Anti-permeation solidified soil for hydraulic engineering

Abstract

The application relates to the technical field of anti-permeation solidified soil and discloses an anti-permeation solidified soil for hydraulic engineering, which is mainly prepared from natural soil as a basic framework, composite cement, fly ash, industrial waste residue and other cementing and filling materials, and is supplemented with solidification aids and specific anti-permeation modifiers; the material significantly improves the mechanical properties and anti-permeation durability of the solidified soil through a double mechanism of chemical cementation and pore hydrophobization; based on the cross-scale synergistic design of the self-prepared amphiphilic organic silicon modified small molecule mixture and the amphiphilic POSS hybrid glass fiber, a multi-element coupling anti-permeation system of chemical anchoring, interface hydrophobization, nano filling and micro crack resistance is constructed; based on the above cross-scale synergistic design, the beneficial technical effects of reducing the permeability coefficient by 3 orders of magnitude and improving the compressive strength by 38% are simultaneously achieved.

Description

Technical Field

[0001] This invention relates to the field of anti-seepage solidification soil technology, specifically an anti-seepage solidification soil for water conservancy projects. Background Technology

[0002] In water conservancy projects, embankments and earth-rock dams often use solidified soil as a seepage barrier. The permeability coefficient of traditional cement-stabilized soil is typically 10. -5 -10 -4 cm / s (according to JGJ / T233-2011 and other regulations), which is less than 10 cm / s as required by high-standard seepage prevention projects. -7 The difference in cm / s (such as the technical requirements for concrete anti-seepage walls SL174-2014 "Technical Specification for Construction of Concrete Anti-seepage Walls in Water Conservancy and Hydropower Projects") is 2-3 orders of magnitude, mainly due to the presence of interconnected pores, microcracks, and hydrophilic capillary walls.

[0003] To improve impermeability, existing technologies attempt to introduce organosilicon hydrophobic agents (such as alkylsilanes). However, these modifiers mostly rely on physical adsorption (binding energy <30kJ / mol), resulting in poor durability. Furthermore, they only act on the surface (penetration depth <5mm), and high dosages (>0.1%) can inhibit cement hydration, leading to a significant decrease in strength. While nanomaterials (such as nano-SiO2) can fill pores, they are prone to agglomeration and difficult to disperse, and high-performance products are expensive (>500 yuan / kg), limiting their engineering applications. Existing composite modification schemes are mostly simple physical blends, with each component acting independently or even interfering with each other. They lack molecular-level synergistic design for anchoring, hydrophobicity, and reinforcement, failing to simultaneously address the contradictions between impermeability, strength, and crack resistance.

[0004] Therefore, there is an urgent need for a new type of impermeable solidification soil technology that can penetrate deep into the matrix, chemically anchor, and combine molecular-level hydrophobicity with micron-level reinforcement. Summary of the Invention

[0005] This invention forms a dense cementitious skeleton by compounding natural soil, industrial solid waste (fly ash, slag, gypsum) with a self-made specific impermeability modifier (amphiphilic organosilicon-modified small molecule mixture and / or amphiphilic POSS hybrid glass fiber). This material utilizes the sealing effect of the small molecule modifier on micropores and the bridging and control effect of the fiber on microcracks to synergistically improve the compressive strength and impermeability durability of the material at different scales. Under the condition of a total admixture of only 0.05%, the permeability coefficient can be reduced by 3 orders of magnitude and the compressive strength can be increased by 38%. It is suitable for seepage prevention treatment of water conservancy projects such as dikes and earth-rock dams.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A type of impermeable solidified soil for hydraulic engineering, comprising a foundation cementing system, an impermeable modifier, and mixing water: Based on 100% of the total dry mass, the basic cementitious system contains 50-70% natural soil, 5-15% cement, 10-30% fly ash, 1-5% industrial waste residue and 1-5% curing aid; The impermeability modifier accounts for 0.03-0.08% of the total dry mass of the base cementitious system; The mixing water has a water-to-solid ratio of 0.12-0.18; The impermeability modifier is an amphiphilic organosilicon-modified small molecule mixture PRAⅠ and / or amphiphilic POSS hybrid glass fiber PRAⅡ, specifically: When PRAⅠ is used alone, the dosage is 0.03-0.05%; When PRAⅡ is used alone, the dosage is 0.02-0.04%; When used in combination, PRAⅠ should be 0.02-0.03%, PRAⅡ should be 0.02-0.03%, and the total dosage should not exceed 0.05%.

[0007] Preferably, the amphiphilic organosilicon-modified small molecule mixture is prepared by a hydrosilylation reaction of vinyltrimethoxysilane, acrylic acid, sodium 2-acrylamido-2-methylpropanesulfonate, acrylamide, and triethylsilane in the presence of a platinum catalyst.

