Water-salt-temperature multi-field coupling effect environment simulation test system and test method

Abstract

The invention belongs to the technical field of civil engineering and material science, and discloses a water-salt-temperature multi-field coupling effect environment simulation test system and test method.The system comprises a hydraulic system, a main testing machine system and a constant-temperature water tank system; and the hydraulic system is connected with a hollow oil cylinder on the main test box through a corresponding pipeline in the pipeline assembly and is placed on the left side of the main tester system. According to the invention, the water tank and the main test box can be controlled by the control system to realize the test process of freeze-thaw cycle, dry-wet cycle and salt solution freeze-thaw cycle; dry-wet cycle, salt freeze-thaw cycle and dry-wet cycle-salt freeze-thaw cycle alternate tests can be carried out on the sample; a main testing machine system is provided with an advanced water, salt, temperature, stress and strain real-time sensing monitoring and data acquisition system, and an intelligent environmental action simulation control operation system improves the automatic and intelligent control level of test research work, greatly reduces the manual test monitoring time, and facilitates research work of researchers.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering and material science, and in particular relates to a water-salt-temperature multi-field coupling environment simulation test system and a test method. Background Art

[0002] In saline soil areas, the water-salt dry-wet cycle and seasonal salt-freeze-thaw cycle have caused serious damage to local road projects, bridge pier foundations, and various building foundations. This environmental effect objectively exists due to its special climate and hydrogeological environment, which will inevitably make the construction and maintenance management of urban road traffic projects along the route more complicated and more expensive. Therefore, it is necessary to conduct systematic research on the mechanism of the coupling effect of the special water-salt dry-wet cycle and seasonal salt-freeze-thaw cycle on geotechnical engineering structures in saline soil areas.

[0003] In the special saline soil environment, there are objective dry-wet cycles and salt-freeze-thaw cycles that affect the safety and durability of engineering structures. The essence of the scientific research on the coupling effects on geotechnical engineering structures is the multi-field coupling effect of moisture field, salt field, temperature field and stress field. Therefore, a water-salt-temperature multi-field coupling environment simulation test system and test method are proposed. Summary of the invention

[0004] The purpose of the present invention is to provide a water-salt-temperature multi-field coupling environment simulation test system and test method to solve the problems raised in the above background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a water-salt-temperature multi-field coupling environment simulation test system, comprising a hydraulic system, a main test machine system and a constant temperature water tank system;

[0006] The hydraulic system includes a switch, an oil tank, a pressurizing handle, a box body, a pressure gauge, a pressurizing and depressurizing handle and a pipeline assembly;

[0007] The hydraulic system is arranged on one side of the main test machine system, and the main test machine system includes a main box, a first compressor, a first condenser, a first drying filter, a first expansion valve, a first evaporator, a heating device, a fan assembly, an inner water tank water inlet, an inner water tank water outlet and a first touch screen control system, and a pressure rod through hole is opened on the main box;

[0008] The constant temperature water tank system is arranged on one side of the main testing machine system, and the constant temperature water tank system includes an inlet water pump, a return water pump, a circulating water pump, an external water tank main unit, a second compressor, a second touch screen control system, a return water pipe and an inlet water pipe;

[0009] The hydraulic system is connected to the hollow oil cylinder on the main test box of the main test machine system through the corresponding pipelines in the pipeline assembly, and the constant temperature water tank system is connected to the main test box of the main test machine system through the water inlet pipe and return pipe of the external water tank host.

[0010] Preferably, the first compressor and the first condenser are both installed in the control cabin of the main box, and the first compressor and the first condenser are connected by a copper pipe;

[0011] The first evaporator and the heating device are installed inside the main test box of the main box.

[0012] Preferably, a reaction frame light bar, a reaction top plate, a reaction middle plate, a support rod and a reaction bottom plate are installed inside the main box, and the reaction frame light bar, the reaction top plate, the reaction middle plate, the support rod and the reaction bottom plate form a reaction frame structure;

[0013] A sample water tank is installed inside the main box, a sample tube is arranged inside the sample water tank, and a sample is placed inside the sample tube.

[0014] Preferably, a pad is placed inside the sample tube, and the pad is located above the sample.

