Method for reinforcing calcareous sand by in-situ cultivation of microorganisms

Abstract

The invention discloses a method for reinforcing calcareous sand through in-situ cultivation of microorganisms, and belongs to the technical field of sand reinforcement. The method comprises the following steps: 1, loading calcareous sand into a sample, and adding a bacterial liquid for immobilization; 2, adding a bacterial culture solution into the sample obtained after immobilization in the step 1, and performing in-situ cultivation; and 3, adding the cementing liquid into the sample obtained after in-situ cultivation in the step 2 for curing, then washing, drying and demolding to obtain a cured calcareous sand sample, and completing the reinforcement of the calcareous sand. The method for in-situ cultivation of microorganisms is adopted, the dosage of the microorganisms is smaller, the requirement for initial bacteria is lower, and the cost is further reduced; the enzymatic ability of bacteria is effectively enhanced, so that the bacterial liquid is uniformly fixed in the soil body, and a more uniform reinforcing effect is achieved; the adopted grouting mode is a direct grouting mode and is made to permeate through gravity and capillary force, the grouting process is more convenient to operate, and practicability is high.

Description

Technical Field

[0001] The invention relates to the technical field of sand reinforcement, and in particular to a method for reinforcing calcareous sand by utilizing in-situ cultivated microorganisms. Background Art

[0002] Calcareous sand, as a marine sand, is the main component of various islands and reefs. For example, it is widely distributed in the South my country Sea, North America and Africa. Due to the unique mechanical properties of calcareous sand, easy to break and porous, it has encountered many difficulties in the construction of islands and reefs, such as the damage of calcareous sand foundations in port construction, residential construction and other projects. Therefore, it is very important to find new reinforcement technologies in the continuous development and construction of green ecological islands.

[0003] Microbial induced calcium carbonate precipitation (MICP) technology uses substances produced by microbial metabolism to cover the surface of rock and soil or fill pores, thereby improving the mechanical properties of rock and soil strength and stiffness. As a new type of rock and soil reinforcement technology, MICP technology has many advantages over traditional methods, including low viscosity, good fluidity, strong permeability, adjustable reaction rate, higher cementation strength and less environmental pollution. Therefore, bio-mediated geological technology represented by MICP, as a nature-based solution, has great application potential in modern geoengineering disciplines.

[0004] After many tests, it has been proved that MICP technology has significant performance in improving the mechanical properties and permeability of soil. However, in the actual on-site reinforcement process, there may be defects such as large demand for bacterial solution, high cost, uneven distribution in the soil, low survival rate, and unsuitability for various actual engineering conditions. When carrying out reinforcement projects on site, in order to fully adsorb bacteria, the flow rate of the fixing liquid needs to be slow so that the bacterial suspension and the fixing liquid can be fully mixed. A large amount of Bacillus pasteurianus is often required to treat the soil, and it is difficult to produce and transport a large amount of these cultures. In addition, the commonly used MICP cementation method in engineering is injection cementation. Common obstacles are blockage of soil pore space near the injection point, uneven distribution of bacteria and calcite, and both are often more concentrated near the injection point. It is difficult to spread the bacterial solution evenly in the soil when it is directly injected, and the reinforcement effect is poor. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a method for reinforcing calcareous sand by in-situ cultivating microorganisms, so as to solve the problems that the existing MICP technology may have in the actual reinforcement process, such as large demand for bacterial solution, high cost, uneven distribution in the soil, low survival rate, poor reinforcement effect, and unsuitability for a variety of actual engineering conditions.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] A method for reinforcing calcareous sand by in-situ cultivation of microorganisms comprises the following steps:

[0008] Step 1: After loading the calcareous sand, add the bacterial solution for fixation;

[0009] Step 2: adding the bacterial culture solution to the sample obtained after fixation in step 1 for in situ cultivation;

[0010] Step 3: Add the binder liquid to the sample obtained after the in-situ cultivation in step 2 for solidification, and then rinse, dry and demould to obtain a solidified calcareous sand sample, thereby completing the reinforcement of the calcareous sand.

