Multifunctional testing device and testing method for clay chemical permeation and consolidation test

Abstract

The invention discloses a multifunctional testing device for a clay chemical permeation and consolidation test, and belongs to the technical field of rock testing, the device comprises a base, a rigid wall sample cylinder is arranged at the upper part of the base, a cap is arranged at the upper part of the rigid wall sample cylinder, and the wall cavity of the rigid wall sample cylinder is hollow; the temperature control is realized by circulating the circulating liquid of the temperature control module in the wall cavity; the device measures pressure through the pressure measuring module, supplements deionized water through the water supplementing module, and supplements a salt solution through the salt solution supplementing module. By adopting the device disclosed by the invention, proper modules are selected as required during testing, various rock and soil performance tests can be carried out, the testing device has various functions, multiple purposes are realized, and the testing cost is reduced. The rock-soil test method provided by the test device provided by the invention considers many factor indexes, can reflect complex environments in practical application more truly, has simple test steps, and can be popularized and applied in a large range.

Description

Technical Field

[0001] The invention belongs to the technical field of rock and soil testing, and in particular relates to a multifunctional testing device and a testing method for clay chemical penetration and consolidation testing. Background Art

[0002] In the field of geotechnical engineering, the study of chemical permeation and consolidation tests of clay is of great importance. However, traditional chemical permeation and consolidation experimental devices often ignore the important effects of temperature and stress level on chemical permeation and consolidation processes.

[0003] On the one hand, temperature plays a key role in many chemical and physical processes. Different temperatures will change the molecular movement speed, diffusion coefficient and chemical reaction rate of substances. In the process of clay chemical penetration, the change of temperature has a significant effect on the permeability coefficient and chemical reaction rate of clay. In the consolidation process, the change of temperature will have a significant effect on compression deformation, etc., which has an important impact on the entire process and results of chemical penetration and consolidation.

[0004] On the other hand, stress level also has a significant impact on the performance and chemical permeation behavior of materials. Stress can change the microstructure of materials, such as causing changes in microscopic pore structure, thereby affecting the transmission channel of permeating substances. In addition, the coupling between stress field, temperature field and chemical field will change the hydro-mechanical behavior of clay.

[0005] Therefore, developing a multifunctional testing device that can be used for clay chemical penetration and consolidation tests under thermal-chemical-mechanical coupling conditions can more realistically reflect the complex environment in actual applications and provide a more accurate and reliable experimental means for in-depth research on chemical penetration and consolidation phenomena, which is of great practical significance for promoting geotechnical engineering under complex geological conditions. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In view of this, the purpose of the present invention is to solve the following problems: ① The existing geotechnical testing device has a single function and cannot achieve multi-purpose use to reduce the test cost. ② The existing geotechnical testing method considers fewer factors and indicators, cannot more truly reflect the complex environment in actual application, and the testing steps are cumbersome.

[0008] (II) Technical solution

[0009] In order to solve technical problem 1, the present invention provides a multifunctional testing device for clay chemical penetration and consolidation test, characterized in that: it includes a base, a rigid-wall sample tube is provided on the upper part of the base, a cap is provided on the upper part of the rigid-wall sample tube, the wall cavity of the rigid-wall sample tube is hollow, and temperature control is achieved by circulating the circulating fluid of the temperature control module in its wall cavity; a through hole is provided in the center of the cap, a force transmission rod is vertically slidably installed in the through hole, the lower part of the force transmission rod is connected to the sample cap, and a displacement sensor is installed on the upper part of the cap; the interior of the rigid-wall sample tube is filled with a soil sample, and the upper and lower ends of the soil sample are respectively provided with upper penetration The base is a water stone and a lower permeable stone, the lower part of the sample cap is abutted against the top of the upper permeable stone; the sample cap is integrated with an upper pressure measuring interface and a salt solution interface, the salt solution interface is connected with a salt solution supply module, the base is integrated with a lower pressure measuring interface and a water supply port, the upper pressure measuring interface and the lower pressure measuring interface are connected through a pressure measuring module to achieve pressure measurement, the pressure measuring module includes a pressure measuring tube directly connected to the pressure measuring interface and a differential pressure sensor installed in the middle of the pressure measuring tube, and a conductivity monitoring module is arranged at the lower part of the pressure measuring tube; the water supply port is connected with a water supply module for replenishing deionized water; the device is a closed system, and the interfaces and pipelines are in a sealed state.

[0010] As a further description of the technical solution of the present invention:

[0011] The temperature control module includes a constant temperature cold room, a liquid inlet pipe and a liquid outlet pipe, wherein the liquid inlet pipe is connected to the lower part of one side of the rigid wall sample tube, and the liquid outlet pipe is connected to the upper part of the other side of the rigid wall sample tube; the water replenishment module includes a water replenishment pipe, a peristaltic pump and a deionized water container, wherein the delivery of the deionized water is controlled by a peristaltic pump to ensure accurate regulation of the flow rate, and the deionized water is replenished by connecting to the water replenishment port through the water replenishment pipe; the salt solution replenishment module includes a salt solution container, a gear pump and a salt solution supply pipe, which is connected to the salt solution interface through the salt solution supply pipe to carry out a chemical permeation test; the salt solution supply pipe and the pressure measuring tube both vertically penetrate the cap.

[0012] As a further description of the technical solution of the present invention:

[0013] The conductivity monitoring module includes a collecting bottle, a conductivity meter and a drainage tube, one end of the drainage tube is connected to the pressure measuring tube, and the other end is introduced into the lower part of the collecting bottle, and the monitoring probe of the conductivity meter extends below the liquid level of the collecting bottle; the pressure measuring module also includes a data acquisition instrument, and the data acquisition instrument is electrically connected to the differential pressure sensor; an infusion tube is arranged on the upper part of the pressure measuring tube, one end of the infusion tube is connected to the upper part of the pressure measuring tube, and the other end extends below the liquid level of the saline solution container.

