496 A JP 2019183496A JP 2018075063 A JP2018075063 A JP 2018075063A JP 2018075063 A JP2018075063 A JP 2018075063A JP 2019183496 A JP2019183496 A JP 2019183496A
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excavation
excavator
cast
place concrete
shaft portion
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JP7012584B2 (en
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英之 眞野
Hideyuki Mano
英之 眞野
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Shimizu Construction Co Ltd
Shimizu Corp
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Abstract

To provide a construction method of cast-in-place concrete pile capable of more efficiently and effectively improving the bearing strength than conventional ones.SOLUTION: The construction method of cast-in-place concrete pile includes the steps of: performing advanced excavation to a predetermined depth of the ground using the excavator for piles to form an excavation hole 10 of the shaft part 2; inserting a bottom expansion excavator 5 for the shaft portion having a smaller diameter than the drilling hole 10 of the shaft part 2 into the front end of the drilling hole 10 in the shaft part 2; holding a rod 4 and/or a guide part of the bottom expansion excavator 5, which is rotatably connected to the bottom expansion excavator 5 by the eccentric positioning and holding means 8 disposed inside the excavation hole 10 of the shaft part 2 in a decentered state by a predetermined amount; and forming an excavation hole 11 in a bottom expanded part 3 by expanding the hole wall of the tip edge of the drilling hole 10 of the shaft part 2 formed by the preceding excavation by the bottom expansion excavator 5.SELECTED DRAWING: Figure 1

Description

本発明は、場所打ちコンクリート杭の構築方法に関する。   The present invention relates to a method for constructing a cast-in-place concrete pile.

従来、超高層ビルなど重量の大きい建物では、杭基礎として場所打ちコンクリート拡底杭が多用されている。   Conventionally, cast-in-place concrete bottom piles are often used as pile foundations in heavy buildings such as high-rise buildings.

場所打ちコンクリート拡底杭（場所打ちコンクリート杭）は、略一定の径の軸部と、軸部の先端部側を必要な支持力に合わせて拡底してなる略円錐台状の拡底部とを備えて構築され、杭先端部に拡底部を設けることで支持耐力を大幅に向上させることができる（例えば、特許文献１参照）。   A cast-in-place concrete pile (cast-in-place concrete pile) has a shaft portion with a substantially constant diameter and a bottom portion in the shape of a truncated cone that is formed by expanding the tip of the shaft portion according to the required support force. The support strength can be significantly improved by providing an expanded bottom portion at the tip of the pile (see, for example, Patent Document 1).

場所打ちコンクリート拡底杭を構築する際には、例えば、掘削機を用いて地表面から略一定の径の掘削孔を所定の深度まで安定液を充填しつつ掘削形成する。次に、ロッドの先端に接続した拡底用掘削機（拡底バケットなどの拡底機）を挿入して掘削孔の先端部に配置した段階で、拡底用掘削機を拡張させつつロッドを中心軸周りに回転させて孔壁部分の地盤を掘削し、掘削孔の先端部を拡底する。そして、拡底した掘削孔に鉄筋籠を建て込むとともにトレミー管を用いて安定液と置換するようにコンクリートを打設し、必要に応じて杭頭部側を埋め戻したり、杭頭基礎を構築するなどし、場所打ちコンクリート拡底杭の施工が完了する。   When constructing the cast-in-place concrete bottom pile, for example, an excavator is used to form an excavation hole having a substantially constant diameter from the ground surface while filling it with a stable liquid to a predetermined depth. Next, at the stage where a bottom-excavating machine (bottom-expanding machine such as a bottom-up bucket) connected to the tip of the rod is inserted and placed at the tip of the excavation hole, the rod is moved around the central axis while expanding the bottom-excavating excavator. Rotate to excavate the ground of the hole wall and widen the tip of the excavation hole. Then, reinforced rods are built into the expanded excavation hole, and concrete is laid to replace the stable liquid using a tremy pipe, and the pile head side is backfilled or a pile head foundation is constructed as necessary. The construction of cast-in-place concrete expanded piles is completed.

特許第２６０７９６６号公報Japanese Patent No. 2607966

ここで、上記のように構築される場所打ちコンクリート拡底杭１は、図６（ａ）に示すように、各種工法ごとにその大きさが異なるが、現状では軸径（軸部２の径）が最大約３ｍ、拡底径（拡底部３の径）が最大４．８ｍ〜５．５ｍである。   Here, as shown in FIG. 6A, the cast-in-place concrete expanded bottom pile 1 constructed as described above has a different size for each method, but at present, the shaft diameter (diameter of the shaft portion 2). Is about 3 m at the maximum and the expanded diameter (the diameter of the expanded portion 3) is at most 4.8 m to 5.5 m.

一方、超高層ビルなど非常に大きな柱軸力を受ける杭では、最大拡底径でも支持力が不足する場合があり、支持力の不足を補うために、例えば図６（ｂ）に示すように、拡底部３を複数形成するなどの対策工法が提案、実用化されている。   On the other hand, in piles that receive very large column axial force such as high-rise buildings, the support force may be insufficient even at the maximum bottom diameter. To compensate for the lack of support force, for example, as shown in FIG. A countermeasure method such as forming a plurality of the widened portions 3 has been proposed and put into practical use.

