A non-saturated clay penetration-membrane effect-ion diffusion integrated testing device and method considering the influence of multi-field coupling

Abstract

The application relates to a non-saturated clay penetration-membrane effect-ion diffusion integrated testing device and method considering the influence of multi-field coupling, which comprises a soil sample sealing chamber, a pressure applying assembly for vertically applying pressure on the soil sample through a piston, a solution injection and extraction cycle assembly for injecting and extracting a solution into the soil sample sealing chamber, which comprises a top solution injection and extraction pipeline and a bottom solution injection and extraction pipeline in communication with the soil sample sealing chamber, a temperature control assembly for regulating the temperature of the soil sample and the injected solution, a suction control assembly for applying air pressure to the soil sample sealing chamber and realizing soil suction control through a high air inlet value porcelain plate at the top and bottom ends of the soil sample, and a penetration pressure difference monitoring assembly for monitoring the chemical penetration pressure difference at the top and bottom ends of the soil sample. Compared with the prior art, the application provides a non-saturated clay penetration-membrane effect-ion diffusion integrated testing device which can simultaneously control the temperature, suction, stress and chemical concentration gradient.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane effect and retardation performance testing of unsaturated clay, and in particular to an integrated testing device and method for unsaturated clay permeability-membrane effect-ion diffusion considering multi-field coupling effects. Background Art

[0002] Clay-based engineering barrier materials are widely used in pollution control projects such as landfills, mine pollution control, and metal smelters due to their excellent low permeability, semi-permeable membrane retardation effect, and strong adsorption properties. Taking landfills as an example, clay liner barriers and clay cover barriers are typically laid on the top and bottom of the garbage pile. During long-term operation, clay-based engineering barriers will be continuously subjected to the coupled thermal-hydraulic-chemical effects of waste degradation heat, groundwater fluctuations and humidity changes caused by rainfall evaporation, the gravitational load of the overlying garbage pile, and chemical intrusion from landfill leachate. This puts the clay material at risk of degradation of its barrier properties or even failure. Summary of the Invention

[0003] The purpose of the present invention is to provide an integrated testing device and method for unsaturated clay permeability-membrane effect-ion diffusion considering the influence of multi-field coupling, and to study the blocking performance of unsaturated clay materials under the influence of thermal-hydraulic-mechanical-chemical coupling.

[0004] The object of the present invention can be achieved by the following technical solution: an integrated testing device for unsaturated clay permeability, membrane effect, and ion diffusion considering the influence of multi-field coupling, comprising:

[0005] A soil sample sealed chamber comprises a rigid side wall, a piston and a base, wherein the soil sample is arranged in a cavity surrounded by the rigid side wall, the piston and the base;

[0006] A vertical pressure component, used for applying vertical pressure to the soil sample through a piston;

[0007] A solution injection and extraction circulation component is used to inject and extract the solution into the soil sample sealed chamber, which includes a top solution injection and extraction pipe and a bottom solution injection and extraction pipe connected to the cavity;

[0008] Temperature control assembly, used to regulate the temperature of soil samples and injection solutions;

[0009] The suction control component is used to apply air pressure to the soil sample sealed chamber and realize soil suction control by means of high air intake value clay plates at the top and bottom of the soil sample;

[0010] Osmotic pressure difference monitoring component is used to monitor the chemical osmotic pressure difference between the top and bottom ends of the soil sample.

[0011] Preferably, the rigid side wall comprises a rigid permeable wall, an annular metal permeable stone and a stainless steel ring;

[0012] The inner ring of the rigid permeable wall is provided with an L-shaped groove, the annular metal permeable stone is placed in the L-shaped groove, and a stainless steel ring is provided on the upper end of the annular metal permeable stone;

[0013] The suction control component includes an air guide tube connected to the air pressure injection interface of the rigid permeable wall, the air pressure injection interface is connected to the annular metal permeable stone, and a high air intake value clay plate is embedded in the upper piston and lower base of the soil sample, and the suction control of the soil sample is achieved by using axis translation technology.

[0014] Further preferably, the lower surface of the annular metal permeable stone and the outer surface of the stainless steel ring are both provided with sealing rings.

[0015] Further preferably, the air pressure injection interface is provided with a sealing ring.

[0016] Further preferably, the air duct is connected to a gas pressure controller, which controls the air pressure to introduce gas into the soil sample sealed chamber. The gas penetrates into the soil sample through the annular metal permeable stone, thereby driving the moisture in the soil sample to be discharged along the high air intake value clay plates at the top and bottom ends of the soil sample, and finally reaching a suction balance state with stable moisture content.

[0017] Further preferably, the annular metal permeable stone is made of copper, and has an inner diameter of 45 to 55 mm, an outer diameter of 60 to 65 mm, and a thickness of 4 to 6 mm.

[0018] More preferably, the annular metal permeable stone has an inner diameter of 50 mm, an outer diameter of 62 mm, and a thickness of 5 mm.

[0019] Further preferably, air pressure injection interfaces are symmetrically provided on the rigid permeable wall.

[0020] More preferably, the rigid permeable wall is made of 316 stainless steel.

[0021] Further preferably, a top cover is provided on the top of the rigid side wall, the stainless steel ring and the top of the rigid permeable wall abut against the top cover, and the top cover is detachably connected to the base via a connector.