[0015] Preferably, a hollow oil cylinder is installed below the reaction force top plate, a sleeve is installed below the hollow oil cylinder, a pressure sensor and a disc spring energy storage assembly are installed in the sleeve, and a pressure shaft is installed below the disc spring energy storage assembly.

[0016] Preferably, a base is installed under the main chassis, and four adjustable feet are installed under the base, the four adjustable feet are arranged in groups of two and are symmetrical in pairs, and a roller is installed above the base.

[0017] Preferably, the second compressor and the second condenser are installed in a control cabin inside the external water tank main unit, and the second compressor and the second condenser are connected by a copper pipe, the second compressor, the second drying filter, the second condenser, the second expansion valve, and the second evaporator are connected by a copper pipe, and the second evaporator and the heating pipe are installed inside the main test box of the external water tank main unit.

[0018] Preferably, the water inlet pump is connected to the water tank inlet pipe, the main tank water inlet, and the inner water tank water inlet through pipelines, and the return water pump is connected to the return pipe, the main tank water outlet, and the inner water tank water outlet through pipelines.

[0019] The water-salt-temperature multi-field coupling environment simulation test method, using the water-salt-temperature multi-field coupling environment simulation test system, comprises the following steps:

[0020] S1: Prepare at least two roadbed structure samples of different pavement types according to the roadbed structure characteristics of the target study area;

[0021] S2: Using the water-salt-temperature multi-field coupling environmental simulation experimental system, three types of environmental action conditions are simulated, namely, dry-wet cycle, salt freeze-thaw cycle, and dry-wet cycle + salt freeze-thaw cycle coupling;

[0022] S3: Accurately control the temperature, water-salt content and other parameters during the test through temperature sensors, water-salt circulation control systems and other equipment;

[0023] S4: Real-time collection and recording of various parameters during the test, such as temperature, deformation, water-salt content, etc., and analysis of the collected data to reveal the damage and failure mechanism of the roadbed structure in a complex environment;

[0024] S5: Design and prepare disaster-resistant roadbed structure specimens, conduct disaster resistance performance verification tests of the roadbed structure simulating the vehicle load effect according to the above-mentioned coupling effect, and evaluate the disaster prevention effectiveness.

[0025] Preferably, in S1, the different road surface types include cement concrete road surface and asphalt concrete road surface.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention simulates engineering environments of three different environmental working conditions respectively, manufactures roadbed structure samples of two different pavement types, and carries out roadbed structure damage and destruction experiments of three environmental working conditions in an environmental simulation experimental system respectively. By monitoring the stress-strain data of the samples and carrying out load tests on the samples at different experimental stages, the physical and mechanical parameter change curves of the roadbed structure samples in the entire test cycle under different environmental working conditions can be obtained; low-field nuclear magnetic resonance technology is used to observe the phase changes and migration and penetration laws of the internal pores and water-salt fluid media of the samples at different experimental stages of the experimental cycle, and the microscopic damage and destruction mechanism of the samples is analyzed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the present invention;

[0029] Figure 2 It is a schematic diagram of the external structure of the hydraulic system of the present invention;

[0030] Figure 3 It is a schematic diagram of the external structure of the main testing machine system of the present invention;

[0031] Figure 4 It is a schematic diagram of the internal structure of the main testing machine system of the present invention;

[0032] Figure 5 It is a front view of the main testing machine system of the present invention;

[0033] Figure 6 It is a schematic diagram of the internal structure of the constant temperature water tank system of the present invention;

[0034] Figure 7 It is a schematic diagram of the external structure of the constant temperature water tank system of the present invention;

[0035] In the figure: 1. Hydraulic system; 2. Main test machine system; 3. Constant temperature water tank system; 4. Switch; 5. Oil tank; 6. Pressurization handle; 7. Box; 8. Pressure gauge; 9. Pressurization and pressure relief handle; 10. Pipeline assembly; 11. First condenser; 12. First expansion valve; 13. First drying filter; 14. First compressor; 15. Main box; 16. First touch screen control system; 17. Pressurization rod through hole; 18. Fan assembly; 19. Heating device; 20. First evaporator; 21. Reaction frame light bar; 22. Reaction top plate; 23. Hollow oil cylinder; 24. Sleeve; 25. Pressure sensor; 26. Support rod; 27. Reaction middle plate ; 28. Inner water tank water inlet; 29. ​​Inner water tank water outlet; 30. Main box water inlet; 31. Main box water outlet; 32. Reaction bottom plate; 33. Roller; 34. Bottom support; 35. Adjustable feet; 36. Press shaft; 37. Pad; 38. Disc spring energy storage assembly; 39. Sample cylinder; 40. Sample water tank; 41. Second condenser; 42. Second expansion valve; 43. Second drying filter; 44. Second compressor; 45. External water tank host; 46. Second touch screen control system; 47. Return pipe; 48. Inlet pipe; 49. Heating pipe; 50. Second evaporator; 51. Inlet pump; 52. Return pump; 53. Circulating pump. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] See also Figure 1-Figure 7 As shown, the present invention provides the following technical solutions:

[0038] Water-salt-temperature multi-field coupling environmental simulation test system, including a hydraulic system 1, a main test machine system 2 and a constant temperature water tank system 3;

[0039] The hydraulic system 1 includes a switch 4, an oil tank 5, a pressurizing handle 6, a box body 7, a pressure gauge 8, a pressurizing and depressurizing handle 9 and a pipeline assembly 10;

[0040] The hydraulic system 1 is arranged on one side of the main test machine system 2. The main test machine system 2 includes a main box 15, a first compressor 14, a first condenser 11, a first drying filter 13, a first expansion valve 12, a first evaporator 20, a heating device 19, a fan assembly 18, an inner water tank water inlet 28, an inner water tank water outlet 29 and a first touch screen control system 16. A pressure rod through hole 17 is opened on the main box 15;

[0041] The constant temperature water tank system 3 is arranged at one side of the main testing machine system 2, and the constant temperature water tank system 3 includes an inlet water pump 51, a return water pump 52, a circulating water pump 53, an external water tank main unit 45, a second compressor 44, a second touch screen control system 46, a return water pipe 47 and an inlet water pipe 48;

[0042] The hydraulic system 1 is connected to the hollow oil cylinder 23 on the main test box of the main test machine system 2 through the corresponding pipeline in the pipeline assembly 10. The constant temperature water tank system 3 is connected to the main test box of the main test machine system 2 through the water inlet pipe 48 and the return pipe 47 of the external water tank host 45. The inner volume of the main test box is approximately (mm): length 1000 width 800 height 1000, the temperature control range of the main test box is -40℃~+85℃, the temperature control accuracy of the main test box is 0.1℃, the temperature uniformity of the main test box is ±0.5℃, the temperature control mode of the main test box is touch screen + PID temperature control, and the main test box can be program-controlled: constant temperature control, freeze-thaw cycle control, dry-wet cycle control, salt-freeze cycle control, dry-wet cycle-salt-freeze cycle control can be performed; it can be set The test process, temperature control and its cycle times are automatically run; the historical temperature values ​​of the test can be saved through a U disk; the real-time curve can be displayed, the loading force value range of the main test box is 0-100kN, the loading accuracy of the main test box is 0.1kN, the number of loading channels of the main test box is 6 (six specimens can be loaded, or they can be loaded independently), the inner liner of the main test box is made of 304 high-quality stainless steel; the welding form adopts full welding, no air leakage, heat preservation and energy saving, the outer shell of the main test box is made of electrostatically sprayed steel plate, the interior of the main test box adopts a unique air duct design to ensure temperature uniformity, the insulation layer of the main test box is made of special rock wool, the main test box is equipped with a four-column high-strength reaction frame, good rigidity, load-bearing performance, and the overall structure of the main test box is equipped with Strengthen the structure configuration, all of which are made of alloy steel plates and have undergone special heat treatment to effectively improve the strength and rigidity. Under pressure, there will be no deformation. The main test box is equipped with a stainless steel inner test box for use in salt solution freeze-thaw cycles and dry-wet cycle tests. The stainless steel water tank of the main test box is equipped with 6 stainless steel sample barrels and a stainless steel bottom plate. There is a porous structure support plate under the bottom plate to ensure that the solution temperature is uniform during the test. The main test box is equipped with six displacement sensor fixtures. Each sample in the main test box is equipped with a force transmission rod and a pressure sensor. The main test box is equipped with a manual loading system with a one-to-six configuration; the jack connected to the top of the sample can pressure-load the six samples, or it can be loaded independently. The main test box is for each sample The loaders are equipped with energy storage devices, and the force value is stable, which can greatly reduce the frequent pressure replenishment workload of users. The main test box can perform sulfate dry-wet cycle tests on concrete samples with a size of 150×150×150mm, and can hold 3×3×3=27 samples. The main test box can realize dry-wet cycle, salt-freeze cycle, and dry-wet cycle-salt-freeze cycle alternating tests on the samples. The main test box is equipped with a track lifting trolley, which is convenient for users to load samples and reduce manpower. In addition, in the present invention, the first compressor 14 and the first condenser 11 are both installed in the control cabin of the main box 15, and the first compressor 14 and the first condenser 11 are connected by copper pipes; the first evaporator 20 and the heating device 19 are installed inside the main test box of the main box 15.

