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

Abstract

This application relates to the field of soil-rock mixture technology, and particularly to a method for preparing a soil-rock mixture sample with uniform ice content. A method for preparing a soil-rock mixture sample with uniform ice content includes the following steps: calculating the weight of soil, rock, and water required to prepare a standard sample; sieving the soil and rock; weighing and mixing the soil and rock; adding water to prepare a standard soil-rock mixture specimen; transferring the standard specimen into a soil-rock mixture specimen box and allowing it to stand in a constant temperature chamber; determining the ice content of the prepared soil-rock mixture specimen; transferring the specimen box to a low-temperature chamber and allowing it to stand at room temperature and then at a low-temperature environment; removing the box, demolding, and measuring the ice content and size of the specimen; if it meets the requirements, it is ready for use; if not, steps 7-9 are repeated. This invention uses a step-by-step freezing method to ensure a relatively uniform ice content in the specimen. This method causes the ice crystals formed by the migration of pore water within the soil-rock mixture to be at different positions, thereby achieving the purpose of producing a soil-rock mixture with uniform ice content.

Description

Technical Field

[0001] This application relates to the field of soil-rock mixture technology, and in particular to a method for preparing a soil-rock mixture sample with uniform ice content. Background Technology

[0002] Soil-rock mixtures are highly heterogeneous composite geological materials that are easily affected by the external environment. Freeze-thaw cycles cause the mechanical properties of the surface soil-rock mixture to deteriorate, affecting the stability of road slopes and leading to geological disasters such as landslides and collapses.

[0003] Patent 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 without interference, providing scientific basis and technical support for the evaluation of hydrate accumulation in frozen soil areas and the formulation of hydrate mining plans.

[0004] Patent CN102230856B discloses a method for preparing high-ice-content frozen soil samples. This method is of great significance for conducting mechanical tests on high-ice-content artificial frozen soil samples with a monolithic structure under low-temperature conditions and analyzing their mechanical properties.

[0005] While the aforementioned patents have improved the production and measurement of frozen soil to some extent, the freezing point of pore water in soil-rock mixtures varies with pore size; smaller pores have lower freezing points and lower freezing temperatures. At the freezing point, water in large pores freezes first, followed by the adsorption of weakly viscous water around adjacent soil particles. Due to the weakened adsorption of the water film, the soil particles lose the balance of electromolecular attraction and draw water from adjacent lower soil particles, migrating the lower water to the upper large pores, gradually freezing and forming ice interlayers. When the freezing rate is high, the freezing depth develops rapidly, and the water migration rate is relatively slow, resulting in small frost heave. Only under a suitable temperature gradient, where the heat dissipated from the frozen surface is exactly equal to the latent heat of phase change when the migrating water transforms to 0°C, and the bottom of the frozen zone is located within the capillary rise zone, does the water below continuously migrate towards the frozen surface, forming ice crystals and gradually accumulating into lenticular ice interlayers. When the 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 lens-shaped ice interlayers are uniform, meaning the ice content of the specimen is uniform. Therefore, the aforementioned patent cannot guarantee uniform internal and external heat transfer during the preparation of the soil-rock mixture. This results in uneven ice content within the soil-rock mixture prepared according to its proposed method.

[0006] Therefore, there is an urgent need to provide a technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0007] To overcome the problem of uneven ice content in soil-rock mixtures caused by uneven heat conduction between the internal and external parts during freeze-thaw cycles, which leads to different locations of ice crystals formed by pore water migration, this invention provides a method for preparing soil-rock mixture samples with uniform ice content. This method ensures that the ice crystals formed by pore water migration within the soil-rock mixture are not at the same location, thereby achieving the goal of producing soil-rock mixtures 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, employing the following technical solution:

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

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

[0011] (2) The soil and stone were screened to obtain soil samples and stone samples respectively;

[0012] (3) Based on the stone content determined in step (1), weigh the soil sample and stone sample from step (2) respectively and mix them to make a uniform soil and stone standard specimen.

[0013] (4) Based on the water content determined in step (1), add water to the soil and rock standard specimen, stir evenly, cover the surface with a moisturizing film, let stand, and make a standard specimen of soil and rock mixture.

