JP2012125668A - In situ insolubilization method for contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in situ insolubilization method that can reduce cost and is highly applicable to contaminated soil at great depth, contaminated soil of the ground containing gravel and cobble stone, contaminated soil immediately below a building, and contaminated soil of a low-permeable layer.SOLUTION: The in situ insolubilization method for contaminated soil that insolubilizes the contaminated soil X by filling a liquid insolubilizer L into the contaminated soil X includes an impermeable wall construction step of constructing an impermeable wall 1, enclosing the contaminated soil X, in the ground G, and an insolubilizer filling step of filling the liquid insolubilizer L into the ground G inside the impermeable wall 1 to saturate the contaminated soil X with the insolubilizer L.

Description

  The present invention relates to a method for insolubilizing contaminated soil in situ.

  Conventionally, excavation backfilling method and in-situ insolubilizing method are generally known as methods for insolubilizing contaminated soil. For example, as shown in Patent Document 1 below, the excavation backfilling method excavates contaminated soil, mixes the excavated soil with an insolubilizing agent, performs insolubilization treatment, and then backfills the excavated soil after treatment to the site. It is a construction method. The in-situ insolubilization method is a method of insolubilizing contaminated soil by kneading the contaminated soil with a kneader while supplying an insolubilizing agent, for example, as shown in Patent Document 2 below. In addition, from the viewpoint of the Contaminated Soil Control Law, contaminated soil that exceeds the second leaching amount standard should be treated with a water shielding wall before being insolubilized by the excavation backfilling method or in-situ insolubilizing method described above. Measures must be taken to contain and prevent the spread of contaminants.

  Conventionally, as a method for insolubilizing contaminated soil, for example, as shown in Patent Document 3 below, an injection method is known in which an injection well is dug into the contaminated soil and an unnecessary agent is injected into the injection well. In the insolubilization treatment by this pouring method, the insolubilizing agent leached from the pouring well soaks into the contaminated soil, so that the contaminated soil is insolubilized. In addition, in the conventional injection method, it is common to recover the insolubilizer from the contaminated soil while supplying the insolubilizer to the contaminated soil. For example, a pumping well is dug in addition to the injection well, and the infusion is insolubilized. There is known a circulation system in which groundwater is pumped from a pumping well while injecting a solution of the agent, an insolubilizing agent is mixed with the water, and the mixture is injected again into the injection well.

JP 2004-8854 A JP 2004-313817 A JP-A-11-207314

  However, the above-described conventional excavation backfilling method and in-situ insolubilization method have a problem that the cost becomes high because of the large-scale construction using large heavy machinery. In particular, in the excavation backfilling method, as the depth of the contaminated soil increases, the excavation cost increases, so the applicability to the deep contaminated soil is low, and there is a problem that it cannot cope with the contaminated soil directly under the building. . Also, the in-situ insolubilization method has a problem that the depth of the contaminated soil is deep, and if there are gravel and cobblestone in the ground, the workability deteriorates and the cost increases, so the applicability to such contaminated soil is low. .

  In the conventional injection method described above, the penetration of the insolubilizing agent into the contaminated soil greatly depends on the water permeability of the contaminated soil. Therefore, for example, when the conventional injection method described above is applied to contaminated soil existing in a poorly permeable layer such as a silt layer having a relatively low permeability, there is a risk that the insolubilization effect and the soil quality after treatment may vary. In the conventional injection method described above, there is a problem that the applicability of the hardly permeable layer to the contaminated soil is low.

  In the present invention, the above-described conventional problems are considered, cost can be reduced, and deeply contaminated soil, contaminated soil of ground including gravel and cobblestone, contaminated soil directly under a building, and It aims at providing the in-situ insolubilization method with high applicability with respect to the contaminated soil of a poorly permeable layer.

  An in-situ insolubilization method for contaminated soil according to the present invention is an in-situ insolubilization method for contaminated soil in which a contaminated soil is filled with a liquid insolubilizing agent to insolubilize the contaminated soil. A water-impervious wall construction step that is constructed inside, and a insolubilizer filling step that saturates the contaminated soil with the insolubilizer by filling the ground inside the impermeable wall with a liquid insolubilizer. Yes.

