Stable groundwater level measuring device and measuring method

Abstract

The present application belongs to the field of groundwater level measurement, and more particularly relates to a stable groundwater level measurement device and a stable groundwater level measurement method. The present application adopts the overall design idea of "first draining the groundwater in the drill hole, then using the principle of the water collecting funnel to lower the measurement device for measurement", which can quickly measure the stable groundwater level, and the test cycle is usually about one week, which is much smaller than the cycle of 1 to 2 years of the conventional long observation hole. In addition, the multi-point wet sensitive resistance sensor measurement method is adopted, a plurality of wet sensitive resistance sensors are installed on the fixed rod at a certain interval, when the wet sensitive resistance sensor contacts water, the resistance corresponding to the wet sensitive resistance sensor will change, and the resistance of the sensor not contacting water remains unchanged. Since the distance between the measurement points of the multi-point wet sensitive resistance sensor is relatively short, the measurement error is also relatively small, and by collecting the changes of these resistances, the depth of the groundwater level can be determined.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of groundwater level measurement, and more particularly relates to a stable groundwater level measurement device and a stable groundwater level measurement method. BACKGROUND

[0002] Stable groundwater level refers to a state in which the groundwater level remains relatively constant within a certain period of time, that is, a balance is achieved between the recharge of groundwater and the discharge of groundwater.

[0003] In recent years, thanks to the demand for energy transformation, policy support, technological progress, and growth in market demand, pumped storage power stations have ushered in a golden period of rapid development worldwide. Currently, they have become a key technology for balancing power grid load and promoting the use of renewable energy, showing strong development momentum and broad application prospects. The construction of pumped storage power stations has the characteristic of short construction period, especially in the early stage (pre-feasibility and feasibility study stage). In the design process of the power station, the groundwater level directly affects the stability design of the underground powerhouse, the selection of the steel lining wall thickness, the arrangement of the drainage gallery, the size of the drainage tunnel diameter, and so on, and its importance is self-evident. The conventional stable groundwater level measurement is obtained through long-term observation of long observation holes, and the observation time is generally 1 to 2 years, which is difficult to meet the needs of pumped storage power station projects. Specifically, the existing water level measurement technology mostly relies on the water level in the borehole reaching a stable state, and after completing the borehole coring operation, the water level in the hole is often higher than the true groundwater level, and it generally takes a long time to recover to a stable state. Therefore, the existing groundwater level measurement technology is not suitable for projects with a short construction period.

[0004] The existing patent documents disclose that the groundwater level measuring device is mostly improved for the measuring method, and the measured is the groundwater level in the hole, not the stable groundwater level. The stable groundwater level often needs to spend a long time to obtain by multiple measurements. For example, the Chinese patent document with publication number CN218937498U discloses an underground water level monitoring device, which uses a pressure sensor to detect the depth of the underground water level. The device lowers the detection head to underwater through a winding rope mechanism, and obtains pressure feedback values according to different water depths to determine the depth change of the underground water. In addition, the Chinese patent document with publication number CN117470351A discloses an underground water level monitoring device, which uses an underwater laser range finder to measure the water level. Furthermore, the Chinese patent document with publication number CN214667136U discloses an underground water level measuring device, which lowers the sensing ball to float above the underground water surface in the hole by linkage installation of the sensing ball and the rope. At this time, the ground acoustic wave sensor detects the distance from the sensing ball to the ground in real time, thereby measuring the underground water level. In addition, the patent with publication number CN220819143U provides an underground water level measuring probe and an underground water level measuring device. When the probe is lowered to contact the underground water in the hole, a measuring device is used to measure the water level. These measuring methods mostly belong to the traditional method, that is, lowering the sensor to the underground water surface in the hole for measurement, and the measured water level is the conventional water level. In order to meet the engineering needs, it is necessary to spend a long time to measure the water level in the hole multiple times, but it is impossible to achieve rapid and accurate measurement. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a stable underground water level measuring device, which can realize rapid and relatively accurate measurement of the stable underground water level.

