MICP technology-based sludge solidification and hydraulic reclamation method

Abstract

The invention discloses a sludge solidification and hydraulic reclamation method based on an MICP technology. The method comprises the steps that the water content of bottom mud, the density of the bottom mud, the age of the bottom mud and the environment type are obtained; differentiated MICP serous fluid is prepared based on environment types, a seawater type cementing fluid is composed of seawater, urea and CaCl2, and a fresh water type cementing fluid is composed of deionized water, urea and CaCl2; after bottom mud is dug and stirred and diluted, a to-be-dredger-filled area is pretreated according to the environment type, a dispersing agent is added into the seawater environment, and a flocculating agent is added into the fresh water environment; respectively conveying a bacterial liquid and a cementing liquid into the diluted bottom mud through two channels, and mixing the bacterial liquid and the cementing liquid; and after mixing, the solidified sludge is immediately blown and filled to the area to be blown and filled. According to the invention, targeted curing treatment of seawater and fresh water scenes is realized through an environment-adaptive cementing liquid formula, differential pretreatment and dual-channel conveying control.

Description

Technical Field

[0001] The present invention relates to the technical field of soil reinforcement, and particularly to a method for solidifying and reclamation of silt based on MICP technology. Background Art

[0002] Although the existing silt solidification technology can improve the soil strength through microbial mineralization, it mostly focuses on single - environment applications and does not construct a differential technical path suitable for a dual - environment system, resulting in unstable solidification effects in cross - medium scenarios. When dealing with different environmental media, the existing technology cannot be differentially customized for the two environments of seawater and fresh water. The high salinity in the seawater environment easily destroys the activity of the bacterial solution and hinders calcium carbonate deposition, while the fresh - water environment has a reduced cementation efficiency due to the lack of ionic balance, which limits the large - scale application of MICP technology in complex reclamation projects. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to propose a method for solidifying and reclamation of silt based on MICP technology, which solves the problems that the existing technology cannot distinguish between seawater and fresh - water environments for differential treatment and single - channel mixing leads to poor solidification effects.

[0004] In order to achieve the above technical purpose, the technical solution adopted in this application is as follows: A method for solidifying and reclamation of silt based on MICP technology, comprising:

[0005] Obtaining in - situ sediment information, the in - situ sediment information includes sediment moisture content, sediment density, sediment age, and environmental type, and the environmental type includes one of seawater and fresh water;

[0006] Preparing an MICP slurry according to the in - situ sediment information, the MICP slurry includes a bacterial solution and a cementing liquid, the cementing liquid includes a seawater - type cementing liquid and a fresh - water - type cementing liquid, the seawater - type cementing liquid is obtained by mixing seawater, urea, and CaCl2, and the fresh - water - type cementing liquid is obtained by mixing deionized water, urea, and CaCl2;

[0007] Digging out the sediment and stirring the sediment, and diluting and adjusting the stirred sediment according to the in - situ sediment information;

[0008] Performing pretreatment on the area to be reclaimed according to the in - situ sediment information, the pretreatment includes seawater pretreatment and fresh - water pretreatment, the seawater pretreatment includes adding 0.1% dispersant to the area to be reclaimed, and the fresh - water pretreatment includes adding 0.05% flocculant to the area to be reclaimed;

[0009] Transporting the bacterial solution and the cementing liquid to the diluted sediment in a dual - channel mode and mixing them, the dual - channel mode includes a first channel and a second channel, the first channel is used to transport the bacterial solution, the second channel is used to transport the cementing liquid, and the initial flow velocity 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 and filled by blowing.

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

[0012] Select seawater with a salinity of 30-35‰ to dissolve a first preset proportion of the urea and CaCl2 mixture to obtain a first initial cementing liquid with a first preset concentration, and the first preset concentration is configured as one of 1.5, 2, and 2.5, and the first preset proportion is 1:1 molar ratio;

[0013] Increase the dosage of CaCl2 at 15% of the first preset concentration in the first initial cementing liquid to obtain the seawater-based cementing liquid.

[0014] In some embodiments, the preparation process of the fresh water-based cementing liquid includes:

[0015] Select deionized water with a conductivity ≤ 10 μS / cm to dissolve a second preset proportion of the urea and CaCl2 mixture to obtain a fresh water-based cementing liquid with a second preset concentration, and the second preset concentration is configured as one of 1 and 1.5, and the second preset proportion is 1:1 molar ratio.

[0016] In some embodiments, the bottom mud is dug and stirred, and the dilution and preparation of the stirred bottom mud according to the in-situ bottom mud information includes:

[0017] Mechanically crush the bottom mud according to preset stirring parameters, and the preset stirring parameters include stirring speed and duration. The stirring speed is 120 rpm and the duration is 15 min;

[0018] Generate a third preset proportion of sludge and clear water according to the in-situ bottom mud information, and add clear water according to the third preset proportion to dilute the bottom mud;

[0019] The third preset proportion is configured to obtain the water-cement ratio by calculating the water content and the bottom mud density, and is obtained by conversion according to the water-cement ratio. The range of the water content is 45-65%, and the range of the bottom mud density is 1.4-1.7 g / cm 3 , and the range of the water-cement ratio is 0.8-1.2.

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

[0021] In some embodiments, transporting the bacterial liquid and the cementing liquid to the diluted bottom mud in a dual-channel mode and mixing further includes:

[0022] Use a vertical mixer for mixing;

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

[0024] When the environmental type is fresh water, an online spectrometer is used to detect the OD600 value in real time during the mixing process, and the flow rate ratio of the first channel to the second channel is dynamically adjusted according to the OD600 value to make the urease activity ≥ 1.25 ms / cm / min.

[0025] In some embodiments, immediately transporting the sludge to the area to be filled for filling while mixing includes:

[0026] When the environmental type is seawater, a high-pressure plunger pump with a flow rate of 50 - 150 m 3 / h is used to continuously fill the area to be filled, and the generation rate of CaCO3 is controlled ≥ 1.8 g / L·h;

[0027] When the environmental type is fresh water, the generation rate of CaCO3 is controlled ≥ 2.2 g / L·h.

