Hole cleaning method

Abstract

[Problem] To provide a hole cleaning method with which it is possible to appropriately remove scale that has formed in hard-to-clean locations around a hole (foundation drainage hole, etc.) using a small, lightweight device that can be transported by human power. [Solution] A cleaning water tank, a bubble generating means, a cleaning water supply pipe, and a cleaning water transfer means are installed in a hole cleaning method for cleaning a cleaning location in a hole (foundation drainage hole, etc.), the cleaning location being near the bottom end of the hole, which should be maintained as an underground water flow inlet. By driving the bubble generating means and the cleaning water transfer means and supplying micro-nano-bubble-containing cleaning water (micro nano bubble water) from the distal end part of the cleaning water supply pipe toward the cleaning location, the cleaning location is cleaned and the cleaning water supplied to the cleaning location is returned to the cleaning water tank through a gap between the inner wall of the hole and the outer wall of the cleaning water supply pipe and a gap between the inner wall of a cleaning water return pipe and the outer wall of the cleaning water supply pipe, whereby cleaning is performed while the cleaning water is circulated between the cleaning water tank and the cleaning location.

Description

Hole Cleaning Method

[0001] The present invention relates to a hole cleaning method that can be suitably used when cleaning foundation drainage holes of dams, etc.

[0002] To maintain and inspect the safety of dams, it is mandatory to periodically measure the uplift pressure and leakage rate of the dam body. These measurements are carried out by drilling a vertical hole that reaches the bedrock foundation directly below the dam body from an inspection gallery located near the bottom of the dam body and installing various sensors in the vertical hole. This vertical hole is called a "foundation drain hole." Foundation drain holes are also used as drainage holes and play an important role in maintaining the integrity of dams. Since the above measurements are usually carried out repeatedly over a long period of time using the same foundation drain hole, proper management of the foundation drain hole is required.

[0003] However, foundation drain holes can become clogged and blocked over time. The clogging substance (blocking material) is thought to be slime derived from microorganisms (see Non-Patent Documents 2 and 3). As this slime grows, the blockage of foundation drain holes progresses. The microorganisms that make up the slime are transported along with the nutrient substrate by groundwater (seepage water supplied to the foundation drain holes through cracks in the foundation bedrock). Furthermore, because steel pipes are inserted into the foundation drain holes and the dam embankment is constructed of concrete, scale (solid-phase interface deposits) such as iron hydroxide and calcium (free lime) due to microbial organic corrosion are produced around the foundation drain holes as slime. The progression of this corrosion clogs the foundation drain holes, reducing their function as measurement holes for measuring the above-mentioned uplift pressure and leakage volume, as well as their function as drainage holes, which can adversely affect the dam's longevity. For this reason, it is necessary to properly remove slime by cleaning and maintain the foundation drain holes.

[0004] The most common method for cleaning foundation drainage holes is high-pressure washing, in which cleaning water is sprayed at high pressure onto the inner wall surface of the steel pipe (see Non-Patent Documents 1 to 3). However, high-pressure washing requires the installation of large-scale equipment, such as a compressor, on the top of the dam body and a high-pressure hose running a long distance (usually about 50 to 100 m) from the large-scale high-pressure washing device to the foundation drainage hole in the inspection gallery.

[0005] Furthermore, while high-pressure washing can remove scale from the inner wall of steel pipes, the scale that breaks off from the inner wall and solidifies moves to the bottom of the hole along with the slime, forming sludge (sediment). Therefore, high-pressure washing can be expected to restore functionality in the short term for foundation drainage holes with a small amount of slime. However, in foundation drainage holes with a large amount of slime, scale develops due to the proliferation of microorganisms and increased slime production in difficult-to-clean areas, such as the narrow interface between the base of the embankment and the top surface of the foundation bedrock. Therefore, high-pressure washing cannot restore the functionality of the foundation drainage hole and is likely to worsen the performance of the foundation drainage hole. Slime is known to be primarily a highly viscous, adhesive polymer produced by microorganisms in groundwater in a nutrient-rich environment. Scale is thought to be produced in this environment. Therefore, even spraying high-pressure washing water cannot completely remove slime from difficult-to-clean areas with small depressions.

[0006] In this way, when it becomes impossible to remove the clogged material from the foundation drain hole by cleaning, or when the foundation drain hole has deteriorated, it becomes necessary to excavate a new foundation drain hole (renew the foundation drain hole). Renewing foundation drain holes is costly, and if this is done repeatedly, many foundation drain holes will be excavated in the inspection gallery. In fact, there are many dams that have many foundation drain holes excavated in the inspection gallery.

[0007] 1. Kubo H., Tsutsui K., “Verification of the cleaning effect of foundation drainage holes at Sasaogawa Dam,” Proceedings of the Kinki Regional Development Bureau Research Presentation Meeting, 2019, General Category (Safety and Security) I, No. 12. Higa H., Kawata A., “Evaluation of the soundness of foundation drainage holes at dams and their functional recovery,” [online], [Retrieved April 1, 2024], Internet <URL: https: / / www.dc.ogb.go.jp / Kyoku / kengyo / kokudo_kenkyukai / 20170626_sougou / pdf / ronbun / 05_hokubudam_kawata.pdf>. Tsuchida T., Kanazu S., “Removing blockages in foundation drainage holes at Naruko Dam,” [online], [Retrieved April 1, 2024], Internet <URL: https: / / www.thr.mlit.go.jp / bumon / b00097 / k00360 / happyoukai / H30 / list%202 / 1-15.pdf>

[0008] The present invention has been made to solve the above-mentioned problems, and provides a hole cleaning method that can effectively remove scale formed in difficult-to-clean areas around holes (foundation drainage holes, etc.) using a small, lightweight device that can be carried by hand, thereby restoring the function of the hole (foundation drainage hole, etc.).

[0009] The above-mentioned problem is solved by a hole cleaning method for cleaning a cleaning point in a hole near the end of the hole bottom side that is to be maintained as a groundwater inlet, comprising: a cleaning water tank for storing cleaning water; bubble generating means for generating micro-nano bubbles in the cleaning water tank; a cleaning water supply pipe that is inserted into the hole and supplies cleaning water from the cleaning water tank to the cleaning point; cleaning water transferring means for transferring the cleaning water in the cleaning water tank to the cleaning point through the cleaning water supply pipe; and a cleaning water return pipe that is inserted onto the cleaning water supply pipe and connects the start end of the hole and the cleaning water tank; and driving the bubble generating means and the cleaning water transferring means to supply cleaning water containing micro-nano bubbles from the tip of the cleaning water supply pipe to the cleaning point, thereby cleaning the cleaning point, and This problem is solved by providing a hole cleaning method characterized in that the cleaning water supplied to the cleaning area is returned to the cleaning water tank through the gap between the inner wall of the hole and the outer wall of the cleaning water supply pipe, and the gap between the inner wall of the cleaning water return pipe and the outer wall of the cleaning water supply pipe, thereby performing the cleaning while circulating cleaning water between the cleaning water tank and the cleaning area.

