JP4538817B2 - Vertical drain method - Google Patents

Vertical drain method Download PDF

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JP4538817B2
JP4538817B2 JP2007305613A JP2007305613A JP4538817B2 JP 4538817 B2 JP4538817 B2 JP 4538817B2 JP 2007305613 A JP2007305613 A JP 2007305613A JP 2007305613 A JP2007305613 A JP 2007305613A JP 4538817 B2 JP4538817 B2 JP 4538817B2
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vertical drain
drain material
vertical
drain
connection tool
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JP2009127357A (en
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衛 三村
秀幸 佐藤
仁文 松島
敏之 武田
健 石黒
隆 伊佐野
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Toray Engineering Co Ltd
Maeda Corp
Aomi Construction Co Ltd
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Maeda Corp
Toyo Construction Co Ltd
Aomi Construction Co Ltd
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Priority to KR1020080016197A priority patent/KR101010067B1/en
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
    • E02D3/02—Improving by compacting
    • E02D3/10—Improving by compacting by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains
    • E02D3/103—Improving by compacting by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains by installing wick drains or sand bags
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02B—HYDRAULIC ENGINEERING
    • E02B11/00—Drainage of soil, e.g. for agricultural purposes
    • E02B11/005—Drainage conduits
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D2300/00—Materials
    • E02D2300/0004—Synthetics
    • E02D2300/0006—Plastics

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Civil Engineering (AREA)
  • Agronomy & Crop Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Mining & Mineral Resources (AREA)
  • Paleontology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Soil Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)

Description

本発明は、軟弱地盤を改良するため地盤改良工法に係り、より詳しくは軟弱地盤中の間隙水をドレーン材を通して排水して軟弱地盤を圧密化するバーチカルドレーン工法に関する。   The present invention relates to a ground improvement method for improving soft ground, and more particularly to a vertical drain method for draining pore water in the soft ground through a drain material to consolidate the soft ground.

この種のバーチカルドレーン工法は、一般に軟弱地盤上に砂を堆積させてサンドマットを造成した後、このサンドマットを通して地盤中に鉛直ドレーン材を打設し、地盤中の間隙水を前記鉛直ドレーン材内の通水路を通して地表へ導き、さらに前記サンドマット内の間隙を通して側方へ排水させるようにしていた。ところで、前記サンドマットは、高い透水性が求められることから良質な砂が必要である。しかし、近年、川砂などの良質な砂の確保が困難になっており、サンドマットを用いないバーチカルドレーン工法の開発が望まれていた。   In this type of vertical drain method, generally, sand is deposited on soft ground to create a sand mat, and then a vertical drain material is placed in the ground through the sand mat, and the pore water in the ground is removed from the vertical drain material. It was led to the surface of the earth through an internal water passage and further drained to the side through a gap in the sand mat. By the way, since the said sand mat is requested | required of high water permeability, good quality sand is required. However, in recent years, it has become difficult to secure high-quality sand such as river sand, and the development of a vertical drain method that does not use a sand mat has been desired.

そこで、例えば、特許文献１には、地盤中に打設した鉛直ドレーン材の余長部を折り曲げ、この折り曲げ部分を隣接する鉛直ドレーン材の折り曲げ部分と連結して水平ドレーン部とする工法が開示されている。しかし、鉛直ドレーン材の折り曲げ部分を連結して水平ドレーン部とする場合は、圧密沈下に伴う地盤変形に水平ドレーン部が追従できず、連結部からの分断やドレーン材自体の切断などのトラブルが発生し易くなる。   Therefore, for example, Patent Document 1 discloses a method of bending a surplus portion of a vertical drain material placed in the ground and connecting the bent portion with a bent portion of an adjacent vertical drain material to form a horizontal drain portion. Has been. However, when the bent parts of the vertical drain material are connected to form a horizontal drain part, the horizontal drain part cannot follow the ground deformation caused by consolidation settlement, and troubles such as separation from the connecting part and cutting of the drain material itself occur. It tends to occur.

一方、特許文献２には、鉛直ドレーン材の余長部を同じ方向へ折り曲げて、相隣接する鉛直ドレーン材の折り曲げ部分を重ね合せて扁平筒状の接続具内に挿入し、該接続具を介して各鉛直ドレーン材の折り曲げ部分を連接して一連の水平ドレーン部とする工法が提案されている。この工法によれば、前・後ドレーン材が、単に重ね合せた状態で接続具内に納められるので、ドレーン材相互の長手方向でのすべりが許容され、地盤変形に対する追従性が高まるものと期待される。   On the other hand, in Patent Document 2, the extra length portion of the vertical drain material is bent in the same direction, the bent portions of the adjacent vertical drain materials are overlapped and inserted into a flat cylindrical connector, and the connector is inserted. A construction method is proposed in which the bent portions of the vertical drain members are connected to form a series of horizontal drain portions. According to this construction method, the front and rear drain materials can be placed in the connector in a state where they are simply overlapped. Therefore, it is expected that slippage in the longitudinal direction between the drain materials is allowed and the followability to ground deformation is improved. Is done.

