A high-cold-season frozen soil area roadbed soil material based on straw and hydrophobic anti-freezing agent and an optimization method of proportioning thereof

Abstract

The present application relates to the technical field of roadbed engineering, and particularly relates to a high-cold seasonal frozen region roadbed soil material based on straw and hydrophobic agent and an optimization method of proportioning of the high-cold seasonal frozen region roadbed soil material. In order to simultaneously improve the mechanical properties and the frost heaving resistance, the straw treated by the hydrophobic film forming agent, the straw length, the soaking time of the straw in the hydrophobic film forming agent and the hydrophobic frost resistant agent content are taken as the influencing factors, the frost heaving rate and the bearing ratio of the roadbed soil material in the seasonal frozen region based on the straw and the hydrophobic agent are taken as the response values, the response surface analysis method is used to carry out the response surface analysis test, and the optimization technical scheme which simultaneously satisfies the double target optimization requirements of the frost heaving rate and the bearing ratio is obtained. The present application realizes the simultaneous improvement of the mechanical properties and the frost heaving resistance of the roadbed soil material in the high-cold seasonal frozen region without using inorganic binding agent or carrying out roadbed replacement, avoids the damage of the ecological environment in the high-cold region, and realizes the resource utilization of the agricultural solid waste straw.

Description

Technical Field

[0001] The present invention relates to the technical field of roadbed engineering, and in particular to a roadbed soil material for seasonally frozen areas in high cold regions based on straw and a hydrophobic antifreeze agent, and a method for optimizing the proportion thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Seasonally frozen ground refers to soil that freezes in winter and thaws in summer. The areas where it occurs are called seasonally frozen ground areas. For roadbeds in seasonally frozen ground areas, during the severe winter, due to the temperature gradient and capillary action, groundwater continuously migrates into the roadbed through capillary pipes, forming ice crystals inside the roadbed, causing frost heave and road surface bulges and cracks. In spring and summer, the ice crystals melt, and the water content inside the roadbed becomes excessive. Under the action of vehicle loads, this causes the roadbed to slurry up and thaw. This phenomenon is particularly pronounced in high-altitude or high-latitude seasonally frozen ground areas, where large temperature differences make the roadbed freeze-thaw particularly severe. This leads to severe damage to roads and severely restricts economic development in these areas.

[0004] Currently, there are two main methods for improving subgrade soil in seasonally frozen areas: one is to use inorganic binders such as cement, lime, or solid waste cementitious materials to improve frost-heaving subgrade soil; the other is to replace frost-heaving subgrade soil with non-frost-heaving or weakly frost-heaving gravel. However, in the first method, the dosage of cement, lime, and solid waste cementitious materials is often as high as 6% to 8%, which is large and costly. The pH value of the leaching solution during the hydration process of the inorganic binder is around 13, which increases the alkalinity of the soil, leading to sandification, hardening, and environmental pollution. Cement and lime production results in high carbon emissions and consumes a large amount of natural resources. Solid waste cementitious materials also pose the risk of heavy metal leaching. Moreover, inorganic binders cannot block the migration channels of capillary water, and the frost heave resistance of the improved soil will gradually decline with service time. The second method, replacing the roadbed with gravel near the project, would alter the natural vegetation, landforms, groundwater runoff, and other environmental characteristics of the cold region, causing environmental disturbance. Transporting the gravel over long distances would significantly increase project costs and construction difficulty. The ecological environment in high-altitude or high-latitude alpine regions is extremely fragile, and once damaged, it is difficult to recover. Therefore, the environmental protection requirements for roadbed construction are extremely high. Therefore, the above two traditional methods are gradually being restricted in improving roadbed soil in seasonally frozen areas.

[0005] To improve soil's frost heave resistance, some studies have incorporated hydrophobic agents into the soil. Hydrophobic agents enhance the soil's water repellency, blocking the pathways through which capillary water in the subgrade migrates to negative temperature zones, thereby improving the frost heave resistance of subgrade soil. However, hydrophobic agents have a limited effect on subgrade soil strength. Excessive additions can even reduce soil strength, rendering the strength of the modified soil lower than that of the original subgrade soil. Consequently, subgrade soil modified with hydrophobic agents alone in seasonally frozen regions cannot withstand heavy traffic loads. Furthermore, to enhance the mechanical properties of soil, some studies have used wheat straw as reinforcement, creating a three-dimensional network structure within the soil. However, wheat straw's high porosity not only reduces corrosion resistance but also increases the soil's porosity and the number of water migration pathways, negatively impacting the subgrade's frost heave resistance. Furthermore, when the length and amount of wheat straw are too large, the straw will tangle together, forming weak areas in the soil and reducing the strength of the reinforced soil. Furthermore, wheat straw is prone to corrosion and its tensile strength needs to be further improved.

[0006] Therefore, there is an urgent need to provide a roadbed soil material that can improve both mechanical properties and frost heave resistance while ensuring the ecological environment and is suitable for high-altitude seasonal frozen soil areas. Summary of the Invention

[0007] In order to overcome the above problems, the present invention provides a method for optimizing roadbed soil materials and their proportions in high-cold seasonal frozen areas based on straw and a hydrophobic antifreeze agent.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0009] The first aspect of the present invention provides a roadbed soil material for seasonally frozen areas in high-cold regions based on straw and a hydrophobic antifreeze agent, the raw materials of which include:

[0010] Straw treated with hydrophobic film-forming agent, hydrophobic antifreeze agent, air-dried roadbed soil and water.

[0011] In one or more embodiments, the straw is selected from highland barley straw or wheat straw, preferably highland barley.

