JP5932124B1 - Steel pipe pile construction method - Google Patents

Steel pipe pile construction method Download PDF

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JP5932124B1
JP5932124B1 JP2015225868A JP2015225868A JP5932124B1 JP 5932124 B1 JP5932124 B1 JP 5932124B1 JP 2015225868 A JP2015225868 A JP 2015225868A JP 2015225868 A JP2015225868 A JP 2015225868A JP 5932124 B1 JP5932124 B1 JP 5932124B1
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steel pipe
pipe pile
hole
construction method
spiral
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孝彦 樫本
孝彦 樫本
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Oak Co Ltd
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【課題】岩盤支持層による支持力及び耐引抜き力が極めて大きく、例えば擁壁の芯柱として使用した場合に、大きな側圧によって擁壁を傾倒させようとする力が働いても持ち上がる懸念はなく、擁壁の倒壊を確実に回避でき、下孔に対してバイブロハンマを用いて効率良く短時間で圧入できる鋼管杭を提供する。【解決手段】鋼管1の下部側の外周面に、鋼管軸線方向Oに対する傾斜角度θが4〜15°の緩螺旋をなす複数本のスパイラルリブ3が形成されてなる鋼管杭P。【選択図】図1An object of the present invention is to provide a rock support layer having a very large support force and pull-out force. Provided is a steel pipe pile that can surely avoid the collapse of a retaining wall and that can be press-fitted efficiently into a pilot hole in a short time using a vibro hammer. A steel pipe pile P in which a plurality of spiral ribs 3 are formed on the outer peripheral surface of the lower side of the steel pipe 1 to form a gentle spiral having an inclination angle θ with respect to the steel pipe axis direction O of 4 to 15 °. [Selection] Figure 1

Description

本発明は、少なくとも深部側に岩盤支持層を有する地盤に打ち込むのに好適な鋼管杭の施工方法に関する。 The present invention relates to a steel pipe pile construction method suitable for driving into a ground having a rock support layer at least on the deep side.

近年、海岸部の防波壁や防潮壁、山際や谷間の土止め壁等の擁壁を構築する場合に、例えば図7に示すように、プレキャストコンクリートからなる縦孔h付きの擁壁ブロックB1〜B4を用い、予め擁壁構築線に沿って地盤Gに複数本の鋼管杭Pを突出状態に打ち込んでおき、その鋼管杭Pの地上突出部を擁壁ブロックB1〜B4の縦孔hに挿嵌する形で、クレーンによって該擁壁ブロックB1〜B4を積み重ねて所要高さの擁壁Wとする構築方式が多用されつつある。この構築方式では、先に地盤Gに打ち込んだ鋼管杭Pが上下の擁壁ブロックB1〜B4を貫通する芯柱になると共に、該鋼管杭Pによって擁壁ブロックB1〜B4が自動的に位置決めされるから、非常に作業能率がよく、工期の短縮や施工コストの低減に繋がるという利点がある。なお、地表に接する最下部の擁壁ブロックB1は自立できるように概して図示の如き縦断面L字形や縦断面逆T字形をなし、その上に縦厚板状の擁壁ブロックB2〜B4を複数段に積み上げて壁状にするのが普通である。また、最下部の擁壁ブロックB1における水平部Baにも縦孔hが設けられ、その縦孔hに鋼管杭Pの地上突出部が挿嵌するようになっている。   In recent years, when constructing retaining walls such as coastal breakwaters, tide walls, and retaining walls such as mountainside or valley walls, for example, as shown in FIG. 7, retaining wall block B1 with vertical holes h made of precast concrete. Using ~ B4, a plurality of steel pipe piles P are driven into the ground G in advance along the retaining wall construction line, and the ground protrusions of the steel pipe piles P are placed in the vertical holes h of the retaining wall blocks B1 to B4. A construction method in which the retaining wall blocks B <b> 1 to B <b> 4 are stacked by a crane to form a retaining wall W having a required height is being used frequently. In this construction method, the steel pipe pile P previously driven into the ground G becomes a core column penetrating the upper and lower retaining wall blocks B1 to B4, and the retaining wall blocks B1 to B4 are automatically positioned by the steel pipe pile P. Therefore, there is an advantage that the work efficiency is very good and the construction period is shortened and the construction cost is reduced. In addition, the lowermost retaining wall block B1 in contact with the ground surface is generally formed in an L-shaped longitudinal section or an inverted T-shaped longitudinal section as shown in the figure so that it can stand on its own, and a plurality of longitudinally thick retaining wall blocks B2 to B4 are formed thereon. They are usually stacked in steps to form a wall. Moreover, the vertical hole h is provided also in the horizontal part Ba in the lowermost retaining wall block B1, and the ground protrusion part of the steel pipe pile P is inserted in the vertical hole h.

しかして、このような擁壁Wは、水際では波浪や津波、山際では土砂崩れや背方地盤の側方流動、谷間では土石流や泥流等によって背面側又は正面側から大きな側圧を受けるから、これら側圧による倒壊を阻止する上で鋼管杭Pによる擁壁Wの支持強度が重要となる。ところが、側圧による擁壁Wを傾倒させようとする力は鋼管杭Pを引き抜く方向に作用するから、これによって鋼管杭Pが持ち上がると、その持ち上がり部分の屈曲を伴って擁壁Wが簡単に倒壊する危険性がある。従って、擁壁Wの倒壊防止のためには、該鋼管杭Pが地盤G中で抜出不能に強固に根固めされている必要がある。更に、これら擁壁以外にも、基礎杭に大きな耐引抜き力が要求される構造物として、排煙塔、鉄塔、高層ビル、ハイピア(高橋脚)等の様々なものがあり、これらの基礎に用いる鋼管杭も岩盤支持層に強固に根固めする必要がある。   Such a retaining wall W receives a large lateral pressure from the back side or the front side due to waves and tsunamis at the water's edge, landslides and lateral flow at the back, and debris flow and mud flow at the valleys. In order to prevent the collapse due to the side pressure, the support strength of the retaining wall W by the steel pipe pile P is important. However, since the force to tilt the retaining wall W due to the side pressure acts in the direction of pulling out the steel pipe pile P, when the steel pipe pile P is lifted by this, the retaining wall W easily collapses with bending of the lifted portion. There is a risk of doing. Therefore, in order to prevent the retaining wall W from collapsing, the steel pipe pile P needs to be firmly rooted in the ground G so that it cannot be pulled out. In addition to these retaining walls, there are various structures such as smoke towers, steel towers, high-rise buildings, high piers (high piers), and other structures that require a large pull-out resistance for foundation piles. The steel pipe pile to be used also needs to be firmly rooted in the bedrock support layer.

従来、鋼管杭の根固め工法として、まずプレボーリングとして、ダウンザホールハンマによって地盤深部の岩盤支持層内に達する掘削孔を形成し、その掘削中及び掘削後のハンマ引上げ中のエアブローによってスライム(掘削屑)を地上へ排出し、ハンマ引上げ後の掘削孔内に鋼管杭を建て込み、該鋼管杭の内外にセメントミルクやモルタル等のグラウトを注入して根固めする方法や、同様のプレボーリングで形成した掘削孔に土砂を埋め戻した上で、バイブロハンマを介して鋼管杭を打ち込み、その鋼管杭と掘削孔との間にグラウトを注入して根固めする方法が汎用されている。しかるに、これらの根固め工法では、鋼管杭の耐引抜き力が杭表面及び掘削孔壁面と間に介在するグラウト硬化層との界面の摩擦力に依存するから、振動等でグラウト硬化層に亀裂や割れを生じたり、該硬化層の表面部が脆化(粉粒化)した場合に、耐引抜き力が著しく低下することになる。また、グラウト注入による根固めの際、該グラウトを鋼管杭の全周に均等に行き渡らすことが困難である上、均等に行き渡ったか否かを判定できず、更に掘削孔内に地下水等が滲み出していると、グラウトが分離したり薄まったりして硬く均質な硬化層を形成できず、これらの要因で根固め強度つまり地盤による鋼管杭の支持力が低下するという問題もあった。   Conventionally, as a method for solidifying steel pipe piles, as a pre-boring method, a drill hole reaching the rock support layer in the deep ground is formed by down-the-hole hammer, and slime (drilling waste) is created by air blow during the excavation and lifting of the hammer after excavation. ) To the ground, steel pipe piles are built in the excavation hole after the hammer is pulled up, and grouts such as cement milk and mortar are injected into the inside and outside of the steel pipe piles and formed by the same pre-boring A method has been widely used in which earth and sand are backfilled in the excavated hole, a steel pipe pile is driven through a vibro hammer, and a grout is injected between the steel pipe pile and the excavated hole for consolidation. However, in these consolidation methods, the pull-out force of the steel pipe pile depends on the frictional force at the interface with the grout hardened layer interposed between the pile surface and the wall surface of the excavation hole. When cracking occurs or the surface portion of the hardened layer becomes brittle (granulated), the pull-out resistance is significantly reduced. In addition, it is difficult to spread the grout evenly around the entire circumference of the steel pipe pile when rooting by grout injection, and it is not possible to determine whether the grout has spread evenly. When it is out, the grout is separated or thinned, so that a hard and homogeneous hardened layer cannot be formed, and due to these factors, there is a problem that the solidification strength, that is, the supporting force of the steel pipe pile by the ground is lowered.

