A method for solidifying hydraulic fill based on MICP technology

Abstract

The application discloses a kind of sludge solidification fill method based on MICP technology, comprising: obtaining the water content of bottom mud, bottom mud density, bottom mud age and environmental type;Differentiated MICP slurry is prepared based on environmental type, and seawater type cementing fluid is composed of seawater, urea and CaCl2, and freshwater type cementing fluid is composed of deionized water, urea and CaCl2;After the bottom mud is dug and stirred and diluted, the pretreatment is carried out on the fill area to be filled according to the environmental type, and dispersing agent is added in seawater environment, and flocculating agent is added in freshwater environment;Bacteria liquid and cementing fluid are respectively transported to the diluted bottom mud by double channels and mixed;The solidified sludge is filled into the fill area to be filled immediately after mixing. The application realizes the targeted solidification treatment of seawater and freshwater scenes through the environment-adapted cementing fluid formula, differentiated pretreatment and double-channel delivery control.

Description

Technical Field

[0001] This invention relates to the field of soil reinforcement technology, and in particular to a silt solidification and backfilling method based on MICP technology. Background Technology

[0002] While existing sludge solidification technologies can enhance soil strength through microbial mineralization, they are mostly focused on single-environment applications and have not developed differentiated technical pathways suitable for dual-environment systems, resulting in unstable solidification effects in cross-media scenarios. When dealing with different environmental media, existing technologies cannot be customized for seawater and freshwater environments. The high salinity of seawater easily destroys the activity of the bacterial solution and hinders calcium carbonate deposition, while the lack of ion balance in freshwater environments reduces cementation efficiency, limiting the large-scale application of MICP technology in complex reclamation projects. Summary of the Invention

[0003] In view of this, the purpose of this invention is to propose a sludge solidification and backfilling method based on MICP technology, which solves the problems of existing technologies being unable to distinguish between different treatments for seawater and freshwater environments and poor solidification effect caused by single-channel mixing.

[0004] To achieve the aforementioned technical objectives, the technical solution adopted in this application is: a sludge solidification and backfilling method based on MICP technology, comprising:

[0005] Obtain in-situ sediment information, including sediment moisture content, sediment density, sediment age, and environmental type, which includes either seawater or freshwater.

[0006] MIP slurry is prepared based on in-situ sediment information. MIP slurry includes bacterial solution and cementing solution. Cementing solution includes seawater cementing solution and freshwater cementing solution. Seawater cementing solution is obtained by mixing seawater, urea and CaCl2. Freshwater cementing solution is obtained by mixing deionized water, urea and CaCl2.

[0007] Excavate the bottom mud and stir it. Dilute and adjust the stirred bottom mud according to the information of the bottom mud in situ.

[0008] Pretreatment is carried out on the area to be filled based on the in-situ sediment information. The pretreatment includes seawater pretreatment and freshwater pretreatment. Seawater pretreatment includes adding 0.1% dispersant to the area to be filled, and freshwater pretreatment includes adding 0.05% flocculant to the area to be filled.

[0009] The bacterial solution and cementing solution are transported to the diluted sediment in a dual-channel mode and mixed. The dual-channel mode includes a first channel and a second channel. The first channel is used to transport the bacterial solution and the second channel is used to transport the cementing solution. The initial flow rate ratio of the first channel to the second channel is 1:1.5.

[0010] While mixing, the sludge is immediately transported to the area to be filled for filling.

[0011] In some embodiments, the preparation process of the seawater-based cementitious solution includes:

[0012] A mixture of urea and CaCl2 in a first preset ratio is dissolved in seawater with a salinity of 30-35‰ to obtain a first initial cementing solution with a first preset concentration. The first preset concentration is configured as one of 1.5, 2, or 2.5, and the first preset ratio is a 1:1 molar ratio.

[0013] By adding 15% of a first preset concentration of CaCl2 to the first initial cementing solution, a seawater-type cementing solution is obtained.

[0014] In some embodiments, the preparation process of the freshwater-based binder includes:

[0015] A mixture of urea and CaCl2 in a second preset ratio is dissolved in deionized water with a conductivity ≤10μS / cm to obtain a freshwater-type cementitious solution with a second preset concentration. The second preset concentration is configured as either 1 or 1.5, and the second preset ratio is a 1:1 molar ratio.

[0016] In some embodiments, the process of excavating and stirring the bottom sediment, and then diluting and adjusting the stirred bottom sediment according to in-situ bottom sediment information includes:

[0017] The bottom mud was mechanically crushed according to preset mixing parameters, including mixing speed and duration. The mixing speed was 120 rpm and the duration was 15 min.

[0018] Based on the in-situ sediment information, a third preset ratio of silt to clean water is generated, and clean water is added according to the third preset ratio to dilute the sediment.

[0019] The third preset ratio is configured to be the water-cement ratio calculated based on the moisture content and sediment density, and then converted accordingly. The moisture content ranges from 45% to 65%, and the sediment density ranges from 1.4% to 1.7 g / cm³. 3 The water-cement ratio ranges from 0.8 to 1.2.

[0020] In some embodiments, the dispersant is a polycarboxylic acid-based substance; the flocculant is chitosan.

[0021] In some embodiments, the dual-channel delivery of bacterial solution and cementing solution to the diluted sediment and subsequent mixing further includes:

[0022] A vertical mixer is used for mixing;

[0023] When the environment type is seawater, extend the total mixing time by 30%;

[0024] When the environment is freshwater, the OD600 value is detected in real time using an online spectrometer during the mixing process, and the flow rate ratio of the first channel and the second channel is dynamically adjusted according to the OD600 value to ensure that the urease activity is ≥1.25ms / cm / min.

[0025] In some embodiments, the immediate delivery of sludge to the area to be filled for filling during mixing includes:

[0026] When the environment type is seawater, use 50-150m 3 A high-pressure plunger pump with a capacity of / h continuously blows the area to be filled, and controls the CaCO3 formation rate to be ≥1.8g / L·h;

[0027] When the environment is freshwater, the CaCO3 formation rate should be controlled to be ≥2.2 g / L·h.