[0022] More preferably, the connecting piece includes a screw and a nut, the top cover is annular in structure, and screws are symmetrically arranged on it, the screws are connected to the base, and the top cover is pressed against the stainless steel ring and the rigid permeable wall by the locking nut.

[0023] Preferably, the piston is arranged above the soil sample and can move along the inner surface of the rigid side wall under the drive of the vertical pressure component.

[0024] Further preferably, a sealing ring is provided on the outer surface of the piston.

[0025] Preferably, the vertical pressure assembly includes a vertical loading frame, a weight, a weight tray, an electronic dial indicator and a metal test bench;

[0026] The vertical loading frame is installed on the metal test bench through a vertical metal screw and a nut. A weight tray is set at the bottom and an electronic dial indicator is set on the top. The weights are placed on the weight tray step by step. The gravity of the weights is transmitted to the piston through the vertical loading frame and then applies vertical pressure to the soil sample. The electronic dial indicator records the vertical deformation of the soil sample during the step-by-step loading process.

[0027] Further preferably, a circular hole for the metal screw to move up and down is opened on the metal test bench.

[0028] More preferably, the circular hole is a non-threaded hole with a diameter not less than the outer diameter of the screw.

[0029] Preferably, each surface of the soil sample is wrapped with filter paper, and the upper and lower ends are sequentially provided with a high air intake value clay plate and a permeable stone;

[0030] The permeable stones at the upper and lower ends of the soil sample are respectively embedded in the piston and the base, and are connected to the solution circulation channels provided in the piston and the base;

[0031] The top solution injection and pumping pipeline and the bottom solution injection and pumping pipeline are respectively communicated with the solution circulation channel of the piston and the solution circulation channel of the base.

[0032] Further preferably, the high air intake value clay plate has a thickness of 5 to 7 mm, a diameter of 40 to 50 mm, and a maximum air intake value of 1500 kPa.

[0033] More preferably, the high air intake value clay plate has a thickness of 6 mm and a diameter of 44 mm.

[0034] More preferably, the same high air intake clay plates are used at the upper and lower ends of the soil sample, that is, the structural morphology, physicochemical parameters, etc. of the high air intake clay plates used at the upper and lower ends of the soil sample are completely the same.

[0035] Further preferably, a top differential pressure sensor interface and a bottom differential pressure sensor interface are respectively provided on the piston and the base, and the top differential pressure sensor interface and the bottom differential pressure sensor interface are both connected to the soil sample sealed chamber and extend into the high air intake value clay plate, and the osmotic pressure differential monitoring component includes a differential pressure sensor connected to the top differential pressure sensor interface and the bottom differential pressure sensor interface, and a data recorder connected to the differential pressure sensor.

[0036] More preferably, the top differential pressure sensor interface and the bottom differential pressure sensor interface extend 3 to 4 mm into the high air intake value clay plate.

[0037] Further preferably, the top solution extraction pipeline and the bottom solution injection pipeline are connected to a syringe pump;

[0038] The temperature control component comprises a heating belt wound around the injection end of the injection pump and the outer surface of the rigid side wall, and a temperature controller connected to the heating belt.

[0039] Preferably, the sealing rings are all O-rings.

[0040] Preferably, the soil sample is a compacted soil sample with D=45-55 mm and H=18-22 mm.

[0041] Preferably, the soil sample is a compacted soil sample with D=50 mm and H=20 mm.

[0042] Preferably, the temperature control component controls the temperature of the soil sample and the injection solution to be within a range of 20 to 80°C.

[0043] Preferably, the vertical pressure component applies a vertical pressure of 0 to 500 kPa to the soil sample.

[0044] Preferably, the suction control component controls the soil suction to be 50-500 kPa.

[0045] Preferably, the chemical solution injected into and extracted from the soil sample by the solution injection and extraction circulation component is a salt solution or a solution containing heavy metals.

[0046] More preferably, the concentration of the salt solution is 0.1-0.001M.

[0047] Further preferably, the salt solution includes but is not limited to KCl, NaCl, and CaCl2 solutions.

[0048] More preferably, the concentration of heavy metals in the heavy metal-containing solution is 10-60 mM.

[0049] Further preferably, the heavy metals include but are not limited to Zn, Pb, and Cr.

[0050] In the present invention, gradient control of temperature, pressure, suction and chemical concentration can be achieved through the temperature control component, vertical pressure component, suction control component and solution injection and extraction circulation component. For example, the temperature of the heating belt can be set step by step from low to high, and the mass of the weight can be increased step by step to achieve a gradient increase in temperature and pressure, and then measure the relevant parameters under different temperature and pressure conditions.

[0051] An integrated test method for unsaturated clay permeability, membrane effect, and ion diffusion considering multi-field coupling effects is performed using the above-mentioned device, comprising the following steps:

[0052] S1: Place the soil sample in a sealed chamber surrounded by rigid side walls, a piston and a base;

[0053] S2: saturate and filter the soil sample;

[0054] S3: The vertical pressure component drives the piston to move along the rigid side wall to apply a vertical (axial) target load to the soil sample. The temperature control component controls the target temperature of the soil sample and the injected solution. The suction control component applies air pressure to the soil sample and controls the change of soil suction. The top solution injection and extraction pipe injects and extracts chemical solutions into and out of the top of the soil sample. The bottom solution injection and extraction pipe injects and extracts deionized water into and out of the bottom of the soil sample. The osmotic pressure difference between the top and bottom of the soil sample is measured in real time by the osmotic pressure difference monitoring component.

