Stone-like well lid and preparation method thereof

Abstract

The invention relates to the technical field of engineering building materials, in particular to a stone-like well lid and a manufacturing method thereof. The stone-like well lid comprises a metal outer frame fixedly embedded in a well mouth, the metal outer frame is provided with an annular outer frame and a supporting part, and the supporting part is fixedly connected with the bottom of the annular outer frame and extends towards the center of the well mouth by a preset distance; the metal inner groove is nested in the outer frame structure and comprises an inner frame geometrically matched with the annular outer frame and a bearing plate for sealing the bottom of the inner frame; the containing cavity of the metal inner groove is filled with the composite force bearing layer, and the composite force bearing layer comprises a fiber-reinforced base material and a steel reinforcement framework fixedly connected with the inner wall of the metal inner groove; and the stone-like surface layer covers the surface of the composite bearing layer. By means of the geometric fit nesting structure of the metal outer frame and the metal inner groove and the integrated design of the composite force bearing layer and the stone-like surface layer, the structural strength and installation precision of the well lid are remarkably improved, and meanwhile maintenance convenience and urban landscape coordination are optimized.

Description

Technical Field

[0001] The invention relates to the technical field of engineering building materials, and in particular to an imitation stone manhole cover and a manufacturing method thereof. Background Art

[0002] In municipal engineering facilities, manhole covers serve as important covering components for urban roads, drainage systems, and underground pipelines. Their mechanical properties and durability are directly related to public safety and maintenance costs. Traditional manhole covers are mostly made of ordinary concrete or cast iron. Ordinary concrete manhole covers have low compressive strength (usually ≤30MPa), are prone to cracking, and have poor corrosion resistance. Long-term exposure to moisture, freeze-thaw, and chemical corrosion can easily lead to surface peeling and steel corrosion, resulting in a sharp drop in bearing capacity. Although cast iron manhole covers have high strength, they are too heavy, easy to be stolen, and poorly coordinated with the urban landscape. Especially in modern municipal construction, where the demand for imitation stone textures is increasing, their single color and industrial texture make it difficult to meet aesthetic requirements.

[0003] In the existing technology, although some improvement plans have tried to increase the strength of manhole covers by adding steel fibers or optimizing the concrete ratio, they focus on the surface spraying process and do not solve the core problems of low installation accuracy and difficult maintenance in the structural design of manhole covers. The metal outer frame and inner groove of traditional manhole covers mostly adopt a vertical nested structure. During maintenance, they need to be lifted synchronously at multiple points or with the help of heavy equipment. The operation efficiency is low and the structure is easily damaged due to uneven force. In addition, the imitation stone surface layer of conventional manhole covers mostly relies on coatings or patch processes, which have problems such as easy fading, insufficient wear resistance, and weak adhesion to the base layer. They are difficult to withstand high-frequency vehicle rolling and extreme climatic conditions.

[0004] Therefore, there is an urgent need for a new manhole cover structure and preparation method that can improve the load-bearing capacity of the manhole cover while facilitating disassembly and maintenance, and solve the technical bottleneck of traditional manhole covers being incompatible with the urban landscape and prone to pollution. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing manhole covers have the problems of low structural strength, poor installation accuracy, difficult maintenance and insufficient coordination with the urban landscape.

[0006] (2) Technical solution In order to solve the above technical problems, the present invention provides an imitation stone manhole cover, which is mainly used for closing manholes on stone pavements, comprising: a metal outer frame, fixedly embedded in the manhole, including an annular outer frame and a support portion, the support portion is fixedly connected to the bottom of the annular outer frame and extends a preset distance toward the center of the manhole to form a channel opening that matches the size of the manhole; The metal inner trough, nested within the outer frame structure, includes an inner frame geometrically matched to the annular outer frame and a support plate enclosing the bottom of the inner frame. The support plate overlaps the upper surface of the support portion to form a support interface. This interface evenly distributes the load, avoiding localized stress concentration and ensuring the long-term stability of the manhole cover under high-frequency vehicle pressure. Furthermore, the geometrically compatible structure of the metal outer frame and the metal inner trough enables rapid positioning and installation, reducing dimensional deviations. The channel opening formed by the support portion extending toward the center of the wellhead, and the support interface formed by the overlap of the support plate, allow the metal inner trough to be lifted and removed in a directional manner, simplifying the inspection process and reducing the risk of structural damage during maintenance.

[0007] The composite load-bearing layer is filled in the accommodating cavity of the metal inner groove, and includes a fiber-reinforced matrix material and a steel skeleton fixedly connected to the inner wall of the metal inner groove; the nested geometric matching design of the metal outer frame and the metal inner groove, combined with the fiber-reinforced matrix material and the steel skeleton in the composite load-bearing layer, forms a multi-level force system, which greatly improves the compression, shear and impact resistance of the manhole cover.

[0008] The imitation stone surface layer is covered on the surface of the composite bearing layer, and the outer surface is flush with the top of the metal inner groove. The imitation stone surface layer and the composite bearing layer are integrally formed, and the surface is flush with the top of the metal inner groove, ensuring that the manhole cover is seamlessly connected to the road surface; the imitation stone surface layer is formed into a natural stone texture through a molding process, achieving a highly simulated visual effect, and the surface has no seams and no color difference, which significantly improves the coordination with the surrounding environment.

[0009] According to one embodiment of the present invention, the fiber-reinforced matrix material of the composite bearing layer is steel fiber reinforced concrete, which comprises, by mass: Cementitious materials: 800-850 parts of Portland cement, 35-45 parts of fly ash, 190-210 parts of mineral powder, 130-140 parts of silica fume; Aggregates: 550-650 parts of quartz sand with a particle size of 1.25-0.63mm, 90-110 parts of quartz sand with a particle size of 0.63-0.315mm, and 190-210 parts of quartz sand with a particle size of 0.315-0.16mm; Steel fiber: 4-6 parts of steel fiber with a diameter of 0.15-0.25mm, a length of 12-15mm, an aspect ratio of 50-70, and a tensile strength of ≥2000MPa; Admixture: 5-8 parts of polycarboxylate water reducer; The water-to-cement ratio of the cementitious material is 0.16-0.20, and the steel fibers are treated with a surface modifier and are three-dimensionally dispersed in the matrix.

[0010] Material properties are further optimized through the proportioning of steel fiber reinforced concrete and three-dimensional random dispersion technology. The synergistic effect of silicate cement, fly ash, mineral powder and silica fume in the cementitious material significantly improves the density and durability of the matrix; three-level continuous gradation of quartz sand forms a dense aggregate accumulation system, combined with an ultra-low water-cement ratio (0.16-0.20) and polycarboxylic acid water reducer to achieve improved slurry fluidity and compressive strength. The surface-modified fine steel fibers are dispersed in the matrix in a three-dimensional random manner, forming a multi-scale reinforcement network with the steel skeleton, greatly inhibiting crack expansion and improving impact resistance, allowing the manhole cover to maintain structural integrity under extreme loads while reducing the risk of installation damage due to material brittleness.

