JP2003010832A - Polluted soil cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excavate and remove polluted soil in the vicinity of a boundary site to clean without constructing an earth retaining wall. SOLUTION: A casing 2 is inserted into the polluted soil under pressure and the polluted soil within the casing is taken out by excavation and subjected to cleaning treatment such as heat treatment to remove pollutants. A solidifying agent such as cement is added to cleaned soil and the casing 2 is again filled with the cleaned soil to be drawn out. In order to excavate polluted soil to discharge the same by arranging the casings in overlapping state, the casings are arranged every other one to excavate and remove the whole polluted soil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying contaminated soil, and more particularly to a method for purifying soil which is contaminated by factory waste and is removed and purified without affecting adjacent land.

[0002]

2. Description of the Related Art Soil pollution due to heavy metals such as cadmium, lead and zinc has been a problem, but in recent years, volatile organic chlorine such as trichlorethylene, tetrachloroethylene and 1,1,1-trichloroethane which have been widely used as cleaning agents. It is a problem that organic solvents such as organic compounds penetrate into the ground and pollute soil and groundwater. These organic solvent contaminants exist in the soil and groundwater as a gas phase or a liquid phase.

Soil pollution by organic solvents directly causes growth inhibition of plants and growth of organisms in soil. In addition, rainwater permeates the soil, dissolves pollutants and becomes contaminated groundwater, spreads over a wide area, pollutes drinking water, and is absorbed by plants, which adversely affects the human body. Further, when pollutants are diffused into the atmosphere, they pollute the atmosphere.

For such soil pollution, the incineration method of excavating and removing the soil and incinerating it in an incinerator or the like, enclosing the contaminated area with a wall such as concrete or confining it, or
Immobilization method of injecting and solidifying grout etc. into the contaminated area, soil cleaning method of excavating and removing contaminated soil and washing with water, chemicals, etc. Bioremediation, which injects degrading microorganisms into contaminated soil and decomposes pollutants in the soil, and vacuum extraction method, which suctions from wells installed in contaminated soil to remove volatile harmful organic substances, has been proposed. .

[0005]

When used, organic solvents and the like are discharged and discharged outside the factory. Drainage facilities were placed around the site, and wastewater treatment facilities were often installed around the perimeter of the site. Therefore, as shown in FIG. 5, the overflow from the drainage facility and the contaminant leaked from the crack inevitably contaminate the soil at the boundary of the site.

[0006] When excavating and removing contaminated soil, the open-cut method is often adopted in terms of cost and construction period. However, if the central part of the site is contaminated, the slope will be removed without providing a retaining wall. It is possible to form and excavate to a certain depth by the excavation method, but when excavating and removing soil at the boundary of the site to a certain depth, in order not to affect the adjacent land, the sheet pile wall or continuous underground There was a problem that the retaining wall of the wall had to be constructed, which was expensive and the construction period was long.

The present invention is intended to enable excavation and removal even at the boundary of a site without providing a soil retaining wall on the contaminated soil, and to carry out construction without noise and vibration.

[0008]

The object of the present invention is to remove the earth and sand in the casing from the contaminated soil by press-fitting the casing to a predetermined depth while removing the soil, and then pulling out the casing while backfilling the harmless soil in the casing. Settled.

Since the casing is press-fitted into the soil and the soil therein is excavated and removed, only a limited area in the casing is excavated and discharged, and the surrounding earth pressure is received by the casing when excavating and discharging, and other Contaminated soil can be excavated and removed without affecting the area, especially adjacent land. Since the casing is sunk in the ground by press fitting, it is possible to remove contaminated soil without noise and vibration without scattering noise and vibration to the surrounding area. In addition, since the casings are overlapped and press-fitted into the ground, it is possible to remove the contaminated soil without omissions.By setting the overlapping portions appropriately, it is not necessary to strictly install the casings and construction efficiency is improved. It is possible to raise.

[0010]

EXAMPLE FIG. 1 is a plan view of excavation of a purification area when the soil purification method of the present invention is carried out. As shown in the figure, the casings are press-fitted and installed in the planned area to be cleaned, and the entire area of the planned cleaning area is excavated and discharged. Since soil is excavated and discharged in duplicate, the actual amount of soil discharged will be about 40% higher than the soil to be purified.

