A method for modifying paste-containing silty mudstone and a method for determining the component content of a modifier

Abstract

The present application discloses a method for modifying gypsum-bearing silty mudstone and a method for determining the component content of a modifier, which relates to the field of modifying gypsum-bearing silty mudstone. The method includes: preparing a modifier based on cement, polypropylene fiber, and sodium methyl silicate; performing a blending and modification operation on the gypsum-bearing silty mudstone with the modifier to obtain modified rock and soil. By modifying the waste residue of gypsum-bearing silty mudstone, it is transformed into a high-performance subgrade filler, reducing the dependence on high-quality fillers. Through scientific design of the modifier components and blending process, this method effectively overcomes the problems such as low strength, poor water stability, and strong corrosiveness of gypsum-bearing silty mudstone in the background technology, significantly improves the strength, stability, and durability of the modified soil body, realizes resource utilization and green development, and has significant engineering value and social benefits.

Description

Technical Field

[0001] This specification relates to the field of modification of gypsum-bearing silty mudstone, and more specifically, this application relates to a method for modifying gypsum-bearing silty mudstone and a method for determining the component content of the modifier. Background Art

[0002] A special chemical sedimentary rock, namely gypsum-bearing silty mudstone, is widely distributed in some areas. Transportation projects inevitably pass through gypsum-bearing silty mudstone. However, for gypsum-bearing silty mudstone with low strength, poor water stability, and strong corrosiveness, it brings challenges and risks to the environment and transportation infrastructure. The specific manifestations are as follows: (1) The excavation waste of gypsum-bearing silty mudstone tunnels causes serious damage to the ecological environment. (2) The roadbed of gypsum-bearing silty mudstone deforms severely, and it is generally difficult to obtain high-quality fillers in the western Sichuan region. How to realize the reuse of the excavation waste of gypsum-bearing silty mudstone tunnels for subgrade filling, and then achieve the goals of carbon peak and carbon neutrality, sustainable development of resources, and reduction of ecological environment impact is one of the major problems that the engineering community urgently needs to solve.

[0003] Therefore, it is necessary to propose a method for modifying gypsum-bearing silty mudstone and a method for determining the component content of the modifier. Summary of the Invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further described in detail in the Detailed Description section. The Summary of the Invention section of this application does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the protection scope of the claimed technical solution.

[0005] In a first aspect, this application proposes a method for modifying gypsum-bearing silty mudstone, and the method includes:

[0006] Producing a modifier based on cement, polypropylene fiber, and sodium methyl silicate;

[0007] Performing a blending modification operation on the gypsum-bearing silty mudstone with the above modifier to obtain modified geotechnical materials.

[0008] In a feasible implementation manner, in terms of the total mass percentage of the above modifier, the modifier includes:

[0009] 2% to 6% of the above cement, 0.25% of the above polypropylene fiber, and 0.25% to 0.5% of the above sodium methyl silicate.

[0010] In a feasible implementation, the above cement includes sulfate-resistant portland cement, the length of the above polypropylene fiber is 6 mm, the diameter of the above polypropylene fiber is 23 um, the solid content of the above sodium methyl silicate is 30%, the alkali content of the above sodium methyl silicate is less than or equal to 12%, the silicone content of the above sodium methyl silicate is greater than or equal to 18%, the specific gravity of the above sodium methyl silicate is greater than or equal to 1.2 and less than or equal to 1.25, and the pH value of the above sodium methyl silicate is greater than or equal to 12 and less than or equal to 13.

[0011] In a second aspect, the present application proposes a method for determining the content of the modifier components for the modifier described in any one of the first aspects, including:

[0012] Determine the basic composition components of the above modifier based on the water dispersion experiment, and the above basic composition components include the above cement, the above polypropylene fiber, and the above sodium methyl silicate;

[0013] Conduct an orthogonal experiment on the soil sample modified by the above modifier to obtain the preliminary selection component information of the modifier;

[0014] Conduct XRD experiments, swelling experiments, and swelling force experiments on the soil sample modified by the above modifier to further limit the preliminary selection component information of the above modifier to obtain the limited component information;

[0015] Determine the target ratio of the modifier based on the 7D saturated compressive strength experiment and the microscopic electron microscope scanning experiment.

[0016] In a feasible implementation, the above orthogonal experiment includes the liquid-plastic limit combined determination experiment, the compaction experiment, and the shear strength experiment, and the above swelling experiment includes the free swelling experiment, the unloaded swelling rate experiment, and the loaded swelling rate experiment.

[0017] In a feasible implementation, the above conducting an orthogonal experiment on the soil sample modified by the above modifier to obtain the preliminary selection component information of the modifier includes:

[0018] Determine the preliminary selection content of the cement in the above modifier based on the above liquid-plastic limit combined determination experiment;

[0019] Determine the preliminary selection content of the polypropylene fiber and the preliminary selection content of the sodium methyl silicate in the above modifier based on the above compaction experiment and the above shear strength experiment.

[0020] In a feasible implementation, the above conducting XRD experiments, swelling experiments, and swelling force experiments on the soil sample modified by the above modifier to further limit the preliminary selection component information of the above modifier to obtain the limited component information includes:

[0021] Perform XRD tests, swelling tests, and swelling force tests on the soil samples modified with the above modifiers to extract the corresponding characteristic indexes and the weight information corresponding to the characteristic indexes;

[0022] Determine the mechanical property evaluation index based on all the above characteristic indexes and the weight information corresponding to the above characteristic indexes;

[0023] Further restrict the preliminary component information of the above modifier based on the above mechanical property evaluation index to obtain the above restricted component information.

[0024] In a feasible implementation manner, the above determination of the mechanical property evaluation index based on all the above characteristic indexes and the weight information corresponding to the above characteristic indexes includes:

[0025] Calculate the performance evaluation index based on the following formula :

[0026]

[0027] Among them, is the number of all tests participated, is the weight of the th test result, is the characteristic index value of the th test, The characteristic index of the RD test is the proportion of mineral content, and the characteristic index of the free swelling test is the free swelling rate, and the characteristic index of the unloaded swelling rate test is the unloaded swelling rate, and the characteristic index of the loaded swelling rate test is the loaded swelling rate, and the characteristic index of the swelling force test is the swelling force;

[0028] The further restriction of the preliminary component information of the above modifier based on the above mechanical property evaluation index to obtain the above restricted component information includes:

[0029] Establish a formula regression model according to historical test data, where the above formula regression model is based on the above mechanical property evaluation , the target content of cement, the target content of polypropylene fiber, and the target content of sodium methyl silicate;

[0030] Determine the above restricted component information according to the above mechanical property evaluation index and the above formula regression model, and the above restricted component information includes the target content of cement, the target content of polypropylene fiber, and the target content of sodium methyl silicate in the modifier;

[0031] The above formula regression model is determined based on the following formula:

[0032]

[0033]

[0034] Among them, is the target content of cement, is the target content of polypropylene fiber, is the target content of sodium methyl silicate, and a, b, c, d, f, g, and h are parameters obtained by regression fitting respectively.

[0035] In a feasible implementation manner, it further includes:

[0036] Modifying the subgrade material with the modifier corresponding to the above-mentioned modifier component content to obtain the modified subgrade material;

[0037] Conducting a dynamic triaxial test on the above-mentioned modified subgrade material to obtain the first test result;

[0038] Conducting a simulation test on the above-mentioned modified subgrade material to obtain the second test result;

[0039] Optimizing the above-mentioned modifier component content based on the above-mentioned first test result and the above-mentioned second test result.

[0040] In a feasible implementation manner, the above-mentioned simulation test is implemented based on a same-scale model established by COMSOL software. The above-mentioned same-scale model includes a steel rail, a CA mortar layer, a track slab, a subgrade, and a foundation structure. The above-mentioned same-scale model is a two-dimensional model. The load in the above-mentioned simulation test is a half-sine wave pulse. An infinite domain boundary is adopted in the foundation and cross-section in the above-mentioned simulation test.

