A test device for simulating the migration law of the vadose zone under different evaporation rates

Abstract

The present invention discloses a test device for simulating the migration law of the vadose zone under different evaporation amounts, including a test soil column and a surface soil tension regulating device; the surface soil tension regulating device includes a flange base, a porous medium ring that is water-permeable and airtight in the case of a water film, a negative pressure cavity arranged outside the porous medium ring, and a vacuum drainage device connected to the bottom low point of the negative pressure cavity, the vacuum degree of the negative pressure cavity is changed by the vacuum drainage device, thereby changing the soil tension of the soil inside the porous medium ring, causing the soil moisture in the soil column to migrate; the porous medium ring includes an inner porous protective ring, an outer porous protective ring and a porous medium clay ring sandwiched between the inner porous medium protective ring and the outer porous medium protective ring arranged on the flange base; the flange base is also provided with an annular shell forming a negative pressure cavity. The present invention changes the surface soil tension through the vacuum drainage device, controls the different upper and lower boundary tensions of the test soil body, and is equipped with a moisture real-time monitoring device to carry out the migration research of the soil body with different tension sections of the vadose zone.

Description

Technical Field

[0001] The present invention belongs to a hydraulic kinematics scientific research simulation test, and relates to a device for automatically and quickly simulating surface evaporation and monitoring the upward replenishment movement and process of soil water in a soil vadose zone environment, and specifically to a test device for simulating the migration law of the vadose zone under different evaporation amounts. Background Art

[0002] The soil vadose zone is also called the unsaturated zone. The main energy for the movement of soil water in the vadose zone depends on the soil pore tension. In the natural vadose zone environment, the reason for the upward recharge of soil water or groundwater is the evaporation of surface soil water, which produces pore tension in the topsoil. The water in the soil below the topsoil moves upward under the suction of the surface pore tension, and there is a hydraulic conduction process of water migration in the entire soil layer. The study of water migration in the soil vadose zone is of great significance to the water replenishment of shallow crops, the migration of solutes in shallow soil, and the process of soil salinization. In current scientific research experiments, conventional monitoring of water migration in the vadose zone mainly includes two methods: indoor soil column simulated evaporation monitoring and long-term monitoring of natural evaporation processes in the field. In both methods, the conventional means of indoor soil column simulated evaporation changes the soil tension of the soil surface by increasing the surface temperature to simulate the acceleration of surface evaporation, and then monitors the upward migration and recharge process of soil water through the changes in soil moisture data buried in the soil column. The main means of monitoring the vadose zone in the field is to rely on the natural evaporation of the topsoil to generate a tension difference with the lower soil layer, so that the water in the lower soil layer can be replenished upwards, and the soil water supply process can be monitored by the changes in soil moisture data buried in the field soil. Both methods are time-consuming and cannot directly and quickly monitor the movement of the soil vadose zone in real time or simulated throughout the process. Researchers need to invest a lot of experimental tracking time to find the law of water migration under different surface tension conditions. Summary of the invention

[0003] The purpose of the present invention is to provide a test device for simulating the migration law of the vadose zone under different evaporation amounts. By directly changing the topsoil tension and realizing adjustable tension, the vadose zone migration related laws can be quickly simulated under different surface natural evaporation conditions. The device can also connect several unit soil columns through a flange structure to form a higher large soil column, control the different upper and lower boundary tensions of the test soil body, and carry out the migration study of the soil body with different tension sections of the vadose zone. The water infiltrated in the surface soil tension regulating device that wraps the surface soil is extracted by a vacuum pump to quickly and directly change the surface soil tension, simulating the natural evaporation of the topsoil. The soil moisture sensor buried at the lower end of the surface soil tension regulating device monitors the upward replenishment movement of soil water in the soil vadose zone caused by the surface tension change. The device can be suitable for indoor experimental soil columns to study the upward replenishment law of soil water under the soil vadose zone, and is also suitable for field vadose zone monitoring simulation control.