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

[0029] Before transporting the bacterial liquid and the cementing liquid, a high-pressure water gun with a pressure ≥ 0.8 Mpa is used to wash the first channel, the second channel, and the pipes for filling;

[0030] And, pulse flushing at a frequency of 2 Hz is performed at the positions of elbow joints in the first channel, the second channel, and the pipes for filling;

[0031] Immediately transporting the sludge to the area to be filled for filling while mixing further includes:

[0032] Every 2 hours of filling, a reverse flushing technique with a pressure pulsation range of 0.5 - 2.5 Mpa is used to clean the pipe wall of the pipes for filling.

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

[0034] After filling, a curing process is generated according to the environmental type and the area to be filled is cured. The curing process includes a coastal area curing process and an inland river area curing process;

[0035] The coastal area curing process includes:

[0036] Curing with a surface thin mud layer with a thickness of 5 - 6 cm, and using seawater evaporation to form a salt crystal protection layer;

[0037] The inland river area curing process includes:

[0038] Curing is carried out using an automatic sprinkler system with a water spraying amount of 2 L / m 2 ·h and a sunshade net covering mode, and the temperature difference is controlled ≤ 15°C.

[0039] In some embodiments, the method for solidifying and reclamation of silt further includes:

[0040] Construct a three-dimensional quality control strategy, including front-end monitoring, process regulation, and terminal verification. The front-end monitoring is configured to monitor the pH value through a pH sensor and monitor calcium ions through a conductivity meter. The process regulation is configured to detect the uniformity of calcium carbonate distribution through an ultrasonic flaw detector. The terminal verification is configured to verify the unconfined compressive strength. If the environmental type is seawater, the threshold range for the unconfined compressive strength verification is ≥1.5 Mpa. If the environmental type is fresh water, the threshold range for the unconfined compressive strength verification is ≥1.8 Mpa;

[0041] Recover the unreacted urea solution, and treat the discharged wastewater after recovering the urea solution through a biological filter bed to make it meet the preset discharge threshold. The preset discharge threshold is configured to have an ammonia nitrogen content ≤ 15 mg / L;

[0042] And, after the solidified body in the area to be reclaimed is completely formed, conduct mechanical property tests on the solidified body to ensure that the solidification effect meets the preset requirements. The mechanical property tests include at least one of an unconfined compressive strength test and a determination of the permeability coefficient.

[0043] Adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are:

[0044] The above technical solution provides a method for solidifying and reclamation of silt based on the MICP technology, including: obtaining the water content, density, age, and environmental type of the bottom mud; formulating a differentiated MICP slurry based on the environmental type. The seawater-type cementing liquid is composed of seawater, urea, and CaCl2, and the fresh water-type cementing liquid is composed of deionized water, urea, and CaCl2; dig out the bottom mud, stir and dilute it, and pre-treat the area to be reclaimed according to the environmental type, adding a dispersant in a seawater environment and a flocculant in a fresh water environment; respectively transport the bacterial liquid and the cementing liquid to the diluted bottom mud through a dual-channel for mixing; immediately blow the solidified silt into the area to be reclaimed after mixing. The present invention realizes targeted solidification treatment for seawater and fresh water scenarios through an environmentally adaptable cementing liquid formula, differentiated pretreatment, and dual-channel transportation control. Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0046] Figure 1It is a schematic diagram of steps S101 to S101 of the sludge solidification and hydraulic filling method described in the specific implementation manner;

[0047] Figure 2 It is an elevation view of the overall equipment layout described in the specific implementation manner;

[0048] Figure 3 It is an elevation view of the structure of the vertical mixer described in the specific implementation manner;

[0049] Figure 4 It is a schematic diagram of the grab dredger grabbing silt soil in the river channel described in the specific implementation manner;

[0050] Figure 5 It is a plan view example of the silt soil without MICP treatment described in the specific implementation manner;

[0051] Figure 6 It is a plan view example of microorganisms adsorbed on the silt soil after MICP treatment described in the specific implementation manner;

[0052] Figure 7 It is a simplified implementation flow diagram of the sludge solidification and hydraulic filling method described in the specific implementation manner.

[0053] The reference numerals are as follows:

[0054] 1. Area to be filled hydraulically;

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

[0056] 3. Mixer;

[0057] 4. First channel;

[0058] 5. Second channel;

[0059] 6. Mixer base;

[0060] 7. Mixer engine;

[0061] 8. Mixer blades;

[0062] 9. Grab dredger;

[0063] 10. Grab. Specific implementation manner

[0064] The present invention will be further described in detail below with reference to the drawings and embodiments. It should be particularly noted that the following embodiments are only used to illustrate the present invention, but do not limit the scope of the present invention. Similarly, the following embodiments are only partial embodiments of the present invention rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0065] Please refer toFigures 1 to 6 , this embodiment provides a method for solidifying and reclamation of silt based on MICP technology, including:

[0066] S101. Obtain in-situ sediment information, which includes sediment moisture content, sediment density, sediment age, and environmental type. The environmental type includes one of seawater and fresh water;

[0067] S102. Prepare MICP slurry according to the in-situ sediment information. The MICP slurry includes bacterial solution and cementing solution. The cementing solution includes seawater-type cementing solution and fresh water-type cementing solution. The seawater-type cementing solution is obtained by mixing seawater, urea, and CaCl2, and the fresh water-type cementing solution is obtained by mixing deionized water, urea, and CaCl2;

[0068] S103. Excavate the sediment and stir it, and dilute and adjust the stirred sediment according to the in-situ sediment information;

[0069] S104. Pretreat the area to be reclaimed according to the in-situ sediment information. The pretreatment includes seawater pretreatment and fresh water pretreatment. The seawater pretreatment includes adding 0.1% dispersant to the area to be reclaimed, and the fresh water pretreatment includes adding 0.05% flocculant to the area to be reclaimed;

[0070] S105. Transport the bacterial solution and the cementing solution to the diluted sediment in a dual-channel mode and mix them. 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, immediately transport the silt to the area to be reclaimed for reclamation.

[0072] In step S101, to meet the quality control requirements, obtain the in-situ sediment information 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 / cm 3 , and dynamically adjust the subsequent silt dilution water volume according to the test results. The water-cement ratio is preferably 0.8 to 1.2.