[0055] An application of the above-mentioned integrated test device for unsaturated clay permeability-membrane effect-ion diffusion considering the influence of multi-field coupling is used to test and analyze the permeability coefficient, membrane efficiency coefficient, effective diffusion coefficient and retardation factor of unsaturated clay under different temperatures, suctions, loads and concentration gradients, revealing the development law of the retardation performance of unsaturated clay under thermal-hydraulic-mechanical-chemical coupling.

[0056] Due to the difficulty in implementing suction control technology, the complexity of the coupling of multiple field factors, and the high requirements for testing technology and precision, most existing testing devices focus on the multi-field coupling response of the membrane effect blocking performance of clay materials under saturated conditions. However, in actual engineering, clay-based engineering barrier systems may be in the vadose zone and be subjected to suction changes such as alternating rainfall and evaporation and groundwater level fluctuations for a long time. Therefore, limited by existing testing devices and testing technologies, the membrane effect blocking characteristics of clay-based engineering barrier materials under unsaturated conditions are still unclear. To this end, the present invention innovatively develops a set of testing devices that can measure the membrane effect blocking performance of clay-based engineering barrier materials under unsaturated conditions, and by setting up temperature control components and loading components, couples the effects of thermal-hydraulic-mechanical-chemical multiple fields, thereby realizing the exploration of the laws and mechanism of the unsaturated clay membrane effect blocking performance considering the influence of multiple field coupling, which is more conducive to guiding engineering practice.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] 1. The present invention provides an integrated testing device for unsaturated clay permeability, membrane effect, and ion diffusion, which takes into account the effects of thermal-hydraulic-mechanical-chemical coupling. The device can simultaneously control temperature, suction, pressure, and chemical concentration gradient to test unsaturated clay.

[0059] 2. The present invention can realize the measurement of the membrane efficiency coefficient of unsaturated soil samples. The suction control component in the device and the high air intake value clay plate in the soil sample sealing chamber can control the unsaturated state of the soil sample, thereby realizing the measurement of the membrane efficiency coefficient of the unsaturated soil sample.

[0060] 3. In the soil suction control, the application uses a gas pressure controller to apply gas pressure to the sealed chamber through symmetrical double channels. By setting the annular water-permeable stone, local structural disturbance to the soil sample during gas pressure application is avoided, effectively realizing suction control and improving test measurement accuracy.

[0061] 4. The application can improve efficiency and realize simultaneous control of temperature, pressure, suction effect and chemical concentration gradient. Various coupling effects can be realized in the application.

[0062] 5. The application divides the rigid side wall into a rigid permeable wall, an annular metal water-permeable stone and a stainless steel ring, and through modular design, the soil sample is easy to take and place, and the assembly is simple and fast.

[0063] 6. The test results of the application are helpful to explore and reveal the multi-field coupling response mechanism of the blocking performance of clay-type pollution prevention barriers in engineering environments such as landfills, high-level waste deep geological disposal repositories, industrial contaminated sites and mine tailings repositories.

[0064] 7. The application can obtain the permeability coefficient curve, membrane efficiency coefficient-time curve, effective diffusion coefficient and blocking factor change curve of the unsaturated clay-type protective barrier. It is conducive to guiding the adjustment and implementation of measures such as site well opening and closing, leachate discharge and site remediation treatment according to the actual working conditions of temperature, load and discharged leachate in engineering practice, and reducing the risk of degradation or even failure of the blocking performance of clay-type protective barriers. BRIEF DESCRIPTION OF DRAWINGS

[0065] Figure 1 is a structural schematic diagram of the test device of the application;

[0066] Figure 2 is a front view structural schematic diagram of the soil sample sealing chamber of the application;

[0067] Figure 3 is a design schematic diagram of the water passage of the base of the soil sample sealing chamber of the application;

[0068] In the figure: 1-soil sample sealed chamber, 10-soil sample, 101-filter paper, 102-high air intake value clay plate, 103-permeable stone, 11-rigid side wall, 111-rigid permeable wall, 1111-air pressure injection interface, 112-annular metal permeable stone, 113-stainless steel ring, 12-piston, 121-top differential pressure sensor interface, 122-top solution injection channel, 123-top solution extraction channel, 13-base, 131-bottom differential pressure sensor interface, 132-bottom solution injection channel, 133-bottom solution extraction channel, 14-top cover, 15-catheter interface, 2-vertical pressure Components, 21-vertical loading frame, 22-weight, 23-weight tray, 24-electronic dial indicator, 25-metal test bench, 3-solution injection and extraction circulation component, 31-top solution injection and extraction pipeline, 32-bottom solution injection and extraction pipeline, 33-syringe pump, 34-three-way valve, 35-solution collection bottle, 36-solution supply bottle, 4-temperature control component, 41-heating belt, 42-temperature controller, 5-suction control component, 51-air guide tube, 52-gas pressure controller, 6-osmotic pressure difference monitoring component, 61-pressure difference sensor, 62-data acquisition instrument, 7-sealing ring, 8-screw, 9-nut. DETAILED DESCRIPTION

[0069] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0070] Example 1

[0071] An integrated test device for unsaturated clay permeability, membrane effect and ion diffusion considering the influence of multi-field coupling, such as Figure 1 As shown, it includes a soil sample sealing chamber 1, a vertical pressure component 2, a solution injection and extraction circulation component 3, a temperature control component 4, a suction control component 5 and an osmotic pressure difference monitoring component 6.

