Vibration reduction pile foundation for subway tunnel and construction method of vibration reduction pile foundation

Abstract

The invention discloses a vibration reduction pile foundation for a subway tunnel and a construction method of the vibration reduction pile foundation, and belongs to the field of civil engineering. The vibration reduction pile foundation comprises a plurality of metamaterial concrete vibration reduction layers arranged in a pile, and each metamaterial concrete vibration reduction layer comprises a plurality of metamaterial concrete unit cells which are located at the top of the pile foundation and the bottom of a bearing platform. The metamaterial concrete vibration reduction layer comprises a central cylindrical lead block, a peripheral rubber pipe and concrete on the inner side and the outer side of the rubber pipe. A plurality of metamaterial concrete unit cells are used as the vibration reduction layer, the structure can prevent steel bars from being broken by a common vibration isolation layer at the pile top and the bearing platform bottom, low-frequency waves of a fixed frequency band generated in the subway operation process can be filtered, and ground vibration caused during subway tunnel operation is effectively reduced; the method has the advantages of good vibration reduction and isolation effect, low cost and easiness in implementation of a construction process.

Description

Technical Field

[0001] The invention relates to a vibration-damping pile foundation for a subway tunnel and a construction method thereof, and belongs to the field of civil engineering. Background Art

[0002] As an efficient, convenient, and environmentally friendly mode of urban transportation, the subway has become an essential component of many large and medium-sized cities. However, the vibration and noise generated by subway operations also negatively impact the surrounding environment. Subway lines often traverse densely populated areas, densely built-up downtown areas, scenic spots, and science and technology parks. Residential buildings and precision instrument rooms may be located above them. Subway vibration can damage building structures, reduce residents' quality of life, and diminish the value of cultural heritage. Therefore, finding effective subway vibration isolation methods is an urgent engineering challenge.

[0003] The traditional vibration isolation method for subways is to set up an isolation layer or buffer layer around the tunnel to reduce the coupling effect between the tunnel and the soil (Wang Shuaishuai, Gao Bo. Research on the vibration reduction mechanism of setting a vibration reduction layer in the tunnel. Journal of Rock Mechanics and Engineering. 2016, 35(03), 592-603; Zhao Bingbing. Research on the seismic isolation performance of asphalt shield tunnel wall grouting material. Southwest Jiaotong University. 2019). However, this method has the following disadvantages: on the one hand, according to the "Technical Specifications for Building Pile Foundations" JGJ94-2018, the connection between the pile foundation and the pedestal should comply with the following regulations: 1) The length of the pile top embedded in the pedestal should be 50mm to 100mm; 2) The pile top should be connected to the pedestal by inserting steel bars into the core concrete. If an integral vibration isolation layer is set up, the steel bars at the connection between the pile foundation and the pedestal will be interrupted; on the other hand, it is difficult to achieve effective vibration isolation in the low-frequency range (20~50Hz). Low-frequency sound waves or vibration waves have longer wavelengths and stronger penetration capabilities.

[0004] In recent years, a new type of material has emerged - metamaterial concrete. Metamaterial concrete is a new type of composite material that combines metamaterials with concrete. It can use metamaterial units to generate local resonance and interact with external sound waves or vibration waves. When the external excitation frequency matches the local resonance frequency, the metamaterial unit will absorb a large amount of energy and produce strong backscattering, and the incident wave will be completely reflected or disappear. This frequency range is called a band gap. In this way, effective low-frequency and broadband vibration isolation can be achieved, and the steel bars at the top of the pile can be connected to the bottom of the pedestal. Therefore, metamaterial concrete can be used to make vibration isolation piles. In order to overcome the limitations of traditional subway vibration isolation methods, the present invention innovatively proposes a vibration-damping pile foundation for subway tunnels and its construction process. Summary of the Invention

[0005] The present invention aims to provide a vibration-damping pile foundation for a subway tunnel and a construction method thereof, thereby solving the problem in the prior art that effective vibration isolation of the subway in the low-frequency range cannot be achieved.

[0006] The present invention uses several metamaterial concrete cells as vibration-damping and isolation layers. Metamaterial concrete can achieve precise vibration isolation within a specific frequency range (20-50Hz). Utilizing the vibration isolation capability of metamaterial concrete, it isolates the waves transmitted during subway operation, preventing the steel bars at the top of the pile and the bottom of the pedestal from being interrupted by the outer ordinary vibration isolation layer, thus ensuring the integrity, safety and stability of the pile structure.

