Quasi-zero stiffness vibration isolation method for urban rail transit tunnel floating slab track bed

Abstract

The application discloses a quasi-zero stiffness vibration isolation method and system device for a tunnel floating slab track bed of urban rail transit. A quasi-zero stiffness vibration isolation device is arranged in a concrete floating slab on the floating slab track bed. The quasi-zero stiffness vibration isolation device comprises a positive stiffness component, a negative stiffness combined component and a height adjusting pad plate. The concrete floating slab is in a floating state on the floating slab track bed through the quasi-zero stiffness vibration isolation device. The negative stiffness combined component is annularly arranged on the positive stiffness component by a plurality of rotatable sheet springs and is floated with an upper end bearing platform of the positive stiffness component. A negative stiffness is formed by the rotatable sheet springs during the floating process, and the quasi-zero stiffness vibration isolation of the concrete floating slab is realized. The negative stiffness is formed by the stiffness change of the plurality of rotatable sheet springs during the vibration process, and the dynamic stiffness of the vibration isolation system is low or tends to be zero, so that good low-frequency vibration isolation performance is obtained, and the vibration isolation efficiency of the system is improved. The application has the characteristics of simple structure, high reliability and long service life.

Description

Technical Field

[0001] This invention relates to a vibration isolation method for floating slab track beds in urban rail transit tunnels, and more particularly to a quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels. This quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels can achieve quasi-zero stiffness vibration isolation on the narrow track beds of urban rail transit tunnels; it belongs to the field of vibration isolation technology for floating slab track beds in rail transit tunnels. Background Technology

[0002] Urban rail transit, with its advantages of high speed, large passenger capacity, high safety and reliability, and zero smoke emission pollution, has been adopted by many large and medium-sized cities both domestically and internationally as a main transportation artery to alleviate traffic pressure brought about by urbanization in recent years. However, with the rapid development of urban rail transit, while bringing great convenience to improve urban traffic conditions, it has also brought significant noise pollution problems. If effective measures are not taken, it will not only reduce passenger comfort and shorten the service life of various vehicle components, but also affect the work and life quality of residents along the railway line, as well as the lifespan of various equipment and buildings. Therefore, environmental vibration and noise control in urban rail transit construction has become a very important issue.

[0003] Research has revealed that noise pollution from urban rail transit primarily stems from vehicle vibrations, air resistance friction, and radiated noise. The most significant contributor is the noise generated by vehicle vibrations during passage. Therefore, current methods employ optimal vibration isolation to address train noise. These methods include using vibration-damping materials and vibration dampers to control train noise; rigorous manufacturing and maintenance of key components to minimize noise generation; the use of appropriate curves and paving stones to reduce noise from friction between rails and concrete; and the installation of soundproof walls to reduce environmental noise from rail transit operations. Regarding track alignment, the most common approach is the combined use of track vibration dampers with elastic support blocks or floating slabs to achieve effective vibration isolation.

[0004] However, according to vibration isolation theory, the larger the participating mass and the smaller the support stiffness of the vibration isolation system, the lower its natural frequency and the better the vibration isolation effect. Currently, the steel spring floating slab vibration isolation track, which has the best vibration isolation effect in urban rail transit vibration reduction measures, utilizes a "mass-spring plus damping" vibration isolation system with large mass and low stiffness—a combination of floating slabs and track vibration dampers. This type of system has good vibration isolation effects on flat road surfaces such as typical stations. However, in actual engineering design, limitations imposed by tunnel space, construction costs, and train operation safety significantly limit the effectiveness of improving the vibration isolation effect by increasing mass and reducing stiffness. Therefore, existing vibration isolation systems combining conventional track dampers with elastic support blocks or floating slabs are insufficient to meet the vibration isolation needs of current urban rail transit, especially in confined spaces such as tunnels or bridges. Current methods of increasing mass and reducing stiffness are ill-suited for such environments. Particularly when trains pass through tunnels at high speeds, the low-frequency vibrations generated within the tunnel result in even weaker vibrations, leading to more intense noise pollution compared to conventional road surfaces. This phenomenon necessitates a solution.

[0005] Quasi-zero stiffness vibration isolation technology achieves excellent low-frequency vibration isolation performance while maintaining load-bearing capacity by obtaining high static stiffness and low dynamic stiffness. In recent years, quasi-zero stiffness vibration isolation technology has become a research hotspot for scholars both domestically and internationally, and some technical solutions have been proposed. However, from the perspective of practical application value, these solutions lack engineering applicability, especially unsuitable for floating slab track beds in urban rail transit. Therefore, the design and application of quasi-zero stiffness vibration isolation devices has become a goal pursued in the field of vibration reduction / isolation technology. Currently, the main approach to engineering applications is still to achieve quasi-zero stiffness by connecting negative stiffness components in parallel to a positive stiffness system. While there are numerous literature reports on so-called "quasi-zero stiffness vibration isolation," most of the currently available "quasi-zero stiffness" vibration isolation devices are merely research projects conducted by universities, lacking truly practical engineering applications. Among these, the following are most relevant to this application:

[0006] 1. The invention patent entitled "Quasi-zero stiffness vibration isolation device floating slab track bed and its design method" (CN201810244688.6) discloses a quasi-zero stiffness vibration isolation device floating slab track bed and its design method, including a floating slab and vibration isolation components disposed in the floating slab. The vibration isolation components are spaced apart along the length of the floating slab. The vibration isolation components are characterized in that the vibration isolation components include an outer sleeve cast in the floating slab and a quasi-zero stiffness vibration isolation device installed in the outer sleeve. A height adjustment shim for adjusting the height of the floating slab is placed between the quasi-zero stiffness vibration isolation device and the outer sleeve. The top of the outer sleeve is covered with an insulating cover plate.

