Shield muck-based self-repairing composite waterproof material

Abstract

The invention discloses a shield muck-based self-repairing composite waterproof material, which is characterized in that pretreated shield muck powder is compounded with a gelling component, an exciting agent and a functional additive according to a specific proportion, and the modulus of the exciting agent is accurately regulated to control the alkali excitation reaction process, so that the composite material is subjected to self-repairing after primary curing; part of incompletely reacted active aluminosilicate and residual excitant can be stably retained in the matrix to form a dormancy repair component. After the material and a post-buried water-stop belt are combined for construction and cured, a formed filling body not only generates high-strength chemical bonding and mechanical occlusion with a concrete base layer, but also generates micro-cracks due to structural deformation, permeated water can immediately trigger secondary hydration and crystallization reaction of dormant components, so that the water-stop belt is prevented from falling off. Meanwhile, the delayed expansion effect of the expanding agent is stimulated, a new gelling product is automatically generated, physical compaction is carried out, and self-repairing of microcracks and recovery of anti-permeability performance are achieved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and more specifically, to a self-healing composite waterproof material based on tunnel boring machine slag. Background Technology

[0002] The construction of shield tunnels generates a large amount of excavated soil, which is currently mainly considered construction waste and typically disposed of by transporting it to landfills. This method not only incurs high transportation and site occupancy fees, increasing the economic cost of the project, but also leads to a series of problems such as land resource depletion, dust pollution, and potential ecological and environmental impacts. Therefore, promoting the resource utilization of shield tunnel excavated soil and reducing its off-site disposal is clearly necessary to reduce project costs and alleviate environmental pressure.

[0003] Shield tunneling excavation soil is a mixture of in-situ soil cut off by the cutterhead during tunnel boring machine (TBM) excavation and grout injected to maintain the stability of the excavation face. Its composition is relatively complex, usually containing mineral components such as clay, silt, sand, and even rock fragments from the tunneling strata. At the same time, additives such as bentonite and carboxymethyl cellulose contained in the injected grout will also remain in it, making shield tunneling excavation soil a mixture with variable composition and high water content. Its main chemical elements are mainly oxides of silicon, aluminum, and calcium. Summary of the Invention

[0004] To achieve the recycling of tunnel boring machine (TBM) excavated soil, this invention provides a self-healing composite waterproof material based on TBM excavated soil. This material is created by combining pretreated TBM excavated soil powder with a specific ratio of cementitious components, activators, and functional additives. The modulus of the activator is precisely controlled to manage the alkali-activated reaction process. After initial curing, the composite material retains some unreacted active aluminosilicates and residual activators within its matrix, forming dormant repair components. When this material is applied and cured in conjunction with a post-embedded waterstop, the resulting filler not only forms a high-strength chemical bond and mechanical interlock with the concrete base, but also, when structural deformation causes micro-cracks in the filler itself, the infiltrated water immediately triggers a secondary hydration and crystallization reaction of the dormant components. Simultaneously, it activates the delayed expansion effect of the expansion agent, automatically generating new cementitious products and causing physical compaction, thus achieving self-repair of micro-cracks and restoration of impermeability.

[0005] The technical solution of this invention is as follows: A self-healing composite waterproof material based on shield tunnel slag includes 100 parts of pretreated shield tunnel slag powder, 20-30 parts of cementitious component, 15-25 parts of activator, 5-10 parts of admixture, and 30-40 parts of water. Among them, the total silica content in the pretreated shield tunnel slag powder is greater than or equal to 40%; The cementitious components include cement clinker, slag powder, and nano silica fume, with a mass ratio of cement clinker: slag powder: nano silica fume = 1:(2.0~3.5):(0.1~0.2). The activator includes sodium silicate and sodium hydroxide, with a mass ratio of sodium silicate:sodium hydroxide = (1.5~4.0):1; The admixtures include polyacrylamide, defoamer, water-reducing agent, and expanding agent, with a mass ratio of polyacrylamide:defoamer:water-reducing agent:expanding agent = 1:(0.2~0.4):(0.5~1.0):(0.5~0.8).

