Soil Moisture Measuring Device and Control Method

Abstract

This invention relates to the field of soil property measurement technology, and discloses a soil moisture measuring device and its control method. The soil moisture measuring device includes: a frame, a mold cylinder, a loading component, a permeable component, and a measuring element. The mold cylinder is located on the frame and is used to hold a soil sample. The top of the mold cylinder has a filling port, and the side wall of the mold cylinder has an air inlet for introducing gas into the mold cylinder. The gas pressure follows a gradient sequence. The loading component can extend into the mold cylinder through the filling port and press the soil sample along the axial direction of the mold cylinder. The permeable component is connected to the bottom of the mold cylinder and is used to collect water seeping from the soil sample. The bottom of the permeable component has a water outlet. The bottom of the measuring element has a water inlet and a water pressure sensor. The water inlet and outlet are connected, and the water pressure sensor is used to detect the water pressure inside the measuring element. This device effectively restores the pore structure and water-holding characteristics of deep soil, improves data reliability, and accurately analyzes soil properties under complex stress conditions.

Description

Technical Field

[0001] This application relates to the field of soil property measurement technology, and in particular to a soil moisture measuring device and its control method. Background Technology

[0002] The determination of soil pore structure's ability to adsorb and retain water is of great theoretical and practical significance. Among related technologies, the pressure plate method, as a recognized standard laboratory testing method in geotechnical engineering and soil physics, only applies air pressure to the pores of the soil sample, ignoring the complex stress environment of the actual soil, reducing the realism of the physical model, lowering the reliability of the measurement data, and hindering the accurate analysis of soil moisture characteristics under complex stress conditions. Summary of the Invention

[0003] This application aims to address at least one of the technical problems existing in the prior art or related technologies.

[0004] The first aspect of this application provides a soil moisture measuring device, which includes: a frame, a mold cylinder, a loading component, a permeable component, and a measuring element. The mold cylinder is located on the frame and is used to hold a soil sample. The top of the mold cylinder has a filling port, and the side wall of the mold cylinder has an air inlet for introducing gas into the mold cylinder. The gas pressure follows a gradient sequence. The loading component can extend into the mold cylinder through the filling port and press the soil sample along the axial direction of the mold cylinder. The permeable component is connected to the bottom of the mold cylinder and is used to collect water seeping from the soil sample. The bottom of the permeable component has a water outlet. The bottom of the measuring element has a water inlet and a water pressure sensor. The water inlet and the water outlet are connected, and the water pressure sensor is used to detect the water pressure inside the measuring element.

[0005] In some of the technical solutions provided in this application, the loading component includes: a pressure plate, which is used to extend into the mold cylinder to press the soil sample. The pressure plate is provided with multiple ventilation holes, any one of which connects the top and bottom surfaces of the pressure plate. When the pressure plate presses the soil sample, gas enters the ventilation hole and applies pressure to the soil sample.

[0006] In some technical solutions provided in this application, the loading assembly further includes: a first driving member and a pressure rod. The first driving member is disposed on the frame, and the two ends of the pressure rod are respectively connected to the first driving member and the pressure plate. The first driving member is used to drive the pressure rod to move axially along the mold cylinder. The frame is provided with a distance detection member, which is used to detect the movement distance of the pressure rod.

[0007] In some of the technical solutions provided in this application, the soil moisture measuring device also includes a sealing component, which includes a sealing ring and a telescopic plate. The sealing ring is located at the filling port, and the telescopic plate is located on the inner side wall of the sealing ring. The telescopic plate can extend and retract along the radial direction of the sealing ring. When the pressure plate is at the height of the telescopic plate, the telescopic plate retracts into the sealing ring. When the pressure plate extends into the mold cylinder, the telescopic plate extends out and seals the filling port.

[0008] In some of the technical solutions provided in this application, the measuring element extends vertically, and the top of the measuring element is provided with an exhaust hole. The soil moisture measuring device also includes an exhaust pipe, the air inlet end of which is connected to the exhaust hole, and the exhaust pipe is bent and extended so that the air outlet end of the exhaust pipe faces the bottom of the measuring element.

[0009] In some of the technical solutions provided in this application, the side wall of the mold cylinder is provided with an air extraction port, which is used to connect to a vacuum pumping device.

[0010] In some technical solutions provided in this application, the permeable component includes: a permeable plate and a water collection component. The permeable plate is located at the bottom of the mold cylinder and is used to support the soil sample. The permeable plate has permeable holes. The water collection component is connected to the bottom surface of the permeable plate. The top of the water collection component is connected to the permeable holes. The bottom of the water collection component gradually narrows in the direction away from the permeable plate. The water outlet is located at the bottom of the water collection component.

