Simple method for evaluating microorganism induced solidification effect based on sedimentation rate

Abstract

The invention belongs to the technical field of biological solidification and microbial geotechnical engineering evaluation, and particularly relates to a simple method for evaluating a microbial induced solidification effect based on a sedimentation rate, and the evaluation method comprises the following steps: S1, microbial culture; comprising an improved calcium carbonate mineralization culture medium; s2, carrying out a biological curing experiment; comprising the steps of solidification experiment design, preparation of to-be-tested matrix flowing solidified soil and preparation of a to-be-tested matrix flowing solidified soil sample. S3, performing unconfined compressive strength experiment; and S4, data analysis. The preparation method of the improved calcium carbonate mineralization culture medium comprises the following steps: S11, preparing the culture medium from 20g / L of yeast extract powder, 10g / L of ammonium chloride, 10mg / L of manganese sulfate monohydrate and 24mg / L of nickel chloride hexahydrate; according to the method, the unconfined compressive strength after biological curing can be quickly and accurately predicted and evaluated by measuring a relatively simple and convenient index, namely the settling volume of the test substrates such as sludge and coal-based solid waste, so that the curing effect is reflected.

Description

Technical Field

[0001] The present invention belongs to the technical field of biosolidification and microbial geotechnical engineering evaluation, and particularly relates to a simple method for evaluating the effect of microbial-induced solidification based on sedimentation rate. Background Art

[0002] At present, the evaluation methods of curing effect mainly include leaching test and physical evaluation method. Leaching test is mainly used to evaluate the leaching of harmful substances in the cured / stabilized products, but there are differences in the evaluation methods in different countries and regions. For example, China’s leaching test methods are mainly sulfuric acid and nitric acid method, pure water leaching method, etc., while the United States, the European Union and Japan also have their own leaching toxicity evaluation standards. Physical evaluation methods are mainly used to evaluate the physical properties of cured products, such as unconfined compressive strength test and permeability test. The commonly used unconfined compressive strength test needs to be carried out in accordance with the "Standard for Geotechnical Test Methods"

[0003] (GB / T50123-1999) and has strict regulations on the size of the sample, sampling method, etc.

[0004] However, these traditional methods also have some shortcomings. First, leaching tests typically require complex equipment and reagents, and the procedures are cumbersome and time-consuming. Second, the unconfined compressive strength test, a physical evaluation method, requires specialized testing equipment and strict sample preparation and testing conditions, making it difficult to quickly and conveniently evaluate the curing effect on-site. Summary of the Invention

[0005] The purpose of the present invention is to provide a simple method for evaluating the effect of microbial-induced solidification based on sedimentation rate. By measuring the sedimentation amount of test matrices such as silt and coal-based solid waste, which is a relatively simple indicator, the unconfined compressive strength after biosolidification can be quickly and accurately predicted and evaluated, thereby reflecting the solidification effect.

[0006] The technical solutions adopted by the present invention are as follows:

[0007] A simple method for evaluating the effect of microbial-induced solidification based on sedimentation rate, the evaluation method comprises the following steps:

[0008] S1: microbial culture;

[0009] Includes modified calcium carbonate mineralization medium;

[0010] In S1, the steps for preparing the improved calcium carbonate mineralization medium are as follows:

[0011] S11: The culture medium formula includes: yeast extract powder 20g / L, ammonium chloride 10g / L, manganese sulfate monohydrate 10mg / L, nickel chloride hexahydrate 24mg / L;

[0012] S12: The pH value was adjusted with 1 mol / L HCl and NaOH.

[0013] S13: The above culture medium was dissolved in 1000 mL of deionized water and the pH was adjusted to 7.3-7.4;

[0014] S14: Sterilization conditions are 121°C, 20 min;

[0015] S15: After sterilization, add 100 mL of 20% urea solution using a bacteria filter;

[0016] S16: Add 1.8-2% agar powder to the solid culture medium.

[0017] The culture medium conditions include the following:

[0018] Open the clean bench and start the expansion culture operation 20 minutes later;

[0019] Pipette 1 mL of the successfully activated Bacillus pasteurianus liquid from the test tube, inject it into a conical flask containing 100 mL of microbial mineralization medium, and seal it with a sealing film;

[0020] After the bacterial solution and the culture medium are evenly mixed, they are placed in a shaker at 30°C and 150 rpm for 24 h;

[0021] The culture medium is turbid if the expansion is successful, with OD600 around 1.0.