[0041] In summary, this method uses cement as the main modifier, and generates cementitious products such as calcium silicate hydrate (C-S-H) through hydration reaction, effectively improving the initial strength and overall bearing capacity of the soil mass. Cement can also react with Ca 2+ and SO4 2-The reaction generates stable compounds, reducing the negative impact of the paste on the soil strength. The modified paste-containing silty mudstone has higher compressive strength and bearing capacity and can be widely used in road and railway projects. The paste-containing silty mudstone is prone to dry shrinkage cracks under the action of wet-dry cycles, affecting the long-term stability of the roadbed. In the modifier of this method, polypropylene fibers are introduced to form a "fiber network", significantly enhancing the crack resistance and tensile strength of the soil. The polypropylene fibers effectively limit the crack propagation, improving the toughness and deformation resistance of the modified soil and extending the service life of the roadbed. The paste-containing silty mudstone has significant water absorption expansion and water loss shrinkage, resulting in serious engineering deformation and poor water stability. In the modifier of this method, through the addition of sodium methyl silicate, the modified soil has strong impermeability, which can reduce the water entering the soil, thereby reducing its water absorption expansion. Sodium methyl silicate reacts with the active minerals in the soil to generate water-insoluble silicate films, further improving the stability and hydrolysis resistance of the soil. The impermeability and anti-expansion properties of the soil are significantly enhanced, and it can be effectively applied in areas with complex water environments (such as western Sichuan). A large amount of waste slag generated during the excavation of paste-containing silty mudstone tunnels causes serious damage to the environment, and it is difficult to obtain high-quality roadbed fillers, resulting in serious resource waste. By modifying the paste-containing silty mudstone waste slag, it is transformed into high-performance roadbed fillers, reducing the dependence on high-quality fillers. The resource utilization of large amounts of solid waste is realized, the stacking amount of tunnel waste slag is reduced, and the damage to the ecological environment is reduced. Traditional modification research mainly focuses on single or double doping of modification materials, and a systematic research on multi-doping and multi-ratio modification has not been formed. This method proposes a modification method based on multi-dosage and multi-ratio (cement, polypropylene fibers, sodium methyl silicate). Traditional methods have poor adaptability at the construction site and often require complex equipment or strict conditions. This method adopts standardized mixing ratios and simple mechanical stirring methods, which can be directly applied at the construction site, with simple operation, short mixing time, and ensuring construction efficiency. It can adjust the water addition according to the natural water content of the soil, adapting to the needs of different regions and environments. Traditional methods are difficult to ensure the long-term durability of the soil, especially in acidic and sulfate erosion environments, where they are prone to failure. The use of sulfate-resistant cement significantly enhances the sulfate erosion resistance of the modified soil and extends its service life. The hydrophobicity and chemical stability of sodium methyl silicate enable the modified soil to maintain good performance in complex environments. Traditional methods have higher modification costs and cause certain damage to the environment. The dosage design of the modifier is scientific and reasonable, with less usage (such as only 2% - 6% for cement, 0.25% for polypropylene fibers, and 0.25% - 0.5% for sodium methyl silicate), reducing the material cost. Reducing the exploitation of natural resources (such as high-quality fillers) and reducing the damage to the ecological environment, it has significant environmental benefits.This method effectively overcomes the problems in the background technology, such as the low strength, poor water stability, and strong corrosiveness of the paste-containing silty mudstone, by scientifically designing the modifier components and blending process. It significantly improves the strength, stability, and durability of the modified soil mass, realizes resource utilization and green development, and has significant engineering value and social benefits.

[0042] For the method proposed in this application, other advantages, objectives, and features of this application will be partially reflected by the following description, and partially will also be understood by those skilled in the art through the research and practice of this application. Brief Description of the Drawings

[0043] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of this specification. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0044] Figure 1 It is a schematic flow chart of a method for modifying paste-containing silty mudstone provided by an embodiment of this application;

[0045] Figure 2 It is an SEM image of the surface morphology of anhydrite before modification of paste-containing silty mudstone provided by an embodiment of this application;

[0046] Figure 3 It is a 50-fold SEM image of the surface morphology of anhydrite after modification of paste-containing silty mudstone provided by an embodiment of this application;

[0047] Figure 4 It is an SEM image of the change in ductility strength before modification of paste-containing silty mudstone provided by an embodiment of this application;

[0048] Figure 5 It is a 25-fold SEM image of the change in ductility strength after modification of paste-containing silty mudstone provided by an embodiment of this application;

[0049] Figure 6 It is a 100-fold SEM image of the change in ductility strength after modification of paste-containing silty mudstone provided by an embodiment of this application;

[0050] Figure 7 It is a 500-fold SEM image of the change in ductility strength after modification of paste-containing silty mudstone provided by an embodiment of this application;

[0051] Figure 8 It is a 50-fold SEM image of the change in surface voids and pores after modification of paste-containing silty mudstone with C0 provided by an embodiment of this application;

[0052] Figure 9SEM images at 50x magnification of the surface voids and pores of a gypsum-bearing silty mudstone modified by XCF1 provided in an embodiment of the present application;

[0053] Figure 10 SEM images at 50x magnification of the surface voids and pores of a gypsum-bearing silty mudstone modified by XCF2 provided in an embodiment of the present application;

[0054] Figure 11 SEM images at 50x magnification of the surface voids and pores of a gypsum-bearing silty mudstone modified by XCF3 provided in an embodiment of the present application;

[0055] Figure 12 SEM images at 100x magnification of the surface voids and pores of a gypsum-bearing silty mudstone modified by C0 provided in an embodiment of the present application;

[0056] Figure 13 SEM images at 100x magnification of the surface voids and pores of a gypsum-bearing silty mudstone modified by XCF1 provided in an embodiment of the present application;

[0057] Figure 14 SEM images at 100x magnification of the surface voids and pores of a gypsum-bearing silty mudstone modified by XCF2 provided in an embodiment of the present application;

[0058] Figure 15 SEM images at 100x magnification of the surface voids and pores of a gypsum-bearing silty mudstone modified by XCF3 provided in an embodiment of the present application;

[0059] Figure 16 Schematic flow chart of a method for determining the content of the modifier components provided in an embodiment of the present application

[0060] Figure 17 Original model diagram of a simulation model provided in an embodiment of the present application;

[0061] Figure 18 Partial enlarged view of the mesh division of a simulation model provided in an embodiment of the present application;

[0062] Figure 19 Numerical simulation diagrams at 2Hz for each part before and after improvement provided in an embodiment of the present application. Detailed implementation manners

[0063] The terms "first", "second", "third", "fourth", etc. (if any) in the description, claims, and the above-mentioned drawings of this application are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments described herein can be implemented in an order other than that illustrated or described. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that comprises a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices. The technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments.

[0064] Waste rock, namely gypsum-bearing siltstone mudstone, as one of the types of bulk solid waste in the field of transportation at present, appears on a large scale in road and railway projects. In the past, the general experience was to solve it as a bad geological problem. As an evaporite sedimentary rock, gypsum-bearing rocks are widely distributed in various parts of our country, especially in marine or lake basins, and almost every geological era has developed, especially in the North China region and the Southwest region of our country. Therefore, due to its special formation environment, it has special engineering geological characteristics. The main content of gypsum is Ca 2+ and SO4 2- and two water molecules. Under the influence of the external environment, the two water molecules are prone to losing water and shrinking and absorbing water and expanding, and Ca 2+ and SO4 2- will also cause damage to the building, thus bringing harm to the actual project. At the present stage, most of the improved soils are mainly siltstone mudstone, mudstone, etc., and the research on the improvement materials is also mainly single admixture or double admixture. There is still little research on using multi-amount and multi-ratio modifiers to improve gypsum-bearing siltstone mudstone and using physical and mechanical tests, microscopic analysis, and road-use deformation characteristics.

