JP3733521B2 - Deep mixing method for sandy ground - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a deep mixing treatment method for sandy ground, and in particular, a low-strength soil cement solidified body while ensuring mixing and workability with the original ground, and establishing uniformity and continuity of quality. The present invention relates to a deep mixing treatment method for sandy ground constructed using concrete crushing fine powder.
[0002]
[Prior art]
The deep-mixing method is a method of building a soil cement solidified body by mechanically mixing and stirring the ground and cement-based solidified material in-situ, mainly increasing the strength against soft viscous ground. Conventionally, it has been used as a construction method suitable for construction for the purpose.
[0003]
The construction of the deep mixing method is generally performed in the form shown in FIG. The cement from the cement silo 11 and the water from the water tank 12 are supplied to the cement mixing plant 13 and are kneaded under a predetermined water cement ratio to smelt the cement slurry.
[0004]
The water-cement ratio of cement milk is determined for the purpose of preventing material separation and ensuring fluidity, and may vary depending on the situation. For example, the water-cement ratio (W / C) is around 1.0. Is mixed.
[0005]
The cement slurry from the cement mixing plant 13 is supplied to the deep mixing processor 15 while preventing excessive pulsation by the grout pump 14.
[0006]
The deep-mixing processor 15 uniformly mixes the cement slurry and the raw soil while driving the stirring auger 16, and although not shown, a soil cement solidified body that ensures material uniformity and continuity is constructed. is doing.
[0007]
However, the recent deep mixing treatment method has expanded its application range, and there are many opportunities to apply it to sandy ground for the purpose of preventing liquefaction.
[0008]
However, when the same deep mixing method as in the past is applied to sandy ground, there has been a problem that an excessively hard soil cement solidified body is frequently generated.
[0009]
That is, in the above-mentioned deep mixing treatment method, 200 kg of cement solidified material composed of ordinary cement containing 60 to 65% of CaO and 200 kg of kneaded water are kneaded as a material composition for constructing 1.0 m ^{3 of} soil cement solidified body. Then, when the cement slurry is smelted and this cement slurry is supplied to the deep mixing processor and mixed with 1252 kg of raw earth, CaO reacts sufficiently, so the soil cement solidified body is as follows. Demonstrates uniaxial compressive strength.
[0010]
○ clay ground 500~1000kN / m ^2,
○ sand silt soil 1000~2000kN / m ^2,
○ Sandy ground over 3000kN / m ²
On the other hand, the design strength required for the ground improvement body for the purpose of preventing liquefaction is several hundred kN / m ² at most, and a strength different by one digit is unnecessarily secured.
[0011]
The basic countermeasure to avoid the above situation is to reduce the amount of cement, but this countermeasure is improved for the following reasons, which are characterized by the mechanical stirring construction machine. It is difficult to reduce the cement amount per 0 m ³ to 80 kg or less. (However, the cement slurry is set to W / C = 1.0, and the lifting speed of the stirring auger is set to about 1.0 m / min.)
(1) If the blending amount of cement is 80 kg / m ³ or less, the amount of cement slurry is insufficient, and uniformity cannot be ensured in the mixing of the raw soil and the solidified material.
[0012]
{Circle around (2)} When the amount of cement slurry to be pumped is about 100 liters / min or less, poor pumping of the cement slurry due to pulsation occurs, resulting in poor workability.
[0013]
(3) If the amount of cement contained is reduced while supplementing the above state, solidification failure occurs due to material separation of cement slurry and insufficient concentration, and quality cannot be ensured.
[0014]
In addition to the above, the actual amount of cement slurry in the actual sandy ground is diverted to the surrounding ground, resulting in a substantial increase in the amount of cement blended. The strength of the solidified body is about 1000 kN / m ² . It will be strengthened.
[0015]
Therefore, in order to apply the deep mixing method to sandy ground, it is necessary to take measures to avoid the construction of an excessively solid soil cement solidified body, and a solution for this is still provided. Is in a situation that is not.
