Multi-field coupling model test monitoring device and method for evaluating microbial mineralization homogeneity

Abstract

The present application relates to a multi-field coupling model test monitoring device and method for evaluating the homogeneity of microbial mineralization, which comprises a test model box, a pressurizing system, a grouting system, a sampling system, a sensor assembly and a computer monitoring system. Compared with the prior art, the device focuses on the process of microbial mineralization solidified soil under the influence of different overburden stresses and grouting rates in multiple environments such as biological field, chemical field, stress field and hydraulic field. The device can effectively evaluate the uniformity and effect of the solidification repair of the microbial mineralization solidified soil, as well as the distribution of the mineral content, providing an important basis for studying the long-term safety of the microbial mineralization solidified soil. This scheme has important significance for the repair and utilization of contaminated soil and energy saving and carbon reduction in engineering application.

Description

Technical Field

[0001] This invention belongs to the field of microbial mineralization and solidification technology, and relates to a multi-field coupled model test monitoring device and method for evaluating the homogeneity of microbial mineralization, and more particularly to a bio-chemical-stress-hydraulic multi-field coupled model test monitoring device and method for evaluating the homogeneity of microbial mineralization. Background Technology

[0002] Modern engineering construction requires greener, more efficient, and energy-saving soil improvement technologies. Microbial-induced carbonate precipitation technology, a research hotspot in soil solidification, has been widely used in the remediation of contaminated soil and the reinforcement of soft soil foundations. This technology primarily utilizes the metabolic activities of microorganisms to promote the hydrolysis of urea, generating a large amount of carbonate ions, which combine with free calcium ions to form calcium carbonate precipitates. These precipitates fill soil pores, thereby increasing soil strength. Microbial mineralization solidification technology has advantages such as low energy consumption, minimal disturbance to the soil, and less secondary pollution. Simultaneously, it achieves biological carbon sequestration while improving soil engineering properties, thus saving energy and protecting the environment.

[0003] In recent years, with the rapid advancement of industrialization, industries such as agriculture, metallurgy, and chemicals have discharged large amounts of pollutants into soil and water bodies during their operations. This pollution not only restricts the redevelopment and utilization of land but also poses a threat to the health and safety of surrounding residents. Furthermore, facing increasingly complex engineering geological environments, the hydraulic and mechanical properties of many soils can no longer meet engineering requirements. Factors such as hydraulic erosion, liquefaction tendency, and freeze-thaw cycles often lead to engineering problems such as roadbed subsidence, slope instability, and coastal erosion.

[0004] However, current research on microbial mineralization and solidification of soil mainly focuses on the strength, permeability, and environmental safety of the solidified soil. Research on the solidification effect under multiple field effects, as well as the scope and uniformity of solidification and remediation, is relatively limited. Therefore, to further explore the uniformity of microbial mineralization and solidification of soil, it is necessary to develop an experimental device capable of real-time monitoring and evaluation of the distribution and evolution of the hydraulic, stress, chemical, and biological fields, as well as the mineral content, of the soil during the solidification process under different overburden pressures and grouting rates. This would allow for a deeper understanding of the internal mechanisms of the solidified soil, providing a theoretical basis and optimal solutions for energy conservation, emission reduction, and biocarbon sequestration in the redevelopment and utilization of contaminated sites and soil improvement projects.

[0005] This invention is based on this premise. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-field coupled model test monitoring device and method for evaluating the homogeneity of microbial mineralization, which can explore and evaluate the effects of overburden stress and grouting rate on the homogeneity of solidified soil under multi-field coupled environment.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] In one aspect, the present invention provides a monitoring device for a multi-field coupled model experiment to evaluate the homogeneity of microbial mineralization, comprising:

[0009] The test model box includes a model box for placing test soil, a sleeve surrounding the model box, and a top cover covering the test soil;

[0010] The grouting system includes a grouting pump and a grouting pipe connected to the grouting outlet of the grouting pump. The grouting pipe is inserted into the test soil along the height direction and has grouting holes distributed on its sidewalls for injecting grout outwards.

[0011] A pressurization system includes a pressurization head located above the top cover and movable vertically, the pressurization head being configured to apply a preset pressure to the top cover;

[0012] A sampling system comprising a sampling tube extending from the bottom into the test soil within the model box;

[0013] And a monitoring system, which includes sensor components pre-placed in the test soil for monitoring multi-field data including stress and strain, pH, conductivity, ammonium ion concentration, and pore water pressure.

