Microorganism synergistic fiber solidified soil and preparation method thereof

Abstract

The invention relates to the technical field of civil engineering preparation, and particularly discloses microorganism synergistic fiber solidified soil and a preparation method thereof. The microorganism synergistic fiber solidified soil is prepared from the following components: sandy soil, modified PE fibers, magnesium oxide, urease bacterium liquid and cementing liquid, the preparation method of the modified PE fiber comprises the following steps: soaking the PE fiber in a solution A; taking out the PE fiber, soaking in the solution B, and drying to obtain the PE fiber. The solution A is composed of 12-18 mmol / L of catechol and 4-6 mmol / L of tetraethylenepentamine, and a solvent is a hydroxymethyl aminomethane aqueous solution; the solution B is prepared from 8 to 12 mmol / L of KH-550 silane coupling agent and 16 to 24 mmol / L of EOS tetraethyl silicate, and the solvent is ethanol. According to the microorganism synergistic fiber solidified soil provided by the invention, an MICP-based soil body solidification effect enhancing technology is perfected, so that the mechanical property and the anti-permeability performance of the solidified soil are improved.

Description

Technical Field

[0001] The present application relates to the technical field of civil engineering preparation, and in particular to a microbial synergistic fiber-solidified soil and a preparation method thereof. Background Art

[0002] At present, traditional soil reinforcement methods mainly include chemical grouting and cement mixing piles. Although these methods can improve the strength and stability of the soil, they have certain limitations in terms of environmental protection and economic benefits. In recent years, with the development of microbial induced calcium carbonate precipitation (MICP) technology, the use of biomineralization to improve soil properties has gradually become a research hotspot. This new technology is not only environmentally friendly, but also can effectively improve the mechanical properties of the soil and reduce engineering costs. However, the single use of MICP technology may not achieve the ideal curing effect under certain conditions. Summary of the invention

[0003] In order to solve the above technical problems, the present application provides a microbial synergistic fiber solidified soil and a preparation method thereof.

[0004] The present application provides a microbial synergistic fiber-solidified soil, which specifically includes the following components: sand, modified PE fiber, magnesium oxide, urease bacterial solution, and cementing solution; The solid-liquid ratio of the sand, the magnesium oxide, the urease bacterial solution, and the cementing solution is 140-160 g: 20-26 g: 180-220 ml: 770-830 ml; The amount of the modified PE fiber is 0.4%-0.6% of the volume of the sand; The preparation method of the modified PE fiber is as follows: at room temperature, immerse the PE fiber in solution A for 20-28 hours; take out the PE fiber and immerse it in solution B for 20-28 hours, and dry it in an oven at 55-70°C to obtain the modified PE fiber; The solution A is composed of components with the following concentrations: 12-18 mmol / L catechol, 4-6 mmol / L tetraethylenepentamine, and the solvent is 8-12 mmol / L hydroxymethylaminomethane aqueous solution; The B solution is composed of the following components: 8-12 mmol / L KH-550 silane coupling agent, 16-24 mmol / L LEOS tetraethyl silicate, and the solvent is ethanol; The cementing fluid is composed of the following components in concentrations: 0.8-1.2 mol / L calcium chloride, 0.8-1.2 mol / L urea, and the solvent is water.

[0005] The technical solution of the present application provides a microbial synergistic fiber-stabilized soil and a preparation method thereof, taking into account the urease bacteria microorganism-induced calcium carbonate precipitation on the cementation of sandy soil particles and the filling of soil pores, and improving the MICP-based soil solidification effect enhancement technology, thereby improving the mechanical properties and impermeability of the stabilized soil.

[0006] In the preparation method of modified PE fiber, catechol and tetraethylene pentamine compounds are first introduced to modify or react PE fiber, which can effectively improve the hydrophilicity of PE fiber; the second step is to use KH-550 silane coupling agent and EOS tetraethyl silicate to change and effectively improve the roughness of PE fiber, promote the synergistic effect between fiber and sand and other raw materials, and thus improve the comprehensive performance of fiber-cured soil. The addition of magnesium oxide can quickly increase the strength of the soil, while ensuring the uniformity of the system and avoiding cracking of the cured soil.

