JPH1077665A - Aquifer cut-off method for existing well - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely and efficiently prevent the incursion of ground water in an optional unnecessary aquifer of the existing well into the well. SOLUTION: A aquifer cut-off method of the existing well excavates a plurality of guide holes H2 up to a position near to a boundary B2 between the surface layer 1 and first aquifer 2 at equal intervals in the outside of a well pipe 10. Then, a shelf section 21 is formed in the bottom of an area corresponding to an unnecessary aquifer 2 in the outside of the well pipe 10 by grouting quick setting grout through the guide holes H2. Then, a wall section 30 is formed on the upper part of the shelf section 21 by grouting the grout through the guide holes H2. An impermeable layer is constituted of the shelf section 21 and wall section 30. Since the shelf section is subsequently piled up by the quick setting grout to make it impermeable, the incursion of ground water in the unnecessary aquifer 2 into the well can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for blocking an aquifer in an existing well so that groundwater in an unnecessary aquifer does not flow into the existing well.

[0002]

2. Description of the Related Art Generally, an underground where a well is excavated has a stratum in which an aquifer containing groundwater and an impermeable layer impermeable to groundwater alternately appear in the depth direction. When a well is newly constructed, groundwater flows into the well pipe at a position where an aquifer containing groundwater to be flown into the well (hereinafter referred to as “aquifer used”) is formed. There is a screen to make it work. Further, a filter is formed on the outside of the well pipe with a filter material such as pea gravel for filtering the inflowing groundwater. On the other hand, groundwater in an aquifer located in a shallow underground layer is contaminated by domestic wastewater and the like. Therefore, well pipes containing such contaminated groundwater (hereinafter referred to as “unnecessary aquifers”) The screen is not provided at the position where the “layer” is formed.

[0003] Even if a well is newly constructed so that the groundwater of the unnecessary aquifer does not flow into the well as described above, the groundwater of the unnecessary aquifer travels through a filter or a well pipe to form a lower aquifer. May flow down to a location and flow into wells with groundwater from the aquifer being used. In such a case, it is necessary to shut off the unnecessary aquifer in order to prevent the groundwater in the unnecessary aquifer from flowing into the well.

[0004] As an aquifer interception method for an existing well, it is conceivable to use a double casing method used for refreshing an aging well. In this double casing method, an inner pipe with a smaller diameter than the well pipe of the existing well is inserted inside the well pipe to form a double pipe structure, and the gap between the well pipe and the inner pipe is filled with filter material. It is. The inner pipe is provided with a screen only at the position of the use aquifer, and no screen is provided at the position of the unnecessary aquifer. However, since this double casing method inserts the inner pipe inside the well pipe,
It is impossible to prevent the groundwater of the unnecessary aquifer from flowing down to the position of the lower aquifer below the filter or the well pipe formed outside the well pipe. Therefore, if a screen is not provided on the inner pipe at the position corresponding to the used aquifer below where the groundwater of the unnecessary aquifer flows down, the unnecessary aquifer can be shut off by the double casing method However, it is not economical because it will also block good aquifers. On the other hand, while inserting the inner pipe inside the well pipe, the gap between the well pipe and the inner pipe was filled with filter material corresponding to the aquifer used, and an impermeable layer was formed on the upper part of the filter material. Later, a method of blocking unnecessary aquifers by filling the upper part of the impermeable layer with grout material has also been developed. In this case, the grout material filled in the upper part of the impermeable layer penetrates the filter through the screen of the well pipe provided corresponding to the unnecessary aquifer (used aquifer when the well was newly constructed). This makes the filter impermeable. However, this method cannot be applied unless the well pipe is provided with a screen corresponding to the unnecessary aquifer. In addition, the above method can be applied by making a hole at a position corresponding to the unnecessary aquifer of the well pipe using a cutting blade or the like, but the cutting blade cuts into the well pipe and becomes unrecoverable, or the well becomes unrecoverable. There is a problem that the strength of the tube is weakened. As described above, conventionally, there has been no method for reliably and efficiently preventing the groundwater of the unnecessary aquifer from flowing into the well in the existing well.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the groundwater of an unnecessary aquifer in an existing well can be used downward through a filter or a well pipe. An object of the present invention is to provide an aquifer interception method for an existing well that can reliably and efficiently prevent the water from flowing down into an aquifer.

