Multi-field coupling model test device and test method under low-temperature phase change condition

Abstract

The invention discloses a multi-field coupling model test device and a test method under a low-temperature phase change condition. The environment load, the environment temperature and underground water of a rock-soil body in a construction process are simulated; the method comprises the following steps: acquiring pressure data of a rock-soil body when an environment load of the rock-soil body is simulated, temperature data of the rock-soil body when an environment temperature of the rock-soil body is simulated, and water level data when underground water in a construction process is simulated; therefore, the stress distribution rule, the temperature distribution rule and the moisture migration rule of the rock-soil body under the influence of the load and the freezing time can be obtained, and winter construction of seasonal frozen soil can be guided. The device is simple in structure, high in applicability and capable of reflecting real rock-soil layer distribution and underground water level height in nature, loads are applied by considering stress distribution in a real environment, different freezing times are applied according to rock-soil layer freezing depths in different northern areas in winter, and the basic requirement for reflecting a prototype rule in a test principle is met.

Description

Technical Field

[0001] The invention relates to the technical field of temperature-stress analysis under low-temperature phase change conditions of rock and soil bodies, and in particular to a multi-field coupling model test device and a test method under low-temperature phase change conditions. Background Art

[0002] In northern my country, seasonal frozen soil has always been a key issue in winter construction. The frost heave of rock and soil is affected by factors such as temperature, moisture, and composition. When the water content inside the rock and soil exceeds the initial frost heave moisture content, the water in the rock and soil undergoes a phase change from liquid to solid under the influence of the negative temperature gradient, and the unfrozen water migrates to the freezing front to form a new frozen zone. Due to the differences in pre-freezing moisture content, ambient temperature, and rock and soil properties, there are also large differences in the freezing rate, freezing depth, and frost heave force in the rock and soil. If the influence of various frost heave factors is not taken into account during the design and construction process, and the frost heave analysis of the rock and soil is not fully performed, the building (structure) will be severely deformed due to the frost heave of the rock and soil, which will cause uneven settlement and tilt of the building foundation, structural cracks and structural damage to the structure, affecting construction safety and the normal use of the building (structure).

[0003] At present, most of the model tests on the frost heave problem of rock and soil are carried out around the impact of frost heave force on buildings (structures), and the test equipment is relatively simple. Since the strata in the actual nature are complex and diverse, the prototypes that the existing experimental equipment can involve are limited and cannot fully reflect factors such as water migration and freezing depth. There is a certain difference between the test equipment and the actual seepage generated by groundwater. Summary of the invention

[0004] The invention discloses a multi-field coupling model test device and a test method under low-temperature phase change conditions to overcome the above technical problems.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] A multi-field coupling model test device under low-temperature phase change conditions, comprising: a servo loading system, a rock and soil simulation module, a refrigeration system, an information acquisition system, and a groundwater application system;

[0007] The rock and soil simulation module is used to carry test materials to simulate the rock and soil during the construction process;

[0008] The servo loading system is used to apply load to the test material to simulate the environmental load of the rock and soil body during the construction process;

[0009] The refrigeration system is used to cool the test materials to simulate the ambient temperature of the rock and soil body during the construction process;

[0010] The groundwater application system is used to apply water pressure to the test material to simulate the groundwater during the construction process;

[0011] The information acquisition system is used to obtain the pressure data of the rock and soil body when simulating the environmental load of the rock and soil body, the temperature data of the rock and soil body when simulating the environmental temperature of the rock and soil body, and the water level data when simulating the groundwater during the construction process, so as to obtain the stress distribution diagram, temperature distribution diagram and water level distribution diagram of the rock and soil body, and then obtain the stress distribution law, temperature distribution law and moisture migration law of the rock and soil body under the influence of load and freezing time, and then guide winter construction on seasonal frozen soil.

