JP2018059285A - Hollow tube for displacement-reduced type compacting sand-pile creation and compacting sand-pile creating method - Google Patents

Hollow tube for displacement-reduced type compacting sand-pile creation and compacting sand-pile creating method Download PDF

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JP2018059285A
JP2018059285A JP2016195693A JP2016195693A JP2018059285A JP 2018059285 A JP2018059285 A JP 2018059285A JP 2016195693 A JP2016195693 A JP 2016195693A JP 2016195693 A JP2016195693 A JP 2016195693A JP 2018059285 A JP2018059285 A JP 2018059285A
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hollow tube
sand pile
pile
ground
compacted sand
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JP6798845B2 (en
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磯谷　修二
Shuji Isotani
修二 磯谷
保明 根岸
Yasuaki Negishi
保明 根岸
浩史 矢部
Hiroshi Yabe
浩史 矢部
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Fudo Tetra Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a hollow tube for compacting sand-pile creation and a compacting sand-pile creating method, which solve a displacement problem adversely affecting existing structures and improve construction efficiency.SOLUTION: A method sequentially repeats, until reaching a ground surface, the following processes: a process to intrude a hollow tube 1, in which a stirring blade 12 is formed at a tip of the hollow tube 1 and an injecting outlet 13 for injecting jet water is formed around the hollow tube 1, into a predetermined depth by rotating the hollow tube 1 with injecting jet water through the injecting outlet 13 so as to loosen soil around the hollow tube 1; a process to discharge a sand-pile material 19 in the hollow tube 1 by pulling out the hollow tube 1 to a proper length; and a process to perform driving-back of the hollow tube 1, in order to create a compacting sand-pile 42 in a soft ground.SELECTED DRAWING: Figure 6

Description

本発明は、締固め時の拡径に伴い発生する変位を低減する締固め砂杭造成用中空管及びこれを用いた締固め砂杭造成方法に関するものである。   TECHNICAL FIELD The present invention relates to a compacted sand pile forming hollow pipe that reduces a displacement caused by diameter expansion during compaction and a compacted sand pile forming method using the same.

従来、図７及び図８に示すように、緩い砂質土地盤や高含水の粘性土地盤などの軟弱地盤Ａ中に締固め砂杭８２を打設することにより、地盤を改良する地盤改良砂杭造成工法がある（特開２００３−１４７７５６号公報）。この地盤改良砂杭造成工法は、例えば、中空管８０を所定の深度Ｈまで貫入した後、中空管８０を適宜の長さ引き抜く工程と中空管８０を再貫入する工程とを順次、地表に至るまで繰り返して、軟弱地盤Ａ中に締固め砂杭８２を造成する締固め砂杭造成工法である。   Conventionally, as shown in FIG. 7 and FIG. 8, the ground improved sand which improves the ground by placing a compacted sand pile 82 in a soft ground A such as a loose sandy ground or a highly watery viscous ground. There is a pile construction method (Japanese Patent Laid-Open No. 2003-147756). This ground improved sand pile construction method is, for example, sequentially inserting a hollow tube 80 to a predetermined depth H, then drawing the hollow tube 80 to an appropriate length and re-penetrating the hollow tube 80. This is a compacted sand pile construction method in which the compacted sand pile 82 is created in the soft ground A repeatedly until reaching the ground surface.

このような締固め砂杭造成工法においては、締固め時の拡径に伴い発生する変位（図８中、矢印Ｚ）が、地盤改良区域９５に近接する地上構造物９２、樹木などの自然物９３、地中構造物９４などの既設構造物９６に悪影響を与えることがある。このため、例えば、地盤改良区域９５と既設構造物９６との間に空掘りの孔や溝９１を設け、変位Ｚを吸収するようにしている（図８中、９１ａ）。   In such a compacted sand pile construction method, the displacement (arrow Z in FIG. 8) that occurs with the diameter expansion during compaction is a natural structure 93 such as a ground structure 92 and trees near the ground improvement area 95. The existing structure 96 such as the underground structure 94 may be adversely affected. For this reason, for example, a hollow hole or groove 91 is provided between the ground improvement area 95 and the existing structure 96 so as to absorb the displacement Z (91a in FIG. 8).

