Microbial soil stabilizing composition for cohesive soils, method of preparation and soil stabilization method

Abstract

The application discloses a microbial soil-fixing component for cohesive soil, a preparation method and a soil-fixing method. The microbial soil-fixing component comprises microbial bacteria liquid, microbial curing liquid and soil permeating agent. The microbial curing liquid comprises urea, calcium dihydrogen phosphate and water; and the soil permeating agent comprises acetylenic alcohol polyether surfactant, polyhydric alcohol surfactant and water. The microbial soil-fixing component has good affinity and permeability with bare cohesive soil, can promote the penetration of the bacillus pasteurii microbial bacteria liquid in the soil, and effectively cures the bare cohesive soil through the mineralization and deposition of the microorganism. The soil-fixing method considers the permeable range of the microbial soil-fixing component, and the microbial soil-fixing component is fully utilized, so that the bare cohesive soil can be efficiently cured. The microbial soil-fixing component and the soil-fixing method are simple in preparation and convenient in construction, the soil-fixing component can also effectively fertilize the surface soil, is beneficial to the growth of the surface vegetation in the later period, and has the advantages of ecological environmental protection and economic applicability.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of microbial soil stabilizing component for cohesive soil, preparation method and soil stabilizing method, belong to the ecological dust suppression technology field of microbial solidification engineering cohesive soil. BACKGROUND

[0002] In the construction process of subway station, comprehensive pipe gallery, building foundation, subgrade excavation, etc., a large amount of topsoil will be excavated and piled up, and the exposed soil body excavated and piled up has become the largest dust source of urban dust pollution. At present, the traditional treatment methods mainly include three types of physical dust suppression, chemical dust suppression and vegetation dust suppression, but there are problems such as poor dust suppression effect, long cycle, relatively high cost or causing secondary environmental pollution in the treatment process. Seeking a collaborative approach for the treatment of bare soil wind erosion and sustainable development of ecological environment is the focus of current research.

[0003] Microbial solidification of bare soil for preventing wind erosion is to use the bacterial microbial reaction process in nature to reinforce and improve the soil, so as to resist wind erosion. Since the microbial reaction process is a process that exists in the ecological environment of the soil, it is very friendly to the environment, so the microbial solidification of bare soil technology has become a research hotspot. Microbial solidification of soil is to use microbial life activities and their metabolic products to induce or control a series of chemical reactions in the soil to improve the engineering properties of the soil, which can mineralize a large amount of calcium carbonate in a short time, thereby achieving the effect of topsoil solidification. However, to achieve good soil stabilization effect, on the one hand, it depends on the variety of microorganisms and the environment, and on the other hand, it requires good permeability to improve the depth and effect of soil stabilization. The patent "Method for repairing concrete cracks by using microbial-induced calcium carbonate deposition" (Patent No. 201811557680.1) uses drip irrigation to penetrate microbial mixed bacteria liquid into concrete cracks. Obviously, the drip irrigation method is greatly affected by human factors. The patent "Microbial sand stabilizing dust suppressant and preparation method thereof" (Patent No. 201410042688.X) directly penetrates microbial mixed bacteria liquid into loose sand. Since the porosity of sand is large, the depth of penetration of microbial mixed bacteria liquid is large, and the effect is good. However, the porosity of cohesive soil excavated in engineering is small, and this method is not good for the solidification of cohesive soil. Therefore, the current microbial solidification is mainly for sandy soil, and it is not suitable for cohesive soil with small porosity. SUMMARY

[0004] In view of the shortcomings of the prior art, the present application aims to provide a microbial soil stabilizing component for cohesive soil, which has good penetration, is eco-friendly, low in cost and convenient to construct, can effectively solve the problems of poor topsoil solidification effect and high cost in the process of ecological dust suppression of bare soil in construction engineering, and form a new method for efficient soil stabilization and dust suppression suitable for exposed cohesive soil in engineering excavation.

