Straw and hydrophobic anti-freezing agent-based subgrade soil material for high and cold seasonal frozen earth region and proportion optimization method of subgrade soil material

Abstract

The invention relates to the technical field of roadbed engineering, in particular to a high and cold season frozen region roadbed soil material based on straw and a water repellent agent and a proportion optimization method of the high and cold season frozen region roadbed soil material. In order to improve the mechanical property and the frost heaving resistance at the same time, the doping amount of straw treated by a hydrophobic film-forming agent, the length of the straw, the soaking time of the straw in the hydrophobic film-forming agent and the doping amount of a hydrophobic anti-freezing agent are used as influence factors, and the frost heaving rate and the bearing ratio of the seasonal frozen soil region roadbed soil material based on the straw and the hydrophobic agent are used as response values; and performing a response surface analysis test by adopting a response surface analysis method to obtain an optimization technical scheme which simultaneously meets the dual-objective optimization requirements of the frost heaving rate and the bearing ratio. The mechanical property and frost heaving resistance of the roadbed soil material in the high and cold seasonal frozen soil region are improved at the same time under the condition that an inorganic binding material is not used or roadbed replacement is not carried out, the ecological environment of the high and cold region is prevented from being damaged, and meanwhile resource utilization of agricultural solid waste straw is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of roadbed engineering, and in particular to a roadbed soil material for high-cold seasonal frozen soil areas 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 the 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 a person skilled in the art.

[0003] Seasonal frozen soil refers to soil that freezes in winter and melts in summer. The area where it is located is called a seasonal frozen soil area. For the roadbed in the seasonal frozen soil area, in the severe winter, due to the temperature gradient and capillary action, groundwater continues to migrate to the inside of the roadbed through capillary pipes, forming ice crystals inside the roadbed, causing the roadbed to frost heave and the road surface to bulge and crack. In the spring and summer, the ice crystals melt, and the water content inside the roadbed is too high. Under the action of vehicle loads, the roadbed will experience mudswelling and thawing. Especially in high-altitude or high-latitude seasonal frozen soil areas, due to the large temperature difference, the freezing and thawing phenomenon of the roadbed is particularly significant, resulting in serious damage to the road, which seriously restricts the economic development of the high-altitude seasonal frozen soil areas.

[0004] At present, 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 use non-frost-heaving or weakly frost-heaving gravel to replace frost-heaving subgrade soil. 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 in dosage and high in cost; the pH value of the leaching solution during the hydration process of inorganic binders is about 13, which will increase the alkalinity of the soil, leading to soil sandification, hardening and environmental pollution; cement and lime production causes high carbon emissions and consumes a lot of natural resources; solid waste cementitious materials also have the risk of heavy metal leaching; and inorganic binders cannot block the migration channel of capillary water. As the service time increases, the anti-frost heaving performance of the improved soil will decrease year by year. In the second method, if gravel near the roadbed project is used for replacement, it will change the natural vegetation, landforms, groundwater runoff and other environmental characteristics of the cold region, causing environmental disturbance; if gravel is transported over long distances, it will greatly increase the cost of the project and increase the difficulty of construction. The ecological environment in high-altitude or high-latitude alpine areas is extremely fragile. Once damaged, it will be difficult to recover. The environmental protection requirements for roadbed construction are extremely high. Therefore, the above two traditional methods are gradually restricted in the improvement of roadbed soil in high-altitude seasonal frozen areas.

[0005] In order to improve the frost heave resistance of soil, some studies have added hydrophobic agents to the soil. Hydrophobic agents can improve the frost heave resistance of subgrade soil by improving the hydrophobic effect of the soil and blocking the channels for capillary water in the roadbed to migrate to the negative temperature zone. However, the effect of hydrophobic agents on improving the strength of subgrade soil is not significant. Excessive addition of hydrophobic agents may even reduce the strength of the soil, making the strength of the soil improved by hydrophobic agents lower than that of the original subgrade soil. Therefore, the subgrade soil materials in seasonal frozen areas improved by hydrophobic agents alone cannot withstand heavy traffic loads. At the same time, in order to improve the mechanical properties of soil, some studies have used wheat straw to reinforce soil and improve the mechanical properties of soil by constructing a three-dimensional network structure in the soil. However, wheat straw has a large number of pores, which not only has poor corrosion resistance, but also increases the porosity of the soil and increases the water migration channels in the soil, which has an adverse effect on the frost heave resistance of subgrade soil. Moreover, when the length and amount of wheat straw are too large, the wheat straw will be entangled, resulting in the formation of weak areas in the soil, which will reduce the strength of the reinforced soil. In addition, wheat straw is prone to corrosion and its tensile properties need to be further improved.

