Saturated frozen soil permeability test device and method

Abstract

The present invention discloses a saturated frozen soil permeability test device, including: a bracket; a base, provided with a lower permeable stone and a liquid inlet hole, the liquid inlet hole is connected to a liquid inlet device; a lower positive temperature circulation tank; a first constant temperature circulation tank, connected to the lower positive temperature circulation tank; a middle negative temperature circulation tank; a second constant temperature circulation tank, connected to the middle negative temperature circulation tank; an upper positive temperature circulation tank; a third constant temperature circulation tank, connected to the upper positive temperature circulation tank; a top cover, the top cover is provided with an upper permeable stone, an air outlet and a liquid outlet hole, the air outlet hole is connected to a gas extraction saturation device, and the liquid outlet hole is connected to a liquid outlet device. The present invention also discloses a saturated frozen soil permeability test method. The test device of the present invention integrates soil sampling, gas extraction saturation, and permeability test, which can eliminate errors in each stage and ensure that the permeability coefficient is more accurate; it can accurately control the temperature of the soil body, so that the soil body can form a "thaw-freeze-thaw" from top to bottom, and there is a transition between the thawed soil and the frozen soil, eliminating the "ice film" on the surface of the frozen soil.

Description

Technical Field

[0001] The invention relates to the technical field of frozen soil testing, and in particular to a saturated frozen soil penetration testing device and method. Background Art

[0002] In frozen soil or frozen soil, water migrates along the temperature gradient and condenses and frosts in the low-temperature frozen zone; external pressure acts on saturated frozen soil to cause water redistribution; heavy metals, organic pollutants, etc. migrate and diffuse in permafrost. These research conclusions all show that frozen soil is not impermeable, but a weakly permeable material with great permeability variation. Under various temperature, pressure, water and structural conditions, permeability, as a controlling factor of water migration, is extremely important for the analysis of permafrost seepage process and the calculation of water-heat coupling. Due to climate warming and human activities, the upper boundary of permafrost in the Qinghai-Tibet Plateau has moved downward and permafrost has degraded, and the permafrost boundary in Northeast China has moved northward significantly, resulting in serious water loss in the two regions. Many serious geological disasters are caused by the melting of frozen soil and the infiltration and flow of water, such as vegetation degradation, irregular surface settlement, release of frozen microorganisms, greenhouse gas emissions, soil pollution, slope instability, etc. Therefore, accurately grasping the permeability characteristics of frozen soil has important practical value for the stability of frozen soil engineering foundations and the restoration of water and soil ecological environment in cold regions.

[0003] Generally speaking, the current measurement of permeability coefficient of frozen soil can be divided into direct measurement and indirect measurement. Direct measurement is to use the permeability medium to flow through the frozen soil sample in the permeation device under the action of gravity or additional force, and calculate the permeability coefficient based on the seepage rate and time. The common unit is cm / s. There are many limitations in the development of direct measurement methods: the temperature instability of frozen soil affects the ice-water balance of frozen soil, the interference of permeability media such as lactose solution, ethylene glycol, diesel, sodium chloride solution, and the obstruction of the "ice film" on the surface of frozen soil directly affect the accuracy of the measured permeability coefficient; water flows through unsaturated frozen soil, ice-water conversion and water retention will occur. Depending on the ambient temperature and liquid water temperature, unsaturated frozen soil will be converted into saturated frozen soil or thawed soil, and the measurement of permeability coefficient will also lose its meaning. Foreign scholars Watanabe and Wake once proposed a method to indirectly measure the permeability coefficient of frozen soil through frost heave test and Clapeyron equation, but its theoretical derivation is too cumbersome and verification also needs to be directly measured, which increases the difficulty of calculating the water-thermal coupling model.

[0004] In previous studies, the permeability coefficient of frozen soil is roughly 10 -5 -10 -9 cm / s level, the closer the temperature is to the melting temperature, the faster the level increases, and the permeability coefficient and temperature are roughly exponentially related. Therefore, the test measurement requires strict requirements and factors that may affect the test accuracy must be avoided, otherwise the permeability coefficient of frozen soil measured will be difficult to be convincing. Therefore, it is urgent to design a device to accurately measure the permeability coefficient of frozen soil. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a saturated frozen soil permeability test device and method.

[0006] In order to achieve the above purpose, the technical solution provided by an embodiment of the present invention is as follows:

[0007] A saturated frozen soil permeability test device, comprising:

[0008] Bracket;

[0009] A base is arranged on the bracket, wherein a lower liquid permeable stone and a liquid inlet hole are arranged in the base, and the liquid inlet hole is connected to a liquid inlet device;

[0010] A lower positive temperature circulation tank, wherein the side wall of the lower positive temperature circulation tank is hollow and is disposed on the base, and the side wall of the lower positive temperature circulation tank is provided with at least one first channel, and a first temperature sensor is disposed in the first channel;

[0011] a first constant temperature circulation tank, wherein the first constant temperature circulation tank is connected to the lower positive temperature circulation tank;

[0012] A middle negative temperature circulation tank, wherein the side wall of the middle negative temperature circulation tank is hollow and is arranged on the lower positive temperature circulation tank, and the side wall of the middle negative temperature circulation tank is provided with at least one second channel, and a second temperature sensor is arranged in the second channel;

