JP4872275B2 - Covering sand at the bottom of the water - Google Patents

Covering sand at the bottom of the water Download PDF

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JP4872275B2
JP4872275B2 JP2005254174A JP2005254174A JP4872275B2 JP 4872275 B2 JP4872275 B2 JP 4872275B2 JP 2005254174 A JP2005254174 A JP 2005254174A JP 2005254174 A JP2005254174 A JP 2005254174A JP 4872275 B2 JP4872275 B2 JP 4872275B2
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blast furnace
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slag
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康人 宮田
達人 高橋
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JFE Steel Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
    • Y02A40/80—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in fisheries management
    • Y02A40/81—Aquaculture, e.g. of fish
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

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Description

本発明は、生物の生育・生息に好適な覆砂構造とこれを得るための覆砂工法に関するものである。   The present invention relates to a sand covering structure suitable for the growth and inhabiting of living organisms and a sand covering method for obtaining the structure.

近年、港湾その他の沿岸海域において、底泥（ヘドロ）の堆積による底質・水質の汚染が問題となっている。なかでも、底質・水質の汚染により直接又は間接に引き起こされる青潮や赤潮の発生、海藻や水中生物の生育・生息環境の衰退、消失等の防止対策が大きな課題となっており、これを解決できる海洋環境改善技術の開発が望まれている。
ヘドロ化した底質を改善するために、水底を天然砂（海砂、山砂）を用いて覆砂する等の対策が採られることがある。また、天然砂で覆砂する場合には、同時に砂質水底に生息する魚介類等の生息場の造成も兼ねて行うことがあり、また、築磯効果を期待して天然砂に代えて天然石を用いる場合もある。 In recent years, sediment and water pollution due to sedimentation of sludge has become a problem in harbors and other coastal waters. In particular, measures to prevent the occurrence of blue tides and red tides caused directly or indirectly by sediment and water pollution, and the growth and loss of habitats of seaweeds and aquatic organisms have become major issues. Development of marine environment improvement technology that can be solved is desired.
In order to improve sludge bottom sediment, measures such as covering the water bottom with natural sand (sea sand, mountain sand) may be taken. In addition, when sand is covered with natural sand, it may also be used to create a habitat for seafood and the like that inhabit sandy water bottoms. May be used.

一方、特許文献１，２には、天然砂に代わる覆砂材として高炉水砕スラグを用いることが示されている。高炉水砕スラグは鉄鋼製造プロセスで大量に発生するものであるため、安価に且つ大量に入手することができる材料であり、しかも、覆砂材として底質・水質の化学的浄化効果が期待できる。
特開２００４−２８５５６０号公報 特開２００４−２４２０４号公報 On the other hand, Patent Documents 1 and 2 show that blast furnace granulated slag is used as a sand covering material instead of natural sand. Since granulated blast furnace slag is generated in large quantities in the steel manufacturing process, it is a material that can be obtained in large quantities at low cost, and it can be expected to have a chemical purification effect on the bottom and water quality as sand-capping material. .
JP 2004-285560 A Japanese Patent Laid-Open No. 2004-24204

しかし、底質を単に天然砂や高炉水砕スラグなどで覆砂しただけでは、底質で発生した硫化水素や底質に含まれる栄養塩が、覆砂層（覆砂材の粒子間）を通じて水中に溶出してしまうという問題がある。
また、水底に堆積する底泥の多くは、水中に浮遊する無機物・有機物が水底に徐々に沈降・堆積し、次第に圧密化されることにより生成する。このため底泥の堆積量が比較的多い水底では、底泥上層に浮泥層（未だ圧密化されず、密度が小さい底泥の層）が比較的厚く存在している。 However, if the sediment is simply covered with natural sand or granulated blast furnace slag, the hydrogen sulfide generated in the sediment and the nutrients contained in the sediment are submerged through the sand-covering layer (between the particles of the sand-covering material). There is a problem of elution.
Moreover, most of the bottom mud that accumulates on the bottom of the water is generated by gradually consolidating and depositing inorganic and organic substances floating in the water and gradually consolidating them. For this reason, in a water bottom where the amount of sediment deposited is relatively large, a floating mud layer (a layer of bottom mud that has not yet been consolidated and has a low density) exists in the upper layer of the bottom mud.

水底の覆砂を行う場合、通常は運搬船上から覆砂材を水底に投入することになるが、上記のように底泥上層に比較的厚い浮泥層が存在する場合、(1)投入された覆砂材が浮泥層を突き抜け、底泥内部に沈み込んでしまう、或いは、(2) 覆砂材の投入により浮泥が水中に巻き上げられ、この浮泥が再び沈降して覆砂材を覆ってしまう、という原因によって覆砂材が底泥内に没入し、適切な覆砂層が形成できなくなるという問題がある。また、水中に巻き上げられた浮泥により水が汚濁されるという問題もある。また、天然砂や高炉水砕スラグの覆砂層は、ある程度の期間が経過すると層全体や局部的な沈み込みが生じ、覆砂層としての機能が低下しやすいという問題もある。   When covering the bottom of the water, the sand-capping material is usually thrown into the bottom of the carrier.However, if there is a relatively thick floating mud layer in the bottom mud layer as described above, (1) The sand covering material penetrates through the floating mud layer and sinks into the bottom mud, or (2) The floating mud is rolled up into the water by the introduction of the sand covering material, and the floating mud sinks again to cover the sand covering material. There is a problem that the sand-capping material is immersed in the bottom mud due to the reason that it covers the surface, and an appropriate sand-capping layer cannot be formed. There is also a problem that water is polluted by floating mud rolled up in water. In addition, the sand-covering layer of natural sand or granulated blast furnace slag has a problem that the entire layer or local subsidence occurs after a certain period of time, and the function as the sand-covering layer is likely to deteriorate.

したがって本発明の目的は、以上のような従来技術の課題を解決し、底質からの硫化水素や栄養塩の溶出を適切に防止することができ且つ沈み込みが生じにくい安定した覆砂構造を提供することにある。
また、本発明の他の目的は、底泥が堆積した水底などにおいても、そのような覆砂構造を適切に形成することができる覆砂方法を提供することにある。 Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, and to prevent the precipitation of hydrogen sulfide and nutrients from the sediment, and to provide a stable sand-covering structure that is unlikely to cause subsidence. It is to provide.
Another object of the present invention is to provide a sand covering method capable of appropriately forming such a sand covering structure even in the bottom of water where sediment is accumulated.

