【０００１】
【発明の属する技術分野】
本発明は、ダム貯水池おける上流部に沈下堆積した土砂を、ダム堤体の排砂ゲート付近まで流下させて、当該排砂ゲートを通じて下流河道に排出供給できるようにした堆積土砂の流下促進用堰構造および流下促進方法に関する。
【０００２】
【背景技術】
発電用、灌漑用、洪水調整用等に供するダム貯水池が各地の河川に多数建設されているが、これらのダム貯水池にあっては、その建設からの年月を経る程に、上流から流下してくる土砂が河床に堆積していき、その増大する堆積土砂によって貯水容量が低下してしまうことを避け難い。
【０００３】
ここで、貯水池内に堆積する土砂は、洪水時などに増水して狭隘な上流側河川を高い流速で流下する流水に運ばれて濁流となって流入するが、当該流速の高い濁流は横幅の広い貯水池内に流入するとその流速が急激に低下するので、土砂はダム堤体の近傍までは運ばれ難く、その殆どが貯水池の上流部にて沈下堆積し、貯水池はその上流部から堆積土砂によって埋められていく。
【０００４】
一方、ダム堤体には一般に上記堆積土砂を下流河道に排出するための排砂ゲートが設けられいるのであるが、この排砂ゲートから排出することのできる堆積土砂は、ダム貯水池内のダム堤体に近接した下流部分に沈下堆積したものがせいぜいであり、上流部に沈下堆積している土砂は当該排砂ゲートから排出されずに残存されてしまうのが現状となっている。
【０００５】
そして、各河川の地盤環境等によって異なるものの、設計時の予想をはるかに上回る土砂の堆積が生じて現貯水容量が設計時の５０〜８０％までにも減少して、その貯水機能の著しい低下を来しているダム貯水池が全国に多々あるとの報告も数多く寄せられている。このため、この様なダム貯水池にあっては、その機能を回復するために堆積土砂の除去を行うことが急務となっている。
【０００６】
そこで、このような堆積土砂の排出を行うために、従来では、例えば、特開平５−５３１８号公報や特開２００１−２６２６１２号公報などに開示されているような、浚渫船や浚渫装置によって堆積土砂を回収して排出する方法、あるいは、貯水池の水位を低下させて掃流力によりダム堤体の排砂ゲート付近まで流下させる方法等が採用されていた。
【０００７】
【特許文献１】特開平５−５３１８号公報
【０００８】
【特許文献２】特開２００１−２６２６１２号公報
【０００９】
【発明が解決しようとする課題】
しかしながら、浚渫船や浚渫装置による排出方法では、ダムサイトの地理的条件や道路事情などにより、回収した土砂の搬出が困難である地点が多くあるという問題がある。また、浚渫による費用は嵩み、しかも定期的に繰り返して行わなければならないため、その整備費は多大なものとなってしまうという問題もある。
【００１０】
一方、水位を低下させて掃流力により流下させる方法では、その低下後に水位を回復させるのに日数を要し、ダム貯水池機能に支障を来してしまう場合があった。
【００１１】
本発明は、このような事情に鑑みてなされたものであり、その目的は、水位を低下させずに、貯水池内への流入速度が高い河川増水時の流水をその速度を落とさないように利用して、当該貯水池内の上流部に堆積した土砂を下流のダム堤体の排砂ゲートの近傍まで流下させることができる、ダム貯水池における堆積土砂の流下促進用堰構造及び流下促進方法を提供することにある。
【００１２】
【課題を解決するための手段】
本発明は上記の目的を達成するために、ダム貯水池における堆積土砂の流下促進用堰構造及び流下促進方法を以下のように構成する。
【００１３】
請求項１に係るダム貯水池における堆積土砂の流下促進用堰構造の発明は、ダム貯水池内に流入して上流部に堆積した土砂を、流入速度が高まる河川増水時の流水を利用してダム堤体の排砂ゲートから排出可能な下流部の排出可能領域まで流下させるべく、該貯水池内の土砂堆積領域に設ける堆積土砂の流下促進用堰構造であって、該貯水池の河道の流路断面績を狭めて該河道の中央部側に流水を集める一対の堰手段を、該河道中央部の両側に所定間隔をあけて配置するとともに、該一対の堰手段を河道中央部に沿って多段に配設したことを特徴とする。
【００１４】
請求項２に係るダム貯水池における堆積土砂の流下促進用堰構造の発明は、前記一対の堰手段は、それぞれその河岸側の端部が該河岸から所定間隔を離間されて設けられていることを特徴とする。
【００１５】
請求項３に係るダム貯水池における堆積土砂の流下促進用堰構造の発明は、前記堰手段はその河岸側端が上流側に向けて所定角度傾斜されて配置されていることを特徴とする。
【００１６】
請求項４に係る発明は、前記堰手段の上端部の高さが、前記貯水池の常時満水位の近傍に設定されていることを特徴とする。
【００１７】
請求項５に係るダム貯水池における堆積土砂の流下促進用堰構造の発明は、前記堰手段は、前記堆積土砂層を貫通して河床に下端を打ち込まれた杭が列設されて構成されていることを特徴とする。
【００１８】
請求項６に係るダム貯水池における堆積土砂の流下促進用堰構造の発明は、前記堰手段は、対面する河岸間に張設された係留ロープに吊下支持されたコンクリートパネルで構成されていることを特徴とする。
【００１９】
請求項７に係るダム貯水池における堆積土砂の流下促進用堰構造の発明は、前記コンクリートパネルは、前記係留ロープにフロートを介して吊下支持されていることを特徴とする。
【００２０】
請求項８に係るダム貯水池における堆積土砂の流下促進方法の発明は、ダム貯水池内に流入して上流部に堆積した土砂の堆積領域に、該貯水池の河道の流路断面績を狭めて該河道の中央部側に流水を集める一対の堰手段を、該河道中央部の両側に所定間隔をあけて配置するとともに、該一対の堰手段を河道中央部に沿って多段に配設し、該多段に配設した一対の堰手段によって河川増水時に高い流入速度で流入する流水を増速させつつダム堤体の排砂ゲートから排出可能な下流部の排出可能領域まで流下させて、該流水の掃流力で該土砂堆積領域の堆積土砂の流下を促進させることを特徴とする。
【００２１】
【発明の実施の形態】
