A method for preparing artificial loess with strong collapsibility

Abstract

The present invention discloses a method for preparing artificial loess with strong collapsibility, using barite powder, river sand, kaolin, cement, industrial salt and quicklime as basic materials to prepare artificial loess with strong collapsibility. Barite powder and river sand can adjust the specific gravity change of soil sample as bulk density sensitive materials, river sand is used to adjust the internal friction angle and deformation modulus of soil sample, cement is used as auxiliary cementing material, kaolin and industrial salt can play a cementing effect between soil particles, and quicklime can form calcium carbonate in the process of reacting with carbon dioxide and water, which can form the special structure of collapsible loess. The raw materials used are all common and cheap, and the preparation method is simple, and large-scale production can be achieved. The physical and mechanical properties of the prepared artificial collapsible loess are similar to those of original loess, and it has strong collapsibility, which can meet the similar requirements of indoor model box tests for materials.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering, and particularly relates to a method for preparing artificial loess with strong collapsibility. Background Art

[0002] Loess is collapsible. When wetted by water, it experiences large, uneven settlements due to the combined effects of its internal weight and external pressure, leading to damage to superstructures. The unique composition of loess is the primary reason for its collapsibility. The process of collecting and transporting natural, undisturbed loess and preparing it as remolded soil samples causes some degree of disturbance in the sample, making this unique structure susceptible to damage. This in turn weakens the soil and eliminates its collapsibility, resulting in differences in properties between remolded and undisturbed loess.

[0003] Similarity model testing is a method for conducting scaled studies of geotechnical engineering models. Based on the principle of similarity, a mechanical model similar to the actual project is established. Under the premise of satisfying the similarity theorem, the physical model at a small scale is used to reveal and analyze the essence of the phenomenon. The mechanical changes in the model follow similar patterns to those in the actual project, making it the most commonly used method in geotechnical engineering research. In similarity model testing, the selection of the correct similar material determines the degree of similarity to the original project. In similarity model testing involving collapsible loess strata, using a reshaped collapsible loess fill model inevitably destroys the collapsible characteristics and structural properties of the original loess, resulting in serious experimental errors.

[0004] Therefore, the correct selection of similar materials of collapsible loess is crucial to the success of similar model tests. However, there is currently no method for preparing artificial loess with strong collapsible properties. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing artificial loess with strong collapsibility in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem that the collapsibility of loess is relatively weak in similar model tests.

[0006] The present invention adopts the following technical solutions:

[0007] The invention discloses a method for preparing artificial loess with strong collapsibility. The method comprises the following steps: uniformly mixing barite powder, river sand, kaolin, cement, industrial salt and calcium oxide to obtain a mixed material; then adding water to the mixed material and stirring the mixed material to obtain artificial loess with strong collapsibility and a moisture content of 12% to 14%.

[0008] Specifically, in the mixed material, the mass ratio of barite powder, river sand, kaolin, cement, industrial salt and calcium oxide is (25-35): (30-35): (25-30): 3:5:2.

[0009] Specifically, before preparing the mixed material, the barite powder, river sand, kaolin and calcium oxide are first dried, and then crushed with cement and industrial salt respectively and sieved.

[0010] Furthermore, the drying temperature is 100-105°C.

[0011] Furthermore, the mesh size of the sieve is 0.25 to 0.5 mm.

[0012] Specifically, adding water to the mixed material for stirring is as follows:

[0013] Water is injected into the mixed material for multiple times, and the mixed material is stirred after each injection to mix the mixed material and water evenly. The evenly mixed material is then sealed and allowed to stand to obtain artificial loess with strong collapsible properties.

[0014] Furthermore, the standing time is 12 to 24 hours.

[0015] Further, after the sealed static treatment, when the moisture content is higher than 14%, the mixed material is placed in the air.

[0016] Further, when the moisture content is lower than 12%, water is injected again for mixing.

