JP6153189B2 - Construction method of low permeability layer structure of waste disposal facility - Google Patents
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本発明は、廃棄物処分施設の低透水層構造の施工方法に関する。 The present invention relates to a method of constructing the low-permeability layer structure of the waste disposal facility.
一般の廃棄物処分場や低レベル放射性廃棄物処分場で廃棄物を埋設処理する場合、廃棄物の下及び上にそれぞれ低透水層を形成し、降雨の処分場への浸透や浸透水（汚染水）の場外への漏出を抑制している。
これらの廃棄物処分施設では、これまで、降水の浸透を防止し、浸透水の場外への漏洩を防止するために、高密度ポリエチレンシートなどの遮水シート、ベントナイト混合土などの低透水性の粘土、毛管力の働きを利用したキャピラリーバリアなどが研究され、これらを用いた遮水工が採られている。
When embedding waste at general waste disposal sites or low-level radioactive waste disposal sites, a low-permeability layer is formed below and above the waste, respectively. The leakage of water) is controlled.
In these waste disposal facilities, in order to prevent the infiltration of precipitation and the leakage of permeated water to the outside of the field, water-permeable sheets such as high density polyethylene sheets and low water permeability such as bentonite mixed soil have been used. Clay, capillary barriers using the action of capillary force, etc. have been studied, and water shielding works using these have been adopted.
近年、この種の低透水層構造ではベントナイトを利用した遮水材が多用されている。このような遮水材としてはジオシンセティッククレイライナー（ＧＣＬ）が周知であり、例えば特許文献１、２などに開示されている。これらの文献１、２に記載のとおり、ＧＣＬはベントナイトを主成分とする遮水材の遮水面となる上下両面に不織布や織布などのジオテキスタイルを積層したもので、上下のジオテキスタイルの間でベントナイトがその吸水性により膨潤して透水性を低減し、高い遮水作用を発揮する。
図５にこのＧＣＬを用いた低透水層構造を例示している。図５に示すように、この低透水層構造は、ＧＣＬ５２と、粘性土又はベントナイト混合土５１、５３の積層構造からなり、現場での施工では、処分場の整地後の基盤上に粘性土又はベントナイト混合土５１、ＧＣＬ５２を順次敷き、このＧＣＬ５２上に粘性土又はベントナイト混合土５３を敷設することによって構築する。このようにしてＧＣＬ５２の高い遮水性能により処分場での降水の浸透、浸透水の場外への漏洩を防止するようになっている。
In recent years, a water-impervious material using bentonite is frequently used in this type of low water-permeable layer structure. As such a water shielding material, a geosynthetic clay liner (GCL) is well known and disclosed in, for example, Patent Documents 1 and 2. As described in these documents 1 and 2, GCL is a laminate of geotextiles such as non-woven fabrics and woven fabrics on the upper and lower surfaces that constitute the water-impervious surface of a water-impervious material mainly composed of bentonite, and bentonite between the upper and lower geotextiles. Swells due to its water absorption, reduces water permeability, and exhibits a high water shielding effect.
FIG. 5 illustrates a low water permeable layer structure using the GCL. As shown in FIG. 5, this low water permeable layer structure is composed of a laminated structure of GCL 52 and viscous soil or bentonite mixed soils 51 and 53. The bentonite mixed soil 51 and the GCL 52 are sequentially spread, and the viscous soil or the bentonite mixed soil 53 is laid on the GCL 52. In this way, the high water shielding performance of GCL 52 prevents the permeation of precipitation at the disposal site and the leakage of permeated water to the outside.
しかしながら、上記従来の廃棄物処分施設の低透水層構造では、ＧＣＬ、及びベントナイト混合土について、次のような問題がある。
（１）ＧＣＬは、ベントナイトを保護するために、既述のとおり、ベントナイトの遮水面側の２面を不織布や織布などのジオテキスタイルで被覆する構造になっているので、ベントナイトは天然の粘土鉱物で長期的かつ安定的にその性能を維持することができるものの、他面で、不織布や織布などのジオテキスタイルが人工材料でその耐久性に限りがある。廃棄物処分施設での廃棄物の処分が長期に亘り、特に低レベル放射性廃棄物処分場にあっては廃棄物の処置が数百年に及ぶことから、廃棄物処分施設の低透水層構造には、長期的な耐久性を考えた場合に、天然の材料のみ又はその組み合わせからなることが望ましい。
（２）ベントナイト混合土はベントナイトそれ自体が高価なので、ベントナイトの混合比率を高くすると、材料費が高額となる。また、ベントナイトは原料土によって均質に混合することが難しく、このため、ベントナイトと原料土との混合に多くの手間と費用が必要になる。したがって、廃棄物処分施設の低透水層構造において、ベントナイトの使用量を増加させると、コスト全体が大きく増大する。
However, in the conventional low water-permeable layer structure of the waste disposal facility, there are the following problems with respect to GCL and bentonite mixed soil.
