Manufacturing method of backfill material

Abstract

To provide: a back-fill material which effectively uses concrete washing water generated in a concrete plant or the like, and which is intended to improve material separation resistance; and a method for manufacturing the back-fill material.SOLUTION: A back-fill material includes a solidification material, kneading water containing calcium carbonate, and sand. A method for manufacturing the back-fill material includes: a raw water recovery step S1 of recovering raw water derived from concrete washing water; a kneading water generation step S2 of generating kneading water in which calcium carbonate is deposited by supplying carbon dioxide to the raw water; and a back-fill material manufacturing step S6 of manufacturing a back-fill material by mixing the kneading water, the solidification material, and sand together.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention uses mixing water derived from concrete washing water. Buried This relates to a manufacturing method of the return material. [Background technology]

[0002] When constructing underground structures or buried objects, voids formed during construction may need to be backfilled. If soil generated during excavation is used as backfill material, the amount of soil to be disposed of can be reduced, and the effort and cost required for disposal of the surplus soil can be reduced. Backfilling work requires transporting and filling the backfill material in a specified location. However, if the backfill material is transported and filled manually in a place where heavy machinery cannot enter, the work is time-consuming. For this reason, in some cases, self-filling materials (such as soil mortar or liquefied soil, which is made by adding water and a solidifying agent to soil and sand to give it fluidity) are used as backfilling material to improve workability. If sludge water collected from concrete washing water generated in a concrete plant or the like is used as the mixing water for the backfilling material, it becomes possible to reduce the labor required for wastewater treatment that involves multiple treatment steps such as classification separation using a settling tank and dehydration using a dehydrator. For example, Patent Document 1 discloses a backfilling material made by mixing a specified amount of sand with cement and sludge water. Furthermore, if the solids concentration in the backfilling material is low, there is a risk that the desired quality (resistance to material separation) cannot be ensured. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-102057 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention effectively utilizes washing wastewater (concrete washing water) generated in concrete plants and improves the material separation resistance. Buried The objective of the present invention is to propose a method for manufacturing a return material. [Means for solving the problem]

[0005] The present invention aims to solve the above problems. Filling The method for manufacturing the backfill material includes a raw water recovery process for recovering raw water derived from concrete washing water, a mixing water production process for supplying carbon dioxide to the raw water to produce mixing water in which calcium carbonate has precipitated, and a backfill material mixing process for mixing the mixing water with a solidification material and soil and sand. Kaka Filled According to the manufacturing method of the backfill material, the mixing water in which calcium carbonate is precipitated by supplying carbon dioxide is used as the mixing water for the backfill material, so that the particulate matter (solid matter) contained in the raw water taken from the concrete washing water is increased, and as a result, the material separation resistance is improved. In addition, by using carbon dioxide released into the atmosphere or carbon dioxide in the atmosphere as a resource, it is possible to fix carbon dioxide. Therefore, in addition to the effective use of construction by-products such as generated soil and concrete washing water, it is also possible to contribute to carbon neutrality. Here, in this specification, "raw water derived from concrete washing water" includes concrete washing water from which aggregates and the like have been removed (recovered water), recovered water from which the supernatant water has been removed, recovered water from which sediments have been removed, or recovered water from which the supernatant water and sediments have been removed (sludge water).

[0006] The method for producing the backfill material preferably further comprises a viscosity density calculation step of calculating the density and viscosity of the mixing water for each batch, and a mix setting step of setting a mix for each batch based on the density and viscosity. According to this method for producing the backfill material, it is possible to suppress the quality of the backfill soil from changing for each batch, and to ensure a certain level of fluidity, resistance to material separation, and strength after hardening. In addition, it is preferable that the viscous density calculation step includes a material storage operation for storing the mixing water in a storage body, a material discharge operation for discharging the mixing water from the bottom of the storage body and measuring the flow rate of the mixing water, and a viscous density calculation operation for calculating the viscosity and density of the mixing water. A plurality of pressure gauges are disposed at different height positions in the storage body, and the viscosity density calculation operation calculates the viscosity and density of the mixing water using the pressure distribution and the flow rate measured by the plurality of pressure gauges. According to this method for manufacturing backfill material, the density can be calculated using the pressure distribution measured by the plurality of pressure gauges, and the viscosity can be grasped from the flow rate of the material. In addition, by measuring the change in the liquid level of the mixing water over time when the mixing water is discharged from the reservoir during the material discharge operation, the flow rate can be easily measured without using a flow meter or the like. It is preferable to further include a density flow specification step of specifying the relationship between the density and flow value of the muddy soil obtained by mixing the soil and the mixing water and the backfilling material as a density-flow relationship, while specifying the density of the muddy soil corresponding to the target flow value of the backfilling material using the density-flow relationship, specifying the target density of the muddy soil as a controlled flow value by setting the density of the backfilling material having the estimated target density and removing the solidification material from the backfilling material having the estimated target density as the target density of the muddy soil and applying the target density of the muddy soil to the density-flow relationship, and adjusting the muddy soil based on the controlled flow value. This makes it possible to specify the controlled flow value of the muddy soil according to the soil particle density of the soil (raw soil), making it easier to manage the backfilling soil to the target performance. Effect of the Invention

