Method for the production of a bio-induced solidified flow plastic soil

Abstract

The application discloses a kind of biological induction solidification flow plastic soil preparation methods, comprising the following steps: step one, citric acid is added to high water content flow plastic soil in pumping process, stirring is carried out in incorporation process, and it is stationary after stirring;Step two, when the water content in flow plastic soil is higher than the liquid limit of soil body, first polyacrylamide is added to flow plastic soil, is fully stirred, and it is stationary after stirring Precipitation, the upper water of flow plastic soil is pumped away, and then mechanical pressure filtration dewatering is carried out;Step three, the mechanical pressure filtration dewatering mud cake is scattered using blade, and nutrient salt is added, and is fully mixed, and mixing is not less than 10min;Step four, microbial solidification agent is uniformly mixed into the mud soil body, and is cured until the soil body solidification.The application can solve the problems of high disposal cost and great utilization difficulty of current engineering flow plastic soil by using the above-mentioned biological induction solidification flow plastic soil preparation method, and is suitable for the solidification and engineering in-situ recycling of flow plastic soil.

Description

Technical Field

[0001] This invention relates to the field of fluid plastic soil solidification technology, and in particular to a method for preparing biologically induced solidified fluid plastic soil. Background Technology

[0002] Currently, the widespread water environment management projects, while cleaning up pollution in rivers, lakes, and waterways, also generate large quantities of fluid plastic soil. Fluid plastic soil has high water content, high organic matter and pollutant content, low strength, high compressibility, and poor drainage, making it difficult to use in engineering design and thus considered waste. Statistics show that the Pearl River Delta region alone generates 8000 × 10⁴ m³ of fluid plastic soil annually. 3 As the nationwide efforts to carry out dredging and clean-up projects have increased year by year, the practical problem of how to deal with fluid plastic soil is hard to avoid.

[0003] In actual engineering projects, construction machinery can generate large amounts of fluid plastic soil in a short period of time once it is started. Direct discharge would pollute the environment and is very costly to transport. On-site treatment is the best solution. Among these methods, solid-liquid separation and solidification are currently the most widely used. Solidification involves adding a solidifying agent to the fluid plastic soil, causing it to react with the agent to form a solid with a certain strength or soil suitable for vegetation growth. This method can significantly reduce the impact of fluid plastic soil on the ecological environment and has advantages such as low cost, convenient operation, and easy backfilling and restoration to farmland.

[0004] However, to date, related achievements are very limited. Application number CN201811631957 discloses a method for solidifying fluidized clay using microorganisms and fly ash. The method is characterized by raw materials comprising, by weight, 20 parts yeast powder, 10 parts ammonium sulfate, 1 part nickel chloride, and 0.3-1.5 parts *Bacillus pasteurellii* seed fermentation broth, which are cultured at 30°C for 24 hours and then sterilized. The resulting culture medium is then mixed with 10-30 parts fly ash and 100-300 parts fluidized clay, stirred evenly, and cured in a humidified container for 28 days. This preparation method requires temperature control and stringent curing conditions. While this invention is suitable for on-site construction to achieve rapid solidification of fluidized clay, it is not directly related to this method.

[0005] Application No. 201710572177.2 discloses a method for microbial solidification of fluid plastic soil. The method involves mixing 40 parts by weight of urea, 70 parts by weight of calcium chloride, 40 parts by weight of Bacillus pasteurellium bacterial solution with 1000 parts by weight of fluid plastic soil, stirring thoroughly, and then curing under natural conditions. While this patent uses calcium chloride to provide calcium ions for Bacillus pasteurellium to generate calcium carbonate for solidification, this invention uses phosphogypsum to provide a substrate for sulfate-reducing bacteria, thus improving waste utilization and conserving resources.

[0006] Application No. 202210171947.3 discloses a solidifying agent for river and lake bottom sediment and a method for solidifying bottom sediment. The solidifying agent has the following mass ratio: 6-12 parts cement, 2-5 parts quicklime, 0.01-0.04 parts triethanolamine, 0.1-0.4 parts polypropylene fiber, and 3-9 parts slag. The main agent in the patent is cement, which is not conducive to resource conservation and energy saving and carbon reduction. The present invention uses microorganisms to solidify fluidized soil, which is more environmentally friendly.

