Method for inhibiting salt heaving and frost heaving of saline soil based on directional induction of non-continuous mineralization lamella network structure by sheet-shaped template

Abstract

The application provides a method for inhibiting salt expansion and frost heaving of saline soil based on directional induction of non-continuous mineralization sheet network structure of sheet template, and belongs to the technical field of geotechnical engineering. The method for inhibiting salt expansion and frost heaving of saline soil comprises the following steps: 1. Preparing a mineralization solution; 2. Adding sheet templates into the saline soil to be treated, mixing, layer-by-layer paving and layer-by-layer compaction, so that the sheet templates are uniformly dispersed in the saline soil to be treated and form a horizontal or low-angle directional arrangement in the saline soil to be treated; 3. Injecting part of the complex calcium source solution and the carbon source solution into each layer of the saline soil to be treated for pre-mineralization, and then cyclically injecting the remaining complex calcium source solution and the carbon source solution into the saline soil to be treated for overall supplementary mineralization, so that the complex calcium source in the complex calcium source solution and the carbonate in the carbon source solution undergo a mineralization reaction; 4. Carrying out unidirectional seepage replacement on the mineralized saline soil to be treated to discharge soluble salt; and 5. Carrying out maintenance after the unidirectional seepage replacement is completed.

Description

Technical Field

[0001] This application belongs to the field of geotechnical engineering technology, specifically relating to a method for inhibiting salt swelling and frost heave in saline soil based on a sheet template-induced discontinuous mineralized sheet network structure. Background Technology

[0002] Saline soils are rich in soluble salts such as chlorides, sulfates, and carbonates. Driven by environmental factors such as wet-dry cycles, temperature changes, freeze-thaw cycles, and evaporation, pore water carries salts and migrates within the soil, accumulating in localized areas. When temperatures decrease, pore water freezes, salt crystals precipitate, and some salts undergo phase transitions. The expansion effect caused by ice crystal growth and salt crystallization leads to soil volume expansion, resulting in a series of engineering defects such as salt heave, frost heave, bulging, cracking, strength reduction, and uneven deformation of the roadbed.

[0003] Currently, biomimetic mineralization reinforcement technology has been applied in the field of geotechnical engineering. Its principle is to improve the cementation strength between soil particles by using calcium carbonate precipitation. However, for saline soil, simply improving the soil strength cannot effectively solve the problems of water and salt migration, water supply at the freezing front, salt enrichment and salt crystal expansion pressure release. Specifically, the existing biomimetic mineralization reinforcement technology has the following shortcomings: (1) Ordinary biomimetic mineralization mainly focuses on strength improvement, and the mineralization products are mostly randomly distributed, making it difficult to directionally control the vertical capillary water and salt migration inside the saline soil. (2) Some biomimetic mineralization technologies inhibit salt rise by forming a continuous and dense mineralization barrier layer, but this method is prone to causing water accumulation and local salt retention near the interface, and at the same time, it causes freeze-thaw stress concentration, which may still cause cracking and local damage during long-term service. (3) The direct reaction rate of calcium chloride and sodium carbonate is relatively fast, and it is easy to precipitate prematurely at the injection end or in local pores, causing surface pore blockage, insufficient deep mineralization and uneven distribution of mineralization products. (4) The reaction of calcium chloride and sodium carbonate will produce soluble byproduct salts such as sodium chloride; at the same time, a certain amount of sodium salt will also be introduced into the mineralization system in which sodium hydroxide is used to adjust the pH. If not effectively treated, the above-mentioned soluble salts may accumulate in the reinforced area, thereby affecting the long-term salt swelling resistance and frost swelling resistance of the treated area.

[0004] In view of this, it is necessary to develop a method for inhibiting salt heave and frost heave that can directionally regulate the migration of water and salt within saline soil and also take into account the function of salt drainage. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a method for inhibiting salt heave and frost heave in saline soil based on a sheet-like template-guided directional-induced discontinuous mineralized sheet network structure, aiming to at least partially solve the above-mentioned technical problems. The specific technical solution provided by this application is as follows.

[0006] This application provides a method for inhibiting salt heave and frost heave in saline soil based on a sheet template-induced discontinuous mineralized sheet network structure, which includes the following steps.

[0007] Step 1: Prepare a mineralization solution for inducing a biomimetic mineralization reaction in the saline soil to be treated, including a complexed calcium source solution and a carbon source solution.

[0008] Step 2: Add the sheet template to the saline soil to be treated, mix, spread and compact layer by layer, so that the sheet template is evenly dispersed in the saline soil and forms a horizontal or low-angle directional arrangement in the saline soil.

[0009] Step 3: During the layer-by-layer compaction process, a portion of complexed calcium source solution and carbon source solution is injected into each layer of saline soil to be treated for pre-mineralization treatment. After all layers are compacted and pre-mineralized, the remaining complexed calcium source solution and carbon source solution are injected into the saline soil to be treated in a cyclical manner for overall supplementary mineralization treatment. This allows the complexed calcium source in the complexed calcium source solution to react with the carbonate ions in the carbon source solution to generate calcium carbonate mineralization products. The calcium carbonate mineralization products grow along the surface and edges of the sheet template and form discontinuous sheet-like connections between adjacent sheet templates, thereby forming a discontinuous mineralized sheet network structure inside the saline soil to be treated.

[0010] Step 4: Perform unidirectional permeation replacement on the mineralized saline soil to be treated, and remove soluble salts.

[0011] Step 5: Curing is carried out after the unidirectional seepage replacement is completed.

[0012] In this embodiment, sheet templates are used to form horizontal or low-angle directional arrangements within the saline soil. This induces calcium carbonate mineralization products to preferentially grow along the surface and edges of the sheet templates, forming discontinuous lamellar connections between adjacent sheet templates. This constructs a discontinuous mineralized lamellar network structure within the soil. This network structure weakens vertical capillary water and salt migration while retaining seepage channels, avoiding the interfacial water accumulation, salt retention, and freeze-thaw stress concentration problems easily caused by continuous dense barrier layers. Simultaneously, layer-by-layer pre-mineralization treatment allows initial calcium carbonate crystal nuclei to form at the sheet template interface and maintains the compactability of the layers, facilitating interlayer particle intercalation. After all layers are compacted and pre-mineralized, a final overall supplementary mineralization treatment is performed, effectively slowing down the mineralization reaction rate and allowing mineralization products to be evenly distributed along the sheet template interface, preventing premature surface blockage and insufficient deep mineralization. Furthermore, through the unidirectional seepage replacement step after mineralization, soluble salts in the soil are discharged, avoiding the accumulation of soluble salts in the reinforced area. This comprehensively achieves long-term effective suppression of salt heave and frost heave in saline soil and improves the freeze-thaw stability of the soil. Attached Figure Description

[0013] Figure 1 This is a schematic flowchart of the method for inhibiting salt heave and frost heave in saline soil in the embodiments of this application;

[0014] Figure 2 This is a schematic diagram of the process of the method for inhibiting salt swelling and frost heave in saline soil in the embodiments of this application. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0016] In realizing the concept of this application, it was found that existing biomimetic mineralization technologies mainly focus on improving soil strength, and the mineralization products are mostly randomly distributed, making it difficult to directionally control the vertical capillary migration of salt and water within saline soil. While forming a continuous and dense mineralization barrier layer can inhibit salt rise, it easily leads to water accumulation, salt retention, and freeze-thaw stress concentration at the interface, which can cause cracking and localized damage during long-term service. Furthermore, the direct reaction rate between calcium chloride and sodium carbonate is too fast, easily causing premature precipitation at the injection end or in local pores, resulting in surface blockage, insufficient deep mineralization, and uneven mineralization distribution. Simultaneously, if the soluble salts produced as byproducts are not removed in time, they will accumulate in the reinforced area, affecting the long-term resistance to salt swelling and frost heave.