一方、プレボーリングを行わずに鋼管杭を地盤に打設する手段として、ダウンザホールハンマによる鋼管杭中堀工法も多用されている。この鋼管杭中堀工法は、非回転に保持された鋼管杭の内側に、アースオーガに垂下連結したダウンザホールハンマを配置し、該鋼管杭の下端から突出した掘削径の拡縮可能なハンマービットの回転打撃によって地盤を削孔しつつ、同時に該鋼管杭を掘削孔内に挿入してゆき、削孔完了後にハンマービットを縮径してダウンザホールハンマを引き上げ、鋼管杭を地中に残すものである。しかるに、この鋼管杭中堀工法では、一般的に掘削孔径を鋼管杭の外径より10〜80mm程度大きく設定することから、掘削孔壁と鋼管杭との間で摩擦力が働かず、根固め材を用いても充分な耐引抜き力が得られない場合があった。   On the other hand, as a means for placing a steel pipe pile on the ground without performing pre-boring, a steel pipe pile intermediate drilling method using a down-the-hole hammer is also frequently used. In this steel pipe pile intermediate drilling method, a down-the-hole hammer suspended from an earth auger is arranged inside a non-rotated steel pipe pile, and a hammer bit that can be expanded and contracted from the lower end of the steel pipe pile is subjected to rotary hammering. While drilling the ground, the steel pipe pile is inserted into the excavation hole at the same time, and after completion of the drilling, the hammer bit is reduced in diameter to raise the down-the-hole hammer and leave the steel pipe pile in the ground. However, in this steel pipe pile intermediate drilling method, since the diameter of the drilling hole is generally set to about 10 to 80 mm larger than the outer diameter of the steel pipe pile, the friction force does not work between the drilling hole wall and the steel pipe pile, and the rooting material In some cases, sufficient pull-out resistance could not be obtained.

そこで、本発明者らは先に、鋼管杭の根固め工法として、先端部外周面に縦方向に沿う支持力増大用リブを周方向一定間隔置きに突設した鋼管杭を用い、地盤の岩盤支持層に該鋼管杭の外径よりも小さい内径の下孔を掘削機によって削孔し、この下孔に該鋼管杭をバイブロハンマによって強制圧入する方法を提案している(特許文献1)。この根固め工法によれば、鋼管杭が岩盤支持層に直接に抱持されて、且つ支持力増大用リブが岩盤に食い込んで係止されるから、該鋼管杭の地盤による支持力が著しく増大し、またグラウト注入が不要になるため、その材料コスト及び施工コストを低減できるという利点がある。   Therefore, the present inventors previously used a steel pipe pile in which ribs for increasing the supporting force along the vertical direction are projected on the outer peripheral surface of the tip portion at regular intervals in the circumferential direction as a steel pipe pile consolidation method. A method has been proposed in which a pilot hole having an inner diameter smaller than the outer diameter of the steel pipe pile is drilled in a support layer by an excavator, and the steel pipe pile is forcibly press-fitted into the lower hole by a vibro hammer (Patent Document 1). According to this solidification method, the steel pipe pile is directly held by the bedrock support layer, and the ribs for increasing the bearing capacity bite into the rock mass and locked, so that the bearing capacity of the steel pipe pile by the ground increases significantly. In addition, since no grout injection is required, there is an advantage that the material cost and construction cost can be reduced.

特開2014−109190号公報JP 2014-109190 A

しかしながら、上記提案に係る根固め工法では、下孔に対して径大の鋼管杭を強制圧入するのに時間がかかり、また根固め強度は大きくなるものの、該鋼管杭に大きな引抜き力が作用した場合、岩盤支持層に食い込んだ各支持力増大用リブが強制圧入過程で生じた掘削孔壁面の縦溝を通過する形で、鋼管杭が持ち上がって該擁壁の倒壊に繋がる可能性があった。   However, in the root consolidation method according to the above proposal, it takes time to force-fit a large-diameter steel pipe pile into the pilot hole, and although the root consolidation strength increases, a large pulling force acts on the steel pipe pile. In some cases, the ribs for increasing the bearing capacity that bite into the bedrock support layer pass through the vertical grooves on the wall surface of the excavation hole generated during the forced press-fitting process, and the steel pipe pile may be lifted up, leading to the collapse of the retaining wall .

本発明は、上述の事情に鑑みて、岩盤支持層による支持力が極めて大きく、例えば擁壁の芯柱として使用した場合に、大きな側圧によって該擁壁を傾倒させようとする力が働いても持ち上がる懸念はなく、極めて大きな耐引抜き力を発揮し、もって該擁壁の倒壊を確実に回避できる上、下孔に対してバイブロハンマを用いて能率良く短時間で圧入できる鋼管杭の施工方法を提供することを目的としている。 In the present invention, in view of the above-described circumstances, the support force by the bedrock support layer is extremely large. For example, when used as a core column of a retaining wall, even if a force is exerted to tilt the retaining wall due to a large lateral pressure. There is no concern about lifting, and it provides an extremely large pull-out force, so that the retaining wall can be reliably prevented from collapsing, and a steel pipe pile construction method that can be press-fitted efficiently and in a short time using a vibro hammer is provided. The purpose is to do.

上記目的を達成するための手段を図面の参照符号を付して示せば、請求項1の発明に係る鋼管杭Pの施工方法は、鋼管1の下部側の外周面に、鋼管軸線方向Oに対する傾斜角度θが4〜15°の緩螺旋をなす複数本のスパイラルリブ3が形成され、且つ各スパイラルリブの下端部に、下端側が先細りで下り勾配のテーパ部31aを形成してなる高硬質チップ31が設けられてなる鋼管杭を用い、先ず、少なくとも深部側に岩盤支持層Grを有する地盤Gに対し、該岩盤支持層Gr中に達する掘削孔Hを形成したのち、この掘削孔H内に、前記鋼管杭Pをバイブロハンマ7を介して打撃圧入することにより、該鋼管杭Pを外周面のスパイラルリブ3及びその下端部の先細り下り勾配のテーパ部30aによる誘導作用で自己回転させつつ岩盤支持層Gr内に到達させると共に、各スパイラルリブ3を孔壁岩盤に食い込ませることを特徴としている。 If the means for achieving the above object is shown with reference numerals in the drawings, the construction method of the steel pipe pile P according to the invention of claim 1 is applied to the outer peripheral surface of the lower side of the steel pipe 1 with respect to the steel pipe axial direction O. A highly rigid chip in which a plurality of spiral ribs 3 forming a gentle spiral with an inclination angle θ of 4 to 15 ° is formed, and a taper portion 31a having a downward slope and a downward slope is formed at the lower end portion of each spiral rib. First, after forming the excavation hole H reaching the rock mass support layer Gr with respect to the ground G having the rock mass support layer Gr at least on the deep side, the steel pipe pile P provided with 31 is formed . In addition, the steel pipe pile P is subjected to impact press-fitting through the vibro hammer 7 so that the steel pipe pile P is self -rotated by an inductive action by the spiral rib 3 on the outer peripheral surface and the taper portion 30a having a tapered downward slope at the lower end thereof. support The spiral ribs 3 are caused to penetrate into the hole wall rock while reaching the layer Gr.

