JP6857566B2 - Ground purification method - Google Patents

Description

The present invention relates to a method for purifying the ground.

The following Patent Document 1 discloses a purification method for purifying a poorly permeable layer and a contaminated portion formed over the first permeable layer and the second permeable layer located above and below the poorly permeable layer. In this purification facility, an underground barrier that surrounds the contaminated area from three sides is constructed, and a nutrient supply well and a pumping well are constructed in the portion surrounded by the underground barrier. Further, the underground barrier, the nutrient supply well and the pumping well are arranged so as to penetrate the first permeable layer, the impervious permeable layer and the second permeable layer.

Japanese Unexamined Patent Publication No. 2005-177658

In the purification method of Patent Document 1, nutrient salts are supplied to both the first permeable layer and the second permeable layer to activate microorganisms in the entire area surrounded by the underground barrier to detoxify the soil in the contaminated area. Processing. In this method, nutrients are supplied not only to the contaminated area but also to the upper and lower layers and the entire area surrounded by the underground barrier, so the equipment is large and the amount of nutrients required is large. ..

Further, when the contaminated portion formed in the poorly permeable layer, that is, the permeated portion in which the pollutant permeates from the first permeable layer to the second permeable layer is thin, it is difficult to distribute the nutrient salt to this permeated portion.

An object of the present invention is to provide a ground purification method capable of efficiently purifying pollutants in a permeated portion in consideration of the above facts.

The method for purifying the ground according to claim 1 is a method for purifying the ground having an upper permeable layer on the upper surface of the low permeable layer having a permeation portion extending in the vertical direction and a lower permeable layer on the lower surface of the low permeable layer. A step of expanding the permeable area of the permeation portion from the upper permeable layer to the lower permeable layer , a purifying agent is injected into the lower permeable layer, and groundwater containing the purifying agent is pumped from the upper permeable layer. It has a process.

If there is a contaminant in the upper or lower permeable layer, the contaminant will reach the lower permeable layer or upper permeable layer through the permeation of the low permeable layer and will also contaminate the permeation of the low permeable layer.
Therefore, in the method for purifying the ground according to claim 1, the permeable area of the permeation portion is expanded from the upper permeable layer to the lower permeable layer, and the permeation from the lower permeable layer to the upper permeable layer via the permeation portion or from the upper permeable layer. Creates a flow of groundwater containing a purifying agent through the section to the lower permeable layer. This makes it possible to purify the contaminants in the permeation area.

Compared to the method of constructing an underground barrier around the permeation part and purifying the entire area surrounded by the underground barrier, this method can intensively purify the pollutants in the permeation part, resulting in more efficient purification work. high.
The method for purifying the ground according to claim 2 is a method for purifying the ground having an upper permeable layer on the upper surface of the low permeable layer having a permeation portion extending in the vertical direction and a lower permeable layer on the lower surface of the low permeable layer. A step of expanding the permeable area of the permeation portion from the upper permeable layer to the lower permeable layer, a purifying agent is injected into the upper permeable layer, and groundwater containing the purifying agent is pumped from the lower permeable layer. It has a process.

The method for purifying the ground according to claim 3 is to insert an injection pipe into the low water permeability layer, inject a split liquid from the injection pipe into the low water permeability layer to expand the water permeability area of the permeation portion, and gravel to the permeation portion. Fill.

In the method for purifying the ground according to claim 3, the water permeation area of the permeation portion is expanded by the splitting liquid. Further, since the permeation portion is filled with gravel, it is possible to prevent the permeation portion having an expanded water permeation area from shrinking due to earth pressure. Therefore, it is possible to maintain a state in which groundwater containing a purifying agent easily flows through the permeated portion.

In the method for purifying the ground according to claim 4, a pipe body surrounding the permeated portion is inserted into the low permeability layer.

According to the method for purifying the ground according to claim 4 , the tubular body is inserted around the infiltration portion. Therefore, the groundwater containing the purifying agent flowing through the permeation portion is suppressed from diffusing to the outside of the pipe body. As a result, the concentration of the purifying agent around the penetrating portion is unlikely to decrease, and pollutants can be efficiently purified.

According to the present invention, pollutants in the penetrating portion can be efficiently purified.

