JP6545523B2 - Diffusion prevention wall and its construction method - Google Patents

Description

  The present invention relates to a diffusion preventing wall and a method for creating the same, which prevent the contaminants contained in contaminated soil from being diffused by groundwater flow.

  In the ruins of various chemical factories, chemical factory, parts factory, metal smelting factory, plating factory etc., waste disposal site, etc., it is spread to prevent the spread of contaminated soil in the soil by groundwater flow. Preventive walls have been constructed.

  A conventional general diffusion preventing wall is disclosed in Patent Document 1. The diffusion prevention wall disclosed here (underground impervious wall in Patent Document 1) constructs the underground impermeable wall reaching the impermeable layer so as to surround the contaminated area to confine the contaminated soil in situ, An underground water collection facility is cyclically laid at a predetermined depth near the inner side of the middle impermeable wall, and the contaminated groundwater in the contaminated area is collected from the underground water collection facility. The groundwater level near the underground water blocking wall is lowered locally along the underground water blocking wall so that the water level outside the water blocking wall is higher than the water level inside, preventing the spread of contaminated groundwater It is supposed to be possible.

  As described above, the diffusion preventing wall of the contaminant contained in the conventional polluted soil forms the diffusion preventing wall (or the impermeable wall) to the impermeable layer as disclosed in Patent Document 1 to prevent the polluted soil from diffusing. It is common to completely confine the wall and the impermeable layer. In this case, the groundwater flow is also blocked, and the groundwater level rises on the upstream side of the water blocking wall, and the water level fluctuates on the downstream side of the water blocking wall.

  This will be described with reference to FIG. As shown in FIG. 6, the contaminated soil PS is present in the soil G1 (for example, an unconfined aquifer), the impermeable layer G2 is present below the soil G1, and the groundwater level WL is at a constant level. The diffusion prevention wall W is created such that the tip of the soil G1 penetrates the impermeable layer G2 on the downstream side of the groundwater flow with respect to the contaminated soil PS. In this case, since the groundwater flow is completely blocked by the diffusion preventing wall W extending to the impermeable layer G2, the groundwater level WL on the upstream side of the groundwater flow of the diffusion preventing wall W largely rises, while the diffusion preventing wall W The groundwater level WL on the downstream side of the groundwater flow is greatly reduced. The groundwater flow direction has a flow direction unique to the soil although there is some seasonal fluctuation.

  Thus, in addition to the problem that the groundwater level largely fluctuates around the diffusion prevention wall W, there is also a problem that the construction cost of the diffusion prevention wall W increases if the impermeable layer G2 is very deep, or When the impermeable layer G2 is a very thin layer, there is also a problem that the construction in which the front end of the diffusion prevention wall W penetrates into the impermeable layer G2 becomes extremely difficult.

  Therefore, in order to solve the above-mentioned various problems, it is conceivable to construct a diffusion preventing wall whose tip does not extend to the impermeable layer. This will be described with reference to FIG.

  As shown in FIG. 7, by constructing a diffusion preventing wall W 'which does not extend to the impermeable layer G2 and the tip stays in the soil G1, the groundwater wraps around the tip of the diffusion preventing wall W' to the downstream side It becomes possible to flow. Therefore, the rise and fall of the groundwater level WL around the diffusion prevention wall W 'are mitigated.

  However, since the ground water circulates to the downstream side at the tip of the diffusion prevention wall W ′ and flows to the downstream side, the contaminated ground water formed by the groundwater passing through the contaminated soil PS is diffused to the downstream side of the diffusion prevention wall W ′ It will not be possible to achieve the original purpose of constructing the prevention wall W '.

JP 2003-33757 A

  The present invention has been made in view of the above problems, and can solve the problems that may occur when constructing a diffusion preventing wall extending to the impermeable layer, and the contaminants contained in the contaminated soil and the contaminated groundwater It is an object of the present invention to provide a diffusion preventing wall capable of suppressing the diffusion of the metal to the outside of the diffusion preventing wall and a method of constructing the same.