[0014] Furthermore, the model box has water outlet holes distributed around its perimeter, and a storage space is formed between the model box and the sleeve to store excess slurry discharged through the water outlet holes.

[0015] Furthermore, the inner wall and bottom of the model box are lined with filter paper. The filter paper on the inner wall is used to filter the test soil, allowing only excess liquid to pass through and enter the liquid storage space between the sleeve and the model box. The filter paper on the bottom is mainly used to prevent the test soil from sticking together and making it difficult to remove the sample.

[0016] Furthermore, the model box is cylindrical in shape, for example, 1m high, 1cm thick, and 2m inner diameter.

[0017] Furthermore, the top cover has an opening for the grouting pipe to extend into. For example, the inner diameter of the top cover opening is 2.3 cm, and the top cover is divided into upper and lower parts. The lower part has a diameter of 199.9 cm and a thickness of 3 cm, which is used to fit the inner wall of the test chamber to press down the test soil sample. The upper part has a diameter of 207 cm and a thickness of 2 cm, which serves as a cover.

[0018] Furthermore, the grouting system also includes a silicone hose and a flexible and rigid pipe joint connected in sequence to the outlet of the grouting pump. The flexible and rigid pipe joint is also connected to the grouting pipe, wherein the grouting pipe is used to deliver grouting slurry to the test soil.

[0019] Furthermore, filter paper is attached to the outside of the grouting pipe to prevent components of the test soil from entering the grouting pipe and affecting the grouting effect.

[0020] Furthermore, the grouting holes on the sidewall of the grouting pipe are distributed in three rows at equal intervals, with a 120° interval between each row. For example, the vertical hole distance between two adjacent grouting holes in each row is 2 cm.

[0021] Furthermore, the pressurization system also includes a fixed frame and a hydraulic pump, with the pressurization head mounted on the fixed frame and powered by the hydraulic pump for vertical movement.

[0022] Furthermore, the fixed frame includes a support rod and a top plate. The support rod is fixedly connected to the outer wall of the sleeve, and the top plate is connected to the top of the support rod. The pressure head is provided on the top plate.

[0023] Furthermore, the sampling system also includes a filter head, a one-way valve, and a sampling connection hose. The filter head is located at one end of the sampling tube that extends into the test soil, and the sampling connection hose is connected to the other end of the sampling tube. A one-way valve is also provided on the sampling connection hose.

[0024] For example, the sampling end of the one-way valve is a Luer interface, and water samples are taken through a Luer syringe; the sampling tube has an outer diameter of 4mm, a wall thickness of 1mm, and a length of 55cm.

[0025] Furthermore, sampling holes are distributed at the bottom of the model box. After the sampling tube is connected to the sampling hole, the bottom of the sampling hole is sealed with glass glue and rubber gasket to prevent leakage and loosening.

[0026] For example, for a certain sleeve or test chamber size, the sampling holes are located at 10cm, 30cm, 50cm, 70cm and 90cm from the center, arranged at 60° intervals, for a total of 30 water sampling points, with a hole diameter of 5mm.

[0027] Furthermore, the sensor assembly includes a distributed optical fiber sensor unit and an electronic sensor unit, wherein the distributed optical fiber sensor unit includes stress-strain sensors and is provided in several columns arranged vertically in the test soil.

[0028] Furthermore, the electronic sensor unit includes a pH sensor, a conductivity sensor, an ammonium ion concentration sensor, and a pore water pressure sensor.

[0029] Furthermore, each sensor in the sensor assembly is connected to an external computer unit via wires extending from the model housing.

[0030] In this invention, a stress field and its stress-strain sensors are used to investigate the stress distribution and deformation patterns during the curing process under overburden pressure, assess its impact on repair uniformity, and determine optimal pressure conditions to improve repair efficiency. The hydraulic field and its pore water pressure sensor are used to study the distribution characteristics of pore water pressure at different grouting rates to understand grout diffusion and its effect on uniformity. The biofield and its viable bacteria count are used to assess the impact of microbial distribution and activity on curing efficiency and curing uniformity. The chemical field and its pH sensor, conductivity sensor, and ammonium ion concentration sensor aim to monitor the influence of the soil's chemical environment on soil curing uniformity and migration and transformation processes.

