An instrument and testing method for testing soil permeability coefficient under different strain states

Abstract

An instrument for testing soil permeability coefficient under different strain states, comprising a water permeability measuring device and a fully automatic triaxial tester, characterized in that the water permeability measuring device comprises a wide-mouth bottle with a double-hole rubber stopper, an organic curved diameter glass tube and an organic diameter glass tube are respectively tightly inserted into the two holes of the double-hole rubber stopper, a hydrophobic PVDF polyvinylidene fluoride gas filter membrane is provided on the end of the organic diameter glass tube exposed outside the wide-mouth bottle, and the end of the organic curved diameter glass tube exposed outside the wide-mouth bottle is connected to the outlet pipe of the fully automatic triaxial tester via a rubber tube with a water stopper. The present invention also provides a testing method using the instrument, which conducts a soil sample permeability test based on the flexible wall constant head method, calculates the permeability coefficient of the sample, and can obtain the permeability coefficient of the soil sample under different strain states under certain controlled temperature conditions. Through the present invention, theoretical and applied research on the permeability of soil samples under different stress and strain states can be carried out.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering, and in particular relates to an instrument and a testing method for testing soil permeability coefficient under different strain states. Background Art

[0002] Soil stress-strain state and permeability characteristics are important factors that must be considered in a range of earthwork projects, including slope protection, foundation pit excavation, and tunneling. However, current research has mostly isolated these two aspects, rarely considering their coupled effects. Previous studies have shown that after earthquakes or human disturbances, soil stress-strain state changes, which can affect both pre-existing and newly formed cracks to varying degrees. When seepage occurs, the seepage path shifts with the changes in cracks, altering the soil's permeability. Furthermore, when the soil is in a seepage state, the pore water pressure within the soil changes, also influencing the stress and strain of the soil. However, limited research has been conducted on the coupled effects of soil stress-strain state and permeability characteristics, and no test methods or instruments are readily available. Therefore, a deeper understanding of the coupled effects of soil stress-strain relationship and permeability characteristics is crucial for conducting a range of earthwork projects. Summary of the Invention

[0003] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide an instrument and a testing method for testing the soil permeability coefficient under different strain states, so as to propose a feasible test method for studying the coupling effect between the stress-strain relationship and the permeability characteristics of the soil. The instrument and the testing method for testing the soil permeability coefficient under different strain states of the present invention can achieve the following: (1) the flexible wall constant water head method is used to measure the permeability coefficient of the sample, which has a certain improvement in accuracy compared with the commonly used rigid wall method; (2) the permeability coefficient of the sample under different strains can be measured to explore the influence of different strains on the permeability performance of the sample; (3) the permeability coefficient of the sample under different strains can be measured by simulating actual engineering, considering the influence of confining pressure, and the strain generated by the sample under pressure, so as to explore the interactive influence of strain and confining pressure on the permeability performance of the sample; (4) only a water permeability measuring device is added to the original fully automatic triaxial instrument, which is easy to operate and low in price.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] An instrument for testing soil permeability coefficient under different strain states, including a water permeability measuring device and a fully automatic triaxial instrument, characterized in that the water permeability measuring device includes a wide-mouth bottle 21 with a double-hole rubber stopper 19, an organic curved glass tube 22 and an organic diameter glass tube 23 are respectively tightly inserted into the two holes of the double-hole rubber stopper 19, and the end of the organic diameter glass tube 23 exposed outside the wide-mouth bottle 21 is provided with a hydrophobic PVDF polyvinylidene fluoride gas filter membrane 20, and the end of the organic curved glass tube 22 exposed outside the wide-mouth bottle 21 is connected to the water outlet pipe 3 of the fully automatic triaxial instrument through a rubber tube 18 with a water stop clamp 17.

[0006] The wide-mouth bottle 21 is a white glass wide-mouth bottle with an inner diameter of 51 mm, a bottom diameter of 102 mm, a total height of 210 mm, and a capacity of 1000 mL.