[0006] Therefore, it is urgent to provide a roadbed soil material that can improve both mechanical properties and frost heave resistance and is suitable for high-cold seasonal frozen soil areas while ensuring the ecological environment. 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 soil 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 in high-cold seasonal frozen soil areas 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 made 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, has a high viscosity, and can play an anti-corrosion and waterproof effect. The nano-SiO2 particles in the nano-silica sol can increase the roughness of the straw surface, increase the friction between the straw and the soil particles, and fill the tiny gaps in the straw, improve the tensile properties of the straw, and thus improve the mechanical properties of the roadbed soil materials in the high-cold seasonal frozen soil area. Silane modifiers can modify the surface of nano-SiO2 particles in nano-silica sol, and replace the original hydrophilic hydroxyl groups on the surface of nano-SiO2 particles with strong hydrophobic groups, which can significantly improve the hydrophobicity of nano-SiO2 particles and promote the uniform dispersion of nano-SiO2 particles in organic media such as cooked tung oil. Sodium alginate is a by-product of extracting iodine and mannitol from kelp or sargassum of brown algae. It is a natural polysaccharide with high viscosity and good film-forming effect. Carboxymethyl cellulose is a natural polysaccharide cellulose with a strong viscosity-increasing effect. It can synergize with sodium alginate to improve the tensile strength of the film formed by the hydrophobic film-forming agent.

[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 with a hydrophobic film-forming agent, not only can the tensile and anti-corrosion properties of straw be improved, achieving a better soil reinforcement effect, but the pores inside the straw can also be blocked, avoiding the increase in soil porosity and the decrease in anti-frost heave performance caused by the addition of straw. The straw treated with a hydrophobic film-forming agent can construct a three-dimensional network structure in the subgrade soil, acting as a stirrup for the subgrade soil, effectively transferring loads through the straw, preventing the subgrade soil from cracking, and thus 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 to 8 parts of sodium methyl silicate solution, 2 to 3 parts of polydimethylsiloxane, 50 to 80 parts of nano silica sol, 6 to 20 parts of silane modifier, 5 to 10 parts of methacryloylethyl sulfobetaine, and 50 to 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 made 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] The molecular formula of sodium methyl silicate is CH5SiO3Na, which can react with water and carbon dioxide in the air to generate methyl silicic acid, and then dehydrate and polymerize into hydrophobic polymethylsiloxane, which can form a layer of polymethylsiloxane film with hydrophobic effect on the surface of roadbed soil particles. Polydimethylsiloxane has physiological inertness, good chemical stability, good hydrophobicity, and can be used to enhance the hydrophobicity of hydrophobic antifreeze agents. Nano-silica sol can infiltrate nano-SiO2 particles into the fine pores inside the roadbed soil, play a certain role in filling the voids, increase the density of the roadbed soil, and thus improve the mechanical properties of the roadbed soil material in the high-cold seasonal frozen land area. Silane modifiers can modify the surface of nano-SiO2 particles in nano-silica sol, replace the original hydrophilic hydroxyl groups on the surface of nano-SiO2 particles with strong hydrophobic groups, which can significantly improve the hydrophobicity of nano-SiO2 particles and promote the uniform dispersion of nano-SiO2 particles in organic media such as sodium methyl silicate and polydimethylsiloxane. Methacryloylethyl sulfobetaine can effectively reduce the freezing temperature of water, prevent the frost heaving of water existing in the subgrade soil after the completion of the subgrade, and thus improve the anti-frost heaving performance of the subgrade soil.

[0025] Hydrophobic antifreeze agents improve the frost heave resistance of roadbed soil by 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, thereby blocking water migration and preventing the increase of water content inside the roadbed; second, by lowering the freezing temperature of the roadbed soil, preventing the water present in the roadbed soil after the roadbed is completed from freezing and heaving.

