Soil permeability tester and testing method under dry-wet or freeze-thaw cycle effect

Abstract

The present application provides a kind of permeability tester of soil under dry-wet or freeze-thaw cycle effect, including static pressure loading device part and core test part, both parts are connected and fixed by support;Static pressure loading device part is composed of hydraulic device, hydraulic rod, main device, bottom pedestal and sliding groove;Core test part is composed of pressure rod, pressure measuring tube and plastic top plate, main device includes water storage pool and sample cylinder, water storage pool is composed of first baffle, second baffle, sample cylinder is composed of third baffle, fourth baffle;Second baffle and third baffle form vertical drainage layer, and water inlet is arranged on second baffle;Fourth baffle is provided with air hole;Bottom guide layer is arranged at the bottom of sample cylinder, resistance wire is built-in in vertical drainage layer and bottom guide layer;And drainage outlet is arranged;Ventilation opening and humidifier are arranged on second baffle, pressure rod includes first valve and second valve;Air outlet is arranged on plastic top plate;Barometer is installed on fourth baffle.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building material permeability testing equipment, in particular to a soil permeability tester under dry-wet or freeze-thaw cycle effect and a testing method. BACKGROUND

[0002] Currently, most soil materials are applied in practical engineering, and the primary consideration is their performance in harsh environments. The dry-wet and freeze-thaw cycle effects in nature have a particularly prominent impact on soil. The dry-wet and freeze-thaw cycle effects caused by seasonal changes and rising or falling groundwater levels can significantly affect the permeability of soil.

[0003] Currently, soil permeability testing requires different test devices. The main steps include compacting or static pressing to make a cutting ring sample, moving the sample to a stacked saturation instrument to experience different dry-wet or freeze-thaw cycle effects, and finally taking out the cutting ring sample to perform a permeability test in a permeability instrument. However, this method is complicated and prone to sample disturbance during the experiment, and the measurement operation is tedious and can affect the measurement accuracy.

[0004] Therefore, it is necessary to design a soil permeability tester under dry-wet or freeze-thaw cycle effect to simplify the related work by unifying the permeability measurement equipment for the same sample under dry-wet or freeze-thaw effect. SUMMARY

[0005] To solve the technical problems described in the background, the present application provides a soil permeability tester under dry-wet or freeze-thaw cycle effect and a testing method, which realizes the functions of single device, single sample, no need to take out the sample, and continuous sequential testing of permeability parameters, effectively simplifying the corresponding operation steps and equipment, and eliminating the influence of sample loss on the test results.

[0006] To solve the above technical problems, the present application provides a soil permeability tester under dry-wet or freeze-thaw cycle effect, which includes a static pressure loading device part and a core testing part, both of which are connected and fixed by a support;

[0007] The static pressure loading device part is composed of a hydraulic device, a hydraulic rod, a main body device, a bottom pedestal, and a sliding groove. The hydraulic rod drives the hydraulic device to lift and lower. The hydraulic rod is fixed at the top of the support;

[0008] The core testing part is composed of a pressure rod, a pressure measuring tube, and a plastic top plate. The pressure measuring tube is installed in the pressure rod, the pressure rod is installed at the top of the support, and the pressure rod can be lifted and lowered. The plastic top plate is installed at the bottom of the pressure rod;

[0009] The bottom pedestal and the sliding groove are extended to the core test part by the static pressure loading device part, the main device is installed on the sliding groove and has sliding movement along the sliding groove; the main device is slidably arranged below the hydraulic device or below the plastic top plate along the sliding groove;

[0010] The main device comprises a water storage pool and a sample cylinder, the water storage pool is composed of a first partition plate and a second partition plate, and the sample cylinder is composed of a third partition plate and a fourth partition plate; the second partition plate and the third partition plate form a vertical drainage layer, and a water inlet is arranged on the second partition plate; the third partition plate is liftable, and the fourth partition plate is provided with a gas permeable hole;

[0011] A bottom drainage layer is arranged at the bottom of the sample cylinder, and heating resistance wires and refrigeration resistance wires are arranged in the vertical drainage layer and the bottom drainage layer; the bottom drainage layer and the vertical drainage layer are both provided with a water outlet;

[0012] A ventilation port and a humidifier are arranged outside the second partition plate, the bottom of the pressure rod is provided with a first valve and a second valve; an air outlet is arranged on the plastic top plate for vacuumizing; a pressure gauge is installed on the fourth partition plate for detecting the change of the internal air pressure of the device main body.

[0013] In a preferred embodiment, the water storage pool is provided with a highest water level line; a pull ring is arranged at the water inlet, and the pull ring is used for controlling the opening and closing of the water inlet; an air permeable layer is arranged at the bottom of the plastic top plate; the pressure measuring pipe is provided with a scale line, and the pressure rod is a transparent rod.

[0014] In a preferred embodiment, a dial indicator is arranged above the vertical drainage layer, and the dial indicator is rotatable in a plane; a thermometer is installed above the vertical drainage layer.

[0015] In a preferred embodiment, the main device comprises a filling layer, and a lower water permeable stone is arranged at the bottom of the sample cylinder.

[0016] The humidifier is connected with a spray head, the spray head is provided with an expansion plate, and the spray head and the expansion plate are installed in the vertical drainage layer.

[0017] The application also provides a test method for the permeability of soil under the effect of dry-wet or freeze-thaw cycles, and the test method comprises the following steps:

[0018] Step 1, the sample (material) is compacted by the static pressure loading device for compactness control, and is compacted in the sample cylinder of the main device; after static pressure loading and standing for 2-3 hours, the sample (material) is kept from deforming, and the main device is moved to below the pressure rod and the pressure measuring pipe through the sliding groove;

[0019] Step 2, after placing the filter paper and the upper water permeable stone on the sample, align the position of the plastic top plate with the top of the sample, and then move the plastic top plate down by the computer-controlled pressure rod to seal the main device, continue to move down until the plastic top plate contacts the top of the sample, and then stop moving down and fix the position of the pressure rod so that the plastic top plate remains unchanged during the entire test;

[0020] Step 3, after ensuring that the plastic top plate is completely fixed on the surface of the sample, check the air tightness of the main device, ensure that the main device is air-tight, then close the water outlet, close the water inlet, the third partition plate does not move upward and remains unchanged, the first valve and the second valve are closed, the humidifier is closed, the air outlet is closed, and the power switch of the equipment is closed before the test;

[0021] Step 4, fill the test solution in the water storage tank, and the maximum capacity of the test solution should not exceed the height of the main device;

[0022] Step 5, after ensuring that the air tightness of the main device is good, open the vacuum air extractor by computer control, and then perform air extraction on the inside of the main device through the air outlet at the plastic top plate, and observe the change of the air pressure inside the sample through the air pressure gauge, and the air extraction time is about 4-5h;

[0023] Step 6, after the main device is completely vacuumized, close the vacuum air extractor, lift the third partition plate upward and fix it to keep the position unchanged, open the water inlet, and let the solution in the water storage tank enter the inside of the sample through the air permeable hole of the fourth partition plate for saturation treatment;

[0024] Step 7, according to the reading change of the air pressure gauge, open the vacuum air extractor again for appropriate air extraction and saturation, and after the reading of the air pressure gauge is stable and unchanged, move the third partition plate downward, close all water inlets, so that the sample is in a closed state, and the sample is saturated after 24h of back pressure saturation;

[0025] Step 8, open the first valve and the second valve at the same time to perform the corresponding permeation test, and read the drop value of the water head height of the solution in the pressure pipe within the corresponding time period to calculate the permeation coefficient;

[0026] Step 9, after the test is completed, open the water outlet of the vertical drainage layer to drain the solution in the vertical drainage layer.