特開２００３−１４７７５６号公報JP 2003-147756 A 特開平９-１２５３５９号公報JP-A-9-125359

しかしながら、締固め砂杭造成工法の場合、変位低減対策の空掘りの孔や溝９１は、幅、深度及び長さにおいて所定の大きさと形状を必要とするため、地盤改良区域９５と既設構造物９６との間に対策用の区域を設ける必要がある。この場合、地盤改良区域９５の範囲が制限されることもある。また、空掘りの孔や溝９１は地盤改良区域９５に近接することから、地盤改良区域９５の改良効果が薄れるという問題もある。更に、締固め砂杭造成工法の他に、空掘りの孔や溝９１を付設するための別途の工程が必要となり、施工が煩雑となるとともに施工コストを上昇させてしまう。   However, in the case of the compacted sand pile construction method, since the holes and grooves 91 for the displacement reduction measures require a predetermined size and shape in width, depth and length, the ground improvement area 95 and the existing structure It is necessary to provide a countermeasure area between In this case, the range of the ground improvement area 95 may be limited. Further, since the hole or groove 91 in the digging is close to the ground improvement area 95, there is also a problem that the improvement effect of the ground improvement area 95 is diminished. Furthermore, in addition to the compacted sand pile construction method, a separate process for attaching the hollow holes and grooves 91 is required, which makes the construction complicated and increases the construction cost.

また、特開平９-１２５３５９号公報には、地盤改良を行う地盤の周辺に複数の掘削孔を設け、該掘削孔内部に液体を装填したゴムチューブ（緩衝体）を設置する工程と、地盤改良を行う地盤内に砂杭を振動させつつ構築する工程とを具備する地盤改良工法が開示されている。この地盤改良工法は、ＳＣＰ工法が用いられる場所と隣接地との間に緩衝体が設置された緩衝帯を設け、隣接地への振動、変位の伝達を抑制するものである。しかしながら、特開平９-１２５３５９号公報記載の工法によれば、前記変位低減対策の空掘りの孔や溝と同様に、地盤改良区域と既設構造物との間に緩衝帯用の区域を設ける必要があり、同様に、地盤改良区域の範囲が制限される。   Japanese Patent Laid-Open No. 9-125359 discloses a step of providing a plurality of excavation holes around the ground for ground improvement, and installing a rubber tube (buffer body) filled with liquid in the excavation hole, and ground improvement The ground improvement construction method which comprises the process of constructing a sand pile while vibrating in the ground which performs is disclosed. In this ground improvement method, a buffer band in which a buffer is installed is provided between a place where the SCP method is used and an adjacent site, and vibration and displacement are prevented from being transmitted to the adjacent site. However, according to the construction method described in Japanese Patent Laid-Open No. 9-125359, it is necessary to provide a buffer zone between the ground improvement area and the existing structure, as in the case of the hole or groove for the above-mentioned displacement reduction measures. Similarly, the scope of ground improvement areas is limited.

また、上記締固め砂杭造成工法以外の地盤改良砂杭造成工法としては、ケーシングチューブを全周回転させ、中掘掘削機にてケーシング孔内を掘削し、掘削完了後に砂を投入し、締固めて砂杭を造成する全旋回場所打ち砂杭造成工法も知られている。この工法によれば、オールケーシングのため高品質な場所打ち砂杭が造成できる。しかしながら、全旋回場所打ち砂杭造成工法の場合、施工効率が悪く、コスト高となる。   In addition, the ground improvement sand pile construction method other than the above compacted sand pile construction method is to rotate the casing tube all around, excavate the inside of the casing hole with a digging excavator, insert sand after excavation is completed, and tighten An all-swivel cast-in-place sand pile construction method that hardens and creates a sand pile is also known. According to this construction method, a high-quality cast-in-place sand pile can be created because of the all casing. However, in the case of the all-swivel cast-in-place sand pile construction method, construction efficiency is poor and the cost is high.

