Shield synchronous grouting material based on viscous muck and preparation method thereof

Abstract

A shield synchronous grouting material based on viscous muck comprises the following components in parts by mass: dehydrated viscous muck, cement, fly ash and / or slag powder, water, a water reducing agent, chitosan and a water-retaining thickening agent. The dehydrated viscous muck is obtained by treating wet viscous muck through an electroosmosis dehydration method; the invention further discloses the preparation method of the grouting material. The grouting material disclosed by the invention has good thixotropy, water-retaining property, layering resistance and relatively high compressive strength, and the pumping performance and construction stability of the grouting material are enhanced by an electroosmosis dehydration method and the use of components such as chitosan; the shield muck treatment problem can be solved, the grouting performance index can be met, the material cost is reduced, and meanwhile the construction efficiency and the grouting quality are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of grouting materials and preparation method thereof, specifically to a kind of synchronous grouting material of shield and preparation method thereof. BACKGROUND

[0002] Shield construction is the main technical means of modern tunnel construction, and is widely used in urban subway, municipal tunnel, railway and other engineering. In the process of shield tunneling, in order to control the disturbance of stratum, fill the void of shield tail, reduce the surface subsidence and improve the stability of lining structure, synchronous grouting operation is usually carried out while the shield machine is advancing. The performance of synchronous grouting material has important influence on construction quality and efficiency, and its fluidity, pumpability, early strength, bleeding rate and other performance parameters are directly related to the safety of tunnel structure and construction efficiency.

[0003] At present, the commonly used synchronous grouting material in engineering mainly uses the following raw materials: (1) cement as the main cementing material; (2) bentonite to provide consistency and water retention; (3) fly ash or slag powder as mineral admixture; (4) fine sand, bentonite or clay as aggregate; (5) various additives to adjust the fluidity, setting retardance and other properties. Although these formula systems have been widely used in engineering practice, there are still the following problems:

[0004] (1) High material cost, dependent on outsourcing: Most of the bentonite, fly ash, slag and other materials used at present are derived from industrial by-products or mineral resources, and some of them need to be transported over a long distance, resulting in high overall material cost;

[0005] (2) Unsustainable resources, heavy environmental burden: The use of natural sand, bentonite and other aggregates consumes a large amount of non-renewable resources, which is not conducive to the green and sustainable development goal of engineering;

[0006] (3) Significant problem of disposal of slag: A large amount of cohesive slag is generated every day during the construction of soil engineering such as foundation pit excavation of underground engineering, and the traditional disposal method is to stack it on site or transport it to landfill, resulting in land occupation, environmental pollution and high transportation cost;

[0007] Although some studies have attempted to use shield slag for backfilling or brick making, due to its high water content, complex organic matter and unstable composition, it is still not possible to achieve stable, systematic and controllable large-scale application of "resource utilization + excellent performance" type synchronous grouting material. If slag is used to replace fine aggregate in grouting system, there are problems such as high viscosity, poor fluidity, weak stability, pipe blockage, slurry stratification or incomplete grouting during pumping, which cannot meet the requirements of continuous and efficient advancement of shield operation. SUMMARY

[0008] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a shield tunnel synchronous grouting material based on cohesive slag that is stable in grouting construction and its preparation method.

[0009] The technical solution adopted by the present invention to solve its technical problem is as follows: a shield tunnel synchronous grouting material based on cohesive slag, comprising, by mass, 25-60 parts of dehydrated cohesive slag, 8-25 parts of cement, 8-30 parts of fly ash and / or slag powder, 25-45 parts of water, less than 1 part of water-reducing agent, less than 1 part of chitosan, and less than 0.5 parts of water-retaining thickening agent;

[0010] The dehydrated cohesive soil is obtained by treating wet cohesive soil through electroosmosis dehydration; the moisture content of the dehydrated cohesive soil is 20wt% to 40wt%; the electroosmosis dehydration process uses direct current to form an electric field with an intensity of 0.4V / cm to 3V / cm.

[0011] Preferably, the moisture content of the dehydrated cohesive slag is 25wt% to 35wt%.

[0012] Preferably, the particle size of the dehydrated cohesive slag is less than 5 mm.

[0013] Preferably, the shield tunneling synchronous grouting material based on cohesive slag soil comprises, by weight, 30-50 parts dehydrated cohesive slag soil, 10-20 parts cement, 10-25 parts fly ash and / or slag powder, 30-40 parts water, 0.1-0.5 parts water-reducing agent, 0.1-0.5 parts chitosan, and 0.05-0.3 parts water-retaining thickener.

[0014] Preferably, the water-retaining and thickening agent is one or more of hydroxyethyl methyl cellulose (HEMC), hydroxypropyl methyl cellulose (HPMC), guar gum, xanthan gum, propyl guar gum (HPG), hydroxyethyl cellulose (HEC), sodium carboxymethyl cellulose (CMC-Na), hydroxypropyl starch (HPS), and carboxymethyl starch (CMS).

