A grouting material suitable for tunnel vault cavity and a preparation method thereof

Abstract

This invention discloses a grouting material suitable for tunnel arch cavities and its preparation method, belonging to the technical field of grouting reinforcement materials for geotechnical engineering. The grouting material comprises the following raw material components in parts by weight: 400-500 parts low-alkali silicate cement, 380-450 parts quartz sand, 50-120 parts active minerals, 20-30 parts strength activator, 2-7 parts pH adjuster, 0.3-1.2 parts solid-alkali flow stabilizer, 0.5-1.5 parts dispersant, 0.5-2.2 parts basalt fiber rod needles, and 180-200 parts water; the active minerals are a compound of microsilica powder and fly ash; the strength activator is a compound of calcium formate, calcium nitrate, and aluminum sulfate; the pH adjuster is a compound of citric acid and glucono-delta-lactone; and the solid-alkali flow stabilizer is a compound of polyepoxysuccinic acid, sodium polyacrylate, and hydroxymethyl chitosan. The grouting material provided by this invention can achieve dense filling and long-term reinforcement of voids in the tunnel arch. The preparation method is simple to operate and is suitable for large-scale application in tunnel construction sites.

Description

Technical Field

[0001] This invention relates to the field of grouting reinforcement materials for geotechnical engineering, and in particular to a grouting material suitable for tunnel arch cavities and its preparation method. Background Technology

[0002] During the excavation of surrounding rock, initial support, and secondary lining pouring, tunnels are highly susceptible to hidden cavities at the arch crown due to factors such as insufficient concrete compaction, surrounding rock settlement and deformation, and groundwater erosion. These cavities alter the stress distribution of the lining, causing localized stress concentration, which can lead to lining cracking, water leakage, and even lining detachment, seriously threatening the operational safety of the tunnel. Currently, ordinary silicate cement-based grouting materials are commonly used for tunnel arch grouting. However, this method has significant drawbacks in practical applications: First, there is a difficult-to-reconcile contradiction between the early strength and fluidity of the grout. To meet the requirements of high-level pumping construction at the arch crown, the fluidity of the grout needs to be increased. However, excessive fluidity can lead to grout loss due to sag, prolonged initial setting time, and poor compaction of voids. Increasing early strength to accelerate setting will result in higher grout viscosity, significantly reducing pumpability and making it difficult to reach deep voids at the arch crown. Second, traditional cement grout has a high alkalinity. An excessively high pH value can easily corrode the surrounding rock and the existing lining structure. Furthermore, it has poor bonding performance with some surrounding rock interfaces, resulting in insufficient durability. The industry often adjusts the pH value of grout by adding acidic components. However, acidic substances interfere with the normal hydration process of cement minerals, causing slow hydration and significant reduction in early strength, which fails to meet the engineering requirements of rapid consolidation after tunnel arch grouting and resistance to surrounding rock disturbance and groundwater erosion. Furthermore, existing grouting materials shrink considerably after hardening, easily forming micro-cracks again, making it difficult to achieve the expected reinforcement effect. Therefore, developing a dedicated tunnel arch grouting material with excellent fluidity, high early strength, and low alkali properties has significant engineering application value. Summary of the Invention

[0003] To address the technical shortcomings of existing tunnel arch grouting materials, such as the contradiction between fluidity and early strength, the slow setting caused by acid addition and pH reduction, and the large shrinkage of the grout body during drying, this invention provides a grouting material suitable for tunnel arch cavities and its preparation method.

[0004] This invention constructs a grouting system with low-alkali general-purpose silicate cement as the cementitious matrix, graded quartz sand as the rigid skeleton, active mineral components regulating the microstructure, multiple inorganic salts synergistically stimulating hydration, and compound dispersants optimizing rheological properties. The components work together to achieve comprehensive performance of the grout, including high fluidity, low bleeding, and early and high strength.

[0005] The grouting material of the present invention, applicable to tunnel arch cavities, comprises the following raw material components in parts by weight: 400-500 parts of low-alkali silicate cement, 380-450 parts of quartz sand, 50-120 parts of active minerals, 20-30 parts of strength activator, 2-7 parts of pH adjuster, 0.3-1.2 parts of solid alkali stabilizing agent, 0.5-1.5 parts of dispersant, 0.5-2.2 parts of basalt fiber rod needles, and 180-200 parts of water.

