Integrated measuring device and method for permeability coefficient of bentonite under thermal-chemical condition

Abstract

The invention discloses an integrated bentonite permeability coefficient measuring device and method under a thermal-chemical condition, and belongs to the technical field of bentonite permeability coefficient measurement, the integrated bentonite permeability coefficient measuring device comprises a water pressure generator, a permeameter and a liquid volume measuring assembly which are communicated through guide pipes, and a soil sample is arranged in the permeameter; the water-chemical conversion system is arranged between the water pressure generator and the permeameter through a guide pipe and is provided with deionized water, spacer fluid and a chemical solution; the temperature controller is in communication connection with a first heating belt, a heating plate and a second heating belt, the first heating belt is arranged on the water-chemical conversion system, the heating plate is arranged at the bottom of the permeameter, and the second heating belt is arranged on the outer wall of the permeameter; and the data processing system is in communication connection with the water pressure generator and is used for setting a pressurization path and pressure of water, recording water inflow and pressure data in real time and calculating a permeability coefficient based on the Darcy law. The problems of soil leakage, instrument corrosion and temperature control during bentonite permeability coefficient measurement in a high-temperature corrosion environment are solved.

Description

Technical Field

[0001] This invention relates to the field of bentonite permeability coefficient measurement technology, specifically to an integrated measuring device and method for bentonite permeability coefficient under thermal-chemical conditions. Background Technology

[0002] Currently, bentonite, due to its high expansibility, low permeability, and strong adsorption, is widely used as a buffer / backfill layer in deep geological repositories for high-level radioactive waste. A dry density of 1.65-1.75 g / cm³ is typically used. 3 High-pressure compacted bentonite blocks. The permeability characteristics of high-pressure compacted bentonite blocks have a direct impact on the barrier function of the buffer / backfill layer. Therefore, the safe operation of deep geological treatment reservoirs requires a thorough understanding of the permeability characteristics of bentonite, which are mainly reflected by the permeability coefficient.

[0003] In this environment, the exothermic decay of radionuclides keeps bentonite at a prolonged high temperature. Simultaneously, the concrete lining, under the combined influence of groundwater and high temperature, decays and releases a large number of OH- ions, creating a high-temperature, strongly alkaline environment. The presence of Na+, Ka+, Cl-, and SO42- ions in the surrounding groundwater further exacerbates the formation of this complex chemical environment. The combined effects of temperature and chemical environment significantly influence the pore structure or mineral composition of bentonite, thus affecting its permeability. Therefore, accurately measuring the permeability coefficient of bentonite under thermo-chemical coupling conditions is of great significance for assessing the long-term safety performance of the treatment reservoir.

[0004] Currently, devices for measuring permeability coefficients are mainly divided into rigid-wall permeameters and flexible-wall permeameters. Rigid-wall permeameters receive water through the bottom inlet, pass through the soil sample, and exit through the top outlet. The permeability coefficient is calculated based on the flow rate. However, conventional rigid-wall permeameters allow for a relatively short permeation distance, making the resulting permeability coefficient unrepresentative for measuring bentonite under thermo-chemical coupling conditions. Furthermore, to accelerate soil saturation, vacuum saturation is often used, which can lead to soil leakage at the contact surface between the permeameter's inner ring and the soil sample. Even when using a rigid-wall permeameter for permeation saturation, sample preparation is required before placing the sample into the permeameter. This process can easily damage the soil sample and cause leakage. During sample preparation, pressing the soil sample through the ring before placing it into the permeameter prevents uniform and complete contact between the upper and lower surfaces of the sample and the instrument. Additionally, the rebound of the soil sample after unloading exacerbates leakage at the bottom connection point.

[0005] The principle of a flexible wall permeameter is the same as that of a rigid wall permeameter. The difference is that the side that is in contact with the soil sample is changed from a rigid material to a flexible latex membrane. However, the flexible wall permeameter has a complex structure and is difficult to operate. In addition, when conducting acid and alkali chemical environment tests, the chemical solution will corrode the rubber membrane. Furthermore, the flexible wall permeameter cannot perform permeation tests that control the porosity or dry density.

[0006] In terms of temperature control, existing technologies mostly employ water baths, oil baths, or temperature-controlled environmental chambers. Water baths provide uniform heating, but are limited by the boiling point of water, making them unsuitable for high-temperature tests above 90℃. While oil baths can achieve higher temperatures, the heat transfer oil is prone to releasing flammable vapors at high temperatures, posing a combustion hazard. Temperature-controlled environmental chambers offer precise temperature control, but their limited volume makes integration with permeation piping systems difficult, and their high cost hinders widespread application. Furthermore, these three temperature control methods are difficult to integrate with permeameter measurement devices.

[0007] In terms of chemical environment simulation, corrosive solutions come into direct contact with the core pressure generating and measuring components of the permeameter, which can easily lead to instrument damage. Existing devices lack effective chemical solution isolation mechanisms, making it difficult to achieve long-term stable chemical permeation tests.

