Slurry material for large-diameter slurry shield and preparation process thereof

Abstract

The invention belongs to the technical field of mortar compositions, and particularly relates to a slurry material for a large-diameter slurry shield and a preparation process of the slurry material. The slurry material is prepared from the following components in parts by mass: 500 parts of water, 1.8 to 2.5 parts of polyacrylamide, 1.5 to 2 parts of sodium carbonate, 2.6 to 4 parts of aluminum salt, 15 to 30 parts of sodium bentonite, 7 to 12 parts of sepiolite powder, 3.5 to 6 parts of a modifier, 2 to 3.5 parts of an intercalator, 0.25 to 0.5 part of sodium metasilicate and 5.5 to 8.5 parts of a tackifier. Wherein the modifier is prepared from H4TCPP, pyridine and methanol according to the mass ratio of 1: (2-2.6): (10-13). The preparation process comprises the following steps: respectively preparing a solution, a suspension and the like, and then stirring the solution, the suspension and other components step by step to prepare the slurry material. The problems that when a traditional slurry material is used for large-diameter slurry shield construction, the film forming quality is poor, leakage is prone to occurring, and then the environmental protection property is poor are solved.

Description

Technical Field

[0001] This invention belongs to the technical field of mortar composition, specifically relating to a mortar material for large-diameter slurry shield tunneling and its preparation process. Background Technology

[0002] In recent years, my country's infrastructure construction has accelerated significantly. The development of underground spaces such as highways, railways, water conservancy projects, and urban municipal utility tunnels is in a golden age of rapid development. Slurry shield tunneling machines (SMTs) are increasingly widely used in river-crossing tunnel projects due to their excellent adaptability to geological formations, effective water pressure control, and efficient operation. Meanwhile, to meet the construction requirements of large-section single-tube tunnels, tunnels in water-rich strata such as those crossing rivers and seas, and underground projects in urban core areas with high requirements for surface settlement control, large-diameter SMT technology has received more attention. Currently, shield tunneling machines with a cutterhead excavation diameter of 5-7 meters are often referred to as conventional diameter shield tunneling machines, while those with a diameter of 10-14 meters are called large-diameter shield tunneling machines.

[0003] Compared to conventional diameter slurry shield tunneling machines, large-diameter slurry shield tunneling machines are often used in complex strata such as large cross-sections, deep burial depths, and areas with well-developed sand, gravel, karst, and fissures. The technical requirements are more stringent. Traditional bentonite-based slurry has the following drawbacks when used in large-diameter slurry shield tunneling: First, the mud film has poor pressure resistance and penetration resistance, making it unsuitable for the water pressure conditions of large-diameter slurry shield tunneling machines; second, the excavation face of large-diameter slurry shield tunneling machines is larger, requiring higher multi-scale grading sealing capabilities from the slurry. Traditional slurry struggles to form an effective mud film in highly permeable strata (such as coarse sand, gravel, and pebbles), leading to instability at the shield excavation face; third, the vertical height difference at the excavation face is greater, resulting in insufficient resistance to stratified settlement and easy pressure imbalance across the entire cross-section; finally, due to the above three drawbacks, traditional slurry is more prone to leakage, posing a greater environmental hazard. In summary, given the problems of poor film formation quality, easy leakage, and poor environmental performance of traditional bentonite-based mud when used in large-diameter slurry shield tunnels, it is essential to research a mud material suitable for large-diameter slurry shield tunnels.

[0004] Chinese patent CN109762534A discloses a mud system suitable for shield tunneling of extra-large diameter tunnels, comprising the following components by weight: 100 parts water, 5-6 parts dispersing and film-forming agent, 1-2 parts filtration loss reducer, 0.2-0.4 parts viscosity enhancer, 0.4-0.6 parts sealing agent, 0.02-0.03 parts selective flocculant, and 0.2-0.4 parts friction-reducing and mud-dissolving agent; wherein the dispersing and film-forming agent is sodium bentonite; the filtration loss reducer is low-viscosity sodium carboxymethyl cellulose; the viscosity enhancer is XC xanthan gum; the sealing agent is ultrafine calcium carbonate; the selective flocculant is polyacrylamide; and the friction-reducing and mud-dissolving agent is a compound of sodium dodecylbenzenesulfonate, polyoxyethylene octylphenol ether, and saponified oil.