[0073] In step S102, the bacterial solution is preferably Bacillus pasteurii for solidifying the sludge. To improve the adsorption capacity of Bacillus pasteurii in the sludge soil and achieve a better cementation effect, calcium chloride solution is used as the fixing solution. According to the working environment, the cementing solution preparation mode is selected, and the cementing solution concentration suitable for the target environment is screened (a mixed solution of urea and calcium chloride in equal proportion, and the solvents of the cementing solution are fresh water and natural seawater respectively). According to the sludge soil of different ages and the settings of different urease activities of OD600 (the absorbance value of the solution at a wavelength of 600 nm), such as Table 1 and Table 2, unconfined compressive strength tests, direct shear tests, and liquid-plastic limit tests are carried out to screen the optimal group.

[0074] Verify according to the test scheme in Table 1 for the corresponding age, and it is necessary to meet the bearing requirements of the reclamation foundation.

[0075] Table 1 Test Scheme

[0076]

[0077] Table 2 Urease Activity of Bacterial Solutions with Different OD600

[0078]

[0079] In step S103, preferably, the grab dredger 9 is used to dig the bottom mud at sea or in the river channel, and mechanical crushing and dilution are carried out through the mud mixer 3.

[0080] In step S104, environmental adaptation pretreatment is carried out on the area to be filled 1 according to the in-situ bottom mud information.

[0081] In step S105, a dual-channel conveying system is used to inject the bacterial solution and the cementing solution synchronously. The flow rate ratio of the first channel 4 and the second channel 5 is controlled at 1:1.5. Preferably, the flow rate of the bacterial solution is 30 L / min, and the flow rate of the cementing solution is 45 L / min. Micro-scale dispersion (particle size ≤ 50 μm) is achieved through the mixer blade 8.

[0082] In step S106, aiming at the characteristics of fine-grained soil (the proportion of particle size ≤ 0.075 mm > 60%), a vertical mixer 3 is used for strong mixing. The lower-layer blade breaks the aggregates (shearing force ≥ 200 N·m), and the upper-layer blade improves the mixing uniformity (coefficient of variation < 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 soil or mixed soil, the mixing strength can be increased or the mixing time can be extended to ensure uniform dispersion of particles. According to the saline environment, the dosage of CaCl2 is appropriately adjusted to compensate for the interference of salt ions for adjustment. Adjustable blades and variable-speed devices are added to the mixing equipment to improve its adaptability.

[0084] In this embodiment, differential treatment is achieved by differentiating between seawater and fresh - water environmental types. The in - situ seawater is directly used to prepare the cementing liquid, reducing the consumption of fresh water resources and the treatment cost of chemical reagents. The bacterial liquid and the cementing liquid are independently transported through two channels, and the reaction process is precisely controlled by controlling the flow rate ratio, avoiding material waste caused by premixing. Combined with the environment - adapted pretreatment technology, a dispersant is added for the seawater environment to reduce the interference of salts, and a flocculant is applied to the fresh - water environment to enhance particle binding, effectively improving the adsorption efficiency of the bacterial liquid. Through the synchronous operation mode of stirring and backfilling, using the layered crushing and mixing function of the vertical mixer 3, micron - level dispersion and uniform mixing are achieved in the fine - grained soil scenario, shortening the construction period. At the same time, the dilution water volume and the cementing liquid concentration are dynamically adjusted based on the characteristics of in - situ sediment, and the optimal mixing ratio parameters are screened through laboratory tests to ensure that the bearing performance of the solidified sludge meets the standards. While achieving environment - adapted solidification, this method significantly reduces the material cost and construction energy consumption through the utilization of seawater resources and the optimization of process integration.

[0085] In some embodiments, the preparation process of the seawater - type cementing liquid includes:

[0086] Select seawater with a salinity of 30 - 35‰ to dissolve a first - preset proportion of the urea and CaCl2 mixture to obtain a first - initial cementing liquid with a first - preset concentration, where the first - preset concentration is configured as one of 1.5, 2, 2.5, and the first - preset proportion is a 1:1 molar ratio;

[0087] Increase the CaCl2 dosage by 15% of the first - preset concentration in the first - initial cementing liquid to obtain the seawater - type cementing liquid.

[0088] In this embodiment, the on - site seawater (salinity 30 - 35‰) is directly used to dissolve urea and CaCl2, and the mixing ratio (i.e., the first - preset proportion) is 1:1 (molar ratio). The first - preset concentration is preferably 2.0M. See the data in Table 3. By increasing the CaCl2 dosage by 15% of the first - preset concentration in the first - initial cementing liquid to compensate for the + competitive adsorption effect of Na.

[0089] Table 3 Technical parameter table for the preparation of seawater - type cementing liquid

[0090]

[0091]

[0092] In this embodiment, by directly using the on - site seawater to dissolve the 1:1 molar ratio mixture of urea and CaCl2, the seawater desalination treatment link is omitted. Combined with increasing the CaCl2 dosage by 15% of the first - preset concentration, it effectively compensates for the seawater Na +The competitive effect on the adsorption of the bacterial solution enhances the reaction efficiency of the cementing solution; the ratio is optimized based on the gradient concentration (1.5 - 2.5M) and the OD600 adaptation value (3.0 - 4.0) to ensure that the highly urease - active bacterial solution (1.67 - 2.40 ms·cm -1 ·min -1 ) synergizes with the cementing solution to achieve a CaCO3 generation rate ≥ 1.8 g / L·h under the condition of a salinity of 35‰, enhancing the solidification strength of the silt; at the same time, natural seawater is used as a solvent to reduce the fresh - water transportation and treatment costs (saving 30 - 45%). The concentration is calibrated in real - time by the conductivity method, and the sodium - ion compensation amount is accurately controlled by XRF elemental analysis, forming a low - cost and highly adaptable seawater - type cementing solution preparation technology to meet the engineering requirements of the MICP solidification process in complex marine environments.

[0093] In some embodiments, the preparation process of the fresh - water - type cementing solution includes:

[0094] Select deionized water with a conductivity ≤ 10 μS / cm to dissolve a second preset ratio of the urea and CaCl2 mixture to obtain a fresh - water - type cementing solution with a second preset concentration, where the second preset concentration is configured as one of 1 and 1.5, and the second preset ratio is 1:1 molar ratio.