[0015] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent.

[0016] Preferably, the chitosan is a low molecular weight chitosan powder with a degree of deacetylation of 70% to 90% and a molecular weight of 5,000 to 200,000.

[0017] Preferably, the electrodes used in the electroosmotic dehydration method are graphite electrodes and / or stainless steel electrodes.

[0018] Preferably, the electroosmotic dehydration method applies a DC voltage of 30 to 60V to form an electric field strength of 0.5V / cm to 2V / cm.

[0019] Preferably, the treatment time of the electroosmotic dehydration method is 4 to 8 hours, and the ambient temperature during the treatment process is 5°C to 35°C.

[0020] Preferably, the wet, cohesive slag is generated during the shield tunneling process and has a moisture content of 60wt% to 80wt%.

[0021] Preferably, the grouting material further includes 0.05 to 0.3 parts by weight of retarder and / or accelerator.

[0022] Preferably, the slump expansion of the grouting material is 180–220 mm.

[0023] Based on the same inventive concept, this invention also provides a method for preparing shield tunneling synchronous grouting material based on cohesive slag: mixing the solid raw materials of the grouting material, then adding liquid raw materials, and stirring evenly to form a uniform slurry; controlling the fluidity of the obtained slurry to meet the requirements of shield tunneling construction, so that it can be used for shield tunneling construction.

[0024] Preferably, the fluidity control of the slurry is achieved by adding water and / or a water-reducing agent.

[0025] The present invention has the following beneficial effects:

[0026] (1) The grouting material of the present invention has good thixotropic properties and water retention. The use of electroosmotic dehydration method and chitosan and other components enhances the pumping performance and construction stability of the grout, enhances the anti-segregation and adhesion of the grout, ensures the uniformity and density of the grout after grouting, and also improves the compressive strength of the grouting material.

[0027] (2) It can solve the problem of shield tunneling slag disposal, meet the grouting performance indicators, reduce material costs, improve construction efficiency and grouting quality, reduce energy consumption and environmental pollution during construction, and has the characteristics of energy saving, environmental protection and high efficiency.

[0028] (3) The grouting material of the present invention can be used in various underground engineering constructions, especially suitable for shield tunnel construction of urban subway, municipal tunnel, railway and other projects.

[0029] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The present invention will now be described in further detail. Detailed Implementation

[0030] To make the objectives, solutions, and beneficial technologies of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be noted that the embodiments described in this specification are merely illustrative of the invention and are not intended to limit the invention.

[0031] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0032] In this description, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, "multiple" in "one or more" means two or more, and "more than" in "one or more" means two or more.

[0033] This invention provides a shield tunneling synchronous grouting material based on viscous slag, comprising, by weight, 25-60 parts dehydrated viscous slag, 8-25 parts cement, 8-30 parts fly ash and / or slag powder, 25-45 parts water, less than 1 part water-reducing agent, less than 1 part chitosan, and less than 0.5 parts water-retaining thickener; (In the formulation, the moisture content of solid raw materials such as dehydrated viscous slag, cement, and fly ash is not included in the total water content of the raw materials, while the content of liquid admixtures is calculated based on their effective components, and the moisture content of liquid admixtures is included in the total water content of the raw materials.)

[0034] The dehydrated cohesive soil is obtained by treating wet cohesive soil through electroosmosis dehydration; the moisture content of the dehydrated cohesive soil is 20wt% to 40wt%; the electroosmosis dehydration process uses direct current to form an electric field with an intensity of 0.4V / cm to 3V / cm.

[0035] The electroosmotic dewatering method involves applying a direct current electric field to cause water in the cohesive slag to migrate towards the cathode and be discharged, thereby efficiently reducing the moisture content of the slag. This allows for greater control over the composition of the resulting cohesive slag, thus ensuring the stability of the grouting material. The deeper effects of electroosmotic dewatering are as follows:

[0036] 1. Homogenize moisture content:

[0037] The moisture content of the excavated soil from the tunnel boring machine is high and extremely uneven. The moisture content varies greatly between different batches and depths of soil, resulting in highly unstable performance of grouting materials. However, by using electro-osmosis to dehydrate the soil, the moisture content can be controlled to a relatively stable and controllable range, providing a consistent and uniform raw material base for subsequent mixing.

[0038] 2. Adjusting and improving the structure of slag and soil:

[0039] The electroosmosis process promotes the rearrangement, compaction, and flocculation of clay particles in the slag, making its internal structure more compact, reducing porosity, significantly improving the workability and physical properties of the slag, and providing more stable physical properties for subsequent use as aggregate.

[0040] 3. Reduce harmful ions or soluble organic matter:

[0041] During electroosmosis, the migration of charged water carries some soluble salts, organic impurities, etc. towards the cathode and is enriched and discharged, thereby effectively removing some harmful components from the shield tunnel slag and improving the durability and environmental safety of the grouting material.