[0011] Furthermore, graphene oxide is added to the cementitious material in an amount of 0.03% to 0.1% of the mass of the Portland cement, and the mass ratio of graphene oxide to steel fiber is 1:50 to 1:30; The mass ratio of the cementitious material is: Portland cement: silica fume: graphene oxide = 100:15:0.05; The graphene oxide is surface-modified by a silane coupling agent and then dispersed in the concrete slurry through ultrasonic vibration.

[0012] Through graphene oxide modification technology, the performance of the composite bearing layer in extreme low temperature environments has been significantly optimized. Graphene oxide is precisely added at 0.03%-0.1% of the mass of silicate cement, and forms a synergistic reinforcement mechanism with steel fibers (mass ratio 1:50 to 1:30). Through surface modification with silane coupling agents and ultrasonic dispersion technology, it is ensured that it is evenly distributed in the cementitious system and tightly covers the surface of the steel fibers. The two-dimensional lamellar structure of graphene oxide effectively fills the micropores of the cement matrix, reduces the porosity and inhibits the initiation of microcracks under freeze-thaw cycles; at the same time, its synergistic effect with silica fume enhances the strength of the matrix interface transition zone and improves the material's crack resistance and frost resistance in a -40°C environment. The modified UHPC matrix has both high toughness and low-temperature stability, which can meet the resistance requirements of manhole covers in high-altitude and cold areas to extreme temperature shocks, and fill the shortcomings of traditional UHPC materials in low-temperature brittleness.

[0013] According to one embodiment of the present invention, the raw materials of the imitation stone surface layer include: White cement: strength grade not less than P·W 42.5, accounting for 30%-50% of the total mass of the imitation stone surface layer; Continuously graded quartz sand: composed of first-grade sand with a particle size of 0.425-0.85 mm and second-grade sand with a particle size of 0.18-0.425 mm, with a mass ratio of (3:7) to (7:3), accounting for 50%-70% of the total mass of the imitation stone surface layer, forming a dense matrix structure; Inorganic pigment: accounting for 0.5%-2% of the mass of the white cement; The surface of the imitation stone surface layer is formed into imitation natural stone texture through a molding process.

[0014] The imitation stone surface layer utilizes a composite system of high-strength white cement and continuously graded quartz sand. Through optimized raw material ratios and molding processes, it achieves high fidelity and durability. Inorganic pigments are precisely incorporated into the white cement, resulting in uniform dispersion at the molecular level for color stability, with no noticeable fading even after long-term exposure to UV rays. The compression molding process directly replicates the texture of natural stone, eliminating artificial joints and seamlessly bonding the surface to the base layer, effectively preventing the risk of surface delamination and significantly enhancing the manhole cover's aesthetics and environmental integration.

[0015] Furthermore, the surface of the imitation stone surface layer is also provided with a nano titanium dioxide (TiO2) photocatalytic coating, the thickness of the photocatalytic coating is 10-20 μm, and comprises the following components: Nano-titanium dioxide particles: particle size 10-50nm, accounting for 3%-8% of the total mass of the coating material; Inorganic binder: silica sol or alumina sol, accounting for 15%-25% of the total mass of the coating material; Dispersant: sodium polyacrylate, accounting for 0.1%-0.5% of the total mass of the coating material; The nano titanium dioxide particles are surface-modified by a silane coupling agent and embedded in the coating in a uniformly dispersed state.

[0016] Self-cleaning and anti-pollution functions are achieved through optimized material ratios and processes. Nano-titanium dioxide particles, surface-modified with a silane coupling agent, form a stable binding system with silica sol / alumina sol, while a sodium polyacrylate dispersant ensures uniform particle dispersion. The coating activates strong oxidative activity under natural light or ultraviolet light, decomposing organic pollutants attached to the surface and significantly reducing stain deposition. Furthermore, the embedded nanoparticles enhance the coating's hardness and wear resistance, and the inorganic bonding system exhibits excellent weather resistance. Long-term exposure to heat, humidity, and acid rain results in no powdering or shedding, ensuring the long-term cleanliness and aesthetics of the manhole cover surface while reducing maintenance frequency.

[0017] According to one embodiment of the present invention, the outer frame of the metal outer frame is composed of two pairs of oppositely arranged enclosing panels, wherein the first pair of oppositely arranged enclosing panels are in an inclined state, forming a geometric adaptation relationship with the support interface at the same inclination angle; the second pair of oppositely arranged enclosing panels remain in a vertical state; The shape of the inner frame of the metal inner groove matches the inclined adaptation relationship of the outer frame, so that the vertical cross-section of the inner groove along the opposite direction of the first pair of enclosing plates has a diamond-shaped profile; The support portion extends circumferentially along the bottom of the metal outer frame, and a deflection notch of the support portion is provided at one end of the inwardly inclined enclosing plate in the first pair of enclosing plates. The size of the deflection notch is configured to allow the metal inner groove to produce a directional deflection around the edge of the deflection notch when the other end is pulled, so that the acute-angle end portion of the metal inner groove is embedded in the support interface to complete the detachment action of the metal inner groove.

[0018] The structural design of the metal outer frame and the inner groove greatly simplifies the operation of taking and placing the inner groove during maintenance of the manhole cover through geometric adaptation and directional deflection mechanism. Of the two pairs of enclosing panels of the outer frame, the first pair is tilted and forms an adaptation angle with the support interface, and the second pair remains vertical, which cooperates with the diamond profile design of the inner groove to achieve rapid alignment and installation, avoiding the positioning deviation of the traditional vertical nested structure. During maintenance, by pulling one end of the inner groove, its sharp-angled end is guided by the deflection notch of the support part and directionally deflected around the edge of the notch, so that the sharp-angled end is embedded in the support interface and detached from the overlap surface. The inner groove can be disassembled by pulling on one side only. This breaks through the limitations of traditional multi-point pulling, reduces the operation steps and tool dependence, reduces the risk of structural deformation or edge damage due to uneven force during the pulling process, and improves maintenance efficiency and safety.

[0019] According to one embodiment of the present invention, the support portion includes a support plate fixedly connected to the outer frame, and the support plate is provided with a lap groove; The metal outer frame further comprises at least one bearing crossbeam, which is detachably overlapped in the overlap groove, and the bearing surface of the bearing crossbeam is flush with the bearing surface of the support plate.