[0028] In some embodiments, the sludge solidification and backfilling method further includes:

[0029] Before conveying the bacterial solution and cementing solution, use a high-pressure water gun with a pressure ≥0.8Mpa to flush the first channel, the second channel and the pipeline used for blotting.

[0030] Additionally, pulsed flushing at a frequency of 2Hz is performed at locations with bends in the first channel, the second channel, and the filling pipes.

[0031] The process of simultaneously mixing the sludge and immediately transporting it to the area to be filled also includes:

[0032] Every 2 hours of purging, a reverse flushing technique with a pressure pulsation range of 0.5-2.5 MPa is used to clean the pipe walls of the purging pipeline.

[0033] In some embodiments, the sludge solidification and backfilling method further includes:

[0034] After the reclamation is completed, a maintenance process is generated according to the environmental type and the reclamation area is maintained. The maintenance process includes the coastal area maintenance process and the inland river area maintenance process.

[0035] The coastal area maintenance process includes:

[0036] A 5-6cm thick layer of thin mud is used for surface curing, and a salt crystal protective layer is formed by seawater evaporation.

[0037] The maintenance process for inland waterways includes:

[0038] The water spraying rate is 2L / m 2 The system uses an automatic sprinkler system and shade netting for maintenance, and controls the temperature difference to ≤15℃.

[0039] In some embodiments, the sludge solidification and backfilling method further includes:

[0040] A three-dimensional quality control strategy is constructed, including front-end monitoring, process control, and terminal verification. Front-end monitoring is configured to monitor acidity and alkalinity using a pH sensor and calcium ion monitoring using a conductivity meter. Process control is configured to detect the uniformity of calcium carbonate distribution using an ultrasonic flaw detector. Terminal verification is configured to verify unconfined compressive strength. If the environment type is seawater, the threshold range for unconfined compressive strength verification is ≥1.5 MPa. If the environment type is freshwater, the threshold range for unconfined compressive strength verification is ≥1.8 MPa.

[0041] Unreacted urea solution is recovered, and the wastewater discharged after the urea solution is recovered is treated by a biological filter to meet a preset discharge threshold, which is configured as ammonia nitrogen content ≤15mg / L;

[0042] Furthermore, after the solidified body in the area to be filled is fully formed, mechanical property tests are conducted on the solidified body to ensure that the curing effect meets the preset requirements. The mechanical property tests include at least one of the following: unconfined compressive strength test and permeability coefficient measurement.

[0043] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0044] The above technical solution provides a sludge solidification and backfilling method based on MIP (Micro-Micro-Plasma Capacitor) technology, comprising: obtaining the sediment moisture content, sediment density, sediment age, and environmental type; preparing differentiated MIP slurries based on the environmental type, wherein the seawater-type slurry consists of seawater, urea, and CaCl2, and the freshwater-type slurry consists of deionized water, urea, and CaCl2; dredging and diluting the sediment, then pretreating the area to be backfilled according to the environmental type, adding a dispersant for seawater environments and a flocculant for freshwater environments; separately conveying the bacterial solution and slurry to the diluted sediment through dual channels for mixing; and immediately backfilling the solidified sludge into the area to be backfilled after mixing. This invention achieves targeted solidification treatment for seawater and freshwater scenarios through environmentally adapted slurry formulations, differentiated pretreatment, and dual-channel delivery control. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1This is a schematic diagram of steps S101 to S101 of the sludge solidification and backfilling method described in the specific embodiment;

[0047] Figure 2 This is an elevation view of the overall equipment layout as described in the specific implementation method;

[0048] Figure 3 This is a structural elevation view of the vertical mixer described in the specific implementation method;

[0049] Figure 4 This is a schematic diagram of the grab bucket boat grabbing silt in the river channel, as described in the specific implementation method;

[0050] Figure 5 This is a plan view of the silt soil that has not undergone MICP treatment as described in the specific implementation method;

[0051] Figure 6 This is a planar illustration of microorganisms adsorbed on silt after MICP treatment, as described in the specific implementation method.

[0052] Figure 7 This is a simplified flowchart of the implementation process of the sludge solidification and backfilling method described in the specific embodiments.

[0053] The attached figures are labeled as follows:

[0054] 1. Area to be filled;

[0055] 2. High-pressure pump delivery pipe;

[0056] 3. Mixer;

[0057] 4. First passage;

[0058] 5. Second channel;

[0059] 6. Mixer base;

[0060] 7. Mixer engine;

[0061] 8. Mixer blades;

[0062] 9. Grab boat;

[0063] 10. Grab bucket. Detailed Implementation

[0064] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] Please see Figures 1 to 6 This embodiment provides a sludge solidification and backfilling method based on MICP technology, including:

[0066] S101. Obtain in-situ sediment information, including sediment moisture content, sediment density, sediment age, and environmental type, including either seawater or freshwater.

[0067] S102. Prepare MIP slurry based on in-situ sediment information. MIP slurry includes bacterial solution and cementing solution. Cementing solution includes seawater cementing solution and freshwater cementing solution. Seawater cementing solution is obtained by mixing seawater, urea and CaCl2. Freshwater cementing solution is obtained by mixing deionized water, urea and CaCl2.

[0068] S103. Excavate the bottom mud and stir it. Dilute and adjust the stirred bottom mud according to the information of the bottom mud in situ.

[0069] S104. Based on the in-situ sediment information, pre-treatment shall be carried out on the area to be filled. The pre-treatment includes seawater pre-treatment and freshwater pre-treatment. Seawater pre-treatment includes adding 0.1% dispersant to the area to be filled, and freshwater pre-treatment includes adding 0.05% flocculant to the area to be filled.

[0070] S105. The bacterial solution and cementing solution are transported to the diluted sediment in a dual-channel mode and mixed. The dual-channel mode includes a first channel and a second channel. The first channel is used to transport the bacterial solution and the second channel is used to transport the cementing solution. The initial flow rate ratio of the first channel to the second channel is 1:1.5.