[0042] 4. Achieve precise proportions:

[0043] After dehydration, dry slag aggregate with known and controllable moisture content can be obtained. Then, by adding quantified fresh water and admixtures during the batching process, key indicators such as water-cement ratio, slurry consistency, and fluidity can be controlled more precisely, meeting the needs of continuous, efficient, and controllable shield tunneling construction.

[0044] Dehydrated cohesive slag is the main raw material for grouting materials, utilizing its rich fine-particle components to provide a binding effect. Cement, as a binding material, plays a role in bonding aggregates and enhancing material strength. Fly ash and / or slag powder, as mineral admixtures, can improve the durability and impermeability of grouting materials, while reducing cement usage and lowering costs. Water, as the liquid phase component of the grout, plays a role in regulating grout fluidity. Water-reducing agents can significantly reduce the water requirement of the grout, improve its fluidity, and reduce cement usage. Chitosan, a natural polymer material extracted from shrimp and crab shells, forms a network structure with slag, mineral admixtures, etc., enhancing the thixotropy, water retention, and cohesiveness of the grout. Chitosan not only improves the fluidity and stability of the grout but also enhances its environmental friendliness, possessing natural biodegradability and meeting the requirements of green building materials. Water-retaining thickeners are used to increase the water retention and consistency of the grout, ensuring that no bleeding occurs during construction.

[0045] In an embodiment of the present invention, the moisture content of the dehydrated cohesive slag is 25wt% to 35wt%.

[0046] In an embodiment of the present invention, the particle size of the dewatered cohesive slag is less than 5 mm. If the particles of the dewatered cohesive slag are too large, they can be screened to ensure that the particle size meets the requirements; this particle size is suitable for mixing with raw materials such as cement and admixtures to ensure the stability of the grouting effect; this scheme can ensure the uniformity of subsequent mixed materials and the pumpability of the slurry.

[0047] In an embodiment of the present invention, the shield tunneling synchronous grouting material based on cohesive slag soil comprises, by weight, 30-50 parts of dehydrated cohesive slag soil, 10-20 parts of cement, 10-25 parts of fly ash and / or slag powder, 30-40 parts of water, 0.1-0.5 parts of water-reducing agent, 0.1-0.5 parts of chitosan, and 0.05-0.3 parts of water-retaining thickening agent.

[0048] In embodiments of the present invention, the water-retaining and thickening agent is one or more of hydroxyethyl methyl cellulose (HEMC), hydroxypropyl methyl cellulose (HPMC), guar gum, xanthan gum, propyl guar gum (HPG), hydroxyethyl cellulose (HEC), sodium carboxymethyl cellulose (CMC-Na), hydroxypropyl starch (HPS), and carboxymethyl starch (CMS).

[0049] In an embodiment of the present invention, the water-reducing agent is a polycarboxylate water-reducing agent.

[0050] In an embodiment of the present invention, the chitosan is a low molecular weight chitosan powder with a degree of deacetylation of 70% to 90% and a molecular weight of 5,000 to 200,000.

[0051] In some embodiments of the present invention, the chitosan is pre-prepared as an acidic chitosan solution with a pH of 4-6 and a concentration of 1wt%-2wt% to ensure uniform mixing with other raw material components.

[0052] In some embodiments of the present invention, the pH value of the chitosan acidic solution is adjusted by acetic acid and / or lactic acid.

[0053] In embodiments of the present invention, the electrodes used in the electroosmotic dehydration method are graphite electrodes and / or stainless steel electrodes.

[0054] In an embodiment of the present invention, the electroosmotic dehydration method applies a DC voltage of 30 to 60V to form an electric field strength of 0.5V / cm to 2V / cm.

[0055] In an embodiment of the present invention, the electroosmotic dehydration process takes 4 to 8 hours, and the ambient temperature during the process is 5°C to 35°C. This temperature range helps to prevent adverse changes in the properties of the slurry.

[0056] In an embodiment of the present invention, the wet cohesive slag is generated during the shield tunneling process and has a moisture content of 60wt% to 80wt%. The cohesive slag generated during the shield tunneling process, after dehydration treatment, can be used as the main raw material of this solution: dehydrated cohesive slag.

[0057] In embodiments of the present invention, the grouting material further includes 0.05 to 0.3 parts by weight of a retarder and / or a accelerator. The retarder and accelerator are used to adjust the setting time of the grout; whether to use these components and their dosage are mainly determined based on the specific conditions of the actual construction site.

[0058] In an embodiment of the present invention, the slump spread of the grouting material is 180–220 mm. The slump spread can be tested using a slump cone. Slump spread is an indicator of grout fluidity; however, after conversion, other indicators that reflect grout fluidity can also be used, such as slump, spread, and Vebe consistency. This indicator of the grouting material mainly comes from the grouting construction requirements of the tunnel boring machine.

