JP2015157267A - Construction method for purifying ground water, and system for purifying ground water - Google Patents
Construction method for purifying ground water, and system for purifying ground water Download PDFInfo
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本発明は、地盤の汚染範囲に通水することにより該汚染範囲の地下水を浄化する地下水浄化工法、及び地下水浄化システムに関する。 The present invention relates to a groundwater purification method for purifying groundwater in a contaminated area by passing water through the contaminated area of the ground, and a groundwater purification system.
汚染された土壌に通水することにより該土壌を浄化する土壌浄化工法（汚染範囲の地下水を浄化する地下水浄化工法）として、ウェルポイント等の注水井戸とディープウェル等の揚水井戸との間にサンドパイルを構築し、注水井戸からサンドパイルを経由して揚水井戸に至る地下水の流れを形成することにより、透水性が悪い土壌の浄化を効果的に実施しようとしたものが知られている（例えば、特許文献１参照）。特許文献１には、揚水井戸をバキュームディープウェル（真空ディープウェル）とすることにより、地盤の深層に存する透水性が悪い土壌の浄化を効果的に実施しようとしたものが記載されている。 As a soil purification method that purifies the soil by passing water through the contaminated soil (a groundwater purification method that purifies the groundwater in the contaminated area), sand is placed between the water injection well such as the well point and the pumping well such as the deep well. It is known that a pile is constructed and an attempt is made to effectively purify soil with poor water permeability by forming a flow of groundwater from a water injection well to a pumping well via a sand pile (for example, , See Patent Document 1). Patent Document 1 describes that a pumping well is a vacuum deep well (vacuum deep well) so as to effectively purify soil having poor water permeability in the deep layer of the ground.
特許文献１に記載のバキュームウェルを揚水井戸とした土壌浄化工法では、サンドパイルの天端が地表面に位置し、サンドパイルが大気に開放されていることにより、サンドパイルが地下水のみならず外気を吸引することになる。従って、サンドパイルの吸引力が弱くなるため、透水性が悪い土壌及び該土壌の地下水を効果的に浄化できない。 In the soil purification method using a vacuum well as a pumping well described in Patent Document 1, the top of the sand pile is located on the ground surface, and the sand pile is open to the atmosphere. Will be sucked. Therefore, since the suction force of the sand pile is weak, it is not possible to effectively purify soil with poor water permeability and groundwater of the soil.
本発明は、上記事情に鑑みてなされたものであり、地盤の汚染範囲に通水することにより該汚染範囲の地下水を浄化する地下水浄化工法において、透水性が悪い汚染範囲の地下水を効果的に浄化することを課題にするものである。 The present invention has been made in view of the above circumstances, and in the groundwater purification method for purifying the groundwater in the contaminated area by passing water through the contaminated area of the ground, the groundwater in the contaminated area having poor water permeability is effectively used. The problem is to purify.
上記課題を解決するために、本発明に係る地下水浄化工法は、地盤の汚染範囲に通水することにより該汚染範囲の地下水を浄化する地下水浄化工法であって、前記汚染範囲に注水する注水ドレーンを構築する工程と、内部が負圧にされ、前記汚染範囲以深から揚水する揚水井戸を構築する工程と、前記揚水井戸の前記負圧により生じる吸引力によって前記汚染範囲の地下水を吸引して前記汚染範囲以深へ降下させる吸引ドレーンを構築する工程と、前記注水ドレーンを通して前記汚染範囲に注水すると共に、前記揚水井戸により前記吸引ドレーンを通して前記汚染範囲の地下水を排水する工程とを備え、前記吸引ドレーンの天端を気密状態で封止するものである。 In order to solve the above-mentioned problem, a groundwater purification method according to the present invention is a groundwater purification method for purifying groundwater in the contaminated area by passing water through the contaminated area of the ground, and is a water injection drain for pouring water into the contaminated area A step of constructing a pumping well in which the inside is made negative pressure and pumping from deeper than the contamination range, and the groundwater in the contaminated range is sucked by the suction force generated by the negative pressure of the pumping well. A step of constructing a suction drain for lowering to a depth below the contamination range, and a step of pouring water into the contamination range through the water injection drain and draining the ground water in the contamination range through the suction drain by the pumping well. Is sealed in an airtight state.
前記地下水浄化工法において、前記汚染範囲は地盤の粘性土層に存在し、該地盤の該粘性土層の下には透水層が存在してもよく、前記揚水井戸を、前記透水層から揚水するように構築し、前記吸引ドレーンを、前記汚染範囲以浅から前記透水層まで延びるように構築してもよい。 In the groundwater purification method, the contamination range may exist in a viscous soil layer of the ground, and a permeable layer may exist under the viscous soil layer of the ground, and the pumping well is pumped from the permeable layer. The suction drain may be constructed so as to extend from shallower than the contamination range to the permeable layer.