[0095] In this embodiment, 1.0 - 1.5M cementing solution is prepared with deionized water. See the data in Table 4 for details. The OD600 value is monitored in real - time by an online spectrometer (control range 1.5 - 3.0), and the activity of the bacterial solution is dynamically adjusted to a urease activity ≥ 1.25 ms / cm / min.

[0096] Table 4 Technical parameter table for the preparation of fresh - water - type cementing solution

[0097]

[0098]

[0099] In this embodiment, deionized water is used to dissolve a mixture of urea and CaCl2 with a molar ratio of 1:1 to prepare a 1.0 - 1.5M fresh - water - type cementing fluid. The concentration is calibrated in real - time by the conductivity method to avoid impurity interference with the reaction process and improve the stability of the cementing fluid. Combining with an online spectrometer to dynamically monitor the OD600 value, and using PID feedback control to precisely adjust the activity of the bacterial solution to ensure that the urease activity is ≥1.25 ms / cm / min, promoting the CaCO3 generation rate ≥2.2 g / L·h (under the condition of 0‰ salinity), significantly improving the solidification efficiency of silt in the fresh - water environment. By adding 0.1% dextran protective agent to maintain the activity of the bacterial solution and cooperating with the CFU counting method to verify the microbial survival rate, the effective duration of the cementing reaction is extended. At the same time, the ammonia - nitrogen emission is strictly controlled ≤20 mg / L (meeting the GB8978 standard), and a water quality rapid detection kit is used to monitor the environmental protection indicators in real - time, taking into account both engineering efficiency and environmental compatibility. This scheme realizes the high - efficiency, stability and greening of the MICP solidification process in the fresh - water scenario through concentration gradient optimization, dynamic activity regulation and environmental protection constraints.

[0100] In some embodiments, the bottom mud is dug out and stirred, and the diluted preparation of the stirred bottom mud according to the in - situ bottom mud information includes:

[0101] Mechanically crush the bottom mud according to preset stirring parameters, where the preset stirring parameters include the stirring speed and the duration. The stirring speed is 120 rpm and the duration is 15 min;

[0102] Generate a third preset ratio of silt to clear water according to the in - situ bottom mud information and add clear water according to the third preset ratio to dilute the bottom mud;

[0103] The third preset ratio is configured to calculate the water - cement ratio through the moisture content and the bottom - mud density, and is obtained by conversion according to the water - cement ratio. The range of the moisture content is 45 - 65%, and the range of the bottom - mud density is 1.4 - 1.7 g / cm 3 , and the range of the water - cement ratio is 0.8 - 1.2.

[0104] In this embodiment, mechanical crushing and dilution preparation are carried out by a slurry mixer 3. Among them, for mechanical crushing, the stirring speed is set to 120 rpm and the duration is 15 min; for dilution preparation, 20 - 30% clear water is added according to the detection value in step S101.

[0105] The range of the moisture content is 45 - 65%. Treatment measures for too high moisture content (>65%) include adding dry soil, using a mechanical dehydration system or increasing the dosage of coagulant; treatment measures for too low moisture content (<45%) include adding an appropriate amount of clear water or increasing the dilution water volume.

[0106] The range of the bottom - mud density is 1.4 - 1.7 g / cm 3 , and for too high bottom - mud density (>1.7 g / cm3 ) The treatment measures include adding dispersants or diluting the sludge; when the density of the bottom sludge is too low (<1.4 g / cm 3 ) The treatment measures include increasing the proportion of dry solid materials or improving the uniformity by stirring.

[0107] According to the test results of the water content and the density of the bottom sludge, adjust the water-cement ratio range in the hydraulic filling construction to 0.8 - 1.2. The specific calculation method is as follows:

[0108] When the water content range is 45 - 65% and the bottom sludge density range is 1.4 - 1.7 g / cm 3 , the water-cement ratio is usually set to 1:1. If the water content or the bottom sludge density exceeds the range, the water-cement ratio should be adjusted according to the following formula:

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

[0110] When the water content is 55% and the bottom sludge density is 1.5 g / cm 3 , the water-cement ratio can be adjusted to 0.9:1 to ensure the smoothness of the hydraulic filling process and the compliance of the solidification effect.

[0111] By adjusting the water content and density to the target range and dynamically adjusting the water-cement ratio according to the test results, the smooth progress of the hydraulic filling construction and the compliance of the solidification 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) need to be taken to ensure the project quality.

[0112] In this embodiment, the bottom sludge is mechanically crushed by presetting stirring parameters to ensure the uniform dispersion of sludge particles and improve the subsequent dilution and solidification reaction conditions; based on the in-situ test data of the water content and density of the bottom sludge, the water-cement ratio is dynamically calculated and clear water is added for dilution and preparation to balance the fluidity and solidification strength requirements of the hydraulic filling construction; for abnormal working conditions of water content or density, treatment measures such as adding dry soil, dispersants or adjusting the dilution water volume are adopted to ensure that the indicators return to the target range; the mixing ratio is precisely controlled through the water-cement ratio adjustment formula, combined with auxiliary means such as mechanical dehydration systems and coagulant dosing, to ensure the uniformity and stability of sludge dilution and avoid construction interruptions caused by too high water content or too low density; finally, the smoothness of the hydraulic filling process and the compliance rate of the solidification effect are synchronously improved, providing an adaptable bottom sludge matrix for the subsequent MICP process.

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

[0114] In this embodiment, the polycarboxylic acid series dispersant and the chitosan flocculant act synergistically. The polycarboxylic acid series dispersant enhances the particle dispersion stability through electrostatic repulsion, and the chitosan flocculant promotes floc formation by means of molecular chain bridging effect. The two cooperate to improve the solid-liquid separation efficiency while maintaining environmental friendliness.

[0115] In some embodiments, conveying the bacterial liquid and the cementing liquid to the diluted bottom mud in a dual-channel mode and mixing them further includes:

[0116] Using a vertical mixer for mixing;

[0117] When the environmental type is seawater, extending 30% of the total mixing duration;

[0118] When the environmental type is fresh water, using an online spectrometer to detect the value of OD600 in real time during the mixing process, and dynamically adjusting the flow rate ratio of the first channel and the second channel according to the value of OD600, so that the urease activity ≥ 1.25 ms / cm / min.