[0031] On the other hand, the present invention also provides a monitoring method for a multi-field coupled model experiment to evaluate the homogeneity of microbial mineralization, which is based on the monitoring device described above, and the monitoring method includes the following steps:

[0032] S1. Place the test soil in layers inside the model box and compact it. Simultaneously set up the sampling system, grouting system, and monitoring system. After filling the test soil, cover it with the top cover.

[0033] S2. Adjust the pressurization system to apply the preset pressure to the test soil;

[0034] S3. Adjust the grouting system to perform grouting operations according to the preset grouting rate;

[0035] S4. After grouting is completed, the test soil is sampled by the sampling system and the number of viable bacteria and urea concentration are measured. The stress-hydraulic-chemical-biological multi-field data monitored by the monitoring system, including stress-strain, pH, conductivity, ammonium ion concentration and pore water pressure, are recorded in real time.

[0036] S5. Repeat S3 and S4 until the test soil has solidified.

[0037] S6. After the demolished test soil is dried, a micro cone penetration test is conducted to determine the strength of the test soil. The soil samples near each sampling port are cut into blocks and the calcite content is determined by acid washing. The test is then completed.

[0038] This invention provides a model test device for studying the uniformity and mechanism of microbial mineralization solidification soil remediation under stress-hydraulic-chemical-biological multi-field coupling, which investigates the effects of grouting rate and overburden pressure. The device examines the uniformity of solidification and remediation of microbial mineralization solidified soil under different grouting rates and overburden pressures, considering factors such as stress field, hydraulic field, chemical field, biological field, and mineral distribution. This device can effectively evaluate the solidification uniformity of microbial mineralization solidified soil at different depths and grouting rates by real-time monitoring of the chemical, biological, stress, and hydraulic field parameters. This provides a research basis for energy conservation, emission reduction, and biocarbon sequestration in the remediation, redevelopment, and utilization of contaminated sites and in soil improvement engineering applications. The proposed solution is of significant importance in addressing the remediation scope and uniformity of microbial mineralization solidified soil.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] (1) Existing technologies focus on analyzing the strength, permeability, and environmental safety of microbially mineralized solidified soil, but there is very little discussion on the scope of solidification and remediation, as well as the uniformity of solidification under different ground depths and grouting rates. The device of this invention can simulate different ground depths by setting different overburden pressures and different grouting rates, thereby effectively evaluating the uniformity of microbially mineralized solidified soil under various conditions, providing an efficient and reasonable solution for energy conservation, emission reduction, and biocarbon sequestration in the redevelopment of contaminated sites and soil improvement engineering applications.

[0041] (2) The device of the present invention has the advantage of real-time monitoring of parameters such as stress field, hydraulic field, chemical field and biological field, which facilitates dynamic research on the solidification uniformity and solidification range of soil at each stage during the microbial mineralization solidification process, effectively avoids the error and inaccuracy of manual sampling and testing data, and improves the convenience and operability of the experiment. Attached Figure Description

[0042] Figure 1 A schematic diagram of a bio-chemical-stress-hydraulic multi-field coupled model test monitoring device used to evaluate the homogeneity of microbial mineralization.

[0043] Figure 2 A schematic diagram of the distributed optical fiber arrangement of the monitoring device for a bio-chemical-stress-hydraulic multi-field coupled model test used to evaluate the homogeneity of microbial mineralization.

[0044] Figure 3 A schematic diagram of the sampling points and sensor placement locations of a bio-chemical-stress-hydraulic multi-field coupled model test monitoring device used to evaluate the homogeneity of microbial mineralization.

[0045] Explanation of markings in the diagram:

[0046] 1. Test model box; 2. Pressurization system; 3. Grouting system; 4. Sampling system; 5. Monitoring system; 6. Wire hole; 7. Model box body; 8. Sleeve; 9. Top cover; 10. Water outlet; 11. Top cover opening; 12. Hydraulic pump; 13. Pressurization head; 14. Fixing frame; 15. Support rod; 16. Top plate; 17. Sampling tube; 18. Filter head; 19. One-way valve; 20. Distributed fiber optic sensor unit; 21. Electronic sensor unit; 22. Computer unit; 23. Grouting pump; 24. Silicone hose; 25. Grouting pipe; 26. Flexible and rigid pipe joint; 27. Grouting hole; 28. Sampling hole. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0048] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0049] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0050] Unless otherwise specified, the functional components or structures in the following embodiments or examples are conventional components or structures used in the art to achieve the corresponding functions.

