An apparatus and method for microbial modified slip soil preparation and permeability dynamic monitoring

Abstract

This invention provides an apparatus and method for preparing microbially modified slip zone soil and dynamically monitoring its permeability. The apparatus includes a modification chamber, the bottom of which is connected to a peristaltic pump via an inlet pipe. The peristaltic pump is connected to a three-loop switching system for permeation and modification. A pressure sensor is installed at the end of the inlet pipe near the modification chamber. Inside the modification chamber, from bottom to top, are a gravel layer, an open-cell polymer foam layer one, a gauze layer one, a sample chamber, a gauze layer two, and another open-cell polymer foam layer two. Based on the pressure data recorded by the pressure sensor before and after modification, the intrinsic permeability of the slip zone soil before and after microbial modification is calculated using Darcy's law. The effect of microbial-induced calcium carbonate precipitation modification is evaluated based on the intrinsic permeability. The apparatus and method provided by this invention can acquire experimental data in real time and obtain the permeability change pattern in real time, so as to analyze and compare the effect of microbial modification of slip zone soil under different conditions.

Description

Technical Field

[0001] This invention relates to the fields of water conservancy engineering and geotechnical engineering, specifically to an apparatus and method for preparing microbially modified slip zone soil and dynamically monitoring its permeability. Background Technology

[0002] Slip zone soil is a weak zone formed during landslides. It has high water content, loose structure, oriented particle arrangement, and extremely low strength, directly controlling landslide stability. Improving the engineering properties of slip zone soil through modification is an effective means of landslide control. Microbial modification of slip zone soil utilizes microorganisms to induce the decomposition of urea, releasing carbonate ions which then react with calcium ions from a calcium source to form calcium carbonate. This process does not disturb the landslide slip zone and produces no environmental pollutants, making it a low-cost, minimally disturbing, and environmentally friendly landslide reinforcement method.

[0003] When evaluating the effects of soil modification, methods such as microstructure testing, triaxial mechanical testing, and permeability testing are generally used. Microstructure testing typically employs electron microscopy to observe the morphology of soil particles, cementation, and micro-cracks in the soil. Alternatively, CT scans can be used to obtain a three-dimensional structural model of the soil, clearly showing the spatial distribution and connectivity of pores and cracks. However, these methods cannot obtain real-time data on soil permeability or observe continuous changes in permeability. Triaxial mechanical testing generally requires placing the soil sample in a triaxial apparatus and applying pressure to obtain soil strength parameters. This method requires removing the soil sample for separate testing and significantly interferes with the microbial-induced calcium carbonate precipitation process. Permeability testing requires placing the soil in a triaxial pressure chamber for seepage testing. This method requires artificially terminating the microbial modification process or conducting the test after modification is complete, and cannot obtain real-time data on changes in soil permeability. Therefore, there is an urgent need to propose an integrated method for the preparation of modified slip zone soil and dynamic monitoring of permeability. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a device for preparing microbially modified slip zone soil and dynamically monitoring its permeability. The device includes a modification chamber, with a peristaltic pump connected to the bottom of the modification chamber via an inlet pipe. The peristaltic pump is connected to a permeation-modification three-loop switching system. A pressure sensor is installed at the end of the inlet pipe near the modification chamber. The interior of the modification chamber, from bottom to top, consists of a gravel layer, an open-cell polymer foam layer one, a gauze layer one, a sample chamber, a gauze layer two, and another open-cell polymer foam layer two.

[0005] Furthermore, the thickness of the crushed stone layer is 8-20mm, and the crushed stone layer is filled with crushed stone with a particle size of 5-12mm.

[0006] Furthermore, both the first and second open-cell polymer foam layers are foam layers filled with open-cell polymer foam with a thickness of 8-15 mm and a pore size of 0.4-0.6 mm.

[0007] Furthermore, both gauze layer one and gauze layer two are gauze layers filled with 1-3 layers of gauze with a thickness of 0.3-0.8mm and a pore size of 0.3-1.0mm.

[0008] Furthermore, the modified cavity is made of transparent plastic; the main body of the modified cavity consists of a left half and a right half of a semi-cylindrical shell, and the top and bottom of the main body of the modified cavity are respectively provided with an upper cover plate and a lower cover plate, which are connected to the upper and lower ends of the main body of the modified cavity by threads, respectively. The middle part of the outer wall of the modified cavity is connected with a cable tie for reinforcement.

