Testing device and testing method for water-force characteristics of soil body under climate simulation condition

Abstract

The invention relates to a device and a method for testing water-force characteristics of a soil body under a climate simulation condition. The device comprises an environmental test box, and a test chamber for accommodating a test sample is arranged in the environmental test box; the humidity-controllable spraying system comprises a saturated salt solution container, a peristaltic pump and a spraying device; a water outlet of the water pressure controller is connected with the spraying pipeline through a water supply pipeline, and a stop valve is arranged on the water supply pipeline; the heating system comprises a heating lamp arranged at the top of the environment test box; the refrigerating system comprises a compressor, a refrigerant bottle and an air conditioner air outlet; a temperature and humidity sensor, a temperature probe, an electronic balance, a tensiometer and a high-definition camera are further arranged in the environmental test box, a data acquisition system is arranged outside the environmental test box, and the tensiometer is inserted into a test sample; according to the test method, the device is adopted to simulate dry-wet circulation and freezing-thawing circulation respectively, and the test requirements of civil engineering and environmental geotechnical engineering discipline fields on soil body water-mechanical parameters are met.

Description

Technical Field

[0001] The invention belongs to the field of soil water-mechanical characteristic testing in environmental geotechnical engineering, and specifically relates to a test device and a test method for soil water-mechanical characteristics under climate simulation conditions. Background Art

[0002] Landfill accounts for a large proportion of the final disposal of garbage. The closure design of landfills mostly uses clay layer compaction, but as the service life of urban landfills increases, the compacted clay cover layer is easily affected by changes in environmental conditions (such as dry-wet, freeze-thaw cycles), resulting in shrinkage and deformation, which weakens its anti-seepage and sealing functions. It may even cause landfill leachate and landfill gas to pollute groundwater and the safety of the surrounding environment. Landfills have become a new risk point for ecological and environmental governance. Problems such as landfill gas escape (methane) and leachate pollution may cause secondary pollution to the greenhouse effect of the atmosphere, surrounding groundwater and soil.

[0003] The hydraulic properties of unsaturated soil are usually expressed by the soil-water characteristic curve (SWCC). The soil-water characteristic curve can reflect many important engineering properties of soil, such as deformation, water retention and permeability. Landfill cover soil is susceptible to micro- and macro-structural changes due to environmental conditions. Therefore, it is very important to test the deformation and internal suction changes of soil.

[0004] Relevant studies have shown that optimizing the landfill cover's ability to adsorb and oxidize landfill gas is an economical and efficient technical means to control the release of greenhouse gases from landfills. At present, the anti-seepage effect of landfill cover soil on landfill gas and leachate is mostly studied using steady-state or semi-steady-state methods, that is, assuming that the physical and chemical properties, hydraulic properties and internal stress state of the soil are not affected by external environmental factors. The deformation morphology of macroscopic cracks during the change of internal suction in the soil is rarely considered. Combined with engineering practice, under the influence of natural environmental factors, such as seasonal freeze-thaw alternation in winter and summer, and changes in rainfall-sun drying and wetting, the internal suction of the soil will change, which will cause cracking and settlement deformation of the macroscopic soil. At the same time, the biodegradation of garbage inside the landfill will cause the settlement of the cover soil, causing the soil to deform under the action of internal and external factors. Changes in internal suction and external factors cause changes in the internal stress state of the soil, thereby causing changes in the physical and chemical properties of the overlying soil, such as density, relative density, pore morphology and pH value. These changes in physical and chemical properties will affect the deformation characteristics, water retention characteristics, and the efficiency of adsorption and oxidation of landfill gas in the overlying layer soil. In order to reasonably select the design parameters of the overlying layer soil, it is very necessary to develop a test device and test method that simulates the hydraulic-mechanical characteristics of soil under climate change conditions to study the deformation and water retention characteristics of the overlying layer soil under different initial conditions such as suction, dry density, and moisture content, so as to obtain more complete hydraulic and mechanical parameters of the overlying layer soil. Summary of the invention

[0005] The purpose of the present invention is to provide a test device and test method for the water-mechanical properties of soil under climate simulation conditions. The test device can be used to determine the deformation parameters of the soil that controls suction. At the same time, the deformation and water retention characteristics of the soil under dry-wet and freeze-thaw environmental changes can be simulated by means of a heating device, salt solution humidification technology, and a refrigeration system, so as to meet the test requirements for the water-mechanical parameters of the soil in the fields of civil engineering and environmental geotechnical engineering. Combined with the requirements for the engineering properties of the final cover layer of the landfill, the airtightness index of the soil can be evaluated, and the test technology and design parameter support can be provided for the design of the final cover layer.