[0004] To solve this problem, the technical solution adopted by the present invention is as follows:

[0005] As shown in the figure, the present invention provides a test device for simulating the migration law of the vadose zone under different evaporation amounts, including a test soil column and a surface soil tension adjusting device arranged at the top of the test soil column for changing the surface test soil tension in the top of the test soil column;

[0006] The surface soil tension regulating device comprises a porous medium ring which is arranged inside and in contact with the test soil and is water-permeable but air-permeable in the presence of a water film, a negative pressure cavity arranged outside the porous medium ring, and a vacuum drainage device connected to the lowest point at the bottom of the negative pressure cavity. The vacuum degree of the negative pressure cavity is changed by the vacuum drainage device, thereby changing the soil tension of the soil inside the porous medium ring.

[0007] In this embodiment, the surface soil tension adjustment device also includes a flange base connected to the top of the test soil column, and the porous medium ring includes an inner porous protective ring, an outer porous protective ring and a porous medium clay ring sandwiched between the inner and outer porous protective rings arranged on the flange base. The porous medium clay ring is permeable to water but not to air in the presence of a water film (a commonly used material in the field of soil tension and infiltration migration, such as the clay material described in CN107064243B); an annular shell forming a negative pressure cavity is also provided on the flange base outside the outer porous protective ring.

[0008] The present invention changes the vacuum degree of the negative pressure cavity through a vacuum drainage device, changes the soil tension of the soil inside the porous medium ring, and thus changes the surface test soil tension in the top of the test soil column to simulate the migration law test of the vadose zone under different evaporation amounts.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] 1. By utilizing the porous ceramic ring's porous medium's water-permeable but air-impermeable property within -100kpa in the presence of a water film, the negative pressure inside the ring can be quickly extracted, thereby directly changing the soil moisture migration on all contact surfaces of the ceramic ring. After the water is discharged, the surface soil tension changes and quickly drives the soil water in the soil column to replenish upward, greatly improving the efficiency of observing and monitoring the soil water migration in the vadose zone.

[0011] 2. The height of the porous ceramic ring is customized to 5cm and the entire 5cm soil on the surface can simulate the 5cm balanced negative pressure environment of the surface soil, which can simulate a close to real natural process.

[0012] 3. The installation structure of the soil moisture sensor of the soil column main body of the present invention is changed, and a detachable cavity is adopted. The sensor chip part is arranged in the cavity, and only the stainless steel probe is in the test soil body. This solves the problem of avoiding the water-passing section of the entire sensor in the soil column due to its large volume affecting the actual soil moisture migration, while improving the service life of the sensor and the convenience of the test.

[0013] 4. The base of the surface soil tension regulating device is a flange structure, which is convenient for disassembly and movement. The surface soil tension regulating device can be taken to the field alone to simulate and control the surface soil tension of the original soil to carry out the original soil test.

[0014] 5. The test soil column of the present invention combines the control of the groundwater depth at the lower boundary of the soil, can simulate the groundwater level at the lower boundary of the soil, soil water monitoring, and surface water negative pressure control tension conditions, forming a new and complete soil water migration simulation device. It provides a new idea for simulation and observation experiments for the research system of vadose zone migration. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The figure is a schematic diagram of the structure of the test device for simulating the migration law of the vadose zone under different evaporation amounts according to the present invention.

[0016] Figure 2 Schematic diagram of the structure of the surface soil tension adjustment device in an embodiment of the present invention.

[0017] Figure 3 It is a three-dimensional schematic diagram of a partial cutaway of the surface soil tension regulating device in an embodiment of the present invention.

[0018] Figure 4 It is a schematic diagram of the structure of the test device of the multi-section soil column body in an embodiment of the present invention.

[0019] 100-test soil column, 101-soil column body, 102-soil column base, 103-porous diverter plate, 104-water supply interface at the bottom of soil column, 105-soil moisture sensor, 106-soil moisture automatic collector, 107-flange sleeve, 108-water supply pipe, 200-surface soil tension adjustment device, 210-porous medium ring, 211-inner porous protection ring, 212-outer porous protection ring, 213-porous medium clay ring, 220-negative pressure cavity, 221-vacuum gauge, 230-vacuum drainage device, 231-negative pressure water bottle, 232-vacuum pump, 240-flange base, 241-annular drainage groove, 242-drainage hole, 243-flange hole, 250-annular shell, 260-annular cover. DETAILED DESCRIPTION

[0020] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0021] In the description of the present invention, it should be noted that this device is not limited to the size or structure of the device, and has a protective effect on those who use this simulation concept and method.