[0006] The above-mentioned self-healing composite waterproof material for shield tunneling slag foundation includes a method for preparing pretreated shield tunneling slag powder as follows: The shield tunneling excavated soil is separated into mud cakes by mud-water separation. The mud cakes are dried until the moisture content is no more than the specified value. The mud cakes are crushed and screened through a two-stage vibrating screen. The particles that pass through the first screen but not the second screen are taken as shield tunneling excavated soil powder raw materials. The shield tunneling excavation soil powder raw material is burned at high temperature, and the organic matter content of the shield tunneling excavation soil powder raw material is tested to reduce the organic matter content to below the specified value.

[0007] The above-mentioned shield tunnel slag-based self-healing composite waterproof material is prepared by mixing pretreated shield tunnel slag powder, cementing components, and dry powder additives in a mixer according to a certain ratio to form a dry mixture. At the same time, the activator is dissolved in part of the mixing water in a certain ratio to prepare a homogeneous solution. A groove of regular size is chiseled out on the concrete base along the expansion joint, and the embedded waterstop is fixed in the center of the groove. Add the activator solution to the dry mixture and stir quickly to form a uniform slurry. Then, through the grouting machine and grouting pipe, slowly and continuously inject the slurry from the bottom of the groove so that the slurry fills the area around the waterstop and wraps around it. The maintenance includes a filling layer consisting of a post-embedded waterstop and a cured waterproof material that completely wraps around the waterstop.

[0008] The aforementioned self-healing composite waterproof material based on tunnel boring machine slag has a total content of more than 50% for silicon dioxide and aluminum oxide, and a total content of more than 70% for silicon dioxide, aluminum oxide, and calcium oxide in the pretreated tunnel boring machine slag powder.

[0009] Furthermore, the tunnel boring machine excavation material contains 10% to 25% alumina.

[0010] Furthermore, the tunnel boring machine excavation material contains 5% to 20% calcium oxide.

[0011] The above-mentioned self-healing composite waterproof material based on tunnel boring machine slag has a sodium silicate modulus of 1.2 to 1.8 in the activator.

[0012] The aforementioned self-healing composite waterproof material for shield tunnel slag foundation uses anionic polyacrylamide with a molecular weight of 6 million to 15 million. The aforementioned self-healing composite waterproof material for shield tunnel slag foundation uses a polycarboxylate superplasticizer as its water-reducing agent.

[0013] The aforementioned self-healing composite waterproof material for shield tunnel slag foundation uses calcium sulfoaluminate or calcium oxide as the expanding agent.

[0014] The aforementioned self-healing composite waterproof material based on tunnel boring machine slag uses an organosilicon defoamer as its defoamer.

[0015] This invention discloses a self-healing composite waterproof material based on tunnel boring machine (TBM) slag. The material uses pretreated TBM slag powder as the main substrate, combined with cementitious components, activators, and functional admixtures. It is then bonded to a post-embedded waterstop via grouting and solidifies within the grooves of concrete deformation joints to form a high-strength filler. The filler exhibits strong chemical and mechanical adhesion to the substrate, connecting the waterstop to the concrete base and providing structural waterproofing. By adjusting the modulus and component ratio of the activator, unreacted active aluminosilicates (from TBM slag and slag powder) and residual activators are stably retained within the substrate after the initial curing of the filler, forming a dormant repair component. When structural deformation leads to microcracks and water seepage, moisture triggers a secondary alkali-activated reaction of the dormant component, generating new hydrated calcium silicate (CSH) gel or crystalline products. Simultaneously, the expanding agent undergoes delayed expansion upon contact with water, producing a physical compaction effect. Together, these factors achieve self-healing, automatically filling microcracks, restoring impermeability, and realizing autonomous repair from molecular reaction to macroscopic function, thus extending the lifespan of the waterproofing system.