[0017] Based on this, this application provides a method for inhibiting salt heave and frost heave in saline soil based on a discontinuous mineralized lamellar network structure induced by sheet templates. By forming horizontal or low-angle directional arrangements of sheet templates within the soil, and utilizing the selective adsorption of complexed calcium sources on the template surface, calcium carbonate mineralization products are induced to preferentially grow along the template surface and edges, forming a discontinuous mineralized lamellar network structure. This network structure reduces the continuity of vertical capillary channels while preserving seepage and salt drainage channels, thus reducing the concentrated migration of water and salt to freezing fronts and evaporation surfaces. Layer-by-layer pre-mineralization involves injecting a portion of the complexed calcium source solution and carbon source solution into each layer of saline soil to be treated, allowing initial calcium carbonate crystal nuclei to form at the template interface and maintaining the compactability of the layers. After all layers are compacted and pre-mineralized, the remaining complexed calcium source solution and carbon source solution are sequentially injected for overall supplementary mineralization, thereby slowing down the mineralization reaction rate and improving the uniformity of mineralization distribution. The soluble salt is then removed by unidirectional permeation, thereby weakening vertical capillary water and salt migration, inhibiting salt swelling and frost deformation, and improving freeze-thaw stability.

[0018] Figure 1 This is a schematic flowchart of the method for inhibiting salt heave and frost heave in saline soil in the embodiments of this application; Figure 2 This is a schematic diagram of the process of the method for inhibiting salt swelling and frost heave in saline soil in the embodiments of this application.

[0019] Specifically, such as Figure 1 and Figure 2As shown, the method for inhibiting salt heave and frost heave in saline soil based on a sheet template-induced discontinuous mineralized sheet network structure provided in this application includes steps S1-S5.

[0020] Step S1: Prepare a mineralization solution for inducing a biomimetic mineralization reaction in the saline soil to be treated, including a complexed calcium source solution and a carbon source solution.

[0021] Step S2: Add the sheet template to the saline soil to be treated, mix, spread and compact layer by layer, so that the sheet template is evenly dispersed in the saline soil to be treated and forms a horizontal or low-angle directional arrangement in the saline soil.

[0022] Step S3: During the layer-by-layer compaction process, a portion of complexed calcium source solution and carbon source solution is injected into each layer of saline soil to be treated for pre-mineralization treatment. After all layers are compacted and pre-mineralized, the remaining complexed calcium source solution and carbon source solution are injected into the saline soil to be treated in a sequential cycle for overall supplementary mineralization treatment. This allows the complexed calcium source in the complexed calcium source solution to react with the carbonate ions in the carbon source solution to generate calcium carbonate mineralization products. The calcium carbonate mineralization products grow along the surface and edges of the sheet template and form discontinuous sheet-like connections between adjacent sheet templates, thereby forming a discontinuous mineralized sheet network structure inside the saline soil to be treated.

[0023] Step S4: Perform unidirectional permeation replacement on the mineralized saline soil to be treated to remove soluble salts.

[0024] Step S5: Curing is carried out after the unidirectional seepage replacement is completed.

[0025] In this embodiment, sheet templates are used to form horizontal or low-angle directional arrangements within the saline soil, providing an ordered induction interface for the mineralization reaction. Through layer-by-layer pre-mineralization and overall supplementary mineralization, calcium carbonate mineralization products preferentially grow along the surface and edges of the sheet templates, forming discontinuous sheet-like connections between adjacent sheet templates. This constructs a discontinuous mineralized sheet network structure within the soil. This network structure can weaken the continuity of vertical capillary channels and reduce the concentrated migration of water and salt to the freezing front and evaporation surface while retaining seepage and salt drainage channels, avoiding the problems of interfacial water accumulation, salt retention, and freeze-thaw stress concentration that are easily caused by continuous dense barrier layers. At the same time, layer-by-layer pre-mineralization forms initial calcium carbonate crystal nuclei at the sheet template interface and maintains the compactability of the layer, which is beneficial for interlayer particle interlocking. Overall supplementary mineralization further allows mineralization products to continue growing along the interfaces of each sheet template layer, effectively slowing down the mineralization reaction rate, improving the uniformity of mineralization product distribution in the depth direction of the soil, and avoiding premature surface blockage and insufficient deep mineralization. Furthermore, by using unidirectional seepage replacement after mineralization, soluble salts in the soil are discharged, avoiding the accumulation of soluble salts in the reinforced area. This comprehensively and effectively suppresses salt swelling and frost heave in saline soil and improves the freeze-thaw stability of the soil.

[0026] In some embodiments, before step S1, i.e., before preparing the complexed calcium source solution and carbon source solution, the method further includes: collecting the saline soil to be treated, measuring the basic property parameters of the saline soil to be treated, and determining the concentration, single application amount, application interval, and number of cycles of the complexed calcium source solution and carbon source solution based on the basic property parameters. The basic property parameters include salt content, water content, dry density, porosity, salt swelling rate, frost heave rate, post-freeze-thaw strength retention rate, and permeability.

[0027] Furthermore, the content of major ions, including Ca2+, in the soil leachate or pore water of the saline soil to be treated was determined. 2 + Mg 2+ Na + Cl - SO4 2- CO3 2- and HCO3 - The pH, electrical conductivity, and permeability of the saline soil to be treated were measured. Based on the above measurement results, the concentrations, single application amounts, application intervals, and number of cycles of the complexed calcium source solution and carbon source solution were adjusted. Specific adjustment methods could include, for example, adjusting the concentrations of available calcium and carbon source solutions in the soil when the soil contains... 2+ When the content is high, the amount of complexed calcium source solution should be reduced accordingly; when the CO3 content in the soil is high... 2- or HCO3 - When the SO4 content is high, the amount of carbon source solution should be reduced accordingly; when the SO4 content in the soil is high... 2- Mg2+ When the content is high or the soil permeability is low, reduce the amount applied at one time and increase the application interval.

[0028] In some embodiments, in step S1, the complexed calcium source solution is a complexed cementitious solution comprising calcium chloride and aspartic acid. The concentration of calcium ions in the complexed cementitious solution is 0.5-1.5 mol / L, for example, 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L, or 1.5 mol / L; the concentration of aspartic acid is 0.5-1.5 mol / L, for example, 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L, or 1.5 mol / L; the molar ratio of calcium ions to aspartic acid is 1:(0.8-1.2), for example, 1:0.8, 1:0.9, 1:1, 1:1.1, or 1:1.2. The pH of the complexed calcium source solution is 9.5-10.0, for example, 9.5, 9.6, 9.7, 9.8, 9.9, or 10.0.