[0005] This patent uses only polyacrylamide as a selective flocculant, without any supporting components for salt resistance, calcium resistance, and pollution resistance. It cannot meet the complex geological requirements of large-diameter slurry shield tunneling. This is because the flocculation effect of polyacrylamide alone is greatly affected by pH and formation water salinity. In high-calcium-magnesium hard water and salt-gypsum formations, it will chelate with calcium and magnesium ions, resulting in a decrease in flocculation performance. Summary of the Invention

[0006] The purpose of this invention is to provide a mud material for large-diameter slurry shield tunneling, aiming to solve the problems of poor film formation quality, easy leakage, and poor environmental performance of traditional bentonite-based mud when used in large-diameter slurry shield tunneling; this invention also provides a preparation process for the mud material.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The mud material for large-diameter slurry shield tunneling machines described in this invention is composed of the following components by weight: 500 parts water, 1.8-2.5 parts polyacrylamide, 1.5-2 parts sodium carbonate, 2.6-4 parts aluminum salt, 15-30 parts sodium bentonite, 7-12 parts sepiolite powder, 3.5-6 parts modifier, 2-3.5 parts intercalating agent, 0.25-0.5 parts sodium metasilicate, and 5.5-8.5 parts thickener; wherein the modifier is prepared by mixing 5,10,15,20-tetracarboxyphenylporphyrin, pyridine, and methanol in a weight ratio of 1:(2-2.6):(10-13).

[0008] in: The polyacrylamide has a weight-average molecular weight of 8 million to 12 million and a degree of hydrolysis of 15 to 35%.

[0009] The intercalating agent is octadecyl dimethyl allyl ammonium chloride; the thickener is composed of 0.5-1 parts potassium polyacrylate and 5-7.5 parts emulsifier SE-10.

[0010] The preparation process of the mud material for large-diameter slurry shield tunneling machines described in this invention includes the following steps: S1. Prepare a hydrolyzed polyacrylamide solution by mixing polyacrylamide, sodium carbonate, and water. S2. Prepare aluminum salt solution A and aluminum salt solution B by mixing aluminum salt and water respectively; S3. Sodium-based bentonite pretreatment, followed by preparation of bentonite suspension with water after pretreatment; S4. Prepare a suspension containing MOFs by using a modifier and aluminum salt solution A; S5. Mix hydrolyzed polyacrylamide solution, bentonite suspension, sepiolite powder, and sodium metasilicate, adjust pH, heat and add intercalating agent for one stirring, then add MOF-containing suspension for a second stirring, and finally add aluminum salt solution B, thickener and water for a third stirring. After the three stirrings are completed, let stand and age to obtain mud material.

[0011] in: In S1, the preparation process is as follows: under stirring conditions, polyacrylamide is dissolved in 100-120 parts of water to obtain solution A; sodium carbonate is dissolved in 20-30 parts of water to obtain solution B; while maintaining stirring of solution A, solution B is added to solution A, the temperature is raised, and the reaction is maintained at this temperature.

[0012] In S1, the stirring rate during the preparation of the hydrolyzed polyacrylamide solution is 60~120 rpm, the addition time of solution B is 15~30 min, the heat preservation temperature is 50~60℃, and the heat preservation time is 1.5~2.5 h.

[0013] In S2, when preparing aluminum salt solution A, the aluminum salt is aluminum chloride, with 0.6 to 1 part aluminum chloride and 60 to 70 parts water; when preparing aluminum salt solution B, the aluminum salt is aluminum sulfate, with 2 to 3 parts aluminum sulfate and 10 to 20 parts water.

[0014] In step S3, the pretreatment of sodium-based bentonite includes sequential air jet milling, drying, and sealed storage. During air jet milling, the air inlet pressure is 0.75~0.9MPa, and the drying temperature is 80~100℃. The bentonite suspension preparation process is as follows: At a stirring speed of 350~600rpm, the pretreated sodium-based bentonite is mixed with 150~200 parts of water. The stirring speed is reduced to 25~50rpm, and stirring is continued for 20~30min to obtain the bentonite suspension.

[0015] In S4, the preparation process is as follows: aluminum salt solution A and modifier are sequentially spread into a container; after the addition is complete, the container is kept at 140~150℃ for 50~60 minutes to obtain a suspension containing MOFs.

