Bacillus cereus GZ-11-1 and method for solidifying granite residual soil

Abstract

Bacillus cereus GZ‑11‑1 and a method for solidifying granite residual soil. The present application belongs to the field of foundation reinforcement technology, and specifically relates to a Bacillus cereus GZ‑11‑1, which has been deposited in the General Microbiology Center of the China Microbiological Culture Collection Administration on June 7, 2024, with a deposit number of CGMCC No. 30879, and the address is: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences. The present application provides a method for solidifying granite residual soil by isolating urease-producing microorganisms derived from granite residual soil. It is more suitable for the reinforcement treatment of granite residual soil and has little impact on the environment. The method of the present application is used to pour the granite residual soil to form solidified granite residual soil with high uniaxial compressive strength. The method can quickly and efficiently stick loose sand particles together, thereby increasing the strength of the foundation sand.

Description

Technical Field

[0001] The present application belongs to the technical field of foundation reinforcement, and specifically relates to a Bacillus cereus GZ-11-1 and a method for solidifying granite residual soil. Background Art

[0002] Granite is an intrusive rock in acidic (SiO2>66%) igneous rocks. It is the most common type of rock in this category, mostly light flesh-red, light gray, grayish white, etc. It has medium-coarse and fine-grained structures and blocky structures. There are also some porphyry structures, spheroidal structures, and gneiss-like structures. The main minerals are quartz, potassium feldspar, and acidic plagioclase, while the secondary minerals are biotite, hornblende, and sometimes a small amount of pyroxene. There are many types of accessory minerals, the most common of which are magnetite, titanite, zircon, apatite, tourmaline, fluorite, etc. The quartz content is the highest among all kinds of igneous rocks, and its content can range from 20~50%, and a few can reach 50~60%. The content of potassium feldspar is generally higher than that of plagioclase. The ratio of the two is often that potassium feldspar accounts for two-thirds of the total amount of feldspar, and plagioclase accounts for one-third. Potassium feldspar in granite is mostly light flesh-red, and there are also grayish white and gray. Grayish-white potassium feldspar and plagioclase are often difficult to distinguish in hand specimens. At this time, we must carefully observe the twinning characteristics of these two feldspars, because plagioclase has polysynthetic twinning. When you rotate the specimen in your hand, you can see regular light and dark polysynthetic sheets on the plagioclase crystals, while potassium feldspar is Karl-Kirsten twinning, which appears as two halves of crystals with different brightness.

[0003] Granite residual soil is the debris left in the original place after physical and chemical weathering of granite, which contains a large amount of minerals such as silicon and aluminum. Granite residual soil has distinct engineering characteristics due to its special origin. It has strong water absorption and is easy to soften and disintegrate when soaked in water. It is easy to induce geological disasters such as landslides and collapse of hills under the action of heavy rainfall and groundwater, which bury safety hazards for engineering construction.

[0004] In recent years, people have conducted in-depth research on the role of microbial technology in civil and geotechnical engineering. Microbial induced calcium carbonate precipitation technology (MICP) has been widely used in the consolidation of concrete, sand and silt. MICP refers to the fact that certain specific microorganisms can use the surrounding urea and other organic matter and calcium ion sources to quickly generate calcium carbonate with gelling properties. The generation speed and strength of this microbial calcium carbonate material are controllable, and it can be used as a binder to bond loose sand particles into artificial gravel with controllable strength and permeability. This latest research result in basic biomaterials science has opened up a new field for the research of civil and geotechnical engineering.

[0005] In foundation reinforcement projects, combining the increasingly developed microbial engineering technology, effectively utilizing the abundant and non-toxic natural resources of microorganisms, and changing the engineering mechanics properties of civil and geotechnical engineering will bring about a technological revolution in the field of foundation reinforcement in civil and geotechnical engineering.

[0006] In traditional technology, Bacillus pasteurianus is mostly used for soil reinforcement, and there is no report on the use of Bacillus cereus for granite soil reinforcement. Summary of the invention

[0007] Based on this, an embodiment of the present application provides a high-urease-producing Bacillus cereus, and applies it to granite soil consolidation.

[0008] On the one hand, the present application provides a Bacillus cereus GZ-11-1, which has been deposited in the General Microbiology Center of the China Microorganism Culture Collection Administration on June 7, 2024, with the deposit number CGMCC No. 30879. The deposit center is referred to as CGMCC, and its address is: No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences.

