JP4520913B2 - Ground improvement method and existing structure foundation reinforcement method - Google Patents

Ground improvement method and existing structure foundation reinforcement method Download PDF

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JP4520913B2
JP4520913B2 JP2005199935A JP2005199935A JP4520913B2 JP 4520913 B2 JP4520913 B2 JP 4520913B2 JP 2005199935 A JP2005199935 A JP 2005199935A JP 2005199935 A JP2005199935 A JP 2005199935A JP 4520913 B2 JP4520913 B2 JP 4520913B2
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ground
ground improvement
rod
foundation
double pipe
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JP2007016507A (en
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渡邊　　徹
俊昌 長尾
裕美 鈴木
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Taisei Corp
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Description

本発明は、高圧噴射撹拌による地盤改良方法とこれを利用した既存構造物基礎の補強方法に関する。   The present invention relates to a ground improvement method by high-pressure jet agitation and a method for reinforcing an existing structure foundation using the same.

高圧噴射撹拌による地盤改良方法は、比較的施工上の制約が少ない方法として、さまざまな場面において使用されている。
例えば、既存建物の基礎地盤の支持力が、何らかの原因により低下した場合や、既存建物が増築などにより重量が増加した場合等において、当該既存建物の基礎地盤の支持力の増加を目的として、高圧噴射撹拌による地盤改良方法が採用される場合がある。 The ground improvement method by high-pressure jet agitation is used in various situations as a method with relatively few restrictions on construction.
For example, if the supporting capacity of the foundation ground of an existing building decreases for some reason, or if the weight of an existing building increases due to expansion, etc., the purpose is to increase the supporting capacity of the foundation ground of the existing building. A ground improvement method using jet agitation may be employed.

このような、既存建物の基礎地盤の支持力の増加を目的とした地盤改良方法としては、例えば、特許文献１に示すように、既設基礎の脇、あるいは既設基礎を貫通して竪孔を穿設し、この竪孔内にロッドを挿入した後、ロッドを通じて硬化材を含む高圧ジェット噴流を地中に噴射することでロッドの下端周辺の地盤を切削しながら硬化材と混合する方法により、既設基礎よりも大きい平面積を有した地盤改良体を既設基礎の下方に形成する方法がある。   As such a ground improvement method for the purpose of increasing the bearing capacity of the foundation ground of an existing building, for example, as shown in Patent Document 1, a fistula is drilled through the side of the existing foundation or through the existing foundation. After the rod is inserted into the hole, a high-pressure jet jet containing the hardener is injected into the ground through the rod to mix with the hardener while cutting the ground around the lower end of the rod. There is a method of forming a ground improvement body having a larger plane area than the foundation below the existing foundation.

ところが、前記の地盤改良方法は、硬化材を地盤内に噴射することにより、地盤の切削と硬化材の混合とを同時に行う方法のため、硬質な地盤では地盤の切削および硬化材の混合が不十分となり、改良径が小さくなる場合があった。そのため、既存建物の基礎地盤を改良する際に、既設基礎の下方に所望の地盤改良体を形成することができない場合があった。   However, the ground improvement method described above is a method of simultaneously cutting the ground and mixing the hardened material by injecting the hardened material into the ground. In some cases, the improved diameter was small. Therefore, when improving the foundation ground of the existing building, a desired ground improvement body may not be formed below the existing foundation.

このような問題点に対して、特許文献２には、硬質な地盤においても確実に所望の平面積を有した地盤改良体を形成することを可能とした地盤改良方法が開示されている。これは、ロッドにより所定深度削孔し、ロッド先端部から横方向に圧縮空気と高圧水からなる水ジェットを２方向に噴射させながらロッドを所定高さまで回転させつつ上昇させることにより地盤を切削し、ロッドが所定高さまで到達したらロッドを再び所定深度まで降下させ、ロッド先端部から水ジェットを噴射させつつ、ロッド先端部において水ジェットと反対方向から硬化材と圧縮空気を噴射させながらロッドを所定高さまで回転させつつ上昇させることにより硬化材と地盤とを撹拌混合し、所定形状の地盤改良体を形成する地盤改良方法である。
特開平６−１４６２５８号公報（［００１０］−［００１２］、図１−図２） 特開平７−１８６５８号公報（［００１１］−［００１８］、図１−図５） In order to solve such a problem, Patent Document 2 discloses a ground improvement method that makes it possible to reliably form a ground improvement body having a desired flat area even on hard ground. This is done by drilling a predetermined depth with a rod and cutting the ground by rotating the rod up to a predetermined height while jetting a water jet of compressed air and high-pressure water in two directions from the tip of the rod in the lateral direction. When the rod reaches a predetermined height, the rod is lowered again to a predetermined depth, and a water jet is ejected from the tip of the rod, while a hard material and compressed air are ejected from the opposite direction of the water jet at the rod tip. This is a ground improvement method in which a hardened material and the ground are mixed by stirring while being rotated up to a height to form a ground improvement body having a predetermined shape.
JP-A-6-146258 ([0010]-[0012], FIGS. 1-2) JP-A-7-18658 ([0011]-[0018], FIGS. 1-5)

ところが、前記従来の地盤改良方法は、高圧水、圧縮空気および硬化材を同時に地中に噴射する必要があることから機器設備が大規模となり、これらの機器設備を配置するために広い作業スペースを必要としていた。そのため、施工が可能な箇所が限られてしまうという問題点を有していた。また、高圧水、圧縮空気および硬化材の噴射を同時に行うためには、ロッドとして３重管を使用しなければならず、その径や重量によりロッドの取り扱いが煩雑となり、施工性が劣るという問題点も有していた。
さらに、前記従来の地盤改良方法は、２方向に水ジェットを噴射させることによる地盤の切削、および、水ジェットの噴射と硬化材の噴射による撹拌混合の各工程で、吐出量が大きく、排泥量が多くなり、その処理費用が嵩むという問題点も有していた。 However, the conventional ground improvement method requires high-pressure water, compressed air, and a hardened material to be injected into the ground at the same time, resulting in large-scale equipment and a large work space for arranging these equipment. I needed it. For this reason, there is a problem in that the places where construction is possible are limited. In addition, in order to simultaneously inject high-pressure water, compressed air, and a hardened material, a triple pipe must be used as a rod, and handling of the rod becomes complicated due to its diameter and weight, resulting in poor workability. Also had a point.
Further, the conventional ground improvement method has a large discharge amount in each step of ground cutting by jetting water jets in two directions and agitation and mixing by jetting water jets and hardeners. There was also a problem that the amount increased and the processing cost increased.

