JP2005256323A - Soil improvement method - Google Patents

Soil improvement method Download PDF

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JP2005256323A
JP2005256323A JP2004066562A JP2004066562A JP2005256323A JP 2005256323 A JP2005256323 A JP 2005256323A JP 2004066562 A JP2004066562 A JP 2004066562A JP 2004066562 A JP2004066562 A JP 2004066562A JP 2005256323 A JP2005256323 A JP 2005256323A
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ground
layer
improvement
hollow rod
granular
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JP4346078B2 (en
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Yukitake Shioi
幸武 塩井
Hisashi Fukada
久 深田
Makoto Otsuka
誠 大塚
Shuji Isotani
修二 磯谷
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Fudo Constr Co Ltd
不動建設株式会社
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil improvement method according to which a defective stratum in the ground can be selectively improved. <P>SOLUTION: The soil improvement method comprises the following steps. In the penetration step, a hollow rod 6 having an ejection port on a lower side thereof is made to penetrate from the ground surface into the ground, and the ejection port is arranged in an improvement objective stratum E2 present in the ground. In the creating step, a mixture containing particulate matter and liquid is ejected from the ejection port of the hollow rod 6, to thereby create a water permeable particulate stratum 9 in the improvement objective stratum E2. In the liquid discharging step, a vacuum suction pipe 10 is made to penetrate from the ground surface into the particulate stratum 9, and interstitial water etc. retained in the improvement objective stratum E2 are sucked and discharged via the particulate stratum 9 and the pipe 10 up to the ground surface by driving a vacuum pump 14 connected to the pipe 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、例えば、軟弱地盤中に含まれる水を真空吸引して排出することにより圧密沈下させる地盤改良工法に関し、特に改良対象の地層が地盤中に部分的に存在したり既存構造物の周囲地盤だけを選択的に改良できるようにした工法に関する。   The present invention relates to a ground improvement method, for example, in which the water contained in soft ground is consolidated by subsidence by vacuum suction and discharge, and in particular, the improvement target layer is partially present in the ground or around an existing structure. The present invention relates to a construction method that can selectively improve only the ground.

軟弱地盤の安定化のためのドレーン工法として、ペーパードレーン工法やサンドドレーン工法が知られている。このうち、ペーパドレーン工法は、特許文献1に記載されているように、マンドレル内に保持させた各種のドレーン材を土中に鉛直に貫入した後、土中に残置した状態でマンドレルを引き抜くもので、土中水を圧力差等によってドレーン材を介して地表側に上昇し排水することにより地盤を圧密させる。また、サンドドレーン工法も類似する原理であり、ケーシングを地盤に貫入し、引き抜くことでケーシングに入れた砂を砂柱として土中に残置するもので、土中水を砂粒子の隙間を伝って地表側に上昇し排出することにより地盤を圧密させる。   As a drain construction method for stabilizing soft ground, a paper drain construction method and a sand drain construction method are known. Among these, the paper drain method is one in which various drain materials held in the mandrel are vertically penetrated into the soil and then pulled out in the state of being left in the soil, as described in Patent Document 1. Then, the soil is consolidated by raising and draining the soil water to the surface side through the drain material due to a pressure difference or the like. The sand drain method is a similar principle, and the sand that has entered the casing is left in the soil as a sand column by penetrating the casing into the ground and pulling it out. The ground is consolidated by rising to the surface and discharging.

他の地盤改良工法としては、特許文献2に記載されているように、地盤中に打設された鉛直ドレーン材と、該鉛直ドレーン材の上部に接続されている水平ドレーンとを有し、気密シートで水平ドレーンや軟弱地盤の上面を覆うとともに、真空ポンプで負圧を作用させることにより軟弱地盤の土中水を各ドレーンを通じ地上側へ吸引し排出するものである。   As another ground improvement construction method, as described in Patent Document 2, it has a vertical drain material placed in the ground and a horizontal drain connected to the upper part of the vertical drain material, and is airtight. The upper surface of the horizontal drain or soft ground is covered with a sheet, and the soil water in the soft ground is sucked and discharged to the ground side through each drain by applying a negative pressure with a vacuum pump.

実公昭63−823号公報Japanese Utility Model Publication No. 63-823 特開2002−242170号公報JP 2002-242170 A

ところで、改良対象地盤には、埋立地盤と異なり、既存の地盤内が均一な土層ではなく、粘土層、シルト層、砂層、砂礫層等が鉛直方向に混在しており、例えば、砂−砂礫層の下層に含水分の多い粘土−シルト層が存在している場合もある。なお、通常は、各土層のうち、砂−砂礫層は透水層であり、水が自由に通過でき、加圧や脱水による体積収縮はほとんど生じない。これに対し、粘土−シルト層は不透水層であり、一般的に含水分が多く軟弱化し易く、加圧や脱水による体積収縮が顕著である。そして、粘土−シルト層が地盤表層に存在する場合には、該表層を良質土砂に比較的簡単に置き換えることができる。しかし、粘土−シルト層が下層に存在した場合には、掘削土量が膨大となり、工期及び経費も莫大となるため置き換え不可能なことも生じ容易には改良できない。このような問題は、例えば、地盤中の所定深さに存在する汚染層を改質処理するような場合も同様である。   By the way, unlike the landfill, the improvement target ground is not a uniform soil layer in the existing ground, but a clay layer, silt layer, sand layer, gravel layer, etc. are mixed in the vertical direction. There may be a clay-silt layer with a high water content below the layer. Normally, among each soil layer, the sand-gravel layer is a water-permeable layer, and water can freely pass through, and volume shrinkage due to pressurization and dehydration hardly occurs. On the other hand, the clay-silt layer is an impermeable layer and generally has a high water content and is easily softened. The volume shrinkage due to pressurization and dehydration is remarkable. And when a clay-silt layer exists in the ground surface layer, the surface layer can be replaced with high quality earth and sand relatively easily. However, when the clay-silt layer is present in the lower layer, the amount of excavated soil becomes enormous, and the construction period and cost also become enormous. Such a problem is the same when, for example, a modification process is performed on a contaminated layer existing at a predetermined depth in the ground.