[0013] A second constant temperature circulation tank, the second constant temperature circulation tank is connected to the middle negative temperature circulation tank;

[0014] An upper positive temperature circulation tank, the side wall of which is hollow and arranged on the middle negative temperature circulation tank, the side wall of which is hollow and arranged with at least one third channel, wherein a third temperature sensor is arranged in the third channel;

[0015] A third constant temperature circulation tank, the third constant temperature circulation tank being connected to the upper positive temperature circulation tank;

[0016] The top cover is arranged on the upper positive temperature circulation tank, and an upper permeable stone, an air outlet and a liquid outlet are arranged inside the top cover. The air outlet is connected to a vacuum saturation device, and the liquid outlet is connected to a liquid outlet device.

[0017] As a further improvement of the present invention, the liquid inlet device includes a liquid inlet pipe, a liquid inlet valve connected to the liquid inlet pipe, a water pump connected to the liquid inlet valve, and a liquid inlet container connected to the water pump, the liquid inlet pipe is connected to the liquid inlet hole, a first weighing sensor is arranged below the liquid inlet container, and a fourth temperature sensor and a temperature regulating component are arranged in the liquid inlet container.

[0018] As a further improvement of the present invention, a pressure regulating valve is connected between the liquid inlet valve and the water pump; and / or the liquid inlet container includes a first beaker and a first beaker cover matching the first beaker, and the first beaker cover is provided with two first through holes; and / or the temperature regulating component includes a cooling rod.

[0019] As a further improvement of the present invention, the liquid outlet device includes a liquid outlet pipe, a liquid outlet valve connected to the liquid outlet pipe, and a liquid outlet container connected to the liquid outlet valve, the liquid outlet pipe is connected to the liquid outlet hole, and a second weighing sensor is arranged below the liquid outlet container.

[0020] As a further improvement of the present invention, the liquid outlet container includes a second beaker and a second beaker cover matched with the second beaker, and the second beaker cover is provided with a second through hole.

[0021] As a further improvement of the present invention, the air saturation device includes an air extraction pipe, an air extraction valve connected to the air extraction pipe, and a vacuum pump connected to the air extraction valve, and the air extraction pipe is connected to the air outlet.

[0022] As a further improvement of the present invention, a first liquid inlet and a first liquid outlet are relatively arranged on the side wall of the lower positive temperature circulation tank, and the first liquid inlet and the first liquid outlet are both connected to the first constant temperature circulation tank, a second liquid inlet and a second liquid outlet are relatively arranged on the side wall of the middle negative temperature circulation tank, and the second liquid inlet and the second liquid outlet are both connected to the second constant temperature circulation tank, and a third liquid inlet and a third liquid outlet are relatively arranged on the side wall of the upper positive temperature circulation tank, and the third liquid inlet and the third liquid outlet are both connected to the third constant temperature circulation tank.

[0023] As a further improvement of the present invention, aerogel interlayers are provided between the lower positive temperature circulation tank and the base, between the middle negative temperature circulation tank and the lower positive temperature circulation tank, between the upper positive temperature circulation tank and the middle negative temperature circulation tank, and between the top cover and the upper positive temperature circulation tank.

[0024] As a further improvement of the present invention, the upper part of the base is respectively provided with a first permeable stone groove and a first interlayer groove, the lower and upper parts of the lower positive temperature circulation tank are respectively provided with a second interlayer groove and a third interlayer groove, the lower and upper parts of the middle negative temperature circulation tank are respectively provided with a fourth interlayer groove and a fifth interlayer groove, the lower and upper parts of the upper positive temperature circulation tank are respectively provided with a sixth interlayer groove and a seventh interlayer groove, and the lower part of the top cover is respectively provided with a second permeable stone groove and an eighth interlayer groove.

[0025] A saturated frozen soil permeability test method, using the saturated frozen soil permeability test device, the test method comprises the following steps:

[0026] (1) Preparing the soil: Before preparing the soil, the first channel, the second channel, and the third channel are blocked, soil is added to the lower positive temperature circulation tank, the middle negative temperature circulation tank, and the upper positive temperature circulation tank and compacted to form the soil. After the soil preparation is completed, the blocking members in the first channel, the second channel, and the third channel are pulled out;

[0027] (2) Soil saturation: Close the liquid outlet device, open the liquid inlet device and the air saturation device. When the permeable medium flows out of the air saturation device stably, close the air saturation device and the liquid inlet device. At this point, the soil is saturated.

[0028] (3) The temperatures of the first constant temperature circulation tank and the third constant temperature circulation tank are both set to positive temperatures, and the temperature of the second constant temperature circulation tank is set to negative temperature, and the first temperature sensor, the second temperature sensor, and the third temperature sensor are used to determine whether the temperature is stable. If the temperature is stable, the test condition is met;

[0029] (4) Start the permeability test: open the liquid inlet and outlet devices, and conduct the test according to the determined permeability test duration. After reaching the specified duration, close the liquid outlet and inlet devices in turn. After the test is completed, the permeability coefficient can be determined based on the mass and density of the liquid collected by the liquid outlet device and the test duration.

