JP6871714B2 - Reinforcement method for embankment on the back of the abutment - Google Patents

Reinforcement method for embankment on the back of the abutment Download PDF

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JP6871714B2
JP6871714B2 JP2016209142A JP2016209142A JP6871714B2 JP 6871714 B2 JP6871714 B2 JP 6871714B2 JP 2016209142 A JP2016209142 A JP 2016209142A JP 2016209142 A JP2016209142 A JP 2016209142A JP 6871714 B2 JP6871714 B2 JP 6871714B2
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abutment
embankment
ground improvement
improvement body
ground
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JP2018071094A (en
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松田　好史
好史 松田
昌隆 藤井
昌隆 藤井
山田　孝弘
孝弘 山田
雅仁 藤原
雅仁 藤原
手塚　広明
広明 手塚
崇寛 山内
崇寛 山内
敦士 川西
敦士 川西
光貴 太田
光貴 太田
勝義 三浦
勝義 三浦
保彦 土井
保彦 土井
隆典 青木葉
隆典 青木葉
哲弥 春名
哲弥 春名
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Maeda Corp
West Japan Railway Co
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West Japan Railway Co
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Description

本発明は、橋台と盛土の接続部である橋台背面盛土の補強工法に関するものであり、詳細には、橋台背面盛土中に透水性を有する地盤改良体を形成することにより、盛土の沈下抑制を行う工法に関するものである。 The present invention relates to a method for reinforcing the abutment back embankment, which is a connection between the abutment and the embankment. Specifically, the subsidence of the embankment is suppressed by forming a water-permeable ground improvement body in the abutment back embankment. It is about the construction method to be carried out.

橋台背面盛土は、施工時の締め固め不足、盛土材の経年劣化、降雨による盛土材の流出等を原因とした地盤の緩み現象により、地盤の沈下や陥没を生じやすい。また、地震発生時には、橋台と背面盛土との相対変位が顕著となり、列車等の走行性を低下させることがある。このような現象を解消するため、盛土中にセメントミルク等による薬液注入を行う対策が実施されている。 The embankment on the back of the abutment is prone to land subsidence and depression due to the loosening phenomenon of the ground caused by insufficient compaction during construction, aging deterioration of the embankment material, and outflow of the embankment material due to rainfall. In addition, when an earthquake occurs, the relative displacement between the pier and the back embankment becomes remarkable, which may reduce the runnability of trains and the like. In order to eliminate such a phenomenon, measures have been taken to inject a chemical solution such as cement milk into the embankment.

橋台背面盛土を補強するための技術として、例えば、特許文献１、特許文献２、特許文献３に記載された技術がある。特許文献１に記載された技術は、鉄道、道路の橋台付近で、鉄道、道路の仮線を設置して橋台の通行を中断した後に、橋台の背面盛土を適当な距離だけ除去し、その除去空間に、橋台背面と間隔を開けて補強盛土を構築する。そして、橋台背面と補強盛土前面との間に背面コンクリートを打設して橋台と補強盛土を一体化することにより、橋台と背面盛土を補強することができるとしている。 As a technique for reinforcing the embankment on the back surface of the abutment, for example, there are techniques described in Patent Document 1, Patent Document 2, and Patent Document 3. The technique described in Patent Document 1 removes the back embankment of the abutment by an appropriate distance after installing a temporary line of the railway or road near the abutment of the railway or road to interrupt the passage of the abutment. A reinforced embankment will be constructed in the space at intervals from the back of the abutment. Then, by placing back concrete between the back of the abutment and the front of the reinforcing embankment to integrate the abutment and the reinforcing embankment, the abutment and the back embankment can be reinforced.

特許文献２に記載された技術は、橋台の前面から背面盛土に向けて、橋桁の軸方向とほぼ平行に棒状補強材を打設する。さらに、盛土の法面から橋桁の軸方向と直交する方向に棒状補強材を打設することにより、鉄道や車両の交通状態を維持したまま、橋台と橋台の背面の盛土とを補強することができるとしている。 In the technique described in Patent Document 2, a rod-shaped reinforcing material is placed from the front surface of the abutment toward the back embankment substantially parallel to the axial direction of the bridge girder. Furthermore, by placing a rod-shaped reinforcing material in the direction orthogonal to the axial direction of the bridge girder from the slope of the embankment, it is possible to reinforce the abutment and the embankment on the back of the abutment while maintaining the traffic conditions of railways and vehicles. It is said that it can be done.