[0027] In a preferred embodiment, if saturation operation is needed in the test method, step 6 is retained, and if saturation operation is not needed, step 6 is omitted.

[0028] If step 6 is omitted, no solution should enter the vertical drainage layer during the entire test process.

[0029] The application also provides a method for testing the permeability of a soil body under the effect of dry-wet cycles, and the application of the permeability tester; the testing method comprises a drying process and a saturation process, and before the drying process and the saturation process are performed, steps 1-3 are performed first;

[0030] The drying process comprises the following steps:

[0031] Step 11, the third partition is moved upward to ensure that the vertical drainage layer is fully dried and no liquid penetrates, then the ventilation opening is opened and connected to the air blower, the air blower is turned on by the computer, and the air volume, air speed and air type of the air blower are controlled by the computer; the air type includes hot air and cold air;

[0032] Step 12, the sample is dried through the vertical drainage layer and the air holes of the fourth partition, and the temperature and efficiency of the heating resistance wire or the refrigeration resistance wire are controlled by the computer;

[0033] The saturation process comprises the following steps:

[0034] Step 21, after the drying is completed, the ventilation opening is closed, the position of the third partition is kept unchanged, the water inlet is opened, the solution in the water storage tank is allowed to enter the sample through the vertical drainage layer and then through the air holes of the fourth partition, and the sample is fully saturated;

[0035] Step 22, the water inlet is opened, then the third partition is moved downward to isolate the sample and the vertical drainage layer, and prevent the solution from entering the fully saturated sample;

[0036] Step 23, the vacuum air extractor is opened to perform appropriate air extraction saturation on the sample through the air extraction opening, the change in the reading of the air pressure gauge is observed to determine whether the pores in the sample are completely and cleanly drained, the pore gas generated in the saturation process of the sample is completely drained, and the saturation air extraction process of the sample is completed;

[0037] Step 24, the drain openings of the bottom drainage layer are opened, the first valve and the second valve are opened, the same solution as that in the water storage tank is injected into the upper part of the pressure measuring tube in the pressure rod, the permeation test of the sample is performed, and corresponding data are recorded for calculation;

[0038] Step 25, all the drain openings are opened to drain the liquid;

[0039] The multiple dry-wet cycle test steps are based on steps 11-12 and steps 21-23, and the final operation of step 24 is performed after the cycle is completed.

[0040] The application also provides a method for testing the permeability of a soil body under the effect of freeze-thaw cycles, and the application of the permeability tester; the testing method comprises a freezing process and a thawing process, and before the freezing process and the thawing process are performed, steps 1-3 are performed first;

[0041] The freezing process includes the following steps:

[0042] Step 111, move the third partition upward to ensure that the vertical drainage layer is fully dried and no liquid penetrates, then open the ventilation port and connect the air blower, open the air blower through the computer, control the size and speed of the air blower through the computer, and the type of air is cold air;

[0043] Step 112, freeze the sample through the vertical drainage layer and the air holes of the fourth partition, and control the temperature and efficiency of the refrigeration resistance wire through the computer;

[0044] The melting process uses solution saturation to melt or uses constant temperature and humidity curing to melt;

[0045] The multiple dry-wet cycle test steps are based on the freezing process and the melting process, and the last step of the melting process is performed after the cycle is completed.

[0046] In a preferred embodiment, the melting using solution saturation includes the following steps:

[0047] Step A, keep the third partition in the upward position unchanged, open the water inlet, let the solution enter the inside of the sample through the vertical drainage layer and the air holes of the fourth partition, so that the inside of the sample is fully saturated and fully melted;

[0048] Step B, open the drainage port of the vertical drainage layer after the melting is completed, and drain the solution in the vertical drainage layer.

[0049] In a preferred embodiment, the melting using constant temperature and humidity curing includes the following steps:

[0050] Step a, after ensuring that the solution in the vertical drainage layer is completely drained, melt the sample according to the constant temperature and humidity curing conditions (20 degrees Celsius), and ensure that the third partition is fixed in the upward position;

[0051] Step b, control the temperature in the vertical drainage layer to be constant at room temperature through the heating resistance wire and the refrigeration resistance wire in the vertical drainage layer, use the computer to control the humidifier to input gas (with a certain humidity), then open the humidifier, and cooperate with the resistance wire to humidify the inside of the sample;

[0052] Step c, after the sample is fully thawed, close the humidifier, move the third partition downward to isolate the vertical drainage layer from the sample, and prevent external solution from entering the sample after the sample is fully saturated;

[0053] Step d, open the drainage port of the vertical drainage layer to drain the solution in the vertical drainage layer;

[0054] Step e, finally in the pressure in the pressure tube after adding the corresponding solution (solution is determined according to the test needs), open the first valve, the second valve and the bottom drainage layer drain to carry out the permeation test.

[0055] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0056] 1. By setting a kind of dry-wet or freeze-thaw cycle effect under the permeability tester of soil mass. Realize single equipment, single sample, do not need to take out sample and continuously order continuous testing permeability related parameters function, effectively simplify the corresponding operation steps and equipment, exclude the influence of the loss of sample caused in the test on the test result.

[0057] 2. By setting the chute to realize the position transfer of the main device between the static pressure loading device and the core test part, realize the compaction of sample and the test of permeability coefficient, the test process is complete, the steps are closely related, ensure that there is no external and artificial interference in the test process, ensure the accuracy of test results.

[0058] 3. The setting of dry-wet, freeze-thaw cycle effect is more reasonable, which can ensure that the two effects directly contact with the sample, is more in line with the actual application scene of the sample, and the transmission between various effects is more uniform and reasonable.

[0059] 4. Through the permeability tester, multiple tests can be compatible, including sample (material) permeation test under the coupling effect of dry-wet-freeze-thaw cycle, sample (material) permeation test under different overburden load, sample surface crack characterization test under different dry-wet or freeze-thaw cycle effect, sample (material) expansion test. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 It is the side view of the overall structure of the permeability tester in the embodiment of the present application.

[0061] Figure 2 It is the top view of the overall structure of the permeability tester in the embodiment of the present application.

[0062] Figure 3 It is the structure side view of the static pressure loading device part in the embodiment of the present application.

[0063] Figure 4 It is the structure side view of the core test part in the embodiment of the present application.

[0064] Figure 5 It is the detailed structure diagram of the main device in the embodiment of the present application.

[0065] Figure 6 It is the top view of the main device and the plastic top plate in the embodiment of the present application.

[0066] Figure 7 is a plan view of the main body of the embodiment of the present application;

[0067] Figure 8 is a distribution diagram of the bottom drainage port of the main body of the embodiment of the present application;

[0068] Figure 9 is Figure 5 is a detailed enlarged view of position A in the embodiment of the present application;

[0069] Figure 10 is Figure 5 is a detailed enlarged view of position B in the embodiment of the present application

[0070] Figure 11 is Figure 5 is a detailed enlarged view of position C in the embodiment of the present application

[0071] Figure 12 is a diagram showing the air vent hole provided in the fourth partition plate in the embodiment of the present application.

