A construction method for microbial soil reinforcement

Abstract

The present invention provides a construction method for microbial soil reinforcement, comprising the following steps: spreading soil layer by layer; measuring the natural moisture content and optimal moisture content of the soil; obtaining the soil permeability coefficient, and determining the speed and required time for water and microbial slurry to penetrate into the soil through the soil permeability coefficient; calculating the total amount of water required to be replenished for the soil to reach the optimal moisture content based on the difference between the natural moisture content and the optimal moisture content of the soil and the total amount of soil; determining the amount of water required to be replenished and the number of times the microbial slurry is sprayed on each soil layer; calculating the infiltration time of the microbial slurry in the soil per unit hydraulic gradient based on the soil permeability coefficient; after the microbial slurry has penetrated, rolling the soil and detecting the soil compaction degree, and then performing a water filling test and a ring knife test on the soil; after the detection shows that the design requirements are met, spreading the next layer of soil; and repeating the steps until the soil reaches the designed elevation and size.

Description

Technical Field

[0001] The present invention relates to the field of soil reinforcement construction, in particular to a construction method for microbial soil reinforcement. Background Art

[0002] Fill refers to the irregular, disordered accumulation formed during human engineering and production activities. In construction, fill sits atop the ground, serving as the bearing layer for new buildings or structures, or as the slope structure and load for foundation pit slopes. Due to its unique origin, fill has its own engineering characteristics, such as common unevenness, underconsolidation, and collapsibility, all of which are detrimental to engineering safety. Therefore, by thoroughly investigating and understanding fill characteristics and developing targeted, rational utilization and treatment plans, these "useless" abandoned fill sites can be transformed into useful land, conserving land resources, protecting surrounding buildings, and improving the regional environment.

[0003] In the existing construction process, chemical or biological solidification methods, such as microbial calcium carbonate deposition technology, are often used to reinforce the fill to improve the physical and mechanical properties of the fill. Microbial calcium carbonate deposition technology is the latest technology that uses microbial metabolic processes to reinforce soil. It sprays or injects a microbial slurry composed of a microbial solution and a reaction liquid into the soil to be reinforced, wherein the microbial solution is one or more of urea-hydrolyzing bacteria and urease-producing bacteria, and the reaction liquid is a mixture of calcium chloride and urea. After the microbial solution and the reaction liquid are mixed, the urease released by the microorganisms hydrolyzes the urea in the reaction liquid to produce ammonium carbonate, and then the ammonium carbonate reacts with the calcium chloride in the reaction liquid to form a calcium carbonate cementing material, which combines the originally loose soil particles together, improves the strength of the soil, reduces soil deformation, and reduces the permeability of the soil. This method is green and environmentally friendly and can produce solidified substances through natural biological processes.

[0004] However, when using existing microbial slurries to reinforce fill, it is difficult to accurately control the spraying of the microbial slurry on the fill, resulting in excessive or insufficient spraying of the microbial slurry, which affects the reinforcement effect of the fill, construction period and engineering economy. Summary of the Invention

[0005] The purpose of the present invention is to provide a construction method for microbial reinforcement of soil that solves the above technical problems.

[0006] To solve the above technical problems, the present invention provides a construction method for microbial soil reinforcement, comprising the following steps:

[0007] Step 1: Spread the soil layer by layer;

[0008] Step 2: Take soil samples for geotechnical testing to measure the natural moisture content of the soil, and perform compaction tests to obtain a curve of soil density versus soil moisture content. The soil moisture content corresponding to the maximum compaction density is taken as the optimal moisture content.

[0009] Step 3: Obtain the soil permeability coefficient, and determine the rate and time required for water and microbial slurry to penetrate the soil through the soil permeability coefficient;

[0010] Step 4: Calculate the total amount of water required to achieve the optimal moisture content of the soil based on the difference between the natural moisture content of the soil and the optimal moisture content and the total amount of soil.

[0011] Step 5: Determine the average amount of water required to replenish each soil layer based on the number and area of soil paving. Then, determine the number of times the microbial slurry is sprayed on each soil layer based on the watering capacity of the sprinkler truck. The soil is then replenished with water and solidified with the microbial slurry.

