High-damping and strong-toughness tunnel lining wall backfill material and preparation method and application thereof

Abstract

The present application relates to the technical field of building materials, in particular to a high-damping and strong-toughness tunnel lining wall back filling material and a preparation method and application thereof. The present application takes cement-based material as the main material, and the added solid waste mineral admixture improves the mechanical properties and preliminarily improves the damping performance under the excitation of the excitation agent, and then the damping and toughness are improved through the synergistic effect of the multi-scale composite agent. The wall back filling material prepared by the present application has the characteristics of excellent damping performance, good vibration reduction effect, excellent mechanical properties and high bending pressure ratio, which is beneficial to reduce the cracks of the stone body, improve the overall mechanical properties, durability and impermeability of the shield tunnel, and reduce the spread of vibration pollution, so as to realize the safe construction and operation of the shield tunnel.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a high-damping, high-toughness tunnel lining wall backfill material, its preparation method, and its application. Background Technology

[0002] The shield tunneling method has many advantages, such as fast construction speed and high safety, and has become an important method for tunnel construction. Backfilling of the tunnel lining wall can alleviate ground deformation, ensure uniform stress on the tunnel segments, and improve the overall impermeability of the tunnel. It is one of the core procedures in shield tunneling.

[0003] Traditional backfill materials for subway linings are mostly cement mortar, which has insufficient load-bearing capacity under repeated cyclic vibrations from trains. It also suffers from weak mechanical properties, being more resistant to compression than flexural stress, leading to cracks in the backfill layer under train load vibrations. Furthermore, backfill materials typically exhibit significant brittleness; deformation under external loads can cause internal structural failure, with extremely low residual strength after failure. This significantly reduces the mechanical properties and impermeability of the backfill layer, negatively impacting the tunnel's load-bearing capacity, impermeability, and safe operation and maintenance lifespan. Moreover, vibration and noise from subway train operation have become one of the most strongly criticized sources of vibration pollution. Traditional backfill materials have weak vibration reduction and damping capabilities, failing to meet the requirements for vibration reduction efficiency and economic benefits.

[0004] Therefore, the development of high-damping and high-toughness backfill materials is of great significance for reducing cracks in the backfill layer, improving the mechanical and durability properties of the backfill layer, improving the control of vibration pollution propagation, and ensuring the long-term safe construction and operation of tunnels. Summary of the Invention

[0005] To overcome the above problems, the present invention provides a high-damping, high-toughness tunnel lining wall backfill material, its preparation method and application.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a high-damping, high-toughness tunnel lining wall backfill material, the raw materials of which, by weight, include: 240-270 parts of silicate cement, 600-800 parts of fine sand, 270-470 parts of solid waste mineral admixture, 270-410 parts of activator, 207.5-413.5 parts of multi-scale composite agent and 440-560 parts of water; Multi-scale composites include micro / nano-scale composites and millimeter-scale composites; millimeter-scale composites are composed of millimeter-particle composites and millimeter-fiber composites; Micro- and nanoscale composites include butyl acrylate-styrene copolymer latex, polyurethane, nano-SiO2, and multi-walled carbon nanotubes. Millimeter-sized particle composites include rubber particles, ceramsite, and expanded perlite; Millimeter fiber composites include steel fibers, polypropylene (PVA) fibers, glass fibers, and polyvinyl alcohol fibers.

[0007] In one or more embodiments, the solid waste mineral admixture includes fly ash, coal gangue powder, steel slag powder, and silica fume.

[0008] Preferably, the mass ratio of fly ash, coal gangue powder, steel slag powder and silica fume is (100~200):(80~120):(60~90):(30~60).

[0009] In one or more embodiments, the activator includes blast furnace slag powder, calcium oxide powder, calcium carbide slag powder, and water glass; Preferably, the mass ratio of blast furnace slag powder, calcium oxide powder, carbide slag powder and water glass is (150~210):(50~80):(60~100):(10~30).

[0010] Preferably, the modulus of the water glass is 2.0 to 2.8, more preferably 2.4, and the Baumé degree is 35 to 45°Bé, more preferably 40.

