An experimental apparatus and method for monitoring capillary ribbon thickness

Abstract

The present application relates to experimental device and method for monitoring capillary zone thickness, the device includes sand column and water level adjusting mechanism, the inside of sand column is provided with partition, sand column is provided with sand column water inlet and sand column drain on it; Sand column is provided with a plurality of pressure water head monitoring holes and a plurality of moisture content monitoring holes;The water level adjusting unit includes container, the container is provided with container water inlet, container water outlet and sand column water supply opening connected by pipeline sand column water inlet;The device of the present application can measure the maximum capillary rise height of different soils through drainage experiment, since the drainage of sandy soil is not instantaneous and has certain hysteresis, therefore, the present application can also observe the dynamic change of unsaturated zone soil moisture profile with groundwater level fluctuation by the driving of external periodic water head;The device can be used for the mechanism research of the influence of inland river flow water level sudden rise on groundwater level and the interaction of coastal groundwater and ocean.

Description

Technical Field

[0001] This invention relates to the field of water pollution control technology, and more specifically, to an experimental apparatus and method for monitoring capillary thickness. Background Technology

[0002] Currently, researchers have discovered that capillary bands have a significant impact on groundwater hydraulic transport and solute transport. The presence of capillary bands causes fluctuations in groundwater levels and the migration of pollutants between saturated and unsaturated zones, which differs significantly from traditional models and understandings. Therefore, research on capillary bands has become a hot topic. However, research on the definition of the upper boundary of capillary bands, the measurement of capillary band thickness, and the variation of capillary band thickness with groundwater level is still not very complete. Capillary band thickness and its variation with groundwater level are difficult to measure; therefore, relevant equipment is needed to assist in the research.

[0003] Indoor sand column apparatus has always been an indispensable piece of equipment in hydrodynamic and water pollution experiments. The water content of the unsaturated zone exhibits a hysteresis loop, and its characteristics differ from those of the pressure head in the saturated zone. Therefore, it is highly significant to consider the changes in parameters of both the saturated and unsaturated zones during groundwater level fluctuations. Traditional sand column experiments primarily focus on observing changes in groundwater level. While water content observations are also conducted, research on the dynamic changes in capillary thickness across the entire soil profile with groundwater level is relatively limited. Therefore, this invention designs an experimental device and method for monitoring capillary thickness to meet the needs of this field. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an experimental device for monitoring capillary thickness, and a research method for monitoring dynamic thickness changes and maximum capillary rise height using the device, in order to address the above-mentioned deficiencies of the prior art.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] An experimental device for monitoring capillary thickness is constructed, comprising a sand column and a water level regulating mechanism for regulating the water level inside the sand column. The sand column is equipped with a baffle that allows water to pass through and blocks sand. The baffle divides the internal space of the sand column into a sand-filled seepage zone at the top and a water-storage zone at the bottom.

[0007] The sand column is equipped with a sand column inlet with a valve for introducing water into the water storage area and a sand column outlet with a valve for draining water from the water storage area.

[0008] The sand column is equipped with multiple pressure head monitoring holes of different heights for pressure head monitoring and multiple moisture content monitoring holes of different heights for moisture content monitoring.

[0009] The water level regulating unit includes a container, which is provided with a container inlet, a container outlet, and a sand column inlet connected to the sand column inlet via a pipe.

[0010] The experimental apparatus for monitoring capillary thickness according to the present invention includes a container with a partition that divides the container into two horizontally distributed compartments; one compartment has a container inlet and a sand column outlet, and the other compartment has a container outlet; the upper parts of the two compartments are connected, and the height of the connection is lower than the lowest height of the container opening.

[0011] The experimental apparatus for monitoring capillary thickness according to the present invention further includes a Z-axis displacement platform that drives the sand column to rise and fall.

[0012] The experimental apparatus for monitoring capillary thickness according to the present invention includes one or more through holes and a mesh covering the through holes on the partition plate.

