A Shield Muck-Based Low-Carbon Synchronous Grouting Material for Microbially Induced CO2 Mineralization and Its Preparation Method

Abstract

The present invention relates to the technical field of shield synchronous grouting materials, and particularly to a low-carbon synchronous grouting material based on microbial CO2 solidification and a preparation method thereof using shield muck, including modified shield mud, Staphylococcus epidermidis solution, fly ash, and cementing liquid. The composition components of the modified shield mud, by mass fraction, include: 50-80 parts of shield muck or shield waste slurry, 0.5-2 parts of consistency regulator, and 20-50 parts of water. By adopting the above low-carbon synchronous grouting material based on microbial CO2 solidification and the preparation method thereof, it is not necessary to use portland cement as a cementitious material, and the material components can be modified to be applicable to shield mucks of various different geological conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of shield synchronous grouting materials, and particularly to a low-carbon shield muck-based synchronous grouting material based on microbial CO2 curing and a preparation method thereof. Background Art

[0002] With the continuous expansion of the scale of urban rail transit construction, shield tunneling for subway tunnels has become increasingly common, and a large amount of shield muck is generated in this process. Currently, shield muck is mainly disposed of by landfill, facing problems such as long transportation distances, high disposal costs, and serious waste of land resources. The excessive accumulation of muck not only causes environmental and economic problems such as environmental pollution and land occupation, but also poses a threat to human health and property safety.

[0003] In addition, during the shield construction process, the reconsolidation of the soil around the tunnel and the infiltration of groundwater will cause ground settlement. To reduce and prevent ground settlement, it is necessary to inject sufficient grouting materials behind the segment lining of the shield tail in a timely manner during the excavation process to fill the annular gap of the shield tail and support the rock mass, thereby effectively controlling ground settlement. The use of synchronous grouting materials can not only improve the waterproof performance of the tunnel, but also provide early stability for the tunnel segments, promoting the bonding between the segments and the surrounding rock mass, which plays an important role in controlling the shield tunneling direction and ensuring the final stability of the tunnel.

[0004] However, currently commercially available conventional shield synchronous grouting materials all rely on a large amount of portland cement as the curing binder, and a large amount of CO2 emissions will be generated during their production and use. Therefore, exploring low-carbon and resource utilization paths for shield muck has an urgent practical significance for the green development of shield construction projects.

[0005] The existing patent CN115286340A discloses a synchronous grouting material based on silt-like shield soil and a preparation method thereof. The synchronous grouting material is composed of a finished soil slurry and a soil binder. Among them, the finished soil slurry is prepared by making slurry from silt-like shield muck, soda ash, and ferrochrome lignosulfonate, and the soil binder is made of portland cement, blast furnace slag powder, steel slag powder, fly ash, etc. Although it realizes the large-scale utilization of silt-like muck and improves the material properties, this solution still has some deficiencies: (1) It is necessary to screen the silt-like muck with a 3mm sieve, and only the part above the sieve is used, resulting in a low utilization rate of muck and failing to achieve large-scale resource utilization of shield muck; (2) The strength of the synchronous grouting material is relatively low, and the setting time is relatively long; (3) It is only applicable to earth pressure balance shield muck with a silt content ≥ 90%, and cannot adapt to other strata and slurry balance shield waste slurry, with limited applicability.

[0006] The existing patent CN118993648A discloses a shield synchronous grouting material suitable for water-rich karst strata. It mainly prepares slurry by pre-treating shield muck in water-rich karst strata, and prepares a synchronous grouting material under the action of portland cement, modified inorganic powder materials, modified water-reducing agents, sulfate early-strength agents and polypropylene fibers. This method solves the technical problems of poor fluidity, poor mechanical strength, inapplicability to shield construction, and low water-reducing efficiency of the water-reducing agent used in the existing grouting materials. However, this solution still has some deficiencies: (1) It is only applicable to shield muck in water-rich karst strata, with strong pertinence and no general applicability; (2) A large amount of portland cement needs to be used, and the environmental friendliness of the material composition is poor; (3) The process is complex, the conditions are relatively harsh, and the technical stability is poor.

[0007] The existing patent CN117735929A discloses a shield muck synchronous grouting material and its preparation method. It mainly prepares a shield synchronous grouting material under the joint action of shield muck, slag powder, water, hydrated lime and anhydrous sodium sulfate. It realizes the resource recycling of muck while reducing carbon emissions, which is of great significance to environmental protection and conforms to the policy of "energy conservation and emission reduction". It can also save construction costs for enterprises and help relieve the economic and social pressures brought by muck treatment of subway construction units. However, this solution still has some deficiencies: (1) It is only applicable to earth pressure balance shield muck in silty clay strata, without general applicability, and its particle size needs to be between 0.01 - 5 mm, with high requirements for shield muck, and it cannot achieve the comprehensive resource utilization of shield muck; (2) A large amount of fine sand needs to be used as aggregate, which has the disadvantage of consuming non-renewable resources such as sand and gravel.

