CN110927038B - Testing device and testing method for soil body soil-water characteristic curve and permeability coefficient test - Google Patents
Testing device and testing method for soil body soil-water characteristic curve and permeability coefficient test Download PDFInfo
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 120
- 239000002689 soil Substances 0.000 title claims abstract description 69
- 238000012360 testing method Methods 0.000 title claims abstract description 56
- 230000035699 permeability Effects 0.000 title claims abstract description 25
- 238000006073 displacement reaction Methods 0.000 claims abstract description 14
- 239000011148 porous material Substances 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 9
- 238000010998 test method Methods 0.000 claims abstract description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 32
- 239000004927 clay Substances 0.000 claims description 20
- 238000003860 storage Methods 0.000 claims description 18
- 229910052742 iron Inorganic materials 0.000 claims description 16
- 239000011159 matrix material Substances 0.000 claims description 16
- 238000009991 scouring Methods 0.000 claims description 11
- 239000011521 glass Substances 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 10
- 229910000831 Steel Inorganic materials 0.000 claims description 9
- 230000008859 change Effects 0.000 claims description 9
- 239000010959 steel Substances 0.000 claims description 9
- 238000003825 pressing Methods 0.000 claims description 5
- 238000007789 sealing Methods 0.000 claims description 4
- 239000007799 cork Substances 0.000 claims description 3
- 238000009738 saturating Methods 0.000 claims description 2
- 238000010521 absorption reaction Methods 0.000 claims 1
- 238000005259 measurement Methods 0.000 abstract description 5
- 238000011010 flushing procedure Methods 0.000 abstract description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 230000008569 process Effects 0.000 description 5
- 238000004891 communication Methods 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 238000011160 research Methods 0.000 description 2
- 239000004575 stone Substances 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000007596 consolidation process Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
- G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
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Abstract
本发明公开了一种测量土体土水特征曲线以及渗透系数的试验装置及试验方法。包括压力室、用于对压力室施加围压和轴力的气压加载系统、量测系统、水头平衡装置、非饱和土底座气体冲刷系统。压力室及底座部分是测量系统的主体，量测系统包括轴力传感器，轴向位移传感器，吸力传感器、反压饱和器以及智能电子天平。本装置结构简洁明了，易于操作，制作成本低廉，使用寿命长，能同时测试土体土水特征曲线及渗透系数，而且本装置可以同时模拟干化路径和湿化路径进行土水特征曲线测试，可以完全排除土体内部孔隙连通程度对土体的力学性质的影响。相比于传统的土水特征曲线测试仪器，本发明装置测得曲线误差更小，精度更高。
The invention discloses a test device and a test method for measuring the soil-water characteristic curve and permeability coefficient of soil. It includes a pressure chamber, a pneumatic loading system for applying confining pressure and axial force to the pressure chamber, a measurement system, a water head balance device, and a gas flushing system for an unsaturated soil base. The pressure chamber and the base part are the main body of the measurement system. The measurement system includes an axial force sensor, an axial displacement sensor, a suction force sensor, a back pressure saturator and an intelligent electronic balance. The device is simple and clear in structure, easy to operate, low in production cost, and has a long service life. It can simultaneously test the soil-water characteristic curve and permeability coefficient of the soil, and the device can simulate the drying path and the humidification path to test the soil-water characteristic curve at the same time. The influence of the degree of pore connectivity inside the soil on the mechanical properties of the soil can be completely excluded. Compared with the traditional soil-water characteristic curve testing instrument, the device of the present invention has smaller error and higher precision in the measured curve.
Description
Technical Field
The invention relates to a hydraulic parameter measuring device in the technical field of geotechnical engineering, in particular to an indoor test device for a permeability coefficient of roadbed polluted soil and a soil-water characteristic curve.