以下に、本発明に係るダム貯水池における堆積土砂の流下促進用堰構造及び流下促進方法の好適な実施の形態について、添付図面に基づき詳述する。
【００２２】
《第１実施形態》
図１は本発明が実施されたダム貯水池の平面を示す概要図であり、図２はその河道に沿った縦断面を示す概要図、図３は図２中におけるα−α線矢視断面図である。図１，図２２に示すように、このダム貯水池２は、山間の河川４の両岸に迫る谷間に掛け渡して構築したダム堤体６によって当該河川４が堰き止められることで形成されており、ダム堤体６にはダム貯水池２内に流入して堆積する土砂を下流の河道に排出して供給する排砂ゲート８が設けられている。そして、この様なダム貯水池２には、これより上流の河川４から流下してくる土砂が当該貯水池２内の元河床４ａ上に沈下して堆積していき、建設後の年月を経るほどに堆積土砂層１０が厚く形成されていく。
【００２３】
この堆積土砂層１０は前述の背景技術の欄でも示したように、主に洪水時の濁流によって運ばれる土砂によって形成されるが、当該濁流は横幅の広がった貯水池２内に流入するとその速度が急激に低下するため、土砂は直ぐに沈下し始め、殆どダム堤体６近傍の下流部まで運ばれることなく、当該貯水池２の上流側に主に沈下してしまい、上記排砂管８による土砂の排出可能領域Ａよりも上流の排出不可能な領域に堆積土砂層１０が厚く形成されてしまう。
【００２４】
そこで、この様な厚い堆積土砂層１０の土砂を、増水した洪水時の流水を可及的に落とさないように利用して、その掃流力で下流の上記土砂排出可能領域Ａまで流下させるために、当該堆積土砂層１０が形成された土砂堆積領域（土砂排出不可領域）Ｂに、堆積土砂の流下促進用堰構造２０を設けている。
【００２５】
即ち、この流下促進用堰構造２０は、貯水池２の河道の流路断面績を狭めて当該河道の中央部側に流水を集める一対の堰手段２２が、当該河道に沿って上・下流方向に適宜間隔をあけて多数配設されて構成されている。これら各一対の堰手段２２は河道の中央部に互いに所定の間隔をあけて河道幅方向の両側に配設されており、それぞれの河道中央部寄りの端部２２ａは最も流速の早い河道中心の河芯４ｂを基準にして対称位置に配されている。また、一対の堰手段２２はそれぞれ河芯４ｂに対して直角に河岸４ｃ方向に延び、それぞれその河岸側の端部２２ｂは当該河岸４ｃから所定間隔をあけて離間された位置に設けられている。
【００２６】
図３に示すように、この実施の形態においては、各堰手段２２は多数の杭２４，２４，…が一列に列設されてなる。当該各杭２４，２４，…は、その下端２４ａが前記堆積土砂層１０を貫通して、その下の河床４ａに打ち込まれて設けられている。また、各杭２４，２４，…の上端部の高さは、貯水池２の常時満水位３０の近傍に設定されている。ここで、当該杭２４にはコンクリート杭あるいは鋼管杭を採用し得るが、腐食等の耐久性の面を考慮するとコンクリート杭を採用する方が好ましい。また、各堰手段２２を構成する多数の杭２４，２４，…は相互に密接配置しても良いし、あるいは若干離間させて配置しても良い。なお、当該図示例では若干離間させて配置してある。
次に、以上の様に構成された流下促進用堰構造２０の作用について述べる。
【００２７】
洪水時に増水した上流側河川から速度の高い大量の流水がダム貯水池２に流れ込んでくると、その流水は貯水池２内の河道に沿ってその両側に一対で多段に設けられている堰手段２２が抵抗となるので、これらの多数の堰手段２２をよけて下流に流れていくことになる。
【００２８】
ここで、各一対の堰手段２２の配設部を流水が通過する際には、当該堰手段２２が設けられていない河道中央部と両側部とにその多くが集まって、ここに集中的に流れることになるが、当然の事ながら、当該堰手段２２の配設部位は、その流路断面積が狭められているので、相対的に当該堰手段２２の配設部位を通過する流水の速度は高くなる。つまり、河道中央部と両側部との流速が大きくなる。
【００２９】
然も、各一対で多段に設けられる各部の堰手段２２はいずれも流水を河道中央部と両側部とに案内するから、横幅の大きく広がった貯水池２内にあっても、流水は当該貯水池２内をその上流部から下流部に至るまで、河道の中央部と両側部とに沿って速い速度を可及的に維持したまま流れ込むことになる。このため、当該河道中央部と両側部とを流れる流水は、上流から運び込んだ新たな土砂と共に、貯水池２内の元河床４ａ上に堆積している土砂をも抉って流下させる掃流力を、堆積土砂層１０が形成された土砂堆積領域（土砂排出不可領域）Ｂよりもさらに下流まで失わずに流れ込むようになる。これ故、当該河道中央部と両側部との元河床４ａ上に堆積した土砂は、ダム堤体６の排砂ゲート８による土砂排出可能領域Ａまで運ばれることになる。そして、当該土砂排出可能領域Ａまで運ばれた土砂は必要に応じて、洪水後などに逐次に排砂ゲート８から下流の河川４の河道に排出供給される。
【００３０】
また、河道中央部の流速はもともと本来的に最も高く、しかも一対の堰手段によってさらに増速されるから、河道両側部を流れる流水は各段の堰手段２２を通過する毎にその一部が中央部へと流れていくことになる。このため、この河道中央部へと流れる流水によって、河道両側部と中央部との間に堆積した土砂が抉られた中央部へと流下されて、ダム堤体６の排砂ゲート８による土砂排出可能領域Ａまで運ばれることになる。
【００３１】
一方、大量の流水が貯水池２内に流入してくるに連れて、貯水池２の水位は上昇し、常時満水位３０からサーチャージ水位３２まで徐々に上昇していく。これ故、流水が堰手段２２の上を越えて流れるようになると、堆積土砂層１０の上側を通過する流水の速度は落ち始めて上記掃流力は徐々に低下していくが、暫くの間は堆積土砂層１０の土砂を抉って流下させる程の掃流力は維持される。
【００３２】