[0008] In summary, the shield muck-based synchronous grouting materials in the existing technology still need to use a large amount of portland cement, with extremely high carbon emissions. Moreover, the requirements for the composition of shield muck are relatively high, the utilization rate is low and the applicability is relatively limited. There is still a large amount of shield muck that needs to be processed and transported, which will also emit a large amount of CO2. Therefore, in order to overcome the deficiencies of the existing technology, the present invention provides a shield muck-based low-carbon synchronous grouting material based on microbial CO2 fixation. Summary of the Invention

[0009] The purpose of the present invention is to provide a shield muck-based low-carbon synchronous grouting material based on microbial CO2 fixation and its preparation method, which does not need to use portland cement as a gelling material and can be modified by adjusting the material components to be applicable to shield mucks in a variety of different geological conditions.

[0010] To achieve the above object, the present invention provides a low-carbon synchronous grouting material based on microbial solidification of CO2 for shield muck, comprising modified shield mud, Staphylococcus epidermidis solution, fly ash and cementing liquid. The composition of the modified shield mud by mass fraction includes: 50-80 parts of shield muck or shield waste slurry, 0.5-2 parts of consistency regulator, and 20-50 parts of water.

[0011] Preferably, the Staphylococcus epidermidis solution is a solution formed by mixing Staphylococcus epidermidis screened and purified from the soil near the salt lake with LB medium.

[0012] Preferably, the specific gravity of the modified shield mud is 1.2-1.6, the viscosity is 1000-3000 mPa s, and the consistency is 100-180 mm;

[0013] The shield muck or shield waste slurry includes the muck or waste slurry from earth pressure balance shield construction or slurry balance shield construction in silty clay stratum, sandy stratum, silty clay layer, gravel layer, gravel layer, soft rock stratum, and clay stratum.

[0014] Preferably, the consistency regulator includes one or more of hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, and hydroxyethylcellulose.

[0015] Preferably, the fly ash has a CaO content ≥ 40%, an SiO2 content ≥ 20%, and a porosity ≥ 60%.

[0016] Preferably, the cementing liquid is a mixed solution of urea and calcium chloride or calcium acetate, the concentration of the mixed solution is 0.25-2.00 mol / L, and the molar ratio of urea to calcium chloride or calcium acetate is 1:1.

[0017] Preferably, the synchronous grouting material is a single-component synchronous grouting material, and its composition by mass fraction includes 10-20 parts of Staphylococcus epidermidis solution, 40-70 parts of modified shield mud, 10-30 parts of fly ash, and 10-20 parts of cementing liquid.

[0018] Preferably, the synchronous grouting material is a two-component synchronous grouting material, and its composition by mass fraction includes 50-70 parts of S1 finished slurry and 30-50 parts of S2 finished slurry;

[0019] The composition of S1 finished slurry by mass fraction includes: 50-80 parts of modified shield mud, 10-25 parts of Staphylococcus epidermidis solution, and 10-25 parts of cementing liquid;

[0020] The composition of S2 finished slurry by mass fraction includes: 50-70 parts of fly ash and 30-50 parts of water.

[0021] The present invention also provides a preparation method of the above-mentioned shield muck-based low-carbon synchronous grouting material based on microbial solidification of CO2, including the preparation steps of single-fluid grout synchronous grouting material as follows:

[0022] (1) Mix shield muck or shield waste slurry with a consistency regulator and water in proportion to prepare a modified shield mud;

[0023] (2) Add a Staphylococcus epidermidis solution, fly ash and a cementing liquid to the modified shield mud in proportion and mix to prepare a single-fluid grout synchronous grouting material.

[0024] The present invention also provides a preparation method of the above-mentioned shield muck-based low-carbon synchronous grouting material based on microbial solidification of CO2, including the preparation steps of double-fluid grout synchronous grouting material as follows:

[0025] (1) Mix shield muck or shield waste slurry with a consistency regulator and water in proportion to prepare a modified shield mud;

[0026] (2) Add a Staphylococcus epidermidis solution and a cementing liquid to the modified shield mud in proportion and mix to prepare a finished S1 slurry;

[0027] (3) Mix fly ash and water in proportion to prepare a finished S2 slurry;

[0028] (4) Mix the finished S1 slurry and the finished S2 slurry in proportion to prepare a double-fluid grout synchronous grouting material.

[0029] Advantages of the present invention:

[0030] (1) The present invention utilizes the microbial-induced calcium carbonate precipitation (MICP) technology, and uses the urease produced by the metabolism of Staphylococcus epidermidis, which can decompose urea. The carbonate ions generated after the decomposition of urea combine with free metal cations in nature to form a gel. This not only can effectively absorb CO2 in the environment during the reaction process, but also can completely replace the use of portland cement, a cementing material that generates a large amount of carbon emissions during production and use, in the shield synchronous grouting material by using the gelling effect during the reaction process, reducing CO2 emissions and effectively solving the problem of poor environmental protection in the prior art.

[0031] (2) The present invention uses a large amount of shield muck (waste slurry) to prepare synchronous grouting material, and is applicable to shield muck and shield waste slurry in different geological conditions (silty clay, sandy soil and hard rock, etc.) and different shield construction methods (earth pressure balance shield construction method and slurry balance shield construction method). It not only realizes the harmless treatment and resource utilization of shield muck (waste slurry), but also solves the problems of low utilization rate and limited applicability of shield muck (waste slurry) in the prior art.

