JPH11169836A - Method for removing soil pollutant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing soil pollutants which surely prevents the pollution of the ground water by the soil pollutants by disposing plural horizontal wells constituting a water suction culvert at prescribed intervals and increasing the suction force of the gravity water in the unsaturation zones of the horizontal wells. SOLUTION: The culvert 1 is built by excavating the plural horizontal well holes apart the prescribed intervals W below the polluted zones 25 existing in the unsaturation zones 2. The gravity water 40 which dissolves the pollutants by penetrating in the ground through the polluted zones 25 from the ground surface GL is forcibly collected from the screen formed in the respective horizontal wells. Further, the collected gravity water 40 is discharged. The collection of the gravity water 40 into the horizontal wells 10a, 10b (10) is executed by sucking air into the horizontal wells 10 and drying the ground strata 31 on the peripheries of the horizontal well holes to induce capillarity in these parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing soil contaminants, and more particularly to a method for removing nitrate nitrogen, cadmium, arsenic, copper, hexachloride existing in an unsaturated zone which is a layer above groundwater table. Chromium, a method of removing low-volatile substances such as heavy metals such as mercury, such as rainwater dissolved such soil contaminants move or descend and forcibly collect before reaching the aquifer, The present invention relates to a method for removing soil pollutants by culvert drainage that enables purification of soil pollutants.

[0002]

2. Description of the Related Art Generally, drainage from a culvert is shown in FIGS.
A culvert having the structure shown in FIG. As shown in FIG. 7, the culvert 1 is cut from the ground surface GL to a depth D substantially equal to the groundwater level WL, and a plurality of water intake conduits 3 are arranged at predetermined intervals W to flow down from the ground surface GL. It is designed to absorb gravity water. The plurality of water inlets 3 are connected to a water drain 4 excavated deeper than the water inlet 3, and collect the gravity water from the water inlet 3. Further, the drainage channel 4 leads to a drainage channel 6 excavated deeper than the drainage channel 4 through the instep 5, so that the gravity water is drained from the drainage channel.

[0003] Since the culvert 1 is excavated as described above, digging the culvert requires a large-scale construction, which increases the cost and requires a long time. Therefore, recently, by excavating a horizontal well without digging, it has been practiced to excavate a culvert quickly and inexpensively.

That is, in order to excavate a horizontal well 10 constituting a culvert as shown in FIG. 2, small pits are formed at both ends at a predetermined distance L as shown in FIG. The pit 12 and the other pit 13. The power unit truck 7 arranged on the ground is driven and the drilling tool 15 provided on the drill head 9 at the tip of the rod 8 is rotated while being guided by the drill unit 14, and the power unit truck 7 digs obliquely from the penetration pit 12 at a predetermined angle α. . At this time, fresh water or the like as a lubricating material is jetted from the tip of the drilling tool 15 to excavate the horizontal well hole 101 while cutting down the soil. In addition,
The drill head 9 is provided with a transmitter, and a signal wave emitted from the transmitter is detected on the ground by the flow locator 16 to confirm the drilling position of the drill head 9.

When the excavation of the horizontal well 10 is completed, a reamer 17 is attached to the tip of the rod 8 in place of the excavation tool 15 as shown in FIG. Further, a cylindrical well material 19 having a large number of holes 18 formed in the screen S following the reamer 17 to form a screen S is attached via a joint 21.
The reamer 17 is rotated while jetting a lubricating material such as fresh water, and is moved in a direction opposite to the excavation direction of the horizontal well hole 101 as shown by an arrow B in FIG. I do. At the same time, the horizontal well 10 is formed by forcibly drawing the well material 19 into the narrow horizontal well hole 101.

[0006]

According to the method for excavating the horizontal well 10 constituting the culvert described above, the horizontal well can be excavated inexpensively and in a short time.
Since the well material 19 is forcibly drawn into the narrow well hole,
There is a problem that the wall surface of the horizontal well hole 101 is compressed and the water permeability and air permeability become extremely poor, and the amount of water absorption per unit screen length becomes smaller than that of the vertical well.

When the soil contaminants are low volatile substances such as nitrates and heavy metals, the soil contaminants stay in the contaminated zone 25 (FIG. 1). This low-volatility pollutant dissolves in rainwater, snowmelt, or the like, and gradually descends and permeates toward the aquifer 20 as gravity water 40 as shown in FIG. Conventional culverts cannot capture all of the gravitational water, resulting in aquifer 20
It has been difficult to prevent the spread of soil and groundwater pollution by causing soil contaminants to enter the area.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem. A plurality of horizontal wells constituting a culvert are provided at predetermined intervals, and the gravity water suction force of the culvert is increased to improve the soil. It is an object of the present invention to provide a method for removing soil pollutants, which surely prevents the soil from being extensively contaminated by pollutants.