(1) In order to protect bentonite, GCL has a structure in which two surfaces on the water-impervious surface side of bentonite are covered with a geotextile such as a nonwoven fabric or a woven fabric, as described above. Therefore, bentonite is a natural clay mineral. Although its performance can be maintained stably for a long time, geotextiles such as non-woven fabrics and woven fabrics are artificial materials and have limited durability. Disposal of waste at a waste disposal facility is long-lasting, especially at low-level radioactive waste disposal sites. In view of long-term durability, it is desirable to consist of only natural materials or a combination thereof.
(2) Bentonite mixed soil itself is expensive. Therefore, if the mixing ratio of bentonite is increased, the material cost becomes high. In addition, it is difficult to mix bentonite uniformly with the raw material soil, so that much labor and cost are required for mixing bentonite and raw material soil. Therefore, if the amount of bentonite used is increased in the low water permeable layer structure of the waste disposal facility, the overall cost is greatly increased.
本発明は、このような従来の課題を解決するものであり、この種の廃棄物処分施設の低透水層構造の施工方法において、天然の材料の組み合わせにより長期的に亘り従来の遮水性能と略同等又はそれ以上の遮水性能を発揮すること、材料費を低く抑えて安価に施工することなど、を目的とする。 The present invention solves such a conventional problem, and in the construction method of the low water permeable layer structure of this kind of waste disposal facility, the conventional water shielding performance can be obtained over a long period by combining natural materials. The purpose is to exhibit substantially the same or higher water shielding performance and to keep the material cost low and to construct it at low cost.
上記目的を達成するために、本発明は、
廃棄物を埋設処理する廃棄物処分施設で、廃棄物の上下にそれぞれ、粘性土とベントナイトを用いた各種の遮水材からなる低透水層を形成することにより、前記廃棄物処分施設での水の浸透や水の前記廃棄物処分施設外への漏洩を抑制する廃棄物処分施設の低透水層構造の施工方法において、
前記低透水層の下層を、粘性土又はベントナイト混合土を重機により撒き出し、敷き均し、転圧して締め固めることにより形成し、
前記遮水材にベントナイト粉体を水に溶かしスラリー状にしてなるベントナイト溶液を採用して、前記ベントナイト溶液を前記低透水層の下層の上面に塗布し、この過程で、当該上面の空隙に浸み込ませ、
この上に前記低透水層の上層を、粘性土又はベントナイト混合土を重機により撒き出し、敷き均し、転圧して締め固めることにより形成して、この過程で、前記低透水層の下層の上面の前記ベントナイト溶液を前記低透水層の上層の下面の空隙に浸み込ませ、
前記低透水層の下層と上層の中間で前記ベントナイト粉体をその膨潤作用により膨潤させて、前記低透水層の下層と上層の中間にベントナイト目止め層を積層形成し、前記下層の上面及び前記上層の下面を前記ベントナイト目止め層で目止めする、
ことを要旨とする。
この場合、ベントナイト粉体にベントナイトの吸水膨潤作用を遅延する材料を含有し、前記ベントナイト粉体の吸水膨張作用を制御するようにしてもよい。
In order to achieve the above object, the present invention provides:
In a waste disposal facility that embeds waste, a low water permeable layer made of various water shielding materials using viscous soil and bentonite is formed above and below the waste, respectively. In the construction method of the low permeability layer structure of the waste disposal facility that suppresses the permeation of water and the leakage of water outside the waste disposal facility,
Said lower low permeability layer, the cohesive soil or bentonite mixed soil out spreaders by heavy machinery, spread smoothing, is formed by compacting rolling pressure tightened,
A bentonite solution in which bentonite powder is dissolved in water to form a slurry is adopted as the water shielding material, and the bentonite solution is applied to the upper surface of the lower layer of the low water permeable layer. Embed,
On top of this, the upper layer of the low water permeable layer is formed by rolling out clay clay or bentonite mixed soil with a heavy machine, spreading, rolling, compacting by pressing , and in this process, the upper surface of the lower layer of the low water permeable layer. Soaking the bentonite solution in the lower surface of the lower layer of the low water permeability layer,
The bentonite powder is swollen by the swelling action between the lower layer and the upper layer of the low water permeable layer, and a bentonite sealing layer is laminated between the lower layer and the upper layer of the low water permeable layer. Sealing the lower surface of the upper layer with the bentonite sealing layer,
This is the gist.