[0065] Please refer to Figure 1 , which is a schematic flow chart of a method for modifying gypsum-bearing siltstone mudstone provided by an embodiment of this application, and specifically may include:

[0066] S110. Prepare a modifier based on cement, polypropylene fiber, and sodium methyl silicate;

[0067] Exemplarily, the modifier consists of three main components: cement, polypropylene fiber, and sodium methyl silicate. The functions and roles of each component are as follows:

[0068] Cement provides initial strength. Through hydration reactions, hydration products (such as Ca(OH)2) are generated, filling the pores of the soil mass and enhancing the overall strength of the soil. Interacting with Ca 2+ and SO4 2- in siltstone mudstone reduces the negative impact of the paste on the soil stability. Cement plays a cementing and filling role in the improved soil and is the core material for enhancing the bearing capacity.

[0069] Polypropylene fibers enhance the crack resistance and tensile strength of the soil, improving the toughness of the modified soil. They provide a certain anti-deformation ability to the soil, reducing the occurrence of dry shrinkage cracks. Polypropylene fibers are a kind of polymer material with excellent tensile strength and durability, especially suitable for soil reinforcement.

[0070] Sodium methyl silicate improves the impermeability and durability of the soil, reducing the infiltration of water, thereby reducing the water absorption and swelling of the paste. Reacting with the mineral components in the soil to form water-insoluble silicates further improves the soil stability. Sodium methyl silicate is an organosilicon modifier with dual effects of chemical and physical modification.

[0071] S120. Carry out blending and modification operations on the above-mentioned paste-containing siltstone mudstone with the above-mentioned modifiers to obtain modified rock and soil.

[0072] Exemplarily, remove impurities in the soil, such as large stones, tree roots, etc. Crush the waste residue to the designed particle size (usually in the range of 0.075mm to 2mm) as required to ensure uniform particle size distribution. Detect the basic performance parameters of the soil (such as natural moisture content, particle size distribution, Ca 2+ and SO4 2- content, etc.) to provide reference for subsequent blending and modification.

[0073] According to the specific characteristics of the soil, combined with the regression formula and target performance, determine the addition ratio of the modifiers. Add the modifiers to the soil gradually in the order of cement, polypropylene fibers and sodium methyl silicate to ensure the uniform distribution of each material. Use a mixer (such as a drum mixer or a rotary mixer) to fully mix the modifiers with the soil to ensure uniform material distribution. For small-scale tests, manual mixing can be used, but the mixing time and strength need to be strictly controlled. Usually, the mixing time can be 5 - 15 minutes to ensure sufficient contact and dispersion between the modifiers and soil particles. According to the natural moisture content of the soil, calculate the amount of water to be added to reach the target water content of the modified soil, for example, it can be 8% - 15%. After adding water, continue to stir to ensure the full progress of the cement hydration reaction and the chemical reaction of sodium methyl silicate. This process will generate cementing products such as calcium silicate hydrate and silicates, significantly enhancing the mechanical properties and stability of the soil.

[0074] In summary, this method uses cement as the main modifier to generate cementitious products such as calcium silicate hydrate (C-S-H) through hydration reactions, effectively improving the initial strength and overall bearing capacity of the soil. Cement can also react with Ca 2+ and SO4 2-The reaction generates stable compounds, reducing the negative impact of the paste on the soil strength. The modified paste-containing silty mudstone has higher compressive strength and bearing capacity and can be widely used in road and railway projects. The paste-containing silty mudstone is prone to dry shrinkage cracks under the action of wet-dry cycles, affecting the long-term stability of the subgrade. In the modifier of this method, polypropylene fibers are introduced to form a "fiber network", significantly enhancing the crack resistance and tensile strength of the soil. The polypropylene fibers effectively limit the crack propagation, improving the toughness and deformation resistance of the modified soil and extending the service life of the subgrade. The paste-containing silty mudstone has significant water absorption swelling and water loss shrinkage, resulting in serious engineering deformation and poor water stability. In the modifier of this method, through the addition of sodium methyl silicate, the modified soil has strong impermeability, which can reduce the water entering the soil, thereby reducing its water absorption swelling property. Sodium methyl silicate reacts with the active minerals in the soil to form a water-insoluble silicate film, further improving the stability and hydrolysis resistance of the soil. The impermeability and anti-swelling property of the soil are significantly enhanced, and it can be effectively applied in areas with complex water environments (such as western Sichuan). A large amount of waste slag generated during the tunnel excavation of the paste-containing silty mudstone causes serious damage to the environment, and it is difficult to obtain high-quality subgrade fillers, resulting in serious resource waste. By modifying the waste slag of the paste-containing silty mudstone, it is transformed into a high-performance subgrade filler, reducing the dependence on high-quality fillers. The resource utilization of bulk solid waste is realized, the stacking amount of tunnel waste slag is reduced, and the damage to the ecological environment is reduced. Traditional modification research mainly focuses on single or double doping of modification materials, and a systematic research on multi-doping and multi-proportion modification has not been formed. This method proposes a modification method based on multi-dosage and multi-proportion (cement, polypropylene fiber, sodium methyl silicate). The traditional method has poor adaptability at the construction site and often requires complex equipment or strict conditions. This method adopts a standardized mixing ratio and a simple mechanical stirring method, which can be directly applied at the construction site, with simple operation, short mixing time, and ensuring construction efficiency. It can adjust the water addition according to the natural moisture content of the soil, adapting to the needs of different regions and environments. The traditional method is difficult to ensure the long-term durability of the soil, especially in acidic and sulfate erosion environments, it is prone to failure. The use of sulfate-resistant cement significantly enhances the sulfate erosion resistance of the modified soil and extends the service life. The hydrophobicity and chemical stability of sodium methyl silicate enable the modified soil to maintain good performance in complex environments. The traditional method has a high modification cost and certain destructiveness to the environment. The dosage design of the modifier is scientific and reasonable, with less usage (such as only 2% - 6% for cement, 0.25% for polypropylene fiber, and 0.25% - 0.5% for sodium methyl silicate), reducing the material cost. Reducing the exploitation of natural resources (such as high-quality fillers) and reducing the damage to the ecological environment, it has significant environmental benefits.By scientifically designing the components of the modifier and the blending process, this method effectively overcomes the problems in the background technology, such as the low strength, poor water stability, and strong corrosiveness of the paste-containing silty mudstone, significantly improves the strength, stability, and durability of the modified soil body, realizes resource utilization and green development, and has significant engineering value and social benefits.

[0075] In some examples, in terms of the percentage of the total mass of the above-mentioned modifier, the above-mentioned modifier includes:

[0076] 2% to 6% of the above-mentioned cement, 0.25% of the above-mentioned polypropylene fiber, and 0.25% to 0.5% of the above-mentioned sodium methyl silicate.

[0077] In some examples, the above-mentioned cement includes sulfate-resistant portland cement, the length of the above-mentioned polypropylene fiber is 6 mm, the diameter of the above-mentioned polypropylene fiber is 23 μm, the solid content of the above-mentioned sodium methyl silicate is 30%, the alkali content of the above-mentioned sodium methyl silicate is less than or equal to 12%, the silicone content of the above-mentioned sodium methyl silicate is greater than or equal to 18%, the specific gravity of the above-mentioned sodium methyl silicate is greater than or equal to 1.2 and less than or equal to 1.25, and the pH value of the above-mentioned sodium methyl silicate is greater than or equal to 12 and less than or equal to 13.

[0078] Exemplarily, in the composition and ratio of the modifier, the total mass percentage of the cement can be 2% to 6%, and the type of cement can be sulfate-resistant portland cement. Sulfate-resistant cement has strong sulfate erosion resistance and can effectively cope with the erosion of SO4 2- in the paste-containing soil body. After the cement is mixed with water, cementitious products such as calcium silicate hydrate (C-S-H gel) are generated, improving the strength and stability of the soil body.

[0079] The total mass percentage of the polypropylene fiber can be 0.25%. The length can be 6 mm, and the diameter is 23 μm. The 6-mm length and 23-μm diameter ensure the uniform distribution of the fiber in the soil body and at the same time can form an effective "reinforcement" effect. The polypropylene fiber can improve the crack resistance, tensile strength, and toughness of the soil body, and prevent the generation of cracks in the soil body during the dry shrinkage or wet swelling process.