[0011] In one or more embodiments, the mass ratio of the micro / nanoscale composite agent to the millimeter-scale composite agent is (122~248):(85.5~165.5).

[0012] In one or more embodiments, the mass ratio of butyl acrylate-styrene copolymer latex, polyurethane, nano-SiO2 and multi-walled carbon nanotubes in the micro-nano scale composite agent is (60~120):(40~80):(15~35):(7~13).

[0013] Preferably, the polyurethane has an elongation at break of ≥150%.

[0014] In one or more embodiments, the mass ratio of millimeter-scale composite agent to millimeter-fiber composite agent in the millimeter-scale composite agent is (80~150):(5.5~15.5).

[0015] In one or more embodiments, the mass ratio of rubber particles, ceramsite and expanded perlite in the millimeter particle composite is (40~60):(15~25):(25~45).

[0016] Preferably, the rubber granules have a particle size of 1-2 mm; the ceramsite has a particle size of 3-5 mm; and the expanded perlite has a particle size of 0.250-0.425 mm.

[0017] In one or more embodiments, the mass ratio of steel fiber, polypropylene fiber, glass fiber and polyvinyl alcohol fiber in the millimeter fiber composite agent is (2~6):(0.5~2.5):(1~3):(2~4).

[0018] Preferably, the average length of the steel fiber is 25-35 mm; the average length of the polypropylene fiber is 10-20 mm; the average length of the glass fiber is 3-6 mm; and the average length of the polyvinyl alcohol fiber is 6-12 mm.

[0019] A second aspect of the present invention provides a method for preparing the high-damping, high-toughness tunnel lining wall backfill material described in the first aspect, comprising the following steps: (1) Silicate cement, fine sand, activator, solid waste mineral admixture, nano-SiO2, multi-walled carbon nanotubes and water are mixed evenly to obtain the matrix of backfill material for tunnel lining wall; (2) Add butyl acrylate-styrene copolymer latex, polyurethane and millimeter-scale composite agent to the matrix of the backfill material of the tunnel lining wall and mix evenly to obtain a high-damping and tough tunnel lining wall backfill material.

[0020] In one or more embodiments, in step (1), the mixture is stirred evenly at a speed of 200-300 rpm for 3-5 minutes.

[0021] In one or more embodiments, in step (2), the mixture is stirred evenly at a speed of 120-200 rpm for a duration of 4-6 min.

[0022] A third aspect of the present invention provides the application of the high-damping toughness tunnel lining wall backfill material described in the first aspect or the high-damping toughness tunnel lining wall backfill material prepared by the preparation method described in the second aspect in the backfilling of tunnel lining walls.

[0023] The beneficial effects of this invention are as follows: This invention uses cement-based materials as the main material. The added solid waste mineral admixtures, under the activation of an activator, not only improve mechanical properties but also initially enhance damping performance. Subsequently, multi-scale composite agents synergistically improve damping and toughness. The backfill material prepared by this invention possesses excellent damping performance, good vibration reduction effect, superior mechanical properties, and a high flexural-to-compression ratio. This is beneficial for reducing cracks in the rock mass, improving the overall mechanical properties, durability, and impermeability of shield tunnels, while also reducing the propagation of vibration pollution, thus achieving safe construction and operation of shield tunnels. Specifically, the high-damping, high-toughness tunnel lining backfill material prepared by this invention has a consistency ≥11 cm, an initial setting time of 4-6 h, compressive strengths at 1d, 3d, and 28d greater than 1.5 MPa, 4 MPa, and 7 MPa, respectively, a toughness index ≥4, a damping ratio ≥10%, a 28-day compressive strength ≥7 MPa after cyclic vibration, and a 28-day flexural-to-compression ratio ≥0.35.