[0029] Specifically, when preparing the complexed calcium source solution, aspartic acid is first added to water, and the pH is adjusted to 9.5-10.0 using sodium hydroxide to ensure that the aspartic acid is fully dissolved and exists in the form of aspartate salt. The pH value should not be significantly higher than 10.0 to reduce the formation of local non-target precipitates. After the aspartic acid is fully dissolved, calcium chloride is slowly added to allow the calcium to fully dissolve. 2+ It forms a calcium-aspartic acid (Ca-Asp) complex with aspartic acid, serving as a calcium source. Calcium chloride is used to provide the calcium required for mineralization. 2+ Sodium hydroxide is used to adjust pH and promote the dissolution of aspartic acid, but it is not a component of the calcium carbonate mineralization framework.

[0030] In some embodiments, in step S1, the carbon source solution is a sodium carbonate cementing solution. The concentration of carbonate ions in the sodium carbonate cementing solution is 0.5-1.5 mol / L, for example, 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L, or 1.5 mol / L.

[0031] Specifically, sodium carbonate provides carbonate ions (CO3-). 2- Upon entering the saline soil to be treated, a mineralization reaction occurs with the Ca-Asp complexed calcium source enriched near the sheet template, inducing calcium carbonate crystallization on the surface, edges, and contact area between the sheet template and soil particles. Calcium chloride, sodium carbonate, and aspartic acid together constitute the mineralization reaction system of this application, enabling a continuous process relationship of calcium source complexation, interfacial enrichment, time-sequential reaction, and soluble salt replacement. Aspartic acid, as a calcium ion complexing and biomimetic mineralization regulating component, has its carboxyl groups reacting with Ca under alkaline conditions. 2+ Coordination, on the one hand, can reduce free Ca2+ With CO3 2- The instantaneous reaction degree at the spraying end and soil surface promotes the adsorption and retention of complexed calcium sources on the surface, edges and micro-defects of the sheet template; on the other hand, it can regulate the nucleation, growth, crystal composition and crystal aggregation state of calcium carbonate, so that more mineralization products can form adhesion and bridging in the contact area between the sheet template and soil particles, and improve the effective cementation degree of calcium carbonate precipitation.

[0032] In some embodiments, in step S2, the sheet-like template is muscovite. The muscovite has a particle size of 0.1mm-0.5mm, for example, 0.1mm, 0.2mm, 0.3mm, 0.4mm, or 0.5mm; a thickness of 1μm-50μm, for example, 1μm, 10μm, 20μm, 30μm, 40μm, or 50μm; and an aspect ratio ≥10, preferably ≥20.

[0033] Furthermore, the amount of muscovite added accounts for 2%-6% of the total dry solids mass of the mixture of muscovite and the saline soil to be treated, for example, 2%, 3%, 4%, 5%, or 6%. It should be noted that the amount of muscovite added is calculated by dry weight.

[0034] In some embodiments, in step S2, the sheet template is pretreated before being added to the saline soil to be treated. Specifically, this includes pre-impregnating the cleaned and dried sheet template with a portion of a complexed calcium source solution, allowing the complexed calcium source in the solution to adsorb onto the surface of the sheet template. Further, the pre-impregnation time is 1.5-2 hours, for example, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, or 2 hours.

[0035] Specifically, after pretreatment with the complexed calcium source solution, the surface, edge cracks, and rough microstructure of the sheet template can adsorb and retain the complexed calcium source, forming a localized calcium-rich reaction zone at the interface of the sheet template. The pretreated sheet template is then dried to constant weight after removing the surface free liquid and used in subsequent steps, with the amount used calculated based on the constant weight after pretreatment.

[0036] In some embodiments, step S2, adding the sheet template to the saline soil to be treated includes: pre-mixing the sheet template with a portion of the saline soil to be treated to form a premix, and then adding the premix to the remaining saline soil to be treated.

[0037] Specifically, pre-treated and dried sheet templates to constant weight are pre-mixed with a portion of air-dried fine soil to form a loose, easily measured, and uniformly spread premix. The air-dried fine soil used in the premix is ​​deducted from the mass of the saline soil to be treated and does not add to the total dry solids mass. Based on the total dry solids mass and the designed dosage, the premix is ​​evenly spread onto the surface of the saline soil to be treated; subsequently, a mixing device is used to repeatedly mix the premix longitudinally and laterally, ensuring the sheet templates penetrate the full designed thickness of this portion of the soil. After mixing, the mixture is spread, leveled, and compacted. Under the combined action of the horizontal shear generated during spreading and the vertical pressure generated during compaction, most of the sheet templates form a horizontal or low-angle dominant orientation.

[0038] It should be noted that "uniform dispersion" in this application means that, on a macroscopic scale, the quantity distribution of sheet templates in different areas of the soil is generally similar, with no obvious enrichment or deficiency areas, thus providing a relatively balanced induction interface for subsequent mineralization reactions. This statement does not imply that the sheet templates must achieve an absolutely equal spacing or quantity distribution in a mathematical sense on a microscopic scale. In the actual mixing, spreading, and compaction process, local aggregation or slight offset of a small number of sheet templates is an acceptable process deviation and does not affect the implementation of the technical solution and the realization of the expected technical effect of this application, as long as a discontinuous mineralized sheet network that can regulate vertical water and salt migration can be formed overall.

[0039] It should be further clarified that the "forming a horizontal or low-angle directional arrangement" in this application refers to the fact that during the mixing, spreading, and compaction processes, the sheet templates are subjected to the combined effects of the horizontal shear force generated during spreading and the vertical pressure generated during compaction, causing the normal direction of the template surface to tend to align with the direction of gravity, i.e., the surface of the sheet templates tends to be close to the horizontal plane. Due to objective factors such as local obstruction by soil particles, uneven compaction, and boundary conditions, the actual orientation of some sheet templates may have a certain angle with the horizontal plane. This angle is usually small (0-30° relative to the horizontal plane) and does not affect the macroscopic blocking function of the sheet templates against vertical water and salt migration. This description aims to describe the statistical trend of the overall orientation of a large number of sheet templates in the soil, rather than requiring each sheet template to be strictly parallel to the horizontal plane. In actual construction, a large-angle tilt or local offset of a small number of sheet templates is an acceptable process deviation and does not affect the implementation of the technical solution and the realization of the expected technical effect of this application, as long as a discontinuous mineralized sheet network that regulates vertical water and salt migration can be formed as a whole.

[0040] In some embodiments, in step S3, the number of cycles is 5-20; in each cycle, the amount of complexed calcium source solution and carbon source solution applied is equal in volume. The molar ratio of calcium ions to carbonate ions during the mineralization reaction is 1:(0.8-1.2) to control the residual amount of by-product salt after the reaction.

[0041] In some embodiments, in step S3, the amount of mineralizing solution used, namely the amount of complexed calcium source solution and carbon source solution used, is determined comprehensively based on the quality of the saline soil to be treated, the target degree of mineralization, the concentration of mineralizing solution, the soil pore conditions, and the degree of utilization of reactants.

[0042] Furthermore, a stepwise mineralization treatment method is adopted when injecting the complexed calcium source solution and carbon source solution, that is, pre-mineralization treatment is performed first, followed by overall supplementary mineralization treatment. Specifically, a portion of the mineralization solution is used for pre-mineralization treatment of the soil, and the remaining mineralization solution is used for overall supplementary mineralization treatment after all soil pre-mineralization treatment is completed. The specific dosage and distribution method are determined according to the actual situation. The degree of transfer of mineralization solution between different depth areas of the soil is affected by the compaction state, permeability, and existing mineralization degree. In specific implementation, the solution addition ratio of each depth area can be adjusted according to the distribution of newly added calcium carbonate and the infiltration state at different depths; the uniformity of mineralization is evaluated by the dispersion of the newly added calcium carbonate content at different locations.