また、本発明に係る地下水浄化システムは、地盤の汚染範囲に通水することにより該汚染範囲の地下水を浄化する地下水浄化システムであって、前記汚染範囲に注水する注水ドレーンと、内部が負圧にされ、前記汚染範囲以深から揚水する揚水井戸と、前記揚水井戸の前記負圧により生じる吸引力によって前記汚染範囲の地下水を吸引して前記汚染範囲以深へ降下させる吸引ドレーンとを備え、前記吸引ドレーンの天端は、気密状態で封止されているものである。 Further, the groundwater purification system according to the present invention is a groundwater purification system for purifying the groundwater in the contaminated area by passing water through the contaminated area of the ground, and an irrigation drain for injecting water into the contaminated area, and an internal negative pressure A suction well that pumps water from deeper than the contaminated area, and a suction drain that sucks groundwater in the contaminated area by a suction force generated by the negative pressure of the pumped well and lowers the groundwater below the contaminated area. The top end of the drain is sealed in an airtight state.
本発明によれば、地盤の汚染範囲に通水することにより該汚染範囲の地下水を浄化する地下水浄化工法において、透水性が悪い汚染範囲の地下水を効果的に浄化できる。 ADVANTAGE OF THE INVENTION According to this invention, in the groundwater purification construction method which purifies the groundwater of this contaminated area by passing water to the contaminated area of the ground, the groundwater of the contaminated area with poor water permeability can be effectively purified.
以下、本発明の一実施形態を、図面を参照しながら説明する。図１は、一実施形態に係る地下水浄化システム１０を示す立断面図であり、図２は、該地下水浄化システム１０の揚水井戸２０、注水ドレーン３０及び吸引ドレーン４０の配置を示す平面図である。これらの図に示すように、地下水浄化システム１０は、止水壁１２の内側の地盤に存在する粘性土層１の汚染範囲Ａ、Ｂの地下水及び土壌を、通水洗浄により浄化する地下水浄化工法並びに土壌浄化工法を実施するためのものである。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a vertical sectional view showing a groundwater purification system 10 according to an embodiment, and FIG. 2 is a plan view showing an arrangement of a pumping well 20, a water injection drain 30, and a suction drain 40 of the groundwater purification system 10. . As shown in these figures, the groundwater purification system 10 is a groundwater purification method that purifies groundwater and soil in the contaminated areas A and B of the viscous soil layer 1 existing on the ground inside the water blocking wall 12 by water washing. In addition, it is for carrying out the soil purification method.
地下水浄化システム１０により地下水及び土壌の浄化を実施する地盤には、地表面（ＧＬ±０ｍ）から順に、粘性土層１、透水層２、不透水層３が存在する。粘性土層１は、砂層や礫層に比して透水性が低いシルト層や沖積粘土層等である。また、透水層２は、砂層や礫層等であり、粘性土層１に比して透水性が高い層である。さらに、不透水層３は、透水層２に比して不透水性の粘土層である。 On the ground where groundwater and soil are purified by the groundwater purification system 10, there are a viscous soil layer 1, a permeable layer 2, and an impermeable layer 3 in order from the ground surface (GL ± 0 m). The cohesive soil layer 1 is a silt layer, an alluvial clay layer, or the like having low water permeability compared to a sand layer or a gravel layer. The water permeable layer 2 is a sand layer, a gravel layer, or the like, and is a layer having a higher water permeability than the viscous soil layer 1. Further, the impermeable layer 3 is a clay layer that is impervious to the water permeable layer 2.
地下水浄化システム１０は、浄化対象の範囲を囲うように構築された止水壁１２と、止水壁１２の内側の地盤に設けられた揚水井戸２０、複数の注水ドレーン３０及び複数の吸引ドレーン４０と、地上に設置された水処理設備５０及び真空ポンプ６０とを備えている。止水壁１２は、遮水性を有する鋼矢板壁等であり、地表面から粘性土層１、透水層２を貫通して不透水層３まで達するように構築されている。また、水処理設備５０は、揚水井戸２０により揚水された汚染水を浄化して注水系統へ給水する。 The groundwater purification system 10 includes a water stop wall 12 constructed so as to surround a range to be purified, a pumping well 20 provided on the ground inside the water stop wall 12, a plurality of water injection drains 30, and a plurality of suction drains 40. And a water treatment facility 50 and a vacuum pump 60 installed on the ground. The water blocking wall 12 is a steel sheet pile wall or the like having water impermeability, and is constructed so as to penetrate the viscous soil layer 1 and the water permeable layer 2 to reach the water impermeable layer 3 from the ground surface. Moreover, the water treatment facility 50 purifies the contaminated water pumped by the pumping well 20 and supplies it to the water injection system.
揚水井戸２０は、井戸内を真空に保ちながら水中ポンプ２２で揚水するバキュームディープウェル（真空ディープウェル）、スーパーウェルポイント（登録商標）、ハイパーディープウェル（登録商標）等の重力排水と強制排水とを組合わせたものであり、地表面から粘性土層１を貫通して透水層２の深部に達するように構築されている。この揚水井戸２０は、孔２６内に配されたケーシング２３と、ケーシング２３内に配された水中ポンプ２２、揚水管２５及び吸引管２８と、ケーシング２３と孔２６の壁面との間に充填されたグラウト材２７−１及びフィルター材２７−２と、ケーシング２３の天端を密閉する蓋２９とを備える。グラウト材２７−１は、粘性土層１に設けられ、フィルター材２７−２は、透水層２に設けられている。 The pumping well 20 is composed of gravity drainage and forced drainage such as vacuum deepwell (vacuum deepwell), superwellpoint (registered trademark), hyper deepwell (registered trademark), etc. And is constructed so as to penetrate the viscous soil layer 1 from the ground surface and reach the deep part of the water permeable layer 2. The pumping well 20 is filled between the casing 23 disposed in the hole 26, the submersible pump 22, the pumping pipe 25 and the suction pipe 28 disposed in the casing 23, and the casing 23 and the wall surface of the hole 26. The grout material 27-1 and the filter material 27-2 and a lid 29 for sealing the top end of the casing 23 are provided. The grout material 27-1 is provided on the viscous soil layer 1, and the filter material 27-2 is provided on the water permeable layer 2.
