Residue soil modifier based on shield construction and construction method

Abstract

The invention relates to the technical field of muck modifying agents, in particular to a muck modifying agent based on shield construction and a construction method, and the muck modifying agent comprises the following raw materials: a composite foaming agent, modified bentonite, carboxymethyl cellulose and lignosulfonate. The composite foaming agent significantly reduces surface tension through betaine, and enhances the foam stability in combination with nano-silica, thereby improving the foaming efficiency; the nano silicon dioxide is embedded into a foam liquid film to form mechanical support, and the abelmoschus manihot gum delays liquid drainage through a thickening effect, prolongs the half-life period of foam and ensures continuous wetting of the muck. Bentonite is modified through acidification of oxalic acid, the interlayer spacing is enlarged, the water absorption capacity is improved, meanwhile, long-acting water locking is achieved through hydrophilic groups of lauryl sodium sulfate, and the residue soil humidity is maintained; anion modification of lauryl sodium sulfate enables the surface of bentonite to be negatively charged, the surface of bentonite and an anion modifier generate like-pole repulsion, the flocculation phenomenon is avoided, and therefore the uniformity of a system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of slag improvers, and in particular to a slag improver based on shield construction and a construction method. Background Art

[0002] As an advanced underground engineering technology, shield construction is widely used in the construction of urban underground projects such as subways and tunnels. It has the advantages of high degree of mechanization and low impact on the surrounding environment, and can effectively ensure the safety and efficiency of construction. However, during the shield construction process, different geological conditions have significantly different requirements for the performance of slag. In silty clay layers, problems such as "mud cake" on the cutter head and poor plastic flow of slag are prone to occur; and in sandy layers, "gushing" is prone to occur. These problems seriously affect the excavation efficiency and construction safety of the shield machine, so the slag needs to be improved.

[0003] At present, commonly used slag conditioners have the problem of insufficient adaptability; when the shield machine is excavating at a high speed, the foam conditioner cannot provide sufficient dosage in time due to flow limitation, resulting in the slag drying and poor fluidity, and easily sticking to the cutterhead and other parts, forming mud cakes, thereby affecting construction efficiency; In view of this, we propose a slag conditioner and construction method based on shield construction. Summary of the Invention

[0004] The purpose of the present invention is to provide a slag conditioner and construction method based on shield construction, so as to solve the problem proposed in the above background technology that when the shield machine is advancing at a fast speed, the foam conditioner cannot provide sufficient dosage in time due to flow limitation, resulting in the slag drying, poor fluidity, and easy adhesion to the cutter head and other parts to form mud cakes, thereby affecting construction efficiency.

[0005] The present invention provides a slag improver based on shield construction, comprising the following raw materials: a composite foaming agent, modified bentonite, carboxymethyl cellulose and lignin sulfonate; The composite foaming agent is prepared by compounding N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine with amino-nanosilica and adding hibiscus gum; wherein the mass ratio of N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine to amino-nanosilica is 1-4:1; Modified bentonite is prepared by treating with oxalic acid and adsorbing sodium lauryl sulfate.

[0006] Preferably, the composite foaming agent comprises 10-20 parts by weight, modified bentonite 30-50 parts by weight, carboxymethyl cellulose 5-15 parts by weight and lignin sulfonate 5-10 parts by weight.

[0007] Preferably, the preparation method of the composite foaming agent is as follows: The amino nano-silica was added to deionized water and ultrasonically treated at a power of 200-300W for 20-30min to form a uniform dispersion; polyethylene glycol was added at a rate of 0.3-0.5% of the total mass of the dispersion and stirred at a speed of 150-200rpm for 0.5-1h to obtain an amino nano-silica dispersion; Add 5-15% of hibiscus gum to deionized water at 60-80°C, stirring at 400-500 rpm for 1-1.5 hours until the mixture is completely swollen into a transparent colloid, to obtain a hibiscus gum base solution; An N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine aqueous solution is mixed with an amino nano-silica dispersion, and the mixture is stirred at a speed of 200-300 rpm at 30-40° C. for 1-2 hours to obtain a mixed solution; the mixed solution is added to a hibiscus gum base liquid, the stirring speed is reduced to 100-200 rpm, and the stirring is continued for 0.5-1 hour; the pH is adjusted to 6.5-7.5 with citric acid, the mixture is allowed to stand for 4-6 hours, and the mixture is circulated through a high-pressure homogenizer at a pressure of 20-30 MPa for 2-3 times to obtain a composite foaming agent.

