Method for improving erosion resistance of low-clay-content dispersed loess

Abstract

The invention discloses a method for improving erosion resistance of low-clay-content dispersed loess, and relates to the field of hydraulic geotechnical engineering, and the method comprises the following steps: S01, material pretreatment: selecting low-clay-content dispersed loess, polyvinyl alcohol powder and aluminum sulfate powder according to a mass ratio, and respectively drying for later use; s02, uniformly mixing the materials in the step S01 in a mixing container; s03, spraying water to the mixture in the step S02 for several times, and stirring; s04, the stirred mixture in the step S03 is subjected to material covering treatment, and improved soil is obtained; according to the method for improving the erosion resistance of the low-clay-content dispersed loess, the low-clay-content dispersed loess has good erosion resistance, the dispersity and the erosion resistance of the low-clay-content dispersed loess are greatly improved, and therefore engineering hazards caused by the low-clay-content dispersed loess serving as filler are reduced.

Description

Technical Field

[0001] This invention relates to hydraulic geotechnical engineering technology, specifically to a method for improving the erosion resistance of loess with low clay content and dispersible particles. Background Technology

[0002] Low-clay-content dispersible loess is widely distributed in Northwest my country. It has low clay content (typically <18%), low liquid limit water content (<30%), and a plasticity index greater than 11, classifying it as low-liquid-limit clay. When this type of loess comes into contact with water, the cementation between soil particles is weak, making it prone to dispersion, turbidity, disintegration, and collapse. This leads to engineering problems such as reduced foundation bearing capacity, building settlement, and cracking.

[0003] Current research on improving dispersed loess mainly focuses on mechanical strength and permeability, while systematic improvement methods specifically targeting erosion resistance (resistance to seepage erosion and water scouring) are relatively rare. Polyvinyl alcohol, as a water-soluble polymer, has good binding properties and is environmentally friendly, making it suitable for soil improvement; aluminum sulfate, on the other hand, has cross-linking strengthening and pore-filling effects, enhancing soil water stability. This invention combines the advantages of both to propose a method for improving the erosion resistance of dispersed loess with low clay content. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the erosion resistance of low clay content dispersible loess. This method improves the resistance of low clay content dispersible loess to seepage and water erosion through bonding enhancement and pore filling.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for improving the erosion resistance of loess with low clay content, comprising the following steps:

[0006] S01. Material pretreatment: Select low-clay-content dispersible loess, polyvinyl alcohol powder, and aluminum sulfate powder according to the mass ratio, and dry them separately for later use.

[0007] S02. Mix the materials from step S01 thoroughly in a mixing container;

[0008] S03. Sprinkle water onto the mixture from step S02 in several batches and stir.

[0009] S04. The mixture from step S03 is subjected to a curing process to obtain improved soil.

[0010] Furthermore, the loess mentioned in step S01 is a dispersible soil with a clay content of less than 18%.

[0011] Furthermore, the amount of polyvinyl alcohol powder is 0.25% to 0.50% of the total mass of loess, and the amount of aluminum sulfate powder is 5% to 10% of the mass of polyvinyl alcohol.

[0012] Furthermore, the polyvinyl alcohol powder has a degree of alcoholysis ≥97% and a degree of polymerization ≥1700.

[0013] Furthermore, the aluminum sulfate powder has a passing rate of ≥95% through a #40 mesh sieve.

[0014] Furthermore, the mixing time in step S02 shall not be less than 15 minutes.

[0015] Furthermore, in step S03, the amount of water applied is controlled according to the optimum moisture content of the loess.

[0016] Furthermore, in step S04, the material is sealed and left to stand at room temperature for more than 24 hours.

[0017] A low-clay-content dispersible modified soil prepared by the method described above.

