CN111501733A - A method for solidifying soil by stimulating and culturing in situ microorganisms - Google Patents

Abstract

The invention discloses a method for solidifying soil by stimulating and culturing in-situ microorganisms. Further, according to the porosity of the soil, the treatment area and the treatment depth, the amount of the excitation liquid and/or cementing liquid added at a time is calculated. By adding the excitation solution in situ, it can promote the reproduction of its own microorganisms in the soil. The microorganisms stimulated in situ have balanced nutrients in the soil environment, and interact with other microorganisms. The growth and reproduction are fast and the urease activity is high. The method of stimulating microorganisms reduces the process of adding bacterial liquid to the soil, greatly reduces the influence of uneven distribution of microorganisms caused by uneven flow of the solution, and effectively improves the effect of MICP.

Description

A method for solidifying soil by stimulating and culturing in-situ microorganisms

technical field

The invention belongs to the cross field of geotechnical engineering and microbial engineering, and more specifically relates to a method for solidifying soil by stimulating and culturing in-situ microorganisms.

Background technique

With the rapid development of the world economy and the rapid increase in population, the demand for construction land continues to increase. Especially in my country, where urbanization continues to intensify, more infrastructure is needed to meet the needs of the growing population. However, in the process of construction, there are serious problems of insufficient land supply, increasing land consumption and poor soil quality, which greatly limit the construction process of urbanization. Therefore, improving the soil that cannot meet the needs of engineering construction and improving the soil utilization rate has become a major event related to the national economy and people's livelihood. How to improve soil in an efficient, environmentally friendly and economical way has become an urgent problem to be solved in today's society.

The traditional soil improvement method is to use mechanical or artificial materials to strengthen the soil physicochemically, which will bring about large energy consumption during mechanical construction and material production. Most of these methods have large soil disturbance, long construction period and heavy workload. Among them, the very common chemical grouting technology mainly achieves the purpose of improving soil strength and reducing soil permeability by adding chemical slurry materials such as cement and chrome lignin into the soil. However, many chemical pulps will bring about changes in soil pH, and are more toxic, which will have harmful effects on soil, groundwater, mineral resources, animals and plants, and humans.

Microbial mineralization is ubiquitous in nature, and some microorganisms can produce a variety of mineral crystals through their own mineralization. Among them, Microbial Induced Calcite Precipitation (MICP) technology has been a research hotspot of microbial mineralization in recent years. In this technology, urease-producing microorganisms produce urease through their own metabolism, continuously decompose urea that diffuses into the bacteria, and the generated CO ₃ ^2- combines with Ca ²⁺ in the environment to form calcium carbonate deposits, the resulting calcium carbonate properties Stable, good mechanical properties, strong durability, and excellent cementation. After research, it is found that MICP technology can be applied in many fields, and has a remarkable effect in soil solidification. In the MICP solidified soil technology, biological energy replaces traditional mechanical energy, and microbial metabolites replace chemical substances. It has the advantages of energy saving and environmental protection, and less disturbance to soil, which is conducive to the sustainable development of the environment.

In the existing research on MICP-solidified soil, most of the urease-producing microorganisms are activated and cultured in laboratory conditions, and then introduced into the soil to induce calcium carbonate deposition, thus playing the role of solidifying the soil. However, when microorganisms are cultivated under laboratory conditions, there are problems such as easy eutrophication of the medium, lack of growth factors, artificial destruction of the connection between microorganisms and neglect of the interaction between microorganisms. These easily lead to microorganisms with metabolic functions, but Slow growth and reproduction (Zhang Zuoyan et al., 2018). Subsequently, after the microorganisms were introduced into the soil, the balance of microorganisms in the natural environment was broken, and the number of exogenous microorganisms further decreased due to the wanton plunder and competition of other native microorganisms in the soil. In addition, in the process of adding bacterial liquid, due to the uneven flow of bacterial liquid in the soil, the distribution of bacteria in the soil is not uniform, which affects the effect of soil solidification (Whiffin et al. 2007; van Paassen et al. 2009).

The prior art with publication number CN106284280A discloses a method for preparing calcium carbonate-solidified sandy soil by using microorganisms. In the method, the sand is poured into a container; gelling liquid and bacterial liquid are added to the container, and the mixed liquid is obtained by constant-temperature shaking culture; a small amount is sucked out of the aforementioned mixed liquid at regular intervals, and then a quantitative amount is added to the remaining mixed liquid. Gelling liquid and sand, after several days in a row, calcium carbonate solidified sand is obtained. The method not only consumes a lot of manpower and material resources for the selection and breeding of bacterial species, but also the microorganisms grow and reproduce slowly during the cultivation, and the soil is unevenly distributed and the survival rate is low after being added to the soil. The cementation method of mixing sand and solution is not suitable for the actual operation on site, and has little engineering significance.

The prior art with publication number CN108441442A discloses a method for preparing calcium carbonate by directly extracting microbial strains from soil. In the method, Bacillus strains are separated from soil by using a solid selective medium, and the isolated strains are propagated and cultured, mixed with gelling liquid, and maintained at a constant temperature to obtain microbe-induced calcium carbonate precipitation. The process of isolating and purifying bacteria in this method is complicated, cumbersome, and labor-intensive. In addition, although the bacteria in the method are isolated from the original soil, the cultivation environment is still laboratory conditions, and the above-mentioned problems in the cultivation process still exist. And the method is limited to the MICP treatment in the solution environment, without the operation of solidifying the soil, and is not suitable for the application under actual engineering conditions.

To sum up, there is no effective solution for cultivating microorganisms efficiently, improving the distribution uniformity and survival rate of microorganisms in soil, and using MICP to solidify soil and applying it to different actual engineering conditions.

SUMMARY OF THE INVENTION

1. The problem to be solved

The purpose of the present invention is to overcome the defects such as slow growth and reproduction of microorganisms through external culture in the existing MICP solidified soil treatment, uneven distribution in the soil body, low survival rate, unsuitable for various actual engineering conditions, etc. The method of stimulating and cultivating in-situ microorganisms to solidify the soil body, by adding the stimulating solution in situ, promotes the reproduction of microorganisms in the soil body, reduces the process of adding bacterial liquid to the soil body, and greatly reduces the uneven flow of the solution. uneven distribution.

