JP2019027134A - Ground improvement method - Google Patents

Ground improvement method Download PDF

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JP2019027134A
JP2019027134A JP2017147451A JP2017147451A JP2019027134A JP 2019027134 A JP2019027134 A JP 2019027134A JP 2017147451 A JP2017147451 A JP 2017147451A JP 2017147451 A JP2017147451 A JP 2017147451A JP 2019027134 A JP2019027134 A JP 2019027134A
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ground
cavity
injection material
injection
loose
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JP6895842B2 (en
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裕泰 石井
Hiroyasu Ishii
裕泰 石井
青木　智幸
Tomoyuki Aoki
智幸 青木
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Taisei Corp
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Abstract

To provide a ground improvement method capable of effectively performing a treatment to a subsoil in which both of a weak ground and an underground cavity exist.SOLUTION: A ground improvement method for a subsoil including an underground cavity Gformed underground and a weak sedimentary layer Gexisting below the underground cavity Gcomprises: a piping work of arranging an outer pipe 2 penetrating the underground cavity Gand reaching the inside of the weak sedimentary layer Gand an inner pipe 3 inserted into the outer pipe 2; an outer pipe lifting work of lifting up the outer pipe 2 and injecting a cavity injection material 6 with plasticity into the underground cavity Gutilizing the outer pipe 2; and a ground injection work of injecting a ground injection material 7 with higher flowability than that of the cavity injection material 6 through the inner pipe 3 into the weak sedimentary layer G.SELECTED DRAWING: Figure 3

Description

本発明は、地盤改良方法に関する。   The present invention relates to a ground improvement method.

土砂等が緩く堆積した軟弱地盤（緩い堆積層）や地中に存在する空洞（以下、「地中空洞」という）は、建設工事における安全性や、工事完了後の健全性を確保するために、適切に処置しておく必要がある。ここで、地中空洞には、防空壕等の地下壕跡、採石や採鉱等の地下採掘場跡等の人工の空洞や、岩盤などの安定した地層や構造物の下の軟弱地盤が何らかの原因により沈下するなどして自然に形成された空洞等がある。また、緩く堆積した軟弱地盤には、自然または人工的に発生した地山の崩落や滑りなどで生じた「緩い堆積層」であって、人工的に積極的に締め固めたとは言えないものを含むものとする。
軟弱地盤に対しては、セメントミルクや薬液注入剤等を土砂の間隙に注入して硬化させる地盤改良方法が広く採用されている。例えば、特許文献１には、水とセメントと尿素とを含む地盤改良組成物を地中に注入する地盤改良方法が開示されている。
また、地中に存在する空洞に対しては、モルタル等のセメント系材料や流動化処理土等を充填する方法が採用される場合がある。例えば、特許文献２には、流動性を備える第二の注入材を地中空洞に注入する前に、可塑性を備える第一の注入材を注入することで、第二の注入材を所定の範囲内に充填する空洞部の充填工法が開示されている。
緩い堆積層の上に空洞が形成されている場合等、緩い堆積層と地中空洞との両方が存在する地盤に対しては、緩い堆積層と地中空洞に対して、個々に前記の対策工（地盤改良方法および空洞部の充填工法）を施すことがある。緩い堆積層の空隙や地中空洞に対して地盤改良や充填工法を講じることで、さらなる地盤変状の併発防止やその上部に構造物を構築するための地耐力確保等の当該層の強度増加を図ることができる。
なお、何らかの原因により地下構造物内に土砂や地下水等が流入した場合において、地上から当該地下構造物内への空洞充填や堆積物への固化材注入を行い、遮水壁（遮水ゾーン）等を構築することができれば、遮水壁等でさえぎられたドライな環境下において復旧工事等の施工が可能となる。 In order to ensure the safety of construction work and soundness after completion of construction, soft ground (loose sedimentation layer) where soil and sand are loosely deposited and cavities existing in the ground (hereinafter referred to as “underground cavities”) Need to be treated appropriately. Here, underground cavities such as air defense pits, artificial cavities such as quarry and mining underground mining pits, and stable ground layers such as rocks and soft ground beneath structures are due to some causes. There are cavities that are naturally formed by sinking. In addition, loosely deposited soft ground is a “loose sedimentary layer” caused by natural or artificial ground collapse or sliding, which cannot be said to have been actively compacted artificially. Shall be included.
For soft ground, a ground improvement method in which cement milk, a chemical solution injection agent, or the like is injected into a gap between the earth and sand and hardened is widely adopted. For example, Patent Document 1 discloses a ground improvement method in which a ground improvement composition containing water, cement, and urea is injected into the ground.
Moreover, a method of filling a cavity existing in the ground with a cement-based material such as mortar or fluidized soil may be employed. For example, in Patent Document 2, before the second injection material having fluidity is injected into the underground cavity, the first injection material having plasticity is injected into the second injection material within a predetermined range. A method for filling a cavity to be filled therein is disclosed.
For the ground where both a loose sediment layer and underground cavities exist, such as when a cavity is formed on a loose sediment layer, the above measures are individually applied to the loose sediment layer and underground cavities. Work (ground improvement method and cavity filling method) may be applied. By applying ground improvement and filling methods to voids in loose sedimentary layers and underground cavities, the strength of the layer can be increased, such as preventing further occurrence of ground deformation and securing ground strength to build structures on top of it. Can be achieved.
In addition, when earth and sand or groundwater flows into the underground structure for some reason, the cavity is filled from the ground into the underground structure and the solidification material is injected into the sediment, and the water shielding wall (water shielding zone) If it can be constructed, restoration work and the like can be performed in a dry environment blocked by a water shielding wall.