[0016] This invention proactively creates a controllable incomplete reaction system, rather than pursuing complete reaction as is common in traditional materials. The activator modulus, i.e., the molar ratio of silica to sodium oxide in sodium silicate, is controlled between 1.2 and 1.8. This range effectively regulates the kinetics of the alkali-activated reaction. A lower modulus means a higher content of free sodium hydroxide in the system, resulting in stronger alkalinity. This allows for rapid dissociation of active aluminosilicates in the shield tunnel slag and slag powder, while also slowing down the reaction rate to prevent excessive consumption of active components in the initial stage, thus reserving space for subsequent repair. The control of the amount and contents of the shield tunnel slag powder ensures that the total amount of active aluminosilicates is slightly in surplus relative to the activator, or that the amount of activator is slightly excessive. Thermodynamically, this ensures that regardless of how the initial hydration proceeds, some reactants will not fully participate in the reaction. This intentionally sets the internal chemical equilibrium of the material to an incomplete state when it solidifies to the required strength, laying the foundation for its self-healing function.

[0017] During the initial curing process, the alkali-activated reaction generates products such as hydrated calcium silicate gel, which gradually form a dense microstructure. However, due to the control of modulus and ratio, the reaction is not complete. Some active aluminosilicate particles and residual activator ions are encapsulated and isolated by the newly formed gel network. These incompletely reacted substances cannot continue to contact and react due to steric hindrance and diffusion limitations, thus entering a stable dormant state. The dormant active aluminosilicates mainly originate from the silica-alumina components and slag powder in the tunnel boring machine slag, while the residual activators, including sodium ions and hydroxide ions, are adsorbed on the surface of the gel pores or trapped in the micropores, maintaining their chemical activity but unable to move freely.

[0018] When external stress causes microcracks in the material, moisture seeps into the matrix along the cracks, activating the dormant repair components. Water molecules first dissolve the encapsulated residual activator, restoring the localized strongly alkaline environment and providing the necessary reaction medium. Ions, transported in the aqueous phase, reach the surface of the dormant active aluminosilicate particles, re-initiating the alkaline activation reaction, i.e., the secondary hydration process. This process generates new hydrated calcium silicate gel or crystal products, which gradually fill and bridge the microcracks, achieving self-sealing. Simultaneously, the expansive agent in the material also undergoes hydration and expansion upon contact with water, producing a physical compaction effect that synergizes with the chemical repair. The entire repair process is entirely triggered by moisture, requiring no external intervention. Through this mechanism, the material not only repairs the damage but also restores its impermeability, extending its service life.

[0019] The structural strength of the self-healing composite waterproof material based on tunnel boring machine (TBM) slag in this invention mainly originates from the reaction products of the cementitious components and partially activated TBM slag, such as hydrated calcium silicate gel and alkali silicate gel, generated under the action of an activator. These reaction products intertwine to form a dense three-dimensional network structure, constituting the skeleton of the solidified body. Although unreacted active aluminosilicates exist, they are firmly encapsulated within this gel skeleton as micro-aggregates, functioning similarly to sand and gravel aggregates in concrete, primarily serving as fillers and physical supports, while the gel skeleton is the main provider of strength. On the other hand, nano-silica fume, in its ultrafine particle state, fills even smaller pores and participates in the reaction to generate more gel, making the gel skeleton denser and stronger. This compensates for the potential strength loss due to unreacted substances, ensuring sufficient strength in the filling layer. Furthermore, by reducing water usage, the water-cement ratio is controlled. The use of polycarboxylate superplasticizers significantly improves the fluidity of the grout without increasing water consumption, ensuring the compactness of the grout and avoiding large voids or weak areas caused by construction defects. This allows for a lower water-cement ratio to be achieved. The adjusted water-cement ratio fundamentally reduces the number and size of capillaries after curing, resulting in a denser gel skeleton. On the other hand, defoamers eliminate harmful air bubbles in the grout, increasing the uniformity and density of the cured body. These measures work together to improve the theoretical density and strength of the material, creating conditions for safely accommodating small amounts of dormant repair components.

