JP3969269B2 - Deep well method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a deep well method.
[0002]
[Prior art]
A deep well method is known as a method that is used to lower the groundwater level when the groundwater level in the ground is deep, or to reduce pressured water and improve soft ground. (See Non-Patent Document 1)
[0003]
FIG. 4 shows a typical example of the deep well method. In the construction method shown in the figure, the excavation hole 1 is formed in the ground by the earth auger method or the like, and the casing 2 is embedded in the excavation hole 1.
[0004]
At this time, the filter layer 3 is formed between the casing 2 and the excavation hole 1 by filling beans gravel, crushed stone, or the like. In the casing 2, a strainer portion 6 for taking in groundwater is formed on the lower side of the casing 2 by forming a slit 4 having an elongated square hole in advance and covering the outer periphery with a screen 5. .
[0005]
When the installation of the casing 2 is completed, the pumping pump 7 is installed therein, and the groundwater collected in the casing 2 is pumped out by the operation of the pumping pump 7.
[0006]
Such a deep well construction method is suitable for a wide range of construction, when large groundwater level reduction is required, or when the amount of pumped water is large on the ground with a large water permeability. There was a technical problem described below.
[0007]
[Non-Patent Document 1]
Sangyo Kenkyukai Encyclopedia Publishing Center, "Civil Engineering Law Encyclopedia", published on August 10, 1988, p339-340
[0008]
[Problems to be solved by the invention]
That is, in the deep well method shown in FIG. 4, for example, when the water permeability coefficient is smaller than the assumed value, water collection into the casing 2 becomes insufficient, and a predetermined water level reduction cannot be obtained. .
[0009]
As a countermeasure in such a case, a new cutting well (additional cutting well) is required. However, such a countermeasure has a problem that a construction period and a construction cost are greatly increased. As a method for lowering the groundwater level, in addition to the deep well method, for example, (1). A vacuum well construction method for forcibly collecting groundwater from the strainer section by providing an upper lid at the top of the casing and evacuating the inside of the casing with a vacuum pump; In this vacuum well method, a super well point method for restricting the inflow of air into the casing, and (3). There is a negative pressure type deep well construction method that generates negative pressure in the casing and strengthens the water collection by this negative pressure, and it is conceivable to adopt such construction method as a countermeasure when the above inconvenience occurs .
[0010]
However, the (1) and (2) methods require a vacuum pump and the like, and the equipment becomes excessive, and the noise of the vacuum pump becomes a problem in urban areas. Further, in the method (3), when the groundwater level drops to the strainer section, there is a problem that the negative pressure does not work in the casing and the water collecting capacity is lowered.
[0011]
The present invention has been made in view of such conventional problems, and the object of the present invention is simple when the water permeability coefficient of the ground is smaller than the assumed value and sufficient water collection cannot be performed. It is to provide a deep well method that can cope with the above.
[0012]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention embeds a hollow cylindrical casing provided with a strainer portion for taking in groundwater on the lower side in the ground, and installs a water pump in the casing, In the deep well construction method in which groundwater collected inside is pumped to the ground side by the operation of the pump, the pump is disposed in the casing so as to be movable up and down, and has a cylindrical shape that can be expanded and contracted. When the diameter of the shielding wall is increased, the inside of the casing on the deeper side is closed, the water is pumped up, the groundwater level is lowered by the pumping, and the groundwater level becomes equal to or lower than the shielding wall. Was interrupted, the shielding wall was contracted, moved downward along the casing, and then the shielding wall was re-expanded to perform pumping.
[0013]
According to the deep well construction method configured as described above, the pump is disposed in the casing so as to be movable up and down, is supported by a cylindrical shielding wall that can be expanded and contracted, expands the shielding wall, The inside of the casing on the deeper side is closed and pumped.
[0014]
According to such a pumping method, when the groundwater in the casing is pumped up, negative pressure is generated in the portion blocked by the shielding wall, and this negative pressure forces the casing into the casing from the surrounding ground via the strainer section. Water can be collected efficiently and efficiently.