[0022] like Figures 1 to 3As shown, the present invention provides a test device for simulating the migration law of the vadose zone under different evaporation amounts, including a test soil column 100 and a surface soil tension adjusting device 200 disposed at the top of the test soil column 100 for changing the surface test soil tension in the top of the test soil column 100;

[0023] like Figure 2 and Figure 3 As shown, the surface soil tension regulating device 200 includes a porous medium ring 210 which is arranged inside and in contact with the test soil and is water-permeable but air-permeable in the presence of a water film, a negative pressure cavity 220 arranged outside the porous medium ring 210, and a vacuum drainage device 230 connected to the lowest point at the bottom of the negative pressure cavity 220. The vacuum degree of the negative pressure cavity 220 is changed by the vacuum drainage device 230, thereby changing the soil tension of the soil inside the porous medium ring 210.

[0024] In this embodiment, the surface soil tension adjustment device 200 also includes a flange base 240 connected to the top of the test soil column 100, and the porous medium ring 210 includes an inner porous protection ring 211, an outer porous protection ring 212 and a porous medium clay ring 213 sandwiched between the inner and outer porous protection rings 212. Both the inner and outer porous protection rings 212 can be made of stainless steel to provide pressure protection for the porous medium clay ring 213; the porous medium clay ring 213 is permeable to water but not to air in the presence of a water film (a commonly used material in the field of soil tension and infiltration migration, such as the clay material recorded in CN107064243B); an annular shell 250 for forming a negative pressure cavity 220 is also provided on the flange base 240 outside the outer porous protection ring 212.

[0025] When in use, install the test soil column 100, install the surface soil tension regulating device 200 on the top of the test soil column 100, and then continue to fill the soil in the surface soil tension regulating device 200 according to the same rule, inject water into the test soil column 100, and after the porous medium ring 210 of the surface soil tension regulating device 200 is moistened, start the vacuum drainage device 230, change the vacuum degree of the negative pressure cavity 220, and then simulate the migration law of the vadose zone under different evaporation amounts.

[0026] As a preferred embodiment, Figure 3As shown, the annular shell 250 includes a cylindrical shell arranged on the outer flange base 240 of the outer porous protective ring 212 and an annular cover plate 260 arranged on the top of the cylindrical shell. The annular shell 250 can be made of stainless steel as a protective shell. The annular cover plate 260 is fixed between the top of the annular shell 250 and the inner porous protective ring 211, so as to form a negative pressure cavity 220 with good sealing performance between the annular shell 250 and the outer porous protective ring 212, so as to facilitate the adjustment of the vacuum degree of the negative pressure cavity 220, thereby achieving the purpose of conveniently adjusting the soil tension of the soil inside the porous medium ring 210.

[0027] As a preferred embodiment, the porous medium clay ring 213 is 5 cm high, which can simulate a 5 cm thick soil tension uniform body as much as possible. Similarly, the inner and outer porous protection rings 212 are also protection bodies with a height of 5 cm.

[0028] As a preferred embodiment, Figure 3 As shown, an annular drainage groove 241 is arranged on the flange base 240 in the negative pressure cavity 220 area, and the vacuum drainage device 230 is connected to the annular drainage groove 241 through a pipeline. The water that penetrates through the porous medium clay ring 213 can be quickly drained through the annular drainage groove 241.

[0029] As a preferred embodiment, Figure 3 As shown, the annular drainage groove 241 has a V-shaped cross-section and is provided with a plurality of drainage holes 242 connected to the vacuum drainage device 230 through pipes. The drainage holes 242 are evenly distributed on the annular drainage groove 241, which is more conducive to drainage and prevents water from gathering in the annular drainage groove 241.

[0030] As a preferred embodiment, Figure 1 and Figure 2 As shown, the vacuum drainage device 230 includes a negative pressure pump and a negative pressure water bottle 231 (the existing technology can be used, the specific structure has no effect on the technical problem solved by the present invention, so it will not be repeated), and the negative pressure pump, the negative pressure water bottle 231 and the drainage hole 242 at the bottom of the negative pressure cavity 220 are connected in sequence through pipes.