[0008] In addition, traditional variable head measurement methods rely on manual observation and recording, which have problems such as large reading errors and low efficiency. Furthermore, the sample saturation process is slow, and the overall test cycle is long, making it difficult to meet the needs of efficient and accurate measurement. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides an integrated measuring device and method for bentonite permeability coefficient under thermal-chemical conditions, realizing integrated operation of sample pressing, saturation, and permeation. Through water-chemical conversion isolation and comprehensive temperature control, it solves the problems of soil leakage, instrument corrosion, and temperature control when measuring bentonite permeability coefficient under high temperature and corrosive environments.

[0010] The technical solution of the present invention is as follows: In a first aspect of the present invention, an integrated measuring device for the permeability coefficient of bentonite under thermal-chemical conditions is provided, comprising: The infiltration system includes a water pressure generator, a permeameter, and a liquid volume measurement assembly connected by a conduit. The permeameter contains a soil sample and is used to perform compression, saturation, and infiltration tests on the soil sample. A water-to-chemical conversion system is installed between a water pressure generator and a permeameter via a conduit. The water-to-chemical conversion system contains deionized water, a separating fluid, and a chemical solution. The temperature control system includes a temperature controller, which is communicatively connected to a first heating belt, a heating plate, and a second heating belt. The first heating belt is installed in the water-to-chemical conversion system, the heating plate is installed at the bottom of the permeameter, and the second heating belt is installed on the outer wall of the permeameter. The data processing system communicates with the water pressure generator to set the water pressurization path and pressure, record the inflow and pressure data in real time, and calculate the permeability coefficient based on Darcy's law. In some embodiments of the present invention, the permeameter is provided with a base, and a heating plate is provided at the lower part of the base; The base is detachably mounted with an intermediate layer and a ring cutter. A permeation cap is detachably mounted on the upper part of the intermediate layer. The upper part of the permeation cap is connected to a liquid volume measuring device through a conduit. In the cavity formed inside the intermediate layer and the ring cutter, a first permeable stone, a first filter paper, a soil sample, a second filter paper, and a second permeable stone are arranged sequentially from bottom to top. In some embodiments of the present invention, the permeameter further includes one or more additional layers disposed between the base and the intermediate layer, for adjusting the soil sample height to suit different test requirements; The base, the reinforcement layer, the intermediate layer, and the permeation cover are provided with a number of reinforcement holes, and each of the reinforcement holes is provided with a reinforcement rod. The main body of the permeameter is connected to the reinforcement holes on the base, the reinforcement layer, the intermediate layer, and the permeation cover through the reinforcement rods. The reinforcement rods are fixed with nuts at the top of the permeation cover. In some embodiments of the present invention, the base is provided with a water inlet and an air outlet, the permeation cover is provided with an outlet, the water inlet is provided with a first water stop valve, the outlet is provided with a second water stop valve, and the air outlet is provided with a third water stop valve. The infiltration cap has a first ring buffer zone at the outlet, and the base has a second ring buffer zone between the inlet and outlet. In some embodiments of the present invention, the permeation cap has a first detachable portion in the middle, and a sealing ring is provided between the first detachable portion and the installation position of the permeation cap; the base has a second detachable portion in the middle, and a sealing ring is provided between the second detachable portion and the installation position of the base. In some embodiments of the present invention, the water-to-chemical conversion system includes a first support, on which a first stainless steel cylinder and a second stainless steel cylinder are mounted. The upper parts of the first and second stainless steel cylinders are connected by a conduit. The bottom of the first stainless steel cylinder is provided with a conversion system inlet, and the bottom of the second stainless steel cylinder is provided with a conversion system outlet. The bottom of the first stainless steel cylinder contains deionized water, and the upper part of the deionized water contains a separating liquid. The bottom of the second stainless steel cylinder contains a chemical solution, and the upper part of the chemical solution contains a separating liquid. The separating liquid is configured to be an immiscible liquid with both the deionized water and the chemical solution. In some embodiments of the present invention, the first heating band is spirally wound around the outer wall of the second stainless steel cylinder, and the first heating band is spirally wound around the outside of the conduit connecting the second stainless steel cylinder and the permeameter. In some embodiments of the present invention, the liquid volume measuring assembly is provided with a second support, on which a liquid volume measuring device is provided, and the top of the liquid volume measuring device is provided with an air hole. In some embodiments of the present invention, the data processing system is configured as a computer, which is connected to the water pressure generator via a data cable to set the water pressurization path and pressure, record the water inflow and pressure data in real time, and calculate the permeability coefficient based on Darcy's law. In a second aspect of the invention, an integrated method for measuring the permeability coefficient of bentonite under thermal-chemical conditions is provided, employing the aforementioned measuring device, comprising: Place the first permeable stone and the first filter paper in sequence on the base of the permeameter, and then insert the ring cutter and the intermediate layer. Fill the space between the ring cutter and the intermediate layer with the prepared soil sample, cover it with the sample compaction cap and compact it with a universal testing machine; When raising the soil sample, place several raised layers between the base and the intermediate layer, fill the soil sample with the above operations and compact it to the set height; Remove the pressure cap, place the second filter paper and the second permeable stone on top of the soil sample in sequence, cover with the permeation cap, and fix the base, intermediate layer and permeation cap together with the reinforcing rod and nut; Remove the first removable part on the permeabilization cap, remove the second removable part on the base, place the entire permeabilization unit in the vacuum saturation cylinder to evacuate the air, and then reinstall the first and second removable parts. Deionized water, isolation fluid, and chemical solution are injected into the water-to-chemical conversion system and connected to the permeameter via a conduit; Connect the liquid volume measuring device to the outlet of the permeameter, and connect the water pressure generator to the data processing system. Start the temperature control system to heat the water-to-chemical conversion system, the conduit connecting the second stainless steel cylinder and the permeameter, and the permeameter to the set temperature; The data processing system controls the water pressure generator to pressurize step by step to conduct a permeation test and records the inflow and outflow of water in real time. When the inflow and outflow rates are equal, the soil sample is considered saturated, and the permeability coefficient is calculated according to Darcy's law.