[0012] Furthermore, the rock and soil simulation module includes a model box, support rods, permeable stones, and a loading plate on the top of the box;

[0013] The side wall surface of the permeable stone is connected to the side wall surface inside the model box;

[0014] The test material is arranged above the permeable stone;

[0015] The bottom of the permeable stone and the inner wall and bottom of the model box form a water tank;

[0016] The support rod is arranged inside the water tank, and the top of the support rod is fixedly connected to the permeable stone, and the bottom of the support rod is fixedly connected to the bottom surface of the model box body;

[0017] The box top loading plate is disposed on the top of the test material and abuts against the test material; and the box top loading plate can move along the side wall surface of the model box;

[0018] A heat-insulating layer is arranged outside the model box.

[0019] Furthermore, a telescopic structure is provided on the side wall surface of the model box;

[0020] The box top loading plate is fixedly connected to the side wall surface of the model box; and the box top loading plate moves along the side wall surface of the model box through the telescopic structure.

[0021] Further, the groundwater application system includes a water storage tank, a water inlet pipe, and a water outlet pipe;

[0022] The water storage tank is communicated with the water inlet pipe and the water outlet pipe respectively;

[0023] The water inlet pipe is connected to a water source, and the water outlet pipe is connected to the water tank;

[0024] A control valve is arranged on the water outlet pipe.

[0025] Further, the servo loading system includes a press computer control terminal, a reaction frame, a press, and a press head;

[0026] The reaction frame is fixedly arranged on the ground and is used to fix the press;

[0027] The pressure head is fixedly arranged at the bottom of the press; and the press can apply a load to the loading plate on the top of the box through the pressure head, and then can apply a load to the test material;

[0028] The bottom of the pressure head abuts against the top of the loading plate at the top of the box body;

[0029] The press computer control terminal is in communication connection with the press.

[0030] Furthermore, the refrigeration system includes a compressor, a condenser tube, and an evaporator tube;

[0031] The compressor is connected to the condenser and the evaporator respectively;

[0032] The evaporation tube is arranged inside the loading plate on the top of the box, so as to cool the test material by the contact between the loading plate on the top of the box and the test material;

[0033] An expansion valve is arranged on the evaporating tube.

[0034] Furthermore, the information collection system includes a sensor computer monitoring terminal, a static and dynamic acquisition instrument, several stress sensors, several temperature sensors, a water level measuring tube,

[0035] The stress sensor and the temperature sensor are both arranged inside the test material; and a plurality of the stress sensors / temperature sensors are arranged in sequence inside the test material along the direction from the top to the bottom of the model box;

[0036] The stress sensor is used to obtain pressure data of the test material when a load is applied to the test material;

[0037] The temperature sensor is used to obtain temperature data of the test material when the test material is cooled;

[0038] The stress sensor is communicatively connected with the sensor computer monitoring terminal through the static and dynamic data acquisition instrument, so as to transmit the pressure data to the computer through the static and dynamic data acquisition instrument;

[0039] The temperature sensor is communicatively connected to the sensor computer monitoring terminal to transmit the temperature data to the sensor computer monitoring terminal;

[0040] The water level measuring tube is used to obtain water level data in the model box.

[0041] A test method for a multi-field coupling model test device under low-temperature phase change conditions comprises the following steps:

[0042] S1: Laying a test material in a model box, and sequentially arranging a stress sensor and a temperature sensor inside the test material in a direction from the top to the bottom of the model box;

[0043] S2: Open the control valve and fill water into the water storage tank of the groundwater application system. When the water tank in the model box is full, observe through the water level measuring tube until the water level in the test material remains constant;

[0044] S3: Start the refrigeration system and the information acquisition system, obtain the temperature data of the test material, and record the start-up time of the refrigeration system, so as to obtain a temperature distribution diagram of the temperature changing with the start-up time through the temperature data and the start-up time of the refrigeration system; and obtain the water level data when the temperature data is zero degrees through the water level measuring tube;

[0045] S4: Start the servo loading system to load the test material and obtain the pressure data of the test material under the starting time and temperature data; then obtain the temperature distribution law, moisture migration law and stress distribution law of the test material under different loads and different starting times, so as to provide data support for the foundation pit stability analysis during the seasonal frozen soil winter construction.

