CN114396038A - Method for reinforcing soil strength by using microorganism induced calcium carbonate deposition - Google Patents
Method for reinforcing soil strength by using microorganism induced calcium carbonate deposition Download PDFInfo
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Abstract
The application provides a method for reinforcing soil body strength by utilizing microorganism induced calcium carbonate deposition, the method is characterized in that double-round injection of an inducing liquid is carried out in the maintenance and reinforcement process, the component of the inducing liquid is urea, the urea provides nutrition for microorganism propagation in the reinforcement and maintenance process and is a substrate for inducing generation of calcium carbonate, and the double-round injection of the inducing liquid can supplement a new nitrogen source and a new substrate after the first round of calcium generation is complete, so that the calcium production efficiency is improved, and the soil body reinforcement effect is improved.
Description
Technical Field
The application relates to the technical field of environmental protection, in particular to a method for reinforcing soil strength by utilizing microorganism induced calcium carbonate deposition.
Background
The solid phase of the saline soil consists of rock debris and salt debris, which is an important difference from the common soil body, so that the saline soil has special geotechnical engineering properties. For a long time, under the influence of extreme natural conditions and new technology development lag, the foundation strengthening method of a salinized soil distribution area adopts the traditional physical methods and chemical methods such as a soil changing cushion layer method, a water soaking pre-dissolving method, an anti-corrosion cement method, a chemical curing agent and the like. The methods not only have high cost and long time consumption, but also generate secondary pollution to engineering geotechnical environment and water body environment, and can not meet the national strategic requirements of China on the environmental protection of the three river sources.
Microorganism Induced Carbonate Precipitation (MICP) is characterized in that urea is promoted to be hydrolyzed into Carbonate by using a metabolic product urease of microorganisms, and under the action of surrounding environmental substances, the Carbonate is mineralized and synthesized together to form calcium Carbonate crystal Precipitation, and soil particles are bonded at the same time, so that the aim of soil reinforcement is fulfilled. Compared with the traditional foundation strengthening method, the MICP directly utilizes microbial activity or microbial products to strengthen the foundation soil body and reduce the disturbance and pollution of the foundation soil body.
The prior art aims at non-saline soil bodies, and a lot of researches are made on components of an inducing liquid, but the actual soil body strengthening process is more important about the environment of the soil body, the configuration process is also an important factor influencing the mineralization effect, and the two methods can cause the difference of the content of strains and the like, so that the strengthening effect is not good enough.
Disclosure of Invention
The application aims to provide a method for reinforcing soil strength by utilizing microorganism-induced calcium carbonate deposition, and aims to solve the problem that the effect of reinforcing the soil strength by utilizing the microorganism-induced calcium carbonate deposition in the prior art is not good enough.
In order to achieve the above object, the present application provides a method for reinforcing soil strength by using microorganism-induced calcium carbonate deposition, comprising:
adjusting the water content of the soil body to be reinforced;
compacting the soil body to be reinforced;
injecting bacterial liquid into the compacted soil body and culturing;
injecting a first inducing liquid after the culture and carrying out first maintenance;
and injecting the inducing liquid for the second time after the first curing, and curing for the second time to obtain the reinforced soil body.
Preferably, the water content is 15% -20%;
preferably, the water content is 18%.
Preferably, the bacterial liquid is staphylococcus xylosus S47 bacterial liquid;
preferably, the OD600 value of the staphylococcus xylosus S47 bacterial liquid is 0.8;
preferably, the staphylococcus xylosus S47 bacterial liquid is obtained by culturing a trypsin soybean culture medium.
Preferably, the adjusting the water content of the soil body to be reinforced specifically comprises:
and adjusting the water content of the soil body to be reinforced by using the bacterial liquid.
Preferably, the inducing liquid is prepared from a mixture of 1:1, mixed solution of calcium chloride and urea;
preferably, the bacterial liquid and the inducing liquid are used for infiltrating the soil body to be reinforced according to the proportion of 1: 1.