ここで、当該掃流力の低下を防ぐには、堰手段２２の各杭２４の上端部の高さをサーチャージ水位３２近辺まで近づけて設定すれば良い。但し、このようにすると杭２４に加わる流動水圧とこれによる曲げモーメントはかなり大きなものとなるから、これに耐えさせるために各杭２４は大型化して、その設置費用が高く付くことになる。即ち、杭２４高さを常時満水位程度に止めれば、堰手段の設計耐力を可及的に下げてその設置費用を低く抑えることができる。よって、杭２４の高さは設置対象となるダム貯水池２に流れ込む河川等の諸条件に応じて、対費用効果の面から決定すればよい。また、杭２４を列設して堰手段２２を構成することにより、高強度で耐力に優れた堰手段を容易に構築できる。
【００３３】
また、貯水池２の水位を低下させることなく、洪水時における速度の高い流水の掃流力を利用して堆積土砂を流下させることができるので、貯水池２の機能に支障を来すことがないばかりか、堰手段２２の設置後には恒久的にこれを機能させて、洪水の度毎に堆積土砂の排出を行わせることができて、その設置後の土砂の堆積を防止することができる。
【００３４】
また、上記図示した第１実施例の説明では、各堰手段２２は河芯４ｂに対して直角となして河岸４ｃ方向に向けて延設させるようにしているが、その河岸側の端部２２ｂを上流側に位置させて、一対の堰手段２２を上流側が開くハの字状に配置するようにしても良い（図示は省略する）。この様にすることで、更に多くの流水を中央部に向けて集中的に流せるようになるので、河道中央部の掃流力をより一層高めることができるようになる。
【００３５】
《第２実施形態》
図４は本発明の第２実施形態を示すものであり、堰手段にコンクリートパネルが用いられた第２実施形態を示す図３に相当する図である。なお、図１の概要図は本第２実施形態にも共通するものであり、図４においては、第１実施形態と同一の部材及び部分には同一の符合を付してその説明は省略する。
【００３６】
この第２実施形態では、図４に示すように、堰手段２２がフローチング方式とされている。即ち、河道中央部の両側に設けられる一対の堰手段２２は対面する河岸４ｃ，４ｃ間に張設された係留ロープ４０に吊下支持されたそれぞれ２枚のコンクリートパネル４２で構成されている。そして、図示するこの実施形態では、各コンクリートパネル４２は、係留ロープ４０にフロート４４を介して吊下支持されて、水面下に水没している。また、係留ロープ４０は両河岸４ｃの岩盤にそれぞれ埋設固定したコンクリートブロック４６に両端を係止されて、常時満水位３０の水面上を横断している。
【００３７】
そして、この第２実施形態のフローチング方式の場合にあっても、前記第１実施形態と同様に、洪水時に増水した上流側河川から速度の高い大量の流水がダム貯水池２に流れ込んでくると、その流水は貯水池２内の河道に沿ってその両側に一対で多段に設けられている堰手段２２が抵抗となるので、これらの多数の堰手段２２をよけて下流に流れていく。即ち、当該貯水池２内をその上流部から下流部に至るまで、河道の中央部と両側部とに沿って集中的に速い速度を可及的に維持したまま流れ込んで、当該河道中央部と両側部との元河床４ａ上に堆積した土砂を、ダム堤体６の排砂ゲート８による土砂排出可能領域Ａまで流下させて運ぶことになる。
【００３８】
ここで、この第２実施形態の場合には、コンクリートパネル４２はその上端部がフロート４４を介して係留ロープ４０に吊下支持されているから、流水の流動圧が上流面に加わると、下端が下流方向に押されてフラップの如く傾くことになる。すると、この傾いたコンクリートパネル４２は流水を下方に案内する案内板の機能を発揮するようになる。このため、流水の一部は当該コンクリートパネル４２の下方を潜って増速されながら流れていき、その際に下方の堆積土砂層１０の土砂を抉って流下させることになる。
【００３９】
また、係留ロープ４０にコンクリートパネル４２を係止する際には、予め当該コンクリートパネル４２をフロート４４で浮かした状態で行うことができ、もってコンクリートパネル４２の取付作業を極めて簡易に行えるようになる。
【００４０】
即ち、前記第１実施形態および第２実施形態のような堆積土砂の流下促進方法によれば、そのいずれにあっても、ダム貯水池２内に流入して上流部に堆積した土砂の堆積領域Ｂに、貯水池２の河道の流路断面績を狭めて当該河道の中央部側に流水を集める一対の堰手段２２を、予めその河道中央部の両側に所定間隔をあけて配置し、かつそれら一対の堰手段２２は河道中央部に沿って多段に配設しておくことで、河川増水時に高い流入速度で流入する流水を、その多段に配設した一対の堰手段２２部位を通過する毎に増速させて、ダム堤体６の排砂ゲート８近傍まで高い速度で流れ込むようになり、もって当該流水の掃流力で土砂堆積領域Ｂの堆積土砂をダム堤体６の排砂ゲート８から排出可能な下流部の排出可能領域Ａまで流下させることができ、洪水などの河川増水が発生する都度に、新たな流入土砂と共に堆積土砂の流下を促進することができる。また、一度設置すれば恒久的に機能させることができて、特に浚渫する必要もないので、整備費用の可及的な低減化が図れるばかりか、掃流力を得るために水位を低下させる必要もないので、ダム貯水池２としての機能に支障を来す虞がない。
【００４１】
【発明の効果】
請求項１に係るダム貯水池における堆積土砂の流下促進用堰構造の発明によれば、土砂堆積領域に貯水池の河道の流路断面績を狭めて該河道の中央部側に流水を集める一対の堰手段を、河道中央部の両側に所定間隔をあけて配置するとともに、その一対の堰手段を河道中央部に沿って多段に配設したので、洪水時に増水した上流側河川から速度の高い大量の流水がダム貯水池２に流れ込んできたときに、当該流水を河道中央部に集めてその流速を可及的に低下させずに、その上流部から下流部に至るまで、河道の中央部に沿って速い速度を可及的に維持したまま流すことができる。このため、当該河道中央部の元河床上に堆積している土砂を抉って流下させる掃流力を、堆積土砂層が形成された土砂堆積領域（土砂排出不可領域）よりもさらに下流まで失わせずに流れ込ませることができるようになり、当該河道中央部の元河床上に堆積した土砂を、ダム堤体の排砂ゲートによる土砂排出可能領域まで流下させて運ぶことができる。そして、当該土砂排出可能領域まで運ばれた土砂は必要に応じて、洪水後などに逐次に排砂ゲートから下流の河川の河道に排出供給することができる。