[0020] Furthermore, the presence of calcium oxide in the shield tunneling slag powder can provide some initial alkalinity and participate in the reaction as a calcium source, which helps to reduce the absolute dependence on external alkaline activators and stabilize the reaction products. The appropriate amount of aluminum incorporated into the silicon-oxygen network in the shield tunneling slag powder can regulate the structure and properties of the gel, improve its early strength development rate, and enhance its resistance to chemical erosion, especially its resistance to sulfate erosion. Within this content range, aluminum oxide can form a stable zeolite-like structure or ettringite phase with sufficient silica and calcium oxide. These products contribute to the dense microstructure and strength enhancement, and the relatively low aluminum content can appropriately delay the setting time, allowing sufficient time for the gelation process to take effect.

[0021] According to the above-described solution, the beneficial effects of this invention are as follows: 1. This invention, through its component ratio design, enables the cured body to autonomously initiate repair when minor damage occurs. The shield tunnel slag-based self-healing composite waterproof material of this invention contains dormant active components that did not fully react during the initial hydration, namely active aluminosilicates from shield tunnel slag and slag powder, and activators that have not yet been completely consumed (the component ratio design ensures that unreacted substances remain after the material is cured). When structural deformation leads to the formation of microcracks and water ingress, water acts as a medium and reactant, reactivating these dormant substances and triggering a continuous alkali-activated reaction, generating new hydrated calcium silicate (CSH) gel or crystal products. Simultaneously, the expansion agent in the admixture also undergoes hydration or crystallization upon contact with water, producing moderate volume expansion, which together effectively fills and densifies the microcracks, thereby restoring or even partially improving their impermeability, extending the service life of waterproof systems for dynamic joints such as expansion joints, and reducing long-term maintenance costs and leakage risks.

[0022] 2. Utilizing the characteristics of tunnel boring machine (TBM) excavated soil to achieve environmental and economic benefits: Besides the soil composition of the construction site, the grout used in TBMs also contains certain substances added to maintain desired properties. This invention's self-healing composite waterproof material based on TBM excavated soil fully utilizes the general properties of TBM excavated soil (containing a large amount of silica and alumina). Through activators and a surplus in the formulation, some silicate crystals in the material do not fully react during the curing process, becoming dormant active components that are activated when micro-cracks form and water seeps in. As a locally sourced raw material, TBM excavated soil has extremely low cost and high economic value. In its use, if combined with local industrial waste heat, energy costs can be further controlled, and resource recycling of construction waste can be achieved, resulting in significant social and environmental benefits.

[0023] 3. Combined with post-embedded waterstops for use in expansion joints, forming a composite waterproofing reinforcement system: In this system, the post-embedded waterstop, as the first line of defense, mainly relies on its high elasticity to adapt to large structural deformations and provide reliable passive waterproofing. The self-healing composite material, after curing, wraps around and anchors the waterstop. On the one hand, it has low permeability and provides structural waterproofing; on the other hand, its self-healing function is specifically designed to address micro-cracks caused by material shrinkage or minor displacement that the waterstop cannot handle.

