Large frost heave test system for coarse-grained soil

Abstract

The invention relates to a large-scale frost heave test system for coarse-grained soil. Currently, most of the research on frost heave test devices focuses on fine-grained soil, while there is little research on frost heave of coarse-grained soil. A large-scale frost heave test system for coarse-grained soil comprises: a base constant temperature water supply system, a temperature monitoring system, a top freezing system and a frost heave deformation monitoring system; in terms of freezing mode, a unidirectional freezing test under more accurate water supply conditions is achieved by freezing a refrigeration top plate (9), a hollow test cylinder (5), a bottom constant temperature device (4), a first and a second water bath refrigerator (15) (20) and a bottom water system; in terms of frost heave deformation monitoring, a digital display dial gauge (16) is used to accurately and automatically monitor the frost heave deformation of the soil, thereby improving the automation and accuracy of the test; the invention is applied to the field of frost heave test of coarse-grained soil, and provides certain support for frost heave problems in projects such as roads, buildings, and water conservancy.

Description

Technical Field

[0001] The invention relates to a large-scale frost heave test system for coarse-grained soil. Background Art

[0002] my country's frozen soil is widely distributed, accounting for about 70% of the country's land area. According to the length of freezing time, it is divided into instantaneous frozen soil, seasonal frozen soil, and permafrost. Frozen soil refers to soil in which the water in the soil freezes into ice at negative temperatures, and the volume of the soil expands, resulting in frost heave. The problem of frost heave involves road engineering, tunnel engineering, bridge engineering, construction engineering, water conservancy engineering, etc. In cold regions, roadbed diseases, bridges, tunnels and other buildings (structures) caused by frost heave are common, causing immeasurable economic losses and traffic safety accidents. Therefore, research on the problem of frozen soil frost heave needs to be solved urgently.

[0003] At present, most of the research on frost heave test equipment is focused on the frost heave of fine-grained soil, while there are very few studies on the frost heave of coarse-grained soil. The application number is: 2016205278944, and the authorization announcement number is: CN205844227U. The Chinese utility model patent named "Frost Heave Test Cylinder" invented a frost heave test cylinder for frost heave test of coarse-grained soil. The cylinder wall is made of organic glass with heating function, and the upper and lower top plates and bottom plates with good thermal conductivity are frozen and insulated by circulating refrigerant. The cylinder wall has a heating function, so that there is a temperature difference between the soil layer near the cylinder wall and the soil layer at the center of the cylinder. When the top plate is frozen, the soil layer center and the soil near the cylinder wall cannot be frozen synchronously. The soil layer near the cylinder wall maintains a higher temperature due to the heating function of the cylinder wall, and it is difficult to freeze. Therefore, the uneven freezing is caused, and the frost heave deformation caused is inaccurate. Summary of the invention

[0004] The purpose of the present invention is to provide a large-scale frost heave test system for coarse-grained soil, which can accurately simulate the natural frost heave mode and condition of coarse-grained soil, realize real-time monitoring, accurate recording, rapid transmission and real-time updating of frost heave events, and provide method and technical support for frozen soil frost heave engineering.

[0005] The above purpose is achieved through the following technical solutions:

[0006] A large-scale frost heave test system for coarse-grained soil, comprising: a base constant temperature water supply system, a temperature monitoring system, a top freezing system, a frost heave deformation monitoring system and a test tube, characterized in that: the base constant temperature water supply system is composed of a base, a water inlet, a water outlet, a bottom constant temperature device, and a second water bath refrigerator, and is used to maintain a constant positive temperature state of the bottom without freezing, and water is introduced through the water inlet and discharged through the water outlet to maintain a constant water level to replenish water to the soil sample;

[0007] The temperature monitoring system comprises temperature sensors arranged equidistantly at different heights of the soil sample and an external temperature digital display recorder, which is used to monitor and record the temperature development characteristics of the soil sample at different heights in real time;

[0008] The top freezing system is composed of a freezing refrigeration top plate, a heat-insulating flat glass plate and a first water bath refrigerator, which is used as a freezing source for one-way freezing refrigeration, and the heat-insulating flat glass plate is used to reduce the loss of cold and fix the digital display dial gauge probe;

[0009] The frost heave deformation monitoring system is composed of a digital display dial gauge, a conversion box and a computer. The digital display dial gauge automatically records the frost heave deformation of the soil sample and transmits the deformation data to the computer through the conversion box, thereby achieving full automation and high precision.

