JP2021042521A - Fine bubble water replacing method - Google Patents

Abstract

To efficiently inject fine bubble water into the ground in a soil improvement work.SOLUTION: A fine bubble water replacing method comprises: a pumping-up step of pumping up ground water W flowing into a well pipe 1 from a ground water inflow hole 1a by a lifting pump 3 while depressurizing inside the well pipe 1; an in-well pipe groundwater replacing step of replacing the ground water W in the well pipe 1 with fine bubble water FB by feeding the fine bubble water FB formed in a fine bubble water generating device into the well pipe 1 while pumping up the water in the well pipe 1 with the lifting pump 3; and a fine bubble water injecting step of injecting the fine bubble water FB into the soil around the well pipe 1 from the ground water inflow hole 1a by feeding the fine bubble water FB into the well pipe 1 in a stopped state of pumping-up of the water in the well pipe 1.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method of replacing groundwater with fine bubble water for the purpose of preventing liquefaction of the ground, and more particularly to a fine bubble water replacement method of injecting fine bubble water into the ground using a pumping well.

In recent years, fine bubble water replacement that prevents liquefaction by replacing groundwater in the ground, which is feared to be liquefied, with fine bubble water, impregnating the interstitial water contained between soil particles with air, and desaturating the ground. Various construction methods have been proposed (for example, Patent Document 1 and Patent Document 2).
The liquefaction phenomenon of the ground occurs when the soil particle structure is destroyed by the pressure increase of the pore water due to the repeated action of seismic motion. As a cushion, it tries to suppress the pressure rise of the pore water.

In such a fine bubble water replacement method, since groundwater is pumped up at the pumping well or fine bubble water is injected while pumping up, it is necessary to erect both the pumping well and the water injection pipe in the ground. In addition to the installation, there is a problem that it takes time and effort to install the water injection pipe.

Therefore, although unpublished, the applicants inject fine bubble water using the pumping well as it is in the previously filed patent application (Patent Document 3), and separately fine bubble water in addition to the pumping well. We are proposing a fine bubble water replacement method that eliminates the need to install a water injection pipe for injecting water.

Japanese Unexamined Patent Publication No. 2012-140789 Japanese Unexamined Patent Publication No. 2014-221969 Japanese Patent Application No. 2018-225077

However, in the fine bubble water replacement method according to Patent Document 3, since the injection of fine bubble water is started with the groundwater remaining in the well pipe after pumping the groundwater, the groundwater not containing the fine bubble water is injected into the ground. There is a problem that the efficiency of injecting fine bubble water is reduced by that amount.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a fine bubble water replacement method capable of efficiently injecting fine bubble water into the ground.

The invention made to solve the above problems is to prevent the inflow of earth and sand into the well pipe with a lid and a bottom, which is erected in the ground and has an underground water inflow hole in the peripheral wall. Fine bubble water that replaces ground water in the ground with fine bubble water using a pumping well equipped with a strainer, a pump that pumps water inside the well pipe, and a fine bubble water generator that forms fine bubble water. The replacement method is a pumping step in which the ground water flowing into the well pipe from the ground water inflow hole is pumped by the pump while depressurizing the inside of the well pipe, and the water in the well pipe is pumped by the pump. The step of replacing the ground water in the well pipe by flowing the fine bubble water formed by the fine bubble water generator into the well pipe to replace the ground water in the well pipe with fine bubble water, and the pumping of water in the well pipe were stopped. It is characterized by comprising a fine bubble water injection step of flowing fine bubble water into the well pipe in a state and injecting fine bubble water from the ground water inflow hole into the ground around the pumping well.
Here, the "water in the well pipe" includes both the groundwater that has flowed in from the groundwater inflow hole and the water in which fine bubbles are mixed.

In the fine bubble water replacement method of the present invention, the groundwater in the well pipe is replaced with fine bubble water by carrying out the groundwater replacement step in the well pipe before moving from the pumping step to the fine bubble water injection step. It is possible to prevent the return of groundwater that does not contain fine bubbles to the ground.