[0051] To explore and evaluate the effects of overlying stress and grouting rate on the homogeneity of solidified soil under multi-field coupling conditions, this invention provides a multi-field coupling model test monitoring device for evaluating the homogeneity of microbial mineralization. Its structure is described in [reference needed]. Figure 1 As shown, including:

[0052] The test model box 1 includes a model box 7 for placing the test soil, a sleeve 8 surrounding the model box 7, and a top cover 9 covering the test soil.

[0053] The grouting system 3 includes a grouting pump 23 and a grouting pipe 25 connected to the grouting outlet of the grouting pump 23. The grouting pipe 25 is inserted into the test soil along the height direction and has grouting holes 27 distributed on its sidewalls for injecting grout outward.

[0054] The pressurization system 2 includes a pressurization head 13 located above the top cover 9 and movable up and down, the pressurization head 13 being configured to apply a preset pressure to the top cover 9;

[0055] Sampling system 4, which includes a sampling tube 17 extending from the bottom into the test soil of the model box 7;

[0056] And monitoring system 5, which includes sensor components pre-placed in the test soil for monitoring multiple field data including stress and strain, pH, conductivity, ammonium ion concentration, and pore water pressure.

[0057] In some specific embodiments, the model box 7 is provided with water outlet holes 10 around its perimeter, and a liquid storage space is formed between the model box 7 and the sleeve 8 to store excess slurry discharged through the water outlet holes 10.

[0058] In a more specific embodiment, filter paper is attached to both the inner wall and the bottom of the model box 7. The filter paper on the inner wall is used to filter the test soil, allowing only excess liquid to pass through and enter the liquid storage space between the sleeve 8 and the model box 7. The filter paper on the bottom is mainly used to prevent the test soil from sticking together and making it difficult to remove the sample.

[0059] In some specific embodiments, the model box 7 is cylindrical in shape, for example, 1m high, 1cm thick, and 2m inner diameter.

[0060] In some specific embodiments, the top cover 9 has a top cover opening 11 for the grouting pipe 25 to extend into. For example, the inner diameter of the top cover opening 11 is 2.3 cm, and the top cover 9 is divided into upper and lower parts. The lower part has a diameter of 199.9 cm and a thickness of 3 cm, which is used to fit the inner wall of the test chamber to press down the test soil sample. The upper part has a diameter of 207 cm and a thickness of 2 cm, which serves as a cover.

[0061] In some specific embodiments, the grouting system 3 further includes a silicone hose 24 and a flexible and rigid pipe joint 26 connected in sequence to the outlet of the grouting pump 23. The flexible and rigid pipe joint 26 is also connected to the grouting pipe 25, wherein the grouting pipe 25 is used to deliver grouting slurry to the test soil.

[0062] In a more specific embodiment, filter paper is attached to the outside of the grouting pipe 25 to prevent components of the test soil from entering the interior of the grouting pipe 25 and affecting the grouting effect.

[0063] In a more specific embodiment, the grouting holes 27 on the side wall of the grouting pipe 25 are distributed in three rows at equal intervals, with a 120° interval between the two rows. For example, the vertical hole distance between two adjacent grouting holes 27 in each row is 2 cm.

[0064] In some specific embodiments, the pressurization system 2 further includes a fixed frame 14 and a hydraulic pump 12, wherein the pressurization head 13 is disposed on the fixed frame 14 and is provided with the power for vertical lifting by the hydraulic pump 12.

[0065] Furthermore, the fixed frame 14 includes a support rod 15 and a top plate 16. The support rod 15 is fixedly connected to the outer wall of the sleeve 8, and the top plate 16 is connected to the top of the support rod 15. The pressure head 13 is provided on the top plate 16.

[0066] In some specific embodiments, the sampling system 4 further includes a filter head 18, a one-way valve 19, and a sampling connection hose. The filter head 18 is disposed at one end of the sampling tube 17 that extends into the test soil, and the sampling connection hose is connected to the other end of the sampling tube 17. A one-way valve 19 is also provided on the sampling connection hose.

[0067] For example, the sampling end of the one-way valve 19 is a Luer interface, and water samples are taken through a Luer syringe; the sampling tube 17 has an outer diameter of 4 mm, a wall thickness of 1 mm, and a length of 55 cm.

