Urban land subsidence monitoring device

Abstract

The invention relates to the technical field of land subsidence monitoring, and discloses an urban land subsidence monitoring device which comprises a water storage tank, a static force level gauge and a data collector, a water inlet pipe and a water return pipe are arranged on the two sides of the static force level gauge respectively, the water return pipe is communicated with the water storage tank, the water inlet pipe is communicated with a dynamic water tank, and the dynamic water tank is communicated with the static force level gauge. The water inlet pipe and the dynamic water tank are directly provided with one-way valves, liquid flows into the dynamic water tank from the water inlet pipe in a one-way mode, and the dynamic water tank is communicated with the water storage tank. According to the urban land subsidence monitoring device, through the dynamic water tank and the driving plug, liquid in the detection device flows in a one-way mode, bubbles newly generated in a pipeline or a static leveling instrument can flow out in time, the influence of the bubbles is reduced, and data are more reliable. Secondly, the dynamic water tank regularly injects liquid with a characteristic volume into the water storage tank, so that the liquid level of the water storage tank is regularly and specifically changed, pressure values in all the static force level gauges are conveniently compared, and abnormity is found out.

Description

Technical Field

[0001] The present application relates to the technical field of ground subsidence monitoring, and in particular to an urban ground subsidence monitoring device. Background Art

[0002] Common methods for urban monitoring of ground subsidence mainly include leveling, global positioning system (GPS) measurement, remote sensing, lidar, groundwater level monitoring, fiber optic sensor monitoring, etc. Among them, the monitoring data of leveling is highly reliable and relatively low in cost, making it more suitable for long-term monitoring.

[0003] The principle of leveling is to establish a horizontal line of sight through a level, measure the height difference between two points, and then obtain the elevation change of ground points in different periods to determine the ground settlement. Among them, the differential pressure static level is a commonly used monitoring device. It is based on the principle of communicating vessels and is usually composed of multiple liquid reservoirs, vents, liquid pipes, and high-precision pressure sensors. A stable point is selected as the reference point, and the liquid reservoir of the reference point is placed at a known elevation. The liquid reservoirs of other measuring points are placed at the position where the settlement needs to be measured. When the measuring point rises and falls relative to the reference point, due to the free flow of liquid in the communicating pipe, the liquid level of each point will change accordingly, causing the pressure of each point to change. This pressure difference is measured by a high-precision pressure sensor, and then based on known parameters such as the density of the liquid and the acceleration of gravity, the elevation change of each measuring point relative to the reference point, that is, the settlement or uplift, can be calculated.

[0004] When installing the static level, it is required that there are no bubbles in the static level and the pipeline. If bubbles are generated, it will have a great impact on the measurement accuracy. Although the staff will try their best to avoid the generation of bubbles during installation, bubbles may be generated again in the hydraulic level or pipeline due to factors such as high temperature exposure or vibration. On the other hand, in actual use, the static levels are far apart, and some measuring points are not easy to observe, so bubbles cannot be discovered in time, which will lead to unreliable monitoring data for a long period of time.

[0005] Secondly, since the range for setting up the static level is large and some places are not convenient for maintenance, it will lead to the inability to discover the fault of the static level in time. Summary of the invention

[0006] The present application proposes an urban ground subsidence monitoring device, which uses a dynamic water tank and a drive plug to make the liquid in the detection device flow in one direction, so that the newly generated bubbles in the pipeline or the static level can flow out in time. At the same time, the dynamic water tank regularly injects a specific volume of liquid into the water tank, which is convenient for comparing data to find out whether there are any abnormalities.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme: an urban ground subsidence monitoring device, including a water tank, a static level and a data collector, wherein a plurality of static levels are provided, wherein one group of static levels is placed at a reference point, and the remaining static levels are placed at a measuring point, and an air pipe and a data line are also provided on the static level, and the data line is electrically connected to the data collector, and air pipes are provided on both sides of each static level, and the air pipes on each static level are connected end to end, the air pipe at the end is connected to the atmosphere, and the air pipe at the head end is connected to the water tank, and a water inlet pipe and a water return pipe are provided on both sides of the static level, respectively, and the water return pipe is connected to the water tank The water inlet pipe is connected to a dynamic water tank, and a one-way valve is directly provided on the water inlet pipe and the dynamic water tank. Liquid flows from the water inlet pipe into the dynamic water tank in one direction. The dynamic water tank is connected to a water storage tank. A one-way valve is provided between the dynamic water tank and the water storage tank. Liquid flows from the dynamic water tank to the water storage tank in one direction. The water storage tank is connected to a driver. The dynamic water tank is a cylinder. A driving plug is provided in the dynamic water tank. The driver can push the driving plug to move, thereby causing a specific volume of liquid to flow into or out of the dynamic water tank. The data collector collects the pressure changes monitored by the static level when the liquid in the water storage tank undergoes a characteristic volume change, and determines whether there is an abnormality in each static level.