[0046] Beneficial effects: The multi-field coupling model test device and test method under low-temperature phase change conditions of the present invention respectively simulates the environmental load, environmental temperature and groundwater of the rock and soil body during the construction process through a servo loading system, a refrigeration system and a groundwater application system, and obtains the pressure data of the rock and soil body when simulating the environmental load of the rock and soil body, the temperature data of the rock and soil body when simulating the environmental temperature of the rock and soil body and the water level data when simulating the groundwater during the construction process through an information acquisition system, so as to obtain the stress distribution diagram, temperature distribution diagram and water level distribution diagram of the rock and soil body, and then the stress distribution law, temperature distribution law and water migration law of the rock and soil body under the influence of load and freezing time can be obtained, and then the winter construction of seasonal frozen soil can be guided. The present invention has a simple structure, and can use the refrigeration system to apply a low-temperature field, use the servo loading system to apply a stress field, and use the groundwater application system to simulate groundwater, so as to obtain the water migration law after freezing, and obtain the influence law between the low-temperature field, seepage field and stress field. The present invention has strong applicability, can reflect the actual distribution of rock and soil layers and groundwater levels in nature, consider the stress distribution in the real environment to apply loads, and impose different freezing times according to the freezing depth of rock and soil layers in different northern regions in winter, thus meeting the basic requirement of reflecting prototype laws in the test principles. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0048] Figure 1 It is a schematic diagram of the overall structure of a multi-field coupling model test device under low-temperature phase change conditions of the present invention;

[0049] Figure 2 It is a schematic diagram of the structure of the servo loading device of the present invention;

[0050] Figure 3 It is a schematic diagram of the structure of the model box and groundwater application system of the present invention;

[0051] Figure 4 It is a structural schematic diagram of the information collection system of the present invention;

[0052] Figure 5 It is a schematic diagram of the refrigeration system structure of the present invention;

[0053] Figure 6 The present invention is a flow chart of a multi-field coupling model test method under low-temperature phase change conditions. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0055] This embodiment introduces a multi-field coupling model test device under low temperature phase change conditions. Figure 1 As shown in Figure 1, a multi-field coupling model test device under low temperature phase change conditions is shown in Figure 1. Figure 1-5 As shown, it includes a servo loading system 1, a rock and soil simulation module 2, a refrigeration system 3, an information acquisition system 4, and a groundwater application system 5;

[0056] The rock and soil simulation module 2 is used to carry test materials to simulate the rock and soil during the construction process;

[0057] The servo loading system 1 is used to apply load to the test material to simulate the environmental load of the rock and soil body during the construction process;

[0058] The refrigeration system 3 is used to cool the test materials to simulate the ambient temperature of the rock and soil body during the construction process;

[0059] The groundwater application system 5 is used to apply water pressure to the test material to simulate the groundwater during the construction process;

[0060] The information acquisition system 4 is used to obtain the pressure data of the rock and soil body when simulating the environmental load of the rock and soil body, the temperature data of the rock and soil body when simulating the environmental temperature of the rock and soil body, and the water level data when simulating the groundwater during the construction process, so as to obtain the stress distribution diagram, temperature distribution diagram and water level distribution diagram of the rock and soil body, and then obtain the stress distribution law, temperature distribution law and moisture migration law of the rock and soil body under the influence of load and freezing time, so as to guide winter construction on seasonal frozen soil.

[0061] Preferably, the rock and soil simulation module 2 includes a model box 21, a test material 23, a support rod 25, a permeable stone 26, and a loading plate 28 on the top of the box;

[0062] The permeable stone 26 is fixedly arranged on the side wall surface inside the model box 21;

[0063] The test material 23 is placed above the permeable stone 26;

[0064] The bottom of the permeable stone 26 and the inner wall of the model box 21 form a water tank 24;

[0065] The support rod 25 is disposed inside the water tank 24, the top of the support rod 25 is fixedly connected to the permeable stone 26, and the bottom of the support rod 25 is fixedly connected to the bottom surface of the model box 21;

[0066] The box top loading plate 28 is disposed on the top of the test material 23 and abuts against the test material 23; the box top loading plate 28 can move along the side wall surface of the model box 21;

[0067] A heat-insulating layer 22 is disposed outside the model box 21 .