[0010] In this way, by using cleaning water containing micro-nano bubbles, it is possible to remove clogging substances that are difficult to remove with high-pressure washing. While scale formed in tiny depressions in narrow areas is difficult to remove with high-pressure washing, cleaning water containing micro-nano bubbles can penetrate these tiny depressions through diffusion (permeation) and remove the scale formed in those tiny depressions. Therefore, it is possible to effectively remove scale and other substances that have formed in difficult-to-clean locations, such as the narrow interface between the base of the embankment and the top surface of the foundation bedrock near the end of the base of the foundation drainage hole (the end that serves as the groundwater supply port for the foundation drainage hole). There is no particular need to add chemicals to the cleaning water, but adding a surfactant or the like can further improve cleaning efficiency.

[0011] Furthermore, a double-pipe structure consisting of a cleaning water supply pipe and a cleaning water return pipe circulates cleaning water between the cleaning water tank equipped with a bubble generating means and the cleaning area, thereby improving the cleaning effect over time. Taking the cleaning of the foundation drain hole described above as an example, before cleaning or immediately after cleaning begins (when the concentration of micro-nano bubbles in the cleaning water is low), the end of the foundation drain hole is clogged with slime, making the entire system a closed system. However, after some time has passed since cleaning began and cleaning water containing micro-nano bubbles begins to circulate, scale peeling occurs. When the scale peels, slime, mainly composed of water-swelling polymers, is transferred to the cleaning water tank, causing the head of the cleaning water tank to continue rising and reach a peak. Subsequently, as the slime decomposes, the head of the cleaning water tank decreases, and the system becomes an open system. As a result, the cleaning water diffuses to the cleaning area (the difficult-to-clean area) while increasing the concentration of micro-nano bubbles, promoting the peeling and decomposition of scale further away. This allows for the flow of water in the hole (the cleaning water in the foundation drain hole) and groundwater. In the cleaning water tank, amphiphilic long-chain polymers, one of the polymer components in the slime, are unwound and shortened, forming spherical micelles with surfactants. The suspended water is purified and becomes highly concentrated cleaning water, which then diffuses from the tip of the cleaning water supply pipe, cleaning scale from distant, difficult-to-clean areas. This eliminates the need for high-pressure spraying of cleaning water to difficult-to-clean areas around the foundation drain hole, and large heavy machinery is not required for this purpose. Additionally, after the cleaning water becomes suspended water, it can be returned and returned, removing scale from the inner wall of the steel pipe in the foundation drain hole. However, before pouring water, scale must be removed so that the tip of the cleaning water supply pipe can reach the difficult-to-clean areas, such as the end of the steel pipe (the hole bottom).

[0012] In the hole cleaning method of the present invention, when cleaning water is injected into the bottom of the hole, the head of the cleaning water tank fluctuates as shown in Figure 1. That is, before the start of the injection of cleaning water (when the "preparatory step" described below is being performed) and immediately after the start of the injection of cleaning water (immediately after the start of the "cleaning step" described below) (T1), the system is closed as described above, so the head of the cleaning water tank is approximately constant at a low level. However, as the cleaning water begins to peel off scale with continued injection, the system becomes an open system, and the large amount of slime sent to the cleaning water tank from the cleaning area (difficult-to-clean area) absorbs and expands, causing the head of the cleaning water tank to rise sharply (T2), and then gradually rises while repeatedly fluctuating up and down (T3). This up and down fluctuation is thought to be due to the location where the above-mentioned slime peeling and decomposition occurs diffusing from the vicinity of the hole to the distance, and the osmotic pressure fluctuations inside and outside the hole due to this repeated process. When the head is rising, it is believed that scale near the hole is being peeled off, and when the head is falling, it is believed that the slime is being decomposed. The highly concentrated wash water caused by the circulation of wash water begins to peel off scale further away, and the peeled scale turns into slime and passes through the wash water return pipe, where it is decomposed in the wash water tank. Therefore, the head of the wash water tank repeatedly fluctuates up and down while reducing its amplitude. Once most of the slime is removed, the above-mentioned fluctuations become smooth, and the head of the wash water tank increases almost monotonically (rising at an approximately constant gradient). At this time, the groundwater pressure (hereinafter referred to as "pore water pressure") from pores (such as the above-mentioned interface and minute pores on the inner surface of the hole) affected by the dam water level, etc., exceeds the water pressure in the hole (hereinafter referred to as "hole water pressure").

[0013] Focusing on such changes in the head of the flush water tank, the hole cleaning method of the present invention preferably provides a head measuring means for measuring the head of the flush water tank and estimates the cleaning effect from the changes in the head measured by the head measuring means. That is, as described above, in the cleaning method of the present invention, while the head of the flush water tank repeatedly fluctuates up and down, it can be determined that the slime that can be removed is in the process of being removed, and when the head of the flush water tank subsequently begins to rise at a substantially constant gradient, it can be determined that most of the slime that can be removed has been removed. While it is not possible to objectively determine whether scale formed in tiny depressions in narrow areas, which are one of the difficult-to-clean locations, has been removed by inserting a camera into the hole, monitoring the head of the flush water tank makes it possible to objectively determine whether the scale has been removed.

[0014] In this case, it is preferable to provide an ATP concentration measuring means for measuring the ATP concentration of the cleaning water in the cleaning water tank, and prior to the process of performing the cleaning while circulating the cleaning water (hereinafter referred to as the "cleaning process"), to perform a process of circulating groundwater between the cleaning water tank and the cleaning location for a predetermined time T1 by driving only the cleaning water transfer means without driving the bubble generating means (hereinafter referred to as the "preliminary process"), and to determine the duration of the cleaning process based on the head measured by the head measuring means during the preliminary process and the head measured by the head measuring means during the cleaning process.

[0015] For example, if the hydraulic head during the preliminary process is approximately constant, it can be considered that the water level in the hole is a closed system in which the area near the groundwater inlet, such as the bottom of the steel pipe hole, is completely blocked by scale. Furthermore, during the cleaning process, as the cleaning water peels off and decomposes the scale over time, the hydraulic head decreases while reducing its fluctuation range, and it can be considered that the system is open. Furthermore, after cleaning, it can be considered that the slime near the groundwater inlet is completely removed and the hydraulic head rises at an approximately constant gradient. Therefore, by monitoring the hydraulic head during the preliminary process, cleaning process, and after cleaning, it is possible to reflect this in determining the cleaning duration for the cleaning process.