[0024] 4. Strong interfacial bonding strength: Under the combined action of the activator and cement hydration, the nano-silica fume and slag in the material can generate a large amount of highly surface-active CSH gel. These gels can form a strong chemical bond and mechanical interlock with the concrete base (after roughening). The silica-alumina components contained in the pretreated shield tunnel slag powder also participate in the reaction, further enhancing the density of the interfacial transition zone. This allows a high-strength bond to be formed between the cured filling layer and the concrete base, effectively preventing interfacial delamination and water seepage under alternating stress, and also acting as an adhesive to connect the waterstop to the concrete base. Detailed Implementation

[0025] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] A self-healing composite waterproof material based on shield tunnel slag includes 100 parts of pretreated shield tunnel slag powder, 20-30 parts of cementitious component, 15-25 parts of activator, 5-10 parts of admixture, and 30-40 parts of water. Among them, the total silica content in the pretreated shield tunnel slag powder is greater than or equal to 40%; The cementitious components include cement clinker, slag powder, and nano silica fume, with a mass ratio of cement clinker: slag powder: nano silica fume = 1:(2.0~3.5):(0.1~0.2). The activator includes sodium silicate and sodium hydroxide, with a mass ratio of sodium silicate:sodium hydroxide = (1.5~4.0):1; The admixtures include polyacrylamide, defoamer, water-reducing agent, and expanding agent, with a mass ratio of polyacrylamide:defoamer:water-reducing agent:expanding agent = 1:(0.2~0.4):(0.5~1.0):(0.5~0.8).

[0027] The following are the material specifications for a self-healing composite waterproof material based on tunnel boring machine slag, according to the present invention.

[0028] Tunnel boring machine (TBM) excavated soil: Fresh excavated soil generated from urban subway and tunnel shield construction projects should be given priority. The soil in the construction area should be free from heavy metal pollution and excessive levels of toxic and harmful organic matter. TBM excavated soil should be equipped with mud-water separation equipment to ensure that its sand content and particle size distribution meet the requirements of subsequent pretreatment. Avoid using excavated soil that has been stockpiled for a long time, is severely weathered, or is mixed with construction waste.

[0029] Cement clinker: P・O42.5 grade ordinary Portland cement clinker is selected, which must meet the standard of "General Portland Cement" (GB175-2007), with free calcium oxide content ≤1.5% and qualified stability.

[0030] Slag powder: S95 grade granulated blast furnace slag powder is used, with a specific surface area ≥400m² / kg and an activity index (28d) ≥95%, which meets the requirements of "Granulated blast furnace slag powder for cement and concrete" (GB / T18046-2017).

[0031] Nano silica fume: purity ≥92%, average particle size ≤50nm, specific surface area ≥15000m² / kg, requires surface modification treatment to improve dispersibility and avoid agglomeration.

[0032] Sodium silicate: Industrial grade solid sodium silicate, with a modulus strictly controlled between 1.2 and 1.8, sodium oxide content ≥28%, silicon dioxide content ≥32%, and no obvious clumping.

[0033] Sodium hydroxide: Industrial grade flake sodium hydroxide, purity ≥96%, moisture content ≤1%. It should be stored in a moisture-proof and sealed manner to prevent moisture absorption and deterioration.

[0034] Polyacrylamide: anionic, molecular weight 6 million to 15 million, degree of hydrolysis 20% to 30%, purity ≥90%, and must have good thickening and water retention properties.

[0035] Defoamer: Organosilicon defoamer, active ingredient content ≥30%, pH value 6~8, defoaming speed ≤5s, foam suppression time ≥24h.

[0036] Water-reducing agent: Polycarboxylate-based high-efficiency water-reducing agent with a water reduction rate of ≥25%, air content of ≤3%, and slump loss over time (1h) of ≤10%, which meets the standard of "Concrete Admixtures" (GB8076-2017).

[0037] Expanding agent: Select calcium sulfoaluminate or calcium oxide expanding agent, limit the expansion rate (7d) to ≥0.025%, the strength loss rate to ≤15%, and eliminate the risk of later shrinkage and cracking.

[0038] Mixing water: Tap water or natural clean water that meets the "Standard for Water Used in Concrete" (JGJ63-2006) is used, with a pH value of 6-8, a chloride ion content of ≤200mg / L, and free from harmful impurities, oil and organic matter.