一方、構造物との関係では、前記粘土−シルト層を下層に残したまま当該地盤の直上に大きな建物荷重が加わると、粘土−シルト層に加わる圧力により長年にわたって土中間隙水を放出しつつ圧密を生じ、地盤沈下現象を生ずる虞がある。このため、構造物の構築に先立ち、予め粘土−シルト層から水を放出させて地盤を圧密し、安定化させておく必要がある。しかし、圧密による地盤改良方法として、前述したドレーン工法を適用した場合には、透水層である砂−砂礫層からも吸水するため、恰も地下水を汲み上げるような作業を行うと同様に、作業そのものが大がかりとなる割には無駄が多く、作業能率が悪い。   On the other hand, in relation to the structure, when a large building load is applied directly above the ground with the clay-silt layer remaining in the lower layer, the pressure applied to the clay-silt layer releases the pore water in the soil for many years. Consolidation may occur, causing ground subsidence. For this reason, prior to the construction of the structure, it is necessary to discharge the water from the clay-silt layer in advance to consolidate and stabilize the ground. However, when the drain method described above is applied as a ground improvement method by consolidation, water is also absorbed from the sand-gravel layer, which is a permeable layer, so that the work itself is similar to pumping up groundwater. Although it is a large scale, it is wasteful and work efficiency is poor.

本発明は以上のような課題を解決することを目的としている。具体的には、地盤中の不良な地層(粘土−シルト層や汚染層、つまり改良対象層)だけを選択的に改良して経費低減を実現することと、例えば耐震改修される既存構造物周囲の地盤も選択的に改良して耐震性を経費を抑えてより向上することにある。   An object of the present invention is to solve the above problems. Specifically, only the poor formations in the ground (clay-silt layer or contaminated layer, that is, the improvement target layer) are selectively improved to reduce costs and, for example, around existing structures that are earthquake-proofed The ground is to improve the seismic performance further by reducing costs by selectively improving the ground.

本発明者らは上記目的を達成するため次のような地盤改良工法を開発した。すなわち、
・請求項1の発明は、噴射口を有した中空ロッドを、地表側より地盤中に貫入して、前記噴射口を当該地盤中に存在する改良対象層内に配置する貫入工程と、粒状物と液体との混合物を前記中空ロッドの噴射口から噴出することにより、前記改良対象層内に透水性の粒状層を造成する造成工程と、地表側より真空吸引用パイプを前記粉状層まで貫入するとともに、前記パイプに接続された真空ポンプの駆動により前記改良対象層内に保留されている間隙水等を前記粒状層及びパイプを通じて地表側に吸引して排出する排液工程とを経ることを特徴としている。
・請求項2の発明は、請求項1に比べて、前記排液工程で使用する真空吸引用パイプを造成工程で使用した中空ロッドで兼用するようにした点で異なっている。
In order to achieve the above object, the present inventors have developed the following ground improvement method. That is,
The invention according to claim 1 is a penetration step in which a hollow rod having an injection port is inserted into the ground from the ground surface side, and the injection port is disposed in an improvement target layer existing in the ground, and a granular material A process of forming a water-permeable granular layer in the improvement target layer by injecting a mixture of liquid and liquid from the injection port of the hollow rod, and a vacuum suction pipe penetrating from the ground surface side to the powder layer And a drainage step of sucking and discharging pore water or the like retained in the improvement target layer to the surface side through the granular layer and the pipe by driving a vacuum pump connected to the pipe. It is a feature.
The invention of claim 2 is different from the invention of claim 1 in that the vacuum suction pipe used in the draining process is also used as the hollow rod used in the creation process.

以上の発明工夫点は、特に、改良対象層が地盤中に部分的に存在するような場合、該改良対象層内に中空ロッドを貫入し、該中空ロッドの噴射口より粒状物と液体との混合物を噴出して透水性の粒状層を形成した後、該粒状層に吸引用パイプを貫入したり前記中空ロッドを利用し、それらパイプや中空ロッドに真空ポンプを接続して、改良対象層内に保留されている間隙水等を粒状層からパイプや中空ロッドを通じて地表側に吸引して排出するようにしたものである。なお、本発明において、「粒状物」は、砂又はそれに類似するものであり、透水性がありかつ噴射し易い粒状のものであればよい。「液体」は、水だけに限られず、例えば水に薬剤等を入れた液でもよい。「混合物」は、粒状物及び液体を必須としているが、他にエア等の気体を含んでいても差し支えない。その一例としては、(砂等の粒状物+水等の液体)を高圧エアに乗せて噴射口より噴出するような態様である。「改良対象層」は、地盤中に存在する不良な地層であり、通常は粘土−シルト層等の不透水層あるいは汚染層の何れかである。   The above invention contrivance points are that, particularly when the improvement target layer partially exists in the ground, a hollow rod is inserted into the improvement target layer, and the particulate matter and liquid are injected from the injection port of the hollow rod. After the mixture is ejected to form a water-permeable granular layer, a suction pipe is inserted into the granular layer, or the hollow rod is used, and a vacuum pump is connected to the pipe or the hollow rod, so The pore water and the like retained in the tank are sucked and discharged from the granular layer to the ground surface through a pipe or a hollow rod. In the present invention, the “granular material” may be sand or a similar material as long as it has water permeability and is easy to spray. “Liquid” is not limited to water, but may be, for example, a liquid in which a drug or the like is added to water. The “mixture” includes a particulate matter and a liquid, but may contain other gas such as air. As an example, it is an aspect in which (particulate matter such as sand + liquid such as water) is put on high-pressure air and ejected from the ejection port. The “improvement target layer” is a defective base layer existing in the ground, and is usually either an impermeable layer such as a clay-silt layer or a contaminated layer.

