JP4051666B2

JP4051666B2 - Consolidation improvement method for water bottom soft ground.

Info

Publication number: JP4051666B2
Application number: JP2002066740A
Authority: JP
Inventors: 宏史米谷; 貴彦椎名; 博新舎
Original assignee: Penta Ocean Construction Co Ltd
Current assignee: Penta Ocean Construction Co Ltd
Priority date: 2002-03-12
Filing date: 2002-03-12
Publication date: 2008-02-27
Anticipated expiration: 2022-03-12
Also published as: JP2003261930A

Description

【０００１】
【発明の属する技術分野】
本発明は、河川、湖沼、海域等の水底軟弱地盤を、上部に構造物を構築するために必要な強度を発現させるため、又は航路確保等のために水深を大きくするために圧密改良する水底軟弱地盤の圧密改良工法に関する。
【０００２】
【従来の技術】
従来、水底にヘドロ等の軟弱土砂が堆積して水深が浅くなった個所を、航路として必要な一定以上の水深とするための工事として浚渫が行われている。この種の浚渫には、バケットエレベータによって水底堆積土砂を掘削揚土する方法や、水底地盤を掘削刃で掘削し、その掘削土をポンプによって水とともに吸い上げる方法があり、浚渫土は搬送管路を通して浚渫土処理池に送られて埋め立て処理されるようにしている。
【０００３】
また、水底軟弱地盤の圧密改良は、軟弱地盤を脱水処理することによってなすことができ、従来は、水底構造物の構築に際し、水底の軟弱地盤を圧密沈下させ、基礎として必要な強度を発揮させるための各種の水底軟弱地盤圧密改良工法が開発されている。
【０００４】
従来の水底軟弱地盤圧密改良工法として、例えば特許第２８４０９０８号公報に示されているように、水底軟弱地盤内に鉛直ドレーンを等間隔に打設し、各鉛直ドレーンの上端に連続させて地盤表面に盛砂等の水平ドレーンを設置し、その表面を遮水材で覆い、その内側を排水ポンプによって排水することにより減圧し、鉛直ドレーンを通して水底軟弱地盤内を減圧させることにより圧密させる工法が提案されている。遮水材としては、天端が閉鎖された下端開放型の函体の他、シート状材を使用するものも提案されている。
【０００５】
【発明が解決しようとする課題】
上述した従来の浚渫による航路水深を確保する方法では、浚渫土の処理のためのエリアが必要となるが、近年は浚渫土処理のための埋め立てエリアが殆ど使い尽くされ、新たな埋め立てエリアが確保できないことが多く、浚渫土処理の問題から浚渫工事ができないという問題があった。
【０００６】
また上述した、水底軟弱地盤内に鉛直ドレーンを打設し、地盤表面を遮水材で閉鎖した状態で各鉛直ドレーン内を減圧させることによって圧密改良する方法では、圧密の進行によって遮水材周囲の部分の沈下が進み、地表面からドレーンに至る水道が発生するとそれ以上の圧密改良ができなくなり、高い耐力の地盤が得られないという問題があった。
【０００７】
更に、上述した従来の水底軟弱地盤圧密改良工法は、その目的が基礎地盤等として利用することを前提とした工法であったため、改良目的地盤全域に亘って均一にドレーン材を打設し、目的地盤全域に均等な耐力を発生させるようにしている。このため目的地盤中に打設される鉛直ドレーン材の間隔は、全域に亘って均一な間隔に打設されおり、高価なドレーン材を多く要し、高コストとなるという問題があった。
【０００８】
本発明の目的は、このような従来の問題に鑑み、水底の軟弱地盤に打設した鉛直ドレーン材内を減圧させることによって圧密改良を行う水底軟弱地盤の圧密改良工法の実施に当り、迅速かつ確実に効率よく圧密改良がなされるようにすることにあり、構築物築造のための耐力発現を目的とした圧密改良に際し、上部に載荷盛土をすることなく大きな強度発現（改良効果）が得られる水底軟弱地盤の圧密改良工法を提供することにある。
【０００９】
本発明の他の目的は、上記圧密改良工法が、低コストで経済的に行うことができ、水路の水深確保のための水底面低下工事に実施する場合においても採算性が確保できるようにすることにある。
【００１０】
【課題を解決するための手段】
上述の如き従来の問題を解決し、所期の目的を達成する本発明の第一の特徴は、周囲に縦向筒状の土中貫入遮水壁を有し、天端が閉鎖された下端開放型の遮水函体を使用し、水底軟弱地盤の表面に、１つの前記遮水函体の大きさに合わせた広さを単位としたドレーン材打設区画を間隔を隔てて複数設定し、その各ドレーン材打設区画毎に、前記水底軟弱地盤表面より多数の鉛直ドレーン材を打設するとともに該水底軟弱地盤表面に各鉛直ドレーン材に連続する水平ドレーン材を設置し、その上面を覆うように前記遮水函体を配置し、前記土中貫入遮水壁を軟弱地盤内に貫入させるとともに、互いに隣り合う前記遮水函体の何れか一方の頂縁部に予め一体化させておいた不透水性の遮水函体間遮蔽材を、互いに隣り合う前記遮水函体間の軟弱地盤表面に跨らせて設置し、然る後、互いに隣り合わせに設置した各遮水函体内の水平ドレーン材内を同時に減圧することにより、水底軟弱地盤内の脱水を行わせて圧密改良することを特徴としてなる水底軟弱地盤の圧密改良工法にある。
【００１１】
尚、上記特徴の水底軟弱地盤の圧密改良工法において、遮水函体間遮蔽材が、遮水函体の天板を延長させて予め一体化させた該遮水函体と同じ材料からなる板状材であること、又は、遮水函体間遮蔽材が、遮水函体の天板を延長させて予め一体化させた可撓性シート状材であることが好ましい。