特許文献３に記載された技術は、鉄道用の橋の抗土圧橋台の背面盛土に対して、軌道の両側に、軌道方向に沿って盛土を上下に貫く複数の盛土改良体を所定間隔で配列して軌道併設改良体群を造成する。そして、盛土改良体の頭部を連結体で一体に剛結する。軌道併設改良体群が軌道に沿って生じる地震時土圧を分断し、さらに背面盛土と盛土改良体との摩擦により地震時土圧を減衰させることで地震時土圧を低減する。これにより、相対的に抗土圧橋台自体を補強しなくとも、橋の耐震性を向上させることができるとしている。 In the technique described in Patent Document 3, a plurality of embankment improved bodies penetrating the embankment up and down along the track direction are provided at predetermined intervals on both sides of the track with respect to the back embankment of the anti-earth pressure abutment of a railway bridge. Arrange them to create an improved group with tracks. Then, the head of the embankment improvement body is integrally rigidly connected by the connecting body. The group of improved bodies attached to the track divides the earth pressure during an earthquake that occurs along the track, and further reduces the earth pressure during an earthquake by the friction between the back embankment and the improved embankment. As a result, the seismic resistance of the bridge can be improved without relatively reinforcing the earth pressure abutment itself.

特開２０１１−２４７０６０号公報Japanese Unexamined Patent Publication No. 2011-247060 特開２０１１−２４７０６４号公報Japanese Unexamined Patent Publication No. 2011-247064 特開２０１５−５５０８２号公報JP-A-2015-55082

しかし、上述した従来の技術では、未だ解決されていない種々の課題が存在した。例えば、セメントミルク等による薬液注入による対策では、列車軌道への影響を考慮し、通常の圧力より低い圧力で薬液注入を実施する必要がある。このため、地盤中の緩み領域に対して効果的な薬液注入が難しく、品質の信頼性が確保できない場合もあった。 However, there are various problems that have not yet been solved by the above-mentioned conventional techniques. For example, as a countermeasure by injecting a chemical solution with cement milk or the like, it is necessary to inject the chemical solution at a pressure lower than the normal pressure in consideration of the influence on the train track. For this reason, it is difficult to effectively inject the chemical solution into the loosened area in the ground, and there are cases where the reliability of quality cannot be ensured.

また、地盤中の緩み領域がどの箇所に存在するか不明であるため、薬液注入では数多くの施工本数となる場合が多い。このため、地盤の緩み領域対策としては、地震時及び列車荷重にも耐えうる一定強度の透水性を有した地盤改良体を形成することが有効である。 In addition, since it is unclear where the loosened area in the ground exists, the number of constructions is often large when injecting chemicals. Therefore, as a countermeasure against the loosened area of the ground, it is effective to form a ground improvement body having a constant strength of water permeability that can withstand an earthquake and a train load.

例えば、透水性を有する地盤改良体を形成するには、界面活性剤を主成分とした起泡剤を使用して、地盤改良体内に微細な連続気泡を形成することが考えられる。現在、気泡の使用は建設分野において、その軽量性、流動性、自立性という特性から、シールド工事や盛土工事、地盤改良工事等、様々な分野で実施されている。 For example, in order to form a ground improvement body having water permeability, it is conceivable to use a foaming agent containing a surfactant as a main component to form fine open cells in the ground improvement body. Currently, the use of air bubbles is carried out in various fields such as shield work, embankment work, and ground improvement work due to their characteristics of lightness, fluidity, and independence in the construction field.

しかし、一般的な起泡剤では、主成分としてアニオン系界面活性剤が使用されており、優れた起泡力を有する反面、疎水性のカルシウム塩が生成されるため、硬化したコンクリートは不透水性となってしまい、透水性を有する地盤改良体を形成するという目的を達成することができない場合が多い。 However, in general foaming agents, anionic surfactants are used as the main component, and while they have excellent foaming power, hydrophobic calcium salts are generated, so hardened concrete is impermeable to water. In many cases, it becomes sexual and the purpose of forming a ground-improved body having water permeability cannot be achieved.

さらに、先行技術文献として挙げた各先行技術では、施工条件が限定されたり、施工に手間が掛かったりする等、さらなる工夫を行う余地がある。 Further, in each prior art listed as the prior art document, there is room for further ingenuity, such as limited construction conditions and laborious construction.