It is preferable that the pumping well is provided with a storage tank for storing the pumped water, and in the well pipe groundwater replacement step, the fine bubble water generator forms fine bubble water from the water pumped into the storage tank. By doing so, even if the fine bubble water of the water in the well pipe is higher than a predetermined saturation degree, the water can be circulated between the well pipe and the storage tank without being discarded to add fine bubbles, which is efficient. The water in the well pipe can often be replaced with fine bubble water.

The pumping well is provided with a return pipe for discharging water excessively supplied into the well pipe, and the groundwater replacement step in the well pipe is performed while discharging air and water in the well pipe through the return pipe. Is preferable. By doing so, the air and groundwater remaining in the well pipe can be discharged by the supply pressure of the fine bubble water, and the air and water in the well pipe can be replaced with the fine bubble water more efficiently.

In the groundwater replacement step in the well pipe, it is preferable that the water discharged from the return pipe is returned to the storage tank. By doing so, the water containing the fine bubbles recirculated from the return pipe can be used, so that the water in the well pipe can be replaced with the fine bubble water more efficiently.

In the fine bubble water replacement method of the present invention, when the saturation of the fine bubble water in the well pipe becomes higher than a predetermined saturation in the fine bubble water injection step, the water in the well pipe is pumped by the pump. While pumping water, the fine bubble water formed by the fine bubble water generator is flowed into the well pipe to reduce the saturation of the fine bubble water in the well pipe to a predetermined saturation level or less. It is preferable to prepare. By doing so, it is possible to prevent fine bubble water having a degree of saturation higher than a predetermined degree from being injected into the ground.
In addition, when the inside of the groundwater inflow hole is clogged with earth and sand in the fine bubble water injection process, this saturation adjustment process is performed to allow groundwater to flow in from the groundwater inflow hole, thereby forming the groundwater inflow hole. Clogs can be suppressed.
Here, the "saturation degree" means (volume of water / (volume of air + volume of water)) × 100 (%).

As described above, according to the fine bubble water replacement method of the present invention, groundwater can be efficiently replaced with fine bubble water.

It is a schematic diagram of the pumping well which concerns on one Embodiment of this invention. It is explanatory drawing of the pumping process which concerns on one Embodiment of this invention. It is explanatory drawing of the groundwater replacement step in a well pipe which concerns on one Embodiment of this invention. It is explanatory drawing of the fine bubble water injection process which concerns on one Embodiment of this invention. It is explanatory drawing when the groundwater inflow hole is clogged in the fine bubble water injection process of FIG. It is explanatory drawing which shows the state of the saturation degree adjustment process which concerns on one Embodiment of this invention.

FIG. 1 shows a pumping well 100 used in the fine bubble water replacement method according to the embodiment of the present invention. The pumping well 100 is a pumping well used in the ultra-deep construction method (registered trademark), and as shown in FIG. 1, a well pipe 1 erected in the ground and a strainer 2 ringed around the well pipe 1 , A pump 3 for pumping water inside the well pipe 2 and a fine bubble water generator 4 for forming fine bubble water FB are mainly provided, and a first notch tank (storage tank) for storing the pumped water. 5. It has a second notch tank (storage tank) 41, a vacuum pump 6 that decompresses the inside of the well pipe 1, and a return pipeline 7 that discharges excess water supplied into the well pipe 1. .. The second notch tank 41 stores the supernatant water that has been refluxed from the first notch tank 5 via the flow pipe 35 and the water that has been refluxed through the return pipe 7. In order to remove earth and sand from the water returned to the second notch tank, a filtration device, a sand removal device, or the like may be further provided in the return pipe 7 or the flow pipe 35.
In FIG. 1, the reference numeral GS indicates the ground surface, W indicates the groundwater, and the alternate long and short dash line indicates the water surface of the groundwater.