[0016]
On the other hand, industrial waste disposal is becoming a social problem, and effective use of industrial waste is required. However, high-priced products are not marketable and difficult to use compared to current competitive products. It has become.
[0017]
Although ground materials, etc. are considered for applications that use a large amount of industrial waste, conventional products of ground materials become low-priced sand and gravel, so new products that can counter this are made. It was difficult.
[0018]
Among industrial waste, concrete generated when rebuilding a building is a relatively safe waste, but its utilization rate remains low for the above reasons, and it is desirable to expand the range of use. ing.
[0019]
[Problems to be solved by the invention]
The present invention has been devised in view of the above situation, so as to be suitable for the purpose of preventing liquefaction in sandy ground, ensuring the mixing and workability with the original ground, the uniformity of quality and We provide a deep mixing method for sandy ground that can be constructed using concrete debris that has been continually established and heated and ground with low-strength soil cement solidified at 300 ° C or higher.
[0020]
[Means for Solving the Problems]
The deep mixing treatment method for sandy ground according to claim 1 comprises the solidification material slurry in the deep mixing treatment method in which the ground and the solidification material slurry are mixed and stirred by a deep mixing treatment machine at the original position. The solidifying material is composed of 10 to 25% CaO, the solidifying material slurry is kneaded at a water powder ratio of around 1.0, and a powder having a specific surface area of 4000 cm 2 / g or more is formed into a slurry. This makes it possible to construct a low-strength soil cement solidified body suitable for the purpose of preventing liquefaction in sandy ground.
[0021]
The deep mixing treatment method for sandy ground according to the second aspect of the invention is the deep mixing treatment method for sandy ground according to the first aspect, wherein the powder is heated and ground at 300 ° C. or higher. In addition to the above functions, it uses materials generated during the processing of concrete waste.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The deep mixing treatment method for sandy ground according to the present invention basically comprises a solidifying material slurry in a deep mixing processing method in which the ground and the solidifying material slurry are mixed and stirred by a deep mixing processing machine in situ. The solidifying material comprises 10 to 25% CaO, and a powder having a specific surface area of 4000 cm ² / g or more is formed into a slurry, and the above conditions are most satisfied at 300 ° C. or more. Utilizing the crushed concrete powder that has been heated and ground, a low-strength soil cement solidified body suitable for the purpose of preventing liquefaction in sandy ground has been constructed.
Embodiments of the present invention will be described below with reference to the drawings.
[0024]
FIG. 1 is a construction process diagram of the deep mixing method for sandy ground according to the present invention.
[0025]
General concrete crushing fine powder is generated when processing concrete waste, and is usually discarded as industrial waste.
[0026]
However, in the embodiment of the deep mixing treatment method for sandy ground according to the present invention, the solidified slurry is formed by kneading the concrete crushed fine powder heated at 300 ° C. or higher and ground with water as a powder. The resulting slurry is used.
[0027]
That is, the component table of the concrete pulverized fine powder shown in FIG. 2 is used as an example of the component of the concrete crushed fine powder that has been heated and ground at 300 ° C. or higher used in the present embodiment. As is clear in the table, the chemical composition of the concrete breaking fines that can be used in sandy system ground for Deep Mixing Method according to the present invention, CaO is 10 to 25%, SiO ₂ is 50~70%, _Al 2 _{O 3} Is 7 to 10%, and Fe ₂ O ₃ is 3 to 7%.
[0028]
In general, CaO acting on the solidification reaction of concrete is contained in the cement state as described above in an amount of 60 to 70%, but the concrete crushing fine powder used in this embodiment is heated and ground at 300 ° C. or higher. Since it has been processed, in the stage where it is formed as concrete crushing fine powder, most of the concrete has completed the solidification reaction, so the content ratio of SiO ₂ that is aggregated and has low reactivity is reduced to about 60%. It is presumed that it has increased, and it forms a different form from the original cement.
[0029]
As described above, the formation of the concrete pulverized fine powder in which the content ratio of SiO ₂ is increased to about 60% is impossible in the heating and grinding process at 300 ° C. or lower, and on the other hand, at 300 ° C. or higher. However, it is difficult to obtain the formation only by the heat treatment, and as described above, it has been confirmed by various experiments that it is constituted only by the heating and grinding process at 300 ° C. or higher.
