JP4169585B2 - Impermeable structure and impermeable construction method for sea surface disposal site - Google Patents

Description

表２ 材料（間）のせん断強度特性
【表２】

【００６２】
図１１は、PVCシート、長繊維不織布について試験片寸法20cm×20cmにより、通常の引張試験と拘束引張試験を実施した結果である。ここで、拘束引張試験には二軸引張り試験機を用いた。土中に敷設された場合、ネッキングが拘束されると考え、拘束引張試験で得られた弾性係数を用いた。
中間保護層・上部被覆層は海中施工が中心となり、締固めを行わない場合、相対密度がDr=50〜60%程度の緩く堆積した状態になると想定される。スラグの強度変形特性は、初期相対密度Dr=60%の大型供試体（寸法D300mm×H600mm）を用いた圧密排水三軸圧縮試験から求めた。なお、単位体積重量は、気中γ=21kN/m³、水中γ'=14kN/m³とした（（財）沿岸開発技術研究センター・鐵鋼スラグ協会：「港湾工事用製鋼スラグ利用手引書」、平成12年3月）。
【００６３】
（３）安定解析
極限平衡法による安定解析から、検討断面（図１０）における遮水工に必要な層間摩擦角を算定した。極限平衡法であるため、土塊や遮水材に発生する変形・ひずみを無視し、最大摩擦角が滑り面に沿って同時に発揮されると仮定している。
【００６４】
安定解析モデルとして、既往の法面部分を対象とする法面モデル（R.M. Koerner: Designing with Geosynthetics - fourth edition, Prentice Hall, Chapter 5 Designing with Geomenbrane, 1999，J.P.Giroud and J.F.Beech: Stability of soil layers on geosynthetic lining system, Proceedings of Geosynthetics '89, Vol.1, pp.35-46, 1989）と底面部を含めた全体モデル（図１２）の２種について解析した。
【００６５】
図１２において、以下の式が成り立つ。
N_A ＝ W_A cosβ − F
N_P = W_P + E_P sinβ − F’
E_A sinβ = W_A − N_A cosβ − ( N_A tanδ +C_a ) sinβ / F_S
E_P cosβ = ( N_P tanδ + C ) / F_S + A_P
E_A = E_P
【００６６】
ここに、W_A：滑動土塊総重量（kN/m)、W_P：抵抗土塊総重量（kN/m）、N_A：斜面垂直方向の反力(kN/m)、N_P：底面垂直方向の反力(kN/m)、β：法勾配(°)、F：法面にかかる波圧(kN/m)、F’：底面にかかる波圧(kN/m)、P_P：抵抗土塊（水平部）による受動土圧(kN/m)、E_A：抵抗荷重の法面水平方向の力(kN/m)、E_P：滑動荷重の法面水平方向の力(kN/m)、δ：土塊と遮水材の層間摩擦角(°)、F_S：遮水材上の土塊滑りの安全率、C_a：土塊と遮水材の付着力(kN/m)、C：土塊の粘着力(kN/m)、φ：土塊の内部摩擦力(°) である。
【００６７】
全体モデルでは、このように底面部の土塊と受働土圧を考慮している。処分場底面にも遮水工を敷設する必要がある場合には、底面遮水工に沿った滑りがクリティカルになる場合がある。
【００６８】
図１０の検討断面におけるａ）下部遮水工と中間保護層、ｂ）上部遮水工と上部被覆層、ｃ）下部遮水工と遮水工全体の３断面に関して、全体モデルによる安定解析結果を図１３に示す。ここで、層間摩擦角δは、多層ライナー構造である遮水工の全体と覆土（中間保護層と上部被覆層）および下地との間で発揮される摩擦角と見なしている。ただし、外力として遮水工に作用する波圧の影響は、法面、底面からの反力N_A、N_Pを低減させる様に働くと考えているが（図１２）、この安定解析では考慮していない。
【００６９】
不織布−シートおよびスラグ−不織布（水中）の層間摩擦角δ=27°が小さく（表２）、法勾配1：2 (傾斜角θ=26.6°)の遮水工全体の滑りについて支配的と考えられる。検討した３断面についてδ=27°に対する安全率Fsは、それぞれa) Fs=1.8, b)Fs=1.4, c)Fs=2.2 である。これは、覆土と遮水工との摩擦抵抗力、覆土底面の土の摩擦抵抗力あるいは受働土圧が発揮され、側面遮水工の安定が確保されることを示している。一方、不織布−シートの層間摩擦角が小さくFs<1.0になる場合には、遮水工を補強して土塊の滑動力に抵抗するか、遮水材の発揮する引張力に期待して必要安全率を満たす必要がある。
【００７０】
＜側面遮水工のFEM解析＞
（１）解析条件
管理型海面処分場の側面遮水工（図１０）を対象として、２次元平面ひずみ弾塑性FEM解析によって施工過程における遮水工の安定と多層ライナー構造の挙動を検討した。
【００７１】
土質材料は平面要素でモデル化し、法面部分は高さ・幅を約0.5mに分割した。材料モデルはMohr−Coulombの降伏側に従う弾塑性体とした。シート(t=3mm)と不織布(t=5mm)は、引張剛性だけもつ（曲げ剛性と圧縮剛性をもたない）部材として、非線形トラス要素でモデル化した。各材料の物性値は表１、表２に示した通りである。スラグ〜不織布、不織布〜シートの境界に弾塑性モデルの境界要素を配置し、一面せん断試験結果のシミュレーションから得たモデルパラメーターを用いた。なお、今回の検討範囲では、境界要素のメッシュサイズ依存性が無視できるくらい小さいことを事前計算により確認している。
境界条件として、裏込め石と基礎地盤との境界は固定境界、処分場側の側方境界は鉛直ローラーとした。シート・不織布の天端は、遮水工の天端位置に固定した。
【００７２】
＜検討条件＞に述べた施工過程に従った解析手順で段階解析を行った（計61ステップ）。法面部の覆土層は高さ0.5m毎（要素高さ）に平面要素を発生させ、その自重を作用させていく形で、段階的な盛土解析を行った。その間のシート・不織布の敷設段階で、非線形トラス要素を発生させた。
【００７３】
（２）解析結果（基本ケース）
ここでは、覆土の滑動力によって多層構造遮水工の各構成材に発生する引張力に着目し、層間せん断抵抗との相互作用を検討する。
上側不織布、下側不織布、シートのそれぞれに発生する引張力とこれらの合力について、天端から法面に沿った距離に対する分布を図１４に示す。法尻の位置は、下部遮水工ではX=37.5m、上部遮水工ではX=29.7mである。ここでは、ａ）下部遮水工の中間保護層完了時（39ステップ）、ｂ）下部遮水工の覆土▲９▼完了時、ｃ）上部遮水工の覆土▲９▼完了時（以降、最終時と称す）、の３通りについて示した。
【００７４】
全般的な傾向として、引張力の発生する範囲は上部法面だけである。ａ）とｂ）を比較すると、上部被覆層の荷重により下部遮水工の引張力が増加していき、引張力の発生する範囲が法面の約1/2から2/3に拡大している。また、ａ）とｃ）は類似の分布傾向を示すが、上部被覆層の方が中間保護層より法面の覆土厚が大きく、底面の覆土厚が薄いため、ｃ）の引張力が大きくなっている。
【００７５】
上側・下側不織布の引張力は、シートの引張力の10倍程度大きく、全体の大部分の力を負担している。この基本ケースに関しては、上部・下部遮水工とも、また中間保護層完了時と最終時の両者ともこの傾向を示す。これは、層間の相対変位が比較的小さく、不織布の方がシートより弾性係数が高いためと考えられる。また、天端付近では、直接覆土層のせん断力を受ける上側不織布の方が下側不織布よりも大きい傾向を示すが、法面の途中では、ほぼ同様な大きさになっている。
【００７６】
なお、シート・不織布に発生しているひずみは、最大で1％程度であり、弾性範囲内にある。安定解析によるとFs>1.4を満足している断面に関して応力変形解析による照査を行ったが、基本ケースの設定条件に対しては、側面遮水工全体および構成材料の応力ひずみについて安定上問題ないと言える。
【００７７】
（３）パラメータースタディ
不織布〜シートの層間せん断強度と不織布の弾性係数に関してパラメータースタディを実施した。各ケースで得られた下部遮水工（最終時）の引張力分布を図１５〜１８に示す。
【００７８】
ａ）不織布〜シートの層間せん断強度の影響
