JP2007154646A - Construction method for placing steel slag under water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction method by which steel slag can be placed stably under water to enable easy construction of an underwater structure having high stability against waves. <P>SOLUTION: A material mainly composed of steel slag is put in a water permeable container, which is then placed under the water to cause the material in the container to set due to the hydraulic setting effect of the slag. Preferably, following the setting of the material in the container, at least the main portion of the container is caused to disappear due to decomposition or/and corrosion. Natural setting of the material in the container due to the hydraulic setting effect of the slag prevents the material from flowing out, which allows easy construction of an underwater structure, etc., having high stability against waves. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a construction method for installing slag generated in a steel manufacturing process underwater, and relates to a construction method suitable for constructing a structure or a foundation in water using the slag.

  For the purpose of coastal conservation (prevention of coastal erosion) and shallow ground creation, a submerged dike is installed at the bottom of the coastal sea area. Such a submerged dike is generally constructed by stacking rubble and concrete blocks on the bottom of the water. In some cases, a rubble foundation is installed at the bottom of the water, and concrete blocks are stacked on top of it to construct a submerged dike.

However, it is difficult to procure natural crushed stone used as rubble every year. Generally, large stones with high resistance to waves are required for offshore construction, but the procurement of such natural stones is becoming particularly difficult. Furthermore, recently, the destruction of natural stones has also become a problem. In addition, the concrete block has a problem of high cost, and further, there is a problem that the environment of the installation sea area is temporarily deteriorated because the block surface is dense and there is no gap, and thus the initial biocompatibility is inferior.
On the other hand, massive steel-making slag having a particle diameter of about 20 to 50 mm has been manufactured as civil engineering materials such as roadbed materials. Patent Document 1 describes the construction of a submerged dike using such massive steel-making slag. Has been shown to do. Steelmaking slag is slag generated in the steel manufacturing process (steel slag), and has an advantage that it can be procured at low cost and in large quantities.
JP 2002-238401 A

However, when a massive steelmaking slag having a particle size of about 20 to 50 mm is used as a submerged levee material as in Patent Document 1, the submerged levee material is washed away by a large wave or the like, and the submerged levee is greatly damaged or severe. The submarine itself collapses and disappears. That is, there is a problem that the submerged dike constructed with massive steelmaking slag has low wave stability.
In addition, for example, it is conceivable to use massive steelmaking slag in construction of revetments, foundations of foundations and foundations, etc., but in this case as well as the above-mentioned submerged dike, there is a big problem in wave stability.
Therefore, the object of the present invention is to stably install steel slag in the water, and thus, it is possible to easily construct an underwater structure or foundation / base having high wave stability using the steel slag. It is to provide a construction method.

  The present inventors have studied to solve the above problems, and as a result, put a material mainly composed of steel slag in a water-permeable container, put this container in water, and put the material in the container into the water of the slag. By solidifying by hard action, materials mainly composed of steel slag can be stably installed in water without causing outflow due to waves, etc., which makes it easy to construct structures, foundations and foundations with high wave stability. It was found that it can be installed. In addition, preferably, a container that decomposes or corrodes with time in water is used as the container, and the container is made garbage by disintegrating or spontaneously disappearing by decomposition or corrosion after the material in the container is consolidated. Thus, it was found that the constructed structure and the like can be made an environment suitable for living and growing of living organisms without causing environmental pollution.

The present invention has been made on the basis of the findings as described above, and has the following gist.
[1] Put slag generated mainly in the steel manufacturing process (including the case of only slag generated in the steel manufacturing process) into a permeable container and place the container in water. A construction method for installing steel slag underwater, wherein the material in the container is consolidated by the hydraulic action of the slag.
[2] An underwater construction method for steel slag according to the construction method of [1] above, wherein the container is a bag.
[3] In the construction method of [1] or [2] above, the container is a container that decomposes or corrodes over time in water, and after the material in the container is consolidated, at least a main part of the container is A construction method for installing steel slag underwater, wherein the steel slag is eliminated by decomposition or / and corrosion.