[0014] As a further description of the technical solution of the present invention:

[0015] The upper part of the base and the lower part of the cap are provided with cylindrical grooves matching the rigid-wall sample tube, the rigid-wall sample tube is clamped in the cylindrical grooves of the base and the cap, and sealing rings are provided at both ends of the rigid-wall sample tube; rigid bolts are evenly distributed on the edge of the base, the rigid bolts pass through the cap, and are firmly connected by nuts; the outer edge of the sample cap is in close contact with the inner wall of the rigid-wall sample tube.

[0016] To solve technical problem 2, the present invention adopts the above device to provide a chemical permeation test method considering the influence of temperature and stress level, comprising the following steps:

[0017] S1. Select a representative clay sample and prepare the soil sample according to the size and shape designed by the test device;

[0018] S2. Insert the rigid-walled sample tube into the base, and sequentially install the lower permeable stone, filter paper, soil sample, filter paper, upper permeable stone, and sample cap into the sample tube, and cover and secure the cap;

[0019] S3. Place the test device on the operating platform and connect it to the loading device of the operating platform, install the displacement sensor, and then connect all the pipes required on the test device and ensure their sealing;

[0020] S4, after the circulating fluid of the temperature control module is heated to the target temperature, the temperature of the rigid wall sample cylinder is controlled through the pipeline circulation; then according to the test requirements, the set vertical stress is applied until the deformation reaches a stable state;

[0021] S5, using the salt solution supply module and the water supply module to replenish deionized water respectively, and when the pressure difference at both ends of the soil sample is stable, the pressure difference can be determined as the reference osmotic pressure;

[0022] S6. After obtaining the reference osmotic pressure, replace the upper deionized water with a salt solution, continue the test and record the conductivity of the solution discharged from the pressure measuring interface and the pressure difference at both ends of the sample. When the average value of the pressure difference at both ends of the sample changes within a certain period of time remains within 5%, the chemical osmotic pressure reaches a stable stage;

[0023] S7. After the test, gradually unload, take out the clay sample, and clean the test device.

[0024] As a further description of the technical solution of the present invention:

[0025] It also includes repeating steps S1-S3, then setting different temperatures and / or stress levels, and continuing the subsequent steps to carry out multiple repeated tests to explore the influence of temperature and / or stress levels on chemical permeation behavior; finally, the difference between the actual pressure difference measured by the pressure difference sensor and the reference osmotic pressure can be used to obtain the chemical osmotic pressure difference, and then the chemical permeation efficiency coefficient is determined by the ratio of the chemical osmotic pressure difference to the theoretical calculated value.

[0026] Also to solve technical problem 2, the present invention adopts the above device to provide a saline clay consolidation test method considering the influence of temperature and osmotic suction, comprising the following steps:

[0027] S1. Select representative saline clay samples and prepare saline clay samples with different salt concentrations according to the size, shape and salt content designed by the test device;

[0028] S2. Insert the rigid-walled sample tube into the base, evenly apply vaseline inside the sample tube, and sequentially install the lower permeable stone, filter paper, soil sample, filter paper, upper permeable stone, and sample cap into the sample tube, and cover and secure the cap;

[0029] S3. Place the test device on the operating platform and connect it to the loading device of the operating platform, install the displacement sensor, and then connect all the pipes required on the test device and ensure their sealing;

[0030] S4, after heating the circulating fluid of the temperature control module to the target temperature, the temperature of the rigid-walled sample cylinder is controlled through the pipeline circulation;

[0031] S5. The loading device applies a preload of 1 kPa and adjusts the displacement sensor to zero;

[0032] S6. Apply loads in stages according to test requirements. After each load stage, let the sample stand for a while to allow it to fully consolidate.

[0033] S7. During the consolidation process, the data of the displacement sensor is recorded regularly to detect the deformation, temperature and conductivity of the discharged solution of the sample;

[0034] S8. After the test, unload the pressure step by step and measure the coefficient of resilience of the sample. Then, take out the clay sample and clean the test device. According to the test data, calculate the compression coefficient and analyze the influence of temperature and penetration suction on the compression characteristics.

[0035] As a further description of the technical solution of the present invention:

[0036] The method also includes selecting a saline clay sample at the same salt concentration, repeating steps S1-S3, and then setting another target temperature to continue with subsequent steps; or replacing saline clay samples at different salt concentrations, repeating the steps, and conducting multiple tests at different temperatures and initial osmotic suctions to explore the effects of temperature, osmotic suction and their interaction on the compression behavior of saline clay.

[0037] Also to solve technical problem 2, the present invention adopts the above-mentioned device to provide a permeability consolidation test method for clay considering the coupling effect of thermal and chemical forces, comprising the following steps:

[0038] S1. Select a representative clay sample, prepare the sample according to the size and shape designed by the test device, and prepare a saline clay sample with pores containing salt solution by means of a vacuum saturation device;

[0039] S2. Insert the rigid-walled sample tube into the base, evenly apply vaseline inside the sample tube, and sequentially install the lower permeable stone, filter paper, soil sample, filter paper, upper permeable stone, and sample cap into the sample tube, and cover and secure the cap;

[0040] S3. Place the test device on the operating platform and connect it to the loading device of the operating platform, install the displacement sensor, and then connect all the pipes required on the test device and ensure their sealing;

[0041] S4, after heating the circulating fluid of the temperature control module to the target temperature, the temperature of the rigid-walled sample cylinder is controlled through the pipeline circulation;

[0042] S5. According to the test requirements, first apply a certain vertical stress, then use the salt solution supply module to replenish the salt solution until the deformation reaches a stable state; then continue to apply pressure and replenish the salt solution until the deformation reaches a stable state; repeatedly apply pressure at each level, and record the deformation, temperature, conductivity of the discharged solution and the data of the differential pressure sensor at each level of pressure;

[0043] S6. After the test, gradually unload, take out the clay sample, and clean the test equipment; combine the data including the deformation, time, and temperature of the clay sample to analyze the influence of factors including clay stress level, temperature, and chemical gradient on the penetration and compression behavior of the sample.

