CN114215041A - Debris flow prevention and control method based on in-situ excitation microorganism curing technology - Google Patents
Debris flow prevention and control method based on in-situ excitation microorganism curing technology Download PDFInfo
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Abstract
The invention discloses a debris flow prevention and control method based on an in-situ excitation microorganism curing technology, and belongs to the field of geological engineering-microorganism interdiscipline. The method comprises the following steps: 1) measuring the area of the object source region, the porosity of the soil body and the gradient degree of the object source region; 2) calculating the amount of a culture medium required for exciting urease bacteria in the in-situ soil body once according to the data obtained in the step 1); 3) spraying an excitation culture medium on the soil body of the debris flow source area until the average urease activity of urease bacteria reaches a standard value, and completing the excitation of the urease bacteria in the soil body of the source area; 4) calculating the amount of the cementing liquid required by the single-curing soil body according to the data obtained in the step 1) and the estimated treatment depth; 5) and spraying a cementing liquid on the soil body of the excited material source region until the content of the calcium carbonate growing in the soil body of the material source region reaches a specific range. The invention utilizes the in-situ microorganism-excited curing technology to cure the surface soil body of the debris flow logistics area in a short time, improves the anti-erosion capability of the surface soil body and prevents the soil body of the logistics area from water and soil loss.
Description
Technical Field
The invention belongs to the field of geological engineering-microorganism interdisciplines, and particularly relates to a debris flow prevention and control method based on an in-situ excitation microorganism curing technology.
Background
In mountainous areas or gully deep-ravine areas, debris flows are usually formed under the action of heavy rainfall, heavy snow or other natural disasters due to the severe terrain, the large-scale catchment areas and the existence of thick loose rock-soil bodies. The debris flow has the characteristics of rapidness, high flow rate, large flow, large solid matter content, strong destructiveness and the like, so once a debris flow disaster occurs, traffic facilities such as roads and railways are usually destroyed, even villages and towns are destroyed, and the human lives and properties are greatly damaged. At present, the prevention and treatment engineering measures of the debris flow mainly comprise blocking engineering, drainage engineering and soil and water conservation. The water and soil conservation is a permanent measure of the debris flow, slope treatment is carried out, and the water and soil conservation is well carried out, so that the debris flow disaster can be effectively prevented. At present, the main measures for water and soil conservation comprise afforestation, mountain sealing and forest cultivation, vegetation protection and the like, but the water and soil conservation takes effect slowly due to the long growth period of the vegetation. In addition, the vegetation development has certain requirements on the soil environment, so the method is not applicable to barren soil. Based on this, there is an urgent need to develop a water and soil conservation method with fast effect, wide application range and environmental friendliness.
In recent years, the microbial rock-soil technology has made an important progress in the soil improvement research fields of soil solidification, water and soil conservation, seepage prevention restoration and the like. One of the most widely studied methods is to improve soil by using a microbial mineralization technology called MICP. The method mainly utilizes urease bacteria commonly existing in nature, such as Sporosarcina pasteurianum (Sporosarcina pasteurii), which can produce urease to decompose urea in an alkaline environment to generate carbonate ions, so that the urease bacteria is combined with calcium ions existing in the environment to induce the generation of calcium carbonate precipitates. For loose sandy soil, soil particles can be cemented into a whole by a microorganism induced calcium carbonate precipitation technology, so that the soil strength is improved, and meanwhile, the generated calcium carbonate can fill the pores among the soil particles to achieve the effect of reducing the soil permeability. Research has shown that MICP technology has achieved good results in addressing water and soil conservation. Spraying the bacterium liquid and the cementing liquid on the surface of the soil body can quickly solidify surface soil particles and improve the strength of the surface soil body, and meanwhile, the interaction between the generated calcium carbonate and the surface soil body can generate a hardened shell on the surface of the soil body, and the hardened shell can effectively prevent rainfall infiltration, so that most rainwater flows away in a surface runoff mode, and water and soil loss is avoided. Therefore, it is possible to prevent debris flow disasters by using the MICP technology to achieve good soil and water conservation.