[0013] The experimental apparatus for monitoring capillary thickness according to the present invention includes a pressure head measuring instrument connected to the pressure head monitoring hole.

[0014] The experimental apparatus for monitoring capillary thickness according to the present invention includes a moisture content monitoring hole connected to a moisture content detector.

[0015] The experimental apparatus for monitoring capillary thickness according to the present invention comprises a plurality of pressure head monitoring holes linearly distributed on the sand column.

[0016] The experimental apparatus for monitoring capillary thickness according to the present invention comprises a plurality of moisture content monitoring holes linearly distributed on the sand column.

[0017] An experimental method for monitoring capillary thickness, using the aforementioned experimental apparatus for monitoring capillary thickness, is implemented as follows:

[0018] Adjust the height and position of the sand column according to the required water level elevation for the experiment, and adjust the height and position of the container so that the bottom height of the container is consistent with the required water level in the sand column;

[0019] The sand column drain outlet is kept closed, and water is introduced into the container. The water enters the sand column through the pipe and the sand column inlet.

[0020] Once the water level inside the sand column reaches the required height, stop filling the container with water. Add sand medium to the sand column's sand-filled seepage zone. The sand will naturally settle to the bottom with the water. The height of the water-bearing medium layer must be less than the water level.

[0021] Connect the pressure head measuring instrument to the pressure head monitoring hole, and connect the moisture content measuring instrument to the moisture content monitoring hole. Once the reading stabilizes, close the sand column inlet.

[0022] Record the water level inside the sand column and the thickness of the aquifer medium. Then, at regular intervals, take a certain amount of water from the sand column's drainage outlet and record it.

[0023] Repeat the previous step until the water level drops below the surface elevation of the medium, and then perform multiple samplings.

[0024] The maximum capillary rise height and water yield of the sandy soil medium were obtained by using the linear correlation between the pressure head monitoring hole and the water content monitoring hole and the corresponding water intake during the sampling process.

[0025] An experimental method for monitoring capillary thickness, using the experimental apparatus for monitoring capillary thickness as described above, is implemented as follows:

[0026] Adjust the height and position of the sand column according to the required water level elevation for the experiment, and adjust the height and position of the container so that the bottom height of the container is consistent with the required water level in the sand column;

[0027] The sand column drain outlet is kept closed, and water is introduced into the container. The water enters the sand column through the pipe and the sand column inlet.

[0028] Once the water level inside the sand column reaches the required height, stop filling the container with water. Add sand medium to the sand column's sand-filled seepage zone. The sand will naturally settle to the bottom with the water. The height of the water-bearing medium layer must be less than the water level.

[0029] Connect the pressure head measuring instrument to the pressure head monitoring hole, and connect the moisture content measuring instrument to the moisture content monitoring hole;

[0030] The height of the sand column can be adjusted to switch between drainage and wetting states for the internal sand, and the interval between the drainage and wetting processes is not less than the set time.

[0031] Data was continuously recorded from the pressure head monitoring well and the water content monitoring well during the process of the water level changing from the lowest point to the initial position within the sand column.

[0032] The beneficial effects of this invention are as follows: This invention can not only measure the maximum capillary rise height of various sands and soils, but also set different fluctuation rates, amplitudes and periods according to actual needs to observe the dynamic changes in capillary thickness when the groundwater level fluctuates, providing a research basis for exploring the influencing factors of the dynamic changes in capillary thickness, and also providing a data foundation for numerical models.

[0033] This invention not only considers the changes in pressure head in the saturated zone under the influence of capillary bands during groundwater level fluctuations, but also the dynamic changes in soil moisture content profiles in the unsaturated zone. It more intuitively demonstrates the variation law of capillary band thickness above the water table during groundwater level fluctuations, providing a new research method for the physical mechanism of groundwater level fluctuations. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort:

[0035] Figure 1 This is a schematic diagram of the sand column structure of the experimental device for monitoring capillary thickness according to a preferred embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the water level adjustment mechanism of the experimental device for monitoring capillary thickness according to a preferred embodiment of the present invention.