[0006] In order to achieve the above-mentioned object, the technical solution adopted by the present invention is: a test device for the hydraulic-mechanical characteristics of soil under climate simulation conditions, comprising an environmental test box, which is used to simulate the climate environment required for the test inside the box, and a test chamber is provided in the environmental test box, and the test chamber is used to accommodate the test sample; A controllable humidity spray system comprises a saturated salt solution container, a peristaltic pump and a spray device, wherein the nozzle of the spray device is located in an environmental test chamber, the inlet of the spray pipe of the spray device is located above the liquid level in the saturated salt solution container, a stop valve is provided on the spray pipe, and the pipe openings connected to the inlet and outlet of the peristaltic pump are both located below the liquid level of the saturated salt solution container; A water pressure controller, the water outlet of which is connected to the spray pipe through a water supply pipe, and a stop valve is provided on the water supply pipe; A heating system, including a heating lamp disposed on the top of the environmental test chamber; The refrigeration system includes a compressor, a refrigerant bottle and an air-conditioning outlet. The air-conditioning outlet is located inside the environmental test chamber, and the compressor and the refrigerant bottle are located outside the environmental test chamber; A temperature and humidity sensor, a temperature probe, an electronic balance, a tensiometer and a high-definition camera are also provided in the environmental test chamber, and a data acquisition system is provided outside the environmental test chamber. The temperature and humidity sensor, the temperature probe, the electronic balance, the tensiometer and the high-definition camera are connected to the data acquisition system, and the tensiometer is inserted into the test sample through the side wall of the test chamber.

[0007] The test chamber is made of transparent material, and includes a first type of test chamber, a second type of test chamber and a third type of test chamber. The first type of test chamber is a cylindrical chamber with a bottom flange plate and an open top, and the bottom flange plate is provided with a plurality of through holes connected to the interior of the chamber; the second type of test chamber is a cylindrical chamber with a top flange plate and a bottom flange plate, and the top flange plate and the bottom flange plate are both provided with a plurality of through holes connected to the interior of the chamber; the third type of test chamber is a cylindrical chamber with a top flange plate and a bottom flange plate, and only the top flange plate is provided with a through hole connected to the interior of the chamber.

[0008] When a single soil body needs to be tested, the first type of test chamber or the third type of test chamber is used alone to accommodate the test sample; when different soil bodies need to be tested, the first type of test chamber, the second type of test chamber and the third type of test chamber are stacked up and used in combination, and each test chamber is respectively placed with the corresponding test sample, and after the combination, the through holes on the top flange plate and the bottom flange plate are aligned.

[0009] The top flange plate and the bottom flange plate are provided with grooves for installing O-rings, and when the two test chambers are combined, the top flange plate and the bottom flange plate are fastened and connected by bolts to compress the O-rings.

[0010] The position where the water supply pipe is connected to the spray pipe is located at the outlet side of the stop valve on the spray pipe.

[0011] The lens cover of the high-definition camera is provided with a transparent protective cover.

[0012] The rear end of the high-definition camera extends out of the top of the environmental test box and is connected to a lifting mechanism.

[0013] The lifting mechanism is a horizontally arranged adjustable support rod, the two ends of the adjustable support rod are movably sleeved on the upper ends of the two vertical rods of the base, and the vertical rods are provided with adjusting nuts, which support the adjustable support rod.

[0014] The environmental test box comprises a detachably connected lower box body and a top box cover, wherein both the lower box body and the top box cover are sandwiched and have a heat-insulating medium cavity capable of accommodating a heat-insulating medium.