[0015]
Therefore, even if the water permeability coefficient of the ground is smaller than the initial plan and the water collection into the casing is insufficient, the water can be collected from a wide range by the negative pressure, so that it is not necessary to take special measures.
[0016]
On the other hand, if the pumping is continued, the groundwater level is lowered by pumping, and if this falls below the impermeable wall, air flows into the casing closed by the impermeable wall and the negative pressure decreases. However, in such a state, the pumping is interrupted, the shielding wall is contracted, this is moved downward along the casing, and then the shielding wall is re-expanded to perform pumping. A decrease in the water collection effect due to a decrease in negative pressure can be avoided.
[0017]
The water-impervious walls are provided on a pair of support plates opposed to each other at a predetermined interval in the vertical direction and on the outer periphery of the support plate, and expand and contract by injecting and discharging a fluid such as gas or liquid. A packer is provided, and a pumping pipe having a lower end connected to the pumping pump can be supported through the pair of support plates.
[0018]
The shielding wall is provided with a vacuum pipe that extends downward through the pair of support plates, and is necessary when pumping water by expanding the diameter of the packer and closing the inside of the casing on the deeper side. Accordingly, intake or pressure can be performed through the vacuum pipe.
[0019]
The casing can be inserted and installed in an excavation hole formed in the ground with a filter layer interposed on the outer peripheral side.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. 1 to 3 show an embodiment of a deep well method according to the present invention.
[0021]
In the deep well method shown in the figure, a hollow cylindrical casing 10 is embedded in the ground, a pumping pump 12 is installed in the casing 10, and groundwater collected in the casing 10 is collected from the pumping pump 12. The basic structure is to pump water to the ground side by operation.
[0022]
The casing 10 is formed in a cylindrical shape having a closed lower end, and is installed in an excavation hole 14 excavated by an auger or the like. Between the casing 10 and the inner surface of the excavation hole 14, a filter layer 16 filled with beans gravel or crushed stone is formed.
[0023]
A strainer portion 18 is provided on the lower end side of the casing 10. The strainer portion 18 is provided for taking ground water into the casing 10. For example, the strainer portion 18 is formed in a staggered manner by arranging elongated rectangular hole-like slits and covering the outer periphery with a screen. The filter layer 16 is prevented from entering crushed stones.
[0024]
The pumping pump 12 is a so-called underwater installation type pump, and the lower end of the pumping pipe 20 is connected to the upper end side, and the pumping pipe 20 extends through the casing 10 to the ground side. In addition, an air vent valve 22 is installed on the ground portion.
[0025]
In the case of the present embodiment, the pumping pump 12 is disposed in the casing 10 so as to be movable up and down, and is supported by a cylindrical shielding wall 24 that can be expanded and contracted. Details of this support structure are shown in FIG.
[0026]
The shielding wall 24 shown in the figure has a pair of support plates 24a and a packer 24b. The support plate 24a is a disk having a diameter smaller than the inner diameter of the casing 10, and a pair of the support plates 24a are arranged to face each other with a predetermined interval in the vertical direction.
[0027]
The packer 24b is formed in a hollow cylindrical shape having a predetermined thickness and length L from a stretchable material such as rubber, and one end of the air supply pipe 24c is connected in communication. Ring-shaped mounting flanges 24d are respectively fixed to the inner peripheral surface of the packer 24b in the vertical direction.
[0028]
Each mounting flange 24d is fixed to the outer peripheral edge of the support plate 24a by a bolt nut or the like so that the packer 24b is positioned on the outer periphery of the support plate 24a.
[0029]
The other end side of the air supply pipe 24c passes through the upper support plate 24a and extends into the ground so as to be inserted into the casing 10, and is connected to the vacuum pump 28 and the compressor via the switching valve 26. 30.
[0030]
The pumping pump 12 is disposed so as to protrude downward from the lower end of the shielding wall 24, and the pumping pipe 20 is disposed so as to penetrate through the centers of the pair of support plates 24a. The outer peripheral surface of 20 is fixed to the support plate 24 a by welding, whereby the pumping pump 12 is supported by the impermeable wall 24 so as to move integrally with the impermeable wall 24.