[0068] Specifically, the test material in this embodiment can be sand, which can obtain the temperature distribution law, moisture migration law and stress distribution law under low-temperature phase change conditions in the sandy soil layer; it can also be a test material similar to the rock and soil body in the study section. According to the actual geological materials of the foundation pit construction, test materials similar to the actual stratum materials can be selected to carry out layered laying of materials to simulate the conditions at the construction site, which can then be used to guide the actual engineering construction.

[0069] Preferably, a telescopic structure 27 is provided on the side wall surface of the model box 21;

[0070] The box top loading plate 28 is fixedly connected to the side wall of the model box 21 ; and the box top loading plate 28 moves along the side wall of the model box 21 through the telescopic structure 27 .

[0071] Preferably, the groundwater application system 5 comprises a water storage tank 51, a water inlet pipe 52, and a water outlet pipe 53;

[0072] The water storage tank 51 is communicated with the water inlet pipe 52 and the water outlet pipe 53 respectively;

[0073] The water inlet pipe 52 is connected to the water source, and the water outlet pipe 53 is connected to the water tank 24;

[0074] The water outlet pipe 53 is provided with a control valve 54 .

[0075] Specifically, the groundwater application system 5 is connected to the water tank 24 to apply water pressure to the test material 23. The water tank 51 is provided with a water inlet and a water outlet, and the water level of the water tank 51 is kept constant by connecting the water source through the water inlet pipe 52, and the water outlet pipe 53 is connected to the water tank 24, and the switch is controlled by the control valve 54.

[0076] The outermost layer of the model box 21 is a heat-insulating material forming a heat-insulating layer 22, which wraps the model box 21 to prevent the low temperature applied to the test material through the loading plate 28 on the top of the box from escaping. The outer shell of the model box 21 is welded by a 10 cm thick steel plate. The inner part of the box is divided into two parts. The test material 23 is located above the permeable stone 26 inside the model box 21, with a size of 1m×1m×1m; the water tank 24 is located below the permeable stone 26, with a size of 1m×1m×0.25m, and is separated by the permeable stone 26. When welding, the steel plate leaves a groove at the position of the permeable stone 26, and the permeable stone 26 is fixed to the groove with waterproof glue. Position; the water tank 24 is isolated from the test material 23 by the permeable stone 26; in order to prevent the permeable stone 26 from being damaged by the load of the test material above, a support rod 25 for supporting the permeable stone 26 is added inside the water tank 24. The telescopic structure 27 is a common technology in the field, which can shrink as the loading plate 28 on the top of the box body descends. The telescopic structure 27 of this embodiment is integrated with the model box body through a plastic film. The plastic film has a certain strength and can be folded into a certain space for deformation. The plastic film has a built-in spring and an iron sheet. When the load is applied from the top, the iron sheet descends. When the load disappears, the spring resets the iron sheet. The loading plate 28 on the top of the box body is located above the test material 23, which is also the position where low temperature is applied. Among them, the loading plate is pushed down by the pressure head 14. When the pressure head 14 is pushed by the press, the loading plate presses the telescopic structure downward and moves.

[0077] Preferably, the servo loading system 1 comprises a press computer control terminal 11, a reaction frame 12, a press 13, and a pressing head 14;

[0078] The reaction frame 12 is fixedly arranged on the ground and used to fix the press 13, so that the press 13 can apply a load to the top loading plate 28 of the box through the pressing head 14, and further apply a load to the test material 23;

[0079] The press machine 13 is fixedly arranged on the top of the reaction frame 12;

[0080] The pressing head 14 is fixedly arranged at the bottom of the press 13;

[0081] The bottom of the pressure head 14 abuts against the top of the box top loading plate 28;

[0082] The press computer control terminal 11 is in communication connection with the press 13 .