特開２０１６−０１１３５３号公報JP 2006-011353 A 特開２０００−３２８８８６号公報JP 2000-328886 A

緩い堆積層に対する地盤改良と、地中空洞への充填材の充填とを個別に行うと、作業に手間がかかり、工期短縮化の妨げとなる。
このような観点から、本発明は、緩い堆積層と地中空洞とが存在する地盤に対して効率的に処置を施すことを可能とした地盤改良方法を提案することを課題とする。 If the ground improvement for the loose sedimentary layer and the filling of the underground cavities are performed individually, the work will be time-consuming and hinder the shortening of the construction period.
From such a viewpoint, an object of the present invention is to propose a ground improvement method capable of efficiently performing treatment on a ground having a loose sedimentary layer and an underground cavity.

前記課題を解決するために、本発明は、地中に形成された空洞と、前記空洞の下方に存在する緩い堆積層とを有する地盤の地盤改良方法であって、前記空洞を貫通して前記緩い堆積層内に至る外管と前記外管に内挿された内管とを配管する配管作業と、前記外管を利用して前記空洞内に空洞注入材を注入しながら当該外管を引き上げる外管引上げ作業と、前記内管から前記緩い堆積層内に地盤注入材を注入する地盤注入作業とを備えている。
かかる地盤改良方法によれば、外管と内管とからなる２重管をボーリング孔に設置した後、この２重管を利用して空洞と緩い堆積層とに注入材を注入するため、地中空洞と緩い堆積層とに対して個別に処置を行う従来の施工方法に比べて施工性に優れている。そのため、工期短縮化および費用の低減化を図ることができる。また、地盤注入材の注入に先立って空洞注入材によって地中空洞と緩い堆積層との境界部を閉塞しておくため、地盤注入材が内管の外面に沿って流出することを防止し、所定範囲に地盤注入材を効果的に注入することができる。ここで、空洞注入材には、可塑性を備える材料あるいは流動性が高い材料を使用することができる。可塑性を備える空洞注入材を使用した場合には、空洞注入材の注入範囲を限定することができ、ひいては、注入量の削減を図ることができる。一方、流動性が高い空洞注入材を使用した場合には、流し込むことで空洞注入材を広範囲に注入することができる。また、可塑性を備える材料（第一の空洞注入材）を先行して注入した後、流動性が高い材料（第二の空洞注入材）を注入することで、第二の空洞注入材の注入範囲を限定してもよい。 In order to solve the above-mentioned problems, the present invention provides a ground improvement method for a ground having a cavity formed in the ground and a loose sedimentary layer existing below the cavity, and penetrating the cavity to Piping work for piping the outer pipe that reaches the loose sediment layer and the inner pipe inserted in the outer pipe, and pulling up the outer pipe while injecting the cavity injection material into the cavity using the outer pipe An outer pipe pulling work and a ground pouring work for pouring ground pouring material from the inner pipe into the loose sedimentary layer are provided.
According to this ground improvement method, a double pipe composed of an outer pipe and an inner pipe is installed in the borehole, and then the injection material is injected into the cavity and the loose sediment layer using this double pipe. Compared to the conventional construction method in which treatment is individually performed for the middle cavity and the loose deposited layer, the construction is superior. Therefore, the construction period can be shortened and the cost can be reduced. In addition, since the boundary between the underground cavity and the loose sedimentary layer is closed by the cavity injection material prior to the injection of the ground injection material, the ground injection material is prevented from flowing out along the outer surface of the inner pipe, The ground injection material can be effectively injected into the predetermined range. Here, as the cavity injection material, a material having plasticity or a material having high fluidity can be used. When a cavity injection material having plasticity is used, the injection range of the cavity injection material can be limited, and consequently the injection amount can be reduced. On the other hand, when a cavity injection material having high fluidity is used, the cavity injection material can be injected over a wide range by pouring. In addition, by injecting a material having plasticity (first cavity injection material) in advance and then injecting a material having high fluidity (second cavity injection material), the injection range of the second cavity injection material May be limited.