特開２００２−４２６３号公報JP 2002-4263 A 特開２００５−６１１４３号公報JP 2005-61143 A

しかしながら、上記特許文献２に記載された工法（バーチカルドレーン工法）によれば、前・後ドレーン材の重ね合せ部分を納める接続具が剛性を有する箱形状となっているため、接続具自体の地盤変形に対する追従性が悪く、場合によっては接続具が地盤変形の方向から大きくずれて、ドレーン材の一方または双方が接続具から離脱し、あるいは接続具のエッジによってドレーン材が損傷を受ける危険がある。   However, according to the construction method (vertical drain construction method) described in the above-mentioned Patent Document 2, the connection tool for storing the overlapping portions of the front and rear drain materials has a rigid box shape. There is a risk that the followability to deformation is poor, and in some cases, the connection tool is greatly displaced from the direction of ground deformation, and one or both of the drain materials are detached from the connection tool, or the drain material is damaged by the edge of the connection tool. .

本発明は、上記した従来の問題点に鑑みてなされたもので、その課題とするところは、地盤変形に対する追従性に優れた接続具を用いることにより、ドレーン材の離脱防止はもとよりドレーン材の損傷防止を図ることができるバーチカルドレーン工法を提供することにある。   The present invention has been made in view of the above-described conventional problems, and the problem is that by using a connection tool that is excellent in followability to ground deformation, the drain material can be prevented from being detached as well as the drain material. An object of the present invention is to provide a vertical drain method capable of preventing damage.

上記課題を解決するため、本発明は、軟弱地盤中に列状に打設した鉛直ドレーン材の余長部を同じ方向へ折り曲げて、各鉛直ドレーン材の折り曲げ部分を、柔軟性を有する袋体を用いた扁平筒状の接続具内に挿入し、折り曲げ方向の前側に位置する鉛直ドレーンの折り曲げ部分上の接続具に対し、後続の鉛直ドレーン材の折り曲げ部分を差込み、この際、前記接続具を折り曲げ部分の曲げ基端側に寄せるようにして、前・後の鉛直ドレーン材の重ね合せ部を前記接続具内に納め、隣接する鉛直ドレーン材の折り曲げ部分同士を相互に重ね合せて、前記接続具を介して連接する作業を繰返し、前記接続具を介して各鉛直ドレーン材の折り曲げ部分を連接して一連の水平ドレーン部とすることを特徴とする。 In order to solve the above-mentioned problems, the present invention folds the extra length portions of vertical drain materials placed in a row in soft ground in the same direction, and the bent portions of the vertical drain materials are flexible bags. Inserted into a flat cylindrical connecting tool, and inserted into the connecting tool on the bent part of the vertical drain located on the front side in the bending direction, the bent portion of the subsequent vertical drain material is inserted. So that the overlapping portion of the vertical drain material before and after is placed in the connector, and the bent portions of the adjacent vertical drain materials are overlapped with each other, The operation of connecting through the connecting tool is repeated, and the bent portions of the vertical drain members are connected through the connecting tool to form a series of horizontal drain portions.

このように行うバーチカルドレーン工法においては、接続具が柔軟性を有しているので、圧密沈下に伴う地盤変形に容易に追従し、接続具からのドレーン材の離脱が防止されると共に、接続具によるドレーン材の損傷が防止される。
また、隣接する鉛直ドレーン材の折り曲げ部分の重ね合せ部はほぼ密着する状態でかつ側面が押えられた状態（横ずれが規制された状態）で接続具内に拘束され、これによって水平ドレーン部の直線性が確保される。しかも、折り曲げ方向の前側に位置する鉛直ドレーンの折り曲げ部分上の接続具に対し、後続の鉛直ドレーン材の折り曲げ部分を差込む時、接続具を、折り曲げ部分の曲げ基端側に寄せるようにすることで、前・後の鉛直ドレーン材の重ね合せ部が確実に接続具内に納まることとなる。
また、バーチカルドレーン工法は、通常、地表面に盛土を行うことで完了し、この盛土による載荷重で軟弱地盤中の間隙水は、鉛直ドレーン材を通して地表へ導かれ、さらに水平ドレーン部を通して、例えば、地盤改良域の周囲に設けられた排水溝へ排水される。この場合、前記した盛土の載荷重で柔軟性を有する袋体を用いた扁平筒状の接続具がより扁平に押し潰されるので、鉛直ドレーン材の重ね合せ部分は完全に密着する状態となる。これにより各鉛直ドレーン材を通して地表へ導かれた間隙水は、各接続具内で隣接する一方の鉛直ドレーン材の折り曲げ部分から他方の鉛直ドレーン材の折り曲げ部分へ円滑に移動し、水平ドレーン部を通して効率よく排水される。 In the vertical drain method performed in this way, since the connecting device has flexibility, it easily follows the ground deformation caused by consolidation settlement and prevents the drain material from being detached from the connecting device. The drain material is prevented from being damaged.
In addition, the overlapping part of the bent portions of the adjacent vertical drain materials is constrained in the connection tool in a state where they are almost in close contact with each other and the side surfaces are pressed (a state in which the lateral displacement is restricted). Sex is secured. In addition, when the bent portion of the subsequent vertical drain material is inserted into the connecting tool on the bent portion of the vertical drain located on the front side in the bending direction, the connecting tool is brought closer to the bent proximal end side of the bent portion. As a result, the overlapping portions of the front and rear vertical drain materials are surely placed in the connector.
Also, the vertical drain method is usually completed by embankment on the ground surface, and the pore water in the soft ground is guided to the ground surface through the vertical drain material by the loading load by this embankment, and further through the horizontal drain part, for example, The water is drained to the drainage ditch provided around the ground improvement area. In this case, since the flat cylindrical connector using the flexible bag body is crushed flatly by the above-described loading of the embankment, the overlapping portion of the vertical drain material is in a state of being in close contact. As a result, the interstitial water introduced to the ground surface through each vertical drain material smoothly moves from the bent part of one vertical drain material adjacent to each other in each connector to the bent part of the other vertical drain material, and passes through the horizontal drain part. It is drained efficiently.

