JP2006132100A - Head-enlarged pile - Google Patents

Head-enlarged pile Download PDF

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JP2006132100A
JP2006132100A JP2004319446A JP2004319446A JP2006132100A JP 2006132100 A JP2006132100 A JP 2006132100A JP 2004319446 A JP2004319446 A JP 2004319446A JP 2004319446 A JP2004319446 A JP 2004319446A JP 2006132100 A JP2006132100 A JP 2006132100A
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pile
diameter
diameter portion
excavation
head
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Hiroshi Wakiya
泰士 脇屋
Takeshi Ochiai
健 落合
Kimihisa Takano
公寿 高野
Masahiro Hayashi
正宏 林
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JFE Steel Corp
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JFE Steel Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a head-enlarged pile for being sunk in a hole excavated in advance, which can suppress a decrease in bearing capacity of a foot-protection bulb part at a lower end. <P>SOLUTION: In this head-enlarged pile 20 as a prefabricated pile 20 for being sunk in the excavated hole 10 formed in advance, a head part constitutes a large-diameter part 21 with a diameter larger than that of its downside. An inflow part 24, where a fluid can flow inward from the outside of a pile 20, is provided in a jointing part between the large-diameter part 21 and the small-diameter part 22 on the downside of the large-diameter part 21. For example, an outside-diameter surface of an upper part of the small-diameter part 22 and an inside-diameter surface of a lower part of the large-diameter part 21 are connected together by means of a plurality of radially arranged ribs, and sections among the plurality of ribs serve as the inflow parts 24. Both a jointing angle θ2 of a lower end of the rib with respect to the outside-diameter surface of the upper part of the small-diameter part 22 and a jointing angle θ1 of an upper end of the rib with respect to the inside-diameter surface of the lower part of the large-diameter part 21, in a side view, are set as acute angles, so that concentrated stress can be reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、プレボーリング工法等により予め形成された掘削孔に沈設される中空の既製杭であって、杭頭部が拡頭した拡頭杭に関する。   The present invention relates to a hollow ready-made pile that is set in an excavation hole formed in advance by a preboring method or the like, and relates to a head-expanded pile in which a pile head is expanded.

プレボーリング工法で掘削穴を形成して既製杭からなる拡頭杭を沈設する杭の施工方法としては、例えば特許文献1に記載されているものがある。
この施工方法は、先端部に拡大ビットを設けた掘削ロッドによってプレボーリングを行い、泥土化した掘削穴を設け、さらに掘削穴下端部において、上記拡大ビットによって拡大掘削して拡大掘削穴を形成し、その拡大掘削穴に根固め液を注入しながら支持層中の土砂を混合攪拌して拡大根固め球根を形成する。その後、既製杭を上記掘削穴内に建て込み沈設する。
As a method for constructing a pile in which a drilling hole is formed by a pre-boring method and a head-up pile made of a ready-made pile is sunk, there is one described in Patent Document 1, for example.
In this construction method, pre-boring is performed by a drilling rod provided with an enlarged bit at the tip, and a mudified drilling hole is provided, and further, an enlarged drilling hole is formed at the lower end of the drilling hole by the above-mentioned enlarged bit. Then, the earth and sand in the support layer are mixed and stirred while injecting the root-setting liquid into the enlarged excavation hole to form an enlarged root-setting bulb. After that, ready-made piles are built into the excavation hole and set.

ここで、上記既製杭としての拡頭杭は、頭部が大径の大径部とその下側の小径部とからなると共に、軸方向に延びる中空部を備え、該中空部は、杭の上端部及び下端部でのみ開口する。
特開昭62−253817号公報
Here, the head-expanded pile as the ready-made pile includes a large-diameter portion having a large-diameter head and a small-diameter portion below the head, and includes a hollow portion extending in the axial direction, and the hollow portion is an upper end of the pile. Open only at the bottom and bottom.
JP 62-253817 A

図5(a)に示すような泥土化した掘削穴10に上記拡頭杭20を沈設すると、杭20の沈降に応じて、杭下端部の開口から杭20内の中空部に流動状の泥土31が入り込む。図5(b)に示すように、杭20の小径部22だけが泥土31内に挿入された途中の状態では、杭20の沈降速度にも依存するが、杭20の中空部内の泥土31の上面と杭20外の泥土31の上面の高さはほぼ同じ高さになっている。しかし、杭20の沈設が進み、杭20の大径部21も掘削穴10内に挿入され、杭20の先端部が拡大掘削穴10bに到達した時点では、杭20内に入ってくる泥土31は、杭20先端部からの流入のみであることから、杭20の中空部内の泥土31の上面と杭20外の泥土31の上面の高さに、図5(c)のように、ヘッド差が生じる。この状態で、杭20が最終位置まで沈降すると、杭20の先端部は根固め液30中に挿入されることから、上記ヘッド差を解消する方向に、つまり根固め液30が上記ヘッド差を解消するだけ杭20内に流れ込む一方、その分、図5(d)のように、拡大掘削穴10bより上側の泥土31が根固め球根部に流れ込むことで、根固め球根部における泥土31の混入量が多くなったり根固め液30が不均一状態となって、根固め球根部における支持力低下の原因の一因となるおそれがある。
本発明は、上記のような点に着目してなされたもので、先に掘削した穴に沈設するための拡頭杭において、下端部の根固め球根部での支持力低下を抑えることが可能な拡頭杭を提供することを課題としている。
When the above-mentioned expanded pile 20 is sunk in the excavated hole 10 that is mud as shown in FIG. 5A, the fluid mud 31 flows from the opening at the lower end of the pile to the hollow portion in the pile 20 according to the settling of the pile 20. Enters. As shown in FIG. 5 (b), in the state where only the small-diameter portion 22 of the pile 20 is inserted into the mud 31, depending on the settling speed of the pile 20, the mud 31 in the hollow portion of the pile 20 The height of the upper surface and the upper surface of the mud 31 outside the pile 20 are substantially the same. However, the sedimentation of the pile 20 proceeds, the large diameter portion 21 of the pile 20 is also inserted into the excavation hole 10, and the mud 31 that enters the pile 20 when the tip of the pile 20 reaches the enlarged excavation hole 10 b. Is only the inflow from the tip of the pile 20, the head difference between the upper surface of the mud 31 in the hollow portion of the pile 20 and the upper surface of the mud 31 outside the pile 20 is as shown in FIG. Occurs. In this state, when the pile 20 sinks to the final position, the tip of the pile 20 is inserted into the root-solidifying liquid 30, so that the head-solidifying liquid 30 reduces the head difference in a direction to eliminate the head difference. While only flowing into the pile 20, the mud 31 above the enlarged excavation hole 10b flows into the root bulb as shown in FIG. 5 (d), so that the mud 31 is mixed in the root bulb. There is a possibility that the amount increases or the root hardening liquid 30 becomes in a non-uniform state, which may contribute to a decrease in the supporting force in the root hardening bulb.
The present invention has been made by paying attention to the above points, and in a head-expanded pile for sinking in a previously excavated hole, it is possible to suppress a decrease in supporting force at a root-fixed bulb at the lower end. The issue is to provide expanded piles.

