A device for monitoring urban ground subsidence

Abstract

This application relates to the field of land subsidence monitoring technology and discloses an urban land subsidence monitoring device, including a water storage tank, a hydrostatic level, and a data acquisition unit. The hydrostatic level has an inlet pipe and a return pipe on both sides, with the return pipe connected to the water storage tank. The inlet pipe is connected to a dynamic water tank, and a one-way valve is directly installed between the inlet pipe and the dynamic water tank, allowing liquid to flow unidirectionally from the inlet pipe into the dynamic water tank, which is connected to the water storage tank. This urban land subsidence monitoring device, through the dynamic water tank and driving plug, enables unidirectional liquid flow in the detection device, allowing newly generated air bubbles in the pipeline or hydrostatic level to flow out promptly, reducing the influence of air bubbles and making the data more reliable. Furthermore, the dynamic water tank periodically injects a specific volume of liquid into the water storage tank, causing the liquid level in the storage tank to change periodically and specifically, facilitating comparison of pressure values ​​in various hydrostatic levels and identifying anomalies.

Description

Technical Field

[0001] This application relates to the field of land subsidence monitoring technology, and in particular to an urban land subsidence monitoring device. Background Technology

[0002] Common methods for monitoring urban land subsidence include leveling, GPS, remote sensing, lidar, groundwater level monitoring, and fiber optic sensor monitoring. Among these, leveling provides highly reliable data and is relatively inexpensive, making it suitable for long-term monitoring.

[0003] The principle of leveling is to establish a horizontal line of sight using a level instrument, measure the elevation difference between two points, and thus obtain the elevation changes of ground points at different times, thereby determining the ground settlement. Among these methods, the differential pressure hydrostatic level is a commonly used monitoring device. Based on the principle of communicating vessels, it typically consists of multiple liquid reservoirs, vent pipes, liquid pipes, and high-precision pressure sensors. A stable point is selected as a reference point, and the liquid reservoir at the reference point is placed at a known elevation. The liquid reservoirs at other measuring points are placed at the locations where settlement needs to be measured. When the measuring points rise or fall relative to the reference point, the liquid level at each point changes accordingly due to the free flow of liquid in the communicating pipes, causing a change in pressure at each point. This pressure difference is measured by a high-precision pressure sensor, and based on known parameters such as the liquid density and gravitational acceleration, the elevation change of each measuring point relative to the reference point, i.e., the settlement or uplift, can be calculated.

[0004] During the installation of a hydrostatic level, it is crucial that there are no air bubbles within the level itself or its piping. The presence of air bubbles can significantly impact measurement accuracy. Although installers strive to minimize air bubble formation, factors such as high temperatures, exposure to sunlight, or vibration can cause air bubbles to re-emerge within the hydrostatic level or its piping. Furthermore, in actual use, the distance between hydrostatic levels and the difficulty in observing certain measurement points can prevent the timely detection of air bubbles, leading to unreliable monitoring data over extended periods.

[0005] Secondly, because the area where static levels are installed is large and some places are inconvenient for maintenance, it may be difficult to detect malfunctions in static levels in a timely manner. Summary of the Invention

[0006] This application proposes an urban ground subsidence monitoring device. Through a dynamic water tank and a driving plug, the liquid in the detection device flows in one direction, which can promptly cause newly generated air bubbles in the pipeline or static level to flow out. At the same time, the dynamic water tank periodically injects a certain volume of liquid into the storage tank, which facilitates data comparison to detect whether there are any anomalies.