請求項2の発明は、上記請求項1の鋼管杭Pの施工方法において、鋼管1の下端又は下端近傍から1〜8mまでの長さ範囲Lに前記スパイラルリブ3が設けられてなる構成としている。 Invention of Claim 2 is set as the structure by which the said spiral rib 3 is provided in the construction range of the steel pipe pile P of the said Claim 1 in the length range L from the lower end or the lower end vicinity of the steel pipe 1 to 1-8 m. .

請求項3の発明は、上記請求項1又は2の鋼管杭Pの施工方法において、4本以上のスパイラルリブ3が鋼管1周方向に等配配置してなる構成としている。 The invention of claim 3, Oite the construction method of the claim 1 or 2 of the steel pipe pile P, 4 or more spiral ribs 3 is an equal distribution arrangement and formed by arrangement in the steel pipe 1 circumferential direction.

請求項の発明は、上記請求項1〜3の何れかに記載の鋼管杭Pの施工方法において、各スパイラルリブ3の孔壁岩盤に対する食い込み深さdを15〜50mmに設定する構成としている。 Invention of Claim 4 is set as the structure which sets the penetration depth d with respect to the hole wall rock of each spiral rib 3 to 15-50 mm in the construction method of the steel pipe pile P in any one of the said Claims 1-3 . .

請求項の発明は、上記請求項1〜4の何れかに記載の鋼管杭Pの施工方法において、掘削孔径D3を鋼管杭Pの鋼管外径D1+0〜10mmの範囲に設定する構成としている。 Invention of Claim 5 sets it as the structure which sets the excavation hole diameter D3 in the range of the steel pipe outer diameter D1 + 0-10 mm of the steel pipe pile P in the construction method of the steel pipe pile P in any one of the said Claims 1-4 .

請求項の発明は、上記請求項1〜5の何れかに記載の鋼管杭Pの施工方法において、掘削孔Hを先端に掘削ビット5を備えたダウンザホールハンマ4によって掘削すると共に、その掘削中に発生したスライムを除去し、形成した掘削孔Hに土砂類Sを投入し、この土砂類Sで埋まった掘削孔Hに鋼管杭Pの打撃圧入を行う構成としている。 Invention of Claim 6 is the construction method of the steel pipe pile P in any one of the said Claims 1-5 , while excavating the excavation hole H with the down-the-hole hammer 4 provided with the excavation bit 5 in the front-end | tip, The slime generated is removed, earth and sand S is put into the formed excavation hole H, and the steel pipe pile P is hit and pressed into the excavation hole H filled with the earth and sand S.

次に、本発明の効果について図面を参照して具体的に説明すると、請求項1の発明に係る鋼管杭Pの施工方法によれば、鋼管1の下部側の外周面に、鋼管軸線方向Oに対する傾斜角度θが4〜15°の緩螺旋をなす複数本のスパイラルリブ3が形成され、且つ各スパイラルリブの下端部に、下端側が先細りで下り勾配のテーパ部31aを形成してなる高硬質チップ31が設けられてなる鋼管杭を用い、先ず地盤Gに深部側の岩盤支持層Grに達する掘削孔Hを形成し、しかる後に、この掘削孔H内に前記鋼管杭Pを強力なバイブロハンマ7を介して打撃圧入するのであるから、岩盤強度の高い岩盤支持層Grであっても、鋼管杭Pの外周面のスパイラルリブ3及びその下端部の先細りで下り勾配のテーパ部31aは岩盤支持層Grの孔壁岩盤に食い込み、これらスパイラルリブ3及び先細りで下り勾配のテーパ部31aによる螺旋誘導作用で自己回転しつつ所定深度まで圧入される。そして、打設した鋼管杭Pは、下部側が岩盤支持層Grによって直接に抱持され、該岩盤支持層Gr自体で根固めされた形になるから、岩盤強度に基づく大きな先端支持力が得られ、水平力の負荷や上部構造物による垂直荷重に対して極めて高い抵抗性が発現する上、各スパイラルリブ3が孔壁岩盤に螺旋の道筋を造って食い込むため、回転力が作用しない限りは岩盤支持層Grから抜出し不能となり、極めて大きな耐引抜き力を発揮する。
ここで、スパイラルリブ3の緩螺旋は、鋼管軸線方向Oに対する傾斜角度θが4〜15°の範囲とする。すなわち、該傾斜角度θが4°未満では、鋼管杭Pを岩盤支持層Gr内まで打ち込んだ状態での耐引抜き力が不充分になる。また逆に、該傾斜角度θが15°を超えると、打撃圧入で鋼管杭Pの下部側を岩盤支持層Gr内へ打ち込む際、螺旋誘導作用による自己回転を生じにくく、非回転状態でスパイラルリブ3が孔壁岩盤を削り取って孔径を拡げてしまうために、岩盤支持層Grによる鋼管杭Pの先端支持力及び耐引抜き力が著しく低下することになる。
又、本発明によれば、鋼管杭Pの各スパイラルリブ3の下端部は、下端側が下り勾配のテーパ部31aに形成されているから、岩盤支持層Grの孔壁岩盤に対する該下端側の食い付きが容易で、且つ充分な食い込み深さを確保できる。
しかも、該下り勾配のテーパ部31aは、耐摩耗性の大きい金属材である高硬質チップ31によって形成されているため、岩盤強度の高い岩盤支持層Grであっても充分な耐摩耗性を発揮し、長期にわたって安定して施工することができる。
Next, the effect of the present invention will be described in detail with reference to the drawings. According to the construction method of the steel pipe pile P according to the invention of claim 1, the steel pipe axial direction O is formed on the outer peripheral surface of the lower side of the steel pipe 1. Is formed with a plurality of spiral ribs 3 that form a gentle spiral with an inclination angle θ of 4 to 15 ° with respect to each other , and at the lower end of each spiral rib, a tapered portion 31a having a taper at the lower end and a downward slope is formed. Using the steel pipe pile P provided with the chip 31 , first, the excavation hole H reaching the rock support layer Gr on the deep side is formed in the ground G, and then the steel pipe pile P is powerfully inserted into the excavation hole H. Since the striking press-fitting is performed through the vibro hammer 7, even in the rock support layer Gr having a high rock strength, the spiral rib 3 on the outer peripheral surface of the steel pipe pile P and the taper portion 31a having a downward slope taper at the lower end thereof are formed in the rock. Hole wall rock of support layer Gr The board bites into the board and is press-fitted to a predetermined depth while self-rotating by the spiral guiding action of the spiral rib 3 and the tapered and downwardly tapered portion 31a. And, since the steel pipe pile P that has been laid is directly held by the rock support layer Gr and is solidified by the rock support layer Gr itself, a large tip support force based on the rock strength is obtained. In addition to exhibiting extremely high resistance to horizontal load and vertical load from the superstructure, each spiral rib 3 bites into the hole wall bedrock by forming a spiral path, so unless the rotation force is applied It becomes impossible to withdraw from the support layer Gr, and exhibits an extremely large pull-out resistance.
Here, the gentle helix of the spiral rib 3 has an inclination angle θ with respect to the steel pipe axial direction O in the range of 4 to 15 °. That is, when the inclination angle θ is less than 4 °, the pulling-out force in a state where the steel pipe pile P is driven into the rock support layer Gr becomes insufficient. On the other hand, when the inclination angle θ exceeds 15 °, when the lower part of the steel pipe pile P is driven into the rock mass support layer Gr by impact press-fitting, it is difficult for self-rotation to occur due to the spiral induction action, and the spiral ribs are not rotated. 3 scrapes the hole wall rock and widens the hole diameter, so that the tip support force and pull-out resistance of the steel pipe pile P by the rock support layer Gr are significantly reduced.
Further, according to the present invention, the lower end portion of each spiral rib 3 of the steel pipe pile P is formed in the tapered portion 31a having a downward slope on the lower end side, so that the lower end side bite with respect to the hole wall rock of the rock support layer Gr. It is easy to attach and a sufficient depth of penetration can be secured.
Moreover, since the downwardly tapered portion 31a is formed by the high-hard tip 31 which is a metal material having high wear resistance, even the rock support layer Gr having high rock strength exhibits sufficient wear resistance. And it can be constructed stably over a long period of time.