[0009]

SUMMARY OF THE INVENTION The present invention is a method for removing soil pollutants, and is configured as follows to solve the above-mentioned technical problems. That is, the method for removing soil contaminants of the present invention comprises the steps of: constructing a culvert by digging a plurality of horizontal well holes at predetermined intervals below a contaminated zone existing in an unsaturated zone; Forcibly collecting gravitational water having permeated the zone to dissolve the contaminant from a screen formed in each of the horizontal wells, and discharging the collected gravitational water, the method comprising: The gravitational water in which the water is dissolved is prevented from reaching the aquifer (claim 1).

In the present invention, the interval between the plurality of horizontal well holes 101 constituting the culvert 1 is a distance sufficient to dissolve the pollutant and to reliably capture rainwater that descends and penetrates. It is set according to soil conditions such as the nature. The gravity water includes surface water, which is rainwater, river water, lake water, and the like, which penetrates into the ground due to snowfall or rainfall.

In order to forcibly collect gravitational water for dissolving the soil contaminants from a screen formed in a horizontal well, the air in the well hole is decompressed by a fan, a blower, a compressor, or the like to reduce the pressure around the culvert. It is preferable to dry the formation and forcefully collect gravity water.

Further, in order to discharge the collected power water, it is preferable to use a self-contained pump (vacuum pump) or a submersible pump which is installed on the ground.

The method for removing soil contaminants comprises the above-mentioned essential components, but the above-described method is also applicable to the following cases. That is, in the step of forcibly collecting gravity water in the horizontal well, the air is sucked into the horizontal well to dry the stratum around the horizontal well hole to form a drying zone, and the drying zone is formed. The gravitational water is sucked into the well hole by a capillary action that occurs (claim 2).

In the present invention, in order to dry the formation around the well hole, the air in the well is decompressed and sucked by a fan, a blower, a compressor, or the like, and dried in a vacuum. Appropriate effective means such as sending air at a high wind speed or sending hot air can be taken.

According to the method for removing soil pollutants according to the present invention, gravity water in the process of infiltrating from the ground surface is forcibly collected in the horizontal well hole. Therefore, the contaminants dissolved in the gravity water that permeates the ground through the pollution zone from the ground will be collected and discharged together with the gravity water in the horizontal well, flow down to the aquifer, and contaminate the groundwater. Is prevented.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the method for removing soil pollutants of the present invention will be described in more detail with reference to an embodiment shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, unless otherwise specified. It is only an illustrative example. FIG. 1 shows a section of a stratum including a culvert used in a method for removing soil contaminants according to an embodiment of the present invention, and a state where a horizontal well constituting the culvert suctions gravitational water that descends and penetrates. FIG. 2 is a cross-sectional view of a horizontal well constituting the culvert along the line II-II in FIG. 1, and FIG. 3 is a partial cross-sectional view of the horizontal well showing an air suction process around the well. 4 and 5 are explanatory diagrams of a state of excavating a horizontal well.

In FIG. 1, the unsaturated zone 2 below the ground surface GL
There is a contaminated zone 25 in which soil contains low volatile soil contaminants such as nitrate nitrogen and heavy metals. A plurality of horizontal wells 10a having a predetermined depth Da and an interval W below the contaminated zone 25 and excavated as shown in FIGS.
The culvert 1 is constructed by excavating 10b. The horizontal well 10
a and 10b have a pair of openings 23 and 24 opening to the ground, and the well material 19 is inserted into the horizontal well hole 101.

In FIG. 1, two horizontal wells 10 are provided.
Although only a and 10b are shown, it goes without saying that three or more horizontal wells can be excavated as appropriate according to the size and soil quality of the contaminated zone 25. Furthermore, the aquifer 20 is located below the culvert 1 and above the impermeable layer 29.

A blower (not shown) is disposed on the ground in the one opening 23. Compressed air is sent from the discharge side of the blower into the horizontal well hole 101 at a high speed. A ground-based self-contained pump (not shown) is provided on the other opening 24 side to discharge the motive water collected in the horizontal well.

