Preparation method of soil-rock mixture sample with uniform ice content

Abstract

The invention relates to the technical field of earth-rock mixtures, in particular to a preparation method of an earth-rock mixture sample with uniform ice content. The invention relates to a preparation method of a soil-rock mixture sample with uniform ice content. The preparation method comprises the following steps: calculating the weight of soil, stone and water required for preparing a standard sample; screening the soil and the stones; weighing soil and stone and mixing; adding water to prepare a standard test piece of an earth-rock mixture; transferring the standard test piece into a soil-rock mixture test piece box, and standing in a constant temperature box; determining the ice content of the prepared soil-rock mixture test piece; transferring the test piece box into a low-temperature box, standing at room temperature, and standing in a low-temperature environment; taking out the box, demolding, and measuring the ice content and the size; if the requirements are met, standby application is performed; and if not, repeating the steps 7-9. A step-by-step freezing method is adopted to ensure that the ice content of the test piece is relatively uniform. According to the method, the positions of ice crystals formed by migration of pore water in the soil-rock mixture are different, so that the purpose of manufacturing the soil-rock mixture with uniform ice content is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of soil-rock mixtures, and in particular to a method for preparing a soil-rock mixture sample with uniform ice content. Background Art

[0002] Soil-rock mixture is an extremely heterogeneous composite geological material that is easily disturbed by the external environment. The mechanical properties of the soil-rock mixture on the surface of the ground deteriorate under the action of freeze-thaw, affecting the stability of the road slope and leading to geological disasters such as landslides and collapses.

[0003] Patent publication number CN104359747B discloses a device for preparing and measuring frozen soil samples. It can not only prepare uniform frozen soil samples indoors, but also measure the thermal and permeability parameters of frozen soil samples in situ under interference-free conditions, providing a scientific basis and technical support for the evaluation of hydrate accumulation in permafrost areas and the formulation of hydrate mining plans.

[0004] Patent publication number CN102230856B discloses a method for preparing high-ice-content frozen soil samples. This method is of great significance for conducting mechanical tests on monolithic, high-ice-content artificial frozen soil samples in low-temperature environments and analyzing their mechanical properties.

[0005] Although the above patents have improved the production and measurement of frozen soil to a certain extent, the freezing point of pore water in soil-rock mixtures varies with the size of the pores. The freezing point and freezing temperature are low in small pores. At the frozen area, the water in the large pores freezes first, and then absorbs the weak viscous water around the adjacent soil particles to freeze. Due to the weakening of the water film adsorption, the soil particles lose the balance of electromolecular attraction, and then absorb water from the adjacent soil particles below, migrating the water below to the large pores above, gradually freezing and forming an ice interlayer. When the freezing rate is high, the freezing depth develops quickly, and the water migration speed is relatively slow, the frost heave is small. Only under a certain suitable temperature gradient, that is, when the heat emitted from the frozen surface is exactly equal to the latent heat of phase change when the migrated water is converted to 0°C, and the bottom of the frozen area is located in the capillary water rising zone, the water below will continuously migrate to the frozen surface to form ice crystals, and gradually gather into a lens-shaped ice interlayer. When internal and external heat transfer is uniform, the heat emitted from the frozen surface is uniform, and the ice crystals formed by pore water migration aggregate into a uniform lens-shaped ice layer, indicating a uniform ice content within the specimen. Therefore, the aforementioned patent fails to ensure uniform internal and external heat transfer during the soil-rock mixture production process. This results in an uneven ice content within the soil-rock mixture produced using the proposed method.

[0006] Therefore, there is an urgent need to provide a technical solution to the above-mentioned deficiencies in the existing technology. Summary of the Invention

[0007] In order to overcome the problem that uneven internal and external heat conduction of a soil-rock mixture during the freeze-thaw cycle leads to different positions of ice crystals formed by pore water migrating in the soil-rock mixture, thereby causing uneven ice content in the soil-rock mixture, the present invention provides a method for preparing a soil-rock mixture sample with uniform ice content. This method makes the positions of ice crystals formed by the migration of pore water in the soil-rock mixture different, thereby achieving the purpose of producing a soil-rock mixture with uniform ice content.