従って、本発明の目的は、地盤改良区域と既設構造物との間に空掘りの孔や溝などの緩衝帯を設けることなく、既存構造物に悪影響をもたらす変位の問題を解消すると共に、施工効率が良い締固め砂杭造成用中空管を提供することにあり、また、本発明の他の目的は、既存構造物に変位を与えることのない、施工効率に優れた締固め砂杭造成工法を提供することにある。   Accordingly, the object of the present invention is to eliminate the problem of displacement that adversely affects the existing structure without providing a buffer band such as a hole or groove for digging between the ground improvement area and the existing structure. Another object of the present invention is to provide a compacted sand pile with excellent construction efficiency that does not give displacement to existing structures. To provide a construction method.

すなわち、本発明は、上記従来の課題を解決したものであり、軟弱地盤中に締固め砂杭を造成する方法に使用される中空管であって、中空管本体の先端部に、攪拌翼と、中空管周りにジェット水を噴射する噴射口とをそれぞれ形成したものであることを特徴とする締固め砂杭造成用中空管を提供するものである。   That is, the present invention solves the above-mentioned conventional problems, and is a hollow tube used in a method for forming a compacted sand pile in soft ground. Provided is a compacted sand pile forming hollow tube characterized in that a wing and an injection port for injecting jet water around the hollow tube are respectively formed.

また、本発明は、該噴射口は、該攪拌翼に形成したものであることを特徴とする前記締固め砂杭造成用中空管を提供するものである。   The present invention also provides the above-mentioned compacted sand pile forming hollow tube, wherein the injection port is formed in the stirring blade.

また、本発明は、更に、掘削ビットを形成したものであることを特徴とする前記締固め砂杭造成用中空管を提供するものである。   The present invention further provides the above-mentioned compacted sand pile hollow tube, wherein a drill bit is formed.

また、本発明は、前記中空管を回転させつつ、該噴射口からジェット水を噴射し、中空管周りを緩ませ又は泥水化させながら所定の深度まで貫入する工程と、ジェット水の噴射を停止し、中空管を適宜の長さ引き抜き該中空管内の砂杭材料を排出する工程と該中空管を打ち戻しする工程とを順次、地表に至るまで繰り返して、軟弱地盤中に締固め砂杭を造成する工程とを行うことを特徴とする締固め砂杭造成方法を提供するものである。   The present invention also includes a step of injecting jet water from the injection port while rotating the hollow tube and penetrating to a predetermined depth while loosening or mudging the periphery of the hollow tube; The hollow pipe is pulled out to an appropriate length, the process of discharging the sand pile material in the hollow pipe and the process of returning the hollow pipe are sequentially repeated until reaching the ground surface and tightened in the soft ground. The present invention provides a compacted sand pile creation method characterized by performing a process of creating a compacted sand pile.

本発明によれば、締固め工程の前に、中空管周りを緩み状態又は泥状化状態とする工程を行う。このため、打ち戻し時の拡径圧力により、緩み状態又は泥状化した部分の土は地表に排出され、緩み状態又は泥状化した領域に、拡径された締固め砂杭が造成される。このため、地盤改良区域と既設構造物との間に緩衝帯を設けることなく、既存構造物に変位の伝達を大きく抑制することができる。   According to the present invention, before the compacting step, a step of making the periphery of the hollow tube into a loose state or a muddy state is performed. For this reason, the loosened or muddy part of the soil is discharged to the ground surface due to the expanded diameter pressure at the time of return, and the expanded sand compaction pile is created in the loosened or muddy area. . For this reason, it is possible to greatly suppress the transmission of displacement to the existing structure without providing a buffer band between the ground improvement area and the existing structure.

