Modified fiber material for microorganism-induced solidification of sandy soil and preparation method of modified fiber material

Abstract

The invention relates to the field of high polymer materials, and discloses a modified fiber material for microorganism-induced solidification of sandy soil and a preparation method thereof.The modified fiber material is prepared from, by weight, 60-85 parts of PET slices, 10-20 parts of a modified additive and 1-3 parts of a cross-linking agent; the modified additive is obtained by copolymerizing modified nano silicon dioxide, an antioxidant and methacryloyloxyethyl trimethyl ammonium chloride. According to the invention, the modified fiber material is prepared by combining a solution polymerization method and an electrostatic spinning technology; the added modified additive endows the modified fiber material with excellent tensile property and aging resistance, the generation amount of calcium carbonate is increased by combining with a microbe-induced calcium carbonate deposition technology, and the compressive strength and impermeability of the sandy soil can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a modified fiber material for microbial-induced solidification of sandy soil and a preparation method thereof. Background Art

[0002] Traditional soil improvement methods usually use chemical curing agents and chemical grouting materials for grouting to reinforce the soil, which is likely to cause environmental pollution. The microbial-induced calcium carbonate precipitation technology is a new type of green soil reinforcement technology that has emerged in the geotechnical field in recent years. Among them, the microbial-induced calcium carbonate precipitation technology based on urea hydrolysis is the most studied and widely used biomineralization technology at present. The principle of this technology is to use calcium carbonate precipitates generated by the metabolism of microorganisms to bind soil particles together, thereby improving the strength and stiffness of the soil. The existing microbial soil reinforcement technologies mainly adopt the grouting method, the soaking method and the mixing method. Among them, the mixing method can reduce the sample preparation time, shorten the curing time, improve the material utilization rate by directly mixing microorganisms and cementing substances once to reinforce the soil. Most importantly, it can avoid the problem of uneven soil reinforcement caused by the first two reinforcement methods and is more easily implemented at the construction site. It is more reasonable to use it for the improvement of aeolian sand and put it into large-scale highway engineering construction.

[0003] As a high-quality soil reinforcement material, fibers have been widely used in the field of geotechnical reinforcement in recent years. By incorporating fibers into the soil, the interaction force between soil particles can be increased, thereby increasing the strength of the soil. At present, fibers are mainly divided into two types: natural fibers and synthetic fibers. Among them, natural fibers have problems such as high water absorption rate and poor mechanical properties. Synthetic fibers mainly include polypropylene fibers, basalt fibers, polyester fibers, glass fibers, etc. Their surfaces are smooth and chemically inert, and the bonding with sandy soil is not firm. When used as the reinforcement of soil reinforcement materials, it is difficult to exert the excellent properties of fibers. Moreover, under the action of external forces, the fibers will break, and their mechanical properties need to be further improved. In addition, fibers are prone to thermal-oxidative aging in a long-term harsh environment, resulting in a decrease in mechanical properties and affecting their reinforcement effect on sandy soil. Summary of the Invention

[0004] To solve the deficiencies mentioned in the above background art, the purpose of the present invention is to provide a modified fiber material for microbial-induced solidification of sandy soil and a preparation method thereof. The modified fiber material is prepared by combining the solution polymerization method and the electrospinning technology. The added modified additives endow the modified fiber material with excellent tensile properties and aging resistance. Its combination with the microbial-induced calcium carbonate precipitation technology increases the generation amount of calcium carbonate, and can effectively improve the compressive strength and impermeability of sandy soil.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A modified fiber material for microbial-induced solidification of sandy soil, comprising the following components in parts by weight: 60-85 parts of PET chips, 10-20 parts of a modified additive, and 1-3 parts of a crosslinking agent;

[0007] The modified additive is a modified additive obtained by copolymerizing modified nano-silica, an antioxidant, and methacryloyloxyethyl trimethyl ammonium chloride;

[0008] The modified nano-silica is a modified nano-silica obtained by reacting nano-silica grafted with γ-glycidoxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane with montmorillonite; the antioxidant is an antioxidant obtained by grafting 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and 2-hydroxyethyl methacrylate.