高炉水砕スラグは潜在水硬性（アルカリ刺激等により水和反応を起こし、硬化する性質）を有することが知られているが、本発明者らは、高炉水砕スラグを破砕処理又は／及び分級して得られた細粒高炉水砕スラグは、元の高炉水砕スラグに較べて潜在水硬性が格段に高くなることを確認し、このような高い潜在水硬性を有する細粒高炉水砕スラグを覆砂材の一部として利用するという着想の下に、上記課題を解決できる覆砂構造及び覆砂方法について検討を行った。その結果、下層側に細粒高炉水砕スラグからなる下部覆砂層を有し、その上に他の覆砂材からなる上部覆砂層を有する覆砂構造とした場合には、下部覆砂層が固結することによって底質からの硫化水素や栄養塩の溶出を遮断する蓋の役目をするため、生物の生育・生息に適した覆砂層を形成でき、しかも覆砂層の沈み込みも生じにくいことが判った。   Although it is known that blast furnace granulated slag has latent hydraulic properties (property of causing hydration reaction and hardening by alkali stimulation or the like), the present inventors have crushed or / and classified blast furnace granulated slag. It was confirmed that the fine granulated blast furnace granulated slag obtained in this way has a significantly higher latent hydraulic property than the original blast furnace granulated slag. Under the idea of using sand as a part of sand-capping material, a sand-capping structure and a sand-capping method that can solve the above problems were studied. As a result, when the lower sand-covering layer has a lower sand-covering layer made of fine blast furnace granulated slag on the lower layer side and an upper sand-covering layer made of another sand-covering material on it, the lower sand-covering layer is solidified. Since it acts as a lid that blocks elution of hydrogen sulfide and nutrients from the sediment, it can form a sand-covering layer suitable for the growth and habitat of organisms, and it is also difficult for subsidence of the sand-covering layer to occur understood.

また、含水量が多い軟弱な底泥を有する水底に上記覆砂構造を適正に形成できる方法について検討した結果、覆砂を行うに当たって、最初に上記細粒高炉水砕スラグを水底に投入し、適当な時間（期間）をおいてから、他の覆砂材を投入するという方法を採ることにより、最初に投入した細粒高炉水砕スラグが底質上層に留まって層状に固結し、この固結層にその後に投入される他の覆砂材が保持されることによって適切な覆砂層が形成できることが判明した。すなわち、最初に投入した細粒高炉水砕スラグは水中を緩やかに沈降し、このため底質上層（浮泥層など）を突き抜けたり、浮泥を水中に巻き上げたりすることなく、多くが底質上層に捕捉される。この細粒高炉水砕スラグは高い潜在水硬性を有しているため短期間のうちに水硬反応を生じ、細粒高炉水砕スラグ層が適度な固さ（少なくとも、後に投入される他の覆砂材が突き抜けない程度の固さ）に固結する。そして、このように固結した細粒高炉水砕スラグ層の上に投入された他の覆砂材は、浮泥を水中に巻き上げることなく、且つ底質内に沈み込んでしまうことなく細粒高炉水砕スラグ層上に保持されることになり、これにより上述した覆砂構造を安定的に形成できることが判った。また、細粒高炉水砕スラグからのＣａの溶出による水のｐＨ上昇は、覆砂層や周囲の水域の生物生息環境に悪影響を与えるほど過剰なものではないことも判明した。   In addition, as a result of examining the method that can properly form the above sand-covering structure on the water bottom having a soft bottom mud with a high water content, when performing sand-covering, first, the above-mentioned fine blast furnace granulated slag is thrown into the water bottom, After taking an appropriate amount of time (period), the method of throwing in other sand-capping material is adopted, so that the first granulated blast furnace granulated slag stays in the upper sediment layer and solidifies in layers. It has been found that an appropriate sand-covering layer can be formed by holding another sand-covering material that is subsequently added to the consolidated layer. In other words, the first granulated blast furnace granulated slag slowly settles in the water, so that most of the bottom sediment does not penetrate through the upper sediments (floating mud layer, etc.) or roll up the floating mud into the water. Captured in the upper layer. Since this fine granulated blast furnace granulated slag has high latent hydraulic properties, it causes a hydraulic reaction within a short period of time, and the fine granulated blast furnace granulated slag layer has an appropriate hardness (at least Hardened so that the sand-capping material does not penetrate through. And the other sand-capping material thrown on the fine-grained blast furnace granulated slag layer consolidated in this way is fine-grained without rolling up floating mud into the water and sinking into the sediment. It will be held on the granulated blast furnace slag layer, and it has been found that the above-described sand-clad structure can be stably formed. It has also been found that the increase in water pH due to Ca elution from fine granulated blast furnace granulated slag is not excessive so as to adversely affect the biological habitat of the sand-covering layer and surrounding water areas.

従来、高炉水砕スラグは粒度が粗めの方が覆砂材に適していると考えられ、このため特許文献２においても、高炉水砕スラグを分級して得られた粗い方のスラグを覆砂材として利用している。一方、従来では細かい粒度の高炉水砕スラグを覆砂工法に積極利用するという考え方はなかった。これに対して、本発明者らが創案した上記覆砂構造及び覆砂方法は、細かい高炉水砕スラグをも有効利用しつつ、適切な覆砂層を形成できるものである。   Conventionally, it is considered that the granulated blast furnace slag has a coarser particle size and is suitable for sand-capping materials. Therefore, in Patent Document 2, the coarser slag obtained by classifying blast furnace granulated slag is covered. Used as sand material. On the other hand, there has been no concept of actively utilizing fine granulated blast furnace granulated slag in the sand-capping method. On the other hand, the above sand-covering structure and sand-covering method created by the present inventors can form an appropriate sand-covering layer while effectively utilizing fine blast furnace granulated slag.

本発明は、以上述べたような知見に基づきなされたもので、以下を要旨とするものである。 The present invention has been made on the basis of the findings as described above, and has the following gist .

［1］高炉水砕スラグを破砕処理又は／及び分級して得られたＤ ５０ が０．２〜０．９ｍｍの粒度を有する細粒高炉水砕スラグ（Ａ）を水底に投入し、底質の上層に捕捉された前記細粒高炉水砕スラグ（Ａ）をその水硬反応により固結させ、しかる後、天然砂、浚渫土、建設残土、砕砂、貝殻の中から選ばれる１種以上からなる覆砂材（Ｂ）を前記水底に投入することにより、細粒高炉水砕スラグ（Ａ）による下部覆砂層と、覆砂材（Ｂ）による上部覆砂層とを有する覆砂層を形成する水底の覆砂方法であって、
前記覆砂材（Ｂ）の水底への投入を、前記細粒高炉水砕スラグ（Ａ）による下部覆砂層の層最下部を含む層下側部分（但し、下部覆砂層の全層厚が１００ｍｍ以下の場合には層厚方向の全部）からコアボーリングで採取された１００ｍｍφ×１００ｍｍＨのコアをJIS A 1102に準拠して篩い振とう機で１分間篩い分けした時に、篩目１０ｍｍの篩上の高炉水砕スラグ量が全体の２０mass％以上となる固結状態となった後に行うことを特徴とする水底の覆砂方法。 [1] the granulated blast furnace slag crushing process and / or classified to D 50 obtained is a fine blast furnace slag (A) was charged into water bottom having a particle size of 0.2 to 0.9 mm, sediment The fine-grained blast furnace granulated slag (A) trapped in the upper layer is consolidated by its hydraulic reaction, and thereafter, one or more selected from natural sand, dredged soil, construction residual soil, crushed sand, and shells by injecting Kutsugaesunazai the (B) to the sea bed comprising, underwater to form a lower clad layer of sand by fine blast furnace slag (a), the sand covered with a sand layer covering the upper by Kutsugaesunazai (B) The sand covering method of
When the sand-clad material (B) is put into the bottom of the water, the lower layer part including the lowest part of the lower sand-clad layer by the fine granulated blast furnace granulated slag (A) (however, the total thickness of the lower sand-clad layer is 100 mm) In the following cases, when a 100 mmφ × 100 mmH core collected by core boring from all in the layer thickness direction is screened for 1 minute with a sieve shaker in accordance with JIS A 1102, A method of covering sand at the bottom of a water, which is carried out after the blast furnace granulated slag amount is 20% by mass or more .