[0007] 2. A utility model patent entitled "A Quasi-Zero Stiffness Vibration Isolation Device and Track Slab for Railway Vibration Reduction Track" (CN202120434799.0) describes a vibration isolator comprising a cylindrical support base and a butterfly spring. The cylindrical support base contains a rubber support, and the top of the rubber support has a lower flange bearing plate. The lower flange bearing plate has a vertically arranged connecting rod, and the connecting rod is threadedly connected to an upper flange bearing plate. The connecting rod passes through the butterfly spring, and the bottom end of the butterfly spring abuts against the top end of the cylindrical support base. The top end of the butterfly spring abuts against the bottom surface of the upper flange bearing plate.

[0008] 3. The invention patent titled "A Flexible Adjustable Quasi-Zero Stiffness Vibration Reduction Platform" (CN201510438515.4) includes a fixed platform, a moving platform, a vibration reduction component, and a thrust component. The vibration reduction component is connected to the fixed and moving platforms. The thrust component is mounted on the fixed platform and applies thrust to the moving platform; multiple thrust components are arranged around the moving platform. This vibration reduction platform can achieve quasi-zero stiffness at its static equilibrium position and nonlinear stiffness near the static equilibrium position, solving the problem of traditional linear vibration isolation systems isolating low-frequency or ultra-low-frequency vibrations. However, this invention only provides a flexible adjustable quasi-zero stiffness vibration reduction platform. Due to its large structural size, numerous components, and low integration, it is not suitable for track bed slabs.

[0009] Problems or shortcomings of existing technologies:

[0010] While these patents all involve negative stiffness elements and propose some improved technical solutions, careful analysis reveals that none of them can be truly applied in practical engineering. Among them,

[0011] Patent 1 only provides a quasi-zero stiffness vibration reduction platform that can be flexibly adjusted. Due to its large structural size, many parts, and low integration, it is not suitable for use in track floating slab track beds.

[0012] Patent 2 proposes a method to achieve negative stiffness using various types of disc springs, including large, medium and small ones. While this method is theoretically feasible, it is difficult to control the deformation of the disc springs in practical applications. In particular, when using disc springs to achieve negative stiffness, the disc springs are prone to flipping when they are close to horizontal, resulting in failure. Therefore, using disc springs to achieve negative stiffness is not advisable.

[0013] Patent 3 proposes a theoretical floating slab track bed quasi-zero stiffness vibration isolation device, but the actual structure cannot achieve the so-called "quasi-zero stiffness" vibration isolation, and therefore has no practical application value.

[0014] To address the problem of existing steel spring or rubber spring vibration isolators' inability to isolate low-frequency or ultra-low-frequency vibrations in floating slab track, and to reduce the initial isolation frequency of the track slab, increase the isolation frequency range, and improve isolation efficiency, it is necessary to develop a quasi-zero stiffness floating slab track vibration isolation device with low dynamic stiffness that can be applied in engineering. Furthermore, with the rapid development of urban rail transit and increased efforts to control environmental pollution, the demand for this product will continue to grow, making it worthy of serious study. Summary of the Invention

[0015] The technical problem to be solved by this invention is to address the shortcomings of existing urban rail tunnels in terms of poor vibration reduction and isolation effects. This invention proposes a method for solving noise pollution from floating slab track beds in urban rail transit using quasi-zero stiffness vibration isolation. This method not only allows for the practical application of quasi-zero stiffness vibration isolation in floating slab track beds of urban rail transit, isolating low-frequency or ultra-low-frequency vibrations, but also features simple manufacturing, full engineering application value, and effective solution to the vibration reduction and noise reduction problems of floating slab track beds in urban rail transit.

[0016] This invention is mainly achieved through the following technical solution: a quasi-zero stiffness vibration isolation method and manufacturing method for a slab track bed in urban rail transit tunnels. A concrete floating slab is installed on the floating slab track bed of the urban rail transit system. A quasi-zero stiffness vibration isolation device is installed in the concrete floating slab. The quasi-zero stiffness vibration isolation device includes a positive stiffness component, a negative stiffness combination component, and a height adjustment pad. The quasi-zero stiffness vibration isolation device keeps the concrete floating slab in a floating state on the floating slab track bed. The negative stiffness combination component is a negative stiffness device formed by a combination of rotatable springs. The negative stiffness combination component is a negative stiffness mechanism formed by the vertical stacking of multiple rotatable leaf springs forming negative stiffness units. The negative stiffness mechanism is arranged above the positive stiffness component and floats with the upper bearing platform of the positive stiffness component. During the floating process, negative stiffness is formed by the up-and-down movement, rotation, and compression of the rotatable leaf springs, thereby achieving quasi-zero stiffness vibration isolation of the concrete floating slab.