[0011] In some of the technical solutions provided in this application, the soil moisture measuring device further includes: a second driving member, which is disposed on the frame and connected to the mold cylinder, and is used to drive the mold cylinder to move axially.

[0012] The second aspect of this application provides a control method for a soil moisture measuring device, which utilizes the soil moisture measuring device provided by any of the above-mentioned technical solutions. The control method for the soil moisture measuring device includes: The pressure plate applies axial pressure to the soil sample inside the mold cylinder; Gas is injected into the mold cylinder step by step according to the pressure level of the pressure gradient sequence. After each level of gas injection and when the drainage of the soil sample reaches equilibrium, the drainage pressure in the metering device and the sinking distance of the pressure plate are obtained until the gas injection of all levels of the pressure gradient sequence is completed. Based on the drainage pressure and settlement distance at each pressure level, the drainage volume, volumetric water content, and volumetric shrinkage rate of the soil sample were determined.

[0013] In some technical solutions provided in this application, and in some embodiments provided in this application, the following steps are included before the initial steps: Water and air were injected into the measuring device until water overflowed from the surface of the soil sample. Control the pressure plate to extend into the mold cylinder; A vacuum operation is performed inside the mold cylinder.

[0014] Compared with related technologies, the present invention has at least the following beneficial effects: The interplay of gradient air pressure and mechanical loads enables a realistic simulation of the in-situ environment of deep soil. While maintaining high soil suction, it effectively recreates the pore structure and water-holding characteristics of deep soil, improving the reliability of the measurement data. By tracking the dynamic changes in soil porosity and saturation under the coupled effects of stress and suction in real time, the moisture characteristics of soil under complex stress conditions can be accurately analyzed. Furthermore, the use of a water pressure sensor achieves vibration-resistant precision measurement, significantly superior to traditional horizontal graduated tubes or electronic balances, enhancing the scientific rigor and accuracy of the data. Attached Figure Description

[0015] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of some embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic diagram of the structure of a soil moisture measuring device according to an embodiment of this application; Figure 2 A partial structural schematic diagram of a soil moisture measuring device according to an embodiment of this application; Figure 3 This is a schematic diagram of the structure of a permeable component according to an embodiment of this application; Figure 4 A connection diagram of a control device according to an embodiment of this application; Figure 5 This is a schematic flowchart illustrating the control method of a soil moisture measuring device according to an embodiment of this application.

[0016] in, Figures 1 to 5 The correspondence between the reference numerals and component names in the attached drawings is as follows: 10. Soil moisture measuring device; 110. Distance detection component; 120. Base plate; 130. Lifting platform; 140. Guide plate; 150. Mounting plate; 160. Support column; 200. Mold cylinder; 210. Filling port; 220. Air inlet; 230. Air extraction port; 240. High-pressure test chamber; 300. Loading assembly; 310. First driving component; 320. Pressure rod; 330. Pressure plate; 340. Pressure sensor; 400. Permeable component; 410. Permeable plate; 411. Permeable hole; 420. Water collection. Components; 421, water outlet; 430, sealing ring; 500, metering component; 510, water pressure sensor; 520, vent; 530, tee fitting; 540, conduit; 600, sealing assembly; 610, sealing ring; 620, telescopic plate; 630, wear-resistant guide sleeve; 700, vent pipe; 800, second drive component; 900, control assembly; 910, air source assembly; 920, precision pressure regulating assembly; 930, air circuit control valve; 940, air inlet component; 950, analysis module; 20, soil sample. Detailed Implementation

[0017] To better understand the above technical solutions, the technical solutions of the embodiments of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0018] The first aspect of this application provides a soil moisture measuring device 10, such as... Figure 1 , Figure 2 and Figure 4 As shown, the soil moisture measuring device 10 includes: a frame, a mold cylinder 200, a loading component 300, a permeable component 400, and a measuring element 500. The mold cylinder 200 is mounted on the frame and is used to hold a soil sample 20. The top of the mold cylinder 200 has a filling port 210, and the side wall of the mold cylinder 200 has an air inlet 220 for introducing gas into the mold cylinder 200. The gas pressure follows a gradient sequence, and the loading component 300 can pass through the filling port. 210 extends into the mold cylinder 200 and presses the soil sample 20 along the axial direction of the mold cylinder 200. The permeable component 400 is connected to the bottom of the mold cylinder 200. The permeable component 400 is used to receive the water seeping out of the soil sample 20. The bottom of the permeable component 400 is provided with an outlet 421. The bottom of the measuring component 500 is provided with an inlet and a water pressure sensor 510. The inlet and outlet 421 are connected. The water pressure sensor 510 is used to detect the water pressure inside the measuring component 500.