[0009] Preferably, the preparation method of the modified additive comprises the following steps:

[0010] A. Take nano-silica and add it to an ethanol solution, stir at room temperature and disperse ultrasonically, add γ-glycidoxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane, react at 50-70 °C for 4-8 h, then add triethylenediamine and montmorillonite, react at 105-120 °C for 2-3 h, and after the reaction is completed, filter, wash, and dry to prepare the modified nano-silica;

[0011] B. Dissolve 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and 2-hydroxyethyl methacrylate in dichloromethane, stir at 0-4 °C for 5-15 min in a nitrogen atmosphere, then add 4-dimethylaminopyridine and continue to stir for 10-15 min to obtain a mixed solution. Take N,N'-dicyclohexylcarbodiimide dissolved in dichloromethane and add it to the mixed solution, react at room temperature for 42-48 h, protect with nitrogen during the reaction, and after the reaction is completed, filter and evaporate, chromatographically separate, wash and dry to prepare the antioxidant;

[0012] C. Mix the modified nano-silica, the antioxidant, and methacryloyloxyethyl trimethyl ammonium chloride evenly, add polyvinyl alcohol and ammonium persulfate, and carry out a polymerization reaction at 40-80 °C. After the reaction is completed, cool to room temperature to prepare the modified additive.

[0013] Preferably, the mass ratio of nano-silica, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and montmorillonite in step A is 1-1.7: 0.2-0.5: 0.2-0.5: 0.8-1.4.

[0014] Preferably, in step B, the mass ratio of 3,5 - di - tert - butyl - 4 - hydroxyphenylpropionic acid to 2 - hydroxyethyl methacrylate is 2 - 3:1.

[0015] Preferably, in step C, the mass ratio of modified nano - silica, antioxidant, methacryloyloxyethyltrimethylammonium chloride, polyvinyl alcohol, and ammonium persulfate is 1.4 - 2:0.4 - 0.7:0.6 - 1:0.2 - 0.5:0.05 - 0.5.

[0016] A preparation method of a modified fiber material for microbial - induced solidification of sandy soil, comprising the following steps:

[0017] S1. Using trifluoroacetic acid and dichloromethane as solvents, adding PET chips to dissolve to obtain a PET spinning solution;

[0018] S2. Adding a modified additive and a cross - linker to the PET spinning solution, and obtaining a mixed spinning stock solution through degassing treatment;

[0019] S3. Electrospinning and thermally cross - linking the mixed spinning stock solution to prepare the modified fiber material.

[0020] Preferably, in step S1, the volume ratio of trifluoroacetic acid to dichloromethane is 3 - 5:1; the concentration of the PET spinning solution is 20 - 35%.

[0021] Preferably, in step S2, the cross - linker is one of N,N - methylenebisacrylamide or glutaraldehyde.

[0022] Preferably, in step S3, in the electrospinning operation, the set voltage is 16 - 25 kV, the feeding rate is 0.4 - 0.8 mL / h, and the distance between the nozzle and the receiving roller is 10 - 20 cm.

[0023] Preferably, in step S3, the temperature of the thermal cross - linking treatment is 120 - 165 °C, and the time is 60 - 120 min.

[0024] Advantages of the present invention:

[0025] The present invention modifies nano - silica with γ - glycidoxypropyltrimethoxysilane and γ - methacryloxypropyltrimethoxysilane, enabling double - bond groups and epoxy groups to be grafted onto the surface of nano - silica. Meanwhile, the carboxyl group on the surface of 3,5 - di - tert - butyl - 4 - hydroxyphenylpropionic acid reacts with the hydroxyl group on the surface of 2 - hydroxyethyl methacrylate to synthesize an antioxidant with a double - bond structure on the surface. Among them, the epoxy group in the structure of the modified nano - silica undergoes a ring - opening reaction with the hydroxyl group on the surface of montmorillonite, and the double - bond group serves as a bridge for polymerization with methacryloyloxyethyltrimethylammonium chloride and the antioxidant. Methacryloyloxyethyltrimethylammonium chloride serves as the antistatic main body, and the formed copolymer molecular chain has stable ammonium cations, which can increase the charge density of the polymer, promote the transfer of charges, and avoid the generation of strong electrostatic forces due to friction between fiber filaments, thereby avoiding affecting the bundling property of the fibers. In addition, polyvinyl alcohol and ammonium persulfate initiator are added. Polyvinyl alcohol penetrates through the polymer chain segments to form a semi - interpenetrating network structure, improving the spinnability of the polymer, and a modified additive is prepared. The present invention mixes PET chips and the modified additive, adds a cross - linker to prepare a mixed spinning dope, then uses electrospinning technology to prepare primary nanofibers, and finally obtains a modified fiber material through heat treatment.