[0022] S2: Biosolidification Experiment;

[0023] It includes the design of solidification experiment, preparation of test matrix flowable solidified soil and preparation of test matrix flowable solidified soil specimens;

[0024] In S2, the solidification experiment used the mass ratio of coal gangue, fly ash, desulfurized gypsum, coal slime, and silt solid waste as the independent variable, and the fixed amount of solid waste after reaction with excess bacterial solution as the dependent variable. Different combinations of the mass ratio of solid waste were performed, and a total of 15 experimental combination designs were designed.

[0025] In S2, the preparation steps of the test matrix flowable solidified soil are as follows:

[0026] S211: Silt and solid waste are weighed in advance using an electronic balance according to the proportions, and placed in a plastic ziplock bag and shaken thoroughly to make the ingredients uniform;

[0027] S212: Add 150 mL of the prepared 24-hour cultured Bacillus pasteurianus bacterial solution, thoroughly mix the test substrate and the Bacillus pasteurianus bacterial solution, and stir to ensure that the water content of the sample preparation is between 45% and 55%;

[0028] The Bacillus pasteurian bacterial solution was a Bacillus pasteurian bacterial solution OD600=1.0;

[0029] The ratio of sludge to Bacillus pasteurianus liquid is 2:1.

[0030] S213: When the test matrix solidified soil is stirred to a completely fluid state, the test matrix fluid solidified soil is prepared.

[0031] In S2, the preparation steps of the test matrix flowable solidified soil sample are as follows:

[0032] S221: The curing mold is a cylinder of plastic material with an inner diameter of 50mm and a height of 100mm. Before sample preparation begins, a label is attached to the mold.

[0033] S222: Since the test matrix solidified soil settles during the solidification process, the test block height is less than 100 mm after demolding. Therefore, a circle of tape is wrapped around the top of the mold to increase the mold height to a certain extent, and vaseline is evenly applied to the bottom and inner wall of the mold.

[0034] S223: Slowly pour the stirred test matrix flowable solidified soil into the mold and stop when it exceeds 1 cm from the top of the mold. No vibration is required during the pouring process.

[0035] S224: After sample preparation is completed, cover the top of the cast test block with plastic wrap and place it at room temperature for curing;

[0036] S225: After 7 days, the specimen was removed and the upper tape was removed to speed up the molding process;

[0037] S226: After 14 days, take out the sample, use a scraper to gently remove the excess part on the upper part of the sample and then demould it. Arrange the demoulded test blocks neatly with equal spacing and cover them with a layer of plastic wrap.

[0038] S3: unconfined compressive strength test;

[0039] In the above-mentioned S3, the unconfined compressive strength test uses a microcomputer-controlled rock indentation hardness tester to measure the mechanical strength of the solidified model after the reaction.

[0040] The specific experimental method for the mechanical strength of the cured model is:

[0041] Cut the sample into appropriate size and ensure that the surface is flat and smooth. Clean the sample surface and remove impurities or dirt. Place the sample on the support plate. The sample is firmly connected to the testing machine through the support plate in a vertical direction.

[0042] Set the loading rate of the testing machine to 0.5 mm / s, start the testing machine, and begin to apply pressure to the specimen;

[0043] Continue loading until the specimen breaks or the preset termination condition is reached;

[0044] The strain and pressure data of the specimen are recorded simultaneously.

[0045] S4: Data analysis.

[0046] In S4, data analysis was performed using a linear regression model:

[0047] UCS=0.849×settlement-2.27(R 2 =0.847).

[0048] The technical effects achieved by the present invention are:

[0049] The present invention provides a simple method for evaluating the effect of microbial-induced solidification based on sedimentation rate. By using a large amount of experimental data, a quantitative relationship model between the amount of biological sedimentation and the unconfined compressive strength of the solidified product is established. This method can quickly and accurately predict and evaluate the unconfined compressive strength after biological solidification by measuring the relatively simple indicator of sedimentation, thereby reflecting the solidification effect.