[0018] Pinhole drilling revealed that the low-clay-content loess sample was highly dispersed (pinhole drilling classification: D1). Further erosion resistance testing showed that the critical shear stress was 1.05 Pa and the erosion resistance index (I) was 1.86. This extremely low erosion resistance does not meet engineering requirements, necessitating treatment measures to restore the loess to the required level. Indoor physical property tests showed that polyvinyl alcohol (PVA) can improve the extremely low erosion resistance of this type of low-clay-content dispersed loess. Aluminum sulfate powder can improve the cross-linking strengthening effect of PVA aggregates and fill pores, thus enhancing the erosion resistance of the dispersed loess. This significantly reduces the hazards of low-clay-content dispersed loess, is low-carbon and environmentally friendly, and saves costs.

[0019] Compared with the prior art, the present invention provides a method for improving the erosion resistance of loess with low clay content and dispersion, which has the following beneficial effects:

[0020] (1) The improved low clay content dispersible loess of the present invention has good anti-erosion performance, which greatly improves the dispersibility and erosion resistance of low clay content dispersible loess, thereby reducing the engineering hazards caused by its use as filler.

[0021] (2) The polyvinyl alcohol used in this invention has a content of less than 0.50%, which is not harmful to soil microorganisms and can degrade the mulch film, making it low-carbon and environmentally friendly. Aluminum sulfate powder has no toxic side effects and plays a role in environmental protection.

[0022] (3) The polyvinyl alcohol used in this invention has a good bonding effect and can form stable aggregates in the soil. Aluminum sulfate powder has the effect of cross-linking reinforcement and filling pores, which can form a stable network structure between the aggregates and fill excessive pores, strengthen the soil and improve the comprehensive performance of the improved soil.

[0023] (4) This invention can more scientifically utilize polyvinyl alcohol and aluminum sulfate powder commonly used in industry and low clay content dispersible loess, providing a beneficial solution for earth-rock dam construction and reinforcement. It is simple to operate and saves costs. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0025] Figure 1 SEM image of loess modified with 0.25% polyvinyl alcohol provided in an embodiment of the present invention;

[0026] Figure 2 SEM images of loess modified with 0.25% polyvinyl alcohol and 5% aluminum sulfate, provided for embodiments of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] As attached Figure 1 and attached Figure 2 As shown:

[0029] Example 1:

[0030] This invention provides a method for improving the erosion resistance of loess with low clay content, comprising the following steps:

[0031] S01. Material pretreatment: Select low-clay-content dispersible loess, polyvinyl alcohol powder, and aluminum sulfate powder according to the mass ratio, and dry them separately for later use.

[0032] S02. Mix the materials from step S01 thoroughly in a mixing container;

[0033] S03. Sprinkle water onto the mixture from step S02 in several batches and stir.

[0034] S04. The mixture from step S03 is subjected to a curing process to obtain improved soil.

[0035] In step S01, the loess is a dispersible soil with a clay content of less than 18%.

[0036] The amount of polyvinyl alcohol powder added is 0.25% to 0.50% of the total mass of loess, and the amount of aluminum sulfate powder added is 5% to 10% of the mass of polyvinyl alcohol.

[0037] The degree of alcoholysis of polyvinyl alcohol powder is ≥97%, and the degree of polymerization is ≥1700.

[0038] The aluminum sulfate powder has a passing rate of ≥95% through a #40 mesh sieve.

[0039] The mixing time in step S02 shall not be less than 15 minutes.

[0040] In step S03, the amount of water applied is controlled according to the optimum moisture content of the loess.

[0041] In step S04, the material is sealed and left to stand at room temperature for more than 24 hours.

[0042] A low-clay-content dispersible improved soil prepared by the above method.

[0043] Test materials

[0044] Low-clay-content dispersible loess: The soil sample was taken from a damaged dam site. The soil was yellowish-brown and loosely structured. Pinhole testing was conducted according to the "Specification for Dispersibility Testing of Soils" (T / CHES 127—2024), and the soil was classified as highly dispersed (Class D1). Its basic physical and mechanical properties are shown in Table 1.