[0011] One or more technical solutions of the present invention have the following beneficial effects: This invention employs an integrated permeameter structure consisting of a base, a ring cutter, an intermediate layer, and a permeation cap, secured by reinforcing rods and nuts. Unlike traditional rigid-wall and flexible-wall permeameters, soil samples are pressed within the ring cutter and do not require transfer. Instead, they undergo saturation and permeation directly within the sealed container. This structural design eliminates lateral and joint leakage caused by sample leakage during sample preparation, sample rebound after loading, or poor interface sealing, ensuring the sealing integrity of the high-expansion bentonite test. A first stainless steel cylinder containing deionized water and a second stainless steel cylinder containing chemical solutions are connected by an upper isolation liquid to form a pressure transmission interface. This completely isolates the corrosive solution from the water pressure generator and core control components, allowing it to contact only the corrosion-resistant second stainless steel cylinder and corresponding pipelines. This effectively protects expensive and precision instruments while simulating complex chemical environments. By wrapping the first heating band around the second stainless steel cylinder and the conduit connecting the second stainless steel cylinder to the permeameter, placing the heating plate at the bottom of the permeameter, and wrapping the second heating band around its side wall, the entire process of solution storage, transportation, and soil sample body is heated in a uniform and safe manner, accurately simulating a high-temperature environment. In addition, the first and second detachable parts facilitate vacuuming to accelerate saturation; the first and second ring buffers ensure uniform water flow during permeation; the vent at the top of the liquid volume measuring device discharges air bubbles to improve measurement accuracy; and the computer automates pressurization and data acquisition, thus integrating a sealed, leak-proof, corrosion-resistant, temperature-controlled, and automated measuring device, successfully solving the long-standing technical bottleneck of accurately measuring the permeability coefficient of high-pressure compacted bentonite under the actual thermal-chemical environment of a simulated nuclear waste disposal facility. This invention solves the problems of sample leakage, instrument corrosion, and temperature control when measuring the permeability coefficient of bentonite in high-temperature and corrosive environments by setting up an integrated permeameter for sample preparation and permeation, combined with a water-to-chemical conversion system, a temperature control system, and a data processing system. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the composition of an integrated measuring device for the permeability coefficient of bentonite under thermal-chemical conditions provided in Embodiment 1 of the present invention; Figure 2 This is a cross-sectional schematic diagram of the permeameter provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the sample pressing cap provided in Embodiment 1 of the present invention; Figure 4 This is a cross-sectional schematic diagram of the permeation cap provided in Embodiment 1 of the present invention; Figure 5 This is a cross-sectional schematic diagram of the base provided in Embodiment 1 of the present invention; Figure 6 This is a top view of the intermediate layer provided in Embodiment 1 of the present invention; Figure 7 This is a top view of the height-added structure provided in Embodiment 1 of the present invention; Figure 8 This is an exploded schematic diagram of the permeameter provided in Embodiment 1 of the present invention; Figure 9 This is a schematic diagram of the water-to-chemical conversion principle provided in Embodiment 1 of the present invention.