[0006] Preferred raw material ratio: 440-480 parts of low-alkali silicate cement, 400-430 parts of quartz sand, 70-100 parts of active minerals, 22-28 parts of strength activator, 3-6 parts of pH adjuster, 0.5-1.0 parts of solid alkali stabilizer, 6-9 parts of dispersant, 1.0-1.8 parts of basalt fiber rod needles, and 180 parts of water.

[0007] Further optimized raw material ratio: 460 parts low-alkali silicate cement, 415 parts quartz sand, 85 parts active minerals, 24.5 parts strength activator, 4 parts pH adjuster, 1.0 part solid alkali stabilizer, 7.5 parts dispersant, 1.5 parts basalt fiber rod needles, and 180 parts water.

[0008] The active mineral is a compound of silica fume and fly ash. Preferably, the silica fume and fly ash are compounded in a mass ratio of 1:(2~5). The silica fume has an average particle size of 0.1~0.3μm and a specific surface area of ​​18000~25000m2 / kg; the fly ash is preferably Grade I with a fineness of 45μm, a sieve residue of ≤12% on a square hole sieve, and a calcination vector of ≤5.0%. The active mineral is a compound of ultrafine silica fume and high-quality fly ash, which has both ultrafine filling effect and pozzolanic activity. On the one hand, it optimizes the particle size distribution of the mortar, improves the density and stability of the mortar, improves the rheological properties, and reduces bleeding and segregation; on the other hand, it undergoes a secondary hydration reaction with cement hydration products, refines the interfacial transition zone, and significantly improves the mechanical strength and impermeability durability of the grouting mortar.

[0009] The strength activator is a compound of calcium formate, calcium nitrate, and aluminum sulfate. Preferably, calcium formate, calcium nitrate, and aluminum sulfate are compounded in a mass ratio of 2:1:(0.5~1.5). Calcium formate plays an early strength-promoting role, accelerating the silicate hydration process and improving early strength; calcium nitrate further enhances the calcium source supply, stabilizes hydration products, and improves mid-term strength; aluminum sulfate plays an aluminum phase activating role, refining the hydration crystal structure and optimizing the interfacial bonding strength.

[0010] Specifically, these three inorganic salts synergistically regulate the hydration pathway of cement clinker minerals at the ionic level, achieving multiple acceleration effects on early hydration. Calcium formate dissociates formate ions, which significantly promote the rupture of the hydration film on the surface of tricalcium silicate, accelerating the dissociation of silicon-oxygen tetrahedra and the formation of hydrated calcium silicate gel, directly improving the early strength and development rate of the grout. Calcium nitrate introduces a large number of free calcium ions, increasing the supersaturation of calcium ions in the liquid phase, promoting the rapid crystallization and precipitation of calcium hydroxide, shortening the cement induction period, and accelerating the overall hydration process. Aluminum sulfate provides sulfate ions, reacting with aluminum phase minerals in the system to form ettringite, creating an early framework. Furthermore, aluminum ions can regulate the morphology of hydration products, making the gel structure more compact, while inhibiting early shrinkage of the hardened body. The combination of these three salts forms a multi-element excitation environment of organic anions, calcium ions, and sulfate ions, accelerating both silicate phase hydration and aluminate phase rapid reaction, enabling cement to achieve rapid setting and hardening even under low water-to-material ratio conditions, significantly improving the early strength and volume stability of the grouting material.

[0011] The pH adjuster is a compound of citric acid and glucono-delta-lactone. Preferably, citric acid and glucono-delta-lactone are compounded in an equal mass ratio. Citric acid and glucono-delta-lactone are weak organic acids. Citric acid plays a rapid pH neutralization and regulation role, quickly neutralizing the free alkali released during cement hydration and rapidly reducing the alkalinity of the slurry liquid phase; glucono-delta-lactone, relying on its hydrolysis-release properties, achieves long-term pH buffering stability, adapting to the acidic and alkaline environment throughout the cement hydration process; the compounding of the two achieves rapid pH adjustment. It has a stable two-way pH regulation function, which takes into account both the rapid initial pH balance of the grouting material and the long-term stability of the hydration environment.

[0012] Specifically, two weak organic acids synergistically regulate the hydration environment of the cement-active mineral composite system at the molecular and ionic levels, achieving precise and stable control of the pH value of the slurry liquid phase. Citric acid, containing multiple carboxyl functional groups, can rapidly dissociate hydrogen ions and precisely neutralize free OH- ions during hydration. - Simultaneously through the carboxyl group and Ca 2+ Al 3+ It forms a weak complex, which quickly inhibits the risk of crystal distortion of hydration products caused by excessive alkalinity; gluconolactone slowly hydrolyzes in water to release gluconic acid, gently and continuously replenishing hydrogen ions, stabilizing the pH value of the system in the long term, avoiding alkalinity rebound and drastic pH fluctuations in the later stage, and ensuring the smooth progress of the hydration reaction; at the same time, gluconate can moderately regulate the ionic activity of the liquid phase, avoiding excessive premature reaction of active mineral components, ensuring the continuous growth of strength in the later stage, and not affecting the long-term mechanical properties of the grouting material.