[0006] In order to solve the above technical problems, the present application adopts the following technical scheme: the stable underground water level measuring device comprises a drainage device, a water removal device, a water blocking device and a measuring device; the drainage device is used for draining underground water in a borehole; the water removal device is used for removing underground water adhered to the inner wall of the borehole; and the water blocking device is used for blocking surface water from entering the borehole; the measuring device comprises a fixed rod, a wet sensitive resistance sensor, a flexible elastic film, an air pump and a data collector; the fixed rod is composed of a plurality of fixed pipes which are coaxially fixedly connected; the side walls of two adjacent fixed pipes are hermetically connected, so that the fixed rod forms a hollow inner cavity; the fixed rod is vertically arranged; the lower end of the fixed rod is provided with a closing piece which closes the inner cavity of the fixed rod; the upper end of the fixed rod is provided with a gas charging and discharging connector which is connected with the inner cavity of the fixed rod; the gas charging and discharging connector is connected with the air pump through a gas pipeline; the side wall of each fixed pipe is provided with a long strip-shaped hole; the length direction of the long strip-shaped hole is consistent with the axis direction of the fixed pipe; the circumferential edge portion of the flexible elastic film is hermetically connected with the circumferential edge portion of the long strip-shaped hole; the wet sensitive resistance sensor is fixedly arranged on the outer surface of the flexible elastic film; the wet sensitive resistance sensor is connected with the data collector through a wire and forms a measuring circuit; the wire is connected through a line connector in the region corresponding to the connecting portion of the two adjacent fixed pipes; when the inner cavity of the fixed rod is inflated by the air pump, the flexible elastic film can be in an expanded state relative to the outer surface of the fixed rod, and the sensing end of the wet sensitive resistance sensor is in close contact with the inner side wall of the borehole; and at this time, the wet sensitive resistance sensor is vertically and spacedly arranged.

[0007] Preferably, the flexible elastic film is a rubber film, and the long strip-shaped hole is a stepped hole; when the flexible elastic film is in a natural state, the wet sensitive resistance sensor and the flexible elastic film are located in the outer end face of the long strip-shaped hole.

[0008] Preferably, the measuring circuit comprises a plurality of unit circuits which are arranged side by side; each unit circuit comprises a plurality of wet sensitive resistance sensors which are spacedly arranged along the length direction of the fixed pipe.

[0009] Preferably, the outer surface of the sensing end of the wet sensitive resistance sensor is sequentially provided with a water permeable film and a semi-water permeable film from outside to inside.

[0010] Preferably, the drainage device comprises a water pump and a water pumping pipeline which are connected in a matched mode.

[0011] Preferably, the water removal device comprises a drilling machine; a ring-shaped water absorbing soft brush is detachably fixedly arranged on the outer surface of the drill rod of the drilling machine; and the ring-shaped water absorbing soft brush is spacedly provided with a plurality of turns along the length direction of the drill rod.

[0012] Preferably, the water blocking device comprises a sleeve; the lower end of the sleeve is used for being inserted into the borehole.

[0013] On the basis of the above-mentioned stable underground water level measuring device, the application also provides a stable underground water level measuring method, which can realize rapid and relatively accurate measurement of the stable underground water level. The stable underground water level measuring method comprises the following steps:

[0014] Step one: after the completion of the construction of the drill hole, a water blocking device is installed at the upper end of the drill hole;

[0015] Step two: the underground water level in the drill hole is lowered to the bottom of the drill hole by using the drainage device;

[0016] Step three: the underground water adhered to the inner wall of the drill hole is removed by using the water removing device;

[0017] Step four: after the water removal, the drill hole is left for 2 to 3 days, and then step three is repeated multiple times;

[0018] Step five: the flexible elastic membrane, the humidity resistance resistance sensor and the wire corresponding to each fixed pipe are fixed and installed in advance, the fixed pipes are lowered one by one, the adjacent two fixed pipes are connected and assembled at the hole opening position of the drill hole, and the wires corresponding to the area are connected through the wire joint; the operation is repeated to form a fixed rod extending from the bottom of the drill hole to the top of the drill hole, and then the fixed rod is connected with the data collector outside the drill hole through the wire and forms a measuring circuit;

