JP2012254432A - Contaminant adsorption material, contaminant adsorption sheet and method for processing residual dug-up soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contaminant adsorption material that can efficiently prevent contaminant from leaking from residual dug-up soil such as excavation muck, and to provide a contaminant adsorption sheet and a method for processing residual dug-up soil.SOLUTION: The contaminant adsorption material 1 for capturing contaminant leaching from an embankment M containing contaminant is characterized in that inorganic material having water retention characteristics is impregnated with a slurry adsorbent for adsorbing contaminant.

Description

  The present invention relates to a pollutant adsorbing material that adsorbs pollutants, a pollutant adsorbing sheet, and a method for treating excavated residual soil.

  In a site where civil engineering works such as tunnels, dams, and construction are carried out, excavation is generated as excavated soil and excavated ground. Since excavations may contain naturally occurring or man-made pollutants, permanent construction against these pollutants is required when embankment or landfill is performed using construction soil containing excavation shear that contains pollutants. Processing is required.

  Permanent treatment methods for construction residual soil containing pollutants include excavation shear removal processing, classification / washing treatment, insolubilization treatment, etc., and other methods are known as adsorption layer construction methods. Such an adsorption layer method lays an adsorption layer under the contaminated soil layer, which is a mixture of an agent that adsorbs and captures contaminants (hereinafter referred to as “adsorbent”) and healthy soil that does not contain contaminants. This is a construction method for capturing contaminants leached from the contaminated soil layer (see, for example, Patent Document 1).

  As the adsorbent used for forming the adsorbing layer in the adsorbing layer construction method described above, powder, granular, and slurry are known (for example, see Patent Document 2).

JP 2009-136895 A JP 2008-168182 A

  However, in the adsorption layer construction method described in Patent Document 1, the adsorption layer is formed by mixing the adsorbent with soil in the field. For this reason, it is difficult to disperse the adsorbent uniformly with respect to the soil even in any form of the adsorbent described in Patent Document 2, and there is a problem in that the adsorption performance in the adsorption layer is uneven. It was. In particular, powdery adsorbents and slurry adsorbents have a property that they tend to harden in one place because of their very small particle sizes, and it is difficult to uniformly disperse the adsorbents. For this reason, there are many portions that do not contain the adsorbent, and there is a high possibility that contaminants will leach into and out of the ground from the portion that does not contain the adsorbent. In order to solve this problem, it is conceivable to suppress the generation of a portion not containing the adsorbent by using a large amount of adsorbent. However, in this case, there is a problem in that the amount of the adsorbent used increases and the utilization efficiency of the adsorbent decreases.

  Accordingly, an object of the present invention is to provide a pollutant adsorbing material, a pollutant adsorbing sheet, and a method for treating excavated residual soil that can efficiently prevent the outflow of pollutants from the excavated residual soil such as excavations. .

  In order to solve the above-mentioned problem, the pollutant adsorbing material according to the present invention is a pollutant adsorbing material that captures a pollutant that leaches out from the excavated residual soil containing the pollutant, and is a pollutant with respect to an inorganic material having water retention. It is configured by impregnating with a slurry adsorbent that adsorbs the water.

  In the pollutant adsorbing material according to the present invention, a pollutant adsorbing material having a low bulk density is formed by impregnating a slurry adsorbent that adsorbs the pollutant into an inorganic material having water retention. can do. For this reason, even if it is the same weight, since a large amount of contaminant adsorbing materials can be used, it is possible to efficiently prevent the contaminants from flowing out from the excavated residual soil such as excavations. In addition, since such a contaminant adsorbing material has a larger particle size than a general adsorbent, it becomes easy to uniformly disperse the adsorbent in the adsorption layer. Therefore, by using this contaminant adsorbing material to capture the contaminants leached from the excavated residual soil containing the contaminants, it is possible to efficiently prevent the contaminants from flowing out from the excavated residual soil such as excavated shear. According to such a pollutant adsorbing material, the volume per unit weight is increased, so that the contact efficiency between the adsorbent and the contaminant leached out from the remaining soil can be increased.