  In order to achieve the above object, the method of creating a diffusion prevention wall according to the present invention is characterized in that in the soil in which the impermeable layer is present, the contaminated soil is present above the impermeable layer, and the groundwater flow is higher than the contaminated soil. A method of creating a diffusion preventing wall for creating a diffusion preventing wall of the pollutant contained in the polluted soil on the downstream side of the soil, comprising an inclined portion inclined downward to the soil contaminated side, and the lower end is an impermeable layer Creating a diffusion barrier that does not reach the

  In the method of creating a diffusion prevention wall of the present invention, the tip has a length not reaching the impermeable layer on the downstream side of the groundwater flow than the polluted soil, and the sloped portion slopes downward toward the polluted soil By creating a built-in diffusion prevention wall, it is made difficult to flow downstream, while allowing the groundwater passing through the contaminated soil to flow around the tip of the diffusion prevention wall and flow downstream. The flow path to the downstream side is lengthened, thereby suppressing the diffusion of pollutants and contaminated groundwater contained in the contaminated soil.

  The fact that the diffusion preventing wall does not extend to the impermeable layer can not cause large fluctuation of the groundwater level around the diffusion preventing wall. Furthermore, when the impermeable layer is deep, there is a problem that the construction cost rises when constructing the diffusion preventing wall extending to the impermeable layer, or when the impermeable layer is thin, the tip of the diffusion preventing wall is penetrated into the impermeable layer. There is no problem that the construction becomes difficult at the same time.

  Since the slope portion constituting the diffusion prevention wall is inclined downward to the contaminated soil side, the flow path length when ground water passing through the contaminated soil goes around the tip of the diffusion prevention wall is lengthened, and this causes In the process up to the intrusion of groundwater, pollutants are left on the upstream side of the diffusion prevention wall and are less likely to be transported to the downstream side of the diffusion prevention wall.

  Here, as an embodiment of a method of creating a diffusion prevention wall having a sloped portion, one embodiment of the creation method includes a sloped portion and a vertical portion connected to both ends of the sloped portion, as viewed in plan Create a U-shaped diffusion prevention wall, and there is contaminated soil on the inside of the U-shape above the slope, so that groundwater flows from the open side of the U-shape to the inside of the U-shape. The form which builds a diffusion prevention wall can be mentioned.

  Here, “C-shaped in plan view” means, in addition to the U-shaped shape in plan view, a shape in which the two sides at both ends are open to the outside (opening is spread), conversely, It includes a shape in which two sides are closed inward (the opening is narrowed), a C-shaped shape as a whole, and the like.

  In the construction method of the present invention, the position of the contaminated soil is precisely specified, and the direction of the groundwater flow is also precisely specified, and the shape (planar shape, side view shape) of the diffusion preventing wall and the shape based on these specified results. It is desirable that layout design be performed. Regarding the direction of groundwater flow, in addition to the inherent flow direction of the target soil, considering the seasonal variation of the flow direction, etc., the contaminated soil is The planar shape and planar dimensions of the diffusion preventing wall should be set so that the flow of underground water passing through can be sufficiently blocked when viewed in a plan view, and the shape and dimensions of the diffusion preventing wall in a side view Also, the shape and length of the diffusion prevention wall are set such that the contaminants will not or will not be transported to the lower end of the diffusion prevention wall when groundwater that has passed through the contaminated soil flows down along the diffusion prevention wall. Good.

  A wall corresponding to one side of the center of the U-shape in plan view is an inclined portion, and two sides at both ends are vertical portions (walls extending in the vertical direction). And, a diffusion prevention wall is constructed such that the contaminated soil exists inside the U-shape above the central inclined portion.

  Ground water flowing inside the U-shaped character passes through the polluted soil, becomes polluted groundwater, and strikes the slope. Contaminated groundwater that has collided with the slope will flow downward along the slope that is opposite to the groundwater flow, and the flow of such contaminated groundwater will cause the contaminants in the contaminated groundwater to be spread at the top of the barrier It can be suppressed to be carried.