[0019] Step six: the upper end of the fixed rod is installed with the gas charging and discharging joint, the gas charging and discharging joint is connected with the air pump through the gas pipeline, the air pump is opened, the inner cavity of the fixed rod is inflated, the flexible elastic membrane is inflated outward, and the sensing end of the humidity resistance resistance sensor is attached to the inner side wall of the drill hole;

[0020] Step seven: the resistance value change of the humidity resistance resistance sensor from top to bottom in the drill hole is monitored through the data collector.

[0021] Preferably, the installation method of the water blocking device in step one is that after the completion of the construction of the drill hole, the mud skin adhered to the inner wall position of the hole opening of the drill hole is removed, then the sleeve is coaxially inserted into the hole opening position of the drill hole, the lower end position of the sleeve is lower than the lower surface position of the covering layer, and the upper end position of the sleeve is higher than the outer end surface of the drill hole.

[0022] Preferably, the water removing device comprises a drilling machine, a plurality of rings of annular water absorbing soft brushes are arranged along the length direction of the drill rod and are detachably fixed on the outer surface of the drill rod of the drilling machine, and the specific method for removing the underground water adhered to the inner wall of the drill hole in step three is that after the annular water absorbing soft brushes are installed, the drill rod is rotated and lowered to remove the underground water adhered to the inner wall of the drill hole; the above-mentioned removing operation is repeated multiple times.

[0023] The beneficial effects of the present application are: the overall design idea of "first draining underground water in the borehole, then lowering the measuring device for measurement" can quickly measure the stable groundwater level, and the test cycle is usually about one week, which is much smaller than the cycle of 1 to 2 years of the conventional long observation hole. In addition, the multi-point wet resistance sensor measurement method is adopted, a plurality of wet resistance sensors are installed on the fixed rod at a certain interval, when the wet resistance sensor contacts water, the resistance corresponding to the wet resistance sensor will change, and the sensor resistance not contacting water remains unchanged, since the distance between the measuring points of the multi-point wet resistance sensor is relatively short, the measurement error is also relatively small, by collecting the changes of these resistances, the depth of the groundwater level can be determined. The wet resistance sensor adopts a double-layer protective structure of water-permeable membrane and semi-permeable membrane, this design not only can effectively filter the impurities that may exist in the underground water, but also can protect the wet resistance sensor to a certain extent, prevent the corrosion of the wet resistance sensor caused by the underground water, thereby ensuring the service life of the wet resistance sensor to a certain extent. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the provided drawings.

[0025] Figure 1 is the schematic diagram of the principle of the present application;

[0026] Figure 2 is the structural schematic diagram of the stable groundwater level measuring device provided by the present application in the specific implementation;

[0027] Figure 3 is Figure 2 the local enlarged schematic diagram of A shown in the figure.

[0028] Figure 4 is the local enlarged schematic diagram of B shown in the figure. Figure 2

[0029] In the figure, the component marks are as follows: fixed pipe 11, wet resistance sensor 12, flexible elastic film 13, air pump 14, data collector 15, gas charging and discharging joint 16, line joint 17, bolt connection assembly 18, sleeve 20, borehole 30, covering layer 40, ground 50, stable groundwater level 60, seepage 70, equipment platform 80. DETAILED DESCRIPTION