[0083] Specifically, the reaction frame 12 in this embodiment is provided with two vertical rods 121 and a cross beam 122. The vertical rod 121 is fixed on the ground and the height is adjustable. The two ends of the cross beam 122 are respectively fixed on the top of the two vertical rods 121. The height of the cross beam can be adjusted by rotating the bolts. The press 13 is fixedly arranged in the middle of the cross beam 122 at the top of the reaction frame 12 and is located above the test material 23. The pressure head 14 is in contact with the loading plate 28 at the top of the box. The computer control terminal 11 of the press controls the press 13 to apply load and displacement, and applies different loading rates and peak loads. The pressure head 14 is located at the lower part of the press 13. A displacement sensor is provided on the pressure head 14, which can monitor the displacement of the top of the rock and soil test material in real time.

[0084] Preferably, the refrigeration system 3 includes a compressor 31, a condenser tube 32, and an evaporator tube 34;

[0085] The compressor 31 is connected to the condenser tube 32 and the evaporator tube 34 respectively;

[0086] The evaporation tube 34 is disposed inside the box top loading plate 28 so as to cool the test material 23 by the contact between the box top loading plate 28 and the test material 23;

[0087] The evaporation tube 34 is provided with an expansion valve 33 .

[0088] Specifically, the refrigerant vaporizes and absorbs heat in the evaporation tube 34, cooling the test material; condenses and releases heat in the condensation tube 32, and the refrigerant flow is controlled by the expansion valve 33. The evaporation tube 34 is laid inside the top loading plate 28 of the box body, and moves as the top loading plate 28 of the box body compresses the test material.

[0089] Preferably, the information collection system 4 includes a sensor computer monitoring terminal 41, a static and dynamic collection instrument 42, a plurality of stress sensors 43, a plurality of temperature sensors 44, and a water level measuring tube 45.

[0090] The stress sensor 43 and the temperature sensor 44 are both arranged inside the test material 23; and a plurality of the stress sensors 43 / temperature sensors 44 are sequentially arranged at different depths of the test material 23 from the top to the bottom of the model box.

[0091] The stress sensor 43 is used to obtain pressure data of the test material 23 when a load is applied to the test material 23;

[0092] The temperature sensor 44 is used to obtain temperature data of the test material 23 when the test material is cooled;

[0093] The stress sensor 43 is connected to the sensor computer monitoring terminal 41 through the static and dynamic acquisition instrument 42 to transmit the pressure data to the computer through the static and dynamic acquisition instrument 42; specifically, the stress sensor 43 transmits the strain signal. Since the data of the stress sensor cannot be directly read through the sensor computer monitoring terminal 41, the data format obtained by the pressure sensor is converted through the static and dynamic acquisition instrument 42 so that the computer can read the pressure data collected by the stress sensor. The static and dynamic acquisition instrument 42 is located on the side of the model box 21.

[0094] The temperature sensor 44 is communicatively connected to the sensor computer monitoring terminal 41 to transmit the temperature data to the sensor computer monitoring terminal 41 .

[0095] Specifically, the temperature sensor 44 transmits a 485 signal and connects to the sensor computer monitoring terminal 41 through a USB adapter to collect data;

[0096] The water level measuring tube 45 is used to obtain the water level in the model box 21 to simulate the groundwater level.

[0097] Specifically, the water level measuring tube 45 is located on the side of the model box 21. The water level measuring tube is transparent and has scales, and the water level data can be directly read.

[0098] The servo loading system 1 of this embodiment applies a load to the top of the test material 23 by bolting the loading plate 28 on the top of the box; the evaporation tube 34 in the refrigeration system 3 is located inside the loading plate 28 on the top of the box, and applies a low temperature to the top of the test material 23.

[0099] This embodiment also discloses a test method for a multi-field coupling model test device under low temperature phase change conditions, such as Figure 6As shown, the following steps are included:

[0100] S1: Laying a test material in a model box 21, and sequentially arranging a stress sensor 43 and a temperature sensor 44 inside the test material 23 along a direction from the top to the bottom of the model box;

[0101] Specifically, the test materials in this embodiment are determined according to the parameters of the selected rock and soil mass in the study section, and the similarity scale is determined. Test materials similar to the rock and soil mass in the study section are selected, and the soil, sand, rock and other materials with parameters (including but not limited to mechanical parameters) and properties after freezing similar to those of the rock and soil mass in the study section are laid in layers in the model box, and pressure sensors and temperature sensors are arranged while laying the materials.