[0015] A test method for the hydraulic properties of soil, using the above-mentioned test device to simulate dry-wet cycle and freeze-thaw cycle, respectively, to test the deformation properties of soil samples; The dry-wet cycle includes a humidification process and a drying process. The humidification process uses a saturated salt solution container or a water pressure controller in conjunction with a spray device to humidify the soil sample in the test chamber; the drying process uses a heating lamp to heat and dry the soil sample; the humidification process and the drying process are repeatedly performed to simulate deformation characteristic tests with different dry-wet cycle times, and the initial values ​​and numerical values ​​of the high-definition camera, tensiometer, temperature and humidity sensor, temperature probe and electronic balance are recorded by a data acquisition system during the test. Finally, the acquired information is processed to form a quantitative analysis of the evolution process of soil cracks; The freeze-thaw cycle includes a freezing process, a melting process and a humidification process. The freezing process is performed by the refrigeration system, and the melting process is performed by the heating lamp. The freezing process, the melting process and the humidification process are repeatedly performed to simulate deformation characteristic tests with different freeze-thaw cycle times. During the test, the initial values ​​of the high-definition camera, the tensiometer, the temperature and humidity sensor, the temperature probe and the electronic balance and the values ​​during the test are recorded by the data acquisition system. Finally, the acquired information is processed to quantitatively analyze soil cracks.

[0016] The beneficial effect of the present invention is that the functions of the device can meet the tests of various civil and environmental geotechnical engineering disciplines. Function 1 can be used to simulate the environmental changes of alternating rainfall and sunshine, measure the deformation parameters and suction values ​​of the soil under different working conditions (such as: the number of dry-wet cycles, the water content, dry density, void ratio and soil type of the soil sample, etc.), and obtain the change law of the volume change and suction index with the test control factors; Function 2 can be used to simulate the environmental changes of winter freezing and summer thawing, measure the deformation parameters and suction values ​​of the soil under different working conditions (such as: the number of freeze-thaw cycles, the water content, dry density, void ratio and soil type of the soil sample, etc.), and obtain the volume change and suction index. The standard changes with the test control factors; Function three can indirectly control the different suction values ​​in the environmental box by changing the saturated salt solution, which can be used to measure the crack deformation index of soil samples with different suctions; Function four can control the internal humidity value of the environmental box by changing the type of salt in the saturated salt solution container, and calculate the moisture content index of the soil sample in real time by combining the reading of the electronic balance, which can indirectly measure the suction value of the soil sample under different working conditions (such as: moisture content, dry density, porosity and soil type, etc.) and draw the soil-water characteristic curve of the soil sample under different working conditions.

[0017] Compared with the prior art, the present invention has the following advantages: 1. The test device of the present invention is multifunctional and can simulate dry-wet and freeze-thaw cycle test conditions. It can also measure the suction value of soil samples and the deformation characteristics of the controlled suction conditions. The above test functions can almost meet the test requirements of the civil engineering and environmental geotechnical engineering disciplines for soil water-mechanical parameters. Combined with the requirements of the final cover of the landfill for the engineering properties of the soil, the airtightness index of the soil can be evaluated, providing test technology and design parameter support for the design of the final cover.

[0018] 2. Aiming at the experimental research on the deformation characteristics of the overburden soil in the field of geotechnical engineering and landfills, a set of experimental equipment is provided to explore the deformation characteristics of soil under different humidity conditions and to test the evolution process of cracks in the final overburden soil under a long-term mechanism.

[0019] 3. The test device of the present invention is connected by multiple test chambers, and can simultaneously measure the suction values ​​of different working conditions such as dry density, moisture content and soil type, and read the mass change of the soil sample in real time through a precise electronic balance, thereby converting the moisture content, saturation and porosity of the soil sample at each suction value. Integrating the soil sample tests of multiple working conditions can greatly shorten the test cycle and facilitate the comparison of test results under the same test conditions.

[0020] The test device of the present invention can be applied to the fields of civil and environmental geotechnical engineering, and can carry out hydraulic tests with multiple functions. Combined with the engineering characteristics of the final cover layer soil of the landfill, the test device can simulate environmental climate change, carry out hydraulic-mechanical characteristic tests under multiple working conditions, and study the evolution of soil deformation under a long-term mechanism. The experimental device is multifunctional, with high test integration, simple sample preparation methods and manufacturing processes, easy to obtain manufacturing materials, and easy operation. A multi-chamber combined specimen can be used to measure hydraulic parameters under multiple working conditions, fully ensuring the consistency of the test process and the rigor of the data, and can greatly shorten the test cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a structural schematic diagram of the test device of the present invention; Figure 2 This is a schematic diagram of the structure of the sample chamber of the present invention using a multi-chamber combination; Figure 3 This is a schematic diagram of the structure of the sample chamber of the present invention using a single chamber; Figure 4 A plan view of a sample chamber base in the test device of the present invention; Figure 5 AA sectional view of the base of the sample chamber in the test device of the present invention; Figure 6 It is a vertical view of the environmental test box in the test device of the present invention; Figure 7 It is a BB cross-sectional view of the environmental test box in the test device of the present invention; Markings in the figure: 1. Water pressure controller, 2. Water inlet, 3. Water outlet, 4. Stop valve, 5. Saturated salt solution container, 6. Peristaltic pump, 7. Base, 8. High-definition camera, 9. Cover bolts, 10. Heating lamp, 11. Transparent protective cover, 12. Environmental test chamber, 1201. Top cover, 1202. Lower box, 13. Spray device, 14. Insulation medium chamber, 15. Air conditioning outlet, 16. Sample chamber, 1601. First Type I test chamber, 1602, Type II test chamber, 1603, Type III test chamber, 1604, bottom flange plate, 1605, top flange plate, 17, O-ring, 18, fixing bolt, 19, tensiometer, 20, temperature and humidity sensor, 21, precision temperature probe, 22, high-precision electronic balance, 23, compressor, 24, refrigerant bottle, 25, data acquisition system, 26, adjustable bracket, 27, adjusting nut, 28, bolt hole. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but they are not intended to limit the invention in any way.

