JP2012219479A - Material using steel slag for sand drainage and sand compaction pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material using steel slag for sand drainage and sand compaction pile, which has non-consolidation properties and water permeability.SOLUTION: A material using steel slag for sand drainage and sand compaction pile, which has non-consolidation properties and water permeability, is manufactured by the steps of: kneading steel slag, blast-furnace slag fine powder, and water as main components to manufacture a solidified steel slag hydrated substance; fracturing the solidified steel slag hydrated substance into artificial stones; carbonating the stones for at least 48 hours; and adjusting the particle size of the stones to a predetermined range.

Description

  The present invention is a steel slag used as an alternative to sand used in sand drain (hereinafter also referred to as SD) method or sand displacement pile (hereinafter also referred to as SCP) method of low substitution rate, which is an improved method for soft clay ground. A ground improvement material with excellent non-consolidating properties and water permeability that has the performance as a drain material produced by curing a hydrated solidified body of artificial stone for a predetermined period, followed by carbonization for at least 48 hours and a predetermined particle size adjustment. About.

  Conventionally, as a ground improvement method, an SD method or an SCP method in which a sand pile is placed on a soft clay ground is known.

In the SD method, sand is cast without compaction, and the load of structures such as embankments that are usually constructed after the main method is applied to the soft clay ground as consolidation stress, thereby promoting drainage of the clay ground (drain length Expected to function as a drain material to promote strength increase due to (shortening). The ground improvement effect by this method is only the increase in the strength of soft clay ground due to normal consolidation, and does not consider the strength of the sand piles that have been cast. On the other hand, the SCP method is a method in which a compacted solid sand pile is placed in soft clay ground. Depending on the improvement rate (volume of sand pile / volume of soft ground to be improved), high replacement There are a rate improvement SCP method and a low replacement rate SCP method.
The high replacement rate improved SCP method is usually a method of forcibly replacing soft clay ground with solid sand piles by placing sand piles compacted so that the improvement rate is 70% or more on soft clay ground. Yes, the ground improvement effect is evaluated by the strength of the composite ground obtained by averaging the strength of the soft clay ground and the strength of the compacted solid sand pile by the improvement rate. In this construction method, only the shear strength is the only performance required for the SCP pile.
On the other hand, the low replacement rate SCP method is usually used at an improvement rate of 30% or less, and the ground improvement effect is evaluated by the strength as a composite ground similar to the high replacement rate SCP method. It is possible to expect an increase in strength by promoting consolidation of clay ground between piles. Therefore, the performance required for the SCP pile in this construction method is not only shear strength but also water permeability for promoting consolidation of clay ground.
Furthermore, in order to ensure the consolidation of soft clay ground by the SD construction method and the low replacement rate SCP construction method, in addition to the above water permeability, the soft clay ground is subjected to an increased load due to the load on the ground after SD and SCP improvements. Need to tell.
In particular, in the low replacement rate SCP method, the rigidity of the compacted and strong sand pile is larger than that of soft clay. Therefore, the ratio between the increased stress Δσs of the sand pile and the increased stress Δσc of the clay ground (stress sharing) The ratio n = Δσs / Δσc) is usually in the range of 2 to 4, but when the SCP pile is consolidated and the rigidity increases, the stress sharing ratio is further increased, making it difficult to transmit stress to the clay ground. Since the predetermined consolidation effect cannot be expected, the SCP pile needs to be a non-consolidated material for a predetermined consolidation period (about 6 months).

  In particular, the low replacement rate SCP method has disadvantages such as a longer process and allow subsidence in the case of important structures compared to the high replacement rate SCP method. In recent years, it has been widely used in harbors because it brings about an economic effect by reducing the disposal amount of uplifted soil (soil) of soft clay ground.

  On the other hand, high-quality natural sand has been conventionally used as a material for sand piles used in the SD method and the SCP method, but in recent years, effective use of recycled materials such as steel slag has been promoted from the viewpoint of protecting natural resources. .

  Materials using steelmaking slag, blast furnace slow-cooled slag, and blast furnace granulated slag are known as filling materials for the SCP method. However, because the steel filling slag, blast furnace slow cooling slag, stuffed material for the SCP method using blast furnace granulated slag is hydraulic (consolidation), even if it can be used as a ground improvement material for high replacement, There is a problem that it is difficult to use as it is as a low-replacement ground improvement material that expects consolidation of the ground (see, for example, Non-Patent Documents 1 and 2).

  In addition, it is known that low-substitution SCP material and non-consolidating material use, besides natural sand, copper granulated slag, ferronickel slag, coal ash granulated material, or concrete waste (for example, However, the material using steel slag is not known.