[0043] Furthermore, regarding the main box 15, a reaction frame light bar 21, a reaction top plate 22, a reaction middle plate 27, a support rod 26 and a reaction bottom plate 32 are installed inside the main box 15, and the reaction frame light bar 21, the reaction top plate 22, the reaction middle plate 27, the support rod 26 and the reaction bottom plate 32 form a reaction frame structure;

[0044] A sample water tank 40 is installed inside the main box 15. A sample tube 39 is arranged inside the sample water tank 40. A sample is placed inside the sample tube 39. A pad 37 is also placed inside the sample tube 39. The pad 37 is above the sample. The sample size is φ150×500mm, and the number of samples placed is 6.

[0045] In addition, in the present invention, a hollow oil cylinder 23 is installed below the reaction force top plate 22, a sleeve 24 is installed below the hollow oil cylinder 23, a pressure sensor 25 and a disc spring energy storage assembly 38 are installed in the sleeve 24, and a pressure shaft 36 is installed below the disc spring energy storage assembly 38.

[0046] Furthermore, in order to make the device more stable during operation, a base bracket 34 is installed under the main case 15 , and four adjustable feet 35 are installed under the base bracket 34 . The four adjustable feet 35 are arranged in groups of two and are symmetrical in pairs. A roller shaft 33 is installed above the base bracket 34 .

[0047] In addition, in the present invention, regarding the above-mentioned second compressor 44 and second condenser 41, the second compressor 44 and the second condenser 41 are installed in a control cabin inside the external water tank main unit 45, and the second compressor 44 and the second condenser 41 are connected by a copper pipe, and the second compressor 44, the second drying filter 43, the second condenser 41, the second expansion valve 42, and the second evaporator 50 are connected by a copper pipe, and the second evaporator 50 and the heating pipe 49 are installed inside the main test box of the external water tank main unit 45.

[0048] Regarding the above-mentioned inlet water pump 51 and return water pump 52, the inlet water pump 51 is connected to the water tank inlet pipe 48, the main tank water inlet 30, and the inner water tank water inlet 28 through pipelines, and the return water pump 52 is connected to the return water pipe 47, the main tank water outlet 31 and the inner water tank water outlet 29 through pipelines.

[0049] In addition, a water-salt-temperature multi-field coupling environment simulation test method is provided, including the following steps:

[0050] The experimental study on the damage and destruction of roadbed structure under the coupling of dry-wet cycle and salt freeze-thaw cycle is carried out after the trial production of the environmental simulation experimental system of water-salt-temperature multi-field coupling is completed, and after functional debugging and calibration of the monitoring and control system, the test is divided into the following steps.

[0051] Step 1: Prepare subgrade structure samples of two different pavement types (A cement concrete pavement, B asphalt concrete pavement) and determine the water-salt-temperature environmental control parameters of the experimental system.

[0052] According to the survey data of typical diseased roads (Aral Junken Avenue, Tarim Avenue, etc.) completed in the early stage of the project, the material ratio of each layer of the roadbed structure layer, design thickness and other parameters were obtained by sampling and analyzing the cross-section of the roadbed structure layer, the subgrade base layer of the roadbed, and water and salt in the diseased section, and the roadbed structure samples A and B of typical diseased roads were prepared; from the data on roadbed and pavement temperature, deformation, average values ​​of water-salt-temperature of different depths of the roadbed structure layer and foundation soil layer, physical indicators of foundation soil, and ion composition of groundwater-salt, which were obtained from three to five consecutive observation seasons (3-5 years) of monitoring of typical diseased sections in the early stage of the project, the temperature and humidity of the natural environment in which the research object is located, and the water-salt-temperature environmental parameters of different depths of the roadbed structure layer were obtained as the water-salt-temperature environmental parameters of the roadbed structure samples controlled by the experimental system.