[0009] In one embodiment, the method comprises the following steps: using the Bacillus cereus GZ-11-1 to solidify the granite residual soil.

[0010] In one embodiment, the steps are as follows:

[0011] The fermentation liquid of Bacillus cereus GZ-11-1, a fixing agent and a bonding agent are poured into the granite residual soil.

[0012] In one embodiment, the steps of preparing the fermentation broth include:

[0013] A single colony of the Bacillus cereus GZ-11-1 is inoculated into a fermentation medium for fermentation. The fermentation conditions include: a temperature of 25° C. to 37° C. and a fermentation time of 12 h to 60 h.

[0014] In one embodiment, the fermentation conditions further include shaking culture.

[0015] In one embodiment, the shaking culture speed is 150 rpm to 250 rpm.

[0016] In one embodiment, the fermentation medium includes 10 g / L-20 g / L yeast extract, 8 g / L-12 g / L ammonium salt and water, and the pH value is 7-9.5.

[0017] In one embodiment, the ammonium salt includes one or more of ammonium sulfate and ammonium chloride.

[0018] In one embodiment, the fixing agent includes 0.04M~0.06M CaCl2.

[0019] In one embodiment, the binder includes 0.4M~0.6M CaCl2 and 0.4M~0.6M urea.

[0020] In one embodiment, the ratio of the injection amount of the fermentation broth of Bacillus cereus GZ-11-1, the fixing agent and the binder is (40mL~160mL): (0.01M~0.1M): (100mL~200mL).

[0021] In one embodiment, the filling rate of the bacterial solution of Bacillus cereus GZ-11-1 is 0.05 mL / min~0.3 mL / min; and / or

[0022] The grouting speed of the fixing agent is 0.05 mL / min to 0.35 mL / min; and / or

[0023] The grouting speed of the adhesive is 0.05 mL / min~0.35 mL / min. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more completely understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0025] Figure 1 It was identified by 16S rDNA method and named as Bacillus cereus GZ-11-1;

[0026] Figure 2 For identification of the colony morphology of Bacillus cereus GZ-11-1;

[0027] Figure 3 This is the result of observing the morphology of Bacillus cereus GZ-11-1 using a scanning electron microscope;

[0028] Figure 4It is the biomass of the bacterial solution of Bacillus cereus GZ-11-1 at -4℃~80℃;

[0029] Figure 5 It is the urease activity of Bacillus cereus GZ-11-1 at -4℃~80℃. DETAILED DESCRIPTION

[0030] Below in conjunction with embodiment and example, the application is further described in detail.It should be understood that these embodiments and examples are only used to illustrate the application and are not used to limit the scope of the application, and the purpose of providing these embodiments and examples is to make the understanding of the disclosure of the application more thorough and comprehensive.It should also be understood that the application can be implemented in many different forms, is not limited to the embodiment and example described herein, and those skilled in the art can make various changes or modifications without violating the connotation of the application, and the equivalent form obtained also falls within the protection scope of the application.In addition, in the description below, a large number of specific details are given in order to provide a more comprehensive understanding of the application, and it should be understood that the application can be implemented without one or more of these details.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0032] the term

[0033] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0034] The terms "and / or", "or / and", and "and / or" used herein include any one of two or more related listed items, and also include any and all combinations of related listed items, wherein the any and all combinations include any combination of two related listed items, any more related listed items, or all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in the present invention, the technical solution undoubtedly includes technical solutions connected by "logical and", and undoubtedly includes technical solutions connected by "logical or". For example, "A and / or B" includes three parallel solutions of A, B and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, the technical solution that is all connected by "logical OR"), and also includes any and all combinations of A, B, C, and D, that is, the combination of any two or any three of A, B, C, and D, and also includes the combination of four of A, B, C, and D (that is, the technical solution that is all connected by "logical AND").

[0035] In the present invention, "plurality", "multiple", "multiple times", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0036] As used herein, "combination thereof", "any combination thereof", "any combination thereof" etc. include all suitable combinations of any two or more of the listed items.

[0037] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc., shall be based on the ability to implement the technical solution of the present invention, solve the technical problem of the present invention, and achieve the expected technical effect of the present invention.

[0038] Herein, “preferred”, “better”, “more preferred” and “suitable” are merely used to describe implementation methods or examples with better effects, and it should be understood that they do not constitute limitations on the scope of protection of the present invention.

