One-dimensional soil column freezing-seepage intelligent regulation system and testing method under axial loading

Abstract

The present invention discloses a one-dimensional soil column freezing-seepage intelligent regulation system and a testing method under axial loading, specifically relating to the technical field of soil seepage. The system includes a one-dimensional soil column freezing apparatus, a freezing cycle device, an axial loading device, and a seepage device. The one-dimensional soil column freezing apparatus includes a soil column mold and a freezing chamber. The freezing chamber is connected to the freezing cycle device for unidirectionally freezing the soil body. The axial loading device is used to apply an axial load to the soil body. The seepage device includes a PID controller, a seepage liquid storage tank, a seepage inlet pipe, a seepage outlet pipe, a peristaltic pump, and a flowmeter. Both the seepage inlet pipe and the seepage outlet pipe are connected to the soil column mold. The peristaltic pump connected to the seepage inlet pipe and the flowmeter connected to the seepage outlet pipe are both connected to the PID controller. The PID controller can adjust the delivery flow rate of the peristaltic pump according to the signal output by the flowmeter. The present invention can maintain the stable seepage of the soil body in the freezing test and improve the accuracy and reliability of the test results.

Description

Technical Field

[0001] The present invention relates to the technical field of soil seepage, and particularly to a one-dimensional soil column freezing-seepage intelligent regulation system and a testing method under axial loading. Background Technique

[0002] The artificial ground freezing method is a green construction method widely used in the construction of underground spaces in coastal areas. It has the characteristics of good water sealing, strong adaptability, convenient and environmentally friendly construction, and has been widely applied to the construction of subway tunnels in soft soil areas, especially the construction of connection channels. However, when the project is near cross-river (cross-sea) tunnels, surface and groundwater discharge channels, and the top and bottom plates of adjacent aquifers, there is still a large seepage situation. In actual projects, seepage and soil freezing often interact and influence each other.

[0003] When simulating the soil seepage process, it is necessary to ensure that the inflow and outflow of seepage are basically the same, so as to ensure the stability of seepage inside the soil. However, the existing devices cannot intelligently adjust the seepage flow according to the inflow and outflow of seepage, which affects the stability of seepage. Summary of the Invention

[0004] The purpose of the present invention is to provide a one-dimensional soil column freezing-seepage intelligent regulation system and a testing method under axial loading to solve the above problems existing in the prior art, and to be able to maintain the stable seepage of the soil in the freezing test, and improve the accuracy and reliability of the test results.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] The present invention provides a one-dimensional soil column freezing-seepage intelligent regulation system under axial loading, including a one-dimensional soil column freezing instrument, a freezing cycle device, an axial loading device, and a seepage device. The one-dimensional soil column freezing instrument includes a soil column mold and a freezing chamber placed under the soil column mold. The soil column mold is used to fill the soil. The freezing chamber is connected and communicated with the freezing cycle device and is used to unidirectionally freeze the soil. The axial loading device is used to apply an axial load to the soil. The soil column mold includes a seepage inlet and a seepage outlet. The seepage device includes a PID controller, a seepage liquid storage tank, a seepage inlet pipe, a seepage outlet pipe, a peristaltic pump, and a flow meter. The seepage liquid storage tank is connected and communicated with the seepage inlet through the seepage inlet pipe. The seepage outlet pipe is connected and communicated with the seepage outlet. The peristaltic pump is connected to the seepage inlet pipe. The flow meter is connected to the seepage outlet pipe. Both the peristaltic pump and the flow meter are signal-connected to the PID controller. The PID controller can adjust the delivery flow of the peristaltic pump according to the signal output by the flow meter.

[0007] Preferably, it further includes a plurality of temperature sensors. A plurality of temperature monitoring holes are provided in the side wall of the soil column mold from top to bottom. The temperature sensors can be inserted into the soil through the temperature monitoring holes to monitor the temperatures at different positions of the soil.

[0008] Preferably, an observation window is further provided in the side wall of the soil column mold.