上記課題を解決するために、本発明のうち請求項1に記載した発明は、先に掘削して形成した掘削穴に中空の既製杭を沈設する杭の施工方法に使用される当該既製杭であって、頭部がその下側よりも大径の大径部を構成する拡頭杭において、
上記大径部と該大径部より下側の小径部との間の接合部及び上記大径部側面の少なくとも一方に対し、杭の外側から内部に向けて流動物が流入可能な流入部を設けたことを特徴とするものである。
In order to solve the above-mentioned problems, the invention described in claim 1 of the present invention is the ready-made pile used in a method for constructing a pile in which a hollow ready-made pile is sunk in an excavation hole formed by excavation previously. In the head-expanded pile in which the head constitutes a large-diameter portion having a larger diameter than the lower side,
An inflow part into which a fluid can flow in from the outside of the pile to the inside is provided for at least one of the joint part between the large diameter part and the small diameter part below the large diameter part and the side surface of the large diameter part. It is characterized by providing.

次に、請求項2に記載した発明は、請求項1に対し、上記小径部と上記大径部との接合構造は、小径部上部の外径面と大径部下部の内径面との間を、放射状に配置された複数のリブで連結して構成され、且つ上記複数のリブ間が上記流入部を構成すると共に、
側面視における、上記小径部上部の外径面に対するリブ下端部の接合角度、及び大径部下部の内径面に対する上記リブ上端部の接合角度を、共に鋭角にして集中応力を緩和したことを特徴とするものである。
Next, the invention described in claim 2 is different from claim 1 in that the joining structure of the small diameter portion and the large diameter portion is between the outer diameter surface of the upper portion of the small diameter portion and the inner diameter surface of the lower portion of the large diameter portion. Are connected by a plurality of radially arranged ribs, and the ribs constitute the inflow portion, and
In the side view, the joining angle of the lower end of the rib with respect to the outer diameter surface of the upper portion of the small diameter portion and the joining angle of the upper end of the rib with respect to the inner diameter surface of the lower portion of the large diameter portion are both acute angles to reduce the concentrated stress. It is what.

本発明によれば、拡頭杭を沈設する際の大径部内外での泥土のヘッド差が、杭上部に設けた流入部を介して杭内に流入する泥土によって解消される結果、根固め球根部での支持力低下を抑えることができる。   According to the present invention, the mud head difference between the inside and outside of the large-diameter portion when sinking the expanded pile is eliminated by the mud flowing into the pile through the inflow portion provided in the upper portion of the pile. It is possible to suppress a decrease in supporting force at the part.

次に、本発明の実施形態を図面を参照しつつ説明する。
まず、本実施形態の拡頭杭の構造について説明する。
図1は、本実施形態に係る拡頭杭20を示す側面図であり、図2は、当該拡頭杭20の大径部21と小径部22との接合部の構造を示す図である。
図1に示すように、拡頭杭20は、頭部が大径の大径部21と、その下側の小径部22とからなる。本実施形態の拡頭杭20は、大径部21は大径の鋼管(以下、大径鋼管21とも呼ぶ)からなり、小径部22は大径鋼管21よりも小径の鋼管(以下、小径鋼管22とも呼ぶ)からなり、その小径鋼管22と大径鋼管21が、図2に示すように、複数のリブパネル23によって接合されて構成される。
Next, embodiments of the present invention will be described with reference to the drawings.
First, the structure of the expanded pile according to the present embodiment will be described.
FIG. 1 is a side view showing a head-expanded pile 20 according to the present embodiment, and FIG. 2 is a diagram showing a structure of a joint portion between a large-diameter portion 21 and a small-diameter portion 22 of the head-expanded pile 20.
As shown in FIG. 1, the head-expanded pile 20 includes a large-diameter portion 21 having a large head and a small-diameter portion 22 below the head. In the expanded pile 20 of this embodiment, the large-diameter portion 21 is made of a large-diameter steel pipe (hereinafter also referred to as a large-diameter steel pipe 21), and the small-diameter portion 22 is smaller than the large-diameter steel pipe 21 (hereinafter, small-diameter steel pipe 22). The small diameter steel pipe 22 and the large diameter steel pipe 21 are joined by a plurality of rib panels 23 as shown in FIG.

その上記小径鋼管22と大径鋼管21との接合構造について詳説すると、図2に示すように、小径鋼管22の上端部外径面に複数のリブパネル23の内径側端面が溶接されている。その複数のリブパネル23は、小径鋼管22を中心に放射状に配置され、その各リブパネル23の外径側端面が上記大径鋼管21の下端部内径面に溶接されている。   The joint structure between the small diameter steel pipe 22 and the large diameter steel pipe 21 will be described in detail. As shown in FIG. 2, the inner diameter side end faces of the plurality of rib panels 23 are welded to the outer diameter face of the upper end portion of the small diameter steel pipe 22. The plurality of rib panels 23 are arranged radially around the small diameter steel pipe 22, and the outer diameter side end face of each rib panel 23 is welded to the lower end inner diameter face of the large diameter steel pipe 21.