本発明の実施の形態における中空管を備える締固め砂杭造成装置の概略図である。It is the schematic of a compacting sand pile formation apparatus provided with the hollow tube in embodiment of this invention. 図１の締固め砂杭造成用中空管の先端部の拡大図である。It is an enlarged view of the front-end | tip part of the hollow pipe for compaction sand pile formation of FIG. 図２の側面図である。FIG. 3 is a side view of FIG. 2. 図２の平面図である。FIG. 3 is a plan view of FIG. 2. 本発明の実施の形態における締固め砂杭造成方法の貫入工程を説明する図である。It is a figure explaining the penetration process of the compacting sand pile creation method in embodiment of this invention. 図５の締固め砂杭造成方法の締固め工程を説明する図である。It is a figure explaining the compacting process of the compacted sand pile production method of FIG. 従来の締固め砂杭造成方法を説明する図である。It is a figure explaining the conventional compaction sand pile creation method. 従来の締固め砂杭造成方法を説明する他の図である。It is another figure explaining the conventional compacting sand pile creation method.

次に、本発明の実施の形態における締固め砂杭造成用中空管（以下、単に「中空管」とも言う。）を図１〜図４を参照して説明する。中空管１は、従来の締固め砂杭造成用中空管において、中空管本体１１の土壌貫入側の先端部に攪拌翼１２と、中空管周りにジェット水を噴射する噴射口１３とをそれぞれ形成したものである。中空管本体１１の上方部は、例えば、回動装置１５及び強制昇降装置１６に接続され、更に砂杭材料１９が投入されるホッパー１７を有している。   Next, a compacted sand pile forming hollow tube (hereinafter also simply referred to as “hollow tube”) according to an embodiment of the present invention will be described with reference to FIGS. The hollow tube 1 is a conventional compacted sand pile building hollow tube. The hollow tube body 11 has a stirring blade 12 at the tip of the soil intrusion side and an injection port 13 for injecting jet water around the hollow tube. Are formed respectively. The upper part of the hollow tube main body 11 has a hopper 17 that is connected to, for example, a rotating device 15 and a forced lifting device 16 and into which a sand pile material 19 is charged.

攪拌翼１２は、中空管１の貫入時、中空管周りを攪拌するものであれば、特に制限されない。攪拌翼１２は、本例では、左右一対の攪拌翼であり、所定の長さを有すると共に、貫入時の回転方向の面は斜め上方を向いた傾斜面となっている。これにより、中空管１は、地盤に貫入し易く、また、中空管周りの土壌の攪拌効率が向上する。攪拌翼１２は、単段又は多段であってもよい。また、攪拌翼１２の貫入時の回転方向の先端に、掘削ビットが形成されていてもよい。攪拌翼１２の全長（翼径）ｌ１は、締固め砂杭径ｌ２の１〜０．７倍程度であればよい。攪拌翼１２の全長（翼径）ｌ１が、締固め砂杭径ｌ２と同じであれば、中空管周りの緩み領域又は泥水領域に、締固め砂杭４２が形成されることになり、１００％置換となる。この場合、既存構造物への変位伝達はほぼゼロとすることができる。一方、攪拌翼１２の全長（翼径）ｌ１が、締固め砂杭径ｌ２の１未満、０．７以上であれば、中空管周りの緩み領域又は泥水領域周りの周辺地盤を少し押し広げて砂杭４２が形成されることになり、既存構造物への変位伝達は、ゼロとすることはできないものの、従来に比して抑制されたものとなる。本明細書中、「中空管周りの緩み状態」とは、砂質土地盤に対して使用される文言であり、「中空管周りの泥水化の状態」とは、粘性土地盤に対して使用される文言である。 The stirring blade 12 is not particularly limited as long as it stirs around the hollow tube 1 when the hollow tube 1 penetrates. In this example, the stirring blade 12 is a pair of left and right stirring blades, has a predetermined length, and the surface in the rotational direction at the time of penetration is an inclined surface facing obliquely upward. Thereby, the hollow tube 1 is easy to penetrate into the ground, and the stirring efficiency of the soil around the hollow tube is improved. The stirring blade 12 may be a single stage or multiple stages. Further, an excavation bit may be formed at the tip in the rotation direction when the stirring blade 12 penetrates. Total length (blade diameter) l 1 of the stirring blade 12 may be any 1 to 0.7 times the compaction Sunakui径l 2. If the total length (blade diameter) l 1 of the stirring blade 12 is the same as the compacted sand pile diameter l 2 , the compacted sand pile 42 will be formed in the loose region or the muddy water region around the hollow tube. , 100% substitution. In this case, the displacement transmission to the existing structure can be made almost zero. On the other hand, the total length (blade diameter) l 1 of the stirring blade 12 is less than one compaction Sunakui径l 2, if at least 0.7, the surrounding ground around the slack region or mud area around the hollow tube a little The sand piles 42 are formed by spreading, and the displacement transmission to the existing structure cannot be made zero, but is suppressed as compared with the conventional structure. In this specification, “the loose state around the hollow pipe” is a term used for sandy ground, and “the state of muddy water around the hollow pipe” is about the viscous ground. It is a wording used.

