A soil stabilizing agent composition and soil stabilizing method

Abstract

The present application relates to a kind of soil solidifying agent composition and soil solidification method, wherein, soil solidifying agent composition, including by weight parts: water-soluble silicate 20-25 parts, humic acid 3-7 parts, soil mineralization microbial inoculant 2-5 parts, silicate reaction catalyst 8-10 parts, cement 10-12 parts.Its beneficial effect is, the soil solidifying agent composition is more suitable for the soil solidification in the roadbed and slope of loose region of soil, can improve the strength and durability of soil solidification, ecological adaptability is strong, with wide application prospect;Replace most traditional cement use, effectively reduce the damage of alkali excitation to loess soil, at the same time, the production energy consumption of silicate is low, environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of civil engineering technology, and in particular to a soil stabilizer composition and a soil stabilization method. Background Technology

[0002] Given the arid climate and fragile ecology of the Loess Plateau region, the solidified layers formed by soil stabilization treatment in roadbeds and slopes have poor erosion resistance and long-term stability, increasing the risk of landslides and collapses. Unstable roadbeds may cause cracks in the pavement, increasing maintenance costs; if the roadbed settles or even breaks, it will cause significant economic losses. Summary of the Invention

[0003] I. Technical problems to be solved

[0004] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a soil stabilizer composition and a soil stabilization method, which solves the technical problems of poor long-term stability and erosion resistance of existing soil stabilization layers in loess areas.

[0005] II. Technical Solution

[0006] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0007] In a first aspect, embodiments of the present invention provide a soil stabilizer composition comprising, by weight: 20-25 parts of water-soluble silicate, 3-7 parts of humic acid, 2-5 parts of soil mineralization microbial agent, 8-10 parts of silicate reaction catalyst, and 10-12 parts of cement.

[0008] In a preferred embodiment of the present invention, the water-soluble silicate in the soil stabilizer composition is sodium silicate or potassium silicate;

[0009] The silicate reaction catalyst is a nano-iron oxide-fly ash composite or red mud;

[0010] When the silicate reaction catalyst is red mud, the pH of the red mud is 7-8.

[0011] In a preferred embodiment of the present invention, the soil stabilizer composition wherein the cement is selected from magnesium phosphate cement or sulfoaluminate cement;

[0012] If sulfoaluminate cement is used, it also includes silica fume, which accounts for 5%-6% of the weight of sulfoaluminate cement.

[0013] In a preferred embodiment of the present invention, the water-soluble silicate to humic acid mass ratio of the soil stabilizer composition is 4-6:1.

[0014] As a preferred embodiment of the present invention, the soil stabilizer composition comprises soil mineralization microbial agents consisting of biochar-supported Bacillus pasteurellii and / or urea-decomposing bacteria, wherein the mass ratio of biochar to bacteria is 5:1-2.

[0015] Biochar is a product of crop residue pyrolysis, and its pore size is 1-10 μm.

[0016] In a preferred embodiment of the present invention, the soil stabilizer composition contains humic acid derived from lignite, wherein the lignite extract contains iron oxide and aluminum oxide.

[0017] The ash content in lignite extract is <15%.

[0018] Secondly, embodiments of the present invention provide a soil stabilization method, employing the aforementioned soil stabilizing agent composition, comprising the following steps:

[0019] S1. Sift the soil, spray a 0.1% urea solution onto the sieved soil, then add soil mineralization microbial agent according to the mass ratio of soil stabilizer composition to soil to be stabilized of 8-12:100, mix well and let stand for later use.

[0020] S2. Soluble silicate and humic acid dry powder are premixed, and water is added at a liquid-to-solid ratio of 0.5-0.6:1. The mixture is stirred to form a homogeneous slurry. Cement and silicate reaction catalyst are added to the slurry in sequence to prepare the first mixed slurry. Water is added again to the first mixed slurry at a volume ratio of 0.3-0.4:1, and the mixture is stirred to obtain the second mixed slurry.

[0021] S3. Add the second mixed slurry to the soil after it has settled, mix well, adjust the soil moisture content to 14-16%, compact in layers, and maintain even moisture and room temperature for 7-28 days.

[0022] In a preferred embodiment of the present invention, if the soil to be solidified is for slope protection, the thickness of the solidified soil layer is 0.5-1m.

[0023] If the solidified soil is used as a roadbed, the thickness of the solidified soil layer is 3-5m.

[0024] As a preferred embodiment of the present invention, in the soil solidification method S3, each layer is loosely laid 30-40cm, and compacted 6-8 times, with the compaction degree of the solidified soil layer being ≥95%.