The construction procedure is as shown in FIG. 2 and FIG.
The hydraulic casing press-fitting device 1 is installed on the ground, is fixed to the ground to take a press-fitting reaction force, and a counterweight is installed if necessary. The casing 2 is lifted by the crane 4 and set in the press-fitting device 1, the verticality is confirmed, and press-fitting is started. The casing 2 has a diameter of 3000 mm and a length of 5
When the excavation depth is deeper than 5 m, the casing 2 is connected to make the length reach a predetermined depth.
The press-fitting device 1 grips the outer peripheral surface of the casing 2 and presses the casing 2 into the ground while rotating it to the left and right. While press-fitting or when press-fitting to a certain depth, the casing 2 is moved by the excavating device 3 such as a hammer grab.
Excavate and remove the soil inside to remove contaminated soil. Excavation and discharging of the soil in the casing 2 and press fitting of the casing are repeated to press the casing 2 to a predetermined depth to excavate and remove all the contaminated soil in the casing.

As shown in FIG. 4, the excavated contaminated soil is transported to the adjacent contaminated soil treatment facility 6. When the pollutant is a volatile organic solvent such as trichlorethylene, the pollutant is volatilized during the excavation work, so it is necessary to cover the work area with a shield so as to prevent it from being released into the atmosphere. For this reason, the temporary hut 7 is constructed in the work area and the contaminated soil treatment facility prior to the start of the excavation work to construct a completely sealed space. In addition, an exhaust device 8 such as a blower is installed in the work area to prevent workers from inhaling contaminants.
And an exhaust treatment device 9 containing a pollutant adsorbing substance composed of activated carbon or the like, and removing the pollutant in the exhaust before releasing it into the atmosphere.

The polluted soil excavated and discharged to the ground is
Instead of taking it out of the enclosed space, it is transported to a contaminated soil treatment facility, and contaminants are removed from the soil by heat treatment or the like. The purified soil is backfilled in the hollow casing 2 using the backhoe 5 by purifying the contaminated soil at the purification treatment site. When backfilling, a solidifying agent such as cement may be mixed if necessary to also serve as ground improvement. If the contaminated soil cannot be cleaned,
Sediment should be prepared separately for backfilling.

When the contaminated soil exists in the boundary area with the adjacent land, the casing is pressed along the boundary as in the case of constructing a column-type underground continuous wall, and the retaining wall is used as the site boundary. The construction will be carried out so that adverse effects such as ground subsidence of adjacent land due to excavation of contaminated soil will not occur.

The order of press-fitting the casings is well known in the construction of a column-type underground continuous wall, and every other press-fitting is performed so that the casings are press-fitted between two completed soil contaminated soils. When the press-fitting of the casing reaches the planned depth, the press-fitting device 1 is moved and installed in a place where the casing diameters are separated, the next casing 2 is press-fitted, and the operating rate of the press-fitting device 1 is increased. The above procedure is repeated to excavate and discharge contaminated soil in the entire purification plan area and replace it with purified soil.

[0016]

According to the soil purification method of the present invention, since the casing is press-fitted into the contaminated soil to be excavated and removed, the contaminated soil is completely excavated and removed without constructing a retaining wall. It is possible to prevent the land subsidence of the adjacent land from being adversely affected.

[Brief description of drawings]

FIG. 1 is a plan view of a casing arrangement to be press-fitted into a purification planning area.

FIG. 2 is a construction process diagram of the soil purification method of the present invention.

FIG. 3 is a process explanatory view of the soil purification method of the present invention.

FIG. 4 is a plan view showing the arrangement of a purification plan area and a contaminated soil treatment facility.

FIG. 5 is an explanatory diagram showing the site and the position of contaminated soil.

[Explanation of symbols]

1 Press-fitting device 2 casing 3 drilling equipment

Claims (5)

[Claims] 1. A method for purifying contaminated soil, which comprises excavating and discharging contaminated soil in a casing into contaminated soil, press-fitting the casing to a predetermined depth, and pulling out the casing while backfilling the harmless soil in the casing. 2. The method for purifying contaminated soil according to claim 1, wherein the excavated contaminated soil is detoxified and backfilled in the casing. 3. The method for purifying contaminated soil according to claim 1, wherein the casing is continuously press-fitted along the boundary line of the land section containing the contaminated soil so as not to affect the adjacent land. 4. The pollution according to claim 1, wherein every other casing is press-fitted and settled to treat contaminated soil, and excavated portions are overlapped between them to press-fit the casing to treat contaminated soil. Soil purification method. 5. The method for purifying contaminated soil according to claim 1, wherein the contaminated soil treatment is heat treatment.