[0008] Betaine surfactant has an amphoteric molecular structure and can be quickly adsorbed on the gas-liquid interface in complex environments, significantly reducing surface tension and generating a large amount of dense foam in a short period of time; amino-type nano-silica attracts and bonds through electrostatic interaction, enhancing the strength of the interfacial film and improving foaming efficiency; nanoparticles are embedded in the foam liquid film to form a three-dimensional network structure, delaying liquid film drainage and gas diffusion, and extending the life of the foam; in addition, betaine combines with water molecules through hydrogen bonds, increasing the liquid phase viscosity and slowing down the foam rupture rate, which is especially suitable for the vibration environment of the shield machine; the foam forms a lubricating layer on the surface of the slag particles, reducing the friction coefficient between the cutterhead and the slag and preventing adhesion; the water-holding capacity of hibiscus gum maintains the moisture of the slag and avoids drying and agglomeration.

[0009] Preferably, the particle size of the amino-modified nano-silica is 20-50 nm; The concentration of the N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine aqueous solution is 20-30%.

[0010] Preferably, the concentration of the citric acid is 0.5-1.0 mol / L.

[0011] Preferably, the preparation method of the modified bentonite is as follows: Bentonite was added to a 0.5-1 mol / L oxalic acid solution at a solid-liquid ratio of 1:9, and stirred at 400-500 rpm at 60-80°C for 3-4 hours. After the reaction, the mixture was filtered and washed with deionized water until neutral, and dried at 100-105°C for 10-12 hours to obtain acidified bentonite. The acidified bentonite was added to the sodium lauryl sulfate solution, stirred at 300-400 rpm for 5-6 hours at 40-50°C, and sodium chloride with a concentration of 0.05-0.1 mol / L was added at the same time; after the reaction, the solution was filtered and washed with deionized water for 2-3 times, and dried at 50-60°C for 12-24 hours to obtain the modified bentonite.

[0012] Sulfate ion (-SO4 - ) is adsorbed onto the surface of bentonite, which will cause it to have a negative charge, forming a charge repulsion effect with the similarly negatively charged carboxymethyl cellulose and lignin sulfonate, thereby avoiding flocculation and improving the dispersion stability of the system; in addition, the long chain of dodecyl (hydrophobic end) forms a hydrophobic lubricating layer on the surface of the slag particles, reducing the friction coefficient between the cutter head and the slag and preventing the formation of mud cakes; oxalic acid-treated bentonite can strip off interlayer impurities, expand the interlayer spacing, and enhance water absorption capacity; bentonite treated with oxalic acid is more easily dispersed into nanosheets, covering the surface of the slag to form a physical barrier, inhibiting particle agglomeration.

[0013] Preferably, the mass ratio of the acidified bentonite to sodium lauryl sulfate is 1:0.3-0.5.

[0014] Preferably, the sodium lauryl sulfate solution is prepared by dissolving sodium lauryl sulfate in deionized water with a concentration of 0.1-0.5 mol / L.

[0015] On the other hand, the present invention provides a construction method of a slag conditioner based on shield construction, which is used for any of the above-mentioned slag conditioners based on shield construction, comprising the following steps: S1.1, weigh the above raw materials respectively; S1.2. Stir the modified bentonite, carboxymethyl cellulose, and lignin sulfonate in a blender at 200-300 rpm for 5-10 min to obtain a premixed dry powder modifier; S1.3. Dilute the composite foaming agent with water in proportion and inject it into the front of the cutterhead through several pipes via the shield machine foam system. The injection pressure is 0.3-0.5 MPa, and the flow rate of the diluted composite foaming agent in each pipe is 20-45 L / min. Add water to the premixed dry powder improver at a mass ratio of 10-15:100 and stir into slurry. Transport it to the front of the cutterhead through a grouting pump. When the shield advances, fully mix the dry powder improver with the slag. Monitor the slag status at the screw machine outlet in real time and adjust the grouting amount in time.

[0016] Preferably, in S1.3, the mass ratio of the composite foaming agent to water is 3-5:100.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. In this slag conditioner and construction method based on shield construction, the composite foaming agent significantly reduces surface tension through betaine amphoteric surfactant, and combines with nano-silica to enhance foam stability, thereby improving foaming efficiency and meeting the flow limit of high-speed tunneling; nano-silica is embedded in the foam liquid film to form mechanical support, while hibiscus gum delays drainage through thickening effect, prolongs the foam half-life, and ensures continuous moisture of the slag; at the same time, the foam lubrication layer effectively reduces the friction coefficient of the cutterhead, and the water retention property of hibiscus gum prevents the slag from drying and agglomerating, reducing the risk of mud cake.