[0026] The modified fiber material prepared by the present invention has excellent tensile properties and aging resistance. The added modified additive increases the surface roughness of the modified fiber material, enhances the mechanical biting force and chemical bonding force between the fiber material and the matrix. At the same time, the rough surface of the modified fiber material can provide more attachment sites for microorganisms, promoting the growth, reproduction, migration and fixation of microorganisms in sandy soil, increasing the amount of calcium carbonate generated, improving the uniformity of calcium carbonate precipitation, reducing the permeability coefficient of sandy soil. Using the modified fiber material combined with the microbial - induced calcium carbonate precipitation technology can effectively cement and fill the pores in sandy soil, improving the compressive strength and impermeability of sandy soil. Detailed implementation mode

[0027] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. 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 scope of protection of the present invention.

[0028] In the examples and comparative examples of the present invention, the intrinsic viscosity of PET chips is 0.675 dL / g, purchased from Jiangsu Silk Group Co., Ltd.; the montmorillonite is 400 mesh, purchased from Shijiazhuang Dinglei Mineral Products Trading Co., Ltd.

[0029] Example 1 A preparation method of a modified additive includes the following steps:

[0030] A. Take 1.2 g of nano-silica and add it to 50 mL of an ethanol solution with a volume fraction of 50%. Stir and ultrasonically disperse at room temperature. Add 0.25 g of γ-glycidoxypropyltrimethoxysilane and 0.23 g of γ-methacryloxypropyltrimethoxysilane, and react at 65 °C for 7 h. Then add 0.05 g of triethylenediamine and 0.95 g of montmorillonite, and react at 110 °C for 3 h. After the reaction is completed, filter, wash, and dry to prepare modified nano-silica;

[0031] B. Take 2.6 g of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and 1.1 g of 2-hydroxyethyl methacrylate and dissolve them in 50 mL of dichloromethane. Stir at 0 °C for 10 min in a nitrogen atmosphere, then add 0.1 g of 4-dimethylaminopyridine and continue stirring for 15 min to obtain a mixed solution. Take 2.5 g of N,N'-dicyclohexylcarbodiimide and dissolve it in 10 mL of dichloromethane and add it to the mixed solution. React at room temperature for 48 h, and protect with nitrogen during the reaction. After the reaction is completed, filter, evaporate, separate by chromatography, wash, and dry to prepare an antioxidant;

[0032] C. Take 1.5 g of modified nano-silica, 0.6 g of antioxidant, and 0.7 g of methacryloyloxyethyltrimethylammonium chloride and mix them evenly. Add 0.3 g of polyvinyl alcohol and 0.14 g of ammonium persulfate, and carry out a polymerization reaction at 70 °C. After the reaction is completed, cool to room temperature to prepare a modified additive.

[0033] Example 2 A modified fiber material for microbial-induced solidification of sandy soil, comprising the following components in parts by weight: 62 parts of PET chips, 10 parts of the modified additive prepared in Example 1, and 1 part of crosslinking agent N,N'-methylenebisacrylamide.

[0034] The preparation method of the above-mentioned modified fiber material for microbial-induced solidification of sandy soil comprises the following steps:

[0035] S1. Prepare a trifluoroacetic acid-dichloromethane solvent according to a volume ratio of 4:1, and add PET chips to dissolve to obtain a PET spinning solution with a concentration of 20%;

[0036] S2. Add the modified additive and crosslinking agent to the PET spinning solution, and obtain a mixed spinning stock solution after degassing treatment;

[0037] S3. Place the mixed spinning stock solution in an electrospinning machine, set the voltage to 20 kV, the feeding rate to 0.6 mL / h, adjust the distance between the nozzle and the receiving roller to 15 cm, and carry out electrospinning to obtain primary fibers. Heat crosslink the primary fibers at 140 °C for 60 min to prepare the modified fiber material.