[0037] Figure 3 This is a schematic diagram of the Z-axis displacement platform structure of the experimental device for monitoring capillary thickness according to a preferred embodiment of the present invention;

[0038] Figure 4 This is a flowchart of an experimental method for monitoring capillary thickness according to a preferred embodiment of the present invention;

[0039] Figure 5 This is an experimental result diagram of the maximum capillary rise height of an experimental method for monitoring capillary thickness according to a preferred embodiment of the present invention.

[0040] Figure 6 This is a flowchart of a second experimental method for monitoring capillary thickness according to a preferred embodiment of the present invention;

[0041] Figure 7 This is a schematic diagram illustrating the changes in groundwater level and soil profile moisture content during the groundwater level decline process of experimental method two for monitoring capillary thickness, which is a preferred embodiment of the present invention.

[0042] Figure 8This is a schematic diagram illustrating the changes in groundwater level and soil profile moisture content during the groundwater level rise process of experimental method two for monitoring capillary thickness, which is a preferred embodiment of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, a clear and complete description will be provided below in conjunction with the technical solutions in the embodiments of the present invention. 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 protection scope of the present invention.

[0044] The experimental apparatus for monitoring capillary thickness according to a preferred embodiment of the present invention, such as... Figure 1 As shown, see also Figure 2 and Figure 3 It includes a sand column and a water level regulating mechanism for regulating the water level inside the sand column. The sand column is equipped with a baffle 10 that allows water to pass through and blocks sand. The baffle 10 divides the internal space of the sand column into a sand-filling seepage zone 7 located at the top and a water storage zone 8 located at the bottom.

[0045] The sand column is equipped with a sand column inlet 9a with a valve for water intake into the water storage area 8 and a sand column outlet 9b with a valve for water drainage into the water storage area.

[0046] The sand column is equipped with multiple pressure head monitoring holes 5 of different heights for pressure head monitoring and multiple moisture content monitoring holes 6 of different heights for moisture content monitoring;

[0047] The water level regulating unit includes a container, which is provided with a container inlet 12, a container outlet 11b, and a sand column inlet 11a connected to the sand column inlet by a pipe.

[0048] This invention can not only measure the maximum capillary rise height of various sands, but also set different fluctuation rates, amplitudes and periods according to actual needs to observe the dynamic changes in capillary thickness when the groundwater level fluctuates. It provides a research basis for exploring the influencing factors of the dynamic changes in capillary thickness and can also provide a data foundation for numerical models.

[0049] This invention not only considers the changes in pressure head in the saturated zone under the influence of capillary bands during groundwater level fluctuations, but also the dynamic changes in soil moisture content profiles in the unsaturated zone. It more intuitively demonstrates the variation law of capillary band thickness above the water table during groundwater level fluctuations, providing a new research method for the physical mechanism of groundwater level fluctuations.

[0050] Preferably, the sand column is made of acrylic material, with an inner diameter of 15cm and a height of 110cm. The height of the sand-filled seepage zone is 100cm, and the height of the water storage zone is 10cm. Scales are marked on the 110cm side of the entire column.

[0051] The medium used to fill the sand seepage zone is generally fine sand, medium sand, or coarse sand. The specific filling medium should be based on the simulated actual site. It should be noted that the maximum capillary rise height of sand varies greatly depending on the particle size. For example, the maximum capillary rise height of fine sand with a particle size of 0.2 mm is about 55 cm, while the maximum capillary rise height of coarse sand with a particle size of 1 mm is about 11 cm.