Another object of the present invention is to overcome the difficulty in quantifying the amount of solution in in-situ excitation and in-situ cementation, and further provide a method for quantifying excitation solution and cementation solution.

Another object of the present invention is to overcome the problem that the excitation time and the cementation time are difficult to determine, and further provide a determination method.

2. Technical solutions

In order to solve the above problems, the technical scheme adopted in the present invention is as follows:

A method for solidifying soil by stimulating and culturing in-situ microorganisms comprises: firstly adding an exciting liquid to the soil to promote the reproduction of microorganisms in the soil, and then adding cementing liquid to the soil to solidify the soil.

Preferably, according to the porosity, treatment area and treatment depth of the soil, the amount of the excitation liquid and/or cementing liquid added in a single time is calculated.

Preferably, the excitation solution includes urea.

Preferably, the challenge solution further includes yeast extract, glucose and buffer.

Preferably, the cementing solution includes urea and calcium chloride.

Preferably, the method specifically includes the following steps:

1) Determine the porosity, treatment area and treatment depth of the soil, and calculate the amount of excitation liquid and cementing liquid added in a single time;

2) Add the excitation solution to the soil according to the amount of the excitation solution calculated in step 1), and add it every 2-5 days;

Before adding the next excitation solution, sample the soil to measure the urease activity in the soil; the urease activity is defined as the amount of urea hydrolyzed per unit mass of soil in unit time; the number of additions of the excitation solution is judged according to the urease activity, and when the urease activity is greater than 0.06 mghydrolysed urea min When ^-1 g ^-1 , stop adding the excitation solution;

3) According to the amount of cementing liquid calculated in step 1), add cementing liquid to the soil, and add it once every 2～5d;

Before preparing to add the next cementitious solution, take a sample to measure the calcium carbonate content in the soil; according to the calcium carbonate content, judge the number of cementitious solution additions. Stop adding cement.

Preferably, the porosity in step 1) is determined by sampling from the soil to be treated, and the treatment area and treatment depth are determined according to engineering requirements.

Preferably, in step 1), the single dosage V _e (m ³ ) of the excitation solution is:

V _e =αnSH (1)

Among them, α is the correction coefficient of the amount of excitation solution, and the value ranges from 1.05 to 1.55; n is the soil porosity (%); S is the treatment area (m ² ); H is the treatment depth (m). In order to ensure the sufficient infiltration and uniform distribution of the excitation liquid and meet the reaction requirements, the waste of the excitation liquid and the extension of the engineering period are avoided.

Preferably, in step 1), the single dosage V _c (m ³ ) of the cementitious liquid is:

V _c =βV _e (2)

Among them, β is V _c /V _e , that is, the ratio of the single dosage of the cementing solution to the single dosage of the excitation solution, and the value ranges from 0.9 to 1.55, and αβ>1 is guaranteed. In order to ensure that the soil pores can be fully filled and evenly distributed after the cementing liquid is added, so as to achieve the requirements of good curing effect, and at the same time, the waste of cementing liquid and the extension of the engineering period are avoided.

Preferably, the values of α and β depend on the soil permeability coefficient, as shown in Table 1 below:

Table 1 Reference values of α and β

Preferably, in step 2), the components of the excitation solution are urea, yeast extract, glucose and Tris-base buffer. The concentration of the urea is 200-500 mM, the concentration of the yeast extract is 10-20 g/L, the concentration of the glucose is 20-40 g/L, and the concentration of the Tris-base buffer is 0.13M. The urea provides a nitrogen source for bacteria, so that the desired urease-producing bacteria can grow and reproduce, and at the same time, the ammonia produced by the hydrolysis of urea can improve the pH of the soil environment, which is beneficial to the survival of bacteria suitable for an alkaline environment, especially the production of urea. Survival of urease bacteria. The yeast extract provides sufficient nutrients for the growth and reproduction of urease-producing bacteria. The glucose provides a carbon source for bacteria, stimulates the initial activity of bacteria in the soil, and provides energy for bacterial activity. The Tris-base buffer adjusts the pH of the solution.

Preferably, the specific steps of sampling and measuring urease activity described in step 2) include:

a) Sterilize the soil shovel and the polyethylene bag holding the soil sample;

b) Divide the soil sample into multiple areas appropriately according to the treatment area, take 100g of soil from the soil surface of each area, put them into polyethylene bags respectively, keep the soil in the dark, and the ambient temperature is the same as the natural environment. Free access to air;

c) Treat the soil sample as soon as possible after sampling, and pass the soil sample through a 2mm sieve (the sieve diameter can also be selected according to the actual soil conditions, and it is appropriate to sieve out larger particles of stones and animal and plant fragments in the soil sample);

d) Determination of urease activity by conductivity method. Take 20 g of the sieved soil sample in c), put it in a conical flask, and add 100 mL of 0.2% sodium pyrophosphate solution. After stirring with a magnetic stirrer, the solution was centrifuged with a centrifuge for 5 min (centrifugation speed is suitable for separating soil bacteria). Take 5mL of the supernatant, add 45mL of 1.6M urea solution to mix, stir evenly, measure the change of the conductivity of the solution within 5min with a conductivity meter, and obtain the average conductivity change value per minute (mSmin ^-1 ). Multiply by the conversion factor 11 of the amount of urea hydrolysis to calculate the amount of urea hydrolyzed by urease in the solution per unit time (mMurea hydrolysedmin ^-1 ). After dividing by 1 g of the corresponding soil sample mass of 5 mL of supernatant, multiply by the volume of the solution 0.05 L and the molar mass of urea 60 g/mol to obtain the mass of urea hydrolyzed per unit mass of soil in unit time, as the measured soil mass Urease activity (mg urea hydrolysed min ^-1 g ^-1 ). The average urease activity of soil samples in each area was taken as the final measured urease activity. It can also be determined by phenol-sodium hypochlorite colorimetry, diffusion method and other methods, but the conductivity method is suitable, which is simple to operate and highly economical.

Preferably, the cementing liquid in step 3) is urea, calcium chloride and nutrient broth. The urea and calcium chloride have a concentration range of 0.1-2.0M, and a ratio of 1:3-3:1. The concentration of the nutrient broth is 5g/L, which provides sufficient nutrients for the stimulated microorganisms and maintains the activity of the microorganisms.