[0018] 2. In this slag conditioner and construction method based on shield construction, bentonite is modified by acidification with oxalic acid to expand its interlayer spacing and increase its water absorption capacity. At the same time, the hydrophilic group of sodium lauryl sulfate is used to achieve long-term water lock and maintain the humidity of the slag; the anionic modification of sodium lauryl sulfate makes the bentonite surface negatively charged, which causes like-charge repulsion with the anionic conditioner, avoiding flocculation and thus improving the uniformity of the system; in addition, the hydrophobic chain of sodium lauryl sulfate forms a lubricating layer on the surface of the slag particles, reducing the friction coefficient of the cutterhead and significantly reducing the formation of mud cake. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] The present invention provides a slag improver based on shield construction, comprising the following raw materials: a composite foaming agent, modified bentonite, carboxymethyl cellulose and lignin sulfonate; The composite foaming agent is prepared by compounding N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine with amino-nanosilica and adding hibiscus gum, wherein the mass ratio of N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine to amino-nanosilica is 1-3:1; Modified bentonite is prepared by treating with oxalic acid and adsorbing sodium lauryl sulfate.

[0021] Aminated nano-silica was purchased from Jinde Chemical Technology (Shanghai) Co., Ltd.

[0022] The synthesis steps of N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine are as follows: Dissolve 20 g of industrial-grade disproportionated abietamine in 100 mL of toluene, add glacial acetic acid to adjust the pH to 4-5, separate the oil phase and the aqueous phase using a separatory funnel, and repeatedly wash with 50 mL of water each time until neutral (pH 6-7) to obtain dehydroabietylamine; The dehydroabietylamine obtained above was dissolved in 150 mL of anhydrous ethanol, and commercially available 85% formic acid and 37% formaldehyde solution (the molar ratio of dehydroabietylamine:formic acid:formaldehyde was 1:5:6) was added dropwise at room temperature, and stirred at below 40°C for 1 hour; the temperature was raised and the reflux reaction was carried out for 12 hours; after the reaction was completed, the unreacted formic acid, formaldehyde and ethanol were removed by vacuum distillation, and the residue was washed with 50 mL of ether each time and filtered to obtain N,N-dimethyldehydroabietylamine; the N,N-dimethyldehydroabietylamine obtained above was mixed with sodium chloroacetate (molar ratio of 1:1.2) at 100°C for 1 hour. The reaction was carried out in a mL ethanol-water mixed solvent (volume ratio of 3:1), sodium bicarbonate was added to adjust the pH to 8-9 (added in batches until the pH stabilized in the target range), and the reaction was stirred at 60-80°C for 8 hours. After the reaction, the crude product was distilled under reduced pressure, washed to remove unreacted sodium chloroacetate, and then decolorized with activated carbon accounting for approximately 1-3% of the weight of the crude product. Finally, separation was performed by silica gel column chromatography (using silica gel 20-30 times the weight of the crude product for separation, developing solvent: chloroform / methanol = 10:1) to obtain N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine.

[0023] The preparation method of the composite foaming agent is as follows: The prepared amino-silica nano-silica was added to deionized water and ultrasonically treated at a power of 200W for 30min to form a uniform dispersion; polyethylene glycol was added at a concentration of 0.4% by weight of the total dispersion and stirred at a speed of 200rpm for 1h to obtain an amino-silica dispersion; Add 10% of the total weight of the composite foaming agent, hibiscus gum, into deionized water at 60-80°C, and stir at 400 rpm for 1 hour until it is completely swollen into a transparent colloid to obtain a hibiscus gum base liquid; A 25% N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine aqueous solution is mixed with an amino-type nano-silica dispersion, and the mixture is stirred at 200-300 rpm for 1-2 hours at 30-40° C. to obtain a mixed solution. The mixed solution is added to a hibiscus gum base liquid, the stirring speed is reduced to 150 rpm, and the stirring is continued for 1 hour. The pH is adjusted to 6.5-7.5 with 0.7 mol / L citric acid, the mixture is allowed to stand for 6 hours, and the mixture is circulated three times through a high-pressure homogenizer at a pressure of 20-30 MPa to obtain a composite foaming agent.