[0025] III. Beneficial Effects

[0026] The beneficial effects of this invention are as follows: The soil stabilizing agent composition and method of this invention utilize water-soluble silicate and humic acid as the main cementing materials. The carboxyl groups of humic acid condense with Si-OH generated from the hydrolysis of silicate to form Si-OC covalent bonds, enhancing network toughness. Humic acid crosslinks with calcium silicate gel through Ca / Mg ions, forming an organic-inorganic hybrid structure. The flexible chains of humic acid buffer shrinkage stress, reducing crack formation. Humic acid is widely available, and the organic phase undergoes hydrophobic modification, reducing water absorption. A silicate reaction catalyst is used to accelerate gel formation. Soil mineralization microbial agents can metabolize and produce carbonate ions. These carbonate ions react with Ca ions in the soil to form calcium carbonate crystals, which fill the pores between loess particles, acting as a cement and enhancing the connection between particles. Within the gel network formed by silicate and humic acid, the soil is further mineralized, thereby improving the overall strength and stability of the soil. Compared with existing technologies, this soil stabilizer composition is more suitable for soil stabilization in roadbeds and slopes in areas with loose soil. It can improve the strength and durability of soil stabilization, has strong ecological adaptability, and has broad application prospects. It can replace most traditional cement, effectively reduce the damage of alkali activation to loess soil, and the production of transport silicate is energy-efficient and environmentally friendly.

[0027] The catalyst for the silicate reaction is a nano-iron oxide-fly ash composite or red mud. The iron oxide in the nano-iron oxide or red mud promotes the breaking of Si-O bonds in the silicate, accelerating the dissolution of SiO3²⁻ ions. The amorphous SiO2 and Al2O3 in the fly ash or red mud dissolve and react with calcium ions in the soil to form a cementitious phase.

[0028] Cement, used as a functional additive in conjunction with sodium silicate, makes the soil more solidified and more frost-resistant.

[0029] The mass ratio of water-soluble silicate to humic acid is 3-6:1, and the amount of humic acid used is appropriate to ensure the colloid coagulation and toughening effect.

[0030] The soil mineralization microbial agent is made of biochar-loaded Bacillus pasteurellii and / or urea-decomposing bacteria. By using biochar-loaded bacteria, the bacteria can be slowly released, with an action period of up to 30 days. It is alkali-resistant, which allows the bacteria to successfully pass through the initial reaction stage of silicate and humic acid (which is relatively alkaline). It is also drought-resistant and has a high CaCO3 precipitation rate.

[0031] Humic acid is an extract from lignite, and the raw materials are widely available, which reduces material costs. Detailed Implementation

[0032] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below through specific embodiments.

[0033] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0034] Example 1

[0035] This embodiment provides a soil stabilizer composition comprising, in parts by weight and placed separately: 20 parts water-soluble silicate, 5 parts humic acid, and Bacillus pasteurellium supported on fruit shell biochar (biochar to bacteria mass ratio of 5:1, loading rate approximately 10%). 7 The mixture consists of 3 parts of CFU / g biochar powder, 8 parts of nano-iron oxide-fly ash composite, and 10 parts of magnesium phosphate cement.

[0036] The nano-iron oxide-fly ash composite can be obtained by ball milling nano-iron oxide and fly ash: the mass ratio of nano-iron oxide to fly ash is 1:5-10, and the mixture is ball-milled for 24-48 hours, or it can be obtained by referring to other preparation methods in the prior art. The biochar has a particle size of 50-200 μm and a specific surface area >300 m² / g, preferably pyrolysis char from straw or fruit shells.

[0037] Example 2

[0038] This embodiment provides a soil stabilizer composition comprising, separately placed and by weight: 25 parts water-soluble silicate, 4 parts humic acid, 5 parts urea-decomposing bacteria supported on fruit shell biochar (biochar to bacteria mass ratio of 5:2), 8 parts red mud powder (acid-washed to pH=7-8), 10 parts sulfoaluminate cement, and 0.5 parts silica fume.

[0039] Red mud is a waste residue from the aluminum industry, containing 30-50% Fe2O3.

[0040] Example 3

[0041] This embodiment provides a soil stabilization method, using the soil stabilizing agent composition from Example 1, for stabilizing roadbeds in a certain area of ​​the Loess Plateau, specifically including the following steps:

[0042] (1) Pass the soil through a 2-3 mm sieve, and spray a 0.1% urea solution onto the sieved soil. Spray 1-2 L of urea solution per cubic meter of soil to increase the nitrogen source for the bacteria and activate the original microorganisms in the soil.

[0043] (2) According to the mass ratio of the soil to be solidified to the soil solidification agent composition of 100:8-12, first add the powder of Bacillus pasteurellium loaded with biochar to the soil treated in step (1), dry mix evenly and let stand for later use.