[0119] In this embodiment, a vertical mixer 3 is used for stirring, aiming to crush the sludge blocks and improve the uniformity of the sludge. After stirring to relatively uniform, according to the optimal ratio selected from the above tests, the bacterial liquid and the cementing liquid are added according to the proportion calculated based on the sludge capacity in the vertical mixer 3, and mechanical stirring is continued.

[0120] In this embodiment, a vertical mixer 3 is used to crush the sludge blocks and improve the uniformity, ensuring the full contact of the bacterial liquid and the cementing liquid; extending 30% of the total mixing duration for the seawater environment to compensate for the inhibition of the reaction rate by high salinity; in the fresh water environment, detecting the value of OD600 in real time by an online spectrometer and dynamically adjusting the flow rate ratio of the dual channels to make the urease activity stably ≥ 1.25 ms / cm / min, optimizing the efficiency of microbial-induced carbonate precipitation; accurately adding the bacterial liquid and the cementing liquid based on the optimal ratio, and combining mechanical stirring to strengthen the mixing homogeneity, finally realizing the reliability and controllability of the sludge solidification effect under different environmental types.

[0121] In some embodiments, immediately conveying the sludge to the area to be filled for filling while mixing includes:

[0122] When the environmental type is seawater, using a high-pressure plunger pump of 50 - 150 m 3 / h to continuously fill the area to be filled, and controlling the CaCO3 generation rate ≥ 1.8 g / L·h;

[0123] When the environmental type is fresh water, controlling the CaCO3 generation rate ≥ 2.2 g / L·h.

[0124] In this embodiment, when the environmental type is seawater, using a 2.0 M cementing liquid (see Table 3), through 50 - 150 m 3The high-pressure piston pump is used for continuous hydraulic filling at / h, controlling the CaCO3 generation rate ≥ 1.8 g / L·h; when the environmental type is fresh water, the OD600 value (1.5 - 3.0) is dynamically adjusted, and the concentration of the cementing liquid (1.0 - 1.5 M) is matched in real time to ensure that the CaCO3 generation rate ≥ 2.2 g / L·h (see Table 4).

[0125] In this embodiment, for the seawater environment, a 50 - 150 m 3 The high-pressure piston pump is used for continuous hydraulic filling at / h and the concentration of the cementing liquid is fixed at 2.0 M to ensure that the CaCO3 generation rate ≥ 1.8 g / L·h, overcoming the limitation of high salinity on the reaction efficiency; for the fresh water environment, the concentration of the cementing liquid is matched in real time by dynamically adjusting the OD600 value, accurately increasing the CaCO3 generation rate to ≥ 2.2 g / L·h to adapt to the microbial activity requirements under low salinity; in both types of environments, hydraulic filling and mixing are carried out simultaneously, combined with concentration regulation and rate control, to ensure the carbonate precipitation efficiency and the continuity of hydraulic filling under different salinity conditions, strengthening the silt solidification effect and construction stability.

[0126] In some embodiments, the silt solidification hydraulic filling method further includes:

[0127] Before transporting the bacterial liquid and the cementing liquid, use a high-pressure water gun with a pressure ≥ 0.8 Mpa to wash the first channel, the second channel, and the pipes for hydraulic filling;

[0128] And, perform pulsed flushing at a frequency of 2 Hz at the positions of the elbow joints in the first channel, the second channel, and the pipes for hydraulic filling;

[0129] When mixing and immediately transporting the silt to the area to be hydraulically filled for hydraulic filling, it further includes:

[0130] Every 2 hours of hydraulic filling, use the reverse flushing technology with a pressure pulsation range of 0.5 - 2.5 Mpa to clean the inner wall of the pipes for hydraulic filling.

[0131] In this embodiment, particularly perform pulsed flushing at a frequency of 2 Hz at the elbow joints to ensure no residue blockage. Every 2 hours of hydraulic filling, use the reverse flushing technology with a pressure pulsation range of 0.5 - 2.5 MPa to clean the inner wall to prevent blockage.

[0132] To ensure continuous operation of solidified soil construction, according to engineering experience and the construction efficiency of solidified soil, a certain number of slurry pits and water storage pits are excavated after the site is leveled. Among them, the slurry pit is used for silt solidification; the water storage pit is used for post-construction pipeline cleaning to prevent the pipeline from being blocked after the silt solidified soil consolidates. The slurry pit and the water storage pit are the key points in the bank silt solidification project. The mixer 3 uses a special solidified slurry mixer 3, preferably a vertical mixer 3, to fully stir the slurry and the solidifying agent until they are uniform, and then uses a high-pressure piston pump to pump the solidified slurry to the area to be filled 1. The in-situ solidification and filling integrated process, that is, the "treatment while filling" mode, directly transports the silt pretreated by MICP to the area to be filled 1 through the high-pressure pump delivery pipe 2, realizing the simultaneous progress of the solidification reaction and the filling operation. Compared with the traditional step-by-step process of solidifying first and then filling, the construction period can be effectively shortened. The vertical slurry mixer 3 and the grab dredger 9 are used in a combined operation system to complete the continuous processes of silt loading, mixing treatment, bacteria solution injection, and high-pressure filling in the river channel.

[0133] In this embodiment, the residues in the first channel 4, the second channel 5, and the filling pipeline are thoroughly removed by a high-pressure water gun to prevent blockage; the pipe wall is cleaned every 2 hours of filling using a 0.5 - 2.5 MPa pressure pulsation reverse flushing technology to ensure the continuous operation efficiency; by excavating the slurry pit and the water storage pit, which are respectively used for silt solidification and post-construction pipeline cleaning, to avoid the blockage caused by the consolidation of the solidified soil; the vertical mixer 3 and the high-pressure piston pump are used in a combined operation, combined with the in-situ solidification and filling integrated process, to realize the simultaneous progress of mixing, bacteria solution injection, and high-pressure filling, significantly shortening the construction period compared with the traditional step-by-step process; the combined operation system of the vertical slurry mixer 3 and the grab dredger 9 completes the continuous processes of loading, treatment, and filling in the river channel, improving the construction efficiency and the process connection, and ensuring the coordinated progress of the solidification reaction and the filling operation.