[0019] In this embodiment, the frame provides a stable support foundation and installation structure for the entire device. The mold cylinder 200 and the loading assembly 300 are located on the frame. The soil sample 20 to be tested is contained in the high-pressure testing chamber 240 formed by the mold cylinder 200. The top and side walls of the mold cylinder 200 are respectively provided with a filling port 210 and an air inlet 220 communicating with the high-pressure testing chamber 240. The mold cylinder 200 realizes convenient filling of the soil sample 20 through the filling port 210. Figure 1 The arrow at position X points in the center, indicating the axial direction of the mold cylinder 200. At least a portion of the loading component 300 can move axially, allowing it to pass through the filling port 210 and extend downwards into the high-pressure testing chamber 240 to press the soil sample 20. This applies a preset axial pressure to the soil sample 20, simulating the enormous self-weight stress of the overlying soil layer on deep soil in a real environment. It also recreates the soil pore state and its water-holding capacity under the self-weight stress of the overlying soil layer. The air inlet 220 connects to the air source component 910, which is connected to the precision pressure regulating component 920 and the air circuit control valve 930. Gradient pressure gas is input into the high-pressure testing chamber 240 through the air inlet component 940, with a pressure stabilization accuracy of ±0.1%FS. The gas and the loading component 300 work together to achieve axial translation technology, generating a corresponding magnitude of matrix suction in the soil sample 20. This simulates soil properties under different humidity and suction conditions, meeting the moisture measurement requirements under different suction conditions.

[0020] For example, the axial pressure loading range of the loading component 300 can be from 0 kPa to 5000 kPa, enabling the axial pressure to simulate the in-situ stress environment of deep strata up to 250 meters deep, meeting the research needs of projects such as deep foundation pits, high earth-rock dams, and deep-buried tunnels. Furthermore, the multi-level air pressure gradient sequence covers the water-holding characteristics of the soil, and the maximum axial pressure of the loading component 300 is greater than the maximum air pressure of the multi-level air pressure. For instance, when the soil sample 20 is cohesive soil, the multi-level air pressure gradient sequence can be: 0 kPa, 10 kPa, 20 kPa, 50 kPa, 100 kPa, 200 kPa, 400 kPa, 800 kPa, 1200 kPa, and 1500 kPa. The mechanical load of up to 5000 kPa can balance the maximum gas pressure of 1500 kPa within the mold cylinder 200, effectively preventing the piston from reverse-lifting due to high-pressure gas, ensuring stable high-pressure consolidation and shrinkage testing of the soil sample 20 throughout the entire suction range.

[0021] The opening at the bottom of the mold cylinder 200 is connected in sequence to the permeable component 400 and the metering component 500, so that the water seeping out of the soil sample 20 under pressure flows through the permeable component 400 and into the metering component 500. The metering component 500 is used to accurately capture the trace amount of seeping water. The high-precision water pressure sensor 510 monitors the water pressure in the metering component 500 in real time in order to determine the seeping water pressure and provide data support for subsequent calculation of drainage volume, volumetric water content and other parameters.

[0022] For example, the metering element 500 can be a graduated transparent glass tube. The material of the metering element 500 is high borosilicate, and the inner diameter of the metering element 500 is 6 mm to 10 mm. For example, the inner diameter of the metering element 500 is 6 mm, 8 mm, or 10 mm. The metering element 500 utilizes the geometric magnification effect to improve the resolution of liquid level changes in micro-drainage. The soil moisture measuring device 10 also includes a fixed bracket, on which the metering element 500 is vertically mounted. The bottom of the metering element 500 is provided with a T-joint 530. One end of the T-joint 530 is connected to the water inlet at the bottom of the metering element 500, one end is connected to the sensing end of the water pressure sensor 510, and the other end is connected to the water outlet 421 at the bottom of the permeable component 400 through a high-pressure resistant conduit 540.

[0023] The interplay of gradient air pressure and mechanical loads enables a realistic simulation of the in-situ environment of deep soil. While maintaining high soil suction, it effectively recreates the pore structure and water-holding characteristics of deep soil, improving the reliability of the measurement data. By tracking the dynamic changes in soil porosity and saturation under the coupled effects of stress and suction in real time, the moisture characteristics of soil under complex stress conditions can be accurately analyzed. Furthermore, the use of the 510 water pressure sensor achieves vibration-resistant precision measurement, significantly outperforming traditional horizontal scale tubes or electronic balances, thus enhancing the scientific rigor and accuracy of the data.