なお、前記外管引上げ作業では、前記外管を引き上げることにより形成された前記内管と前記緩い堆積層との隙間に間詰め材を注入した後、前記空洞注入材を注入すれば、内管と緩い堆積層との隙間が空洞注入材によって充填されることが防止できる。すなわち、空洞注入材が内管の外周囲を塞ぐおそれがない。
前記空洞注入材のフロー値は１４０ｍｍ〜３００ｍｍの範囲内であるのが望ましい。また、前記地盤注入材は、セメントに対する水の重量比が０．５〜５．０のセメントミルクを主体とした材料であるのが望ましい。さらに、前記空洞注入材は、前記セメントミルクとベントナイトミルクとの混合体であるのが望ましい。 In the outer pipe pulling up operation, after the filling material is injected into the gap between the inner pipe formed by pulling up the outer pipe and the loose deposited layer, the inner pipe is injected. It is possible to prevent the gap between the layer and the loose deposited layer from being filled with the cavity injection material. That is, there is no possibility that the cavity injection material will block the outer periphery of the inner tube.
The flow value of the cavity injection material is preferably in the range of 140 mm to 300 mm. The ground injection material is preferably a material mainly composed of cement milk having a weight ratio of water to cement of 0.5 to 5.0. Furthermore, it is desirable that the cavity injection material is a mixture of the cement milk and bentonite milk.

本発明の地盤改良方法によれば、緩い堆積層と地中空洞とが存在する地盤に対して効率的に処置を施すことができる。   According to the ground improvement method of the present invention, it is possible to efficiently treat a ground having a loose sedimentary layer and an underground cavity.

本発明の実施形態に係る地盤改良方法を示すフローチャートである。It is a flowchart which shows the ground improvement method which concerns on embodiment of this invention. （ａ）は本実施形態の地盤改良の対象地盤を示す断面図、（ｂ）および（ｃ）は本実施形態の地盤改良方法の配管作業を示す断面図、（ｄ）は同じく外管引上げ作業を示す断面図である。(A) is a cross-sectional view showing the target ground for ground improvement of the present embodiment, (b) and (c) are cross-sectional views showing the piping work of the ground improvement method of the present embodiment, (d) is also the outer pipe lifting work FIG. （ａ）は図２（ｄ）に続く空洞注入材を注入しながらの外管引上げ作業を示す断面図、（ｂ）は外管引上げ作業後を示す断面図、（ｃ）は地盤注入材の地盤注入作業を示す断面図、（ｄ）は地盤注入材の地盤注入作業後を示す断面図である。2A is a cross-sectional view showing the outer pipe pulling operation while injecting the cavity injection material following FIG. 2D, FIG. 2B is a cross-sectional view showing the outer pipe pulling work, and FIG. Sectional drawing which shows a ground injection | pouring operation | work, (d) is sectional drawing which shows the ground injection | pouring operation | work after a ground injection | pouring material.

本実施形態では、地中に存在する緩い堆積層を地上から改良する地盤改良方法について説明する。本実施形態の地盤改良方法は、図１に示すように、配管作業Ｓ１と、外管引上げ作業Ｓ２と、地盤注入作業Ｓ３とを有している。図２（ａ）に示すように、本実施形態において地盤改良の対象となる地盤は、地中の深い位置において緩く堆積した地盤である緩い堆積層Ｇ２であって、この緩い堆積層Ｇ２の上面は地中に形成された空洞（地中空洞ＧＡ）に面している。すなわち、本実施形態では、地表から順にＮ値４以上を目安とする表層Ｇ１、地中空洞ＧＡ、Ｎ値４未満を目安とする緩い堆積層Ｇ２が積層された地盤を対象としている。なお、各層の層厚および各層を構成する土質等は限定されるものではない。また、各地層のＮ値も限定されるものではない。さらに、地中空洞ＧＡ上には、複数の地層が積層されていてもよい。 In this embodiment, a ground improvement method for improving a loose sediment layer existing in the ground from the ground will be described. As shown in FIG. 1, the ground improvement method of the present embodiment includes a piping operation S1, an outer pipe pulling operation S2, and a ground injection operation S3. As shown in FIG. 2 (a), the ground to be ground improvement in this embodiment is a loose deposit layer G 2 is ground with loose deposited in underground deep position, the loose deposit layer G 2 The upper surface of is facing a cavity (underground cavity G A ) formed in the ground. That is, in the present embodiment, the ground layer in which the surface layer G 1 with an N value of 4 or more as a guide, the underground cavity G A , and the loose sediment layer G 2 with an N value of less than 4 as a guide in order from the ground surface is targeted. . In addition, the layer thickness of each layer, the soil which comprises each layer, etc. are not limited. Further, the N value of each region is not limited. Further, on the ground cavity G A, a plurality of strata may be laminated.