[0007] The present invention provides a vibration-damping pile foundation for subway tunnels. The foundation comprises several metamaterial concrete vibration-damping layers embedded within the pile. These layers consist of several metamaterial concrete cells located at the top of the pile foundation and at the bottom of the pedestal. Each cell comprises a central cylindrical lead block, a peripheral rubber tube, and concrete surrounding the tube's inner and outer sides. The dimensions of the pile, pedestal, metamaterial concrete cells, and their components, as well as the specific material of the rubber tube, can be adjusted based on actual conditions.

[0008] Furthermore, the piles are square piles with a prefabricated structure on top and the rest being cast in situ.

[0009] Furthermore, the metamaterial concrete vibration damping layer includes a plurality of metamaterial concrete cells (i.e., metamaterial concrete blocks), which are located at the top of the pile foundation and the bottom of the pedestal.

[0010] The design of the metamaterial concrete of this invention begins with selecting the appropriate artificial aggregate: metal spheres coated with an elastic layer. The material, density, and radius of the metal spheres, as well as the material, thickness, and stiffness of the elastic layer, all influence the band gap characteristics and impact resistance of the metamaterial concrete. The metal spheres should be made of high-density lead; the elastic layer should be made of low-density, low-stiffness rubber. The radius of the metal spheres and the thickness of the elastic layer should be minimized to maximize the aggregate volume ratio and the ratio of the core length to the soft coating thickness, thereby widening the band gap.

[0011] Furthermore, the center of each metamaterial concrete unit cell is a cylindrical lead block.

[0012] Furthermore, the metamaterial concrete vibration isolation layer is composed of a plurality of metamaterial concrete cells, each of which contains a circular cylindrical rubber tube. Furthermore, the thickness of the rubber tube is 5-30 mm.

[0013] Furthermore, the side length of the metamaterial concrete unit cell section is 150 mm to 900 mm.

[0014] Furthermore, the radius of the central cylindrical lead block of the metamaterial concrete unit cell is 50mm-300mm.

[0015] Furthermore, the rubber material selected for the rubber tube is made of one or more of butyl rubber, halogenated butyl rubber, butyl regenerated rubber, styrene-butadiene rubber, and natural rubber.

[0016] Furthermore, the vibration isolation layer outside the support platform is an ordinary vibration isolation layer, and the existing vibration isolation layer can be used without special reference.

[0017] The present invention also provides the above-mentioned construction method of the vibration-damping pile foundation for a subway tunnel, which comprises the following steps: (1) Statistically analyze the range of vibration frequency f1 generated by the interaction between the wheels and the subway track during subway train operation. The frequency range of the band gap of the metamaterial concrete is determined based on this frequency range, thereby determining the size of the metamaterial concrete unit cell, the size of the cylindrical lead block, the size of the annular rubber material, and the layout planning of the metamaterial concrete unit cell. The statistical vibration frequency f1 is used to determine the frequency range of vibration isolation required, and the required geometric size parameters of the metamaterial concrete unit cell are calculated through the formula; (2) Before pile construction, the steel bars in the steel cage are used to pass through and fix the lead block and the outer rubber tube at the center of the metamaterial concrete unit cell; then concrete is poured into the gap between the lead block and the rubber tube. This structure constitutes the metamaterial concrete vibration reduction layer; (3) After the concrete has initially set, place the steel cage in the excavated pile hole and pour the concrete. After the concrete strength reaches the specified value, the subsequent foundation construction can be carried out. (4) The construction method of the meta-material concrete vibration isolation layer at the bottom of the pedestal is the same as that of the vibration isolation layer at the top of the pile, forming the vibration reduction and isolation layer of the pile foundation; after laying the ordinary vibration isolation layer on the land outside the pedestal, the soil layer is backfilled and the remaining concrete of the pedestal is poured; (5) After the concrete strength of the foundation pile reaches the specified value, backfill the upper soil layer and construct the upper structure.

[0018] The beneficial effects brought by the present invention are: (1) The present invention uses several metamaterial concrete cells as vibration-damping layers. This structure can prevent the steel bars at the top of the pile and the bottom of the pedestal from being interrupted by ordinary vibration-isolating layers, and can filter low-frequency waves of a fixed frequency band generated during subway operation, effectively reducing ground vibrations caused by subway tunnel operation. (2) The vibration-damping pile foundation for subway tunnels and the manufacturing method thereof of the present invention have the advantages of good vibration reduction and isolation effect, low cost, simple and easy construction process; (3) Active vibration reduction and isolation measures taken during subway tunnel construction in vibration-sensitive areas can effectively solve the problem of adverse effects of subway vibration on surrounding buildings, residents' lives and instrument operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention.

[0020] Figure 2 It is a schematic diagram of the structure of a single metamaterial concrete vibration isolation layer.