[0009] Furthermore, the permeation-modification three-loop switching system includes liquid containers and hoses, each of which is equipped with a solenoid valve and a relay, with the solenoid valve switching controlled by a computer.

[0010] Furthermore, a drain pipe is led out from the peristaltic pump, and a waste liquid container is provided at the bottom of the drain pipe.

[0011] Furthermore, the front end of the drain pipe is equipped with a solenoid valve and a relay, with the solenoid valve being switched on and off by a computer.

[0012] Furthermore, the pressure sensor is connected to the computer via a data acquisition card.

[0013] This invention also provides a method for preparing microbially modified slip zone soil and dynamically monitoring its permeability, using the above-mentioned apparatus and comprising the following steps:

[0014] (1) The bottom of the modified cavity body is tightened with the lower cover plate by threads, and the modified cavity is reinforced with cable ties; the interior of the modified cavity body is filled with gravel, open-cell polyurethane foam, gauze, slip zone soil, gauze and open-cell polyurethane foam from bottom to top, and the top cover plate is placed on the top of the modified cavity body and tightened. (2) Pump clean water into the modification chamber and record the data from the pressure sensor in real time; (3) Stop pumping clean water and switch to pumping urea; (4) Stop pumping urea and switch to pumping bacterial solution; (5) Stop pumping bacterial solution and switch to pumping calcium chloride solution, and record the pressure sensor data in real time; Furthermore, based on the pressure sensor data recorded in steps (2) and (5), the intrinsic permeability of the slip zone soil before and after microbial modification is calculated using Darcy's law. The effect of microbial-induced calcium carbonate precipitation modification is evaluated based on the intrinsic permeability. The formula for Darcy's law is:

[0015] Where: k is the characteristic permeability of the soil sample; μ is the dynamic viscosity of the liquid flowing through the soil sample; Q is the recorded flow rate of the peristaltic pump; L is the seepage diameter of the soil sample; A is the cross-sectional area of ​​the soil sample; ρ is the density of the liquid flowing through the soil sample; g is the acceleration due to gravity. p is the pressure head calculated from data collected by a pressure sensor.

[0016] Furthermore, the slip zone soil is added in batches. After each batch of slip zone soil is added, the surface is first scratched and compacted, and then a ring of glass glue is applied along the edge of the compacted surface before the next batch of slip zone soil is added. The modification chamber is made of transparent PVC material and can be directly sent to the nuclear magnetic resonance analyzer for analysis.

[0017] The beneficial effects of this invention are as follows: (1) In natural environments such as soil, rocks, and marine sediments, certain microorganisms can produce urease through metabolism. This enzyme can catalyze the hydrolysis of urea, change the chemical conditions of the surrounding microenvironment (such as increasing the pH value), and ultimately induce calcium ions dissolved in the environment to combine with carbonate ions to generate calcium carbonate crystals with cementing properties. The modification method of this invention is to add highly efficient urease-producing microorganisms, urea, and calcium sources to the slip zone soil to simulate and accelerate the biomineralization phenomenon of soil under the action of microorganisms under natural conditions. This method is applicable to most soil types, has high feasibility, strong applicability, and leaves no chemical residue.

[0018] (2) The device and method provided by the present invention can acquire test data in real time and obtain the permeability change law in real time, so as to analyze and compare the effect of microbial modification of slip zone soil under different conditions. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the device structure described in this invention; Figure 2 This is a schematic diagram of the modified cavity structure described in this invention; Figure 3 This is a comparison diagram of the pore size distribution of soil samples before and after the slip zone soil modification test in the embodiment; Figure 4 This is a graph showing the change in liquid pressure during water injection before modification of the slip zone soil in the embodiment. Figure 5 This is a graph showing the change in liquid pressure during the injection of calcium chloride in the process of modifying the slip zone soil in the example; Figure 6 This is a graph showing the change in intrinsic permeability during the modification of slip zone soil in the example.