[0072] Among them, such as Figure 2As shown, the soil sample sealed chamber 1 includes rigid sidewalls 11, a piston 12, and a base 13, which enclose a cavity in which a soil sample 10 is placed. A vertical pressure assembly 2 applies vertical pressure to the soil sample 10 within the sealed chamber via the piston 12. A solution injection and extraction circulation assembly 3 includes a top solution injection and extraction pipeline 31 and a bottom solution injection and extraction pipeline 32, respectively, for injecting and extracting solution from the top and bottom ends of the soil sample 10 within the sealed chamber. A temperature control assembly 4 regulates and controls the temperature of the soil sample 10 within the sealed chamber and the solution injected into the cavity via the solution injection and extraction circulation assembly 3. A suction control assembly 5 introduces gas into the sealed chamber, thereby applying air pressure to the sample 10 within the chamber. Suction control of the sample 10 is achieved via high-intake clay plates 102 at the top and bottom ends of the sample 10. An osmotic pressure differential monitoring assembly 6 monitors the chemical osmotic pressure differential between the top and bottom ends of the sample 10 within the sealed chamber.

[0073] This embodiment can perform a retardation performance test on unsaturated clay taking into account the effects of thermal-hydraulic-mechanical-chemical coupling, which is closer to the application environment of clay in actual engineering.

[0074] Example 2

[0075] An integrated testing device for unsaturated clay permeability, membrane effect, and ion diffusion considering the effects of multi-field coupling is disclosed. The rigid side wall 11 includes a rigid permeable wall 111, an annular metal permeable stone 112, and a stainless steel ring 113. An L-shaped groove is provided on the inner ring of the rigid permeable wall 111. The annular metal permeable stone 112 is placed in the L-shaped groove and a stainless steel ring 113 is provided on the upper end. A pneumatic injection interface 1111 is symmetrically provided on the rigid permeable wall 111, and the pneumatic injection interface 1111 is connected to the annular metal permeable stone 112. Furthermore, a top cover 14 is provided on the top of the rigid permeable wall 11. The stainless steel ring 113 and the top of the rigid permeable wall 111 abut against the top cover 14. The top cover 14 is connected to the base 13 via a screw 8 and a nut 9.

[0076] The suction control assembly 5 includes an air pipe 51 and a gas pressure controller 52 connected to the air pipe 51. The air pipe 51 is connected to the air pressure injection port 1111. The gas pressure controller 52 controls the air pressure to introduce gas into the soil sample sealed chamber 1 through the air pipe 51 and the air pressure injection port 1111. The gas diffuses and penetrates into the soil sample 10 through the annular metal permeable stone 112, driving the moisture in the soil sample 10 to be discharged along the high-intake clay plates 102 at the top and bottom ends of the soil sample 10, ultimately achieving a suction equilibrium state with stable moisture content.

[0077] The vertical pressure-applying assembly 2 includes a vertical loading frame 21, weights 22, a weight tray 23, an electronic dial indicator 24, and a metal test bench 25. The vertical loading frame 21 is mounted on the metal test bench 25 via a vertical metal screw 8 and nut 9. The weight tray 23 is located at the bottom, and the electronic dial indicator 24 is located at the top. The vertical loading frame 21 can move downward under the load of the weights 22. The piston 12 is positioned above the soil sample 10. By gradually placing weights 22 of a certain mass on the weight tray 23, the weight of the weights 22 is transmitted to the piston 12 via the vertical loading frame 21, thereby applying vertical pressure to the soil sample 10. The electronic dial indicator 24 records the vertical deformation of the soil sample 10 during the step-by-step loading process.

[0078] Each surface of the soil sample 10 is wrapped with filter paper 101. A high-air-intake clay plate 102 and a permeable stone 103 are sequentially provided at the upper end of the soil sample 10 from bottom to top. A high-air-intake clay plate 102 and a permeable stone 103 are sequentially provided at the lower end of the soil sample 10 from top to bottom. In addition, the permeable stone 103 at the upper end of the soil sample 10 is embedded in the piston 12 and communicates with the solution circulation channel provided in the piston 12. The permeable stone 103 at the lower end of the soil sample 10 is embedded in the base 13 and communicates with the solution circulation channel provided in the base 13. The solution circulation channel provided in the base 13 is as shown in FIG. Figure 3 shown.

[0079] The piston 12 is provided with a top differential pressure sensor interface 121, a top solution injection channel 122, and a top solution extraction channel 123. The base 13 is provided with a bottom differential pressure sensor interface 131, a bottom solution injection channel 132, and a bottom solution extraction channel 133. The top solution injection channel 122 and the top solution extraction channel 123 are connected to the solution circulation channel provided within the piston 12 and are connected to the top solution injection and extraction pipeline 31. The bottom solution injection channel 132 and the bottom solution extraction channel 133 are connected to the solution circulation channel provided within the base 13 and are connected to the bottom solution injection and extraction pipeline 32. This allows the top solution injection and extraction pipeline 31 and the bottom solution injection and extraction pipeline 32 to communicate with the solution circulation channel of the piston 12 and the solution circulation channel of the base 13, respectively. The top solution extraction pipeline 31 and the bottom solution extraction pipeline 32 are connected to a syringe pump 33.