[0024] In some embodiments provided in this application, such as Figure 2 As shown, the loading component 300 includes a pressure plate 330, which is used to extend into the mold cylinder 200 to press the soil sample 20. The pressure plate 330 is provided with multiple ventilation holes, any one of which connects the top and bottom surfaces of the pressure plate 330. When the pressure plate 330 presses the soil sample 20, gas enters the ventilation hole and applies pressure to the soil sample 20.

[0025] In this embodiment, the pressure plate 330 is uniformly provided with multiple through-holes. When the pressure plate 330 is pressed against the surface of the soil sample 20, the gas input through the air inlet 220 can contact the soil sample 20 through the through-holes to apply air pressure to the surface of the soil sample 20. This ensures that under axial pressure, the gas can simultaneously act on the surface of the soil sample 20, and, in conjunction with axial translation technology, efficiently drive the water out of the soil sample 20. Furthermore, the dispersed through-holes allow the gas to penetrate evenly to all parts of the soil sample 20, avoiding differences in matrix suction distribution caused by uneven local air pressure and improving the uniformity of pressure application.

[0026] In some embodiments provided in this application, such as Figure 1 As shown, the loading assembly 300 further includes a first driving member 310 and a pressure rod 320. The first driving member 310 is disposed on the frame, and the two ends of the pressure rod 320 are respectively connected to the first driving member 310 and the pressure plate 330. The first driving member 310 is used to drive the pressure rod 320 to move axially along the mold cylinder 200. The frame is provided with a distance detection member 110, which is used to detect the movement distance of the pressure rod 320.

[0027] In this embodiment, the specific structure of the loading component 300 is provided. The first driving member 310 can be a high-rigidity precision servo electric cylinder or a precision hydraulic cylinder. The driving end of the first driving member 310 is connected to the pressure rod 320. The first driving member 310 is used to drive the pressure rod 320 to move axially downward, so as to drive the pressure plate 330 at the bottom of the pressure rod 320 to extend into the mold cylinder 200 and apply axial soil pressure to the soil sample 20. The first driving member 310 provides a stable and controllable axial driving force for the pressure rod 320 and the pressure plate 330, realizing the precise application of the preset pressure, replacing manual operation, and improving the accuracy and repeatability of pressure control. The distance detection member 110 monitors the axial displacement of the pressure rod 320 in real time, directly reflecting the height shrinkage of the soil sample 20 after being compressed, providing key data for calculating the volume shrinkage rate of the soil sample 20.

[0028] For example, the frame includes: a base plate 120, a mounting plate 150, a guide plate 140, and support columns 160. The number of support columns 160 can be four, with any one support column 160 passing through the guide plate 140, so that both ends of the support column 160 are connected to the base plate 120 and the mounting plate 150 respectively. A first driving member 310 is disposed on the top mounting plate 150. The guide plate 140 is connected to the pressure rod 320. When the pressure rod 320 moves up and down, it drives the guide plate 140 to slide along the support column 160. The guide plate 140 provides guidance for the movement of the pressure rod 320, making the axial movement of the pressure rod 320 smoother. The distance detection member 110 can be a grating ruler, possessing micron-level displacement resolution, and is used to detect the distance between the mounting plate 150 and the guide plate 140, thereby detecting the axial movement distance of the pressure rod 320.

[0029] For example, the soil moisture measuring device 10 also includes a control component 900, in which a water pressure sensor 510 and a distance detection element 110 transmit the detection data to the control component 900. The control component 900 includes an analysis module 950, which determines the drainage volume, volumetric water content, and volumetric shrinkage rate based on the drainage pressure and the sinking distance of the pressure plate 330.

[0030] For example, the soil moisture measuring device 10 also includes a high-precision pressure sensor 340, which is used to detect the axial pressure applied by the loading component 300. The control component 900 receives the axial pressure detected by the pressure sensor 340 and controls the operation of the first drive component 310 based on the PID (Proportional Integral Differential) algorithm. When soil sample 20 undergoes slight volume shrinkage under suction, leading to stress relaxation (e.g., axial deformation of soil sample 20 < 0.01 mm), pressure sensor 340 can immediately detect the slight pressure drop. Control component 900 supports pressure adjustment steps from 0.1 kPa to 1 kPa and drives first drive component 310 for flexible compensation with the minimum step size, controlling the fluctuation of overburden pressure on soil sample 20 within ±0.5%FS or ±1 kPa. The closed-loop control system formed by first drive component 310 and pressure sensor 340 applies constant axial pressure to soil sample 20 by pressure plate 330, avoiding the stress impact caused by traditional step loading methods that disturb the soil skeleton.

