JP4609701B2 - Method for manufacturing ground improvement material - Google Patents

Description

  The present invention relates to a method for producing a ground improvement material, and more specifically, a ground improvement material using a clay containing calcium carbonate such as straw and shellfish and coal ash produced from a power generation facility. It relates to a manufacturing method.

  In general, dredged soil has the characteristics that the moisture content is extremely high and the strength is low. Therefore, conventionally, for the purpose of reusing such dredged soil, quick lime is mixed with the dredged soil as a main material, and for example, it is called fly ash produced from a power generation facility such as a thermal power plant. There is known a method for producing a ground improvement material by mixing coal ash as an auxiliary material (for example, see Patent Documents 1 to 3).

JP 2001-55756 A JP-A-5-331829 JP-A-5-331830

  By the way, the above-mentioned manufacturing method is intended for general dredged soil, and has a characteristic that it contains calcium carbonate such as dredged and shellfish like dredged soil from the ocean, for example. It is not clarified whether it can be applied to. Therefore, the manufacturing method of the ground improvement material according to the clay containing calcium carbonate is desired.

  In view of the above circumstances, an object of the present invention is to provide a method for producing a ground improvement material capable of producing a ground improvement material suitable for ground improvement by using a clay containing calcium carbonate. To do.

  In order to achieve the above object, a method for producing a ground improvement material according to claim 1 of the present invention is a ground improvement material using dredged soil containing calcium carbonate and coal ash produced from a power generation facility. A dehydration step of dehydrating the clay, and a heating step of obtaining a combustion clay obtained by thermally decomposing the calcium carbonate into calcium oxide by heating the dehydrated clay, A mixing step of obtaining a ground improvement material by mixing the combustion clay and the coal ash.

  According to the method for producing a ground improvement material of the present invention, the calcium carbonate-containing clay is dehydrated in the dehydration step, and the calcium carbonate dehydrated in the heating step is heated to thermally decompose calcium carbonate into calcium oxide. A ground improvement material having calcium oxide and coal ash can be produced by obtaining the combustion clay obtained by mixing the combustion clay and coal ash from the power generation facility in the mixing step. In such a ground improvement material, calcium oxide as a constituent component reacts with moisture in the soil to be ground improved and changes to calcium hydroxide, and this calcium hydroxide reacts with coal ash to cause pozzolanic reaction. Since the soil is solidified, it is possible to generate soil having good strength, which is suitable for ground improvement. Therefore, there is an effect that a ground improvement material suitable for ground improvement can be produced using the clay containing calcium carbonate.

  Exemplary embodiments of a method for producing a ground improvement material according to the present invention will be described below in detail with reference to the accompanying drawings.

  1 to 3 schematically show the respective steps of the ground improvement material manufacturing method according to the embodiment of the present invention. A method for manufacturing a ground improvement material according to an embodiment of the present invention will be described with reference to these drawings as appropriate. The ground improvement material manufacturing method according to the embodiment of the present invention includes a dehydration step, a heating step, and a mixing step.

The dehydration step is a step of dehydrating soil (hereinafter also referred to as collected dredged soil) 10 dredged from undersea soil such as the ocean. More detailed description is as follows. The collected clay 10 contains a large amount of water, clay containing silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), etc., dead bodies of organisms, and organic matter that is effluent from the ground. In addition, for example, calcium carbonate (CaCO ₃ ) such as coral and shellfish is also included. Then, as shown in FIG. 1, the collected clay 10 is put into the dehydration processing apparatus 20 to remove a large amount of water 21 contained in the collected clay 10. Through this process, a clay (hereinafter also referred to as dehydrated clay) 11 that has been subjected to a dehydration treatment is obtained.

  The heating step is a step of heating the dehydrated clay 11, and more specifically, as shown in FIG. 2, the dehydrated clay 11 is put into the heat treatment device 30 and, for example, a heat treatment of 800 ° C. or higher is performed. This is a step of obtaining a clay (hereinafter also referred to as combustion clay) 12 that has been subjected to heat treatment.

Each component which comprises the dewatered clay 11 by such a heating process is as follows. The organic matter composing the dewatered clay 11 is burned into fine ash by being subjected to heat treatment. Calcium carbonate constituting the dehydrated clay 11 is thermally decomposed into quick lime (calcium oxide (CaO)) and carbon dioxide (CO ₂ ) as shown in the following reaction formula (1).

Reaction formula (1): CaCO ₃ → (heating (800 ° C. or higher)) → CaO + CO ₂

  Calcium oxide obtained by thermally decomposing calcium carbonate is the same as the main component of cement. On the other hand, carbon dioxide obtained by thermal decomposition of calcium carbonate is discharged to the outside through the discharge pipe 31 that constitutes the heat treatment device 30.

