Slurry prepared from filter-press tail water and used for slurry shield clay stratum tunneling and preparation method of slurry

Abstract

The invention discloses slurry shield clay stratum tunneling slurry prepared from filter-press tail water and a preparation method thereof, the slurry comprises the following components in parts by weight: 1000-1250 parts of waste slurry, 700-800 parts of plate-frame filter-press tail water, 0.1-5 parts of TOCNF, 200-550 parts of clear water, 0.2-4 parts of a lubricant, 0.1-3 parts of a stabilizer and 0.1-5 parts of a tackifier, and the waste slurry is generated when a shield passes through a stratum. The plate-and-frame filter pressing tail water and the waste slurry are fully utilized, 150-300 kg of bentonite, 1200-1500 kg of clear water and 3-8 kg of tackifier can be saved when each cubic meter of slurry shield clay stratum tunneling slurry is prepared, the plate-and-frame filter pressing tail water and the waste slurry are fully utilized, the problems that tail water is discharged and waste slurry is difficult to store can be effectively solved, and the mud can be recycled. According to the present invention, the mud can form the compact mud film on the clay stratum excavation surface so as to effectively maintain the stability of the excavation surface, reduce the friction between the shield tunneling machine and the mud during the tunneling process, and prolong the service life of the shield tunneling machine cutter head.

Description

Technical Field

[0001] The invention relates to the technical field of slurry shield tunnel engineering, and in particular to a slurry for preparing slurry for slurry shield clay stratum excavation by filtering tail water under pressure, and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of social economy and urbanization, slurry shield tunnel technology has become an indispensable key technology in the construction of major transportation and other infrastructure in my country.

[0003] During the excavation of slurry shield tunnels, a large amount of waste mud and slag with high water content will be generated. Plate and frame filter press is generally used to treat the waste mud. During the treatment process, a large amount of filter press tail water will inevitably be generated, and the properties of the tail water are relatively complex, so the project faces great pressure for treatment and discharge. During the construction of river crossing and submarine tunnels, a large amount of mud is consumed for shield excavation, and a large amount of water is required to prepare the excavation mud.

[0004] Using plate and frame filter press tailwater to prepare the waste slurry produced by shield tunneling as slurry for slurry shield tunneling can make full use of waste resources and has great engineering significance. However, there is no such technical solution in the industry at present, and it is urgently needed to be developed.

[0005] The Chinese invention patent with publication number CN202210246270.5 discloses a construction method for solidifying waste mud from drilling foundation treatment, which mentions that the waste mud generated by the foundation treatment at the construction site is squeezed by a filter press to achieve mud and water separation, and the separated tail water is used for subsequent mud solidification, concrete curing, and drilling rig construction. This invention patent emphasizes the treatment process of waste mud, but does not clearly explain the specific use method and proportion of tail water in mud solidification and concrete curing, and its role in the mud-water shield is unclear. Therefore, how to make full use of filter press tail water to prepare mud for excavation is an important project that urgently needs to be developed. Summary of the invention

[0006] The main purpose of the present invention is to propose a method for preparing mud for excavation in clay strata using filter press tail water and a preparation method thereof, aiming to make full use of the tail water from plate and frame filter press and a large amount of waste mud generated when the shield passes through the clay stratum to prepare excavation mud, thereby effectively alleviating the pressure of tail water discharge and storage.

[0007] To achieve the above-mentioned purpose, the present invention proposes a slurry for mud shield tunneling in clay strata prepared from filter press tail water, comprising the following components in parts by weight: 1000-1250 parts of waste mud, 700-800 parts of plate and frame filter press tail water, 0.1-5 parts of TOCNF, 200-550 parts of clean water, 0.2-4 parts of lubricant, 0.1-3 parts of stabilizer and 0.1-5 parts of viscosity enhancer, wherein the waste mud is generated when the shield tunnel passes through the stratum.