[0020] The coordinated design of the support part and the load-bearing beam significantly improves the load-bearing stability and maintenance convenience of the manhole cover. The precise coordination of the support plate and the overlap groove ensures that the load-bearing beam can be quickly installed or disassembled. Its load-bearing surface is level with the support plate, realizing uniform load transfer, reducing local stress concentration, and avoiding deformation or cracking of the manhole cover under high-frequency rolling. During maintenance, it is only necessary to remove the load-bearing beam to release the inner groove constraint and directly open the wellhead without the need for complex tools or destructive operations, simplifying the maintenance process and shortening the operation time. The modular design also supports flexible adjustment of the number of beams according to the actual load requirements of the wellhead, adapting to different working conditions, taking into account both structural strength and maintenance efficiency, and significantly reducing construction costs and long-term operation and maintenance difficulties.

[0021] Furthermore, at least one of the bearing beams is arranged at the edge of the deflection notch, and one side of the top deflection notch is arranged in an arc surface, forming an abutting surface that abuts against the bearing plate when the metal inner groove performs a disengagement action.

[0022] The curved abutment surface of the supporting crossbeam further optimizes the smoothness and structural reliability of the metal inner trough's release process. The crossbeam is positioned at the edge of the deflection notch, and its top curved surface forms a sliding contact interface with the metal inner trough's supporting plate. This guides the inner trough along a predetermined trajectory during release, reducing friction and contact stress concentration. This curved surface also disperses transient impact loads during the release process, preventing edge wear or deformation caused by angular contact, and extending the service life of the metal inner trough and outer frame.

[0023] According to one embodiment of the present invention, the outer frame and the inner frame are respectively provided with a limiting groove and a limiting protrusion that cooperate with each other. The limiting groove and limiting protrusion design of the outer frame and the inner frame significantly improve the installation accuracy and structural stability of the manhole cover. The geometric adaptation of the limiting protrusion and the limiting groove ensures that the metal inner groove and the outer frame are quickly and accurately aligned, avoiding local stress concentration or sealing failure caused by misalignment. The limiting mechanism simultaneously restrains the lateral displacement of the inner groove under vehicle rolling or vibration conditions, preventing structural loosening caused by micro-wear during long-term use. In addition, the limiting structure provides clear guidance when resetting after maintenance and disassembly, ensuring the consistency of repeated installation, reducing the difficulty of manual calibration, and improving construction efficiency and the overall reliability of the manhole cover.

[0024] The present invention also provides a method for preparing an imitation stone manhole cover, which is used to manufacture any of the above-mentioned imitation stone manhole covers, and the steps are as follows: S1: putting the gelling component of the fiber-reinforced matrix material, the graded aggregate and the reinforcing fiber into a high-speed mixer and mixing and stirring to form a slurry with fluidity that meets the pouring requirements; S2: pouring the slurry into the accommodating cavity of the metal inner tank, and compacting the slurry by internal and external coordinated vibration; S3: Perform preliminary temperature control and maintenance on the formed base layer; Pour the imitation stone surface slurry on the base surface and make the surface slurry evenly distributed through the vibration process; S4: The manhole cover is subjected to steam curing and natural curing in sequence to control the hydration reaction process and stabilize the material properties; S5: The surface of the manhole cover after maintenance is subjected to multi-stage grinding treatment, including coarse grinding, fine grinding and polishing, to obtain the predetermined surface roughness and glossiness.

[0025] This preparation method achieves efficient production and controllable performance of imitation stone manhole covers by optimizing material processing and molding processes. The high-speed mixing process ensures the full dispersion and uniform mixing of cementitious materials, graded aggregates and steel fibers, and the fluidity of the slurry meets the casting requirements of complex cavities. The coordinated vibration of the internal (inserted vibrator) and external (attached vibrator) increases the density of the matrix, reduces the porosity, and significantly improves the compressive strength and impermeability. Layered casting combined with temperature-controlled maintenance ensures the interfacial bonding strength between the base layer and the imitation stone surface layer, avoiding interlayer peeling. Step-by-step maintenance accurately controls the hydration process, improves the compressive strength of the material, and reduces shrinkage. The multi-stage grinding process reduces the surface roughness while improving the glossiness, while retaining the details of the imitation stone texture, achieving stable mass production of high-strength, high-simulation and high-durability manhole covers.

[0026] (III) Beneficial effects of the present invention: The present invention significantly improves the structural strength and installation accuracy of the manhole cover through the geometrically adaptive nested structure of the metal outer frame and the metal inner groove and the integrated design of the composite load-bearing layer and the imitation stone surface layer, while optimizing the convenience of maintenance and the coordination with the urban landscape. The support part of the metal outer frame and the bearing plate of the metal inner groove form a uniformly stressed support interface, which effectively disperses the load and avoids stress concentration, ensuring high load-bearing stability; the nested structure is combined with a directional pull-out design to simplify maintenance operations and reduce the risk of maintenance damage. The imitation stone surface layer is seamlessly connected to the surface of the manhole cover, and a highly simulated stone texture is achieved through a molding process to ensure visual uniformity, without joints or color differences, greatly enhancing the integration with the urban environment. In addition, the fiber-reinforced matrix and the steel skeleton work together to inhibit crack propagation, and combined with the anti-rust sealing design, the durability and corrosion resistance of the manhole cover in harsh environments are comprehensively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 A schematic diagram of the three-dimensional structure of an imitation stone manhole cover provided by one embodiment of the present invention; Figure 2 A schematic cross-sectional view of the imitation stone manhole cover in the extension direction provided by one embodiment of the present invention; Figure 3 A schematic diagram of the three-dimensional structure of an imitation stone manhole cover in an uncast state provided by one embodiment of the present invention; Figure 4 A schematic diagram of the three-dimensional structure of the metal outer frame and the metal inner groove of the imitation stone manhole cover provided by one embodiment of the present invention in a separated state; Figure 5 A schematic diagram of the three-dimensional structure of an imitation stone manhole cover in an uncast state provided by one embodiment of the present invention; Figure 6 A schematic diagram of the three-dimensional structure of a metal outer frame and a metal inner tank in a separated state provided by an embodiment of the present invention; Figure 7 A schematic diagram of a three-dimensional structure of a metal outer frame provided in one embodiment of the present invention; Figure 8 A schematic diagram of the three-dimensional structure of a metal outer frame provided by an embodiment of the present invention with the supporting crossbeam removed.