[0012] In one or more embodiments, the hydrophobic film-forming agent is composed of the following raw materials in parts by weight: 5-8 parts of cooked tung oil, 1-2 parts of nano-silica sol, 3-5 parts of silane modifier, 5-10 parts of sodium alginate, 1-2 parts of carboxymethyl cellulose, and 50 parts of water;

[0013] Nano-silica sol is a sol prepared by dispersing nano-SiO2 in a NaOH solution with a mass concentration of 0.001% to 0.005%, wherein the particle size of SiO2 is 10 to 20 nm, the mass fraction of SiO2 is 29 to 31%, and the pH value of the nano-silica sol is 9.0 to 10.5;

[0014] The silane modifier is a mixture of perfluorodecyltrimethoxysilane, hexadecyltrimethoxysilane and silane coupling agent KH570 in a mass ratio of 2-3:2-3:1.

[0015] Cooked tung oil is processed from raw tung oil and has a high viscosity, providing corrosion and water resistance. The nano-SiO2 particles in nano-silica sol can increase the surface roughness of straw, enhance the frictional resistance between straw and soil particles, and fill microscopic gaps in straw, improving the tensile strength of straw and, in turn, enhancing the mechanical properties of roadbed soil materials in high-altitude seasonally frozen regions. Silane modifiers can modify the surface of the nano-SiO2 particles in nano-silica sol, replacing the hydrophilic hydroxyl groups on the nano-SiO2 particles with strongly hydrophobic groups. This significantly increases the hydrophobicity of the nano-SiO2 particles and promotes their uniform dispersion in organic media such as cooked tung oil. Sodium alginate, a byproduct of the extraction of iodine and mannitol from brown algae such as kelp and sargassum, is a natural polysaccharide with high viscosity and excellent film-forming properties. Carboxymethyl cellulose, a natural polysaccharide with strong viscosity-increasing properties, can synergize with sodium alginate to enhance the tensile strength of films formed by hydrophobic film-forming agents.

[0016] In one or more embodiments, the method for treating straw with a hydrophobic film-forming agent comprises:

[0017] The dried straw is split into two parts along the radial direction and cut into a defined length;

[0018] Soak the straw in the hydrophobic film-forming agent, take out the straw and dry it.

[0019] By soaking straw in a hydrophobic film-forming agent, not only can the straw's tensile and corrosion resistance be improved, providing better soil reinforcement, but it can also block the pores within the straw, preventing the increased porosity and decreased frost heave resistance associated with straw addition. The straw treated with a hydrophobic film-forming agent creates a three-dimensional network within the subgrade soil, acting as a stirrup. This effectively transfers load through the straw, preventing cracking and improving the mechanical properties of the subgrade soil.

[0020] In one or more embodiments, the hydrophobic antifreeze agent is composed of the following raw materials in parts by weight: 5-8 parts of sodium methyl silicate solution, 2-3 parts of polydimethylsiloxane, 50-80 parts of nano-silica sol, 6-20 parts of silane modifier, 5-10 parts of methacryloylethyl sulfobetaine, and 50-80 parts of water;

[0021] Wherein, the mass fraction of sodium methyl silicate in the sodium methyl silicate solution is ≥25%.

[0022] Nano-silica sol is a sol prepared by dispersing nano-SiO2 in a NaOH solution with a mass concentration of 0.001% to 0.005%, wherein the particle size of SiO2 is 10 to 20 nm, the mass fraction of SiO2 is 29 to 31%, and the pH value of the nano-silica sol is 9.0 to 10.5;

[0023] The silane modifier is a mixture of perfluorodecyltrimethoxysilane, hexadecyltrimethoxysilane and silane coupling agent KH570 in a mass ratio of 2-3:2-3:1.

[0024] Sodium methyl silicate, with the molecular formula CH5SiO3Na, reacts with water and carbon dioxide in the air to form methyl silicic acid, which then dehydrates and polymerizes into hydrophobic polymethylsiloxane, forming a hydrophobic polymethylsiloxane film on the surface of roadbed soil particles. Polydimethylsiloxane, with its physiological inertness, good chemical stability, and excellent hydrophobicity, can be used to enhance the hydrophobicity of hydrophobic antifreeze agents. Nano-silica sol can penetrate nano-SiO2 particles into the fine pores within roadbed soil, filling them to a certain extent and increasing the density of the roadbed soil, thereby improving the mechanical properties of roadbed soil materials in high-altitude seasonally frozen areas. Silane modifiers can modify the surface of the nano-SiO2 particles in nano-silica sol, replacing the original hydrophilic hydroxyl groups on the surface of the nano-SiO2 particles with strongly hydrophobic groups. This can significantly improve the hydrophobicity of the nano-SiO2 particles and promote their uniform dispersion in organic media such as sodium methyl silicate and polydimethylsiloxane. Methacryloylethyl sulfobetaine can effectively lower the freezing temperature of water, prevent the frost heave of water existing in the subgrade soil after the completion of the subgrade, and thus improve the anti-frost heave performance of the subgrade soil.

[0025] Hydrophobic antifreeze agents improve the frost heave resistance of roadbed soil through the following two effects: first, by improving the hydrophobic effect of the soil, blocking the infiltration of upper water and the rise of groundwater through capillary action, blocking water migration, and thus preventing the increase of moisture content inside the roadbed; second, lowering the freezing temperature of the roadbed soil to prevent the frost heave of water existing in the roadbed soil after the roadbed is completed.