JP 2006-348466 A

Issuance of Coastal Development Technology Center, Steelmaking Slag Use Handbook for Port Construction P19-P20, 2000.3 Issued by Coastal Development Technology Center, Technical manual for using granulated slag for port construction P58-P60, 2007.12. Steel slag hydrated solidified body Technical manual Effective technical manual for steelmaking slag Published by Coastal Development Technology Development Center February 2008

  As a measure for suppressing consolidation of steel slag having hydraulic properties as described above, a method of mixing steel slag with natural sand or natural stone is known. However, when mixing in this way, it takes time to mix them. There is also a problem in terms of protecting natural resources.

The present invention is a non-consolidating low replacement SCP method material that can be applied to SD method and low replacement rate improvement (general improvement rate ≦ 30%) without mixing steel slag with natural sand or natural stone ( That is, an object of the present invention is to provide a low replacement SCP material filling material: a material that is introduced into a steel casing and discharged from the lower end of the steel casing at the time of SCP pile formation.
Moreover, the present invention relates to a non-consolidating SD having a performance as a drain material and a low substitution rate SCP construction material, and setting an artificial stone material obtained by crushing a steel slag hydrated solidified body within a predetermined particle size range, This material is further cured to suppress the remaining hydration reaction, thereby providing a low substitution rate SCP material having non-consolidating properties and water permeability as a drain material (water permeability coefficient k ₁₅ = 10 ⁻³ cm / S or more). The purpose is to provide.

In order to solve the above-mentioned problem advantageously, the sand drain material and the sand compaction pile material using the steel slag of the first invention are made by mixing steelmaking slag, blast furnace slag fine powder and water as main components. After that, it was solidified to produce a hydrated solidified body of steel slag, and an artificial stone material produced by crushing the hydrated solidified body of steel slag was produced by adjusting the carbonization treatment for at least 48 hours and a predetermined particle size. It is characterized by being a non-consolidating and water-permeable material.
In the second invention, in the sand drain material and the sand compaction pile material using the steel slag of the first invention, the artificial stone material has a maximum particle size of 50 mm or less and a 10% passing particle size D ₁₀ of at least 0.00. It is 9 mm, and the curing period M (month) after manufacturing the artificial stone material obtained by crushing the hydrated solidified steel slag satisfies the condition of at least 1.0 month or more.

  Since the material for sand drain and sand compaction pile using steel slag of the present invention is carbonized with the protection of natural resources by effective use of steel slag, the carbon dioxide gas can be reduced by the effective use of carbon dioxide. Contribute.

It is a graph which shows the relationship between the particle size of the SD material using the steel slag made of artificial stone, and the filling material for SCP and the passing weight percentage. It is a graph which shows the relationship between a 10% passage particle size and an initial hydraulic conductivity. For axes 10% passing diameter D ₁₀ of the sand drain material and sand compaction pile material and curing period M (month) using a steel slag consisting of artificial stone, consolidated, a graph showing the relationship between non-caking There is a graph showing a range of conditions with 10% passing diameter D ₁₀ available as a non-caking artificial stone curing period M (month) in the present invention.

    Next, the present invention will be described in detail based on the illustrated embodiment.

  First, the steel slag hydrated solid body used in the present invention is one having any combination shown in Non-Patent Document 3, specifically, steelmaking slag, ground granulated blast furnace slag, and water. , Solidified (cured), and may contain blast furnace granulated slag, fly ash, slaked lime, cement, or two or more alkali stimulants as necessary.

Wherein A steelmaking slag, molten iron, etc. and refining scrap, toughness, CaO produced in the steelmaking process of manufacturing a steel having a processability, a inorganic material as a main component such as SiO _2. In general, it has a crushed stone appearance.

  Steelmaking slag is a by-product mainly composed of lime generated in the steelmaking process. It is a converter slag, hot metal pretreatment slag, decarburization slag, dephosphorization slag, desulfurization slag, desiliconization slag, electric furnace reduction slag, It is a mixture of one or more of furnace oxidation slag, secondary refining slag and ingot slag.

  In the embodiment of the present invention, the curing period (acceleration of hydration reaction by storage) and carbonation treatment after the production of the cured artificial stone material, and the tamped preparation specimen with the particle size range of the cured artificial stone material as factors Skillfully combining the unconsolidated conditions.

Next, an embodiment of the present invention will be described.
(Embodiment)

As shown in Table 1, as steelmaking slag 1397kg / m ^3, blast furnace slag to ^{530kg / m 3, 290kg / m} 3 of water, it was mixed kneaded mixture to solidify by filling in the mold Then, after producing the solidified steel slag, this was crushed to produce an artificial stone material. A sample obtained by sieving the artificial stone sample thus manufactured so as to have a particle size of 50 mm or less is adjusted to the three particle sizes shown in FIG. 1, and is at least 1.0 month or more outdoors (1.0 month or more). After natural curing in a curing period M (month) of ˜2 months), carbonization treatment was performed for 48 hours to produce a sample in which SD material using steel slag made of artificial stone material and a filling material for SCP were screened.
The carbonation treatment is a treatment for accelerating carbonation by placing the sample adjusted to the three particle sizes in a carbon dioxide atmosphere for at least 48 hours.

