Gradient metamaterial seismic isolation barrier and construction method thereof

Abstract

The present application relates to a kind of gradient metamaterial shock isolation barriers and its construction method. Specifically, a kind of gradient metamaterial shock isolation barriers, wherein shock isolation barrier is formed by the arrangement of two-dimensional lattice in the periodic arrangement of mutually perpendicular two directions by structural unit cell, and closed area is formed in the inside of shock isolation barrier;Structural unit cell is spaced apart a certain distance between each other in two directions;Wherein structural unit cell is composed of steel blank, rubber layer and concrete layer square, steel blank is solid square, rubber layer is wrapped outside steel blank, and concrete layer is wrapped outside rubber layer, and the geometric center of steel blank, rubber layer and concrete layer coincide with each other;Wherein the side length of steel blank is gradiently decreased from the outermost layer to the innermost layer of shock isolation barrier.

Description

Technical Field

[0001] This invention relates to a gradient metamaterial seismic isolation barrier and a construction method for the gradient metamaterial seismic isolation barrier. Background Technology

[0002] Millions of earthquakes occur worldwide each year, with thousands exceeding magnitude 5. Earthquakes are among the most destructive disasters known to human life and property. The resulting building collapses and secondary disasters, such as natural gas leaks, pose a significant threat to human safety. If an earthquake occurs near a densely populated large city or a critical facility like a nuclear power plant, the damage is immeasurable. The energy generated by an earthquake is primarily carried by surface waves propagating across the Earth's surface, with frequencies mainly concentrated below 15 Hz. Since the resonant frequencies of common buildings also fall within this range, seismic surface waves can cause significant damage to building structures. Furthermore, large-scale construction operations in cities, such as blasting and pile driving, while less destructive than earthquakes, can still impact surrounding buildings and facilities (especially laboratories or processing workshops related to precision instruments). Traditional earthquake protection primarily relies on passive protection through increasing structural strength or installing vibration isolation pads. However, this approach often significantly increases construction costs, is relatively complex in design and construction, and has limited applicability.

[0003] In recent years, the development of bandgap metamaterial structures has provided a new direction for seismic isolation. Within the bandgap range of metamaterials, seismic waves cannot pass through the metamaterial barrier, thus blocking the propagation of vibrations and achieving the effect of vibration reduction or isolation. Currently, metamaterials are mainly divided into two types: Bragg scattering type and localized resonance type.

[0004] The working mechanism of Bragg scattering metamaterials is the destructive interference of forward and backward waves, therefore the wavelength that can be effectively controlled needs to be close to the size of the structural unit cell. Seismic wave wavelengths are typically tens or even hundreds of meters. If designed according to the Bragg scattering mechanism, the final structure would be unacceptable due to excessively high construction costs and large footprint.

[0005] In contrast, the working mechanism of locally resonant metamaterials is the resonant energy absorption of structural unit cells. The operating wavelength of locally resonant metamaterials depends on the dynamic characteristics of the structural unit cells themselves, offering greater design flexibility and typically enabling the control of large-wavelength vibrations with small-sized metamaterials. Currently, most mainstream seismic metamaterial isolation barriers are designed based on the locally resonant mechanism. However, while this type of design is theoretically effective in preventing the propagation of seismic surface waves, in reality, seismic waves contain enormous energy. After the structural unit cells capture seismic wave energy through local resonance, this energy accumulates within the isolation barrier, making it easily susceptible to damage and failure.

[0006] There is a further need in this field for metamaterial seismic isolation barriers that are suitable for a variety of different working conditions and are not easily damaged. Summary of the Invention

[0007] The purpose of this invention is to overcome the deficiencies in the existing technical field by periodically arranging structural unit cells with gradient-variable geometric parameters in a two-dimensional lattice configuration. This provides a gradient metamaterial seismic isolation barrier that can both prevent the impact of vibrations during early construction on surrounding facilities and provide seismic protection for buildings within the enclosed area after construction (i.e., it provides bidirectional seismic isolation). Furthermore, this seismic isolation barrier utilizes two different control mechanisms for seismic waves traveling from the outside in and from the inside out, preventing it from failing due to resonant energy absorption when facing seismic waves. In other words, the seismic isolation barrier of this invention can prevent damage from seismic waves traveling from the outside in or prevent the outward propagation of vibrations within the enclosed area of ​​the barrier under two different conditions. Therefore, the seismic isolation barrier of this invention is of great significance for protecting urban buildings from earthquake damage and for protecting highly vibration-sensitive buildings (such as precision instrument laboratories and ancient buildings) from the impact of large-scale construction operations.