[0080] The total mass percentage of sodium methyl silicate is 0.25% to 0.5%, the solid content is 30%, the alkali content ≤ 12%, the silicone content: ≥ 18%, 1.2 ≤ specific gravity ≤ 1.25, 12 ≤ pH value ≤ 13. The high silicone content can improve the reaction ability with active minerals (such as silica) in the soil body, form water-insoluble silicate compounds, and significantly improve the impermeability of the soil body. The control of the alkali content can ensure that it has no adverse chemical effects on other components (such as fibers, cement) during the soil body modification process. The high pH value provides a strong alkaline environment, promotes the silicate reaction, and improves the anti-expansion and anti-hydrolysis ability of the soil body.

[0081] With a low cement content (2% - 6%), through the superior performance of sulfate-resistant Portland cement, while reducing the cement consumption, it can still ensure the strength and durability of the modified soil mass, reducing material costs. With a low polypropylene fiber content (0.25%), although the amount of polypropylene fiber used is small, its high-efficiency strengthening effect enables the soil mass to have good crack resistance.

[0082] With a low sodium methyl silicate content (0.25% - 0.5%), due to its high activity, a small amount of sodium methyl silicate can significantly improve the impermeability and stability of the soil mass, avoiding material waste.

[0083] The synergistic effect of cement, fiber, and sodium methyl silicate: cement provides the basic strength, polypropylene fiber enhances the crack resistance and toughness of the soil mass, and sodium methyl silicate improves the impermeability and chemical stability. The synergistic effect of the three ensures the overall improvement of the modified soil mass in terms of mechanical properties and durability.

[0084] This method significantly improves the engineering applicability of gypsum-containing silty mudstone through scientific material selection (sulfate-resistant cement, high-performance polypropylene fiber, sodium methyl silicate) and precise dosage design. The modified soil mass has high strength, good crack resistance, excellent durability and impermeability, can meet the requirements of road and railway projects, and provides a reliable solution for the resource utilization of bulk solid wastes.

[0085] As shown in Table 1, the mix ratios of several modifiers are as follows:

[0086] Table 1 Mix Ratio Table of Modifiers

[0087] Type of improver Ratio number Dosage design Cement dosage (%) Cement: Polypropylene fiber (mass ratio) Sodium methyl silicate (%) Cement C-0 Single admixture 2 - - Cement + Polypropylene fiber XCF1 Triple admixture 2 8:1 2 Cement + Polypropylene fiber XCF2 Triple admixture 4 8:1 2 Cement + Polypropylene fiber XCF3 Triple admixture 6 8:1 2

[0088] As Figures 2 to 10 shown, Figure 2 it can be seen that the morphology of gypsum before modification is crystal-like, and the state is directly exposed on the surface. For the modified gypsum Figure 3 as shown, its surface is covered by a layer of covering. This is because under the action of sodium methyl silicate, through the reaction with water molecules, a tightly bound and impermeable sodium methyl silicate waterproof film is formed and attached to the surface of the gypsum crystal, preventing water molecules from penetrating into the gypsum crystal, and thus effectively inhibiting the occurrence of adverse geological phenomena such as anhydrite water absorption and expansion and corrosion caused by the erosion of running water.

[0089] From Figures 4 to 7 it can be seen that after adding polypropylene fibers, it can be found that the fibers cross and shuttle in all directions in the soil mass to form a network constraint. Therefore, this structure can not only improve the toughness of the soil mass, but also provide an attachment site for the polymer formed after the reaction of cement and sodium methyl silicate with the substances in the soil. The fibers can also form a bonding and coupling relationship with the polymer, further enhancing the cohesion and binding force between the formed grids.

[0090] Figures 8 to 11 It can be analyzed that on a relatively macroscopic surface, the state of the soil sample is loose, the voids between soil particles are large and the fissures are significantly developed, and there is no obvious cementing substance between the particle surfaces and voids. Therefore, in this state, the strength of the soil is low and the bearing capacity is poor, and during rainfall, water flow can easily invade the soil body, resulting in a further decrease in the strength of the soil. Therefore, the undisturbed soil is not suitable as subgrade fill for direct filling. It can be seen from a scanning electron microscope at 1000 times magnification that with the addition of cement, from the perspective of the surface morphological structure, compared with the loose stacking state in the initial state, after improvement, such as Figure 13 the state of soil particles presents a small cluster shape, and with the increase of the cement content, it gradually develops into block, columnar, and lump shapes, such as Figure 14 and Figure 15 , and polymers are formed on the surfaces of soil particles, which are interconnected with each other in a network structure. These morphologies can greatly enhance the internal structural strength of the soil body. From the aspects of voids and pores, with the incorporation of the modifier, the number of voids significantly decreases, and it shows a non-linear inverse relationship with the increase of the cement content. The generated polymers significantly fill the voids, and the pore range gradually shrinks from the original quasi-network structure and finally becomes local short and narrow small pores.

[0091] Therefore, it can be analyzed from the microscopic level that the improved soil body not only reduces the number of voids, reduces the degree of pore development, changes the connection situation between soil particles, but also through the incorporation of polypropylene fibers, forms a bonding and coupling relationship with the polymer to enhance the toughness ability. Coupled with the waterproof agent generated by the reaction of sodium methyl silicate and water, it protects the expansion of anhydrite and the dissolution of gypsum. Thus, the engineering mechanical properties of the entire soil body are improved.

[0092] Second aspect, as Figure 16 shown, the present application proposes a method for determining the component content of a modifier, which is used to determine the modifier described in any item of the first aspect, and includes:

[0093] S210. Based on the water dispersibility experiment, determine the basic composition components of the above-mentioned modifier, and the above basic composition components include the above cement, the above polypropylene fiber, and the above sodium methyl silicate;

[0094] Exemplarily, according to previous research findings, the gypsum-bearing silty mudstone in the study area has properties such as low liquid limit, low strength, poor gradation, and poor hydrogeological properties. Therefore, based on the experience of treating improved soil and the characteristics of the gypsum-bearing silty mudstone in the study area, inorganic and organic modifiers were selected for comprehensive improvement. Three types of inorganic modifiers, namely fly ash, cement, and lime, were selected; polypropylene fiber and sodium methyl silicate were selected as organic modifiers. The specimen size was 50mm×50mm, and it was cured for 24 hours under standard conditions. The improvement plan was finally determined through this short-term water stability test. The mixing ratio of the initially selected modifiers and their states after saturation are shown in Table 2.

[0095] Table 2 Corresponding Table of Mixing Ratio of Initially Selected Modifiers and Their States after Saturation

[0096] Improver Dosage of inorganic improver (%) 1D 7D 14D Cement 6 Not dispersed Not dispersed Not dispersed Lime 6 Not dispersed Dispersed Not dispersed Fly ash 6 Not dispersed Dispersed Not dispersed Cement: Polypropylene fiber = 12:1 6 Not dispersed Not dispersed Not dispersed Lime: Polypropylene fiber = 12:1 6 Not dispersed Dispersed Dispersed Fly ash: Polypropylene fiber = 12:1 6 Not dispersed Dispersed Dispersed Cement: Polypropylene fiber: Sodium methyl silicate = 12:1:4 6 Not dispersed Not dispersed Not dispersed Lime: Polypropylene fiber: Sodium methyl silicate = 12:1:4 6 Not dispersed Dispersed Dispersed Fly ash: Polypropylene fiber: Sodium methyl silicate = 12:1:4 6 Not dispersed Dispersed ​

[0097] As shown in Table 2, after the water dispersion test, it was found that only the specimen improved with cement could still maintain an undispersed state after 14D, and the others had become loose. Based on the improvement experience of poor soil, the research results of the improvement test of general subgrade soil fillers, and the special situation of this test, after preliminary screening, it was decided to adopt the combined scheme of cement + polypropylene fiber + sodium methyl silicate as the main modifiers.