[0039] In the present invention, “further”, “furthermore”, “particularly”, etc. are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present invention.

[0040] In the present invention, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel solutions of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0041] In the present invention, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0042] In the present invention, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical range, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1-10, indicating that t is any integer selected from the integer group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0043] The temperature parameters in the present invention, if not specifically limited, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0044] On the one hand, the present application provides a Bacillus cereus GZ-11-1, which has been deposited in the General Microbiology Center of the China Microorganism Culture Collection Administration on June 7, 2024, with the deposit number CGMCC No. 30879. The deposit center is referred to as CGMCC, and its address is: No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences.

[0045] The present application screens microorganisms capable of producing calcium carbonate from the granite residual soil to be reinforced, and identifies unknown bacteria, thereby providing candidate resources for obtaining microbial strains that can be used to reinforce the granite residual soil.

[0046] That is, the present application is a method for reinforcing granite residual soil by isolating urease-producing microorganisms from granite residual soil. The microorganisms used in the present application come from the soil to be reinforced, so they are more suitable for reinforcing granite residual soil and have little impact on the environment. The method of the present application is used to pour granite residual soil to form solidified granite residual soil with high uniaxial compressive strength. The method can quickly and efficiently stick loose sand particles together, thereby improving the strength of foundation sand.

[0047] On the other hand, the present application provides a method for solidifying granite residual soil, comprising the following steps:

[0048] Providing the Bacillus cereus GZ-11-1; and

[0049] The Bacillus cereus GZ-11-1, a fixative and a binder are poured into the granite residual soil. The fixative and the binder are added to form a microorganism-calcium carbonate-sand consolidation body in the sand-solution system, thereby enhancing the bonding degree and strength of the sand.

[0050] The Bacillus cereus GZ-11-1 provided in the present application has the characteristic of high urease production. Urea is decomposed into ammonium radicals and carbon dioxide under the action of urease produced by microorganisms, and the pH around the bacteria is increased. In the case of providing calcium ions, water-insoluble calcium carbonate salts are generated to bond the surrounding sand particles together; it has the function of increasing the ability of granite urease to catalyze the decomposition of urea to produce ammonia, which is of great significance in the fields of agriculture and medicine.

[0051] Bacterial urease proteins include structural proteins (UreA, UreB and UreC) and auxiliary proteins (UreD / UreH, UreE, UreF and UreG), which each have a unique role in the urease activation process. The structural proteins form the urease active center, while the auxiliary proteins are mainly responsible for the transfer of nickel ions. The residual soil strength is short and the effect is good.

[0052] In a specific example, after the step of providing Bacillus cereus GZ-11-1 and before injecting the Bacillus cereus GZ-11-1, the method further includes:

[0053] A single colony of Bacillus cereus GZ-11-1 is inoculated into a fermentation medium, and the culture conditions include: a temperature of 25°C to 37°C and a culture time of 12h to 60h. For example, the temperature is 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C. The culture time is 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 36h, 38h, 40h, 42h, 44h, 46h, 48h, 50h, 52h, 54h, 56h, 58h, 60h.

[0054] Optionally, the culture conditions further include shaking culture; for example, culture is performed on a shaker.

[0055] Further optionally, the parameter of shaking culture is 150 rpm to 250 rpm, for example 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm.

[0056] In a specific example, the fermentation medium includes 10 g / L to 20 g / L yeast extract, 8 g / L to 12 g / L ammonium salt, and a pH of 7 to 9.5. For example, 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, 20 g / L yeast extract, and a pH of 7, 7.5, 8, 8.5, 9, 9.5.

[0057] Yeast extract (also known as yeast flavor, English name Yeast extract), abbreviated as YE, is a brown-yellow soluble paste or light yellow powder pure natural product made according to the provisions of the Chinese Pharmacopoeia. It uses edible yeast rich in protein as raw material and uses modern biological high-tech such as autolysis, enzymolysis, separation, and concentration to degrade the protein and nucleic acid in the yeast cells and then purify them.

[0058] In a specific example, the ammonium salt includes, but is not limited to, one or more of ammonium sulfate and ammonium chloride.

[0059] Ammonium salts are isoelectronic bodies of ammonium ions and sodium ions. The radius of ammonium ions (143 pm) is similar to that of potassium ions (133 pm) and rubidium ions (147 pm). Therefore, the properties of ammonium salts are similar to those of alkali metal salts, and they are often isomorphous with potassium salts and rubidium salts, and have similar colors, solubility, crystal forms, etc. In the classification of compounds, ammonium salts and alkali metal salts are often listed together.