[0009] Preferably, the axial loading device includes a loading controller, a base, a loading head, a driving device and a pressure sensor. The one-dimensional soil column freezing instrument is placed on the base. The driving device is connected to the loading head. The pressure sensor is provided on the loading head. The driving device and the pressure sensor are both signal-connected to the loading controller.

[0010] Preferably, it further includes a temperature boundary control device. The temperature boundary control device includes a temperature control circulating liquid inlet pipe, a temperature control circulating liquid outlet pipe and a temperature control circulating pump. The loading head includes a loading head inlet and a loading head outlet. The loading head inlet is connected and communicated with the outlet of the temperature control circulating pump through the temperature control circulating liquid inlet pipe. The loading head outlet is connected and communicated with the inlet of the temperature control circulating pump through the temperature control circulating liquid outlet pipe.

[0011] Preferably, the freezing cycle device includes a freezing cycle liquid inlet pipe, a freezing cycle liquid outlet pipe and a freezing cycle pump. The freezing chamber includes a freezing chamber inlet and a freezing chamber outlet. The freezing chamber inlet is connected and communicated with the outlet of the freezing cycle pump through the freezing cycle liquid inlet pipe. The freezing chamber outlet is connected and communicated with the inlet of the freezing cycle pump through the freezing cycle liquid outlet pipe.

[0012] Preferably, the seepage inlet includes a horizontal seepage inlet and a vertical seepage inlet. The seepage outlet includes a horizontal seepage outlet and a vertical seepage outlet. The horizontal seepage inlet is provided on one side wall of the soil column mold. The horizontal seepage outlet is provided on the other side wall of the soil column mold. The top opening of the soil column mold is the vertical seepage inlet. The loading head is provided with a vertical seepage inlet hole which is connected and communicated with the vertical seepage inlet. The vertical seepage outlet is provided at the bottom of the side wall of the soil column mold. When simulating the horizontal seepage condition, the vertical seepage inlet hole and the vertical seepage outlet are closed. The horizontal seepage inlet is connected and communicated with the seepage inlet pipe. The horizontal seepage outlet is connected and communicated with the seepage outlet pipe. When simulating the vertical seepage condition, the horizontal seepage inlet and the horizontal seepage outlet are closed. The vertical seepage inlet hole is connected and communicated with the seepage inlet pipe. The vertical seepage outlet is connected and communicated with the seepage outlet pipe.

[0013] The present invention also provides a test method for the one-dimensional soil column freezing-seepage intelligent regulation system under axial loading, comprising the following steps:

[0014] Step 1: Soil sample preparation. Air-dry and crush the obtained silty sand sample. The preparation adopts the layered compaction method. According to the test requirements and the size of the soil column mold, weigh the mass of the silty sand powder and the mass of water. Then mix the soil and water and stir evenly. Fill the soil body into the consolidation mold in three layers. During filling, each layer needs to be compacted. After filling, wrap the consolidation mold with plastic wrap and let it stand for 12 h. Then apply an overburden load to the soil body for consolidation according to the actual overburden pressure of the formation.

[0015] Step 2: Transfer the soil sample after consolidation in Step 1 from the consolidation mold to the soil column mold, fix the soil column mold with the lower freezing chamber, and then place the one-dimensional soil column freezing instrument under the loading head of the axial loading device.

[0016] Step 3: Connect the seepage inlet to the peristaltic pump through the seepage inlet pipe, and connect the seepage outlet to the flowmeter through the seepage outlet pipe.

[0017] Step 4: Connect the freezing chamber to the freezing cycle device. The freezing chamber is used to unidirectionally freeze the soil body from the bottom upwards.

[0018] Step 5: Turn on the axial loading device, set the load value and loading speed to be applied, and control the loading head to apply a fixed load to the soil body.

[0019] Step 6: After the loading is completed, turn on the peristaltic pump and the flowmeter. The PID controller sets the seepage flow rate of the peristaltic pump according to the test requirements. The PID controller adjusts the seepage flow rate of the peristaltic pump in real time according to the flow rate of the seepage monitored by the flowmeter to ensure that the seepage inlet flow rate and the seepage outlet flow rate are within the set error range, thereby ensuring a stable seepage is applied.

