Novel method for solidifying foundation through cooperation of microorganisms and active magnesium oxide

Abstract

The invention discloses a novel method for solidifying a foundation through cooperation of microorganisms and active magnesium oxide, and belongs to the technical field of foundation treatment. In a traditional foundation treatment method, a large amount of ore energy needs to be consumed in the production process of a reinforcing material, harm can be brought to the surrounding environment, and serious noise pollution, air pollution and the like are generated. According to the novel method for solidifying the foundation through cooperation of microorganisms and active magnesium oxide, the carbonation reaction between HCO3 <-> in a NaHCO3 solution and active MgO is accelerated through the catalytic acceleration effect of carbonic anhydrase on the CO2 hydration reaction, so that a large number of carbonates such as magnesium carbonate and basic magnesium carbonate with the good gelling effect are generated, solidified soil particles are cemented, and the effect of solidifying the foundation through cooperation of microorganisms and active magnesium oxide is achieved. And the effect of reinforcing the foundation is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ground treatment, and particularly relates to a new method for solidifying the ground by microorganisms in cooperation with active magnesium oxide. Background Technique

[0002] With the acceleration of the process of social modernization development in China, the demand for construction land has also increased accordingly. However, in the process of engineering construction, it is inevitable to encounter poor soil that does not meet the requirements of engineering construction. If the soil is not reinforced in advance, it will inevitably lead to engineering disasters to varying degrees in the future. Therefore, it is necessary to reinforce the soil. The carbonation solidification technology of active MgO-CO2 is an innovative ground improvement method. This method first mixes active magnesium oxide (MgO) with soil, and then injects carbon dioxide (CO2) under high pressure in a short time to carbonize the active MgO. The carbonation products cement and solidify the soil particles, thereby rapidly improving the strength of the ground. The reaction process is as follows:

[0003] MgO + H2O → Mg(OH)2

[0004] Mg(OH)2 + CO2 + 2H2O → MgCO3·3H2O

[0005] 5Mg(OH)2 + 4CO2 + H2O → (Mg)5(CO3)4(OH)2·5H2O

[0006] 5Mg(OH)2 + 4CO2 → (Mg)5(CO3)4(OH)2·4H2O

[0007] This is a new type of soil solidification method with low carbon, environmental protection and rapidity, and is expected to replace the traditional cement soil solidification method. However, this method requires the installation of special CO2 pressurized injection equipment, and the purchase and transportation of high-purity CO2 also require a large amount of money. The present invention is inspired by the fact that microorganisms in nature actively participate in the carbon cycle and stimulate the carbonization phenomenon, and uses the enzyme catalytic action of carbonic anhydrase secreted by microorganisms to innovatively propose a method of promoting the carbonization of active MgO and increasing its effect of reinforcing the soil by incorporating Bacillus mucilaginosus and sodium bicarbonate solution.

[0008] Carbonic anhydrase is one of the enzymes with the fastest known catalytic rate. It has the characteristic of accelerating the hydration of CO2 to generate HCO3 - (by about 10 7 times), and can significantly improve the absorption efficiency and absorption rate of CO2. The reaction formula is as follows:

[0009]

[0010] The present invention selects sodium bicarbonate solution, which is inexpensive and easily available, as the auxiliary solution to provide the carbonate ions required for the carbonation of active MgO. This method can not only significantly improve the strength of the soil mass, but also is simpler and less costly in operation compared with the traditional active MgO-CO2 carbonation solidification technology, and also avoids the leakage of CO2 during the construction process. Summary of the Invention

[0011] The present invention provides a new method for curing foundation by microorganism synergistic active magnesium oxide.

[0012] (I) Technical Solution

[0013] In order to achieve the object of the present invention, the present invention discloses a new method for curing foundation by microorganism synergistic active magnesium oxide, which is characterized in that the steps of the method are as follows:

[0014] Use mechanical tillage on the silty soil foundation to be treated, and add active MgO, NaHCO3 solution, and Bacillus mucilaginosus bacterium agent to the soil during the tillage process. Add 10 g of active MgO, 3 g of Bacillus mucilaginosus bacterium agent, and 11.3 g of 1 mol / L NaHCO3 solution to every 100 g of silty soil, and fully stir and mix the silty soil, active MgO, Bacillus mucilaginosus bacterium agent, and NaHCO3 solution, and then level the site.