[0005] To achieve the above object, one of the technical solutions of the present application is:

[0006] A microbial soil stabilizing component for cohesive soil comprises microbial bacteria solution, microbial curing solution and soil permeating agent; the volume ratio of soil body permeating agent, microbial curing solution and microbial bacteria solution is 20:10:1; wherein,

[0007] The microbial curing solution comprises the following raw materials in the following weight ratio: urea 10-15, calcium dihydrogen phosphate 10-15, water 60;

[0008] The soil permeating agent comprises the following raw materials in the following weight ratio: acetylenic alcohol polyether surfactant 2-4, polyol surfactant 4-8, water 40-60.

[0009] Further, the microbial bacteria solution is a bacillus pasteurii microbial bacteria solution with a concentration of 1.0≤OD 600 ≤6.0.

[0010] Further, the acetylenic alcohol polyether surfactant is ZY-1420 acetylenic alcohol polyether surfactant; and the polyol surfactant is polysorbate 80.

[0011] One of the technical solutions of the present application is a preparation method of a microbial soil stabilizing component, comprising the following steps:

[0012] (1) preparing soil permeating agent: weighing acetylenic alcohol polyether surfactant and polyol surfactant, adding water, and mixing and stirring uniformly;

[0013] (2) preparing microbial curing solution: weighing urea and calcium dihydrogen phosphate, adding water, and mixing and stirring uniformly;

[0014] (3) mixing and stirring microbial bacteria solution and microbial curing solution within 3-5 hours before spraying the microbial soil stabilizing component;

[0015] (4) adding prepared soil body permeating agent to the mixture of microbial curing solution and microbial bacteria solution within 1-2 hours before spraying the microbial soil stabilizing component.

[0016] One of the technical solutions of the present application is a soil stabilizing method using the microbial soil stabilizing component, comprising the following steps:

[0017] (1) determining the soil stabilizing range of excavated exposed cohesive soil body and the dosage of microbial soil stabilizing component;

[0018] (2) taking soil on site and testing the void ratio of cohesive soil; determining the spraying frequency according to the void ratio of soil body;

[0019] (3) using steel drill to insert small holes in the soil stabilizing range of exposed cohesive soil body;

[0020] (4) The prepared microbial soil-fixing component is loaded into a sprayer, and is uniformly sprayed on the soil-fixing range of the bare cohesive soil according to the metering in steps (1) and (2).

[0021] Further, in step (1), the dosage of the microbial soil-fixing component is determined as 1.5-2 liters per square meter of the surface area of the cohesive soil.

[0022] Further, in step (2), when the soil porosity ratio e is greater than 1.0, the spraying is performed twice; and when e is less than 1.0, the spraying is performed three times.

[0023] Further, in step (3), the diameter of the steel drill is 4-6 mm, the depth of the small holes is 50-100 mm, and the interval is 50-80 mm.

[0024] Further, in step (4), the spraying mode is manual spraying or unmanned aerial vehicle spraying according to the size of the soil-fixing range; and the interval time for each spraying is 24 hours.

[0025] Further, after 3 days of spraying, the soil is taken from the site for testing the soil-fixing depth and strength, and when the soil-fixing depth is small due to the influence of bad weather, the spraying is supplemented once according to steps (1)-(4).

[0026] Principle of the present application: Microbial solidification of soil mainly through the urease produced by bacillus pasteurii to decompose urea and calcium ion to generate calcium carbonate, and then to carry out soil reinforcement. But the urease produced by microorganisms has poor solubility in clay soil, and bacillus pasteurii is a kind of microorganism that can survive in alkaline environment and has negative charge, and the surface tension of the bacterial solution is large, and the porosity of clay soil is small. Therefore, the penetration depth of single microbial solution in clay soil is shallow, which will affect the soil solidification effect. The penetrating agent used in the present application is not easily affected by strong electrolyte, and has acid and alkali resistance (the penetrating agent used in the present application will not dissociate into ions in aqueous solution, has good stability, and is not affected by strong acid, strong base and salt), which can effectively reduce the charge coupling phenomenon generated in the penetration process of microbial solution, so that the clay soil is not easy to be cemented, and it is beneficial to the affinity penetration of the soil solidification component on the surface of clay soil. The penetrating agent in the present application is designed according to the physical properties of the mixture of microbial solution and microbial solidification liquid, which can effectively solve the problems of solubilization and affinity penetration of clay soil. The polyol surfactant polysorbate 80 in the penetrating agent component can improve the solubility of organic matter such as urease produced by microorganisms, increase the urease content in the soil solidification component, and enhance the soil solidification effect. The surface tension of the mixture of microbial solution and microbial solidification liquid is large, and foam layer is easily generated on the soil surface during spraying, which affects the affinity penetration of the bacterial solution on the surface of the soil. The acetylenic alcohol polyether surfactant in the penetrating agent component can reduce the surface tension of the mixture of microbial solution and microbial solidification liquid, so that the soil solidification component has excellent super diffusion and spraying covering performance during spraying, can quickly infiltrate on the surface of the soil, and form a very thin liquid film, so that the soil solidification component can quickly penetrate on the surface of the soil. The synergistic effect of polyol surfactant and acetylenic alcohol polyether surfactant will further promote the dissolution and penetration of bacterial solution and solidification liquid in clay soil, and enhance the soil solidification effect. At the same time, the solidification liquid itself contains N, P and other nutrient elements required for plant growth, which can effectively fertilize the surface soil and is beneficial to the growth of vegetation on the surface soil in the later period.