[0013] The solid-alkali flow stabilizer is composed of polyepoxysuccinic acid, sodium polyacrylate, and hydroxymethyl chitosan in a mass ratio of (3-6):(3-6):(1-3). Preferably, the mass ratio of polyepoxysuccinic acid, sodium polyacrylate, and hydroxymethyl chitosan is 2:2:1. Polyepoxysuccinic acid plays a role in alkalinity chelation and fixation, complexing free alkali metal ions in the system and stabilizing the alkalinity of the slurry liquid phase. Sodium polyacrylate optimizes the colloidal dispersibility of the slurry and inhibits particle agglomeration and sedimentation. Hydroxymethyl chitosan enhances the adsorption at the hydration interface, improves the water retention and flow stabilization capacity of the slurry, and is suitable for high-level gravity-flow grouting conditions in tunnel arches.

[0014] Specifically, these three polymeric additives in the solid-alkali flow stabilizer synergistically regulate the colloidal structure and alkali balance of the cement-active mineral composite slurry through ion chelation, colloidal dispersion, and interfacial adsorption, achieving multiple synergistic regulation of the system's alkalinity and rheological stability. Among them, the carboxyl and ether functional groups on the polyepoxysuccinic acid molecular chain can efficiently chelate free Ca in the system. 2+ OH - Plasma anchors free alkali components within the hydration gel network, inhibiting alkali migration and precipitation, stabilizing the weakly alkaline environment of the system, and mitigating the risk of alkali-aggregate reactions. Sodium polyacrylate adsorbs onto the surface of solid particles through its anionic groups, forming a double-layer repulsion effect, improving particle dispersion, preventing sedimentation and segregation of quartz sand and fiber aggregates, and enhancing the homogeneity of the slurry. Hydroxymethyl chitosan, with its polyhydroxy and amino hydrophilic groups, adsorbs water molecules and forms a flexible hydration film, improving the water retention of the slurry.

[0015] The dispersant is a compound of polycarboxylate superplasticizer and calcium lignosulfonate in a mass ratio of (4~6):1. Polycarboxylate superplasticizer has excellent dispersing and water-reducing effects, significantly reducing the water-to-material ratio of the grout and improving the density and mechanical strength of the aggregate. Calcium lignosulfonate also has the functions of assisting dispersion, water retention, and retarding setting, improving the workability of the grout, inhibiting bleeding and segregation, and preventing the grout from setting too quickly and affecting the grouting construction.

[0016] Specifically, under low water-to-material ratio conditions, the dispersant achieves high slurry flow and low bleeding through a triple effect of electrostatic repulsion, steric hindrance, and slurry stabilization. After being incorporated into the slurry, the polycarboxylate superplasticizer can be quickly adsorbed onto the surface of cement and mineral particles, uniformly imbuing the solid particles with a negative charge. The strong electrostatic repulsion between particles due to the same charge effectively breaks down the flocculated agglomeration structure formed by van der Waals forces in cement, fully releasing the free water trapped within the flocs. This significantly improves slurry flowability under extremely low water consumption conditions, achieving highly efficient water reduction. Calcium lignosulfonate, as an auxiliary dispersant, has a longer molecular chain and forms a flexible adsorption layer on the particle surface, generating a steric hindrance effect that further prevents particle re-agglomeration. Simultaneously, it possesses a certain water-retention and thickening capacity, regulating slurry viscosity, inhibiting fine particle sedimentation, and preventing bleeding and stratification. When combined, the two form a complementary structure: polycarboxylate superplasticizer is responsible for efficient water reduction and improved fluidity, while calcium lignosulfonate is responsible for stabilizing the slurry and improving workability. Together, they solve the problems of high slurry viscosity, easy agglomeration, and poor stability under low water-to-material ratio.

[0017] The low-alkali silicate cement has an alkali content of ≤0.6% and a strength grade of P·O 42.5. By using 42.5 grade silicate cement with strictly controlled alkali content, the overall alkalinity of the system is significantly reduced while ensuring basic mechanical strength. Combined with quartz sand of a specific particle size distribution, a continuous and stable aggregate skeleton is formed, effectively inhibiting late-stage drying shrinkage cracking of the grout.