[0080] The temperature control assembly 4 includes a heating belt 41 and a temperature controller 42. The heating belt 41 is wound around the injection end of the injection pump 33 and the outer wall of the soil sample sealing chamber 1. The temperature controller 42 heats the injected solution and the soil sample 10 in the chamber to a constant temperature respectively.

[0081] The osmotic pressure difference monitoring component 6 includes a pressure difference sensor 61 and a data acquisition instrument 62. The pressure difference sensor 61 tests the osmotic pressure difference of the solution at the top and bottom ends of the soil sample 10 through the top pressure difference sensor interface 121 and the bottom pressure difference sensor interface 131, and displays and records it through the data acquisition instrument 62.

[0082] In this embodiment, sealing rings are provided on the outer surface of the piston 12, the lower surface of the annular metal permeable stone 112, the outer surface of the stainless steel ring 113, the air pressure injection port 1111, etc. The rest is the same as in the first embodiment.

[0083] Example 3

[0084] An integrated testing device for unsaturated clay permeability, membrane effect, and ion diffusion considering the effects of thermal-hydraulic-mechanical-chemical coupling includes a temperature-humidity controlled soil sample sealing chamber 1, a temperature control component 4, a suction control component 5, a step-by-step loading component (vertical pressure component 2), a solution injection and extraction circulation component 3, and an osmotic pressure difference monitoring component 6.

[0085] The soil sample sealed chamber 1 includes a stainless steel piston 12, a stainless steel ring 113, an O-ring 7, a soil sample 10, an annular metal permeable stone 112, a stainless steel base 13, a conduit port 15, a bottom solution injection channel 132, a permeable stone 103, a high-air-intake clay plate 102, a bottom differential pressure sensor port 131, a bottom solution extraction channel 133, an air pressure injection port 1111, an annular filter paper 101, a rigid permeable wall 111, a stainless steel top cover 14, a top solution extraction channel 123, a top differential pressure sensor port 121, a top solution injection channel 122, a heating belt 41, a screw 8, a nut 9, an air guide tube 51, and the like. The soil sample 10 is placed within the rigid permeable wall 111, with the filter paper 101 wrapped around the sidewalls. The upper and lower surfaces of the soil sample 10 are padded with filter paper 101 and wrapped by the high-air-intake clay plate 102. The lower high-air-intake clay plate 102 is embedded in the stainless steel base 13 and padded with permeable stone 103. The upper high-air-intake clay plate 102 is embedded in the stainless steel piston 12 and also padded with permeable stone 103. The upper and lower permeable stones 103 are embedded in the stainless steel piston 12 and base 13, respectively, and communicate with channels within the base 13 and piston 12. The stainless steel piston 12 is provided with an O-ring groove on its periphery, which accommodates an O-ring 7. This ensures close contact between the piston 12 and the rigid permeable wall 111, forming a sealed water circulation chamber and preventing solution and gas leakage. Solution circulation channels are provided inside the stainless steel piston 12 and on the stainless steel base 13 to circulate the solution along the upper and lower surfaces of the soil sample 10. Three external conduit interfaces on the top of the piston 12 connect to the top solution injection channel 122, the top solution extraction channel 123, and the top differential pressure sensor interface 121, respectively. Water is circulated through the top solution injection channel 122 and extraction through the top solution extraction channel 123. An annular metal permeable stone 112 is placed within the L-shaped groove of the rigid permeable wall 111, with a stainless steel ring 113 placed at its upper end. Both the lower surface of the annular metal permeable stone 112 and the outer surface of the stainless steel ring 113 are provided with O-ring grooves to prevent the leakage of solution and gas after the O-ring 7 is inserted. The stainless steel top cover 14, the rigid permeable wall 111, and the base 13 are connected by screws 8. The top cover 14 is secured by tightening nuts 9. The outer periphery of the rigid permeable wall 111 is connected to the air duct 51 via a pressure injection port 1111.

[0086] The temperature control assembly 4 includes a heating tape 41 and a temperature controller 42. The heating tape 41 is wrapped around the injection end of the TSD01 series laboratory syringe pump 33 and the outer wall of the soil sample sealed chamber 1. The temperature controller 42 heats the injected solution and the soil sample 10 in the chamber to a constant temperature.

[0087] The suction control assembly 5 includes a gas pressure controller 52 and an air guide tube 51. The air guide tube 51 is connected to the air pressure injection interface 1111 on the outside of the rigid permeable wall 111. The air pressure injection interface 1111 is installed with an O-ring 7 to prevent gas overflow. The gas pressure controller 52 is used to control the air pressure to apply air pressure to the soil sample sealed chamber 1. The gas diffuses and penetrates into the soil sample 10 through the annular metal permeable stone 112, and the suction control of the soil sample 10 is achieved with the help of the high air intake value clay plates 102 at the top and bottom ends of the soil sample 10.

