Shield waterstop paste and preparation method thereof

Abstract

The invention discloses shield waterproof paste and a preparation method thereof. The waterproof paste is prepared from a water-borne epoxy resin emulsion, a curing agent, sodium bentonite, chopped fibers, a sulphoaluminate-based cementing material, a thixotropic agent and water according to a specific ratio. Through triple synergistic effects of an organic epoxy network, an inorganic hydration reaction and a physical fiber network, the product has excellent water dispersibility resistance (24h retention rate gt, 97%), high thixotropy, rapid early strength (6h strength gt, 0.8 MPa) and micro-expansion characteristics. The preparation method adopts step-by-step feeding and rotating speed control to ensure that the product is uniform and stable. The technical problems that a traditional shield tail gap filling material is prone to loss in the flowing water environment and supporting is slow are effectively solved, and the method is particularly suitable for shield construction of the water-rich complex stratum.

Description

Technical Field

[0001] This invention belongs to the field of tunnel and underground engineering shield construction technology, specifically relating to a shield sealing compound for filling the gap at the tail of a shield machine, which has excellent water dispersibility, high thixotropy and micro-expansion early strength characteristics, and its preparation method. Background Technology

[0002] In shield tunneling, the diameter of the shield machine's outer shell is typically larger than the outer diameter of the tunnel segments. As the shield machine advances, a ring-shaped gap (referred to as the "tail gap") forms between the shield shell and the surrounding soil. If this gap is not filled in a timely and effective manner, the stress released from the overlying soil will cause it to move into the gap, leading to surface subsidence and even causing a collapse. In water-rich strata, groundwater carrying sediment will be lost in large quantities through this gap, not only exacerbating surface subsidence but also potentially causing serious engineering problems such as tail seal failure and instability of the tunnel face.

[0003] The "mud-filling" method is a commonly used gap-filling technique, the core of which involves injecting a special paste-like material into the shield tail gap. Traditional mud-filling materials mainly rely on bentonite as a base material, using its water-absorbing and swelling properties to seal the voids. However, traditional materials have the following significant drawbacks: 1. Poor resistance to water dispersibility: Under the action of dynamic water pressure, bentonite paste is easily washed away, diluted and lost, leading to failure of water sealing.

[0004] 2. Insufficient initial stability: After injection, the paste is prone to segregation and sedimentation under its own weight and the scouring of groundwater, making it difficult to form effective support at the top of the arch.

[0005] 3. Slow and uncontrollable strength growth: Bentonite alone cannot form a stable structure, and its long-term stability support for the strata is limited.

[0006] Limited adaptability: It has poor adaptability to different strata (especially high water pressure and gravel strata).

[0007] Therefore, developing a shield-type waterproofing compound with excellent water-dispersibility, high thixotropy, rapid formation of micro-expansion early strength, and adaptability to complex strata has become an urgent technical problem to be solved in this field. Summary of the Invention

[0008] The main objective of this invention is to overcome the shortcomings of the prior art and provide a shield tunneling waterproofing compound with anti-erosion, high thixotropy, micro-expansion, and early strength properties, as well as its preparation method.

[0009] The shield tunneling waterproofing compound of the present invention, by weight, comprises the following components: 15-25 parts of waterborne epoxy resin emulsion; 4 to 7 parts of water-based epoxy curing agent; Sodium-based bentonite 20-30 parts; 1 to 2 parts of chopped synthetic fibers; 8-12 parts of cementitious material; Thixotropic agent 1 to 1.5 parts; 35-45 parts water; The three-dimensional cross-linked network formed by the reaction of the waterborne epoxy resin emulsion and the waterborne epoxy curing agent can combine with the hydration products of the sodium-based bentonite and the cementitious material through hydrogen bonds and / or ionic bonds to form an organic-inorganic hybrid structure. The cementitious material is composed of rapid-hardening sulfoaluminate cement clinker and anhydrous gypsum in a weight ratio of 4:1. When the cementitious material is hydrated, it can generate ettringite crystals, causing the waterproofing sealant to undergo a slight volume expansion of 0.5% to 2.0%.

[0010] Preferably, the chopped synthetic fiber is a polypropylene fiber or a polyvinyl alcohol fiber with a length of 6-12 mm.

[0011] Preferably, the thixotropic agent is attapulgite clay with a mesh size of 300-500.

[0012] Preferably, it further comprises 0.1-0.3% of a polycarboxylate superplasticizer by weight of the paste.