【００４２】
また、貯水池の水位を低下させることなく、洪水時における速度の高い流水の掃流力を利用して堆積土砂を流下させることができるので、貯水池の機能に支障を来すことがないばかりか、堰手段の設置後には恒久的にこれを機能させて、洪水の度毎に堆積土砂の排出を行わせることができて、土砂の堆積を防止することができる。
【００４３】
請求項２に係るダム貯水池における堆積土砂の流下促進用堰構造の発明によれば、一対の堰手段は、それぞれその河岸側の端部が該河岸から所定間隔を離間されて設けられているので、当該河道両側部にそって高い流速で流水を流すことができ、上記中央部と同様に、河道両側部の堆積土砂をダム堤体の排砂ゲートによる土砂排出可能領域まで流下させて運ぶことができる。また、河道中央部の流速はもともと本来的に最も高く、しかも一対の堰手段によってさらに増速されるから、河道両側部を流れる流水は各段の堰手段を通過する毎にその一部が中央部へと流れていくことになり、この河道中央部へと流れる流水によって、河道両側部と中央部との間に堆積した土砂が中央部へと流下されて、ダム堤体の排砂ゲートによる土砂排出可能領域まで運ばれることになる。
【００４４】
請求項３に係るダム貯水池における堆積土砂の流下促進用堰構造の発明によれば、堰手段の河岸側端を上流側に向けて所定角度傾斜させて配置するので、より多くの流水を中央部に向けて集中的に流せるようになり、河道中央部の掃流力をより一層高めることができる。
【００４５】
請求項４に係るダム貯水池における堆積土砂の流下促進用堰構造の発明によれば、堰手段の上端部の高さを、貯水池の常時満水位の近傍に設定しているので、常時満水位を越えて増水した流水の流動圧を受けることがなく、もって堰手段の設計耐力を可及的に下げてその施工費用の低減化が図れる。
【００４６】
請求項５に係るダム貯水池における堆積土砂の流下促進用堰構造の発明によれば、堆積土砂層を貫通して河床に下端が打ち込まれた杭を列設して堰手段を構成するので、高強度で耐力に優れた堰手段を容易に構築できる。
【００４７】
請求項６に係るダム貯水池における堆積土砂の流下促進用堰構造の発明によれば、コンクリートパネルに流水の流動圧が加わると、下端が下流方向に押されてフラップの如く傾いて流水を下方に案内する案内板の機能を発揮し、流水は当該コンクリートパネルの下方を潜って増速されながら流れるようになり、もってその際に、下方の堆積土砂層の土砂を抉って流下させることができる。また、コンクリートパネルは対面する河岸間に張設した係留ロープに吊下支持させるので、貯水池内の河床に対する施工作業を可及的に無くすことができてその施工性に優れる。
【００４８】
請求項７に係るダム貯水池における堆積土砂の流下促進用堰構造の発明によれば、コンクリートパネルを、前記係留ロープにフロートを介して吊下支持させているので、係留ロープに係止する際に、フロートで浮かした状態で行うことができ、コンクリートパネルの取付作業を極めて簡易に行えるようになる。
【００４９】
請求項８に係るダム貯水池における堆積土砂の流下促進方法の発明によれば、ダム貯水池内に流入して上流部に堆積した土砂の堆積領域に、該貯水池の河道の流路断面績を狭めて該河道の中央部側に流水を集める一対の堰手段を、該河道中央部の両側に所定間隔をあけて配置するとともに、該一対の堰手段を河道中央部に沿って多段に配設しておくことにより、河川増水時に高い流入速度で流入する流水は、該多段に配設した一対の堰手段部位を通過する毎に増速されて、ダム堤体の排砂ゲート近傍まで高い速度で流れ込むようになり、もって該流水の掃流力で該土砂堆積領域の堆積土砂をダム堤体の排砂ゲートから排出可能な下流部の排出可能領域まで流下させることができ、洪水などの河川増水が発生する都度に、新たな流入土砂と共に堆積土砂の流下を促進することができる。また、堰手段を多段に、一度設置すれば恒久的に機能させることができて、特に浚渫する必要もないので、整備費用の可及的な低減化が図れるばかりか、掃流力を得るために水位を低下させる必要もないので、ダム貯水池としての機能に支障を来す虞がない。
【図面の簡単な説明】
【図１】本発明が実施されたダム貯水池の平面を示す概要図である。
【図２】堰手段に杭が用いられた本発明の第１実施形態を示すもので、ダム貯水池の河道中央部に沿った縦断面の概要図である。
【図３】図２中におけるα−α線矢視部の断面図である。
【図４】図３に相当する堰手段にコンクリートパネルが用いられた第２実施形態を示す図である。
【符号の説明】
２ ダム貯水池内 ４ 河川
４ａ 河床 ４ｃ 河岸
６ ダム堤体 ８ 排砂ゲート
１０ 堆積土砂層 ２０ 流下促進用堰構造
２２ 堰手段
２２ａ 稼働中央側端部 ２２ｂ 河岸側端部
２４ 杭 ２４ａ 下端部
３０ 常時満水位 ４０ 係留ロープ
４２ コンクリートパネル ４４ フロート
Ａ 土砂排出可能領域 Ｂ 土砂堆積領域[0001]
BACKGROUND OF THE INVENTION
The present invention is a dam for accelerating the flow of sedimentary sediment that allows sediment deposited in the upstream part of a dam reservoir to flow down to the vicinity of the sand discharge gate of the dam body and to be discharged and supplied to the downstream river through the sand discharge gate. The present invention relates to a structure and a flow promotion method.