[0007] The present invention Filling This method of manufacturing return soil makes it possible to effectively utilize not only generated soil (residual soil) but also washing wastewater (concrete washing water) generated at concrete plants, etc., while improving the resistance to material separation. [Brief description of the drawings]

[0008] [Figure 1] 4 is a flowchart showing the steps of a method for manufacturing a backfilling material according to the present embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing an outline of a raw water recovery process and a mixing water production process. [Diagram 3] FIG. 2 is a schematic diagram showing a usage state of the viscosity density measuring device according to the present embodiment. [Figure 4] FIG. 13 is an explanatory diagram for explaining an overview of a backfilling material mixing process. [Diagram 5] FIG. 2 is a schematic diagram showing an outline of a raw water recovery step and a mixing water production step according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In the present embodiment, a backfilling material used to backfill an excavation in a construction work and a method for manufacturing the backfilling material will be described. The backfill material of this embodiment is so-called liquefied treated soil obtained by adding and mixing cement (solidification material) and mixing water to excavated soil (soil and sand) generated by excavation. The mixing water used is calcium carbonate-containing mixing water, which is obtained by supplying carbon dioxide to raw water derived from concrete washing water and reacting the calcium component in the raw water with the carbon dioxide to precipitate calcium carbonate.

[0010] The manufacturing method of the backfilling material will be described below. The manufacturing method of the backfilling material is shown in Figure 1. As shown in Figure 1, the backfilling material manufacturing method includes a raw water recovery process S1, a mixing water production process S2, a viscous density calculation process S3, a density flow specification process S4, a mix setting process S5, and a backfilling material mixing process S6. In the raw water recovery step S1, raw water (recovered water) W1 is recovered. An overview of the raw water recovery step S1 is shown in Fig. 2. The raw water W1 is recovered from concrete washing water generated by washing the inside of the drum of an agitator vehicle, washing the inside of a concrete mixer, etc. In this embodiment, as shown in Fig. 2, recovered water collected by separating aggregate A from concrete washing water W0 using a classifier M or the like is used as raw water W1 for mixing water W.

[0011] In the mixing water production step S2, as shown in FIG. 2, carbon dioxide is supplied to raw water (recovered water) W1. By supplying carbon dioxide to the raw water W1, mixing water W in which calcium carbonate has been precipitated is produced. By precipitating calcium carbonate in the raw water W1, the solids concentration in the raw water W1 increases. If the solids concentration in the raw water W1 (mixing water W) is too high, water may be added to dilute it. The supply of calcium carbonate to the raw water W1 is performed, for example, by supplying a gas G containing calcium carbonate (air, liquefied carbon dioxide, combustion exhaust gas generated in industrial facilities, exhaust gas generated from vehicles, etc.) to the raw water W1 stored in a container T1 (i.e., bringing the gas G into gas-liquid contact with the raw water W1).

[0012] In the viscous density calculation step S3, the density and viscosity of the mixing water W are calculated for each batch. A viscous density measuring device 1 is used to measure the density and viscosity of the mixing water W. FIG. 3 shows the viscous density measuring device 1. As shown in FIG. 3, the viscous density measuring device 1 is provided near a mixing water tank T2 in which the mixing water W is stored. The viscous density measuring device 1 includes a reservoir 2, a pressure gauge 3, a distance meter 4, an inlet pipe 5, an inlet valve 6, a discharge pipe 7, and a discharge valve 8. The reservoir 2 is made of a hollow member. The main body (upper part) of the reservoir 2 has a uniform cylindrical cross-sectional shape, and the lower part of the reservoir 2 is tapered in an inverted truncated cone shape, with an outlet formed in the center of the lower end of the lower part. In addition, the upper surface of the reservoir 2 in this embodiment is open, and an inlet is formed on the upper side surface of the reservoir 2 (at a position a predetermined height lower than the upper end). The reservoir 2 is installed so that the central axis is vertical (including approximately vertical).