[0007] To achieve the above objectives, this application adopts the following technical solution: A city ground subsidence monitoring device, comprising a water tank, a hydrostatic level, and a data acquisition unit. Multiple sets of hydrostatic levels are provided, with one set placed at a reference point and the remaining hydrostatic levels placed at measurement points. Each hydrostatic level is also equipped with an air tube and a data cable, the data cable being electrically connected to the data acquisition unit. Each hydrostatic level has air tubes on both sides, with the air tubes on each hydrostatic level connected end-to-end. The end air tube is connected to the atmosphere, and the beginning air tube is connected to the water tank. Each hydrostatic level has an inlet pipe and an outlet pipe on both sides, with the outlet pipe connected to the water tank. The inlet pipe is connected to a dynamic water tank. A one-way valve is directly installed between the inlet pipe and the dynamic water tank, allowing liquid to flow unidirectionally from the inlet pipe into the dynamic water tank. The dynamic water tank is connected to a storage tank, and a one-way valve is installed between the dynamic water tank and the storage tank, allowing liquid to flow unidirectionally from the dynamic water tank to the storage tank. The storage tank is connected to a driver. The dynamic water tank is cylindrical, and a driver plug is installed inside the dynamic water tank. The driver can push the driver plug to move, thereby causing a specific volume of liquid to flow into or out of the dynamic water tank. The data acquisition device collects the pressure changes monitored by the hydrostatic level when the liquid in the storage tank undergoes a characteristic volume change, and determines whether there are any abnormalities in each hydrostatic level.

[0008] Furthermore, the actuator includes an air chamber that is connected to a dynamic water tank, and an actuator is provided inside the air chamber to change the air pressure inside the air chamber.

[0009] Furthermore, the actuator is an air pump, and the side wall of the air chamber is also provided with a control valve. Both the air pump and the control valve are connected to the atmosphere.

[0010] Furthermore, the actuator is an airbag, which contains a gas with a volume expansion coefficient greater than that of air. When the airbag expands, the air pressure in the air chamber is greater than atmospheric pressure. When the airbag contracts after expansion, the pressure in the air chamber is less than atmospheric pressure.

[0011] Furthermore, the gas chamber is equipped with a one-way control valve one and a one-way control valve two. Both one-way control valve one and one-way control valve two are equipped with a one-way valve. When one-way control valve one is open, gas flows out in one direction. When one-way control valve two is open, gas flows in in one direction. Only one of one-way control valve one and one-way control valve two is always open. One-way control valve one is opened when the driving plug is moved to the bottom, and one-way control valve two is opened when the driving plug is moved to the top.

[0012] Furthermore, the driving plug includes a main piston and a pressure plug, the diameter of which is larger than that of the main piston. The main piston is connected to the pressure plug via a connecting rod. The inner diameters of the upper and lower sections of the dynamic water tank are respectively matched with the outer diameters of the pressure plug and the main piston. The dynamic water tank is provided with a vent pipe corresponding to the part between the main piston and the pressure plug. The interior of the dynamic water tank is provided with two sets of limiting blocks that restrict the movement of the main piston.

[0013] Furthermore, both sets of limiting blocks are provided with a restraining structure, which releases the main piston when the pressure difference on both sides of the driving piston reaches a specific value.

[0014] Furthermore, the inner wall of the dynamic water tank is equipped with a sensor that senses the movement of the main piston. The sensor can sense the movement of the main piston. When the sensor senses that the main piston moves from the highest point to the lowest point, it triggers the opening of one-way control valve one and the closing of one-way control valve two. When the sensor senses that the main piston moves from the lowest point to the highest point, it triggers the closing of one-way control valve one and the opening of one-way control valve two.

[0015] Furthermore, the dynamic water tank is characterized by having an observation tube corresponding to the lowest point of the driving piston, and the end of the observation tube is provided with a sealing plug.

[0016] Furthermore, the bottom of the main piston is provided with an inclined surface, the highest point of which is aligned with the inlet of the observation tube. The sealing plug includes a plug body, the bottom of which is provided with a funnel-shaped cavity. An electrode post is provided in the middle of the plug body, and an electrode plate is provided on the side of the plug body. The liquid is conductive, and the data acquisition device periodically detects the conductivity of the electrode post and the electrode plate. If the electrode post and the electrode plate are not conductive, it is determined that there are too many air bubbles in the observation tube, and there are many air bubbles in the pipeline and the hydrostatic level. The acquired data is unreliable, and an early warning is issued.