[0050] The method of the present invention for evaluating the effect of microbial-induced solidification based on sedimentation rate has significant advantages over previous methods. The previous unconfined compressive strength test was complicated to operate, required professional equipment and strict sample preparation, and was time-consuming. The new method only needs to measure the sedimentation of the test matrix, which is simple to operate, fast and efficient, reduces the requirements for equipment and personnel professional skills, can complete the measurement and obtain results in a relatively short time, and timely evaluate the solidification effect, providing timely feedback for process optimization and quality control. At the same time, this method has good applicability for evaluating the biosolidification effect of different types of sludge and coal-based solid waste within a certain range. By adjusting and verifying the model parameters, it can adapt to different curing agents, raw materials and process conditions, and provide support for the widespread application of biosolidification technology. In addition, the linear regression equation established based on a large amount of experimental data can make a more accurate prediction of the unconfined compressive strength of untested samples, evaluate the solidification effect in advance, and assist in the research and development, process design and engineering application of biosolidification technology, with strong predictability and practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is the CEI and UCS correlation fitting curve (R 2 =0.847). DETAILED DESCRIPTION

[0052] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is described in detail below with reference to the following examples. It should be understood that the following text is only used to describe one or more specific embodiments of the present invention and does not strictly limit the scope of protection of the present invention.

[0053] like Figure 1 As shown, a simple method for evaluating the effect of microbial induced solidification based on sedimentation rate includes the following steps:

[0054] S1: microbial culture;

[0055] Includes modified calcium carbonate mineralization medium;

[0056] In S1, the modified calcium carbonate mineralization medium was prepared as follows:

[0057] S11: The culture medium formula includes: yeast extract powder 20g / L, ammonium chloride 10g / L, manganese sulfate monohydrate 10mg / L, nickel chloride hexahydrate 24mg / L;

[0058] S12: The pH value was adjusted with 1 mol / L HCl and NaOH.

[0059] S13: The above culture medium was dissolved in 1000 mL of deionized water and the pH was adjusted to 7.3-7.4;

[0060] S14: Sterilization conditions are 121°C, 20 min;

[0061] S15: After sterilization, add 100 mL of 20% urea solution using a bacteria filter;

[0062] S16: Add 1.8-2% agar powder to the solid culture medium.

[0063] The culture medium conditions include the following:

[0064] Open the clean bench and start the expansion culture operation 20 minutes later;

[0065] Pipette 1 mL of the successfully activated Bacillus pasteurianus liquid from the test tube, inject it into a conical flask containing 100 mL of microbial mineralization medium, and seal it with a sealing film;

[0066] After the bacterial solution and the culture medium are evenly mixed, they are placed in a shaker at 30°C and 150 rpm for 24 h;

[0067] The culture medium is turbid if the expansion is successful, with OD600 around 1.0.

[0068] S2: Biosolidification Experiment;

[0069] It includes the design of solidification experiment, preparation of test matrix flowable solidified soil and preparation of test matrix flowable solidified soil specimens;

[0070] In S2, the solidification experiment uses the ratio of solid wastes such as coal gangue (A), fly ash (B), desulfurized gypsum (C), coal slime (D), and silt (E) as the independent variable, and the fixed amount of solid waste after reaction with excess bacterial liquid as the dependent variable. The mass ratio of solid waste is combined to obtain 15 experimental combinations for testing.

[0071] Table 1: Curing test combination table

[0072]

[0073] In S2, the preparation steps of the test matrix flowable solidified soil are as follows:

[0074] S211: Prepare the test matrix in advance by weighing it with an electronic balance according to the ratio, and place it in a plastic self-sealing bag and shake it thoroughly to make the composition uniform;

[0075] S212: Add 150 mL of the prepared 24-hour cultured Bacillus pasteurianus solution, thoroughly mix the sludge and the Bacillus pasteurianus solution, and stir to ensure that the water content of the sample is between 45% and 55%.

[0076] The Bacillus pasteurian bacterial solution was a Bacillus pasteurian bacterial solution OD600=1.0;

[0077] The ratio of sludge to Bacillus pasteurianus liquid is sludge (g): liquid (mL) = 2:1.

[0078] S213: When the test matrix solidified soil is stirred to a completely fluid state, the test matrix fluid solidified soil is prepared.

[0079] In S2, the preparation steps of the test matrix flowable solidified soil sample are as follows:

[0080] S221: The curing mold is a cylinder of plastic material with an inner diameter of 50mm and a height of 100mm. Before sample preparation begins, a label is attached to the mold.