[0008] Preferably, the preparation method of the lubricant comprises the following steps:

[0009] S1. Prepare graphene oxide by the Hummer method, then mix the graphene oxide with N,N-dimethylformamide and then add thionyl chloride, and then stir and reflux under an inert gas, filter, wash, and dry to obtain acyl chloride graphene oxide;

[0010] S2. Dissolve the acyl chloride graphene oxide and palm alcohol in N,N-dimethylformamide, perform ultrasonic treatment, stir and reflux, filter, wash, and dry to obtain the lubricant.

[0011] Preferably, in step S1, the temperature of the stirring and refluxing is 70-90 °C, the time of the stirring and refluxing is 3.5-4.5 h, and the dosage ratio of the graphene oxide, N,N-dimethylformamide, and thionyl chloride is (90-110 mg):(4-5 mL):(15-25 mL);

[0012] In step S2, the temperature of the stirring and refluxing is 70-90 °C, the time of the stirring and refluxing is 1.5-2.5 h, and the mass ratio of the acyl chloride graphene oxide and palm alcohol is (2-3):(10-15).

[0013] Preferably, the preparation method of the stabilizer comprises the following steps:

[0014] S3. Add polyvinyl alcohol and deionized water into a reactor, stir until the polyvinyl alcohol is completely dissolved, adjust the pH value to 9-10, add hydrogen peroxide, react, add N,N,N',N'-tetramethyl-1,4-butanediamine, react again, wash, filter to remove the filtrate, and dry the filter cake to obtain modified polyvinyl alcohol;

[0015] S4. Add an acid to a reactor containing corn starch and perform heating hydrolysis. After hydrolysis, add a surfactant and perform ultrasonic treatment, and then centrifuge and wash to obtain starch nanoparticles; then add 3-aminopropyltriethoxysilane and potassium persulfate to the starch nanoparticles under stirring, heat and react, and after the reaction, wash and dry to obtain modified nano starch particles;

[0016] S5. Mix the modified polyvinyl alcohol and the modified nano starch particles, stir, and perform ultrasonic treatment to obtain the stabilizer.

[0017] Preferably, in step S3, the temperature of the reaction is 75-85 °C, the time of the reaction is 6-12 min; the temperature of the re-reaction is 80-95 °C, the time of the re-reaction is 2-4 h; the temperature of the drying is 50-60 °C, and the time of the drying is 7-9 h;

[0018] In step S4, the acid is sulfuric acid or hydrochloric acid; the temperature of the hydrolytic heating is 35-45 °C; the surfactant is Span 80 or Tween 20; the dosage ratio of the starch nanoparticles, aminoethylaminopropyltrimethoxysilane, and potassium persulfate is (20-40 g):(1-2 mL):(1-2 mL); the temperature of the heating reaction is 60-70 °C; the time of the heating reaction is 3-5 h.

[0019] Preferably, the clay content of the waste mud is 30%-60%, the density of the waste mud is 1.2-1.35 g / cm 3 , and the Marsh funnel viscosity of the waste mud is 20-60 s.

[0020] Preferably, the viscosifier is sodium carboxymethylcellulose with high viscosity; sodium carboxymethylcellulose is abbreviated as CMC, which is an artificially synthesized cellulose ether and belongs to water-soluble salts. It has excellent water retention and viscosity-increasing effects and can be used to adjust the viscosity of mud in projects such as oil drilling and slurry shield tunneling with slurry pressure.

[0021] The TOCNF is TEMPO-oxidized cellulose nanofibers. Through the TEMPO oxidation method, long plant fibers are reduced to the nanoscale to obtain cellulose TOCNF, and its aspect ratio exceeds 250. The oxidized cellulose nanofibers have the characteristics of high recycling rate, environmental friendliness, high specific strength, and large specific surface area, and play a significant role in reducing the mud filtration loss.

[0022] Preferably, the clay content of the slurry for tunneling is 25%-40%, the density is 1.15-1.25 g / cm 3 , and the Marsh funnel viscosity is 20-40 s.

[0023] The present invention also provides a method for preparing slurry for tunneling in clay strata by using the filter press tail water as described above, including the following steps: When the shield machine passes through the clay strata, the generated waste mud is pumped into the slurry adjustment tank for preparation, and by adding clear water, plate and frame filter press tail water, viscosifier, lubricant, and stabilizer, a product that meets the quality index requirements of the slurry for tunneling in clay strata of the slurry shield is adjusted.