【００１２】
本発明の第二の特徴は、周囲に縦向筒状の土中貫入遮水壁を有し、天端が閉鎖された下端開放型の遮水函体を使用し、水底軟弱地盤の表面に、１つの前記遮水函体の大きさに合わせた広さを単位としたドレーン材打設区画を間隔を隔てて複数設定し、その各ドレーン材打設区画毎に、前記水底軟弱地盤表面より多数の鉛直ドレーン材を打設するとともに該水底軟弱地盤表面に各鉛直ドレーン材に連続する水平ドレーン材を設置し、その上面を覆うように前記遮水函体を配置し、前記土中貫入遮水壁を軟弱地盤内に貫入させ、然る後、互いに隣り合わせに設置した各遮水函体内の水平ドレーン材内を同時に減圧するとともに、遮水函体間軟弱地盤が沈下する際に、互いに隣り合う前記遮水函体の土中貫入遮水壁間に、前記遮水函体間軟弱地盤の表面が、該表面から鉛直ドレーン材に至る水道ができない高さに維持されるように軟弱土を補充しつつ水底軟弱地盤内の脱水を行わせて圧密改良することを特徴としてなる水底軟弱地盤の圧密改良工法にある。
【００１３】
尚、上記第二の特徴の水底軟弱地盤の圧密改良工法において、互いに隣り合う遮水函体の何れか一方の頂縁部に軟弱土を搬送して散布する排泥管を固定しておき、該排泥管を通して軟弱土を補充することが好ましい。
【００１４】
また、上記第一、第二の特徴の水底軟弱地盤の圧密改良工法において、複数のドレーン材打設区画を、該ドレーン材打設区画内の鉛直ドレーン材間隔より広い間隔を隔てて設定することにより、使用するドレーン材料を削減できる。
【００１５】
【発明の実施の形態】
次に本発明の実施の形態を図面について説明する。
【００１６】
図１〜図７は本発明の第一実施例を示しており、図中符号１は本発明方法に使用する遮水函体１を示している。この遮水函体１は、周囲に縦向筒状をした土中貫入遮水壁１ａを有し、頂部が天板１ｂによって閉鎖された下端開放型に成形されている。この遮水函体１の天板１ｂには吸水孔が開けられ、これに減圧用ホースが連結されるようになっている。
【００１７】
遮水函体１の頂部の互いに隣り合う二辺に連続させて遮水函体間遮蔽材２が一体に備えられている。この遮水函体間遮蔽材２は遮水函体１の天板１ｂを延長させて成形されており、遮水函体１と同じ鋼板によって構成されている。
【００１８】
遮水函体遮蔽材２の先端縁部下面には止水パッキンの役目を持たせるシール材３が固定されている。このシール材３はゴムなどの不透水性弾性材が使用されている。
【００１９】
本発明工法の実施に際し、まず施工しようとする水底地盤に、上述した遮水函体１の広さを１単位としたドレーン材打設区画１０，１０……を並べて設定する。この各ドレーン材打設区画１０は、図３に示すように隣り合う区画１０，１０間に所定の間隔ａを隔てた配置に設定する。尚、この間隔ａは、ドレーン材打設間隔（各区画１０内において鉛直方向に打設される鉛直ドレーン材１２，１２間の水平方向の間隔をいう）ｂより広い所定（後述する）の間隔とする。
【００２０】
次いで、各区画１０に、図４に示すように水面上に浮かべたドレーン材打設船１１を使用して鉛直ドレーン材１２，１２……を一定の間隔ｂ毎に多数打設する。この鉛直ドレーン材１２の打設は、図に示すように、上端を水底面より一定長さだけ突出させて打設する。
【００２１】
ドレーン材打設間隔ｂは、水底地盤の軟弱度や地盤内水分の流動性に応じて、地盤内の土壌間隙水の排水効率及び使用ドレーン材の経済性を考慮して決定する。
【００２２】
使用するドレーン材としては、プラスチックボードドレーン材、天然繊維を用いたファイバードレーン材、有孔管からなるドレーン材、砂柱からなるドレーン材、透水性織布袋に砂又は砕石を詰めた袋詰ドレーン材、不織布を重ね合わせて透水性能を持たせたドレーン材等が使用できるが、プラスチックボードドレーン材が好ましい。
【００２３】
このようにして鉛直ドレーン材１２，１２……を各区画１０，１０……に打設した後、その区画１０毎に、鉛直ドレーン材１２の上端を埋め込んでサンドマットからなる水平ドレーン１３を敷設する。
【００２４】
次いで図５に示すように、各ドレーン材打設区画１０，１０……毎に、水平ドレーン１３の上から前述した遮水函体１を被せる。遮水函体１の設置に際しては、クレーン船１４を使用するとともに、遮水函体１上に枠状の取り付け冶具１５を固定し、これをクレーン１６の吊りワイヤー１６ａで吊り下げ、水底に降下させ、遮水函体１及び取り付け冶具１５の重量によって、土中貫入遮水壁１ａを地盤中に貫入させる。このようにして遮水函体１を、その頂部内側に水平ドレーン１３が収容されるように被せる。
【００２５】
また、互いに隣り合う遮水函体１，１間においては、一方の遮水函体１から張り出している遮水函体間遮蔽材２を、他方の遮水函体１の上面にシール材３を介在させて重ね合わせ、遮水函体間軟弱地盤Ｂの表面を遮水函体間遮蔽材２をもって遮蔽する。
【００２６】
このようにして各ドレーン材打設区画１０毎に遮水函体１被せ、取り付け冶具１５を取り外すとともに、図６に示すように各遮水函体１給水孔に減圧用ホース１７を連結し、これを集水井１８の底部に連結する。
【００２７】
集水井１８は、密閉タンクからなっており、底部に排水用の水中ポンプ１９が収容され、排水パイプ２０を通して集水井１８内の水を排出させるようにするとともに、頂部に真空ポンプ２１による減圧パイプ２２を連結し、この減圧ポンプによって集水井１８の内を減圧可能にする。
【００２８】
このようにして互いに隣り合う複数の遮水函体１，１の減圧ホース１７を集水井１８に連結し、集水井１８内の水を排出させて内部の水位を低下させるとともに真空ポンプ２１によって内部を減圧する。これによって集水井１８内の圧力と大気圧との差圧分が遮水函体１の頂面にかかることとなり、圧密、脱水が促進される。