[0008] According to one aspect of the present invention, a gradient metamaterial seismic isolation barrier is provided, wherein the seismic isolation barrier is formed by periodically arranging structural unit cells in a two-dimensional lattice arrangement in two mutually perpendicular directions, and forming a closed region inside the seismic isolation barrier; the structural unit cells are spaced apart from each other in both directions; wherein the structural unit cell is a cube composed of a steel billet, a rubber layer and a concrete layer, the steel billet is a solid cube, the rubber layer is wrapped around the outside of the steel billet, and the concrete layer is wrapped around the outside of the rubber layer, and the geometric centers of the steel billet, the rubber layer and the concrete layer coincide; wherein the side length of the steel billet decreases in a gradient from the outermost layer to the innermost layer of the seismic isolation barrier.

[0009] In addition to one or more of the features described above, or as an alternative, in another embodiment, the structural unit cell is located below the ground and the upper surface of the structural unit cell is flush with the ground.

[0010] In addition to one or more of the features described above, or as an alternative, in another embodiment, the structural unit cells are spaced 4m apart from each other in both directions from body center to body center.

[0011] In addition to one or more of the features described above, or as an alternative, in another embodiment, the side length of the structural unit cell is 2m, the thickness of the rubber layer is 0.2m, and the side length of the steel billet is in the range of 0.2m to 1.6m; the structural unit cell forms an omnidirectional bandgap in the range of 5.2Hz to 14.8Hz.

[0012] In addition to one or more of the features described above, or as an alternative, in another embodiment, the side length of the steel billet decreases linearly from 1.6m to 0.2m from the outermost to the innermost layer of the seismic isolation barrier, while the thickness of the rubber layer and the side length of the structural unit cell remain unchanged.

[0013] In addition to one or more of the features described above, or as an alternative, in another embodiment, when seismic surface waves are transmitted from outside the seismic isolation barrier, the enclosed area is protected from damage by the seismic surface waves as a protected area; when construction is taking place in the enclosed area and vibrations are generated and propagate outwards, the enclosed area is isolated from the surrounding area by the seismic isolation barrier as a construction area, so as to prevent the vibrations from construction in the enclosed area from propagating to the surrounding area and affecting the facilities in the surrounding area.

[0014] In addition to one or more of the features described above, or as an alternative, in another embodiment, when seismic surface waves travel from the outside of the seismic isolation barrier and pass through the barrier, the seismic surface waves are transformed into body waves by the barrier and guided deep underground, thereby protecting the enclosed area from damage caused by the seismic surface waves; when construction in the enclosed area generates vibrations that propagate outward through the seismic isolation barrier, the structural unit cells of the barrier generate local resonances, thereby capturing the vibrating surface waves and preventing them from continuing to propagate outward, thus avoiding impact on facilities in the surrounding area.

[0015] In addition to one or more of the features described above, or as an alternative, in another embodiment, the density of the steel ρ1 = 7850 kg / m³. 3 Young's modulus E1 = 2.1 × 10 11 Pa, Poisson's ratio μ1=0.3; density of rubber ρ2=1300kg / m³ 3 Young's modulus E2 = 1.02 × 10 5 Pa, Poisson's ratio μ1=0.3; density of concrete ρ3=2300kg / m³ 3 Young's modulus E3 = 2.5 × 10 10 Pa, Poisson's ratio μ3 = 0.2.

[0016] According to another aspect of the present invention, a construction method for the above-mentioned gradient metamaterial seismic isolation barrier is provided, comprising the following steps:

[0017] Based on the target operating frequency and the area available for designing seismic isolation barriers, design the geometric parameters and corresponding quantity of the structural unit cell. The geometric parameters include the side length of the structural unit cell, the thickness of the rubber layer, and the side length of the steel billet.

[0018] Mass production of structural unit cells;

[0019] Within the area of ​​the seismic isolation barrier, pits (e.g., earthen pits) are dug below the ground, and the pits are periodically arranged in two mutually perpendicular directions in a two-dimensional lattice arrangement.