[0018] The quartz sand is 40-70 mesh, with a particle size range of 0.2-0.4 mm and a mud content of ≤1.0%.

[0019] The basalt fiber rods described are a type of basalt fiber material. They are needle-shaped, similar to steel fibers, and are easily and evenly dispersed after addition, significantly improving performance. A common drawback of ordinary basalt fibers used in this industry is that in concrete or cement-based materials, even slightly higher dosages are difficult to disperse evenly, tending to clump together and even having negative effects.

[0020] This invention also provides a method for preparing a grouting material suitable for tunnel arch cavities, the steps of which are as follows: (1) Raw material pretreatment: Low alkali silicate cement, active minerals, strength activator and dispersant are passed through a 200-mesh sieve; pH adjuster is ground to a particle size ≤40um; solid alkali stabilizer is prepared into a 20% aqueous solution; (2) Dry material premixing: Put the dry material components into the mixer and dry mix for 3~5 minutes at a speed of 80~120 r / min until they are evenly mixed to obtain a dry powder mixture; (3) Slurry preparation: Add water to the dry powder mixture and stir at a low speed of 150-200 r / min for 4-6 min; slowly add pH adjuster and stir for 2-3 min; then add solid alkali stabilizer aqueous solution and continue stirring for 3-5 min to obtain grouting slurry. Avoid excessive stirring to prevent premature coagulation of the slurry.

[0021] The resulting grouting material has an outlet flowability of 400~410mm, a 90min flowability of 350~360mm, a pH value of 9~11, a 1d compressive strength of 25MPa, and a 28d compressive strength of ≥50MPa. It also has strong adhesion to the lining concrete, enabling it to achieve dense filling and long-term reinforcement of the tunnel arch cavity.

[0022] Compared with the prior art, the advantages of the present invention are: (1) The grouting material of the present invention works synergistically by combining low-alkali silicate cement, active mineral components and strength activators and high-efficiency dispersants in a specific compound ratio. Under the premise of constructing a continuous and stable aggregate skeleton and ensuring high flowability and low bleeding of the grout, it significantly improves the early strength and high strength performance of the grout, effectively inhibits the later drying shrinkage cracking, greatly improves the volume stability and durability of the grouting material, and can better adapt to the complex construction conditions of tunnel arch cavity, thus broadening the engineering application scenarios of the grouting material.

[0023] (2) The grouting material of the present invention takes into account the characteristics of high flowability, early strength, low alkali and low shrinkage. Through multi-component functional synergistic design, it achieves high flowability to prevent collapse, low alkali control, stable early strength, and low shrinkage and crack resistance after hardening, thus meeting the grouting reinforcement requirements under high arch position, narrow space and complex hydrological conditions.

[0024] (3) The grouting material preparation method of the present invention is simple to operate and the process is controllable. It can make the components fully and evenly mixed, and stably produce grouting material with high flowability, low bleeding, early strength and stable volume, which can effectively meet the requirements of tunnel arch cavity grouting construction.

[0025] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0026] Figure 1 This is a morphological diagram of basalt fiber needles. Detailed Implementation

[0027] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0028] Example 1 A grouting material suitable for tunnel arch cavities, with the following component dosages by weight: The composition includes 460 parts low-alkali silicate cement, 415 parts quartz sand, 85 parts active minerals (28 parts microsilica powder, 57 parts fly ash), 24.5 parts strength activator (14 parts calcium formate, 7 parts calcium nitrate, 3.5 parts aluminum sulfate), 4 parts pH adjuster (2 parts citric acid, 2 parts glucono-delta-lactone), 1 part solid-alkali stabilizer (0.4 parts polyepoxysuccinic acid, 0.4 parts sodium polyacrylate, 0.2 parts hydroxymethyl chitosan), 7 parts dispersant (5 parts polycarboxylate superplasticizer, 2 parts calcium lignosulfonate), 1.5 parts basalt fiber rods, and 180 parts water. The low-alkali silicate cement is from Jiahua Special Cement Co., Ltd., and the polycarboxylate superplasticizer is from Sichuan Tieke New Building Materials Co., Ltd. The basalt fiber rods have a length of 12 mm, a diameter of 0.2 mm, and an apparent density of 2000 kg / m³. 3 Appearance Figure 1 As shown.