各リブパネル23は、図2(a)に示すように、側面視で矩形形状となっていて、左右の縦方向に延びる辺(側端面)が平行且つ杭20の軸に沿って延びると共に、上下で対向する2つの辺(上端面及び下端面)は、共に径方向外方に向かうにつれて上側に向かって傾斜している。これによって、側面視における、上記小径部22の外径面に対するリブパネル23の下端部の接合角度θ2、及び大径部21の内径面に対する上記リブパネル23上端部の接合角度θ1が、共に鋭角となる。なお、両接合角度θ1、θ2は同一の角度とする必要はない。
なお、図2では、小径鋼管22の外径面及び大径鋼管21の内径面に対して杭20の軸と平行な線に沿って各リブパネル23の側端面が溶接されているが、軸に対し若干斜めの線に沿って溶接されていても良い。
As shown in FIG. 2A, each rib panel 23 has a rectangular shape in a side view. Sides (side end surfaces) extending in the left and right vertical directions are parallel and extend along the axis of the pile 20, and The two sides (upper end surface and lower end surface) that are opposed to each other are inclined upward as they go outward in the radial direction. As a result, the joint angle θ2 of the lower end portion of the rib panel 23 with respect to the outer diameter surface of the small diameter portion 22 and the joint angle θ1 of the upper end portion of the rib panel 23 with respect to the inner diameter surface of the large diameter portion 21 in the side view are both acute angles. . Note that the joint angles θ1 and θ2 need not be the same angle.
In FIG. 2, the side end surfaces of the rib panels 23 are welded to the outer diameter surface of the small diameter steel pipe 22 and the inner diameter surface of the large diameter steel pipe 21 along a line parallel to the axis of the pile 20. On the other hand, it may be welded along a slightly oblique line.

また、上記リブパネル23間の空間が流入部24を構成する。この流入部24の断面積は、流動状の泥土31が杭20内に支障無く流入可能な大きさになっていればよい。すなわち、掘削穴10への杭20の沈降時に沈降速度に応じて杭20内外の泥土31にヘッド差が生じない程度の泥土31の流入が確保できる程度の大きさとなっていればよい。杭20の沈降速度がゆっくりであれば、流入部24の断面積は小さくても良いし、沈降速度が速ければそれに応じた量が流入するだけの流入部24の断面積に設定する。   The space between the rib panels 23 constitutes the inflow portion 24. The cross-sectional area of the inflow portion 24 only needs to be large enough for the fluid mud 31 to flow into the pile 20 without hindrance. That is, it is only necessary that the size of the mud 31 is such that the inflow of the mud 31 is ensured such that no head difference occurs in the mud 31 inside and outside the pile 20 according to the settling speed when the pile 20 sinks into the excavation hole 10. If the settling speed of the pile 20 is slow, the cross-sectional area of the inflow portion 24 may be small, and if the settling speed is high, the cross-sectional area of the inflow portion 24 is set such that an amount corresponding to the inflow portion 24 flows.

次に、上記構成からなる拡頭杭20をプレボーリング工法で施工する方法の一例を説明する。図3はその施工手順を示す図である。
まず、使用する掘削ロッド3について説明する。この施工例で使用する掘削ロッド3は、下側の第1掘削ロッド部材1と、その上側に連結される第2掘削ロッド部材2とから構成される(図3(c)などを参照)。
Next, an example of a method for constructing the head-expanded pile 20 having the above-described configuration by a pre-boring method will be described. FIG. 3 shows the construction procedure.
First, the excavation rod 3 to be used will be described. The excavation rod 3 used in this construction example is composed of a lower first excavation rod member 1 and a second excavation rod member 2 connected to the upper side thereof (see FIG. 3C and the like).

第1掘削ロッド部材1は、先端に対し当該先端から下方に突出する掘削刃としての掘削用のビット4が取り付けられると共に、先端部に公知の拡大ビット5が設けられている。さらに、第1掘削ロッド部材1の側面には軸方向に沿って、アジテータと呼ばれる複数の攪拌翼6が設けられている。この攪拌翼6の突出量が拡頭杭20の小径部22より若干径が大きい量となっている、掘削ロッド3部材を使用する。
なお、第1掘削ロッド部材1の先端部には、従来と同様に、液を噴出可能な噴出孔12が設けられていて、その噴出孔から掘削液や固化剤を掘削穴10内に注入可能となっている。なお、固化剤としては、セメントミルクが最も良く使われるので、セメントミルクを用いた場合で説明する。
The first excavation rod member 1 is provided with an excavation bit 4 as an excavation blade protruding downward from the distal end with respect to the distal end, and a known enlarged bit 5 is provided at the distal end. Furthermore, a plurality of stirring blades 6 called agitators are provided on the side surface of the first excavation rod member 1 along the axial direction. The excavation rod 3 member in which the protruding amount of the stirring blade 6 is slightly larger than the small diameter portion 22 of the head pile 20 is used.
In addition, the tip of the first drilling rod member 1 is provided with an ejection hole 12 through which liquid can be ejected, as in the prior art, and the drilling fluid and solidifying agent can be injected into the drilling hole 10 from the ejection hole. It has become. As the solidifying agent, cement milk is most often used, so the case where cement milk is used will be described.

また、第2掘削ロッド部材2は、その側面に対し軸方向に沿って複数の攪拌翼7,8が設けられている。この第2掘削ロッド部材2の攪拌翼7,8のうち、第1掘削ロッド部材1の先端部が目的の深さまで掘削したときに拡頭杭20の大径部21の埋設位置(大径部21のための拡大掘削が要求される位置)に位置するはずの上側の攪拌翼8は、その下側の攪拌翼7よりも突出量が大きく設定されており、上記拡頭杭20の大径部21の径よりも若干径が大きくなるように設定されている。下側の攪拌翼7の突出量は、上記第1掘削ロッド部材1の攪拌翼6と同じ突出量となっている。すなわち、第2掘削ロッド部材2の径は、下側が第1掘削ロッド部材1と同径となっているが、上側は、当該第1掘削ロッド部材1より大径となっている。   Moreover, the 2nd excavation rod member 2 is provided with the some stirring blades 7 and 8 along the axial direction with respect to the side surface. Of the stirring blades 7 and 8 of the second excavation rod member 2, when the tip of the first excavation rod member 1 is excavated to a target depth, the embedded position (the large diameter portion 21) of the large diameter portion 21 of the head pile 20. The upper agitating blade 8 that should be located at a position where expansion excavation is required) is set to have a larger protruding amount than the lower agitating blade 7, and the large-diameter portion 21 of the expanded pile 20 described above. The diameter is set to be slightly larger than the diameter. The amount of protrusion of the lower stirring blade 7 is the same as the amount of protrusion of the stirring blade 6 of the first excavation rod member 1. That is, the diameter of the second excavation rod member 2 has the same diameter as that of the first excavation rod member 1 on the lower side, but the larger diameter than that of the first excavation rod member 1 on the upper side.