[0011] The beneficial effects of the present invention are as follows: the present invention can achieve the purpose of expanding the strain in the soil by first adding a small amount of low-activity strains to the calcareous sand to be reinforced, and then adding bacterial culture fluid for in-situ cultivation and enrichment, so that the strain can grow secondary in the soil and be more evenly adsorbed on the soil particles, thereby improving the solidification effect of the calcareous sand.

[0012] Furthermore, in step 1, the particle size of the calcareous sand is 0.3-0.5 mm.

[0013] Preferably, the particle size of the calcareous sand in step 1 is 0.4 mm.

[0014] Furthermore, the method for loading the calcareous sand in step one adopts the layered loading and under-compaction method, and the amount of calcareous sand is calculated according to the density of 50%, and the loading is divided into three parts. Copy paper is laid along the inner wall of the loading mold, a piece of scouring pad is placed at each end, and a water stop clamp is set at the bottom of the mold.

[0015] The beneficial effects of adopting the above-mentioned further technical scheme are as follows: by setting the copy paper, the mold can be prevented from sticking and falling off during the subsequent sample removal, the scouring pad can effectively prevent interference when adding bacterial liquid, bacterial culture liquid and binder liquid, and the water stop clamp can be set to ensure that the sample is in a saturated state during the in-situ cultivation and curing stages, and facilitate the discharge of excess liquid after the in-situ cultivation and curing stages.

[0016] Furthermore, the OD of the bacterial solution in step 1 600 is 0.9-1.0, the conductivity is 0.06-0.10mS / min, the bacterial species in the bacterial solution is Bacillus pasteurianus; the amount of bacterial solution added is 40-60% of the total pore volume of the calcareous sand after sampling; the fixing time is 1-3h.

[0017] Preferably, the OD of the bacterial solution in step 1 is 600 is 0.948, the conductivity is 0.08mS / min, the bacteria in the bacterial solution is Bacillus pasteurianus; the amount of bacterial solution added is 50% of the total pore volume of the calcareous sand after sampling; the fixing time is 2h.

[0018] Furthermore, the bacterial culture solution in step 2 includes yeast extract, ammonium chloride, nickel chloride solution, urea, sodium hydroxide and water.

[0019] Furthermore, the mass volume ratio of yeast extract, ammonium chloride, nickel chloride solution, urea and water in the bacterial culture solution is 10-30g:10-20g:0.5-2mL:10-20g:800-1200mL, and sodium hydroxide is added to adjust the pH to 9-10; the concentration of the nickel chloride solution is 0.5-2mol / L.

[0020] Preferably, the mass volume ratio of yeast extract, ammonium chloride, nickel chloride solution, urea and water in the bacterial culture solution is 20g:15g:1mL:15g:1000mL, and sodium hydroxide is added to adjust the pH to 9.2; the concentration of the nickel chloride solution is 1 mol / L.

[0021] Furthermore, in step 2, in situ cultivation is performed by the following method: 50-150% of the total pore volume of the calcareous sand is added to the sample, and the sample is allowed to stand for 40-60 hours after infiltration, and the addition of the bacterial culture solution and the standing are repeated 1-3 times to complete the in situ cultivation.

[0022] Preferably, in step 2, in-situ cultivation is performed by the following method: adding bacterial culture solution of 100% of the total pore volume of calcareous sand to the sample, letting it stand for 48 hours after infiltration, repeating the addition of bacterial culture solution and letting it stand for 2 times to complete the in-situ cultivation.

[0023] Furthermore, in step three, the binder liquid is a mixed aqueous solution of calcium chloride, urea and yeast extract; the concentration of calcium chloride is 0.5-2 mol / L, the concentration of urea is 0.5-2 mol / L, and the concentration of yeast extract is 0.1-0.3 g / L.

[0024] Preferably, the binder in step three is a mixed aqueous solution of calcium chloride, urea and yeast extract; the concentration of calcium chloride is 1 mol / L, the concentration of urea is 1 mol / L, and the concentration of yeast extract is 0.2 g / L.

[0025] The beneficial effect of adopting the above further technical solution is: the present invention adds yeast extract to the cementing liquid, which helps the continued growth of bacteria during the cementing and curing process, allowing the bacteria to continue to remain active inside the soil, thereby improving the reinforcement effect of calcareous sand.