[0038] Example 3 A modified fiber material for microbial-induced solidification of sandy soil, comprising the following components in parts by weight: 70 parts of PET chips, 15 parts of the modified additive prepared in Example 1, and 2 parts of crosslinking agent glutaraldehyde.

[0039] The preparation method of the above-mentioned modified fiber material for microbial-induced solidification of sandy soil is the same as that of Example 2.

[0040] Example 4 A modified fiber material for microbial-induced solidification of sandy soil, comprising the following components in parts by weight: 84 parts of PET chips, 20 parts of the modified additive prepared in Example 1, and 3 parts of crosslinking agent glutaraldehyde.

[0041] The preparation method of the above-mentioned modified fiber material for microbial-induced solidification of sandy soil is the same as that of Example 2.

[0042] Comparative Example 1 The preparation method of a modified additive comprises the following steps:

[0043] A. Take 1.2 g of nano-silica and add it to 50 mL of an ethanol solution with a volume fraction of 50%. Stir and ultrasonically disperse at room temperature, add 0.23 g of γ-methacryloxypropyltrimethoxysilane, and react at 65 °C for 7 h. After the reaction is completed, filter, wash, and dry to prepare modified nano-silica;

[0044] B. Take 2.6 g of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and 1.1 g of 2-hydroxyethyl methacrylate and dissolve them in 50 mL of dichloromethane. Stir at 0 °C for 10 min in a nitrogen atmosphere, then add 0.1 g of 4-dimethylaminopyridine and continue stirring for 15 min to obtain a mixed solution. Take 2.5 g of N,N'-dicyclohexylcarbodiimide and dissolve it in 10 mL of dichloromethane and add it to the mixed solution. React at room temperature for 48 h, and protect with nitrogen during the reaction. After the reaction is completed, filter, evaporate, separate by chromatography, wash, and dry to prepare an antioxidant;

[0045] C. Take 1.5 g of modified nano-silica, 0.6 g of antioxidant, and 0.7 g of methacryloxyethyltrimethylammonium chloride and mix them evenly. Add 0.3 g of polyvinyl alcohol and 0.14 g of ammonium persulfate, and carry out a polymerization reaction at 70 °C. After the reaction is completed, cool to room temperature to prepare a modified additive.

[0046] Comparative Example 2 The preparation method of a modified additive comprises the following steps:

[0047] A. Take 1.2 g of nano-silica and add it to 50 mL of an ethanol solution with a volume fraction of 50%. Stir and ultrasonically disperse at room temperature. Add 0.25 g of γ-glycidoxypropyltrimethoxysilane and 0.23 g of γ-methacryloxypropyltrimethoxysilane, and react at 65 °C for 7 h. Then add 0.05 g of triethylenediamine and 0.95 g of montmorillonite, and react at 110 °C for 3 h. After the reaction is completed, filter, wash, and dry to prepare modified nano-silica;

[0048] B. Take 1.5 g of modified nano-silica and 0.7 g of methacryloxyethyltrimethylammonium chloride and mix them evenly. Add 0.3 g of polyvinyl alcohol and 0.14 g of ammonium persulfate, and carry out a polymerization reaction at 70 °C. After the reaction is completed, cool to room temperature to prepare a modified additive.

[0049] Comparative Example 3 A method for preparing a modified additive includes the following steps:

[0050] A. Take 1.2 g of nano-silica and add it to 50 mL of an ethanol solution with a volume fraction of 50%. Stir and ultrasonically disperse at room temperature. Add 0.25 g of γ-glycidoxypropyltrimethoxysilane and 0.23 g of γ-methacryloxypropyltrimethoxysilane, and react at 65 °C for 7 h. Then add 0.05 g of triethylenediamine and 0.95 g of montmorillonite, and react at 110 °C for 3 h. After the reaction is completed, filter, wash, and dry to prepare modified nano-silica;

[0051] B. Dissolve 2.6 g of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and 1.1 g of 2-hydroxyethyl methacrylate in 50 mL of dichloromethane. Stir at 0 °C for 10 min in a nitrogen atmosphere, then add 0.1 g of 4-dimethylaminopyridine and continue stirring for 15 min to obtain a mixed solution. Dissolve 2.5 g of N,N'-dicyclohexylcarbodiimide in 10 mL of dichloromethane and add it to the mixed solution. React at room temperature for 48 h, and protect with nitrogen during the reaction. After the reaction is completed, filter, evaporate, separate by chromatography, wash, and dry to prepare an antioxidant;

[0052] C. Take 1.5 g of modified nano-silica and 0.6 g of antioxidant and mix them evenly. Add 0.3 g of polyvinyl alcohol and 0.14 g of ammonium persulfate, and carry out a polymerization reaction at 70 °C. After the reaction is completed, cool to room temperature to prepare a modified additive.