[0026] The second aspect of this aspect provides a method for optimizing the proportion of roadbed soil materials in high-cold seasonal frozen areas based on straw and hydrophobic antifreeze agents, 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 are fitted by a quadratic regression equation. Based on the limited conditions of the upper and lower roadbeds of the roadbed, the optimal straw dosage, optimal straw length, optimal immersion time of the straw in the hydrophobic film-forming agent, and optimal hydrophobic antifreeze agent dosage are 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 straw treated with the hydrophobic film-forming agent in the mass of the air-dried roadbed soil.

[0030] Preferably, the dosage 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 length of the straw 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 design.

[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 roadbed soil material shall not be less than 8%;

[0038] A2) The frost heave rate of roadbed 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 hydrophobic antifreeze agent takes the minimum value.

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

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

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

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

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

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

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

[0047] The present invention relates to the technical field of roadbed engineering, and in particular to an optimization method for roadbed soil materials and their proportions in high-cold seasonal frozen soil areas based on straw and hydrophobic antifreeze agents. In order to simultaneously improve mechanical properties and anti-frost heaving properties, the present invention uses the amount of straw treated 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 uses the frost heaving rate and the bearing ratio as response values. The response surface analysis test is carried out 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 heaving rate and the bearing ratio. The present invention achieves the simultaneous improvement of the mechanical properties and anti-frost heaving properties of roadbed soil materials in high-cold seasonal frozen soil areas without using an inorganic binder or performing roadbed replacement, and also avoids the destruction of the ecological environment in high-cold areas, while realizing the resource utilization of agricultural solid waste straw. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings in the specification, 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 2 is a response surface diagram of the influence of the influencing factors in Example 2 on the frost heave rate of the roadbed soil material; wherein, (a) is a response surface diagram of the interaction of influencing factor A (the amount of straw treated with hydrophobic film-forming agent) and influencing factor B (straw length) on the frost heave rate of the roadbed soil material; (b) is a response surface diagram of 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 the hydrophobic film-forming agent) on the frost heave rate of the roadbed soil material; (c) is a response surface diagram of 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) on the frost heave rate of the roadbed soil material. (d) is the response surface diagram of the interaction between influencing factors B (straw length) and influencing factor C (the soaking time of straw in hydrophobic film-forming agent) on the frost heave rate of roadbed soil materials; (e) is the response surface diagram of the interaction between influencing factors B (straw length) and influencing factor D (hydrophobic antifreeze agent dosage) on the frost heave rate of roadbed soil materials; (f) is the response surface diagram of the interaction between influencing factors C (the soaking time of straw in hydrophobic film-forming agent) and influencing factor D (hydrophobic antifreeze agent dosage) on the frost heave rate of roadbed soil materials;

[0050] Figure 2 2 is a 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 a response surface diagram of the interaction between the influencing factor A (the amount of straw treated with the hydrophobic film-forming agent) and the influencing factor B (the length of the straw) on the bearing ratio of the roadbed soil material; (b) is a response surface diagram of the interaction between the influencing factor A (the amount of straw treated with the hydrophobic film-forming agent) and the influencing factor C (the soaking time of the straw in the hydrophobic film-forming agent) on the bearing ratio of the roadbed soil material; (c) is a response surface diagram of the interaction between the influencing factor A (the amount of straw treated with the hydrophobic film-forming agent) and the influencing factor D (the amount of the hydrophobic antifreeze agent) 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 influencing factor C (the soaking time of straw in hydrophobic film-forming agent) on the bearing ratio of roadbed soil materials; (e) is the response surface diagram of the interaction between influencing factors B (straw length) and influencing factor D (hydrophobic antifreeze agent dosage) on the bearing ratio of roadbed soil materials; (f) is the response surface diagram of the interaction between influencing factors C (the soaking time of straw in hydrophobic film-forming agent) and influencing factor D (hydrophobic antifreeze agent dosage) on the bearing ratio of roadbed 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 are 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 exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates 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 in conjunction with specific embodiments.

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

[0056] The air-dried roadbed soil 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 Geotechnical 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 the roadbed project is located in the heavy and medium frozen areas of the seasonal frozen soil area. The groundwater level or the surface water level is at a distance (h 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 filling material of this section of roadbed engineering should be ≤1.0%, and the bearing ratio should be ≥8.0%; the frost heave rate of the lower roadbed filling material should be ≤3.5%, and the bearing ratio should be ≥5.0%; the frost heave rate of the embankment filling material should be ≤6.0%, and the bearing ratio should be ≥4.0%. Therefore, this silt can only be used as embankment filling material, not as roadbed filling material, and needs to be improved.

