Method for producing a membrane, membrane, method for determining the inlet value of a membrane, device and method

Abstract

The application provides a membrane preparation method, a membrane, a membrane air entry value determination method, a device and a method. The membrane preparation method comprises the following steps: selecting bentonite to prepare a slurry; preparing a mud pipe composite; performing a centrifugal test on the mud pipe composite, recording the height of the soil-water interface of the slurry in the mud pipe composite at different time points and marking the height as h t ; when the deviation of the three continuous measurements h t is less than 1%, the mud pipe composite is taken out, the pipe caps at both ends of the mud pipe composite are removed, and a water-passing air-closing membrane is formed. The membrane air entry value determination method comprises the following steps: cutting one end of the water-passing air-closing membrane according to the soil-water interface and installing a middle filter screen valve, and weighing; performing a centrifugal test on the water-passing air-closing membrane; recording the weight of the water-passing air-closing membrane at the corresponding rotational speed, and when the weight deviation of three continuous times is less than 1%, the weight is weighed, and the height of the interface of the water-passing air-closing membrane is marked as H i ; calculating the sample suction at different rotational speeds; drawing a soil-water characteristic curve to obtain the air entry value of the water-passing air-closing membrane. The method can effectively evaluate the influence of pore structure on the relaxation distribution of liquid-phase pollutants.

Description

Technical Field

[0001] This application relates to the fields of geotechnical engineering and resource environment, and in particular to methods for preparing membranes, membranes, methods for measuring the air inlet value of membranes, apparatus and methods. Background Technology

[0002] Microfluidics is a technique that uses two-dimensional visualization technology to analyze the flow behavior of fluids in pores. Improving the simulation accuracy of microfluidic physical simulations is an important requirement for extending indoor prediction results to engineering practice.

[0003] Current microfluidic technologies in geotechnical and resource environment fields mainly employ single or mixed fluids to drive phase changes or motions of fluids already embedded in microfluidic chips. For example, in oil development, carbon dioxide is used to simulate crude oil (or water-oil mixtures) flowing through rock pores; in resource environment, water or air is used to drive the relative seepage of gaseous and liquid pollutants. However, these methods cannot screen for downstream overflow substances; they are relative seepage behaviors that directly determine the relationship between saturation and permeability coefficient. Engineering prediction, on the other hand, requires direct measurement of steady-state seepage parameters, such as the relationship between suction and saturation. The main technical challenges in conducting steady-state seepage simulations are: ① the inability to prepare membranes that screen for downstream overflow substances; and ② the inability to assess air intake values ​​and determine applicable pressure ranges for existing membranes. Therefore, there is an urgent need to develop a device that can overcome the shortcomings of the aforementioned technologies and fulfill the function of water-passing and air-sealing in unsaturated microfluidic simulations, enabling geotechnical engineering construction and resource environment development. Summary of the Invention

[0004] One of the purposes of this application is to provide a method for preparing a membrane, a membrane, a method for measuring the inlet gas value of the membrane, an apparatus and a method that are applicable to measuring the relationship between constant gas phase pressure and liquid discharge rate during a steady-state gas phase displacement of the liquid phase, and can effectively evaluate the relaxation distribution of liquid phase pollutants by pore structure.

[0005] The technical solution of this application is:

[0006] A method for preparing a water-permeable, airtight membrane includes the following steps:

[0007] Bentonite was selected and prepared into a mud slurry with a soil-to-water ratio of 1:3 to 1:5. The mud slurry was then vibrated. The mud slurry was then drawn up in several batches and injected into a PVC pipe.

[0008] The two ends of the PVC pipe are sealed with PVC pipe caps to form a mud-pipe composite; the mud-pipe composite is placed in a centrifuge tube, and the mud-pipe composite is parallel to the axial direction of the centrifuge tube.

[0009] Set centrifuge speed r The centrifuge was then started, and records were taken at different times.t The height of the soil-water interface of the mud slurry within the mud pipe composite body is denoted as [height of mud slurry]. h t ;

[0010] In three consecutive measurements h t When the deviation is less than 1%, the mud pipe composite is removed, and the PVC pipe caps at both ends of the mud pipe composite are removed to form a water-sealed air membrane.

[0011] As one technical solution of this application, the bentonite includes interlayer spacing. d (001) is sodium-based bentonite with a thickness of 1~1.2 nm.

[0012] As one technical solution of this application, the mud is subjected to ultrasonic vibration for 40-60 minutes.

[0013] As one technical solution of this application, the inner diameter of the PVC pipe n The numerical range is 0 < n <50mm, length is L The weight was drawn in several doses using a syringe. m The slurry is injected into the PVC pipe.

[0014] A water-permeable air-tight membrane is prepared by the water-permeable air-tight membrane preparation method described above.