[0029] The preparation method is as follows: (1) Raw material pretreatment: Low alkali silicate cement, micro silica fume, fly ash, strength activator and dispersant are passed through a 200-mesh sieve; pH adjuster is ground to a particle size ≤40um; solid alkali stabilizer is prepared into a 20% aqueous solution.

[0030] (2) Dry material premixing: The pretreated low-alkali silicate cement, microsilica powder, fly ash, strength activator, dispersant, basalt fiber rod needles and quartz sand are put into a high-speed mixer and dry-mixed for 3-5 minutes until the solid powders are evenly mixed to obtain dry powder mixture.

[0031] (3) Slurry preparation: Add the required amount of water to the dry powder mixture and stir at low speed for 4-6 minutes; slowly add the pH adjuster and stir for 2-3 minutes; then add the solid alkali stabilizer aqueous solution and continue stirring for 3-5 minutes to obtain the grouting slurry.

[0032] Example 2 A grouting material suitable for tunnel arch cavities, with the following component dosages by weight: The composition includes 500 parts low-alkali silicate cement, 400 parts quartz sand, 85 parts active minerals (28 parts microsilica fume, 57 parts fly ash), 27 parts strength activator (14 parts calcium formate, 9 parts calcium nitrate, 4 parts aluminum sulfate), 4.8 parts pH adjuster (2 parts citric acid, 2.8 parts glucono-delta-lactone), 0.9 parts solid-alkali stabilizer (0.4 parts polyepoxysuccinic acid, 0.3 parts sodium polyacrylate, 0.2 parts hydroxymethyl chitosan), 7.5 parts dispersant (5.5 parts polycarboxylate superplasticizer, 2 parts calcium lignosulfonate), 1.5 parts basalt fiber rods, and 180 parts water. The low-alkali silicate cement is from Jiahua Special Cement Co., Ltd., and the polycarboxylate superplasticizer is from Sichuan Tieke New Building Materials Co., Ltd.

[0033] The preparation method is the same as in Example 1.

[0034] Example 3 A grouting material suitable for tunnel arch cavities, with the following component dosages by weight: The composition includes 400 parts low-alkali silicate cement, 450 parts quartz sand, 85 parts active minerals (28 parts microsilica fume, 57 parts fly ash), 23 parts strength activator (12 parts calcium formate, 8 parts calcium nitrate, 3 parts aluminum sulfate), 4.2 parts pH adjuster (2.2 parts citric acid, 2 parts glucono-delta-lactone), 0.7 parts solid-alkali stabilizing agent (0.3 parts polyepoxysuccinic acid, 0.2 parts sodium polyacrylate, 0.2 parts hydroxymethyl chitosan), 7.5 parts dispersant (5.5 parts polycarboxylate superplasticizer, 2 parts calcium lignosulfonate), 1.5 parts basalt fiber rods, and 180 parts water. The low-alkali silicate cement is from Jiahua Special Cement Co., Ltd., and the polycarboxylate superplasticizer is from Sichuan Tieke New Building Materials Co., Ltd.

[0035] The preparation method is the same as in Example 1.

[0036] Comparative Example 1 Compared with Example 1, no active minerals were added, but the types, mass fractions, and preparation methods of all other components were exactly the same.

[0037] Comparative Example 2 Compared with Example 1, the active mineral content was increased to 200 parts (the ratio of microsilica powder to fly ash was the same as in Example 1), while the types, mass fractions, and preparation methods of the other components were completely identical.

[0038] Comparative Example 3 Compared with Example 1, the active mineral component was reduced to 50 parts (the ratio of microsilica powder to fly ash was the same as in Example 1), while the types, mass fractions, and preparation methods of the remaining components were exactly the same.

[0039] Comparative Example 4 Compared to Example 1, the strength activator used only 24.5 parts of calcium formate, without using calcium nitrate and aluminum sulfate, while all other conditions remained the same.

[0040] Comparative Example 5 Compared with Example 1, the strength activator ratio was adjusted to 10.5 parts calcium formate, 10 parts calcium nitrate and 4 parts aluminum sulfate, with the total number of parts remaining at 24.5 parts, and all other conditions remained the same.

[0041] Comparative Example 6 Compared with Example 1, the pH adjuster was changed to 3 parts citric acid and 1 part gluconolactone, while the types, mass fractions and preparation methods of the other components were exactly the same.

[0042] Comparative Example 7 Compared with Example 1, 2 parts gluconolactone were replaced with 2 parts lactic acid, while the types, mass fractions and preparation methods of all other components were exactly the same.