In this case, the bentonite powder may contain a material that delays the water absorption swelling action of bentonite, and the water absorption expansion action of the bentonite powder may be controlled.
本発明の廃棄物処分施設の低透水層構造の施工方法によれば、低透水層の下層を、粘性土又はベントナイト混合土を重機により撒き出し、敷き均し、転圧して締め固めることにより形成し、ベントナイト粉体を水に溶かしスラリー状にしてなるベントナイト溶液を低透水層の下層の上面に塗布し、当該上面の空隙に浸み込ませ、この上に低透水層の上層を、粘性土又はベントナイト混合土を重機により撒き出し、敷き均し、転圧して締め固めることにより形成して、この過程で、低透水層の下層の上面のベントナイト溶液を低透水層の上層の下面の空隙に浸み込ませ、低透水層の下層と上層の中間でベントナイト粉体をその膨潤作用により膨潤させて、低透水層の下層と上層の中間にベントナイト目止め層を積層形成し、下層の上面及び上層の下面をベントナイト目止め層で目止めするので、天然の材料の組み合わせにより長期的に亘り従来の遮水性能と略同等又はそれ以上の遮水性能を発揮することができ、しかも材料費を低く抑えて安価に施工することができる、という効果を奏する。 According to the construction method of waste disposal low water layer structure of the facility of the present invention, formed by a lower low permeability layer, the cohesive soil or bentonite mixed soil out spreaders by heavy machinery, laying leveling, compacting rolling pressure to tighten Then, a bentonite solution in which bentonite powder is dissolved in water to form a slurry is applied to the upper surface of the lower layer of the low water permeable layer, soaked in the voids of the upper surface, and the upper layer of the low water permeable layer is placed on the viscous soil. Alternatively, the bentonite mixed soil is squeezed out with a heavy machine, spread, and compacted by rolling and compacting . In this process, the bentonite solution on the upper surface of the lower water permeable layer is placed in the lower surface of the lower water permeable layer. The bentonite powder is swelled by the swelling action between the lower layer and the upper layer of the low water-permeable layer, and a bentonite sealing layer is laminated between the lower layer and the upper layer of the low water-permeable layer. Upper layer Since the bottom surface is sealed with a bentonite sealing layer, a combination of natural materials can provide a water-blocking performance that is almost the same as or better than conventional water-blocking performance over a long period of time, while keeping material costs low. And can be constructed at low cost.
次に、この発明を実施するための形態について図を用いて説明する。
図１に廃棄物処分施設の低透水層構造を示している。図１に示すように、この低透水層構造は、粘性土層（ベントナイト混合土層を含む。）１、３とベントナイトを用いた遮水材２１が積層されて形成される。特に、この構造では、遮水材２１にベントナイト粉体が採用され、ベントナイト粉体２１が粘性土層１、３の遮水側の面の粘性土粒子間の空隙１０、３０に充填されてなり、ベントナイト粉体２１の吸水膨潤作用により、粘性土層１、３の遮水側の面間にベントナイト目止め層２を積層形成する。
この場合、この構造は下層、中間層、上層の３層構造からなる。上下の層はそれぞれ粘性土層１、３で、これらの粘性土層１、３は一般に廃棄物処分場で積層される低透水層相当になっている。中間層はベントナイト粉体２１の層で、ベントナイト粉体２１が含水状態で下層の粘性土層１の遮水側の面である上面と上層の粘性土層３の遮水側の面である下面との間に当該各面の粘性土粒子間の空隙１０、３０に浸み込んだ状態となるように積層される。このようにしてベントナイト粉体２１の膨潤作用により、下層の粘性土層１の上面（遮水面）及び上層の粘性土層３の下面（遮水面）がベントナイト粉体２１からなるベントナイト目止め層２で目止め（遮水面の粘性土粒子間の空隙１０、３０が水密に閉塞）される。
Next, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows a low water permeability structure of a waste disposal facility. As shown in FIG. 1, this low water-permeable layer structure is formed by laminating viscous soil layers (including bentonite mixed soil layers) 1 and 3 and a water shielding material 21 using bentonite. In particular, in this structure, bentonite powder is adopted as the water shielding material 21, and the bentonite powder 21 is filled in the voids 10 and 30 between the viscous soil particles on the water shielding side surfaces of the viscous soil layers 1 and 3. The bentonite sealing layer 2 is laminated between the water-impervious surfaces of the viscous soil layers 1 and 3 by the water absorption swelling action of the bentonite powder 21.
