A method for backfilling a trench based on MICP technology
By using MIP technology to induce calcium carbonate deposition reaction in fertilizer trench backfilling, calcium carbonate cemented soil particles are generated, which solves the problems of poor compaction and high pollution in traditional fertilizer trench backfilling construction, and achieves low-cost and high-quality fertilizer trench backfilling effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING ZHONGJIAN CONSTR RES INST CO LTD
- Filing Date
- 2023-08-30
- Publication Date
- 2026-05-29
AI Technical Summary
Traditional backfilling methods for fertilizer trenches have problems such as limited construction space, poor compaction, high cost, and high pollution, making it difficult to guarantee construction quality.
Using MICP technology, calcium carbonate deposition reaction is induced by microorganisms, generating calcium carbonate cemented soil particles during the backfilling process of fertilizer trenches. The self-compacting process is carried out using microbial slurry of urea and calcium salts, avoiding manual or mechanical compaction.
It achieves low-cost, low-pollution, and high-density backfilling of fertilizer trenches, with simple construction and excellent quality, avoiding settlement.
Smart Images
Figure CN117364798B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of trench backfilling technology, specifically to a trench backfilling construction method based on MICP technology. Background Technology
[0002] A backfill trench refers to an extra space excavated between the exterior wall of a building's basement or foundation and the edge of the excavation pit to provide a working surface. After the basement exterior wall construction is completed, the backfill trench is then filled. The traditional backfilling method involves pouring backfill material into the trench, followed by manual or mechanical compaction.
[0003] However, in actual trench backfilling construction, the narrow width of the trench and the presence of numerous pipelines within it limit the construction space, making compaction difficult and resulting in poor backfill density and compromised construction quality. Furthermore, trench backfilling typically uses lime-soil, sand, gravel, or concrete as materials. Lime-soil, sand, gravel, and plain soil have poor compaction, making them prone to settlement after backfilling. While concrete (cement) offers slightly better compaction, its high material cost and significant environmental pollution necessitate a suitable trench backfilling method that is cost-effective, simple to implement, and achieves high backfill density. Therefore, there is an urgent need for a trench backfilling construction method that is low-cost, simple to implement, and produces high-density backfill. Summary of the Invention
[0004] In order to reduce the cost of backfilling trenches and improve the compactness of backfilling trenches, this application provides a trench backfilling construction method based on MICP technology.
[0005] Firstly, this application provides a trench backfilling construction method based on MICP technology, employing the following technical solution:
[0006] A trench backfilling construction method based on MICP technology includes the following steps:
[0007] Soil property determination: Determining the maximum dry density ρ of the soil. dmax With the optimum moisture content w;
[0008] Preparation of microbial slurries and cementing solutions;
[0009] Preparation of backfill soil: Add cementing liquid to the soil to obtain backfill soil;
[0010] Backfilling: Backfill the fertilizer trench with backfill soil to a depth of 300-400mm, then spray microbial slurry on the surface of the backfill soil. After the microbial slurry has penetrated to the bottom of the backfill soil, repeat the above fertilizer trench backfilling and microbial slurry spraying operations until the fertilizer trench is backfilled.
[0011] This application provides a construction method for fertilizer trench backfilling using Microbial Induced Mineralization (MICP) technology. This method utilizes calcium carbonate generated through a bio-induced mineralization reaction to fill the pores of the backfill soil, simultaneously promoting cementation between the calcium carbonate and soil particles, thereby effectively improving the compactness of the backfill soil. Compared with related fertilizer trench backfilling methods, the MIP-based fertilizer trench backfilling method provided in this application eliminates the need for manual or mechanical compaction during subsequent construction. Furthermore, the backfill material used is either lime-soil or plain soil, which is widely available, non-toxic, harmless, low-carbon, and environmentally friendly. Therefore, the construction method is low-cost, simple to operate, and pollution-free. Moreover, this method achieves self-filling of soil pores through microbial induced mineralization, resulting in high compactness and good construction quality of the fertilizer trench backfill.
[0012] MICP technology, or Microbial Induced Calcium Carbonate Deposition Technology, is applied to the backfilling process of fertilizer trenches. It utilizes urease produced by bacterial metabolism to decompose urea, thereby generating carbonate ions. These carbonate ions then combine with free metal cations (calcium ions) in the soil to form gel crystals, which are distributed and fill the pores of the soil, significantly improving the soil's self-compacting properties.
[0013] In this application, the soil includes, but is not limited to, one or more of plain soil, gray soil, or black soil.
[0014] Preferably, the cementing solution is prepared by mixing urea and calcium salt in a molar ratio of 1:(0.8-1.2) until homogeneous, and then mixing with water to obtain the cementing solution.