[0098] The basic parameters of sulfate-resistant cement can be determined according to Table 3:

[0099] Table 3 Basic Parameters of Sulfate-resistant Cement

[0100] ​ <![CDATA[SiO2]]> ​ <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> ​ <![CDATA[Na2O]]> <![CDATA[SO3]]> ​ 22.77 53.25 5.16 8.27 1.84 0.37 2.34

[0101] The basic parameters of polypropylene fiber can be determined according to Table 4:

[0102] Table 4 Basic Parameters of Polypropylene Fiber

[0103] ​ ​ ​ ​ ​ ​ ​ ​ ​ 6 23 3800 600 13 ​ 1.38

[0104] S220. Orthogonal tests were carried out on the soil samples modified with the above modifiers to obtain the initial component information of the modifiers;

[0105] Exemplarily, through the orthogonal experimental design method, the effects of different modifier components on the properties of the modified soil are systematically analyzed to determine the initial selected range of modifier component ratios. According to the experimental variables (such as the dosages of cement, polypropylene fiber, and sodium methyl silicate) and response indicators (such as strength and expansibility), an orthogonal experimental table is designed. For example, three factors (cement dosage, fiber dosage, and sodium methyl silicate dosage) are selected, and different levels (such as high, medium, and low) are set for each factor to form an orthogonal experimental table, and the physical and mechanical properties of the test samples are tested (such as compressive strength and expansibility). The results of the orthogonal experiment are analyzed to determine the influence degree of each factor on the target properties, and the initially selected modifier components and their approximate mixing ratio ranges are screened out.

[0106] S230. Conduct XRD tests, expansibility tests, and swelling force tests on the soil samples modified with the above modifiers to further narrow down the information on the initially selected components of the above modifiers to obtain the restricted component information.

[0107] Exemplarily, through further chemical and physical tests, the effectiveness of the initially selected components is verified, and the component range is narrowed down to ensure the optimization of the properties of the modified soil samples.

[0108] XRD test (X-Ray Diffraction) is used to analyze the changes in mineral components in the modified soil, especially the formation of cement hydration products and sulfate minerals. Through the test for determination and screening, the method of XRD phase analysis is adopted, and the modification effect is determined by measuring the relative contents of CaSO4 and CaSO4·2H2O in the modifier.

[0109] The expansibility test is used to measure the volume change of the modified soil sample in the water-absorbing state to evaluate the inhibitory effect of the modifier on expansibility. The soil sample is saturated with water, the swelling rate is recorded, and it is compared with the unmodified soil sample.

[0110] The swelling force test is used to measure the vertical swelling force generated by the soil on the constrained environment during the water-absorbing expansion process. The modified soil sample is placed in a swelling force measuring instrument, and the stress change during the swelling process of the soil sample is recorded.

[0111] According to the results of the XRD test, expansibility test, and swelling force test, the components and ratios of the modifier are screened and narrowed down to ensure that it can effectively improve properties such as expansibility and strength.

[0112] S240. Determine the target ratio of the modifier based on the 7D saturated compressive strength test and the microscopic electron microscope scanning test.

[0113] Exemplarily, through further mechanical property tests and microscopic analysis, the performance of the modifier is verified, and its target ratio is finally determined.

[0114] The 7D saturated compressive strength test is used to evaluate the compressive strength of the modified soil under the saturated state for 7 days, reflecting the water stability and bearing capacity of the soil mass. Different ratios of modified soil samples are prepared, cured in a saturated water environment for 7 days, and a compressive strength tester is used to measure the compressive strength values of the samples, and comparative analysis is carried out according to the specification requirements or control group data.

[0115] Scanning Electron Microscope (SEM) analysis is used to observe the microscopic structural changes of the modified soil samples through a scanning electron microscope, and analyze the distribution and effect of the modifier in the soil mass. Observation is mainly carried out according to the changes in the surface morphology of gypsum before and after modification, the changes in soil strength and toughness characterization substances, as well as the connection mode between soil particles, the number of voids, the degree of pore development, and the generation of polymers, so as to study and analyze its engineering properties before and after modification.

[0116] Combining the results of the 7D saturated compressive strength and SEM tests, the final target ratio of the modifier is determined to ensure the optimal performance of the modified soil sample in actual engineering.

[0117] Through the liquid-plastic limit combined determination test, compaction test, and shear strength test on the specimens, a certain modified ratio scheme can be screened out. Then, through the above-mentioned several dosages, macroscopic and microscopic tests are carried out to further determine the relatively optimal modified ratio.

[0118] In summary, through the scientific screening and optimization of the modifier components, this method significantly improves the bearing capacity, water stability, and shear strength of the soil. A series of scientific means such as water dispersion test, orthogonal test, chemical and physical tests, 7-day saturated compressive test, and microscopic structure analysis are used to gradually optimize the modifier ratio. The modification scheme is customized according to the soil characteristics of the research area and the specific engineering requirements, enhancing the applicability of the modified soil. It improves the durability and stability of the modified soil sample, reduces the frequency of later maintenance and reconstruction, and saves the long-term engineering cost.

[0119] In some examples, the above-mentioned orthogonal experiment includes liquid-plastic limit combined determination test, compaction test, and shear strength test, and the above-mentioned swelling experiment includes free swelling test, unloaded swelling ratio test, and loaded swelling ratio test.

[0120] Exemplarily, the liquid-plastic limit combined determination test is a common test method for determining the liquid limit and plastic limit of soil. In this test, by determining the liquid-plastic limit, plasticity index, and liquidity index of the soil, the engineering properties of the soil can be understood, such as its bearing capacity, deformation characteristics, and stability, etc. These information have important guiding significance for the engineering application of the subgrade and provide a test basis for the subsequent compaction test.

[0121] The compaction test is a common test method used to evaluate the dynamic response and engineering properties of soil under impact loads. In this method, the light compaction test is adopted, combined with material improvement techniques, to study the relationship between various improved materials and the maximum dry density and the optimum moisture content, further verify the accuracy, and obtain the maximum dry density of each dosage as a prerequisite for preparing samples for the subsequent dynamic triaxial compaction degree.

[0122] The shear strength, cohesion c, and internal friction angle φ values of each improved soil sample are obtained through direct shear tests. The instrument used in the experiment is a strain-controlled direct shear apparatus.

[0123] The swelling experiment includes free swelling test, unloaded swelling ratio test, and loaded swelling ratio test.

[0124] In the free swelling ratio test, when the soil mass has no self-structure, its volume expands due to the absorption of water molecules, and the ratio of the expanded volume to the original volume is the free swelling ratio. The instruments used in the test are: a graduated cylinder with a range of 50 mL, a soil cup, and a 5% NaCl solution. Weigh 10 mL of soil sample with the soil cup, pour it into the graduated cylinder, then add 30 mL of pure water and 5 mL of the prepared 5% pure sodium chloride (NaCl) solution into the graduated cylinder. Stir the solution up and down with a glass rod, and finally rinse the glass rod and the inner wall of the graduated cylinder with pure water until the suspension reaches 50 mL, and let it stand for 24 h. After the liquid level of the solution becomes clear, read the stable reading (the difference in the last 2 h does not exceed 0.2 mL); during the test, two graduated cylinders are used for parallel tests, and the arithmetic mean is taken as the final result.

[0125] The unloaded swelling ratio is the swelling ratio of the soil sample under the condition of no load but with lateral confinement, which can be used to simulate the swelling ratio of the geotechnical body under the condition of no train. Prepare the specimens according to the optimum moisture content of each improved soil sample, embed the pervious stones with the same moisture content, fix the specimens, and add pervious stones and hole covers on the upper part. Install the dial gauge and record the initial reading (set to 0.000 mm uniformly after stabilization). Start injecting pure water into the container from top to bottom until it reaches 5 mm above the top of the specimen. Record the dial gauge readings every 2 h after injection until the difference in the dial gauge readings twice does not exceed 0.01 mm, which is regarded as swelling stability, and terminate the test.