[0044] As a further description of the technical solution of the present invention:

[0045] Repeat steps S1-S3, then heat the circulating fluid to another target temperature and continue the test. The test needs to be repeated multiple times at different temperatures, stress levels, and chemical gradients to explore the effects of temperature, stress level, and osmotic suction gradient on the penetration and compression behavior of the sample.

[0046] (III) Beneficial effects

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The present invention has the ability to simultaneously perform clay chemical permeation and consolidation tests under thermal-chemical-mechanical coupling conditions, and can accurately calculate the permeability efficiency coefficient, compression index and hydraulic permeability coefficient of saline clay under different environmental loads based on the test results. In addition, it can also deeply explore the influence mechanism of the interaction between temperature, permeability suction and stress level on the hydro-mechanical properties of saline clay, and monitor the deformation during the test in real time. This invention provides strong technical support for studying the hydraulic behavior of clay under complex geological environment conditions.

[0049] (2) The test device integrates multiple functions of clay chemical penetration and consolidation testing, and can comprehensively cover all aspects from penetration efficiency determination to consolidation strength assessment. Whether it is a single experiment or a complex study, it can provide accurate and reliable test results to meet the diverse needs of scientific research and production.

[0050] (3) The test device effectively reduces the cost of purchasing and maintaining multiple test equipment by integrating multiple test functions. A one-time investment can provide comprehensive test capabilities, which is highly cost-effective in the long run. In addition, it can reduce repeated testing and resource waste, further reducing experimental costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic diagram of the structural principle of the testing device provided by the present invention;

[0052] Figure 2 A schematic diagram of a three-dimensional structural model of the test device provided by the present invention;

[0053] Figure 3 An exploded schematic diagram of a three-dimensional model of the test device structure provided by the present invention;

[0054] Figure 4 A schematic diagram of a three-dimensional model of the test device structure provided by the present invention when it is assembled;

[0055] In the figure: 1. base; 2. rigid wall sample tube; 3. cover cap; 5. circulating temperature control module; 51. constant temperature cold room; 52. liquid inlet pipe; 53. liquid outlet pipe; 6. water supply module; 61. water supply pipe; 62. peristaltic pump; 63. deionized water container; 7. conductivity monitoring module; 71. collecting bottle; 72. conductivity meter; 73. drainage tube; 8. pressure measuring module; 81. pressure measuring tube; 82. differential pressure sensor; 83. data acquisition instrument; 9. force transmission rod; 10. sample cap; 11. permeable stone; 111. upper permeable stone; 112. lower permeable stone; 12. soil sample; 13. sealing ring; 14. rigid bolt; 15. displacement sensor; 16. salt solution supply module; 161. salt solution container; 162. gear pump; 163. salt solution supply pipe; 17. infusion tube. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] like Figure 1-3As shown, the present invention provides a multifunctional testing device for clay chemical penetration and consolidation test, the testing device comprises a base 1, a rigid-walled sample tube 2 is provided on the upper part of the base 1, a cap 3 is provided on the upper part of the rigid-walled sample tube 2, a cylindrical groove matching the rigid-walled sample tube 2 is provided on the upper part of the base 1 and the lower part of the cap 3, the rigid-walled sample tube 2 is clamped inside the cylindrical groove of the base 1 and the cap 3, a sealing ring 13 is provided at the contact between the two ends of the rigid-walled sample tube 2 and the base 1 and the cap 3, by clamping the rigid-walled sample tube 2 inside the cylindrical groove, the stress deformation of the rigid-walled sample tube 2 during the test loading can be effectively avoided, the sealing ring 13 can be installed to prevent the solution from seeping out, and the device can be in a sealed state. state, to avoid affecting the test accuracy; the wall cavity of the rigid-wall sample tube 2 is hollow, and the temperature control is achieved by circulating the circulating liquid of the temperature control module 5 in its wall cavity. The preset temperature is set by the circulating temperature control module 5, and the temperature of the rigid-wall sample tube 2 is changed, which drives the temperature change of the internal sample to carry out tests under different temperatures; a through hole is provided in the center of the cap 3, and a force transmission rod 9 is vertically slidably installed in the through hole. The lower part of the force transmission rod 9 is connected to the sample cap 10, which is vertically arranged to ensure that it is in the center position when force is applied, thereby ensuring that the sample is evenly stressed and preventing the sample cap 10 from deflecting and leaking. A displacement sensor 15 is installed on the upper part of the cap 3 to monitor the displacement under different test conditions; the interior of the rigid-wall sample tube 2 is filled with The sample cap 10 is filled with a soil sample 12, which is prepared according to the requirements. An upper permeable stone 111 and a lower permeable stone 112 are respectively arranged at the upper and lower ends of the soil sample 12. Filter paper needs to be placed on the contact surface between the soil sample 12 and the permeable stone 11. On the one hand, the percolation effect of the filter paper makes the replenishment enter the soil sample 12 more evenly, and on the other hand, it prevents fine particles in the soil sample 12 from entering the permeable stone 11; the lower part of the sample cap 10 abuts against the top of the upper permeable stone 111, and the upper pressure measuring interface and the salt solution interface are integrated on the sample cap 10. The salt solution interface is connected to the salt solution supply module 16, and a chemical permeation test is carried out by supplying salt solution; the lower pressure measuring interface and the water supply port are integrated inside the base 1, and the upper pressure measuring interface and the lower pressure measuring interface are connected through the pressure measuring module 8 is connected to realize pressure measurement. The pressure measuring module 8 includes a pressure measuring tube 81 directly connected to the pressure measuring interface and a differential pressure sensor 82 installed in the middle of the pressure measuring tube 81. The differential pressure sensor 82 is used to accurately measure the pressure difference between the upper and lower ends of the sample. The lower part of the pressure measuring tube 81 is provided with a conductivity monitoring module 7 for monitoring the conductivity of the liquid discharged from the lower part, thereby realizing the integration of pressure measurement and conductivity monitoring; the water replenishment port is connected to a water replenishment module 6 for replenishing deionized water; the device is a closed system, and the interfaces and pipelines are all in a sealed state. It should be noted that all connected pipelines are provided with valves as needed. When a certain module is not used, you can choose not to install it and block the interface, or install it normally and close the corresponding valve to ensure sealing.