[0008] To achieve the above objectives, the present application provides a method for preparing a soil-rock mixture sample with uniform ice content, which adopts the following technical solutions:

[0009] A method for preparing a soil-rock mixture sample with uniform ice content comprises the following steps:

[0010] (1) Calculate the weight of soil, rock, and water based on the rock content, water content, dry density of the soil-rock mixture, and the size of the specimen box;

[0011] (2) screening the soil and stone to obtain soil samples and stone samples respectively;

[0012] (3) According to the rock content determined in step (1), the soil sample and the rock sample in step (2) are weighed and mixed to prepare a uniform soil and rock standard specimen;

[0013] (4) Add water to the soil-rock standard specimen according to the water content determined in step (1), stir evenly, and then cover its surface with a moisturizing film, let it stand, and make a soil-rock mixture standard specimen;

[0014] (5) moving the standard specimen of the soil-rock mixture in step (4) into a soil-rock mixture specimen box, placing it in a constant temperature box and allowing it to stand to ensure that the temperature inside and outside the soil-rock mixture specimen box is uniform;

[0015] (6) Determine the ice content of the soil-rock mixture specimen (the ice content in the soil-rock mixture can be calculated according to the following formula);

[0016] Qtotal=Qwater+QSRM+Qice→water

[0017] Qwater=mwaterCwaterΔT

[0018] QSRM=mSRMCSRMΔT

[0019] Qice→water=miceL

[0020] m water =Mω / (1+ω)

[0021] Where Qwater represents the heat absorbed by water (including ice and liquid water) in the soil-rock mixture, and QSRM represents

[0022] Qice→water represents the latent heat absorbed by the soil matrix and gravel particles in the soil-rock mixture, L is the latent heat of ice, M is the total weight of the sample, and ω is the water content of the soil-rock mixture.

[0023] Since the sample absorbs heat and heats up from 0℃ to 20℃, the influence of super-cold water (liquid water with a temperature less than 0℃) does not need to be considered in the calculation process.

[0024] (7) taking out the soil-rock mixture specimen box after standing in step (5), transferring it to a low-temperature box and allowing it to stand, so that the outside of the soil-rock mixture specimen box is frozen;

[0025] (8) taking out the soil-rock mixture specimen box after standing in the low-temperature box in step (7), and placing it at room temperature to allow the outside of the soil-rock mixture specimen box to thaw;

[0026] (9) placing the soil-rock mixture specimen box after standing at room temperature in step (8) in a low-temperature environment and standing there, so that the temperature inside the soil-rock mixture specimen box is uniform;

[0027] (10) Take out the soil-rock mixture specimen box after standing in the low-temperature environment in step (9), demold the specimen, and measure the ice content of the specimen, as well as the size and weight of the specimen; if it meets the requirements of the above experiment, put the specimen into a sealed standard oil-proof rubber sleeve and put it into a low-temperature box to complete the sample preparation for the experiment; if it does not meet the requirements, perform steps 7-9 again until the required ice content is reached.

[0028] Preferably, in step (1), the weight of soil, stone and water required for preparing the standard sample is calculated based on the stone content, water content and dry density of the sample required for the experiment and the size of the specimen box; wherein, m 石 =m 总 *w 石 , m 水 =m 总 *w 水 . M 土 =m 总 -m 石 -m 水 .

[0029] Preferably, in step (2), the soil and stone are sieved, wherein the particle size of the soil sample is ≤2.0 mm; and the diameter of the stone sample is 5 to 20 mm.

[0030] Preferably, in step (5), the soil-rock mixture specimen box includes an upper cover, a specimen box body and a lower cover arranged in sequence; a copper conduit is provided at the center of the upper cover, and one end of the copper conduit extends into the specimen box body; the specimen box body is a barrel-shaped structure made of copper.

[0031] Further preferably, the diameter of the copper conduit is φ=2 mm; the inner diameter of the test box is φ'=60 mm; and the height of the test box is h=120 mm.

[0032] Preferably, in step (5), the temperature of the thermostat is 20-25°C.

[0033] Preferably, in step (7), the temperature of the low-temperature box is -25 to -20°C.

[0034] Preferably, in step (8), the room temperature is 20-25°C.

[0035] Preferably, in step (8), the temperature of the low-temperature environment is 0±5°C.

[0036] Beneficial effects:

[0037] (1) The soil-rock mixture specimen box of the present invention is made of copper with good thermal conductivity, which ensures that the specimen is cooled evenly during the freezing process. A copper tube is connected to the center of the upper cover and inserted into the soil-rock mixture sample. The specimen box is made of copper with good thermal conductivity. Firstly, it is to allow the sample to freeze not only from the four sides to the inside, but also from the middle to the four sides during the freezing process; secondly, it can be directly used as a channel to measure the thermal conductivity coefficient of the specimen after freezing. While ensuring the integrity of the original sample, the present invention will not destroy the position where pore water migrates in the soil-rock mixture to form ice crystals due to the influence of external factors such as measurement.