上側・下側の不織布〜シートの層間せん断強度だけを変化させた場合について解析した。これは不織布〜シート間の摩擦係数を低下させた場合に相当する。上側・下側の不織布〜シートの層間せん断強度を基本ケースの0.5倍にすると、層間摩擦角ではφ=27.0°からφ=14.3°に低下させることに相当し、遮水工全体の安全率はFs=1.1になる（図１３）。直接土塊からせん断力を受ける上側不織布の引張力が基本ケースの2〜5倍程度大きくなり、下側不織布の分担する引張力は相対的に小さくなる。引張力の発生する範囲は法長の90%程度となり、引張力の合力は4倍程度増加する（図１５）。一方、不織布〜シートの層間せん断強度を1.5倍にした場合（φ=37.4°）、すなわち、摩擦係数を上げた場合、大きな変化はないが、基本ケース（図１４ｂ）と比較した場合、基本ケースでは上側不織布の引張力が下側不織布より高くなっているが、層間せん断強度を1.5倍にした場合では上側不織布と下側不織布とで同等の引張力となっている。したがって、シートと下側不織布との摩擦係数を高くすれば下側不織布が引張力を分担する割合を増やしてシートにかかる引張力を減少させることができる。
【００７９】
極端なケースとして、上側・下側の不織布〜シートの層間せん断強度を基本ケースの0.05倍にした場合（φ=1.5°）、引張力の合力が基本ケースの20倍程度に増加し、そのほとんどを上側不織布の引張力が負担している。これは、不織布の引張強さの1/2程度の値である。一方、下側不織布とシートには、基本ケースと同様な引張力しか生じていない（図１７）。
以上のことから、上側不織布とシートとのせん断強度は小さく、下側不織布とシートとのせん断強度は大きくすると、シートにかかる引張力は極力小さくすることができると考えられる。
【００８０】
ｂ）不織布の引張剛性の影響
上側・下側不織布の弾性係数を基本ケースの1/10倍にしたケースの下部遮水工（最終時）の引張力分布を図１８に示す。不織布の引張力は、不織布の剛性に対してほぼ比例関係を示し、1/10倍になった。上側・下側不織布の弾性係数を10倍にした場合も上記と同様な傾向であった。
一方、シートの引張力は不織布の剛性に関係なくほぼ一定値であった。このため、不織布の引張剛性が低い時には相対的に大きな引張力をシートが負担し、反対に不織布の引張剛性が高い時には不織布が負担する引張力が大きくなると考えられる。したがって、シートより不織布の引張剛性が高いほうがよいと考えられる。
【００８１】
実験３．
図１９に示すように、転炉スラグで作成した方面角度１：２、高さ５ｍの盛土斜面８１に、５００g/m²、ヤング率３５０００kN/m²のポリエステル製長繊維不織布３１（保護材）と、３ｍｍの塩ビの遮水シート３２とを、保護マット３１〜遮水シート３２〜保護マット３１の順に積層し敷設した。遮水シート３２は下面をエンボス加工して摩擦係数を高くした。各材料の上端は遮水シート３２、保護マット３１を個別に斜面８１の上の固定部８４に固定し、個別に移動量を測定できるように各固定部にコイル式のエキスパンダー８２を設置した。遮水シート３２、保護マット３１を固定後に法面上端と同じ高さまで山砂８３を積み立てて遮水シート３２、保護マット３１の移動量を確認した。
【００８２】
評価方法として材料間の摩擦係数はＪＩＳ Ｋ７１２５を用いて各３回測定し最大値を採用した。
【００８３】
比較例として上下の保護マットに通常の５００g/m²、ヤング率１５０００kN/m²の短繊維不織布とエンボス加工のない３ｍｍ塩ビ遮水シートを敷設しテストした。その結果を表３に示す。
【００８４】
【表３】

【００８５】
以上に示したように、本発明の実施例によれば、ヤング率が高い保護マット３１を使用し、また遮水シート３２の下面をエンボス加工して下側の保護マット３１との摩擦係数を大きくしたことにより、遮水シートの移動量を大幅に抑えることができ、また上側の保護マットの移動量も大幅に抑えることができた。
【００８６】
【発明の効果】
以上説明したように、請求項１記載の発明によれば、前記多層シートが、遮水シートとこの遮水シートの上下面にそれぞれ設けられた長繊維不織布からなる保護材とから３層以上に形成されているので、遮水シートが受ける負荷を遮水シートの上下面に設けられた保護材に分散してより一層、減ずることができる。
【００８７】
また、土質材料を投入することで第１の多層シートの少なくとも法面部分上に中間保護層及び第２の多層シートの少なくとも法面部分上に上部被覆層を形成するので、中間保護層及び上部被覆層の重量で、潮汐や波浪による楊圧力によって遮水シートが浮き上がるのを防ぐことができる。また、中間保護層及び上部被覆層として土質材料を用いても、中間保護層及び上部被覆層と遮水シートとの間には保護材が配置されるので、土質材料によって遮水シートが傷つくことが無い。
また、前記保護材の引張剛性は前記遮水シートの引張剛性よりも高いので、保護材に載荷された荷重による保護材の変形を極力小さく抑え、遮水シートに与える応力を極力小さく抑えることができる。
さらに、前記遮水シートと下側の前記保護材との摩擦係数は上側の前記保護材との摩擦係数よりも大きいので、上側の保護材から遮水シートに伝達されるせん断応力を減少させ、また遮水シートにかかる引張力を下側の保護材に伝達しやすくなる。
【００８８】
請求項２に記載の発明によれば、請求項１記載の発明と同様の効果が得られることに加え、前記遮水シートを下側の前記保護材と、または下側及び上側の前記保護材と、一部若しくは全面で接合することで、遮水シートと保護材とを同時に敷設することができ、敷設時の手間を省略し工期を短縮することができる。
【００９３】
請求項３に記載の発明によれば、請求項１または２に記載の発明と同様の効果が得られる。
【図面の簡単な説明】
【図１】本発明の実施の形態例を示す管理型廃棄物最終処理場（海面処分場）が造成される埋立予定地である。
【図２】図１の海面処分場の遮水構造を示す断面図である。
【図３】海面処分場１０の法面部分の断面のモデル図である
【図４】実験１の多層せん断実験（５層実験）の概念図である。
【図５】実験１の４層実験の構造図である。
【図６】実験１の４層実験におけるF_i〜u₁と F₂₃(=F_r)〜u₁の関係を示す図である。
【図７】実験２の５層実験におけるF_i〜u₁と F₂₃(=F_r)〜u₁の関係を示す図である。
【図８】実験１の４層構造の実験結果について荷重分担率F_i / F₁〜せん断変位u₁の関係を示す図である。
【図９】実験１の５層構造の実験結果について荷重分担率F_i / F₁〜せん断変位u₁の関係を示す図である。
【図１０】実験２で検討する管理型海面処分場の二重遮水シートから成る表面遮水工に関する検討断面図である。
【図１１】実験２の解析に用いたPVCシート、長繊維不織布についての引張試験結果である。
【図１２】実験２で検討する底面図の土塊と受動土圧を考慮した安定解析のための全体モデルを示す図である。
【図１３】図１２の全体モデルによる安定解析結果を示す図である。
【図１４】実験２において、ａ）下部遮水工の中間保護層完了時、ｂ）中間保護層の覆土完了時、ｃ）最終時の、上側不織布、下側不織布、シートのそれぞれに発生する引張力とこれらの合力について、天端から法面に沿った距離に対する分布を示す図である。
【図１５】実験２において、不織布〜シートのφ＝14.3°における最終時の引張力分布を示す図である。
【図１６】実験２において、不織布〜シートのφ＝37.4°における最終時の引張力分布を示す図である。
【図１７】実験２において、不織布〜シートのφ＝1.5°における最終時の引張力分布を示す図である。
【図１８】実験２において、上側・下側不織布の弾性係数を基本ケースの1/10倍にしたケースの下部遮水工の最終時の引張力分布を示す図である。
【図１９】実験３の装置を示す図である。
【図２０】従来の海面処分場の遮水構造を示す断面図である。
【符号の説明】
１ 埋立地
２ 水域
３ 既設護岸
４ 外周護岸
５ 中仕切護岸
６ 水処理施設
７ 海底面
１１ａ 腹付け土
１１ｂ 下地
１２ 上部被覆層
２０ 遮水構造
３０ 多層シート
３１ 保護マット（保護材）
３２ 遮水シート
４０ 中間保護層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water shielding structure for a sea surface disposal site for waste and a water shielding method for a sea surface disposal site.