Disclosure of Invention
1. Problems to be solved
Aiming at the problems that in the prior art, water and soil conservation is well achieved through modes such as tree planting and forestation, the effect taking speed is low and the application range is narrow in preventing debris flow disasters, the invention provides a debris flow prevention and control method based on an in-situ activated microorganism curing technology.
2. Technical scheme
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a debris flow prevention and control method based on an in-situ excitation microorganism curing technology comprises the following steps:
1) measuring the area of a debris flow material source area, the porosity of a soil body and the gradient degree of the material source area;
if the landform and the source information of the debris flow source area can be obtained by combining field investigation and a remote sensing observation technology, the area of the source area, the porosity of soil and the slope degree of the statistical source area are estimated;
2) calculating the culture medium dosage required for single excitation of urease bacteria in the in-situ soil body according to the area of the source area, the porosity of the soil body and the estimated treatment depth obtained in the step 1);
3) spraying an excitation culture medium on the soil body of the debris flow source area, stopping spraying the excitation culture medium when the average urease activity of the urease bacteria reaches or exceeds a standard value, and completing the excitation of the urease bacteria in the soil body of the source area;
when the average urease activity is measured, respectively digging soil bodies in a specific amount (such as 100 g) within a treatment depth range in a plurality of different areas of the material source area, and detecting the urease activity in the soil bodies, when the average urease activity of urease bacteria exceeds a standard value, stopping spraying an excitation culture medium, and at the moment, completing the excitation of the urease bacteria in the soil bodies of the material source area;
4) calculating the dosage of the cementing liquid required by the single-curing soil body according to the area of the material source region, the gradient degree of the material source region, the porosity of the soil body and the estimated treatment depth obtained in the step 1);
5) and spraying a cementing liquid on the soil body of the excited material source region until the content of the calcium carbonate growing in the soil body of the material source region reaches a specific range.
In addition, before the treatment of the cementing liquid, the content of calcium carbonate in the soil body needs to be tested by sampling, and the content of calcium carbonate generated by the induction of microorganisms is obtained by subtracting the content of calcium carbonate in the soil body from the measured total content of calcium carbonate. And when the average calcium carbonate content generated by the MICP reaction exceeds a standard value, stopping spraying the cementing liquid, and finishing the soil body solidification in the material source area.
In the steps 3) and 5), preferably, soil samples are taken from a plurality of different areas of the source area respectively to be tested so as to reduce random errors brought by the testing process, and the testing area is recommended to be 3-5.
Preferably, the area S (m) of the source region in the step 2)2) Soil porosity n (%), estimated treatment depth D (m) and in situ excitation medium dosage Vb(L) satisfies the following relationship:
Vb＝a×n×S×D (1)
wherein, a in the formula (1) is the in-situ excitation culture medium dosage correction coefficient, and the value range thereof is as follows: 0.5 to 2.0.
Preferably, the area S (m) of the source region in the step 4)2) The gradient degree H (%) of the source area, the porosity n (%) of the soil body, the estimated treatment depth D (m) and the dosage V of the cementing liquidc(L) satisfies the following relationship:
Vc＝b×n×(H+1)×S×D (2)
wherein, b in the formula (2) is a cementing liquid dosage correction coefficient, and the value range thereof is as follows: 0.8 to 3.0.
When the cementing liquid is sprayed on the slope surface, part of the cementing liquid flows away along the slope toward the slope toe direction under the action of gravity, and the phenomenon becomes more and more obvious along with the increase of the slope degree of the source region, so that the single cementing liquid dosage can be properly increased along with the increase of the slope degree of the soil body, and the empirical relationship between the single cementing liquid dosage and the soil body slope degree obtained after multiple tests is shown in a formula (2). The single cementing liquid amount is determined according to the slope degree of the soil body in the material source area, on one hand, the soil body in the expected treatment depth range of the slope can be guaranteed to be effectively cemented, on the other hand, the cementing efficiency of the soil body can be improved, and meanwhile, the resource waste caused by excessive spraying of the cementing liquid is avoided. Besides, the damage of the fluidity of the surface soil body caused by excessive spraying can be avoided.