The well pipe 1 is made of a bottomed cylindrical steel pipe, and as shown in FIG. 2, a flange 13 is provided on the upper end edge and is closed by a lid member 14. In the well pipe 1, a large number of groundwater inflow holes 1a, 1a, ... Consisting of circular through holes are dispersedly arranged in the circumferential direction and the longitudinal direction on the peripheral wall located slightly upward from the bottom wall 11. The space 12 from the groundwater inflow hole 1a to the bottom wall 11 constitutes a sand pool. In the illustrated example, the groundwater inflow hole 1a is a circular hole, but the hole is not limited to this and may be a slit or the like. The well pipe 1 is inserted into a vertical hole 8 suspended in the ground, and then erected so as to fill the periphery with a filter material 9 made of sand, silica sand, or the like.

The strainer 2 has a cylindrical coil shape in which a wire rod is wound around the well pipe 1 using a pipe material (not shown) extending in the axial direction of the well pipe 1 as a pillow material. The strainer 2 has a slight gap 2a between adjacent wires, and allows the groundwater W to flow from the gap 2a into the groundwater inflow hole 1a while preventing the inflow of earth and sand into the groundwater inflow hole 1a.
The strainer 2 is provided so as to substantially cover the entire portion of the well pipe 1 provided with the groundwater inflow hole 1a, and the uppermost end of the gap 2a is located above the groundwater inflow hole 1a at a sufficient distance from the groundwater inflow hole 1a. There is.
As the strainer 2, for example, a wedge wire having a zinc-plated steel wire having a triangular cross section is used, but the material and shape are not limited to this.

As shown in FIG. 2, the pump 3 is suspended at the lower end of the pump pipe 31 that hangs down inside the well pipe 1, and pumps the ground water that has flowed into the well pipe 1 through the ground water inflow holes 1a, 1a, ... It is configured to be pumped up and stored in the first notch tank 5 via a pumping pipe 31, a pumping flow pipe 32, a gate valve 33, and a check valve 34.

As shown in FIG. 1, the fine bubble water generator 4 includes a vortex turbine pump 42, a surplus air separation tank 43, and a bubble generation valve 44. The vortex turbine pump 42 sucks the outside air together with the water sent from the second notch tank 41, and pressurizes and dissolves the air in the water by the vortex flow generated by the turbine. The pressurized air dissolved water thus formed is discharged from the surplus air separation tank 43 and then discharged from the bubble generation valve 44 to be depressurized to generate fine bubbles.

The return pipe 7 connects the well pipe 1 and the second notch tank 41 via the safety valve 71 and the lid material 14, and allows air and water in the well pipe 1 to flow from the upper end of the well pipe 1 to the second notch. It returns to the tank 41.

(Pump pumping process S1)
Next, the fine bubble water replacement method according to the present embodiment will be described in detail. In the present embodiment, first, the groundwater W in the ground is pumped up by the pumping step S1 (hereinafter, may be simply referred to as “step S1”). To pump the groundwater W, the vacuum pump 6 is started, the air A at the upper part of the well pipe is sucked through the suction hose 61, and the inside of the well pipe 1 is depressurized. Then, the groundwater in the surrounding ground flows into the well pipe 1 through the strainer 2 and the groundwater inflow hole 1a due to the weight of the groundwater W and the negative pressure inside the well pipe 1. When the groundwater W is sufficiently accumulated in the well pipe 1, the pumping pump 3 is started to pump the groundwater W to the first notch tank 5. The first notch tank 5 settles the earth and sand contained in the pumped groundwater W, and sends the supernatant water to the second notch tank 41 via the flow pipe 35. When the groundwater W is pumped up by the amount determined in advance by design, the vacuum pump 6 is stopped and the pumping step S1 is completed.