[0020] The diagram is labeled as follows: 1. Liquid container 1; 2. Liquid container 2; 3. Liquid container 3; 4. Solenoid valve 1; 5. Relay 1; 6. Solenoid valve 2; 7. Relay 2; 8. Solenoid valve 3; 9. Relay 3; 10. Peristaltic pump; 11. Inlet pipe; 12. Pressure sensor; 131. Gauze layer 1; 132. Gauze layer 2; 14. Crushed stone layer; 151. Open-cell polymer foam layer 1; 152. Open-cell polymer foam layer 2; 16. Outlet pipe; 17. Modification chamber; 18. Soil sample layer; 19. Permeation-modification three-loop switching system; 20. Cable tie; 21. Data acquisition card; 22. Waste liquid container 1; 23. Waste liquid container 2; 24. Solenoid valve 4; 25. Relay 4; 26. Drain pipe; 27. Top cover plate; 28. Left flap of modification chamber; 29. ​​Right flap of modification chamber; 30. Bottom cover plate. Detailed Implementation

[0021] The embodiments of the present invention will be described in detail below with reference to the examples. The following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0022] Example 1 A device for preparing microbially modified slip zone soil and dynamically monitoring its permeability includes a modification chamber 17. The bottom of the modification chamber 17 is connected to a peristaltic pump 10 via an inlet pipe 11. The peristaltic pump 10 is connected to a permeation-modification three-loop switching system 19. A pressure sensor 12 is provided at one end of the inlet pipe 11 near the modification chamber 17. The interior of the modification chamber 17, from bottom to top, consists of a gravel layer 14, an open-cell polymer foam layer 151, a gauze layer 131, a sample chamber 18, a second gauze layer 132, and another open-cell polymer foam layer 152.

[0023] Furthermore, the thickness of the crushed stone layer 14 is 8-20 mm, and the crushed stone layer 14 is a crushed stone layer filled with crushed stone with a particle size of 5-12 mm.

[0024] Furthermore, both open-cell polymer foam layer 151 and open-cell polymer foam layer 152 are foam layers filled with open-cell polymer foam with a thickness of 8-15 mm and a pore size of 0.4-0.6 mm.

[0025] Furthermore, both gauze layer 131 and gauze layer 132 are gauze layers filled with 1-3 layers of gauze with a thickness of 0.3-0.8 mm and a pore size of 0.3-1.0 mm.

[0026] Furthermore, the modified cavity 17 is a modified cavity made of transparent plastic material; the main body of the modified cavity 17 is composed of two semi-cylindrical shell-shaped modified cavity left lobe 28 and modified cavity right lobe 29. The top and bottom of the main body of the modified cavity 17 are respectively provided with an upper cover plate 27 and a lower cover plate 30. The upper cover plate 27 and the lower cover plate 30 are respectively connected to the upper end and the lower end of the main body of the modified cavity 17 by threads. The middle part of the outer wall of the modified cavity 17 is connected with a cable tie 20 for reinforcement.

[0027] Furthermore, the permeation-modification three-loop switching system 19 includes liquid containers and hoses, each of which is equipped with a solenoid valve and a relay, with the solenoid valve switching controlled by a computer.

[0028] Furthermore, a drain pipe 26 is led out from the peristaltic pump 10, and a waste liquid container 23 is provided at the bottom of the drain pipe 26.

[0029] Furthermore, the front end of the drain pipe 26 is equipped with a solenoid valve 4 24 and a relay 4 25, and the solenoid valve 4 is switched on and off by a computer.

[0030] Furthermore, the pressure sensor 12 is connected to the computer via the data acquisition card 21.

[0031] Example 2 (1) According to Figure 1 and Figure 2 The device is assembled according to the structure shown. Liquid containers 1, 2, and 3 are connected to peristaltic pump 10 via solenoid valve 4 and relay 5, solenoid valve 6 and relay 7, and solenoid valve 8 and relay 9, respectively, through rubber tubes. Relays 5, 7, and 9 are connected to a computer. A drain pipe 26 leads out from the front end of peristaltic pump 10 and drains to waste liquid container 23. Solenoid valve 24 and relay 25 are installed at the front end of drain pipe 26. Relay 25 is connected to the computer. Peristaltic pump 10 is connected to modification chamber 17 via inlet pipe 11. A pressure sensor 12 is installed at the end of inlet pipe 11 near modification chamber 17. The data from pressure sensor 12 is transmitted to computer via acquisition card 21. The main body of the modified cavity 17 consists of two semi-cylindrical modified cavity halves, left halves 28 and right halves 29. The lower cover plate 30 is connected to the main body by threads, and the threads are wrapped with PTFE tape. It is then secured with cable ties in the middle of the outer wall of the modified cavity 17. The entire modified cavity 17 is made of transparent PVC plastic. The interior of the modified cavity 17 is filled from bottom to top with crushed stone (crushed stone particle size 5-12mm, filling thickness 10mm), open-cell polyurethane foam (foam pore size 0.4mm, filling thickness 10mm), gauze (single layer thickness 0.5mm, gauze pore size 0.4mm, gauze layers 2), slip zone soil (thickness 80mm), gauze (single layer thickness 0.5mm, pore size 0.4mm, gauze layers 2), and polyurethane foam (foam pore size 0.4mm, filling thickness 10mm). Then, PTFE tape is wrapped around it and the upper cover plate 27 is tightened by threads. The upper cover plate 27 is connected to the liquid outlet pipe 16 by an adapter, and the liquid outlet pipe 16 leads to the waste liquid container 22.