[0024] The preparation method of modified bentonite is as follows: Bentonite was added to a 0.6 mol / L oxalic acid solution at a solid-liquid ratio of 1:9, and stirred at 500 rpm at 60-80°C for 4 hours. After the reaction, the mixture was filtered and washed with deionized water until neutral, and dried at 100-105°C for 12 hours to obtain acidified bentonite. The acidified bentonite was added to a 0.3 mol / L sodium lauryl sulfate solution, stirred at 400 rpm at 40-50°C for 5 hours, and sodium chloride at a concentration of 0.07 mol / L was added at the same time. After the reaction, the solution was filtered and washed with deionized water three times, and dried at 50-60°C for 24 hours to obtain modified bentonite.

[0025] In the following examples, sodium lauryl sulfate (CAS No. 151-21-3), oxalic acid (CAS No. 144-62-7), carboxymethyl cellulose (CAS No. 9000-11-7), lignin sulfonate (CAS No. 8062-15-5), and hibiscus gum (CAS No. 54163-78-5) were used.

[0026] Example 1: A slag improver and construction method based on shield construction, comprising the following steps: S1.1. Weigh the following raw materials in parts by weight: 10 parts by weight of composite foaming agent, 30 parts by weight of modified bentonite, 5 parts by weight of carboxymethyl cellulose, and 5 parts by weight of lignin sulfonate; S1.2. Stir the modified bentonite, carboxymethyl cellulose, and lignin sulfonate in a blender at 300 rpm for 10 min to obtain a premixed dry powder modifier; S1.3. Dilute the composite foaming agent with water at a mass ratio of 3:100. Inject the composite foaming agent through the shield machine foam system through several pipelines in front of the cutterhead. The injection pressure is 0.5 MPa, and the flow rate of the diluted composite foaming agent in each pipeline is 20 L / min. The premixed dry powder improver is added with water in a mass ratio of 10:100 and stirred into slurry, which is then transported to the front of the cutterhead through a grouting pump. When the shield advances, the dry powder improver is fully mixed with the slag. The grouting amount is adjusted by monitoring the slag status at the slag outlet of the screw machine in real time.

[0027] The composite foaming agent is prepared by compounding N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine with amino-nanosilica and adding hibiscus gum; wherein the mass ratio of N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine to amino-nanosilica is 1:1.

[0028] The modified bentonite is prepared by treating with oxalic acid and adsorbing sodium lauryl sulfate; the mass ratio of the acidified bentonite to the sodium lauryl sulfate is 1:0.3.

[0029] Example 2: A slag improver and construction method based on shield construction, comprising the following steps: S1.1. Weigh the following raw materials in parts by weight: 20 parts by weight of composite foaming agent, 50 parts by weight of modified bentonite, 15 parts by weight of carboxymethyl cellulose, and 10 parts by weight of lignin sulfonate; S1.2. Stir the modified bentonite, carboxymethyl cellulose, and lignin sulfonate in a blender at 300 rpm for 10 min to obtain a premixed dry powder modifier; S1.3. Dilute the composite foaming agent with water at a mass ratio of 5:100. Inject the composite foaming agent through the shield machine foam system through several pipelines in front of the cutterhead. The injection pressure is 0.5 MPa, and the flow rate of the diluted composite foaming agent in each pipeline is 45 L / min. The premixed dry powder modifier is added with water in a mass ratio of 15:100 and stirred into slurry, which is then transported to the front of the cutterhead through a grouting pump. When the shield advances, the dry powder modifier is fully mixed with the slag. The slag status at the slag outlet of the screw machine is monitored in real time to adjust the grouting amount.

[0030] The composite foaming agent is prepared by compounding N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine with amino-nanosilica and adding hibiscus gum; wherein the mass ratio of N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine to amino-nanosilica is 3:1.

[0031] The modified bentonite is prepared by treating with oxalic acid and adsorbing sodium lauryl sulfate; the mass ratio of the acidified bentonite to the sodium lauryl sulfate is 1:0.5.

[0032] Example 3: A slag improver and construction method based on shield construction, comprising the following steps: S1.1. Weigh the following raw materials in parts by weight: 15 parts by weight of composite foaming agent, 40 parts by weight of modified bentonite, 10 parts by weight of carboxymethyl cellulose, and 8 parts by weight of lignin sulfonate; S1.2. Stir the modified bentonite, carboxymethyl cellulose, and lignin sulfonate in a blender at 300 rpm for 10 min to obtain a premixed dry powder modifier; S1.3. Dilute the composite foaming agent with water at a mass ratio of 4:100. Inject the composite foaming agent through the shield machine foam system through several pipelines in front of the cutterhead. The injection pressure is 0.5 MPa, and the flow rate of the diluted composite foaming agent in each pipeline is 35 L / min. The premixed dry powder improver is added with water in a mass ratio of 12:100 and stirred into slurry, which is then transported to the front of the cutterhead through a grouting pump. When the shield advances, the dry powder improver is fully mixed with the slag, and the slag status at the slag outlet of the screw machine is monitored in real time to adjust the grouting amount.