[0043] Comparative Example 8 Compared with Example 1, 2 parts gluconolactone were replaced with 2 parts tartaric acid, while the types, mass fractions and preparation methods of all other components were exactly the same.

[0044] Comparative Example 9 Compared with Example 1, 2 parts gluconolactone were replaced with 2 parts oxalic acid, while the types, mass fractions and preparation methods of all other components were exactly the same.

[0045] Comparative Example 10 Compared with Example 1, the solid alkali flow stabilizer was adjusted to 0.3 parts of polyepoxysuccinic acid, 0.3 parts of sodium polyacrylate, and 0.4 parts of hydroxymethyl chitosan, while the types, mass fractions, and preparation methods of the remaining components were exactly the same.

[0046] Comparative Example 11 Compared with Example 1, the hydroxymethyl chitosan in the solid alkali flow stabilizer was replaced with an equal amount of sodium hydroxymethyl cellulose, while the types, mass fractions, and preparation methods of the other components were exactly the same.

[0047] Comparative Example 12 Compared with Example 1, the hydroxymethyl chitosan in the solid alkali flow stabilizer was replaced with an equal amount of hydroxyethyl chitosan, while the types, mass fractions, and preparation methods of the other components were exactly the same.

[0048] Comparative Example 13 Compared to Example 1, only 7 parts of polycarboxylate superplasticizer were used as the dispersant, while all other conditions remained the same.

[0049] Comparative Example 14 Compared with Example 1, the proportion of the dispersant was adjusted to 3 parts polycarboxylate superplasticizer and 4 parts calcium lignosulfonate, with the total number of parts remaining 7, while the other conditions remained the same.

[0050] Comparative Example 15 Compared with Example 1, 1.5 parts of basalt fiber rod needles were replaced with ordinary basalt fiber, while the types, mass fractions and preparation methods of the other components were exactly the same.

[0051] Comparative Example 16 Compared to Example 1, the low-alkali silicate cement was replaced with ordinary silicate cement, while the types, mass fractions, and preparation methods of all other components remained completely identical. The ordinary silicate cement was sourced from Jiahua Special Cement Co., Ltd.

[0052] The performance of the grouting materials obtained in Examples 1-3 and Comparative Examples 1-16 was tested, and the results are shown in Table 1.

[0053] Table 1 Performance test results of various grouting materials

[0054] As can be seen from the data in the table, the grouting materials of Examples 1-3 all have comprehensive properties of high flowability, low bleeding, early strength and high strength. Among them, Example 1 has the best performance in all aspects and is the optimal formulation of the present invention.

[0055] Comparative Examples 1, 2, and 3, through gradient adjustments of the active mineral component dosage, fully verified that there exists a reasonable dosage range for this component. Specifically, when no active mineral component was added or the dosage was too low, the particle size distribution of the system was insufficiently optimized, resulting in reduced fluidity, severe water bleeding, and a significant decrease in long-term durability. Conversely, excessive dosage diluted the cementitious system, inhibited the hydration reaction, and caused a significant reduction in early strength.

[0056] Comparative Example 4 used only calcium formate as a single strength activating component, omitting the combination of calcium nitrate and aluminum sulfate. Therefore, it failed to form a multi-ion synergistic regulation mechanism involving calcium and aluminum ions, exhibiting only limited early-stage coagulation acceleration effects. It was difficult to continuously activate the potential activity of the active mineral components, resulting in poor controllability of the slurry setting rate, lower overall compressive strength and interfacial bonding strength, and limited optimization of slurry fluidity and bleeding rate. Comparative Example 5, while maintaining the total amount of strength activating components unchanged, significantly increased the proportion of aluminum sulfate, altering the ratio of the ternary components. Excessive aluminum sulfate changes the pH of the slurry hydration environment, disrupts the formation pathway of hydration products, and easily forms unstable crystalline phases. This weakens the early-strength activation effect, reduces the strength of the hardened body and interfacial bonding performance, and also affects slurry stability, leading to increased bleeding rate and fluctuations in fluidity.

[0057] In Example 1, the pH adjuster used was a combination of citric acid and glucono-delta-lactone. Compared to Comparative Example 7 (citric acid + lactic acid), Comparative Example 8 (citric acid + tartaric acid), and Comparative Example 9 (citric acid + oxalic acid), Example 1 has significant advantages: citric acid can quickly regulate the initial pH, while glucono-delta-lactone achieves a gradual and stable decrease in pH through hydrolysis and slow release, avoiding the local over-acidity and pH fluctuation problems easily caused by directly dissociated acids such as lactic acid, tartaric acid, and oxalic acid; at the same time, the gluconic acid produced by the hydrolysis of glucono-delta-lactone has a mild chelating effect, which can moderately delay the early hydration exothermic reaction of the cementitious material and extend the construction window, without excessively inhibiting hydration like other acids, resulting in less negative impact on early strength and stable strength development in the later stages.