[0053] Step 2: Use the environmental simulation experimental system with water-salt-temperature multi-field coupling to simulate three types of environmental action conditions (1. dry-wet cycle, 2. salt freeze-thaw cycle, 3. dry-wet cycle + salt freeze-thaw cycle) to carry out simulation tests on roadbed samples of two different pavement types.

[0054] Experimental design:

[0055] ① Environmental action condition 1: dry-wet cycle environmental action simulation test

[0056] Three groups of samples of type A and type B (9 samples in each category) were prepared, and one group (3 samples in each type A and type B, 6 samples in total) was selected for three different degrees of wet-dry cycle tests (referred to as: DW1, DW2, DW3). The number of wet-dry cycles was controlled within 50 times until the sample was destroyed. The test samples were placed in a water-salt-temperature multi-field coupled environmental simulation test cylinder. The density of the coarse sand filled between the samples was not based on the radial and vertical deformation of the constrained samples. The water-salt solution for soaking the samples was a 5% Na2SO4 solution, which was injected into the water-salt-temperature multi-field coupled environmental simulation test cylinder through a water-salt circulation control system.

[0057] The temperature control and duration of the sample soaking and drying stages after completing a dry-wet cycle test: the sample is soaked at 20-25℃ for 480-500min, and then dried at 70-75℃ for 600min. The drying heating rate is controlled at 25-30℃ / 60min. The soaking and drying time can be adjusted appropriately according to the degree of wetness of the sample. Temperature control is achieved by placing a temperature sensor on the surface area of ​​the sample in the water-salt-temperature multi-field coupled environment simulation test cylinder.

[0058] The first group of dry-wet cycle test DW1: the height of the sample is completely in the water-salt solution infiltration state in each cycle immersion stage; the second group of dry-wet cycle test DW2: 1 / 3 to 1 / 2 of the height of the sample is in the water-salt solution infiltration state (semi-infiltration state) in each cycle immersion stage; the third group of dry-wet cycle test DW3: the height of the sample is above the infiltration surface of the water-salt solution in each cycle immersion stage (no infiltration state, the bottom surface of the sample is above the water-salt solution surface, but within the range of the capillary water rise effect height). The infiltration state of the samples in the three groups of dry-wet cycle tests is achieved by controlling the pressure of the Na2SO4 solution injected into the water-salt-temperature multi-field coupled environmental simulation test cylinder by the water-salt cycle control system.

[0059] In each group of dry-wet cycle tests, after completing 5 cycles, 10 cycles and until the sample is destroyed, one sample is taken out for loading destruction test and sample microscopic damage observation and analysis.

[0060] ②Environmental action condition 2: Salt freeze-thaw cycle environmental action simulation test

[0061] Test specimens and environmental control requirements: Prepare 3 groups of specimens of type A and type B (9 specimens in each category), and take one group (3 specimens in each category, 6 specimens in total) to carry out three different salt saturation salt freeze-thaw cycle tests (referred to as FT1, FT2, and FT3 respectively). The number of salt freeze-thaw cycles is controlled within 40 times until the specimen is destroyed. The specimens are placed in a water-salt-temperature multi-field coupled environmental simulation test cylinder. The density of the coarse sand filled between the specimens is not based on the radial and vertical deformation of the constrained specimens. The main fluid medium in the roadbed structure environment is a Na2SO4 water-salt solution with a mass content of about 5%. The water-salt solution is injected into the water-salt-temperature multi-field coupled environmental simulation test cylinder through a water-salt circulation control system. The temperature control of the salt freeze-thaw cycle test is realized by the temperature control program of the main test box, the ambient temperature sensor in the box and the temperature sensors of different structural layers of the roadbed structure specimens buried in the test cylinder through a temperature synchronization control system. Temperature sensors are buried vertically on the surface of the roadbed structure sample at the cement concrete (asphalt concrete) surface layer, the lower interface of the surface layer, the bottom surface of the semi-rigid base layer (cement soil stabilized base layer), and the interface between the cushion layer and the soil base as temperature control monitoring points.