[0026] Furthermore, in step three, solidification is performed by the following method: a binder of 100-200% of the total pore volume of the calcareous sand is added to the sample, and the sample is allowed to stand for 10-15 hours after infiltration, and the addition of the binder and the standing are repeated for 3-12 times to complete solidification.

[0027] Preferably, in step three, curing is performed by the following method: adding a binder of 150% of the total pore volume of the calcareous sand to the sample, allowing it to stand for 12 hours after infiltration, repeating the addition of the binder and allowing it to stand for 9 times to complete curing.

[0028] Furthermore, in step three, the drying temperature is 70-90° C. and the drying time is 40-60 hours.

[0029] Preferably, the drying temperature in step 3 is 80° C. and the drying time is 48 hours.

[0030] Furthermore, in step three, the demoulding process uses a hot melt knife to cut the mold and remove the sample.

[0031] The present invention has the following beneficial effects:

[0032] (1) The present invention adopts a method of in-situ cultivation of microorganisms. Compared with the conventional MICP process, the present invention uses less initial external microorganisms and has lower requirements for initial bacteria, making the bacterial cultivation and transportation process simpler and further reducing costs.

[0033] (2) The present invention adopts a method of in-situ cultivation of microorganisms. After adding a small amount of bacteria, bacterial culture solution is added to the calcareous sand for in-situ cultivation and enrichment, so that the bacteria can further grow in the soil. This not only effectively enhances the enzymatic ability of the bacteria, but also makes the bacterial solution evenly fixed in the soil, so that a more uniform reinforcement effect can be obtained in subsequent reinforcement.

[0034] (3) The grouting methods used in the method of the present invention are all direct grouting and the method of allowing it to penetrate through gravity and capillary force. The grouting process is more convenient to operate and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the process of in-situ culturing microorganisms to consolidate calcareous sand according to the present invention;

[0036] Figure 2 This is a diagram of a solidified calcareous sand sample obtained by in-situ culturing microorganisms to consolidate calcareous sand in Example 2 of the present invention. DETAILED DESCRIPTION

[0037] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0038] Embodiment 1:

[0039] A method for strengthening calcareous sand by in-situ cultivation of microorganisms (schematic diagram as shown in FIG. Figure 1As shown), comprising the following steps:

[0040] (1) Bacterial culture: Inoculate Bacillus pasteurianus into liquid culture medium and culture until OD 600 The conductivity of the bacterial solution is 0.948 and 0.88 mS / min. It is placed in a 4°C refrigerator for later use.

[0041] (2) The calcareous sand was sieved using a 0.3-0.5 mm round hole sieve to obtain calcareous sand with an average particle size of 0.4 mm, and then loaded into a syringe-shaped sample mold with a diameter of 39.1 mm at a density of 50%. The loading height was 80 mm. A piece of photocopy paper was placed along the inner wall of the syringe to prevent adhesion and falling off when removing the sample. A piece of scouring pad was placed above and below the syringe, and a water stop clamp was set at the bottom of the syringe.

[0042] (3) Preparation of bacterial culture solution: Using deionized water as solvent, prepare a bacterial culture solution containing 20 g / L yeast extract, 0.01 g / L nickel chloride hexahydrate, 15 g / L ammonium chloride and 15 g / L urea, add sodium hydroxide solution to adjust the pH value to 9.2, and set aside.

[0043] (4) Preparation of a binder solution: Using deionized water as solvent, prepare a binder solution containing 0.5 mol / L urea, 0.5 mol / L calcium chloride, and 0.2 g / L yeast extract for later use.

[0044] (5) Close the water stop clamp and pour 24 mL of bacterial solution on the top of the sample. Allow the bacterial solution to flow in the sand under the action of gravity and let it stand for 2 h to allow Bacillus pasteurianus to be fixed on the sand sample.