[0033] The composite foaming agent is prepared by compounding N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine with amino-nanosilica and adding hibiscus gum; wherein the mass ratio of N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine to amino-nanosilica is 2:1.

[0034] The modified bentonite is prepared by treating with oxalic acid and adsorbing sodium lauryl sulfate; the mass ratio of the acidified bentonite to the sodium lauryl sulfate is 1:0.4.

[0035] Example 4: A slag improver and construction method based on shield construction, comprising the following steps: S1.1. Weigh the following raw materials in parts by weight: 5 parts by weight of composite foaming agent, 40 parts by weight of modified bentonite, 10 parts by weight of carboxymethyl cellulose, and 8 parts by weight of lignin sulfonate; S1.2. Stir the modified bentonite, carboxymethyl cellulose, and lignin sulfonate in a blender at 300 rpm for 10 min to obtain a premixed dry powder modifier; S1.3. Dilute the composite foaming agent with water at a mass ratio of 4:100. Inject the composite foaming agent through the shield machine foam system through several pipelines in front of the cutterhead. The injection pressure is 0.5 MPa, and the flow rate of the diluted composite foaming agent in each pipeline is 35 L / min. The premixed dry powder improver is added with water in a mass ratio of 12:100 and stirred into slurry, which is then transported to the front of the cutterhead through a grouting pump. When the shield advances, the dry powder improver is fully mixed with the slag, and the slag status at the slag outlet of the screw machine is monitored in real time to adjust the grouting amount.

[0036] The composite foaming agent is prepared by compounding N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine with amino-nanosilica and adding hibiscus gum; wherein the mass ratio of N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine to amino-nanosilica is 2:1.

[0037] The modified bentonite is prepared by treating with oxalic acid and adsorbing sodium lauryl sulfate; the mass ratio of the acidified bentonite to the sodium lauryl sulfate is 1:0.4.

[0038] Example 5: A slag improver and construction method based on shield construction, comprising the following steps: S1.1. Weigh the following raw materials in parts by weight: 15 parts by weight of composite foaming agent, 20 parts by weight of modified bentonite, 10 parts by weight of carboxymethyl cellulose, and 8 parts by weight of lignin sulfonate; S1.2. Stir the modified bentonite, carboxymethyl cellulose, and lignin sulfonate in a blender at 300 rpm for 10 min to obtain a premixed dry powder modifier; S1.3. Dilute the composite foaming agent with water at a mass ratio of 4:100. Inject the composite foaming agent through the shield machine foam system through several pipelines in front of the cutterhead. The injection pressure is 0.5 MPa, and the flow rate of the diluted composite foaming agent in each pipeline is 35 L / min. The premixed dry powder improver is added with water in a mass ratio of 12:100 and stirred into slurry, which is then transported to the front of the cutterhead through a grouting pump. When the shield advances, the dry powder improver is fully mixed with the slag, and the slag status at the slag outlet of the screw machine is monitored in real time to adjust the grouting amount.

[0039] The composite foaming agent is prepared by compounding N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine with amino-nanosilica and adding hibiscus gum; wherein the mass ratio of N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine to amino-nanosilica is 2:1.

[0040] The modified bentonite is prepared by treating with oxalic acid and adsorbing sodium lauryl sulfate; the mass ratio of the acidified bentonite to the sodium lauryl sulfate is 1:0.4.

[0041] Example 6: A slag improver and construction method based on shield construction, comprising the following steps: S1.1. Weigh the following raw materials in parts by weight: 15 parts by weight of composite foaming agent, 40 parts by weight of modified bentonite, 10 parts by weight of carboxymethyl cellulose, and 8 parts by weight of lignin sulfonate; S1.2. Stir the modified bentonite, carboxymethyl cellulose, and lignin sulfonate in a blender at 300 rpm for 10 min to obtain a premixed dry powder modifier; S1.3. Dilute the composite foaming agent with water at a mass ratio of 4:100. Inject the composite foaming agent through the shield machine foam system through several pipelines in front of the cutterhead. The injection pressure is 0.5 MPa, and the flow rate of the diluted composite foaming agent in each pipeline is 35 L / min. The premixed dry powder improver is added with water in a mass ratio of 12:100 and stirred into slurry, which is then transported to the front of the cutterhead through a grouting pump. When the shield advances, the dry powder improver is fully mixed with the slag, and the slag status at the slag outlet of the screw machine is monitored in real time to adjust the grouting amount.