[0102] S2: Open the control valve and inject water into the water storage tank of the groundwater application system. When the water tank in the model box is full, water seeps into the test material through the permeable stone and is observed through the water level measuring tube until the water level in the test material remains constant.

[0103] Specifically, due to the water permeability of the test material, when the infiltrated water in the test material reaches a certain height, the water can no longer pass through the test material, that is, the water level in the test material will be maintained at a certain position.

[0104] S3: starting the refrigeration system 3 and the information acquisition system 4, obtaining temperature data of the test material, and recording the start-up time of the refrigeration system 3, so as to obtain a temperature distribution diagram of temperature change with start-up time through the temperature data and the start-up time of the refrigeration system 3;

[0105] The water level data when the temperature data is zero degrees can be obtained through the water level measuring tube;

[0106] Specifically, when the startup time of the refrigeration system 3 exceeds the set stable startup time threshold, the temperature data is collected by burying a temperature sensor at a different depth from the test material, and when the temperature data is below zero degrees, the location of the temperature sensor is regarded as the freezing position, and the freezing depth is determined according to the location of the temperature sensor below zero degrees, and then the freezing depth at different freezing times is analyzed.

[0107] Specifically, through the water level measuring tube, the changes in water level data at different freezing times are observed, and then the water level changes are analyzed, that is, the water level value when the test material reaches the freezing temperature of zero degrees is compared with the unfrozen water level value. The above is the process of analyzing water level changes at different freezing times.

[0108] S4: Start the servo loading system 1, load the test material 23, obtain the displacement data of the pressure head 14 and the pressure data of the test material at the starting time and temperature data; then obtain the temperature distribution law, moisture migration law and stress distribution law of the test material under different loads and different starting times, and provide data support for the foundation pit stability analysis during winter construction on seasonally frozen soil.

[0109] Specifically, turn on the power to make the refrigeration system work, and start the information collection system at the same time. After working for a certain period of time, collect data from the temperature sensor, analyze the freezing depth at different freezing times, and observe the changes in the water level measuring tube to analyze the water level changes.

[0110] Specifically, the servo loading system is started, the test material is loaded, the pressure head displacement data and the stress sensor data are collected, and step S3 is repeated under different loads to obtain the temperature distribution law, moisture migration law and stress distribution law under different loads and different freezing times.

[0111] Example 1: A foundation pit project is taken as the research object. The research section is 30m long, 30m wide and 30m high. The overlying soil layers are miscellaneous fill, silty silty clay, strongly weathered dolomite and medium weathered dolomite. The model box size is 1m×1m×1m. The similarity scale is 1:30. Similar materials are selected according to the similarity scale. Mechanical, thermal and permeability tests are performed on the prepared similar materials to ensure that the similar materials meet the test requirements. The above test materials are laid from bottom to top. First, the medium weathered dolomite layer is laid. After the maintenance of the medium weathered dolomite layer is completed, the strongly weathered dolomite layer is laid. Finally, the silty silty clay layer and the miscellaneous fill layer are laid. At the same time, the underground continuous wall and the steel support are arranged in the rock and soil layer according to the construction organization design. Strain gauges are laid on the underground continuous wall, and axial force gauges are laid on the steel support. When a certain amount of water is stored in the water tank, open the control valve to allow water to seep into the rock and soil layer through the permeable stone, adjust the height of the water tank, observe the height of the water in the water level measuring tube, and fix the water tank after reaching the groundwater level of the actual working condition. Turn on the power to make the refrigeration system work, and collect data from the temperature sensor and stress sensor in the rock and soil layer, as well as the strain gauge of the ground-connected wall and the steel support axial force gauge after working for a certain period of time, analyze the freezing depth at different freezing times, the influence of the frost heave force in the rock and soil layer on the stability of the foundation pit, and observe the water level changes in the water level measuring tube.