(Groundwater replacement step S2 in the well pipe)
In the groundwater replacement step S2 in the well pipe, while pumping the water in the well pipe 1 with the pump 3, the fine bubble water FB formed by the fine bubble water generator 4 is sent into the well pipe 1 to flow into the well pipe 1. This is a step of replacing water with fine bubble water FB having a predetermined saturation degree predetermined as a sufficient saturation degree to be injected into the ground.

That is, when the pumping step S1 is completed, the gate valve 33, the check valve 34, and the safety valve 71 are opened to drive the vortex turbine pump 42. Subsequently, the bubble generation valve 44 is opened, and the fine bubble water FB is sent into the well pipe 1 as shown in FIG.

In parallel with the flow of the fine bubble water FB into the well pipe 1, the water in the well pipe 1 by the pump 3 (groundwater W flowing in from the groundwater inflow hole 1a and the well pipe 1 from the fine bubble water flow pipe 45). Continue pumping the fine bubble water FB mixed water that has flowed into the water.
In FIG. 3, reference numeral A indicates air remaining in the well pipe 1, the black arrow indicated by reference numeral W indicates the flow of groundwater W, and the white arrow indicated by reference numeral FB indicates the flow of groundwater W. The flow of fine bubble water FB is shown. The places where the white and black arrows are alternately described indicate that the groundwater W and the fine bubble water FB are mixed.

Here, when the amount of fine bubble water FB flowing into the well pipe 1 is smaller than the amount of water pumped by the pump 3, the groundwater W flows into the well pipe 1 through the groundwater inflow hole 1a, so that the well The fine bubble water FB in the tube 1 is diluted. On the contrary, when the amount of water pumped by the pump 3 is smaller than the amount of fine bubble water FB flowing into the well pipe 1, the water in the well pipe 1 is not replaced with the fine bubble water having a predetermined saturation. It flows out into the surrounding ground through the groundwater inflow hole 1a and the strainer 2.

Therefore, in this step S2, the amount of water pumped by the pump 3, the amount of fine bubble water FB sent to the well pipe 1, and the amount of water returned from the return pipe 7 to the second notch tank are adjusted. Therefore, water entering and exiting through the groundwater inflow hole 1a is suppressed. By doing so, the groundwater W in the well pipe 1 can be efficiently replaced with fine bubble water.

(Fine bubble water injection step S3)
In the fine bubble water injection step S3, the fine bubble water FB is sent into the well pipe 1 in a state where the pumping of water in the well pipe 1 is stopped, and fine bubbles are sent from the groundwater inflow hole 1a to the ground around the pumping well 100. This is the process of injecting water.

In step S2, when the saturation of the fine bubble water in the well pipe 1 drops to a predetermined saturation, step S2 is terminated, the gate valve 33 is closed, and the pump 3 is stopped in order to carry out step S3. .. As a result, the fine bubble water FB filled in the well pipe 1 passes around the well pipe 1 through the groundwater inflow hole 1a and the strainer 2 due to the pressure of the fine bubble water FB flowing from the fine bubble water flow pipe 45. It is injected into the ground.
At this time, since all the water in the well pipe 1 is replaced with fine bubble water FB having a predetermined saturation, groundwater containing no fine bubbles or fine bubble water having a predetermined saturation is injected into the ground. Groundwater in the ground can be efficiently replaced with fine bubble water FB.
As a low saturation degree (predetermined saturation degree) suitable for injecting fine bubble water FB into the ground, for example, a saturation degree of less than 90% can be mentioned, and a saturation degree higher than an appropriate value is 91. The degree of saturation of% or more and 100% or less can be mentioned.