Preferably, the injection rate of the bacterial liquid is 3-8 ml/min;
preferably, the injection rate of the bacterial liquid is 5 ml/min.
Preferably, injecting a bacterial liquid into the compacted soil body and culturing for 20-30 h;
preferably, the compacted soil is injected with bacterial liquid and cultured for 24 h.
Preferably, the first curing time is 72 to 96 hours.
Preferably, the second curing time is 96 to 120 hours.
Preferably, the soil body to be reinforced is saline soil.
Compared with the prior art, the beneficial effect of this application includes:
the application provides a method for reinforcing soil body strength by utilizing microorganism induced calcium carbonate deposition, wherein double-round injection of an induction liquid is carried out in the maintenance reinforcing process, the component of the induction liquid is urea, in the reinforcing maintenance process, the urea provides nutrition for microorganism propagation and is a substrate for inducing calcium carbonate generation, and the induction liquid can supplement a new nitrogen source and a new substrate after the first round of calcium generation is complete, so that the calcium production efficiency is improved, and the soil body reinforcing effect is improved.
Drawings
To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments are briefly described below, and it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope of the present application.
FIG. 1 is a graph showing the results of the urease activity test of the present application strain S47;
FIG. 2 is a graph of white precipitate formed by mineralization of the S47 strain of the present application;
FIG. 3 is an X-ray diffraction component measurement and scanning electron microscope characterization of the white precipitate of FIG. 2;
FIGS. 4a and 4B are graphs showing the results of the envelope curve and the stress-strain curve of the test group B, respectively;
FIGS. 5a and 5B are graphs showing the envelope curve and the stress-strain curve of control group B, respectively;
FIGS. 6a and 6b are graphs showing the envelope curve and the stress-strain curve of the test group C, respectively;
FIGS. 7a and 7b are graphs showing the envelope curve and the stress-strain curve of the C control group, respectively;
FIGS. 8a and 8b are graphs showing the results of the envelope curve and the stress-strain curve of the test group D, respectively;
FIGS. 9a and 9b are graphs showing the envelope curve and the stress-strain curve of the D control group, respectively;
FIGS. 10a and 10b are graphs showing the envelope curve and the stress-strain curve of the experimental group E, respectively;
FIGS. 11a and 11b are graphs showing the envelope curve and the stress-strain curve of the E control group, respectively;
FIGS. 12a and 12b are graphs showing the results of the envelope curve and the stress-strain curve of the experimental group F, respectively;
FIGS. 13a and 13b are graphs showing the envelope curve and the stress-strain curve result of the test group G, respectively;
FIG. 14 is a graph of stress versus time for the experimental group B and the control group B;
FIG. 15 is a graph of stress versus time for the test group C and the control group C;
FIG. 16 is a graph of stress versus time for the test group D and the control group D;
FIG. 17 is a graph of stress versus time for the experimental group E and the control group E;
FIG. 18 is a graph of stress versus time for the experimental group F and the control group F;
FIG. 19 is a graph of stress versus time for the test group G and the control group G;
FIG. 20 is a graph showing the comparison of the shear strength in the single-wheel and double-wheel gluing mode when bacteria are added;
FIG. 21 is a graph showing the comparison of shear strength in a single-wheel and double-wheel gluing mode without adding bacteria.
Detailed Description
The terms as used herein:
"prepared from … …" is synonymous with "comprising". The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.
The conjunction "consisting of … …" excludes any unspecified elements, steps or components. If used in a claim, the phrase is intended to claim as closed, meaning that it does not contain materials other than those described, except for the conventional impurities associated therewith. When the phrase "consisting of … …" appears in a clause of the subject matter of the claims rather than immediately after the subject matter, it defines only the elements described in the clause; other elements are not excluded from the claims as a whole.
When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when the range "1 ~ 5" is disclosed, the ranges described should be construed to include the ranges "1 ~ 4", "1 ~ 3", "1 ~ 2 and 4 ~ 5", "1 ~ 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.