ケーシング２３のスクリーン２４は、透水層２の上端以深に設けられており、水中ポンプ２２は、透水層２の深部に設置されている。また、揚水管２５の一端は水中ポンプ２２に接続され、揚水管２５の他端は、水処理設備５０に接続されている。また、吸引管２８の一端は、蓋２９を通してケーシング２３内に挿入され、吸引管２８の他端は、地上に設置された真空ポンプ６０に接続されている。このため、真空ポンプ６０が作動されてケーシング２３内が真空にされると共に水中ポンプ２２が作動されることにより、透水層２の地下水がスクリーン２４からケーシング２３内に真空圧により吸引され水中ポンプ２２により揚水管２５を通して地上へ排水される。 The screen 24 of the casing 23 is provided deeper than the upper end of the water permeable layer 2, and the submersible pump 22 is installed in a deep portion of the water permeable layer 2. One end of the pumping pipe 25 is connected to the submersible pump 22, and the other end of the pumping pipe 25 is connected to the water treatment facility 50. One end of the suction tube 28 is inserted into the casing 23 through the lid 29, and the other end of the suction tube 28 is connected to a vacuum pump 60 installed on the ground. For this reason, the vacuum pump 60 is actuated to evacuate the casing 23 and the submersible pump 22 is actuated, whereby the groundwater in the permeable layer 2 is sucked into the casing 23 from the screen 24 by the vacuum pressure, and the submersible pump 22. Is discharged to the ground through the pumping pipe 25.
揚水井戸２０は、浄化対象の地盤の中心に配されており、複数の注水ドレーン３０は、揚水井戸２０の周囲に格子状に配されている。ここで、注水ドレーン３０が所定ピッチＰで並んだ列と、注水ドレーン３０が所定ピッチ２Ｐ（所定ピッチＰの２倍）で並んだ列とが交互に配されており、後者の列では、注水ドレーン３０と吸引ドレーン４０とが交互に配されている。 The pumping wells 20 are arranged at the center of the ground to be purified, and the plurality of water injection drains 30 are arranged in a grid around the pumping wells 20. Here, a row in which the water injection drains 30 are arranged at a predetermined pitch P and a row in which the water injection drains 30 are arranged at a predetermined pitch 2P (twice the predetermined pitch P) are alternately arranged. The drains 30 and the suction drains 40 are alternately arranged.
注水ドレーン３０は、ペーパードレーンであり、地表面から粘性土層１の深部あるいは中間部まで延びている。地表面には、水処理設備５０に接続された給水管５２が格子状に配されており、注水ドレーン３０の天端は給水管５２に接続されている。ここで、注水ドレーン３０の天端は、改良対象範囲Ａの天端よりも上側に位置し、注水ドレーン３０の下端は、改良対象範囲Ａの下端よりも下側に位置する。また、注水ドレーン３０の粘性土層１に位置する部位は、水路が形成された板状の樹脂製の芯材を不織布等の面状の透水性材で挟んだ帯状体で構成されている。このため、浄水が水処理設備５０から給水管５２を通して注水ドレーン３０に供給されると、浄水が、注水ドレーン３０の芯材の水路を通って降下すると共にフィルターを透過して粘性土層１の改良対象範囲Ａ、Ｂに浸透する。 The water injection drain 30 is a paper drain, and extends from the ground surface to a deep part or an intermediate part of the viscous soil layer 1. On the ground surface, water supply pipes 52 connected to the water treatment facility 50 are arranged in a lattice shape, and the top end of the water injection drain 30 is connected to the water supply pipe 52. Here, the top end of the water injection drain 30 is located above the top end of the improvement target range A, and the bottom end of the water injection drain 30 is located below the bottom end of the improvement target range A. Moreover, the site | part located in the viscous soil layer 1 of the water injection drain 30 is comprised with the strip | belt-shaped body which pinched | interposed the plate-shaped resin core material in which the water channel was formed with planar water-permeable materials, such as a nonwoven fabric. For this reason, when purified water is supplied from the water treatment facility 50 to the water injection drain 30 through the water supply pipe 52, the purified water descends through the water channel of the core material of the water injection drain 30 and passes through the filter to form the viscous soil layer 1. It penetrates the improvement target areas A and B.