[0032] (3) The synchronous grouting material of the present invention can be applied not only to single-fluid grouting materials and double-fluid grouting materials, and all performance indicators fully meet the technical requirements in existing shield construction, and the mechanical properties after hardening exceed those of traditional synchronous grouting materials.

[0033] The following will, through the accompanying drawings and embodiments, make a further detailed description of the technical solution of the present invention. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of the preparation process of the single-fluid synchronous grouting material in Embodiment 1 of the present invention;

[0035] Figure 2 It is a schematic diagram of the preparation process of the double-fluid synchronous grouting material in Embodiment 5 of the present invention. Specific Embodiments

[0036] The following will, in combination with the accompanying drawings and embodiments, further describe the present invention. Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those with ordinary skills in the field to which the present invention belongs. The above-mentioned features mentioned in the present invention or the features mentioned in the specific examples can be combined arbitrarily, and these specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0037] The solution of Staphylococcus epidermidis used in the present invention is a solution formed by mixing Staphylococcus epidermidis screened, purified and cultured from the soil near the salt lake with LB medium.

[0038] The method for screening, purifying and culturing Staphylococcus epidermidis includes the following steps:

[0039] S1. Take a small amount of soil near the salt lake, add 100 mL of normal saline, place it in a shaker and shake for 10 min. After standing for 2 h, take 1 mL of the supernatant and inject it into 100 mL of LB liquid medium, and culture it in a shaker at a temperature of 37 °C and an oscillation frequency of 160 r / min for 24 h.

[0040] S2. Take 1 mL of the cultured bacterial solution and dilute it successively with sterile water according to the gradients of 10 -1 , 10 -2 , 10 -3 , 10 -4 , 10 -5 , 10 -6 , 10 -5 , 10 -6 . Select the diluted bacterial solutions with gradients of 10 -5 , 10 -6 and coat them on sterile plates respectively. After culturing at 37 °C until single colonies grow out, separate the single colonies and inoculate them into urea liquid separation medium.

[0041] S3. Pick the clear red single colonies on the urea liquid separation medium in S2 and streak them on a sterile plate using the streak plate method. Repeat the above steps multiple times until the colony morphology on the plate is stable.

[0042] S4. Culture the colonies on the plate with LB liquid medium, place them in a shaker at a temperature of 37 °C and an oscillation frequency of 160 r / min for 12 h. At this time, the absorbance OD of the bacterial solution at a wavelength of 600 nm 600 is approximately 0.7, and store it in a -20 °C refrigerator with glycerol for later use.

[0043] The urea liquid separation medium in S2 is a mixed solution containing 5.000 g of NaCl, 2.000 g of KH2PO4, 1.000 g of glucose, 0.012 g of phenol red, 0.200 g of peptone, 950 mL of distilled water, 50 mL of a mixed solution of glucose with a unit volume mass of 20 g / L and urea with a unit volume mass of 24 g / L.

[0044] In S4, each liter of the LB liquid medium contains 10 g of peptone, 5 g of yeast extract, 1 g of NaCl, and 1000 mL of water.

[0045] The preparation of the Staphylococcus epidermidis solution is as follows: After taking out and activating the stored bacterial solution of Staphylococcus epidermidis after culturing, inoculate it into the LB medium at a ratio of 1:500, place it in a shaker at a temperature of 37 °C and an oscillation frequency of 180 r / min for 12 h, and take the bacterial solution when the OD 600 measured by the ultraviolet spectrophotometer is approximately 1.5 and mix it with the LB medium.

[0046] Example 1

[0047] The present invention provides a single-fluid synchronous grouting material suitable for silty clay strata, which is composed of 15 parts of Staphylococcus epidermidis solution, 60 parts of modified shield mud, 10 parts of fly ash, and 15 parts of cementing liquid. The requirements for each component are as follows:

[0048] Staphylococcus epidermidis solution: The OD of the contained bacterial solution 600 measured by the ultraviolet spectrophotometer is 1.48 - 1.51;

[0049] The specific gravity of the modified shield mud is 1.4, the viscosity is 2000 mPa s, and the consistency is 150 mm. The modified shield mud is prepared by mixing 60 parts of shield muck, 38.8 parts of water, and 1.2 parts of consistency regulator in proportion and stirring evenly.

[0050] Among them, the shield muck is the muck from the earth pressure balance shield construction in the silty clay strata.

[0051] Consistency regulator: Hydroxypropyl methylcellulose;

[0052] Fly ash: CaO content is 50%, SiO2 content is 20%, porosity is 65%;

[0053] Cementing liquid: A mixed solution of 1 mol / L urea and 1 mol / L calcium chloride with a molar ratio of 1:1, and the solution concentration is 1.5 mol / L.

[0054] The preparation method of the single-fluid synchronous grouting material applicable to silty clay stratum is as Figure 1 shown, and includes the following steps:

[0055] (1) Add shield muck, water, and consistency regulator into a high-speed eddy mixer according to the above proportions, with a rotation speed of 200 r / min and a stirring time of 5 min to prepare modified shield mud;

[0056] (2) Add the modified shield mud, Staphylococcus epidermidis solution, fly ash, and cementing liquid into a finished slurry mixer according to the above proportions, with a rotation speed of 200 r / min and a stirring time of 3 min to prepare the finished single-fluid slurry synchronous grouting material, denoted as MTGM-1.