・請求項3の発明は、前記中空ロッドを前記造成工程で回転しながら前記混合物を噴射する構成である。
・請求項4の発明は、請求項1又は2の地盤改良工法において、前記改良対象層が地盤中の複数の深度位置に存在している場合、前記造成工程では前記中空ロッドによりそれぞれの改良対象層内に前記粒状物を順に形成し、前記排水工程では前記各改良対象層の位置に対応した複数の吸引孔を有した吸引用パイプ又は中空ロッドを用いる構成である。
・請求項5の発明は、請求項1又は2の地盤改良工法において、前記貫入工程を所定間隔毎に行うことにより、前記造成工程で形成される粒状層同士を横方向に接続して一体ものにする構成である。
・請求項6の発明は、請求項1又は2の地盤改良工法において、前記中空ロッドが既存構造物の基礎直下の地盤と周囲地盤とを仕切るための矢板に取り付けられ、該矢板の地盤内への建て込みと同時に前記中空ロッドを地盤内に貫入するとともに、前記噴射口を通じて周囲地盤内に粒状物と液体との混合物を噴出させることにより、当該矢板の側近傍に前記粒状層を造成する構成である。
-Invention of Claim 3 is a structure which injects the said mixture, rotating the said hollow rod at the said formation process.
-The invention of claim 4 is the ground improvement construction method of claim 1 or 2, wherein when the improvement target layer is present at a plurality of depth positions in the ground, in the creation step, each improvement object is provided by the hollow rod. The granular material is sequentially formed in a layer, and in the draining step, a suction pipe or a hollow rod having a plurality of suction holes corresponding to the positions of the respective improvement target layers is used.
-The invention of claim 5 is the ground improvement method of claim 1 or 2, wherein the penetration step is performed at predetermined intervals, thereby connecting the granular layers formed in the creation step in a lateral direction. It is the composition to make.
-The invention of claim 6 is the ground improvement method of claim 1 or 2, wherein the hollow rod is attached to a sheet pile for partitioning the ground immediately below the foundation of the existing structure and the surrounding ground, and into the ground of the sheet pile The hollow rod penetrates into the ground simultaneously with the erection of the structure, and the granular layer is formed in the vicinity of the sheet pile side by ejecting a mixture of the granular material and the liquid into the surrounding ground through the injection port. It is.

上記した本発明の地盤改良工法にあっては次のような効果を有している。
・請求項1と2の発明では、例えば、改良対象層である不透水層(粘土−シルト層等)内に保留されている間隙水を効率よく排出でき、圧密のための従来ドレーン工法に比べて安価かつ効率よく実施できる。また、地盤中の汚染層を改質処理するような場合に部分処理の採用により有用なものとなる。
・請求項3の発明では、目的の透水性粒状層を中空ロッドの回転に伴って効率よく形成できる。
・請求項4の発明では、不透水層(粘土−シルト層等)が透水層(砂−砂礫層等)と互層をなして縦方向に複数存在している地層においても、経費を抑えて効率よく実施できる。
・請求項5の発明では、不透水層(粘土−シルト層等)が面的に広い領域に存在する場合、広範な領域からの間隙水を効率よく吸引し除去できる。
・請求項6の発明では、例えば、既存建物の基礎直下の耐震改修を行う場合、周囲地盤の地盤改良も付随して行うことができるため、耐震改修効果を向上できる。
The above ground improvement method of the present invention has the following effects.
In the inventions of claims 1 and 2, for example, pore water retained in an impermeable layer (clay-silt layer, etc.) that is an improvement target layer can be efficiently discharged, compared with a conventional drain method for consolidation. Can be implemented inexpensively and efficiently. Moreover, it becomes useful by adopting a partial treatment when a contaminated layer in the ground is modified.
-In invention of Claim 3, the target water-permeable granular layer can be formed efficiently with rotation of a hollow rod.
-In the invention of claim 4, even in a stratum in which a plurality of impermeable layers (clay-silt layer, etc.) and a water permeable layer (sand-sand gravel layer, etc.) exist in the vertical direction, the cost is reduced and efficiency is improved. Can be implemented well.
-In invention of Claim 5, when a water-impermeable layer (clay-silt layer etc.) exists in a surface wide area | region, the pore water from a wide area | region can be attracted | sucked and removed efficiently.
-In invention of Claim 6, for example, when performing earthquake-proof repair just under the foundation of an existing building, since the ground improvement of a surrounding ground can also be performed incidentally, the earthquake-proof repair effect can be improved.

以下、本発明の実施の形態を添付図面を参照して説明する。この説明では、図1〜図4に示した第1実施例と、図5〜図6に示した第2実施例とにより本発明の構成及びその考え方を明らかにする。   Embodiments of the present invention will be described below with reference to the accompanying drawings. In this description, the configuration of the present invention and its concept are clarified by the first embodiment shown in FIGS. 1 to 4 and the second embodiment shown in FIGS.