本発明において、上記扁平状態とした接続具の内空幅Ｗは、接続具に対する鉛直ドレーン材挿入の作業性、得られる水平ドレーン部の直線性等を考慮して、鉛直ドレーン材の幅ｗ、鉛直ドレーン材の厚さｔおよび係数Ｋを含む下記の関係式
Ｗ＝[ｗ＋２ｔ]×Ｋ
に基づき、Ｋを１．１〜１．３の範囲から選択した任意の値を用いて設定するのが望ましい。 In the present invention, the width W of the vertical drain material in consideration of the workability of inserting the vertical drain material into the connection tool, the linearity of the obtained horizontal drain portion, etc. The following relational expression including the thickness t and coefficient K of the vertical drain material W = [w + 2t] × K
It is desirable to set K using an arbitrary value selected from the range of 1.1 to 1.3.

本発明において、上記接続具の長さは、相隣接するドレーン材１の重ね合せ部に必要とする重ね合せ長に応じて設定するが、その長さは、３０ｃｍ以上望ましくは４０ｃｍ以上とすれば十分である。   In the present invention, the length of the connecting tool is set according to the overlapping length required for the overlapping portions of the adjacent drain materials 1, and the length is 30 cm or more, preferably 40 cm or more. It is enough.

また、上記袋体は、特にその材種を問うものではないが、生分解性プラスチック材からなるものとするのが望ましい。   Further, the bag body is not particularly limited as to its material type, but is preferably made of a biodegradable plastic material.

本発明に係るバーチカルドレーン工法によれば、柔軟性を有する接続具を用いて隣接する鉛直ドレーン材の折り曲げ部分を接続するので、地盤沈下に伴う地盤変形に接続具が容易に追従し、ドレーン材の離脱防止はもとよりドレーン材の損傷防止を図ることができ、地盤改良に対する信頼性が大きく向上する。   According to the vertical drain method according to the present invention, since the bent portion of the adjacent vertical drain material is connected using a flexible connecting device, the connecting device easily follows the ground deformation accompanying ground subsidence, and the drain material. In addition to preventing detachment, it is possible to prevent damage to the drain material and greatly improve the reliability of ground improvement.

以下、本発明を実施するための最良の形態を添付図面に基づいて説明する。   The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

図１〜３は、本発明に係るバーチカルドレーン工法の一つの実施形態を示したものである。本バーチカルドレーン工法では、軟弱地盤Ｇ中に列状に打設した鉛直ドレーン材１、１・・・の余長部を同じ方向へ折り曲げて、相隣接する鉛直ドレーン材１の折り曲げ部分１ａを重ね合せて扁平筒状の接続具２内に挿入し、該接続具２を介して各鉛直ドレーン材１の折り曲げ部分１ａを連接して一連の水平ドレーン部３とする。   1 to 3 show one embodiment of the vertical drain method according to the present invention. In this vertical drain method, the extra length portions of the vertical drain materials 1, 1... Placed in a row in the soft ground G are bent in the same direction, and the bent portions 1a of the adjacent vertical drain materials 1 are overlapped. In addition, they are inserted into a flat cylindrical connector 2, and the bent portions 1 a of the vertical drain members 1 are connected via the connector 2 to form a series of horizontal drain portions 3.

鉛直ドレーン材１は、ここでは帯状をなすプラスチックボードドレーン材からなっている。このプラスチックボードドレーン材は、一例として三次元網目構造の心材を透水性の表皮（不織布）で覆った構造となっており、耐圧性が高いにも拘わらず柔軟性を有している。したがって、その余長部を図示のように９０度近く折り曲げても潰れることはなく、その内部には十分なる通水面積が確保される。なお、鉛直ドレーン材１がプラスチックボードドレーン材に限定されないことはもちろんで、より柔軟性に富むファイバードレーン材やペーパードレーン材などを選択することができる。   The vertical drain material 1 is here made of a plastic board drain material having a strip shape. This plastic board drain material has, for example, a structure in which a core material having a three-dimensional network structure is covered with a water-permeable skin (nonwoven fabric), and has high flexibility despite high pressure resistance. Therefore, even if the extra length portion is bent nearly 90 degrees as shown in the figure, it will not be crushed, and a sufficient water passage area is secured in the inside. The vertical drain material 1 is not limited to the plastic board drain material, and a fiber drain material, a paper drain material, or the like with higher flexibility can be selected.