本発明は、上述した事情に鑑み提案されたもので、橋台背面盛土中に微細な連続気泡を混入することにより透水性を有する地盤改良体を形成し、橋台背面盛土を確実かつ容易に補強することが可能な工法を提供することを目的とする。 The present invention has been proposed in view of the above circumstances. By mixing fine open cells into the abutment back embankment, a water-permeable ground improvement body is formed to reliably and easily reinforce the abutment back embankment. The purpose is to provide a construction method that is possible.

本発明に係る橋台背面盛土の補強工法は、上述した目的を達成するため、以下の特徴点を有している。すなわち、本発明に係る橋台背面盛土の補強工法は、改良対象となる橋台背面盛土中に透水性を有する地盤改良体を形成して橋台背面盛土の沈下抑制を行う工法である。 The method for reinforcing the back embankment of the abutment according to the present invention has the following features in order to achieve the above-mentioned object. That is, the abutment back embankment reinforcement method according to the present invention is a method of forming a water-permeable ground improvement body in the abutment back embankment to be improved to suppress the subsidence of the abutment back embankment.

そして、橋台背面盛土中に、ノニオン系界面活性剤を主成分とした起泡剤を用いて生成した気泡とセメントミルクの混合物であるエアミルクを注入して原地盤と撹拌混合して、微細気泡が連続してみずみちが形成された透水性を有する地盤改良体を構築することを特徴とするものである。Then, air milk, which is a mixture of air bubbles and cement milk generated by using a foaming agent containing a nonionic surfactant as a main component, is injected into the embankment on the back of the abutment and mixed with the original ground by stirring to generate fine bubbles. It is characterized by constructing a ground improvement body having water permeability in which water bubbles are continuously formed.

また、上述した橋台背面盛土の補強工法において、エアミルクを注入して原地盤と撹拌混合する機械撹拌装置は、撹拌ロッドの外周面にスクリューからなる排土機構を備えていることが好ましい。 Further, in the above-mentioned reinforcement method for embankment on the back surface of the abutment, it is preferable that the mechanical stirring device that injects air milk and stirs and mixes with the original ground is provided with a soil discharging mechanism composed of a screw on the outer peripheral surface of the stirring rod.

また、上述した橋台背面盛土の補強工法において、流動化剤や早期強度発現剤（例えば、早強セメント、早期凝結剤）等のフロー値調整剤を添加することにより、原地盤とエアミルクの混合物のフロー値を目標値２００ｍｍのプラスマイナス５ｍｍ以内に調整することが好ましい。 Further, in the above-mentioned reinforcement method for the back embankment of the abutment, by adding a flow value adjusting agent such as a fluidizing agent and an early strength developing agent (for example, early strength cement, early coagulant), a mixture of the original ground and air milk is added. It is preferable to adjust the flow value within plus or minus 5 mm of the target value of 200 mm.

また、上述した橋台背面盛土の補強工法において、透水性を有する地盤改良体の側方に、高圧噴射撹拌工法を用いて第２の地盤改良体を形成することが可能である。透水性を有する地盤改良体の側方とは、透水性を有する地盤改良体の一側、透水性を有する地盤改良体を挟んで両側のことであり、透水性を有する地盤改良体の一側に第２の地盤改良体を形成し、あるいは透水性を有する地盤改良体を挟んで、その両側に第２の地盤改良体を形成する。 Further, in the above-mentioned reinforcement method for the back embankment of the abutment, it is possible to form a second ground improvement body on the side of the water-permeable ground improvement body by using the high-pressure injection stirring method. The sides of the water-permeable ground improvement body are one side of the water-permeable ground improvement body and both sides of the water-permeable ground improvement body, and one side of the water-permeable ground improvement body. A second ground improvement body is formed on the surface, or a second ground improvement body is formed on both sides of the ground improvement body having water permeability.

本発明に係る橋台背面盛土の補強工法によれば、原地盤と、気泡及びセメントミルクの混合物からなるエアミルクを混合撹拌することで、耐震性を有するとともに透水性を有する地盤改良体を形成することができる。透水性を有する地盤改良体内に存在する気泡は、連続気泡となっており、「みずみち」を形成するため、透水性を発揮することが可能となる。 According to the abutment back embankment reinforcement method according to the present invention, a ground improvement body having earthquake resistance and water permeability is formed by mixing and stirring the original ground and air milk composed of a mixture of air bubbles and cement milk. Can be done. Ground improvement having water permeability The bubbles existing in the body are open cells and form "water", so that water permeability can be exhibited.