Preferably, the content of the soil body calcium carbonate in the source area in the step 5) is as follows:
aiming at the matter source region with the gradient degree of less than 10 percent, the content of calcium carbonate increased in the soil body after MICP treatment (namely the treatment of the steps 2-5) reaches 5-7 percent; or
Aiming at the source region with the gradient degree of 10-30%, the content of calcium carbonate increased in the soil body after MICP treatment reaches 7-10%; or
Aiming at the matter source region with the gradient degree of more than 30 percent, the content of calcium carbonate increased in the soil body after MICP treatment reaches more than 10 percent. And simultaneously, the mud-rock flow can be effectively prevented by combining other water and soil conservation measures.
Generally speaking, the larger the degree of slope fall in a material source area is, the more easily water and soil loss occurs under the action of rainfall scouring, and thus debris flow disasters are more easily caused. Therefore, different degrees of microorganism reinforcement treatment are needed for different slope sizes of the object source areas.
Preferably, in the step 2) and/or the step 4), for clay soil layers, the value range of the microbial curing treatment depth D is as follows: 0 to 0.1 m; for sandy soil layers, the value range of the microbial curing treatment depth D is as follows: 0 to 0.5 m. The MICP solution has good permeability in sandy soil but poor permeability in clay, so that the curing treatment depth D of microorganisms in different soil layers has different value ranges.
Preferably, the culture medium in step 2) consists of urea, ammonium chloride, sodium acetate, yeast extract, acid-base buffer (Tris base) and pure water; wherein the contents of all the substances are respectively as follows: urea: 0.1-0.5 mol/L; ammonium chloride: 0.01-0.1 mol/L; sodium acetate: 0.05-0.5 mol/L; yeast extract (B): 0.1-1.0 g/L; acid-base buffer: 0.1 to 1.4 g/L.
Preferably, the standard value for the average urease activity of the urease bacteria is 10 mM/h. That is, when urease bacteria contained in 100g of soil can decompose 10mM urea per hour, it is considered that the excitation of urease bacteria in the soil has been completed.
Preferably, the method for detecting urease activity in step 3) comprises the following steps: filling 100g of soil into a conical flask, adding 1L of deionized water, then placing the conical flask into a shaking table, oscillating for 3 hours to enable all microorganisms in the soil to be dissolved in water, then filtering out soil particles by using a filtering device, taking 5mL of filtered solution, adding 45mL of 1.6mol/L urea solution, uniformly stirring, measuring the change of the conductivity value within 5min by using a conductivity meter, then converting to obtain the urea decomposition amount of urease in unit time, and finally multiplying by the dilution factor to obtain the urease activity of urease bacteria contained in 100g of soil.
Preferably, the cementing liquid in the step 4) consists of urea, calcium chloride, nutrient broth and pure water; wherein the contents of all the substances are respectively as follows: urea: 0.1-1.0 mol/L; calcium chloride: 0.1-1.0 mol/L; nutrient broth: 0.1 to 3.0 g/L.
Preferably, the frequency of the culture medium spraying in the step 3) is once a day; the spraying frequency of the cementing liquid in the step 5) is once per day.