[0031] As a preferred embodiment, a vacuum gauge 221 is provided on the negative pressure cavity 220 to facilitate real-time monitoring of the vacuum degree of the negative pressure cavity 220 .

[0032] As a preferred embodiment, the test soil column 100 includes a soil column body 101 and a soil column base 102, the soil column body 101 is fixed on the soil column base 102, the soil column base 102 is provided with a soil column bottom water supply interface 104 leading to the soil column body 101, and the soil column body 101 above the soil column bottom water supply interface 104 is provided with a porous diversion plate 103, which can simulate the uniform and stable infiltration of groundwater from the bottom.

[0033] As a preferred embodiment, the water supply interface 104 at the bottom of the soil column is processed into a tapered shape, which can supply water from the bottom to control different groundwater levels during testing or drain the leaking water in the soil after infiltration occurs in the soil column.

[0034] The soil column body 101 above the porous diverter plate 103 is equipped with several soil moisture sensors 105 through a flange sleeve 107. For example, a CS655 / TDR315 soil moisture sensor can be used. The multiple soil moisture sensors 105 collect data through an automatic soil moisture collector 106, which can monitor and record the changes in moisture in each layer and the moisture migration process in real time.

[0035] When testing the migration law of the air-filled zone, water is injected into the soil column main body 101 through the water supply interface 104 at the bottom of the soil column. The water is dispersed through the porous diverter plate 103 and migrates upward evenly. The soil moisture in each part of the soil column main body 101 is measured through the soil moisture sensor 105.

[0036] As a preferred embodiment, a flange sleeve 107 is provided at the sensor installation position of the side wall of the soil column body 101, and the sensor probe is inserted and buried in the soil of the soil column. The sensor circuit measurement part is detachably installed in the flange sleeve 107, which solves the problem that the original soil column test sensor is buried as a whole in the soil column, and the water-passing cross-section is too large, which affects the natural soil water flow direction. At the same time, it solves the problem that the sensor is buried in the soil for a long time, and the sensor fails after water and soil enter the sensor, and the scientific research test cannot be continued without disturbing the test soil.

[0037] As a preferred embodiment, Figure 4 As shown, the soil column main body 101 has multiple sections, and a surface soil tension regulating device 200 is provided on the top of each section of the soil column main body 101. Except for the soil column main body 101 at the bottom, only a plurality of soil moisture sensors 105 are provided in the other soil column main bodies 101. The different upper and lower boundary tensions of the test soil are controlled by multiple surface soil tension regulating devices 200, and the real-time moisture monitoring equipment is used to carry out the migration research of different tension sections of the soil in the air-filling zone.

[0038] The multi-section soil column main body 101 can also be connected through flanges to form a soil column with a higher scale to study the simulated migration in a thick aeration zone environment.

[0039] The present invention also provides a specific test method for simulating the migration law of the vadose zone under different evaporation rates, and the specific steps are as follows:

[0040] exist Figure 1 In the figure, the soil column body 101 is an organic glass soil column with an inner diameter of 280 mm and a height of 550 mm. A soil column base 102 of matching size is installed underneath, and a water supply interface 104 at the bottom of the soil column is installed under the soil column base 102; a porous diverter plate 103 with a height of 5 cm is installed at the bottom of the soil column body 101, and then the soil is backfilled into the test soil column 100 in layers according to the bulk density of the test soil. When backfilling to the installation position of the buried soil moisture sensor 105 (5 cm, 15 cm, 25 cm, 35 cm, 45 cm, 65 cm below the surface soil of the organic glass soil column), while backfilling the soil, the CS655 / TDR315 soil moisture sensor is detachably inserted into the soil column body 101 through the flange-type sleeve flange preset on the side wall of the organic glass soil column, and the test soil in the soil column is fully in contact with the CS655 / TDR315 soil moisture sensor.

[0041] After the test soil in the soil column body 101 is backfilled, the top is connected and fixed with the surface soil tension adjustment device 200 by flange screws; after the porous medium ring 210 of the surface soil tension adjustment device 200 is moistened, the porous medium ring 210 is backfilled according to the soil bulk density specified in the test soil column 100. After the soil is backfilled, the negative pressure water bottle 231 is connected to the negative pressure cavity 220, and the vacuum pump 232 is connected to the negative pressure water bottle 231. The vacuum pump 232 is turned on and the corresponding soil surface negative pressure value interval is adjusted to extract the moisture of the surface soil. The surface soil water is discharged outward under negative pressure, thereby changing the soil tension of the surface soil, so that the soil moisture in the soil column is replenished upward, and the surface soil moisture sensor 105 is connected to the soil moisture automatic collector 106CR1000X data and automatically collects soil moisture data after power is turned on.