[0029] Icons: 1. Metal outer frame; 11. Outer frame; 111. Limiting groove; 12. Support part; 121. Deflection notch; 122. Overlap groove; 13. Channel opening; 14. Load-bearing beam; 2. Metal inner groove; 21. Inner frame; 211. Limiting protrusion; 22. Load-bearing plate; 23. Fixing part; 231. Pulling hole; 24. Steel skeleton; 3. Composite bearing layer; 4. Imitation stone surface layer. DETAILED DESCRIPTION

[0030] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Specific embodiment: Example 1: like Figures 1 to 4 As shown, this embodiment provides an imitation stone manhole cover, including a metal outer frame 1 and a metal inner groove 2, the metal inner groove 2 is filled with a composite bearing layer 3 and an imitation stone surface layer 4, specifically as follows: The metal outer frame 1 is fixedly embedded in the wellhead and is made of corrosion-resistant steel (such as 304 stainless steel, 316L stainless steel, or hot-dip galvanized carbon steel. In this embodiment, 304 stainless steel with a thickness of 3-5 mm is selected). It includes an annular outer frame 11 and a support portion 12. The annular outer frame 11 can be configured as a rectangular frame, a circular frame, or other customized shape according to the actual needs of the wellhead. In this embodiment, the annular outer frame 11 is a rectangular frame. The support portion 12 is fixedly connected to the bottom of the annular outer frame 11. Its purpose is to provide support for the metal inner tank 2 and extend a preset distance toward the center of the wellhead. After the metal inner tank 2 is removed, a passage opening 13 matching the wellhead size is formed. The support portion 12 can be a plurality of support blocks or support plates arranged along the bottom circumference of the annular outer frame 11. The support blocks or support plates can be fixedly connected to the annular outer frame 11 or can be integrally formed. In this embodiment, the support portion 12 is a support plate fixedly welded to the outer frame, which forms a support edge along the bottom circumference of the annular outer frame 11.

[0032] The metal inner tank 2 is nested in the metal outer frame 1 and is made of corrosion-resistant steel consistent with the outer frame (for example, 304 stainless steel, 316L stainless steel or hot-dip galvanized carbon steel. In this embodiment, 304 stainless steel is selected with a thickness of 3-5 mm). The structure of the metal inner tank 2 includes an inner frame 21 that is geometrically matched with the annular outer frame 11 and a load-bearing plate 22 that closes the bottom opening. The size of the inner frame 21 is designed to be slightly smaller than the outer frame to form a moderate assembly gap (usually 1-2 mm) to ensure that no external force is required for forced adjustment during installation to avoid structural deformation. The load-bearing plate 22 is a flat structure. The bottom of the inner frame 21 is closed by continuous welding. The surface is flat and warp-free after welding, ensuring the stability of the overall structure. The outer edge of the bottom of the load-bearing plate 22 is designed with an overlapping edge, and the bottom surface of the overlapping edge is provided with anti-slip grooves, which fits with the upper surface of the support plate of the support portion 12 to form a stable support interface.

[0033] The metal inner tank 2 and the metal outer frame 1 are assembled through precise matching, ensuring that the inner tank can be smoothly embedded in the outer frame and can be easily removed when needed. The assembly gap between the inner tank and the outer frame is 1-2mm, which can ensure the installation accuracy of the manhole cover. The design of the metal inner tank 2 allows it to be easily removed from the metal outer frame 1 by a simple pulling operation during the use of the manhole cover, which is convenient for inspection and maintenance. The metal inner tank 2 is also provided with a steel frame 24 welded to the side wall of the metal inner tank 2. The steel frame 24 of this embodiment is a double-layer vertical arrangement. The material of the metal inner tank 2 is 304 stainless steel, which has strong corrosion resistance and excellent mechanical properties, and is suitable for long-term exposure to various harsh environments. In addition, 316L stainless steel can be used as an alternative material, suitable for special environments that require higher corrosion resistance; for some occasions with lighter loads, hot-dip galvanized carbon steel is also a suitable alternative, which can provide sufficient strength and corrosion resistance while controlling costs.

[0034] The nested relationship between the metal inner trough 2 and the metal outer frame 1 allows the manhole cover to have high installation accuracy and easy disassembly. It does not rely on welding or bolting, but rather ensures stability and safety in long-term use through a nested design. After the manhole cover is installed, the metal inner trough 2 can be removed from the outer frame by a pulling operation, which simplifies the inspection and replacement of the manhole cover. Specifically, the four block-shaped fixings 23 fixedly welded at the inner corners of the metal inner frame serve to enhance the compressive strength of the adjacent frames. At the same time, its top surface is flush with the surface of the imitation stone surface layer 4, and is provided with pulling holes 231, which facilitates the removal of the metal inner trough 2 by pulling simultaneously through the four pulling holes 231, thereby opening the manhole cover to complete subsequent inspection and maintenance operations.

[0035] The fiber-reinforced matrix material of the composite bearing layer 3 is steel fiber reinforced concrete (UHPC), which comprises the following components in parts by mass: Cementitious materials: Portland cement: 830 parts (the preferred value in this embodiment is 800-850 parts) Fly ash: 40 parts (this value is selected within the range of 35-45 parts to provide better fluidity and impermeability) Mineral powder: 200 parts S95 or higher grade mineral powder (select between 190-210 parts to ensure higher compressive strength and excellent durability) Silica fume: 135 parts (select within the range of 130-140 parts to improve the crack resistance and density of the matrix) In this embodiment, 830 parts of Portland cement are used. This amount ensures the compressive strength of the cement and its excellent compatibility with other materials. The advantages of using Portland cement include its common production process and relatively low cost. Furthermore, it has good fluidity and high initial strength, making it suitable as the base cementitious material in this embodiment.

[0036] Aggregate ratio: Quartz sand with a particle size of 1.25-0.63mm: preferably 600 parts (within the range of 550-650 parts, providing better aggregate packing properties); Quartz sand with a particle size of 0.63-0.315mm: preferably 100 parts (within the range of 90-110 parts, ensuring the fluidity of the concrete); Quartz sand with a particle size of 0.315-0.16mm: preferably 200 parts (within the range of 190-210 parts, forming a dense aggregate system). Using these three quartz sand particle size combinations can improve the density of concrete and effectively reduce the void content, thereby enhancing its compressive strength and impermeability. The selection of fine aggregate ensures that the concrete has better crack resistance and stability in different usage environments, adapting to different environmental conditions.

[0037] Steel Fiber: Steel fiber with a diameter of 0.20 mm, a length of 13 mm, an aspect ratio of 65, and a tensile strength of ≥ 2000 MPa: 5 parts; In this embodiment, the steel fibers are 0.20 mm in diameter and 13 mm in length, with an aspect ratio of 65. This design effectively improves the crack resistance and toughness of concrete. The tensile strength of the steel fibers is ≥2000 MPa, ensuring that the concrete is less susceptible to crack propagation when subjected to external forces. The addition of steel fibers eliminates the need for concrete to rely solely on the cement matrix for strength. Instead, the synergistic effect of the fibers and the matrix enhances its bending, tensile, and fatigue resistance, making it particularly suitable for the design of structures such as large manhole covers.