そして、上記第2掘削ロッド部材2における、上記突出量が大きく設定された攪拌翼部分が、上側の攪拌ロッド部分を構成する。
ここで、下記の説明において、攪拌翼を区別する場合には、相対的に突出量が小さな攪拌翼を小径攪拌翼6,7と、相対的に突出量が大きな攪拌翼を大径攪拌翼8と呼ぶ。
上記突出量が大きく設定された大径攪拌翼8のうち、最下部に位置する大径攪拌翼8には、その下側の小径攪拌翼よりも突出した外周部分に対し下方に突出する1又は2以上の掘削ビット(不図示)が掘削刃として設けられている。
And the stirring blade part in which the said protrusion amount was set large in the said 2nd excavation rod member 2 comprises an upper stirring rod part.
Here, in the following description, when the stirring blades are distinguished, the stirring blades having a relatively small protruding amount are the small-diameter stirring blades 6 and 7, and the stirring blade having a relatively large protruding amount is the large-diameter stirring blade 8. Call it.
Among the large-diameter agitating blades 8 set to have a large protruding amount, the large-diameter agitating blade 8 located at the lowermost portion projects 1 downward from the outer peripheral portion projecting from the lower-diameter agitating blade below. Two or more excavation bits (not shown) are provided as excavation blades.

さらに、上記第2掘削ロッド部材2における上記掘削ビットが設けられた高さ位置にも、液を噴出可能な上側噴出孔(不図示)が設けられている。この上側噴出孔は、軸部に設けても良いし、大径攪拌翼8の外周側に開口させても良い。また、上記上側噴出孔に液を供給するパイプ等からなる通路は、上記第1掘削ロッド部材1の噴出孔12に液を供給する通路を共用しても良いし、別途個別の通路を設けても良い。なお、上記通路は、掘削ロッド3の軸部内を上下に延在するように設けられる。   Furthermore, an upper ejection hole (not shown) through which liquid can be ejected is also provided at the height position where the excavation bit is provided in the second excavation rod member 2. The upper ejection hole may be provided in the shaft portion or may be opened on the outer peripheral side of the large-diameter stirring blade 8. In addition, the passage composed of a pipe or the like for supplying liquid to the upper ejection hole may share the passage for supplying liquid to the ejection hole 12 of the first excavation rod member 1 or may be provided with a separate passage. Also good. In addition, the said channel | path is provided so that the inside of the axial part of the excavation rod 3 may be extended up and down.

次に、上記図3を参照しつつ本実施形態の施工例を説明する。
まず、図3(a)に示すように、第1掘削ロッド部材1の上部を、掘削機の回転駆動部9に連結して、掘削作業を開始する。すなわち、図3(b)に示すように、回転駆動部9を駆動して掘削ロッド3を回転させて、先端部の掘削ビット4で掘削していく。このとき、掘削ロッド3の先端部の噴出孔12からセメントミルクを掘削穴10に注入しながら掘削を行う。
Next, a construction example of this embodiment will be described with reference to FIG.
First, as shown to Fig.3 (a), the upper part of the 1st excavation rod member 1 is connected with the rotation drive part 9 of an excavator, and excavation work is started. That is, as shown in FIG. 3B, the rotation driving unit 9 is driven to rotate the excavation rod 3 and excavation is performed with the excavation bit 4 at the tip. At this time, excavation is performed while cement milk is injected into the excavation hole 10 from the ejection hole 12 at the tip of the excavation rod 3.

上記第1掘削ロッド部材1で所定深さまで掘削したら、その第1掘削ロッド部材1の上部に第2掘削ロッド部材2を連結すると共に、その第2掘削ロッド部材2の上部に上記回転駆動部9を連結し直して掘削を続行する(図3(c)参照)。
このとき、最下部に位置する大径攪拌翼8の外周側には、ビットが設けられていることから、先に掘削された穴の外周部が当該ビットによって拡大掘削される。またこのとき、第2掘削ロッド部材2の位置からもセメントミルクを掘削穴10に注入して、拡径した掘削穴10の上部10aでも必要なだけのセメントミルクを供給するようにする。
When the first excavation rod member 1 excavates to a predetermined depth, the second excavation rod member 2 is connected to the upper portion of the first excavation rod member 1, and the rotation drive unit 9 is connected to the upper portion of the second excavation rod member 2. Are connected again to continue excavation (see FIG. 3C).
At this time, since the bit is provided on the outer peripheral side of the large-diameter stirring blade 8 located at the lowermost part, the outer peripheral portion of the hole excavated earlier is expanded and excavated by the bit. At this time, cement milk is also injected into the excavation hole 10 from the position of the second excavation rod member 2 so that only the necessary amount of cement milk is supplied even in the upper portion 10a of the expanded excavation hole 10.

次に、図3(d)のように、掘削ロッド3を回転させながら所定ストロークだけ当該掘削ロッド3を上下動させて、注入したセメントミルクと土砂とを攪拌混練してソイルセメント(泥土31)にする。
続いて、図3(e)のように、拡大ビット5を拡径して掘削穴10の下端部を拡径して根固め球根部を形成し、その根固め球根部に対し、根固め液30を注入する。
Next, as shown in FIG. 3 (d), the excavation rod 3 is moved up and down by a predetermined stroke while rotating the excavation rod 3, and the injected cement milk and earth and sand are agitated and kneaded to obtain a soil cement (mud 31). To.
Subsequently, as shown in FIG. 3 (e), the expansion bit 5 is expanded in diameter to expand the lower end portion of the excavation hole 10 to form a root-fixing bulb portion. 30 is injected.