[0031]
In the above configuration, when the switching valve 26 is operated to send gas from the compressor 30 to the air supply pipe 24c, the gas is injected into the packer 24b and the diameter of the packer 24b is expanded.
[0032]
When the diameter of the packer 24b is increased, the outer peripheral surface thereof comes into close contact with the inner peripheral surface of the casing 10, and the casing 10 deeper from the portion where the packer 24b is provided is hermetically closed.
[0033]
From this state, when the switching valve 26 is operated to connect the air supply pipe 24c to the vacuum pump 28 side and the gas injected from the packer 24b is discharged, the packer 24b contracts.
[0034]
When the packer 24b contracts, the outer peripheral surface thereof is separated from the inner peripheral surface of the casing 10, the hermetically closed state is released, and the shielding wall 24 can move up and down along the longitudinal axis direction in the casing 10. Become.
[0035]
In addition, the vertical movement of the shielding wall 24 can be moved up and down using the pumping pipe 20, for example, or another means, for example, a rod for vertical movement is attached to the support plate 24a of the water shielding wall 24. Thus, it may be moved up and down, or may be hung by a winch or the like. Moreover, although the fluid injected in order to expand and contract the packer 24b is exemplified by compressed air in this embodiment, it is not limited to this, and may be a liquid such as water, for example.
[0036]
1 to 3 is a vacuum pipe having a lower end extending to the vicinity of the pumping pump 12, and the vacuum pipe 32 passes through the pair of support plates 24a. The lower end side is open in the vicinity of the pumping pump 12, and the upper end side is connected to the vacuum pump 28 and the compressor 30 via the switching valve 34 so as to be switchable.
[0037]
The vacuum pipe 32 is used when it is necessary to assist the water collecting capacity, and when this is connected to the vacuum pump 28 and sucked, a negative pressure region is formed in the vicinity of the pumping pump 12. , Can assist the water collection ability.
[0038]
Further, when the compressor 30 is connected to the vacuum pipe 32 and compressed air is ejected from the front end side thereof, the compressed air can be used for cleaning, for example, when the strainer portion 18 is clogged.
[0039]
As shown in FIG. 1, the shielding wall 24 configured as described above is configured so that the groundwater level WL1 in the ground is approximately in the middle of the length L of the packer 24b of the shielding wall 24. In the state where the diameter is expanded and the casing 10 on the deeper side is hermetically closed, the pumping pump 12 is operated to perform pumping.
[0040]
In the installed state of the shielding wall 24 shown in FIG. 1, the upper end of the strainer portion 18 of the casing 10 and the lower end of the shielding wall 24 are substantially aligned with each other. For this purpose, the depth of the groundwater level WL1 is investigated in advance, and the length L of the shielding wall 24 may be designed in consideration of the length of the strainer portion 18 of the casing 10 and the groundwater level WLl. In the case of the present embodiment, the length L of the shielding wall 24 is set to be slightly longer than ½ of the length of the strainer portion 18.
[0041]
If it sets so that it may be in the state shown in FIG. 1, it will become unnecessary to provide the strainer part 18 in an extra part, and more efficient pumping will be attained, utilizing the full length L of the shielding wall 24 effectively. .
[0042]
According to the pumping method as described above, when the groundwater in the casing 10 is pumped, a negative pressure is generated in the portion blocked by the shielding wall 24, and this negative pressure causes the surrounding ground to pass through the strainer portion 18. Water can be forcibly and efficiently collected in the casing 10.
[0043]
On the other hand, if the pumping as described above is continued, the groundwater level WL1 is gradually lowered by the pumping. When the lowered groundwater level reaches below the lower end of the impermeable wall 24, a gap is generated between the groundwater level and the impermeable wall 24, and air enters the casing 10 that is blocked by the impermeable wall 24 from this gap. Flows in.
[0044]
When such an inflow of air occurs, the negative pressure in the blocked portion decreases, and efficient water collection is hindered. Therefore, in this embodiment, when such a state occurs, the pumping is interrupted and the following operation is performed.
[0045]
That is, the operation of the pump 12 is stopped, and then the packer 24b of the shielding wall 24 is contracted and moved downward along the casing 10, and then the packer 24b of the shielding wall 24 is re-expanded. The diameter is made to create a new hermetically closed area, and then the pumping pump 12 is operated to pump the water.