[0024] ① Improvement of mechanical properties of solid waste mineral admixtures under the activation of activators: By designing a synergistic hydration effect of silicate cement, blast furnace slag powder, fly ash, steel slag powder, coal gangue powder, calcium oxide, carbide slag, and silica fume, a multi-element cementitious system is formed, which constitutes the basis for the high strength and durability of the material. Cement hydration generates calcium hydroxide, which activates the pozzolanic activity of slag, fly ash, and coal gangue powder, generating more hydrated calcium silicate gel, improving density. The extremely small particle size of silica fume can fill the voids between cement particles, forming a dense "microcrystalline nucleus" effect, significantly improving strength, and fully utilizing the pozzolanic effect and micro-aggregate filling effect. Calcium oxide powder and carbide slag powder provide a strongly alkaline environment in the system, which can accelerate the hydration of slag and fly ash, and can also react with the active components in coal gangue powder. In addition, calcium oxide and steel slag powder will produce a certain degree of micro-expansion during hydration, which can compensate for the shrinkage of cement-based materials, which is beneficial to prevent cracking and improve toughness.

[0025] ② Improvement of damping performance: Adding solid waste mineral admixtures is one of the important ways to improve the damping capacity of cement-based materials. This is because: enriching the structural composition of the material at the nanoscale of the hydrated gel, by adding solid waste rich in aluminosilicate minerals (fly ash, coal gangue powder, steel slag powder and silica fume), and adding blast furnace slag powder, calcium oxide powder and carbide slag powder with calcium oxide as the main component, can increase the calcium-silicon ratio of the system, thereby increasing the loss factor of CSH gel and reducing its storage modulus.

[0026] ③ Damping and toughness were improved through the synergistic effect of multi-scale composite agents: Damping is enhanced at the micro- and nanoscale using butyl acrylate-styrene copolymer latex, polyurethane, nano-SiO2, and multi-walled carbon nanotubes. The butyl acrylate-styrene copolymer latex, along with the hydration products of cement-based materials and solid waste mineral admixtures, forms a micro-constrained damping structure, consuming vibrational energy through the torsion and sliding of polymer molecular chains. Viscoelastic polyurethane can cover the surface of the hydration products, forming a free damping structure. Furthermore, polyurethane fills the gaps between hydrates, forming a unique continuous honeycomb structure that deforms during opening and closing to dissipate energy. Nano-SiO2 optimizes the matrix through physical filling and chemical activation, forming a stronger and more robust micro-network structure, increasing resistance during microcrack propagation, and bridging the microcracks across their sides through a nano-bridging effect, delaying their development into macroscopic destructive cracks. Multi-walled carbon nanotubes alter the morphology of hydrated calcium silicate (CSH) gel to increase friction between CSH particles, and enhance damping through Coulomb friction at the gel interface via a bridging effect.

[0027] Damping is enhanced at the millimeter scale using rubber granules, ceramsite, and expanded perlite. Rubber granules, as a typical viscoelastic material, improve the material's viscoelasticity; furthermore, rubber introduces more interfaces and defects, lengthening the stress wave propagation path, thus synergistically enhancing damping. Ceramsite, with its low strength and porous, rough surface, undergoes minute elastic deformation or even compression when subjected to alternating stress or vibration, forming internal friction damping. Furthermore, minute relative slippage and friction occur between the ceramsite and the surrounding cement paste, converting vibrational mechanical energy into heat energy and dissipating it, thus significantly improving the overall damping performance of the material. Expanded perlite, with its low strength and fragile structure, undergoes plastic deformation and localized crushing under stress, absorbing vibrational energy through its own destruction, thereby improving damping. Moreover, as a pre-existing defect, cracks preferentially initiate and propagate at these weak perlite particles, guiding the formation of multiple microcracks rather than a single fatal crack. This process absorbs a large amount of fracture energy, thus exhibiting good toughness.