[0038] Admixtures: Polycarboxylate water reducer: 7 parts (within the range of 5-8 parts) The advantage of using polycarboxylate superplasticizers is that they can significantly improve the fluidity of concrete and reduce the amount of cement used, effectively reducing the water-binder ratio. This not only makes the concrete stronger, but also improves its impermeability and reduces cracking.

[0039] The cementitious material has a water-binder ratio of 0.18 (within the range of 0.16-0.20). This ratio balances the concrete's fluidity and ultimate strength, ensuring high density and compressive resistance. A high water-binder ratio can lead to insufficient concrete strength, while a low ratio can affect fluidity and workability during construction. Therefore, a water-binder ratio of 0.18 ensures the concrete's fluidity while fully utilizing its compressive strength.

[0040] The steel fibers are treated with a surface modifier and are dispersed in the matrix in a three-dimensional random manner. The use of the modifier can improve the bonding force between the steel fibers and the cement matrix, ensure that the steel fibers are evenly distributed in the concrete, and effectively improve the crack resistance and impact toughness of the composite bearing layer 3.

[0041] The following is a comparative analysis of tests on ordinary concrete, traditional high-performance concrete, and the steel fiber reinforced concrete (UHPC) in this example. The testing standards comply with the "Standard for Test Methods for Mechanical Properties of Ordinary Concrete" GB / T 50081 and the "Standard for Test Methods for Long-term Properties and Durability of Concrete" GB / T 50082: As can be seen from the table, UHPC is superior to ordinary concrete and traditional high-performance concrete in all performance indicators, especially in compressive strength, fracture energy, chloride ion diffusion, carbonation depth, freeze-thaw shedding and oxygen permeability, showing its advantages in high strength, high durability and high permeability resistance.

[0042] The cementitious material also incorporates graphene oxide, at a concentration of 0.05% by mass of Portland cement, with a mass ratio of 1:35 between graphene oxide and steel fiber. The addition of graphene oxide significantly improves the concrete's crack resistance, durability, and low-temperature crack resistance, particularly in low temperatures and harsh environments.

[0043] The mass ratio of the gelling material is: Portland cement:silica fume:graphene oxide=100:15:0.05 After being surface-modified with a silane coupling agent, graphene oxide is dispersed into the concrete paste using ultrasonic vibrations, ensuring uniform distribution within the concrete matrix. The modified graphene oxide effectively fills the micropores in the cement matrix, reducing porosity and thereby improving the concrete's impermeability and frost resistance. Furthermore, graphene oxide enhances concrete's crack resistance, particularly in low-temperature environments, preventing cracks caused by temperature fluctuations.

[0044] The imitation stone surface layer 4, covering the composite bearing layer 3, is flush with the top of the metal inner channel 2, ensuring the overall smoothness and aesthetics of the manhole cover. Made primarily of high-quality white cement, continuously graded quartz sand, and inorganic pigments, it utilizes an advanced compression molding process to accurately reproduce the texture and color of natural stone. Its surface is flat and smooth, offering exceptional wear resistance and durability.

[0045] The raw materials of the imitation stone surface layer 4 include: White cement: strength grade not less than P·W 42.5, accounting for 30%-50% of the total mass of the imitation stone surface layer 4, preferably 40% in this embodiment.

[0046] White cement, the primary binder for the imitation stone surface layer 4, possesses excellent hydration properties and compressive strength, making it particularly suitable for applications requiring high strength and durability. Selecting white cement with a strength grade no less than P·W 42.5 ensures the stability and long-term load-bearing capacity of the imitation stone surface layer 4 during use. This cement not only provides ideal hardening properties but also effectively combines with other ingredients to enhance the surface layer's crack resistance and impermeability.

[0047] Continuously graded quartz sand: composed of first-grade sand with a particle size of 0.425-0.85 mm and second-grade sand with a particle size of 0.18-0.425 mm, with a mass ratio of (3:7) to (7:3), accounting for 50%-70% of the total mass of the imitation stone surface layer 4, and preferably 60% in this embodiment.

[0048] The role of quartz sand in the imitation stone surface layer 4 is to act as an aggregate to provide structural strength and stability. Continuously graded quartz sand can increase the density of the surface layer and reduce the porosity, thereby improving the overall compression resistance, wear resistance and aging resistance. Depending on the particle size, quartz sand can optimize the density of the surface layer, making it exhibit better weather resistance and long-term stability in different environments. At the same time, quartz mortar can make the manhole cover colorful and stable, highly integrated with the environment, and have a high degree of imitation stone effect, simulating the texture, color and texture of natural stone (such as marble, granite, slate, etc.), with a visual effect close to that of real stone, and the texture connection is natural.

[0049] Inorganic pigment: accounts for 0.5%-2% of the mass of white cement, preferably 1% in this embodiment.

[0050] Inorganic pigments are added to imitation stone surfacing to mimic the color of natural stone. Their high color fastness and weather resistance ensure that the manhole cover retains its color over long-term use, maintaining its aesthetic appeal and environmental integration. A moderate amount of pigment achieves the desired color effect while preserving the surface's physical properties.

[0051] The surface of the imitation stone surface layer 4 is molded to mimic the texture of natural stone. This process involves pressing the raw materials of the imitation stone surface layer 4 into shape, then subjecting them to high temperature and pressure to fully fuse the surface materials, creating a texture and feel similar to natural stone. This process not only ensures the precise shape of the imitation stone surface layer 4, but also effectively reduces seams and air bubbles, improving the overall appearance and quality of the manhole cover.

[0052] The surface of the imitation stone surface layer 4 is also provided with a nano titanium dioxide (TiO2) photocatalytic coating, the thickness of the coating is 10-20 μm, and has the following composition: Nano-titanium dioxide particles: particle size 10-50 nm, accounting for 3%-8% of the total mass of the coating material, preferably 5% in this embodiment.

[0053] The addition of nano-titanium dioxide provides a self-cleaning function to the imitation stone surface layer 4. Titanium dioxide exhibits strong photocatalytic activity under ultraviolet light, breaking down organic pollutants and dirt, keeping the manhole cover surface clean. The nano-titanium dioxide particles are sized between 10 and 50 nm to increase their specific surface area, significantly enhancing their photocatalytic activity and stain removal effectiveness.

[0054] Inorganic binder: silica sol or alumina sol, accounting for 15%-25% of the total mass of the coating material, preferably 20% in this embodiment.