[0053] Comparative Example 4 A method for preparing a modified additive includes the following steps:

[0054] A. Take 2.6 g of 3,5 - di - tert - butyl - 4 - hydroxyphenylpropionic acid and 1.1 g of 2 - hydroxyethyl methacrylate and dissolve them in 50 mL of dichloromethane. Place the mixture in a nitrogen atmosphere at 0 °C and stir for 10 min. Then add 0.1 g of 4 - dimethylaminopyridine and continue stirring for 15 min to obtain a mixed solution. Take 2.5 g of N,N - dicyclohexylcarbodiimide and dissolve it in 10 mL of dichloromethane, then add it to the mixed solution. React at room temperature for 48 h, and protect the reaction by passing nitrogen during the reaction. After the reaction is completed, filter, evaporate, separate by chromatography, wash, and dry to prepare an antioxidant.

[0055] B. Take 0.6 g of the antioxidant and 0.7 g of methacryloyloxyethyltrimethylammonium chloride and mix them evenly. Add 0.3 g of polyvinyl alcohol and 0.14 g of ammonium persulfate, and carry out a polymerization reaction at 70 °C. After the reaction is completed, cool to room temperature to prepare a modified additive.

[0056] Comparative Example 5 A modified fiber material for microbial - induced solidification of sandy soil, comprising the following components in parts by weight: 84 parts of PET chips, 20 parts of the modified additive prepared in Comparative Example 1, and 3 parts of cross - linker glutaraldehyde.

[0057] The preparation method of the above - mentioned modified fiber material for microbial - induced solidification of sandy soil is the same as that in Example 2.

[0058] Comparative Example 6 A modified fiber material for microbial - induced solidification of sandy soil, comprising the following components in parts by weight: 84 parts of PET chips, 20 parts of the modified additive prepared in Comparative Example 2, and 3 parts of cross - linker glutaraldehyde.

[0059] The preparation method of the above - mentioned modified fiber material for microbial - induced solidification of sandy soil is the same as that in Example 2.

[0060] Comparative Example 7 A modified fiber material for microbial - induced solidification of sandy soil, comprising the following components in parts by weight: 84 parts of PET chips, 20 parts of the modified additive prepared in Comparative Example 3, and 3 parts of cross - linker glutaraldehyde.

[0061] The preparation method of the above - mentioned modified fiber material for microbial - induced solidification of sandy soil is the same as that in Example 2.

[0062] Comparative Example 8 A modified fiber material for microbial - induced solidification of sandy soil, comprising the following components in parts by weight: 84 parts of PET chips, 20 parts of the modified additive prepared in Comparative Example 4, and 3 parts of cross - linker glutaraldehyde.

[0063] The preparation method of the above - mentioned modified fiber material for microbial - induced solidification of sandy soil is the same as that in Example 2.

[0064] Performance testing

[0065] A. The modified fiber materials prepared in Examples 2-4 and Comparative Examples 5-8 were subjected to mechanical property tests with reference to the GB / T14337-2022 standard. They were cured for 24 h and 72 h at 100 °C and 95% relative humidity, and their mechanical properties were tested. The data results are shown in Table 1.

[0066] Table 1 Test results of the mechanical properties of the specimens

[0067]

[0068] It can be seen from the data in Table 1 that the modified fiber materials prepared in Examples 2-4 of the present invention have excellent tensile properties and aging resistance and are not easily broken. Among them, in Comparative Example 5, the nano-silica grafted montmorillonite was not treated, and the measured fracture strength and tensile strength were slightly worse than those in Examples 2-4. In Comparative Example 6, no antioxidant was added, and the fracture strength after treatment at 100 °C for 24 h and 72 h decreased significantly compared with that in Examples 2-4. In Comparative Example 7, methylacryloyloxyethyltrimethylammonium chloride was not added, and the measured fracture strength and tensile strength were slightly worse than those in Examples 2-4. In Comparative Example 8, no modified nano-silica was added, and the measured fracture strength and tensile strength were significantly lower than those in Examples 2-4.