[0008] Preferably, the amphiphilic organosilicon-modified small molecule mixture comprises the following raw materials in parts by weight: 3 parts vinyltrimethoxysilane, 1.5 parts acrylic acid, 4.2 parts sodium 2-acrylamido-2-methylpropanesulfonate, 1.4 parts acrylamide, 0.06 parts polymerization inhibitor, and 11.6 parts triethylsilane.

[0009] Preferably, the amphiphilic POSS hybrid glass fiber is prepared by grafting vinyltrimethoxysilane, acrylic acid, sodium 2-acrylamido-2-methylpropanesulfonate, and acrylamide via a hydrosilylation reaction using the active Si-H bonds on the carrier and a platinum catalyst.

[0010] Preferably, the preparation method of the amphiphilic POSS hybrid glass fiber is as follows: Trichlorosilane was reacted with methanol, toluene, and n-hexane under ferric chloride / hydrochloric acid catalysis to prepare hydrogen-containing POSS, which was then hydrolyzed with tetraethylammonium hydroxide, capped with 3-chloropropyltrichlorosilane, and substituted with sodium azide to prepare heptahydromonazidopropyl POSS. Glass fiber was purified with acetone, aminated with KH-550, and then amidated with propynic acid under the action of an activator to obtain a reactive carrier with alkyne groups on its surface. Heptahydro-monazidopropyl POSS and alkyne-functionalized glass fibers undergo a click cycloaddition reaction catalyzed by copper sulfate / sodium ascorbate to anchor POSS onto the fiber surface, yielding an intermediate. Vinyltrimethoxysilane, acrylic acid, sodium 2-acrylamido-2-methylpropanesulfonate, acrylamide, and a platinum catalyst are then added to the system, followed by a hydrosilylation reaction to obtain amphiphilic POSS hybrid glass fibers.

[0011] Preferably, the natural soil is an equal volume mixture of clay and sand, passed through a 2mm sieve, with a liquid limit of 25-35% and a plastic limit of 15-20%. The industrial waste residue is one or more of S95 grade finely ground blast furnace slag, furnace slag, and coal slag, with a specific surface area ≥400m² / kg; The curing aid is desulfurized gypsum or phosphogypsum, with calcium sulfate dihydrate as its main component and a purity of ≥90%.

[0012] Preferably, the preparation method of the impermeable solidified soil for water conservancy projects includes the following steps: (1) Dry mixing: Add natural soil, cement, fly ash, industrial waste residue and curing agent into the mixer according to the formula ratio, and dry mix for 60 seconds to make the powder evenly dispersed; (2) Pretreatment with anti-permeability modifier: Amphiphilic organosilicon modified small molecule mixture: Weigh at a dosage of 0.03-0.05%, dilute with 10 times the mass of deionized water, adjust the pH to 4-5 with oxalic acid / citric acid, stir for 30 min for pre-hydrolysis, and use within 4 h; Amphiphilic POSS hybrid glass fiber: Weigh at a dosage of 0.02-0.04%, add 1 / 3 of the mixing water, disperse at 3000 rpm for 5 minutes, add 0.2% xanthan gum as a suspension stabilizer, and let stand for no more than 2 hours; (3) Wet mixing: Add the pretreated modifier 1 minute before adding the cement, mix it with the remaining mixing water and then add it to the dry material. Wet mix for 120 seconds until it reaches a uniform fluid state. (4) Molding and curing: The mold is filled in two layers, each layer is tamped and vibrated, the surface is covered with plastic film, and it is placed in a standard curing room at a temperature of 20±2°C and a relative humidity of ≥95% to cure until the specified age.

[0013] Preferably, the pre-hydrolyzed solution of the amphiphilic organosilicon modified small molecule mixture is added to the mixture 1 minute before the cement is added; The amphiphilic POSS hybrid glass fiber suspension is stirred again for 30 seconds before use to prevent sedimentation.

[0014] Preferably, the seepage prevention body of the water conservancy project includes dikes, earth-rock dams, sluice gate bottom slabs, and channel linings.