Preferably, the sampling method in step 3) is the same as a) to b) in step 2). Described soil calcium carbonate content determination uses hydrochloric acid pickling drainage method, and concrete steps include:

a) Sterilize the soil shovel and the polyethylene bag holding the soil sample;

b) Divide the soil sample into multiple areas appropriately according to the treatment area, take 100g of soil from the soil surface of each area, put them into polyethylene bags respectively, keep the soil in the dark, and the ambient temperature is the same as the natural environment. Free access to air;

e) Take 10 g of the soil sample in b); soak the soil sample in deionized water for 12 h, then centrifuge (4000 rpm, 5 min), take the sediment, dry it and weigh it. Grind the dried soil sample to powder, take 5g, add 10mL of 1.0M hydrochloric acid solution to soak for 12h, use the drainage method to measure the volume of CO ₂ generated; compare with the standard curve, and remove the original calcium carbonate content in the soil, calculate the soil the actual calcium carbonate content. The actual calcium carbonate content of the soil samples in each area was averaged as the final measured calcium carbonate content. It can also be determined by methods such as acid washing weighing method.

Preferably, the methods of adding the solution in steps 2) to 3) include spraying, grouting, drip irrigation and flood irrigation.

Preferably, the process selection is different according to different actual engineering conditions. Such as: shallow treatment depth, or cohesive soil conditions, suitable for spraying method and drip irrigation method; deep treatment depth, or sandy soil conditions, suitable for flood irrigation method and grouting method; flat soil conditions, suitable for drip irrigation or flood irrigation method; slope Condition, apply spraying or grouting method; dam reinforcement conditions, apply grouting method; anti-erosion, repair cracking treatment, apply spray method, drip irrigation or flood irrigation method; shallow small-scale building foundation reinforcement applies flood irrigation method; deep medium and large-scale building foundation reinforcement , apply the grouting method.

Preferably, in steps 2) to 3), the number of days between the addition of the cementing solution and the excitation solution adjacent to each other is that the solution is fully infiltrated and reacted completely. In general, the interval days are affected by soil conditions, and the interval days decrease with the increase of soil permeability coefficient.

Preferably, the on-site ambient temperature in steps 2) to 3) is 5°C to 40°C. And the construction should be carried out in the weather without rain as much as possible. If it rains within 1 day of adding the cementitious liquid, in addition to the calcium carbonate content test, a strength test should be carried out. influence on the curing effect.

3. Beneficial effects

Adopting the technical scheme provided by the present invention, compared with the existing known technology, has the following remarkable effects:

(1) The present invention solidifies the soil through urease-producing microorganisms, and the urease produced by the microorganisms decomposes urea, and the generated CO ₃ ^2- combines with Ca ²⁺ in the environment to form calcium carbonate deposits, fill soil pores, and bridge soil particles, The soil strength is significantly improved, the permeability is reduced, and the solidification effect is obvious; due to the simple hydrolysis mechanism of urea, the method has high controllability and short reaction time. In addition, the method has low cost, good environmental compatibility and wide application range; the microorganisms stimulated in situ, because they belong to the natural environment, maintain the ecological balance of the natural environment, have strong survivability and high survival rate; the present invention adopts the stimulation culture In the method of in situ microorganisms, the microorganisms stimulated in situ have balanced nutrients in the soil environment, interact with other microorganisms, and grow rapidly and multiply, and have high urease activity;

(2) The present invention adopts the method of stimulating and cultivating in-situ microorganisms. Since the microorganisms are stimulated after the stimulating liquid enters, the process of adding bacterial liquid to the soil is reduced, and the uneven distribution of microorganisms caused by the uneven flow of the solution is greatly reduced. At the same time, due to the relatively low viscosity of the excitation liquid and good fluidity, it can infiltrate more fully, especially in the cohesive soil, overcoming the difficulty of infiltration of the bacteria liquid, and the stimulated microorganisms in the soil The distribution is relatively deep; thus, it can achieve better curing effect;

(3) The present invention adopts the method of stimulating and cultivating in-situ microorganisms, which avoids the complicated process of culturing microorganisms in the laboratory, and exerts the effect of the original urease-producing microorganisms in the soil, with high economy, simple and convenient operation, short engineering cycle and strong practical applicability;

(4) According to the soil porosity, treatment area and treatment depth, the present invention uses the formulas _Ve = αnSH and V _c = βV _e to quantify the single dosage of the excitation liquid and the cementing liquid in the in-situ treatment, respectively. It is difficult to quantify the amount of solution in in-situ excitation and in-situ cementation; the correction coefficient α for the amount of excitation solution and the ratio β of the single dosage of cementing solution to the single dosage of excitation solution are taken into appropriate ranges, so that the dosage of excitation solution and cementing solution is It can fully infiltrate and fill the pores, which not only meets the requirements of the reaction process, but also avoids the waste of solution and increases the feasibility of practical engineering applications;

(5) In the present invention, the completion time of microbial excitation is determined according to the activity of soil urease, so that the microorganisms are fully stimulated to facilitate the progress of the cementation reaction; to reach maximum. While solidifying the soil to the greatest extent, it also avoids solution and waste and prolonging the engineering cycle;

(6) The present invention provides four excitation and cementing processes of spraying, grouting, drip irrigation and flood irrigation. The invention has a wide range of application scenarios and can be applied to various soil conditions, including sandy soil, silt soil and cohesive soil, etc. And a variety of required engineering conditions, including soil and water conservation, soil crack prevention, foundation reinforcement and dam reinforcement, etc., the invention provides suitable processes according to different actual conditions, and has strong engineering applicability;

(7) The chemical substances used in the excitation liquid and the cementing liquid in the present invention are all non-toxic and harmless substances, and have high environmental protection; wherein the urea used is an important fertilizer for vegetation growth, and plants can be planted on the soil body for ecological restoration in the later stage. ; In addition, no exogenous microorganisms are introduced into the soil, and the microbial balance of the natural environment is maintained.

Description of drawings

1 is a schematic diagram of in-situ excitation and cultivation of microorganisms to solidify soil by spraying method in Example 1;

2 is a schematic diagram of in-situ excitation and cultivation of microorganisms to solidify soil by drip irrigation method in Example 12;

FIG. 3 is a schematic diagram of the in-situ excitation and cultivation of microorganisms to solidify the soil by the flood irrigation method in Example 13. FIG.

