JP3841339B2 - Viscous ground purification structure and purification method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a viscous ground purification structure and a purification method for purifying gaseous pollutants present in ground above the groundwater level in a viscous ground having a ventilation layer below the viscous soil layer.
[0002]
[Prior art]
Volatile organic compounds such as trichlorethylene, which are used in large quantities in the cleaning process of semiconductor manufacturing plants, etc., may contaminate the soil or groundwater due to leakage, etc. There is a problem that the use of groundwater is restricted.
[0003]
As a method for purifying such contaminated soil and contaminated groundwater, conventionally, a well is dug around the contaminated ground area and pumped to pump the pollutant dissolved in the pumped groundwater to an aeration treatment device or activated carbon on the ground. Groundwater pumping method that collects with an adsorption treatment device, or a soil gas suction method that sucks gaseous pollutants that exist in the ground above the groundwater level and that are lower than the groundwater level, and collects the contaminants with an activated carbon adsorption treatment device on the ground and so on.
[0004]
[Problems to be solved by the invention]
However, the application range and purification efficiency of the groundwater pumping method and soil gas suction method are greatly affected by the ground conditions. That is, the groundwater pumping method and the soil gas suction method are effective methods with good purification efficiency in sandy gravel ground or sandy ground with high water permeability or air permeability, but in viscous ground with low water permeability or air permeability, Since the range of influence of pumping water or gas suction is small and the purification efficiency is poor, the processing cost may be enormous or even difficult to apply. In particular, in ground with a high altitude such as a hill, the groundwater level is deep in the ground, and gaseous pollutants may be present above the groundwater level, and the ground is, for example, sandy ground. However, the groundwater pumping method is not applicable.
[0005]
Therefore, the object of the present invention is to apply the soil gas suction method to the viscous ground with low air permeability where the contaminated layer exists in the ground above the groundwater level, and the purification efficiency is high and the treatment period is greatly shortened. It is in providing the viscous ground purification structure and purification method which can aim at.
[0006]
[Means for Solving the Problems]
In such a situation, the present inventors have conducted intensive studies, and as a result, in a viscous ground having a ventilation layer below the viscous soil layer, the groundwater level is located below the ventilation layer or the ventilation layer and is lower than the groundwater level. A large number of ventilation pillars were created at an appropriate pitch on the ground where the contaminated layer exists above, and the air permeability of the ground was improved. Then, the gas suction device was operated and disposed in the ventilation layer portion of the suction hole. If a purification method that collects gaseous pollutants on the ground via the suction point is adopted, the soil gas suction method can be applied even to viscous ground with low air permeability. The present inventors have found that the processing cost can be reduced because it can be greatly shortened, and the present invention has been completed.
[0007]
That is, the present invention (1) is a viscous ground having a ventilation layer below the viscous soil layer, wherein the groundwater level is located below the ventilation layer or the ventilation layer, and the contaminated layer is above the groundwater level. A structure for purifying existing ground, the suction hole penetrating the viscous soil layer and reaching the ventilation layer; and a gas suction device for arranging a suction point in the ventilation layer portion of the suction hole; A viscous ground purification structure comprising a sand pile or a crushed stone pile distributed around the gas suction device and penetrating through the viscous soil layer to reach at least the ventilation layer is provided.
[0008]
Further, the present invention (2) is a viscous ground having a ventilation layer below the viscous soil layer, wherein the groundwater level is located below the ventilation layer or the ventilation layer, and the contaminated layer is above the groundwater level. A large number of sand piles or crushed stone piles were created on the existing ground at an appropriate pitch to improve the air permeability of the viscous soil layer, and then the gas suction device was operated and installed in the ventilation layer portion of the suction hole The present invention provides a viscous ground purification method for recovering the gaseous pollutant to the ground via a suction point.
[0009]
According to the present invention, it is possible to apply the soil gas suction method even in a viscous ground with low air permeability where a contaminated layer exists in the ground above the groundwater level, and the purification efficiency is improved, and the treatment period is greatly shortened. Therefore, the processing cost can be reduced.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, the purification method of the viscous ground in the embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view schematically showing the purification structure of the viscous ground of this example, FIG. 2 is a cross-sectional view schematically showing the purification structure of FIG. 1, and FIG. 3 explains the purification method of the viscous ground of this example Each figure is shown. In addition, the arrow in FIG. 3 shows the flow of a gaseous pollutant.