ここで、図１中の左側に示すように、汚染範囲Ａが、粘性土層１の浅部から深部まで広がる場合には、注水ドレーン３０により注水する範囲を粘性土層１の浅部から深部までの広範囲とする。一方、図１中の右側に示すように、汚染範囲Ｂが、粘性土層１の浅部にのみ存在する場合には、注水ドレーン３０により注水する範囲を粘性土層１の浅部にのみ制限する。 Here, as shown on the left side in FIG. 1, when the contamination range A extends from the shallow part to the deep part of the cohesive soil layer 1, the range of water injection by the water injection drain 30 is changed from the shallow part to the deep part of the cohesive soil layer 1. Up to a wide range. On the other hand, as shown on the right side in FIG. 1, when the contamination range B exists only in the shallow portion of the viscous soil layer 1, the range of water injection by the water injection drain 30 is limited only to the shallow portion of the viscous soil layer 1. To do.
吸引ドレーン４０は、ペーパードレーンであり、粘性土層１の浅部から透水層２の深部まで延びている。この吸引ドレーン４０の天端には、樹脂製の帯状体４２が接続されており、該帯状体４２が吸引ドレーン４０の天端から地表面まで延びている。 The suction drain 40 is a paper drain and extends from a shallow portion of the viscous soil layer 1 to a deep portion of the water permeable layer 2. A resin strip 42 is connected to the top end of the suction drain 40, and the strip 42 extends from the top of the suction drain 40 to the ground surface.
吸引ドレーン４０の天端は、汚染範囲Ａ、Ｂの天端よりも上側に位置し、吸引ドレーン４０の下端は、透水層２に位置する。ここで、吸引ドレーン４０の天端から下端までの全体が、水路が形成された帯状の樹脂製の芯材を不織布等の面状の透水材で挟んだ帯状体で構成されている。このため、注水ドレーン３０から粘性土層１の汚染範囲Ａ、Ｂに注入された浄水及び汚染範囲Ａ、Ｂの汚染水が、フィルターを透過して芯材の水路に流入し、該水路を通って透水層２まで降下する。 The top end of the suction drain 40 is located above the top end of the contamination ranges A and B, and the bottom end of the suction drain 40 is located in the water permeable layer 2. Here, the whole from the top end to the lower end of the suction drain 40 is constituted by a band-shaped body in which a band-shaped resin core material having a water channel formed is sandwiched between planar water-permeable materials such as a nonwoven fabric. For this reason, the purified water injected from the water injection drain 30 into the contaminated areas A and B of the clay soil layer 1 and the contaminated water in the contaminated areas A and B permeate the filter and flow into the core water channel and pass through the water channel. Descend to the permeable layer 2.
ここで、吸引ドレーン４０の天端は、粘性土層１の粘土又はシルトにより気密状態で封止されている。これにより、揚水井戸２０のケーシング２３内が真空ポンプ６０により真空にされて吸引ドレーン４０内に吸引力が生じた状態で、該吸引力で外気が吸引されることがない。従って、吸引ドレーン４０の吸引力の全てが粘性土層１内に作用する。 Here, the top end of the suction drain 40 is sealed in an airtight state with clay or silt of the viscous soil layer 1. Thereby, in the state where the inside of the casing 23 of the pumping well 20 is evacuated by the vacuum pump 60 and the suction force is generated in the suction drain 40, the outside air is not sucked by the suction force. Therefore, all of the suction force of the suction drain 40 acts in the viscous soil layer 1.
図３〜図５は、本実施形態に係る地下水浄化システム１０を構築する手順を説明する立断面図である。まず、図３に示すように、止水壁１２を地表面から不透水層３に達するように構築する。次に、図４及び図５に示すように、注水ドレーン３０及び吸引ドレーン４０を止水壁１２の内側の地盤中に構築すると共に、揚水井戸２０を止水壁１２の内側の地盤中に構築する。 3 to 5 are vertical sectional views for explaining a procedure for constructing the groundwater purification system 10 according to the present embodiment. First, as shown in FIG. 3, the water blocking wall 12 is constructed so as to reach the impermeable layer 3 from the ground surface. Next, as shown in FIGS. 4 and 5, the water injection drain 30 and the suction drain 40 are constructed in the ground inside the water blocking wall 12, and the pumping well 20 is built in the ground inside the water blocking wall 12. To do.
図４に示すように、注水ドレーン３０及び吸引ドレーン４０を構築する工程では、ドレーン材５を供給リール６から送り出してケーシング７を用いて地盤中に打設する。この工程では、ドレーン材５をケーシング７に挿通してドレーン材５の先端にプレート８を取り付けた状態で、これらを地盤中に圧入し、その後、ケーシング７を地盤中から引き抜く。そして、給水管５２を設置して、注水ドレーン３０の天端を給水管５２に接続する。 As shown in FIG. 4, in the step of constructing the water injection drain 30 and the suction drain 40, the drain material 5 is sent out from the supply reel 6 and placed in the ground using the casing 7. In this step, the drain material 5 is inserted into the casing 7 and the plate 8 is attached to the tip of the drain material 5, and these are press-fitted into the ground, and then the casing 7 is pulled out from the ground. Then, the water supply pipe 52 is installed, and the top end of the water injection drain 30 is connected to the water supply pipe 52.