しかしながら、拡底部３を２つ以上形成する場合には、その分硬質な支持層Ｇ１を掘削して杭長を長くする必要があり、工費、工程に与える影響が非常に大きい。このため、より効率的且つ効果的に支持耐力を向上させることを可能にする手法が強く望まれている。   However, when forming two or more bottom expanded parts 3, it is necessary to excavate the hard support layer G1 and lengthen the pile length, and the influence on construction cost and process is very large. For this reason, a technique that makes it possible to improve the bearing strength more efficiently and effectively is strongly desired.

上記事情に鑑み、本発明は、従来と比較し、より効率的且つ効果的に支持耐力を向上させることが可能な場所打ちコンクリート杭の構築方法を提供することを目的とする。   In view of the above circumstances, an object of the present invention is to provide a method for constructing a cast-in-place concrete pile capable of improving the bearing strength more efficiently and effectively than in the past.

上記の目的を達するために、この発明は以下の手段を提供している。   In order to achieve the above object, the present invention provides the following means.

本発明の場所打ちコンクリート杭の構築方法は、円柱状の軸部と、該軸部の先端部を拡張してなる略円錐台状の拡底部を備えた場所打ちコンクリート杭を構築する方法であって、杭用の掘削機を用いて地盤の所定の深度まで前記軸部の掘削孔を先行掘削して形成し、前記軸部の掘削孔よりも小径の軸部用の拡底用掘削機を前記軸部の掘削孔の先端部に挿入し、且つ、前記軸部の掘削孔の内部に配設した偏心位置決め保持手段によって前記拡底用削孔機に接続したロッド及び／又は前記拡底用掘削機のガイド部を、前記ロッド及び前記拡底用掘削機の中心軸を前記軸部の中心軸に対して所定量偏心させた状態で前記ロッド及び前記拡底用掘削機の中心軸周りに回転可能に保持させ、先行掘削して形成した前記軸部の掘削孔の先端部の孔壁を前記拡底用掘削機で拡底掘削して前記拡底部の掘削孔を形成し、前記軸部と前記拡底部の掘削孔にコンクリートを打設することを特徴とする。   The method for constructing a cast-in-place concrete pile according to the present invention is a method for constructing a cast-in-place concrete pile having a columnar shaft portion and a substantially truncated cone-shaped widened portion obtained by expanding the tip portion of the shaft portion. The excavator for the shaft is formed by preceding excavation of the excavation hole of the shaft portion to a predetermined depth of the ground using an excavator for piles, and the excavator for expanding the bottom of the shaft portion having a smaller diameter than the excavation hole of the shaft portion is formed. A rod connected to the drilling machine for expanding the bottom and / or the excavator for expanding the bottom, which is inserted into the tip of the drilling hole of the shaft part and connected to the drilling machine for expanding the bottom by an eccentric positioning holding means disposed inside the drilling hole of the shaft part. The guide unit is rotatably held around the central axis of the rod and the bottom-excavating excavator in a state where the central axis of the rod and the bottom-excavating excavator is decentered by a predetermined amount with respect to the central axis of the shaft unit. The hole wall at the tip of the drilling hole of the shaft portion formed by preceding excavation And 拡底 drilled at the bottom for an excavator to form a borehole of the 拡底 portion, characterized in that concrete is cast into the wellbore of the 拡底 portion and the shaft portion.

本発明の場所打ちコンクリート杭の構築方法においては、前記拡底用掘削機の先端部に、前記拡底用掘削機の中心軸と同軸で掘削刃よりも下方に突出する位置決め凸部であるスタビライザーを設け、前記スタビライザーを掘削孔の底面の地盤に突き刺すようにして拡底掘削することが望ましい。   In the method for constructing a cast-in-place concrete pile according to the present invention, a stabilizer that is a positioning convex portion that is coaxial with the central axis of the bottom-excavating excavator and projects below the excavating blade is provided at the tip of the bottom-excavating excavator. It is preferable that the stabilizer is drilled to expand the bottom so as to pierce the ground at the bottom of the drilling hole.

本発明の場所打ちコンクリート杭の構築方法においては、超高層ビルなど非常に大きな柱軸力を好適に支持できる高支持耐力の場所打ちコンクリート拡底杭を、効率的且つ効果的に構築することが可能になる。   In the method for constructing a cast-in-place concrete pile according to the present invention, it is possible to efficiently and effectively construct a cast-in-place concrete expanded pile with a high support strength capable of suitably supporting a very large column axial force such as a high-rise building. become.