(A) is a vertical cross-sectional view showing a state in which pollutants are diffused into an upper permeable layer in the ground to which the ground purification method according to the embodiment of the present invention is applied, and (B) is a vertical sectional view showing a state in which pollutants are diffused into a low permeable layer. It is a vertical cross-sectional view which shows the state which permeated into the permeation part of. FIG. 5 is a vertical cross-sectional view showing a state in which pollutants are diffused into the lower permeable layer in the ground to which the ground purification method according to the embodiment of the present invention is applied. In (A), in the ground to which the ground purification method according to the embodiment of the present invention is applied, among the methods for specifying the position of the permeation portion, an injection well is constructed in the lower permeable layer and a thermocouple is provided in the upper permeable layer. It is a vertical sectional view which shows the buried state, and (B) is the vertical sectional view which shows the state which warm water was injected from the injection well into the lower permeable layer. In (A), in the ground to which the ground purification method according to the embodiment of the present invention is applied, among the methods for specifying the position of the permeation portion, the groundwater warmed by the warm water injected into the lower permeable layer is the low permeable layer. It is a vertical sectional view which shows the state which permeated into a permeation part, and (B) is the vertical sectional view which shows the state which the groundwater warmed by the warm water injected into the lower permeable layer reached the upper permeable layer. (A) is a vertical sectional view showing a state in which a casing surrounding the permeation portion is installed in the ground in the ground purification method according to the embodiment of the present invention, and (B) is a vertical sectional view showing a state in which a fracturing fluid is injected into the inside of the casing. It is a vertical sectional view which shows the state which inserted the injection tube. (A) is a vertical sectional view showing a state in which a high-pressure water flow is injected from an injection pipe to form a notch in a low permeability layer in the ground purification method according to the embodiment of the present invention, and (B) is an injection pipe. It is an elevation view which shows the state which expanded the permeation part by injecting a fracturing fluid from. FIG. 5 is a vertical cross-sectional view showing a state in which a fracturing fluid containing gravel is injected from an injection pipe in the ground purification method according to the embodiment of the present invention. (A) is a vertical sectional view showing a state in which a casing is pulled out from the ground and an injection well and a pumping well are installed in the ground purification method according to the embodiment of the present invention, and (B) is a lower permeable layer from the injection well. It is a vertical sectional view which shows the state which the purifying agent is injected into a well. FIG. 5 is a vertical cross-sectional view showing a state in which a purifying agent has permeated into contaminated ground in the ground purification method according to the embodiment of the present invention. It is a vertical sectional view which showed the modification which did not pull out a casing in the ground purification method which concerns on embodiment of this invention.

(ground)
As shown in FIG. 1A, the ground G to which the ground purification method according to the embodiment of the present invention is applied is an upper permeable layer G1 which is a surface layer ground and a low permeable layer in contact with the lower surface of the upper permeable layer G1. It includes a G2 and a lower permeable layer G3 in contact with the lower surface of the low permeable layer G2.

The upper permeable layer G1 and the lower permeable layer G3 are formed of sandy soil and are an aquifer in which groundwater can flow, and the low permeable layer G2 is formed of cohesive soil and is an impermeable layer in which groundwater is difficult to flow. The low water permeability layer G2 may be a layer having a lower water permeability than the upper water permeability layer G1 and the lower water permeability layer G3.

The low water permeability layer G2 is formed with a permeation portion 20 extending in the vertical direction and penetrating from the upper surface to the lower surface of the low water permeability layer G2. The permeation portion 20 is a crack or a gap in the cohesive soil formed in the low water permeability layer G2, and is formed of a cavity (in a state where no earth and sand exists) or a sandy soil having a higher water permeability than the surrounding cohesive soil. Compared to the cohesive soil of No. 1, it has a high permeability and is a channel through which groundwater can flow.

In addition to naturally formed objects such as groundwater and gas ejection holes, the infiltration portion 20 has traces of piles, wells, boring holes, etc. at the time of ground survey, for example, when a building is constructed on the ground G. .. In FIG. 1A, the position represented by the sign GL represents the ground surface, and the position represented by the sign WL represents the groundwater level.

(Pollutants)
The pollutant E generated from the pollutant source 10 in such a ground G is washed away by groundwater and diffuses into the upper permeable layer G1. Further, as shown in FIG. 1 (B), it permeates into the permeation portion 20 in the low water permeability layer G2. Further, as shown in FIG. 2, it diffuses into the lower permeable layer G3. In addition, it gradually penetrates into the cohesive soil around the permeation portion 20 in the low water permeability layer G2.

In this way, a contaminated ground GE in which the pollutant E is diffused is formed over the permeation portion 20 in the upper permeable layer G1 and the low permeable layer G2 and the lower permeable layer G3.

