Tunnel prefabricated inverted arch block waterproof structure and manufacturing method

Abstract

The manufacturing method mainly comprises the following steps that firstly, an adhesive tape core layer is prepared, specifically, ethylene propylene diene monomer, 2, 6-butylated hydroxytoluene, nanoscale silicon dioxide particles, polytetrafluoroethylene fibers and a silane coupling agent are prepared according to the specific weight part, and the adhesive tape core layer is prepared; the preparation method comprises the steps of surface modification, mixing, plastication, vulcanization molding and the like. Then preparing a porous outer layer, preparing polyurethane sponge, water-absorbent resin powder, a water-based binder and an auxiliary agent in proportion, preparing filling slurry, filling and drying; then bonding and curing the adhesive tape core layer and the two porous outer layers; and finally, spraying a protective coating outside the combined structure, and drying and curing to obtain the sealing rubber strip. Aiming at special working conditions such as tunnel TBM construction vibration and complex environment, the defects of a traditional sealing rubber strip in the aspects of vibration environment adaptability, raw material collaboration, protection durability and the like are effectively overcome, and the waterproof reliability and durability of a tunnel are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction waterproofing, and more specifically, to a tunnel prefabricated invert block waterproofing structure and a manufacturing method thereof. Background Art

[0002] In the field of tunnel engineering, with the widespread application of tunnel boring machine (TBM) construction technology, the waterproofing problem of tunnel TBM invert precast blocks has become increasingly critical. TBM construction is characterized by high efficiency and speed, but the construction process is accompanied by strong and continuous vibrations, and its vibration frequency is usually in the range of 10 Hz to 50 Hz. At the same time, the construction site space is limited and the environment is complex and changeable, including temperature and humidity fluctuations and frequent mechanical and sand and gravel interference and other unfavorable factors.

[0003] When traditional sealing strips are used to waterproof tunnel invert precast blocks, conventional rubber materials are mostly used and are not optimized for the vibration environment of TBM construction. Ordinary rubber has poor damping performance under long-term vibration and is prone to fatigue damage, resulting in a sharp decline in sealing performance. It is unable to effectively prevent groundwater leakage, threatening the durability and stability of the tunnel structure. In addition, the compatibility between the raw materials of traditional sealing strips is poor. For example, the silica particles are not firmly bonded to the rubber matrix, and it is difficult to coordinate the force under vibration conditions, and it is impossible to provide sufficient mechanical strength support for the strips. If polytetrafluoroethylene fibers are not specially treated, they are easy to shift during vibration and cannot stably exert their tear-resistant reinforcement effect.

[0004] Therefore, the existing tunnel invert precast block waterproofing technology cannot adapt to the special working conditions of TBM construction. There is an urgent need for a new waterproof structure manufacturing method specifically for tunnel TBM invert precast blocks to ensure the waterproofing quality of the tunnel under complex construction conditions and ensure the long-term stable operation of the tunnel project. Summary of the invention

[0005] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0006] The present invention aims to provide a waterproof structure and a manufacturing method thereof that can effectively cope with the special working conditions of tunnel TBM invert prefabricated blocks, overcome the defects of traditional sealing strips in terms of adaptability to vibration environments, raw material synergy, and protective durability, and ensure the reliability and durability of tunnel waterproofing.

[0007] In order to achieve these purposes and other advantages according to the present invention, a method for manufacturing a tunnel prefabricated invert block waterproof structure is provided, comprising the following steps: S1. Preparation of rubber strip core layer: Prepare, by weight, 60 to 70 parts of EPDM rubber, 3 to 5 parts of 2,6-di-tert-butyl-p-cresol, 5 to 10 parts of nano-scale silica particles, 3 to 6 parts of polytetrafluoroethylene fibers, and 1 to 3 parts of silane coupling agent; Premixing nano-sized silica particles with a silane coupling agent to perform surface modification treatment; The surface-modified nano-scale silica particles are mixed with EPDM rubber and 2,6-di-tert-butyl-p-cresol at an initial temperature of 60°C to 70°C and a final temperature of 90°C to 110°C for 8 min to 12 min. Add polytetrafluoroethylene fiber, continue to heat to 100℃~120℃ and mix for 6 min~10 min to obtain a mixed rubber compound; The mixed rubber material is first plasticized and then vulcanized to obtain the rubber strip core layer; S2. Preparation of porous outer layer: Prepare polyurethane sponge and water-absorbent resin powder at a weight ratio of 1:0.4-0.6, prepare water-based binder at a mass fraction of 10%-20% of the water-absorbent resin powder, and prepare an appropriate amount of auxiliary agent; Processing polyurethane sponge into a porous sponge-like structure with a porosity of 30% to 40%; The water-absorbent resin powder and the auxiliary agent are pre-mixed uniformly, and then the aqueous binder is added and mixed uniformly to obtain a filling slurry; The filling slurry is uniformly filled into the porous sponge structure, and then dried to obtain the porous outer layer; S3, bonding the upper and lower surfaces of the rubber strip core layer to the two porous outer layers respectively by bonding, and performing a curing treatment to obtain a combined structure; A protective coating is sprayed on the outer surface of the combined structure, and dried and cured to obtain a sealing strip, namely the tunnel prefabricated invert block waterproof structure.

[0008] Preferably, the total thickness of the sealing rubber strip is 8 mm to 12 mm, wherein the thickness of the core layer of the rubber strip is 4 mm to 6 mm, and the thickness of the porous outer layer is 2 mm to 3 mm.

[0009] Preferably, in step S1, before mixing, the EPDM rubber is subjected to thin-pass plastication, wherein the roller distance is set to 0.5 mm to 1 mm, and the number of thin-passes is set to 5 to 8 times.

[0010] Preferably, in step S1, the surface modification treatment specifically comprises: stirring the nano-scale silica particles and the silane coupling agent at a rotation speed of 1000 rpm to 1500 rpm for 30 min to 60 min.

[0011] Preferably, in step S1, before mixing, the polytetrafluoroethylene fibers are cut into pieces having a length of 3 mm to 5 mm.

[0012] Preferably, in step S1, vulcanization molding is performed at a preset temperature and pressure, wherein the preset temperature is 140° C. to 160° C., the pressure is 10 MPa to 15 MPa, and the vulcanization time is 8 min to 10 min per millimeter of thickness.

[0013] Preferably, in step S2, the water-absorbent resin powder is sodium polyacrylate resin powder, the aqueous binder is aqueous polyurethane binder, and the auxiliary agents are sodium hexametaphosphate and a defoaming agent; The water-absorbent resin powder is stirred at a speed of 300 rpm~500 rpm for 3 min~5 min, then sodium hexametaphosphate and a defoamer are added and stirring is continued for 2 min~3 min, and then sodium polyacrylate resin powder is added, the speed is increased to 800 rpm~1000 rmp, stirring is continued for 5 min~8 min, and then the speed is increased to 1200 rpm~1500 rmp, stirring is continued for 8 min~10 min to obtain the filling slurry.