Background
In the process of constructing the roadbed, the roadbed is generally compacted under the optimal moisture content to reach the maximum dry density; under the maximum dry density, the used roadbed soil has the maximum compactness and bearing capacity; however, in the actual service process of the roadbed, the moisture content in the foundation can change gradually along with the time due to the influences of weather, underground water, capillary action and the like; the change of the water content can cause the change of the suction inside the soil body, reduce the bearing capacity of the soil body, increase the subgrade settlement and cause the early failure of the subgrade; the size of the permeability coefficient plays a key role in solving the problems of the dissipation rate of the pore water pressure in the soil body, the multiphase flow of the pore medium and the like; therefore, the determination of soil body hydraulic parameters has very important significance in unsaturated soil research and engineering practice.
Currently, most of the measurements for soil-water characteristic curves are measured on a drying path (the water content is gradually reduced and the substrate suction is gradually increased in the measurement process). In actual conditions, due to rainfall and evaporation, the change of the water content (matrix suction) in the soil body is not a single drying path or a humidifying path (the water content is increased in the measuring process, and the matrix suction is gradually reduced); therefore, an instrument is needed to be developed, and soil and water characteristic curves under the history of complex matrix suction can be measured;
disclosure of Invention
The invention aims to provide a soil-water characteristic curve and permeability coefficient combined test instrument which is simple in structure and easy to operate, and can accurately measure the soil-water characteristic curve and permeability coefficient of a soil body under the complex matrix suction history, especially for coarse-grained polluted soil.
The invention aims to realize the test device for testing the soil-water characteristic curve and the permeability coefficient of the soil body by the following technical means, and the test device comprises a pressure chamber, an air pressure loading system, a measuring system, a water head balancing device and an unsaturated soil base air scouring system, wherein the air pressure loading system is used for applying confining pressure and axial force to the pressure chamber;
the pressure chamber comprises a top cover, a pressure chamber base and a cylinder body fixed between the top cover and the pressure chamber base, wherein the pressure chamber base consists of a clay plate and a steel plate arranged below the clay plate; the top cover is provided with a through hole, and the water head balancing device is connected into the pressure chamber through the through hole on the top cover; the height of the water head balancing device is higher than that of the pressure chamber; a plurality of through holes are formed in the circumference of the pressure chamber base; the pressure chamber and the base are main bodies of the equipment, the experimental object is arranged in the pressure chamber and is connected with the argil plate base, and the argil plate can control the substrate suction force in the sample.
The air pressure loading system comprises an air pressure loading device, an iron rod fixedly connected with the air pressure loading device, a pressing plate and an air pressure controller for controlling the air pressure loading device to pressurize; the bottom end of the iron rod vertically penetrates through the center of the top cover and is fixedly connected with a pressure plate positioned in the pressure chamber; the diameter of the pressure plate is matched with the diameter of the cylinder body of the pressure chamber. The air pressure loading system can be used for further consolidation after soil body compaction, and simulating the hydraulic characteristics of the soil body at different depths and under different stress histories.
The measuring system comprises an axial force sensor, an axial displacement sensor, a suction sensor, a back pressure saturator and an intelligent electronic balance. The axial force sensor and the axial displacement sensor are arranged on the iron rod, and the suction sensor is fixed on the top cover of the pressure chamber; the back pressure saturator and the unsaturated soil base gas scouring system are connected with the through hole on the pressure chamber base; the intelligent electronic balance is used for measuring the flow rate of the permeability coefficient or the change of the water content in the soil body under the condition of suction change.
Furthermore, the device also comprises a loading frame for fixing the device, the pressure chamber is placed on a base of the loading frame, the top end of the iron rod penetrates through a cross beam of the loading frame and is fixedly connected with the air pressure loading device, and the air pressure loading device is fixed on the cross beam of the loading frame.
Furthermore, the device also comprises a data acquisition instrument and a computer, wherein the axial force sensor, the axial displacement sensor, the suction sensor, the back pressure saturator and the intelligent electronic balance are connected with a data input port of the data acquisition instrument, and an output port of the data acquisition instrument is connected with the computer.