[0020] The structural unit cell is buried in the pit so that the upper surface of the structural unit cell is flush with the ground. The side length of the steel billet decreases in a gradient from the outermost layer to the innermost layer of the seismic isolation barrier, for example, in a gradient linear decrease from 1.6m to 0.2m.

[0021] In addition to one or more of the features described above, or as an alternative, in another embodiment, the pits are cubes with a side length of 2m, and the pits are spaced 4m apart from each other in both directions from the center to the center.

[0022] Compared with existing seismic isolation technologies, this invention has the following advantages:

[0023] (1) Simple structure and easy to manufacture. The components of the structural unit cell are all common industrial raw materials or finished products, which are inexpensive and have simple shapes, making them easy to process.

[0024] (2) Wide applicability and high design flexibility. The invented seismic isolation barrier does not rely on the Bragg scattering mechanism, thus achieving the effect of controlling large-wavelength vibrations with a small-sized seismic isolation barrier. In addition, the effective operating frequency of the seismic isolation barrier is highly related to the geometric dimensions of the structural unit cell and the selected materials. Specific geometric parameters can be adjusted to suit different application scenarios and target frequencies.

[0025] (3) The structure is small in size and easy to arrange. The side length of the structural unit cell can be only 2m. It is laid under the ground and occupies very little underground space. It does not occupy the above-ground space and will not affect the city's aesthetics or people's activities.

[0026] (4) It can be installed either in the early stages or later. Traditional seismic isolation technologies generally involve reinforcing key parts of the building or installing seismic isolation pads. These technologies need to be designed in advance during the building planning stage and assembled during construction. If they are added later after the building is completed, the difficulty and cost are unacceptable. Unlike traditional technologies, the seismic isolation barrier designed in this invention does not directly contact the building, but only requires sufficient space for installation. It can protect a large number of existing buildings or building complexes that were not specially designed for seismic resistance during the design and construction stages at a lower cost.

[0027] (5) It has multiple working mechanisms for various working conditions. Unlike traditional resonant energy-absorbing metamaterials, the invented seismic isolation barrier can convert seismic surface waves transmitted from outside the barrier into body waves and guide them deep underground, thus effectively avoiding the energy accumulation caused by the capture of seismic waves in resonant energy-absorbing seismic isolation barriers (and the corresponding failure of structural units due to the destruction of seismic waves). When facing vibrations generated by construction in a closed area, the invented seismic isolation barrier can use resonant energy absorption to prevent the vibration from propagating further outward. At the same time, since the vibration energy generated by manual work is relatively small, there is no need to worry about the structural units being destroyed after the seismic isolation barrier resonates and absorbs energy. Therefore, the seismic isolation barrier of this invention can both limit vibrations to the construction area during the early stage of construction to avoid affecting surrounding facilities, and provide earthquake protection for buildings in the area after construction is completed. Attached Figure Description

[0028] These and other features, aspects, and advantages of the invention will be more readily understood by those skilled in the art upon reading the following detailed description with reference to the accompanying drawings. For clarity, the drawings are not necessarily drawn to scale, and some portions may be exaggerated to show detail. In all the drawings, the same reference numerals denote the same or similar parts, wherein:

[0029] Figure 1a This is a schematic diagram and a cross-sectional view along A-A' of a seismic isolation barrier protecting a closed area (as the protected area) from damage by seismic surface waves under condition 1, where seismic surface waves are transmitted from the outside of the seismic isolation barrier, according to an embodiment of the present invention.

[0030] Figure 1b This is a schematic diagram and a cross-sectional view along A-A' of a seismic isolation barrier according to an embodiment of the present invention, which isolates a closed area (as a construction area) from the surrounding area under working condition 2, where construction in the closed area generates vibrations that propagate outwards.