[0016] In S5, the pH is 7.5-8, the heating temperature is 75-85℃, the stirring rate is 60-80 rpm, and the stirring time is 2-3 hours.

[0017] In S5, the secondary stirring rate is 100~150 rpm and the secondary stirring time is 25~35 min; the tertiary stirring rate is 130~160 rpm and the tertiary stirring time is 5~8 min; the aging temperature is 40~45℃ and the aging time is 1~2 h.

[0018] The beneficial effects of this invention are as follows: (1) The mud film of traditional bentonite mud is formed by the disordered stacking of montmorillonite lamellae, which has a large number of nanoscale pores and structural defects. The mud film has poor pressure resistance and puncture resistance, and is prone to forming water seepage channels, which leads to plastic deformation or even puncture of the mud film. This invention improves the density, cohesion and water pressure deformation resistance of the mud film through multi-component synergy: Montmorillonite lamellae in sodium-based bentonite were hydrated and exfoliated through intercalation with octadecyldimethylallylammonium chloride. Multifunctional elements (MOFs) were prepared using 5,10,15,20-tetracarboxyphenylporphyrin, pyridine, and aluminum chloride. The montmorillonite lamellae and MOFs achieved a staggered and interlocked synergistic stacking through van der Waals forces, hydrogen bonds, and hydrophobic interactions. Aluminum sulfate and sodium metasilicate, through in-situ hydrolysis to generate precipitates (aluminum hydroxide and silica), acted as both fillers and binders in the synergistic stacking, achieving both densification and integration of the framework structure.

[0019] Montmorillonite lamellae provide a flat substrate and deformation buffer for rigid MOFs, avoiding the inherent brittleness and fragility of MOFs. The staggered stacking of MOFs and montmorillonite lamellae restricts the relative slippage and structural collapse of the montmorillonite lamellae, enhancing the overall deformation resistance of the mud film. Sodium metasilicate and aluminum sulfate can form precipitates to fill the gaps remaining after the staggered stacking of montmorillonite and MOFs. At the same time, the precipitates form hydrogen bonds and coordination with the silicon-oxygen bonds of the montmorillonite lamellae and the central ions of the MOF ligands through polar groups such as silanol groups. The precipitates cement the montmorillonite lamellae and MOFs into a continuous whole, eliminating weak interfacial bonding points between lamellae and preventing lamellae peeling and breakdown. The staggered stacking and composite of the three structurally blocks the water seepage and breakdown path of the montmorillonite lamellae.

[0020] (2) Large-diameter shield tunnels traverse gravel and coarse sand strata with large pores, good connectivity, and difficult particle compression, resulting in high permeability. Traditional bentonite can only achieve single-scale sealing at the micron level, and its multi-scale hierarchical sealing capability is insufficient. It is difficult to form a continuous mud film in coarse-grained strata, and mud loss is prone to occur. This system achieves effective sealing of complex strata through multi-stage sealing and composite synergistic film formation: When applied as drilling mud, sepiolite, a needle-like / fibrous silicate mineral with a high aspect ratio, can form a three-dimensional overlapping framework in complex strata. Hydrolyzed polyacrylamide undergoes coordination cross-linking with aluminum ions to form a three-dimensional flexible network. This network is adsorbed onto the three-dimensional overlapping framework at multiple points through hydrogen bonds, locking the loose fibrous framework into a stable whole. At the same time, montmorillonite monolayers, MOFs, and precipitates that have undergone intercalation modification and hydration exfoliation in sodium-based bentonite together form a composite structure. The three-dimensional flexible network, the composite structure, and the three-dimensional overlapping framework form an interwoven and stacked structure, effectively improving the leakage plugging performance of the mud film in complex strata with large pores, good connectivity, and high permeability. This significantly improves the overall flexural and deformation resistance of the mud film, maintaining the continuity of the mud film structure even under pressure fluctuations at the excavation face, preventing cracking and detachment, and ensuring the stability of the leakage plugging performance in multi-level pores.