[0016] The hole cleaning method described above is for cleaning holes with an open start end and a closed end (hereinafter, sometimes referred to as a "closed-end hole"). For example, foundation drainage holes drilled in the inspection gallery of a dam are closed-end holes, and the hole cleaning method of the present invention can be suitably used to clean such foundation drainage holes. However, the technology in the hole cleaning method of the present invention can be applied not only to cleaning holes with closed ends, but also to cleaning holes with both open ends (hereinafter, sometimes referred to as a "double-open hole").

[0017] That is, a hole cleaning method for cleaning the inside of a hole that is open at both its beginning and end (a hole that is open at both ends), comprising: a cleaning water tank for storing cleaning water; bubble generating means for generating micro-nano bubbles in the cleaning water tank; a cleaning water supply pipe connected to the beginning of the hole for supplying cleaning water from the cleaning water tank to a location to be cleaned within the hole; cleaning water transferring means for transferring the cleaning water in the cleaning water tank to the location to be cleaned via the cleaning water supply pipe; and a cleaning water return pipe connected to the end of the hole for returning the cleaning water that has come out of the hole to the cleaning water tank; and by driving the bubble generating means and the cleaning water transferring means, the location to be cleaned is cleaned by supplying cleaning water containing micro-nano bubbles to the location to be cleaned, and by returning the cleaning water sprayed at the location to be cleaned to the cleaning water tank via the cleaning water return pipe, the cleaning can be performed while circulating cleaning water between the cleaning water tank and the location to be cleaned by this hole cleaning method, which is characterized by the above.

[0018] In the hole cleaning method assuming a one-end closed hole described above, the cleaning water supplied to the cleaning area is returned to the cleaning water tank through the gap between the inner wall of the cleaning water return pipe connected to the mouth of the hole and the outer wall of the cleaning water supply pipe, after removing scale from the difficult-to-clean areas near the bottom of the hole, including the inner and outer walls of the hole. In contrast, in the hole cleaning method assuming a both-end open hole, the suspension water that has removed scale from the inner and outer walls of the hole is stored in a suspension water storage tank (casing) connected to the end of the hole and then returned to the cleaning water tank through the cleaning water return pipe. Even with this circulation mode, the concentration of micro-nano bubbles in the cleaning water increases over time, allowing for more efficient cleaning. Furthermore, the cleaning effectiveness and the duration of the cleaning process can still be determined by the head of the cleaning water tank.

[0019] As described above, the holes to be cleaned by the hole cleaning method of the present invention include holes with one closed end and holes with both open ends, and the orientation of the holes varies depending on the purpose of the hole. For example, in the case of the foundation drainage hole described above, the hole (foundation drainage hole) is a vertical hole extending in an approximately vertical direction. Also, culverts excavated under roads are horizontal holes extending in an approximately horizontal direction. The hole cleaning method of the present invention can clean both vertical and horizontal holes. It can also clean inclined holes that are inclined relative to the vertical or horizontal direction.

[0020] As described above, the present invention makes it possible to provide a hole cleaning method that can effectively remove scale formed in difficult-to-clean areas around holes (foundation drainage holes, etc.) using a small, lightweight device that can be carried by hand, thereby restoring the function of the hole (foundation drainage hole, etc.).

[0021] Fig. 1 is a graph showing the change in the water head of a cleaning water tank over time, and a diagram showing a schematic representation of the change in the state of the cleaning point in a hole (foundation drainage hole). Fig. 2 is a diagram explaining a hole cleaning method of a first embodiment. Fig. 3 is a diagram explaining a hole cleaning method of a second embodiment. Fig. 4 is a diagram explaining a hole cleaning method of a third embodiment. Fig. 5 is a diagram explaining a hole cleaning method of a fourth embodiment. Fig. 6 is a diagram explaining a hole cleaning method of a fifth embodiment. Fig. 7 is a diagram explaining a hole cleaning method of a sixth embodiment.

[0022] The hole cleaning method of the present invention will be described in more detail with reference to the drawings. Below, the hole cleaning method of the present invention will be described using six embodiments, from the first embodiment to the sixth embodiment, as examples. However, these are merely preferred embodiments, and the technical scope of the hole cleaning method of the present invention is not limited to these embodiments. The hole cleaning method of the present invention can be modified as appropriate within the scope that does not impair the spirit of the invention.

[0023] 1. Hole Cleaning Method of the First Embodiment First, the hole cleaning method of the first embodiment will be described. The hole cleaning method of the first embodiment is intended to clean holes (foundation drainage holes) provided in the inspection gallery of a dam, which have been excavated or cleaned for a long time. Foundation drainage holes are used as measurement holes for measuring the uplift pressure and leakage rate of the dam embankment, and as drainage holes, and therefore play an important role in maintaining the integrity of the dam. For this reason, foundation drainage holes must be cleaned periodically to remove any slime that has adhered to them. The hole cleaning method of the first embodiment can be suitably employed when performing this cleaning.

[0024] Figure 2 is a diagram illustrating the hole cleaning method of the first embodiment. While foundation drainage holes are sometimes drilled vertically from the floor of the inspection gallery, the foundation drainage hole shown in Figure 2 is drilled vertically after drawing a curve from the side of the inspection gallery's gutter. The diameter (inner diameter) of the foundation drainage hole is approximately 40 mm, and a steel pipe is inserted into its vertical portion. The depth of the foundation drainage hole varies depending on the dam, but is typically approximately 5 to 20 m. The lower end of the foundation drainage hole reaches near the boundary between the dam body and the foundation bedrock. In other words, the foundation drainage hole corresponds to the "one-end closed hole" described above. In particular, near the interface between the dam body and the foundation bedrock (near the end of the foundation drainage hole), iron hydroxide and calcium scale are likely to form due to microbial corrosion of the steel pipe inserted into the hole and the concrete that makes up the dam body. To remove this, the following cleaning is performed.

[0025] In the hole cleaning method of the first embodiment, as shown in Figure 2, a foundation drain hole is cleaned using a cleaning water tank, a bubble generating means, a cleaning water supply pipe, a cleaning water transfer means, and a cleaning water return pipe.