［2］上記［1］の覆砂方法において、覆砂すべき水底は、人為的に投入された底泥を有することを特徴とする水底の覆砂方法。
［3］上記［1］の覆砂方法において、覆砂すべき水底は、上層が浮泥層で構成された底泥からなることを特徴とする水底の覆砂方法。 [2] The method for sand-covering a water bottom according to the above [1] , wherein the bottom of the water to be sanded has artificially added bottom mud.
[3] In the sand-capping method according to [1], the water-bottom sand-capping method is characterized in that the bottom of the water to be sanded consists of bottom mud whose upper layer is formed of a floating mud layer.

本発明の覆砂構造によれば、高い潜在水硬性を有する細粒高炉水砕スラグ（Ａ）により形成された下部覆砂層が固結することで底質の蓋の役目をするため、底質からの硫化水素や栄養塩の溶出を適切に防止することができ、一方において、覆砂材（Ｂ）により形成された上部覆砂層が生物の生育・生息場所となる本来的な覆砂層の役目をし、このため生物の生育・生息に適した覆砂層を形成することができる。また、下部覆砂層が固結することにより、覆砂層の全体的或いは局所的な沈み込みも抑制することができる。   According to the sand-capping structure of the present invention, the bottom sand-covering layer formed by the fine granulated blast furnace granulated slag (A) having high latent hydraulic properties acts as a bottom cover by consolidating. Elution of hydrogen sulfide and nutrients from the seawater can be properly prevented, while the upper sand-covering layer formed by the sand-covering material (B) serves as a natural sand-covering layer that serves as a place for growth and habitat of living organisms. Therefore, it is possible to form a sand-covering layer suitable for the growth and inhabiting of living organisms. Moreover, when the lower sand covering layer is consolidated, it is possible to suppress the entire or local sinking of the sand covering layer.

また、本発明の覆砂方法によれば、最初に投入した高い潜在水硬性を有する細粒高炉水砕スラグ（Ａ）が底質上層に留まって固結するため、その後投入された覆砂材（Ｂ）が細粒高炉水砕スラグ（Ａ）の固結層に保持されることで、底質内への沈み込みが防止され、所望の覆砂構造を安定的に形成することができる。また、細粒高炉水砕スラグ（Ａ）の投入や覆砂材（Ｂ）の投入による浮泥の水中への巻き上げを効果的に防止できるため、覆砂施工時の浮泥の巻き上げによる水の汚濁も防止できる。また、細粒高炉水砕スラグからのＣａの溶出による水のｐＨ上昇は、覆砂層や周囲の水域の生物生息環境に悪影響を与えるほど過剰なものではない。以上のことから、本発明の覆砂方法によれば、底泥が堆積した水底などに生物の生息環境として好適な覆砂層を安定的に形成することができ、また、覆砂施工に伴う水の汚濁なども極力抑制することができる。   Further, according to the sand-capping method of the present invention, the finely ground granulated blast furnace slag (A) having a high potential hydraulic property that has been initially charged stays in the upper layer of the bottom sediment and solidifies. Since (B) is held in the consolidated layer of the fine-grained blast furnace granulated slag (A), sinking into the sediment can be prevented, and a desired sand-covering structure can be stably formed. In addition, since it is possible to effectively prevent the floating mud from being rolled up by adding fine granulated blast furnace granulated slag (A) or sand-capping material (B), Pollution can also be prevented. Moreover, the increase in the pH of water due to the elution of Ca from the fine granulated blast furnace granulated slag is not excessive so as to adversely affect the biological habitat environment of the sand cover layer and the surrounding water area. From the above, according to the sand covering method of the present invention, it is possible to stably form a sand covering layer suitable as a living habitat for organisms on the bottom of the bottom where sediment has accumulated, and the water associated with sand covering construction. It is possible to suppress the contamination of water as much as possible.

高炉水砕スラグは、高炉から排出された高温の溶融スラグを噴流水で急冷（水砕処理）して得られるものであり、このような生成過程を経て生成したままの高炉水砕スラグ（以下、これを「生成ままの高炉水砕スラグ」という）は粒状の形態を有し、一般に粒径５ｍｍ以下のスラグ粒子の割合が９０mass％以上で、Ｄ５０が１ｍｍ〜１．５ｍｍ程度の粒度分布を有する。
本発明では、このような生成ままの高炉水砕スラグを破砕処理又は／及び分級することにより細粒高炉水砕スラグ（Ａ）を得て、この細粒高炉水砕スラグ（Ａ）を底質の蓋として機能する覆砂材として利用するものである。 Blast furnace granulated slag is obtained by quenching (hydrocracking) hot molten slag discharged from the blast furnace with jet water. , Which is referred to as “as-produced blast furnace granulated slag” has a granular form, and generally has a particle size distribution in which the proportion of slag particles having a particle size of 5 mm or less is 90 mass% or more and D 50 is about 1 mm to 1.5 mm. Have
In the present invention, the granulated blast furnace granulated slag (A) is obtained by crushing or / and classifying the as-produced blast furnace granulated slag, and the fine blast furnace granulated slag (A) is used as the bottom sediment. It is used as a sand covering material that functions as a lid.