[0126] Due to the influence of train dynamic loads and overlying soil stresses on the railway subgrade, the swelling rate test under load is considered during the swelling test. The preparation and installation steps of the specimen refer to the swelling rate test without load. The difference is that after installing the dial gauge, a prestress of 1 kPa is applied to ensure full contact of the instrument. Then record the initial reading of the dial gauge, and apply the load in stages until the deformation is stable (the swelling amount per hour should not be greater than 0.01 mm). Then add pure water from top to bottom to exceed the specimen surface by 5 mm and record the start time. After adding water, record the dial gauge reading every 2 h until the swelling is stable (the difference in swelling between two times should not be greater than 0.01 mm). The swelling rate under load is calculated according to the following formula:

[0127]

[0128] is the swelling rate (%) under the load pressure P; is the reading (mm) after swelling stability under the load pressure P; R is the deformation of the instrument under the load pressure P ); is the reading of the dial gauge before applying the load (mm); is the initial height of the specimen ;

[0129] The swelling force test is the vertical stress generated by the test soil absorbing water molecules while keeping the volume of the soil sample unchanged. In the method, the swelling force generated by the specimen is mainly due to the anhydrite in the soil sample absorbing water molecules to form gypsum, and the sulfate ions reacting with the substances in the cement to form other crystal substances or flocculent substances, resulting in volume expansion.

[0130] In some examples, the above orthogonal test is carried out on the soil sample modified based on the above modifier to obtain the preliminary component information of the modifier, including:

[0131] Determine the preliminary content of cement in the above modifier based on the above liquid-plastic limit combined determination test;

[0132] Determine the preliminary content of polypropylene fiber and the preliminary content of sodium methyl silicate in the above modifier based on the above compaction test and the above shear strength test.

[0133] Exemplarily, the orthogonal test is an experimental design method used to study the influence of multiple factors and their interactions on the test results, so as to find the best ratio or combination in fewer test times. The orthogonal test is used in this scheme to determine the preliminary formula of the modifier components to improve efficiency.

[0134] The soil is modified with modifiers to improve its physical and mechanical properties. The modifiers usually include cement, polypropylene fiber, and sodium methyl silicate. Each component has a different role in soil modification, so experiments are needed to determine the optimal initial content of each component to optimize the modification effect.

[0135] The liquid-plastic limit test is a key index for measuring the water content of soil and is used to evaluate the plastic properties of soil. The liquid limit is the water content at which the soil changes from a plastic state to a liquid state, while the plastic limit is the water content at which the soil changes from a plastic state to a semi-solid state. The initial content of cement in the modifier is determined based on the liquid-plastic limit combined determination test. Cement is a common soil stabilizer that can change the plastic and liquid properties of soil, so its addition amount is initially determined by the change in the liquid-plastic limit.

[0136] The compaction test is a test used to evaluate the compactness of soil and its optimal water content, and the optimal dry density of soil is obtained through compaction. This is very important for evaluating the engineering properties of soil. The shear strength test is used to measure the shear strength of soil, reflecting the ability of soil to resist shear failure. The shear strength has a direct impact on the stability and bearing capacity of soil. The initial contents of polypropylene fiber and sodium methyl silicate in the modifier are determined based on the compaction test and the shear strength test. The role of polypropylene fiber is to increase the toughness and tensile strength of soil, reduce the formation of cracks, and thus improve the overall stability of the soil mass. Sodium methyl silicate is an organic silicon waterproofing agent that can enhance the waterproof performance and durability of soil.

[0137] Through these tests, the influence of the content of these components on soil density and shear strength can be determined, and then the dosage of them in the modifier can be optimized. Through orthogonal experimental design combined with various tests such as liquid-plastic limit, compaction, and shear strength, the initial contents of each component (such as cement, polypropylene fiber, and sodium methyl silicate) in the soil modifier are determined. This method can obtain an optimized modifier formula with fewer test times, thereby improving the engineering properties of soil, such as plasticity, compactness, and shear strength. The optimal content of each component in the modifier is initially determined by different test methods to ensure an ideal modification effect in practical applications.

[0138] In some examples, the soil samples modified based on the above modifiers are subjected to XRD tests, swelling tests, and swelling force tests to further limit the initial component information of the above modifiers to obtain limited component information, including:

[0139] XRD tests, swelling tests, and swelling force tests are carried out on the soil samples modified based on the above modifiers to extract the corresponding characteristic indexes and the weight information corresponding to the characteristic indexes;

[0140] Determine the mechanical property evaluation index based on all the above characteristic indexes and the weight information corresponding to the above characteristic indexes;

[0141] Further limit the preliminary selection component information of the above modifier based on the above mechanical property evaluation index to obtain the above limited component information.

[0142] Exemplarily, in soil modification, XRD can be used to analyze the new mineral phases formed after the reaction between the modifier and the soil to determine the influence of the modifier composition on the mineral structure of the soil. By conducting XRD tests on the soil modified with the modifier, characteristic indexes related to the soil mineral composition after the reaction with the modifier can be extracted. This can help understand the chemical reactions of different modifier components in the soil and their effects.

[0143] The swelling test is used to measure the volume swelling characteristics of the soil after water absorption, and is particularly suitable for analyzing swelling soils. Swelling soils will significantly increase in volume after water absorption, which has a greater impact on the engineering properties of the soil. Usually, modification is required to reduce its swelling potential. The swelling test can be used to measure the inhibitory effect of the modifier on the swelling performance of the soil and extract characteristic indexes related to the improvement effect of the modifier on the soil swelling.

[0144] The swelling force test is used to measure the swelling pressure generated by the soil during water absorption and swelling. The higher the swelling pressure, the greater the impact of the soil on the structure. Therefore, reducing the swelling force is one of the important goals of modification. The swelling force test is used to evaluate the inhibitory effect of the modifier on the swelling pressure of the soil, and characteristic indexes of the modifier's inhibition of the swelling force can be obtained through the test.

[0145] By conducting XRD, swelling, and swelling force tests on the modified soil samples, multiple characteristic indexes related to the improvement effect can be extracted. These characteristic indexes can include, but are not limited to: changes in mineral components and crystal structure characteristics in the XRD test, the amount of soil volume change (swelling rate) in the swelling test, and the swelling pressure value in the swelling force test.

[0146] The determination of the weight information refers to assigning a weight reflecting its importance to each characteristic index so as to consider the importance of each characteristic index in the subsequent comprehensive evaluation.

[0147] Based on all the characteristic indexes and their corresponding weight information, determine the mechanical property evaluation index of the soil through a certain method (such as multi-objective optimization, weighted summation, etc.). These evaluation indexes are used to reflect the comprehensive mechanical properties of the modified soil samples. The mechanical property evaluation indexes can be used to comprehensively evaluate the improvement effect of the modifier on the soil properties, such as shear strength, stability, swelling characteristics, etc.

[0148] After initially determining the components of the modifier, the characteristic indicators and evaluation indicators obtained through the above-mentioned multiple tests can be used to further narrow down the initially selected components of the modifier, that is, to screen and adjust the content or type of the components to achieve a better modification effect. Narrowing down the component information means determining which modifier components have a more significant effect on performance improvement through the comprehensive evaluation of test results and mechanical properties, so as to retain the effective components, reduce the ineffective or components with greater side effects, and finally obtain an optimized formula of the modifier. By conducting XRD tests, swelling tests, and swelling force tests on the modified soil samples, characteristic indicators related to the modification effect are extracted, and then a comprehensive mechanical property evaluation system is constructed based on these indicators and their weight information. By comprehensively evaluating the modification effect of the soil, the components in the modifier are further screened and optimized to obtain a more accurate and effective ratio, thereby achieving optimal control of the soil modification effect. Such a process can not only improve the engineering properties of the soil but also reduce unnecessary material waste and side effects.

[0149] In some examples, determining the mechanical property evaluation index based on all the above-mentioned characteristic indicators and the weight information corresponding to the characteristic indicators includes:

[0150] Calculating the performance evaluation index based on the following formula :

[0151]

[0152] Wherein, is the number of all tests participated, is the weight of the th test result, is the th characteristic index value of the test, The characteristic index of the RD test is the proportion of mineral content, the characteristic index of the free swelling test is the free swelling rate, the characteristic index of the unloaded swelling rate test is the unloaded swelling rate, the characteristic index of the loaded swelling rate test is the loaded swelling rate, the characteristic index of the swelling force test is the swelling force;

[0153] Based on the above-mentioned mechanical property evaluation index, further narrow down the initially selected component information of the above-mentioned modifier to obtain the above-mentioned narrowed-down component information, including:

[0154] Establish a formula regression model according to historical test data, wherein the above formula regression model is based on the above-mentioned mechanical property evaluation , the target content of cement, the target content of polypropylene fiber, and the target content of sodium methyl silicate are established;

[0155] Determine the above shrinkage component information according to the above mechanical property evaluation index and the above formulation regression model. The above shrinkage component information includes the target content of cement in the modifier, the target content of polypropylene fiber, and the target content of sodium methyl silicate.