噴射口１３は、中空管周りにジェット水を噴射する開口であり、ジェット水噴射管２１の一方の先端である。ジェット水噴射管２１は、中空管１の中空部を通り、他方の先端は、地表のジェット水供給ポンプ（不図示）に接続する。噴射口１３の設置位置としては、中空管１又は攪拌翼１２である。噴射口１３からでるジェット水の噴射方向は、回転方向又は反回転方向のいずれでもよいが、回転方向に噴射することが、効率良く、均一な緩み状態又は泥水状態を得ることができる点で好ましい。本例では、噴射口１３は、攪拌翼１２の中空管１の貫入時の回転方向に位置する面に、回転方向で且つ略水平方向に向くように設置されている。すなわち、一対の攪拌翼１２に一対の噴射口１３が形成されている。これにより、中空管１の貫入時、中空管周りで且つ攪拌翼１２の前方の土砂に対して、ジェット水を噴射することができる。   The ejection port 13 is an opening that ejects jet water around the hollow tube, and is one end of the jet water ejection tube 21. The jet water jet pipe 21 passes through the hollow portion of the hollow pipe 1, and the other end is connected to a jet water supply pump (not shown) on the ground surface. The installation position of the injection port 13 is the hollow tube 1 or the stirring blade 12. The direction of jet water jetting from the jet port 13 may be either the rotational direction or the counter-rotating direction, but it is preferable that the jet water be jetted in the rotational direction in that a uniform loose state or muddy water state can be obtained efficiently. . In this example, the injection port 13 is installed on the surface located in the rotation direction when the hollow tube 1 of the stirring blade 12 penetrates so as to face the rotation direction and substantially in the horizontal direction. That is, a pair of injection ports 13 are formed in the pair of stirring blades 12. Thereby, when the hollow tube 1 penetrates, jet water can be jetted to the earth and sand around the hollow tube and in front of the stirring blade 12.