本発明の水底の覆砂構造は、前記細粒高炉水砕スラグ（Ａ）により形成された下部覆砂層と、細粒高炉水砕スラグ（Ａ）以外の覆砂材（Ｂ）により、前記下部覆砂層の上に形成された上部覆砂層とを有する。
下部覆砂層を構成する細粒高炉水砕スラグ（Ａ）の粒度としては、水中において短期間のうちに固結するための高い潜在水硬性を備えさせるという観点から、Ｄ５０が１．０ｍ以下、好ましくは０．９ｍｍ以下が望ましい。但し、細粒高炉水砕スラグ（Ａ）の粒度が過剰に小さいと、投入しても水中に拡散したり、水流に流されたりしやすいため、Ｄ５０が０．２ｍｍ以上、好ましくは０．３ｍｍ以上が望ましい。 The bottom sand-covering structure of the present invention comprises a lower sand-covering layer formed by the fine-grained blast furnace granulated slag (A) and a sand-covering material (B) other than the fine-grained blast furnace granulated slag (A). And an upper sand covering layer formed on the sand covering layer.
As the particle size of the fine granulated blast furnace granulated slag (A) constituting the lower sand-capping layer, D 50 is 1.0 m or less from the viewpoint of providing high latent hydraulic properties for consolidation in a short period of time in water. Preferably, 0.9 mm or less is desirable. However, if the particle size of the fine blast furnace slag (A) is excessively small, or diffuse into the water be charged, and is easily or shed water, D 50 is 0.2mm or more, preferably 0. 3 mm or more is desirable.

細粒高炉水砕スラグ（Ａ）としては、(1)生成ままの高炉水砕スラグを破砕処理したもの、(2)生成ままの高炉水砕スラグを篩い分け等により分級して得られた細かい方のスラグ、(3)生成ままの高炉水砕スラグを破砕処理し、次いで、篩い分け等により分級して得られた細かい方のスラグ、(4)生成ままの高炉水砕スラグを篩い分け等により分級して得られた細かい方のスラグをさらに破砕処理したもの、などを用いることができる。   Fine granulated blast furnace granulated slag (A) includes (1) crushed granulated blast furnace slag, (2) fine pulverized granulated blast furnace slag obtained by sieving, etc. (3) Crushed blast furnace granulated slag, (3) Fine slag obtained by classification by sieving, etc., (4) Sifted blast furnace granulated slag, etc. The finer slag obtained by classification according to the above can be further crushed.

上記分級の方式としては、乾式篩い、湿式篩い、気流分離などの適宜な方法を用いることができる。
なお、高炉水砕スラグは、その製法上の理由から針状物が多く含まれており、覆砂材として利用する場合に、この針状物を取り除くために分級が行われることがあるが、このような目的で行われる分級により得られた細かい方のスラグ或いはこれを破砕処理したものを、細粒高炉水砕スラグ（Ａ）として用いてもよい。
また、細粒高炉水砕スラグ（Ａ）として、少なくとも１週間程度屋外で野積みして表面を水和反応させたものを用いることにより、水底に投入した後の固結を早めることができる。 As the classification method, an appropriate method such as dry sieving, wet sieving, or airflow separation can be used.
In addition, blast furnace granulated slag contains a lot of needles for reasons of its manufacturing method, and when used as sand covering material, classification may be performed to remove these needles, Fine slag obtained by classification performed for such a purpose or a crushed slag may be used as the fine granulated blast furnace granulated slag (A).
Moreover, as fine-grained blast furnace granulated slag (A), it is possible to speed up the consolidation after throwing it into the bottom of the water by using a material that has been piled outdoors for at least one week and subjected to a hydration reaction on the surface.

下部覆砂層を構成する細粒高炉水砕スラグ（Ａ）は高い潜在水硬性を有するため、水底に投入してからある程度の期間が経過すると（細粒高炉水砕スラグ（Ａ）の粒度や投入量等にもよるが、例えば１日〜２週間程度）、水硬反応を生じて固結した状態となり、底質の蓋としての機能を発揮する。また、上部覆砂層が形成された後は、上部覆砂層を保持して覆砂層の全体的或いは局所的な沈み込みを抑制する機能を発揮する。なお、底質はケイ酸塩を含有しているため、細粒高炉水砕スラグ（Ａ）は底質の一部を取り込んだ状態で固結する場合もある。   Since the fine granulated blast furnace granulated slag (A) that constitutes the lower sand cover layer has high latent hydraulic properties, after a certain period of time has passed since it was introduced into the bottom of the water (the particle size and input of fine granulated blast furnace granulated slag (A)) Depending on the amount and the like, for example, about 1 day to 2 weeks), a hydraulic reaction is caused to become a solidified state, and functions as a bottom sediment lid. In addition, after the upper sand cover layer is formed, the upper sand cover layer is held and the function of suppressing the entire or local sinking of the sand cover layer is exhibited. Since the bottom sediment contains silicate, the fine granulated blast furnace granulated slag (A) may be consolidated in a state where a part of the bottom sediment is taken in.

ここで、本発明において下部覆砂層を構成する細粒高炉水砕スラグ（Ａ）が固結した（或いは下部覆砂層が固結した）状態とは、下部覆砂層の層高方向における少なくとも一部領域のスラグ粒子どうしが、上部覆砂層を構成する覆砂材（Ｂ）を保持できる程度の割合及び強度で結合した状態であればよい。ここで、下部覆砂層は、層下側部分ほど海水の交換が少なく且つ圧密されやすいために、固結しやすい。したがって、細粒高炉水砕スラグ（Ａ）（或いは下部覆砂層）が固結したか否かの評価方法として、下部覆砂層を重機によりコアボーリングして、層最下部を含む層下側部分（下部覆砂層の全層厚が１００ｍｍ以下の場合には層厚方向の全部）から１００ｍｍφ×１００ｍｍＨのコアを採取し、このコアをＪＩＳ
Ａ １１０２に準拠して篩い振とう機で１分間篩い分けした時に、篩目１０ｍｍの篩上の高炉水砕スラグ量が全体の１０mass％以上であれば、細粒高炉水砕スラグ（Ａ）（或いは下部覆砂層）が固結した状態と評価してよい。また、同篩上の高炉水砕スラグ量が全体の２０mass％以上、特に望ましくは３０mass％以上であれば、より好ましい固結状態であると言える。なお、覆砂領域全体を対象とした場合、局所的に上記のような固結状態に達しない領域（非固結領域）が生じる場合があるが、このような局所的な非固結領域が生じても本発明の作用効果を得る上で特に大きな問題はなく、したがって、覆砂層全体としては細粒高炉水砕スラグ（Ａ）（或いは下部覆砂層）が固結した状態として評価できる。
下部覆砂層の層厚に特に制限はないが、底質の蓋としての機能の観点からして、通常、１００ｍｍ以上、好ましくは２００ｍｍ以上の層厚とすることが好ましい。 Here, the state in which the fine granulated blast furnace granulated slag (A) constituting the lower sand-covering layer in the present invention is consolidated (or the lower sand-covering layer is consolidated) is at least a part of the lower sand-covering layer in the layer height direction. What is necessary is just the state which the slag particle | grains of the area | region couple | bonded with the ratio and intensity | strength of the grade which can hold | maintain the sand covering material (B) which comprises an upper sand covering layer. Here, the lower sand-covering layer tends to consolidate because the lower part of the layer has less exchange of seawater and is more easily consolidated. Therefore, as a method for evaluating whether the fine granulated blast furnace granulated slag (A) (or the lower sand-covering layer) has consolidated, the lower sand-covering layer is core-bored by a heavy machine, and the lower layer portion including the lowest layer ( When the total thickness of the lower sand-capping layer is 100 mm or less, a core of 100 mmφ × 100 mmH is collected from the whole in the layer thickness direction), and this core is extracted from JIS.
If the amount of granulated blast furnace slag on a sieve with a mesh size of 10 mm is 10 mass% or more when sieving with a sieve shaker according to A 1102, the fine granulated blast furnace granulated slag (A) ( Alternatively, it may be evaluated that the lower sand covering layer) is consolidated. Moreover, it can be said that it is a more preferable consolidated state if the amount of granulated blast furnace slag on the sieve is 20 mass% or more, particularly preferably 30 mass% or more. In addition, when the entire sand-capped region is targeted, there may be a region that does not reach the consolidated state as described above (non-consolidated region). Even if it occurs, there is no particular problem in obtaining the effects of the present invention. Therefore, the entire sand-covering layer can be evaluated as a state where the fine granulated blast furnace granulated slag (A) (or lower sand-covering layer) is consolidated.
Although there is no restriction | limiting in particular in the layer thickness of a lower sand covering layer, From a viewpoint of the function as a bottom cover, it is usually preferable to set it as 100 mm or more, Preferably it is 200 mm or more.