Further, the water head balancing device comprises a closed water storage tank and an open water storage tank; the closed water storage tank is provided with a glass tube which vertically penetrates into the water of the closed water storage tank, and the top end of the glass tube is plugged by a cork; the closed water storage tank is connected with the open water storage tank through a pipeline; the water level in the open water storage tank is equal to the position of the bottom of the glass tube in the closed water storage tank.
A soil-water characteristic curve test method of the test device comprises the following steps:
preparing a sample: compacting soil in a circular steel cylinder with the same size as the pressure chamber in a layering mode by using a wet-tamping method to reach required compactness, and dismantling the steel cylinder;
sample loading: the pottery clay plate on the base of the saturation pressure chamber is provided with permeable stones and samples in sequence, the outer part of the pottery clay plate is sleeved with a cylinder of the pressure chamber, and the cylinder is covered with a top cover and sealed:
simulating a stress path: applying axial stress through an air pressure loading system according to test requirements;
and (3) testing a soil-water characteristic curve: the pore water pressure and the pore air pressure in the soil body are respectively adjusted through the back pressure saturator and the air pressure loading system, so that the target matrix suction value is achieved. Recording the change of the water volume in the back pressure saturator after the suction of the soil matrix is balanced; and calculating the water content under the suction force of the corresponding matrix according to the initial state of the sample and the water inlet and outlet amount. Measuring the water content of the sample under different matrix suction forces to obtain a soil-water characteristic curve of a soil body; and sequentially testing soil-water characteristic curves under two conditions of a drying path and a humidifying path. When the next suction value test is carried out, firstly, the clay plate is scoured by the unsaturated soil base scouring system;
a permeability coefficient testing method of the testing device specifically comprises the following steps:
removing the clay plate on the base of the pressure chamber, preparing a sample, and then placing the sample into the pressure chamber and sealing the sample; and (3) connecting the water head balancing device with the through hole on the top cover, adjusting the height of the water head, and calculating the water content and the permeability coefficient inside the soil body by utilizing the Darcy law when the water inflow and the water drainage inside the soil body are balanced.
The invention has the beneficial effects that: (1) the device has the advantages of simple and clear structure, easy operation, low manufacturing cost, long service life and various functions, can simultaneously test soil body soil-water characteristic curves and permeability coefficients, improves the permeability coefficient or soil-water characteristic curve under the condition that the previous permeability test can only simulate a single stress path, and can simulate and measure the soil-water characteristic curves and the permeability coefficients under the condition of a complex stress path. (2) The device can simulate the drying path and the humidifying path to test the soil-water characteristic curve, and can completely eliminate the influence of the internal pore communication degree of the soil body on the mechanical property of the soil body. Compared with the traditional soil-water characteristic curve testing instrument, the device disclosed by the invention has the advantages that the measured curve error is smaller and the precision is higher.
Drawings
FIG. 1 is a diagram of soil-water characteristic curves and permeability coefficient testing device under different stress paths. In the figure, the soil body loading system comprises: the device comprises a loading frame 1, an iron rod 2, an air pressure loading device 3 and an air pressure controller 4; the device comprises a pressure chamber 5, a through hole 6, a pressure chamber base 7, a pressure plate 8, an unsaturated soil base flushing system 9, an axial force sensor 10, an axial displacement sensor 11, a suction sensor 12 and a back pressure saturator 13; a computer 14 and a data acquisition instrument 15; a closed reservoir 16, an open reservoir 17, a pipe 18, a glass tube 19.
Fig. 2 is a top view of a clay plate base.
FIG. 3 is an overall assembly view of the test apparatus of the present invention.
FIG. 4 is a soil-water characteristic curve measured by the testing device of the present invention.