[0058] Compared to Example 1, the alkalinity stabilizing ability and flow-stabilizing dispersion effect of the solid-alkali flow stabilizer in Comparative Example 10 were weakened. This is because although the combination of polyepoxysuccinic acid and sodium polyacrylate has a certain dispersing effect, the proportion of hydroxymethyl chitosan is too high, which easily leads to an increase in system viscosity and a decrease in fluidity. In Comparative Example 11, hydroxymethyl chitosan was replaced with sodium hydroxymethyl cellulose, and in Comparative Example 12, hydroxymethyl chitosan was replaced with hydroxyethyl chitosan. Compared with these two comparative examples, Example 1 has significant advantages in terms of slurry fluidity, stability, and mechanical properties. The main reason is that hydroxymethyl chitosan has multiple functions of chelation, thickening, flow stabilization, and retarding. The carboxyl and amino groups on its molecular chain can form weak chelation with metal ions in the system. It can not only work synergistically with polyepoxysuccinic acid and sodium polyacrylate to achieve stable pH control of the slurry, but also form a uniform three-dimensional network structure, effectively inhibiting aggregate sedimentation and bleeding segregation, and improving the thixotropy and fluidity retention of the slurry. In contrast, sodium hydroxymethyl cellulose in Comparative Example 11 only has a single thickening and water-retaining effect, lacking chelation and hydration regulation capabilities. It cannot form a synergistic effect with polyepoxysuccinic acid and sodium polyacrylate, easily leading to problems such as excessively high slurry consistency or excessively rapid loss of fluidity. Hydroxyethyl chitosan in Comparative Example 12 has a non-ionic structure and weak chelation ability, resulting in insufficient regulation of the hydration process. It is difficult to achieve synergistic retarding with other components, leading to uneven early hydration heat release, affecting the construction window and later strength development. In contrast, the compound system containing hydroxymethyl chitosan used in Example 1 can ensure good workability of the slurry while gently delaying early hydration heat release, avoiding excessive retarding or rapid setting problems. It has a smaller negative impact on early strength, and the hydration products are denser, resulting in better long-term mechanical properties and durability. Overall, its performance is significantly better than that of Comparative Examples 11 and 12.

[0059] Comparative Example 13 used only polycarboxylate superplasticizer as a single component, without the addition of calcium lignosulfonate. Therefore, it only achieved basic particle dispersion and lacked the auxiliary effect of water retention and slurry stabilization. The slurry had insufficient water retention, was prone to bleeding and stratification, had poor fluidity stability, and increased defects in the interfacial transition zone after hardening, directly causing a decrease in interfacial bonding strength and compressive strength. Comparative Example 14, although a combination of polycarboxylate superplasticizer and calcium lignosulfonate, significantly increased the proportion of calcium lignosulfonate, resulting in a serious imbalance in the compounding ratio. Excessive calcium lignosulfonate had a significant retarding side effect, not only prolonging the setting time but also weakening the dispersing ability of the superplasticizer, leading to reduced slurry fluidity and increased bleeding rate, ultimately causing a significant deterioration in the overall mechanical properties and interfacial bonding performance of the hardened body.

[0060] Comparative Example 15 replaced basalt fiber rods with ordinary basalt fibers. Ordinary basalt fibers have a large specific surface area, poor dispersion stability, and are extremely prone to agglomeration. At the same volume dosage, they significantly reduce the fluidity of the slurry, weaken the effect of inhibiting shrinkage, and can only bridge microcracks, resulting in limited improvement in mechanical properties. The working performance and mechanical properties of the slurry are significantly weaker than those of Example 1.

[0061] Comparative Example 16 uses ordinary silicate cement to replace low-alkali silicate cement, which significantly increases the overall alkali content of the system. This makes it very easy for the system to react with the quartz sand aggregate, generating internal expansion stress during long-term service and directly increasing the risk of cracking in the later stages. At the same time, the high-alkali environment will disrupt the morphology of hydration products, increase the bleeding rate of the slurry, and reduce the fluidity stability, ultimately resulting in a significant deterioration of the interfacial bonding strength and long-term durability.