[0156] The above formulation regression model is determined based on the following formula:

[0157]

[0158]

[0159] Wherein, is the target content of cement, is the target content of polypropylene fiber, is the target content of sodium methyl silicate, and a, b, c, d, f, g, and h are parameters obtained by regression fitting respectively.

[0160] Exemplarily, based on the calculated MEI index, further shrink the initially selected modifier component information to obtain the information of the shrunk components, determine the final composition and its optimal ratio, so as to improve the soil improvement effect. Establish a linear regression model for each component of the modifier based on historical test data to quantify the influence of the modifier components on the MEI index. Use the regression equation to determine the final target content of each modifier component based on the calculated MEI value. This can make the formulation of the modifier more scientific to ensure

[0161] The method proposed in this embodiment uses the MEI mechanical property evaluation index to comprehensively evaluate the performance of the modified soil sample. By extracting the characteristic indexes of different tests and determining their weights, an overall evaluation index is obtained. Then, by establishing multiple regression models to quantify the relationship between MEI and different modifier components, the target content of each component is determined, and finally the modifier formulation is optimized. This method can effectively improve the soil modification effect, reduce expansibility, enhance mechanical properties, and achieve the optimal combination of modifier components.

[0162] In some examples, it further includes:

[0163] Modify the subgrade material with the modifier corresponding to the above modifier component content to obtain the modified subgrade material;

[0164] Conduct a dynamic triaxial test on the above modified subgrade material to obtain the first test result;

[0165] Conduct a simulation test on the above modified subgrade material to obtain the second test result;

[0166] Optimize the above modifier component content based on the above first test result and the above second test result.

[0167] Exemplarily, the dynamic triaxial test is a basic test method in soil mechanics. By applying dynamic loads to soil samples, it simulates the complex stress states that soils bear under actual working conditions, thereby studying the mechanical behaviors and deformation characteristics of soils under dynamic loads. It includes dynamic parameters such as the dynamic elastic modulus and dynamic Poisson's ratio of soils, and can also study the fatigue performance, cumulative deformation characteristics, and failure mechanisms of soil structures.

[0168] In the dynamic triaxial test, subgrade materials are subjected to axial cyclic loads, and thus their bearing capacity, stiffness, and fatigue resistance can be measured. The first test results are obtained through the dynamic triaxial test, and these results include the mechanical behaviors of the materials under dynamic loads, such as parameters like dynamic modulus, shear strength, and cumulative strain. These parameters can be used to judge the performance of the modified subgrade materials in actual roads. The simulation test is a way to simulate the behaviors of modified materials under actual environmental conditions through computer technology. Simulations usually adopt numerical methods such as finite element analysis (FEA). By inputting material parameters, boundary conditions, and load conditions, the stress conditions of the modified subgrade materials in the road structure are simulated.

[0169] The second test results are obtained through simulation, including displacements, stress distributions, deformation characteristics, etc. of the materials under different stress states. These results can provide virtual test data for real subgrades and help better understand the behaviors of the materials under complex stress conditions.

[0170] Based on the first test results (dynamic triaxial test) and the second test results (simulation), the component contents of the modifier are optimized. The first test results provide the physical responses of the modified materials under actual loads, such as deformation and fatigue performance; the second test results provide virtual behaviors under various complex boundary conditions, including stress-strain distributions, etc.

[0171] By comparing and analyzing these two test results, the influence laws of the modifier components on the material properties can be found, and then it can be judged which component contents need to be adjusted to achieve better modification effects. The optimization means may include adjusting the cement content, polypropylene fiber dosage, methyl sodium silicate ratio, etc. in the modifier to ensure that the performance of the modified subgrade materials reaches the optimum under both dynamic and static loads.

[0172] The optimized modified materials should be able to withstand higher loads without obvious deformation or failure. Under cyclic loads, the optimized materials should exhibit lower cumulative strain to reduce subgrade settlement and uneven deformation. The durability of the materials under long-term traffic loads should be enhanced to extend the service life of the subgrade. By optimizing the components of the modifier, ensure that the subgrade materials remain stable in a humid environment and do not experience a strength decline due to water absorption.

[0173] In some examples, the above simulation test is implemented based on a 1:1 scale model established by COMSOL software. The above 1:1 scale model includes a steel rail, a CA mortar layer, a track slab, a subgrade, and a foundation structure. The above 1:1 scale model is a two-dimensional model. The load in the above simulation test is a half-sine wave pulse. An infinite domain boundary is adopted for the foundation and cross-section in the above simulation test.

[0174] Exemplarily, as ​ shown, this application uses COMSOL software to establish a 1:1 model of the railway subgrade, with an overall height of 8 m, where the height of the subgrade is 3 m, and the slopes on both sides of the subgrade bed are set at 1:1.5. The analysis model mainly consists of structures such as steel rails, CA mortar layers, track slabs, subgrades (including the subgrade bed surface, subgrade bed bottom layer, and embankment body), and foundations. The materials of the subgrade bed and the materials in the embankment are regarded as isotropic bodies. Only the load action of the locomotive in the vertical direction is studied. The geometric model of the established mathematical model is simplified to a two-dimensional problem, which can reduce the calculation amount and does not affect the calculation accuracy, meeting the practical significance. The finally established finite element model is as ​ shown as the original model is modeled according to the original dimensions, ​ and this is a partially enlarged view after mesh division of the model.

[0175] The solution of the subgrade filling in the finite element is a very complex problem, and the model is relatively idealized and cannot be completely consistent with the on-site working conditions. Therefore, we need to set relevant parameters and make some relevant assumptions:

[0176] (1) The anisotropy of the soil body is ignored, and the soil body is regarded as an isotropic porous medium;

[0177] (2) Since the compactness of the improved soil body is good, the soil body is regarded as an elastic body, and the action of other coupled fields is not considered;

[0178] (3) The solid substances are uniformly homogenized, and only the overall change occurs with the change of the operator's parameters.

[0179] According to the dynamic triaxial test, it is finally found that the specimens of 4% cement + 0.25% polypropylene fiber + 2% sodium methyl silicate (XCF2) and 6% cement + 0.25% polypropylene fiber + 2% sodium methyl silicate (XCF3) show performance that meets the relevant specification standards in the subgrade project. Considering the economic benefit problem, the test data of 4% cement + 0.25% polypropylene fiber + 2% sodium methyl silicate are finally selected as the simulation parameters for the fill soil.

[0180] In the numerical simulation, only the deformation degree of the improved soil under vertical load at different burial depths and different frequencies is considered. According to past experience, for the interaction force generated by the load of the wheel-rail acting on the lower object, a semi-sine wave pulse can be adopted:

[0181] The simulation of each model for 10,000 times can be controlled by time. The time of the simulated load can be obtained from the load frequency. After the previous analysis, the amplitude of the dynamic stress applied this time is taken as 90 MPa, and the load frequencies are taken as 1 Hz, 2 Hz, and 4 Hz. It can be known that the corresponding periods T are 0.5 s, 0.25 s, and 0.125 s, and the burial depths are 2.5 m, 5 m, and 7.5 m. From the perspective of simulation, it is simplified into the surface layer of the subgrade, the bottom layer of the subgrade, and the part below the subgrade for analysis.

[0182] Since the foundation is an infinite model and only a part of it is selected for this simulation test, infinite domain boundaries are adopted on the foundation and cross-section. Also, in order to more clearly and intuitively represent the surface deformation of each layer of the filled subgrade, the software is used to form an assembly by union, and then the contact pairs between them are set to achieve the setting of conditions. Other domains, points, and boundaries adopt fixed boundary conditions, roller supports, and load boundaries, etc. to solve such problems.