[0057] Example 2

[0058] The present invention provides a single-fluid synchronous grouting material applicable to sandy soil stratum, which is composed of 10 parts of Staphylococcus epidermidis solution, 65 parts of modified shield mud, 15 parts of fly ash, and 10 parts of cementing liquid. The requirements for each component are as follows:

[0059] Staphylococcus epidermidis solution: The OD of the contained bacterial liquid 600 The test value of the ultraviolet spectrophotometer is 1.46 - 1.55;

[0060] The specific gravity of the modified shield mud is 1.2, the viscosity is 1500 mPa s, the consistency is 120 mm, and the modified shield mud is prepared by mixing 50 parts of shield muck, 48 parts of water, and 2 parts of consistency regulator in proportion and stirring evenly.

[0061] Among them, the shield muck is the muck from the earth pressure balance shield construction in the sandy soil stratum.

[0062] Consistency regulator: Hydroxypropyl methylcellulose and hydroxyethyl cellulose with a mass ratio of 1:1;

[0063] Fly ash: CaO content is 42%, SiO2 content is 30%, porosity is 60%;

[0064] Cementing liquid: A mixed solution of 1 mol / L urea and 1 mol / L calcium chloride with a molar ratio of 1:1, and the solution concentration is 0.75 mol / L.

[0065] The preparation method and steps of the above single-fluid synchronous grouting material applicable to sandy soil layers are as follows:

[0066] (1) Add shield muck, water, and consistency regulator into a high-speed eddy current mixer at the above ratios, with a rotation speed of 200 r / min and a stirring time of 5 min to prepare modified shield mud;

[0067] (2) Add the modified shield mud, Staphylococcus epidermidis solution, fly ash, and cementing liquid into a finished slurry mixer at the above ratios, with a rotation speed of 200 r / min and a stirring time of 3 min to prepare the finished single-fluid slurry synchronous grouting material, denoted as MTGM-2.

[0068] Example 3

[0069] The present invention provides a single-fluid synchronous grouting material applicable to silty soil layers, which is composed of 20 parts of Staphylococcus epidermidis solution, 50 parts of modified shield mud, 15 parts of fly ash, and 15 parts of cementing liquid. The requirements for each component are as follows:

[0070] Staphylococcus epidermidis solution: The OD of the bacterial solution contained 600 The test value of the ultraviolet spectrophotometer is 1.48 - 1.51;

[0071] The specific gravity of the modified shield mud is 1.2, the viscosity is 1500 mPa s, the consistency is 120 mm, and the modified shield mud is prepared by mixing 70 parts of shield waste slurry, 29 parts of water, and 1 part of consistency regulator in proportion and stirring evenly.

[0072] Among them, the shield waste slurry is the waste slurry from the balance shield construction in the silty soil layer.

[0073] Consistency regulator: Methyl cellulose;

[0074] Fly ash: The CaO content is 50%, the SiO2 content is 20%, and the porosity is 65%;

[0075] Cementing liquid: A mixed solution of 1 mol / L urea and 1 mol / L calcium chloride with a molar ratio of 1:1, and the solution concentration is 1.5 mol / L.

[0076] The preparation method and steps of the above single-fluid synchronous grouting material applicable to silty soil layers are as follows:

[0077] (1) Add the shield waste slurry, water, and consistency regulator into a high-speed eddy current mixer at the above ratios, with a rotation speed of 200 r / min and a stirring time of 5 min to prepare modified shield mud;

[0078] (2) Add the modified shield mud, Staphylococcus epidermidis solution, fly ash, and cementing liquid into the finished slurry mixer according to the above ratios, with a rotation speed of 200 r / min and a stirring time of 3 min to prepare the finished single-fluid slurry synchronous grouting material, denoted as MTGM-3.

[0079] Example 4

[0080] The present invention provides a single-fluid synchronous grouting material applicable to sandy gravel layers, which is composed of 10 parts of Staphylococcus epidermidis solution, 70 parts of modified shield mud, 10 parts of fly ash, and 10 parts of cementing liquid. The requirements for each component are as follows:

[0081] Staphylococcus epidermidis solution: The OD of the contained bacterial liquid 600 The test value of the ultraviolet spectrophotometer is 1.46 - 1.55;

[0082] Modified shield mud, with a specific gravity of 1.2, a viscosity of 1500 mPa s, a consistency of 120 mm. The modified shield mud is prepared by mixing 60 parts of shield waste slurry, 38 parts of water, and 2 parts of consistency regulator in proportion and stirring evenly.

[0083] Among them, the shield waste slurry is the waste slurry from the slurry balance shield construction in sandy gravel layers.

[0084] Consistency regulator: Carboxymethyl cellulose;

[0085] Fly ash: The CaO content is 42%, the SiO2 content is 30%, and the porosity is 60%;

[0086] Cementing liquid: A mixed solution of 1 mol / L urea and 1 mol / L calcium chloride with a molar ratio of 1:1, and the solution concentration is 0.75 mol / L.