In these examples, the parts and percentages are by mass unless otherwise indicated.
"part by mass" means a basic unit of measure indicating a mass ratio of a plurality of components, and 1 part may represent any unit mass, for example, 1g or 2.689 g. If we say that the part by mass of the component A is a part by mass and the part by mass of the component B is B part by mass, the ratio of the part by mass of the component A to the part by mass of the component B is a: b. alternatively, the mass of the A component is aK and the mass of the B component is bK (K is an arbitrary number, and represents a multiple factor). It is unmistakable that, unlike the parts by mass, the sum of the parts by mass of all the components is not limited to 100 parts.
"and/or" is used to indicate that one or both of the illustrated conditions may occur, e.g., a and/or B includes (a and B) and (a or B).
The application provides a method for reinforcing soil strength by utilizing microorganism-induced calcium carbonate deposition, which comprises the following steps.
The method comprises the following steps: and adjusting the water content of the soil body to be reinforced.
Specifically, because the soil body to be consolidated is usually dry saline-alkali soil, for example, saline soil of the chada wood basin, dry soil cannot be compacted, therefore, the soil body to be consolidated cannot be directly subjected to microbial grouting treatment, and the water content of the soil body to be consolidated needs to be adjusted firstly. Preferably, the water content is 15% to 20%, for example 15%, 16%, 17%, 18%, 19% or 20%; more preferably, the water content is 18%.
In a preferred embodiment, the adjusting the water content of the soil body to be reinforced may specifically be: and adjusting the water content of the soil body to be reinforced by using the bacterial liquid. Namely, the water content of the soil body to be reinforced is adjusted by using the microorganism culture solution for inducing the calcium carbonate deposition by the microorganism, so that the effect of inducing the calcium carbonate deposition by the microorganism can be further improved.
Step two: and compacting the soil body to be reinforced.
Firstly, the soil body to be reinforced is compacted to obtain a stable foundation, so that the soil body obtained after the subsequent microorganism induced calcium carbonate deposition is compact.
Step three: injecting bacterial liquid into the compacted soil body and culturing.
Specifically, the bacterial solution is a culture solution of microorganisms capable of inducing the deposition of calcium carbonate by the microorganisms, and the microorganisms may be, for example, bacillus pasteurii.
Preferably, the bacterial liquid used in the invention is staphylococcus xylosus S47 bacterial liquid. The Staphylococcus xylosus S47 was disclosed in non-patent literature before filing date, which was filed as a research on the technical feasibility of microbial mineralization of calcium carbonate in saline environments [ J ]. Heilongjiang animal veterinarian 2020, (13):26-31.) and available to the public from the institute of civil engineering, Qinghai university, Zhang Xuanhong, Wanglon Lin, Xunwei.
Preferably, the OD600 value of the staphylococcus xylosus S47 bacterial liquid is 0.8;
preferably, the staphylococcus xylosus S47 bacterial liquid is obtained by culturing a trypsin soybean culture medium.
Preferably, the injection rate of the bacterial liquid is 3-8 ml/min; for example, (3, 4, 5, 6, 7 or 8) ml/min, and more preferably, the injection rate of the bacterial suspension is 5 ml/min.
Preferably, injecting a bacterial liquid into the compacted soil body and culturing for 20-30 h; for example, it may be 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 h; more preferably, the compacted soil is inoculated with a bacterial liquid and cultured for 24 hours.
Step four: and injecting a first inducing liquid after the culture and carrying out first maintenance.
Preferably, the inducing liquid is prepared from a mixture of 1:1 of calcium chloride and urea.
Preferably, the bacterial liquid and the inducing liquid are used for infiltrating the soil body to be reinforced according to the proportion of 1: 1.
Preferably, the first curing time is 72 to 96 hours.
Step five: and injecting the inducing liquid for the second time after the first curing, and curing for the second time to obtain the reinforced soil body.