【００２９】
この他、集水井１８は、図には示してないが、上端開放型の縦長タンクを使用しても良く、この場合には、集水井１８を水底から水面上に至る長さに形成し、底部に収容した排水用の水中ポンプ１９により排水パイプ２０を通して集水井１８内の水を排出させることによってタンク内の水位を低下させる。これによって集水井１８内の水位が外の水位より下がると、その水頭差ｈによって生じる差圧分だけ遮水函体１内が減圧されることとなり、これによって鉛直ドレーン材１２を通して軟弱地盤内の脱水及び水圧による圧密がなされる。
【００３０】
このようにして遮水函体１内を減圧させることにより、鉛直ドレーン材１２内が減圧されて各ドレーン材打設区画１０の軟弱地盤、即ち遮水函体下軟弱地盤Ａの排水圧密がなされるが、このとき該軟弱地盤Ａは、図８に示すように鉛直方向に圧密されると同時に水平方向にも収縮する。この収縮によって隣り合う遮水函体１，１間の軟弱地盤、即ち遮水函体間軟弱地盤Ｂが引き込まれて該地盤の表面を低下させる方向の力が作用する。
【００３１】
このとき、遮水函体間遮蔽材２が存在しないと図９に示すように遮水函体間軟弱地盤Ｂが左右の遮水函体間軟弱地盤Ａ，Ａの収縮によって引き込まれてその表面が沈下し、遮水函体１の土中貫入壁１ａ下に水道ができ、鉛直ドレーン材１２に地盤上の水が直接流れ込むこととなって圧力漏れが生ずる。このため鉛直ドレーン材１２内外の圧力差が維持できなくなり、効果的な圧密脱水ができなくなる事態が生じる。
【００３２】
しかし、この実施例では互いに隣り合う遮水函体１，１間が遮水函体間遮蔽材２によって遮蔽されているため、遮水函体間軟弱地盤Ｂの沈下が規制され、鉛直ドレーン材１２内外の圧力差が維持され、水底軟弱地盤の効率的な圧密改良がなされる。
【００３３】
図１０〜図１１は本発明の第二実施例を示しており、この実施例では遮水函体１，１間を遮蔽する遮水函体間遮蔽材４としてシート状材を使用している。尚、第一実施例と同一部分には同一符号を付して重複説明を省略する（以下同じ）。
【００３４】
遮水函体間遮蔽材４は、不透水性の可撓性シート状材を使用しており、これを遮水函体１の頂面の互いに隣り合う二辺にそれぞれ一端側を予め固着し、図１０に示すように筒状に巻いた状態で設置しておく。
【００３５】
このようにして遮水函体間遮蔽材４を固定した遮水函体１，１……を使用して前述した第一実施例と同様にして遮水函体１を水平ドレーン１３の上から被せるようにそれぞれ設置した後、図１１に示すように遮水函体間遮蔽材４を広げて遮水函体１，１間を遮蔽する。
【００３６】
然る後、第一実施例と同様に集水井１８内の水を排出するとともにその内部を減圧させる。これによって第一実施例と同様、互いに隣り合う遮水函体１，１間が遮水函体間遮蔽材４によって遮蔽されているため、遮水函体間軟弱地盤Ｂの沈下が規制され、鉛直ドレーン材１２内外の圧力差が維持され、水底軟弱地盤の効率的な圧密改良がなされる。
【００３７】
図１２〜図１３は本発明の第三実施例を示しており、この実施例では前述した遮水函体間遮蔽材２及び４の代わりに、軟弱土補充手段を使用している。この軟弱土補充手段は、遮水函体１の互いに隣り合う２辺の頂縁部に設置した排泥管５と、該排泥管５に軟弱土を搬送する軟弱土搬送パイプ６、軟弱土搬送パイプ６に軟弱土を送り込むポンプ７及び貯泥槽８をもって構成されている。
【００３８】
排泥管５には多数の軟弱土吐出口５ａが開口されており、軟弱土搬送パイプ６を通じて送り込まれる軟弱土を全長に亘って均一に放出されるように構成されている。
【００３９】
このように排泥管５を設置した遮水函体１，１……を使用して前述した第一実施例と同様にして遮水函体１を水平ドレーン１３の上から被せるようにそれぞれ設置した後、図１３に示すように各排泥管遮５に軟弱土搬送パイプ６を連結する。
【００４０】
然る後、第一実施例と同様に集水井１８内の水を排出するとともにその内部を減圧させる。これによって鉛直ドレーン材１２内が減圧されて遮水函体軟弱地盤Ａの脱水圧密がなされる。このときの減圧による遮水函体下軟弱地盤Ａの水平方向の収縮によって遮水函体間軟弱地盤Ｂが沈下する。その沈下部分に軟弱土補充手段によって遮水函体間、即ち土中貫入遮水壁間に軟弱土を補充させる。
【００４１】
補充する軟弱土には粘性土やベントナイトを使用する。また、この補充は、遮水函体間軟弱地盤Ｂの表面が遮水函体１，１の降下より早く進むことによって、該表面から鉛直ドレーン材１２に至る水道ができない高さに維持させることを目的としているものであり、遮水函体間軟弱地盤Ｂの表面の遮水函体に対する高さが上記目的が達成される一定の範囲に保たれるように行う。これによって鉛直ドレーン材１２内外の圧力差が維持され、水底軟弱地盤の効率的な圧密改良がなされる。
【００４２】
尚、上述した各実施例では、水平ドレーン１３にサンドマットを使用しているが、この他図１４に示すように、遮水函体１の頂部内に不織布などの透水材からなる水平ドレーン材１３ａを収容しておき、鉛直ドレーン材１２を打設後、その上に遮水函体１を被せることによって、鉛直ドレーン材１２に連通した水平ドレーン材１３ａによって構成させるようにしてもよい。
【００４３】
また、第一、第二実施例において遮水函体間遮蔽材を何れかの遮水函体に予め一体化させておいて施工する例を示しているが、遮水函体を並べて水底に設置した後、隣り合う遮水函体の頂部間に跨らせて固定しても良い。
【００４４】
【試験例】
本発明における
１．軟弱地盤と遮水函体１の沈下変形挙動の把握
２．沈下量、減容量などの改良効果
３．複数の遮水函体１を設置した場合の沈下挙動の把握
を目的として室内模型実験を行った。
【００４５】
実験対象土
第１表に示す土性の海成粘土

