Dust suppression method

Abstract

To provide a dust suppression method realizing excellent dust suppression in low cost.SOLUTION: A dust suppressing method capable of effectively suppressing dust from the ground is to spray mixed material including calcium carbonate and phosphoric acid solution on the ground using a hydroseeder. The sprayed mixed material forms a layer in which phosphoric acid produced through chemical reaction of calcium carbonate and phosphoric acid is included on the ground to realize excellent duct suppression effect. Further, material cost can be reduced by using crushed shell (such as oyster shell) for calcium carbonate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a dust suppression method that is applied to civil engineering work sites and the like. [Background technology]

[0002] At civil engineering construction sites such as land development work, dust can be generated from the ground due to strong winds and the movement of construction vehicles. This dust can be inhaled by workers and cause health problems, and can also cause problems with third parties, including nearby residents. Current dust control measures include laying steel plates under the vehicle running areas, sprinkling water using a water truck (see, for example, Patent Document 1), installing dustproof nets (see, for example, Patent Document 2), and covering the ground with sheets (e.g., blue tarps). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-154939 [Patent Document 2] JP 2018-105013 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, while conventional dust control measures can be expected to be effective to a certain extent, they do not provide a fundamental solution, and there is an issue that the effectiveness is insufficient compared to the cost and effort required for the measures. [Means for solving the problem]

[0005] The present invention was created in view of the above-mentioned circumstances and with the aim of solving these problems. The invention of claim 1 is a dust suppression method for suppressing the generation of dust from the ground, characterized by scattering a mixed material containing calcium carbonate and an aqueous solution of phosphoric acid on the ground. The invention of claim 2 is the dust suppression method according to claim 1, characterized in that the calcium carbonate is crushed seashells. The invention of claim 3 is the dust suppression method according to claim 2, characterized in that the shells are oyster shells. The invention of claim 4 is the dust suppression method according to claim 1, characterized in that the mixed material further contains sand. The invention of claim 5 is the dust suppression method according to claim 1, characterized in that the mixed material is spread using a hydroseeder. [Effects of the Invention]

[0006] According to the invention of claim 1, a layer containing calcium phosphate compounds can be formed on the ground through a chemical reaction between calcium carbonate and phosphoric acid. Calcium phosphate compounds have hardening properties and exhibit excellent strength, so they can suppress the generation of dust from the ground for a long period of time. Furthermore, according to the invention of claim 2, the calcium carbonate is made from crushed shells, so that material costs can be reduced by utilizing shells that would otherwise be treated as waste. Furthermore, according to the invention of claim 3, the shells are oyster shells, which are discarded in large quantities at oyster farms, thereby further reducing material costs. According to the invention of claim 4, the mixed material further contains sand, which functions as aggregate and can improve strength characteristics. Furthermore, according to the invention of claim 5, the mixed material is spread using a hydroseeder, so not only is there no need for dedicated spreading equipment, but dust control can also be achieved through work equivalent to that used in ordinary seed spraying work. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram showing an overview of a dust suppression method according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram showing the procedure of each experimental example. [Figure 3] FIG. 10 is a diagram showing the levels of each experimental example. [Figure 4] FIG. 10 is a graph showing the change over time in the amount of flying dust in each experimental example and the blank. [Figure 5] FIG. 1 shows the soil hardness of each experimental example (10 days after application) and the blank. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] FIG. 1 is a diagram showing an outline of a dust suppression method according to an embodiment of the present invention. A dust suppression method according to an embodiment of the present invention is a method applicable to civil engineering construction sites such as land development work, and is characterized by spreading a mixed material containing calcium carbonate and an aqueous phosphoric acid solution on the ground, as shown in Fig. 1. According to this dust suppression method, a layer containing calcium phosphate compounds is formed on the ground through a chemical reaction between calcium carbonate and phosphoric acid, thereby suppressing dust generation from the ground for a long period of time. This is because calcium phosphate compounds have the property of hardening, and once hardened, they exhibit excellent strength. Furthermore, calcium phosphate compounds exist in nature as components of bones and teeth, and therefore have the advantage of reducing environmental impact.

[0010] It is desirable to use crushed shells, which contain calcium carbonate as the main component, as calcium carbonate. In this way, material costs can be reduced by using shells that would otherwise be treated as waste.

[0011] The type of shell used as calcium carbonate can be any shell whose main component is calcium carbonate, but it is preferable to select oyster shells. This will further reduce material costs by utilizing oyster shells that are discarded in large quantities at oyster farms. In addition, because oysters use calcium and carbon dioxide in the sea to form their shells, crushing oyster shells and scattering them on the ground will also contribute to carbon fixation.

[0012] It is desirable to use phosphoric acid supplied as a fertilizer. This allows for the use of a highly safe fertilizer material, further reducing the burden on the environment. Furthermore, by mixing phosphoric acid with calcium carbonate in the form of an aqueous solution, uneven mixing can be prevented and the chemical reaction between calcium carbonate and phosphoric acid can be promoted.

[0013] The mixed material preferably contains sand. In this case, the sand acts as an aggregate and improves the strength characteristics. An adhesive (glue) can also be added to the mixed material. The adhesive not only accelerates the hardening of the mixed material but also improves the strength characteristics.

[0014] It is desirable to spread the mixed material using a hydroseeder (seed spreader), which not only eliminates the need to develop dedicated spreading equipment, but also makes it possible to take measures against dust using the same work as regular seed spraying.