[0030] ​The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0031] Please refer to Figures 1 to 4 The present application discloses a stable groundwater level measuring device, comprising a drainage device, a water removal device, a water blocking device and a measuring device; the drainage device is used for draining the groundwater in the drill hole 30, the water removal device is used for removing the groundwater adhered to the inner wall of the drill hole 30, and the water blocking device is used for blocking the surface water from entering the drill hole 30; the measuring device comprises a fixed rod, a wet sensitive resistance sensor 12, a flexible elastic film 13, a gas pump 14 and a data collector 15; the fixed rod is composed of a plurality of fixed pipes 11 fixedly connected coaxially, the side walls of two adjacent fixed pipes 11 are connected airtight to form a hollow structure in the inner cavity of the fixed rod, the fixed rod is vertically arranged, the lower end of the fixed rod is provided with a closing piece closing the inner cavity thereof, and the upper end of the fixed rod is provided with a gas charging and discharging connector 16 connected with the inner cavity thereof; the gas charging and discharging connector 16 is connected with the gas pump 14 through a gas pipeline; the side wall of each fixed pipe 11 is provided with a long strip-shaped hole, the length direction of the long strip-shaped hole is consistent with the axis direction of the fixed pipe 11, the circumferential edge part of the flexible elastic film 13 is connected airtight with the circumferential edge part of the long strip-shaped hole, the wet sensitive resistance sensor 12 is fixedly arranged on the outer surface of the flexible elastic film 13, and the wet sensitive resistance sensor 12 is connected with the data collector 15 through a wire and forms a measuring circuit; the wire is connected through a line connector 17 in the region corresponding to the connecting part of the two adjacent fixed pipes 11; when the inner cavity of the fixed rod is inflated by the gas pump 14, the flexible elastic film 13 can be in an expanded state relative to the outer surface of the fixed rod, and the sensing end of the wet sensitive resistance sensor 12 is attached to the inner side wall of the drill hole 30, and at this time, the wet sensitive resistance sensor 12 is vertically and spacedly arranged.

[0032] The above-mentioned stable groundwater level measuring device in the specific implementation includes the following steps:

[0033] Step one, after the construction of the drill hole 30 is completed, the water blocking device is installed at the upper end of the drill hole 30;

[0034] Step two, the groundwater level in the drill hole 30 is lowered to the bottom of the hole (the groundwater in the hole is drained as much as possible) by using the drainage device;

[0035] Step three, the groundwater adhered to the inner wall of the drill hole 30 is removed by using the water removal device;

[0036] Step four, after the water is removed, the drill hole 30 is left for 2 to 3 days, and then step three is repeated multiple times;

[0037] Step 5: Each fixed tube 11 is pre-installed with its corresponding flexible elastic membrane 13, humidity-sensitive resistor sensor 12, and wires. The fixed tubes 11 are lowered one by one, and two adjacent fixed tubes 11 are connected and assembled at the opening of the borehole 30. At the same time, the wires corresponding to this area are connected through the line connector 17. The operation is repeated to form a fixed rod extending from the bottom of the borehole 30 to the top of the hole. The rod is then connected to the data acquisition device 15 outside the borehole 30 via wires to form a measurement circuit.

[0038] Step 6: Install the inflation / discharge connector 16 on the upper end of the fixed rod and connect the inflation / discharge connector 16 to the air pump 14 through the gas pipeline; turn on the air pump 14 to inflate the inner cavity of the fixed rod, causing the flexible elastic membrane 13 to expand outward and allowing the sensing end of the humidity sensor 12 to fit the inner wall of the borehole 30;

[0039] Step 7: Monitor the resistance change of the humidity sensor 12 from top to bottom in the borehole 30 through the data collector 15. The data acquisition process can generally last for 1 day. The depth of the stable groundwater level 60 can be determined based on the data collected in this step.

[0040] The design principle of the present invention is to drain the groundwater in the borehole 30 to the bottom of the hole, form a water collecting funnel in the hole, and then remove the groundwater attached to the bedrock wall in the hole, and the water retaining device blocks the surface water from entering the borehole 30. The groundwater (i.e. Figure 1 The elevation where the seepage depth is the shallowest is the stable groundwater level (i.e. Figure 1 The stable groundwater level 60 shown in FIG. 1 is a diagram illustrating a stable groundwater level 60. When measuring the stable groundwater level 60, a multi-point humisistor sensor measurement method is used. Multiple humisistor sensors 12 are installed at a certain interval on a fixed rod. When a humisistor sensor 12 contacts water, the resistance corresponding to the humisistor sensor 12 changes, while the resistance of the sensor not in contact with water remains unchanged. Since the distance between the measuring points of the multi-point humisistor sensor is short, the measurement error is relatively small. By collecting data on the changes in these resistances, the depth of the groundwater level can be determined. The specific spacing can be flexibly designed according to the measurement accuracy requirements. After the measurement is completed, the inner cavity of the fixed rod is deflated through the inflation and deflation joint 16, and then the device can be removed in a conventional manner. In addition, to facilitate the installation of the air pump 14 and the data acquisition unit 15, an equipment platform 80 can generally be set at the outer end of the borehole 30 in the form of backfill.