本発明は、前記の問題点を解決するためになされたものであり、施工性に優れ、かつ、施工条件による制限が少なく、なおかつ、経済性に優れた地盤改良方法およびこの地盤改良方法を利用した既存構造物基礎の補強方法を提案することを課題とする。   The present invention has been made in order to solve the above-mentioned problems, and uses a ground improvement method and a ground improvement method that are excellent in workability, less limited by construction conditions, and excellent in economic efficiency. The problem is to propose a method for reinforcing existing foundations.

前記の課題を解決するために、本発明は、地盤改良の対象となる領域を高さ方向に連なる複数の小領域に分割し、最下段にある小領域から順に地盤を改良する地盤改良方法であって、各小領域において、所定の深度まで挿入されたロッドの先端部から横方向に高圧水と圧縮空気とを噴射させつつ該ロッドを回転させながら所定高さ引き上げる切削工程と、前記切削工程により引き上げたロッドを引き上げた分だけ下降させるロッド下降工程と、前記ロッド下降工程により下降させた前記ロッドの先端部から横方向に硬化材と圧縮空気とを噴射させつつ該ロッドを回転させながら所定高さ引き上げる噴射撹拌工程とを行うことを特徴としている。   In order to solve the above-mentioned problems, the present invention is a ground improvement method in which a ground improvement target area is divided into a plurality of small areas that are continuous in the height direction, and the ground is improved in order from the bottom small area. In each small region, a cutting step of pulling up a predetermined height while rotating the rod while injecting high-pressure water and compressed air in the lateral direction from the tip of the rod inserted to a predetermined depth, and the cutting step A rod lowering step in which the rod pulled up by the rod is lowered by the amount raised, and a predetermined amount while rotating the rod while injecting a hardening material and compressed air laterally from the tip of the rod lowered by the rod lowering step. And a jet stirring step of raising the height.

かかる地盤改良方法は、切削工程により地盤をほぐした後、噴射撹拌工程により硬化材と地盤との撹拌混合を行うため、所定範囲の地盤内に均等に硬化材を配置して、所望の改良体を構築することを可能としている。また、高圧水と硬化材の噴射をそれぞれ別工程により行うため、２重管による施工を可能としており、管材の取り扱いが容易で、施工性に優れている。また、これに伴い、施工に要する機器設備が簡易になるため、比較的狭い作業スペースでの施工が可能となり、比較的適用範囲が広い。さらに、噴射撹拌工程における排泥量は、切削工程と分けることで硬化材の吐出量を低減できるため、従来に比べて排泥量が少なく、経済性や環境面で優れている。   In this ground improvement method, after the ground is loosened by the cutting process, the hardened material and the ground are stirred and mixed by the jet stirring process. It is possible to build. Moreover, since the injection of high-pressure water and the curing material is performed in separate processes, construction by a double pipe is possible, the handling of the pipe material is easy, and the workability is excellent. In addition, since the equipment required for construction is simplified, construction in a relatively narrow work space is possible, and the application range is relatively wide. Furthermore, since the amount of mud discharged in the jet stirring step can be reduced by separating the amount of the hardened material by dividing it from the cutting step, the amount of discharged mud is smaller than in the past, which is excellent in terms of economy and environment.

また、地盤改良の対象となる領域を高さ方向に連なる複数の小領域に分割し、最下段にある小領域から順に地盤改良体を構築していくことにより、所定の長さからなる地盤改良体を形成すれば、切削工程により地盤をほぐしてから噴射撹拌工程により混合された硬化材による地盤の固化までの時間を短縮することが可能となり、地盤を不安定な状態（ほぐされて強度が低下された状態）で長時間放置することにより孔壁が崩壊すること等を防止することが可能となる。また、長時間ほぐした地盤を放置することにより、地中内において土砂の性状が変化することを防止するため、下降工程や噴射撹拌工程の支障となることが少なく、施工性に優れている。さらに、切削を分割することにより、多量の土砂が地表に堆積することがないため、排泥処理の平準化が図れ、作業効率が上がる。   In addition, the ground improvement object is divided into a plurality of small areas that are continuous in the height direction, and the ground improvement body is constructed in order from the small area at the bottom, thereby improving the ground. If the body is formed, it will be possible to shorten the time from the loosening of the ground by the cutting process to the solidification of the ground by the hardened material mixed by the jet agitation process. It is possible to prevent the hole wall from collapsing by leaving it in a lowered state for a long time. Further, by leaving the ground loosened for a long time, the property of the earth and sand is prevented from changing in the ground, so that it is less likely to hinder the descent process and the jet stirring process, and is excellent in workability. Furthermore, by dividing the cutting, a large amount of earth and sand does not accumulate on the ground surface, so that the leveling of the sludge treatment can be achieved and the work efficiency can be improved.

なお、前記切削工程において高圧水とともに圧縮空気を噴射することにより、より広範囲に高圧水を噴射することが可能となる。また、高圧水とともに圧縮空気を噴射することにより、地中内においてこの空気分が上昇するため、空気のリフト作用によって、切削された土粒子も上昇し、土砂の地表面への排出効果が得られるとともに、噴射撹拌工程における硬化材を配置するための空間が形成される。   In addition, by injecting compressed air together with high-pressure water in the cutting step, it becomes possible to inject high-pressure water in a wider range. In addition, by jetting compressed air together with high-pressure water, this air component rises in the ground, so the lifted air action also raises the cut soil particles, and the effect of discharging soil to the ground surface is obtained. In addition, a space for arranging the curing material in the jet stirring step is formed.

また、前記切削工程におけるロッドの引き上げ速度を、地盤の強度に応じて、前記噴射撹拌工程におけるロッドの引き上げ速度よりも早めれば、地山を迅速にほぐすことができ、その結果、地盤改良方法に要する全体の施工時間を短縮することが可能となり好適である。   Further, if the rod pulling speed in the cutting step is made faster than the rod pulling speed in the jet stirring step according to the strength of the ground, the ground can be quickly loosened, and as a result, the ground improvement method Therefore, it is possible to shorten the entire construction time required for the process.

また、本発明の既存構造物基礎の補強方法は、前記地盤改良方法を利用して既存構造物の基礎下方に地盤改良体を形成することを特徴としている。   Moreover, the reinforcement method of the existing structure foundation of this invention is characterized by forming a ground improvement body under the foundation of an existing structure using the said ground improvement method.

かかる既存構造物基礎の補強方法によれば、限られた作業スペースにおける施工が強いられることが多い、既存構造物の補強について、簡易な設備により施工を行うことを可能とし、確実に既存構造物基礎の周囲および下方に地盤改良体を構築して、補強することを可能とする。   According to such a method for reinforcing an existing structure foundation, the construction in a limited work space is often forced. The reinforcement of an existing structure can be performed with simple equipment, and the existing structure is surely secured. It is possible to build and reinforce ground improvement bodies around and below the foundation.