接続具２は、柔軟性を有する袋体からなっている。この接続具２としての袋体は、ここでは図４に示されるように、二つに折り畳んだシートの端縁部を縫着する（縫い目を点線で示す）ことにより製作されている。なお、この接続具２を構成する袋体の材種は、柔軟性を有していれば任意であり、透水性を有していても不透水性であっても、あるいは透明であっても不透明であってもよい。また、この袋体の材種としては、生分解性プラスチック材を用いてもよく、この場合は、数年後に分解して消失するので、環境保全を図る上で有用となる。   The connector 2 is made of a flexible bag. Here, as shown in FIG. 4, the bag body as the connection tool 2 is manufactured by sewing the end edges of the sheet folded in two (seam is indicated by a dotted line). Note that the material of the bag constituting the connector 2 is arbitrary as long as it has flexibility, whether it is water-permeable, water-impermeable, or transparent. It may be opaque. In addition, a biodegradable plastic material may be used as a material type of the bag body, and in this case, it is decomposed and disappears after several years, which is useful for environmental protection.

上記接続具２は、鉛直ドレーン材１を二枚重ねで収納できる必要最小限の大きさとなるようにその内空断面が設定されている。より詳しくは、扁平状態とした接続具２の内空幅Ｗは、鉛直ドレーン材１の幅ｗ、鉛直ドレーン材１の厚さｔおよび係数Ｋを含む下記の関係式（１）に基づいて設定されている。
Ｗ＝[ｗ＋２ｔ]×Ｋ （１） The connecting tool 2 has a hollow cross section set so as to have a minimum required size capable of storing two vertical drain materials 1 in a stacked manner. More specifically, the inner space width W of the connector 2 in the flat state is set based on the following relational expression (1) including the width w of the vertical drain material 1, the thickness t of the vertical drain material 1, and the coefficient K. Has been.
W = [w + 2t] × K (1)

上記（１）式において、係数Ｋは１．１〜１．３の範囲から選択した任意の値とする。これは、Ｋが１．１より小さいと鉛直ドレーン材１を二枚重ねの状態で接続具２に挿入することが困難となり、逆にＫが１．３超では、二枚重ねの鉛直ドレーン材１が幅方向でずれを起こし易くなるためである。このように接続具２の内空断面を設定することにより、接続具２にドレーン材１を二枚重ねで挿入する際の作業性は良好となり、その上、前・後ドレーン材１の幅方向でのずれが押えられるので、水平ドレーン部３の直線性が保たれ、排水性能は安定的に維持される。   In the above equation (1), the coefficient K is an arbitrary value selected from the range of 1.1 to 1.3. This is because if K is smaller than 1.1, it becomes difficult to insert the vertical drain material 1 into the connector 2 in a stacked state, and conversely if K exceeds 1.3, the double vertical drain material 1 is in the width direction. This is because it becomes easy to cause a shift. Thus, by setting the inner cross section of the connection tool 2, workability when inserting the drain material 1 into the connection tool 2 in two layers is improved, and in addition, the width of the front / rear drain material 1 in the width direction is improved. Since the displacement is suppressed, the linearity of the horizontal drain portion 3 is maintained, and the drainage performance is stably maintained.

一方、接続具２の長さＬは、相隣接する鉛直ドレーン材１の重ね合せ部に必要とする重ね合せ長に応じて設定する。この鉛直ドレーン材１の必要重ね合せ長は、圧密沈下に伴う地盤変形によって生じる長手方向の最大すべり量（ずれ量）よりも大きな値となっており、接続具２の長さＬは、前記した鉛直ドレーン材１の必要重ね合せ長よりも長めに設定される。   On the other hand, the length L of the connector 2 is set according to the overlapping length required for the overlapping portions of the adjacent vertical drain materials 1. The required overlap length of the vertical drain material 1 is larger than the maximum slip amount (displacement amount) in the longitudinal direction caused by ground deformation accompanying consolidation settlement, and the length L of the connector 2 is as described above. It is set longer than the required overlapping length of the vertical drain material 1.