[0030] The beneficial effects of the present invention are:

[0031] (1) The test device of the present invention integrates soil sampling, air saturation and permeability test, which can eliminate errors in each stage and ensure that the permeability coefficient is more accurate. At the same time, the present invention performs saturated frozen soil infiltration in a closed system. During the measurement, the amount of water in and out can be accurately determined and it can be ensured that there is no residual water in the test device. The precise quantification of water ensures the accurate measurement of the magnitude of the permeability coefficient.

[0032] (2) This system can accurately control the temperature of the soil, so that the soil can form a "thaw-freeze-thaw" state from top to bottom. There is a transition between thawed soil and frozen soil, providing a natural connection of "thaw-freeze-thaw" soil, eliminating the "ice film" on the surface of frozen soil, reserving a natural infiltration channel and being more in line with the laws of nature.

[0033] (3) By setting up the air saturation device, it is ensured that the test soil is saturated frozen soil, that the permeability coefficient of frozen soil is measured under saturated frozen soil, and that the measured permeability coefficient of frozen soil is meaningful.

[0034] (4) The overall test of the present invention adopts bottom water inlet and top water outlet, and the effect of gravity can be considered separately when determining the water inlet pressure, making the test result more accurate.

[0035] (5) The setting of the liquid inlet device facilitates pressure control, and fitting calculations can be performed based on the different permeability coefficients measured at different pressures, providing a reference for actual engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 It is a structural schematic diagram of a preferred embodiment of the present invention;

[0038] Figure 2 It is a structural schematic diagram of the lower positive temperature circulation tank of a preferred embodiment of the present invention;

[0039] Figure 3 A schematic structural diagram of a base according to a preferred embodiment of the present invention;

[0040] In the figure: 1, bracket, 2, base, 21, lower permeable stone, 211, first permeable stone groove, 212, first interlayer groove, 22, liquid inlet hole, 23, liquid inlet pipe, 231, first liquid inlet branch pipe, 232, second liquid inlet branch pipe, 233, third liquid inlet branch pipe, 24, liquid inlet valve, 26, water pump, 270, pressure regulating valve, 271, first weighing sensor, 272, fourth temperature sensor, 273, cooling rod, 274, power supply, 28, first beaker, 29, first beaker cover, 3, lower positive temperature circulation tank, 31, first channel, 32, first liquid inlet, 33, first liquid outlet, 34, second interlayer groove, 35, third interlayer groove, 11, first constant temperature circulation groove, 12, second constant temperature circulation groove, 13 , the third constant temperature circulation tank, 4, the middle negative temperature circulation tank, 41, the second channel, 42, the fourth interlayer tank, 43, the fifth interlayer tank, 5, the upper positive temperature circulation tank, 51, the third channel, 52, the sixth interlayer tank, 53, the seventh interlayer tank, 6, the top cover, 61, the upper permeable stone, 62, the air outlet, 63, the liquid outlet, 71, the first temperature sensor, 72, the second temperature sensor, 73, the third temperature sensor, 81, the liquid outlet pipe, 811, the liquid outlet branch pipe, 82, the liquid outlet valve, 83, the second weighing sensor, 84, the second beaker, 85, the second beaker cover, 86, the exhaust pipe, 861, the exhaust branch pipe, 87, the exhaust valve, 88, the vacuum pump, 91, the aerogel interlayer, 92, the data acquisition instrument, 93, the computer. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions 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 only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0042] See also Figure 1-Figure 3 The embodiment of the present application discloses a saturated frozen soil permeability test device, including: a bracket 1, a base 2, a lower positive temperature circulation tank 3, a first constant temperature circulation tank 11, a middle negative temperature circulation tank 4, a second constant temperature circulation tank 12, an upper positive temperature circulation tank 5, a third constant temperature circulation tank 13, and a top cover 6. The base 2 is arranged on the bracket 1, and a lower permeable stone 21 and a liquid inlet hole 22 are arranged in the base 2, and the liquid inlet hole 22 is connected to a liquid inlet device. The side wall of the lower positive temperature circulation tank 3 is hollow inside and is arranged on the base 2. The side wall of the lower positive temperature circulation tank 3 is provided with at least one first channel 31, and a first temperature sensor 71 is arranged in the first channel 31; the first constant temperature circulation tank 11 is connected to the lower positive temperature circulation tank 3. The side wall of the middle negative temperature circulation tank 4 is hollow inside and is arranged on the lower positive temperature circulation tank 3. The side wall of the middle negative temperature circulation tank 4 is provided with at least one second channel 41, and a second temperature sensor 72 is arranged in the second channel 41; the second constant temperature circulation tank 12 is connected to the middle negative temperature circulation tank 4. The side wall of the upper positive temperature circulation tank 5 is hollow inside and is arranged on the middle negative temperature circulation tank 4. The side wall of the upper positive temperature circulation tank 5 is provided with at least one third channel 51, and a third temperature sensor 73 is arranged in the third channel 51; the third constant temperature circulation tank 13 is connected to the upper positive temperature circulation tank 5. The top cover 6 is arranged on the upper positive temperature circulation tank 5, and an upper permeable stone 61, an air outlet 62 and a liquid outlet 63 are arranged in the top cover 6. The air outlet 62 is connected to a saturation device for exhausting gas, and the liquid outlet 63 is connected to a liquid outlet device.