[0015] A method for determining the air intake value based on the above-described water-sealed air-tight membrane includes the following steps:

[0016] Cut one end of the water-tight air-tight membrane along the soil-water interface and install an intermediate filter valve. Weigh the water-tight air-tight membrane and record the weight as follows: m 0; Place the water-sealed membrane in a centrifuge tube, and keep the mud-tube composite parallel to the axial direction of the centrifuge tube;

[0017] Set multiple different speed levels for the centrifuge R i According to the speed from smallest to largest R i Conduct centrifugation tests; record the corresponding rotational speed every 4 hours. R i The weight of the aforementioned water-sealed air-tight membrane is recorded as follows: if the weight deviation is less than 1% for three consecutive weighings, the last weighing is recorded as... m i The interface height of the water-sealed air-tight membrane at this time is recorded as... H i ;

[0018] Calculate the rotational speed of each stage of the centrifuge. Ri The suction force of the sample under the water-sealed air-tight membrane; with the sample suction force as the horizontal axis, and ( m 0- m i ) / m s Plot a two-dimensional experimental curve on the vertical axis, denoted as the soil-water characteristic curve, where... m s The weight of the bentonite in the mud-pipe composite;

[0019] The air intake value of the water-tight membrane is obtained through the soil-water characteristic curve. P a .

[0020] As a technical solution of this application, the rotational speed of each stage of the centrifuge is calculated using the following formula. R i The sample suction force of the water-sealed air-tight membrane below P :

[0021] ;

[0022] In the formula: P The matrix suction of the water-sealed air-tight membrane, kPa ; R i The rotational speed of the centrifuge. rpm ; H i For the water-sealed air-tight membrane in i The height of the interface at any given moment, in cm; R The distance from the center of the centrifuge rotor to the bottom of the water-sealed air-tight membrane, in cm; r The distance from the center of the centrifuge rotor to the top of the water-sealed air-tight membrane, in cm; Dh The settling height of the water-sealed air-tight membrane at each centrifugal level, and Δh=H (i-1) -H i cm; r The density of water is expressed in g / cm³. 3 ; g The acceleration due to gravity is taken as 9.8 m / s². 2 .

[0023] As one technical solution of this application, a first tangent line at the initial water plateau end and a second tangent line at the middle inclined section are plotted on the soil-water characteristic curve. A perpendicular line is drawn from the intersection of the first and second tangent lines to the horizontal axis of the sample suction. The suction force corresponding to the perpendicular line is the air intake value of the water-tight air-tight membrane. P a .

[0024] A non-saturated steady-state seepage simulation device includes a microfluidic chip, a pressure controller, an eddy current temperature controller, a high-speed high-definition camera, a backup pressure unit, a data acquisition and control unit, a microbalance water collection box, and the aforementioned water-tight membrane. The two ends of the microfluidic chip are respectively connected to the pressure controller and one end of the water-tight membrane. The pressure controller provides driving power to the microfluidic chip. An intermediate filter valve is installed in the soil-water interface cut at the other end of the water-tight membrane, and one end of the intermediate filter valve is connected to the backup pressure unit. The backup pressure unit is connected to the microbalance water collection box via a drain pipe, and the backup pressure unit provides auxiliary pressure. The microbalance... The water collection box is used to collect and measure the weight of the liquid discharged from the water-sealed membrane; the high-speed high-definition camera and the eddy current temperature controller are respectively and spaced apart on one side of the microfluidic chip. The high-speed high-definition camera is used to monitor the dynamics of the microfluidic chip in real time, and the eddy current temperature controller is used to monitor the temperature of the microfluidic chip in real time; the acquisition and control unit is electrically connected to the pressure controller, the eddy current temperature controller, the high-speed high-definition camera, the backup pressure unit, and the microbalance water collection box, and is used to acquire various data measured by the pressure controller, the eddy current temperature controller, the high-speed high-definition camera, the backup pressure unit, and the microbalance water collection box in real time.

[0025] A test method based on the above-described unsaturated steady-state seepage simulation device includes the following steps:

[0026] One end of the microfluidic chip, saturated with water in its pores, is connected to the pressure controller, and the other end is connected to one end of the water-tight membrane. The other end of the water-tight membrane is cut at the soil-water interface and an intermediate filter valve is installed. The lower end of the intermediate filter valve is connected to the backup pressure unit. The backup pressure unit is connected to the microbalance water collection box. The high-speed, high-definition camera is spaced apart on one side of the microfluidic chip. The acquisition and control unit is electrically connected to the pressure controller, the eddy current temperature controller, the high-speed, high-definition camera, the backup pressure unit, and the microbalance water collection box.