[0021] (3) The vertical height difference of the excavation face of a large-diameter slurry shield tunnel is too large. Solid particles in traditional slurry are prone to settling under gravity, resulting in serious unevenness in the density, viscosity and support pressure of the slurry, which eventually leads to local instability of the excavation face: When applied to mud materials, this invention utilizes a three-dimensional flexible network of hydrolyzed polyacrylamide, a three-dimensional overlapping skeleton of sepiolite, and a composite structure formed by montmorillonite sheets, MOFs, and precipitation to create an interlocking and stacked structure. Through the organic combination of the flexible three-dimensional network, precipitation, and rigid MOFs and montmorillonite sheets, the interlocking and stacked structure is promoted to penetrate the excavation face, while effectively inhibiting the gravity settlement of the originally loose sodium bentonite-based mud. This avoids the loosening and collapse of the network structure under long-term static conditions and solves the problem of stratified settlement under large elevation differences. Detailed Implementation

[0022] The present invention will now be described and illustrated in detail with reference to the embodiments.

[0023] The raw materials used in the following examples and comparative examples are all commercially available products. Among them, potassium polyacrylate was provided by Shanghai Huayuan Century Trading Co., Ltd.; and polyacrylamide with a weight average molecular weight of 8 million to 12 million and a degree of hydrolysis of 15% to 35% was provided by Henan Guohong Water Treatment Materials Co., Ltd.

[0024] Example 1

[0025] The raw materials required for this embodiment are prepared in the following proportions by weight: 500 parts water, 1.8 parts polyacrylamide (weight average molecular weight of 12 million, degree of hydrolysis of 35%), 1.5 parts sodium carbonate, 0.8 parts aluminum chloride, 2.5 parts aluminum sulfate, 15 parts sodium bentonite, 7 parts sepiolite powder, 3.5 parts modifier, 2.5 parts octadecyl dimethyl allyl ammonium chloride, 0.3 parts sodium metasilicate, and 8.5 parts thickener (including 1 part potassium polyacrylate and 7.5 parts emulsifier SE-10); wherein the modifier is 5,10,15,20-tetracarboxyphenylporphyrin (H4TCPP), pyridine and methanol are prepared in a mass ratio of 1:2:13.

[0026] The specific preparation process steps are as follows: S1. At a stirring speed of 60 rpm, polyacrylamide was added to 100 parts of water and stirred until completely dissolved without lumps to obtain solution A; sodium carbonate was dissolved in 30 parts of water to obtain solution B. While maintaining the stirring speed of solution A at 60 rpm, solution B was slowly added to solution A and the addition was completed within 15 minutes; the temperature was raised to 55℃ and kept at that temperature for 2 hours. After the holding time was completed, the viscosity of the system was measured to be 35 mPa·s, which is consistent with the characteristics of non-Newtonian pseudoplastic fluid, thus obtaining a hydrolyzed polyacrylamide solution.

[0027] S2. Take 60 parts of deionized water, add 0.8 parts of aluminum chloride, and stir until completely dissolved to obtain aluminum salt solution A; take 10 parts of deionized water, add 2.5 parts of aluminum sulfate, and stir until completely dissolved to obtain aluminum salt solution B.

[0028] S3. Place sodium-based bentonite in an air jet mill and pulverize it under an inlet pressure of 0.75 MPa to remove obvious agglomerated particles. After pulverization, dry it at 80°C until constant weight, and then remove it after cooling to room temperature. Under stirring at 600 rpm, mix it with 200 parts of water until the sodium-based bentonite is free of adhering to the walls and agglomerates. Reduce the stirring speed to 50 rpm and continue stirring for 30 minutes to obtain a bentonite suspension.

[0029] S4. Prepare a modifier by mixing H4TCPP, pyridine, and methanol in a mass ratio of 1:1:160; degas aluminum salt solution A and slowly spread it evenly along the inner wall of a trough container; then slowly spread the modifier evenly along the inner wall of the trough container, keeping the surface of aluminum salt solution A stable without fluctuation throughout the process, and keep it at 140℃ for 60 min to obtain a suspension containing MOFs.