[0012] Step 6: Calculate the infiltration time of the microbial slurry in the soil per unit hydraulic gradient based on the soil permeability coefficient;

[0013] Step 7: After the microbial slurry is infiltrated, the soil is rolled and the soil compaction is tested to ensure that the soil compaction is greater than or equal to 94%. The soil is then subjected to a water injection test and a ring knife test. The soil after rolling is sampled and tested. If the test meets the design requirements, the next layer of soil is spread.

[0014] Step 8. Repeat steps 5 to 7 until the soil reaches the designed elevation and size.

[0015] Furthermore, the microbial slurry includes a microbial solution and a reaction solution, wherein the microbial solution is one or more of urea-hydrolyzing bacteria and urease-producing bacteria, and the reaction solution is a mixture of calcium chloride and urea.

[0016] Furthermore, in step 2, the natural moisture content of the soil ;in, To test the quality of water in the soil, To test the quality of the soil after drying.

[0017] Furthermore, in step 3, the soil permeability coefficient ; Among them: Q Z is the injection flow of the inner ring, F is the bottom area of the inner ring, H is the test water head, Ha is the capillary rise height of the test soil layer, and z is the penetration depth from the bottom of the test pit.

[0018] Furthermore, in step 4, the total amount of water required to be added to the soil ;in, The soil quality.

[0019] Furthermore, in step 5, the number of spraying times ;in, The number of soil paving layers, The soil paving area is The amount of water used by a sprinkler truck to spray the soil once.

[0020] Furthermore, in step 7, the infiltration time t of the microbial slurry in the soil per unit hydraulic gradient is 渗 =Q s微生物浆液 / k 微生物浆液 Among them, Q s微生物浆液 is the amount of microorganism sprayed, k 微生物浆液 is the permeability coefficient of soil to microbial slurry.

[0021] Furthermore, when the sprinkler truck sprays the microbial slurry, the spraying speed of the sprinkler truck is calculated according to the driving speed of the sprinkler truck so that V 车 =L×V q微生物浆液 / Q s微生物浆液 ; Among them, V 车 is the driving speed of the sprinkler truck, is the construction length for spraying microbial slurry, V q微生物浆液 The spraying speed of the microbial slurry sprayed by the sprinkler truck.

[0022] The beneficial effects of the present invention are:

[0023] 1. Spray the microbial slurry with a sprinkler truck so that the water in the microbial slurry can provide the soil with an optimal moisture content, which is conducive to compaction. At the same time, the microorganisms and ions in the microbial slurry promote the formation of calcium carbonate solids in the soil, thereby reinforcing the soil. The spraying of microbial slurry can also suppress dust and avoid splashing and dust.

[0024] 2. By calculating the soil permeability coefficient, the total amount of water required to be replenished in the soil, the infiltration time, etc., the spraying amount and speed of the microbial slurry can be accurately controlled;

[0025] 3. By controlling the driving speed of the sprinkler truck, the optimal spraying speed of the sprinkler truck is calculated in real time to ensure uniform spraying of the microbial slurry, thereby accurately controlling the operation time and optimizing the use of the slurry;

[0026] 4. The sprinkler truck adopts the scheme of upper and lower tank arrangement. When the solutions in the upper and lower tanks are sprayed in any proportion, the center of gravity of the liquid storage tank can be centered, ensuring the stability of the vehicle body and ensuring the safe driving of the sprinkler truck in loose fillers.

[0027] 5. Based on the amount of water required for the soil to reach the optimal moisture content and the mass of calcium carbonate solids required to reinforce the soil, prepare microbial solutions and reaction liquids of corresponding concentrations so that the water in the sprayed microbial solutions and reaction liquids can just allow the soil to reach the optimal moisture content. At the same time, the calcium carbonate solids generated after the reaction of the microbial solution and the reaction liquid can just achieve the required reinforcement effect on the soil, without wasting water resources and raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the test for obtaining the soil permeability coefficient in the present invention.