[0052] Preferred, such as Figure 2 As shown, the container is provided with a partition 13, which divides the container into two horizontally distributed compartments; one compartment is provided with a container inlet 12 and a sand column inlet 11a, and the other compartment is provided with a container outlet 12; the upper parts of the two compartments are connected, and the height of the connection is lower than the lowest height of the container opening; the container inlet 12 can be connected to a water pipe or a peristaltic pump to provide a water source;

[0053] With this structure, a certain liquid level can be maintained in the compartment with the container inlet 12 and the sand column inlet 11a, so as to complete the experimental steps of water level rise and fall in the sand column based on the principle of communicating vessels. When the liquid level exceeds the separator 13, the water can be automatically drained into another compartment for buffering or discharge. Of course, it is understood that this structure is not intended to limit the structure of the water level adjustment mechanism, and there can be other water level adjustment methods.

[0054] Preferably, the device also includes a Z-axis displacement platform that drives the sand column to rise and fall. The function of the platform is to drive the sand column to rise and fall. It can be manual, automatic, or a combination of both, all of which can achieve the testing purpose.

[0055] A better Z-axis displacement platform, such as Figure 3 As shown, the Z-axis displacement platform includes a sand column mounting component 1, an electric Z-axis displacement platform that drives the sand column mounting component 1 to rise and fall, a manual Z-axis displacement platform 4 that drives the electric Z-axis displacement platform to rise and fall, and a mounting frame 3 for mounting the manual Z-axis displacement platform; of course, it is understood that this structure is not intended to limit the platform structure, and there may be other lifting methods.

[0056] Preferably, the partition 10 is provided with one or more through holes and a mesh covering the through holes to achieve the purpose of allowing water to pass through and blocking sand; of course, it is understood that this structure is not the only structure, and other existing structures with this function can be used as replacements.

[0057] Preferably, the pressure head monitoring hole is connected to a pressure head measuring instrument, and the moisture content monitoring hole is connected to a moisture content detector.

[0058] Preferably, three pressure head monitoring holes 5 are distributed on the left side of the sand-filled seepage zone 7. The holes are 1 cm in diameter and threaded, with the mesh partition 10 as the zero potential surface. The heights from bottom to top are 5 cm, 10 cm, and 15 cm. Fourteen moisture content monitoring holes 6 are distributed on the right side of the sand-filled seepage zone 7. The holes are 2 cm in diameter and threaded, with the mesh partition 10 as the zero potential surface. The heights from bottom to top are 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, 55 cm, 60 cm, 65 cm, 70 cm, 75 cm, 80 cm, 85 cm, 90 cm, and 95 cm. Of course, it is understood that the above dimensions are only illustrative examples and are not intended to limit the scope. Those skilled in the art can adjust them according to the actual situation.

[0059] An experimental method for monitoring capillary thickness, such as Figure 4 As shown, the experimental apparatus for monitoring capillary thickness described above is implemented as follows:

[0060] S01: Adjust the height and position of the sand column according to the required water level elevation for the experiment, and adjust the height and position of the container so that the bottom height inside is consistent with the required water level inside the sand column;

[0061] S02: Keep the sand column drain closed and allow water to enter the container. Water enters the sand column through the pipe and the sand column inlet.

[0062] S03: Stop filling the container with water when the water level inside the sand column reaches the required water level. Add sand medium to the sand-filled seepage zone of the sand column. The sand will naturally settle to the bottom with the water. The height of the water-bearing medium layer must be less than the water level.

[0063] S04: Connect the pressure head measuring instrument to the pressure head monitoring hole, connect the moisture content measuring instrument to the moisture content monitoring hole, and close the sand column inlet after the reading stabilizes.

[0064] S05: Record the height of the water level inside the sand column and the thickness of the aquifer medium, and then take out a certain amount of water from the sand column drainage outlet at regular intervals and record it.

[0065] S06: Repeat the previous step until the water level drops below the surface elevation of the medium, and then perform multiple samplings;

[0066] S07: The maximum capillary rise height and water yield of sandy soil media are obtained based on the linear correlation between the pressure head monitoring hole and the water content monitoring hole and the corresponding water intake during the sampling process.