[0006]

According to a first aspect of the present invention, there is provided a method for forming a passage leading to a region corresponding to an unnecessary aquifer outside a well pipe. Forming a water-impermeable layer in the region by injecting a grout material into the region. By using the aquifer blocking method for an existing well according to the first aspect, any unnecessary aquifer can be reliably and efficiently blocked. According to a second aspect of the present invention, in the method for blocking an aquifer of an existing well according to the first aspect, the grout material is injected into the area through the passage before the grout material is injected into the area through the passage. And a shelf portion is formed at the bottom of the region by injecting a flash grout material. If the aquifer blocking method for an existing well according to claim 2 is used, since the glite material is injected after the shelf is formed, it is possible to prevent the grout material from penetrating downward through a filter or the like. The grout material can be injected efficiently. According to a third aspect of the present invention, in the method for constructing an aquifer of an existing well according to the first aspect, a step of forming a shelf in the region by injecting instantaneous setting grout material through the passage is provided. A water-impermeable layer is formed in the region by repeating a plurality of times. Claim 3
By using the aquifer blocking method for an existing well described in (1), an impermeable layer can be easily formed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an aquifer interception method for an existing well according to the present invention will be described with reference to the drawings.
In this embodiment, the basement where the existing well is installed
As shown in FIG. 1, a surface layer 1 appearing on the ground, a first aquifer 2 containing groundwater, a first clay layer 3 that does not penetrate groundwater, a second aquifer 4 containing groundwater, groundwater A second clay layer 5 that does not permeate, a second aquifer 6 containing groundwater, a third clay layer 7 that does not penetrate groundwater, and a fourth aquifer 8 that contains groundwater form a stratum on the bedrock 9. Then, the existing well pipe 10 is dug up to the fourth aquifer 8, does not flow groundwater from the first aquifer 2, which is an unnecessary aquifer, and uses the second, third, and third aquifers. Groundwater flows from the fourth aquifers 4, 6, and 8.

As shown in FIG. 1, the well pipe 10 has a screen 11, which allows groundwater to flow into the well only at positions corresponding to the second, third, and fourth aquifers 4, 6, and 8. 1
2 and 13 are provided respectively. Each screen is
For example, a large number of pores are radially opened on the outer periphery of the well tube 10. In addition, a filter F is formed between the well pipe 10 and the excavation hole 15 by filling a filter material 14 such as pea gravel for filtering groundwater.

While the well is being used, the groundwater in the first aquifer 2 flows down through the filter F and the well pipe 10 to the position of the second aquifer 4 below.
When the groundwater in the aquifer 2 flows into the well from the screen 11 together with the groundwater in the second aquifer 4, the first aquifer is cut using the aquifer blocking method for the existing well according to the present invention. 2
A method for blocking groundwater from flowing into the wells will be described.

First, as shown in FIG. 1, a region corresponding to the first aquifer 2 outside the well pipe 10 (at least it is necessary to include a filter region corresponding to the first aquifer 2).
A water-impervious shelf 21 is formed at the bottom of the slab.

One embodiment of the method of forming the shelf 21 will be described below. First, the guide hole H1 is excavated to a position below the boundary B1 between the first aquifer 2 and the first clay layer 3 so as to cover the filter F outside the filter F. The guide holes H1 are excavated at equal intervals outside the filter F, for example, at three locations. Next, an injection pipe for injecting the instantaneous grout material is inserted into each guide hole H1, and the instantaneous grout material 20 is injected from the injection pipe. The instantaneous setting grout material 20 injected from the injection pipe is, for example, one having a time required for gelling of several tens of seconds or less, and within this time, the upper portion of the first clay layer 3 and the lower portion of the first aquifer 2 And penetrates to the outer peripheral surface of the well tube 10 through the filter F, and then solidifies to form an impermeable shelf 21. Since the flashing grout material 20 injected from each injection pipe penetrates around the well pipe 10 without any gap, the shelf 21 is formed at the bottom of the area corresponding to the first aquifer 2 outside the well pipe 10. Is done.

Next, as shown in FIG. 2, an impermeable wall 30 is formed above the shelf 21. A method of forming the wall portion 30 by using the column jet grouting method will be described with reference to FIGS. First, the shelf 2 is placed outside the filter F.
Excavate the guide hole H2 to a position near the upper part of 1.
As shown in FIG. 4, the guide holes H2 are excavated at equal intervals, for example, at three locations outside the filter F. next,
An injection pipe 31 for grout material injection is inserted into the guide hole H2 to a position near the upper part of the shelf 21. This injection tube 3
Reference numeral 1 denotes a triple pipe structure in which ultra-high pressure water, compressed air, and grout material are independently injected. Next, the injection tube 31
Is raised from near the upper position of the shelf 21 while rotating while spraying ultra-high pressure water, compressed air and grout material from the tip end portion 32. By the injection of the ultrahigh-pressure water and the compressed air, the soil of the first aquifer 2 around the distal end portion 32, the filter material of the filter F, and the like are pulverized into particles. Further, as the tip 32 rotates, the soil, filter material, and the like around the tip 32 are uniformly crushed. The granulated soil, filter material, and the like are discharged to the opening 33 of the guide hole H2 through the gap between the guide hole H2 and the injection pipe 31 together with the ultrahigh-pressure water and the compressed air. Then, the soil, the filter material, and the like are replaced with the grout material by the soil and the filter material being discharged and formed and the grout material flowing into the void. The soil, the filter material and the like discharged into the opening 33 of the guide hole H2 are sucked by a vacuum truck or the like. As the grout material, it is preferable to use a material that requires a longer time for gelation than the instantaneous setting grout material used to form the shelf 21. FIG. 4 shows a state in which the grout material injected from each injection pipe 31 is replaced with soil, a filter material, and the like on the treatment side of the well pipe 10 in this manner. When the grout material solidifies, the impermeable wall 3
0 is formed. With the shelf 21 and the wall 30,
An impermeable layer is formed to prevent the groundwater in the first aquifer 2 from flowing into the well. The wall may be formed only by injecting the grout material without injecting the ultra-high pressure water and the compressed air. In addition, the impermeable wall 3
0 is other than column jet grout method, for example, JSG
It can also be formed by a construction method or the like.