Preferably, the calcium carbonate content testing method in the step 5) is a drainage method, and specifically comprises the following steps: firstly, 500g of soil is taken and filled into a closed reactor, then excessive dilute hydrochloric acid is added into the reactor through a separating funnel, carbon dioxide gas generated by reaction is led into a container filled with water through a guide pipe at the top of the reactor, the water in the container is discharged under the action of air pressure, after the reaction is completed, the volume of the discharged water is approximately equal to the volume of the gas generated by the reaction, and the content of calcium carbonate in the soil can be calculated by measuring the volume of the discharged water.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention provides a debris flow control method based on an in-situ activated microorganism curing technology, aiming at the problems that in the prior art, water and soil conservation is well achieved through modes of afforestation and the like, so that the debris flow disaster prevention effect is low, and the application range is narrow. The method is mainly applied to surface soil solidification in a debris flow source area by utilizing the MICP technology, and the anti-erosion capability of the surface soil is improved. Meanwhile, calcium carbonate generated by microorganism induction interacts with the soil body to generate a hardened shell on the surface of the soil body, so that most rainwater flows away in a surface runoff manner instead of infiltrating into the soil body to cause water and soil loss in rainfall; the MICP reaction mechanism is simple, the process is easy to control, the effect taking speed is very high, and the effect can be exerted in a short time, so that the soil body (as shown in figure 1) in the debris flow thing source area is solidified by utilizing the technology, the water and soil loss can be effectively prevented, and further the debris flow disaster is prevented; meanwhile, the culture medium amount of urease bacteria in the single-excitation in-situ soil body and the cementing liquid amount required by single-solidification of the soil body are calculated according to the area of the material source area, the gradient degree of the material source area, the porosity of the soil body and the estimated treatment depth, so that the economic cost and the time cost are saved while the soil body improvement effect is ensured, the solidification efficiency of the soil body in the material source area is greatly improved, and meanwhile, the phenomenon that the surface soil body is damaged in liquidity due to excessive spraying can be avoided.
(2) The invention is based on the parameters of the area of the source area, the porosity of the soil body, the estimated treatment depth and the likeProvides a corresponding formula VbThe culture medium dosage required for single excitation of urease bacteria in the in-situ soil body is calculated according to the formula axnxSxD, so that the excitation efficiency of the urease bacteria in the in-situ soil body is improved, and the waste caused by excessive culture medium spraying is avoided.
(3) The invention provides a corresponding formula V according to the parameters of the area size of the source area, the porosity of the soil body, the estimated processing depth, the gradient degree of the source area and the likecThe dosage of the cementing liquid required by the soil body solidified at one time is calculated according to b multiplied by n multiplied by (H +1) multiplied by S multiplied by D, so that the reinforcing efficiency of the soil body in the material source region is improved, the soil body in the material source region with different slope descending degrees can be ensured to effectively prevent water and soil loss, resources are reasonably distributed and utilized, and the economic cost is saved to the maximum extent.
(4) According to the method, the MICP treatment of different degrees is carried out on the soil bodies of the material source regions with different slope degrees, so that the increased calcium carbonate content of the soil bodies of the material source regions with different slope degrees can reach a specific range, and the soil bodies of the material source regions with different slope degrees can be effectively cemented and the anti-erosion capability is improved; resources are reasonably distributed, and waste of the bacterial liquid and the cementing liquid is avoided.
(5) The microbial solidification technology adopted by the invention is very friendly to the ecological environment, and the whole reaction process of MICP can not generate harmful chemical substances; moreover, the final product ammonium chloride generated by the reaction is a nitrogen fertilizer and has certain promotion effect on the growth and development of vegetation. In addition, the calcium carbonate hardened shell generated on the surface of the soil body through MICP reaction can inhibit the evaporation of water in the soil body and improve the water holding capacity of the soil body, thereby ensuring that the vegetation has sufficient water in the growth and development process.
(6) According to the invention, the urease bacteria in the soil body of the material source region are enriched by adopting an in-situ excitation mode, although the speed of culturing the urease bacteria in the material source region is possibly slower than that of culturing the urease bacteria in a traditional laboratory, once the urease bacteria are excited out, the urease bacteria growing in situ have better environmental adaptability and stronger vitality, and can be distributed in the soil body more uniformly, so that the method is very favorable for the cementation and solidification of the soil body of the material source region; in addition, because the in-situ excitation of bacteria does not need a series of test steps such as sterilization operation, shaking culture and the like unlike the laboratory culture of bacteria, the cost can be greatly reduced by adopting the in-situ excitation mode to culture the urease bacteria.