因みに、「種々の軟弱地盤上の載荷盛土」に対する既往の「土／水連成弾粘塑性二次元ＦＥＭ解析」から算出した地表面１ｍあたりの最大相対変位δｒと基礎地盤最大沈下量との関係は、図５に示すとおりとなっている。図５より最大沈下量が１０ｍを超える場合であっても、地表面の最大相対変位δｒは１０ｃｍ／ｍ程度であり、現状の鉛直ドレーン材の打設ピッチが最大で３ｍ程度であることを考慮すると、上記した鉛直ドレーン材１の必要重ね合せ長は３０ｃｍでも十分であることが分かる。したがって、接続具２の長さＬは少なくとも３０ｃｍとする。ただし、鉛直ドレーン材１の重ね合せ部分に十分なる排水流路を確保するには、地盤変形後も、ある程度の重ね合せ長が確保されているのが望ましく、安全を見れば接続具２の長さＬは、少なくとも４０ｃｍとするのがよいといえる。   Incidentally, the relationship between the maximum relative displacement δr per 1 m of the ground surface calculated from the existing “soil / water coupled elastic-viscoplastic two-dimensional FEM analysis” for the “loading embankment on various soft ground” and the maximum subsidence of the foundation ground. Is as shown in FIG. Even if the maximum subsidence amount exceeds 10 m, it is considered that the maximum relative displacement δr of the ground surface is about 10 cm / m, and the current vertical drain material placement pitch is about 3 m at the maximum. Then, it can be seen that the required overlapping length of the above vertical drain material 1 is sufficient even at 30 cm. Therefore, the length L of the connector 2 is at least 30 cm. However, in order to secure a sufficient drainage flow path at the overlapping portion of the vertical drain material 1, it is desirable that a certain overlapping length is secured even after the ground is deformed. It can be said that the length L should be at least 40 cm.

ここで、各鉛直ドレーン材１の折り曲げ部分１ａの長さｌは、少なくとも鉛直ドレーン材１の打設ピッチＰに上記必要重ね合せ長（接続具２の長さＬ）を加えた大きさとなるが（図１参照）、接続具２に対する鉛直ドレーン材１の確実な挿入を確認するには、図２によく示されるように、折り曲げ部分１ａの先端を接続具２からわずかの長さδだけ突出させるのが望ましい。したがって、折り曲げ部分１ａの長さｌは、前記突出させる長さδと折り曲げ部分１ａの曲げアール部の長さδ´とを見込んで、前記打設ピッチＰと接続具２の長さＬとを加えた値よりもよりもわずか長めにする（Ｐ＋Ｌ＋α）。この場合、余裕代αは５〜１０ｃｍ程度で十分である。ただし、接続具２として透明なものを用いた場合は、前記した余裕代αは不要である。   Here, the length l of the bent portion 1a of each vertical drain material 1 is a size obtained by adding at least the required overlapping length (the length L of the connection tool 2) to the placement pitch P of the vertical drain material 1. (Refer to FIG. 1) In order to confirm the reliable insertion of the vertical drain material 1 into the connector 2, the tip of the bent portion 1a protrudes from the connector 2 by a slight length δ, as well shown in FIG. It is desirable to let them. Therefore, the length l of the bent portion 1a is set so that the length P to be projected and the length δ 'of the bent round portion of the bent portion 1a are set so that the placement pitch P and the length L of the connector 2 are Slightly longer than the added value (P + L + α). In this case, a margin of about 5 to 10 cm is sufficient. However, when a transparent one is used as the connection tool 2, the margin allowance α described above is not necessary.

本バーチカルドレーン工法の施工に際しては、軟弱地盤Ｇ中に所定のピッチＰで列状に鉛直ドレーン材１を打設した後、各列の鉛直ドレーン材１の余長部を同じ方向へ折り曲げると共に、各鉛直ドレーン材１の折り曲げ部分１ａに前記接続具２を差込む。次に、折り曲げ方向の前側に位置する鉛直ドレーン１の折り曲げ部分１ａ上の接続具２に対し、後続の鉛直ドレーン材１の折り曲げ部分１ａを差込む。この時、接続具２は、折り曲げ部分１ａの曲げ基端側（曲げアール部側）にできるだけ寄せるようにし、これによって前・後の鉛直ドレーン材１の重ね合せ部が確実に接続具２内に納まる。   In the construction of this vertical drain method, after the vertical drain material 1 is placed in a row at a predetermined pitch P in the soft ground G, the extra length portions of the vertical drain materials 1 in each row are bent in the same direction, The connector 2 is inserted into the bent portion 1 a of each vertical drain material 1. Next, the bent portion 1a of the subsequent vertical drain material 1 is inserted into the connector 2 on the bent portion 1a of the vertical drain 1 positioned on the front side in the bending direction. At this time, the connection tool 2 is moved as close as possible to the bending base end side (bending radius part side) of the bent portion 1a, so that the overlapping portion of the front and rear vertical drain members 1 is surely placed in the connection tool 2. Fit.

このようにして隣接する鉛直ドレーン材１の折り曲げ部分１ａ同士を相互に重ね合せて接続具２を介して連接する作業を繰返し、これによって軟弱地盤Ｇの地表面には一連の水平ドレーン部３が設置される。接続具２は、上記したように鉛直ドレーン材１を二枚重ねで収納できる必要最小限の内空断面を有しているので、隣接する鉛直ドレーン材１の折り曲げ部分１ａの重ね合せ部はほぼ密着する状態でかつ側面が押えられた状態（横ずれが規制された状態）で接続具２内に拘束され、これによって水平ドレーン部３の直線性が確保される。   In this way, the operation of repeatedly connecting the bent portions 1a of the adjacent vertical drain materials 1 to each other and connecting them via the connection tool 2 is repeated, whereby a series of horizontal drain portions 3 are formed on the ground surface of the soft ground G. Installed. Since the connecting tool 2 has the minimum necessary internal cross section that can store two vertical drain materials 1 as described above, the overlapping portions of the bent portions 1a of the adjacent vertical drain materials 1 are almost in close contact with each other. In a state where the side surface is pressed (a state in which the lateral displacement is restricted), the connection tool 2 is restrained, and thereby the linearity of the horizontal drain portion 3 is ensured.