[0024] Preferably, during the preparation process, when the density and viscosity of the mud are too high, clear water and plate and frame filter press tail water are added for dilution, and when the viscosity of the mud is too low, a viscosifier is added for adjustment.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) Compared with the existing pulping technology, the present invention makes full use of the plate-and-frame filter press tail water and waste mud. When preparing the slurry for tunneling in clay strata of slurry shield per cubic meter, it can save 150 - 300 kg of bentonite, 1200 - 1500 kg of fresh water, and 3 - 8 kg of thickening agent. By making full use of the plate-and-frame filter press tail water and waste mud, it can effectively alleviate the problems of tail water discharge and waste slurry storage difficulties, effectively save resources, reduce the impact on the environment. At the same time, by innovatively adding TOCNF (TEMPO-oxidized cellulose nanofibers), it can prepare high-quality slurry with stable physical and chemical properties. This slurry can form a dense mud film on the excavation surface of the clay strata and effectively maintain the stability of the excavation surface, which is an efficient, environmentally friendly, and energy-saving method for preparing slurry for slurry shield tunneling that conforms to China's national conditions.

[0027] (2) The lubricant provided by the present invention uses palm alcohol-modified graphene oxide to improve the dispersibility of the lubricant in the slurry, and at the same time has a good anti-friction effect, improving the lubrication performance of the lubricant, thereby reducing the friction between the shield machine and the soil during tunneling and extending the service life of the cutter head of the shield machine.

[0028] (3) For the stabilizer provided by the present invention, first, polyvinyl alcohol is degraded, then treated with a surfactant to enhance its reactivity, and then reacted with aminoethyl aminopropyl trimethoxysilane under the action of an initiator, so that the polyvinyl alcohol contains amino groups. The amino groups on the polyvinyl alcohol chain can adsorb on the clay, connect the clay together and coat it, making the clay not easily dispersed. At the same time, water molecules cannot easily enter the clay strata, thereby effectively preventing the clay strata from swelling and dispersing due to hydration, thus achieving a stabilizing effect. Subsequently, an organosilicon cross-linking agent and starch nanoparticles are subjected to a cross-linking reaction to prepare microspheres with a three-dimensional network structure. Then, the modified polyvinyl alcohol and the modified nano-starch particles are mixed to make it have excellent stability and ductility, strengthening the environmental stability at the shield construction site. At the same time, it combines with the mud film formed by TEMPO-oxidized cellulose nanofibers to synergistically improve the stability of the excavation surface, thereby ensuring the safe construction of the tunnel. Detailed implementation mode

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments without indicating the manufacturer can be obtained as conventional products through commercial purchase. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions conflicts with each other or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0030] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0031] It should be noted that unless otherwise specified, the chemical reagents involved in the present invention are all purchased through commercial channels.

[0032] Sodium carboxymethyl cellulose, with the product model of FVH6, is purchased from Zibo Daoqin New Materials Co., Ltd., and its molecular weight is 2000 - 5000 cps.

[0033] Example 1

[0034] The slurry for tunneling in clay strata of slurry shield per cubic meter is prepared from the following raw materials: 1200 kg of waste slurry (density 1.3 g / cm 3 , Marsh funnel viscosity 40 s, clay content 40%), 750 kg of plate and frame tail water, 300 kg of fresh water, 0.3 kg of TOCNF, 0.5 kg of lubricant, 0.6 kg of stabilizer, and 0.6 kg of sodium carboxymethyl cellulose. The above raw materials are placed in a slurry mixing tank and mixed evenly for use;

[0035] Among them, the preparation method of the lubricant includes the following steps:

[0036] (1) Graphene oxide is prepared by the Hummer method. Then, 100 mg of graphene oxide is mixed with 4.5 mL of N,N-dimethylformamide, and then 20 mL of thionyl chloride is added. Subsequently, it is stirred and refluxed under an inert gas N 2 , filtered, washed, and dried to obtain acyl chloride graphene oxide;