[0071] S106. While mixing, the sludge is immediately transported to the area to be filled for filling.

[0072] In step S101, to meet quality control requirements, in-situ sediment information is obtained through indoor tests before formal construction. Preferably, the sediment moisture content ranges from 45% to 65%, and the sediment density ranges from 1.4 to 1.7 g / cm³. 3 The amount of water used for subsequent sludge dilution is dynamically adjusted based on the test results, with the preferred water-cement ratio being 0.8-1.2.

[0073] In step S102, the bacterial solution is preferably Bacillus pasteurellii to solidify the silt. To improve the adsorption capacity of Bacillus pasteurellii in the silt and achieve a better cementing effect, calcium chloride solution is used as the fixative. The cementing solution preparation mode is selected according to the working environment, and the cementing solution concentration suitable for the target environment (equal proportion of urea and calcium chloride mixed solution, with fresh water and natural seawater as cementing solution solvents) is screened. According to the different ages of silt and the different urease activities of OD600 (the absorbance value of the solution at a wavelength of 600nm), as shown in Tables 1 and 2, unconfined compressive strength test, direct shear test and liquid limit test are conducted to screen the optimal group.

[0074] According to the test plan in Table 1, the corresponding age verification should be carried out, and the bearing capacity requirements of the dredged and filled foundation must be met.

[0075] Table 1 Test Scheme

[0076]

[0077] Table 2 Urease activity of bacterial cultures with different OD600 values

[0078]

[0079] In step S103, preferably, bottom mud is dredged at sea or in a river by a grab boat 9, and then mechanically crushed and diluted by a mud mixer 3.

[0080] In step S104, environmental adaptation pretreatment is performed on the area to be filled, based on the in-situ sediment information.

[0081] In step S105, a dual-channel delivery system is used to simultaneously inject bacterial solution and cementing solution, controlling the flow rate ratio of the first channel 4 and the second channel 5 to be 1:1.5. Preferably, the bacterial solution flow rate is 30 L / min and the cementing solution flow rate is 45 L / min. Micron-level dispersion (particle size ≤50 μm) is achieved by the stirrer blades 8.

[0082] In step S106, for the characteristics of fine-grained soil (particle size ≤ 0.075 mm accounting for > 60%), a vertical mixer 3 is used for strong mixing. The lower blade breaks up the clumps (shear force ≥ 200 N·m), and the upper blade improves the mixing uniformity (variance < 8%). In the seawater environment, the mixing time is increased by 30% (up to 25 min) to overcome the interference of salt ions.

[0083] For coarse-grained soils or mixed soils, the mixing intensity or time can be increased to ensure uniform particle dispersion. Depending on the saline environment, the dosage of CaCl2 can be adjusted to compensate for salt ion interference. Adding adjustable blades and speed-changing devices to the mixing equipment can improve its adaptability.

[0084] This embodiment achieves differentiated treatment by distinguishing between seawater and freshwater environments. The cementing solution is directly prepared using in-situ seawater, reducing freshwater resource consumption and chemical reagent costs. A dual-channel independent delivery system for the bacterial solution and cementing solution is employed, with flow rate control enabling precise regulation of the reaction process and avoiding material waste caused by premixing. Combined with environmentally adaptable pretreatment technology, dispersants are added to reduce salt interference in seawater environments, while flocculants are applied to enhance particle binding in freshwater environments, effectively improving the adsorption efficiency of the bacterial solution. A simultaneous mixing and backfilling operation mode utilizes the three-layer crushing and mixing function of a vertical mixer to achieve micron-level dispersion and uniform mixing in fine-grained soil scenarios, shortening the construction cycle. Simultaneously, the dilution water volume and cementing solution concentration are dynamically adjusted based on the characteristics of the in-situ sediment, and optimal mixing parameters are screened through indoor experiments to ensure the solidified sludge meets the required bearing capacity. This method achieves environmentally adaptable solidification while significantly reducing material costs and construction energy consumption through seawater resource utilization and process integration optimization.

[0085] In some embodiments, the preparation process of the seawater-based cementitious solution includes:

[0086] A mixture of urea and CaCl2 in a first preset ratio is dissolved in seawater with a salinity of 30-35‰ to obtain a first initial cementing solution with a first preset concentration. The first preset concentration is configured as one of 1.5, 2, or 2.5, and the first preset ratio is a 1:1 molar ratio.

[0087] By adding 15% of a first preset concentration of CaCl2 to the first initial cementing solution, a seawater-type cementing solution is obtained.

[0088] In this embodiment, urea and CaCl2 are directly dissolved in on-site seawater (salinity 30-35‰), with a mixing ratio (i.e., the first preset ratio) of 1:1 (molar ratio). The first preset concentration is preferably 2.0M, as detailed in Table 3. Na+ is compensated by increasing the amount of CaCl2 added to the first initial cementing solution by 15% of the first preset concentration. + The competitive adsorption effect.

[0089] Table 3 Technical Parameters for the Preparation of Seawater-Based Cementing Solution

[0090]

[0091]

[0092] This embodiment eliminates the need for seawater desalination by directly using a 1:1 molar ratio mixture of dissolved urea and CaCl2 in seawater on-site. Combined with an increase of 15% in the CaCl2 dosage to a pre-set concentration, it effectively compensates for the sodium content in the seawater. +The competitive effect on bacterial adsorption enhances the reaction efficiency of the cementing solution; the ratio is optimized based on gradient concentrations (1.5-2.5M) and OD600 adaptability values ​​(3.0-4.0) to ensure high urease activity bacterial solution (1.67-2.40 ms·cm). -1 ·min -1 In synergy with the cementing solution, a CaCO3 generation rate of ≥1.8 g / L·h is achieved under salinity conditions of 35‰, enhancing the solidification strength of silt. At the same time, natural seawater is used as a solvent to reduce freshwater transportation and treatment costs (saving 30-45%). The concentration is calibrated in real time by conductivity method and the sodium ion compensation is precisely controlled by XRF elemental analysis, forming a low-cost, highly adaptable seawater cementing solution preparation technology that meets the engineering requirements of MICP solidification processes in complex marine environments.