[0013] The pressure gauge 3 is provided inside the storage body 2. The pressure gauge 3 measures the pressure of the mixed water W stored in the storage body 2. In this embodiment, a plurality of pressure gauges 3, 3, ... are arranged in parallel at a predetermined interval along the height direction of the general part of the storage body 2 (part with a constant cross-sectional area above the lower part). The number of pressure gauges 3 and the intervals between the pressure gauges 3 are not limited and may be determined appropriately. The height position of the pressure gauge 3 is a known distance from the lower end (discharge port) of the storage body 2. In other words, each pressure gauge 3 is arranged vertically in a state where the height from the lowest point of the mixed water W stored in the storage body 2 is known.

[0014] The range finder 4 is provided above the reservoir 2 and measures the liquid level (upper surface) of the mixed water W in the reservoir 2 from the upper surface (opening) of the reservoir 2. The range finder 4 is fixed at a position a preset distance from the upper end of the reservoir 2. The range finder 4 may be fixed to the reservoir 2 or to another member (for example, the mixed water tank T2 or a separately provided support member, etc.). The range finder 4 in this embodiment is a laser range finder, which is a type of non-contact range finder, and calculates the distance to the liquid level of the mixed water W from the time it takes to irradiate the liquid level (upper surface) of the mixed water W with a laser beam and receive the reflected laser beam.

[0015] As shown in Fig. 2, the inflow pipe 5 is a pipe leading from the mixing water tank T2 to the storage body 2. The inflow pipe 5 is connected to the storage body 2 (inlet) via an inflow valve 6. The inflow pipe 5 transports the mixing water W in the mixing water tank T2 to the storage body 2. The inflow pipe 5 is provided at a position lower than the liquid level of the mixing water W at the top of the mixing water tank T2 so that the mixing water W in the mixing water tank T2 flows down to the storage body 2. The inflow valve 6 controls communication / non-communication between the storage body 2 and the inflow pipe 5 (opens and closes the inlet of the storage body 2). When the inflow valve 6 is opened, the mixed water W transported through the inflow pipe 5 is supplied into the storage body 2. On the other hand, when the inflow valve 6 is closed, the supply of the mixed water W to the storage body 2 is stopped.

[0016] As shown in Fig. 2, the discharge pipe 7 is a pipeline for transporting the mixed water W discharged from the storage body 2. The discharge pipe 7 is connected to the lower end (discharge port) of the storage body 2 via a discharge valve 8. In this embodiment, a temporary receiving tank T3 is provided below the storage body 2, and the mixed water W discharged from the storage body 2 flows down through the discharge pipe 7 into the temporary receiving tank T3. The discharge valve 8 controls communication between the storage body 2 and the discharge pipe 7 (opens and closes the discharge port). When the discharge valve 8 is opened, the mixing water W in the storage body 2 is discharged from the storage body 2 and transported to the temporary receiving tank T3 via the discharge pipe 7. In this embodiment, a return pipe 71 is installed from the temporary receiving tank T3 to the mixing water tank T2. The return pipe 71 pumps the mixing water W discharged from the reservoir 2 and stored in the temporary receiving tank T3 via a pump 72 provided in the temporary receiving tank T3 to the mixing water tank T2.

[0017] In the viscous density calculation process S3, a material storage operation is performed in which the mixing water W is stored in the storage body 2, a material discharge operation is performed in which the mixing water W is discharged from the bottom of the storage body 2 and the flow rate of the mixing water W is measured, and a viscous density calculation operation is performed in which the viscosity and density of the mixing water W are calculated. In the material discharge operation, the distance meter 4 is used to measure the change over time in the liquid level of the mixing water W when the mixing water W is discharged from the reservoir 2. In the viscosity density calculation work, the viscosity and density of the mixing water W are calculated using the pressure distribution and flow rate measured by the multiple pressure gauges 3, 3, . . .