【００４６】
実験装置
土槽：縦１５０ｃｍ×横１５０ｃｍ×深さ１００
遮水函体１：ポリカーボネート製函体、
縦２５ｃｍ×横２５ｃｍ×土中貫入遮水壁の貫入深さ２０ｃｍ
水平ドレーン１３材：不織布
鉛直ドレーン材１２：プラスチックドレーン
図１５、図１６に示すように他の土槽内に仕切り板を入れ、片側に寄せて９個所のドレーン材打設区画を設定し、図示のように鉛直ドレーン材１２、水平ドレーン１３材及び遮水函体１を設置した。
【００４７】
実験結果
上記実験装置において、遮水函体１内を減圧した結果、図１７に示す実験結果が得られた。
【００４８】
これによると、遮水函体１間の地盤が、実験終了時に遮水函体１頂部と比べて５〜１０ｃｍも沈下する現象が生じた。この現象は図１８に示すように、遮水函体１，１間の粘土が鉛直ドレーン材１２に向けて圧密されながら落ち込む（沈下する）ためであった。
【００４９】
実験開始後３時間程で大量の水が減圧ポンプから排水され、圧密加重である負圧がかからなくなった。これは図９に示すように、遮水函体１下に水道ができ、水密性が維持できなくなったためである。
【００５０】
この結果から、計画水底面の全域を均一に圧密改良するためには、遮水函体間の水密性を保つための対策が必要であることが証明された。
【００５１】
尚、上述した各例では、１つの前記遮水函体の大きさに合わせた広さを単位としたドレーン材打設区画間の間隔、即ち隣り合う遮水函体間の間隔ａを、各区画内のドレーン材打設間隔ｂより大きくしているが、上部に構築物を築造することを目的とした場合等、耐力増強を目的とした圧密改良を行う場合には、図１９に示すように、圧密改良区域全域に亘って均一な間隔ｂに鉛直ドレーン材１２，１２…を打設する等、発現させようとする圧密改良後の地盤強度に応じて、ドレーン材打設区画１０，１０間の間隔ａを適宜設定する。
【００５２】
【発明の効果】
上述のように、本発明に係る水底軟弱地盤の圧密改良工法は、周囲に縦向筒状の土中貫入遮水壁を有し、天端が閉鎖された下端開放型の遮水函体を使用し、水底軟弱地盤の表面に、１つの前記遮水函体の大きさに合わせた広さを単位としたドレーン材打設区画を間隔を隔てて複数設定し、その各ドレーン材打設区画毎に、前記水底軟弱地盤表面より多数の鉛直ドレーン材を打設するとともに該水底軟弱地盤表面に各鉛直ドレーン材に連続する水平ドレーン材を設置し、その上面を覆う配置に前記遮水函体を、前記土中貫入遮水壁を軟弱地盤内に貫入させて被せ、然る後、互いに隣り合わせに設置した各遮水函体内の水平ドレーン材内を同時に減圧させて、水底軟弱地盤内の脱水を行わせて圧密改良するようにしたことにより、遮水函体間の軟弱地盤沈下が規制されて鉛直ドレーン材内外の圧力差が維持されることとなり、水底軟弱地盤の高い圧密が迅速かつ効率的になされ、構築物築造のための耐力発現を目的とした圧密改良に際し、上部に載荷盛土をすることなく大きな強度発現（改良効果）が得られる。
【００５３】
また、互いに隣り合う前記遮水函体間の軟弱地盤表面に、該遮水函体に跨らせて不透水性の遮水函体間遮蔽材を設置して水底軟弱地盤内の脱水を行わせて圧密改良するか、又は、遮水函体間軟弱地盤が沈下する際に、互いに隣り合う遮水函体の土中貫入遮水壁間に、遮水函体間軟弱地盤表面の高さが前記遮水函体に対して一定範囲に維持されるように軟弱土を補充しつつ水底軟弱地盤内の脱水を行わせて圧密改良することにより、遮水函体間軟弱地盤の過度な沈下による水道の発生が防止され、鉛直ドレーン材内外の圧力差を所望の設定値に維持させることができ、確実かつ高効率に水底軟弱地盤の圧密改良がなされる。
【００５４】
また、上記遮水函体間遮蔽材を、互いに隣り合う遮水函体の何れか一方の頂縁部に予め一体化させておくことにより、水底における遮水函体間の遮蔽作業が容易となる。
【００５５】
また、上記遮水函体間遮蔽材を、遮水函体の天板を延長させて予め一体化させた剛性の高い板状材とすることにより、遮水函体の設置と同時に該函体間を遮水函体間遮蔽材で閉鎖でき、作業効率が良い。
【００５６】
この他、遮水函体間遮蔽材を、遮水函体の天板を延長させて予め一体化させた可撓性シート状材とすることにより、遮水函体の製造時に特別の加工を要せず、製造コストを低く押えることができる。
【００５７】
更に、互いに隣り合う遮水函体の何れか一方の頂縁部に軟弱土を搬送して散布する排泥管を固定しておき、該排泥管を通して軟弱土を補充するようにすることにより、遠隔操作によって軟弱土の補充ができ作業性が良い。
【００５８】
更に、複数のドレーン材打設区画を、該ドレーン材打設区画内の鉛直ドレーン材間隔より広い間隔を隔てて設定し、その遮水函体間の鉛直ドレーン材を打設しない部分を、従来の軟弱地盤の圧密改良工法に比べ、広く取るようにしても、その部分の圧密が効果的に行われるため、使用する鉛直ドレーン材数の削減が可能となり、使用資材費用が減少するとともに鉛直ドレーン材打設作業も少なくなり、工費が削減され、工期を短縮でき、経済性が高く、航路水深確保等のための水底面の低下工事にも充分に高い採算性が得られる。
【図面の簡単な説明】
【図１】本発明に使用する遮水函体の一例を示す縦断面図である。
【図２】同上の平面図である。
【図３】本発明方法の実施の一例におけるドレーン材区画設定を示す平面図である。
【図４】同上の鉛直ドレーン材打設工程を示す縦断面図である。
【図５】同上のサンドマットによる水平ドレーンの設置後の遮水函体設置工程を示す縦断面図である。
【図６】同上の圧密脱水工程を示す縦断面図である。
【図７】同上の圧密脱水によって圧密改良された状態を示す縦断面図である。
【図８】同上の圧密原理を示す断面図である。
【図９】遮水函体間遮蔽材を使用しない場合の遮水函体間地盤の沈下状態を示す断面図である。
【図１０】本発明に使用する遮水函体の他の一例を示す斜視図である。
【図１１】本発明方法の他の実施例における遮水函体設置工程を示す縦断面図である。
【図１２】本発明に使用する遮水函体のその他の一例を示す斜視図である。
【図１３】本発明方法のその他の実施例における遮水函体間地盤の沈下規制工程を示す縦断面図である。
【図１４】本発明方法の他の実施例における遮水函体設置工程を示す縦断面図である。
【図１５】本発明の複数の函体を使用した実験設備を示す平面図である。
【図１６】同上の縦断面図である。
【図１７】実験結果を示すグラフである。
【図１８】実験結果における遮水函体間の沈下原理を示す縦断面図である。
【図１９】本発明方法におけるドレーン材区画設定の他の例を示す平面図である。
【符号の説明】
Ａ遮水函体下軟弱地盤
Ｂ遮水函体間軟弱地盤
ａ，ｂ間隔
１遮水函体
１ａ土中貫入遮水壁
１ｂ天板
２遮水函体間遮蔽材
３シール材
４遮水函体間遮蔽材
５排泥管
５ａ軟弱土吐出口
６軟弱土搬送パイプ
７ポンプ
８貯泥槽
１０ドレーン材打設区画
１１ドレーン材打設船
１２鉛直ドレーン材
１３水平ドレーン
１３ａ水平ドレーン材
１４クレーン船
１５取り付け冶具
１６クレーン
１６ａ吊りワイヤー
１７減圧用ホース
１８集水井
１９水中ポンプ
２０排水パイプ
２１真空ポンプ
２２減圧パイプ[0001]
BACKGROUND OF THE INVENTION
The present invention provides a water bottom that is consolidated to improve the water bottom soft ground such as rivers, lakes, marine areas, etc., in order to develop the strength necessary for constructing a structure in the upper part, or to increase the water depth for securing a navigation route, etc. The present invention relates to a consolidation method for soft ground.
[0002]
[Prior art]
Conventionally, dredging has been carried out as a construction to make a part where soft soil such as sludge accumulates on the bottom of the water and the water depth becomes shallower than a certain level necessary for the channel. For this type of dredging, there are a method of excavating and depositing bottom sediment with a bucket elevator, a method of excavating the bottom soil with a drilling blade, and sucking the excavated soil with water by a pump. It is sent to dredged soil ponds for landfill treatment.
[0003]
In addition, consolidation improvement of the bottom soft ground can be achieved by dehydrating the soft ground. Conventionally, when constructing a bottom structure, the bottom soft ground is consolidated and subsidized to provide the necessary strength as a foundation. Various water bottom soft ground consolidation improvement methods have been developed for this purpose.
[0004]
As a conventional water bottom soft ground consolidation improvement method, for example, as shown in Japanese Patent No. 2840908, vertical drains are placed at equal intervals in the water bottom soft ground, and are continuously connected to the upper ends of the vertical drains. A horizontal drain, such as embankment sand, is installed, the surface is covered with a water-impervious material, the inside is drained by a drainage pump, and the pressure is reduced by draining the water. Has been. As a water shielding material, a sheet-shaped material is proposed in addition to a lower-end open box with the top end closed.
[0005]
[Problems to be solved by the invention]
In the conventional method for securing the channel water depth by dredging as described above, an area for dredging soil treatment is required, but in recent years, the landfill area for dredging soil treatment is almost exhausted and a new landfill area is secured. There were many problems that could not be done, and there was a problem that dredging work could not be done due to the problem of dredging.
[0006]
In addition, in the above-described method for improving consolidation by placing a vertical drain in a soft ground at the bottom and depressurizing each vertical drain with the ground surface closed with a water shielding material, However, when subsidence progressed and water from the ground surface to the drain was generated, further consolidation improvement could not be achieved, and there was a problem that high strength ground could not be obtained.
[0007]
Furthermore, the conventional water-floor soft ground consolidation improvement method described above is a method based on the premise that the purpose is to be used as a foundation ground, etc. It is designed to generate a uniform strength throughout the ground. For this reason, the intervals between the vertical drain materials placed in the target ground are evenly spaced over the entire area, which requires a lot of expensive drain materials, resulting in a high cost.