[0002]
[Background]
Many dam reservoirs for power generation, irrigation, flood control, etc. have been constructed in rivers around the country, but these dam reservoirs flow down from the upstream as time passes by the construction. It is unavoidable that the sediments that come will accumulate on the riverbed, and that the accumulated sediment will reduce the water storage capacity.
[0003]
Here, the sediment deposited in the reservoir is increased in a flood and is carried to a stream that flows down a narrow upstream river at a high flow velocity and flows into a muddy flow. When flowing into a large reservoir, the flow velocity drops rapidly, so it is difficult for the sediment to be transported to the vicinity of the dam body, and most of it settles and deposits in the upstream part of the reservoir, and the reservoir is deposited by sedimentary sediment from the upstream part. It will be buried.
[0004]
On the other hand, the dam body is generally provided with a sand removal gate for discharging the sedimentary sediment to the downstream river channel. The sedimentary sediment that can be discharged from the sedimentation gate is the dam bank in the dam reservoir. At most, the sediment deposited in the downstream portion adjacent to the body is at most, and the sediment deposited in the upstream portion remains without being discharged from the sand removal gate.
[0005]
And although it depends on the ground environment of each river, the sediment accumulation far exceeds the design time expectation and the current water storage capacity is reduced to 50-80% of the design time. There are many reports that there are many dam reservoirs in the country. For this reason, in such a dam reservoir, it is urgent to remove the sediment in order to restore its function.
[0006]
Therefore, in order to discharge such sedimentary sediment, conventionally, sedimentary sediment is disclosed by dredgers or dredging devices as disclosed in, for example, Japanese Patent Laid-Open Nos. 5-5318 and 2001-262612. The method of recovering and discharging the wastewater, or the method of lowering the water level of the reservoir and letting it flow down to the vicinity of the sand discharge gate of the dam body by the sweeping force, etc. were adopted.
[0007]
[Patent Document 1] JP-A-5-5318
[Patent Document 2] Japanese Patent Laid-Open No. 2001-262612 [0009]
[Problems to be solved by the invention]
However, the discharging method using dredgers and dredging devices has a problem that there are many points where it is difficult to carry out the collected earth and sand due to the geographical conditions of the dam site and road conditions. In addition, the cost of the kite is high, and the maintenance cost is significant because it must be repeated periodically.
[0010]
On the other hand, in the method of lowering the water level and using the scavenging force, it takes days to recover the water level after the drop, which may impede the dam reservoir function.
[0011]
The present invention has been made in view of such circumstances, and the purpose thereof is to use the water flow at the time of river increase with a high inflow rate into the reservoir without lowering the water level without reducing the water level. Provided is a weir structure for promoting the flow of sediment in the dam reservoir, and a method for promoting the flow, in which the sediment deposited in the upstream portion of the reservoir can flow down to the vicinity of the sand discharge gate of the downstream dam dam body. There is.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises a weir structure for promoting the flow of sediment and sediment in a dam reservoir and a flow promoting method as follows.
[0013]
The invention of the dam structure for promoting sedimentation of sediment in the dam reservoir according to claim 1 is characterized in that the sediment that has flowed into the dam reservoir and accumulated in the upstream portion is used for the dam A dam structure for promoting the flow of sediment in the sediment accumulation area in the reservoir so as to flow from the sand drain gate of the body to the drainable area in the downstream portion, wherein the channel cross-section of the river channel of the reservoir A pair of weir means for collecting flowing water on the central side of the river channel with a narrowing is arranged at predetermined intervals on both sides of the central part of the river channel, and the pair of weir means are arranged in multiple stages along the central part of the river channel It was set up.
[0014]
According to the invention of a dam structure for promoting sedimentation and sediment flow in a dam reservoir according to claim 2, the pair of dam means is provided such that the ends on the riverside are spaced apart from the riverbank by a predetermined interval. Features.
[0015]
The invention for the dam structure for promoting sedimentation and sediment flow in the dam reservoir according to claim 3 is characterized in that the dam means is arranged with its riverside end inclined at a predetermined angle toward the upstream side.
[0016]
The invention according to claim 4 is characterized in that the height of the upper end portion of the weir means is set in the vicinity of the constantly full water level of the reservoir.
[0017]
The invention of the dam structure for promoting the flow of sedimentary sediment in the dam reservoir according to claim 5 is configured such that the dam means is arranged in a row with piles penetrating the sedimentary sediment layer and driving a lower end into the river bed. It is characterized by that.
[0018]
In the invention of the dam structure for promoting the flow of sediment in the dam reservoir according to claim 6, the dam means is composed of a concrete panel suspended and supported by a mooring rope stretched between facing riverbanks. It is characterized by.
[0019]
The invention of the dam structure for promoting the flow of sediment in the dam reservoir according to claim 7 is characterized in that the concrete panel is suspended and supported by the mooring rope via a float.