本発明の地盤改良方法により、施工性に優れ、かつ、施工条件による制限が少なく、なおかつ、経済性に優れた地盤改良が可能となり、この地盤改良方法を利用した既存構造物基礎の補強方法によれば、既存構造物の基礎の補強を確実に行うことが可能となる。   By the ground improvement method of the present invention, it is excellent in workability, less limited by construction conditions, and can be improved in the ground with excellent economic efficiency. According to this, the foundation of the existing structure can be reliably reinforced.

本発明の好適な実施の形態について、図面を参照して説明する。なお、説明において同一要素には同一の符号を用い、重複する説明は省略する。   Preferred embodiments of the present invention will be described with reference to the drawings. In the description, the same reference numerals are used for the same elements, and duplicate descriptions are omitted.

ここで、図１は、第一の実施の形態に係る地盤改良方法を示す断面図であって、施工完了状況を示している。また、図２は、第一の実施の形態に係る地盤改良方法の各施工段階を示す断面図であって、（ａ）は準備工程、（ｂ）は竪孔構築工程、（ｃ）は切削工程をそれぞれ示している。また、図３は、図２に示す各施工段階の後施工段階を示す断面図であって、（ａ）は噴射撹拌工程、（ｂ）は第二の切削工程、（ｃ）は第二の噴射撹拌工程をそれぞれ示している。
また、図４は、第二の実施の形態に係る既存構造物基礎の補強方法を示す図であって、（ａ）は断面図、（ｂ）は平面図である。また、図５乃至図７は、第二の実施の形態に係る既存構造物基礎の補強方法の変形例を示す断面図である。 Here, FIG. 1 is sectional drawing which shows the ground improvement method which concerns on 1st embodiment, Comprising: The construction completion status is shown. Moreover, FIG. 2 is sectional drawing which shows each construction step of the ground improvement method which concerns on 1st embodiment, (a) is a preparatory process, (b) is a fistula construction process, (c) is cutting. Each process is shown. Moreover, FIG. 3 is sectional drawing which shows the post-construction stage of each construction stage shown in FIG. 2, (a) is a jet stirring process, (b) is a 2nd cutting process, (c) is a 2nd cutting process. Each of the jet stirring steps is shown.
FIGS. 4A and 4B are diagrams showing a method for reinforcing an existing structure foundation according to the second embodiment, in which FIG. 4A is a cross-sectional view and FIG. 4B is a plan view. Moreover, FIG. 5 thru | or FIG. 7 is sectional drawing which shows the modification of the reinforcement method of the existing structure foundation based on 2nd embodiment.

＜第一の実施の形態＞
第一実施形態では、図１に示すように、高圧噴射撹拌工法により、地中に所定形状（所定の高さおよび所定の直径を有した略円柱状）の地盤改良体１を構築する地盤改良方法について説明する。 <First embodiment>
In the first embodiment, as shown in FIG. 1, a ground improvement for constructing a ground improvement body 1 having a predetermined shape (substantially cylindrical shape having a predetermined height and a predetermined diameter) in the ground by a high-pressure jet stirring method. A method will be described.

第一実施形態に係る地盤改良方法は、地盤改良の対象となる領域を高さ方向に連なる複数の小領域に分割し、最下段にある小領域から順に地盤を改良する地盤改良方法であって、（１）地盤改良に使用する施工機械Ｍの据え付け等を行う準備工程（図２（ａ）参照）と、（２）二重管（ロッド）１０の先端から下方向に高圧水Ｗを噴射させながら所定の深度まで竪孔１１を切削し、この二重管１０を地盤Ｇに挿入する竪孔構築工程（図２（ｂ）参照）と、（３）所定の深度まで挿入された二重管１０の先端部から横方向に高圧水と圧縮空気（以下、単に「水ジェット」という場合がある）Ｊｗを噴射させつつ二重管１０を回転させながら所定高さ引き上げる切削工程（図２（ｃ））と、（４）切削工程により引き上げた二重管１０を所定の深度まで下降させるロッド下降工程と、（５）ロッド下降工程により下降させた二重管１０の先端部から横方向に硬化材と圧縮空気（以下、単に「硬化材ジェット」という場合がある）Ｊｇを噴射させつつ二重管１０を回転させながら所定高さ引き上げる噴射撹拌工程（図３（ａ）参照）とにより、地盤改良体１を構築するものである。   The ground improvement method according to the first embodiment is a ground improvement method in which an area to be ground improved is divided into a plurality of small areas that are continuous in the height direction, and the ground is improved in order from the lowermost area. (1) Preparatory process (see FIG. 2 (a)) for installing the construction machine M used for ground improvement, and (2) Injecting high-pressure water W downward from the tip of the double pipe (rod) 10. And cutting the fistula 11 to a predetermined depth while inserting the double pipe 10 into the ground G (see FIG. 2B), and (3) the double inserted to a predetermined depth. A cutting process (FIG. 2 (FIG. 2)) of rotating the double pipe 10 while injecting high-pressure water and compressed air (hereinafter sometimes referred to simply as “water jet”) Jw from the tip of the pipe 10 in the lateral direction. c)) and (4) the double pipe 10 pulled up by the cutting process is moved to a predetermined depth. A rod lowering step for lowering to a point, and (5) a hardening material and compressed air (hereinafter sometimes simply referred to as “hardening material jet”) Jg from the tip of the double pipe 10 lowered by the rod lowering step. The ground improvement body 1 is constructed | assembled by the injection stirring process (refer FIG. 3 (a)) which raises predetermined height, rotating the double pipe | tube 10 while making it inject.

（１）準備工程
準備工程は、図２（ａ）に示すように、地中に地盤改良体１（図１参照）を形成する施工箇所の上方に施工に要する施工機械Ｍおよびその他の各種機器設備（図示省略）を据え付ける。この時、施工箇所の地表には、ピット１２を形成し、竪孔構築工程、切削工程、噴射撹拌工程に伴い、竪孔１１から地表に流出する排泥１ｃ（図１参照）を一時的に堆積できるように構成する。なお、ピット１２の上面には架台Ｓを設置して、施工機械Ｍの据え付けを可能に構成する。ここで、ピット１２は、必要に応じて構築すればよく、既存構造物があることなどによりピット１２の構築が困難な場合には省略しても良い。また、前記機器設備は、公知の高圧噴射撹拌工法において用いる機器設備と同様のものを配置すればよく、詳細な説明は省略する。 (1) Preparatory process As shown in FIG. 2 (a), the preparatory process is a construction machine M and other various devices required for construction above the construction site where the ground improvement body 1 (see FIG. 1) is formed in the ground. Install equipment (not shown). At this time, the pit 12 is formed on the ground surface of the construction site, and the mud 1c (see FIG. 1) flowing out from the borehole 11 to the ground surface is temporarily associated with the borehole construction process, the cutting process, and the jet stirring process. Configure for deposition. A gantry S is installed on the upper surface of the pit 12 so that the construction machine M can be installed. Here, the pit 12 may be constructed as necessary, and may be omitted when it is difficult to construct the pit 12 due to the existence of an existing structure. Moreover, what is necessary is just to arrange | position the equipment similar to the equipment used in the well-known high-pressure jet stirring method, and detailed description is abbreviate | omitted.