本発明の一実施形態に係る場所打ちコンクリート杭の構築方法を示す図である。It is a figure which shows the construction method of the cast-in-place concrete pile which concerns on one Embodiment of this invention. 従来の拡底掘削機を用いて拡底部を形成した場合を示す図である。It is a figure which shows the case where a bottom expansion part is formed using the conventional bottom expansion excavator. 本発明の一実施形態に係る場所打ちコンクリート杭を示す図であり、３箇所の偏心位置で拡底掘削を行った場合の場所打ちコンクリート杭を示す図である。It is a figure which shows the cast-in-place concrete pile which concerns on one Embodiment of this invention, and is a figure which shows the cast-in-place concrete pile at the time of performing bottom expansion excavation in three eccentric positions. 本発明の一実施形態に係る場所打ちコンクリート杭を示す図であり、４箇所の偏心位置で拡底掘削を行った場合の場所打ちコンクリート杭を示す図である。It is a figure which shows the cast-in-place concrete pile which concerns on one Embodiment of this invention, and is a figure which shows the cast-in-place concrete pile at the time of performing bottom expansion excavation in four eccentric positions. 本発明の一実施形態に係る場所打ちコンクリート杭の構築方法の変更例を示す図である。It is a figure which shows the example of a change of the construction method of the cast-in-place concrete pile which concerns on one Embodiment of this invention. 従来の場所打ちコンクリート杭（拡底杭）を示す図である。It is a figure which shows the conventional cast-in-place concrete pile (expanded bottom pile).

以下、図１から図５を参照し、本発明の一実施形態に係る場所打ちコンクリート杭の構築方法について説明する。   Hereinafter, a method for constructing a cast-in-place concrete pile according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5.

本実施形態の場所打ちコンクリート杭の構築方法では、従来と同様、アースドリルなどの掘削機を用いて地表面から所定の深度まで安定液を充填しつつ掘削し、場所打ちコンクリート杭１’の略一定の径の円柱状の軸部２の掘削孔１０を形成する（図１参照）。次に、ロッド４の下端に接続した拡底用掘削機（拡底バケットなどの拡底機）５を軸部２の掘削孔１０に挿入して先端部に配置し、拡底用掘削機５を拡張しつつ中心軸Ｏ１周りに回転させて先端部の掘削孔１０の孔壁部分を拡底掘削し、先端部に略円錐台状の拡底部３の掘削孔１１を形成する。そして、掘削孔１０、１１にトレミー管を用いて安定液と置換するようにコンクリートを打設し場所打ちコンクリート杭１’を構築する。なお、掘削孔１０、１１内に鉄筋篭を挿入したり、必要に応じて杭頭部側を埋め戻したり、杭頭基礎を構築するなどし、場所打ちコンクリート拡底杭の施工が完了する。   In the construction method of the cast-in-place concrete pile according to the present embodiment, the excavation machine such as an earth drill is used to excavate from the ground surface to a predetermined depth while filling with a stable liquid, and the cast-in-place concrete pile 1 ′ is abbreviated. The excavation hole 10 of the cylindrical shaft portion 2 having a constant diameter is formed (see FIG. 1). Next, a bottom-excavating machine (a bottom-extended machine such as a bottomed bucket) 5 connected to the lower end of the rod 4 is inserted into the excavation hole 10 of the shaft portion 2 and disposed at the tip, and the bottom-excavating machine 5 is expanded. By rotating around the central axis O1, the hole wall portion of the excavation hole 10 at the tip end is excavated at the bottom, and the excavation hole 11 of the broadened portion 3 having a substantially truncated cone shape is formed at the tip end portion. Then, concrete is placed in the excavation holes 10 and 11 so as to replace the stabilizing liquid using a tremy pipe, and a cast-in-place concrete pile 1 'is constructed. The cast-in-place concrete bottom-pile construction is completed by inserting reinforcing bars into the excavation holes 10 and 11, refilling the pile head side as needed, or constructing a pile head foundation.

ここで、従来周知の通り、拡底用掘削機５は、図２に示すように、例えばφ２．１〜３．０ｍなど、ある範囲の径の軸部２に対応して拡底部３（軸部２の掘削孔１０に対応して拡底部３の掘削孔１１）を形成できるようになっている。   Here, as is conventionally known, the bottom-excavating excavator 5 has a bottom-expanding portion 3 (shaft portion) corresponding to the shaft portion 2 having a certain range of diameters, for example, φ2.1 to 3.0 m, as shown in FIG. The excavation hole 11) of the bottom expanded portion 3 can be formed corresponding to the two excavation holes 10.

本実施形態の場所打ちコンクリート杭の構築方法では、この拡底用掘削機５がある範囲の径の軸部２に対応して拡底部３を形成できることを利用する。   In the construction method of the cast-in-place concrete pile of this embodiment, it is utilized that the bottom expanded part 3 can be formed corresponding to the shaft part 2 having a diameter in a certain range.

