JP2012246729A - Method for backfilling dredged depression - Google Patents
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本発明は、浚渫土砂と製鋼スラグを混合した「スラグ混合土」を用いて浚渫窪地を埋め戻す方法に関する。 The present invention relates to a method for backfilling a depression using “slag mixed soil” in which dredged sand and steelmaking slag are mixed.
まず、海域内湾に見られる「浚渫窪地」の現状と「浚渫窪地」の存在による海域環境への悪影響について説明する。
東京湾、三河湾等の内湾には海砂採取の跡地や海底土砂掘削の跡地が散見される。これらは、戦後、沿岸埋め立て用の材料として、あるいは、海砂利の採取のための安価な土砂の供給源として掘削利用されたものである。浚渫跡地の中で、周辺の海底よりも特に深く掘り下げた窪地状の浚渫跡地が「浚渫窪地」と呼ばれている。例えば、東京湾では、このような「浚渫窪地」が約１億ｍ３存在していることが明らかになっている。
First, the current situation of “Ogikubochi” seen in the inner bay and the adverse effects on the marine environment due to the existence of “Ogikubochi” will be explained.
In the inner bays such as Tokyo Bay and Mikawa Bay, there are sites of sea sand collection and sites of excavation of seabed sediments. These were excavated and used after the war as materials for coastal land reclamation or as a source of inexpensive earth and sand for collecting sea gravel. Among the ruins, the ruins of a depression that has been dug deeper than the surrounding seabed is called “Ogikubochi”. For example, in Tokyo Bay, it is clear that there are about 100 million m 3 of such “Ogikubochi”.
また、このような「浚渫窪地」では、夏季に硫化物が生成・集積し易く、この生成した硫化物が(１)式のように海水中の溶存酸素を消費する。このため、青潮、苦潮等と呼ばれる酸素を含まない水塊(「貧酸素水塊」)が生成し易い。この「貧酸素水塊」が沿岸域に押し寄せると、魚介類が死滅し、大きな漁業被害が生じる。このため、近年、浚渫窪地の埋め戻し等による修復の必要性が強く指摘されるようになっている(非特許文献１)。
[硫化物と溶存酸素との反応式]Ｓ２−＋２Ｏ２→ＳＯ４ ２− （１）
Further, in such “Ogikubochi”, sulfides are easily generated and accumulated in the summer, and the generated sulfides consume dissolved oxygen in seawater as shown in the equation (1). For this reason, a water mass not containing oxygen called “blue tide, bitter tide, etc.” (“anoxic water mass”) is easily generated. When this “anoxic water mass” rushes to the coastal area, fish and shellfish are killed, causing serious fishery damage. For this reason, in recent years, the necessity of the restoration | repair by the backfill etc. of the depression is strongly pointed out (nonpatent literature 1).
[Reaction Formula of Sulfide and Dissolved Oxygen] S 2 + 2O 2 → SO 4 2− (1)
この「浚渫窪地」における硫化物と貧酸素水塊域の生成メカニズムについて詳細に説明する。海水中には、表１に示すように、硫酸イオン（ＳＯ４ ２−）が２８ｍＭ（２．７ｇ／Ｌ、ＳＯ４ ２−−Ｓとして９３０ｍｇ／Ｌ）も存在する。このため、「浚渫窪地」内の海域底質に有機物が十分に存在し、また、ＳＯ４ ２−よりも高次の酸化剤（溶存酸素等)が無くなる環境条件（嫌気条件と呼ばれる）が整えば、硫酸還元菌（ＳＲＢ：Ｓｕｌｆａｔｅ Ｒｅｄｕｃｉｎｇ Ｂａｃｔｅｒｉａ）が活性化し、（２）式のような硫酸還元反応が容易に進行する。硫酸還元菌（ＳＲＢ）とは、酸化剤として硫酸イオン（ＳＯ４ ２−）を用い有機物を酸化する細菌群の総称である。この結果、硫化水素（Ｈ２Ｓ）の生成が促進される（図１）。
ＳＯ４ ２−＋２ＣＨ２Ｏ＋２Ｈ＋⇔Ｈ２Ｓ＋２Ｈ２Ｏ＋ＣＯ２ （２）
The generation mechanism of sulfide and anoxic water mass in this “Ogikubo” will be described in detail. In seawater, as shown in Table 1, sulfate ions (SO 4 2− ) are also present as 28 mM (2.7 g / L, SO 4 2− -S as 930 mg / L). For this reason, environmental conditions (called anaerobic conditions) in which organic matter is sufficiently present in the seabed sediments in “Ogikubochi” and higher-level oxidants (dissolved oxygen, etc.) are eliminated from SO 4 2− are established. For example, a sulfate reducing bacterium (SRB) is activated, and the sulfate reduction reaction as expressed by the formula (2) easily proceeds. Sulfate-reducing bacteria (SRB) are a general term for a group of bacteria that oxidize organic substances using sulfate ions (SO 4 2− ) as an oxidizing agent. As a result, the generation of hydrogen sulfide (H 2 S) is promoted (FIG. 1).
SO 4 2− + 2CH 2 O + 2H + ⇔H 2 S + 2H 2 O + CO 2 (2)
さらに、このようにして、底質において生成し海水中に溶出した硫化水素（Ｈ２Ｓ）の存在形態は、以下のようにｐＨによって支配される。
［Ｈ＋］［ＨＳ−］／［H２Ｓ（ｇ）］= １０−7 （３）
［Ｈ＋］［Ｓ２−］／［ＨＳ−]＝１０−１３ （４）
Further, the existence form of hydrogen sulfide (H 2 S) generated in the sediment and eluted in the seawater is governed by the pH as follows.
[H + ] [HS − ] / [H 2 S (g)] = 10 −7 (3)
[H + ] [S 2− ] / [HS − ] = 10 −13 (4)
水中の全硫化物濃度は、以下のように整理される。
全硫化物＝懸濁態硫化物（ＦｅＳ、ＭｎＳ等）＋溶存態硫化物
ここで、溶存態硫化物＝硫化水素［H２Ｓ（ｇ）］+ 硫化物イオン
＝［H２Ｓ（ｇ）］+ ［ＨＳ−］+ ［Ｓ２−］
≒［H２Ｓ（ｇ）］+［ＨＳ−］（通常の海水域のｐＨ)
The total sulfide concentration in water is organized as follows.
Total sulfide = Suspension sulfide (FeS, MnS, etc.) + Dissolved sulfide Here, dissolved sulfide = hydrogen sulfide [H 2 S (g)] + sulfide ion
= [H 2 S (g)] + [HS − ] + [S 2− ]
≒ [H 2 S (g)] + [HS − ] (normal seawater pH)
溶存態硫化物の中で最も毒性の強いとされる遊離態の硫化水素［H２Ｓ（ｇ）］の存在割合は、ｐＨが７以下では５０％以上であるが、ｐＨが８を超えると１０％以下まで下がる。一方、ｐＨが７〜１３の領域では溶存態の硫化物イオン［ＨＳ−］の存在割合が最も高い。通常、海水のｐＨは、８〜８．５程度であるから、溶存態硫化物の中で、大半が溶存態の硫化物イオン［ＨＳ−］として存在すると考えられる。 The proportion of free hydrogen sulfide [H 2 S (g)], which is considered to be the most toxic among the dissolved sulfides, is 50% or more when the pH is 7 or less, but 10% when the pH exceeds 8. % Or less. On the other hand, in the region where the pH is 7 to 13, the abundance of dissolved sulfide ions [HS − ] is the highest. Usually, since the pH of seawater is about 8 to 8.5, it is considered that most of the dissolved sulfides exist as dissolved sulfide ions [HS − ].
いずれにせよ、硫化物は、（２）式のように海水中の溶存酸素を短時間で消費し、海水の「貧酸素化」を招くと共に、硫化物自体も水生生物への毒性があるため、硫化物は海水中への溶出を極力抑制することが望ましい。
このため、「浚渫窪地」の埋め戻しが各地で進められるようになってきている。この場合、埋め戻し材としては、海域での航路の維持や港湾工事等で大量に生成する「浚渫土砂」が用いられていることが多い。「浚渫土砂」は、「廃棄物」には相当しないため、海域で容易に有効利用され得る資材である。
In any case, the sulfide consumes dissolved oxygen in the seawater in a short time as shown in the formula (2), causing “poor oxygenation” of the seawater, and the sulfide itself is toxic to aquatic organisms. It is desirable to suppress the elution of sulfide into seawater as much as possible.
For this reason, the backfilling of “Ogikubo” has been promoted in various places. In this case, as the backfill material, “soil and sand” that is generated in large quantities in the maintenance of the sea route in the sea area, port construction, etc. is often used. “Soil and sand” does not correspond to “waste” and is a material that can be easily and effectively used in the sea area.
一方で、硫酸還元反応の律速要因は、海水中の硫酸塩ではなく、土砂に含まれる有機物である。したがって、硫化物生成に由来する「貧酸素化」を防止するためには、埋め戻し材に用いる「浚渫土砂」も、有機物含有量が極力小さいことが望ましいと考えられる。
このため、発明者らは、「浚渫土砂」に鉄鋼プロセスから生成する「製鋼スラグ」を混合し、有機物含有割合を低下させると共に、固化を促進した「スラグ混合土」を用いて浚渫窪地を埋め戻して海域環境の改善を図る方法を提案している（非特許文献２) 。
On the other hand, the rate-limiting factor of the sulfate reduction reaction is not sulfate in seawater but organic matter contained in earth and sand. Therefore, in order to prevent “poor oxygenation” derived from sulfide generation, it is considered desirable that the “soil sand” used for the backfilling material also has a minimum organic content.
For this reason, the inventors mixed “steel slag” generated from the steel process with “silk sand” to reduce the organic matter content and fill the depression using “slag mixed soil” that promoted solidification. A method for improving the marine environment by returning it has been proposed (Non-Patent Document 2).