上部覆砂層を構成する覆砂材（Ｂ）の種類に特別な制限はなく、例えば、天然砂、浚渫土、建設残土、砕砂、貝殻、スラグなどの中から選ばれる１種以上を用いることができる。また、これらの２種以上を混合したものであってもよい。但し、内部摩擦角が大きい材料の方が敷設後に沈み込みを生じにくいので、この観点からはスラグ、砕砂、貝殻などを用いるのが好ましい。
天然砂としては、海砂、川砂、山砂等を、浚渫土としては、港湾建設や航路掘削等の海洋土木工事（浚渫）で発生したもの等を用いることができる。なお、浚渫土は、事前に乾燥処理（例えば、天日乾燥等）や脱水処理（薬剤を添加して凝集させた後に脱水・減容化する方法）を施したものであってもよい。 There is no special restriction on the type of sand-capping material (B) that constitutes the upper sand-capping layer. For example, one or more kinds selected from natural sand, dredged soil, construction residual soil, crushed sand, shells, slag, and the like are used. it can. Moreover, what mixed these 2 or more types may be used. However, since a material having a large internal friction angle is less likely to sink after laying, it is preferable to use slag, crushed sand, shells, etc. from this viewpoint.
As natural sand, sea sand, river sand, mountain sand and the like can be used, and as dredged soil, sand generated by marine civil engineering work (dredge) such as harbor construction and channel excavation can be used. The clay may be subjected to a drying treatment (for example, sun drying) or a dehydration treatment (a method of dehydrating and reducing the volume after adding and aggregating chemicals) in advance.

また、スラグとしては、高炉水砕スラグ（前記細粒高炉水砕スラグよりも粒度が大きい高炉水砕スラグ）、高炉徐冷スラグ（但し、この高炉徐冷スラグは水中でＳが溶出しないようにするため、十分にエージング処理したものが好ましい）、製鋼スラグ、鉱石還元スラグなどの鉄鋼製造プロセスで発生するスラグ、都市ゴミ溶融スラグ、都市ゴミ焼却灰溶融スラグ等の各種スラグを用いることができる。また、製鋼スラグとしては、脱燐スラグ・脱硫スラグ・脱珪スラグ等の溶銑予備処理スラグ、脱炭スラグ、鋳造スラグ、電気炉スラグ等が挙げられる。製鋼スラグとしては、特に脱炭スラグと脱燐スラグが好適である。
また、貝殻としては、アサリ、ホタテ、カキなどの貝殻そのもの、これらの貝殻を粉砕処理又は／及び熱処理したものなどを用いることができる。
また、覆砂層は、異なる種類の覆砂材（２種以上の材料の混合物の場合も含む）
で構成される２層以上からなるものであってもよい。 Also, as slag, blast furnace granulated slag (blast furnace granulated slag having a larger particle size than the above-mentioned fine granulated blast furnace granulated slag), blast furnace annealed slag (however, this blast furnace annealed slag does not dissolve S in water) Therefore, it is preferable to use a sufficiently aged one), various slags such as slag generated in steel manufacturing processes such as steelmaking slag and ore reduction slag, municipal waste melting slag, municipal waste incineration ash melting slag, and the like. Steelmaking slag includes hot metal pretreatment slag such as dephosphorization slag, desulfurization slag, and desiliconization slag, decarburization slag, cast slag, electric furnace slag, and the like. As the steelmaking slag, decarburization slag and dephosphorization slag are particularly suitable.
As the shell, shells such as clams, scallops and oysters themselves, those obtained by pulverizing or / and heat-treating these shells can be used.
In addition, the sand covering layer is a different type of sand covering material (including a mixture of two or more materials).
It may consist of two or more layers composed of

以上のような本発明の覆砂構造では、細粒高炉水砕スラグ（Ａ）により形成された下部覆砂層が固結することで底質の蓋の役目をするため、底質からの硫化水素や栄養塩の溶出を適切に防止することができ、また、覆砂材（Ｂ）により形成された上部覆砂層が生物の生育・生息場所となる本来的な覆砂層の役目をし、このため生物の生育・生息に適した水底環境を形成できる。また、下部覆砂層が固結することにより、覆砂層の全体的或いは局所的な沈み込みも抑制される。   In the sand-capped structure of the present invention as described above, the lower sand-clad layer formed by the fine granulated blast furnace granulated slag (A) acts as a lid for the bottom by consolidation, so hydrogen sulfide from the bottom And the elution of nutrients can be appropriately prevented, and the upper sand-covering layer formed by the sand-covering material (B) serves as the natural sand-covering layer that is the place where organisms grow and live. Underwater environment suitable for the growth and inhabiting of organisms can be formed. In addition, when the lower sand-covering layer is consolidated, overall or local sinking of the sand-covering layer is also suppressed.