ここで、汚染範囲Ａの注水ドレーン３０は、地表面から粘性土層１の深部の汚染範囲Ａの下端以深まで延びるように構築し、汚染範囲Ｂの注水ドレーン３０は、地表面から粘性土層１の中間部の汚染範囲Ｂの下端以深まで延びるように構築する。一方、吸引ドレーン４０は、粘性土層１の浅部の汚染範囲Ａ、Ｂの天端以浅から透水層２に達するように構築する。 Here, the water injection drain 30 in the contamination range A is constructed so as to extend from the ground surface to the depth below the lower end of the contamination range A in the deep part of the viscous soil layer 1, and the water injection drain 30 in the contamination range B extends from the ground surface to the viscous soil layer. 1 is constructed so as to extend to the depth below the lower end of the contamination range B in the middle part. On the other hand, the suction drain 40 is constructed so as to reach the water permeable layer 2 from shallower than the top of the contaminated areas A and B in the shallow part of the viscous soil layer 1.
また、図５に示すように、揚水井戸２０を構築する工程では、孔２６を地表面から透水層２の深部に達するように掘削し、ケーシング２３を孔２６に挿入する。この際、スクリーン２４を透水層２の上端以深に設ける。そして、水中ポンプ２２と揚水管２５とをケーシング２３内に設置し、ケーシング２３と孔２６の孔壁との間は、粘性土層１の深度ではグラウト材２７−１を充填して止水処理を行い、透水層２の深度ではフィルター材２７−２を充填する。この際、水中ポンプ２２を透水層２の深部に設置する。また、ケーシング２３の天端を、吸引管２８を取り付けた蓋２９で封止する。 As shown in FIG. 5, in the step of constructing the pumped well 20, the hole 26 is excavated from the ground surface to reach the deep part of the permeable layer 2, and the casing 23 is inserted into the hole 26. At this time, the screen 24 is provided deeper than the upper end of the water permeable layer 2. And the submersible pump 22 and the pumping pipe 25 are installed in the casing 23, and between the casing 23 and the hole wall of the hole 26 is filled with grout material 27-1 at the depth of the viscous soil layer 1 to stop the water. The filter material 27-2 is filled at the depth of the water permeable layer 2. At this time, the submersible pump 22 is installed deep in the water permeable layer 2. Further, the top end of the casing 23 is sealed with a lid 29 to which a suction pipe 28 is attached.
以上のようにして地下水浄化システム１０を構築した後、止水壁１２の内側の地盤の地下水の浄化を実施する。この地下水浄化工程では、図１に示すように、真空ポンプ６０を作動させて揚水井戸２０内を真空状態にし、水中ポンプ２２を作動させて透水層２の地下水を揚水すると共に、水処理設備５０を作動させて、揚水した地下水を浄水にして給水管５２及び注水ドレーン３０を通して粘性土層１の汚染範囲Ａ、Ｂに注水する。 After constructing the groundwater purification system 10 as described above, the groundwater in the ground inside the water blocking wall 12 is purified. In this groundwater purification process, as shown in FIG. 1, the vacuum pump 60 is operated to bring the pumping well 20 into a vacuum state, the submersible pump 22 is operated to pump the groundwater in the permeable layer 2, and the water treatment facility 50. , The pumped groundwater is purified and injected into the contaminated areas A and B of the cohesive soil layer 1 through the water supply pipe 52 and the water injection drain 30.
揚水井戸２０内の真空圧により、透水層２の地下水が揚水井戸２０内に吸い込まれると共に、吸引ドレーン４０に吸引力が生じる。これにより、汚染範囲Ａ、Ｂに存する汚染水が、吸引ドレーン４０内に吸引されて吸引ドレーン４０を通して透水層２に降下する。 Due to the vacuum pressure in the pumping well 20, the groundwater of the permeable layer 2 is sucked into the pumping well 20 and suction force is generated in the suction drain 40. Thereby, the contaminated water existing in the contaminated areas A and B is sucked into the suction drain 40 and falls to the water permeable layer 2 through the suction drain 40.
ここで、吸引ドレーン４０の天端が粘性土層１の粘土又はシルトにより気密状態で封止されていることにより、吸引ドレーン４０の吸引力で外気が吸引されることがなく、吸引ドレーン４０の吸引力の全てが粘性土層１内に作用する。これにより、該吸引ドレーン４０を粘性土層１に設けることで、汚染範囲Ａ、Ｂの汚染水の横方向への移動距離を短くできるのみならず、該汚染水の横方向への移動速度を増加させることができ、粘性土層１内の集水機能を向上させることができる。よって、透水性の低い粘性土層１においても、効果的に汚染水を吸引ドレーン４０に集め、吸引ドレーン４０を通して透水層２に降下させて揚水井戸２０により排水することができる。従って、透水性の低い粘性土層１の汚染範囲Ａ、Ｂに存在する汚染水を効果的に浄化できる。 Here, since the top end of the suction drain 40 is sealed in an airtight state by clay or silt of the viscous soil layer 1, the outside air is not sucked by the suction force of the suction drain 40, and the suction drain 40 All of the suction force acts in the clay soil layer 1. Accordingly, by providing the suction drain 40 in the viscous soil layer 1, not only the moving distance of the contaminated water in the contaminated areas A and B in the lateral direction can be shortened but also the moving speed of the contaminated water in the lateral direction can be increased. The water collecting function in the cohesive soil layer 1 can be improved. Therefore, even in the viscous soil layer 1 with low water permeability, the contaminated water can be effectively collected in the suction drain 40, dropped to the water permeable layer 2 through the suction drain 40, and drained by the pumping well 20. Therefore, it is possible to effectively purify the contaminated water existing in the contaminated areas A and B of the viscous soil layer 1 having low water permeability.