[4] In the construction method according to any one of [1] to [3] above, the material in the container is made of an adhesive (however, a uniaxial sample obtained based on “uniaxial compression test method of soil” in JIS A 1216) A construction method for installing steel slag underwater, characterized in that the slag is consolidated so that the compression strength (qu) is 15 kN / m ² or more.
[5] In the construction method according to any one of [1] to [3] above, the material in the container is made of an adhesive (however, the uniaxial sample obtained based on the “uniaxial compression test method for soil” in JIS A 1216) A construction method for installing steel slag underwater, characterized in that the slag is consolidated so that a compressive strength (qu) is 20 kN / m ² or more.
[6] In the construction method according to any one of the above [1] to [5], in order to install steel slag in water, the material in the container is characterized in that the ratio of granulated blast furnace slag is 30 mass% or more. Construction method.
[7] To install steel slag underwater in the construction method according to any one of [1] to [6] above, wherein at least a part of the submerged dike outer layer is constructed by a container containing material. Construction method.

  According to the construction method of the present invention, the material in the container is naturally consolidated after construction by utilizing the hydraulic action of the steel slag, so that the material mainly composed of the steel slag is submerged without causing outflow due to waves or the like. Can be installed stably. For this reason, it is possible to easily construct structures, foundations and foundations having high wave stability, and is particularly useful for construction and construction of submerged dikes.

In the construction method of the present invention, a material mainly composed of slag (steel slag) generated in a steel manufacturing process (hereinafter referred to as material A) is placed in a water-permeable container, and the container is placed in water to place the material in the container. A is consolidated by the hydraulic action of the slag. Since the material A is contained in the container, there is no fear of flowing out by waves or the like, and high wave stability is obtained even if the container disappears after consolidation.
The container may be moved to the construction site after solidifying the material A in the water other than the construction site (for example, construction site such as structure or foundation) for installing the slag underwater. It is preferable that the material A in the container is consolidated in a state where it is installed at the construction site because the construction is easy.

As the steel slag constituting the material A, blast furnace granulated slag, blast furnace slow-cooled slag (however, this blast furnace slow-cooled slag is preferably sufficiently aged to prevent S from eluting in water), steel making Various slags such as slag and ore reduction slag can be used. 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.
The material A has a granular or / and massive shape, and a particle size of about 100 mm or less is usually usable. Normally used steelmaking slag has a particle size of 85 mm or less, and blast furnace granulated slag has a particle size of 5 mm or less. However, when it is already consolidated, a particle having a larger particle size can be used.
The material A may be composed only of the steel slag, but it is one or more kinds of granular materials and aggregates other than the steel slag, such as natural sand, natural crushed stone, artificial sand processed natural crushed stone, and recycled concrete. Can be included as long as the caking properties are not impaired. However, since the present invention consolidates the material A using the hydraulic action of steel slag, the material A is mainly composed of steel slag, that is, the ratio of steel slag is 50 mass% or more, Preferably it is 70 mass% or more.

Usually, the operation | work which puts the material A in a container is performed on land or a ship.
The container needs to be permeable to water. However, in the case of a container having water permeability, the material constituting the container is non-permeable, in addition to the material itself constituting the container being water permeable. A container having a gap or a hole through which water can permeate is also included.
Here, the water permeability of the container may be a water permeability that allows water to permeate the material A in the container, and does not require water permeability such that seawater exchange is performed. Rather, it is preferable to reduce seawater exchange as much as possible in order to accelerate the consolidation of the material A in the container. From this point of view, the container has a sheet bag body having a gap enough to allow water to permeate and low water permeability. It is preferable to use a net bag or the like.
In addition, in order to build up a structure or the like by stacking containers according to the shape of the water bottom or the like, it is preferable that the container containing the material A can be deformed. From this viewpoint, the container is a bag (for example, a flexible container bag in general). It is preferable that the container is a so-called bag body), but may be a container having a certain degree of rigidity (for example, a box, a bag, etc.).