FIG. 4 is a schematic diagram of the in-situ excitation and cultivation of microorganisms to solidify soil by the grouting method in Example 14. FIG.

FIG. 5 is a graph showing the variation of urease activity with the number of measurements in Example 1 and Comparative Examples 1A and 1B before each spraying of the excitation liquid or bacterial liquid.

FIG. 6 is a graph showing the variation of calcium carbonate content with the number of measurements measured before each spraying of cementitious solution in Example 1 and Comparative Examples 1A and 1B.

In the picture: 1. Nozzle; 2. Exciting liquid/cementing liquid; 3. Cementing and solidifying layer; 4. Untreated soil layer; 5. Drip irrigation pipe; 6. Dripper; 7. Faucet; 8. Grouting pump; 9. Grouting pipe; 10. Drilling holes.

Detailed ways

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 invention belongs; as used herein, the term "and/or" includes one or more of the associated listed Any and all combinations of items.

If the specific conditions are not indicated in the examples, it is carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used without the manufacturer's indication are conventional products that can be purchased from the market.

As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measure or value. The degree of flexibility of a particular variable can be readily determined by one skilled in the art.

Concentrations, amounts, and other numerical data may be presented herein in range format. It is to be understood that such range formats are used for convenience and brevity only, and are to be flexibly construed to include not only the values expressly recited as the limits of the range, but also all individual values or subranges subsumed within the stated range, As if each numerical value and sub-range were expressly stated. For example, a numerical range of about 1 to about 4.5 should be construed to include not only the expressly recited limit of 1 to about 4.5, but also individual numbers (such as 2, 3, 4) and subranges (such as 1 to 3, 2) to 4, etc.). The same principle applies to ranges reciting only one numerical value, such as "less than about 4.5," which should be construed to include all of the aforementioned values and ranges. Furthermore, this interpretation should apply regardless of the breadth of the scope or features described.

The present invention will be further described below with reference to specific embodiments.

Example 1

In this example, the soil is a 45° slope, silty clay, the soil permeability coefficient is 5×10 ^-6 cm/s, and the engineering environment temperature is 25°C. The engineering requirements are to improve the soil erosion resistance and solve the problem of water and soil loss. .

1) The penetration strength of the soil is measured by the standard penetration test, and the scour resistance of the soil is measured by the scour test, where the scour resistance of the soil is defined as the amount of soil produced per unit time.

2) Take samples from the soil to be treated, and measure the porosity of the soil to be 60%. The soil treatment area S is 10m ² and the treatment depth H is 0.1m. According to the relational formula (1) V _e =αnSH, the single dosage of excitation solution V _e (m ³ ) is calculated. Wherein, the correction coefficient α of the dosage of the excitation liquid is taken as 1.05, and the single dosage of the excitation liquid is calculated as 0.63m ³ . According to the relational formula (2) V _c =βV _e , the single dosage of cementitious liquid V _c (m ³ ) is calculated. Wherein, the ratio β of the single dosage of the cementing solution to the single dosage of the excitation solution was 1.0, and the single dosage of the excitation solution was calculated to be 0.63 m ³ .

3) As shown in Figure 1, spray the excitation solution in the soil according to the amount of the excitation solution calculated in step 2). The components of the excitation solution are 300mM urea, 20g/L yeast extract, 40g/L glucose and 0.13M Tris-base buffer. . One day before adding the next challenge solution, take a sample and measure the bacterial urease activity in the soil by the conductivity method. When the urease activity is greater than 0.06mghydrolysed urea min ^-1 g ^-1 , stop adding the challenge solution. In this embodiment, spray once every 5d, and the spraying process is slow and uniform to ensure that the target treatment area is covered. After the fifth round of spraying the excitation liquid, the above-mentioned indicators are reached (see Fig. 5), and the liquid addition is stopped.

4) As shown in Figure 1, according to the amount of cementing liquid calculated in step 2), adding cementing liquid to the soil, the cementing liquid components are 1.0M urea, 1.0M calcium chloride and 5g/L nutrient broth. One day before the next cementing solution is to be added, samples are taken, and the calcium carbonate content in the soil is measured by the hydrochloric acid pickling drainage method. When the calcium carbonate content is greater than 4.0%, the cementing solution is stopped. In this example, the addition was done once every 5d, and after the fifth round of spraying the cementitious solution, the above-mentioned index was reached, and the addition of the solution was stopped.

5) Carry out a penetration test on the solidified soil, and measure the penetration strength and erosion resistance of the soil again.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 5%, the penetration strength of the soil was increased by 55%, and the erosion resistance of the soil was improved by 55%. %.

Comparative Example 1A

The soil conditions and engineering requirements of this comparative example are the same as those in Example 1, and the processing steps are basically the same as those in Example 1. The differences are:

Instead of adding the excitation solution to the soil body, directly add the bacterial solution of Bacillus Pasteurella cultured under the medium condition to the soil body (Bacillus Pasteurella is a urease-producing bacterium commonly used in engineering for MICP treatment), add The urease activity of the bacterial solution is 2.0 mM hydrolysed urea min ^-1 (the bacterial solution with this activity is the bacterial solution with higher urease activity cultivated under normal medium conditions). Similarly, the day before adding the next bacterial solution, measure Bacterial urease activity in the soil, when the urease activity is greater than 0.06mg hydrolysed urea min ^-1 g ^-1 , stop adding bacterial solution. After the 8th round of spraying the bacterial liquid, the above indicators were reached, and the liquid addition was stopped. After that, the cementing solution was added to the soil, and the addition round was 6 rounds.

Experimental results: In this comparative example, by adding a bacterial solution containing urease-producing microorganisms to the soil, and after MICP treatment, the calcium carbonate content of the soil was 2.5%, the penetration strength of the soil was increased by 35%, and the resistance of the soil was increased by 35%. 38% more washout.

Comparative Example 1B

The soil conditions and engineering requirements of this comparative example are the same as those in Example 1, and the processing steps are basically the same as those in Example 1. The differences are:

The value of αβ is less than 1. The correction coefficient α of the dosage of the excitation solution is taken as 0.8; According to the relational formula (1) V _e =αnSH, the single dosage of the excitation solution is 0.48m ³ , and the single dosage of the cementitious liquid is 0.384m ³ according to the relational formula (2) V _c =βV _e .