[0007] Preferably, the solid-to-liquid ratio of the sand, the magnesium oxide, the urease bacterial solution and the cementing liquid is: 145-155g: 22-24g: 190-210ml: 790-810ml.

[0008] Preferably, the sand is a mixture of 5-15 μm sand, 40-60 μm sand and 80-100 μm sand in a weight ratio of 8-12:1-5:0.1-0.7.

[0009] Preferably, the sand is a mixture of 5-15 μm sand, 40-60 μm sand and 80-100 μm sand in a weight ratio of 9-11:2-4:0.3-0.5.

[0010] Preferably, the preparation method of the urease bacterial solution is: inoculate Bacillus pasteurianus onto a sterilized culture medium, and culture the culture medium in an oscillating incubator at a temperature of 30° C. and a rotation speed of 150-250 rpm for 40-56 hours to obtain the urease bacterial solution.

[0011] Preferably, the preparation method of the modified PE fiber is: ultrasonically immersing the PE fiber in a 1:1 ethanol-acetone mixed solution for 50-70 minutes to remove impurities on the surface of the PE fiber, rinsing with deionized water, and then drying in an oven at 55-70°C; at room temperature, immersing the cleaned PE fiber in solution A and soaking in the solution for 20-28 hours; then adding it to solution B, soaking it for 20-28 hours, and drying it in an oven at 55-70°C to obtain the modified PE fiber.

[0012] Preferably, the solution A is composed of components having the following concentrations: 14-16 mmol / L catechol, 4.5-5.5 mmol / L tetraethylenepentamine, and the solvent is 9-11 mmol / L hydroxymethylaminomethane aqueous solution; the pH of the solution A is 8.0-9.0.

[0013] Preferably, the B solution is composed of components having the following concentrations: 9-11 mmol / L KH-550 silane coupling agent, 18-22 mmol / L EOS tetraethyl silicate, and the solvent is ethanol; the pH of the B solution is 9.0-10.0.

[0014] In a specific embodiment, the solution A is composed of components having the following concentrations: 15 mmol / L catechol, 5 mmol / L tetraethylenepentamine, and the solvent is 10 mmol / L hydroxymethylaminomethane aqueous solution; the pH of the solution A is 8.5.

[0015] In a specific embodiment, the B solution is composed of components having the following concentrations: 10 mmol / L KH-550 silane coupling agent, 20 mmol / L EOS tetraethyl silicate, and the solvent is ethanol; the pH of the B solution is 9.5.

[0016] On the other hand, the present application provides a method for preparing the above-mentioned microorganism-synergistic fiber-solidified soil, which specifically comprises the following steps in sequence: Premixing: the sand, the modified PE fiber and the magnesium oxide are mixed evenly to prepare a premix, the premix is ​​poured into a mold, and geotextiles are placed at the bottom and top of the sample; Grouting: The urease bacterial solution and the cementing solution are pumped into the mold in batches of 3-5 times at a rate of 0.4-0.6 ml / min by a peristaltic pump.

[0017] Preferably, the grouting step is specifically as follows: the urease bacterial solution and the cementing solution are pumped into the mold in batches 4 times at a rate of 0.5 ml / min by a peristaltic pump; after each batch of bacterial solution is injected, it is allowed to stand for 2-4 hours before injecting the next batch of bacterial solution; after each batch of cementing solution is injected, it is allowed to stand for 5-7 hours before injecting the next batch of cementing solution.

[0018] In a specific embodiment, the standing time after each batch of bacterial solution injection can be 2h, 2.5h, 3h, 3.5h, or 4h before the next batch of bacterial solution injection is performed.

[0019] In a specific embodiment, the standing time after each batch of cementing liquid injection can be 5h, 5.5h, 6h, 6.5h, 7h before the next batch of cementing liquid injection.

[0020] In the preparation process of microbial fiber-solidified soil, the present application uses a peristaltic pump to pump the urease bacterial solution and the cementing solution into the mold in batches at a specific rate, and controls the standing time of each batch of materials after the addition is completed. In this multiple step-by-step cycle process, a dense and uniform precipitation can be formed inside the soil, thereby further improving the performance of the solidified soil.