Preferably, the second curing time is 96 to 120 hours.
The application provides a method for reinforcing soil body strength by utilizing microorganism induced calcium carbonate deposition, wherein double-round injection of an induction liquid is carried out in the maintenance reinforcing process, the component of the induction liquid is urea, in the reinforcing maintenance process, the urea provides nutrition for microorganism propagation and is a substrate for inducing calcium carbonate generation, and the induction liquid can supplement a new nitrogen source and a new substrate after the first round of calcium generation is complete, so that the calcium production efficiency is improved, and the soil body reinforcing effect is improved.
Embodiments of the present application will be described in detail below with reference to specific examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
Example 1 urease Activity and mineralization Capacity of the microorganism S47
In a strong salting environment (the concentration of chloride ions is more than 5%), the urease activity of S47 tends to rise first and then slowly fall, and as shown in figure 1, the urease activity is basically maintained between 3.02U and 5.03U within 24-96 h. Wherein, the maximum value of urease activity is 5.03U at 48 h.
The existing research shows that the activity range of urease is 4.4-9.5U, and calcium carbonate forms stronger aggregates at a lower urea hydrolysis rate. Therefore, urease activity of S47 was induced by the microbial mineralization test under the condition of 5.03U, and the results are shown in FIG. 2, wherein the left side of FIG. 2 is S47 test group, which produces a large amount of white solid precipitate in the test tube, and the right side of FIG. 2 is blank control group, which has only a small amount of white floc.
Analysis of the white precipitate in the test tubes of the S47 test group using an X-ray diffractometer produced a peak at 30 ° 2 θ, which was calcium carbonate as the component in comparison with the mineral X-ray diffraction pattern, as shown in fig. 3, indicating that the white precipitate produced in the test tubes by S47 was calcium carbonate. When the calcium white calcium carbonate precipitates were observed by scanning electron microscopy, it was found that these white calcium carbonate minerals were adsorbed and cemented to the surface of the S47 strain, as shown in fig. 4.
To sum up, the experiment result shows that the protogenic high-yield urease microbial strain S47 found in the strong saline environment of the firewood basin has better adaptability to the strong saline environment than the Pasteur bacillus strain and has the basic capability of developing MICP.
Example 2 sample preparation
The saline soil of the firewood basin is selected for the test, the grain diameter ranges from 0.25 mm to 0.50mm accounting for 20%, from 0.50mm to 1.00mm accounting for 60%, and from 1.00mm to 2.00mm accounting for 20%. Analysis of the soluble salt content data shows that the total salt content of the three sampling points reaches up to 81200mg/kg, the content of the total salt reaches up to 50906mg/kg, and the ion content of the total salt reaches up to 10634 mg/kg.
The bacterial liquid OD600 value of the S47 strain was 0.8. Tryptic soy medium. The inducing liquid is composed of a mixed solution of calcium chloride and urea, and the molar ratio is 1: 1.
a200 mL syringe injector with an inner diameter of 5cm and a height of 16cm is selected as a hard boundary die for the test. The inner diameter of the water-permeable and air-permeable flexible boundary die is 3.91cm, and the height of the water-permeable and air-permeable flexible boundary die is 8 cm.
(1) B, C, D group
Experimental groups: 150g of test soil is weighed for each experimental group, 27mL of S47 bacterial liquid is added to ensure that the water content of the test soil is 18%, and the test soil is kept stand for 24h to enable the bacterial liquid to fully permeate. Each experimental component is divided into three parts, each part is 50g, a sample is prepared by adopting a layering compaction method, the height of the sample is controlled to be 80mm, and groups B1, B2 and B3, groups C1, C2 and C3, and groups D1, D2 and D3 are respectively obtained.