[0037] (2) 100 mg of acyl chloride graphene oxide and 550 mg of palm alcohol are dissolved in N,N-dimethylformamide, ultrasonically treated for 0.5 h, stirred and refluxed at 85 °C for 2 h, filtered, washed, and dried to obtain the lubricant;

[0038] The preparation method of the stabilizer comprises the following steps:

[0039] (3) Add 100 mg of polyvinyl alcohol and 200 mL of deionized water into a reactor, stir until the polyvinyl alcohol is completely dissolved, adjust the pH value to 9.5, add 10 mL of hydrogen peroxide, react for 10 min, add 5 mL of N,N,N',N'-tetramethyl-1,4-butanediamine, react again, wash, filter to remove the filtrate, and dry the filter cake to obtain modified polyvinyl alcohol;

[0040] (4) Add 100 mL of sulfuric acid into a reactor containing 50 g of corn starch, heat and hydrolyze at 40 °C. After hydrolysis, add span 80, perform ultrasonic treatment for 10 min, then centrifuge and wash to obtain starch nanoparticles; Then, under stirring conditions, add 3 mL of aminoethylaminopropyltrimethoxysilane and 3 mL of potassium persulfate to the starch nanoparticles, heat and react at 65 °C. After the reaction, wash and dry to obtain modified nano starch particles;

[0041] (5) Mix the modified polyvinyl alcohol and the modified nano starch particles, stir, and perform ultrasonic treatment to obtain the stabilizer.

[0042] Example 2

[0043] Prepare the slurry for tunneling in the clay stratum of the slurry shield per cubic meter, including the following raw materials: 1250 kg of waste slurry (density 1.25 g / cm 3 ³, Marsh funnel viscosity 30 s, clay content 30%), 800 kg of plate and frame tail water, 200 kg of fresh water, 0.2 kg of TOCNF, 0.2 kg of lubricant, 3 kg of stabilizer, 5 kg of sodium carboxymethyl cellulose. Place the above raw materials in a slurry mixing tank, mix evenly, and set aside;

[0044] Among them, the preparation method of the lubricant comprises the following steps:

[0045] (1) Prepare graphene oxide by the Hummer method. Then mix 100 mg of graphene oxide with 4 mL of N,N-dimethylformamide, and then add 15 mL of thionyl chloride. Subsequently, stir and reflux under an inert gas N 2 ₂, filter, wash, and dry to obtain acyl chloride graphene oxide;

[0046] (2) Dissolve 100 mg of acyl chloride graphene oxide and 550 mg of palm alcohol in N,N-dimethylformamide, perform ultrasonic treatment for 0.5 h, stir and reflux at 70 °C for 2 h, filter, wash, and dry to obtain the lubricant;

[0047] The preparation method of the stabilizer comprises the following steps:

[0048] (3) 100 mg of polyvinyl alcohol and 200 mL of deionized water were added to a reactor, stirred until the polyvinyl alcohol was completely dissolved, the pH value was adjusted to 9, 10 mL of hydrogen peroxide was added, reacted for 10 min, 4 mL of N,N,N',N'-tetramethyl-1,4-butanediamine was added, reacted again, washed, filtered to remove the filtrate, and the filter cake was dried to obtain modified polyvinyl alcohol;

[0049] (4) adding 100 mL of sulfuric acid to a reactor containing 40 g of corn starch, and heating and hydrolyzing at 40° C., adding Span 80 after hydrolysis, ultrasonically treating for 10 min, and then centrifuging and washing to obtain starch nanoparticles; then adding 2 mL of aminoethylaminopropyltrimethoxysilane and 1 mL of potassium persulfate to the starch nanoparticles under stirring, heating at 60° C. for reaction, washing after the reaction, and drying to obtain modified nano starch particles;

[0050] (5) Mixing the modified polyvinyl alcohol and the modified nano starch particles, stirring, and ultrasonically treating to obtain a stabilizer.