[0017] The beneficial effects of this invention are as follows:

[0018] This application provides an urban ground settlement monitoring device. According to the measurement requirements, measurement points are arranged on the structure to be measured. The measurement points are arranged at key parts of the structure, such as the bottom of beams, column bases, and floor slabs of urban buildings, so as to accurately reflect the deformation and ground settlement of the structure. Through a dynamic water tank and a driving plug, the liquid in the detection device flows in one direction, which can promptly cause newly generated air bubbles in the pipeline or static level to flow out, reduce the influence of air bubbles, and make the urban ground settlement data obtained from the monitoring more reliable.

[0019] The dynamic water tank periodically injects a specific volume of liquid into the storage tank, causing the liquid level in the storage tank to change periodically. By comparing the pressure values ​​of each hydrostatic level at the time of the specific liquid level change, it is possible to determine whether the data of each hydrostatic level is abnormal, so as to detect abnormal data in time and carry out timely repairs.

[0020] When the detected settlement reaches the warning value, the liquid inside the urban ground settlement monitoring device can be continuously circulated through a dynamic water tank to reduce the temperature difference between the various hydrostatic levels. This reduces the impact of uneven temperature when comparing data before and after the event. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort:

[0022] Figure 1 This is a schematic diagram of Embodiment 1 of the present invention;

[0023] Figure 2 This is a schematic diagram of the water storage tank in Embodiment 1 of the present invention;

[0024] Figure 3 This is a three-dimensional schematic diagram of the water storage tank in Embodiment 1 of the present invention;

[0025] Figure 4 This is a schematic diagram of the water storage tank in Embodiment 2 of the present invention;

[0026] Figure 5 For the present invention Figure 4 A magnified view of A in the middle.

[0027] In the diagram: 1. Water storage tank; 101. Outer casing; 102. Inner casing; 103. Connecting port; 104. Outlet; 105. Return port; 2. Static level; 3. Data acquisition unit; 4. Inlet pipe; 5. Return pipe; 6. Air pipe; 7. Data cable; 8. Driver; 81. Air chamber; 82. Air pump; 83. Control valve; 84. One-way control valve one; 85. One-way control valve two; 86. Airbag; 9. Dynamic water tank; 10. Driving plug; 1001. Main piston; 1002. Pressure plug; 1003. Connecting rod; 1004. Limiting block; 11. Water inlet; 12. Observation tube; 13. Sealing plug; 131. Plug body; 132. Electrode post; 133. Electrode plate. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1, please refer to Figures 1-3A city ground settlement monitoring device includes a water storage tank 1, a hydrostatic level 2, and a data acquisition unit 3. Multiple sets of hydrostatic level 2 are provided, with one set placed at a benchmark point and the remaining sets placed at measurement points. These measurement points are typically located at key locations of buildings, key locations of urban infrastructure, areas with special geological conditions, open areas such as parks and squares, and areas undergoing large-scale construction. Each hydrostatic level 2 has an inlet pipe 4 and a return pipe 5 on either side. The return pipe 5 is connected to the water storage tank 1. The inlet pipe 4 is connected to a dynamic water tank 9. A one-way valve is directly installed between the inlet pipe 4 and the dynamic water tank 9, allowing liquid to flow unidirectionally from the inlet pipe 4 into the dynamic water tank 9. The dynamic water tank 9 is connected to the water storage tank 1, and a one-way valve is installed between the dynamic water tank 9 and the water storage tank 1, allowing liquid to flow unidirectionally from the inlet pipe 4 into the dynamic water tank 9. The dynamic water tank 9 flows to the storage tank 1. The static level 2 is also equipped with an air pipe 6 and a data cable 7. The data cable 7 is electrically connected to the data acquisition unit 3. The data acquisition unit 3 collects the pressure data of the static level 2 and supplies power to the sensor. To ensure power supply, the data acquisition unit 3 can be equipped with a solar panel. Each static level 2 has an air pipe 6 on both sides. The air pipes 6 on each static level 2 are connected end to end. The end air pipe 6 is connected to the atmosphere, and the beginning air pipe 6 is connected to the storage tank 1. In this embodiment, the inlet pipe 4 and the return pipe 5 are connected in parallel. That is, each inlet pipe 4 is connected to the first main pipe, which is connected to the storage tank 1. Each return pipe 5 is connected to the second main pipe, which is connected to the dynamic water tank 9. In other embodiments, the inlet pipe 4 and the return pipe 5 can also be connected in series.