[0028] The Coulomb friction damping and toughness of materials reinforced at the millimeter scale were improved using steel fibers, polypropylene fibers, glass fibers, and polyvinyl alcohol fibers. Steel fibers, an inorganic fiber with high mechanical strength, high flexibility, and usability, induce multi-crack behavior in brittle materials, absorbing more energy under both static and dynamic loads, thus enhancing the material's resistance to vibration and impact. Polypropylene fibers, an organic fiber with high flexibility and low hardness, improve the toughness, impact resistance, and ductility of cement-based materials. Glass fibers, a brittle inorganic fiber with high tensile strength and high elastic modulus, effectively bear and transfer stress, acting as a bridge. Numerous dispersed glass fibers form a dense network within the matrix, effectively dispersing stress and converting mechanical energy into heat energy through interfacial friction. This induces numerous microcracks simultaneously at multiple weak points, rather than forming concentrated macroscopic cracks, significantly improving toughness and damping. Experimental results show that the filler material obtained using the above combination exhibits superior damping performance and toughness.

[0029] Furthermore, at the macroscopic scale, steel fibers primarily act as a bridge after cracks appear, preventing further crack propagation and providing high fracture energy and toughness. At the microscopic scale, polypropylene fibers, PVA fibers, and glass fibers prevent the formation of plastic shrinkage cracks in the early stages of hardening. PVA fibers have good adhesion to the cement matrix and can absorb a large amount of cracking energy. At the nanoscopic scale, multi-walled carbon nanotubes play a role in the early stages of crack initiation, consuming energy through pull-out and fracture, preventing microcracks from propagating into macroscopic cracks. This gradient fiber system at the nano-micro-millimeter scale constitutes a three-dimensional network that progressively bears the load and bridges cracks, thereby achieving high toughness.

[0030] Furthermore, by designing nano-SiO2, multi-walled carbon nanotubes, silica fume, and water glass, a synergistic nano-reinforcement effect was achieved in the interfacial transition zone. The interfacial transition zone between aggregates and slurry is a weak point in backfill materials. Nano-SiO2 has extremely high activity, which can consume the enriched calcium hydroxide in the interfacial zone to generate CSH gel and fill the pores. In addition, water glass, as an alkali activator, can activate the activity of materials such as slag, resulting in faster early strength development. The synergy between water glass and nanomaterials makes the matrix more compact, improves the adhesion between fibers and the matrix, and thus promotes the toughening effect of fibers. Detailed Implementation

[0031] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] The butyl acrylate-styrene copolymer latex has been published in the following paper: Zhang CY, Wang J, Zhang SF, Hou XW, Kong XM. Damping performance of hardened cement pastes containing styrene-butyl acrylate polymers with varied glass transition temperature and surface charges[J]. Cement&Concrete Composites, 2024, 145:105312. In the following embodiments: The average particle size of silicate cement, blast furnace slag powder, calcium oxide powder, calcium carbide slag powder, fly ash, coal gangue and steel slag powder is less than 37 μm; The specific surface area of ​​silica fume is ≥15000 m². 2 / kg, SiO2 content ≥85%; The fine sand has a particle size ≤2.36 mm and an average particle size between 0.15 mm and 1.18 mm; The elongation at break of polyurethane is ≥150%; The effective content of nano-SiO2 is ≥99%; Multi-walled carbon nanotubes have a fixed carbon content of 99.9% and an expansion coefficient of 0.5. The particle size of the rubber granules is 1~2 mm; The particle size of the expanded clay aggregate is 3~5mm; The grain size of expanded perlite is 0.250~0.425 mm; The average length of the steel fibers is 25~35 mm; The average length of the polypropylene fibers is 10~20 mm; The average length of the glass fiber is 3~6 mm; The average length of polyvinyl alcohol fibers is 6~12 mm; The water glass has a modulus of 2.4 and a Baumé degree of 40°Bé.

[0034] In the following examples, the chemical composition of each substance is shown in Table 1.

[0035] Table 1 Chemical composition of each substance

[0036] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0037] Example 1 A high-damping, high-toughness tunnel lining wall backfill material, the raw materials of which include: The ingredients are: 270 parts silicate cement, 600 parts fine sand, 150 parts fly ash, 100 parts coal gangue powder, 90 parts steel slag powder, 45 parts silica fume, 210 parts blast furnace slag powder, 80 parts calcium oxide powder, 60 parts calcium carbide slag powder, 30 parts water glass, 90 parts butyl acrylate-styrene copolymer latex, 80 parts polyurethane, 15 parts nano-SiO2, 13 parts multi-walled carbon nanotubes, 50 parts rubber granules, 15 parts ceramsite, 45 parts expanded perlite, 2 parts steel fiber, 2.5 parts polypropylene fiber, 3 parts glass fiber, 4 parts polyvinyl alcohol fiber, and 470 parts water.