浚渫窪地は、元々は良質な無機物が主体の海砂から成っていたと推定される。したがって、本来であれば、浚渫窪地への埋め戻し材としては有機物を極力含まない天然砂等の無機物が望ましい。しかし、実際には大量の天然砂はもはや入手が難しく、地元の海域から生成する「浚渫土砂」が入手の容易さ、コスト、安定的な量の確保の観点から最も現実的な埋め戻しの有用資材と考えられる。加えて、鉄鋼プロセスから生成する「製鋼スラグ」もまた、入手の容易さ、コスト、安定的な量の確保、安全性の観点から現実的な埋め戻しの有用資材と考えられる。 It is estimated that the Ogikubo area originally consisted of sea sand mainly composed of high-quality inorganic substances. Therefore, originally, an inorganic material such as natural sand that contains as little organic material as possible is desirable as a material for backfilling the depression. However, in practice, a large amount of natural sand is no longer available, and the “soil-sand” generated from the local waters is the most practical backfill useful in terms of availability, cost, and securing a stable amount. It is considered a material. In addition, “steel slag” produced from the steel process is also considered as a practical material for backfilling in terms of availability, cost, securing a stable amount, and safety.
浚渫窪地においては、硫酸還元細菌による硫酸還元反応（図１参照）が硫化物生成の主要な要因であり、この硫酸還元反応を抑制することが、硫化物生成に由来する海水中の「貧酸素化」を防止する最も効果的な手段である。即ち、浚渫窪地内底質での硫酸還元反応をどのように制御し、低減するかが海域環境改善のポイントとなる。
これに対して、発明者らは、「浚渫土砂」に鉄鋼プロセスから生成する「製鋼スラグ」を混合し、固化を促進した「スラグ混合土」を用いて、浚渫窪地を埋め戻して海域環境改善方法を提案している（非特許文献２）。
In the Ogikubo area, the sulfate reduction reaction by sulfate-reducing bacteria (see Fig. 1) is a major factor in the formation of sulfides. Suppression of this sulfate reduction reaction is the "poor oxygen in seawater derived from sulfide formation. It is the most effective means to prevent In other words, how to control and reduce the sulfuric acid reduction reaction in the sediment in the Ogikubo area is the key to improving the marine environment.
In contrast, the inventors mixed “steel-making slag” generated from the steel process with “soil-sand” and used “slag-mixed soil” that promoted solidification to backfill the depression and improve the marine environment. A method has been proposed (Non-Patent Document 2).
しかし、従来技術では「スラグ混合土」の相当の固化促進を前提としているが、「スラグ混合土」の固化程度と硫酸還元反応抑制の関係は必ずしも明確ではない。
そこで、本発明は、「浚渫土砂」及び鉄鋼プロセスから生成する「製鋼スラグ」を少なくとも含む「スラグ混合土」を用いて浚渫窪地を埋め戻して海域環境改善効果を図る際に、「スラグ混合土」の固化の制御が硫酸還元反応制御の最も重要となる視点であると考え、「スラグ混合土」での硫酸還元反応を抑制する簡易な固化指標を提供し、より効率的に海域環境改善を達成することを目的とする。
However, although the prior art presupposes considerable solidification promotion of “slag mixed soil”, the relationship between the degree of solidification of “slag mixed soil” and the suppression of sulfate reduction reaction is not necessarily clear.
Therefore, when the present invention aims to improve the marine environment by refilling the depression using “slag mixed soil” containing at least “steel slag” and “steel slag” generated from a steel process, Is the most important viewpoint of sulfate reduction reaction control, and provides a simple solidification index that suppresses the sulfate reduction reaction in “slag mixed soil” to improve the marine environment more efficiently. The goal is to achieve.
本発明者らは、上記の課題を解決するため検討を重ねた結果、浚渫土砂に製鋼スラグを混合した「スラグ混合土」内において、硫酸還元細菌による硫酸還元反応を抑制する簡易な固化指標を見出し、効率的に海域の環境改善を達成する方法の確立に成功した。
本発明の要旨とするところは、次の（１）〜（７）である。
As a result of repeated studies to solve the above-mentioned problems, the present inventors have found a simple solidification index for suppressing a sulfate reduction reaction by sulfate-reducing bacteria in “slag mixed soil” in which steelmaking slag is mixed with dredged soil. The headline and succeeded in establishing a method to efficiently improve the environment of the sea area.
The gist of the present invention is the following (1) to (7).
（１） 海域環境を改善するために海底の浚渫窪地を埋め戻す方法であって、少なくとも浚渫土砂と製鋼スラグとを混合してスラグ混合土を製造する混合工程と、前記スラグ混合土を用いて前記浚渫窪地を埋め戻す工程とを備え、前記混合工程において、前記スラグ混合土中の前記製鋼スラグの混合率を、製造後に海水中で１日〜１０日間養生してから測定した前記スラグ混合土の圧入抵抗値が２０ｋＰａ以上となるようにすることを特徴とする浚渫窪地の埋め戻し方法。
（２） 前記スラグ混合土の圧入抵抗値が、山中式硬度計で測定した値であることを特徴とする（１）に記載の浚渫窪地の埋め戻し方法。
（３） 前記スラグ混合土中の製鋼スラグの混合率が５０質量％以下であることを特徴とする（１）又は（２）に記載の浚渫窪地の埋め戻し方法。
（４） 前記製鋼スラグは、５０%粒径が１０ｍｍ未満の微細スラグを５０質量%以上含むことを特徴とする（１）〜（３）のいずれかに記載の浚渫窪地の埋め戻し方法。
（５） 前記混合工程において、前記浚渫土砂と前記製鋼スラグと高炉水砕スラグ微粉とを混合して前記スラグ混合土を製造することを特徴とする（１）〜(４)のいずれかに記載の浚渫窪地の埋め戻し方法。
（６） 前記スラグ混合土中に前記高炉水砕スラグ微粉を、前記浚渫土砂と前記製鋼スラグとの合計量の０．１質量％以上２質量％以下の範囲で含有させることを特徴とする（５）記載の浚渫窪地の埋め戻し方法。
（７） 前記混合工程の前に、少なくとも前記浚渫土砂と前記製鋼スラグとを混合して試験用混合物を製造し、前記試験用混合物の圧入抵抗値を測定する工程と、前記試験用混合物の圧入抵抗値を用いて前記スラグ混合土中の製鋼スラグの混合率を決定する混合率決定工程とを備えることを特徴とする（１）〜(６)のいずれかに記載の浚渫窪地の埋め戻し方法。
(1) A method for refilling a seafloor depression in order to improve the marine environment, wherein at least a dredged sand and steelmaking slag are mixed to produce a slag mixed soil, and the slag mixed soil is used. A step of refilling the depression, and in the mixing step, the mixing ratio of the steelmaking slag in the slag mixing soil is measured after curing in seawater for 1 to 10 days after production. The press-in resistance value is set to 20 kPa or more.
(2) The method of refilling an overlying depression according to (1), wherein the press-fit resistance value of the slag mixed soil is a value measured with a Yamanaka hardness meter.
(3) The refilling method of the depressions according to (1) or (2), wherein a mixing ratio of the steelmaking slag in the slag mixed soil is 50% by mass or less.
(4) The said steelmaking slag contains 50 mass% or more of fine slag whose 50% particle size is less than 10 mm, The backfilling method of the depression of any one of (1)-(3) characterized by the above-mentioned.
(5) In the mixing step, the slag mixed soil is manufactured by mixing the dredged sand, the steelmaking slag, and blast furnace granulated slag fine powder, according to any one of (1) to (4), How to backfill the Ogikubo area.
(6) The blast furnace granulated slag fine powder is contained in the slag mixed soil in a range of 0.1% by mass or more and 2% by mass or less of a total amount of the dredged sand and the steelmaking slag ( 5) The backfilling method of the Ogikubo land described in the above.
(7) Before the mixing step, at least the dredged sand and the steelmaking slag are mixed to produce a test mixture, and a press resistance value of the test mixture is measured; and the test mixture is press-fitted And a mixing rate determining step of determining a mixing rate of the steelmaking slag in the slag mixed soil using a resistance value. .
本発明により、スラグ混合土を用いて浚渫窪地を埋め戻す際に、固化程度を指標として硫化物生成抑制効果を推定し、浚渫窪地内の硫酸還元反応をより効率的に抑制して海域の貧酸素化を防止することができる。 According to the present invention, when refilling the Ogikubo land using slag mixed soil, the effect of suppressing sulfide generation is estimated using the degree of solidification as an index, and the sulfuric acid reduction reaction in the Ogikubo land is more effectively suppressed, resulting in poor sea areas. Oxygenation can be prevented.
本発明は、「浚渫土砂」に鉄鋼プロセスから生成する製鋼スラグを混合して得られる「スラグ混合土」を用いて浚渫窪地を埋め戻して海域環境改善効果を図る際に、「スラグ混合土」内部での硫酸還元反応を抑制する簡易な固化指標を提供し、より効率的に海域環境改善を達成する方法である。即ち、発明者らは、後述する「山中式硬度計」を用いてスラグ混合土の「圧入抵抗値」を測定し、スラグ混合土の「圧入抵抗値」と硫酸還元反応抑制に密接な関係があることを見出し、より効率的に海域環境の改善を達成することに成功したものである。 The present invention uses a “slag mixed soil” that is obtained by mixing steelmaking slag generated from a steel process with “soil-mixed sand” to refill the depression and reinforce the marine environment improvement effect. It provides a simple solidification index that suppresses the internal sulfuric acid reduction reaction and achieves better marine environment improvement. That is, the inventors measured the “press-in resistance value” of the slag mixed soil using a “Yamanaka hardness meter” described later, and had a close relationship with the “press-in resistance value” of the slag mixed soil and the suppression of the sulfate reduction reaction. We found something and succeeded in achieving the improvement of the marine environment more efficiently.
以下、本発明について詳細に説明する。
まず、「スラグ混合土」を用いた際の硫化物生成抑制機構について説明する。
発明者らは、製鋼スラグと浚渫土砂を混合し、固化を促進した「スラグ混合土」を用いて浚渫窪地を埋め戻すと、硫化物の生成抑制と海域での貧酸素化を防止できることを知見している（非特許文献２）。
図１に示すように、浚渫窪地底質において嫌気化が進行すると、硫酸還元菌は、海水中の硫酸イオン（ＳＯ４ ２−）を底質中の有機物（ＣＨ２Ｏ）によって還元し、この結果、硫化水素（Ｈ２Ｓ）等の硫化物を生成する。これに対して、「スラグ混合土」を用いて、浚渫窪地を埋め戻した際の硫化物の生成抑制機構として、以下のような機構を推定している。
Hereinafter, the present invention will be described in detail.
First, the sulfide generation suppression mechanism when “slag mixed soil” is used will be described.
The inventors have found that mixing steel-making slag and dredged sand and backfilling the depression with “slag mixed soil” that promotes solidification can prevent the formation of sulfides and prevent hypoxia in the sea area. (Non-Patent Document 2).
