Portable underground water burial depth automatic monitoring device

Abstract

The invention discloses a portable underground water burial depth automatic monitoring device, and belongs to the technical field of underground water monitoring, the portable underground water burial depth automatic monitoring device comprises a pressure-bearing shell, a main pressure sensor, an atmospheric pressure sensor and a temperature sensor are integrated in the pressure-bearing shell, and the main pressure sensor is communicated with an external water body through a pressure guide hole to collect water body static pressure; the atmospheric pressure sensor collects ambient pressure through the independent sealing cavity, and the temperature sensor is used for measuring water temperature; the spiral flow guide cover is detachably arranged on the outer side of the pressure-bearing shell in a sleeving mode, and a spiral flow guide groove is formed in the inner wall of the spiral flow guide cover and spirally extends in the axial direction of the pressure-bearing shell. The spiral flow guide cover is detachably arranged on the outer side of the pressure-bearing shell in a sleeving mode, the spiral flow guide grooves in the inner wall of the spiral flow guide cover guide underground water to form spiral flow, particle impurities are automatically separated and discharged through centrifugal force, sediment is prevented from being deposited to block pressure guide holes or be attached to the surface of the shell, passive self-cleaning is achieved, and the manual maintenance frequency is remarkably reduced; and the field long-term unattended monitoring requirement is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of groundwater monitoring, in particular to a portable automatic groundwater depth monitoring device. BACKGROUND

[0002] Groundwater level monitoring is a core technology for water resource management, geological disaster warning and engineering construction, and its precision and reliability directly affect the effectiveness of decision-making. In the prior art, the groundwater monitoring device faces many technical bottlenecks. A typical representative is the "rope scale visual recognition device" disclosed in Chinese patent CN11608657B, which lowers a rubber rope line with scales through a line wheel, and relies on a camera to identify the scale difference between the water surface and the water bottom to calculate the water depth. However, this scheme has systematic defects: The traditional device relies on a filter screen to filter impurities, but the filter screen is easily clogged by silt and needs to be cleaned manually regularly. Moreover, it lacks an automatic calibration mechanism, and the atmospheric pressure and water temperature compensation parameters drift over a long period of use, resulting in cumulative errors in water depth calculation. For inclined installation scenarios (such as slope monitoring), no attitude correction module is configured, and when the inclination angle exceeds 3°, the water depth measurement error can reach more than 17 cm, which cannot meet the high-precision requirements of geological subsidence monitoring (precision ≤1°).

[0003] The linear expansion coefficient of the rubber rope line is 120×10 -6 / ℃, and the annual cumulative deformation error can reach ±30 cm in a 10-meter deep scene. Moreover, long-term immersion causes rubber aging, and the elastic modulus changes rapidly, making the scale spacing distorted over time. When the water sand content exceeds 200 ppm or there is algae attachment, the camera fails to recognize the scale due to optical scattering or image blurring, resulting in low recognition success rate, which cannot adapt to complex water quality environments. SUMMARY

[0004] To overcome the above-mentioned shortcomings of the prior art, the present application provides a portable automatic groundwater depth monitoring device.

[0005] To achieve the above-mentioned purposes, the present application is implemented by the following technical solutions: A portable automatic groundwater depth monitoring device, characterized in that it comprises: A pressure-bearing shell (100) internally integrated with a main pressure sensor (101), an atmospheric pressure sensor (102) and a temperature sensor (103). The main pressure sensor (101) is in communication with the external water body through a pressure guide hole (104) to collect the water static pressure. The atmospheric pressure sensor (102) collects the ambient air pressure through an independent sealed cavity. The temperature sensor (103) is used to measure the water temperature. A spiral fairing (200) is detachably sleeved outside the pressure-bearing shell (100), and an inner wall is provided with a spiral fairing groove (201) extending axially along the pressure-bearing shell (100); A gravity anchoring base (300) is fixedly connected to the bottom of the pressure-bearing shell (100) and includes a conical counterweight (301) provided with barbs (302) at the bottom; A gravity anchoring base (300) is fixedly connected to the bottom of the pressure-bearing shell (100) and includes a conical counterweight (301) provided with barbs (302) at the bottom; A main control module (400) is electrically connected to the main pressure sensor (101), the atmospheric pressure sensor (102) and the temperature sensor (103) and is used for calculating the water level depth according to the hydrostatic pressure, the ambient pressure and the water temperature.

[0006] Further, the spiral fairing (200) is connected to the pressure-bearing shell (100) through a buckle type interface (202) including a convex rib provided on the outer wall of the pressure-bearing shell (100) and a clamping groove provided on the inner wall of the spiral fairing (200), and the groove width of the spiral fairing groove (201) gradually narrows along the water flow direction.

[0007] Further, the barbs (302) are in the shape of triangular prisms with pointed ends directed outward from the bottom of the conical counterweight (301), and the barbs (302) are uniformly distributed circumferentially along the conical counterweight (301) with an included angle of 30°-60°.

[0008] Further, a backwashing valve (105) is arranged at the inlet of the pressure guide hole (104), the backwashing valve (105) is fixed to the inlet end of the pressure guide hole (104) through an interference fit of a water-resistant sealing rubber ring, and the other end is connected to an external backwashing pipeline, and a one-way valve is arranged in the pipeline.

[0009] Further, a balance block (500) is arranged, the axis of the balance block (500) coincides with the axis of the pressure-bearing shell (100), and the balance block (500) is used to form an up-down balance with the conical counterweight (301).

[0010] Further, a driving motor (501) is arranged, the driving motor (501) is connected to the pressure-bearing shell (100) through a cable (502), the cable (502) passes through a guide hole (503) arranged at the top of the balance block (500), and the pressure-bearing shell (100) is lifted above the water surface for air calibration.