上記のように掘削作業が完了したら、図3(f)のように、掘削ロッド3を引き抜き、第2掘削ロッド部材2が地上部に全部引き抜けたら、第2掘削ロッド部材2を外して、続いて第1掘削ロッド部材1を引き抜く。
続いて、図3(g)及び(h)のように、順次、拡頭杭20を、自重沈設及び回転埋沈によって、上記形成した掘削穴10内に建て込んでいく。なお、本実施形態では、拡頭杭20が2本の既製杭20A、20Bからなる場合を例示している。すなわち、小径部22が下側の既製杭20Aと上側の既製杭20Bに分割されている。
When the excavation work is completed as described above, as shown in FIG. 3 (f), the excavation rod 3 is pulled out, and when the second excavation rod member 2 is completely pulled out to the ground, the second excavation rod member 2 is removed, Subsequently, the first excavation rod member 1 is pulled out.
Subsequently, as shown in FIGS. 3G and 3H, the head-expanded pile 20 is sequentially built into the excavated hole 10 formed as described above by its own weight settling and rotary settling. In addition, in this embodiment, the case where the head-expansion pile 20 consists of two ready-made piles 20A and 20B is illustrated. That is, the small-diameter portion 22 is divided into a lower ready-made pile 20A and an upper ready-made pile 20B.

拡頭杭20の沈設は、土砂とソイルセメントにより泥土化した掘削穴10に対し、小径部22の部分だけが建て込まれた状態では、従来と同様に、杭20の沈降に応じて、杭20の下端部の開口から杭20内の中空部に流動状の泥土31が入り込む(図5(b)参照)。この杭20の小径部22が泥土31内に挿入された途中の状態では、杭20の沈降速度にも依存するが、杭20の中空部内の泥土31の上面と杭20外の泥土31の上面の高さはほぼ同じ高さになっている。   In the state where only the portion of the small diameter portion 22 is built in the excavation hole 10 mud with earth and sand and soil cement, the pile-up pile 20 is set according to the settling of the pile 20 in the conventional manner. The fluid mud 31 enters the hollow portion in the pile 20 from the opening at the lower end of the slab (see FIG. 5B). While the small-diameter portion 22 of the pile 20 is being inserted into the mud 31, the upper surface of the mud 31 inside the hollow portion of the pile 20 and the upper surface of the mud 31 outside the pile 20 are dependent on the settling speed of the pile 20. Are almost the same height.

杭20の沈設が進み、杭20の大径部21も掘削穴10内に挿入されると、泥土31は、図4のように、小径部22と大径部21との接合部に設けた流入部24からも杭20内に流れ込むことで、杭20内外における泥土31のヘッド差が無いか小さい。ここで、土砂とソイルセメントとからなる泥土31は所定の粘性を持っていることから、大径部21内に充填される泥土31は、大径部21から遠い位置にある杭20の下端部の開口よりも、大径部21に近い流入部24からの流入によって充填されやすいと想定される。
したがって、杭20の先端部が拡大掘削穴10bに到達し、当該拡大掘削穴10b中の根固め液30中に挿入されても、根固め液30が杭20の先端部から杭20内に流れ込むことが防止される結果、拡大掘削穴10中の根固め液30の性状が所望の状態に保持されて、根固め球根部における支持力低下が防止される。
When the pile 20 is set and the large-diameter portion 21 of the pile 20 is also inserted into the excavation hole 10, the mud 31 is provided at the joint between the small-diameter portion 22 and the large-diameter portion 21 as shown in FIG. By flowing into the pile 20 also from the inflow part 24, the head difference of the mud 31 inside and outside the pile 20 is small or small. Here, since the mud 31 composed of earth and sand and soil cement has a predetermined viscosity, the mud 31 filled in the large-diameter portion 21 is the lower end of the pile 20 located far from the large-diameter portion 21. It is assumed that it is more easily filled by the inflow from the inflow portion 24 closer to the large-diameter portion 21 than the opening.
Therefore, even if the tip of the pile 20 reaches the enlarged excavation hole 10b and is inserted into the root hardening liquid 30 in the enlarged excavation hole 10b, the root hardening liquid 30 flows into the pile 20 from the tip of the pile 20. As a result, the properties of the root hardening liquid 30 in the enlarged excavation hole 10 are maintained in a desired state, and a decrease in the supporting force in the root hardening bulb portion is prevented.

また、小径部22より大径の大径部21を沈設する時に、小径部22と大径部21との接合部に設けられて上下に延びる流入部24から泥土31を杭20内に流入させながら杭20の沈降が行われることで、小径部22よりも張り出した形状の大径部21の沈降時の抵抗を当該流入部24により小さく抑えると共に、杭20の横方向へのブレを抑える働きもする。また、本実施形態では、さらに、リブパネル23の下端面を外径に向かうにつれて上側に向かうようにテーパが形成されていることからも、横への振れを抑えつつ杭20の沈降を容易にしている。   Further, when sinking the large diameter portion 21 larger than the small diameter portion 22, the mud 31 is caused to flow into the pile 20 from the inflow portion 24 provided at the joint portion between the small diameter portion 22 and the large diameter portion 21 and extending vertically. However, the sedimentation of the pile 20 is performed, so that the resistance at the time of sedimentation of the large-diameter portion 21 protruding from the small-diameter portion 22 is suppressed by the inflow portion 24 and the lateral movement of the pile 20 is suppressed. Also do. Moreover, in this embodiment, since the taper is formed so that the lower end surface of the rib panel 23 is further directed upward as it goes to the outer diameter, the settling of the pile 20 is facilitated while suppressing lateral deflection. Yes.