[0042] The composite foaming agent is prepared by compounding N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine with amino-nanosilica and adding hibiscus gum; wherein the mass ratio of N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine to amino-nanosilica is 4:1.

[0043] The modified bentonite is prepared by treating with oxalic acid and adsorbing sodium lauryl sulfate; the mass ratio of the acidified bentonite to the sodium lauryl sulfate is 1:0.4.

[0044] Comparative Example 1: Using the method of Example 3, in a construction method of a slag conditioner based on shield construction, N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine is directly used as a foaming agent.

[0045] Comparative Example 2: The method of Example 3 was adopted, but hibiscus gum was not added in a construction method of a slag conditioner based on shield construction.

[0046] Comparative Example 3: The method of Example 3 was adopted to directly use bentonite in a construction method of a slag improver based on shield construction.

[0047] The present invention is a slag improver based on shield construction prepared by a composite foaming agent and modified bentonite, wherein the performance index test items and test standards of the slag improver based on shield construction are as follows: Dilute the foaming agent proportionally and record the initial volume (V0). Use a standard foaming device to foam the soil, collect the foam into a bottomless graduated cylinder (e.g., 250 mL), scrape the surface of the foam flat, and record the total volume of the foam (V1). Calculate the foaming ratio using the formula: Foaming ratio = V1 / V0. A higher foaming ratio indicates that the foam can reduce the internal friction of the soil, making it easier to be discharged by the screw conveyor and reducing wear on the cutter disc and screw conveyor.

[0048] Mix the slag improver and standard sand in proportion, add water and stir evenly, then load them into the slump cone (300mm high, 100mm upper opening, 200mm lower opening) in three layers. Use a tamping rod to evenly tamp each layer 25 times to ensure that the tamping evenly covers the entire cross-section. After filling, use a scraper to smooth the surface and remove excess material from the cone mouth. Slowly lift the slump cone vertically and measure the height difference between the highest point of the slag after collapse and the top of the cone, which is the slump value. A higher slump indicates that the slag has good fluidity and can be discharged more easily through a screw conveyor, reducing the risk of blockage.

[0049] The improved slag is compacted layer by layer according to the standard to form cylindrical samples with a diameter of ≥50mm and a height of ≥40mm; the vacuum saturation method or the water injection saturation method is used to ensure that there is no bubble overflow from the sample and that the saturation state requirements are met; the sample is placed on the permeameter, and the water head difference is connected and adjusted to ensure that the water supply pipe and the overflow pipe are balanced to avoid overflow; the timer is turned on to measure the amount of water that penetrates through the sample within the set time; the water head difference and the penetration time at both ends of the sample are recorded, and the permeability coefficient is calculated according to the Darcy permeability formula; a lower permeability coefficient indicates that the slag has good permeability and can effectively drain groundwater, reducing the impact of groundwater on construction.

[0050] The slag conditioners prepared in Examples 1-6 and Comparative Examples 1-3 were tested based on shield construction using the above standards. The obtained data are shown in Table 1: Table 1 Performance data of soil conditioners for shield construction in Examples 1-6 and Comparative Examples 1-3 It can be seen from Examples 1-3 and Example 4 that when other components in a slag conditioner based on shield construction remain unchanged and the weight of the composite foaming agent increases, the foaming ratio and slump of the slag conditioner based on shield construction continue to increase, and the permeability coefficient continues to decrease.

[0051] The increase in the weight of the composite foaming agent means an increase in the concentration of surfactants in the system, thereby significantly improving the foam generation ability; surfactants (such as N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine) can form more foam by reducing the surface tension of the liquid; in addition, the synergistic effect of amino-containing nano-silica and hibiscus gum further enhances the stability of the foam, allowing the foam to form a dense monomolecular film on the liquid surface, reducing gas leakage and thus improving the stability of the foam.

[0052] As the concentration of surfactant increases, the speed and capacity of foam generation are significantly enhanced, and the volume of foam and system viscosity also increase accordingly, which helps to improve the fluidity of the slag; the foam can fully wrap the slag particles, reduce the friction between the particles, thereby improving the plastic flow of the slag, and the slump increases accordingly; in addition, the lubricating and filling effects of the foam can improve the pore structure of the slag, reduce permeability, and thus further reduce the permeability coefficient of the slag.