[0045] (6) Open the water stop clamp, pour 48 mL of bacterial culture solution on the top of the sample, and allow the bacterial culture solution to flow in the sand body under the action of gravity. After the bacterial culture solution fully penetrates all the sand bodies, close the water stop clamp and let it stand for 48 hours. Then open the water stop clamp, discharge the waste liquid and collect it, measure the urease activity of the waste liquid, take the in-situ sand soil in the parallel sample, and measure the urease activity of the in-situ sand soil. To measure the urease activity of the waste liquid, mix 2 mL of the waste liquid with 18 mL of urea solution (1 mol / L) and then measure the conductivity change value per minute (mS / min), and convert it to the current bacterial solution urease activity value. For in-situ urease activity determination, take about 10 g of sand from different depths of the sand column, add 15 mL of urea solution (1 mol / L), mix and measure the conductivity change value per minute (mS / min), and convert it to the current bacterial solution urease activity value.

[0046] (7) Pour 70 mL of cementing liquid on the top of the sample and allow the cementing liquid to flow in the sand under the action of gravity. After the cementing liquid has fully penetrated all the sand, close the water stop clamp. After standing for 12 h, open the water stop clamp, collect the waste liquid and determine the calcium ion concentration using the EDTA titration method. Calculate the calcium ion utilization rate and repeat the cementation process 9 times.

[0047] (8) After bonding, rinse the sample with deionized water, determine the permeability of the sand sample using the constant head method, place the sample in an oven at 80°C and dry for 48 h, use a hot melt knife to cut the syringe to remove the sample, weigh and grind the top and bottom surfaces of the sample until they are parallel, and perform an unconfined compressive strength test on the sample.

[0048] Test results: In this embodiment, cementation was performed after in-situ cultivation of microorganisms once. After MICP treatment, the in-situ urease activity in the soil was increased by 41.25% compared with the initial bacterial urease activity, and the calcium carbonate content of the soil was 13.17%. After the 9th cementation, the calcium ion utilization rate reached 20.63%, the permeability coefficient of the sample was reduced by 96.28% compared with that of the unreinforced sample, and the unconfined compressive strength of the sample was 0.806MPa.

[0049] Embodiment 2:

[0050] A method for reinforcing calcareous sand by in-situ cultivation of microorganisms comprises the following steps:

[0051] (1) Bacterial culture: Inoculate Bacillus pasteurianus into liquid culture medium and culture until OD 600 The conductivity of the bacterial solution is 0.948 and 0.88 mS / min. It is placed in a 4°C refrigerator for later use.

[0052] (2) The calcareous sand was sieved using a 0.3-0.5 mm round hole sieve to obtain calcareous sand with an average particle size of 0.4 mm, and then loaded into a syringe-shaped sample mold with a diameter of 39.1 mm at a density of 50%. The loading height was 80 mm. A piece of photocopy paper was placed along the inner wall of the syringe to prevent adhesion and falling off when removing the sample. A piece of scouring pad was placed above and below the syringe, and a water stop clamp was set at the bottom of the syringe.

[0053] (3) Preparation of bacterial culture solution: Using deionized water as solvent, prepare a bacterial culture solution containing 20 g / L yeast extract, 0.01 g / L nickel chloride hexahydrate, 15 g / L ammonium chloride and 15 g / L urea, add sodium hydroxide solution to adjust the pH value to 9.2, and set aside.

[0054] (4) Preparation of a binder solution: Using deionized water as solvent, prepare a binder solution containing 0.5 mol / L urea, 0.5 mol / L calcium chloride, and 0.2 g / L yeast extract for later use.

[0055] (5) Close the water stop clamp and pour 24 mL of bacterial solution on the top of the sample. Allow the bacterial solution to flow in the sand under the action of gravity and let it stand for 2 h to allow Bacillus pasteurianus to be fixed on the sand sample.

[0056] (6) Open the water stop clamp, pour 48 mL of bacterial culture solution on the top of the sample, and allow the bacterial culture solution to flow in the sand body under the action of gravity. After the bacterial culture solution fully penetrates all the sand bodies, close the water stop clamp and let it stand for 48 hours. Then open the water stop clamp, discharge the waste liquid and collect it, measure the urease activity of the waste liquid, take the in-situ sand soil in the parallel sample, and measure the urease activity of the in-situ sand soil. To measure the urease activity of the waste liquid, mix 2 mL of the waste liquid with 18 mL of urea solution (1 mol / L) and then measure the conductivity change value per minute (mS / min), and convert it to the current bacterial solution urease activity value. For in-situ urease activity determination, take about 10 g of sand from different depths of the sand column, add 15 mL of urea solution (1 mol / L) and mix to measure the conductivity change value per minute (mS / min), and convert it to the current bacterial solution urease activity value; repeat the in-situ cultivation twice.