[0062] Application examples A tunnel entrance arch had a deficiency in lining thickness and void formation. Through high-frequency radar re-measurement and borehole verification, the minimum secondary lining thickness was measured to be 41 cm, and the maximum void depth was 19 cm. The void length was approximately 2 m, extending circumferentially from 1.4 m to 1.2 m to the right of the tunnel centerline (2.6 m wide). Tunnel grouting with formwork was employed to fill the void. The grouting material used was the one provided in this embodiment of the invention, and the construction was carried out according to the following steps: First, during the binding of the secondary lining reinforcement, grouting pipes and vent pipes are pre-embedded and fixed at the arch crown. Then, the lining formwork trolley is installed, the joints are sealed, and the secondary lining concrete is poured. After the concrete has initially set, the grout prepared according to the proportions of this invention is injected under low pressure through the pre-embedded grouting pipes, with the grouting pressure controlled at 0.2–0.4 MPa. After the vent pipe discharges continuous thick grout, the pressure is stabilized for 3–5 minutes, and then the hole is sealed to complete the grouting. This construction method is simple and controllable, effectively eliminating voids at the arch crown and significantly improving the overall density and structural durability of the secondary lining.

[0063] In summary, this invention provides a grouting material specifically designed for tunnel arches, possessing excellent fluidity, high early strength, and low alkali properties. By synergistically combining low-alkali silicate cement, active mineral components, and strength-enhancing components and dispersants in specific proportions, it significantly improves the early-strength and high-quality performance of the grout while ensuring a continuous and stable aggregate skeleton and high fluidity and low bleeding of the grout. This effectively inhibits later-stage drying shrinkage cracking and greatly improves the volume stability and durability of the grouting material. It is better suited to the complex construction conditions of tunnel arch cavities, thus broadening the engineering application scenarios of grouting materials.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A grouting material suitable for cavities in tunnel arches, characterized in that, The raw material components include the following parts by weight: Low-alkali silicate cement 400-500 parts, quartz sand 380-450 parts, active minerals 50-120 parts, strength activator 20-30 parts, pH adjuster 2-7 parts, solid alkali stabilizer 0.3-1.2 parts, dispersant 0.5-1.5 parts, basalt fiber rod needles 0.5-2.2 parts, water 180-200 parts; The active mineral is composed of a mixture of silica fume and fly ash. The strength activator is a compound of three components: calcium formate, calcium nitrate and aluminum sulfate. The pH adjuster is a compound of citric acid and gluconolactone; The solid alkali stabilizer is composed of polyepoxysuccinic acid, sodium polyacrylate and hydroxymethyl chitosan.

2. The grouting material for tunnel arch cavities as described in claim 1, characterized in that, The active mineral is composed of silica fume and fly ash in a mass ratio of 1:(2~5).

3. The grouting material for tunnel arch cavities as described in claim 1, characterized in that, The strength activator is a compound of calcium formate, calcium nitrate and aluminum sulfate in a mass ratio of 2:1:(0.5~1.5).

4. The grouting material for tunnel arch cavities as described in claim 1, characterized in that, The pH adjuster is a compound of citric acid and gluconolactone in equal mass ratios.

5. The grouting material for tunnel arch cavities as described in claim 1, characterized in that, The solid alkali stabilizer is composed of polyepoxysuccinic acid, sodium polyacrylate and hydroxymethyl chitosan in a mass ratio of (3-6):(3-6):(1-3).

6. The grouting material for tunnel arch cavities as described in claim 1, characterized in that, The dispersant is a compound of polycarboxylate superplasticizer and calcium lignosulfonate in a mass ratio of (4~6):

1.

7. The grouting material for tunnel arch cavities as described in claim 1, characterized in that, The low-alkali silicate cement has an alkali content of ≤0.6% and a strength grade of P·O 42.

5.

8. A method for preparing a grouting material suitable for tunnel arch cavities as described in any one of claims 1-7, characterized in that, The steps are as follows: (1) Raw material pretreatment: Low alkali silicate cement, active minerals, strength activator and dispersant are passed through a 200-mesh sieve; pH adjuster is ground to a particle size ≤40um; solid alkali stabilizer is prepared into a 20% aqueous solution; (2) Dry material premixing: Put the dry material components into the mixer and dry mix for 3-5 minutes until they are evenly mixed to obtain a dry powder mixture; (3) Slurry preparation: Add water to the dry powder mixture and stir for 4-6 minutes; slowly add pH adjuster and stir for 2-3 minutes; then add solid alkali stabilizer aqueous solution and continue stirring for 3-5 minutes to obtain grouting slurry.

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