[0013] A method for preparing shield tunnel waterproofing compound includes the following steps: (1) Pre-hydration pulping: Water, thixotropic agent, and sodium bentonite are mixed at a high shear rate of 500-600 rpm for 15 minutes to form a base pulp; (2) Mixing of main materials: Add waterborne epoxy resin emulsion and chopped synthetic fibers to the base slurry at a speed of 200-300 rpm and disperse for 3-5 minutes; (3) Dispersion of cementitious materials: Add the cementitious materials at a speed of 200-300 rpm and stir for 2-3 minutes; (4) Final setting trigger: Add water-based epoxy curing agent and stir at 200-300 rpm for 3-5 minutes to obtain the shield water-stopping paste.

[0014] Preferably, in step (1), if a water-reducing agent is used, the water-reducing agent is added together with the water.

[0015] Compared with the prior art, the shield tunneling waterproofing compound and its preparation method of the present invention are as follows: 1. "Epoxy-Bentonite" Organic-Inorganic Composite Framework: Waterborne epoxy resin and curing agent form a three-dimensional organic network in the slurry, firmly encapsulating and bonding bentonite particles and hydration products of cementing materials together, greatly enhancing the integrity and water erosion resistance of the paste. This is fundamentally different from traditional materials that rely solely on bentonite.

[0016] 2. Synergistic thickening and anti-settling effect of fibers and thixotropic agents: Fibers form a three-dimensional support in the paste, while thixotropic agents impart extremely high static shear strength to the paste. The synergistic effect of the two gives the paste excellent thixotropic properties (it thins during stirring to facilitate pumping and thickens rapidly when at rest), effectively resisting segregation and settlement during construction and ensuring perfect filling even in tunnel arches.

[0017] 3. Micro-expansion early strength system: The specially selected sulfoaluminate cement-based cementitious material rapidly generates ettringite in the early stage of hydration, producing a micro-expansion effect, which can compensate for the shrinkage of the paste. It works together with the epoxy network and bentonite to quickly form early strength and provide immediate support for the formation.

[0018] 4. By using a step-by-step, speed-controlled feeding and stirring process, the uniform dispersion of each component (especially the epoxy emulsion and curing agent) is ensured, avoiding localized solidification caused by premature contact, and guaranteeing the stability of the paste's working and final performance. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 A flowchart illustrating the method for preparing shield tunneling waterproofing compound according to an embodiment of the present invention.

[0021] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Any simple improvements to the preparation method of this invention based on the inventive concept are within the scope of protection of this invention.

[0023] One aspect of the present invention provides a shield tunnel waterproofing compound, which, by weight, comprises the following components: 15-25 parts of waterborne epoxy resin emulsion; 4 to 7 parts of water-based epoxy curing agent; Sodium-based bentonite 20-30 parts; 1 to 2 parts of chopped synthetic fibers; 8-12 parts of cementitious material; Thixotropic agent 1 to 1.5 parts; 35-45 parts water; In this embodiment, the three-dimensional cross-linked network formed by the reaction of the waterborne epoxy resin emulsion and the waterborne epoxy curing agent can combine with the hydration products of the sodium-based bentonite and the cementitious material through hydrogen bonds and / or ionic bonds to form an organic-inorganic hybrid structure.

[0024] This invention innovatively uses a reactive waterborne epoxy resin system as the organic binder phase. The organic binder phase is not simply physically mixed with the inorganic phase (bentonite, cement hydration products), but forms a three-dimensional interpenetrating network structure through interfacial chemical interaction.

[0025] Aqueous epoxy resin emulsion: An aqueous dispersion emulsified with bisphenol A type epoxy resin and a nonionic surfactant, with an epoxy value of 0.20-0.25 eq / 100g and a solid content of 50±2%. Its core epoxy group structure is as follows: O / / -CC- (Epoxy Cylindrical) \ O

[0026] Waterborne epoxy curing agent: A modified aliphatic amine adduct curing agent with an amine value of 220±10 mgKOH / g. Its molecule contains a -NH-CH2-CH2-NH- structure, which can react efficiently with epoxy groups.