[0031] In some embodiments provided in this application, such as Figure 2 As shown, the soil moisture measuring device 10 also includes a sealing assembly 600, which includes a sealing ring 610 and a telescopic plate 620. The sealing ring 610 is located at the filling port 210, and the telescopic plate 620 is disposed on the inner side wall of the sealing ring 610. The telescopic plate 620 can extend and retract along the radial direction of the sealing ring 610. When the pressure plate 330 is at the height of the telescopic plate 620, the telescopic plate 620 retracts into the sealing ring 610. When the pressure plate 330 extends into the mold cylinder 200, the telescopic plate 620 extends out and seals the filling port 210.

[0032] In this embodiment, a sealing structure for the soil moisture measuring device 10 is provided. The sealing assembly 600 is a high-pressure resistant dynamic sealing assembly, and a sealing ring 610 is provided at the top of the mold cylinder 200. For example, the sealing ring 610 is a Glyd ring combination sealing structure. A telescopic plate 620 that can extend and retract radially is provided on the inner side of the sealing ring 610. When the pressure plate 330 is at the height of the telescopic plate 620, the telescopic plate 620 retracts radially outward into the sealing ring 610 to avoid the pressure plate 330. When the pressure plate 330 descends into the mold cylinder 200, the telescopic plate 620 extends radially inward and wraps around the outer periphery of the pressure rod 320 to seal the filling port 210, thereby sealing the high-pressure test chamber 240 and ensuring a stable air pressure environment. When the air inlet 220 applies air pressure into the mold cylinder 200, the sealing assembly 600 can prevent gas from leaking along the gap of the pressure rod 320, while allowing the pressure rod 320 to make small axial movements under PID control, ensuring the effective implementation of the axial translation technology and the smoothness of constant pressure control.

[0033] For example, the sealing assembly 600 also includes a wear-resistant guide sleeve 630, which is disposed on the top surface of the sealing ring 610. The wear-resistant guide sleeve 630 forms a limiting support for the top of the sealing ring 610 through its own rigid structure, preventing the sealing ring 610 from warping and deforming due to the air pressure inside the mold cylinder 200, improving the sealing reliability of the filling port 210, and avoiding air pressure leakage.

[0034] In some embodiments provided in this application, such as Figure 1 As shown, the measuring element 500 extends vertically, and the top of the measuring element 500 is provided with an exhaust hole 520. The soil moisture measuring device 10 also includes an exhaust pipe 700, the air inlet end of the exhaust pipe 700 is connected to the exhaust hole 520, and the exhaust pipe 700 is bent and extended so that the air outlet end of the exhaust pipe 700 faces the bottom of the measuring element 500.

[0035] In this embodiment, when the pore water discharged from the soil sample 20 enters the metering element 500, the tiny air bubbles entrained in the water float upwards under the action of buoyancy and are discharged through the vent 520 at the top. The vertically positioned metering element 500 uses buoyancy to automatically discharge the air bubbles, avoiding the "airlock" phenomenon that is very likely to occur in traditional horizontal pipelines, reducing airlock interference, and improving the accuracy of the measurement data. The vent pipe 700 is bent in the middle and the two ends face the same direction. For example, the vent pipe 700 can be a U-shaped pipe. While quickly expelling the air in the metering element 500, the vent pipe 700 prevents dust and impurities in the air from falling into the metering element 500 through the vent 520, thus avoiding affecting the accuracy of the test data.

[0036] In some embodiments provided in this application, such as Figure 1As shown, the side wall of the mold cylinder 200 is provided with an air extraction port 230, which is used to connect to a vacuum pumping device.

[0037] In this embodiment, the air extraction port 230 is connected to a vacuum pumping device. Before measurement, the control component 900 draws air into the mold cylinder 200 through the air extraction port 230 to perform a vacuum pumping operation, so that the high-pressure test chamber 240 forms a sealed vacuum chamber, the water permeable plate 410 achieves vacuum saturation, and ensures that the water permeable holes 411 of the water permeable plate 410 are filled with water and have an air blocking function.

[0038] In some embodiments provided in this application, such as Figure 3 As shown, the permeable component 400 includes: a permeable plate 410 and a water collection component 420. The permeable plate 410 is located at the bottom of the mold cylinder 200 and is used to support the soil sample 20. The permeable plate 410 is provided with permeable holes 411. The water collection component 420 is connected to the bottom surface of the permeable plate 410. The top of the water collection component 420 is connected to the permeable holes 411. The bottom of the water collection component 420 gradually narrows in the direction away from the permeable plate 410. The water outlet 421 is located at the bottom of the water collection component 420.