[0072] BRIEF DESCRIPTION OF THE DRAWINGS: 1, main device; 11, dial indicator; 111, support; 12, upper water-permeable stone; 13, filling layer; 131, air and water-permeable layer; 14, barometer; 15, water reservoir; 151, first partition plate; 152, second partition plate; 1521, first water inlet; 1522, second water inlet; 1523, third water inlet; 1524, fourth water inlet; 1525, pull ring; 153, highest water level line; 16, sample cylinder; 161, third partition plate; 162, fourth partition plate; 1621, air vent hole; 163, iron pad; 17, vertical drainage layer; 171, heating resistance wire; 172, refrigeration resistance wire; 173, thermometer; 18, bottom drainage layer; 181, first drainage port; 182, second drainage port; 183, third drainage port; 184, fourth drainage port; 185, fifth drainage port; 19, lower water-permeable stone; 101, ventilation opening; 102, ventilation duct; 103, humidifier; 104, humidification duct; 105, spray head; 106, expansion plate; 2, iron support; 21, iron base; 3, hydraulic device; 4, bottom pedestal; 5, hydraulic rod; 6, sliding chute; 7, pressure rod; 71, first valve; 72, second valve; 8, pressure measuring tube; 9, plastic top plate; 91, air suction opening; 92, air suction duct; 10, air-permeable layer. DETAILED DESCRIPTION

[0073] Clearly, the embodiments described are only a part of the embodiments of the present application, and not all the embodiments, based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of the present application.

[0074] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom end" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0075] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "sleeved / connected", "connected" and the like should be broadly understood, for example, "connected" can be wall-mounted connection, can be detachable connection, or integral connection, can be mechanical connection, can be electrical connection, can be direct connection, can be indirect connection through an intermediate medium, can be internal communication of two elements, and for a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0076] Reference Figures 1-12 The present embodiment provides a soil permeability tester under dry-wet or freeze-thaw cycle effect, which comprises a static pressure loading device part and a core test part, both of which are connected and fixed by a support.

[0077] The static pressure loading device part comprises a hydraulic device 3, a hydraulic rod 5, a main body device 1, a bottom pedestal 4 and a sliding groove 6. The hydraulic device 3 is arranged at the driving end of the hydraulic rod 5, the hydraulic rod 5 can be controlled by a computer to rise and fall, the hydraulic device 3 is connected with the hydraulic rod 5, the hydraulic rod 5 is installed on the top of the support through a fixing device, and the main body device 1 is installed below the hydraulic device 3. The main body device 1 is used for containing the sample (material) to be tested, the hydraulic device 3 is driven by the hydraulic rod 5 to rise or fall and to prepare the sample (material) in the main body device 1. The sliding groove 6 is arranged on the bottom pedestal 4, and the main body device 1 is installed on the sliding groove 6, and the main body device 1 has sliding movement along the sliding groove 6.

[0078] The core test part includes a pressure rod 7, a pressure measuring pipe 8, a plastic top plate 9, a dial gauge 11, and the inner slide groove 6 and the bottom pedestal 4 of the support are extended from the static pressure loading device part to the core test part, the main device 1 is slidably arranged and can be slid from the static pressure loading device part to the core test part along the slide groove 6. The pressure measuring pipe 8 is installed in the pressure rod 7, and the bottoms of the two are connected with the plastic top plate 9, the top of the pressure measuring rod and the pressure rod 7 is installed on the iron stand through a fixing device, when the main device 1 is slid to the core test part, the main device 1 is slid to the lower side of the pressure measuring rod and the pressure rod 7, the main device 1 can be slid at the bottom and fixed at the corresponding position through the slide groove 6, the slide groove 6 is provided with a certain slope at the connection part of the static pressure loading device part and the core test part, so as to facilitate the transfer of the main device 1.

[0079] The support includes a frame formed by the iron support 2 and an iron base 21 supported at the bottom, vertical connecting rods and horizontal connecting rods are installed on the frame to stably support, the bottom pedestal 4 is built on the iron base 21, and the slide groove 6 is laid on the bottom pedestal 4 to facilitate the sliding of the main device 1; the hydraulic rod 5 and the pressure rod 7 are connected with the computer, and the compaction of the sample and the test of the permeability coefficient are realized through the program system of the computer.

[0080] The permeability tester is divided into two parts, the first part is the static pressure loading part of the sample, and the second part is the core part of the permeability test, the compaction quality of the sample (material) can be determined according to the optimal water content and the maximum dry density obtained by the compaction of the sample.

[0081] Firstly, the main device 1 is slid to the lower side of the hydraulic device 3 through the slide groove 6 and is fixed at the position, the sample (material) is added into the main device 1, the hydraulic rod 5 is controlled by the computer, the hydraulic device 3 is lowered to compact the sample and the compaction is continuously maintained for 1-2 hours.

[0082] After the continuous compaction is maintained for 1-2 hours, the hydraulic rod 5 is raised, the fixation of the main device 1 is released, and the main device 1 is moved to the core test part, is moved to the lower side of the pressure measuring pipe 8 and the pressure rod 7 and is fixed at the position, the pressure rod 7 is controlled to be raised and lowered by the computer, the plastic top plate 9 connected below the pressure rod 7 is moved downward to the upper part of the sample, the plastic top plate 9 is controlled to stop the lowering of the pressure rod 7 when it is moved downward to the surface of the sample by the computer, and then whether the sample needs to be continuously loaded and the permeability test is completed or not loaded and the permeability test is completed in this state according to the test requirement.

[0083] The permeability tester has different test functions, which are as follows:

[0084] (a) sample (material) permeability test under dry-wet and freeze-thaw cycle coupling: the basic process of single dry-wet and freeze-thaw cycle is combined, and the sample (material) permeability test under the coupling of two different conditions can be completed;

[0085] (b) Penetration test of the sample (material) under different overburden loads: Different loads are applied to the upper part of the sample (material) by the computer-controlled pressure rod 7, and the load loading range is determined according to the material of the pressure rod 7 (the loading range is 0-800 kPa). Then, according to the same operation steps in (a), the sample (material) is subjected to a penetration test under the action of overburden pressure and different pressures;

[0086] (c) Fracture characterization test of the sample surface under different dry-wet or freeze-thaw cycle effects: After each cycle, the pressure rod 7 is moved upward by the computer, and then the camera is used to take pictures and save the state of the sample surface, and the corresponding software or program is used to calculate the development law of the sample (material) surface cracks under different dry-wet or freeze-thaw cycle conditions;

[0087] (d) Swelling amount test of the sample (material): The pressure rod 7 is lowered to the sample surface by computer control, and the position of the pressure rod 7 is not fixed so that the plastic top plate 9 can move freely upward when the sample swells and deforms, and the swelling and deformation of the sample is measured by the dial gauge 11 combined with the scale.

[0088] The specific structure design of the core test part is as follows:

[0089] The pressure measuring tube 8 is installed inside the pressure rod 7 and fixed to the top of the support with the pressure rod 7. The pressure measuring tube 8 and the bottom of the pressure rod 7 have air holes with the plastic top plate 9, and the dial gauge 11 is fixed on both sides of the plastic top plate 9 through the support 111, and the dial gauge 11 is in contact with the top of the plastic top plate 9.