[0008]
In view of such conventional problems, the object of the present invention is to provide a quick and easy method for improving the consolidation of water bottom soft ground by improving the consolidation by reducing the pressure in the vertical drain material placed on the soft ground of the water bottom. It is to ensure that consolidation improvement is performed efficiently and efficiently, and in the consolidation improvement for the purpose of expressing the strength for building construction, the bottom of the sea where large strength expression (improvement effect) can be obtained without loading embankment on the upper part. The purpose is to provide a method for improving consolidation of soft ground.
[0009]
Another object of the present invention is to enable the above consolidation improvement method to be economically performed at low cost, and to ensure profitability even when it is carried out for water bottom reduction construction for securing the water depth of the water channel. There is.
[0010]
[Means for Solving the Problems]
The first feature of the present invention that solves the conventional problems as described above and achieves the intended object is a lower end having a vertically cylindrical underground water-impervious wall and a top end closed. Using an open-type impermeable box, a plurality of drain material placement sections with a space corresponding to the size of the one impermeable box are set at intervals on the surface of the bottom soft ground. , the each drain material hitting設区image, the horizontal drain material continuous to the vertical drain material in the aqueous bottom soft ground surface while pouring a number of vertical drain material from the sea bed soft ground surface is installed, the upper surface The impermeable box is arranged so as to cover, and the intrusion impermeable wall is penetrated into the soft ground, and is integrated in advance with the top edge of one of the adjacent impermeable boxes. Oita water-impervious water shielding box shielding material, soft ground between the water shielding boxes adjacent to each other It is installed across the surface, and after that, by simultaneously depressurizing the horizontal drain material in each impermeable box installed next to each other, dehydration in the bottom soft ground is performed to improve consolidation. It is in the consolidation improvement method of the water bottom soft ground which is the feature.
[0011]
In addition, in the consolidation improvement method for water bottom soft ground having the above characteristics, the shielding material between the water shielding boxes is a plate made of the same material as the water shielding box in which the top plate of the water shielding box is extended and integrated in advance. it is Jo material, or water-impervious box-body between the shielding member is preferably a flexible sheet-like material with integrated advance to extend the top plate of the water shield a box body.
[0012]
The second feature of the present invention is the use of a bottom-opening-type water-impervious box having a vertically-cylindrically penetrating impermeable wall in the surroundings, with the top end closed, on the surface of the bottom soft ground. A plurality of drain material placement sections with an interval corresponding to the size of the one water-blocking box are set at intervals, and for each drain material placement section, from the surface of the bottom soft ground A number of vertical drain materials are placed, horizontal drain materials that are continuous to each vertical drain material are installed on the surface of the bottom soft ground, the water shielding box is arranged so as to cover the upper surface, and the soil penetration barrier is arranged. The water wall penetrates into the soft ground, and after that, the horizontal drain material in each impermeable box installed next to each other is depressurized at the same time, and when the soft ground between the impermeable bodies sinks, wherein the soil penetrating water shield walls of the water shield a box body, the water shield box making body between soft ground fit Face, of the underwater soft ground composed as characterized by made to perform dehydration in the sea bed soft ground while replenishing the soft soil so as to maintain the high can not tap lead to vertical drain material from the surface of compacting improved It is in consolidation improvement method.
[0013]
In addition, in the consolidation improvement method of the water bottom soft ground of the second feature, a drainage pipe that transports and spreads soft soil to any one of the top edges of adjacent water shielding boxes is fixed, It is preferable to replenish soft soil through the drainage pipe.
[0014]
Further, in the consolidation improvement method for the bottom soft ground according to the first and second features, the plurality of drain material placement sections are set with a wider interval than the vertical drain material interval in the drain material placement section. Therefore, the drain material to be used can be reduced.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0016]
1-7 has shown the 1st Example of this invention, and the code | symbol 1 in the figure has shown the water-impervious box 1 used for this invention method. The water-blocking box 1 has a vertically penetrating water-impervious wall 1a which is formed in a vertically cylindrical shape, and is formed into a lower end open mold whose top is closed by a top plate 1b. A water absorption hole is formed in the top plate 1b of the water shielding box 1, and a pressure reducing hose is connected to the water absorption hole.
[0017]
A shielding material 2 between the impermeable boxes is provided integrally with the two adjacent sides of the top of the impermeable box 1. The shielding material 2 between the water shielding boxes 2 is formed by extending the top plate 1 b of the water shielding box 1, and is made of the same steel plate as the water shielding box 1.
[0018]
A sealing material 3 that serves as a water-stopping packing is fixed to the lower surface of the tip edge portion of the water shielding box shielding material 2. The sealing material 3 is made of an impermeable elastic material such as rubber.
[0019]
In carrying out the method of the present invention, first, the drain