[0081] S222: Since the test matrix solidified soil settles during the solidification process, the test block height is less than 100 mm after demolding. Therefore, a circle of tape is wrapped around the top of the mold to increase the mold height to a certain extent, and vaseline is evenly applied to the bottom and inner wall of the mold to facilitate demolding.

[0082] S223: Slowly pour the stirred test matrix flowable solidified soil into the mold and stop when it exceeds 1 cm from the top of the mold. No vibration is required during the pouring process.

[0083] S224: After sample preparation is completed, cover the top of the cast test block with plastic wrap and place it at room temperature (20°C) for curing;

[0084] S225: After 7 days, the specimen was removed and the upper tape was removed to speed up the molding process;

[0085] S226: After 14 days, take out the sample, use a scraper to gently remove the excess part on the upper part of the sample and then demould it. Arrange the demoulded test blocks neatly with equal spacing and cover them with a layer of plastic wrap.

[0086] Among them, the present invention adopts the sedimentation test of the test matrix, and sludge and coal-based solid waste are only a few of the multiple materials. However, biosolidification is not limited to sludge and coal-based solid waste. Silt and coal-based solid waste are used as examples to facilitate intuitive recording and observation of changes in sedimentation values.

[0087] S3: unconfined compressive strength test;

[0088] In S3, the unconfined compressive strength test used a microcomputer-controlled rock indentation hardness tester to measure the mechanical strength of the reacted silt model.

[0089] The specific experimental method for the mechanical strength of the test matrix model is as follows:

[0090] Cut the sample into appropriate size and ensure that the surface is flat and smooth. Clean the sample surface and remove impurities or dirt. Place the sample on the support plate. The sample is firmly connected to the testing machine through the support plate in a vertical direction.

[0091] Set the loading rate of the testing machine to 0.5 mm / s, start the testing machine, and begin to apply pressure to the specimen;

[0092] Continue loading until the specimen breaks or the preset termination condition is reached;

[0093] The strain and pressure data of the specimen are recorded simultaneously.

[0094] Table 2: Fixation amount and compressive strength test data

[0095] Experimental groups 1 2 3 4 5 Fixed amount / g 3.8711 3.0482 3.2739 3.8148 3.5118 Compressive strength / Mpa 1.075 0.470 0.382 1.081 0.658 Experimental groups 6 7 8 9 10 Fixed amount / g 3.3320 3.9019 3.6509 3.7422 3.7473 Compressive strength / Mpa 0.610 1.081 0.718 0.760 0.905 Experimental groups 11 12 13 14 15 Fixed amount / g 3.8150 3.6556 3.6488 3.7990 3.9129 Compressive strength / Mpa 1.046 0.807 0.785 0.964 1.098

[0096] S4: Data analysis.

[0097] In S4, data analysis was performed using a linear regression model:

[0098] UCS=0.849×settlement-2.27(R 2 =0.847).

[0099] The foregoing is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained herein shall, unless otherwise specified or limited, be implemented in accordance with conventional means in the art.

Claims

1. A simple method for evaluating the effect of microbial induced solidification based on sedimentation rate, characterized by: The evaluation method comprises the following steps: S1: microbial culture; Includes modified calcium carbonate mineralization medium; S2: Biosolidification Experiment; It includes the design of solidification experiment, preparation of test matrix flowable solidified soil and preparation of test matrix flowable solidified soil specimens; S3: unconfined compressive strength test; S4: Data analysis.

2. A simple method for evaluating the effect of microbial induced solidification based on sedimentation rate according to claim 1, characterized in that: In S1, the steps for preparing the improved calcium carbonate mineralization medium are as follows: S11: The culture medium formula includes: yeast extract powder 20g / L, ammonium chloride 10g / L, manganese sulfate monohydrate 10mg / L, nickel chloride hexahydrate 24mg / L; S12: The pH value was adjusted with 1 mol / L HCl and NaOH. S13: The above culture medium was dissolved in 1000 mL of deionized water and the pH was adjusted to 7.3-7.4; S14: Sterilization conditions are 121°C, 20 min; S15: After sterilization, add 100 mL of 20% urea solution using a bacteria filter; S16: Add 1.8-2% agar powder to the solid culture medium.

