An improved soil frost heaving property testing device and testing method

Abstract

This invention relates to the field of soil frost heave characteristic testing technology, and particularly to an improved soil frost heave characteristic testing device and method, comprising an acrylic mold, wherein several threaded holes are respectively opened on both sides of the acrylic mold along its height direction, and a special hole bolt is threaded into the threaded holes. The special hole bolt includes a bolt part and a flared mouth with an integral structure. A circular hole is opened in the middle of the bolt part, and the flared mouth is threaded on the outside. A matching rubber stopper is installed in the middle of the flared mouth. The matching rubber stopper is frustoconical and is divided into four equal parts. The matching rubber stopper fits tightly with the flared mouth. The contraction of the flared mouth causes the middle hole of the rubber stopper to shrink, thereby fitting tightly with the sensor cable. A hexagonal metal washer is threadedly connected to the outside of the flared mouth. The hexagonal metal washer is used in combination with the flared mouth to tighten the flared mouth.

Description

Technical Field

[0001] This invention relates to the field of soil frost heave characteristics testing technology, and in particular to an improved soil frost heave characteristics testing device and testing method. Background Technology

[0002] Permafrost refers to various rocks and soils with temperatures at or below 0°C and containing ice. Perennial and seasonal permafrost are widely distributed across the Earth's surface. Complex interactions exist between permafrost soils and the atmosphere, environment, and human activities. A large number of major infrastructure projects have been constructed or planned in permafrost regions (such as the Sichuan-Tibet Railway, Qinghai-Tibet Expressway, and Harbin-Dalian High-Speed ​​Railway), placing high demands on the serviceability and stability of the soil in these areas. In permafrost regions, if the soil strata contain a certain amount of fine-grained soil (such as silt and clay), the unfrozen water in the permafrost will migrate along the liquid water film under the influence of temperature or low-temperature suction gradients, forming discontinuous ice lens interlayers, resulting in significant frost heave deformation of the soil surface. The frost heave characteristics of soil are an important component of its physical and mechanical properties, crucial for geography, agriculture, and civil engineering in permafrost regions.

[0003] When conducting frost heave tests on soil in the laboratory, the test apparatus typically includes a cylindrical plexiglass mold (containing the soil sample), a temperature control device, a water supply device, insulation materials, sensors (temperature sensors, moisture sensors, and displacement sensors), and a data acquisition instrument. To accommodate the placement of temperature and moisture sensors inside the soil sample, holes or grooves are usually made in the side wall of the cylindrical plexiglass mold. After the sensors are placed, clay is used to seal the large gaps between the sensors and the holes (grooves), and then the frost heave test is conducted. However, the above frost heave test apparatus has the following defects: (1) the clay filling cannot guarantee that the gaps between the sensors and the holes (grooves) are completely sealed; (2) the clay itself has a high water content, which will affect the migration path and amount of water inside the soil sample during the frost heave test, thus having a significant impact on the test results; (3) the test operation (such as the filling of clay) is cumbersome. Summary of the Invention

[0004] The purpose of this invention is to solve the problems mentioned in the background art and to propose an improved soil frost heave characteristic test device and test method.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An improved soil frost heave characteristic testing device is characterized by comprising an acrylic mold 1, wherein the acrylic mold 1 has a plurality of threaded holes 101 on both sides along its height direction, and a special hole bolt 2 is threadedly connected to the threaded holes 101. The special hole bolt 2 includes an integral bolt part 201 and a flared end 202. A circular hole 203 is formed in the middle of the bolt part 201, and the flared end 202 is threaded on the outside. A matching rubber stopper 3 is installed in the middle of the flared end 202. The matching rubber stopper 3 is frustoconical and divided into four equal parts. The matching rubber stopper 3 fits tightly with the flared end 202. The contraction of the flared end 202 causes the central hole of the rubber stopper to shrink, thereby fitting tightly with the sensor cable. A hexagonal metal washer 4 is threadedly connected to the outside of the flared end 202. The hexagonal metal washer 4 is used in combination with the flared end 202 to tighten the flared end 202.