Drawings
FIG. 1 is a schematic diagram of a debris flow prevention and control method based on an in-situ excitation microorganism curing technology.
FIG. 2 is a diagram showing the effect of soil slope treatment based on in-situ activated microorganism curing technology in comparative example 1.
Detailed Description
The present invention will now be described in detail with reference to examples
Example 1
In order to research the anti-erosion effect of the in-situ excited microorganism solidified soil body, A, B, C slope surfaces with the same area size (1.5m multiplied by 0.5m) and the same slope drop size (8 percent of slope drop) are selected on suburban mountain slopes in the Suxia region of Nanjing city for carrying out in-situ test. Slope A and slope B were treated by the in situ-activated microbial curing technique described above, and slope C was treated with pure water alone as a control. Firstly, preparing a liquid culture medium required by urease excitation bacteria, wherein the formula of the culture medium is as follows: 0.5mol/L urea, 0.05mol/L ammonium chloride, 0.1mol/L sodium acetate, 0.5g/L yeast extract, 1.0g/L acid-base buffer (Trisbase). According to the size S of the processing area (S is 0.75 m)2) The soil porosity n (the natural porosity of the lower hollywood is generally about 20%), the expected treatment depth D (the treatment depth is set to 0.05m because the soil layer to be treated is the lower hollywood and belongs to silty clay) and the parameters such as the culture medium dosage correction coefficient a (the value of a is 1.2) are calculated according to the formula (1) VbCalculating the using amount of the single-spraying in-situ excitation culture medium as axnxsxsxDm, then spraying the slope surface A and the slope surface B every day, and spraying the slope surface C with the same amount of pure water. Meanwhile, 100g of surface soil (soil within 5cm below the ground surface) is taken from the slope surface B before the culture medium is sprayed for the next time to detect the urease activity (the soil sample is taken only once to detect the urease activity because the area of the test site is small). The specific test process is as follows: filling 100g of the soil into a conical flask, adding 1L of deionized water into the conical flask, and then placing the conical flask into a shaking table to oscillate for 3 hours so that microorganisms in the soil are completely dissolved in waterThen, filtering soil particles by using a filtering device, taking 5mL of filtered solution, adding 45mL of 1.6mol/L urea solution into the solution, uniformly stirring the solution, measuring the change of the conductivity value within 5min by using a conductivity meter, then converting the change to obtain the urea decomposition amount of urease in unit time, and finally multiplying the urea decomposition amount by the dilution factor to obtain the urease activity of urease bacteria contained in 100g of soil. When urease bacteria contained in 100g of soil can decompose 10mM urea per hour (namely, urease activity reaches 10mM/h), spraying of the excitation culture medium is stopped, the excitation of the urease bacteria in the soil is completed, and the number and the activity of the urease bacteria in the soil can meet the subsequent MICP curing reaction requirements. As shown in table 1, the change of urease activity of urease bacteria in the soil after daily culture medium excitation treatment was recorded in this experiment, and it was found that the urease activity in the soil was continuously increased with the increase of treatment rounds. Until 8 cycles of culture medium excitation treatment, the urease activity in 100g of soil body reaches 10.67mM/h, and the curing requirement of MICP is met. And then, spraying a cementing liquid on the slope A and the slope B from the 9 th day for cementing and curing, wherein the formula of the cementing liquid is as follows: 0.5mol/L urea, 0.5mol/L calcium chloride, 1.0g/L nutrient broth. According to the size S of the processing area (S is 0.75 m)2) The parameters of the soil porosity n (n is 20%), the expected treatment depth D (D is 0.05m), the gradient size H (H is 8%), the cementing liquid dosage correction coefficient b (where b is 2.0), and the like are represented by the formula (2) VcThe amount of cement used for a single spraying was calculated as b × n × (H +1) × sx D, and the same amount of pure water was sprayed on the slope C. And digging 500g of a surface soil sample (soil within 5cm below the ground surface) of the treated slope surface B on the next day to test the calcium carbonate content (the calcium carbonate content is tested by taking the soil sample once because the test site area is small). In addition, calcium carbonate content test is carried out on the soil sample of the test field before the treatment of the cementing liquid, and the calcium carbonate content of the soil body is found to be 0.36%. Table 2 records the change of calcium carbonate content in the soil after the daily microbial solidification treatment, and finds that the calcium carbonate content in the soil is continuously increased with the increase of the treatment rounds of the cementing liquid. Until 5 rounds of consolidation treatment of the cementing liquid are carried out, the content of calcium carbonate generated in soil body by microorganism inductionAnd 5.35% is reached, and the slope soil body solidification is completed.