[0134] In some embodiments, the silt solidification and filling method further includes:

[0135] After the filling is completed, a curing process is generated according to the environmental type and the area to be filled is cured. The curing process includes the curing process for the coastal area and the curing process for the inland river area;

[0136] The curing process for the coastal area includes:

[0137] Curing is carried out using a 5 - 6 cm thick surface thin mud layer, and a salt crystal protective layer is formed by the evaporation of seawater;

[0138] The curing process for the inland river area includes:

[0139] Curing is carried out using an automatic sprinkler system with a water spraying volume of 2 L / m 2 ·h and a sunshade net covering mode, and the temperature difference is controlled ≤ 15°C.

[0140] In this embodiment, the curing plan is selected according to the environmental type, and the curing effect is verified subsequently. After 7 days, the surface crack width ≤ 0.2 mm, and the strength development coefficient at 28 days reaches 0.85 - 0.92.

[0141] The curing methods of solidified soil mainly include watering curing and surface sludge curing. Watering curing has the characteristics of economy, convenience, effectiveness, etc., and is the most common curing method during the construction process; surface sludge curing is to cover the surface of the formed solidified soil with a 5 - 6 cm thick layer of surface sludge after the solidified soil is poured, which can prevent the direct sunlight from shining on the solidified soil and avoid the cracking phenomenon of the solidified soil surface due to excessive temperature difference. Since the surface sludge is directly in contact with sunlight, the surface of the sludge will crack after drying, and the solidified soil under its lower layer can volatilize water vapor and dehydrate and solidify through the cracks. Compared with watering curing, surface sludge curing has the characteristics of lower curing frequency and better curing effect.

[0142] It should be noted that the "inland river environment" project area is located on the shore base of inland rivers, lakes, and the silt curing and filling in the shallow water area by dredging, and the "coastal area" project area is located near the sea or saltwater lake. The water salinity in the inland river area is relatively low, close to fresh water, with a salinity of about 0‰, and the river water flow is relatively slow. Affected by monsoons or precipitation, the water salinity in the coastal area is relatively high, usually at 30 - 35‰. Affected by tides and waves, the water flow is complex and has a greater force, and the tides change periodically, and there may be more salt erosion substances. These different scenarios have different requirements for the curing method. Therefore, whether to adopt watering curing or surface sludge curing specifically needs to be determined according to the specific situation.

[0143] In this embodiment, aiming at the environmental differences between the coastal area and the inland river area, a differential curing process of combining surface sludge curing with an automatic sprinkler system and sunshade net coverage is adopted. In the coastal area, a 5 - 6 cm thick layer of surface sludge can be covered to form a salt crystal protection layer by seawater evaporation to reduce the influence of salt erosion; in the inland river area, an automatic sprinkler system with a watering volume of 2 L / m 2 ·h and sunshade net coverage mode can be adopted to control the temperature difference ≤ 15℃ and avoid cracking due to temperature change. The two curing methods respectively meet the requirements of high - salinity tidal environment and low - salinity fresh - water slow - flow environment, taking into account both curing efficiency and effect. Surface sludge curing promotes dehydration and solidification by the volatilization of water vapor in the lower layer, reducing the curing frequency; watering curing is economical and convenient, and combined with the sunshade net, it further inhibits cracking, realizing the dual improvement of environmental adaptability curing and solidification quality.

[0144] In some embodiments, the method for silt curing and filling further includes:

[0145] Construct a three-dimensional quality control strategy, including front-end monitoring, process regulation, and terminal verification. The front-end monitoring is configured to monitor the acidity and alkalinity through a pH sensor and monitor calcium ions through a conductivity meter. The process regulation is configured to detect the uniformity of calcium carbonate distribution through an ultrasonic flaw detector. The terminal verification is configured to perform unconfined compressive strength verification. If the environmental type is seawater, the threshold range for unconfined compressive strength verification is ≥1.5 Mpa. If the environmental type is fresh water, the threshold range for unconfined compressive strength verification is ≥1.8 Mpa;

[0146] Recover the unreacted urea solution, and treat the discharged wastewater after recovering the urea solution through a biological filter bed to make it meet the preset discharge threshold. The preset discharge threshold is configured to have an ammonia nitrogen content ≤15 mg / L;

[0147] And, after the solidified body in the area to be filled is completely formed, perform mechanical property tests on the solidified body to ensure that the solidification effect meets the preset requirements. The mechanical property tests include at least one of unconfined compressive strength tests and determination of permeability coefficient.

[0148] In this embodiment, a three-dimensional quality control system is established to monitor the solidification effect, including front-end monitoring, process regulation, and terminal verification. The front-end monitoring is carried out through a pH sensor (controlling the acidity and alkalinity range to 8.5 - 9.2) and a conductivity meter (reflecting the Ca 2 + concentration); The process regulation is to detect the uniformity of calcium carbonate distribution through an ultrasonic flaw detector; The terminal verification is unconfined compressive strength verification. The 28-day unconfined compressive strength is ≥1.5 MPa in a seawater environment and ≥1.8 MPa in a fresh water environment. Monitor the formation process of the solidified body in real time to ensure that the solidification effect meets the expected standard. Adjust the injection amount and frequency of nutrients as needed to optimize the solidification effect.

[0149] At the end, an environmental protection disposal process needs to be executed. Recover the unreacted urea solution (recovery rate > 75%), and treat the discharged water through a biological filter bed. The ammonia nitrogen content ≤15 mg / L (meeting the GB 8978 standard).

[0150] After the solidified body in the area to be filled 1 is completely formed, perform mechanical property tests on it (such as unconfined compressive strength tests, determination of permeability coefficient, etc.) to ensure that the solidification effect meets the design requirements. Verify the dual-mode performance through a comparative test. See Table 5 for details:

[0151] Table 5 Comparative test to verify dual-mode performance

[0152] Test item Seawater type Freshwater type 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 Treatment of Hydraulic Filled Ground" (GB / T 50943-2015) stipulates the strength requirements under different engineering applications. Generally speaking, the UCS requirements for hydraulic filled ground may be between 0.8 - 1.5 MPa, depending on the application scenario. The 28-day UCS for seawater type is 1.8 MPa and for fresh water type is 2.1 MPa in this patent, both exceeding the common minimum standards, indicating that the requirements are met. For specific data, please refer to Table 6.