（２）竪孔構築工程
竪孔構築工程は、図２（ｂ）に示すように、施工機械Ｍを利用して、二重管１０の先端に形成された下方向の噴射口１０ｂから、下方向に高圧水Ｗを噴射させながら、先端ビット１０ａを回転させて竪孔を削孔する工程である。この時、二重管１０の回転数とストローク速度は、地盤Ｇの地質や強度に応じて設定する。また、二重管１０は、二重管スイベル１３を介してクレーンＣに吊り上げられている。なお、施工機械Ｍへの二重管１０の設置、二重管１０の方向（角度）等の保持は、クレーンＣを用いて行う。 (2) Fistula construction process As shown in FIG. 2 (b), the fistula construction process is performed by using a construction machine M from the downward injection port 10b formed at the tip of the double pipe 10 to the bottom. In this process, the tip bit 10a is rotated while the high-pressure water W is jetted in the direction to drill the hole. At this time, the rotation speed and stroke speed of the double pipe 10 are set according to the geology and strength of the ground G. Further, the double pipe 10 is lifted by the crane C via a double pipe swivel 13. The crane C is used to install the double pipe 10 on the construction machine M and hold the direction (angle) of the double pipe 10.

なお、二重管１０による削孔の前に、削孔精度の確保、変位防止およびジャーミング防止を目的として、予め削孔径１４０ｍｍ以上で先行削孔し、計画された地盤改良体１の天端付近までガイド管１１ａ（図１参照）を配置してもよい。   In addition, prior to drilling with the double pipe 10, in order to ensure drilling accuracy, prevent displacement, and prevent jamming, a prior drilling with a drilling diameter of 140 mm or more is performed in advance, and the top end of the planned ground improvement body 1 is prepared. You may arrange | position the guide pipe | tube 11a (refer FIG. 1) to the vicinity.

第一実施形態では、高圧水Ｗを噴射することにより竪孔１１を構築したが、二重管１０の先端部に形成された先端ビット１０ａにより地盤Ｇの切削が可能であれば、必ずしも高圧水Ｗを噴射する必要はなく、適宜、水圧を下げてもよい。このように、竪孔１１の構築方法は地盤Ｇの地質や強度に応じて、公知の手段から選定して行えばよい。また、竪孔１１の切削に伴いピット１２に堆積された排泥１ｃは、適宜サンドポンプ（図示省略）等により搬出する。
また、第一実施形態では、クレーンＣを使用して二重管１０の設置および角度調整等を行うものとしたが、例えば既設構造物の内部や近傍での作業によりクレーンＣの配置が困難な場合等、クレーンＣは必ずしも使用しなくてもよいことはいうまでもない。 In the first embodiment, the fistula 11 is constructed by jetting high-pressure water W. However, if the ground G can be cut by the tip bit 10a formed at the tip portion of the double pipe 10, the high-pressure water is not necessarily used. It is not necessary to inject W, and the water pressure may be appropriately reduced. Thus, the construction method of the fistula 11 may be selected from known means according to the geology and strength of the ground G. Moreover, the waste mud 1c accumulated in the pits 12 with the cutting of the hole 11 is appropriately carried out by a sand pump (not shown) or the like.
In the first embodiment, the crane C is used to install the double pipe 10 and adjust the angle. However, for example, it is difficult to place the crane C inside or near the existing structure. Needless to say, the crane C is not necessarily used.

（３）切削工程
切削工程は、図２（ｃ）に示すように、竪孔１１内に挿入された二重管１０を所定速度で引き上げながら回転させつつ、二重管１０の先端部から、横方向に水ジェットＪｗを噴射させることにより、所定範囲において地盤Ｇをほぐし、所定形状のゆるみ地盤体（第１ゆるみ地盤体１ａ’）を形成する工程である。ここで、第一実施形態で使用する二重管１０は、公知の高圧噴射撹拌工法で使用する二重管と同様に、その先端部の横方向の噴射口１０ｃから二重管１０内を個別に圧送された高圧水と圧縮空気とを同時に噴射可能に構成されている。つまり、二重管１０の下端に形成された下方向への噴射口１０ｂを閉塞するとともに、二重管１０の側面に形成された横方向への噴射口１０ｃを開放することで、水ジェットＪｗが横方向に噴射されるように構成されている。この時、高圧ポンプは、竪孔構築工程の時と同様に水槽に接続されており、高圧水を二重管１０に供給する。 (3) Cutting process As shown in FIG.2 (c), a cutting process is carried out from the front-end | tip part of the double pipe 10, rotating while rotating the double pipe 10 inserted in the fistula 11 at a predetermined speed, In this step, the ground G is loosened in a predetermined range by spraying the water jet Jw in the lateral direction to form a loose ground body (first loose ground body 1a ′) having a predetermined shape. Here, the double pipe 10 used in the first embodiment is individually separated in the double pipe 10 from the lateral injection port 10c at the tip, similarly to the double pipe used in the known high-pressure jet stirring method. The high-pressure water and the compressed air that have been pumped into the tank can be jetted simultaneously. That is, by closing the downward injection port 10b formed at the lower end of the double tube 10 and opening the lateral injection port 10c formed on the side surface of the double tube 10, the water jet Jw Is configured to be jetted in the lateral direction. At this time, the high-pressure pump is connected to the water tank in the same manner as in the fistula construction step, and supplies high-pressure water to the double pipe 10.