[0027] The beneficial effects of the present application are as follows: (1) The microbial soil solidification component of the present application has good affinity penetration with bare clay soil, which can promote the penetration of bacillus pasteurii microbial solution in the soil, and effectively solidify the bare clay soil through the mineralization and deposition of microorganisms. (2) The soil solidification method of the present application considers the permeable range of microbial soil solidification component, and the microbial soil solidification component is fully utilized, which can efficiently solidify the bare clay soil. (3) The microbial soil solidification component and the soil solidification method of the present application are simple to prepare and convenient to construct, and the soil solidification component can also effectively fertilize the surface soil, which is beneficial to the growth of vegetation on the surface soil in the later period, and has the advantages of ecological protection, economy and applicability. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below with examples. The specific examples described herein are only used to explain the present application and not to limit the present application.

[0029] Example 1

[0030] A microbial soil stabilizing component for cohesive soil, comprising microbial bacteria solution, microbial curing solution and soil permeating agent; the volume ratio of soil permeating agent: microbial curing solution: microbial bacteria solution is 20:10:1; wherein,

[0031] The microbial curing solution comprises raw materials in the following weight ratio: urea 15: calcium dihydrogen phosphate 15: water 60;

[0032] The soil permeating agent comprises raw materials in the following weight ratio: ZY-1420 acetylenic alcohol polyether surfactant 2: polysorbate 80 4: water 60.

[0033] The microbial bacteria solution is Bacillus pasteurii microbial bacteria solution, with a concentration OD 600 =4.0.

[0034] A preparation method of a microbial soil stabilizing component for cohesive soil, comprising the following steps:

[0035] (1) preparing soil permeating agent: weighing ZY-1420 acetylenic alcohol polyether surfactant and polysorbate 80, adding water, and mixing and stirring uniformly;

[0036] (2) preparing microbial curing solution: weighing urea and calcium dihydrogen phosphate, adding water, and mixing and stirring uniformly;

[0037] (3) mixing and stirring microbial bacteria solution with microbial curing solution within 3-5 hours before spraying the microbial soil stabilizing component;

[0038] (4) adding the prepared soil permeating agent to the mixture of microbial curing solution and microbial bacteria solution within 1-2 hours before spraying the microbial soil stabilizing component, and obtaining the microbial soil stabilizing component.

[0039] The soil body targeted by the present example is an engineering exposed cohesive soil, taken from the accumulated soil body on the construction project site. The soil body has a void ratio of 0.6, a water content of 1.625%, a liquid limit of 34.80%, and a plastic limit of 9.22%, and is a strongly plastic cohesive soil.

[0040] A soil stabilizing method using a microbial soil stabilizing component, comprising the following steps:

[0041] (1) determining the soil stabilizing range of the excavated exposed cohesive soil body, and determining the dosage (once) of the microbial soil stabilizing component according to the dosage of 1.5 liters per square meter;

[0042] (2) On-site soil sampling, test the void ratio of clay; according to the void ratio of the soil, determine the spraying of 3 times of microbial soil stabilizing components;

[0043] (3) According to the soil stabilization range determined in step (1), a steel drill with a diameter of 6 mm is used to insert a small hole with a depth of 50 mm and a spacing of 50 mm in the exposed clay soil stabilization range, to increase the soil permeability;

[0044] (4) The prepared microbial soil stabilizing components are loaded into a sprayer, and according to the metering described in steps (1) and (2), uniform spraying is carried out on the exposed clay soil stabilization range. Continuous spraying for 3 times, each time interval is 24 hours, and after spraying for 3 days, maintenance for 3 days;

[0045] (5) After spraying for 3 days, on-site soil sampling, test the soil stabilization depth and strength.