[0017] Another technical solution of the present invention is a kind of artificial loess with strong collapsibility.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] The invention discloses a method for preparing artificial loess with strong collapsibility, wherein the artificial loess with strong collapsibility is prepared by mixing different materials.

[0020] Furthermore, the various proportions of barite powder, river sand, kaolin, cement, industrial salt and calcium oxide in a type of artificial loess with strong collapsibility are basically close to the contents of clay particles, silt particles, etc. in the original loess.

[0021] Furthermore, drying, crushing and screening the barite powder, river sand, kaolin, cement, industrial salt and calcium oxide can reduce the influence of the differences in the properties of the materials themselves on the preparation results.

[0022] Furthermore, drying the barite powder, river sand, kaolin and calcium oxide can ensure that each material does not carry moisture, and can ensure that the prepared artificial loess with strong collapsibility meets the specified moisture content requirement.

[0023] Furthermore, crushing the barite powder, river sand, kaolin, cement, industrial salt and calcium oxide and then screening them can prevent the presence of large particles in the mixed materials, so that the overall distribution of the materials is more uniform.

[0024] Furthermore, adding water several times continuously for stirring can fully mix the mixed material with water.

[0025] Furthermore, standing still can ensure uniform mixing of the material and the water.

[0026] Furthermore, when the mixed material has a moisture content higher than a specific value, exposing the material to air can reduce excess moisture in the material and obtain a material that meets the moisture content requirement.

[0027] Furthermore, when the moisture content of the mixed material is lower than a specific value, water can be injected again for mixing to obtain a material that meets the moisture content requirement.

[0028] A kind of artificial loess with strong collapsibility, which belongs to the strong collapsibility type.

[0029] In summary, the raw materials used in the present invention are common and cheap, the preparation method is simple, and large-scale production can be achieved. The physical and mechanical properties of the prepared artificial collapsible loess are similar to those of the original loess, and it has strong collapsibility, which can meet the similar requirements of indoor model box tests for materials.

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The void ratio-load curves of artificial loess with strong collapsibility and different material ratios. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0034] In the present invention, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0035] In the present invention, unless otherwise specified, percentages (%) or parts refer to percentages by weight or parts by weight relative to the composition.

[0036] In the present invention, unless otherwise specified, the components involved or their preferred components can be combined with each other to form a new technical solution.

[0037] In this disclosure, unless otherwise specified, the numerical range "a-b" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6-22" indicates that all real numbers between "6-22" are listed herein, and "6-22" is merely an abbreviation for these numerical combinations.

[0038] The "range" disclosed in the present invention is in the form of lower limit and upper limit, which can be one or more lower limits, and one or more upper limits respectively.

[0039] In the present invention, the term "and / or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0040] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the order. Preferably, the reaction method herein is carried out sequentially.

[0041] Unless otherwise indicated, the professional and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied to the present invention.

[0042] The present invention provides a method for preparing artificial loess with strong collapsibility, using barite powder, river sand, kaolin, cement, industrial salt and quicklime as basic materials to prepare artificial loess with strong collapsibility. Barite powder and river sand can adjust the specific gravity change of soil samples as bulk density sensitive materials, river sand is used to adjust the internal friction angle and deformation modulus of soil samples, cement is used as an auxiliary cementing material, kaolin and industrial salt can play a cementing role between soil particles, and quicklime will form calcium carbonate in the process of reacting with carbon dioxide and water, which can form the special structure of collapsible loess. The raw materials used are all common and cheap, the preparation method is simple, and large-scale production can be achieved. The physical and mechanical properties of the prepared artificial collapsible loess are similar to those of original loess, with strong collapsibility, which can meet the similar requirements of indoor model box tests for materials.

[0043] See also Figure 1 The present invention provides a method for preparing artificial loess with strong collapsibility, comprising the following steps:

[0044] S1. Drying and screening

[0045] Place barite powder, river sand, kaolin and quicklime in an oven at 100-105°C to dry to remove moisture from the materials, then grind them with cement and industrial salt and pass through a 0.25-0.5mm sieve.