[0087] The preparation method and steps of the above single-fluid synchronous grouting material applicable to sandy gravel layers are as follows:

[0088] (1) Add the shield waste slurry, water, and consistency regulator into the high-speed eddy mixer according to the above ratios, with a rotation speed of 200 r / min and a stirring time of 5 min to prepare the modified shield mud;

[0089] (2) Add the modified shield mud, Staphylococcus epidermidis solution, fly ash, and cementing liquid into the finished slurry mixer according to the above ratios, with a rotation speed of 200 r / min and a stirring time of 3 min to prepare the finished single-fluid slurry synchronous grouting material, denoted as MTGM-4.

[0090] Comparative Example 1

[0091] It is a traditional single-fluid grouting material with a mixing ratio of P.O42.5 cement:sand:bentonite:fly ash:water = 1:2.17:0.44:2.28:2.44, numbered TSGM-1.

[0092] Example 5

[0093] The present invention provides a double-fluid synchronous grouting material suitable for pebble strata, which is composed of 50 parts of S1 finished slurry and 50 parts of S2 finished slurry.

[0094] S1 finished slurry is made by uniformly mixing 60 parts of modified shield mud, 20 parts of Staphylococcus epidermidis solution and 20 parts of cementing liquid. The requirements for each component are as follows:

[0095] Modified shield mud, with a specific gravity of 1.35, a viscosity of 1000 mPa s, and a consistency of 110 mm. It is made by mixing 80 parts of shield waste slurry, 2 parts of consistency regulator and 18 parts of water and stirring evenly.

[0096] Among them, the shield waste slurry is the waste slurry from the slurry balance shield construction in the pebble strata.

[0097] Consistency regulator: hydroxypropyl methylcellulose and hydroxyethyl cellulose with a mass ratio of 2:1;

[0098] Staphylococcus epidermidis solution: the OD of the contained bacterial liquid 600 The test value of the ultraviolet spectrophotometer is 1.48 - 1.5;

[0099] Cementing liquid: a mixed solution of 1 mol / L urea and 1 mol / L calcium chloride with a molar ratio of 1:1, and the solution concentration is 1.5 mol / L.

[0100] S2 finished slurry is composed of 70 parts of fly ash and 30 parts of water.

[0101] Among them, for fly ash, the CaO content is 50%, the SiO2 content is 30%, and the porosity is 70%;

[0102] The preparation method of the above double-fluid synchronous grouting material suitable for pebble strata is as Figure 2 shown, and includes the following steps:

[0103] (1) Add the shield waste slurry, consistency regulator and water into a high-speed vortex mixer according to the above ratio, with a rotation speed of 100 r / min and a stirring time of 8 min to prepare the modified shield mud.

[0104] (2) Add the modified shield mud, staphylococcus solution and cementing liquid into the finished slurry mixer according to the above ratio, with a rotation speed of 150 r / min and a stirring time of 3 min to prepare the S1 finished slurry.

[0105] (3) Add fly ash and water into the finished slurry mixer according to the above ratio, with a rotation speed of 200 r / min and a mixing time of 5 min to prepare the finished S2 slurry.

[0106] (4) Add the finished S1 slurry and the finished S2 slurry into the finished slurry mixer according to the above ratio, with a rotation speed of 200 r / min and a mixing time of 5 min to prepare the double-fluid slurry synchronous grouting material, denoted as MTGM-5.

[0107] Example 6

[0108] The present invention provides a double-fluid synchronous grouting material suitable for sandy soil strata, which is composed of 50 parts of finished S1 slurry and 50 parts of finished S2 slurry.

[0109] The finished S1 slurry is made by uniformly mixing 60 parts of modified shield mud, 15 parts of Staphylococcus epidermidis solution and 25 parts of cementing liquid. The requirements for each component are as follows:

[0110] The modified shield mud has a specific gravity of 1.35, a viscosity of 1000 mPa s, and a consistency of 110 mm. It is made by mixing 70 parts of shield waste slurry, 1.5 parts of consistency regulator and 28.5 parts of water and uniformly stirring;

[0111] Among them, the shield waste slurry is the waste slurry from the slurry balance shield construction in sandy soil strata.

[0112] Consistency regulator: hydroxypropyl methylcellulose and hydroxyethyl cellulose with a mass ratio of 2:1;

[0113] Staphylococcus epidermidis solution: the OD of the contained bacterial liquid 600 The test value of the ultraviolet spectrophotometer is 1.48 - 1.5;

[0114] Cementing liquid: a mixed solution of 1 mol / L urea and 1 mol / L calcium chloride with a molar ratio of 1:1, and the solution concentration is 1.5 mol / L.

[0115] The finished S2 slurry is composed of 60 parts of fly ash and 40 parts of water.

[0116] Among them, the fly ash has a CaO content of 50%, a SiO2 content of 30%, and a porosity of 70%;

[0117] The preparation method of the above double-fluid synchronous grouting material suitable for sandy soil strata includes the following steps:

[0118] (1) Add the shield waste slurry, the consistency regulator and water into the high-speed eddy mixer according to the above ratio, with a rotation speed of 100 r / min and a mixing time of 8 min to prepare the modified shield mud.