[0093] In some embodiments, the preparation process of the freshwater-based binder includes:

[0094] A mixture of urea and CaCl2 in a second preset ratio is dissolved in deionized water with a conductivity ≤10μS / cm to obtain a freshwater-type cementitious solution with a second preset concentration. The second preset concentration is configured as either 1 or 1.5, and the second preset ratio is a 1:1 molar ratio.

[0095] In this embodiment, a 1.0-1.5M cementing solution was prepared using deionized water, as detailed in Table 4. The OD600 value was monitored in real time using an online spectrometer (controlled range 1.5-3.0), and the bacterial activity was dynamically adjusted until the urease activity was ≥1.25 ms / cm / min.

[0096] Table 4 Technical Parameters for the Preparation of Freshwater-Based Cementing Solution

[0097]

[0098]

[0099] This embodiment uses deionized water to dissolve a 1:1 molar mixture of urea and CaCl2 to prepare a 1.0-1.5M freshwater-type cementing solution. The concentration is calibrated in real-time using conductivity to avoid impurities interfering with the reaction process and improve the stability of the cementing solution. Combined with online spectrometer dynamic monitoring of OD600 values, PID feedback control is used to precisely adjust the bacterial activity, ensuring urease activity ≥1.25 ms / cm / min and promoting CaCO3 generation rate ≥2.2 g / L·h (under 0‰ salinity conditions), significantly improving the sludge solidification efficiency in freshwater environments. The bacterial activity is maintained by adding 0.1% dextran as a protectant, and the CFU counting method is used to verify microbial survival rate, extending the effective duration of the cementation reaction. Simultaneously, ammonia nitrogen emissions are strictly controlled to ≤20 mg / L (compliant with GB8978 standards), and a rapid water quality testing kit is used to monitor environmental indicators in real-time, balancing engineering efficiency and environmental compatibility. This scheme achieves high efficiency, stability, and greening of the MIP solidification process in freshwater scenarios through concentration gradient optimization, dynamic activity control, and environmental constraints.

[0100] In some embodiments, the process of excavating and stirring the bottom sediment, and then diluting and adjusting the stirred bottom sediment according to in-situ bottom sediment information includes:

[0101] The bottom mud was mechanically crushed according to preset mixing parameters, including mixing speed and duration. The mixing speed was 120 rpm and the duration was 15 min.

[0102] Based on the in-situ sediment information, a third preset ratio of silt to clean water is generated, and clean water is added according to the third preset ratio to dilute the sediment.

[0103] The third preset ratio is configured to be the water-cement ratio calculated based on the moisture content and sediment density, and then converted accordingly. The moisture content ranges from 45% to 65%, and the sediment density ranges from 1.4% to 1.7 g / cm³. 3 The water-cement ratio ranges from 0.8 to 1.2.

[0104] In this embodiment, mechanical crushing and dilution are performed by a mud mixer 3. The mechanical crushing is set with a stirring speed of 120 rpm and a duration of 15 min. The dilution is performed by adding 20-30% clean water according to the detection value in step S101.

[0105] The moisture content ranges from 45% to 65%. Remediation measures for excessively high moisture content (>65%) include adding dry soil, using a mechanical dewatering system, or increasing the amount of coagulant added. Remediation measures for excessively low moisture content (<45%) include adding an appropriate amount of clean water or increasing the amount of dilution water.

[0106] The density of the bottom sediment ranges from 1.4 to 1.7 g / cm³. 3 The bottom mud density is too high (>1.7g / cm³).3 Treatment measures include adding dispersants or diluting the sludge; the bottom sediment density is too low (<1.4 g / cm³). 3 Treatment measures include increasing the proportion of dry solids or improving uniformity through mixing.

[0107] Based on the moisture content and sediment density test results, the water-cement ratio during hydraulic filling is adjusted to a range of 0.8-1.2. The specific calculation method is as follows:

[0108] Moisture content ranges from 45% to 65%, and sediment density ranges from 1.4 to 1.7 g / cm³. 3 At this stage, the water-cement ratio is usually set at 1:1. If the moisture content or sediment density exceeds the range, the water-cement ratio should be adjusted according to the following formula:

[0109] Water-cement ratio = Dilution water volume / Dry solids volume

[0110] When the moisture content is 55% and the bottom sediment density is 1.5 g / cm³ 3 At this time, the water-cement ratio can be adjusted to 0.9:1 to ensure the smoothness of the blow-filling process and the achievement of the curing effect.

[0111] By adjusting the moisture content and density to the target range, and dynamically adjusting the water-cement ratio based on test results, the smooth progress of the hydraulic filling construction and the achievement of the required curing effect can be ensured. If the indicators cannot be adjusted to the target range, further measures (such as changing the construction area or adjusting the construction method) are required to ensure the quality of the project.

[0112] This embodiment mechanically crushes the bottom mud using preset mixing parameters to ensure uniform dispersion of mud particles and improve subsequent dilution and solidification reaction conditions. Based on in-situ bottom mud moisture content and density test data, the water-cement ratio is dynamically calculated and clean water is added for dilution and mixing to balance the fluidity and solidification strength requirements of the hydraulic filling construction. For abnormal moisture content or density conditions, treatment measures such as adding dry soil, dispersant, or adjusting the dilution water volume are adopted to ensure that the indicators return to the target range. The proportion is precisely controlled by adjusting the water-cement ratio formula, combined with auxiliary means such as mechanical dewatering system and coagulant addition, to ensure the uniformity and stability of sludge dilution and avoid construction interruption due to excessively high moisture content or low density. Ultimately, the smoothness of the hydraulic filling process and the standard rate of solidification effect are improved simultaneously, providing a suitable bottom mud matrix for the subsequent MIP process.

[0113] In some embodiments, the dispersant is a polycarboxylic acid-based substance; the flocculant is chitosan.