[0046] S2. Ingredients

[0047] Mix barite powder, river sand, kaolin, cement, industrial salt and calcium oxide in a given mass ratio.

[0048] Table 1 shows the different mass ratios of basic materials of artificial loess with strong collapsibility

[0049]

[0050] According to the physical and mechanical properties of artificial loess with strong collapsibility and its collapsibility obtained in Tables 2, 3 and 4, the mass ratio closest to the properties of the original collapsible loess on site is selected.

[0051] S3, add water and mix

[0052] According to the requirement of moisture content of 12% to 14%, water is injected into the mixed material several times with a spray bottle. After each injection, it is fully stirred to ensure that the material and water are initially mixed evenly.

[0053] S4, let it stand

[0054] Seal the mixed materials with plastic wrap and let them stand for 12 to 24 hours to ensure that the materials and water are fully mixed. After standing, take out some of the materials that have been stood, measure their moisture content, and add water again to the materials with a moisture content of less than 12% to mix them. Place the materials with a moisture content higher than 14% in the air to allow excess water to dissipate until the moisture content requirements are met.

[0055] S5. Sample Preparation

[0056] Calculate the volume of the ring knife and put it into the sample preparation device according to 1.3g / cm 3 The dry density is converted into material mass and ring knife sampling is prepared.

[0057] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, 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 part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0058] Example 1

[0059] S1. Drying and screening

[0060] Place barite powder, river sand, kaolin and quicklime in an oven at 100°C to dry to remove moisture from the materials, and then grind them with cement and industrial salt and pass through a 0.25mm sieve.

[0061] S2. Ingredients

[0062] Mix barite powder, river sand, kaolin, cement, industrial salt and calcium oxide in a given mass ratio.

[0063] Table 1 shows the different mass ratios of basic materials of artificial loess with strong collapsibility

[0064]

[0065] According to the physical and mechanical properties of artificial loess with strong collapsibility and its collapsibility obtained in Tables 2, 3 and 4, the mass ratio closest to the properties of the original collapsible loess on site is selected.

[0066] S3, add water and mix

[0067] In accordance with the requirement of 12% moisture content, water is injected into the mixed material several times using a spray bottle. Stir thoroughly after each injection to ensure that the material and water are initially mixed evenly.

[0068] S4, let it stand

[0069] Seal the mixed materials with plastic wrap and let them stand for 12 hours to ensure that the materials and water are fully mixed. After standing, take out some of the materials that have been stood, measure their moisture content, and add water again to the materials with a moisture content of less than 12% to mix them. Place the materials with a moisture content higher than 12% in the air to allow excess water to dissipate until the moisture content requirements are met.

[0070] S5. Sample Preparation

[0071] Calculate the volume of the ring knife and put it into the sample preparation device according to 1.3g / cm 3 The dry density is converted into material mass and ring knife sampling is prepared.

[0072] Example 2

[0073] S1. Drying and screening

[0074] Place barite powder, river sand, kaolin and quicklime in an oven at 105°C to dry to remove moisture from the materials, and then grind them with cement and industrial salt and pass through a 0.5mm sieve.

[0075] S2. Ingredients

[0076] Mix barite powder, river sand, kaolin, cement, industrial salt and calcium oxide in a given mass ratio.

[0077] Table 1 shows the different mass ratios of basic materials of artificial loess with strong collapsibility

[0078]

[0079] According to the physical and mechanical properties of artificial loess with strong collapsibility and its collapsibility obtained in Tables 2, 3 and 4, the mass ratio closest to the properties of the original collapsible loess on site is selected.

[0080] S3, add water and mix

[0081] According to the requirement of moisture content of 14, water is injected into the mixed material several times with a spray bottle. Stir thoroughly after each injection to ensure that the material and water are initially mixed evenly.

[0082] S4, let it stand

[0083] Seal the mixed materials with plastic wrap and let them stand for 24 hours to ensure that the materials and water are fully mixed. After standing, take out some of the materials that have been stood, measure their moisture content, and add water again to the materials with a moisture content of less than 14% to mix them. Place the materials with a moisture content higher than 14% in the air to allow excess water to dissipate until the moisture content reaches 14%.