[0024] Embodiment 1: A test device for the water-mechanical properties of soil under climate simulation conditions, comprising a water pressure controller 1, a humidity-controllable spray system, a refrigeration system, a heating system, a high-definition camera 8, an environmental test chamber 12, a tensiometer 19, a sample chamber 16, a high-precision electronic balance 22, and a data acquisition system 25. The inner cavity of the sample chamber 16 is used to hold the sample to be tested, and the test chamber 16 is placed in the environmental test chamber 12. The spray system, the refrigeration system, and the heating system cooperate in the environmental test chamber 12 to simulate the dry-wet and freeze-thaw environmental changes, and measure the water-mechanical characteristic parameters under multiple working conditions.

[0025] The environmental test box 12 includes a lower box body 1202 and a top cover plate 1201. The top of the lower box body 1202 is open, and the top cover plate 1201 is fixedly connected to the top opening of the lower box body 1202 by cover plate bolts 9. In order to ensure the sealing between the top cover plate 1201 and the lower box body 1202, O-rings 17 or other sealing strips are embedded on the four sides of the top opening of the lower box body 1202. The top cover plate 1201 squeezes the O-ring 17 or the sealing strip to make it elastically deformed, thereby improving the sealing of the joint. In order to reduce the influence of the external ambient temperature on the temperature of the inner cavity of the environmental test box, the lower box body 1202 and the top cover plate 1201 are both made of pressure-resistant plastic plates, and the pressure-resistant plastic plates are double-layer plates to form a heat-insulating medium cavity 14 that can accommodate a heat-insulating medium to surround the inner cavity of the environmental test box 12. In this embodiment, the heat preservation medium is argon, that is, the heat preservation medium cavity 14 is filled with argon to meet the heat preservation and thermal insulation requirements of the environmental test box.

[0026] The controllable humidity spray system comprises a saturated salt solution container 5, a peristaltic pump 6 and a spray device 13. The saturated salt solution container 5 and the peristaltic pump 6 are both located outside the environmental test box 12, the saturated salt solution container 5 is filled with a saturated salt solution of known concentration, and a rubber plug is arranged at the container mouth. The pipes connected to the inlet and outlet of the peristaltic pump 6 all pass through the rubber plug and extend below the liquid level of the saturated salt solution. The spray device 13 is a nozzle, which is located in the environmental test box 12 and is connected to the saturated salt solution container 5 through a spray pipe, and the inlet of the spray pipe is located above the liquid level of the saturated salt solution. A stop valve 4 is arranged on the spray pipe.

[0027] The water outlet 3 of the water pressure controller 1 is connected to one end of the water supply pipe, the other end of the water supply pipe is connected to the side of the spray pipe, and the connection position of the water supply pipe and the spray pipe is located at the outlet side of the stop valve 4 on the spray pipe. Another stop valve 4 is installed on the water supply pipe. The water pressure controller 1 is connected to the spray system to supply water to the spray system, and the spray device 13 atomizes the water into water mist and sprays it onto the surface of the sample in the environmental test box 12 to humidify the sample.

[0028] The spray system improves the circulation efficiency of the saturated salt solution in the salt solution container 5 through the peristaltic pump 6, accelerates the vapor pressure equilibrium process in the environmental test box, and shortens the test period. During the test, the corresponding humidity value can be changed by changing the type of salt in the saturated salt solution container 5, thereby changing the size of the equilibrium vapor pressure in the environmental test box 12, and indirectly controlling different suction values.