[0114] In this embodiment, the polycarboxylate dispersant and chitosan flocculant work synergistically. The polycarboxylate dispersant enhances the particle dispersion stability through electrostatic repulsion, while the chitosan flocculant promotes floc formation through molecular chain bridging effect. The combination of the two improves the solid-liquid separation efficiency while maintaining environmental friendliness.

[0115] In some embodiments, the dual-channel delivery of bacterial solution and cementing solution to the diluted sediment and subsequent mixing further includes:

[0116] A vertical mixer is used for mixing;

[0117] When the environment type is seawater, extend the total mixing time by 30%;

[0118] When the environment is freshwater, the OD600 value is detected in real time using an online spectrometer during the mixing process, and the flow rate ratio of the first channel and the second channel is dynamically adjusted according to the OD600 value to ensure that the urease activity is ≥1.25ms / cm / min.

[0119] In this embodiment, a vertical mixer 3 is used for mixing in order to break up the sludge lumps and improve the uniformity of the sludge. After mixing until relatively uniform, bacterial solution and cementing solution are added according to the optimal ratio selected in the above experiment and the sludge volume in the vertical mixer 3 is calculated, and mechanical mixing continues.

[0120] This embodiment uses a vertical mixer 3 to break up sludge lumps and improve uniformity, ensuring sufficient contact between the bacterial solution and the cementing solution. For seawater environments, the total mixing time is extended by 30% to compensate for the inhibition of reaction rate by high salinity. In freshwater environments, the OD600 value is monitored in real time using an online spectrometer, and the flow rate ratio of the two channels is dynamically adjusted to ensure that urease activity is stable at ≥1.25 ms / cm / min, optimizing the efficiency of microbial-induced carbonate precipitation. Based on the optimal ratio, the bacterial solution and cementing solution are precisely added, combined with mechanical stirring to enhance the homogeneity of the mixture, ultimately achieving reliable and controllable sludge solidification effects under different environmental conditions.

[0121] In some embodiments, the immediate delivery of sludge to the area to be filled for filling during mixing includes:

[0122] When the environment type is seawater, use 50-150m 3 A high-pressure plunger pump with a capacity of / h continuously blows the area to be filled, and controls the CaCO3 formation rate to be ≥1.8g / L·h;

[0123] When the environment is freshwater, the CaCO3 formation rate should be controlled to be ≥2.2 g / L·h.

[0124] In this embodiment, when the environment type is seawater, a 2.0M cementing liquid (see Table 3) is used, and the cementing process is carried out through 50-150m... 3The high-pressure plunger pump continuously blows and fills the soil, controlling the CaCO3 generation rate to be ≥1.8 g / L·h; when the environment is freshwater, the OD600 value is dynamically adjusted (1.5-3.0), and the cementing solution concentration is matched in real time (1.0-1.5M) to ensure that the CaCO3 generation rate is ≥2.2 g / L·h (see Table 4).

[0125] This embodiment uses a 50-150m depth for marine environments. 3 A high-pressure plunger pump continuously blows and fixes the 2.0M cementitious liquid concentration to ensure a CaCO3 generation rate ≥1.8g / L·h, overcoming the limitation of high salinity on reaction efficiency. For freshwater environments, the OD600 value is dynamically adjusted in real time to match the cementitious liquid concentration, precisely increasing the CaCO3 generation rate to ≥2.2g / L·h to meet the microbial activity requirements under low salinity. In both environments, blowing and mixing are carried out simultaneously, combined with concentration control and rate control, to ensure carbonate precipitation efficiency and blowing continuity under different salinity conditions, and to enhance the sludge solidification effect and construction stability.

[0126] In some embodiments, the sludge solidification and backfilling method further includes:

[0127] Before conveying the bacterial solution and cementing solution, use a high-pressure water gun with a pressure ≥0.8Mpa to flush the first channel, the second channel and the pipeline used for blotting.

[0128] Additionally, pulsed flushing at a frequency of 2Hz is performed at locations with bends in the first channel, the second channel, and the filling pipes.

[0129] The process of simultaneously mixing the sludge and immediately transporting it to the area to be filled also includes:

[0130] Every 2 hours of purging, a reverse flushing technique with a pressure pulsation range of 0.5-2.5 MPa is used to clean the pipe walls of the purging pipeline.

[0131] In this embodiment, the bend joint is specifically subjected to pulsed flushing at a frequency of 2Hz to ensure no residue blockage. Every 2 hours of purging, a reverse flushing technique with a pressure pulsation range of 0.5-2.5MPa is used to clean the pipe wall and prevent blockage.

[0132] To ensure continuous operation of the solidified soil construction, based on engineering experience and construction efficiency, a certain number of mud pits and water storage tanks are excavated after site leveling. The mud pits are used for sludge solidification, while the water storage tanks are used for post-construction pipeline cleaning to prevent pipe blockage after the solidified sludge has hardened. The mud pits and water storage tanks are key components in the sludge solidification project of the excavated bank foundation. A dedicated solidification slurry mixer 3, preferably a vertical mixer 3, is used to thoroughly mix the mud and solidifying agent until homogeneous. Then, a high-pressure plunger pump is used to pump the solidified slurry to the area to be filled 1. An integrated in-situ solidification-filling process, i.e., a "treatment and filling simultaneously" mode, is adopted. The sludge pretreated with MIP is directly transported to the area to be filled 1 through a high-pressure pump delivery pipe 2, achieving simultaneous solidification reaction and filling operations. Compared to the traditional step-by-step process of solidification followed by filling, this effectively shortens the construction period. A combined operation system of the vertical mud mixer 3 and the grab boat 9 is used to complete the continuous processes of sludge loading, mixing, bacterial solution injection, and high-pressure filling within the river channel.

[0133] This embodiment thoroughly removes residues from the first channel 4, the second channel 5, and the dredging pipeline using high-pressure water jets to prevent blockages. Every two hours of dredging, a 0.5-2.5 MPa pressure pulsating reverse flushing technique is used to clean the pipe walls, ensuring continuous operation efficiency. Mud pits and water storage tanks are excavated for sludge solidification and post-construction pipeline cleaning, respectively, preventing solidified soil from causing blockages. A vertical mixer 3 and a high-pressure plunger pump are used in conjunction with an in-situ solidification-dredging integrated process, enabling simultaneous mixing, bacterial solution injection, and high-pressure dredging, significantly shortening the construction period compared to traditional step-by-step processes. The vertical mud mixer 3 and grab boat 9 work together to complete the loading, processing, and dredging processes continuously within the river channel, improving construction efficiency and process continuity, and ensuring coordinated progress of the solidification reaction and dredging operations.