具体的に、本実施形態の場所打ちコンクリート杭の構築方法では、図１に示すように、掘削機（軸部大径用拡底機）５によって例えば３．０ｍなどの大きな軸径で軸部２の掘削孔１０を先行掘削し、次に、例えば、最大拡底径が２．１ｍなどの拡底用掘削機（軸部小径用拡底機）５を用い、軸部２の中心軸Ｏ１に対して拡底用掘削機５（ロッド４）の中心軸Ｏ２を偏心させて、先行掘削して形成した軸部２の掘削孔１０の先端部の孔壁を拡底掘削する。また、複数箇所の偏心位置に拡底用掘削機５を配置して拡底掘削を行い、拡底部３の掘削孔１１を形成する。   Specifically, in the construction method of the cast-in-place concrete pile according to the present embodiment, as shown in FIG. 1, the shaft portion 2 with a large shaft diameter such as 3.0 m is provided by an excavator (a shaft portion large-diameter bottom expander) 5. Next, for example, using a bottom-excavating machine (bottoming machine for small-diameter shaft diameter) 5 having a maximum bottom expansion diameter of 2.1 m or the like, the bottom expansion is performed with respect to the central axis O1 of the shaft portion 2. The center axis O2 of the excavator 5 (rod 4) is decentered, and the hole wall at the tip of the excavation hole 10 of the shaft portion 2 formed by the previous excavation is excavated at the bottom. Also, the bottom-excavating excavator 5 is disposed at a plurality of eccentric positions to perform bottom-expanding excavation, thereby forming the excavation holes 11 of the bottom expansion portion 3.

また、本実施形態の場所打ちコンクリート杭の構築方法では、このとき、偏心位置決め保持手段の偏心拡底掘削用ガイド８を使用する。   Moreover, in the construction method of the cast-in-place concrete pile of this embodiment, the eccentric widening excavation guide 8 of the eccentric positioning holding means is used at this time.

図１に示すように、偏心拡底掘削用ガイド８は、鋼製であり、軸部２の掘削孔１０の径よりもわずかに小さな直径を有し、側面が軸部２の掘削孔１０の孔壁面に当接あるいは近接して沿うように円環状に形成された外環保持部８ａと、外環保持部８ａの中心軸Ｏ３に対して所定の量ずれた偏心位置に上下方向に貫通形成され、拡底用掘削機５に接続されたロッド４を挿通するとともにロッド４及び拡底用掘削機５を中心軸Ｏ２周りに回転可能に保持するロッド保持部８ｂとを備えて形成されている。   As shown in FIG. 1, the eccentric bottom-excavated excavation guide 8 is made of steel, has a diameter slightly smaller than the diameter of the excavation hole 10 of the shaft portion 2, and has a side surface with a hole of the excavation hole 10 of the shaft portion 2. An outer ring holding portion 8a formed in an annular shape so as to come into contact with or close to the wall surface, and is formed to penetrate in an up-down direction at an eccentric position shifted by a predetermined amount with respect to the central axis O3 of the outer ring holding portion 8a. The rod 4 connected to the bottom-excavating excavator 5 is inserted, and the rod 4 and the bottom-excavating excavator 5 are provided with a rod holding portion 8b that rotatably supports the central axis O2.

そして、軸部２の掘削孔１０を形成した段階で、ロッド保持部８ｂにロッド４を挿通し、ロッド４に接続した拡底用掘削機５を軸部２の掘削孔１０の先端部に配置するとともに、偏心拡底掘削用ガイド８を軸部２の掘削孔１０の所定位置に挿入配置する。   Then, at the stage where the excavation hole 10 of the shaft portion 2 is formed, the rod 4 is inserted into the rod holding portion 8b, and the bottom-excavating excavator 5 connected to the rod 4 is disposed at the distal end portion of the excavation hole 10 of the shaft portion 2. At the same time, the eccentric bottom-excavated excavation guide 8 is inserted and disposed at a predetermined position of the excavation hole 10 of the shaft portion 2.

この状態で、拡底用掘削機５を拡張しつつ中心軸Ｏ２周りに回転させて先端部の掘削孔１０の孔壁を拡底掘削すると、拡底用掘削機５が偏心拡底掘削用ガイド８によってその偏心位置で保持され、好適に拡底掘削を行うことができる。   In this state, when the bottom expanding excavator 5 is expanded and rotated around the central axis O 2 to expand the bottom wall of the excavation hole 10 at the tip, the bottom expanding excavator 5 is eccentrically moved by the eccentric bottom expanding excavation guide 8. It is hold | maintained in a position, and a bottom expansion excavation can be performed suitably.

また、図１（ａ）に示すように一箇所の偏心位置で拡底掘削を行った後、図１（ｂ）に示すように偏心拡底掘削用ガイド８を軸部２の中心軸Ｏ１周りに所定量回動させて設置し、他の偏心位置で拡底用掘削機５を保持して拡底掘削を行う。   1 (a), after performing a bottom-expanded excavation at one eccentric position, an eccentric bottom-expanded excavation guide 8 is placed around the central axis O1 of the shaft portion 2 as shown in FIG. 1 (b). It is installed with a fixed amount of rotation, and the bottom expanding excavator 5 is held at another eccentric position to perform bottom expanding excavation.