[0010] The test tube is made of organic glass, and the center of the tube wall is a closed vacuum environment.

[0011] In the large-scale frost heave test system for coarse-grained soil, the test tube is fixed with the limit ring by a limit screw and a limit ring of the base, so as to prevent the deviation caused by the frost heave force of the soil sample.

[0012] In the large-scale frost heave test system for coarse-grained soil, water from the outside enters through the water inlet of the constant temperature water replenishment system of the base, and water is replenished evenly and slowly through the dehydration stone. A drainage hole is set 5 mm above the bottom of the soil sample for drainage.

[0013] The large-scale frost heave test system for coarse-grained soil has a glass plate with three small pinhole grooves in which a digital dial indicator probe can be embedded, thereby fixing the probe to prevent it from slipping and affecting the result. Finally, the average value of three sets of data is taken to improve the accuracy of the test.

[0014] Beneficial effects of the present invention:

[0015] 1. The present invention overcomes the shortcomings and deficiencies in previous studies on the frost heave characteristics of coarse-grained soil. The design of its bottom water replenishment system can realize the test of frost heave deformation monitoring under one-way freezing without water replenishment, one-way freezing with water replenishment, and one-way freezing with water replenishment and saturated freezing. It has wide application and high accuracy.

[0016] The present invention uses the center of the test cylinder wall as a vacuum environment, which can effectively isolate the cold and heat exchange with the outside world, and realizes one-way freezing from top to bottom through the top freezing refrigeration device. The bottom is a constant positive temperature water replenishment condition, which more accurately simulates the actual water replenishment and freezing conditions and methods in nature.

[0017] The present invention effectively isolates the heat exchange with the outside world by freezing the heat-insulating organic glass plate on the upper part of the refrigeration device. The digital display 100% meter pinhole on the plate plays a role in fixing the dial meter probe, keeping it horizontal, preventing slippage and affecting the experimental results, and finally taking the average value of three groups of data to improve the accuracy.

[0018] The deformation monitoring system of the present invention realizes full automation through a digital display dial gauge probe, a conversion box and a computer, thereby avoiding errors caused by human operation and reducing manpower.

[0019] The cylinder wall of the present invention is made of organic glass material, and the center of the cylinder wall is a vacuum environment, which better isolates the cold and heat exchange with the outside world, achieves the effect of thermal insulation, and realizes unidirectional one-dimensional freezing. The bottom plate is provided with four channels at the bottom of the device, two for water replenishment circulation, and two for antifreeze circulation. The drainage hole is set 5mm above the bottom of the soil sample, so that the soil sample can always be fully and evenly replenished with water, thereby improving the accuracy of the test. The present invention proposes a test cylinder, which cooperates with a temperature sensor, a digital display dial indicator, a data acquisition transmission box, and a computer to achieve full automation, avoid the interference of many human factors, reduce test errors, and improve test accuracy. At the same time, it is simple to operate, low cost, widely used, and cost-effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attached Figure 1 It is a schematic structural plane diagram of the present invention.

[0021] Attached Figure 2 It is a three-dimensional schematic diagram of the base water replenishment system and the limit rod of the present invention.

[0022] Attached Figure 3 It is a schematic diagram of the base constant temperature system of the present invention.

[0023] Attached Figure 4 It is a three-dimensional schematic diagram of a test tube of the present invention.

[0024] Attached Figure 5 It is a three-dimensional schematic diagram of the upper limiting ring of the present invention.

[0025] Attached Figure 6 It is a three-dimensional schematic diagram of the upper freezing refrigeration device of the present invention.

[0026] Attached Figure 7 It is a three-dimensional schematic diagram of the heat-insulating flat glass plate of the present invention.

[0027] Attached Figure 8 The present invention is a schematic diagram of the adjustment and fixing principle of the digital display dial indicator.