[0055] Silica sol and alumina sol, as inorganic binders, effectively enhance the bonding between the nano-titanium dioxide particles and the surface of the imitation stone surface layer 4, ensuring that the coating resists shedding over extended use and improving weather resistance. Their excellent adhesion ensures a uniform distribution of the nano-titanium dioxide particles, enhancing the coating's photocatalytic effect.

[0056] Dispersant: sodium polyacrylate, accounting for 0.1%-0.5% of the total mass of the coating material, preferably 0.3% in this embodiment.

[0057] Sodium polyacrylate acts as a dispersant to ensure uniform distribution of nano-titanium dioxide particles within the coating, preventing particle aggregation. Its excellent dispersibility helps maintain uniformity and stability, ensuring the photocatalytic coating's continued effectiveness over long-term use.

[0058] The preparation method of the imitation stone manhole cover comprises the following steps: S1. Mixing and stirring of base materials: The gelling components of the fiber-reinforced matrix material, graded aggregate, steel fiber and admixtures are put into a high-speed mixer, the stirring speed is set to 800-1000r / min, and the stirring is continued for 4-5 minutes to obtain a colloidal UHPC slurry with a fluidity of 150-200mm.

[0059] During this process, steel fibers, acting as reinforcements, are thoroughly mixed with the cementitious material. The steel fibers, with lengths of 12-15mm and diameters of 0.15-0.25mm, are evenly distributed throughout the slurry using a three-dimensional, random dispersion method. This mixing process ensures a good bond between the steel fibers and the matrix, thereby improving the concrete's resistance to cracking, impact, and fatigue after hardening.

[0060] S2. Base pouring and vibration: The prepared UHPC slurry is quickly poured into the accommodating cavity of the metal inner tank 2. First, an attached high-frequency flat vibrator (frequency 50-60 Hz, amplitude 0.5-1.0 mm) is used for internal vibration to ensure that the slurry can fully fill the various details of the inner tank, reduce the generation of voids and bubbles, and ensure the density of the base layer. Subsequently, an off-mold vibrator (frequency 100-120 Hz) is used to apply auxiliary vibration to the outer wall of the mold. Through two vibrations, the entire vibration time is controlled within 3-5 minutes, ensuring that the slurry is dense and free of bubbles, further improving the structural strength of the base layer.

[0061] S3. Primary maintenance and surface treatment: The vibrated base requires preliminary curing. Steam cure the base for 1.5-2 hours at 60-80°C, with humidity maintained at ≥90%, to promote the hydration reaction of the cement matrix and improve the initial strength and density of the concrete.

[0062] After primary curing, the surface layer is treated. A simulated stone surface layer 4 slurry composed of white cement, graded quartz sand, and inorganic pigments is poured onto the base surface. The water-to-binder ratio of this slurry is set at 0.18-0.22, which ensures the concrete slurry's fluidity and surface adhesion without compromising concrete strength.

[0063] To ensure uniformity and tight bonding of the imitation stone surface layer 4, a high-frequency attached flat plate vibrator (frequency 40-50Hz) and a surface flat plate vibrator are used to simultaneously vibrate the surface layer. The vibration time is 2-3 minutes. This process ensures that the surface layer slurry is fully bonded to the base layer, forming a seamless and uniform surface.

[0064] S4. Composite curing: The composite maintenance of imitation stone manhole cover is divided into two stages: Phase 1: Steam curing, maintaining the temperature at 60±5°C and humidity at ≥95% for 12 hours. This phase of curing accelerates the completion of the hydration reaction within the concrete and improves the density and strength of the material.

[0065] Phase 2: Natural curing, maintained at a temperature between 15-30°C and a humidity of 60-80%, away from direct sunlight, for 7 days. This phase helps the concrete solidify further, reduces shrinkage cracks, and prevents surface cracks caused by rapid evaporation.

[0066] S5. Surface finishing: After composite curing, the manhole cover needs to be finely ground to ensure its appearance quality and physical properties. A fully automatic grinder is used for three-stage grinding: Rough grinding: Use 80-120 mesh diamond grinding wheel, speed 800-1000r / min, pressure 0.2-0.4MPa. This stage mainly removes large areas of surface unevenness to ensure surface flatness.

[0067] Fine grinding: Use 200-400 mesh resin grinding wheel, speed 1200-1500r / min, pressure 0.1-0.2MPa. This stage is mainly to further refine the surface to achieve higher flatness and smoothness.

[0068] Polishing: Use 800-1200 mesh polishing pad, rotation speed 2000-2500r / min, pressure 0.05-0.1MPa. This stage is the final polishing stage to improve the surface gloss and ensure that the surface of the manhole cover achieves the ideal appearance effect.

[0069] After grinding, the surface roughness Ra is controlled at ≤0.8μm and the glossiness is ≥80GU, which not only ensures the aesthetics of the manhole cover, but also improves its wear resistance and anti-pollution properties.

[0070] The following is a comprehensive test analysis of traditional reinforced concrete manhole covers, cast iron covers, and the imitation stone manhole cover in this embodiment: It can be seen that the imitation stone manhole cover of this embodiment is suitable for places with high requirements for corrosion resistance, durability and installation convenience, and is particularly suitable for long-term use and maintenance cost control.

[0071] Example 2: This embodiment is basically the same as the solution of embodiment 1, except that the structural improvements of the metal outer frame 1 and the metal inner tank 2 are as follows: The outer frame 11 of the metal outer frame 1 is composed of two pairs of oppositely arranged enclosing panels, of which the first pair of oppositely arranged enclosing panels are inclined, forming a geometric adaptation relationship with the support interface at the same inclination angle; the second pair of oppositely arranged enclosing panels remain in a vertical state. The inclination angle of the first pair of enclosing panels forms the same angle as the support portion 12, ensuring that the metal inner tank 2 can be tightly embedded in the metal outer frame 1 and ensuring high precision and stability during installation. The overall structural design of the metal outer frame 1 makes the metal inner tank 2 more convenient during installation and disassembly. In particular, when maintenance is required, the inclined structure can effectively guide the positioning and disassembly of the metal inner tank 2.

[0072] Specifically, the first pair of enclosure panels is tilted, with the tilt angle determined based on the standard wellhead design and the actual use of the manhole cover. This angle is typically 15°-20°, making the metal inner tank 2 easier to install and maintaining a more stable structure during use. The second pair of enclosure panels remains upright, providing support and restraint, ensuring that the metal inner tank 2 is not easily displaced.