[0011]
The viscous ground purification structure 10 in the present embodiment is a viscous ground 9 having a ventilation layer 2 below the viscous soil layer 1, the groundwater level WL is located below the ventilation layer 2 or the ventilation layer 2, and the groundwater This is a structure for purifying the ground where the contaminated layer 4 exists above the position WL. In the present invention, the viscous ground 9 is not particularly limited as long as it has the ventilation layer 2 below the viscous soil layer 1, and the ratio of the viscous soil layer 1 and the ventilation layer 2 occupying in the viscous ground 9 is used. It is not limited. That is, the viscous ground 9 includes both a ground in which the thickness of the viscous soil layer 1 is equal to or greater than that of the ventilation layer 2 and a ground in which the thickness of the ventilation layer 2 is greater than the thickness of the viscous soil layer 1. .
[0012]
The viscous ground 9 is not particularly limited as long as it has the ventilation layer 2 below the viscous soil layer 1, and may have a surface layer portion above the viscous soil layer 1. The viscous soil layer 1 is a ground called silty or clay, and the ventilation layer 2 is a ground called a sandy soil layer or a gravel soil layer. Moreover, as a pollutant, the volatile organic chlorine compound etc. which exist in gaseous form are mentioned. The contaminated layer 4 contaminated with the pollutant is usually present in the viscous soil layer 1 above the natural groundwater level WL, but is not limited to this. For example, it exists from the viscous soil layer 1 to the ventilation layer 2. You may do it.
[0013]
The suction hole 6 penetrates the viscous soil layer 1 and further reaches the ventilation layer 2, and for example, a hollow tube or the like is used. The depth of the ventilation layer portion 61 of the suction hole 6 may be as long as the suction point 7 of the gas suction device can be installed, but may reach the groundwater level WL as shown in FIG. The gas suction device is not particularly limited as long as the suction point 7 is disposed in the ventilation layer portion 61 of the suction hole 6, and has a pump body near the suction point, or the pump body is located at the place. Instead, suction may be performed by a ground vacuum pump through a suction pipe connected to the suction point 7. Further, the place where the suction point 7 is disposed is not particularly limited, but it is the ventilation layer portion 61 of the suction hole 6 and the vicinity of the surface of the ventilation layer 2. This is preferable in that the substance can be sucked immediately and the diffusion of contaminants in the ventilation layer 2 can be prevented.
[0014]
The ventilation column 5 is intended to improve the air permeability of the viscous soil layer 1 and is not particularly limited as long as it is distributed around the suction point 7. It penetrates the cohesive soil layer 1 and reaches at least the ventilation layer 2. Therefore, the bottom of the vent column 5 is used up to the surface of the vent layer 2, the one in the middle of the vent layer 2, or the one that penetrates the vent layer 2 and reaches the groundwater level WL (see FIG. 2). it can. Among these, the thing with the lower end part of the ventilation column 5 to the surface of the ventilation layer 2 is suitable at the point that the construction material of the ventilation column 5 can be saved and a construction work period can also be shortened. As the ventilation column 5, a sand pile and a crushed stone pile can be used. The sand pile and the crushed stone pile can be constructed by a known sand pile construction method. Specifically, a sand drain construction method can be applied in which a sand pile is formed by discharging sand inserted into the pipe after the hollow pipe has been penetrated to the design depth in the ground and then pulled out to the ground surface. The viscous soil layer 1 in which the contaminated layer 4 exists has a ventilation path formed by the formation of the large number of ventilation columns 5, so that the air permeability is enhanced. For this reason, application of the soil gas suction method to the viscous soil layer 1 becomes practical, and the purification efficiency for the contaminated viscous ground, which has been difficult in the past, is increased. Moreover, the ground strength of the viscous soil layer 1 can be raised by creation of a sand pile or a crushed stone pile.
[0015]
The interval between the ventilation pillars 5 distributed around the suction point 7 is appropriately determined based on the ground conditions and the requirements of the purification period. That is, when the clay soil layer 1 is a silty ground, the spacing between the ventilation columns 5 can be increased. When the clay soil is a clay soil, the spacing between the ventilation columns 5 is decreased. Thus, according to the air permeability of a viscous soil layer, the placement interval of the ventilation column 5 is appropriately determined. Moreover, when the purification period can be extended, the interval between the ventilation columns 5 can be increased. When the purification period is desired to be shortened, the interval between the ventilation columns 5 is decreased. As described above, the placement interval of the ventilation columns 5 is appropriately determined even in accordance with the request for the purification period.