[0029] Figure 2 It is a loading schematic diagram of the sprinkler truck of the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0031] It should be understood by those skilled in the art that, in the disclosure of the present invention, the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0032] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the elements may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0033] like Figure 1-Figure 2 The present invention provides a construction method for microbial soil reinforcement, comprising the following construction steps:

[0034] Step 1: Spread the soil layer by layer, with each layer being 50 to 100 cm thick;

[0035] Step 2: Take samples for indoor geotechnical testing and use the drying method to test the natural moisture content of the soil , and conduct compaction tests to obtain the curve of soil density changing with moisture content, and take the moisture content corresponding to the maximum compaction density as the optimal moisture content Where, 1 is the moisture content; To test the mass of water in the soil (that is, the difference between the mass of natural soil and the mass of dry soil); To test the mass of soil particles after drying (also known as dry soil mass, which is the remaining mass after drying natural soil in an oven);

[0036] Step 3: Conduct an in-situ permeability test using the double-ring method to obtain the soil permeability coefficient:

[0037]

[0038] Where: K is the permeability coefficient of the test soil layer, cm / s; Q Z is the injection flow rate of the inner ring, L / min, and the evaporation water volume should be deducted under dry and hot conditions; F is the bottom area of the inner ring, cm2; H is the test water head, cm; Ha is the capillary rise height of the test soil layer, cm, and the empirical value can be obtained according to different soil types; z is the penetration depth from the bottom of the test pit, cm;

[0039] The permeability coefficient of the soil is used to determine the subsequent infiltration speed and time of microbial slurry, providing a reference for the operation time of the sprinkler truck;

[0040] Step 4: Calculate the total amount of water required to achieve the optimal moisture content based on the difference between the natural moisture content of the soil and the optimal moisture content and the total amount of soil. Where, The amount of water needed to replenish the soil to achieve the optimal moisture content. The total amount of water at this point is the same as the total amount of water contained in the microbial slurry that a regular sprinkler truck would spray. Spraying the microbial slurry with a sprinkler truck replenishes moisture in the soil, allowing it to reach its optimal moisture content, facilitating compaction. This also suppresses dust and purifies the construction site environment.

[0041] Among them, the microbial slurry includes a microbial solution and a reaction liquid, wherein the microbial solution is one or more of urea-hydrolyzing bacteria and urease-producing bacteria, and the reaction liquid is a mixture of calcium chloride and urea; and both the microbial solution and the reaction liquid contain water, so the soil can be replenished with water by spraying the microbial slurry until the optimal moisture content is reached, and since the microbial solution and the reaction liquid can be selected and proportioned as needed, the moisture content contained therein can be accurately detected to ensure the accuracy of the soil moisture content replenishment process.

[0042] In one embodiment of the present solution, Sporosarcina pasteurii is used in the microbial solution.

[0043] Step 5: According to the number of layers of soil paving and area , determine the average distribution of water required to replenish each layer of soil, and then determine the number of times the microbial slurry is sprayed on each layer of soil according to the tonnage of the sprinkler truck Where, The soil area is During construction, a water truck sprays the soil with water, and the microbial slurry replenishes moisture and solidifies the soil. The benefits of spraying the microbial slurry at this time include: ① replenishing moisture, bringing the soil to an optimal moisture content, facilitating compaction; ② the microorganisms and ions in the microbial slurry form calcium carbonate solids, which strengthen the soil; and ③ suppressing dust and purifying the construction site environment.

[0044] Step 6: Based on the soil permeability coefficient obtained from the in-situ permeability test, estimate the infiltration time t of the microbial slurry in the soil per unit hydraulic gradient. 渗 =Q s微生物浆液 / k 微生物浆液 , where Q s微生物浆液 is the amount of microbial slurry sprayed, k 微生物浆液 is the permeability coefficient of soil to microbial slurry. Since the soil has not been compacted at this time, the permeability coefficient is large, so the infiltration speed of microbial slurry is relatively fast.

[0045] Step 7: After the microbial slurry has completely penetrated, use a roller to compact the soil. According to the provisions of the "Highway Roadbed Design Code" (JTG D30), the soil compaction degree (that is, the ratio of the dry density of the soil after compaction to the standard maximum dry density, expressed as a percentage) is tested. The compaction degree is greater than or equal to 94%. When using the water injection test, the soil sample is taken at the bottom of each layer. When using the ring knife test, the sample is taken at a depth of 1 / 2 the thickness of the compacted layer. The testing frequency is: every 500m of each compacted layer. 2 At least three measuring points should be used. Samples of the compacted soil should also be taken and sent to a geotechnical laboratory for testing. If the compaction and mechanical properties do not meet the design requirements, the next construction process cannot be carried out. If they do, the next layer of soil can be spread. Otherwise, compaction will continue until the specifications are met. Vibratory compaction of the soil allows the microbial slurry to more fully blend with the soil, resulting in more uniform reinforcement and a more effective effect.