[0014] Preferably, in step S3, the rubber strip core layer and the porous outer layer are bonded by a two-component polyurethane adhesive, and the two-component polyurethane adhesive comprises component A and component B in a mass ratio of 1:0.1-0.3, wherein component A is a prepolymer containing active hydroxyl groups, and component B is an isocyanate curing agent, and components A and B are mixed evenly within 10 minutes before performing the bonding action.

[0015] Preferably, in step S3, the protective coating is an anti-organic fluorine protective coating, nanoparticles are added to the anti-organic fluorine protective coating, the nanoparticles are selected from titanium dioxide or aluminum oxide, the average particle size of the nanoparticles is 20 nm~50 nm, and the amount of nanoparticles added is 3%~5% of the total mass of the anti-organic fluorine protective coating.

[0016] The invention provides a tunnel prefabricated invert block waterproof structure manufactured based on the manufacturing method.

[0017] The present invention has at least the following beneficial effects: First, the selected EPDM rubber has a damping coefficient of not less than 0.2 under low-frequency vibration, which can effectively absorb the vibration energy of TBM construction and reduce fatigue damage of the sealing strip. In the test simulating TBM construction vibration, after a long period of vibration, the sealing strip of the present invention has good structural integrity and no obvious damage caused by vibration occurs.

[0018] Second, the nano-scale silica particles are tightly combined with the rubber matrix after surface modification to improve the mechanical strength; the polytetrafluoroethylene fibers are evenly dispersed in the rubber after treatment to form an effective tear-resistant network; the silane coupling agent ensures the connection between the raw materials. According to the test, the tensile strength of the rubber strip of the present invention can reach 12 MPa~14 MPa, which is much higher than the 8 MPa~10 MPa of the traditional rubber strip, effectively enhancing the ability of the rubber strip to resist external pulling and extrusion.

[0019] Third, the water absorption of the porous outer layer and the waterproof sealing performance of the core layer of the rubber strip work together to form a double waterproof barrier. In the simulated tunnel groundwater environment test, after one year, the leakage rate of the sealing rubber strip of the present invention was only 5% when the water pressure rose to 2 MPa, while the leakage rate of other sealing rubber strips was as high as 40%~50% when the water pressure was 1.2 MPa~1.3 MPa, which significantly improved the waterproof effect.

[0020] Fourth, the anti-organic fluorine protective coating adds nanoparticles to enhance wear resistance and scratch resistance, and extend the life of the sealing strip. In a one-year test simulating a complex tunnel environment (containing minerals, microorganisms and corrosive gases), the surface of the sealing strip of the present invention only has a slight color change, and the physical property decay rate is low, while other sealing strips have severe aging phenomena such as hardening, cracking, and microbial breeding, with a tensile strength decay of 30% to 40%, and a break elongation reduction of 25% to 33.3%.

[0021] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a schematic diagram of the manufacturing process of the tunnel prefabricated invert block waterproof structure. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0024] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the orientation or positional relationship indicated by the terms is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0025] like Figure 1As shown, the present invention provides a method for manufacturing a tunnel prefabricated invert block waterproof structure, comprising the following steps: S1. Preparation of rubber strip core layer: In terms of weight, 60 to 70 parts of EPDM rubber, 3 to 5 parts of 2,6-di-tert-butyl-p-cresol, 5 to 10 parts of nano-silica particles, 3 to 6 parts of polytetrafluoroethylene fibers and 1 to 3 parts of silane coupling agent are prepared; specifically, EPDM rubber has high damping properties, and the damping coefficient of the EPDM rubber is not less than 0.2 under a low-frequency vibration environment (frequency range 10 Hz to 50 Hz, simulating the vibration frequency of TBM construction). Its special molecular structure design can convert vibration energy into heat energy through friction and slippage between molecular chains when it is vibrated, effectively absorb the vibration energy during TBM construction, greatly reduce the fatigue damage of the sealing strip caused by long-term vibration, and provide stable basic support performance for the sealing strip. Specifically, nano-scale silica particles, with a particle size in the range of 20 nm to 40 nm, are dried in a vacuum oven at 90°C to 100°C for 2 h to 2.5 h before use. The small particle size gives them a large specific surface area, which can form more contact points with the rubber matrix (EPDM rubber). After drying to remove surface moisture, they can better entangle and combine with the rubber molecule (EPDM rubber) chain in subsequent processing, significantly improving the mechanical strength of the sealing strip in a vibrating environment and enhancing the ability of the strip to resist external pulling and extrusion. Specifically, polytetrafluoroethylene fibers are cleaned in an ultrasonic cleaner with anhydrous ethanol for 12 min to 15 min before use to remove surface impurities and ensure good dispersion in the rubber matrix. When the sealing strip is impacted by external forces, the polytetrafluoroethylene fibers can effectively restrain the movement of the rubber molecule chain, prevent crack propagation, and stably exert their tear-resistant reinforcement effect. Specifically, the silane coupling agent has good compatibility with EPDM rubber and nano-scale silica particles, and strong hydrolysis stability. The silane coupling agent has a unique bifunctional structure, and one end can chemically react with the hydroxyl groups on the surface of nano-scale silica particles to form a strong chemical bond, and the other end can entangle with the EPDM rubber molecular chain to build a "molecular bridge" to ensure effective connection between raw materials, adapt to the complex environment during construction, promote the uniform dispersion of various raw materials, and synergistically improve the comprehensive performance of the materials.

[0026] Premix the nano-silica particles with the silane coupling agent for surface modification; specifically, premix the nano-silica particles with the silane coupling agent in a high-speed mixer, control the speed at 1000 rpm~1500 rpm, and stir for 30 min~60 min to complete the surface modification. The strong shear force generated by high-speed stirring enables the silane coupling agent to quickly and evenly coat the surface of the nano-silica particles, ensuring that each nano-silica particle can be fully modified, paving the way for subsequent fusion with rubber, avoiding agglomeration, and ensuring the consistency of the performance improvement effect.

[0027] The surface-modified nano-scale silica particles are mixed with EPDM rubber and 2,6-di-tert-butyl-p-cresol for 8 min to 12 min at an initial temperature of 60°C to 70°C and a final temperature of 90°C to 110°C; specifically, before mixing, the EPDM rubber is thin-passed and plasticized on an open mill, with the roller spacing set to 0.5 mm to 1 mm and the number of thin passes set to 5 to 8 times. During this process, the EPDM rubber is subjected to the shear force of the roller, and the molecular chains are oriented, broken and reorganized, which effectively reduces the rubber Mooney viscosity, makes it easier to process, and significantly improves its plasticity. In this way, in the subsequent mixing process, the EPDM rubber can quickly adapt to stress changes, reduce the impact of process fluctuations on the quality of the sealing strip, ensure that the raw materials can be evenly mixed, and form a rubber with stable performance. Specifically, the EPDM rubber after thin-pass plasticization, the nano-scale silica particles after surface modification, and 2,6-di-tert-butyl-p-cresol are transferred to an internal mixer and mixed for 8 min to 12 min at an initial temperature of 60°C to 70°C and a final temperature of 90°C to 110°C. 60°C to 70°C can make the nano-scale silica particles evenly dispersed in the rubber matrix. As the mixing proceeds, the temperature of the internal mixer increases to 90°C to 110°C, the movement of the rubber molecular chain intensifies, and the combination with the nano-scale silica becomes tighter, forming a stable reinforced structure, thereby improving the overall strength of the sealing strip.