また、施工後の杭20に上下荷重が負荷された場合に、小径部22とリブパネル23の下端部、及び大径部21とリブパネル23の上端部に荷重が集中するが、本実施形態では、当該小径部22とリブパネル23の下端部との接合角度θ2、及び大径部21とリブパネル23の上端部との接合角度θ1をともに鋭角(切欠き側からみれば鈍角となる)にすることで、上記荷重の集中位置での応力集中を緩和する結果、小径部22及び大径部21とリブパネル23との接合部分で杭20が降伏することが防止している。
ここで、上記説明では、拡頭杭20を鋼管製の場合を例示したが、コンクリート製その他の既製杭20であっても構わない。
Further, when a vertical load is applied to the pile 20 after construction, the load concentrates on the lower end portion of the small diameter portion 22 and the rib panel 23 and on the upper end portion of the large diameter portion 21 and the rib panel 23. By making the joining angle θ2 between the small diameter portion 22 and the lower end portion of the rib panel 23 and the joining angle θ1 between the large diameter portion 21 and the upper end portion of the rib panel 23 both acute (when viewed from the notch side, an obtuse angle). As a result of relaxing the stress concentration at the load concentration position, the pile 20 is prevented from yielding at the joint portion between the small diameter portion 22 and the large diameter portion 21 and the rib panel 23.
Here, in the above description, the case where the head-expanded pile 20 is made of steel pipe is exemplified, but it may be made of concrete or other ready-made pile 20.

また、上記説明では、大径部21と小径部22との接合を複数のリブパネル23から構成し、リブパネル23間の空間を流入部24としているがこれに限定されない。大径部21と小径部22との接合は、例えば円環状の板部材などで接合される接合構造であっても良い。また、そのときには、当該板部材に穴を設けて流入部としても良い。   Moreover, in the said description, joining of the large diameter part 21 and the small diameter part 22 is comprised from the some rib panel 23, and the space between the rib panels 23 is made into the inflow part 24, However, It is not limited to this. The joining of the large diameter portion 21 and the small diameter portion 22 may be a joining structure that is joined by, for example, an annular plate member. At that time, a hole may be provided in the plate member to form an inflow portion.

また、上記説明では、大径部21と小径部22との接合部に流入部24を設ける場合を例示しているが、当該接合部に設ける代わり、若しくは、接合部の流入部24と共に、大径部21の側面に穴を開けて流入部としても良い。なお、大径部21に穴を形成した場合、ソイルセメントとなる泥土31が当該穴を通じて連通することで、杭20とソイルセメントとの接着強度が向上する。   Moreover, although the case where the inflow part 24 is provided in the junction part of the large diameter part 21 and the small diameter part 22 is illustrated in the said description, it is large with the inflow part 24 of a junction part instead of providing in the said junction part. It is good also as an inflow part by making a hole in the side surface of the diameter part 21. In addition, when the hole is formed in the large diameter part 21, the adhesive strength of the pile 20 and the soil cement improves because the mud 31 used as the soil cement communicates through the hole.

また、本実施形態では、掘削ロッド3の上側に設ける大径攪拌翼8の突出量を大きくすることで、1回の掘削によって上部の拡大掘削をしている。また、大径攪拌翼8の外周側にもビットを設けることで効率良く掘削穴10の上部の拡大掘削を行っている。なお、ビットを設けなくとも良いが、その分、大径攪拌翼8の強度を高めて確実に拡大掘削を可能とする必要がある。また、掘削穴10の上部は突出量の大きな大径攪拌翼8で改めて拡大掘削されるが、掘削ロッド3先端部の噴出孔12から注入されるセメントミルクが当該拡大掘削された上側の大径部21分に供給され難い。このため、そのままでは土砂の割合が相対的に多くなることで泥土31の品質が悪くなって上部での強度がその分悪くなるが、本実施形態では、第2掘削ロッド部材2からもセメントミルクを噴出することで、新たに拡大掘削された土砂分のセメントミルクが掘削穴10の上部にも適正に供給可能となる。この結果、掘削穴10の上部を拡大掘削しても充分な品質のソイルセメントを確保することができる。
なお、掘削穴10の形成は、本実施形態の施工方法に限定されない。例えば、従来例のように拡大ビット5を使用して掘削穴10の上部を掘削しても良いし、掘削穴10の上部を別途、違う掘削ロッドで拡大掘削しても良い。
In the present embodiment, the upper portion of the large-diameter stirring blade 8 provided on the upper side of the excavating rod 3 is enlarged so that the upper portion of the excavation is expanded by one excavation. In addition, by providing a bit on the outer peripheral side of the large-diameter agitating blade 8, the upper portion of the excavation hole 10 is efficiently expanded. Although it is not necessary to provide a bit, it is necessary to increase the strength of the large-diameter agitating blade 8 and to make sure that expanded excavation is possible. Further, the upper part of the excavation hole 10 is enlarged and excavated again by a large-diameter stirring blade 8 having a large protruding amount, but the cement milk injected from the ejection hole 12 at the tip of the excavation rod 3 has an enlarged large diameter on the upper side. It is hard to be supplied to the part 21 minutes. For this reason, if the ratio of the earth and sand is relatively increased as it is, the quality of the mud 31 is deteriorated and the strength at the upper part is deteriorated accordingly. However, in the present embodiment, the second excavation rod member 2 also uses cement milk. As a result, the newly expanded and expanded excavated cement milk can be properly supplied to the upper part of the excavation hole 10. As a result, even if the upper part of the excavation hole 10 is expanded and excavated, a sufficient quality soil cement can be secured.
In addition, formation of the excavation hole 10 is not limited to the construction method of this embodiment. For example, the upper part of the excavation hole 10 may be excavated using the enlarged bit 5 as in the conventional example, or the upper part of the excavation hole 10 may be separately excavated with a different excavation rod.

また、上記実施形態では、掘削時のセメントミルクを掘削穴10に注入するように説明しているが、掘削時には、水などの掘削液を注入し、混合・攪拌時にセメントミルクを注入するようにしても良い。
なお、上記構成の拡頭杭20を打込み杭に転用した場合には、リブパネル間の空間は、土で塞がれて当該土が杭20内に入り込むことが無い。つまり、上記構成の拡頭杭20を打込み杭とした場合には、流入部が存在しないこととなる。沈設する杭として使用して、初めてリブパネル間は流入部として作用する。
Further, in the above embodiment, the explanation is made so that the cement milk at the time of excavation is injected into the excavation hole 10, but at the time of excavation, the excavating liquid such as water is injected, and the cement milk is injected at the time of mixing and stirring. May be.
In addition, when the head-expansion pile 20 of the said structure is diverted to a driving pile, the space between rib panels is block | closed with soil, and the said soil does not enter into the pile 20. FIG. That is, when the head-expanded pile 20 having the above configuration is a driven pile, no inflow portion exists. Only when used as a pile to be laid, the rib panel acts as an inflow part.