[0014] (5) Transfer the standard specimen of soil-rock mixture from step (4) into the soil-rock mixture specimen box, place it in a constant temperature chamber and let it 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 prepared 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] In the formula, Qwater represents the heat absorbed by water (including ice and liquid water) in the soil-rock mixture, and QSRM represents...

[0022] The heat absorption of soil matrix and gravel particles in the soil-rock mixture, Qice→water represents the latent heat absorption of ice turning into liquid water 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 from 0℃ to 20℃, the influence of ultracooled water (liquid water with a temperature below 0℃) does not need to be considered in the calculation.

[0024] (7) Take out the soil-rock mixture specimen box after step (5) and transfer it to a low temperature chamber to freeze the outside of the soil-rock mixture specimen box.

[0025] (8) Take out the soil-rock mixture specimen box after it has been placed in the low temperature chamber in step (7), and place it at room temperature to allow the outside of the soil-rock mixture specimen box to thaw.

[0026] (9) Place the soil-rock mixture specimen box that has been left to stand at room temperature in step (8) in a low temperature environment to make the temperature inside the soil-rock mixture specimen box uniform.

[0027] (10) Take out the soil-rock mixture specimen box after it has been placed in a low-temperature environment in step (9), demold the specimen, and determine the ice content, size and weight of the specimen. If it meets the above experimental requirements, put the specimen into a sealed standard oil-proof rubber sleeve and place it in a low-temperature chamber to complete the sample preparation for the experiment. If it does not meet the requirements, repeat steps 7-9 until the required ice content is reached.

[0028] Preferably, in step (1), the weight of soil, stone, and water required to prepare the standard sample is calculated based on the stone content, water content, and dry density of the sample required for the experiment, as well as the size of the sample 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 screened, wherein the particle size of the soil sample is ≤2.0mm and the diameter of the stone sample is 5-20mm.

[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 cylindrical structure made of copper.

[0031] More preferably, the copper conduit has a diameter φ = 2 mm; the inner diameter of the specimen box φ' = 60 mm; and the height of the specimen box h = 120 mm.

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

[0033] Preferably, in step (7), the temperature of the low-temperature chamber 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℃.

[0036] Beneficial effects:

[0037] (1) The soil-rock mixture specimen box of this invention is made of copper with good thermal conductivity to ensure uniform cooling of the specimen during the freezing process. A copper conduit is connected to the center of the top cover and inserted into the soil-rock mixture sample. The specimen box is made of copper with good thermal conductivity to ensure that the sample can be frozen not only from the outside to the inside, but also from the center to the outside during the freezing process; secondly, it can be directly used as a channel for measuring the thermal conductivity coefficient of the specimen after freezing. This invention ensures the integrity of the original sample and will not disrupt the position of pore water migration and ice crystal formation in the soil-rock mixture due to external factors such as measurement.

[0038] (2) This invention employs a stepwise freezing method, which differs from the traditional direct freezing method. Direct freezing involves placing the specimen directly into a low-temperature environment for preservation and then removing it. During this process, the temperature only gradually decreases, and the migration displacement of pore water in the soil-rock mixture does not change significantly. The generated ice crystals gradually aggregate into large, lens-shaped ice layers. In contrast, the stepwise freezing method used in this invention places the specimen in a low-temperature environment and then removes it to a 20°C environment to thaw the exterior. Simultaneously, due to heat conduction, the internal temperature of the specimen redistributes. During this process, the location of the ice crystals generated by pore water migration gradually moves within the pores. When the specimen is placed back into a freezing environment, the ice crystals in the pores uniformly aggregate into lens-shaped ice layers, ensuring a relatively uniform ice content throughout the specimen.

