Construction method for reinforcing soil body through microorganisms

Abstract

The invention provides a construction method for reinforcing a soil body through microorganisms. The construction method comprises the following steps that the soil body is paved layer by layer; measuring the natural moisture content and the optimal moisture content of the soil body; obtaining a soil body permeability coefficient, and determining the infiltration speed and required time of the moisture and the microorganism slurry in the soil body according to the soil body permeability coefficient; according to the difference value of the natural moisture content and the optimal moisture content of the soil body and the total amount of the soil body, the total amount of moisture needing to be supplemented for achieving the optimal moisture content of the soil body is calculated; determining the water required to be supplemented for averagely distributing each layer of soil body and the spraying times of the microorganism slurry required by each layer of soil body; according to the permeability coefficient of the soil body, calculating the infiltration time of the microorganism slurry per unit hydraulic gradient in the soil body; after permeation of the microorganism slurry is completed, the soil body is rolled, the compaction degree of the soil body is detected, and then a water filling test and a cutting ring test are conducted on the soil body; after it is detected that the design requirement is met, the next layer of soil body is paved; and repeating the steps until the soil body reaches the designed elevation and size.

Description

Technical Field

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

[0002] Fill refers to the irregular and disordered accumulation formed by filling in the process of human engineering and production activities. In construction projects, fill is located at the top of the stratum, or serves as the foundation bearing layer of new buildings (structures), or as the slope structure and load of the foundation pit slope. Fill has its own particularity in engineering sense due to its special cause, such as common unevenness, underconsolidation, and collapsibility, which are all characteristics that are not conducive to engineering safety. Therefore, on the basis of a full investigation and understanding of the characteristics of fill, a targeted and reasonable utilization and treatment plan can be proposed to turn this "useless" abandoned fill site into a useful place, which can not only save land resources, but also protect surrounding buildings (structures) and improve 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 a new 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 is mixed with the reaction liquid, 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 produce 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 biological processes in nature.

[0004] However, when the existing microbial slurry is used to reinforce the 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, the construction period and the economic efficiency of the project. 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] In order 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, and take the soil moisture content corresponding to the maximum compaction density as the optimal moisture content;

[0009] Step 3: Obtain the soil permeability coefficient, and determine the infiltration speed and time required for water and microbial slurry in 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 amount of water required to be evenly distributed on each soil layer according to the number of soil layers and area, and then determine the number of times the microbial slurry is sprayed on each soil layer according to the watering tonnage of the sprinkler truck, and use the microbial slurry to replenish moisture and solidify the soil;

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

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

[0014] Step 8. Repeat steps 5-7 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 Among them, m w To test the quality of water in the soil, m s To test the quality of the soil after drying.

[0017] Furthermore, in step 3, the soil permeability coefficient Where: 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 Among them, m 土 The soil quality.

[0019] Further, in step 5, the number of spraying times Among them, n 土 is the number of soil paving layers, The soil spreading area is s 土 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, L 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 watering 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, so as to reinforce 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 supplemented 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 upper and lower tanks are arranged for the sprinkler truck. 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. According to the 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 make the soil 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 desired 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 an experiment for obtaining soil permeability coefficient in the present invention.

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

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

[0031] Those skilled in the art should understand that, in the disclosure of the present invention, the orientation or position relationship indicated by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientation or position relationship shown in the 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 element 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 tests and use the drying method to test the natural moisture content of the soil A compaction test was carried out to obtain the curve of soil density changing with water content, and the water content corresponding to the maximum compaction density was taken as the optimal water content ω2. In the formula, ω1 is the water content; M w To test the mass of water in the soil (i.e. the difference between the mass of natural soil and the mass of dry soil); m s To test the mass of soil particles after soil drying (i.e. dry soil mass, the remaining mass after natural soil is dried 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 taken according to different soil bodies; 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 speed and time required for subsequent microbial slurry infiltration, providing a reference for the sprinkler operation time;

[0040] Step 4: Calculate the total amount of water required to make the soil reach 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. In the formula, m 水 The amount of water required to replenish the soil to achieve the optimal moisture content, m 土 The total amount of water at this time is the total amount of water contained in the microbial slurry to be sprayed by an ordinary sprinkler truck. The soil is replenished with water by spraying microbial slurry by a sprinkler truck, so that the soil reaches the optimal moisture content, which is conducive to compaction. At the same time, it can also suppress dust and purify 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, the microbial solution uses Sporosarcina pasteurii.