In the method of the present invention, the material A in the container is consolidated by the hydraulic action of the slag, and even after the container disappears, the adhesive force (consolidating force) necessary for obtaining high wave stability is provided. is there. Specifically, the adhesive strength of the material A in the container (however, a value of ½ of the uniaxial compressive strength qu of the sample obtained based on the “uniaxial compressive test method of soil” of JIS A 1216) is 15 kN / It is preferable to solidify such that m ² or more, desirably 20 kN / m ² or more, and particularly desirably 35 kN / m ² or more. The reason for limiting the adhesive strength will be described later.
The material A needs to be consolidated in a relatively short time due to the hydraulic action of the slag. For example, the material A is in a predetermined consolidated state (desirably within 6 months, preferably within 3 months after the container is placed in water). Is preferably 15 kN / m ² or more, more preferably 20 kN / m ² or more, and particularly preferably 35 kN / m ² or more.

As material A, a blast furnace granulated slag single material as shown below, a mixed material of blast furnace granulated slag + steelmaking slag, a mixed material of blast furnace granulated slag + steelmaking slag + sea sand, and a single steelmaking slag material are consolidated. A test was conducted. Here, both the granulated blast furnace slag and the steelmaking slag (decarburized slag) had a CaO content of 30 mass% or more and a ratio of a particle size of 2 mm or less was 20 mass% or more.
Material (a): Blast furnace granulated slag only Material (b): Blast furnace granulated slag (mass ratio: 2) + Steelmaking slag (mass ratio: 1)
Material (c): Blast furnace granulated slag (mass ratio: 1) + steelmaking slag (mass ratio: 1)
Material (d): Blast furnace granulated slag (mass ratio: 1) + steelmaking slag (mass ratio: 1) + sea sand (mass ratio: 1)
Material (e): Blast furnace granulated slag (mass ratio: 1) + steelmaking slag (mass ratio: 2) + sea sand (mass ratio: 2)
Material (f): Steelmaking slag only

In this test, a plastic container of φ100 mm × H200 mm is filled with artificial seawater, each material (a) to (f) is dropped freely from the position 10 cm above it and filled into the plastic container, and then the upper surface is ground. This was used as a specimen. Among the specimens of each material, one is left as it is (uncoated specimen), and the other is wrapped with medical gauze (coated specimen) on the upper surface of the container, and a water tank containing artificial seawater as shown in FIG. (Inside the room), while reciprocating flow was applied, the number of days until the adhesive strength of each material reached 20 kN / m ² or more (however, 91 days was the upper limit) and the material flowability were examined. The results are shown below.

○ Uncoated specimen Material (a) Adhesive strength after 91 days: 20 kN / m ² or more. The top surface is washed away by a maximum of 8 mm.
Material (b) Adhesive strength after 21 days: 20 kN / m ² or more. The top surface is washed away by up to 3 mm.
Material (c) Adhesive strength after 28 days: 20 kN / m ² or more. The top surface is washed away by up to 3 mm.
Material (d) Adhesive strength after 56 days: 20 kN / m ² or more. The upper surface is washed away by a maximum of 5 mm.
Material (e) Adhesive strength after 91 days: 18 kN / m ² . The upper surface is washed away by a maximum of 5 mm.
Material (f) Adhesive strength cannot be measured even after 91 days (no solidification). The top surface is washed away by a maximum of 1 mm.
○ Coated specimens In both materials (a) to (f), the adhesive strength after the passage of each day is the same as that of the uncoated specimens. However, there is no loss of the top surface of any material.

Moreover, from the viewpoint of caking property, blast furnace granulated slag having high latent hydraulic property is particularly preferable as the steel slag. For this reason, it is preferable that at least a part of the material A (steel slag alone or a mixture of steel slag and other materials) is blast furnace granulated slag. In particular, it is desirable that the material A has a ratio of granulated blast furnace slag of 30 mass% or more, more preferably 50 mass% or more, and further preferably 70 mass% or more.
Here, since the granulated blast furnace slag has a greater adhesive strength after being hydraulic as the particle size is finer, the material A contains blast furnace granulated slag having a particle size of 2 mm or less (under 2 mm sieve) of 20 mass% or more. It is preferred that The reason why the adhesive strength after hydraulic working increases as the particle size of the granulated blast furnace slag becomes fine is that the number of contacts between the slag particles increases. The reason why the particle size is preferable is as follows.