[0002]
[Prior art]
As a water-impervious structure of a sea surface disposal site, there is a water-impervious structure using a synthetic resin-based water-impervious material such as rubber or vinyl chloride. When a synthetic resin-based water shielding material is used, it is described in the standards of related government agencies that a synthetic fibrous protective material such as a nonwoven fabric is used in combination. As shown in FIG. 20, a protective mat that doubles a water shielding sheet and lays an intermediate protective layer made of a nonwoven fabric between the two water shielding sheets to protect the water shielding sheet from the ground and soil material up and down. There is a need for a water-blocking structure. The intermediate protective layer is made of a material such as a nonwoven fabric having a sufficient thickness and strength for the purpose of preventing the upper and lower impermeable sheets from being simultaneously damaged by a load such as landfill disposal of waste.
[0003]
At the sea surface disposal site, a double layer of water shielding material is laid, and on top of that, a covering layer of soil material is laid as a counterweight for preventing the floating of the water shielding structure due to tide level and wave force. When constructing a water-impervious structure on the slope of the bottom of the sea surface disposal site, it is usually constructed with a gradient of 1: 1.5 to 1: 3, and the shear force due to the weight of the soil covering is applied to the entire impermeable structure.
[0004]
In patent document 1, a slip stopper is provided on the surface of the protective mat that contacts the water-impervious sheet, and the protective mat laid on the upper surface of the water-impervious sheet on the slope of the disposal site is prevented from sliding down.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-314830
[Problems to be solved by the invention]
By the way, in the method of Patent Document 1, the protective mat does not slide down, but most of the load received by the protective mat is applied to the water shielding sheet based on the load of the upper covering layer and the landfill waste introduced. In the unlikely event that the impervious sheet is damaged, it could be easily repaired on land, but in the sea, the waste and covering soil that had already been thrown in are removed once, the impervious sheet is lifted to the sea, and welded on board. It was necessary to reconstruct the water-impervious structure by submerging it again.
[0007]
In the prior art, non-woven fabric was used as the protective material (protective mat), but the protective material is mainly used to prevent protrusions from piercing the water-impervious sheet or tearing the water-impervious sheet. The influence which the tension | tensile_strength generation | occurrence | production to the lower part by the weight has on the protective material and the synthetic resin water shielding material was not considered. When the final covering of the slope or side impermeable structure is laid, the nearest protective material is pulled down by friction to share a harmful load on the seat. Therefore, in order to prevent stress deformation of the protective material, it is necessary to loosen the legal gradient of the covering soil so as to ensure sufficient stability. Or it was necessary to take measures to prevent the collapse of the slope by reinforcing the protective material.
[0008]
An object of the present invention is to reduce a tensile force applied to a water shielding sheet by covering soil or the like to reduce deformation of the water shielding sheet, and to provide a water shielding structure for a sea surface disposal site that is safe and has good workability.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention described in claim 1 is a water-impervious construction method for a sea surface disposal site, which is composed of a water-impervious sheet and upper and lower nonwoven fabrics having a higher tensile rigidity than the water-impervious sheet . The protective material is joined so that the friction coefficient between the water shielding sheet and the lower protective material is larger than the friction coefficient between the water shielding sheet and the upper protective material . A multilayer sheet is formed, the first multilayer sheet is submerged and laid on at least a slope portion of the sea bottom having a slope of the sea surface disposal site, and then at least the law of the laid first multilayer sheet An intermediate protective layer is formed on the surface portion by introducing a soil material, and then a second multilayer sheet is laid and laid in the sea on at least the slope portion of the intermediate protective layer. on at least Homen portion of the second multilayer sheet, a soil material And forming an upper coating layer by entering.
[0010]
According to the invention of claim 1, since the multilayer sheet is formed in three or more layers from a water shielding sheet and a protective material made of a long-fiber nonwoven fabric provided on each of the upper and lower surfaces of the water shielding sheet, It is possible to further reduce the load received by the water-impervious sheet by dispersing it on the protective material provided on the upper and lower surfaces of the water-impervious sheet.
[0012]
Furthermore, since on at least Homen portion of the first intermediate protective layer and the second at least Homen over portions of the multilayer sheet of the multilayer sheet by pouring the soil material forming the top coat layer, the intermediate protective layer, and an upper The weight of the coating layer can prevent the water-impervious sheet from being lifted by the tide pressure caused by tides and waves. In addition, even if a soil material is used as the intermediate protective layer and the upper covering layer, the protective material is disposed between the intermediate protective layer and the upper covering layer and the water shielding sheet, so that the water shielding sheet is damaged by the soil material. There is no.
Moreover, since the tensile rigidity of the protective material is higher than the tensile rigidity of the water shielding sheet, the deformation of the protective material due to the load loaded on the protective material is suppressed as much as possible, and the stress applied to the water shielding sheet is suppressed as small as possible. it can.
Furthermore, since the friction coefficient between the water shielding sheet and the lower protective material is larger than the friction coefficient with the upper protective material, the shear stress transmitted from the upper protective material to the water shielding sheet is reduced, Moreover, it becomes easy to transmit the tensile force concerning a water-impervious sheet to a lower protective material.
[0013]
The invention according to claim 2 is a water-impervious construction method of the sea surface disposal site according to claim 1, wherein the water-proof sheet is the lower protective material, or the lower and upper protective materials, It is characterized by being partly or entirely joined .
[0014]
According to the second aspect of the present invention, in addition to the same effects as the first aspect of the invention, the water shielding sheet can be used with the lower protective material or the lower and upper protective materials. In addition, the water shielding sheet and the protective material can be laid at the same time by joining a part or the entire surface, so that the labor for laying can be omitted and the construction period can be shortened.
[0020]
The invention described in claim 3 is a water-impervious structure for a sea surface disposal site, and is constructed by the water-impervious construction method for a sea surface disposal site described in claim 1 or 2 .
[0024]
According to the invention described in claim 5 , the same effect as that of the invention described in claim 1 or 2 can be obtained.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be specifically described below, but the present invention is not limited to these.
[0026]
FIG. 1 shows a planned landfill site where a managed waste final disposal site (sea surface disposal site) showing an embodiment of the present invention is established. Adjacent to the reclaimed land 1, a reclaimed land is created by surrounding a part of the sea area 2 with the existing revetment 3 and the outer periphery revetment 4. The interior surrounded by the outer revetment 4 is further divided by a middle partition revetment 5. The section is a sea level disposal site 10 that uses the embodiment of the present invention. A water treatment facility 6 is provided at one corner of the sea surface disposal site 10, and the water held in the sea surface disposal site 10 is purified and discharged to the sea area 2.