請求項2の発明によれば、鋼管杭Pは、スパイラルリブ3が鋼管1の下端又は下端近傍から特定の長さ範囲Lに設けられているから、岩盤支持層Gr内へ容易に打ち込んで充分な耐引抜き力を確保できる。   According to the second aspect of the present invention, the steel pipe pile P has a spiral rib 3 provided in a specific length range L from the lower end or the vicinity of the lower end of the steel pipe 1, so that it can be easily driven into the rock support layer Gr. Can withstand high pull-out force.

請求項3の発明によれば、鋼管杭Pは、4本以上のスパイラルリブ3が鋼管1周方向に等配配置しているから、岩盤支持層Grの孔壁岩盤に対する食い込みを周方向均等に充分に確保して大きな耐引抜き力を発揮できる。   According to the invention of claim 3, since the steel pipe pile P has four or more spiral ribs 3 arranged equally in the circumferential direction of the steel pipe, the biting of the rock support layer Gr into the hole wall rock is made uniform in the circumferential direction. Sufficiently secures sufficient pull-out resistance.

請求項の発明によれば、上記施工方法において、鋼管杭Pの各スパイラルリブ3の孔壁岩盤に対する食い込み深さdを特定範囲に設定することから、該鋼管杭Pを岩盤支持層Gr内まで容易に打ち込んで充分な耐引抜き力を付与できる。 According to invention of Claim 4 , in the said construction method, since the penetration depth d with respect to the hole wall rock of each spiral rib 3 of the steel pipe pile P is set to a specific range, this steel pipe pile P is set in the rock mass support layer Gr. Can be easily driven in to provide sufficient pull-out force.

請求項の発明によれば、上記施工方法において、掘削孔径D3を鋼管杭Pの鋼管外径D1に対して特定範囲に設定することから、該鋼管杭Pを岩盤支持層Gr内まで容易に打ち込んで、該鋼管杭Pに大きな先端支持力及び耐引抜き力を付与できる。 According to the invention of claim 5, in the construction method, since the excavation hole diameter D3 is set in a specific range with respect to the steel pipe outer diameter D1 of the steel pipe pile P, the steel pipe pile P can be easily moved into the bedrock support layer Gr. It can drive in and can give big tip support force and pull-out-proof power to this steel pipe pile P.

請求項の発明によれば、上記施工方法において、掘削孔Hを先端に掘削ビット5を備えたダウンザホールハンマ4によって掘削し、その掘削中に発生したスライムを除去し、形成した掘削孔Hに土砂類Sを投入し、この土砂類Sで埋まった掘削孔Hに鋼管杭Pの打撃圧入を行うことから、掘削孔Hの内周壁と鋼管杭Pの鋼管1との僅かな隙間ならびに該鋼管1内が土砂類Sで充填され、もって該鋼管杭Pが揺るぎない打設状態となり、地盤Gによる保持力がより増大する。 According to the invention of claim 6, in the construction method described above, the excavation hole H is excavated by the down-the-hole hammer 4 provided with the excavation bit 5 at the tip, the slime generated during the excavation is removed, and the excavation hole H is formed. Since the earth and sand S is thrown in and the steel pipe pile P is blown into the excavation hole H filled with the earth and sand S, a slight gap between the inner peripheral wall of the excavation hole H and the steel pipe 1 of the steel pipe pile P and the steel pipe 1 is filled with earth and sand S, so that the steel pipe pile P is placed in a stable state and the holding force by the ground G is further increased.

本発明に係る鋼管杭の一実施形態を示し、(a)は鋼管杭の下部側の側面図、(b)は(a)のX−X線の矢視断面図、(c)は鋼管杭下端部のスパイラルリブ形成部分の縦断側面図、(d)は該スパイラルリブの高硬質チップの平面図である。1 shows an embodiment of a steel pipe pile according to the present invention, (a) is a side view of the lower side of the steel pipe pile, (b) is a sectional view taken along line XX of (a), and (c) is a steel pipe pile. A longitudinal side view of a spiral rib forming portion at the lower end, (d) is a plan view of a highly rigid chip of the spiral rib. 同鋼管杭の他の実施形態を示し、(a)は断面三角形のスパイラルリブを形成した鋼管杭の半横断面図、(b)は断面円形のスパイラルリブを形成した鋼管杭の半横断面図である。The other embodiment of the steel pipe pile is shown, (a) is a half cross-sectional view of a steel pipe pile in which a spiral rib having a triangular section is formed, (b) is a half cross-sectional view of a steel pipe pile in which a spiral rib having a circular cross section is formed. It is. 同鋼管杭のスパイラルリブ本数が異なる構成例を例示し、(a)は4本、(b)は6本、(c)は8本、(d)は12本、のそれぞれスパイラルリブを設けた該鋼管杭の概略横断面図である。The example of the structure in which the number of spiral ribs of the steel pipe pile is different is illustrated, (a) is provided with 4 spiral ribs, (b) is provided with 6 spirals, (c) is provided with 8 spiral ribs, and (d) is provided with 12 spiral ribs. It is a schematic cross-sectional view of this steel pipe pile. 本発明の一実施形態に係る鋼管杭の施工方法における掘削孔の形成手順について、(a)〜(e)の工程順に示す模式縦断側面図である。It is a model longitudinal cross-sectional side view shown in order of the process of (a)-(e) about the formation procedure of the excavation hole in the construction method of the steel pipe pile which concerns on one Embodiment of this invention. 同施行方法における鋼管杭の打込み手順について、(a)〜(d)の工程順に示す模式縦断側面図である。It is a model vertical side view shown in order of the process of (a)-(d) about the driving procedure of the steel pipe pile in the enforcement method. 打ち込んだ同鋼管杭の岩盤支持層中の配置状態を示し、(a)は横断面図、(b)は(a)の仮想線円Y内の拡大図である。The arrangement | positioning state in the bedrock support layer of the same steel pipe pile piled in is shown, (a) is a cross-sectional view, (b) is an enlarged view in the phantom line circle Y of (a). 鋼管杭を利用して構築される擁壁を例示する斜視図である。It is a perspective view which illustrates the retaining wall constructed | assembled using a steel pipe pile.

以下に、本発明に係る鋼管杭とその施工方法の実施形態について、図面を参照して具体的に説明する。   Below, the embodiment of the steel pipe pile concerning the present invention and its construction method is described concretely with reference to drawings.

図1(a)(b)に示す実施形態の鋼管杭Pは、その円筒状の鋼管1の下部側の外周面に、緩螺旋をなす複数本(図では8本)のスパイラルリブ3が周方向に等配して形成されている。各スパイラルリブ3は、下端部を除いて、断面が略正方形の鋼棒30からなり、溶接によって鋼管1の表面に固着されている。そして、該スパイラルリブ3の下端部は、図1(c)(d)で拡大して示すように、鋼棒30とは別体の高硬質チップ31にて構成され、鋼管1の下端に外嵌固着した円環状の補強バンド2上に溶接固着されている。この高硬質チップ31は、例えば超硬合金材や機械構造用炭素鋼材55C,45C等の耐摩耗性の大きい金属材からなり、鋼棒30と同幅であるが、上面を該鋼棒30と面一にするために厚みが補強バンド2の分だけ薄くなると共に、下端側が先細りで且つ下り勾配のテーパ部31aをなしている。   The steel pipe pile P according to the embodiment shown in FIGS. 1 (a) and 1 (b) has a plurality of loose ribs (eight in the figure) spiral ribs 3 on the outer peripheral surface on the lower side of the cylindrical steel pipe 1. It is formed with equal distribution in the direction. Each spiral rib 3 includes a steel rod 30 having a substantially square cross section except for the lower end portion, and is fixed to the surface of the steel pipe 1 by welding. And the lower end part of this spiral rib 3 is comprised by the hard-hard tip 31 separate from the steel bar 30, as shown expanded in FIG. It is welded and fixed on the annular reinforcing band 2 fitted and fixed. The high-hardness tip 31 is made of a metal material having high wear resistance, such as a cemented carbide material or a carbon steel material for mechanical structure 55C, 45C, and has the same width as the steel rod 30, but the upper surface is the same as the steel rod 30. In order to make it flush, the thickness is reduced by the amount corresponding to the reinforcing band 2, and the lower end side is tapered and forms a taper portion 31a having a downward slope.