ジェット水としては、低圧水、中圧水又は高圧水などの水、高圧空気に水を同伴させたもの、及びこれらに流動化剤を配合したものが挙げられる。流動化剤は、砂質土系の軟弱地盤に使用することで、中空管周りの土壌を緩めることができる。流動化剤としては、吸水性ポリマー及び高分子凝集剤等が挙げられる。吸水性ポリマーとしては、アクリル酸ナトリウム重合体部分架橋物、アクリル酸ナトリウム重合体架橋物が挙げられる。高分子凝集剤としては、ノニオン系高分子凝集剤、アニオン系高分子凝集剤、カチオン系高分子凝集剤及び両性高分子凝集剤が挙げられる。流動化剤の配合割合は、適宜決定される。ジェット水の噴射は、攪拌翼１２内の土を緩める圧力であればよく、軟弱地盤の土質や攪拌翼１２の長さなど応じて適宜決定される。   Examples of jet water include water such as low-pressure water, medium-pressure water or high-pressure water, water in which high-pressure air is entrained, and water blended with these. The fluidizing agent can be used for sandy soil-based soft ground to loosen the soil around the hollow tube. Examples of the fluidizing agent include a water-absorbing polymer and a polymer flocculant. Examples of the water-absorbing polymer include sodium acrylate polymer partially crosslinked products and sodium acrylate polymer crosslinked products. Examples of the polymer flocculant include nonionic polymer flocculants, anionic polymer flocculants, cationic polymer flocculants, and amphoteric polymer flocculants. The blending ratio of the fluidizing agent is appropriately determined. The jet water jet may be a pressure that loosens the soil in the stirring blade 12 and is appropriately determined according to the soil quality of the soft ground, the length of the stirring blade 12, and the like.

掘削ビット１４は、任意の構成要素であり、中空管１の貫入時、中空管周りの土砂を掘削し、中空管１の貫入を円滑にする。掘削ビット１４は、本例では、中空管１の先端に、平面視で攪拌翼１２とは９０度位相がずれた位置において、一対のビットが形成されている。   The excavation bit 14 is an optional component, and excavates the earth and sand around the hollow tube 1 when the hollow tube 1 penetrates, thereby facilitating the penetration of the hollow tube 1. In this example, the excavation bit 14 is formed with a pair of bits at the tip of the hollow tube 1 at a position that is 90 degrees out of phase with the stirring blade 12 in plan view.

次に、中空管１０を用いた締固め砂杭造成方法について、図５及び図６を参照して説明する。先ず、中空管１を所定の位置にセットする。この際、中空管本体１１には砂杭材料１９を装填しておく。中空管１を正回転させつつ、噴射口１３からジェット水を噴射し、中空管周りを緩ませ又は泥水化させながら所定の深度Ｈまで貫入する工程を行う（図５（Ａ）〜（Ｃ））。なお、中空管１の貫入速度は、一定速度とすることが好ましい。中空管１の貫入工程において、中空管周りの土壌は、地表に排出され、中空管周りには、緩んだ状態又は泥水化状態３０が形成される。これにより、貫入時の変位はほぼゼロに近くなる。また、地表に排出される土壌３１は、中空管貫入体積と地表への排出土をほぼ同体積とすることが、貫入時に周辺への変位影響を低減させる点で好ましい。砂杭材料１９としては、従来の締固め砂杭造成工法と同様の公知のものが使用できる。中空管１の貫入工程においては、中空管１を地表から地中に貫入する過程で、一時、中空管１の貫入を停止してもよく、また、中空管１の引き上げをしてもよい。これにより、排土量を制御することができる。   Next, a method for forming a compacted sand pile using the hollow tube 10 will be described with reference to FIGS. First, the hollow tube 1 is set at a predetermined position. At this time, the sand pile material 19 is loaded in the hollow tube main body 11. While the hollow tube 1 is rotated in the forward direction, jet water is injected from the injection port 13 to perform a process of penetrating to a predetermined depth H while loosening or mudging around the hollow tube (FIGS. 5A to 5 ( C)). The penetration speed of the hollow tube 1 is preferably a constant speed. In the penetration process of the hollow tube 1, the soil around the hollow tube is discharged to the ground surface, and a loose state or a muddy water state 30 is formed around the hollow tube. Thereby, the displacement at the time of penetration becomes nearly zero. Moreover, it is preferable that the soil 31 discharged | emitted on the ground surface makes the hollow pipe penetration volume and the soil discharged | emitted to the ground surface substantially the same volume at the point which reduces the displacement effect to the periphery at the time of penetration. As the sand pile material 19, the well-known thing similar to the conventional compacted sand pile construction method can be used. In the penetration process of the hollow tube 1, the penetration of the hollow tube 1 may be temporarily stopped in the process of penetrating the hollow tube 1 from the ground surface into the ground. May be. Thereby, the amount of soil removal can be controlled.