[0068] In a more specific embodiment, sampling holes 28 are also distributed at the bottom of the model box 7. After the sampling tube 17 is connected to the sampling hole 28, the bottom of the sampling hole 28 is sealed with glass glue and rubber gasket to prevent leakage and loosening.

[0069] For example, for a certain sleeve 8 or test chamber size, the sampling holes 28 are located at 10cm, 30cm, 50cm, 70cm and 90cm from the center, arranged at 60° intervals, for a total of 30 water sampling points, with a hole diameter of 5mm.

[0070] In some specific embodiments, the sensor assembly includes a distributed optical fiber sensor unit 20 and an electronic sensor unit 21. The distributed optical fiber sensor unit 20 includes stress-strain sensors and is arranged in several columns along a vertical direction within the test soil. For example, please refer to [link to example]. Figure 3 As shown, several rings can be arranged around the central axis of the test soil, with six rings in each ring. The spacing between adjacent rings is set according to the testing requirements.

[0071] In some specific embodiments, the electronic sensor unit 21 includes a pH sensor, a conductivity sensor, an ammonium ion concentration sensor, and a pore water pressure sensor.

[0072] In some specific embodiments, each sensor in the sensor assembly is also connected to an external computer unit 22 via wires extending from the model housing 7. The computer unit 22 can receive, record, and process the various biological-chemical-stress-hydraulic multi-field data fed back by each sensor according to a preset program. The computer unit 22 itself is not an innovative point of protection of this invention, but is a conventional device in the art, and will not be described in detail here.

[0073] Each of the above implementation methods can be implemented individually, or in any combination of two or more.

[0074] The above implementation methods will be described in more detail below with reference to specific embodiments.

[0075] Example 1:

[0076] refer to Figure 1 This embodiment provides a research experimental device for studying the uniformity law and mechanism of microbial mineralization solidification soil remediation under stress-hydraulic-chemical-biological multi-field under the influence of grouting rate and overburden pressure. The model test device is used to study the solidification uniformity of biotechnology solidification remediation of heavy metal contaminated soil under the influence of different overburden pressures and different grouting rates. The model test device includes a test model box 1, a pressurization system 2, a grouting system 3, a sampling system 4, a sensor assembly, and a computer unit 22.

[0077] The model test chamber comprises three parts: a model box body 7, a sleeve 8, and a top cover 9. The model box body 7 and the sleeve 8 are connected at the bottom center. Holes are opened around the perimeter of the model box body 7 to allow excess grout to seep into the area between the model box body 7 and the sleeve 8. The interior area of ​​the model box body 7 is used to place the test soil for solidification. A central hole is opened in the top cover 9 for inserting a grouting pipe 25.

[0078] The pressurization system 2 includes a hydraulic pump 12, a pressure head 13, and a fixed frame 14. The fixed frame 14 includes support rods 15 and a top plate 16. In this embodiment, there are three support rods 15 distributed at 120° intervals, each connected to the outer wall of the sleeve 8. The top ends of the support rods 15 are at the same height and connected to the top plate 16. In this embodiment, the overlay pressure is mainly adjusted by the hydraulic pump 12. The hydraulic pump 12 is a Moxin WCB model with a pressure range of 0-0.3 MPa.

[0079] The grouting system 3 includes a grouting pump 23 (preferably a peristaltic pump in this embodiment), a silicone hose 24, a grouting pipe 25, and a flexible and rigid pipe connector 26, all connected in sequence as shown. In this embodiment, the grouting rate is adjusted by setting the parameters of the peristaltic pump. The peristaltic pump is a Chuangrui WT600 with a flow rate range of 2.1-6000 mL / min.

[0080] The sampling system 4 includes a sampling tube 17, a filter head 18, a one-way valve 19 (with a Luer interface), and a silicone hose 24. In this embodiment, the bottom of the sleeve 8 has a sampling hole 28. One end of the sampling tube 17 is connected to the filter head 18 and inserted into the sampling hole. The tube is placed in the middle of the model box 7, with all sampling tubes 17 at the same height. The other end of the sampling tube 17 extends outside the bottom surface of the sleeve 8 and is connected to one end of the silicone hose 24. The other end of the silicone hose 24 is connected to the one-way valve 19.