[0020] Step 7: Turn on the freezing cycle device, set the freezing temperature according to the test requirements. The freezing cycle device is used to freeze the soil body.

[0021] The present invention has achieved the following technical effects compared with the prior art:

[0022] The present invention provides a one-dimensional soil column freezing-seepage intelligent regulation system and a testing method under axial loading. A peristaltic pump is connected to a seepage inlet pipe, and a flowmeter is connected to a seepage outlet pipe. Both the peristaltic pump and the flowmeter are connected to a PID controller in terms of signal. The PID controller can adjust the delivery flow rate of the peristaltic pump in real time according to the flow signal output by the flowmeter, thereby controlling the seepage inflow and outflow, enabling the seepage field to be in a stable state, facilitating the accurate measurement and analysis of various parameters during the soil freezing process, such as the changes in the temperature field, stress field, etc.; the stable seepage conditions can ensure that the test conditions are closer to the actual situation, making the research results more repeatable and comparable, and contributing to a deeper understanding of the coupling mechanism between seepage and soil freezing. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a schematic diagram of a one-dimensional soil column freezing apparatus and an axial loading device in Embodiment 1 of the present application;

[0025] Figure 2 It is an overall connection diagram of the test device layout and the simulated horizontal seepage condition in Embodiment 1 of the present application;

[0026] Figure 3 It is an overall connection diagram of the test device layout and the simulated vertical seepage condition in Embodiment 1 of the present application;

[0027] Figure 4 It is a right side view of the one-dimensional soil column freezing apparatus in Embodiment 1 of the present application;

[0028] Figure 5 It is a left side view of the one-dimensional soil column freezing apparatus in Embodiment 1 of the present application;

[0029] Figure 6 It is a control principle flow chart of the PID controller in Embodiment 1 of the present application;

[0030] Figure 7 It is a structural schematic diagram of the temperature control circulation pump in Embodiment 1 of the present application.

[0031] In the figure: 1. Axial loading device; 2. Base; 3. Loading head; 4. Vertical seepage inlet; 5. Liquid inlet of the loading head; 6. Liquid outlet of the loading head; 7. One-dimensional soil column freezing instrument; 8. Display screen; 9. Soil column mold; 10. Freezing chamber; 11. Inlet of the freezing chamber; 12. Outlet of the freezing chamber; 13. Horizontal seepage inlet; 14. Horizontal seepage outlet; 15. Vertical seepage outlet; 16. Seepage inlet pipe; 17. Peristaltic pump; 18. Flowmeter; 19. PID controller; 20. Temperature monitoring hole; 21. Observation window; 22. Industrial camera; 23. Seepage outlet pipe; 24. Temperature control circulation pump; 25. Temperature control circulation liquid inlet pipe; 26. Temperature control circulation liquid outlet pipe; 27. Freezing circulation pump; 28. Freezing circulation liquid inlet pipe; 29. Freezing circulation liquid outlet pipe; 30. Circulation controller; 31. Outlet of the box body; 32. Inlet of the box body; 33. First three-way control valve; 34. Second three-way control valve; 35. Inner circulation pipe. Specific embodiments

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] The purpose of the present invention is to provide an intelligent regulation system and testing method for one-dimensional soil column freezing-seepage under axial loading to solve the problems existing in the above-mentioned prior art, and to be able to maintain the stable seepage of the soil body in the freezing test and improve the accuracy and reliability of the test results.