[0090] The pressure rod 7 is used to control the swelling deformation or swelling and sliding or particle dispersion of the sample (material) inside. The outside of the pressure rod 7 is transparent, and the scale line on the inside of the pressure measuring tube 8 can be observed to facilitate reading the change of the water head in the pressure measuring tube 8.

[0091] When testing the permeability coefficient of the sample, after compacting the sample by the static pressure loading device, a filter paper with the same size as the sample is placed on its surface, and then the upper water permeable stone 12 is placed on the filter paper. The plastic top plate 9 is lowered to just contact the upper surface of the compacted sample by computer control of the pressure rod 7, and the pressure rod 7 is fixed at this position, at this time the plastic top plate 9 limits the swelling deformation of the sample and the dispersion of the material.

[0092] If the influence of the upper pressure of the sample is considered when testing the permeability coefficient, the pressure rod 7 can be controlled by the computer to press down and apply pressure to the sample through the plastic top plate 9, and the material of the sample can be subjected to a penetration test by the pressure measuring tube 8.

[0093] The pressure measuring tube 8 passes through the inside of the plastic top plate 9 and the air permeable layer 10, and the lowest part of the pressure measuring tube 8 can pass through the top surface of the upper permeable stone 12. The permeability test can be carried out by injecting a solution into the pressure measuring tube 8, and the change in the solution height of the internal pressure measuring tube 8 can be observed through the transparent pressure rod 7.

[0094] The pressure measuring tube 8 is arranged in the pressure rod 7, and the pressure measuring tube 8 can be connected to the support through a horizontal connecting rod and a bolt, and the position can be adjusted upward or downward through the operation of the bolt. First and second valves 71 and 72 are arranged at the port where the pressure rod 7 contacts the plastic top plate 9, and are used to control the solution in the pressure measuring tube 8 to carry out the internal sample. Scale lines are arranged on the pressure measuring tube 8, which are used to measure the difference in water head drop of the solution in different time periods.

[0095] The material of the plastic top plate 9 is light and hard, which can be moved upward when the test is free to expand. The corresponding hardness can ensure that it is not damaged under different pressures. Due to the difference of the test solution, the material of the plastic top plate 9 also has the characteristics of acid resistance, alkali resistance, heat resistance, and chemical corrosion resistance, and the plastic top plate 9 is water and air tight. The plastic top plate 9 is used to seal the top of the sample, and the plastic top plate 9 is arranged on the upper part of the upper permeable stone 12.

[0096] The plastic top plate 9 is provided with two air exhaust ports 91, which are arranged on the surface of the plastic top plate 9, and the air exhaust ports 91 are connected to two air exhaust pipes 92 outside. The air exhaust pipes 92 are communicated to the upper end of the air permeable layer 10 through the air exhaust ports 91, and the vacuum air extractor controlled by the computer is used to exhaust the sample through the air exhaust pipes 92, and the change of the air pressure in the main body of the detection device is detected by the barometer 14.

[0097] The air permeable layer 10 is made of air permeable and water impermeable material, which can prevent water from being extracted from the sample when the sample is vacuumed through the air exhaust pipes 92 and the air exhaust ports 91, and protects the equipment from water. The air exhaust ports 91 pass through the plastic top plate 9, but do not pass through the air permeable layer 10, only allowing air to enter the air exhaust pipes 92 to be extracted, ensuring that the solution is not extracted by the vacuum air extractor.

[0098] The size of the upper permeable stone 12 can be changed according to the size of the sample, and the size of the upper permeable stone 12 should be selected according to the size of the filling layer 13 and the size of the sample, and the upper permeable stone 12 should not be damaged under a certain upper load and can resist a certain pressure.

[0099] The filling layer 13 is used to fill the space in the main device 1, and is used to control the height and diameter of the sample. The filling layer 13 can be filled according to the size of the sample selected. The material of the filling layer 13 is selected to have a certain strength to resist the deformation and expansion of the sample under the action of the solution during the test. The filling layer 13 can be slightly deformed under the pressure of the pressure rod 7, but the extrusion effect caused by the lateral expansion of the sample during the saturation process or other external forces will not affect the filling layer 13, and the filling layer 13 has a certain pressure resistance.

[0100] If the test solution is a salt ion solution or a real leachate, the material of the filling layer 13 also needs to have acid resistance, alkali resistance and chemical corrosion resistance. At the same time, the material of the filling layer 13 is a breathable material (can transmit hot air, cold air, moisture), has heat resistance (dry condition), heat dissipation and moisture dissipation performance (fast heat dissipation after drying, easy to dry after humidification), is not easy to deform and damage, can be vertically compressed, and cannot pass through granular material.

[0101] The structure of the main device 1 includes a water storage tank 15 and a sample cylinder 16. The water storage tank 15 is formed by the space region surrounded by the first partition plate 151 and the second partition plate 152, and is used to store the solution. The sample cylinder 16 is formed by the space region surrounded by the third partition plate 161 and the fourth partition plate 162. Four iron pads 163 are arranged at the bottom of the sample cylinder 16 for supporting.

[0102] The outer part of the iron pad 163 should be attached with a protective layer to prevent rust and damage in the environment or different electrolyte solutions, which affects the stability of the device. The iron pad 163 is placed at the bottom of the entire device for supporting the device.

[0103] A plastic plate is arranged at the upper part of the water storage tank 15 to close the water storage tank 15, so as to prevent evaporation of the solution and entry of pollutants. A highest water level line 153 is arranged at the upper part of the water storage tank 15 to ensure that the solution in the water storage tank 15 does not overflow the device. The space formed by the first partition plate 151 is square, and the space formed by the second partition plate 152 is cylindrical. The second partition plate 152 is arranged at the outer periphery of the sample cylinder 16. The materials of the first partition plate 151 and the second partition plate 152 have acid resistance, alkali resistance and chemical corrosion resistance.

[0104] Four water inlets are arranged on the side wall of the second partition plate 152, which are divided into a first water inlet 1521, a second water inlet 1522, a third water inlet 1523 and a fourth water inlet 1524. A pull ring 1525 is arranged to control the opening and closing of the water inlets, so as to control the solution in the water storage tank 15 to enter or exit the sample cylinder 16.

[0105] The second partition plate 152 and the third partition plate 161 outside the sample cylinder 16 have a gap, and the second partition plate 152 and the third partition plate 161 form a sealed space, which serves as a vertical drainage layer 17, and a bottom drainage layer 18 is arranged at the bottom of the sample cylinder 16, the upper part of the vertical drainage layer 17 is sealed, and whether the vertical drainage layer 17 and the bottom drainage layer 18 are filled with solution is controlled according to the needs of the test. Heating resistance wires 171 and cooling resistance wires 172 are arranged in the vertical drainage layer 17 and the bottom drainage layer 18, and the resistance wires are arranged at the side and bottom of the sample cylinder 16, and the resistance wires are controlled by the computer to heat or cool according to the needs of the test to complete the test. The resistance wires should have the properties of acid resistance, alkali resistance, chemical corrosion resistance, high temperature resistance and low temperature resistance.

[0106] A thermometer 173 is installed at the upper part of the vertical drainage layer 17, and the probe of the thermometer 173 is inserted into the vertical drainage layer 17 for testing the internal temperature, which will be described in detail below. Figure 9 .