[0007] Application No. 201810667689.1 discloses a method for reinforcing riverbed sediment through microbial grouting. This method involves conveying a calcium source, a mixed solution of Bacillus subtilis and silicate bacteria, and carbon dioxide into the fluid plastic soil of the riverbed via a conveying device. The mixed solution is then added to the surface of the fluid plastic soil. After the soil has fully flocculated and formed a stratification of sediment and upper clear water, the upper water layer is removed using a pumping device. This patent requires numerous devices and involves complex procedures. In contrast, this invention uses a single bacterial species, the materials are readily available, and the operation is quick and easy, meeting the requirements of on-site construction. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing bio-induced solidified fluidized soil, which can solve the problems of high disposal costs and difficulty in utilization of fluidized soil in current engineering projects. It is applicable to the solidification of fluidized soil and on-site recycling in engineering projects, which can effectively save engineering costs, reduce environmental pollution, and achieve significant social and economic benefits.

[0009] To achieve the above objectives, the present invention provides a method for preparing bio-induced solidification fluidized soil, comprising the following steps:

[0010] Step 1: Add citric acid to the high water content fluid plastic soil during the pumping process, stirring during the mixing process, and let it stand for 100-150 minutes after stirring.

[0011] Step 2: When the water content in the fluid plastic soil is higher than the soil liquid limit, first add polyacrylamide to the fluid plastic soil, stir thoroughly for 10-20 minutes, let it stand and settle for 2-3 hours, remove the water from the upper layer of the fluid plastic soil, and then perform mechanical pressure filtration dewatering to control the water content of the fluid plastic soil to be less than 35%; when the water content in the fluid plastic soil is lower than the soil liquid limit, directly use mechanical pressure filtration dewatering.

[0012] Step 3: Use a blade to break up the mechanically pressed filter cake, add nutrient salts, mix thoroughly for at least 10 minutes, and obtain the broken-up soil.

[0013] Step 4: Mix the microbial solidifying agent evenly into the mud and cure until the soil is solidified.

[0014] Preferably, in step one, 5-7.4 kg of citric acid is added to each ton of fluidized soil.

[0015] Preferably, in step two, 1-2 kg of polyacrylamide is added to each ton of fluidized soil, and the mechanical pressure filtration dewatering time is not less than 12 minutes.

[0016] Preferably, the nutrients in step three are a mixture of phosphogypsum, quicklime, sodium sulfite, sodium acetate, glucose, and ferrous ammonium sulfate. For each ton of fluid plastic soil, 150-250 kg of phosphogypsum, 50-80 kg of quicklime, 5-20 kg of sodium sulfite, 5 kg of sodium acetate, 1 kg of glucose, and 0.5 kg of ferrous ammonium sulfate are added.

[0017] Preferably, the microbial curing agent is composed of yeast extract and sulfate-reducing bacteria; the fluidized clay, phosphogypsum, quicklime, citric acid, polyacrylamide, sodium acetate, yeast extract, glucose, ferrous ammonium sulfate, sodium sulfite, and sulfate-reducing bacteria are in a mass ratio of 1:0.15-0.25:0.05-0.08:0.005-0.0074:0.001-0.002:0.005:0.002:0.001:0.0005:0.005-0.02:0.006-0.007.

[0018] Therefore, the present invention employs the above-mentioned method for preparing bio-induced solidified fluidized soil, which has the following advantages:

[0019] Beneficial effects:

[0020] (1) The solidification treatment of fluid plastic soil using this technical solution effectively promotes the resource utilization of industrial solid waste (phosphogypsum) and engineering solid waste (fluid plastic soil), realizes sustainable development of waste treatment, and has good engineering application prospects.

[0021] (2) Compared with the traditional grouting method, the addition of bacteria and nutrients by mixing can significantly improve the uniformity of bacterial distribution in fluid plastic soil while ensuring bacterial activity, which is conducive to inducing the formation of calcium carbonate precipitation and the solidification effect of fluid plastic soil is better.

[0022] (3) Biologically induced solidified fluidized soil can provide a new source of filler for engineering projects. At the same time, it solves the problem of disposing of a large amount of fluidized soil generated during engineering construction and accelerates the progress of engineering implementation.