[0119] (2) Add the modified shield mud, Staphylococcus solution, and cementing liquid into the finished slurry mixer according to the above ratios, with a rotation speed of 150 r / min and a stirring time of 3 min to prepare the S1 finished slurry.

[0120] (3) Add fly ash and water into the finished slurry mixer according to the above ratios, with a rotation speed of 200 r / min and a stirring time of 5 min to prepare the S2 finished slurry.

[0121] (4) Add the S1 finished slurry and S2 finished slurry into the finished slurry mixer according to the above ratios, with a rotation speed of 200 r / min and a stirring time of 5 min to prepare the double-fluid synchronous grouting material, denoted as MTGM-6.

[0122] Example 7

[0123] The present invention provides a double-fluid synchronous grouting material suitable for soft rock strata, which is composed of 60 parts of S1 finished slurry and 40 parts of S2 finished slurry.

[0124] The S1 finished slurry is made by uniformly mixing 80 parts of modified shield mud, 10 parts of Staphylococcus epidermidis solution, and 10 parts of cementing liquid. The requirements for each component are as follows:

[0125] Modified shield mud, with a specific gravity of 1.35, a viscosity of 1000 mPa s, and a consistency of 110 mm. It is made by mixing 60 parts of shield muck, 2 parts of consistency regulator, and 38 parts of water and stirring evenly;

[0126] Among them, the shield muck is the muck from the earth pressure balance shield construction in soft rock strata.

[0127] Consistency regulator: hydroxypropyl methylcellulose and hydroxyethyl cellulose with a mass ratio of 2:1;

[0128] Staphylococcus epidermidis solution: the OD of the bacterial solution 600 The test value of the ultraviolet spectrophotometer is 1.48 - 1.5;

[0129] Cementing liquid: a mixed solution of 1 mol / L urea and 1 mol / L calcium chloride with a molar ratio of 1:1, and the solution concentration is 1.5 mol / L.

[0130] The S2 finished slurry is composed of 70 parts of fly ash and 30 parts of water.

[0131] Among them, fly ash, with a CaO content of 50%, a SiO2 content of 30%, and a porosity of 70%;

[0132] The preparation method of the above double-fluid synchronous grouting material suitable for soft rock strata includes the following steps:

[0133] (1) Add shield muck, consistency regulator and water into a high-speed eddy current mixer according to the above ratios, with a rotation speed of 100 r / min and a mixing time of 8 min to prepare modified shield mud.

[0134] (2) Add the modified shield mud, Staphylococcus solution and cementing liquid into a finished slurry mixer according to the above ratios, with a rotation speed of 150 r / min and a mixing time of 3 min to prepare S1 finished slurry.

[0135] (3) Add fly ash and water into a finished slurry mixer according to the above ratios, with a rotation speed of 200 r / min and a mixing time of 5 min to prepare S2 finished slurry.

[0136] (4) Add S1 finished slurry and S2 finished slurry into a finished slurry mixer according to the above ratios, with a rotation speed of 200 r / min and a mixing time of 5 min to prepare a double-fluid synchronous grouting material, denoted as MTGM-7.

[0137] Example 8

[0138] The present invention provides a double-fluid synchronous grouting material suitable for cohesive soil strata, which is composed of 70 parts of S1 finished slurry and 30 parts of S2 finished slurry.

[0139] S1 finished slurry is made by mixing and stirring 65 parts of modified shield mud, 20 parts of Staphylococcus epidermidis solution and 15 parts of cementing liquid evenly. The requirements for each component are as follows:

[0140] Modified shield mud, with a specific gravity of 1.35, a viscosity of 1000 mPa s, and a consistency of 110 mm. It is made by mixing and stirring evenly 65 parts of shield muck, 1 part of consistency regulator and 34 parts of water;

[0141] Among them, the shield muck is the muck from the earth pressure balance shield construction in the cohesive soil strata.

[0142] Consistency regulator: hydroxypropyl methylcellulose and hydroxyethyl cellulose with a mass ratio of 2:1;

[0143] Staphylococcus epidermidis solution: the OD of the bacterial liquid 600 The test value of the ultraviolet spectrophotometer is 1.48 - 1.5;

[0144] Cementing liquid: a mixed solution of 1 mol / L urea and 1 mol / L calcium chloride with a molar ratio of 1:1, and the solution concentration is 1.5 mol / L.

[0145] S2 finished slurry is composed of 65 parts of fly ash and 35 parts of water.

[0146] Among them, for fly ash, the CaO content is 50%, the SiO2 content is 30%, and the porosity is 70%;

[0147] The preparation method of the above-mentioned double-fluid synchronous grouting material applicable to cohesive soil stratum comprises the following steps:

[0148] (1) Add shield muck, consistency regulator and water into a high-speed eddy current mixer according to the above ratio, with a rotation speed of 100 r / min and a stirring time of 8 min to prepare modified shield mud.

[0149] (2) Add the modified shield mud, staphylococcus solution and cementing liquid into a finished slurry mixer according to the above ratio, with a rotation speed of 150 r / min and a stirring time of 3 min to prepare S1 finished slurry.

[0150] (3) Add fly ash and water into a finished slurry mixer according to the above ratio, with a rotation speed of 200 r / min and a stirring time of 5 min to prepare S2 finished slurry.