[0027] The lower end of the drain pipe is dripped into the water collection box of the microbalance; the pressure of the pressure controller is set by the acquisition and control unit. P k The control temperature of the eddy current temperature controller and the back pressure of the backup pressure unit are set, wherein, P k < P a Record stress P k The weight in the water collection box of the microbalance belowm ki ,in, i =0, 1, 2, ..., e, and simultaneously record the image number of the high-speed high-definition camera. F ki ,in, i =0, 1, 2, ..., e; pressure to be applied P k When the weight change in the water collection box of the microbalance described below is less than 0.00001g, the next level of pressure is applied. P k+1 ,in, P k < P k+1 < P a And record the weight of the water collection box of the microbalance at this time. m ke and the image number of the high-speed high-definition camera F ke Until the measurement is completed P k+n Level pressure, among which, P k < P k+n < P a ;

[0028] Calculate the pressure of the same level P k The drainage volume through the water-sealed air membrane M k = m k0 - m ke and with pressure P k With the horizontal axis as the base, M k Plot a curve on the vertical axis;

[0029] right F ki to F ke Analyze the images between them to obtain the coefficient of difference. R k Further, the difference coefficient under different pressures was obtained. R k The variance.

[0030] The beneficial effects of this application are:

[0031] (1) This application provides a method for preparing a water-sealed air-tight membrane, which obtains a tubular structure formed by saturated bentonite by density difference separation through centrifugation. The capillary force of the granular material is used to bind the liquid water under a certain pressure so that it is not broken down by the gas, thus achieving the water-sealed air-tight effect. Through simple physical action, the granular particles form a water-sealed air-tight structure in a saturated state, avoiding the problems of insufficient saturation and inaccurate testing that occur when the finished water-sealed air-tight membrane needs to be saturated in advance. This greatly improves the water-sealed air-tight effect and reduces the technical labor intensity of the operators.

[0032] (2) This application provides a water-sealed air-tight membrane, which obtains a tubular structure formed by saturated bentonite through density difference separation by centrifugation. Through simple physical action, the granular particles form a water-sealed air-tight structure in a saturated state, avoiding the problems of insufficient saturation and inaccurate testing that occur when the finished water-sealed air-tight membrane needs to be saturated in advance, and greatly improving the water-sealed air-tight effect.

[0033] (3) This application provides a method for determining the air intake value of a water-sealed air-tight membrane, which determines the air intake value by obtaining the soil-water characteristic curve through conventional centrifugation. This method avoids the shortcomings of the water-sealed air-tight membrane formed by sintering of finished products having different air intake values ​​that cannot be measured. It can specifically determine the air intake value of the water-sealed air-tight membrane formed each time this technology is implemented, thereby determining the operating pressure range of each water-sealed air-tight membrane. This method can improve the problem of the inability to quantify the application range of the water-sealed air-tight membrane caused by uneven preparation of finished materials or unstable process, and specifically reduce the labor cost of engineering technicians.

[0034] (4) This application provides an unsaturated steady-state seepage simulation device, which applies air pressure upstream of a microfluidic chip and observes the total amount of liquid discharged from the microfluidic chip under stable air pressure conditions. The microfluidic chip is made of silicon or other materials and serves as a soil and rock simulation material. At the same time, a water-sealed air-sealed membrane is set downstream of the microfluidic chip to prevent the gas and liquid from being directly discharged when air pressure is applied. Thus, steady-state seepage tests simulating pore structures under air pressure conditions can be carried out directly. Therefore, the design of this device solves the problem of the relative permeability of pore structures measured by the relative seepage method (transient method) to indirectly predict steady-state seepage parameters.

[0035] (5) This application provides a test method for an unsaturated steady-state seepage simulation device. Air pressure is applied upstream of a microfluidic chip, and the total amount of liquid discharged from the microfluidic chip under stable air pressure conditions is observed. The microfluidic chip is made of silicon or other materials and serves as a soil and rock simulation material. Simultaneously, a water-sealed air-tight membrane is set downstream of the microfluidic chip to prevent both gas and liquid from being directly discharged when air pressure is applied, thus allowing direct steady-state seepage testing of the simulated pore structure under air pressure conditions. Therefore, this method measures the relaxation performance of the microfluidic chip structure to water, which is used to analyze the influence of the soil and rock pore structure on liquid holding capacity. This result can evaluate the evolution gradient of the liquid holding properties of the pore structure and is a parameter characterizing the continuity of the material structure. Furthermore, this method can evaluate the continuity of the structural distribution of pore materials, guiding pore structure design or the particle uniformity design of soil and rock materials. Moreover, this method directly connects the macroscopic statistical parameters of the pore structure (soil-water characteristic curve) with its microscopic image structure evaluation, achieving both functional design evaluations in a single experiment. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the preparation method of the water-permeable air-tight membrane provided in the first embodiment of this application;

[0038] Figure 2 This is a schematic diagram of the method for determining the air inlet value of the water-sealed air-tight membrane provided in the second embodiment of this application;

[0039] Figure 3 This is a schematic diagram of the unsaturated steady-state seepage simulation device provided in the third embodiment of this application;

[0040] Figure 4 This is a partial flow diagram of the test method for the unsaturated steady-state seepage simulation device provided in the fourth embodiment of this application.