(Method of identifying the position of the penetrating part)
In the contaminated ground GE, in order to purify the permeation portion 20 which is a route for the pollutant E to diffuse from the upper permeation layer G1 to the lower permeation layer G3, first, as an example, the position of the permeation portion 20 is specified by the following procedure. ..

In order to specify the position of the infiltration portion 20, first, as shown in FIG. 3 (A), the injection well 30 is placed at an arbitrary location in the portion where the pollutant E is detected by the soil contamination survey or the like or the portion around it. To construct. The injection well 30 is constructed so that the tip portion reaches the lower permeable layer G3.

Then, a plurality of thermocouples 32 are embedded in the upper permeable layer G1. The thermocouple 32 is a temperature sensor capable of detecting the temperature of the groundwater in the upper permeable layer G1, and a plurality of thermocouples 32 are arranged not only in the left-right direction of the paper surface in FIG. 3A but also in the front-rear direction of the paper surface. Each thermocouple 32 is connected to a measuring device (not shown) by a lead wire 32A, and the temperature at each point of the upper permeable layer G1 can be measured.

Next, as shown in FIG. 3B, hot water is injected from the injection well 30 into the lower permeable layer G3. As the hot water, water having a temperature higher than that of the groundwater in the lower permeable layer G3 and the upper permeable layer G1 is used. As a result, in the lower permeable layer G3, the groundwater around the injection well 30 is mixed with the hot water and warmed. On the other hand, since the low water permeable layer G2 above the lower water permeable layer G3 has a lower water permeability than the lower water permeable layer G3, it is difficult for hot water to diffuse and to be warmed.

The region indicated by the symbol H in FIG. 3B indicates groundwater (hereinafter referred to as groundwater H) in which hot water injected from the injection well 30 and groundwater are mixed and warmed.

When the injection of warm water from the injection well 30 into the lower permeable layer G3 is continued, the warmed groundwater H as shown in FIG. 4 (A) permeates into the inside of the infiltration portion 20, and as shown in FIG. 4 (B). It diffuses into the upper permeable layer G1.

At this time, in the upper permeable layer G1, the groundwater H warmed from the permeation portion 20 diffuses, so that the temperature detected by the thermocouple 32 is higher in the portion near the permeation portion 20 than in the portion far away. That is, in the thermocouples 32B, 32C, and 32D in FIG. 4B, the distance to the penetrating portion 20 is the thermocouple 32B <32C <32D, so that the temperature of the groundwater H detected is the thermocouple 32B> 32C> 32D. Is.

Although the position of the penetrating portion 20 cannot be confirmed from the ground, the temperature detected by each thermocouple 32 can be measured by a measuring device connected by a lead wire 32A. Therefore, by specifying the thermocouple 32 that has detected the highest temperature, the thermocouple 32 closest to the penetrating portion 20 can be specified. Thereby, the position of the penetrating portion 20 can be specified.

In order to measure the position of the penetrating portion 20 more accurately, the thermocouple 32 is added near the thermocouple 32B that has detected the highest temperature. A more accurate position can be known from the temperature indicated by the added thermocouple 32.

(How to purify the ground)
Next, a method of purifying the penetrating portion 20 will be described. In order to purify the permeation portion 20, first, as shown in FIG. 5A, a steel casing 40 is inserted into the ground G so as to surround the permeation portion 20. The casing 40 is inserted so that the tip portion reaches the lower permeable layer G3 and penetrates the low permeable layer G2.

Next, as shown in FIG. 5B, the injection pipe 42 is inserted into the casing 40. The injection pipe 42 is a steel pipe provided with a discharge port 42A on the pipe wall at the tip portion thereof, and is arranged so that the discharge port 42A faces the permeation portion 20.

Next, as shown in FIG. 6A, a high-pressure water stream is applied from the discharge port 42A toward the permeation portion 20 to form a notch 20J that communicates the discharge port 42A and the permeation portion 20. The fracturing fluid (splitting liquid) F is pumped from the notch 20J to the permeation portion 20, and the permeation portion 20 is laterally expanded to expand the water permeation area as shown in FIG. 6 (B).

The fracturing fluid F is water to which a chemical substance used when excavating soil or rock body by water pressure is added, and in this embodiment, a viscous fluid having self-decomposability is used. .. Further, in order to promote the purification of the pollutant E, a decomposing substance of the pollutant E is contained. The autolytic property is a property that the viscosity decreases with the passage of time, and due to this property, the fracturing fluid F is recovered from the pumping well 46 described later without staying inside the permeation portion 20.