[0059] This invention relates to a method for preparing a shield tunneling synchronous grouting material based on viscous slag: Solid raw materials for the grouting material are mixed, then liquid raw materials are added and stirred until a homogeneous slurry is formed. The fluidity of the resulting slurry is controlled to meet the requirements of shield tunneling construction, making it suitable for shield tunneling. Solid raw materials generally include dehydrated viscous slag, cement, fly ash, etc., while liquid raw materials include water and various possible liquid additives. Chitosan is considered a solid raw material if added in solid form, and a liquid raw material if added in solution form. After all raw materials are added, they are mixed for several minutes (e.g., 5-10 minutes) to obtain the grouting material.

[0060] In embodiments of the present invention, the fluidity control of the grout is achieved by adding water and / or a water-reducing agent. The fluidity requirements of the grouting material mainly stem from the grouting construction needs of the tunnel boring machine.

[0061] In an embodiment of the present invention, the grouting material is grouted within 2 hours after preparation to ensure that its performance does not degrade.

[0062] In an embodiment of the present invention, the fly ash is siliceous aluminous fly ash emitted from a coal-fired power plant, and the mass percentage of its main chemical components is as follows:

[0063] Silicon dioxide (SiO2): 40%–60%;

[0064] Aluminum oxide (Al2O3): 20%–35%;

[0065] Iron oxide (Fe2O3): 4%–10%;

[0066] Calcium oxide (CaO): 1%–8%;

[0067] Magnesium oxide (MgO): 0.5%–2%;

[0068] The total amount of sulfides and other impurities is less than 5%.

[0069] In some embodiments of the present invention, the fly ash contains a total content of active SiO2 and Al2O3 of not less than 50%, a loss on ignition of less than 5%, and a specific surface area greater than 250 m². 2 / kg. The main mineral phases of the fly ash are glass and small amounts of mullite and quartz.

[0070] In an embodiment of the present invention, the slag powder is obtained by grinding blast furnace water-quenched granulated slag, and the mass percentage of its main chemical components is as follows:

[0071] Silicon dioxide (SiO2): 30%–38%;

[0072] Aluminum oxide (Al2O3): 8%–15%;

[0073] Calcium oxide (CaO): 35%–45%;

[0074] Magnesium oxide (MgO): less than 5%;

[0075] The total amount of impurities such as titanium dioxide (TiO2), manganese oxide (MnO), and potassium oxide (K2O) is less than 5%.

[0076] In some embodiments of the present invention, the slag powder has a glass content greater than 85% and a specific surface area of ​​300-500 m². 2 / kg. This slag powder has good potential hydration activity.

[0077] In embodiments of the present invention, the dehydrated cohesive slag is mainly composed of clay minerals, including one or more of kaolinite, illite, and montmorillonite. The dehydrated cohesive slag possesses good cementing and water retention properties, and may also contain small amounts of quartz, feldspar, and other detrital minerals.

[0078] In some embodiments of the present invention, the particle size of the dehydrated cohesive slag is in the range of 0.1 to 5 mm.

[0079] Compared with existing shield tunneling grouting materials and their preparation methods, this solution has significant advantages in the following key aspects:

[0080] (1) Improve the fluidity and stability of grouting materials

[0081] The introduction of chitosan: As a natural polymer material, chitosan contains amino and hydroxyl groups in its molecules, which can form a network structure in alkaline systems. This network, combined with fine soil particles, significantly enhances the thixotropy and water retention of the grout. This greatly improves the grout's fluidity and makes it more stable during the tunnel boring machine's grouting process.

[0082] Application of electroosmotic dewatering technology: Electroosmotic dewatering can rapidly remove moisture from construction waste, effectively controlling its moisture content and avoiding the uneven moisture control problems associated with traditional natural air drying or thermal drying methods. The resulting construction waste has a more uniform moisture content, further ensuring the stability and pumpability of the grouting material.

[0083] (2) Enhance the cohesiveness and anti-segregation properties of the slurry

[0084] The bridging effect of chitosan: Chitosan molecules enhance the cohesive force of the grout by forming hydrogen bonds or complexes with cement hydration products, thereby increasing the density of the grout after injection. This bridging effect can significantly improve the grout's resistance to segregation, avoiding the common grout segregation phenomenon during the grouting process and ensuring the continuity and uniformity of the grouting.

[0085] (3) Improve the compressive strength and density of grouting materials

[0086] Through the synergistic effect of chitosan and cement hydration products, the synchronous grouting material of this invention exhibits higher initial strength and compressive strength. Experimental results show that the material using chitosan achieves a 28-day compressive strength of 4.5 MPa, significantly outperforming conventional materials and meeting the requirements of shield tunnel construction for high-strength materials.

[0087] After the slag is treated with electro-osmotic dehydration, the uniformity and stability of the grout are further improved, avoiding problems such as uneven grout consolidation or cracks caused by uneven moisture content in the slag. The tunnel lining structure after grouting is more stable, can better resist external pressure, and improves the safety of the tunnel.