[0043] Support is provided by the bracket 1. The lower permeable stone 21 and the upper permeable stone 61 are arranged to prevent the slurry of the thawed soil from clogging the liquid inlet hole 22 and the liquid outlet hole 63 or gushing out with the liquid outlet hole 63 and the air outlet hole 62. The first temperature sensor 71, the second temperature sensor 72, and the third temperature sensor 73 are in contact with the soil body respectively, and the lower positive temperature circulation tank 3, the middle negative temperature circulation tank 4, and the upper positive temperature circulation tank 5 respectively use the first constant temperature circulation tank 11, the second constant temperature circulation tank 12, and the third constant temperature circulation tank 13 to cooperate with the first temperature sensor 71, the second temperature sensor 72, and the third temperature sensor 73 to independently and accurately control the temperature of the soil body, so that the soil body can form "thaw-freeze-thaw" from top to bottom, and there is a transition between the thawed soil and the frozen soil, eliminating the "ice film" on the surface of the frozen soil. The overall test adopts bottom water inlet and top water outlet, and the effect of gravity can be considered separately when determining the water inlet pressure. The liquid inlet device is used to accurately control the pressure of water inlet; the liquid outlet device is used to allow the infiltration medium to flow out and accurately quantify; the air extraction device cooperates with the liquid inlet device to extract air and saturate the soil with water to ensure that the frozen soil is saturated frozen soil.

[0044] The bracket 1 has a hollow structure inside, which is convenient for reserving installation space for the partial structure of the liquid inlet device. Preferably, the outer diameters of the base 2, the lower positive temperature circulation tank 3, the middle negative temperature circulation tank 4, the upper positive temperature circulation tank 5, and the top cover 6 are the same. Preferably, the inner diameters of the lower positive temperature circulation tank 3, the middle negative temperature circulation tank 4, and the upper positive temperature circulation tank 5 are the same. Preferably, the inner walls of the first channel 31, the second channel 41, and the third channel 51 are all provided with Teflon coatings and hollow cylindrical aerogel interlayers to prevent the temperatures of the lower positive temperature circulation tank 3, the middle negative temperature circulation tank 4, and the upper positive temperature circulation tank 5 from affecting the accuracy of the first temperature sensor 71, the second temperature sensor 72, and the third temperature sensor 73, respectively, to ensure the accuracy of the first temperature sensor 71, the second temperature sensor 72, and the third temperature sensor 73 in measuring the soil temperature.

[0045] In this embodiment, the liquid inlet device includes a liquid inlet pipe 23, a liquid inlet valve 24 connected to the liquid inlet pipe 23, a water pump 26 connected to the liquid inlet valve 24, and a liquid inlet container connected to the water pump 26. The liquid inlet pipe 23 is connected to the liquid inlet hole 22. A first weighing sensor 271 is arranged below the liquid inlet container, and a fourth temperature sensor 272 and a thermostat are arranged in the liquid inlet container. The liquid inlet container is filled with a test permeable medium, and the specific permeable medium can be selected according to the test plan. The first weighing sensor 271 can monitor the change of the total weight of water in the liquid inlet container in real time, and the fourth temperature sensor 272 is used to monitor the liquid temperature in the liquid inlet container. The working voltage of the thermostat is adjusted according to the value output by the fourth temperature sensor 272 to ensure that the temperature of the permeable medium meets the requirements during the test, so that the permeable medium maintains its ice-water balance after entering the frozen soil. When the liquid inlet valve 24 is opened, the liquid inlet pipe 23 and the water pump 26 can be connected, so that the water pump 26 can pump water into the liquid inlet pipe 23; when the liquid inlet valve 24 is closed, it is convenient to prevent water from flowing back after the air saturation is completed.

[0046] Preferably, the liquid inlet pipe 23 is rigidly connected to the liquid inlet hole 22 by threading to ensure water tightness. Preferably, a pressure regulating valve 270 is connected between the liquid inlet valve 24 and the water pump 26, so as to accurately control the water inlet pressure, provide multiple water inlet pressure variables during subsequent tests, and improve the reliability of the test. Preferably, the liquid inlet container includes a first beaker 28, a first beaker cover 29 matched with the first beaker 28, and two first through holes (not shown in the figure) are arranged on the first beaker cover 29. The first beaker cover 29 can prevent the water in the first beaker 28 from evaporating and running away. Preferably, the temperature regulating part includes a cooling rod 273, which is used to cool the permeable medium and maintain the test temperature, and the power supply 274 provides energy for the cooling rod 273. The setting of the two first through holes can facilitate the cooling rod 273 to extend out of the first beaker cover 29 and the pipe connected to the water pump 26 to enter the first beaker 28.

[0047] In this embodiment, the liquid outlet device includes a liquid outlet pipe 81, a liquid outlet valve 82 connected to the liquid outlet pipe 81, and a liquid outlet container connected to the liquid outlet valve 82. The liquid outlet pipe 81 is connected to the liquid outlet hole 63, and a second weighing sensor 83 is arranged below the liquid outlet container. The liquid outlet valve 82 is used to prevent water backflow and provide sealing conditions when the gas is saturated.