  With such a feature, it is not necessary to use a large heavy machine, and the contaminated soil can be insolubilized by a small-scale construction. Moreover, diffusion of the insolubilizing agent is prevented by the impermeable wall, the liquid insolubilizing agent stays in the impermeable wall, and the soil inside the impermeable wall is filled with the liquid insolubilizing agent. Therefore, even if the contaminated soil has low water permeability, the contaminated soil is reliably insolubilized by the insolubilizing agent.

  Moreover, it is preferable that the in-situ insolubilization method of the contaminated soil which concerns on this invention constructs the box which encloses the said contaminated soil as the said water-impervious wall.

  This prevents the insolubilizing agent from diffusing even when there is no impermeable layer below the contaminated soil or when the impermeable layer is deep.

According to the in-situ insolubilization method for contaminated soil according to the present invention, since a small-scale construction is sufficient, the cost can be reduced.
In addition, according to the in-situ insolubilization method of contaminated soil according to the present invention, it can be constructed at low cost even in deeply contaminated soil, and there is a case where gravel and cobblestone exist in the ground. However, it can be applied even when there is contaminated soil directly under the building and the soil permeability of the contaminated soil is low. Even if it exists, the effect of an insolubilization process and the soil quality after a process can be stabilized. As described above, according to the in-situ insolubilization method for contaminated soil according to the present invention, high applicability can be exhibited for various contaminated soils, which has been difficult with the conventional construction method.

It is sectional drawing for demonstrating the 1st Embodiment of this invention. It is sectional drawing for demonstrating the 2nd Embodiment of this invention.

  Hereinafter, first and second embodiments of a method for insolubilizing contaminated soil according to the present invention will be described with reference to the drawings.

[First Embodiment]
First, a first embodiment of the in-situ insolubilizing method for contaminated soil according to the present invention will be described with reference to FIG.

  The in-situ insolubilization method in the present embodiment is a method for insolubilizing contaminated soil X present in the ground G of the impermeable layer in situ as shown in FIG. This is a method of insolubilizing the contaminated soil X by filling the soil. The ground G is a ground in which an impermeable layer G2 such as a rock layer or a clay layer having extremely low water permeability is located below a hardly water permeable layer G1 such as a silt layer having a relatively low water permeability. Contaminated soil X exists in the layer G1. Contaminants in contaminated soil X are, for example, type 2 specified hazardous substances (heavy metals) stipulated in the Soil Contamination Countermeasures Law. Specifically, cadmium, hexavalent chromium, cyan, mercury, alkyl mercury, selenium Lead, arsenic, fluorine, boron and the like.

  First, as shown to Fig.1 (a), the impermeable wall construction process which constructs the impermeable wall 1 in the above-mentioned ground G is performed. The impermeable wall 1 is a cylindrical wall portion that surrounds the contaminated soil X in a plan view and surrounds the contaminated soil X, and the contaminated soil X is disposed inside the impermeable wall 1. The impermeable wall 1 extends from the surface (ground surface) of the ground G to the impermeable layer G2. However, the impermeable wall 1 should just be constructed | assembled more than the same height as the upper end of the contaminated soil X, and does not necessarily need to be extended to the ground surface. That is, a bottomed cylindrical impermeable tank having the impermeable wall 1 as a peripheral wall portion and the impermeable layer G2 as a bottom wall portion is formed, and the contaminated soil X is accommodated in the impermeable tank; Become. In addition, the water-impervious wall 1 is a wall part for preventing a liquid insolubilizer described later from flowing out, and is a water-impermeable wall exhibiting water-impervious performance. As this impermeable wall 1, a known impermeable wall can be used, and it is constructed by, for example, a steel sheet pile method, a muddy water solidification method, an SMW (Soil Mixing Wall) method, a chemical solution injection method, or the like.