[0088] The vertical pressure assembly 2 includes a vertical loading frame 21, weights 22, a weight tray 23, an electronic dial indicator 24, a screw 8, a nut 9, and a metal test bench 25. The weights 22 are placed step by step on the weight tray 23. The weight of the weights 22 is transmitted to the piston via the vertical loading frame 21, applying vertical pressure to the soil sample 10. An electronic dial indicator 24 is mounted on top of the vertical loading frame 21 to record the vertical deformation of the soil sample 10 during the step-by-step loading process. The vertical loading frame 21 is mounted on the metal test bench 25 using the screw 8 and nut 9.

[0089] The solution extraction circulation assembly 3 includes a liquid guide tube (i.e., a top solution injection and extraction pipeline 31 and a bottom solution injection and extraction pipeline 32), a three-way valve 34, a solution collection bottle 35, a TSD01 series laboratory syringe pump 33, and a solution supply bottle 36. The injection syringes of two TSD01 series laboratory syringe pumps 33 are connected to the liquid guide tube, which is connected to the three-way valve 34. One end of the three-way valve 34 is connected to the solution supply bottle 36, and the other end is connected to the top solution injection channel 122 or the bottom solution injection channel 132 of the soil sample sealed chamber 1. The extraction syringe is also connected to the three-way valve 34, one end of which is connected to the solution collection bottle 35, and the other end is connected to the top solution extraction channel 123 or the bottom solution extraction channel 133 of the soil sample sealed chamber 1. One of the two syringe pumps 33 injects and extracts water into the top of the chamber to achieve top water circulation, while the other injects and extracts water into the bottom of the chamber to achieve bottom water circulation.

[0090] The osmotic pressure differential monitoring assembly 6 includes a differential pressure sensor 61 and a data acquisition device 62. The data acquisition device 62 is a MEACONMIK-R200T six-channel paperless recorder that displays and records the soil sample expansion force and the osmotic pressure differential between the top and bottom ends of the solution. The differential pressure sensor 61 is an MC PCM610 differential pressure transmitter with a pressure range of 10 kPa, capable of measuring the osmotic pressure differential between the top and bottom ends of the solution.

[0091] The functions of the main components in the device of this embodiment are as follows:

[0092] TSD01 series laboratory syringe pump 33: continuous injection and withdrawal of solutions.

[0093] Weight 22: Apply vertical pressure step by step.

[0094] Vertical loading frame 21: transmits the vertical pressure applied by the weight.

[0095] Electronic dial indicator 24: records the vertical deformation of the soil sample in the rigid wall infiltration chamber.

[0096] Soil sample sealed chamber 1: for storing soil samples.

[0097] Catheter: a channel for transporting solution.

[0098] Airway tube 51: gas transport channel.

[0099] Gas pressure controller 52: controls the gas pressure.

[0100] Differential pressure sensor 61: measures the chemical osmotic pressure difference at both ends of the soil sample.

[0101] Data acquisition instrument 62: displays and records the chemical osmotic pressure difference between the two ends of the soil sample.

[0102] Heating tape 41: Heats the rigid wall infiltration chamber and the injection end of the syringe pump.

[0103] Temperature controller 42: adjusts the temperature of the heating belt.

[0104] Solution supply bottle 36: replenishes the infiltration solution in the syringe.

[0105] Solution collection bottle 35: collects the exudate solution in the syringe.

[0106] Three-way valve 34: controls the flow direction of the solution.

[0107] The working principle of the device in this embodiment:

[0108] A compacted clay soil sample 10 of a certain size and dry density is pressed in the soil sample sealing chamber 1 , and a layer of filter paper 101 is padded on the side, top and bottom surfaces of the soil sample 10 .

[0109] Below the soil sample 10, in order, are filter paper 101, a high-air-intake clay plate 102, a permeable stone 103, and a stainless steel base 13. Above the soil sample 10, in order, are filter paper 101, a high-air-intake clay plate 102, a permeable stone 103, a stainless steel piston 12, and a stainless steel top cover 14. From bottom to top, the sides of the soil sample 10 are a rigid permeable wall 111, an annular metal permeable stone 112, and a stainless steel ring 113. After assembly, screw 8 is installed and nut 9 is tightened. The top water inlet of the chamber (top solution injection channel 122) is connected to a volume / pressure controller. The injection pressure is set to 100 kPa, and deionized water is introduced. After air bubbles are expelled from the chamber, saturation of the soil sample begins. Once saturation is complete, deionized water is continued to filter out salts from the soil sample. During the filtration and washing process, leachate is continuously collected and its conductivity is measured. Filtration and washing are stopped when the leachate conductivity is less than 50% of the conductivity of the lowest concentration solution used in the experiment.

[0110] The filtered and washed soil sample sealed chamber 1 is connected to a temperature control assembly 4, a suction control assembly 5, a vertical pressure assembly 2, a solution injection and extraction circulation assembly 3, and an osmotic pressure differential monitoring assembly 6. A target load is applied to the upper end of the soil sample 10 by adding a weight 22. The target temperature of the soil sample 10 and the injection end solution is controlled by setting a temperature controller 42 to ensure that the injection end solution and the soil sample sealed chamber 1 are kept constant at the target temperature. A gas pressure controller 52 is used to apply gas pressure to the soil sample 10. Using axial translation technology, the matrix suction of the soil sample 10 is calculated based on the difference between the gas pressure and the water pressure, achieving suction control of the soil sample 10. A micro-injection / extraction integrated syringe pump 33 is used to circulate deionized water between the top and bottom of the soil sample. A pressure differential sensor 61 and a data acquisition device 62 are used to record the background pressure differential of the soil sample 10 when the circulating fluid is stable. By replacing the solution in the top syringe pump 33 with the target salt solution, chemical solution gradient control is achieved at the top and bottom of the soil sample.