As shown in FIG. 1, when anaerobization proceeds in the Ogikubo sediment, sulfate-reducing bacteria reduce sulfate ions (SO 4 2− ) in seawater with organic matter (CH 2 O) in the sediment, As a result, sulfides such as hydrogen sulfide (H 2 S) are generated. In contrast, the following mechanism has been estimated as a mechanism for suppressing the formation of sulfides when backfilling the depression using “slag mixed soil”.
１)スラグ混合により浚渫土砂単独の場合と比較し、有機物量が減少し、有機物律速となり、硫化物生成が抑制される。
２)土砂の固化により、海水からの硫酸イオンの供給が困難となり、硫酸イオン律速となり、硫化物生成が抑制される。
３)土砂の固化進行に伴い、硫化物が生成したとしても、硫化物の水中への溶出が抑制される。
1) Compared to the case of dredged sand alone by mixing slag, the amount of organic matter is reduced, the rate of organic matter is controlled, and sulfide formation is suppressed.
2) Due to the solidification of the earth and sand, it becomes difficult to supply sulfate ions from seawater, the rate of sulfate ions is limited, and sulfide formation is suppressed.
3) Even if sulfides are generated as the soil solidifies, elution of sulfides into water is suppressed.
まず、１）の有機物律速の機構を説明する。
浚渫窪地の埋め立て材として「浚渫土砂」に製鋼スラグの一定量を混合した「スラグ混合土」を用いると、「浚渫土砂」単独で浚渫窪地の埋め戻し材とするよりも、埋め戻し材に含まれる有機物量は削減する。製鋼スラグは、Ｃａ、Ｓｉ、Ａｌ、Ｆｅ等の化合物からなり、１５００℃の高温で処理されているため、有機物は含まれていない。また、硫酸還元菌は一般の土壌に生息しており、「浚渫土砂」中にも生息しているが、製鋼スラグは、１５００℃の高温で処理されており、また、水分も殆ど無いため、硫酸還元菌の生息は難しいと思われる。即ち、浚渫土砂と製鋼スラグを混合して活用する「スラグ混合土」を埋め立て材として用いることにより、浚渫土砂中の有機物割合及び硫酸還元菌数を減らせ、硫酸還元反応に伴う硫化物の生成を抑制することが可能となる。
First, the organic material rate limiting mechanism 1) will be described.
Using “slag mixed soil” in which a certain amount of steelmaking slag is mixed with “soil sand” as the reclaimed material of the Ogikubo land is included in the backfill material rather than using the “soil sand” alone as a backfill material for the Ogikubo land. Reduce the amount of organic matter produced. Steelmaking slag is composed of compounds such as Ca, Si, Al, and Fe, and is processed at a high temperature of 1500 ° C., and therefore does not contain organic substances. In addition, sulfate-reducing bacteria inhabit general soil and inhabit “soil-sand”, but steelmaking slag is treated at a high temperature of 1500 ° C. and has almost no moisture. It seems difficult to live with sulfate-reducing bacteria. In other words, by using `` slag mixed soil '' that mixes and utilizes dredged sand and steelmaking slag as a landfill material, the proportion of organic matter and the number of sulfate-reducing bacteria in the dredged soil can be reduced, and sulfide formation associated with the sulfate reduction reaction can be achieved. It becomes possible to suppress.
次に、２）の硫酸イオンを減らし、硫化物の生成を抑制する機構、及び、３）の硫化物が生成したとしても、水中への溶出を防止する機構について説明する。
浚渫窪地を埋め戻し材で埋め戻した場合、埋め戻し材に有機物が例え含まれているとしても、海水が埋め戻し材中に容易に浸透しなければ、海水中の硫酸イオンが常に硫酸還元菌に供給されなくなる。この結果、硫酸還元反応は抑制され、硫化物の生成も抑制される。硫酸イオンの供給は、土壌の透水性に依存するものであるから、浚渫窪地への埋め戻し材が透水性の小さい材料であればあるほど、海水から硫酸イオンが供給されなくなり、硫酸イオン律速となって硫化物の生成が抑制される。また、仮に、浚渫窪地内の埋め戻し材のさらに下部において、嫌気化が進行し、硫化物が生成・蓄積したとしても、上部の埋め戻し材が透水性の小さい材料であれば、硫化物は海水中へ容易に溶出できなくなる。
Next, a mechanism for reducing sulfate ions in 2) to suppress the formation of sulfides, and a mechanism for preventing elution into water even if sulfides in 3) are generated will be described.
When the Ogikubochi is backfilled with backfill material, even if organic materials are included in the backfill material, if seawater does not easily penetrate into the backfill material, sulfate ions in the seawater will always be sulfate-reducing bacteria. No longer supplied. As a result, the sulfuric acid reduction reaction is suppressed, and the generation of sulfide is also suppressed. Since the supply of sulfate ions depends on the permeability of the soil, the lower the permeability of the backfill material to the depression, the less the sulfate ions are supplied from seawater, Thus, the generation of sulfide is suppressed. In addition, even if anaerobization progresses in the lower part of the backfill material in the depression, and sulfide is generated and accumulated, if the upper backfill material is a material with low water permeability, the sulfide Elution into sea water is difficult.
このように、水の透水性を減少させることが、土砂内での硫酸還元反応を抑制する上で極めて重要である。土砂の透水性とは、土砂の間隙中における水の移動し易さであり、一般的には、表２に示すような、透水係数ｋ（ｃｍ／ｓｅｃ）で評価される。また、このような土砂の透水性は、土砂の固化状態と密接な関係にある。土木工事の分野では、軟弱な土砂や地盤の改良のため、さまざまな材料を用いた固化処理が公知であり、また、固化処理土の透水性に関しては、固化処理することで固化処理前よりも小さな透水係数が得られるとされている。また、固化剤の添加量を増加させ、固化強度が大きいほど透水性も小さくなり、また、長期養生による固化強度増加に伴い、透水係数はさらに小さくなるとされている（非特許文献３）。 Thus, it is extremely important to reduce the water permeability of water in order to suppress the sulfuric acid reduction reaction in the earth and sand. The water permeability of earth and sand is the ease of movement of water in the gap between the earth and sand, and is generally evaluated by a water permeability coefficient k (cm / sec) as shown in Table 2. Moreover, the permeability of such earth and sand is closely related to the solidified state of the earth and sand. In the field of civil engineering work, solidification treatment using various materials is known for improving soft soil and ground, and regarding the water permeability of solidified soil, solidification treatment is better than before solidification treatment. It is said that a small hydraulic conductivity can be obtained. Further, the amount of solidifying agent added is increased, and the greater the solidification strength, the smaller the water permeability, and the water permeability coefficient is further reduced as the solidification strength is increased by long-term curing (Non-patent Document 3).
今回の発明に用いている製鋼スラグは、製鋼スラグ単独でも弱い水硬性があり、水中に製鋼スラグを放置すれば、製鋼スラグの透水性は長期的に低下し、ｋ＝１０−5〜１０−６ｃｍ／ｓｅｃ程度まで低下する。 The steelmaking slag used in the present invention has weak hydraulic properties even with the steelmaking slag alone. If the steelmaking slag is left in the water, the water permeability of the steelmaking slag is lowered in the long term, and k = 10 −5 to 10 − It decreases to about 6 cm / sec.
また、浚渫土砂そのものは透水性が極めて大きいが、製鋼スラグを混合した「スラグ混合土」の場合には、固化が進行し易くなる。これは、浚渫土砂から溶解性シリカが、また、製鋼スラグからカルシウムイオンが主として供給され、これらの反応によって、浚渫土砂粒子間にケイ酸カルシウム（ＣＳＨ）が生成し、「スラグ混合土」の固化が進むと考えられている。固化が進んだ「スラグ混合土」の場合、その透水係数は、１×１０−６〜１０−７ｃｍ／ｓｅｃまで低下し、硫化物の生成を抑制すると考えられる。 In addition, dredged sand itself has extremely high water permeability, but in the case of “slag mixed soil” in which steelmaking slag is mixed, solidification is likely to proceed. This is because soluble silica is mainly supplied from dredged sand and calcium ions are supplied from steelmaking slag, and by these reactions, calcium silicate (CSH) is generated between dredged sand particles to solidify “slag mixed soil”. Is thought to progress. In the case of “slag mixed soil” that has been solidified, the water permeability coefficient is considered to decrease to 1 × 10 −6 to 10 −7 cm / sec, and suppress the formation of sulfides.
発明者らは、このような「スラグ混合土」の固化の進行の指標として、「山中式硬度計」を用いてスラグ混合土の「圧入抵抗値」を用いることを発案し、また、スラグ混合土の初期の「圧入抵抗値」と硫化物の生成の抑制が密接な関係があることを見出した。即ち、海域環境を改善するために、海底の浚渫窪地を浚渫土砂と製鋼スラグを混合したスラグ混合土を用いて埋め戻しする方法であって、浚渫土砂に対して製鋼スラグを混合して得られた試験用混合物の圧入抵抗値を測定し、その圧入抵抗値を用いて、製造後に海水中で１日〜１０日間養生してから測定したスラグ混合土の圧入抵抗値が２０ｋＰａ以上となるよう「スラグ混合土」中の製鋼スラグの混合率を決定する（混合率決定工程）。 The inventors have invented the use of the “press-in resistance value” of the slag mixed soil using the “Yamanaka hardness tester” as an indicator of the progress of solidification of such “slag mixed soil”. We found that there is a close relationship between the initial "press-fit resistance value" of soil and the suppression of sulfide formation. That is, in order to improve the marine environment, a method of backfilling the seafloor depression in the seabed using slag mixed soil mixed with dredged sand and steelmaking slag, obtained by mixing steelmaking slag with dredged soil. Measure the indentation resistance value of the test mixture, and use the indentation resistance value so that the indentation resistance value of the slag mixed soil measured after curing in seawater for 1 to 10 days after production is 20 kPa or more. The mixing rate of the steelmaking slag in the “slag mixing soil” is determined (mixing rate determining step).
土壌硬度の測定方法としては、「山中式土壌硬度計法」、「貫入式土壌硬度計法」、「代かき土壌硬度法」等が広く知られており（非特許文献４）、どのような測定方法で測定してもかまわない。中でも「山中式土壌硬度計法」は、測定装置が安価に入手でき、かつ、操作も簡易でかつ短時間で測定可能であり、また、測定者による誤差も生じ難いため、土壌硬度の測定法として最も望ましいものである。 As a method for measuring soil hardness, “Yamanaka-type soil hardness test method”, “intrusion-type soil hardness test method”, “plumbing soil hardness test method”, etc. are widely known (Non-Patent Document 4). You may measure by the method. Among them, the “Yamanaka soil hardness tester” is a method for measuring soil hardness because the measuring device can be obtained at a low price, it is easy to operate and can be measured in a short time, and it does not easily cause errors by the measurer. As the most desirable.