[0015] In one specific implementation, the molar ratio of urea to calcium salt is 1:1.
[0016] Preferably, the weight ratio of urea to water is (1-1.2):1.
[0017] Preferably, the calcium salt is selected from one or more of calcium chloride, calcium acetate, calcium nitrate, calcium sulfate, calcium silicate, and calcium gluconate.
[0018] In one specific implementation, the calcium salt is calcium chloride.
[0019] Preferably, in the step of preparing backfill soil, the amount of calcium salt added is calculated using the following formula:
[0020]
[0021] Where, λ c ρ is the compaction coefficient. dmax For maximum dry density, V 土体 M is the volume of the soil. 钙盐M is the molecular weight of the calcium salt; 碳酸钙 is the molecular weight of calcium carbonate.
[0022] In this application, the amount of calcium salt added is calculated based on the mixing volume of the backfill soil and the compaction coefficient to be achieved after backfilling. That is, the amount of calcium salt added depends on the properties of the soil itself (maximum dry density ρ). dmax That is, before preparing the backfill soil, the maximum dry density ρ of the soil must first be tested. dmax Then, combined with the required compaction coefficient λ for backfilling. c To calculate the amount of calcium salt to add.
[0023] According to Article 4.2.7 of the "Technical Specification for Building Pile Foundations" JGJ 94-2008, the gap between the foundation cap and the basement exterior wall and the foundation pit sidewall should be filled with plain concrete or mixed fluid cement-soil, or layered compacted plain soil composed of lime-soil, graded sand and gravel, and well-compacted soil, with a compaction coefficient λ. c It should not be less than 0.94.
[0024] In a specific implementation plan, the required compaction coefficient λ for backfilling is set. c It is 0.94.
[0025] Optionally, before preparing the backfill soil, the soil needs to be dried so that the moisture content w0 of the dried soil is less than 0.5%.
[0026] In this application, before the backfill soil is prepared, it is also necessary to test the actual moisture content and optimum moisture content of the soil. When the actual moisture content is greater than the optimum moisture content, the soil needs to be dried so that the moisture content w0 of the dried soil is as close as possible to 0%. The above operation is to ensure that the moisture content of the backfill soil can be at the optimum moisture content level after the subsequent microbial slurry is filled into the backfill soil.
[0027] The amount of microbial slurry added is calculated using the following formula:
[0028]
[0029] Where m0 is the mass of the dried soil, w0 is the moisture content of the dried soil, w is the optimum moisture content, and m1 is the mass of water in the cementitious solution.
[0030] In this application, the amount of microbial slurry required to be added to a certain mass of dried soil can be calculated using the above formula. The amount of microbial slurry added can ensure that the moisture content in the soil reaches the optimal moisture content level. Under the optimal moisture content, the backfill soil can reach the most compact state, thereby effectively preventing the backfill soil from settling.
[0031] Preferably, the concentration of Bacillus pasteurellium in the microbial slurry is (4-8)×10⁻⁶. 8The concentration of yeast powder is 3-5 g / L, and the concentration of sucrose is 2-5 g / L.
[0032] In summary, this application has the following beneficial effects:
[0033] 1. This application provides a construction method for backfilling fertilizer trenches based on MIP (Microbial Induction Mineralization) technology. This method uses lime-soil and plain soil as backfill materials. By adding urea, calcium salts, and microorganisms, a microbial-induced mineralization reaction is induced in the soil, resulting in calcium carbonate filling the pores of the backfill material, further improving the compactness of the backfill soil. The backfill materials used in this construction method are widely available, non-toxic, and harmless, thus the method is low-cost and environmentally friendly. Furthermore, this method achieves automatic filling of the pores in the backfill soil without the need for manual vibration or mechanical compaction, making the construction method simple and producing high-quality results.
[0034] 2. This application provides a method for calculating the amount of calcium salt and microbial slurry to be added. The amount of calcium salt and microbial slurry to be added obtained by this calculation method can ensure that the calcium salt and microbial slurry fully fill the backfill soil and make the backfill soil reach the optimal compaction state, effectively avoiding the settlement of the backfill soil.
[0035] 3. In this application, the moisture content of the backfill soil needs to be lower than the optimum moisture content of the soil, so as to ensure that the moisture content of the backfill soil can be at the optimum moisture content level after the subsequent microbial slurry is filled into the backfill soil. Attached Figure Description
[0036] Figure 1 This is a flowchart of the trench backfilling construction method based on MICP technology provided in this application. Detailed Implementation
[0037] A trench backfilling construction method based on MICP technology includes the following steps:
[0038] (1) Soil property determination: Select a suitable soil (lime soil or plain soil) and measure the maximum dry density ρ of the soil through a soil compaction test. dmax With the optimum moisture content w.