ｅ：間隙比（−）
ｄ：スラグ粒子径（ｃｍ）
で表されるものとすると、接点数Ｎが概ね５００個／ｃｍ^３以上あれば、高炉水砕スラグは水硬作用により固結しやすくなることが本発明者らの実験で確認されている。ここで、スラグ粒子径が２ｍｍ以下のスラグの平均粒径を求めたところ約０．９２ｍｍであり、水中自由落下により堆積したスラグの間隙比は平均で１．０５であったことから、粒径２ｍｍ以下の割合が２０mass％である場合の接点数Ｎを求めると、

となり、材料中に粒径２ｍｍ以下の高炉水砕スラグが２０mass％以上含まれれば、材料が固結しやすい条件であると言える。 The apparent volume of the granulated blast furnace slag is V, and the ratio Vv / Vs between the volume Vs occupied by the slag particles in the slag volume V and the volume Vv of the gap between the slag particles is defined as the slag gap ratio e. When the number of contact points N of slag particles per volume V (cm ³ ) of blast furnace granulated slag is

e: Gap ratio (-)
d: Slag particle diameter (cm)
If the number N of contacts is approximately 500 / cm ³ or more, it has been confirmed by experiments of the present inventors that the granulated blast furnace slag is easily consolidated by hydraulic action. Here, when the average particle diameter of the slag having a slag particle diameter of 2 mm or less was obtained, it was about 0.92 mm, and the gap ratio of the slag deposited by free fall in water was 1.05 on average. When the number of contacts N when the ratio of 2 mm or less is 20 mass%,

If the material contains 20 mass% or more of granulated blast furnace slag having a particle size of 2 mm or less, it can be said that the material is easily consolidated.

For the above reasons, it is preferable that the material A contains 20 mass% or more of granulated blast furnace slag having a particle size of 2 mm or less. Generally, blast furnace granulated slag of 80 mass% or more has a particle size of 2 mm or less. If the ratio of granulated blast furnace slag in A is 30 mass% or more, the above preferable conditions are almost satisfied.
Furthermore, steelmaking slag (particularly preferably, decarburized slag or / and dephosphorized slag) acts effectively as an alkali stimulator for blast furnace granulated slag, so that blast furnace granulated slag and steelmaking slag are mixed at an appropriate ratio. And most preferably used. The above points are supported by the results of the consolidation test mentioned above and the results of Example 2 described later. That is, according to these results, particularly high wave stability is obtained when the mass ratio of granulated blast furnace slag: steel slag is approximately 6: 1 to 1: 1.

Next, the adhesive force that the consolidated material A should have will be described.
This adhesive strength is a value of ½ of the uniaxial compressive strength qu of the sample obtained based on the “uniaxial compression test method of soil” of JIS A1216. In general, the adhesive strength is determined more directly by a triaxial compression test (for example, JGS 0521-2000 soil unconsolidated undrained (UU) triaxial compression test method). This is desirable because the effect of combining is taken into consideration. However, it is not necessary to consider the meshing effect of the slag particles in the design matters such as the loss of the underwater construction material (for example, the submerged dike material) in view of design safety. For this reason, in this invention, adhesive force was prescribed | regulated based on the said uniaxial compression strength qu which can obtain | require the comparatively highly accurate adhesive force more simply and at low cost.
In the method of the present invention, the material A in the container is preferably consolidated so that the adhesive strength is 15 kN / m ² or more, desirably 20 kN / m ² or more, and particularly desirably 35 kN / m ² or more.