[0017] Furthermore, the negative stiffness assembly is a negative stiffness mechanism formed by vertically stacking multiple rotatable leaf springs forming negative stiffness units. The negative stiffness mechanism being arranged above the positive stiffness component means that multiple negative stiffness units formed by individual rotatable leaf springs are arranged in a ring to form a ring-shaped negative stiffness unit assembly. These multiple negative stiffness unit assemblies are then vertically stacked together to form a negative stiffness mechanism, which is then installed in a closed annular cylinder to form the negative stiffness assembly. Finally, the negative stiffness assembly is placed above the positive stiffness component.

[0018] Furthermore, the negative stiffness achieved by the up-and-down movement, rotation, and compression of the rotatable leaf spring is achieved by using a long strip-shaped leaf spring with a width smaller than its length. The two ends of the long strip-shaped leaf spring are respectively mounted on the upper support block and the lower support block of the negative stiffness assembly through rotating nodes. As the upper support block and the lower support block move up and down relative to each other, the long strip-shaped leaf spring rotates around the rotating nodes during the up-and-down movement, while simultaneously compressing the rotatable leaf spring. By changing the magnitude of the vertical component of the rotatable leaf spring through its up-and-down movement, rotation, and compression, negative stiffness is achieved.

[0019] Furthermore, the aforementioned change in the vertical component of the rotatable leaf spring through its up-and-down movement, rotation, and compression refers to the use of a buckling leaf spring, which is installed between the upper and lower support blocks of the negative stiffness unit. As the buckling leaf spring moves up and down with the upper and lower support blocks, the buckling deformation of the leaf spring changes the vertical component of the rotatable leaf spring, creating negative stiffness that matches the positive stiffness, thus forming quasi-zero stiffness vibration isolation.

[0020] The aforementioned method of changing the vertical component of the rotatable leaf spring through its up-and-down movement, rotation, and compression refers to the use of elastic rotatable nodes. Both ends of the rotatable leaf spring are connected to the upper and lower support blocks of the negative stiffness unit through rotatable nodes, and at least one end of the rotatable node is an elastic rotatable node. As the rotatable leaf spring moves up and down with the upper and lower support blocks, the compression of the elastic rotatable node by the leaf spring changes the vertical component of the rotatable leaf spring, forming negative stiffness, which matches the positive stiffness, thus forming quasi-zero stiffness vibration isolation.

[0021] Furthermore, the method of changing the vertical component of the rotatable leaf spring by moving up and down, rotating, and compressing the rotatable leaf spring employs a buckling leaf spring in conjunction with an elastic rotatable node to form negative stiffness. The rotatable leaf spring is a buckling leaf spring, with both ends connected to the upper and lower support blocks of the negative stiffness unit via rotatable nodes, and at least one end of the rotatable node is an elastic rotatable node. As the rotatable buckling leaf spring moves up and down with the upper and lower support blocks, it undergoes buckling deformation on one side and compression of the elastic rotatable node on the other, causing deformation of the elastic rotatable node. The combined effect of these two factors changes the vertical component of the buckling leaf spring, forming negative stiffness that matches the positive stiffness, thus achieving quasi-zero stiffness vibration isolation.

[0022] Furthermore, the bending leaf spring is a flat spring sheet, which is rectangular in shape. Its width is 1 / 3 to 1 / 2 of its length, and it is slightly bent downward along the middle of the length direction. At both ends of the length direction, there are cylindrical surfaces with the width direction as the axis. The radius of the cylindrical surface is about 1.3 to 1.8 times the thickness of the spring sheet. The cylindrical surface at the end is connected to the upper and lower surfaces of the spring sheet in the thickness direction by a rounded transition.

[0023] Preferably, the spring sheet length (L) is 14-25mm and the thickness is 0.6-1mm; this can effectively ensure the buckling deformation effect of the buckling spring. The radius of the cylindrical surface is about 1.3-1.8 times the thickness of the spring sheet, and the end cylindrical surface and the upper and lower surfaces in the thickness direction of the spring sheet are rounded.

[0024] Furthermore, the bending leaf spring is inclined at an angle between its length direction and the horizontal plane, and the cylindrical surfaces at both ends of the spring respectively form the upper and lower joint support surfaces of the upper support block and the lower support block; the inclination angle (A) is between 15 and 25 degrees.

[0025] Furthermore, copper tiles are wrapped around the rotatable node cylindrical surfaces at both ends of the buckling leaf spring, namely the upper support copper tile and the lower support copper tile.

[0026] Furthermore, the elastic rotatable node includes a rubber layer and a supporting spring sheet; the rubber layer and the supporting spring sheet are vulcanized together, and the rubber layer is vulcanized at the joint positions of the upper support block and the lower support block respectively, with both ends of the rotatable spring sheet inserted into the supporting spring sheet to form an elastic rotatable node.

[0027] Furthermore, the supporting spring plate is a spring plate with a width consistent with the width of the leaf spring, but bent into an arc-like shape in the length direction. The cylindrical concave surface in the middle part forms a friction pair connection with the supporting copper tile of the leaf spring.

[0028] Furthermore, the upper support block and the lower support block are each a single load-bearing component that allows vertical movement. They have an arc-shaped concave surface in their opposite directions, which corresponds to the arc-shaped convex surface of the support spring plate. The gap between the arc-shaped concave surface of the support block and the arc-shaped convex surface of the support spring plate is filled with a support rubber component and bonded and vulcanized together to form an elastic layer.