[0062] Temperature control requirements for each temperature control monitoring area of ​​the sample test environment:

[0063] The temperature control interval of the test specimen surface interface is set as follows: The interface temperature of the cement concrete (asphalt concrete) surface layer is the multi-year extreme minimum and maximum average temperature of the natural environment. The temperature control interval is [-25℃, 50℃], which is the temperature control interval in the main test chamber, and the temperature change interval of a salt freeze-thaw cycle is proposed to be: 25℃↘0℃↘-25℃↗0℃↗25℃↗50℃↘25℃. In the temperature range of [-25℃, 50℃], the temperature control points of 50℃ and -25℃ are maintained for 480 minutes, and the temperature control point of 0℃ is maintained for 120 minutes. The cooling and heating rates are 25-30℃ / 60min. The temperature gradient can be appropriately adjusted according to the actual freezing and thawing conditions of the specimens. It takes 24 hours to complete a temperature cycle.

[0064] The temperature control interval of the bottom surface of the semi-rigid base (cement soil stabilized base) is set as follows: the average of the lowest and highest temperatures measured in winter and summer at the bottom of the roadbed at the cement soil stabilized base of the road is monitored, and the temperature range of [-6℃, 25℃] is its temperature control range. In a salt freeze-thaw cycle, the temperature change range is controlled as follows: normal temperature 25℃↘0℃↘-6℃↗0℃↗25℃. In the temperature range of [-6℃, 25℃], the temperature control points of 25℃ and -6℃ are maintained for about 480 minutes respectively. The temperature control point of the temperature range of the structural layer needs to be controlled by the temperature synchronization control system of the experimental system in the first level, followed by the temperature control of the sample surface layer interface as the second level. The temperature control range at the interface between the cushion layer and the soil base is [4℃, 16℃], and the first and second level temperature control are used for coordinated adjustment. The cycle to complete a temperature cycle control interval is synchronized with the surface layer interface for 24 hours.

[0065] Control requirements for water-salt content in low-porosity media environments of three types of roadbed structures with different water-salt saturations:

[0066] The first group of salt freeze-thaw cycle tests FT1: The saturation of the main fluid medium (water-salt) in the low-porosity medium environment around the roadbed structure specimen is controlled at a water-salt content above the critical salt content and critical water content that causes the roadbed material to undergo salt expansion deformation and frost expansion deformation simultaneously in the salt expansion and frost expansion temperature range.

[0067] The second group of salt freeze-thaw cycle tests FT2: The saturation of the main fluid medium (water-salt) in the low-porosity medium environment around the roadbed structure specimen is controlled below the critical salt content that does not produce salt expansion deformation in the salt expansion and frost heave temperature range of the roadbed material, and only produces frost heave deformation and there is a convergence effect that causes salt migration and accumulation.

[0068] The third group of salt freeze-thaw cycle tests FT3: The saturation of the main fluid medium (water-salt) in the low-porosity medium environment around the roadbed structure specimen is controlled to a water-salt content below the critical water content that does not cause salt expansion deformation and frost expansion deformation in the salt expansion and frost expansion temperature range of the roadbed material, and does not cause the presence of convergence effect.

[0069] The water-salt content required for saturation control of the main fluid medium (water-salt) in the low-porosity medium environment around the above three groups of salt freeze-thaw cycle test specimens needs to be determined through on-site salt expansion-frost expansion experiments, and can also be selected based on the results of previous experimental studies; the water-salt fluid medium is input into the water-salt-temperature multi-field coupled environment simulation test cylinder at a controlled pressure through a water-salt circulation control system.

[0070] Observation and analysis of sample micro-damage: For each group of salt freeze-thaw cycle test specimens, one specimen was taken out for loading destruction test and sample micro-damage observation and analysis after completing 5 cycles, 10 cycles and until the specimen was destroyed.

[0071] ③ Environmental action condition 3: Dry-wet cycle + salt freeze-thaw cycle coupling test

[0072] Dry-wet cycle + salt freeze-thaw cycle coupling test combination

[0073] The experimental combination of the dry-wet cycle of three types of infiltration and the salt freeze-thaw cycle of three different water-salt saturations is shown in Table 1:

[0074] Table 1: Dry-wet cycle + salt freeze-thaw cycle coupling test combination

[0075]

[0076] Specimen grouping and quantity requirements: Prepare 4 groups of specimens of type A and type B (16 specimens in each category), and take one group of each (4 specimens in each category, 8 specimens in one group) to carry out simulation tests on the coupling effect of dry-wet cycle + salt freeze-thaw cycle.