[0048] The liquid outlet pipe 81 is preferably threadedly rigidly connected to the liquid outlet hole 63 to ensure water tightness. The liquid outlet container preferably includes a second beaker 84 and a second beaker cover 85 matched with the second beaker 84, and a second through hole (not shown in the figure) is provided on the second beaker cover 85. The second beaker cover 85 can prevent the water in the second beaker 84 from evaporating and escaping. The diameter of the second through hole is equal to or slightly larger than the outer diameter of the liquid outlet pipe 81, so that the liquid outlet pipe 81 can pass through and extend into the second beaker 84.

[0049] The air extraction and saturation device is used to prepare saturated soil. Preferably, the air extraction and saturation device includes an air extraction pipe 86, an air extraction valve 87 connected to the air extraction pipe 86, and a vacuum pump 88 connected to the air extraction valve 87. The air extraction pipe 86 is connected to the air outlet 62. Preferably, the air extraction pipe 86 is threadedly connected to the air outlet 62 of the top cover 6 to ensure sealing.

[0050] In this embodiment, the first liquid inlet 32 ​​and the first liquid outlet 33 are arranged on the side wall of the lower positive temperature circulation tank 3, and the first liquid inlet 32 ​​and the first liquid outlet 33 are connected to the first constant temperature circulation tank 11. The second liquid inlet (not shown in the figure) and the second liquid outlet (not shown in the figure) are arranged on the side wall of the middle negative temperature circulation tank 4, and the second liquid inlet and the second liquid outlet are connected to the second constant temperature circulation tank 12. The third liquid inlet (not shown in the figure) and the third liquid outlet (not shown in the figure) are arranged on the side wall of the upper positive temperature circulation tank 5, and the third liquid inlet and the third liquid outlet are connected to the third constant temperature circulation tank 13. The first liquid inlet 32 ​​and the first liquid outlet 33 are connected to the inside of the side wall of the lower positive temperature circulation tank 3, the second liquid inlet and the second liquid outlet are connected to the inside of the side wall of the middle negative temperature circulation tank 4, and the third liquid inlet and the third liquid outlet are connected to the inside of the side wall of the upper positive temperature circulation tank 5. Preferably, the first liquid inlet 32 ​​and the first channel 31, the second liquid inlet and the second channel 41, and the third liquid inlet and the third channel 51 are all arranged orthogonally. After the circulating liquid is evenly diffused, the temperature sensor detects the temperature again to further ensure that the temperature at the upper and lower ends of the frozen soil is consistent.

[0051] Preferably, an aerogel interlayer 91 is provided between the lower positive temperature circulation tank 3 and the base 2, between the middle negative temperature circulation tank 4 and the lower positive temperature circulation tank 3, between the upper positive temperature circulation tank 5 and the middle negative temperature circulation tank 4, and between the top cover 6 and the upper positive temperature circulation tank 5. The aerogel interlayer 91 not only plays a sealing role, but also prevents the temperature transfer between the lower positive temperature circulation tank 3, the middle negative temperature circulation tank 4, and the upper positive temperature circulation tank 5.

[0052] In order to better arrange the aerogel interlayer 91, it is preferred that the upper part of the base 2 is respectively provided with a first permeable stone groove 211 and a first interlayer groove 212, the lower and upper parts of the lower positive temperature circulation tank 3 are respectively provided with a second interlayer groove 34 and a third interlayer groove 35, the lower and upper parts of the middle negative temperature circulation tank 4 are respectively provided with a fourth interlayer groove 42 and a fifth interlayer groove 43, the lower and upper parts of the upper positive temperature circulation tank 5 are respectively provided with a sixth interlayer groove 52 and a seventh interlayer groove 53, and the lower part of the top cover 6 is respectively provided with a second permeable stone groove 64 and an eighth interlayer groove 65.

[0053] Preferably, the first temperature sensor 71, the second temperature sensor 72, the third temperature sensor 73, and the fourth temperature sensor 272 are all connected to the data acquisition instrument 92. The first weighing sensor 271 and the second weighing sensor 83 are all connected to the data acquisition instrument 92. The data acquisition instrument 92 is connected to the computer 93. The temperature and quality data collected by the data acquisition instrument 92 are transmitted to the computer 93, and the computer 93 processes in real time, collects the values ​​of temperature and quality, and can observe real-time changes.

[0054] The present application also discloses a saturated frozen soil permeability test method. Using the saturated frozen soil permeability test device of the above embodiment, the test method includes the following steps:

[0055] (1) Preparing the soil: Before preparing the soil, the first hole 31, the second hole 41, and the third hole 51 are blocked, and soil is added to the lower positive temperature circulation tank 3, the middle negative temperature circulation tank 4, and the upper positive temperature circulation tank 5 and compacted to form a soil. After the soil preparation is completed, the blocking pieces in the first hole 31, the second hole 41, and the third hole 51 are pulled out;

[0056] (2) Soil saturation: Close the liquid outlet device, open the liquid inlet device and the air saturation device. When the permeable medium flows out of the air saturation device stably, close the air saturation device and the liquid inlet device. At this point, the soil is saturated.

