JP3570675B2

JP3570675B2 - Ground improvement method

Info

Publication number: JP3570675B2
Application number: JP2000007981A
Authority: JP
Inventors: 諭松沢; 英雄浜渡; 勝彦大塚; 伸太郎松尾
Original assignee: 不動建設株式会社
Priority date: 2000-01-17
Filing date: 2000-01-17
Publication date: 2004-09-29
Anticipated expiration: 2020-01-17
Also published as: JP2001193053A

Description

【０００１】
【発明の属する技術分野】
本発明は、地盤中に粉粒体の地盤改良材を供給して、原位置土と強制的に攪拌混合し、土と地盤改良材とを反応させて土質性状を安定化し、且つ強度を高める地盤改良工法に関するものである。
【０００２】
【従来の技術】
従来、この種の地盤改良工法における空気抜きは、回転軸を角形にしたり、回転軸にフィンを設けて、回転軸外周と地盤とに隙間を形成し、この隙間を利用して用済みの空気を地上に導き、回転軸に嵌挿し地盤上に設置したフード内に回収するようにしている（特開昭５７−６１１０８号公報参照）。しかし、この従来例では回転軸が長尺の場合に隙間を維持するのが困難であり、また地盤の種類により空気の抜け具合が異なり、安定した地盤改良の施工が難しく、場合により地盤中に空気が残留するおそれがある。
【０００３】
このような状況から、確実な空気抜きを行うことのできる工法として、（１）地盤改良材と空気の混合流体を、上面は閉じられ底面のみ開いた中空体の攪拌翼内に吐出させ、地盤改良材は攪拌翼内の原位置土に付着させ、空気は回転軸の内部を通り地上で回収するようにした地盤改良工法が開示されている（特公昭６１−１６８０８号公報参照）。また、（２）攪拌翼より僅かに上方の回転軸に、内部空間が回転軸内の空気回収路に連通している空気回収フードを装着し、この空気回収フードの下方開口に回転軸の昇降に応じて自動的に開閉する蓋を設けた地盤改良装置が開示されている（特公平５−８２９５号公報参照）。更に、（３）地盤改良材を空気で圧送し、水底の地盤中に噴出させ、原位置土と攪拌混合する一方、用済みの空気を水底に設置したフードを経て大気中に放出し、その際フード内に水圧に相当する空気圧をかける水底地盤改良工法が開示されている（特公昭６２−４９４０９号公報参照）。
【０００４】
【発明が解決しようとする課題】
上記した公報例の空気抜きを行うことのできる地盤改良工法等は、いずれも空気の抜け道が作られ、用済みの空気はその抜け道から地上で回収され、誠に都合がよい。しかしながら、従来法により形成された空気の抜け道では、用済み空気の抜けは必ずしも十分ではなかった。すなわち、（１）の公報例では、何らかの事情で中空体の攪拌翼外に出た空気や更に攪拌翼上面に回り込んだ空気は回収し難く、（２）及び（３）の公報例でも空気回収フードから外れた空気は回収し難く、回収されない空気による他の構造物の変位や地盤改良材の吐出抑制などの弊害が生ずるという問題があった。
【０００５】
一方、軟弱地盤改良工法において、回転軸の外周に排土用スクリューを設け、装置の下降（貫入）時に排土用スクリューによって設計上決定される地盤改良材の混入量に対応する量の排土を行い、装置の上昇（引き抜き）時の攪拌翼により回転軸の内部を通して送られた地盤改良材と地盤土壌との攪拌混合を行う工法が知られている（特開昭６２−６８９１７号公報）。この工法では、例え下降時の回転軸の正転による作用で、回転軸外周に沿った空隙が形成されたとしても、装置の上昇（引き抜き）時の回転軸の回転は逆転方向で行われており、この場合、排土用スクリューの空隙部閉塞効果により、空気の抜け道は確実に形成されるものではなかった。
【０００６】
従って、本発明の目的は、地盤改良の深さや地盤の種類に影響されず、回転軸周りに空気の抜け道を確実に形成して、用済み空気を地上に排出して、他の構造物の変位や地盤改良材の吐出抑制などの弊害を防止できる地盤改良工法を提供することにある。
【０００７】
【課題を解決するための手段】
かかる実情において、本発明者らは、上記目的を達成するため鋭意検討を行った結果、回転軸の外周にスパイラル状のスクリューを設け、前記回転軸の回転を貫入時及び引き抜き時共に正転方向で行えば、引き抜き時に用済み空気を前記回転軸外周に沿って確実に地上に排出することができ、他の構造物の変位や地盤改良材の吐出抑制などの弊害を防止できることなどを見出し、本発明を完成するに至った。
【０００８】
すなわち、本発明は、回転軸の下部に放射状に設けた１以上の攪拌翼の回転域の地盤中に、空気と共に粉粒体の地盤改良材を吐出させ、原位置土と攪拌混合し、空気は地上にて回収してなる地盤改良工法において、前記回転軸の外周にスパイラル状のスクリューを設け、該回転軸の回転は貫入時及び引き抜き時共に正転方向で行うことにより、前記空気を前記回転軸外周に沿って排出して地上にて回収することを特徴とする地盤改良工法を提供するものである。かかる構成を採ることにより、回転軸の回転は引き抜き時も正転方向で行うため、回転軸外周に沿って地上に達する空気通路が確実に形成され、用済みの空気を該空気通路を通じて地上にて回収することができる。
【０００９】
【発明の実施の形態】
以下、本発明の実施の形態における地盤改良工法を図１〜図３に基づいて説明する。図１は本発明の実施の形態である地盤改良工法で使用する施工装置を模式的に示す部分図、図２は図１のＡ−Ａ線に沿って見た図、図３は本発明の実施の形態の地盤改良工法の工程を説明する模式図である。本発明の地盤改良工法は、施工装置１０の回転軸１の下方部に放射状に設けた１以上の攪拌翼２の回転域の地盤中に、空気と共に粉粒体の地盤改良材を地盤改良材吐出口４から吐出させ、原位置土と攪拌混合し、空気は地上にて回収してなるものである。回転軸１の外周で、上側攪拌翼２ａの上方にはスパイラル状のスクリュー５が形成されている。スパイラル状のスクリュー５は貫入時には排出土用としての機能を有すると共に、引き抜き時には、貫入時と同じ正転で回転するため、前記用済み空気を排出するための空気の抜け道を形成する機能を有する。