[0026] A second aspect of this aspect provides a method for optimizing the ratio of roadbed soil materials in high-cold seasonal frozen areas based on straw and a hydrophobic antifreeze agent, comprising:

[0027] S1. Taking the dosage of straw treated with hydrophobic film-forming agent, straw length, soaking time of straw in hydrophobic film-forming agent and dosage of hydrophobic antifreeze agent as influencing factors, and the frost heave rate and bearing ratio of roadbed soil material as response values, a response surface analysis test was conducted using a 4-factor 3-level response surface analysis method to obtain the response surface analysis test results;

[0028] S2. Based on the response surface analysis test results, the influencing factors were fitted by a quadratic regression equation. Based on the limiting conditions of the upper and lower roadbeds of the roadbed, the optimal straw dosage, optimal straw length, optimal immersion time of straw in the hydrophobic film-forming agent, and optimal hydrophobic antifreeze dosage were obtained based on the response surface method fitting.

[0029] In one or more embodiments, in step S1, the amount of straw treated with the hydrophobic film-forming agent refers to the percentage of the mass of the straw treated with the hydrophobic film-forming agent in the mass of the air-dried roadbed soil.

[0030] Preferably, the addition amount of the straw treated with the hydrophobic film-forming agent ranges from 0.1% to 0.3%.

[0031] In one or more embodiments, in step S1, the straw length ranges from 10 mm to 20 mm.

[0032] In one or more embodiments, in step S1, the soaking time of the straw in the hydrophobic film-forming agent ranges from 12 hours to 24 hours.

[0033] In one or more embodiments, in step S1, the dosage of the hydrophobic antifreeze agent refers to the percentage of the hydrophobic antifreeze agent in the mass of the air-dried roadbed soil.

[0034] Preferably, the dosage of the hydrophobic antifreeze agent ranges from 0.25% to 0.75%.

[0035] In one or more embodiments, in step S1, the Box-Benhnken model of the response surface methodology is used to design the experimental scheme.

[0036] In one or more embodiments, in step S2, the limiting conditions of the upper roadbed of the roadbed are:

[0037] A1) The bearing capacity of the subgrade soil material shall not be less than 8%;

[0038] A2) The frost heave rate of subgrade soil materials should not exceed 0.9%;

[0039] A3) When the conditions of A1) and A2) are met at the same time, the dosage of the hydrophobic antifreeze agent is the minimum.

[0040] In one or more embodiments, in step S2, the limiting conditions of the lower roadbed of the roadbed are:

[0041] B1) The bearing capacity of the roadbed soil material shall not be less than 5%;

[0042] B2) The frost heave rate of subgrade soil materials should not exceed 3.4%;

[0043] B3) When the conditions of B1) and B2) are met at the same time, the amount of hydrophobic antifreeze agent is taken as the minimum value.

[0044] In one or more embodiments, in step S2, based on the limiting conditions of the upper roadbed of the roadbed, the optimal straw content is 0.15%, the optimal straw length is 15.7 mm, the optimal soaking time of the straw in the hydrophobic film-forming agent is 23.9 h, and the optimal hydrophobic antifreeze content is 0.61% obtained based on the response surface method fitting.

[0045] In one or more embodiments, in step S2, based on the limiting conditions of the lower roadbed of the roadbed, the optimal straw content is 0.20%, the optimal straw length is 10.0 mm, the optimal soaking time of the straw in the hydrophobic film-forming agent is 18.0 h, and the optimal hydrophobic antifreeze content is 0.25% obtained by response surface methodology fitting.

[0046] The beneficial effects of the present invention are:

[0047] The present invention relates to the field of roadbed engineering technology, and in particular to a method for optimizing roadbed soil materials and their proportions in high-cold seasonal frozen soil areas based on straw and a hydrophobic antifreeze agent. In order to simultaneously improve mechanical properties and frost heave resistance, the present invention uses the amount of straw after treatment with a hydrophobic film-forming agent, the length of the straw, the soaking time of the straw in the hydrophobic film-forming agent, and the amount of the hydrophobic antifreeze agent as influencing factors, and the frost heave rate and the bearing ratio as response values. A response surface analysis test is performed using a 4-factor 3-level response surface analysis method to obtain an optimization technical solution that simultaneously meets the dual-objective optimization requirements of the frost heave rate and the bearing ratio. The present invention achieves the simultaneous improvement of the mechanical properties and frost heave resistance of roadbed soil materials in high-cold seasonal frozen soil areas without using an inorganic binder or performing roadbed replacement, avoids the damage to the ecological environment in high-cold areas, and realizes the resource utilization of agricultural solid waste straw. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0049] Figure 1 Response surface diagram of the influence of the influencing factors in Example 2 on the frost heave rate of the subgrade soil material; wherein, (a) is the response surface diagram of the interaction between influencing factor A (the amount of straw after the hydrophobic film-forming agent treatment) and influencing factor B (straw length) on the frost heave rate of the subgrade soil material; (b) is the response surface diagram of the interaction between influencing factor A (the amount of straw after the hydrophobic film-forming agent treatment) and influencing factor C (the soaking time of straw in the hydrophobic film-forming agent) on the frost heave rate of the subgrade soil material; (c) is the response surface diagram of the interaction between influencing factor A (the amount of straw after the hydrophobic film-forming agent treatment) and influencing factor D (the amount of hydrophobic antifreeze agent treatment) on the frost heave rate of the subgrade soil material. (d) is the response surface diagram of the interaction between influencing factors B (straw length) and C (soaking time of straw in hydrophobic film-forming agent) on the frost heave rate of subgrade soil materials; (e) is the response surface diagram of the interaction between influencing factors B (straw length) and D (hydrophobic antifreeze dosage) on the frost heave rate of subgrade soil materials; (f) is the response surface diagram of the interaction between influencing factors C (soaking time of straw in hydrophobic film-forming agent) and D (soaking time of hydrophobic antifreeze agent) on the frost heave rate of subgrade soil materials;