[0151] (4) Add S1 finished slurry and S2 finished slurry into a finished slurry mixer according to the above ratio, with a rotation speed of 200 r / min and a stirring time of 5 min to prepare the double-fluid synchronous grouting material, denoted as MTGM-8.

[0152] Comparative Example 2

[0153] It is a traditional double-fluid synchronous grouting material for shield tunneling, consisting of S1 slurry: PO42.5 cement 276 kg / m 3 , bentonite 30 kg / m 3 , stabilizer 5 kg / m 3 (liquid), water 775 kg / m 3 ; S2 slurry: sodium silicate 120 L / m 3 (modulus 2.8, concentration 30%), denoted as TBGM-1.

[0154] The composition components of the single-fluid synchronous grouting materials prepared in Examples 1-4 are shown in Table 1.

[0155] Table 1 Composition components of the single-fluid synchronous grouting materials in Examples 1-4

[0156] ;

[0157] Perform performance tests on the single-fluid synchronous grouting materials prepared in Examples 1-4, and refer to (GB / T8077-2012 Test Methods for Uniformity of Concrete Admixtures and GB / T609 Test Method for Viscosity of Cement Paste) to test the setting time of the slurry, the compressive strength of the cube at 1 d, 7 d, 28 d, the consolidation body shrinkage rate at 7 d and 28 d, and the changes in fluidity, consistency, bleeding rate and viscosity of the slurry within 2 h.

[0158] Compare with the traditional single-fluid grouting material of Comparative Example 1, and the results are shown in Table 2.

[0159] Table 2 Performance results of the single-fluid synchronous grouting materials of Examples 1-4 and Comparative Example 1

[0160] ;

[0161] As can be seen from Table 2, the initial setting time and final setting time of the single-fluid synchronous grouting material (MTGM-1 to 4) of the present invention are much lower than those of the traditional single-fluid synchronous grouting material (TSGM-1). The 1-day, 7-day, and 28-day compressive strengths of MTGM-1 to 4 are all better than those of TSGM-1, indicating that the synchronous grouting material provided by the present invention has a fast setting speed, can quickly fill the shield tail gap, effectively control the ground settlement, and is especially suitable for highly permeable or water-rich strata.

[0162] The consolidation shrinkage rates of MTGM-1 to 4 of the present invention at 7 days and 28 days are both lower than those of TSGM-1, and the retention rates of fluidity and consistency within 2 hours are both better than those of TSGM-1, indicating that the synchronous grouting material provided by the present invention has good stability, is not prone to segregation during transportation, is suitable for long-distance pumping or grouting in complex strata, and is convenient for construction control. And it can reduce the risk of cracking of the grouted body, improve the waterproof performance and long-term stability of the tunnel.

[0163] The viscosity growth rate of MTGM-1 to 4 of the present invention within 2 hours is higher than that of TSGM-1, and the bleeding rate within 2 hours is lower than that of TSGM-1, indicating that the synchronous grouting material provided by the present invention has a gradually enhanced gelling reaction, a faster formation of structural strength, better slurry stability, and reduces the strength loss caused by water separation.

[0164] In summary, the single-fluid type synchronous grouting material proposed by the present invention can be adapted to different strata, shield muck, and shield waste slurry of different shield construction methods by adjusting the composition of the material. The finished single-fluid synchronous grouting slurry prepared has good working performance, can better adapt to different shield construction environments, and all its physical and mechanical properties are better than those of the traditional single-fluid synchronous grouting material for shields.

[0165] The composition components of the double-fluid synchronous grouting materials of Examples 5-8 are shown in Table 3.

[0166] Table 3 Composition components of the double-fluid synchronous grouting materials of Examples 5-8

[0167] ;

[0168] The performance of the double-slurry synchronous grouting materials prepared in Examples 5-8 was tested. Referring to (GB / T8077-2012 "Test Methods for the Homogeneity of Concrete Admixtures" and GB / T609 "Test Method for the Viscosity of Cement Paste"), the setting time of the slurry, the compressive strength of the cube at 1d, 7d, and 28d, the consolidation body shrinkage rate at 7d and 28d, and the changes in fluidity, consistency, bleeding rate, and viscosity of the slurry within 2h were tested. A comparison was made with the traditional double-fluid slurry synchronous grouting material in Comparative Example 2, and the results are shown in Table 4.

[0169] Table 4 Performance Results of the Double-Slurry Synchronous Grouting Materials in Examples 5-8 and Comparative Example 2

[0170] ;

[0171] As can be seen from Table 4, the initial setting time and final setting time of the double-slurry synchronous grouting material (MTGM-5~8) of the present invention are significantly lower than those of the double-fluid slurry synchronous grouting material (TBGM-1). The compressive strength of MTGM-5~8 at 1d, 7d, and 28d is better than that of TBGM-1, indicating that the synchronous grouting material provided by the present invention has a fast setting speed, can quickly stop water and plug leaks, and is suitable for the emergency grouting requirements of water-rich and highly permeable strata (such as pebble layers and sand layers). The early strength grows rapidly, and the strength advantage in the later stage continues to expand, meeting the dual requirements of "rapid support and long-term stability" for the grouting material in shield tunnels.