[0021] In summary, the technical solution of this application has the following effects: The technical solution of the present application provides a microbial synergistic fiber-stabilized soil and a preparation method thereof, taking into account the urease bacteria microorganism-induced calcium carbonate precipitation on the cementation of sandy soil particles and the filling of soil pores, and improving the MICP-based soil solidification effect enhancement technology, thereby improving the mechanical properties and impermeability of the stabilized soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The permeability coefficient of the stabilized soil prepared by using different amounts of modified PE fibers in this application.

[0023] Figure 2 The unconfined compressive strength of the stabilized soil prepared by using different amounts of modified PE fibers in this application.

[0024] Figure 3 Diagram of a simple device for measuring the permeability of a soil column for this application. DETAILED DESCRIPTION

[0025] The present application is further described in detail below in conjunction with examples, comparative examples and performance testing experiments. These examples should not be construed as limiting the scope of protection claimed in the present application. Example Examples 1-5

[0026] Examples 1-5 respectively provide a microbial synergistic fiber-solidified soil and a preparation method thereof.

[0027] The difference between the above embodiments is that the solid-liquid ratios of sand, magnesium oxide, urease bacterial solution and cementing solution are different, as shown in Table 1.

[0028] The preparation method of microorganism-assisted fiber-solidified soil in the above embodiment is: Preparation of modified PE fiber: PE fiber (diameter 20-30μm, length 12-22mm) was ultrasonically immersed in a 1:1 ethanol-acetone mixed solution for 60min to remove impurities on the surface of the PE fiber, rinsed with deionized water, and then dried in an oven at 60℃; at room temperature, the cleaned PE fiber was immersed in solution A and soaked in the solution for 24h; the PE fiber was taken out, added to solution B, soaked for 24h, and dried in an oven at 60℃ to obtain; solution A consisted of components containing the following concentrations: 15mmol / L catechol, 5mmol / L tetraethylenepentamine, and the solvent was 10mmol / L hydroxymethylaminomethane aqueous solution; solution B consisted of components containing the following concentrations: 10mmol / L KH-550 silane coupling agent, 20mmol / L EOS tetraethyl silicate, and the solvent was ethanol.

[0029] Preparation of urease bacterial solution: Bacillus pasteurianus is inoculated into the sterilized culture medium, and cultured in an shaking incubator at a temperature of 30°C and a rotation speed of 200 rpm for 48 hours to obtain urease bacterial solution; the culture medium uses a 250 mL conical flask as a liquid culture medium container, 7.5 g of urea, 2.5 g of soy peptone, 1 g of sodium chloride, 2 g of beef extract, and 250 mL of pure water are added into the bottle, and the culture medium is sterilized at a sterilization temperature of 121°C and a sterilization time of 20 minutes.

[0030] The sand is composed of a mixture of 5-15 μm sand, 40-60 μm sand and 80-100 μm sand in a weight ratio of 10:3:0.4.

[0031] According to Table 1, weigh the corresponding amounts of each raw material component; the amount of modified PE fiber is 0.5% of the volume of sand; Premixing: Mix sand, modified PE fiber and magnesium oxide evenly to prepare a premix. Place the premix in a mold and geotextile at the bottom and top of the sample to prevent soil loss and grouting scouring; Grouting: Use a peristaltic pump to pump urease bacterial solution and cementing solution into the mold in batches 4 times at a rate of 0.5 ml / min to achieve the purpose of cementing; after each batch of bacterial solution injection, let it stand for 3 hours before injecting the next batch of bacterial solution; after each batch of cementing solution injection, let it stand for 6 hours before injecting the next batch of cementing solution.

[0032] Table 1 Solid-liquid ratio of sand, magnesium oxide, urease bacterial solution and cementing solution in Examples 1-5 Examples 6-12

[0033] Examples 6-12 respectively provide a microbial synergistic fiber solidified soil and a preparation method thereof.

[0034] The differences between the above embodiment and embodiment 3 are as follows: the preparation method and dosage of the modified PE fiber are different, as shown below.