[0016]
In the viscous ground purification structure 10 of this example, a shielding wall (not shown) may be formed so as to surround the contaminated layer 4. The shielding wall divides the purification target area where the contaminated layer 4 is present and the other non-purification area, and can prevent the contaminant from flowing out to the non-purification area. The shielding wall is not particularly limited, and a pullable steel sheet pile can be used. For example, a shielding wall that penetrates the viscous soil layer 1 and the ventilation layer 2 where the contaminated layer 4 exists and reaches the groundwater level WL is suitable.
[0017]
A construction method for purifying the viscous ground using the purification structure 10 will be described with reference to FIG. First, the ground conditions and the contamination status are grasped, the size of the purification structure 10 is determined, and the above-described purification structure 10 is constructed. That is, in the viscous ground 9 having the ventilation layer 2 below the viscous soil layer 1 and the ground where the groundwater level WL is located in the ventilation layer 2 and the contaminated layer 4 exists above the groundwater level WL, the ventilation column 5 is formed at an appropriate pitch to improve the air permeability of the viscous soil layer 1 (FIG. 2). From this state, the gas suction device is operated.
[0018]
Gaseous contaminants present in the contamination layer 4 flow into the ventilation column 5 by the suction action of the suction point 7 (in the direction of arrow X in FIG. 3). Next, the air flow sucked in the contaminant moves downward in the ventilation column 5 and reaches the ventilation layer portion 51 of the ventilation column 5, and similarly, the suction point 7 sucks the inside of the ventilation layer 2 by the suction action of the suction point 7. Flows in the direction (in the direction of arrow Y in FIG. 3). Subsequently, it is recovered from the suction point 7 to the ground surface by a suction pipe (not shown). The contaminant contained in the suction gas is recovered by a known ground recovery device such as an activated carbon adsorption processing device. Such treatment of contaminants is performed until the concentration of contamination in the suction gas becomes a certain value or less.
[0019]
According to the purification method of the viscous ground 9 using such a purification structure 10, the viscous soil layer 1 in which the contaminated layer 4 is present is formed with an aeration path by the creation of the numerous ventilation columns 5. Air permeability is increased. For this reason, application of the soil gas suction method to the viscous soil layer 1 becomes practical, and the purification efficiency for the contaminated viscous ground, which has been difficult in the past, is increased.
[0020]
【The invention's effect】
According to the present invention, even if a contaminated layer exists in the ground above the groundwater level, and the ground is a viscous soil layer with low air permeability, the soil gas suction method can be applied, the purification efficiency is increased, and the treatment is performed. Since the period can be significantly shortened, the processing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a plan view schematically showing a viscous ground purification structure according to an embodiment of the present invention.
2 is a cross-sectional view schematically showing the viscous ground purification structure of FIG. 1. FIG.
FIG. 3 is a diagram for explaining a viscous ground purification method according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cohesive soil layer 2 Ventilation layer 4 Contamination layer 5 Ventilation column 6 Suction hole 7 Suction point 9 Viscous ground 10 Viscous ground purification structure 51 Ventilation layer portion 61 of ventilation column Ventilation layer portion X, Y of suction hole Gaseous contamination Material flow direction WL Groundwater level

Claims (2)

This is a structure that purifies the ground where the groundwater level is located below the aeration layer or above the aeration layer and the contamination layer exists above the groundwater level. A suction hole penetrating the viscous soil layer and reaching the ventilation layer, a gas suction device having a suction point disposed in the ventilation layer portion of the suction hole, and a distributed distribution around the gas suction device. And a sand pile or a crushed stone pile passing through the viscous soil layer and reaching at least the ventilation layer. A sand pile or crushed stone in a viscous ground having a ventilation layer below the viscous soil layer, in which the groundwater level is located below the ventilation layer or the ventilation layer, and the contaminated layer exists above the groundwater level. A large number of piles are formed at an appropriate pitch to improve the air permeability of the viscous soil layer, and then the gas suction device is operated and the gas state is passed through the suction point provided in the ventilation layer portion of the suction hole. A purification method for viscous ground, characterized by collecting the pollutants of the soil on the ground.

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