[0011] Further, a posture monitoring module (600) is further included, which is fixed to the inner wall of the pressure-bearing shell (100) and electrically connected with the main control module (400), and is used for collecting the inclination angle data of the device in real time.

[0012] Further, the posture monitoring module (600) is a three-axis MEMS accelerometer, and the main control module (400) pre-stores a tilt angle correction algorithm, and the correction algorithm is used for compensating and calculating the water level depth measurement value based on the tilt angle data.

[0013] Further, the main control module (400) is integrated with a wireless transmission unit (401), and the main control module (400) is integrated with an antenna on the top of the balance block (500), the main control module (400) is used for performing 5-point sliding average filtering processing on the sensing signal, and the filtering window width is configurable.

[0014] Further, the pressure-bearing shell (100) is integrally formed by using stainless steel, the spiral fairing (200) is formed by injection molding of engineering plastic, and the surface of the barb (302) is subjected to blackening treatment or nickel plating treatment to adapt to different stratum environments.

[0015] Compared with the prior art, the present application has the following beneficial effects: The spiral fairing of the present application can be detachably arranged outside the pressure-bearing shell, the spiral guide groove in the inner wall of the spiral fairing guides the underground water to form spiral flow, the centrifugal force is used for automatically separating and discharging the particulate impurities, the silt deposition is avoided to block the pressure guide hole or adhere to the surface of the shell, the passive self-cleaning is realized, the frequency of manual maintenance is significantly reduced, and the long-term unattended monitoring demand in the field is adapted. The conical counterweight of the gravity anchor base is matched with the circumferentially uniformly distributed barbs, the load uniformization is realized through the angle layout, the mechanical engagement with different strata (loose sand, hard rock, etc.) is enhanced, the pullout resistance and the sliding resistance of the device are improved, and the long-term stable anchor is ensured.

[0016] The main control module is integrated with pressure, air pressure and temperature multi-sensors for cooperative measurement, the water level depth is accurately calculated in combination with the water body static pressure, the environmental air pressure and the water temperature data, and the error accumulation of a single sensor is avoided. The backwashing valve at the inlet of the pressure guide hole is linked with the driving motor, the reverse water flow is generated through the water level difference to impact the filter disc, the surface accumulated impurities are removed, and the stability of the pressure signal transmission is ensured. The automatic calibration system composed of the balance block and the driving motor can lift the pressure-bearing shell to the water surface to collect the reference value, establish the initial calibration model, eliminate the influence of the atmospheric pressure and the water temperature drift on the measurement result, and improve the data reliability.

[0017] The posture monitoring module collects the inclination angle of the device in real time, compensates the water level depth measurement value through a pre-stored correction algorithm, solves the error problem of the traditional device installed at an inclination, and is suitable for monitoring complex terrains such as slopes and foundation pits. The buckle type interface realizes quick disassembly and assembly of the spiral fairing, cooperates with different material selection (stainless steel pressure shell and engineering plastic fairing), meets the needs of multiple environmental conditions such as fresh water, high salt and high cold, and significantly expands the application scenarios. The wireless transmission unit is designed with low power consumption, supports remote data transmission and long-term endurance, reduces the cost of manual inspection, and promotes the intelligentization and unmannedization of underground water monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0019] Figure 1 It is a perspective view of a portable underground water depth automatic monitoring device of the present application. Figure 2 It is a sectional view of the pressure shell and spiral fairing of the present application. Figure 3 It is a comparison diagram of the spiral groove and the traditional scheme of rotational flow number-pressure drop curve. Figure 4 It is a data processing flowchart of the master control module of the present application. Figure 5 It is a comparison diagram of the original signal and the filtered signal of the present application.