In the above-described embodiment, first, the shelf 21 is formed from the instantaneously-set grout material, and the water-impermeable layer is formed by forming the wall portion 30 on the shelf 21 from the grout material. The water-impermeable layer can be formed using only the instantaneous grout material. This embodiment is shown in FIG. In this embodiment, first, guide holes H3 are excavated at a plurality of locations outside the filter F to a position below the boundary B1 between the first aquifer 2 and the first clay layer 3 so as to cover the filter F. Then, an injection pipe for injecting the instantaneous grout material is inserted into each guide hole. Next, a flash grout material is injected from the insertion pipe, and a shelf 41 is formed at the bottom of a region corresponding to the first aquifer 2 outside the well pipe 10. Next, the injection pipe is raised slightly to inject the instantaneous setting grout material, and a shelf 42 is formed above the shelf 41. Then, in the same manner, the shelves 4
The water-impermeable layer 40 is formed by stacking 3, 44, 45.

In the above embodiment, the present invention is applied to prevent the aquifer from flowing into the well without a screen formed in the well pipe, but the screen is formed in the well pipe. It can also be applied to prevent groundwater in an aquifer from flowing into a well. Also,
Although the shelf is formed of the instantaneous grout material and the wall is formed of the grout material, the material forming the shelf and the wall is not limited to this, and the same material may be used. The excavation positions and numbers of the guide holes H1, H2, H3 can be changed as appropriate. Further, the method of forming the shelf and the wall is not limited to the above embodiment.

[0015]

As described above, according to the aquifer blocking method for an existing well according to the first aspect, any unnecessary aquifer can be reliably and efficiently shut off. Further, according to the aquifer blocking method for an existing well described in claim 2, the grout material can be prevented from penetrating downward through the filter, and the grout material can be injected efficiently. In addition, according to the aquifer blocking method for an existing well described in claim 3, an impermeable layer can be easily formed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of an aquifer blocking method for an existing well according to the present invention.

FIG. 2 is a diagram illustrating an embodiment of an aquifer blocking method for an existing well according to the present invention.

FIG. 3 is a diagram illustrating a method of injecting a grout material.

FIG. 4 is a diagram showing a state in which soil, a filter material, and the like outside a well pipe are replaced with a grout material.

FIG. 5 is a diagram illustrating another embodiment of the aquifer blocking method for an existing well according to the present invention.

[Explanation of symbols]

 2,4,6,8 Aquifer 10 Well pipe H1-H3 Guide hole 11,12,13 Screen 14 Filter material 21,41-45 Shelf 30 Wall 40 Water-impermeable layer F Filter

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[Procedure amendment]

[Submission date] September 26, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0002

[Correction method] Change

[Correction contents]

[0002]

2. Description of the Related Art Generally, an underground where a well is provided has a stratum in which an aquifer containing groundwater and an impermeable layer impermeable to groundwater alternately appear in the depth direction. When a well is newly constructed, groundwater is placed in the well pipe at a position where an aquifer containing groundwater to be flown into the well (hereinafter referred to as “aquifer used”) is formed. A screen for inflow is provided. Further, a filter is formed on the outside of the well pipe with a filter material such as pea gravel for filtering the flowing underground water. On the other hand, the groundwater of the aquifer located in the shallow underground contains domestic wastewater, etc., and such aquifer (hereinafter referred to as "unnecessary aquifer") is formed in the well pipe. No screen is provided at the position indicated.

Claims (3)

[Claims] 1. A method of forming a passage leading to a region corresponding to an unnecessary aquifer outside a well pipe and injecting a grout material into the region through the passage to form an impermeable layer in the region. Characterized by the aquifer cutoff method for existing wells. 2. The method according to claim 1, wherein before the grout material is injected into the region through the passage, a flashing grout material is injected into the region to form a shelf at the bottom of the region. The aquifer cutoff method for existing wells described in the above. 3. A water-impermeable layer is formed in the region by repeating a step of injecting the instantaneous grout material through the passage and forming a shelf in the region a plurality of times. The aquifer cutoff method for existing wells described in the above.