[0039] In this embodiment, an embedded layered structure of the permeable component 400 is provided. The permeable plate 410, while sealing the bottom opening of the mold cylinder 200, supports the soil sample 20. The permeable plate 410 has multiple through-holes 411, with both ends of the holes 411 connected to the high-pressure testing chamber 240 and the water collection component 420, respectively. The permeable plate 410 blocks the high-pressure gas inside the mold cylinder 200 while allowing pore water to pass through, allowing water seeping from the soil sample 20 to enter the water collection component 420 through the through-holes 411 and then enter the metering component 500 through the outlet 421 at the bottom of the water collection component 420. The bottom of the water collection component 420 gradually tapers into a cone shape, with the larger end of the water collection component 420 facing the soil sample 20. The conical surface inside the water collection component 420 uses gravity to collect the trace amounts of water discharged from the soil sample 20, preventing water from stagnating inside the water collection component 420 and improving drainage efficiency and metering accuracy.

[0040] For example, the permeable plate 410 can be a clay plate with a high air intake value. The air intake value of the permeable plate 410 is greater than or equal to the maximum gas pressure of the gas filled in the mold cylinder 200, so that the permeable plate 410 only allows pore water to drain out and prevents gas in the mold cylinder 200 from penetrating the permeable plate 410. For example, the air intake value of the permeable plate 410 is 15 bar.

[0041] Exemplarily, the permeable assembly 400 further includes a porous support plate and / or a sealing ring 430. The porous support plate is embedded in a recessed area on the top surface of the water collecting member 420, and the permeable plate 410 is disposed on the top surface of the porous support plate. The porous support plate provides mechanical support for the permeable plate 410, preventing it from rupturing under high pressure. The sealing ring 430 is located between the water collecting member 420 and the permeable plate 410 to prevent water leakage along the installation gap between the water collecting member 420 and the permeable plate 410. Alternatively, the sealing ring 430 is disposed on the contact surface between the permeable plate 410 and the mold cylinder 200 to prevent high-pressure gas leakage along the installation gap between the permeable plate 410 and the mold cylinder 200.

[0042] In some embodiments provided in this application, such as Figure 1 As shown, the soil moisture measuring device 10 also includes a second driving member 800, which is disposed on the frame and connected to the mold cylinder 200. The second driving member 800 is used to drive the mold cylinder 200 to move axially.

[0043] In this embodiment, the second driving component 800 can be an electric cylinder or a hydraulic cylinder. The driving end of the second driving component 800 is connected to the mold cylinder 200. The second driving component 800 drives the mold cylinder 200 to rise and fall axially, which can flexibly adjust the relative position of the mold cylinder 200, the pressure plate 330, and the permeable component 400. During the sample loading stage, the second driving component 800 drives the mold cylinder 200 to descend, reducing the height of the mold cylinder 200, so that the operator can easily embed the saturated permeable component 400 into the bottom of the mold cylinder 200, install the permeable plate 410, and fill the soil sample 20, which facilitates the filling of the soil sample 20 before the experiment. After the experiment, the second driving component 800 drives the mold cylinder 200 to rise, separating the mold cylinder 200 from the permeable component 400. The stationary pressure plate 330 easily pushes out the compacted soil sample 20, avoiding soil sample disturbance caused by sampling difficulties in traditional equipment, facilitating the demolding of the soil sample 20 after the experiment, and optimizing the operating experience.

[0044] For example, the frame also includes a lifting platform 130, which is slidably connected to the support column 160. A second drive member 800 is disposed on the mounting plate 150, and a mold cylinder 200 is disposed on the lifting platform 130. The second drive member 800 is connected to the mold cylinder 200 through the lifting platform 130.

[0045] A second aspect of this application provides a control method for a soil moisture measuring device, such as... Figure 5 As shown, the control method of this soil moisture measuring device utilizes the soil moisture measuring device provided in any of the above embodiments. The control method of the soil moisture measuring device includes: Step 1: Control the pressure plate to apply axial pressure to the soil sample inside the mold cylinder; Step 2: Inject gas into the mold cylinder step by step according to the pressure level of the pressure gradient sequence. After each level of gas injection and when the drainage of the soil sample reaches equilibrium, obtain the drainage pressure in the metering device and the sinking distance of the pressure plate until the gas injection of all levels of the pressure gradient sequence is completed. Step 3: Determine the drainage volume, volumetric water content, and volumetric shrinkage rate of the soil sample based on the drainage pressure and settlement distance under each pressure level.

[0046] In this embodiment, the control component applies a preset axial pressure to the soil sample using a pressure plate, and utilizes a pressure sensor for closed-loop control of the axial pressure to maintain a constant axial pressure throughout the measurement process, thereby simulating in-situ overburden pressure. Specifically, the control component determines the axial pressure based on the simulated depth of the soil sample to recreate the pore structure of the soil at different burial depths. For example, when the simulated depth is 5m underground, the axial pressure is 100kPa, and when the simulated depth is 200m underground, the axial pressure is 4000kPa.