[0030] The water storage tank 1 is connected to the driver 8. The dynamic water tank 9 is a cylinder. The dynamic water tank 9 is equipped with a driving plug 10. The driver 8 can push the driving plug 10 to move, thereby causing the liquid to flow into or out of the dynamic water tank 9. When the liquid flows out, it flows unidirectionally towards the water storage tank 1. When the liquid flows in, it flows back from each hydrostatic level 2 and the pipes to the dynamic water tank 9. The entire system flows in one direction. If bubbles are generated in the system, they will flow with the liquid until they accumulate in the dynamic water tank 9. For a single hydrostatic level 2, if the bubbles are on the left side or inside the hydrostatic level 2, they will affect the connectivity of the liquid, hinder the connectivity of the liquid, and cause a false liquid level. When the bubbles flow past the hydrostatic level 2, there are no bubbles on the left side, which reduces the influence of the bubbles on the hydrostatic level 2. On the other hand, the volume of liquid injected into the system is fixed each time the drive plug 10 moves, the change in the liquid level in the water tank 1 is a specific value, and the pressure change of each hydrostatic level 2 is also a specific value. The pressure change of each hydrostatic level 2 is used to determine whether there is a fault in each hydrostatic level 2.

[0031] The water storage tank 1 includes an outer casing 101, which is higher than the hydrostatic level 2. An inner casing 102 is fixedly connected inside the outer casing 101, forming a dynamic water tank 9 inside the inner casing 102. Liquid is stored between the inner casing 102 and the outer casing 101. A connecting port 103 is fixedly provided between the inner casing 102 and the outer casing 101, and a one-way valve is provided on the connecting port 103. An outlet 104 is provided at the bottom of the outer casing 101, and a return port 105 is provided at the bottom of the dynamic water tank 9. Both the outlet 104 and the return port 105 are equipped with one-way valves.

[0032] The actuator 8 includes an air chamber 81, which is connected to the dynamic water tank 9. The air chamber 81 is equipped with an air pump 82 and a control valve 83. The air pump 82 injects gas into the air chamber 81 to increase the air pressure in the air chamber 81. The air pressure drives the actuator 10 to move. The air chamber 81 is located at the top of the water tank 1. The side of the water tank 1 is equipped with a water inlet 11 for adding liquid, which is generally antifreeze. When the actuator 10 moves to the bottom, the air pump 82 is turned off, the control valve 83 is opened, and the air pressure is released. Under the pressure difference, the actuator 10 resets. The dynamic water tank 9 is equipped with a limit block to ensure that the actuator 10 moves a consistent distance each time. In this embodiment, the actuator 10 is moved by the air pump 82 and air pressure, which has a simple structure and requires a small volume. In other embodiments, the actuator 10 can also be moved by the cooperation of a motor and a lead screw.

[0033] In Example 2, unlike Example 1 where the actuator 8 requires additional power to operate, Example 2 utilizes temperature changes to drive the actuator 10. In Example 2, the air pump 82 and control valve 83 are replaced by an airbag 86. An airbag 86 is installed in the air chamber 81, containing a gas with a coefficient of thermal expansion greater than air. The gas can be helium or hydrogen. An air inlet for the airbag 86 is located outside the air chamber 81. The air pressure is adjusted according to temperature changes in different seasons. In this example, helium is used. Due to the large coefficient of thermal expansion of helium, the airbag 86 expands or contracts more significantly with temperature changes, resulting in greater pressure changes in the air chamber 81. During the day, the air pressure in the air chamber 81 is greater than atmospheric pressure, driving the actuator 10 downwards, and liquid flows from the dynamic water tank 9 to the storage tank 1. At night, the pressure in the air chamber 81 is less than atmospheric pressure, and liquid flows into the dynamic water tank 9. The actuator 10 completes one movement per day.