Control group: 150g of test soil is weighed for each control group, 27mL of sterile culture medium is added to ensure that the water content of the test soil is 18%, and the test soil is kept stand for 24h to ensure that the culture medium fully permeates. Each control group is divided into three parts, samples are prepared by a layering compaction method, the height of the sample is controlled to be 80mm, and groups B4, B5 and B6, groups C4, C5 and C6, and groups D4, D5 and D6 are respectively obtained.
(2) Group E
Experimental groups: 150g of test soil is weighed, 27mL of mixed solution of S47 bacterial liquid and induction liquid in a volume ratio of 1:1 is added to ensure that the water content of the test soil is 18%, and the test soil is stood for 24 hours to enable the bacterial liquid to fully permeate. Dividing into three parts, each 50g, preparing sample by a layering compaction method, and controlling the height of the sample to be 80mm to obtain groups E1, E2 and E3.
Control group: 150g of test soil is weighed, 27mL of mixed solution of a sterile culture medium and an inducing solution in a volume ratio of 1:1 is added, the water content of the test soil is ensured to be 18%, and the test soil is kept stand for 24 hours to enable the culture medium to fully permeate. Dividing into three parts, preparing sample by layering compaction method, controlling sample height to 80mm, and obtaining E4, E5 and E6 groups.
(3) F, G group
Experimental groups: 150g of test soil is weighed, 27mL of sterile culture medium is added to ensure that the water content of the test soil is 18%, and the test soil is kept stand for 24h to ensure that the culture medium fully permeates. Dividing into three parts, each 50g, preparing sample by a layering compaction method, and controlling the height of the sample to be 80mm to obtain F1, F2 and F3 groups.
Experimental groups: 150g of test soil is weighed, 27mL of sterile culture medium is added to ensure that the water content of the test soil is 18%, and the test soil is kept stand for 24h to ensure that the culture medium fully permeates. Dividing into three parts, each 50G, preparing a sample by adopting a layering compaction method, and controlling the height of the sample to be 80mm to obtain G1, G2 and G3 groups.
The preparation of 12 groups of samples, 6 groups of which were experimental groups and 6 groups of which were control groups, each group contained three samples, is shown in table 1, wherein the control groups of groups F and G were shared with the control groups of groups B and C.
TABLE 1 preparation of different groups of samples
Example 3 slip casting
Group B: the sample adopts a single-round injection method of bacterial liquid and a single-round injection method of induction liquid. And putting the compacted sample into a flexible boundary mould, and putting the upper part of the compacted sample into a hard boundary mould after sewing. 60mL of bacterial liquid is injected at the speed of 5mL/min by controlling the rotating speed of a peristaltic pump, 60mL of induction liquid is injected after 24 hours, and the mixture is maintained for 7 days.
Group C; the sample adopts a mode of multi-single-round bacterium injection and double-round induction liquid injection. And putting the compacted sample into a flexible boundary mould, and putting the upper part of the compacted sample into a hard boundary mould after sewing. 60mL of bacterial liquid is injected at the speed of 5mL/min by controlling the rotating speed of a peristaltic pump so as to completely submerge the sample, 30mL of induction liquid is injected after 24 hours of culture, 30mL of induction liquid is injected for the second time after three days of maintenance, and the maintenance is carried out for 4 days.
Group D: the test adopts a single-round mixed liquid injection mode. And putting the compacted sample into a flexible boundary mould, and putting the upper part of the compacted sample into a hard boundary mould after sewing. Injecting the bacteria liquid at the speed of 5mL/min by controlling the rotating speed of a peristaltic pump, wherein the volume ratio of the bacteria liquid to the induction liquid is 1:1, 120mL, and curing for 8 days.
Group E: the sample adopts a double-round mixed liquid injection mode. And putting the compacted sample into a flexible boundary mould, and putting the upper part of the compacted sample into a hard boundary mould after sewing. Injecting an inducing liquid into the culture medium at a speed of 5mL/min by controlling the rotating speed of a peristaltic pump, wherein the volume ratio of the inducing liquid to the bacterial liquid is 1:1, culturing for 24h, then continuously injecting 60mL of the mixed solution, and maintaining for 7 days.