[0030] S5. Start stirring, mix the hydrolyzed polyacrylamide solution, bentonite suspension, sepiolite powder, and sodium metasilicate, adjust the pH of the system to 8, heat to 85℃, add octadecyl dimethyl allyl ammonium chloride and stir once at a stirring speed of 60 rpm, and keep stirring at this temperature for 2 hours; after the reaction is complete, keep the system temperature constant, add the suspension containing MOFs and stir a second time at a stirring speed of 100 rpm, stirring while adding, for 35 minutes; finally, add aluminum salt solution B, thickener (potassium polyacrylate and emulsifier SE-10) and the remaining water and stir a third time at a stirring speed of 130 rpm for 5 minutes; after the three stirrings are completed, let stand at 40℃ for 1 hour to obtain the mud material.

[0031] Example 2

[0032] The raw materials required for this embodiment are prepared in the following parts by weight: 500 parts water, 2.5 parts polyacrylamide (weight average molecular weight of 9 million, degree of hydrolysis of 20%), 2 parts sodium carbonate, 1 part aluminum chloride, 3 parts aluminum sulfate, 24 parts sodium bentonite, 12 parts sepiolite powder, 6 parts modifier, 3.5 parts octadecyl dimethyl allyl ammonium chloride, 0.5 parts sodium metasilicate, and 5.5 parts thickener (including 0.5 parts potassium polyacrylate and 5 parts emulsifier SE-10); wherein the modifier is 5,10,15,20-tetracarboxyphenylporphyrin (H4TCPP), pyridine and methanol are prepared in a mass ratio of 1:2.6:10.

[0033] The specific preparation process steps are as follows: S1. At a stirring speed of 120 rpm, polyacrylamide was added to 110 parts of water and stirred until completely dissolved without lumps to obtain solution A; sodium carbonate was dissolved in 20 parts of water to obtain solution B. While maintaining the stirring speed of solution A at 120 rpm, solution B was slowly added to solution A and the addition was completed within 30 minutes; the temperature was raised to 60℃ and held for 2.5 hours. After the holding period, the viscosity of the system was measured to be 37 mPa·s, which is consistent with the characteristics of a non-Newtonian pseudoplastic fluid, thus obtaining a hydrolyzed polyacrylamide solution.

[0034] S2. Take 70 parts of deionized water, add 1 part of aluminum chloride, and stir until completely dissolved to obtain aluminum salt solution A; take 12 parts of deionized water, add 3 parts of aluminum sulfate, and stir until completely dissolved to obtain aluminum salt solution B.

[0035] S3. Place sodium-based bentonite in an air jet mill and pulverize it under an inlet pressure of 0.8 MPa to remove obvious agglomerated particles. After pulverization, dry it at 100°C until constant weight, and then remove it after cooling to room temperature. Mix it with 150 parts of water under stirring at 350 rpm until the sodium-based bentonite is free of clumping and agglomeration. Reduce the stirring speed to 25 rpm and continue stirring for 25 min to obtain a bentonite suspension.

[0036] S4. Prepare a modifier by mixing H4TCPP, pyridine, and methanol in a mass ratio of 1:1.6:100; degas aluminum salt solution A and slowly spread it evenly along the inner wall of a trough container; then slowly spread the modifier evenly along the inner wall of the trough container, keeping the surface of aluminum salt solution A stable without fluctuation throughout the process, and keep it at 145℃ for 50 min to obtain a suspension containing MOFs.

[0037] S5. Start stirring, mix the hydrolyzed polyacrylamide solution, bentonite suspension, sepiolite powder, and sodium metasilicate, adjust the pH of the system to 7.5, heat to 75℃, add octadecyl dimethyl allyl ammonium chloride and stir once at a stirring speed of 80 rpm, and keep stirring at this temperature for 2.5 h; after the reaction is complete, keep the system temperature constant, add the suspension containing MOFs and stir a second time at a stirring speed of 150 rpm, stirring while adding, for 25 min; finally, add aluminum salt solution B, thickener (potassium polyacrylate and emulsifier SE-10) and the remaining water and stir a third time at a stirring speed of 150 rpm for 6 min; after the three stirrings are completed, let stand at 45℃ for 2 h to obtain the mud material.