[0042] After the simulation is completed, the data automatically stored in the data logger and the surface pressure control data are provided to scientific researchers to analyze relevant operating rules.

[0043] When high evaporation is required to be simulated or a segmented simulation test is required, multiple soil column bodies 101 can be stacked up, and a surface soil tension adjustment device 200 is set on the top of each soil column body 101 to perform segmented simulation tests on the migration law of the vadose zone under different evaporation rates.

[0044] The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that various combinations, modifications or equivalent substitutions of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and should be included in the scope of the claims of the present invention.

Claims

1. A test device for simulating the migration law of the vadose zone under different evaporation rates, characterized by: It comprises a test soil column and a surface soil tension adjusting device arranged at the top of the test soil column and used for changing the surface test soil tension in the top of the test soil column; The surface soil tension regulating device comprises a porous medium ring which is arranged inside and in contact with the test soil and is water-permeable but air-permeable in the presence of a water film, a negative pressure cavity arranged outside the porous medium ring, and a vacuum drainage device connected to the lowest point at the bottom of the negative pressure cavity, and the vacuum degree of the negative pressure cavity is changed by the vacuum drainage device, thereby changing the soil tension of the soil inside the porous medium ring; The surface soil tension adjustment device also includes a flange base connected to the top of the test soil column, the porous medium ring includes an inner porous protection ring, an outer porous protection ring and a porous medium clay ring sandwiched between the inner and outer porous protection rings arranged on the flange base, the porous medium clay ring is water-permeable but air-permeable in the presence of a water film; an annular shell forming a negative pressure cavity is also provided on the flange base outside the outer porous protection ring.

2. The test device for simulating the migration law of the vadose zone under different evaporation rates according to claim 1, characterized in that: The annular shell comprises a cylindrical shell arranged on a flange base outside an outer porous protective ring and an annular cover plate arranged on the top of the cylindrical shell.

3. The test device for simulating the migration law of the vadose zone under different evaporation rates according to claim 1, characterized in that: An annular drainage groove is provided on the flange base in the negative pressure cavity area, and the vacuum drainage device is connected to the annular drainage groove through a pipeline.

4. The test device for simulating the migration law of the vadose zone under different evaporation rates according to claim 3, characterized in that: The annular drainage groove has a V-shaped cross section and is provided with a plurality of drainage holes connected to the vacuum drainage device through pipelines. The drainage holes are evenly distributed on the annular drainage groove.

5. The test device for simulating the migration law of the vadose zone under different evaporation rates according to any one of claims 1 to 4, characterized in that: The vacuum drainage device comprises a negative pressure pump and a negative pressure water collection bottle, and the negative pressure pump, the negative pressure water collection bottle and the lowest point at the bottom of the negative pressure cavity are connected in sequence through pipelines.

6. The test device for simulating the migration law of the vadose zone under different evaporation rates according to claim 5, characterized in that: A vacuum gauge is provided on the negative pressure cavity.

7. The test device for simulating the migration law of the vadose zone under different evaporation rates according to claim 5, characterized in that: The test soil column includes a soil column body and a soil column base, wherein the soil column body is fixed on the soil column base, a soil column bottom water supply interface leading to the soil column body is arranged in the soil column base, a porous diverter plate is arranged in the soil column body above the soil column bottom water supply interface, and a plurality of soil moisture sensors detachably installed through flange sleeves are arranged in the soil column body above the porous diverter plate.

8. The test device for simulating the migration law of the vadose zone under different evaporation rates according to claim 7, characterized in that: The soil column body has multiple sections, and a surface soil tension adjustment device is provided on the top of each section of the soil column body, or multiple sections of the soil column body are connected by flanges to form a soil column with a higher scale to study the simulated migration of the thick aeration zone environment; except for the soil column body at the bottom, only a number of soil moisture sensors are arranged in the remaining soil column bodies.

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