[0069] B. The modified fiber materials prepared in Examples 2-4 and Comparative Examples 5-8 were subjected to performance tests in combination with the microbial-induced calcium carbonate deposition technology:

[0070] a. Preparation of bacterial solution and cementation solution: Bacillus pasteurii was selected for bacterial solution culture. First, a liquid medium for the survival and reproduction of the bacterial strain was prepared. Urea, sodium chloride, tryptone, and peptone were added to this liquid medium in amounts of 20 g / L, 5 g / L, 15 g / L, and 5 g / L respectively. The pH was controlled at 7.3 by titration with 1 mol / L sodium hydroxide and hydrochloric acid. Then, the activated bacterial strain was added to the liquid medium sterilized by high-pressure steam and cultured in a constant-temperature shaker at 30 °C for 48 h. The shaking rate was 130 r / min. After the culture was completed, a small amount of the upper-layer bacterial solution was taken, and the bacterial solution concentration (represented by OD600) was measured with a spectrophotometer, and the OD600 of the bacterial solution was controlled to be 0.9. Finally, it was stored in a refrigerator at 4 °C; the cementation solution was a mixed solution of 1 mol / L calcium chloride and 1 mol / L urea.

[0071] b. Sample preparation: Select the modified fiber material prepared in Examples 2-4 and Comparative Examples 5-8 with a dosage of 1%, and prepare the sample by mixing method. Weigh the required sand sample and modified fiber material and mix them thoroughly. To ensure the uniformity of the sample, use a spray pot to quantitatively spray the bacterial solution and the binder solution in a mass ratio of 2:1 into the fiber soil in layers and stir manually. Use the method of spraying and stirring to mix thoroughly for 15 minutes. After stirring evenly, keep it in a constant temperature and humidity sealed state for maintenance. The maintenance temperature is 20±2℃, the humidity of the moisturizing cylinder is 95%, and the maintenance is carried out for 7 days to allow the microorganisms to fully react.

[0072] c. Determination of calcium carbonate content: The acid washing method is used to determine the calcium carbonate content of the sample after microbial solidification. First, take an appropriate amount of the sample, dry it, grind it into fine particles, wash it repeatedly with deionized water, dry it, and weigh it to record it as m 1 Then, it is titrated with hydrochloric acid until no more bubbles are generated, and then the excess hydrochloric acid is washed with deionized water. Finally, the sample is dried and weighed and recorded as m 2 Repeat the operation three times to get the average value of calcium carbonate content. The formula for calculating calcium carbonate content is: G = (m 1 -m 2 ) / m 1 ×100%, and the data results are shown in Table 2.

[0073] d. Test of unconfined compressive strength: refer to the "Standard for Geotechnical Test Methods" (GB / T50123-2019), and the data results are shown in Table 2.

[0074] e. Determination of permeability coefficient: The variable head method is used to determine the permeability coefficient of the solidified sand. The specific operation is as follows:

[0075] (1) Tightly connect one end of the sample to a long glass tube with a scale, with a water stop clamp in the middle. Water flows through the sample from top to bottom, while ensuring that the connecting pipe does not leak;

[0076] (2) Inject airless water into the glass tube and record the water head H in the glass tube 1 , open the water stop clamp, after time Δt, close the water stop clamp, and then record the water head H in the glass tube 2 This step is repeated six times, and the average value is calculated. At the same time, the water temperature is measured with a thermometer, and the permeability coefficient of the solidified sand is calculated using the formula: K = 2.3aL / AΔt˙lg(H 1 / H 2 ), where a is the cross-sectional area of ​​the glass tube, cm 2 ; A is the cross-sectional area of ​​the solidified sand sample, cm 2 ; L is the height of the solidified sand sample, cm, and the data results are shown in Table 2.

[0077] Table 2 Test results of sample performance

[0078]

[0079] As can be seen from the data in Table 2, the modified fiber materials prepared in Examples 2-4 of the present invention combined with the microbial-induced calcium carbonate precipitation technology increase the amount of calcium carbonate generated and can effectively improve the compressive strength and impermeability of sandy soil.