[0021] Figure 3 for Figure 1 Side view of a single metamaterial concrete isolation layer.

[0022] In the figure: 1. Pile; 2. Metamaterial concrete vibration reduction layer; 3. Ordinary vibration isolation layer; 4. Cap; 5. Ground outside the soil layer; 6. Superstructure; 7. Concrete; 8. Rubber tube; 9. Lead block; 10. Vertical steel bars; 11. Horizontal steel bars. DETAILED DESCRIPTION

[0023] To further understand the content, features and effects of the present invention, the following embodiments are listed and described in detail with reference to the accompanying drawings: like Figures 1-3 As shown, a vibration-damping pile foundation for a subway tunnel includes a metamaterial concrete vibration-damping layer 2 arranged between a pile 1 and a cap 4.

[0024] Preferably, the pile 1 is a square pile, the top of which is prefabricated and the rest is cast in situ.

[0025] Preferably, the metamaterial concrete vibration damping layer 2 comprises a plurality of metamaterial concrete cells, that is, metamaterial concrete blocks are arranged in parallel one by one, and are located on the top of the pile foundation 1 and the bottom of the cap 4 .

[0026] Preferably, the center of each metamaterial concrete unit cell is a cylindrical lead block 9.

[0027] Preferably, each metamaterial concrete unit cell contains a circular rubber tube 8. The concrete 7, rubber tube 8 and lead block 9 are bonded to each other, and the vertical steel bars 10 and horizontal steel bars 11 are tied at the joints.

[0028] The vertical steel bars 10 in the steel cage pass through and fix the lead block 9 and the outer rubber tube 8 at the center of the metamaterial concrete unit cell, and the rubber tube 8 is located between the two layers of concrete 7; the horizontal steel bars 11 pass through and fix the lead block 9; the gap between the lead block 9 and the rubber tube 8 is filled with concrete 7.

[0029] Preferably, the cross-section of a single metamaterial concrete unit cell is square, with a side length of 150mm-900mm. The total thickness of the metamaterial concrete vibration isolation layer on the pile top is consistent with that of the pile, and the total thickness of the metamaterial concrete vibration isolation layer on the base is consistent with that of the base.

[0030] Preferably, the radius of the cylindrical lead block 9 inside a single metamaterial concrete unit cell is 50 mm to 300 mm.

[0031] Preferably, the thickness of the annular rubber tube 8 is 5-30 mm.

[0032] Preferably, the rubber tube 8 is made of one or more materials selected from the group consisting of butyl rubber, halogenated butyl rubber, butyl regenerated rubber, styrene-butadiene rubber, natural rubber and butadiene rubber.

[0033] Preferably, the vibration isolation layer outside the support platform 4 is a common vibration isolation layer 3 .

[0034] The present invention also provides a construction method for the vibration-damping pile foundation for a subway tunnel, the construction method comprising the following steps: (1) Statistically analyze the range of vibration frequency f1 generated by the interaction between the wheels and the subway track during subway train operation, and determine the band gap frequency range of the metamaterial concrete based on this frequency range, thereby determining the size of the metamaterial concrete unit cell, the size of the cylindrical lead block 9, the size of the annular rubber tube 8, and the layout of the concrete 7; The frequency range of f1 is the frequency range for which we need to perform vibration isolation, which is also the band gap frequency range of the metamaterial concrete we need. The two are numerically consistent. The lower limit of the frequency range of f1 is the starting frequency. When the starting frequency is known, the equivalent stiffness value of the metamaterial concrete unit cell can be inversely calculated through theoretical formulas. Subsequently, all formulas can be reversed to obtain the required size of the metamaterial concrete unit cell and the size of each internal component. It can also be obtained through experimental data using experimental methods.

[0035] The required vibration isolation frequency range in this embodiment is 35Hz~50Hz, which can be designed as follows: the side length of the outer concrete block is 0.4m, the radius of the inner cylindrical concrete is 0.11m, the thickness of the rubber tube is 0.02m, and the radius of the cylindrical lead block is 0.04m.

[0036] (2) Before the construction of pile 1, the steel bars in the steel cage are used to pass through and fix the lead block 9 at the center of the metamaterial concrete unit cell and the outer rubber tube 8; (3) Then, concrete is poured into the gap between the lead block 9 and the rubber tube 8, and this structure constitutes the metamaterial concrete vibration damping layer 2; (4) After the concrete has initially set, place the steel cage in the excavated pile hole and pour the concrete. After the concrete strength reaches the specified value, the subsequent construction of the foundation 4 can be carried out. (5) The construction method of the metamaterial concrete vibration reduction layer 2 at the bottom of the pedestal 4 is the same as that of the vibration isolation layer 1 at the top of the pile, forming the vibration reduction and isolation layer of the pile foundation; after laying the ordinary vibration isolation layer 3 on the land outside the pedestal 4, the soil layer is backfilled and the remaining concrete of the pedestal 4 is poured; (6) After the concrete strength of the foundation 4 reaches the specified value, the upper soil layer will be backfilled and the upper structure 6 will be constructed.