[0008] Furthermore, the driver includes an air cavity, which is connected to the dynamic water tank, and an actuator is provided in the air cavity to change the air pressure in the air cavity.

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

[0010] Furthermore, the actuator is an airbag, which contains gas with a volume expansion coefficient greater than that of air. After the airbag is inflated, the air pressure in the air cavity is greater than the atmospheric pressure. After the airbag is inflated and then contracts, the pressure in the air cavity is less than the atmospheric pressure.

[0011] Furthermore, a one-way control valve 1 and a one-way control valve 2 are provided on the air cavity, and both the one-way control valve 1 and the one-way control valve 2 are provided with a one-way valve. When the one-way control valve 1 is opened, the gas flows out in one direction, and when the one-way control valve 2 is opened, the gas flows in in one direction. Only one of the one-way control valve 1 and the one-way control valve 2 is always kept open. The one-way control valve 1 is opened when the driving plug moves to the bottom, and the one-way control valve 2 is opened when the driving plug moves to the top.

[0012] Furthermore, the driving plug includes a main piston and a pressure plug. The diameter of the pressure plug is larger than the diameter of the main piston. The main piston is connected to the pressure plug through a connecting rod. The inner diameters of the upper and lower sections are respectively adapted to the pressure plug and the main piston. The dynamic water tank is provided with a ventilation pipe corresponding to the part between the main piston and the pressure plug. Two sets of limit blocks are provided inside the dynamic water tank to limit the movement of the main piston.

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

[0014] Furthermore, the inner wall of the dynamic water tank is provided with a sensor for sensing the movement of the main piston position. The sensor can sense the movement of the main piston. When the sensor senses that the main piston moves downward from the highest point to the lowest point, it triggers one-way control valve one to open and one-way control valve two to close. When the sensor senses that the main piston moves upward from the lowest point to the highest point, it triggers one-way control valve one to close and one-way control valve one to open.

[0015] Furthermore, it is characterized in that the dynamic water tank is provided with an observation tube corresponding to the position where the driving plug moves to the lowest point, and a sealing plug is provided at the end of the observation tube.

[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 the plug body is provided with a trumpet-shaped cavity, the middle of the plug body is provided with an electrode column, the side of the plug body is provided with an electrode sheet, the liquid is conductive, and the data collector periodically detects the conduction of the electrode column and the electrode sheet. If the electrode column and the electrode sheet are not conductive, it is judged that there are too many bubbles in the observation tube, there are many bubbles in the pipeline and the static level, the collected data is unreliable, and an early warning is issued. The beneficial effects of the present invention are as follows:

[0017] The present application provides an urban ground subsidence monitoring device, which arranges measurement points on the structure to be measured according to measurement requirements. The measurement points are arranged at key positions of the structure, such as the bottom of beams, column foundations, and floor slabs of urban buildings, so as to accurately reflect the deformation of the structure and the ground subsidence. Through a dynamic water tank and a drive plug, the liquid in the detection device flows in one direction, which can promptly make newly generated bubbles in the pipeline or the static level flow out, reduce the impact of the bubbles, and make the monitored urban ground subsidence data more reliable.

[0018] The dynamic water tank regularly injects a specific volume of liquid into the water storage tank, causing the liquid level of the water storage tank to change regularly. The pressure values ​​corresponding to the specific liquid level changes in each static level are then compared to determine whether the data of each static level is abnormal. Abnormal data can be discovered and repaired in time.