図2に示す接合部についての検討結果を示す。
下記の条件で、接合角度θ1、θ2、ラップ長L、リブパネル枚数nの違いによる性能・コスト比較して、コストパフォーマンスの高くなる接合構造を、FEM解析により評価した。
小径部22の杭径D2:φ500mm以上φ1200mm以下
大径部21の杭径D1:φ750mm以上φ1800mm以下
杭頭倍率(D1/D2):1.2〜1.5倍
杭20の板厚t1,t2:1%≦t1/D1、t2/D2≦3.17%
(t1:大径部21の板厚、t2:小径部22の板厚)
The examination result about the junction part shown in FIG. 2 is shown.
Under the conditions described below, a joint structure with higher cost performance was evaluated by FEM analysis in comparison with performance and cost due to differences in the joint angles θ1, θ2, lap length L, and the number n of rib panels.
Pile diameter D2 of the small diameter portion 22: φ500 mm or more and φ1200 mm or less Pile diameter D1 of the large diameter portion 21: φ750 mm or more and φ1800 mm or less Pile head magnification (D1 / D2): 1.2 to 1.5 times Pile thickness t1, t2 : 1% ≦ t1 / D1, t2 / D2 ≦ 3.17%
(T1: thickness of the large diameter portion 21, t2: thickness of the small diameter portion 22)

「FEM解析結果による性能を満足するための必要範囲」
FEM解析結果によると、各拡頭倍率における板厚径比(t1/D1、t2/D2)にの全てにおいて必要性能を満足する、接合角度θ1、θ2、ラップ長L、及びリブパネル枚数の3つの要因の範囲は、下記の通りであった。
10度≦θ1,θ2≦90度
L=0.0〜0.8×D2
リブパネルの枚数n=8枚から16枚
“Necessary range to satisfy performance based on FEM analysis results”
According to the FEM analysis results, the three factors of the joining angles θ1, θ2, the wrap length L, and the number of rib panels satisfying the required performance in all of the plate thickness diameter ratios (t1 / D1, t2 / D2) at each heading magnification. The range of was as follows.
10 degrees ≦ θ1, θ2 ≦ 90 degrees L = 0.0 to 0.8 × D2
Number of rib panels n = 8 to 16

「FEM解析を踏まえたコスト比較」
各拡頭倍率における各板厚径比において、必要性能を満足する要因(θ1,θ2,L、n)の組み合わせの中で、経済的となる仕様をFEM解析により検討した。
コスト試算には以下の要因を考慮した。
・ラップ長L:鋼管の重複分による鋼管材料費の無駄分
・リブパネルの高さL1,L2:接合の際の溶接費及びリブ材料費
・リブパネル枚数n:リブ材料費、及び接合の際の溶接費
"Cost comparison based on FEM analysis"
Among the combinations of factors (θ1, θ2, L, n) that satisfy the required performance at each plate thickness-diameter ratio at each heading magnification, economical specifications were examined by FEM analysis.
The following factors were considered in the cost estimation.
・ Lap length L: Waste of steel pipe material cost due to overlap of steel pipe ・ Rib panel height L1, L2: Welding cost and rib material cost for joining ・ Number of rib panels n: Rib material cost and welding for joining Expense

コスト比較の傾向は次の通りである。
・リブパネルの接合部の応力集中を緩和するため、接合角度θ1、θ2が鋭角なほど有利な構造となる。
(同一リブパネルの取付け長さでは、鋭角の方が必要リブ枚数は少なくなる。)
・鋭角になりすぎると、必要リブパネル高さ(L1,L2)が長くなり、取り付ける際の溶接費及び材料費が高くなる。
・同一の角度では、ラップ長Lが長いほど、リブ枚数を減らすことができるが、コストは鋼管の重複分の鋼管材料費、及び取付けの際の溶接費(枚数n、リブパネル高さL1,L2による)のバランスにより、各拡頭倍率の各板厚径比によって異なる。
The trend of cost comparison is as follows.
In order to alleviate stress concentration at the joint portion of the rib panel, the sharper the joint angles θ1 and θ2, the more advantageous the structure.
(If the same rib panel is installed, the sharper angle requires fewer ribs.)
-If the angle is too acute, the required rib panel height (L1, L2) becomes long, and the welding costs and material costs for mounting become high.
-At the same angle, the longer the lap length L, the more the number of ribs can be reduced. However, the cost is the steel pipe material cost for the overlap of steel pipes, and the welding cost for installation (number n, rib panel height L1, L2 Depending on the thickness ratio of each head expansion magnification.

「試算結果によるコストパフォーマンスの高い仕様」
上の検討結果から、各拡頭倍率における各板厚径比に応じた最もコストパフォーマンスの高い仕様は、それぞれのケースでばらつきがあるが、下記の範囲であることが分かった。
10度≦θ1,θ2≦45度
ラップ長L=0〜0.4×D2
従って、この条件を満足するように設計することが好ましい。たとえば、コスト及び仕様の煩雑さを踏まえ、ラップ長L=0.3×D2、接合角度θ1=θ2=30度と固定して、この値に基づき拡頭倍率及び板厚径比に応じたリブパネルの必要枚数nを決定する。
“Specifications with high cost performance based on trial calculation results”
From the above examination results, it was found that the specifications with the highest cost performance according to each thickness ratio at each head-expansion magnification vary in each case, but are within the following ranges.
10 degrees ≦ θ1, θ2 ≦ 45 degrees Lap length L = 0 to 0.4 × D2
Therefore, it is preferable to design so as to satisfy this condition. For example, based on the complexity of cost and specifications, the wrap length L = 0.3 × D2 and the joining angle θ1 = θ2 = 30 degrees are fixed, and based on this value, the rib panel according to the head expansion magnification and the plate thickness-diameter ratio is fixed. The required number n is determined.