(第1実施例)図1(a)〜(c)、図2(a)〜(c)は施工の工程手順を、図3,4は土中に形成された粒状層としてのサンドマット層の形状例を示している。まず、図1(a)において、この施工対象地盤は、事前のボーリング等による土質調査により、表層が砂−砂礫層E1、その下部側の層が粘土−シルト層E2、その下部側の層が砂−砂礫層E1を挟んで粘土−シルト層E2、最深部が砂−砂礫層E1となっている互層構造であることが判明している。つまり、この例では、これら複数の地層のうち、2層目と4層目の各粘土−シルト層E2が改良対象層となる。但し、これは、あくまでも一例に過ぎず、これ以外に例えば2層目と4層目の粘土−シルト層E2が連続して厚くなっている場合等でも差し支えない。なお、各図は理解し易くするため模式化している。砂−砂礫層E1と粘土−シルト層E2とは区別容易になるよう作図した。 (First Embodiment) FIGS. 1 (a) to 1 (c) and FIGS. 2 (a) to 2 (c) show construction process procedures, and FIGS. 3 and 4 show sand mat layers as granular layers formed in the soil. An example of the shape is shown. First, in FIG. 1 (a), this construction target ground has a sand-gravel layer E1 as a surface layer, a clay-silt layer E2 as a lower layer, and a lower layer as a lower layer by a preliminary soil survey by boring or the like. It has been found that the clay-silt layer E2 is sandwiched between the sand-sand gravel layer E1 and the deepest part is a sand-gravel layer E1. That is, in this example, among the plurality of formations, the second and fourth clay-silt layers E2 are the improvement target layers. However, this is merely an example, and there may be other cases where, for example, the second and fourth clay-silt layers E2 are continuously thick. Each figure is schematically shown for easy understanding. The sand-gravel layer E1 and the clay-silt layer E2 were drawn so as to be easily distinguished.

施工に際しては、例えば、地表部GL側にあってアースドリルマシン1、砂−水の混合プラント2、及び混合プラント2に接続して砂−水の混合物を高圧輸送する高圧ポンプ3等が最初に用意される。アースドリルマシン1は、例えば、キャタピラ走行式のベースマシン4及び該ベースマシン4の先端に支持された鉛直ガイド5を備え、鉛直ガイド5を起立した状態でこれに沿って造成用中空ロッド6を地盤中に貫入するものである。この場合、中空ロッド6は、通常、鉛直ガイド5に沿って昇降される回転機構により回転されながら地盤中に貫入されたり引き抜かれる。また、中空ロッド6は、下側外周ないしは先端外周に噴射口を有し、又、上端側がスイベルジョイント7を介して前記ポンプ3の吐出端に接続されているフレキシブルなホース8に接続されている。   At the time of construction, for example, the earth drill machine 1, the sand-water mixing plant 2, and the high-pressure pump 3 that transports the sand-water mixture at a high pressure by connecting to the ground drill machine 1, the mixing plant 2, etc. Prepared. The earth drill machine 1 includes, for example, a caterpillar traveling type base machine 4 and a vertical guide 5 supported at the tip of the base machine 4, and the forming hollow rod 6 is formed along the vertical guide 5 in a standing state. It penetrates into the ground. In this case, the hollow rod 6 is usually inserted into or extracted from the ground while being rotated by a rotating mechanism that is moved up and down along the vertical guide 5. The hollow rod 6 has an injection port on the lower outer periphery or the outer periphery of the tip, and the upper end side is connected to a flexible hose 8 connected to the discharge end of the pump 3 via a swivel joint 7. .

なお、この例は、混合プラント2で作られた砂と水との混合物を高圧ポンプ3及びホース8を介して中空ロッド6へ圧送し噴射口(噴射ノズルを含む。以下同じ)より噴出する構成であるが、本発明はこれに限られない。他の例を挙げると、砂と水との混合物を高圧エアに乗せて中空ロッド6へ圧送し噴射口より噴出する構成、砂−水の混合物と高圧エアとをそれぞれ独立して中空ロッド6の下側へ圧送し、噴射口を構成している混合式噴射ノズルを介して砂−水の混合物を高圧エアに乗せて噴出する構成などであってもよい。   In this example, the mixture of sand and water produced in the mixing plant 2 is pumped to the hollow rod 6 via the high-pressure pump 3 and the hose 8 and ejected from the injection port (including the injection nozzle, the same applies hereinafter). However, the present invention is not limited to this. As another example, a structure in which a mixture of sand and water is put on high-pressure air and pumped to the hollow rod 6 and ejected from the injection port, and the sand-water mixture and high-pressure air are independently formed in the hollow rod 6. A configuration may be employed in which a sand-water mixture is ejected by being put on high-pressure air via a mixing-type injection nozzle that constitutes an injection port by pumping downward.

そして、本発明の地盤改良工法は次のような工程を経る。まず、中空ロッド6が図1(a)に示すように鉛直ガイド5に沿って地盤中へ貫入される。この貫入は、中空ロッド6が図1(b)に示すように、下端側が2層目の粘土−シルト層E2の内部に到達した時点で、一旦停止される(貫入工程)。   And the ground improvement construction method of this invention goes through the following processes. First, the hollow rod 6 is penetrated into the ground along the vertical guide 5 as shown in FIG. This penetration is temporarily stopped when the hollow rod 6 reaches the inside of the second clay-silt layer E2 as shown in FIG. 1B (penetration process).