[0057] (3) The temperatures of the first constant temperature circulation tank 11 and the third constant temperature circulation tank 13 are both set to positive temperatures, and the temperature of the second constant temperature circulation tank 12 is set to negative temperatures. The first temperature sensor 71, the second temperature sensor 72, and the third temperature sensor 73 are used to determine whether the temperatures are stable. If the temperatures are stable, the test conditions are met.

[0058] (4) Start the permeability test: open the liquid inlet and outlet devices, and conduct the test according to the determined permeability test duration. After reaching the specified duration, close the liquid outlet and inlet devices in turn. After the test is completed, the permeability coefficient can be determined based on the mass and density of the liquid collected by the liquid outlet device and the test duration.

[0059] In order to better illustrate the test method of this application, the following are detailed test steps.

[0060] 1. Install the test circulation tank: install the lower permeable stone 21 in the first permeable stone groove 211 on the upper part of the base 2, install the aerogel interlayer 91 in the first interlayer groove 212, and then install the lower positive temperature circulation tank 3 above the base 2. The outer diameter and inner diameter of the second interlayer groove 34 of the lower positive temperature circulation tank 3, the first interlayer groove 212 of the base 2, and the aerogel interlayer 91 are the same, forming a precise connection; install the aerogel interlayer 91 in the third interlayer groove 35 of the lower positive temperature circulation tank 3, and then install the middle negative temperature circulation tank 4 above the lower positive temperature circulation tank 3. The third interlayer groove 35 of the lower positive temperature circulation tank 3 is the same as the inner diameter of the second interlayer groove 34 of the base 2. , the outer diameter and inner diameter of the fourth insulation groove 42 of the middle negative temperature circulation tank 4 and the aerogel insulation layer 91 are the same, forming a precise connection; the aerogel insulation layer 91 is installed in the fifth insulation groove 43 of the middle negative temperature circulation tank 4, and then the upper positive temperature circulation tank 5 is installed above the middle negative temperature circulation tank 4, the outer diameter and inner diameter of the fifth insulation groove 43 of the middle negative temperature circulation tank 4, the sixth insulation groove 52 of the upper positive temperature circulation tank 5, and the aerogel insulation layer 91 are the same, forming a precise connection; all joints on the outside of the lower positive temperature circulation tank 3, the middle negative temperature circulation tank 4, and the upper positive temperature circulation tank 5 are painted with water-stopping paint and wrapped with water-stopping tape.

[0061] 2. Prepare the soil: Before preparing the soil, the first channel 31, the second channel 41, and the third channel 51 need to be plugged in advance. Add soil to the installed lower positive temperature circulation tank 3, the middle negative temperature circulation tank 4, and the upper positive temperature circulation tank 5. The soil can be selected according to the test plan for different soil types, dry density, moisture content, etc. The total volume of the lower positive temperature circulation tank 3, the middle negative temperature circulation tank 4, and the upper positive temperature circulation tank 5 is known. Weigh the required soil samples and use a conventional sample preparation machine to compact and prepare the samples. After the preparation is completed, pull out the plugs in the first channel 31, the second channel 41, and the third channel 51, install the first temperature sensor 71, the second temperature sensor 72, and the third temperature sensor 73, and fix and seal them at the same time. Then connect the first temperature sensor 71, the second temperature sensor 72, and the third temperature sensor 73 to the data acquisition instrument 92.

[0062] 3. After the soil is prepared, install the aerogel interlayer 91 in the seventh interlayer groove 53 of the upper positive temperature circulation tank 5, install the upper permeable stone 61 in the second permeable stone groove 64 of the top cover 6, and then connect the top cover 6 with the upper positive temperature circulation tank 5. The outer diameter and inner diameter of the eighth interlayer groove 65 of the top cover 6, the seventh interlayer groove 53 of the upper positive temperature circulation tank 5, and the aerogel interlayer 91 are the same, forming a precise connection; apply water-stopping paint on the joints and wrap them with water-stopping tape. After the overall assembly is completed, place it on the bracket 1.

[0063] 4. Connect the liquid inlet pipe 23 to the liquid inlet hole 22 of the base 2, connect the liquid inlet valve 24 to the liquid inlet pipe 23, and connect the liquid inlet valve 24, the pressure regulating valve 270, the water pump 26, and the first beaker 28 in sequence. Specifically, the first liquid inlet branch pipe 231 is connected between the pressure regulating valve 270 and the liquid inlet valve 24, the second liquid inlet branch pipe 232 is connected between the water pump 26 and the pressure regulating valve 270, and the third liquid inlet branch pipe 233 is connected between the first beaker 28 and the water pump 26. The third liquid inlet branch pipe 233 passes through the first beaker cover 29 and extends into the first beaker 28, and the cooling rod 273 passes through the first beaker cover 29. The liquid inlet pipe 23, the first liquid inlet branch pipe 231, and the second liquid inlet branch pipe 232 are all rigid pipes to prevent the pipe body from bursting due to excessive pressure and the expansion of the pipe body, causing measurement errors. The third liquid inlet branch pipe 233 between the water pump 26 and the first beaker 28 is not required to be rigid. The data acquisition instrument 92 is connected to the computer 93, and the first weighing sensor 271 and the fourth temperature sensor 272 are connected to the data acquisition instrument 92. The liquid inlet pipe 23, the first liquid inlet branch pipe 231, the second liquid inlet branch pipe 232, and the third liquid inlet branch pipe 233 are all wrapped with hollow cylindrical rubber-plastic insulation materials.