ここで、スパイラルリブ3の緩螺旋は、図1(a)で示す鋼管軸線方向Oに対する傾斜角度θが4〜15°の範囲とする。すなわち、該傾斜角度θが4°未満では、後述するように鋼管杭Pを岩盤支持層Gr(図5参照)内まで打ち込んだ状態での耐引抜き力が不充分になる。また逆に、該傾斜角度θが15°を超えると、打撃圧入で鋼管杭Pの下部側を岩盤支持層Gr内へ打ち込む際、螺旋誘導作用による自己回転を生じにくく、非回転状態でスパイラルリブ3が孔壁岩盤を削り取って孔径を拡げてしまうために、岩盤支持層Grによる鋼管杭Pの先端支持力及び耐引抜き力が著しく低下することになる。なお、スパイラルリブ3の上記傾斜角度θは、鋼管杭Pを打ち込む岩盤支持層Grの岩質に応じて4〜15°の範囲内で更に最適範囲に設定すればよく、例えば硬岩では4〜6°程度、中硬岩では4〜10°程度、軟岩では6〜15°程度がそれぞれ好ましい。   Here, the gentle helix of the spiral rib 3 has an inclination angle θ with respect to the steel pipe axial direction O shown in FIG. That is, when the inclination angle θ is less than 4 °, the pulling-out force in a state where the steel pipe pile P is driven into the rock support layer Gr (see FIG. 5) as described later becomes insufficient. On the other hand, when the inclination angle θ exceeds 15 °, when the lower part of the steel pipe pile P is driven into the rock mass support layer Gr by impact press-fitting, it is difficult for self-rotation to occur due to the spiral induction action, and the spiral ribs are not rotated. 3 scrapes the hole wall rock and widens the hole diameter, so that the tip support force and pull-out resistance of the steel pipe pile P by the rock support layer Gr are significantly reduced. In addition, what is necessary is just to set the said inclination | tilt angle (theta) of the spiral rib 3 in the optimal range within the range of 4-15 degrees according to the rock quality of the rock mass support layer Gr which drives the steel pipe pile P, for example, 4 ~ About 6 °, about 4 to 10 ° for medium hard rock, and about 6 to 15 ° for soft rock are preferable.

鋼管1におけるスパイラルリブ3を形成する長さ範囲L〔図1(a)参照〕は、鋼管1の下端又は下端近傍から1〜8m、最適には3〜6mとするのがよく、これによって鋼管杭Pを比較的少ない圧入抵抗で岩盤支持層Gr内まで容易に打ち込んで大きな支持力及び耐引抜き力を確保できる。しかるに、該長さ範囲Lが短すぎては支持力及び耐引抜き力が不充分となり、逆に長過ぎては岩盤支持層Gr内への鋼管杭Pの打撃圧入に過大な力を要することになる。なお、スパイラルリブ3の螺旋ピッチは2〜8m程度がよい。また、鋼管1における各スパイラルリブ3の螺旋ピッチ数(周回数)は、図1では0.5ピッチ(1/2周回)として例示したが、上記傾斜角度θが4〜15°の範囲で2ピッチ(2周回)以下とするのがよく、多過ぎては圧入抵抗の増大によって施工効率が悪化する。   The length range L (see FIG. 1 (a)) for forming the spiral rib 3 in the steel pipe 1 is preferably 1 to 8 m, most preferably 3 to 6 m from the lower end of the steel pipe 1 or the vicinity of the lower end. The pile P can be easily driven into the rock support layer Gr with a relatively small press-fit resistance to ensure a large support force and pull-out resistance. However, if the length range L is too short, the supporting force and the pulling-out force are insufficient, and conversely, if the length range L is too long, an excessive force is required to inject the steel pipe pile P into the rock support layer Gr. Become. The spiral pitch of the spiral rib 3 is preferably about 2 to 8 m. Further, although the spiral pitch number (number of turns) of each spiral rib 3 in the steel pipe 1 is exemplified as 0.5 pitch (1/2 turn) in FIG. 1, it is 2 in the range where the inclination angle θ is 4 to 15 °. The pitch (two rounds) or less is preferable, and if it is too large, the construction efficiency deteriorates due to an increase in press-fit resistance.

また、スパイラルリブ3の鋼管1表面からの高さt〔図1(c)参照〕は、15〜50mmの範囲が好ましく、低過ぎては孔壁岩盤に対するスパイラルリブ3の食い込みが浅くなるため、鋼管杭Pの支持力及び耐引抜き力を充分に確保できず、逆に高過ぎては岩盤支持層Gr内への鋼管杭Pの打撃圧入に過大な力を要することになる。更に、スパイラルリブ3(高硬質チップ31)の下端側のテーパ部31aの勾配角α〔図1(c)参照〕は、45°以下が好ましく、大き過ぎては孔壁岩盤に対する食い付き抵抗が大きくなって鋼管杭Pの打撃圧入に大きな力を要することになる。   Further, the height t of the spiral rib 3 from the surface of the steel pipe 1 (see FIG. 1C) is preferably in the range of 15 to 50 mm, and if it is too low, the spiral rib 3 bites into the hole wall bedrock becomes shallow. Sufficient support force and pull-out force of the steel pipe pile P cannot be ensured. Conversely, if it is too high, an excessive force is required to press the steel pipe pile P into the rock support layer Gr. Furthermore, the slope angle α of the tapered portion 31a on the lower end side of the spiral rib 3 (highly hard tip 31) (see FIG. 1 (c)) is preferably 45 ° or less, and if it is too large, the resistance to biting against the hole wall rock is high. It becomes large and requires a large force to hit and press the steel pipe pile P.

なお、スパイラルリブ3としては、図1で例示した断面が略正方形のものに限らず、例えば図2(a)に示す鋼管杭P1のような三角形、図2(b)に示す鋼管杭P2のような円形、更には図示しない長方形や楕円等の様々な断面形状のものを採用できる。また、既述のスパイラルリブ3の下端部は前述のように上位主要部の鋼棒30とは別材の高硬質チップ31からなるものである。 In addition, as the spiral rib 3, the cross section illustrated in FIG. 1 is not limited to the one having a substantially square shape. For example, a triangle such as a steel pipe pile P1 shown in FIG. 2A, a steel pipe pile P2 shown in FIG. Such circular shapes and various cross-sectional shapes such as rectangles and ellipses (not shown) can be employed. Further, the lower end portion of the spiral rib 3 described above is composed of the high-hard tip 31 which is a different material from the steel rod 30 of the upper main part as described above .

一方、スパイラルリブ3の本数は、孔壁岩盤に対する食い込み強度面より4本以上であることが望ましいが、鋼管1の外径に応じて、例えば図3の(a)で示す鋼管外径500mm未満の鋼管杭P3では4本、同(b)で示す鋼管外径500〜600mm程度の鋼管杭P4では6本、同(c)で示す鋼管外径700〜1000mm程度の鋼管杭P5では8本、同(d)で示す鋼管外径1100mm以上の鋼管杭P6では12本のように、鋼管外径が大きいほど多くするのがよい。   On the other hand, the number of spiral ribs 3 is preferably four or more from the surface of the bite strength against the hole wall rock, but depending on the outer diameter of the steel pipe 1, for example, the outer diameter of the steel pipe shown in FIG. 4 in the steel pipe pile P3, 6 in the steel pipe pile P4 with a steel pipe outer diameter of about 500 to 600 mm shown in (b), 8 in the steel pipe pile P5 with a steel pipe outer diameter of about 700 to 1000 mm shown in (c), In the steel pipe pile P6 having a steel pipe outer diameter of 1100 mm or more shown in (d), it is better to increase the steel pipe outer diameter as the steel pipe outer diameter is larger, such as twelve.