次いで、中空ロッド6が停止位置から僅かに上下に往復(当該粘土−シルト層E2の厚さ分だけ上下に往復)され、かつ回転されつつ、地表部側で高圧ポンプ3を駆動させることにより、砂−水の混合物が噴射口からジェット噴射され、中空ロッド6の周囲に所定厚みの扁平ドーナツ形のサンドマット層9を造成する(造成工程)。なお、造成されるサンドマット層9の直径は、例えば、高圧ポンプ3の出力と事前調査で判明した粘土−シルト層E2の軟弱度合いに応じて容易に予測できる大きさであり、厚み寸法が中空ロッド6の上下の往復量によって確定される。また、中空ロッド6の停止位置は、例えば、事前調査で得られている各土層の深さや厚さ等を考慮し、又、不図示の深度センサ等の検出値を基にして制御される。   Next, the hollow rod 6 is reciprocated up and down slightly from the stop position (reciprocated up and down by the thickness of the clay-silt layer E2), and while rotating, the high pressure pump 3 is driven on the ground surface side, A sand-water mixture is jetted from an injection port, and a flat donut-shaped sand mat layer 9 having a predetermined thickness is formed around the hollow rod 6 (formation step). The diameter of the sand mat layer 9 to be formed is, for example, a size that can be easily predicted according to the output of the high-pressure pump 3 and the degree of softness of the clay-silt layer E2 that has been clarified in the preliminary survey, and the thickness dimension is hollow. It is determined by the amount of reciprocation of the rod 6 up and down. In addition, the stop position of the hollow rod 6 is controlled based on the detection value of a depth sensor or the like (not shown) in consideration of, for example, the depth and thickness of each soil layer obtained in the preliminary survey. .

2層目の施工後は、高圧ポンプ3の稼働を一旦停止し、さらに中空ロッド6の貫入深度を深め、図1(c)に示すように4層目の粘土−シルト層E2に到達した時点で2層目と同様の作業、つまり貫入工程と造成工程を実施してサンドマット層9を形成する。なお、施工手順としては、下側の4層目から先にサンドマット層9を形成し、中空ロッド6を引き上げつつ上側の2層目にサンドマット層9を形成するようにしてもよい。   After the construction of the second layer, the operation of the high-pressure pump 3 is temporarily stopped, the penetration depth of the hollow rod 6 is further deepened, and when the fourth layer of clay-silt layer E2 is reached as shown in FIG. Thus, the sand mat layer 9 is formed by performing the same operation as that of the second layer, that is, the penetration step and the creation step. As a construction procedure, the sand mat layer 9 may be formed first from the lower fourth layer, and the sand mat layer 9 may be formed as the second upper layer while pulling up the hollow rod 6.

また、実際には、以上の貫入工程と造成工程を予測されたサンドマット層9の直径に応じて間隔をあけて繰り返すことで、図2に示すごとく各層E2内に造成される単位サンドマット層9同士を横方向に連続一体化させる。この一体化では、図3に示すごとく、単位サンドマット層9を隙間なく連続させた形状でもよいし、図4に示すごとく、間隔をあけて格子状に連続させてもよい。要は、施工対象の土層内全域にわたって全面連続または格子状に連続させたサンドマット層9を形成したり、さらに例えば中空パイプ6を回転しながら引き抜くことで螺旋状の粒状層を形成してもよく、改良目的や必要度に応じて最適な形状に設定される。   In practice, the unit sand mat layer formed in each layer E2 as shown in FIG. 2 by repeating the above penetration process and creation process at intervals according to the predicted diameter of the sand mat layer 9. 9 are continuously integrated in the horizontal direction. In this integration, as shown in FIG. 3, the unit sand mat layer 9 may have a continuous shape without a gap, or as shown in FIG. In short, the entire surface of the soil layer to be constructed is formed as a sand mat layer 9 continuously or in a lattice pattern, or a spiral granular layer is formed by pulling out the hollow pipe 6 while rotating, for example. The shape is optimally set according to the purpose of improvement and necessity.

中空ロッド6は、サンドマット層9を形成した後に地盤中より引き抜かれる。その後は、図2(a)に示すように、真空吸引用のパイプ10が同一のアースドリルマシン1又専用のアースドリルマシンを使ってサンドマット層9に貫入される。この場合、パイプ10は、サンドマット層9の中心部(図3,図4参照)に貫入することが好ましい。このパイプ10は、先端側周囲及び途中周囲の複数箇所に図2(a)の一部に拡大して示すような真空吸引孔12が形成されている。各吸引孔12は、2層目の粘土−シルト層E2と4層目の粘土−シルト層E2との間隔を保っている。また、構造的には、吸引孔12の外周を金網11で覆うことにより、砂の侵入を防止しつつ粘土−シルト層E2内の間隙水と空気だけを専ら吸引できるよう工夫されているが、金網11に代えてパイプ10内に砂礫等の濾過材を詰めるようにしてもよい。そして、図2(b)に示すようにアースドリルマシン1を撤去し、パイプ10の上端がホース等を介して真空吸引ポンプ14に接続され、該ポンプ14の吐出側がホース等を介して適宜箇所に設けられた地表側の側溝15等に接続される。ポンプ14が駆動されると、土中間隙水はサンドマット層9からパイプ10内を伝ってポンプ14に真空吸引され、側溝15に放流される(排液工程)。なお、図では1本のパイプ10しか示していないが、サンドマット層9の大きさに応じて所定間隔で複数本のパイプ10を配置し、各パイプ10をそれぞれポンプ14に接続して真空吸引することもある。   The hollow rod 6 is pulled out from the ground after the sand mat layer 9 is formed. Thereafter, as shown in FIG. 2A, the vacuum suction pipe 10 is inserted into the sand mat layer 9 using the same earth drill machine 1 or a dedicated earth drill machine. In this case, it is preferable that the pipe 10 penetrates into the center portion of the sand mat layer 9 (see FIGS. 3 and 4). This pipe 10 is formed with vacuum suction holes 12 at a plurality of locations around the tip side and in the middle of the pipe 10 as shown in an enlarged manner in a part of FIG. Each suction hole 12 maintains a distance between the second clay-silt layer E2 and the fourth clay-silt layer E2. In addition, structurally, the outer periphery of the suction hole 12 is covered with a wire mesh 11 so that only the interstitial water and air in the clay-silt layer E2 can be sucked while preventing the intrusion of sand. Instead of the wire mesh 11, a filter medium such as gravel may be packed in the pipe 10. Then, as shown in FIG. 2 (b), the earth drill machine 1 is removed, the upper end of the pipe 10 is connected to the vacuum suction pump 14 via a hose or the like, and the discharge side of the pump 14 is appropriately placed via the hose or the like. Is connected to a gutter 15 or the like on the surface side provided on the surface. When the pump 14 is driven, the interstitial water in the soil is sucked by the pump 14 from the sand mat layer 9 through the pipe 10 and discharged into the side groove 15 (drainage process). Although only one pipe 10 is shown in the figure, a plurality of pipes 10 are arranged at predetermined intervals according to the size of the sand mat layer 9, and each pipe 10 is connected to a pump 14 for vacuum suction. Sometimes.