[0019] When the detected settlement reaches the warning value, the liquid in the city's ground settlement monitoring device can be continuously circulated through a dynamic water tank, thereby reducing the temperature difference of each static level meter and comparing the data before and after to reduce the impact of uneven temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the provided drawings without creative work:

[0021] Figure 1 is a schematic diagram of Embodiment 1 of the present invention;

[0022] Figure 2 is a schematic diagram of a water storage tank in Embodiment 1 of the present invention;

[0023] Figure 3 It is a three-dimensional schematic diagram of a water storage tank in Embodiment 1 of the present invention;

[0024] Figure 4 is a schematic diagram of a water storage tank in Embodiment 2 of the present invention;

[0025] Figure 5 For the present invention Figure 4 A is an enlarged view of the middle image.

[0026] In the figure: 1. water storage tank; 101. outer box body; 102. inner box body; 103. connecting port; 104. water outlet; 105. water return port; 2. static level; 3. data collector; 4. water inlet pipe; 5. water return pipe; 6. air pipe; 7. data line; 8. driver; 81. air cavity; 82. air pump; 83. control valve; 84. one-way control valve 1; 85. one-way control valve 2; 86. air bag; 9. dynamic water tank; 10. driving plug; 1001. main piston; 1002. pressurizing plug; 1003. connecting rod; 1004. limiting block; 11. water supply port; 12. observation tube; 13. sealing plug; 131. plug body; 132. electrode column; 133. electrode sheet. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] For example, see Figure 1-Figure 3A device for monitoring urban ground subsidence comprises a water storage tank 1, a static level 2 and a data collector 3. The static level 2 is provided with a plurality of groups, wherein one group of static levels 2 is placed at a reference point, and the remaining static levels 2 are placed at measuring points. The measuring points are usually arranged at key positions of buildings, key positions of urban infrastructure, areas with special geological conditions, open areas such as parks and squares, and areas undergoing large-scale construction. An inlet pipe 4 and a return pipe 5 are provided on both sides of the static level 2, respectively. The return pipe 5 is connected to the water storage tank 1, and 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, and liquid flows from the inlet pipe 4 to the dynamic water tank 9 in one direction. The dynamic water tank 9 is connected to the water storage tank 1, and a one-way valve is provided between the dynamic water tank 9 and the water storage tank 1. Liquid flows from the dynamic water tank 9 in one direction. The dynamic water tank 9 flows to the water storage tank 1. The static level 2 is also provided with an air pipe 6 and a data line 7. The data line 7 is electrically connected to the data collector 3. The data collector 3 collects the pressure data of the static level 2 and supplies power to the sensor at the same time. In order to ensure the power supply, a solar panel can be provided on the data collector 3. Air pipes 6 are provided on both sides of each static level 2. The air pipes 6 on each static level 2 are connected end to end. The air pipes 6 at the end are connected to the atmosphere, and the air pipes 6 at the head end are connected to the water storage tank 1. In this embodiment, the water inlet pipe 4 and the return pipe 5 are respectively connected in parallel, that is, each water inlet pipe 4 is connected to the first main pipe, the main pipe is connected to the water storage tank 1, and each return pipe 5 is connected to the second main pipe, and the second main pipe is connected to the dynamic water tank 9. In other embodiments, the water inlet pipe 4 and the return pipe 5 can also be connected in series.

[0029] The water tank 1 is connected to a driver 8. The dynamic water tank 9 is a cylinder. A driving plug 10 is provided inside the dynamic water tank 9. 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 toward the water tank 1. When the liquid flows in, the liquid flows back from each static level 2 and the pipeline 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 flow into the dynamic water tank 9 and gather. For a single static level 2, when the bubbles are on the left side or in the static level 2, it will affect the connectivity of the liquid, hinder the liquid connectivity, and cause an illusion of liquid level. When the bubbles flow through the static level 2, there are no bubbles on the left side, which reduces the impact of the bubbles on the static level 2. On the other hand, each time the driving plug 10 moves, the volume of liquid injected into the system is fixed, the liquid level change in the water tank 1 is a specific value, and the pressure change of each static level 2 is also a specific value. The pressure change of each static level 2 can be used to determine whether each static level 2 has a fault.

[0030] The water storage tank 1 includes an outer box body 101, which is higher than the static level 2. An inner box body 102 is fixedly connected to the outer box body 101, and a dynamic water tank 9 is formed inside the inner box body 102. Liquid is stored between the inner box body 102 and the outer box body 101. A connecting port 103 is fixedly provided between the inner box body 102 and the outer box body 101, and a one-way valve is provided on the connecting port 103. A water outlet 104 is provided at the bottom of the outer box body 101, and a water return port 105 is provided at the bottom of the dynamic water tank 9. Both the water outlet 104 and the water return port 105 are provided with one-way valves.