[0027]
FIG. 2 is a cross-sectional view showing a water shielding structure of the sea surface disposal site 10 of FIG. On the back surface (slope) of the middle partition revetment 5, a bellows soil 11a and a base 11b covering the sea bottom 7 are installed. The belly soil 11a and the base 11b are made of a soil material. As the soil material, mountain soil, stone, slag or the like can be used.
A water-impervious structure 20 (water-impervious construction) is laid on the bellowing soil 11a and the base 11b, and is covered with the upper covering layer 12 (covering soil). The water-impervious structure 20 includes double multilayer sheets 30 and 30 and an intermediate protective layer 40 sandwiched therebetween.
[0028]
FIG. 3 is a model diagram of a cross section of the slope portion of the sea surface disposal site 10. The multilayer sheet 30, the intermediate protective layer 40, the multilayer sheet 30, and the upper covering layer 12 are superposed on the bellows soil 11 a and the base 11 b in this order. The upper and lower multilayer sheets 30 and 30 are each formed of a synthetic fibrous protective material (protective mat 31) and a synthetic resin water-impervious sheet 32 whose upper and lower surfaces are covered by the protective mats 31 and 31, respectively.
[0029]
The tensile rigidity of the protective mat 31 is preferably larger than the tensile rigidity of the water shielding sheet. Here, the tensile stiffness is a product of Young's modulus and cross-sectional area. The Young's modulus of the protective mat 31 is 20000 kN / m ² or more, preferably 35000 kN / m ² or more, more preferably 45000 kN / m ² or more. Here, the Young's modulus is obtained by a constrained tensile test using a biaxial tensile tester. By increasing the Young's modulus of the protective material 31, the deformation of the protective material 31 due to the load loaded on the protective material 31 can be suppressed as much as possible, and the stress applied to the water shielding sheet 32 can be suppressed as small as possible. The protective mat 31, for example, can be used as the polyester long fiber nonwoven fabric, as long as it satisfies the Young's modulus of the above may be used other synthetic fibers made of long-fiber nonwoven fabric.
[0030]
The water shielding sheet 32 has a Young's modulus of 6000 kN / m ² or more, preferably 6600 kN / m ² or more so that it can withstand the shear stress received from the protective material 31. Similarly, the Young's modulus is obtained by a constrained tensile test using a biaxial tensile tester. As the water shielding sheet 32, a PVC sheet or the like can be used, but other synthetic resin sheets or the like may be used as long as the Young's modulus is satisfied.
[0031]
Here, the friction coefficient between the water shielding sheet 32 and the lower protection mat 31 may be designed to be larger than the friction coefficient between the water shielding sheet 32 and the upper protection mat 31. By reducing the friction coefficient between the water-impervious sheet 32 and the upper protective mat 31, the upper protective material receives much of the sliding force of the upper covering layer 12 applied downward in the slope direction. The transmitted shear stress is minimized. Further, by increasing the coefficient of friction between the water shielding sheet 32 and the lower protective mat 31, the shear stress that the water shielding sheet 32 receives from the upper protective mat 31 is efficiently transmitted to the lower protective mat 31. Moreover, the tensile force borne by the water shielding sheet 32 can be reduced.
[0032]
As a method of reducing the friction coefficient between the water shielding sheet 32 and the upper protective material 31, there is a method of finishing the surface of the water shielding sheet smoothly. Further, there is a method of finishing the surface of the water shielding sheet smoothly and increasing the hardness of the water shielding sheet. Also, a method of smoothing the surface of the upper protective material 31 by flame treatment, a method of reducing the contact area by providing a resin projection on the upper side of the water-impervious sheet 32, or the water-impervious sheet 32 and the upper protective member 31. There is a method such as putting a lubricant in between. As a method of increasing the coefficient of friction between the water-impervious sheet 32 and the lower protective material 31, a method of embossing the lower surface of the water-impervious sheet 32 to make unevenness, or the water-impervious sheet 32 and the lower protective material 31. There is a method such as putting a non-slip in between.
[0033]
A water shield sheet 32 and the protective member 31 is joined with part or the entire surface. In the case of partial joining, point joining or line joining may be performed at many places.
As a bonding method, a heat sealing method may be used in which the surface of the water shielding sheet is melted by heat and the fibers of the protective mat are pressed into the melted water shielding sheet surface. Alternatively, an acrylic adhesive that decomposes by heat and generates tackiness (such as an adhesive made by hirodine) may be used. Other adhesives such as urethane, acrylic, rubber asphalt and epoxy can be used as the adhesive. Alternatively, a mechanical bonding method in which the surface of the water-impervious sheet is fluffed into, for example, a male surface fastener and entangled with the fibers of the protective mat may be used.
[0034]
When the water shielding sheet 32 and the lower protective material 31 are joined, the shear stress that the water shielding sheet 32 receives from the upper protective material 31 is efficiently transmitted from the joined portion to the lower protective material 31. The tensile force borne by the water shielding sheet 32 can be reduced.
Further, the water shielding sheet and the lower protective material 31 can be laid at the same time, and the construction period at the time of laying can be shortened.
[0035]
When the water shielding sheet 32 and the lower protective material 31 are joined, and the water shielding sheet 31 and the upper protective material 32 are joined and integrated, the water shielding sheet 32 and the upper and lower two protective materials are protected. The materials 31 and 31 can all be laid at the same time, and the construction period at the time of laying can be further shortened.
In addition, when a water-soluble adhesive is used for joining the water-impervious sheet 32 and the upper protective material 31, it is removed in water after construction. Even if it is not water-soluble, it tends to come off in water when adhered with an adhesive. Therefore, the shearing force applied to the upper protective material 31 is not easily transmitted to the water shielding sheet 32.
For joining the water-impervious sheet 32 and the lower protective material 31, an adhesive method that does not come off after construction, such as a heat fusion method or a mechanical adhesive method, is applied to the water-impervious sheet 32. The tensile force is efficiently transmitted from the bonded portion to the lower protective material 31, and the tensile force borne by the water shielding sheet 32 can be minimized.
[0036]
An intermediate protective layer 40 is formed between the multilayer sheets 30 and 30. Further, the upper covering layer 12 is formed on the upper multilayer sheet 30. As the intermediate protective layer 40 and the upper covering layer 12, a soil material can be used. In the case where a soil material is used as the intermediate protective layer 40 and the upper covering layer 12, it is possible to obtain an effect of preventing the water-impervious structure 20 from being lifted against the dredging pressure caused by waves and tides.
As the soil material used for the intermediate protective layer 40 and the upper covering layer 12, mountain soil, stone, slag and the like can be suitably used. In particular, when steelmaking slag and copper slag having a large specific gravity are used, the volume of the intermediate protective layer 40 and the upper covering layer 12 required to sink the water-impervious structure 20 into the sea can be reduced, and the limited site The waste disposal capacity in can be increased.
[0037]
Next, a water shielding method for constructing the water shielding structure 20 will be described. First, the belly soil 11a is installed on the back surface of the outer revetment 4, the base 11b is installed so as to cover the sea bottom surface 7, and the lower multilayer sheet 30 is laid thereon . An anti-slip or lubricant may be appropriately sandwiched between the protective mat 31 and the water shielding sheet 32.
[0038]
Since the water shield sheet 32 and the protective mat 31 and upper protective mat 31 on the lower side it is bonded, laying the water shield sheet 32 and the protective mat 31 bonded to its upper and lower surfaces simultaneously.
[0039]
Next, an intermediate protective layer 40 is formed on the lower multilayer sheet 30. By forming the intermediate protective layer 40 made of a soil material, it is possible to prevent the lower multilayer sheet 30 from being lifted by a tidal pressure or a wave pressure caused by waves.