[0057] Example 1

[0058] A roadbed soil material for high-cold seasonal frozen areas based on straw and a hydrophobic antifreeze agent, wherein the raw materials 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] Among them, the cooked tung oil is the Jingchen brand plant cooked tung oil produced by Jingchen Anticorrosion and Waterproof Materials Co., Ltd.

[0062] The nano-silica sol is the alkaline nano-silica sol model 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. Perfluorodecyltrimethoxysilane is a Ron brand liquid reagent produced by Shanghai Yien Chemical Technology Co., Ltd., with a purity grade of analytical grade (AR); hexadecyltrimethoxysilane is a Macklin brand liquid reagent with a concentration of ≥85%; silane coupling agent KH570 is a Hushi brand liquid reagent produced by Sinopharm Chemical Reagent Co., Ltd., with a content of ≥98%.

[0064] Sodium alginate is a powder reagent of the Shanghai Test brand produced by Sinopharm Chemical Reagent Co., Ltd., and its purity grade is chemically pure (CP).

[0065] Carboxymethyl cellulose is a powder reagent of the Shanghai Test brand produced by Sinopharm Chemical Reagent Co., Ltd., and its purity grade is chemically 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 high speed according to the ratio at 50° C., with a stirring speed of 1000 r / min for 30 minutes to obtain the hydrophobic film-forming agent.

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

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

[0070] The dried highland barley stalks are cut into two parts along the radial direction and cut into 10 mm to 20 mm pieces;

[0071] The straw was immersed in the hydrophobic film-forming agent, and the straw was taken out and placed in an oven at 40° C. for 12 hours 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: 7 parts of sodium methyl silicate solution, 2.5 parts of polydimethylsiloxane, 60 parts of nano silica sol, 10 parts of silane modifier, 7 parts of methacryloylethyl sulfobetaine, and 70 parts of water.

[0073] The sodium methyl silicate solution was model 3010 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 model JN-30 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., and the purity grade is analytical 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] Methacryloylethyl sulfobetaine 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 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 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 are fitted by a quadratic regression equation. Based on the limited conditions of the upper and lower roadbeds of the roadbed, the optimal straw dosage, optimal straw length, optimal immersion time of the straw in the hydrophobic film-forming agent, and optimal hydrophobic antifreeze agent dosage are 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 mass of the 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 length of the straw 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. 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 level 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 level of influencing factors

[0094]

[0095] In the response surface analysis test scheme in Table 2, the air-dried roadbed soil is 100 parts and the water is 12 parts. After the air-dried roadbed soil and water are mixed evenly, they are sealed in a plastic bag for 12 hours to simulate the wet roadbed soil with natural moisture content at the construction site. According to the material ratio in Table 2, the straw treated with the hydrophobic film-forming agent, the hydrophobic antifreeze agent, the wet roadbed soil and water are mixed in proportion and stirred for 20 minutes to allow the sodium methyl silicate to fully react with the water and the CO2 in the air to form a hydrophobic film, and the roadbed soil material specimens are prepared with a compaction degree of 96%.

[0096] The frost heave rate and bearing ratio of the subgrade soil materials corresponding to the 29 groups of tests obtained by the test are shown in Table 3. The frost heave rate was tested according to T0187-2007 in the Chinese industry standard "Highway Geotechnical Test Code" (JTG E40-2007); the bearing ratio was tested according to T 0134-2019 in the Chinese industry standard "Highway Geotechnical Test Code" (JTG E40-2007).

[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 treated with hydrophobic film-forming agent A, straw length B, straw soaking time in the hydrophobic film-forming agent C, and hydrophobic antifreeze agent dosage D) and the response values ​​(frost heave rate Y1, bearing ratio Y2), which was expressed by a quadratic polynomial regression equation as follows:

[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 a significant difference, indicated by *; P < 0.01 indicates an 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 predicted value of the frost heave rate response surface model has a good correlation with the measured value; Adjusted R 2and Predicted R 2 The difference between them is less than 0.2, indicating that there is consistency between them. Adeq Precision is much greater than 4, indicating that the influence of accidental errors on the response surface model of frost heave rate is very low. The amount of straw treated with hydrophobic film-forming agent, straw length, straw soaking time in hydrophobic film-forming agent and the amount of hydrophobic antifreeze agent have a very significant effect on the frost heave rate.