  In addition, according to the numerical analysis by the present inventors, the upper side of the inclined portion is the remaining area of the contaminated ground water, and therefore, the contaminated ground water does not flow around the tip of the inclined portion and does not flow downstream Has been identified.

  The present invention also extends to a diffusion prevention wall, which is an impervious layer, a contaminated soil exists above the impermeable layer, and in a soil having a groundwater flow, the contaminated soil is more than the contaminated soil. Is also a diffusion prevention wall of the contaminants contained in the contaminated soil created on the downstream side of the groundwater flow, and has a slope inclined downward to the contaminated soil side, and the lower end reaches the impermeable layer Not.

  As an embodiment of this diffusion preventing wall, it comprises an inclined portion and a vertical portion connected to both ends of the inclined portion, and is U-shaped in plan view, and is above the inclined portion inside the U-shape. There is polluted soil, and groundwater can flow into the inside of the U-shape from the open side of the U-shape.

  As can be understood from the above description, according to the diffusion preventing wall of the present invention and the method for constructing the same, the diffusion preventing wall is provided with the inclined portion inclined downward to the contaminated soil side and the lower end does not reach the impermeable layer Contamination contained in contaminated soil without creating large fluctuation of groundwater level around the diffusion prevention wall by creating a wall, and without causing problems such as increase in construction cost and difficulty in construction It can effectively control the diffusion of substances and contaminated groundwater.

It is the perspective view which showed the diffusion prevention wall of this invention typically. It is II arrow line view of FIG. It is III arrow line view of FIG. (A), (b), (c) is a top view of an embodiment of a diffusion prevention wall. It is a figure showing conditions of numerical analysis and a result, and (a) is a figure showing an initial condition, (b) is a figure showing an analysis result of a diffusion prevention wall of conventional structure, (b) These are the figures which showed the analysis result of the diffusion prevention wall of this invention. It is a schematic diagram which showed embodiment of the conventional diffusion prevention wall, Comprising: It is a figure explaining that the fluctuation | variation of a groundwater level is severe. It is a schematic diagram which showed embodiment of the conventional diffusion prevention wall, Comprising: It is a figure explaining that the contaminated groundwater spreads around the lower end of the diffusion prevention wall.

  Hereinafter, embodiments of the diffusion preventing wall of the present invention will be described with reference to the drawings.

(Embodiment of the diffusion prevention wall and its construction method)
FIG. 1 is a perspective view schematically showing the diffusion preventing wall of the present invention, FIG. 2 is a view taken in the direction of arrow II in FIG. 1, and FIG. 3 is a view taken in the direction of arrow III in FIG.

  As shown in FIG. 1, the diffusion preventing wall 10 is between and connected to the left and right vertical parts 2 extending in the vertical direction and between the left and right vertical parts 2 and 2 and inclined downward toward the contaminated soil PS The sloped portion 1 is generally configured, and as shown in FIG. 2, it has a U-shape in plan view.

  As shown, the diffusion preventing wall 10 is designed such that the contaminated soil PS is located above the slope portion 1 and the groundwater flow in the target soil G1 is U-shaped through the opening of the diffusion preventing wall 10 It is designed to flow into the inside of the and is built based on this design.

  Both the inclined portion 1 and the vertical portion 2 may be made of reinforced concrete, or may be formed of, for example, a steel sheet pile or the like, and one of them is made of reinforced concrete and the other is made of a steel sheet pile or the like. It is also good.

  An impermeable layer G2 exists below the soil G1 in which the diffusion prevention wall 10 is created, and there is groundwater having a certain level of groundwater level and having a flow in a certain direction.

  The lower ends of the inclined portion 1 and the vertical portion 2 of the diffusion prevention wall 10 do not extend to the impermeable layer G2, and are constructed so as to stay in the soil G1 such as an unpressured aquifer.