配管作業Ｓ１では、図２（ｂ）および（ｃ）に示すように、地表から表層Ｇ１を貫通して緩い堆積層Ｇ２内に至るボーリング孔１を形成するとともに、このボーリング孔１に外管２（ボーリングロッド）とこの外管２に内挿された内管３とを配管する。外管２は、表層Ｇ１および地中空洞ＧＡを貫通して緩い堆積層Ｇ２に至る。外管２の外面は、地中空洞ＧＡに露出している。
本実施形態では、まず、図２（ｂ）に示すように、ボーリングマシンを利用して、地盤を削孔しつつボーリングロッドを地中に圧入することによりボーリング孔１を形成する。ボーリングロッドは、φ７５〜１２５ｍｍ程度の円筒状の鋼管からなる。なお、ボーリングロッドの構成は限定されるものではなく、ボーリングロッドの材質、内径、長さ等は適宜決定すればよい。本実施形態では、複数本のボーリングロッドを連結しながら地中に圧入することで、所定長さの外管２を形成する。外管２の先端（下端）は、緩い堆積層Ｇ２の底部（下面）近傍にまで到達している。なお、外管２の下端の位置は限定されるものではなく、例えば、緩い堆積層Ｇ２よりも深い位置まで到達させていてもよい。また、外管２（ボーリングロッド）は、地盤にボーリング孔１を形成してから、当該ボーリング孔１に挿入してもよい。 In plumbing S1, as shown in FIG. 2 (b) and (c), to form a borehole 1 extending in the loose sediments G 2 through the surface layer G 1 from the ground, outside the borehole 1 A pipe 2 (boring rod) and an inner pipe 3 inserted in the outer pipe 2 are piped. Outer tube 2, reaches the loose sediments G 2 through the surface layer G 1 and ground cavity G A. The outer surface of the outer tube 2 is exposed in the ground cavity G A.
In the present embodiment, first, as shown in FIG. 2B, a boring hole 1 is formed by press-fitting a boring rod into the ground while drilling the ground using a boring machine. The boring rod is made of a cylindrical steel pipe having a diameter of about 75 to 125 mm. The configuration of the boring rod is not limited, and the material, inner diameter, length, etc. of the boring rod may be determined as appropriate. In this embodiment, the outer tube 2 having a predetermined length is formed by press-fitting into the ground while connecting a plurality of boring rods. Of the outer tube 2 leading end (lower end) is reached near the bottom of the loose sedimentary layer G 2 (lower surface). The position of the lower end of the outer tube 2 is not limited, for example, may be allowed to reach a position deeper than the loose deposit layer G 2. The outer tube 2 (boring rod) may be inserted into the boring hole 1 after the boring hole 1 is formed in the ground.

地中に外管２を配管したら、図２（ｃ）に示すように、外管２内に内管３を挿入する。本実施形態では、内管３の先端（下端）を外管２の先端（下端）から突出させて地盤に挿入する。なお、内管３の先端の位置は限定されるものではなく、例えば、外管２の先端と同じ深さに位置させてもよい。
内管３は、φ４０ｍｍ程度の複数本の塩化ビニル管を使用する。なお、内管３の構成は限定されるものではなく、内管３を構成する管材の材質、内径、長さ等は適宜決定すればよい。内管３の先端は、塩化ビニル製のキャップ（図示省略）により遮蔽されていて、貫入時の土砂等の流入や間詰め材５等の流入が防止されている。内管３へのキャップの固定方法は限定されるものではないが、例えば、有機溶剤を利用して一体化してもよいし、内管３の外面とキャップの内面にそれぞれネジ加工を施して締着してもよいし、接着剤等により接着してもよい。なお、内管３の先端の構造（遮蔽方法）は限定されるものではない。内管３には、直径５ｍｍ程度の微細な注入孔が複数形成されている。なお、注入孔の位置および形状は限定されるものではなく、適宜決定すればよい。また、注入孔は、複数の深度（複数箇所）に形成してもよい。内管３の外面には、少なくとも注入孔を覆うようにゴム製のスリーブ４が設けられている。スリーブ４は、注入孔を保護するとともに、注入孔を介して内管３の内部に異物（土砂や間詰め材５等）が流入することを防止する。スリーブ４の構成は限定されるものではなく、例えば、所定の厚さを有する筒体を、内管３の外面に固定することにより形成すればよい。また、スリーブ４を構成する材料は限定されるものではない。さらに、スリーブ４は、必要に応じて設置すればよく、省略してもよい。なお、図面では、スリーブ４が内管３の外面よりも突出するように記載されているが、スリーブ４の外面は、内管３の外面と面一あるいは内管３の外面よりも内側に位置しているのが望ましい。 When the outer pipe 2 is piped in the ground, the inner pipe 3 is inserted into the outer pipe 2 as shown in FIG. In the present embodiment, the tip (lower end) of the inner tube 3 is projected from the tip (lower end) of the outer tube 2 and inserted into the ground. Note that the position of the tip of the inner tube 3 is not limited, and may be positioned at the same depth as the tip of the outer tube 2, for example.
The inner tube 3 uses a plurality of polyvinyl chloride tubes having a diameter of about 40 mm. The configuration of the inner tube 3 is not limited, and the material, inner diameter, length, and the like of the pipe material that forms the inner tube 3 may be determined as appropriate. The tip of the inner tube 3 is shielded by a cap (not shown) made of vinyl chloride to prevent the inflow of earth and sand and the inflow of the filling material 5 at the time of penetration. The method of fixing the cap to the inner tube 3 is not limited. For example, the cap may be integrated using an organic solvent, or the outer surface of the inner tube 3 and the inner surface of the cap may be threaded and tightened. You may wear, and you may adhere | attach by an adhesive agent etc. In addition, the structure (shielding method) of the front-end | tip of the inner tube 3 is not limited. A plurality of fine injection holes having a diameter of about 5 mm are formed in the inner tube 3. The position and shape of the injection hole are not limited and may be determined as appropriate. Moreover, you may form an injection hole in several depth (plural places). A rubber sleeve 4 is provided on the outer surface of the inner tube 3 so as to cover at least the injection hole. The sleeve 4 protects the injection hole and prevents foreign matters (such as earth and sand and the filling material 5) from flowing into the inner tube 3 through the injection hole. The configuration of the sleeve 4 is not limited. For example, the sleeve 4 may be formed by fixing a cylindrical body having a predetermined thickness to the outer surface of the inner tube 3. Moreover, the material which comprises the sleeve 4 is not limited. Furthermore, the sleeve 4 may be installed as necessary and may be omitted. In the drawing, the sleeve 4 is described so as to protrude from the outer surface of the inner tube 3. However, the outer surface of the sleeve 4 is flush with the outer surface of the inner tube 3 or inside the outer surface of the inner tube 3. It is desirable to do.