[0028] Add polytetrafluoroethylene fiber, continue to heat up to 100℃~120℃ and mix for 6 min~10 min to obtain a mixed rubber material; specifically, continue to heat up to 100℃~120℃ and mix for 6min~10 min. At this temperature, the surface activity of polytetrafluoroethylene fiber is enhanced, and it can quickly bond with the rubber matrix to form a stable reinforcement network in the rubber, give full play to its tear resistance, effectively adapt to the local strong tensile conditions that may occur during TBM construction, and prevent the sealing strip from tearing and breaking when subjected to stress.

[0029] The mixed rubber is first plasticized and then vulcanized to obtain the core layer of the rubber strip; specifically, the mixed rubber is taken out of the internal mixer and re-mixed on the open mixer to adjust the uniformity and plasticity of the rubber. The roller distance is appropriately adjusted according to the thickness requirements of the rubber strip, generally set at 2.5 mm to 3.5 mm. Through re-mixing, the internal structure of the rubber is further optimized to achieve the best molding state, laying a good foundation for subsequent vulcanization molding, ensuring that the internal structure of the core layer of the rubber strip after molding is uniform, without stress concentration points, and stable and reliable performance. Specifically, a rapid vulcanization method is used to put the re-mixed rubber into the mold of a flat vulcanizer, the mold temperature is pre-heated to 140°C to 160°C, and vulcanization molding is performed at a pressure of 10 MPa to 15 MPa, and the vulcanization time is 8 min to 10 min per millimeter of thickness. Based on the cross-linking reaction characteristics of rubber, appropriate high temperature promotes the rapid movement and cross-linking of rubber molecular chains, and high pressure ensures uniform and dense cross-linking. The precisely controlled vulcanization time is adjusted according to the thickness of the rubber strip to ensure that the degree of cross-linking of the rubber strip from the inside to the outside is consistent, and efficiently converted into a high-strength, high-elasticity sealing strip core layer.

[0030] S2. Preparation of porous outer layer: Prepare polyurethane sponge and water-absorbent resin powder at a weight ratio of 1:0.4~0.6, prepare water-based binder at a mass fraction of 10%~20% of water-absorbent resin powder, and prepare appropriate amount of auxiliary agent; specifically, polyurethane sponge is selected from high elasticity and fatigue-resistant varieties, with a tensile strength of not less than 1.5 MPa and a compression permanent deformation rate of not more than 10% (under 70℃, 22h test conditions) to adapt to TBM construction vibration. Specifically, BASF water-based polyurethane dispersion 2655 can be selected as the water-based binder. Specifically, the auxiliary agents include dispersants and defoamers, and the amount of dispersants is 0.6%~0.8% (based on the mass of water-absorbent resin powder), and the amount of defoamers is 0.15%~0.25% (based on the mass of water-absorbent resin powder). Dispersants prevent water-absorbent resin powder from agglomerating and ensure uniform dispersion, and defoamers eliminate stirring bubbles to ensure the density of filling slurry, which together improve the filling effect so that the filling slurry can be quickly and evenly filled in the porous sponge structure.

[0031] The polyurethane sponge is processed into a porous sponge-like structure with a porosity of 30%~40%. Specifically, the porosity is precisely controlled to be 30%~40% to ensure that the pore structure is stable under vibration, creating good conditions for subsequent water absorption, buffering and filling. It can not only effectively absorb the infiltrated moisture, but also buffer the external impact force and protect the core layer of the rubber strip.

[0032] The water-absorbent resin powder and the auxiliary agent are pre-mixed uniformly, and then the water-based binder is added and mixed uniformly to obtain a filling slurry; specifically, the viscosity of the filling slurry is controlled to be between 1200 mPa·s and 2500 mPa·s before filling. Through a multi-step stirring process, the auxiliary agent and the binder are added in sequence, and the rotation speed is gradually increased to ensure uniform mixing, so as to form a slurry with excellent fluidity and adhesion, which is convenient for rapid and uniform filling in the porous sponge structure, so that the water-absorbent resin powder is firmly attached, and the porous outer layer has both water absorption and protection functions, thereby improving the overall waterproofness of the sealing strip.

[0033] The filling slurry is uniformly filled in the porous sponge structure and dried to obtain the porous outer layer; specifically, the filling slurry is uniformly filled in the porous sponge structure by vacuum impregnation, the vacuum degree is maintained at -0.08 MPa~-0.09 MPa, the impregnation time is 10 min~15 min, and the filling fullness is ensured to be more than 90%, and then dried in an oven at a temperature of 65°C~75°C for 2 h~2.5 h, so that the water-absorbent resin powder is stably solidified in the pores to obtain a porous outer layer with stable performance.

[0034] S3. The upper and lower surfaces of the core layer of the rubber strip are respectively bonded to the two porous outer layers, and cured to obtain a combined structure; specifically, a special adhesive that is room temperature curing type and has high toughness and anti-vibration peeling properties is used, and the adhesive must be evenly applied. The adhesive is a two-component polyurethane adhesive, including component A and component B with a mass ratio of 1:0.1~0.3, wherein component A is a prepolymer containing active hydroxyl groups, and component B is an isocyanate curing agent. Components A and B are mixed evenly within 10 minutes before performing the bonding action, and react and cross-link rapidly after mixing to form a high-strength bonding layer at room temperature in a short time, tightly "stitching" the core layer of the rubber strip and the porous outer layer to ensure the integrity of the structure and effectively prevent the layers from peeling off during vibration. Specifically, during the bonding process, the combined structure is fixed by a fixture. The fixture has elastic buffer components that can absorb construction vibrations, ensure bonding accuracy, and prevent dislocation of the layers of sealing strips. The elastic stiffness ranges from 50 N / mm to 100 N / mm, ensuring stable support for the bonding process in a vibrating environment and ensuring the bonding quality.

[0035] A protective coating is sprayed on the outer surface of the combined structure, and dried and cured to obtain a sealing strip, that is, the waterproof structure of the tunnel prefabricated invert block. Specifically, the protective coating is an anti-organic fluorine protective coating, and nanoparticles are added to the anti-organic fluorine protective coating. The nanoparticles are selected from titanium dioxide or aluminum oxide, and the average particle size of the nanoparticles is 20 nm~50 nm, and the addition amount accounts for 3%~5% of the total mass of the anti-organic fluorine protective coating. The role of adding nanoparticles is to enhance the wear resistance and scratch resistance of the protective coating, so that it can effectively cope with the mechanical friction and sand and gravel impact in TBM construction, protect the internal structure from damage, and extend the life of the sealing strip. The spraying thickness is 0.15 mm~0.25 mm, which can not only ensure the protective effect, but also will not affect the flexibility and installation performance of the sealing strip due to the excessive thickness of the protective coating. Specifically, the sprayed sealing strip is cured in an oven at a temperature of 50℃~60℃ and a humidity of 40%~60% for 1.5 h~2 h to ensure the stable adhesion of the protective coating.