【００１０】
施工装置１０において、回転軸１の外周に形成されるスパイラル状のスクリュー５は、引き抜き時に回転軸１の外周に空気の抜け道が形成されるものであればよく、回転軸１の全長に亘り形成されたものでも、また、回転軸１の全長の一部に形成されたものでもよい。また、攪拌翼２は、回転軸１の下方に複数翼設けられるが、その設置数については特に制限されない。
【００１１】
回転軸１は、施工設備の回転駆動機７に昇降自在、且つ回転自在に吊り下げられ、丸パイプ状をなし、パイプ内には地盤改良材や空気が流通する通路６が通されている。回転軸１の下部には複数の攪拌翼２が設けられ、それらの１の攪拌翼２ａにおける回転方向裏側のつけ根部分の回転軸１の外周に地盤改良材吐出口４が設けられている。また、回転軸の下方に位置する他の攪拌翼２ｂにおける回転方向裏側のつけ根部分の回転軸１の外周に空気吐出口３が設けられている。この地盤改良材吐出口４及び空気吐出口３はいずれも通路６に接続し、この通路６は地上１３の地盤改良材供給設備及び圧縮空気の吐出空気供給設備（不図示）に接続している。回転軸１は丸パイプ状以外に、例えば、角パイプ状であってもよい。施工装置１０は回転駆動機７に接続される回転軸が１本の単軸型であっても、回転軸が２本の２軸型であってもよい。尚、空気吐出口３は地盤改良材吐出口として使用してもよい。図１中、符号２１は掘削用ビットである。
【００１２】
次に、本発明の実施の形態における地盤改良工法を図３を参照して説明する。図３は模式図であり、攪拌翼は図面作成の便宜上回転軸１個当たり１段とし、２軸型施工装置１０を使用する例で説明する。回転駆動機７により回転軸１を正転方向に回転させながら地盤９に貫入させる際、地上１３の吐出空気供給設備から、例えば３〜１０ｋｇ／ｃｍ^２の圧縮空気を図３では省略する空気吐出口３から吐出させ、回転軸１の外周回りの地盤を予めほぐしておく（図３（Ａ））。回転軸１は正転方向に回転するため、スパイラル状のスクリュー５はスクリュー５の回転域にある土１１を地上に排出するように作用する。所定の深度まで到達すると、空気吐出口３からの空気の吐出を停止し、回転軸貫入工程は終了する（図３（Ｂ））。次に、回転軸１を貫入時と同じ正転方向に回転させながら地盤から引き抜く際、地上１３の地盤改良材供給設備から空気輸送さた地盤改良材を地盤改良材吐出口４から吐出し、地盤中に攪拌混合させて改良柱体１２を形成する。その際生じる用済みの空気は、スパイラル状のスクリュー５の正転により形成される回転軸１の外周回りの抜け道１１ａから図３中（Ｃ）の矢印の示す方向に排出され、地上１３にて回収される。なお、回転軸１を地盤に貫入させる際、あるいは貫入及び引き抜き双方の際、地盤改良材吐出口４から地盤改良材を吐出させ、地盤中で攪拌混合させてもよい。
【００１３】
本実施の形態例によれば、回転軸の外周にスパイラル状のスクリューを設けて、回転軸の回転を貫入時及び引き抜き時共に正転方向で行うため、引き抜き時において、回転軸周りに空気の抜け道が確実に形成される。このため、用済み空気をこの空気の抜け道を通って確実に地上に排出することができ、他の構造物の変位や地盤改良材の吐出抑制などの弊害を防止できる。
【００１４】
以上、本発明の実施形態を説明したが、具体的な構成はこれに限定されず、本発明の趣旨を逸脱しない範囲内での変更、追加は本発明の範囲内である。
【００１５】
【発明の効果】
本発明によれば、回転軸の外周にスパイラル状のスクリューを設けて、回転軸の回転を貫入時及び引き抜き時共に正転方向で行うため、引き抜き時において、地盤改良の深さや地盤の種類に影響されることなく、空気の抜け道が確実に形成される。このため、用済み空気をこの空気の抜け道を通って確実に地上に排出することができ、他の構造物の変位や地盤改良材の吐出抑制などの弊害を防止できる。
【図面の簡単な説明】
【図１】本発明の実施の形態である地盤改良工法で使用する施工装置を模式的に示す部分図である。
【図２】図１のＡ−Ａ線に沿って見た図である。
【図３】本発明の実施の形態の地盤改良工法の工程を説明する模式図である。
【符号の説明】
１回転軸
２攪拌翼
３空気吐出口（地盤改良材吐出口）
４地盤改良材吐出口
５スパイラル状スクリュー
６地盤改良材又は吐出空気の通路
７回転駆動機
８原位置土
９地盤
１０施工装置
１１スクリュー回転域にある土
１１ａ空気の抜け道
１２改良柱体
１３地上[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention supplies a ground improvement material of a granular material to the ground, forcibly mixes the soil with the in-situ soil, reacts the soil with the ground improvement material, stabilizes the soil properties, and increases the strength. It relates to the ground improvement method.
[0002]
[Prior art]