In this case, this structure has a three-layer structure of a lower layer, an intermediate layer, and an upper layer. The upper and lower layers are respectively viscous soil layers 1 and 3, and these viscous soil layers 1 and 3 are generally equivalent to low water-permeable layers laminated at a waste disposal site. The intermediate layer is a bentonite powder 21, and the bentonite powder 21 is in a water-containing state, the upper surface being the water-blocking side surface of the lower viscous soil layer 1 and the lower surface being the water-blocking side surface of the upper viscous soil layer 3. Are laminated so as to be immersed in the voids 10 and 30 between the viscous soil particles on the respective surfaces. In this way, due to the swelling action of the bentonite powder 21, the upper surface (water-blocking surface) of the lower viscous soil layer 1 and the lower surface (water-blocking surface) of the upper viscous soil layer 3 are bentonite sealing layers 2 made of bentonite powder 21. (The voids 10, 30 between the viscous soil particles on the water-impervious surface are closed in a watertight manner).
図２にこの低透水層構造の施工方法を示している。この施工方法では、粘性土層１、３とベントナイト粉体２を次のように積層して形成する。
まず、下層を一般に廃棄物処分場で形成される低透水層相当の粘性土層（ベントナイトをまったく含有していないもの）又はベントナイト混合土層（ベントナイトを低い割合で混合したもの）１として形成する。この場合、粘性土又はベントナイト混合土を油圧ショベルやブルドーザーなどによって撒き出し、敷き均す。そして、この粘性土又はベントナイト混合土全体を転圧ローラーなどを用いて均一に転圧し締め固める。なお、この層の厚みは数ｃｍ〜数十ｃｍ程度を考える。
次に、ベントナイト粉体２１を水に溶かしスラリー状にした液（ベントナイト溶液）を下層の粘性土層又はベントナイト混合土層１の表面に塗布し、この過程で、ベントナイト溶液を粘性土層又はベントナイト混合土層１の表面の空隙１０に浸み込ませていく。
そして、このベントナイト粉体２１の中間層の上に、上層を、下層と同様に、一般に廃棄物処分場で形成される低透水層相当の粘性土層又はベントナイト混合土層３として形成する。ベントナイト混合土層３を形成する際には、転圧ローラーや振動ローラーを用いることによりベントナイト粉体（あるいはベントナイト溶液）をベントナイト混合土層１や３の空隙により効果的に浸透させることができる。
このようにして吸水状態のベントナイト粉体２１を粘性土層又はベントナイト混合土層１、３に充填し、膨潤させて、下層の粘性土層１の上面（遮水面）及び上層の粘性土層３の下面（遮水面）をベントナイト目止め層２で目止めする。
FIG. 2 shows a construction method of this low water permeability layer structure. In this construction method, the viscous soil layers 1 and 3 and the bentonite powder 2 are laminated and formed as follows.
First, the lower layer is formed as a viscous soil layer (not containing any bentonite) or bentonite mixed soil layer (a mixture of bentonite at a low rate) 1 equivalent to a low water permeability layer generally formed at a waste disposal site. . In this case, cohesive soil or bentonite mixed soil is spread out with a hydraulic excavator, bulldozer, etc., and leveled. Then, the entire clay or bentonite mixed soil is uniformly pressed and compacted using a rolling roller or the like. Note that the thickness of this layer is about several centimeters to several tens of centimeters.
Next, a solution obtained by dissolving bentonite powder 21 in water to form a slurry (bentonite solution) is applied to the surface of the lower viscous soil layer or bentonite mixed soil layer 1, and in this process, the bentonite solution is applied to the viscous soil layer or bentonite. It is immersed in the space 10 on the surface of the mixed soil layer 1.