[0036] In the above technical solution, the porous outer layer is like a "sponge armor" with fine pores, which is conducive to quickly absorbing the infiltrated water, and can also buffer the external impact to a certain extent, protecting the inner rubber strip core layer. As the "backbone" of the sealing strip, the inner rubber strip core layer has the characteristics of high elasticity and high strength. It is made of raw materials such as EPDM rubber through careful mixing and vulcanization, providing the basic sealing and supporting performance for the entire sealing strip, ensuring that the overall shape and sealing effect of the sealing strip are maintained when subjected to external forces such as pressure and stretching.

[0037] In addition, based on the effect of the two-component polyurethane adhesive, a tough and elastic bonding layer is formed between the porous outer layer and the core layer of the strip. This bonding layer is like a "bridge" that tightly connects the two layers together, allowing them to deform synergistically when subjected to force, without delamination or peeling, thus ensuring the integrity and reliability of the sealing strip.

[0038] In addition, the water absorption of the porous outer layer cooperates with the waterproof and sealing performance of the core layer of the rubber strip. When water seeps in from the outside, the pores in the outer layer first capture the water and slow down the speed of water penetration into the interior, while the inner core layer of the rubber strip relies on its own density to further block the passage of water, forming a double waterproof barrier, which greatly improves the waterproof and sealing effect of the sealing strip in a humid environment.

[0039] In another technical solution, the total thickness of the sealing strip is 8 mm to 12 mm, wherein the thickness of the core layer of the strip is 4 mm to 6 mm, and the thickness of the porous outer layer is 2 mm to 3 mm.

[0040] In the above technical solution, the thickness design can ensure that it has sufficient pore space to realize functions such as water absorption and buffering, and will not weaken the dominant role of the core layer of the rubber strip due to excessive thickness, so as to maintain the main strength and sealing performance of the sealing strip. The width depends on the sealing application scenario. When used for sealing the joints of prefabricated arch blocks of tunnel TBM, the width is mostly between 20 mm and 30 mm to ensure that the joint area can be fully covered, effectively blocking the leakage of groundwater, air and other media, adapting to the changes in the size of the gaps between prefabricated blocks, and providing reliable sealing protection. The sealing strip is customized and produced according to actual use requirements and made into different length specifications. Construction personnel can cut and splice according to the specific length of the sealing part to ensure the convenience and fit of installation.

[0041] In another technical solution, in step S1, before mixing, the polytetrafluoroethylene fibers are cut to 3 mm~5 mm. In the rubber matrix, the shorter fiber length (3 mm~5 mm) can effectively avoid the problem of mutual entanglement and agglomeration between polytetrafluoroethylene fibers, making it easier to disperse evenly. When the rubber material is subjected to processing such as mixing, the short fibers can quickly diffuse in the rubber to ensure that polytetrafluoroethylene fibers are evenly distributed in all parts of the core layer of the rubber strip, thereby providing a stable and consistent reinforcement effect for the entire core layer of the rubber strip, avoiding local performance weaknesses caused by uneven distribution of polytetrafluoroethylene fibers. More importantly, polytetrafluoroethylene fibers in this length range can be more efficiently interwoven to form a tight and regular tear-resistant network structure when blended with rubber. When the sealing strip is pulled by external force, especially under the frequent vibrations caused by TBM construction and possible local strong tensile conditions, these interwoven short fibers are like a dense "reinforcement mesh", which can quickly restrain the movement of rubber molecular chains, prevent the generation and expansion of cracks, greatly improve the tear resistance of the sealing strip, ensure the integrity of the sealing strip structure, and thus maintain a good waterproof sealing effect.

[0042] In another technical solution, in step S2, the water-absorbent resin powder is sodium polyacrylate resin powder, the aqueous binder is aqueous polyurethane binder, and the auxiliary agent is sodium hexametaphosphate and a defoamer; specifically, the defoamer is an existing Foamaster NXZ defoamer or TEGO Foamex 810 defoamer, etc.; The water-absorbent resin powder is stirred at a speed of 300 rpm~500 rpm for 3 min~5 min, then sodium hexametaphosphate and a defoamer are added and stirring is continued for 2 min~3 min, and then sodium polyacrylate resin powder is added, the speed is increased to 800 rpm~1000 rmp, stirring is continued for 5 min~8 min, and then the speed is increased to 1200 rpm~1500 rmp, stirring is continued for 8 min~10 min to obtain the filling slurry.

[0043] In the above technical solution, in the tunnel environment, when groundwater has a tendency to infiltrate, the sodium polyacrylate resin powder can quickly capture and lock in moisture to prevent further penetration of moisture into the sealing strip. This type of resin has good compatibility with different water qualities (such as groundwater containing minerals and with certain changes in pH), and can stably absorb water in complex tunnel water environments. It will not fail or significantly reduce performance due to water quality problems, ensuring a long-term and effective waterproof barrier. The sodium polyacrylate molecular chain contains a large number of hydrophilic groups such as carboxyl groups, which can form hydrogen bonds with water molecules. Water molecules are adsorbed around the resin molecules in large quantities through hydrogen bonding, thereby achieving a rapid water absorption and expansion process and building a strong water absorption network. For the combination of water-absorbent resin powder and polyurethane sponge, the water-based polyurethane binder can form a high-strength bonding layer between the two, ensuring that the water-absorbent resin powder will not fall off from the porous sponge structure during TBM construction vibration and subsequent long-term use, maintaining the integrity of the outer layer structure, and ensuring the synergistic performance of water absorption and buffering functions. As a dispersant, sodium hexametaphosphate can effectively prevent the agglomeration of absorbent resin powder during the mixing process. Under limited stirring conditions, the powder particles are evenly dispersed in the system, making the subsequent mixing with the binder more uniform, ensuring the consistent performance of the filling slurry everywhere, and thus making the water absorption performance of the porous outer layer after filling uniform and stable without local weak points. During the stirring process, air is easily introduced to form bubbles due to high-speed rotation and other operations. The defoaming agent can quickly reduce the surface tension of the liquid and break and eliminate the bubbles. Avoid bubbles mixed in the filling slurry, resulting in loose filling, affecting the strength of the outer layer structure and the filling effect of the absorbent resin powder, and ensuring the density and stability of the outer layer structure.