バーチカルドレーン工法は、通常、地表面に盛土を行うことで完了し、この盛土による載荷重で軟弱地盤Ｇ中の間隙水は、鉛直ドレーン材１を通して地表へ導かれ、さらに水平ドレーン部３を通して、例えば、地盤改良域の周囲に設けられた排水溝へ排水される。この場合、前記した盛土の載荷重で柔軟性を有する袋体を用いた接続具２が扁平に押し潰されるので、鉛直ドレーン材１の重ね合せ部分は完全に密着する状態となる。これにより各鉛直ドレーン材１を通して地表へ導かれた間隙水は、各接続具２内で隣接する一方の鉛直ドレーン材１の折り曲げ部分１ａから他方の鉛直ドレーン材１の折り曲げ部分１ａへ円滑に移動し、水平ドレーン部３を通して効率よく排水される。 The vertical drain method is usually completed by embankment on the ground surface, and the pore water in the soft ground G is guided to the ground through the vertical drain material 1 by the loading load by this embankment, and further through the horizontal drain part 3, For example, the water is drained into drainage grooves provided around the ground improvement area. In this case, since the connecting tool 2 using the flexible bag body is flattened by the loading load of the above-described embankment, the overlapping portion of the vertical drain material 1 is in a state of being completely adhered. As a result, the interstitial water introduced to the ground surface through each vertical drain material 1 smoothly moves from the bent portion 1a of one vertical drain material 1 adjacent in each connector 2 to the bent portion 1a of the other vertical drain material 1. Then, the water is efficiently drained through the horizontal drain portion 3.

一方、上記排水により軟弱地盤Ｇの圧密化が進行して、地盤沈下（地盤変形）が起こる。しかし、各接続具２は柔軟性を有しているので、水平ドレーン部３は各接続具２を含めて前記地盤変形に追従する。このとき、接続具２内で前・後の鉛直ドレーン材１の重ね合せ部に相対的なすべりが生じるが、両者の間には、地表面の最大相対変位を考慮した十分なる重ね合せ長が確保されているので、地盤変形後も前・後の鉛直ドレーン材１の重ね合せ状態が維持され、この結果、所望の排水性能が維持される。また、接続具２が柔軟性を有していることから、接続具２によって鉛直ドレーン材１の折り曲げ部分１ａが傷付けられることもなく、この面からも排水性能が維持される。   On the other hand, consolidation of the soft ground G progresses due to the drainage, and ground subsidence (ground deformation) occurs. However, since each connector 2 has flexibility, the horizontal drain part 3 includes each connector 2 and follows the ground deformation. At this time, a relative slip occurs in the overlapping portion of the front and rear vertical drain materials 1 in the connection tool 2, but there is a sufficient overlapping length in consideration of the maximum relative displacement of the ground surface between them. Since it is secured, the superposed state of the vertical drain material 1 before and after the ground deformation is maintained, and as a result, the desired drainage performance is maintained. Moreover, since the connector 2 has flexibility, the bent part 1a of the vertical drain material 1 is not damaged by the connector 2, and the drainage performance is maintained from this surface.

ところで、上記のように盛土の載荷重を受けて密着状態にあるドレーン材の相互間に、地盤変形によるすべりを生じさせる場合は、両者間の摩擦抵抗によってドレーン材に大きな張力が発生し、該張力が過大になるとドレーン材が破断してしまう。   By the way, when a slip due to ground deformation occurs between the drain materials that are in close contact under the loading load of the embankment as described above, a large tension is generated in the drain material due to the frictional resistance between the two, If the tension is excessive, the drain material will break.