material placing sections

10, 10... Are set side by side on the water bottom ground to be constructed, with the width of the above-described water shielding box 1 as one unit. Each of the drain material placement sections 10 is set to have a predetermined interval a between

adjacent sections

10 and 10 as shown in FIG. This interval a is a drain material placement interval (referred to as a horizontal interval between the

vertical drain materials

12 and 12 placed in the vertical direction in each section 10 ). A predetermined interval (described later) wider than b. And
[0020]
Next, as shown in FIG. 4, a number of

vertical drain materials

12, 12... Are placed in each section 10 at regular intervals b using a drain material placing ship 11 floating on the water surface. As shown in the figure, the vertical drain member 12 is placed with its upper end protruding from the bottom surface by a certain length.
[0021]
The drain material placement interval b is determined in consideration of the drainage efficiency of soil pore water in the ground and the economical efficiency of the drain material used according to the softness of the water bottom ground and the fluidity of the moisture in the ground.
[0022]
The drain materials used are plastic board drain materials, fiber drain materials using natural fibers, drain materials made of perforated pipes, drain materials made of sand pillars, and bag drains packed with sand or crushed stone in a permeable woven fabric bag. A drain material or the like having water permeability by overlapping materials and nonwoven fabrics can be used, but a plastic board drain material is preferable.
[0023]
In this way, after the

vertical drain members

12, 12... Are placed in the

respective sections

10, 10,..., The horizontal drains 13 made of sand mats are laid in each section 10 by embedding the upper ends of the vertical drain members 12. To do.
[0024]
Next, as shown in FIG. 5, the above-described water shielding box 1 is placed on the horizontal drain 13 in each drain

material placing section

10, 10. When installing the water-impervious box 1, the crane ship 14 is used, and a frame-shaped mounting jig 15 is fixed on the water-impervious box 1, and this is hung by a hanging wire 16 a of the crane 16 and lowered to the bottom of the water. The soil penetrating impermeable wall 1a is penetrated into the ground by the weight of the impermeable box 1 and the attachment jig 15. In this way, the water shielding box 1 is covered so that the horizontal drain 13 is accommodated inside the top portion.
[0025]
Further, between the

water shielding boxes

1 and 1 adjacent to each other, the shielding material 2 between the water shielding boxes 1 protruding from one of the water shielding boxes 1 is disposed on the upper surface of the other water shielding box 1. And the surface of the soft ground B between the impermeable boxes is shielded by the shielding material 2 between the impermeable boxes.
[0026]
In this way, each drain material placing section 10 is covered with the water shielding box 1 and the attachment jig 15 is removed, and as shown in FIG. 6, a pressure reducing hose 17 is connected to each water shielding box 1 water supply hole, This is connected to the bottom of the drainage well 18.
[0027]
The drainage well 18 is composed of a sealed tank, and a drainage submersible pump 19 is accommodated at the bottom, and the water in the drainage well 18 is discharged through the drainage pipe 20, and a decompression pipe by a vacuum pump 21 at the top. 22 is connected, and the inside of the water collection well 18 can be decompressed by this decompression pump.
[0028]
In this way, the decompression hoses 17 of the plurality of

water shielding boxes

1 and 1 adjacent to each other are connected to the water collection well 18, the water in the water collection well 18 is discharged to lower the internal water level, and the vacuum pump 21 The pressure is reduced. As a result, a differential pressure between the pressure in the drainage well 18 and the atmospheric pressure is applied to the top surface of the water shielding box 1, and consolidation and dehydration are promoted.
[0029]
In addition, although the drainage well 18 is not shown in the drawing, a vertically long tank with an open top end may be used. In this case, the drainage well 18 is formed to a length from the bottom to the surface of the water, The water level in the tank is lowered by discharging the water in the drainage well 18 through the drainage pipe 20 by the submersible pump 19 for drainage accommodated in the bottom. As a result, when the water level in the drainage well 18 falls below the outside water level, the inside of the impermeable box 1 is depressurized by the differential pressure caused by the head difference h, and thereby the inside of the soft ground through the vertical drain material 12. Consolidation is performed by dehydration and water pressure.
[0030]
By depressurizing the inside of the water shielding box 1 in this way, the inside of the vertical drain material 12 is depressurized, and the drainage consolidation of the soft ground in each drain material placing section 10, that is, the soft ground A under the water shielding box is made. However, at this time, as shown in FIG. 8, the soft ground A is consolidated in the vertical direction and simultaneously contracted in the horizontal direction. Due to this contraction, the soft ground between the adjacent

water shielding boxes

1, 1, that is, the soft ground B between the water shielding boxes is drawn in, and a force in a direction to lower the surface of the ground acts.
[0031]
At this time, if there is no shielding material 2 between the impermeable bodies, the soft ground B between the impermeable bodies is drawn by the contraction of the left and right impermeable body soft grounds A and A as shown in FIG. Sinks, water is created under the penetrating wall 1a of the impermeable body 1 and water on the ground flows directly into the vertical drain material 12, causing pressure leakage. For this reason, the pressure difference between the vertical drain member 12 and the outside cannot be maintained, and a situation in which effective consolidation dehydration cannot be performed occurs.
[0032]
However, in this embodiment, since the space between the

impermeable bodies

1 and 1 adjacent to each other is shielded by the shielding material 2 between the impermeable bodies, the settlement of the soft ground B between the impermeable bodies is restricted, and the vertical drain material. The pressure difference between the inside and outside 12 is maintained, and effective consolidation improvement of the water bottom soft ground is made.
[0033]
FIGS. 10-11 has shown the 2nd Example of this invention, In this Example, the sheet-like material is used as the shielding material 4 between the

impermeable bodies

1 and 1 which shields between the

impermeable bodies

1 and 1. . Note that the same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted (hereinafter the same).
[0034]
The shielding material 4 between the impermeable boxes is made of an impermeable flexible sheet-like material, and one end side thereof is fixed in advance to two adjacent sides of the top surface of the impermeable box 1. As shown in FIG. 10, it is installed in a state of being wound in a cylindrical shape.
[0035]
In this way, the water shielding body 1 is fixed from above the horizontal drain 13 in the same manner as the first embodiment using the

water shielding bodies

1, 1. After each installation so as to cover, the shielding material 4 between the water shielding boxes 4 is spread to shield between the

water shielding boxes

1 and 1 as shown in FIG.
[0036]
Thereafter, the water in the water collection well 18 is discharged and the inside is depressurized in the same manner as in the first embodiment. As in the first embodiment, the space between the

impermeable bodies

1 and 1 adjacent to each other is shielded by the shielding material 4 between the impermeable bodies, so that the settlement of the soft ground B between the impermeable bodies is regulated, The pressure difference between the inside and outside of the vertical drain material 12 is maintained, and efficient consolidation improvement of the water bottom soft ground is made.
[0037]
12 to 13 show a third embodiment of the present invention. In this embodiment, soft soil replenishing means is used in place of the above-described