[0038] A method for preparing a high-damping, high-toughness tunnel lining backfill material includes the following steps: (1) Silicate cement, blast furnace slag powder, calcium oxide powder, carbide slag powder, fly ash, coal gangue powder, steel slag powder, silica fume, fine sand, nano SiO2, multi-walled carbon nanotubes, water glass and water are stirred at a rate of 250 rpm for 4 min to obtain the backfill material matrix for tunnel lining wall.

[0039] (2) Add butyl acrylate-styrene copolymer latex, polyurethane, rubber particles, ceramsite, expanded perlite, steel fiber, polypropylene fiber, glass fiber and polyvinyl alcohol fiber to the backfill material matrix of the tunnel lining wall, and stir at a rate of 160 rpm for 5 min to obtain a high-damping and tough tunnel lining wall backfill material.

[0040] Example 2 A high-damping, high-toughness tunnel lining wall backfill material, the raw materials of which include: The ingredients are: 300 parts silicate cement, 700 parts fine sand, 150 parts fly ash, 120 parts coal gangue powder, 60 parts steel slag powder, 60 parts silica fume, 150 parts blast furnace slag powder, 65 parts calcium oxide powder, 100 parts calcium carbide slag powder, 20 parts water glass, 60 parts butyl acrylate-styrene copolymer latex, 60 parts polyurethane, 35 parts nano-SiO2, 10 parts multi-walled carbon nanotubes, 60 parts rubber granules, 15 parts ceramsite, 35 parts expanded perlite, 4 parts steel fiber, 1.5 parts polypropylene fiber, 2 parts glass fiber, 3 parts polyvinyl alcohol fiber, and 440 parts water.

[0041] The preparation method of the high-damping and high-toughness tunnel lining wall backfill material is the same as in Example 1.

[0042] Example 3 A high-damping, high-toughness tunnel lining wall backfill material, the raw materials of which include: The ingredients are: 240 parts silicate cement, 800 parts fine sand, 100 parts fly ash, 80 parts coal gangue, 80 parts steel slag powder, 60 parts silica fume, 180 parts blast furnace slag powder, 80 parts calcium oxide powder, 80 parts calcium carbide slag powder, 30 parts water glass, 120 parts butyl acrylate-styrene copolymer latex, 40 parts polyurethane, 35 parts nano-SiO2, 7 parts multi-walled carbon nanotubes, 50 parts rubber granules, 20 parts ceramsite, 35 parts expanded perlite, 4 parts steel fiber, 2.5 parts polypropylene fiber, 1 part glass fiber, 3 parts polyvinyl alcohol fiber, and 470 parts water.

[0043] The preparation method of the high-damping and high-toughness tunnel lining wall backfill material is the same as in Example 1.

[0044] Example 4 A high-damping, high-toughness tunnel lining wall backfill material, the raw materials of which include: The ingredients are: 300 parts silicate cement, 700 parts fine sand, 200 parts fly ash, 120 parts coal gangue, 75 parts steel slag powder, 60 parts silica fume, 180 parts blast furnace slag powder, 65 parts calcium oxide powder, 80 parts calcium carbide slag powder, 10 parts water glass, 60 parts butyl acrylate-styrene copolymer latex, 80 parts polyurethane, 25 parts nano-SiO2, 13 parts multi-walled carbon nanotubes, 40 parts rubber granules, 20 parts ceramsite, 25 parts expanded perlite, 2 parts steel fiber, 0.5 parts polypropylene fiber, 3 parts glass fiber, 4 parts polyvinyl alcohol fiber, and 500 parts water.

[0045] The preparation method of the high-damping and high-toughness tunnel lining wall backfill material is the same as in Example 1.