[0007] The double-hole rubber stopper 19 is divided into a cylindrical bottom and a truncated cone-shaped upper part. The cylindrical bottom has a diameter of 55 mm and a height of 5 mm. The bottom surface diameter of the truncated cone-shaped upper part is 55 mm, the top surface diameter is 48 mm, and the height is 15 mm. The apertures of the two holes of the double-hole rubber stopper 19 are both 7 mm. The centers of the two holes are 22 mm apart. The midpoint of the line connecting the centers of the two holes passes through the axis of the double-hole rubber stopper 19. The double-hole rubber stopper 19 is tightly plugged in the mouth of the wide-mouth bottle 21, and the organic curved diameter glass tube 22 and the organic diameter glass tube 23 are both tightly fitted with the double-hole rubber stopper 19.

[0008] The organic curved glass tube 22 has an inner diameter of 6 mm, an outer diameter of 8 mm, an inner angle of 100°, and two side lengths of 120 mm and 200 mm respectively.

[0009] The organic glass tube 23 has an inner diameter of 6 mm, an outer diameter of 8 mm, and a length of 10 mm.

[0010] The hydrophobic PVDF gas filter membrane 20 is in the shape of a disc with a diameter of 12 mm and is tied with a common rubber rope and tightly wrapped around the end of the organic diameter glass tube 23 exposed outside the wide-mouth bottle 21.

[0011] The present invention also provides a testing method for an instrument for testing soil permeability coefficient under different strain states, the steps of which are as follows:

[0012] Step (1): After the instrument's deadweight balance adjustment is completed, the permeability coefficient K0 of the sample is measured under the zero strain state, that is, when ε0=0. The triaxial test data acquisition system interface of the fully automatic triaxial instrument is opened, and the test conditions are input one by one. The temperature controller should stabilize the test temperature at 20±1°C. The required confining pressure is selected. After the confining pressure reaches the preset value and stabilizes, the osmotic pressure P is applied. The purpose of applying the osmotic head is achieved by controlling the pressure of the sample cap pressure head.

[0013] Step (2): After the outlet pipe 3 is filled with water, the test is suspended, the water stop clamp 17 is clamped, and the clamped position is calibrated. The water in the water permeability measuring device is drained, and the water permeability measuring device is weighed with an electronic scale 26, which is recorded as W1. Then, the water outlet and the water permeability measuring device are reassembled, and the permeation test is continued. During the permeation process, the water stop clamp 17 is opened. After time t, the water stop clamp 17 is first clamped to the original calibrated position, and then the test is suspended. The water permeability measuring device is weighed with an electronic scale 26, which is recorded as W2. The measurement of the permeability coefficient K0 of the sample under zero strain state is completed;

[0014] Step (3), input the preset shear rate into the triaxial test data acquisition system, then shear the sample, observe the triaxial test data acquisition system interface, and quickly stop shearing when the shear displacement reading is equal to the preset axial deformation of the sample. After the deformation of the sample gradually stabilizes, record the shear displacement reading. The difference before and after the shear displacement is the actual axial deformation of the sample. According to the ratio of the axial deformation to the original axial height of the sample, the axial strain ε1 of the sample at this time is obtained;

[0015] Step (4), repeating steps (1) and (2) to measure the permeability coefficient K1 of the sample under the axial strain ε1 state;

[0016] According to steps (3) and (4), the axial strain is ε2, ε3, ..., ε n The permeability coefficient of the sample in the state is the last level of axial strain ε n After the penetration test, stop the test, remove the sample, turn off the instrument, and the test ends, where 0<ε1<ε2<ε3<…<ε n , n is the preset axial deformation of the nth level specimen, that is, the last level deformation;

[0017] The permeability coefficient is calculated using the following formula:

[0018]

[0019] K i The sample is at a temperature of 20°C and an axial strain of ε i The permeability coefficient at the time of the test, W1 and W2 are the weights of the water permeability measuring device before and after the permeability test, H is the initial height of the sample, ε i is the axial strain of the specimen, ε i =ε1,ε2,ε3,…,ε n , A is the cross-sectional area of ​​the sample, P is the osmotic pressure, t is the time of the osmotic test, ρ 20 is the density of water when the temperature is regulated by the temperature controller at 20℃, and g is the acceleration due to gravity.

[0020] In the present invention, the specifications of the sample can be consistent with those of the sample used in the fully automatic triaxial instrument. Before testing the soil permeability coefficient under different strain states, the preparation, saturation, installation and instrument deadweight balance of the sample are consistent with the steps of the fully automatic triaxial stress-strain test of saturated soil.