Next, as shown in FIG. 1 (b), an insolubilizing agent filling step is performed in which the liquid insolubilizing agent L is filled inside the water shielding wall 1 and the contaminated soil X is saturated with the insolubilizing agent L.
More specifically, one or a plurality of injection wells 2 are installed in the ground G in the region within the impermeable wall 1. As the injection well 2, a known injection well can be used. For example, a perforated pipe is inserted inside a vertical hole drilled from the ground surface, and a sand pack is inserted between the pipe and the vertical hole. It consists of a filled configuration. This injection well 2 reaches at least the depth in which the contaminated soil X exists in the poorly permeable layer G1, and extends to the front of the impermeable layer G2.

Subsequently, the insolubilizing agent L is injected into the injection well 2 using a known injector 3. The insolubilizing agent L injected into the injection well 2 is leached from the injection well 2 into the surrounding ground G (the hardly permeable layer G1) and penetrates into the soil gap of the hardly permeable layer G1. At this time, since the area filled with the insolubilizing agent L is surrounded by the impermeable wall 1 and the lower part is closed by the impermeable layer G2, the insolubilizing agent L that has penetrated into the hardly permeable layer G1 is formed. The insolubilizing agent L is gradually accumulated in the impermeable wall 1 as the insolubilizing agent L is injected without flowing out (diffusing) into the external region. Then, in the hardly permeable layer G1 in the impermeable wall 1, when the contaminated soil X is saturated with the insolubilizing agent L until at least the depth of the upper end of the contaminated soil X and the contaminated soil X is saturated with the insolubilizing agent L, the insolubilizing agent L is injected. To stop.
The construction of the in-situ insolubilization process for the contaminated soil X is thus completed.

  According to the in-situ insolubilization method of the contaminated soil X described above, since the injection method of filling the contaminated soil X with the insolubilizing agent L by the injection well 2 is adopted, it is not necessary to use a large heavy machine, and the construction is small. That's it. Therefore, the cost reduction in the insolubilization treatment construction of the contaminated soil X can be achieved.

  Moreover, according to the in-situ insolubilization method of the contaminated soil X described above, even if the contaminated soil X exists deep in the ground, it can be constructed at a low cost. Even if it exists, the influence by the fall of workability is comparatively small, a cost increase can be suppressed, and even if it is a case where the contaminated soil X exists directly under a building, it can construct.

Moreover, according to the above-mentioned in-situ insolubilization method of the contaminated soil X, diffusion of the insolubilizing agent L is prevented by the impermeable wall 1, and the liquid insolubilizing agent L stays in the impermeable wall 1. The inner soil is filled with a liquid insolubilizer L. Thereby, even if the contaminated soil X is soil having low water permeability, the contaminated soil X is reliably insolubilized by the insolubilizing agent L, and the effect of the insolubilization treatment and the soil quality after the treatment can be stabilized.
Thus, according to the above-mentioned in-situ insolubilization method, high applicability can be exhibited with respect to various contaminated soils X, which has been difficult with the conventional construction method.

[Second Embodiment]
Next, a second embodiment of the contaminated soil insolubilizing method according to the present invention will be described with reference to FIG.
In addition, about the structure similar to 1st Embodiment mentioned above, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  First, as shown in FIG. 2 (a), the impermeable wall construction process for constructing the impermeable wall 11 in the ground G is performed. This impermeable wall 11 is a box constructed so as to enclose the contaminated soil X. As a schematic configuration, the impermeable wall 11 has a cylindrical shape surrounding the contaminated soil X in a plan view. It is a bottomed cylindrical body provided with the surrounding wall part 111 and the bottom wall part 112 which is arrange | positioned under the contaminated soil X and obstruct | occludes the lower end of the surrounding wall part 111. The impermeable wall 11 is an impermeable underground wall constructed by a chemical solution injection method, and the peripheral wall portion 111 only needs to be constructed to a height equal to or higher than the upper end of the contaminated soil X. It does not need to be extended to. As the injection solution used for the construction of the impermeable wall 11, a chemical solution having a chemical property that does not impair the function of the insolubilizing agent L is used. Specifically, for example, when an acidic insolubilizing agent L is used. The water-impervious wall 11 is constructed using an acidic to neutral injection solution.