[0050] Figure 2 Response surface diagram of the influence of the influencing factors in Example 2 on the bearing ratio of the roadbed soil material; wherein, (a) is the response surface diagram of the interaction between influencing factor A (the amount of straw after the hydrophobic film-forming agent treatment) and influencing factor B (straw length) on the bearing ratio of the roadbed soil material; (b) is the response surface diagram of the interaction between influencing factor A (the amount of straw after the hydrophobic film-forming agent treatment) and influencing factor C (the soaking time of straw in the hydrophobic film-forming agent) on the bearing ratio of the roadbed soil material; (c) is the response surface diagram of the interaction between influencing factor A (the amount of straw after the hydrophobic film-forming agent treatment) and influencing factor D (the amount of hydrophobic antifreeze agent treatment) on the bearing ratio of the roadbed soil material. (d) is the response surface diagram of the interaction between influencing factors B (straw length) and C (soaking time of straw in hydrophobic film-forming agent) on the bearing ratio of subgrade soil materials; (e) is the response surface diagram of the interaction between influencing factors B (straw length) and D (hydrophobic antifreeze agent dosage) on the bearing ratio of subgrade soil materials; (f) is the response surface diagram of the interaction between influencing factors C (soaking time of straw in hydrophobic film-forming agent) and D (hydrophobic antifreeze agent dosage) on the bearing ratio of subgrade soil materials;

[0051] Figure 3 It is the implementation layer position of the optimization technical solution for the upper roadbed and lower roadbed of the roadbed in Example 2. DETAILED DESCRIPTION

[0052] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0053] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0054] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0055] The experimental water in the following examples is all pure water.

[0056] The air-dried roadbed soil used in the following examples was taken from a highway fill roadbed construction site in Qinghai Province. It is silt soil with a natural moisture content of 12%. According to the Chinese industry standard "Highway Soil Test Code" (JTG E40-2007), the frost heave rate of the silt soil was measured to be 5.4% and the bearing ratio was 4.8%. This section of roadbed project is located in a heavy or medium frozen area in a seasonally frozen area. The groundwater level or the surface water level is at a distance (h) from the road surface. w ) ≤3m. According to my country's industry standard "Technical Specifications for Highway Roadbed Construction" (JTG / T3610-2019), the frost heave rate of the upper roadbed filler in this section of roadbed construction should be ≤1.0% and the bearing ratio should be ≥8.0%; the frost heave rate of the lower roadbed filler should be ≤3.5% and the bearing ratio should be ≥5.0%; and the frost heave rate of the embankment filler should be ≤6.0% and the bearing ratio should be ≥4.0%. Therefore, this silt can only be used as embankment filler, not as roadbed filler, and requires improvement.

[0057] Example 1

[0058] A roadbed soil material for seasonally frozen areas in high-cold regions based on straw and a hydrophobic antifreeze agent, the raw materials of which include, by weight:

[0059] 0.1-0.3 parts of straw treated with a hydrophobic film-forming agent, 0.25-0.75 parts of a hydrophobic antifreeze agent, 100 parts of air-dried roadbed soil and 12 parts of water.

[0060] (1) The hydrophobic film-forming agent used is composed of the following raw materials in parts by weight: 6 parts of cooked tung oil, 1.5 parts of nano-silica sol, 4 parts of silane modifier, 7 parts of sodium alginate, 1.5 parts of carboxymethyl cellulose, and 50 parts of water.

[0061] The cooked tung oil is the Jingchen brand plant cooked tung oil produced by Jingchen Anti-corrosion Waterproof Material Co., Ltd.

[0062] The nano-silica sol is the alkaline nano-silica sol JN-30 produced by Shandong Yousuo Chemical Technology Co., Ltd., and the tested pH value is 9.4;

[0063] The silane modifier is a mixture of perfluorodecyltrimethoxysilane, hexadecyltrimethoxysilane and silane coupling agent KH570 in a mass ratio of 2:3:1. The perfluorodecyltrimethoxysilane is a liquid reagent produced by Shanghai Yinan Chemical Technology Co., Ltd., with a purity grade of analytical pure (AR); the hexadecyltrimethoxysilane is a liquid reagent of the brand of Mclean, with a concentration of ≥85%; and the silane coupling agent KH570 is a liquid reagent produced by the Chemical Reagent Co., Ltd. of the National Medicine Group, with a content of ≥98%.

[0064] The sodium alginate is a powder reagent produced by the Chemical Reagent Co., Ltd. of the National Medicine Group, with a purity grade of chemical pure (CP).

[0065] The carboxymethyl cellulose is a powder reagent produced by the Chemical Reagent Co., Ltd. of the National Medicine Group, with a purity grade of chemical pure (CP).

[0066] The preparation method of the hydrophobic film-forming agent is as follows:

[0067] The raw materials of the hydrophobic film-forming agent are stirred at a high speed at 50°C, with a stirring speed of 1000 r / min, and stirred for 30 min, to obtain the hydrophobic film-forming agent.

[0068] (2) The straw used is highland barley stem.

[0069] The method for treating the highland barley stem with the hydrophobic film-forming agent is as follows:

[0070] The dried highland barley stem is cut into two parts along the radial direction, and is cut into 10mm-20mm;

[0071] The straw is soaked in the above-mentioned hydrophobic film-forming agent, and the straw is taken out and placed in a 40°C oven for 12h, to form the straw treated with the hydrophobic film-forming agent.