また、止水壁１２が不透水層３に達していることにより、止水壁１２の内側の粘性土層１及び透水層２には、止水壁１２の外側及び透水層２の下側から地下水が流入しない。これにより、地下水の排水量を低減できると共に、周辺地盤に及ぶ影響を抑えることができる。 Further, since the water blocking wall 12 reaches the impermeable layer 3, the viscous soil layer 1 and the water permeable layer 2 on the inner side of the water blocking wall 12 are separated from the outside of the water blocking wall 12 and the lower side of the water permeable layer 2. Groundwater does not flow. Thereby, while being able to reduce the amount of drainage of groundwater, the influence on surrounding ground can be suppressed.
ここで、本実施形態に係る地下水浄化システム１０の一実施例について説明する。本実施例では、注水ドレーン３０同士の間隔ａあるいは注水ドレーン３０と吸引ドレーン４０との間隔ａを１ｍとする。これにより、注水ドレーン３０から吸引ドレーン４０までの通水距離は、１ｍあるいは下記（１）で示すように、１．５７ｍとなる。
Here, an example of the groundwater purification system 10 according to the present embodiment will be described. In this embodiment, the interval a between the water injection drains 30 or the interval a between the water injection drain 30 and the suction drain 40 is 1 m. Thereby, the water flow distance from the water injection drain 30 to the suction drain 40 is 1 m or 1.57 m as shown in the following (1).
粘性土層１の透水係数をｋ＝１×１０-4ｃｍ／ｓｅｃ、粘性土層１の真空度を５０％程度とすると、動水勾配は、下記（２）式で示すように、３．１８となる。また、通水距離ｌ（＝１．５７ｍ）間での地下水の移動時間ｔは、下記（３）式で示すように、２．３日となる。
Assuming that the hydraulic conductivity of the cohesive soil layer 1 is k = 1 × 10 −4 cm / sec and the degree of vacuum of the cohesive soil layer 1 is about 50%, as shown in the following equation (2), the dynamic gradient is 3. 18 Moreover, the movement time t of groundwater between the water flow distances 1 (= 1.57 m) is 2.3 days as shown by the following formula (3).
粘性土層１の有効間隙率を０．１５とすると、１本の吸引ドレーン４０が負担する面積は、４ｍ2（＝２ａ×２ａ）であるため、１回通水する毎の水量（吸引ドレーン４０の単位長さあたり）Ｑは、下記（４）式で示すように、０．６ｍ3となる。そして、単位当たりの吸引量ｑ1は、下記（５）式で示すように、０．１８ｌ／ｍｉｎ・ｍとなる。
Assuming that the effective porosity of the cohesive soil layer 1 is 0.15, the area that one suction drain 40 bears is 4 m 2 (= 2a × 2a), so the amount of water every time water is passed (suction drain) Q per unit length of 40 is 0.6 m 3 as shown in the following formula (4). The suction amount q 1 per unit is 0.18 l / min · m as shown by the following equation (5).
また、本実施例では、浄化対象の範囲の面積を１０ｍ×１０ｍの１００ｍ2、深度を７ｍとする。これにより、１日あたりの全通水量ΣＱは、下記（６）式で示すように、４５．３６ｍ3／日となる。
In this embodiment, the area of the purification target range is 100 m 2 of 10 m × 10 m, and the depth is 7 m. Accordingly, the total water flow amount ΣQ per day is 45.36 m 3 / day as shown by the following formula (6).
以上説明したように、本実施形態に係る地下水浄化工法では、地盤の汚染範囲Ａ、Ｂに通水することにより該汚染範囲Ａ、Ｂの地下水を浄化するにあたり、汚染範囲Ａ、Ｂに注水する注水ドレーン３０を構築する工程と、内部が負圧（真空）にされ、汚染範囲Ａ、Ｂの以深から揚水する揚水井戸２０を構築する工程と、揚水井戸２０の負圧により生じる吸引力によって汚染範囲Ａ、Ｂの地下水を吸引して汚染範囲Ａ、Ｂの以深へ降下させる吸引ドレーン４０を構築する工程と、注水ドレーン３０を通して汚染範囲Ａ、Ｂに注水すると共に、揚水井戸２０により吸引ドレーン４０を通して汚染範囲Ａ、Ｂの地下水を排水する工程とを実施する。 As described above, in the groundwater purification method according to the present embodiment, water is poured into the contaminated areas A and B when purifying the groundwater in the contaminated areas A and B by passing water through the contaminated areas A and B of the ground. Contamination by the step of constructing the water injection drain 30, the step of constructing the pumping well 20 that pumps water from deeper than the contamination areas A and B, and the suction force generated by the negative pressure of the pumping well 20. The step of constructing a suction drain 40 for sucking the groundwater in the ranges A and B and lowering the groundwater to the depth of the pollution ranges A and B, water is poured into the contaminated ranges A and B through the water injection drain 30, and the suction drain 40 is used by the pumping well 20. And the step of draining groundwater in the contaminated areas A and B.