[0043] During mineralization injection, a mobile multi-nozzle sprayer is used to uniformly spray the current compacted area. The complexed calcium source solution and carbon source solution are stored separately and delivered in stages. The complexed calcium source solution is sprayed first, and after it has largely infiltrated and adsorbed and retained at the interface of the sheet-like template, the carbon source solution is then sprayed along the same area. Pre-mineralization of the current area is controlled to form initial calcium carbonate crystal nuclei and local mineralization connections, keeping the soil surface moist, granular, and compactable. After shallow roughening (e.g., 3-10 mm deep), the previous compacted area is covered, and the compaction of the previous area causes the soil particles in adjacent areas to interlock. After all areas have undergone pre-mineralization treatment, a small-dose, multi-stage, intermittent spraying method is used for overall supplementary mineralization treatment.

[0044] The pre-mineralization process is controlled by the principles of forming initial calcium carbonate crystal nuclei, maintaining soil surface moisture, and ensuring compactability. When persistent liquid accumulation, a continuous hard crystalline layer, or a significant decrease in permeability occurs on the soil surface, the amount of liquid sprayed per application should be reduced, the application interval between the complexed calcium source solution and the carbon source solution should be extended, or the pre-mineralization treatment in that area should be stopped.

[0045] During the pre-mineralization and overall supplementary mineralization processes, the concentrations of the complexed calcium source solution and carbon source solution used are determined based on the soil permeability, the existing degree of mineralization, and the infiltration state of the solution. The degree of mineralization at each stage is controlled by the single addition amount, the application interval, and the number of cycles.

[0046] In some embodiments, in step S4, low-salinity water is used to perform unidirectional seepage replacement on the mineralized saline soil to be treated. Utilizing the concentration gradient and seepage carrying effect, the byproduct soluble salts (such as sodium chloride) generated by the mineralization reaction, as well as the soluble salts remaining in the original soil, are carried out of the treatment area and discharged centrally. Specifically, after the final injection of the carbon source solution, the soil is allowed to stand to continue the mineralization reaction before low-salinity replacement. The replacement direction is determined according to experimental or engineering conditions; for example, low-salinity water is sprayed evenly from the top, flowing downwards through the mineralization treatment area and draining from the bottom. Low-salinity water refers to water with a conductivity lower than that of the leachate from the saline soil before treatment at 25°C. Preferably, the conductivity of the low-salinity water is no more than 30% higher than that of the leachate from the saline soil before treatment, more preferably no more than 20%. The low-salinity water is preferably deionized water or low-mineralization water that meets the above requirements. Natural drainage and low-salinity replacement drainage during the mineralization process should be collected separately to avoid mixing the two types of drainage for evaluation.

[0047] It should be noted that "removing soluble salts" should be understood as significantly reducing the soluble salt content in the soil to the expected level, rather than requiring the complete absence of any soluble salts in the soil. In actual engineering, due to factors such as soil structure, seepage path, and replacement efficiency, the residue of a small amount of soluble salts is unavoidable and does not affect the implementation of the technical solution of this application or the realization of the expected technical effect.

[0048] In some embodiments, in step S5, after unidirectional seepage replacement is completed, curing is performed, and the salt swelling rate, frost heave rate, capillary rise height, and strength retention rate after freeze-thaw cycles are measured. The calcium carbonate content is uniformly converted to the total dry solids mass benchmark of the corresponding saline soil to be treated before mineralization. The increase in calcium carbonate content is calculated by subtracting the calcium carbonate content before mineralization from the calcium carbonate content after treatment, and the uniformity of mineralization distribution is evaluated accordingly.

[0049] In summary, this application provides a method for inhibiting salt heave and frost heave in saline soil based on a sheet template-oriented induced discontinuous mineralized sheet network structure. This method uses muscovite as a sheet template to construct a near-horizontal oriented microscale induced interface in saline soil.

[0050] A mineralization reaction system was constructed using a calcium chloride-aspartic acid complex cementing solution and a sodium carbonate cementing solution. Sodium hydroxide was used to adjust the pH of the complexed calcium source solution to 9.5-10.0. Aspartic acid reacts with Ca through its carboxyl groups. 2+ The formation of calcium-aspartic acid (Ca-Asp) complex calcium sources regulates calcium ion release, as well as the nucleation, growth, crystal composition, and aggregation state of calcium carbonate. It also promotes the enrichment of calcium sources on the surface, edges, and micro-defects of the sheet template, and enhances the adhesion and effective bridging of mineralization products in the contact area between the sheet template and soil particles.

[0051] The concentrations, single application amounts, application intervals, and number of cycles of the complexed calcium source solution and carbon source solution are adjusted according to the basic properties of saline soil, such as its main ionic composition, salt content, and permeability.

[0052] In both indoor and engineering tests, the dosage of sheet templates was calculated based on the total dry solid mass of the sheet template and saline soil mixture, and a portion of the saline soil was replaced by an equal mass. In the engineering tests, the sheet templates were uniformly incorporated into each construction layer by metering and spreading the premixed material, mechanical mixing, paving and leveling, and compaction and orientation. Each construction layer was pre-mineralized with a small amount of complexed calcium source solution and carbon source solution to form initial calcium carbonate crystal nuclei at the sheet template interface and maintain the granular shape of the layer, making it compactable. After the previous construction layer was compacted, interlayer particle interlocking was formed. Most of the mineralization solution was replenished in a multi-cycle manner after all construction layers were completed, so that the mineralization products continued to grow along the sheet template interface and interlayer contact area. The concentrations of the complexed calcium source solution and carbon source solution used for layered pre-mineralization and overall replenishment mineralization were determined according to the soil permeability, the existing degree of mineralization, and the infiltration state of the solution. The degree of mineralization at each stage was controlled by the single addition amount, application time interval, and number of cycles.

[0053] The total amount of mineralized liquid in the project is determined based on the properties of the saline soil to be treated. The pre-mineralization amount of each layer and the overall replenishment amount are adjusted according to the pore conditions, infiltration status, cumulative liquid flow, and mineralization distribution of the test section in the construction layer. Mineralized products near adjacent sheet templates accumulate and precipitate, and locally connect to form a multi-layered, misaligned, and discontinuous mineralized sheet network structure.

[0054] A reverse-filtration drainage layer and perforated water collection pipes were installed at the bottom of the treatment area. After the final application of the carbon source solution, the soil was allowed to stand for reaction before low-salt water replacement and desalination. Natural drainage and additional low-salt water replacement solution were collected and measured separately during the mineralization process. The residual soluble salt content of the soil was measured separately after treatment. The resulting mineralized lamellar network structure weakens vertical capillary water and salt migration while retaining a certain seepage and desalination capacity, and improves soil strength and freeze-thaw stability.

[0055] The present application is further illustrated below through embodiments and related test experiments. In the detailed description below, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present application. However, it is apparent that one or more embodiments may be implemented without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict. All instruments, consumables, and reagents used in the following embodiments are commercially available unless otherwise specified.