[0030]
Moreover, FIG. 3 has shown the measurement result of the fineness and specific surface area of the concrete crushing fine powder and normal Portland cement which were used for this Embodiment.
[0031]
The specific surface area is one of the indicators to display the state of the mixed powder or granule, and is expressed as the total surface area per unit mass of the powder or granule particles. Depending on the shape and surface properties.
[0032]
As an example of the specific surface area, assuming a silt composed of a uniform sphere having a diameter of 5 _μm, it is calculated to be about 5000 cm ² / g. A large numerical value is indicated according to the degree of flattening of the shape, and the increase makes the water absorption and colloidal properties of the target particles remarkable.
[0033]
For example, taking clay as an example, the particle size is small and flat, and the surface area is expressed by the outer surface of the particle and the inner surface between the layers, so the specific surface area becomes very large, and the result The increase in specific surface area increases the activity of clay.
[0034]
Returning to FIG. 3 and examining it, it can be seen that in concrete crushing fine powder, there are about 15 to 26% of the residual residue of 150 _μm and about 25 to 36% of the residual residue of 90 _μm fineness. Show. On the other hand, in normal Portland cement, the 150 _μm sieve residue is 0, and even if the fine powder residue is 90 _μm, it is about 1.4%. It reveals that there are very many particles with a _{fineness of} 90 _μm .
[0035]
Thus, the specific surface area is 5300-6520 cm ² / g for the concrete crushed fine powder, whereas the normal Portland cement is 3320 cm ² / g.
[0036]
Thus, while concrete breaking fines comprise about 40.3 to 62.5% a sieve residue of 90 to 150 _mu m, it shows a large specific surface area with respect to ordinary portland cement, this Presumably, it is thought that it contains a lot of very fine particles of 2 _μm or less compared to ordinary cement.
[0037]
In the present embodiment, as shown in FIG. 3, it is confirmed that the specific surface area of the concrete crushed fine powder is in the range of 5300 to 6520 cm ² / g, prevents material separation in the slurry state, and ensures fluidity. However, these functions are ensured at 4000 cm ² / g or more by securing a value larger than the specific surface area of ordinary Portland cement, and in the case of less than 4000 cm ² / g, the solidified material slurry This is because the workability is lowered due to a decrease in viscosity and solidification failure due to material separation.
[0038]
In the cement silo in the present embodiment, the concrete pulverized fine powder composed of the above components and the powder diameter is stored as a mixed powder, and in the following embodiments of the deep mixing treatment method according to the present invention, It is carried out in the construction process shown in FIG.
[0039]
Concrete breaking fines 1 cement silo is fed to a cement mixing plants with water 2 from the water tank, to be drilling powder milk 1.0 m ^3, powder specific and concrete breaking fines 1 and water 752kg of 752kg The powder slurry 3 is smelted on the basis of kneading below about 1.0.
[0040]
The powder slurry 3 from the cement mixing plant is supplied to the deep-mixing processor 4 while preventing excessive pulsation at a pumping rate of 100 l / min or more by a grout pump.
[0041]
The deep layer processor 4 uniformly mixes 100 liters / min of the powder slurry 3 and the raw soil 5 while driving the stirring auger, and ensures uniformity and continuity of the material in units of 1 m ³ . The soil cement solidified body is constructed.
[0042]
The soil cement solidified body constructed by the above steps exhibits a desired low uniaxial compressive strength, and its state is confirmed in comparison with the conventional example in FIG.
[0043]
That is, FIG. 4 shows the uniaxial compressive strength for each material age of a soil cement solidified body constructed using concrete crushed fine powder as a solidified material and a soil cement solidified body constructed using ordinary cement as a solidified material. These experimental results are experimental values in the case of using concrete pulverized fine powder and ordinary Portland cement, both heated and ground at 167 / m ³ unit or more at 300 ° C. or higher.