また、ノニオン系界面活性剤を主成分とした起泡剤を用いて気泡を生成することにより、疎水性のカルシウム塩が生成されることがなく、硬化したコンクリートは透水性を有することになる。 Further, by generating bubbles using a foaming agent containing a nonionic surfactant as a main component, hydrophobic calcium salt is not generated, and the hardened concrete has water permeability.

また、エアミルクを注入して原地盤と撹拌混合する機械撹拌装置において、撹拌ロッドの外周面にスクリューからなる排土機構を備えることにより、橋台背面盛土中に撹拌ロッドを貫入する際の抵抗が少なくなり、１．０ｔ未満の小型機械であっても、斜め施工や水平施工が可能となり、太径の透水性を有する地盤改良体を構築することが可能となる。また、貫入時の排土を容易に行うことができ、原地盤とエアミルクの混合状態が安定し、良質な透水性を有する地盤改良体を形成することが可能となる。 In addition, in a mechanical agitator that injects air milk and agitates and mixes with the ground, by providing a soil discharge mechanism consisting of screws on the outer peripheral surface of the agitation rod, resistance when the agitation rod penetrates into the embankment on the back of the abutment is reduced. Therefore, even with a small machine of less than 1.0 ton, diagonal construction and horizontal construction are possible, and it is possible to construct a ground improvement body having a large diameter and water permeability. In addition, soil can be easily discharged at the time of intrusion, the mixed state of the original ground and air milk is stable, and a ground improvement body having good water permeability can be formed.

ところで、一般的なベントナイト泥水のような泥水削孔の場合には、斜め施工および水平施工を行うと、坑口より泥水が漏出して、改良範囲内が一時空洞化し、地盤が沈下することが考えられる。これに対して、撹拌ロッドの外周面にスクリューからなる排土機構を備えることにより、撹拌ロッドを貫入する際に、一時的に橋台背面盛土中に空洞が生じることを防止して、地盤の変位を抑制した施工が可能となる。 By the way, in the case of muddy water drilling such as general bentonite muddy water, if diagonal construction and horizontal construction are performed, muddy water leaks from the wellhead, the improvement area is temporarily hollowed out, and the ground may sink. Be done. On the other hand, by providing a soil discharge mechanism consisting of a screw on the outer peripheral surface of the stirring rod, it is possible to prevent a cavity from being temporarily formed in the embankment on the back surface of the abutment when the stirring rod is penetrated, and the displacement of the ground. It is possible to carry out the construction while suppressing the above.

また、流動化剤や早期強度発現剤（例えば、早強セメント、早期凝結剤）等のフロー値調整剤を添加して、フロー値を目標値の２００プラスマイナス５ｍｍ以内に設定することで、異なる地盤条件であっても安定した透水性を有する地盤改良体を形成することが可能となる。 Further, it differs by adding a flow value adjusting agent such as a fluidizing agent or an early strength developing agent (for example, an early strength cement or an early coagulant) and setting the flow value within 200 plus or minus 5 mm of the target value. It is possible to form a ground improvement body having stable water permeability even under ground conditions.

また、透水性を有する地盤改良体の側方に、高圧噴射撹拌工法を用いて第２の地盤改良体を形成することにより、透水性を有する地盤改良体により排水を行って、橋台背面盛土の補強をより一層確実に行うことができる。 In addition, by forming a second ground improvement body on the side of the water-permeable ground improvement body using the high-pressure injection stirring method, drainage is performed by the water-permeable ground improvement body, and the abutment back embankment is filled. Reinforcement can be performed more reliably.

本発明の実施形態に係る橋台背面盛土の補強工法を説明する側面図。The side view explaining the reinforcement construction method of the back embankment of the abutment which concerns on embodiment of this invention. 本発明の実施形態に係る橋台背面盛土の補強工法の施工手順を示す模式図。The schematic diagram which shows the construction procedure of the reinforcement construction method of the back embankment of the abutment which concerns on embodiment of this invention. 本発明の実施形態に係る橋台背面盛土の補強工法により形成した透水性を有する地盤改良体と、第２の地盤改良体とを正面から見た状態の断面模式図。FIG. 3 is a schematic cross-sectional view of a water-permeable ground improvement body formed by the abutment back embankment reinforcement method according to the embodiment of the present invention and a second ground improvement body as viewed from the front.