The contaminant adsorbing material according to the present invention can have a water permeability coefficient of 10 ⁻⁶ m / s or more.

  In this case, since the pollutant adsorbing material has high water permeability, it becomes easy to pass through the pollutant adsorbing material having high water permeability in which moisture digs up and exudes from the remaining soil. Therefore, the contaminant contained in the excavated residual soil and the contaminant adsorbing material can be efficiently contacted, and the contaminant can be adsorbed on the contaminant adsorbing material and captured. In addition, since the pollutant adsorbing material has high water permeability, it is possible to prevent the moisture that has been dug up and leached from the remaining soil from overflowing to the outside without penetrating the pollutant adsorbing material. Therefore, it is possible to suitably prevent the outflow of pollutants from the excavated residual soil such as excavation.

  The contaminant adsorbing material according to the present invention can have a volumetric water content of 45% or more in a saturated state.

  In this case, since the pollutant adsorbing material has a high water retention capacity, the moisture excavated and leached from the remaining soil will remain in the pollutant adsorbing material for a long time. Therefore, the pollutant contained in the excavation can be efficiently contacted with the pollutant adsorbing material, and the pollutant can be adsorbed and captured by the pollutant adsorbing material. Therefore, it is possible to suitably prevent the outflow of pollutants from the excavated residual soil such as excavation.

  The pollutant adsorbing material according to the present invention may have a color different from that of the excavated residual soil.

  In this case, since the excavated residual soil and the pollutant adsorbing material have different colors, when the adsorbing layer is formed by mixing the pollutant adsorbing material with the healthy soil, the pollutant adsorbing material is evenly mixed in the mixed soil constituting the adsorbing layer. It is possible to easily determine visually whether or not they are dispersed.

  In the pollutant adsorbing sheet according to the present invention, the first sheet is disposed above the pollutant adsorbing material, and the second sheet is disposed below the pollutant adsorbing material, and is contaminated by the first sheet and the second sheet. It is composed of material adsorption materials.

  Since the contaminant adsorbing sheet according to the present invention is configured by sandwiching the contaminant adsorbing material inside, the contaminant adsorbing material can be easily transported and installed.

  The processing method of the excavated residual soil according to the present invention is to form a contaminant adsorbing material layer in which the pollutant adsorbing material is laid as a single layer in the excavating and excavating residual soil processing region, and on the contaminant adsorbing material layer, Digging up and depositing surplus soil to form embankment, and excavating and surfacing the surplus soil.

  In the method for treating excavated residual soil according to the present invention, since the pollutant adsorbing material is laid as a single layer, the adsorbing performance in the pollutant adsorbing material layer can be made uniform, and uneven adsorption performance can be prevented. Can do. Therefore, it is possible to suitably prevent the outflow of pollutants from the excavated residual soil such as excavation.

  The processing method of the excavated surplus soil according to the present invention, when processing the excavated surplus soil in the excavated surplus soil treatment region, laying a pollutant adsorbing sheet, depositing the excavated surplus soil on the pollutant adsorbing sheet, forming embankment, Digging up and processing the remaining soil.

  In the method for treating excavated surplus soil according to the present invention, the contaminant adsorbing sheet sandwiching the pollutant adsorbing material is laid up below the embankment of the excavated residual soil, so that the pollutant contained in the excavated residual soil is captured by the contaminant adsorbing sheet. can do. Further, since the pollutant adsorbing material is sandwiched inside, it is easy to transport and install the pollutant adsorbing material in the processing of the excavated residual soil.

  According to the pollutant adsorbing material, the pollutant adsorbing sheet, and the excavated residual soil processing method according to the present invention, the outflow of the pollutant from the excavated residual soil such as excavation can be efficiently prevented.