(Saturation adjustment step S4)
In the saturation adjustment step S4, when the saturation of the fine bubble water FB in the well pipe 1 becomes higher than the predetermined saturation, the saturation of the fine bubble water FB in the well pipe 1 becomes a predetermined saturation. This is the process of recovery.
In step S3, when the saturation of the fine bubble water FB becomes high for some reason, the fine bubble water generator 4 is used to prevent the fine bubble water FB having a high saturation from flowing out into the ground. While the supply of the fine bubble water FB to the well pipe 1 is continued, the pump 3 is started, the gate valve 33 is opened, and the fine bubble water FB having a degree of saturation higher than the predetermined saturation in the well pipe 1 is first. Pump up to the notch tank 5.
By doing so, it is possible to prevent fine bubble water having a higher saturation than a predetermined value from flowing out to the surrounding ground through the groundwater inflow hole 1a. When the fine bubble water FB in the well pipe 1 recovers to a predetermined saturation degree, the pump 3 is stopped again, the gate valve 33 is closed, and the fine bubble water injection step S3 is restarted. By doing so, the fine bubble water FB having a predetermined saturation can be supplied to the ground, so that the groundwater W can be efficiently replaced with the fine bubble water FB.

Further, in the fine bubble water injection step S3, the strainer 2 may be clogged from the inside due to earth and sand or the like, and as shown in FIG. 5, the injection amount of the fine bubble water FB from the strainer 2 may decrease. In such a case, clogging inside the strainer 2 can be eliminated by carrying out the saturation adjustment step S4 and allowing the surrounding groundwater to flow in from the strainer 2.
Further, in the pumping step S1 (FIG. 2) and the groundwater replacement step S2 (FIG. 3) in the well pipe, the strainer 2 may be clogged from the outside due to earth and sand or the like, and the inflow of groundwater W from the strainer 2 may be reduced. By carrying out the fine bubble water injection step S3 or the saturation adjustment step S4 and injecting the fine bubble water FB from the groundwater inflow hole 1a, clogging on the outside of the strainer 2 can be eliminated.
Depending on the component contained in the ground, the component may be adsorbed on the screen as an individual and cause clogging. If the clogging is not improved by the above-mentioned inflow of groundwater, the substance causing the clogging is analyzed, a drug that dissolves the substance is selected, the drug is injected into the well, and the well is washed. Consider a separate clogging elimination method.

The present invention is not limited to the above-described embodiment, and for example, the air remaining in the well pipe 1 after the pumping step S1 may be discharged by the vacuum pump 6. The vacuum pump may be a gas-liquid pump. In the groundwater replacement step S2 in the well pipe, in the fine bubble water injection step S3 or the saturation adjustment step S4, water other than the water pumped by the pump is formed into fine bubble water and supplied to the well pipe 1. Alternatively, the safety valve 71 of the return line 7 may be closed.

The number of pumping wells is not limited to one, and multiple wells may be provided. In this case, while carrying out the pumping step in some pumping wells, the groundwater replacement step in the well pipe or the fine bubble water injection step may be carried out in other pumping wells.

100 Pumping well 1 Well pipe 1a Groundwater inflow hole 2 Strainer 3 Pumping pump 4 Fine bubble water generator 41 Second notch tank (storage tank)
7 Return pipeline FB Fine bubble water W Groundwater

The invention made to solve the above problems is to prevent the inflow of earth and sand into the well pipe with a lid and a bottom, which is erected in the ground and has an underground water inflow hole in the peripheral wall. A strainer, a pumping pipe inserted into the well pipe, a pumping pump connected to the pumping pipe to pump water inside the well pipe, a fine bubble water generator for forming fine bubble water, and the well. A pumping well equipped with a fine bubble water flow pipe that is connected to a pipe and flows the fine bubble water formed by the fine bubble water generator to the well pipe is used to pump water, and the pumping well that pumped the water. This is a fine bubble water replacement method in which fine bubble water is injected into the ground to replace the ground water in the ground with pumped fine bubble water, and the inside of the well pipe is depressurized from the ground water inflow hole into the well pipe. a pumping step of pumping the groundwater flowing in the water pumps, while pumping in water pumps water internal of the well pipe used in the pumping process through the pumping tube, formed by the fine bubble water generator Fine and Nagareoku the bubble water to the well pipe direct from the fine bubble water feed tube, and a well pipe ground water replacement step of replacing the groundwater inside of the well pipe to the fine bubble water, pumping the water inside of the well pipe was Nagareoku fine bubble water in the well pipe in a stopped state, characterized in that from the ground water inlet and a fine bubble water injection step of injecting the fine bubble water into the surrounding ground of the pumping well.
Here, the "water in the well pipe" includes both the groundwater that has flowed in from the groundwater inflow hole and the water in which fine bubbles are mixed.