[0007] Preferably, it also includes a hexagonal sealing bolt 6, which is threadedly connected to the threaded hole 101. The hexagonal sealing bolt 6 is used to seal the threaded hole 101 where no sensor is installed during the test.

[0008] Preferably, the acrylic mold 1 is cylindrical, and the dimensions of the acrylic mold 1 are: inner diameter 100mm, outer diameter 140mm, wall thickness 20mm, and height 400mm.

[0009] Preferably, the front end of the special perforated bolt 2 is fitted with a perforated rubber gasket 5, which has a certain curvature and can fit tightly against the cylindrical wall of the plexiglass mold 1.

[0010] Preferably, the diameter of the threaded hole 101 is 10mm, and the center-to-center distance of the plurality of threaded holes 101 is 50mm.

[0011] Preferably, the outer diameter of the bolt portion 201 is 10mm, the length of the bolt portion 201 is 20mm, the diameter of the round hole 203 is 6mm; the maximum outer diameter of the flared mouth 202 is 14mm, the minimum outer diameter of the flared mouth 202 is 10mm, the wall thickness of the flared mouth 202 is 1mm, and the height of the flared mouth 202 is 16mm.

[0012] Preferably, the maximum diameter of the matching rubber stopper 3 is 13mm, the minimum diameter of the matching rubber stopper 3 is 9mm, and the height of the matching rubber stopper 3 is 15mm.

[0013] Preferably, the thickness of the hexagonal metal gasket 4 is 4mm, and the inner diameter of the hexagonal metal gasket 4 is 13mm.

[0014] Preferably, the thickness of the perforated rubber gasket 5 is 4mm, and the inner diameter of the perforated rubber gasket 5 is 10mm.

[0015] Preferably, the threaded portion of the hexagonal sealing bolt 6 has a diameter of 10mm and a length of 20mm, and the hexagonal sealing bolt 6 cooperates with the perforated rubber gasket 5 to seal the threaded hole 101.

[0016] An improved method for testing the frost heave properties of soil, characterized by comprising the following steps:

[0017] Step 1: After collecting and packaging the natural soil sample, transport it to the laboratory for air drying, crushing, impurity removal, and sieving through a 2mm standard sieve;

[0018] Step 2: Weigh a certain mass of dry soil and weigh the corresponding mass of distilled water according to the target moisture content; mix the dry soil and distilled water evenly and let it stand for more than 24 hours to make the moisture in the soil sample evenly distributed.

[0019] Step 3: Measure the moisture content of the soil sample. Based on the difference between the moisture content and the target moisture content, adjust the moisture content by adding appropriate water or adding a suitable amount of dry soil and then steaming the soil again. Repeat this step until the target moisture content is reached.

[0020] Step 4: Using a loading frame, the wet soil particles with adjusted moisture content are statically pressed into a frost heave mold (i.e., an acrylic mold) using the dry density control method to prepare a cylindrical unsaturated soil sample (100 mm in diameter and 350 mm in height).

[0021] Step 5: During the soil sample compaction process, in order to make the soil sample have a relatively uniform dry density, it is compacted in 7 layers, each layer being 50mm thick.

[0022] Step 6: After each layer of soil sample is compacted, roughen its surface with a knife to enhance its adhesion to the next layer of soil sample.

[0023] Step 7: Pass the ends of the cables of a temperature sensor 7 and a moisture sensor 8 through the circular openings (i.e., threaded holes) on both sides of the frost heave test mold, and combine them with the special opening bolts and other components; adjust the placement of the probe ends of the temperature sensor 7 and moisture sensor 8 in the soil sample, tighten the combined components into the circular openings, and ensure that the frustum-shaped rubber stopper is in close contact with the sensor cables; then, compact the next layer of soil sample and place the sensors.