ここでは、「山中式硬度計」を用いたスラグ混合土の圧入抵抗値の測定について説明する。山中式硬度計は、加えられた外力に対する土壌の抵抗力（圧入抵抗値）を計測する機器である。山中式硬度計の円錐部を土壌に圧入すると、土壌の硬度に応じて円錐部が抵抗を受け、円錐底面を支えているコイルばねが縮み、その分だけ円錐部分は内部に後退する。山中式硬度計の胴体部側面の指標硬度（ｍｍ）値から圧入抵抗値（ｋＰａ）を計算する。圧入抵抗値（ｋＰａ）は、土壌の性状把握や農業用用地といった土壌の目的に適しているかを判断する際の指標となっている（表３、非特許文献４）。 Here, the measurement of the press-fit resistance value of the slag mixed soil using the “Yamanaka hardness tester” will be described. The Yamanaka hardness tester is a device that measures the resistance (press-fit resistance value) of soil to an applied external force. When the conical part of the Yamanaka hardness tester is pressed into the soil, the conical part receives resistance according to the hardness of the soil, the coil spring supporting the conical bottom surface contracts, and the conical part retracts to the inside. The press-fit resistance value (kPa) is calculated from the index hardness (mm) value on the side surface of the body part of the Yamanaka hardness tester. The press-fit resistance value (kPa) is an index for determining whether it is suitable for the purpose of soil such as grasping of soil properties or agricultural land (Table 3, Non-Patent Document 4).
「スラグ混合土」の圧入抵抗値の具体的な測定方法は、以下のように実施する。まず、浚渫土砂に製鋼スラグを（スラグ混合土中製鋼スラグ混合率：０〜５０質量％）を混合した「スラグ混合土」を１ｋｇ作成する。この「スラグ混合土」１ｋｇを２Lのポリ容器にいれ、海水１Ｌで容器を満たして養生する。その後、海水で満たした「スラグ混合土」を常温・静置で３０日間放置すると共に、「スラグ混合土」表面の複数点（３〜５か所）の圧入抵抗値を山中式硬度計によって、経日で３０日間測定する。 A specific method for measuring the press-fit resistance value of “slag mixed soil” is performed as follows. First, 1 kg of “slag mixed soil” is prepared by mixing steelmaking slag with steelmaking slag (steel slag mixing ratio in slag mixed soil: 0 to 50 mass%). 1 kg of this “slag mixed soil” is put into a 2 L plastic container, and the container is filled with 1 L of seawater and cured. After that, the “slag mixed soil” filled with seawater is allowed to stand at room temperature and standing for 30 days, and the press resistance values at multiple points (3 to 5 locations) on the surface of the “slag mixed soil” are measured by the Yamanaka hardness tester. Measure for 30 days.
なお、海水量は特に限定するものではなく、コンクリートなどの湿潤養生試験と同様に、養生期間中に「スラグ混合土」の表面が蒸発して乾燥しない海水量程度でもかまわない。養生中におけるｐＨなど海水の水質変化を見たい場合には多めに海水を添加する必要があるが、海水量と養生期間中におけるスラグ混合土の固化促進には特に関係はない。養生期間が３０日間である場合、製造後のスラグ混合土の圧入抵抗値は、養生期間の経過に伴って増大する。 Note that the amount of seawater is not particularly limited, and may be about the amount of seawater that does not evaporate and dry the surface of the “slag mixed soil” during the curing period, as in the wet curing test for concrete and the like. In order to see changes in seawater quality such as pH during curing, it is necessary to add more seawater, but there is no particular relationship with the amount of seawater and the promotion of solidification of slag mixed soil during the curing period. When the curing period is 30 days, the press-fit resistance value of the slag mixed soil after production increases with the lapse of the curing period.
「スラグ混合土」の圧入抵抗値が、海水中で早期に上昇すればするほど、硫化物の生成抑制効果は大きい。本実施形態においては、製造後に海水中で１日〜１０日間養生した「スラグ混合土」の圧入抵抗値を固化指標として用いる。「スラグ混合土」の圧入抵抗値は、「スラグ混合土」の表面の複数点（３〜５か所）を、山中式硬度計を用いて測定した平均値であることが望ましい。硫化物の溶出が大きくない場合には、「スラグ混合土」の固化進行の指標として用いる圧入抵抗値として、スラグ混合後２０〜３０日の圧入抵抗値の平均値を固化指標として用いてもかまわない。
The faster the press-fit resistance value of “slag mixed soil” rises in seawater, the greater the effect of suppressing sulfide formation. In this embodiment, the press-fit resistance value of “slag mixed soil” cured in seawater for 1 to 10 days after production is used as a solidification index. The press-fit resistance value of the “slag mixed soil” is preferably an average value obtained by measuring a plurality of points (3 to 5 locations) on the surface of the “slag mixed soil” using a Yamanaka hardness meter. When the elution of sulfide is not large, the average value of the press-
次に、このようにして測定した「スラグ混合土」の圧入抵抗値と硫化物生成の関係の把握し、製鋼スラグの混合量を決定する方法について説明する。
まず、浚渫土砂に製鋼スラグを０〜５０質量％混合した「スラグ混合土」（試験用混合物）を複数種類作製する。浚渫土砂が採取後、時間を経ている等の理由から、生物分解可能な有機物量が減少し、浚渫土砂単独では硫化物の検出ができないと判断される場合には、グルコース等の有機物を浚渫土砂に予め混入しておく。このようにして作製した各「スラグ混合土」１００ｇをそれぞれ１L容器（ガラスびん）に添加後、窒素で曝気し溶存酸素（ＤＯ）を除去した表１のイオン濃度の人工海水０．９Ｌを各ガラスびんに添加して養生する。なお、人工海水でなく淡水などがまじっていない実海水をもちいてもかまわない。その後、密閉状態、光遮断、室温で０〜３０日間放置して養生する。
Next, a method for determining the mixing amount of steelmaking slag by grasping the relationship between the press-fit resistance value of the “slag mixed soil” thus measured and sulfide generation will be described.
First, a plurality of types of “slag mixed soil” (mixture for testing) in which 0-50 mass% of steelmaking slag is mixed with dredged soil is prepared. If the amount of organic matter that can be biodegraded decreases due to reasons such as the passage of time since the dredged soil has been collected, and it is judged that sulfide cannot be detected by dredged sand alone, organic matter such as glucose should be removed. In advance. After adding 100 g of each “slag mixed soil” thus prepared to a 1 L container (glass bottle), 0.9 L of artificial seawater having the ion concentration shown in Table 1 was aerated with nitrogen to remove dissolved oxygen (DO). Add to glass bottle and cure. It is also possible to use real seawater that is not artificial water and not fresh water. Then, it is cured by standing for 0 to 30 days in a sealed state, light blocking, and room temperature.
その後、１日以降１０日以内、例えば、５日間又は１０日間養生した容器中の海水を０．４５μmフィルター（ミリポア社製）を充填した注射器で採取（以下、ろ過海水）する。このろ過海水に硫酸（容積比で水１と硫酸１を混合した液）を添加し、窒素曝気し、硫化水素を発生させ、生成した硫化水素を酢酸亜鉛溶液でＺｎＳとして固定化する。その後、ＺｎＳを再溶解させ、よう素滴定法で５日後又は１０日後にろ過海水中に存在している硫化物濃度を測定する。 Thereafter, the seawater in the container cured for 5 days or 10 days is collected with a syringe filled with a 0.45 μm filter (manufactured by Millipore) (hereinafter, filtered seawater) within 10 days after 1 day. To this filtered seawater, sulfuric acid (a liquid in which water 1 and sulfuric acid 1 are mixed in a volume ratio) is added, aerated with nitrogen, hydrogen sulfide is generated, and the generated hydrogen sulfide is immobilized as ZnS with a zinc acetate solution. Thereafter, ZnS is re-dissolved, and the sulfide concentration present in the filtered seawater is measured after 5 days or 10 days by iodine titration.
また、山中式硬度計を用いて、前述した方法によって、製造後に海水中で１日〜１０日間養生した「スラグ混合土」の圧入抵抗値、例えば、５日間又は１０日間養生した「スラグ混合土」の圧入抵抗値を測定し、近傍の海水中の硫化物濃度との関係を検討する。 Moreover, the press-in resistance value of “slag mixed soil” cured in seawater for 1 day to 10 days after production using the Yamanaka hardness tester, for example, “slag mixed soil” cured for 5 days or 10 days. ”Is measured, and the relationship with the sulfide concentration in the nearby seawater is examined.
後述の実施例１で示すように、「スラグ混合土」の1日以降１０日以内の圧入抵抗値が僅かに上昇しただけで、海水中の硫化物濃度は、浚渫土砂単独の場合と比較し、急速に低下する。「スラグ混合土」の圧入抵抗値が２０ｋＰａ以上になると、海水中の硫化物濃度は１ｍｇ／Ｌ以下まで低下する。硫化物濃度が１ｍｇ／Ｌ以下となれば、消費される溶存酸素濃度は（１）式から２ｍｇ／Ｌ以下と推定される。海域の溶存酸素は通常５ｍｇ／Ｌ以上はあるため、海域底層の溶存酸素濃度を水産用水基準の３ｍｇ／Ｌ以上に維持することは可能と考えられる。 As shown in Example 1 to be described later, the press-fit resistance value within 10 days after the first day of “slag mixed soil” only slightly increased, and the sulfide concentration in seawater was compared with the case of dredged sand alone. , Decline rapidly. When the press-fit resistance value of “slag mixed soil” is 20 kPa or more, the sulfide concentration in seawater decreases to 1 mg / L or less. If the sulfide concentration is 1 mg / L or less, the dissolved oxygen concentration consumed is estimated to be 2 mg / L or less from the equation (1). Since the dissolved oxygen in the sea area is usually 5 mg / L or more, it is considered possible to maintain the dissolved oxygen concentration in the bottom of the sea area at 3 mg / L or more of the water standard for fisheries.