これにより、本実施形態の場所打ちコンクリート杭の構築方法によれば、図３や図４に示すように、拡底用掘削機５の最大拡底径を超えた場所打ちコンクリート杭（拡底杭）１’、すなわち、高支持耐力の場所打ちコンクリート杭１’を構築することが可能になる。例えば、軸部大径用拡底機５を用いて従来通りに拡底部３を形成した場合の杭底面積に対し、本実施形態の場所打ちコンクリート杭の構築方法においては１．３倍以上の杭底面積の拡底部３を形成、構築することが可能である。   Thereby, according to the construction method of the cast-in-place concrete pile of this embodiment, as shown in FIG.3 and FIG.4, the cast-in-place concrete pile (bottom-expanded pile) 1 'exceeding the maximum expanded diameter of the excavator 5 for expanded floor is shown. That is, it becomes possible to construct a cast-in-place concrete pile 1 ′ having a high bearing capacity. For example, in the construction method of the cast-in-place concrete pile according to the present embodiment, the pile is 1.3 times or more than the pile bottom area when the bottom widened portion 3 is formed as usual using the shaft large diameter widening machine 5. It is possible to form and construct the widened portion 3 having a bottom area.

ここで、図３は３箇所か所の偏心位置で拡底掘削を行った場合の場所打ちコンクリート杭１’、図４は４箇所の偏心位置で拡底掘削を行った場合の場所打ちコンクリート杭１’の形状をそれぞれ示している。   Here, FIG. 3 shows a cast-in-place concrete pile 1 ′ when bottomed excavation is performed at three eccentric positions, and FIG. 4 shows a cast-in-place concrete pile 1 ′ when bottomed excavation is performed at four eccentric positions. Each of the shapes is shown.

図３、図４に示すように、上記のように構築した本実施形態の場所打ちコンクリート杭１’は、その拡底部（杭底面１ａ）が平断面視で軸部２の中心軸Ｏ１を中心とした円形外面から径方向外側に突出する凸円弧部（凸円弧面）６を備えた形で構築される。これにより、拡底部３が円弧凹凸状の外面によって従来の円錐台形状の拡底部３よりも鉛直部分の面の摩擦耐力を向上させることができ、この点からも、高支持耐力の拡底杭を実現することが可能になる。   As shown in FIGS. 3 and 4, the cast-in-place concrete pile 1 ′ of the present embodiment constructed as described above has an expanded bottom portion (pile bottom surface 1 a) centered on the central axis O <b> 1 of the shaft portion 2 in a plan view. It is constructed in a form provided with a convex arc portion (convex arc surface) 6 projecting radially outward from the circular outer surface. Thereby, the bottom expansion part 3 can improve the frictional resistance of the surface of a vertical part rather than the conventional truncated cone-shaped bottom expansion part 3 by the arc-shaped uneven | corrugated outer surface. Can be realized.

一方、従来、アースドリルなどの掘削機によって形成した杭の底面は、中心軸Ｏ１から径方向外側に向かうに従い漸次上方に傾斜するすり鉢状になる。このため、例えば、支持層Ｇ１が砂礫などの場合には、拡底用掘削機（軸部小径用拡底機）５の中心軸Ｏ２を偏心させた状態で後行掘削する際に杭の底面に当接する掘削機５の底部が安定せず、底面地盤が崩壊したり、拡底用掘削機５が軸部２の中心軸Ｏ１側に滑って芯ずれが生じ、小口径の拡底用掘削機５で拡底部３の掘削孔１１を拡張形成できなくなることも考えられる。   On the other hand, the bottom surface of a pile conventionally formed by an excavator such as an earth drill has a mortar shape that gradually inclines upward from the central axis O1 toward the radially outer side. For this reason, for example, when the support layer G1 is gravel or the like, the bottom of the pile is touched when the excavating machine (bottoming machine for small-diameter shafts) 5 is decentered with the central axis O2 being excavated. The bottom portion of the excavator 5 in contact is not stable, the bottom ground collapses, or the bottom-excavating excavator 5 slides toward the central axis O1 side of the shaft portion 2 to cause misalignment, and the bottom is expanded by the small-diameter bottom expanding excavator 5 It is also conceivable that the excavation hole 11 of the portion 3 cannot be expanded.

これに対し、本実施形態では、図１に示すように、拡底用掘削機５の底部に、中心軸Ｏ１と同軸で底面から下方に突出し、掘削孔１０の底面に突き当たって突き刺さるなどし拡底用掘削機５を安定させるための位置決め凸部であるスタビライザー７を設ける。また、スタビライザー７は、拡底用掘削機５の底部の掘削刃よりも下方に突出するように形成されている。なお、本実施形態のスタビライザー７はその突出方向先端部がテーパー状、尖った形で形成されている。また、ドリルやオーガー状にして下方地盤に突き刺さりやすくしても良い。   On the other hand, in this embodiment, as shown in FIG. 1, the bottom of the bottom-excavating machine 5 protrudes downward from the bottom surface coaxially with the central axis O <b> 1, and hits the bottom surface of the excavation hole 10. A stabilizer 7 which is a positioning convex portion for stabilizing the excavator 5 is provided. Further, the stabilizer 7 is formed so as to protrude downward from the excavation blade at the bottom of the excavator 5 for expanding the bottom. In addition, the stabilizer 7 of this embodiment is formed in the protrusion direction front-end | tip part in the taper shape and the sharp shape. Moreover, you may make it easy to stab in a downward ground by making it a drill or an auger shape.