[0026] 1.1 Flush Water Tank The flush water tank is used to store flush water. In the hole cleaning method of the first embodiment, an acrylic pipe with a diameter of 160 mm and a length of 1500 mm is placed upright and the bottom is blocked off, and used as the flush water tank. As will be described later, the flush water tank also functions as a sensor that determines the cleaning effect, etc., from fluctuations in the water head. By making the flush water tank vertically long (higher than it is wide), fluctuations in the water head in the flush water tank can be more easily detected.

[0027] 1.2 Bubble Generating Means The bubble generating means is used to generate micro-nano bubbles in the cleaning water tank. In the hole cleaning method of the first embodiment, the bubble generating means is composed of a bubble generator, an air pump, a flow regulator, and a cavitation generator.

[0028] The bubble generator is immersed in the cleaning water in the cleaning water tank and generates bubbles (micro-nano bubbles) in the cleaning water. In the hole cleaning method of the first embodiment, a model "FP40-670" Foamest (registered trademark) column series manufactured by NAC Corporation is used as the bubble generator. This bubble generator is a cylindrical column made of a specially processed porous film. Air supplied into the column is converted into fine bubbles by the porous film and sent out of the column. Three such columns can be accommodated in one cleaning water tank. This bubble generator generates bubbles with a relatively wide size range, from 20 nm to 200 μm in diameter, with a particularly large number of bubbles around 120 nm in diameter. The number of bubbles around 120 nm in diameter generated in 1 mL of cleaning water is 10 ６ This is an order.

[0029] The air pump takes in outside air and supplies it to the air bubble generator. Therefore, the air pump and the air generator are connected by an air flow path (tube). The type of air pump is not particularly limited, but AC 100V is supplied to the inspection gallery. In the hole cleaning method of the first embodiment, a FIT series model "FIT13093B" manufactured by Anest Iwata Corporation is used. This air pump has a rated pressure of 0.7 MPa and a rated air discharge rate (at 50 Hz) of 36 L / min.

[0030] The flow regulator is provided at a branching point in the air flow path (tube) connecting the air pump and the air generator, and regulates the flow rate of air flowing through the air flow path. By controlling this flow regulator, it is possible to adjust the diameter and number of bubbles (micro-nano bubbles) generated by the bubble generator. In the hole cleaning method of the first embodiment, the flow regulator allows the air flow rate to be adjusted within a range of 1 to 10 L / min.

[0031] The cavitation generator is provided on the discharge side (downstream side) of the cleaning water transfer means described below, and generates a cavitation phenomenon in the cleaning water discharged from the cleaning water transfer means. This converts dissolved gas in the cleaning water into micro-nano bubbles, and increases the concentration of these macro-nano bubbles. In the hole cleaning method of the first embodiment, a stainless steel series model "ProSUS25A" manufactured by micro-bub Co., Ltd. is used as the cavitation generator.

[0032] 1.3 Cleaning Water Supply Pipe: The cleaning water supply pipe guides the cleaning water from the cleaning water tank to the cleaning location. The cleaning water supply pipe is typically a flexible pipe (hose). In the hole cleaning method of the first embodiment, a polybutene pipe is used as the cleaning water supply pipe. The inner diameter and length of the cleaning water supply pipe vary depending on the site and are not particularly limited. In the hole cleaning method of the first embodiment, the inner diameter of the cleaning water supply pipe is approximately 10 to 20 mm (e.g., 16 mm or 19 mm), and the length of the cleaning water supply pipe is approximately 20 to 30 m. The tip of the cleaning water supply pipe (the cleaning location side) is inserted into the steel pipe of the foundation drainage hole. A nozzle may be attached to the tip of the cleaning water supply pipe to protect the tip.

[0033] 1.4 Flush Water Transfer Means: The flush water transfer means is interposed between the flush water tank and the flush water supply pipe and transfers flush water from the flush water tank through the flush water supply pipe to difficult-to-clean areas near the end of the foundation drainage hole. While various pumps can be used as the flush water transfer means, the hole cleaning method of the first embodiment uses a line pump, model "PE2-255-0.4S," manufactured by Kawamoto Manufacturing Co., Ltd. This line pump has an allowable pressure of 0.53 MPa and a rated discharge rate of 25 L / min (at a total head of 15.5 m) to 80 L / min (at a total head of 13.2 m).

[0034] 1.5 Cleaning Water Return Pipe: The cleaning water return pipe is connected to the mouth of the steel pipe inside the foundation drain hole (the beginning of the foundation drain hole), connecting the foundation drain hole and the cleaning water tank and serving as a flow path for guiding the suspended water to the cleaning water tank. Here, "suspended water" refers to a blend of the slime that is formed when cleaning water released from the end of the cleaning water supply pipe diffuses into difficult-to-clean areas and dissociates with scale, the groundwater that flows in due to the detachment of the slime, and the cleaning water that is circulated without being used for diffusion. The inner diameter of the cleaning water return pipe is set approximately equal to the inner diameter of the foundation drain hole. Like the cleaning water supply pipe, the cleaning water return pipe is a flexible pipe (hose). In the hole cleaning method of the first embodiment, a suction hose is used as the cleaning water return pipe. A band is provided at the downstream end of the cleaning water return pipe (the end on the foundation drain hole side) to prevent cleaning water from leaking from the connection between the cleaning water return pipe and the foundation drain hole. In addition, a ball valve is installed near the downstream side of the cleaning water return pipe, so that the flow of cleaning water inside the cleaning water return pipe can be controlled (opened and closed) at that point.

[0035] In the hole cleaning method of the first embodiment, the flush water return pipe is inserted onto the flush water supply pipe and connected in a state where it surrounds the outer periphery of the steel pipe at the mouth of the foundation drain hole. In other words, the flush water supply pipe is inserted into the flush water return pipe. The upstream end (the end on the flush water tank side) of the flush water return pipe is connected to a flow path branching device (tee) attached to the top of the flush water tank. The flush water supply pipe is inserted into the flush water return pipe, with the upper end of this tee as an insertion port.

[0036] A downflow guide pipe is connected to the outlet pipe provided in the tube wall of the above-mentioned cheese, and the above-mentioned suspended water (washing water returned by the wash water return pipe) that has flowed through the wash water return pipe (outside the wash water supply pipe) is returned to the wash water tank through this downflow guide pipe. As already mentioned, the cheese (flow path branching device) is attached to the top of the wash water tank, and when suspended water is discharged from a high position in the wash water tank, the short-chain polymers and micro-nano bubbles that become surfactants in the suspended water are dispersed into the air, slowing the rate of spherical micelle formation, i.e., the decomposition (solubilization) of the suspended matter. In this regard, by returning the wash water through the downflow guide pipe, it is possible to prevent such problems from occurring.