In this comparative example, after the 7th round of spraying the excitation liquid, the liquid addition was stopped; after the 6th round of spraying the cementitious liquid, the liquid addition was stopped.

Experimental results: In this comparative example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 3.6%, the penetration strength of the soil was increased by 42%, and the erosion resistance of the soil was improved by 45%. %.

In Example 1 and Comparative Examples 1A and 1B, the urease activity data measured before each spraying of the excitation solution or bacterial solution is shown in Figure 5; the calcium carbonate content data measured before each spraying of the cementitious solution is shown in Figure 6. By comparing Example 1 and Comparative Example 1A, it can be found that in Example 1, the in-situ excitation method is used to stimulate the growth and reproduction of microorganisms rapidly, the urease activity increases rapidly, and the concentration of microorganisms required for the MICP reaction is reached faster. In the cementation process, calcium carbonate The formation rate is high, and the demand for cementing liquid can be reached faster. In Example 1, the number of times of adding the solution is small, which greatly saves the engineering cost and shortens the engineering cycle. At the same time, the penetration strength and scour resistance of the solidified soil in Example 1 are greatly improved compared to Comparative Example 1A, which shows that the method of stimulating the cultivation of in-situ microorganisms to solidify the soil applied in the present invention has a better soil improvement effect. Obviously, the improvement of soil mechanical properties and engineering performance is more significant, which is related to the more uniform distribution of microorganisms, deeper depth and higher microbial activity cultivated by this method. By comparing Example 1 and Comparative Example 1B, it can be found that when αβ<1, the urease activity of the microorganisms in the soil increases more slowly, that is, the speed at which the microorganisms are stimulated in the soil is slower. At the same time, the resulting calcium carbonate precipitation rate is also slower, it is more difficult to achieve the required calcium carbonate content index, and the mechanical properties of the solidified soil are also poor. This will increase the engineering period, reduce the soil treatment effect, and make it difficult to meet the engineering requirements, which further illustrates the necessity of ensuring αβ>1 in the present invention.

Example 2

The soil conditions and engineering requirements of this example are the same as those of Example 1, and the processing steps are basically the same as those of Example 1. The differences are:

The correction coefficient α of the dosage of the excitation solution is taken as 1.15; According to the relational formula (1) V _e =αnSH, the single dosage of the excitation liquid is 0.69m ³ , and the single dosage of the cementing liquid is 0.621m ³ calculated from the relational formula (2) V _c =βV _e .

In this example, after the fifth round of spraying the excitation liquid, the liquid addition was stopped; after the sixth round of spraying the cementitious liquid, the liquid addition was stopped.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 6.3%, the penetration strength of the soil was increased by 56%, and the erosion resistance of the soil was improved by 58%. %.

Example 3

The soil conditions and engineering requirements of this example are the same as those of Example 1, and the processing steps are basically the same as those of Example 1. The differences are:

The correction coefficient α of the dosage of the excitation solution is taken as 1.1; According to the relational formula (1) V _e =αnSH, the single dosage of the excitation solution is 0.66m ³ , and the single dosage of the cementing liquid is 0.726m ³ according to the relational formula (2) V _c =βV _e .

The components of the excitation solution are 200mM urea, 20g/L yeast extract, 40g/L glucose and 0.13M Tris-base buffer; the components of the cementing solution are 1.0M urea, 1.0M calcium chloride and 5g/L nutrient broth.

In this example, after the fifth round of spraying the excitation liquid, the liquid addition was stopped; after the sixth round of spraying the cementitious liquid, the liquid addition was stopped.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 5.5%, the penetration strength of the soil was increased by 40%, and the erosion resistance of the soil was improved by 45%. %.

Example 4

The soil conditions and engineering requirements of this embodiment are the same as those of embodiment 1, and the processing steps are basically the same as those of embodiment 3. The differences are:

The components of the excitation solution are 300mM urea, 20g/L yeast extract, 40g/L glucose and 0.13M Tris-base buffer; the components of the cementing solution are 1.0M urea, 1.0M calcium chloride and 5g/L nutrient broth.

In this example, after the fifth round of spraying the excitation liquid, the liquid addition was stopped; after the sixth round of spraying the cementitious liquid, the liquid addition was stopped.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 6.8%, the penetration strength of the soil was increased by 65%, and the erosion resistance of the soil was improved by 65%. %.

Example 5

The soil conditions and engineering requirements of this embodiment are the same as those of embodiment 1, and the processing steps are basically the same as those of embodiment 3. The differences are:

The components of the excitation solution are 500mM urea, 20g/L yeast extract, 40g/L glucose and 0.13M Tris-base buffer; the components of the cementing solution are 1.0M urea, 1.0M calcium chloride and 5g/L nutrient broth.

In this example, after the 6th round of spraying the excitation liquid, the liquid addition was stopped; after the 6th round of spraying the cementitious liquid, the liquid addition was stopped.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 6.5%, the penetration strength of the soil was increased by 60%, and the erosion resistance of the soil was improved by 58%. %.

Example 6

The soil conditions and engineering requirements of this embodiment are the same as those of embodiment 1, and the processing steps are basically the same as those of embodiment 3. The differences are:

The components of the excitation solution are 300mM urea, 20g/L yeast extract, 40g/L glucose and 0.13M Tris-base buffer; the components of the cementing solution are 0.1M urea, 0.3M calcium chloride and 5g/L nutrient broth.

In this example, after the fifth round of spraying the excitation liquid, the liquid addition was stopped; after the sixth round of spraying the cementitious liquid, the liquid addition was stopped.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 4%, the penetration strength of the soil was increased by 20%, and the erosion resistance of the soil was improved by 25%. %.

Example 7

The soil conditions and engineering requirements of this embodiment are the same as those of embodiment 1, and the processing steps are basically the same as those of embodiment 3. The differences are:

The components of the excitation solution are 300mM urea, 20g/L yeast extract, 40g/L glucose and 0.13M Tris-base buffer; the components of the cementing solution are 0.1M urea, 0.3M calcium chloride and 5g/L nutrient broth.