[0084] S5. Sample Preparation

[0085] Calculate the volume of the ring knife and put it into the sample preparation device according to 1.3g / cm 3 The dry density is converted into material mass and ring knife sampling is prepared.

[0086] Example 3

[0087] S1. Drying and screening

[0088] Place barite powder, river sand, kaolin and quicklime in an oven at 102°C to dry to remove moisture from the materials, and then grind them with cement and industrial salt and pass through a 0.5mm sieve.

[0089] S2. Ingredients

[0090] Mix barite powder, river sand, kaolin, cement, industrial salt and calcium oxide in a given mass ratio.

[0091] Table 1 shows the different mass ratios of basic materials of artificial loess with strong collapsibility

[0092]

[0093] According to the physical and mechanical properties of artificial loess with strong collapsibility and its collapsibility obtained in Tables 2, 3 and 4, the mass ratio closest to the properties of the original collapsible loess on site is selected.

[0094] S3, add water and mix

[0095] According to the requirement of 13% moisture content, water is injected into the mixed material several times with a spray bottle. After each injection, it is fully stirred to ensure that the material and water are initially mixed evenly.

[0096] S4, let it stand

[0097] Seal the mixed materials with plastic wrap and let them stand for 20 hours to ensure that the materials and water are fully mixed. After standing, take out some of the materials that have been stood, measure their moisture content, and add water again to the materials with a moisture content of less than 13% and mix them. Place the materials with a moisture content higher than 13% in the air to allow excess water to dissipate until the moisture content reaches 13%.

[0098] S5. Sample Preparation

[0099] Calculate the volume of the ring knife and put it into the sample preparation device according to 1.3g / cm 3 The dry density is converted into material mass and ring knife sampling is prepared.

[0100] Example 4

[0101] S1. Drying and screening

[0102] Place barite powder, river sand, kaolin and quicklime in an oven at 102°C to dry to remove moisture from the materials, and then grind them with cement and industrial salt and pass through a 0.5mm sieve.

[0103] S2. Ingredients

[0104] Mix barite powder, river sand, kaolin, cement, industrial salt and calcium oxide in a given mass ratio.

[0105] Table 1 shows the different mass ratios of basic materials of artificial loess with strong collapsibility

[0106]

[0107] According to the physical and mechanical properties of artificial loess with strong collapsibility and its collapsibility obtained in Tables 2, 3 and 4, the mass ratio closest to the properties of the original collapsible loess on site is selected.

[0108] S3, add water and mix

[0109] In accordance with the requirement of 12% moisture content, water is injected into the mixed material several times using a spray bottle. Stir thoroughly after each injection to ensure that the material and water are initially mixed evenly.

[0110] S4, let it stand

[0111] Seal the mixed materials with plastic wrap and let them stand for 24 hours to ensure that the materials and water are fully mixed. After standing, take out some of the materials that have been stood, measure their moisture content, and add water again to the materials with a moisture content of less than 12% and mix them. Place the materials with a moisture content higher than 12% in the air to allow excess water to dissipate until the moisture content reaches 12%.

[0112] S5. Sample Preparation

[0113] Calculate the volume of the ring knife and put it into the sample preparation device according to 1.3g / cm 3 The dry density is converted into material mass and ring knife sampling is prepared.

[0114] Table 2 shows the physical properties of artificial loess with strong collapsibility with different material ratios

[0115]

[0116] The liquid limit, plastic limit, and plasticity index in Table 2 were measured using the LP-100D digital soil liquid limit and plastic limit combined tester. Three groups of soil penetration depths were measured for each moisture content sample and the average value was taken.