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Embodiment 1

[0036] This embodiment provides an intelligent regulation system for one-dimensional soil column freezing-seepage under axial loading, as Figures 1-5As shown in the figure, it includes a one-dimensional soil column freezing instrument 7, a freezing cycle device, an axial loading device 1, and a seepage device. The one-dimensional soil column freezing instrument 7 includes a soil column mold 9 and a freezing chamber 10 placed below the soil column mold 9. The soil column mold 9 is used to fill the soil body. The freezing chamber 10 is connected and communicated with the freezing cycle device and is used to cool the soil body. The axial loading device 1 is used to apply an axial load to the soil body. The soil column mold 9 includes a seepage inlet and a seepage outlet. The seepage device includes a PID controller 19, a seepage liquid storage tank, a seepage inlet pipe 16, a seepage outlet pipe 23, a peristaltic pump 17, and a flowmeter 18. The seepage liquid storage tank is connected and communicated with the seepage inlet through the seepage inlet pipe 16. The seepage outlet pipe 23 is connected and communicated with the seepage outlet and is connected to the seepage inlet pipe 16 through the peristaltic pump 17. The flowmeter 18 is connected to the seepage outlet pipe 23, and both the peristaltic pump 17 and the flowmeter 18 are signal-connected to the PID controller 19. The PID controller 19 can adjust the delivery flow rate of the peristaltic pump 17 according to the signal output by the flowmeter 18. A peristaltic pump 17 is provided on the seepage inlet pipe 16, a flowmeter 18 is provided on the seepage outlet pipe 23, and both the peristaltic pump 17 and the flowmeter 18 are signal-connected to the control system. The control system can adjust the delivery flow rate of the peristaltic pump 17 in real time according to the flow signal output by the flowmeter 18, thereby controlling the seepage inflow and outflow, enabling the seepage field to be in a stable state, facilitating the accurate measurement and analysis of various parameters during the soil freezing process, such as the changes in the temperature field, stress field, etc.; the stable seepage conditions can ensure that the test conditions are closer to the actual situation, making the research results more repeatable and comparable, and helping to deeply understand the coupling mechanism between seepage and soil freezing.

[0037] As Figure 6 shown, in the PID controller 19, a proportional-integral-derivative control unit is used to adjust the delivery flow rate of the peristaltic pump 17, and the control equation of the control unit is:

[0038]

[0039] In the formula, u(n) is the adjusted signal, which is the adjusted input flow rate in this embodiment; e(n) is the error feedback, defined as: , where y(n) is the output signal, which is the displayed flow rate of the flowmeter 18 in this embodiment; r(n) is the input signal, which is the displayed flow rate of the peristaltic pump 17 in this embodiment; K P is the proportional gain coefficient; K I is the integral gain coefficient; K D is the differential gain coefficient; n is the number of sampling times.

[0040] The control unit can perform continuous sampling, continuously monitor and control the input and output flow rates, ensure the stability of seepage during the soil freezing process, and be closer to the actual working conditions.

[0041] In a further preferred embodiment of the present embodiment, the one-dimensional soil column freezing-seepage intelligent regulation system under axial loading further includes a plurality of temperature sensors. A plurality of temperature monitoring holes 20 are provided in the side wall of the soil column mold 9 from top to bottom. The temperature sensors can be inserted into the soil through the temperature monitoring holes 20 to monitor the temperature at different heights of the soil during freezing.

[0042] In a further preferred embodiment of the present embodiment, an observation window 21 for observing the freezing condition of the soil in real time and collecting images is further provided on the side wall of the soil column mold 9. An industrial camera 22 for collecting images of the soil sample during freezing is placed in front of the observation window 21 to record the changes of the soil sample during the freezing process and provide materials for subsequent image processing.

[0043] In a further preferred embodiment of the present embodiment, the axial loading device 1 includes a loading controller, a base 2, a loading head 3, a driving device, and a pressure sensor. The one-dimensional soil column freezer 7 is placed on the base 2. The driving device is connected to the loading head 3, and a pressure sensor is provided on the loading head 3. Both the driving device and the pressure sensor are signal-connected to the loading controller. In order to make the axial load received by each part of the soil sample uniform during the test, the size of the loading head 3 is the same as the inner diameter of the soil column mold 9, so as to ensure that the soil column is not affected by eccentric loads. The axial loading device 1 further includes a display screen 8. The load value to be applied and the loading speed are set on the display screen 8. When the load display value on the display screen 8 changes suddenly, it is considered that the loading head 3 contacts the soil sample. When the load value displayed on the display screen 8 reaches near the set value and remains basically unchanged, it can be considered that the loading is completed.