[0018] An example of a method for calculating the viscosity and density of the mixing water W will be described below. When calculating the density of the mixing water W, first, the unit volume weight of the mixing water W is calculated by dividing the pressure difference between the measurements of the pressure gauges 3 arranged above and below by the elevation difference, and then the density is calculated by dividing this by the acceleration of gravity (9.81). The density of the mixing water W is calculated for each layer, assuming that the space between each pair of pressure gauges 3 is a layer. When calculating the viscosity of the mixed water W, first, the flow rate of the mixed water W is calculated based on the time change in the liquid level. Since the internal space area of ​​the main body (part other than the lower part) of the reservoir 2 in this embodiment is constant, the flow rate (change in the liquid level per unit time) is calculated by dividing the change in the liquid level by time. Next, the flow value is calculated by substituting the calculated flow rate into an approximation formula that represents the relationship between the flow rate and the flow value, which is created based on indoor tests and past data. The viscosity of the mixed water W is evaluated based on the flow value. Note that the flow rate is affected by the frictional force generated between the inner surface of the reservoir 2 and the mixed water W, so it is preferable to measure the liquid level in a section with a constant internal cross section (cylindrical part in this embodiment) so that the influence of the frictional force is constant.

[0019] In the density flow determination step S4, the soil particle density of the soil is determined, and the relationship between the density and flow value of the muddy soil obtained by mixing the soil and mixing water W and the backfill material is determined as a density-flow relationship. In the mixture setting step S5, the mixture of the backfilling material is set. The mixture of the backfilling material is set for each batch based on the density and viscosity so that a certain level of fluidity, material separation resistance, and strength after hardening can be ensured.

[0020] In the backfilling material mixing step S6, the mixing water W, the solidification material, and the soil and sand are mixed to produce the backfilling material. In the backfilling material mixing process, first, the target density of the backfilling material is estimated from the target flow value of the backfilling material using the density-flow relationship. FIG. 4 is a graph (trend curve) created based on Equation 1 that specifies the relationship between density and cylinder flow. In this embodiment, the target flow value of the backfilling material is set to 200 mm. After the target flow value of the backfilling material is set, the target density is estimated from the intersection of the target flow value and the trend curve. The target density can also be calculated using Equation 1. CF=(2.758G s 13.259 ) / (ρ t 15.881 )+80 ··· Formula 1 CF: Cylinder flow value (mm) G s :Average soil particle density (g / cm 3 ) ρ t : Wet density (g / cm 3 )

[0021] Along with estimating the target density, the amount of solidification material to be added is determined based on factors such as the strength required for the backfill material. Next, the target density of the muddy soil (muddy soil target density) is calculated as the density when the solidification material is removed from the backfill material with the estimated target density. Furthermore, the calculated target density of the muddy soil is applied to a trend curve (density-flow relationship) to identify the target flow value of the muddy soil as the controlled flow value. Note that the target flow value of the muddy soil can also be calculated by substituting the target density into Equation 1. Then, using the controlled flow value as a standard, the amount of water is adjusted so that the muddy soil falls within the controlled flow value or its acceptable range. In this way, a solidifying material is added to the muddy soil adjusted based on the controlled flow value to produce backfill soil.

[0022] According to the backfilling material and the backfilling material manufacturing method of this embodiment, the mixing water W in which calcium carbonate has been precipitated by supplying carbon dioxide is used as the mixing water for the backfilling material, so that the amount of fine particles (solids) contained in the raw water W1 increases, and as a result, the material separation resistance is improved. In addition, carbon dioxide released into the atmosphere and carbon dioxide in the atmosphere can be used as a resource to fix the carbon dioxide. Therefore, in addition to making effective use of construction by-products such as generated soil and concrete washing water, it is also possible to contribute to carbon neutrality.