[0077] Requirements for water, salt and temperature control and test cycle times for coupled test combinations:

[0078] The four groups of coupling tests DW1+FT1, DW1+FT2, DW2+FT1, and DW2+FT2 were carried out in the corresponding dry-wet cycle (DWx) and salt freeze-thaw cycle (FTx) water, salt, and temperature control requirements and test cycle periods according to the water, salt, and temperature control requirements and cycle test cycles corresponding to environmental action conditions 1 and 2. The total number of test cycles, the number of various test cycles, and the test combination sequence of each combination of coupling tests in the entire test cycle are designed as follows:

[0079] DW1+FT1 combination: 1st to 5th cycle DW1 → 6th to 10th cycle FT1 → 11th to 20th cycle DW1 → 21st to 30th cycle FT1 → 31st to 40th cycle DW1 → 41st to 50th cycle FT1;

[0080] DW1+FT2 combination: 1st to 5th cycle DW1→6th to 10th cycle FT2→11th to 20th cycle DW1→21st to 30th cycle FT2→31st to 40th cycle DW1→41st to 50th cycle FT2;

[0081] DW2+FT1 combination: 1st to 5th cycle DW2 → 6th to 10th cycle FT1 → 11th to 20th cycle DW2 → 21st to 30th cycle FT1 → 31st to 40th cycle DW2 → 41st to 50th cycle FT1;

[0082] DW2+FT2 combination: 1st to 5th cycle DW2 → 6th to 10th cycle FT2 → 11th to 20th cycle DW2 → 21st to 30th cycle FT2 → 31st to 40th cycle DW2 → 41st to 50th cycle FT2;

[0083] The above four combined coupling tests are carried out in sequence according to the cyclic order. When the total number of test cycles is less than 50, the specimen is damaged and the test group can be terminated.

[0084] Observation and analysis of sample micro-damage: After completing the 5th, 10th, 20th (or 40th), and 30th (or 50th) cycles, one sample was taken out from each of the four groups of coupled test samples for loading and destruction tests and observation and analysis of sample micro-damage.

[0085] Step 3: Carry out disaster resistance performance test of disaster prevention roadbed structure under environmental coupling in indoor water-salt-temperature multi-field coupling environmental simulation experimental system.

[0086] The test specimens are engineering disaster prevention roadbed structure specimens that have been optimized and designed based on the results of previous experimental research and numerical simulation. According to the second step coupling test DW1+FT1, DW1+FT2, DW2+FT1, and DW2+FT2, the four coupling effects of the roadbed structure were simulated to carry out the disaster resistance performance verification test of the vehicle load effect (static load is applied to the specimen). At the same time, the corresponding micro damage effect analysis was carried out to evaluate the disaster prevention effectiveness.

[0087] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Water-salt-temperature multi-field coupling environmental simulation test system, characterized by: It includes a hydraulic system (1), a main testing machine system (2) and a constant temperature water tank system (3); The hydraulic system (1) comprises a switch (4), an oil tank (5), a pressurizing handle (6), a box body (7), a pressure gauge (8), a pressurizing and depressurizing handle (9) and a pipeline assembly (10); The hydraulic system (1) is arranged on one side of the main test machine system (2), and the main test machine system (2) comprises a main box (15), a first compressor (14), a first condenser (11), a first drying filter (13), a first expansion valve (12), a first evaporator (20), a heating device (19), a fan assembly (18), an inner water tank water inlet (28), an inner water tank water outlet (29) and a first touch screen control system (16), and a pressure rod through hole (17) is opened on the main box (15); The constant temperature water tank system (3) is arranged on one side of the main testing machine system (2), and the constant temperature water tank system (3) comprises an inlet water pump (51), a return water pump (52), a circulating water pump (53), an external water tank main unit (45), a second compressor (44), a second touch screen control system (46), a return water pipe (47) and an inlet water pipe (48); The hydraulic system (1) is connected to the hollow oil cylinder (23) on the main test box of the main test machine system (2) through the corresponding pipeline in the pipeline assembly (10), and the constant temperature water tank system (3) is connected to the main test box of the main test machine system (2) through the water inlet pipe (48) and the water return pipe (47) of the external water tank main unit (45).