And F group: the sample adopts single round of bacteria injection and single round of induction liquid injection. And putting the compacted sample into a flexible boundary mould, and putting the upper part of the compacted sample into a hard boundary mould after sewing. 60mL of bacterial liquid is injected at the speed of 5mL/min by controlling the rotating speed of a peristaltic pump, 60mL of induction liquid is injected after 24 hours, and the mixture is maintained for 7 days.
Group G: the sample adopts single round of fungus injection and double round of induction liquid injection. And putting the compacted sample into a flexible boundary mould, and putting the upper part of the compacted sample into a hard boundary mould after sewing. 60mL of bacterial liquid is injected at the speed of 5mL/min by controlling the rotating speed of a peristaltic pump so as to completely submerge the sample, 30mL of induction liquid is injected after 24 hours of culture, 30mL of induction liquid is injected for the second time after three days of maintenance, and the maintenance is carried out for 4 days.
The grouting pattern of the different groups of samples is shown in table 2. And after the maintenance is finished, taking out each group of soil columns and recording appearance characteristics. Drying at 70 deg.C for 48h in a constant temperature drying oven, and removing the mold.
TABLE 2 slip casting method for different groups of samples
Example 4 MICP reinforced saline soil test
The triaxial test is a relatively perfect method for measuring the shear strength of soil, and an SLB-1 type stress-strain tester of geological engineering of Qinghai university is selected for testing. In order to further analyze the situations of adding the bacterial liquid and not adding the bacterial liquid and the influence of different grouting modes on the mechanical property of the soil body, four variables of a cementing mode are set. On the basis of controlling the structure, density and water content of the soil body not to change greatly, the mechanical properties of the soil body are researched by controlling the injection mode of the bacterial liquid to perform a triaxial test.
(1) Test preparation and test equipment inspection: the SLB-1 type stress-strain tester is checked, the communication condition and the sealing condition of all parts of the tester are checked, and data distortion caused by damage to instrument equipment due to liquid discharge in the test process is prevented.
(2) The test method comprises the following steps: after the flexible boundary die is disassembled, the sample is put into a rubber sleeve, filter paper and permeable stones are stacked at two ends of the rubber sleeve, the rubber sleeve is put on a base of the triaxial apparatus and fixed by a rubber band, and a wrench is used for tightening the outer cover to prevent water leakage in the experimental process.
(3) Shear strain rate: the test adopts a consolidation non-drainage triaxial shear test, confining pressure is respectively added to 100KPa, 200KPa and 300KPa, then the shear test is carried out, axial deformation is not more than 0.01mm/h in a standard mode, shearing is carried out according to the regulation of 0.5-1.0% strain per minute, and the shear speed is set to be 0.8mm/min in the test.
Example 5 MICP Reinforcement of saline soil mechanical Strength test results and analysis
In actual engineering, the soil body is a spatial body which exists continuously, and in view of the experience of the past academic circles on soil body reinforcement tests, a triaxial unconsolidated and non-drainage test is selected to measure the reinforcement effect of the MICP on the saline soil of the firewood wood basin. The shear strength of the sample is improved because calcium carbonate is generated and then gradually enriched by taking the surface of the thalli as a carrier, and the original particle size of the sample is changed. In order to better embody the reinforcing capacity of S47 on the saline soil, the cohesive force and the internal friction angle of the sample are determined according to the coulomb theory. Fig. 4 to 13 show triaxial shear test results of the test soil of each experimental group and the control group, including envelope curve results (fig. 4a to 13a) and stress-strain curve results (fig. 4b to 13b), wherein the envelope curve is the test results of the confining pressure added to 100KPa, 200KPa and 300KPa from left to right, and the stress-strain curve is the test results of the confining pressure added to 100KPa, 200KPa and 300KPa from bottom to top.