[0015] The beneficial effects of this invention are as follows: This invention is based on the cross-scale synergistic design of a self-made amphiphilic organosilicon modified small molecule mixture and amphiphilic POSS hybrid glass fiber, and constructs a multi-element coupled antipermeability system with chemical anchoring, interface hydrophobicity, nanofilling and micron crack resistance. In a preferred embodiment, the present invention uses a compound of PRAⅠ (0.03-0.05%) and PRAⅡ (0.02-0.03%), with a total admixture of only 0.05%, which can reduce the permeability coefficient of the solidified soil from 10 -5 The speed decreased to 10 cm / s. -8 The permeability is at the cm / s level, while the compressive strength is increased from 4.2MPa to 5.8MPa, achieving the technical effect of reducing the permeability coefficient by 3 orders of magnitude and increasing the compressive strength by 38%. Detailed Implementation

[0016] This invention provides an anti-seepage solidified soil for water conservancy projects, which is mainly composed of natural soil as the basic framework, cement, fly ash, industrial waste residue and other cementing and filling materials, and is supplemented with solidification aids and specific anti-seepage modifiers. This material significantly improves the mechanical properties and anti-seepage durability of the solidified soil through the dual mechanism of chemical bonding and pore hydrophobicity. The specific formulation of the solidified soil by weight is shown in Table 1 below; Table 1. Formulation of anti-seepage solidification soil for water conservancy projects

[0017] The preparation and chemical mechanism of the anti-permeability modifier are as follows: The amphiphilic organosilicon-modified small molecule mixture is prepared by a hydrosilylation reaction using vinyltrimethoxysilane, acrylic acid, sodium 2-acrylamido-2-methylpropanesulfonate, and acrylamide as double bond donors and triethylsilane as a silane-hydrogen donor, under the action of a platinum catalyst. Its molecules simultaneously contain hydrophilic groups (carboxyl, sulfonic acid, and amide groups) and hydrophobic groups (triethylsilyl and trimethoxysiloxane fragments), as well as hydrolyzable alkoxysilane groups. Based on this, in the alkaline porous environment of solidified soil, its hydrolyzable groups hydrolyze and condense with hydroxyl groups on the surface of soil particles / hydration products to form Si-O-Si chemical bonds; the hydrophobic groups arrange outwards to form a hydrophobic layer, blocking capillary water absorption channels. Amphiphilic POSS hybrid glass fiber is prepared by using heptahydro POSS-type glass fiber (i.e., glass fiber with a heptahydro cage-like silsesquioxane structure modified on its surface) as a reactive carrier. Utilizing the abundant active Si-H bonds on the carrier, monomers containing C=C double bonds (vinyltrimethoxysilane, acrylic acid, sodium 2-acrylamido-2-methylpropanesulfonate, acrylamide) are grafted onto the fiber surface via hydrosilylation reaction under the action of a platinum catalyst. This introduces a cage-like POSS structure and amphiphilic organic segments onto the fiber surface, combining the physical reinforcement of the fiber with the chemical hydrophobic modification function of organosilicon. Based on this, the fiber's bridging and microcrack control limit crack propagation, while the amphiphilic organic layer on the surface constructs a hydrophobic barrier at the fiber-matrix interface, further enhancing the system's impermeability and crack resistance. Example 1:

[0018] The composition formulations (by weight) of the amphiphilic organosilicon-modified small molecule mixtures are shown in Table 2 below; Table 2 Composition and Formulation of Amphiphilic Organosilicon Modified Small Molecule Mixtures

[0019] The preparation steps of the amphiphilic organosilicon-modified small molecule mixture are as follows: In a 250 mL three-necked flask equipped with a constant pressure dropping funnel, a reflux condenser, a magnetic stirrer, and a thermometer, add 0.06 g of 2,6-di-tert-butyl-p-methylphenol, 3 g of vinyltrimethoxysilane, 1.5 g of acrylic acid, 4.2 g of sodium 2-acrylamido-2-methylpropanesulfonate, 1.4 g of acrylamide, 80 mL of anhydrous ethanol, and 0.5 mL of isopropanol chloroplatinic acid solution. Start stirring and fully purge the reaction system with dry nitrogen for 30 minutes. Under nitrogen protection, heat the system and maintain it at 60°C. Slowly add 16 mL of triethylsilane (density approximately 0.728 g / mL, approximately 11.6 g) to the flask through a constant pressure dropping funnel, controlling the dropping time to 20 minutes. After the addition was completed, the reaction was stirred at 60°C for 8 hours. After the reaction was completed, 2g of activated carbon was added and stirred for 2 hours to adsorb. The activated carbon and the adsorbed platinum catalyst were removed by filtration. The filtrate was distilled under reduced pressure to recover ethanol. The residue was dried under vacuum at 60°C for 10 hours to obtain an amphiphilic organosilicon modified small molecule mixture. Among them, the amphiphilic organosilicon-modified small molecule mixture can be uniformly dispersed in the pore system of solidified soil under the action of mixing water. Its hydrophilic groups enhance its dispersibility and migration ability in pore water. After entering the pores, hydrolyzable groups such as trimethoxysiloxane in the molecules hydrolyze in alkaline pore water and condense with hydroxyl groups (especially silanol groups) on the surface of solidified soil particles and hydration products, forming Si-O-Si chemical bonds at the interface. Simultaneously, ionizable groups such as carboxyl and sulfonic acid groups are electrostatically adsorbed through hydrogen bonds, and polar groups such as amide groups further enhance interfacial anchoring through hydrogen bonding. As the molecules are fixed on the solid surface, trimethoxysiloxane... Low surface energy groups such as silicon-based and trimethoxysiloxane hydrolysis condensation fragments are arranged outward in an orderly manner to form a continuous hydrophobic layer on the pore wall, which significantly reduces the surface energy of the solid-water interface and increases the contact angle, thereby effectively inhibiting capillary water absorption and pore permeation. In addition, the presence of the hydrophobic layer reduces the effective water passage cross section of the pore, increases the tortuosity of the water flow path, and forms local micro-blocking at the pore throat through moderate cross-linking, further improving the overall impermeability. Since the organosilicon hydrophobic treatment does not block the pore channels and has good air permeability, this treatment allows water vapor to pass through while blocking liquid water infiltration, which helps maintain the internal moisture balance and durability of the solidified soil. Example 2:

[0020] The composition of the amphiphilic POSS hybrid glass fiber (by weight) is shown in Table 3 below; Table 3 Composition and formulation of amphiphilic POSS hybrid glass fibers

[0021] The preparation steps of amphiphilic POSS hybrid glass fibers are as follows: (1) Preparation of heptahydromonazopropyl POSS: Under nitrogen protection, 25 g of ferric chloride and 10 mL of concentrated hydrochloric acid were added to a 250 mL three-necked flask. After mixing, 20 mL of methanol, 25 mL of toluene, and 175 mL of n-hexane were added sequentially. The mixture was stirred for 30 min, and then 75 mL of n-hexane solution containing 10 mL of trichlorosilane was slowly added dropwise over a period of 6 h. After the addition was complete, the system temperature was maintained at 50°C, and the reaction was stirred for another 1 h. After the reaction was completed, the n-hexane layer was separated and filtered. 5 g of anhydrous calcium chloride and 7 g of anhydrous potassium carbonate were added to the filtrate. After stirring, the mixture was filtered again. The filtrate was distilled under reduced pressure at 45°C and concentrated until crystals just precipitated. The solution was then transferred to a refrigerator for cooling, and the crystals were collected and washed twice with n-hexane to obtain hydrogen-containing POSS. Subsequently, 2.06 g of hydrogen-containing POSS and 60 mL of tetrahydrofuran were added to a 250 mL round-bottom flask, stirred evenly, and then 2.0 mL of 35% tetraethylammonium hydroxide aqueous solution was added. The mixture was refluxed at 66 °C for 4 h. 1.7 mL of 10% dilute hydrochloric acid was added to neutralize the reaction solution, and the solvent was removed by rotary evaporation. The residue was placed in 50 mL of diethyl ether, treated with anhydrous magnesium sulfate, and filtered to obtain heptahydrotrihydroxy POSS. Next, 1.59 g of heptahydrotrihydroxy POSS was added to 20 mL of anhydrous tetrahydrofuran and stirred until completely dissolved. After the system was sealed to remove water and oxygen, it was placed in an ice-water bath. 4 mL of triethylamine was added to the system and stirred until well mixed. Then, 20 mL of anhydrous tetrahydrofuran solution containing 0.9 g of 3-chloropropyltrichlorosilane was slowly added dropwise. After 30 min, the ice-water bath was removed, the reaction system was heated to 25 °C, and the reaction was continued for 4 h. The mixture after the reaction was filtered, and the filtrate was concentrated into a saturated solution using a rotary evaporator. The solution was added dropwise to 60 mL of ice-cold anhydrous methanol while it was being stirred. After the addition was completed, the mixture was allowed to stand overnight, filtered, and dried to obtain heptahydromonochloropropyl POSS. Finally, 4 g of heptahydromonochloropropyl POSS and 0.6 g of sodium azide were added to 40 mL of N,N-dimethylformamide and stirred until completely dissolved. The mixture was reacted at room temperature for 24 h under nitrogen protection. After the reaction was complete, the solution was concentrated by rotary evaporation, then added to 100 mL of deionized water, filtered, and vacuum dried at 40 °C for 24 h to obtain heptahydromonochloropropyl POSS, whose chemical structural formula is as follows: ; The 1H NMR spectrum of heptahydropropyl azidopropyl POSS is characterized as follows: 1 HNMR (CDCl3, 400MHz) δ: 1.61-1.68 (m, 4H), 3.22-3.26 (m, 2H), 3.56 (s, 3H), 3.61 (s, 3H), 3.75 (s, 1H); (2) Preparation of alkyne-functionalized glass fiber carrier: Add 5g of glass fiber (10μm in diameter and 40μm in length) and 50mL of acetone to a three-necked flask, reflux at 70°C for 2h, filter, and dry at 80°C for 24h to complete the purification. 5g of purified glass fiber was placed in 100mL of 2% KH550 ethanol solution, mixed well, refluxed at 80°C for 2h, filtered, washed 3 times with anhydrous ethanol, and dried at 120°C for 12h to obtain amino-functionalized glass fiber. 5g of amino-functionalized glass fiber was ultrasonically dispersed in 50mL of N,N-dimethylformamide, 0.6g of propynic acid and 1.8g of N,N'-dicyclohexylcarbodiimide (DCC) were added, the system temperature was raised to 80°C, the reaction was stirred for 6h, cooled to room temperature, the solvent was removed by vacuum distillation, the glass fiber was washed three times with ethanol and deionized water respectively, and dried under vacuum at 50°C to constant weight to obtain alkynyl-functionalized glass fiber. (3) Click hybridization and amphiphilic functionalization modification: 4.34 g of heptahydromonoazidopropyl POSS and 5 g of alkynyl-functionalized glass fiber were added to 80 mL of N,N-dimethylformamide and ultrasonically dispersed. 5 mL of an aqueous solution containing 0.1 g of copper sulfate and 0.25 g of sodium ascorbate was added as a catalytic system. The mixture was reacted at 25°C for 24 h under a nitrogen atmosphere to carry out a click cycloaddition reaction, anchoring POSS to the fiber surface and obtaining a heptahydroPOOSS-type glass fiber intermediate. Subsequently, 0.08 g of 2,6-di-tert-butyl-p-methylphenol, 4.5 g of vinyltrimethoxysilane, 2.2 g of acrylic acid, 4.1 g of sodium 2-acrylamido-2-methylpropanesulfonate, 1.4 g of acrylamide, and 1.5 mL of isopropanol solution of chloroplatinic acid (0.02 g / mL) were added to the system. The system temperature was raised to 60°C, and the reaction was stirred for 8 h to carry out hydrosilylation grafting. After the reaction was completed, the solvent and low-boiling substances were removed by vacuum distillation. The mixture was washed four times with anhydrous ethanol and deionized water, respectively, and then dried under vacuum at 50°C to constant weight to obtain amphiphilic POSS hybrid glass fibers. The antipermeability mechanism of amphiphilic POSS hybrid glass fiber is as follows: amphiphilic POSS and organosilicon chains are grafted onto the fiber surface through click chemistry and hydrosilylation. The hydrophilic groups (carboxyl groups, sulfonic acid groups, amide groups) face the matrix to form good adhesion, while the hydrophobic segments and trimethoxysiloxane face the pores and hydrolyze and condense in alkaline pore water to form Si-O-Si chemical bonds and a low surface energy hydrophobic barrier, which reduces the surface energy of the solid-water interface and inhibits capillary water absorption. The hydrophobic layer does not clog pores and maintains air permeability; micron-sized glass fibers are distributed in three dimensions in the solidified soil, bridging and constraining the initiation and propagation of microcracks, reducing the formation of interconnected cracks, and blocking seepage channels; the POSS rigid Si-O cage forms a nano-reinforcement zone at the fiber-matrix interface, improving the local modulus and interfacial bonding strength, inhibiting interfacial microcracks, and limiting the migration of water along the interface; the POSS-fiber hybrid inhibits the formation of interconnected macropores through physical occupation and template effect, promotes pore size refinement, and works synergistically with the hydrophobic layer on the fiber surface to form a multi-layered anti-seepage system of physical barrier and hydrophobic barrier, significantly reducing the effective permeability coefficient and water absorption rate. Example 3:

[0022] The basic formula (by weight parts) for anti-seepage solidification soil used in water conservancy projects is shown in Table 4 below; Table 4. Basic Formula for Impermeable Solidified Soil Used in Water Conservancy Projects

[0023] The preparation process of anti-seepage solidified soil for water conservancy projects is as follows: Dry mixing: Add natural soil, cement, fly ash, industrial waste residue and curing additives to the mixer according to the formula weight parts, turn on the mixer to dry mix, and control the dry mixing time to 60 seconds to ensure that each powder component is evenly dispersed. Pretreatment with impermeable modifier: For the two different impermeable modifiers, the following pretreatments were performed respectively: Amphiphilic organosilicon modified small molecule mixture: Weigh accurately according to the designed dosage, dilute with 10 times the mass of deionized water in advance, adjust the pH value to 4-5 with oxalic acid / citric acid, and stir continuously for 30 minutes to promote the pre-hydrolysis reaction to obtain a pre-diluted solution (this solution has limited stability and a shelf life of <4h, and must be prepared and used immediately). Amphiphilic POSS hybrid glass fiber: Weigh precisely according to the designed dosage, add to part of the mixing water, and disperse using a high-speed disperser at 3000 rpm for 3 minutes to obtain a uniform suspension; In order to prevent the fiber from settling during the standing process, 0.1% (relative to the mass of the mixing water) of xanthan gum can be added to the suspension as a thickening suspending agent. Wet mixing: Add the pretreated modifier liquid (organosilicon pre-diluted liquid and fiber suspension) 1 minute before adding the cement, then add it to the dry material, turn on the mixer for mechanical mixing, and control the wet mixing time to 120 seconds to ensure that the mixture reaches a uniform, clumping fluid state. Molding and curing: The mixture is placed into a mold in two layers (φ50mm×50mm, height-to-diameter ratio 1.0). Each layer is tamped and compacted on a vibrating table. After molding, the surface is immediately covered with plastic film to prevent moisture evaporation. Then it is placed in a standard curing room (temperature 20±2°C, relative humidity ≥95%) for curing until the specified age (e.g., 7 days, 28 days). Example 4:

[0024] The specific implementation formula of anti-seepage solidification soil for water conservancy projects (by weight parts) is shown in Table 5 below; Table 5. Specific Examples and Comparative Examples of Anti-seepage Stabilized Soil for Hydraulic Engineering Performance testing:

[0025] I. Compressive strength and freeze-thaw resistance test According to JGJ / T233-2011 "Specification for Cement-Soil Mix Design", the 28-day compressive strength of the specimens (using φ50mm×50mm cylindrical standard specimens with a height-to-diameter ratio of 1.0) was tested. The specific method was as follows: the mixture was layered and poured into the mold and compacted, the surface was covered with plastic film, and cured in a standard curing room (temperature 20±2℃, relative humidity ≥95%) until the specified age; the specimens were removed, the surface moisture was wiped dry, and the compressive strength test was carried out on a universal testing machine. The strain rate was controlled at 1.0% / min (approximately 0.5mm / min); the compressive strength = maximum failure load / specimen compression area. According to GB / T50082-2009 and SL237-1999, the samples were subjected to freeze-thaw cycles. The specific method was as follows: the rapid freezing method was used, and 50 cycles (F50) were performed under the conditions of freezing in air at -18℃ for 4 hours and thawing in water at 20℃ for 4 hours. The compressive strength loss rate after the cycle was tested. The test results are shown in Table 6 below; Table 6. Compressive strength and freeze-thaw cycle test results of impermeable solidified soil for water conservancy projects.

[0026] II. Permeability Coefficient Test The permeability coefficient of the specimens was tested at 28d, 90d and 180d in accordance with GB / T50123-2019 "Standard for Geotechnical Testing Methods" and ASTM D5084. For permeability coefficients expected to be <10 -6 For samples with a flow rate of cm / s, the steady-state method using a flexible wall permeameter was employed: a confining pressure of 200 kPa and a back pressure of 100 kPa were set to ensure a sample saturation B-value ≥ 0.95, and the pressure gradient was controlled within 50 to avoid hydraulic fracturing, thus ensuring accurate determination of 10 -8 Low permeability coefficient at the cm / s level; For permeability coefficient >10 -5 For samples with a flow rate of cm / s, the variable head method was used for determination. The test results are shown in Table 7 below; Table 7. Test results of permeability coefficient of impermeable solidified soil for water conservancy projects

[0027] III. Contact Angle and Water Absorption Rate Test According to ISO 19403, the contact angle of the sample was tested using an optical contact angle meter (lying drop method). The specific method is as follows: the sample was rapidly frozen in liquid nitrogen and then broken by tapping to expose the undisturbed internal surface. The sample was then dried in a vacuum drying oven at 40°C (absolute pressure <1 kPa) for 24 hours. The sample was then placed on a stage, and 10 μL of deionized water was added using a micro-syringe. The droplet image was captured immediately, and the left and right contact angles were calculated by fitting the profile using software. The average value (apparent contact angle) was then taken. According to GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the water absorption rate (24h) of the sample was tested. The specific method is as follows: the sample was vacuum dried to constant weight at 40℃ and weighed (m0). Then, it was immersed in water at a temperature of 20±5℃, with the water level at least 20mm above the top surface of the sample, and kept for 24 hours. After the sample was removed, it was hung to drain for 2 minutes, and the surface water was gently absorbed with a wrung-out damp sponge. The sample was weighed immediately (m1). The water absorption rate of the sample was calculated as W = [(m1-m0) / m0]×100%. The test results are shown in Table 8 below; Table 8. Test results of contact angle and water absorption rate of anti-seepage solidified soil for water conservancy projects.