In order to investigate the appropriate adhesive strength that the underwater structure should have, a hydraulic model was created by making a submerged dike model as shown in Fig. 2 on a scale of 1/20 of the actual size and allowing irregular waves to act for 48 hours and 96 hours. went. The model had a seabed gradient of 1/50, a water depth of 20 cm, a submerged dike height of 10 cm, a submerged dike width of 30 cm, and a submerged dike gradient of 1/2. The experimental conditions were determined by the fluid similarity law.
There were two types of submerged dike, one constructed with a rectangular concrete block equivalent to an actual 200 kg / piece, and one constructed with clay (adhesive strength was adjusted by adjusting the water content ratio etc.).
Table 1 shows the experimental results. According to this, if the adhesive strength is about 15 kN / m ² or more, preferably about 20 kN / m ² or more, high wave stability can be obtained, and it functions sufficiently as a submerged dike. I understand. It can also be seen that particularly high wave stability can be obtained when the adhesive strength is approximately 35 kN / m ² or more.

In the method of the present invention, a container that decomposes or corrodes with time in water is used as the container, and after the material A in the container is consolidated, at least the main part of the container disappears by decomposition or / and corrosion (natural disappearance). It is particularly preferable to make them.
FIG. 3 shows an embodiment (a submerged longitudinal section) in the case of constructing a submerged dike by this method, and 2 is a container (bag) containing material A (hereinafter referred to as submerged dike material). . In this method, a dike structure 1 (submerged dike) is constructed by placing a dike material in a container 2 that is water permeable and decomposes or / and corrodes over time in water.

  Constructing the container 2 with a material that decomposes and / or corrodes over time in water as in this method, and finally eliminating it spontaneously prevents the container 2 from becoming contaminated and causing environmental pollution. In order to make structures such as submersibles suitable for the inhabiting and growth of living organisms (underwater animals and plants), the granular material solidified on the surface of the structure must be exposed (rock surface) Because it is necessary.

Examples of the material of the container 2 include a biodegradable plastic sheet or net, a plant or plant fiber sheet or net (for example, cocoon, hemp cloth, etc.), a metal foil made of steel, a metal net, or the like. Although it can be used, it is not limited to this. In water (especially in seawater), for example, for several months to one year, at least the main part gradually decomposes and / or corrodes and eventually spontaneously disappears, and the decomposition and corrosion is underwater. Those that do not adversely affect the environment are preferred.
Further, as described above, in order to build up a structure or the like by stacking the containers 2 in accordance with the shape of the water bottom or the like, the containers 2 are preferably bag bodies made of the above materials or the like.
Further, the container 2 may be selected for its type, composition, thickness, etc. so that it does not disappear as long as the material A inside the container 2 does not consolidate and fulfills the necessary anti-flow-off function.

FIG. 4 shows another embodiment (submerged vertical longitudinal section) in the case of constructing a submerged dike, and a container 2 (particularly, a submerged dike material (material A) is placed in the outer layer portion of the dike structure 1. A bag body is preferable), and the inner layer portion is formed by stacking the submerged dike material as it is. Moreover, you may use latent-bank materials other than the material A which this invention prescribes | regulates (for example, 1 type, such as construction residual soil, dredged soil, and massive steel-making slag) for an inner layer part.
FIG. 5 shows an embodiment (a revetment longitudinal section) in the case of constructing an inclined revetment, and a container 2 (particularly a bag body) containing material A as an anchor material for the inclined revetment 3 is installed. The other revetment material 4 is installed on top of it.

The biodegradable plastic used for the container 2 refers to a plastic that is decomposed by microorganisms and finally becomes water and carbon dioxide when placed in an environment such as soil or seawater. This type of plastic has functions (strength, etc.) equivalent to other general plastics under normal use conditions.
There are no particular restrictions on the type of biodegradable plastic used, but for example, polylactic acid mainly made from plant starch such as corn, PHB produced by microorganisms, and bacterial cellulose can be used. When these are used, for example, bacterial cellulose having a high decomposition rate and polylactic acid having a low decomposition rate are mixed, and the decomposition rate of the container 2 can be adjusted by adjusting the mixing ratio thereof.

The biodegradable plastic container 2 is placed in water and then decomposed over time by the microorganisms in the water, eventually disappearing. Select the type and composition of the biodegradable plastic and the thickness of the coating. By doing so, the decomposition / disappearance period in water can be set.
Biodegradable plastic decomposes into CO ₂ and water, so there is no risk of adverse effects on the natural environment.