[0107] The third partition plate 161 has heat resistance and frost resistance, and has the properties of acid resistance, alkali resistance, and chemical corrosion resistance. The third partition plate 161 is arranged to be movable upward and fixed, and the main body thereof is annular (upward or downward). The third partition plate 161 is not fixed, and can be raised or lowered according to the needs of the test, and a fixing device is arranged on the plastic top plate 9 for fixing the third partition plate 161.

[0108] The fourth partition plate 162 serves as an inner partition plate of the sample cylinder 16, and the fourth partition plate 162 is fixed. The fourth partition plate 162 has air-permeable holes 1621, which can allow heat, cold air and solution to be transferred into the sample. An air-permeable and water-permeable layer 131 is arranged on the inner side of the fourth partition plate 162. In the absence of the filler layer 13, the air-permeable and water-permeable layer 131 plays a role of isolating the sample from the external environment, preventing the loss of components in the sample (material) during the test.

[0109] A lower water-permeable stone 19 is arranged at the bottom of the sample cylinder 16, and the lower water-permeable stone 19 is arranged between the bottom drainage layer 18 and the sample, which serves to isolate the sample from the bottom drainage layer 18 and has the functions of air permeability and water permeability. The size of the lower water-permeable stone 19 can be made according to the maximum size of the sample, and the size and height of the sample are controlled by the filler layer 13, and the size of the lower water-permeable stone 19 is fixed.

[0110] The thickness of the bottom drainage layer 18 is set to be 1-2 cm, and a slope is arranged in the bottom drainage layer 18 for more convenient drainage of the solution. The material of the drainage layer can transfer and disperse heat and cold air, and has good heat conduction and refrigeration effect. The material of the drainage layer should be resistant to acid, alkali, chemical corrosion, and able to resist a large pressure without being easily deformed.

[0111] The first drainage port 181 is arranged on the bottom drainage layer 18, and the first drainage port 181 is matched with the slope. The solution is converged at the first drainage port 181 through the slope, and the solution penetrating the sample is drained through the first drainage port 181. Meanwhile, the solution can be collected through the first drainage port 181, and the collected solution is used to measure the corresponding flow and the conductivity of the solution.

[0112] Four drainage ports are arranged on the outermost layer of the bottom drainage layer 18, which are used to drain the solution in the vertical drainage layer 17. The four drainage ports are the second drainage port 182, the third drainage port 183, the fourth drainage port 184, and the fifth drainage port 185. The thickness of the plastic plate on the outermost layer of the bottom drainage layer 18 is 2-3 mm. The plastic plate on the outermost layer of the bottom drainage layer 18 has the properties of acid resistance, alkali resistance, and chemical corrosion resistance. The second drainage port 182, the third drainage port 183, the fourth drainage port 184, and the fifth drainage port 185 can be connected to pipelines outside the device to extend to the corresponding collection pool outside the device, which is used to measure the seepage flow and the conductivity of the solution.

[0113] A baffle plate is arranged on the vertical drainage layer 17, and a dial gauge 11 is installed on the baffle plate. The dial gauge 11 is used to test the swelling deformation of the sample. The dial gauge 11 is installed on the baffle plate through a support 111, and the dial gauge 11 can be rotated in the plane through the support 111, which is used to observe the swelling deformation of the sample.

[0114] Eight ventilation openings 101 are arranged around the entire main device 1. The eight ventilation openings 101 are designed in two layers, with four ventilation openings 101 in each layer, which are respectively marked as T1-T8. Details are shown in Figures 6-7 The eight ventilation openings 101 can accelerate the drying of moisture in the main device 1, achieving the purpose of drying and dehumidifying.

[0115] The ventilation openings 101 are connected to ventilation pipelines 102. The eight ventilation pipelines 102 are connected to a blower outside the device. The speed and strength of the air in the blower are controlled by a computer. Meanwhile, air holes 1621 are arranged on the fourth baffle plate 162, which cooperate with the ventilation pipelines 102 and the ventilation openings 101 to dry or cool the sample. Details are shown in Figure 12 .

[0116] The heating resistance wire 171 and the refrigeration resistance wire 172 are connected to the computer. The temperature is controlled by the computer to heat or refrigerate, and the blower is used to dry or cool the sample through the ventilation pipelines 102 and the ventilation openings 101. The temperature range of the heating resistance wire 171 is 0-300℃, and the temperature range of the refrigeration resistance wire 172 is -200-0℃. The heating resistance wire 171 or the refrigeration resistance wire 172 is used to heat or refrigerate, cooperating with the ventilation openings 101 and the air holes of the fourth baffle plate 162 to dry or freeze the inside of the sample.

[0117] There are 12 humidifiers 103 outside the whole main device 1, which are arranged on the outer surface of the second partition plate 152, and there are two rows of 6 humidifiers 103 from top to bottom, respectively marked as Z1-Z12, see Figures 6-7 The humidification gas is connected with a humidification pipeline 104, which is connected to the humidifier outside the device. The motor part of the humidifier is controlled by the computer to perform humidification operation. The humidity and speed of the gas blown out of the humidifier are controlled by the computer, and the size and strength of the wind are also controlled.

[0118] The humidifier 103 is connected with a spray head 105, and an expansion plate 106 is arranged at the spray head 105. The spray head 105 and the expansion plate 106 are installed in the vertical guide layer 17. According to the arrangement of the humidifier 103, 35 spray heads 105 are installed to better diffuse the steam into the sample. The spray head 105 and the expansion plate 106 have fire resistance, heat resistance, acid resistance, alkali resistance, and chemical corrosion resistance. The humidifier 103 has waterproof function and corrosion resistance. The steam enters the sample through the fourth partition plate 162 by the spray head 105 and the expansion plate 106.

[0119] A protective layer is arranged outside the resistance wire, humidifier 103, ventilation pipeline 102, humidification pipeline 104 and expansion plate 106. A layer of protective material is applied to the devices and the outside that contact the solution to prevent corrosion by chemical solution.

[0120] The barometer 14 is installed on the fourth partition plate 162, and the air and water permeable layer 131 is used to directly monitor the air pressure in the sample to determine whether the sample is in a vacuum state, see Figure 9 .

[0121] The permeability tester has the following test functions:

[0122] The first test is the conventional permeability test operation step (this test step is performed according to the requirements in GBT50123-2019 "Standard for Soil Test Methods"):

[0123] Step 1, the sample (material) is compacted by the static pressure loading device to control the compaction degree, and is compacted in the main device 1. Before static pressure loading, the lower water permeable stone 19 is installed at the bottom of the sample (material). After static pressure loading and standing for 2-3h, the sample (material) is kept from deforming, and the main device 1 is moved to the lower side of the pressure rod 7 and the pressure measuring tube 8 through the sliding groove 6;

[0124] Step 2, after placing the filter paper and the upper water stone 12 on the sample, align the position of the plastic top plate 9 with the top of the sample, and then move the plastic top plate 9 downward by the computer-controlled pressure rod 7 to seal the main device 1, and continue to move downward until the plastic top plate 9 contacts the top of the sample, and then stop moving downward and fix the position of the pressure rod 7, so that the plastic top plate 9 remains in this position during the entire test;