[0038] (2) The present invention adopts a step-by-step freezing method, which is different from the traditional direct freezing method. The direct freezing method is to place the specimen directly in a low-temperature environment for storage and then take it out. During this process, the temperature only tends to gradually decrease, and the migration displacement of pore water in the soil-rock mixture will not change significantly. The generated ice crystals will gradually gather into large lens-shaped ice interlayers. However, the step-by-step freezing method adopted by the present invention is to place the specimen in a low-temperature environment and then take it out and place it in a 20°C environment to thaw the outside of the specimen. At the same time, due to the effect of heat conduction, the temperature inside the specimen is redistributed. In this process, the position where the pore water migrates to generate ice crystals will gradually move in the pores. When it is placed in a freezing point environment again, the ice crystals in the pores will evenly gather into lens-shaped ice interlayers to ensure that the ice content of the entire specimen is relatively uniform.

[0039] (3) The present invention combines a step-by-step freezing method with a trial-and-error method to control the ice content of each group of standard test specimens. The trial-and-error method is used to control the ice content of each group. Specifically, the freezing time of the sample is manually selected, and the ice content of the sample is tested after freezing. The freezing and thawing times in the step-by-step freezing method are dynamically adjusted according to the ice content until the target ice content is achieved.

[0040] (4) The present invention abandons the complex device system, has a simple and flexible process, and is low-cost. It can produce an artificial soil-rock mixture with uniform ice content under low-temperature conditions according to the actual required size, providing sample guarantee for conducting frozen soil test research. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings and descriptions that constitute part of this application are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. Among them:

[0042] Figure 1 is a schematic diagram of a test piece device of the present invention;

[0043] Figure 2 is a flow chart of the steps of the present invention;

[0044] Figure 3 It is a flow chart of the experimental process of the present invention.

[0045] In the figure: 1. Upper cover; 2. Copper conduit; 3. Test piece box; 4. Lower cover. DETAILED DESCRIPTION

[0046] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application and does not limit the present application. In fact, it will be clear to those skilled in the art that modifications and variations can be made in the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as part of one embodiment can be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention should fall within the scope of protection of the embodiments of the present invention.

[0047] Example 1

[0048] A method for preparing a soil-rock mixture sample with uniform ice content, such as Figure 1-3 As shown, the following steps are included:

[0049] (1) Calculate the weight of soil, rock and water required to prepare the sample: Based on the stone content, water content and dry density of the soil-rock mixture measured for the given sample, as well as the size and temperature conditions of the homemade sample box, calculate the weight of soil, rock and water required to prepare the standard sample.

[0050] (2) Screen and grade the soil and stone according to the standards to obtain soil samples and stone samples respectively.

[0051] (3) Soil and stone mixing: According to the stone content determined in step (1), weigh the soil sample and stone sample in step (2) respectively, mix them, and stir slowly. When there are no larger stone particles at the edge of the box, stop stirring and let it stand to make a uniform soil and stone standard specimen.

[0052] (4) Mixing soil, rock, and water: Based on the water content determined in step (1), distilled water is added to the soil-rock standard specimen. After adding water, it should be stirred slowly to prevent the unsoaked part from overflowing. When agglomerates appear, the stirring speed should be increased to ensure that the water is evenly distributed throughout the soil and rock. After stirring evenly, a moisturizing film should be applied to the surface and allowed to stand for 4-6 hours to form a standard specimen of soil-rock mixture.

[0053] (5) Determine the amount of ice contained in the prepared soil-rock mixture specimen.

[0054] (6) Take out the standard specimen of the soil-rock mixture prepared in step (4) and put it into the soil-rock mixture specimen box to prepare the specimen. Figure 1 The soil-rock mixture specimen box consists of three parts: an upper cover 1, a specimen box body 3, and a lower cover 4. A copper conduit 2 is connected to the center of the upper cover 1, one end of which is inserted into the specimen box body 3. The specimen box body 3, upper cover 1, and lower cover 4 are all made of copper, which has good thermal conductivity. The soil-rock mixture specimen box was placed in a constant temperature chamber at 20°C for 48 hours to ensure uniform temperature distribution inside and outside the specimen.