2. The water-salt-temperature multi-field coupling environment simulation test system according to claim 1 is characterized by: The first compressor (14) and the first condenser (11) are both installed in a control cabin of a main engine box (15), and the first compressor (14) and the first condenser (11) are connected via a copper pipe; The first evaporator (20) and the heating device (19) are installed inside a main test box of the main box (15).

3. The water-salt-temperature multi-field coupling environment simulation test system according to claim 1 is characterized by: The main housing (15) is internally installed with a reaction frame light bar (21), a reaction top plate (22), a reaction middle plate (27), a support rod (26) and a reaction bottom plate (32), and the reaction frame light bar (21), the reaction top plate (22), the reaction middle plate (27), the support rod (26) and the reaction bottom plate (32) form a reaction frame structure; A sample water box (40) is installed inside the main box (15), a sample cylinder (39) is arranged inside the sample water box (40), and a sample is placed inside the sample cylinder (39).

4. The water-salt-temperature multi-field coupling environment simulation test system according to claim 3 is characterized by: A pad (37) is also placed inside the sample tube (39), and the pad (37) is located above the sample.

5. The water-salt-temperature multi-field coupling environment simulation test system according to claim 3 is characterized by: A hollow oil cylinder (23) is installed below the reaction force top plate (22), a sleeve (24) is installed below the hollow oil cylinder (23), a pressure sensor (25) and a disc spring energy storage assembly (38) are installed in the sleeve (24), and a pressure shaft (36) is installed below the disc spring energy storage assembly (38).

6. The water-salt-temperature multi-field coupling environment simulation test system according to claim 1 is characterized by: A base (34) is installed below the main chassis (15), and four adjustable feet (35) are installed below the base (34). The four adjustable feet (35) are arranged in groups of two and are symmetrical in pairs. A roller shaft (33) is installed above the base (34).

7. The water-salt-temperature multi-field coupling environment simulation test system according to claim 1 is characterized by: The second compressor (44) and the second condenser (41) are installed in a control cabin inside the external water tank main unit (45), and the second compressor (44) and the second condenser (41) are connected by a copper pipe, and the second compressor (44), the second drying filter (43), the second condenser (41), the second expansion valve (42), and the second evaporator (50) are connected by a copper pipe, and the second evaporator (50) and the heating pipe (49) are installed inside the main test box of the external water tank main unit (45).

8. The water-salt-temperature multi-field coupling environment simulation test system according to claim 1 is characterized by: The water inlet pump (51) is connected to a water tank water inlet pipe (48), a main tank water inlet (30), and an inner tank water inlet (28) through pipelines, and the water return pump (52) is connected to a water return pipe (47), a main tank water outlet (31), and an inner tank water outlet (29) through pipelines.

9. Water-salt-temperature multi-field coupling environmental simulation test method, characterized by: The water-salt-temperature multi-field coupling environment simulation test system according to any one of claims 1 to 8 comprises the following steps: S1: Prepare at least two roadbed structure samples of different pavement types according to the roadbed structure characteristics of the target study area; S2: Using the water-salt-temperature multi-field coupling environmental simulation experimental system, three types of environmental action conditions are simulated, namely, dry-wet cycle, salt freeze-thaw cycle, and dry-wet cycle + salt freeze-thaw cycle coupling; S3: Accurately control the temperature, water-salt content and other parameters during the test through temperature sensors, water-salt circulation control systems and other equipment; S4: Real-time collection and recording of various parameters during the test, such as temperature, deformation, water-salt content, etc., and analysis of the collected data to reveal the damage and failure mechanism of the roadbed structure in a complex environment; S5: Design and prepare disaster-resistant roadbed structure specimens, conduct disaster resistance performance verification tests of the roadbed structure simulating the vehicle load effect according to the above-mentioned coupling effect, and evaluate the disaster prevention effectiveness.

10. The water-salt-temperature multi-field coupling environment simulation test method according to claim 9, characterized in that: In S1, the different road surface types include cement concrete road surface and asphalt concrete road surface.

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