[0057] (7) Pour 70 mL of cementing liquid on the top of the sample and allow the cementing liquid to flow in the sand under the action of gravity. After the cementing liquid has fully penetrated all the sand, close the water stop clamp. After standing for 12 h, open the water stop clamp, collect the waste liquid and determine the calcium ion concentration using the EDTA titration method. Calculate the calcium ion utilization rate and repeat the cementation process 9 times.

[0058] (8) After bonding, rinse the sample with deionized water, measure the permeability of the sand sample with the constant head method, dry the sample in an oven at 80°C for 48 h, cut the syringe with a hot melt knife to remove the sample, weigh it, and grind the top and bottom surfaces of the sample until they are parallel. Figure 2 As shown, the specimens were subjected to unconfined compressive strength tests.

[0059] Test results: In this embodiment, cementation was performed after in-situ microbial cultivation. After MICP treatment, the in-situ urease activity in the soil was increased by 50.00% compared with the initial bacterial urease activity, and the calcium carbonate content of the soil was 21.80%. After the 9th cementation, the calcium ion utilization rate reached 38.94%, the permeability coefficient of the sample was reduced by 91.35% compared with the unreinforced sample, and the unconfined compressive strength of the sample was 3.941 MPa. Compared with Example 1, the reduction in porosity and the increase in strength in this embodiment are due to the role of calcium carbonate in filling pores and cementing soil particles inside the soil.

[0060] Comparative Example 1:

[0061] A method for reinforcing calcareous sand using microorganisms comprises the following steps:

[0062] (1) Bacterial culture: Inoculate Bacillus pasteurianus into liquid culture medium and culture until OD 600 The conductivity of the bacterial solution is 0.948 and 0.88 mS / min. It is placed in a 4°C refrigerator for later use.

[0063] (2) The calcareous sand was sieved using a 0.3-0.5 mm round hole sieve to obtain calcareous sand with an average particle size of 0.4 mm, and then loaded into a syringe-shaped sample mold with a diameter of 39.1 mm at a density of 50%. The loading height was 80 mm. A piece of photocopy paper was placed along the inner wall of the syringe to prevent adhesion and falling off when removing the sample. A piece of scouring pad was placed above and below the syringe, and a water stop clamp was set at the bottom of the syringe.

[0064] (3) Preparation of a binder solution: Using deionized water as solvent, prepare a binder solution containing 0.5 mol / L urea, 0.5 mol / L calcium chloride, and 0.2 g / L yeast extract for later use.

[0065] (4) Close the water stop clamp and pour 24 mL of bacterial solution on the top of the sample. Allow the bacterial solution to flow in the sand under the action of gravity and let it stand for 2 h to allow Bacillus pasteurianus to be fixed on the sand sample.

[0066] (5) Pour 70 mL of cementing liquid on the top of the sample and allow the cementing liquid to flow in the sand under the action of gravity. After the cementing liquid fully penetrates all the sand, close the water stop clamp. After standing for 12 h, open the water stop clamp, collect the waste liquid and determine the calcium ion concentration by EDTA titration method. Calculate the calcium ion utilization rate, repeat the bacterial liquid injection and cementation for 9 times, and perform cementation once after each addition of the bacterial liquid.

[0067] (6) After bonding, rinse the sample with deionized water, determine the permeability of the sand sample using the constant head method, place the sample in an oven at 80°C and dry for 48 h, use a hot melt knife to cut the syringe to remove the sample, weigh and grind the top and bottom surfaces of the sample until they are parallel, and then perform an unconfined compressive strength test on the sample.

[0068] Test results: In this comparative example, no in-situ microbial cultivation was performed. After MICP treatment, the calcium carbonate content of the soil was 8.53%, the calcium ion utilization rate was 5.4% after the 9th cementation, the permeability coefficient of the sample was reduced by 81.36%, and the unconfined compressive strength of the sample was 0.286 MPa.