ここで、第一実施形態において使用する二重管１０は、公知の高圧噴射撹拌工法で使用する二重管と同様の構成であって、管（ロッド）の内部において圧縮空気を圧送する空気路と高圧水または硬化材を圧送する圧送路とに分割されている。そして、この空気路により圧送された圧縮空気と圧送路により圧送された高圧水または硬化材が二重管１０の下端に形成された噴射口１０ｂまたは噴射口１０ｃから同時に噴射されることで、水ジェットＪｗまたは硬化材ジェットＪｇとして、地盤Ｇに噴射されるように構成されている。また、二重管１０は、地盤改良体１の深度が深い場合においては、随時ロッドを継ぎ足すことにより所定の深度まで挿入する。
なお、空気路の上端部には図示しないエアコンプレッサが接続され、圧送路の上端部には図示しない高圧ポンプが接続されている。竪坑構築工程では、高圧ポンプを介して、図示しない水槽に貯留された水を二重管１０へと圧送する。 Here, the double pipe 10 used in the first embodiment has the same configuration as the double pipe used in the known high-pressure jet agitation method, and is an air passage that pumps compressed air inside the pipe (rod). And a pumping path for pumping high-pressure water or a hardener. And the compressed air pumped by this air path and the high-pressure water or hardened material pumped by the pump path are jetted simultaneously from the jet port 10b or jet port 10c formed at the lower end of the double pipe 10, thereby It is configured to be jetted to the ground G as a jet Jw or a hardened material jet Jg. Moreover, when the depth of the ground improvement body 1 is deep, the double pipe 10 is inserted to a predetermined depth by adding a rod at any time.
An air compressor (not shown) is connected to the upper end of the air passage, and a high pressure pump (not shown) is connected to the upper end of the pressure feeding passage. In the shaft construction process, water stored in a water tank (not shown) is pumped to the double pipe 10 via a high-pressure pump.

第一実施形態では、切削工程における二重管１０の引き上げ高さを１ｍ程度とし、計画された地盤改良体１を高さ方向に連なる複数の小領域に分割して形成するものとする。また、切削工程における二重管の引き上げ速度は、地山の状況に応じて適宜設定するものであるが、本実施形態では、５〜１０ｍｉｎ／ｍ程度として、後記する噴射撹拌工程における噴射撹拌時の二重管１０の引き上げ速度の３〜４倍程度の速度で行うものとする。
また、高圧水および圧縮空気の噴射圧力は限定されるものではないが、第一実施形態では、高圧水の噴射圧力を２０〜３０ＭＰａ、圧縮空気の噴射圧力を０．７ＭＰａで行う。 In the first embodiment, the lifting height of the double pipe 10 in the cutting process is set to about 1 m, and the planned ground improvement body 1 is divided into a plurality of small regions continuous in the height direction. Moreover, although the pulling-up speed of the double pipe in the cutting process is appropriately set according to the situation of the natural ground, in this embodiment, it is set to about 5 to 10 min / m, and during the jet stirring in the jet stirring process described later. The double pipe 10 is pulled up at a speed of about 3 to 4 times the pulling speed.
Moreover, although the injection pressure of high pressure water and compressed air is not limited, in 1st embodiment, the injection pressure of high pressure water is 20-30 Mpa, and the injection pressure of compressed air is 0.7 Mpa.

ここで、地盤Ｇの切削に伴い竪孔１１を上昇してピット１２に堆積された排泥１ｃは、適宜サンドポンプ（図示省略）等により搬出する。   Here, the sludge 1c that has risen up the fist hole 11 and accumulated in the pits 12 with the cutting of the ground G is appropriately carried out by a sand pump (not shown) or the like.

（４）ロッド下降工程
ロッド下降工程は、切削工程において引き上げた二重管１０を引き上げた分（１ｍ程度）下降させて切削前の位置に戻す工程である。この時、第１ゆるみ地盤体１ａ’は切削工程により強度が低下させられているため、クレーンＣにより二重管スイベル１３を下降させることにより、二重管１０を下降させることが可能となる。なお、第１ゆるみ地盤体１ａ’の状況により、必要に応じて二重管１０を施工機械Ｍにより回転力および推力を付与して下降させてもよい。
ここで、ロッド下降工程における二重管１０の下降させる長さは、切削工程において引き上げた長さと同等であればよく、多少上下してもよい。 (4) Rod lowering step The rod lowering step is a step of lowering the double pipe 10 pulled up in the cutting step (about 1 m) and returning it to the position before cutting. At this time, since the strength of the first loose ground body 1a ′ is reduced by the cutting process, the double pipe 10 can be lowered by lowering the double pipe swivel 13 by the crane C. Depending on the situation of the first loose ground body 1a ′, the double pipe 10 may be lowered by applying a rotational force and a thrust by the construction machine M as necessary.
Here, the length by which the double pipe 10 is lowered in the rod lowering process may be equal to the length raised in the cutting process, and may be slightly increased or decreased.

（５）噴射撹拌工程
噴射撹拌工程は、図３（ａ）に示すように、切削工程において地盤Ｇを切削して形成された第１ゆるみ地盤体１ａ’に二重管１０の先端部から、横方向に硬化材ジェットＪｇを噴射させつつ、二重管１０を引き上げながら回転させることにより、第１ゆるみ地盤体１ａ’に硬化材を混合撹拌して、第１混合体１ａ（小領域）を形成する工程である。 (5) Injecting and stirring step As shown in FIG. 3A, the injecting and stirring step is performed from the distal end portion of the double tube 10 to the first loosened ground body 1a ′ formed by cutting the ground G in the cutting step. The hardened material is mixed and stirred in the first loose ground body 1a ′ by rotating the double pipe 10 while rotating the jetting hard material jet Jg in the lateral direction, and the first mixed body 1a (small region) is stirred. It is a process of forming.

この時、二重管１０に接続された高圧ポンプは図示しないグラウト槽に接続されており、硬化材であるグラウトが、圧送路を介して地中に噴射される。なお、第一実施形態では、切削工程における高圧ポンプと水槽との接続と、噴射撹拌工程における高圧ポンプとグラウト槽との接続との切り替えを公知の切替手段を介して行うものとするが、手動により配管を切り替える構成としてもよく、その切替方法は限定されるものではない。   At this time, the high-pressure pump connected to the double pipe 10 is connected to a grout tank (not shown), and the grout, which is a hardening material, is injected into the ground through the pressure feed path. In the first embodiment, the connection between the high-pressure pump and the water tank in the cutting process and the connection between the high-pressure pump and the grout tank in the jet stirring process are performed via known switching means. It is good also as a structure which switches piping by, and the switching method is not limited.

噴射撹拌時の二重管１０の引き上げ速度は、地山の状況に応じて決定すればよく、限定されるものではないが、本実施形態では１５〜４０ｍｉｎ／ｍ程度とする。また、硬化材および圧縮空気の噴射圧力は限定されるものではないが、第一実施形態では、硬化材の噴射圧力を２０〜３０ＭＰａ、圧縮空気の噴射圧力を０．７ＭＰａで行う。   The pulling-up speed of the double pipe 10 at the time of jetting agitation may be determined according to the condition of the natural ground, and is not limited, but is set to about 15 to 40 min / m in this embodiment. Moreover, although the injection pressure of a hardening material and compressed air is not limited, in 1st embodiment, the injection pressure of hardening material is 20-30 Mpa, and the injection pressure of compressed air is 0.7 Mpa.