[0015] Next, experimental examples of the dust suppression method according to the present invention will be described with reference to Figures 2 to 5. In the following description, the steps of each experimental example will be indicated by numbers 1) to 13) in parentheses. In the drawings, experimental examples 1 to 8 will be indicated by numbers 1 to 8 only.

[0016] FIG. 2 is a diagram showing the procedure of each experimental example, and FIG. 3 is a diagram showing the level of each experimental example. 1) Container A, with internal dimensions of 175 x 115 x 86 mm, was filled to 90% capacity with soil collected from a development site in Joso City, Ibaraki Prefecture, and pressure was applied from above with a metal plate to compact it and create test soil B.

[0017] 2) Oyster shells (calcium carbonate) were crushed to the experimental particle size shown in Figure 3. Two types of crushed oyster shells were used: one that passed through a 2 mm sieve C1 and was retained on a 425 μm sieve C2, and the other that passed through a 425 μm sieve C2 and was retained on a 75 μm sieve C3. The oyster shells were subjected to high-temperature heat treatment (800-900°C) in a sterilization and drying oven to remove impurities such as organic components adhering to the surface. The oyster shells were also washed with water to reduce the salt concentration, and the moisture content was 10% or less.

[0018] 3) The phosphoric acid aqueous solution was diluted with distilled water to the experimental level concentrations shown in Figure 3.

[0019] 4) Each level of phosphoric acid solution was added to a 362.25g sample of oyster shell and sand mixture, and the mixture was stirred in a plastic bag D. Mountain sand was used as the sand. The oyster shell and sand were mixed in a weight ratio of 1:1.

[0020] 5) After mixing, the contents E (mixed material) were cured in a plastic bag D for one day.

[0021] 6) After curing, the contents E of 5) were piled on top of the test soil B of 1) to a thickness of 10 mm, and then spread evenly using a metal spatula to create test specimen F.

[0022] 7) The weight of specimen F was measured before the air blowing test.

[0023] 8) Using blower G, air was blown at a speed of 15 m / s onto the soil surface of specimen F at an angle of 20° for 5 minutes.

[0024] 9) After the air blowing test, the weight of specimen F was measured.

[0025] 10) The difference in weight before and after the air blowing test was calculated as the amount of dust scattering.

[0026] 11) After the air blowing test, each specimen F was wrapped in plastic to prevent evaporation of moisture and then stored and cured.

[0027] 12) The curing period lasted for 10 days, and within that period, operations 8) to 11) were carried out 3 days (only Experimental Examples 1 to 4 and the blank), 7 days (only Experimental Examples 1 to 4 and the blank), and 10 days later, and the amount of dust dispersion was measured.

[0028] 13) After the air blowing test, the soil strength of specimen F was measured at five points on the soil surface using a Yamanaka soil hardness meter.

[0029] FIG. 4 is a graph showing the change in the amount of dust scattering over time in each experimental example and the blank, and FIG. 5 is a graph showing the soil hardness in each experimental example (10 days after application) and the blank. As shown in Figure 10, a material made by mixing oyster shells with a diluted phosphoric acid solution was confirmed to have the effect of suppressing dust generation. This suppression effect was confirmed three days after spraying. This is thought to be because the calcium carbonate that makes up the oyster shells reacted with phosphoric acid to form calcium phosphate three days after spraying.

[0030] As shown in Figure 5, the soil hardness of all test specimens 10 days after application was greater than the blank value. The soil hardness values ​​were greater in Experimental Examples 5 to 8, where the particle size of the oyster shells was 75 to 425 μm, than in Experimental Examples 1 to 4, where the particle size was 425 to 2000 μm. The largest difference was observed between Experimental Examples 1 and 8, where the difference was more than two times. This is thought to be because the smaller the particle size of the oyster shells, the greater the surface area, allowing calcium phosphate to be formed more efficiently.

[0031] According to the theoretical design method, the ground pressure of a typical 10-ton dump truck (total weight 20 tons) is 0.61 to 0.65 MPa. For Experimental Example 5 (24.7 mm) to Experimental Example 8 (33.3 mm), where the soil hardness (hardness index) exceeds 20 mm, the theoretical bearing capacity strength is 12.82 kg / cm (Experimental Example 5). 2 =1.25MPa) ~ Experimental Example 8 (84.70kg / cm 2= 8.30 MPa), which is higher than the ground pressure of a typical 10-ton dump truck. Therefore, it is believed that Experimental Examples 5 to 8 will provide excellent dust suppression effects over the long term even when applied to a site where a 10-ton dump truck travels.

[0032] According to the present embodiment configured as described above, a dust suppression method for suppressing dust generation from the ground involves scattering a mixed material containing calcium carbonate and an aqueous solution of phosphoric acid on the ground, which allows a chemical reaction between the calcium carbonate and the phosphoric acid to form a layer containing calcium phosphate compounds on the ground. Furthermore, calcium phosphate compounds have hardening properties and exhibit excellent strength, making it possible to suppress dust generation from the ground for a long period of time. [Explanation of symbols]

[0033] A Container B Test soil C1~C3 sieves D. Plastic bag E Mixed material (contents) F Specimen G. Air blower

Claims

1. A dust suppression method for suppressing dust generation from the ground, comprising: A dust suppression method comprising spreading a mixed material containing calcium carbonate and an aqueous solution of phosphoric acid on the ground.

2. 2. The dust suppression method of claim 1, wherein the calcium carbonate is ground seashells.

3. 3. The dust suppression method according to claim 2, wherein the shells are oyster shells.

4. 2. The dust suppression method of claim 1, wherein the mixed material further comprises sand.

5. 2. The dust suppression method of claim 1, wherein the mixed material is spread using a hydroseeder.

Images