次に、上記の鋼管杭Pを用いた本発明の施工方法の一実施形態について、図4及び図5を参照して説明する。なお、図4及び図5では、模式図として、掘削孔Hの深さ及び鋼管杭Pの長さを短縮した形で図示している。また、図示の地盤Gは、浅部層Gsが砂層、土泥層、転石層、礫層等からなるが、深部側に岩盤支持層Grを有するものである。   Next, an embodiment of the construction method of the present invention using the steel pipe pile P will be described with reference to FIGS. 4 and 5. 4 and 5, as schematic diagrams, the depth of the excavation hole H and the length of the steel pipe pile P are illustrated in a shortened form. In the illustrated ground G, the shallow layer Gs is composed of a sand layer, a mud layer, a boulder layer, a gravel layer, etc., but has a rock support layer Gr on the deep side.

この施工方法では、まず図4(a)で示すようにダウンザホールハンマ4をアースオーガ6にて垂直に支持し、同(b)に示すように該ダウンザホールハンマ4を回転させながら先端の掘削ビット5を地盤Gに打撃圧入して削孔ゆくことにより、同(c)に示すように深部の岩盤支持層Gr0内に達する掘削孔Hを穿設すると共に、この削孔過程で生じるスライムを掘削ビット5から噴出するハンマ駆動用圧縮エアの排気によって地上側へ放出させる。そして、所定深度の掘削孔Hを形成後、図4(d)に示すようにダウンザホールハンマ4を回転させながら引き上げてゆき、その引上げ過程でも更にハンマ駆動用圧縮エアの排気によってスライムを地上へ排出し、同(e)に示すように空所化した掘削孔Hからダウンザホールハンマ4を抜出する。   In this construction method, first, the down-the-hole hammer 4 is vertically supported by the earth auger 6 as shown in FIG. 4A, and the excavation bit 5 at the tip is rotated while the down-the-hole hammer 4 is rotated as shown in FIG. 4B. As shown in (c), a drilling hole H that reaches into the deep rock support layer Gr0 is drilled, and slime generated during this drilling process is drilled into the drill bit. 5 is discharged to the ground side by exhausting compressed air for driving a hammer. Then, after forming the excavation hole H at a predetermined depth, the down-the-hole hammer 4 is pulled up while rotating as shown in FIG. 4 (d), and slime is discharged to the ground by exhausting the compressed air for driving the hammer even during the pulling process. Then, as shown in (e), the down-the-hole hammer 4 is extracted from the vacated excavation hole H.

なお、形成する掘削孔Hの孔径D3〔図4(e)参照〕は、後述の如く孔壁に各スパイラルリブ3を食い込ませる必要から、図1(b)に示す鋼管杭Pの鋼管1の外径D1以上で、且つ該鋼管杭Pにおける複数本のスパイラルリブ3に対する外接円径D2より小さく設定する。すなわち、D2>D3≧D1であるが、より好ましくはD3=D1+(0〜10mm)とするのがよい。
In addition, since the hole diameter D3 [refer FIG.4 (e)] of the excavation hole H to form needs to make each spiral rib 3 bite into a hole wall so that it may mention later, the steel pipe 1 of the steel pipe pile P shown in FIG.1 (b). The outer diameter D1 is set to be larger than the circumscribed circle diameter D2 with respect to the plurality of spiral ribs 3 in the steel pipe pile P. That is, D2> D3 ≧ D1 , but more preferably D3 = D1 + (0 to 10 mm).

かくして形成した掘削孔Hには、鋼管杭Pの打込み前に、図5(a)に示すように、土砂類Sを投入して埋め戻す。この土砂類Sには削孔時に地上側へ排出したスライムも含まれる。次に、図5(b)に示すように、クレーン(図示省略)で吊持したバイブロハンマ7のチャック7aによって鋼管杭Pの上端部を把持し、この鋼管杭Pを埋め戻した掘削孔Hの真上に垂直に配置し、図5(c)に示すように、バイブロハンマ7の駆動によって該鋼管杭Pを掘削孔Hに打撃圧入してゆく。そして、図5(d)に示すように、該鋼管杭Pを掘削孔H内の所定深度(通常は孔底)まで圧入させたのち、バイブロハンマ7のチャック7aを開放し、該バイブロハンマ7を引き上げて鋼管杭Pの打設を完了する。   Before the steel pipe pile P is driven, the excavation hole H thus formed is filled with earth and sand S as shown in FIG. This earth and sand S includes slime discharged to the ground side during drilling. Next, as shown in FIG.5 (b), the upper end part of the steel pipe pile P is hold | gripped with the chuck | zipper 7a of the vibro hammer 7 hung with the crane (illustration omitted), and the excavation hole H of this steel pipe pile P was refilled. As shown in FIG. 5 (c), the steel pipe pile P is hit and pressed into the excavation hole H by driving the vibro hammer 7. Then, as shown in FIG. 5 (d), after the steel pipe pile P is press-fitted to a predetermined depth (usually the bottom of the hole) in the excavation hole H, the chuck 7a of the vibrator hammer 7 is released, and the vibrator hammer 7 is pulled up. To complete the installation of the steel pipe pile P.

上記の鋼管杭Pの圧入過程では、バイブロハンマ7の起振力に基づく高速打撃と該バイブロハンマ7及び鋼管杭Pの自重により、該鋼管杭Pが掘削孔H内に圧入してゆくが、その下端側外周面に複数本のスパイラルリブ3が突設されているため、これらスパイラルリブ3による螺旋誘導作用で鋼管杭Pは自己回転しつつ圧入してゆくことになる。この鋼管杭Pの自己回転は、クレーンの動滑車8とバイブロハンマ7を吊持するフック81とのスイベル連結部における相対回転によって許容される。そして、該鋼管杭Pの下部側が岩盤支持層Gr内に圧入してゆく際には、外周面の各スパイラルリブ3が掘削孔Hの孔壁岩盤に食い込んで螺旋溝を刻設してゆくことになる。また、掘削孔H内を埋めていた土砂類Sは、鋼管1内に入り込むと共に、掘削孔Hの内周壁と鋼管杭Pの鋼管1との僅かな隙間にも充填される。   In the press-fitting process of the steel pipe pile P, the steel pipe pile P is press-fitted into the excavation hole H due to the high-speed impact based on the vibration force of the vibro hammer 7 and the dead weight of the vibro hammer 7 and the steel pipe pile P. Since the plurality of spiral ribs 3 project from the side outer peripheral surface, the steel pipe pile P is press-fitted while being self-rotated by the spiral induction action by these spiral ribs 3. The self-rotation of the steel pipe pile P is allowed by relative rotation at the swivel connecting portion between the crane pulley 8 and the hook 81 that holds the vibrator hammer 7. And when the lower part side of this steel pipe pile P press-fits into the rock mass support layer Gr, each spiral rib 3 of an outer peripheral surface bites into the hole wall rock mass of the excavation hole H, and engraves a spiral groove. become. Further, the earth and sand S filling the inside of the excavation hole H enters the steel pipe 1 and is also filled in a slight gap between the inner peripheral wall of the excavation hole H and the steel pipe 1 of the steel pipe pile P.