[0055] (7) The soil-rock mixture specimen box after being placed in the constant temperature box in step (6) is taken out and placed in a -20°C environment for several hours to freeze the outer part of the specimen.

[0056] (8) Take out the soil-rock mixture specimen box after standing at -20°C in step (7), and stand it at 20°C for several hours to thaw the outside of the specimen.

[0057] (9) The soil-rock mixture specimen box after being left at 20°C in step (8) is placed in a 0°C environment and left to stand for 48 hours, so that the temperature inside the specimen is uniform and the freezing degree of different parts of the specimen changes with temperature redistribution. Since the specimen is at the freezing point, no new liquid water will freeze into ice, and no new ice will melt into liquid water.

[0058] (10) Determine the sample parameters; remove the soil-rock mixture specimen box after standing at 0°C in step (9), demould the specimen, and measure the ice content of the specimen, as well as the size and weight of the specimen. If the requirements are met, place the specimen in a sealed standard oil-proof rubber sleeve and place it in a low-temperature box to complete the sample preparation. Prepare for the experiment. If not, repeat steps 7-9 until the required ice content is reached.

[0059] Example 2

[0060] A method for preparing a soil-rock mixture sample with uniform ice content comprises the following steps:

[0061] (1) Calculate the mass of ice and water required to prepare a clay specimen, based on the given sample moisture content. 80%, dry density 0.80g / cm 3 The sample size is 120 mm high and 60 mm in diameter. The temperature of the low-temperature test chamber is between -25°C and -20°C. Calculate the mass M of dry soil-rock mixture required to prepare a sample. 土 =ρ 干 ·V 试样 , the total water volume is M 水 =M 土 ·ω 水 . And the stone content of the determined specimen.

[0062] (2) According to the soil, stone and water contents required for a test piece in step (1), the soil and stone are screened and graded to obtain soil samples and stone samples respectively.

[0063] (3) Soil and stone mixing: According to the stone content determined in step (1), weigh the soil sample and stone sample in step (2) respectively, mix them, and stir slowly. When there are no larger stone particles at the edge of the box, stop stirring and let it stand to make a uniform soil and stone standard specimen.

[0064] (4) Mixing soil, rock, and water: Based on the water content determined in step (1), distilled water is added to the soil-rock standard specimen. After adding water, it should be stirred slowly to prevent the unsoaked part from overflowing. When agglomerates appear, the stirring speed should be increased to ensure that the water is evenly distributed throughout the soil and rock. After stirring evenly, a moisturizing film should be applied to the surface and allowed to stand for 4-6 hours to form a standard specimen of soil-rock mixture.

[0065] (5) Determine the amount of ice contained in the prepared soil-rock mixture specimen.

[0066] (6) Take out the standard specimen of the soil-rock mixture prepared in step (4) and place it in a soil-rock mixture specimen box to prepare a specimen. The soil-rock mixture specimen box is divided into three parts: an upper cover 1, a specimen box body 3, and a lower cover 4. A copper conduit 2 is connected to the center of the upper cover 1, and one end of the copper conduit 2 is inserted into the specimen box body 3. The specimen box body 3, the upper cover 1, and the lower cover 4 are made of copper with good thermal conductivity. Place the soil-rock mixture specimen box in a constant temperature box at 20°C and let it stand for 48 hours to ensure that the temperature distribution inside and outside the specimen is uniform.

[0067] (7) The soil-rock mixture specimen box after being placed in the constant temperature box in step (6) is taken out and placed in a -20°C environment for several hours to freeze the outer part of the specimen.

[0068] (8) Take out the soil-rock mixture specimen box after standing at -20°C in step (7), and stand it at 20°C for several hours to thaw the outside of the specimen.

[0069] (9) The soil-rock mixture specimen box after being left at 20°C in step (8) is placed in a 0°C environment and left to stand for 48 hours, so that the temperature inside the specimen is uniform and the freezing degree of different parts of the specimen changes with temperature redistribution. Since the specimen is at the freezing point, no new liquid water will freeze into ice, and no new ice will melt into liquid water.

[0070] (10) Determine the sample parameters; remove the soil-rock mixture specimen box after standing at 0°C in step (9), demould the specimen, and measure the ice content of the specimen, as well as the size and weight of the specimen. If the requirements are met, place the specimen in a sealed standard oil-proof rubber sleeve and place it in a low-temperature box to complete the sample preparation. Prepare for the experiment. If not, repeat steps 7-9 until the required ice content is reached.