[0183] Since there will be a certain gravity of the materials in the modeling, the initial stress balance needs to be carried out before the simulation. By calculating the initial self-weight stress, and then adding it to each layer in the form of a tensor as an external stress to balance the gravity of the simulated soil layer. The subgrade of high-speed railway and ballastless track has strict requirements for deformation. At present, there is no clear regulation on the control of subgrade deformation during operation. Therefore, the control deformation of this improvement is carried out according to the uplift deformation control of the expansive soil subgrade. According to the relevant regulations in the "Code for Design of Railway Subgrade" and referring to Article 9.2.1 of the "Code for Design of High-Speed Railway" (TB10621 - 2014), the deformation is controlled not to exceed 2 mm. For strictness, both the subgrade bed bottom layer and the part below the subgrade bed are regarded as having a deformation limit value of 2 mm, and the deformation displacement is observed using a probe map.

[0184] ​This is a numerical simulation diagram of 2Hz at various positions before and after improvement provided by the embodiments of this application. After applying 10,000 cycles of load to the embankment subgrade, it can be further seen from the above figure the relationship between the vertical displacement deformation of the subgrade, the frequency, and the filling position. Generally speaking, the vertical displacement decreases with the increase of frequency and the increase of filling depth, and this law is consistent with the law of the dynamic triaxial test. From the perspective of the filling position, the vertical deformation of the unimproved filling soil is the largest on the surface layer of the subgrade, reaching more than 10mm at all load frequencies, and the maximum value reaches more than 20mm. The vertical deformation of the subgrade body is the smallest, but most of the values are also above 10mm. From the perspective of the load frequency, the vertical displacement on the y-axis shows a non-linear decreasing trend with the increase of frequency. When the frequency is 1Hz, the vertical deformation is the largest, and when it is 4Hz, it is the smallest. Although there are certain changes in the vertical deformation between 1Hz and 2Hz, the amplitude between 2Hz and 4Hz is relatively small. However, no matter which frequency, it has exceeded the specified 2mm in the specification. It can be analyzed from the improved embankment subgrade that the overall law of its deformation influencing factors is consistent with the dynamic triaxial test. The difference is that after 10,000 cycles of load action, the vertical deformations of each improved part have been significantly improved. Among them, the largest vertical displacement occurs when the load frequency is 1Hz and the filling position is the surface layer of the subgrade, and the deformation value is 1.92mm, which is reduced by 91.48% compared with 22.54mm before improvement; the smallest vertical displacement occurs when the load frequency is 4Hz and the filling position is the subgrade body, and the deformation value is 0.537mm, which is reduced by 88.14% compared with 4.527mm before improvement. It can be seen that the deformation of the improved gypsum powder-sandy mudstone subgrade can basically meet the engineering deformation requirements of railway subgrade fillers.

[0185] The above embodiments are only used to illustrate the technical solutions of this application, rather than to limit it; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of this application.

Claims

1. A method for determining the content of an improver component, characterized in that, Comprising: Determine the basic composition components of the modifier based on the water dispersion experiment, and the basic composition components include cement, polypropylene fiber, and sodium methyl silicate; Conduct an orthogonal experiment on the soil sample modified by the modifier to obtain the preliminary selection component information of the modifier; Conduct XRD tests, swelling tests, and swelling force tests on the soil sample modified by the modifier to further narrow down the preliminary selection component information of the modifier to obtain the narrowed-down component information; Determine the target ratio of the modifier based on the 7-day saturated compressive strength test, microscopic electron microscope scanning test, and the narrowed-down component information; The orthogonal experiment includes liquid-plastic limit combined determination test, compaction test, and shear strength test, and the swelling test includes free swelling test, unloaded swelling ratio test, and loaded swelling ratio test; Conduct XRD tests, swelling tests, and swelling force tests on the soil sample modified by the modifier to further narrow down the preliminary selection component information of the modifier to obtain the narrowed-down component information, including: Extract the corresponding characteristic indexes and the weight information corresponding to the characteristic indexes from the XRD test, swelling test, and swelling force test on the soil sample modified by the modifier; Determine the mechanical property evaluation index based on all the characteristic indexes and the weight information corresponding to the characteristic indexes; Further narrow down the preliminary selection component information of the modifier based on the mechanical property evaluation index to obtain the narrowed-down component information; Determine the mechanical property evaluation index based on all the characteristic indexes and the weight information corresponding to the characteristic indexes, including: Calculate the performance evaluation index based on the following formula :[[]]END]] ； Among them, is the quantity of all participants in the test, is the weight of the th test result, is the characteristic index value of the th test. The characteristic index of the XRD test is the proportion of mineral content. The characteristic index of the free swelling test is the free swelling rate. The characteristic index of the unloaded swelling rate test is the unloaded swelling rate. The characteristic index of the loaded swelling rate test is the loaded swelling rate. The characteristic index of the swelling force test is the swelling force; Further narrow down the preliminary selection component information of the modifier based on the mechanical property evaluation index to obtain the narrowed-down component information, including: Establish a formulation regression model based on historical test data, wherein the formulation regression model is established based on the mechanical property evaluation , the target content of cement, the target content of polypropylene fiber, and the target content of sodium methyl silicate; Determine the narrowed-down component information according to the mechanical property evaluation index and the formula regression model, and the narrowed-down component information includes the target content of cement, the target content of polypropylene fiber, and the target content of sodium methyl silicate in the modifier; The formula regression model is determined based on the following formula: ； Among them, is the target content of cement, is the target content of polypropylene fiber, is the target content of sodium methyl silicate, and a, b, c, d, f, g, and h are parameters obtained by regression fitting respectively.

2. The method for determining the content of the modifier component according to claim 1, characterized in that, Conduct an orthogonal experiment on the soil sample modified by the modifier to obtain the preliminary selection component information of the modifier, including: Determine the preliminary selection content of cement in the modifier based on the liquid-plastic limit combined determination test; Determine the preliminary selection content of polypropylene fiber and the preliminary selection content of sodium methyl silicate in the modifier based on the compaction test and the shear strength test.

3. The method for determining the content of the modifier component according to claim 1, characterized in that, Also including: Modify the subgrade material with the modifier corresponding to the component content of the modifier to obtain the modified subgrade material; Conduct a dynamic triaxial test on the modified subgrade material to obtain the first test result; Conduct a simulation test on the modified subgrade material to obtain the second test result; Optimize the component content of the modifier based on the first test result and the second test result.

4. The method for determining the content of the modifier component according to claim 3, wherein The simulation test is implemented based on a scaled model established by COMSOL software. The scaled model includes a steel rail, a CA mortar layer, a track slab, a subgrade, and a foundation structure. The scaled model is a two-dimensional model. The load in the simulation test is a half-sine wave pulse. An infinite domain boundary is adopted in the foundation and cross-section in the simulation test.

5. A method for modifying paste-containing silty mudstone, characterized in that, The component information of the modifier is determined by any one of the methods described in claims 1-4. The modification method includes: Producing the modifier based on the cement, the polypropylene fiber, and sodium methyl silicate; Performing a blending modification operation on the paste-containing silty mudstone with the modifier to obtain modified rock and soil.

6. The method for modifying paste-containing silty mudstone according to claim 5, characterized in that, The total mass of the modifier is in percentage, and the modifier includes: 2% to 6% of the cement, 0.25% of the polypropylene fiber, and 0.25% to 0.5% of the sodium methyl silicate.

7. The method for modifying paste-containing silty mudstone according to claim 5 or 6, characterized in that, The cement includes sulfate-resistant portland cement. The length of the polypropylene fiber is 6 mm, the diameter of the polypropylene fiber is 23 um, the solid content of the sodium methyl silicate is 30%, the alkali content of the sodium methyl silicate is less than or equal to 12%, the silicone content of the sodium methyl silicate is greater than or equal to 18%, the specific gravity of the sodium methyl silicate is greater than or equal to 1.2 and less than or equal to 1.25, and the pH value of the sodium methyl silicate is greater than or equal to 12 and less than or equal to 13.

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