そこで、図６に示すように、上記した鉛直ドレーン材１（プラスチックボードドレーン材）から採取した二枚の供試材１０を重ね合せてせん断試験機１１にセットし、せん断試験を行ってドレーン材に発生する張力を確認した。せん断試験機１１は、盛土材１２が充填された下せん断箱１３と同じく盛土材１２が充填された上せん断箱１４とを備えている。上せん断箱１４は、位置を固定した下せん断箱１３に重ねて配置され、この状態で図示を略すせん断付与手段により、図６の左方向へ横移動させられるようになっている。また、上せん断箱１４の上部側には、その内部の盛土材１２に載荷板１５を介して載荷重を加える載荷手段（図示略）が配置されている。せん断試験に際しては、二枚の供試材１０のうちの一方が下せん断箱１３の上面に配置され、その一端部が該下せん断箱１３の一側面に突設した固定部材１３ａに固定される。また、他方の供試材１０は、前記一方の供試材１０に重ね合せて配置され、その一端部が一方の供試材１０と反対方向で、該上せん断箱１４の側面に突設した固定部材１４ａに固定される。   Therefore, as shown in FIG. 6, two specimens 10 taken from the above vertical drain material 1 (plastic board drain material) are overlapped and set in a shear testing machine 11, and a shear test is performed to drain the material. The tension generated was confirmed. The shear tester 11 includes a lower shear box 13 filled with the embankment material 12 and an upper shear box 14 filled with the embankment material 12. The upper shear box 14 is arranged so as to overlap the lower shear box 13 whose position is fixed, and in this state, the upper shear box 14 is moved laterally in the left direction in FIG. 6 by a shearing means not shown. Further, on the upper side of the upper shear box 14, loading means (not shown) for applying a loading load to the embankment material 12 inside the upper shearing box 14 via the loading plate 15 is arranged. In the shear test, one of the two specimens 10 is arranged on the upper surface of the lower shear box 13, and one end thereof is fixed to a fixing member 13 a protruding from one side of the lower shear box 13. . The other sample material 10 is arranged so as to overlap with the one sample material 10, and one end portion thereof projects from the side surface of the upper shear box 14 in the opposite direction to the one sample material 10. It is fixed to the fixing member 14a.

試験は、予め二枚の供試材１０の一方にひずみゲージ１５を貼付けて、これを、前後方向に整列して配置した下せん断箱１３と上せん断箱１４との間にセットする。そして、上せん断箱１４内の盛土材１２に加える載荷重を１６０ｋＮ／ｍ2（盛土高さ１０ｍに相当）と２４０ｋＮ／ｍ2（盛土高さ１５ｍに相当）の二水準に変化させると共に、土質工学学会基準案（ＪＩＳ Ｔ ９４１−１９９Ｘ）「土とジオテキスタイルの摩擦特性試験方法」に示されるジオテキスタイルの標準引き抜き変位速度１ｍｍ／ｍｉｎに準拠する、せん断速度１．０ｍｍ／ｍｉｎの条件で上せん断箱１４を横移動させて行い、供試材１０の合せ面に貼り付けた歪ゲージ１５に発生する張力を測定した。 In the test, a strain gauge 15 is pasted on one of the two specimens 10 in advance, and this is set between a lower shear box 13 and an upper shear box 14 arranged in the front-rear direction. Then, the changing in two levels of fill material 12 is added placing a load 160 kN / m 2 of the upper shear box 14 (corresponding to the embankment height 10m) and 240kN / m 2 (equivalent to fill height 15 m), soil Upper shear box under conditions of shear rate of 1.0 mm / min, conforming to the standard pull-out displacement rate of 1 mm / min of geotextile shown in “Standard Method for Friction Properties of Soil and Geotextile”, Standards of Engineering Society (JIS T 941-199X) 14 was moved laterally, and the tension generated in the strain gauge 15 attached to the mating surface of the specimen 10 was measured.

図７は、上記のように行ったせん断試験結果を示したものである。なお、図７では、ドレーン材に発生する張力を１ｍ幅あたりで整理して示している。図７より載荷重を１６０ｋＮ／ｍ2に設定した場合、２４０ｋＮ／ｍ2に設定した場合共に、発生張力は２ｋＮ／ｍ以下であり、ドレーン材の公称許容強度２０ｋＮ／ｍと比較しても極めて低い値となっている。したがって、上記実施形態において前・後の鉛直ドレーン材１の重ね合せ部分に盛土の載荷重が作用した状態で相対的なすべりが生じても、鉛直ドレーン材１の折り曲げ部分１ａが破断する危険が全くないことが明らかとなった。また、試験後、せん断試験機１１を解体して供試材１０（ドレーン材）の表面状態を観察したところ、全く損傷は認められず、耐久性も十分であることを確認できた。 FIG. 7 shows the result of the shear test performed as described above. In FIG. 7, the tension generated in the drain material is shown per 1 m width. If you set the load mounting from 7 to 160 kN / m 2, both when set to 240kN / m 2, developed tension is less than or equal 2 kN / m, very even compared to nominal allowable strength 20 kN / m in the drain member The value is low. Therefore, in the above embodiment, even if a relative slip occurs in a state where the loading load of the embankment is applied to the overlapped portions of the front and rear vertical drain materials 1, there is a risk that the bent portion 1a of the vertical drain material 1 is broken. It became clear that there was nothing at all. Further, after the test, when the shear tester 11 was disassembled and the surface state of the specimen 10 (drain material) was observed, no damage was observed and it was confirmed that the durability was sufficient.