[0088] (4) Reduce material costs and improve environmental friendliness

[0089] Reduced raw material costs: This invention uses dehydrated slag as the main raw material, reducing reliance on purchased raw materials (such as bentonite, fine sand, etc.) and significantly lowering the production cost of synchronous grouting materials. Meanwhile, although the use of chitosan slightly increases material costs, it significantly improves material performance and reduces the use of other high-cost chemical additives, achieving a balance between economy and performance.

[0090] Environmental friendliness: Chitosan, as a natural and biodegradable polymer material, possesses excellent biodegradability and eco-friendliness, meeting the requirements of green building materials. Treating construction waste using electroosmotic dehydration technology not only avoids significant energy consumption but also reduces environmental pollution, complying with energy conservation and emission reduction requirements. The synchronous grouting material prepared using this method can not only solve the problem of construction waste disposal during tunnel boring machine (TBM) construction but also promote the resource utilization of construction waste, reducing the consumption of natural resources.

[0091] (5) Improve construction efficiency and safety

[0092] Enhanced pumpability: Due to the ability of chitosan to improve the thixotropy and fluidity of the grout, the synchronous grouting material of this invention exhibits excellent pumpability during pumping, avoiding pipe blockage and construction interruptions caused by excessively dense or uneven grout. During grouting, the grout can smoothly fill the voids in the soil, ensuring the compactness and uniformity of the tunnel lining structure.

[0093] Improved construction continuity: The stability of the grout has been significantly enhanced, preventing stratification and backflow after grouting. This is crucial for the continuous and efficient advancement required in tunnel boring machine (TBM) construction. The stable performance of the material ensures the continuity of tunnel construction and avoids construction delays caused by fluctuations in material properties.

[0094] Example

[0095] The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight. Unless otherwise stated, all reagents used in the examples are available commercially or synthesized using conventional methods and are ready for use without further processing. Unless otherwise stated, all instruments used in the examples are available commercially.

[0096] The fly ash used in the various embodiments and comparative examples is siliceous aluminous fly ash emitted from coal-fired power plants, wherein the sum of active SiO2 and Al2O3 content is not less than 50%, the loss on ignition is less than 5%, and the specific surface area is greater than 250 m². 2 / kg. The main mineral phase of the fly ash is glass and small amounts of mullite and quartz. The mass percentage of the main chemical components is:

[0097] Silicon dioxide (SiO2): 40%–60%;

[0098] Aluminum oxide (Al2O3): 20%–35%;

[0099] Iron oxide (Fe2O3): 4%–10%;

[0100] Calcium oxide (CaO): 1%–8%;

[0101] Magnesium oxide (MgO): 0.5%–2%;

[0102] The total amount of sulfides and other impurities is less than 5%.

[0103] The slag powder involved in each embodiment and comparative example is obtained by grinding blast furnace water-quenched granulated slag, with a glass content greater than 85% and a specific surface area of ​​300-500 m². 2 / kg. It exhibits good potential hydration activity. The mass percentage of its main chemical components is:

[0104] Silicon dioxide (SiO2): 30%–38%;

[0105] Aluminum oxide (Al2O3): 8%–15%;

[0106] Calcium oxide (CaO): 35%–45%;

[0107] Magnesium oxide (MgO): less than 5%;

[0108] The total amount of impurities such as titanium dioxide (TiO2), manganese oxide (MnO), and potassium oxide (K2O) is less than 5%.

[0109] Example 1

[0110] The shield tunneling synchronous grouting material based on cohesive slag in this embodiment comprises, by weight, 40 parts dehydrated cohesive slag, 15 parts cement, 20 parts fly ash, 34 parts water, 0.3 parts polycarboxylate water-reducing agent, 0.3 parts chitosan, and 0.2 parts water-retaining thickener (HEMC). The chitosan is a low molecular weight chitosan powder with a degree of deacetylation of 70%–90% and a molecular weight of 5,000–200,000.

[0111] The source of the dehydrated cohesive slag is: wet cohesive slag with a moisture content of 60wt% to 80wt% generated during the shield tunneling process. The wet cohesive slag is treated by electroosmosis dehydration. The specific operation of electroosmosis dehydration is to apply a 45V DC electric field to the electroosmosis device to form an electric field strength of 1 to 1.5V / cm, and treat it at 25℃ for 5 hours. Under the action of the electric field, the water inside the cohesive slag migrates towards the cathode and is discharged in a concentrated manner, finally obtaining dehydrated cohesive slag with a moisture content of 30wt%.

[0112] The dehydrated cohesive slag obtained by electroosmosis is then screened to remove particles larger than 5mm, thus meeting the requirements for grouting material preparation.