[0037] 1.6 Cleaning Flow Next, the cleaning flow of the hole cleaning method of the first embodiment will be described. First, the bubble generating means and cleaning water transfer means are driven, and cleaning water (micro-nano bubble water) is released from the tip of the cleaning water supply pipe toward the difficult-to-clean area (the cleaning area near the end of the foundation drainage hole). Although the end of the foundation drainage hole is a dead end macroscopically, the cleaning water diffuses (penetrates) into microscopic cracks that are difficult to clean, such as narrow areas near the boundary between the dam embankment base and the top surface of the foundation bedrock, thereby peeling off and breaking down the scale that causes clogging. This eliminates clogging of the foundation drainage hole.

[0038] However, because the wash water circulates through this system, the wash water discharged from the tip of the wash water supply pipe is a suspension that is a blend of slime that has separated from the scale by diffusion, groundwater that flows in after peeling off this, and wash water that is circulating without being used for diffusion. This suspension rises through the gap between the inner wall surface of the perforated steel pipe and the outer wall surface of the wash water supply pipe, and is returned to the wash water tank through a tee (flow path branching device) attached to the wash water tank.

[0039] Since micro-nano bubbles remain in the cleaning water returned to the cleaning water tank, by returning this to the cleaning water tank, the micro-nano bubbles in the cleaning water in the cleaning water tank gradually become more concentrated, and the slime that has been released and returned is gradually decomposed in the cleaning water return pipe and the cleaning water tank. In this way, by performing cleaning while circulating micro-nano bubble water between the cleaning water tank and difficult-to-clean areas, the cleaning can be performed more efficiently.

[0040] Furthermore, by circulating the cleaning water, the surfactant concentration increases, and the amount of cleaning water added can be reduced. In the hole cleaning method of the first embodiment, the capacity of the cleaning water tank is approximately 30 L, but if approximately 40 to 50 L of cleaning water is initially added to this cleaning water tank (any cleaning water that does not fit into the cleaning water tank enters the cleaning water supply pipe, foundation drain hole, or cleaning water return pipe), cleaning can be continued without adding more cleaning water. Inspection galleries with foundation drain holes often have a supply of groundwater, so this amount of cleaning water can be stored in a plastic container or similar and carried around.

[0041] 1.7 Additional Improvements When cleaning the foundation drain hole using the above method, the head of the cleaning water tank fluctuates, and the head becomes higher immediately after cleaning starts, as shown in Figure 1. From this, it can be understood that the higher the head of the cleaning water tank, the greater the amount of scale that has formed, and by increasing the concentration of micro-nano bubbles, the diffusion and peeling of scale progresses, and finally, when the head of the cleaning water tank rises at a substantially constant gradient, it can be determined that most of the scale that can be removed has been removed.

[0042] The reason why the head of the wash water tank fluctuates during cleaning is thought to be due to the influence of fluctuations in osmotic pressure caused by the wash water peeling off scale that has formed in areas that are difficult to clean. Also, as already mentioned, the suspended water returned to the wash water tank from areas that are difficult to clean contains a large amount of slime that has peeled off from the areas that are difficult to clean, and it is thought that another cause is that this slime absorbs water and swells in the wash water tank.

[0043] From the above, by monitoring the head of the cleaning water tank, it is possible to estimate the cleaning effect (to determine whether the scale that should be removed has been removed). In the hole cleaning method of the first embodiment, as shown in Figure 2, a head measuring means is provided to measure the head of water stored inside the cleaning water tank, and the cleaning effect is determined from the head measured by this head measuring means. There are no particular restrictions on the type of head measuring means, but in the hole cleaning method of the first embodiment, a head meter model "S&DL mini" manufactured by OYO Corporation is used.

[0044] In addition, because the head of the cleaning water tank fluctuates as described above, in the hole cleaning method of the first embodiment, a "preliminary process" is performed prior to the "cleaning process" to maintain a substantially constant head, as shown in Figure 1. This is thought to be because slime was produced near the groundwater inlet, such as at the bottom of the steel pipe hole, when the water level in the hole was high, resulting in the water in the hole remaining stored, or because slime was produced when the water level in the hole was low, resulting in the groundwater being blocked by the slime, resulting in a low water level in the hole. Here, the cleaning process is a process of circulating cleaning water between the cleaning water tank and the difficult-to-clean area by driving the bubble generating means and the cleaning water transfer means. The preliminary process is a process of circulating cleaning water between the cleaning water tank and the cleaning area by driving the groundwater transfer means only without driving the bubble generating means, and large, high-viscosity flocs (floating matter) that have detached from the slime in the steel pipe are transferred to the cleaning water tank in advance.

[0045] As a result, the head after sufficient cleaning will rise at a substantially constant gradient in the higher range than the head before cleaning, since the groundwater environment before cleaning is different from the groundwater environment after cleaning.

[0046] In addition, in the hole cleaning method of the first embodiment, as shown in Figure 2, the cleaning water returned from the downflow guide pipe to the cleaning water tank is sampled. Specifically, a dipstick is immersed in the stored water returned to the cleaning water tank through the downflow guide pipe, and the ATP concentration (RLU value) is measured in situ. ATP (adenosine triphosphate) is a substance involved in the storage and utilization of energy used in the life activities of living organisms, and there is a correlation between the amount of slime, a source of contamination derived from microorganisms including bacteria, and the RLU value. As already mentioned, slime dirt detached by cleaning water in difficult-to-clean areas is returned to the cleaning water tank through the inner wall of the foundation drain hole and the cleaning water return pipe due to the decomposition action of the cleaning water. If the ATP concentration of the cleaning water stored in the cleaning water tank decreases, it can be determined that the decomposition of slime detached from the difficult-to-clean areas is progressing (the cleaning effect is being exerted). Since the RLU value of the test water is measured in about 10 seconds, if the ATP concentration is also measured after the predetermined time T1 of the preliminary step and after the predetermined times T2 and T3 of the cleaning step, it will be possible to reflect the measurement results in determining the cleaning duration of the cleaning step. Also, by combining the head of the cleaning water tank with monitoring data, it is possible to estimate the cleaning effect (determine whether or not the scale that should be removed has been removed).

[0047] 2. Hole Cleaning Method of Second Embodiment Next, a hole cleaning method of the second embodiment will be described. FIG. 3 is a diagram illustrating the hole cleaning method of the second embodiment. As shown in FIG. 3, the hole cleaning method of the second embodiment involves cleaning a groundwater observation hole drilled in the ground. By measuring the water level in this groundwater observation hole, the surrounding groundwater level can be determined, and by testing the water quality of the groundwater pumped from this groundwater observation hole, the water quality of the surrounding groundwater can be determined. If this groundwater observation hole becomes clogged, the groundwater level in the surrounding ground will no longer be linked to the water level in the groundwater observation hole, making it impossible to perform the intended measurements, etc. Therefore, the groundwater observation hole also needs to be cleaned periodically.