[0064] 5. Connect the liquid outlet pipe 81 to the liquid outlet hole 63 of the top cover 6, connect the liquid outlet valve 82 to the liquid outlet pipe 81, and connect the second beaker 84 to the liquid outlet valve 82 through the liquid outlet branch pipe 811. The liquid outlet branch pipe 811 needs to pass through the second beaker cover 85. The second weighing sensor 83 is connected to the data acquisition instrument 92.

[0065] 6. Install the air extraction pipe 86, the air extraction valve 87 is connected to the air extraction pipe 86, and the vacuum pump 88 is connected to the air extraction valve 87 through the air extraction branch pipe 861. The air extraction pipe 86 and the air extraction branch pipe 861 are both rigid pipes.

[0066] 7. Soil saturation: close the liquid inlet valve 24, the liquid outlet valve 82, and the air extraction valve 87, open the water pump 26 and the pressure regulating valve 270, the water in the first beaker 28 is sucked in and blocked by the liquid inlet valve 24, and the value of the first weighing sensor 271 is recorded after it stabilizes, then open the vacuum pump 88, the liquid inlet valve 24, and the air extraction valve 87 in turn, and after the permeable medium has stably flowed out of the air extraction valve 87, close the air extraction valve 87, the vacuum pump 88, the liquid inlet valve 24, the pressure regulating valve 270, and the water pump 26 in turn, and record the value of the first weighing sensor 271. At this point, the soil is saturated and the amount of water used for soil saturation can be recorded.

[0067] 8. Connect the lower positive temperature circulation tank 3 to the first constant temperature circulation tank 11, the middle negative temperature circulation tank 4 to the second constant temperature circulation tank 12, and the upper positive temperature circulation tank 5 to the third constant temperature circulation tank 13. The first constant temperature circulation tank 11 and the third constant temperature circulation tank 13 are set to a positive temperature close to 0°C, and the second constant temperature circulation tank 12 is set to a selected negative temperature. The positive temperature does not exceed the absolute value of the negative temperature. The first constant temperature circulation tank 11, the second constant temperature circulation tank 12, and the third constant temperature circulation tank 13 are kept at a constant temperature for a period of time to make the soil reach the "thaw-freeze-thaw" test condition. The specific time needs to be determined according to the changes of the first temperature sensor 71, the second temperature sensor 72, and the third temperature sensor 73. The fourth temperature sensor 272 and the cooling rod 273 control the temperature of the permeable medium in the first beaker 28 to make it the same as the temperature of the lower soil. The test conditions can only be achieved after the values ​​of all temperature sensors are stable and last for a period of time.

[0068] 9. Start the permeability test: Turn on the water pump 26 and the pressure regulating valve 270, and adjust the water inlet pressure according to the test plan. Open the liquid inlet valve 24 and the liquid outlet valve 82 in sequence to start the permeability test. Perform the test according to the determined permeability test duration. After reaching the specified duration, close the liquid outlet valve 82, the liquid inlet valve 24, the water pump 26 and the pressure regulating valve 270 in sequence. After the test is completed, the permeability coefficient can be calculated. Calculation of permeability coefficient: According to Darcy's law formula , where v is the permeability coefficient, in mm / s; Q is the seepage rate, in mm³ / s; A is the soil cross-sectional area, in mm 2 First, the volume of the permeable medium is calculated based on the mass and density of the permeable medium in the second beaker 84, and then Q is determined by the ratio of the volume of the permeable medium to the permeation time. A is the inner diameter area of ​​the lower positive temperature circulation tank 3. The second weighing sensor 83 monitors the mass change regularly throughout the whole process, which can be used to analyze the stability of the permeation. The value change of the first weighing sensor 271 can be used to compare with the second weighing sensor 83. If the value difference is large, it means that there is a problem in the saturation process, and re-saturation and testing are required.

[0069] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0070] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A saturated frozen soil permeability test device, characterized in that: include: Bracket; A base is arranged on the bracket, wherein a lower liquid permeable stone and a liquid inlet hole are arranged in the base, and the liquid inlet hole is connected to a liquid inlet device; A lower positive temperature circulation tank, wherein the side wall of the lower positive temperature circulation tank is hollow and is disposed on the base, and the side wall of the lower positive temperature circulation tank is provided with at least one first channel, and a first temperature sensor is disposed in the first channel; a first constant temperature circulation tank, wherein the first constant temperature circulation tank is connected to the lower positive temperature circulation tank; A middle negative temperature circulation tank, wherein the side wall of the middle negative temperature circulation tank is hollow and is arranged on the lower positive temperature circulation tank, and the side wall of the middle negative temperature circulation tank is provided with at least one second channel, and a second temperature sensor is arranged in the second channel; A second constant temperature circulation tank, the second constant temperature circulation tank is connected to the middle negative temperature circulation tank; An upper positive temperature circulation tank, the side wall of which is hollow and arranged on the middle negative temperature circulation tank, the side wall of which is hollow and arranged with at least one third channel, wherein a third temperature sensor is arranged in the third channel; A third constant temperature circulation tank, the third constant temperature circulation tank being connected to the upper positive temperature circulation tank; The top cover is arranged on the upper positive temperature circulation tank, and an upper permeable stone, an air outlet and a liquid outlet are arranged inside the top cover. The air outlet is connected to a vacuum saturation device, and the liquid outlet is connected to a liquid outlet device.