本発明において、「緩ませる」とは、中空管周りの砂質土が、ジェット水又はジェット水に含まれる流動化剤により、土粒子間の摩擦が低減され、さらに攪拌翼の回転で均一になり、流動化状態となったものを言う。なお、泥水化は、中空管周りの土壌が粘性質の場合、同様に、均一に攪拌され流動化状態となったものを言う。流動化状態は、手で把持し、体感で判断することもできる。すなわち、緩ませた土壌を手で把持した場合、把持した手から押し出されるような流動性を持つものである。   In the present invention, “relaxing” means that sandy soil around the hollow tube is reduced in friction between soil particles by jet water or a fluidizing agent contained in jet water, and is further uniform by rotation of a stirring blade. And say what is fluidized. In the meantime, mudification means that when the soil around the hollow tube is viscous, it is uniformly stirred and fluidized. The fluidized state can also be judged by hand grasping and experiencing. That is, when the loosened soil is grasped by hand, it has fluidity so as to be pushed out from the grasped hand.

次に、ジェット水の噴射を停止し、中空管１を適宜の長さ引き抜き、中空管１内の砂杭材料１９を排出する工程と中空管１を打ち戻し（再貫入）する工程とを順次、地表に至るまで繰り返して、軟弱地盤中に締固め砂杭４２を造成する工程を行う（図６（Ａ）〜（Ｄ））。締固め砂杭造成工程は、従来の締固め砂杭造成工程と同様であり、打ち戻しは、管理計器により、抜けた砂杭材料の量に応じた長さを打ち戻せばよい。また、締固め砂杭造成工程においては、打ち戻し時の拡径圧力で、緩んだ部分あるいは泥状化した部分の土が地表に排出される。図６中、符号３２は、砂杭造成時の排出土である。   Next, the jet water is stopped, the hollow tube 1 is pulled out to an appropriate length, the sand pile material 19 in the hollow tube 1 is discharged, and the hollow tube 1 is driven back (re-penetrated). Are sequentially repeated until reaching the ground surface, and a step of creating a compacted sand pile 42 in the soft ground is performed (FIGS. 6A to 6D). The compacted sand pile creation process is the same as the conventional compacted sand pile creation process, and the strike back may be made back by a management instrument to a length corresponding to the amount of the sand pile material that has come off. Also, in the compacted sand pile creation process, the loosened or muddy soil is discharged to the ground surface by the expanding pressure at the time of backlash. In FIG. 6, the code | symbol 32 is discharge soil at the time of sand pile construction.

締固め砂杭造成工程において、造成時の排出土量３２と、締固め砂杭（拡径分）の土量とがほぼ同じであれば、造成時の変位は、ほぼゼロとすることができる。また、締固め砂杭（拡径分）の土量に対して、造成時の排出土量３２が少ない場合、造成時の変位は、ゼロとすることはできないものの、従来の締固め砂杭造成工程と比べて、低減することができる。   In the compacted sand pile creation process, if the discharged soil volume 32 at the time of creation and the soil volume of the compacted sand pile (expanded portion) are substantially the same, the displacement at the time of creation can be made substantially zero. . In addition, when the amount of discharged soil 32 at the time of creation is small compared to the amount of soil of the compacted sand pile (expanded portion), the displacement at the time of creation cannot be made zero, but the conventional compacted sand pile construction Compared with the process, it can be reduced.