[0035] In Example 6: The preparation method of the modified PE fiber is as follows: at room temperature, immerse the PE fiber in solution A for 24 hours; take out the PE fiber, add it to solution B, soak it for 24 hours, and dry it in an oven at 60°C to obtain; solution A consists of components containing the following concentrations: 12mmol / L catechol, 6mmol / L tetraethylenepentamine, and the solvent is 10mmol / L hydroxymethylaminomethane aqueous solution; solution B consists of components containing the following concentrations: 10mmol / L KH-550 silane coupling agent, 20mmol / L EOS tetraethyl silicate, and the solvent is ethanol.

[0036] In Example 7: The preparation method of the modified PE fiber is as follows: at room temperature, immerse the PE fiber in solution A and soak it in the solution for 24 hours; take out the PE fiber, add it to solution B, soak it for 24 hours, and dry it in an oven at 60°C to obtain; solution A consists of components containing the following concentrations: 18mmol / L catechol, 4mmol / L tetraethylenepentamine, and the solvent is 10mmol / L hydroxymethylaminomethane aqueous solution; solution B consists of components containing the following concentrations: 10mmol / L KH-550 silane coupling agent, 20mmol / L EOS tetraethyl silicate, and the solvent is ethanol.

[0037] In Example 8: The preparation method of the modified PE fiber is as follows: at room temperature, immerse the PE fiber in solution A for 24 hours; take out the PE fiber, add it to solution B, soak it for 24 hours, and dry it in an oven at 60°C to obtain; solution A consists of components containing the following concentrations: 15mmol / L catechol, 5mmol / L tetraethylenepentamine, and the solvent is 10mmol / L hydroxymethylaminomethane aqueous solution; solution B consists of components containing the following concentrations: 8mmol / L KH-550 silane coupling agent, 24mmol / L EOS tetraethyl silicate, and the solvent is ethanol.

[0038] In Example 9: The preparation method of the modified PE fiber is as follows: at room temperature, immerse the PE fiber in solution A for 24 hours; take out the PE fiber, add it to solution B, soak it for 24 hours, and dry it in an oven at 60°C to obtain; solution A consists of components containing the following concentrations: 15mmol / L catechol, 5mmol / L tetraethylenepentamine, and the solvent is 10mmol / L hydroxymethylaminomethane aqueous solution; solution B consists of components containing the following concentrations: 12mmol / L KH-550 silane coupling agent, 16mmol / L EOS tetraethyl silicate, and the solvent is ethanol.

[0039] In Example 10: The preparation method of the modified PE fiber is as follows: at room temperature, immersing the PE fiber in solution A for 24 hours; taking out the PE fiber, adding it to solution B, immersing it for 24 hours, and drying it in an oven at 60°C to obtain; solution A consists of components containing the following concentrations: 14mmol / L catechol, 5.5mmol / L tetraethylenepentamine, and the solvent is 10mmol / L hydroxymethylaminomethane aqueous solution; solution B consists of components containing the following concentrations: 9mmol / L KH-550 silane coupling agent, 22mmol / LEOS tetraethyl silicate, and the solvent is ethanol.

[0040] In Example 11: The preparation method of the modified PE fiber is as follows: at room temperature, immerse the PE fiber in solution A and soak it in the solution for 24 hours; take out the PE fiber, add it to solution B, soak it for 24 hours, and dry it in an oven at 60°C to obtain; solution A consists of components containing the following concentrations: 16mmol / L catechol, 4.5mmol / L tetraethylenepentamine, and the solvent is 10mmol / L hydroxymethylaminomethane aqueous solution; solution B consists of components containing the following concentrations: 11mmol / L KH-550 silane coupling agent, 18mmol / LEOS tetraethyl silicate, and the solvent is ethanol.

[0041] In Example 12: the amount of modified PE fiber used is 0.4% of the volume of the sand.

[0042] The other process parameters in the above embodiment are the same as those in embodiment 3. Examples 13-16

[0043] Examples 13-16 respectively provide a microbial synergistic fiber-solidified soil and a preparation method thereof.

[0044] The difference between the above embodiment and embodiment 3 is that the composition of the sand is different, as shown below.

[0045] In Example 13: the sand is composed of a mixture of 5-15 μm sand, 40-60 μm sand and 80-100 μm sand in a weight ratio of 0.4:10:10.