Conventionally, air bleeding in this type of ground improvement method involves forming a gap between the outer periphery of the rotating shaft and the ground by making the rotating shaft square or providing fins on the rotating shaft, and using this gap to remove used air. It is guided to the ground, inserted into a rotating shaft, and collected in a hood set on the ground (see Japanese Patent Application Laid-Open No. 57-61108). However, in this conventional example, it is difficult to maintain the gap when the rotating shaft is long, and the degree of air release differs depending on the type of ground, and it is difficult to perform stable ground improvement, and in some cases, the ground Air may remain.
[0003]
Under such circumstances, as a method of assured air release, (1) a ground improvement material and a mixed fluid of air are discharged into a hollow agitating blade that is closed at the top and only open at the bottom to improve the ground. A ground improvement method has been disclosed in which the material is attached to an in situ soil in a stirring blade, and the air passes through the inside of the rotating shaft and is collected on the ground (see Japanese Patent Publication No. 61-16808). (2) An air recovery hood whose internal space communicates with an air recovery passage in the rotary shaft is mounted on the rotary shaft slightly above the stirring blade, and the rotary shaft is raised and lowered at a lower opening of the air recovery hood. (See Japanese Patent Publication No. 5-8295). Further, (3) the ground improvement material is pumped by air, ejected into the ground at the bottom of the water, and mixed with the soil in situ, while the used air is discharged into the atmosphere through a hood installed at the bottom of the water. An underwater ground improvement method for applying air pressure equivalent to water pressure in a hood has been disclosed (see Japanese Patent Publication No. 62-49409).
[0004]
[Problems to be solved by the invention]
In any of the ground improvement methods and the like capable of bleeding air described in the above publications, air vents are formed, and the used air is collected from the vents on the ground, which is very convenient. However, in the air passage formed by the conventional method, the escape of the used air is not always sufficient. That is, in the publication examples of (1), it is difficult to collect air that has come out of the stirring blade of the hollow body for some reason or air that has further circulated to the upper surface of the stirring blade. In the publication examples of (2) and (3), There is a problem that it is difficult to recover the air that has come off from the recovery hood, and the unrecovered air causes adverse effects such as displacement of other structures and suppression of discharge of the ground improvement material.
