JP3598342B2 - Methods of containment of underground pollutants by impermeable walls - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method for containing underground pollutants by using impermeable walls.
[0002]
[Prior art]
Underground contaminants usually elute into groundwater and travel with and diffuse with groundwater.However, in order to keep the contaminants in a specific area of the ground, water is conventionally impermeable around the contaminants. It is surrounded by a vertical impermeable wall that reaches the formation, and measures are taken to completely block the movement of groundwater between the inside and the outside of the vertical impermeable wall. The same applies to the case where it is only necessary to keep the data within a limited range for a limited period until the processing is completed.
[0003]
However, as described above, the conventional technology for completely contaminating contaminants includes a long impermeable wall, which increases the construction cost when the water-impermeable layer is deep, and also blocks the groundwater flow by the impermeable wall. As a result, there is a problem that groundwater obstruction occurs on the downstream side (in some cases, on the upstream side at the same time).
[0004]
[Problems to be solved by the invention]
The problem to be solved by the present invention (the object of the present invention) has no such problems as described above, and is particularly effective when the underground pollutants are kept within a limited range for a limited period. It is an object of the present invention to provide a method for containing underground pollutants by impermeable walls.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problems, in the present invention, basically, a water-impervious wall having a length that does not reach the impermeable layer is cast around the underground contaminant, and is surrounded by the water-impervious wall. The velocity of the internal groundwater flow is reduced to slow the movement of groundwater from which pollutants have eluted.
[0006]
Then, in the present invention, the specific width of the inner part surrounded by the impermeable wall is changed by changing one or both of the installation width of the impermeable wall and the installation depth of the impermeable wall in a direction orthogonal to the groundwater flow. The groundwater flow velocity is adjusted.
[0007]
According to the findings obtained by the present inventors from analysis and experiments, the velocity of the groundwater flow inside the vertical impermeable wall gradually decreases as it goes upward, and The flow velocity of the groundwater flow at a specific location in the area is such that the installation width (interval) of the vertical impermeable wall in the direction orthogonal to the groundwater flow is smaller or the depth of the vertical impermeable wall (lower depth) is larger. When it becomes, it becomes small.
[0008]
And if the ratio between the installation width of the vertical impermeable wall in the direction perpendicular to the groundwater flow and the installation depth of the vertical impermeable wall is constant, the inside of the vertical Since the flow velocity of the groundwater flow is constant and similarity is established, it is possible to design using a nomogram created using this.
[0009]
The effect of reducing the velocity of the groundwater flow by surrounding with the impermeable wall described above can be expected not only when the impermeable wall is vertical but also when the impermeable wall is inclined. If there is a medium contaminant and the installation width of the impermeable wall in the direction perpendicular to the groundwater flow becomes too large when the impermeable wall is installed vertically on the side of the existing building, To reduce the distance between the lower ends of the impermeable walls by using the nomogram created based on the ratio of the distance to the depth of the lower ends of the impermeable walls. Can be reduced.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
1 and 2, which are explanatory views of an embodiment of the present invention (when the impermeable wall is vertical), 1 is an underground contaminant, 2 is an impermeable layer, 3 is an impermeable wall, and The water wall 3 is made of a material having a sufficient water-blocking property, and is vertically installed so as to surround the contaminant 1 and to a depth that does not reach the impermeable layer 2.
[0011]
The flow rate of the groundwater flow in the interior 4 surrounded by the water-blocking wall 3 decreases as it goes upward, and the installation width of the water-blocking wall 3 in a direction perpendicular to the groundwater flow (flows in the direction of arrow X). , H is the installation depth of the impermeable wall 3, the flow rate of the groundwater flow at a specific portion (usually, but not exclusively, the center portion) of the interior 4 is such that the installation width B becomes smaller or When the driving depth H increases, the driving depth decreases.
[0012]
Therefore, by changing one or both of the installation width B and the casting depth H of the impermeable wall 3, the flow velocity of the groundwater flow in a specific portion of the interior 4 surrounded by the impermeable wall 3 is adjusted. be able to.
[0013]
In addition, the flow velocity of the groundwater flow in the specific part of the interior 4 surrounded by the water barrier 3 can be relatively displayed, for example, as shown in FIG.
[0014]
As described above, when the ratio between the installation width B of the impermeable wall 3 and the casting depth H is constant, the flow rate of the groundwater flow in the relatively same place in the interior 4 is constant. Utilizing this, for example, a nomogram as shown in FIG. 3 is created, whereby the water impermeability for reducing the flow velocity of the groundwater flow in a predetermined range in the interior 4 surrounded by the water impermeable wall 3 to a certain value or less. The installation width B and the casting depth H of the wall 3 can be easily set.
[0015]
FIG. 3 shows that the ratio of the installation width B of the impermeable wall 3 to the installation depth H when the installation depth H of the impermeable wall 3 is 10 m is 3.0, 2, 0, 1.0, and 0. .5, the velocity ratio V / V ₀ of the groundwater flow at each depth D at an intermediate position of the installation width B of the impermeable wall 3 (where V ₀ is the flow velocity without the impermeable wall 3) For example, if it is desired to secure a range in which the velocity ratio of the groundwater flow decreases to 0.1 to a depth of 5 m, the ratio of D to H is 0.5. It can be seen that the length of the impermeable wall at which the ratio of H and H becomes 0.5 can be selected, and B should be set to 5 m.
[0016]
It goes without saying that, in addition to the nomogram in which the installation depth H of the impermeable wall 3 is constant as shown in FIG. 3, a nomogram in which the installation width B of the impermeable wall 3 is constant can also be created.
[0017]
And even when the impermeable wall is not vertical, the above-mentioned nomogram can be used by setting the distance between the lower ends of the impermeable walls in the direction perpendicular to the groundwater flow to B and the depth of the lower end of the impermeable wall to H. it can.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view for explaining an embodiment of the present invention.
FIG. 2 is a horizontal sectional view of the same.
FIG. 3 is an example of a nomogram when the installation depth of a vertical impermeable wall is constant.
[Explanation of symbols]
1: contaminant, 2: impermeable layer, 3: impermeable wall, 4: inside, X: arrow, B: installation width, H: casting depth.

Claims (1)

A permeation wall surrounding the underground contaminant is installed with a length that does not reach the lower impermeable layer, and the flow rate of the underground water flow inside the permeate layer is reduced to reduce the contaminant. In the method of containing underground pollutants by the impermeable wall that delays the movement of the eluted groundwater, change either the installation width of the impermeable wall in the direction perpendicular to the groundwater flow and / or the installation depth of the impermeable wall. Te, containment method underground pollutants by water shield wall, characterized in that adjusting the flow rate of the groundwater flow in the particular portion stations inside surrounded by water shield wall.

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