[0024] Step 8: After the soil sample is compacted, the temperature-controlled top plate 9 and temperature-controlled bottom plate 10 are installed on the top and bottom of the frost heave test mold, respectively, to ensure close contact with the soil sample surface; the temperature-controlled top plate 9 and temperature-controlled bottom plate 10 are respectively connected to the first constant temperature cold bath box 13 and the second constant temperature cold bath box 14; a displacement sensor 11 is installed on the temperature-controlled top plate 9; the temperature-controlled bottom plate 10 has a water flow channel connected to the Marshall bottle 15 (with graduations marked on its wall), which can supply water to the bottom of the soil sample at a constant head pressure;

[0025] Step 9: Use insulating cotton to tightly wrap the side walls of the frozen expansion mold to ensure that the side walls are not affected by the external temperature.

[0026] Step 10: Connect temperature sensor 7, moisture sensor 8, and displacement sensor 11 to the data acquisition instrument, control the temperature of the top plate 9 to a negative temperature (e.g., -20°C), and control the temperature of the bottom plate 10 to a positive temperature (e.g., 5°C), so that the soil sample is frozen in one dimension from top to bottom.

[0027] Step 11: During the experiment, the temperature and moisture distribution changes along the height of the soil sample were measured using temperature sensor 7 and moisture sensor 8; the frost heave deformation of the soil sample was measured using displacement sensor 11; and the water absorption of the soil sample was measured using Marvin bottle 15.

[0028] Step 12: Maintain the temperature of the top control plate 9 and the bottom control plate 10 for 7 days to complete a set of frost heave tests.

[0029] Preferably, in step 6, during the soil sample compaction process, the surface of each soil sample layer is aligned with the center of the threaded hole in that layer.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] (1) The present invention designs a frost heave test mold and related components. The sensor is convenient to set up, the components are assembled and disassembled, and the components are beautiful and durable. Using this device can avoid the use of clay in the traditional frost heave test, reduce test errors, and prevent the sensor end from being stuck by the rectangular slot (affecting the measurement of frost heave and easily damaging the sensor). This device gives the sensor a large space to move, does not affect frost heave, and can prevent water leakage, air leakage and soil leakage.

[0032] (2) This invention proposes a method for setting up sensors and a test method for soil frost heave test, which simplifies the test steps and improves the test accuracy. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the acrylic mold used in this invention;

[0034] Figure 2 This is a schematic diagram of the special perforated bolt used in this invention;

[0035] Figure 3 This is a schematic diagram of the rubber stopper used in this invention;

[0036] Figure 4 This is a schematic diagram of the hexagonal metal gasket in this invention;

[0037] Figure 5 This is a schematic diagram of the perforated rubber gasket in this invention;

[0038] Figure 6 This is a schematic diagram of the hexagonal sealing bolt in this invention;

[0039] Figure 7 This is a schematic diagram of the structure of the special perforated bolt installed on the plexiglass mold in this invention;

[0040] Figure 8 This is a schematic diagram of the structure of the hexagonal sealing bolt installed on the plexiglass mold in this invention;

[0041] Figure 9 This is a schematic diagram of the frost heave test in this invention. Figure 1 ;

[0042] Figure 10 This is a schematic diagram of the frost heave test in this invention. Figure 2 .

[0043] The diagram shows: 1. Acrylic glass mold; 2. Special hole bolt; 3. Matching rubber stopper; 4. Hexagonal metal gasket; 5. Hole rubber gasket; 6. Hexagonal sealing bolt; 7. Temperature sensor; 8. Moisture sensor; 9. Temperature control top plate; 10. Temperature control bottom plate; 11. Moisture sensor; 12. Fixed bracket; 13. First constant temperature cold bath; 14. Second constant temperature cold bath; 15. Marshall bottle; 101. Threaded hole; 201. Bolt part; 202. Flared mouth; 203. Round hole. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Example

[0045] An improved soil frost heave characteristic testing device is characterized by comprising an acrylic mold 1, wherein the acrylic mold 1 has a plurality of threaded holes 101 on both sides along its height direction, and a special hole bolt 2 is threadedly connected to the threaded holes 101. The special hole bolt 2 includes an integral bolt part 201 and a flared end 202. A circular hole 203 is formed in the middle of the bolt part 201, and the flared end 202 is threaded on the outside. A matching rubber stopper 3 is installed in the middle of the flared end 202. The matching rubber stopper 3 is frustoconical and divided into four equal parts. The matching rubber stopper 3 fits tightly with the flared end 202. The contraction of the flared end 202 causes the central hole of the rubber stopper to shrink, thereby fitting tightly with the sensor cable. Figure 7 As shown; the external thread of the flared mouth 202 is connected to a hexagonal metal washer 4. The hexagonal metal washer 4 is used in combination with the flared mouth 202 to tighten the flared mouth 202.