The pumping well is connected to the well pipe and includes a return pipeline for discharging excess water supplied into the well pipe, and the groundwater replacement step in the well pipe is used in the pumping step by the return pipeline. It is preferable to discharge the air and water in the well pipe. By doing so, the air and groundwater remaining in the well pipe can be discharged by the supply pressure of the fine bubble water, and the air and water in the well pipe can be replaced with the fine bubble water more efficiently.

Fine bubble water replacement method of the present invention, the in fine bubble water injection process, when the degree of saturation of the fine bubble water well pipe used in the pumping process is higher than a predetermined saturation, water of the well pipe while pumping by the pumping pump, fine bubbles water formed by the fine bubble water generator in Nagareoku to the well pipe, reducing the degree of saturation of the fine bubble water of the well pipe below a predetermined saturation It is preferable to include a saturation adjustment step. By doing so, it is possible to prevent fine bubble water having a degree of saturation higher than a predetermined degree from being injected into the ground.
In addition, when the inside of the groundwater inflow hole is clogged with earth and sand in the fine bubble water injection step, this saturation adjustment step is carried out to allow the groundwater to flow in from the groundwater inflow hole.
Clogged groundwater inflow holes can be suppressed.
Here, the "saturation degree" means (volume of water / (volume of air + volume of water)) × 100 (%).

Claims (5)

A well pipe with a lid and a bottom that is erected in the ground and has a groundwater inflow hole on the peripheral wall, a strainer that prevents the inflow of earth and sand into the groundwater inflow hole, and water inside the well pipe are pumped up. It is a fine bubble water replacement method that replaces groundwater in the ground with fine bubble water using a pumping well equipped with a pump and a fine bubble water generator that forms fine bubble water.
A pumping step in which the groundwater flowing into the well pipe from the groundwater inflow hole is pumped by the pump while depressurizing the inside of the well pipe.
While pumping the water in the well pipe with the pump, the fine bubble water formed by the fine bubble water generator is sent into the well pipe to replace the groundwater in the well pipe with fine bubble water. Replacement process and
A fine bubble water injection step in which fine bubble water is flowed into the well pipe with the pumping of water in the well pipe stopped, and fine bubble water is injected from the groundwater inflow hole into the ground around the pumping well. A fine bubble water replacement method characterized by being prepared. The pumping well is equipped with a storage tank for storing the pumped water.
The fine bubble water replacement method according to claim 1, wherein in the well pipe groundwater replacement step, fine bubble water is formed from the water pumped into the storage tank by the fine bubble water generator. The pumping well is provided with a return pipe for discharging excess water supplied into the well pipe.
The fine bubble water replacement method according to claim 2, wherein the groundwater replacement step in the well pipe is performed while discharging air and water in the well pipe through the return pipe. The fine bubble water replacement method according to claim 3, wherein in the groundwater replacement step in the well pipe, the water discharged from the return pipe is returned to the storage tank. In the fine bubble water injection step, when the saturation of the fine bubble water in the well pipe becomes higher than a predetermined saturation degree, the fine bubble water generator while pumping the water in the well pipe with the pump. Any of claims 1 to 4, further comprising a saturation adjustment step of flowing the fine bubble water formed in the above well into the well pipe to reduce the saturation of the fine bubble water in the well pipe to a predetermined saturation or less. The fine bubble water replacement method according to item 1.

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