これにより、先行掘削した掘削孔１０の底面がすり鉢状に形成されていたり、砂礫などの崩れやすい地盤Ｇであっても、後行掘削によって拡底部３の掘削を行う際に、軸部２の掘削孔１０の中心軸Ｏ１から偏心した位置の底面にスタビライザー７が突き刺さるなどして拡底用掘削機５が安定し、この状態で拡底用掘削機５が中心軸Ｏ２周りに回転して掘削孔１０の孔壁を拡底掘削することができる。すなわち、偏心位置に配置した拡底用掘削機５が芯ずれすることなく拡底掘削を行うことができ、確実で好適に拡底用掘削機５の最大拡底径を超えた場所打ちコンクリート杭（拡底杭）１’を構築することが可能になる。   Thereby, even when the bottom surface of the excavation hole 10 that has been excavated in advance is formed in a mortar shape or the ground G is easily collapsed such as gravel, when the bottom expansion portion 3 is excavated by the subsequent excavation, the shaft portion 2 The bottom excavator 5 is stabilized by, for example, the stabilizer 7 being stuck into the bottom surface of the excavation hole 10 at a position eccentric from the central axis O1, and in this state, the excavation machine 5 for bottom expansion rotates around the central axis O2 and the excavation hole 10 is rotated. It is possible to drill the bottom of the hole wall. That is, the bottom expanding excavator 5 arranged at the eccentric position can perform the bottom expanding excavation without misalignment, and the cast-in-place concrete pile (the bottom expanded pile) exceeding the maximum bottom expanding diameter of the bottom expanding excavator 5 can be surely and suitably performed. It becomes possible to build 1 '.

ここで、本実施形態では、偏心位置決め保持手段の偏心拡底掘削用ガイド８が掘削ロッド４を偏心位置で回転可能に保持するものとして説明を行ったが、偏心位置決め保持手段の偏心拡底掘削用ガイド９が拡底用掘削機５を偏心位置で回転可能に保持するように構成されていてもよい。   Here, in the present embodiment, the explanation has been made on the assumption that the eccentric widening excavation guide 8 of the eccentric positioning holding means holds the excavation rod 4 so as to be rotatable at the eccentric position, but the eccentric widening excavation guide of the eccentric positioning holding means. 9 may be configured to hold the excavator 5 for expanding the bottom so as to be rotatable at an eccentric position.

例えば、図５に示すように、偏心拡底掘削用ガイド９を構成してもよい。
この偏心拡底掘削用ガイド９は、鋼管（外環保持部）や、鋼管（外環保持部）９ａと鉄筋９ｂを用いるなどして軸部２の掘削孔１０に挿入可能で且つ掘削孔１０内で保持可能な略円筒状、略円筒籠状に形成されている。そして、掘削孔１０の地表開口部から軸部２の掘削孔１０の所定深度まで挿入した状態で保持されるとともに、拡底用掘削機５のガイド部５ａを挿通して鉛直方向に進退自在に且つ横方向に略変位不能に保持するガイド保持部９ｃが鋼管９ａによって中心軸Ｏ１に対して所定量偏心した偏心位置に設けられている。なお、重量に支障がなければ鋼管（外部保持部）９ａで偏心拡底掘削用ガイド９を構成してもよい。 For example, as shown in FIG. 5, an eccentric bottom-excavated excavation guide 9 may be configured.
The eccentric bottom-excavated excavation guide 9 can be inserted into the excavation hole 10 of the shaft portion 2 by using a steel pipe (outer ring holding portion), a steel pipe (outer ring holding portion) 9a, and a reinforcing bar 9b. It is formed in a substantially cylindrical shape and a substantially cylindrical bowl shape that can be held by the. And while being hold | maintained in the state inserted from the ground surface opening part of the excavation hole 10 to the predetermined depth of the excavation hole 10 of the axial part 2, it can penetrate the guide part 5a of the excavator 5 for bottom expansion, and can move forward and backward in the vertical direction, and A guide holding portion 9c that holds substantially indisplaceable in the lateral direction is provided at an eccentric position that is eccentric by a predetermined amount with respect to the central axis O1 by the steel pipe 9a. In addition, you may comprise the eccentric bottom-excavated excavation guide 9 with the steel pipe (external holding | maintenance part) 9a if there is no trouble in a weight.

この場合には、杭用の掘削機で軸部２の掘削孔１０を先行掘削した後に、軸部２の掘削孔１０に偏心拡底掘削用ガイド９を挿入設置し、偏心拡底掘削用ガイド９のガイド保持部９ｃを通して拡底用掘削機５を軸部２の掘削孔１０の先端部に配置する。このように配置することにより、偏心拡底掘削用ガイド９のガイド保持部９ｃに拡底用掘削機５のガイド部５ａが保持されるようにする。   In this case, after excavating the excavation hole 10 of the shaft portion 2 with the excavator for piles, the eccentric widening excavation guide 9 is inserted and installed in the excavation hole 10 of the shaft portion 2, and the eccentric widening excavation guide 9 The bottom-excavating excavator 5 is disposed at the tip of the excavation hole 10 of the shaft portion 2 through the guide holding portion 9c. By arranging in this way, the guide portion 5a of the bottom-excavating excavator 5 is held by the guide holding portion 9c of the eccentric bottom-extended excavating guide 9.