[0112] Example 2: Sand is used as the research object to study the changes in the physical and mechanical properties of sandy soil layers under the coupling of low temperature, stress and seepage. Sand is laid in the model box, and temperature and stress sensors are arranged. The groundwater level is applied in the same way as in Example 1. Turn on the power to make the refrigeration system work, collect the data of the temperature sensor and stress sensor in the sandy soil layer after working for a certain period of time, start the servo loading system, load the test material, collect the data of the pressure head displacement, temperature sensor and stress sensor, and repeat the above steps under different loads to obtain the temperature distribution law, water migration law and stress distribution law under different loads and different freezing times.

[0113] The present embodiment provides a multi-field coupling model test device and test method under low-temperature phase change conditions. The environmental load, environmental temperature and groundwater of the rock and soil body during the construction process are simulated by a servo loading system, a refrigeration system and a groundwater application system respectively. The pressure data of the rock and soil body when simulating the environmental load of the rock and soil body, the temperature data of the rock and soil body when simulating the environmental temperature of the rock and soil body and the water level data when simulating the groundwater during the construction process are obtained by the information acquisition system, so as to obtain the stress distribution diagram, temperature distribution diagram and water level distribution diagram of the rock and soil body, and then the stress distribution law, temperature distribution law and water migration law of the rock and soil body under the influence of load and freezing time can be obtained, so as to guide winter construction of seasonal frozen soil. The present embodiment has a simple structure, and can apply a low-temperature field by using a refrigeration system, apply a stress field by using a servo loading system, and simulate groundwater by using a groundwater application system. The freezing depth and stress distribution of the rock and soil layer are obtained by using a temperature sensor and a stress sensor. The water migration law after freezing is obtained by observing the water level measuring tube, and the influence law between the low-temperature field, the seepage field and the stress field is obtained. In addition, this embodiment has strong applicability, can reflect the actual distribution of rock and soil layers and groundwater levels in nature, consider the stress distribution in the real environment to apply loads, and impose different freezing times according to the freezing depth of rock and soil layers in different northern regions in winter, thus meeting the basic requirements of reflecting prototype laws in the test principles.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-field coupling model test device under low temperature phase change conditions, characterized in that: include: Servo loading system (1), rock and soil simulation module (2), refrigeration system (3), information acquisition system (4), groundwater application system (5); The rock and soil simulation module (2) is used to carry the test material (23) to simulate the rock and soil during the construction process; The servo loading system (1) is used to apply load to the test material to simulate the environmental load of the rock and soil body during the construction process; The refrigeration system (3) is used to cool the test material to simulate the ambient temperature of the rock and soil body during the construction process; The groundwater application system (5) is used to apply water pressure to the test material to simulate the groundwater during the construction process; The information acquisition system (4) is used to obtain the pressure data of the rock and soil body when simulating the environmental load of the rock and soil body, the temperature data of the rock and soil body when simulating the environmental temperature of the rock and soil body, and the water level data when simulating the groundwater during the construction process, so as to obtain the stress distribution diagram, temperature distribution diagram and water level distribution diagram of the rock and soil body, and then obtain the stress distribution law, temperature distribution law and water migration law of the rock and soil body under the influence of load and freezing time, and then guide the winter construction of seasonal frozen soil.

2. A multi-field coupling model test device under low temperature phase change conditions according to claim 1, characterized in that: The rock and soil simulation module (2) comprises a model box (21), support rods (25), permeable stones (26), and a loading plate (28) on the top of the box; The side wall surface of the permeable stone (26) is connected to the side wall surface inside the model box (21); The test material (23) is arranged above the permeable stone (26); The bottom of the permeable stone (26) forms a water tank (24) with the inner wall and bottom of the model box (21); The support rod (25) is arranged inside the water tank (24), and the top of the support rod (25) is fixedly connected to the permeable stone (26), and the bottom of the support rod (25) is fixedly connected to the bottom surface of the model box (21); The box top loading plate (28) is disposed on the top of the test material (23) and abuts against the test material (23); and the box top loading plate (28) can move along the side wall surface of the model box (21); A heat-insulating layer (22) is arranged outside the model box (21).