  As shown in FIG. 3, the groundwater which has passed through the contaminated soil PS flows down along the slope 1, for example. Although the tip of the sloped part 1 does not reach the impermeable layer G2, the groundwater passing through the contaminated soil PS goes around the tip of the sloped part 1 by being inclined downward toward the contaminated soil PS side. Contaminants contained in the contaminated soil PS are transported to the lower end of the inclined portion 1 by allowing the flow toward the lower end of the inclined portion 1 while increasing the flow length to the lower end of the inclined portion 1 while allowing the flow to the downstream side Of the polluted soil PS are effectively suppressed.

  In addition, the inclined surface 1 and the vertical portion 2 do not extend to the impermeable layer G2, and the groundwater level is allowed to flow around at the lower end of these, so that the groundwater level is around the diffusion prevention wall 10 The problem of large fluctuations can not occur.

  In addition, since the inclined portion 1 and the vertical portion 2 do not extend to the impermeable layer G2, when the impermeable layer G2 is located in a deep layer, the length of the diffusion preventing wall becomes long, which causes a problem that the working cost increases. I can not get it. Furthermore, the problem that the impermeable layer G2 is a thin layer and it becomes difficult to penetrate the tip of the diffusion preventing wall into the impermeable layer G2 can not occur.

  In addition, although the inclination part 1 to show in figure is the form which inclined in linear form, the inclination part of various forms, such as a combination form of a curve shape of convex downward, a linear part, and a curve part of the tip, for example, is applicable It is.

  Although the diffusion preventing wall 10 shown in the figure is a combination of the inclined portion 1 and the two vertical portions 2, it has three inclined portions if at least a central portion facing the flow of groundwater is provided with the inclined portion. Various forms of the diffusion preventing wall are applicable, such as a form or a form including one vertical part and two inclined parts. In any of the forms, the presence of the contaminated soil immediately above the central inclined portion creates a diffusion preventing wall, whereby the contaminants contained in the contaminated soil are diffused through the tip of the inclined portion. Is effectively suppressed.

  FIGS. 4A, 4B, and 4C are all plan views of the embodiment of the diffusion preventing wall.

  In the diffusion preventing wall 10A shown in FIG. 4A, the vertical portion 2A is connected to both ends of the central inclined portion 1A so as to open outward, and this is also a U-shaped diffusion preventing wall in plan view It is.

  On the other hand, the diffusion preventing wall 10B shown in FIG. 4 (b) has the vertical portion 2B connected to both ends of the central inclined portion 1B so as to be closed inside, and this is also a U-shaped diffusion in plan view. It is a prevention wall.

  According to the diffusion prevention wall 10B, it is difficult for ground water that has entered into the U-shape to flow out of the U-shape. Therefore, the diffusion suppression effect of the pollutant contained in polluted soil PS becomes still higher.

  Furthermore, in the diffusion preventing wall 10C shown in FIG. 4C, the planar view has an arc shape, and the planar arc-shaped vertical portions 2C at both ends are connected to the central semi-arc-shaped inclined portion 1C. This is also a U-shaped diffusion preventing wall in plan view.

  According to the diffusion preventing wall 10C, since it is difficult for the ground water entering the U-shape of the curved form to flow out to the outside of the U, diffusion of the contaminants contained in the contaminated soil PS is the same as the diffusion preventing wall 10B. The suppression effect is further enhanced.

(Numerical analysis and its results)
The present inventors conducted numerical analysis in each case of the conventional diffusion prevention wall and the diffusion prevention wall of the present invention, and conducted a verification to compare the results of the two. Here, FIG. 5 (a) shows the initial condition, FIG. 5 (b) shows the analysis result of the diffusion preventing wall of the conventional structure, and FIG. 5 (c) shows the diffusion of the present invention. It is a figure showing an analysis result of a prevention wall.