[0041] Icons: 1-Microfluidic chip; 2-Pressure controller; 3-Eddy current temperature controller; 4-High-speed HD camera; 5-Water-passing air-tight membrane; 6-Backup pressure unit; 7-Data acquisition and control unit; 8-Microbalance water collection box; 9-Drain pipe. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0044] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0045] In the description of this application, it should be noted that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only used to facilitate the description of this application and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0046] Furthermore, in this application, unless otherwise expressly specified and limited, "above or below" the first feature may include direct contact between the first and second features, or contact between the first and second features through another feature between them. Moreover, "above," "over," and "on" the first feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the first feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0047] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0048] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0049] First embodiment:

[0050] Please refer to Figure 1 This embodiment provides a method for preparing a water-sealed air-tight membrane, which specifically includes the following steps:

[0051] Selecting the interlayer spacing d (001) Sodium-based bentonite with a density of 1~1.2 nm was prepared into a mud with a soil-to-water ratio of 1:3~1:5, and ultrasonic vibration was applied for 40~60 min to ensure uniform soil-water distribution; the mud was then drawn up in several batches and injected into a PVC pipe.

[0052] Take a PVC pipe with an inner diameter of n (0 < n < 50 mm) and a length of L, and use a syringe to draw up the prepared mud slurry weighing m in several times and inject it into the PVC pipe; seal both ends of the PVC pipe filled with mud slurry with PVC pipe caps to form a mud-pipe composite; place the prepared mud-pipe composite into a centrifuge tube and keep the mud-pipe composite parallel to the axis of the centrifuge tube.

[0053] Set centrifuge speed r Then start the centrifuge and record the data at different times. t The height of the soil-water interface of the mud in the mud pipe composite is recorded as follows: h t ;

[0054] In three consecutive measurements h t When the deviation is less than 1%, remove the mud pipe composite and remove the PVC pipe caps at both ends of the mud pipe composite. At this time, the mud pipe composite is the water-sealed air-tight membrane 5.

[0055] In summary, this application provides a method for preparing a water-sealed air-tight membrane. It obtains a tubular structure formed by the accumulation of saturated bentonite through density difference separation by centrifugation. The capillary force of the granular material forming capillaries binds the liquid water under certain pressure, preventing it from being broken down by gas, thus achieving a water-sealed air-tight effect. Through simple physical action, the granular material forms a sealed water-sealed air-tight structure in a saturated state, avoiding the problems of insufficient saturation leading to air leakage and inaccurate testing that occur with pre-saturated finished water-sealed air-tight membranes. This significantly improves the water-sealed air-tight effect and reduces the technical labor intensity of operators.

[0056] Second embodiment:

[0057] Please refer to Figure 2 This embodiment provides a method for determining the air inlet value of a water-sealed air-tight membrane, which specifically includes the following steps:

[0058] The water-permeable air-tight membrane 5 is prepared according to the preparation method in the first embodiment;

[0059] Cut one end of the water-tight air-tight membrane 5 at the soil-water interface and install the intermediate filter valve. Weigh the water-tight air-tight membrane 5 and record the weight as follows: m 0; Place the water-sealed membrane 5 in the centrifuge tube, and keep the mud-tube composite parallel to the axis of the centrifuge tube;

[0060] Set multiple different speed levels for the centrifuge R i According to the speed from smallest to largest R i Conduct centrifugation tests; record the corresponding rotational speed every 4 hours. R i The weight of the water-sealed air-tight membrane 5 is recorded as follows: when the weight deviation is less than 1% for three consecutive weighings, the last weighing is recorded as... m i And record the interface height of the water-sealed air-tight membrane 5 at this time as H i ;

[0061] Calculate the rotational speed of each stage of the centrifuge R i The suction force of the sample under the water-sealed air-tight membrane 5 is specifically calculated using the following formula for each speed stage of the centrifuge. R i The suction force of the sample under the water-sealed air-tight membrane 5 P :

[0062] ;

[0063] In the formula: P For the matrix suction of the water-sealed air-tight membrane 5, kPa ; R i The speed of the centrifuge. rpm ; H i For water-sealed air membrane 5 in i The height of the interface at any given moment, in cm; R The distance from the center of the centrifuge rotor to the bottom of the water-sealed air-tight membrane 5 is in cm; r The distance from the center of the centrifuge rotor to the top of the water-sealed air-tight membrane 5 is in cm; DhThe settling height of the water-sealed air-tight membrane 5 at each centrifugal level, and Δh=H (i-1) -H i cm; r The density of water, in g / cm³ 3 ; g The acceleration due to gravity is taken as 9.8 m / s². 2 ;

[0064] With the sample suction force as the horizontal axis, and ( m 0- m i ) / m s Plot a two-dimensional experimental curve on the vertical axis, denoted as the soil-water characteristic curve, where... m s The weight of the bentonite in the mud-pipe composite;

[0065] Plot the first tangent at the initial water plateau end and the second tangent at the middle inclined section on the soil-water characteristic curve. Draw a perpendicular line from the intersection of the first and second tangents to the horizontal axis of the sample suction. The suction corresponding to this perpendicular line is the air inlet value of the water-tight air-tight membrane 5. P a .