[0013] In the diagram: 1. Computer; 2. Water pressure generator; 3a. First support; 3b. Second support; 4a. First stainless steel cylinder; 4b. Second stainless steel cylinder; 5a. First heating band; 5b. Heating plate; 5c. Second heating band; 6. Permeameter; 7. Temperature controller; 8. Water pipe; 9. Liquid volume measuring device; 10. Air hole; 11. Nut; 12a. First permeable stone; 12b. Second permeable stone; 13a. First filter paper; 13b. Second filter paper; 14a. First stop valve; 14b. Second stop valve Valve; 14c, Third stop valve; 15, Outlet; 16, Intermediate layer; 17, Reinforcement layer; 18, Base; 19, Sealing ring; 20, Sample pressing cap; 21, Air outlet; 22, Water inlet; 23a, First ring buffer zone; 23b, Second ring buffer zone; 24, Reinforcement hole; 25, Infiltration cap; 26, Ring cutter; 27a, First detachable part; 27b, Second detachable part; 28, Data cable; 29, Soil sample; 30, Reinforcement rod; 31, Deionized water; 32, Isolation fluid; 33, Chemical solution. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] Example 1 In a typical embodiment of the present invention, such as Figures 1 to 9 As shown, an integrated measuring device for the permeability coefficient of bentonite under thermal-chemical conditions is proposed, comprising: The infiltration system includes a water pressure generator, a permeameter 6, and a liquid volume measuring component connected by a conduit. The permeameter 6 contains a soil sample 29, which is used to perform compression, saturation, and infiltration tests on the soil sample 29. The water-to-chemical conversion system is installed between the water pressure generator and the permeameter 6 via a conduit. The water-to-chemical conversion system contains deionized water 31, isolation liquid 32 and chemical solution 33. The temperature control system is equipped with a temperature controller 7. The temperature controller 7 is communicatively connected to a first heating belt 5a, a heating plate 5b, and a second heating belt 5c. The first heating belt 5a is installed in the water-to-chemical conversion system, the heating plate 5b is installed at the bottom of the permeameter 6, and the second heating belt 5c is installed on the outer wall of the permeameter 6. The data processing system communicates with the water pressure generator to set the water pressurization path and pressure, record the inflow and pressure data in real time, and calculate the permeability coefficient based on Darcy's law. Through the above setup, a fully integrated and automated permeation test is achieved under simulated high temperature and corrosive chemical environment. By organically combining functional modules for water pressure generation, chemical solution isolation and transmission, precise temperature control, and automatic data acquisition and processing, this device can complete all operations from sample preparation to permeability coefficient calculation in a closed and controllable environment. This fundamentally solves the problems of low efficiency, large human error, and unrealistic environmental simulation caused by the dispersed functions and multiple operation links of traditional devices. It provides a reliable and efficient test platform for accurately obtaining the permeability parameters of bentonite under complex thermo-chemical coupling conditions.

[0016] The permeameter 6 is equipped with a base 18, and a heating plate 5b is provided at the bottom of the base 18; A middle layer 16 and a ring cutter 26 are detachably installed on the base 18. A permeation cover 25 is detachably installed on the upper part of the middle layer 16. The upper part of the permeation cover 25 is connected to the liquid volume measuring device 9 through a conduit. In the cavity formed inside the middle layer 16 and the ring cutter 26, a first permeable stone 12a, a first filter paper 13a, a soil sample 29, a second filter paper 13b, and a second permeable stone 12b are arranged sequentially from bottom to top. The heating area of ​​the heating plate 5b is larger than the contact area with the base 18, which can provide uniform heating to the base 18.

[0017] Furthermore, by designing the base 18, ring cutter 26, intermediate layer 16, and permeation cover 25 as a detachable and assembleable integrated structure, and precisely arranging the first permeable stone 12a, first filter paper 13a, soil sample 29, second filter paper 13b, and second permeable stone 12b sequentially from bottom to top inside, this structure forms a closed test unit with distinct internal layers and clear boundaries after sample compression. This design allows the soil sample 29 to be compacted, saturated, and subsequently permeate and expand within the permeameter 6, avoiding the problem of sample leakage during sample transfer after preparation. Throughout the process, the lateral and upper and lower interfaces of the soil sample 29 are effectively constrained and sealed, completely avoiding the problem of high-pressure compacted bentonite leaking from the connection between the ring cutter 26, base 18, and cover body due to sample rebound, poor interface contact, or vacuum operation. This ensures the sealing integrity of the test and improves the representativeness and accuracy of the measurement results.

[0018] The permeameter 6 also includes one or more additional layers 17 disposed between the base 18 and the intermediate layer 16, for adjusting the height of the soil sample 29 to suit different test requirements; The base 18, the upper layer 17, the middle layer 16, and the permeation cover 25 are provided with several reinforcing holes 24, and each of the several reinforcing holes 24 is provided with a reinforcing rod 30. The main body of the permeameter 6 is connected to the reinforcing holes 24 on the base 18, the upper layer 17, the middle layer 16, and the permeation cover 25 through the reinforcing rods 30. The reinforcing rods 30 are fixed with nuts 11 at the top of the permeation cover 25. By adding one or more reinforced layers 17, the height of the sample chamber can be flexibly adjusted simply by adding or removing standardized reinforced layers 17 without changing the core components. This adapts to the testing needs of soil samples 29 of different heights or volumes, expanding the applicability of the device and saving costs associated with preparing molds of different specifications. Simultaneously, the reinforcing rod 30, which runs through the base 18, reinforced layers 17, intermediate layer 16, and permeation cover 25, and the locking mechanism of the top nut 11 tightly connects each layered component into a rigid whole. This not only effectively resists the enormous lateral pressure generated by the expansion of the internal soil sample 29 during high-pressure saturation and permeation, preventing displacement or leakage between components, but also ensures the stability of the entire seepage path length, providing a stable structural foundation for the accurate application of Darcy's Law.