[0038] Example 3

[0039] The raw materials required for this embodiment are prepared in the following parts by weight: 500 parts water, 2.2 parts polyacrylamide (weight average molecular weight of 8 million, degree of hydrolysis of 15%), 1.8 parts sodium carbonate, 0.6 parts aluminum chloride, 2 parts aluminum sulfate, 30 parts sodium bentonite, 9 parts sepiolite powder, 4.5 parts modifier, 2 parts octadecyl dimethyl allyl ammonium chloride, 0.25 parts sodium metasilicate, and 7 parts thickener (including 0.8 parts potassium polyacrylate and 6.2 parts emulsifier SE-10); wherein the modifier is 5,10,15,20-tetracarboxyphenylporphyrin (H4TCPP), pyridine and methanol are prepared in a mass ratio of 1:2.2:12.

[0040] The specific preparation process steps are as follows: S1. At a stirring speed of 90 rpm, polyacrylamide was added to 120 parts of water and stirred until completely dissolved without lumps to obtain solution A; sodium carbonate was dissolved in 25 parts of water to obtain solution B. While maintaining the stirring speed of solution A at 90 rpm, solution B was slowly added to solution A and the addition was completed within 25 minutes; the temperature was raised to 50℃ and held for 1.5 hours. After the holding time was completed, the viscosity of the system was measured to be 32 mPa·s, which is consistent with the characteristics of non-Newtonian pseudoplastic fluid, thus obtaining a hydrolyzed polyacrylamide solution.

[0041] S2. Take 65 parts of deionized water, add 0.6 parts of aluminum chloride, and stir until completely dissolved to obtain aluminum salt solution A; take 20 parts of deionized water, add 2 parts of aluminum sulfate, and stir until completely dissolved to obtain aluminum salt solution B.

[0042] S3. Place sodium-based bentonite in an air jet mill and pulverize it under an inlet pressure of 0.9 MPa to remove obvious agglomerated particles. After pulverization, dry it at 95°C until constant weight, and then remove it after cooling to room temperature. Mix it with 170 parts of water under stirring at 450 rpm until the sodium-based bentonite is free of clumping and agglomeration. Reduce the stirring speed to 40 rpm and continue stirring for 20 minutes to obtain a bentonite suspension.

[0043] S4. Prepare a modifier by mixing H4TCPP, pyridine, and methanol in a mass ratio of 1:1.2:150; degas aluminum salt solution A and slowly spread it evenly along the inner wall of a trough container; then slowly spread the modifier evenly along the inner wall of the trough container, keeping the surface of aluminum salt solution A stable without fluctuation throughout the process, and keep it at 150℃ for 55 min to obtain a suspension containing MOFs.

[0044] S5. Start stirring, mix the hydrolyzed polyacrylamide solution, bentonite suspension, sepiolite powder, and sodium metasilicate, adjust the pH of the system to 7.8, heat to 80℃, add octadecyl dimethyl allyl ammonium chloride and stir once at a stirring speed of 75 rpm, and keep stirring at this temperature for 3 hours; after the reaction is complete, keep the system temperature constant, add the suspension containing MOFs and stir a second time at a stirring speed of 130 rpm, stirring while adding, for 30 minutes; finally, add aluminum salt solution B, thickener (potassium polyacrylate and emulsifier SE-10) and the remaining water and stir a third time at a stirring speed of 160 rpm for 8 minutes; after the three stirrings are completed, let stand at 42℃ for 1.5 hours to obtain the mud material.

[0045] Comparative Example 1 Without adding a modifier, the remaining steps are the same as in Example 1 to obtain the mud material.

[0046] Comparative Example 2 Without adding an intercalating agent, the remaining steps are the same as in Example 1 to obtain the mud material.

[0047] Comparative Example 3 Without adding sepiolite powder, the remaining steps are the same as in Example 1 to obtain the mud material.

[0048] Comparative Example 4 Without adding sodium metasilicate, the remaining steps are the same as in Example 1 to obtain the mud material.

[0049] Implementation effect evaluation

[0050] Four core performance tests were conducted on the mud materials (test mud materials) prepared in the examples and comparative examples, respectively, focusing on Sowerg funnel viscosity, medium-pressure filtration loss, dynamic shear force, and gel strength. The operation procedures for each test are as follows: Funnel viscosity test procedure: A standard Souwer funnel viscometer was selected. Before the test, the instrument was calibrated with 946 mL of clean water at 20±0.5℃ for the outflow time. The mud material to be tested was taken, stirred thoroughly, and sieved to remove large particles of impurities. The funnel nozzle was blocked with a finger, and the mud material to be tested was poured into the funnel to the lower edge of the sieve. The measuring cup was placed directly below the nozzle. The stopwatch was started at the same time as the finger was released, and the time (unit: s) for the mud to fill the 946 mL measuring cup was recorded. This is the Souwer funnel viscosity. The test was performed in parallel for 3 times, and the arithmetic mean was taken as the final result.