[0056] The following section provides further explanation of this application in conjunction with indoor testing and engineering applications.

[0057] The indoor tests used columnar treatment units, where pretreated sheet templates were mixed with saline soil at the designed ratio and the moisture content was adjusted. The mixture was layered, leveled, and compacted in the same direction to give the sheet templates a horizontal or low-angle preferred orientation. Specific examples illustrate the specimen dimensions, material usage, dry density, and porosity.

[0058] The dosage of the sheet template is calculated based on the equivalent dry basis mass of the pretreated sheet template. In laboratory tests, the material is washed and dried to constant weight before weighing. For engineering construction, dried material can be used, or the equivalent dry basis mass can be calculated after removing free liquid and determining the moisture content. The complexed calcium source solution is prepared according to the formula of calcium chloride, aspartic acid, and sodium hydroxide, and the carbon source solution is sodium carbonate solution. The concentration, pH, pretreatment time, and weighing method of each component are detailed in the specific examples.

[0059] In the indoor columnar test, the mixture of sheet template and saline soil was layered into a cylindrical mold. After each layer was loosely laid, it was scraped back and forth in the same direction 3-5 times, and then compacted with a flat pressure head that matched the inner diameter of the mold. After completing one layer, the surface was slightly roughened before the next layer was laid to simulate the spreading, leveling and compaction orientation process in engineering.

[0060] The indoor columnar test employed a combination of layered pre-mineralization and overall supplementary mineralization. After each sample layer was compacted, a small amount of complexed calcium source solution was applied first. Once the solution had largely infiltrated, a carbon source solution was then applied to allow initial calcium carbonate crystal nuclei to form at the interface of the sheet-like template. After all sample layers were formed, multiple rounds of intermittent overall supplementary mineralization were performed. Specific solution concentrations, single application amounts, and number of cycles are described in the examples.

[0061] The liquid discharged from the bottom during the mineralization process is collected separately. After overall mineralization is completed, the mixture is first allowed to stand for reaction, followed by low-salinity replacement and subsequent curing. Low-salinity water refers to water with an electrical conductivity lower than that of a 1:5 soil-water extract of saline soil before treatment at 25°C; preferably, its electrical conductivity is not higher than 30% of that of the soil-water extract, more preferably not higher than 20%; the low-salinity water is preferably deionized water or low-mineralization water that meets the above requirements. Specific circulation times, dosage, discharge volume, replacement conditions, and curing regimes are detailed in the specific embodiments.

[0062] It should be noted that the replacement direction of unidirectional seepage replacement is determined based on experimental or engineering conditions. In indoor columnar tests, the low-salinity water flows unidirectionally from the bottom to the top of the sample and exits from the top. In engineering applications, the low-salinity water is uniformly sprayed from the top of the treatment area, passes through the mineralization treatment layer from top to bottom, and exits from the bottom. The indoor columnar test uses a bottom-up unidirectional seepage method because the sample size is small and the test water volume is limited, making it impossible to effectively utilize gravity for top-down seepage replacement. In engineering applications, with larger treatment areas and depths and sufficient water volume, a top-down spraying method can be used, utilizing gravity to allow the low-salinity water to pass through the treatment layer and be centrally discharged through the bottom drainage system.

[0063] Example 1

[0064] In this embodiment, a columnar processing unit with a diameter of 35 mm and a height of 80 mm was used, with a volume of approximately 76.97 mL. The total dry solids mass in each columnar processing unit was controlled at 123.1 ± 0.2 g to ensure that the samples in each columnar processing unit had consistent compaction and porosity conditions.

[0065] The total soluble salt content of the saline soil used was 1.50%, the pH was 8.3, the conductivity of the 1:5 soil-water extract was 4.8 mS / cm, and the permeability coefficient was 1.2 × 10⁻⁶. -6 m / s. Na in the extract + Ca 2+ Mg 2+ Cl - SO4 2- HCO3 - and CO3 2- The contents were 778, 150, 90, 1082, 700, 180 and 20 mg / L, respectively, mainly showing that they were chloride-sulfate composite saline soils.

[0066] The above ionic composition indicates that the Ca in the original saline soil... 2+ and CO3 2- HCO3 - The content is relatively low and cannot be used as the main reactant source for the formation of the calcium carbonate mineralization structure in this embodiment; SO4 2- and Mg 2+ The content is relatively high, which may affect Ca. 2+ The effective utilization of calcium carbonate and the calcium carbonate crystallization process are somewhat affected. Therefore, in this embodiment, the main calcium source and carbonate source are provided by an externally added complexed calcium source solution and carbon source solution, and a time-sharing and multi-stage application method is adopted to reduce the amount of calcium carbonate. 2+ With CO3 2- Rapid reaction at the top of the columnar processing unit. The complexed calcium source solution is a calcium chloride-aspartic acid complex cemented solution, in which Ca... 2+The concentration of aspartic acid was 1 mol / L, and the pH was adjusted to 9.8 using sodium hydroxide; the carbon source solution was a 1 mol / L sodium carbonate solution. Since the original soil could utilize Ca²⁺ and CO₃²⁻... 2- Both sources are relatively scarce, and the two solutions are used at the same concentration, so that the added Ca... 2+ With CO3 2- The molar ratio is approximately 1:1. Aspartic acid is used to chelate Ca. 2+ Slow down free Ca 2+ With CO3 2- The instantaneous reaction promotes the enrichment of calcium sources on the surface, edges, and contact area between the sheet template and soil particles. For the 80mm high columnar treatment unit used in this embodiment, 1mol / L mineralizing solution can provide sufficient mineralization dosage under multiple rounds of intermittent addition; by controlling the single addition amount and the application interval between the two solutions, high-concentration mineralizing solution is avoided from accumulating and precipitating in the upper part of the columnar treatment unit.

[0067] The sheet template is made of muscovite microflakes with a particle size of 0.2-0.3 mm, a thickness of 10-15 μm, and an aspect ratio of approximately 20. The muscovite is pretreated with a complexed calcium source solution, rinsed, and dried to constant weight before use, at a dosage of 3% of the total dry solid mass of the mixture. In each columnar treatment unit, approximately 3.7 g of the sheet template and approximately 119.3 g of the original saline soil are weighed out, and approximately 0.06 g of a composite salt with the same salt composition as the original soil is added. This ensures that after the muscovite replaces a portion of the saline soil, the initial soluble salt content of the mixture in each columnar treatment unit remains at approximately 1.50%. After thoroughly mixing the above solid materials, approximately 19.7 g of deionized water is added to maintain the moisture content of the mixture at approximately 16%, and the mixture is sealed and allowed to stand for 24 hours to allow the moisture to distribute evenly throughout the mixture. A uniform sample moisture content allows different test groups to have similar compaction conditions, pore state, and initial water absorption capacity, reducing the impact of initial moisture content differences on mineralization infiltration and mineralization distribution.