[0058] In the embodiment of the present invention, the temperature control module 5 includes a constant temperature cold room 51, a liquid inlet pipe 52 and a liquid outlet pipe 53. The liquid inlet pipe 52 is connected to the lower part of one side of the rigid wall sample tube 2, and the liquid outlet pipe 53 is connected to the upper part of the other side of the rigid wall sample tube 2. The liquid circulates from bottom to top, so that the circulation in the rigid wall sample tube 2 is more uniform, and the temperature control is more accurate; the water replenishment module 6 includes a water replenishment pipe 61, a peristaltic pump 62 and a deionized water container 63. The delivery of deionized water is controlled by the peristaltic pump 62 to ensure accurate regulation of the flow rate. The water replenishment is connected to the water replenishment port through the water replenishment pipe 61; the salt solution replenishment module 16 includes a salt solution container 161, a gear pump 162 and a salt solution replenishment pipe 163, which is connected to the salt solution interface through the salt solution replenishment pipe 163 Carry out chemical permeation test, and the gear pump 162 controls the rehydration; the salt solution supply pipe 163 and the pressure measuring pipe 81 both vertically penetrate the cap 3. The parts of the salt solution supply pipe 163 and the pressure measuring pipe 81 that penetrate the cap 3 are preferably rigid pipes. This setting can be inserted into the corresponding pipe body from the hole opened on the cap 3 after the device is assembled. Because it is vertical, the pipe body can be directly connected to the upper pressure measuring interface and the salt solution interface integrated on the sample cap 10 after insertion, avoiding installation failure. At the same time, it can also simplify the assembly process and benefit the safety of the equipment. For example, after the equipment is assembled and placed on the operating table, the salt solution supply pipe 163 and the pressure measuring pipe 81 are inserted, and then the corresponding modules are installed, so as to avoid that there are too many overall components and some components fall and break when moving to the operating table. Of course, if a flexible pipe is selected, the pipeline can also be installed first, and then the cap 3 and other structures can be installed. The specific selection is based on actual needs.

[0059] In the embodiment of the present invention, the conductivity monitoring module 7 includes a collection bottle 71, a conductivity meter 72 and a drainage tube 73, one end of the drainage tube 73 is connected to the pressure measuring tube 81, and the other end is introduced into the lower part of the collection bottle 71, and the monitoring probe of the conductivity meter 72 extends below the liquid level of the collection bottle 71; the pressure measuring module 8 also includes a data acquisition instrument 83, which is electrically connected to the pressure difference sensor 82 and is responsible for collecting and processing relevant data; the upper part of the pressure measuring tube 81 is provided with an infusion tube 17, one end of the infusion tube 17 is connected to the upper part of the pressure measuring tube 81, and the other end extends to below the liquid level of the salt solution container 161. In the present invention, the collection bottle 71, the salt solution container 161 and the deionized water container 63 are all provided with a cover to avoid direct contact with air to affect the accuracy of the test.

[0060] In the embodiment of the present invention, rigid bolts 14 are evenly distributed on the edge of the base 1, preferably 6 rigid bolts 14, 1 of which is set every 60°, and the rigid bolts 14 penetrate the cap 3 and are firmly connected by nuts to realize the device as a whole, and at the same time make the device more stable; the outer edge of the sample cap 10 is close to the inner wall of the rigid wall sample tube 2, which can avoid leakage and other phenomena, and avoid affecting the test accuracy as much as possible. The size of the device can be enlarged or reduced in the same proportion without affecting the test results.

[0061] The present invention uses the test device in the above embodiment to carry out a chemical permeation test taking into account the influence of temperature and stress level. The test method includes the following steps:

[0062] S1. Select a representative clay sample and prepare a soil sample 12 according to the size and shape designed by the test device;

[0063] S2, embed the rigid wall sample tube 2 into the base 1, and sequentially install the lower permeable stone 112, filter paper, soil sample 12, filter paper, upper permeable stone 111, and sample cap 10 into the sample tube, and cover the cap 3. A sealing ring 13 is set at the position where the rigid wall sample tube 2 contacts the base 1 and the cap 3, and a rigid bolt 14 passes through the cap 3 and is firmly connected by a nut;

[0064] S3. The force transmission rod 9 connected to the upper part of the sample cap 10 passes through the through hole in the center of the cap 3. The test device is placed on the operating platform and the force transmission rod 9 is connected to the loading device of the operating platform for loading pressure. The displacement sensor 15 is installed, and then the required pipelines on the test device are connected and ensured to be tight.