[0041] It can be understood that in specific embodiments, the side walls of two adjacent fixed tubes 11 are connected in airtight manner, and the specific connection structure involved in the connection of the wires at the connection part of the two adjacent fixed tubes 11 can be realized by the common knowledge of those skilled in the art. For example, the two fixed tubes 11 can be connected and fixed by using a fixed ring matched with a bolt connection assembly 18, and a sealing ring can be provided at the joint to ensure airtightness. The use of the inflation and deflation joint 16 to realize inflation and deflation can also be realized by the common knowledge of those skilled in the art. For example, the inflation and deflation joint 16 can be in the form of an air nozzle (for reference, see the inflation and deflation method of a football, a basketball, etc.), and in some alternative embodiments, the inflation and deflation joint 16 can also be in the form of a three-way valve, one interface is used to connect the upper end of the fixed rod, one interface is used to connect the air pump 14, and the other interface is used to connect the openable exhaust port.

[0042] The flexible elastic film 13 can be made of elastic material, flexible material, or material with both elasticity and flexibility, as long as it meets the following technical requirements: when the fixed rod inner cavity is not inflated, the hole-in structure part of the measuring device can be smoothly lowered into the drill hole 30; after inflating the fixed rod inner cavity, the flexible elastic film 13 can be in an expanded state relative to the outer surface of the fixed rod, and the sensing end of the humidity resistance resistance sensor 12 is attached to the inner wall of the drill hole 30, and at this time the humidity resistance resistance sensor 12 is vertically spaced. The preferred scheme is that the flexible elastic film 13 is a rubber film, and the long strip-shaped hole is a stepped hole, when the flexible elastic film 13 is in a natural state, the humidity resistance resistance sensor 12 and the flexible elastic film 13 are located in the outer end face of the long strip-shaped hole. After using this structure design, it is not only beneficial to control the distribution point of the humidity resistance resistance sensor 12, but also in the process of lowering the hole-in structure part of the measuring device into the drill hole 30, the humidity resistance resistance sensor 12 and the flexible elastic film 13 are located in the outer end face of the long strip-shaped hole, and they will not contact the inner wall of the drill hole 30, which more effectively protects the electrical elements. It can be understood that the measuring device has at least two states of the fixed rod inner cavity not being inflated (in the process of lowering into the drill hole 30) and the fixed rod inner cavity being inflated (the sensing end of the humidity resistance resistance sensor 12 is attached to the inner wall of the drill hole 30), and the wires between the two adjacent humidity resistance resistance sensors 12 should be reserved with appropriate connection length to meet the switching between the above two states of the measuring device.

[0043] In some preferred embodiments, the measuring circuit comprises a plurality of unit circuits arranged side by side, and preferably three unit circuits arranged side by side, each of which comprises a plurality of humidity-sensitive resistance sensors 12 arranged along the length direction of the fixed tube 11. With this structure, on the one hand, the failure of a single line will not affect the entire line, and on the other hand, under normal circumstances, a plurality of unit circuits are measured at the same time, and the measurement accuracy can be improved by integrating all the data. Figure 2 and Figure 3 In the preferred embodiments shown in Figs. 8 and 9, three unit circuits arranged side by side are arranged in the left region of the borehole 30.