[0068] The conditioned mixture was divided into four equal layers and loaded into a columnar treatment unit. Each layer was loosely laid and leveled four times in the same direction, then compacted using a flat compactor to allow the muscovite to form a horizontal or low-angle dominant orientation under the action of leveling shearing and vertical compaction. After each layer was compacted, 5 mL of complexed calcium source solution was added evenly. After it had basically penetrated and the calcium-aspartic acid (Ca-Asp) complexed calcium source was adsorbed and retained at the muscovite interface, 5 mL of carbon source solution was added to form initial calcium carbonate crystal nuclei on the surface of the muscovite and in the contact area between the muscovite and soil particles. When the liquid had basically penetrated, the layer remained moist, and a continuous hard crystalline layer had not yet formed, the layer was slightly roughened, and then the next layer was filled and compacted.

[0069] After all four layers have been formed, 13 overall replenishment mineralization cycles are performed from the top of the mixture. In each cycle, 10 mL of complexed calcium source solution and 10 mL of carbon source solution are added sequentially, and the next liquid is added only after the previous liquid has basically seeped in. The total amount of complexed calcium source solution and carbon source solution used in each columnar treatment unit is 150 mL, which is equivalent to 15 equivalent mineralization cycles of 10 mL each.

[0070] During the mineralization process, the drain port at the bottom of the columnar treatment unit was kept open, and approximately 290 mL of naturally drained liquid was collected. A small amount of liquid that was not drained remained in the pores of the mixture and participated in the mineralization reaction. Some liquid was lost during the dripping, settling, and transfer processes. After the final application of the carbon source solution, the mixture was allowed to stand for 24 hours to allow calcium carbonate to continue crystallizing and growing.

[0071] After settling, 46 mL of low-salt water was introduced in reverse through the bottom drain of the columnar treatment unit at a flow rate of 0.10 mL / min, allowing the low-salt water to flow upwards through the mixture, carrying away some of the NaCl produced by the mineralization reaction and the soluble salts from the original soil. Approximately 46 mL of replacement liquid was collected during the replacement process and the settling drainage stage. After replacement, the mixture was sealed and cured at 20±2℃ for 7 days.

[0072] After curing, the salt swelling rate of the mixture decreased from 1.20% to 0.72%, the frost heave rate decreased from 3.50% to 2.28%, and the strength retention rate after 10 freeze-thaw cycles increased from 55% to 75%. The 24-hour capillary water rise height of the 80mm high parallel columnar treatment unit of the same specification decreased from 76mm to 52mm, and the residual soluble salt content of the treated soil was 0.98%.

[0073] Before mineralization, the calcium carbonate content of the mixture of muscovite and saline soil was 0.020%. After treatment, the newly added calcium carbonate contents in the upper, middle and lower parts were 10.28%, 9.98% and 9.68%, respectively, with an average of 9.98% and a coefficient of variation of 3.0%. This indicates that after layered pre-mineralization and overall supplementary mineralization, the calcium carbonate was distributed relatively evenly along the height of the columnar treatment unit.

[0074] Comparative Example 1

[0075] This comparative example uses the same columnar treatment unit, saline soil source, muscovite specifications, and formulations of complexed calcium source solution and carbon source solution as Example 1. For each columnar treatment unit, approximately 3.7 g of pretreated and constant-weight muscovite and approximately 119.3 g of original saline soil were weighed, and approximately 0.06 g of composite salt was added; the total dry solids mass was controlled at 123.1 ± 0.2 g. Deionized water was added at approximately 16% of the total dry solids mass, with approximately 19.7 g of water added to the mixture in each columnar treatment unit. The mixture was sealed and allowed to stand for 24 hours. The mixture was packed in four layers. After each layer was compacted, 5 mL of complexed calcium source solution and 5 mL of carbon source solution were added dropwise for pre-mineralization. After the four layers were formed, 13 overall replenishment mineralization cycles were performed, with 10 mL of complexed calcium source solution and 10 mL of carbon source solution added sequentially in each cycle. The total volume of each solution was 150 mL.

[0076] The drain port at the bottom of the columnar treatment unit remained open during the mineralization process, collecting approximately 290 mL of naturally drained liquid. The undischarged liquid remained in the pores of the mixture and participated in the reaction; a small amount of liquid was lost during operation. After mineralization, the mixture was near saturation. No additional low-salt water replacement was performed in this comparative example. After the final application of the carbon source solution, the mixture was allowed to stand for 24 hours, followed by sealed curing at 20±2℃ for 7 days.

[0077] After curing, the salt swelling rate of the mixture decreased from 1.20% to 0.86%, the frost heave rate decreased from 3.50% to 2.62%, and the strength retention rate after 10 freeze-thaw cycles increased from 55% to 70%. The 24-hour capillary water rise height of the 80mm high parallel sample of the same specification was 58mm, and the residual soluble salt content of the soil after treatment was 1.68%. The comparison between Example 1 and this comparative example shows that natural drainage during the mineralization process can remove some by-product salts, and additional low-salt water replacement can further reduce the residual soluble salt in the soil.

[0078] Comparative Example 2

[0079] This comparative example uses the same columnar treatment unit, saline soil source, complexed calcium source solution and carbon source solution formulation, mineralization solution addition method and curing conditions as Example 1, but without adding muscovite. Approximately 123.1 g of the original saline soil was weighed into each columnar treatment unit and prepared according to the same filling and compaction method as in Example 1.

[0080] To ensure that this comparative example has consistent initial sample preparation conditions with each treatment group containing muscovite, deionized water was added to each columnar treatment unit at approximately 16% of the dry weight of the saline soil, with an addition amount of approximately 19.7 g. After thorough mixing, the mixture was sealed and allowed to stand for 24 hours to allow the moisture to fully distribute within the soil. This step was used to standardize the initial water content, compaction conditions, and pore structure of each group before mineralization, reducing the impact of differences in sample moisture content on the infiltration of the mineralizing solution and the treatment effect.

[0081] The conditioned saline soil was divided into four layers of equal mass and placed into columnar treatment units. Each layer was loosely laid and leveled four times in the same direction, then compacted using a flat compactor. After each compaction, 5 mL of complexed calcium source solution and 5 mL of carbon source solution were added sequentially for pre-mineralization. After the liquid had largely infiltrated, the next layer was filled and compacted. After all four layers were formed, 13 overall replenishment mineralization cycles were performed from the top of the saline soil, with 10 mL of complexed calcium source solution and 10 mL of carbon source solution added sequentially in each cycle. The total amount of complexed calcium source solution and carbon source solution used in each columnar treatment unit was 150 mL.

[0082] During the mineralization process, the drain port at the bottom of the columnar treatment unit was kept open, and the naturally discharged liquid was collected separately. After the last application of carbon source solution, the mixture was allowed to stand for 24 hours, and then 46 mL of low-salt water was circulated in reverse through the drain port at a flow rate of 0.10 mL / min for replacement. After replacement, the mixture was allowed to stand and drain for 2 hours, and then sealed and cured at 20±2℃ for 7 days.

[0083] After curing, the salinity of the saline soil was 0.94%, the frost heave was 2.85%, the strength retention rate after 10 freeze-thaw cycles was 64%, and the capillary rise height of the 24-hour treatment unit of the same specification with a height of 80mm parallel column was 65mm.

[0084] Before mineralization treatment, the calcium carbonate content of the saline soil was 0.020%. After treatment, the newly added calcium carbonate contents in the upper, middle, and lower parts were 9.78%, 8.38%, and 6.98%, respectively, with an average of 8.38% and a coefficient of variation of 16.7%. Compared with Example 1, in the absence of muscovite, the distribution of newly added mineralized products in the height direction differed significantly, indicating that the muscovite interface is beneficial to improving the vertical uniformity of mineralized product distribution.