[0031] The driver 8 includes an air cavity 81, which is connected to the dynamic water tank 9. An air pump 82 and a control valve 83 are provided on the air cavity 81. The air pump 82 injects gas into the air cavity 81 to increase the air pressure in the air cavity 81, and the air pressure drives the driving plug 10 to move. The air cavity 81 is arranged at the top of the water storage tank 1, and a water replenishment port 11 is arranged on the side of the water storage tank 1. The water replenishment port 11 is used to add liquid, and the liquid is generally antifreeze. When the driving plug 10 moves to the bottom, the air pump 82 is closed, the control valve 83 is opened, and the air pressure is released. Under the pressure difference, the driving plug 10 is reset. A limit block is provided in the dynamic water tank 9 to ensure that the driving plug 10 moves the same distance each time. In this embodiment, the driving plug 10 is driven to move by the air pump 82 and air pressure. The structure is simple and the required volume is small. In other embodiments, the driving plug 10 can also be driven to move by the cooperation of a motor and a lead screw.

[0032] Embodiment 2. In embodiment 1, the driver 8 consumes additional electricity when it is running. Based on embodiment 1, embodiment 2 utilizes temperature changes to drive the driving plug 10 to move. In embodiment 2, the air pump 82 and the control valve 83 are replaced by an air bag 86. An air bag 86 is provided in the air cavity 81. The air bag 86 is filled with a gas whose volume expansion coefficient is greater than that of air. The gas can be helium or hydrogen. An air inlet for the air bag 86 is provided on the outside of the air cavity 81. The air pressure is adjusted according to the temperature difference in different seasons. In this embodiment, helium is used. Since the volume expansion coefficient of helium is large, when the temperature changes, the air bag 86 expands or contracts more, causing the pressure in the air cavity 81 to change greatly. During the day, the air pressure in the air cavity 81 is greater than the atmospheric pressure, driving the driving plug 10 to move downward, and the liquid flows from the dynamic water tank 9 to the water storage tank 1. At night, the pressure in the air cavity 81 is less than the atmospheric pressure, and the liquid flows into the dynamic water tank 9. The driving plug 10 completes one movement every day.

[0033] A one-way control valve 84 and a one-way control valve 85 are provided on the air cavity 81. Both the one-way control valve 84 and the one-way control valve 85 are provided with a one-way valve. When the one-way control valve 84 is opened, the gas flows out in one direction. When the one-way control valve 85 is opened, the gas flows in in one direction. The one-way control valve 84 and the one-way control valve 85 are opened and closed regularly, and only one of them is always kept open. In the early morning, the one-way control valve 84 is closed and the one-way control valve 85 is opened, so that the gas can enter but not exit, so that the air in the air cavity 81 is in a larger amount. When the temperature is highest at noon, the pressure in the air cavity 81 changes more. In the afternoon, the one-way control valve 84 is opened and the one-way control valve 85 is closed, so that the gas can exit but not enter. The gas in the air cavity 81 is in a smaller amount, and the pressure in the gas cavity 81 can be lower.

[0034] In order to amplify the effect of pressure changes in the air cavity 81, the driving plug 10 includes a main piston 1001 and a pressurizing plug 1002. The diameter of the pressurizing plug 1002 is larger than the diameter of the main piston 1001. The main piston 1001 is connected to the pressurizing plug 1002 through a connecting rod 1003. The inner diameters of the upper and lower sections 1009 are adapted to the pressurizing plug 1002 and the main piston 1001 respectively. The dynamic water tank 9 is provided with a ventilation pipe corresponding to the part between the main piston 1001 and the pressurizing plug 1002. The pipe is higher than the highest liquid level of the water storage tank 1. Two groups of limit blocks 1004 for limiting the movement of the main piston 1001 are provided inside the dynamic water tank 9. When the airbag 86 contracts, the main piston 1001 is limited by the upper limit block 1004. When the airbag 86 expands, the main piston 1001 is limited by the lower limit block 1004, ensuring that the volume change caused by each action of the driving plug 10 is the same.