[0067] More specific implementation methods:

[0068] (1) Adjust the manual z-axis displacement platform 4 according to the water level elevation required for the experiment, and adjust the height of the container so that the bottom height is consistent with the required water level in the sand column.

[0069] (2) Connect the sand column inlet 9a to the sand column inlet 11a of the water level regulating device, connect the water level regulating device inlet (12) to the faucet, and connect the water level regulating device outlet 11b to the empty water tank. Ensure that the water valve of the sand column outlet 9b is closed, and then open the water pipe to inject water into it.

[0070] (3) After the water level reaches the required height and stabilizes for a period of time, the water pipe is closed. Then, the medium that meets the actual requirements is added to the sand-filled seepage zone 7 of the sand column, so that the sand settles naturally to the bottom with the water. Note that the thickness of the aquifer medium should not exceed the water level height controlled by the manual z-axis displacement platform. In this case, the surface height of the aquifer is 93.7cm and the initial water level height is 95.8cm.

[0071] (4) Connect the pressure head measuring instrument to the pressure head monitoring hole 5, and then connect the moisture content measuring instrument to the moisture content monitoring hole 6. After the reading stabilizes, close the water valve and tap of the sand column inlet 9a.

[0072] (5) Record the height of the water level inside the sand column and the thickness of the aquifer medium. Then, use a graduated cylinder to take a certain amount of water from the sand column drainage outlet 9b at regular intervals and record it. After recording, pour out the water in the graduated cylinder. Repeat this process until the groundwater level drops below the surface elevation of the medium. After about twenty more samplings, stop. Based on the linear correlation between the pressure head monitoring hole 5 and the water content monitoring hole 6 and the corresponding water intake during the sampling process, the maximum capillary rise height and specific yield of the soil used can be analyzed. The results are as follows: Figure 5 As shown;

[0073] (6) During the gradual decline of the groundwater level, the readings of pressure head monitoring well 5 showed changes in three stages, among which:

[0074] In the first stage, when the water level inside the sand column is greater than the thickness of the aquifer, as the water intake gradually increases, the reading of the pressure head monitoring hole 5 gradually decreases, and the slope of the linear relationship between the cumulative water intake and the ratio of the cross-sectional area of ​​the sand column and the pressure head monitoring results is 1.

[0075] In the second stage, when the water level inside the sand column is close to the thickness of the aquifer, as the water intake gradually increases, the reading of the pressure head monitoring hole 5 decreases sharply. The slope of the linear relationship between the sum of water intake and the ratio of the cross-sectional area of ​​the sand column and the pressure head monitoring results is generally greater than 30.

[0076] In the third stage, when the water level inside the sand column drops below the surface of the medium and the pressure head no longer changes drastically as in the second stage, as the water intake gradually increases, the rate of decrease in the reading of the pressure head monitoring hole 5 is between the first and second stages. The slope of the linear relationship between the cumulative water intake and the ratio of the cross-sectional area of ​​the sand column and the pressure head monitoring results is generally between 1 and 30.

[0077] The trend of moisture content change is similar to that of pressure head, but with a significant lag. The maximum rise height of the capillary band can be determined based on the vertical distance in the second stage, while the reciprocal of the slope of the fitted line in the third stage is the specific water yield of the soil used.

[0078] An experimental method for monitoring capillary thickness, such as Figure 6 As shown, the experimental apparatus for monitoring capillary thickness, as described above, is implemented as follows:

[0079] S11: Adjust the height and position of the sand column according to the required water level elevation for the experiment, and adjust the height and position of the container so that the bottom height inside is consistent with the required water level inside the sand column;

[0080] S12: Keep the sand column drain closed and allow water to enter the container. Water enters the sand column through the pipe and the sand column inlet.