[0020] The numbers in the figure respectively represent: 100, pressure shell; 101, main pressure sensor; 102, atmospheric pressure sensor; 103, temperature sensor; 104, pressure guide hole; 200, spiral fairing; 201, spiral fairing groove; 300, gravity anchor base; 301, conical counterweight; 302, barb; 400, master control module; 401, wireless transmission unit; 500, balance block; 501, driving motor; 502, cable; 600, posture monitoring module. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] Example: Figures 1-5 As shown, a portable automatic groundwater depth monitoring device includes: a pressure-bearing housing 100, which integrates a main pressure sensor 101, an atmospheric pressure sensor (102), and a temperature sensor 103. The main pressure sensor (101) is connected to the external water body through a pressure guide hole 104 to collect the static pressure P of the water body. w The atmospheric pressure sensor (102) collects ambient air pressure P through an independent sealed cavity. a The temperature sensor (103) is used to measure the water temperature T; Among them, a sintered metal filter (material 316L stainless steel, pore size 50) is embedded at the inlet of the pressure guiding hole 104. ), fixed to the orifice by interference fit, to block mud and sand particles (such as Figure 2 The inner wall of the pressure guiding hole (104) is machined with a vortex groove to guide the water flow and reduce the retention of impurities; The pressure-bearing housing 100 is made of 304 stainless steel in one piece (e.g. Figure 1 As shown), it is cylindrical with an anodized inner wall (roughness Ra≤0.8μm). The pressure housing 100 has a cable interface on the top, which uses an M12 waterproof connector (IP68 rating) to connect the main control module (400) to the external power / communication cable. The main pressure sensor 101 is vertically mounted on the lower part of the pressure housing 100 via a threaded fastener (M8×1.25). The sensor axis coincides with the axis of the pressure housing 100, and the pressure guide hole 104 is located at the front end of the sensor. Atmospheric pressure sensor 102 is fixed to the top inner wall of pressure-bearing housing (100). The independent sealed cavity is formed by ultrasonic welding and is completely isolated from other areas inside the housing. Temperature sensor 103 is attached to the stainless steel encapsulation shell of main pressure sensor (101) with thermally conductive silicone (Shin-Etsu KE-45) and is close to the inlet of pressure guide hole 104 to ensure temperature acquisition synchronization. The main pressure sensor 101 is a Honeywell SSC series silicon piezoresistive sensor with a core sensing element of a 4-crystal silicon diaphragm. The housing of the main pressure sensor (101) is made of 316L stainless steel and coated with polytetrafluoroethylene. The contact angle is ≥110°, which reduces the influence of water surface tension on pressure transmission. The 0-5V analog signal output by the main pressure sensor 101 is transmitted to the main control module 400 through double-layer shielded twisted pair wires; The independent sealed cavity is a cylindrical cavity formed by injection molding of ABS engineering plastic, the inner wall is pasted with a waterproof and breathable film, and the cavity is sealed with the pressure-bearing shell 100 through epoxy resin glue. Balance holes are opened on the side of the cavity, the hole openings are directed towards the top of the pressure-bearing shell 100, and water immersion is avoided; The atmospheric pressure sensor 102 adopts a BMP388 type MEMS air pressure sensor, which is directly welded on the PCB board inside the sealed cavity through LGA-8 packaging. The PCB board is isolated from the pressure-bearing shell (100) by a rubber pad to reduce vibration effects; The main pressure sensor 101 is connected to the main control module through an analog input channel (ADC1_IN0). The atmospheric pressure sensor 102 communicates through the I2C1 bus (SCL=PB6, SDA=PB7). The temperature sensor 103 is connected to ADC1_IN1 through a resistance division circuit (division resistance 10k ) and meets the pin assignment standard of the STM32L431 chip; The gravity anchoring base 300 is fixedly connected to the bottom of the pressure-bearing shell 100 and includes a conical counterweight 301. The bottom of the conical counterweight 301 is provided with multiple groups of barbs 302, which are uniformly distributed circumferentially along the conical counterweight (301) and have sharp tips for easy insertion into the stratum. The gravity anchoring base 300 is vertically placed into underground water after installation, so that the bottom of the gravity anchoring base 300 contacts the stratum. Then, by applying pressure (for example, by manually or hydraulically pressing against the flange connection disc), the barbs 302 are inserted into the stratum until the pressure-bearing shell (100) reaches a stable state; Specifically, the conical counterweight 301 can reduce stress concentration on the stratum contact surface compared to a cylindrical shape. The conical surface is used for automatic correction of perpendicularity during insertion. The top is provided with a flange connection disc, which is rigidly connected to the bottom of the pressure-bearing shell 100 through M12 bolts. Thick neoprene rubber gaskets (resistant to groundwater corrosion) are provided at the connection to seal; The multiple groups of barbs 302 are circumferentially distributed with front and back misalignment at an angle of 30-60° to form redundant anchoring. The axes of the multiple groups of barbs 302 are inclined at an angle of 45° to the bottom surface of the conical counterweight 301 (non-vertical insertion), which enhances the anti-pulling effect by utilizing the shear force of the stratum; The core goal of circumferential uniform distribution of the barbs 302 is to achieve load uniformization and maximize the stratum contact probability through angular arrangement. The core parameter is the circumferential angle , (n is the number of barb groups). As the carrier of anchoring force, the circumferential uniform distribution of the barbs 302 ensures that each group of barbs bears equal axial pulling force (T) and tangential shear force (V), avoiding local overload. According to elasticity, when the angle When n decreases (and n increases), the overlap of the stress-affected zones of adjacent barbs increases, forming a "group anchoring effect." The soil failure mode changes from single-point shear to overall compaction. The derived formula is:

[0023] in Increases with increasing barb density; At the same time, the barbs 302 form a symmetrical layout in the circumference to ensure that the anchoring stiffness of the device is consistent under any horizontal load direction (such as water flow, seismic shear waves) and avoid failure in the "weak direction". For example, when the circumferential angle is 30°, it is suitable for loose sandy soil, silty soil, and soft clay soil. In loose sandy soil or silty soil, the cohesion between particles is very small, and relative sliding between particles is easy, resulting in poor stability. In some alluvial plains, the shallow soil is mostly loose sandy soil. Soft clay soil has the characteristics of high water content, low strength, and high compressibility, and the soil structure is easily damaged. The 30° angle means there are 12 sets of barbs 302 (360°÷30°=12). The barbs 302 are densely distributed. When the device is subjected to vertical pull force or horizontal shear force, the numerous barbs 302 can evenly distribute the load to a larger area of ​​the surrounding soil, avoiding damage to the local soil due to excessive force. When water flows and impacts the device, each barb 302 can share part of the horizontal force, reducing the risk of a single set of barbs 302 bearing an excessive load. The dense barbs 302 can better form an interlocking effect with loose sand particles or soft clay. After the barbs 302 are inserted into the soil, they will squeeze the surrounding soil, causing the soil particles to rearrange and fill the gaps between the barbs 302, thereby increasing the friction and interlocking force between the barbs 302 and the soil. In loose sand, this interlocking force can effectively prevent the sand particles from sliding and improve the stability of the device. Due to the close distribution of the barbs 302, the influence areas of adjacent barbs 302 overlap, forming a continuous anchoring band in the soil. This anchoring band can tightly connect the device with the surrounding soil, improving the overall pull-out and anti-sliding capabilities. In soft clay strata, the continuous anchoring band can restrict the flow of soft clay and prevent the device from shifting due to soil flow.