ここで、吸引ドレーン４０の天端を気密状態で封止することにより、吸引ドレーン４０の吸引力で外気が吸引されることを防止し、吸引ドレーン４０の吸引力の全てを粘性土層１内に作用させる。これにより、上述したように、透水性の低い粘性土層１においても、効果的に汚染水を吸引ドレーン４０に集め、吸引ドレーン４０を通して透水層２に降下させて揚水井戸２０により排水することができる。従って、透水性の低い粘性土層１の汚染範囲Ａ、Ｂに存在する汚染水を効果的に浄化できる。 Here, by sealing the top end of the suction drain 40 in an airtight state, it is possible to prevent the outside air from being sucked by the suction force of the suction drain 40, and all of the suction force of the suction drain 40 is within the viscous soil layer 1. To act on. As a result, as described above, even in the viscous soil layer 1 with low water permeability, the contaminated water can be effectively collected in the suction drain 40, lowered to the water permeable layer 2 through the suction drain 40, and drained by the pumping well 20. it can. Therefore, it is possible to effectively purify the contaminated water existing in the contaminated areas A and B of the viscous soil layer 1 having low water permeability.
図６は、他の実施形態に係る地下水浄化システム１００を示す立断面図である。この図に示すように、地下水浄化システム１００を適用する浄化対象の地盤では、粘性土層１の浅部には汚染範囲が存在しておらず、粘性土層１の深部にのみ汚染範囲Ｃが存在している。 FIG. 6 is an elevational sectional view showing a groundwater purification system 100 according to another embodiment. As shown in this figure, in the ground to be purified to which the groundwater purification system 100 is applied, there is no contamination range in the shallow part of the viscous soil layer 1, and the contamination range C is present only in the deep part of the viscous soil layer 1. Existing.
かかる地盤に適用する地下水浄化システム１００では、注水ドレーン１３０の地表面から汚染範囲Ｃの天端近傍（以浅）までの範囲１３０−１を、水路が形成された帯状の樹脂製の芯材を樹脂等の面状の不透水材料で挟んだ帯状体で構成し、その下の汚染範囲Ｃの天端以浅から透水層２（汚染範囲Ｃの下端以深）までの範囲１３０−２を、水路が形成された帯状の樹脂製の芯材を不織布等の面状の透水材料で挟んだ帯状体で構成する。また、吸引ドレーン４０を、汚染範囲Ｃの天端近傍（以浅）から透水層２（汚染範囲Ｃの下端以深）まで構築し、帯状体４２を、地表面から吸引ドレーン４０の天端まで構築する。 In the groundwater purification system 100 applied to the ground, the range 130-1 from the ground surface of the water injection drain 130 to the vicinity of the top of the contaminated area C (shallow) is used as the resin core material in the form of a belt with a water channel. A water channel forms a range 130-2 from the top of the contaminated area C below the top to the permeable layer 2 (below the bottom of the contaminated area C). The belt-shaped resin core material is formed of a belt-shaped body sandwiched between planar water-permeable materials such as nonwoven fabric. In addition, the suction drain 40 is constructed from the vicinity (hereinafter shallow) of the contamination range C to the permeable layer 2 (deep beyond the bottom end of the contamination range C), and the strip 42 is constructed from the ground surface to the top end of the suction drain 40. .
即ち、地下水浄化システム１００では、粘性土層１の汚染範囲Ｃが存在する深部にのみ通水することにより、通水範囲の厚みを抑え、循環１回毎の通水量を抑える。これにより、循環１回毎の通水時間を短縮でき、地下水浄化の工期を短縮でいる。 That is, in the groundwater purification system 100, by passing water only to the deep part where the contaminated area C of the cohesive soil layer 1 exists, the thickness of the water passing area is suppressed and the amount of water flow per circulation is suppressed. Thereby, the water flow time for each circulation can be shortened, and the construction period of groundwater purification can be shortened.
なお、上述の実施形態は、本発明の理解を容易にするためのものであり、本発明を限定するものではない。本発明はその趣旨を逸脱することなく、変更、改良され得ると共に本発明にはその等価物が含まれることは勿論である。例えば、上述の実施形態では、粘性土層１に汚染範囲Ａ〜Ｃが存在する場合を例に挙げたが、透水層に汚染範囲が存在する地盤を対象としてもよい。また、上述の実施形態では、粘性土層の粘土やシルト等により吸引ドレーン４０の天端を気密状態で封止したが、吸引ドレーン４０の天端と地表面との間にグラウト材を充填する等して吸引ドレーン４０の天端を気密状態で封止してもよい。 In addition, the above-mentioned embodiment is for making an understanding of this invention easy, and does not limit this invention. It goes without saying that the present invention can be changed and improved without departing from the gist thereof, and that the present invention includes equivalents thereof. For example, in the above-described embodiment, the case where the contaminated areas A to C exist in the cohesive soil layer 1 is taken as an example, but the ground where the contaminated area exists in the permeable layer may be targeted. Further, in the above-described embodiment, the top end of the suction drain 40 is sealed in an airtight state with clay or silt of a viscous soil layer, but a grout material is filled between the top end of the suction drain 40 and the ground surface. For example, the top end of the suction drain 40 may be sealed in an airtight state.