[0046] In Example 14: the sand is composed of a mixture of 5-15 μm sand, 40-60 μm sand and 80-100 μm sand in a weight ratio of 6:6:0.1.

[0047] In Example 15: the sand is composed of a mixture of 5-15 μm sand, 40-60 μm sand and 80-100 μm sand in a weight ratio of 8:5:0.7.

[0048] In Example 16: the sand is composed of a mixture of 5-15 μm sand, 40-60 μm sand and 80-100 μm sand in a weight ratio of 12:1:0.1.

[0049] The other process parameters in the above embodiment are the same as those in embodiment 3. Examples 17-20

[0050] Examples 17-20 respectively provide a microbial synergistic fiber-solidified soil and a preparation method thereof.

[0051] The difference between the above embodiment and embodiment 3 is that the specific steps of grouting are different, as shown below.

[0052] In Example 17: the urease bacterial solution and the binder solution were pumped into the mold in batches 4 times at a rate of 0.5 ml / min by a peristaltic pump to achieve the purpose of binderization; after each batch of bacterial solution was injected, it was allowed to stand for 1 hour before the next batch of bacterial solution was injected; after each batch of binder solution was injected, it was allowed to stand for 8 hours before the next batch of binder solution was injected.

[0053] In Example 18: the urease bacterial solution and the binder solution were pumped into the mold in batches 4 times at a rate of 0.5 ml / min by a peristaltic pump to achieve the purpose of binderization; after each batch of bacterial solution injection, it was allowed to stand for 5 hours before the next batch of bacterial solution injection; after each batch of binder solution injection, it was allowed to stand for 4 hours before the next batch of binder solution injection.

[0054] In Example 19: the urease bacterial solution and the binder solution were pumped into the mold in batches 4 times at a rate of 0.5 ml / min by a peristaltic pump to achieve the purpose of binderization; after each batch of bacterial solution was injected, it was allowed to stand for 2 hours before the next batch of bacterial solution was injected; after each batch of binder solution was injected, it was allowed to stand for 7 hours before the next batch of binder solution was injected.

[0055] In Example 20: the urease bacterial solution and the binder solution were pumped into the mold in batches 4 times at a rate of 0.5 ml / min by a peristaltic pump to achieve the purpose of binderization; after each batch of bacterial solution injection, it was allowed to stand for 4 hours before the next batch of bacterial solution injection; after each batch of binder solution injection, it was allowed to stand for 5 hours before the next batch of binder solution injection.

[0056] The other process parameters in the above embodiment are the same as those in embodiment 3. Comparative Example Comparative Example 1-2

[0057] The above comparative examples respectively provide a microbial synergistic fiber solidified soil and a preparation method thereof.

[0058] The difference between the above comparative example and Example 3 is that the solid-liquid ratios of sand, magnesium oxide, urease bacterial solution and cementing solution are different, as shown below.

[0059] In Comparative Example 1: the solid-liquid ratio of sand, magnesium oxide, urease bacterial solution and cementing liquid is 120g:28g:160ml:860ml.

[0060] In Comparative Example 2: the solid-liquid ratio of sand, magnesium oxide, urease bacterial solution and cementing liquid is 180g:18g:240ml:740ml.

[0061] The other process parameters in the above comparative example are the same as those in Example 3. Comparative Examples 3-8

[0062] The above comparative examples respectively provide a microbial synergistic fiber solidified soil and a preparation method thereof.

[0063] The differences between the above comparative example and Example 3 are specifically as follows.

[0064] In Comparative Example 3: an equal amount of unmodified PE fibers was used to replace the modified PE fibers.

[0065] In Comparative Example 4: The preparation method of the modified PE fiber is as follows: at room temperature, immersing the PE fiber in solution A for 24 hours; taking out the PE fiber, adding it to solution B, immersing it for 24 hours, and drying it in an oven at 60°C; solution A is composed of components containing the following concentrations: 5mmol / L catechol, 15mmol / L tetraethylenepentamine, and the solvent is 10mmol / L hydroxymethylaminomethane aqueous solution; solution B is composed of components containing the following concentrations: 22mmol / L KH-550 silane coupling agent, 10mmol / L EOS tetraethyl silicate, and the solvent is ethanol.