[0047] The control unit inputs graded gas into the mold cylinder through the air inlet. The soil sample generates matrix suction under the axial translation technology, causing the water in the soil sample to be discharged into the metering device. The operator monitors the drainage process in real time through the metering device, and the air bubbles in the water flow float to the surface and are discharged due to buoyancy.

[0048] When the drainage of the soil sample meets the equilibrium condition, the control component determines the drainage pressure within the metering device and the sinking distance of the pressure plate under the current pressure level using a water pressure sensor and a distance detection device. Specifically, the water pressure sensor monitors changes in the hydrostatic pressure within the metering device; the water pressure and liquid level have a strictly linear relationship. The control component receives the water pressure data collected by the water pressure sensor and determines the drainage pressure under the current pressure as the difference between the water pressure of the soil sample in its initial state and after gas delivery. The distance detection device monitors the height of the pressure bar, which is correlated with the height of the soil sample. The control component receives changes in the height of the pressure bar collected by the distance detection device to determine the sinking distance of the pressure plate under the current pressure, and thus determine the total sinking distance of the soil sample.

[0049] For example, the equilibrium conditions include: within a preset time period, when the drainage rate of the permeable component remains below a drainage threshold, and / or the rate of change of the bar height remains below a deformation threshold, the drainage threshold and deformation threshold being determined based on the soil type. For instance, if for four consecutive hours the drainage rate of the permeable component is below 0.01 ml / h and the rate of change of the bar height is below 0.005 mm / h, the control component determines that the current air pressure level is in equilibrium and records the data.

[0050] The gas pressure follows a gradient sequence. After the control component completes the data acquisition of the current pressure level, it adjusts the gas pressure to the next level, repeating the gas delivery and measurement operations until all preset pressure levels are measured.

[0051] The control component calculates the drainage volume, volumetric water content, and volumetric shrinkage rate under any recorded sequence pressure and the sinking distance of the pressure plate, and plots and generates the soil sample moisture characteristic curve and shrinkage curve considering the effect of overburden pressure.

[0052] The control component is based on the principle of hydrostatics, and determines the drainage volume ΔV by the drainage pressure ΔP: ΔV = (ΔP / ρg) × S; Where S is the cross-sectional area of ​​the metering element, ρ is the density of water, and g is the acceleration due to gravity. The accuracy of the control component in calculating the drainage volume ΔV is 0.01 ml.

[0053] Because soil shrinks in volume under high pressure, the control component calculates the volumetric water content. and volume shrinkage rate At that time, a real-time volume correction was introduced, the specific formula of which is: ; ; in, This represents the initial water volume of the soil sample in its initial state. Determined by saturation weighing method. Let be the volume of water discharged when the i-th stage of air pressure is in equilibrium. The real-time height of the soil sample under the i-th pressure level is equal to the difference between the initial height of the soil sample in its initial state and the settlement distance under the i-th pressure level. A is the cross-sectional area of ​​the soil sample, i.e., the cross-sectional area of ​​the high-pressure test chamber of the mold. The denominator in the formula uses the real-time height of the soil sample instead of the initial height. Calculating the current volume of the soil sample using the real-time height avoids overestimating the calculated water content due to neglecting soil shrinkage, thus providing more rigorous test data for unsaturated soil mechanics research.

[0054] The control component determines the corrected SWCC (Soil Water Characteristic Curve) based on the volumetric water content of soil samples under all sequence pressures, revealing the soil sample's pore structure's ability to adsorb and retain water. This provides comprehensive data for the study of soil sample water transport patterns. By tracking the dynamic changes in soil void ratio and saturation under the coupling effect of stress and suction in real time, the water characteristics of soil under complex stress conditions can be accurately analyzed.

[0055] In some embodiments provided in this application, prior to step 1, the method further includes: Step 4: Fill the measuring device with water and vent air until water overflows from the surface of the soil sample; Step 5: Control the pressure plate to extend into the mold cylinder; Step 6: Perform a vacuuming operation inside the mold cylinder.

[0056] In this embodiment, preparatory work before measurement is provided. After the soil sample is filled onto the surface of the permeable component inside the mold cylinder, the operator or control component injects water into the measuring device until water overflows from the surface of the soil sample. After the operator or control component confirms that there are no obvious air bubbles in the measuring device, the water injection and air venting operations of the measuring device are completed. The water injection and air venting process can establish an initial continuous hydraulic connection, ensure that the pores of the soil sample are fully saturated, and eliminate the interference of air in the pipeline and initial pore air on the experiment.