本発明に係るバーチカルドレーン工法の実施形態を示す断面図である。It is sectional drawing which shows embodiment of the vertical drain construction method which concerns on this invention. 図１の一部を拡大して示す断面図である。It is sectional drawing which expands and shows a part of FIG. 本バーチカルドレーン工法で設置された水平ドレーン部の状態を示す平面図である。It is a top view which shows the state of the horizontal drain part installed by this vertical drain construction method. 本バーチカルドレーン工法で用いる接続具の外観形状を示す斜視図である。It is a perspective view which shows the external appearance shape of the connector used by this vertical drain construction method. 地表面１ｍあたりの最大相対変位δｒと基礎地盤最大沈下量との関係を示すグラフである。It is a graph which shows the relationship between the maximum relative displacement (delta) r per 1m of ground surfaces, and the foundation ground maximum subsidence amount. ドレーン材に発生する張力を確認するためのせん断試験の実施形態を示す断面図である。It is sectional drawing which shows embodiment of the shear test for confirming the tension | tensile_strength which generate | occur | produces in a drain material. せん断試験の結果を示すグラフである。It is a graph which shows the result of a shear test.

符号の説明Explanation of symbols

１ 鉛直ドレーン材
１ａ 鉛直ドレーン材の折り曲げ部分
２ 接続具
３ 水平ドレーン部
Ｇ 軟弱地盤 DESCRIPTION OF SYMBOLS 1 Vertical drain material 1a Bending part of vertical drain material 2 Connection tool 3 Horizontal drain part G Soft ground

Claims (5)

軟弱地盤中に列状に打設した鉛直ドレーン材の余長部を同じ方向へ折り曲げて、各鉛直ドレーン材の折り曲げ部分を、柔軟性を有する袋体を用いた扁平筒状の接続具内に挿入し、折り曲げ方向の前側に位置する鉛直ドレーンの折り曲げ部分上の接続具に対し、後続の鉛直ドレーン材の折り曲げ部分を差込み、この際、前記接続具を折り曲げ部分の曲げ基端側に寄せるようにして、前・後の鉛直ドレーン材の重ね合せ部を前記接続具内に納め、隣接する鉛直ドレーン材の折り曲げ部分同士を相互に重ね合せて、前記接続具を介して連接する作業を繰返し、前記接続具を介して各鉛直ドレーン材の折り曲げ部分を連接して一連の水平ドレーン部とすることを特徴とするバーチカルドレーン工法。 Bend the extra lengths of vertical drain materials placed in a row in soft ground in the same direction, and fold each vertical drain material into a flat cylindrical connector using a flexible bag. Insert and insert the bent portion of the subsequent vertical drain material into the connecting tool on the bent portion of the vertical drain located on the front side in the bending direction, and at this time, bring the connecting tool closer to the bending base side of the bent portion. Then, the overlapping part of the vertical drain material before and after is placed in the connection tool, the bent portions of the adjacent vertical drain materials are overlapped with each other, and the operation of connecting via the connection tool is repeated. vertical drain method, characterized in that by connecting the bent portions of the vertical drain material through said connecting device and a series of horizontal drain portion. 扁平状態とした接続具の内空幅Ｗを、鉛直ドレーン材の幅ｗ、鉛直ドレーン材の厚さｔおよび係数Ｋを含む下記の関係式
Ｗ＝[ｗ＋２ｔ]×Ｋ
に基づき、Ｋを１．１〜１．３の範囲から選択した任意の値を用いて設定することを特徴とする請求項１に記載のバーチカルドレーン工法。 The following relational expression including the width w of the vertical drain material, the thickness t of the vertical drain material, and the coefficient K is used as the inner space width W of the connecting device in the flat state W = [w + 2t] × K
The vertical drain method according to claim 1, wherein K is set using an arbitrary value selected from a range of 1.1 to 1.3. 接続具の長さを、３０ｃｍ以上に設定することを特徴とする請求項１または２に記載のバーチカルドレーン工法。   The vertical drain construction method according to claim 1, wherein the length of the connection tool is set to 30 cm or more. 接続具の長さを、４０ｃｍ以上に設定することを特徴とする請求項１または２に記載のバーチカルドレーン工法。   The vertical drain method according to claim 1 or 2, wherein the length of the connection tool is set to 40 cm or more. 袋体が、生分解性プラスチック材からなることを特徴とする請求項１乃至４の何れか１項に記載のバーチカルドレーン工法。   The vertical drain method according to any one of claims 1 to 4, wherein the bag is made of a biodegradable plastic material.
JP2007305613A 2007-11-27 2007-11-27 Vertical drain method Active JP4538817B2 (en)

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JP5555571B2 (en) * 2010-08-17 2014-07-23 錦城護謨株式会社 Drain material connection structure
CN114319307B (en) * 2022-01-06 2023-07-25 益阳市博然科技有限公司 Tightly wrapped plastic drainage plate and filter tube binding equipment

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JP2002004263A (en) * 2000-06-16 2002-01-09 Taiyo Kiso Kk Ground improving method
JP2005061143A (en) * 2003-08-19 2005-03-10 Mamoru Mimura Connector of drain material and driving method of the drain material
JP2005061142A (en) * 2003-08-19 2005-03-10 Mamoru Mimura Driving method of drain material

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JP2002004263A (en) * 2000-06-16 2002-01-09 Taiyo Kiso Kk Ground improving method
JP2005061143A (en) * 2003-08-19 2005-03-10 Mamoru Mimura Connector of drain material and driving method of the drain material
JP2005061142A (en) * 2003-08-19 2005-03-10 Mamoru Mimura Driving method of drain material

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