[0044] (3) Premix sodium silicate and humic acid dry powder in the soil stabilizer composition, add water at a liquid-to-solid ratio of 0.5-0.6:1, and stir to form a homogeneous slurry; add cement and silicate reaction catalyst to the slurry in sequence, and add cement and catalyst slowly while stirring to prevent clumping, and prepare the first mixed slurry; add water again to the first mixed slurry at a volume ratio of water to the first mixed slurry of 0.3-0.4:1, and mix well to obtain the second mixed slurry;

[0045] (4) Add the second mixed slurry to the soil treated in step (2), mix well, adjust the soil moisture content to 14-16%, compact in layers, each layer is 30cm, compaction degree ≥95%, keep moist and at room temperature for 7-28 days: cover with breathable film for heat preservation (25-30℃), promote microbial proliferation and accelerate calcium carbonate precipitation.

[0046] (5) Take solidified soil samples for the following tests:

[0047] 1) 28-day compressive strength test: according to JTG E51-2009 (T 0805) and GB / T 50123-2019 (T0134);

[0048] 2) 90-day shrinkage rate test: based on JTG E51-2009 (T 0854) and GB / T 50082-2009

[0049] 3) Strength loss rate after 50 freeze-thaw cycles: based on JTG E51-2009 (T 0858) and GB / T 50082-2009 (rapid freezing method);

[0050] 4) Permeability coefficient: Based on GB / T 50123-2019 (T 0129 / T 0130) and JTG 3430-2020 (T0130);

[0051] 5) CBR value test: according to JTG E40-2007;

[0052] The results of the above tests are detailed in Table 1.

[0053] 6) The soil samples were crushed and sieved (<9.5 mm) in accordance with the "Solid Waste Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method" (HJ / T 299-2007) and then leached to test the amount of heavy metals leached. The results are detailed in Table 2.

[0054] Example 4

[0055] This embodiment provides a soil solidification method. The difference between this embodiment and embodiment 3 is that 25 parts of water-soluble silicate and 12 parts of magnesium phosphate cement are used, while the other steps are the same.

[0056] Example 5

[0057] This embodiment provides a soil solidification method. The difference between this embodiment and embodiment 3 is that the soil solidification agent composition used in soil solidification is from embodiment 2, and the remaining steps are the same.

[0058] Comparative Example 1

[0059] This comparative example provides a soil solidification method. The difference between this comparative example and Example 3 is that the humic acid component is removed.

[0060] Comparative Example 2

[0061] This comparative example provides a soil solidification method. The difference between this comparative example and Example 3 is that the amount of humic acid is 10 parts.

[0062] Comparative Example 3

[0063] This comparative example provides a soil solidification method. The difference between this comparative example and Example 3 is that the nano-iron oxide-fly ash composite is replaced with fly ash.

[0064] Comparative Example 4

[0065] This comparative example provides a soil stabilization method. The difference between this comparative example and Example 3 is that the powder of Bacillus pasteurellium loaded with fruit shell biochar is removed.

[0066] Comparative Example 5

[0067] This comparative example provides a soil solidification method. The difference between this comparative example and Example 3 is that magnesium phosphate cement is removed.

[0068] Table 1 Test results of solidified soil samples

[0069]

[0070] Table 2 Results of heavy metal leaching tests on solidified soil samples

[0071]

[0072] Referring to Tables 1 and 2, the specific analysis is as follows:

[0073] Example 3, as the preferred embodiment, exhibits the highest compressive strength (3.2 MPa), lowest shrinkage rate, lowest freeze-thaw cycle strength loss, improved durability, and lowest collapsibility coefficient, enhancing impermeability. It is suitable for solidifying loose soils in the Loess Plateau region. The soil stabilizer composition forms a reinforcing network through the carboxyl groups of humic acid and silicates. Humic acid cross-links with calcium silicate gel via Ca / Mg ions, forming an organic-inorganic hybrid structure. Microbial inoculants fix carbon and settle free calcium ions in the soil, further strengthening the interparticle bonding. Within the gel network formed by silicates and humic acid, the soil undergoes further mineralization, thereby improving the overall strength and stability of the soil. The additional use of magnesium phosphate cement or sulfoaluminate cement accelerates soil solidification and enhances freeze-thaw resistance. The multi-stage synergistic reaction of the soil stabilizer composition addresses the significant impact of Loess Plateau soil characteristics on road engineering stability. Furthermore, the heavy metal leaching content of the Example 3 sample is far below the limit in standard GB / T 25499, meeting the usage standards.

[0074] The CBR values ​​of the samples prepared in Examples 3, 4 and 5 all meet the requirements of secondary highway subgrade. The main contributions are that the nano-iron oxide-fly ash composite improves the compactness; and the biochar-loaded bacterial agent generates CaCO3, which enhances water stability.

[0075] A comparison of Examples 3 and 4 shows that increasing the amount of water-soluble silicate and magnesium phosphate cement based on Example 3 does not significantly contribute to the compressive strength and CBR value of the samples. In Example 3, the mass ratio of water-soluble silicate to humic acid is 4:1, resulting in the best overall performance of the samples.