[0037] The advantages and positive effects of the present invention are as follows: The present invention utilizes a plurality of metamaterial concrete cells to form a metamaterial concrete vibration damping layer, which can serve as a vibration damping and isolation layer for subway pile foundations. The vibration damping and isolation layer is arranged between the pile 1 and the pedestal 4 and comprises a cylindrical lead block 9 at the center of the metamaterial concrete cell, a peripheral rubber tube 8, and concrete 7 on both sides of the tube. The dimensions of the pile 1, pedestal 4, metamaterial concrete 2, and their components, as well as the specific material of the rubber tube 8, can be adjusted according to actual conditions. This structure prevents steel bars from being interrupted by the conventional vibration isolation layer 3 at the top of the pile 1 and the bottom of the pedestal 4. It can also filter low-frequency waves within a fixed frequency band generated during subway operation, effectively reducing ground vibrations caused by subway tunnel operation and significantly minimizing the adverse effects of subway operation on surrounding buildings, residents' lives, and instrument operation.

[0038] The above embodiments are only used to illustrate the technical ideas and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The patent scope of the present invention cannot be limited by these embodiments alone. That is, any equivalent changes or modifications made to the spirit disclosed by the present invention still fall within the patent scope of the present invention.

Claims

1. A vibration-damping pile foundation for a subway tunnel, characterized by: It includes several metamaterial concrete vibration reduction layers set in the pile. The metamaterial concrete vibration reduction layers contain several metamaterial concrete cells, which are located at the top of the pile foundation and the bottom of the pedestal. The metamaterial concrete vibration reduction layers include a central cylindrical lead block, an outer rubber tube and concrete on both sides of the rubber tube.

2. The vibration-damping pile foundation for a subway tunnel according to claim 1, characterized in that: The aggregate of metamaterial concrete is metal balls wrapped in an elastic layer. The metal balls are high-density lead balls; the elastic layer is low-density, low-rigidity rubber.

3. The vibration-damping pile foundation for a subway tunnel according to claim 1, characterized in that: The side length of the cross section of the metamaterial concrete unit cell is 150mm-900mm.

4. The vibration-damping pile foundation for a subway tunnel according to claim 1, characterized in that: The radius of the central cylindrical lead block of the metamaterial concrete unit cell is 50mm-300mm.

5. The vibration-damping pile foundation for a subway tunnel according to claim 1, characterized in that: The thickness of the rubber tube of the metamaterial concrete vibration reduction layer is 5-30mm.

6. The vibration-damping pile foundation for a subway tunnel according to claim 5, characterized in that: The rubber material selected for the rubber tube is made of one or more of butyl rubber, halogenated butyl rubber, butyl regenerated rubber, styrene-butadiene rubber, and natural rubber.

7. A construction method for a vibration-damping pile foundation for a subway tunnel according to any one of claims 1 to 6, characterized in that The steps include: (1) Statistically analyze the range of vibration frequency f1 generated by the interaction between the wheels and the subway track during subway train operation. The frequency range of the band gap of the metamaterial concrete is determined based on this frequency range, thereby determining the size of the metamaterial concrete unit cell, the size of the cylindrical lead block, the size of the annular rubber material, and the layout planning of the metamaterial concrete unit cell. (2) Before pile construction, the steel bars in the steel cage are used to pass through and fix the lead block and the outer rubber tube at the center of the metamaterial concrete unit cell; then concrete is poured into the gap between the lead block and the rubber tube. This structure constitutes the metamaterial concrete vibration reduction layer; (3) After the concrete has initially set, place the steel cage in the excavated pile hole and pour the concrete. After the concrete strength reaches the specified value, the subsequent foundation construction can be carried out. (4) The construction method of the meta-material concrete vibration isolation layer at the bottom of the pedestal is the same as that of the vibration isolation layer at the top of the pile, forming the vibration reduction and isolation layer of the pile foundation; after laying the ordinary vibration isolation layer on the land outside the pedestal, the soil layer is backfilled and the remaining concrete of the pedestal is poured; (5) After the concrete strength of the foundation pile reaches the specified value, backfill the upper soil layer and construct the upper structure.

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