[0046] Example 5 A high-damping, high-toughness tunnel lining wall backfill material, the raw materials of which include: The ingredients are: 270 parts silicate cement, 600 parts fine sand, 200 parts fly ash, 80 parts coal gangue, 90 parts steel slag powder, 30 parts silica fume, 150 parts blast furnace slag powder, 50 parts calcium oxide powder, 60 parts calcium carbide slag powder, 20 parts water glass, 90 parts butyl acrylate-styrene copolymer latex, 60 parts polyurethane, 25 parts nano-SiO2, 7 parts multi-walled carbon nanotubes, 60 parts rubber granules, 25 parts ceramsite, 25 parts expanded perlite, 6 parts steel fiber, 0.5 parts polypropylene fiber, 2 parts glass fiber, 2 parts polyvinyl alcohol fiber, and 500 parts water.

[0047] The preparation method of the high-damping and high-toughness tunnel lining wall backfill material is the same as in Example 1.

[0048] Example 6 A high-damping, high-toughness tunnel lining wall backfill material, the raw materials of which include: The ingredients are: 240 parts silicate cement, 800 parts fine sand, 100 parts fly ash, 80 parts coal gangue, 80 parts steel slag powder, 60 parts silica fume, 210 parts blast furnace slag powder, 50 parts calcium oxide powder, 100 parts calcium carbide slag powder, 10 parts water glass, 120 parts butyl acrylate-styrene copolymer latex, 40 parts polyurethane, 15 parts nano-SiO2, 10 parts multi-walled carbon nanotubes, 40 parts rubber granules, 25 parts ceramsite, 45 parts expanded perlite, 6 parts steel fiber, 1.5 parts polypropylene fiber, 1 part glass fiber, 2 parts polyvinyl alcohol fiber, and 440 parts water.

[0049] The preparation method of the high-damping and high-toughness tunnel lining wall backfill material is the same as in Example 1.

[0050] Comparative Example 1 Compared with Comparative Example 1, no solid waste mineral admixtures were added, that is, no fly ash, coal gangue powder, steel slag powder and silica fume were added, and the remaining materials and preparation methods were the same as in Example 1.

[0051] Comparative Example 2 The difference from Example 1 is that water glass was not added, but the other materials and preparation methods are the same as in Example 1.

[0052] Comparative Example 3 The difference from Example 1 is that no micro / nano-scale composite agent was added, that is, no butyl acrylate-styrene copolymer latex, polyurethane, nano-SiO2 and multi-walled carbon nanotubes were added. The other materials and preparation methods are the same as in Example 1.

[0053] Comparative Example 4 The difference from Example 1 is that no millimeter-scale composite agent was added, that is, no rubber particles, ceramsite, expanded perlite, steel fibers, polypropylene fibers, glass fibers and polyvinyl alcohol fibers were added. The remaining materials and preparation methods are the same as in Example 1.

[0054] Comparative Example 5 The difference from Example 1 is that no millimeter particle composite agent was added, that is, no rubber particles, ceramsite and expanded perlite were added, while the other materials and preparation methods were the same as in Example 1.

[0055] Comparative Example 6 The difference from Example 1 is that butyl acrylate-styrene copolymer latex was not added, while the other materials and preparation methods are the same as in Example 1.

[0056] Comparative Example 7 The difference from Example 1 is that polyurethane was not added, but the other materials and preparation methods are the same as in Example 1.

[0057] Comparative Example 8 The difference from Example 1 is that multi-walled carbon nanotubes were not added, while the other materials and preparation methods are the same as in Example 1.

[0058] Comparative Example 9 The difference from Example 1 is that no millimeter fiber composite agent was added, that is, no steel fiber, polypropylene fiber, glass fiber and polyvinyl alcohol fiber were added, while the other materials and preparation methods were the same as in Example 1.

[0059] Comparative Example 10 The difference from Example 1 is that the content of glass fiber and polyvinyl alcohol fiber in the millimeter fiber composite agent is adjusted to 6 parts glass fiber and 8 parts polyvinyl alcohol fiber, while the remaining materials and preparation methods are the same as in Example 1.