[0065] The pipelines that need to be connected in this experiment include: connecting the water supply pipe 61, the peristaltic pump 62 and the deionized water container 63 in sequence, connecting the water supply pipe 61 to the water supply port. It should be noted that the water supply port is not only a port, but also includes a pipe hole opened on the base 1. The connection can be achieved by inserting the water supply pipe 61 into the pipe hole; connecting the salt solution container 161, the gear pump 162 and the salt solution supply pipe 163 in sequence. The salt solution supply pipe 163 is a rigid pipe, which is directly inserted into the hole opened on the cap 3 and connected to the salt solution interface on the upper part of the sample cap 10; connecting the pressure measuring tube 81 to the upper and lower pressure measuring interfaces in sequence, and connecting the differential pressure sensor 82 in the middle. The differential pressure sensor 82 is connected to a data acquisition instrument 83, and an infusion tube 17 is arranged on the upper part of the pressure measuring tube 81, one end of the infusion tube 17 is connected to the upper part of the pressure measuring tube 81, and the other end extends below the liquid level of the salt solution container 161, and the lower part of the pressure measuring tube 81 is connected to the conductivity monitoring module 7, wherein one end of the drainage tube 73 is connected to the pressure measuring tube 81, and the other end is introduced into the lower part of the collecting bottle 71, and the monitoring probe of the conductivity meter 72 extends below the liquid level of the collecting bottle 71; the liquid inlet pipe 52 of the temperature control module 5 is connected to the lower part of one side of the rigid wall sample tube 2, and the liquid outlet pipe 53 is connected to the upper part of the other side of the rigid wall sample tube 2, and the connection of the pipeline is completed.

[0066] S4, after the circulating fluid of the temperature control module 5 is heated to the target temperature, the temperature of the rigid wall sample tube 2 is controlled through the pipeline circulation; then according to the test requirements, the set vertical stress is applied, and the deformation is considered to be stable when the variable is less than 0.01mm / h;

[0067] S5, after the deformation is stabilized, the salt solution supply module 16 and the water supply module 6 are used to replenish deionized water respectively, and when the pressure difference at both ends of the soil sample 12 is stable, the pressure difference can be determined as the reference osmotic pressure;

[0068] S6. After obtaining the reference osmotic pressure, replace the upper deionized water with a salt solution, continue the test and record the conductivity of the solution discharged from the pressure measuring interface, and record the pressure difference at both ends of the sample through the pressure difference sensor 82 and the data acquisition instrument 83. When the average value of the pressure difference at both ends of the sample changes within a certain period of time remains within 5%, the chemical osmotic pressure reaches a stable stage;

[0069] S7. After the test, gradually unload, take out the clay sample, and clean the test device.

[0070] The above completes one test. When multiple tests are needed, repeat steps S1-S3, then set different temperatures and / or stress levels, and continue with subsequent steps to conduct multiple repeated tests to explore the influence of temperature and / or stress levels on chemical permeation behavior; finally, the difference between the actual pressure difference measured by the differential pressure sensor and the reference osmotic pressure can be used to obtain the chemical osmotic pressure difference, and then the chemical permeation efficiency coefficient is determined by the ratio of the chemical osmotic pressure difference to the theoretical calculated value.

[0071] The theoretical value can be calculated according to the Van't Hoff equation.

[0072] π=vRTcφ (1)

[0073] Where R is the gas constant, T is the absolute temperature Kelvin, c is the concentration of the pore solution, and φ is the solute permeability coefficient, which can be calculated according to the electrolyte permeability coefficient formula proposed by Pitzer:

[0074]

[0075] In the formula, z M , z X are the charges of electrolyte cations M and anions X, respectively, v is the total number of ions after the salt is dissolved, and v M is the total number of cationic ions, v X is the total number of anions, that is, v = v M +v X ; m is the mass molar concentration of the salt solution; fφ is the Debye-Huckel term; and is the ion interaction coefficient.

[0076] The present invention adopts the test device in the above embodiment to carry out a saline clay consolidation test considering the influence of temperature and osmotic suction. The test method includes the following steps:

[0077] S1. Select representative saline clay samples, and prepare saline clay samples under different salt concentrations (different osmotic suction) according to the size, shape and salt content designed by the test device;

[0078] S2, embed the rigid-wall sample tube 2 into the base 1, evenly apply vaseline inside the sample tube to eliminate the influence of the friction between the inner wall and the sample on the test results, sequentially install the lower permeable stone 112, filter paper, soil sample 12, filter paper, upper permeable stone 111, and sample cap 10 into the sample tube, ensure that the permeable stone 11 and the filter paper are flat and fit, cover the cap 3, set a sealing ring 13 at the position where the rigid-wall sample tube 2 contacts the base 1 and the cap 3, and the rigid bolt 14 passes through the cap 3 and is firmly connected by the nut;

[0079] S3. The force transmission rod 9 connected to the upper part of the sample cap 10 passes through the through hole in the center of the cap 3. The test device is placed on the operating platform and the force transmission rod 9 is connected to the loading device of the operating platform for loading pressure, and the displacement sensor 15 is installed. This test does not require too much pipeline supply, such as Figure 4 As shown, only the conductivity monitoring module 7 can be set, the lower part of the pressure measuring tube 81 is connected to the lower pressure measuring interface, one end of the drainage tube 73 is connected to the pressure measuring tube 81, and the other end is introduced into the lower part of the collecting bottle 71, and the monitoring probe of the conductivity meter 72 is extended below the liquid level of the collecting bottle 71. The other end of the pressure measuring tube 81 is blocked, and all other connection ports are blocked, and a special sealing plug is used to ensure its sealing. Of course, pipelines can also be installed and controlled by valves, which is especially suitable for flexible pipes such as the salt solution supply pipe 163 and the pressure measuring tube 81. After other tests are carried out, it is not necessary to remove it from the pipe mouth and it can be directly used for this test.