It is a sectional side view of the digging residual soil in the processing method of the digging residual soil which concerns on 1st Embodiment. It is a figure which shows the hydraulic conductivity according to the kind of soil. It is a graph which shows the water retention according to the kind of soil. It is a sectional side view of the excavation residual soil in the processing method of the excavation residual soil which concerns on 2nd Embodiment. It is a sectional side view of adsorption sheet 12.

    Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each embodiment, portions having the same function are denoted by the same reference numerals, and redundant description may be omitted.

  FIG. 1 is a side sectional view of excavated residual soil in the excavated residual soil processing method using the contaminant adsorbing material 1 according to the first embodiment. As shown in FIG. 1, in the method for processing excavated residual soil according to the present embodiment, the embankment M is formed on the original ground Y (excavated residual soil processing region). The embankment M in the present embodiment is excavation (excavated residual soil) generated by excavation of a tunnel, for example. Further, an adsorption layer (contaminant adsorbing material layer) 11 using a pollutant adsorbing material 1 described later is formed between the raw ground Y and the embankment M.

  The adsorption layer 11 is configured by laying the contaminant adsorbing material 1 as a single layer. The adsorption layer 11 is laid with a thickness of, for example, 2 to 10 cm according to the contamination concentration of the embankment M and the amount of the embankment M. In addition, the adsorption layer 11 can also be formed by mixing the contaminant adsorbing material 1 and soil such as healthy soil not containing the contaminant.

  Here, the pollutant adsorbing material 1 constituting the adsorption layer 11 will be described in detail. The pollutant adsorbing material 1 is for adsorbing pollutants contained in the excavated residual soil, and is constituted by impregnating a slurry adsorbent that adsorbs pollutants into an inorganic material having water retention capacity. It is characterized by that.

  As the inorganic material having water retention, any inorganic material that is lightweight and highly water-absorbing can be used. For example, vermiculite, pearlite, etc. are mentioned as inorganic materials having water retention. The inorganic material is preferably granular, but may be in a form other than granular.

  The adsorbent that adsorbs the pollutant is a drug having a property of adsorbing and capturing heavy metals such as arsenic, cadmium, and lead. Various adsorbents having such properties are known. In the present embodiment, a slurry adsorbent is used, and specifically, a heavy metal adsorbent “CAMZ-S” manufactured by Amron is used.

  The contaminant adsorbing material 1 is obtained, for example, by mixing a granular inorganic material and a slurry adsorbent, and attaching a heavy metal adsorbing component of the adsorbent to the inorganic material. That is, the contaminant adsorbing material 1 is obtained by impregnating an inorganic material with a slurry adsorbent.

  The pollutant adsorbing material 1 can adjust properties such as an average particle diameter, a bulk density, a water permeability coefficient, and an effective water retention amount by changing the combination of the inorganic material and the adsorbent to be mixed.

The pollutant adsorbing material 1 preferably has a water permeability of 10 ⁻⁶ m / s or more, more preferably 10 ⁻⁵ m / s or more, and still more preferably 10 ⁻⁴ m / s or more. . Thus, since the pollutant adsorbing material 1 has high water permeability, it becomes easy to pass through the pollutant adsorbing material 1 having high water permeability in which moisture digs up and leaches out from the residual soil. Therefore, the contaminant contained in the excavated residual soil and the contaminant adsorbing material 1 can be efficiently contacted, and the contaminant can be adsorbed on the contaminant adsorbing material 1 and captured. In addition, since the pollutant adsorbing material has high water permeability, it is possible to prevent the moisture that has been dug up and leached from the residual soil from overflowing to the outside without penetrating the pollutant adsorbing material 1. Therefore, it is possible to suitably prevent the outflow of pollutants from the excavated residual soil such as excavation. On the other hand, when the water permeability coefficient of the pollutant adsorbing material is smaller than 10 ⁻⁶ m / s, the moisture containing the pollutant becomes difficult to pass through the pollutant adsorbing material 1, so that the effect of capturing the pollutant is impaired. Tend.