[0039] (3) This invention combines step-by-step freezing and trial-and-error methods to control the ice content of each group of standard specimens. The trial-and-error method is used to control the ice content of each group. First, the freezing time of the specimen is manually selected. After freezing, the ice content of the specimen is tested. The freezing and melting 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) This invention eliminates the complex device system, the process is simple and flexible, and the cost is low. It can produce a uniform artificial soil-rock mixture with ice content under low temperature conditions according to the actual required size, so as to provide a sample guarantee for carrying out frozen soil test research. Attached Figure Description

[0041] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. Wherein:

[0042] Figure 1 This is a schematic diagram of the specimen apparatus of the present invention;

[0043] Figure 2 This is a flowchart of the steps of the present invention;

[0044] Figure 3 This is a flowchart of the experimental process of the present invention.

[0045] In the diagram: 1. Top cover; 2. Copper conduit; 3. Specimen box; 4. Bottom cover. Detailed Implementation

[0046] The present application will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will understand that modifications and variations can be made to 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 may be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those skilled in the art based on the embodiments of 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, it includes the following steps:

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

[0050] (2) Soil and stone are screened and graded according to the standard 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) and mix them. Stir slowly until there are no large stone particles on the edge of the box, then stop stirring and let it stand to make a uniform soil and stone standard specimen.

[0052] (4) Soil and water mixing: Based on the moisture content determined in step (1), add distilled water to the soil and rock standard specimen. After adding water, stir slowly to prevent the unwetted parts from overflowing. When aggregated clumps appear, increase the stirring speed to ensure that the moisture is evenly distributed in the soil and rock. After stirring evenly, cover the surface with a moisturizing film and let it stand for 4-6 hours to prepare a standard specimen of soil and rock mixture.

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

[0054] (6) Take out the standard specimen of the soil-rock mixture prepared in step (4) and place it into the soil-rock mixture specimen box to prepare the specimen. The soil-rock mixture specimen box is as follows: Figure 1 As shown, 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, with one end of the copper conduit 2 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℃ for 48 hours to ensure a uniform temperature distribution inside and outside the specimen.

[0055] (7) Take out the soil-rock mixture specimen box after it has been left to stand in the constant temperature chamber in step (6), and place it in an environment of -20℃ 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℃ in step (7), and let it stand at 20℃ for several hours to allow the outside of the specimen to thaw.

[0057] (9) Place the soil-rock mixture specimen box that has been left to stand at 20°C in step (8) in an environment of 0°C for 48 hours to make the internal temperature of the specimen uniform. The degree of freezing of different parts of the specimen changes with the temperature redistribution. Since the specimen is at the freezing point, no new liquid water will freeze into ice, nor will new ice melt into liquid water.

[0058] (10) Determine the sample parameters; remove the soil-rock mixture specimen box after standing at 0℃ in step (9), demold the specimen, determine the ice content of the specimen, and measure the specimen size and weight. If it meets the requirements, put the specimen into a sealed standard oil-proof rubber sleeve and place it in a low-temperature chamber to complete the sample preparation for experimentation. If it does not meet the requirements, repeat steps 7-9 until the required ice content is achieved.

[0059] Example 2

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

[0061] (1) Calculate the mass of ice and water required to prepare one clay specimen, based on the given sample moisture content. 80%, dry density 0.80 g / cm³ 3 The sample dimensions (height 120 mm, diameter 60 mm) and the low-temperature test chamber temperature range between -25℃ and -20℃ are given. Calculate the mass M of the dry soil-rock mixture required to prepare one sample. 土 =ρ 干 ·V 试样 The total water volume is M 水 =M 土 ·ω 水 And the determined stone content of the specimen.

[0062] (2) According to the required soil, stone, and water content for taking one specimen in step (1), the soil and stone are screened and graded to obtain soil 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) and mix them. Stir slowly until there are no large stone particles on the edge of the box, then stop stirring and let it stand to make a uniform soil and stone standard specimen.

[0064] (4) Soil and water mixing: Based on the moisture content determined in step (1), add distilled water to the soil and rock standard specimen. After adding water, stir slowly to prevent the unwetted parts from overflowing. When aggregated clumps appear, increase the stirring speed to ensure that the moisture is evenly distributed in the soil and rock. After stirring evenly, cover the surface with a moisturizing film and let it stand for 4-6 hours to prepare a standard specimen of soil and rock mixture.