[0044]
According to this, the soil cement solidified body constructed using ordinary cement as a solidified material increases its strength as the age of the material progresses, and it is 1200 kN / m ² in 7 days and 1750 kN / in 14 days. whereas in m ^2, 35 days are recorded as 2400kN / m ^2, in the soil cement solidified bodies were constructed using concrete breaking fines solidifying material, and 230kN / m ² at the final wood age 35 days The value is reduced to about 1/10 or less, and the strength effective as a ground improvement body by the deep mixing treatment method used for the purpose of liquefaction prevention in sandy ground is formed.
[0045]
As described above, the deep mixing treatment method for sandy ground according to the present invention is as described in detail in the embodiment in which the concrete pulverized fine powder heated and ground at 300 ° C. or higher is used as the solidification material. In the deep layer mixing method in which the ground and the solidified material slurry are mixed and stirred at a position by a deep layer processing machine, the solidified material constituting the solidified material slurry comprises 10 to 25% CaO, and the specific surface area is 4000 cm. ^By constructing a powder of ² / g or more in a slurry state, a low-strength soil cement solidified body suitable for the purpose of preventing liquefaction in sandy ground can be constructed.
[0046]
As described above, the present invention has been described in detail based on the embodiment. However, the present invention is not limited to the above embodiment, and the content of CaO or the like as a solidifying material or the specific surface area of particles is not limited. It does not exclude other examples in the selection of the composition and further the ratio of the water powder for smelting the solidified slurry, and it is obvious that various modifications can be made without departing from the spirit of the present invention. is there.
[0047]
【The invention's effect】
In the deep mixing treatment method for sandy ground of the present invention , the solidification material constituting the solidification material slurry is the deep mixing treatment method in which the ground and the solidification material slurry are mixed and stirred in a deep layer mixing processor in the original position. It is characterized by comprising 10-25% CaO and having a specific surface area of 4000 cm 2 / g or more in the form of a slurry, so it has a low strength suitable for the purpose of preventing liquefaction in sandy ground It is effective in building solid soil cement.
[0048]
In addition, sandy-based soil for Deep Mixing method of the present invention, since is characterized by kneading the solid-reduction material slurry before and after Mizuko isomer ratio 1.0, in addition to the above effects, a slurry-like material Prevents the separation of the liquid and exhibits the effect of ensuring fluidity.
[0049]
Sandy type soil for Deep Mixing method of the present invention, since the heating and sliding the powder at 300 ° C. or higher is also characterized in that it constitutes a real treated concrete breaking fines, in addition to the above effects, the concrete blocks Utilizing materials generated in the treatment process, it has the effect of utilizing and reducing industrial waste.
[Brief description of the drawings]
[Fig. 1] Construction process of the deep mixing treatment method for sandy ground according to the present invention [Fig. 2] Chemical composition of concrete crushing fine powder used in the deep mixing treatment method for sandy ground according to the present invention [Fig. 3] Concrete crushing Test result showing fineness and specific surface area of fine powder and ordinary cement [Fig. 4] Uniaxial compressive strength of soil cement solidified body constructed by the deep sand mixing method for sandy ground according to the present invention [Fig. 5] Conventional deep layer Layout of equipment / equipment used in the mixed processing method [Explanation of symbols]
1 concrete crushing fine powder, 2 water, 3 powder slurry,
4 deep mixing processing machine, 5 raw soil,
11 cement silos, 12 water tanks,
13 cement mixing plant, 14 grout pump,
15 deep mixing machine, 16 stirring auger,

Claims (2)

It is a deep layer processing method that mixes and stirs the ground and the solidified material slurry with a deep layer processing machine at the original position,
The solidifying material constituting the solidifying material slurry comprises 10 to 25% CaO;
The solidifying material slurry is kneaded at a water powder ratio of around 1.0,
A deep mixing treatment method for sandy ground, characterized by comprising a powder having a specific surface area of 4000 cm ² / g or more. The deep mixing treatment method for sandy ground according to claim 1, wherein the powder is composed of a concrete pulverized fine powder heated and ground at 300 ° C or higher.

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