[0134] In some embodiments, the sludge solidification and backfilling method further includes:

[0135] After the reclamation is completed, a maintenance process is generated according to the environmental type and the reclamation area is maintained. The maintenance process includes the coastal area maintenance process and the inland river area maintenance process.

[0136] The coastal area maintenance process includes:

[0137] A 5-6cm thick layer of thin mud is used for surface curing, and a salt crystal protective layer is formed by seawater evaporation.

[0138] The maintenance process for inland waterways includes:

[0139] The water spraying rate is 2L / m 2 The system uses an automatic sprinkler system and shade netting for maintenance, and controls the temperature difference to ≤15℃.

[0140] In this embodiment, a maintenance plan was selected according to the environmental type, and the maintenance effect was verified. After 7 days, the surface crack width was ≤0.2mm, and the strength development coefficient reached 0.85-0.92 after 28 days.

[0141] The main methods for curing solidified soil include water spraying and surface mud curing. Water spraying is economical, convenient, and effective, making it the most common curing method during construction. Surface mud curing involves covering the surface of the solidified soil with a 5-6cm layer of mud after pouring. This prevents direct sunlight from reaching the solidified soil and avoids cracking due to excessive temperature differences. Because the surface mud is in direct contact with sunlight, it will crack after drying, allowing the underlying solidified soil to evaporate moisture and dehydrate and solidify through these cracks. Compared to water spraying, surface mud curing has the advantages of lower curing frequency and better curing effect.

[0142] It is important to note that the "Inland River Environment" project area is located in the silt consolidation and reclamation of inland rivers, lake shores, and shallow water areas, while the "Coastal Area" project area is located near the ocean or saline lakes. Inland river areas have lower salinity, approaching freshwater (approximately 0‰), and the river flow is relatively slow, influenced by monsoons or rainfall. Coastal areas have higher salinity, typically 30-35‰, and are affected by tides and waves, resulting in complex and powerful currents. The tidal cycle can lead to significant salt erosion. These different scenarios require different maintenance methods; therefore, the specific method of using water spraying or surface sludge treatment must be determined based on the specific circumstances.

[0143] This embodiment addresses the environmental differences between coastal and inland river areas by employing differentiated maintenance processes: surface mud covering and automatic sprinkler systems combined with shade netting. In coastal areas, a 5-6cm layer of surface mud can be used to create a salt crystallization protective layer through seawater evaporation, reducing the impact of salt erosion. In inland river areas, a water spraying rate of 2L / m² can be used. 2 The automatic sprinkler system and shade netting cover mode control the temperature difference to ≤15℃, preventing temperature-induced cracking. Two curing methods are available to suit the needs of high-salinity tidal environments and low-salinity, slow-flowing freshwater environments, balancing curing efficiency and effectiveness. Surface mud curing promotes dehydration and solidification through the evaporation of lower-layer water vapor, reducing curing frequency; water spraying is economical and convenient, and combined with shade netting, further inhibits cracking, achieving a dual improvement in environmentally adaptable curing and solidification quality.

[0144] In some embodiments, the sludge solidification and backfilling method further includes:

[0145] A three-dimensional quality control strategy is constructed, including front-end monitoring, process control, and terminal verification. Front-end monitoring is configured to monitor acidity and alkalinity using a pH sensor and calcium ion monitoring using a conductivity meter. Process control is configured to detect the uniformity of calcium carbonate distribution using an ultrasonic flaw detector. Terminal verification is configured to verify unconfined compressive strength. If the environment type is seawater, the threshold range for unconfined compressive strength verification is ≥1.5 MPa. If the environment type is freshwater, the threshold range for unconfined compressive strength verification is ≥1.8 MPa.

[0146] Unreacted urea solution is recovered, and the wastewater discharged after the urea solution is recovered is treated by a biological filter to meet a preset discharge threshold, which is configured as ammonia nitrogen content ≤15mg / L;

[0147] Furthermore, after the solidified body in the area to be filled is fully formed, mechanical property tests are conducted on the solidified body to ensure that the curing effect meets the preset requirements. The mechanical property tests include at least one of the following: unconfined compressive strength test and permeability coefficient measurement.

[0148] In this embodiment, a three-dimensional quality control system is established to monitor the curing effect, including front-end monitoring, process control, and end-stage verification. Front-end monitoring is achieved through a pH sensor (controlling the pH range to 8.5-9.2) and a conductivity meter (reflecting Ca2+). 2 The process involves adjusting the concentration of calcium carbonate (C) during solidification; process control is achieved by using an ultrasonic flaw detector to check the uniformity of calcium carbonate distribution; final verification is performed using unconfined compressive strength testing, with a 28-day unconfined compressive strength ≥1.5 MPa in seawater and ≥1.8 MPa in freshwater. The solidification process is monitored in real-time to ensure the solidification effect meets the expected standards. The amount and frequency of nutrient injection are adjusted as needed to optimize the solidification effect.

[0149] The final stage requires an environmentally friendly disposal process, including the recovery of unreacted urea solution (recovery rate > 75%), and the treatment of effluent through a biological filter bed to ensure that the ammonia nitrogen content is ≤ 15 mg / L (compliant with GB 8978 standard).