[0081] S13: Stop filling the container with water when the water level inside the sand column reaches the required height. Add sand medium to the sand-filled seepage zone of the sand column. The sand will naturally settle to the bottom with the water. The height of the water-bearing medium layer must be less than the water level.

[0082] S14: Connect the pressure head measuring instrument to the pressure head monitoring hole, and connect the moisture content measuring instrument to the moisture content monitoring hole;

[0083] S15: Adjust the height of the sand column to switch between drainage and wetting states for the internal sand, and the interval between the drainage and wetting processes shall not be less than the set time.

[0084] S16: Continuously record data from the pressure head monitoring hole and the water content monitoring hole during the process of the water level in the sand column changing from the lowest point to the initial position;

[0085] More specific implementation methods:

[0086] (1) Adjust the manual z-axis displacement platform 4 according to the water level elevation required for the experiment, and adjust the height of the container so that the bottom height is consistent with the required water level in the sand column.

[0087] (2) Set the program on the controller in advance according to the water level fluctuation range required for the experiment, and connect it to the electric z-axis displacement platform 2;

[0088] (3) Connect the sand column inlet 9a to the sand column inlet 11a of the water level regulating device, connect the water level regulating device inlet 12 to the faucet, and connect the water level regulating device outlet 11b to the empty water tank. Ensure that the water valve of the sand column outlet 9b is closed, and then open the water pipe to inject water into it.

[0089] (4) After the water level reaches the required height and stabilizes for a period of time, the water pipe is closed. Then, the medium that meets the actual requirements is added to the sand-filled seepage zone 7 of the sand column, so that the sand settles naturally to the bottom with the water. Note that the thickness of the aquifer medium should not exceed the water level height controlled by the manual z-axis displacement platform.

[0090] (5) Set the movement program of the electric z-axis displacement platform 2 through the controller. There should be a ten-minute interval between the drainage process and the wetting process to ensure that the unsaturated soil moisture content profiles of the two stages are more distinct. The water level fluctuation and relevant experimental parameters are shown in Table 1.

[0091] Table 1. Parameters of the water level fluctuation experiment

[0092]

[0093] (6) Start the controller to let the water level of the electric z-axis displacement platform 2 drop first, then wait for ten minutes at the lowest point, and then raise the water level back to the initial water level. During this period, data is continuously recorded through the pressure head monitoring hole 5 and the moisture content monitoring hole 6. The obtained data can not only observe the changes in soil moisture characteristics during the soil drainage and wetting process, but also observe the dynamic changes in the moisture content of the unsaturated zone and the thickness of the capillary zone. The experimental parameters are shown in Table 2 and Table 3, where t is the ratio of the actual time to the period, i.e. dimensionless time.

[0094] Table 2. Soil moisture content at different locations during the groundwater level drop.

[0095]

[0096] Table 3. Soil moisture content at different locations during the groundwater level rise process.

[0097]

[0098]

[0099] (7) Based on Tables 2 and 3 and the changes in groundwater level measured by pressure head, a profile of groundwater level height and soil moisture content at a certain moment can be observed, and the results are as follows: Figure 7 (Changes in groundwater level and soil moisture content during groundwater level decline) Figure 8As shown in the figure (changes in groundwater level and soil profile moisture content during groundwater level rise), it is worth noting that the moisture content in the figure is the ratio of the measured actual value to the saturated moisture content. By analyzing the height of the groundwater level and the height at which saturated or near-saturated profiles are generated at different times, the change in capillary thickness with groundwater level fluctuations is observed. This provides some new ideas and insights for numerical simulation as well as groundwater hydrodynamic transport and solute transport.