TABLE 1 urease activity in the soil after different rounds of medium treatment
TABLE 2 calcium carbonate content in soil after different rounds of treatment with binding liquid
After the slope surface solidification treatment is completed, the soil mass loss of the slope surface A and the slope surface C in the rainfall process is respectively calculated to reflect the anti-erosion capacity of each slope surface. The specific operation process is as follows: before rainfall, corresponding containers are respectively placed at the slope surface A and the slope surface C for containing the water and soil loss amount of the slope surface in the rainfall process, and a rain measuring device is placed on the flat ground for measuring the rainfall intensity. And after the rainfall is finished, filtering out the soil particles collected in the container, drying and weighing to obtain the mass of the soil particles eroded by the rainfall. In addition, the volume of the rainwater in the container is measured, and the amount of the slope runoff rainwater can be obtained. Table 3 records the soil and water loss during a single rainfall on slope a and slope C. Obviously, the surface runoff of the slope A treated by the microbial solidification technology in the rainfall process is obviously greater than that of the slope C of the control group, because a layer of hardened shell formed by interaction of soil and calcium carbonate is formed on the surface of the slope A, the rainfall infiltration is effectively prevented, and more rainwater is drained in a surface runoff manner. In addition, calcium carbonate generated by microorganism induction is used for cementing, solidifying and molding soil particles on the surface layer of the slope A, so that the overall strength of the soil body is improved, the mass of the soil particles on the slope A eroded by rainwater in the rainfall process is far smaller than that of the untreated slope C, which shows that the erosion resistance of the soil body is remarkably improved under the action of the in-situ microorganism-stimulated solidification technology, so that the soil and water are kept to play an important positive role, and disasters such as debris flow and the like can be effectively prevented.
TABLE 3 soil and water loss during rainfall on slope A and slope C (control group)
Example 2
This example is essentially the same as example 1 except that the degree of slope D, E, F is 15%. Conventional MICP curing treatment is carried out on the slope D and the slope E, the slope D is used for detecting the slope reinforcement effect, the slope E is used for sampling and testing the urease activity and the calcium carbonate content in soil, the slope F is a control group, and only pure water is used for treatment. After 8 rounds of excitation culture medium treatment, the urease activity in the soil body exceeds the standard value and reaches 11.03 mM/h. Then according to the formula (2) VcAnd (2) calculating to obtain the single cementing liquid dosage (the value of the cementing liquid dosage correction coefficient b is 2.0) by b × n × (H +1) × S × D, and after 7 cycles of cementing liquid treatment, the increased calcium carbonate content in the soil body reaches 8.31%, and at this time, the slope soil body solidification is completed. And then, the soil mass loss of each slope surface in the rainfall process is counted, and the test result is shown in table 4. Obviously, after the MICP treatment, the soil mass loss of the slope (the slope degree is 15%) is greatly reduced, which shows that the erosion resistance of the slope soil mass is obviously improved.