[0028] In the figure: 1. base, 2. water inlet, 3. water outlet, 4. bottom constant temperature device, 5. test tube, 6. limit screw, 7. temperature sensor, 8. temperature digital display recorder, 9. freezing refrigeration top plate, 10. first water bath refrigerator connecting port 11. thermal insulation flat glass plate, 12. digital display dial indicator probe, 13. limit ring, 14. limit ring buckle, 15. first water bath refrigerator, 16. digital display dial indicator, 17. digital display dial indicator limit nut, 18. conversion box, 19. second water bath refrigerator connecting port, 20. second water bath refrigerator. DETAILED DESCRIPTION

[0029] Embodiment 1:

[0030] A large-scale frost heave test system for coarse-grained soil, characterized in that it comprises: a base constant temperature water supply system, a temperature monitoring system, a top freezing system, a frost heave deformation monitoring system, and a test tube 5;

[0031] The base constant temperature water replenishment system is composed of a base 1, a water inlet 2, a water outlet 3, a bottom constant temperature device 4, and a second water bath refrigerator, which is used to maintain a constant positive temperature state at the bottom without freezing, and water is introduced through the water inlet and discharged through the water outlet to maintain a constant water level to replenish water to the soil sample;

[0032] The temperature monitoring system includes temperature sensors 7 arranged equidistantly at different heights of the soil sample, and an external temperature digital display recorder 8, which is used to monitor and record the temperature development characteristics of the soil sample at different heights in real time;

[0033] The top freezing device is composed of a freezing refrigeration top plate 9, a heat-insulating flat glass plate 11 and a first water bath refrigerator, which is used as a freezing source for one-way freezing refrigeration, and the heat-insulating flat glass plate is used to reduce the loss of cold and fix the digital display dial gauge probe 12;

[0034] The frost heave deformation monitoring system is composed of a digital display dial gauge 16, a conversion box 18 and a computer. The digital display dial gauge automatically records the frost heave deformation of the soil sample and transmits the deformation data to the computer through the conversion box, thereby achieving full automation and high precision.

[0035] The test tube is made of organic glass, and the center of the tube wall is a closed vacuum environment, which reduces the heat and cold exchange between the side of the soil sample and the outside world and improves the accuracy of one-way freezing.

[0036] Embodiment 2:

[0037] According to the large-scale frost heave test system for coarse-grained soil described in Example 1, the test tube is fixed by the limiting screw 6 and the limiting ring 13 of the base and the limiting ring buckle 14 to prevent deviation caused by the frost heave force of the soil sample.

[0038] Embodiment 3:

[0039] According to the large-scale frost heave test system for coarse-grained soil described in Example 1 or 2, external water enters through the water inlet and passes through the dehydration stone to replenish water evenly and slowly, and a drainage hole is set 5 mm above the bottom of the soil sample for drainage.

[0040] Embodiment 4:

[0041] According to the large-scale frost heave test system for coarse-grained soil described in Example 1, 2 or 3, the thermal insulation plexiglass plate has three small pinhole grooves, in which the digital dial indicator probe can be embedded, and the probe can be fixed to prevent its slippage from affecting the results. Finally, the average value of the three sets of data is taken to improve the accuracy of the test.

[0042] Embodiment 5:

[0043] According to the large-scale frost heave test system for coarse-grained soil described in Example 1, 2, 3 or 4, the digital display dial indicator records data automatically, avoiding the inaccuracy of manual readings. The three meters collect data to a transmission box, and then transmit the data to a computer, which is operated and run through designated software to monitor and record the frost heave deformation of the soil sample in real time.

[0044] Embodiment 6:

[0045] like Figure 1 As shown, permeable stones and filter paper are arranged at the bottom of the soil sample, so that water can be added evenly and slowly.

[0046] Temperature sensors are arranged equidistantly at different heights of the soil sample and connected to a temperature digital recorder to monitor the temperature development characteristics inside the soil sample in real time.

[0047] After compacting the soil sample, place a layer of filter paper on top of the soil sample, and then place a freezing refrigeration device on top. Figure 6 As shown, the first water bath refrigerator connecting port 10 and the second water bath refrigerator connecting port 19 are externally connected to the first water bath refrigerator 15 and the second water bath refrigerator 20 respectively.