The air inside the well is depressurized by driving the blower to flow air from the opening 24 side into the horizontal well hole 101 at a high speed as shown in FIG. Many holes 1 in screen S of horizontal well 10
Aspirate from 8. The horizontal well 10
The stratum around is vacuum dried. For this reason, the dried stratum is in a state in which minute gaps are generated between the soil particles.

As shown in FIG. 1, the stratum around the horizontal well 10 is surrounded by iso-pressure lines 35a, and
The drying zone 31 directly surrounds 0a and 10b. Further, a semi-dry zone 32 is formed around the drying zone 31 and is surrounded by the iso-pressure line 35b. Then, a wet zone 33 is formed which is surrounded by the iso-pressure line 35c surrounding the semi-dry zone 32. The water pressure of the iso-pressure line 35 gradually decreases toward the center of the horizontal well 10 (10a, 10b).

Thus, the gravitational water 40 that has infiltrated into the ground from the ground surface GL due to rainfall or snowfall naturally flows down in the unsaturated zone 2 by gravity as shown in FIG. In the drying zone 31, as described above, minute gaps are generated between the soil particles (not shown), so that a capillary phenomenon occurs, and the gravitational water 40 forms the screen S of the horizontal wells 10a and 10b due to a difference in water content. From the large number of holes 18 into the horizontal well hole 101. Note that a predetermined interval W is set between the horizontal well and the adjacent horizontal well, so that the gravity water 41a does not move or descend and permeate so as to permeate the aquifer 20 without being sucked into the horizontal well.

Next, a gravitational water 40 is discharged by operating a self-contained pump or a submersible pump (not shown) installed on the ground.
Thereafter, nitrate nitrogen and heavy metals dissolved in the motive water are separated from the motive water to purify the soil.

Further, a horizontal well 1 located on the right side of FIG.
If the tray 36 is installed at the lower part as shown in FIG. 0b, the gravity water 40 which falls from above the horizontal well 10 and flows downstream, and the gravity water 4 which cannot be absorbed by the horizontal well 10
It is prevented that 0 further descends and penetrates into the aquifer 20 to widely pollute the soil.

[0025]

As described above, according to the method for removing soil contaminants of the present invention, horizontal wells are arranged at predetermined intervals below the contaminated zone existing in the unsaturated zone, and contaminated soil is removed from the ground surface. Since gravitational water that permeates into the ground and dissolves contaminants through the band is forcibly collected from the screen formed in the horizontal well, the gravitational water can be reliably captured in the horizontal well. By preventing the gravity water from migrating to the water layer, soil pollution can be effectively prevented.

Further, by moving the air in the well and drying the stratum around the well, the gravity water is forcibly sucked into the well hole by capillary action. The movement of gravity water in which water is dissolved is more reliably prevented.

Further, if a tray is provided below the horizontal well, even if the gravitational water cannot be captured in the well, the tray receives the gravitational water for dissolving the contaminants and removes it. Since the water can be discharged, the spread of the contamination due to the infiltration of the pollutant into the aquifer can be more reliably prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a stratum including a culvert used in a method for removing soil contaminants according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, showing a horizontal well forming a culvert.

FIG. 3 is a partial cross-sectional view of a horizontal well showing a process of sucking air around the well.

FIG. 4 is a schematic view showing a state of excavation of a horizontal well.

FIG. 5 is a schematic view showing a state where well materials are incorporated into a horizontal well.

FIG. 6 is a plan view showing an open state of a conventional culvert.

FIG. 7 is a sectional view taken along line VII-VII in FIG. 6;

[Explanation of symbols]

 Reference Signs List 1 culvert 2 unsaturated zone 10 horizontal well 101 horizontal well hole 20 aquifer 25 polluted zone 31 drying zone 36 tray 40 gravity water GL ground surface S screen W horizontal well interval

Claims (2)

[Claims] 1. A step of digging a plurality of horizontal well holes at predetermined intervals below a contaminated zone existing in an unsaturated zone to construct a culvert, and dissolving contaminants by permeating the contaminated zone from the ground surface. Forcibly collecting the collected gravitational water from the screen formed in each of the horizontal wells, and discharging the collected gravitational water, wherein the gravitational water in which the contaminants are dissolved is aquifer. A method for removing soil contaminants, wherein the method comprises preventing migration to soil. 2. The step of forcibly collecting gravity water in the horizontal well, wherein air is sucked into the horizontal well to dry a stratum around the horizontal well hole to form a drying zone. A method for removing soil contaminants, wherein the gravity water is sucked into a well hole by capillary action occurring in a drying zone.