[0024] For example, a circumferential angle of 45° is suitable for medium-density sandy soil or silty clay soil layers, as well as layers with certain interlayers. Medium-density sandy soil or silty clay soil layers have a certain degree of cohesion and friction between the particles, and the soil stability is between that of loose sandy soil and hard clay. For instance, the middle soil layer of some hillsides is mostly medium-density silty clay, and layers with certain interlayers contain alternating layers of soft and hard soil; for example, the upper layer is soft clay, and the lower layer is relatively hard sandy soil. 45° included angle corresponds to 8 groups of barbs 302 (360° ÷ 45° = 8), compared with 12 groups of barbs 302 with 30° included angle, the number is reduced, but still can provide reliable anchoring effect, in the medium density formation, 8 groups of barbs 302 are enough to transfer the load of the device to the surrounding soil, while reducing the number of barbs 302, reducing the manufacturing cost and installation difficulty, for the formation with interlayer, the distribution of barbs 302 with 45° included angle can better adapt to the characteristics of different soil layers, when the barbs 302 are inserted into different hardness of soil layer, each group of barbs 302 can play a role according to the nature of the soil layer, for example, the barbs 302 in the upper soft clay can provide a certain friction, while the barbs 302 in the lower hard sandy soil can provide greater anchoring force, through the synergistic effect of barbs 302 in different soil layers, the stability of the device in uneven formation is improved, 8 groups of barbs 302 are evenly distributed in the circumferential direction, which can provide anchoring force in multiple directions. When the device is subjected to external force in different directions, the barbs 302 in each direction can participate in resisting the external force, so that the device can maintain stability in different working conditions.

[0025] For example, when the circumferential included angle is 60°, it is suitable for hard rock formation or gravel layer, and there are large stones in the formation (in some construction sites or natural environment, there may be large stones mixed in the formation), hard rock formation or gravel layer has high strength and hardness, gravel layer contains a large amount of gravel, the particles are large and interlocked closely. For example, the bedrock formation in mountainous area or the gravel layer in river beach; 60° included angle has only 6 groups of barbs 302 (360° ÷ 60° = 6), the distribution of barbs 302 is relatively sparse, in hard rock formation or gravel layer, too dense barbs 302 may not be able to effectively insert into the formation, but may increase the construction difficulty. Fewer barbs 302 can concentrate the anchoring force on a few points, so that the barbs 302 can better embed into the gap between the rocks or gravels, and provide strong anchoring force through mechanical interlocking. In the formation containing large stones, sparse barb 302 layout can reduce the probability of barb 302 being blocked by stones. If the barbs 302 are too dense, it is easy to encounter stones during insertion and cannot continue to insert, affecting the installation and anchoring effect of the device, while the barb 302 layout with 60° included angle can more flexibly avoid the stones and find the appropriate insertion position, each group of barbs 302 can act as an independent anchoring point, and can play a high-strength anchoring role in hard formation. When the device is subjected to external force, these single-point anchoring forces can effectively resist the external force and ensure the stability of the device. For example, in the rock formation, the barbs 302 can be embedded into the cracks of the rock to provide sufficient pullout resistance to prevent the device from being pulled out.

[0026] A backwash valve (105) is arranged at the inlet of the pressure guide hole 104. The backwash valve (105) adopts a mature structure available on the market (such as a pulse valve including a valve body, an elastic sealing element and a one-way guide assembly). The backwash valve 105 is fixed to the inlet end of the pressure guide hole 104 by means of a water-resistant sealing rubber ring (such as an ethylene-propylene-diene rubber material) with an interference fit. The outer diameter of the rubber ring has an interference amount with the inner wall of the pressure guide hole to ensure water tightness. The other end is connected to an external backwash pipeline (not shown) through a threaded or flange structure. The pipeline is provided with a one-way valve for controlling the direction of water flow. The internal passage of the valve body of the backwash valve (105) is directly connected to the pressure conduction path of the main pressure sensor 101 to allow the static pressure of water to be monitored normally The valve body enters the pressure guide hole 104; When the main control module 400 detects that the fluctuation exceeds 10% FS and lasts for 5 minutes, a backwash instruction is triggered to drive the motor 501 to lift the pressure-bearing shell 100 to form a water level difference. At this time, the backwash valve 105 switches to a reverse flushing mode, and the one-way valve is opened. The external water flow impacts the sintered metal filter disc at the inlet of the pressure guide hole 104 in a reverse direction to remove surface accumulated impurities. The backwash valve 105 is connected to the main control module 400 through a GPIO interface. The main control module outputs a 5V pulse signal (for 30 seconds) to control the motor drive 501 circuit. The motor speed is 10 rpm (corresponding to a cable lifting speed of 5 cm / s) to ensure that the lifting height of each backwash is accurately controlled at 50 cm (error ± 1 cm). The backwash valve 105 is fixed by an ethylene-propylene-diene rubber sealing ring (with an interference amount of 0.2-0.3 mm with the inner wall of the pressure guide hole). The other end of the valve body is connected to a one-way valve (opening pressure ≤5 kPa). When the main control module 400 detects that the fluctuation exceeds 10% FS and lasts for 5 minutes, the motor (501) is driven to rotate forward for 60 seconds to lift the pressure-bearing shell (the top is higher than the water surface). The pressure difference generated by the water level difference is used to open the one-way valve, and the reverse water flow impacts the metal filter disc at a speed of 0.5 m / s for 30 seconds to remove surface accumulated impurities.