以下、図面を参照して、本発明の実施形態に係る橋台背面盛土の補強工法を説明する。図１〜図３は本発明の実施形態に係る橋台背面盛土の補強工法を説明するもので、図１は側面図、図２は施工手順を示す模式図、図３は透水性を有する地盤改良体及び第２の地盤改良体の断面模式図である。 Hereinafter, a method for reinforcing the back embankment of the abutment according to the embodiment of the present invention will be described with reference to the drawings. 1 to 3 show a method for reinforcing the back embankment of the abutment according to the embodiment of the present invention. FIG. 1 is a side view, FIG. 2 is a schematic view showing a construction procedure, and FIG. 3 is a ground improvement having water permeability. It is sectional drawing of the body and the 2nd ground improvement body.

＜橋台背面盛土の補強工法の概要＞
本発明の実施形態に係る橋台背面盛土の補強工法は、機械撹拌工法を用いて橋台背面盛土８０の内部に透水性を有する地盤改良体７０を形成するものであり、機械撹拌装置１０を用いて、橋台背面盛土８０中に気泡とセメントミルクの混合物であるエアミルクを注入して原地盤と撹拌混合する。橋台背面盛土８０中に気泡とエアミルクを注入して、原地盤と撹拌混合すると、微細気泡が連続して「みずみち」が形成された地盤改良体７０を構築することができ、この地盤改良体７０は透水性を有することになる。 <Outline of reinforcement method for embankment on the back of the pier>
The method for reinforcing the abutment back embankment according to the embodiment of the present invention is to form a ground improvement body 70 having water permeability inside the abutment back embankment 80 by using the mechanical agitation method, and the mechanical agitation device 10 is used. , Air milk, which is a mixture of air bubbles and cement milk, is injected into the abutment back embankment 80 and mixed with the original ground by stirring. By injecting air bubbles and air milk into the abutment back embankment 80 and stirring and mixing with the original ground, it is possible to construct a ground improvement body 70 in which fine bubbles are continuously formed to form "mizumichi". 70 will have water permeability.

＜施工機械の設置＞
橋台背面盛土８０の法面の傾斜角度に応じて、足場６０を設置する必要がある。すなわち、機械撹拌装置１０が自走できる傾斜角度である場合には、そのまま地盤改良体７０の形成を行うことができるが、機械撹拌装置１０が自走できない傾斜角度である場合には、機械撹拌装置１０を含む施工機器を設置するための足場６０を施工する。この場合には、例えば、図１に示すように、橋台背面盛土８０の側方に、単管パイプ等を用いて足場６０を組み立てる。また、本実施形態では、一般的な機械撹拌工法で使用する施工機器よりも小型の施工機器（例えば、機械重量１．０ｔ程度）を用いるため、それに見合った強度を有していればよい。 <Installation of construction machine>
It is necessary to install the scaffolding 60 according to the inclination angle of the slope of the embankment 80 on the back of the abutment. That is, if the mechanical stirring device 10 has an inclination angle that allows it to run on its own, the ground improvement body 70 can be formed as it is, but if the mechanical stirring device 10 has an inclination angle that does not allow it to run on its own, mechanical stirring can be performed. A scaffold 60 for installing construction equipment including the device 10 is constructed. In this case, for example, as shown in FIG. 1, a scaffold 60 is assembled on the side of the embankment 80 on the back surface of the abutment using a single pipe or the like. Further, in the present embodiment, since the construction equipment smaller than the construction equipment used in the general mechanical stirring method (for example, the machine weight is about 1.0 ton) is used, it is sufficient that the strength is commensurate with the construction equipment.

足場６０上には、詳細には図示しないが、地盤改良体７０を形成するための施工機器として、小型の機械撹拌装置１０、電源装置、コンプレッサ、硬化剤や水等を送出するためのポンプ等を設置する。なお、図１に示す例では、橋台背面盛土８０に対して、撹拌ロッド２０を斜め下向きに貫入するようになっているが、撹拌ロッド２０の貫入方向は、下向きであってもよいし、水平方向であってもよい。 Although not shown in detail on the scaffold 60, as construction equipment for forming the ground improvement body 70, a small mechanical agitator 10, a power supply device, a compressor, a pump for delivering a hardening agent, water, etc. To install. In the example shown in FIG. 1, the stirring rod 20 penetrates diagonally downward with respect to the embankment 80 on the back surface of the abutment, but the penetration direction of the stirring rod 20 may be downward or horizontal. It may be a direction.