外管引上げ作業Ｓ２では、図２（ｄ）に示すように、外管２を引き上げて当該外管２を回収する。
外管２を引き上げることにより緩い堆積層Ｇ２に形成された内管３とボーリング孔１の孔壁との隙間には、間詰め材５を注入する。間詰め材５は、外管２を引き上げながら外管２の先端から排出することにより隙間に充填する。内管３の注入孔はスリーブ４により覆われているため、外管２を引き上げた際に注入孔から土砂や間詰め材等が内管３の内部に流入することが防止されている。本実施形態では、間詰め材５として、セメントベントナイトを使用する。なお、間詰め材５を構成する材料は、内管３とボーリング孔１の孔壁との隙間への空洞注入材６の浸透を防ぐとともに、地盤注入作業Ｓ３における地盤注入材７の注入を妨げない材料であれば限定されるものではない。例えば、セメントベントナイトに代えて、シール充填用のグラウト等を使用してもよい。
間詰め材５の充填後、外管２をさらに引き上げることで、外管２の先端が地中空洞ＧＡ内に開口したら、図３（ａ）に示すように、外管２の先端から地中空洞ＧＡ内に空洞注入材６を注入する。本実施形態では、空洞注入材６の注入状況に応じて外管２を上昇させながら地中空洞ＧＡへ空洞注入材６を注入する。なお、地中空洞ＧＡへの空洞注入材６の注入は、外管２を固定させた状態で所定量注入してもよい。空洞注入材６には、可塑性を有した材料を使用する。本実施形態では、空洞注入材６として、セメントミルクとベントナイトミルクとの混合体であって、フロー値が１４０ｍｍ〜３００ｍｍの範囲内のものを使用する。なお、空洞注入材６を構成する材料は限定されるものではなく、例えば、モルタル、流動化処理土または可塑性グラウトを使用してもよい。空洞注入材６は、図３（ｂ）に示すように、外管２を回収することにより表層Ｇ１に形成された内管３とボーリング孔１の孔壁との隙間にも注入する。すなわち、本実施形態では、外管２の先端が表層Ｇ１内に到達した後も空洞注入材６を注入し続ける。 In the outer pipe pulling operation S2, as shown in FIG. 2D, the outer pipe 2 is pulled up and the outer pipe 2 is collected.
The gap between the loose sedimentary layer G inner tube 3 formed 2 and borehole 1 hole wall by pulling the outer tube 2 is injected between wadding 5. The filling material 5 fills the gap by discharging from the tip of the outer tube 2 while pulling up the outer tube 2. Since the injection hole of the inner tube 3 is covered with the sleeve 4, when the outer tube 2 is pulled up, it is prevented that earth and sand, a filling material, etc. flow into the inner tube 3 from the injection hole. In this embodiment, cement bentonite is used as the interlining material 5. Note that the material constituting the filling material 5 prevents penetration of the cavity injection material 6 into the gap between the inner tube 3 and the hole wall of the boring hole 1 and prevents injection of the ground injection material 7 in the ground injection operation S3. There is no limitation as long as there is no material. For example, instead of cement bentonite, a grout for sealing and the like may be used.
After filling between filling material 5, by further pulling the outer tube 2, when the distal end of the outer tube 2 opens into the underground cavity G A, as shown in FIG. 3 (a), the land from the tip of the outer tube 2 A cavity injection material 6 is injected into the middle cavity GA. In the present embodiment, injecting the cavity injection material 6 into the ground cavity G A with increasing outer tube 2 in accordance with the injection condition of the cavity grout 6. Incidentally, cavity injection of injection material 6 into the ground cavity G A may be a predetermined amount injected in a status of fixing the outer tube 2. A material having plasticity is used for the cavity injection material 6. In this embodiment, as the cavity injection material 6, a mixture of cement milk and bentonite milk having a flow value in the range of 140 mm to 300 mm is used. In addition, the material which comprises the cavity injection material 6 is not limited, For example, you may use mortar, fluidization processing soil, or plastic grout. As shown in FIG. 3 (b), the cavity injection material 6 is also injected into the gap between the inner tube 3 formed in the surface layer G 1 and the hole wall of the boring hole 1 by collecting the outer tube 2. That is, in this embodiment, keeps injecting cavity injection member 6 even after the leading end of the outer tube 2 has reached the inside surface G 1.