[0117] Table 3 shows the shear parameters of artificial loess with strong collapsibility with different material ratios

[0118]

[0119] The cohesion and internal friction angles in Table 3 were obtained through direct shear testing. Four specimens were prepared for each mix ratio, and the shear stress of the specimens was measured under different pressures by applying four sets of vertical pressure (100kPa, 200kPa, 300kPa, and 400kPa) to the upper surfaces. A shear strength curve was plotted, with the vertical pressure applied during the test as the abscissa and the final shear strength result as the ordinate. Shear strength indicators such as cohesion and internal friction angle of the soil samples were obtained based on the fitted curve of the data results.

[0120] Table 4 shows the compression and collapsibility properties of artificial loess with strong collapsibility at different material ratios.

[0121]

[0122]

[0123] The compression coefficient, compression modulus, and bulk compression modulus shown in Table 4 were obtained through consolidation tests. Consolidation pressures of 25 kPa, 100 kPa, 200 kPa, 300 kPa, 400 kPa, and 600 kPa were selected for the consolidation tests, with the next load applied only after the deformation of the previous load stabilized. To prevent moisture evaporation, the pressure cover was surrounded by wet cotton during the test.

[0124] According to the Code for Design of Building Foundations (GB 50007-2011), the compression coefficient of highly compressible soil shall not be less than 0.5 MPa. -1 , the compression coefficient of low compressibility soil is less than 0.1MPa -1 , while the compression coefficient of medium compressible soil is 0.1MPa -1 and 0.5MPa -1 From the compression coefficients of artificial loess with strong collapsibility of different proportions in Table 4, it can be seen that the compression coefficients of artificial loess with strong collapsibility are between 0.39 and 0.45 MPa. -1 All of them are medium compressible soils.

[0125] The collapsibility coefficients in Table 4 were obtained through collapsibility tests. Artificial collapsible loess samples of varying proportions were immersed in water at a pressure of 200 kPa and subjected to collapse. Data was collected after the dial indicator reading remained unchanged for two consecutive hours, indicating that the sample deformation had stabilized. The collapsibility coefficients were then calculated. According to the "Construction Standard for Collapsible Loess Regions (GB50025-2018)," all artificial collapsible loess samples were of the severe collapsibility type.

[0126] See also Figure 1 The void ratio-load curve of artificial loess with strong collapsibility and different material ratios is gentle, which is consistent with the void ratio-load curve law of original loess.

[0127] In summary, the present invention provides a method for preparing artificial loess with strong collapsibility. The physical and mechanical properties of the prepared artificial loess with strong collapsibility are similar to those of undisturbed loess, meeting the similar material requirements for indoor model box testing. The raw materials used are common and inexpensive, and the preparation method is simple.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing artificial loess with strong collapsibility, characterized in that: Barite powder, river sand, kaolin, cement, industrial salt and calcium oxide are uniformly mixed to obtain a mixed material. In the mixed material, the mass ratio of barite powder, river sand, kaolin, cement, industrial salt and calcium oxide is (25-35): (30-35): (25-30): 3:5:

2. Water is then added to the mixed material for stirring to obtain highly collapsible artificial loess with a moisture content of 12%-14%. The specific steps of adding water to the mixed material for stirring are as follows: Water is injected into the mixed material several times continuously, and stirred after each injection to mix the mixed material and water evenly. The evenly mixed material is then sealed and allowed to stand to obtain artificial loess with strong collapsible properties. The standing time is 12 to 24 hours. After the sealed and standing treatment, when the moisture content is higher than 14%, the mixed material is placed in the air. When the moisture content is lower than 12%, water is injected again for mixing.

2. The method for preparing artificial loess with strong collapsibility according to claim 1, characterized in that: Before preparing the mixed materials, the barite powder, river sand, kaolin and calcium oxide are first dried, then crushed with cement and industrial salt respectively and sieved.

3. The method for preparing artificial loess with strong collapsibility according to claim 2, characterized in that: The drying temperature is 100~105℃.

4. The method for preparing artificial loess with strong collapsibility according to claim 2, characterized in that: The pore size of the sieve is 0.25~0.5mm.

5. Strongly collapsible artificial loess prepared according to the method according to any one of claims 1 to 4.

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