＜機械撹拌装置＞
機械撹拌装置１０は、地盤改良等に使用されている一般的な装置であり、本実施形態では、機械重量が１．０ｔ程度の小型の装置を使用している。この機械撹拌装置１０は、詳細には図示しないが、本体４０と、撹拌ロッド２０と、撹拌ロッド２０の先端部に設けた攪拌翼３０とを備えており、撹拌ロッド２０の先端部からエアミルク等を噴出するようになっている。また、撹拌ロッド２０の外周面には、スクリューからなる排土機構５０を設けてある。 <Mechanical stirrer>
The mechanical stirring device 10 is a general device used for ground improvement and the like, and in the present embodiment, a small device having a mechanical weight of about 1.0 ton is used. Although not shown in detail, the mechanical stirring device 10 includes a main body 40, a stirring rod 20, and a stirring blade 30 provided at the tip of the stirring rod 20, and air milk or the like is provided from the tip of the stirring rod 20. Is designed to spout. Further, a soil discharging mechanism 50 made of a screw is provided on the outer peripheral surface of the stirring rod 20.

＜地盤改良体の形成＞
本実施形態では、図２に示すように、所定の高さにおいて、橋台背面盛土８０中に撹拌ロッド２０を斜め下向きに貫入して空堀を行い、所定深さまで撹拌ロッド２０を貫入したら（ａ）〜（ｃ）、撹拌ロッド２０（攪拌翼３０）の先端部からエアミルク（気泡及びセメントミルクの混合物）を吐出させ、攪拌翼３０を回転させて原地盤と混合撹拌しながら撹拌ロッド２０を引き抜いて地盤改良体７０を形成する（ｄ）。 <Formation of ground improvement body>
In the present embodiment, as shown in FIG. 2, the stirring rod 20 is penetrated diagonally downward into the abutment back filling 80 at a predetermined height to perform an empty moat, and the stirring rod 20 is penetrated to a predetermined depth (a). ~ (C), Air milk (mixture of air bubbles and cement milk) is discharged from the tip of the stirring rod 20 (stirring blade 30), the stirring blade 30 is rotated, and the stirring rod 20 is pulled out while mixing and stirring with the original ground. The ground improvement body 70 is formed (d).

続いて、排泥を行いながら撹拌ロッド２０を貫入し、再度、撹拌ロッド２０の先端部からエアミルク（気泡及びセメントミルクの混合物）を吐出させ、攪拌翼３０を回転させて原地盤と混合撹拌しながら撹拌ロッド２０を引き抜く（ｅ）〜（ｆ）。さらに、撹拌を継続しながら撹拌ロッド２０の貫入と引き抜きを実施し、透水性を有する地盤改良体７０を形成する（ｇ）〜（ｈ）。なお、改良対象となる橋台背面盛土８０の性状に応じて、撹拌ロッド２０の貫入及び引き抜きによる混合撹拌の回数を調整すればよい。 Subsequently, the stirring rod 20 is penetrated while draining mud, air milk (a mixture of air bubbles and cement milk) is discharged again from the tip of the stirring rod 20, and the stirring blade 30 is rotated to mix and stir with the original ground. While pulling out the stirring rod 20, (e) to (f). Further, the stirring rod 20 is penetrated and pulled out while continuing stirring to form the ground improvement body 70 having water permeability (g) to (h). The number of times of mixing and stirring by penetrating and pulling out the stirring rod 20 may be adjusted according to the properties of the embankment 80 on the back surface of the abutment to be improved.

＜エアミルク＞
本実施形態で、橋台背面盛土８０中に注入するエアミルクは、気泡とセメントミルクの混合物であり、気泡はノニオン系界面活性剤を主成分とした起泡剤を用いて生成する。本実施形態で使用するエアミルクの比重は、一般的な地盤改良工法で使用するセメントミルクの比重（ρ＝１．６０ｇ／ｃｍ3）と比較して小さい（ρ＝０．５７ｇ／ｃｍ3、空気量７０％）。したがって，一般的な斜面補強工法のような施工手順で施工した場合には，エアミルクが土砂と混合される前に地上に排出されることが懸念される。そこで、撹拌ロッド２０の貫入時にエアミルクの吐出は行わずに、撹拌ロッド２０の引き抜き時にエアミルクの吐出を行いながら撹拌を行うことで土（原地盤）との一体化を図ることが可能となる。 <Air milk>
In the present embodiment, the air milk to be injected into the embankment 80 on the back of the abutment is a mixture of air bubbles and cement milk, and the air bubbles are generated by using a foaming agent containing a nonionic surfactant as a main component. The specific gravity of Eamiruku used in this embodiment, common ground improvement method in the cement milk to be used a specific gravity (ρ = 1.60g / cm 3) smaller than the (ρ = 0.57g / cm 3, air Amount 70%). Therefore, there is a concern that air milk will be discharged to the ground before it is mixed with earth and sand when it is constructed by a construction procedure such as a general slope reinforcement method. Therefore, it is possible to integrate with the soil (original ground) by stirring while discharging the air milk when the stirring rod 20 is pulled out, without discharging the air milk when the stirring rod 20 is penetrated.