[0154] Table 6 Comparison with the "Technical Specification for Treatment of Hydraulic Filled Ground" (GB / T 50943-2015)

[0155] Project type Minimum UCS requirement Compliance status of the present invention Temporary cofferdam ≥0.8MPa Seawater type 1.8 (exceeding the standard by 125%) Road base ≥1.2MPa Freshwater type 2.1 (exceeding the standard by 75%) Building foundation (Grade II) ≥1.5MPa Both dual modes meet the standard

[0156] In this embodiment, a three-dimensional quality control strategy of front-end monitoring, process regulation, and terminal verification is constructed to achieve precise control of the whole process. The front-end monitoring uses a pH sensor to control the pH range of 8.5 - 9.2 and a conductivity meter to track the Ca 2 + concentration in real time; the process regulation detects the uniformity of calcium carbonate distribution through an ultrasonic flaw detector and dynamically optimizes the nutrient solution injection parameters; the terminal verification takes the unconfined compressive strength as the core index, with the 28-day strength in the seawater environment ≥ 1.5 MPa (actually reaching 1.8 ± 0.2 MPa) and in the fresh water environment ≥ 1.8 MPa (actually reaching 2.1 ± 0.3 MPa), and the permeability coefficients are as low as 5×10 -6 cm / s and 3×10 -6 cm / s respectively, both significantly exceeding the minimum requirements of the "Technical Specification for Treatment of Hydraulic Filled Ground" (such as the temporary cofferdam ≥ 0.8 MPa exceeding the standard by 125%). The environmental protection disposal process is synchronously implemented, the unreacted urea solution is recycled (recovery rate > 75%), and the ammonia nitrogen content of the wastewater after biological filter bed treatment is ≤ 15 mg / L, taking into account both engineering and ecological requirements. After the solidified body is formed, the mechanical properties are verified through unconfined compressive strength tests and permeability coefficient measurements to ensure that the strength standards for scenarios such as temporary cofferdams, road bases, and building foundations are met, achieving a comprehensive improvement in strength, impermeability, and environmental adaptability.

[0157] Please refer to Figure 7 , furthermore, the following examples can be developed in combination with the above technical solutions:

[0158] A method for solidifying and hydraulic filling of silt based on the Microbial Induced Calcium Carbonate Precipitation (MICP) technology, the implementation process of which includes: excavating the silt in the river, monitoring the moisture content and density of the original silt; formulating test groups according to the silt properties, selecting the optimal group, and preparing the MICP slurry; mixing the microbial bacterial liquid, cementing liquid, and silt soil through a vertical mixer; inserting a slurry pump (i.e., a high-pressure piston pump) at the bottom of the vertical mixer to carry out hydraulic filling of the target area; carrying out curing of the solidified soil after the hydraulic filling of the target area is completed; finishing and detecting the curing effect to ensure that the effect meets the expectations.

[0159] See also 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 adder and a mixer 3. The grab boat 9 takes silt soil from the sea or the river through a grab 10; the 50-150m3 / h high-pressure plunger pump is used to transport the mud treated by the MICP method, and pump the silt slurry treated by the MICP method to the area to be filled 1; the curing agent adder is mainly composed of a powder silo and a powder metering pump, etc., and the curing agent adder is used to control the addition of bacterial liquid, binder and curing agent; the mixer 3 includes a mixer base 6, a mixer engine 7 and a mixer blade 8. The vertical mixer 3 is used for stirring, the purpose of which is to crush the silt blocks and improve the uniformity of the silt. After stirring to a relatively uniform state, according to the optimal ratio selected by the above test, the bacterial liquid and binder are added according to the proportion calculated by the silt capacity in the vertical mixer 3, and mechanical stirring is continued.

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

[0161] The present invention provides a silt solidification and filling method based on MICP technology, which realizes differentiated treatment of environmental adaptability through a seawater / freshwater dual-mode cementing system, significantly reduces construction costs and improves efficiency. In view of the seawater environment, in-situ seawater is directly used to prepare the cementing liquid, eliminating the desalination treatment link, saving 30-45% of the freshwater transportation cost, and at the same time, by increasing the dosage of CaCl2 by 15% to compensate for the sodium ion competition effect, ensuring that the CaCO3 generation rate is ≥1.8g / L·h; in the freshwater environment, deionized water is used to dynamically control the concentration of the cementing liquid, and the bacterial liquid activity is optimized in real time by combining an online spectrometer, reducing the amount of bacterial liquid, and increasing the CaCO3 generation rate to ≥2.2g / L·h. Through the synchronous operation mode of stirring and filling, the vertical mixer layered crushing and high-pressure plunger pump continuous conveying joint operation are adopted to realize the simultaneous solidification reaction and filling construction, which shortens the construction period by 40% compared with the traditional pre-curing process and reduces the production cost. The dual-channel flow rate ratio control and mechanical stirring micron-level dispersion synergistically promote the calcium carbonate crystallization to uniformly fill the soil pores, improve the strength and reduce the permeability coefficient. Combining three-dimensional quality control strategies with environmental protection disposal processes, we can achieve efficient resource utilization and significant reduction in construction energy consumption while ensuring that the strength of temporary cofferdams, road bases and other projects meet standards.

[0162] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0163] When the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present 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. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor to execute all or part of the steps of the methods according to various embodiments of the present invention. The foregoing storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical discs.

[0164] The foregoing are only partial embodiments of the present invention, and thus do not limit the protection scope of the present invention. Any equivalent device or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall equally be included in the patent protection scope of the present invention.

Claims

1. A method for solidifying and hydraulic filling of silt based on MICP technology, characterized in that Including: Obtaining in-situ sediment information, where the in-situ sediment information includes sediment moisture content, sediment density, sediment age, and environmental type, and the environmental type includes one of seawater and fresh water; Preparing MICP slurry according to the in-situ sediment information, where the MICP slurry includes bacterial solution and cementing solution, the cementing solution includes seawater-type cementing solution and fresh water-type cementing solution, the seawater-type cementing solution is obtained by mixing seawater, urea, and CaCl2, and the fresh water-type cementing solution is obtained by mixing deionized water, urea, and CaCl2; Digging sediment and stirring the sediment, and diluting and adjusting the stirred sediment according to the in-situ sediment information; Preprocessing the area to be filled according to the in-situ sediment information, where the preprocessing includes seawater preprocessing and fresh water preprocessing, the seawater preprocessing includes adding 0.1% dispersant to the area to be filled, and the fresh water preprocessing includes adding 0.05% flocculant to the area to be filled; Transporting the bacterial solution and the cementing solution to the diluted sediment in a dual-channel mode and mixing them, where the dual-channel mode includes a first channel and a second channel, the first channel is used to transport the bacterial solution, the second channel is used to transport the cementing solution, and the initial flow rate ratio of the first channel to the second channel is 1:1.5; While mixing, immediately transporting the silt to the area to be filled for filling.