[0028] The above data represents the average value ± standard deviation of three parallel samples. The following conclusions can be drawn from the test results: (1) Gradient effect and optimal dosage of amphiphilic organosilicon-modified small molecule mixture PRAⅠ: As the dosage increased from 0.03% to 0.05%, the 28-day permeability coefficient increased from 6.2 × 10⁻⁶. -7 cm / s decreased to 8.5×10 -8 cm / s, reduced by about one order of magnitude, cumulatively reduced by about three orders of magnitude compared to the control, 0.05% doping is close to monolayer saturation coverage, contact angle reaches 128°, and has the best cost performance; Example 2 (0.05%) maintained a permeability coefficient of 7.8 × 10⁻ at 90 days and 180 days, respectively. 8 cm / s and 8.2×10 -8 The permeability coefficient was cm / s, which is on the same order of magnitude as the 28-day data, demonstrating excellent chemical anchoring stability; while Example 3 (0.08%) had a slightly lower initial permeability coefficient (9.1 × 10⁻⁶). -8 The permeability coefficient was 1.5 × 10⁻⁶ cm / s, but at 180 days it increased by 65% ​​compared to 28 days (to 1.5 × 10⁻⁶ cm / s). - 7The permeability reduction of PRAⅠ was approximately 39% after 28 days, and the strength after 28 days decreased by 6% (5.2 → 4.9 MPa) compared to Example 2. This indicates that excessive hydrophobic modification not only inhibits cement hydration, but also that insufficiently anchored free molecules may migrate with the pore fluid, leading to a decrease in long-term permeability resistance. Therefore, 0.05% is the optimal dosage of PRAⅠ. (2) Reinforcing effect and durability of amphiphilic POSS hybrid glass fiber PRAⅡ: The compressive strength of Example 4 reached 5.5 MPa, which was 31% higher than that of the comparative example, demonstrating the synergistic effect of fiber bridging and POSS nano-reinforcement; its 28-day permeability coefficient was 1.8 × 10⁻⁶. -7 cm / s, approximately 8.5 × 10 cm / s as in Example 2. -8 The strength of F50 is 2.1 times that of the control (cm / s), but still about 2.5 orders of magnitude lower than the control. After freeze-thaw cycles, the strength loss of F50 is only 4%, which is significantly better than the control (35%). This confirms the key role of fiber crack-resistant mechanism in maintaining structural integrity under harsh conditions and is suitable for environments with high stress or large temperature differences. (3) Synergistic effect of PRAⅠ and PRAⅡ combined use: Example 5 uses PRAⅠ (0.03%) and PRAⅡ (0.02%) combined, with a total dosage of only 0.05%, achieving significant synergistic effect; Mechanical properties: The 28-day compressive strength reached 5.8 MPa, which is 38% higher than that of the comparative example and superior to the single component (5.2 MPa in Example 2 and 5.5 MPa in Example 4). Impermeability: Permeability coefficient as low as 3.1×10⁻⁶ after 28 days. -8 The speed was reduced by approximately 3.2 orders of magnitude compared to the comparative example, which is superior to that of a single component (8.5 × 10⁻⁶ in Example 2). -8 cm / s, Example 4 is 1.8 × 10 -7 cm / s); Interface characteristics: Contact angle reaches 135°, water absorption rate is only 2.8% after 24 hours; Long-term durability: The permeability coefficient remains stable at 3.0 × 10⁻⁶ days. -8 cm / s, with no signs of decay; after F50 freeze-thaw cycles, the strength loss was only 3%, the best among all groups; This demonstrates that the physical constraint of fibers on microcracks and the chemical barrier of the hydrophobic layer against water intrusion work together to greatly improve the service life of materials in harsh hydraulic environments such as high water head, strong erosion, and large temperature difference.

Claims

1. A type of impermeable and solidified soil for hydraulic engineering, characterized in that, It consists of a basic cementitious system, an impermeable modifier, and mixing water: Based on 100% of the total dry mass, the basic cementitious system contains 50-70% natural soil, 5-15% cement, 10-30% fly ash, 1-5% industrial waste residue and 1-5% curing aid; The impermeability modifier accounts for 0.03-0.08% of the total dry mass of the base cementitious system; The mixing water has a water-to-solid ratio of 0.12-0.18; The impermeability modifier is an amphiphilic organosilicon-modified small molecule mixture PRAⅠ and / or amphiphilic POSS hybrid glass fiber PRAⅡ, specifically: When PRAⅠ is used alone, the dosage is 0.03-0.05%; When PRAⅡ is used alone, the dosage is 0.02-0.04%; When used in combination, PRAⅠ should be 0.02-0.03%, PRAⅡ should be 0.02-0.03%, and the total dosage should not exceed 0.05%.

2. The anti-seepage solidified soil for water conservancy projects according to claim 1, characterized in that, The amphiphilic organosilicon-modified small molecule mixture is prepared by a hydrosilylation reaction of vinyltrimethoxysilane, acrylic acid, sodium 2-acrylamido-2-methylpropanesulfonate, acrylamide, and triethylsilane in the presence of a platinum catalyst.