[0027] Formation mechanism of organic-inorganic hybrid networks: The selected waterborne epoxy resin emulsion has epoxy groups at the ends of its molecular chains, and its general structural formula can be represented as: RO-CH2-CH(-CH2-O-R')-CH2- | | Epoxy Group Polymer Backbone (Where R and R' are polymer backbones)

[0028] Under the action of water-based amine curing agents (e.g., modified polyetheramines, whose molecular structure contains active hydrogen atoms -NH- or -NH2), the epoxy groups undergo ring-opening and cross-linking reactions to form a three-dimensional network. Crucially, the hydroxyl groups -OH and ether bonds -O- in this network can form strong hydrogen bonds with the silanol groups -SiOH on the surface of bentonite particles and the -OH groups in the calcium silicate hydrate (CSH) gel, a cement hydration product, and even partially undergo chemical bonding. Their interactions are shown below: [Epoxy Network]-OH···HO-Si-[Bentonite] (Hydrogen Bonding) [Epoxy Network]-O- + Ca²⁺ → [Epoxy Network]-O-Ca- (ionic bonding, bridging CSH gel) Furthermore, the cementitious material is composed of rapid-hardening sulfoaluminate cement clinker and anhydrous gypsum in a weight ratio of 4:1. When the cementitious material is hydrated, it can generate ettringite crystals, causing the waterproofing sealant to undergo a slight volume expansion of 0.5% to 2.0%.

[0029] The cementitious material used in this embodiment consists of sulfoaluminate cement clinker (the main mineral being anhydrous calcium sulfoaluminate C4A3Š) and anhydrous gypsum (CaSO4). Its micro-expansion originates from the controlled formation reaction of ettringite (AFt): C4A3Š + 2CŠ + 38H → C3A·3CŠ·32H (Ettringite, AFt) (Where Š represents SO3, C represents CaO, A represents Al2O3, and H represents H2O) By precisely controlling the ratio of C4A3Š to CaSO4 to 4:1, sufficient gypsum was ensured to generate stable and appropriate amounts of needle-like ettringite crystals. These crystals generate moderate expansion stress during growth, which not only compensates for the plastic shrinkage and chemical shrinkage during the initial curing stage of the paste, but also intertwines with the epoxy network and bentonite, significantly enhancing early strength. This is fundamentally different from the shrinkage that may occur during the hydration of ordinary silicate cement.

[0030] Another aspect of the present invention provides a method for preparing a shield tunnel waterproofing compound, referring to... Figure 1 This includes the following steps: (1) Pre-hydration pulping: Water, thixotropic agent, and sodium bentonite are mixed at a high shear rate of 500-600 rpm for 15 minutes to form a base pulp; (2) Mixing of main materials: Add waterborne epoxy resin emulsion and chopped synthetic fibers to the base slurry at a speed of 200-300 rpm and disperse for 3-5 minutes; (3) Dispersion of cementitious materials: Add the cementitious materials at a speed of 200-300 rpm and stir for 2-3 minutes; (4) Final setting trigger: Add water-based epoxy curing agent and stir at 200-300 rpm for 3-5 minutes to obtain the shield water-stopping paste.

[0031] The core of this invention lies in the design of a material with "instantaneous sealing, continuous support, and adaptive micro-expansion" characteristics, based on a profound understanding of the dynamic formation and evolution of the shield tail gap. This material is achieved through the temporal synergistic effect of its components, as detailed below: 1. The "thixotropic-rheological" control principle in the injection stage: The shield tunneling sealing compound must first possess excellent construction performance. The compound of this invention is a typical yield-pseudoplastic fluid. Under the high shear rate of pumping, the fragile three-dimensional network structure formed by attapulgite soil and short fibers is destroyed, and the compound viscosity drops sharply (shear thinning), making it easy to pump. Once injected into the low-shear or even shear-free environment of the shield tail gap, the network structure instantly recovers (thixotropy), the viscosity rapidly increases, generating sufficient yield stress to resist the scouring force of groundwater and its own weight, thus immediately adhering to the shield shell and effectively filling the voids, achieving "instantaneous sealing." This is fundamentally different from the principle of traditional bentonite slurry, which is prone to flow after injection and requires a long period of settling to thicken.

[0032] 2. The synergistic gelation principle of "organic-inorganic dual network" in the stabilization stage: After the initial sealing, the paste needs to quickly establish a stable structure. Two key, mutually reinforcing reactions occur during this stage: Rapid Construction of Inorganic Network: A specially formulated sulfoaluminate cementitious material rapidly hydrates upon contact with water, generating a large number of needle-like ettringite crystals and hydrated calcium silicate (CSH) gel. The growth of ettringite crystals fills the micropores and generates micro-expansion pressure (see point 3 below for the principle), while the CSH gel provides early strength. This process can form a preliminary inorganic framework within hours.