地盤注入作業Ｓ３では、図３（ｃ）に示すように、地盤注入材７を内管３から緩い堆積層Ｇ２内に注入することで柱状の地盤改良体７１を形成する。地盤注入材７の緩い堆積層Ｇ２内への注入は、内管３に形成された注入孔から地盤注入材７を排出（圧入）することにより行うものとする。注入孔から地盤注入材７を排出すると、スリーブ４が膨張する。スリーブ４には複数の孔またはスリットが形成されており、膨張することにより当該孔またはスリットが開口するため、注入孔から圧入された地盤注入材７が周囲の地盤に向けて噴射される。このとき、内管３の外面に間詰めが施されている（間詰め材５が充填されている）とともに、先行して地中空洞ＧＡが空洞注入材６によって閉塞されているため、地盤注入材７が内管３の外面に沿って地上に噴出することが防止されている。本実施形態の地盤注入材７は、セメントに対する水の重量比が０．５〜５．０のセメントミルクを主体とする材料であって空洞注入材６よりも流動性が高い。なお、地盤注入材７を構成する材料は限定されなく、例えば、セメントグラウトの他、水ガラスやセメント等を主体とした薬液を使用してもよい。地盤注入材７は、内管３の先端側から注入する。すなわち、本実施形態では、緩い堆積層Ｇ２内において、深い位置に形成された注入孔（スリーブ４）から地盤注入材７の噴射を開始し、徐々に地盤注入材７を噴射する注入孔（スリーブ４）を上方に移動することで、ボーリング孔１の周囲に柱状の地盤改良体７１を形成する。なお、必要に応じてパッカーを使用して、地盤注入材７を注入する注入孔を選択してもよい。地盤改良体７１の形成後、内管３を残置させておくことで、その後の地盤調査や探査等に内管３を活用すればよい。なお、内管３は、地盤改良体７１の注入後に撤去してもよい。 In ground implantation operation S3, as illustrated in FIG. 3 (c), to form a columnar ground improvement body 71 by injecting the loose sediments G in 2 ground grout 7 from the inner tube 3. Injection into ground grout 7 loose deposit layer G in 2, and the ground grout 7 from the injection holes formed in the inner tube 3 to perform by discharging (press-fit). When the ground injection material 7 is discharged from the injection hole, the sleeve 4 expands. A plurality of holes or slits are formed in the sleeve 4, and the holes or slits are opened by expanding, so that the ground injection material 7 press-fitted from the injection holes is sprayed toward the surrounding ground. At this time, since the conjunction between filling the outer surface of the inner tube 3 is applied (during filling material 5 is filled), the underground cavity G A prior is closed by the cavity injection member 6, ground The injection material 7 is prevented from being ejected to the ground along the outer surface of the inner tube 3. The ground injection material 7 of the present embodiment is a material mainly composed of cement milk having a weight ratio of water to cement of 0.5 to 5.0 and has a higher fluidity than the cavity injection material 6. In addition, the material which comprises the ground injection material 7 is not limited, For example, you may use the chemical | medical solution which mainly has water glass, cement, etc. other than cement grout. The ground injection material 7 is injected from the distal end side of the inner tube 3. That is, in this embodiment, loose in the deposition layer G 2, deep positions in the formed injection hole from (sleeve 4) injection of the ground grout 7 starts gradually injection hole for injecting ground grout 7 ( By moving the sleeve 4) upward, a columnar ground improvement body 71 is formed around the borehole 1. In addition, you may select the injection hole which inject | pours the ground injection material 7 using a packer as needed. After the formation of the ground improvement body 71, the inner pipe 3 may be used for the subsequent ground investigation or exploration by leaving the inner pipe 3 left. The inner tube 3 may be removed after the ground improvement body 71 is injected.