[0066] In Comparative Example 5: the amount of modified PE fiber used is 0.0% of the volume of the sand.

[0067] In Comparative Example 6: the amount of modified PE fiber used is 0.2% of the volume of the sand.

[0068] In Comparative Example 7: the amount of modified PE fiber used is 0.8% of the volume of the sand.

[0069] In Comparative Example 8: the amount of modified PE fiber used is 1.0% of the volume of the sand.

[0070] The other process parameters in the above comparative example are the same as those in Example 3. Performance testing

[0071] (1) Impermeability: According to the relevant contents of the Geotechnical Test Method Standard GB / T 50123-2019, a simple device for measuring the permeability of soil columns was made using the variable head method test principle (such as Figure 3The device is composed of a transparent silicone hose, a scale, a Büchner funnel, and an iron stand, wherein the silicone hose, the Büchner funnel, and the sample are sealed.

[0072] The test is carried out by slowly adding distilled water to the transparent silicone tube. Due to gravity, distilled water continuously enters the soil from the bottom of the sample. After a period of time, water seeps out from the top of the sample and accumulates continuously until it overflows from the top of the PVC tube. At this time, add distilled water to the silicone tube to a suitable height and stop adding water. Note the height difference H1 from the concave liquid surface in the tube to the upper end of the PVC tube (overflowing liquid surface). At the same time, press the stopwatch to start timing. After a period of time t, note the height difference H2 between the concave liquid surface in the silicone tube and the overflowing liquid surface. At this time, the permeability coefficient of the sample is calculated according to the following formula (1):

[0073] (2) Unconfined compressive strength: The unconfined compressive strength of the sample was tested using a uniaxial compression tester in displacement control mode, with a loading rate of 1 mm / min. Before the unconfined compressive strength test, the cylindrical sample was placed in an oven and dried at 60°C. After drying, both ends of the sample were sanded to be flat and level, thereby reducing the impact of eccentric compression on the unconfined compressive strength of the sample.

[0074] Test results: as shown in Table 2.

[0075] Table 2 Performance test results of microorganism-fiber-solidified soil in the examples and comparative examples

[0076] like Figure 1 The permeability coefficient of the solidified soil prepared by using different amounts of modified PE fibers in this application; Figure 2 The unconfined compressive strength of the cured soil prepared by using different amounts of modified PE fibers in this application (wherein, 0.0% fiber content means that the amount of modified PE fiber is 0.0% of the volume of sand, which is Comparative Example 5; 0.2% fiber content means that the amount of modified PE fiber is 0.2% of the volume of sand, which is Comparative Example 6; 0.4% fiber content means that the amount of modified PE fiber is 0.4% of the volume of sand, which is Example 12; 0.6% fiber content means that the amount of modified PE fiber is 0.6% of the volume of sand, which is Example 3; 0.8% fiber content means that the amount of modified PE fiber is 0.8% of the volume of sand, which is Comparative Example 7; 1.0% fiber content means that the amount of modified PE fiber is 1.0% of the volume of sand, which is Comparative Example 8).

[0077] Combined with Table 2, by comparing the test results of the embodiment and the comparative example, the anti-permeability coefficient of the microorganism-fiber-solidified soil of the present application is ≤7.05×10-5 cm / s, unconfined compressive strength ≥2.12MPa. The above data show that the microbial synergistic fiber-solidified soil prepared by the technical solution of the present application has good anti-permeability and mechanical properties.