[0080] S4, after the circulating fluid of the temperature control module 5 is heated to the target temperature, the temperature of the rigid-walled sample cylinder 2 is controlled through the pipeline circulation to achieve the purpose of temperature control;

[0081] S5. The loading device loads a preload of 1 kPa and adjusts the displacement sensor 15 to zero to ensure the accuracy of the measurement;

[0082] S6. Apply loads in stages according to test requirements. After each load stage, let the sample stand for a while to allow it to fully consolidate.

[0083] S7, during the consolidation process, regularly record the data of the displacement sensor 15 to detect the deformation, temperature and conductivity of the discharged solution of the sample;

[0084] S8. After the test, unload the pressure step by step and measure the coefficient of resilience of the sample; then, take out the clay sample and clean the test device; calculate the compression coefficient based on the test data and analyze the influence of temperature and infiltration suction on the compression characteristics. This completes a set of tests.

[0085] When multiple groups of tests need to be carried out, the saline clay sample under the same salt concentration (osmotic suction) can be selected, steps S1-S3 can be repeated, and then another target temperature can be set to continue the subsequent steps; or the saline clay sample under different salt concentrations (osmotic suction) can be replaced, and the steps can be repeated to carry out multiple tests at different temperatures and initial osmotic suctions to explore the effects of temperature, osmotic suction and their interaction on the compression behavior of saline clay.

[0086] The present invention uses the test device in the above embodiment to carry out a permeability consolidation test of clay considering the coupling effect of thermal and chemical forces, including the following steps:

[0087] S1. Select representative clay samples, prepare samples according to the size and shape designed by the test device, and use a vacuum saturation device to prepare saline clay samples with pores containing salt solution; in order to consider the influence of chemical osmotic gradient, select a salt solution with different concentration from the circulating fluid to prepare the saline clay sample;

[0088] S2, embed the rigid-wall sample tube 2 into the base 1, evenly apply vaseline inside the sample tube to eliminate the influence of the friction between the inner wall and the sample on the test results, sequentially install the lower permeable stone 112, filter paper, soil sample 12, filter paper, upper permeable stone 111, and sample cap 10 into the sample tube, ensure that the permeable stone 11 and the filter paper are flat and fit, cover the cap 3, set a sealing ring 13 at the position where the rigid-wall sample tube 2 contacts the base 1 and the cap 3, and the rigid bolt 14 passes through the cap 3 and is firmly connected by the nut;

[0089] S3. The force transmission rod 9 connected to the upper part of the sample cap 10 passes through the through hole in the center of the cap 3. The test device is placed on the operating platform and the force transmission rod 9 is connected to the loading device of the operating platform for loading pressure. The displacement sensor 15 is installed, and then the required pipelines on the test device are connected and ensured to be tight.

[0090] The pipelines that need to be connected in this experiment include: connecting the water supply pipe 61, the peristaltic pump 62 and the deionized water container 63 in sequence, connecting the water supply pipe 61 to the water supply port. It should be noted that the water supply port is not only a port, but also includes a pipe hole opened on the base 1. The connection can be achieved by inserting the water supply pipe 61 into the pipe hole; connecting the salt solution container 161, the gear pump 162 and the salt solution supply pipe 163 in sequence. The salt solution supply pipe 163 is a rigid pipe, which is directly inserted into the hole opened on the cap 3 and connected to the salt solution interface on the upper part of the sample cap 10; connecting the pressure measuring tube 81 to the upper and lower pressure measuring interfaces in sequence, and connecting the differential pressure sensor 82 in the middle. The differential pressure sensor 82 is connected to a data acquisition instrument 83, and an infusion tube 17 is arranged on the upper part of the pressure measuring tube 81, one end of the infusion tube 17 is connected to the upper part of the pressure measuring tube 81, and the other end extends below the liquid level of the salt solution container 161, and the lower part of the pressure measuring tube 81 is connected to the conductivity monitoring module 7, wherein one end of the drainage tube 73 is connected to the pressure measuring tube 81, and the other end is introduced into the lower part of the collecting bottle 71, and the monitoring probe of the conductivity meter 72 extends below the liquid level of the collecting bottle 71; the liquid inlet pipe 52 of the temperature control module 5 is connected to the lower part of one side of the rigid wall sample tube 2, and the liquid outlet pipe 53 is connected to the upper part of the other side of the rigid wall sample tube 2, and the connection of the pipeline is completed.

[0091] S4, after the circulating fluid of the temperature control module 5 is heated to the target temperature, the temperature of the rigid-wall sample cylinder 2 is controlled through the pipeline circulation;

[0092] S5. According to the test requirements, a certain vertical stress is first applied, and then the salt solution is replenished by the salt solution replenishment module 16 until the deformation reaches a stable state; then, pressure is continued to be applied and salt solution is replenished until the deformation reaches a stable state; pressures at various levels are repeatedly applied, and during the process, the deformation, temperature, conductivity of the discharged solution, and data of the pressure difference sensor at various levels are recorded with the help of the data acquisition instrument 83, the pressure difference sensor 82, the conductivity meter 72, the displacement sensor 15, etc.;

[0093] S6. After the test, unload gradually, take out the clay sample, clean the test device; combine the data including the deformation, time, temperature, etc. of the clay sample, and analyze the influence of factors including clay stress level, temperature, chemical gradient, etc. on the permeability and compression behavior of the sample. The above completes a set of tests.