[0015] Application and effect: The unconfined compressive strength of the foundation after 7 days is 2.8 MPa.

[0016] The dosage of the active magnesium oxide is 5-30% of the mass of the silty soil; the dosage of the Bacillus mucilaginosus is 3-8% of the solid mass; the concentration of the used sodium bicarbonate solution is 0.5-2 mol / L.

[0017] The microorganism is Bacillus mucilaginosus, and the density of the bacterium is 1.0×10 9 ~1.0×10 10 cell / g, and the enzyme activity is 80-200 U·mL -1 .

[0018] The curing time is 7 days.

[0019] Advantages of the present invention:

[0020] Through the synergistic solidification of active magnesium oxide and microorganisms, the pores of the soil mass can be effectively filled, and the strength of the soil mass can be increased; the reinforcement treatment process does not require high-pressure injection of CO2, and the operation is simple and easy. Brief Description of the Drawings

[0021] Figure 1 For the unconfined compressive strength and mass growth rate of soil samples under different dosages of Bacillus mucilaginosus and different concentrations of sodium bicarbonate solution in Example 1.

[0022] Figure 2 It is a diagram showing the mechanism of soil fixation by carbonic anhydrase. Specific implementation methods

[0023] Example 1

[0024] In this example, a new method for solidifying the foundation by microorganisms and activated magnesium oxide includes the following steps:

[0025] a. Take out the previously dried silt from the 105°C oven and weigh the required mass.

[0026] b. Add activated magnesium oxide (10%), Bacillus mucilaginosus (3%), water (10%), and sodium bicarbonate aqueous solution concentration (1.0 mol / L) to the sand, and stir evenly.

[0027] c. Pour the evenly stirred mixture into a PVC mold with an inner diameter of 30 mm and a height of 120 mm in three equal layers with equal drop heights, and scrape the contact surface between layers to prevent the specimen from delaminating. Repeat the above operation to fill the syringe to the designed height.

[0028] d. Place the prepared silt specimen in a constant temperature curing box and cure it to the designed age at 30 ± 2°C and a humidity of not less than 95%. After the curing is completed, remove the specimen and demold it with a demolding knife. The unconfined compressive strength of the soil sample can reach up to 6 MPa.

[0029] Example 2

[0030] In this example, a method for strengthening the foundation by microorganisms and activated MgO is used to strengthen silt, and the method includes the following steps:

[0031] Use mechanical tillage on the silt foundation to be treated, and add activated MgO, NaHCO3 solution, and Bacillus mucilaginosus bacterium agent to the soil during the tillage process. Add 10 g of activated MgO, 3 g of Bacillus mucilaginosus bacterium agent, and 11.3 g of 1.5 mol / L NaHCO3 solution to every 100 g of silt, and stir and mix the silt, activated MgO, Bacillus mucilaginosus bacterium agent, and NaHCO3 solution thoroughly, and level the site.

[0032] Application and effect: The unconfined compressive strength of the foundation after 7 days is 3.9 MPa.

Claims

1. Carbonic anhydrase is used to accelerate the carbonation of active MgO.

2. The source of carbonic anhydrase selected is Bacillus mucilaginosus, not bovine erythrocytes. It secretes extracellular carbonic anhydrase. The density of the bacteria is 1.0×10 9 ~1.0×10 10 cell / g, and the enzyme activity is 80~200 U·mL -1 .

3. Sodium bicarbonate solution is used as an auxiliary solution to provide carbonate ions required for the carbonation of active MgO, and the concentration is 0.5 - 2 mol / L.

4. The dosage of Bacillus mucilaginosus is 3 - 8% of the soil mass.

5. The dosage of active MgO is 5 - 30% of the soil mass, and the activity coefficient is 50 - 80%.

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