[0005]
On the other hand, in the soft ground improvement method, an earth removal screw is provided on the outer circumference of the rotating shaft, and the earth removal amount corresponding to the mixed amount of the soil improvement material is determined by the earth removal screw when the equipment is lowered (penetrated). And a method of stirring and mixing the ground improvement material and ground soil sent through the inside of the rotating shaft by a stirring blade when the apparatus is raised (pulled out) (Japanese Patent Application Laid-Open No. 62-68917). . In this method, even if a gap is formed along the outer periphery of the rotating shaft by the action of the forward rotation of the rotating shaft at the time of descent, the rotation of the rotating shaft at the time of ascending (drawing) the device is performed in the reverse direction. In this case, the air passage is not reliably formed due to the effect of closing the gap of the earth discharging screw.
[0006]
Therefore, the object of the present invention is not affected by the depth of ground improvement or the type of ground, and reliably forms an air passage around the rotation axis, discharges used air to the ground, and removes other structures. An object of the present invention is to provide a ground improvement method capable of preventing adverse effects such as displacement and suppression of discharge of a ground improvement material.
[0007]
[Means for Solving the Problems]
Under these circumstances, the present inventors have conducted intensive studies to achieve the above object, and as a result, provided a spiral screw on the outer periphery of the rotating shaft, and set the rotation of the rotating shaft in the forward rotation direction both when penetrating and when pulling out. If it is carried out, it can be found that the spent air can be reliably discharged to the ground along the outer periphery of the rotating shaft at the time of pulling out, and it is possible to prevent adverse effects such as displacement of other structures and suppression of discharge of ground improvement material, etc. The present invention has been completed.
[0008]
That is, the present invention discharges a ground improvement material of a granular material together with air into the ground in the rotation region of one or more stirring blades provided radially below the rotation shaft, and stirs and mixes the soil with the in-situ soil to form air. In the ground improvement method collected on the ground, a spiral screw is provided on the outer periphery of the rotating shaft, and the rotation of the rotating shaft is performed in the normal rotation direction both at the time of penetration and at the time of pulling out, so that the air is discharged. It is an object of the present invention to provide a ground improvement method characterized by discharging along the outer periphery of a rotating shaft and collecting it on the ground. By adopting such a configuration, the rotation of the rotating shaft is performed in the normal rotation direction even at the time of pulling out, so that an air passage reaching the ground along the outer periphery of the rotating shaft is reliably formed, and the used air is transferred to the ground through the air passage. Can be collected.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a ground improvement method according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a partial view schematically showing a construction apparatus used in a ground improvement method according to an embodiment of the present invention, FIG. 2 is a view taken along line AA of FIG. 1, and FIG. It is a schematic diagram explaining the process of the ground improvement method of embodiment. The ground improvement method according to the present invention is a method for improving the ground improvement material of powder and granules together with air in the ground in the rotation region of one or more stirring blades 2 provided radially below the rotation shaft 1 of the construction apparatus 10. The air is discharged from the discharge port 4, mixed with the soil in situ, and the air is collected on the ground. A spiral screw 5 is formed on the outer periphery of the rotating shaft 1 and above the upper stirring blade 2a. The spiral screw 5 has a function of discharging soil when penetrating, and has a function of forming an air passage for discharging the used air because the screw 5 rotates at the same normal rotation as at the time of pulling out when it is pulled out. .
[0010]
In the construction apparatus 10, the spiral screw 5 formed on the outer periphery of the rotating shaft 1 may be any as long as an air passage is formed on the outer periphery of the rotating shaft 1 at the time of pulling out. May be formed, or may be formed on a part of the entire length of the rotating shaft 1. Further, a plurality of stirring blades 2 are provided below the rotating shaft 1, but the number of the stirring blades 2 is not particularly limited.