[0044] In a further preferred embodiment of the present embodiment, the one-dimensional soil column freezing-seepage intelligent regulation system under axial loading further includes a temperature boundary control device. The temperature boundary control device includes a temperature-controlled circulating liquid inlet pipe 25, a temperature-controlled circulating liquid outlet pipe 26, and a temperature-controlled circulating pump 24. The loading head 3 includes a loading head liquid inlet 5 and a loading head liquid outlet 6. The loading head liquid inlet 5 is connected and communicated with the outlet of the temperature-controlled circulating pump 24 through the temperature-controlled circulating liquid inlet pipe 25, and the loading head liquid outlet 6 is connected and communicated with the inlet of the temperature-controlled circulating pump 24 through the temperature-controlled circulating liquid outlet pipe 26. The temperature boundary control device is used to control the temperature boundary condition at the top of the soil body during the test, avoid the influence of room temperature change on soil freezing, and improve the accuracy of the experiment.

[0045] Further preferably, as Figure 7As shown in the figure, the temperature-controlled circulation pump 24 includes a circulation controller 30, a circulating liquid storage tank, a pump body, an internal circulation pipe 35, a cooling device, and a temperature measuring device. The circulating liquid storage tank includes a tank outlet 31 and a tank inlet 32. The tank outlet 31 is connected to the first port of the first three-way control valve 33. The temperature-controlled circulating liquid inlet pipe 25 is connected to the second port of the first three-way control valve 33. The tank inlet 32 is connected to the first port of the second three-way control valve 34. The temperature-controlled circulating liquid outlet pipe 26 is connected to the second port of the second three-way control valve 34. The two ends of the internal circulation pipe 35 are respectively connected to the third port of the first three-way control valve 33 and the third port of the second three-way control valve 34. The pump body is placed inside the circulating liquid storage tank, and the outlet of the pump body is connected to the tank outlet 31. The cooling device is used to cool the liquid. The temperature measuring device is arranged inside the circulating liquid storage tank and is used to detect the temperature of the liquid inside the circulating liquid storage tank. The pump body, the first three-way control valve 33, and the second three-way control valve 34 are all connected to the circulation controller by signals. When the temperature-controlled circulation pump 24 is turned on, the circulation controller 30 adjusts the first three-way control valve 33 and the second three-way control valve 34 to form a passage among the tank outlet 31, the internal circulation pipe 35, and the tank inlet 32, starts the pump body to perform internal circulation on the liquid inside the circulating liquid storage tank, cools the liquid inside the circulating liquid storage tank to about 20 °C through the cooling device, and the temperature measuring device displays the real-time temperature of the circulating liquid. When the temperature reaches the set temperature, the circulation controller 30 adjusts the first three-way control valve 33 and the second three-way control valve 34 to form a passage among the tank outlet 31, the temperature-controlled circulating liquid inlet pipe 25, the loading head 3, the temperature-controlled circulating liquid outlet pipe 26, and the tank inlet 32, and feeds the temperature-controlled circulating liquid that has reached the preset temperature into the loading head to realize the external circulation of the temperature-controlled circulating liquid and control the temperature boundary condition at the top of the soil body during the test.

[0046] In a further preferred embodiment of the present embodiment, the freezing circulation device includes a freezing circulation liquid inlet pipe 28, a freezing circulation liquid outlet pipe 29, and a freezing circulation pump 27. The freezing chamber 10 includes a freezing chamber inlet 11 and a freezing chamber outlet 12. The freezing chamber inlet 11 is connected and communicated with the outlet of the freezing circulation pump 27 through the freezing circulation liquid inlet pipe 28. The freezing chamber outlet 12 is connected and communicated with the inlet of the freezing circulation pump 27 through the freezing circulation liquid outlet pipe 29.