[0060] Comparative Example 11 The difference from Example 1 is that rubber particles and ceramic particles are not added, while the other materials and preparation methods are the same as in Example 1.

[0061] The performance testing method is as follows: 1. The consistency test was conducted according to the method in JGJ / T 70-2009 "Test Method for Basic Performance of Building Mortar" and the test instrument was a mortar consistency meter.

[0062] 2. The initial setting time test was conducted according to the method in T / CECS 563-2018 "Technical Specification for Application of Synchronous Grouting Materials in Shield Tunneling". The test instrument used was a penetration resistance meter, and the setting time was determined by the penetration resistance method.

[0063] 3. Compressive strength and flexural strength tests shall be conducted in accordance with the methods in GB / T 17671-2021 "Test Methods for Strength of Cement Mortar (ISO Method)".

[0064] 4. Flexural-compression ratio: The compressive strength and flexural strength of the material are tested according to the method in GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)", and the flexural-compression ratio is calculated by dividing the flexural strength by the compressive strength.

[0065] 5. The toughness index test shall be conducted in accordance with the bending toughness test method in JG / T 472-2015 "Steel Fiber Reinforced Concrete", and the toughness index shall be calculated based on the load-deflection curve.

[0066] 6. The damping ratio test shall be conducted in accordance with the method in ASTM C215:2019 and obtained by the half-power bandwidth method of the resonance curve.

[0067] 7. The compressive strength after cyclic vibration (2000 cycles) test aims to simulate the effect of repeated periodic vibration of a train on the compressive strength of the material. Referring to the relevant clauses on fatigue testing in GB / T 50448-2015 "Technical Specification for Application of Cement-based Grouting Materials", the compressive strength before and after 2000 cycles of cyclic vibration of the vibratory machine is used for characterization.

[0068] The working performance and toughness of each embodiment and comparative example were tested, including consistency, initial setting time, 1-day compressive strength, 3-day compressive strength, 28-day compressive strength, 1-day flexural-compression ratio, 3-day flexural-compression ratio, 28-day flexural-compression ratio, toughness index, damping ratio, and compressive strength after cyclic vibration (2000 times). The results are shown in Tables 2 and 3.