  Next, as shown in FIG. 2 (b), an insolubilizing agent filling step is performed in which the liquid insolubilizing agent L is filled inside the water shielding wall 11 and the contaminated soil X is saturated with the insolubilizing agent L. In the insolubilizing agent filling step, as in the first embodiment described above, the injection well 2 is installed in the ground G in the region within the impermeable wall 1, and the insolubilizing agent is injected into the injection well 2 using the injector 3. Perform by injecting L. Then, in the hardly permeable layer G1 in the impermeable wall 1, when the contaminated soil X is saturated with the insolubilizing agent L until at least the depth of the upper end of the contaminated soil X and the contaminated soil X is saturated with the insolubilizing agent L, the insolubilizing agent L is injected. To stop.

  According to the in-situ insolubilization method of the contaminated soil X described above, since the box containing the contaminated soil X is constructed as the impermeable wall 11, even if the impermeable layer G2 below the contaminated soil X is deep, Diffusion of the insolubilizing agent L is prevented. Thereby, even if the contaminated soil X is soil having low water permeability, the contaminated soil X is reliably insolubilized by the insolubilizing agent L, and the effect of the insolubilization treatment and the soil quality after the treatment can be stabilized.

As mentioned above, although embodiment of the in-situ insolubilization method of the contaminated soil which concerns on this invention was described, this invention is not limited to above-described embodiment, In the range which does not deviate from the meaning, it can change suitably. .
For example, the in-situ insolubilization method for contaminated soil according to the present invention can be applied not only to the above-described ground G but also to various grounds. For example, contaminated soil X exists in highly permeable grounds. Even if it is, it is applicable. In that case, in 1st Embodiment, what is necessary is just to extend the water-impervious wall 1 to the stratum which is lower in water permeability than the stratum where the contaminated soil X exists and does not leak the insolubilizing agent.

  In the above-described embodiment, the injection well 2 is installed in the ground G, and the insolubilizing agent L is injected into the injection well 2, so that it is insolubilized in the ground G (the hardly permeable layer G 1) in the impermeable wall 1. Although the agent L is filled, in the present invention, the insolubilizing agent L can be filled in the ground G in the impermeable wall 1 by another method. For example, when the depth of the contaminated soil X is shallow, the insolubilizer L can be filled into the ground G in the impermeable wall 1 by injecting the insolubilizer L into the ground G from the ground surface.

The insolubilizing agent used in the present invention may be a liquid insolubilizing agent, and the type of the insolubilizing agent can be appropriately changed. An effective drug is selected and used depending on the type of contaminant.
Moreover, the impermeable wall in the present invention may be anything as long as it surrounds the contaminated soil X, and the shape of the impermeable wall can be appropriately changed. For example, it may be an annular or rectangular annular impermeable wall in plan view. Alternatively, it may be a water shielding wall inclined obliquely with respect to the vertical direction, or may be a hemispherical water shielding wall.

  In addition, in the range which does not deviate from the main point of this invention, it is possible to replace suitably the component in above-mentioned embodiment with a well-known component, and you may combine the above-mentioned modification suitably.

1, 11 Impermeable wall L Insolubilizer G Ground X Contaminated soil

Claims (2)

An in-situ insolubilization method for contaminated soil in which the contaminated soil is filled with a liquid insolubilizer to insolubilize the contaminated soil,
Impermeable wall construction process for constructing an impermeable wall surrounding the contaminated soil in the ground,
An insolubilizer filling step of filling the ground inside the impermeable wall with a liquid insolubilizer and saturating the contaminated soil with the insolubilizer;
An in-situ insolubilization method for contaminated soil, comprising: In-situ insolubilization method of contaminated soil according to claim 1,
An in-situ insolubilizing method for contaminated soil, wherein a box containing the contaminated soil is constructed as the water-impervious wall.

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