[0048] (1) If a saturation test is to be performed, place a dehydrated stone on the soil sample filter paper to soak it in water and saturate it with air. Then remove the dehydrated stone and place it in a freezing refrigeration device for one-way freezing.

[0049] (2) If a water replenishment frost heave test is to be conducted, filter paper is placed on the top of the soil sample and a freezing refrigeration device is placed. The water replenishment device system at the bottom replenishes water from the bottom water inlet and drains water from the drainage hole on the test cylinder 5 mm away from the bottom of the soil sample. The replenishment liquid level is always kept higher than the soil sample to achieve uniform water replenishment.

[0050] (3) If the frost heave test is conducted without water replenishment, it is only necessary to remove the water replenishment system on the basis of the frost heave test with water replenishment.

[0051] The upper freezing refrigeration device has a connectable circulation pipeline inside, which is connected to the first water bath refrigerator through the first water bath refrigerator connecting port. The target freezing temperature can be freely adjusted, and the frost heave test in different regions and different freezing temperatures can be simulated.

[0052] Place a heat-insulating flat plate on top of the freezing refrigeration device, such as Figure 7 As shown, on the one hand, it plays the role of thermal insulation to ensure that the refrigeration device achieves the maximum refrigeration effect, and on the other hand, it ensures that the plane is level. The three pinholes set to fix the digital dial indicator prevent the probe from slipping and affecting the reading, that is, affecting the frost heave amount.

[0053] For the installation and fixation of digital dial indicator, Figure 8 As shown, the fixed dial indicator support rod is fixed on the limiting threaded rod through the digital display dial indicator limiting nut 17. The advantage is that the height and length can be freely adjusted, and it can be disassembled at any time, which is convenient for operation. The fixed dial indicator rod clamp can also freely adjust the height of the dial indicator.

[0054] For the digital display micrometer, the readings are recorded automatically and powered by button batteries. The data is collected and transmitted to the computer through a data collection and transmission box. Through specific software operation and operation, the frost heave deformation of the soil sample is monitored and recorded in real time.

[0055] The above description is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any local modification or replacement within the technical scope disclosed by the present invention by any person familiar with the technology should be included in the scope of the present invention.

Claims

1. A large-scale frost heave test system for coarse-grained soil, comprising: The base constant temperature water replenishment system, the temperature monitoring system, the top freezing system, the frost heave deformation monitoring system and the test tube are characterized in that: the base constant temperature water replenishment system is composed of a base, a water inlet, a water outlet, a bottom constant temperature device, and a second water bath refrigerator, which is used to maintain a constant positive temperature state at the bottom and prevent it from being frozen, and water is introduced through the water inlet and discharged through the water outlet to maintain a constant water level to replenish water for the soil sample; The temperature monitoring system comprises temperature sensors arranged equidistantly at different heights of the soil sample and an external temperature digital display recorder, which is used to monitor and record the temperature development characteristics of the soil sample at different heights in real time; The top freezing system is composed of a freezing refrigeration top plate, a heat-insulating flat glass plate and a first water bath refrigerator, which is used as a freezing source for one-way freezing refrigeration, and the heat-insulating flat glass plate is used to reduce the loss of cold and fix the digital display dial gauge probe; The frost heave deformation monitoring system is composed of a digital display dial gauge, a conversion box and a computer. The digital display dial gauge automatically records the frost heave deformation of the soil sample and transmits the deformation data to the computer through the conversion box, thereby achieving full automation and high precision. The test tube is made of organic glass, and the center of the tube wall is a closed vacuum environment; the test tube is fixed by a limit screw and a limit ring on the base and a limit ring buckle to prevent displacement due to the frost heave force of the soil sample; the glass plate of the test tube has three small pinhole grooves, in which the digital display dial indicator probe can be embedded, and the probe can be fixed to prevent it from slipping and affecting the result. Finally, the average value of three sets of data is taken to improve the accuracy of the test.

2. The large-scale frost heave test system for coarse-grained soil according to claim 1 is characterized by: The external water source enters through the water inlet of the constant temperature water supply system of the base and replenishes water evenly and slowly through the dehydration stone. A drainage hole is set 5mm above the bottom of the soil sample for drainage.

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