In this example, after the 6th round of spraying the excitation liquid, the liquid addition was stopped; after the 6th round of spraying the cementitious liquid, the liquid addition was stopped.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 4%, the penetration strength of the soil was increased by 25%, and the erosion resistance of the soil was improved by 23%. %.

Example 8

The soil conditions and engineering requirements of this embodiment are the same as those of embodiment 1, and the processing steps are basically the same as those of embodiment 3. The differences are:

The components of the excitation solution are 300mM urea, 20g/L yeast extract, 40g/L glucose and 0.13M Tris-base buffer; the components of the cementing solution are 2.0M urea, 2.0M calcium chloride and 5g/L nutrient broth.

In this example, after the 6th round of spraying the excitation liquid, the liquid addition was stopped; after the 7th round of spraying the cementitious liquid, the liquid addition was stopped.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 4%, the penetration strength of the soil was increased by 25%, and the erosion resistance of the soil was improved by 25%. %.

Example 9

The soil conditions and engineering requirements of this embodiment are basically the same as those of embodiment 1, and the processing steps are the same as those of embodiment 4, except that:

The engineering ambient temperature in this embodiment is 5°C.

In this example, after the 7th round of spraying the excitation liquid, the liquid addition was stopped; after the 7th round of spraying the cementitious liquid, the liquid addition was stopped. Standard penetration tests were performed before and after treatment to determine soil penetration strength.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 4%, the penetration strength of the soil was increased by 30%, and the erosion resistance of the soil was improved by 35%. %.

Example 10

The soil conditions and engineering requirements of this embodiment are basically the same as those of embodiment 1, and the processing steps are the same as those of embodiment 4, except that:

The engineering ambient temperature in this embodiment is 40°C.

In this example, after the 7th round of spraying the excitation liquid, the liquid addition was stopped; after the 7th round of spraying the cementitious liquid, the liquid addition was stopped. Standard penetration tests were performed before and after treatment to determine soil penetration strength.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 4%, the penetration strength of the soil was increased by 35%, and the erosion resistance of the soil was increased by 40%. %.

Example 11

The soil in this example is flat land, silt, the soil permeability coefficient is 5 × 10 ^-5 cm/s, and the engineering ambient temperature is 25°C. The engineering requirement is small-scale reconstruction of the walkway, and only a hardened shell needs to be provided.

1) Determination of soil penetration strength by standard penetration test.

2) Take samples from the soil to be treated, and measure the porosity of the soil to be 55%. The soil treatment area S is 10m ² and the treatment depth H is 0.2m. According to the relational formula (1) V _e =αnSH, the single dosage of excitation solution V _e (m ³ ) is calculated. Among them, the correction coefficient α of the amount of excitation liquid is taken as 1.2, and the single consumption of the excitation liquid is calculated as 1.32m ³ . According to the relational formula (2) V _c =βV _e , the single dosage of cementitious liquid V _c (m ³ ) is calculated. Wherein, the ratio β of the single dosage of the cementing solution to the single dosage of the excitation solution was 1.2, and the single dosage of the excitation solution was calculated to be 1.584m ³ .

3) As shown in Figure 2, according to the amount of excitation liquid calculated in step 2), the excitation liquid is added to the soil by drip irrigation method, the distance between adjacent drip irrigation pipes is 1.0m, and the distance between adjacent drippers is 1.0m. The components of the challenge solution were 300 mM urea, 20 g/L yeast extract, 40 g/L glucose and 0.13 M Tris-base buffer. One day before adding the next challenge solution, take a sample and measure the bacterial urease activity in the soil by conductivity method. When the urease activity is greater than 0.06mg hydrolysed urea min ^-1 g ^-1 , stop adding the challenge solution. In this example, the addition was done once every 4 d, and after the fifth round of adding the excitation solution, the above-mentioned index was reached, and the addition of the solution was stopped.

4) As shown in Figure 2, according to the amount of cementing liquid calculated in step 2), adding cementing liquid to the soil, the cementing liquid components are 1.0M urea, 1.0M calcium chloride and 5g/L nutrient broth. One day before the next cementing solution is to be added, samples are taken, and the calcium carbonate content in the soil is measured by the hydrochloric acid pickling drainage method. When the calcium carbonate content is greater than 4.0%, the cementing solution is stopped. In this embodiment, it is added every 4d. After the fifth round of adding the cementitious liquid, the above-mentioned indicators were reached, and the liquid addition was stopped.

5) Carry out a penetration test on the solidified soil, and measure the penetration strength of the soil again.

Experimental results: In this example, the method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 7.5%, and the penetration strength of the soil was increased by 70%.

Example 12

The soil in this example is flat land, silt soil, the soil permeability coefficient is 5×10 ^-4 cm/s, and the engineering ambient temperature is 25°C. The engineering requirement is to improve the foundation bearing capacity of small buildings.

1) The penetration strength of the soil mass is determined by the standard penetration test, and the unconfined compressive strength of the soil mass is determined by the unconfined compressive strength test.

2) Take samples from the soil to be treated, and measure the porosity of the soil to be 45%. The soil treatment area S is 10m ² and the treatment depth H is 0.8m. According to the relational formula (1) V _e =αnSH, the single dosage of excitation solution V _e (m ³ ) is calculated. Among them, the correction coefficient α of the amount of the excitation liquid is taken as 1.3, and the single consumption of the excitation liquid is calculated to be 4.68m ³ . Through the relational formula (2) V _c =βV _e , the single dosage of cementing solution V _e (m ³ ) is calculated. Wherein, the ratio β of the single dosage of the cementing solution to the single dosage of the excitation solution was taken as 1.3, and the single dosage of the excitation solution was calculated to be 6.084m ³ .

3) As shown in Figure 3, according to the amount of the excitation solution calculated in step 2), the excitation solution is added to the soil by the flood irrigation method, and the water flow during the flood irrigation process is not easy to be too fast or too slow, to ensure that the solution infiltrates uniformly and covers the target treatment area. . The components of the challenge solution were 300 mM urea, 20 g/L yeast extract, 40 g/L glucose and 0.13 M Tris-base buffer. One day before adding the next challenge solution, take a sample and measure the bacterial urease activity in the soil by the conductivity method. When the urease activity is greater than 0.06mghydrolysed urea min ^-1 g ^-1 , stop adding the challenge solution. In this example, the addition was done once every 3 days to reach the above-mentioned index, and after the fifth round of adding the excitation solution, the addition of the solution was stopped.