[0125] Step 3, after ensuring that the plastic top plate 9 is completely fixed on the surface of the sample, check the air tightness of the main device 1, and then close all the water outlets, including the first water outlet 181, the second water outlet 182, the third water outlet 183, the fourth water outlet 184, and the fifth water outlet 185; close all the water inlets, including the first water inlet 1521, the second water inlet 1522, the third water inlet 1523, and the fourth water inlet 1524; the third partition plate 161 does not move upward and remains unchanged; the first valve 71 and the second valve 72 are closed, all the humidifiers 103 are closed, the air outlet 91 is closed, the air suction pipe 92, the ventilation pipe 102, and the humidification pipe 104 are connected to the vacuum air pump, the air blower, and the humidifier respectively; and the power switch of the equipment is turned off before the test;

[0126] Step 4, fill the test solution in the water reservoir 15 according to the highest water level line 153 of the water reservoir 15, and the maximum capacity of the test solution does not exceed the height of the main device 1;

[0127] Step 5, after ensuring that the air tightness of the main device 1 is good, open the vacuum air pump by computer control, start to suck air in the main device 1 through the communication between the air outlet 91 at the plastic top plate 9 and the air suction pipe 92, and observe the change of the air pressure inside the sample through the barometer 14, and the air suction is about 4-5h;

[0128] Step 6, after the main device 1 is completely vacuumized, close the vacuum air pump, lift the third partition plate 161 upward and fix it by the fixing device on the plastic top plate 9 so that it remains in position, then pull the ring 1525 and open all the water inlets, so that the solution in the water reservoir 15 enters the sample through the air permeable hole 1621 of the fourth partition plate 162 to saturate the sample;

[0129] Step 7, according to the reading change of the barometer 14, open the vacuum air pump again to saturate appropriately, and after the reading of the barometer 14 is stable and unchanged, move the third partition plate 161 downward, close all the water inlets, so that the sample is in a closed state, and saturate the sample for 24h to complete the saturation of the sample;

[0130] Step 8, open the first valve 71 and the second valve 72 at the same time, and carry out the corresponding permeation test, and read the drop value of the water head height of the solution in the measuring pipe 8 in the corresponding time period to calculate the permeation coefficient;

[0131] Step 9, after the test is completed, open the second drain 182, the third drain 183, the fourth drain 184 and the fifth drain 185 to drain the solution in the vertical drainage layer 17.

[0132] In the conventional permeation test operation, if the saturation operation is not performed and the test of the permeation coefficient is directly performed, step 6 can be omitted, and if the operation of step 6 is not performed, the solution in the vertical drainage layer 17 needs to be kept empty at all times during the entire test process, that is, all water inlets are kept closed. If it is necessary to perform a saturation operation on the test sample in advance, the vertical drainage layer 17 needs to be filled with solution at all times.

[0133] The second test, the permeation test operation steps under dry-wet cycle:

[0134] The compaction, installation, fixation of the test sample and steps 1-3 in the conventional permeation test operation steps are the same;

[0135] The basic process of drying:

[0136] Step 11, move the third partition plate 161 upward to ensure that the vertical drainage layer 17 is fully dried and no liquid penetrates, then open all the ventilation openings 101, which are connected to the ventilation ducts 102 connected to the external air blower, and open the air blower through the computer, and control the size and speed of the air blower through the computer. The type of wind includes hot wind and cold wind.

[0137] Step 12, dry or freeze and humidify (thaw) the test sample through the air holes 1621 of the vertical drainage layer 17 and the fourth partition plate 162, and control the temperature and efficiency of the heating resistance wire 171 or the refrigeration resistance wire 172 through the computer.

[0138] The basic process of saturation:

[0139] Step 21, after the drying is completed, close all the ventilation openings 101, continue to keep the position of the third partition plate 161 unchanged, open all the water inlets, and let the solution in the water storage tank 15 enter the test sample through the vertical drainage layer 17 and then through the air holes 1621 of the fourth partition plate 162, so that the test sample is fully saturated;

[0140] Step 22, open all the water inlets, then move the third partition plate 161 downward to isolate the test sample and the vertical drainage layer 17 to prevent the solution from entering the fully saturated test sample;

[0141] Step 23, open the vacuum valve at the same time, through the air exhaust pipe 92 and the air exhaust port 91 to the sample for proper air saturation, to observe the change of the reading of the air pressure gauge 14 to determine whether the pores in the sample are completely discharged, so that the pore gas generated in the saturation process of the sample is completely discharged, that is, the saturation air extraction process of the sample is completed;

[0142] Step 24, open the first drainage port 181, and open the first valve 71 and the second valve 72, inject the same solution as in the reservoir 15 into the pressure tube 8 at the upper part of the pressure rod 7, and conduct a permeability test on the sample, and record the corresponding data for calculation;

[0143] Step 25, open all the drainage ports to discharge the liquid in the vertical drainage layer 17 for the next test operation;

[0144] The steps 1-3 in the conventional permeability test operation steps, the steps 11-12 in the drying basic process and the steps 21-25 in the saturation basic process are the operation process of the permeability test of the sample under one dry-wet cycle. If the dry-wet cycle amplitude of the sample is to be controlled, the moisture content change of the sample can be determined, but this needs to be further determined by pre-test (ring knife sample) before the test.

[0145] The above test process is in the order of dry first and wet later, and in actual test, the order can be adjusted according to the needs, and dry first and wet later or wet first and dry later can be realized (only the permeability test is conducted in the unsaturated state or in the saturated state); the time and temperature of the dry-wet cycle are set according to the actual test needs.

[0146] The third test, multiple dry-wet cycle test steps:

[0147] On the basis of the permeability test operation steps under dry-wet cycle, the permeability test steps under single dry-wet cycle, including steps 11-12, steps 21-23, are cycled, and step 24 in the saturation basic process is operated at the end.

[0148] During the entire dry-wet cycle process, all the drainage ports are always closed, and the solution in the reservoir 15 is replenished after each cycle and kept full of enough solution in the reservoir 15, but the solution shall not exceed the highest water level line.

[0149] But after each saturation process, i.e. after step 23, the second drain 182, the third drain 183, the fourth drain 184 and the fifth drain 185 need to be opened to drain the solution in the vertical drainage layer 17, and then all the drains are closed. Then all the vents 101 are opened to dry the vertical drainage layer 17 completely, and then the next drying and saturation process is carried out. After the last drying and saturation process, the step 24 is carried out to carry out the permeability test on the sample under different drying and wetting cycles.

[0150] The fourth test, the permeability test under freeze-thaw cycles, is operated as follows:

[0151] The compaction, installation, fixation of the sample and steps 1-3 in the conventional permeability test operation steps are the same.

[0152] The basic process of freezing:

[0153] This process is the same as steps 11-12 in the basic process of drying, except that the main process of freezing is achieved by the refrigeration resistance wire 172.

[0154] The refrigeration effect is achieved by the refrigeration resistance wire 172 in cooperation with all the vents 101, the third partition plate 161 is lifted up and fixed, ensuring that the vertical drainage layer 17 is fully dried and no solution exists, the air blower is turned on and cold air is sent into the sample through the vent pipe 102.

[0155] The computer controls the size of the air flow and air speed of the air blower through the terminal program, and ensures that the blowing is cold air. The cold air is blown into the vertical drainage layer 17 through the vent pipe and into the sample through the fourth partition plate 162, achieving the refrigeration effect.

[0156] The temperature during the freezing process of the sample is controlled by the computer, and the temperature in the main device 1 is monitored in real time by the thermometer 173.