岩盤支持層Gr内に達した鋼管杭Pの下部側では、図6(a)(b)に示すように、鋼管1の外周面が掘削孔Hの内周面に近接ないし密接した状態で、各スパイラルリブ3が孔壁岩盤に食い込んでいる。従って、打設した鋼管杭Pは、下部側が岩盤支持層Grによって直接に抱持され、該岩盤支持層Gr自体で根固めされた形になり、岩盤強度に基づく大きな先端支持力が得られ、水平力の負荷や上部構造物による垂直荷重に対して極めて高い抵抗性が発現する上、孔壁岩盤に対して複数本のスパイラルリブ3が周方向均等に螺旋の道筋を造って食い込んでおり、回転力が作用しない限りは岩盤支持層Grから抜出し不能となるから、極めて大きな耐引抜き力を発揮する。一方、打設後の鋼管杭Pは、スパイラルリブ3の螺旋抜出し方向に回転力を加えつつ引き上げることで、地盤Gから容易に引抜き可能である。   On the lower side of the steel pipe pile P that has reached the bedrock support layer Gr, the outer peripheral surface of the steel pipe 1 is close to or in close contact with the inner peripheral surface of the excavation hole H, as shown in FIGS. Each spiral rib 3 bites into the hole wall rock. Therefore, the cast steel pipe pile P has a shape in which the lower side is directly held by the rock support layer Gr and solidified by the rock support layer Gr itself, and a large tip support force based on the rock strength is obtained. Extremely high resistance to horizontal load and vertical load from the superstructure is developed, and multiple spiral ribs 3 bite into the hole wall rock evenly in the circumferential direction. As long as the rotational force does not act, it cannot be pulled out from the rock support layer Gr, and thus exhibits a very large pull-out resistance. On the other hand, the steel pipe pile P after placement can be easily pulled out from the ground G by pulling up while applying a rotational force in the spiral pulling-out direction of the spiral rib 3.

このように岩盤支持層Grに達した鋼管杭Pのスパイラルリブ3が孔壁岩盤に対して螺旋の道筋を造って食い込んでいるか否かは、バイブロハンマ7による打撃圧入中に該鋼管杭Pの回転度合を観察することで確認できる。すなわち、鋼管杭Pの圧入長さ当りの回転量は、スパイラルリブ3のスパイラルピッチから算出できるから、その算出値から設定した許容範囲に実際の観測値が入れば、大きな耐引抜き力を付与できたことになる。   Whether or not the spiral rib 3 of the steel pipe pile P that has reached the rock support layer Gr forms a spiral path with respect to the hole wall rock is determined by whether or not the steel pipe pile P is rotated during the impact injection by the vibro hammer 7. This can be confirmed by observing the degree. That is, since the rotation amount per press-fit length of the steel pipe pile P can be calculated from the spiral pitch of the spiral rib 3, if the actual observation value falls within the allowable range set from the calculated value, a large pull-out force can be imparted. That's right.

岩盤支持層Grにおけるスパイラルリブ3の孔壁岩盤への食い込み深さd〔図6(b)参照〕は、該スパイラルリブ3の鋼管1表面からの高さt、ならびに掘削孔Hの内径D3と鋼管1の外径D1との差(D3−D1)によって定まり、d=t−(D3−D1)/2となるが、15〜50mmの範囲が好適である。この食い込み深さdが浅過ぎては、該鋼管杭Pの耐引抜き力が不充分になり、逆に深過ぎては打撃圧入に過大な力を要すると共に施工能率が低下することになる。   The depth d (see FIG. 6 (b)) of the spiral rib 3 in the rock wall support layer Gr to the hole wall rock is determined by the height t of the spiral rib 3 from the surface of the steel pipe 1 and the inner diameter D3 of the excavation hole H. It is determined by the difference (D3−D1) from the outer diameter D1 of the steel pipe 1 and becomes d = t− (D3−D1) / 2, but a range of 15 to 50 mm is preferable. If the bite depth d is too shallow, the pull-out force of the steel pipe pile P will be insufficient, and conversely if it is too deep, an excessive force will be required for impact pressing and the construction efficiency will be reduced.

また、実施形態の施工方法では、先に削孔した掘削孔Hを土砂類Sで埋め戻した上で鋼管杭Pを打撃圧入するから、掘削孔Hの内周壁と鋼管杭Pの鋼管1との僅かな隙間ならびに該鋼管1内が土砂類Sで充填され、該鋼管杭Pは揺るぎない打設状態となって地盤Gによる支持力がより増大するという利点がある。しかるに、本発明の施工方法は、掘削孔Hを埋め戻すことなく、空所のままでバイブロハンマ7による鋼管杭Pの打撃圧入を行う手法も包含する。このように空所の掘削孔Hに鋼管杭Pを打撃圧入する手法でも、該鋼管杭Pは下部側が岩盤支持層Grに直接に保持されることで十分な支持力及び耐引抜き力が得られる。   Further, in the construction method of the embodiment, since the steel pipe pile P is hit and pressed after the excavated hole H drilled previously is backfilled with earth and sand S, the inner peripheral wall of the excavated hole H and the steel pipe 1 of the steel pipe pile P The steel pipe 1 is filled with earth and sand S, and the steel pipe pile P is in an undisturbed driving state, and the support force by the ground G is further increased. However, the construction method of the present invention also includes a method of hitting and pressing the steel pipe pile P with the vibro hammer 7 without refilling the excavation hole H. Thus, even in the method of hitting and pressing the steel pipe pile P into the excavation hole H in the empty space, the steel pipe pile P can obtain a sufficient supporting force and pulling-out force by the lower side being directly held by the rock support layer Gr. .

更に、この施工方法では、鋼管杭Pを岩盤支持層Gr自体で直接に根固めすることで、、根固め材を省略できるから、それだけ材料コストを低減できると共に、品質管理が容易になり、施工能率も向上する上、根固め材による周辺環境の汚染を回避できるという利点がある。ただし、本発明の施工方法においては、掘削孔Hを埋め戻す土砂類Sと共にセメントミルク等のグラウトを注入してもよく、これによって掘削孔Hの内周壁と鋼管杭Pの鋼管1との僅かな隙間を充填する土砂類Sが硬化層となるから、該鋼管杭Pの地盤Gによる保持力を更に増大することができる。   Furthermore, in this construction method, since the steel pipe pile P is directly solidified by the bedrock support layer Gr itself, the solidification material can be omitted, so that the material cost can be reduced and the quality control becomes easy. In addition to improving efficiency, there is an advantage that contamination of the surrounding environment by the root-capping material can be avoided. However, in the construction method of the present invention, a grout such as cement milk may be injected together with the earth and sand S for refilling the excavation hole H, whereby a slight amount of the inner peripheral wall of the excavation hole H and the steel pipe 1 of the steel pipe pile P may be obtained. Since the earth and sand S filling the gaps becomes a hardened layer, the holding force of the steel pipe pile P by the ground G can be further increased.

なお、図5では打設完了後の鋼管杭Pが頂部のみを地表から突出した形で図示しているが、その突出高さは鋼管杭Pの長さによって任意に設定できる。従って、この鋼管杭Pの複数本を上部側が地上に所定高さで突出する状態で地盤Gの岩盤支持層Gr内に達するまで打ち込んでおき、例えば図8に示すように、その地上突出部を利用して縦孔h付きの擁壁ブロックB1〜B4を複数段に積み重ねて擁壁Wを構築した場合、この擁壁Wに大きな側圧が加わっても、各鋼管杭Pは回転力が作用しないために持ち上がらず、もって鋼管杭Pの持ち上がりを伴う擁壁Wの倒壊が阻止されることになる。しかして、本発明の施工方法によれば、鋼管杭Pが極めて大きな耐引抜き力を発揮するから、擁壁Wに限らず、排煙塔、鉄塔、高層ビル、ハイピア等の基礎杭に大きな耐引抜き力が要求される各種構造物についても、この施工方法を好適に適用できる。   In addition, in FIG. 5, although the steel pipe pile P after completion of placement has been illustrated in a form in which only the top portion protrudes from the ground surface, the protruding height can be arbitrarily set depending on the length of the steel pipe pile P. Therefore, a plurality of the steel pipe piles P are driven until they reach the rock support layer Gr of the ground G with the upper side protruding above the ground at a predetermined height. For example, as shown in FIG. When the retaining wall W is constructed by stacking the retaining wall blocks B1 to B4 with the vertical holes h in a plurality of stages, even if a large lateral pressure is applied to the retaining wall W, each steel pipe pile P does not act on the rotational force. Therefore, it does not lift up, and the collapse of the retaining wall W accompanying the lifting of the steel pipe pile P is prevented. Therefore, according to the construction method of the present invention, the steel pipe pile P exhibits an extremely large pull-out resistance, so that not only the retaining wall W but also a large pile-proof pile such as a smoke tower, steel tower, high-rise building, high pier, etc. This construction method can also be suitably applied to various structures that require a pulling force.