[0111] Figure 1 This is the response surface diagram of the influencing factors on 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), as the amount of straw treated with hydrophobic film-forming agent increases, the frost heave rate of the roadbed soil material gradually increases; as the length of straw increases, the frost heave of the roadbed soil material first decreases and then increases. Figure 1 (b) It can be seen that under the interaction of influencing factor A (the amount of straw treated with the hydrophobic film-forming agent) and influencing factor C (the soaking time of the straw in the hydrophobic film-forming agent), the frost heave rate of the roadbed soil material gradually increases with the increase of the amount of straw treated with the hydrophobic film-forming agent and the decrease of the soaking time of the straw in the hydrophobic film-forming agent. Figure 1 (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), 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 (the soaking time of straw in the hydrophobic film-forming agent), as the straw length increases, the frost heave of the roadbed soil material first decreases and then increases; as the soaking time of straw in the 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 agent dosage), as the straw length increases, the frost heave of the roadbed soil material first decreases and then increases; as the hydrophobic antifreeze agent dosage 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 immersion 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 immersion 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 a significant difference, indicated by *; P < 0.01 indicates an extremely significant difference, indicated by **.

[0116] Table 5 shows the results of variance analysis of the bearing ratio response surface model of roadbed soil materials. As can be seen from 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 value of the load ratio response surface model and the measured value is good; Predicted R 2 With Adjusted R 2 The difference between them is less than 0.2, indicating that there is consistency between the two. Adeq Precision is much greater than 4, indicating that the influence of accidental errors in the response surface model of the bearing ratio is very low. The amount of straw treated with hydrophobic film-forming agent, straw length, and straw soaking time in the hydrophobic film-forming agent have a very significant effect on the bearing ratio.

[0117] Figure 2 It 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 (the soaking time of straw in the hydrophobic film-forming agent), as the straw length increases, the bearing ratio of the roadbed soil material first increases and then decreases; as the soaking time of straw in the 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 immersion time of straw in the hydrophobic film-forming agent) and influencing factor D (the dosage of hydrophobic antifreeze agent), with the increase of the immersion time of straw in the hydrophobic film-forming agent and the decrease of the dosage of hydrophobic antifreeze agent, the bearing ratio of the roadbed soil material gradually increases.

[0118] Based on the results of variance analysis and response surface diagram analysis of the above response surface model, the influencing factors have a significant impact on the frost heave rate and bearing ratio of roadbed soil materials. The reliability of the response surface model of 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 not be less than 8%, and the bearing ratio of the lower roadbed filling materials should not be less than 5%; (2) In heavy and moderate freezing 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 roadbed filler on the roadbed should not be higher than 1%, and the frost heave rate of the roadbed filler under the roadbed should not be higher than 3.5%. In order to make the frost heave resistance and mechanical properties of the roadbed soil material meet the requirements of the roadbed filler of the expressway and first-class highway in heavy and medium freezing areas, and to minimize the amount of hydrophobic antifreeze agent to reduce the project cost, the dual-objective optimization requirements of the frost heave rate and bearing ratio of the roadbed soil material in the upper and lower roadbed applications of the roadbed (i.e., the limiting conditions of the upper and lower roadbed of the roadbed) are formulated, as shown in Table 6.

[0120] Table 6 Dual-objective optimization requirements

[0121]

[0122] Through the "Optimization-Numerical" module of the response surface analysis Box-Benhnken model of the data analysis software Design Expert, the requirements of Table 6 were input, and the optimization technical solution that simultaneously met the dual-objective requirements of the roadbed on the roadbed was obtained: the optimal straw content was 0.15%, the optimal straw length was 15.7mm, the optimal soaking time of straw in the hydrophobic film-forming agent was 23.9h, and the optimal hydrophobic antifreeze agent content was 0.61%. Under these conditions, according to the response surface model, the predicted value of the frost heave rate was determined to be 0.9%, and the predicted value of the bearing ratio was 10.1%; the optimization technical solution that simultaneously met the dual-objective requirements of the roadbed under the roadbed was obtained: the optimal straw content was 0.20%, the optimal straw length was 10.0mm, the optimal soaking time of straw in the hydrophobic film-forming agent was 18.0h, and the optimal hydrophobic antifreeze agent content was 0.25%. Under this condition, according to the response surface model, the predicted value of the frost heave rate of the roadbed soil material is determined to be 2.67%, and the predicted value of the bearing ratio is 10.0%. Figure 3 shown.