[0023] (4) The implementation method is simple to operate, saves land, can effectively save engineering costs, reduce environmental pollution, and has significant social and economic benefits.

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0025] Figure 1This is a flowchart of an embodiment of a method for preparing bio-induced solidification fluidized soil according to the present invention;

[0026] Figure 2 This is a graph showing the relationship between the shear strength and vertical pressure of a sample from an embodiment of the method for preparing biologically induced solidified fluidized soil according to the present invention. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0029] Example

[0030] like Figure 1 The present invention provides a method for preparing bio-induced solidified fluidized soil, comprising the following steps:

[0031] Step 1: During the pumping process, add 5-7.4 kg of citric acid per ton of high moisture content fluid plastic soil. Stir during the mixing process, and let it stand for 100-150 minutes after stirring to fully complex and inertize heavy metal ions.

[0032] Step 2: When the water content in the fluid plastic soil is higher than the soil liquid limit, first add polyacrylamide to the fluid plastic soil, stir thoroughly for 10-20 minutes, let it stand and settle for 2-3 hours, remove the water from the upper layer of the fluid plastic soil, and then perform mechanical pressure filtration dewatering. The filtration time should not be less than 12 minutes, and the water content of the fluid plastic soil should be controlled to be less than 35%. When the water content in the fluid plastic soil is lower than the soil liquid limit, mechanical pressure filtration dewatering can be used directly.

[0033] Step 3: Use a blade to break up the mechanically pressed filter cake, and add nutrients. The nutrients are a mixture of phosphogypsum, quicklime, sodium sulfite, sodium acetate, glucose, and ferrous ammonium sulfate. Add 150-250 kg of phosphogypsum, 50-80 kg of quicklime, 5-20 kg of sodium sulfite, 5 kg of sodium acetate, 1 kg of glucose, and 0.5 kg of ferrous ammonium sulfate to each ton of fluid plastic soil. Mix thoroughly for at least 10 minutes. If the organic matter content of the fluid plastic soil is high enough to support the growth of microorganisms, there is no need to add yeast extract or glucose.

[0034] Step 4: Mix the microbial solidifying agent into the fluid plastic soil and mix evenly. The main component of phosphogypsum is calcium sulfate dihydrate. Sulfate-reducing bacteria can reduce sulfate ions to H2S. At the same time, CO2 is produced when degrading organic matter, which combines with calcium ions to form calcium carbonate precipitate. Calcium carbonate ions can fill the voids in the fluid plastic soil particles, causing the particles to bind together, thereby achieving the purpose of strengthening the fluid plastic soil.

[0035] The fluidized clay, phosphogypsum, quicklime, citric acid, polyacrylamide, sodium acetate, yeast extract, glucose, ferrous ammonium sulfate, sodium sulfite, and sulfate-reducing bacteria are present in a mass ratio of 1:0.15-0.25:0.05-0.08:0.005-0.0074:0.001-0.002:0.005:0.002:0.001:0.0005:0.005-0.02:0.006-0.007.

[0036] Example 1

[0037] The fluid plastic soil was taken from a depth of 4-6m below the riverbed, and its basic physical properties are shown in Table 1.

[0038] Table 1 Basic Physical Properties of Fluid Plastic Soil

[0039]

[0040] One ton of fluid plastic soil was mixed with 150g of phosphogypsum and 80g of quicklime, and stirred thoroughly. Citric acid, a dehydrating flocculant, nutrients, and sodium sulfite were then added sequentially to create a suitable environment for sulfate-reducing bacteria growth. Finally, the reducing bacteria were added for solidification. A direct shear test was conducted on soil samples excavated using a standard 61.8mm × 2mm ring cutter. The specific implementation steps are as follows:

[0041] (1) Add 7g of citric acid to the fluid plastic soil while stirring. After the addition is complete, continue stirring for 30 minutes and let stand for 100 minutes.

[0042] (2) Add 10g of dewatering flocculant to the fluid plastic soil, stir thoroughly for 20min, let it stand for 3h after stirring, remove the water from the top layer of sludge, and control the water content of the fluid plastic soil to 30%. The dewatering flocculant is polyacrylamide flocculant.