[0040]
After forming the intermediate protective layer 40, the upper multilayer sheet 30 is laid on the intermediate protective layer 40 in the same manner as the lower multilayer sheet 30. Thereafter, similarly to the intermediate protective layer 40, the upper covering layer 12 is formed on the upper multilayer sheet 30. By forming the upper covering layer 12, it is possible to prevent the upper and lower multilayer sheets 30, 30 and the intermediate protective layer 40 from being lifted due to tidal pressures caused by tides and waves.
[0041]
As described above, according to this embodiment, the shear stress to the water shielding sheet 32 received from the sliding force below the slope by the intermediate protective layer 40 and the upper covering layer 12 on the upper protective mat 31 is suppressed as much as possible. Moreover, since the tensile force received by the water shielding sheet 32 is efficiently transmitted to the lower protective mat 31, the load on the water shielding sheet 32 can be reduced as much as possible, and construction of a safe and efficient sea surface disposal site can be performed. It is possible to measure the stability of the slope at the time of use, that is, when the waste is landfilled.
[0042]
【Example】
The experimental results showing the evaluation relating to the present invention are described below.
[0043]
Experiment 1. Load transfer characteristics of geosynthetic multilayer liner subjected to shear force Multi-layer shear device was developed for a partial model of multilayer liner (water-impervious structure) laid on the slope, and geosynthetic multilayer liner subjected to shear force A slope model experiment was conducted.
[0044]
<Experiment method>
(1) A conceptual diagram of the experimental apparatus and the principle multilayer shear test apparatus (in the case of a five-layer structure) is shown in FIG. The shear box 51 (B188mm × L288mm × H150mm) packed with the soil material 61 of the uppermost layer (first layer) corresponds to the soil block on the slope, and the shear force F acting horizontally on this is the sliding force due to the weight of the soil block. Equivalent to. It is a partial structure model for the actual overall structure of the side water-impervious construction, and the non-woven fabric 62 and the sheet 63 are each fixed to the support column with a fastener having a high rigidity and a hinge. It is fixed. The tension generated in each layer is measured with a load cell set at the fixed end. Between the fixed end of each layer and the rear end of the shear box (free length), elongation occurs freely according to the tensile force. Further, although the soil material 61 (lower soil tank 52) is illustrated as the boundary condition of the lowermost layer, elongation restraint (fixed) and freedom of elongation (roller) can also be selected.
[0045]
In this experiment, the width of the sheet / nonwoven fabric specimen was set to 30 cm so that the influence of necking in the sheared portion was less than the loading range (B = 188 mm or 240 mm) of the sheared portion. Shear force was loaded at a displacement speed of 50 mm / min until the displacement of the shear box reached 150 mm. In the experiment using the first layer as the nonwoven fabric, a specimen was used in which the nonwoven fabric was bonded to a dummy plate (B240 mm × L340 mm) fixed to a shear box.
[0046]
(2) Interlayer shear force / shear stress In FIG. 4, the shear force / shear stress acting between the layers will be described. In the case of a five-layer structure, the first layer: soil material 61 (shear box 51), the second layer: nonwoven fabric 62, the third layer: sheet 63, the fourth layer: nonwoven fabric 62, the fifth layer: soil material 61 (lower soil) It is comprised from the tank 52). The basic measurement items of the experiment are the relationship between the shear force F ₁ and the tensile force (i = 2, 3, 4) generated in the i-th layer (sheet 63 / nonwoven fabric 62) and the displacement u ₁ of the shear box 51. is there. F _r is the shear force F ₄₅ of the shear force or the fourth layer and the fifth layers fifth layer exhibits, obtained from the balance of the total force by the following equation.
F _r = F ₁ − F ₂ − F ₃ − F ₄ (1)
[0047]
F _ij is an interlayer shear force acting between the i-th layer and the j-th layer in contact. From the balance of forces in each layer, there is the following relationship, which is calculated from the measured values F _i (i = 1 to 4).
F ₁₂ = F ₁
F ₂₃ = F ₁₂ − F ₂ = F ₁ − F ₂ (2)
F ₃₄ = F ₂₃ − F ₃ = F ₁ − F ₂ − F ₃
F ₄₅ = F ₃₄ − F ₄ = F ₁ − F ₂ − F ₃ − F ₄ = F _r
[0048]
Accordingly, the shear stress τ _ij acting between the i-th layer and the j-th layer in contact with each other can be obtained as follows.
τ _ij = F _ij / A (A: contact area) (3)
[0049]
If the displacements generated at arbitrary points in the i-th layer and the j-th layer are u _i and u _j , the relative displacement u _ij between these two points is as follows.
u _ij = u _i − u _j (4)
[0050]
In a range where the shear force F ₁ acts, the displacement of the seat nonwoven, and elongation [delta] L _i of free length L _i, the sum of elongation of the shearing section portion directly below. Further, the displacement of the soil material in the shear box does not necessarily coincide with the displacement of the shear box. Here, for the sake of simplicity, the displacement of the first layer is the directly measured shear box displacement u ₁ . The displacement u _i of the second to fourth layers is the free length elongation δL _i of each layer.
u _i = δL _i = F _i / (EAs) _i × L _i (i> 1) (5)
Here, (EAs) _i is the tensile rigidity of the free length portion of the i-th layer, E is the Young's modulus, and As is the cross-sectional area.
[0051]
(3) A four-layer structure constituting a multilayer liner was tested against the experimental case and the prototype of the experimental material five-layer structure. The constituent material and the constraint condition of the lowermost layer (elongation constraint / free) were used as experimental parameters.
[0052]
A PVC sheet having a thickness of 3 mm was used as the water shielding sheet, a short fiber nonwoven fabric and a long fiber nonwoven fabric corresponding to a thickness of 5 mm were used as the protective mat, and a loose steelmaking slag having a relative density Dr = 50-60% was used as the soil material. These are materials that have been studied for sea surface disposal sites.
[0053]
The tensile stiffness EAs of the experimental material was determined by applying a shear force to the shear box fixed to the sheet / nonwoven fabric specimen using a dummy plate in the calibration of the test apparatus. It measured from the relationship of the amount of free length elongation. As a result, the sheet had EAs = 4.22 kN, the short fiber nonwoven fabric had EAs = 3.04 kN, and the long fiber nonwoven fabric had EAs = 7.43 kN. These values were used in equation (5).
[0054]
<Experimental results and discussion>
In this report, experimental results and considerations are shown for the case of four-layer and five-layer structures using long-fiber nonwoven fabric.
[0055]
(1) Relationship between shear force / shear stress and displacement / relative displacement a) Four-layer experiment Slag 65 in which the first layer is packed in a shear box, the second layer is a long-fiber nonwoven fabric 62, the third layer is a sheet 63, the fourth layer Is a four-layer structure in which the long-fiber nonwoven fabric 62 is used, the second to third layers are free to stretch, and the fourth layer is stretch-constrained (FIG. 5). FIG. 6 shows the relationship between F _{1 to} u ₁ and F _{ij to} u ₁ obtained for a vertical stress σ _n = 30 (kN / m ² ). It can be seen that F ₃ is small and the tensile force acting on the sheet 63 is extremely small. Further, since the friction coefficients are not changed between the second layer and the third layer, and between the third layer and the fourth layer, the magnitudes of F ₂₃ and F ₃₄ (= F _r ) are very close.
[0056]
b) Five-layer structure In the five-layer structure, the first layer is a slag packed in a shear box, the second to fourth layers are composed of a long-fiber non-woven fabric-sheet-long-fiber non-woven fabric, and are freely stretchable. It is a slag (see FIG. 4). In the 5-layer experiment, two cases of σ _n = 30, 50 (kN / m ² ) were carried out. Here, a case where σ _n = 50 (kN / m ² ) in which a large tensile force is generated is shown. FIG. 7 shows the relationship between F _{1 to} u ₁ and F _{ij to} u ₁ . It can be seen that F ₃ and F ₄ are small, and the tensile force acting on the sheet 63 and the fourth layer long fiber nonwoven fabric 62 is extremely small.