[0023] In addition, the method includes a viscosity density calculation step for calculating the density and viscosity of the mixing water W for each batch, and a mix setting step for setting the mix for each batch based on the density and the viscosity, which prevents the quality of the backfill soil from changing from batch to batch, and ensures a certain level of fluidity, resistance to material separation, and strength after hardening. The fine particles contained in the raw water W1 (recycled water, etc.) are mainly solidifying materials such as cement and fine aggregates (specific gravity: 2.6 g / cm 3 The relationship between density and viscosity changes depending on the ratio of fine particles, which have different specific gravities, but by calculating the density and viscosity for each batch, it is possible to standardize the quality. In addition, the density is calculated using the pressure distribution measured by multiple pressure gauges, and the mixture is set while properly understanding the degree of viscosity of the mixing water W from the flow speed of the material, so that high-quality backfill material can be produced. In addition, since the change in the liquid level over time when the mixing water W is discharged from the reservoir 2 is measured, the flow rate can be easily measured without using a flow meter or the like. It also makes it possible to specify the management flow value of muddy soil according to the soil particle density of the soil (raw soil), making it easier to manage the backfill material to achieve the target performance.

[0024] Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and each of the above-described components can be appropriately modified without departing from the spirit of the present invention. The backfill material produced is not limited to liquefied treated soil, but may be, for example, soil mortar. In the above embodiment, the case has been described where so-called recovered water obtained by removing aggregate A from concrete washing water W0 is used as raw water W1 for mixing water W, but the raw water W1 is not limited to this. For example, as shown in Fig. 5, recovered water is stored in a water tank T4 and separated into supernatant water W2, sludge water W3, and sediment S, and then the raw water may be the water from which only the supernatant water W2 has been removed (sludge water W3 + sediment S), the water from which only the sediment S has been removed (supernatant water W2 + sludge water W3), or the water from which both the supernatant water W2 and the sediment S have been removed (sludge water W3) (see Fig. 5). When the solids concentration in the raw water W1 (mixing water W) is too high, the so-called supernatant water W2 may be used as the water used to dilute the concentration. In the above embodiment, cement is used as the solidification material, but the material constituting the solidification material may be blast furnace slag, fly ash, etc. in addition to cement, or may be a mixture of at least two of these materials. In the above embodiment, the pressure gauge 3 is installed in the reservoir 2, but the location where the pressure gauge 3 is installed is not limited, and it may be installed, for example, in the mixing water tank T2. [Explanation of symbols]

[0025] 1 Viscous density measuring device 2 Reservoir 3. Pressure gauge 4 Rangefinder W Mixing water W1 Raw water (reclaimed water) W2 Clear water W3 Sludge water

Claims

1. A raw water recovery process for recovering raw water derived from concrete washing water; a mixing water producing step of producing mixing water in which calcium carbonate is precipitated by supplying carbon dioxide to the raw water; A backfill material manufacturing method comprising: a backfill material mixing step of mixing the mixing water, a solidification material, and soil and sand.

2. A viscous density calculation step of calculating the density and viscosity of the mixing water for each batch; The method for manufacturing a backfill material according to claim 1, further comprising a blending setting step of setting a blending ratio for each batch based on the density and the viscosity, the blending ratio being capable of ensuring a certain degree of fluidity, material separation resistance, and strength after hardening.

3. In the viscosity density calculation step, A material storing operation of storing the mixing water in a storage body; A material discharge operation of discharging the mixing water from the lower part of the storage body and measuring the flow rate of the mixing water; A viscosity and density calculation operation is performed to calculate the viscosity and density of the mixing water. A plurality of pressure gauges are disposed at different height positions in the reservoir, 3. The method for manufacturing backfill material according to claim 2, characterized in that in the viscosity density calculation process, the viscosity and density of the mixing water are calculated using the pressure distribution and the flow velocity measured by a plurality of pressure gauges.

4. 4. The method for manufacturing a backfill material according to claim 3, wherein in the material discharging operation, a change in a liquid level of the mixing water with time is measured when the mixing water is discharged from the reservoir.

5. The method further includes a density flow specification step of specifying the soil particle density of the soil and specifying the relationship between the density and flow value of the muddy soil obtained by mixing the soil and the mixing water and the backfill material as a density-flow relationship; In the backfilling material mixing step, estimating a corresponding target density of the backfilling material from a target flow value of the backfilling material using the density-flow relationship; A task of determining the density of the muddy soil when the solidification material is removed from the backfill material having the estimated target density as the target density of the muddy soil, and specifying the target flow value of the muddy soil as a controlled flow value by applying the target density of the muddy soil to the density-flow relationship; The method for manufacturing a backfill material according to any one of claims 1 to 4, further comprising the step of adjusting the muddy soil based on the controlled flow value.

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