[0048] The hole cleaning method of the second embodiment will be described mainly with respect to the configurations different from the hole cleaning method of the first embodiment described above. The configurations of the hole cleaning method of the second embodiment that are not specifically mentioned can be the same as those described in the hole cleaning method of the first embodiment.

[0049] As shown in FIG. 3 , groundwater observation holes are generally bored vertically from the ground surface and closed at one end. In the hole cleaning method of the second embodiment, the inner diameter of groundwater observation holes is often 40 to 50 mm, and the depth of groundwater observation holes is often several meters to several hundred meters. A bottom (sludge reservoir) is provided at the terminal end (lower end) of the groundwater observation hole, and the section of the groundwater observation hole near the terminal end is surrounded by a cylindrical screen and filter material. The section above that is further surrounded by backfill material. A water-stop material is provided at the boundary between the section where the filter material is provided (the terminal section) and the section where the backfill material is provided (the starting section). Scale forms on the filter material on the outer wall of the screen near the terminal end of the groundwater observation hole. Micro-nano bubble water (cleaning water) supplied to the difficult-to-clean area is diffused from the inside to the outside of the screen to remove and decompose the scale.

[0050] In the hole cleaning method of the second embodiment, when a larger amount of cleaning water is used than in the hole cleaning method of the first embodiment, two cleaning water tanks are provided. Each cleaning water tank is connected near its top by a connecting pipe. Therefore, the water head of each cleaning water tank is equal. Each cleaning water tank contains two to three bubble generators (columns) of the bubble generating means (a total of four to six). A water head measuring means is provided in only one of the cleaning water tanks. The flow regulator of the bubble generating means is capable of adjusting the air flow rate in the range of 2 to 20 L / min.

[0051] The cleaning water in the cleaning water tank flows through the cleaning water supply pipe by the cleaning water transfer means to reach the difficult-to-clean areas, and then passes through the gap between the inner wall of the groundwater observation hole and the outer wall of the cleaning water supply pipe, and the gap between the inner wall of the cleaning water return pipe and the outer wall of the cleaning water supply pipe, before being returned to the cleaning water tank.This circulation path is approximately the same as the hole cleaning method of the first embodiment.

[0052] 3. Hole Cleaning Method of the Third Embodiment Next, a hole cleaning method of the third embodiment will be described. FIG. 4 is a diagram illustrating the hole cleaning method of the third embodiment. While the hole cleaning methods of the first embodiment (FIG. 2) and the second embodiment (FIG. 3) described above were both designed to clean holes (foundation drainage holes and groundwater observation holes) extending in a generally vertical direction (approximately vertical), the hole cleaning method of the third embodiment, as shown in FIG. 4, is designed to clean holes extending in a generally horizontal direction. Examples of holes extending in a generally horizontal direction include horizontal drains and horizontal bores excavated on the inner wall of a shaft or in horizontal boring work on a slope for the purpose of lowering the water level as a liquefaction countermeasure or slope stabilization measure. In horizontal boring work on a slope, a cleaning water tank is generally arranged near the mouth of the horizontal borehole. Below, the hole cleaning method of the third embodiment will be described using the example of cleaning a horizontal drain excavated on the inner wall of a shaft.

[0053] The hole cleaning method of the third embodiment will be described mainly with respect to the configurations different from the hole cleaning method of the first embodiment described above. The configurations of the hole cleaning method of the third embodiment that are not specifically mentioned can be the same as those described in the hole cleaning method of the first embodiment.

[0054] As shown in Figure 4, the horizontal drain is a closed-end hole extending approximately horizontally from the shaft wall. However, although the horizontal drain is "horizontal," it is slightly inclined so that the end (starting end) on the shaft side is lower than the end, in order to allow groundwater and other substances to flow through it. Furthermore, the horizontal drain must be strong enough to prevent collapse. To prevent fine soil from entering the horizontal drain, the drain is surrounded by a tubular filter material (a resin material with numerous fine perforations in the peripheral wall) while allowing surrounding groundwater to enter the horizontal drain. If slime, including scale, adheres to this filter material, the horizontal drain becomes clogged, preventing water from draining into the shaft. Therefore, the horizontal drain must also be periodically cleaned. Similar cleaning is required for horizontal borings in horizontal boring construction.

[0055] The circulation path, in which flush water from the flush water tank flows through the flush water supply pipe by the flush water transfer means to the difficult-to-clean area, then passes through the gap between the inner wall of the horizontal drain and the outer wall of the flush water supply pipe, and between the inner wall of the flush water return pipe and the outer wall of the flush water supply pipe, and is returned to the flush water tank, is substantially the same as the hole cleaning method of the first embodiment. Upon reaching the difficult-to-clean area, the flush water diffuses to the outside of the perforated pipe through the water passage holes formed in the peripheral wall of the perforated pipe, peeling off and decomposing slime that has formed in the difficult-to-clean area on the outer wall side. While conventional high-pressure washing can remove scale from the difficult-to-clean area on the inner wall of the perforated pipe, it cannot fully remove scale on the outer wall side of the perforated pipe. The hole cleaning method of the third embodiment can remove scale on the outer wall side of the perforated pipe and fully eliminate clogging, making it effective for cleaning horizontal drains that have become clogged over a long period of time. This problem and solution also apply to horizontal boring work.

[0056] 4. Hole Cleaning Method of Fourth Embodiment Next, a hole cleaning method of a fourth embodiment will be described. Figure 5 is a diagram illustrating the hole cleaning method of the fourth embodiment. The hole cleaning method of the fourth embodiment is for cleaning a horizontal drain, similar to the third embodiment (Figure 4) described above.

[0057] The hole cleaning method of the fourth embodiment will be described mainly with respect to the configurations different from the hole cleaning method of the third embodiment described above. The configurations of the hole cleaning method of the fourth embodiment that are not specifically mentioned can be the same as those described in the hole cleaning method of the third embodiment.

[0058] In the hole cleaning method of the fourth embodiment, the horizontal drain is longer than in the hole cleaning method of the third embodiment. Therefore, the total length of the cleaning water supply pipe may be as long as approximately 100 m. When the horizontal drain or cleaning water supply pipe is long, a large amount of cleaning water is required to perform cleaning while circulating cleaning water. Therefore, in the hole cleaning method of the fourth embodiment, a large water tank (160 cm in diameter, 80 cm in height) that can easily hold approximately 1000 L of cleaning water is used as the cleaning water tank. Furthermore, a submersible pump that can be immersed in the cleaning water is used as the cleaning water transfer means. Specifically, a submersible pump model "WUP3-505" manufactured by Kawamoto Manufacturing Co., Ltd. is used as the cleaning water transfer means.