[0111] During the experiment, two syringe pumps 33 were controlled to achieve top and bottom solution injection and withdrawal cycles at the same flow rate. Leakage fluid was collected from the top and bottom of soil sample 10, and the chemical osmotic pressure difference between the top and bottom of soil sample 10 was measured in real time using an osmotic pressure differential monitoring assembly 6. The volume, ion concentration, and cumulative ion content of the top and bottom seepage fluids were recorded over a period of time. The permeability coefficient, membrane efficiency coefficient, effective diffusion coefficient, and retardation factor of the soil were then calculated under different temperatures, suction forces, loads, and chemical concentration gradients. This revealed the development patterns of the membrane effect retardation properties of clay materials under the coupled effects of heat, water, force, and chemical reaction.

[0112] Permeability: The permeability can be monitored during both the saturation and filtration phases. The permeability is determined using the equal head method and calculated using Darcy's law (Equation 1).

[0113]

[0114] Where ΔQ is the flow rate difference between the top and bottom ends of the seepage liquid within Δt, A is the cross-sectional area perpendicular to the direction of water flow, and I is the hydraulic gradient.

[0115] Determination of membrane efficiency coefficient: According to the test device of the present invention, the membrane efficiency coefficient is obtained by the ratio of the actual chemical osmotic pressure difference measured by the osmotic pressure difference monitoring component to the theoretical chemical osmotic pressure difference, as shown in Formula 2.

[0116]

[0117] Where Δπ is the theoretical chemical osmotic pressure difference, which can be calculated using the Van't Hoff formula, and ΔP is the actual chemical osmotic pressure difference between the top and bottom of the soil sample, as shown in Formula 3.

[0118] Δπ=vRTΔC#(3)

[0119] Where v is the total number of ions contained in the chemical formula of the electrolyte, and R is the universal gas constant (8.314 J·mol -1 ·K -1 ), T is the absolute temperature, and ΔC is the difference in chemical concentration between the top and bottom of the soil sample.

[0120] The membrane efficiency coefficient varies within the range of 0 < ω < 1. ω = 1 indicates no solute passes through; ω = 0 indicates all solutes pass through. Natural clay semipermeable membranes are not ideal and cannot completely prevent solute passage.

[0121] The combination of the upper and lower high-air-intake clay plates and the soil sample is similar to a layered structure of a porous medium. The effective diffusion coefficient of the soil sample can be calculated by Equation 4.

[0122]

[0123] Among them, L clay and θ clay are the thickness and volumetric moisture content of the soil sample, ΔC clay is the concentration difference between the upper and lower surfaces of the soil sample, J d,ss is the solute diffusion flux when the soil sample-clay plate system reaches stability, which is the same as the solute diffusion flux of the high air inlet value clay plate and soil sample, that is, J d,ss =J HAE,ss =J clay,ss .

[0124] The calculation of the retardation factor is shown in Equation 5.

[0125]

[0126] Among them, T L For the delay time.

[0127] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. An integrated testing device for unsaturated clay permeability, membrane effect, and ion diffusion considering the effects of multi-field coupling, characterized in that: include: A soil sample sealed chamber (1) comprises a rigid side wall (11), a piston (12) and a base (13); a soil sample (10) is arranged in a cavity surrounded by the rigid side wall (11), the piston (12) and the base (13); A vertical pressure component (2) is used to apply vertical pressure to the soil sample (10) via a piston (12); A solution injection and extraction circulation assembly (3) is used for injecting and extracting a solution into the soil sample sealed chamber (1), and comprises a top solution injection and extraction pipe (31) and a bottom solution injection and extraction pipe (32) in communication with the soil sample sealed chamber (1); A temperature control component (4) for regulating the temperature of the soil sample (10) and the injection solution; A suction control assembly (5) is used to apply air pressure to the soil sample sealed chamber (1) to achieve soil suction control with the help of high air intake value clay plates (102) at the top and bottom ends of the soil sample (10); An osmotic pressure difference monitoring component (6) for monitoring the chemical osmotic pressure difference between the top and bottom ends of the soil sample (10); The rigid side wall (11) comprises a rigid permeable wall (111), an annular metal permeable stone (112) and a stainless steel ring (113); An L-shaped groove is provided on the inner ring of the rigid permeable wall (111), an annular metal permeable stone (112) is placed in the L-shaped groove, and a stainless steel ring (113) is provided on the upper end of the annular metal permeable stone (112); Sealing rings are provided between the lower surface of the annular metal permeable stone (112), the outer surface of the stainless steel ring (113) and the rigid permeable wall (111); The suction control assembly (5) comprises an air guide tube (51) connected to an air pressure injection interface (1111) of a rigid permeable wall (111), the air pressure injection interface (1111) being connected to an annular metal permeable stone (112), and a high air intake value clay plate (102) being embedded in an upper piston (12) and a lower base (13) of a soil sample (10), and the suction control of the soil sample (10) is achieved by using an axis translation technology.