ここで、地盤の切削時の二重管１０の引き上げ速度と噴射撹拌時の二重管１０の引き上げ速度との関係は限定されるものではなく、同一としてもよいが、噴射撹拌時における硬化材ジェットＪｇの噴射も、硬化材と地盤Ｇとの混合撹拌とともに地盤Ｇを切削する要素を有していることから、切削工程における地盤Ｇの切削は地盤Ｇをほぐす程度でもよく、施工時間の短縮の観点からすれば、切削時の二重管１０の引き上げ速度を噴射撹拌時の引き上げ速度よりも早めるのが好ましい。また、噴射撹拌工程において硬化材ジェットＪｇを噴射する範囲は、切削工程においてほぐされた範囲よりも多少広範囲に行ってもよい。   Here, the relationship between the pulling speed of the double pipe 10 at the time of cutting the ground and the pulling speed of the double pipe 10 at the time of jet stirring is not limited and may be the same, but the hardening material at the time of jet stirring The jet Jg injection also has an element that cuts the ground G together with the mixing and stirring of the hardened material and the ground G. Therefore, the cutting of the ground G in the cutting process may be to loosen the ground G and shorten the construction time. From this point of view, it is preferable to raise the pulling speed of the double tube 10 at the time of cutting faster than the pulling speed at the time of jet stirring. Further, the range in which the hardener jet Jg is sprayed in the jet stirring step may be performed in a slightly wider range than the range loosened in the cutting step.

噴射撹拌工程による第１混合体１ａの構築が完了したら、引き続き二重管１０を所定速度で引き上げながら回転させつつ、二重管１０の先端部から、横方向に水ジェットＪｗを噴射させることにより、所定範囲において地盤Ｇをほぐし、所定形状の第２ゆるみ地盤体１ｂ’を第１混合体１ａの上端に接した状態で形成する（切削工程）。そして、切削工程において引き上げた分だけ二重管１０を下降させて、二重管１０の先端部を第１混合体１ａの上端部に位置させた後（下降工程）、第２ゆるみ地盤体１ｂ’に二重管１０の先端部から、横方向に硬化材ジェットＪｇを噴射させつつ、二重管１０を引き上げながら回転させることにより、第２ゆるみ地盤体１ｂ’に硬化材を混合撹拌して、第２混合体１ｂを形成する（噴射撹拌工程）。
さらに、切削工程、下降工程、噴射撹拌工程を同様に繰り返し行うことにより、計画された地盤改良体１を構築する。ここで、後行して構築される混合体（第２混合体）を、先行して構築された混合体（第１混合体）の上部とラップさせた状態で構築することにより、地盤改良体１の各小領域を確実に隙間のない状態で構築してもよい。 After the construction of the first mixture 1a by the jet stirring step is completed, the water jet Jw is jetted in the lateral direction from the tip of the double pipe 10 while continuously rotating the double pipe 10 at a predetermined speed and rotating. The ground G is loosened within a predetermined range, and a second loose ground body 1b ′ having a predetermined shape is formed in contact with the upper end of the first mixture 1a (cutting process). Then, the double pipe 10 is lowered by the amount raised in the cutting process and the tip of the double pipe 10 is positioned at the upper end of the first mixture 1a (down process), and then the second loose ground body 1b. By mixing and stirring the hardened material to the second loose ground body 1b ′ by rotating the double pipe 10 while rotating the double pipe 10 while ejecting the hardened material jet Jg in the lateral direction from the tip of the double tube 10. Then, the second mixture 1b is formed (injection stirring step).
Furthermore, the planned ground improvement body 1 is constructed by repeating the cutting process, the descent process, and the jet stirring process in the same manner. Here, the ground improvement body is constructed by constructing the mixture (second mixture) that is constructed in the following manner in a state of being overlapped with the upper part of the mixture (first mixture) that is constructed in advance. Each small area of 1 may be constructed without a gap.

第一実施形態の地盤改良方法によれば、水ジェットＪｗにより地盤Ｇをほぐしてから硬化材ジェットＪｇを噴射して地盤Ｇと硬化材との混合撹拌を行うため、地盤Ｇの地質等に限定されることなく、大口径かつ高品質（断面内での強度のばらつきが少ない均質な強度を有する）な地盤改良体１を計画された形状に形成することが可能となる。   According to the ground improvement method of the first embodiment, the ground G is loosened by the water jet Jw and then the hardened material jet Jg is jetted to mix and stir the ground G and the hardened material. Accordingly, the ground improvement body 1 having a large diameter and high quality (having a uniform strength with little variation in strength within the cross section) can be formed into a planned shape.

また、地盤改良体１の形成を所定の高さで分割して行うため、計画された地盤改良体１の形状が大きい場合でも、地盤Ｇの切削から硬化材の混合までの１サイクルの時間を短時間で行うことが可能となる。そのため、地盤Ｇ内において、ほぐされた土砂の土粒子が沈殿するなどして、地盤改良体１の深度による性状の変化が生じることがなく、一定の品質を保持した地盤改良体１を形成することが可能となる。また、１サイクルを短時間で行うため、地盤Ｇがほぐされることにより竪孔１１の孔壁が崩壊する危険性も少ない。
また、排泥が一度に多量発生することがないため、排泥処理が容易であるとともに、排泥が竪孔１１の直上に堆積することにより施工に支障をきたすことがないため、施工性に優れている。 Further, since the formation of the ground improvement body 1 is performed by dividing it at a predetermined height, even if the planned shape of the ground improvement body 1 is large, the time of one cycle from the cutting of the ground G to the mixing of the hardener is reduced. This can be done in a short time. Therefore, in the ground G, soil particles of loosened earth and sand are settled, so that the property of the ground improvement body 1 does not change due to the depth, and the ground improvement body 1 maintaining a certain quality is formed. It becomes possible. Moreover, since one cycle is performed in a short time, there is little risk that the hole wall of the fistula 11 will collapse when the ground G is loosened.
In addition, since a large amount of waste mud is not generated at one time, the waste mud treatment is easy, and since the waste mud does not interfere with the construction due to accumulation directly above the fistula 11, the workability is improved. Are better.

また、二重管を使用していることにより、ロッドの取り扱いが容易で、施工性に優れている。
また、三重管を使用する従来の地盤改良方法に比べて機器設備が簡易なため、適用可能な施工箇所が制限されない。 Moreover, since the double pipe is used, the handling of the rod is easy and the workability is excellent.
Moreover, since the equipment is simpler than the conventional ground improvement method using a triple pipe, applicable construction sites are not limited.