[0031] Figure 2a This is a three-dimensional perspective view of a structural unit cell of a seismic isolation barrier according to an embodiment of the present invention;

[0032] Figure 2b This is a three-dimensional sectional view of a structural unit cell of a seismic isolation barrier according to an embodiment of the present invention;

[0033] Figure 3 This is a band structure diagram of a structural unit cell of a seismic isolation barrier according to an embodiment of the present invention;

[0034] Figure 4a This is a transmission spectrum of a seismic isolation barrier according to an embodiment of the present invention for surface waves propagating along the x-direction under operating condition 1;

[0035] Figure 4bThis is a transmission spectrum of a seismic isolation barrier according to an embodiment of the present invention for surface waves propagating along the x-direction under operating condition 2;

[0036] Figure 5a This is a displacement field distribution diagram of a seismic isolation barrier according to an embodiment of the present invention, which converts a 5.9Hz surface wave propagating from the outside to the inside along the x-direction into a body wave under operating condition 1.

[0037] Figure 5b This is a displacement field distribution diagram of a seismic isolation barrier according to an embodiment of the present invention, which blocks a 5.9Hz surface wave propagating from the inside out along the x-direction under working condition 2 through local resonance energy absorption. Detailed Implementation

[0038] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Those skilled in the art should understand that these descriptions merely exemplify exemplary embodiments of the present invention and are in no way intended to limit the scope of protection of the present invention.

[0039] Figure 1a This is a schematic diagram and a cross-sectional view along A-A' of a seismic isolation barrier protecting a closed area (as the protected area) from damage by seismic surface waves under condition 1, where seismic surface waves propagate from the outside of the barrier, according to an embodiment of the present invention; and Figure 1b This is a schematic diagram and a cross-sectional view along A-A' of a seismic isolation barrier according to an embodiment of the present invention, which isolates a closed area (as a construction area) from the surrounding area under condition 2, where construction in the closed area generates vibrations that propagate outwards.

[0040] Specifically, a gradient metamaterial seismic isolation barrier 2 is formed by periodically arranging structural unit cells in a two-dimensional lattice arrangement in two mutually perpendicular directions (i.e., the x and y directions), forming a gapped metamaterial structure, and creating a closed region 1 within the barrier 2. The structural unit cells are spaced apart in both directions. Each structural unit cell is a cube composed of a steel billet 5, a rubber layer 4, and a concrete layer 3. The steel billet 5 is a solid cube, the rubber layer 4 surrounds the steel billet, and the concrete layer surrounds the rubber layer 4. The geometric centers of the steel billet 5, rubber layer 4, and concrete layer 3 coincide. The side length of the steel billet 5 decreases gradually from the outermost to the innermost layer of the seismic isolation barrier. Specifically, the structural unit cells are located below the ground surface, and their upper surfaces are flush with the ground.

[0041] Specifically, under condition 1, when seismic surface waves are transmitted from outside the seismic isolation barrier, the enclosed area 1 is protected by the seismic isolation barrier from damage caused by the seismic surface waves. Under condition 2, when construction is carried out in the enclosed area 1 and vibrations are generated and propagate outwards, the enclosed area 1 is isolated from the surrounding area by the seismic isolation barrier as a construction area, so as to prevent the vibrations of construction (such as blasting, pile driving and other large-scale manual operations) in the enclosed area 1 from propagating to the surrounding area and affecting the facilities in the surrounding area.

[0042] More specifically, in condition 1, when seismic surface waves travel from the outside of the seismic isolation barrier and pass through it, the surface waves are transformed into body waves by the barrier and guided deep underground, thus protecting the buildings within the enclosed area from damage by the surface waves (its working mechanism does not rely on local resonance, therefore it can avoid the seismic isolation barrier from being damaged by seismic waves due to resonance energy absorption). In condition 2, when construction work in the enclosed area generates vibrations that propagate outward through the seismic isolation barrier, the structural unit cells of the barrier generate local resonance, thereby capturing the surface waves and preventing them from continuing to propagate outward, thus avoiding impact on surrounding facilities (the working mechanism of the seismic isolation barrier in condition 2 is the same as that of traditional seismic metamaterial seismic isolation barriers, i.e., resonance energy absorption, but condition 2 is for vibrations generated by large-scale manual operations, whose energy is insufficient to damage the structural unit cells). In other words, the seismic isolation barrier according to embodiments of the present invention has bidirectional seismic isolation characteristics and relies on two different working mechanisms.