The sizes of F ₂₃ , F ₃₄ , and F ₄₅ (= F _r ) are very close. The displacement at which F ₁ is maximized is u ₁ = 30 mm, which is larger than that of the four-layer structure. In the five-layer experiment shown here, since the vertical stress σ _n is larger, it is considered that the maximum shear force is increased and the elongation of each layer is increased. The point where F ₃ > F ₄ is due to both the difference in rigidity between the third layer and the fourth layer and the difference in shear strength between the third to fourth layers and the fourth to fifth layers. Seem.
[0057]
(2) Load transfer rate The ratio F _i / F ₁ of the tensile force F _i generated in the i-th layer to the shear force F ₁ in the multilayer shear experiment is defined as a load sharing rate. FIG. 8 and FIG. 9 show the relationship between the load sharing ratio F _i / F ₁ to the shear displacement u ₁ for the experimental results of the 4-layer and 5-layer structures, respectively.
In any of the four-layer and five-layer structures, the load transmission rate F ₃ / F ₁ with respect to the sheet is the smallest, and it can be seen that the long-fiber nonwoven fabric of the second layer bears much of the load.
[0058]
Experiment 2. FEM analysis (simulation) on slope slip in surface impervious construction of managed sea surface disposal site
The purpose of this study is to develop a mechanical design method and numerical analysis method based on the results of the model experiment (multi-layer shear experiment, experiment 1) conducted in the stability study on the side water-impervious construction at the managed sea surface disposal site. The cross section considered here is a surface impermeable work with a double impermeable sheet, and the upper impermeable work and the lower impermeable work are each from five layers of “soil material-nonwoven fabric-waterproof sheet-nonwoven fabric-soil material”. (FIG. 2). First, a numerical analysis model was constructed for the shear characteristics between materials obtained from the single shear test, and this was applied to the FEM analysis of the multilayer shear experiment to verify the validity of the numerical analysis method for the multilayer structure. Using this analysis method, we evaluated the overall behavior of the side impervious works at the sea surface disposal site.
[0059]
<Consideration conditions>
(1) Study cross section FIG. 10 shows a study cross section regarding a surface water-impervious work (water-impervious structure 20) composed of a double water-impervious sheet for a managed sea surface disposal site in FIG. The pressure due to the waves that permeate the seawall around the sea surface disposal site and the hydrostatic pressure due to the water level difference generated inside and outside the disposal site due to tidal fluctuations act as a lifting pressure on the impoundment. In order to resist the lifting due to the lifting pressure, the structure is such that both the intermediate protective layer and the upper covering layer of the surface impermeable construction use a soil material to serve as a load. The thicknesses of the intermediate protective layer 40 and the upper covering layer 12 are 3 m and 5 m, respectively, and the total thickness is 8 m. The sea conditions that determined this were: design wave height Ho = 3.1 m, period T = 5.8 sec, water depth h = 14.5 m (MSL from the seabed), and tidal level difference HWL-LWL: 3.6 m.
[0060]
The numbers in the figure of FIG. 10 indicate the construction stage of the side impermeable construction. After installing (1) bellows soil 11a on the back of the revetment and (2) foundation layer (base 11b) with soil material on the bottom, (3) laying a lower water-impervious work (multilayer sheet 30). After the intermediate protective layer 40 is formed on (4) the bottom surface and (5) side surface, (6) an upper water shielding work (multilayer sheet 30) is laid. After the upper covering layer 12 is formed on the bottom surface and the side surface portion of (7), (9) is covered with soil. Here, the upper and lower water-impervious works are each composed of a protective mat (long-fiber nonwoven fabric), a water-impervious sheet (PVC sheet), and a protective mat (long-fiber nonwoven fabric). Consider when to use it.
[0061]
(2) Tables 1 and 2 show physical property values relating to deformation / strength characteristics of the materials used for the material property value analysis.
Table 1 Deformation characteristics of materials [Table 1]

Table 2 Shear strength characteristics of material (between) [Table 2]

[0062]
FIG. 11 shows the results of conducting a normal tensile test and a constrained tensile test on a PVC sheet and a long-fiber nonwoven fabric with a test piece size of 20 cm × 20 cm. Here, a biaxial tensile tester was used for the restraint tensile test. When laid in the soil, the necking was considered to be restrained, and the elastic modulus obtained in the restraint tensile test was used.
The intermediate protective layer and the upper cover layer are mainly underwater construction, and if the compaction is not performed, it is assumed that the relative density will be loosely deposited with Dr = 50-60%. The strength deformation characteristics of the slag were obtained from a consolidated drainage triaxial compression test using a large specimen (dimension D300mm × H600mm) with an initial relative density Dr = 60%. In addition, unit volume weight, airborne γ = 21kN / m ^3, water γ '= 14kN / m ³ and the ((goods) Coastal Development Research Center, KS Summit Steel Slag Association: "harbor construction work for steelmaking slag use handbook ", March 2000).
[0063]
(3) Stability analysis From the stability analysis by the ultimate equilibrium method, the interlaminar friction angle required for the impervious work in the cross section (Fig. 10) was calculated. Because it is an extreme equilibrium method, it is assumed that the maximum friction angle is exhibited along the sliding surface at the same time, ignoring deformations and strains that occur in soil blocks and water shielding materials.
[0064]
As a stability analysis model, the existing slope model (RM Koerner: Designing with Geosynthetics-fourth edition, Prentice Hall, Chapter 5 Designing with Geomenbrane, 1999, JPGiroud and JFBeech: Stability of soil layers on geosynthetic lining system, Proceedings of Geosynthetics '89, Vol.1, pp.35-46, 1989) and the whole model (Fig. 12) including the bottom part was analyzed.
[0065]
In FIG. 12, the following expression is established.
N _A = W _A cosβ − F
N _P = W _P + E _P sinβ − F '
_{E A sinβ = W A - N} A cosβ - (N A tanδ + C a) sinβ / F S
E _P cosβ = (N _P tanδ + C) / F _S + A _P
E _A = E _P
[0066]
Where, W _A : Total weight of sliding soil block (kN / m), W _P : Total weight of resistive soil block (kN / m), N _A : Reaction force in vertical direction of slope (kN / m), N _P : Vertical direction of bottom surface Reaction force (kN / m), β: normal gradient (°), F: wave pressure on the slope (kN / m), F ': wave pressure on the bottom (kN / m), P _P : resistance mass Passive earth pressure (kN / m) by (horizontal part), E _A : Force in the horizontal direction of resistance load (kN / m), E _P : Force in the horizontal direction of sliding load (kN / m), δ: Interlaminar friction angle between soil mass and water shielding material (°), F _S : Safety factor of soil mass sliding on water shielding material, C _a : Adhesive force between soil mass and water shielding material (kN / m), C: Mass of soil mass Adhesive strength (kN / m), φ: Internal frictional force (°) of the soil mass.
[0067]
In the whole model, the bottom mass and passive earth pressure are taken into consideration. If it is necessary to lay a water barrier on the bottom of the disposal site, slipping along the bottom water barrier may be critical.
[0068]
Results of stability analysis using the overall model for the three sections of a) lower impervious work and intermediate protective layer, b) upper impervious work and upper cover layer, and c) lower impermeable work and whole impermeable work Is shown in FIG. Here, the interlayer friction angle δ is regarded as a friction angle exerted between the entire water-impervious structure having a multilayer liner structure, the cover soil (intermediate protective layer and upper cover layer), and the base. However, the influence of the wave pressure acting on the impervious work as an external force is thought to work to reduce the reaction forces N _A and N _P from the slope and bottom (Fig. 12). Not done.