[0066] In summary, this application provides a method for determining the air inlet value of a water-tight air-tight membrane, which determines the air inlet value by obtaining the soil-water characteristic curve using conventional centrifugation. This method avoids the inability to measure the differences in air inlet value of the water-tight air-tight membrane 5 formed by the sintering of finished products. It can specifically measure the air inlet value of the water-tight air-tight membrane 5 formed each time this technology is implemented, thereby determining the operating pressure range of each water-tight air-tight membrane 5. This method can improve the problem of the inability to quantify the application range of the water-tight air-tight membrane 5 caused by uneven preparation of finished materials or unstable processes, and specifically reduces the labor costs of engineering technicians.

[0067] Third embodiment:

[0068] Please refer to Figure 3This embodiment provides an unsaturated steady-state seepage simulation device, which includes a microfluidic chip 1, a pressure controller 2, an eddy current temperature controller 3, a high-speed high-definition camera 4, a backup pressure unit 6, a data acquisition and control unit 7, a microbalance water collection box 8, and a water-tight membrane 5 prepared in the first embodiment and subjected to an air intake value measurement test. The two ends of the microfluidic chip 1 are connected to the pressure controller 2 and one end of the water-tight membrane 5, respectively. The pressure controller 2 provides driving power to the microfluidic chip 1. Simultaneously, an intermediate filter valve is installed in the soil-water interface cut at the other end of the water-tight membrane 5, and one end of the intermediate filter valve is connected to the backup pressure unit 6. The backup pressure unit 6 is connected to the microbalance water collection box via a drain pipe 9. 8. The backup pressure unit 6 is used to provide auxiliary pressure, and the microbalance water collection box 8 is used to collect and measure the weight of the liquid discharged from the water-sealed membrane 5. In addition, the high-speed high-definition camera 4 and the eddy current temperature controller 3 are respectively arranged at intervals on one side of the microfluidic chip 1. The high-speed high-definition camera 4 is used to monitor the dynamics of the microfluidic chip 1 in real time, and the eddy current temperature controller 3 is used to monitor the temperature of the microfluidic chip 1 in real time. Furthermore, its acquisition and control unit 7 is electrically connected to the pressure controller 2, the eddy current temperature controller 3, the high-speed high-definition camera 4, the backup pressure unit 6, and the microbalance water collection box 8, respectively, and is used to acquire various data measured by the pressure controller 2, the eddy current temperature controller 3, the high-speed high-definition camera 4, the backup pressure unit 6, and the microbalance water collection box 8 in real time.

[0069] It should be noted that its flow control chip, pressure controller 2, eddy current temperature controller 3, high-speed high-definition camera 4, backup pressure unit 6, data acquisition and control unit 7, and micro balance water collection box 8 all adopt the structure of existing technology, and their specific structure and working principle will not be described in detail here.

[0070] In summary, this device applies air pressure upstream of the microfluidic chip 1 and observes the total amount of liquid discharged from the microfluidic chip 1 under stable air pressure conditions. The microfluidic chip 1 is made of silicon or other materials and serves as a soil and rock simulation material. Simultaneously, a water-sealed air-sealing membrane 5 is set downstream of the microfluidic chip 1 to prevent both gas and liquid from being directly discharged when air pressure is applied. This allows for direct steady-state seepage testing of simulated pore structures under air pressure conditions. Therefore, the design of this device solves the shortcomings of the relative seepage method (transient method) in indirectly predicting steady-state seepage parameters by measuring the relative permeability of pore structures.

[0071] Fourth embodiment:

[0072] Please refer to Figure 4 (Refer to) Figure 1 to Figure 3 This embodiment provides a test method for an unsaturated steady-state seepage simulation device, which specifically includes the following steps:

[0073] Preparation of a water-sealed air-tight membrane 5;

[0074] The air inlet value of the water-sealed air membrane 5 was measured.

[0075] One end of the microfluidic chip 1, saturated with water in its pores, is connected to the pressure controller 2, and the other end is connected to one end of the water-sealed air-tight membrane 5. The other end of the water-sealed air-tight membrane 5, after the air intake value measurement test is completed, is cut along the soil-water interface and an intermediate filter valve is installed. The lower end of the intermediate filter valve is connected to the backup pressure unit 6. The backup pressure unit 6 is connected to the microbalance water collection box 8. The high-speed high-definition camera 4 is spaced apart on one side of the microfluidic chip 1. The acquisition and control unit 7 is electrically connected to the pressure controller 2, the eddy current temperature controller 3, the high-speed high-definition camera 4, the backup pressure unit 6, and the microbalance water collection box 8, respectively.