Further, as shown in FIG. 7, a fracturing fluid mixed with silica sand, gravel and gravel (hereinafter referred to as gravel S) having a particle size larger than that of the particles forming the low water permeability layer G2 is discharged from the discharge port 42A through the permeation portion 20. The gravel S is filled in the penetrating portion 20. As a result, it is possible to prevent the permeation portion 20 having an expanded water permeation area from returning to its original state due to earth pressure. In the following description, the permeation portion 20 having an expanded water permeation area and filled with gravel S is referred to as an extended permeation portion 20W.

Next, as shown in FIG. 8A, the casing 40 and the injection pipe 42 are pulled out from the ground G, and the injection well 44 and the pumping well 46 are inserted into the ground G. The injection well 44 is inserted from the trace of the extracted injection pipe 42, and is arranged so that the tip portion reaches the lower permeable layer G3. The pumping well 46 is arranged so that the tip portion is located in the upper permeable layer G1.

Since the low permeable layer G2 is formed of cohesive soil, it is difficult for surrounding earth and sand (clay) to flow into the withdrawal traces of the casing 40, and a gap 40W of cohesive soil is formed in the withdrawal traces of the casing 40.

Next, as shown in FIG. 8B, the purifying agent is injected from the injection well 44 into the lower permeable layer G3. In addition, groundwater is withdrawn from the pumping well 46. FIG. 8B shows how the groundwater C containing the purifying agent injected from the injection well 44 spreads to the lower permeable layer G3. At this time, the groundwater C moves upward inside the low permeable layer G2 through the expansion infiltration portion 20W and the gap 40W.

When the purification agent is continuously injected from the injection well 44, as shown in FIG. 9, the groundwater C containing the purification agent diffuses to the range covering the pollutant E in the lower permeable layer G3 and the upper permeable layer G1. Further, it permeates into the cohesive soil of the low permeability layer G2 from the extended permeation portion 20W and the gap 40W, and covers the pollutant E.

The purifying agent is soaked in the contaminated ground GE after being injected for a predetermined period so that the groundwater C containing the purifying agent is not pumped from the pumping well 46 before it is diffused and permeated to the extent that it covers the pollutant E. After securing the period, start the injection again. By injecting the purifying agent intermittently in this way, the amount of the purifying agent used is rationalized, and the pollutant E is gradually purified.

By the above steps, the pollutants E of the permeation section 20 (extended permeation section 20W), the low water permeation layer G2 around the permeation section 20, the upper water permeation layer G1 and the lower water permeation layer G3 are purified.

(Action / effect)
According to the ground purification method according to the present embodiment, a flow of groundwater C containing a purifying agent is created from the lower permeable layer G3 to the upper permeable layer G1 via the extended permeable portion 20W and the gap 40W. As a result, the pollutant E in the permeation portion 20 and the low water permeation layer G2 around the permeation portion 20 can be purified.

This method is compared with, for example, a method of constructing an underground barrier around the portion of the permeation portion 20, the upper permeable layer G1 and the lower permeable layer G3 containing the pollutant E, and purifying the entire area surrounded by the underground barrier. Therefore, the pollutants in the penetrating portion 20 can be intensively purified, so that the purification work efficiency is high. Further, as compared with the method of excavating the ground around the infiltration portion 20, for example, and removing the cohesive soil containing the pollutant E, the cohesive soil does not have to be removed, so that the construction work is light.

Further, in the present embodiment, the permeation portion 20 is expanded in a state where the permeation portion 20 is surrounded by the casing 40. Therefore, it is difficult for the fracturing fluid F pumped from the injection pipe 42 to the permeation portion 20 to open the low water permeability layer G2 in the lateral direction, and the fracturing fluid F flows in the inside of the permeation portion 20 in the vertical direction. The wall of the penetrating portion 20 is eroded by this water flow, so that the flow path area of the penetrating portion 20 is expanded.

In the present embodiment, the casing 40 is pulled out after the expansion penetration portion 20W is formed, but the embodiment of the present invention is not limited to this, and as shown in FIG. 10, the purifying agent is left in the casing 50. May be injected. By doing so, the groundwater C containing the purifying agent flowing through the expanded permeation portion 20W is suppressed from permeating to the outside of the casing 50. As a result, the concentration of the purifying agent around the expanded permeation portion 20W is unlikely to decrease, and the pollutant E in the permeation portion 20 (expanded permeation portion 20W) and the low water permeation layer G2 around the permeation portion 20 can be efficiently purified.