[0011]
The rotating shaft 1 is hung up and down and rotatably by a rotary driving machine 7 of the construction equipment, has a round pipe shape, and a passage 6 through which ground improvement material and air flow is passed through the pipe. A plurality of agitating blades 2 are provided below the rotating shaft 1, and a ground improvement material discharge port 4 is provided on the outer periphery of the rotating shaft 1 at the base of the one agitating blade 2 a on the back side in the rotating direction. In addition, an air discharge port 3 is provided on the outer periphery of the rotating shaft 1 at the base of the other stirring blade 2b located below the rotating shaft on the back side in the rotating direction. Both the ground improvement material discharge port 4 and the air discharge port 3 are connected to a passage 6, and the passage 6 is connected to a ground improvement material supply facility on the ground 13 and a compressed air discharge air supply facility (not shown). . The rotating shaft 1 may have, for example, a square pipe shape other than the round pipe shape. The construction device 10 may be a single-shaft type having one rotating shaft connected to the rotary driving machine 7 or a two-axis type having two rotating shafts. Note that the air discharge port 3 may be used as a ground improvement material discharge port. In FIG. 1, reference numeral 21 is a bit for excavation.
[0012]
Next, a ground improvement method according to an embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram, and an example will be described in which the stirring blade is one stage per rotating shaft for the convenience of drawing drawing, and the two-shaft type construction apparatus 10 is used. When the rotary shaft 1 is caused to penetrate the ground 9 while rotating the rotary shaft 1 in the normal rotation direction by the rotary driving device 7, compressed air of, for example, 3 to 10 kg / cm ² is discharged from the discharge air supply facility on the ground 13 in FIG. The liquid is discharged from the outlet 3, and the ground around the outer periphery of the rotating shaft 1 is loosened in advance (FIG. 3A). Since the rotating shaft 1 rotates in the normal rotation direction, the spiral screw 5 acts to discharge the soil 11 in the rotation range of the screw 5 to the ground. When the air reaches the predetermined depth, the discharge of the air from the air discharge port 3 is stopped, and the rotation shaft penetration process ends (FIG. 3B). Next, when the rotating shaft 1 is pulled out from the ground while rotating in the same normal rotation direction as when penetrating, the ground improving material pneumatically transported from the ground improving material supply equipment on the ground 13 is discharged from the ground improving material discharge port 4, The improved column 12 is formed by stirring and mixing into the ground. The used air generated at that time is discharged in a direction indicated by an arrow in FIG. 3 (C) from a passageway 11a around the outer periphery of the rotary shaft 1 formed by the normal rotation of the spiral screw 5 and is discharged on the ground 13. Collected. When the rotating shaft 1 penetrates into the ground, or when both penetrating and pulling out, the ground improving material may be discharged from the ground improving material discharge port 4 and agitated and mixed in the ground.
[0013]
According to the present embodiment, a spiral screw is provided on the outer periphery of the rotating shaft, and the rotation of the rotating shaft is performed in the normal rotation direction at both the time of penetration and the time of drawing. A loophole is reliably formed. For this reason, the used air can be reliably discharged to the ground through the passage of the air, and adverse effects such as displacement of other structures and suppression of discharge of the ground improvement material can be prevented.
[0014]
Although the embodiment of the present invention has been described above, the specific configuration is not limited to this, and changes and additions without departing from the spirit of the present invention are within the scope of the present invention.
[0015]
【The invention's effect】
According to the present invention, a spiral screw is provided on the outer periphery of the rotation shaft, and the rotation of the rotation shaft is performed in the normal rotation direction both at the time of penetration and at the time of pulling out. Without being affected, an air passage is reliably formed. For this reason, the used air can be reliably discharged to the ground through the passage of the air, and adverse effects such as displacement of other structures and suppression of discharge of the ground improvement material can be prevented.
[Brief description of the drawings]
FIG. 1 is a partial view schematically showing a construction apparatus used in a ground improvement method according to an embodiment of the present invention.
FIG. 2 is a view taken along the line AA of FIG. 1;
FIG. 3 is a schematic diagram illustrating steps of a ground improvement method according to the embodiment of the present invention.
[Explanation of symbols]
1 rotating shaft 2 stirring blade 3 air discharge port (ground improvement material discharge port)
4 Ground Improvement Material Discharge Port 5 Spiral Screw 6 Ground Improvement Material or Discharge Air Passage 7 Rotary Drive 8 In-situ Soil 9 Ground 10 Construction Device 11 Soil in Screw Rotation Area 11a Air Evacuation Path 12 Improved Column 13 Ground

Claims

The ground improvement material of the granular material is discharged together with air into the ground in the rotation area of one or more stirring blades provided radially below the rotation shaft, and mixed with the in-situ soil, and the air is collected on the ground. In the ground improvement method, a spiral screw is provided on the outer periphery of the rotating shaft, and the rotation of the rotating shaft is performed in the forward rotation direction both at the time of penetration and at the time of extraction, so that the air flows along the outer periphery of the rotating shaft. Ground improvement method characterized by discharging and collecting on the ground.