[0043] Figure 2a This is a three-dimensional perspective view of a structural unit cell of a seismic isolation barrier according to an embodiment of the present invention; Figure 2b This is a three-dimensional sectional view of a structural unit cell of a seismic isolation barrier according to an embodiment of the present invention. Specifically, the side length of the structural unit cell can be 2m, the thickness of the rubber layer 4 can be 0.2m, and the side length of the steel billet 5 can be in the range of 0.2m to 1.6m; the structural unit cell can form an omnidirectional bandgap (i.e., having a low-frequency bandgap) in the range of 5.2Hz to 14.8Hz (i.e., the effective operating frequency range of the seismic isolation barrier). More specifically, the spacing between the structural unit cells from body center to body center in both directions can be 4m. More specifically, the side length of the steel billet 5 can decrease linearly from 1.6m to 0.2m from the outermost layer to the innermost layer of the seismic isolation barrier, while the thickness of the rubber layer and the side length of the structural unit cell remain unchanged. It should be noted that the side length of the structural unit cell is not necessarily 2m, but can be larger (e.g., 3m, 4m, 5m, etc.) or smaller (e.g., 1.5m, 1m, 0.5m, etc.) depending on the construction environment of the seismic isolation barrier. In this case, other geometric parameters (e.g., the thickness of the rubber layer 4, the side length of the steel billet 5, etc.) are increased or decreased proportionally or otherwise (i.e., not proportionally) adjusted, so that the frequency range of the omnidirectional bandgap also changes accordingly.

[0044] More specifically, the density of steel ρ1 = 7850 kg / m³ 3 Young's modulus E1 = 2.1 × 10 11 Pa, Poisson's ratio μ1=0.3; density of rubber ρ2=1300kg / m³ 3 Young's modulus E2 = 1.02 × 10 5 Pa, Poisson's ratio μ1=0.3; density of concrete ρ3=2300kg / m³ 3 Young's modulus E3 = 2.5 × 10 10 Pa, Poisson's ratio μ3 = 0.2.

[0045] Additionally, a construction method for gradient metamaterial seismic isolation barriers is provided, comprising the following steps:

[0046] Based on the target operating frequency and the area available for designing seismic isolation barriers, design the geometric parameters and corresponding quantity of the structural unit cell. The geometric parameters include the side length of the structural unit cell, the thickness of the rubber layer, and the side length of the steel billet.

[0047] Mass production of structural unit cells;

[0048] Within the area of ​​the seismic isolation barrier, pits are dug below the ground, and the pits are arranged periodically in two mutually perpendicular directions in a two-dimensional lattice arrangement.

[0049] The structural unit cell is buried in the pit so that the upper surface of the structural unit cell is flush with the ground. The side length of the steel billet decreases in a gradient from the outermost layer to the innermost layer of the seismic isolation barrier, for example, in a gradient linear decrease from 1.6m to 0.2m.

[0050] More specifically, the pits are cubes with a side length of 2m, and the distance between each pit from its center to its center can be 4m in both directions.

[0051] Figure 3 This is a band structure diagram of a structural unit cell of a seismic isolation barrier according to an embodiment of the present invention. Specifically, the structural unit cell of the seismic isolation barrier according to an embodiment of the present invention can generate an omnidirectional bandgap, i.e., a light gray region, in the range of 5.2 Hz to 14.8 Hz. Within the range of the bandgap, the propagation of surface waves will be attenuated or blocked.

[0052] Figure 4a This is a transmission spectrum of a seismic isolation barrier according to an embodiment of the present invention for surface waves propagating along the x-direction under operating condition 1; Figure 4bThis is a transmission spectrum of a seismic isolation barrier according to an embodiment of the present invention for surface waves propagating in the x-direction under operating condition 2. The light gray area represents the attenuation region in the transmission spectrum (a transmission coefficient less than 0 indicates that the vibration signal detected after the isolation barrier is less than the vibration signal before entering the isolation barrier along the wave propagation direction). Calculations show that the seismic isolation barrier according to the embodiment of the present invention can effectively attenuate surface waves of approximately 5Hz to 15Hz under both operating conditions 1 and 2. The attenuation region shown in the transmission spectrum is related to... Figure 3 The band gap regions of the structural unit cells are highly consistent, meaning that the seismic isolation barrier of this invention can attenuate surface waves located within the band gap range in both directions.