4) As shown in Figure 3, according to the amount of cementing liquid calculated in step 2), adding cementing liquid to the soil, the cementing liquid components are 1.0M urea, 1.0M calcium chloride and 5g/L nutrient broth. One day before the next cementing solution is to be added, the samples are taken, and the calcium carbonate content in the soil is measured by the hydrochloric acid pickling drainage method. When the calcium carbonate content is greater than 8.0%, the cementing solution is stopped. In this example, the addition was done once every 3 days to reach the above-mentioned index, and after the sixth round of adding the cementitious liquid, the addition of the liquid was stopped.

5) Carry out a penetration test on the solidified soil, and measure the penetration strength and unconfined compressive strength of the soil again.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 8%, the penetration strength of the soil was increased by 90%, and the unconfined compressive strength was improved. 80%.

Example 13

The soil in this example is a 40° slope, fine sandy soil, the soil permeability coefficient is 5×10 ^-3 cm/s, and the engineering ambient temperature is 25°C.

1) The penetration strength of the soil mass is determined by the standard penetration test, and the unconfined compressive strength of the soil mass is determined by the unconfined compressive strength test.

2) Take samples from the soil to be treated, and measure the porosity of the soil to be 40%. The soil treatment area S is 10m ² and the treatment depth H is 2m. According to the relational formula (1) V _e =αnSH, the single dosage of excitation solution V _e (m ³ ) is calculated. Wherein, the correction coefficient α of the dosage of the excitation liquid is taken as 1.4, and the single dosage of the excitation liquid is calculated as 11.2m ³ . According to the relational formula (2) V _c =βV _e , the single dosage of cementitious liquid V _c (m ³ ) is calculated. Among them, the ratio β of the single dosage of the cementing solution to the single dosage of the excitation solution was taken as 1.4, and the single dosage of the excitation solution was calculated to be 15.68m ³ .

3) As shown in Figure 4, according to the amount of the excitation liquid calculated in step 2), the excitation liquid is added to the soil by the grouting method, and the concrete method is to open a hole in the soil body, the inner diameter of the hole is 10cm, and the depth of the hole is 2.0m, The spacing between adjacent drilling holes is 1.0m, and the drilling holes are evenly distributed in a square grid shape, and grouting is carried out through a grouting pipe. The components of the challenge solution were 300 mM urea, 20 g/L yeast extract, 40 g/L glucose and 0.13 M Tris-base buffer. One day before adding the next challenge solution, take a sample and measure the bacterial urease activity in the soil by conductivity method. When the urease activity is greater than 0.06mg hydrolysed urea min ^-1 g ^-1 , stop adding the challenge solution. In this example, the addition was performed once every 3 days, and after the fifth round of adding the excitation solution, the above-mentioned index was reached, and the addition of the solution was stopped.

4) As shown in Figure 4, according to the amount of cementing liquid calculated in step 2), adding cementing liquid to the soil, the cementing liquid components are 1.0M urea, 1.0M calcium chloride and 5g/L nutrient broth. One day before the next cementing solution is to be added, samples are taken, and the calcium carbonate content in the soil is measured by the hydrochloric acid pickling drainage method. When the calcium carbonate content is greater than 4.0%, the cementing solution is stopped. In this example, the addition was done once every 3 days, and after the fifth round of adding the cementitious solution, the above-mentioned index was reached, and the addition of the solution was stopped.

5) Carry out a penetration test on the solidified soil, and measure the penetration strength and unconfined compressive strength of the soil again.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 10%, the penetration strength of the soil was increased by 150%, and the unconfined compressive strength was improved. 120%.

Example 14

The soil in this example is a 40° slope, medium sandy soil, the soil permeability coefficient is 5×10 ^-2 cm/s, and the engineering ambient temperature is 25°C.

1) The penetration strength of the soil mass is determined by the standard penetration test, and the unconfined compressive strength of the soil mass is determined by the unconfined compressive strength test.

2) Take samples from the soil to be treated, and measure the porosity of the soil to be 35%. The soil treatment area S is 10m ² and the treatment depth H is 3m. According to the relational formula (1) V _e =αnSH, the single dosage of excitation solution V _e (m ³ ) is calculated. Among them, the correction coefficient α of the amount of excitation liquid is taken as 1.5, and the single consumption of excitation liquid is calculated as 15.75m ³ . According to the relational formula (2) V _c =βV _e , the single dosage of cementing solution V _e (m ³ ) is calculated. Among them, the ratio β of the single dosage of the cementing solution to the single dosage of the excitation solution was taken as 1.5, and the single dosage of the excitation solution was calculated to be 23.625m ³ .

3) As shown in Figure 4, according to the amount of the excitation solution calculated in step 2), the excitation solution is added to the soil by the grouting method, and the components of the excitation solution are 300mM urea, 20g/L yeast extract, 40g/L glucose and 0.13MTris- base buffer. One day before adding the next challenge solution, take a sample and measure the bacterial urease activity in the soil by conductivity method. When the urease activity is greater than 0.06mg hydrolysed urea min ^-1 g ^-1 , stop adding the challenge solution. In this example, the addition was performed once every 2 d, and after the fourth round of adding the excitation solution, the above-mentioned index was reached, and the addition of the solution was stopped.

4) As shown in Figure 4, according to the amount of cementing liquid calculated in step 2), adding cementing liquid to the soil, the cementing liquid components are 1.0M urea, 1.0M calcium chloride and 5g/L nutrient broth. One day before the next cementing solution is to be added, the samples are taken, and the calcium carbonate content in the soil is measured by the hydrochloric acid pickling drainage method. When the calcium carbonate content is greater than 8.0%, the cementing solution is stopped. In this example, the addition was done once every 2d, and after the fifth round of adding the excitation solution, the above-mentioned index was reached, and the addition of the solution was stopped.

5) Carry out a penetration test on the solidified soil, and measure the penetration strength and unconfined compressive strength of the soil again.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 12%, the penetration strength of the soil was increased by 200%, and the unconfined compressive strength was improved. 150%.