[0071] The present invention combines a step-by-step freezing method with a trial-and-error approach to control the ice content of each set of standard test specimens. The trial-and-error approach controls the ice content of each set by manually selecting the freezing time for the specimens. After freezing, the specimens are tested for ice content. Based on the ice content, the freezing and thawing times in the step-by-step freezing method are dynamically adjusted until the target ice content is achieved.

[0072] In the present invention, the terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0073] The foregoing description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a soil-rock mixture sample with uniform ice content, characterized in that: The following steps are involved: (1) Calculate the weight of soil, stone and water based on the rock content, water content, dry density of the soil-rock mixture and the size of the specimen box; (2) screening the soil and stone to obtain soil samples and stone samples respectively; (3) According to the rock content determined in step (1), the soil sample and the rock sample in step (2) are weighed and mixed to prepare a uniform soil-rock standard specimen; (4) According to the water content determined in step (1), water is added to the soil-rock standard specimen, and after being stirred evenly, a layer of moisturizing film is coated on the surface of the specimen, and the specimen is allowed to stand to prepare a soil-rock mixture standard specimen; (5) moving the standard test piece of the soil-rock mixture in step (4) into a soil-rock mixture test piece box, placing it in a constant temperature box and allowing it to stand to ensure that the temperature inside and outside the soil-rock mixture test piece box is uniform; (6) Determine the ice content of the soil-rock mixture specimens; (7) taking out the soil-rock mixture specimen box after being allowed to stand in step (5), transferring it to a low-temperature box and allowing it to stand, so that the outside of the soil-rock mixture specimen box is frozen; (8) taking out the soil-rock mixture specimen box after being placed in the low-temperature box in step (7), and placing it at room temperature to allow the outside of the soil-rock mixture specimen box to thaw; (9) placing the soil-rock mixture specimen box after standing at room temperature in step (8) in a low-temperature environment to make the temperature inside the soil-rock mixture specimen box uniform; (10) Take out the soil-rock mixture specimen box after standing in the low temperature environment in step (9), demold the specimen, and measure the ice content of the specimen, as well as the size and weight of the specimen; if it meets the requirements of the above experiment, put the specimen into a sealed standard oil-proof rubber sleeve and put it into a low-temperature box to complete the sample preparation for the experiment; if it does not meet the requirements, perform steps 7-9 again until the required ice content is reached.

2. The method for preparing a soil-rock mixture sample with uniform ice content according to claim 1, characterized in that: In step (1), the weight of soil, stone and water required for preparing the standard sample is calculated based on the stone content, water content and dry density of the sample required for the experiment and the size of the specimen box; where m 石 =m 总 *w 石 , m 水 =m 总 *w 水 . M 土 =m 总 -m 石 -m 水 .

3. The method for preparing a soil-rock mixture sample with uniform ice content according to claim 1, characterized in that: In step (2), the soil and stone are sieved, wherein the particle size of the soil sample is ≤2.0 mm; and the diameter of the stone sample is 5 to 20 mm.

4. The method for preparing a soil-rock mixture sample with uniform ice content according to claim 1, characterized in that: In step (5), the soil-rock mixture specimen box includes an upper cover, a specimen box body and a lower cover which are arranged in sequence; a copper conduit is provided at the center of the upper cover, and one end of the copper conduit extends into the specimen box body; the specimen box body is a cylindrical structure made of copper.

5. The method for preparing a soil-rock mixture sample with uniform ice content according to claim 3, characterized in that: The diameter of the copper conduit is φ=2 mm; the inner diameter of the test box is φ'=60 mm; and the height of the test box is h=120 mm.

6. The method for preparing a soil-rock mixture sample with uniform ice content according to claim 1, characterized in that: In step (5), the temperature of the thermostat is 20-25°C.

7. The method for preparing a soil-rock mixture sample with uniform ice content according to claim 1, characterized in that: In step (7), the temperature of the low temperature box is -25 to -20°C.

8. The method for preparing a soil-rock mixture sample with uniform ice content according to claim 1, characterized in that: In step (8), the room temperature is 20-25°C.

9. The method for preparing a soil-rock mixture sample with uniform ice content according to claim 1, characterized in that: In step (8), the temperature of the low-temperature environment is 0±5°C.

Images