＜排土機構＞
例えば、透水性の地盤改良体７０（１００％）に対して、土（原地盤）とセメントミルクと気泡との割合を、それぞれ２０％、２５％、５５％とした場合に、原地盤の土を８０％（１００％−２０％）除去しなければならない。そこで、撹拌ロッド２０の外周面には、スクリューからなる排土機構５０を設けてある。 <Soil removal mechanism>
For example, when the ratios of soil (original ground), cement milk, and air bubbles to the permeable ground improvement body 70 (100%) are 20%, 25%, and 55%, respectively, the soil of the original ground. Must be removed by 80% (100% -20%). Therefore, a soil removal mechanism 50 made of a screw is provided on the outer peripheral surface of the stirring rod 20.

このような排土機構５０を設けることにより、貫入時の排土を容易に行うことができるので、撹拌ロッド２０の貫入抵抗を減少させ、撹拌ロッド２０を貫入する際に生じる空洞の発生を防止して、地盤の変位を抑制している。 By providing such a soil discharge mechanism 50, soil can be easily discharged at the time of penetration, so that the penetration resistance of the stirring rod 20 is reduced and the generation of cavities generated when the stirring rod 20 is penetrated is prevented. Therefore, the displacement of the ground is suppressed.

＜目標フロー値＞
本実施形態では、施工の際に材料分離を生じず、安定した透水性の品質を確保する必要があるため、原地盤とエアミルクの混合物のフロー値の目標値を２００ｍｍとし、プラスマイナス５ｍｍの範囲を許容値として設定した。この目標値を達成するため、流動化剤や早期強度発現剤（例えば、早強セメント、早期凝結剤）等のフロー値調整剤を添加している。本実施形態の地盤改良体７０では、フロー値を適切に管理することにより、透水係数が１．０×１０-2ｃｍ／ｓｅｃ程度となり、有効な透水性を確保することができた。 <Target flow value>
In this embodiment, since it is necessary to ensure stable water permeability without causing material separation during construction, the target value of the flow value of the mixture of the raw ground and air milk is set to 200 mm, and the range is plus or minus 5 mm. Was set as the allowable value. In order to achieve this target value, a flow value adjusting agent such as a fluidizing agent and an early strength developing agent (for example, early strength cement and early coagulant) is added. In the ground improvement body 70 of the present embodiment, the water permeability coefficient was about 1.0 × 10-2 cm / sec by appropriately managing the flow value, and effective water permeability could be ensured.

＜第２の地盤改良体＞
図３に示すように、上述した工程により形成した透水性を有する地盤改良体７０の側方に、高圧噴射撹拌工法を用いて第２の地盤改良体９０を形成してもよい。図３に示す例では、透水性を有する地盤改良体７０を挟んで、その両側に第２の地盤改良体９０を形成しているが、透水性を有する地盤改良体７０の一側にのみ第２の地盤改良体９０を形成してもよい。第２の地盤改良体９０を形成することにより、橋台背面盛土８０の補強が確実なものとなるとともに、透水性を有する地盤改良体７０により橋台背面盛土８０から排水を行うことができる。なお、橋台背面盛土８０からの排水を確実なものとするため、透水性を有する地盤改良体７０は橋台背面盛土８０の底部まで達している。 <Second ground improvement body>
As shown in FIG. 3, a second ground improvement body 90 may be formed on the side of the water-permeable ground improvement body 70 formed by the above-mentioned steps by using a high-pressure jet stirring method. In the example shown in FIG. 3, the second ground improvement body 90 is formed on both sides of the water-permeable ground improvement body 70, but the second ground improvement body 70 is formed only on one side of the water-permeable ground improvement body 70. The ground improvement body 90 of 2 may be formed. By forming the second ground improvement body 90, the reinforcement of the abutment back embankment 80 is ensured, and the water-permeable ground improvement body 70 can drain water from the abutment back embankment 80. The water-permeable ground improvement body 70 reaches the bottom of the abutment back embankment 80 in order to ensure drainage from the abutment back embankment 80.