なお、スラグからのＣａの溶出によって水のｐＨが過剰に上昇すると、覆砂層や周囲の水域での生物生息環境に悪影響を与えるおそれがあるが、細粒高炉水砕スラグ（Ａ）からのＣａの溶出による水のｐＨ上昇は、生物の生息環境に悪影響を与えるほど過剰なものではない。ここで、底質の蓋を形成することだけを目的とするのであれば、下部覆砂層にセメントなどを使用することも考えられるが、セメントを使用した場合には水のｐＨがかなり高くなり、生物の生息環境に悪影響を与えてしまうおそれがある。   If the pH of the water rises excessively due to the elution of Ca from the slag, there is a risk of adversely affecting the biological habitat environment in the sand-covering layer and the surrounding water area, but the Ca from the fine-grained blast furnace granulated slag (A) The increase in the pH of water due to elution is not so much as to adversely affect the habitat of the organism. Here, if it is only intended to form a bottom cover, it may be possible to use cement or the like for the lower sand-covering layer, but when cement is used, the pH of the water becomes considerably high, There is a risk of adversely affecting the habitat of the organism.

本発明の覆砂構造が適用される水域は、海域だけでなく、湖沼・内海・河口などの水域を含む。また、覆砂を養浜、浅場造成、干潟造成等を兼ねて行ってもよい。
また、適用される水底の状態にも特別な制限はなく、含水量が少ない底泥やレキなどからなる水底、含水量が多い底泥などからなる軟弱な水底など、任意の水底に適用することができる。また、人工的に浚渫土を投入して形成された水底、例えば、深掘部や潜堤などで囲った領域に浚渫土を投入して形成した水底などに適用することもできる。 The water area to which the sand covering structure of the present invention is applied includes not only sea areas but also water areas such as lakes, inland seas, and estuaries. In addition, sand cover may be used for beach nourishment, shallow ground creation, tidal flat creation, and the like.
In addition, there are no special restrictions on the state of the applied water bottom, and it should be applied to any water bottom, such as a bottom made of bottom mud or reki with a low water content, or a soft bottom made of bottom mud with a high water content. Can do. The present invention can also be applied to a water bottom formed by artificially throwing dredged soil, for example, a water bottom formed by dredging dredged soil into a region surrounded by a deep excavation or a submerged dike.

以上のような本発明の覆砂構造を形成するための方法（覆砂方法）については、水底の状態に応じて適宜選択することが好ましい。一般に、覆砂の対象と水底は、その状態により下記(a),(b)に大別できる。
(a) 含水量が少ない水底やレキなどを比較的多く含む水底
(b) 含水量が多い底泥などからなる軟弱な水底
上記(a)の水底の形態としては、(a1)微細な堆積物の圧密が進行し、含水量が比較的少ない底泥からなる水底、(a2)粗粒やレキなどを比較的多く含む水底、などが考えられ、このうち(a1)の具体例としては、堆積物層が形成されてからかなり期間が経過した水底、海底の地形が極相（時間を経て海底地形の変化がほとんど無く安定している状態）に達した堆積物層を有する水底などが挙げられ、また、(a2)の具体例としては、元々レキが主体の底質に堆積物が混合している水底、カキ、アサリなどの貝殻と堆積物とが混合している水底、堆積物と砂が入り混じった水底（河口域近くなど）などが挙げられる。 About the method (sand covering method) for forming the sand covering structure of the present invention as described above, it is preferable to select appropriately according to the state of the water bottom. In general, the object of sand cover and the bottom of the water can be roughly classified into the following (a) and (b) according to the state.
(a) Water bottom with low water content and water bottom with relatively high water content
(b) Soft bottom composed of bottom mud with a high water content The form of the bottom of the above (a) is as follows: (a1) The bottom of the bottom mud with relatively small water content due to the consolidation of fine sediment (A2) The bottom of the sea that contains a relatively large amount of coarse grains and reki, etc. are considered.Specific examples of (a1) include the bottom of the seabed and the topography of the seabed that have passed a considerable period of time since the formation of the sediment layer. Is the bottom of the sediment that has reached the extreme phase (a stable state with little change in seafloor topography over time), and as a specific example of (a2), Examples include bottoms where sediment is mixed with sediments, bottoms where shells such as oysters and clams and sediments are mixed, and bottoms where sediments and sand are mixed (near estuaries, etc.).

このような上記(a)の水底では、投入した覆砂材が底質内部に沈み込むような恐れは殆どないため、本発明の覆砂構造を形成する場合、細粒高炉水砕スラグ（Ａ）を投入後、その固結を待つことなく、覆砂材（Ｂ）を投入することができ、これにより細粒高炉水砕スラグ（Ａ）による下部覆砂層と、覆砂材（Ｂ）による上部覆砂層が適正に形成される。ここで、細粒高炉水砕スラグ（Ａ）が固結しない段階で、その上に覆砂材（Ｂ）が投入されても、細粒高炉水砕スラグ（Ａ）はその後固結し、底質の蓋としての機能を発揮する。   In the water bottom of the above (a), there is almost no fear that the sand-carrying material thrown into the inside of the bottom sediment. Therefore, when forming the sand-clad structure of the present invention, fine granulated blast furnace granulated slag (A ), The sand-capping material (B) can be introduced without waiting for its consolidation, and thereby the lower sand-covering layer by the granulated blast furnace granulated slag (A) and the sand-capping material (B) The upper sand-capping layer is properly formed. Here, even if the fine sand blast furnace slag (A) is not solidified and the sand-capping material (B) is put on the fine blast furnace granulated slag (A), the fine granulated blast furnace water granulated slag (A) is subsequently consolidated, It functions as a quality lid.

一方、上記(b)の水底としては、(b1)上層が浮泥層で構成された底泥からなる水底、(b2)人為的に投入された軟弱な底泥からなる水底、などが考えられ、(b2)の具体例としては、浅場造成などにおいて、浚渫土などのような含水量の多い中詰め材を投入した水底が挙げられる。
このような上記(b)の水底において、上述した本発明の覆砂構造を形成する場合、覆砂材の底質内部への沈み込みを防止するため、細粒高炉水砕スラグ（Ａ）を水底に投入し、底質上層に捕捉された細粒高炉水砕スラグ（Ａ）をその水硬反応により固結させ、しかる後、覆砂材（Ｂ）を投入するという、本発明の覆砂方法を採ることが好ましい。すなわち、この本発明の覆砂方法では、最初に投入した細粒高炉水砕スラグ（Ａ）を底質上層に捕捉させてそこで固結させ、この細粒高炉水砕スラグ（Ａ）の固結層に覆砂材（Ｂ）が保持されることで、底質内への沈み込みが防止されるようにするものである。 On the other hand, the water bottom of (b) above may be (b1) a water bottom made of bottom mud composed of a floating mud layer, or (b2) a water bottom made of soft bottom mud artificially added. As a specific example of (b2), there is a bottom of water filled with a filling material having a high water content such as dredged soil in the construction of shallow ground.
In the case of forming the above-described sand-covering structure of the present invention in the water bottom of the above (b), in order to prevent the sand-covering material from sinking into the bottom sediment, fine granulated blast furnace granulated slag (A) is used. The fine sand blast furnace granulated slag (A) trapped in the bottom layer and solidified by the hydraulic reaction, and then the sand covering material (B) is charged. The method is preferably taken. That is, in this sand-capping method of the present invention, the first-charged fine blast furnace granulated slag (A) is captured by the upper sediment layer and consolidated there, and the fine-grained blast furnace granulated slag (A) is consolidated. By holding the sand-capping material (B) in the layer, sinking into the sediment is prevented.