[0081] The monitoring system 5 includes an electronic sensor unit 21, comprising: a pH sensor (Qijue Electronics S-PH-A1LT), a conductivity sensor (Qijue Electronics S-EC-B2LT), an ammonium ion concentration sensor (Xinyangbang S-CGNF), and a pore water pressure sensor (Synno SCYG318); a distributed optical fiber sensor including a stress-strain sensor (YOFC-SBOA10002); and a computer unit 22, used for real-time monitoring of pH, conductivity, ammonium ion concentration, shear wave velocity, and pore water pressure. The sleeve 8 has a wire hole 6 at its bottom, through which the wires of the electronic sensor unit 21 and the distributed optical fiber sensor are connected to the computer unit 22.

[0082] In this embodiment, the grouting pipe 25 has an opening in its wall, and the grouting holes 27 are arranged in three rows at 120° intervals.

[0083] In this embodiment, the sampling tube 17, the silicone hose 24, and the connection between the silicone hose 24 and the one-way valve 19 are all sealed and fixed with clamps to prevent leakage.

[0084] In this embodiment, the top plate 16 has a central hole, and the pressure head 13 is fixedly connected to the top plate 16 by fixing screws. The top plate 16 is used to provide reaction force support for the pressure head 13.

[0085] Example 2

[0086] Based on Example 1, this example provides a method for using the experimental apparatus described above for studying the uniformity and mechanism of heavy metal contaminated soil remediation under stress-hydraulic-chemical-biological multi-field conditions using traditional enhancement methods, including the following steps:

[0087] Step S1: Filter paper is laid at the bottom and inside of the model box 7 to prevent soil from directly adhering to the model box 7 and to prevent soil from seeping out of the model box 7 to the space between the sleeve 8 and the model box 7.

[0088] Step S2: After installing the sampling tube 17 and the filter head 18, insert the sampling hole 28 to the middle position of the model box 7, fix the electronic sensor unit 21 tightly against the sampling tube 17 in the middle of the model box 7, and then install the distributed fiber optic sensor according to... Figure 3 The sampling points are arranged longitudinally inside the model box 7 to detect parameters of biological field, chemical field, hydraulic field and stress. Then, the wires of the sensor assembly are passed through the wire hole 6, and the sampling hole 28 and the wire hole 6 are sealed with glass glue and rubber gasket to prevent leakage.

[0089] Step S3: Filter paper is attached to the outer wall of the grouting pipe 25 and placed in the center of the model box 7. A 20cm thick layer of clay is laid at the bottom of the model box 7 for seepage prevention and fixing of the grouting pipe 25. A thin geomembrane is laid on top of the clay, and then a 60cm thick layer of lead-contaminated soil is placed and compacted in layers. Then, a thin geomembrane is laid on top of the lead-contaminated soil, and then a 20cm thick layer of clay is laid for seepage prevention.

[0090] Step S4: Place the top cover 9 through the grouting pipe 25 over the model box 7. After confirming that the fit is complete and there is no tilt, adjust the parameters of the hydraulic pump 12 to the overburden pressure of 30 kPa. Apply the required overburden pressure to the test soil through the pressure head 13 above the top cover 9.

[0091] Step S5: Connect the peristaltic pump, silicone tubing 24, flexible and rigid pipe connector 26, and grouting pipe 25 in sequence, sealing and securing the connections with clamps. Then adjust the peristaltic pump parameters to a rate of 0.2 PV / h and begin injecting the exogenous bacterial solution (urea: 350 mM; ammonium chloride: 12.5 mM; sodium acetate: 42.5 mM; yeast extract: 0.1 g / L; S. pasteurii: 3.5 × 10⁻⁶). 7 (cells / mL)

[0092] Step S6: Use a Luer interface syringe to take a sample from the sampling port and perform viable count and urea concentration determination.

[0093] Step S7: Monitor and record the test parameters of the test soil in real time through computer unit 22.

[0094] Step S8: Inject exogenous bacterial solution again every 24 hours, repeating steps S6 and S7 until the pH of each water sample stabilizes at 9.0-9.5. Then, stop injecting exogenous bacterial solution and start injecting the gelling solution (urea: 350mM; ammonium chloride: 12.5mM; sodium acetate: 42.5mM; yeast extract: 0.1g / L; calcium acetate: 250mM).