[0100] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An experimental method for monitoring capillary thickness, the method being based on an experimental apparatus for monitoring capillary thickness, characterized in that, The device includes a sand column and a water level regulating mechanism for regulating the water level inside the sand column. The sand column is equipped with a baffle that allows water to pass through and blocks sand. The baffle divides the internal space of the sand column into a sand-filling seepage zone at the top and a water storage zone at the bottom. The sand column is equipped with a sand column inlet with a valve for introducing water into the water storage area and a sand column outlet with a valve for draining water from the water storage area. The sand column is equipped with multiple pressure head monitoring holes of different heights for pressure head monitoring and multiple moisture content monitoring holes of different heights for moisture content monitoring. The water level regulating unit includes a container, which is provided with a container inlet, a container outlet, and a sand column inlet connected to the sand column inlet by a pipe. The experimental method can be either Method 1 or Method 2; Method 1: Adjust the height and position of the sand column according to the required water level elevation for the experiment, and adjust the height and position of the container so that the bottom height of the container is consistent with the required water level in the sand column; The sand column drain outlet is kept closed, and water is introduced into the container. The water enters the sand column through the pipe and the sand column inlet. Once the water level inside the sand column reaches the required height, stop filling the container with water. Add sand medium to the sand column's sand-filled seepage zone. The sand will naturally settle to the bottom with the water. The height of the water-bearing medium layer must be less than the water level. Connect the pressure head measuring instrument to the pressure head monitoring hole, and connect the moisture content measuring instrument to the moisture content monitoring hole. Once the reading stabilizes, close the sand column inlet. Record the water level inside the sand column and the thickness of the aquifer medium. Then, at regular intervals, take a certain amount of water from the sand column's drainage outlet and record it. Repeat the previous step until the water level drops below the surface elevation of the medium, and then perform multiple samplings. The maximum capillary rise height and water yield of the sandy soil medium were obtained by the linear correlation between the pressure head monitoring hole and the water content monitoring hole and the corresponding water intake during the sampling process. Method 2: Adjust the height and position of the sand column according to the required water level elevation for the experiment, and adjust the height and position of the container so that the bottom height of the container is consistent with the required water level in the sand column; The sand column drain outlet is kept closed, and water is introduced into the container. The water enters the sand column through the pipe and the sand column inlet. Once the water level inside the sand column reaches the required height, stop filling the container with water. Add sand medium to the sand column's sand-filled seepage zone. The sand will naturally settle to the bottom with the water. The height of the water-bearing medium layer must be less than the water level. Connect the pressure head measuring instrument to the pressure head monitoring hole, and connect the moisture content measuring instrument to the moisture content monitoring hole; The height of the sand column can be adjusted to switch between drainage and wetting states for the internal sand, and the interval between the drainage and wetting processes is not less than the set time. Data was continuously recorded from the pressure head monitoring well and the water content monitoring well during the process of the water level changing from the lowest point to the initial position within the sand column.

2. The experimental method for monitoring capillary thickness according to claim 1, characterized in that, The container is provided with a partition that divides the container into two horizontally distributed compartments; one of the compartments is provided with the container inlet and the sand column inlet, and the other is provided with the container outlet; the upper parts of the two compartments are connected, and the height of the connection is lower than the minimum height of the container opening.

3. The experimental method for monitoring capillary thickness according to claim 1, characterized in that, The device also includes a Z-axis displacement platform that drives the sand column to rise and fall.

4. The experimental method for monitoring capillary thickness according to claim 1, characterized in that, The partition is provided with one or more through holes and a mesh covering the through holes.

5. The experimental method for monitoring capillary thickness according to claim 1, characterized in that, The pressure head monitoring hole is connected to a pressure head measuring instrument.

6. The experimental method for monitoring capillary thickness according to claim 1, characterized in that, The moisture content monitoring hole is connected to a moisture content detector.

7. The experimental method for monitoring capillary thickness according to any one of claims 1-6, characterized in that, The multiple pressure head monitoring holes are linearly distributed on the sand column.

8. The experimental method for monitoring capillary thickness according to any one of claims 1-6, characterized in that, The multiple moisture content monitoring holes are linearly distributed on the sand column.

Images