また、「スラグ混合土」の圧入抵抗値が５００ｋＰａ以上となると、海水中の硫化物濃度は０．２〜０．６ｍｇ／Ｌ、２０００ｋＰａ以上となると検出限界（０．２ｍｇ／Ｌ）以下まで低下する。したがって、スラグ混合土を製造する際には、製造後に海水中で１日〜１０日間養生してから測定したスラグ混合土の圧入抵抗値の下限が２０ｋＰａ以上、望ましくは５００ｋＰａ以上となるように、浚渫土砂に対する製鋼スラグの混合量（スラグ混合土中の製鋼スラグの混合率）を決定する（混合工程）。「スラグ混合土」の圧入抵抗値の上限は、特に定める必要はないが、２０００ｋＰａ以上あれば、海水中の硫化物溶出は無視できる程度まで抑制できると考えられる。 Moreover, when the press-fit resistance value of “slag mixed soil” is 500 kPa or more, the sulfide concentration in seawater is 0.2 to 0.6 mg / L, and when it is 2000 kPa or more, the detection limit (0.2 mg / L) or less is lowered. To do. Therefore, when producing slag mixed soil, the lower limit of the indentation resistance value of the slag mixed soil measured after curing in seawater for 1 to 10 days after production is 20 kPa or more, preferably 500 kPa or more, The amount of steelmaking slag mixed with dredged soil (mixing rate of steelmaking slag in the slag mixed soil) is determined (mixing step). The upper limit of the press-fit resistance value of “slag mixed soil” is not particularly required, but if it is 2000 kPa or more, it is considered that sulfide elution in seawater can be suppressed to a negligible level.
次に、浚渫土砂に混合する製鋼スラグについて説明する。
製鐵所から生成する鉄鋼スラグは、鉄鋼製造工程において副産物として発生する。鉄鋼スラグは大別して、高炉スラグと製鋼スラグに分けられ、それぞれ、有用資材として各方面で利用されている。本発明の海底の浚渫窪地修復に用いる鉄鋼スラグは、高炉スラグではなく、製鋼スラグである。
Next, the steelmaking slag mixed with dredged soil will be described.
Steel slag generated from the steelworks is generated as a by-product in the steel manufacturing process. Steel slag is roughly divided into blast furnace slag and steelmaking slag, and each is used as a useful material in various fields. The steel slag used for the seafloor depression restoration of the present invention is not blast furnace slag but steelmaking slag.
また、製鋼スラグは、製鋼炉(転炉、電気炉)において、銑鉄やスクラップから鋼を製造する際に生成するスラグの総称であるが、本発明の海底の浚渫窪地修復に用いる製鋼スラグは、転炉系の製鋼スラグであることが好ましい。転炉系の製鋼スラグは電気炉系製鋼スラグと比較し、成分組成が安定しており、品質管理が容易である。また、近年、鋼品質の高度化に対応するため、転炉による精錬のみでは不純物の除去が不十分となり、転炉前後の工程(溶銑予備処理、２次精錬)を付加された高級鋼製造工程から生成する溶銑予備処理スラグや２次精錬スラグも、転炉スラグと同様に転炉系の製鋼スラグに含まれる。 Steelmaking slag is a general term for slag generated when steel is produced from pig iron and scrap in a steelmaking furnace (converter, electric furnace). It is preferably a converter steelmaking slag. Compared with electric furnace steelmaking slag, converter steelmaking slag has a stable component composition and is easy to control quality. In recent years, in order to respond to the advancement of steel quality, the removal of impurities has become insufficient only by refining with a converter, and a high-grade steel manufacturing process to which processes before and after the converter (hot metal pretreatment, secondary refining) are added. The hot metal pretreatment slag and secondary refining slag generated from the slag are also included in the steelmaking slag of the converter system in the same manner as the converter slag.
転炉系の製鋼スラグは、粗鋼１t当たり約１１０〜１３０ｋｇ生成し、ヤードやピットに高温の溶けた状態のスラグを流し込み、自然放冷と適度の散水によってゆっくりと冷却し製造する。転炉系スラグは、ｆ−ＣａＯ（可溶性石灰）の含有量が高く、水と接触すると膨張し易い特性があるため、屋外エージング処理や蒸気等を用いた促進エージング処理により、膨張防止対策を施した後、道路用路盤材等、セメントクリンカー原料（ＦｅＯ供給材）、地盤改良材、土木工事用資材として広く用いられている。 The steelmaking slag of the converter system is produced about 110-130 kg per ton of crude steel, poured into a yard or pit and melted at a high temperature and slowly cooled by natural cooling and moderate watering. Converter-type slag has a high content of f-CaO (soluble lime) and tends to expand when it comes into contact with water. Therefore, measures to prevent expansion are taken by outdoor aging treatment or accelerated aging treatment using steam or the like. After that, it is widely used as a roadbed material for roads, cement clinker raw material (FeO supply material), ground improvement material, and civil engineering material.
さらに、このような転炉系の製鋼スラグを浚渫土砂に混合して「スラグ混合土」として用いる場合、「スラグ混合土」中の製鋼スラグの混合率は、５０質量％以下とする。これは、浚渫土砂に製鋼スラグを混合して用いても、海水による希釈効果により、近傍の海水のｐＨが上昇することは殆どないが、「スラグ混合土」中の製鋼スラグの混合率をあまりに高めると、海水交換速度が小さい場合等、近傍の海水のｐＨが一時的に９．５を超えて上昇する可能性もあるためである。 Further, when such converter steelmaking slag is mixed with dredged soil and used as “slag mixed soil”, the mixing ratio of the steelmaking slag in the “slag mixed soil” is 50 mass% or less. This is because even if steelmaking slag is mixed with dredged soil, the pH of seawater in the vicinity hardly rises due to the dilution effect of seawater, but the mixing ratio of steelmaking slag in “slag mixed soil” is too high. This is because the pH of seawater in the vicinity may temporarily exceed 9.5 when the seawater exchange rate is low.
ｐＨが９．５を超えると、海水中のＭｇ２+がＭｇ（ＯＨ）２となり、析出し易くなる。したがって、「スラグ混合土」中の製鋼スラグの混合率は５０質量％が上限と考えられる。また、用いる製鋼スラグは、「スラグ混合土」の早期の固化促進の観点からは、５０％粒径が１０ｍｍ未満の微細スラグを５０質量％以上含むことが望ましい。粒径が１０ｍｍよりも大きい製鋼スラグは、ｐＨが上昇し難いものの、逆に、固化促進に必要なカルシウムイオンやシリカの溶解速度が低下するため、固化速度が低下する。したがって、用いる製鋼スラグはカルシウムイオンやシリカの溶解速度が大きい５０％粒径が１０ｍｍ未満の微細スラグを５０質量％以上含むことが望ましい。 When pH exceeds 9.5, Mg <2+ > in seawater will become Mg (OH) 2 , and will precipitate easily. Therefore, the upper limit of the mixing ratio of the steelmaking slag in the “slag mixed soil” is considered to be 50 mass%. The steelmaking slag to be used preferably contains 50% by mass or more of fine slag having a 50% particle size of less than 10 mm from the viewpoint of promoting early solidification of the “slag mixed soil”. Steelmaking slag having a particle size larger than 10 mm is less likely to increase the pH, but conversely, the dissolution rate of calcium ions and silica necessary for accelerating solidification is reduced, so that the solidification rate is reduced. Therefore, it is desirable that the steelmaking slag to be used contains 50% by mass or more of fine slag having a 50% particle size of less than 10 mm and a high dissolution rate of calcium ions and silica.
いずれにせよ、スラグ混合土中の製鋼スラグの混合率は５０質量％以下を目安とし、事前にバッチ実験等を実施し、固化促進と共に近傍の海水のｐＨが８以上９．５以下となるように、浚渫土砂への製鋼スラグの混合率を定めることが望ましい。 In any case, the mixing ratio of steelmaking slag in the slag mixed soil should be 50% by mass or less, and a batch experiment etc. will be carried out in advance, so that the pH of seawater in the vicinity will be 8 or more and 9.5 or less as the solidification is promoted. In addition, it is desirable to determine the mixing ratio of steelmaking slag to dredged soil.
スラグ混合土の圧入抵抗値は、スラグ混合土に用いる浚渫土砂の含水率やＣＯＤ（化学的酸素要求量）が高いと低くなる。本発明では、浚渫土砂の水分量が特に多い場合は、前記「スラグ混合土」中の製鋼スラグ混合率が５０質量％であっても、該スラグ混合土の圧入抵抗値が２０ｋＰａ未満となる場合があることを知見した。このような場合でも、ｐHが上昇し易いため、製鋼スラグ混合率を５０質量％超とすることは困難である。そこで、スラグ混合土の圧入抵抗値が２０ｋＰａ以上となるよう、浚渫土砂に製鋼スラグとともに高炉水砕スラグ微粉を加えて混合し、「スラグ混合土」の固化を促進することが好ましい。 The press-fit resistance value of the slag mixed soil becomes low when the moisture content or COD (chemical oxygen demand) of the dredged sand used for the slag mixed soil is high. In the present invention, when the water content of dredged soil is particularly large, even if the steelmaking slag mixing ratio in the “slag mixed soil” is 50 mass%, the press-fit resistance value of the slag mixed soil is less than 20 kPa. I found out that there is. Even in such a case, since the pH is likely to rise, it is difficult to make the steelmaking slag mixing ratio more than 50 mass%. Therefore, it is preferable to promote solidification of the “slag mixed soil” by adding and mixing the blast furnace granulated slag fine powder together with the steelmaking slag to the dredged soil so that the press-fit resistance value of the slag mixed soil becomes 20 kPa or more.
このような場合に用いる高炉水砕スラグ微粉について説明する。高炉スラグは、高炉で銑鉄を製造する際に生成するスラグの総称である。高炉で溶融された鉄鉱石の鉄以外の成分や副原料の石灰石やコークスの灰分が高炉スラグとなる。高炉スラグは、銑鉄１ｔあたり２９０〜３００ｋｇ程度生成する(スラグ比ｋｇ／ｔ−銑鉄)。高炉から取り出されたばかりのスラグは、約１５００℃の溶融状態にあるが、製造方法(冷却方法)によって、さらに、高炉水砕スラグと高炉徐冷スラグの２種類のスラグに分類される。 The blast furnace granulated slag fine powder used in such a case will be described. Blast furnace slag is a general term for slag generated when pig iron is produced in a blast furnace. Components other than iron of iron ore melted in the blast furnace, limestone of auxiliary raw materials, and ash of coke become blast furnace slag. About 290 to 300 kg of blast furnace slag is produced per ton of pig iron (slag ratio kg / t-pig iron). Slag just taken out from the blast furnace is in a molten state of about 1500 ° C., but is further classified into two types of slag, blast furnace granulated slag and blast furnace slow-cooled slag, depending on the production method (cooling method).