[0094] When multiple sets of tests need to be carried out, repeat steps S1-S3, and then heat the circulating fluid to another target temperature and continue the test. The test needs to be repeated multiple times at different temperatures, stress levels, and chemical gradients. The steps are the same, and one variable is controlled each time to conduct the test to explore the effects of temperature, stress level, and penetration suction gradient on the penetration and compression behavior of the sample.

[0095] By adopting the device of the present invention, a variety of geotechnical performance tests can be carried out. The test device has various functions, which realizes multi-purpose use of one machine and reduces the test cost. The geotechnical test method provided by the test device of the present invention takes into account many factors and indicators, can more truly reflect the complex environment in practical applications, and the test steps are simple, which can be widely promoted and applied. In addition, the device is not limited to geotechnical performance testing, but can also test some related new materials.

[0096] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multifunctional testing device for clay chemical penetration and consolidation tests, characterized in that: The invention comprises a base (1), wherein a rigid-walled sample tube (2) is provided on the upper part of the base (1), and a cap (3) is provided on the upper part of the rigid-walled sample tube (2); the wall cavity of the rigid-walled sample tube (2) is hollow, and temperature control is achieved by circulating a circulating fluid of a temperature control module (5) in the wall cavity; a through hole is provided at the center of the cap (3), and a force transmission rod (9) is vertically slidably installed in the through hole; a sample cap (10) is connected to the lower part of the force transmission rod (9), and a displacement sensor (15) is installed on the upper part of the cap (3); the interior of the rigid-walled sample tube (2) is filled with a soil sample (12), and an upper permeable stone (111) and a lower permeable stone (112) are respectively provided at the upper and lower ends of the soil sample (12); the sample cap (10) is provided at the upper and lower ends of the sample 0) is in contact with the top of the upper permeable stone (111); the sample cap (10) is integrated with an upper pressure measuring interface and a salt solution interface, the salt solution interface is connected to a salt solution supply module (16), the base (1) is internally integrated with a lower pressure measuring interface and a water supply port, the upper pressure measuring interface and the lower pressure measuring interface are connected via a pressure measuring module (8) to achieve pressure measurement, the pressure measuring module (8) comprises a pressure measuring tube (81) directly connected to the pressure measuring interface and a differential pressure sensor (82) installed in the middle of the pressure measuring tube (81), and a conductivity monitoring module (7) is arranged at the lower part of the pressure measuring tube (81); the water supply port is connected to a water supply module (6) for replenishing deionized water; the device is a closed system, and the interface and pipeline are both in a sealed state.

2. The multifunctional testing device for clay chemical penetration and consolidation test according to claim 1, characterized in that: The temperature control module (5) comprises a constant temperature cold room (51), a liquid inlet pipe (52) and a liquid outlet pipe (53), wherein the liquid inlet pipe (52) is connected to the lower part of one side of the rigid wall sample tube (2), and the liquid outlet pipe (53) is connected to the upper part of the other side of the rigid wall sample tube (2); the water replenishment module (6) comprises a water replenishment pipe (61), a peristaltic pump (62) and a deionized water container (63), wherein the delivery of the deionized water is controlled by the peristaltic pump (62) to ensure accurate regulation of the flow rate, and the water replenishment is carried out by connecting the water replenishment pipe (61) to the water replenishment port; the salt solution replenishment module (16) comprises a salt solution container (161), a gear pump (162) and a salt solution replenishment pipe (163), and is connected to the salt solution interface through the salt solution replenishment pipe (163) to carry out a chemical permeation test; the salt solution replenishment pipe (163) and the pressure measuring pipe (81) both vertically penetrate the cap (3).

3. The multifunctional testing device for clay chemical penetration and consolidation test according to claim 2, characterized in that: The conductivity monitoring module (7) comprises a collecting bottle (71), a conductivity meter (72) and a drainage tube (73); one end of the drainage tube (73) is connected to the pressure measuring tube (81), and the other end is introduced into the lower part of the collecting bottle (71); the monitoring probe of the conductivity meter (72) extends below the liquid level of the collecting bottle (71); the pressure measuring module (8) also comprises a data acquisition instrument (83), and the data acquisition instrument (83) is electrically connected to the differential pressure sensor (82); an infusion tube (17) is arranged on the upper part of the pressure measuring tube (81); one end of the infusion tube (17) is connected to the upper part of the pressure measuring tube (81), and the other end extends below the liquid level of the saline solution container (161).

4. The multifunctional testing device for clay chemical penetration and consolidation test according to claim 1, characterized in that: The upper part of the base (1) and the lower part of the cover cap (3) are provided with cylindrical grooves matching the rigid-walled sample tube (2); the rigid-walled sample tube (2) is clamped in the cylindrical grooves of the base (1) and the cover cap (3); sealing rings (13) are provided at both ends of the rigid-walled sample tube (2); rigid bolts (14) are evenly distributed on the edge of the base (1); the rigid bolts (14) penetrate the cover cap (3) and are firmly connected by nuts; the outer edge of the sample cap (10) is tightly attached to the inner wall of the rigid-walled sample tube (2).