[0029] The heating system is a plurality of heating lamps 10 arranged in the environmental test box 12. The heating lamps 10 are installed on the inner surface of the top cover plate 1201. By controlling the current of the heating lamps 10, the heat generated by the heating lamps 10 can be controlled to control the ambient temperature and dryness in the environmental test box 12. Therefore, by alternately using the spray device 13 and the heating lamps 10, the actual rainfall-sunlight climate change conditions, that is, the dry-wet cycle can be simulated.

[0030] The refrigeration system includes a compressor 23, an air-conditioning outlet 15 and a refrigerant bottle 24. The air-conditioning outlet 15 is located inside the environmental test box 12, and the compressor 23 is located outside the environmental test box 12. The refrigerant in the refrigerant bottle 24 is compressed by the compressor 23 to form cold mist, which is then sent into the environmental test box 12 through the air-conditioning outlet 15 to achieve a low temperature state in the environmental test box 12. The purpose of precise control of low temperature is achieved by using a precision temperature probe 21 and controlling the flow rate of cold mist. The lower limit of low temperature depends on the type of refrigerant medium. Through the cooperation of the refrigeration system and the heating system, the freeze-thaw cycle of the soil sample is realized. In actual engineering applications, the environmental temperature changes or freezing construction can be simulated to measure the deformation parameters of different types of soil affected by the freeze-thaw cycle factors.

[0031] The changes in temperature and humidity in the environmental test box 12 are monitored by a temperature and humidity sensor 20 and a precision temperature probe 21. The temperature and humidity sensor 20 and the precision temperature probe 21 are connected to a data acquisition system 25 outside the environmental test box 12, and the collected data information is sent to the data acquisition system 25 for subsequent calculation and analysis.

[0032] A high-definition camera 8 is also arranged on the top of the environmental test box 12, and the lens of the high-definition camera 8 is downward, facing the sample below. The lens cover of the high-definition camera 8 is arranged in a transparent protective cover 11 to reduce the influence of temperature and humidity changes on the lens.

[0033] Furthermore, in order to adjust the height of the high-definition camera 8, an adjustable bracket 26 is provided outside the environmental test box 12, and the two ends of the adjustable bracket 26 are horizontally supported on the two vertical poles of the base 7, and can move up and down along the vertical poles, and the high-definition camera 8 is fixed on the adjustable bracket 26. The movement of the adjustable bracket 26 on the vertical pole can be achieved through a variety of structures, for example, the upper end of the vertical pole is provided with an external thread and connected to an adjusting nut 27, and the two ends of the adjustable bracket 26 are sleeved on the upper end of the vertical pole through a sleeve and supported on the adjusting nut 27. By adjusting the position of the adjusting nut 27, the height of the high-definition camera 8 can be adjusted.

[0034] When the high-definition camera 8 is fixed on the adjustable bracket 26 , an opening needs to be formed on the top cover plate of the environmental test box 12 to allow the lens of the high-definition camera 8 to extend into the environmental test box 12 .

[0035] The test chamber 16 is made of transparent materials such as high-strength acrylic plastic, and includes the following types: a first type of test chamber 1601 is a cylindrical chamber with a bottom flange plate 1604 and an open top, and the bottom flange plate 1604 is provided with a plurality of through holes connected to the interior of the chamber; a second type of test chamber 1602 is a cylindrical chamber with a top flange plate 1605 and a bottom flange plate 1604, and the top flange plate 1605 and the bottom flange plate 1604 are both provided with a plurality of through holes connected to the interior of the chamber; a third type of test chamber 1603 is based on the second type of test chamber 1602, but does not have a through hole connected to the interior of the chamber on the bottom flange plate 1604.

[0036] During the test, different test chambers 16 can be combined or used alone to meet different test requirements. For example, only the first type of test chamber 1601 can meet the requirements of a single soil deformation test; the combination of the first type of test chamber 1601, the second type of test chamber 1602 and the third type of test chamber 1603, or the combination of the first type of test chamber 1601 and the third type of test chamber 1603, can meet the test requirements of different soils with different initial dry density, moisture content and other factors, and at the same time achieve the determination of suction and crack parameters. The third type of test chamber 1603 can also be used alone, and has the same function as the first type of test chamber.