[0051] Example 3

[0052] The following raw materials are used to prepare the mud for each cubic meter of mud shield tunneling in clay strata: 1000 kg of waste mud (density 1.3 g / cm 3 , Soxhlet funnel viscosity 40s, clay content 40%), plate and frame tail water 700kg, clean water 550kg, TOCNF5kg, lubricant 0.2kg, stabilizer 0.1kg, sodium carboxymethyl cellulose 0.1kg, put the above raw materials in a slurry mixing tank and mix them evenly for use;

[0053] The method for preparing the lubricant comprises the following steps:

[0054] (1) Graphene oxide was prepared by the Hummer method. Then, 100 mg of graphene oxide was mixed with 5 mL of N,N-dimethylformamide and 25 mL of thionyl chloride was added. Then, the mixture was heated to 40 ℃ under an inert gas atmosphere of N 2 Stirring and refluxing, filtering, washing and drying to obtain acylated graphene oxide;

[0055] (2) dissolving 100 mg of chlorinated graphene oxide and 650 mg of palmityl alcohol in N,N-dimethylformamide, ultrasonically treating for 0.5 h, stirring and refluxing at 90° C. for 2.5 h, filtering, washing, and drying to obtain a lubricant;

[0056] The preparation method of the stabilizer comprises the following steps:

[0057] (3) Add 100 mg of polyvinyl alcohol and 200 mL of deionized water to a reactor, stir until the polyvinyl alcohol is completely dissolved, adjust the pH value to 10, add 10 mL of hydrogen peroxide, react for 10 min, add 6 mL of N,N,N',N'-tetramethyl-1,4-butanediamine, react again, wash, filter to remove the filtrate, and dry the filter cake to obtain modified polyvinyl alcohol;

[0058] (4) Add 100 mL of hydrochloric acid to a reactor containing 30 g of corn starch and heat hydrolyze at 45 °C. After hydrolysis, add Tween 20 and ultrasonically treat for 10 min, then centrifuge and wash to obtain starch nanoparticles; then add 1 mL of aminoethylaminopropyltrimethoxysilane and 1 mL of potassium persulfate to the starch nanoparticles under stirring, heat and react at 70 °C, wash after the reaction is completed, and dry to obtain modified nano starch particles;

[0059] (5) Mix the modified polyvinyl alcohol and the modified nano starch particles, stir, and ultrasonically treat to obtain a stabilizer.

[0060] Comparative Example 1

[0061] Prepare the slurry for tunneling in the clay stratum of the slurry shield per cubic meter, including the following raw materials: 1200 kg of waste slurry (density 1.3 g / cm 3 , Marsh funnel viscosity 40 s, clay content 40%), 750 kg of plate and frame tail water, 300 kg of fresh water, 0.3 kg of TOCNF, 0.6 kg of stabilizer, 0.6 kg of sodium carboxymethylcellulose. Place the above raw materials in a slurry mixing tank, mix them evenly and set aside;

[0062] Among them, the preparation method of the stabilizer includes the following steps:

[0063] (1) Add 100 mg of polyvinyl alcohol and 200 mL of deionized water to a reactor, stir until the polyvinyl alcohol is completely dissolved, adjust the pH value to 9.5, add 10 mL of hydrogen peroxide, react for 10 min, add 5 mL of N,N,N',N'-tetramethyl-1,4-butanediamine, react again, wash, filter to remove the filtrate, and dry the filter cake to obtain modified polyvinyl alcohol;

[0064] (2) Add 100 mL of sulfuric acid to a reactor containing 50 g of corn starch and heat hydrolyze at 40 °C. After hydrolysis, add Span 80 and ultrasonically treat for 10 min, then centrifuge and wash to obtain starch nanoparticles; then add 3 mL of aminoethylaminopropyltrimethoxysilane and 3 mL of potassium persulfate to the starch nanoparticles under stirring, heat and react at 65 °C, wash after the reaction is completed, and dry to obtain modified nano starch particles;

[0065] (3) Mix the modified polyvinyl alcohol and the modified nano-starch particles, stir, and perform ultrasonic treatment to obtain a stabilizer.