Detailed Description
As shown in fig. 1 and 3, a testing apparatus for testing soil-water characteristic curve and permeability coefficient of soil body comprises a pressure chamber 5, an air pressure loading system for applying confining pressure and axial force to the pressure chamber 5, a measuring system, a water head balancing device for adjusting the height of a water head, and an unsaturated soil base air scouring system; the unsaturated soil base gas scouring system is used for scouring unsaturated soil base gas to keep the interior of the pottery clay plate saturated.
The pressure chamber 5 comprises a top cover, a pressure chamber base 7 and a cylinder body fixed between the top cover and the pressure chamber base 7, wherein the pressure chamber base 7 consists of a clay plate and a steel plate arranged below the clay plate, and is shown in figure 2; wherein the clay plate is used for loading suction force; the top cover is provided with a through hole, and the water head balancing device is connected into the pressure chamber 5 through the through hole on the top cover; the height of the water head balancing device is higher than that of the pressure chamber 5; a plurality of through holes 6 are arranged on the circumference of the pressure chamber base 7;
the air pressure loading system comprises an air pressure loading device 3, an iron rod 2 fixedly connected with the air pressure loading device 3, a pressing plate 8 and an air pressure controller 4 for controlling the air pressure loading device 3 to pressurize; the air pressure loading device 3 is also communicated with the pressure chamber 5 through a pipeline, and the air pressure controller 4 comprises two control valves, wherein one control valve is used for controlling the air pressure loading device 3 to apply axial force, and the other control valve is used for controlling air pressure to be introduced into the pressure chamber 5 to apply confining pressure. The bottom end of the iron rod 2 vertically penetrates through the center of the top cover and is fixedly connected with a pressing plate 8 positioned in the pressure chamber 5; the diameter of the pressure plate 8 matches the diameter of the cylinder of the pressure chamber 5.
The measuring system comprises an axial force sensor 10, an axial displacement sensor 11, a suction sensor 12, a back pressure saturator 13 and an intelligent electronic balance. The axial force sensor 10 is arranged on the iron rod 2, and the axial force sensor 10 is used for measuring the axial pressure applied to the sample; the axial displacement sensor 11 is arranged on the iron rod 2, the top of the axial displacement sensor is connected with the top of the pressure chamber 5, and the displacement of the iron rod 2 can be measured through the axial displacement sensor after the iron rod 2 moves up and down; the suction sensor 12 is fixed on the top cover of the pressure chamber 5 and is connected with the inside of the sample through an air pipe; the back pressure saturator 13, the intelligent electronic balance and the unsaturated soil base gas scouring system are connected with the through hole 6 on the pressure chamber base 7; wherein, the water intake and discharge amount of the sample in the test process is recorded by the back pressure saturator 13, and the water content of the soil body under a certain suction force is calculated by measuring the mass of discharged and absorbed water;
the water head balancing device structure comprises a closed water storage tank 16 and an open water storage tank 17; the closed water storage tank 16 is provided with a glass tube 19 vertically penetrating into the water of the closed water storage tank 16, and the top end of the glass tube 19 is plugged by a cork; the closed water storage tank 16 is connected with the open water storage tank 17 through a pipeline 18; the level of water in the open reservoir 17 is equal to the position of the bottom of the glass tube in the closed reservoir 16.
Preferably, the device also comprises a load carrier 1 for fixing the device, the pressure chamber 5 is placed on the base of the load carrier 1, the top end of the iron rod 2 penetrates through the cross beam of the load carrier 1 to be fixedly connected with the air pressure loading device 3, and the air pressure loading device 3 is fixed on the cross beam of the load carrier 1, so that the air pressure loading system can apply axial force to the pressure chamber 5.
In addition, the device also comprises a data acquisition instrument 15 and a computer 14, the axial force sensor 10, the axial displacement sensor 11, the suction sensor 11, the back pressure saturator 13 and the intelligent electronic balance are connected with a data input port of the data acquisition instrument 15, and an output port of the data acquisition instrument 15 is connected with the computer 14, so that data acquisition and data processing are facilitated.