  Table 2 shows the passing mass percentage of the sample screened in three as described above together with the uniformity coefficient Uc.

Using sand drain material and sand compaction pile material made of steel slag made of artificial stone material that has been screened into the above three, it is packed to the maximum dry density by the Ec method according to the tamping test (JIS A 1220). After each cylindrical specimen (diameter D = 150 mm × height H = 300 mm) was prepared, it was accelerated and cured in a constant temperature water bath at 80 ° C., and a consolidation condition test after 3 months and an initial water permeability test immediately after tamping were conducted. The caking was determined. The determination results are shown in Table 3.
The determination of consolidation is uniaxial compressive strength qu = 30kN / m ² or less so that the specimen can be broken by hand after removing the curing container filled with the material after 3 months of accelerated curing in an 80 ° C water bath. Unconsolidate things.

In the particle size curve A of the lower limit set value indicated by the black triangle (▲) in FIG. 1, as shown in Table 3, the initial hydraulic conductivity is 5.83 × 10 ⁻⁴ cm / s, and the hydraulic conductivity necessary as a drain material. Since 10 ⁻³ cm / s is not satisfied, it can be seen that it cannot be used as a material for a low substitution rate sand compaction pile.
In the particle size curve B of the upper limit set value indicated by the black square (■) in FIG. 1, as shown in Table 3, the initial hydraulic conductivity is 8.46 × 10 ⁻² cm / s and is not less than 1.0 month. It can be seen that it can be used as a filling material for SCP with a low replacement rate because it is not consolidated by curing.
In the particle size distribution curve C of the average set value indicated by a white square (□) in FIG. 1, the initial permeability coefficient is 3.24 × 10 ⁻³ cm / s as shown in Table 3, and the permeability required for the drain material It can be seen that since it satisfies the coefficient of 10 ⁻³ cm / s and does not solidify after curing for 2.0 months or more, it can be used as a material for sand compaction pile with a low substitution rate.

  From FIG. 1 and Table 3, when artificial stone material that has been cured and carbonized is used as a material for SD and low-replacement SCP construction methods, water in the soft ground can be drained as a drain material, and the soft ground can be consolidated. The steel slag hydrated solid body including steelmaking slag can be effectively used.

FIG. 2 shows the relationship between D ₁₀ in the particle size curve shown in FIG. 1 and the initial hydraulic conductivity before curing immediately after tamping shown in Table 3. From this figure, it can be seen that in order to obtain an initial hydraulic conductivity of 10 ⁻³ cm / s or more, it is necessary to use a 10% passing particle diameter (D ₁₀ ) of 0.9 mm or more (at least 0.9 mm). . More preferably, by increasing the initial hydraulic conductivity to 10 ⁻² cm / s or more, a 10% passing particle diameter (D ₁₀ ) that can be expected to further enhance the consolidation is 2.7 mm or more (at least 2.7 mm). It is desirable to use it.
In FIG. 2, E-01 to E-04 are used to mean × 10 ⁻¹ to 10 ⁻⁴ .

FIG. 3 is a graph of the relationship between the 10% passing particle size (D ₁₀ ) and the curing period (month). The sand drain material using steel slag made of non-consolidated artificial stone in the present invention, and It is a graph which shows the range which can be utilized as a material for sand compaction pile. In addition, from this figure, in order to prevent consolidation, the curing period M (month) after manufacturing the artificial stone material crushed steel slag hydrated solidified body is indicated by dotted lines of the consolidation condition and the non-consolidation condition. It can be seen that the upper right range from the boundary line is sufficient.

Claims (2)

  Steelmaking slag, blast furnace slag fine powder and water as main components are kneaded and then solidified to produce a hydrated solidified body of steel slag, and an artificial stone material produced by crushing the hydrated solidified body of steel slag. A sand drain material and a sand compaction pile material using steel slag produced by carbonation treatment for at least 48 hours and a non-consolidating and water-permeable material produced by adjusting to a predetermined particle size . The artificial stone has a maximum particle size of 50 mm or less, a 10% passing particle size D ₁₀ of at least 0.9 mm, and a curing period M (month) after production of the artificial stone obtained by crushing the hydrated solidified steel slag. Satisfying the condition of at least 1.0 month, the sand drain material and the material for sand compaction pile using the steel slag according to claim 1.

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