[0039] The excavated soil generated during shield tunneling is transported to a mud-water separation system. Large gravel and debris are initially removed by a vibrating screen (5mm aperture), and then solid-liquid separation is carried out by a filter press. The separation pressure is controlled at 0.3-0.5MPa and the separation time is 15-20min to obtain mud cake with a moisture content of ≤30%.

[0040] The mud cake is sent to a drying kiln for drying. The drying temperature is controlled at 105±5℃, and the drying time is 4 to 6 hours to ensure that the final moisture content of the mud cake is ≤5%. The dried mud cake is then crushed to a particle size of ≤10mm using a jaw crusher. Impurities should be avoided during the crushing process. The crushed particles should be promptly conveyed to the screening process to prevent moisture absorption and clumping.

[0041] A two-stage vibrating screen is used for grading and screening. The first-stage screen has a mesh size of 200 mesh (75μm), and the second-stage screen has a mesh size of 300 mesh (48μm). Particles that pass through the 200-mesh screen but not the 300-mesh screen are used as raw materials for tunnel boring machine (TBM) slag powder, ensuring uniform particle size with a distribution range of 48–75μm. Large particles on the oversize screen are returned to the crusher for further crushing, while the undersize fine powder is collected and stored separately for use as filler material.

[0042] The screened tunnel boring machine (TBM) slag powder is fed into a high-temperature incinerator at 600±50℃ for 3–4 hours to remove organic matter through high-temperature decomposition. During incineration, the heating rate is controlled at 5℃ / min to prevent sudden temperature increases that could damage the powder structure. After incineration, the powder is cooled to room temperature, and the organic matter content is tested. It must be ensured that the organic matter content is ≤0.8%; if this is not met, the incineration time is extended by 0.5–1 hour.

[0043] The pretreated tunnel boring machine (TBM) slag powder needs to undergo chemical composition testing to ensure that the silica content is ≥40%, the total content of silica and alumina is ≥50%, and the total content of silica, alumina, and calcium oxide is ≥70%. Preferably, the alumina content is 10%–25% and the calcium oxide content is 5%–20%. The qualified powder is stored in a sealed silo equipped with a dehumidifier to control the relative humidity to ≤60% to prevent moisture absorption and deterioration. The storage time should not exceed 3 months.

[0044] Precisely measure the following proportions (by weight): 100 parts pretreated tunnel boring machine (TBM) slag powder, 20-30 parts cementitious components (cement clinker: slag powder: nano silica fume = 1:(2.0-3.5):(0.1-0.2)), 15-25 parts activator (sodium silicate: sodium hydroxide = (1.5-4.0):1), 5-10 parts admixtures (polyacrylamide: defoamer: water-reducing agent: expansion agent = 1:(0.2-0.4):(0.5-1.0):(0.5-0.8)), and 30-40 parts water. Use an electronic weighing scale with an accuracy ≤ ±0.5%. Calibrate the weighing equipment before batching to ensure accurate proportions.

[0045] The pretreated tunnel boring machine (TBM) slag powder, cement clinker, slag powder, nano-silica fume, and dry powder additives (polyacrylamide, defoamer, water-reducing agent, and expanding agent) are sequentially added to a twin-shaft mixer. The mixing speed is 300–400 rpm, and the dry mixing time is 5–8 minutes, until the materials are uniformly mixed and there is no obvious color difference or clumping. During the dry mixing process, the uniformity of mixing should be checked periodically using a sieve analysis method, and the passing rate deviation should be ≤3%.

[0046] Use 60%–70% of the total mixing water as the solvent. First, add sodium silicate to the solvent and stir to dissolve (stirring speed 200–250 r / min, time 10–15 min). Then, slowly add sodium hydroxide and continue stirring for 5–8 min to prepare a homogeneous activator solution. During the preparation process, control the solution temperature at 20–30℃ to avoid the volatilization of sodium hydroxide due to high temperature. After the solution is prepared, the modulus needs to be tested to ensure it is within the range of 1.2–1.8. If the deviation exceeds ±0.1, the ratio of sodium silicate to sodium hydroxide needs to be adjusted.