[0057] The control component controls the pressure plate to extend downward into the mold cylinder, the sealing component seals the top of the mold cylinder, and the control component draws air into the mold cylinder through the air extraction port to perform a vacuum operation, so that the high-pressure test chamber forms a sealed vacuum chamber, the permeable plate achieves vacuum saturation, and ensures that the permeable holes of the permeable plate are filled with water and have an air-blocking function.

[0058] In this invention, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; the term "multiple" refers to two or more unless otherwise explicitly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0059] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or unit referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0060] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0061] The above are merely some embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A soil moisture measuring device, characterized in that, include: Frame; A mold cylinder is provided on the frame. The mold cylinder is used to hold soil samples. The top of the mold cylinder is provided with a filling port, and the side wall of the mold cylinder is provided with an air inlet. The air inlet is used to input gas into the mold cylinder. The pressure of the gas follows a gradient sequence. A loading component that can extend into the mold cylinder through the filling port and press the soil sample along the axial direction of the mold cylinder; A permeable component is connected to the bottom of the mold cylinder. The permeable component is used to collect water seeping out of the soil sample. The bottom of the permeable component is provided with a water outlet. The metering component has an inlet and a water pressure sensor at its bottom. The inlet is connected to the outlet, and the water pressure sensor is used to detect the water pressure inside the metering component.

2. The soil moisture measuring device according to claim 1, characterized in that, The loading component includes: A pressure plate is used to extend into the mold cylinder to press the soil sample. The pressure plate is provided with multiple ventilation holes, any one of which connects the top and bottom surfaces of the pressure plate. When the pressure plate presses the soil sample, the gas enters the ventilation hole and applies pressure to the soil sample.

3. The soil moisture measuring device according to claim 2, characterized in that, The loading component also includes: A first driving component is disposed on the frame; A pressure rod, the two ends of which are respectively connected to the first driving member and the pressure plate, the first driving member being used to drive the pressure rod to move along the axial direction of the mold cylinder; The frame is equipped with a distance detection device, which is used to detect the movement distance of the pressure rod.

4. The soil moisture measuring device according to claim 3, characterized in that, It also includes a sealing assembly, the sealing assembly comprising: A sealing ring is located at the packing inlet; A telescopic plate is disposed on the inner side wall of the sealing ring. The telescopic plate can move in a radial direction along the sealing ring. When the pressure plate is at the height of the telescopic plate, the telescopic plate retracts into the sealing ring. When the pressure plate extends into the mold cylinder, the telescopic plate extends out and seals the filling port.

5. The soil moisture measuring device according to any one of claims 1 to 4, characterized in that, The measuring element extends vertically, and a vent is provided at the top of the measuring element. The soil moisture measuring device further includes: An exhaust pipe, wherein the air inlet end of the exhaust pipe is connected to the exhaust port, and the exhaust pipe is bent and extended so that the air outlet end of the exhaust pipe faces the bottom of the metering element.

6. The soil moisture measuring device according to any one of claims 1 to 4, characterized in that, The side wall of the mold cylinder is provided with an air extraction port, which is used to connect to a vacuum pumping device.

7. The soil moisture measuring device according to any one of claims 1 to 4, characterized in that, The permeable component includes: A permeable plate is provided at the bottom of the mold cylinder. The permeable plate is used to support the soil sample and has permeable holes. A water collecting component is connected to the bottom surface of the permeable plate. The top of the water collecting component is connected to the permeable hole. The bottom of the water collecting component gradually narrows in the direction away from the permeable plate. The water outlet is located at the bottom of the water collecting component.

8. The soil moisture measuring device according to any one of claims 1 to 4, characterized in that, Also includes: A second driving member is disposed on the frame and connected to the mold cylinder. The second driving member is used to drive the mold cylinder to move axially.

9. A control method for a soil moisture measuring device, characterized in that, The control method using the soil moisture measuring device as described in any one of claims 1 to 8 includes: The pressure plate applies axial pressure to the soil sample inside the mold cylinder; Gas is injected into the mold cylinder step by step according to the pressure level of the pressure gradient sequence. After each level of gas injection and when the drainage of the soil sample reaches equilibrium, the drainage pressure in the metering device and the sinking distance of the pressure plate are obtained until the gas injection of all levels of the pressure gradient sequence is completed. Based on the drainage pressure and the sinking distance at each pressure level, the drainage volume, volumetric water content, and volumetric shrinkage rate of the soil sample are determined.

10. The control method for the soil moisture measuring device according to claim 9, characterized in that, Before the steps, it also includes: Water is injected and air is vented from the metering device until water overflows from the surface of the soil sample. Control the pressure plate to extend into the mold cylinder; A vacuum operation is performed inside the mold cylinder.

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