3. The anti-seepage solidified soil for water conservancy projects according to claim 2, characterized in that, The amphiphilic organosilicon-modified small molecule mixture comprises the following raw materials in parts by weight: 3 parts vinyltrimethoxysilane, 1.5 parts acrylic acid, 4.2 parts sodium 2-acrylamido-2-methylpropanesulfonate, 1.4 parts acrylamide, 0.06 parts polymerization inhibitor, and 11.6 parts triethylsilane.

4. The anti-seepage solidified soil for water conservancy projects according to claim 1, characterized in that, The amphiphilic POSS hybrid glass fiber is prepared by grafting heptahydroPOSS type glass fiber with vinyltrimethoxysilane, acrylic acid, sodium 2-acrylamido-2-methylpropanesulfonate, and acrylamide via hydrosilylation reaction using active Si-H bonds on the carrier and under the action of a platinum catalyst.

5. The anti-seepage solidified soil for water conservancy projects according to claim 4, characterized in that, The preparation method of the amphiphilic POSS hybrid glass fiber is as follows: Trichlorosilane was reacted with methanol, toluene, and n-hexane under ferric chloride / hydrochloric acid catalysis to prepare hydrogen-containing POSS, which was then hydrolyzed with tetraethylammonium hydroxide, capped with 3-chloropropyltrichlorosilane, and substituted with sodium azide to prepare heptahydromonazidopropyl POSS. Glass fiber was purified with acetone, aminated with KH-550, and then amidated with propynic acid under the action of an activator to obtain a reactive carrier with alkyne groups on its surface. Heptahydro-monazidopropyl POSS and alkyne-functionalized glass fibers undergo a click cycloaddition reaction catalyzed by copper sulfate / sodium ascorbate to anchor POSS onto the fiber surface, yielding an intermediate. Vinyltrimethoxysilane, acrylic acid, sodium 2-acrylamido-2-methylpropanesulfonate, acrylamide, and a platinum catalyst are then added to the system, followed by a hydrosilylation reaction to obtain amphiphilic POSS hybrid glass fibers.

6. The anti-seepage solidified soil for water conservancy projects according to claim 1, characterized in that, The natural soil is an equal volume mixture of clay and sand, passed through a 2mm sieve, with a liquid limit of 25-35% and a plastic limit of 15-20%. The industrial waste residue is one or more of S95 grade finely ground blast furnace slag, furnace slag, and coal slag, with a specific surface area ≥400m² / kg; The curing aid is desulfurized gypsum or phosphogypsum, with calcium sulfate dihydrate as its main component and a purity of ≥90%.

7. The anti-seepage solidified soil for water conservancy projects according to any one of claims 1-6, characterized in that, The preparation method of the impermeable solidified soil for water conservancy projects includes the following steps: (1) Dry mixing: Add natural soil, cement, fly ash, industrial waste residue and curing agent into the mixer according to the formula ratio, and dry mix for 60 seconds to make the powder evenly dispersed; (2) Pretreatment with anti-permeability modifier: Amphiphilic organosilicon modified small molecule mixture: Weigh at a dosage of 0.03-0.05%, dilute with 10 times the mass of deionized water, adjust the pH to 4-5 with oxalic acid / citric acid, stir for 30 min for pre-hydrolysis, and use within 4 h; Amphiphilic POSS hybrid glass fiber: Weigh at a dosage of 0.02-0.04%, add 1 / 3 of the mixing water, disperse at 3000 rpm for 5 minutes, add 0.2% xanthan gum as a suspension stabilizer, and let stand for no more than 2 hours; (3) Wet mixing: Add the pretreated modifier 1 minute before adding the cement, mix it with the remaining mixing water and then add it to the dry material. Wet mix for 120 seconds until it reaches a uniform fluid state. (4) Molding and curing: The mold is filled in two layers, each layer is tamped and vibrated, the surface is covered with plastic film, and it is placed in a standard curing room at a temperature of 20±2°C and a relative humidity of ≥95% to cure until the specified age.

8. The preparation method according to claim 7, characterized in that, The pre-hydrolyzed solution of the amphiphilic organosilicon modified small molecule mixture is added to the mixture 1 minute before the cement is added; The amphiphilic POSS hybrid glass fiber suspension is stirred again for 30 seconds before use to prevent sedimentation.

9. The application of the anti-seepage solidified soil for water conservancy projects according to any one of claims 1-6 in the seepage prevention body of water conservancy projects, characterized in that, The seepage prevention structure of the water conservancy project includes dikes, earth-rock dams, sluice gate bottom slabs, and channel linings.

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