2. A saturated frozen soil permeability test device according to claim 1, characterized in that: The liquid inlet device includes a liquid inlet pipe, a liquid inlet valve connected to the liquid inlet pipe, a water pump connected to the liquid inlet valve, and a liquid inlet container connected to the water pump. The liquid inlet pipe is connected to the liquid inlet hole, a first weighing sensor is arranged below the liquid inlet container, and a fourth temperature sensor and a temperature regulating component are arranged in the liquid inlet container.

3. A saturated frozen soil permeability test device according to claim 2, characterized in that: A pressure regulating valve is connected between the liquid inlet valve and the water pump; and / or the liquid inlet container includes a first beaker and a first beaker cover matching the first beaker, and the first beaker cover is provided with two first through holes; and / or the temperature regulating component includes a cooling rod.

4. A saturated frozen soil permeability test device according to claim 1, characterized in that: The liquid outlet device includes a liquid outlet pipe, a liquid outlet valve connected to the liquid outlet pipe, and a liquid outlet container connected to the liquid outlet valve. The liquid outlet pipe is connected to the liquid outlet hole, and a second weighing sensor is arranged below the liquid outlet container.

5. A saturated frozen soil permeability test device according to claim 4, characterized in that: The liquid outlet container comprises a second beaker and a second beaker cover matched with the second beaker, and the second beaker cover is provided with a second through hole.

6. A saturated frozen soil permeability test device according to claim 1, characterized in that: The air extraction and saturation device comprises an air extraction pipe, an air extraction valve connected to the air extraction pipe, and a vacuum pump connected to the air extraction valve, and the air extraction pipe is connected to the air outlet.

7. A saturated frozen soil permeability test device according to claim 1, characterized in that: The side wall of the lower positive temperature circulation tank is provided with a first liquid inlet and a first liquid outlet, and the first liquid inlet and the first liquid outlet are both connected to the first constant temperature circulation tank. The side wall of the middle negative temperature circulation tank is provided with a second liquid inlet and a second liquid outlet, and the second liquid inlet and the second liquid outlet are both connected to the second constant temperature circulation tank. The side wall of the upper positive temperature circulation tank is provided with a third liquid inlet and a third liquid outlet, and the third liquid inlet and the third liquid outlet are both connected to the third constant temperature circulation tank.

8. A saturated frozen soil permeability test device according to claim 1, characterized in that: Aerogel interlayers are arranged between the lower positive temperature circulation tank and the base, between the middle negative temperature circulation tank and the lower positive temperature circulation tank, between the upper positive temperature circulation tank and the middle negative temperature circulation tank, and between the top cover and the upper positive temperature circulation tank.

9. A saturated frozen soil permeability test device according to claim 8, characterized in that: The upper part of the base is respectively provided with a first liquid-permeable stone groove and a first interlayer groove, the lower and upper parts of the lower positive temperature circulation tank are respectively provided with a second interlayer groove and a third interlayer groove, the lower and upper parts of the middle negative temperature circulation tank are respectively provided with a fourth interlayer groove and a fifth interlayer groove, the lower and upper parts of the upper positive temperature circulation tank are respectively provided with a sixth interlayer groove and a seventh interlayer groove, and the lower part of the top cover is respectively provided with a second liquid-permeable stone groove and an eighth interlayer groove.

10. A saturated frozen soil permeability test method, characterized in that: Using the saturated frozen soil penetration test device as described in any one of claims 1 to 9, the test method comprises the following steps: (1) Preparing the soil: Before preparing the soil, the first channel, the second channel, and the third channel are blocked, soil is added to the lower positive temperature circulation tank, the middle negative temperature circulation tank, and the upper positive temperature circulation tank and compacted to form the soil. After the soil preparation is completed, the blocking members in the first channel, the second channel, and the third channel are pulled out; (2) Soil saturation: Close the liquid outlet device, open the liquid inlet device and the air saturation device. When the permeable medium flows out of the air saturation device stably, close the air saturation device and the liquid inlet device. At this point, the soil is saturated. (3) The temperatures of the first constant temperature circulation tank and the third constant temperature circulation tank are both set to positive temperatures, and the temperature of the second constant temperature circulation tank is set to negative temperature, and the first temperature sensor, the second temperature sensor, and the third temperature sensor are used to determine whether the temperature is stable. If the temperature is stable, the test condition is met; (4) Start the permeability test: open the liquid inlet and outlet devices, and conduct the test according to the determined permeability test duration. After reaching the specified duration, close the liquid outlet and inlet devices in turn. After the test is completed, the permeability coefficient can be determined based on the mass and density of the liquid collected by the liquid outlet device and the test duration.

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