[0069] Table 2 Performance Test Results

[0070] Table 3 Toughness Test Results

[0071] Comparing the data from Example 1 and Comparative Example 1, it can be seen that adding solid waste mineral admixtures shortens the initial setting time of the material and significantly improves its mechanical properties, toughness, and damping ratio. Comparing the data from Example 1 and Comparative Example 2, it can be seen that adding water glass shortens the setting time of the material, significantly improves its mechanical properties, especially the early mechanical properties, and increases its toughness and damping ratio. Comparing the data from Example 1 and Comparative Example 3, it can be seen that adding micro / nano-scale composite agents mainly improves the material's toughness index, damping ratio, and flexural-compression ratio. Comparing the data from Example 1 and Comparative Example 4, it can be seen that adding millimeter-scale composite agents slightly shortens the setting time and significantly improves the material's toughness and damping ratio. Comparing the data from Example 1 and Comparative Example 5, it can be seen that adding millimeter-particle composite agents slightly improves the material's mechanical properties, while significantly improving its toughness and damping performance. Comparing the data from Example 1 and Comparative Example 6, it can be seen that... The addition of butyl acrylate-styrene copolymer latex mainly improved the toughness index, damping ratio, and flexural-compression ratio of the material. Comparison of data from Example 1 and Comparative Example 7 shows that the addition of polyurethane significantly improved the toughness and damping performance of the material. Comparison of data from Example 1 and Comparative Example 8 shows that the addition of multi-walled carbon nanotubes enhanced the mechanical properties of the material, while also improving its toughness and damping performance. Comparison of data from Example 1 and Comparative Example 9 shows that the addition of millimeter fiber composite significantly improved the toughness and damping performance of the material. Comparison of data from Example 1 and Comparative Example 10 shows that when the content of glass fiber and polyvinyl alcohol fiber in the millimeter fiber composite is outside the limits specified in this invention, the consistency of the material decreases, the mechanical properties decrease significantly, and the toughness and flexural-compression ratio also decrease slightly. Comparison of data from Example 1 and Comparative Example 1 shows that the absence of rubber particles and ceramsite significantly reduced the mechanical properties, toughness, and damping performance of the material.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-damping, high-toughness tunnel lining wall backfill material, characterized in that, Its raw materials, by weight, include: 240-270 parts silicate cement, 600-800 parts fine sand, 270-470 parts solid waste mineral admixture, 270-410 parts activator, 207.5-413.5 parts multi-scale composite agent, and 440-560 parts water; Solid waste mineral admixtures include fly ash, coal gangue powder, steel slag powder, and silica fume; the mass ratio of fly ash, coal gangue powder, steel slag powder, and silica fume is (100~200):(80~120):(60~90):(30~60); The activator includes blast furnace slag powder, calcium oxide powder, carbide slag powder and water glass; the mass ratio of blast furnace slag powder, calcium oxide powder, carbide slag powder and water glass is (150~210):(50~80):(60~100):(10~30); Multiscale composite agents include micro / nanoscale composite agents and millimeter-scale composite agents; the mass ratio of micro / nanoscale composite agents to millimeter-scale composite agents is (122~248):(85.5~165.5). Micro- and nanoscale composite agents include butyl acrylate-styrene copolymer latex, polyurethane, nano-SiO2, and multi-walled carbon nanotubes; the mass ratio of butyl acrylate-styrene copolymer latex, polyurethane, nano-SiO2, and multi-walled carbon nanotubes is (60~120):(40~80):(15~35):(7~13); The millimeter-scale composite agent is composed of millimeter-particle composite agent and millimeter-fiber composite agent; the mass ratio of millimeter-particle composite agent to millimeter-fiber composite agent is (80~150):(5.5~15.5). The millimeter particle composite agent includes rubber particles, ceramsite, and expanded perlite; the mass ratio of rubber particles, ceramsite, and expanded perlite is (40~60):(15~25):(25~45). The millimeter fiber composite agent includes steel fiber, polypropylene fiber, glass fiber and polyvinyl alcohol fiber; the mass ratio of steel fiber, polypropylene fiber, glass fiber and polyvinyl alcohol fiber is (2~6):(0.5~2.5):(1~3):(2~4); The average length of steel fibers is 25-35 mm; the average length of polypropylene fibers is 10-20 mm; the average length of glass fibers is 3-6 mm; and the average length of polyvinyl alcohol fibers is 6-12 mm. The high-damping, high-toughness tunnel lining wall backfill material has a consistency ≥11 cm, an initial setting time of 4~6 h, compressive strengths at 1d, 3d and 28d greater than 1.5 MPa, 4 MPa and 7 MPa respectively, a toughness index ≥4, a damping ratio ≥10%, a compressive strength ≥7 MPa after 28d of cyclic vibration, and a flexural-compression ratio ≥0.35 at 28d.

2. The method for preparing the high-damping, high-toughness tunnel lining wall backfill material according to claim 1, characterized in that, Includes the following steps: (1) Silicate cement, fine sand, activator, solid waste mineral admixture, nano-SiO2, multi-walled carbon nanotubes and water are mixed evenly to obtain the matrix of backfill material for tunnel lining wall; (2) Add butyl acrylate-styrene copolymer latex, polyurethane and millimeter-scale composite agent to the matrix of the backfill material of the tunnel lining wall and mix evenly to obtain a high-damping and tough tunnel lining wall backfill material.

3. The preparation method according to claim 2, characterized in that, In step (1), the mixture is stirred evenly at a speed of 200-300 rpm for 3-5 minutes. In step (2), the mixture is stirred evenly at a speed of 120-200 rpm for 4-6 minutes.

4. The application of the high-damping toughness tunnel lining wall backfill material according to claim 1 or the high-damping toughness tunnel lining wall backfill material prepared by the preparation method according to claim 2 or 3 in the backfilling of tunnel lining walls.

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