[0059] 5. Hole Cleaning Method of Fifth Embodiment Next, a hole cleaning method of the fifth embodiment will be described. FIG. 6 is a diagram illustrating the hole cleaning method of the fifth embodiment. In the hole cleaning methods of the first embodiment (FIG. 2), the second embodiment (FIG. 3), the third embodiment (FIG. 4), and the fourth embodiment (FIG. 5) described above, the hole to be cleaned is a one-end closed hole, with the end closed. In contrast, the hole to be cleaned in the hole cleaning method of the fifth embodiment is a double-open hole, with both the start end and the end open.

[0060] An example of a hole with both ends open is a culvert excavated in a substantially horizontal direction beneath a road, etc. As shown in Figure 6, this type of culvert is installed in a substantially horizontal direction so as to connect the lower portions of multiple shafts excavated at predetermined intervals. For the same reason as the horizontal drain described above, this culvert is also surrounded by a tubular filter material (a resin material with many fine water-permeable holes in the peripheral wall). If scale forms on this filter material, the culvert will become clogged and will no longer be able to lower the groundwater level, so this type of culvert also needs to be cleaned periodically.

[0061] The hole cleaning method of the fifth embodiment will be described mainly with respect to the configurations different from the hole cleaning method of the fourth embodiment described above. The configurations not specifically mentioned in the hole cleaning method of the fifth embodiment can be the same as those described in the hole cleaning method of the fourth embodiment.

[0062] In the hole cleaning method of the fifth embodiment, the downstream end of the cleaning water supply pipe (the end connected to the underdrain) is connected to the underdrain to be cleaned via a branch pipe (a branch pipe provided at the bottom of the shaft on the left side in FIG. 6) connected to one end (starting end) of the underdrain to be cleaned. Also, the upstream end of the cleaning water return pipe (the end connected to the underdrain) is connected to the underdrain to be cleaned via a branch pipe (a branch pipe provided at the bottom of the shaft on the right side in FIG. 6) connected to the other end (terminating end) of the underdrain to be cleaned. The downstream end of the cleaning water return pipe is placed in a cleaning water tank via a cavitation generator, thereby increasing the concentration of micro-nano bubbles.

[0063] In the hole cleaning methods of the first to fourth embodiments described above (FIGS. 2 to 5), the tee is arranged at an appropriate height, the cleaning water supply pipe is inserted inside the cleaning water return pipe, and the cleaning water return pipe and the cleaning water supply pipe form a double-pipe structure, whereas in the hole cleaning method of the fifth embodiment (FIG. 6), the cleaning water return pipe and the cleaning water supply pipe do not need to have such a double-pipe structure, so the cleaning water return pipe is provided independently from the cleaning water supply pipe. That is, in the hole cleaning method of the fifth embodiment, the cleaning water enters the start end of the underdrain through the cleaning water supply pipe and is supplied to the cleaning point in the underdrain, is sent out from the end end of the underdrain, and is returned to the cleaning water tank via the cleaning water return pipe.

[0064] However, there is a height from the underdrain to the flushing water tank, and if the length of the underdrain section becomes long, the flushing water sent out from the end side of the underdrain will not rise up inside the flushing water return pipe and reach the flushing water tank due to insufficient water supply pressure. For this reason, in the hole cleaning method of the fifth embodiment, a casing is provided near the upstream end of the branch pipe, and a deep well pump is provided inside it to return the water to the flushing water tank via the flushing water return pipe to prevent overflow from the top end of the casing.

[0065] Even if the cleaning water is circulated in the manner described above, the concentration of micro-nano bubbles contained in the cleaning water increases, and cleaning can be performed more efficiently. In addition, there is no particular change in the fact that the cleaning effect and the duration of the cleaning process can be determined by the water head in the cleaning water tank, and approximately the same effects can be obtained as in the hole cleaning methods of the first to fourth embodiments.

[0066] 6. Hole Cleaning Method of Sixth Embodiment Finally, the hole cleaning method of the sixth embodiment will be described. The hole cleaning method of the sixth embodiment will be described mainly with respect to the configurations that differ from the hole cleaning method of the second embodiment ( FIG. 3 ). The configurations of the hole cleaning method of the sixth embodiment that are not specifically mentioned can be the same as those described for the hole cleaning method of the second embodiment.

[0067] FIG. 7 is a diagram illustrating a hole cleaning method according to a sixth embodiment. The hole cleaning method according to the sixth embodiment, like the second embodiment ( FIG. 3 ), targets a vertical hole extending in the up-down direction (vertical direction). Examples of vertical holes include water wells for industrial or agricultural use. Below, the hole cleaning method according to the sixth embodiment will be described using a water well as an example. A typical water well is a closed-end hole excavated vertically from the ground surface, as shown in FIG. 7 . This type of water well needs to be periodically cleaned because the amount of groundwater pumped (water intake) decreases over time.

[0068] The inner wall of the water well is protected by a protective pipe inserted into the water well (except for the screen section described below). The outer wall of the protective pipe is filled with backfill material. The inner diameter of the protective pipe is not particularly limited, but is often set to approximately 200 to 400 mm, larger than the outer diameter of a submersible pump (usually approximately 100 to 300 mm), so that a permanent groundwater intake device (submersible pump) that draws groundwater from the water well can be inserted into the water well. Furthermore, the water well is often several tens to several hundred meters deep. In the sixth embodiment of the hole cleaning method, the submersible pump is pulled out of the water well and the water well is cleaned using a cleaning water transfer means. This eliminates the need for a separate pump to clean the water well (transport cleaning water).

[0069] A bottom (sludge reservoir) is provided at the terminal end (lower end) of the water well. The section slightly above the terminal end of the water well is a section (screen section) where a cylindrical screen is arranged instead of a protective pipe. The outer periphery of the screen is surrounded by gravel (filling gravel) for filtering groundwater. An upper water-stop material is provided at the upper end of the screen section (the boundary between the filling gravel and the upper backfill material), and a lower water-stop material is provided at the lower end of the screen section (the boundary between the filling gravel and the lower backfill material). The screen section sandwiched between these upper and lower water-stop materials is the section for drawing groundwater (water intake section).