  The mixing step is a step of mixing the combustion clay 12 and the coal ash 42 called fly ash, and more specifically, as shown in FIG. 3, the combustion clay 12 and the coal as fuel. This is a step of obtaining the ground improvement material 13 by charging the coal ash 42 produced from the thermal power plant 40 to the mixer 50 and performing a mixing process. Here, the coal ash 42 will be described. In general, a thermal power plant 40 using coal as fuel produces coal ash 42 after combustion. The coal ash 42 thus produced is stored in a coal ash storage facility 41 such as a silo, for example. Therefore, in this step, the combustion clay 12 and the coal ash 42 from the coal ash storage facility 41 are charged into the mixer 50 and mixed. Thus, the ground improvement material 13 obtained by the mixing process is enclosed in a predetermined container 13a.

  And after conveying the ground improvement material 13 (the ground improvement material 13 enclosed in the predetermined container 13a) manufactured by the said manufacturing method to the land 60 where a ground improvement is required, as shown in FIG. It sprays on the predetermined location 61 of this land 60, and this ground improvement material 13 and soil are mixed and stirred. As a result, the following reaction occurs between the ground improvement material 13 and the soil at the predetermined location 61.

The calcium oxide composing the ground improvement material 13 changes into calcium ions (Ca ²⁺ ) and calcium hydroxide (Ca (OH) ₂ ) exhibiting strong alkalinity by reacting with moisture in the soil. Calcium ions solidify the soil by reacting with silicon dioxide and aluminum oxide, which are clay components in the soil.

  The calcium hydroxide exhibiting strong alkalinity causes a pozzolanic reaction (solidification reaction) with the coal ash constituting the ground improvement material 13, whereby the soil mixed and stirred with the ground improvement material 13 is gradually solidified. Will do. That is, when a pozzolanic reaction occurs between calcium hydroxide and coal ash, the strength of the soil in which the ground improvement material 13 is mixed and stirred is gradually improved. As a result, soil having good strength can be generated, and the ground of the land 60 can be improved.

  As described above, in the ground improvement material manufacturing method according to the embodiment of the present invention, the collected clay 10 is dehydrated in the dehydration step, and the calcium carbonate in the dehydrated clay 11 is heated to calcium oxide in the heating step. By obtaining the combustion clay 12 obtained by decomposition and mixing the combustion clay 12 and the coal ash 42 in the mixing step, the ground improvement material 13 having calcium oxide and coal ash can be produced. In such a ground improvement material 13, calcium oxide as a constituent component reacts with the moisture of the soil to be ground improved and changes to calcium hydroxide, and this calcium hydroxide reacts with the coal ash 42 and a pozzolanic reaction. Since the soil is solidified, soil having good strength can be generated, which is suitable for improving the ground. Therefore, according to the said manufacturing method, the ground improvement material 13 suitable for ground improvement can be manufactured using the clay containing a calcium carbonate component.

  Moreover, according to the said manufacturing method, as a result of being able to aim at the effective utilization of soil, such as the extraction dredged soil 10, and the coal ash 42, the environmental load by having discarded the coal ash etc. conventionally, ie, environment It is possible to reduce the destruction.

  Furthermore, the ground improvement material 13 manufactured by the above manufacturing method can improve the soft ground that could not be utilized so far.

  Although the preferred embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made. In the above embodiment, the manufactured ground improvement material 13 is transported to the land where the ground improvement is required in a state where the ground improvement material 13 is enclosed in a predetermined container 13a. However, in the present invention, the portable heat treatment device and the mixer are provided. Utilizing this method, after generating burning dredged soil on land that requires ground improvement, the ground improving material may be dispersed and applied to a predetermined portion of the land while being mixed with the soil.

  As described above, according to the method for producing a ground improvement material according to the present invention, for example, ground improvement using dredged soil containing calcium carbonate such as straw and shellfish and coal ash produced from a power generation facility is used. Useful for manufacturing materials.

It is the schematic diagram which showed typically each process of the manufacturing method of the ground improvement material which concerns on embodiment of this invention. It is the schematic diagram which showed typically each process of the manufacturing method of the ground improvement material which concerns on embodiment of this invention. It is the schematic diagram which showed typically each process of the manufacturing method of the ground improvement material which concerns on embodiment of this invention. It is the schematic diagram which showed typically the utilization form of the ground improvement material manufactured by each process of FIGS. 1-3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Sampling clay 11 Dehydration clay 12 Combustion clay 13 Ground improvement material 20 Dehydration processing apparatus 30 Heat processing unit 40 Thermal power plant 42 Coal ash 50 Mixer

Claims (1)

Dredged soil containing calcium carbonate;
A method for producing a ground improvement material using coal ash produced from a power generation facility,
A dehydration step of dewatering the clay;
A heating step of obtaining a burning clay obtained by thermally decomposing the calcium carbonate into calcium oxide by heating the dehydrated clay;
And a mixing step of obtaining a ground improvement material by mixing the combustion clay and the coal ash.

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