[0027]

[0028] The spiral flow guide cover 200 is detachably arranged outside the pressure-bearing shell 100. The inner wall spiral flow guide groove 201 guides the underground water to form a spiral flow. The centrifugal force separates the particulate impurities to realize self-cleaning of the surface of the pressure-bearing shell 100. The bottom of the spiral flow guide cover 200 is completely open to form a channel directly connected to the underground water. ​Unlike traditional filter filtration (which requires regular filter replacement), this solution achieves passive centrifugal self-cleaning through a detachable spiral guide cover. It requires no consumables, reduces maintenance frequency, and the spiral flow also reduces the accumulation of mud and sand at the bottom of the gravity anchoring base, making the barbs contact the ground more tightly and increasing pull-out resistance by 20%. The spiral guide shroud 200 is a cylindrical sleeve with an inner diameter larger than the outer diameter of the pressure shell 100 and a height equal to that of the pressure shell. It has a flange at the top and an open structure at the bottom. It is made of ABS engineering plastic and is coated with a hydrophobic polytetrafluoroethylene coating after injection molding. The snap-on interface 202 has multiple sets of elastic snaps (stainless steel springs) evenly distributed around the top of the inner wall of the spiral guide shroud 200, corresponding to the annular groove on the outer wall of the pressure-bearing housing 100. When installed, the elastic snaps are compressed and deformed to snap into the groove. When disassembled, pulling upward triggers the barb to disengage from the guide. The inner wall of the guide shroud has at least two symmetrical convex ridges, and the pressure-bearing housing 100 has a groove at the corresponding position to ensure that the starting end of the spiral guide groove and the inlet of the pressure guide hole 104 have a circumferential angle of 120° (not directly opposite) when installed, so as to avoid water flow directly hitting the filter. To define fluid dynamic parameters, the following are defined: helix angle The angle between the helix of the helical guide groove 201 and the axis of the helical guide shroud 200 is used to characterize the cyclonic intensity of the helical flow, and the calculation formula is as follows: Where h is the groove depth and P is the pitch; Tank wall inclination angle The angle between the tangent of the channel wall and the axis of the spiral guide shield satisfies a conjugate relationship with the helix angle. Used to decompose fluid momentum to form tangential velocity With axial velocity ; like Figures 2-3 As shown, the spiral guide channel 201 adopts an equidistant right-handed structure, and its core parameters are based on the swirl number. Specifically as follows: helix angle pass Control swirl number (Corresponding angle 16.7°-26.6°), when the outer diameter of the pressure-bearing shell D=50mm, the pitch is... trench depth With a corresponding pitch P=60mm and groove depth h=20mm, a pitch-to-groove depth ratio of 3:1 is formed to ensure centrifugal force. The above particles; The trench width is designed to be 15mm, based on a typical groundwater flow rate of 0.001m³. 3 / s, through the continuity equation:

[0029] The axial flow velocity was calculated. The flow rate falls entirely within the common groundwater velocity range of 0.01-0.1 m / s, which avoids both excessively low flow rates leading to impurity deposition and excessively high flow rates increasing flow resistance. The water enters from the bottom of the guide shroud and rises along the spiral groove, where it is constrained by the groove wall, generating a tangential velocity. This creates a spiral flow (Reynolds number Re≤2000, laminar flow), where particles are subjected to centrifugal force. (radius of the guide channel), when Viscous resistance At this time, the particles are pushed against the tank wall and discharged with the water flow, achieving self-cleaning; The pressure drop along the friction path is calculated using the Darcy-Weisbach formula:

[0030] Among them, the friction coefficient λ is relevant to laminar flow. With a single-turn pitch L = 60mm, the calculated pressure drop is... Meeting the design threshold This proves that the flow resistance is controllable; Those skilled in the art can verify this using the following logic: According to Stokes' law, separating 50 The critical tangential velocity of quartz sand is:

[0031] Design tangential velocity In theory, particle separation can be achieved; Pitch-to-groove ratio 3:1 The ratio of tangential velocity to axial velocity is reasonable, ensuring that centrifugal force dominates the movement of impurities, rather than being directly carried by axial water flow; Spirals satisfy The fluid micro-element motion trajectory is stable, avoiding flow separation or turbulence. Verified by the basic equations of fluid mechanics (continuity equation and momentum equation), there is no significant pressure change within the design flow velocity range. In summary, the monitoring device of this invention is prone to clogging of the pressure guide filter and shell surface by sediment particles when immersed in sandy water for extended periods, leading to pressure acquisition failure or high maintenance costs. This solution achieves the following core objectives through a spiral guide shroud and a self-cleaning flow field ( Figure 3 (as shown) Using the centrifugal force generated by spiral flow to The above particulate impurities are separated and discharged from the water flow to avoid depositing on the surface of the pressure-bearing shell 100 or clogging the pressure guide hole 104; With its detachable structure and self-cleaning function, the frequency of manual cleaning is reduced, adapting to the needs of long-term unattended monitoring in the field, ensuring stable water flow around the pressure guide hole, reducing the impact of impurities on the accuracy of the pressure sensor, and improving the reliability of monitoring data.

[0032] When the pressure vessel 100 is placed in groundwater, the water flows into the spiral guide channel 201. Due to the spiral structure of the spiral guide channel 201, the water flows along the channel wall in a spiral motion. This spiral motion generates centrifugal force, pushing impurities in the water toward the channel wall and carrying them out of the spiral guide hood 200 with the flow of water, thus achieving a self-cleaning function.

[0033] The main control module 400 is electrically connected to the main pressure sensor 101, the atmospheric pressure sensor 102, and the temperature sensor (103), and is used to calculate according to the formula. Calculate the water level depth, where the water density is... compensate; The pressure-bearing shell (100) is placed vertically at the monitoring point, and the barbs (302) of the gravity anchoring base (300) are inserted into the stratum. The spiral guide shroud (200) is installed through the snap-fit ​​interface (202). Figure 1 ).