Then, the upper layer is formed on the intermediate layer of the bentonite powder 21 as a viscous soil layer or bentonite mixed soil layer 3 corresponding to a low water permeable layer generally formed in a waste disposal site, similarly to the lower layer. When the bentonite mixed soil layer 3 is formed, bentonite powder (or bentonite solution) can be effectively infiltrated into the voids of the bentonite mixed soil layer 1 or 3 by using a rolling roller or a vibrating roller.
In this way, the bentonite powder 21 in a water-absorbing state is filled into the viscous soil layer or the bentonite mixed soil layers 1 and 3 and is swollen so that the upper surface (water shielding surface) of the lower viscous soil layer 1 and the upper viscous soil layer 3 are filled. The bentonite sealing layer 2 is used to seal the lower surface (water shielding surface).
このような施工により、上下各層の粘性土層又はベントナイト混合土層３、１は下面、上面がそれぞれ粘性土粒子間の空隙３０、１０にベントナイト溶液が浸み込み膨潤することで水密に閉塞され、これによりこれら粘性土層又はベントナイト混合土層３、１の透水係数がさらに低下して、止水性が高められる。 As a result of such construction, the upper and lower viscous soil layers or bentonite mixed soil layers 3 and 1 are water-tightly blocked by the bentonite solution penetrating into the voids 30 and 10 between the viscous soil particles on the lower and upper surfaces, respectively, and swelling. As a result, the water permeability coefficient of these viscous soil layers or bentonite mixed soil layers 3 and 1 is further lowered, and the water stoppage is increased.
本願発明者は、この低透水層構造の止水効果を確認するために、室内透水試験を実施した。図３（右側）に示すように、従来の粘性土層としてクニボンド（ベントナイトの一種）を混合した粘性土を用い、その中間にスラリー状のベントナイトペーストを塗布した供試体と、ベントナイトペーストを塗布していない供試体を作成し、透水試験を行って、透水性の比較を行った。
試験結果を図３（左側）に示す。
この結果から、ベントナイトを塗布していない供試体に比べ、ベントナイトを塗布した供試体は透水係数が１桁以上低下し透水性が低くなっており、止水性能が高められていることが確認された。
The inventor of the present application conducted an indoor water permeability test in order to confirm the water blocking effect of the low water permeability layer structure. As shown in Fig. 3 (right side), a viscous soil mixed with kunibond (a type of bentonite) is used as a conventional viscous soil layer, and a test specimen coated with a slurry-like bentonite paste is applied in between and a bentonite paste is applied. A test specimen was prepared, a water permeability test was performed, and the water permeability was compared.
The test results are shown in FIG. 3 (left side).
From this result, it was confirmed that the specimens coated with bentonite had a permeability coefficient lower by one digit or more and the permeability was lower than that of the specimens not coated with bentonite, and the water stopping performance was enhanced. It was.
以上説明したように、この廃棄物処分施設の低透水層構造及びその施工方法によれば、遮水材にベントナイト粉体２１を採用し、ベントナイト粉体２１の溶液を粘性土層（ベントナイト混合土を含む。）１、３の遮水側の面に塗布して当該面の粘性土粒子間の空隙１０、３０に充填し、ベントナイト溶液の膨潤作用により、粘性土層１、３の遮水側の面を目止めするようにしたので、次のような効果を奏する。
（１）粘性土層１、３の遮水面のベントナイトによる目止めにより、従来の低透水層に比較して透水係数を１桁以上低下させるまでに止水作用を向上させることができる。
（２）粘性土とベントナイトの天然の材料の組み合わせにより、長期的かつ安定的に遮水性能を維持することができる。
（３）所定の低透水性の遮水層が求められる場合でも、トータルとしてベントナイトの使用料を低減して、低コストの低透水層を構築することができる。また、ＧＣＬなど他の工法に比べて、安価に施工することができる。
As described above, according to the low water permeable layer structure and construction method of this waste disposal facility, the bentonite powder 21 is adopted as the water shielding material, and the solution of the bentonite powder 21 is converted into a viscous soil layer (bentonite mixed soil). And applied to the surfaces of the water-impervious side of 1 and 3 to fill the voids 10 and 30 between the viscous soil particles of the surface, and the water-impervious side of the viscous soil layers 1 and 3 by the swelling action of the bentonite solution The following effects can be obtained.
(1) By sealing the water-impervious surfaces of the viscous soil layers 1 and 3 with bentonite, the water-stopping action can be improved before the water-permeability coefficient is reduced by one digit or more as compared with the conventional low-water-permeable layer.