以上のようにして、本発明の地盤改良工法では、ポンプ14の連続運転により、粘土−シルト層E2内の間隙水があらかた絞り出されてしまうと、吸引抵抗が急速に高くなり、排水量も減少する。また、空隙の低下による体積収縮に伴い上層地盤の土圧が各粘土−シルト層E2に加わり、これにより生ずる圧密沈下によって図2(c)に模式化したように、地表部GLの地盤が所定高さhまで沈下する。このため、実際の施工では以上の現象を見極めることで地盤改良の終了等が判定される。なお、以上の施工後は、パイプ10を含む機材撤去の後、良質土砂による地表部の覆土、整地等の二次施工が必要に応じて行われる。   As described above, in the ground improvement method of the present invention, if the pore water in the clay-silt layer E2 is squeezed out by continuous operation of the pump 14, the suction resistance increases rapidly and the amount of drainage also decreases. To do. In addition, earth pressure of the upper ground is applied to each clay-silt layer E2 as the volume shrinks due to the decrease in the gap, and the ground of the ground surface portion GL is predetermined as schematically shown in FIG. Sink to height h. For this reason, in actual construction, the end of ground improvement is determined by determining the above phenomenon. In addition, after the above construction, after the equipment including the pipe 10 is removed, secondary construction such as soil covering of the surface part with high quality earth and sand, leveling, etc. is performed as necessary.

以上の実施例では、土中間隙水の除去とこれに伴う圧密沈下作用による地盤改良に適用した場合を示したが、例えば、不透水層中に有害金属イオンなどの有害物質が水に溶けた状態で混在している汚染土壌の場合にも以上の工法を同様の手順で適用可能である。この場合、排液工程では、吸引される液体を処理設備で無害化処理した後に放流することになる。また、このような汚染層では、例えば、サンドマット層9の一方側から水や薬剤を供給しつつ、他方側でパイプ10及び真空ポンプ14を介して真空吸引することにより、有害物質を効率よく希釈したり回収することが好ましい。汚染度が基準値を下回った後は、粘土−シルト層E2と同じく真空吸引のみを行うようにする。   In the above embodiment, the case of applying to ground improvement by removing pore water in the soil and the accompanying consolidation settlement action was shown. For example, harmful substances such as harmful metal ions were dissolved in water in the impermeable layer. In the case of contaminated soil mixed in the state, the above construction method can be applied in the same procedure. In this case, in the draining step, the sucked liquid is discharged after detoxifying the processing equipment. In such a contaminated layer, for example, water and chemicals are supplied from one side of the sand mat layer 9 and vacuum suction is performed on the other side via the pipe 10 and the vacuum pump 14 to efficiently remove harmful substances. It is preferable to dilute or recover. After the contamination level falls below the reference value, only vacuum suction is performed as in the clay-silt layer E2.

(第2実施例)次に本発明工法を構造物の耐震補強工法に適用した場合の一例を図5(a),(b)及び図6を参照し説明する。図5において、既設構造物は橋脚20であって、橋脚20のフーチング20aは下端又は先端が支持地盤(図示省略)にまで到達するよう設けられた複数の杭21により支持されている。 (Second Embodiment) Next, an example in which the method of the present invention is applied to the seismic reinforcement method for a structure will be described with reference to FIGS. 5 (a), 5 (b) and FIG. In FIG. 5, the existing structure is a pier 20, and the footing 20 a of the pier 20 is supported by a plurality of piles 21 provided so that the lower end or the tip reaches a support ground (not shown).

以上の既設構造物において、例えば、前記杭21が上部荷重、すなわち橋脚20及び図示しない橋桁などの荷重を受け、その過荷重により破損の虞があると判定されたり、地震による水平力が杭21に作用して破損する虞があると判定されときに、次のような耐震補強が施される。   In the above existing structure, for example, the pile 21 receives an upper load, that is, a load such as a bridge pier 20 and a bridge girder (not shown), and it is determined that there is a risk of breakage due to the overload. The following seismic reinforcement is applied when it is determined that there is a risk of damage due to the action.

この施工の手順は、まず、図5(a)及び図6に示すように、フーチング20aの周囲に鋼矢板22を建て込み用重機23を用いて所定深度まで順に建て込み、建て込まれた多数の鋼矢板22によりフーチング20aを周囲地盤から隔離する。その後は、図5(b)に示すように、フーチング20aの下部に斜め側方からセメントミルクなどの薬液を注入し、混合攪拌処理により固化体24を造成する。次に、フーチング20aの側面と鋼矢板22との間を掘削し、この間に鉄筋コンクリートを打設して増設部25を造成した後、フーチング20aの上部を土砂により埋め戻すことにより耐震補強工事を完成する。   As shown in FIGS. 5 (a) and 6, the construction procedure is as follows. A steel sheet pile 22 is built around a footing 20a in order to a predetermined depth using a heavy machine 23, and a large number of built The steel sheet pile 22 separates the footing 20a from the surrounding ground. Thereafter, as shown in FIG. 5 (b), a chemical solution such as cement milk is poured into the lower portion of the footing 20a from an oblique side, and the solidified body 24 is formed by a mixing and stirring process. Next, after excavating between the side surface of the footing 20a and the steel sheet pile 22, reinforced concrete is placed between them to create the expansion part 25, and then the upper part of the footing 20a is backfilled with earth and sand to complete the seismic reinforcement work. To do.