[0029] The beneficial effects of this invention are as follows: By replacing the steel springs or rubber springs in the existing floating slab track bed of urban rail transit with a quasi-zero stiffness vibration isolation device, the dynamic stiffness can be low or close to zero under static equilibrium conditions. This solves the problem of traditional linear vibration isolation systems isolating low-frequency or ultra-low-frequency vibrations, reduces the initial isolation frequency, increases the isolation frequency range, and improves the system's vibration isolation efficiency. At the same time, it completely preserves the load-bearing capacity and reliability of existing floating slab vibration-damping tracks. Attached Figure Description

[0030] Figure 1 A schematic diagram of a vibration reduction system for urban rail transit tunnels;

[0031] Figure 2 Schematic diagram of the vibration isolation system of the present invention;

[0032] Figure 3 for Figure 2 A partially enlarged schematic diagram of a quasi-zero stiffness vibration damper;

[0033] Figure 4 This is a schematic diagram of the overall structure of the quasi-zero stiffness vibration damper of the present invention;

[0034] Figure 5 This is a schematic diagram of the outer cylinder structure of the quasi-zero stiffness vibration damper of the present invention;

[0035] Figure 6 This is a schematic diagram of the positive stiffness component structure of the quasi-zero stiffness vibration damper of the present invention;

[0036] Figure 7 This is a schematic diagram of the negative stiffness combination component of the quasi-zero stiffness vibration damper of the present invention;

[0037] Figure 8 This is a schematic diagram of the negative stiffness combination structure of the quasi-zero stiffness vibration damper of the present invention;

[0038] Figure 9 This is a schematic diagram of the negative stiffness unit structure of the quasi-zero stiffness vibration damper of the present invention;

[0039] Figure 10 This is a schematic diagram of the negative stiffness unit principle of the quasi-zero stiffness vibration damper of the present invention;

[0040] Figure 11 This is a schematic diagram of the negative stiffness variation curve of a negative stiffness element.

[0041] Figure 12 This is a schematic diagram of the planar arrangement of the negative stiffness unit of the quasi-zero stiffness vibration damper of the present invention;

[0042] Figure 13 This is a schematic diagram of the planar arrangement of the negative stiffness unit of a quasi-zero stiffness damper according to another embodiment of the present invention;

[0043] Figure 14This is a schematic diagram of the planar arrangement of the negative stiffness unit of a quasi-zero stiffness damper according to another embodiment of the present invention. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Example 1

[0045] This embodiment describes a quasi-zero stiffness vibration isolation device for a floating slab track bed used in tunnel spaces, as shown in the attached diagram. Figure 1 As shown, a floating slab track bed (34) is laid on the foundation track bed (33) of the urban rail transit system. A concrete floating slab (1) is installed on the floating slab track bed (34), and a track (35) is installed on the concrete floating slab (1). A quasi-zero stiffness vibration isolation device (36) is installed between the floating slab track bed (33) and the concrete floating slab (1). The quasi-zero stiffness vibration isolation device (36) includes a positive stiffness component (8), a negative stiffness combination component (10), and an adjustment pad (9). The quasi-zero stiffness vibration isolation device (36) makes the concrete... The floating concrete slab (1) is in a floating state on the floating slab track bed (34); the negative stiffness combination component (10) is a rotatable spring-type quasi-zero stiffness vibration isolation device. The negative stiffness combination component (10) consists of multiple rotatable leaf springs arranged in a ring on the positive stiffness component (8), and floats with the upper bearing platform of the positive stiffness component (8). During the floating process, the negative stiffness is formed by the up-and-down movement, rotation and compression of the rotatable leaf springs of the negative stiffness combination component (10), thereby realizing the quasi-zero stiffness vibration isolation of the concrete floating slab (1).

[0046] Moreover, the positive stiffness component (8), the height adjustment plate (9), and the negative stiffness combination component (10) are all installed inside the outer sleeve (2), and the bottom surface of the positive stiffness component (8) extends from the bottom of the outer sleeve (2) and exceeds the bottom surface of the outer sleeve (2), forming a horizontal height difference; the negative stiffness combination component (10) is installed inside the outer sleeve (2) and is located above the positive stiffness component (8); the upper end surface of the negative stiffness combination component (10) extends out of the upper end surface of the outer sleeve (2) and contacts the bottom surface of the track (35), and the negative stiffness combination component (10) moves together with the outer sleeve (2) as it moves up and down with the floating slab track bed, and generates negative stiffness in the process of moving, and the resultant force formed by the positive stiffness component (8) and the upward elastic force generated by the positive stiffness component (8) remains basically constant, thereby constituting the quasi-zero stiffness vibration isolation.

[0047] Because the quasi-zero stiffness vibration isolation device has low or near-zero dynamic stiffness in static equilibrium, it solves the problem of traditional linear vibration isolation systems isolating low-frequency or ultra-low-frequency vibrations, reduces the initial isolation frequency, increases the isolation frequency range, and improves the system's vibration isolation efficiency.

[0048] like Figure 2As shown: The novel floating slab track isolation device (36) of the present invention consists of an outer sleeve (2) and a quasi-zero stiffness vibration isolation system (3). Among them, the outer sleeve (2) is evenly embedded at symmetrical positions on both sides of the centerline of the rail on the concrete floating slab (1) track, and the quasi-zero stiffness vibration isolation system (3) for supporting the concrete floating slab (1) is installed inside the outer sleeve (2).