[0020]
The invention of the method for facilitating sediment sediment flow in a dam reservoir according to claim 8 is characterized in that the channel cross section of the river channel of the reservoir is narrowed to the sediment accumulation region flowing into the dam reservoir and deposited upstream. A pair of weir means for collecting running water on the central side of the river channel are arranged at predetermined intervals on both sides of the central part of the river channel, and the pair of weir means are arranged in multiple stages along the central part of the river channel, A pair of weir means arranged in the river is used to accelerate the flowing water flowing in at a high inflow rate when the river is increased while flowing down from the sand discharge gate of the dam dam body to a dischargeable area in the downstream portion, thereby sweeping the flowing water. It is characterized by facilitating the flow of sedimentation sediment in the sediment accumulation region by flow force.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a weir structure for promoting the flow of sediment and sediment and a flow promoting method in a dam reservoir according to the present invention will be described in detail with reference to the accompanying drawings.
[0022]
<< First Embodiment >>
FIG. 1 is a schematic diagram showing a plane of a dam reservoir in which the present invention is implemented, FIG. 2 is a schematic diagram showing a longitudinal section along the river channel, and FIG. 3 is a sectional view taken along the line α-α in FIG. It is. As shown in FIGS. 1 and 22, this dam reservoir 2 is formed by the river 4 being dammed up by a dam dam body 6 constructed across a valley approaching both sides of the mountain river 4. The dam dam body 6 is provided with a sand discharge gate 8 for discharging and supplying earth and sand accumulated in the dam reservoir 2 to the downstream river channel. And in such a dam reservoir 2, the sediment flowing down from the upstream river 4 sinks and accumulates on the former river bed 4a in the reservoir 2, and so that it passes through the years after construction. As a result, the thick sediment layer 10 is formed thickly.
[0023]
As shown in the background art section, the sedimentary sediment layer 10 is formed mainly by sediment transported by turbulent flow during flooding. When the turbulent flow flows into the reservoir 2 having a wide width, the velocity of the sedimentary sediment layer 10 increases. Because of the rapid drop, the sediment begins to sink immediately, and is mostly transported to the upstream side of the reservoir 2 without being transported to the downstream portion in the vicinity of the dam body 6. The sedimentary sediment layer 10 is thickly formed in a region that cannot be discharged upstream from the dischargeable region A.
[0024]
Therefore, in order to make the sediment of such a thick sediment layer 10 flow down to the above-mentioned sediment dischargeable area A downstream by using the tractive force so as not to drop as much as possible the flowing water at the time of flooding. In addition, a sedimentation sediment flow weir structure 20 is provided in a sediment accumulation region (a sediment undischargeable region) B where the sedimentary sediment layer 10 is formed.
[0025]
That is, in this weir structure 20 for promoting the flow-down, a pair of dam means 22 for narrowing the channel cross-section of the river channel of the reservoir 2 and collecting the flowing water at the central part of the river channel are arranged upstream and downstream along the river channel. Many are arranged at appropriate intervals. Each of the pair of dam means 22 is disposed on both sides in the width direction of the river channel at a predetermined distance from each other in the central portion of the river channel, and the end portions 22a closer to the central portion of the river channel are located at the center of the river channel with the fastest flow velocity. They are arranged symmetrically with respect to the river core 4b. The pair of dam means 22 extend in the direction of the river bank 4c at right angles to the river core 4b, and the end 22b on the river bank side is provided at a position spaced apart from the river bank 4c by a predetermined distance. .
[0026]
As shown in FIG. 3, in this embodiment, each dam means 22 has a large number of piles 24, 24,. Each of the piles 24, 24,... Is provided such that a lower end 24a thereof penetrates the sedimentary sediment layer 10 and is driven into the river bed 4a therebelow. Moreover, the height of the upper end part of each pile 24,24, ... is set to the vicinity of the constantly full water level 30 of the reservoir 2. Here, although a concrete pile or a steel pipe pile can be adopted as the pile 24, it is preferable to adopt a concrete pile in consideration of durability such as corrosion. In addition, a large number of piles 24, 24,... Constituting each dam means 22 may be arranged closely to each other or may be arranged slightly apart. In the illustrated example, they are arranged slightly apart.
Next, the operation of the weir structure 20 for promoting the flow configured as described above will be described.
[0027]
When a large amount of high-speed water flows into the dam reservoir 2 from the upstream river that has increased during flooding, the water flows along the river channel in the reservoir 2 by a pair of dam means 22 provided in multiple stages on both sides. Since it becomes resistance, it will flow downstream through these many weir means 22.
[0028]
Here, when flowing water passes through the arrangement portions of each pair of dam means 22, most of them gather at the river channel center portion and both side portions where the dam means 22 are not provided. Naturally, since the flow passage cross-sectional area of the arrangement portion of the dam means 22 is narrowed, the flow speed of the flowing water that relatively passes through the arrangement portion of the dam means 22. Becomes higher. That is, the flow velocity between the river channel center and both sides increases.
[0029]
However, since the dam means 22 of each part provided in multiple stages in each pair guides the flowing water to the central part of the river channel and both side parts, the flowing water is stored in the reservoir 2 even if it is in the reservoir 2 having a wide width. From the upstream part to the downstream part of the river, it flows along the central part and both sides of the river channel while maintaining as fast as possible. For this reason, the flowing water flowing through the center and both sides of the river channel, along with the new earth and sand brought in from the upstream, has a sweeping force that flows down the earth and sand accumulated on the former river bed 4a in the reservoir 2, It flows without losing further to the downstream of the sediment accumulation region (the sediment discharge impossible region) B where the sedimentary sediment layer 10 is formed. Therefore, the earth and sand deposited on the original river bed 4 a at the center and both sides of the river channel is transported to the sediment dischargeable area A by the sand discharge gate 8 of the dam body 6. And the earth and sand conveyed to the said earth and sand dischargeable area A are discharged and supplied to the river channel of the downstream river 4 from the sand discharge gate 8 sequentially after flooding as necessary.