この状態で、拡底用掘削機５を拡張しつつ中心軸Ｏ２周りに回転させて先端部の掘削孔１０の孔壁を掘削すると、拡底用掘削機５が偏心拡底掘削用ガイド９によってその偏心位置で保持され、好適に拡底掘削を行うことができる。   In this state, when the bottom excavator 5 is rotated around the central axis O2 while being expanded and the hole wall of the excavation hole 10 at the tip is excavated, the excavator 5 for the bottom expansion is moved to the eccentric position by the guide 9 for the eccentric bottom expansion. It is hold | maintained by this, and a bottom expansion excavation can be performed suitably.

また、一箇所の偏心位置で拡底掘削を行った後、偏心拡底掘削用ガイド９を軸部２の中心軸Ｏ１周りに所定量回動させれば、他の偏心位置で拡底用掘削機５を確実に保持して拡底掘削を行うことができる。   In addition, after performing the bottom expansion excavation at one eccentric position, if the eccentric bottom expansion excavation guide 9 is rotated by a predetermined amount around the central axis O1 of the shaft portion 2, the bottom expansion excavator 5 can be installed at another eccentric position. Drilling with expanded bottom can be performed with certainty.

これにより、順次複数箇所の偏心位置にガイド保持部９ｃを位置合わせしながら拡底掘削を行うことによって、所定形状の大きな拡底部３を備えた場所打ちコンクリート杭１’を形成することが可能になる。   Thereby, it becomes possible to form the cast-in-place concrete pile 1 'provided with the large bottom expanded portion 3 having a predetermined shape by performing the bottom expanded excavation while sequentially aligning the guide holding portions 9c at a plurality of eccentric positions. .

よって、拡底用掘削機５を偏心位置で保持する偏心拡底掘削用ガイド９を用いる場合であっても、上記のロッド４を保持する偏心拡底掘削用ガイド８と同様に、機械の最大拡底径よりも大きく、高支持耐力の拡底杭１’を構築、実現することが可能になる。   Therefore, even when the eccentric bottom expanding excavation guide 9 that holds the bottom expanding excavator 5 in the eccentric position is used, as with the eccentric bottom expanding excavation guide 8 that holds the rod 4, the maximum bottom expansion diameter of the machine is increased. It is possible to construct and realize an expanded bottom pile 1 ′ having a large bearing capacity.

以上、本発明に係る場所打ちコンクリート杭の構築方法の一実施形態について説明したが、本発明は上記の一実施形態に限定されるものではなく、その趣旨を逸脱しない範囲で適宜変更可能である。   As mentioned above, although one Embodiment of the construction method of the cast-in-place concrete pile concerning this invention was described, this invention is not limited to said one Embodiment, It can change suitably in the range which does not deviate from the meaning. .

例えば、予め、杭底部直下の地盤全体やスタビライザーが突き当たる部分の地盤（偏心位置の杭底部直下の地盤）を、深層地盤改良工法などを用いて地盤改良しておいてもよい。この場合には、後行掘削によって拡底部の掘削を行う際に、さらに拡底用掘削機を安定した状態にして掘削孔の孔壁を拡底掘削することができ、より確実で好適に拡底用掘削機の最大拡底径を超えた拡底杭を構築することが可能になる。なお、この地盤改良部は、例えば、杭支持力の３倍以上の一軸圧縮強度となるように形成する。   For example, the entire ground directly under the pile bottom or the ground where the stabilizer abuts (the ground directly under the pile bottom at the eccentric position) may be improved using a deep ground improvement method or the like. In this case, when excavating the bottom expanded part by the following excavation, it is possible to further expand the hole wall of the excavation hole while keeping the excavator for expanding the bottom in a stable state. It becomes possible to construct an expanded pile that exceeds the maximum expanded diameter of the machine. In addition, this ground improvement part is formed so that it may become a uniaxial compressive strength 3 times or more of pile support force, for example.

１ 従来の場所打ちコンクリート杭（拡底杭）
１’ 場所打ちコンクリート杭（拡底杭）
２ 軸部
３ 拡底部
４ ロッド
５ 拡底用掘削機
６ 凸円弧部
７ スタビライザー（位置決め凸部）
８ 偏心拡底掘削用ガイド
８ａ 外環保持部
８ｂ ロッド保持部
９ 偏心拡底掘削用ガイド
９ａ 鋼管（外環保持部）
９ｂ 鉄筋
９ｃ ガイド保持部
１０ 軸部の掘削孔
１１ 拡底部の掘削孔
Ｇ 地盤
Ｇ１ 支持層 1 Conventional cast-in-place concrete pile (expanded bottom pile)
1 'Cast-in-place concrete pile (expanded bottom pile)
2 Shaft part 3 Expanded bottom part 4 Rod 5 Excavator 6 for expanding bottom Convex arc part 7 Stabilizer (positioning convex part)
8 Eccentric bottom expanding excavation guide 8a Outer ring holding portion 8b Rod holding portion 9 Eccentric bottom expanding excavation guide 9a Steel pipe (outer ring holding portion)
9b Reinforcing bar 9c Guide holding portion 10 Shaft excavation hole 11 Bottom excavation hole G Ground G1 Support layer