[0046] Step 8. Repeat steps 5 to 7 until the fill reaches the designed elevation and size.

[0047] When the microbial slurry is sprayed by a sprinkler truck, the spraying speed V of the microbial slurry is controlled according to the driving speed. 车 =L×V q微生物浆液 / Q s微生物浆液 , where V 车 is the driving speed of the sprinkler truck, V q微生物浆液 is the spraying speed of the microbial slurry by the sprinkler truck, The construction length for spraying microbial slurry. Ensure that the microbial slurry is sprayed evenly to facilitate compaction.

[0048] It is worth mentioning that this solution uses a double-tank sprinkler truck when spraying the microbial slurry through a sprinkler truck, one tank is used to load the microbial solution and the other tank is used to load the reaction liquid, so that the microbial solution and the reaction liquid can be sprayed synchronously through the sprinkler truck at the same time.

[0049] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, any technical solution that is the same or similar to that of the present application falls within the scope of protection of the present invention.

Claims

1. A construction method for microbial soil reinforcement, characterized in that: The following steps are involved: Step 1: Spread the soil layer by layer; Step 2: Take soil samples for geotechnical testing to measure the natural moisture content of the soil, and perform compaction tests to obtain a curve of soil density versus soil moisture content. The soil moisture content corresponding to the maximum compaction density is taken as the optimal moisture content. Step 3: Obtain the soil permeability coefficient, and determine the rate and time required for water and microbial slurry to penetrate the soil through the soil permeability coefficient; In step 3, the soil permeability coefficient ; Among them: Q Z is the injection flow rate of the inner ring, F is the bottom area of the inner ring, H is the test water head, Ha is the capillary rise height of the test soil layer, and z is the penetration depth from the bottom of the test pit; Step 4: Calculate the total amount of water required to achieve the optimal moisture content of the soil based on the difference between the natural moisture content of the soil and the optimal moisture content and the total amount of soil. Step 5: Determine the average amount of water required to replenish each soil layer based on the number and area of soil paving. Then, determine the number of times the microbial slurry is sprayed on each soil layer based on the watering capacity of the sprinkler truck. The soil is then replenished with water and solidified with the microbial slurry. In step 5, spray the number of times ;in, The number of soil paving layers, The soil paving area is The amount of water used by the sprinkler truck to spray the soil once; The microbial slurry includes a microbial solution and a reaction solution, wherein the microbial solution is one or more of urea-hydrolyzing bacteria and urease-producing bacteria, and the reaction solution is a mixture of calcium chloride and urea; Step 6: Calculate the infiltration time of the microbial slurry in the soil per unit hydraulic gradient based on the soil permeability coefficient; In step 6, the infiltration time t of the microbial slurry in the soil per unit hydraulic gradient is 渗 =Q s微生物浆液 / k 微生物浆液 Among them, Q s微生物浆液 is the amount of microorganism sprayed, k 微生物浆液 is the permeability coefficient of soil to microbial slurry; Step 7: After the microbial slurry is infiltrated, the soil is rolled and the soil compaction is tested to ensure that the soil compaction is greater than or equal to 94%. The soil is then subjected to a water injection test and a ring knife test. The soil after rolling is sampled and tested. If the test meets the design requirements, the next layer of soil is spread. Step 8. Repeat steps 5 to 7 until the soil reaches the designed elevation and size.

2. The construction method for microbial soil reinforcement according to claim 1, characterized in that: In step 2, the natural moisture content of the soil ;in, To test the quality of water in the soil, To test the quality of soil after drying.

3. The construction method for microbial soil reinforcement according to claim 1, characterized in that: In step 4, the total amount of water required to replenish the soil ;in, is the soil mass, 1 is the moisture content, The optimal moisture content.

4. The construction method for microbial soil reinforcement according to claim 1, characterized in that: When the sprinkler truck is spraying the microbial slurry, the spraying speed of the sprinkler truck is calculated according to the driving speed of the sprinkler truck so that V 车 =L×V q微生物浆液 / Q s微生物浆液 ; Among them, V 车 is the driving speed of the sprinkler truck, is the construction length for spraying microbial slurry, V q微生物浆液 The spraying speed of the microbial slurry sprayed by the sprinkler truck.

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