  From the figure which showed the initial condition of Fig.5 (a), the contaminant existed in the surface layer (central dark area), and the groundwater flow was set to the direction which goes to the right of the figure from the left. The conventional diffusion preventing wall is a wall extending in the vertical direction as shown in FIG. 5 (b), and the diffusion preventing wall of the present invention is a wall inclined to the contaminant side as shown in FIG. 5 (c), Contaminants are present directly above the wall. Groundwater flow was applied in each case to identify and compare the behavior of pollutant concentrations in groundwater.

  First, in the conventional diffusion prevention wall shown in FIG. 5 (b), a high contamination degree area remains on the groundwater flow upstream side of the diffusion prevention wall, and an area with a relatively low contamination degree is formed therebelow. It turns out that the lower end of the diffusion prevention wall is wound from the lower side to the downstream side, and a region with a further reduced degree of contamination is formed.

  In FIG. 5 (b), the flow rate of the groundwater passing through the pollutants is hardly reduced, and as shown in the figure, the result is that the pollutants circulate around the downstream side of the diffusion prevention wall and diffuse downstream by the groundwater flow. became.

  On the other hand, in the diffusion preventing wall of the present invention shown in FIG. 5 (c), a region having a high degree of contamination is formed above the diffusion preventing wall (contaminant remains), and a region where the degree of contamination decreases downward Although formed, the groundwater flow did not cause the contaminants to flow downstream around the lower end of the inclined diffusion preventing wall, and the result was that the diffusion of the contaminants was reduced at the inclined diffusion preventing wall.

  From the analysis results, it can be seen that the inclined diffusion preventing wall of the present invention can suppress the diffusion of contaminants to the downstream side of the diffusion preventing wall due to the groundwater flow.

  In both cases, contaminants remain above the groundwater level, which is due to the very low flow rate of groundwater flow in the unsaturated area.

  As mentioned above, although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like within the scope of the present invention. Also, they are included in the present invention.

  1, 1A, 1B, 1C: inclined portion, 2, 2A, 2B, 2C: vertical portion, 10, 10A, 10B, 10C: diffusion preventing wall, G1: soil (unconfined aquifer), G2: impermeable layer , WL ... groundwater level, PS ... polluted soil

Claims (4)

In the soil where there is an impermeable layer, the polluted soil exists above the impervious layer, and there is a groundwater flow, create a diffusion prevention wall of the pollutant contained in the polluted soil downstream of the groundwater flow rather than the polluted soil A method of creating a diffusion prevention wall,
It has a slope that slopes down to the polluted soil side, and the lower end is a diffusion prevention wall that does not reach the impermeable layer , groundwater flows into the polluted soil, and the groundwater passing through the polluted soil is along the slope A method of creating a diffusion prevention wall, which is caused to flow down and form a diffusion prevention wall which causes ground water to flow downstream by turning around the tip of the inclined portion .   It consists of an inclined part and a vertical part connected to both ends of the inclined part, creating a diffusion prevention wall in a U-shape in plan view, and there is contaminated soil above the inclined part inside the U-shape. The method according to claim 1, wherein the diffusion preventing wall is constructed such that the groundwater flows from the open side of the U into the inside of the U. In the soil where there is an impermeable layer, the polluted soil exists above the impervious layer, and there is a groundwater flow, the diffusion prevention wall of the pollutant contained in the polluted soil that is constructed downstream of the groundwater flow rather than the polluted soil. And
It has a slope that slopes down to the contaminated soil side, and the lower end is a diffusion prevention wall that has not reached the impermeable layer , groundwater flows into the contaminated soil, and the groundwater that has passed through the contaminated soil becomes the slope A diffusion-preventing wall that flows down along with the tip of the slope and flows down the groundwater to the downstream side .   It consists of an inclined part and a vertical part connected to both ends of the inclined part, and it has a U-shape in plan view, there is polluted soil above the inclined part inside the U-shape, and underground water is The diffusion prevention wall according to claim 3, which flows into the inside of the U-shape from the open side of the H-shape.

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