[0044] Also, at a lower speed, the agglomerates of the water-absorbent resin powder can be initially broken up, making them relatively loose. Since the powder may clump to a certain extent due to storage, transportation and other factors when it is first added to the mixing container, low-speed stirring can not only avoid excessive dust causing material loss and environmental pollution, but also gently separate the powder particles initially to prepare for subsequent uniform mixing. The shear force generated by the stirring speed at this time is small, just enough to overcome the weak agglomeration force between the powder particles, causing the particles to begin to loosen, while not destroying the structural integrity of the powder itself, ensuring that its water absorption performance is not affected. Timely mixing the auxiliary agent with the initially broken up water-absorbent resin powder allows sodium hexametaphosphate to quickly adsorb on the surface of the powder particles to play a dispersing role, preventing re-agglomeration during subsequent high-speed stirring; the defoaming agent is quickly distributed in the system, ready to respond to bubbles generated by stirring, ensuring the stability of the mixing system, and optimizing the initial mixing quality of the slurry. The shorter stirring time is based on the high-efficiency characteristics of the additive, the rapid adsorption kinetics of sodium hexametaphosphate and the rapid migration of the defoamer to the gas-liquid interface, so that the synergistic effect of the additive and the powder can be initially achieved within 2 min~3 min, avoiding energy waste and possible changes in material properties caused by excessive stirring. As the speed increases, the mixing uniformity between the powder and the additive, as well as the subsequently added waterborne polyurethane binder, is further enhanced. The stirring intensity at this time can make the various components fully contact, prompting the waterborne polyurethane binder to initially wrap around the surface of the powder particles and begin to build a bonding system, while maintaining the dispersion effect of sodium hexametaphosphate, laying the foundation for the final formation of a uniform and stable filling slurry. The moderate shear force generated by medium-speed stirring, on the one hand, accelerates the convection diffusion of the material and allows different components to mix quickly; on the other hand, for the waterborne polyurethane binder, this shear force helps its molecular chain to stretch, better interact with the active sites on the surface of the powder particles, and begin to form a preliminary chemical connection to ensure the uniformity and effectiveness of the bonding. After the initial mixing and paving, under this high-speed stirring, the various components are promoted to achieve uniform mixing at the molecular level, forming a filling slurry with stable performance and good fluidity. The chemical cross-linking reaction between the waterborne polyurethane binder and the absorbent resin powder is fully carried out to form a high-strength bonding network; the defoamer continuously eliminates newly generated bubbles to ensure the density of the slurry; the final filling slurry can meet the requirements of uniform and rapid filling in the porous sponge structure, ensuring the quality of the outer layer structure. The strong shear force generated by high-intensity high-speed stirring completely breaks the microscopic uneven areas that may exist between the materials, allowing the waterborne polyurethane binder molecular chains to fully entangle and react with the absorbent resin powder particles, additives, etc. From a rheological point of view, the rheological parameters such as viscosity and thixotropy of the slurry reach the optimal state at this time, which not only has sufficient fluidity for filling, but also can maintain a certain shape stability after filling, ensuring the durability of the filling effect.

[0045] Embodiment 1: 1. Raw material preparation: 65 parts of EPDM rubber, whose damping coefficient at a frequency of 10 Hz to 50 Hz was tested to be 0.2; 5 parts of 2,6-di-tert-butyl-p-cresol; 6 parts of nano-scale silica particles, with a particle size of 20 nm to 40 nm, dried in a vacuum oven at 90°C for 2 h; 4 parts of polytetrafluoroethylene fiber, with a length of 4 mm, ultrasonically cleaned with anhydrous ethanol for 12 min; 2 parts of silane coupling agent; Polyurethane sponge (tensile strength 1.5 MPa, compression permanent deformation rate 10%, porosity 30%) and water-absorbent resin powder are prepared in a weight ratio of 1:0.45. The water-based binder is a quick-drying water-based polyurethane binder (surface drying 10 min, actual drying 30 min). The weight ratio of water-absorbent resin powder to water-based binder is 1:0.15. The additives contain sodium hexametaphosphate (accounting for 0.6% of the weight of the water-absorbent resin powder) and a defoaming agent (accounting for 0.15%).

[0046] 2. Preprocessing: Nano-silica and silane coupling agent were stirred in a high-speed mixer at 1200 rpm for 40 min; EPDM rubber was thinly passed 6 times on an open mill with a roller distance of 0.6 min.

[0047] 3. Mixing: The plasticized EPDM rubber was put into an internal mixer, initially at 65°C, and the pre-treated mixture was added and mixed for 9 min, then the temperature was raised to 95°C; polytetrafluoroethylene fiber was added and mixed at 105°C for 7 min.

[0048] 4. Molding: The rubber compound of the internal mixer was re-refined in an open mixer with a roller distance of 2.5 mm; the mold of the flat vulcanizing machine was set at 150°C and a pressure of 12 MPa, and the vulcanization time was 6 min for every millimeter of thickness to obtain the core layer of the rubber strip.

[0049] 5. Outer layer preparation: The water-absorbent resin powder was stirred at 300 rpm for 3 min, the auxiliary agent was added and stirred for 2 min, and the aqueous binder was added and stirred at 800 rpm for 5 min and 1200 rpm for 8 min in sequence to obtain a filling slurry with a viscosity of 1200 mPa·s and a solid content of 45%; Vacuum impregnation, vacuum degree -0.08 MPa, 10 min, drying at 65℃ for 2 h, to obtain a porous outer layer.

[0050] 6. Combination: Two-component polyurethane adhesive (component A and component B, weight ratio of 1:0.1) was used to bond the core layer of the rubber strip and the porous outer layer. The adhesive was evenly applied and mixed 10 min before bonding. The adhesive was cured at 50°C and 40% humidity for 2 h and fixed with a fixture (rubber spring, stiffness 50 N / mm).

[0051] 7. Protection: The nano-modified anti-organic fluorine protective coating (titanium dioxide, particle size 20 nm, accounting for 3%) was sprayed with a thickness of 0.15 mm; the sealing strip was obtained by drying at 40°C and 40% humidity for 1.5 h.

[0052] 8. Test data: Sealing strip tensile strength: 12MPa, meeting the vibration and pulling requirements of TBM construction; Water absorption rate: 300 times (its own weight), highly efficient water absorption and waterproofing; Wear resistance: wear loss 0.05 g / 1000 revolutions, protective coating is effective; Bonding strength: 2.5 MPa between the core layer of the rubber strip and the porous outer layer, and the structure is stable.

[0053] Embodiment 2: 1. Raw material preparation: 68 parts of EPDM rubber, whose damping coefficient at a frequency of 10 Hz to 50 Hz was tested to be 0.22; 4 parts of 2,6-di-tert-butyl-p-cresol, 7 parts of nano-scale silica particles, with a particle size of 20 nm to 40 nm, dried in a vacuum oven at 95°C for 2 h; 4 parts of polytetrafluoroethylene fiber, with a length of 5 mm, ultrasonically cleaned with anhydrous ethanol for 12 min; 2.5 parts of silane coupling agent; Polyurethane sponge (tensile strength 1.6 MPa, compression permanent deformation rate 8%, porosity 32%) and water-absorbent resin powder are prepared in a weight ratio of 1:0.5. The water-based binder is a quick-drying water-based polyurethane binder (surface drying 8 min, actual drying 25 min). The weight ratio of water-absorbent resin powder to water-based binder is 1:0.18. The additives contain sodium hexametaphosphate (accounting for 0.7% of the weight of the water-absorbent resin powder) and a defoamer (accounting for 0.2%).

[0054] 2. Preprocessing: Nano-silica and silane coupling agent were stirred in a high-speed mixer at 1200 rpm for 45 min; EPDM rubber was thinly passed 7 times in an open mill with a roller distance of 0.7 min.

[0055] 3. Mixing: The plasticized EPDM rubber was put into an internal mixer, initially at 65°C, and the pre-treated mixture was added and mixed for 10 min, then the temperature was raised to 100°C; polytetrafluoroethylene fiber was added and mixed at 110°C for 8 min.