[0049] like Figure 3 As shown: The outer sleeve (2) is a cylindrical steel cylinder (5), with a square steel plate (4) welded to its lower end. A reinforcing steel bar for pre-embedding is welded to the middle part of the outer side of the cylinder. A load-bearing support ring (6) and a construction support ring (7) are welded to the inner cavity near the upper end and the top end, respectively. The outer sleeve (2) is pre-embedded in the concrete floating slab (1), and the height of the outer sleeve (2) is consistent with the thickness of the concrete floating slab (1).

[0050] like Figure 4 As shown: The quasi-zero stiffness vibration isolation system (3) is composed of a positive stiffness component (8), a height adjustment pad (9), and a negative stiffness combination component (10). The positive stiffness component (8) and the negative stiffness combination component (10) are coaxially connected in parallel and supported on the bearing support ring (6) in the outer sleeve (2) by the height adjustment pad (9). The height adjustment pad (9) consists of multiple pads of different thicknesses with through holes in the center. The static load-bearing capacity of the quasi-zero stiffness vibration isolation system (3) is mainly borne by the positive stiffness component (8), but near the static equilibrium position, because the positive stiffness component (8) and the negative stiffness combination component (10) are connected in parallel and simultaneously bear the impact force from the upper structure, the dynamic stiffness of the vibration isolation system is low or close to zero, thereby achieving good low-frequency vibration isolation performance and improving the system's vibration isolation efficiency.

[0051] like Figure 4 , 5 As shown: The positive stiffness component (8) includes a base (11), a cylindrical helical spring (12), and an upper cover bearing cylinder (13). The base (11) is a cylindrical structure, and the cylindrical helical spring (12) is placed inside the base (11). The base (11) has a central shaft pin (14) on the bottom plate of the barrel. The lower end of the central shaft pin (14) is firmly connected to the bottom plate, and the top end is set as a stepped shaft. The upper cover bearing cylinder (13) is installed on the top of the cylindrical helical spring and serves as the upper bearing platform of the vibration isolator. The upper cover bearing cylinder (13) has a stepped through hole at its axial center. The upper end of the through hole has an internal thread, and the lower end of the through hole is a tubular structure. The lower end face of the tubular structure has a damping disc (15). The central stepped through hole of the upper cover bearing cylinder (13) and the central shaft pin (14) of the base (11) are in a gap-type coaxial assembly relationship.

[0052] The positive stiffness component (8) is set in the concrete floating slab (1) between the track (25) and the floating slab track bed (34); wherein the base (11) is installed on the foundation ground of the floating slab track bed (34); the outer edge of the height adjustment pad (9) installed on the top surface of the upper cover bearing cylinder (13) is supported on the bearing support ring (6) of the inner cavity of the outer sleeve (2).

[0053] A liquid damping material is placed in the gap between the base (11) and the cylindrical helical spring (12). The damping disc (15) on the lower end face of the upper cover bearing cylinder (13) is immersed in the liquid damping material.

[0054] like Figure 4 , 5 As shown in Figure 6: The negative stiffness assembly (10) includes an outer bearing component (16), an inner bearing component (17), a negative stiffness mechanism (18), and an upper cover plate (19). The outer bearing component (16) is a stepped cylindrical structure with a larger upper end and a smaller lower end along the axial direction; its upper inner cavity is a stepped hole structure, and an internal thread is provided near the end position. The upper cover plate (19) is screwed onto the internal thread at the port of the outer bearing component (16), so that the inner cavity of the outer bearing component (16) forms a closed cavity; the inner bearing component (16), the negative stiffness mechanism (18), and the upper cover plate (19) are coaxially installed in its inner cavity; an external thread is provided on the outer cylinder at its lower end, and it forms an assembly relationship with the internal thread at the upper end of the stepped hole in the center of the upper cover bearing cylinder (13) in the positive stiffness assembly (8). The inner bearing component (17) is a cylindrical structure with a bottom outer diameter larger than the outer diameter of the barrel, forming a shoulder. A central circular hole is opened at the bottom of the barrel, and the central circular hole and its end face are assembled with the top stepped shaft of the central shaft pin (14) provided on the base plate (11) of the positive stiffness component (8). The inner bearing component (17) is coaxially installed at the bottom of the upper inner cavity of the outer bearing component (16). The negative stiffness mechanism (18) is coaxially installed between the upper inner cavity of the outer bearing component (16) and the cylindrical inner bearing component (17).

[0055] like Figure 7 As shown: The negative stiffness mechanism (18) is a negative stiffness mechanism formed by stacking multiple negative stiffness unit combinations (20) along the plumb line. The negative stiffness unit combination (20) is a negative stiffness unit (23) formed by multiple rotatable leaf springs, which are arranged in a ring in the same plane to form a ring combination; then the multiple negative stiffness unit combinations (20) are vertically stacked together to form the negative stiffness mechanism (18), and the negative stiffness mechanism (18) is installed in the negative stiffness combination component (10).

[0056] The upper cover plate (19) of the negative stiffness assembly (10) is a cylindrical disc-shaped structure. Its outer cylinder is provided with external threads and is assembled with the internal threads provided with the upper inner cavity of the outer bearing component (16). The lower end face of the upper cover plate (19) is assembled with the top surface of the outer ring (22) of the negative stiffness mechanism (18).