[0047] Slowly add the activator solution to the dry mix, while simultaneously adding the remaining mixing water. Start the mixer at high speed (500–600 rpm) for 3–5 minutes, until a uniform, lump-free, and highly fluid slurry is formed. Slurry fluidity is tested using a spread test, with the spread controlled at 200–250 mm. If the spread is insufficient, the amount of mixing water can be increased appropriately (not exceeding 5% of the total water volume). If the fluidity is excessive, a small amount of dry mix can be added to adjust.

[0048] Along the expansion joint of the concrete structure, chisel out a groove of regular size on the concrete base. The width of the groove is determined according to the width of the expansion joint, generally 20-30cm, and the depth is 15-25cm. The sides of the groove need to be chiseled to a rough surface (roughness ≥3mm). Remove scum, dust, oil and loose concrete, wash it clean with a high-pressure water gun, and let it dry until there is no standing water on the surface.

[0049] Select a post-embedded waterstop that meets the design requirements (such as rubber waterstop or steel edge waterstop), fix it in the center of the groove, align the length of the waterstop with the expansion joint, and fix it at intervals of 50-80cm. Ensure that the waterstop is flat, without twisting or damage, and that the deviation between the center line of the waterstop and the center line of the expansion joint is ≤5mm.

[0050] A grouting pipe, made of PVC pipe with a diameter of 20-25mm, is installed at the bottom of the groove. Grouting holes with a diameter of 3-5mm are cut into the pipe wall, spaced 10-15cm apart. The grouting pipe is positioned 5-10cm from the bottom of the groove, with one end connected to the grouting machine and the other end extending to the end of the groove. Simultaneously, vent holes are installed at the top of the groove, spaced 50-100cm apart, to ensure smooth gas discharge during grouting.

[0051] Before grouting, check the sealing of the grouting machine and grouting pipe, and conduct a trial run to ensure that the equipment is working properly. After the grout is mixed, it should be injected within 30 minutes to avoid the grout setting prematurely and affecting the construction quality.

[0052] Pressure grouting is employed, with the grouting pressure controlled between 0.3 and 0.5 MPa. Grouting is initiated slowly and continuously from the bottom of the groove, proceeding from one end to the other to ensure the grout gradually fills the area around the waterstop from the bottom up. During grouting, the vent holes are observed. When uniform grout overflows from a vent hole without air bubbles, the vent hole is sealed, and grouting continues until qualified grout overflows from the next vent hole, and so on.

[0053] If grout leakage or a sudden drop in pressure occurs during grouting, grouting must be stopped immediately. The leaking area should be inspected and sealed (e.g., with quick-setting cement). Grouting should be resumed after the sealing material has cured. If a sudden increase in pressure occurs, the grouting speed should be reduced, the grouting pipe should be checked for blockages, and the blockages should be cleared before continuing construction.

[0054] After the grout fills the groove, maintain the grouting pressure for 3-5 minutes to stabilize the pressure and ensure that the grout is dense and free of voids or pores. After stabilizing the pressure, turn off the grouting machine and seal the grouting pipe port to prevent grout backflow.