[0034] The gas chamber 81 is equipped with a one-way control valve 84 and a one-way control valve 85. Both one-way control valves 84 and 85 are equipped with one-way valves. When one-way control valve 84 is open, gas flows out in one direction. When one-way control valve 85 is open, gas flows in in one direction. One-way control valves 84 and 85 are opened and closed at regular intervals, and only one of them is always open. At dawn, one-way control valve 84 is closed and one-way control valve 85 is open, allowing gas to enter but not exit, resulting in a larger volume of air in the gas chamber 81. At midday when the temperature is highest, the pressure change in the gas chamber 81 is greater. In the afternoon, one-way control valve 84 is open and one-way control valve 85 is closed, allowing gas to exit but not enter, resulting in a smaller volume of gas in the gas chamber 81, and the pressure in the gas chamber 81 can be even lower.

[0035] To amplify the effect of pressure changes in the air chamber 81, the driving plug 10 includes a main piston 1001 and a pressure plug 1002. The diameter of the pressure plug 1002 is larger than that of the main piston 1001. The main piston 1001 is connected to the pressure plug 1002 via a connecting rod 1003. The inner diameters of the upper and lower sections of the dynamic water tank 9 are matched with the outer diameters of the pressure plug 1002 and the main piston 1001, respectively. The dynamic water tank 9 is provided with a vent pipe corresponding to the part between the main piston 1001 and the pressure plug 1002. The vent pipe is higher than the highest liquid level of the water storage tank 1. The interior of the dynamic water tank 9 is provided with two sets of limiting blocks 1004 that restrict the movement of the main piston 1001. When the air bladder 86 contracts, the main piston 1001 is limited by the upper limiting block 1004. When the air bladder 86 expands, the main piston 1001 is limited by the lower limiting block 1004, ensuring that the volume change caused by each action of the driving plug 10 is the same.

[0036] Because the temperature changes gradually, the time for the airbag 86 to complete one contraction or expansion is relatively long. Therefore, the data collection time is too long when the water tank 1 is caused by a quantitative change in liquid level through the driving plug 10, and the data collection time is too long when the liquid level change is fed back by each hydrostatic level 2 to determine whether each hydrostatic level 2 is working properly, which reduces the reliability of the data. For this reason, both sets of limit blocks 1004 are equipped with a restraining structure. The main piston 1001 is released when the pressure difference on both sides of the driving plug 10 reaches a specific value. After the main piston 1001 is released, it immediately moves to the stop position. In this embodiment, the restraining structure is a permanent magnet. The permanent magnet is set on the main piston 1001 (or limit block 1004), and the limit block 1004 (or main piston 1001) is equipped with a corresponding magnetic armature.

[0037] The inner wall of the dynamic water tank 9 is equipped with a sensor that detects the movement of the main piston 1001. In this embodiment, the sensor is an induction coil, which is located on the main piston 1001 or the limiting block 1004. The induction coil detects changes in the magnetic field of the permanent magnet to determine whether the main piston 1001 has moved. In other embodiments, the sensor can detect the movement of the main piston 1001 through electromagnetic induction, inductance, or optical sensing. When the sensor detects that the main piston 1001 has moved from its highest point to its lowest point... When the one-way control valve 84 is triggered to open and the one-way control valve 85 is triggered to close, gas can exit but not enter. At this time, the airbag 86 is inflating, gradually expelling the air from the air chamber 81. When the airbag 86 begins to contract, the air pressure change in the air chamber 81 is greater. When the sensor detects that the main piston 1001 has moved from the lowest point to the highest point, the one-way control valve 84 is triggered to close and the one-way control valve 85 is triggered to open, gas can enter but not exit. At this time, the airbag 86 is contracting, allowing more air to flow in. When the temperature rises and the airbag expands, the pressure in the air chamber 81 increases even more.