shielding materials

2 and 4 between the water shielding boxes. The soft soil replenishing means includes a drainage pipe 5 installed at the top edges of two adjacent sides of the water shielding box 1, a soft soil transport pipe 6 that transports the soft soil to the drainage pipe 5, and soft soil. The pump 7 and the mud storage tank 8 are configured to feed soft soil into the transport pipe 6.
[0038]
A large number of soft soil discharge ports 5 a are opened in the mud discharge pipe 5, and the soft soil fed through the soft soil transport pipe 6 is uniformly discharged over the entire length.
[0039]
In this way, each of the

water shielding cases

1, 1... With the mud pipe 5 installed is installed so that the water shielding case 1 is covered from the horizontal drain 13 in the same manner as in the first embodiment. Then, as shown in FIG. 13, the soft soil transport pipe 6 is connected to each of the sludge pipe shields 5.
[0040]
Thereafter, the water in the water collection well 18 is discharged and the inside is depressurized in the same manner as in the first embodiment. As a result, the inside of the vertical drain material 12 is depressurized, and the dehydration and consolidation of the water-proof enclosure soft ground A is performed. At this time, the soft ground B between the water shielding boxes sinks due to the horizontal contraction of the soft ground A under the water shielding boxes due to the reduced pressure. The subsidence portion is replenished with soft soil by means of soft soil replenishment means, between the water shielding boxes, that is, between the soil penetrating walls .
[0041]
Use viscous soil or bentonite for soft soil to replenish. Moreover, this replenishment is made to maintain the height where the water supply from the surface to the vertical drain material 12 cannot be performed by the surface of the soft ground B between the impermeable bodies moving faster than the descent of the

impermeable bodies

1, 1. The height of the surface of the soft ground B between the water shielding boxes relative to the water shielding box is maintained within a certain range in which the above purpose is achieved. As a result, the pressure difference between the inside and outside of the vertical drain material 12 is maintained, and efficient consolidation improvement of the bottom soft ground is achieved.
[0042]
In each of the above-described embodiments, a sand mat is used for the horizontal drain 13. However, as shown in FIG. 14, a horizontal drain material made of a water permeable material such as a nonwoven fabric in the top of the water shielding box 1 is used. 13a may be accommodated, and after the vertical drain material 12 is placed, the horizontal drain material 13a communicated with the vertical drain material 12 may be configured by covering the water shielding box 1 thereon.
[0043]
In addition, in the first and second embodiments, an example in which the shielding material between the impermeable boxes is integrated with any of the impermeable boxes in advance is shown, but the impermeable boxes are arranged side by side on the bottom of the water. After installing, you may straddle and fix between the top parts of adjacent water-proofing boxes.
[0044]
[Test example]
1. In the present invention. 1. Understand subsidence deformation behavior of soft ground and impermeable box 1. 2. Improvement effects such as subsidence and volume reduction An indoor model experiment was conducted for the purpose of grasping the settlement behavior when a plurality of impermeable boxes 1 were installed.
[0045]
Soil marine clay shown in Table 1

[0046]
Experimental equipment soil tank: Length 150cm x width 150cm x depth 100
Impermeable box 1: Polycarbonate box,
25cm long x 25cm wide x 20cm deep penetration depth
Horizontal drain 13 material: Non-woven fabric Vertical drain material 12: Plastic drain As shown in FIGS. 15 and 16, a partition plate is placed in another earthen tank, and nine drain material placement sections are set by moving to one side. The vertical drain material 12, the horizontal drain 13 material, and the water shielding box 1 were installed as shown in FIG.
[0047]
Experimental Results As a result of depressurizing the inside of the water shielding box 1 in the experimental device, the experimental results shown in FIG. 17 were obtained.
[0048]
According to this, the phenomenon that the ground between the water shielding boxes 1 sinks by 5 to 10 cm as compared with the top of the water shielding box 1 occurred at the end of the experiment. As shown in FIG. 18, this phenomenon is because the clay between the

water shielding bodies

1, 1 falls (sinks) while being consolidated toward the vertical drain material 12.
[0049]
About 3 hours after the start of the experiment, a large amount of water was drained from the vacuum pump, and no negative pressure, which was a consolidation load, was applied. This is because, as shown in FIG. 9, water is created under the water shielding box 1, and water tightness cannot be maintained.
[0050]
From this result, it was proved that measures to maintain the water tightness between the water-impervious enclosures are necessary to improve the consolidation of the whole area of the planned water bottom uniformly.
[0051]
In each of the above-described examples, the interval between the drain material placing sections in units of the width according to the size of one of the water shielding boxes, that is, the distance a between the adjacent water shielding boxes, When the consolidation improvement for the purpose of strengthening the strength is performed, such as the purpose of constructing a structure in the upper part, although it is larger than the drain material placement interval b in the compartment, as shown in FIG. Depending on the ground strength after consolidation improvement to be expressed, such as by placing

vertical drain materials

12, 12,... At uniform intervals b over the entire consolidation improvement area, between the drain