[0072] (3) The hydrophobic antifreeze agent used in the following examples is composed of the following raw materials in parts by weight: sodium methyl silicate solution 7 parts, polydimethylsiloxane 2.5 parts, nano-silica sol 60 parts, silane modifier 10 parts, methacryloyl ethyl sulfobetaine 7 parts, and water 70 parts.

[0073] The sodium methyl silicate solution is the 3010 type produced by Jinan Xingfeilong Chemical Co., Ltd.

[0074] Polydimethylsiloxane is a Ron brand reagent produced by Shanghai Yien Chemical Technology Co., Ltd., and its purity grade is analytical grade (AR);

[0075] The nano-silica sol is the alkaline nano-silica sol JN-30 model produced by Shandong Yousuo Chemical Technology Co., Ltd., and the tested pH value is 9.4;

[0076] The silane modifier is a mixture of perfluorodecyltrimethoxysilane, hexadecyltrimethoxysilane, and silane coupling agent KH570 in a mass ratio of 2:3:1; the perfluorodecyltrimethoxysilane is a Ron brand liquid reagent produced by Shanghai Yien Chemical Technology Co., Ltd., with an analytical purity grade (AR); the hexadecyltrimethoxysilane is a Macklin brand liquid reagent with a concentration of ≥85%; the silane coupling agent KH570 is a Hushi brand liquid reagent produced by Sinopharm Chemical Reagent Co., Ltd., with a content of ≥98%;

[0077] Methacryloylethylsulfobetaine is a powder reagent produced by Shanghai Aladdin Biochemical Technology Co., Ltd. with a purity of ≥97%.

[0078] The preparation method of the hydrophobic antifreeze agent is:

[0079] The hydrophobic antifreeze agent is stirred at high speed at 30° C. according to the ratio, with a stirring speed of 1500 r / min and stirring for 30 minutes to obtain the hydrophobic antifreeze agent.

[0080] Example 2

[0081] A method for optimizing the proportion of roadbed soil materials in high-cold seasonal frozen areas based on straw and a hydrophobic antifreeze agent, comprising:

[0082] S1. Taking the dosage of straw treated with hydrophobic film-forming agent, straw length, soaking time of straw in hydrophobic film-forming agent and dosage of hydrophobic antifreeze agent as influencing factors, and the frost heave rate and bearing ratio of roadbed soil material as response values, a response surface analysis test was conducted using a 4-factor 3-level response surface analysis method to obtain the response surface analysis test results;

[0083] S2. Based on the response surface analysis test results, the influencing factors were fitted by a quadratic regression equation. Based on the limiting conditions of the upper and lower roadbeds of the roadbed, the optimal straw dosage, optimal straw length, optimal immersion time of straw in the hydrophobic film-forming agent, and optimal hydrophobic antifreeze dosage were obtained based on the response surface method fitting.

[0084] In step S1, the amount of straw treated with the hydrophobic film-forming agent refers to the percentage of the amount of straw treated with the hydrophobic film-forming agent in the air-dried roadbed soil. The amount of straw treated with the hydrophobic film-forming agent ranges from 0.1% to 0.3%.

[0085] In step S1, the straw length ranges from 10 mm to 20 mm.

[0086] In step S1, the soaking time of the straw in the hydrophobic film-forming agent ranges from 12 hours to 24 hours.

[0087] In step S1, the dosage of the hydrophobic antifreeze agent refers to the percentage of the hydrophobic antifreeze agent in the mass of the air-dried roadbed soil, and the dosage of the hydrophobic antifreeze agent ranges from 0.25% to 0.75%.

[0088] In step S1, the Box-Benhnken model of the response surface methodology was used to design the experimental scheme, and the coding of the influencing factors is shown in Table 1.

[0089] Table 1 Coding and levels of influencing factors

[0090]

[0091]

[0092] The response surface analysis experimental plan includes 29 experimental combinations, as shown in Table 2.

[0093] Table 2 Coding and levels of influencing factors

[0094]

[0095] In the response surface analysis test scheme shown in Table 2, 100 parts air-dried subgrade soil and 12 parts water were mixed evenly and then sealed in a plastic bag for 12 hours to simulate the natural moisture content of wet subgrade soil at the construction site. Straw treated with a hydrophobic film-forming agent, a hydrophobic antifreeze agent, wet subgrade soil, and water were mixed according to the material ratios shown in Table 2 and stirred for 20 minutes to allow the sodium methyl silicate to react with the water and CO2 in the air to form a hydrophobic film. Subgrade soil specimens were then prepared with a compaction degree of 96%.

[0096] The frost heave rate and bearing ratio of the subgrade soil materials corresponding to the 29 test groups were obtained and the test results are shown in Table 3. The frost heave rate was tested according to T0187-2007 of the "Highway Soil Test Code" (JTG E40-2007), and the bearing ratio was tested according to T0134-2019 of the "Highway Soil Test Code" (JTG E40-2007), a national industry standard.

[0097] Table 3 Test results of frost heave rate and bearing ratio of roadbed soil materials

[0098]

[0099]

[0100] A response surface model was established between the influencing factors (the dosage of straw after hydrophobic film-forming agent treatment A, straw length B, straw soaking time C in hydrophobic film-forming agent, and hydrophobic antifreeze agent dosage D) and the response values ​​(frost heave rate Y1 and bearing ratio Y2), which was expressed as follows using a quadratic polynomial regression equation:

[0101] Y1=8.761-6.01A-0.241B-0.233C-6.649D+0.29AB-0.163AC-1.2AD-0.00225BC-

[0102] 0.106BD+0.03CD+20.767A 2 +0.0101B 2 +0.00573C 2 +4.443D 2

[0103] Y2=-21.451+126.3A+2.449B+0.124C+3.72D-0.05AB-0.167AC+2AD+

[0104] 0.00333BC-0.18BD-0.0167CD-302.833A 2 -0.0786B 2 -0.00148C 2 -7.053D 2

[0105] The established response surface model was subjected to variance analysis, and the results are shown in Tables 4 and 5:

[0106] Table 4 Results of variance analysis of frost heave rate response surface model

[0107]

[0108]

[0109] Note: P < 0.05 indicates significant difference, indicated by *; P < 0.01 indicates extremely significant difference, indicated by **.