[0095] Step S9: Inject the cementing solution again every 24 hours, repeating steps S6 to S7 until the urea content is completely decomposed about 6 hours after the cementing solution is injected, at which point the consolidation is complete.

[0096] Step S10: Rinse the solidified lead-contaminated soil with deionized water to remove excess ions so as not to affect the pickling results.

[0097] Step S11: After rinsing, remove the sample and put the test soil sample into an oven to dry for 24 hours.

[0098] Step S12: Conduct micro-cone penetration tests near each sampling port of the dried test soil sample, and cut the soil sample near each sampling port into blocks for acid washing to determine the calcite content. When the strength of each part of the micro-cone penetration test is similar, and the final calcite content of each part is similar as determined by acid washing, it proves that the repair and solidification uniformity is good.

[0099] Example 3

[0100] Based on Example 1, this example provides a method for using the experimental apparatus for studying the uniformity and mechanism of heavy metal contaminated soil remediation under stress-hydraulic-chemical-biological multi-field in-situ induced remediation, including the following steps:

[0101] Step S1: Filter paper is laid at the bottom and inside of the model box 7 to prevent soil from directly adhering to the model box 7 and to prevent soil from seeping out of the model box 7 to the space between the sleeve 8 and the model box 7.

[0102] Step S2: After installing the sampling tube 17 and the filter head 18, insert the sampling hole 28 to the middle position of the model box 7, fix the electronic sensor unit 21 tightly against the sampling tube 17 in the middle of the model box 7, and then install the distributed fiber optic sensor according to... Figure 3 The sampling points are arranged longitudinally inside the model box 7 to detect parameters of the biological field, chemical field, hydraulic field and stress field. Then, the wires of the sensor assembly are passed through the wire hole 6, and the sampling hole 28 and the wire hole 6 are sealed with glass glue and rubber gasket to prevent leakage.

[0103] Step S3: Filter paper is attached to the outer wall of the grouting pipe 25 and placed in the center of the model box 7. A 20cm thick layer of clay is laid at the bottom of the model box 7 for seepage prevention and fixing of the grouting pipe 25. A thin geomembrane is laid on top of the clay, and then a 60cm thick layer of lead-contaminated soil is placed and compacted in layers. Then, a thin geomembrane is laid on top of the lead-contaminated soil, and then a 20cm thick layer of clay is laid for seepage prevention.

[0104] Step S4: Place the top cover 9 through the grouting pipe 25 over the model box 7. After confirming that the fit is complete and there is no tilt, adjust the hydraulic pump 12 to the overburden pressure of 30 kPa. Apply the required overburden pressure to the test soil through the pressure head 13 above the top cover 9.

[0105] Step S5: Connect the peristaltic pump, silicone tubing 24, flexible and rigid pipe connector 26, and grouting pipe 25 in sequence, and seal and fix the connection with clamps. Then adjust the peristaltic pump parameters to a rate of 0.2PV / h and start injecting the activation solution (urea: 350mM; ammonium chloride: 12.5mM; sodium acetate: 42.5mM; yeast extract: 0.1g / L).

[0106] Step S6: Use a Luer interface syringe to take a sample from the sampling port and perform viable count and urea concentration determination.

[0107] Step S7: Monitor and record the test parameters of the test soil in real time through computer unit 22.

[0108] Step S8: Inject the activation solution again every 24 hours. Repeat steps S6 and S7 after 24 hours until the pH of each water sample stabilizes at 9.0-9.5. Activation is then complete, exogenous bacterial solution injection is finished, and the injection of cementing solution (urea: 350mM; ammonium chloride: 12.5mM; sodium acetate: 42.5mM; yeast extract: 0.1g / L; calcium acetate: 250mM) begins.

[0109] Step S9: Inject the cementing solution again every 24 hours, repeating steps S6 to S7 until the urea content is completely decomposed about 6 hours after the cementing solution is injected, at which point the consolidation is complete.

[0110] Step S10: Rinse the solidified lead-contaminated soil with deionized water to remove excess ions so as not to affect the pickling results.

[0111] Step S11: After rinsing, remove the sample and put the test soil sample into an oven to dry for 24 hours.

[0112] Step S12: Conduct micro-cone penetration tests near each sampling port of the dried test soil sample, and cut the soil sample near each sampling port into blocks for acid washing to determine the calcite content. When the strength of each part of the micro-cone penetration test is similar, and the final calcite content of each part is similar as determined by acid washing, it proves that the repair and solidification uniformity is good.