本発明に基づく実施形態に係る拡頭杭を示す側面図である。It is a side view which shows the head-expansion pile which concerns on embodiment based on this invention. 本発明に基づく実施形態に係る大径部と小径部との接合構造を説明する図で、(a)は断面図、(b)は上面図である。It is a figure explaining the joining structure of the large diameter part and small diameter part which concern on embodiment based on this invention, (a) is sectional drawing, (b) is a top view. 本発明に基づく実施形態に係る杭の施工を説明する図である。It is a figure explaining construction of a pile concerning an embodiment based on the present invention. 本発明に基づく実施形態に係る杭と泥土その他との関係を示す図である。It is a figure which shows the relationship between the pile and mud etc. which concern on embodiment based on this invention. 従来の課題を説明する図である。It is a figure explaining the conventional subject.

符号の説明Explanation of symbols

1 第1掘削ロッド部材
2 第2掘削ロッド部材
3 掘削ロッド
4 掘削用ビット
5 拡大ビット
6、7 小径攪拌翼
8 大径攪拌翼
9 回転駆動部
10 掘削穴
10b 拡大掘削穴
12 下側の噴出孔
20 拡頭杭
21 大径部
22 小径部
23 リブパネル
24 流入部
θ1,θ2 接合角度θ1、θ2
DESCRIPTION OF SYMBOLS 1 1st excavation rod member 2 2nd excavation rod member 3 Excavation rod 4 Excavation bit 5 Expansion bit 6, 7 Small diameter stirring blade 8 Large diameter stirring blade 9 Rotation drive part 10 Excavation hole 10b Expansion excavation hole 12 Lower ejection hole 20 Expanded pile 21 Large diameter portion 22 Small diameter portion 23 Rib panel 24 Inflow portion θ1, θ2 Joining angles θ1, θ2

Claims (2)

先に掘削して形成した掘削穴に中空の既製杭を沈設する杭の施工方法に使用される当該既製杭であって、頭部がその下側よりも大径の大径部を構成する拡頭杭において、
上記大径部と該大径部より下側の小径部との間の接合部及び上記大径部側面の少なくとも一方に対し、杭の外側から杭内部に向けて流動物が流入可能な流入部を設けたことを特徴とする拡頭杭。
A prefabricated pile used in the construction method of a pile in which a hollow ready-made pile is sunk in an excavation hole formed by excavation first, and the head has a large-diameter portion whose diameter is larger than its lower side. In the pile,
An inflow portion into which a fluid can flow from the outside of the pile toward the inside of the pile with respect to at least one of the joint portion between the large diameter portion and the small diameter portion below the large diameter portion and the side surface of the large diameter portion. Expanded pile characterized by providing.
上記小径部と上記大径部との接合構造は、小径部上部の外径面と大径部下部の内径面との間を、放射状に配置された複数のリブで連結して構成され、且つ上記複数のリブ間が上記流入部を構成すると共に、
側面視における、上記小径部上部の外径面に対するリブ下端部の接合角度、及び大径部下部の内径面に対する上記リブ上端部の接合角度を、共に鋭角にして集中応力を緩和したことを特徴とする請求項1に記載した拡頭杭。
The joining structure of the small diameter portion and the large diameter portion is configured by connecting a plurality of radially arranged ribs between the outer diameter surface of the upper portion of the small diameter portion and the inner diameter surface of the lower portion of the large diameter portion, and Between the plurality of ribs constitute the inflow portion,
In the side view, the joining angle of the lower end of the rib with respect to the outer diameter surface of the upper portion of the small diameter portion and the joining angle of the upper end of the rib with respect to the inner diameter surface of the lower portion of the large diameter portion are both acute angles to reduce the concentrated stress. The expanded head pile according to claim 1.
JP2004319446A 2004-11-02 2004-11-02 Head-enlarged pile Pending JP2006132100A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008045327A (en) * 2006-08-15 2008-02-28 Japan Pile Corp Construction method for head-enlarged pile
CN103233462A (en) * 2013-05-07 2013-08-07 山东同圆设计集团有限公司 Assembling external restraining precast pile with stiffening ribs and capable of preventing bending and shear damage
JP2016164327A (en) * 2015-03-06 2016-09-08 Jfeスチール株式会社 Joint structure between tubes with different diameter

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5616726A (en) * 1979-07-16 1981-02-18 Top Pairu Kogyo Kk Foundation pile having diameter expanding section and driving method of the same
JPS62185742U (en) * 1986-05-14 1987-11-26
JPH0336315A (en) * 1989-06-30 1991-02-18 Kajima Corp Pile for concurrently serving as earth anchor
JP2000045274A (en) * 1998-07-31 2000-02-15 Nippon Steel Corp Burying construction method of bearing pile and bearing pile
JP2000073365A (en) * 1998-08-27 2000-03-07 Nkk Corp Screwed type steel pipe pile and its execution method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5616726A (en) * 1979-07-16 1981-02-18 Top Pairu Kogyo Kk Foundation pile having diameter expanding section and driving method of the same
JPS62185742U (en) * 1986-05-14 1987-11-26
JPH0336315A (en) * 1989-06-30 1991-02-18 Kajima Corp Pile for concurrently serving as earth anchor
JP2000045274A (en) * 1998-07-31 2000-02-15 Nippon Steel Corp Burying construction method of bearing pile and bearing pile
JP2000073365A (en) * 1998-08-27 2000-03-07 Nkk Corp Screwed type steel pipe pile and its execution method

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008045327A (en) * 2006-08-15 2008-02-28 Japan Pile Corp Construction method for head-enlarged pile
CN103233462A (en) * 2013-05-07 2013-08-07 山东同圆设计集团有限公司 Assembling external restraining precast pile with stiffening ribs and capable of preventing bending and shear damage
CN103233462B (en) * 2013-05-07 2016-05-25 山东同圆设计集团有限公司 A kind of prefabricated pile with the anti-bending failure by shear of the outer constraint of ribbed stiffener assembled
JP2016164327A (en) * 2015-03-06 2016-09-08 Jfeスチール株式会社 Joint structure between tubes with different diameter

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