[0021] The back pressure should be smaller than the confining pressure of 20 kPa, and the shear rate should be 0.02 mm / min-0.05 mm / min.

[0022] Compared with the prior art, the present invention utilizes the existing fully automatic triaxial instrument and only adds a water permeability measuring device, which is convenient for the experimenters. At the same time, it is easy to operate and saves the learning of the operating specifications of the new test instrument. The cost of making the water permeability measuring device is low, and it does not damage the parts of the original test instrument. After the permeability test is completed, a normal triaxial shear test can also be carried out. At the same time, the accuracy of measuring the water permeability is high. On the basis of adopting the flexible wall constant head method, the accuracy of measuring the permeability coefficient of the sample is further improved. Due to the presence of the triaxial instrument pressure chamber, the permeability coefficient of the sample can also be measured under different lateral limit conditions, which greatly improves the use of the instrument and is economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the fully automatic triaxial apparatus.

[0024] Figure 2 It is a schematic diagram of the measuring device of the present invention that can accurately measure water permeability.

[0025] Figure 3 Schematic diagram of an organic curved glass tube 19.

[0026] Figure 4 yes Figure 3 Middle AA section view.

[0027] Figure 5 is a schematic diagram of an organic diameter glass tube 20.

[0028] Figure 6 yes Figure 5 Middle BB cross-section.

[0029] Figure 7 It is a schematic diagram of the wide-mouth bottle 21.

[0030] Figure 8 Schematic diagram of the double-hole rubber plug 22.

[0031] Figure 9 yes Figure 8 Cross-section of the CC.

[0032] Figure 10 yes Figure 8 Middle DD cross-section.

[0033] Figure 11 Schematic diagram of the hydrophobic PVDF polyvinylidene fluoride gas filter membrane 23.

[0034] The relevant recommended preferred dimensions (unit: 1 mm) are marked in the accompanying drawings. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0036] The invention discloses an instrument for testing soil permeability coefficient under different strain states, which mainly comprises two parts: a water permeability measuring device and a full-automatic triaxial instrument.

[0037] See also Figure 1 , is a schematic diagram of a fully automatic triaxial apparatus, which is an existing device and mainly includes a manual control terminal 1; a base 2; a water outlet pipe 3; a back-pressure base 4; a back-pressure pressurizing head 5; a pressure chamber 6; a sample cap pressurizing head 7; a column 8; an axial load sensor 9; a crossbeam 10; a permeable stone 11; a pressurized water pipe 12; a pressure chamber base 13; an axial displacement sensor 14; a back-pressure water inlet pipe 15; a temperature controller 16; a data collector 24; a laptop computer 25; and an electronic scale 26.

[0038] See also Figure 2 , the present invention Figure 1 A water permeability measuring device is designed and added on the basis, including a water stopper 17; a rubber tube 18; a double-hole rubber stopper 19; a hydrophobic PVDF polyvinylidene fluoride gas filter membrane 20; a 1000ml wide-mouth bottle 21; an organic curved diameter glass tube 22; and an organic diameter glass tube 23.

[0039] The organic curved glass tube 22 and the organic diameter glass tube 23 are respectively tightly inserted into the two holes of the double-hole rubber stopper 19. The end of the organic diameter glass tube 23 exposed outside the wide-mouth bottle 21 is provided with a hydrophobic PVDF polyvinylidene fluoride gas filter membrane 20. The end of the organic curved glass tube 22 exposed outside the wide-mouth bottle 21 is connected to the water outlet pipe 3 of the fully automatic triaxial instrument through a rubber tube 18 with a water stop clamp 17.

[0040] See also Figure 3 and Figure 4 As shown, a curved organic glass tube 22 is designed. Made of organic glass, it has an inner diameter of 6 mm, an outer diameter of 8 mm, an inner angle of 100°, and side lengths of 120 mm and 200 mm, respectively. The 100° inner angle allows water from the outlet pipe to flow smoothly into the wide-mouth bottle 21, reducing errors in water permeability measurement.

[0041] See also Figure 5 and Figure 6As shown, the organic glass tube 23 is designed. Made of organic glass, it has an inner diameter of 6 mm, an outer diameter of 8 mm, and a length of 10 mm. A glass tube connected to the atmosphere balances the internal and external atmospheric pressures, allowing the water released from the organic glass tube 22 to drip smoothly into the wide-mouth bottle 21.