[0057] like Figure 6 , 7 As shown in Figure 8: The negative stiffness unit assembly (20) includes an inner ring (21), an outer ring (22), and negative stiffness units (23). The negative stiffness unit assembly (20) is equivalent to being composed of multiple negative stiffness units (23) arranged continuously along the circumferential direction on the same plane and installed in the inner ring (21) and the outer ring (22); and the multiple negative stiffness unit assemblies (20) stacked along the plumb line constitute a negative stiffness mechanism (18).

[0058] The inner ring (21) of the negative stiffness unit assembly (20) or negative stiffness mechanism (18) is clearance-fitted with the outer diameter of the inner bearing component (17), and the inner diameter and bottom end face of the inner ring (21) are respectively assembled with the outer diameter of the inner bearing component (17) and the outer edge shoulder of the bottom of the barrel. The outer ring (22) of the negative stiffness unit assembly (20) or negative stiffness mechanism (18) is assembled with the inner diameter of the inner cavity of the outer bearing component (16).

[0059] like Figure 9 As shown: The negative stiffness unit (23) includes an upper support block (24), an upper support rubber component (25), an upper support copper tile (26), an upper support spring plate (27), a buckling leaf spring (28), a lower support spring plate (29), a lower support copper tile (30), a lower support rubber component (31), and a lower support block (32). The upper support block (24), the upper support rubber piece (25), and the upper support spring sheet (27) are bonded and vulcanized into a whole; the lower support spring sheet (29), the lower support rubber piece (31), and the lower support block (32) are bonded and vulcanized into a whole; one end of the upper support rubber piece (25), the upper support spring sheet (27), the upper support copper tile (26), and the bent leaf spring (28) forms an elastic rotatable node; the other end of the lower support rubber piece (31), the lower support spring sheet (29), the lower support copper tile (30), and the bent leaf spring (28) forms another elastic rotatable node. When the bent leaf spring (28) moves up and down, it can deform by compressing the rubber layer to meet the deformation requirements of the bent leaf spring (28).

[0060] The buckling leaf spring (28) is a rectangular spring sheet with a width approximately half of its length (L). Preferably, the length (L) is 14-25 mm and the thickness is 0.6-1 mm. This effectively ensures the buckling deformation effect of the buckling leaf spring (28) and effectively controls the deformation of each buckling leaf spring (28) to prevent it from becoming too large. Then, the required negative stiffness is obtained by using multiple and multi-layered ring-arranged buckling leaf springs (28). The buckling leaf spring (28) is slightly bent downward in the middle along the length direction to control the direction of buckling deformation and prevent reverse deformation. The two ends of the buckling leaf spring (28) in the length direction are provided with cylindrical surfaces with the width direction as the axis. The radius of the cylindrical surface is approximately 1.3-1.8 times the thickness of the spring sheet. The cylindrical surface at the end is connected to the upper and lower surfaces in the thickness direction of the spring sheet by a circular arc transition.

[0061] The bending leaf spring (28) is inclined at an angle (A) between its length direction and the horizontal plane. The cylindrical surfaces at both ends of the spring form the upper and lower articulated support surfaces, respectively. The initial angle (A) of the bending leaf spring is between 15 and 25 degrees to ensure that the dimensional changes of the rotatable leaf spring in the horizontal direction are within a controllable range. Copper tiles, namely the upper support copper tile (26) and the lower support copper tile (30), are wrapped on the cylindrical surfaces at both ends of the spring.

[0062] The upper support spring plate (27) is a spring plate with a width consistent with the width of the bent leaf spring (28), but bent into an arc-like shape in the length direction. The cylindrical concave surface in the middle part of the spring plate forms a friction pair with the upper support copper plate (26) of the bent leaf spring (28). The lower support spring plate (29) is a spring plate with a width consistent with the width of the bent leaf spring (28), but bent into an arc-like shape in the length direction. The cylindrical concave surface in the middle part of the spring plate forms a friction pair with the lower support copper plate (30) of the bent leaf spring (28). The upper support block (24) is a load-bearing component that only allows up and down movement. Its lower left side is designed with an arc-shaped concave surface, which corresponds to the arc-shaped convex surface of the upper support spring plate (27). The gap between the arc-shaped concave surface of the upper support block (24) and the arc-shaped convex surface of the upper support spring plate (27) is filled by the upper support rubber part (25) and bonded and vulcanized together as a whole. The lower support block (32) is a load-bearing component placed on the base platform that restricts horizontal movement. Its upper right side is designed as an arc-shaped concave surface, which forms a corresponding mating relationship with the arc-shaped convex surface of the lower support spring plate (29). The gap between the arc-shaped concave surface of the lower support block (32) and the arc-shaped convex surface of the lower support spring plate (29) is filled by the lower support rubber part (31) and bonded and vulcanized together as a whole.