[0033] Simultaneous cross-linking of the organic network: The reaction between the waterborne epoxy resin and the curing agent occurs simultaneously, forming a tough, continuous three-dimensional polymer network. The key functions of this organic network are: a) to encapsulate incompletely hydrated cement and bentonite particles, preventing them from being washed away by water; b) to bridge newly formed inorganic hydration products, firmly binding brittle inorganic crystals together through intermolecular hydrogen bonds and van der Waals forces, forming an organic-inorganic interpenetrating network (IPN) structure. This "rigid-flexible" structure allows the paste to achieve early strength while also possessing excellent toughness and crack resistance, avoiding the risk of brittle cracking inherent in pure cement materials.

[0034] 3. The self-stress principle of "micro-expansion-compensation contraction" during the densification stage: Traditional materials often experience volume shrinkage during hardening due to water loss or chemical reduction, leading to "gaps" between the material and the shield or soil, creating seepage channels. One of the core innovations of this invention lies in the proactive introduction of a controllable micro-expansion effect. The principle involves precisely controlling the ratio of sulfoaluminate cement to gypsum, promoting the hydration reaction to primarily produce ettringite. Etringite crystals contain a large amount of water of crystallization, with a volume approximately 1.5 times that of the reactants. This volume expansion within the confined space (shield tail gap) generates self-stress, actively compacting the pores of the paste and ensuring a tight fit against the shield and surrounding soil, perfectly compensating for any shrinkage that might be caused by other components. This "self-expansion, self-compacting" effect ensures the long-term reliability of the sealing effect.

[0035] 4. The "fiber toughening and impermeability" barrier principle for long-term durability: Dispersed chopped synthetic fibers act as physical reinforcements, similar to steel bars, within the system. Randomly distributed in three-dimensional space, they effectively dissipate and disperse energy generated by external loads (such as changes in ground pressure and vibrations from tunnel boring machine correction), preventing the propagation of microcracks and significantly improving the impact toughness and durability of the paste. The resulting dense organic-inorganic composite, with its pores filled with polymers and hydration products, exhibits extremely high tortuosity, forming a long-term and effective impermeability barrier.

[0036] In summary, this invention is designed based on the principle of "time-sequential synergy": the thixotropic agent and fiber ensure instantaneous sealing; the synergistic gelation of epoxy resin and cementing material achieves rapid stabilization; the controlled formation of ettringite brings active compaction; and the fiber ensures long-term durability. These four stages are interconnected, jointly achieving comprehensive performance that is unattainable by existing technologies.

[0037] The present invention will be further described below through preferred embodiments and comparative examples, but the scope of protection of the present invention is not limited thereto.

[0038] Example 1 Formula: 20 parts waterborne epoxy resin emulsion, 5.5 parts modified waterborne amine epoxy curing agent, 25 parts sodium bentonite, 1.5 parts short-cut polypropylene fiber (9mm), 10 parts cementitious material (sulfoaluminate cement clinker: anhydrous gypsum = 4:1), 1.2 parts attapulgite, 40 parts water, and 0.2 parts polycarboxylate superplasticizer (as a percentage of total).

[0039] preparation: 1. Pre-hydration pulping: Add 40 parts water and 0.16 parts water-reducing agent to a planetary mixer. Slowly add 25 parts sodium bentonite and 1.2 parts attapulgite at 300 rpm. After the addition is complete, increase the speed to 550 rpm and continue high-speed shearing and mixing for 15 minutes to obtain a uniform and viscous base slurry.

[0040] 2. Mixing the main ingredients: Reduce the speed of the mixer to 250 rpm, add 20 parts of water-based epoxy resin emulsion and 1.5 parts of polypropylene fiber to the base slurry, stir for 4 minutes until the fiber is completely dispersed and there are no visible fiber clumps.

[0041] 3. Dispersing the gelling material: Keep the speed at 250 rpm, slowly add 10 parts of gelling material (pre-mixed evenly), stir for 3 minutes to ensure that the powder is completely wetted and the slurry is uniform.

[0042] 4. Final setting trigger: Finally, add 5.5 parts of water-based epoxy curing agent and stir at 250 rpm for 4 minutes to obtain a uniform, delicate, and glossy paste, which is the shield tunneling waterstop paste of this invention.