[0066] Comparative Example 2

[0067] Prepare the slurry for tunneling in the clay stratum of the slurry shield per cubic meter, including the following raw materials: 1200 kg of waste slurry (density 1.3 g / cm 3 , Marsh funnel viscosity 40 s, clay content 40%), 750 kg of plate-and-frame tail water, 300 kg of fresh water, 0.3 kg of TOCNF, 0.5 kg of lubricant, and 0.6 kg of sodium carboxymethylcellulose. Place the above raw materials in a slurry mixing tank and mix evenly for standby;

[0068] Among them, the preparation method of the lubricant includes the following steps:

[0069] (1) Prepare graphene oxide by the Hummer method. Then, mix 100 mg of graphene oxide with 4.5 mL of N,N-dimethylformamide, and then add 20 mL of thionyl chloride. Subsequently, stir and reflux under the inert gas N 2 and filter, wash, and dry to obtain acyl chloride graphene oxide;

[0070] (2) Dissolve 100 mg of acyl chloride graphene oxide and 550 mg of palm alcohol in N,N-dimethylformamide, perform ultrasonic treatment for 0.5 h, stir and reflux at 85 °C for 2 h, and filter, wash, and dry to obtain the lubricant.

[0071] Comparative Example 3

[0072] Prepare the slurry for tunneling in the clay stratum of the slurry shield per cubic meter, including the following raw materials: 1200 kg of waste slurry (density 1.3 g / cm 3 , Marsh funnel viscosity 40 s, clay content 40%), 750 kg of plate-and-frame tail water, 300 kg of fresh water, 0.5 kg of lubricant, 0.6 kg of stabilizer, and 0.6 kg of sodium carboxymethylcellulose. Place the above raw materials in a slurry mixing tank and mix evenly for standby;

[0073] Among them, the preparation method of the lubricant includes the following steps:

[0074] (1) Prepare graphene oxide by the Hummer method. Then, mix 100 mg of graphene oxide with 4.5 mL of N,N-dimethylformamide, and then add 20 mL of thionyl chloride. Subsequently, stir and reflux under the inert gas N 2 and filter, wash, and dry to obtain acyl chloride graphene oxide;

[0075] (2) Dissolve 100 mg of acyl chloride graphene oxide and 550 mg of palm alcohol in N,N-dimethylformamide, ultrasonically treat for 0.5 h, stir and reflux at 85 °C for 2 h, filter, wash, and dry to obtain a lubricant;

[0076] The preparation method of the stabilizer includes the following steps:

[0077] (3) Add 100 mg of polyvinyl alcohol and 200 mL of deionized water to a reactor, stir until the polyvinyl alcohol is completely dissolved, adjust the pH value to 9.5, add 10 mL of hydrogen peroxide, react for 10 min, add 5 mL of N,N,N',N'-tetramethyl-1,4-butanediamine, react again, wash, filter to remove the filtrate, and dry the filter cake to obtain modified polyvinyl alcohol;

[0078] (4) Add 100 mL of sulfuric acid to a reactor containing 50 g of corn starch and heat hydrolyze at 40 °C. After hydrolysis, add Span 80, ultrasonically treat for 10 min, then centrifuge and wash to obtain starch nanoparticles; then add 3 mL of aminoethylaminopropyltrimethoxysilane and 3 mL of potassium persulfate to the starch nanoparticles under stirring, heat and react at 65 °C, wash after the reaction, and dry to obtain modified nano starch particles;

[0079] (5) Mix the modified polyvinyl alcohol and the modified nano starch particles, stir, and ultrasonically treat to obtain a stabilizer.