(2) The combination of cohesive soil and bentonite natural materials can maintain the water shielding performance for a long time and stably.
(3) Even when a predetermined low-permeability water-impervious layer is required, a low-cost low-permeability layer can be constructed by reducing the use of bentonite as a whole. Moreover, it can construct cheaply compared with other construction methods, such as GCL.
なお、上記実施の形態では、廃棄物処分施設の低透水層構造及びその施工方法に関して、ベントナイト粉体２１を含水状態で粘性土層（ベントナイト混合土を含む。）１、３の遮水側の面の粘性土粒子間の空隙１０、３０に充填するものとしたが、ベントナイト粉体２１を粘性土層１、３の遮水側の面に充填した状態から吸水するようにしてもよい。
この場合、図４に示すように、まず、下層を一般に廃棄物処分場で形成される低透水層相当の粘性土層又はベントナイト混合土層１として形成した後、この粘性土層又はベントナイト混合土層１の遮水側の面となる上面にベントナイト粉体２１を噴霧若しくは撒布することにより当該面の粘性土粒子間の空隙１０に充填する。続いて、このベントナイト粉体２１の中間層の上に、上層を、下層と同様に、一般に廃棄物処分場で形成される低透水層相当の粘性土層又はベントナイト混合土層３として形成する。この過程で、下層の粘性土層又はベントナイト混合土層１上に載っているベントナイト粉体２１が、振動などにより、上層の粘性土層又はベントナイト混合土層３の遮水側の面となる下面の粘性土粒子間の空隙３０にも充填されながら、上下の粘性土層又はベントナイト混合土層１、３間に介挿される。そして、充填後のベントナイト粉体２１に降雨などにより吸水させるようにすればよい。雨が降ると、雨水は上層の粘性土層又はベントナイト混合土層３から中間層のベントナイト粉体２１に浸透して容易に含水状態となり、ベントナイトの粉末がスラリー状に変化して、上下各層の粘性土層又はベントナイト混合土層３、１の遮水面の粘性土粒子間の空隙３０、１０に浸み込んでいく。このようにしてこのベントナイトの吸水膨潤作用により、上下各層の粘性土層又はベントナイト混合土層３、１の遮水面を目止めする。このようにしても上記実施の形態と同様の効果を得ることができる。
また、ベントナイト粉体２１を含水状態で粘性土層１、３の遮水側の面の粘性土粒子間の空隙１０、３０に充填する場合に、施工上の必要により、ベントナイト粉体２１にベントナイトの吸水膨潤作用を遅延する材料を含有して、ベントナイトの止水効果を遅延させるように制御してもよい。この場合、ベントナイト粉体２１を水に代えて塩水やエタノールなどのベントナイトの膨潤性を抑える液体に溶かして、このスラリー状のベントナイト溶液を粘性土層１、３の空隙１０、３０に浸入させておき、雨水などの淡水が粘性土層１、３のベントナイト溶液に浸透して塩分を洗い流す時点でベントナイト溶液を膨潤させて、止水効果を発揮するようにすればよい。
In addition, in the said embodiment, regarding the low water-permeable layer structure of a waste disposal facility, and its construction method, the bentonite powder 21 is hydrated and a viscous soil layer (including bentonite mixed soil) 1 and 3 on the impermeable side. The voids 10 and 30 between the viscous soil particles on the surface are filled, but the bentonite powder 21 may be absorbed from the state where the water-impervious surface of the viscous soil layers 1 and 3 is filled.
In this case, as shown in FIG. 4, first, the lower layer is formed as a viscous soil layer or bentonite mixed soil layer 1 corresponding to a low water permeability layer generally formed in a waste disposal site, and then the viscous soil layer or bentonite mixed soil is formed. The bentonite powder 21 is sprayed or distributed on the upper surface of the layer 1 on the water-impervious side to fill the voids 10 between the viscous soil particles on the surface. Subsequently, on the intermediate layer of the bentonite powder 21, the upper layer is formed as a viscous soil layer or bentonite mixed soil layer 3 corresponding to a low water permeable layer generally formed in a waste disposal site, similarly to the lower layer. In this process, the bentonite powder 21 placed on the lower viscous soil layer or bentonite mixed soil layer 1 becomes a water-impervious side surface of the upper viscous soil layer or bentonite mixed soil layer 3 due to vibration or the like. It is inserted between the upper and lower viscous soil layers or the bentonite mixed soil layers 1 and 3 while also filling the gaps 30 between the viscous soil particles. Then, the bentonite powder 21 after filling may be absorbed by rain or the like. When it rains, the rainwater penetrates from the upper viscous soil layer or bentonite mixed soil layer 3 to the bentonite powder 21 of the intermediate layer and easily becomes water-containing, and the bentonite powder changes into a slurry state, The viscous soil layer or bentonite mixed soil layers 3 and 1 are immersed in the gaps 30 and 10 between the viscous soil particles on the water-impervious surface. Thus, the water-absorbing swelling action of this bentonite keeps the upper and lower viscous soil layers or the water-impervious surfaces of the bentonite mixed soil layers 3 and 1 in mind. Even if it does in this way, the effect similar to the said embodiment can be acquired.