Example 15

The soil conditions and engineering requirements of this example are the same as those of Example 14. The processing steps of this embodiment are basically the same as those of Embodiment 14, the differences are:

The correction coefficient α of the dosage of the excitation solution is taken as 1.55; According to the relational formula (1) V _e =αnSH, the single dosage of the excitation solution is 16.275m ³ , and the single dosage of the cementitious liquid is 25.22625m ³ calculated from the relational formula (2) V _c =βV _e .

In this example, after the 4th round of adding the excitation liquid, the liquid addition was stopped; after the 5th round of adding the cementitious liquid, the liquid addition was stopped.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 12.5%, the penetration strength of the soil was increased by 220%, and the erosion resistance of the soil was increased by 160%. %.

Example 16

The soil conditions and engineering requirements of this example are the same as those of Example 14. The processing steps of this embodiment are basically the same as those of Embodiment 14, the differences are:

The interval between two consecutive additions of the cementing solution and the exciting solution was 4 days.

In this example, after the 4th round of adding the excitation liquid, the liquid addition was stopped; after the 4th round of adding the cementitious liquid, the liquid addition was stopped.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 12.8%, the penetration strength of the soil was increased by 230%, and the erosion resistance of the soil was improved by 165%. %.

Example 17

The soil conditions and engineering requirements of this example are the same as those of Example 1, and the processing steps are basically the same as those of Example 1. The differences are:

The soil treatment area is 1000m ² .

The correction coefficient α of the dosage of the excitation solution is taken as 1.15; According to the relational formula (1) V _e = αnSH, the single dosage of the excitation solution is 69 m ³ , and the single dosage of the cementing liquid is 62.1 m ³ calculated from the relation (2) V _c = βV _e .

In this example, after the fifth round of spraying the excitation liquid, the liquid addition was stopped; after the sixth round of spraying the cementitious liquid, the liquid addition was stopped.

Experimental results: In this example, this method was used to stimulate urease-producing microorganisms in situ, and after MICP treatment, the calcium carbonate content of the soil was 6.1%, the penetration strength of the soil was increased by 58%, and the erosion resistance of the soil was improved by 68%. %. The present invention has no limitation on the treatment area of the soil body, and has universality, which is further described with this embodiment.

The present invention and its embodiments have been described above schematically, and the description is not restrictive, and what is shown in the accompanying drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if those of ordinary skill in the art are inspired by it, without departing from the purpose of the present invention, any structural modes and embodiments similar to this technical solution are designed without creativity, which shall belong to the protection scope of the present invention. .

Claims (10)

1. A method for solidifying soil by utilizing an activated culture in-situ microorganism is characterized by comprising the following steps: firstly, adding an exciting liquid into a soil body to promote the propagation of microorganisms in the soil body, and then adding a cementing liquid into the soil body to solidify the soil body.

2. The method for solidifying the soil mass by using the activated culture in-situ microorganisms according to claim 1, wherein the dosage of the single addition of the activating liquid and/or the cementing liquid is calculated according to the porosity, the treatment area and the treatment depth of the soil mass.

3. The method for solidifying a soil mass by means of microorganisms in situ using activated culture according to claim 2, characterized in that it comprises in particular the following steps:

1) determining the porosity, the treatment area and the treatment depth of the soil body, and calculating the usage of the exciting liquid and the cementing liquid which are added once;

2) adding the excitation liquid into the soil body according to the amount of the excitation liquid calculated in the step 1), and adding the excitation liquid once every 2-5 days;

before preparing to add the next exciting liquid, sampling and measuring the urease activity in the soil body; the urease activity is defined as the urea amount hydrolyzed by unit mass of soil body in unit time; judging the adding times of the exciting liquid according to the urease activity, when the urease activity is more than 0.06mg hydrosed urea min^-1g^-1Stopping adding the exciting liquid;

3) adding the cementing liquid into the soil body according to the amount of the cementing liquid calculated in the step 1), and adding the cementing liquid once every 2-5 days;

before preparing to add the next cementing liquid, sampling and measuring the content of calcium carbonate in the soil body; judging the adding times of the cementing liquid according to the calcium carbonate content, and stopping adding the cementing liquid when the calcium carbonate content of the fine-grained soil is more than 4.0% or the calcium carbonate content of the coarse-grained soil is more than 8.0%.

4. The method for cultivating in-situ solidified soil mass by using excitation according to claim 2, wherein the exciting liquid is used in a single dose V in the step 1)_eThe method comprises the following steps:

V_e＝αnSH (1)

wherein, V_eUnit is m³α is the correction coefficient of exciting liquid dosage, n is the porosity of soil body,%, S is the area treated, m²(ii) a H is the treatment depth, m.

5. The method for solidifying the soil mass by using the activated culture in-situ microorganisms according to claim 4, wherein the single dosage V of the cementing liquid in the step 1) is_cComprises the following steps:

V_c＝βV_e(2)

wherein, V_cUnit is m³β is V_c/V_eThe ratio of the single dosage of the cementing liquid to the single dosage of the exciting liquid is 0.9 to 1.55.

6. The method of claim 5 wherein αβ > 1.

7. The method of claim 6 wherein the values of α and β are determined by the soil permeability coefficient, as shown in Table 1:

reference values for tables 1 α and β

8. The method for solidifying soil mass by using microorganisms in situ under the excitation culture according to any one of claims 1 to 7, wherein the excitation solution in the step 2) comprises urea, yeast extract, glucose and Tris-base buffer, wherein the concentration of the urea is 200 to 500mM, the concentration of the yeast extract is 10 to 20 g/L, the concentration of the glucose is 20 to 40 g/L, and the concentration of the Tris-base buffer is 0.13M.

9. The method for solidifying the soil body by utilizing the activated culture in-situ microorganisms according to any one of claims 1 to 7, wherein the cementing liquid in the step 3) is urea, calcium chloride and nutrient broth, the concentration of the urea and the calcium chloride is 0.1-2.0M, the mixing ratio is 1: 3-3: 1, and the concentration of the nutrient broth is 5 g/L.

10. The method for solidifying the soil body by utilizing the activated culture of the in-situ microorganisms according to any one of claims 1 to 7, wherein the solution in the steps 2) to 3) is added in one or more of spraying, grouting, drip irrigation or flood irrigation.

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