[0055] After construction, promptly cover with geotextile or plastic film for moisture retention and curing. During curing, control the ambient temperature to 5–35℃ and the relative humidity to ≥90%, avoiding direct sunlight, rain, and strong winds. In low-temperature environments (5–10℃), insulation measures (such as covering with insulating blankets) are required, and open flame heating is prohibited. Curing should last at least 7 days in normal environments, at least 10 days in high-temperature dry environments (temperature ≥30℃, humidity ≤60%), and at least 14 days in low-temperature environments (5–10℃). Regularly spray water during curing to ensure the surface of the filling layer remains moist. During curing, avoid collisions, rolling, or disturbance of the filling layer, and prohibit high-temperature operations such as welding and cutting near the waterstop to prevent damage to the waterstop and uncured waterproofing material.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-healing composite waterproof material for shield tunnel slag foundation, characterized in that, It includes 100 parts of pretreated shield tunnel slag powder, 20-30 parts of cementitious components, 15-25 parts of activator, 5-10 parts of admixture, and 30-40 parts of water; Among them, the total silica content in the pretreated shield tunnel slag powder is greater than or equal to 40%; The cementitious components include cement clinker, slag powder, and nano silica fume, with a mass ratio of cement clinker: slag powder: nano silica fume = 1:(2.0~3.5):(0.1~0.2). The activator includes sodium silicate and sodium hydroxide, with a mass ratio of sodium silicate:sodium hydroxide = (1.5~4.0):1; The admixtures include polyacrylamide, defoamer, water-reducing agent, and expanding agent, with a mass ratio of polyacrylamide:defoamer:water-reducing agent:expanding agent = 1:(0.2~0.4):(0.5~1.0):(0.5~0.8).

2. The self-healing composite waterproof material for shield tunnel slag foundation as described in claim 1, characterized in that, The preparation methods for pretreated shield tunneling slag powder include: The shield tunneling excavated soil is separated into mud cakes by mud-water separation. The mud cakes are dried until the moisture content is no more than the specified value. The mud cakes are crushed and screened through a two-stage vibrating screen. The particles that pass through the first screen but not the second screen are taken as shield tunneling excavated soil powder raw materials. The shield tunneling excavation soil powder raw material is burned at high temperature, and the organic matter content of the shield tunneling excavation soil powder raw material is tested to reduce the organic matter content to below the specified value.

3. The self-healing composite waterproof material for shield tunnel slag foundation as described in claim 1, characterized in that, The pretreated shield tunnel slag powder, cementing components, and dry powder additives are put into a mixer according to the proportion to form a dry mixture. At the same time, the activator is dissolved in part of the mixing water in proportion to prepare a homogeneous solution. A groove of regular size is chiseled out on the concrete base along the expansion joint, and the embedded waterstop is fixed in the center of the groove. Add the activator solution to the dry mixture and stir quickly to form a uniform slurry. Then, through the grouting machine and grouting pipe, slowly and continuously inject the slurry from the bottom of the groove so that the slurry fills the area around the waterstop and wraps around it. The maintenance includes a filling layer consisting of a post-embedded waterstop and a cured waterproof material that completely wraps around the waterstop.

4. The self-healing composite waterproof material for shield tunnel slag foundation as described in claim 1, characterized in that, In the pretreated shield tunnel slag powder, the total content of silicon dioxide and aluminum oxide is greater than 50%, and the total content of silicon dioxide, aluminum oxide and calcium oxide is greater than 70%.

5. The self-healing composite waterproof material for shield tunnel slag foundation as described in claim 4, characterized in that, The slag and powder from tunnel boring machines contain 10% to 25% alumina.

6. The self-healing composite waterproof material for shield tunnel slag foundation as described in claim 4, characterized in that, The slag and powder from tunnel boring machines contain 5% to 20% calcium oxide.

7. The self-healing composite waterproof material for shield tunnel slag foundation as described in claim 1, characterized in that, The modulus of sodium silicate in the activator is 1.2 to 1.

8.

8. The self-healing composite waterproof material for shield tunnel slag foundation as described in claim 1, characterized in that, The water-reducing agent is a polycarboxylate-based water-reducing agent.

9. The self-healing composite waterproof material for shield tunnel slag foundation as described in claim 1, characterized in that, The expanding agent is a calcium sulfoaluminate or calcium oxide expanding agent.

10. A self-healing composite waterproof material for shield tunnel slag foundation as described in claim 1, characterized in that, The defoamer is an organosilicon defoamer.