[0037] Specifically, when the test chambers are used in combination, the test chambers are stacked layer by layer, for example Figure 2 As shown, in the combination of the first type test chamber 1601, the second type test chamber 1602 and the third type test chamber 1603, the through holes and the bolt holes 28 of the top flange plates 1605 and the bottom flange plates 1604 of adjacent chambers are aligned, and grooves are reserved on the top flange plates 1605 and the bottom flange plates 1604 to install the O-ring 17, and the top flange plate 1605 and the bottom flange plate 1604 are fastened to each other by bolts to tighten the O-ring 17 to ensure good sealing in the chamber.

[0038] The test chamber 16 is also provided with a tensiometer 19 into which the sample is inserted, and the tensiometer 19 is connected to an external data acquisition system 25. During the test, the suction value of the soil is read by the tensiometer 19, the mass of each equilibrium soil sample is weighed by a high-precision electronic balance 22, and then the soil-water characteristic curve of the soil under different working conditions is obtained by analysis by the data acquisition system 25.

[0039] Example 2 The deformation test under the action of dry-wet cycle was carried out using the device of Example 1, and the specific steps are as follows: Step 1: Installation of the device (1) Remove the adjustable bracket 26 on the upper part of the base 7 and place the base 7 on the test bench; place the test environment box 12 on the base 7 and adjust the position of the test environment box 12 so that it is centered. (2) Open the bolts 9 of the upper cover 1201 of the environmental test chamber 12, remove the upper cover 1201 and carefully place it on the test bench to avoid damaging the heating lamp 10 and the high-definition camera 8, place the high-precision electronic balance 22 and the first-type test chamber 1601 inside the test chamber 12, adjust the position of the first-type test chamber 1601 so that it is centered on the table of the high-precision electronic balance 22, and at the same time, reset the value of the high-precision electronic balance 22; install the tensiometer 19 inside the sample of the first-type test chamber 1601 to test the suction value of the sample in real time; (3) Install the transparent protective cover 11 on the upper cover 1201 of the environmental test chamber 12, then cover the upper cover 1201, tighten the bolts 9, and ensure its sealing; then install the upper adjustable bracket 26 and connect it to the high-definition camera 8, and place the high-definition camera 8 in a suitable position by adjusting the height of the adjustable bracket 26, and ensure that the picture of the high-definition camera 8 is clear by fine-tuning the camera focus.

[0040] Step 2: Simulation of dry-wet cycle, including humidification process and drying process. The specific operations are as follows: A: During the humidification process, a saturated salt solution is prepared in a saturated salt solution container 5, and a peristaltic pump 6 is installed, and a stop valve 4 and a spray device 13 are connected; There are two humidification methods in the humidification process: (1) During the humidification test of controlled suction, the stop valve 4 in the front section of the water pressure controller 1 needs to be closed, and the peristaltic pump 6 and the spray device 13 need to be turned on; (2) Humidification is performed using water as the medium. The test process is as follows: close the stop valve 4 and the peristaltic pump 6 at the front end of the saturated salt solution container 5, adjust the water pressure controller 1 so that the water pressure at its outlet 3 reaches the specified water flow rate, and the outlet of the precision water pressure controller 1 is connected to the stop valve 4 and the spray device 13; during the test, open the stop valve 4, and after the water flow at the upper outlet of the sample is stable, humidify the soil sample at a certain interval; B: During the drying process, the heating lamp 10 on the top of the test environment box 12 is turned on. The temperature can be controlled by adjusting the current of the heating lamp 10. During this period, the temperature change inside the test environment box 12 is read by the precision temperature probe 21.

[0041] Step 3: Data Collection and Processing Open the data acquisition system 25, connect the high-definition camera 8, the tensiometer 19, the temperature and humidity sensor 20 and the precision temperature probe 21 to the data acquisition system 25, and read the initial values ​​of the high-definition camera 8, the tensiometer 19, the temperature and humidity sensor 20, the precision temperature probe 21 and the high-precision electronic balance 22 respectively. The test starts the second step of the drying process, and records the relevant test data at the same time. After the sample quality and crack development are stable, the humidification process is started to carry out the humidification test. The humidification test is based on the initial control state of the sample, and the drying process is repeated after the humidification is completed. Repeating the drying process and the humidification process can simulate the deformation characteristic test of different dry-wet cycle times. After the test, the photos collected by the high-definition camera 8 are subjected to a series of image preprocessing operations such as binarization processing → image noise processing → crack skeleton processing → measurement, so as to form a quantitative analysis of the evolution process of soil cracks.