最初に投入された細粒高炉水砕スラグ（Ａ）は水中を緩やかに沈降し、このため主たる細粒高炉水砕スラグ（Ａ）は底質上層（例えば浮泥層）を突き抜けたり、浮泥を水中に巻き上げたりすることなく、底質上層付近に静かに堆積することで底質上層に捕捉される。
細粒高炉水砕スラグ（Ａ）は、粒度が小さいために水との接触面積が大きく且つＣａの溶出性が高いため、生成ままの高炉水砕スラグに較べて高い潜在水硬性を示し、このため底質上層に捕捉された細粒高炉水砕スラグ（Ａ）は、直ぐに自ら溶出するＣａのアルカリ刺激により水和硬化反応を生じ、細粒高炉水砕スラグ層は短期間（細粒高炉水砕スラグの粒度や投入量等にもよるが、例えば１日〜２週間程度）のうちに適度な固さに固結する。また、底質はケイ酸塩を含有しているため、細粒高炉水砕スラグ層は底質の一部を取り込んだ状態で固結する場合もある。 The first fine granulated blast furnace granulated slag (A) slowly settled in the water, so the main fine granulated blast furnace granulated slag (A) penetrates the upper sediment layer (for example, floating mud layer) or floated mud. Without being rolled up in water, it is trapped in the upper sediment layer by gently depositing near the upper sediment layer.
Fine granulated blast furnace granulated slag (A) has a large contact area with water because of its small particle size and high elution of Ca. Therefore, it shows high hydraulic potential compared to the as-produced blast furnace granulated slag. Therefore, the fine granulated blast furnace granulated slag (A) trapped in the upper sediment layer causes a hydration hardening reaction due to the alkali stimulation of Ca that elutes immediately, and the fine granulated blast furnace granulated slag layer has a short period (fine blast furnace water) Although it depends on the particle size and input amount of crushed slag, for example, it is consolidated to an appropriate hardness within about 1 day to 2 weeks. In addition, since the sediment contains silicate, the fine-grained blast furnace granulated slag layer may be consolidated in a state where a part of the sediment is taken in.

この細粒高炉水砕スラグ（Ａ）の固結の程度は、少なくとも後に投入される主たる覆砂材（Ｂ）が下方に突き抜けない程度の適度な固さであればよい。したがって、最終的な固結状態に至らない段階の固結状態であってもよい。
なお、本発明の覆砂方法で用いる細粒高炉水砕スラグ（Ａ）やこれにより形成される下部覆砂層の条件は、さきに述べたとおりである。
上述のように細粒高炉水砕スラグ（Ａ）を投入し、底質上層で適度な固さに固結させた後、この固結した細粒高炉水砕スラグ層の上に、覆砂材（Ｂ）を投入する。 The degree of consolidation of the fine granulated blast furnace granulated slag (A) may be at least as hard as the main sand-clad material (B) to be charged later does not penetrate downward. Therefore, it may be a consolidated state that does not reach the final consolidated state.
In addition, the conditions of the fine granulated blast furnace granulated slag (A) used by the sand covering method of this invention and the lower sand covering layer formed by this are as having stated previously.
After the fine granulated blast furnace granulated slag (A) is charged as described above and consolidated to an appropriate hardness in the bottom sediment, the sand covering material is placed on the consolidated granulated blast furnace granulated slag layer. Input (B).

底質上層に固結した細粒高炉水砕スラグ層が形成されているため、投入された覆砂材（Ｂ）は、浮泥を水中に巻き上げることなく且つ底質内に沈み込んでしまうことなく固結した細粒高炉水砕スラグ層上に保持され、適切な覆砂層が安定的に形成される。この覆砂材（Ｂ）の投入（敷設）後、覆砂層が重しとなって底泥全体が圧密化され、これに伴い覆砂層も沈降する場合もあるが、覆砂層が底質内に没入するようなことはない。
なお、本発明の覆砂方法で用いる覆砂材（Ｂ）やこれにより形成される上部覆砂層の条件は、さきに述べたとおりである。 Because the fine granulated blast furnace granulated slag layer solidified on the bottom sediment is formed, the thrown sand covering material (B) will sink into the sediment without rolling up the floating mud into the water. It is retained on the fine granulated blast furnace granulated slag layer that has been consolidated, and an appropriate sand covering layer is stably formed. After the introduction (laying) of the sand-capping material (B), the sand-carrying layer overlaps and the entire bottom mud is consolidated. There is no such thing as immersion.
The conditions of the sand-capping material (B) used in the sand-capping method of the present invention and the upper sand-capping layer formed thereby are as described above.

以上述べたような覆砂方法に限らず、本発明の覆砂構造を得るための細粒高炉水砕スラグ（Ａ）の投入量は特に制限はないが、さきに述べたように１００ｍｍ以上、好ましくは２００ｍｍ以上の層厚になるように投入されることが好ましい。
また、細粒高炉水砕スラグ（Ａ）の水底への投入は、通常、覆砂材（Ｂ）と同じく運搬船等の上から行われるが、その際、生成ままの高炉水砕スラグを船上で篩い分け（分級）し、篩下のスラグが細粒高炉水砕スラグ（Ａ）としてそのまま水中に投入されるようにしてもよい。この場合、篩上のスラグが覆砂材（Ｂ）の少なくとも一部として用いられる。 The amount of the fine granulated blast furnace granulated slag (A) for obtaining the sand-covering structure of the present invention is not particularly limited, as described above, but as described above, 100 mm or more, Preferably, the layer thickness is 200 mm or more.
In addition, fine granulated blast furnace granulated slag (A) is usually poured into the bottom of the water from the top of a transport ship etc. like the sand-capping material (B). Sieving (classification) may be performed, and the slag under the sieve may be put into the water as it is as the fine granulated blast furnace granulated slag (A). In this case, the slag on the sieve is used as at least a part of the sand-capping material (B).

また、覆砂材（Ｂ）により形成される覆砂層の厚さにも特別な制限はないが、通常、２００ｍｍ以上が適当である。
また、本発明の覆砂方法では、さきに述べたように覆砂施工時の浮泥の水中への巻き上げが極力抑えられるが、若干生じる可能性がある浮泥の巻き上げを考慮して、必要に応じて覆砂水域をオイルフェンスで囲むなどの浮泥対策を採ってもよい。 Moreover, although there is no special restriction | limiting also in the thickness of the sand covering layer formed with a sand covering material (B), Usually, 200 mm or more is suitable.
Moreover, in the sand-capping method of the present invention, as described above, the lifting of floating mud into the water at the time of sand-covering construction is suppressed as much as possible, but it is necessary in consideration of the hoisting of floating mud that may occur slightly. Depending on, measures against floating mud such as surrounding the sand-covered water area with an oil fence may be taken.