[0069]
Non-woven fabric-sheet and slag-non-woven fabric (underwater) interlayer friction angle δ = 27 ° is small (Table 2), and it is considered to be dominant for slippage of the whole impervious construction with normal gradient 1: 2 (tilt angle θ = 26.6 °) It is done. The safety factors Fs with respect to δ = 27 ° for the three cross sections studied are a) Fs = 1.8, b) Fs = 1.4, and c) Fs = 2.2, respectively. This shows that the frictional resistance between the soil covering and the impervious work, the frictional resistance of the soil on the bottom of the covered soil, or the passive earth pressure is exhibited, and the stability of the side impervious work is ensured. On the other hand, when the interlayer friction angle between the nonwoven fabric and the sheet is small and Fs <1.0, it is necessary to reinforce the water shielding work to resist the sliding force of the soil mass or to expect the tensile force exerted by the water shielding material. It is necessary to satisfy the rate.
[0070]
<FEM analysis of side impermeable construction>
(1) Analytical condition management-type sea surface disposal site side water-impervious construction (Fig. 10) The stability of the impervious work and the behavior of the multilayer liner structure in the construction process were examined by two-dimensional plane strain elastic-plastic FEM analysis.
[0071]
The soil material was modeled with plane elements, and the slope was divided into heights and widths of about 0.5 m. The material model is an elasto-plastic material according to the yield side of Mohr-Coulomb. The sheet (t = 3mm) and non-woven fabric (t = 5mm) were modeled with nonlinear truss elements as members having only tensile stiffness (no bending stiffness and compression stiffness). The physical properties of each material are as shown in Tables 1 and 2. Boundary elements of an elastoplastic model were placed at the boundary between slag and nonwoven fabric and nonwoven fabric to sheet, and model parameters obtained from simulation of one-side shear test results were used. In addition, in the examination range this time, it has been confirmed by preliminary calculation that the mesh size dependence of the boundary element is negligibly small.
As boundary conditions, the boundary between the backfill stone and the foundation ground was a fixed boundary, and the lateral boundary on the disposal site side was a vertical roller. The top edge of the sheet / nonwoven fabric was fixed at the top edge position of the impermeable work.
[0072]
A step analysis was performed using the analysis procedure according to the construction process described in <Considerations> (total 61 steps). The slope covering layer in the slope section was subjected to step-by-step embankment analysis in which a flat element was generated every 0.5 m (element height) and its own weight was applied. In the meantime, a non-linear truss element was generated at the stage of laying the sheet and nonwoven fabric.
[0073]
(2) Analysis results (basic case)
Here, the interaction with the interlaminar shear resistance is examined by paying attention to the tensile force generated in each component of the multi-layer structure impermeable construction by the sliding force of the cover soil.
FIG. 14 shows the distribution of the tensile force generated in each of the upper nonwoven fabric, the lower nonwoven fabric, and the sheet and the resultant force with respect to the distance along the slope from the top edge. The position of Hoshijiri is X = 37.5m for the lower impervious work and X = 29.7m for the upper impervious work. Here, a) When the intermediate protective layer of the lower impermeable work is completed (39 steps), b) Covering of the lower impermeable work ▲ 9 ▼, c) Covering of the upper impermeable work ▲ 9 ▼ This is shown in the following three cases.
[0074]
As a general tendency, the range where the tensile force is generated is only the upper slope. Comparing a) and b), the tensile force of the lower water-impervious construction increases due to the load of the upper coating layer, and the range where the tensile force is generated is expanded from about 1/2 to 2/3 of the slope. Yes. In addition, a) and c) show similar distribution trends, but the upper covering layer has a larger slope covering thickness than the intermediate protective layer and a thinner bottom covering thickness, so that the tensile force of c) becomes larger. ing.
[0075]
The tensile force of the upper and lower nonwoven fabrics is about 10 times larger than the tensile force of the sheet, and bears most of the overall force. With regard to this basic case, both upper and lower impermeable works, and both when the intermediate protective layer is completed and when it is final, show this tendency. This is presumably because the relative displacement between the layers is relatively small, and the nonwoven fabric has a higher elastic modulus than the sheet. In the vicinity of the top edge, the upper nonwoven fabric that is directly subjected to the shearing force of the soil covering layer tends to be larger than the lower nonwoven fabric, but is approximately the same size in the middle of the slope.
[0076]
The strain generated in the sheet / nonwoven fabric is about 1% at the maximum and is within the elastic range. According to the stability analysis, the cross section satisfying Fs> 1.4 was verified by the stress deformation analysis. It can be said.
[0077]
(3) Parameter Study A parameter study was conducted on the interlaminar shear strength of the nonwoven fabric to sheet and the elastic modulus of the nonwoven fabric. 15 to 18 show the tensile force distribution of the lower water-impervious work (final time) obtained in each case.
[0078]
a) Influence of interlaminar shear strength of nonwoven fabric to sheet The case where only the interlaminar shear strength of the upper and lower nonwoven fabric to sheet was changed was analyzed. This corresponds to a case where the friction coefficient between the nonwoven fabric and the sheet is lowered. If the interlaminar shear strength of the upper and lower nonwoven fabrics to sheets is 0.5 times that of the base case, the interlaminar friction angle is equivalent to a decrease from φ = 27.0 ° to φ = 14.3 °. Fs = 1.1 (FIG. 13). The tensile force of the upper nonwoven fabric that directly receives the shear force from the soil mass is about 2 to 5 times larger than that of the basic case, and the tensile force shared by the lower nonwoven fabric is relatively small. The range where the tensile force is generated is about 90% of the length, and the resultant force of the tensile force is increased about 4 times (Fig. 15). On the other hand, when the interlayer shear strength of the nonwoven fabric to the sheet is increased 1.5 times (φ = 37.4 °), that is, when the friction coefficient is increased, there is no significant change, but when compared with the basic case (FIG. 14b), the basic case The upper nonwoven fabric has a higher tensile force than the lower nonwoven fabric, but when the interlaminar shear strength is 1.5 times, the upper nonwoven fabric and the lower nonwoven fabric have the same tensile force. Therefore, if the coefficient of friction between the sheet and the lower nonwoven fabric is increased, the ratio of the lower nonwoven fabric sharing the tensile force can be increased to reduce the tensile force applied to the sheet.
[0079]
As an extreme case, when the interlaminar shear strength of the upper and lower nonwoven fabrics to sheets is 0.05 times that of the basic case (φ = 1.5 °), the resultant tensile force increases to about 20 times that of the basic case, most of which Is borne by the tensile force of the upper nonwoven fabric. This is about half the tensile strength of the nonwoven fabric. On the other hand, only the tensile force similar to that of the basic case is generated in the lower nonwoven fabric and the sheet (FIG. 17).
From the above, it is considered that when the shear strength between the upper nonwoven fabric and the sheet is small and the shear strength between the lower nonwoven fabric and the sheet is increased, the tensile force applied to the sheet can be minimized.
[0080]
b) Influence of Tensile Rigidity of Nonwoven Fabric FIG. 18 shows the tensile force distribution of the lower water-impervious construction (final) of the case where the elastic modulus of the upper and lower nonwoven fabrics is 1/10 times that of the basic case. The tensile force of the non-woven fabric was almost proportional to the stiffness of the non-woven fabric and was 1/10 times. The same tendency was observed when the elastic modulus of the upper and lower nonwoven fabrics was increased 10 times.
On the other hand, the tensile force of the sheet was almost constant regardless of the rigidity of the nonwoven fabric. For this reason, it is thought that when the tensile stiffness of the nonwoven fabric is low, the sheet bears a relatively large tensile force, and conversely, when the tensile stiffness of the nonwoven fabric is high, the tensile force that the nonwoven fabric bears increases. Therefore, it is considered that the nonwoven fabric should have higher tensile rigidity than the sheet.
[0081]
Experiment 3.