[0046] like Figure 6 As shown, it also includes a hexagonal sealing bolt 6, which is threadedly connected to the threaded hole 101. The hexagonal sealing bolt 6 is used to seal the threaded hole 101 where no sensor is installed during the test. Figure 8 As shown. The thickness of the perforated rubber gasket 5 is 4mm, and the inner diameter of the perforated rubber gasket 5 is 10mm.

[0047] like Figure 1 As shown, the acrylic mold 1 is cylindrical, and its dimensions are: inner diameter 100mm, outer diameter 140mm, wall thickness 20mm, and height 400mm. The diameter of the threaded hole 101 is 10mm, and the center-to-center distance of the threaded holes 101 is 50mm.

[0048] like Figure 5 As shown, the front end of the special perforated bolt 2 is fitted with a perforated rubber gasket 5, which has a certain curvature and can fit tightly against the cylindrical wall of the plexiglass mold 1.

[0049] like Figure 2 As shown, the outer diameter of the bolt portion 201 is 10mm, the length of the bolt portion 201 is 20mm, and the diameter of the round hole 203 is 6mm; the maximum outer diameter of the flared mouth 202 is 14mm, the minimum outer diameter of the flared mouth 202 is 10mm, the wall thickness of the flared mouth 202 is 1mm, and the height of the flared mouth 202 is 16mm.

[0050] like Figure 3 As shown, the maximum diameter of the matching rubber stopper 3 is 13mm, the minimum diameter of the matching rubber stopper 3 is 9mm, and the height of the matching rubber stopper 3 is 15mm.

[0051] like Figure 4 As shown, the thickness of the hexagonal metal gasket 4 is 4mm, and the inner diameter of the hexagonal metal gasket 4 is 13mm.

[0052] like Figure 6 As shown, the threaded portion of the hexagonal sealing bolt 6 has a diameter of 10mm and a length of 20mm. The hexagonal sealing bolt 6 cooperates with the perforated rubber gasket 5 to seal the threaded hole 101. Example

[0053] An improved method for testing the frost heave properties of soil, characterized by comprising the following steps:

[0054] Step 1: After collecting and packaging the natural soil sample, transport it to the laboratory for air drying, crushing, impurity removal, and sieving through a 2mm standard sieve;

[0055] Step 2: Weigh a certain mass of dry soil and weigh the corresponding mass of distilled water according to the target moisture content; mix the dry soil and distilled water evenly and let it stand for more than 24 hours to make the moisture in the soil sample evenly distributed.

[0056] Step 3: Measure the moisture content of the soil sample. Based on the difference between the moisture content and the target moisture content, adjust the moisture content by adding appropriate water or adding a suitable amount of dry soil and then steaming the soil again. Repeat this step until the target moisture content is reached.

[0057] Step 4: Using a loading frame, the wet soil particles with adjusted moisture content are statically pressed into a frost heave mold (i.e., an acrylic mold) using the dry density control method to prepare a cylindrical unsaturated soil sample (100 mm in diameter and 350 mm in height).

[0058] Step 5: During the soil sample compaction process, in order to make the soil sample have a relatively uniform dry density, it is compacted in 7 layers, each layer being 50mm thick.

[0059] Step 6: After each layer of soil sample is compacted, roughen its surface with a knife to enhance its adhesion to the next layer of soil sample.

[0060] Step 7: Pass the ends of the cables of a temperature sensor 7 and a moisture sensor 8 through the circular openings (i.e., threaded holes) on both sides of the frost heave test mold, and combine them with the special opening bolts and other components; adjust the placement of the probe ends of the temperature sensor 7 and moisture sensor 8 in the soil sample, tighten the combined components into the circular openings, and ensure that the frustum-shaped rubber stopper is in close contact with the sensor cables; then, compact the next layer of soil sample and place the sensors.