[0044] To effectively protect the humidity-sensitive resistance sensor 12, the outer surface of the sensing end of the humidity-sensitive resistance sensor 12 is provided with a water-permeable membrane and a semi-water-permeable membrane from outside to inside. The double-protection structure of the water-permeable membrane and the semi-water-permeable membrane can not only effectively filter impurities that may exist in underground water, but also protect the humidity-sensitive resistance sensor to a certain extent, preventing the humidity-sensitive resistance sensor from being corroded by underground water, thereby ensuring the service life of the humidity-sensitive resistance sensor to a certain extent.

[0045] The drainage device is used to drain underground water in the borehole 30, and as long as it can meet the technical requirements of draining the underground water in the borehole 30 as much as possible, the preferred solution is that the drainage device comprises a water pump and a water suction pipeline connected in a matched manner, and the water pump can be directly used for water suction.

[0046] The water removal device is used to remove underground water adhered to the inner wall of the borehole 30, and as long as it can meet the technical requirements of wiping off the residual underground water on the sidewall of the borehole 30, the preferred solution is that the water removal device comprises a drilling machine, and the outer surface of the drill rod of the drilling machine is detachably fixed with an annular water suction soft brush, and the annular water suction soft brush is provided with a plurality of rings arranged along the length direction of the drill rod.

[0047] The water blocking device is used to block surface water from entering the borehole 30, and as long as it can avoid the surface water from entering the borehole 30, the preferred solution is that the water blocking device comprises the sleeve 20, and the lower end of the sleeve 20 is used to be inserted into the borehole 30.

[0048] In the preferred embodiments described above, in the specific implementation process, the corresponding stable underground water level measuring method is preferably implemented in the following manner.

[0049] The water retaining device installation method of step one is to remove the mud attached to the inner wall of the borehole 30 after the construction of the borehole 30 is completed, and then insert the sleeve 20 coaxially at the borehole 30, the lower end of the sleeve 20 is lower than the lower surface of the covering layer 40, and the upper end of the sleeve 20 is higher than the outer end surface of the borehole 30. The specific method of removing the groundwater attached to the inner wall of the borehole 30 in step three is to rotate and lower the drill pipe to remove the groundwater attached to the inner wall of the borehole 30 after the annular water absorbing soft brush is installed; repeat the above-mentioned removal action several times, generally repeat at least three times to ensure the water removal effect.

[0050] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0051] The above description of the disclosed embodiments enables those skilled in the art to carry out or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A stable groundwater level measuring device, characterized by, The measuring device comprises a fixed rod, a humidity-sensitive resistance sensor (12), a flexible elastic film (13), a gas pump (14) and a data collector (15). The fixed rod is composed of multiple fixed pipes (11) fixedly connected coaxially. The side walls of two adjacent fixed pipes (11) are connected airtight to form a hollow structure. The fixed rod is vertically arranged. The lower end of the fixed rod is provided with a closing member to close the inner cavity. The upper end of the fixed rod is provided with a gas charging and discharging connector (16) connected with the inner cavity. The connector is connected with the gas pump (14) through a gas pipeline. The side wall of each fixed pipe (11) is provided with a long strip-shaped hole. The length direction of the long strip-shaped hole is consistent with the axis direction of the fixed pipe (11). The circumferential edge of the flexible elastic film (13) is connected with the circumferential edge of the long strip-shaped hole. The humidity-sensitive resistance sensor (12) is fixedly arranged on the outer surface of the flexible elastic film (13) and connected with the data collector (15) through a wire to form a measuring circuit. The wire is connected through a line connector (17) in the area corresponding to the connection part of two adjacent fixed pipes (11). When the inner cavity of the fixed rod is inflated by the gas pump (14), the flexible elastic film (13) can be expanded relative to the outer surface of the fixed rod, and the sensing end of the humidity-sensitive resistance sensor (12) is attached to the inner side wall of the drill hole (30). At this time, the humidity-sensitive resistance sensor (12) is vertically and spacedly arranged. The flexible elastic film (13) is a rubber film, and the long strip-shaped hole is a stepped hole. When the flexible elastic film (13) is in a natural state, the humidity-sensitive resistance sensor (12) and the flexible elastic film (13) are located in the outer end face of the long strip-shaped hole.