[0110] Table 4 shows the results of variance analysis of the frost heave rate response surface model. As shown in Table 4, the frost heave rate response surface model is extremely significant; the lack of fit term is not significant, indicating that the proportion of abnormal errors in the test data fitting process is very small, and the frost heave rate response surface model is credible; R 2 、Adjusted R 2 are very close to 1, indicating that the correlation between the predicted value of the frost heave rate response surface model and the measured value is good; Adjusted R 2and Predicted R 2 The difference between the two values ​​is less than 0.2, indicating consistency between the two. The Adeq Precision is much greater than 4, indicating that the impact of random errors in the frost heave response surface model is very low. The hydrophobic film-forming agent dosage, straw length, straw soaking time in the hydrophobic film-forming agent, and hydrophobic antifreeze agent dosage all have significant effects on the frost heave rate.

[0111] Figure 1 This is the response surface diagram of the factors affecting the frost heave rate of roadbed soil materials. Figure 1 (a) It can be seen that under the interaction of influencing factors A (the amount of straw treated with hydrophobic film-forming agent) and B (the length of straw), the frost heave rate of the roadbed soil material gradually increases with the increase of the amount of straw treated with hydrophobic film-forming agent; and the frost heave rate of the roadbed soil material first decreases and then increases with the increase of straw length. Figure 1 (b) It can be seen that under the interaction of influencing factor A (the amount of straw treated with hydrophobic film-forming agent) and influencing factor C (the soaking time of straw in hydrophobic film-forming agent), the frost heave rate of roadbed soil material gradually increases with the increase of the amount of straw treated with hydrophobic film-forming agent and the decrease of the soaking time of straw in hydrophobic film-forming agent. Figure 1 (c) It can be seen that under the interaction of influencing factor A (the amount of straw treated with hydrophobic film-forming agent) and influencing factor D (the amount of hydrophobic antifreeze agent), the frost heave rate of the roadbed soil material gradually increases with the increase of the amount of straw treated with hydrophobic film-forming agent and the decrease of the amount of hydrophobic antifreeze agent. Figure 1 (d) It can be seen that under the interaction of influencing factors B (straw length) and C (straw soaking time in hydrophobic film-forming agent), as the straw length increases, the frost heave of the roadbed soil material first decreases and then increases; as the straw soaking time in hydrophobic film-forming agent decreases, the frost heave rate of the roadbed soil material gradually increases. Figure 1 (e) It can be seen that under the interaction of influencing factors B (straw length) and D (hydrophobic antifreeze content), as the straw length increases, the frost heave of the roadbed soil material first decreases and then increases; as the hydrophobic antifreeze content decreases, the frost heave rate of the roadbed soil material gradually increases. Figure 1 (f) It can be seen that under the interaction of influencing factor C (the soaking time of straw in the hydrophobic film-forming agent) and influencing factor D (the dosage of hydrophobic antifreeze agent), the frost heave rate of the roadbed soil material gradually increases with the decrease of the soaking time of straw in the hydrophobic film-forming agent and the decrease of the dosage of hydrophobic antifreeze agent.

[0112] Table 5 Results of variance analysis of the response surface model for load ratio

[0113]

[0114]

[0115] Note: P < 0.05 indicates significant difference, indicated by *; P < 0.01 indicates extremely significant difference, indicated by **.

[0116] Table 5 shows the results of variance analysis of the response surface model of the bearing ratio of roadbed soil materials. As shown in Table 5, the bearing ratio response surface model is extremely significant; the lack of fit term is not significant, indicating that the proportion of abnormal errors in the test data fitting process is very small, and the bearing ratio response surface model is credible; R 2 、Predicted R 2 are very close to 1, indicating that the correlation between the predicted values ​​of the bearing ratio response surface model and the measured values ​​is good; Predicted R 2 With Adjusted R 2 The difference between the two values ​​is less than 0.2, indicating consistency between the two. The Adeq Precision is much greater than 4, indicating that the impact of random errors in the loading ratio response surface model is very low. The amount of hydrophobic film-forming agent-treated straw, straw length, and straw soaking time in the hydrophobic film-forming agent all have a significant impact on the loading ratio.