[0080] In the description of this specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0081] 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 by the above embodiments, and the above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A modified fiber material for microbial induced sand solidification, characterized in that: The invention comprises the following components by weight: 60 to 85 parts of PET chips, 10 to 20 parts of modified additives, and 1 to 3 parts of cross-linking agents; The modified additive is a modified additive obtained by copolymerizing modified nano silicon dioxide, an antioxidant and methacryloyloxyethyl trimethyl ammonium chloride; The modified nano-silica is obtained by co-grafting nano-silica with γ-glycidyloxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane and then reacting with montmorillonite; the antioxidant is obtained by grafting 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and hydroxyethyl methacrylate.

2. The modified fiber material for microbial induced sand solidification according to claim 1, characterized in that: The preparation method of the modified additive comprises the following steps: A. Add nano-silica to an ethanol solution, stir at room temperature and disperse by ultrasonic, add γ-glycidyloxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane, react at 50-70°C for 4-8h, then add triethylenediamine and montmorillonite, react at 105-120°C for 2-3h, filter, wash and dry after the reaction to obtain modified nano-silica; B. Dissolve 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid and hydroxyethyl methacrylate in dichloromethane, stir for 5-15 min at 0-4°C in a nitrogen atmosphere, then add 4-dimethylaminopyridine and continue stirring for 10-15 min to obtain a mixed solution, dissolve N,N-dicyclohexylcarbodiimide in dichloromethane and add it to the mixed solution, react at room temperature for 42-48 h, pass nitrogen protection during the reaction, and after the reaction is completed, filter, evaporate, separate by chromatography, wash and dry to prepare an antioxidant; C. Take modified nano-silica, antioxidant and methacryloyloxyethyl trimethyl ammonium chloride and mix them evenly, add polyvinyl alcohol and ammonium persulfate, place them at 40-80° C. for polymerization reaction, cool them to room temperature after the reaction is completed, and prepare the modified additive.

3. The modified fiber material for microbial induced sand solidification according to claim 2, characterized in that: In the step A, the mass ratio of nano silicon dioxide, γ-glycidyloxypropyl trimethoxysilane, γ-methacryloxypropyl trimethoxysilane and montmorillonite is 1-1.7: 0.2-0.5: 0.2-0.5: 0.8-1.

4.

4. The modified fiber material for microbial induced sand solidification according to claim 2, characterized in that: In the step B, the mass ratio of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid to hydroxyethyl methacrylate is 2 to 3:

1.

5. The modified fiber material for microbial induced sand solidification according to claim 2, characterized in that: In the step C, the mass ratio of modified nano silicon dioxide, antioxidant, methacryloyloxyethyl trimethyl ammonium chloride, polyvinyl alcohol and ammonium persulfate is 1.4-2: 0.4-0.7: 0.6-1: 0.2-0.5: 0.05-0.

5.

6. The method for preparing modified fiber material for microbial induced sand solidification according to claim 1, characterized in that: The following steps are involved: S1, using trifluoroacetic acid and dichloromethane as solvent, adding PET slices to dissolve to obtain PET spinning solution; S2, adding a modifying additive and a cross-linking agent to the PET spinning solution, and obtaining a mixed spinning solution by degassing; S3, subjecting the mixed spinning solution to electrostatic spinning and thermal cross-linking treatment to prepare the modified fiber material.

7. The method for preparing modified fiber material for microbial induced sand solidification according to claim 6, characterized in that: In the step S1, the volume ratio of trifluoroacetic acid to dichloromethane is 3-5:1; and the concentration of the PET spinning solution is 20-35%.

8. The method for preparing modified fiber material for microbial induced sand solidification according to claim 6, characterized in that: In step S2, the cross-linking agent is one of N,N-methylenebisacrylamide and glutaraldehyde.

9. The method for preparing modified fiber material for microbial induced sand solidification according to claim 6, characterized in that: In the electrospinning operation in step S3, the voltage is set to 16-25 kV, the propulsion rate is set to 0.4-0.8 mL / h, and the distance between the nozzle and the receiving roller is set to 10-20 cm.

10. The method for preparing modified fiber material for microbial induced sand solidification according to claim 6, characterized in that: The heat cross-linking treatment temperature in step S3 is 120-165° C. and the time is 60-120 min.

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