From the envelope curve of the shear strength of the sample, the stress-strain curve of the saline soil is basically in a strain softening type. FIGS. 4a and 4B show that the sample with bacteria in the experimental group B has a cohesive force of 7.34kPa and an internal friction angle of 23.33 degrees, respectively, and FIGS. 5a and 5B show that the sample without bacteria in the control group B has a cohesive force of 3.91kPa and an internal friction angle of 22.32 degrees, respectively; FIGS. 6a and 6b show the sample having the applied bacteria of experiment group C having the cohesive force and the internal friction angle of 10.63kPa, 25.81 degrees, respectively, and FIGS. 7a and 7b show the sample having no applied bacteria of control group C having the cohesive force and the internal friction angle of 8.34kPa, 24.64 degrees, respectively; FIGS. 8a and 8b show that the cohesive force and the internal friction angle of the samples with bacteria in the experiment group D are 8.17kPa and 23.65 degrees, respectively, and FIGS. 9a and 9b show that the cohesive force and the internal friction angle of the samples without bacteria in the control group D are 7.79kPa and 22.56 degrees, respectively; FIGS. 10a and 10b show the samples with bacteria in the test group E having cohesive force and internal friction angle of 10.42kPa, 24.37 degrees, respectively, and FIGS. 11a and 11b show the samples with no bacteria in the control group E having cohesive force and internal friction angle of 8.94kPa, 23.60 degrees, respectively; FIGS. 12a and 12B show that the cohesive force and the internal friction angle of the samples in group F are 4.33kPa and 23.23 degrees, respectively, and the cohesive force and the internal friction angle of the samples in group B, which are not added with bacteria, are 3.91kPa and 22.32 degrees, respectively; FIGS. 13a and 13b show that the cohesive force and the internal friction angle of the samples in group G were 8.73kPa and 24.80 degrees, respectively, and the non-bacteria sample was the non-bacteria sample in group C, and the cohesive force and the internal friction angle were 8.34kPa and 24.64 degrees, respectively.
According to the comparison of the cohesive force and the internal friction angle of the samples with bacteria and the samples without bacteria in different groups, the cohesive force of the samples with bacteria is increased by 0.38-3.43 kPa compared with that of the samples without bacteria, the internal friction angle is increased by 0.16-1.17 degrees, and the cohesive force and the internal friction angle of the samples with bacteria in the group C are the largest.
After being mineralized and reinforced by microorganisms, the saline soil sample is dried and subjected to triaxial shear tests under the ambient pressure of 100kPa, 200kPa and 300kPa, and stress-time change result graphs of B, C, D, E, F, G groups are respectively shown in figures 14 to 19. By comparing B, C, D, E, F, G groups of stress-time relationship graphs, the same group of samples with and without bacteria are deformed within 10-15 min to be damaged. The time for reaching the peak value under different confining pressures of different groups of samples is different, the time for reaching the destruction of the samples of the groups C, E and G is longer, the destruction is reached in about 15min, and the samples of the groups B, D and F need longer shearing time than the samples of the groups B, D and F, which shows that the brittleness of the samples of the groups B, D and F is higher than that of the samples of the groups C, E and G. The time for destroying the bacteria-added samples and the bacteria-free samples is not obvious, the speed for destroying the bacteria-added samples and the bacteria-free samples under different confining pressures of the same group of samples is different, and a single change rule is not presented, for example, the bacteria-free samples in the group E are destroyed first, and the bacteria-added samples in the group D are destroyed first.