[0045] Table 1 Basic physical and mechanical properties of dispersible loess with low clay content

[0046] Soil particle density <![CDATA[Maximum dry density / (g·cm -3 )]]> Optimal moisture content / % Liquid limit W_L / % Plastic Limit W_P / % Plasticity index I_P Soil classification pH value 2.71 1.76 14.5 27.1 16.1 11.0 CL 8.96

[0047] Polyvinyl alcohol powder: Commercially available high molecular weight polymer powder with a degree of alcoholysis ≥97%, an average degree of polymerization of 1750±50, a viscosity of 54.0~66.0 mPa·s, a pH value of 5.0~7.0, volatile matter ≤5.0%, and residue on ignition ≤0.5%.

[0048] Aluminum sulfate powder: Commercially available chemical reagent, molecular formula Al2(SO4)3, aluminum oxide (Al2O3) content ≥17.00%, iron content ≤0.005%, water-insoluble matter ≤0.050%, pH (1% aqueous solution) ≥3.0, #40 mesh sieve passing rate ≥95%.

[0049] Test instruments

[0050] Laser particle size analyzer, pinhole test device, corrosion resistance tester, compactor, demolding device, electronic scale, drying oven, mixing drum, preservation box, plastic wrap, etc.

[0051] Sample preparation

[0052] Prepare modified soil samples with different polyvinyl alcohol content according to the following steps:

[0053] Material pretreatment: Place the low clay content dispersible loess in an oven and dry it at 105℃ for 12 hours. After cooling, it is ready for use.

[0054] Weighing and mixing: Weigh the corresponding materials according to the mass ratio of polyvinyl alcohol to loess of 100:0, 100:0.05, 100:0.10, 100:0.15, 100:0.25, 100:0.50, and 100:1.00, place them in the mixing bucket, and mechanically mix for 15 minutes to ensure uniform mixing.

[0055] Watering and mixing: Based on the optimal moisture content of loess (14.5%), calculate the total amount of clean water required and spray it evenly into the dry mixture in 3 to 4 times. While spraying water, stir manually to avoid the formation of mud clumps due to excessive local moisture content, until the soil sample can be kneaded into a ball, is not sticky, and does not bleed water.

[0056] Precipitation treatment: Place the mixture into a preservation box, cover the surface with plastic wrap and put on a lid, and let it stand in a cool, room temperature environment for 24 hours to complete the preparation of improved soil.

[0057] Experimental methods and results

[0058] According to the "Standard for Geotechnical Testing Methods" (GB / T 50123-2019), erosion resistance tests were conducted on the prepared soil samples to test the critical shear stress and erosion resistance index. The results are shown in Tables 2 and 3.

[0059] Table 2. Critical shear stress for erosion resistance of improved loess under different polyvinyl alcohol contents.

[0060] Sample number Polyvinyl alcohol content / % Critical shear stress for corrosion resistance / Pa 1# 0 1.05 2# 0.05 2.39 3# 0.10 10.93 4# 0.15 14.45 5# 0.25 86.81 6# 0.50 69.80 7# 1.00 44.76

[0061] Table 3. Erosion resistance index of improved loess with different polyvinyl alcohol contents

[0062] Sample number Polyvinyl alcohol content / % Corrosion resistance index 1# 0 1.86 2# 0.05 3.42 3# 0.10 3.96 4# 0.15 4.26 5# 0.25 4.90 6# 0.50 4.62 7# 1.00 4.50

[0063] Results Analysis

[0064] Polyvinyl alcohol (PVA) significantly improves the erosion resistance of dispersible loess with low clay content. At a concentration of 0.25%, the critical shear stress reaches 86.81 Pa, 82.7 times that of the unmodified soil sample; at a concentration of 0.50%, the critical shear stress is 69.80 Pa, 66.5 times that of the unmodified soil sample. According to Briaud's (2019) erosion resistance index classification, a concentration of 0.25%–0.50% results in an erosion resistance index of 4.62–4.90, falling within the low-erosion range and meeting engineering requirements.

[0065] Example 2: Modification Experiment with Polyvinyl Alcohol and Aluminum Sulfate

[0066] The polyvinyl alcohol content was fixed at 0.25% and 0.50%, and aluminum sulfate was added at 0%, 5%, 10%, and 15% of the polyvinyl alcohol mass, respectively. The preparation steps were the same as in Example 1, and the specific proportions are shown in Table 4.