[0038] Please see Figure 5 As the monitoring time increases, if new bubbles are generated in the pipeline or static level 2, the bubbles will accumulate in the dynamic water tank 9 with the unidirectional flow of liquid. Specifically, they will accumulate on the lower side of the main piston 1001. The dynamic water tank 9 is equipped with an observation tube 12 corresponding to the position where the main piston 1001 moves to the lowest point. The bubbles accumulated on the lower side of the main piston 1001 are introduced into the drive plug 10 to gather. The staff judges the operating status by observing the bubbles in the observation tube 12. If a large number of bubbles are generated in the observation tube 12 in a short period of time, it indicates that there is a leak in the pipeline, which will continuously mix in air and needs to be repaired in time. The end of the observation tube 12 is equipped with a sealing plug 13, which releases gas when the sealing plug 13 is opened.

[0039] To ensure that the gas is smoothly introduced into the observation tube 12, the bottom of the main piston 1001 is provided with an inclined surface. The highest point of the inclined surface is aligned with the inlet of the observation tube 12. The air bubbles at the bottom of the main piston 1001 will move upward and flow into the observation tube 12.

[0040] The sealing plug 13 includes a plug body 131. The bottom of the plug body 131 has a funnel-shaped cavity. The middle of the plug body 131 has an electrode post 132. The side of the plug body 131 has an electrode plate 133. When there are no bubbles or few bubbles in the observation tube 12, the electrode post 132 and the electrode plate 133 are submerged in liquid. As the bubbles accumulate, the electrode post 132 flows out of the water. The sealing plug 13 is electrically connected to the data acquisition device 3. The data acquisition device 3 periodically detects the conductivity of the electrode post 132 and the electrode plate 133. If the electrode post 132 and the electrode plate 133 are not conductive, it is determined that there are too many bubbles in the observation tube 12, and there are many bubbles in the pipeline and the hydrostatic level 2. The collected data is unreliable, and an early warning is issued to remind the staff to carry out timely maintenance.

[0041] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A city ground settlement monitoring device, comprising a water tank (1), a hydrostatic level (2), and a data acquisition unit (3), wherein the hydrostatic level (2) is provided in multiple sets, one set of hydrostatic level (2) is placed at a reference point, and the remaining hydrostatic level (2) are placed at measurement points, and the hydrostatic level (2) is also provided with an air tube (6) and a data cable (7), the data cable (7) being electrically connected to the data acquisition unit (3), and each hydrostatic level (2) is provided with an air tube (6) on both sides, the air tubes (6) on each hydrostatic level (2) being connected end to end, the end air tube (6) being connected to the atmosphere, and the beginning air tube (6) being connected to the water tank (1), characterized in that, The hydrostatic level (2) has an inlet pipe (4) and a return pipe (5) on both sides. The return pipe (5) is connected to the water storage tank (1). The inlet pipe (4) is connected to a dynamic water tank (9). A one-way valve is directly provided between the inlet pipe (4) and the dynamic water tank (9). Liquid flows unidirectionally from the inlet pipe (4) into the dynamic water tank (9). The dynamic water tank (9) is connected to the water storage tank (1). A one-way valve is provided between the dynamic water tank (9) and the water storage tank (1). Liquid flows unidirectionally from the dynamic water tank (9). The water storage tank (1) is connected to a driver (8). The dynamic water tank (9) is a cylinder. The dynamic water tank (9) is equipped with a driving plug (10). The driver (8) can push the driving plug (10) to move, thereby causing a specific volume of liquid to flow into or out of the dynamic water tank (9). The data acquisition device (3) collects the pressure changes monitored by the hydrostatic level (2) when the liquid in the water storage tank (1) undergoes a characteristic volume change, and determines whether each hydrostatic level (2) is abnormal.