[0065] (5) Determine the ice content 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 into the soil-rock mixture specimen box to make the specimen. The soil-rock mixture specimen box is divided into three parts: upper cover 1, specimen box body 3, and 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, upper cover 1, and lower cover 4 are made of copper with good thermal conductivity. Place the soil-rock mixture specimen box in a constant temperature chamber at 20℃ for 48 hours to ensure that the internal and external temperature distribution of the specimen is uniform.

[0067] (7) Take out the soil-rock mixture specimen box after it has been left to stand in the constant temperature chamber in step (6), and place it in an environment of -20℃ 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℃ in step (7), and let it stand at 20℃ for several hours to allow the outside of the specimen to thaw.

[0069] (9) Place the soil-rock mixture specimen box that has been left to stand at 20°C in step (8) in an environment of 0°C for 48 hours to make the internal temperature of the specimen uniform. The degree of freezing of different parts of the specimen changes with the temperature redistribution. Since the specimen is at the freezing point, no new liquid water will freeze into ice, nor will new ice melt into liquid water.

[0070] (10) Determine the sample parameters; remove the soil-rock mixture specimen box after standing at 0℃ in step (9), demold the specimen, determine the ice content of the specimen, and measure the specimen size and weight. If it meets the requirements, put the specimen into a sealed standard oil-proof rubber sleeve and place it in a low-temperature chamber to complete the sample preparation for experimentation. If it does not meet the requirements, repeat steps 7-9 until the required ice content is achieved.

[0071] This invention combines a step-by-step freezing method with a trial-and-error method to control the ice content of each group of standard specimens. The trial-and-error method controls the ice content of each group by first manually selecting the freezing time for the sample, then testing the ice content after freezing, and dynamically adjusting the freezing and thawing times in the step-by-step freezing method based on the ice content until the target ice content is achieved.

[0072] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions 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 one or more embodiments or examples.

[0073] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a soil-rock mixture sample with uniform ice content, characterized in that, Includes the following steps: (1) Calculate the weight of soil, stone and water based on the stone content, water content and dry density of soil-stone mixture and the size of the specimen box; (2) The soil and stone were screened to obtain soil samples and stone samples respectively; (3) Based on the stone content determined in step (1), weigh the soil sample and stone sample from step (2) and mix them to prepare a uniform soil and stone standard sample. (4) According to the water content determined in step (1), add water to the soil and rock standard sample, stir evenly, cover the surface with a moisturizing film, let stand, and make a standard sample of soil and rock mixture. (5) Transfer the standard sample of soil-rock mixture from step (4) into the soil-rock mixture specimen box and place it in a constant temperature chamber to ensure that the temperature inside and outside the soil-rock mixture specimen box is uniform; 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 cylindrical structure made of copper; (6) Determine the ice content of the soil-rock mixture sample; (7) Take out the soil-rock mixture specimen box after step (5) and transfer it to a low temperature chamber to freeze the outside of the soil-rock mixture specimen box; the temperature of the low temperature chamber is -25 to -20℃. (8) Take out the soil-rock mixture specimen box after it has been placed in the low temperature chamber in step (7), and place it at room temperature to allow the outside of the soil-rock mixture specimen box to thaw; the room temperature is 20-25℃. (9) Place the soil-rock mixture specimen box that has been left to stand at room temperature in step (8) into a low-temperature environment to make the temperature inside the soil-rock mixture specimen box uniform; the temperature of the low-temperature environment is 0±5℃. (10) Take out the soil-rock mixture specimen box after it has been placed in the low temperature environment in step (9), demold the specimen, and determine the ice content, size and weight of the specimen. If it meets the experimental requirements, put the specimen into the sealed standard oil-proof rubber sleeve and place it in the low temperature chamber to complete the preparation of the specimen for the experiment. If it does not meet the requirements, repeat steps 7-9 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), based on the stone content, water content, and dry density of the sample required for the experiment, as well as the dimensions of the specimen box, the weight of soil, stone, and water needed to prepare the standard sample is calculated; 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 screened, wherein the particle size of the soil sample is ≤2.0mm and the diameter of the stone sample is 5-20mm.

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

5. 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 constant temperature chamber is 20-25℃.

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