噴射撹拌時の硬化材の噴射圧力を超高圧（２０〜３０ＭＰａ）とすることで、地山を切削しながら硬化材を投入することが可能となり、切削工程における地盤Ｇの切削を、引き上げ時間を早めてほぐす程度としても、均質に硬化材を混合することが可能としている。   By setting the injection pressure of the hardened material at the time of jet stirring to an ultra-high pressure (20 to 30 MPa), it becomes possible to input the hardened material while cutting the ground, and the cutting time of the ground G in the cutting process can be increased. It is possible to mix the curing material uniformly even if it is loosened early.

切削時の高圧水の噴射圧力を超高圧（２０〜３０ＭＰａ）としているため、地盤の切削能力が高く、二重管の引き上げ速度を速めて短時間による切削でも、地盤Ｇを所望の強度にほぐすことを可能としている。   Since the jet pressure of high-pressure water at the time of cutting is set to an ultra-high pressure (20-30 MPa), the ground cutting ability is high, and the ground G is loosened to a desired strength even by cutting in a short time by increasing the pulling speed of the double pipe. Making it possible.

＜第二の実施の形態＞
第二実施形態では、図４に示すように、第一実施形態で説明した地盤改良方法を使用して、既存構造物２の基礎（既存構造物基礎２０）の補強を行う場合について説明する。
つまり、二重管１０を、既存構造物基礎２０を貫通して形成された竪孔１１を介して所定の深度まで挿入することにより、既存構造物基礎２０下方の地盤Ｇを改良して所望の地盤改良体１を形成する。 <Second Embodiment>
In 2nd embodiment, as shown in FIG. 4, the case where the foundation (existing structure foundation 20) of the existing structure 2 is reinforced is demonstrated using the ground improvement method demonstrated in 1st embodiment.
That is, by inserting the double pipe 10 to a predetermined depth through the hole 11 formed through the existing structure foundation 20, the ground G below the existing structure foundation 20 is improved and desired. The ground improvement body 1 is formed.

第二実施形態では、図４（ａ）に示すように、基礎スラブ２１と基礎杭２２と基礎梁２３とからなる既存構造物基礎２０を有する既存構造物２について、既存構造物基礎２０の近傍に基礎スラブ２１の下端よりも深い竪孔１１を形成し、この竪孔１１を利用して、地盤改良体１を形成する。なお、第二実施形態では、図４（ｂ）基礎スラブ２１の周囲を覆うように６本の地盤改良体１，１，…を互いにラップするように形成することで、既存構造物基礎２０の基礎地盤（地盤Ｇ）の強度を高めて、既存構造物２の耐震性を向上する。ここで、図４（ａ）において、符号２４は捨てコンクリート、符号２５は敷砂利または栗石である。   In 2nd embodiment, as shown to Fig.4 (a), about the existing structure 2 which has the existing structure foundation 20 which consists of the foundation slab 21, the foundation pile 22, and the foundation beam 23, the vicinity of the existing structure foundation 20 A deep hole 11 deeper than the lower end of the foundation slab 21 is formed, and the ground improvement body 1 is formed using the deep hole 11. In the second embodiment, the six ground improvement bodies 1, 1,... Are wrapped so as to cover the periphery of the foundation slab 21 in FIG. The strength of the foundation ground (Ground G) is increased and the earthquake resistance of the existing structure 2 is improved. Here, in Fig.4 (a), the code | symbol 24 is abandoned concrete and the code | symbol 25 is a paving gravel or a chestnut stone.

なお、竪孔１１は、既存構造物基礎２０の構成と計画された地盤改良体１の配置（地盤改良体１の本数や改良径等）との位置関係により、基礎スラブ２１や基礎梁２３等を貫通して形成してもよい。また、竪孔１１の形成方法は限定されるものではなく、二重管１０を地盤Ｇ内に挿入することにより形成する方法や、二重管１０を挿入する前に予めボーリング等により形成する方法など、公知の手段から適宜選定して行えばよい。また、第二実施形態では、６本の地盤改良体１，１，…を形成することで、既存構造物基礎２０を補強するものとしたが、既存構造物基礎２０を補強するために構築する地盤改良体１の本数は限定されるものではなく、地盤Ｇの地質により決定される改良径や既存構造物基礎２０の規模に応じて、適宜設定すればよい。   The fistula 11 has a foundation slab 21, a foundation beam 23, etc., depending on the positional relationship between the configuration of the existing structure foundation 20 and the planned placement of the ground improvement bodies 1 (number of ground improvement bodies 1, improved diameter, etc.). May be formed. Moreover, the formation method of the fistula 11 is not limited, The method of forming by inserting the double pipe 10 in the ground G, The method of forming by boring etc. in advance before inserting the double pipe 10 For example, it may be appropriately selected from known means. Moreover, in 2nd embodiment, although the existing ground foundation 20 was reinforced by forming the six ground improvement bodies 1,1, ..., it constructs in order to reinforce the existing ground foundation 20. The number of the ground improvement bodies 1 is not limited, and may be set as appropriate according to the improved diameter determined by the geology of the ground G and the scale of the existing structure foundation 20.

なお、前記既存構造物２について、鉛直支持性能を向上させる場合には、図５に示すように、基礎杭２２の先端よりも深く形成された竪孔１１を利用して、基礎杭２２の先端部に地盤改良体１を形成することにより行う。   In addition, about the said existing structure 2, when improving vertical support performance, as shown in FIG. 5, the front-end | tip of the foundation pile 22 is utilized using the hole 11 formed deeper than the front-end | tip of the foundation pile 22. As shown in FIG. It is performed by forming the ground improvement body 1 in the part.

また、直接基礎形式の既存構造物２’について、鉛直支持性能を向上させる場合は、図６に示すように、基礎スラブ２１の下部に地盤改良体１を形成すればよい。   Further, in the case of improving the vertical support performance of the existing foundation type structure 2 ′, the ground improvement body 1 may be formed below the foundation slab 21 as shown in FIG. 6.

さらに、直接基礎形式の既存構造物２’について、耐震性能を向上させる場合は、図７に示すように、基礎スラブ２１の周囲に地盤改良体１を形成すればよい。   Further, in the case of improving the seismic performance of the existing foundation structure 2 ′ of the direct foundation type, the ground improvement body 1 may be formed around the foundation slab 21 as shown in FIG. 7.

以上、本発明について、好適な実施形態について説明したが、本発明は前記の実施形態に限られず、本発明の趣旨を逸脱しない範囲で適宜設計変更が可能である。
例えば、前記各実施形態では、地盤改良体を高さ方向において分割して、複数回にわけて混合体を形成することで地盤改良体を形成するものとしたが、地盤改良体の分割数やその高さ等は、計画された地盤改良体の規模や周辺地盤の地質等に応じて適宜設定されることはいうまでもない。 As mentioned above, although preferred embodiment was described about this invention, this invention is not limited to the said embodiment, A design change is possible suitably in the range which does not deviate from the meaning of this invention.
For example, in each of the above embodiments, the ground improvement body is divided in the height direction, and the ground improvement body is formed by dividing the ground improvement body into a plurality of times. It goes without saying that the height and the like are appropriately set according to the planned scale of the ground improvement body and the geology of the surrounding ground.