[0076] The lower end of the drain pipe 9 is dripped into the water collection box 8 of the microbalance; the pressure of the pressure controller 2 is set by the data acquisition and control unit 7. P k The control temperature of the eddy current temperature controller 3 and the back pressure of the backup pressure unit 6 are set, wherein... P k < P a Record stress P k The weight of the water collection box 8 of the microbalance m ki ,in, i =0, 1, 2, ..., e, simultaneously recording the image numbers from the high-speed high-definition camera 4. F ki ,in, i =0, 1, 2, ..., e; pressure to be applied P k When the weight change in the water collection box 8 of the microbalance is less than 0.00001g, apply the next level of pressure. P k+1 ,in, P k < P k+1 < P a Record the weight of the microbalance water collection box 8 at this time. m ke Image number of high-speed HD camera 4 F ke Until the measurement is completed P k+n Level pressure, among which, P k < P k+n < P a ;

[0077] Calculate the pressure of the same level P k The drainage volume through the water-sealed air membrane 5 M k = m k0 - m ke and with pressure P k With the horizontal axis as the base, M k Plot a curve on the vertical axis;

[0078] right F ki to F ke Analyze the images between them to obtain the coefficient of difference. R k Further, the difference coefficient under different pressures was obtained. R k The variance.

[0079] Furthermore, the preparation of its water-permeable air-tight membrane 5 specifically includes the following steps:

[0080] Selecting the interlayer spacing d (001) Sodium-based bentonite with a density of 1~1.2 nm was prepared into a mud with a soil-to-water ratio of 1:3~1:5, and ultrasonic vibration was applied for 40~60 min to ensure uniform soil-water distribution; the mud was then drawn up in several batches and injected into a PVC pipe.

[0081] Take a PVC pipe with an inner diameter of n (0 < n < 50 mm) and a length of L, and use a syringe to draw up the prepared mud slurry weighing m in several times and inject it into the PVC pipe; seal both ends of the PVC pipe filled with mud slurry with PVC pipe caps to form a mud-pipe composite; place the prepared mud-pipe composite into a centrifuge tube and keep the mud-pipe composite parallel to the axis of the centrifuge tube.

[0082] Set centrifuge speed r Then start the centrifuge and record the data at different times. t The height of the soil-water interface of the mud in the mud pipe composite is recorded as follows: h t ;

[0083] In three consecutive measurements h t When the deviation is less than 1%, remove the mud pipe composite and remove the PVC pipe caps at both ends of the mud pipe composite. At this time, the mud pipe composite is the water-sealed air-tight membrane 5.

[0084] It obtains a tubular structure formed by the accumulation of saturated bentonite through density difference separation by centrifugation. The capillary force of the granular material is used to bind the liquid water under certain pressure, preventing it from being broken down by gas, thus achieving the effect of water-passing and air-tightening. Through simple physical action, the granular particles form a water-passing and air-tight structure in a saturated state, avoiding the problems of insufficient saturation and inaccurate testing that occur with pre-saturated water-passing and air-tight membranes. This greatly improves the water-passing and air-tightening effect and reduces the technical labor intensity of operators.

[0085] Meanwhile, the determination of the air intake value of its water-sealed air-tight membrane 5 specifically includes the following steps:

[0086] Cut one end of the prepared water-tight air-tight membrane 5 at the soil-water interface and install the intermediate filter valve. Weigh the water-tight air-tight membrane 5 and record the weight as follows: m 0; Place the water-sealed membrane 5 in the centrifuge tube, and keep the mud-tube composite parallel to the axis of the centrifuge tube;

[0087] Set multiple different speed levels for the centrifuge R i According to the speed from smallest to largest R i Conduct centrifugation tests; record the corresponding rotational speed every 4 hours. R i The weight of the water-sealed air-tight membrane 5 is recorded as follows: when the weight deviation is less than 1% for three consecutive weighings, the last weighing is recorded as... m i And record the interface height of the water-sealed air-tight membrane 5 at this time as H i ;

[0088] Calculate the rotational speed of each stage of the centrifuge R i The suction force of the sample under the water-sealed air-tight membrane 5 is specifically calculated using the following formula for each speed stage of the centrifuge. R i The suction force of the sample under the water-sealed air-tight membrane 5 P :

[0089] ;

[0090] In the formula: P For the matrix suction of the water-sealed air-tight membrane 5, kPa ; R i The speed of the centrifuge. rpm ; H i For water-sealed air membrane 5 in i The height of the interface at any given moment, in cm; RThe distance from the center of the centrifuge rotor to the bottom of the water-sealed air-tight membrane 5 is in cm; r The distance from the center of the centrifuge rotor to the top of the water-sealed air-tight membrane 5 is in cm; Dh The settling height of the water-sealed air-tight membrane 5 at each centrifugal level, and Δh=H (i-1) -H i cm; r The density of water is expressed in g / cm³. 3 ; g The acceleration due to gravity is taken as 9.8 m / s². 2 ;

[0091] With the sample suction force as the horizontal axis, and ( m 0- m i ) / m s Plot a two-dimensional experimental curve on the vertical axis, denoted as the soil-water characteristic curve, where... m s The weight of the bentonite in the mud-pipe composite;

[0092] Plot the first tangent at the initial water plateau end and the second tangent at the middle inclined section on the soil-water characteristic curve. Draw a perpendicular line from the intersection of the first and second tangents to the horizontal axis of the sample suction. The suction corresponding to this perpendicular line is the air inlet value of the water-tight air-tight membrane 5. P a .