[0053] It can be seen from Examples 1-3 and Example 5 that when other components in a slag conditioner based on shield construction remain unchanged and the weight of the modified bentonite increases, the foaming ratio and slump of the slag conditioner based on shield construction continue to increase, and the permeability coefficient continues to decrease.

[0054] As the weight of modified bentonite increases, its stabilizing effect on the foam is enhanced, making the foam less likely to break, thereby increasing the foaming ratio, which helps to better wrap the slag particles, improve the fluidity and plasticity of the slag, thereby reducing excavation resistance and improving excavation efficiency; as the weight of modified bentonite increases, the internal friction of the slag is further reduced, the fluidity is enhanced, and the slump is increased; the increase in slump indicates that the slag has better fluidity and can be discharged more easily through the screw conveyor, reducing the risk of blockage, while also causing less wear on the cutter disc and screw conveyor, extending the service life of the equipment; as the weight of modified bentonite increases, its filling effect is more significant, the pores are more effectively filled, resulting in a lower permeability coefficient.

[0055] Furthermore, it can be seen from Examples 1-3 and Example 6 that when the mass ratio of N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine to amino-silica increases, the foaming ratio and slump of the slag conditioner based on shield construction continue to increase, and the permeability coefficient continues to decrease.

[0056] N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine is a surfactant that can reduce the surface tension of liquids, thereby improving foaming ability; due to its large specific surface area and surface activity, amino-containing nano-silica can synergize with surfactants to further enhance the foaming effect; when the mass ratio of the two increases, the synergistic effect becomes more significant, the foam generation ability and stability are enhanced, thereby improving the foaming ratio.

[0057] The addition of amino-group nano-silica improves the lubricity of the slag, reduces the internal friction between particles, and makes the slag easier to flow; at the same time, the increase in surfactant concentration makes the foam more stable, better wraps the slag particles, reduces the friction between particles, improves the fluidity of the slag and increases the slump; in addition, the small particle size of amino-group nano-silica can fill the pores of the slag, forming a dense structure and reducing the permeability; and the increase in surfactant concentration improves the pore structure of the slag, making it difficult for water molecules to pass through, further reducing the permeability coefficient.

[0058] According to the above test experiments, embodiment 3 is regarded as the optimal embodiment; By comparing Example 3 with Comparative Example 1, it can be seen that in a construction method of a slag conditioner based on shield construction, when N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine is directly used as a foaming agent, the foaming rate and slump of the slag conditioner are significantly reduced, while the permeability coefficient is significantly increased; when betaine is used alone, the foam ruptures rapidly due to insufficient interfacial film strength, resulting in a decrease in the foaming rate, a thinning of the foam liquid film, an accelerated rupture rate, and an increase in the viscosity of the slag; in addition, due to the lack of the dispersing effect of nanoparticles, the foam easily aggregates to form large pore channels, further improving the permeability.

[0059] By comparing Example 3 with Comparative Example 2, it can be seen that: in a construction method of a slag conditioner based on shield construction, when hibiscus gum is not added, the foaming rate and slump of the slag conditioner based on shield construction are significantly reduced, and the permeability coefficient is significantly improved; when hibiscus gum is not added, the liquid film stability of the foam is reduced, and the synergistic foaming effect of nano-silica and betaine surfactant is weakened, resulting in an accelerated foam bursting speed and a reduced foaming rate; at the same time, the polymer chain of hibiscus gum forms a three-dimensional network structure, locks in moisture and enhances the cohesion between slag particles, preventing segregation; in addition, its water retention property reduces the loss of free water in the slag and maintains fluidity. The colloidal molecules can also fill the pores between the slag particles, reduce the infiltration channels, and the viscous properties further delay moisture migration and inhibit slag water exudation, thereby optimizing the stability and performance of the foam.

[0060] By comparing Example 3 with Comparative Example 3, it can be seen that: in a construction method of a slag conditioner based on shield construction, when bentonite is directly used, the slump of the slag conditioner based on shield construction is significantly reduced and the permeability coefficient is significantly improved; the slump reflects the fluidity and pumpability of the slag. Although bentonite can thicken, it lacks the water retention and lubrication effects of high molecular polymers, resulting in a decrease in slump; in addition, bentonite forms a colloidal structure by adsorbing water molecules, but excessive thickening will limit the fluidity of the slag; the permeability coefficient reflects the anti-seepage ability of the slag. If bentonite is used alone and the ratio is improper or the concentration is insufficient, it cannot effectively fill the pores, resulting in increased permeability.