[0046]
FIG. 2 shows a state after such an operation is performed. When the operation as described above is performed, it is possible to avoid a decrease in water collection effect due to a decrease in negative pressure accompanying a decrease in groundwater level.
[0047]
In addition, when performing the above-described operation associated with the lowering of the groundwater level, for example, the load state of the pumping pump 12 is detected, or the change in the groundwater level is constantly measured with a liquid level gauge or the like, and quantitatively performed. It is desirable to do.
[0048]
Now, according to the deep well construction method configured as described above, the pumping pump 12 is arranged in the casing 10 so as to be movable up and down, supported by a cylindrical shielding wall 24 that can be expanded and contracted, and the shielding wall 24. Is expanded, and the casing 10 on the deeper side is closed to pump water.
[0049]
According to such a pumping method, when the groundwater in the casing 10 is pumped, a negative pressure is generated in a portion blocked by the shielding wall 24, and the negative pressure causes the casing to pass through the strainer portion 18 from the surrounding ground. 10 can be forcibly and efficiently collected.
[0050]
Therefore, even if the water permeability coefficient of the ground is smaller than the initial plan and water collection into the casing 10 is insufficient, water can be collected from a wide range by negative pressure, so a new well (additional well) is created. It becomes unnecessary, and it becomes unnecessary to adopt special measures such as a separate method such as a vacuum well method using a large vacuum pump.
[0051]
In the above embodiment, the case of constructing a new deep well has been illustrated. However, the implementation of the present invention is not limited to this. For example, an existing well is used and a shielding wall 24 is provided inside the well. It can also be installed to improve pumping efficiency. If existing wells are used, the effect of improving the construction period and cost will be even greater.
[0052]
【The invention's effect】
As described above in detail, according to the deep well method according to the present invention, when the water permeability coefficient of the ground is smaller than the assumed value and sufficient water collection cannot be performed, it can be easily handled, and the construction period・ A significant reduction in construction costs can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory sectional view of an initial state showing an embodiment of a deep well method according to the present invention.
FIG. 2 is a cross-sectional explanatory diagram of steps performed when pumping proceeds from the state shown in FIG. 1 and the groundwater level decreases.
FIG. 3 is a detailed view of a shielding wall used in the deep well method according to the present invention.
FIG. 4 is an explanatory diagram of a construction state of a conventional deep well method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Casing 12 Pumping pump 14 Excavation hole 16 Filter layer 18 Strainer part 20 Pumping pipe 24 Shielding wall 24a Support plate 24b Packer

Claims (4)

A hollow cylindrical casing provided with a strainer section for taking in groundwater on the lower side is embedded in the ground, a pump is installed in the casing, and the groundwater collected in the casing is used as the pump. In the deep well construction method that pumps water to the ground side by the operation of
The pump is disposed in the casing so as to be movable up and down, and is supported by a cylindrical shielding wall that can be expanded and contracted,
The diameter of the shielding wall is expanded, the inside of the casing on the deeper side is closed and pumped up,
When the groundwater level drops due to pumping and the groundwater level falls below the shielding wall, the pumping is interrupted,
A deep well construction method characterized in that the shielding wall is contracted, moved downward along the casing, and then the diameter of the shielding wall is re-expanded to perform pumping. The water-impervious walls are provided on a pair of support plates opposed to each other at a predetermined interval in the vertical direction and on the outer periphery of the support plate, and expand and contract by injecting and discharging a fluid such as gas or liquid. With a packer,
The deep well method according to claim 1, wherein a pumping pipe having a lower end connected to the pumping pump is supported through the pair of support plates. The shielding wall is provided with a vacuum tube that extends downward through the pair of support plates,
3. When the diameter of the packer is expanded and the inside of the casing on the deeper side is closed to perform pumping, intake or pressurized air is performed through the vacuum pipe as necessary. Deep well method. 2. The deep well method according to claim 1, wherein the casing is inserted and installed in an excavation hole formed in the ground with a filter layer interposed on the outer peripheral side.

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