[0113] The preparation method of the shield tunneling synchronous grouting material based on cohesive slag in this embodiment is as follows:

[0114] (1) Weigh each raw material according to the above formula. First, add the dehydrated viscous slag, cement, fly ash and other solid raw materials into a twin-shaft forced mixer for dry mixing for 1 to 2 minutes. Then, slowly add water and chitosan (with added lactic acid, pH 4.1, concentration 1.8wt%), as well as polycarboxylate water-reducing agent and water-retaining thickener. Continue mixing for 5 to 10 minutes to make the slurry uniform and free of lumps, ensuring its fluidity and stability.

[0115] (2) After mixing, the slump spread of the grout is tested using a slump tester to ensure that its fluidity meets the requirements of shield tunneling. Grouting is completed within 2 hours to prevent the grout's performance from deteriorating due to prolonged time.

[0116] Testing revealed that the slump expansion of the grouting material in this embodiment was 210 mm, its fluidity met the requirements for shield tunneling, and it could be pumped smoothly without blockage. The grout exhibited strong thixotropy, maintaining stable pressure during the grouting process. After grouting, the grout solidified uniformly and densely without significant stratification. The 28-day compressive strength was 4.5 MPa, meeting the engineering requirements for shield tunnels.

[0117] Comparative Example 1

[0118] This comparative example differs from Example 1 in that the electroosmotic dehydration method is replaced with natural air drying. All other formulations and preparation methods remain the same as in Example 1, as detailed below:

[0119] The shield tunneling synchronous grouting material based on cohesive slag in this comparative example includes, by weight, 40 parts dehydrated cohesive slag, 15 parts cement, 20 parts fly ash, 34 parts water, 0.3 parts polycarboxylate superplasticizer, 0.3 parts chitosan, and 0.2 parts water-retaining thickener (HEMC).

[0120] The source of the dehydrated cohesive slag is: wet cohesive slag with a moisture content of 60wt% to 80wt% is generated during the shield tunneling process. The wet cohesive slag is dehydrated by natural air drying, and after a period of time, dehydrated cohesive slag with a moisture content of 30wt% is finally obtained.

[0121] The dehydrated cohesive slag obtained by electroosmosis is then screened to remove particles larger than 5mm, thus meeting the requirements for grouting material preparation.

[0122] The preparation method of the shield tunneling synchronous grouting material based on cohesive slag in this comparative example is as follows:

[0123] (1) Weigh each raw material according to the above formula. First, add the dehydrated viscous slag, cement, fly ash and other solid raw materials into a twin-shaft forced mixer for dry mixing for 1 to 2 minutes. Then, slowly add water and chitosan (with added lactic acid, pH 4.1, concentration 1.8wt%), as well as polycarboxylate water-reducing agent and water-retaining thickener. Continue mixing for 5 to 10 minutes to make the slurry uniform and free of lumps, ensuring its fluidity and stability.

[0124] (2) After mixing, the slump spread of the grout is tested using a slump tester to ensure that its fluidity meets the requirements of shield tunneling. Grouting is completed within 2 hours to prevent the grout's performance from deteriorating due to prolonged time.

[0125] Testing revealed that the slump spread of the grouting material in this comparative example was 195 mm, meeting the requirements for shield tunneling construction. The thixotropy of the grout was moderate, with occasional minor blockages occurring during pumping. After grouting, the grout solidified relatively uniformly, but slight stratification was observed. The 28-day compressive strength was 4.1 MPa. This comparative example used natural air drying dehydration instead of electroosmotic dehydration. Besides the slow efficiency of natural air drying and its greater susceptibility to environmental and climatic influences, it also led to decreased stability and controllability of the grout. Although the measured slump spread of the grouting material met the requirements for shield tunneling construction, the actual construction results were not ideal.

[0126] Comparative Example 2

[0127] This comparative example is based on Example 1, but without chitosan, and with the appropriate addition of water-reducing agents and water-retaining thickeners to ensure that the final slump spread of the grouting material meets the requirements. Other formulations and preparation methods are the same as in Example 1, as detailed below:

[0128] The shield tunneling synchronous grouting material based on cohesive slag in this comparative example includes, by weight, 40 parts dehydrated cohesive slag, 15 parts cement, 20 parts fly ash, 34.3 parts water, 0.5 parts polycarboxylate superplasticizer, and 0.3 parts water-retaining thickener (HEMC).

[0129] The source of the dehydrated cohesive slag is: wet cohesive slag with a moisture content of 60wt% to 80wt% generated during the shield tunneling process. The wet cohesive slag is treated by electroosmosis dehydration. The specific operation of electroosmosis dehydration is to apply a 45V DC electric field to the electroosmosis device to form an electric field strength of 1 to 1.5V / cm, and treat it at 25℃ for 5 hours. Under the action of the electric field, the water inside the cohesive slag migrates towards the cathode and is discharged in a concentrated manner, finally obtaining dehydrated cohesive slag with a moisture content of 30wt%.

[0130] The dehydrated cohesive slag obtained by electroosmosis is then screened to remove particles larger than 5mm, thus meeting the requirements for grouting material preparation.