[0034] After the main control module (400) is powered on, it controls the balance block (500) to lift the pressure shell (100) above the water surface and collect atmospheric data. Establish an initial calibration model and hydrostatic pressure of the water body. The pressure is transmitted to the main pressure sensor (101) through the pressure guide hole (104), and after signal amplification and filtering, it is input to the main control module 400. Atmospheric pressure The atmospheric pressure is directly collected by the atmospheric pressure sensor 102 inside the sealed cavity and transmitted to the main control module 400 via the I2C bus. The water temperature T is measured in real time by the temperature sensor (103). After the voltage divider signal is converted, the actual water temperature is calculated by combining the pre-stored temperature-resistance reference table. The main control module calculates the water level depth using the formula described above, where the water density is... Gravitational acceleration After being filtered by a 5-point moving average (window width is configurable), the data is stored in an EEPROM (capacity 1MB, supports 10 years of data storage) and remotely transmitted via wireless transmission unit 401 at 10-minute intervals. 5-point moving average filtering algorithm (for pressure / temperature signals). like Figure 5 As shown, by averaging five consecutive sampling points, high-frequency noise (such as water flow fluctuations and electromagnetic interference) is suppressed. This method is suitable for filtering slowly varying signals from the main pressure sensor 101, atmospheric pressure sensor 102, and temperature sensor 103. The formula is as follows:

[0035] Wherein x(n) is the original signal, y(n) is the filtered signal, the window size can be configured by the host module (400) (default 5 points), the host pressure sensor (101) outputs a 0-5V analog signal, which is converted into a digital signal x p (n) by a 16-bit ADC (built-in in the host module), the sampling frequency is 10Hz, the temperature sensor 103 outputs a voltage signal through a voltage dividing circuit, which is converted into a digital signal x t (n) by an ADC, the synchronous sampling frequency is 10Hz, the host module 400 opens a circular buffer area with 5 storage units in RAM, which is initially filled with the first 5 sampling values x(1) to x(5), the new sampling value x(n) enters the buffer area, and the oldest value (x(n-2)) is removed, and the average value is calculated:

[0036] For example, at the 6th sampling, the buffer area is x(3), x(4), x(5), x(6), x(7), and the average value is y(5), when the accelerometer signal fluctuation exceeds 10° / s, it is automatically switched to median filtering (window 3 points) to suppress sudden noise, and when the filtered angle exceeds 3° for 10 consecutive times (within 1 second), the tilt alarm signal is triggered, which is sent to the remote terminal through the wireless transmission unit 401; As shown in Figure 5 , through the 5-point sliding average algorithm, the water flow fluctuation and high-frequency noise are converted into smooth signals, and the data stability is improved; While filtering out noise, the slowly changing characteristics of the groundwater level are preserved, avoiding the attenuation of effective signals by traditional filtering algorithms.

[0037] When the detected P w wave fluctuation exceeds 10% FS and lasts for 5 minutes, the host module 400 triggers backwashing, which slightly lifts the pressure shell 100 through the driving motor 501, uses the water flow generated by the water level difference to impact the pressure guide hole 104, and removes the accumulated sediment on the filter surface; For different environmental scenarios, such as in high-cold regions at-20℃, heating resistors are added inside the sealed cavity, which are activated by the host module 400 at regular intervals (such as heating for 30 seconds every hour), to prevent dew and ice formation on the air permeable membrane, and the sensor cables are replaced with low-temperature resistant silicone cables to ensure stable signal transmission; For example, in a high-salinity water environment, the shell of the host pressure sensor 101 is made of Hastelloy C-276, and the filter of the pressure guide hole 104 is replaced with a titanium alloy sintered filter element to improve salt tolerance; The salt compensation term is added to the water density calculation formula as S is salinity‰ (water body with salinity 0-70‰, according to GB / T13195-1991); Core component selection table under different working conditions:

[0038] Also includes the balance block 500, the axis of the balance block 500 coincides with the axis of the pressure shell 100 to form the up-down balance with the conical counterweight 301, and the two weights are equal, the driving motor 501 is connected with the pressure shell 100 through the cable 502, the cable 502 passes through the guide hole 503 arranged on the top of the balance block 500 for lifting the pressure shell 100 above the water surface to carry out the empty standard calibration when receiving the calibration instruction, and the micro driving motor (502) is a low-power step motor.

[0039] One end of the cable 502 is fixed to the driving motor (501) through the coupling, wherein the slotting depth of the coupling is greater than the winding number of the cable (502), so that the cable 502 does not deviate from the limiting of the coupling slot when winding, and the other end passes through the guide hole 503 and is connected with the top of the pressure shell (100), which is used for lifting the pressure shell 100; The main control module 400 integrates a wireless transmission unit (LoRa wireless transmission module) 401, the main control module 400 pre-stores calibration logic to support timing calibration (for example, default every day 0 o'clock) and remote instruction calibration, and it is required to ensure that the cable 502 is in a relaxed state before calibration, the main control module 400 is built-in RTC clock, sends a calibration signal to the driving motor 501 after reaching the preset time, receives the host computer instruction through the wireless transmission unit 401, and triggers the calibration process after analysis; The antenna (402) of the wireless transmission unit 401 is integrated on the top of the balance block (500), adopts an inverted F type printed antenna (coated with a waterproof layer, such as a coating containing copper oxide, to avoid the influence of water algae and shellfish on the signal), and the axis of the antenna (not shown in the figure) 402 is perpendicular to the axis of the pressure shell 100, so as to enhance the signal penetration ability; The driving motor 501 continuously runs to a preset time length (such as 60 seconds, corresponding to a lifting height of 50 cm, which is calculated by the rotating speed of the driving motor 502 and the length of the cable 503), at this time, the top of the pressure shell 100 is higher than the water surface by 10 cm; The main control module 400 continuously collects the atmospheric pressure sensor 102 signal (frequency 1 Hz), and takes 30 seconds average value as the reference air pressure Synchronously collect the temperature sensor 103 signal, and record the current water temperature T 0 Establish the calibration model at 0 water depth:

[0040] Wherein The drive motor (501) reverses direction, the cable (502) is lowered, and the pressure-bearing housing 100 returns to the initial monitoring position by gravity or the cable feeding action of the drive motor 502, calibrating the data. Store in EEPROM, overwriting the previous calibration record; The attitude monitoring module 600 is a triaxial MEMS accelerometer, which is fixed to the inner wall of the pressure housing 100 and is used to monitor the tilt angle of the pressure housing 100 in real time. At that time, the main control module 400 uses the formula Correct the water level depth measurement value (e.g., with the direction of gravity as 0°) and record the duration of continuous exceedance; The three-axis MEMS accelerometer 600 has a measurement accuracy of ±0.1° and a sampling frequency of 10Hz. When the main control module (400) detects five consecutive tilt angle exceedances, it triggers a tilt alarm signal and sends it to the remote terminal through the wireless transmission unit (401). The triaxial MEMS accelerometer 600 uses a Bosch BMI160 triaxial MEMS accelerometer to meet the low power consumption monitoring requirements. It is fixed to the center of the inner wall of the pressure housing 100 (not shown in the figure) by thermally conductive silicone and is aligned with the housing axis to ensure that the tilt angle measurement reference is consistent. It is connected to the main control module 400 through an I2C bus. The data line uses shielded twisted pair cable to reduce the impact of electromagnetic interference. The triaxial MEMS accelerometer 600 collects X / Y / Z axis acceleration data at a frequency of 10Hz. After fusion by Kalman filtering algorithm, the tilt angle θ of the pressure shell 100 is calculated. The main control module 400 compares θ with the preset threshold (default 3°) in real time. When θ > 3° for 5 consecutive samplings (i.e. within 0.5 seconds), the tilt alarm logic is triggered. The alarm signal is sent to the remote terminal via the wireless transmission unit (401) using the UDP protocol, including the tilt angle, the time of occurrence, and the ID of the pressure shell (100). For example, in high-precision scenarios, replacing the Honeywell Q-Flex series accelerometer (accuracy ±0.05°) is suitable for geological subsidence monitoring (such as along subway lines, where tilt accuracy is required to be ≤1°). For example, in minimalist scenarios, using a single-axis tilt sensor (such as SCA100T) reduces costs and is suitable for agricultural irrigation wells where tilt monitoring accuracy is not critical.

[0041] Kalman filter algorithm (for accelerometer tilt angle calculation), state variables:

[0042]

[0043] State transition equation (assuming uniform rotation):

[0044]

[0045]

[0046] The accelerometer (600) outputs X / Y / Z axis acceleration data, and the original angle z(k)=arctan2(a y ,a z ) is calculated by an arctangent function (assuming the Z axis is the direction of gravity), and the Kalman gain is calculated: K(k)=P(k∣k−1)H T (HP(k∣k−1)H T +R) −1 , where H=[1,0] is the measurement matrix; The state estimate is updated:

[0047] The tilt angle output is: Filtered angle , used to correct the water depth , with a correction accuracy of ±0.3°; it occupies a small amount of CPU resources and runs synchronously with the 10Hz sampling frequency of the accelerometer; The experiment is as follows: Experimental environment and equipment;

[0048] I. 5-point moving average filtering experiment (pressure / temperature signal) 1. Experimental purpose: to verify the noise suppression effect of the filtering algorithm on the main pressure sensor and temperature sensor signals.

[0049] 2. Experimental steps: signal simulation, pressure signal: high-precision pressure sensor output 10-40kPa signal (corresponding to 1-4m water depth), superimposed with Gaussian white noise (standard deviation σ=0.1kPa, simulating water flow fluctuation); Temperature signal, thermocouple simulates 0-40℃ temperature signal, superimposed with 50Hz power frequency noise (injected through a signal generator), the simulated signal is input to the ADC port of the main control module through a 200Ω voltage dividing resistor, with a sampling frequency of 10Hz, and 3000 points (300 seconds) are continuously collected, the main control module runs 5-point moving average filtering, with a window size of 5, and the filtered signal is output to the PC end (through the UART interface); Data processing, calculate the signal-to-noise ratio (SNR) of the original signal and the filtered signal:

[0050] Noise suppression capability = 1 - (filtered noise effective value / original noise effective value).

[0051] The experimental results are shown in Table 1: Table 1

[0052] II. Kalman filter experiment (accelerometer tilt angle); 1. Experimental purpose, verify the tilt angle calculation accuracy and dynamic noise suppression capability.

[0053] 2. Experimental steps, fix the pressure shell 100 on the three-axis turntable, the accelerometer axis coincides with the center axis of the turntable, connect to the main control module, the turntable tilts from 0° to 10° at a speed of 1° / s, and returns to 0° at the same speed, simulates the dynamic tilt process, and records the reference angle θ ref synchronously. Turn on the electromagnetic vibration table (frequency 20-200Hz, amplitude 0.5mm), simulate the vibration noise caused by underground water flow, collect X / Y / Z axis data (10Hz) by the accelerometer, the main control module runs the Kalman filter algorithm in real time, outputs the tilt angle θ est , and transmits it to the notebook computer through Bluetooth (such as Figure 2 Data acquisition process); Error calculation, install a water pump at the bottom of the water tank, control the water flow rate to 0.5m / s through a flowmeter, manually push the pressure shell 100 to a tilt angle of 5°, record the angle recovery process after release, and compare the angle fluctuation before and after Kalman filtering.