[0030]
In addition, the flow velocity in the central part of the river channel is inherently the highest and is further increased by the pair of dam means, so that a portion of the flowing water flowing on both sides of the river channel passes through the dam means 22 of each stage. It will flow to the center. For this reason, by the flowing water flowing to the central part of the river channel, the sediment deposited between the both sides of the river channel and the central part is flowed down to the central part where the sand is sown, and the sediment is discharged by the sand discharge gate 8 of the dam body 6 It will be carried to the possible area A.
[0031]
On the other hand, as a large amount of flowing water flows into the reservoir 2, the water level of the reservoir 2 rises and gradually rises from the full water level 30 to the surcharge water level 32 at all times. Therefore, when the flowing water flows over the weir means 22, the speed of the flowing water passing over the sedimentary sediment layer 10 begins to decrease and the scavenging force gradually decreases, but for a while The scavenging force is maintained so that the sediment of the sedimentary sediment layer 10 can be swept down.
[0032]
Here, in order to prevent the reduction of the scavenging force, the height of the upper end portion of each pile 24 of the weir means 22 may be set close to the vicinity of the surcharge water level 32. However, since the fluidized hydraulic pressure applied to the pile 24 and the bending moment due to this are considerably increased in this way, the piles 24 are increased in size to withstand this, and the installation cost is increased. In other words, if the height of the pile 24 is always kept at about the full water level, the design strength of the weir means can be lowered as much as possible to keep the installation cost low. Therefore, what is necessary is just to determine the height of the pile 24 from the surface of cost effectiveness according to various conditions, such as a river which flows into the dam reservoir 2 used as installation object. Further, by arranging the piles 24 to form the weir means 22, it is possible to easily construct a weir means having high strength and excellent proof stress.
[0033]
Moreover, since sedimentary sediment can be made to flow down by using the high-speed water sweeping force without lowering the water level of the reservoir 2, the function of the reservoir 2 is not hindered. Alternatively, after the dam means 22 is installed, it can be made to function permanently, and sedimentary sediment can be discharged every flood, and sedimentation after the installation can be prevented.
[0034]
In the description of the first embodiment shown above, each dam means 22 is perpendicular to the river core 4b and extends in the direction of the river bank 4c, but the end 22b on the river bank side. May be positioned upstream, and the pair of dam means 22 may be arranged in a square shape that opens upstream (not shown). In this way, more flowing water can be concentrated toward the central part, so that the scavenging force in the central part of the river channel can be further increased.
[0035]
<< Second Embodiment >>
FIG. 4 shows a second embodiment of the present invention, and is a view corresponding to FIG. 3 showing a second embodiment in which a concrete panel is used as the weir means. The schematic diagram of FIG. 1 is common to the second embodiment. In FIG. 4, the same members and portions as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. .
[0036]
In the second embodiment, as shown in FIG. 4, the dam means 22 is a floating type. That is, the pair of dam means 22 provided on both sides of the river channel central part is composed of two concrete panels 42 each suspended and supported by a mooring rope 40 stretched between facing riverbanks 4c, 4c. And in this embodiment shown in figure, each concrete panel 42 is suspended and supported by the mooring rope 40 via the float 44, and is submerged under the water surface. Also, the mooring rope 40 is locked at both ends by concrete blocks 46 embedded and fixed in the rocks of both river banks 4c, and always crosses the water surface at the full water level 30.
[0037]
And even in the case of the floating system of the second embodiment, as in the first embodiment, when a large amount of high-speed water flows into the dam reservoir 2 from the upstream river that increased during flooding. The flowing water flows along the river channel in the reservoir 2 by a pair of multi-stage weir means 22 provided on both sides thereof, and therefore flows downstream through these many weir means 22. That is, it flows into the reservoir 2 from its upstream part to its downstream part, while maintaining a centrally high speed as much as possible along the central part and both side parts of the river channel. The sediment deposited on the former riverbed 4a with the section is carried down to the sediment dischargeable area A by the sand discharge gate 8 of the dam body 6.
[0038]
Here, in the case of the second embodiment, the upper end of the concrete panel 42 is suspended and supported by the mooring rope 40 via the float 44. Therefore, when the flow pressure of running water is applied to the upstream surface, the lower end Is pushed downstream and tilts like a flap. Then, the inclined concrete panel 42 exhibits the function of a guide plate that guides the flowing water downward. For this reason, a part of the flowing water flows under the concrete panel 42 while being increased in speed, and at that time, the sediment of the sedimentary sediment layer 10 below is swept down.
[0039]
Further, when the concrete panel 42 is locked to the mooring rope 40, the concrete panel 42 can be preliminarily floated by the float 44, so that the concrete panel 42 can be attached very easily. .
[0040]
That is, according to the sedimentation sediment flow promotion method as in the first embodiment and the second embodiment, the sediment accumulation region B of the sediment that flows into the dam reservoir 2 and accumulates in the upstream portion in any of them. In addition, a pair of weir means 22 for narrowing the channel cross-section of the river channel of the reservoir 2 and collecting the flowing water on the central part side of the river channel are arranged in advance at predetermined intervals on both sides of the central part of the river channel, and the pair The weir means 22 are arranged in multiple stages along the central part of the river channel so that the flowing water flowing in at a high inflow rate when the river is increased passes through each pair of the weir means 22 arranged in the multiple stages. The speed is increased, and the dam body 6 flows into the vicinity of the sand discharge gate 8 at a high speed, so that the sediment flow in the sediment accumulation region B is discharged from the sand discharge gate 8 of the dam body 6 by the scavenging force of the flowing water. Flow down to the dischargeable area A in the downstream part where discharge is possible. Can, each time the river swollen floods occur, it is possible to promote the falling of the sediment with a new inflow sediment. Also, once installed, it can function permanently, and there is no need to hesitate, so maintenance costs can be reduced as much as possible, and the water level needs to be lowered to obtain a scavenging force. Therefore, there is no possibility that the function as the dam reservoir 2 will be hindered.