[0032] The specific steps for filling the slip zone soil are as follows: 160g of slip zone soil sample is added in four stages. First, 40g of soil sample is added and compacted to a thickness of 20mm. The compacted surface is then roughened with a scraper. A ring of transparent silicone sealant is applied along the outer edge of the compacted surface on the pipe wall. Another 40g of soil sample is added, and the above steps are repeated until 160g of soil sample is added. The final total soil sample thickness is 80mm. Since the inner diameter of the modified cavity 17 is 38mm, the cross-sectional area of ​​the soil sample is 1134.11mm². 2 .

[0033] (2) Using computer control, solenoid valves 1-4, 2-6, and 4-24 are closed, while solenoid valve 3-8 is opened. Liquid container 3-3 is filled with clean water. Peristaltic pump 10 is turned on to pump the clean water into modification chamber 17 via inlet pipe 11. The clean water flows from bottom to top and exits through outlet pipe 16. Waste liquid collection container 22 collects the outflowing clean water. During this process, the peristaltic pump flow rate is maintained at 1.1802 mL / min, and pressure head changes over time are recorded in real time using pressure sensor 12. Once the pressure head recorded by pressure sensor 12 is relatively stable, peristaltic pump 10 is turned off.

[0034] (3) Disconnect the modified cavity 17 from the inlet pipe 11 and the outlet pipe 16, put the entire modified cavity into the low field nuclear magnetic resonance analyzer, and export the pore size distribution data of the sliding zone soil before modification.

[0035] (4) Reconnect the modified chamber 17 to the inlet pipe 11 and the outlet pipe 16. Fill the first container 1 with a 1 mol / L urea solution, and the second container 2 with 1 × 10⁻⁶ mol / L urea solution. 9 A bacterial culture of CFU / mL was placed in container 3 (or container 3) with 1 mol / L calcium chloride solution. Using computer control, solenoid valves 2 (6), 3 (8), and 4 (24) were closed, while solenoid valve 4 (1) was opened. The peristaltic pump flow rate was confirmed to be 1.1802 mL / min. Peristaltic pump 10 was then turned on, and urea solution was slowly injected into the soil sample. After 20 minutes, the urea solution seeped out. Using computer control, solenoid valves 4 (1), 2 (6), and 3 (8) were closed, while solenoid valve 24 (4) was opened. Peristaltic pump 10 was turned off. The rubber tubing in container 1 (or container 1) was removed from the urea solution, and the remaining liquid in the tubing was drained through drain pipe 26. The rubber tubing was then returned to the urea solution.

[0036] (5) Using computer control, close solenoid valve 1 (4), solenoid valve 3 (8), and solenoid valve 4 (24), and open solenoid valve 2 (6). Confirm that the flow rate of the peristaltic pump is 1.1802 mL / min. Turn on the peristaltic pump 10 and slowly inject the bacterial solution into the soil sample. After 20 minutes, the bacterial solution seeps out. Using computer control, close solenoid valve 1 (4), solenoid valve 2 (6), and solenoid valve 3 (8), and open solenoid valve 4 (24). Turn off the peristaltic pump 10. Remove the rubber tube from the bacterial solution in container 2 (2), drain the remaining liquid in the tube through drain pipe 26, and then put the rubber tube back into the bacterial solution.

[0037] The specific steps for preparing the bacterial culture are as follows: A 250mL Erlenmeyer flask is used as the culture container. 150mL of sterilized culture medium is added. The culture medium formula is 5g / L yeast extract and 0.5mol / L urea. *Bacillus pasteurellii* inoculates the culture medium at a rate of 1% (V / V) and incubates for 48 hours in a constant-temperature shaker set at 30℃ and 150r / min. After incubation, the culture is centrifuged at 4000r / min for 10 minutes. The supernatant is discarded, and the bacterial cells are resuspended in sterile physiological saline. The bacterial concentration is adjusted to 1×10⁻⁶. 9 CFU / mL, transfer to a 4°C refrigerator and refrigerate for later use.