[0042] See also Figure 7 As shown, a wide-mouth bottle 21 is designed. It is a white glass wide-mouth bottle with an inner diameter of 51 mm, a bottom diameter of 102 mm, a full height of 210 mm, and a capacity of 1000 mL. It is a common wide-mouth bottle on the market, easy to purchase, and inexpensive.

[0043] See also Figure 8 、 Figure 9 and Figure 10 As shown, a double-hole rubber stopper 19 is designed. It consists of a cylindrical bottom and a truncated cone-shaped top. The cylindrical bottom has a diameter of 55mm and a height of 5mm. The truncated cone-shaped top has a bottom diameter of 55mm and a top diameter of 48mm, and a height of 15mm. The pore diameter of the double-hole rubber stopper 19 is 7mm, and the centers of the two pores are 22mm apart. The midpoint of the line connecting the centers of the two pores passes through the axis of the double-hole rubber stopper 19. The truncated cone-shaped top of the double-hole rubber stopper 19 allows the inner diameter of the mouth of the wide-mouth bottle 21 to coincide with a certain cross-section of the truncated cone-shaped top, thereby allowing it to fit tightly within the bottle opening. The pore diameter of the double-hole rubber stopper 19 is set to 7mm, which is smaller than the outer diameter of the organic glass tube of 8mm. This pore size difference allows the organic curved-diameter glass tube 22 and the organic wide-diameter glass tube 23 to fit tightly within the double-hole rubber stopper 19.

[0044] See also Figure 11 As shown, a hydrophobic PVDF polyvinylidene fluoride gas filter membrane 20 is designed. It is disc-shaped, with a diameter of 12mm, and is tied with a common rubber rope and tightly wrapped around the end of the organic diameter glass tube 23 exposed outside the wide-mouth bottle 21. After the organic curved diameter glass tube 22 and the organic diameter glass tube 23 are tightly inserted into the double-hole rubber stopper 19, and the double-hole rubber stopper 19 is tightly plugged into the wide-mouth bottle 21, the hydrophobic PVDF polyvinylidene fluoride gas filter membrane 20 is tied with a common rubber rope and tightly wrapped around the end of the organic diameter glass tube 23 exposed outside the wide-mouth bottle 21. Due to the air-permeable and water-impermeable nature of the hydrophobic PVDF polyvinylidene fluoride gas filter membrane 20, this design reduces the loss of permeate effluent water and balances the atmospheric pressure inside and outside the water permeability measuring device, allowing the permeate effluent water to flow from the water outlet 3 into the wide-mouth bottle 21, greatly improving the accuracy of the permeate effluent water quality measurement.

[0045] Since the present invention adds a water permeability measuring device on the basis of the original fully automatic triaxial apparatus, the specifications and preparation of the sample are consistent with the fully automatic triaxial stress-strain test of saturated soil before testing the soil permeability coefficient under different strain states. The saturation of the sample adopts the vacuum saturation method. Then, a comprehensive inspection is carried out on all parts of the fully automatic triaxial apparatus to check whether the ambient pressure system, the counter-pressure system, and the axial pressure system can work normally, whether the drainage pipeline is unobstructed, and whether there is any water leakage or air leakage at the connection of the pipeline valve. Check whether the latex membrane has any water leakage or air leakage. After the inspection is completed, remove the organic glass cover of the pressure chamber 6 and load the sample. After the loading is completed, click the function key of the manual control end 1 to raise the base of the container so that the axial parts are roughly in contact, and then fill the pressure chamber 6 with water, and then balance the instrument by its own weight. The assembly of the water permeability measuring device is in accordance with Figure 2 Proceed as shown.