[0039] (2) Preparation of microbial slurry: Bacillus pasteurellii was suspended in water, and yeast powder and sucrose were added to obtain microbial slurry; the concentration of Bacillus pasteurellii was (4-8)×10 8 The concentration of yeast powder is 3-5 g / L, and the concentration of sucrose is 2-5 g / L.
[0040] (3) Preparation of cementing solution: Mix urea and calcium salt in a molar ratio of 1:1 until homogeneous, then add water and stir to obtain cementing solution. The calcium salt is selected from one or more of calcium chloride, calcium acetate, calcium nitrate, calcium sulfate, calcium silicate, and calcium gluconate. The weight ratio of urea to water is (1-1.2):1.
[0041] (4) Preparation of backfill soil: Dry the soil so that the moisture content w0 of the dried soil is about 2-5% lower than the optimum moisture content w; then add cement to the soil to obtain backfill soil;
[0042] The mass of calcium salts in the cementitious solution is calculated using the following formula:
[0043]
[0044] Where, λ c ρ is the compaction coefficient. dmax For maximum dry density, V 土体 M is the volume of the soil. 钙盐 M is the molecular weight of the calcium salt; 碳酸钙 is the molecular weight of calcium carbonate.
[0045] (5) Backfilling construction: Clean the fertilizer pit thoroughly to ensure that the pit is clean and free of debris; backfill the fertilizer pit with backfill soil to a depth of 300-400mm, and then spray microbial slurry on the surface of the backfill soil. After the microbial slurry has penetrated to the bottom of the backfill soil, about 1.5-2 hours later, continue to backfill the fertilizer pit and spray microbial slurry. Repeat the above operation until the fertilizer pit is backfilled.
[0046] The amount of microbial slurry added is calculated using the following formula:
[0047]
[0048] Where m0 is the mass of the dried soil, w0 is the moisture content of the dried soil, w is the optimum moisture content, and m1 is the mass of water in the cementitious solution.
[0049] In this application, *Pasteurella spp.* is *Pasteurella sporogenes*, with accession number ATCC11859; the other raw materials, reagents, solvents, etc., can all be obtained commercially.
[0050] The present application will be further described in detail below with reference to embodiments, performance testing tests and accompanying drawings.
[0051] Example
[0052] Example 1
[0053] Example 1 provides a trench backfilling construction method based on MICP technology, including the following steps:
[0054] (1) Soil property determination: Take 1m 3 The lime-soil, weighing 1314 kg, had its maximum dry density ρ determined through a soil compaction test. dmax 1400 kg / m 3 The optimum moisture content w is 17%.
[0055] (2) Preparation of microbial slurry: Bacillus pasteurellii was suspended in water, and yeast powder and sucrose were added to obtain microbial slurry; the concentration of Bacillus pasteurellii in the above microbial slurry was (4-8)×10 8 The concentration of yeast powder is 3-5 g / L, and the concentration of sucrose is 2-5 g / L.
[0056] (3) Preparation of cementing solution: λ c With a compaction coefficient of 0.94, the amount of calcium chloride to be added is calculated to be 173.16 kg using the formula for the amount of calcium salt to be added, and the amount of urea to be added is 93.69 kg. The urea and calcium chloride are mixed evenly, and then 100 kg of water is added and mixed evenly.
[0057] (4) Preparation of backfill soil: Dry the lime soil. After testing, the mass of the dried lime soil is 1265 kg and the moisture content is 0.2%. Then add the cementing liquid obtained in step (2) to the dried lime soil to obtain backfill soil.
[0058] (5) Backfilling: Clean the fertilizer pit thoroughly, ensuring it is free of debris; backfill the fertilizer pit with backfill soil to a depth of 300-400mm, then spray microbial slurry onto the surface of the backfill soil (the spraying rate of microbial slurry is 112.1kg / m³). 3 (Calculate the amount of "ash soil"). After the microbial slurry has penetrated to the bottom of the backfill soil, about 1.5 hours later, continue backfilling the fertilizer trench and spraying microbial slurry. Repeat the above operation until the fertilizer trench is backfilled.
[0059] Performance testing
[0060] Twelve hours after backfilling the trench, the compaction coefficient and moisture content of the backfill soil were tested using the ring cutter test method in JTG 3450—2019 "Specifications for Field Testing of Highway Subgrade and Pavement" T 0923-2019.
[0061] Testing revealed that the compaction coefficient of the backfill soil in the fertilizer trench of Example 1 was 0.95, and the moisture content was 17.1%, which were consistent with the expected compaction coefficient and moisture content.