[実施例１]
軟弱な堆積物（底泥）が平均厚さ約１ｍで堆積している比較的平坦な海底（水深１０ｍ）に、種々の粒度を有する高炉水砕スラグ又は天然砂を下部覆砂材として平均厚さ３０ｃｍで敷設し、下部覆砂層を施工した。７日経過後、下部覆砂層の上に上部覆砂材を平均厚さ３０ｃｍで敷設し、上部覆砂層を施工した。なお、各実施例の覆砂区画の面積は５ｍ２とした。
本発明例では、下部覆砂材として、破砕処理した後分級（篩い分け）した高炉水砕スラグを用いた。また、Ｎｏ．５の比較例では、下部覆砂材として生成ままの高炉水砕スラグを用いた。 [Example 1]
Average thickness using soft blast furnace granulated slag or natural sand as the lower sand covering material on a relatively flat seabed (water depth 10m) where soft sediment (bottom mud) is deposited with an average thickness of about 1m Laying at a height of 30 cm, a lower sand covering layer was constructed. After 7 days, the upper sand-capping material was laid on the lower sand-clad layer with an average thickness of 30 cm, and the upper sand-clad layer was constructed. The area of the covering sand compartment of each example was 5 m 2.
In the examples of the present invention, blast furnace granulated slag which was classified after crushing (sieving) was used as the lower sand-capping material. No. In Comparative Example 5, blast furnace granulated slag as generated was used as the lower sand covering material.

下部覆砂層施工時の底泥（浮泥）の巻き上げの有無を、施工直後に下部覆砂層上に沈降・再堆積した底泥の厚さで評価した。また、下部覆砂層を施工して７日経過後（上部覆砂層の施工前）に、下部覆砂層の固結の有無を下記測定試験の結果に基づき評価した。
下部覆砂層の中央付近の任意の箇所を重機によりコアボーリングして、層最下部を含む層下側部分から１００ｍｍφ×１００ｍｍＨのコアを採取し、これをＪＩＳ
Ａ １１０２に準拠して篩い振とう機で１分間篩い分けし、篩目１０ｍｍの篩上の高炉水砕スラグ量が全体の１０mass％以上の場合を“固結有り”、１０mass％未満の場合を“固結無し”と評価した。さらに、上部覆砂層を施工してから１ヶ月後に、上層覆砂層上面の沈み込み量（施工直後のレベルからの沈み込み量）を測定した。それらの結果を、下部覆砂材の種類及び粒度、上部覆砂材の種類とともに表１に示す。 Whether the bottom mud (floating mud) was rolled up during the construction of the lower sand-covering layer was evaluated by the thickness of the bottom mud that settled and redeposited on the lower sand-covering layer immediately after the construction. In addition, after 7 days have passed since the lower sand-covering layer was constructed (before the upper sand-covering layer was constructed), the presence or absence of consolidation of the lower sand-covering layer was evaluated based on the results of the following measurement test.
Core boring is performed at an arbitrary position near the center of the lower sand-covering layer with a heavy machine, and a core of 100 mmφ × 100 mmH is collected from the lower layer part including the lowermost part of the layer.
According to A1102, when sieving with a sieve shaker for 1 minute and the amount of granulated blast furnace slag on a sieve with a mesh size of 10 mm is 10 mass% or more of the whole, “solidified” and less than 10 mass% Evaluated as “no consolidation”. Further, one month after the construction of the upper sand-capping layer, the amount of subsidence on the upper surface of the upper sand-capping layer (the amount of subsidence from the level immediately after construction) was measured. The results are shown in Table 1 together with the type and particle size of the lower sand-capping material and the type of the upper sand-capping material.

Figure 0004872275
Figure 0004872275

Claims (3)

高炉水砕スラグを破砕処理又は／及び分級して得られたＤ ５０ が０．２〜０．９ｍｍの粒度を有する細粒高炉水砕スラグ（Ａ）を水底に投入し、底質の上層に捕捉された前記細粒高炉水砕スラグ（Ａ）をその水硬反応により固結させ、しかる後、天然砂、浚渫土、建設残土、砕砂、貝殻の中から選ばれる１種以上からなる覆砂材（Ｂ）を前記水底に投入することにより、細粒高炉水砕スラグ（Ａ）による下部覆砂層と、覆砂材（Ｂ）による上部覆砂層とを有する覆砂層を形成する水底の覆砂方法であって、
前記覆砂材（Ｂ）の水底への投入を、前記細粒高炉水砕スラグ（Ａ）による下部覆砂層の層最下部を含む層下側部分（但し、下部覆砂層の全層厚が１００ｍｍ以下の場合には層厚方向の全部）からコアボーリングで採取された１００ｍｍφ×１００ｍｍＨのコアをJIS A 1102に準拠して篩い振とう機で１分間篩い分けした時に、篩目１０ｍｍの篩上の高炉水砕スラグ量が全体の２０mass％以上となる固結状態となった後に行うことを特徴とする水底の覆砂方法。 D 50 obtained a water-granulated blast furnace slag crushing or / and by classifying the fine blast furnace slag (A) was charged into water bottom having a particle size of 0.2 to 0.9 mm, the upper layer of sediment The captured fine granulated blast furnace granulated slag (A) is consolidated by its hydraulic reaction, and then covered with at least one selected from natural sand, dredged soil, construction residual soil, crushed sand, and shells. Covering the bottom of the water to form a sand-covering layer having a lower sand-covering layer made of fine granulated blast furnace granulated slag (A) and an upper sand-covering layer made of sand-covering material (B) by introducing the material (B) into the water-bottom A method,
When the sand-clad material (B) is put into the bottom of the water, the lower layer part including the lowest part of the lower sand-clad layer by the fine granulated blast furnace granulated slag (A) (however, the total thickness of the lower sand-clad layer is 100 mm) In the following cases, when a 100 mmφ × 100 mmH core collected by core boring from all in the layer thickness direction is screened for 1 minute with a sieve shaker in accordance with JIS A 1102, A method of covering sand at the bottom of a water, which is carried out after the blast furnace granulated slag amount is 20% by mass or more . 覆砂すべき水底は、人為的に投入された底泥を有することを特徴とする請求項１に記載の水底の覆砂方法。   The method of claim 1, wherein the bottom of the water to be sanded has artificially added bottom mud. 覆砂すべき水底は、上層が浮泥層で構成された底泥からなることを特徴とする請求項１に記載の水底の覆砂方法。2. The method for sand-covering a water bottom according to claim 1, wherein the water-bottom to be sand-covered comprises bottom mud having an upper layer composed of a floating mud layer.
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