[0131] The preparation method of the shield tunneling synchronous grouting material based on cohesive slag in this comparative example is as follows:

[0132] (1) Weigh each raw material according to the above formula. First, add the dehydrated viscous slag, cement, fly ash and other solid raw materials into the twin-shaft forced mixer for dry mixing. The mixing time is 1 to 2 minutes. Then, slowly add water, polycarboxylate water-reducing agent and water-retaining thickener, and continue mixing for 5 to 10 minutes to make the slurry uniform and free of lumps, so as to ensure its fluidity and stability.

[0133] (2) After mixing, the slump spread of the grout is tested using a slump tester to ensure that its fluidity meets the requirements of shield tunneling. Grouting is completed within 2 hours to prevent the grout's performance from deteriorating due to prolonged time.

[0134] Testing revealed that the slump spread of the grouting material in this comparative example was 200 mm, and its fluidity met the requirements for shield tunneling construction. However, the grout exhibited poor thixotropy and was prone to backflow during grouting. After grouting, the grout showed obvious stratification and poor compactness. The 28-day compressive strength was 3.8 MPa. The comparative example did not use chitosan, which significantly affected the performance of the grouting material. Although the measured slump spread of the grouting material met the requirements for shield tunneling construction, the actual effect could not meet the construction needs.

[0135] Example 2

[0136] The shield tunneling synchronous grouting material based on viscous slag in this embodiment comprises, by weight, 35 parts dehydrated viscous slag, 15 parts cement, 20 parts slag powder, 38 parts water, 0.3 parts polycarboxylate water-reducing agent, 0.2 parts chitosan, and 0.3 parts water-retaining thickener (xanthan gum). The chitosan is a low molecular weight chitosan powder with a degree of deacetylation of 70%–90% and a molecular weight of 5,000–200,000.

[0137] The source of the dehydrated cohesive slag is: wet cohesive slag with a moisture content of 60wt% to 80wt% generated during the shield tunneling process. The wet cohesive slag is treated by electroosmosis dehydration. The specific operation of electroosmosis dehydration is to apply a 60V DC electric field to the electroosmosis device to form an electric field strength of 1.5 to 2V / cm, and treat it at 15℃ for 5 hours. Under the action of the electric field, the water inside the cohesive slag migrates towards the cathode and is discharged in a concentrated manner, finally obtaining dehydrated cohesive slag with a moisture content of 25wt%.

[0138] The dehydrated cohesive slag obtained by electroosmosis is then screened to remove particles larger than 5mm, thus meeting the requirements for grouting material preparation.

[0139] The preparation method of the shield tunneling synchronous grouting material based on cohesive slag in this embodiment is as follows:

[0140] (1) Weigh each raw material according to the above formula. First, add the dehydrated viscous slag, cement, fly ash and other solid raw materials into a twin-shaft forced mixer for dry mixing for 1 to 2 minutes. Then, slowly add water and chitosan (with added acetic acid, pH 5.6, concentration 1.1wt%), as well as polycarboxylate water-reducing agent and water-retaining thickener. Continue mixing for 5 to 10 minutes to make the slurry uniform and free of lumps, ensuring its fluidity and stability.

[0141] (2) After mixing, the slump spread of the grout is tested using a slump tester to ensure that its fluidity meets the requirements of shield tunneling. Grouting is completed within 2 hours to prevent the grout's performance from deteriorating due to prolonged time.

[0142] Testing revealed that the slump expansion of the grouting material in this embodiment was 221 mm, its fluidity met the requirements for shield tunneling, and it could be pumped smoothly without blockage. The grout exhibited strong thixotropy, maintaining stable pressure during the grouting process. After grouting, the grout solidified uniformly and densely without significant stratification. The 28-day compressive strength was 5.0 MPa, meeting the engineering requirements for shield tunnels.

[0143] Example 3

[0144] The shield tunneling synchronous grouting material based on cohesive slag in this embodiment comprises, by weight, 45 parts dehydrated cohesive slag, 12 parts cement, 15 parts slag powder, 34 parts water, 0.4 parts polycarboxylate water-reducing agent, 0.3 parts chitosan, and 0.1 parts water-retaining thickener (carboxymethyl starch). The chitosan is a low molecular weight chitosan powder with a degree of deacetylation of 70%–90% and a molecular weight of 5,000–200,000.

[0145] The source of the dehydrated cohesive slag is: wet cohesive slag with a moisture content of 60wt% to 80wt% generated during the shield tunneling process. The wet cohesive slag is treated by electroosmosis dehydration. The specific operation of electroosmosis dehydration is to apply a 35V DC electric field to the electroosmosis device to form an electric field strength of 0.6 to 1.2V / cm, and treat it at 30℃ for 6 hours. Under the action of the electric field, the water inside the cohesive slag migrates towards the cathode and is discharged in a concentrated manner, finally obtaining dehydrated cohesive slag with a moisture content of 35wt%.