[0035] Since the temperature changes gradually, it takes a long time for the airbag 86 to complete a contraction or expansion. Therefore, the driving plug 10 causes a quantitative liquid level change in the water tank 1. When the numerical value of the liquid level change is fed back by each static level 2 to judge whether each static level 2 is working normally, the data collection time is too long, which reduces the reliability of the data. For this reason, a restraint structure is provided on both sets of limit blocks 1004. The restraint structure releases the main piston 1001 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 restraint structure is a permanent magnet, which is provided on the main piston 1001 (or the limit block 1004), and the limit block 1004 (or the main piston 1001) is provided with a corresponding magnetic armature.

[0036] The inner wall of the dynamic water tank 9 is provided with a sensor for sensing the position movement of the main piston 1001. The sensor can sense the movement of the main piston 1001. In this embodiment, the sensor is an induction coil, which is provided on the main piston 1001 or the limit block 1004. The induction coil senses the magnetic field change of the permanent magnet to determine whether the main piston 1001 moves. In other embodiments, the sensor can sense the movement of the main piston 1001 by electromagnetic induction, inductance, light sensing, etc. When the sensor senses that the main piston 1001 moves downward from the highest point to the lowest point, The one-way control valve 84 is triggered to open and the one-way control valve 85 is closed, so gas can go out but not go in. At this time, the airbag 86 is expanding, gradually discharging the air in the air cavity 81. When the airbag 86 begins to shrink, the air pressure in the air cavity 81 changes more. When the sensor senses that the main piston 1001 moves from the lowest point to the highest point, the one-way control valve 84 is triggered to close and the one-way control valve 84 is opened, so gas can go in but not go out. At this time, the airbag 86 is shrinking, which allows more air to flow in. When the temperature rises and expands, the pressure in the air cavity 81 increases more.

[0037] See also Figure 5 As the monitoring time increases, if new bubbles are generated in the pipeline or the static level 2, the bubbles will accumulate in the dynamic water tank 9 as the liquid flows in one direction. Specifically, they will accumulate on the lower side of the main piston 1001. The dynamic water tank 9 is provided 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 for aggregation. The staff judges the operation 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 means that there is a leak in a certain pipeline, which will continuously mix in air and needs to be repaired in time. A sealing plug 13 is provided at the end of the observation tube 12, and the sealing plug 13 is opened to release the gas.

[0038] In order to ensure that the gas is smoothly introduced into the observation tube 12, a slope is provided at the bottom of the main piston 1001, and the highest point of the slope is aligned with the inlet of the observation tube 12. The bubbles at the bottom of the main piston 1001 will move upwards and flow into the observation tube 12.

[0039] The sealing plug 13 includes a plug body 131, a trumpet-shaped cavity is provided at the bottom of the plug body 131, an electrode column 132 is provided in the middle of the plug body 131, and an electrode sheet 133 is provided on the side of the plug body 131. When there are no bubbles or few bubbles in the observation tube 12, the electrode column 132 and the electrode sheet 133 are both submerged in liquid. As the bubbles gather, the electrode column 132 flows out of the water, and the sealing plug 13 is electrically connected to the data collector 3. The data collector 3 periodically detects the conductivity of the electrode column 132 and the electrode sheet 133. If the electrode column 132 and the electrode sheet 133 are not conductive, it is judged that there are too many bubbles in the observation tube 12, and there are many bubbles in the pipeline and the static level 2, and the collected data is unreliable, and an early warning is issued to remind the staff to repair in time.

[0040] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An urban ground subsidence monitoring device, comprising a water tank (1), a static level (2) and a data collector (3), wherein the static level (2) is provided with a plurality of groups, wherein one group of static levels (2) is placed at a reference point, and the remaining static levels (2) are placed at a measuring point, wherein the static level (2) is further provided with an air pipe (6) and a data line (7), wherein the data line (7) is electrically connected to the data collector (3), and each static level (2) is provided with an air pipe (6) on both sides, wherein the air pipes (6) on each static level (2) are connected end to end, wherein the air pipe (6) at the end is connected to the atmosphere, and the air pipe (6) at the head end is connected to the water tank (1), wherein the static level (2) is provided with an air pipe (6) on both sides, wherein the air pipe (6) on each static level (2) is connected end to end, wherein the air pipe (6) at the end end is connected to the atmosphere, and the air pipe (6) at the head end is connected to the water tank (1), wherein the static level (2) is provided with an air pipe (6) on both sides ... A water inlet pipe (4) and a water return pipe (5) are respectively provided on both sides of the static level (2); the water return pipe (5) is connected to the water storage tank (1); the water inlet pipe (4) is connected to the dynamic water tank (9); a one-way valve is directly provided between the water inlet pipe (4) and the dynamic water tank (9); liquid flows from the water inlet pipe (4) to the dynamic water tank (9) in one direction; 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 from the dynamic water tank (9) to the dynamic water tank (9) in one direction; The water tank (1) is connected to a driver (8). The dynamic water tank (9) is a cylinder. A driving plug (10) is provided in the dynamic water tank (9). 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 collector (3) collects pressure changes monitored by the static level (2) when the liquid in the water tank (1) undergoes a characteristic volume change, and determines whether each static level (2) has an abnormality.