As shown in FIG. 19, a polyester long fiber non-woven fabric 31 (protective material) of 500 g / m ² and Young's modulus of 35000 kN / m ² is applied to an embankment slope 81 having a direction angle of 1: 2 and a height of 5 m made of converter slag. And a 3 mm PVC water shielding sheet 32 were laminated and laid in the order of the protective mat 31 to the water shielding sheet 32 to the protective mat 31. The water shielding sheet 32 was embossed on the lower surface to increase the friction coefficient. At the upper end of each material, the water shielding sheet 32 and the protective mat 31 were individually fixed to a fixing portion 84 on the slope 81, and a coil type expander 82 was installed in each fixing portion so that the amount of movement could be individually measured. After fixing the water-impervious sheet 32 and the protective mat 31, pile sand 83 was piled up to the same height as the upper end of the slope, and the amount of movement of the water-impervious sheet 32 and the protective mat 31 was confirmed.
[0082]
As an evaluation method, the friction coefficient between materials was measured three times using JIS K7125, and the maximum value was adopted.
[0083]
As a comparative example, a normal short fiber nonwoven fabric of 500 g / m ² and a Young's modulus of 15000 kN / m ^{2 and} a 3 mm PVC waterproof sheet without embossing were laid on the upper and lower protective mats and tested. The results are shown in Table 3.
[0084]
[Table 3]

[0085]
As described above, according to the embodiment of the present invention, the protective mat 31 having a high Young's modulus is used, and the lower surface of the water shielding sheet 32 is embossed so that the friction coefficient with the lower protective mat 31 is increased. By increasing the size, the amount of movement of the water-impervious sheet could be greatly reduced, and the amount of movement of the upper protective mat could be greatly reduced.
[0086]
【The invention's effect】
As described above, according to the invention of claim 1, the multilayer sheet is composed of three layers or more from the water shielding sheet and the protective material made of the long-fiber nonwoven fabric provided on the upper and lower surfaces of the water shielding sheet, respectively. Since it is formed, it is possible to further reduce the load received by the water shielding sheet by dispersing it on the protective material provided on the upper and lower surfaces of the water shielding sheet.
[0087]
Furthermore, since on at least Homen portion of the first intermediate protective layer and the second at least Homen over portions of the multilayer sheet of the multilayer sheet by pouring the soil material forming the top coat layer, the intermediate protective layer, and an upper The weight of the coating layer can prevent the water-impervious sheet from being lifted by the tide pressure caused by tides and waves. In addition, even if a soil material is used as the intermediate protective layer and the upper covering layer, the protective material is disposed between the intermediate protective layer and the upper covering layer and the water shielding sheet, so that the water shielding sheet is damaged by the soil material. There is no.
Moreover, since the tensile rigidity of the protective material is higher than the tensile rigidity of the water shielding sheet, the deformation of the protective material due to the load loaded on the protective material is suppressed as much as possible, and the stress applied to the water shielding sheet is suppressed as small as possible. it can.
Furthermore, since the friction coefficient between the water shielding sheet and the lower protective material is larger than the friction coefficient with the upper protective material, the shear stress transmitted from the upper protective material to the water shielding sheet is reduced, Moreover, it becomes easy to transmit the tensile force concerning a water-impervious sheet to a lower protective material.
[0088]
According to the second aspect of the present invention, in addition to the same effects as the first aspect of the invention, the water shielding sheet can be used with the lower protective material or the lower and upper protective materials. Further, by joining partly or entirely, the water shielding sheet and the protective material can be laid at the same time, and the labor for laying can be omitted and the construction period can be shortened.
[0093]
According to the invention described in claim 3 , the same effect as that of the invention described in claim 1 or 2 can be obtained.
[Brief description of the drawings]
FIG. 1 is a planned landfill site where a managed waste final disposal site (sea surface disposal site) showing an embodiment of the present invention is established.
FIG. 2 is a cross-sectional view showing a water shielding structure of the sea surface disposal site in FIG. 1;
3 is a model diagram of a cross section of a slope portion of the sea surface disposal site 10. FIG. 4 is a conceptual diagram of a multi-layer shear experiment (five-layer experiment) of Experiment 1.
5 is a structural diagram of a four-layer experiment of Experiment 1. FIG.
6 is a diagram showing the relationship between F _{i to} u ₁ and F ₂₃ (= F _r ) to u ₁ in the four-layer experiment of Experiment 1. FIG.
7 is a diagram showing the relationship between F _{i to} u ₁ and F ₂₃ (= F _r ) to u ₁ in the five-layer experiment of Experiment 2. FIG.
8 is a diagram showing the relationship between load sharing ratio F _i / F ₁ to shear displacement u ₁ for the experimental results of the four-layer structure of Experiment _1. FIG.
9 is a diagram showing the relationship between load sharing ratio F _i / F ₁ to shear displacement u ₁ with respect to the experimental results of the five-layer structure of Experiment _1. FIG.
FIG. 10 is a cross-sectional view for examining a surface impermeable construction composed of a double impermeable sheet for a managed sea surface disposal site studied in Experiment 2;
FIG. 11 shows the tensile test results for the PVC sheet and the long-fiber nonwoven fabric used in the analysis of Experiment 2.
FIG. 12 is a diagram showing an overall model for stability analysis in consideration of a soil block and a passive earth pressure in a bottom view examined in Experiment 2.
13 is a diagram showing a stability analysis result based on the overall model of FIG. 12. FIG.
FIGS. 14A and 14B are generated in the upper nonwoven fabric, the lower nonwoven fabric, and the sheet in Experiment 2, respectively, a) when the intermediate protective layer of the lower impermeable construction is completed, b) when the soil covering of the intermediate protective layer is completed, and c) at the final time. It is a figure which shows distribution with respect to the distance along a slope from a ceiling about tensile force and these resultant force.
FIG. 15 is a diagram illustrating a final tensile force distribution of a nonwoven fabric to a sheet at φ = 14.3 ° in Experiment 2.
FIG. 16 is a diagram illustrating a final tensile force distribution of a nonwoven fabric to a sheet at φ = 37.4 ° in Experiment 2.
FIG. 17 is a diagram illustrating a final tensile force distribution of a nonwoven fabric to a sheet at φ = 1.5 ° in Experiment 2.
FIG. 18 is a diagram illustrating a final tensile force distribution of a lower water-impervious work in a case where the elastic modulus of the upper and lower nonwoven fabrics is 1/10 times that of a basic case in Experiment 2.
FIG. 19 is a diagram showing an apparatus of Experiment 3.
FIG. 20 is a cross-sectional view showing a water shielding structure of a conventional sea surface disposal site.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Landfill 2 Water area 3 Existing revetment 4 Perimeter revetment 5 Middle partition revetment 6 Water treatment facility 7 Sea bottom 11a Lined soil 11b Base 12 Upper covering layer 20 Water shielding structure 30 Multilayer sheet 31 Protective mat (protective material)
32 Water shielding sheet 40 Intermediate protective layer

Claims (3)

A water impervious construction method at a sea surface disposal site,
A water-impervious sheet, and upper and lower protective materials made of a long-fiber nonwoven fabric having higher tensile rigidity than the water-impervious sheet, and a coefficient of friction between the water-impervious sheet and the lower protective material, The first and second multilayer sheets are joined to be larger than the coefficient of friction with the protective material ,
Laying the first multilayer sheet in the sea on at least the slope part of the sea floor with the slope of the sea surface disposal site,
Next, an intermediate protective layer is formed by introducing a soil material on at least the slope portion of the laid first multilayer sheet,
Next, lay down the second multilayer sheet in the sea on at least the slope of this intermediate protective layer,
Then, a water-impervious construction method for a sea surface disposal site, wherein an upper covering layer is formed by introducing a soil material on at least a slope portion of the laid second multilayer sheet.   2. The water-impervious construction method for a sea surface disposal site according to claim 1, wherein the water-impervious sheet is joined to the lower protective material or to the lower and upper protective materials partially or entirely. A water-blocking structure for a sea surface disposal site, which is constructed by the water-blocking method for a sea surface disposal site according to claim 1 or 2 .

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