[0061] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A slag improver based on shield construction, characterized in that: The invention comprises the following raw materials: composite foaming agent, modified bentonite, carboxymethyl cellulose and lignin sulfonate; The composite foaming agent is prepared by compounding N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine with amino-nanosilica and adding hibiscus gum; wherein the mass ratio of N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine to amino-nanosilica is 1-4:1; Modified bentonite is prepared by treating with oxalic acid and adsorbing sodium lauryl sulfate.

2. The slag improver based on shield construction according to claim 1, characterized in that: The composite foaming agent comprises 10-20 parts by weight, modified bentonite 30-50 parts by weight, carboxymethyl cellulose 5-15 parts by weight and lignin sulfonate 5-10 parts by weight.

3. The slag improver based on shield construction according to claim 2, characterized in that: The preparation method of the composite foaming agent is as follows: The amino nano-silica was added to deionized water and ultrasonically treated at a power of 200-300W for 20-30min to form a uniform dispersion; polyethylene glycol was added at a rate of 0.3-0.5% of the total mass of the dispersion and stirred at a speed of 150-200rpm for 0.5-1h to obtain an amino nano-silica dispersion; Add 5-15% of hibiscus gum to deionized water at 60-80°C, stirring at 400-500 rpm for 1-1.5 hours until the mixture is completely swollen into a transparent colloid, to obtain a hibiscus gum base solution; An N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine aqueous solution is mixed with an amino nano-silica dispersion, and the mixture is stirred at a speed of 200-300 rpm at 30-40° C. for 1-2 hours to obtain a mixed solution; the mixed solution is added to a hibiscus gum base liquid, the stirring speed is reduced to 100-200 rpm, and the stirring is continued for 0.5-1 hour; the pH is adjusted to 6.5-7.5 with citric acid, the mixture is allowed to stand for 4-6 hours, and the mixture is circulated through a high-pressure homogenizer at a pressure of 20-30 MPa for 2-3 times to obtain a composite foaming agent.

4. The slag improver based on shield construction according to claim 3, characterized in that: The particle size of the amino-type nano-silica is 20-50 nm; The concentration of the N-dehydroabietyl-N,N-dimethylcarboxymethyl betaine aqueous solution is 20-30%.

5. The slag improver based on shield construction according to claim 3, characterized in that: The concentration of the citric acid is 0.5-1.0 mol / L.

6. The slag improver based on shield construction according to claim 1, characterized in that: The preparation method of the modified bentonite is as follows: Bentonite was added to a 0.5-1 mol / L oxalic acid solution at a solid-liquid ratio of 1:9, and stirred at 400-500 rpm at 60-80°C for 3-4 hours. After the reaction, the mixture was filtered and washed with deionized water until neutral, and dried at 100-105°C for 10-12 hours to obtain acidified bentonite. The acidified bentonite was added to the sodium lauryl sulfate solution, stirred at 300-400 rpm for 5-6 hours at 40-50°C, and sodium chloride with a concentration of 0.05-0.1 mol / L was added at the same time; after the reaction, the solution was filtered and washed with deionized water for 2-3 times, and dried at 50-60°C for 12-24 hours to obtain the modified bentonite.

7. The slag improver based on shield construction according to claim 6, characterized in that: The mass ratio of the acidified bentonite to sodium lauryl sulfate is 1:0.3-0.

5.

8. The slag improver based on shield construction according to claim 6, characterized in that: The sodium lauryl sulfate solution is prepared by dissolving sodium lauryl sulfate in deionized water with a concentration of 0.1-0.5 mol / L.

9. A method for constructing a slag conditioner based on shield construction, for applying the slag conditioner based on shield construction according to any one of claims 1 to 8, characterized in that: The construction method of the slag improver based on shield construction is as follows: S1.1, weigh the above raw materials respectively; S1.

2. Stir the modified bentonite, carboxymethyl cellulose, and lignin sulfonate in a blender at 200-300 rpm for 5-10 min to obtain a premixed dry powder modifier; S1.

3. Dilute the composite foaming agent with water in proportion and inject it into the front of the cutterhead through the shield machine foam system through the pipeline. The injection pressure is 0.3-0.5MPa. The flow rate of the diluted composite foaming agent in each pipeline is 20-45L / min. Add water to the premixed dry powder improver at a mass ratio of 10-15:100 and stir into slurry. Transport it to the front of the cutterhead through a grouting pump. When the shield advances, fully mix the dry powder improver with the slag. Monitor the slag status at the screw machine outlet in real time to adjust the grouting amount.

10. The method for applying a slag improver based on shield construction according to claim 9, wherein: In S1.3, the mass ratio of the composite foaming agent to water is 3-5:100.

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