TABLE 4 soil and water loss during rainfall on slope D and slope F (control group)
Example 3
This example is substantially the same as example 1 except that the degree of slope G, H, I is 32%. Carry out conventional MICP solidification to domatic G and H, domatic G is used for detecting domatic reinforcement effect, and domatic H is arranged in sampling test soil's ureaEnzyme activity and calcium carbonate content, slope I was a control group and treated with pure water only. After 8 rounds of excitation culture medium treatment, the urease activity in the soil body exceeds the standard value and reaches 10.95 mM/h. Then according to the formula (2) VcAnd (2) calculating to obtain the single cementing liquid dosage (the value of the cementing liquid dosage correction coefficient b is 2.0) by b × n × (H +1) × S × D, and after 10 cycles of cementing liquid treatment, the increased calcium carbonate content in the slope G and H soil bodies reaches 10.64%, and at the moment, the slope soil body solidification is completed. And then, the soil mass loss of each slope surface in the rainfall process is counted, and the test result is shown in table 5. Obviously, after MICP treatment, the soil mass loss of the slope surface with the slope falling degree exceeding 30% in the rainfall process can be effectively controlled, and compared with the untreated slope surface, the soil mass loss of the soil mass slope surface reinforced by microorganisms in the rainfall process is reduced by about 90%.
TABLE 5 soil and water loss during rainfall on slope G and slope I (control group)
Comparative example 1
This comparative example was substantially the same as example 1 except that the degree of slope of the soil mass slope D, E, F, M was 15% (D, E, F treatment was the same as in example 2) as shown in figure 2. Carry out conventional MICP solidification to domatic D, E and M, domatic D is used for detecting domatic reinforcement effect, and domatic E is arranged in the urease activity and the calcium carbonate content of sample test soil, and domatic M is used for comparing the domatic anti-erosion ability of different calcium carbonate contents, and domatic F is the control group, only handles with pure water. After 8 rounds of excitation culture medium treatment, the urease activity in the soil body exceeds the standard value and reaches 11.03 mM/h. Then according to the formula (2) VcThe single cementing liquid dosage is calculated (here, the cementing liquid dosage correction coefficient b is 2.0). In order to compare the erosion resistance of the slopes with different calcium carbonate contents, the increased calcium carbonate content in the soil body after 5 rounds of treatment of the cementing liquid reaches 5.69 percent, at the moment, the same amount of cementing liquid is used instead of spraying the cementing liquid on the slope surface MAnd (5) treating the pure water. And (4) continuously treating the slope surfaces D and E by using the cementing liquid. After 7 rounds of treatment by the cementing liquid, the content of calcium carbonate added in soil bodies of the slope surfaces D and E reaches 8.31 percent, and at the moment, the soil bodies of the slope surfaces are solidified. And then, the soil mass loss of each slope surface in the rainfall process is counted, and the test result is shown in table 6. Compared with the slope D, because the slope M is only treated by 5 times of cementing liquid, the calcium carbonate in the soil is only 5.69 percent, and the corresponding standard of the calcium carbonate content of the slope body with the slope descending degree of 10-30 percent is not reached, so that the water and soil loss of the slope M in the rainfall process is large, and the anti-erosion capability of the soil body is not good.
TABLE 6 soil and water loss during rainfall on slope D, slope M and slope F (control group)
The above description is illustrative of the present invention and its embodiments, and is not to be construed as limiting, and the embodiments shown in the drawings are illustrative of the invention and are not intended to limit the scope of the invention. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.