[0019] The base 18 is provided with a water inlet 22 and an air outlet 21. The permeation cover 25 is provided with a water outlet 15. A first water stop valve 14a is provided at the water inlet 22, a second water stop valve 14b is provided at the water outlet 15, and a third water stop valve 14c is provided at the air outlet 21. A first ring buffer zone 23a is provided at the outlet 15 of the infiltration cover 25, and a second ring buffer zone 23b is provided between the inlet 22 and the outlet 21 of the base 18. The inlet 22 and outlet 21 are each equipped with a stop valve, which allows for easy removal of gas from the flow channel of the base 18 at the beginning of the test, ensuring that the liquid enters smoothly and fills the system. The first loop buffer zone set at the outlet 15 and the second loop buffer zone set between the inlet 22 and the outlet 21 constitute a fluid uniform distribution structure, which can dissipate the local high-speed water flow during water inflow or outflow, so that the liquid pressure acts stably and evenly on the entire cross-section of the permeable stone and soil sample 29, avoiding local structural disturbance or boundary effects of soil sample 29 caused by concentrated water flow impact. This makes the seepage field more consistent with the theoretical assumption of one-dimensional seepage and improves the accuracy of permeability coefficient measurement.

[0020] The permeation cap 25 has a first detachable part 27a in the middle, and a sealing ring 19 is provided at the installation position of the first detachable part 27a and the permeation cap 25. The base 18 has a second detachable part 27b in the middle, and a sealing ring 19 is provided at the installation position of the second detachable part 27b and the base 18. During the saturation operation of soil sample 29, only the first detachable part 27a and the second detachable part 27b need to be removed. The assembled main structure of the permeameter 6 can then be placed in the vacuum saturation cylinder for evacuation. This allows for efficient extraction of gas from the pores of the soil sample 29 and the instrument's flow channels while keeping the soil sample 29 structure undisturbed. Compared to traditional methods that require separate evacuation of the soil sample 29 before installation into the permeameter 6, or overall evacuation of complex piping systems, this design is simpler and more efficient, and avoids the structural damage or leakage risks that may occur during soil sample 29 transfer. The sealing ring 19 ensures the sealing reliability of the first detachable part 27a and the second detachable part 27b after installation, enabling the pretreatment step of vacuum saturation to be completed safely, quickly, and effectively.

[0021] The water-to-chemical conversion system includes a first support 3a, on which a first stainless steel cylinder 4a and a second stainless steel cylinder 4b are mounted. The upper parts of the first stainless steel cylinder 4a and the second stainless steel cylinder 4b are connected by a conduit. The bottom of the first stainless steel cylinder 4a is provided with a conversion system inlet, and the bottom of the second stainless steel cylinder 4b is provided with a conversion system outlet. The bottom of the first stainless steel cylinder 4a contains deionized water 31, and the upper part of the deionized water 31 contains an isolation liquid 32. The bottom of the second stainless steel cylinder 4b contains a chemical solution 33, and the upper part of the chemical solution 33 contains an isolation liquid 32. The isolation liquid 32 is configured to be a liquid that is immiscible with both the deionized water 31 and the chemical solution 33. The first stainless steel cylinder 4a and the second stainless steel cylinder 4b are connected by an upper conduit, forming a U-shaped pressure transmission structure. The bottom of the first stainless steel cylinder 4a contains deionized water 31 and is connected to a water pressure generator. The bottom of the second stainless steel cylinder 4b contains the target chemical solution 33 and is connected to the permeameter 6. The space above the liquid surface in the two cylinders is physically isolated by an isolation fluid 32 (such as silicone oil). The pressure generated by the water pressure generator is transmitted through the deionized water 31 and indirectly acts on the chemical solution 33 in the second stainless steel cylinder 4b via the isolation fluid 32, thereby pushing the chemical solution 33 into the permeameter 6.

[0022] This design ensures that the corrosive chemical solution 33 only comes into contact with the corrosion-resistant second stainless steel cylinder 4b and related pipelines throughout the entire process, while the expensive and sophisticated water pressure generator and core control system only come into contact with deionized water 31, thus achieving effective protection. The overall structure is simple and inexpensive, yet it achieves reliable corrosion isolation, making it possible to conduct long-term, stable permeation tests in harsh chemical environments such as strong acids, strong alkalis, or high salts.