[0061] Step 8: After the soil sample is compacted, the temperature-controlled top plate 9 and temperature-controlled bottom plate 10 are installed on the top and bottom of the frost heave test mold, respectively, ensuring close contact with the soil sample surface. The temperature-controlled top plate 9 and temperature-controlled bottom plate 10 are connected to the first constant temperature cold bath 13 and the second constant temperature cold bath 14, respectively. A displacement sensor 11 is installed on the temperature-controlled top plate 9, and the displacement sensor 11 is installed on the top of the temperature-controlled top plate 9 through a fixing bracket 12. The temperature-controlled bottom plate 10 has a water flow channel connected to a Marshall bottle 15 (with graduations marked on its wall), which can supply water to the bottom of the soil sample at a constant head pressure. Figure 9 and Figure 10 As shown;

[0062] Step 9: Use insulating cotton to tightly wrap the side walls of the frozen expansion mold to ensure that the side walls are not affected by the external temperature.

[0063] Step 10: Connect temperature sensor 7, moisture sensor 8, and displacement sensor 11 to the data acquisition instrument, control the temperature of the top plate to negative (e.g., -20°C), and control the temperature of the bottom plate 10 to positive (e.g., 5°C), so that the soil sample is frozen in one dimension from top to bottom.

[0064] Step 11: During the experiment, the temperature and moisture distribution changes along the height of the soil sample were measured using temperature sensor 7 and moisture sensor 8; the frost heave deformation of the soil sample was measured using displacement sensor 11; and the water absorption of the soil sample was measured using a Marshall bottle.

[0065] Step 12: Maintain the temperature of the top and bottom temperature control plates for 7 days to complete a set of frost heave tests.

[0066] Preferably, in step 6, during the soil sample compaction process, the surface of each soil sample layer is aligned with the center of the threaded hole in that layer.

[0067] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An improved testing device for soil frost heave characteristics, characterized in that, The system includes an acrylic mold (1), on both sides of which are provided with several threaded holes (101) along their height direction. A special bolt (2) is threaded into each of the threaded holes (101). The special bolt (2) includes an integral bolt portion (201) and a flared end (202). A round hole (203) is provided in the center of the bolt portion (201), and the flared end (202) is threaded on the outside. A matching rubber stopper is installed in the center of the flared end (202). 3) The matching rubber stopper (3) is frustum-shaped and is divided into four equal parts. The matching rubber stopper (3) fits tightly with the flared mouth (202). The shrinkage of the flared mouth (202) causes the hole in the middle of the rubber stopper to shrink, thereby fitting tightly with the sensor cable. The external thread of the flared mouth (202) is connected to a hexagonal metal washer (4). The hexagonal metal washer (4) is used in combination with the flared mouth (202). The flared mouth (202) is tightened by the hexagonal metal washer (4). It also includes a hexagonal sealing bolt (6), which is threadedly connected to a threaded hole (101). The hexagonal sealing bolt (6) is used to seal the threaded hole (101) where no sensor is installed during the test. The thickness of the hexagonal metal gasket (4) is 4 mm, and the inner diameter of the hexagonal metal gasket (4) is 13 mm. The special perforated bolt (2) is fitted with a perforated rubber gasket (5) at its outer front end. The thickness of the perforated rubber gasket (5) is 4mm and the inner diameter of the perforated rubber gasket (5) is 10mm. The perforated rubber gasket (5) has a certain curvature and can fit tightly against the cylindrical wall of the plexiglass mold (1). The threaded portion of the hexagonal sealing bolt (6) has a diameter of 10mm and a length of 20mm. The hexagonal sealing bolt (6) cooperates with the perforated rubber gasket (5) to seal the threaded hole (101).

2. The improved soil frost heave characteristic testing device according to claim 1, characterized in that: The acrylic mold (1) is cylindrical, and the dimensions of the acrylic mold (1) are: inner diameter 100mm, outer diameter 140mm, wall thickness 20mm, and height 400mm; the diameter of the threaded hole (101) is 10mm, and the center-to-center distance of the threaded holes (101) is 50mm.