[0093] The method determines the air intake value by obtaining the soil-water characteristic curve through conventional centrifugation. This method avoids the inability to measure the differences in air intake value of the water-sealed air-tight membrane 5 formed by the sintering of finished products. It can specifically measure the air intake value of the water-sealed air-tight membrane 5 formed each time this technology is implemented, thereby determining the operating pressure range of each water-sealed air-tight membrane 5. This method can improve the problem of the inability to quantify the application range of the water-sealed air-tight membrane 5 caused by uneven preparation of finished materials or unstable process, and specifically reduce the labor cost of engineering technicians.

[0094] In summary, this application provides a test method for simulating unsaturated steady-state seepage. Air pressure is applied upstream of a microfluidic chip 1, and the total amount of liquid discharged from the microfluidic chip 1 under stable air pressure conditions is observed. The microfluidic chip 1 is made of silicon or other materials and serves as a soil / rock simulation material. Simultaneously, a water-sealed air-tight membrane 5 is installed downstream of the microfluidic chip 1 to prevent both gas and liquid from being directly discharged when air pressure is applied, thus allowing for direct steady-state seepage testing of the simulated pore structure under air pressure conditions. Therefore, this method measures the relaxation performance of the microfluidic chip 1 structure to water, and is used to analyze the influence of soil / rock pore structure on liquid retention capacity. The results can evaluate the evolution gradient of the liquid retention properties of the pore structure and are parameters characterizing the continuity of the material structure. Furthermore, this method can evaluate the continuity of the structural distribution of pore materials, guiding the design of pore structures or the particle uniformity design of soil / rock materials. Furthermore, this method directly connects the macroscopic statistical parameters of the pore structure, the soil-water characteristic curve, with its microscopic image structure evaluation, enabling the evaluation of two functional designs through a single experiment.

[0095] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a water-permeable, airtight membrane, characterized in that, Includes the following steps: Bentonite was selected and prepared into a mud slurry with a soil-to-water ratio of 1:3 to 1:

5. The mud slurry was then vibrated. The mud slurry was then drawn up in several batches and injected into a PVC pipe. The two ends of the PVC pipe are sealed with PVC pipe caps to form a mud-pipe composite. The mud-tube composite is placed in a centrifuge tube, with the mud-tube composite parallel to the axial direction of the centrifuge tube. Set centrifuge speed r The centrifuge was then started, and records were taken at different times. t The height of the soil-water interface of the mud slurry within the mud pipe composite body is denoted as [height of mud slurry]. h t ; In three consecutive measurements h t When the deviation is less than 1%, the mud pipe composite is removed, and the PVC pipe caps at both ends of the mud pipe composite are removed to form a water-sealed air membrane.

2. The method for preparing the water-permeable air-tight membrane according to claim 1, characterized in that, The bentonite includes interlayer spacing. d (001) is sodium-based bentonite with a thickness of 1~1.2 nm.

3. The method for preparing the water-permeable, airtight membrane according to claim 1, characterized in that, The mud was subjected to ultrasonic vibration for 40-60 minutes.

4. The method for preparing the water-permeable air-tight membrane according to claim 1, characterized in that, The inner diameter of the PVC pipe n The numerical range is 0 < n <50mm, length is L The weight was drawn in several doses using a syringe. m The slurry is injected into the PVC pipe.

5. A water-permeable air-tight membrane, characterized in that, It is prepared by the method of any one of claims 1 to 4 for preparing a water-permeable air-tight membrane.

6. A method for determining the air intake value based on the water-sealed air-tight membrane described in claim 5, characterized in that, Includes the following steps: Cut one end of the water-tight air-tight membrane along the soil-water interface and install an intermediate filter valve. Weigh the water-tight air-tight membrane and record the weight as follows: m 0; Place the water-sealed membrane in a centrifuge tube, and keep the mud-tube composite parallel to the axial direction of the centrifuge tube; Set multiple different speed levels for the centrifuge R i According to the speed from smallest to largest R i Conduct centrifugation tests; record the corresponding rotational speed every 4 hours. R i The weight of the aforementioned water-sealed air-tight membrane is recorded as follows: if the weight deviation is less than 1% for three consecutive weighings, the last weighing is recorded as... m i The interface height of the water-sealed air-tight membrane at this time is recorded as... H i ; Calculate the rotational speed of each stage of the centrifuge. R i The suction force of the sample under the water-sealed air-tight membrane; with the sample suction force as the horizontal axis, and ( m 0- m i ) / m s Plot a two-dimensional experimental curve on the vertical axis, denoted as the soil-water characteristic curve, where... m s The weight of the bentonite in the mud-pipe composite; The air intake value of the water-tight membrane is obtained through the soil-water characteristic curve. Ψ a .