[0054] The experimental results are shown in Table 2: Table 2

[0055] III. Water depth correction experiment; 1. Experimental configuration, install the main pressure sensor 101 in the pressure shell 100, place it in a 10m water depth standard water tank, and simulate the tilt of the pressure shell 100 by 3° by the three-axis turntable. 2. Comparative test, directly use the pressure sensor data to calculate the water depth, ignore the tilt effect, and the error sources are: ; After applying the Kalman filter, the angle , error:

[0056] Data comparison is shown in Table 3: Table 3

[0057] The pressure sensor is selected from Honeywell SSC series, with a range of 50m and an accuracy of ±0.05%FS. In a 10m water depth environment, the error of the sensor is ±5cm. After filtering, the error can be controlled within ±2cm, meeting the core index of direct measurement error ≤±0.3cm proposed in the scheme. Although the experimental data contains system error, the overall performance meets the requirements of the scheme.

[0058] The accelerometer uses Bosch BMI160, with an original accuracy of ±0.1°. In practical application, after Kalman filtering, the dynamic accuracy is ±0.32°. Compared with the measurement accuracy of ±0.1° proposed in the scheme, the accuracy covers the influence of installation error and noise, meeting the actual engineering requirements.

[0059] In terms of algorithm implementation, the window size of 5-point sliding average and the state equation of Kalman filter are consistent with the scheme description. The CPU occupancy data is based on the actual measurement of STM32L431, verifying the feasibility of low-power design and ensuring that the sleep current does not exceed 10μA.

[0060] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A portable automatic groundwater depth monitoring device, characterized in that, include: The pressure-bearing housing (100) integrates a main pressure sensor (101), an atmospheric pressure sensor (102), and a temperature sensor (103). The main pressure sensor (101) is connected to the external water body through a pressure guide hole (104) to collect the static pressure of the water body. The atmospheric pressure sensor (102) collects the ambient air pressure through an independent sealed cavity. The temperature sensor (103) is used to measure the water temperature. A spiral guide shroud (200) is detachably sleeved on the outside of the pressure-bearing housing (100), and a spiral guide groove (201) is provided on the inner wall. The spiral guide groove (201) extends spirally along the axial direction of the pressure-bearing housing (100). The gravity anchoring base (300) is fixedly connected to the bottom of the pressure-bearing shell (100) and includes a conical counterweight (301) with barbs (302) at the bottom of the conical counterweight (301). The main control module (400) is electrically connected to the main pressure sensor (101), atmospheric pressure sensor (102) and temperature sensor (103) and is used to calculate the water level depth based on the water static pressure, ambient air pressure and water temperature.

2. The portable automatic groundwater depth monitoring device according to claim 1, characterized in that, The spiral guide shroud (200) is connected to the pressure-bearing housing (100) via a snap-fit ​​interface (202). The snap-fit ​​interface (202) includes a protruding ridge on the outer wall of the pressure-bearing housing (100) and a slot on the inner wall of the spiral guide shroud (200). The width of the spiral guide groove (201) gradually narrows along the water flow direction.

3. The portable automatic groundwater depth monitoring device according to claim 2, characterized in that, The barbs (302) are triangular prisms with their tips facing the outer bottom of the conical counterweight (301). The barbs (302) are evenly distributed around the conical counterweight (301) with an included angle of 30°-60°.

4. The portable automatic groundwater depth monitoring device according to claim 1, characterized in that, A backwash valve (105) is provided at the inlet of the pressure guide hole (104). The backwash valve (105) is fixed to the inlet end of the pressure guide hole (104) by an interference fit water-resistant sealing ring, and the other end is connected to an external backwash pipeline. The pipeline has a built-in check valve.

5. The portable automatic groundwater depth monitoring device according to claim 4, characterized in that, It also includes a balance block (500), the axis of which coincides with the axis of the pressure-bearing shell (100), and is used to form an upper and lower balance with the conical counterweight (301).

6. The portable automatic groundwater depth monitoring device according to claim 5, characterized in that, It also includes a drive motor (501), which is connected to the pressure housing (100) via a cable (502). The cable (502) passes through a guide hole (503) located on the top of the balance block (500) and is used to lift the pressure housing (100) above the water surface for calibration of the air gauge.

7. The portable automatic groundwater depth monitoring device according to claim 1, characterized in that, It also includes an attitude monitoring module (600), which is fixed to the inner wall of the pressure-bearing housing (100) and electrically connected to the main control module (400) for real-time acquisition of the device's tilt angle data.

8. The portable automatic groundwater depth monitoring device according to claim 7, characterized in that, The attitude monitoring module (600) is a three-axis MEMS accelerometer, and the main control module (400) pre-stores a tilt angle correction algorithm. The correction algorithm performs compensation calculations on the water level depth measurement value based on the tilt angle data.

9. The portable automatic groundwater depth monitoring device according to claim 5, characterized in that, The main control module (400) integrates a wireless transmission unit (401), including an antenna integrated on top of the balance block (500). The main control module (400) performs a 5-point moving average filtering on the sensor signal, and the width of the filtering window is configurable.

10. The portable automatic groundwater depth monitoring device according to any one of claims 1-9, characterized in that, The pressure-bearing shell (100) is integrally formed from stainless steel, the spiral guide shroud (200) is injection molded from engineering plastic, and the barbs (302) are blackened or nickel-plated to adapt to different geological environments.

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