高炉徐冷スラグは、ヤードやピットに高温のスラグを流し込み、自然放冷と適度の散水によってゆっくりと冷却し製造したスラグであり、結晶質・岩石状である。徐冷スラグは、主としてコンクリート用粗骨材やセメントクリンカー原料(粘土代替材)として用いられている。また、１〜３ヶ月の屋外養生処理(以下、エージングと称する)により、硫黄臭や黄濁水の生成防止対策を施した後、道路用の路盤材等にも用いられている。 Blast furnace slow-cooled slag is a slag produced by pouring high-temperature slag into a yard or pit and slowly cooling it by natural cooling and moderate sprinkling. It is crystalline and rocky. Slowly cooled slag is mainly used as coarse aggregate for concrete and cement clinker raw material (clay substitute material). Further, after taking measures for preventing generation of sulfurous odor and cloudy water by outdoor curing treatment for 1 to 3 months (hereinafter referred to as aging), it is also used for roadbed materials and the like for roads.
これに対して、高炉水砕スラグは、約１５００℃の溶融状態にあるスラグに加圧水を噴射し、急激に冷却して製造したスラグであり、非晶質(ガラス質)・粒状である。高炉水砕スラグ微粉は、このような高炉水砕スラグを粉砕処理したもので、強い潜在水硬性を有しており、高炉セメント原料、コンクリート混和剤等に広く使用されている。 On the other hand, granulated blast furnace slag is slag produced by injecting pressurized water into slag in a molten state at about 1500 ° C. and rapidly cooling it, and is amorphous (glassy) and granular. Blast furnace granulated slag fine powder is a pulverized blast furnace granulated slag, has strong latent hydraulic properties, and is widely used in blast furnace cement raw materials, concrete admixtures and the like.
本発明の「スラグ混合土」に用いる高炉スラグは、強い潜在水硬性を有している高炉水砕スラグ微粉である。高炉水砕スラグ微粉は、スラグ混合土中に、浚渫土砂と製鋼スラグとの合計量の０．１質量％以上２質量％以下の範囲で含有することが望ましい。高炉水砕スラグ微粉の使用は、固化促進に対して大きな効果は得られるものの、コスト、操作性の観点から極力小さいことが望ましいが、浚渫土砂と製鋼スラグとの合計量の０．１質量％以下では、顕著な効果は得られない。後述する実施例２に示すように、スラグ混合土中の製鋼スラグ混合率を５０質量％にしても圧入抵抗値が２０ｋＰａ以上に固化が進行し難い浚渫土砂であっても、浚渫土砂と製鋼スラグに加え、高炉水砕スラグ微粉を浚渫土砂と製鋼スラグとの合計量の０．１質量％〜２質量％添加して使用すると、固化促進に対して大きな効果が得られる。圧入抵抗値（１０日後）は、２８ｋＰａ〜１２００ｋＰａに達した。硫化物の生成は、浚渫土砂単独の場合と比較し急速に低下し、圧入抵抗値が２０ｋＰａ以上になると、硫化物は１ｍｇ／Ｌ以下と、浚渫土砂単独の場合と比較し６0％以上低下した。また、圧入抵抗値が５００ｋＰａ以上となると０．３ｍｇ／Ｌ以下、１２００ｋＰａ以上となると検出限界（０．２ｍｇ／Ｌ）以下まで低下した。 The blast furnace slag used in the “slag mixed soil” of the present invention is ground granulated blast furnace slag having strong latent hydraulic properties. Blast furnace granulated slag fine powder is desirably contained in the slag mixed soil in a range of 0.1 mass% to 2 mass% of the total amount of dredged sand and steelmaking slag. Although the use of granulated blast furnace slag fine powder is highly effective in promoting solidification, it is desirable that it be as small as possible from the viewpoint of cost and operability, but 0.1% by mass of the total amount of dredged sand and steelmaking slag In the following, no significant effect is obtained. As shown in Example 2 to be described later, even if the steelmaking slag mixing ratio in the slag mixed soil is 50% by mass, even if it is dredged sand that does not easily solidify to a press-fit resistance value of 20 kPa or more, dredged sand and steelmaking slag. In addition to this, when blast furnace granulated slag fine powder is added and used in an amount of 0.1% by mass to 2% by mass of the total amount of dredged sand and steelmaking slag, a great effect on solidification promotion is obtained. The press-fit resistance value (after 10 days) reached 28 kPa to 1200 kPa. Sulfide formation decreased rapidly compared with dredged sand alone, and when the indentation resistance value was 20 kPa or higher, sulfide decreased to 1 mg / L or less, 60% or lower compared to dredged sand alone. . In addition, when the press-fit resistance value was 500 kPa or more, it was 0.3 mg / L or less, and when it was 1200 kPa or more, it was reduced to a detection limit (0.2 mg / L) or less.
なお、スラグ混合土として、浚渫土砂と製鋼スラグと高炉水砕スラグ微粉とを混合してなるものを製造する場合、スラグ混合土中の製鋼スラグの混合率は特に限定されるものではない。しかし、スラグ混合土中の製鋼スラグの混合率を、近傍の海水のｐＨが９．５以下となる５０質量％以下の範囲で多くするほど、少ない高炉水砕スラグ微粉の含有量で、製造後に海水中で１日〜１０日間養生してから測定したスラグ混合土の圧入抵抗値を２０ｋＰａ以上とすることができ好ましい。 In addition, when manufacturing what mixes dredged sand, steelmaking slag, and blast furnace granulated slag fine powder as slag mixing soil, the mixing rate of steelmaking slag in slag mixing soil is not specifically limited. However, as the mixing rate of steelmaking slag in the slag mixed soil is increased in the range of 50 mass% or less where the pH of the neighboring seawater is 9.5 or less, the content of blast furnace granulated slag fine powder is less after production. The press-fit resistance value of the slag mixed soil measured after curing for 1 to 10 days in seawater is preferably 20 kPa or more.
（実施例１）製鋼スラグを浚渫土砂に混合し固化を促進したスラグ混合土の事例
表４に性状を示したＴ湾浚渫土砂と転炉系製鋼スラグを表５に示す６条件（Ｔ０〜Ｔ５）の割合で混合し、「スラグ混合土」５系列を作製した。なお、事前調査でＴ湾浚渫土砂単独で、表５に示すスラグ混合土を用いた場合の溶存態硫化物濃度を測定する後述する方法と同様にして溶存態硫化物濃度を測定したが、有機物量が少なく硫化物の検出ができなかった。このため、有機物源としてＴ湾浚渫土砂５０ｇ当たりグルコース２５ｍｇを事前に添加し、よく混合した。また、Ｔ湾浚渫土砂はＣＯＤや含水率が比較的低いため、製鋼スラグを用いて固化させやすいことが予想された。
(Example 1) Example of slag mixed soil in which steelmaking slag was mixed with dredged soil and promoted solidification Six conditions shown in Table 5 (T0 to T5) for T bay dredged soil and converter steelmaking slag whose properties are shown in Table 4 ) To produce 5 series of “slag mixed soil”. In the preliminary survey, the dissolved sulfide concentration was measured in the same manner as the method described later for measuring the dissolved sulfide concentration when the slag mixed soil shown in Table 5 was used alone with the T bay dredged soil. The amount was too small to detect sulfide. For this reason, 25 mg of glucose per 50 g of T-bay dredged soil was added in advance as an organic substance source and mixed well. In addition, since T Bay dredged sand has relatively low COD and moisture content, it was expected to be easily solidified using steelmaking slag.
各系列の「スラグ混合土」をガラスびん（容量：１Ｌ）に添加した後、窒素で曝気し溶存酸素（ＤＯ）を除去した表１のイオン濃度の人工海水０．９Ｌを各ガラスびんに添加した。なお、人工海水でなく淡水などがまじっていない実海水をもちいてもかまわない。各系列で計６本作成し、密閉状態、光遮断、室温で１０日間（養生）放置し、１０日後に海水の水質分析を実施した。 After adding each series of “slag mixed soil” to glass bottles (capacity: 1 L), add 0.9 L of artificial seawater with the ion concentration in Table 1 that was aerated with nitrogen to remove dissolved oxygen (DO). did. It is also possible to use real seawater that is not artificial water and not fresh water. A total of 6 bottles were prepared for each series, and were allowed to stand for 10 days (curing) in a sealed state, light-blocked, and room temperature, and after 10 days, water quality analysis of seawater was performed.
硫化物は、分析過程で散逸し易いため、以下の方法で分析した。１０日後に容器中の海水を０．４５μｍフィルター（ミリポア社製）を充填した注射器で採取し、ろ過海水とした。このろ過海水に硫酸（容積比で水１と硫酸１を混合した液）を添加し、窒素曝気し、硫化水素を発生させ、生成した硫化水素を酢酸亜鉛溶液でＺｎＳとして固定化した。その後、ＺｎＳを再溶解させ、よう素滴定法で１０日後にろ過海水中に存在している硫化物濃度を測定した（以下、溶存態硫化物濃度）。
また、ｐH計によって、ろ過海水のｐHを測定した。
Since sulfide is easily dissipated in the analysis process, it was analyzed by the following method. Ten days later, the seawater in the container was collected with a syringe filled with a 0.45 μm filter (Millipore) and used as filtered seawater. Sulfuric acid (a liquid in which water 1 and sulfuric acid 1 were mixed in a volume ratio) was added to the filtered seawater, aerated with nitrogen to generate hydrogen sulfide, and the generated hydrogen sulfide was immobilized as ZnS with a zinc acetate solution. Thereafter, ZnS was redissolved, and the sulfide concentration present in the filtered seawater was measured 10 days later by iodine titration (hereinafter referred to as dissolved sulfide concentration).
The pH of the filtered seawater was measured with a pH meter.