また、本発明の地盤改良方法は、既存構造物の基礎の補強工事にのみ適用されるものではなく、あらゆる地盤強度補強工事に適用可能であることはいうまでもない。   Moreover, the ground improvement method of the present invention is not only applied to the reinforcement work for the foundation of the existing structure, but needless to say, can be applied to any ground strength reinforcement work.

また、前記実施形態では、硬化材としてグラウトを使用する場合について説明したが、硬化材の種類が限定されないことはいうまでもなく、適宜公知の硬化材を選定して使用すればよい。   Moreover, although the said embodiment demonstrated the case where grout was used as a hardening | curing material, it cannot be overemphasized that the kind of hardening | curing material is limited, What is necessary is just to select and use a well-known hardening | curing material suitably.

さらに、前記実施形態では、高圧水と硬化材の噴射圧力を、同等の範囲で行うものとしたが、必ずしも同等とする必要がないことはいうまでもない。また、高圧水および硬化材の噴射圧力は、前記の範囲に限定されるものではなく、周辺地盤の地質状況、完了範囲、機械の能力等に応じて、適宜設定すればよい。   Furthermore, in the said embodiment, although the injection pressure of the high pressure water and the hardening | curing material shall be performed in the equivalent range, it cannot be overemphasized that it is not necessarily required to be equivalent. Further, the injection pressure of the high-pressure water and the hardener is not limited to the above range, and may be appropriately set according to the geological condition of the surrounding ground, the completion range, the machine capability, and the like.

第一の実施の形態に係る地盤改良方法を示す断面図であって、施工完了状況を示している。It is sectional drawing which shows the ground improvement method which concerns on 1st embodiment, Comprising: The construction completion status is shown. 第一の実施の形態に係る地盤改良方法の各施工段階を示す断面図であって、（ａ）は準備工程、（ｂ）は竪孔構築工程、（ｃ）は切削工程をそれぞれ示している。It is sectional drawing which shows each construction step of the ground improvement method which concerns on 1st embodiment, (a) is a preparatory process, (b) is a fistula construction process, (c) has each shown the cutting process. . 図２に示す各施工段階の後施工段階を示す断面図であって、（ａ）は噴射撹拌工程、（ｂ）は第二の切削工程、（ｃ）は第二の噴射撹拌工程をそれぞれ示している。It is sectional drawing which shows the post-installation stage of each construction stage shown in FIG. 2, (a) shows an injection stirring process, (b) shows a 2nd cutting process, (c) shows a 2nd injection stirring process, respectively. ing. 第二の実施の形態に係る既存構造物基礎の補強方法を示す図であって、（ａ）は断面図、（ｂ）は平面図である。It is a figure which shows the reinforcement method of the existing structure foundation which concerns on 2nd embodiment, Comprising: (a) is sectional drawing, (b) is a top view. 第二の実施の形態に係る既存構造物基礎の補強方法の変形例を示す断面図である。It is sectional drawing which shows the modification of the reinforcement method of the existing structure foundation which concerns on 2nd embodiment. 第二の実施の形態に係る既存構造物基礎の補強方法の他の変形例を示す断面図である。It is sectional drawing which shows the other modification of the reinforcement method of the existing structure foundation which concerns on 2nd embodiment. 第二の実施の形態に係る既存構造物基礎の補強方法のその他の変形例を示す断面図である。It is sectional drawing which shows the other modification of the reinforcement method of the existing structure foundation which concerns on 2nd embodiment.

符号の説明Explanation of symbols

１ 地盤改良体
１ａ 第１混合体
１ｂ 第２混合体
１０ 二重管
２ 既存構造物
２０ 既存構造物基礎
２１ 基礎スラブ
２２ 基礎杭
２３ 基礎梁
Ｇ 地盤
Ｊｇ 硬化材ジェット
Ｊｗ 水ジェット DESCRIPTION OF SYMBOLS 1 Ground improvement body 1a 1st mixture 1b 2nd mixture 10 Double pipe 2 Existing structure 20 Existing structure foundation 21 Foundation slab 22 Foundation pile 23 Foundation beam G Ground Jg Hardening material jet Jw Water jet

Claims (3)

地盤改良の対象となる領域を高さ方向に連なる複数の小領域に分割し、最下段にある小領域から順に地盤を改良する地盤改良方法であって、
各小領域において、
所定の深度まで挿入されたロッドの先端部から横方向に高圧水と圧縮空気とを噴射させつつ該ロッドを回転させながら所定高さ引き上げる切削工程と、
前記切削工程により引き上げたロッドを引き上げた分だけ下降させるロッド下降工程と、
前記ロッド下降工程により下降させた前記ロッドの先端部から横方向に硬化材と圧縮空気とを噴射させつつ該ロッドを回転させながら所定高さ引き上げる噴射撹拌工程と、を行うことを特徴とする、地盤改良方法。 A ground improvement method that divides a target area for ground improvement into a plurality of small areas that continue in the height direction, and that improves the ground in order from the small area at the bottom,
In each subregion
A cutting step of pulling up a predetermined height while rotating the rod while injecting high-pressure water and compressed air laterally from the tip of the rod inserted to a predetermined depth;
A rod lowering step of lowering the rod pulled up by the cutting step by the amount raised;
Performing a jet stirring step of pulling up a predetermined height while rotating the rod while jetting the hardened material and compressed air in the lateral direction from the tip portion of the rod lowered by the rod lowering step, Ground improvement method. 前記切削工程におけるロッドの引き上げ速度が、前記噴射撹拌工程におけるロッドの引き上げ速度よりも早いことを特徴とする、請求項１に記載の地盤改良方法。   The ground improvement method according to claim 1, wherein a rod pulling speed in the cutting step is faster than a rod pulling speed in the jet stirring step. 請求項１または請求項２に記載の地盤改良方法を利用した既存構造物基礎の補強方法であって、既存構造物の基礎下方に地盤改良体を形成することを特徴とする、既存構造物基礎の補強方法。   An existing structure foundation using the ground improvement method according to claim 1 or 2, wherein a ground improvement body is formed below the foundation of the existing structure. Reinforcement method.
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JP5348781B2 (en) * 2009-12-04 2013-11-20 株式会社不動テトラ Repair method of substructure
KR101173877B1 (en) 2012-05-24 2012-08-14 케이에프티이엔씨주식회사 non-drilling top-down grouting type jet grouting pile structure and construction method thereof
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