[0023] The first heating band 5a is spirally wound around the outer wall of the second stainless steel cylinder 4b, and the first heating band 5a is spirally wound around the outside of the conduit connecting the second stainless steel cylinder 4b and the permeameter 6. The first heating band 5a is tightly wound in a spiral shape around the outer wall of the second stainless steel cylinder 4b containing the chemical solution 33, and also around the outside of the water pipe 8 connecting the second stainless steel cylinder 4b to the permeameter 6. This allows for simultaneous heating of the chemical solution 33 throughout its entire flow path from storage to before it enters the sample. This heating method provides direct and uniform heat transfer, rapidly raising the temperature of the chemical solution 33 and maintaining it at the set temperature, effectively preventing heat loss or temperature unevenness during long-distance transport. Furthermore, because the heating area is clearly defined and electric heating is used, this solution is more energy-efficient and has higher temperature control accuracy compared to traditional overall oil bath or environmental chamber heating. It also completely eliminates the potential flammability hazards associated with oil baths, making it particularly suitable for high-temperature chemical solution 33 permeation tests in a laboratory environment.

[0024] The liquid volume measuring assembly is provided with a second bracket 3b, on which a liquid volume measuring device 9 is provided, and the top of the liquid volume measuring device 9 is provided with an air hole 10. The vent 10 on the top of the liquid volume measuring device 9 allows tiny air bubbles that are discharged along with the seeping liquid to escape smoothly into the atmosphere, preventing air bubbles from accumulating inside the measuring device and occupying volume, which would lead to a smaller reading. This design enables accurate comparison of the inflow and outflow of water to determine the saturation state and calculate the permeability coefficient accordingly. It ensures that the outflow data truly reflects the actual seepage flow through the soil sample 29, reduces systematic errors introduced by gas interference, and makes the saturation judgment more accurate, resulting in a more reliable permeability coefficient.

[0025] The data processing system is set as computer 1, which is connected to the water pressure generator via data cable 28. It is used to set the water pressurization path and pressure, record the water inflow and pressure data in real time, and calculate the permeability coefficient based on Darcy's law. Computer 1, through a pre-programmed complex pressurization path, controls the water pressure generator to achieve gradual and stable pressure application and maintenance, simulating different head difference conditions with precise and repeatable operation. During the experiment, Computer 1 automatically records the water flow and pressure changes of the water pressure generator in real time, eliminating errors and delays caused by manual observation and recording. Finally, based on the real-time collected flow and pressure data and known sample size parameters, Computer 1 can automatically apply Darcy's law to calculate the permeability coefficient quickly, and can perform data processing such as averaging multiple measurements. This significantly reduces the workload and technical threshold for operators, and improves the efficiency, accuracy, and standardization of the entire testing process.

[0026] In this embodiment, the first support 3a and the second support 3b are set as iron frames. The first support 3a provides stable support for the first stainless steel cylinder 4a and the second stainless steel cylinder 4b, and the second support 3b provides stable support for the liquid volume measuring device 9. The first heating belt 5a, the heating plate 5b and the second heating belt 5c are made of rubber sheet material, which is low in cost and provides uniform and controllable heating. The conduit is made of PU material, which is resistant to high temperature and corrosion. The sealing ring 19 is an O-ring rubber sealing ring 19, which is resistant to high temperature and corrosion. The isolation liquid 32 can be set as silicone oil, and the chemical solution 33 can be set as one of alkaline solution, acidic solution or salt solution.

[0027] In a second aspect of the invention, an integrated method for measuring the permeability coefficient of bentonite under thermal-chemical conditions is provided, employing the aforementioned measuring device, comprising: Place the first permeable stone 12a and the first filter paper 13a on the base 18 of the permeameter 6 in sequence, and then insert the ring cutter 26 and the intermediate layer 16. Fill the space formed by the ring cutter 26 and the intermediate layer 16 with the prepared soil sample 29, cover it with the sample compaction cover 20 and compact it with a universal testing machine; When raising the soil sample 29, several raised layers 17 are placed between the base 18 and the intermediate layer 16. The soil sample 29 is filled in and compacted to the set height through the above operation. Remove the sample pressing cover 20, place the second filter paper 13b and the second permeable stone 12b on top of the soil sample 29 in sequence, cover with the permeation cover 25 and fix the base 18, the intermediate layer 16 and the permeation cover 25 together by the reinforcing rod 30 and the nut 11; Remove the first removable part 27a on the permeation cap 25, remove the second removable part 27b on the base 18, place the entire permeameter 6 in a vacuum saturation cylinder to evacuate the air, and then reinstall the first removable part 27a and the second removable part 27b. Deionized water 31, isolation fluid 32 and chemical solution 33 are injected into the water-to-chemical conversion system and connected to the permeameter 6 through a conduit; Connect the liquid volume measuring device 9 to the outlet 15 of the permeameter 6, and connect the water pressure generator to the data processing system. Start the temperature control system to heat the water-to-chemical conversion system, the conduit connecting the second stainless steel cylinder 4b and the permeameter 6, and the permeameter 6 to the set temperature; The data processing system controls the water pressure generator to pressurize step by step to conduct a permeation test and records the inflow and outflow of water in real time. When the inflow and outflow are equal, soil sample 29 is considered saturated, and the permeability coefficient is calculated according to Darcy's law.