[0146] The dehydrated cohesive slag obtained by electroosmosis is then screened to remove particles larger than 5mm, thus meeting the requirements for grouting material preparation.

[0147] The preparation method of the shield tunneling synchronous grouting material based on cohesive slag in this embodiment is as follows:

[0148] (1) Weigh each raw material according to the above formula. First, add the dehydrated viscous slag, cement, fly ash and other solid raw materials into a twin-shaft forced mixer for dry mixing for 1 to 2 minutes. Then, slowly add water and chitosan (with added acetic acid, pH 5.2, concentration 1.4wt%), as well as polycarboxylate water-reducing agent and water-retaining thickener. Continue mixing for 5 to 10 minutes to make the slurry uniform and free of lumps, ensuring its fluidity and stability.

[0149] (2) After mixing, the slump spread of the grout is tested using a slump tester to ensure that its fluidity meets the requirements of shield tunneling. Grouting is completed within 2 hours to prevent the grout's performance from deteriorating due to prolonged time.

[0150] Testing revealed that the slump expansion of the grouting material in this embodiment was 225mm, its fluidity met the requirements for shield tunneling, and it could be pumped smoothly without blockage. The grout exhibited strong thixotropy, maintaining stable pressure during the grouting process. After grouting, the grout solidified uniformly and densely without significant stratification. The 28-day compressive strength was 5.3MPa, meeting the engineering requirements for shield tunnels.

Claims

1. A shield tunneling synchronous grouting material based on cohesive slag soil, characterized in that, By weight, it includes 25-60 parts of dehydrated viscous slag, 8-25 parts of cement, 8-30 parts of fly ash and / or slag powder, 25-45 parts of water, less than 1 part of water-reducing agent, less than 1 part of chitosan, and less than 0.5 parts of water-retaining thickener. The dehydrated cohesive soil is obtained by treating wet cohesive soil through electroosmosis dehydration; the moisture content of the dehydrated cohesive soil is 20wt% to 40wt%; the electroosmosis dehydration process uses direct current to form an electric field with an intensity of 0.4V / cm to 3V / cm.

2. The shield tunneling synchronous grouting material based on cohesive slag soil according to claim 1, characterized in that, The dehydrated cohesive slag has a moisture content of 25wt% to 35wt% and a particle size of less than 5mm.

3. The shield tunneling synchronous grouting material based on cohesive slag soil according to claim 1, characterized in that, By weight, it includes 30-50 parts dehydrated viscous slag, 10-20 parts cement, 10-25 parts fly ash and / or slag powder, 30-40 parts water, 0.1-0.5 parts water-reducing agent, 0.1-0.5 parts chitosan, and 0.05-0.3 parts water-retaining thickener.

4. The shield tunneling synchronous grouting material based on cohesive slag soil according to any one of claims 1 to 3, characterized in that, The water-retaining and thickening agent is one or more of the following: hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, guar gum, xanthan gum, propyl guar gum, hydroxyethyl cellulose, sodium carboxymethyl cellulose, hydroxypropyl starch, and carboxymethyl starch. The water-reducing agent is a polycarboxylate water-reducing agent; The chitosan is a low molecular weight chitosan powder with a degree of deacetylation of 70% to 90% and a molecular weight of 5,000 to 200,000.

5. The shield tunneling synchronous grouting material based on cohesive slag soil according to any one of claims 1 to 3, characterized in that, The electrodes used in the electroosmotic dehydration method are graphite electrodes and / or stainless steel electrodes; The electroosmotic dehydration method applies a DC voltage of 30-60V, resulting in an electric field strength of 0.5V / cm-2V / cm; The electroosmotic dehydration process takes 4 to 8 hours and the ambient temperature during the process is 5°C to 35°C.

6. The shield tunneling synchronous grouting material based on cohesive slag soil according to any one of claims 1 to 3, characterized in that, The wet, cohesive slag was generated during the shield tunneling process and has a moisture content of 60wt% to 80wt%.

7. The shield tunneling synchronous grouting material based on cohesive slag soil according to any one of claims 1 to 3, characterized in that, The grouting material also includes 0.05 to 0.3 parts by weight of retarder and / or accelerator.

8. The shield tunneling synchronous grouting material based on cohesive slag soil according to any one of claims 1 to 3, characterized in that, The slump expansion of the grouting material is 180–220 mm.

9. The method for preparing shield tunneling synchronous grouting material based on cohesive slag as described in any one of claims 1 to 8, characterized in that, The solid raw materials of the grouting material are mixed, and then liquid raw materials are added and stirred evenly to form a uniform slurry. The fluidity of the resulting slurry is controlled to meet the requirements of shield tunneling construction, and then it can be used for shield tunneling construction.

10. The method for preparing shield tunneling synchronous grouting material based on cohesive slag soil according to claim 9, characterized in that, The fluidity control of the slurry is achieved by adding water and / or a water-reducing agent.