When the purifying agent is injected with the casing 50 left, the range in which the pollutant E permeates around the permeation portion 20 is estimated from the water permeability coefficient of the low water permeability layer G2 and the generation time of the pollutant E. However, it is preferable to use a casing 50 having a diameter capable of surrounding the estimated range.

Further, even when the casing 50 is left when purifying the permeation portion 20, after purifying the pollutant E of the low water permeation layer G2 around the permeation portion 20 and the permeation portion 20, the casing 50 is pulled out to form the upper water permeation layer G1. Purify the contaminant E1 on the outer portion of the casing 50. In purifying the pollutant E1, it is preferable to pull up the tip of the injection well 44 to the upper permeable layer G1 and inject the purifying agent into the upper permeable layer G1.

Further, when the purifying agent is injected into the upper permeable layer G1 and the purification of the pollutant E in the lower permeable layer G3 is completed, the traces of the expanded permeation portion 20W and the casing 50 are filled with an improving material. However, it is advisable to block the flow of groundwater. As a result, it is possible to prevent the purifying agent injected into the upper permeable layer G1 from flowing out to the lower permeable layer G3 through the traces of the expanded permeation portion 20W and the casing 50.

Further, in the present embodiment, as shown in FIGS. 6A and 6B, the injection pipe 42 and the fracturing fluid F are used in order to increase the water permeation area in the permeation portion 20, but the embodiment of the present invention is used. Is not limited to this. For example, the ground G may be excavated from the ground directly above or in the vicinity of the infiltration portion 20 to form a water permeable hole that penetrates the low water permeable layer G2 up and down. By allowing the groundwater C containing the purifying agent to flow through the water permeation holes, the pollutant E of the permeation portion 20 and the low permeation layer G2 around the permeation portion 20 can be purified.

Further, in the present embodiment, as shown in FIGS. 8A and 8B, the injection well 44 is inserted into the lower permeable layer G3, and the pumping well 46 is inserted into the upper permeable layer G1. The form is not limited to this. That is, the pumping well 46 may be inserted into the lower permeable layer G3, and the injection well 44 may be inserted into the upper permeable layer G1. In this case, the groundwater C containing the purifying agent injected from the injection well 44 into the upper permeable layer G1 easily reaches the lower permeable layer G3 by flowing through the expanded permeation portion 20W and the gap 40W due to gravity. As a result, the output of the pump that drives the pumping well 46 can be reduced.

Further, in the present embodiment, the injection well 44 is inserted from the trace of the injection pipe 42, but the embodiment of the present invention is not limited to this, and may be inserted from the outside of the gap 40W which is the trace of the casing 40, for example. .. Further, the number of injection wells 44 is not limited to one, and a plurality of injection wells may be installed. The location and number of pumping wells 46 can be arbitrarily set. As described above, the embodiments of the present invention can be implemented in various aspects.

20 Penetration part F Fracturing fluid (split liquid)
G Ground G1 Upper permeable layer G2 Low permeable layer G3 Lower permeable layer 32 Thermocouple (temperature sensor)
C Groundwater containing purifying agent S Gravel 40, 50 Casing (tube)

Claims (4)

This is a method for purifying the ground with an upper permeable layer on the upper surface of the low permeable layer having a permeation portion extending in the vertical direction and a lower permeable layer on the lower surface of the low permeable layer.
A step of expanding the water permeable area of the permeation portion from the upper water permeable layer to the lower water permeable layer, and
A step of injecting a purifying agent into the lower permeable layer and pumping groundwater containing the purifying agent from the upper permeable layer.
How to purify the ground with. This is a method for purifying the ground with an upper permeable layer on the upper surface of the low permeable layer having a permeation portion extending in the vertical direction and a lower permeable layer on the lower surface of the low permeable layer.
A step of expanding the water permeable area of the permeation portion from the upper water permeable layer to the lower water permeable layer, and
A step of injecting a purifying agent into the upper permeable layer and pumping groundwater containing the purifying agent from the lower permeable layer.
How to purify the ground with. According to claim 1 or 2 , an injection pipe is inserted into the low water permeability layer, and a split liquid is injected from the injection pipe into the low water permeability layer to expand the water permeability area of the permeation portion and fill the permeation portion with gravel. The described ground purification method. The method for purifying the ground according to any one of claims 1 to 3, wherein a pipe body surrounding the permeation portion is inserted into the low water permeability layer.

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