「スラグ混合土」の圧入抵抗値は、以下のように測定した。表５に示す６条件と同じ割合でＴ湾浚渫土砂と転炉系製鋼スラグとを混合し「スラグ混合土」を１ｋｇ作成する。この「スラグ混合土」１ｋｇを２Lのポリ容器にいれ、海水１Lで容器を満たし、常温・静置で１０日間（養生）放置した。その後、１０日後の「スラグ混合土」表面の複数点（５か所）の圧入抵抗値を山中式硬度計によって測定した。
Ｔ湾浚渫土砂（Ｔ０）及び「スラグ混合土砂（Ｔ１〜Ｔ５）」の１０日後の圧入抵抗値と溶存態硫化物濃度を表６に、また、スラグ混合土を製造後、１０日間養生した後の圧入抵抗値と溶存態硫化物濃度の関係を図２に示す。
The press-fit resistance value of “slag mixed soil” was measured as follows. T bay dredged sand and converter steelmaking slag are mixed at the same rate as the six conditions shown in Table 5 to make 1 kg of “slag mixed soil”. 1 kg of this “slag mixed soil” was placed in a 2 L plastic container, filled with 1 L of seawater, and allowed to stand at room temperature for 10 days (curing). Thereafter, the press-fit resistance values at a plurality of points (five places) on the surface of the “slag mixed soil” 10 days later were measured with a Yamanaka hardness tester.
Table 6 shows the indentation resistance value and dissolved sulfide concentration after 10 days for T-bay dredged soil (T0) and “slag mixed soil (T1 to T5)”, and after curing the slag mixed soil for 10 days The relationship between the press-fit resistance value and the dissolved sulfide concentration is shown in FIG.
Ｔ湾浚渫土砂（Ｔ０）の場合、１０日後の圧入抵抗値は０ｋＰａであり、溶存態硫化物濃度は２．４ｍｇ／Ｌまで上昇した。本硫化物濃度は（１）式から４．８ｍｇ／Ｌの溶存酸素（ＤＯ）を消費し、海域底層の貧酸素化を招いてしまうと考えられる。 In the case of T bay dredged soil (T0), the press-fit resistance value after 10 days was 0 kPa, and the dissolved sulfide concentration increased to 2.4 mg / L. It is considered that this sulfide concentration consumes 4.8 mg / L of dissolved oxygen (DO) from the equation (1), leading to poor oxygenation in the ocean bottom.
一方、製鋼スラグを浚渫土砂に混合した「スラグ混合土」の場合、固化は容易に進行した。製鋼スラグの混合率が９質量％のＴ２系では、１０日後の圧入抵抗値が２０ｋＰａ以上に達し、溶存態硫化物濃度は１ｍｇ／Ｌ以下まで低下していた。溶存態硫化物濃度が１ｍｇ／Ｌ以下であれば、通常の海域では５ｍｇ／Ｌ以上の溶存酸素が存在するため、極端な貧酸素化を防止でき、海域底層の溶存酸素を３ｍｇ／Ｌ以上に維持することは可能と思われる。このように、浚渫土砂に対して製鋼スラグを比較的少量混合することによって、固化が進行すると共に、顕著な溶存態硫化物削減率が得られた。 On the other hand, in the case of “slag mixed soil” in which steelmaking slag was mixed with dredged soil, solidification proceeded easily. In the T2 system in which the steelmaking slag mixing ratio was 9% by mass, the press-fit resistance value after 10 days reached 20 kPa or more, and the dissolved sulfide concentration decreased to 1 mg / L or less. If the dissolved sulfide concentration is 1 mg / L or less, since there is 5 mg / L or more of dissolved oxygen in the normal sea area, extreme hypoxia can be prevented, and the dissolved oxygen in the bottom of the sea area is 3 mg / L or more. It seems possible to maintain. Thus, by mixing a relatively small amount of steelmaking slag with dredged soil, solidification progressed and a remarkable dissolved sulfide reduction rate was obtained.
さらに、１０日後の海水中の溶存態硫化物濃度は、「スラグ混合土」の１０日後の圧入抵抗値が５００ｋＰａ以上となるＴ３系では０．３ｍｇ／Ｌ、「スラグ混合土」の１０日後の圧入抵抗値が２０００ｋＰａ以上となるＴ４、Ｔ５系では、溶存態硫化物濃度は検出限界（０．２ｍｇ／Ｌ）以下まで低下していた。
したがって、スラグ混合土の圧入抵抗値の下限が２０ｋＰａ以上となるように浚渫土砂に製鋼スラグを混合すれば、海域底層の貧酸素化を防止できると共に、スラグ混合土の圧入抵抗値が５００ｋＰａ以上となるように製鋼スラグを混合し固化を促進すれば、硫化物の影響は無視できる程度まで改善されると思われる。
Furthermore, the dissolved sulfide concentration in the seawater after 10 days is 0.3 mg / L in the T3 system where the indentation resistance value after 10 days of “slag mixed soil” is 500 kPa or more, and 10 days after “slag mixed soil”. In the T4 and T5 systems in which the press-fit resistance value is 2000 kPa or more, the dissolved sulfide concentration was lowered to the detection limit (0.2 mg / L) or less.
Therefore, if steelmaking slag is mixed with dredged sand so that the lower limit of the indentation resistance value of the slag mixed soil is 20 kPa or more, it is possible to prevent anoxic formation of the bottom of the sea area and the indentation resistance value of the slag mixed soil is 500 kPa or more. If steelmaking slag is mixed and the solidification is promoted, the influence of sulfides will be improved to a negligible level.
また、「スラグ混合土」中の製鋼スラグ混合率とスラグ混合土を製造後、１０日間養生した海水ｐHの関係を図３に示す。製鋼スラグの混合率が５０質量％であるＴ５系でもｐＨ９．２前後で推移しており、ｐＨ９．５以下に維持されていた。 Moreover, the relationship between the steelmaking slag mixing rate in "slag mixed soil" and the seawater pH cured for 10 days after manufacturing the slag mixed soil is shown in FIG. Even in the T5 system in which the mixing ratio of steelmaking slag was 50% by mass, it was maintained at about pH 9.2 and was maintained at pH 9.5 or less.
（実施例２）製鋼スラグと高炉水砕スラグ微粉を浚渫土砂に混合し固化を促進したスラグ混合土の事例
表７に性状を示したM湾浚渫土砂と転炉系製鋼スラグ及び高炉水砕スラグ微粉を表８に示す６条件（Ｍ０〜Ｍ５）の割合で混合し、「スラグ混合土」５系列を作成した。M湾浚渫土砂は、含水率が６３．３％と高く、さらに、ＣＯＤも１９．７ｍｇ/ｇと高い。このため、浚渫土砂と製鋼スラグとを混合して、製鋼スラグの混合率が５０質量％の混合物としても、混合物を１０日間養生した後の圧入抵抗値が２０ｋＰａ未満と固化し難いことが判った。このように水分やＣＯＤで表示される有機物が多い浚渫土砂の場合は、浚渫土砂に製鋼スラグを単独で添加しても固化を促進することが難しい場合がある。このため、表８に示すように、浚渫土砂に、製鋼スラグに加えて、高炉水砕スラグ微粉を浚渫土砂と製鋼スラグとの合計量の０．１〜２質量％混合した。
(Example 2) Example of slag mixed soil in which steelmaking slag and ground granulated blast furnace slag were mixed with dredged sand to accelerate solidification Fine powder was mixed at a ratio of 6 conditions (M0 to M5) shown in Table 8 to create 5 series of “slag mixed soil”. M Bay dredged sand has a high water content of 63.3%, and COD is also high at 19.7 mg / g. For this reason, it turned out that it is hard to solidify with the press-fit resistance value after less than 20 kPa after mixing for 10 days even if it mixes dredged sand and steelmaking slag and the mixture rate of steelmaking slag is 50 mass%. . Thus, in the case of dredged sand with a lot of organic matter displayed by moisture and COD, it may be difficult to promote solidification even if steelmaking slag is added alone to dredged sand. For this reason, as shown in Table 8, in addition to the steelmaking slag, 0.1-2 mass% of the total amount of the granulated blast furnace slag and the steelmaking slag was mixed with the clay.
また、事前調査でM湾浚渫土砂単独で実施例１と同様にして溶存態硫化物濃度を測定したが、有機物量が少なく硫化物の検出ができなかったため、有機物源としてＭ湾浚渫土砂５０ｇ当たりグルコース２５ｍｇをさらに添加しよく混合した。
各系列の「スラグ混合土」をガラスびん（容量：１Ｌ）に添加した後、窒素で曝気し溶存酸素（ＤＯ）を除去した表１のイオン濃度の人工海水０．９Ｌを各ガラスびんに添加した。人工海水でなく淡水などがまじっていない実海水をもちいてもかまわない。各系列で計６本作製し、密閉状態、光遮断、室温で１０日間（養生）放置し、１０日後に海水の水質分析を実施した。
In addition, the dissolved sulfide concentration was measured in the same way as in Example 1 with M Bay dredged sand alone in the preliminary survey. However, since the amount of organic matter was small and sulfide could not be detected, the organic matter source per 50 g of M Bay dredged soil An additional 25 mg of glucose was added and mixed well.
After adding each series of “slag mixed soil” to glass bottles (capacity: 1 L), add 0.9 L of artificial seawater with the ion concentration in Table 1 that was aerated with nitrogen to remove dissolved oxygen (DO). did. You can use real seawater that is not artificial water and not fresh water. A total of 6 were produced for each series, sealed, light-blocked, allowed to stand at room temperature for 10 days (curing), and water quality analysis of seawater was carried out 10 days later.
硫化物は、分析過程で散逸し易いため、以下の方法で分析した。１０日後に容器中の海水を０．４５μｍフィルター（ミリポア社製）を充填した注射器で採取し、ろ過海水とした。このろ過海水に硫酸（容積比で水１と硫酸１を混合した液）を添加し、窒素曝気し、硫化水素を発生させ、生成した硫化水素を酢酸亜鉛溶液でＺｎＳとして固定化した。その後、ＺｎＳを再溶解させ、よう素滴定法で１０日後にろ過海水中に存在している硫化物濃度を測定した（以下、溶存態硫化物濃度）。
また、ｐH計によって、ろ過海水のｐHを測定した。
Since sulfide is easily dissipated in the analysis process, it was analyzed by the following method. Ten days later, the seawater in the container was collected with a syringe filled with a 0.45 μm filter (Millipore) and used as filtered seawater. Sulfuric acid (a liquid in which water 1 and sulfuric acid 1 were mixed in a volume ratio) was added to the filtered seawater, aerated with nitrogen to generate hydrogen sulfide, and the generated hydrogen sulfide was immobilized as ZnS with a zinc acetate solution. Thereafter, ZnS was redissolved, and the sulfide concentration present in the filtered seawater was measured 10 days later by iodine titration (hereinafter referred to as dissolved sulfide concentration).