本発明において、上記実施の形態に限定されず、種々の変形を採ることができる。例えば、噴射口１３は、本例では、２箇所に設置されているが、これに限定されず、一対の攪拌翼の一方に、１箇所設置してもよい。また、本発明において、「噴射口」は開口のみを言うのではなく、１端が開口の短管あるいはジェット水噴射管の先端部を含む意味である。   In the present invention, the present invention is not limited to the above embodiment, and various modifications can be made. For example, although the injection port 13 is installed in two places in this example, it is not limited to this, You may install one place in one of a pair of stirring blades. Further, in the present invention, “injection port” does not mean only an opening, but means that one end includes a short tube having an opening or a tip of a jet water injection tube.

本発明によれば、打ち戻し時の拡径圧力により、緩み状態の部分又は泥状化した部分の土は地表に排出され、緩み状態又は泥状化した領域に、拡径された締固め砂杭が造成される。このため、地盤改良区域と既設構造物との間に緩衝帯を設けることなく、既存構造物に変位の伝達を大きく抑制することができる。   According to the present invention, due to the diameter expansion pressure at the time of backlash, the soil in the loosened or muddy part is discharged to the ground surface, and the compacted sand that has been expanded in the loosened or muddy area A pile is created. For this reason, it is possible to greatly suppress the transmission of displacement to the existing structure without providing a buffer band between the ground improvement area and the existing structure.

１ 中空管
１０ 締固め砂杭造成装置
１２ 攪拌翼
１３ 噴射口
１４ 掘削ビット
１５ 回動装置
１６ 強制昇降装置
１７ ホッパー
１９ 砂杭材料
３０ 緩み状態又は泥水化状態の部分
３１ 貫入時の排出土
３２ 造成時の排出泥水 DESCRIPTION OF SYMBOLS 1 Hollow pipe 10 Compaction sand pile formation apparatus 12 Stirring blade 13 Injection port 14 Excavation bit 15 Rotating device 16 Forced raising / lowering device 17 Hopper 19 Sand pile material 30 Loose state or muddy water part 31 Discharge soil 32 at the time of penetration Muddy water discharged at the time of creation

Claims (4)

軟弱地盤中に締固め砂杭を造成する方法に使用される中空管であって、
中空管本体の先端部に、攪拌翼と、中空管周りにジェット水を噴射する噴射口とをそれぞれ形成したものであることを特徴とする締固め砂杭造成用中空管。 A hollow tube used in a method of creating a compacted sand pile in soft ground,
A hollow pipe for forming a compacted sand pile, wherein a stirrer blade and an injection port for injecting jet water around the hollow pipe are formed at the tip of the hollow pipe main body. 該噴射口は、該攪拌翼に形成したものであることを特徴とする請求項１記載の締固め砂杭造成用中空管。   The hollow pipe for forming a compacted sand pile according to claim 1, wherein the injection port is formed in the stirring blade. 更に、掘削ビットを形成したものであることを特徴とする請求項１又は２記載の締固め砂杭造成用中空管。   The hollow pipe for forming a compacted sand pile according to claim 1 or 2, further comprising a drill bit. 請求項１〜３記載の中空管を回転させつつ、該噴射口からジェット水を噴射し、中空管周りを緩ませ又は泥水化させながら所定の深度まで貫入する工程と、
ジェット水の噴射を停止し、中空管を適宜の長さ引き抜き該中空管内の砂杭材料を排出する工程と該中空管を打ち戻しする工程とを順次、地表に至るまで繰り返して、軟弱地盤中に締固め砂杭を造成する工程とを行うことを特徴とする締固め砂杭造成方法。

A step of injecting jet water from the injection port while rotating the hollow tube according to claims 1 to 3 and penetrating to a predetermined depth while loosening or mudging the periphery of the hollow tube;
The jet water is stopped, the hollow tube is pulled out to an appropriate length, and the sand pile material in the hollow tube is discharged and the hollow tube is returned back to the ground surface in order. A method for forming a compacted sand pile, comprising: forming a compacted sand pile in the ground.

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