[0085] Example 2

[0086] This embodiment uses the same columnar treatment unit, saline soil source, mineralization solution formula, addition method and curing conditions as in Example 1. The amount of muscovite is increased to 6% of the total dry solid mass of the mixture of muscovite and saline soil to investigate the effect of the increased amount of muscovite on salt swelling, frost heave, water and salt migration and freeze-thaw stability.

[0087] The total dry solids mass in each columnar treatment unit was controlled at 123.1 ± 0.2 g. For each columnar treatment unit, approximately 7.4 g of muscovite, pretreated with a complexed calcium source solution, rinsed, and dried to constant weight, and approximately 115.6 g of the original saline soil were weighed, and approximately 0.11 g of a composite salt with the same salt composition as the original soil was added. The composite salt was used to compensate for the reduction in soluble salts in the original soil after the muscovite and other materials partially replaced the saline soil, ensuring that the initial soluble salt content in both this example and Example 1 remained at approximately 1.50%.

[0088] After thoroughly mixing the above solid materials, approximately 19.7 g of deionized water was added to maintain the moisture content of the mixture at approximately 16%. The mixture was then sealed and allowed to stand for 24 hours to allow the moisture to distribute evenly throughout the mixture. Using the same moisture content as in Example 1 helps to ensure that mixtures with different muscovite content have similar filling, compaction, and initial seepage conditions, reducing the impact of differences in moisture content on the seepage of the mineralized solution and the test results.

[0089] Since the source and main salt composition of the saline soil used in this embodiment are the same as those in Example 1, the Ca in the complexed calcium source solution... 2+ The concentration of aspartic acid was 1 mol / L, and the pH was adjusted to 9.8; the carbon source solution was a 1 mol / L sodium carbonate solution, so that the main variable between this example and Example 1 was the amount of muscovite added.

[0090] The mixture was divided into four layers of equal mass and loaded into the treatment unit. After each layer was loosely laid, it was leveled and compacted in the same direction. Then, 5 mL of complexed calcium source solution and 5 mL of carbon source solution were added dropwise for pre-mineralization, so that initial calcium carbonate crystal nuclei were formed on the surface of muscovite and in the contact area between muscovite and soil particles. After the liquid had basically seeped in, the layer remained moist, and no continuous hard crystalline layer had formed, the surface was slightly roughened and the next layer was filled in.

[0091] After all four layers were formed, 13 integral replenishment mineralization cycles were performed from the top of the mixture. In each cycle, 10 mL of complexed calcium source solution and 10 mL of carbon source solution were added sequentially. The total volume of complexed calcium source solution and carbon source solution used in each columnar treatment unit was 150 mL. After the final application of carbon source solution, the mixture was allowed to stand for 24 hours, and then 46 mL of low-salt water was purged in reverse at a flow rate of 0.10 mL / min from the bottom drain of the columnar treatment unit for replacement. After replacement, the mixture was allowed to stand and drain for 2 hours, and then sealed and cured at 20±2℃ for 7 days.

[0092] After curing, the salt swelling rate of the mixture decreased from 1.20% to 0.64%, the frost swelling rate decreased from 3.50% to 2.05%, and the strength retention rate after 10 freeze-thaw cycles increased from 55% to 79%. The 24-hour capillary rise height of the 80mm high parallel columnar treatment unit of the same specification decreased from 76mm to 45mm. Compared with Example 1, this example increased the amount of muscovite, providing more calcium-aspartic acid (Ca-Asp) complex calcium source enrichment and calcium carbonate nucleation interface, further inhibiting vertical capillary migration, salt swelling, frost swelling, and freeze-thaw strength loss.

[0093] Engineering Experiment

[0094] The engineering test section has a treatment area of ​​100m². 2 The total treatment thickness is 0.40m, divided into four construction layers, each 0.10m thick and compacted. The compacted dry density of the treated soil is approximately 1.65g / cm³.3 With an effective porosity of 35%, the total dry mass of the treated soil is calculated to be approximately 66.0 t, and the total effective pore volume is approximately 14.0 m³. 3 Muscovite was added at 3% of the total dry solids mass of the muscovite and saline soil mixture, replacing a portion of the saline soil by an equal mass. The dry mass of the muscovite was approximately 1.98 t, and the dry mass of the saline soil was approximately 64.02 t. After pretreatment with a complexed calcium source solution, the muscovite could be used after leaching and drying to constant weight, or the dosage could be determined based on the equivalent dry mass after leaching off free liquid and measuring moisture content. The air-dried fine soil used to prepare the muscovite premix was taken from the saline soil of this construction layer. The effective pore volume of the treated area was approximately 14.0 m³. 3 Before construction, a reverse filter layer, a gravel drainage layer, and a perforated water collection pipe are installed at the bottom of the treatment area.

[0095] Before construction, the total soluble salt content of the saline soil in the test section was measured to be 1.48%, mainly a chloride-sulfate composite saline soil. Combined with the original soil's Ca... 2+ Mg 2+ SO4 2- CO3 2- and HCO3 - Based on the main ionic composition and the permeability of the compacted soil layer, Ca was selected as the material for engineering mineralization. 2+ A complexed calcium source solution with a concentration of 0.5 mol / L and a pH of 9.8, and a carbon source solution with a concentration of 0.5 mol / L sodium carbonate were used. This concentration is lower than the 1 mol / L concentration used in the laboratory tests, which can slow down the rapid precipitation of the mineralized solution on the soil surface and near the spraying area, and prolong the migration distance of the effective reactants in the compacted soil layer. Based on the existing Ca in the original soil... 2+ The detection results of carbonate source were compared with those of complexed calcium source solution and carbon source solution according to the addition of Ca. 2+ and CO3 2- An approximate 1:1 ratio is applied; local original soil Ca 2+ CO3 2- and HCO3 - When the content is high, the amount of the corresponding mineralizing solution added should be reduced accordingly.

[0096] During construction, a portion of air-dried fine soil is first extracted from the saline soil of this construction layer and uniformly mixed with muscovite to form a premix. After the saline soil of this construction layer is loosely spread, the premix is ​​evenly spread on the soil surface using a spreading device equipped with a metering device. Then, a stabilized soil mixer or road mixer is used to mix it repeatedly in the longitudinal and transverse directions, ensuring that the muscovite is evenly incorporated into the entire thickness of this construction layer. After mixing, a grader is used to spread and level the mixture, and a road roller is used to compact it, causing the muscovite to form a dispersed, staggered, horizontal, or low-angle dominant orientation under the leveling shearing and vertical compaction action.

[0097] like Figure 2As shown, after each construction layer is compacted, a complexed calcium source solution is evenly sprayed using a mobile multi-nozzle sprayer. After standing for 2 hours to allow for basic infiltration and for the calcium-aspartic acid (Ca-Asp) complexed calcium source to be adsorbed and retained on the surface, edges, and in the contact area between muscovite and soil particles, a carbon source solution is then sprayed along the same area to form initial calcium carbonate crystal nuclei at the muscovite interface. Only a small amount of pre-mineralization is performed on each construction layer. When the surface layer remains moist, granular, and has not formed a continuous hard crystalline layer, a shallow roughening process of approximately 5 mm is performed, followed by the laying and compaction of the next construction layer.