In addition, the biodegradable plastic container 2 may be a mixture of materials other than the biodegradable plastic or a physical combination of the biodegradable plastic 2 in addition to the one composed entirely of the biodegradable plastic (that is, Covers and containers mainly made of biodegradable plastics are also included. The point is that the main component of the container 2 can be lost by the biodegradable plastic as the main constituent material or component being decomposed and lost over time.
The method of the present invention is suitable for, for example, construction of structures such as submersibles and revetments, construction of various foundations and foundations at the bottom of the water, and particularly suitable for construction and construction of submersibles. Not limited to, it can be applied to any construction work for installing steel slag underwater. In addition, the applicable water areas are not limited to coastal sea areas such as harbors and inland seas, but are also arbitrary such as rivers, estuaries and lakes.

[Example 1]
A mixture of 14 kg of granulated blast furnace slag and 6 kg of dephosphorized slag (steel slag) having a particle size of 40 mm or less is put in a hemp bag. Then, 1000 bodies were put in 5 to 2 m below the sea level. As a result of investigating one month after the introduction, the hemp bag was kept in a deformed state due to the solidification of the internal slag without being swept away by waves. Furthermore, three months after the injection, a sample of slag consolidated from some hemp bags was collected and its adhesive strength was measured. The adhesive strength was 28 kN / m ² .

[Example 2]
A mixture of 850 kg of granulated blast furnace slag and 150 kg of dephosphorized slag (steel slag) having a particle size of 20 mm or less is put into a ton bag made of biodegradable plastic. As a part, 24 bodies were thrown 10 to 3 m below the sea surface in the form shown in FIG. As a result of investigating three months after the injection, the ton bag was kept in a deformed state due to the solidification of the internal slag without being swept away by waves. Moreover, when the sample of the slag solidified from some ton bags was extract | collected and the adhesive force was measured, the adhesive force was 37 kN / m < ² >. Further, when examined one year after the introduction, more than half of the biodegradable plastic ton bag was decomposed and disappeared, and adhesion of shellfish and the like was observed on the solidified slag surface layer.

Explanatory drawing showing the method for conducting the consolidation test of materials Explanatory drawing showing a submerged dike model used for the adhesion test of underwater structures Explanatory drawing which shows one Embodiment (submerged dike longitudinal section) at the time of applying this invention method to construction of a submerged dike Explanatory drawing which shows other embodiment at the time of applying this invention method to construction of a submerged dike (submerged dike longitudinal section) Explanatory drawing which shows one embodiment (the revetment longitudinal section) at the time of applying this invention method to construction of a slope revetment Explanatory drawing which shows the construction situation in an Example

Explanation of symbols

1 Levee structure 2 Container 3 Inclined revetment 4 Revetment material

Claims (7)

  Put slag generated mainly in the steel manufacturing process (including the case of material consisting only of slag generated in the steel manufacturing process) into a water-permeable container and place the container in water A construction method for installing steel slag underwater, wherein the material is consolidated by the hydraulic action of the slag.   The construction method for installing the steel slag according to claim 1, wherein the container is a bag.   The container is a container that decomposes or corrodes over time in water, and after the material in the container is consolidated, at least a main part of the container is lost by decomposition or / and corrosion. The construction method for installing the steel slag of 1 or 2 underwater. Adhesive strength of the material in the container (however, a value of 1/2 of the uniaxial compressive strength qu of the sample obtained based on the “uniaxial compressive test method of soil” of JIS A 1216) is 15 kN / m ² or more. The construction method for installing the steel slag in any one of Claims 1-3 characterized by the above-mentioned. Adhesive strength of the material in the container (however, a value of 1/2 of the uniaxial compressive strength qu of the sample obtained based on the “uniaxial compressive test method of soil” of JIS A 1216) is 20 kN / m ² or more. The construction method for installing the steel slag in any one of Claims 1-3 characterized by the above-mentioned. The construction method for installing steel slag in any one of Claims 1-5 characterized by the ratio of blast furnace granulated slag being 30 mass% or more as for the material in a container.   The construction method for installing steel slag in any one of Claims 1-6 characterized by constructing at least one part of a submerged dike outer layer part with the container which put material.

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