material placement sections

10, 10. Is set as appropriate.
[0052]
【The invention's effect】
As described above, the consolidation improvement method for the bottom soft ground according to the present invention includes a bottom-opening type water-impervious box having a vertically-cylindrically penetrating water-impervious wall and a top end closed. A plurality of drain material placement sections are set on the surface of the water bottom soft ground with an interval in accordance with the size of one of the water shielding boxes, and each drain material placement section Each time, a large number of vertical drain materials are placed from the surface of the bottom soft ground, and a horizontal drain material continuous to each vertical drain material is installed on the surface of the bottom soft ground, and the water shielding box is arranged so as to cover the upper surface thereof. Cover the soil-penetrating impermeable walls with penetration into the soft ground, and then depressurize the horizontal drains in each impermeable box installed next to each other at the same time, thereby dehydrating the water-floor soft ground. By improving the consolidation by performing The subsidence is regulated and the pressure difference between the vertical drain material and the vertical drain material is maintained, and high consolidation of the bottom soft ground is made quickly and efficiently, and in the consolidation improvement for the purpose of expressing the strength for building construction, Large strength development (improvement effect) can be obtained without loading embankment.
[0053]
In addition, on the surface of the soft ground between the water-proofing boxes adjacent to each other, an impermeable shielding material between the water-proofing boxes is installed across the water-proofing box to dehydrate the bottom soft ground. or consolidating improve Te Align or when water shield box making interbody poor ground subsidence, the soil penetrating water shield walls of the water shield box making bodies adjacent, the height of the water shield box making body between soft ground surface Over-subsidence of soft ground between impermeable boxes by improving the consolidation by dehydrating in the bottom soft ground while replenishing soft soil so that is maintained within a certain range with respect to the impermeable box Generation of water is prevented, the pressure difference between the inside and outside of the vertical drain material can be maintained at a desired set value, and consolidation of the bottom soft ground is reliably and efficiently performed.
[0054]
In addition, by previously integrating the shielding material between the water shielding boxes at the top edge of one of the adjacent water shielding boxes, the shielding work between the water shielding boxes at the bottom of the water is easy. Become.
[0055]
Further, the shielding material between the water shielding boxes is a highly rigid plate-like material in which the top plate of the water shielding box is extended and integrated in advance, so that the box is installed simultaneously with the installation of the water shielding box. The space can be closed with a shielding material between the water-proofing boxes, and work efficiency is good.
[0056]
In addition, by making the shielding material between the impermeable boxes into a flexible sheet-like material that is integrated in advance by extending the top plate of the impermeable box, special processing is performed during the production of the impermeable box. It is not necessary, and the manufacturing cost can be kept low.
[0057]
Furthermore, by fixing a drainage pipe that transports and spreads soft soil to the top edge of one of the adjacent water shielding boxes, the soft soil is replenished through the drainage pipe. , Soft soil can be replenished by remote control, and workability is good.
[0058]
Further, a plurality of drain material placement sections are set with a gap wider than the vertical drain material interval in the drain material placement section, and a portion where no vertical drain material is placed between the water shielding boxes is conventionally used. Compared with the soft ground consolidation improvement method, even if it is widely used, because the consolidation of that part is performed effectively, it is possible to reduce the number of vertical drain materials to be used, reducing the cost of materials used and vertical drains The material placing work is reduced, the construction cost is reduced, the construction period can be shortened, the cost is high, and the profitability is sufficiently high even in the construction of lowering the bottom of the water for securing the channel depth.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an example of a water shielding box used in the present invention.
FIG. 2 is a plan view of the above.
FIG. 3 is a plan view showing drain material section setting in an example of the implementation of the method of the present invention.
FIG. 4 is a longitudinal sectional view showing the vertical drain material placing process of the above.
FIG. 5 is a longitudinal sectional view showing a water shielding box installation process after the horizontal drain is installed by the sand mat.
FIG. 6 is a longitudinal sectional view showing the consolidation dehydration step.
FIG. 7 is a longitudinal sectional view showing a state where consolidation is improved by consolidation dehydration.
FIG. 8 is a cross-sectional view showing the consolidation principle described above.
FIG. 9 is a cross-sectional view showing a subsidence state of the ground between the impermeable bodies when the shielding material between the impermeable bodies is not used.
FIG. 10 is a perspective view showing another example of a water shielding box used in the present invention.
FIG. 11 is a longitudinal sectional view showing a water shielding box installation process in another embodiment of the method of the present invention.
FIG. 12 is a perspective view showing another example of a water shielding box used in the present invention.
FIG. 13 is a longitudinal sectional view showing a settlement regulation step of the ground between the impermeable bodies in another embodiment of the method of the present invention.
FIG. 14 is a longitudinal sectional view showing a water shielding box installation process in another embodiment of the method of the present invention.
FIG. 15 is a plan view showing an experimental facility using a plurality of boxes according to the present invention.
FIG. 16 is a longitudinal sectional view of the above.
FIG. 17 is a graph showing experimental results.
FIG. 18 is a longitudinal sectional view showing the principle of settlement between impermeable bodies in the experimental results.
FIG. 19 is a plan view showing another example of the drain material section setting in the method of the present invention.
[Explanation of symbols]
A Soft ground under the water-blocking box B Soft ground between the water-blocking boxes a, b Interval 1 Water-blocking box 1a Underwater impermeable wall 1b Top plate 2 Water-blocking box shielding material 3 Sealing material 4 Water-blocking box Body shielding material 5 Drainage pipe 5a Soft soil discharge port 6 Soft soil transport pipe 7 Pump 8 Mud storage tank 10 Drain material placement section 11 Drain material placement ship 12 Vertical drain material 13 Horizontal drain 13a Horizontal drain material 14 Crane ship 15 Mounting jig 16 Crane 16a Hanging wire 17 Depressurization hose 18 Drainage well 19 Submersible pump 20 Drain pipe 21 Vacuum pump 22 Decompression pipe

Claims

Use a bottom-open type water-blocking box with a vertical cylindrical intrusion impermeable wall around it, with the top end closed, and one of the above-mentioned water-blocking boxes on the surface of the bottom soft ground. A plurality of drain material placement sections with an interval corresponding to the size are set at intervals, and a number of vertical drain materials are placed from the surface of the bottom soft ground for each drain material placement section. In addition, a horizontal drain material continuous to each vertical drain material is installed on the surface of the bottom soft ground, the water shielding box is disposed so as to cover the upper surface, and the soil penetrating impermeable wall penetrates into the soft ground. In addition, a non-permeable impermeable shielding body shielding material that has been integrated in advance with the top edge portion of any one of the adjacent shielding structures, is soft between the adjacent shielding structures. Installed across the ground surface, and then in each impermeable box installed next to each other By reducing the pressure of the flat drain material in the same time, consolidation improved method of the sea bed soft ground composed as characterized by compacting improved to perform the dehydration in the sea bed soft ground.

2. The water bottom soft ground according to claim 1, wherein the shielding material between the water shielding boxes is a plate-like material made of the same material as the water shielding box which is previously integrated by extending the top plate of the water shielding box. Consolidation improvement method.

The consolidation improvement method for water-bottomed soft ground according to claim 1, wherein the shielding material between the impermeable bodies is a flexible sheet-like material in which the top plate of the impermeable box is extended and integrated in advance.

Use a bottom-open type water-blocking box with a vertical cylindrical intrusion impermeable wall around it, with the top end closed, and one of the above-mentioned water-blocking boxes on the surface of the bottom soft ground. A plurality of drain material placement sections with an interval corresponding to the size are set at intervals, and a number of vertical drain materials are placed from the surface of the bottom soft ground for each drain material placement section. In addition, a horizontal drain material continuous to each vertical drain material is installed on the surface of the bottom soft ground, the water shielding box is disposed so as to cover the upper surface, and the soil penetrating impermeable wall is penetrated into the soft ground. After that, while simultaneously depressurizing the horizontal drain material in each impermeable box installed next to each other, and when the soft ground between the impermeable bodies sinks, the penetration water barrier walls, the surface of the water shield box making interbody poor ground, vertical from the surface Consolidation improved method of the sea bed soft ground composed as characterized by being supplemented with soft soil so as to maintain a height that can not tap leading to lane material to perform the dehydration of the water bottom soft ground by compacting improved.

The bottom of water according to claim 4, wherein a drainage pipe for conveying and dispersing soft soil is fixed to one of the top edges of adjacent water shielding boxes, and the soft soil is replenished through the drainage pipe. Consolidation improvement method for soft ground.

The water bottom soft ground according to any one of claims 1 to 4 or 5, wherein the plurality of drain material placement sections are set at a wider interval than the horizontal distance between the vertical drain materials in the drain material placement section. Consolidation improvement method.