本発明の施工方法で使用するバイブロハンマ7としては、特に制約されないが、硬岩や中硬岩に対する削孔を効率よく行う上で、最大起振力が1000kN以上、最大周波数が2000rpm以上の油圧式超高起振力バイブロハンマが推奨される。このような油圧式超高起振力バイブロハンマの具体例として、オランダ国IEC社製の商品名20RF(最大起振力:1100kN、最大周波数:2300rpm)、同28RF(最大起振力:1600kN、最大周波数:2300rpm)、オランダ国PVE社製の商品名24VM(最大起振力:1400kN、最大周波数:2300rpm)等が挙げられる。   The vibro hammer 7 used in the construction method of the present invention is not particularly limited. However, in order to efficiently drill holes in hard rocks and medium hard rocks, a hydraulic type having a maximum excitation force of 1000 kN or more and a maximum frequency of 2000 rpm or more. A super high vibratory vibro hammer is recommended. As a specific example of such a hydraulic ultra-high vibration force vibratory hammer, product name 20RF (maximum vibration force: 1100 kN, maximum frequency: 2300 rpm), 28 RF (maximum vibration force: 1600 kN, maximum) manufactured by IEC, the Netherlands. Frequency: 2300 rpm), trade name 24VM (maximum excitation force: 1400 kN, maximum frequency: 2300 rpm) manufactured by PVE, the Netherlands, and the like.

1 鋼管
3,3A,3B スパイラルリブ
31a テーパー部
4 ダウンザホールハンマ
5 掘削ビット
7 バイブロハンマ
D1 鋼管外径
D3 掘削孔径
G 地盤
Gr 岩盤支持層
H 掘削孔
L 長さ範囲
O 鋼管軸線方向
P 鋼管杭
S 土砂類
d 食い込み深さ
θ 傾斜角度
t スパイラルリブの鋼管表面からの高さ
DESCRIPTION OF SYMBOLS 1 Steel pipe 3,3A, 3B Spiral rib 31a Taper part 4 Down-the-hole hammer 5 Drilling bit 7 Vibro hammer D1 Steel pipe outer diameter D3 Drilling hole diameter G Ground Gr Rock bed support layer H Drilling hole L Length range O Steel pipe pile direction S Steel pipe pile S Sediment d Depth of penetration θ Inclination angle t Height of spiral rib from steel pipe surface

Claims (6)

鋼管の下部側の外周面に、鋼管軸線方向に対する傾斜角度が4〜15°の緩螺旋をなす複数本のスパイラルリブが形成され、且つ各スパイラルリブの下端部に、下端側が先細りで下り勾配のテーパ部を形成してなる高硬質チップが設けられてなる鋼管杭を用い、先ず、少なくとも深部側に岩盤支持層を有する地盤に対し、該岩盤支持層中に達する掘削孔を形成したのち、前記鋼管杭をバイブロハンマを介して打撃圧入することにより、該鋼管杭を外周面のスパイラルリブ及びその下端部の先細り下り勾配のテーパ部による誘導作用で自己回転させつつ岩盤支持層内に到達させると共に、各スパイラルリブを孔壁岩盤に食い込ませることを特徴とする鋼管杭の施工方法。 A plurality of spiral ribs forming a gentle helix with an inclination angle of 4 to 15 ° with respect to the axial direction of the steel pipe is formed on the outer peripheral surface of the lower side of the steel pipe, and the lower end side of each spiral rib is tapered and has a downward slope. Using a steel pipe pile provided with a high-hard tip formed with a tapered portion, first, after forming a drilling hole reaching the rock mass support layer, at least for the ground having a rock mass support layer on the deep side, By hitting the steel pipe pile through a vibro hammer, the steel pipe pile is allowed to reach the bedrock support layer while being self-rotated by the induction action of the spiral rib on the outer peripheral surface and the taper portion of the lower end of the taper, and A steel pipe pile construction method characterized in that each spiral rib bites into the hole wall bedrock. 鋼管の下端又は下端近傍から1〜8mまでの長さ範囲に前記スパイラルリブが設けられてなる請求項1に記載の鋼管杭の施工方法 The construction method of the steel pipe pile of Claim 1 in which the said spiral rib is provided in the length range from the lower end of a steel pipe or the lower end vicinity to 1-8 m. 4本以上のスパイラルリブが鋼管周方向に等配配置してなる請求項1又は2に記載の鋼管杭の施工方法 The construction method of the steel pipe pile of Claim 1 or 2 formed by arranging four or more spiral ribs equally in the steel pipe circumferential direction. 各スパイラルリブの孔壁岩盤に対する食い込み深さを15〜50mmに設定する請求項1〜3の何れかに記載の鋼管杭の施工方法 The construction method of the steel pipe pile in any one of Claims 1-3 which sets the penetration depth with respect to the hole wall bedrock of each spiral rib to 15-50 mm. 掘削孔径を鋼管杭の鋼管外径+0〜10mmの範囲に設定する請求項1〜4の何れかに記載の鋼管杭の施工方法。 The construction method of the steel pipe pile in any one of Claims 1-4 which sets a drilling hole diameter in the range of the steel pipe outer diameter + 0-10mm of a steel pipe pile. 前記掘削孔を先端に掘削ビットを備えたダウンザホールハンマによって掘削すると共に、その掘削中に発生したスライムを除去し、形成した掘削孔に土砂類を投入し、この土砂類で埋まった掘削孔に前記鋼管杭の打撃圧入を行う請求項1〜5の何れかに記載の鋼管杭の施工方法。 The drilling hole is drilled by a down-the-hole hammer equipped with a drilling bit at the tip, slime generated during the drilling is removed, earth and sand is introduced into the formed drilling hole, and the drilling hole filled with the earth and sand is The construction method of the steel pipe pile in any one of Claims 1-5 which performs the impact press injection of a steel pipe pile.
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JP2018178382A (en) * 2017-04-04 2018-11-15 東亜建設工業株式会社 Method of driving pile to bedrock
CN109814617A (en) * 2018-12-25 2019-05-28 中铁十七局集团有限公司 A kind of pile sinking adaptive vibration frequency adjustment control method
CN111705854A (en) * 2020-07-24 2020-09-25 陈崇凯 Uplift construction method for foundation pile by large-diameter high-strength special type stabilized steel bar anchoring connection method
CN113774909A (en) * 2021-08-05 2021-12-10 深圳宏业基岩土科技股份有限公司 Hole forming construction method for double-layer steel casing in deep rockfill and sludge area

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JP6860895B2 (en) * 2019-03-26 2021-04-21 株式会社カヌカデザイン Retaining wall and its construction method
WO2022149421A1 (en) * 2021-01-06 2022-07-14 Jfeスチール株式会社 Piling, method for installing piling, structure, method for constructing structure, method for designing piling, and method for manufacturing piling

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2018178382A (en) * 2017-04-04 2018-11-15 東亜建設工業株式会社 Method of driving pile to bedrock
CN109814617A (en) * 2018-12-25 2019-05-28 中铁十七局集团有限公司 A kind of pile sinking adaptive vibration frequency adjustment control method
CN111705854A (en) * 2020-07-24 2020-09-25 陈崇凯 Uplift construction method for foundation pile by large-diameter high-strength special type stabilized steel bar anchoring connection method
CN113774909A (en) * 2021-08-05 2021-12-10 深圳宏业基岩土科技股份有限公司 Hole forming construction method for double-layer steel casing in deep rockfill and sludge area

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