＜本発明の有利な作用効果＞
橋台背面盛土８０が鉄道軌道の付帯設備である場合に、鉄道の運行に影響を与えずに既設の橋台背面盛土８０の地盤改良を行うためには、周辺地盤の変状に対する影響が小さく、軌道へ影響を及ぼさない工法であることが前提となる。また、軌道上からの施工であると夜間施工となり、工期上の制約が大きい。そのため、昼間施工が可能であり、かつ安定した地盤改良体７０の品質が得られる工法を採用する必要がある。本発明では、橋台背面盛土８０の軌道上からではなく、側面からの施工が可能な機械撹拌工法を採用し、透水性を有する地盤改良体７０を形成しており、特に鉄道の橋台背面盛土８０の地盤改良を行う際に、本発明に特有の優れた作用効果を奏する。 <Advantageous action and effect of the present invention>
When the abutment back embankment 80 is ancillary equipment of the railway track, in order to improve the ground of the existing abutment back embankment 80 without affecting the operation of the railway, the influence on the deformation of the surrounding ground is small and the track It is assumed that the construction method does not affect the area. In addition, if the construction is done from the track, it will be done at night, and there are many restrictions on the construction period. Therefore, it is necessary to adopt a construction method that enables daytime construction and can obtain stable quality of the ground improvement body 70. In the present invention, a mechanical agitation method that allows construction from the side surface of the abutment back embankment 80 rather than from the track is adopted to form a ground improvement body 70 having water permeability, and particularly, the abutment back embankment 80 of a railway is formed. When the ground is improved, the excellent action and effect peculiar to the present invention are exhibited.

１０ 機械撹拌装置
２０ 撹拌ロッド
３０ 攪拌翼
４０ 本体
５０ 排土機構
６０ 足場
７０ 地盤改良体
８０ 橋台背面盛土
９０ 第２の地盤改良体 10 Mechanical stirrer 20 Stirrer rod 30 Stirrer blade 40 Main body 50 Soil removal mechanism 60 Scaffolding 70 Ground improvement body 80 Abutment back embankment 90 Second ground improvement body

Claims (4)

改良対象となる橋台背面盛土中に透水性を有する地盤改良体を形成して橋台背面盛土の沈下抑制を行う工法であって、
前記橋台背面盛土中に、ノニオン系界面活性剤を主成分とした起泡剤を用いて生成した気泡とセメントミルクの混合物であるエアミルクを注入して原地盤と撹拌混合して、微細気泡が連続してみずみちが形成された透水性を有する地盤改良体を構築することを特徴とする橋台背面盛土の補強工法。 It is a construction method that suppresses the subsidence of the abutment back embankment by forming a ground improvement body with water permeability in the abutment back embankment to be improved.
Air milk, which is a mixture of air bubbles and cement milk generated using a foaming agent containing a nonionic surfactant as a main component , is injected into the embankment on the back of the abutment and mixed with the original ground by stirring to create continuous fine bubbles. A method of reinforcing the embankment on the back of the abutment, which is characterized by constructing a water-permeable ground improvement body in which water is formed. 前記エアミルクを注入して原地盤と撹拌混合する機械撹拌装置は、撹拌ロッドの外周面にスクリューからなる排土機構を備えていることを特徴とする請求項１に記載の橋台背面盛土の補強工法。 The method for reinforcing the back embankment of an abutment according to claim 1 , wherein the mechanical agitator for injecting air milk and agitating and mixing with the original ground is provided with an earth removal mechanism including a screw on the outer peripheral surface of the agitation rod. .. フロー値調整剤を添加することにより、前記原地盤と前記エアミルクの混合物のフロー値を目標値２００ｍｍのプラスマイナス５ｍｍ以内に調整することを特徴とする請求項１または２に記載の橋台背面盛土の補強工法。 The abutment back embankment according to claim 1 or 2 , wherein the flow value of the mixture of the original ground and the air milk is adjusted within plus or minus 5 mm of a target value of 200 mm by adding a flow value adjusting agent. Reinforcement method. 前記透水性を有する地盤改良体の側方に、高圧噴射撹拌工法を用いて第２の地盤改良体を形成することを特徴とする請求項１〜３のいずれか１項に記載の橋台背面盛土の補強工法。 The abutment back embankment according to any one of claims 1 to 3, wherein a second ground improvement body is formed on the side of the water-permeable ground improvement body by using a high-pressure injection stirring method. Reinforcement method.
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