[0056] 4. Molding: The rubber compound of the internal mixer was re-refined on an open mixer with a roller distance of 3 mm; the mold of the flat vulcanizing machine was set at 155°C and a pressure of 12 MPa, and the vulcanization time was 7 min for every millimeter of thickness to obtain the core layer of the rubber strip.

[0057] 5. Outer layer preparation: The water-absorbent resin powder was stirred at 500 rpm for 4 min, the auxiliary agent was added and stirred for 2 min, and the aqueous binder was added and stirred at 900 rpm for 6 min and 1200 rpm for 8 min, respectively, to obtain a filling slurry with a viscosity of 1800 mPa·s; Vacuum impregnation, vacuum degree -0.08 MPa, 12 min, drying at 65℃ for 2 h, to obtain a porous outer layer.

[0058] 6. Combination: Two-component polyurethane adhesive (component A and component B, weight ratio of 1:0.2) is used to bond the core layer of the rubber strip and the porous outer layer. It is evenly applied and mixed 10 min before bonding. It is cured at 50°C and 40% humidity for 2 h and fixed with a tooling fixture (rubber spring, stiffness 70 N / mm).

[0059] 7. Protection: The nano-modified anti-organic fluorine protective coating (aluminum oxide, particle size 30 nm, accounting for 4%) was sprayed with a thickness of 0.2 mm; the sealing strip was obtained by drying at 40°C and 50% humidity for 1.8 h.

[0060] 8. Test data: Sealing strip tensile strength: 13 MPa, meeting the vibration and pulling requirements of TBM construction; Water absorption rate: 320 times (its own weight), highly efficient water absorption and waterproofing; Wear resistance: wear loss 0.04 g / 1000 revolutions, protective coating is effective; Bonding strength: 2.8 MPa between the core layer of the rubber strip and the porous outer layer, with a stable structure.

[0061] Embodiment 3: 1. Raw material preparation: 70 parts of EPDM rubber, whose damping coefficient at a frequency of 10 Hz to 50 Hz was tested to be 0.25; 5 parts of 2,6-di-tert-butyl-p-cresol, 8 parts of nano-scale silica particles, with a particle size of 20 nm to 40 nm, dried in a vacuum oven at 100°C for 2 h; 5 parts of polytetrafluoroethylene fiber, with a length of 5 mm, ultrasonically cleaned with anhydrous ethanol for 12 min; 2.5 parts of silane coupling agent; Polyurethane sponge (tensile strength 1.6 MPa, compression permanent deformation rate 6%, porosity 35%) and water-absorbent resin powder are prepared in a weight ratio of 1:0.5. The water-based binder is a quick-drying water-based polyurethane binder (surface drying 8 min, actual drying 25 min). The weight ratio of water-absorbent resin powder to water-based binder is 1:0.2. The additives contain sodium hexametaphosphate (accounting for 0.8% of the weight of the water-absorbent resin powder) and a defoamer (accounting for 0.2%).

[0062] 2. Preprocessing: Nano-silica and silane coupling agent were stirred in a high-speed mixer at 1500 rpm for 50 min; EPDM rubber was thinly passed 8 times on an open mill with a roller distance of 0.8 min.

[0063] 3. Mixing: The plasticized EPDM rubber was put into an internal mixer, initially at 70°C, and the pre-treated mixture was added and mixed for 10 min, then the temperature was raised to 105°C; polytetrafluoroethylene fiber was added and mixed at 115°C for 8 min.

[0064] 4. Molding: The rubber compound of the internal mixer was re-refined on an open mixer with a roller distance of 3 mm; the mold of the flat vulcanizing machine was set at 160°C and a pressure of 15 MPa, and the vulcanization time was 8 min per millimeter thickness to obtain the core layer of the rubber strip.

[0065] 5. Outer layer preparation: The water-absorbent resin powder was stirred at 500 rpm for 4 min, the auxiliary agent was added and stirred for 3 min, and the aqueous binder was added and stirred at 1000 rpm for 6 min and 1500 rpm for 8 min, respectively, to obtain a filling slurry with a viscosity of 2500 mPa·s; Vacuum impregnation, vacuum degree -0.09 MPa, 15 min, drying at 65℃ for 2 h, to obtain a porous outer layer.

[0066] 6. Combination: Two-component polyurethane adhesive (component A and component B, weight ratio of 1:0.2) was used to bond the core layer of the rubber strip and the porous outer layer. The adhesive was evenly applied and mixed 10 min before bonding. The adhesive was cured at 50°C and 40% humidity for 2 h and fixed with a fixture (rubber spring, stiffness 100 N / mm).

[0067] 7. Protection: The nano-modified anti-organic fluorine protective coating (titanium dioxide, particle size 50 nm, accounting for 5%) was sprayed with a thickness of 0.2 mm; the sealing strip was obtained by drying at 50°C and 50% humidity for 1.8 h.

[0068] 8. Test data: Sealing strip tensile strength: 14 MPa, meeting the vibration and pulling requirements of TBM construction; Water absorption rate: 350 times (its own weight), highly efficient water absorption and waterproofing; Wear resistance: wear loss 0.03 g / 1000 revolutions, protective coating is effective; Bonding strength: 3 MPa between the core layer of the rubber strip and the porous outer layer, and the structure is stable.

[0069] Comparative Example 1: 1. Raw material preparation: 70 parts of ordinary EPDM rubber; 5 parts of 2,6-di-tert-butyl-p-cresol, 8 parts of nano-scale silica particles, with a particle size of 20 nm~40 nm, dried in a vacuum oven at 100℃ for 2 h; 5 parts of polytetrafluoroethylene fiber, with a length of 5 mm, ultrasonically cleaned with anhydrous ethanol for 12 min; 2.5 parts of silane coupling agent; A polyurethane sponge (tensile strength of 1.6 MPa, compression permanent deformation of 6%, porosity of 25%, wherein the porosity was not optimized for vibration) and a water-absorbent resin powder were prepared in a weight ratio of 1:0.5. The water-based binder was a quick-drying water-based polyurethane binder (surface drying for 8 min, actual drying for 25 min). The weight ratio of the water-absorbent resin powder to the water-based binder was 1:0.2. The additives contained sodium hexametaphosphate (accounting for 0.8% of the weight of the water-absorbent resin powder) and a defoamer (accounting for 0.2%).

[0070] 2. Preprocessing: Nano-silica and silane coupling agent were stirred in a high-speed mixer at 1500 rpm for 50 min; EPDM rubber was thinly passed 8 times on an open mill with a roller distance of 0.8 min.

[0071] 3. Mixing: The plasticized EPDM rubber was put into an internal mixer, initially at 70°C, and the pre-treated mixture was added and mixed for 10 min, then the temperature was raised to 105°C; polytetrafluoroethylene fiber was added and mixed at 115°C for 8 min.

[0072] 4. Molding: The rubber compound of the internal mixer was re-refined on an open mixer with a roller distance of 3 mm; the mold of the flat vulcanizing machine was set at 160°C and a pressure of 15 MPa, and the vulcanization time was 8 min per millimeter of thickness to obtain the core layer of the rubber strip.