5. A chemical permeation test method taking into account the influence of temperature and stress level, characterized in that The multifunctional testing device according to any one of claims 1 to 4 comprises the following steps: S1. Select a representative clay sample and prepare a soil sample (12) according to the size and shape designed by the test device; S2, embed the rigid-wall sample tube (2) into the base (1), sequentially install the lower permeable stone (112), filter paper, soil sample (12), filter paper, upper permeable stone (111), and sample cap (10) into the sample tube, and cover and secure the cover cap (3); S3, placing the test device on the operating platform and connecting it to the loading device of the operating platform, and installing the displacement sensor (15), and then connecting all the required pipelines on the test device and ensuring their sealing; S4, after the circulating fluid of the temperature control module (5) is heated to the target temperature, the temperature of the rigid wall sample cylinder (2) is controlled through the pipeline circulation; then, according to the test requirements, a set vertical stress is applied until the deformation reaches a stable state; S5, using the salt solution supply module (16) and the water supply module (6) to replenish deionized water respectively, and when the pressure difference at both ends of the soil sample (12) is stable, the pressure difference can be determined as the reference osmotic pressure; S6. After obtaining the reference osmotic pressure, replace the upper deionized water with a salt solution, continue the test and record the conductivity of the solution discharged from the pressure measuring interface and the pressure difference at both ends of the sample. When the average value of the pressure difference at both ends of the sample changes within a certain period of time remains within 5%, the chemical osmotic pressure reaches a stable stage; S7. After the test, gradually unload, take out the clay sample, and clean the test device.

6. The chemical permeation test method considering the influence of temperature and stress level as claimed in claim 5, characterized in that: It also includes repeating steps S1-S3, then setting different temperatures and / or stress levels, and continuing the subsequent steps to carry out multiple repeated tests to explore the influence of temperature and / or stress levels on chemical permeation behavior; finally, the difference between the actual pressure difference measured by the pressure difference sensor and the reference osmotic pressure can be used to obtain the chemical osmotic pressure difference, and then the chemical permeation efficiency coefficient is determined by the ratio of the chemical osmotic pressure difference to the theoretical calculated value.

7. A consolidation test method for saline clay taking into account the influence of temperature and osmotic suction, characterized in that The multifunctional testing device according to any one of claims 1 to 4 comprises the following steps: S1. Select representative saline clay samples and prepare saline clay samples with different salt concentrations according to the size, shape and salt content designed by the test device; S2, embed the rigid-walled sample tube (2) into the base (1), evenly apply vaseline inside the sample tube, sequentially install the lower permeable stone (112), filter paper, soil sample (12), filter paper, upper permeable stone (111), and sample cap (10) into the sample tube, and cover and secure the cover cap (3); S3, placing the test device on the operating platform and connecting it to the loading device of the operating platform, and installing the displacement sensor (15), and then connecting all the required pipelines on the test device and ensuring their sealing; S4, after the circulating fluid of the temperature control module (5) is heated to the target temperature, the temperature of the rigid-walled sample cylinder (2) is controlled through the pipeline circulation; S5, the loading device applies a preload of 1 kPa and adjusts the displacement sensor (15) to zero; S6. Apply loads in stages according to test requirements. After each load stage, let the sample stand for a while to allow it to fully consolidate. S7, during the consolidation process, regularly record the data of the displacement sensor (15) to detect the deformation, temperature and conductivity of the discharged solution of the sample; S8. After the test, unload the pressure step by step and measure the coefficient of resilience of the sample. Then, take out the clay sample and clean the test device. According to the test data, calculate the compression coefficient and analyze the influence of temperature and penetration suction on the compression characteristics.

8. The consolidation test method of saline clay considering the influence of temperature and osmotic suction as claimed in claim 7, characterized in that: The method also includes selecting a saline clay sample at the same salt concentration, repeating steps S1-S3, and then setting another target temperature to continue with subsequent steps; or replacing saline clay samples at different salt concentrations, repeating the steps, and conducting multiple tests at different temperatures and initial osmotic suctions to explore the effects of temperature, osmotic suction and their interaction on the compression behavior of saline clay.

9. A permeability consolidation test method for clay considering the coupling of thermal and chemical forces, characterized in that The multifunctional testing device according to any one of claims 1 to 4 comprises the following steps: S1. Select a representative clay sample, prepare the sample according to the size and shape designed by the test device, and prepare a saline clay sample with pores containing salt solution by means of a vacuum saturation device; S2, embed the rigid-walled sample tube (2) into the base (1), evenly apply vaseline inside the sample tube, sequentially install the lower permeable stone (112), filter paper, soil sample (12), filter paper, upper permeable stone (111), and sample cap (10) into the sample tube, and cover and secure the cover cap (3); S3, placing the test device on the operating platform and connecting it to the loading device of the operating platform, and installing the displacement sensor (15), and then connecting all the required pipelines on the test device and ensuring their sealing; S4, after the circulating fluid of the temperature control module (5) is heated to the target temperature, the temperature of the rigid-walled sample cylinder (2) is controlled through the pipeline circulation; S5. According to the test requirements, a certain vertical stress is first applied, and then the salt solution is supplied by the salt solution supply module (16) until the deformation reaches a stable state; then, pressure is continuously applied and salt solution is supplied until the deformation reaches a stable state; pressure at each level is repeatedly applied, and the deformation amount, temperature, conductivity of the discharged solution and data of the differential pressure sensor at each level are recorded; S6. After the test, gradually unload, take out the clay sample, and clean the test equipment; combine the data including the deformation, time, and temperature of the clay sample to analyze the influence of factors including clay stress level, temperature, and chemical gradient on the penetration and compression behavior of the sample.

10. A method for testing the permeability consolidation of clay under the effect of thermal-chemical coupling as claimed in claim 9, characterized in that The following steps are also included: Repeat steps S1-S3, then heat the circulating fluid to another target temperature and continue the test. The test needs to be repeated multiple times at different temperatures, stress levels, and chemical gradients to explore the effects of temperature, stress level, and osmotic suction gradient on the penetration and compression behavior of the sample.

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