[0076] A comparison of Example 3 with Example 5 and Comparative Example 5 shows that the composition of the soil stabilizer in Example 1 is superior to that in Example 2 and Comparative Example 5 in improving the performance of stabilized soil. A comparison of Example 3 with Comparative Example 5 shows that supplementing the soil with magnesium phosphate cement and silicate results in faster soil stabilization and stronger frost resistance.

[0077] As can be seen from Example 3 compared with Comparative Example 1, removing humic acid from the soil stabilizer composition significantly reduced the compressive strength and CBR value of the corresponding stabilized soil sample, while significantly increasing the drying shrinkage rate, freeze-thaw cycle strength loss rate, permeability coefficient, and collapsibility coefficient of the sample. This indicates that humic acid plays a significant role in improving the overall performance of stabilized soil.

[0078] A comparison of Example 3 and Comparative Example 2 shows that excessive humic acid significantly affects the compressive strength and CBR value of the solidified soil sample, because excessive humic acid delays coagulation. Meanwhile, a comparison of Example 3 with Comparative Examples 1 and 2 shows that humic acid can effectively inhibit the leaching of heavy metals from the sample.

[0079] A comparison of Example 3 and Comparative Example 3 shows that in the nano-iron oxide-fly ash composite, fly ash is the main carrier, while nano-iron oxide provides highly active sites to catalyze silicate reactions and fill micropores. Fly ash is a solid waste resource; combined with nano-modification, it significantly enhances the added value of fly ash. The nano-iron oxide-fly ash composite can significantly improve compressive strength and CBR value, reduce permeability coefficient, significantly increase the compactness and impermeability of solidified soil, and extend its service life.

[0080] A comparison of Example 3 and Comparative Example 4 shows that the calcium carbonate precipitate formed by the microbial powder can significantly improve the compressive strength and CBR value of the solidified soil; at the same time, it can significantly reduce the collapsibility coefficient.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 soil stabilizer composition, characterized in that, Including, by weight: 20-25 parts water-soluble silicate, 3-7 parts humic acid, 2-5 parts soil mineralization microbial agent, 8-10 parts silicate reaction catalyst, and 10-12 parts cement. The silicate reaction catalyst is a nano-iron oxide-fly ash composite or red mud.

2. The soil stabilizer composition according to claim 1, characterized in that, Water-soluble silicates are sodium silicate or potassium silicate; When the silicate reaction catalyst is red mud, the pH of the red mud is 7-8.

3. The soil stabilizer composition according to claim 1, characterized in that, The cement is selected from magnesium phosphate cement or sulfoaluminate cement. If sulfoaluminate cement is used, it also includes silica fume, which accounts for 5%-6% of the weight of sulfoaluminate cement.

4. The soil stabilizer composition according to claim 1, characterized in that, The mass ratio of water-soluble silicate to humic acid is 4-6:

1.

5. The soil stabilizer composition according to claim 1, characterized in that, Soil mineralization microbial agents are biochar-loaded with Bacillus pasteurellii and / or urea-decomposing bacteria; Biochar is a product of crop residue pyrolysis, and its pore size is 1-10 μm.

6. The soil stabilizer composition according to claim 1, characterized in that, Humic acid is an extract from lignite, which contains iron oxides and aluminum oxides. The ash content in lignite extract is <15%.

7. A soil consolidation method, characterized in that, Using the soil stabilizer composition according to any one of claims 1-6, the method comprises the following steps: S1. Sift the soil, spray a 0.1% urea solution onto the sieved soil, then add soil mineralization microbial agent according to the mass ratio of soil stabilizer composition to soil to be stabilized of 8-12:100, mix well and let stand for later use. S2. Soluble silicate and humic acid dry powder are premixed, and water is added at a liquid-to-solid ratio of 0.5-0.6:

1. The mixture is stirred to form a homogeneous slurry. Cement and silicate reaction catalyst are added to the slurry in sequence to prepare the first mixed slurry. Water is added again to the first mixed slurry at a volume ratio of 0.3-0.4:1, and the mixture is stirred to obtain the second mixed slurry. S3. Add the second mixed slurry to the soil after it has settled, mix well, adjust the soil moisture content to 14-16%, compact in layers, and maintain even moisture and room temperature for 7-28 days.

8. The soil consolidation method as described in claim 7, characterized in that, If the solidified soil is used for slope protection, the thickness of the solidified soil layer should be 0.5-1m; If the solidified soil is used as a roadbed, the thickness of the solidified soil layer is 3-5m.

9. The soil consolidation method as described in claim 7, characterized in that, In S3, each layer is loosely laid for 30-40cm, and compacted 6-8 times to achieve a compaction degree of ≥95% for the solidified soil layer.

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