[0060] Optionally, the fixing agent includes 0.04M-0.06M CaCl2, such as 0.04M, 0.05M, 0.06M CaCl2.

[0061] Further optionally, the binder includes 0.4M-0.6M CaCl2 and 0.4M-0.6M urea, for example, 0.4M, 0.5M, 0.6M CaCl2 and 0.4M, 0.5M, 0.6M urea.

[0062] In a specific example, the ratio of the injection amount of the Bacillus cereus GZ-11-1, the fixative and the binder is (40mL~160mL): (0.01M~0.1M): (100mL~200mL).

[0063] Grouting is the process of pouring certain solidifying materials, such as cement, lime or other chemical materials, into the foundation rock and soil within a certain range under the foundation to fill the cracks and pores in the rock and soil, prevent foundation leakage, and improve the integrity, strength and rigidity of the rock and soil. Grouting is often used to construct a foundation anti-seepage curtain in water-retaining structures such as gates, dams, and dikes, and is the main foundation treatment measure for hydraulic structures.

[0064] Optionally, the grouting is performed using a syringe, and the grouting speed of the bacterial solution of Bacillus cereus GZ-11-1 is 0.05 mL / min~0.3 mL / min; for example, the grouting speed of the bacterial solution is 0.05 mL / min, 0.1 mL / min, 0.15 mL / min, 0.2 mL / min, 0.25 mL / min, and 0.3 mL / min.

[0065] The grouting speed of the fixing agent is 0.05 mL / min~0.35 mL / min; for example, the grouting speed of the fixing agent is 0.05 mL / min, 0.1 mL / min, 0.15 mL / min, 0.2 mL / min, 0.25 mL / min, 0.3 mL / min, and 0.35 mL / min.

[0066] The grouting speed of the binder is 0.05 mL / min to 0.35 mL / min. For example, the grouting speed of the binder is 0.05 mL / min, 0.1 mL / min, 0.15 mL / min, 0.2 mL / min, 0.25 mL / min, 0.3 mL / min, and 0.35 mL / min.

[0067] The embodiments of the present application will be described in detail below in conjunction with examples. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are preferably referred to the guidance provided in the present application, and can also be based on the experimental manual or normal conditions in this area, can also be based on the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0068] In the following specific embodiments, the measured parameters of raw material components may have slight deviations within the range of weighing accuracy unless otherwise specified. For temperature and time parameters, acceptable deviations caused by instrument test accuracy or operation accuracy are allowed.

[0069] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0070] Example 1

[0071] 1. Isolation and screening of urease-producing strains that induce calcium carbonate production

[0072] The urease-producing strain was isolated from Wangzishan Forest Park, Huadu District, Guangzhou City, Guangdong Province. The bacteria have urease, which can decompose urea to produce a large amount of ammonia, making the culture medium alkaline and red. This experiment took advantage of this characteristic. The test sample was first enriched and cultured at 37°C and 5M high-concentration urea for 24 hours to kill various microbial vegetative cells that could not tolerate and utilize high-concentration urea. The treated culture medium was then gradient diluted and coated on a urease screening culture plate. The plate was cultured at 37°C, and the strain that made the culture medium red was picked. The single colony was separated by streaking. The microorganism obtained was a urease-producing microorganism. The strain with the highest urease activity was selected and identified using the 16S rDNA method. It was named Bacillus cereus GZ-11-1. The results are as follows Figure 1 On the NH4-YE (Yeast extract 20g / L, ammonium sulfate 10g / L) plate, the colonies are round, with a moist and smooth surface, neat edges, a colony size of 2-3mm, and a light yellow color. Figure 2 As shown. It can grow in the medium temperature range of 4℃-37℃ and pH7-9.5. The morphology was observed using a scanning electron microscope. The results are as follows Figure 3 shown.

[0073] The nucleotide sequence of 16s DNA of Bacillus cereus GZ-11-1 is shown in SEQ ID NO.1:

[0074] SEQ ID NO.1:

[0075]

[0076] 2. Verification of urease activity of urease-producing strains

[0077] Prepare NH4-YE and high salt culture medium separately

[0078] Prepare NH4-YE medium and high salt medium according to the following formulas:

[0079] NH4-YE medium: Yeast extract 20g / L, ammonium sulfate 10g / L, pH adjusted to 7.5~9.0.