[0028] In this embodiment, the specific measurement method is as follows: (1) Place the first permeable stone 12a and the first filter paper 13a on the base 18 in sequence; (2) After applying a layer of Vaseline to the ring cutter 26 and the intermediate layer 16, place them on the first filter paper 13a in sequence; (3) Place the prepared and weighed soil sample 29 into the space formed by the ring cutter 26 and the intermediate layer 16, cover it with the sample pressing cover 20 coated with a layer of Vaseline, compact it with a universal testing machine, and let it stand. (4) When raising the sample, in step (2), several raising layers 17 are placed between the base 18 and the intermediate layer 16, and steps (2) and (3) are repeated.

[0029] (5) Remove the pressure cover 20, place the second filter paper 13b and the second permeable stone 12b on top of the soil sample 29 in sequence, cover with the permeation cover 25, insert the four reinforcing rods 30 into the reinforcing holes 24 respectively, and tighten the nuts 11. (6) Remove the first detachable part 27a and the second detachable part 27b, evacuate the air with a vacuum saturation cylinder for 3 hours, and then reinstall the first detachable part 27a and the second detachable part 27b. (7) Connect the first stainless steel cylinder 4a and the second stainless steel cylinder 4b through the water pipe 8, and inject deionized water 31, isolation liquid 32 and chemical solution 33 from the first stainless steel cylinder 4a and the second stainless steel cylinder 4b, and connect them to the permeameter 6 through the water pipe 8. (8) Connect the liquid volume measuring device 9 to the second stop valve 14b of the permeameter 6 through the water pipe 8 and place it on the second bracket 3b. Connect the water pressure generator 2 to the first stainless steel cylinder 4a through the water pipe 8 and place the first stainless steel cylinder 4a and the second stainless steel cylinder 4b on the first bracket 3a. (9) The first heating band 5a is evenly wrapped around the surface of the conduit that is connected to the second stainless steel straight cylinder and the second stainless steel cylinder 4b and the permeameter 6. The heating plate 5b is placed at the bottom of the base 18 of the permeameter 6. The second heating band 5c is evenly wrapped around the side of the permeameter 6. (10) Connect the temperature controller 7 to the first heating belt 5a, the heating plate 5b, and the second heating belt 5c via the data cable 28, and connect the computer 1 to the water pressure generator 2 via the data cable 28; (11) The pressure and temperature are controlled by the temperature controller 7 and the computer 1 to conduct the test. The first stop valve 14a and the third stop valve 14c are opened. The gas inside the base 18 is discharged from the third stop valve 14c. When there is a continuous flow of water, the third stop valve 14c is closed, and then the second stop valve 14b is opened. (12) After the permeation test begins, the water pressure generator 2 is set to gradually increase the inlet water pressure so that the sample expands and fits tightly against the inner wall of the main body of the permeameter 6, and finally stabilizes at 400 kPa. (13) Simultaneously record the inflow and outflow of water. When the outflow of water in the liquid volume measuring device and the inflow of water in the water pressure generator 2 are equal, the sample is considered saturated, and the permeability coefficient is measured. The computer 1 reads the inflow of water at consecutive fixed time intervals multiple times, and the permeability coefficient is calculated by Darcy's law:

[0030] In the formula, K represents the permeability coefficient; Q represents the amount of water that seeps through the sample per unit time; L represents the seepage path length; and A represents the cross-sectional area of ​​the water flow. h represents the head difference (converted from the inlet pressure). The test ends when the permeability coefficient stabilizes after multiple consecutive measurements, and the average value is taken as the permeability coefficient of the sample.

[0031] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. An integrated measuring device for the permeability coefficient of bentonite under thermal-chemical conditions, characterized in that, include: The infiltration system includes a water pressure generator, a permeameter, and a liquid volume measurement assembly connected by a conduit. The permeameter contains a soil sample and is used to perform compression, saturation, and infiltration tests on the soil sample. A water-to-chemical conversion system is installed between a water pressure generator and a permeameter via a conduit. The water-to-chemical conversion system contains deionized water, a separating fluid, and a chemical solution. The temperature control system includes a temperature controller, which is communicatively connected to a first heating belt, a heating plate, and a second heating belt. The first heating belt is installed in the water-to-chemical conversion system, the heating plate is installed at the bottom of the permeameter, and the second heating belt is installed on the outer wall of the permeameter. The data processing system communicates with the water pressure generator to set the water pressurization path and pressure, record the inflow and pressure data in real time, and calculate the permeability coefficient based on Darcy's law.

2. The integrated measuring device for the permeability coefficient of bentonite under thermal-chemical conditions as described in claim 1, characterized in that, The permeameter is equipped with a base, and a heating plate is provided at the bottom of the base; The base is detachably mounted with an intermediate layer and a ring cutter. A permeation cap is detachably mounted on the upper part of the intermediate layer. The upper part of the permeation cap is connected to a liquid volume measuring device through a conduit. In the cavity formed inside the intermediate layer and the ring cutter, a first permeable stone, a first filter paper, a soil sample, a second filter paper, and a second permeable stone are arranged sequentially from bottom to top.