[0080] The quality indexes of the slurry for tunneling prepared in Test Examples 1 to 3 and Comparative Examples 1 to 3 were measured by the weighing method. A certain volume of the slurry was weighed and then the density was calculated. The viscosity of the slurry was measured using a Brookfield viscometer. The slurries for tunneling prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were weighed respectively, left standing for 24 hours, the exuded water was observed and collected, and the amount of exuded water was compared with the amount of liquid water in the initial slurry sample. The water bleeding rate was calculated using the formula: water bleeding rate = amount of exuded water / total amount of liquid in the initial slurry × 100%. The slurries for tunneling prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were weighed respectively, and the samples were screened using a sieve by the wet screening separation method. The solids passing through a 2-micron sieve were weighed and compared with the initial mass of the sample to calculate the clay particle content: clay particle content = mass of clay particles / total mass of the sample × 100%. The colloidal particles in the slurries for tunneling prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were separated by centrifugation and then filtered through filter paper. The remaining solids in the filtrate were weighed, and the colloid ratio was calculated using the corresponding formula: colloid ratio = mass of colloidal particles / total mass of the sample × 100%. Using an API fluid loss test device, the slurry samples for tunneling prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were placed in the device, the system was pressurized to 100 psi and maintained for 30 minutes, and the amount of water lost during this period was measured and the results were recorded. The API fluid loss was expressed in mL / 30 min. The test results were statistically analyzed to obtain Table 1.

[0081] Table 1 Quality Indexes of the Slurry for Tunneling

[0082]

[0083] As can be seen from the above table, the density of the slurry for tunneling prepared in Examples 1 to 3 of the present invention is between 1.18 and 1.25 g / cm 3 ³, the viscosity is 30 to 35 s, the water bleeding rate in 24 h is 10 to 13 s, the clay particle content is between 31% and 33%, the colloid ratio is between 97.9% and 99.2%, and the API fluid loss is between 17 and 20 mL / 30 min. The quality indexes within this range meet the requirements of engineering construction, have the advantages of good physical and chemical stability, are suitable for tunneling construction in clay strata, the construction effect of this slurry is better, a dense mud film is formed in the clay strata, and it can well maintain the stability of the excavation face, having the value of popularization and application.

[0084] The slurries for tunneling prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were poured into the sample cups of an EP extreme pressure lubrication tester to test the lubrication coefficient, and the lubrication coefficients were compared with those of clear water and 4% bentonite slurry. The results are shown in Table 2.

[0085] Table 2 Lubrication Coefficients of the Slurries for Tunneling

[0086] Group Lubrication coefficient Fresh water group 0.33 4% bentonite mud 0.47 Example 1 0.15 Example 2 0.17 Example 3 0.14 Comparative example 1 0.29 Comparative example 2 0.30 Comparative example 3 0.27

[0087] As can be seen from Table 2 above, the lubrication coefficients of the slurry for tunneling provided in Embodiments 1 to 3 of the present invention are significantly smaller than those of the slurry for tunneling prepared in Comparative Examples 1 to 3, indicating that the slurry prepared by the present invention has good lubrication performance, has a good anti-friction effect, and prolongs the service life of the cutter head of the shield machine.

[0088] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the patent protection scope of the present invention.

Claims

1. A method for preparing mud for mud shield tunneling in clay strata by using filter press tail water, characterized in that: The invention comprises the following components in parts by weight: 1000-1250 parts of waste mud, 700-800 parts of plate and frame filter press tail water, 0.1-5 parts of TOCNF, 200-550 parts of clean water, 0.2-4 parts of lubricant, 0.1-3 parts of stabilizer and 0.1-5 parts of viscosity enhancer. The waste mud is generated when the shield tunnel passes through the stratum.

2. The slurry for preparing mud shield tunneling in clay strata using filter press tail water as claimed in claim 1, characterized in that: The preparation method of the lubricant comprises the following steps: S1. Graphene oxide is prepared by Hummer method, and then the graphene oxide is mixed with N,N-dimethylformamide and then thionyl chloride is added, followed by stirring and refluxing under inert gas, filtering, washing and drying to obtain chlorinated graphene oxide; S2. Dissolving the chlorinated graphene oxide and palmityl alcohol in N,N-dimethylformamide, ultrasonically treating, stirring and refluxing, filtering, washing and drying to obtain a lubricant.