The pH of the filtered seawater was measured with a pH meter.
「スラグ混合土」の圧入抵抗値は、以下のように測定した。表９に示す６条件と同じ割合でＴ湾浚渫土砂と転炉系製鋼スラグとを混合し「スラグ混合土」を１ｋｇ作成する。この「スラグ混合土」１ｋｇを２Lのポリ容器にいれ、海水１Lで容器を満たし、常温・静置で１０日間（養生）放置した。その後、１０日後の「スラグ混合土」表面の複数点（５か所）の圧入抵抗値を山中式硬度計によって測定した。
Ｔ湾浚渫土砂（Ｍ０）及び「スラグ混合土砂（Ｍ１〜Ｍ５）」の１０日後の圧入抵抗値と溶存態硫化物濃度を表９に、また、高炉水砕スラグ微粉を含むスラグ混合土を製造後、１０日間養生した後の圧入抵抗値と溶存態硫化物濃度の関係を図４に示す。
The press-fit resistance value of “slag mixed soil” was measured as follows. T bay dredged sand and converter steelmaking slag are mixed at the same rate as the six conditions shown in Table 9 to make 1 kg of “slag mixed soil”. 1 kg of this “slag mixed soil” was placed in a 2 L plastic container, filled with 1 L of seawater, and allowed to stand at room temperature for 10 days (curing). Thereafter, the press-fit resistance values at a plurality of points (five places) on the surface of the “slag mixed soil” 10 days later were measured with a Yamanaka hardness tester.
Table 9 shows the pressure resistance and dissolved sulfide concentration after 10 days for T-bay dredged soil (M0) and “slag mixed soil (M1 to M5)”, and also produces slag mixed soil containing ground granulated blast furnace slag. FIG. 4 shows the relationship between the press-fit resistance value and the dissolved sulfide concentration after curing for 10 days.
Ｍ湾浚渫土砂（Ｍ０）の場合、１０日後の圧入抵抗は０ｋＰａであり、溶存態硫化物濃度は２ｍｇ／Ｌ以上まで上昇した。本硫化物濃度は（１）式から４ｍｇ／Ｌ以上の溶存酸素（ＤＯ）を消費し、海域底層の貧酸素化を招いてしまうと考えられる。一方、製鋼スラグと高炉水砕スラグ微粉を浚渫土砂に混合した「スラグ混合土」の場合、固化は容易に進行した。 In the case of M Bay dredged soil (M0), the indentation resistance after 10 days was 0 kPa, and the dissolved sulfide concentration increased to 2 mg / L or more. It is considered that this sulfide concentration consumes 4 mg / L or more of dissolved oxygen (DO) from the formula (1), leading to poor oxygenation in the sea bottom. On the other hand, in the case of “slag mixed soil” in which steelmaking slag and ground granulated blast furnace slag were mixed with dredged soil, solidification proceeded easily.
高炉水砕スラグ微粉の混合率が０．１質量％のＭ１系では、１０日後の圧入抵抗値が２０ｋＰａ以上に達し、また、溶存態硫化物濃度は１ｍｇ／Ｌ以下まで低下した。溶存態硫化物濃度が１ｍｇ／Ｌ以下であれば極端な貧酸素化を防止でき、海域底層の溶存酸素を３ｍｇ／Ｌ以上に維持することは可能と思われる。このように、浚渫土砂に対して製鋼スラグ単独では固化しにくい土砂の場合、高炉水砕スラグ微粉を比較的少量混合することによって、固化が進行し、同時に溶存態硫化物を削減できる。 In the M1 system in which the mixing ratio of ground granulated blast furnace slag was 0.1% by mass, the press-fit resistance value after 10 days reached 20 kPa or more, and the dissolved sulfide concentration decreased to 1 mg / L or less. If the dissolved sulfide concentration is 1 mg / L or less, extreme hypoxia can be prevented, and it is possible to maintain the dissolved oxygen in the sea bottom at 3 mg / L or more. Thus, in the case of the earth and sand which is hard to solidify with the steelmaking slag alone with respect to the dredged sand, the solidification progresses by mixing a relatively small amount of ground granulated blast furnace slag, and at the same time the dissolved sulfide can be reduced.
さらに、１０日後の海水中の溶存態硫化物濃度は、「スラグ混合土」の１０日後の圧入抵抗値が５００ｋＰａ以上となるＭ４系では０．３ｍｇ／Ｌ以下、「スラグ混合土」の１０日後の圧入抵抗値が１０００ｋＰａ以上となるＭ５系では、検出限界（０．２ｍｇ／Ｌ）以下まで低下した。 Furthermore, the dissolved sulfide concentration in the seawater after 10 days is 0.3 mg / L or less in the M4 system in which the press-fit resistance value after 10 days of “slag mixed soil” is 500 kPa or more, 10 days after “slag mixed soil” In the M5 system in which the press-fit resistance value is 1000 kPa or more, it decreased to the detection limit (0.2 mg / L) or less.
したがって、スラグ混合土の圧入抵抗値の下限が２０ｋＰａ以上となるように浚渫土砂に製鋼スラグ及び高炉水砕スラグ微粉を混合すれば、海域底層の貧酸素化を防止できると考えられる。また、スラグ混合土の圧入抵抗値が５００ｋＰａ以上となるように浚渫土砂に製鋼スラグ及び高炉水砕スラグ微粉を混合し固化を促進すれば、硫化物の影響は無視できる程度まで改善されると思われる。 Therefore, if steelmaking slag and ground granulated blast furnace slag are mixed with dredged sand so that the lower limit of the press-fitting resistance value of the slag mixed soil is 20 kPa or more, it is considered that the poor oxygenation of the sea area bottom layer can be prevented. In addition, if the steelmaking slag and ground granulated blast furnace slag are mixed with dredged soil so that the indentation resistance value of the slag mixed soil is 500 kPa or more and solidification is promoted, the effect of sulfide will be improved to a negligible level. It is.
また、「スラグ混合土（Ｍ１〜Ｍ５）」は、製鋼スラグの混合率が５０質量％以下で一定であったため、いずれの「スラグ混合土（Ｍ１〜Ｍ５）」の１０日後のｐHも９．２前後で推移しており、ｐＨ９．５以下に維持されていた。高炉水砕スラグ微粉添加のｐHへの影響はほぼ無視できる。
また、本検討では製鋼スラグの混合率は、浚渫土砂と製鋼スラグとの混合物の５０質量％で一定であったが、高炉水砕スラグ微粉を混合して、１０日後の圧入抵抗が２０ｋＰａ以上に達するのであれば、製鋼スラグの混合率を５０質量％以下としてもかまわない。
In addition, since the “slag mixed soil (M1 to M5)” had a constant steelmaking slag mixing rate of 50% by mass or less, the pH after 10 days of any “slag mixed soil (M1 to M5)” was 9. It was maintained at around 2, and was maintained at pH 9.5 or lower. The effect of blast furnace granulated slag fine powder addition on pH is almost negligible.
In this study, the mixing ratio of steelmaking slag was constant at 50% by mass of the mixture of dredged sand and steelmaking slag, but the blast furnace granulated slag fine powder was mixed and the press-fit resistance after 10 days was 20 kPa or more. If it reaches, the mixing rate of the steelmaking slag may be 50% by mass or less.
Claims (7)
少なくとも浚渫土砂と製鋼スラグとを混合してスラグ混合土を製造する混合工程と、
前記スラグ混合土を用いて前記浚渫窪地を埋め戻す工程とを備え、
前記混合工程において、前記スラグ混合土中の前記製鋼スラグの混合率を、製造後に海水中で１日〜１０日間養生してから測定した前記スラグ混合土の圧入抵抗値が２０ｋＰａ以上となるようにすることを特徴とする浚渫窪地の埋め戻し方法。 A method for refilling the underwater depressions to improve the marine environment,
A mixing step of mixing at least dredged soil and steelmaking slag to produce slag mixed soil;
And backfilling the depression using the slag mixed soil,
In the mixing step, the mixing resistance ratio of the steelmaking slag in the slag mixed soil is measured such that the press-fit resistance value of the slag mixed soil measured after curing in seawater for 1 to 10 days is 20 kPa or more. A backfilling method for the Ogikubo land characterized by:
前記試験用混合物の圧入抵抗値を用いて前記スラグ混合土中の製鋼スラグの混合率を決定する混合率決定工程とを備えることを特徴とする請求項１〜７のいずれか１項に記載の浚渫窪地の埋め戻し方法。 Before the mixing step, at least the dredged sand and the steelmaking slag are mixed to produce a test mixture, and a press-fit resistance value of the test mixture is measured;
The mixing rate determination process of determining the mixing rate of the steelmaking slag in the said slag mixing soil using the press-fit resistance value of the said test mixture, The one of Claims 1-7 characterized by the above-mentioned. How to backfill the Ogikubo land.
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| JP2015063881A (en) * | 2013-08-30 | 2015-04-09 | Ｊｆｅスチール株式会社 | Artificial shoal or tidal flat and repair method thereof |
| JP2018065131A (en) * | 2015-05-15 | 2018-04-26 | Ｊｆｅスチール株式会社 | Method for modifying dredge soil |
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|---|---|---|---|---|
| JP2005320230A (en) * | 2004-04-09 | 2005-11-17 | Nippon Steel Corp | Environmental preservation material for water area and its using method |
| WO2010116602A1 (en) * | 2009-03-30 | 2010-10-14 | 新日本製鐵株式会社 | Method for backfilling subaqueous borrow pit |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005320230A (en) * | 2004-04-09 | 2005-11-17 | Nippon Steel Corp | Environmental preservation material for water area and its using method |
| WO2010116602A1 (en) * | 2009-03-30 | 2010-10-14 | 新日本製鐵株式会社 | Method for backfilling subaqueous borrow pit |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103437318A (en) * | 2013-08-29 | 2013-12-11 | 中国水电顾问集团华东勘测设计研究院 | Method for calculating and predicating post-construction settlement of suspension seawall |
| CN103437318B (en) * | 2013-08-29 | 2015-09-09 | 中国水电顾问集团华东勘测设计研究院 | The settlement after construction computational prediction method of floated sea wall |
| JP2015063881A (en) * | 2013-08-30 | 2015-04-09 | Ｊｆｅスチール株式会社 | Artificial shoal or tidal flat and repair method thereof |
| JP2018065131A (en) * | 2015-05-15 | 2018-04-26 | Ｊｆｅスチール株式会社 | Method for modifying dredge soil |
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