The difference in shear strength is mainly reflected in the difference in the manner of cementing, and therefore, comparative analysis of the manner of preparing the sample into a cementing may be performed, as shown in fig. 20 to 21. In the sample preparation process, B, C, D test group is added with bacterial liquid, and control group is added with culture medium; the group E test group is added with a mixed solution of a bacterial liquid and an inducing liquid, and the group E control group is provided with a mixed solution of a culture medium and an inducing liquid; F. group G is provided with a feeding medium. Adding single-round inducing liquid into the group B in the process of reinforcing and maintaining; adding double round inducing liquid into group C; adding a single round of mixed liquid of the bacterial liquid and the inducing liquid into the test group D, and adding a mixed liquid of the culture medium and the inducing liquid into the control group; adding a mixed solution of a double-round bacterial liquid and an inducing liquid into the test group E, and adding a mixed solution of a culture medium and the inducing liquid into the control group; f group of single-round bacterium injection, single-round induction liquid injection; and G groups of single-round bacterium injection and double-round induction liquid injection. The single variable difference exists between different groups, and the shearing strength of the sample subjected to double-round injection of the inducing liquid is comprehensively judged to be stronger. The component of the inducing liquid is urea, in the process of reinforcement and maintenance, the urea provides nutrition for the propagation of microorganisms and is a substrate for inducing the generation of calcium carbonate, and the inducing liquid can supplement new nitrogen sources and substrates after the first round of calcium production is complete, so that the calcium production efficiency is improved. The shear strength of the added bacteria liquid in group C is highest, and is respectively tau 100-298 kPa, tau 200-524 kPa and tau 300-805 kPa.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present application.
Moreover, those skilled in the art will appreciate that while some embodiments herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the application and form different embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is only for enhancement of understanding of the general background of the application and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Claims (10)
1. A method for reinforcing soil strength by utilizing microorganism-induced calcium carbonate deposition is characterized by comprising the following steps:
adjusting the water content of the soil body to be reinforced;
compacting the soil body to be reinforced;
injecting bacterial liquid into the compacted soil body and culturing;
injecting a first inducing liquid after the culture and carrying out first maintenance;
and injecting the inducing liquid for the second time after the first curing, and curing for the second time to obtain the reinforced soil body.
2. The method for reinforcing soil strength by using microorganism-induced calcium carbonate deposition according to claim 1, wherein the water content is 15-20%;
preferably, the water content is 18%.
3. The method for reinforcing soil strength by using microorganism-induced calcium carbonate deposition according to claim 1, wherein the bacterial liquid is staphylococcus xylosus S47 bacterial liquid;
preferably, the OD600 value of the staphylococcus xylosus S47 bacterial liquid is 0.8;
preferably, the staphylococcus xylosus S47 bacterial liquid is obtained by culturing a trypsin soybean culture medium.
4. The method for reinforcing soil strength by using microorganism-induced calcium carbonate deposition according to claim 1, wherein the adjusting of the water content of the soil to be reinforced specifically comprises:
and adjusting the water content of the soil body to be reinforced by using the bacterial liquid.
5. The method for reinforcing soil body strength by using microorganism-induced calcium carbonate deposition according to claim 1, wherein the inducing liquid is prepared by mixing the components in a molar ratio of 1:1, mixed solution of calcium chloride and urea;
preferably, the bacterial liquid and the inducing liquid are used for infiltrating the soil body to be reinforced according to the proportion of 1: 1.
6. The method for reinforcing soil strength by using microorganism-induced calcium carbonate deposition according to claim 1, wherein the injection rate of the bacterial liquid is 3-8 ml/min;
preferably, the injection rate of the bacterial liquid is 5 ml/min.
7. The method for reinforcing soil strength by using microorganism-induced calcium carbonate deposition according to claim 1, wherein the compacted soil is cultured for 20-30 hours after a bacterial solution is injected;
preferably, the compacted soil is injected with bacterial liquid and cultured for 24 h.
8. The method for reinforcing soil mass strength by using microorganism-induced calcium carbonate deposition according to claim 1, wherein the first curing time is 72 to 96 hours.
9. The method for reinforcing soil mass strength by using microorganism-induced calcium carbonate deposition according to claim 1, wherein the second curing time is 96 to 120 hours.
10. The method for reinforcing soil strength by using microorganism-induced calcium carbonate deposition according to claim 1, wherein the soil to be reinforced is saline soil.
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