The test device has various functions, can be used for testing soil body soil water characteristic curves and soil body permeability coefficients, and the method for testing the soil body soil water characteristic curves comprises the following steps:
(1) preparing a sample: compacting the soil body in a circular steel cylinder with the same size as the pressure chamber 5 in a layering mode by a wet-tamping method to the required compactness, and dismantling the steel cylinder;
(2) sample loading: and (3) saturating the clay plate on the pressure chamber base 7, and controlling the back pressure saturator 13 to continuously apply back pressure until water beads seeped on the surface of the clay plate completely cover the clay plate to discharge air bubbles in the clay plate. And placing permeable stone and a sample on the clay plate in sequence, sleeving a cylinder body of a pressure chamber on the outside, covering a top cover and sealing:
(3) simulating a stress path: applying axial stress through an air pressure loading system according to test requirements;
(4) and (3) testing a soil-water characteristic curve: the pore water pressure and the pore air pressure in the soil body are respectively adjusted through the back pressure saturator 13 and the air pressure loading system, so that the target matrix suction value is achieved. Recording the change of the volume of water in the back pressure saturator 13 after the suction of the soil matrix is balanced; and calculating the water content under the suction force of the corresponding matrix according to the initial state of the sample and the water inlet and outlet amount. Measuring the water content of the sample under different matrix suction forces to obtain a soil-water characteristic curve of a soil body; and sequentially testing soil-water characteristic curves under two conditions of a drying path and a humidifying path. When the next suction value test is carried out, the argil plate is firstly washed by the unsaturated soil base washing system 9;
through the counter-pressure saturator, when the soil-water characteristic curve is tested, the test device can saturate a sample firstly, then starts to drain water, resets the counter-pressure saturator to start to absorb water after being discharged to a certain degree, and simultaneously simulates a drying path and a humidifying path, so that the soil-water characteristic measuring instrument can research the water holding characteristic and permeability of a soil body under a complex substrate suction historical condition.
The measured curves are shown in fig. 4, and it can be seen that the curves measured by the digestion path and the humidification path are not completely consistent, the difference between the two curves can reflect the pore communication degree in the soil body, and the size of the two curves has great influence on the mechanical property of the soil body. Along with the increase of the test times, the difference is gradually reduced, and after the test for the third time, the difference is basically superposed, so that the influence of the communication degree of the pores in the soil body on the mechanical property of the soil body can be completely eliminated. Compared with the traditional soil-water characteristic curve testing instrument, the device disclosed by the invention has the advantages that the measured curve error is smaller and the precision is higher.
In addition, the permeability coefficient testing method of the testing device specifically comprises the following steps:
removing the clay plate on the pressure chamber base 7, preparing a sample, placing the sample into the pressure chamber 5 and sealing; the water head balance device is connected with the through hole in the top cover and adjusted to be at a proper water head height, when water inflow and drainage inside the soil body reach balance, the flow rate of water is obtained through the intelligent electronic balance, and the water content and the permeability coefficient inside the soil body are calculated by utilizing the Darcy law.