[0063] The working principle of the negative stiffness unit is as follows: Figure 10As shown: The upper support block (24) and lower support block (32) of the negative stiffness unit assembly (20) are both restricted from moving in the horizontal direction and are assembled into a whole with the other elastic components by rubber bonding vulcanization and assembly. The lower support block (24) is placed on the foundation platform, and when the upper support block (32) is subjected to vertical load, it will generate vertical displacement. Under the action of the load force, its force transmission path is: upper support block (24) → upper support rubber part (25) → upper support spring plate (27) → upper support copper tile (26) → buckling leaf spring (28) → lower support copper tile (30) → lower support spring plate (29) → lower support rubber part (31) → lower support block (32). Among them, the rubber part generates elastic compression deformation, the metal spring plate generates elastic buckling deformation, and at the same time, the angle (A) between the length direction of the buckling leaf spring (28) and the horizontal plane changes, that is, it changes from large to small. Under continuous loading, the buckling leaf spring (28) will gradually move downward by a distance H. When the angle between the length direction of the buckling leaf spring (28) and the horizontal plane is zero, the component of the negative stiffness element in the vertical direction, i.e., the support reaction force, is also zero. Therefore, the stiffness curve formed by the vertical force and displacement acting on the upper support block (24) is a stiffness curve similar to a parabola, as shown in the attached figure. Figure 11 As shown; through curve analysis, it can be found that it matches the positive stiffness perfectly.

[0064] like Figure 7 , 8 As shown in Figures 9 and 12: The negative stiffness unit combination (20) is a ring-shaped, evenly distributed ring. The lower support block (32) of each negative stiffness unit is designed as a ring, which constitutes the inner ring (21) of the negative stiffness unit combination (20); the upper support block (24) of the negative stiffness unit is designed as a ring, which constitutes the outer ring (22) of the negative stiffness unit combination (20); the buckling leaf spring (28) in the negative stiffness unit is evenly arranged along the circumferential direction to form a similar slotted disc spring, and is combined with the upper and lower support copper tiles (26, 30) and the upper and lower support spring plates (27, 29). The rubber ring formed by the upper and lower rubber parts (25, 31) is bonded and vulcanized together with the inner ring (21) and the outer ring (22) to form a whole, which constitutes the negative stiffness unit combination (20).

[0065] like Figure 6 As shown: The upper cover plate (19) is a cylindrical disc-shaped structure with a countersunk hole on its upper end face. A nut (33) is welded at the center of the countersunk hole. The outer cylinder is provided with an external thread, which is in an assembly relationship with the internal thread provided in the upper inner cavity of the outer bearing component (16). The lower end face of the upper cover plate (19) is in an assembly relationship with the top surface of the outer ring (22) of the negative stiffness mechanism (18).

[0066] In summary, the beneficial effects of this invention are as follows: By replacing the steel springs or rubber springs in the existing track bed slab with a quasi-zero stiffness vibration isolation device, low or near-zero dynamic stiffness can be achieved under static equilibrium conditions. This solves the problem of traditional linear vibration isolation systems isolating low-frequency or ultra-low-frequency vibrations, reduces the initial isolation frequency, increases the isolation frequency range, and improves the system's vibration isolation efficiency. Simultaneously, it completely preserves the load-bearing capacity and reliability of existing floating slab vibration-damping tracks. Example 2

[0067] The basic principle of Embodiment 2 is the same as that of Embodiment 1, except that the structure is slightly different. It is a quasi-zero stiffness vibration isolation device for floating slab track beds in tunnel spaces. The quasi-zero stiffness vibration isolation device includes a positive stiffness component, a negative stiffness combination component, and a height adjustment plate. The positive stiffness component, negative stiffness combination component, and height adjustment plate are all installed inside an outer sleeve, with the bottom surface of the positive stiffness component extending beyond the bottom surface of the outer sleeve, forming a horizontal height difference. The negative stiffness combination component is installed inside the outer sleeve and is located above the positive stiffness component. The upper end face of the negative stiffness combination component extends beyond the upper end face of the outer sleeve and moves along with the floating slab track bed as it moves up and down, generating negative stiffness during this movement. The resultant force formed by this negative stiffness and the upward elastic force generated by the positive stiffness component remains essentially constant, thus constituting the quasi-zero stiffness vibration isolation. The negative stiffness combination component is a composite sheet spring negative stiffness combination component, which generates negative stiffness.

[0068] However, the negative stiffness assembly (210) includes an outer load-bearing component (216), an inner load-bearing component (217), and a negative stiffness mechanism (218), all of which have a square shape, forming a square negative stiffness mechanism, as shown in the attached figure. Figure 13 As shown.

[0069] Moreover, each negative stiffness unit has only a buckling leaf spring and a rotatable node. The buckling leaf spring has ball joints at both ends. The ball joints at both ends of the buckling leaf spring are respectively hinged to the elastic support plates that are stuck in the outer and inner load-bearing components, forming rotatable nodes. As the outer and inner load-bearing components move up and down, the buckling leaf spring rotates and buckles around the two rotatable nodes, forming negative stiffness.

[0070] The rest is the same as in Embodiment 1. This embodiment only changes the leaf spring structure, using a bent leaf spring with rotatable ball ends. This embodiment is the simplest way to form the negative stiffness of a rotating leaf spring, but it requires high performance from the bent leaf spring, which needs to have a large deformation. Therefore, the manufacturing of the bent leaf spring is quite difficult. Example 3

[0071] The structure of Embodiment 3 is the same as that of Embodiment 1, except that there are slight differences in structure. It is a quasi-zero stiffness vibration isolation device for floating slab track beds in tunnel spaces. The quasi-zero stiffness vibration isolation device includes a positive stiffness component, a negative stiffness combination component, and a height adjustment plate. The positive stiffness component, the negative stiffness combination component, and the height adjustment plate are all installed inside the outer sleeve, and the bottom surface of the positive stiffness component extends from the bottom of the outer sleeve, exceeding the bottom surface of the outer sleeve to form a horizontal height difference. The negative stiffness combination component is installed inside the outer sleeve and is located above the positive stiffness component. The upper end surface of the negative stiffness combination component extends from the upper end surface of the outer sleeve and moves with the outer sleeve as it moves up and down with the floating slab track bed. During this movement, it generates negative stiffness, and the resultant force formed by the negative stiffness and the upward elastic force generated by the positive stiffness component remains basically constant, thereby constituting the quasi-zero stiffness vibration isolation. The negative stiffness combination component is a composite sheet spring negative stiffness combination component, which generates negative stiffness.