3. A simple method for evaluating the effect of microbial induced solidification based on sedimentation rate according to claim 2, characterized in that: The culture medium conditions include the following: Open the clean bench and start the expansion culture operation 20 minutes later; Pipette 1 mL of the successfully activated Bacillus pasteurianus liquid from the test tube, inject it into a conical flask containing 100 mL of microbial mineralization medium, and seal it with a sealing film; After the bacterial solution and the culture medium are evenly mixed, they are placed in a shaker at 30°C and 150 rpm for 24 h; The culture medium is turbid if the expansion is successful, with OD600 around 1.

0.

4. A simple method for evaluating the effect of microbial-induced solidification based on sedimentation rate according to claim 1, characterized in that: In S2, the experiment used the mass of coal gangue, fly ash, desulfurized gypsum, coal slime, and sludge as independent variables, and the fixed amount of the test matrix after reaction with excess bacterial solution as the dependent variable. Different mass proportions of the test matrix were designed to form 15 experimental combinations for testing.

5. The simple method for evaluating the effect of microbial-induced solidification based on sedimentation rate according to claim 1, characterized in that: In S2, the preparation steps of the test matrix flowable solidified soil are as follows: S211: According to the experimental design, the sludge and solid waste are weighed in advance using an electronic balance, and placed in a plastic self-sealing bag and shaken thoroughly to make the composition uniform; S212: Add 150 mL of the prepared 24-hour cultured Bacillus pasteurianus bacterial solution, thoroughly mix the test substrate and the Bacillus pasteurianus bacterial solution, and stir to ensure that the water content of the sample preparation is between 45% and 55%. S213: When the test matrix solidified soil is stirred to a completely fluid state, the test matrix fluid solidified soil is prepared.

6. A simple method for evaluating the effect of microbial-induced solidification based on sedimentation rate according to claim 5, characterized in that: The Bacillus pasteurianus bacterial solution was a Bacillus pasteurianus bacterial solution OD600=1.0; The ratio of sludge to Bacillus pasteurianus liquid is 2:

1.

7. The simple method for evaluating the effect of microbial-induced solidification based on sedimentation rate according to claim 1, characterized in that: In S2, the preparation steps of the fluidized solidified soil sample are as follows: S221: The curing mold is a cylinder of plastic material with an inner diameter of 50mm and a height of 100mm. Before sample preparation begins, a label is attached to the mold. S222: Since the solidified soil settles during the solidification process, the test block height is less than 100 mm after demolding. Therefore, a circle of tape is wrapped around the top of the mold to increase the mold height to a certain extent, and vaseline is evenly applied to the bottom and inner wall of the mold. S223: Slowly pour the stirred fluidized solidified soil into the mold and stop when it exceeds 1 cm from the top of the mold. No vibration is required during the pouring process. S224: After sample preparation is completed, cover the top of the cast test block with plastic wrap and place it at room temperature for curing; S225: After 7 days, the specimen was removed and the upper tape was removed to speed up the molding process; S226: After 14 days, take out the sample, use a scraper to gently remove the excess part on the upper part of the sample and then demould it. Arrange the demoulded test blocks neatly with equal spacing and cover them with a layer of plastic wrap.

8. The simple method for evaluating the effect of microbial-induced solidification based on sedimentation rate according to claim 1, characterized in that: In the above-mentioned S3, the unconfined compressive strength test uses a microcomputer-controlled rock indentation hardness tester to measure the mechanical strength of the solidified model after the reaction.

9. A simple method for evaluating the effect of microbial-induced solidification based on sedimentation rate according to claim 8, characterized in that: The specific experimental method for the mechanical strength of the cured model is: Cut the sample into appropriate size and ensure that the surface is flat and smooth. Clean the sample surface and remove impurities or dirt. Place the sample on the support plate. The sample is firmly connected to the testing machine through the support plate in a vertical direction. Set the loading rate of the testing machine to 0.5 mm / s, start the testing machine, and begin to apply pressure to the specimen; Continue loading until the specimen breaks or the preset termination condition is reached; The strain and pressure data of the specimen are recorded simultaneously.

10. The simple method for evaluating the effect of microbial-induced solidification based on sedimentation rate according to claim 1, characterized in that: In S4, data analysis was performed using a linear regression model: UCS=0.849×settlement-2.27(R 2 =0.847).

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