[0073] Furthermore, the top surfaces of the two fixing parts 23 on the lifting side of the four fixing parts 23 fixedly welded at the inner corners of the metal inner frame only need to be flush with the surface of the imitation stone surface layer 4, and the other two fixing parts 23 are located in the composite bearing layer 3. The metal inner groove 2 is tilted and pulled out by lifting the two lifting holes 231 on the lifting side, thereby opening the manhole cover to complete subsequent maintenance work. Compared with Example 1, this setting exposes only two lifting holes 231 on the fixing parts 23, which further increases the area of ​​the imitation stone surface layer 4 while increasing the stability of the metal inner groove 2, so that the imitation effect of the manhole cover surface and the stone road surface is better.

[0074] The shape of the inner frame 21 of the metal inner trough 2 matches the inclined fitting relationship of the outer frame 11, so that the vertical cross-section of the inner trough along the opposite direction of the first pair of enclosing plates has a diamond-shaped profile. The design of the inner frame 21 and the coordination between the inclined enclosing plates ensure that the metal inner trough 2 can form a firm connection with the metal outer frame 1, avoiding looseness or instability caused by position deviation or external force. The diamond-shaped profile design of the inner trough not only enhances the geometric fitting relationship between the inner trough and the outer frame, but also enables the metal inner trough 2 to evenly distribute pressure when subjected to force, thereby improving the overall compressive performance of the manhole cover.

[0075] The support portion 12 extends circumferentially along the bottom of the metal outer frame 1, and a deflection notch 121 for the support portion 12 is provided at one end of the inwardly inclined enclosing plate of the first pair of enclosing plates. The size of this notch is configured to allow the metal inner tank 2 to directional deflect around the edge of the deflection notch 121 when the other end is pulled, thereby allowing the acute-angled end of the metal inner tank 2 to partially embed within the support interface, completing the release action of the metal inner tank 2.

[0076] Specifically, the deflection notch 121 is designed with a specific size and shape, which should be adapted to the actual size of the metal inner groove 2. Typically, the notch is 5-10mm wide and 8-12mm deep, and the notch is designed at an angle that matches the shape of the metal inner groove 2. This allows the metal inner groove 2 to smoothly deflect along the edge of the deflection notch 121 during the lifting operation, with the sharp-angled end of the inner groove automatically embedding into the support interface and smoothly separating from the metal outer frame 1.

[0077] This structural improvement not only improves the stability of the metal inner trough 2, but also effectively simplifies the installation and disassembly process of the manhole cover. Especially when the manhole cover needs regular maintenance or replacement, the deflection notch 121 can make the inner trough easier to remove, reducing the operational complexity and damage risk during disassembly.

[0078] Different from Example 1, the support plate in this embodiment is provided with a lap groove 122, and the metal outer frame 1 also includes at least one supporting beam 14, which is detachably lapped on the lap groove 122, and the supporting surface of the supporting beam 14 is flush with the supporting surface of the support plate.

[0079] The upper surface of the pallet is provided with an overlapping groove 122, which is used to cooperate with the load-bearing beam 14. The load-bearing beam 14 is connected to the pallet by sliding overlapping. The precision of the overlapping groove 122 design enables the load-bearing beam 14 to form a tight connection with the pallet, ensuring that the load-bearing surface of the beam is completely flush with the load-bearing surface of the pallet. This design ensures that when the manhole cover is under stress, the load-bearing beam 14 can evenly distribute the load and improve the stability of the overall structure. The detachable connection of the load-bearing beam 14 makes the maintenance of the manhole cover more convenient. It can be quickly installed or disassembled as needed, avoiding complicated operations and reliance on too many tools.

[0080] In this embodiment, the load-bearing beam 14 is made of the same material as the metal outer frame 1, usually 304 stainless steel or hot-dip galvanized carbon steel. The thickness and width are customized according to the load-bearing requirements. The common thickness range is 5-10 mm, and the width is between 50-100 mm, which can ensure that the beam has sufficient load-bearing capacity and corrosion resistance.

[0081] Furthermore, at least one of the supporting crossbeams 14 is disposed at the edge of the deflection notch 121, and one side of the top deflection notch 121 is configured as an arc, forming an abutment surface for the metal inner tank 2 to abut against the supporting plate 22 when the metal inner tank 2 is disengaged. This design allows the supporting crossbeam 14 to effectively guide the movement of the metal inner tank 2 when it is pulled to disengage, preventing unbalanced or asymmetric forces from causing unsmooth disengagement or structural damage.

[0082] Specifically, the edge of the deflection notch 121 is designed with a curved surface, forming a smooth interface with the contact surface at the top of the support beam 14. This design effectively reduces damage caused by collision or friction during the disassembly process. The curved surface design disperses the instantaneous impact force exerted when the inner groove is disengaged, ensuring that the sharp-angled end of the metal inner groove 2 smoothly embeds into the support interface, completing the disassembly. This design makes the manhole cover disassembly process smoother and extends the service life of the metal inner groove 2 and the support beam 14.

[0083] The outer frame 11 and the inner frame 21 are respectively provided with a limiting groove 111 and a limiting protrusion 211 that cooperate with each other. Their specific function is to guide the movement trajectory when the metal inner groove 2 is lifted on one side, and at the same time make the support point of the unilateral pulling up smoother, thereby improving the stability and operability of the manhole cover disassembly process.

[0084] Specifically, the retaining groove 111 is curved and designed to cooperate with the retaining protrusion 211 of the inner frame 21 to form a smooth guiding structure. When the metal inner tank 2 is lifted from one side, the retaining groove 111 and the retaining protrusion 211, through precise geometric adaptation, ensure the inner tank's motion trajectory is stable, preventing improper operation from causing the inner tank to move unsmoothly or deviate, thereby affecting the efficiency and safety of manhole cover removal. The curved design of the retaining groove 111 effectively disperses the pressure applied during the lifting process, ensuring that the metal inner tank 2 can be smoothly separated from the outer frame.

[0085] The limiting protrusion 211 matches the limiting groove 111 and is generally a strip-shaped structure with a width slightly smaller than the width of the limiting groove 111. This design not only ensures a tight fit but also provides room for error. This allows the metal inner tank 2 to fit smoothly during installation and removal, even with small dimensional errors or machining tolerances, thus avoiding jamming or deformation caused by installation errors. This error-tolerant design improves tolerance during production and installation while ensuring stability during use.

[0086] To further enhance stability and prevent the ingress of dust and debris, a blocking block is installed at the top of the retaining groove 111 to seal the top opening. This block effectively prevents foreign matter from entering the retaining groove 111, preventing the retaining groove 111 from malfunctioning due to accumulated dust or debris during long-term use. Furthermore, the blocking block design improves the sealing performance of the manhole cover, making the overall structure more durable and waterproof.