本発明工法では、以上の施工に加え、各鋼矢板22の外側面に下端を閉じた中空ロッド26を溶接などにより鉛直に固定しておく。該中空ロッド26は、鋼矢板22の上下寸法とほぼ同じか、若干長く設定され、砂−水の混合物の噴射と真空吸引の双方を兼用するものである。構造は、図6の一部に拡大して示すように、ロッド下側外周の一箇所に砂の放出と真空吸引を兼用する孔26aが開口されている。   In the construction method of the present invention, in addition to the above construction, a hollow rod 26 having its lower end closed on the outer surface of each steel sheet pile 22 is fixed vertically by welding or the like. The hollow rod 26 is set to be approximately the same as or slightly longer than the vertical dimension of the steel sheet pile 22, and serves both for jetting the sand-water mixture and for vacuum suction. As shown in an enlarged view of a part of FIG. 6, the structure has a hole 26a that is used for both sand discharge and vacuum suction at one location on the outer periphery of the lower side of the rod.

そして、鋼矢板22の建て込みに際しては、図5(a)に示すように、中空ロッド26の上端を予め上述した第1実施例と同様に高圧ポンプ3を介して砂−水の混合プラントに接続しておき、鋼矢板22の建て込み作業と同時に中空ロッド26の孔26aから土中に向けて砂−水の混合物を連続して噴射する。そして、これを繰り返すことにより、図6に示すように、各鋼矢板22の周囲に複数のサンドドレーン層28を放射状に形成する。   When the steel sheet pile 22 is installed, as shown in FIG. 5 (a), the upper end of the hollow rod 26 is put into a sand-water mixing plant via the high-pressure pump 3 in the same manner as in the first embodiment described above. The sand-water mixture is continuously sprayed from the hole 26a of the hollow rod 26 into the soil at the same time as the steel sheet pile 22 is built. By repeating this, a plurality of sand drain layers 28 are formed radially around each steel sheet pile 22 as shown in FIG.

その後は、フーチング20aの下部及び側面の耐震補強工事完了後にロッド26の上端を、真空吸引ポンプ14に接続し、かつ、ポンプ14の吐出端側をホース等を介して側溝15に接続しておき、ポンプ14を駆動すると、鋼矢板周囲の土中間隙水が真空吸引されて上昇され、側溝14側に順次排出され、周囲地盤が圧密沈下して地盤改良される。なお、施工最終時には地表側の必要部が良質土砂により埋め戻されることもある。   After that, after the seismic reinforcement work for the lower and side surfaces of the footing 20a is completed, the upper end of the rod 26 is connected to the vacuum suction pump 14, and the discharge end side of the pump 14 is connected to the side groove 15 via a hose or the like. When the pump 14 is driven, the pore water in the soil around the steel sheet pile is vacuumed and raised, and is sequentially discharged to the side groove 14 side, and the surrounding ground is consolidated and subsidized to improve the ground. At the end of construction, necessary parts on the ground surface may be backfilled with high quality earth and sand.

以上の本発明を適用した補強構造では、フーチング20aと周囲地盤とが鋼矢板22によって縁切りされ、また耐震補強工事完成後に行うため、圧密作用による不具合は全くなく、却って構造物そのものだけでなく周囲地盤も改良されるため、耐震性もさらに向上するものとなる。   In the reinforcing structure to which the present invention is applied, since the footing 20a and the surrounding ground are edged by the steel sheet piles 22 and are performed after the seismic reinforcement work is completed, there is no problem due to the compaction effect. Since the ground is also improved, the earthquake resistance will be further improved.

なお、以上の実施例は本発明を何ら制約するものではない。本発明の地盤改良工法は、請求項1又は2で特定される要件を除いて種々変形したり展開可能であり、使用機器類も以上の実施例を参考として適宜選定されるものである。   In addition, the above Example does not restrict | limit this invention at all. The ground improvement method of the present invention can be variously modified or developed except for the requirements specified in claim 1 or 2, and the equipment used is appropriately selected with reference to the above embodiments.

(a)〜(c)は本発明の第1実施例による施工手順を示す説明図である。(A)-(c) is explanatory drawing which shows the construction procedure by 1st Example of this invention. (a)〜(c)は図1に引き続く施工手順を示す説明図である。(A)-(c) is explanatory drawing which shows the construction procedure following FIG. サンドマット層(粒状層)の施工形状の一例を示す斜視図である。It is a perspective view which shows an example of the construction shape of a sand mat layer (granular layer). サンドマット層(粒状層)の施工形状の他の例を示す斜視図である。It is a perspective view which shows the other example of the construction shape of a sand mat layer (granular layer). (a)(b)は本発明を既存構造物の周囲地盤の部分改良に適用した場合の第2実施例を示す説明図である。(A) (b) is explanatory drawing which shows 2nd Example at the time of applying this invention to the partial improvement of the surrounding ground of the existing structure. 図5のA−A線おける断面図である。It is sectional drawing in the AA line of FIG.