[0157] The basic process of thawing (thawing method 1 or thawing method 2 can be selected):

[0158] Thawing method 1, solution saturation:

[0159] Step A, keep the third partition plate 161 in the lifted position, open all the water inlets, let the solution enter the sample through the vertical drainage layer 17 and the air holes 1621 of the fourth partition plate 162, so that the sample is fully saturated and fully thawed. The time required for this step is relatively longer.

[0160] Step B, after thawing is completed, open the second drain 182, the third drain 183, the fourth drain 184 and the fifth drain 185 to drain the solution in the vertical drainage layer 17.

[0161] Melting method 2, constant temperature and humidity maintenance:

[0162] Step a, after ensuring that the solution in the vertical drainage layer 17 is completely drained, the sample is melted according to the constant temperature and humidity maintenance conditions (20 degrees Celsius), and the third partition plate 161 is fixed in the upper moving position;

[0163] Step b, by controlling the heating resistance wire 171 and the refrigeration resistance wire 172 in the vertical drainage layer 17, the temperature in the vertical drainage layer 17 is kept constant under normal temperature conditions, the computer controls the humidifier to input gas (with a certain humidity), then the humidification pipeline 104 and the humidifier 103 are opened, and the inside of the sample is humidified and treated in cooperation with the resistance wire;

[0164] Step c, after the sample is fully thawed, all the humidification pipelines 104 and the humidifier 103 are closed, the third partition plate 161 is moved downward to isolate the vertical drainage layer 17 from the sample, and after the sample is fully saturated, the external solution is prevented from entering the sample;

[0165] Step d, the second drainage outlet 182, the third drainage outlet 183, the fourth drainage outlet 184 and the fifth drainage outlet 185 are opened to drain the solution in the vertical drainage layer 17, so as to facilitate the next test;

[0166] Step e, finally, after adding the corresponding solution (the solution is determined according to the test requirements) in the pressure measuring tube 8 in the pressure, the first valve 71, the second valve 72 and the first drainage outlet 181 are opened for the permeation test.

[0167] The above-mentioned permeation test operation steps under the freeze-thaw cycle are the operation process of the permeation test of the sample (material) under one freeze-thaw cycle, and the time and temperature of the freeze-thaw cycle are set according to the actual test requirements.

[0168] The fifth test, multiple freeze-thaw cycle test operation steps:

[0169] Based on the steps other than step e in the permeation test operation steps under the freeze-thaw cycle, the step e is operated at the end.

[0170] During the whole dry-wet cycle process, all the drainage outlets are always closed. After each cycle, the solution in the water storage tank 15 is supplemented and it is ensured that the water storage tank 15 is full of enough solution, but not more than the highest water level position.

[0171] But after each saturation process, the second, third, fourth and fifth drainage ports 182, 183, 184 and 185 need to be opened to drain the solution in the vertical drainage layer 17, and then all the drainage ports are closed. Then all the vents 101 are opened to let the vertical drainage layer 17 dry completely, and then the next drying and saturation process is performed. After the last drying and saturation process is completed, the step e is performed to conduct the permeation test on the sample under different dry freeze-thaw cycle numbers.

[0172] The above merely describes the preferred embodiments of the present application, but the design concept of the present application is not limited to this. Any person skilled in the art can make non-substantial changes to the present application within the technical scope disclosed by the present application, and such changes shall not be regarded as departing from the scope of the present application.

Claims

1. A soil permeability testing instrument under wet-dry or freeze-thaw cycle effects, characterized in that: It includes a static pressure loading device and a core testing component, both of which are connected and fixed by brackets. The static pressure loading device consists of a hydraulic device, a hydraulic rod, a main body, a bottom platform, and a slide groove; the hydraulic rod drives the hydraulic device to move up and down; the hydraulic rod is fixed to the top of the support. The core testing component includes a pressure rod, a pressure measuring tube, a plastic top plate, and a dial indicator. The pressure measuring tube is installed inside the pressure rod, which is mounted on top of the support frame and is adjustable in height. The plastic top plate is installed at the bottom of the pressure rod. The bottom platform and slide rail extend from the static pressure loading device to the core testing part. The main body device is installed on the slide rail and has sliding motion along the slide rail. The main body device can be slidably placed below the hydraulic device or below the plastic top plate along the slide rail. The main device includes a water storage tank and a sample tube. The water storage tank is composed of a first partition and a second partition, and the sample tube is composed of a third partition and a fourth partition. The second partition and the third partition form a vertical guide layer, and a water inlet is provided on the second partition. The third partition is liftable, and the fourth partition is provided with vent holes. A bottom guide layer is provided at the bottom of the sample tube, and heating resistance wire and cooling resistance wire are built into the vertical guide layer and the bottom guide layer; both the bottom guide layer and the vertical guide layer are provided with drainage outlets. A vent and a humidifier are provided on the outside of the second partition. A first valve and a second valve are provided at the bottom of the pressure rod. An air extraction port is provided on the plastic top plate for vacuuming. A barometer is installed on the fourth partition for detecting changes in the air pressure inside the main body of the device.

2. The soil permeability testing instrument under wet-dry or freeze-thaw cycle effects according to claim 1, characterized in that: The water storage tank is equipped with a maximum water level line; a pull ring is provided at the water inlet to control the opening and closing of the water inlet; a breathable layer is provided at the bottom of the plastic top plate; the pressure measuring tube is equipped with scale lines, and the pressure rod is a transparent rod.

3. The soil permeability testing instrument under wet-dry or freeze-thaw cycle effects according to claim 1, characterized in that: A dial indicator is installed above the vertical guide layer, and the dial indicator is rotatable in the plane; a thermometer is installed above the vertical guide layer.

4. The soil permeability testing instrument under wet-dry or freeze-thaw cycle effects according to claim 1, characterized in that: The main device includes a filling layer and a permeable stone is provided at the bottom of the sample tube; The humidifier is connected to a nozzle, and an extension plate is provided at the nozzle. The nozzle and the extension plate are installed in the vertical guide layer.

5. A method for testing the permeability of soil under wet-dry or freeze-thaw cycles, characterized in that: The permeability testing instrument according to any one of claims 1-4 is used; the testing method includes the following steps: Step 1: Compact the sample by using a static pressure loading device to control the compaction degree and compact it into the sample cylinder of the main device; after static pressure loading and standing for 2-3 hours, keep the sample from deforming, and move the main device to below the pressure rod and pressure measuring tube through the slide groove. Step 2: After placing filter paper and permeable stones of the appropriate size on top of the sample, align the position of the plastic top plate with the main device, i.e. the top of the sample. Use the computer to control the pressure rod to move the plastic top plate downward to seal the main device. Continue to move downward until the plastic top plate contacts the top of the sample and then stop moving downward. Fix the position of the pressure rod so that the plastic top plate remains in the same position throughout the test. Step 3: After ensuring the plastic top plate is completely fixed to the sample surface, check the airtightness of the main device. After ensuring that the main device is airtight, close the drain outlet and the water inlet. The third partition should not move upward and should remain unchanged. Close the first valve and the second valve, close the humidifier, close the air extraction port, and ensure that the power switch of the equipment is turned off before the test. Step 4: Fill the water tank with the test solution. The maximum capacity of the test solution shall not exceed the height of the main device. Step 5: After ensuring the airtightness of the main device, turn on the vacuum pump through the computer control and pump air into the main device through the air extraction port at the plastic top plate. Observe the air pressure change inside the sample through the barometer. Pump air for 4 to 5 hours. Step 6: After the main device is completely vacuumed, turn off the vacuum pump, lift the third partition upward and fix it in place, open the water inlet, and let the solution in the water tank enter the sample through the air vent of the fourth partition to saturate it. Step 7: Based on the change in the barometer reading, turn on the vacuum pump again to perform appropriate saturation. After the barometer reading stabilizes, move the third partition downwards and close all water inlets to keep the sample in a closed state. After the sample is back-saturated for 24 hours, the saturation of the sample is complete. Step 8: Simultaneously open the first valve and the second valve, conduct the corresponding permeation test, and read the drop in the water head height of the solution in the pressure measuring tube within the corresponding time period to calculate the permeability coefficient; Step 9: After the experiment, open the drain outlet of the vertical guide layer to drain the solution in the vertical guide layer.