[0117] Figure 2 This is the response surface diagram of the influence factors on the bearing ratio of roadbed soil materials. Figure 2 (a) It can be seen that under the interaction of influencing factor A (the amount of straw treated with hydrophobic film-forming agent) and influencing factor B (the length of straw), as the amount of straw treated with hydrophobic film-forming agent increases and as the length of straw increases, the bearing ratio of the roadbed soil material first increases and then decreases. Figure 2 (b) It can be seen that under the interaction of influencing factors A (the amount of straw treated with the hydrophobic film-forming agent) and C (the soaking time of the straw in the hydrophobic film-forming agent), as the amount of straw treated with the hydrophobic film-forming agent increases, the bearing ratio of the roadbed soil material first increases and then decreases; as the soaking time of the straw in the hydrophobic film-forming agent increases, the bearing ratio of the roadbed soil material gradually increases. Figure 2 (c) It can be seen that under the interaction of influencing factors A (the amount of straw treated with hydrophobic film-forming agent) and D (the amount of hydrophobic antifreeze agent), as the amount of straw treated with hydrophobic film-forming agent increases, the bearing ratio of the roadbed soil material first increases and then decreases; as the amount of hydrophobic antifreeze agent decreases, the bearing ratio of the roadbed soil material gradually increases; Figure 2(d) It can be seen that under the interaction of influencing factors B (straw length) and C (straw soaking time in hydrophobic film-forming agent), as the straw length increases, the bearing ratio of the roadbed soil material first increases and then decreases; as the straw soaking time in hydrophobic film-forming agent increases, the bearing ratio of the roadbed soil material gradually increases; Figure 2 (e) It can be seen that under the interaction of influencing factors B (straw length) and D (hydrophobic antifreeze agent dosage), as the straw length increases, the bearing ratio of the roadbed soil material first increases and then decreases; as the hydrophobic antifreeze agent dosage decreases, the bearing ratio of the roadbed soil material gradually increases. Figure 2 (f) It can be seen that under the interaction of influencing factor C (the soaking time of straw in the hydrophobic film-forming agent) and influencing factor D (the dosage of hydrophobic antifreeze agent), the bearing ratio of the roadbed soil material gradually increases with the increase of the soaking time of straw in the hydrophobic film-forming agent and the decrease of the dosage of hydrophobic antifreeze agent.

[0118] Based on the results of variance analysis and response surface diagram analysis of the above response surface model, the influencing factors have a very significant impact on the frost heave rate and bearing ratio of the roadbed soil material. The reliability of the response surface model of the frost heave rate and bearing ratio is extremely high, which can effectively simulate the actual test results and make accurate predictions.

[0119] According to my country's industry standard "Technical Specifications for Highway Roadbed Construction" (JTG / T3610-2019), the soil filling materials within the frozen depth range of the roadbed of expressways and first-class highways in seasonally frozen areas should meet the following two requirements: (1) the bearing ratio of the roadbed filling materials on the roadbed should be no less than 8%, and the bearing ratio of the lower roadbed filling materials should be no less than 5%; (2) in heavy and medium frozen areas, the distance between the groundwater level or the surface water level and the road surface (h w ) ≤ 3m, the frost heave rate of the upper roadbed filler should be no higher than 1%, and the frost heave rate of the lower roadbed filler should be no higher than 3.5%. To ensure that the frost heave resistance and mechanical properties of the subgrade soil material meet the requirements for subgrade and roadbed fillers for expressways and first-class highways in heavy and moderate freezing areas, and to minimize the amount of hydrophobic antifreeze agent to reduce project costs, dual-objective optimization requirements for the frost heave rate and bearing capacity of the subgrade soil material in both the upper and lower roadbed applications (i.e., the limiting conditions for the upper and lower roadbeds of the subgrade) were established, as shown in Table 6.

[0120] Table 6 Dual-objective optimization requirements

[0121]

[0122] The optimization technical scheme which simultaneously satisfies the double target demand conditions of the roadbed above the roadbed is obtained by inputting the demand conditions in Table 6 into the Box-Benhnken mode of the 'Optimization-Numerical' module of the response surface analysis software Design Expert, and is: the optimal straw content is 0.15%, the optimal straw length is 15.7mm, the optimal soaking time of the straw in the hydrophobic film forming agent is 23.9h, and the optimal hydrophobic antifreeze agent content is 0.61%. Under the condition, according to the response surface model, the predicted value of the frost heaving rate is 0.9%, and the predicted value of the bearing ratio is 10.1%; the optimization technical scheme which simultaneously satisfies the double target demand conditions of the roadbed below the roadbed is: the optimal straw content is 0.20%, the optimal straw length is 10.0mm, the optimal soaking time of the straw in the hydrophobic film forming agent is 18.0h, and the optimal hydrophobic antifreeze agent content is 0.25%. Under the condition, according to the response surface model, the predicted value of the frost heaving rate of the roadbed soil material is 2.67%, and the predicted value of the bearing ratio is 10.0%. The implementation layer position of the optimization technical scheme of the roadbed above the roadbed and the roadbed below the roadbed is as shown in Figure 3

[0123] In order to verify the reliability of the optimization technical scheme, the roadbed soil is improved again according to the optimization technical scheme, and the frost heaving rate and the bearing ratio of the roadbed soil material are tested, and the test results are shown in Table 7.

[0124] Table 7 Test verification results of the optimization technical scheme

[0125]

[0126] As shown in Table 7, the deviation between the predicted value and the measured value of the frost heaving rate and the bearing ratio of the roadbed soil material above and below the roadbed under the optimization technical scheme is very small, and the measured value also satisfies the double target optimization demand conditions, which verifies the reliability of the response surface model and the optimization technical scheme.

[0127] In order to simultaneously improve the mechanical properties and the frost heaving resistance, in the application, the straw content after being treated by the hydrophobic film forming agent, the straw length, the soaking time of the straw in the hydrophobic film forming agent and the hydrophobic antifreeze agent content are taken as influencing factors, the frost heaving rate and the bearing ratio of the roadbed soil material are taken as response values, the response surface analysis method of 4 factors and 3 levels is used to carry out the response surface analysis test, and the optimization technical scheme which simultaneously satisfies the double target optimization demand of the frost heaving rate and the bearing ratio is obtained. In the application, the mechanical properties and the frost heaving resistance of the roadbed soil material in the high-cold seasonal frozen soil area are simultaneously improved without using inorganic binders or replacing the roadbed, the destruction of the ecological environment in the high-cold area is also avoided, and the resource utilization of the agricultural solid waste straw is realized.