3. A multi-field coupling model test device under low temperature phase change conditions according to claim 2, characterized in that: A telescopic structure (27) is provided on the side wall surface of the model box (21); The box top loading plate (28) is fixedly connected to the side wall surface of the model box (21); and the box top loading plate (28) moves along the side wall surface of the model box (21) through the telescopic structure (27).

4. A multi-field coupling model test device under low temperature phase change conditions according to claim 2, characterized in that: The groundwater application system (5) comprises a water storage tank (51), a water inlet pipe (52), and a water outlet pipe (53); The water storage tank (51) is connected to the water inlet pipe (52) and the water outlet pipe (53) respectively; The water inlet pipe (52) is connected to a water source, and the water outlet pipe (53) is connected to the water tank (24); The water outlet pipe (53) is provided with a control valve (54).

5. The multi-field coupling model test device under low temperature phase change conditions according to claim 2, characterized in that: The servo loading system (1) comprises a press computer control terminal (11), a reaction frame (12), a press (13), and a press head (14); The reaction frame (12) is fixedly arranged on the ground and is used to fix the press (13); The pressing head (14) is fixedly arranged at the bottom of the press (13); and the press (13) can apply a load to the loading plate (28) at the top of the box through the pressing head (14), thereby applying a load to the test material (23); The bottom of the pressure head (14) abuts against the top of the loading plate (28) at the top of the box; The press computer control terminal (11) is communicatively connected with the press (13).

6. The multi-field coupling model test device under low temperature phase change conditions according to claim 2, characterized in that: The refrigeration system (3) comprises a compressor (31), a condenser tube (32), and an evaporator tube (34); The compressor (31) is connected to the condenser (32) and the evaporator (34) respectively; The evaporation tube (34) is arranged inside the box top loading plate (28) so as to cool the test material (23) by the contact between the box top loading plate (28) and the test material (23); The evaporation tube (34) is provided with an expansion valve (33).

7. The multi-field coupling model test device under low temperature phase change conditions according to claim 2, characterized in that: The information collection system (4) comprises a sensor computer monitoring terminal (41), a static and dynamic data collection instrument (42), a plurality of stress sensors (43), a plurality of temperature sensors (44), and a water level measuring tube (45). The stress sensor (43) and the temperature sensor (44) are both arranged inside the test material (23); and a plurality of the stress sensors (43) / temperature sensors (44) are arranged in sequence inside the test material (23) along a direction from the top to the bottom of the model box; The stress sensor (43) is used to obtain pressure data of the test material (23) when a load is applied to the test material (23); The temperature sensor (44) is used to obtain temperature data of the test material (23) when the test material is cooled; The stress sensor (43) is connected to the sensor computer monitoring terminal (41) through the static and dynamic data acquisition instrument (42) so as to transmit the pressure data to the computer through the static and dynamic data acquisition instrument (42); The temperature sensor (44) is communicatively connected to the sensor computer monitoring terminal (41) to transmit the temperature data to the sensor computer monitoring terminal (41); The water level measuring tube (45) is used to obtain water level data in the model box (21).

8. The test method of a multi-field coupling model test device under low temperature phase change conditions according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: Laying a test material in a model box, and sequentially arranging a stress sensor and a temperature sensor inside the test material in a direction from the top to the bottom of the model box; S2: Open the control valve and fill water into the water storage tank of the groundwater application system. When the water tank in the model box is full, observe through the water level measuring tube until the water level in the test material remains constant; S3: Start the refrigeration system and the information acquisition system, obtain the temperature data of the test material, and record the start-up time of the refrigeration system, so as to obtain a temperature distribution diagram of the temperature changing with the start-up time through the temperature data and the start-up time of the refrigeration system; and obtain the water level data when the temperature data is zero degrees through the water level measuring tube; S4: Start the servo loading system to load the test material and obtain the pressure data of the test material under the starting time and temperature data; then obtain the temperature distribution law, moisture migration law and stress distribution law of the test material under different loads and different starting times, so as to provide data support for the foundation pit stability analysis during the seasonal frozen soil winter construction.

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