Claims (9)
1. A debris flow prevention and control method based on an in-situ excitation microorganism curing technology is characterized by comprising the following steps:
1) measuring the area of the object source region, the porosity of the soil body and the gradient degree of the object source region;
2) calculating the amount of a culture medium required for single excitation of urease bacteria in the in-situ soil body according to the area size of the source area, the porosity of the soil body and the estimated treatment depth obtained in the step 1);
3) spraying an excitation culture medium on the soil body of the debris flow source area until the average urease activity of urease bacteria reaches a standard value, and completing the excitation of the urease bacteria in the soil body of the source area;
4) calculating the dosage of the cementing liquid required by the single-curing soil body according to the area of the material source region, the gradient degree of the material source region, the porosity of the soil body and the estimated treatment depth obtained in the step 1);
5) and spraying a cementing liquid on the soil body of the excited material source region until the content of the calcium carbonate growing in the soil body of the material source region reaches a specific range.
2. The debris flow control method based on in-situ activated microorganism curing technology as claimed in claim 1, wherein the area S (m) of the source region in the step 2)2) Soil porosity n (%), estimated treatment depth D (m) and in situ excitation medium dosage Vb(L) satisfies the following relationship:
Vb＝a×n×S×D (1)
wherein, a in the formula (1) is the in-situ excitation culture medium dosage correction coefficient, and the value range thereof is as follows: 0.5 to 2.0.
3. The debris flow control method based on in-situ activated microorganism curing technology as claimed in claim 2, wherein the source area S (m) in the step 4) is the area S (m)2) The gradient degree H (%) of the source area, the porosity n (%) of the soil body, the estimated treatment depth D (m) and the dosage V of the cementing liquidc(L) satisfies the following relationship:
Vc＝b×n×(H+1)×S×D (2)
wherein, b in the formula (2) is a cementing liquid dosage correction coefficient, and the value range thereof is as follows: 0.8 to 3.0.
4. The debris flow control method based on the in-situ activated microorganism curing technology as claimed in claim 3, wherein the content of the calcium carbonate in the soil in the source area in the step 5) is as follows:
aiming at the source region with the gradient degree less than 10 percent, the content of calcium carbonate increased in the soil body after MICP treatment reaches 5 to 7 percent; or
Aiming at the source region with the gradient degree of 10-30%, the content of calcium carbonate increased in the soil body after MICP treatment reaches 7-10%; or
Aiming at the matter source region with the gradient degree of more than 30 percent, the content of calcium carbonate increased in the soil body after MICP treatment reaches more than 10 percent.
5. The debris flow prevention and treatment method based on the in-situ excitation microbial curing technology as claimed in claim 3, wherein in the step 2) and/or the step 4), the value range of the microbial curing treatment depth D for the clay soil layer is as follows: 0 to 0.1 m; for sandy soil layers, the value range of the microbial curing treatment depth D is as follows: 0 to 0.5 m.
6. The method for preventing and treating the mud-rock flow based on the in-situ activated microorganism curing technology as claimed in claim 3, wherein the culture medium in the step 2) is composed of urea, ammonium chloride, sodium acetate, yeast extract, acid-base buffer and pure water; wherein the contents of all the substances are respectively as follows: urea: 0.1-0.5 mol/L; ammonium chloride: 0.01-0.1 mol/L; sodium acetate: 0.05-0.5 mol/L; yeast extract (B): 0.1-1.0 g/L; acid-base buffer: 0.1 to 1.4 g/L.
7. The method for preventing and treating the mud-rock flow based on the in-situ excited microbial curing technology as claimed in claim 6, wherein the standard value of the average urease activity of the urease bacteria is 10 mM/h.
8. The method for preventing and treating the mud-rock flow based on the in-situ activated microorganism curing technology as claimed in claim 7, wherein the cementing liquid in the step 4) is composed of urea, calcium chloride, nutrient broth and pure water; wherein the contents of all the substances are respectively as follows: urea: 0.1-1.0 mol/L; calcium chloride: 0.1-1.0 mol/L; nutrient broth: 0.1 to 3.0 g/L.
9. The method for preventing and treating the debris flow based on the in-situ activated microorganism curing technology as claimed in claim 7, wherein the frequency of spraying the activated culture medium in the step 3) is once a day; the spraying frequency of the cementing liquid in the step 5) is once per day.
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