[0046] Example 2

[0047] A microbial soil stabilizing component for clay, comprising microbial bacteria solution, microbial curing solution and soil permeation agent; the volume ratio of soil permeation agent: microbial curing solution: microbial bacteria solution is 20:10:1; wherein,

[0048] The microbial curing solution comprises the following raw materials in a weight ratio: urea 15: calcium dihydrogen phosphate 15: water 60;

[0049] The soil permeation agent comprises the following raw materials in a weight ratio: ZY-1420 acetylenic alcohol polyether surfactant 4: polysorbate 80 8: water 60.

[0050] The microbial bacteria solution is a Bacillus pasteurii microbial bacteria solution with a concentration OD 600 =4.0.

[0051] The preparation method of the microbial soil stabilizing component for clay in this example is the same as that in Example 1.

[0052] The soil body targeted by this example is an exposed clay soil in engineering, taken from the accumulated soil body on the construction project site. The void ratio of the soil body is 0.6, the water content is 1.625%, the liquid limit is 34.80%, and the plastic limit is 9.22%, which is a strong plastic clay.

[0053] The soil stabilization method using microbial soil stabilizing components in this example is basically the same as that in Example 1, the difference is that in step (3), a steel drill with a diameter of 6 mm is used to insert a small hole with a depth of 100 mm and a spacing of 50 mm in the exposed clay soil stabilization range.

[0054] Example 3

[0055] A microbial soil stabilizing component for cohesive soil comprises microbial bacteria solution, microbial curing solution and soil permeating agent; the volume ratio of soil permeating agent, microbial curing solution and microbial bacteria solution is 20:10:1; wherein,

[0056] The microbial curing solution comprises raw materials in the following weight ratio: urea 10: calcium dihydrogen phosphate 10: water 60;

[0057] The soil permeating agent comprises raw materials in the following weight ratio: ZY-1420 acetylenic alcohol polyether surfactant 4: polysorbate 80 8: water 60.

[0058] The microbial bacteria solution is Bacillus pasteurii microbial bacteria solution with a concentration OD 600 = 4.0.

[0059] The preparation method of the microbial soil stabilizing component for cohesive soil in this example is the same as that in Example 1.

[0060] The soil body in this example is engineering exposed cohesive soil, which is taken from the accumulated soil body on the construction site. The soil body has a void ratio of 1.1, a water content of 1.72%, a liquid limit of 32.4%, and a plastic limit of 9.19%, and is a strongly plastic cohesive soil.

[0061] The soil stabilizing method using the microbial soil stabilizing component in this example is basically the same as that in Example 1, except that the spraying is performed twice; in step (3), a steel drill with a diameter of 4 mm is used to drill small holes with a depth of 100 mm and a spacing of 80 mm in the range of the exposed cohesive soil body.

[0062] Comparative Example 1

[0063] The microbial soil stabilizing component for cohesive soil in this comparative example is basically the same as that in Example 1, except that no soil permeating agent is added.

[0064] The preparation method of the microbial soil stabilizing component for cohesive soil in this comparative example is basically the same as that in Example 1, except that no soil permeating agent is added.

[0065] The soil body in this comparative example is engineering exposed cohesive soil, which is taken from the accumulated soil body on the construction site. The soil body has a void ratio of 0.6, a water content of 1.625%, a liquid limit of 34.80%, and a plastic limit of 9.22%, and is a strongly plastic cohesive soil.

[0066] The soil stabilizing method using the microbial soil stabilizing component in this comparative example is the same as that in Example 1.

[0067] Comparative Example 2

[0068] The comparative example is used for the preparation of a microbial soil stabilizing component for cohesive soil, and is basically the same as example 1, except that the soil penetrant comprises the following raw materials in weight ratio: ZY-1420 acetylenic alcohol polyether surfactant 6: water 60.