[0113] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A multi-field coupling model test monitoring device for evaluating the homogeneity of microbial mineralization, characterized in that, The test model box comprises a model box body for placing a test soil body, a sleeve surrounding the model box body, and a top cover covering the test soil body; the model box body is provided with water outlet holes around the periphery and forms a storage space between the model box body and the sleeve for storing excess slurry discharged through the water outlet holes; the test soil body is placed in the model box body in layers and is synchronously provided with a sampling system, a grouting system and a monitoring system; The grouting system comprises a grouting pump and a grouting pipe in communication with a grouting outlet of the grouting pump, the grouting pipe is inserted into the test soil body in the height direction, and the side wall is provided with grouting holes in the vertical direction for discharging slurry outward; the grouting system further comprises a silica gel hose and a soft and hard pipe joint connected in sequence to the outlet of the grouting pump, and the soft and hard pipe joint is further connected to the grouting pipe, wherein the grouting pipe is used for sending grouting slurry to the test soil body; The pressurizing system comprises a pressurizing head above the top cover and capable of moving up and down, the pressurizing head is configured to apply a preset pressure to the top cover; the pressurizing system further comprises a fixed frame and a hydraulic pump, the pressurizing head is arranged on the fixed frame and is provided with power for up and down movement by the hydraulic pump; The sampling system comprises a sampling pipe inserted into the test soil body from the bottom of the model box body; the sampling system further comprises a filter head, a one-way valve and a sampling connection hose, the filter head is arranged at one end of the sampling pipe inserted into the test soil body, and the sampling connection hose is connected to the other end of the sampling pipe and is further provided with a one-way valve; The monitoring system comprises a sensor assembly prearranged in the test soil body and used for monitoring multi-field data including stress and strain, pH, conductivity, ammonium ion concentration and pore water pressure; the sensor assembly comprises a distributed optical fiber sensor unit and an electronic sensor unit and adopts a layout of several columns arranged in the vertical direction and several circles arranged around the central axis; wherein the distributed optical fiber sensor unit comprises a stress and strain sensor, and the electronic sensor unit comprises a pH sensor, a conductivity sensor, an ammonium ion concentration sensor and a pore water pressure sensor; each sensor in the sensor assembly is further connected to an external computer unit through a lead wire extending out of the model box body. The inner wall and the bottom of the model box body are attached with filter paper; 2. The multi-field coupled model test monitoring device for evaluating the homogeneity of microbial mineralization according to claim 1, characterized in that, The model box body is in the shape of a cylinder; The top cover is provided with a top cover opening for the grouting pipe to extend into. The grouting pipe is attached with filter paper on the outside to prevent the test soil body components from entering the inside of the grouting pipe; 3. The multi-field coupled model test monitoring device for evaluating the homogeneity of microbial mineralization according to claim 1, characterized in that, The grouting holes of the side wall of the grouting pipe are equally spaced in three columns. The fixed frame comprises a support rod and a top plate, the support rod is fixedly connected to the outer wall of the sleeve, and the top plate is connected to the top of the support rod, and the pressurizing head is arranged on the top plate.

4. The multi-field coupled model test monitoring device for evaluating the homogeneity of microbial mineralization according to claim 1, characterized in that, The monitoring method comprises the following steps:

5. A multi-field coupled model test monitoring method for evaluating the homogeneity of microbial mineralization, based on the monitoring device according to any one of claims 1 to 4, characterized in that, S1, placing the test soil body in layers in the model box body by layer-wise compaction and synchronously arranging the sampling system, the grouting system and the monitoring system, and covering the top cover after filling the test soil body; S2, adjusting the pressurizing system to apply a preset pressure to the test soil body; S3, adjusting the grouting system to perform grouting operation at a preset grouting rate; ​ S4, after grouting, the test soil is sampled by the sampling system and the viable count and urea concentration are measured, and the stress-hydraulic-chemical-biological multi-field data monitored by the real-time recording monitoring system, including stress, strain, pH, conductivity, ammonium ion concentration, pore water pressure, are recorded; S5, repeat S3 and S4 until the test soil is solidified; S6, the test soil after being removed is dried, the miniature cone penetration test is carried out, the strength of the test soil is measured, the soil samples near each sampling port are cut and sampled, the calcite content is measured by acid washing method, and the test is ended.

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