[0043] Step 5: According to the number of layers n of soil paving 土 and area s 土 , determine the average distribution of water required for 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 In the formula, The soil area is s 土 The water truck sprays the soil with water once, and the microbial slurry replenishes moisture and solidifies the soil. The benefits of spraying microbial slurry at this time are: ① replenishing moisture so that the soil reaches the optimal moisture content, which is conducive to rolling and compacting; ② the microorganisms and ions in the microbial slurry generate calcium carbonate solids to strengthen the soil; ③ it can suppress dust and purify 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 It is the permeability coefficient of soil to microbial slurry. Since the soil has not been compacted at this time, the permeability coefficient is relatively large, so the infiltration rate of microbial slurry is relatively fast.

[0045] Step 7: After the microbial slurry has completely penetrated, use a roller to roll the soil. According to the provisions of the Highway Roadbed Design Specification (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 depth is 1 / 2 of the compacted layer thickness. The detection frequency is: every 500m of each compacted layer 2 At least 3 measuring points. At the same time, the soil after rolling is sampled and sent to the geotechnical laboratory for testing. If the compaction degree and mechanical indicators do not meet the design requirements, the next process cannot be carried out; if the requirements are met, the next layer of soil can be spread, otherwise the rolling will continue until the requirements of the specification are met. Through the vibration rolling of the soil, the microbial slurry is more fully integrated with the soil, so that the reinforcement is more uniform and the effect is more significant.

[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 watering 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, Vq微生物浆液 is the spraying speed of the microbial slurry by the sprinkler truck, L It is the construction length for spraying microbial slurry. It ensures that the microbial slurry is sprayed evenly to facilitate compaction.

[0048] It is worth mentioning that when spraying the microbial slurry through a sprinkler truck, this scheme uses a double-tank 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 various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope 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, and take the soil moisture content corresponding to the maximum compaction density as the optimal moisture content; Step 3: Obtain the soil permeability coefficient, and determine the infiltration speed and time required for water and microbial slurry in the soil through the soil permeability coefficient; 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 amount of water required to be evenly distributed on each soil layer according to the number of soil layers and area, and then determine the number of times the microbial slurry is sprayed on each soil layer according to the watering tonnage of the sprinkler truck, and use the microbial slurry to replenish moisture and solidify the soil; Step 6: Calculate the infiltration time of the microbial slurry in the soil per unit hydraulic gradient according to the soil permeability coefficient; Step 7: After the microbial slurry infiltration is completed, the soil is rolled and the soil compaction degree is tested to ensure that the soil compaction degree is greater than or equal to 94%. Then, the soil is subjected to water filling test and ring knife test. The soil after rolling is sampled and tested. After the test meets the design requirements, the next layer of soil is spread. Step 8. Repeat steps 5-7 until the soil reaches the designed elevation and size.

2. The construction method of microbial soil reinforcement according to claim 1, characterized in that: The microbial slurry comprises 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.

3. The construction method of microbial soil reinforcement according to claim 1, characterized in that: In step 2, the natural moisture content of the soil Among them, m w To test the quality of water in the soil, m s To test the quality of the soil after drying.

4. The construction method of microbial soil reinforcement according to claim 1 is characterized in that: In step 3, the soil permeability coefficient Where: 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.

5. The construction method of microbial soil reinforcement according to claim 1, characterized in that: In step 4, the total amount of water that needs to be added to the soil Among them, m 土 The soil quality.

6. The construction method of microbial soil reinforcement according to claim 1, characterized in that: In step 5, spray the Among them, n 土 is the number of soil paving layers, The soil spreading area is s 土 The amount of water used by a sprinkler truck to spray the soil once.

7. The construction method of microbial soil reinforcement according to claim 1, characterized in that: 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.

8. The construction method of 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 speed of the sprinkler truck, L is the construction length of the microbial slurry spraying, V q微生物浆液 The spraying speed of the microbial slurry sprayed by the sprinkler truck.

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