[0046] After the instrument's deadweight balance adjustment and the water permeability measurement device are assembled, the permeability coefficient K0 of the sample under zero axial strain is measured first. The steps are as follows:

[0047] Step (1): After the instrument's deadweight balance adjustment is completed, the permeability coefficient K0 of the sample is measured first under the zero strain state, that is, when ε0 = 0. Open the triaxial test data acquisition system interface of the fully automatic triaxial instrument, enter the test conditions one by one, and the temperature controller should stabilize the test temperature at 20 ± 1 ° C. Select the required confining pressure to be applied. After the confining pressure reaches the preset value and stabilizes, apply the osmotic pressure P. The purpose of applying the osmotic head is achieved by controlling the pressure of the sample cap pressure head;

[0048] Step (2): After the outlet pipe 3 is filled with water, the test is suspended, the water stop clamp 17 is clamped, and the clamped position is calibrated. The water in the water permeability measuring device is drained, and the water permeability measuring device is weighed with an electronic scale 26, which is recorded as W1. Then, the water outlet and the water permeability measuring device are reassembled, and the permeation test is continued. During the permeation process, the water stop clamp 17 is opened. After time t, the water stop clamp 17 is first clamped to the original calibrated position, and then the test is suspended. The water permeability measuring device is weighed with an electronic scale 26, which is recorded as W2. The measurement of the permeability coefficient K0 of the sample under zero strain state is completed.

[0049] Step (3), input the preset shear rate into the triaxial test data acquisition system, then shear the sample, observe the triaxial test data acquisition system interface, and quickly stop shearing when the shear displacement reading is equal to the preset axial deformation of the sample. After the deformation of the sample gradually stabilizes, record the shear displacement reading. The difference before and after the shear displacement is the actual axial deformation of the sample. According to the ratio of the axial deformation to the original axial height of the sample, the axial strain ε1 of the sample at this time can be obtained;

[0050] Step (4), repeating steps (1) and (2) to measure the permeability coefficient K1 of the sample under the axial strain ε1 state;

[0051] According to steps (3) and (4), the axial strain is ε2, ε3, ...ε n The permeability coefficient of the sample in the state is the last level of axial strain ε n After the penetration test, stop the test, remove the sample, turn off the instrument, and the test ends. n (n is the preset axial deformation of the nth level specimen, i.e. the last level deformation).

[0052] Permeability coefficient K of the sample i (i=0,1,2,3...) The following formula is used for calculation:

[0053]

[0054] K i : The sample is at a temperature of 20°C and an axial strain of ε i The permeability coefficient at , unit: cm / s;

[0055] W1, W2: weight of the water permeability measuring device before and after the permeation test, unit: g;

[0056] H: initial height of the sample, unit: cm;

[0057] ε i : axial strain of the specimen;

[0058] A: cross-sectional area of ​​the sample, unit: cm 2 ;

[0059] P: back pressure applied during permeation test, unit: kPa;

[0060] t: time of penetration test, unit: s;

[0061] ρ 20 : The density of water when the temperature controller (16) controls the water temperature to 20°C. Unit: g / cm 3 .

[0062] In summary, the present invention adds a water permeability measuring device. According to steps (1), (2), (3) and (4), the operation is performed and the formula is used: Calculate the permeability coefficient and obtain the sample temperature is 20℃, axial strain is ε iThe present invention uses the flexible wall constant head method to measure the permeability coefficient of the sample, and the added permeability measurement device can improve the accuracy of measuring the permeability, thereby improving the accuracy of the sample permeability coefficient test. The present invention can be used to test the soil permeability coefficient under different strain states and study the permeability of soil samples under different stress-strain states.