[0062] Example 2
[0063] Example 2 provides a trench backfilling construction method based on MICP technology, including the following steps:
[0064] (1) Soil property determination: Take 1m 3 The raw soil, weighing 1448 kg, had its maximum dry density ρ determined through a soil compaction test. dmax 1500 kg / m 3 The optimum moisture content w is 16%.
[0065] (2) Preparation of microbial slurry: Bacillus pasteurellii was suspended in water, and yeast powder and sucrose were added to obtain microbial slurry; the concentration of Bacillus pasteurellii in the above microbial slurry was (4-8)×10 8 The concentration of yeast powder is 3-5 g / L, and the concentration of sucrose is 2-5 g / L.
[0066] (3) Preparation of cementing solution: λ c With a compaction coefficient of 0.94, the amount of calcium chloride to be added is calculated to be 277.5 kg using the formula for the amount of calcium salt to be added, and the amount of urea to be added is 150.15 kg. The urea and calcium chloride are mixed evenly, and then 155 kg of water is added and mixed evenly.
[0067] (4) Preparation of backfill soil: Dry the plain soil. After testing, the mass of the dried plain soil is 1432 kg and the moisture content is 0.1%. Then add the cementing liquid obtained in step (2) to the dried plain soil to obtain backfill soil.
[0068] (5) Backfilling: Clean the fertilizer pit thoroughly, ensuring it is free of debris; backfill the fertilizer pit to a depth of 300-400mm using backfill soil, and then spray microbial slurry onto the surface of the backfill soil (the spraying rate of microbial slurry is 72.46kg / m³). 3 (Calculate the amount of "plain soil"). After the microbial slurry has penetrated to the bottom of the backfill soil, about 2 hours later, continue backfilling the fertilizer trench and spraying microbial slurry. Repeat the above operation until the fertilizer trench is backfilled.
[0069] Performance testing
[0070] Twelve hours after backfilling the trench, the compaction coefficient and moisture content of the backfill soil were tested using the ring cutter test method in JTG 3450—2019 "Specifications for Field Testing of Highway Subgrade and Pavement" T 0923-2019.
[0071] Testing revealed that the compaction coefficient of the backfill soil in the fertilizer trench of Example 2 was 0.96, and the moisture content was 16.2%, which were consistent with the expected compaction coefficient and moisture content.
[0072] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.
Claims
1. A trench backfilling construction method based on MICP technology, characterized in that, Includes the following steps: Soil property determination: Determining the maximum dry density of the soil. With optimum moisture content ; Preparation of microbial slurries and cementing solutions; Preparation of backfill soil: Add cementing solution to the soil to obtain backfill soil; The cementing solution is prepared by mixing urea and calcium salt in a molar ratio of 1:(0.8-1.2) until homogeneous, and then mixing with water to obtain cementing solution; The amount of calcium salt added is calculated using the following formula: in, This refers to the amount of calcium salt added. This is the compaction coefficient. The maximum dry density of the soil. For the volume of the soil, The molecular weight of the calcium salt; This represents the molecular weight of calcium carbonate. Backfilling: Backfill the fertilizer trench with backfill soil to a depth of 300-400mm, then spray microbial slurry on the surface of the backfill soil. After the microbial slurry has penetrated to the bottom of the backfill soil, repeat the above fertilizer trench backfilling and microbial slurry spraying operations until the fertilizer trench is backfilled.
2. The trench backfilling construction method based on MICP technology according to claim 1, characterized in that, The weight ratio of urea to water is (1-1.2):
1.
3. The trench backfilling construction method based on MICP technology according to claim 1, characterized in that, The calcium salt is selected from one or more of calcium chloride, calcium acetate, calcium nitrate, calcium sulfate, calcium silicate, and calcium gluconate.
4. The trench backfilling construction method based on MICP technology according to claim 1, characterized in that, Before preparing the backfill soil, the soil needs to be dried to reduce its moisture content. Less than 0.5%.
5. The trench backfilling construction method based on MICP technology according to claim 4, characterized in that, The amount of microbial slurry added is calculated using the following formula: in, This refers to the amount of microbial slurry added. To ensure the quality of the dried soil, This refers to the moisture content of the dried soil. This represents the optimum moisture content of the soil. This represents the mass of water in the cementitious solution.
6. The trench backfilling construction method based on MICP technology according to any one of claims 1-5, characterized in that, The concentration of Bacillus pasteurellium in the microbial slurry was (4-8) × 10⁻⁶. 8 The concentration of yeast powder is 3-5 g / L, and the concentration of sucrose is 2-5 g / L.