[0051] Filtration loss test procedure: Select a standard medium-pressure filtration loss tester, take the mud material to be tested, stir it thoroughly and evenly, the mud temperature is 25℃, take 350mL of mud material and pour it into the filtration loss tester, stabilize the pressure at 120psi, start the stopwatch at the same time, continue to pressurize for 30min, then turn off the air source and release the internal pressure of the instrument, read the volume of filtrate collected in the graduated cylinder (unit: mL), which is the filtration loss.

[0052] Dynamic shear force test procedure: A rotational viscometer was used to measure the dynamic shear force of the mud material to be tested, referring to GB / T22235-2008 "Determination of viscosity of liquids - Rotational viscometer method".

[0053] Gel strength test procedure: Using a rotational viscometer, take the mud material to be tested, pour it into the sample cup, stir at 600 r / min for 10 s, stop stirring, let stand for 15 s, turn on the viscometer and adjust it to 3 r / min, and read the maximum deflection value Φ on the scale. max Calculate the gel strength (unit: Pa) according to the formula: gel strength = 0.511 × Φ max .

[0054] The test results of the mud material properties are shown in Table 1.

[0055] Table 1. Test results of mud material properties

[0056] This invention comprehensively evaluates the film-forming quality, impermeability, deformation resistance, and stratification resistance of mud materials using four core indicators: Sowert funnel viscosity, 120 psi filtration loss, dynamic shear force, and gel strength. Among these: The Soothelium funnel viscosity reflects the overall fluidity and slag-carrying capacity of the mud; the filtration loss at 120 psi directly characterizes the density and water pressure rupture resistance of the mud film (the lower the value, the better the film quality and the stronger the anti-leakage ability); the dynamic shear force reflects the strength of the three-dimensional network structure formed by the mud and its resistance to shear deformation; the gel strength reflects the mud's resistance to gravity stratification and settling when it is left to stand.

[0057] In addition, large-diameter shield tunnels, due to their large excavation face, high water pressure, large vertical height difference, and complex geological formations, place higher demands on the viscosity, dynamic shear force, and gel strength of the Souvrell funnel. If the viscosity of the Souvrell funnel is too low, the slag-carrying capacity will be insufficient, and a stable mud film cannot be formed. If the dynamic shear force is too low, the mud film will be easily broken down by water pressure. If the gel strength is too low, the mud film will easily stratify and settle under large vertical height difference conditions.

[0058] As shown in Table 1, compared with Comparative Examples 1-4, the core performance indicators of Examples 1-3 of the present invention remain at an excellent and stable level: the funnel viscosity is stable at 48~53s, which meets the requirements of mud fluidity and slag carrying capacity for large-diameter slurry shield construction; the filtration loss at 120psi medium pressure is only 7.7~9.5mL / 30min, which is far lower than the conventional level of traditional bentonite mud; the dynamic shear force reaches 28.8~31.5Pa, and the gel strength reaches 41.3~42.9Pa, both of which can effectively support the stability of the large-diameter excavation face.

[0059] In Comparative Examples 1-4, no modifier, no intercalating agent, no sepiolite powder, and no sodium metasilicate were added, respectively. The funnel viscosity of the products obtained in these examples was lower than that of the products in Examples 1-3. Similarly, the filtration loss at 120 psi of the products obtained in Comparative Examples 1-4 was higher than that in Examples 1-3, while the dynamic shear strength and gel strength were lower, indicating that the absence of any one of these substances would prevent the achievement of the objectives of this invention.

Claims

1. A slurry material for large-diameter slurry shield tunneling, characterized in that, The product is composed of the following components by weight: 500 parts water, 1.8-2.5 parts polyacrylamide, 1.5-2 parts sodium carbonate, 2.6-4 parts aluminum salt, 15-30 parts sodium bentonite, 7-12 parts sepiolite powder, 3.5-6 parts modifier, 2-3.5 parts intercalating agent, 0.25-0.5 parts sodium metasilicate, and 5.5-8.5 parts thickener; wherein the modifier is 5,10,15,20-tetracarboxyphenylporphyrin, pyridine, and methanol in a mass ratio of 1:(2-2.6):(10-13).