[0042] Before the humidification process, when preparing the saturated salt solution, select a salt according to the humidity value required by the test, and pour the selected salt into the saturated salt solution container 5. Deionized water is required to prepare the salt solution, and the deionized water is poured into the saturated salt solution container 5. Use a magnetic stirrer to fully stir. When salt crystals appear at the bottom of the container and no longer melt, it proves that the prepared salt solution is supersaturated. It should be noted that the prepared salt solution needs to be left to stand for 48 hours in order to fully dissolve it and reach a supersaturated state.

[0043] Embodiment 3: The deformation test under the action of freeze-thaw cycle was carried out using the device of Example 1, and the specific steps are as follows: Step 1: Installation of the device The installation steps are the same as those in Example 2, except that this embodiment uses a combination of the first type of test chamber, the second type of test chamber, and the third type of test chamber, and each test chamber is loaded with soil samples of different working conditions to shorten the test cycle.

[0044] Step 2: Simulation of freeze-thaw cycle, including freezing process, melting process and humidification process. The specific operations are as follows: A: During the freezing process, the refrigerant is compressed by the compressor 23 to form cold mist, which is then sent into the environmental test box 12 through the air outlet 15 of the air conditioner to achieve a low temperature state of the environmental test box 12. During this period, the low temperature is precisely controlled by the precision temperature probe 21 and the control of the cold mist flow rate. The lower limit of the low temperature depends on the type of refrigeration medium; B: During the melting process, the heating lamp 10 on the top of the test environment box 12 is turned on. The temperature can be controlled by adjusting the current of the heating lamp 10. During this period, the temperature change inside the environment box 12 is read by the precision temperature probe 21 to observe the melting and sinking phenomenon of the soil sample.

[0045] C: During the humidification process, the stop valve 4 and the peristaltic pump 6 at the front end of the saturated salt solution container 5 are closed, and the precision water pressure controller 1 is adjusted so that the water pressure at the water outlet 3 reaches the specified water flow rate. The water outlet of the precision water pressure controller 1 is connected to the stop valve 4 and the spray device 13. During the test, the stop valve 4 is opened, and after the water flow at the upper water outlet of the sample is stable, the soil sample is humidified according to the test requirements.

[0046] Step 3: Data Collection and Processing Open the data acquisition system 25, and connect the high-definition camera 8, the tensiometer 19, the temperature and humidity sensor 20, and the precision temperature probe 21 to the data acquisition system 25 respectively. Read the initial values ​​of the high-definition camera 8, the tensiometer 19, the temperature and humidity sensor 20, the precision temperature probe 21, and the high-precision electronic balance 22 respectively. Start the freezing process at the beginning of the test, and record the relevant test data at the same time. Stop the freezing process after a certain period of time after the temperature setting value is reached; start the test melting process and observe the melting and settling phenomenon. If the soil sample needs to be humidified during the test, start the humidification process. Repeated freezing, melting, and humidification operations can simulate deformation characteristic tests with different freeze-thaw cycles. After the test, numerical analysis is performed on the appearance of the soil sample and the photos collected by the high-definition camera 8, and quantitative analysis is performed on indicators such as the number, area, perimeter, and shape of soil cracks.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Those skilled in the art should understand that the specific implementation modes of the present invention may be modified or replaced by equivalents with reference to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the pending claims.

Claims

1. A test device for the hydraulic-mechanical properties of soil under climatic simulation conditions, characterized by: It includes an environmental test box, which is used to simulate the climate environment required for the test inside the box, and a test chamber is arranged inside the environmental test box, and the test chamber is used to accommodate the test sample; A controllable humidity spray system comprises a saturated salt solution container, a peristaltic pump and a spray device, wherein the nozzle of the spray device is located in an environmental test chamber, the inlet of the spray pipe of the spray device is located above the liquid level in the saturated salt solution container, a stop valve is provided on the spray pipe, and the pipe openings connected to the inlet and outlet of the peristaltic pump are both located below the liquid level of the saturated salt solution container; A water pressure controller, the water outlet of which is connected to the spray pipe through a water supply pipe, and a stop valve is provided on the water supply pipe; A heating system, including a heating lamp disposed on the top of the environmental test chamber; The refrigeration system includes a compressor, a refrigerant bottle and an air-conditioning outlet. The air-conditioning outlet is located inside the environmental test chamber, and the compressor and the refrigerant bottle are located outside the environmental test chamber; A temperature and humidity sensor, a temperature probe, an electronic balance, a tensiometer and a high-definition camera are also provided in the environmental test chamber, and a data acquisition system is provided outside the environmental test chamber. The temperature and humidity sensor, the temperature probe, the electronic balance, the tensiometer and the high-definition camera are connected to the data acquisition system, and the tensiometer is inserted into the test sample through the side wall of the test chamber.