[0038] (6) After injecting the bacterial solution, let it stand for 2.5 hours to allow the microorganisms to fully adhere to the surface of the soil particles. Use a computer to control solenoid valves 1-4, 2-6, and 4-24 to close, and solenoid valve 3-8 to open. Confirm that the peristaltic pump flow rate is 1.1802 mL / min, turn on peristaltic pump 10, and slowly inject calcium chloride solution into the soil sample. Record the changes in pressure head over time in real time using pressure sensor 3.

[0039] (7) Disconnect the modified cavity 17 from the lower inlet pipe 11 and the outlet pipe 16. Place the entire modified cavity into a low-field nuclear magnetic resonance analyzer and export the pore size distribution data of the modified slip zone soil.

[0040] (8) Based on the pore size distribution data obtained from low-field nuclear magnetic resonance in steps (3) and (7), a comparison diagram of the pore size distribution of soil samples before and after the slip zone soil modification test is shown in the figure. Figure 3 As shown in the figure, the distribution rate of pores with a diameter of 0-0.25 μm increased after the modification test of the slip zone soil, while the distribution rate of pores with a diameter of 0.4-10.0 μm decreased. This indicates that the calcium carbonate induced by microorganisms during the modification process adheres to the pore walls in the soil sample, making the overall pore size in the soil sample smaller, thereby reducing the permeability of the soil sample.

[0041] Based on the data recorded in steps (2) and (6), a water pressure change curve was plotted. Darcy's law was used to calculate the intrinsic permeability of the slip zone soil before and after microbial modification. The effect of microbial-induced calcium carbonate precipitation modification was evaluated based on the intrinsic permeability. The formula for Darcy's law is:

[0042] Where: k is the characteristic permeability of the soil sample; μ is the dynamic viscosity of the liquid flowing through the soil sample; Q is the recorded flow rate of the peristaltic pump; L is the seepage diameter of the soil sample; A is the cross-sectional area of ​​the soil sample; ρ is the density of the liquid flowing through the soil sample; g is the acceleration due to gravity. p is the pressure head calculated from data collected by a pressure sensor.

[0043] Throughout the experiment, the laboratory temperature was approximately 20°C; the dynamic viscosity of water, as determined from the table, was 1.005 × 10⁻⁶. -3 Pa·s, water density is 998.2 kg / m³ 3 The dynamic viscosity of a 1 mol / L calcium chloride solution is 1.081 × 10⁻⁶. -3 Pa·s, density 1085.5 kg / m³ 3 g is taken as 9.8 m / s 2 .

[0044] The data recorded in step (2) is used to create a curve showing the change in liquid pressure during water injection, as shown below. Figure 4 As shown, using Darcy's law, the intrinsic permeability of the soil sample before microbial modification of the slip zone soil under saturated conditions is approximately 7.76 × 10⁻⁶. -18 m 2 .

[0045] The data recorded in step (5) is used to plot the liquid pressure change curve during calcium chloride injection, as shown in the figure. Figure 5 As shown, the soil sample saturates at approximately 120 seconds, after which the liquid pressure initially decreases and then slowly increases. When calcium chloride is first injected, the reaction is intense, rapidly generating a large number of calcium carbonate particles that block some of the pores. As the calcium chloride solution continues to be introduced, the reaction stabilizes, and the calcium carbonate particles that have not yet adhered to the soil particle surface before the water flow clears them, forming seepage channels and causing a decrease in liquid pressure. As subsequent calcium carbonate particles adhere to the soil particle surface, reducing the pore size of the seepage channels, the liquid pressure gradually increases. Therefore, the intrinsic permeability change curve at soil saturation can be plotted based on the water pressure change curve, as shown below. Figure 6 .

[0046] according to Figure 6 The data shows the change in permeability of the slip zone soil during the modification process. Furthermore, under saturation, the permeability of the soil sample modified based on microbial-induced calcium carbonate precipitation ultimately decreased to approximately 6.68 × 10⁻⁶. -18 m 2 The soil permeability changes continuously during the modification process, eventually decreasing gradually.

[0047] By combining the results of low-field nuclear magnetic resonance and dynamic monitoring of permeability changes during the modification process, the process of microbial modification of slip zone soil can be clearly understood, indicating that the method proposed in this patent is a reliable scheme for studying the microbial-induced calcium carbonate precipitation modification process of slip zone soil.