6. The method for testing the permeability of soil under wet-dry or freeze-thaw cycles according to claim 5, characterized in that: In the test method, if a saturation operation is required, step 6 is retained; otherwise, step 6 is omitted. If step 6 is omitted, then throughout the entire test process, no solution needs to be introduced into the vertical guide layer.

7. A method for testing the permeability of soil under wet-dry cycle effects, characterized in that: The permeability tester according to any one of claims 1-4 is used; the test method includes a drying process and a saturation process, and the following steps are performed before the drying process and the saturation process: Step 1: Compact the sample by using a static pressure loading device to control the compaction degree and compact it into the sample cylinder of the main device; after static pressure loading and standing for 2-3 hours, keep the sample from deforming, and move the main device to below the pressure rod and pressure measuring tube through the slide groove. Step 2: After placing filter paper and permeable stones of the appropriate size on top of the sample, align the position of the plastic top plate with the main device, i.e. the top of the sample. Use the computer to control the pressure rod to move the plastic top plate downward to seal the main device. Continue to move downward until the plastic top plate contacts the top of the sample and then stop moving downward. Fix the position of the pressure rod so that the plastic top plate remains in the same position throughout the test. Step 3: After ensuring the plastic top plate is completely fixed to the sample surface, check the airtightness of the main device. After ensuring that the main device is airtight, close the drain outlet and the water inlet. The third partition should not move upward and should remain unchanged. Close the first valve and the second valve, close the humidifier, close the air extraction port, and ensure that the power switch of the equipment is turned off before the test. The drying process includes the following steps: Step 11: Move the third partition upward to ensure that the vertical guide layer is fully dry and no liquid seeps in. Then open the vent and connect the blower. Turn on the blower through the computer and control the blower's wind force, wind speed, and wind type through the computer. The wind type includes hot air and cold air. Step 12: Dry the sample through the ventilation holes of the vertical guide layer and the fourth partition, and control the temperature and efficiency of the heating or cooling resistance wire by computer. The saturation process includes the following steps: Step 21: After drying, close the vent, keep the position of the third partition unchanged, open the water inlet, and let the solution in the water tank pass through the vertical guide layer and then through the air vent on the fourth partition into the sample, so that the sample is fully saturated. Step 22: Open the water inlet, and then move the third baffle downward to isolate the sample from the vertical guide layer and prevent the solution from entering the fully saturated sample. Step 23: Turn on the vacuum pump and saturate the sample with appropriate air through the pumping port. Observe the change in the barometer reading to determine whether the pores in the sample have been completely emptied. This completes the saturation pumping process of the sample. Step 24: Open the drain outlet of the bottom guide layer, and open the first valve and the second valve. Inject the same solution as in the water storage tank into the upper part of the pressure measuring tube in the pressure rod to conduct a permeation test on the sample and record the corresponding data for calculation. Step 25: Open all drain outlets to drain the liquid; The procedure for multiple wet-dry cycle tests is as follows: based on steps 11-12 and 21-23, perform the cycle, and then perform the final operation in step 24 after the cycle is completed.

8. A method for testing the permeability of soil under freeze-thaw cycles, characterized in that: The permeability tester according to any one of claims 1-4 is used; the test method includes a freezing process and a thawing process, and the following steps are performed before the freezing and thawing processes: Step 1: Compact the sample by using a static pressure loading device to control the compaction degree and compact it into the sample cylinder of the main device; after static pressure loading and standing for 2-3 hours, keep the sample from deforming, and move the main device to below the pressure rod and pressure measuring tube through the slide groove. Step 2: After placing filter paper and permeable stones of the appropriate size on top of the sample, align the position of the plastic top plate with the main device, i.e. the top of the sample. Use the computer to control the pressure rod to move the plastic top plate downward to seal the main device. Continue to move downward until the plastic top plate contacts the top of the sample and then stop moving downward. Fix the position of the pressure rod so that the plastic top plate remains in the same position throughout the test. Step 3: After ensuring the plastic top plate is completely fixed to the sample surface, check the airtightness of the main device. After ensuring that the main device is airtight, close the drain outlet and the water inlet. The third partition should not move upward and should remain unchanged. Close the first valve and the second valve, close the humidifier, close the air extraction port, and ensure that the power switch of the equipment is turned off before the test. The freezing process includes the following steps: Step 111: Move the third partition upward to ensure that the vertical guide layer is fully dry and no liquid seeps in. Then open the vent and connect the blower. Turn on the blower through the computer and control the blower's wind force, wind speed, and wind type. The wind type is cold air. Step 112: Freeze the sample through the ventilation holes of the vertical guide layer and the fourth partition, and control the temperature and efficiency of the cooling resistance wire by computer. The melting process can be carried out by saturating the solution or by curing under constant temperature and humidity. The procedure for multiple wet-dry cycle tests is as follows: the freezing process and the thawing process are cycled, and the last step of the thawing process is performed after the cycle is completed.

9. The method for testing the permeability of soil under freeze-thaw cycle effects according to claim 8, characterized in that: Melting using a saturated solution involves the following steps: Step A: Keep the third partition in the upward position, open the water inlet, and let the solution enter the sample through the vertical guide layer and the air vent of the fourth partition, so that the sample is fully saturated and fully melted. Step B: After melting is complete, open the drain outlet of the vertical guide layer to drain the solution from the vertical guide layer.

10. The method for testing the permeability of soil under freeze-thaw cycle effect according to claim 8, characterized in that: Melting using constant temperature and humidity curing includes the following steps: Step a: After ensuring that the solution in the vertical guide layer is completely drained, melt the sample according to the curing conditions of constant temperature and humidity at 20 degrees Celsius, and ensure that the third partition is fixed in the upward position. Step b: The temperature in the vertical guide layer is kept constant at room temperature by controlling the heating and cooling resistance wires in the vertical guide layer. The humidifier with a certain humidity is input by computer control. Then the humidifier is turned on and the resistance wires are used to humidify the inside of the sample. Step c: After the sample has fully thawed, turn off the humidifier and move the third partition downward to isolate the vertical guide layer from the sample. After the sample is fully saturated, prevent external solutions from entering the sample. Step d: Open the drain outlet of the vertical guide plate to drain the solution in the vertical guide plate; Step e: Finally, after adding the appropriate solution to the pressure testing tube (the solution is determined according to the test requirements), open the first valve, the second valve, and the drain outlet of the bottom guide layer to conduct a permeation test.

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