3. The improved soil frost heave characteristic testing device according to claim 1, characterized in that: The outer diameter of the bolt part (201) is 10mm, the length of the bolt part (201) is 20mm, and the diameter of the round hole (203) is 6mm; the maximum outer diameter of the flared mouth (202) is 14mm, the minimum outer diameter of the flared mouth (202) is 10mm, the wall thickness of the flared mouth (202) is 1mm, and the height of the flared mouth (202) is 16mm; the maximum diameter of the matching rubber stopper (3) is 13mm, the minimum diameter of the matching rubber stopper (3) is 9mm, and the height of the matching rubber stopper (3) is 15mm.

4. An improved method for testing the frost heave characteristics of soil, wherein the method employs the apparatus described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: After collecting and packaging the natural soil sample, transport it to the laboratory for air drying, crushing, impurity removal, and sieving through a 2mm standard sieve; Step 2: Weigh a certain mass of dry soil and weigh the corresponding mass of distilled water according to the target moisture content; mix the dry soil and distilled water evenly and let it stand for more than 24 hours to make the moisture in the soil sample evenly distributed. Step 3: Measure the moisture content of the soil sample. Based on the difference between the moisture content and the target moisture content, adjust the moisture content by adding appropriate water or adding a suitable amount of dry soil and then steaming the soil again. Repeat this step until the target moisture content is reached. Step 4: Using a loading frame, the wet soil particles with adjusted moisture content are statically pressed into a frost heave mold using the dry density control method to prepare a cylindrical unsaturated soil sample. The cylindrical unsaturated soil sample has a diameter of 100 mm and a height of 350 mm. Step 5: During the soil sample compaction process, in order to make the soil sample have a relatively uniform dry density, it is compacted in 7 layers, each layer being 50mm thick. Step 6: After each layer of soil sample is compacted, roughen its surface with a knife to enhance its adhesion to the next layer of soil sample. During the compaction process, the surface of each layer of soil sample should be level with the center of the threaded hole of that layer. Step 7: Pass the ends of the cables of a temperature sensor (7) and a moisture sensor (8) through the circular openings on both sides of the frost heave test mold, and combine them with the special opening bolt assembly; adjust the placement of the probe ends of the temperature sensor (7) and moisture sensor (8) in the soil sample, tighten the assembly into the circular opening, and ensure that the frustum-shaped rubber stopper is in close contact with the sensor cable; then, compact the next layer of soil sample and place the sensors. Step 8: After the soil sample is compacted, the temperature control top plate (9) and temperature control bottom plate (10) are installed on the top and bottom of the frost heave test mold respectively to ensure that they are in close contact with the soil sample surface; the temperature control top plate (9) and temperature control bottom plate (10) are respectively connected to the first constant temperature cold bath box (13) and the second constant temperature cold bath box (14); a displacement sensor (11) is installed on the temperature control top plate (9); the temperature control bottom plate (10) has a water flow channel connected to the Marshall bottle (15), the Marshall bottle (15) is marked with a scale, and its constant water head pressure supplies water to the bottom of the soil sample; Step 9: Use insulating cotton to tightly wrap the side walls of the frozen expansion mold to ensure that the side walls are not affected by the external temperature. Step 10: Connect the temperature sensor (7), moisture sensor (8), and displacement sensor (11) to the data acquisition instrument. The temperature of the top temperature control plate (9) is negative, and the temperature of the bottom temperature control plate (10) is positive, so that the soil sample is frozen in one dimension from top to bottom. Step 11: During the experiment, the temperature and moisture distribution changes along the height of the soil sample were measured by temperature sensor (7) and moisture sensor (8); the frost heave deformation of the soil sample was measured by displacement sensor (11); and the water absorption of the soil sample was measured by Marshall bottle (15). Step 12: Maintain the temperature of the temperature-controlled top plate (9) and temperature-controlled bottom plate (10) for 7 days to complete a set of frost heave tests.

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