[0172] The consolidation body shrinkage rates of MTGM-5~8 of the present invention at 7d and 28d are comparable to those of TBGM-1, but the material of the present invention forms a more uniform calcium carbonate skeleton through microbial gelation, and the structural stability is better. The retention rates of fluidity and consistency of MTGM-5~8 of the present invention within 2h are better than those of TBGM-1, indicating that the double-slurry synchronous grouting material of the present invention has good stability. The viscosity growth rate of MTGM-5~8 within 2h is higher than that of TBGM-1, indicating that the gelation reaction of the double-slurry synchronous grouting material of the present invention continues to strengthen. The bleeding rate of MTGM-5~8 within 2h is slightly higher than that of TBGM-1, but it is still within the engineering allowable range (≤5%), and due to the high water retention of microbial gelation, the slurry stratification phenomenon is more minor.

[0173] In summary, the double-fluid slurry synchronous grouting material provided by the present invention can be well applied to shield muck and shield waste slurry in different strata and different shield construction methods, and has obvious advantages in working performance compared with the traditional double-fluid slurry synchronous grouting material.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A low-carbon synchronous grouting material based on microbial solidification of CO2 for shield muck, characterized in that: It includes modified shield mud, Staphylococcus epidermidis solution, fly ash and cementing liquid. The composition components of the modified shield mud, by mass fraction, include: 50 - 80 parts of shield muck or shield waste slurry, 0.5 - 2 parts of consistency regulator, and 20 - 50 parts of water; The shield muck or shield waste slurry includes the muck or waste slurry from earth pressure balance shield construction or slurry balance shield construction in silty clay stratum, sandy stratum, silty clay stratum, gravel stratum, soft rock stratum, and clay stratum; The consistency regulator includes one or more of hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, and hydroxyethylcellulose.

2. The low-carbon synchronous grouting material based on shield muck with microbial solidified CO2 according to claim 1, wherein: The Staphylococcus epidermidis solution is a solution formed by mixing Staphylococcus epidermidis screened and purified from the soil near the salt lake with LB medium.

3. The low-carbon synchronous grouting material based on shield muck with microbial CO2 solidification according to claim 2, characterized in that: The specific gravity of the modified shield mud is 1.2 - 1.6, the viscosity is 1000 - 3000 mPa·s, and the consistency is 100 - 180 mm.

4. A low-carbon synchronous grouting material based on microbial solidification of CO2 for shield muck according to claim 3, characterized in that: The fly ash has a CaO content ≥ 40%, an SiO2 content ≥ 20%, and a porosity ≥ 60%.

5. The low-carbon synchronous grouting material based on microbial solidified CO2 and shield muck according to claim 4, characterized in that: The cementing liquid is a mixed solution of urea and calcium chloride or calcium acetate. The concentration of the mixed solution is 0.25 - 2.00 mol / L, and the molar ratio of urea to calcium chloride or calcium acetate is 1:

1.

6. The low-carbon synchronous grouting material based on microbial solidified CO2 for shield muck according to claim 5, wherein: The synchronous grouting material is a single - liquid synchronous grouting material. Its composition, by mass fraction, includes 10 - 20 parts of Staphylococcus epidermidis solution, 40 - 70 parts of modified shield mud, 10 - 30 parts of fly ash, and 10 - 20 parts of cementing liquid.

7. A low-carbon synchronous grouting material based on microbial solidification of CO2 for shield muck according to claim 5, characterized in that: The synchronous grouting material is a double - liquid synchronous grouting material. Its composition, by mass fraction, includes 50 - 70 parts of S1 finished slurry and 30 - 50 parts of S2 finished slurry; The composition of S1 finished slurry, by mass fraction, includes: 50 - 80 parts of modified shield mud, 10 - 25 parts of Staphylococcus epidermidis solution, and 10 - 25 parts of cementing liquid; The composition of S2 finished slurry, by mass fraction, includes: 50 - 70 parts of fly ash and 30 - 50 parts of water.

8. A preparation method of a shield muck-based low-carbon synchronous grouting material for microbial solidification of CO2 as described in claim 6, characterized in that: It includes the preparation steps of the single - liquid slurry synchronous grouting material as follows: (1) Mix shield muck or shield waste slurry with a consistency regulator and water in proportion to prepare modified shield mud; (2) Add Staphylococcus epidermidis solution, fly ash, and cementing liquid to the modified shield mud in proportion and mix to prepare the single - liquid slurry synchronous grouting material.

9. A preparation method of a shield muck-based low-carbon synchronous grouting material for microbial solidification of CO2 as described in claim 7, characterized in that: It includes the preparation steps of the double - liquid slurry synchronous grouting material as follows: (1) Mix shield muck or shield waste slurry with a consistency regulator and water in proportion to prepare modified shield mud; (2) Add Staphylococcus epidermidis solution and cementing liquid to the modified shield mud in proportion and mix to prepare S1 finished slurry; (3) Mix fly ash and water in proportion to prepare S2 finished slurry; (4) Mix S1 finished slurry and S2 finished slurry in proportion to prepare the double - liquid slurry synchronous grouting material.

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