2. The slurry material for large-diameter slurry shield tunneling machines according to claim 1, characterized in that, The intercalating agent is octadecyl dimethyl allyl ammonium chloride; the thickener is composed of 0.5 to 1 part potassium polyacrylate and 5 to 7.5 parts emulsifier SE-10.

3. A process for preparing slurry material for large-diameter slurry shield tunneling machines, characterized in that, The method for preparing the slurry material for large-diameter slurry shield tunneling as described in any one of claims 1-2 comprises the following steps: S1. Prepare a hydrolyzed polyacrylamide solution by mixing polyacrylamide, sodium carbonate, and water. S2. Prepare aluminum salt solution A and aluminum salt solution B by mixing aluminum salt and water respectively; S3. Sodium-based bentonite pretreatment, followed by preparation of bentonite suspension with water after pretreatment; S4. Prepare a suspension containing MOFs by using a modifier and aluminum salt solution A; S5. Mix hydrolyzed polyacrylamide solution, bentonite suspension, sepiolite powder, and sodium metasilicate, adjust pH, heat and add intercalating agent for one stirring, then add MOF-containing suspension for a second stirring, and finally add aluminum salt solution B, thickener and water for a third stirring. After the three stirrings are completed, let stand and age to obtain mud material.

4. The preparation process of the mud material for large-diameter slurry shield tunneling machines according to claim 3, characterized in that, In S1, the preparation process is as follows: under stirring conditions, polyacrylamide is dissolved in 100-120 parts of water to obtain solution A; sodium carbonate is dissolved in 20-30 parts of water to obtain solution B; while maintaining stirring of solution A, solution B is added to solution A, the temperature is raised, and the reaction is maintained at this temperature.

5. The preparation process of the slurry material for large-diameter slurry shield tunneling machines according to claim 4, characterized in that, In S1, the stirring rate during the preparation of the hydrolyzed polyacrylamide solution is 60~120 rpm, the addition time of solution B is 15~30 min, the heat preservation temperature is 50~60℃, and the heat preservation time is 1.5~2.5 h.

6. The preparation process of the slurry material for large-diameter slurry shield tunneling machines according to claim 3, characterized in that, In S2, when preparing aluminum salt solution A, the aluminum salt is aluminum chloride, with 0.6 to 1 part aluminum chloride and 60 to 70 parts water; when preparing aluminum salt solution B, the aluminum salt is aluminum sulfate, with 2 to 3 parts aluminum sulfate and 10 to 20 parts water.

7. The preparation process of the mud material for large-diameter slurry shield tunneling machines according to claim 3, characterized in that, In S3, the pretreatment of sodium-based bentonite includes sequential air jet milling, drying, and sealed storage. The air jet milling process involves an air inlet pressure of 0.75~0.9MPa and a drying temperature of 80~100℃. The bentonite suspension preparation process is as follows: the pretreated sodium-based bentonite is mixed with 150~200 parts of water at a stirring speed of 350~600rpm. The stirring speed is then reduced to 25~50rpm, and stirring is continued for 20~30min to obtain the bentonite suspension.

8. The preparation process of the mud material for large-diameter slurry shield tunneling machines according to claim 3, characterized in that, In S4, the preparation process is as follows: aluminum salt solution A and modifier are sequentially spread into the container; after the addition is complete, the mixture is kept at 140~150℃ for 50~60 min to obtain a suspension containing MOFs.

9. The preparation process of the mud material for large-diameter slurry shield tunneling machines according to claim 3, characterized in that, In S5, the pH is 7.5~8, the heating temperature is 75~85℃, the stirring rate is 60~80 rpm, and the stirring time is 2~3h.

10. The preparation process of the mud material for large-diameter slurry shield tunneling machines according to claim 9, characterized in that, In S5, the secondary stirring rate is 100~150 rpm and the secondary stirring time is 25~35 min; the tertiary stirring rate is 130~160 rpm and the tertiary stirring time is 5~8 min; the aging temperature is 40~45℃ and the aging time is 1~2 h.

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