2. The stable groundwater level measuring device according to claim 1, characterized by The measuring circuit comprises multiple unit circuits arranged side by side. Each unit circuit comprises multiple humidity-sensitive resistance sensors (12) arranged along the length direction of the fixed pipe (11).

3. The stable groundwater level measuring device according to claim 1, characterized by, The outer surface of the sensing end of the humidity-sensitive resistance sensor (12) is sequentially provided with a water-permeable film and a semi-water-permeable film from outside to inside.

4. The stable groundwater level measuring device according to claim 1, characterized by, The drainage device comprises a water pump and a water pumping pipeline connected in a matched manner.

5. The stable groundwater level measuring apparatus according to any one of claims 1 to 4, characterized by The water removal device comprises a drilling machine. The outer surface of the drill rod of the drilling machine is detachably fixedly provided with an annular water absorption soft brush. The annular water absorption soft brush is spacedly provided with multiple turns along the length direction of the drill rod.

6. The stable groundwater level measuring apparatus according to any one of claims 1 to 4, characterized by The water blocking device comprises a sleeve (20). The lower end of the sleeve (20) is used for inserting into the drill hole (30).

7. The stable groundwater level measuring apparatus according to any one of claims 1 to 4, characterized by The stable underground water level measuring device is used, and the following steps are included.

8. A method of stabilizing a groundwater level measurement, characterized by, Step one: after the construction of the drill hole (30) is completed, the water blocking device is installed at the upper end of the drill hole (30). Step two: the underground water level in the drill hole (30) is lowered to the bottom of the hole by using the drainage device. Step three: the underground water adhered to the inner wall of the drill hole (30) is removed by using the water removal device. Step four: after the water is removed, the drill hole (30) is left for 2-3 days, and then step three is repeated multiple times. ​ Step five, each fixed pipe (11) is pre-fixedly installed with corresponding flexible elastic film (13), humidity resistance sensor (12) and wire, and the fixed pipes (11) are sequentially lowered, and the adjacent two fixed pipes (11) are connected and assembled at the hole position of the borehole (30), and the wires corresponding to the area are connected through the wire joint (17); the operation is repeated to assemble a fixed rod extending from the bottom of the borehole (30) to the top of the borehole (30), and then the fixed rod is connected with the data collector (15) outside the borehole (30) through the wire and forms a measurement circuit; Step six, the upper end of the fixed rod is installed with the gas charging and discharging joint (16), the gas charging and discharging joint (16) is connected with the air pump (14) through the gas pipeline, the air pump (14) is opened, the inner cavity of the fixed rod is inflated, the flexible elastic film (13) is inflated outward, and the sensing end of the humidity resistance sensor (12) is attached to the inner side wall of the borehole (30); Step seven, the resistance value change of the humidity resistance sensor (12) from top to bottom in the borehole (30) is monitored through the data collector (15).

9. The method of stabilizing groundwater level measurements of claim 8, wherein, The water blocking device installation method of step one is that after the construction of the borehole (30) is completed, the mud skin attached to the inner wall position of the borehole (30) is removed, then the sleeve (20) is coaxially inserted into the borehole (30) at the hole position, the lower end position of the sleeve (20) is lower than the lower surface position of the covering layer (40), and the upper end position of the sleeve (20) is higher than the outer end surface of the borehole (30).

10. The method of stabilizing groundwater level measurements of claim 8, wherein, The water removal device comprises a drilling machine, and a ring-shaped water absorption soft brush is detachably and fixedly arranged on the outer surface of the drill rod of the drilling machine, a plurality of rings are arranged along the length direction of the drill rod, and the specific method for removing the underground water attached to the inner wall of the borehole (30) is that after the ring-shaped water absorption soft brush is installed, the drill rod is rotated and lowered to remove the underground water attached to the inner wall of the borehole (30); the above removing operation is repeated for multiple times.

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