Claims (2)

円柱状の軸部と、該軸部の先端部を拡張してなる略円錐台状の拡底部を備えた場所打ちコンクリート杭を構築する方法であって、
杭用の掘削機を用いて地盤の所定の深度まで前記軸部の掘削孔を先行掘削して形成し、
前記軸部の掘削孔よりも小径の軸部用の拡底用掘削機を前記軸部の掘削孔の先端部に挿入し、且つ、前記軸部の掘削孔の内部に配設した偏心位置決め保持手段によって前記拡底用削孔機に接続したロッド及び／又は前記拡底用掘削機のガイド部を、前記ロッド及び前記拡底用掘削機の中心軸を前記軸部の中心軸に対して所定量偏心させた状態で前記ロッド及び前記拡底用掘削機の中心軸周りに回転可能に保持させ、
先行掘削して形成した前記軸部の掘削孔の先端部の孔壁を前記拡底用掘削機で拡底掘削して前記拡底部の掘削孔を形成し、
前記軸部と前記拡底部の掘削孔にコンクリートを打設することを特徴とする場所打ちコンクリート杭の構築方法。 A method of constructing a cast-in-place concrete pile having a columnar shaft portion and a substantially truncated cone-shaped expanded bottom portion formed by expanding the tip portion of the shaft portion,
Using the excavator for piles, the excavation hole of the shaft portion is pre-excavated to a predetermined depth of the ground, and formed,
Eccentric positioning and holding means for inserting a bottom-excavating excavator for a shaft having a diameter smaller than that of the shaft portion into the tip portion of the shaft portion, and disposed inside the shaft portion. The rod connected to the bottom hole drilling machine and / or the guide portion of the bottom drilling machine is decentered by a predetermined amount with respect to the central axis of the shaft part. In a state to be able to rotate around the central axis of the rod and the bottom-excavating excavator,
Excavating the hole wall at the tip of the excavation hole of the shaft portion formed by preceding excavation with the excavator for expanding the bottom, forming the excavation hole of the expanded bottom,
A method for constructing a cast-in-place concrete pile, wherein concrete is placed in the excavation holes of the shaft portion and the expanded bottom portion. 請求項１記載の場所打ちコンクリート杭の構築方法において、
前記拡底用掘削機の先端部に、前記拡底用掘削機の中心軸と同軸で掘削刃よりも下方に突出する位置決め凸部であるスタビライザーを設け、
前記スタビライザーを掘削孔の底面の地盤に突き刺すようにして拡底掘削することを特徴とする場所打ちコンクリート杭の構築方法。 In the construction method of the cast-in-place concrete pile of Claim 1,
Provided at the tip of the bottom-excavating excavator is a stabilizer that is a positioning convex portion that is coaxial with the central axis of the bottom-excavating excavator and projects below the excavating blade;
A method for constructing a cast-in-place concrete pile, wherein the stabilizer is pierced to expand the bottom so as to pierce the ground at the bottom of the excavation hole.
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Publication number Priority date Publication date Assignee Title
JPS63156288U (en) * 1987-03-30 1988-10-13
JPH04228797A (en) * 1991-05-28 1992-08-18 Hitachi Constr Mach Co Ltd Method for executing widened bottom pile by earth drill process
JPH10184260A (en) * 1996-12-26 1998-07-14 Mitsubishi Materials Corp Excavating tool
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JP2006307593A (en) * 2005-05-02 2006-11-09 Taisei Corp Grout pipe and grouting in cast-in-place concrete pile
JP2010255212A (en) * 2009-04-22 2010-11-11 System Keisoku Kk Bell bucket, casing, and method for constructing bell pipe
JP2014141844A (en) * 2013-01-25 2014-08-07 System Keisoku Kk Bottom enlarged bucket
JP2017218810A (en) * 2016-06-08 2017-12-14 株式会社大林組 Construction method for cast-in-place concrete pile

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JP4228797B2 (en) 2003-06-25 2009-02-25 株式会社デンソー Exhaust gas purification system for internal combustion engine

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Publication number Priority date Publication date Assignee Title
JPS63156288U (en) * 1987-03-30 1988-10-13
JPH04228797A (en) * 1991-05-28 1992-08-18 Hitachi Constr Mach Co Ltd Method for executing widened bottom pile by earth drill process
JPH10184260A (en) * 1996-12-26 1998-07-14 Mitsubishi Materials Corp Excavating tool
JP2004211492A (en) * 2003-01-08 2004-07-29 Mitsubishi Materials Corp Excavating tool
JP2006307593A (en) * 2005-05-02 2006-11-09 Taisei Corp Grout pipe and grouting in cast-in-place concrete pile
JP2010255212A (en) * 2009-04-22 2010-11-11 System Keisoku Kk Bell bucket, casing, and method for constructing bell pipe
JP2014141844A (en) * 2013-01-25 2014-08-07 System Keisoku Kk Bottom enlarged bucket
JP2017218810A (en) * 2016-06-08 2017-12-14 株式会社大林組 Construction method for cast-in-place concrete pile

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