以上、本実施形態の地盤改良方法によれば、外管２と内管３とからなる２重管をボーリング孔１に設置した後、この２重管を利用して地中空洞ＧＡと緩い堆積層Ｇ２とに注入材を注入するため、地中空洞ＧＡと緩い堆積層Ｇ２とに対して個別に処置を行う従来の施工方法に比べて施工性に優れている。そのため、工期短縮化および費用の低減化を図ることができる。また、流動性が高い（浸透しやすい）地盤注入材７の注入に先立って空洞注入材６を注入しておくため、地盤注入材７の拡散や流出を防止し、所定範囲に地盤注入材７を効果的に注入することができる。
空洞注入材６として、可塑性を有した材料を使用しているため、限定した目的範囲のみに行き渡らせることができる。そのため、空洞注入材６が必要以上に広範囲に流出することを防止し、注入量を必要最小限に抑え、ひいては、材料費の低減化を図ることができる。なお、空洞注入材６として、可塑性を備えた材料に代えて流動性が高い材料（自己充填性が高い材料）を使用すれば、空洞注入材６を地中空洞ＧＡに流し込むことで広範囲に注入することができる。流動性が高い材料としては、例えば、地盤注入材７と同じ材料を使用することができる。また、地中空洞ＧＡには、可塑性を備えた第一の空洞注入材を注入した後、流動性が高い第二の空洞注入材を注入してもよい。こうすることで、地中空洞ＧＡ内における注入範囲を限定することができる。 As described above, according to the ground improvement method of this embodiment, after the setting of the double tube consisting of an outer tube 2 and the inner tube 3 which the borehole 1, loose and underground cavity G A by utilizing the double tube for injecting the injection material into the deposition layer G 2, it is excellent in workability as compared with conventional construction methods of performing individual action on the underground cavity G a and loose sedimentary layer G 2. Therefore, the construction period can be shortened and the cost can be reduced. Moreover, since the cavity injection material 6 is injected prior to the injection of the ground injection material 7 having high fluidity (easy to permeate), the ground injection material 7 is prevented from diffusing and flowing out, and the ground injection material 7 falls within a predetermined range. Can be effectively injected.
Since a material having plasticity is used as the cavity injection material 6, it can be distributed only in a limited target range. Therefore, it is possible to prevent the hollow injection material 6 from flowing out over a wider range than necessary, to suppress the injection amount to the minimum necessary, and to reduce the material cost. As cavity injection member 6, the use of highly liquid instead of materials with plastic material (self-filling material having high), extensively by pouring a hollow injection material 6 into the ground cavity G A Can be injected. As the material having high fluidity, for example, the same material as the ground injection material 7 can be used. Further, the ground cavity G A, after injecting a first cavity injection material having a plasticity, may be injected highly liquid second cavity injection material. In this way, it is possible to limit the injection range within the underground cavity G A.

地中空洞ＧＡに空洞注入材６を予め注入しておくことで、地盤注入材７が地中空洞ＧＡに流出することを防止できる。地盤注入材７として流動性が高い材料を使用しているため、緩く堆積した緩い堆積層Ｇ２の土粒子間（空隙）に地盤注入材７が浸透し、その結果、地盤改良体７１を形成することができる。
また、外管２を引き上げることにより形成された内管３と緩い堆積層Ｇ２との隙間に間詰め材５を充填しているので、ボーリング孔１の孔壁が崩れることを防止することができるとともに、空洞注入材６が当該隙間に流入することを防止することができる。そのため、内管３の注入孔が空洞注入材６によって塞がれることはなく、地盤注入材７の注入が空洞注入材６によって妨げられることもない。 By previously injecting cavity injection material 6 into the ground cavity G A, it is possible to prevent the ground grout 7 flows out into the ground cavity G A. Since a material having high fluidity is used as the ground injection material 7, the ground injection material 7 permeates between the soil particles (voids) of the loosely deposited loosely deposited layer G <b> 2, and as a result, the ground improvement body 71 is formed. be able to.
Further, since the filled between filling material 5 into the gap between the inner tube 3 and the loose sedimentary layer G 2 which is formed by pulling the outer tube 2, it is possible to prevent the hole wall of the borehole 1 is lost In addition, the cavity injection material 6 can be prevented from flowing into the gap. Therefore, the injection hole of the inner tube 3 is not blocked by the cavity injection material 6, and the injection of the ground injection material 7 is not hindered by the cavity injection material 6.

なお、地盤改良材としては、溶液型薬液が一般的に想定される。溶液型薬液は、作用力におおむね比例して流れの度合いが増加するため、緩く堆積した地盤に容易に浸透させることができる。また、セメントに対する水の重量比が０．５〜５．０程度で作成されたセメントミルクや、これに分離抵抗性や流動性を向上させるために添加剤を加えたもの（セメントミルク）は、一定の作用力が働かないと流れが生じない特性を有しているものの、比較的その作用力は低い水準にある。そのため、これらのセメントミルク（地盤注入材７）は、溶液型薬液と同様に、緩く堆積した地盤（緩い堆積層Ｇ２）に浸透させることができる。一方、これらのセメントミルクは、地中空洞ＧＡに流し込むと自重により広範囲に広がるため、大量打設が必要となる。そのため、本実施形態では、地中空洞ＧＡへの注入材として、フロー値が１４０ｍｍ〜３００ｍｍの範囲内の空洞注入材６あるいは可塑性を保持する空洞注入材６を使用することで、打設量を制限している。 In addition, as a ground improvement material, a solution type chemical | medical solution is generally assumed. Since the degree of flow increases in proportion to the acting force, the solution-type chemical solution can easily penetrate into the loosely accumulated ground. In addition, cement milk prepared with a weight ratio of water to cement of about 0.5 to 5.0, and those added with additives to improve separation resistance and fluidity (cement milk) Although there is a characteristic that a flow does not occur unless a constant acting force is applied, the acting force is at a relatively low level. Therefore, these cement milks (ground injection material 7) can permeate the loosely deposited ground (loose deposited layer G 2 ) as in the case of the solution type chemical solution. On the other hand, these cement milk, because spread wide by its own weight and flow into the underground cavity G A, it is necessary to mass strokes set. Therefore, in the present embodiment, as an injection material into the ground cavity G A, by using a cavity injection material 6 flows value holding cavity injection material 6 or plastic in the range of 140Mm～300mm, hitting設量Is limiting.