In addition, when the bentonite powder 21 is filled in the voids 10 and 30 between the viscous soil particles on the water-impervious side of the viscous soil layers 1 and 3 in a water-containing state, the bentonite powder 21 may be added to the bentonite powder 21 depending on construction requirements. It may be controlled so as to delay the water-stopping effect of bentonite by containing a material that delays the water absorption swelling action. In this case, the bentonite powder 21 is dissolved in a liquid that suppresses the swelling property of bentonite such as salt water or ethanol in place of water, and this slurry-like bentonite solution is infiltrated into the voids 10 and 30 of the viscous soil layers 1 and 3. In addition, the bentonite solution may be swollen when fresh water such as rainwater penetrates into the bentonite solution of the viscous soil layers 1 and 3 and the salt content is washed away, thereby exhibiting a water stop effect.
１ 粘性土層（ベントナイト混合土層を含む。）
１０ 空隙
２ ベントナイト目止め層
２１ 遮水材（ベントナイト粉体）
３ 粘性土層（ベントナイト混合土層を含む。）
３０ 空隙
1 Cohesive soil layer (including bentonite mixed soil layer)
10 Void 2 Bentonite sealing layer 21 Water barrier material (bentonite powder)
3 Cohesive soil layer (including bentonite mixed soil layer)
30 gap
Claims (2)
前記低透水層の下層を、粘性土又はベントナイト混合土を重機により撒き出し、敷き均し、転圧して締め固めることにより形成し、
前記遮水材にベントナイト粉体を水に溶かしスラリー状にしてなるベントナイト溶液を採用して、前記ベントナイト溶液を前記低透水層の下層の上面に塗布し、この過程で、当該上面の空隙に浸み込ませ、
この上に前記低透水層の上層を、粘性土又はベントナイト混合土を重機により撒き出し、敷き均し、転圧して締め固めることにより形成して、この過程で、前記低透水層の下層の上面の前記ベントナイト溶液を前記低透水層の上層の下面の空隙に浸み込ませ、
前記低透水層の下層と上層の中間で前記ベントナイト粉体をその膨潤作用により膨潤させて、前記低透水層の下層と上層の中間にベントナイト目止め層を積層形成し、前記下層の上面及び前記上層の下面を前記ベントナイト目止め層で目止めする、
ことを特徴とする廃棄物処分施設の低透水層構造の施工方法。 In a waste disposal facility that embeds waste, a low water permeable layer made of various water shielding materials using viscous soil and bentonite is formed above and below the waste, respectively. In the construction method of the low permeability layer structure of the waste disposal facility that suppresses the permeation of water and the leakage of water outside the waste disposal facility,
Said lower low permeability layer, the cohesive soil or bentonite mixed soil out spreaders by heavy machinery, spread smoothing, is formed by compacting rolling pressure tightened,
A bentonite solution in which bentonite powder is dissolved in water to form a slurry is adopted as the water shielding material, and the bentonite solution is applied to the upper surface of the lower layer of the low water permeable layer. Embed,
On top of this, the upper layer of the low water permeable layer is formed by rolling out clay clay or bentonite mixed soil with a heavy machine, spreading, rolling, compacting by pressing , and in this process, the upper surface of the lower layer of the low water permeable layer. Soaking the bentonite solution in the lower surface of the lower layer of the low water permeability layer,
The bentonite powder is swollen by the swelling action between the lower layer and the upper layer of the low water permeable layer, and a bentonite sealing layer is laminated between the lower layer and the upper layer of the low water permeable layer. Sealing the lower surface of the upper layer with the bentonite sealing layer,
The construction method of the low-permeable layer structure of the waste disposal facility characterized by this.
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