[0069] It can be seen from the test data of Example 1, Example 2 and Comparative Example 1 of the present invention that after one in-situ cultivation of microorganisms, cementation is performed and MICP treatment is performed, and the calcium carbonate content of the soil is increased by 54.40% compared with Comparative Example 1, and the calcium ion utilization rate after the 9th cementation is increased by 2.8 times compared with Comparative Example 1, the sample permeability coefficient is reduced by 18.36% compared with Comparative Example 1, and the sample unconfined compressive strength is increased by 1.8 times compared with Comparative Example 1. After two in-situ cultivation of microorganisms, cementation is performed and MICP treatment is performed, and the calcium carbonate content of the soil is increased by 1.5 times compared with Comparative Example 1, the calcium ion utilization rate after the 9th cementation is increased by 6.2 times compared with Comparative Example 1, the sample permeability coefficient is reduced by 12.28% compared with Comparative Example 1, and the sample unconfined compressive strength is increased by 12.8 times compared with Comparative Example 1. The present invention uses an in-situ cultivation method, and only one addition of bacterial solution is required for 9 reinforcements. Compared with the traditional MICP method, the amount of bacterial solution used is reduced by 89%, and the number of times can continue to decrease as the reinforcement times increase.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for strengthening calcareous sand by in-situ cultivation of microorganisms, characterized in that: The following steps are involved: Step 1: After loading the calcareous sand, add the bacterial solution for fixation; Step 2: adding the bacterial culture solution to the sample obtained after fixation in step 1 for in situ cultivation; Step 3: Add the binder liquid to the sample obtained after the in-situ cultivation in step 2 for solidification, and then rinse, dry and demould to obtain a solidified calcareous sand sample, thereby completing the reinforcement of the calcareous sand.

2. The method for consolidating calcareous sand by in-situ cultivation of microorganisms according to claim 1, characterized in that: The particle size of the calcareous sand in step 1 is 0.3-0.5 mm.

3. The method for consolidating calcareous sand by in-situ cultivation of microorganisms according to claim 1, characterized in that: The OD of the bacterial solution in step 1 600 is 0.9-1.0, the conductivity is 0.06-0.10mS / min, the bacterial species in the bacterial solution is Bacillus pasteurianus; the amount of bacterial solution added is 40-60% of the total pore volume of the calcareous sand after sampling; the fixing time is 1-3h.

4. The method for consolidating calcareous sand by in-situ cultivation of microorganisms according to claim 1, characterized in that: The bacterial culture solution in step 2 comprises yeast extract, ammonium chloride, nickel chloride solution, urea, sodium hydroxide and water.

5. The method for consolidating calcareous sand by in-situ cultivation of microorganisms according to claim 4, characterized in that: The mass volume ratio of yeast extract, ammonium chloride, nickel chloride solution, urea and water in the bacterial culture solution is 10-30g:10-20g:0.5-2mL:10-20g:800-1200mL, and sodium hydroxide is added to adjust the pH to 9-10; the concentration of the nickel chloride solution is 0.5-2mol / L.

6. The method for consolidating calcareous sand by in-situ cultivation of microorganisms according to claim 1, characterized in that: In step 2, in-situ cultivation is performed by the following method: adding bacterial culture solution of 50-150% of the total pore volume of calcareous sand to the sample, letting it stand for 40-60 hours after infiltration, repeating the addition of bacterial culture solution and letting it stand for 1-3 times to complete the in-situ cultivation.

7. The method for consolidating calcareous sand by in-situ cultivation of microorganisms according to claim 1, characterized in that: The binder in step three is a mixed aqueous solution of calcium chloride, urea and yeast extract; the concentration of calcium chloride is 0.5-2 mol / L, the concentration of urea is 0.5-2 mol / L, and the concentration of yeast extract is 0.1-0.3 g / L.

8. The method for consolidating calcareous sand by in-situ cultivation of microorganisms according to claim 1, characterized in that: In the step three, the curing is performed by the following method: adding a binder of 100-200% of the total pore volume of the calcareous sand to the sample, allowing it to stand for 10-15 hours after infiltration, repeating the addition of the binder and allowing it to stand for 3-12 times to complete the curing.

9. The method for consolidating calcareous sand by in-situ culturing microorganisms according to claim 1, characterized in that: The drying temperature in step 3 is 70-90° C. and the drying time is 40-60 hours.

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