[0043] (3) Add phosphogypsum, quicklime, sodium acetate, glucose, ferrous ammonium sulfate, and sodium sulfite to the fluid plastic soil, mix for 10 minutes, and stir until homogeneous. Specifically, add 150g phosphogypsum, 80g quicklime, 5g anhydrous sodium acetate, 2g yeast extract, 1g glucose, 0.5g ferrous ammonium sulfate, and 20g sodium sulfite per ton of fluid plastic soil. Stir rapidly during the addition process until the mixture is homogeneous.

[0044] (4) Add the microbial solidifying agent to the fluid plastic soil and mix evenly. The amount of microbial agent added accounts for 0.6% of the total amount of fluid plastic soil.

[0045] Example 2

[0046] The preparation method for this example is the same as that for Example 1, except that the amount of sulfate-reducing bacteria added is 0.7% of the fluidized soil.

[0047] Figure 2 The graph shows the relationship between the shear strength of the sample and the vertical pressure. As can be seen from the graph, the fluidized soil solidified by sulfate-reducing bacteria has a certain strength and the solidification effect is good. At the same time, the strength of the solidified fluidized soil varies slightly depending on the content of the bacteria. The strain content of Example 2 is higher, and the strength of the fluidized soil is also slightly increased.

[0048] Therefore, the present invention adopts the above-mentioned method for preparing biologically induced solidified fluidized soil, which can solve the problems of high disposal cost and difficulty in utilization of fluidized soil in current engineering projects. It is suitable for the solidification of fluidized soil and on-site recycling in engineering projects, which can effectively save engineering costs, reduce environmental pollution, and achieve significant social and economic benefits.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method of preparing a bio-induced solidified flow plastic soil, characterized in that: The method comprises the following steps: Step one, adding citric acid to the flow plastic soil with high water content during pumping, stirring during mixing, and standing for 100-150 minutes after stirring to fully complex and inert heavy metal ions; Step two, when the water content in the flow plastic soil is higher than the liquid limit of the soil body, first adding polyacrylamide to the flow plastic soil, fully stirring for 10-20 minutes, standing for 2-3 hours after stirring, pumping away the water on the upper layer of the flow plastic soil, and then performing mechanical pressure filtration dewatering to control the water content of the flow plastic soil to be less than 35%; when the water content in the flow plastic soil is lower than the liquid limit of the soil body, directly performing mechanical pressure filtration dewatering; Step three, dispersing the mechanical pressure filtration dewatering cake by using a blade to break the mud, and adding nutrient salt, fully mixing for more than 10 minutes to obtain a broken mud soil body; the nutrient salt is a mixture of phosphogypsum, quicklime, sodium sulfite, sodium acetate, glucose and ferrous ammonium sulfate; Step four, uniformly mixing the microbial solidification agent into the broken mud soil body, and curing until the soil body is solidified; the microbial solidification agent is composed of yeast extract and sulfate-reducing bacteria.

2. A method of preparing a bio-induced solidified flow plastic soil according to claim 1, characterized in that: In step one, 5-7.4 kg of citric acid is added per ton of flow plastic soil.

3. A method of preparing a bio-induced solidified flow plastic soil according to claim 1, characterized in that: In step two, 1-2 kg of polyacrylamide is added per ton of flow plastic soil, and the mechanical pressure filtration dewatering time is not less than 12 minutes.

4. A method of preparing a bio-induced solidified flow plastic soil according to claim 1, characterized in that: Phosphogypsum 150-250 kg, quicklime 50-80 kg, sodium sulfite 5-20 kg, sodium acetate 5 kg, glucose 1 kg and ferrous ammonium sulfate 0.5 kg are added per ton of flow plastic soil.

5. A method of preparing a bio-induced solidified flow plastic soil according to claim 1, characterized in that: The flow plastic soil, phosphogypsum, quicklime, citric acid, polyacrylamide, sodium acetate, yeast extract, glucose, ferrous ammonium sulfate, sodium sulfite, sulfate-reducing bacteria are in a mass ratio of 1:0.15-0.25:0.05-0.08:0.005-0.0074:0.001-0.002:0.005:0.002:0.001:0.0005:0.005-0.02:0.006-0.007.

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