また、上述の実施形態では、止水壁１２を不透水層３まで構築する例を挙げたが、止水壁１２を、透水層２あるいは粘性土層１まで構築する等してもよい。ここで、止水壁１２を構築しなくても同様の作用効果を生じるが、止水壁１２を構築することは、周囲から浄化対象範囲への水の流入を防止できることにより、排水量を低減でき、周囲の地盤に及ぶ影響を抑制できるという点で効果的である。さらに、上述の実施形態では、注水ドレーン３０及び吸引ドレーン４０をペーパードレーンとしたが、サンドドレーン等の他のドレーンを採用してもよい。 Moreover, although the example which builds the water blocking wall 12 to the impermeable layer 3 was given in the above-described embodiment, the water blocking wall 12 may be built to the water permeable layer 2 or the viscous soil layer 1. Here, although the same effect is produced even if the water blocking wall 12 is not constructed, the construction of the water blocking wall 12 can reduce the amount of drainage by preventing the inflow of water from the surroundings to the purification target range. It is effective in that the influence on the surrounding ground can be suppressed. Furthermore, in the above-described embodiment, the water injection drain 30 and the suction drain 40 are paper drains, but other drains such as a sand drain may be adopted.
１ 粘性土層、２ 透水層、３ 不透水層、５ ドレーン材、６ リール、７ ケーシング、８ プレート、１０ 地下水浄化システム、１２ 止水壁、２０ 揚水井戸、２２ 水中ポンプ、２３ ケーシング、２４ スクリーン、２５ 揚水管、２６ 孔、２７−１ グラウト材、２７−２ フィルター材、２８ 吸引管、２９ 蓋、３０ 注水ドレーン、４０ 吸引ドレーン、４２ 帯状体、５０ 水処理設備、５２ 給水管、６０ 真空ポンプ、１００ 地下水浄化システム、１３０ 注水ドレーン、１３０−１、１３０−２ 範囲 1 viscous soil layer, 2 permeable layer, 3 impermeable layer, 5 drain material, 6 reel, 7 casing, 8 plate, 10 groundwater purification system, 12 water barrier, 20 pumping well, 22 submersible pump, 23 casing, 24 screen , 25 Pumping pipe, 26 holes, 27-1 Grout material, 27-2 Filter material, 28 Suction pipe, 29 Lid, 30 Injection drain, 40 Suction drain, 42 Band, 50 Water treatment facility, 52 Water supply pipe, 60 Vacuum Pump, 100 Groundwater purification system, 130 Water injection drain, 130-1, 130-2 Range
Claims (3)
前記汚染範囲に注水する注水ドレーンを構築する工程と、
内部が負圧にされ、前記汚染範囲以深から揚水する揚水井戸を構築する工程と、
前記揚水井戸の前記負圧により生じる吸引力によって前記汚染範囲の地下水を吸引して前記汚染範囲以深へ降下させる吸引ドレーンを構築する工程と、
前記注水ドレーンを通して前記汚染範囲に注水すると共に、前記揚水井戸により前記吸引ドレーンを通して前記汚染範囲の地下水を排水する工程とを備え、
前記吸引ドレーンの天端を気密状態で封止する地下水浄化工法。 A groundwater purification method for purifying groundwater in the contaminated area by passing water through the contaminated area of the ground,
Constructing a water injection drain for water injection into the contaminated area;
A process of constructing a pumping well in which the inside is made negative and pumped from deeper than the contamination range;
Constructing a suction drain that sucks the groundwater in the contaminated area by the suction force generated by the negative pressure of the pumping well and lowers the groundwater below the contaminated area;
Injecting water into the contaminated area through the water drain, and draining groundwater in the contaminated area through the suction drain by the pumping well,
A groundwater purification method for sealing the top end of the suction drain in an airtight state.
前記揚水井戸を、前記透水層から揚水するように構築し、
前記吸引ドレーンを、前記汚染範囲以浅から前記透水層まで延びるように構築する請求項１に記載の地下水浄化工法。 The contamination range exists in the clay soil layer of the ground, a permeable layer exists under the clay soil layer of the ground,
The pumping well is constructed to pump water from the permeable layer,
The groundwater purification method according to claim 1, wherein the suction drain is constructed so as to extend from shallower than the contamination range to the permeable layer.
前記汚染範囲に注水する注水ドレーンと、
内部が負圧にされ、前記汚染範囲以深から揚水する揚水井戸と、
前記揚水井戸の前記負圧により生じる吸引力によって前記汚染範囲の地下水を吸引して前記汚染範囲以深へ降下させる吸引ドレーンとを備え、
前記吸引ドレーンの天端は、気密状態で封止されている地下水浄化システム。 A groundwater purification system that purifies groundwater in the contaminated area by passing water through the contaminated area of the ground,
An irrigation drain for irrigating the contaminated area;
A pumping well that has a negative pressure inside and pumps water from deeper than the contamination range;
A suction drain that sucks the groundwater in the contaminated area by the suction force generated by the negative pressure of the pumping well and lowers the groundwater below the contaminated area;
The top end of the suction drain is a groundwater purification system sealed in an airtight state.
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| JP2019147109A (en) * | 2018-02-27 | 2019-09-05 | 鹿島建設株式会社 | Oil recovery method |
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