[0047] In a further preferred embodiment of the present embodiment, the freezing circulation pump 27 has the same structure as the temperature control circulation pump 24. When using the freezing circulation pump 27, first adjust the two three-way control valves to form a passage among the box outlet 31, the internal circulation pipe 35, and the box inlet 32. Start the pump body to perform internal circulation on the liquid in the circulation liquid storage tank, cool the liquid in the circulation liquid storage tank through the cooling device, and the temperature measuring device displays the real-time temperature of the circulation liquid. When the temperature reaches the set freezing temperature, the circulation controller adjusts the two three-way control valves to form a passage among the box outlet 31, the freezing circulation liquid inlet pipe 28, the freezing chamber 10, the freezing circulation liquid outlet pipe 29, and the box inlet 32, and introduce the cooled freezing circulation liquid into the freezing chamber 10 to realize the external circulation of the freezing circulation liquid and freeze the soil sample.

[0048] In a further preferred embodiment of the present embodiment, heat insulation layers are sleeved outside the one-dimensional soil column freezer 7, the freezing circulation liquid inlet pipe 28, the freezing circulation liquid outlet pipe 29, the temperature control circulation liquid inlet pipe 25, and the temperature control circulation liquid outlet pipe 26. The heat insulation layer can reduce the influence of the external environment on the soil freezing experiment and improve the freezing efficiency.

[0049] In a further preferred embodiment of the present embodiment, the seepage inlet includes a horizontal seepage inlet 13 and a vertical seepage inlet, and the seepage outlet includes a horizontal seepage outlet 14 and a vertical seepage outlet 15. The horizontal seepage inlet 13 is arranged on one side wall of the soil column mold 9, the horizontal seepage outlet 14 is arranged on the other side wall of the soil column mold 9, the top opening of the soil column mold 9 is the vertical seepage inlet, the loading head is provided with a vertical seepage inlet hole 4, and the vertical seepage inlet hole 4 is communicated with the vertical seepage inlet. The vertical seepage outlet 15 is arranged at the bottom of the side wall of the soil column mold 9. The horizontal seepage inlet 13 or the vertical seepage inlet hole 4 is used to be connected and communicated with the seepage inlet pipe 16, and the horizontal seepage outlet 14 or the vertical seepage outlet 15 is used to be connected and communicated with the seepage outlet pipe 23. When simulating the horizontal seepage condition, close the vertical seepage inlet hole 4 and the vertical seepage outlet 15, connect the horizontal seepage inlet 13 with the peristaltic pump 17, and connect the horizontal seepage outlet 14 with the flowmeter 18; when simulating the vertical seepage condition, close the horizontal seepage inlet 13 and the horizontal seepage outlet 14, connect the vertical seepage inlet hole 4 with the peristaltic pump 17, and connect the vertical seepage outlet 15 with the flowmeter 18. In the horizontal seepage condition, in order to make the seepage stable and uniform during the test, multiple channels are provided at both the horizontal seepage inlet 13 and the horizontal seepage outlet 14. Both the peristaltic pump 17 and the flowmeter 18 are multi-channel and correspond to the number of channels of the horizontal seepage inlet 13 and the horizontal seepage outlet 14.

[0050] Embodiment 2

[0051] This embodiment provides a test method for the one-dimensional soil column freezing-seepage intelligent regulation system under axial loading in Embodiment 1, including the following steps:

[0052] Step 1: Soil sample preparation. Air-dry and crush the obtained silty sand sample. The preparation method uses the layered compaction method. According to the test requirements and the dimensions of the soil column mold 9, weigh the mass of the silty sand powder and the mass of water. Then mix the soil and water evenly, and fill the soil body into the consolidation mold in three layers. During filling, each layer needs to be compacted. After filling, wrap the consolidation mold with plastic wrap and let it stand for 12 hours. Then apply an overburden load to the soil body according to the actual overburden pressure of the formation for consolidation.

[0053] Step 2: Transfer the consolidated soil sample in Step 1 from the consolidation mold to the soil column mold 9, fix the soil column mold to the lower freezing chamber, and then place the one-dimensional soil column freezer 7 under the loading head 3 of the axial loading device 1.