[0069] The comparative example is used for the preparation of a microbial soil stabilizing component for cohesive soil, and is basically the same as example 1, except that the soil penetrant comprises the following raw materials in weight ratio: ZY-1420 acetylenic alcohol polyether surfactant 6: water 60.

[0070] The soil body targeted by the comparative example is an engineering exposed cohesive soil, which is taken from the accumulated soil body on the construction project site. The soil body has a void ratio of 0.6, a water content of 1.625%, a liquid limit of 34.80%, and a plastic limit of 9.22%, and is a strongly plastic clay soil.

[0071] The soil stabilizing method using the microbial soil stabilizing component of the comparative example is the same as example 1.

[0072] Comparative Example 3

[0073] The comparative example is used for the preparation of a microbial soil stabilizing component for cohesive soil, and is basically the same as example 1, except that the soil penetrant comprises the following raw materials in weight ratio: ZY-1420 acetylenic alcohol polyether surfactant 6: water 60.

[0074] The comparative example is used for the preparation of a microbial soil stabilizing component for cohesive soil, and is basically the same as example 1, except that the soil penetrant comprises the following raw materials in weight ratio: ZY-1420 acetylenic alcohol polyether surfactant 6: water 60.

[0075] The soil body targeted by the comparative example is an engineering exposed cohesive soil, which is taken from the accumulated soil body on the construction project site. The soil body has a void ratio of 0.6, a water content of 1.625%, a liquid limit of 34.80%, and a plastic limit of 9.22%, and is a strongly plastic clay soil.

[0076] The soil stabilizing method using the microbial soil stabilizing component of the comparative example is the same as example 1.

[0077] Comparative Example 4

[0078] The comparative example is used for the preparation of a microbial soil stabilizing component for cohesive soil, and is basically the same as example 1, except that the soil penetrant comprises the following raw materials in weight ratio: ZY-1420 acetylenic alcohol polyether surfactant 6: water 60.

[0079] The comparative example is used for the preparation of a microbial soil stabilizing component for cohesive soil, and is basically the same as example 1, except that the soil penetrant comprises the following raw materials in weight ratio: ZY-1420 acetylenic alcohol polyether surfactant 6: water 60.

[0080] The soil body of the present comparative example is the exposed engineering clay, which is taken from the accumulated soil body on the construction site. The soil body has a porosity ratio of 0.6, a water content of 1.625%, a liquid limit of 34.80%, and a plastic limit of 9.22%, and is a strongly plastic clay.

[0081] The soil fixation method of the present comparative example utilizes the microbial soil fixation component, which is the same as that of Example 1.

[0082] Comparative Example 5

[0083] The microbial soil fixation component for clay of the present comparative example is basically the same as that of Example 1, except that the soil penetration agent comprises the following raw materials in a weight ratio: ZY-1420 acetylenic alcohol polyether surfactant 2: alkyl phenoxy polyethyleneoxy ethanol 4: water 60.

[0084] The preparation method of the microbial soil fixation component for clay of the present comparative example is basically the same as that of Example 1, except that the soil penetration agent comprises the following raw materials in a weight ratio: ZY-1420 acetylenic alcohol polyether surfactant 2: alkyl phenoxy polyethyleneoxy ethanol 4: water 60.

[0085] The soil body of the present comparative example is the exposed engineering clay, which is taken from the accumulated soil body on the construction site. The soil body has a porosity ratio of 0.6, a water content of 1.625%, a liquid limit of 34.80%, and a plastic limit of 9.22%, and is a strongly plastic clay.

[0086] The soil fixation method of the present comparative example utilizes the microbial soil fixation component, which is the same as that of Example 1.

[0087] After the soil fixation components produced in Examples 1-3 and Comparative Examples 1-5 are sprayed and cured for 3 days, the soil is detected, and the specific results are shown in Table 1:

[0088] Table 1 Soil property detection table

[0089] Surface strength (kPa) Soil binding depth (mm) Example 1 97.23 18.77 Example 2 113.56 29.6 Example 3 96.56 27.5 Comparative Example 1 75.44 6.15 Comparative Example 2 77.44 11.15 Comparative Example 3 80.44 10.15 Comparative Example 4 81.23 12.23 Comparative Example 5 76.23 13.05

[0090] As can be seen from Table 1, compared with the comparative examples, the microbial soil fixation components of Examples 1, 2 and 3 added with the soil penetration agent of the present application have stronger penetration, can penetrate into the soil, and have higher surface strength and good curing effect. Although Comparative Examples 2, 3, 4 and 5 added the soil penetration agent, the soil fixation depth is only slightly increased, and the soil fixation effect is greatly reduced.