[0070] Scale forms on the fill gravel in the screen section of a water well. When scale forms, it becomes impossible to draw water from the aquifer that supplies groundwater. This location is difficult to clean because the scale formed there is difficult to clean. In this regard, the hole cleaning method of the sixth embodiment supplies micro-nano bubble water (cleaning water) to this difficult-to-clean location and diffuses the micro-nano bubble water (cleaning water) from the inside to the outside of the screen, thereby peeling and decomposing the scale formed in the difficult-to-clean location and cleaning the water well. After the water well has been cleaned, the submersible pump serving as the water intake device is lowered into the water well and restored to its original state. By performing this cleaning operation periodically, the water well can be kept in good condition.

[0071] In the hole cleaning method of the second embodiment described above (Figure 3), the section in the groundwater observation hole sandwiched between the water-stop material provided at the boundary between the filter material and the backfill material (the upper end of the filter material) and the bottom (terminal end) (the section continuing upward from the bottom) was the section to be cleaned.In the hole cleaning method of the sixth embodiment (Figure 7), the section to be cleaned is the screen section in the water well sandwiched between the upper water-stop material and the lower water-stop material (the section away from the bottom upward).

[0072] Furthermore, while the hole cleaning method of the second embodiment ( FIG. 3 ) described above often uses a resin protective tube to protect the groundwater observation hole, the hole cleaning method of the sixth embodiment ( FIG. 7 ) often uses a metal (steel pipe) protective tube to protect the water well. Therefore, over time, the portion of the protective tube located above the upper water-stop material in the water well is prone to electrical corrosion, often resulting in hole rupture. While such corrosion is difficult to clean using the hole cleaning method of the sixth embodiment, it can be cleaned by temporarily installing a cleaning water transfer means (temporary submersible pump) below the corroded area, transferring micro-nano bubble water (cleaning water) to a cleaning water tank, and circulating the cleaning water in a manner similar to the hole cleaning method of the first embodiment ( FIG. 3 ).

[0073] Furthermore, in the second embodiment of the hole cleaning method (Figure 3), the groundwater observation hole is primarily used to observe the natural groundwater level, so no submersible pump is installed within the hole. In the sixth embodiment of the hole cleaning method (Figure 7), a permanently installed water intake device (submersible pump) is used. As a method for cleaning a submersible pump without lifting it from the water well, if the gap between the outer diameter of the water intake device that draws groundwater and the inner diameter of the protective pipe is approximately 50 mm or more, a cleaning water supply pipe can be inserted and its tip can be inserted to the bottom of the water well. In this case, the permanently installed water intake device (submersible pump) is usually connected to a water tank or the like via a lift pipe. During cleaning, the piping valve to the water tank is closed, and micro-nano bubble water (cleaning water) is taken in by the permanent water intake device through a tee and transferred to the cleaning water tank. The cleaning water is circulated in a manner similar to the first embodiment of the hole cleaning method, thereby reducing the labor required for raising and lowering the permanent water intake device (submersible pump) during cleaning.

[0074] 7. Summary The hole cleaning methods described above are not limited to the applications mentioned above and can be used to clean difficult-to-clean areas of various holes (holes with one closed end or holes with both open ends). These hole cleaning methods can effectively remove scale that cannot be completely removed by high-pressure washing. Furthermore, circulating the cleaning water increases the concentration of micro-nano bubbles, increasing the short-chain polymers contained in the slime that has detached the scale. This increases the number of micelles, further solubilizing the detached slime and enhancing the cleaning effect. Therefore, even in locations where tap water is difficult to use, this method can be suitably used with in-situ groundwater. Furthermore, the equipment and parts used can be easily transported. Therefore, this method can be suitably used in locations where large equipment cannot be transported.

Claims

1. A hole cleaning method for cleaning a cleaning point near the end of the hole bottom side that is to be maintained as a groundwater inlet, comprising: a cleaning water tank for storing cleaning water; bubble generating means for generating micro-nano bubbles in the cleaning water tank; a cleaning water supply pipe inserted into the hole for supplying cleaning water from the cleaning water tank to the cleaning point; cleaning water transferring means for transferring the cleaning water in the cleaning water tank through the cleaning water supply pipe to the cleaning point; and a cleaning water return pipe inserted onto the cleaning water supply pipe and connecting the start of the hole and the cleaning water tank; and driving the bubble generating means and cleaning water containing micro-nano bubbles is supplied from the tip of the cleaning water supply pipe to the cleaning point, thereby cleaning the cleaning point, and A hole cleaning method characterized in that the cleaning water supplied to the cleaning area is returned to the cleaning water tank through the gap between the inner wall of the hole and the outer wall of the cleaning water supply pipe, and the gap between the inner wall of the cleaning water return pipe and the outer wall of the cleaning water supply pipe, thereby circulating the cleaning water between the cleaning water tank and the cleaning area.

2. A hole cleaning method as claimed in claim 1, in which a head measuring means is provided for measuring the head of the cleaning water tank, which changes in conjunction with the pressure of the cleaning water in the hole, and the cleaning effect is estimated from the change in the head measured by the head measuring means.

3. A hole cleaning method as described in claim 2, which provides an ATP concentration measuring means for measuring the ATP concentration of the cleaning water in the cleaning water tank, and prior to the process of performing the cleaning while circulating the cleaning water (hereinafter referred to as the "cleaning process"), a process of circulating groundwater between the cleaning water tank and the cleaning location (hereinafter referred to as the "preliminary process") is carried out for a predetermined time T1 by driving only the cleaning water transfer means without driving the bubble generating means, and determines the duration of the cleaning process and estimates the cleaning effect based on the head measured by the head measuring means and the ATP concentration measured by the ATP concentration measuring means during the preliminary process and the head measured by the head measuring means and the ATP concentration measured by the ATP concentration measuring means during the cleaning process.

4. A hole cleaning method for cleaning the inside of a hole whose starting and ending ends are both open, comprising: a cleaning water tank for storing cleaning water; bubble generating means for generating micro-nano bubbles in the cleaning water tank; a cleaning water supply pipe connected to the starting end of the hole for supplying cleaning water from the cleaning water tank to a location to be cleaned within the hole; cleaning water transferring means for transferring the cleaning water in the cleaning water tank to the location to be cleaned via the cleaning water supply pipe; and a cleaning water return pipe connected to the end of the hole for returning the cleaning water coming out of the hole to the cleaning water tank; the hole cleaning method characterized in that the bubble generating means and the cleaning water transferring means are driven to supply cleaning water containing micro-nano bubbles to the location to be cleaned, and the cleaning water sprayed at the location to be cleaned is returned to the cleaning water tank via the cleaning water return pipe, thereby circulating the cleaning water between the cleaning water tank and the location to be cleaned.

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