符号の説明Explanation of symbols

1…アースドリルマシン
2…砂−水の混合プラント
3…ポンプ
6…中空ロッド
9…サンドマット層(粒状層)
10…真空吸引用パイプ
12…真空吸引孔
14…真空吸引ポンプ
20…既存構造物
20a…フーチング(基礎)
26…地盤貫入及び真空吸引兼用中空ロッド
28…サンドドレーン層(粒状層)

DESCRIPTION OF SYMBOLS 1 ... Earth drill machine 2 ... Sand-water mixing plant 3 ... Pump 6 ... Hollow rod 9 ... Sand mat layer (granular layer)
DESCRIPTION OF SYMBOLS 10 ... Vacuum suction pipe 12 ... Vacuum suction hole 14 ... Vacuum suction pump 20 ... Existing structure 20a ... Footing (basic)
26 ... Hollow rod for both ground penetration and vacuum suction 28 ... Sand drain layer (granular layer)

Claims (6)

噴射口を有した中空ロッドを、地表側より地盤中に貫入して、前記噴射口を当該地盤中に存在する改良対象層内に配置する貫入工程と、
粒状物と液体との混合物を前記中空ロッドの噴射口から噴出することにより、前記改良対象層内に透水性の粒状層を造成する造成工程と、
地表側より真空吸引用パイプを前記粉状層まで貫入するとともに、前記パイプに接続された真空ポンプの駆動により前記改良対象層内に保留されている間隙水等を前記粒状層及びパイプを通じて地表側に吸引して排出する排液工程と
を経ることを特徴とする地盤改良工法。
A penetration step of penetrating a hollow rod having an injection port into the ground from the ground surface side and arranging the injection port in an improvement target layer existing in the ground;
A step of forming a water-permeable granular layer in the improvement target layer by ejecting a mixture of the granular material and the liquid from the injection port of the hollow rod;
A vacuum suction pipe penetrates from the ground surface to the powder layer, and pore water or the like retained in the improvement target layer by driving a vacuum pump connected to the pipe is grounded through the granular layer and the pipe. A ground improvement method characterized by passing through a draining process of sucking and discharging.
噴射口を有した中空ロッドを、地表側より地盤中に貫入して、前記噴射口を当該地盤中に存在する改良対象層内に配置する貫入工程と、
粒状物と液体との混合物を前記中空ロッドの噴射口から噴出することにより、前記改良対象層内に透水性の粒状層を造成する造成工程と、
前記中空ロッドに真空ポンプを接続し、該真空ポンプの駆動により前記改良対象層内に保留されている間隙水等を前記粒状層及び中空ロッドを通じて地表側に吸引して排出する排液工程と
を経ることを特徴とする地盤改良工法。
A penetration step of penetrating a hollow rod having an injection port into the ground from the ground surface side and arranging the injection port in an improvement target layer existing in the ground;
A step of forming a water-permeable granular layer in the improvement target layer by ejecting a mixture of the granular material and the liquid from the injection port of the hollow rod;
A drainage step of connecting a vacuum pump to the hollow rod and sucking and discharging pore water or the like retained in the improvement target layer to the surface side through the granular layer and the hollow rod by driving the vacuum pump; Ground improvement method characterized by passing.
請求項1又は2の地盤改良工法において、前記中空ロッドを前記造成工程で回転しながら前記混合物を噴射することを特徴とする地盤改良工法。   The ground improvement construction method according to claim 1 or 2, wherein the mixture is injected while rotating the hollow rod in the creation step. 請求項1又は2の地盤改良工法において、前記改良対象層が地盤中の複数の深度位置に存在している場合、前記造成工程では前記中空ロッドによりそれぞれの改良対象層内に前記粒状物を順に形成し、前記排水工程では前記各改良対象層の位置に対応した複数の吸引孔を有した吸引用パイプ又は中空ロッドを用いることを特徴とする地盤改良工法。   In the ground improvement construction method according to claim 1 or 2, when the improvement target layer exists at a plurality of depth positions in the ground, in the creation step, the particulate matter is sequentially put into each improvement target layer by the hollow rod. A ground improvement method characterized by using a suction pipe or a hollow rod formed and having a plurality of suction holes corresponding to the positions of the respective improvement target layers. 請求項1又は2の地盤改良工法において、前記貫入工程を所定間隔毎に行うことにより、前記造成工程で形成される粒状層同士を横方向に接続して一体ものにすることを特徴とする地盤改良工法。   3. The ground improvement method according to claim 1, wherein the intrusion step is performed at predetermined intervals to connect the granular layers formed in the forming step in a lateral direction so as to be integrated. Improved construction method. 請求項1又は2の地盤改良工法において、前記中空ロッドが既存構造物の基礎直下の地盤と周囲地盤とを仕切るための矢板に取り付けられ、該矢板の地盤内への建て込みと同時に前記中空ロッドを地盤内に貫入するとともに、前記噴射口を通じて周囲地盤内に粒状物と液体との混合物を噴出させることにより、当該矢板の側近傍に前記粒状層を造成することを特徴とする地盤改良工法。

3. The ground improvement method according to claim 1 or 2, wherein the hollow rod is attached to a sheet pile for partitioning the ground immediately below the foundation of the existing structure and the surrounding ground, and the hollow rod is simultaneously installed in the ground. The ground improvement method is characterized in that the granular layer is formed near the side of the sheet pile by injecting into the ground and ejecting a mixture of particulate matter and liquid into the surrounding ground through the injection port.

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007303270A (en) * 2007-05-07 2007-11-22 Asahi Techno:Kk Ground improvement construction method
JP2008208631A (en) * 2007-02-27 2008-09-11 Nishimatsu Constr Co Ltd Seismically reinforcing structure for pile foundation
JP2012180738A (en) * 2012-04-06 2012-09-20 Asahi Techno:Kk Ground improvement method

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008208631A (en) * 2007-02-27 2008-09-11 Nishimatsu Constr Co Ltd Seismically reinforcing structure for pile foundation
JP2007303270A (en) * 2007-05-07 2007-11-22 Asahi Techno:Kk Ground improvement construction method
JP2012180738A (en) * 2012-04-06 2012-09-20 Asahi Techno:Kk Ground improvement method

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