2. The urban land subsidence monitoring device according to claim 1, characterized in that: The driver (8) comprises an air cavity (81), the air cavity (81) is in communication with the dynamic water tank (9), and an actuator for changing the air pressure in the air cavity (81) is arranged in the air cavity (81).

3. The urban land subsidence monitoring device according to claim 2, characterized in that: The actuator air pump (82) and the air cavity (81) are also provided with a control valve (83) on their side walls, and both the air pump (82) and the control valve (83) are connected to the atmosphere.

4. The urban land 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. When the airbag (86) is expanded, the air pressure in the air cavity (81) is greater than the atmospheric pressure. When the airbag (86) is expanded and then contracts, the pressure in the air cavity (81) is less than the atmospheric pressure.

5. The urban land subsidence monitoring device according to claim 4, characterized in that: The air cavity (81) is provided with a one-way control valve (84) and a one-way control valve (85). Both the one-way control valve (84) and the one-way control valve (85) are provided with one-way valves. When the one-way control valve (84) is opened, gas flows out in one direction. When the one-way control valve (85) is opened, gas flows in in one direction. Only one of the one-way control valve (84) and the one-way control valve (85) is always kept open. The one-way control valve (84) is opened when the driving plug (10) moves to the bottom, and the one-way control valve (85) is opened when the driving plug (10) moves to the top.

6. The urban land subsidence monitoring device according to claim 5, characterized in that: The driving plug (10) comprises a main piston (1001) and a pressurizing plug (1002). The diameter of the pressurizing plug (1002) is larger than that of the main piston (1001). The main piston (1001) is connected to the pressurizing plug (1002) via a connecting rod (1003). The inner diameters of the upper and lower sections (1009) are adapted to the pressurizing plug (1002) and the main piston (1001) respectively. The dynamic water tank (9) is provided with a vent pipe corresponding to the portion between the main piston (1001) and the pressurizing plug (1002). Two sets of limit blocks (1004) for limiting the movement of the main piston (1001) are provided inside the dynamic water tank (9).

7. The urban land subsidence monitoring device according to claim 6, characterized in that: Both groups of the limit blocks (1004) are provided with a restraining structure, which releases the main piston (1001) when the pressure difference on both sides of the driving plug (10) reaches a specific value.

8. The urban land subsidence monitoring device according to claim 7, characterized in that: The inner wall of the dynamic water tank (9) is provided with a sensor for sensing the position 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 downward from the highest point to the lowest point, the one-way control valve (84) is triggered to open and the one-way control valve (85) is closed. When the sensor senses that the main piston (1001) moves upward from the lowest point to the highest point, the one-way control valve (84) is triggered to close and the one-way control valve (84) is opened.

9. An urban land subsidence monitoring device according to any one of claims 1 to 8, characterized in that: The dynamic water tank (9) is provided with an observation tube (12) corresponding to the position where the driving plug (10) moves to the lowest point, and a sealing plug (13) is provided at the end of the observation tube (12).

10. The urban land subsidence monitoring device according to claim 9, characterized in that: The bottom of the main piston (1001) is provided with an inclined surface, the highest point of which is aligned with the inlet of the observation tube (12); the sealing plug (13) comprises 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 column (132); the side of the plug body (131) is provided with an electrode sheet (133); the liquid is conductive; the data acquisition device (3) periodically detects the conductivity of the electrode column (132) and the electrode sheet (133); if the electrode column (132) and the electrode sheet (133) are not conductive, it is judged that there are too many bubbles in the observation tube (12), there are many bubbles in the pipeline and the static level (2), the collected data is unreliable, and an early warning is issued.

Images