[0053] Figure 5a This is a displacement field distribution diagram of a seismic isolation barrier according to an embodiment of the present invention, which converts a 5.9Hz surface wave propagating from the outside to the inside along the x-direction into a body wave under operating condition 1. Figure 5b This is a displacement field distribution diagram showing how a seismic isolation barrier, according to an embodiment of the present invention, blocks 5.9Hz surface waves propagating from the inside out along the x-direction under load condition 2 through localized resonant energy absorption. It can be clearly seen that in load condition 1, when seismic surface waves propagate from the outside of the isolation barrier to the inside, they are converted into body waves and guided deep underground, protecting surface buildings in the enclosed area (the protected area) from earthquake damage. In load condition 2, when seismic surface waves propagate from the inside of the isolation barrier to the outside, they excite resonant energy absorption in the structural unit cells, thereby blocking the propagation of surface waves and preventing large-scale manual operations in the construction area from affecting surrounding buildings.

[0054] Compared with existing seismic isolation technologies, this invention has the following advantages:

[0055] (1) Simple structure and easy to manufacture. The components of the structural unit cell are all common industrial raw materials or finished products, which are inexpensive and have simple shapes, making them easy to process.

[0056] (2) Wide applicability and high design flexibility. The invented seismic isolation barrier does not rely on the Bragg scattering mechanism, thus achieving the effect of controlling large-wavelength vibrations with a small-sized seismic isolation barrier. In addition, the effective operating frequency of the seismic isolation barrier is highly related to the geometric dimensions of the structural unit cell and the selected materials. Specific geometric parameters can be adjusted to suit different application scenarios and target frequencies.

[0057] (3) The structure is small in size and easy to arrange. The side length of the structural unit cell can be only 2m. It is laid under the ground and occupies very little underground space. It does not occupy the above-ground space and will not affect the city's aesthetics or people's activities.

[0058] (4) It can be installed either in the early stages or later. Traditional seismic isolation technologies generally involve reinforcing key parts of the building or installing seismic isolation pads. These technologies need to be designed in advance during the building planning stage and assembled during construction. If they are added later after the building is completed, the difficulty and cost are unacceptable. Unlike traditional technologies, the seismic isolation barrier designed in this invention does not directly contact the building, but only requires sufficient space for installation. It can protect a large number of existing buildings or building complexes that were not specially designed for seismic resistance during the design and construction stages at a lower cost.

[0059] (5) It has multiple working mechanisms for various working conditions. Unlike traditional resonant energy-absorbing metamaterials, the invented seismic isolation barrier can convert seismic surface waves transmitted from outside the barrier into body waves and guide them deep underground, thus effectively avoiding the energy accumulation caused by the capture of seismic waves in resonant energy-absorbing seismic isolation barriers (and the corresponding failure of structural units due to the destruction of seismic waves). When facing vibrations generated by construction in a closed area, the invented seismic isolation barrier can use resonant energy absorption to prevent the vibration from propagating further outward. At the same time, since the vibration energy generated by manual work is relatively small, there is no need to worry about the structural units being destroyed after the seismic isolation barrier resonates and absorbs energy. Therefore, the seismic isolation barrier of this invention can both limit vibrations to the construction area during the early stage of construction to avoid affecting surrounding facilities, and provide earthquake protection for buildings in the area after construction is completed.

[0060] It should be noted that the above-described implementation examples are only for illustrating the design method of the present invention and demonstrating its effectiveness. Within the scope of the concept and principles of the present invention, several improvements and redesigns can be made, such as adjusting material parameters, geometric parameters, etc. These modifications should also be considered within the scope of protection of the present invention.

[0061] The foregoing description only mentions preferred embodiments of the invention. However, the invention is not limited to the specific embodiments described herein. Those skilled in the art will readily appreciate that various obvious modifications, adjustments, and substitutions can be made to these embodiments to suit specific circumstances without departing from the spirit of the invention. In fact, the scope of protection of the invention is defined by the claims and may include other examples that are foreseeable to those skilled in the art. If such other examples have structural elements that are indistinguishable from the literal language of the claims, or if they include equivalent structural elements that are not significantly different from the literal language of the claims, then they will fall within the scope of protection of the claims.