Claims

1. A device for preparing microbially modified slip zone soil and dynamically monitoring its permeability, characterized in that, It includes a modification chamber (17), the bottom of which is connected to a peristaltic pump (10) via an inlet pipe (11), and the peristaltic pump (10) is connected to a permeation-modification three-loop switching system (19); a pressure sensor (12) is provided at one end of the inlet pipe (11) near the modification chamber (17); the interior of the modification chamber (17) from bottom to top consists of a gravel layer (14), an open-cell polymer foam layer one (151), a gauze layer one (131), a sample chamber (18), a gauze layer two (132), and an open-cell polymer foam layer two (152).

2. The device for preparing microbially modified slip zone soil and dynamically monitoring its permeability according to claim 1, characterized in that, The thickness of the crushed stone layer (14) is 8-20 mm. The crushed stone layer (14) is a crushed stone layer filled with crushed stone with a particle size of 5-12 mm.

3. The device for preparing microbially modified slip zone soil and dynamically monitoring its permeability according to claim 1, characterized in that, Both open-cell polymer foam layer one (151) and open-cell polymer foam layer two (152) are foam layers filled with open-cell polymer foam with a thickness of 8-15 mm and a pore size of 0.4-0.6 mm.

4. The device for preparing microbially modified slip zone soil and dynamically monitoring its permeability according to claim 1, characterized in that, Both gauze layer one (131) and gauze layer two (132) are gauze layers filled with 1-3 layers of gauze with a thickness of 0.3-0.8 mm and a pore size of 0.3-1.0 mm.

5. The device for preparing microbially modified slip zone soil and dynamically monitoring its permeability according to claim 1, characterized in that, The modified cavity (17) is a modified cavity made of transparent plastic material; the main body of the modified cavity (17) is composed of two semi-cylindrical shell-shaped modified cavity left petal (28) and modified cavity right petal (29). The top and bottom of the main body of the modified cavity (17) are respectively provided with an upper cover plate (27) and a lower cover plate (30). The upper cover plate (27) and the lower cover plate (30) are respectively connected to the upper end and the lower end of the main body of the modified cavity (17) by threads. The middle part of the outer wall of the modified cavity (17) is connected with a cable tie (20) for reinforcement.

6. The device for preparing microbially modified slip zone soil and dynamically monitoring its permeability according to claim 1, characterized in that, The permeation-modification three-loop switching system (19) includes a liquid container and a hose. Each liquid container is equipped with a solenoid valve and a relay, and the solenoid valve is controlled by a computer. A drain pipe (26) is led out from the peristaltic pump (10). Waste liquid container two (23) is provided at the bottom of the drain pipe (26). Solenoid valve four (24) and relay four (25) are provided at the front end of the drain pipe (26), and the solenoid valve four is controlled by a computer.

7. The device for preparing microbially modified slip zone soil and dynamically monitoring its permeability according to claim 1, characterized in that, The pressure sensor (12) is connected to the computer via the data acquisition card (21).

8. A method for preparing microbially modified slip zone soil and dynamically monitoring its permeability, characterized in that, The apparatus according to any one of claims 1-7 comprises the following steps: (1) The bottom of the modified cavity body is tightened with the lower cover plate by threads, and the modified cavity is reinforced with cable ties; the interior of the modified cavity body is filled with gravel, open-cell polyurethane foam, gauze, slip zone soil, gauze and open-cell polyurethane foam from bottom to top, and the top cover plate is placed on the top of the modified cavity body and tightened. (2) Pump clean water into the modification chamber and record the data from the pressure sensor in real time; (3) Stop pumping clean water and switch to pumping urea; (4) Stop pumping urea and switch to pumping bacterial solution; (5) Stop pumping bacterial solution and switch to pumping calcium chloride solution, and record the data from the pressure sensor in real time.

9. A method for preparing microbially modified slip zone soil and dynamically monitoring its permeability according to claim 8, characterized in that, Based on the pressure sensor data recorded in steps (2) and (5), the intrinsic permeability of the slip zone soil before and after microbial modification is calculated using Darcy's law, and the effect of microbial-induced calcium carbonate precipitation modification is evaluated based on the intrinsic permeability.

10. A method for preparing microbially modified slip zone soil and dynamically monitoring its permeability according to claim 8, characterized in that, The slip zone soil is added in batches. After each batch of slip zone soil is added, the surface is first scraped and compacted, and then a ring of glass glue is applied along the edge of the compacted surface before the next batch of slip zone soil is added. The modification chamber is made of transparent PVC material and can be directly sent to the nuclear magnetic resonance analyzer for analysis.

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