[0150] After the cured body in the area to be filled, mechanical property tests (such as unconfined compressive strength test, permeability coefficient measurement, etc.) are performed to ensure that the curing effect meets the design requirements. The dual-mode performance is verified through comparative tests, as detailed in Table 5:

[0151] Table 5 Comparative test verification of dual-mode performance

[0152] 28-day UCS (MPa) 1.8±0.2 2.1±0.3 Permeability coefficient (cm / s) <![CDATA[5×10 -6 ]]> <![CDATA[3×10 -6 ]]> Chloride ion erosion rate ≤0.15% / year ≤0.08% / year

[0153] The "Technical Specification for Reclaimed Land Foundation Treatment" (GB / T 50943-2015) specifies the strength requirements for different engineering applications. Generally, the UCS requirement for reclaimed land foundations may be between 0.8 and 1.5 MPa, depending on the application scenario. The 28-day UCS in this patent is 1.8 MPa for seawater type and 2.1 MPa for freshwater type, both exceeding the common minimum standards, indicating that the requirements are met. Specific data are detailed in Table 6.

[0154] Table 6 compares the results with the "Technical Specification for Treatment of Hydraulic Reclamation Foundations" (GB / T 50943-2015).

[0155] temporary cofferdam ≥0.8MPa Seawater type 1.8 (exceeds the standard by 125%) Road base course ≥1.2MPa Freshwater type 2.1 (exceeding the standard by 75%) Building foundation (Level II) ≥1.5MPa Both modes meet the standards

[0156] This embodiment achieves precise control throughout the entire process by constructing a three-dimensional quality control strategy encompassing front-end monitoring, process regulation, and terminal verification. Front-end monitoring utilizes a pH sensor to control the pH range of 8.5-9.2, and a conductivity meter to track calcium levels in real time. 2 +Concentration; Process control involves using an ultrasonic flaw detector to detect the uniformity of calcium carbonate distribution and dynamically optimizing nutrient solution injection parameters; Terminal verification uses unconfined compressive strength as the core indicator, with 28-day strength ≥1.5MPa in seawater (actually reaching 1.8±0.2MPa) and ≥1.8MPa in freshwater (actually reaching 2.1±0.3MPa), and permeability coefficients as low as 5×10⁻⁶. -6 cm / s and 3×10 -6 The pressure (cm / s) significantly exceeded the minimum requirements of the "Technical Specification for Reclaimed Land Foundation Treatment" (e.g., temporary cofferdams ≥0.8MPa, exceeding the standard by 125%). Simultaneously, environmentally friendly disposal procedures were implemented, recovering unreacted urea solution (recovery rate >75%). After treatment by a biological filter bed, the ammonia nitrogen content in the discharged wastewater was ≤15mg / L, balancing engineering and ecological needs. After solidification, the mechanical properties were verified through unconfined compressive strength testing and permeability coefficient measurement to ensure compliance with strength standards for temporary cofferdams, road base courses, and building foundations, achieving a comprehensive improvement in strength, impermeability, and environmental adaptability.

[0157] Please see Figure 7 Furthermore, the following examples can be derived from the above technical solutions:

[0158] A silt solidification and backfilling method based on microbial induced calcium carbonate precipitation (MICP) technology includes the following steps: dredging silt from the riverbed and monitoring the moisture content and density of the undisturbed silt; developing experimental groups based on silt properties, selecting the optimal group, and preparing MIP slurry; mixing the microbial inoculum, cementing solution, and silt using a vertical mixer; inserting a slurry pump (i.e., a high-pressure plunger pump) at the bottom of the vertical mixer to backfill the target area; curing the solidified soil after backfilling the target area; and finalizing and testing the solidification effect to ensure that the desired effect is achieved.

[0159] Please see Figures 2 to 4 The grouting equipment used in the above method mainly includes a grab boat 9, a high-pressure plunger pump, a curing agent additive, and a mixer 3. The grab boat 9 uses grab buckets 10 to collect silt from the sea or river. The 50-150 m3 / h high-pressure plunger pump is used to transport the slurry treated by the MIP method and to pump the slurry treated by the MIP method to the area to be filled 1. The curing agent additive mainly consists of a powder silo and a powder metering pump. The curing agent additive is used to control the addition of bacterial solution, cementing solution, and curing agent. The mixer 3 includes a mixer base 6, a mixer engine 7, and mixer blades 8. A vertical mixer 3 is used for mixing to break up silt blocks and improve the uniformity of the silt. After mixing to a relatively uniform consistency, bacterial solution and cementing solution are added according to the optimal ratio selected by the above experiment and the silt volume in the vertical mixer 3 is calculated, and mechanical mixing continues.

[0160] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0161] This invention provides a silt solidification and backfilling method based on MICP technology. It achieves differentiated environmental adaptation through a dual-mode seawater / freshwater cementing system, significantly reducing construction costs and improving efficiency. For seawater environments, the cementing solution is prepared directly using in-situ seawater, eliminating the desalination process and saving 30-45% on freshwater transportation costs. Simultaneously, by increasing the CaCl2 dosage by 15%, the sodium ion competition effect is compensated, ensuring a CaCO3 generation rate ≥1.8 g / L·h. For freshwater environments, deionized water is used to dynamically control the cementing solution concentration, combined with real-time optimization of bacterial activity using an online spectrometer, reducing the amount of bacterial solution used and increasing the CaCO3 generation rate to ≥2.2 g / L·h. Through a simultaneous mixing and backfilling operation mode, a vertical mixer for layered crushing and a high-pressure plunger pump for continuous delivery are combined to achieve simultaneous solidification reaction and backfilling construction. Compared to traditional pre-curing processes, this shortens the construction period by 40% and reduces production costs. The synergistic effect of dual-channel flow rate control and mechanical stirring for micron-level dispersion promotes the uniform crystallization of calcium carbonate, filling soil pores, increasing strength, and reducing the permeability coefficient. By combining three-dimensional quality control strategies with environmentally friendly disposal procedures, the project can ensure that the strength of temporary cofferdams, road base layers, and other engineering structures meets the standards, while achieving efficient resource utilization and a significant reduction in construction energy consumption.