2. The urban ground subsidence monitoring device according to claim 1, characterized in that, The driver (8) includes an air chamber (81) which is connected to a dynamic water tank (9). An actuator is provided in the air chamber (81) to change the air pressure inside the air chamber (81).

3. The urban ground subsidence monitoring device according to claim 2, characterized in that, The actuator is an air pump (82), and the side wall of the air chamber (81) is also provided with a control valve (83). Both the air pump (82) and the control valve (83) are connected to the atmosphere.

4. The urban ground subsidence monitoring device according to claim 2, characterized in that, The actuator is an airbag (86), which contains a gas with a volume expansion coefficient greater than that of air. After the airbag (86) expands, the air pressure in the air chamber (81) is greater than atmospheric pressure. After the airbag (86) contracts during expansion, the pressure in the air chamber (81) is less than atmospheric pressure.

5. The urban ground subsidence monitoring device according to claim 4, characterized in that, The gas chamber (81) is equipped with a one-way control valve 1 (84) and a one-way control valve 2 (85). Both the one-way control valve 1 (84) and the one-way control valve 2 (85) are equipped with one-way valves. When the one-way control valve 1 (84) is open, the gas flows out in one direction. When the one-way control valve 2 (85) is open, the gas flows in in one direction. Only one of the one-way control valve 1 (84) and the one-way control valve 2 (85) is always open. The one-way control valve 1 (84) is opened when the drive plug (10) is moved to the bottom. The one-way control valve 2 (85) is opened when the drive plug (10) is moved to the top.

6. The urban ground subsidence monitoring device according to claim 5, characterized in that, The driving plug (10) includes a main piston (1001) and a pressure plug (1002). The diameter of the pressure plug (1002) is larger than that of the main piston (1001). The main piston (1001) is connected to the pressure plug (1002) through a connecting rod (1003). The inner diameters of the upper and lower sections of the dynamic water tank (9) are matched with the outer diameters of the pressure plug (1002) and the main piston (1001), respectively. The dynamic water tank (9) is provided with a vent pipe corresponding to the part between the main piston (1001) and the pressure plug (1002). The interior of the dynamic water tank (9) is provided with two sets of limiting blocks (1004) that restrict the movement of the main piston (1001).

7. The urban ground subsidence monitoring device according to claim 6, characterized in that, Both sets of limiting blocks (1004) are provided with a binding structure. The binding structure releases the main piston (1001) when the pressure difference on both sides of the drive piston (10) reaches a specific value.

8. The urban ground subsidence monitoring device according to claim 7, characterized in that, The inner wall of the dynamic water tank (9) is equipped with a sensor that senses the movement of the main piston (1001). The sensor can sense the movement of the main piston (1001). When the sensor senses that the main piston (1001) moves from the highest point to the lowest point, it triggers the opening of one-way control valve one (84) and the closing of one-way control valve two (85). When the sensor senses that the main piston (1001) moves from the lowest point to the highest point, it triggers the closing of one-way control valve one (84) and the opening of one-way control valve one (84).

9. A city land subsidence monitoring device according to any one of claims 6-8, characterized in that, The dynamic water tank (9) is provided with an observation tube (12) corresponding to the lowest point position of the drive plug (10), and the end of the observation tube (12) is provided with a sealing plug (13).

10. A city land subsidence monitoring device according to claim 9, characterized in that, The bottom of the main piston (1001) is provided with an inclined surface, and the highest point of the inclined surface is aligned with the inlet of the observation tube (12). The sealing plug (13) includes a plug body (131), the bottom of the plug body (131) is provided with a trumpet-shaped cavity, the middle of the plug body (131) is provided with an electrode post (132), and the side of the plug body (131) is provided with an electrode plate (133). The liquid is conductive. The data acquisition device (3) periodically detects the conductivity of the electrode post (132) and the electrode plate (133). If the electrode post (132) and the electrode plate (133) are not conductive, it is determined that there are too many air bubbles in the observation tube (12), and there are many air bubbles in the pipeline and the hydrostatic level (2). The collected data is unreliable, and an early warning is issued.

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