[0041]
【The invention's effect】
According to the invention of the weir structure for promoting sedimentation and sediment flow in the dam reservoir according to claim 1, the pair of weirs that collect the flowing water in the central portion of the river channel by narrowing the cross-sectional profile of the river channel of the reservoir in the sediment accumulation region Since the means are arranged at predetermined intervals on both sides of the river channel central part, and the pair of weir means are arranged in multiple stages along the river channel central part, a large amount of high speed can be obtained from the upstream river that increased during flooding. When the flowing water flows into the dam reservoir 2, the flowing water is collected in the central part of the river channel and the flow velocity is reduced as much as possible, from the upstream part to the downstream part, along the central part of the river channel. It is possible to flow while maintaining a high speed as much as possible. For this reason, the scavenging force that causes the sediment deposited on the former riverbed in the center of the river channel to flow down is lost further downstream than the sediment accumulation area where the sedimentary sediment layer is formed (the area where sediment cannot be discharged). The sediment deposited on the former river bed at the center of the river channel can be transported down to the sediment dischargeable area by the sand discharge gate of the dam bank. And the earth and sand carried to the said earth and sand discharge | emission possible area | region can be discharged | emitted and supplied to the river channel of a downstream river from a sand removal gate one by one after flooding etc. as needed.
[0042]
In addition, since sedimentary sediment can be flowed down by using the high-speed water sweeping force without lowering the water level of the reservoir, it will not hinder the function of the reservoir. After installation of the weir means, it can be made to function permanently, and sediment sediment can be discharged every flood, and sediment accumulation can be prevented.
[0043]
According to the invention of the dam structure for promoting sedimentation and flow of sediment in the dam reservoir according to claim 2, the pair of dam means are provided with their riverside ends spaced apart from the riverbank by a predetermined interval. The river can be run at a high flow velocity along both sides of the river channel, and the sediment on both sides of the river channel can be carried down to the area where the sediment can be discharged by the sand discharge gate of the dam dam body, as in the central part. Can do. In addition, the flow velocity in the middle of the river channel is inherently the highest, and is further increased by a pair of weir means. The sediment that has accumulated between both sides of the river channel and the central part flows down to the central part by the flowing water that flows to the central part of the river channel, and the sand discharge gate of the dam body It will be transported to the area where sediment can be discharged.
[0044]
According to the invention of the dam structure for promoting the flow of sedimentation sediment in the dam reservoir according to claim 3, since the riverbank side end of the dam means is arranged to be inclined at a predetermined angle toward the upstream side, a larger amount of running water is placed in the central part It becomes possible to flow intensively toward the river, and the scavenging force in the center of the river channel can be further increased.
[0045]
According to the invention of the weir structure for promoting sedimentation and sediment flow in the dam reservoir according to claim 4, the height of the upper end of the weir means is set in the vicinity of the constantly full water level of the reservoir. Therefore, the design pressure of the weir means can be lowered as much as possible, and the construction cost can be reduced.
[0046]
According to the invention of the dam structure for promoting the flow of sediment in the dam reservoir according to claim 5, the dam means is configured by arranging the piles penetrating the sediment soil layer and having the lower end driven into the river bed. Weir can be easily constructed with strength and strength.
[0047]
According to the invention of the weir structure for promoting the flow of sediment in the dam reservoir according to claim 6, when the flow pressure of the flowing water is applied to the concrete panel, the lower end is pushed in the downstream direction, and the flowing water is inclined downward like a flap. The function of the guiding plate is exhibited, and the flowing water flows under the concrete panel while being increased in speed, and at that time, it is possible to flow down the sediment of the sedimentary sediment layer below. In addition, since the concrete panel is suspended and supported by a mooring rope stretched between facing riverbanks, construction work on the riverbed in the reservoir can be eliminated as much as possible, and the workability is excellent.
[0048]
According to the invention of the dam structure for promoting the flow of sediment in the dam reservoir according to claim 7, since the concrete panel is suspended and supported by the mooring rope through the float, when locking to the mooring rope, It can be performed in a floated state, and the concrete panel can be attached very easily.
[0049]
According to the invention of the method for facilitating sediment sediment flow in the dam reservoir according to claim 8, the channel cross-sectional performance of the river channel of the reservoir is narrowed to the sediment accumulation region that has flowed into the dam reservoir and accumulated upstream. A pair of dam means for collecting running water on the central part side of the river channel are arranged at predetermined intervals on both sides of the central part of the river channel, and the pair of dam means are arranged in multiple stages along the central part of the river channel Therefore, the flowing water that flows in at a high inflow rate when the river is flooded is increased every time it passes through the pair of weir means arranged in multiple stages, and flows into the vicinity of the sand discharge gate of the dam dam body at a high speed. As a result, the sedimentation sediment in the sediment accumulation area can be caused to flow down to the dischargeable area in the downstream part where it can be discharged from the sand discharge gate of the dam dam body by the sweeping force of the flowing water. Along with new inflowing earth and sand It can promote flow down product sediment. In addition, once weir units are installed in multiple stages, they can be made to function permanently, and there is no need for dredging, so that not only maintenance costs can be reduced as much as possible, but also to obtain a scavenging force. Therefore, there is no need to lower the water level, so there is no risk of hindering the function of the dam reservoir.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a plane of a dam reservoir in which the present invention is implemented.
FIG. 2 shows a first embodiment of the present invention in which a pile is used as a weir means, and is a schematic diagram of a longitudinal section along the center of a river channel of a dam reservoir.
3 is a cross-sectional view taken along the line α-α in FIG.
FIG. 4 is a view showing a second embodiment in which a concrete panel is used for the dam means corresponding to FIG. 3;
[Explanation of symbols]
2 Inside the dam reservoir 4 River 4a River bed 4c River shore 6 Dam dam body 8 Drainage gate 10 Deposited sediment layer 20 Flow dam structure 22 Weir means 22a Operation center side edge 22b River shore edge 24 Pile 24a Lower edge 30 Always full Position 40 Mooring rope 42 Concrete panel 44 Float A Sediment discharge area B Sediment accumulation area