Claims (6)
1. A test device for testing soil-water characteristic curves and permeability coefficients of soil bodies is characterized by comprising a pressure chamber (5), an air pressure loading system, a measuring system, a water head balancing device and an unsaturated soil base air scouring system (9), wherein the air pressure loading system is used for applying confining pressure and axial force to the pressure chamber (5);
the pressure chamber (5) comprises a top cover, a pressure chamber base (7) and a cylinder body fixed between the top cover and the pressure chamber base (7), wherein the pressure chamber base (7) consists of a clay plate and a steel plate arranged below the clay plate; the top cover is provided with a through hole, and the water head balancing device is connected into the pressure chamber (5) through the through hole on the top cover; the height of the water head balancing device is higher than that of the pressure chamber (5); a plurality of through holes (6) are arranged on the circumference of the pressure chamber base (7);
the air pressure loading system comprises an air pressure loading device (3), an iron rod (2) fixedly connected with the air pressure loading device (3), a pressing plate (8) and an air pressure controller (4) for controlling the air pressure loading device (3) to pressurize; the bottom end of the iron rod (2) vertically penetrates through the center of the top cover and is fixedly connected with a pressing plate (8) positioned inside the pressure chamber (5); the diameter of the pressure plate (8) is matched with the diameter of the cylinder of the pressure chamber (5);
the measuring system comprises an axial force sensor (10), an axial displacement sensor (11), a suction sensor (12), a back pressure saturator (13) and an intelligent electronic balance; an axial force sensor (10) and an axial displacement sensor (11) are arranged on the iron rod (2), and a suction sensor (12) is fixed on a top cover of the pressure chamber (5); the back pressure saturator (13) and the unsaturated soil base gas scouring system (9) are connected with the through hole (6) on the pressure chamber base (7);
the back pressure saturator (13) is used for saturating the sample, then draining water, resetting the back pressure saturator to start water absorption after draining to a certain degree, and simulating a drying path and a humidifying path.
2. The test device according to claim 1, further comprising a loading frame (1) for fixing the device, wherein the pressure chamber (5) is placed on the base of the loading frame (1), the top end of the iron rod (2) penetrates through the cross beam of the loading frame (1) and is fixedly connected with the air pressure loading device (3), and the air pressure loading device (3) is fixed on the cross beam of the loading frame (1).
3. The testing device according to claim 1, characterized by further comprising a data acquisition instrument (15) and a computer (14), wherein the axial force sensor (10), the axial displacement sensor (11), the suction sensor (12), the counter pressure saturator (13) and the intelligent electronic balance are connected with a data input port of the data acquisition instrument (15), and an output port of the data acquisition instrument (15) is connected with the computer (14).
4. Testing device according to claim 1, characterized in that the head balancing device comprises a closed reservoir (16), an open reservoir (17); the closed water storage tank (16) is provided with a glass tube (19) which vertically penetrates into the water of the closed water storage tank (16), and the top end of the glass tube (19) is plugged by a cork; the closed water storage tank (16) is connected with the open water storage tank (17) through a pipeline (18); the water level in the open reservoir (17) is equal to the position of the bottom of the glass tube (19) in the closed reservoir (16).
5. A soil-water characteristic curve test method of the test device of claim 1, which comprises the following steps:
(1) preparing a sample: compacting the soil body in a circular steel cylinder with the same size as the pressure chamber (5) in a layering mode by using a wet-tamping method to reach required compactness, and dismantling the steel cylinder;
(2) sample loading: the pot body of the pressure chamber is sleeved outside the pot body, and the top cover is covered and sealed:
(3) simulating a stress path: applying axial stress through an air pressure loading system according to test requirements;
(4) and (3) testing a soil-water characteristic curve: the pore water pressure and the pore air pressure in the soil body are respectively adjusted through a back pressure saturator (13) and an air pressure loading system to reach the target matrix suction value; recording the change of the water volume in the back pressure saturator (13) after the suction of the soil matrix is balanced; calculating the water intake and discharge amount according to the initial state of the sample to obtain the water content under the suction force of the corresponding matrix; measuring the water content of the sample under different matrix suction forces to obtain a soil-water characteristic curve of a soil body; sequentially testing soil-water characteristic curves under two conditions of a drying path and a humidifying path; and finally, scouring the argil plate by an unsaturated soil base gas scouring system (9).
6. A method for testing the permeability coefficient of the test device according to claim 1, which is characterized in that:
removing the clay plate on the pressure chamber base (7), preparing a sample, putting the sample into the pressure chamber (5) and sealing; and (3) connecting the water head balancing device with the through hole on the top cover, adjusting the height of the water head, and calculating the water content and the permeability coefficient inside the soil body by utilizing the Darcy law when the water inflow and the water drainage inside the soil body are balanced.
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