[0080] High salt culture medium: Yeast extract 20g / L, ammonium chloride 10g / L, pH adjusted to 7.5~9.0.

[0081] 100 mL of fermentation medium was placed in a 500 mL culture bottle for sterilization. A single colony of Bacillus cereus GZ-11-1 was picked from the plate and inoculated into the fermentation medium. The culture was cultured at 30°C and the rotation speed was 150-250 rpm. After 16 hours of culture, the bacterial solution was collected and the biomass (expressed by OD600 value) and urease activity of the bacterial solution were detected. Among them, OD600 refers to the absorbance value of a certain solution at a wavelength of 600 nm. The absorbance value is proportional to the concentration of the absorbing substance in the solution, and correspondingly inversely proportional to the transmittance T value of the sample. Numerically speaking, there is a logarithmic relationship between them.

[0082] The results showed that the obtained microorganisms have a wide growth temperature range and can survive and grow at -4℃~80℃. Figure 4 As shown. And has higher urease activity, such as Figure 5 shown.

[0083] 3. Solidification process of granite residual soil

[0084] (1) fermenting Bacillus cereus GZ-11-1 in a fermentation medium at 25° C. to 37° C. for 12 to 60 hours to obtain a bacterial solution;

[0085] The fermentation medium includes 10 g / L to 20 g / L of yeast extract, 10 g / L of ammonium sulfate or ammonium chloride, and a pH value of 7 to 9.5.

[0086] (2) Granite residual soil was sampled from Wangzishan Forest Park, Huadu District, Guangzhou City, Guangdong Province, China. 110 g ± 0.5 g of dry granite residual soil was loaded into a 50 mL sterile model column with a height of 110 mm and a diameter of 30 mm. In addition, two layers of coarse sand were used at both ends of the syringe as a filter to avoid clogging during the calcium carbonate precipitation process.

[0087] This experiment adopted the step-by-step grouting method, which was divided into three steps: first, the bacterial solution of Bacillus cereus GZ-11-1 was poured, then the fixative was poured, and then the mixed solution of the binder (CaCl2 and urea) was poured.

[0088] The sand column mold used this time is a plastic shell with a volume of 50mL, an inner diameter of 30mm, and a length of 110mm. In the middle of the sand column mold is a sand column to be solidified, about 100mm long. A syringe is used for perfusion. The upper end of the syringe is plugged with a rubber stopper with a three-way pipe. Two layers of coarse sand are used at both ends of the syringe as a filter to avoid clogging during the calcium carbonate precipitation process. The aeolian sand used was sampled from Wangzishan Forest Park, Huadu District, Guangzhou City, Guangdong Province, China.

[0089] Before the experiment, 150 mL of deionized water was first pumped into the sand column at a speed of 10 rpm (about 1 mL / min) using a peristaltic pump to saturate the sand column as much as possible. Then 40 mL of bacterial solution was poured into each sand column. After that, a fixative solution of 0.05 M CaCl2 solution was poured to achieve a relatively uniform distribution of calcium carbonate. Then, a binder (mixed solution of CaCl2 and urea) was poured into each sand column in batches to generate MICP in situ in the sand column. The binders used were 0.5 M CaCl2 and 0.5 M urea. The volume of the binder (mixed solution of CaCl2 and urea) poured each time was 150 mL, and the grouting speed was about 0.1 mL / min. A microorganism-calcium carbonate-sand consolidation body was formed in the sand-solution system, thereby enhancing the bonding degree and strength of the sand. Each group of experimental sand columns had 3 replicates.

[0090] 4. Analysis of the sand column formed

[0091] 1. Uniaxial compressive strength test of sand column

[0092] The obtained sand columns were demolded, and the sand columns were all bonded and formed, and it was observed that they had a certain strength. A uniaxial compression test was carried out. Uniaxial compressive strength refers to the load that a rock specimen can withstand per unit area when it is compressed in one direction to failure, referred to as compressive strength. It is measured by compressing standard specimens according to their water content, and can be divided into dry compressive strength, natural compressive strength and saturated compressive strength.

[0093] Measurement method: The uniaxial compressive strength of rock refers to the ultimate destructive strength obtained when the sample is compressed in only one direction. That is to say, the rock sample is placed between the upper and lower plates of the press and pressurized until the sample is crushed to obtain the pressure strength value.