  Further, the pollutant adsorbing material 1 preferably has a volume water content of 45% or more, more preferably 55% or more, and still more preferably 65% or more. As described above, the pollutant adsorbing material 1 has high water retention, so that the moisture excavated and leached from the residual soil stays in the pollutant adsorbing material 1 for a long time. Therefore, the contaminant contained in the excavation shear and the contaminant adsorbing material 1 can be efficiently contacted, and the contaminant can be adsorbed on the contaminant adsorbing material 1 and captured. Therefore, it is possible to suitably prevent the outflow of pollutants from the excavated residual soil such as excavation. On the other hand, when the volumetric water content is less than 45%, the contact efficiency between the adsorbent and the pollutant decreases, so that the trapping effect of the pollutant tends to be impaired.

  Moreover, it is preferable that the pollutant adsorbing material 1 has a color different from that of a drilling shear having a generally black or brown color, such as orange. The color of the contaminant adsorbing material may be the color of an inorganic material or an adsorbent, or may be colored separately. Thus, the visibility in the case of mixing the pollutant adsorbing material 1 and the soil is improved because the pollutant adsorbing material 1 has a color different from that of excavation.

For example, as an example of the pollutant adsorbing material 1, a pollutant adsorbing material obtained using pearlite as an inorganic material and “CAMZ-S” as a slurry adsorbent has the following properties.
(1) Average particle diameter: 0.5-2 mm
(2) Bulk density: 0.2 g / cm ³
(3) Water permeability: 4 × 10 ⁻³ m / s
(4) Effective moisture retention: 78 L / m ³ (85% volumetric moisture content in moisture saturation state)

FIG. 2 shows the hydraulic conductivity according to the type of soil. The water permeability coefficient of the pollutant adsorbing material obtained by using pearlite as the inorganic material and using “CAMZ-S” as the slurry adsorbent is 4 × 10 ⁻¹ cm / s (that is, 4 × 10 ⁻³ m / s). Therefore, it is included in the range of hydraulic conductivity equivalent to sand and gravel. Thus, the contaminant adsorbing material according to the present embodiment has a relatively high water permeability.

  FIG. 3 is a graph showing water retention according to the type of soil. The horizontal axis represents the pF value, and the vertical axis represents the volumetric water content. The pF value is a logarithm of the height of water that rises due to capillary force, and the higher the pF value, the more dry it is. When the pF value is high, the difference in volumetric moisture content for each type of soil is small, and when the pF value is low, the difference in volumetric moisture content for each type of soil tends to be large. The effective moisture retention of the pollutant adsorbing material obtained by using pearlite as the inorganic material and “CAMZ-S” as the slurry adsorbent is 85% of the volume water content in the water saturation state (pF = 0). Therefore, it shows the same volumetric water content as volcanic ash soil. Thus, the contaminant adsorbing material according to the present embodiment has a relatively high effective moisture retention.

  As described above, the contaminant adsorbing material according to the present embodiment has high water permeability like volcanic ash while having high water permeability like sand.

  Returning to FIG. 1, the embankment M is formed by raising earth and sand such as excavation shears caused by civil engineering work such as a tunnel. Excavations may contain naturally occurring or artificial contaminants depending on the soil on which the civil engineering work is performed. From the embankment M, moisture flows out to the adsorption layer 11. From the embankment M, the pollutants contained in the embankment M flow out together with moisture.

  Then, the covering soil S is laid around the temporary embankment M. The soil covering S is composed of bentonite mixed soil or concrete. By covering the embankment M with the covering soil S, the inflow of rainwater to the embankment M is prevented.

  When the embankment is raised and the embankment M is formed, moisture flows down from the embankment M toward the base ground Y. During this time, if the water that has flowed down reaches the original ground Y, the pollutants contained in the water will leach into and out of the original ground Y.