3. The integrated measuring device for bentonite permeability coefficient under thermal-chemical conditions as described in claim 2, characterized in that, The permeameter also includes one or more additional layers disposed between the base and the intermediate layer, for adjusting the soil sample height to suit different test requirements; The base, the reinforcement layer, the intermediate layer, and the permeation cover are provided with a number of reinforcement holes, and each of the reinforcement holes is provided with a reinforcement rod. The main body of the permeameter is connected to the reinforcement holes on the base, the reinforcement layer, the intermediate layer, and the permeation cover through the reinforcement rods. The reinforcement rods are fixed with nuts at the top of the permeation cover.

4. The integrated measuring device for the permeability coefficient of bentonite under thermal-chemical conditions as described in claim 2, characterized in that, The base is provided with a water inlet and an air outlet, the permeation cover is provided with a water outlet, the water inlet is provided with a first water stop valve, the water outlet is provided with a second water stop valve, and the air outlet is provided with a third water stop valve. The infiltration cap has a first ring buffer zone at the outlet, and the base has a second ring buffer zone between the inlet and outlet.

5. The integrated measuring device for the permeability coefficient of bentonite under thermal-chemical conditions as described in claim 2, characterized in that, The permeation cap has a first detachable part in the middle, and a sealing ring is provided at the installation position of the first detachable part and the permeation cap. The base has a second detachable part in the middle, and a sealing ring is provided at the installation position of the second detachable part and the base.

6. The integrated measuring device for the permeability coefficient of bentonite under thermal-chemical conditions as described in claim 1, characterized in that, The water-to-chemical conversion system includes a first support frame, on which a first stainless steel cylinder and a second stainless steel cylinder are mounted. The upper parts of the first and second stainless steel cylinders are connected by a conduit. The bottom of the first stainless steel cylinder has a conversion system inlet, and the bottom of the second stainless steel cylinder has a conversion system outlet. The bottom of the first stainless steel cylinder contains deionized water, and the upper part of the deionized water contains a separating liquid. The bottom of the second stainless steel cylinder contains a chemical solution, and the upper part of the chemical solution contains a separating liquid. The separating liquid is configured to be immiscible with both the deionized water and the chemical solution.

7. The integrated measuring device for bentonite permeability coefficient under thermal-chemical conditions as described in claim 6, characterized in that, The first heating band is spirally wound around the outer wall of the second stainless steel cylinder, and the first heating band is spirally wound around the outside of the conduit connecting the second stainless steel cylinder and the permeameter.

8. The integrated measuring device for the permeability coefficient of bentonite under thermal-chemical conditions as described in claim 1, characterized in that, The liquid volume measuring assembly is provided with a second bracket, on which a liquid volume measuring device is provided, and the top of the liquid volume measuring device is provided with an air hole.

9. The integrated measuring device for bentonite permeability coefficient under thermal-chemical conditions as described in claim 1, characterized in that, The data processing system is configured as a computer, which is connected to the water pressure generator via a data cable. It is used to set the water pressurization path and pressure, record the water inflow and pressure data in real time, and calculate the permeability coefficient based on Darcy's law.

10. A method for integrated measurement of the permeability coefficient of bentonite under thermal-chemical conditions, employing the measuring device as described in any one of claims 1-9, characterized in that, include: Place the first permeable stone and the first filter paper in sequence on the base of the permeameter, and then insert the ring cutter and the intermediate layer. Fill the space between the ring cutter and the intermediate layer with the prepared soil sample, cover it with the sample compaction cap and compact it with a universal testing machine; When raising the soil sample, place several raised layers between the base and the intermediate layer, fill the soil sample with the above operations and compact it to the set height; Remove the pressure cap, place the second filter paper and the second permeable stone on top of the soil sample in sequence, cover with the permeation cap, and fix the base, intermediate layer and permeation cap together with the reinforcing rod and nut; Remove the first removable part on the permeabilization cap, remove the second removable part on the base, place the entire permeabilization unit in the vacuum saturation cylinder to evacuate the air, and then reinstall the first and second removable parts. Deionized water, isolation fluid, and chemical solution are injected into the water-to-chemical conversion system and connected to the permeameter via a conduit; Connect the liquid volume measuring device to the outlet of the permeameter, and connect the water pressure generator to the data processing system. Start the temperature control system to heat the water-to-chemical conversion system, the conduit connecting the second stainless steel cylinder and the permeameter, and the permeameter to the set temperature; The data processing system controls the water pressure generator to pressurize step by step to conduct a permeation test and records the inflow and outflow of water in real time. When the inflow and outflow rates are equal, the soil sample is considered saturated, and the permeability coefficient is calculated according to Darcy's law.

Images