[0054] Step 3: Connect the seepage inlet to the peristaltic pump 17 through the seepage inlet pipe 16, and connect the seepage outlet to the flowmeter 18 through the seepage outlet pipe 23. Insert the temperature sensor into the soil sample through the temperature monitoring hole 20 in sequence to monitor the soil temperature at different heights during the freezing process.

[0055] Step 4: Connect the freezing chamber 10 to the freezing cycle device. The freezing chamber 10 is used to freeze the soil body unidirectionally from the bottom upwards.

[0056] Step 5: Turn on the axial loading device 1, set the required load value and loading speed, and control the loading head to apply a fixed load to the soil body. When the load value reaches near the set value and is basically unchanged, it can be considered that the loading is completed.

[0057] Step 6: After the loading is completed, turn on the peristaltic pump 17 and the flowmeter 18. The PID controller 19 sets the seepage flow rate of the peristaltic pump 17 according to the test requirements. The PID controller 19 adjusts the seepage flow rate of the peristaltic pump 17 in real time according to the seepage flow rate monitored by the flowmeter 18 to ensure that the seepage inlet flow rate and the seepage outlet flow rate are within the set error range, thereby ensuring a stable seepage is applied.

[0058] Step 7: Turn on the freezing cycle device, set the freezing temperature according to the test requirements. The freezing cycle device is used to freeze the soil sample. Turn on the internal circulation function of the circulation pump. When the temperature drops to the set temperature, turn off the internal circulation and turn on the external circulation to start the soil body freezing.

[0059] Step 8: Turn on the industrial camera 22 and aim it directly at the observation window 21. When the temperature sensor shows that the temperature at the bottom of the soil sample has dropped to 0 °C, take pictures of the soil sample at the same interval to record the changes in the soil during the freezing process, providing materials for later image processing.

[0060] In the present invention, specific examples are used to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A one-dimensional soil column freezing-seepage intelligent regulation system under axial loading, characterized by: The invention comprises a one-dimensional soil column freezing instrument, a freezing circulation device, an axial loading device and a seepage device. The one-dimensional soil column freezing instrument comprises a soil column mold and a freezing chamber placed below the soil column mold. The soil column mold is used to fill the soil. The freezing chamber is connected and communicated with the freezing circulation device and is used to freeze the soil in one direction. The axial loading device is used to apply an axial load to the soil. The axial loading device comprises a loading controller, a base, a loading head, a driving device and a pressure sensor. The one-dimensional soil column freezing instrument is placed on the base. The driving device is connected to the loading head. The pressure sensor is arranged on the loading head. The driving device and the pressure sensor are connected. The force sensors are all connected to the loading controller signal, the soil column mold includes a seepage inlet and a seepage outlet, the seepage device includes a PID controller, a seepage liquid storage box, a seepage water inlet pipe, a seepage water outlet pipe, a peristaltic pump and a flow meter, the seepage liquid storage box is connected and communicated with the seepage inlet through the seepage water inlet pipe, the seepage water outlet pipe is connected and communicated with the seepage outlet, the peristaltic pump is connected to the seepage water inlet pipe, the flow meter is connected to the seepage water outlet pipe, the peristaltic pump and the flow meter are both connected to the PID controller signal, and the PID controller can adjust the delivery flow of the peristaltic pump according to the signal output by the flow meter.

2. The one-dimensional soil column freezing-seepage intelligent adjustment system under axial loading according to claim 1 is characterized in that: It also includes a plurality of temperature sensors. The side wall of the soil column mold is provided with a plurality of temperature monitoring holes from top to bottom. The temperature sensors can be inserted into the soil through the temperature monitoring holes to monitor the temperature at different positions of the soil.

3. The one-dimensional soil column freezing-seepage intelligent adjustment system under axial loading according to claim 1 is characterized in that: The side wall of the soil column mold is also provided with an observation window.