[0087] The process of removing the metal inner tank 2: Use lifting equipment to simultaneously connect the lifting holes 231 on both sides of the metal inner trough 2. Through the lifting operation, the sharp-angled end of the bottom of the metal inner trough 2 is deflected toward the channel opening 13, so that the metal inner trough 2 is tilted toward the channel opening 13 around the smooth arc surface of the supporting beam 14, thereby ensuring that the inner trough can be smoothly separated from the metal outer frame 1 and easily taken out.

[0088] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. An imitation stone manhole cover, characterized in that: include: A metal outer frame is fixedly embedded in the wellhead, comprising an annular outer frame and a support portion, wherein the support portion is fixedly connected to the bottom of the annular outer frame and extends a preset distance toward the center of the wellhead to form a passage opening matching the size of the wellhead; A metal inner tank is nested in the outer frame structure, comprising an inner frame geometrically matched with the annular outer frame and a bearing plate closing the bottom of the inner frame, wherein the bearing plate overlaps with the upper surface of the support portion to form a support interface; A composite load-bearing layer is filled in the accommodating cavity of the metal inner tank, and comprises a fiber-reinforced matrix material and a steel skeleton fixedly connected to the inner wall of the metal inner tank; The imitation stone surface layer covers the surface of the composite bearing layer, and the outer surface is flush with the top of the metal inner groove.

2. The imitation stone manhole cover according to claim 1, characterized in that: The fiber-reinforced matrix material of the composite bearing layer is steel fiber reinforced concrete, which comprises, by mass: Cementitious materials: Portland cement 800-850 parts, fly ash 35-45 parts, mineral powder 190-210 parts, silica fume 130-140 parts; Aggregate: 550-650 parts of quartz sand with a particle size of 1.25-0.63mm, 90-110 parts of quartz sand with a particle size of 0.63-0.315mm, and 190-210 parts of quartz sand with a particle size of 0.315-0.16mm; Steel fiber: 4-6 parts of steel fiber with a diameter of 0.15-0.25mm, a length of 12-15mm, an aspect ratio of 50-70, and a tensile strength of ≥2000MPa; Admixture: 5-8 parts of polycarboxylate water reducer; The water-to-cement ratio of the cementitious material is 0.16-0.20, and the steel fibers are treated with a surface modifier and are three-dimensionally dispersed in the matrix.

3. The imitation stone manhole cover according to claim 2, characterized in that: Graphene oxide is also added to the cementitious material in an amount of 0.03% to 0.1% of the mass of the Portland cement, and the mass ratio of graphene oxide to steel fiber is 1:50 to 1:30; The mass ratio of the cementitious material is: Portland cement: silica fume: graphene oxide = 100: 15: 0.05; The graphene oxide is surface-modified by a silane coupling agent and then dispersed in the concrete slurry through ultrasonic vibration.

4. The imitation stone manhole cover according to claim 1, characterized in that: The raw materials of the imitation stone surface layer include: White cement: strength grade not less than P·W 42.5, accounting for 30%-50% of the total mass of the imitation stone surface layer; Continuously graded quartz sand: composed of first-grade sand with a particle size of 0.425-0.85 mm and second-grade sand with a particle size of 0.18-0.425 mm, with a mass ratio of (3:7) to (7:3), accounting for 50%-70% of the total mass of the imitation stone surface layer; Inorganic pigment: accounting for 0.5%-2% of the mass of the white cement; The surface of the imitation stone surface layer is formed into imitation natural stone texture through a molding process.

5. The imitation stone manhole cover according to claim 4, characterized in that: The surface of the imitation stone surface layer is also provided with a nano titanium dioxide (TiO2) photocatalytic coating, the thickness of the photocatalytic coating is 10-20 μm, and comprises the following components: Nano-titanium dioxide particles: particle size 10-50nm, accounting for 3%-8% of the total mass of the coating material; Inorganic binder: silica sol or alumina sol, accounting for 15%-25% of the total mass of the coating material; Dispersant: sodium polyacrylate, accounting for 0.1%-0.5% of the total mass of the coating material; The nano titanium dioxide particles are surface-modified by a silane coupling agent and embedded in the coating in a uniformly dispersed state.

6. The imitation stone manhole cover according to any one of claims 1 to 5, characterized in that: The outer frame of the metal outer frame is composed of two pairs of oppositely arranged enclosing panels, wherein the first pair of oppositely arranged enclosing panels are in an inclined state, forming a geometric adaptation relationship with the support interface at the same inclination angle; the second pair of oppositely arranged enclosing panels remain in a vertical state; The shape of the inner frame of the metal inner groove matches the inclined adaptation relationship of the outer frame, so that the vertical cross-section of the inner groove along the opposite direction of the first pair of enclosing plates has a diamond-shaped profile; The support portion extends circumferentially along the bottom of the metal outer frame, and a deflection notch of the support portion is provided at one end of the inwardly inclined enclosing plate in the first pair of enclosing plates. The size of the deflection notch is configured to allow the metal inner groove to produce a directional deflection around the edge of the deflection notch when the other end is pulled, so that the acute-angle end portion of the metal inner groove is embedded in the support interface to complete the detachment action of the metal inner groove.

7. The imitation stone manhole cover according to claim 6, characterized in that: The support portion includes a support plate fixedly connected to the outer frame, and the support plate is provided with a lap groove; The metal outer frame further comprises at least one bearing crossbeam, which is detachably overlapped in the overlap groove, and the bearing surface of the bearing crossbeam is flush with the bearing surface of the support plate.

8. The imitation stone manhole cover according to claim 7, characterized in that: At least one of the bearing beams is arranged at the edge of the deflection notch, and one side of the top deflection notch is arranged in an arc surface, forming an abutting surface for the metal inner groove to abut against the bearing plate when the metal inner groove performs a disengagement action.

9. The imitation stone manhole cover according to claim 6, characterized in that: The outer frame and the inner frame are respectively provided with a limiting groove and a limiting protrusion that cooperate with each other.

10. A method for preparing an imitation stone manhole cover, characterized in that: The steps for manufacturing the imitation stone manhole cover according to any one of claims 1 to 9 are as follows: S1: putting the gelling component of the fiber-reinforced matrix material, the graded aggregate and the reinforcing fiber into a high-speed mixer and mixing and stirring to form a slurry with fluidity that meets the pouring requirements; S2: pouring the slurry into the accommodating cavity of the metal inner tank, and compacting the slurry by internal and external coordinated vibration; S3: Perform preliminary temperature control and maintenance on the formed base layer; Pour the imitation stone surface slurry on the base surface and make the surface slurry evenly distributed through the vibration process; S4: The manhole cover is subjected to steam curing and natural curing in sequence to control the hydration reaction process and stabilize the material properties; S5: The surface of the manhole cover after maintenance is subjected to multi-stage grinding treatment, including coarse grinding, fine grinding and polishing, to obtain the predetermined surface roughness and glossiness.

Images