[0098] The four construction layers and pre-mineralization were completed from bottom to top using the method described above. With a target increase in average calcium carbonate content of approximately 1.50% in the treated soil, and assuming an effective conversion rate of approximately 85% for the mineralization reactants, the total amount of complexed calcium source solution and carbon source solution used was determined to be approximately 23.3 m³ each. 3 The direct premineralization amount of each solution in the four construction layers, from bottom to top, is 0.30m. 3 0.35m 3 0.40m 3 and 0.45m 3 Total 1.50m 3 After all construction layers are completed, 21.8m of each type of mineralization solution remains. 3 Used for overall mineralization, and applied in 10 cycles, with each cycle spraying approximately 2.18 m of complexed calcium source solution and carbon source solution. 3 The interval between each cycle is 6 hours.

[0099] The mineralization solution was sprayed in strips and strokes, with appropriate overlap between adjacent sprays to avoid continuous concentrated application at the same location. The dosage of mineralization solution for each layer was adjusted based on the permeability of the original soil, the infiltration status after spraying, and the distribution of newly added calcium carbonate at different depths. When persistent sludge accumulation, continuous white crystalline layers, or significantly prolonged infiltration time occurred in localized areas, the amount of solution sprayed per unit area per application was reduced, and the application interval between the complexed calcium source solution and the carbon source solution was extended. The bottom drainage system remained open during mineralization, and the naturally drained solution was collected separately and not mixed with the subsequent low-salinity replacement solution for statistical purposes.

[0100] After the final application of the carbon source solution, the reaction was allowed to stand for 24 hours, followed by low-salt water replacement from the top of the treatment zone. The total amount of low-salt water was approximately 28.0 m³. 3 Spray evenly in four applications, each covering approximately 7.0 m. 3 Sufficient infiltration time is allowed after each spraying. The low-salinity water flows from top to bottom through each mineralization treatment layer, carrying reaction byproducts and some soluble salts from the original soil into the bottom gravel drainage layer, and then into the collection well through perforated collection pipes. After replacement, the treatment layer is covered with geotextile and kept moist for 7 days.

[0101] After treatment in the engineering test section, the salt swelling rate decreased from 1.18% to 0.74%, the frost heave rate decreased from 3.42% to 2.26%, the strength retention rate after 10 freeze-thaw cycles increased from 56% to 74%, the 24-hour capillary water rise height decreased from 75 mm to 51 mm, and the residual soluble salt content in the soil decreased from 1.48% to 0.99%. Before mineralization treatment, the calcium carbonate content of the muscovite and saline soil mixture was 0.020%; after treatment, the newly added calcium carbonate content in the four construction layers from bottom to top were 1.38%, 1.47%, 1.53%, and 1.62%, respectively, with an average of 1.50% and a coefficient of variation of 6.7%, indicating that the overall mineralization distribution in each construction layer was relatively uniform.

[0102] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for inhibiting salt heave and frost heave in saline soil based on a sheet-like template-induced discontinuous mineralized sheet network structure, characterized in that, Includes the following steps: Step 1: Prepare a mineralization solution for inducing a biomimetic mineralization reaction in the saline soil to be treated, wherein the mineralization solution includes a complexed calcium source solution and a carbon source solution; Step 2: Add the sheet template to the saline soil to be treated, mix, spread and compact layer by layer, so that the sheet template is evenly dispersed in the saline soil to be treated and forms a horizontal or low-angle directional arrangement in the saline soil to be treated; Step 3: During the layer-by-layer compaction process, a portion of the complexed calcium source solution and the carbon source solution are injected into each layer of the saline soil to be treated for pre-mineralization treatment. After all layers are compacted and pre-mineralized, the remaining complexed calcium source solution and the carbon source solution are injected into the saline soil to be treated in a cyclical manner for overall supplementary mineralization treatment. This allows the complexed calcium source in the complexed calcium source solution to react with the carbonate ions in the carbon source solution to generate calcium carbonate mineralization products. The calcium carbonate mineralization products grow along the surface and edges of the sheet template and form discontinuous sheet-like connections between adjacent sheet templates, thereby forming a discontinuous mineralized sheet network structure inside the saline soil to be treated. Step 4: Perform unidirectional seepage displacement on the mineralized saline soil to be treated to remove soluble salts; Step 5: Curing is carried out after the unidirectional seepage replacement is completed.

2. The method for inhibiting salt heave and frost heave in saline soil according to claim 1, characterized in that, The sheet-like template is muscovite; The muscovite has a particle size of 0.1mm-0.5mm, a thickness of 1μm-50μm, and an aspect ratio of ≥10. The amount of muscovite added accounts for 2%-6% of the total dry solid mass of the mixture of muscovite and the saline soil to be treated.

3. The method for inhibiting salt heave and frost heave in saline soil according to claim 1, characterized in that, Before adding the sheet template to the saline soil to be treated, the method further includes: taking a portion of the complexed calcium source solution to pre-impregnate the cleaned and dried sheet template, so that the complexed calcium source in the complexed calcium source solution is adsorbed onto the surface of the sheet template.

4. The method for inhibiting salt heave and frost heave in saline soil according to claim 3, characterized in that, The pre-soaking treatment time is 1.5-2 hours.

5. The method for inhibiting salt heave and frost heave in saline soil according to claim 1, characterized in that, The complexed calcium source solution is a complexed cementitious solution comprising calcium chloride and aspartic acid; The concentration of calcium ions in the complexing cement solution is 0.5-1.5 mol / L, the concentration of aspartic acid is 0.5-1.5 mol / L, and the molar ratio of calcium ions to aspartic acid is 1:(0.8-1.2). The pH of the complexed calcium source solution is 9.5-10.

0.

6. The method for inhibiting salt heave and frost heave in saline soil according to claim 1, characterized in that, The carbon source solution is a sodium carbonate cementing solution; The concentration of carbonate ions in the sodium carbonate cementing solution is 0.5-1.5 mol / L.

7. The method for inhibiting salt heave and frost heave in saline soil according to claim 1, characterized in that, The number of cycles is 5-20. In each cycle, the amount of the complexed calcium source solution and the carbon source solution applied is equal in volume.

8. The method for inhibiting salt heave and frost heave in saline soil according to claim 1, characterized in that, Before preparing the complexed calcium source solution and the carbon source solution, the method further includes: Collect saline soil to be treated, determine the basic property parameters of the saline soil to be treated, and determine the concentration, single application amount, application interval and number of cycles of the complexed calcium source solution and the carbon source solution based on the basic property parameters; The basic property parameters include salt content, water content, dry density, porosity, salt swelling rate, frost swelling rate, strength retention rate after freeze-thaw, and permeability.

9. The method for inhibiting salt heave and frost heave in saline soil according to claim 1, characterized in that, The mineralized saline soil to be treated was subjected to unidirectional seepage replacement using low-salinity water. The low-salinity water refers to water whose conductivity at 25°C is lower than that of the leachate from the saline soil to be treated before treatment.

10. The method for inhibiting salt heave and frost heave in saline soil according to claim 1, characterized in that, The step of adding the sheet template to the saline soil to be treated includes: pre-mixing the sheet template with a portion of the saline soil to be treated to form a premix, and then adding the premix to the remaining saline soil to be treated.

Images