2. The test device for the hydraulic properties of soil according to claim 1, characterized in that: The test chamber is made of transparent material, and includes a first type of test chamber, a second type of test chamber and a third type of test chamber. The first type of test chamber is a cylindrical chamber with a bottom flange plate and an open top, and the bottom flange plate is provided with a plurality of through holes connected to the interior of the chamber; the second type of test chamber is a cylindrical chamber with a top flange plate and a bottom flange plate, and the top flange plate and the bottom flange plate are both provided with a plurality of through holes connected to the interior of the chamber; the third type of test chamber is a cylindrical chamber with a top flange plate and a bottom flange plate, and only the top flange plate is provided with a through hole connected to the interior of the chamber.

3. The test device for the hydraulic properties of soil according to claim 2, characterized in that: When a single soil body needs to be tested, the first type of test chamber or the third type of test chamber is used alone to accommodate the test sample; when different soil bodies need to be tested, the first type of test chamber, the second type of test chamber and the third type of test chamber are stacked up and used in combination, and each test chamber is respectively placed with the corresponding test sample, and after the combination, the through holes on the top flange plate and the bottom flange plate are aligned.

4. The test device for the hydraulic properties of soil according to claim 2, characterized in that: The top flange plate and the bottom flange plate are provided with grooves for installing O-rings, and when the two test chambers are combined, the top flange plate and the bottom flange plate are fastened and connected by bolts to compress the O-rings.

5. The soil hydraulic properties testing device according to claim 1, characterized in that: The position where the water supply pipe is connected to the spray pipe is located at the outlet side of the stop valve on the spray pipe.

6. The soil hydraulic properties testing device according to claim 1, characterized in that: The lens cover of the high-definition camera is provided with a transparent protective cover.

7. The soil hydraulic properties testing device according to claim 1, characterized in that: The rear end of the high-definition camera extends out of the top of the environmental test box and is connected to a lifting mechanism.

8. The test device for the hydraulic properties of soil according to claim 7, characterized in that: The lifting mechanism is a horizontally arranged adjustable support rod, the two ends of the adjustable support rod are movably sleeved on the upper ends of the two vertical rods of the base, and the vertical rods are provided with adjusting nuts, which support the adjustable support rod.

9. The soil hydraulic properties testing device according to claim 1, characterized in that: The environmental test box comprises a detachably connected lower box body and a top box cover, wherein both the lower box body and the top box cover are sandwiched and have a heat-insulating medium cavity capable of accommodating a heat-insulating medium.

10. A test method for the hydraulic properties of soil, characterized in that: Using the test device described in any one of claims 1 to 9, respectively simulating dry-wet cycles and freeze-thaw cycles, and conducting deformation characteristic tests of soil samples; The dry-wet cycle includes a humidification process and a drying process. The humidification process uses a saturated salt solution container or a water pressure controller in conjunction with a spray device to humidify the soil sample in the test chamber; the drying process uses a heating lamp to heat and dry the soil sample; the humidification process and the drying process are repeatedly performed to simulate deformation characteristic tests with different dry-wet cycle times, and the initial values ​​and numerical values ​​of the high-definition camera, tensiometer, temperature and humidity sensor, temperature probe and electronic balance are recorded by a data acquisition system during the test. Finally, the acquired information is processed to form a quantitative analysis of the evolution process of soil cracks; The freeze-thaw cycle includes a freezing process, a melting process and a humidification process. The freezing process is performed by the refrigeration system, and the melting process is performed by the heating lamp. The freezing process, the melting process and the humidification process are repeatedly performed to simulate deformation characteristic tests with different freeze-thaw cycle times. During the test, the initial values ​​of the high-definition camera, the tensiometer, the temperature and humidity sensor, the temperature probe and the electronic balance and the values ​​during the test are recorded by the data acquisition system. Finally, the acquired information is processed to quantitatively analyze soil cracks.

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