3. The slurry for preparing mud shield tunneling in clay strata using filter press tail water as claimed in claim 2, characterized in that: In step S1, the stirring and reflux temperature is 70-90° C., the stirring and reflux time is 3.5-4.5 h, and the amount ratio of graphene oxide, N,N-dimethylformamide and thionyl chloride is (90-110 mg): (4-5 mL): (15-25 mL); In step S2, the stirring and reflux temperature is 70-90°C, the stirring and reflux time is 1.5-2.5h, and the mass ratio of the acylated chloride graphene oxide to palmityl alcohol is (2-3): (10-15).

4. The slurry for preparing mud shield tunneling in clay strata using filter press tail water as claimed in claim 1, characterized in that: The preparation method of the stabilizer comprises the following steps: S3, adding polyvinyl alcohol and deionized water into a reactor, stirring until the polyvinyl alcohol is completely dissolved, adjusting the pH value to 9-10, adding hydrogen peroxide, reacting, adding N,N,N',N'-tetramethyl-1,4-butanediamine, reacting again, washing, filtering to remove the filtrate, and drying the filter cake to obtain modified polyvinyl alcohol; S4, adding acid to a reactor containing corn starch, and heating and hydrolyzing, adding a surfactant after hydrolysis, ultrasonic treatment, centrifugation, washing to obtain starch nanoparticles; then adding aminoethylaminopropyltrimethoxysilane and potassium persulfate to the starch nanoparticles under stirring, heating for reaction, washing after the reaction, and drying to obtain modified nano starch particles; S5, mixing the modified polyvinyl alcohol and the modified nano starch particles, stirring, and ultrasonically treating to obtain a stabilizer.

5. The slurry for preparing mud shield tunneling in clay strata using filter press tail water as claimed in claim 4, characterized in that: In step S3, the reaction temperature is 75-85°C, and the reaction time is 6-12 minutes; the secondary reaction temperature is 80-95°C, and the secondary reaction time is 2-4 hours; the drying temperature is 50-60°C, and the drying time is 7-9 hours; In step S4, the acid is sulfuric acid or hydrochloric acid; the temperature of the heating hydrolysis is 35-45°C; the surfactant is Span 80 or Tween 20; the dosage ratio of the starch nanoparticles, aminoethylaminopropyltrimethoxysilane and potassium persulfate is (20-40g): (1-2mL): (1-2mL); the temperature of the heating reaction is 60-70°C; and the time of the heating reaction is 3-5h.

6. The slurry for preparing mud shield tunneling in clay strata using filter press tail water as claimed in claim 1, characterized in that: The clay content of the waste mud is 30%-60%, and the density of the waste mud is 1.2-1.35g / cm 3 The waste mud has a Soderbergh funnel viscosity of 20-60s.

7. The slurry for preparing mud shield tunneling in clay strata using filter press tail water as claimed in claim 1, characterized in that: The viscosity enhancer is high viscosity sodium carboxymethyl cellulose; The TOCNF is TEMPO oxidized cellulose nanofiber. The longer plant fibers are reduced to nanometer scale by TEMPO oxidation method. The obtained cellulose TOCNF has an aspect ratio of more than 250.

8. The slurry for preparing mud shield tunneling in clay strata using filter press tail water as claimed in claim 1, characterized in that: The clay content of the tunneling mud is 25%-40% and the density is 1.15-1.25 g / cm 3 , the viscosity of the Sohler funnel is 20-40s.

9. The method for preparing slurry for mud shield tunneling in clay strata using filter press tail water according to any one of claims 1 to 8, characterized in that: The following steps are involved: When the shield passes through the clay stratum, the waste mud generated is pumped into the slurry mixing tank for mixing. By adding TOCNF, clean water, plate and frame filter press tail water, thickener, lubricant and stabilizer into it, a product that meets the mud quality index requirements for mud shield excavation in clay strata is adjusted.

10. The method for preparing slurry for mud shield tunneling in clay strata using filter press tail water as claimed in claim 9, characterized in that: During the mixing process, when the mud density and viscosity are too high, clean water and plate and frame filter press tail water are added to dilute it. When the mud viscosity is too low, thickener is added to adjust it.

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