[0128] ​The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A roadbed soil material for seasonally frozen areas in high-cold regions based on straw and a hydrophobic antifreeze agent, characterized in that: Ingredients include: Straw treated with a hydrophobic film-forming agent, a hydrophobic antifreeze agent, air-dried roadbed soil, and water; The hydrophobic film-forming agent is composed of the following raw materials in parts by weight: 5-8 parts of cooked tung oil, 1-2 parts of nano-silica sol, 3-5 parts of a silane modifier, 5-10 parts of sodium alginate, 1-2 parts of carboxymethyl cellulose, and 50 parts of water; wherein the nano-silica sol is a sol prepared by dispersing nano-SiO2 in a NaOH solution with a mass concentration of 0.001% to 0.005%, wherein the particle size of SiO2 is 10-20 nm, the mass fraction of SiO2 is 29-31%, and the pH value of the nano-silica sol is 9.0-10.5; the silane modifier is a mixture of perfluorodecyltrimethoxysilane, hexadecyltrimethoxysilane, and a silane coupling agent KH570 in a mass ratio of 2-3:2-3:1; The hydrophobic antifreeze agent is composed of the following raw materials in parts by weight: 5-8 parts of sodium methyl silicate solution, 2-3 parts of polydimethylsiloxane, 50-80 parts of nano-silica sol, 6-20 parts of a silane modifier, 5-10 parts of methacryloylethyl sulfobetaine, and 50-80 parts of water; wherein the mass fraction of sodium methyl silicate in the sodium methyl silicate solution is ≥25%; the nano-silica sol is a sol prepared by dispersing nano-SiO2 in a NaOH solution with a mass concentration of 0.001%-0.005%, wherein the particle size of SiO2 is 10-20 nm, the mass fraction of SiO2 is 29-31%, and the pH value of the nano-silica sol is 9.0-10.5; and the silane modifier is a mixture of perfluorodecyltrimethoxysilane, hexadecyltrimethoxysilane, and a silane coupling agent KH570 in a mass ratio of 2-3:2-3:

1.

2. The seasonally frozen soil area roadbed material based on straw and a hydrophobic agent according to claim 1, characterized in that: The straw is selected from barley straw or wheat straw.

3. The seasonally frozen soil area roadbed material based on straw and a hydrophobic agent according to claim 1, characterized in that: Methods for treating straw with a hydrophobic film-forming agent include: The dried straw is split into two parts along the radial direction and cut into a defined length; Soak the straw in the hydrophobic film-forming agent, take out the straw and dry it.

4. The method for optimizing the proportion of roadbed soil materials in high-cold seasonal frozen areas based on straw and a hydrophobic antifreeze agent according to any one of claims 1 to 3, characterized in that: include: S1. Taking the dosage of straw treated with hydrophobic film-forming agent, straw length, soaking time of straw in hydrophobic film-forming agent and dosage of hydrophobic antifreeze agent as influencing factors, and the frost heave rate and bearing ratio of roadbed soil material as response values, a response surface analysis test was conducted using a 4-factor 3-level response surface analysis method to obtain the response surface analysis test results; S2. Based on the response surface analysis test results, the influencing factors were fitted by a quadratic regression equation. Based on the limiting conditions of the upper and lower roadbeds of the roadbed, the optimal straw dosage, optimal straw length, optimal immersion time of straw in the hydrophobic film-forming agent, and optimal hydrophobic antifreeze dosage were obtained based on the response surface method fitting.

5. The optimization method according to claim 4, wherein: In step S1, the amount of straw treated with the hydrophobic film-forming agent refers to the percentage of the amount of straw treated with the hydrophobic film-forming agent in the mass of the air-dried roadbed soil; the amount of straw treated with the hydrophobic film-forming agent ranges from 0.1% to 0.3%; In step S1, the straw length range is 10 mm to 20 mm; In step S1, the soaking time of the straw in the hydrophobic film-forming agent ranges from 12 h to 24 h; In step S1, the dosage of the hydrophobic antifreeze agent refers to the percentage of the hydrophobic antifreeze agent in the mass of the air-dried roadbed soil; the dosage of the hydrophobic antifreeze agent ranges from 0.25% to 0.75%; In step S1, the Box-Benhnken model of the response surface methodology is used to design the experimental scheme.

6. The optimization method according to claim 4, wherein: In step S2, the limiting conditions of the upper roadbed of the roadbed are: A1) The bearing capacity of the roadbed soil material shall not be less than 8%; A2) The frost heave rate of subgrade soil materials should not exceed 0.9%; A3) When both A1) and A2) are met, the dosage of the hydrophobic antifreeze agent shall be the minimum.

7. The optimization method according to claim 4, wherein: In step S2, the limiting conditions of the lower roadbed of the roadbed are: B1) The bearing capacity of subgrade soil materials shall not be less than 5%; B2) The frost heave rate of subgrade soil materials should not exceed 3.4%; B3) When the conditions of B1) and B2) are met at the same time, the dosage of hydrophobic antifreeze agent shall be the minimum.

8. The optimization method according to claim 4, wherein: In step S2, based on the limited conditions of the roadbed, the optimal straw content was obtained as 0.15%, the optimal straw length was 15.7 mm, the optimal soaking time of straw in the hydrophobic film-forming agent was 23.9 h, and the optimal hydrophobic antifreeze content was 0.61% based on the response surface methodology fitting. In step S2, based on the limited conditions of the lower roadbed of the roadbed, the optimal straw content was 0.20%, the optimal straw length was 10.0 mm, the optimal soaking time of the straw in the hydrophobic film-forming agent was 18.0 h, and the optimal hydrophobic antifreeze content was 0.25%.

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