[0073] 5. Outer layer preparation: The water-absorbent resin powder was stirred at 500 rpm for 4 min, the auxiliary agent was added and stirred for 3 min, and the aqueous binder was added and stirred at 1000 rpm for 6 min and 1500 rpm for 8 min, respectively, to obtain a filling slurry with a viscosity of 2500 mPa·s; Vacuum impregnation, vacuum degree -0.09 MPa, 15 min, drying at 65℃ for 2 h, to obtain a porous outer layer.

[0074] 6. Combination: Two-component polyurethane adhesive (component A and component B, weight ratio of 1:0.2) was used to bond the core layer of the rubber strip and the porous outer layer. The adhesive was evenly applied and mixed 10 min before bonding. The adhesive was cured at 50°C and 40% humidity for 2 h and fixed with a fixture (rubber spring, stiffness 100 N / mm).

[0075] 7. Protection: Ordinary anti-organic fluorine protective coating, spray 0.2 mm thick; 50℃, 50% humidity, dry for 1.8 h to obtain the sealing strip.

[0076] 8. Test data: Sealing strip tensile strength: 8 MPa, unable to withstand the vibration and pulling requirements of TBM construction; Water absorption rate: 200 times (its own weight), poor water absorption effect; Wear resistance: wear loss 0.15 g / 1000 revolutions, poor protection; Bonding strength: 1.5 MPa between the core layer of the adhesive strip and the porous outer layer, easy to delaminate.

[0077] Comparative Example 2: 1. Raw material preparation: 70 parts of EPDM rubber, whose damping coefficient at a frequency of 10 Hz to 50 Hz was tested to be 0.25; 8 parts of nano-scale silica particles, with a particle size of 20 nm to 40 nm, dried in a vacuum oven at 100°C for 2 h; 5 parts of polytetrafluoroethylene fiber, with a length of 5 mm, ultrasonically cleaned with anhydrous ethanol for 12 min; 2.5 parts of silane coupling agent; Polyurethane sponge (tensile strength 1.6 MPa, compression permanent deformation rate 6%, porosity 35%) and water-absorbent resin powder are prepared in a weight ratio of 1:0.5. The water-based binder is a quick-drying water-based polyurethane binder (surface drying 8 min, actual drying 25 min). The weight ratio of water-absorbent resin powder to water-based binder is 1:0.2. The additives contain sodium hexametaphosphate (accounting for 0.8% of the weight of the water-absorbent resin powder) and a defoamer (accounting for 0.2%).

[0078] 2. Preprocessing: Nano-silica and silane coupling agent were stirred in a high-speed mixer at 1500 rpm for 50 min; EPDM rubber was thinly passed 8 times on an open mill with a roller distance of 0.8 min.

[0079] 3. Mixing: The plasticized EPDM rubber was put into an internal mixer, initially at 70°C, and the pre-treated mixture was added and mixed for 10 min, then the temperature was raised to 105°C; polytetrafluoroethylene fiber was added and mixed at 115°C for 8 min.

[0080] 4. Molding: The rubber compound of the internal mixer was re-refined on an open mixer with a roller distance of 3 mm; the mold of the flat vulcanizing machine was set at 160°C and a pressure of 15 MPa, and the vulcanization time was 8 min per millimeter thickness to obtain the core layer of the rubber strip.

[0081] 5. Outer layer preparation: The water-absorbent resin powder was stirred at 500 rpm for 4 min, the auxiliary agent was added and stirred for 3 min, and the aqueous binder was added and stirred at 1000 rpm for 6 min and 1500 rpm for 8 min, respectively, to obtain a filling slurry with a viscosity of 2500 mPa·s; Vacuum impregnation, vacuum degree -0.09 MPa, 15 min, drying at 65℃ for 2 h, to obtain a porous outer layer.

[0082] 6. Combination: Use common adhesive to bond the two parts, apply evenly, cure at 50℃ and 40% humidity for 2 h, and fix with a fixture (rubber spring, stiffness 100N / mm).

[0083] 7. Protection: The nano-modified anti-organic fluorine protective coating (titanium dioxide, particle size 50 nm, accounting for 5%) was sprayed with a thickness of 0.2 mm; the sealing strip was obtained by drying at 50°C and 50% humidity for 1.8 h.

[0084] 8. Test data: Sealing strip tensile strength: 10 MPa, limited vibration resistance; Water absorption rate: 300 times (own weight), normal water absorption; Wear resistance: wear loss 0.1 g / 1000 revolutions, general protection; Bonding strength: 1.8 MPa between the core layer of the rubber strip and the porous outer layer. Local peeling is prone to occur under vibration.

[0085] Application examples: The mountain tunnel project is 10 kilometers long and uses the TBM construction method. The humidity inside the tunnel is maintained at 80% to 90% all year round. The groundwater is abundant, and the water contains various minerals such as calcium, magnesium, and iron. The microbial content is also high. At the same time, the air in the cave contains a certain amount of corrosive gases such as sulfur dioxide. The selection of the sealing strip of the prefabricated block waterproof structure of the tunnel invert is very important. For this reason, the improved sealing strip (the sealing strip made in Example 3) and the sealing strips made in Comparative Examples 1 and 2 (respectively recorded as strip A and strip B) are compared and tested.

[0086] 1. Specimen preparation: Three types of sealing strips were used to make prefabricated block specimens of the same specifications. There were 10 specimens in each group. The specimen dimensions were based on the actual tunnel use standards, with a length of 1 m and a width of 0.5 m. The joint width between the prefabricated blocks was uniformly set to 15 mm.

[0087] Install corresponding sealing strips at the joints of prefabricated blocks and follow standard construction processes to ensure consistent installation quality to simulate the actual splicing of prefabricated blocks of tunnel inverts.

[0088] 2. Test environment simulation: A special simulated tunnel environment test chamber was built, the temperature inside the chamber was controlled at 10℃~40℃, the humidity was maintained at 80%~90% through a spray device, and calcium and magnesium ion concentrations of 100 mg / L and 50 mg / L, respectively, were injected into the test chamber, and microorganisms (Escherichia coli, sulfate-reducing bacteria, concentrations of 10³~10 4 CFU / mL) and simulated groundwater with a sulfur dioxide concentration of 10 ppm were continuously circulated to simulate the humid and chemically complex environment in the tunnel.

[0089] 3. Test data: After one year of simulation test, the test pieces were taken out for observation. The surface of the rubber strip A showed obvious hardening and cracking, with white mineral precipitates in some areas, yellowing, loss of luster, and obvious decrease in elasticity, and it was difficult to deform by hand; the rubber strip B also showed signs of aging to varying degrees, with the surface becoming soft and sticky, black spots formed by microbial growth, weakened elasticity, and easy to break when stretched; while the surface of the improved sealing strip (Example 3) had only slight color changes, the texture was still clear, the elasticity was good, and it could quickly return to its original state after being pressed, with no obvious hardening, softening or microbial growth.