  In this regard, in the method for treating excavated residual soil according to the present embodiment, an adsorption layer 11 in which the contaminant adsorbing material 1 is laid as a single layer is interposed between the raw ground Y and the embankment M. For this reason, the water | moisture content which flows down from the embankment M can be made to adsorb | suck to the contaminant adsorbing material 1 in the adsorption layer 11, and can be captured. Therefore, the leaching and outflow of contaminants to the inside and outside of the original ground Y can be prevented.

  Here, in the pollutant adsorbing material 1 according to the present embodiment, since it is configured by impregnating a slurry adsorbent that adsorbs the pollutant into an inorganic material having water retention properties such as vermiculite and pearlite, it is uniform. It is possible to form a pollutant adsorbing material having a good adsorption performance. Further, since inorganic materials having water retention properties such as vermiculite and pearlite are lightweight, it is possible to form a pollutant adsorbing material having a low bulk density. For this reason, it is possible to reduce the cost per unit capacity. Specifically, the pollutant adsorbing material obtained by using pearlite as the inorganic material and “CAMZ-S” as the slurry adsorbent has a lower cost per unit capacity than the conventional granular adsorbing member. It can be reduced to 1/10. Therefore, the pollutant adsorbing material 1 can be laid as a single layer at low cost.

  Moreover, since the pollutant adsorbing material 1 has high water permeability, the moisture leached from the embankment M easily passes through the adsorption layer 11 having high water permeability. Therefore, the contaminant contained in the excavation shear and the contaminant adsorbing material can be efficiently contacted, and the contaminant can be adsorbed on the contaminant adsorbing material 1 and captured. In addition, since the pollutant adsorbing material 1 has high water permeability, it is possible to prevent water leached from the embankment M from overflowing outside without penetrating the pollutant adsorbing material 1. Therefore, the outflow of contaminants from the embankment M such as excavation can be suitably prevented.

  Moreover, since the pollutant adsorbing material 1 has high water retention, moisture leached from the embankment M stays in the adsorption layer 11 for a long time. Therefore, the contaminant contained in the excavation shear and the contaminant adsorbing material 1 can be efficiently contacted, and the contaminant can be adsorbed on the contaminant adsorbing material 1 and captured. Therefore, the outflow of contaminants from the embankment M such as excavation can be suitably prevented.

  Conventionally, when the adsorbent is mixed with healthy soil to form the adsorbed layer 11, it is necessary to sample the mixed soil every predetermined amount to check whether the adsorbent is uniformly dispersed. In that respect, in the pollutant adsorbing material 1 having a color different from that of the excavated residual soil, the visibility is improved. Therefore, the adsorbing layer 11 is formed when the adsorbing layer 11 is formed by mixing the pollutant adsorbing material 1 with healthy soil. Whether or not the contaminant adsorbing material 1 is uniformly dispersed in the mixed soil can be easily determined visually.

  Moreover, in the processing method of the excavated residual soil according to the present embodiment, the adsorption layer 11 is configured by laying the contaminant adsorbing material as a single layer, so that the adsorption performance in the adsorption layer 11 can be made uniform, It is possible to prevent unevenness in adsorption performance due to the fact that the adsorbent and the healthy soil are not uniformly mixed. Therefore, the outflow of contaminants from the embankment M such as excavation can be suitably prevented.

  Next, a second embodiment of the present invention will be described. The processing method of the excavated residual soil according to the present embodiment according to the present embodiment is that the adsorption sheet 12 is used in place of the adsorbing layer 11 to prevent the outflow of contaminants, and the excavated residual soil processing method according to the first embodiment. And different. Hereinafter, description of the same or equivalent items as those in the first embodiment will be omitted.