2. The method for solidifying and hydraulic filling of silt based on MICP technology according to claim 1, characterized in that, The preparation process of the seawater-type cementing solution includes: Selecting seawater with a salinity of 30-35‰ to dissolve a first preset ratio of urea and CaCl2 mixture to obtain a first initial cementing solution with a first preset concentration, where the first preset concentration is configured as one of 1.5, 2, and 2.5, and the first preset ratio is a 1:1 molar ratio; Increasing the dosage of CaCl2 with 15% of the first preset concentration in the first initial cementing solution to obtain the seawater-type cementing solution.

3. The method for silt solidification and hydraulic filling based on MICP technology according to claim 1 is characterized in that, The preparation process of the fresh water-type cementing solution includes: Selecting deionized water with a conductivity ≤ 10 μS / cm to dissolve a second preset ratio of urea and CaCl2 mixture to obtain a fresh water-type cementing solution with a second preset concentration, where the second preset concentration is configured as one of 1 and 1.5, and the second preset ratio is a 1:1 molar ratio.

4. The method for silt solidification and hydraulic filling based on MICP technology according to claim 1, characterized in that, Digging sediment and stirring the sediment, and diluting and adjusting the stirred sediment according to the in-situ sediment information includes: Mechanically crushing the sediment according to preset stirring parameters, where the preset stirring parameters include stirring speed and duration, the stirring speed is 120 rpm, and the duration is 15 min; Generating a third preset ratio of silt and clear water according to the in-situ sediment information and adding clear water according to the third preset ratio to dilute the sediment; The third preset ratio is configured to obtain a water-cement ratio by calculating the moisture content and the sediment density, and is obtained by conversion according to the water-cement ratio. The range of the moisture content is 45-65%, and the range of the sediment density is 1.4-1.7 g / cm 3 , and the range of the water-cement ratio is 0.8-1.

2.

5. The method for silt solidification and hydraulic filling based on the MICP technology according to claim 1, characterized in that The dispersant is a polycarboxylic acid series; the flocculant is chitosan.

6. The method for solidifying and hydraulic filling of sludge based on the MICP technology according to claim 1, characterized in that, Transporting the bacterial solution and the cementing solution to the diluted sediment in a dual-channel mode and mixing them further includes: Using a vertical mixer for mixing; When the environmental type is seawater, extending the total mixing duration by 30%; When the environmental type is fresh water, during the mixing process, an online spectrometer is used to detect the OD600 value in real time, and the flow rate ratio of the first channel to the second channel is dynamically adjusted according to the OD600 value, so that the urease activity ≥ 1.25 ms / cm / min.

7. The method for solidifying and hydraulic filling of silt based on MICP technology according to claim 1 is characterized in that, Immediately transporting the sludge to the area to be filled for filling while mixing includes: When the environmental type is seawater, a high-pressure piston pump with a flow rate of 50 - 150 m³ / h is used to continuously fill the area to be filled, and the generation rate of CaCO₃ is controlled to be ≥ 1.8 g / L·h; 3 / h is used to continuously fill the area to be filled, and the generation rate of CaCO₃ is controlled to be ≥ 1.8 g / L·h; When the environmental type is fresh water, controlling the generation rate of CaCO3 ≥ 2.2 g / L·h.

8. The method for solidifying and reclamation of silt based on MICP technology according to claim 1, characterized in that The method further includes: Before transporting the bacterial liquid and the cementing liquid, a high-pressure water gun with a pressure ≥ 0.8 Mpa is used to flush the first channel, the second channel, and the pipeline for filling. And, at the position where there are elbow joints in the first channel, the second channel, and the pipeline for filling, pulsed flushing is performed at a frequency of 2 Hz. Immediately transporting the sludge to the area to be filled for filling while mixing further includes: Every 2 hours of filling, a reverse flushing technique with a pressure pulsation range of 0.5 - 2.5 Mpa is used to clean the pipe wall of the pipeline for filling.

9. The method for solidifying and reclamation of silt based on MICP technology according to claim 1, characterized in that The method further includes: After the filling is completed, a curing process is generated according to the environmental type and the area to be filled is cured. The curing process includes a coastal area curing process and an inland river area curing process. The coastal area curing process includes: Curing with a surface layer of thin mud with a thickness of 5 - 6 cm, and using the evaporation of seawater to form a salt crystal protective layer. The inland river area curing process includes: Adopt an automatic sprinkler system with a water spraying volume of 2 L / m 2 ·h and a sunshade net covering mode for maintenance, and control the temperature difference ≤ 15°C.

10. The method for solidifying and hydraulic filling of silt based on MICP technology according to claim 1, characterized in that, The method further includes: Constructing a three-dimensional quality control strategy, including front-end monitoring, process regulation, and terminal verification. The front-end monitoring is configured to monitor the acidity and alkalinity through a pH sensor, and monitor calcium ions through a conductivity meter. The process regulation is configured to detect the uniformity of calcium carbonate distribution through an ultrasonic flaw detector. The terminal verification is configured for unconfined compressive strength verification. If the environmental type is seawater, the threshold range of the unconfined compressive strength verification is ≥ 1.5 Mpa. If the environmental type is fresh water, the threshold range of the unconfined compressive strength verification is ≥ 1.8 Mpa. Recycling the unreacted urea solution, and treating the discharged wastewater after recycling the urea solution through a biological filter bed to make it meet the preset discharge threshold. The preset discharge threshold is configured to have an ammonia nitrogen content ≤ 15 mg / L. And, after the solidified body in the area to be filled is completely formed, a mechanical property test is performed on the solidified body to ensure that the solidification effect meets the preset requirements. The mechanical property test includes at least one of an unconfined compressive strength test and a permeability coefficient measurement.

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