2. The unsaturated clay permeability-membrane effect-ion diffusion integrated testing device considering multi-field coupling effects according to claim 1 is characterized in that: The air pressure injection interface (1111) is provided with a sealing ring; The air guide tube (51) is connected to a gas pressure controller (52), and gas pressure is applied to the soil sample sealed chamber (1) by the gas pressure controller (52). The gas penetrates into the soil sample (10) through the annular metal permeable stone (112), driving the moisture in the soil sample (10) to be discharged along the high air intake value clay plates (102) at the top and bottom ends of the soil sample (10), and finally reaching a suction balance state with stable moisture content.

3. The unsaturated clay permeability-membrane effect-ion diffusion integrated testing device considering multi-field coupling effects according to claim 1 is characterized in that: A top cover (14) is provided on the top of the rigid side wall (11), the stainless steel ring (113) and the top of the rigid permeable wall (111) abut against the top cover (14), and the top cover (14) is detachably connected to the base (13) via a connecting piece.

4. The unsaturated clay permeability-membrane effect-ion diffusion integrated testing device considering multi-field coupling effects according to claim 1 is characterized in that: The piston (12) is arranged above the soil sample (10) and can move along the inner surface of the rigid side wall (11) under the drive of the vertical pressure component (2). A sealing ring is provided on the outer surface of the piston.

5. The unsaturated clay permeability-membrane effect-ion diffusion integrated testing device considering multi-field coupling effects according to claim 1 is characterized in that: The vertical pressure assembly (2) includes a vertical loading frame (21), a weight (22), a weight tray (23), an electronic dial indicator (24) and a metal test bench (25); The vertical loading frame (21) is mounted on a metal test bench (25) via a vertical metal screw (8) and a nut (9), a weight tray (23) is provided at the bottom, and an electronic dial indicator (24) is provided at the top. By placing weights (22) of a certain mass on the weight tray (23) step by step, the gravity of the weights (22) is transmitted to the piston (12) by means of the vertical loading frame (21), thereby applying vertical pressure to the soil sample (10), and the electronic dial indicator (24) is used to record the vertical deformation of the soil sample (10) during the step-by-step loading process.

6. The unsaturated clay permeability-membrane effect-ion diffusion integrated testing device considering multi-field coupling effects according to claim 1 is characterized in that: Each surface of the soil sample (10) is wrapped with filter paper (101), and the upper and lower ends are sequentially provided with a high air intake value clay plate (102) and a permeable stone (103); The permeable stones at the upper and lower ends of the soil sample (10) are respectively embedded in the piston (12) and the base (13), and are connected to the solution circulation channels provided in the piston (12) and the base (13); The top solution injection and extraction pipeline (31) and the bottom solution injection and extraction pipeline (32) are respectively connected to the solution circulation channel of the piston (12) and the solution circulation channel of the base (13); The piston (12) and the base (13) are respectively provided with a top differential pressure sensor interface (121) and a bottom differential pressure sensor interface (131), both of which are in communication with the soil sample sealed chamber (1). The permeability differential pressure monitoring assembly (6) comprises a differential pressure sensor (61) connected to the top differential pressure sensor interface (121) and the bottom differential pressure sensor interface (131), and a data acquisition instrument (62) connected to the differential pressure sensor (61).

7. The unsaturated clay permeability-membrane effect-ion diffusion integrated testing device considering multi-field coupling effects according to claim 6, characterized in that: The top solution extraction pipeline (31) and the bottom solution injection pipeline (32) are connected to a syringe pump (33); The temperature control assembly (4) includes a heating belt (41) wound around the injection end of the injection pump (33) and the outer surface of the rigid side wall (11), and a temperature controller (42) connected to the heating belt (41).

8. An integrated test method for unsaturated clay permeability, membrane effect, and ion diffusion considering multi-field coupling effects, characterized in that: The method is carried out using the device according to any one of claims 1 to 7, comprising the following steps: S1: placing a soil sample (10) in a sealed chamber surrounded by a rigid side wall (11), a piston (12) and a base (13); S2: Saturation and filtration treatment of soil sample (10); S3: A vertical target load is applied to the soil sample (10) by driving the piston (12) along the rigid side wall (11) through the vertical pressure component (2), the target temperature of the soil sample (10) and the injected solution is controlled through the temperature control component (4), air pressure is applied to the soil sample (10) and the suction change of the soil (10) is controlled through the suction control component (5), a chemical solution is injected into and extracted from the top of the soil sample (10) through the top solution injection and extraction pipe (31), deionized water is injected into and extracted from the bottom of the soil sample (10) through the bottom solution injection and extraction pipe (32), and the chemical osmotic pressure difference between the top and bottom of the soil sample (10) is measured in real time through the osmotic pressure difference monitoring component (6).

9. An application of the unsaturated clay permeability-membrane effect-ion diffusion integrated testing device considering multi-field coupling effects according to any one of claims 1 to 7, characterized in that: The test device is used to test and analyze the permeability coefficient, membrane efficiency coefficient, effective diffusion coefficient and retardation factor of unsaturated clay under different temperatures, suctions, loads and concentration gradients, revealing the development law of the retardation performance of unsaturated clay under the coupling of thermal-hydraulic-mechanical-chemical effects.

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