[0078] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A microbial synergistic fiber solidified soil, characterized in that: Specifically, it includes the following components: sand, modified PE fiber, magnesium oxide, urease bacterial solution, and cementing solution; The solid-liquid ratio of the sand, the magnesium oxide, the urease bacterial solution, and the cementing solution is 140-160 g: 20-26 g: 180-220 ml: 770-830 ml; The amount of the modified PE fiber is 0.4%-0.6% of the volume of the sand; The preparation method of the modified PE fiber is as follows: at room temperature, immerse the PE fiber in solution A for 20-28 hours; take out the PE fiber and immerse it in solution B for 20-28 hours, and dry it in an oven at 55-70°C to obtain the modified PE fiber; The solution A is composed of components with the following concentrations: 12-18 mmol / L catechol, 4-6 mmol / L tetraethylenepentamine, and the solvent is 8-12 mmol / L hydroxymethylaminomethane aqueous solution; The B solution is composed of the following components in concentrations: 8-12 mmol / L KH-550 silane coupling agent, 16-24 mmol / L EOS tetraethyl silicate, and the solvent is ethanol; The cementing fluid is composed of the following components in concentrations: 0.8-1.2 mol / L calcium chloride, 0.8-1.2 mol / L urea, and the solvent is water.

2. The microorganism-synergistic fiber-solidified soil according to claim 1, characterized in that: The solid-liquid ratio of the sand, the magnesium oxide, the urease bacterial solution and the cementing liquid is: 145-155g: 22-24g: 190-210ml: 790-810ml.

3. The microorganism-synergistic fiber-stabilized soil according to claim 1, characterized in that: The sand is composed of a mixture of 5-15 μm sand, 40-60 μm sand and 80-100 μm sand in a weight ratio of 8-12:1-5:0.1-0.

7.

4. The microorganism-synergistic fiber-solidified soil according to claim 3, characterized in that: The sand is composed of a mixture of 5-15 μm sand, 40-60 μm sand and 80-100 μm sand in a weight ratio of 9-11:2-4:0.3-0.

5.

5. The microorganism-synergistic fiber-stabilized soil according to claim 1, characterized in that: The preparation method of the urease bacterial liquid is as follows: inoculating Bacillus pasteurianus into a sterilized culture medium, placing the medium in an oscillating culture box at a temperature of 30° C. and a rotation speed of 150-250 rpm for 40-56 hours to obtain the urease bacterial liquid.

6. The microorganism-synergistic fiber-stabilized soil according to claim 1, characterized in that: The preparation method of the modified PE fiber is as follows: ultrasonically immersing the PE fiber in a 1:1 ethanol-acetone mixed solution for 50-70 minutes to remove impurities on the surface of the PE fiber, washing with deionized water, and then drying in an oven at 55-70°C; immersing the washed PE fiber in solution A for 20-28 hours at room temperature; taking out the PE fiber and immersing it in solution B for 20-28 hours, and drying it in an oven at 55-70°C to obtain the modified PE fiber.

7. The microorganism-synergistic fiber-stabilized soil according to claim 1, characterized in that: The solution A is composed of components having the following concentrations: 14-16 mmol / L catechol, 4.5-5.5 mmol / L tetraethylene pentamine, and the solvent is 9-11 mmol / L hydroxymethylaminomethane aqueous solution; the pH of the solution A is 8.0-9.

0.

8. The microorganism-synergistic fiber-stabilized soil according to claim 1, characterized in that: The B solution is composed of components having the following concentrations: 9-11 mmol / L KH-550 silane coupling agent, 18-22 mmol / L EOS tetraethyl silicate, and the solvent is ethanol; the pH of the B solution is 9.0-10.

0.

9. The method for preparing microorganism-synergistic fiber-solidified soil according to any one of claims 1 to 8, characterized in that: Specifically, the following steps are performed in sequence: Premixing: the sand, the modified PE fiber and the magnesium oxide are mixed evenly to prepare a premix, the premix is ​​poured into a mold, and geotextiles are placed at the bottom and top of the sample; Grouting: The urease bacterial solution and the cementing solution are pumped into the mold in batches of 3-5 times at a rate of 0.4-0.6 ml / min by a peristaltic pump.

10. The method for preparing microorganism-synergistic fiber-solidified soil according to claim 9, characterized in that: The grouting steps are specifically as follows: the urease bacterial solution and the cementing solution are pumped into the mold in batches 4 times at a rate of 0.5 ml / min by a peristaltic pump; after each batch of bacterial solution is injected, it is allowed to stand for 2-4 hours before the next batch of bacterial solution is injected; after each batch of cementing solution is injected, it is allowed to stand for 5-7 hours before the next batch of cementing solution is injected.

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