[0123] In order to verify the reliability of the optimized technical scheme, the subgrade soil was improved again according to the optimized technical scheme and the frost heave rate and bearing ratio of the subgrade soil material were tested. The test results are shown in Table 7.

[0124] Table 7 Test verification results of the optimized technical solution

[0125]

[0126] It can be seen from Table 7 that the deviations between the predicted values ​​and the measured values ​​of the frost heave rate and bearing ratio of the subgrade soil materials used for the upper and lower roadbeds under the optimization technical scheme are very small, and the measured values ​​also meet the requirements of the dual-objective optimization, verifying the reliability of the response surface model and the optimization technical scheme.

[0127] In order to improve the mechanical properties and anti-frost heave performance at the same time, the present invention takes the amount of straw treated 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, takes the frost heave rate and the bearing ratio of the roadbed soil material as response values, and adopts a response surface analysis method with 4 factors and 3 levels to carry out a response surface analysis test 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 anti-frost heave performance of the roadbed soil material in the high-cold seasonal frozen land area without using an inorganic binder or performing roadbed replacement, and also avoids the destruction of the ecological environment in the high-cold area, while realizing the resource utilization of agricultural solid waste straw.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A roadbed soil material for high-cold seasonal frozen soil areas based on straw and hydrophobic antifreeze agent, characterized in that: Ingredients include: Straw treated with hydrophobic film-forming agent, hydrophobic antifreeze agent, air-dried roadbed soil and water.

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

3. The roadbed soil material in seasonal frozen soil areas based on straw and a hydrophobic agent according to claim 1, characterized in that: 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; 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 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; The silane modifier is a mixture of perfluorodecyltrimethoxysilane, hexadecyltrimethoxysilane and silane coupling agent KH570 in a mass ratio of 2-3:2-3:

1.

4. The roadbed soil material in seasonally frozen areas based on straw and a hydrophobic agent according to claim 1, characterized in that: The method of treating straw with a hydrophobic film-forming agent includes: 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.

5. The roadbed soil material in seasonally frozen areas based on straw and a hydrophobic agent according to claim 1, characterized in that: 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; Wherein, the mass fraction of sodium methyl silicate in the sodium methyl silicate solution is ≥25%. Nano-silica sol is a sol made 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; The silane modifier is a mixture of perfluorodecyltrimethoxysilane, hexadecyltrimethoxysilane and silane coupling agent KH570 in a mass ratio of 2-3:2-3:

1.

6. A method for optimizing the proportion of roadbed soil materials in high-cold seasonal frozen areas based on straw and hydrophobic antifreeze agent, 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 are fitted by a quadratic regression equation. Based on the limited conditions of the upper and lower roadbeds of the roadbed, the optimal straw dosage, optimal straw length, optimal immersion time of the straw in the hydrophobic film-forming agent, and optimal hydrophobic antifreeze agent dosage are obtained based on the response surface method fitting.

7. The optimization method according to claim 6, characterized in that: 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 air-dried roadbed soil; the range of the amount of straw treated with the hydrophobic film-forming agent is 0.1% to 0.3%; In step S1, the interval range of the straw length is 10 mm to 20 mm; In step S1, the soaking time of the straw in the hydrophobic film-forming agent ranges from 12 hours to 24 hours; 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.

8. The optimization method according to claim 6, characterized in that: 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 roadbed soil materials should not exceed 0.9%; A3) When the conditions of A1) and A2) are met at the same time, the dosage of hydrophobic antifreeze agent takes the minimum value.

9. The optimization method according to claim 6, characterized in that: In step S2, the limiting conditions of the lower roadbed of the roadbed are: B1) The bearing capacity of roadbed soil materials shall not be less than 5%; B2) The frost heave rate of roadbed 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 takes the minimum value.

10. The optimization method according to claim 6, characterized in that: In step S2, based on the limited 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 agent content is 0.61% obtained based on the response surface method fitting; In step S2, based on the limited 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 immersion time of the straw in the hydrophobic film-forming agent is 18.0 h, and the optimal hydrophobic antifreeze agent content is 0.25% based on the response surface method fitting.

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