Claims

1. A gradient metamaterial vibration isolation barrier (2), wherein the vibration isolation barrier (2) is formed by structural unit cells arranged periodically in two mutually perpendicular directions in a two-dimensional lattice arrangement, and a closed region (1) is formed inside the vibration isolation barrier (2); The structural unit cells are spaced apart from each other in both directions by a certain distance; The structural unit cell is a cube composed of a steel billet (5), a rubber layer (4), and a concrete layer (3). The steel billet (5) is a solid cube. The rubber layer (4) is wrapped around the outside of the steel billet (5), and the concrete layer (3) is wrapped around the outside of the rubber layer (4). The geometric centers of the steel billet (5), the rubber layer (4), and the concrete layer (3) coincide with each other. The side length of the steel billet (5) decreases in a gradient from the outermost layer to the innermost layer of the seismic isolation barrier.

2. The gradient metamaterial seismic isolation barrier (2) according to claim 1, characterized in that, The structural unit cell is located below the ground and its upper surface is flush with the ground.

3. The gradient metamaterial seismic isolation barrier (2) according to claim 1, characterized in that, The distance between each structural unit cell in both directions from body center to body center is 4m.

4. The gradient metamaterial seismic isolation barrier (2) according to claim 3, characterized in that, The structural unit cell has a side length of 2m, the rubber layer (4) has a thickness of 0.2m, and the steel billet (5) has a side length between 0.2m and 1.6m; the structural unit cell forms an omnidirectional bandgap in the range of 5.2Hz to 14.8Hz.

5. The gradient metamaterial seismic isolation barrier (2) according to claim 4, characterized in that, The side length of the steel billet (5) decreases linearly from 1.6m to 0.2m from the outermost to the innermost layer of the seismic isolation barrier, while the thickness of the rubber layer and the side length of the structural unit cell remain unchanged.

6. The gradient metamaterial seismic isolation barrier (2) according to any one of claims 1 to 5, characterized in that, When seismic surface waves are transmitted from outside the seismic isolation barrier, the enclosed area (1) is protected by the seismic isolation barrier from damage caused by the seismic surface waves as a protected area; when construction is carried out in the enclosed area (1) and vibrations are generated and propagate outward, the enclosed area (1) is isolated from the surrounding area by the seismic isolation barrier as a construction area, so as to prevent the seismic surface waves generated by construction in the enclosed area (1) from propagating to the surrounding area and affecting the facilities in the surrounding area.

7. The gradient metamaterial seismic isolation barrier (2) according to claim 6, characterized in that, When a seismic surface wave travels from the outside of the seismic isolation barrier and passes through the barrier, the seismic surface wave is transformed into a body wave by the barrier and guided deep underground, thereby protecting the enclosed area (1) from damage by the seismic surface wave; when construction occurs in the enclosed area (1) and causes vibrations that propagate outward through the seismic isolation barrier, the structural unit cell of the seismic isolation barrier generates local resonance, thereby capturing the vibration surface wave and preventing it from continuing to propagate outward, thus avoiding impact on the facilities in the surrounding area.

8. The gradient metamaterial seismic isolation barrier (2) according to claim 1, characterized in that, The density of steel is ρ1 = 7850 kg / m³ 3 Young's modulus E1 = 2.1 × 10 11 Pa, Poisson's ratio μ1=0.3; density of rubber ρ2=1300kg / m³ 3 Young's modulus E2 = 1.02 × 10 5 Pa, Poisson's ratio μ1=0.3; density of concrete ρ3=2300kg / m³ 3 Young's modulus E3 = 2.5 × 10 10 Pa, Poisson's ratio μ3 = 0.

2.

9. A construction method for the gradient metamaterial seismic isolation barrier (2) according to any one of claims 1 to 8, comprising the following steps: Based on the target operating frequency and the area available for designing the seismic isolation barrier, the geometric parameters and corresponding quantity of the structural unit cell are designed. The geometric parameters include the side length of the structural unit cell, the thickness of the rubber layer (4), and the side length of the steel billet (5). Mass production of the aforementioned structural unit cells; Within the area of ​​the seismic isolation barrier, pits are dug below the ground, and the pits are periodically arranged in two mutually perpendicular directions in a two-dimensional lattice configuration. The structural unit cell is buried in the pit so that the upper surface of the structural unit cell is flush with the ground, wherein the side length of the steel billet (5) decreases in a gradient from the outermost layer to the innermost layer of the seismic isolation barrier.

10. The construction method according to claim 9, characterized in that, The pit is a cube with a side length of 2m, and the distance between the pits from the center to the center in both directions is 4m.

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