7. The method for determining the air inlet value of the water-sealed air-tight membrane according to claim 6, characterized in that, The rotational speed of each stage of the centrifuge is calculated using the following formula. R i The sample suction force of the water-sealed air-tight membrane below Ψ : ； In the formula: Ψ The matrix suction of the water-sealed air-tight membrane, kPa ; R i The rotational speed of the centrifuge. r / min ; H i For the water-sealed air-tight membrane in i The height of the interface at any given moment, in cm; R The distance from the center of the centrifuge rotor to the bottom of the water-sealed air-tight membrane, in cm; r The distance from the center of the centrifuge rotor to the top of the water-sealed air-tight membrane, in cm; Δh The settling height of the water-sealed air-tight membrane at each centrifugal level, and Δh=H (i-1) -H i cm; ρ The density of water is expressed in g / cm³. 3 ; g The acceleration due to gravity is taken as 9.8 m / s². 2 .

8. The method for determining the air inlet value of the water-sealed air-tight membrane according to claim 6, characterized in that, Plot the first tangent line at the initial water plateau end and the second tangent line at the middle inclined section on the soil-water characteristic curve. Draw a perpendicular line from the intersection of the first and second tangent lines to the horizontal axis of the sample suction. The suction force corresponding to this perpendicular line is the air inlet value of the water-tight air-tight membrane. Ψ a .

9. A device for simulating unsaturated steady-state seepage, characterized in that, The system includes a microfluidic chip, a pressure controller, an eddy current temperature controller, a high-speed high-definition camera, a backup pressure unit, a data acquisition and control unit, a microbalance water collection box, and the water-tight membrane as described in claim 5. The two ends of the microfluidic chip are respectively connected to the pressure controller and one end of the water-tight membrane. The pressure controller provides driving power to the microfluidic chip. An intermediate filter valve is installed in the soil-water interface cut at the other end of the water-tight membrane, and one end of the intermediate filter valve is connected to the backup pressure unit. The backup pressure unit is connected to the microbalance water collection box via a drain pipe. The backup pressure unit provides auxiliary pressure, and the microbalance water collection box is used for... The system collects and measures the weight of liquid discharged from the water-sealed membrane; the high-speed high-definition camera and the eddy current temperature controller are respectively and spaced apart on one side of the microfluidic chip, the high-speed high-definition camera is used to monitor the dynamics of the microfluidic chip in real time, and the eddy current temperature controller is used to monitor the temperature of the microfluidic chip in real time; the acquisition and control unit is electrically connected to the pressure controller, the eddy current temperature controller, the high-speed high-definition camera, the backup pressure unit, and the microbalance water collection box, and is used to acquire various data measured by the pressure controller, the eddy current temperature controller, the high-speed high-definition camera, the backup pressure unit, and the microbalance water collection box in real time.

10. A test method based on the unsaturated steady-state seepage simulation device described in claim 9, characterized in that, Includes the following steps: One end of the microfluidic chip, saturated with water in its pores, is connected to the pressure controller, and the other end is connected to one end of the water-tight membrane. The other end of the water-tight membrane is cut at the soil-water interface and an intermediate filter valve is installed. The lower end of the intermediate filter valve is connected to the backup pressure unit. The backup pressure unit is connected to the microbalance water collection box. The high-speed, high-definition camera is spaced apart on one side of the microfluidic chip. The acquisition and control unit is electrically connected to the pressure controller, the eddy current temperature controller, the high-speed, high-definition camera, the backup pressure unit, and the microbalance water collection box. The lower end of the drain pipe is dripped into the water collection box of the microbalance; The pressure of the pressure controller is set by the acquisition and control unit. P k The control temperature of the eddy current temperature controller and the back pressure of the backup pressure unit are set, wherein, P k < Ψ a Record stress P k The weight in the water collection box of the microbalance below m ki ,in, i =0, 1, 2, ..., e, and simultaneously record the image number of the high-speed high-definition camera. F ki ,in, i =0, 1, 2, ..., e; pressure to be applied P k When the weight change in the water collection box of the microbalance described below is less than 0.00001g, the next level of pressure is applied. P k+1 ,in, P k < P k+1 < Ψ a And record the weight of the water collection box of the microbalance at this time. m ke and the image number of the high-speed high-definition camera F ke Until the measurement is completed P k+n Level pressure, among which, P k < P k+n < Ψ a ; Calculate the pressure of the same level P k The drainage volume through the water-sealed air membrane M k = m k0 - m ke and with pressure P k With the horizontal axis as the base, M k Plot a curve on the vertical axis; right F ki to F ke Analyze the images between them to obtain the coefficient of difference. R k Further, the difference coefficient under different pressures was obtained. R k The variance.

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