Claims

1. A method for testing soil permeability coefficient under different strain states, which is implemented using an instrument for testing soil permeability coefficient under different strain states, wherein the instrument includes a water permeability measuring device and a fully automatic triaxial tester, wherein the water permeability measuring device includes a wide-mouth bottle with a double-hole rubber stopper, an organic curved diameter glass tube and an organic diameter glass tube are respectively tightly inserted into two holes of the double-hole rubber stopper, an end of the organic diameter glass tube exposed outside the wide-mouth bottle is provided with a hydrophobic PVDF polyvinylidene fluoride gas filter membrane, and an end of the organic curved diameter glass tube exposed outside the wide-mouth bottle is connected to the water outlet pipe of the fully automatic triaxial tester via a rubber tube with a water stopper, characterized in that: The test steps are as follows: Step (1): After the instrument's deadweight balance adjustment is completed, the permeability coefficient K0 of the sample is measured under the zero strain state, that is, when the axial strain ε0=0. The triaxial test data acquisition system interface of the fully automatic triaxial instrument is opened, and the test conditions are input one by one. The temperature controller should stabilize the test temperature at 20±1°C. The required confining pressure is selected. After the confining pressure reaches the preset value and stabilizes, the osmotic pressure P is applied. The purpose of applying the osmotic head is achieved by controlling the pressure of the sample cap pressure head. Step (2): After the outlet pipe is filled with water, the test is suspended, the water stop clamp is tightened, and the clamped position is calibrated. The water in the water permeability measuring device is drained, and the water permeability measuring device is weighed with an electronic scale, which is recorded as W1. The water outlet and the water permeability measuring device are then reassembled, and the permeation test is continued. During the permeation process, the water stop clamp is opened. After time t, the water stop clamp is first clamped to the original calibrated position, and then the test is suspended. The water permeability measuring device is weighed with an electronic scale, which is recorded as W2. The measurement of the permeability coefficient K0 of the sample under zero strain state is completed; Step (3), input the preset shear rate into the triaxial test data acquisition system, then shear the sample, observe the triaxial test data acquisition system interface, and quickly stop shearing when the shear displacement reading is equal to the preset axial deformation of the sample. After the deformation of the sample gradually stabilizes, record the shear displacement reading. The difference before and after the shear displacement is the actual axial deformation of the sample. According to the ratio of the axial deformation to the original axial height of the sample, the axial strain ε1 of the sample at this time is obtained; Step (4), repeating steps (1) and (2) to measure the permeability coefficient K1 of the sample under the axial strain ε1 state; According to steps (3) and (4), the axial strain is ε2, ε3, ..., ε n The permeability coefficient of the sample in the state is the last level of axial strain ε n After the penetration test, stop the test, remove the sample, turn off the instrument, and the test ends, where 0<ε1<ε2<ε3<…<ε n , n is the preset axial deformation of the nth level specimen, that is, the last level deformation; The permeability coefficient is calculated using the following formula: K i The sample is at a temperature of 20°C and an axial strain of ε i The permeability coefficient at the time of the test, W1 and W2 are the weights of the water permeability measuring device before and after the permeability test, H is the initial height of the sample, ε i is the axial strain of the specimen, ε i =ε1,ε2,ε3,…,ε n , A is the cross-sectional area of ​​the sample, P is the osmotic pressure, t is the time of the osmotic test, ρ 20 is the density of water when the temperature is regulated by the temperature controller at 20℃, and g is the acceleration due to gravity.

2. The testing method according to claim 1, characterized in that: The specifications of the specimens are consistent with those used in the fully automatic triaxial instrument. Before testing the soil permeability coefficient under different strain states, the preparation, saturation, installation and instrument deadweight balance of the specimens are consistent with the procedures of the fully automatic triaxial stress-strain test on saturated soil.

3. The testing method according to claim 1, characterized in that: The wide-mouth bottle is a white glass wide-mouth bottle with an inner diameter of 51 mm, a bottom diameter of 102 mm, a total height of 210 mm, and a capacity of 1000 mL.

4. The testing method according to claim 1, wherein: The double-hole rubber stopper is divided into a cylindrical bottom and a truncated cone-shaped upper part. The cylindrical bottom has a diameter of 55 mm and a height of 5 mm. The bottom surface diameter of the truncated cone-shaped upper part is 55 mm, the top surface diameter is 48 mm, and the height is 15 mm. The diameter of the two holes of the double-hole rubber stopper is 7 mm. The centers of the two holes are 22 mm apart. The midpoint of the line connecting the centers of the two holes passes through the axis of the double-hole rubber stopper. The double-hole rubber stopper is tightly plugged in the mouth of the wide-mouth bottle. The organic curved diameter glass tube and the organic diameter glass tube are both tightly fitted with the double-hole rubber stopper.

5. The testing method according to claim 1, characterized in that: The organic curved glass tube has an inner diameter of 6 mm, an outer diameter of 8 mm, an inner angle of 100°, and two side lengths of 120 mm and 200 mm respectively.

6. The testing method according to claim 1, characterized in that: The organic glass tube has an inner diameter of 6 mm, an outer diameter of 8 mm, and a length of 10 mm.

7. The testing method according to claim 1, characterized in that: The hydrophobic PVDF polyvinylidene fluoride gas filter membrane is in the shape of a disc with a diameter of 12 mm, and is tied with a common rubber rope and tightly wrapped around the end of the organic diameter glass tube exposed outside the wide-mouth bottle.

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