[0094] The specific experimental process is:

[0095] (1) Install the uniaxial compression test fixture on the base of the RMT-150C rock and concrete mechanics test system. Apply a thin layer of lubricant (vaseline) on the upper and lower surfaces of the specimen and place it in the center of the base. Place a rigid pad between the upper end of the specimen and the pressure plate of the testing machine. Install the axial displacement extensometer and radial displacement extensometer. Adjust the positions of the axial and radial displacement extensometers so that the displacement extensometers have initial readings.

[0096] (2) Adjust the pressure head so that the rigid pad is in even contact with the pressure plate of the testing machine, so that the specimen is evenly stressed;

[0097] (3) Load at a rate of 0.1 MPa to 0.5 MPa per second until the specimen fails, with a lower loading rate for soft rocks and relatively soft rocks;

[0098] (4) Record the experimental failure load and the phenomena occurring during the experiment, and describe the specimen after failure.

[0099] The test results show that the uniaxial compressive strength of the sand column is between 0.2Mpa and 0.6Mpa. The specific data are shown in Table 1.

[0100] Table 1 Uniaxial compressive strength of MICP bonded granite residual soil columns

[0101]

[0102] 2. Analysis of substances generated on the surface of sand particles

[0103] XRD analysis of the precipitated white substance

[0104] (1) Testing process:

[0105] The collected spectra were qualitatively analyzed, and the phase composition was determined through matching and retrieval, and the crystal structure data file of the phase was found. The mass fraction of CaCO3 in the sample was given. The accuracy of the test method was investigated by the spike recovery test, and 6 samples were prepared and measured in parallel to test the repeatability.

[0106] (2) XRD data processing

[0107] The XRD data were analyzed using MDI JADE software.

[0108] The results showed that the substances formed were all calcium carbonate.

[0109] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solution of the present application in detail, but it cannot be understood as a limitation on the scope of protection of the patent application. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several deformations and improvements can be made, which all belong to the protection scope of the present application. In addition, it should be understood that after reading the above-mentioned teaching content of the present application, the technicians in this field can make various changes or modifications to the present application, and the equivalent forms obtained also fall within the protection scope of the present application. It should also be understood that the technical solutions obtained by the technicians in this field through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the protection scope of the claims attached to the present application. Therefore, the protection scope of the patent of the present application shall be based on the content of the attached claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A method for solidifying granite residual soil, characterized in that: The steps include: Injection of Bacillus cereus into granite residual soil Bacillus cereus )Fermentation broth, fixative and binder of GZ-11-1; The Bacillus cereus GZ-11-1 was deposited in the General Microbiology Center of China Microorganism Culture Collection Administration on June 7, 2024, with the deposit number CGMCC No.30879, address: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences; The steps of preparing the fermentation broth include: Inoculating a single colony of the Bacillus cereus GZ-11-1 into a fermentation medium for fermentation, wherein the fermentation conditions include: a temperature of 25° C. to 37° C. and a fermentation time of 12 h to 60 h; The fermentation medium includes 10 g / L to 20 g / L of yeast extract, 8 g / L to 12 g / L of ammonium salt and water, and the pH is 7 to 9.5; The ammonium salt includes one or more of ammonium sulfate and ammonium chloride; The ratio of the amount of the fermentation liquid of Bacillus cereus GZ-11-1, the fixing agent and the binder injected is (40mL~160mL): (0.01M~0.1M): (100mL~200mL).

2. The method for consolidating granite residual soil according to claim 1, characterized in that: The fermentation conditions also include shaking culture.

3. The method for consolidating granite residual soil according to claim 2, characterized in that: The shaking culture speed is 150 rpm to 250 rpm.

4. The method for solidifying granite residual soil according to any one of claims 1 to 3, characterized in that: The fixing agent includes 0.04M~0.06M CaCl2.

5. The method for solidifying granite residual soil according to any one of claims 1 to 3, characterized in that: The binder includes 0.4M~0.6M CaCl2 and 0.4M~0.6M urea.

6. The method for solidifying granite residual soil according to any one of claims 1 to 3, characterized in that: The Bacillus cereus ( Bacillus cereus )The grouting speed of GZ-11-1 bacterial solution is 0.05mL / min~0.3mL / min; The grouting speed of the fixing agent is 0.05mL / min~0.35mL / min; The grouting speed of the adhesive is 0.05 mL / min~0.35 mL / min.

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