[0043] Example 2 Formula: 18 parts epoxy emulsion, 5 parts curing agent, 22 parts bentonite, 1.2 parts fiber, 9 parts cementing material, 1.0 part attapulgite, 38 parts water, and 0.15 parts water-reducing agent.

[0044] The preparation method is the same as in Example 1.

[0045] Comparative Example 1 (Traditional mud-repelling effect) Mix 30 parts sodium bentonite and 70 parts water with simple mechanical stirring for 20 minutes.

[0046] Comparative Example 2 (without epoxy system) The formulation is the same as in Example 1, but without the addition of water-based epoxy resin emulsion and curing agent; water is used to make up the difference.

[0047] Comparative Example 3 (Cementitious material replaced with ordinary Portland cement) The formula is the same as in Example 1, but the cementitious material is replaced with an equal amount of PO 42.5 ordinary Portland cement.

[0048] Comparative Example 4 (Change in preparation process) All components of Example 1 were added at once and stirred at the same speed (400 rpm) for 15 minutes.

[0049] Performance testing methods and results Table 1: Test Results of Basic Physical and Mechanical Properties Test Project Test standards / methods Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Density (g / cm³) GB / T 208 1.68 1.65 1.45 1.62 1.70 1.69 Water exudation rate (2h, %) static observation 0 0 8.5 1.2 2.8 0.5 Initial setting time (min) Vicat method 145 155 - 110 185 130 6-hour compressive strength (MPa) GB / T 17671 1.05 0.88 0.02 (Unformed) 0.40 0.15 0.65 24-hour compressive strength (MPa) GB / T 17671 2.65 2.20 0.10 1.35 1.80 2.40 28-day compressive strength (MPa) GB / T 17671 4.50 4.10 0.15 3.20 25.50 4.80 24h free expansion rate (%) Length measurement method +1.30 +1.10 -4.20 (contraction) +0.70 -0.50 (contraction) +0.25 Thixotropic ratio Rotational viscometer (6 rpm / 60 rpm) 4.10 3.80 2.90 3.50 3.20 3.60

[0050] Table 2: Results of Water Dispersion Resistance and Durability Tests Test Project Test methods Example 1 Comparative Example 1 Comparative Example 2 Formation after 24 hours of water preservation Immerse the Φ50mm×50mm cylindrical specimen in the water tank. The shape is intact, the edges are clear, and the surface is not softened or peeling. Completely disintegrates, mixes with water to form a slurry The surface is severely softened and the edges are peeling off. Water dispersibility (weight retention, %) Mass loss rate of specimens after immersion in water for 24 hours 98.2% 28.5% 83.0% Resistance to dynamic water erosion (mass loss rate, %) The specimen was flushed with 0.2 MPa water for 30 minutes. 2.1% 100% (completely dissolved) 15.5% Wet bond strength (with concrete, MPa) Test after immersion in water for 7 days 1.20 Unable to test 0.45 Impermeability pressure (MPa) Permeability test was conducted on the specimens after 28 days of curing. >1.5 Unable to form 0.4 28-day shrinkage rate (%) Length measurement method +0.05 (Slight expansion) -0.85 (contraction) -0.20 (contraction)

[0051] Table 3: Performance Tests under Simulated Engineering Conditions Test Project Test methods Results of Example 1 Comparative Example 1 Results Fill rate test The paste was injected into a transparent model simulating the shield tail gap (the upper wall is a steel plate and the lower wall is sand), left to stand for 2 hours, and the thickness difference between the upper and lower layers of paste was measured. Thickness difference < 1%, paste adheres evenly to the top plate, no settling. The lower layer of paste deposits while the upper layer precipitates clear water, with a thickness difference of >30%, indicating that the top plate filling has failed. Adaptability to different strata The paste was injected into a mold containing saturated medium sand and pebbles (10-20mm in diameter), and after curing for 7 days, the interface was cut open to observe. The paste is tightly bonded to the sand and pebbles, forming a whole, with no visible gaps at the interface. The paste and aggregate are loosely bonded, with obvious water film and gaps at the interface. Long-term water immersion stability The specimens were soaked in tap water for 90 days. The strength increased to 5.0 MPa, the specimen remained intact, the surface hardness was high, and there was no softening or cracking. The specimen completely disintegrated within 7 days.