[0067] Table 4 Mixture Design for Compound Admixture Experiment

[0068] Sample number Polyvinyl alcohol content / % Aluminum sulfate content (percentage of PVA mass) / % 1# 0.25 0 2# 0.25 5 3# 0.25 10 4# 0.25 15 5# 0.50 0 6# 0.50 5 7# 0.50 10 8# 0.50 15

[0069] The results of the erosion resistance test are shown in Tables 5 and 6.

[0070] Table 5. Critical shear stress for erosion resistance of improved loess under different admixture ratios

[0071] Sample number Polyvinyl alcohol content / % Aluminum sulfate dosage / % Critical shear stress for corrosion resistance / Pa 1# 0.25 0 86.8 2# 0.25 5 227.3 3# 0.25 10 198.2 4# 0.25 15 120.5 5# 0.50 0 69.8 6# 0.50 5 172.6 7# 0.50 10 134.5 8# 0.50 15 92.6

[0072] Table 6. Erosion resistance index of improved loess under different admixture ratios

[0073] Sample number Polyvinyl alcohol content / % Aluminum sulfate dosage / % Corrosion resistance index 1# 0.25 0 4.9 2# 0.25 5 5.9 3# 0.25 10 5.6 4# 0.25 15 5.3 5# 0.50 0 4.6 6# 0.50 5 5.8 7# 0.50 10 5.4 8# 0.50 15 4.8

[0074] Results Analysis

[0075] The addition of aluminum sulfate further enhances the erosion resistance. The optimal ratio is 0.25% polyvinyl alcohol + 5% aluminum sulfate, at which the critical shear stress reaches 227.3 Pa, 216.5 times that of the unamended soil sample, and the erosion resistance index reaches 5.9, which is within the extremely low erosion range. With a ratio of 0.50% polyvinyl alcohol + 5% aluminum sulfate, the critical shear stress is 172.6 Pa, and the erosion resistance index is 5.8, also showing excellent performance.

[0076] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for improving the erosion resistance of low-clay-content dispersible loess, characterized in that, Includes the following steps: S01. Material pretreatment: Select low-clay-content dispersible loess, polyvinyl alcohol powder, and aluminum sulfate powder according to the mass ratio, and dry them separately for later use. S02. Mix the materials from step S01 thoroughly in a mixing container; S03. Sprinkle water onto the mixture from step S02 in several batches and stir. S04. The mixture from step S03 is subjected to a curing process to obtain improved soil.

2. The method for improving the erosion resistance of low-clay-content dispersible loess according to claim 1, characterized in that, The loess mentioned in step S01 is a dispersible soil with a clay content of less than 18%.

3. The method for improving the erosion resistance of low-clay-content dispersible loess according to claim 1, characterized in that, The amount of polyvinyl alcohol powder is 0.25% to 0.50% of the total mass of loess, and the amount of aluminum sulfate powder is 5% to 10% of the mass of polyvinyl alcohol.

4. The method for improving the erosion resistance of low-clay-content dispersible loess according to claim 1, characterized in that, The polyvinyl alcohol powder has a degree of alcoholysis ≥97% and a degree of polymerization ≥1700.

5. The method for improving the erosion resistance of low-clay-content dispersible loess according to claim 1, characterized in that, The aluminum sulfate powder has a passing rate of ≥95% through a #40 mesh sieve.

6. The method for improving the erosion resistance of low-clay-content dispersible loess according to claim 1, characterized in that, The mixing time in step S02 shall not be less than 15 minutes.

7. The method for improving the erosion resistance of low-clay-content dispersible loess according to claim 1, characterized in that, In step S03, the amount of water applied is controlled according to the optimum moisture content of the loess.

8. The method for improving the erosion resistance of low-clay-content dispersible loess according to claim 1, characterized in that, In step S04, the material is sealed and left to stand at room temperature for more than 24 hours.

9. A low-clay-content dispersible modified soil prepared by the method of any one of claims 1 to 8.

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