  FIG. 4 is a side sectional view showing a method of using the contaminant adsorbing material 1 according to the second embodiment. As shown in FIG. 4, in the adsorption layer method according to the present embodiment, the embankment M is formed on the raw ground Y. Further, an adsorption sheet 12 using the contaminant adsorbing material 1 is laid between the raw ground Y and the embankment M. The suction sheet 12 to be laid may be two or more, or may be one sheet.

  As shown in FIG. 5, the adsorbing sheet 12 is formed by sandwiching the contaminant adsorbing material 1 between two sheets 12A, 12B such as non-woven fabric. The materials of the sheets 12A and 12B are not limited as long as they are permeable to moisture.

  In the present embodiment, as compared with the first embodiment, a suction sheet 12 is provided instead of the suction layer 11. Thus, even in the configuration in which the adsorption sheet 12 is provided, the water flowing down from the embankment M can be adsorbed and captured by the contaminant adsorbing material 1 in the adsorption sheet 12 as in the first embodiment. . Therefore, the leaching and outflow of contaminants to the inside and outside of the original ground Y can be prevented.

  Further, in the method for treating excavated residual soil according to the present embodiment, since the adsorbing sheet 12 is configured by sandwiching only the contaminant adsorbing material 1, the adsorbing performance of the adsorbing sheet 12 can be made uniform, and the adsorbing performance. Can be prevented. Therefore, the outflow of contaminants from the embankment M such as excavation can be suitably prevented.

  In the method for treating excavated residual soil according to the present embodiment, the adsorbing sheet 12 sandwiching the pollutant adsorbing material 1 is excavated and laid below the embankment M of the residual soil, so that the adsorbing sheet 12 supplements the pollutant contained in the residual soil. can do. Moreover, since the pollutant adsorbing material 1 is sandwiched inside, it is easy to transport and install the pollutant adsorbing material 1 in the processing of the excavated residual soil.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, in the above embodiment, the permanent treatment method of the excavated residual soil has been described. However, the excavation shear is temporarily placed in a predetermined temporary storage yard or the like until the degree of contamination in the excavation shear is obtained by the dissolution test. Can be used.

DESCRIPTION OF SYMBOLS 1 ... Pollutant adsorption material 11 ... Adsorption layer 12 ... Adsorption sheet 12A, 12B ... Sheet M ... Filling S ... Cover soil Y ... Raw ground

Claims (7)

A pollutant adsorbing material that captures pollutants leaching from excavated residual soil containing pollutants,
A pollutant adsorbing material constituted by impregnating a slurry adsorbent that adsorbs a pollutant to an inorganic material having water retention. The contaminant adsorbing material according to claim 1, wherein the contaminant adsorbing material has a water permeability coefficient of 10 ⁻⁶ m / s or more.   The pollutant adsorbing material according to claim 1 or 2, wherein the pollutant adsorbing material has a volumetric water content of 45% or more in a saturated state.   The pollutant adsorbing material according to any one of claims 1 to 3, wherein the pollutant adsorbing material has a color different from that of the excavated residual soil. A first sheet is disposed above the contaminant adsorbing material according to any one of claims 1 to 4, and a second sheet is disposed below the contaminant adsorbing material,
A contaminant adsorbing sheet, wherein the contaminant adsorbing material is sandwiched between the first sheet and the second sheet. When excavating and processing residual soil in the excavated residual soil treatment area,
A pollutant adsorbing material layer in which the pollutant adsorbing material according to any one of claims 1 to 4 is laid as a single layer on the excavated residual soil treatment region,
A method for treating excavated residual soil, comprising depositing the excavated residual soil on the pollutant adsorbing material layer to form an embankment and treating the excavated residual soil. When excavating and processing residual soil in the excavated residual soil treatment area,
The pollutant adsorbing sheet according to claim 5 is laid on the excavated residual soil treatment region,
A method for treating excavated residual soil, comprising depositing the excavated residual soil on the pollutant adsorbing sheet to form an embankment and treating the excavated residual soil.

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