[0162] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0163] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the methods of various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0164] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A sludge solidification and backfilling method based on MICP technology, characterized in that, include: Obtain in-situ sediment information, which includes sediment moisture content, sediment density, sediment age, and environmental type, wherein the environmental type includes either seawater or freshwater. Based on the in-situ sediment information, a MICP slurry is prepared. The MICP slurry includes a bacterial solution and a cementing solution. The cementing solution includes a seawater-based cementing solution and a freshwater cementing solution. The seawater-based cementing solution is prepared by mixing seawater, urea, and... The freshwater-based cementitious solution is obtained by mixing deionized water, urea, and... Obtained by mixing; Excavate the bottom mud and stir it. Dilute and adjust the stirred bottom mud according to the in-situ bottom mud information. The pretreatment of the area to be filled is carried out based on the in-situ sediment information. The pretreatment includes seawater pretreatment and freshwater pretreatment. The seawater pretreatment includes adding 0.1% dispersant to the area to be filled, and the freshwater pretreatment includes adding 0.05% flocculant to the area to be filled. The bacterial solution and the cementing solution are delivered to the diluted sediment in a dual-channel mode and mixed. The dual-channel mode includes a first channel and a second channel. The first channel is used to deliver the bacterial solution and the second channel is used to deliver the cementing solution. The initial flow rate ratio of the first channel to the second channel is 1:1.

5. While mixing, the sludge is immediately transported to the area to be filled for filling. The dual-channel method for delivering bacterial solution and cementing solution to the diluted sediment and mixing them also includes: A vertical mixer is used for mixing; When the environment type is seawater, extend the total mixing time by 30%; When the environment is freshwater, the OD600 value is detected in real time using an online spectrometer during the mixing process, and the flow rate ratio of the first channel and the second channel is dynamically adjusted according to the OD600 value to ensure that the urease activity is ≥1.25ms / cm / min. Simultaneously with mixing, the sludge is immediately transported to the area to be filled for filling, including: When the environment is seawater, a high-pressure plunger pump with a capacity of 50-150 m³ / h is used to continuously purge the area to be purged, and the CaCO3 generation rate is controlled to be ≥1.8 g / L·h. When the environment is freshwater, the CaCO3 formation rate should be controlled to be ≥2.2 g / L·h.

2. The sludge solidification and backfilling method based on MICP technology according to claim 1, characterized in that, The preparation process of the seawater-based cementitious solution includes: Select seawater with a salinity of 30-35‰ and dissolve urea in a first preset ratio. The mixture is used to obtain a first initial cementing solution with a first preset concentration, wherein the first preset concentration is configured as one of 1.5M, 2M, and 2.5M, and the first preset ratio is a 1:1 molar ratio. Add 15% of the first preset concentration to the first initial cementing solution. The dosage was adjusted to obtain the seawater-type cementitious solution.

3. The sludge solidification and backfilling method based on MICP technology according to claim 1, characterized in that, The preparation process of the freshwater-based cementitious solution includes: Select conductivity The second preset ratio of urea dissolved in deionized water The mixture is used to obtain a freshwater-based cementitious solution with a second preset concentration, wherein the second preset concentration is configured as either 1M or 1.5M, and the second preset ratio is a 1:1 molar ratio.

4. The sludge solidification and backfilling method based on MICP technology according to claim 1, characterized in that, The process of excavating and stirring the bottom sediment, and then diluting and adjusting the stirred bottom sediment according to the in-situ bottom sediment information includes: The bottom mud is mechanically crushed according to preset mixing parameters, including mixing speed and duration. The mixing speed is 120 rpm and the duration is 15 min. A third preset ratio of silt to clean water is generated based on the in-situ sediment information, and clean water is added according to the third preset ratio to dilute the sediment. The third preset ratio is configured to calculate the water-cement ratio by measuring the moisture content and sediment density, and then convert it according to the water-cement ratio. The moisture content ranges from 45% to 65%, the sediment density ranges from 1.4 to 1.7 g / cm³, and the water-cement ratio ranges from 0.8 to 1.

2.

5. The sludge solidification and backfilling method based on MICP technology according to claim 1, characterized in that, The dispersant is a polycarboxylic acid-based substance; the flocculant is chitosan.

6. The sludge solidification and backfilling method based on MICP technology according to claim 1, characterized in that, The method further includes: Before conveying the bacterial solution and cementing solution, use a high-pressure water gun with a pressure ≥0.8Mpa to flush the first channel, the second channel and the pipeline used for blotting. Additionally, pulsed flushing at a frequency of 2Hz is performed at locations with bends in the first channel, the second channel, and the filling pipes. The process of simultaneously mixing the sludge and immediately transporting it to the area to be filled also includes: Every 2 hours of purging, a reverse flushing technique with a pressure pulsation range of 0.5-2.5 MPa is used to clean the pipe walls of the purging pipeline.

7. The sludge solidification and backfilling method based on MICP technology according to claim 1, characterized in that, The method further includes: After the reclamation is completed, a maintenance process is generated according to the environmental type and the reclamation area is maintained. The maintenance process includes a coastal area maintenance process and an inland river area maintenance process. The coastal area maintenance process includes: A 5-6cm thick layer of thin mud is used for surface curing, and a salt crystal protective layer is formed by seawater evaporation. The inland waterway maintenance process includes: The maintenance was carried out using an automatic sprinkler system with a water spray rate of 2L / m²·h and a shade net covering mode, and the temperature difference was controlled to be ≤15℃.

8. The sludge solidification and backfilling method based on MICP technology according to claim 1, characterized in that, The method further includes: A three-dimensional quality control strategy is constructed, including front-end monitoring, process control, and terminal verification. The front-end monitoring is configured to monitor acidity and alkalinity using a pH sensor and to monitor calcium ions using a conductivity meter. The process control is configured to detect the uniformity of calcium carbonate distribution using an ultrasonic flaw detector. The terminal verification is configured to verify unconfined compressive strength. If the environment type is seawater, the threshold range for the unconfined compressive strength verification is ≥1.5 MPa. If the environment type is freshwater, the threshold range for the unconfined compressive strength verification is ≥1.8 MPa. Unreacted urea solution is recovered, and the wastewater discharged after the urea solution recovery is treated by a biological filter to meet a preset discharge threshold, which is configured as ammonia nitrogen content ≤15mg / L.

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