4. The one-dimensional soil column freezing-seepage intelligent adjustment system under axial loading according to claim 1 is characterized in that: It also includes a temperature boundary control device, which includes a temperature control circulating liquid inlet pipe, a temperature control circulating liquid outlet pipe and a temperature control circulating pump. The loading head includes a loading head inlet and a loading head outlet. The loading head inlet is connected and communicated with the outlet of the temperature control circulating pump through the temperature control circulating liquid inlet pipe, and the loading head outlet is connected and communicated with the inlet of the temperature control circulating pump through the temperature control circulating liquid outlet pipe.

5. The one-dimensional soil column freezing-seepage intelligent adjustment system under axial loading according to claim 1 is characterized in that: The freezing circulation device includes a freezing circulation liquid inlet pipe, a freezing circulation liquid outlet pipe and a freezing circulation pump. The freezing chamber includes a freezing chamber inlet and a freezing chamber outlet. The freezing chamber inlet is connected and communicated with the outlet of the freezing circulation pump through the freezing circulation liquid inlet pipe, and the freezing chamber outlet is connected and communicated with the inlet of the freezing circulation pump through the freezing circulation liquid outlet pipe.

6. The one-dimensional soil column freezing-seepage intelligent adjustment system under axial loading according to claim 1 is characterized in that: The seepage inlet includes a horizontal seepage inlet and a vertical seepage inlet, and the seepage outlet includes a horizontal seepage outlet and a vertical seepage outlet. The horizontal seepage inlet is arranged on one side wall of the soil column mold, and the horizontal seepage outlet is arranged on the other side wall of the soil column mold. The top opening of the soil column mold is the vertical seepage inlet, and the loading head is provided with a vertical seepage inlet hole, the vertical seepage inlet hole is connected with the vertical seepage inlet, and the vertical seepage outlet is arranged at the bottom of the side wall of the soil column mold; when simulating horizontal seepage conditions, the vertical seepage inlet hole and the vertical seepage outlet are closed, the horizontal seepage inlet is connected and connected with the seepage water inlet pipe, and the horizontal seepage outlet is connected and connected with the seepage water outlet pipe; when simulating vertical seepage conditions, the horizontal seepage inlet and the horizontal seepage outlet are closed, the vertical seepage inlet hole is connected and connected with the seepage water inlet pipe, and the vertical seepage outlet is connected and connected with the seepage water outlet pipe.

7. A method for testing a one-dimensional soil column freezing-seepage intelligent regulation system under axial loading according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: soil sample preparation. The obtained silt sand sample is air-dried and crushed. The preparation adopts the layered compaction method. According to the test requirements and the size of the soil column mold, the silt sand powder mass and water mass are weighed, and then the water and soil are mixed and stirred evenly. The soil is divided into three layers and filled into the consolidation mold. Each layer needs to be compacted during filling. After filling, the consolidation mold is wrapped with plastic wrap and left to stand for 12 hours. Then, an overburden load is applied to the soil according to the actual stratum overburden pressure for consolidation; Step 2, transferring the soil sample after consolidation in step 1 from the consolidation mold to the soil column mold, fixing the soil column mold and the lower freezing chamber, and then placing the one-dimensional soil column freezer under the loading head of the axial loading device; Step three, connecting the seepage inlet to the peristaltic pump through the seepage water inlet pipe, and connecting the seepage outlet to the flow meter through the seepage water outlet pipe; Step 4, connecting the freezing chamber to the freezing circulation device, wherein the freezing chamber is used to freeze the soil from the bottom to the top in one direction; Step 5, turning on the axial loading device, setting the load value and loading speed to be applied, and controlling the loading head to apply a fixed load to the soil; Step 6: After loading is completed, the peristaltic pump and the flow meter are turned on, and the PID controller sets the seepage flow rate of the peristaltic pump according to the test requirements. The PID controller adjusts the seepage flow rate of the peristaltic pump in real time according to the seepage outflow flow rate monitored by the flow meter to ensure that the seepage inlet flow rate and the seepage outlet flow rate are within the set error range, thereby ensuring the application of stable seepage; Step seven, turn on the freezing cycle device and set the freezing temperature according to the test requirements. The freezing cycle device is used to freeze the soil.

Images