[0091] Clay is produced by the interaction between clay particles and water, and the clay particles and the soil particles themselves are mostly composed of silicate minerals, which have strong water and fertilizer retention capacity, but small pores and poor permeability. The penetration agent used in the present application can improve the hydrophilicity of the soil fixation component and has good solubilizing effect. The microbial soil fixation component and the soil fixation method of the present application can effectively improve the permeability of clay and increase the reinforcement thickness.

[0092] Meanwhile, the substance used in the application is non-toxic, biodegradable, harmless to soil, and can increase the permeability of soil, improve water retention, and improve soil fertility, which is conducive to the growth of plants in the later period.

Claims

1. A microbial soil stabilisation composition for use in cohesive soils, characterised in that, The microbial bacteria solution, the microbial solidification solution and the soil penetration agent are included; the volume ratio of the soil penetration agent, the microbial solidification solution and the microbial bacteria solution is 20:10:1; wherein, The microbial solidification solution includes the following raw materials in the weight ratio: urea 10-15, calcium dihydrogen phosphate 10-15, water 60; The soil penetration agent includes the following raw materials in the weight ratio: acetylenic alcohol polyether surfactant 2-4, polyol surfactant 4-8, water 40-60; The acetylenic alcohol polyether surfactant is ZY-1420 acetylenic alcohol polyether surfactant; the polyol surfactant is polysorbate 80; The microbial solution is a Bacillus pasteurii microbial solution, and the concentration is 1.0≤OD 600 ≤6.

0.

2. A method of preparing the microorganism soil binding component of claim 1, wherein, The method includes the following steps: (1) preparing the soil penetration agent: weighing the acetylenic alcohol polyether surfactant and the polyol surfactant, adding them into water, and mixing and stirring them uniformly; (2) preparing the microbial solidification solution: weighing the urea and the calcium dihydrogen phosphate, adding them into water, and mixing and stirring them uniformly; (3) mixing and stirring the microbial bacteria solution and the microbial solidification solution within 3-5 hours before spraying the microbial soil solidification component; (4) adding the prepared soil penetration agent into the mixture of the microbial solidification solution and the microbial bacteria solution within 1-2 hours before spraying the microbial soil solidification component, and obtaining the microbial soil solidification component.

3. A soil stabilizing method using the soil stabilizing component of claim 1, characterized by, The method includes the following steps: (1) determining the soil solidification range of the excavated bare cohesive soil and the dosage of the microbial soil solidification component; (2) taking soil on site and testing the void ratio of the cohesive soil; according to the void ratio of the soil, determining the spraying times; (3) using a steel drill to punch small holes in the soil solidification range of the bare cohesive soil; (4) loading the prepared microbial soil solidification component into a sprayer, and uniformly spraying the microbial soil solidification component on the soil solidification range of the bare cohesive soil according to the dosage and times determined in steps (1) and (2).

4. The soil stabilizing method of claim 3, wherein, In step (1), the dosage of the microbial soil solidification component is determined according to 1.5-2 liters per square meter of the surface area of the cohesive soil.

5. The soil stabilizing method of claim 3, wherein, In step (2), the void ratio e of the soil is greater than 1.0 or less than 1.0; when the void ratio e of the soil is greater than 1.0, the spraying times are 2; when the void ratio e of the soil is less than 1.0, the spraying times are 3.

6. The soil stabilizing method of claim 3, wherein, In step (3), the diameter of the steel drill is 4-6 mm, the depth of the small holes is 50-100 mm, and the spacing is 50-80 mm.

7. The soil stabilizing method of claim 3, wherein, In step (4), the spraying mode is manual spraying or unmanned aerial vehicle spraying according to the size of the soil solidification range; the interval time of each spraying is 24 hours.