以上、本発明の実施形態について説明したが、本発明は、前述の実施形態に限られず、前記の各構成要素については本発明の趣旨を逸脱しない範囲で適宜変更が可能である。
例えば、内管３の配管方法は限定されるものではなく、例えば、ダブルパッカー工法を採用する等、従来の工法を適宜採用してもよい。
空洞注入材６を構成する材料は、目的に応じて選定すればよい。例えば、地中空洞ＧＡ内に固化補強体を構築する場合にはセメントグラウトや注入薬液等を使用すればよいし、地中空洞ＧＡ内に止水構造を構築する場合にはモルタル、流動化処理土、可塑性グラウト等を使用すればよい。
本発明の地盤改良方法による改良の対象となる空洞は、構造物の直下や、地中構造物内に形成された空洞であってもよい。 Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the above-described components can be appropriately changed without departing from the spirit of the present invention.
For example, the piping method of the inner pipe 3 is not limited. For example, a conventional construction method such as a double packer construction method may be adopted as appropriate.
What is necessary is just to select the material which comprises the cavity injection material 6 according to the objective. For example, it may be used to cement grout or injection liquid medicine or the like in the case of building a solidified reinforcement in underground cavity G A, mortar when constructing water stopping structure in the underground cavity G A, flow Chemically treated soil, plastic grout, etc. may be used.
The cavity to be improved by the ground improvement method of the present invention may be a cavity directly under the structure or a cavity formed in the underground structure.

１ ボーリング孔
２ 外管
３ 内管
４ スリーブ
５ 間詰め材
６ 空洞注入材
７ 地盤注入材
７１ 地盤改良体
ＧＡ 地中空洞（空洞）
Ｇ２ 緩い堆積層
Ｓ１ 配管作業
Ｓ２ 外管引上げ作業
Ｓ３ 地盤注入作業 DESCRIPTION OF SYMBOLS 1 Boring hole 2 Outer pipe 3 Inner pipe 4 Sleeve 5 Filling material 6 Cavity injection material 7 Ground injection material 71 Ground improvement body G A Underground cavity (cavity)
G 2 loose sedimentary layers S1 plumbing S2 outer pipe pulling operations S3 ground injection operation

Claims (5)

地中に形成された空洞と、前記空洞の下方に存在する緩い堆積層とを有する地盤の地盤改良方法であって、
前記空洞を貫通して前記緩い堆積層内に至る外管と前記外管に内挿された内管とを配管する配管作業と、
前記外管を引き上げるとともに、当該外管を利用して前記空洞内に空洞注入材を注入する外管引上げ作業と、
前記内管から前記緩い堆積層内に地盤注入材を注入する地盤注入作業と、を備えていることを特徴とする地盤改良方法。 A ground improvement method for a ground having a cavity formed in the ground and a loose sediment layer existing below the cavity,
A piping operation for piping an outer pipe that penetrates the cavity and reaches the loose sediment layer and an inner pipe inserted into the outer pipe;
Pulling up the outer tube and pulling up the outer tube using the outer tube to inject a cavity injection material into the cavity;
And a ground injection operation for injecting a ground injection material from the inner pipe into the loose sedimentary layer. 前記外管引上げ作業では、前記外管を引き上げることにより形成された前記内管と前記緩い堆積層との隙間に間詰め材を注入した後、前記空洞注入材を注入することを特徴とする、請求項１に記載の地盤改良方法。   In the outer pipe pulling operation, after the filling material is injected into the gap between the inner pipe formed by pulling up the outer pipe and the loose deposit layer, the cavity injection material is injected, The ground improvement method according to claim 1. 前記空洞注入材のフロー値が１４０ｍｍ〜３００ｍｍの範囲内であることを特徴とする、請求項１または請求項２に記載の地盤改良方法。   The ground improvement method according to claim 1 or 2, wherein a flow value of the cavity injection material is within a range of 140 mm to 300 mm. 前記地盤注入材が、セメントに対する水の重量比が０．５〜５．０のセメントミルクを主体とする材料であることを特徴とする、請求項１乃至請求項３のいずれか１項に記載の地盤改良方法。   4. The ground injection material according to any one of claims 1 to 3, wherein the ground injection material is a material mainly composed of cement milk having a weight ratio of water to cement of 0.5 to 5.0. Ground improvement method. 前記空洞注入材が、前記セメントミルクとベントナイトミルクとの混合体であることを特徴とする、請求項４に記載の地盤改良方法。   The ground improvement method according to claim 4, wherein the cavity injection material is a mixture of the cement milk and bentonite milk.
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