[0090] Physical performance test: Tensile strength: According to GB / T 528-2009 standard, the specimens were tested on a universal material testing machine after one year of use. The initial tensile strength of the rubber strip A was 8 MPa, which decayed to 4.8 MPa after one year, with a decay rate of 40%; the initial tensile strength of the rubber strip B was 10 MPa, which decayed to 7 MPa after one year, with a decay rate of about 30%; the initial tensile strength of the improved sealing strip was 14 MPa, which remained at 12 MPa after one year, with a decay rate of no more than 14.3%, indicating that it can better maintain its own strength while resisting environmental erosion.

[0091] Elongation at break: Also tested according to the above standards, the initial elongation at break of Strip A was 300%, which dropped to 200% after one year, a decrease of 33.3%; the initial elongation at break of Strip B was 320%, which dropped to 240% after one year, a decrease of 25%; the initial elongation at break of the improved sealing strip was 350%, which was still maintained above 300% after one year, with a decrease of no more than 14.3%, showing good flexibility maintenance ability.

[0092] Waterproof performance test: The three groups of specimens were put back into the simulated environmental test chamber, and the water pressure was gradually increased from 0 to 12 hours after each increase of 0.5 MPa. When the water pressure of strip A reached 1.2 MPa, 50% of the specimens leaked; when the water pressure of strip B reached 1.3 MPa, the leakage rate reached 40%; and when the water pressure of the improved sealing strip rose to 2 MPa, the leakage rate was only 5%, which fully proved its excellent waterproof performance. Even after one year of erosion in the harsh environment, it can still effectively seal the joints and prevent groundwater infiltration.

[0093] The test data is shown in Table 1: Table 1 Test data Through comparative tests in simulated tunnel environments with humid and complex chemical environments, the improved sealing strip has shown excellent resistance to erosion by minerals, microorganisms contained in groundwater and air components in the cave. Compared with strips A and B, it can significantly reduce rubber aging, maintain good elasticity, physical properties and waterproof properties, effectively ensure the waterproof effect of the joints of the TBM invert precast blocks, greatly extend the service life of the sealing strip, and provide strong support for the long-term and stable operation of the tunnel project.

[0094] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for manufacturing a tunnel prefabricated invert block waterproof structure, characterized in that: The following steps are involved: S1. Preparation of rubber strip core layer: Prepare, by weight, 60 to 70 parts of EPDM rubber, 3 to 5 parts of 2,6-di-tert-butyl-p-cresol, 5 to 10 parts of nano-scale silica particles, 3 to 6 parts of polytetrafluoroethylene fibers, and 1 to 3 parts of silane coupling agent; Premixing nano-sized silica particles with a silane coupling agent to perform surface modification treatment; The surface-modified nano-scale silica particles are mixed with EPDM rubber and 2,6-di-tert-butyl-p-cresol at an initial temperature of 60°C to 70°C and a final temperature of 90°C to 110°C for 8 min to 12 min. Add polytetrafluoroethylene fiber, continue to heat to 100℃~120℃ and mix for 6 min~10 min to obtain a mixed rubber compound; The mixed rubber material is first plasticized and then vulcanized to obtain the rubber strip core layer; S2. Preparation of porous outer layer: Prepare polyurethane sponge and water-absorbent resin powder at a weight ratio of 1:0.4-0.6, prepare water-based binder at a mass fraction of 10%-20% of the water-absorbent resin powder, and prepare an appropriate amount of auxiliary agent; Processing polyurethane sponge into a porous sponge-like structure with a porosity of 30% to 40%; The water-absorbent resin powder and the auxiliary agent are pre-mixed uniformly, and then the aqueous binder is added and mixed uniformly to obtain a filling slurry; The filling slurry is uniformly filled into the porous sponge structure, and then dried to obtain the porous outer layer; S3, bonding the upper and lower surfaces of the rubber strip core layer to the two porous outer layers respectively by bonding, and performing a curing treatment to obtain a combined structure; A protective coating is sprayed on the outer surface of the combined structure, and dried and cured to obtain a sealing strip, namely the tunnel prefabricated invert block waterproof structure.

2. The method for manufacturing a tunnel prefabricated invert block waterproof structure according to claim 1, characterized in that: The total thickness of the sealing rubber strip is 8 mm to 12 mm, wherein the thickness of the core layer of the rubber strip is 4 mm to 6 mm, and the thickness of the porous outer layer is 2 mm to 3 mm.

3. The method for manufacturing a tunnel prefabricated invert block waterproof structure according to claim 1, characterized in that: In step S1, before mixing, the EPDM rubber is subjected to thin-pass plastication, wherein the roller distance is set to 0.5 mm to 1 mm, and the number of thin-passes is set to 5 to 8 times.

4. The method for manufacturing a tunnel prefabricated invert block waterproof structure according to claim 1, characterized in that: In step S1, the surface modification treatment specifically includes: stirring the nano-scale silica particles and the silane coupling agent at a rotation speed of 1000 rpm to 1500 rpm for 30 min to 60 min.

5. The method for manufacturing a tunnel prefabricated invert block waterproof structure according to claim 1, characterized in that: In step S1, before mixing, the polytetrafluoroethylene fiber is cut into pieces of 3 mm to 5 mm.

6. The method for manufacturing a tunnel prefabricated invert block waterproof structure according to claim 1, characterized in that: In step S1, vulcanization molding is performed at a preset temperature and pressure, wherein the preset temperature is 140° C. to 160° C., the pressure is 10 MPa to 15 MPa, and the vulcanization time is 8 min to 10 min per millimeter of thickness.

7. The method for manufacturing a tunnel prefabricated invert block waterproof structure according to claim 1, characterized in that: In step S2, the water-absorbent resin powder is sodium polyacrylate resin powder, the aqueous binder is aqueous polyurethane binder, and the auxiliary agents are sodium hexametaphosphate and a defoaming agent; The water-absorbent resin powder is stirred at a speed of 300 rpm~500 rpm for 3 min~5 min, then sodium hexametaphosphate and a defoamer are added and stirring is continued for 2 min~3 min, and then sodium polyacrylate resin powder is added, the speed is increased to 800 rpm~1000rmp, stirring is continued for 5 min~8 min, and then the speed is increased to 1200 rpm~1500 rmp, stirring is continued for 8 min~10 min to obtain the filling slurry.

8. The method for manufacturing a tunnel prefabricated invert block waterproof structure according to claim 1, characterized in that: In step S3, the rubber strip core layer and the porous outer layer are bonded by a two-component polyurethane adhesive, wherein the two-component polyurethane adhesive comprises component A and component B in a mass ratio of 1:0.1-0.3, wherein component A is a prepolymer containing active hydroxyl groups, and component B is an isocyanate curing agent, and component A and component B are mixed evenly within 10 minutes before performing the bonding action.

9. The method for manufacturing a tunnel prefabricated invert block waterproof structure according to claim 1, characterized in that: In step S3, the protective coating is an anti-organic fluorine protective coating, nanoparticles are added to the anti-organic fluorine protective coating, the nanoparticles are selected from titanium dioxide or aluminum oxide, the average particle size of the nanoparticles is 20 nm~50 nm, and the amount of nanoparticles added is 3%~5% of the total mass of the anti-organic fluorine protective coating.

10. A tunnel prefabricated invert block waterproof structure manufactured by the manufacturing method according to any one of claims 1 to 9.

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