[0052] Data Analysis and Conclusions 1. The core role of the epoxy system: Compared with Comparative Example 2, the introduction of epoxy resin increased the 6-hour early strength by 162% (from 0.40 MPa to 1.05 MPa) and the water dispersion resistance from 83% to 98.2%. This eloquently demonstrates the decisive contribution of the organic three-dimensional network to providing immediate structural strength and erosion resistance, which is not found in conventional materials and Comparative Example 2.

[0053] 2. The criticality of specialized cementitious materials: Comparing Example 1 and Comparative Example 3, although Comparative Example 3 showed high 28-day strength, its 6-hour strength was low (0.15 MPa), and its volume shrinkage was 0.5% after 24 hours. In contrast, Example 1 of this invention exhibited 1.3% micro-expansion within 24 hours, and its 6-hour strength reached 1.05 MPa. This demonstrates the unique advantages of sulfoaluminate-based cementitious materials in achieving "early strength" and "micro-expansion," perfectly meeting the requirements of shield tunneling for rapid support and zero shrinkage.

[0054] 3. Importance of precise proportioning: The 24-hour expansion rate of Comparative Example 4 (cement: gypsum = 2:1) was only 0.25%, far lower than the 1.30% of Example 1. This indicates that insufficient gypsum content leads to insufficient formation of ettringite, significantly weakening the micro-expansion effect, thus verifying the non-obviousness and technical effectiveness of the specific proportion of 4:1 in this invention.

[0055] 4. Superior Overall Performance: In tests simulating actual working conditions, the product of this invention (Example 1) performed perfectly in terms of topslab filling, resistance to dynamic water erosion, and adhesion to the formation, while the traditional material (Comparative Example 1) completely failed. This fully demonstrates that this invention provides a practical and effective solution to address engineering pain points.

[0056] In summary, the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any changes, modifications, and evolutions made by those skilled in the art without departing from the scope of the present invention based on the disclosed technical content shall be considered equivalent embodiments of the present invention. Furthermore, any changes, modifications, and evolutions made to the above embodiments based on the essential technology of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A shield tunnel waterproofing compound, characterized in that, By weight, it consists of the following components: 15-25 parts of waterborne epoxy resin emulsion; 4 to 7 parts of water-based epoxy curing agent; Sodium-based bentonite 20-30 parts; 1 to 2 parts of chopped synthetic fibers; 8-12 parts of cementitious material; Thixotropic agent 1 to 1.5 parts; 35-45 parts water; The three-dimensional cross-linked network formed by the reaction of the waterborne epoxy resin emulsion and the waterborne epoxy curing agent can combine with the hydration products of the sodium-based bentonite and the cementitious material through hydrogen bonds and / or ionic bonds to form an organic-inorganic hybrid structure. The cementitious material is composed of rapid-hardening sulfoaluminate cement clinker and anhydrous gypsum in a weight ratio of 4:

1. When the cementitious material is hydrated, it can generate ettringite crystals, causing the waterproofing sealant to undergo a slight volume expansion of 0.5% to 2.0%.

2. The shield tunneling waterproofing compound as described in claim 1, characterized in that, The chopped synthetic fibers are polypropylene fibers or polyvinyl alcohol fibers with a length of 6-12 mm.

3. The shield tunneling waterproofing compound as described in claim 1, characterized in that, The thixotropic agent is attapulgite clay with a mesh size of 300-500.

4. The shield tunneling waterproofing compound as described in claim 1, characterized in that, It also contains 0.1-0.3% polycarboxylate superplasticizer by weight of the paste.

5. A method for preparing a shield tunneling waterproofing compound, characterized in that, Includes the following steps: (1) Pre-hydration pulping: Water, thixotropic agent, and sodium bentonite are mixed at a high shear rate of 500-600 rpm for 15 minutes to form a base pulp; (2) Mixing of main materials: Add waterborne epoxy resin emulsion and chopped synthetic fibers to the base slurry at a speed of 200-300 rpm and disperse for 3-5 minutes; (3) Dispersion of cementitious materials: Add the cementitious materials at a speed of 200-300 rpm and stir for 2-3 minutes; (4) Final setting trigger: Add water-based epoxy curing agent and stir at 200-300 rpm for 3-5 minutes to obtain the shield water-stopping paste.

6. The method for preparing a shield tunneling waterproofing compound as described in claim 5, characterized in that, In step (1), if a water-reducing agent is used, the water-reducing agent is added together with the water.

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