[0072] However, the negative stiffness assembly (310) includes an outer load-bearing component (316), an inner load-bearing component (317), and a negative stiffness mechanism (318), all of which have a hexagonal shape, forming a hexagonal negative stiffness mechanism, as shown in the attached figure. Figure 14 As shown.

[0073] Moreover, each negative stiffness unit is composed of a rigid leaf spring and an elastic rotatable node. The rigid leaf spring has ball joints at both ends, which are respectively hinged to elastic support plates that are locked in the outer and inner load-bearing components. The elastic support plates are then bonded to the outer and inner load-bearing components through elastic rubber layers, forming elastic rotatable nodes. As the rigid leaf spring moves up and down with the outer and inner load-bearing components, it only rotates at the hinge points of the elastic support plates without buckling deformation. Instead, it compensates for the change in the length of the rigid leaf spring in the horizontal direction by compressing the rubber layers of the elastic rotatable nodes at both ends, causing the magnitude of the vertical component force at both ends of the rigid leaf spring to change, thus forming negative stiffness.

[0074] The adjustments to other parts are the same as in Embodiment 1. This embodiment solves the adverse effects of the change in length of the leaf spring during the process of moving from an inclined to a horizontal state by setting the elastic deformation of the elastic rotatable node. Moreover, it is made of elastic rubber, and the required deformation can be achieved by adjusting the hardness and stiffness of the rubber material. It has good elastic control effect and can easily achieve variable stiffness adjustment of negative stiffness, so it will become the first choice for negative stiffness adjustment. Example 4

[0075] The structure of Embodiment 4 is the same as that of Embodiment 1, except that there are slight differences in structure. It is a quasi-zero stiffness vibration isolation device for floating slab track beds in tunnel spaces. The quasi-zero stiffness vibration isolation device includes a positive stiffness component, a negative stiffness combination component, and a height adjustment plate. The positive stiffness component, the negative stiffness combination component, and the height adjustment plate are all installed inside the outer sleeve, and the bottom surface of the positive stiffness component extends from the bottom of the outer sleeve, exceeding the bottom surface of the outer sleeve to form a horizontal height difference. The negative stiffness combination component is installed inside the outer sleeve and is located above the positive stiffness component. The upper end surface of the negative stiffness combination component extends from the upper end surface of the outer sleeve and moves with the outer sleeve as it moves up and down with the floating slab track bed. During this movement, it generates negative stiffness, and the resultant force formed by the negative stiffness and the upward elastic force generated by the positive stiffness component remains basically constant, thereby constituting the quasi-zero stiffness vibration isolation. The negative stiffness combination component is a composite sheet spring negative stiffness combination component, which generates negative stiffness.

[0076] Each negative stiffness unit of the negative stiffness assembly is composed of a buckling leaf spring and a composite rotatable node, wherein one end of the composite rotatable node is an elastic rotatable node and the other end is a rigid rotatable node.

[0077] Furthermore, the upper support block of the negative stiffness unit is a load-bearing component that only allows up and down movement. Its lower left direction is designed as an arc-shaped concave surface, which forms a corresponding mating relationship with the arc-shaped convex surface of the upper support spring plate. The gap between the arc-shaped concave surface of the upper support block and the arc-shaped convex surface of the upper support spring plate is filled with the upper support rubber component and bonded and vulcanized together as a whole.

[0078] The lower support block of the negative stiffness unit is a load-bearing component placed on the foundation platform that restricts horizontal movement. Its upper right direction is designed as an arc-shaped concave surface, which forms a corresponding mating relationship with the arc-shaped convex surface of the lower support spring plate. The arc-shaped convex surface of the lower support spring plate is directly embedded in the arc-shaped concave surface of the lower support block, forming an elastically compressible and rotatable node at one end.

[0079] The adjustments to other parts are the same as in Embodiment 1. This embodiment simply uses a combination of a buckling leaf spring and a rotatable elastic node at one end. This utilizes both the buckling deformation advantage of the buckling leaf spring and the compressibility of elastic rubber. The combination of the two can alleviate the difficulty caused by the excessively high requirements of a single structure in achieving negative stiffness, as mentioned above, and better achieve the adjustment and variation of negative stiffness. At the same time, the use of a rigid rotatable node at one end of the buckling leaf spring facilitates processing and manufacturing, making mass production easier.

[0080] It should be noted that the above-listed embodiments are merely a clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Furthermore, terms such as "upper," "lower," "front," "rear," and "middle" used in this specification are only for clarity of description and are not intended to limit the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention. Simultaneously, the structures, proportions, sizes, etc., depicted in the accompanying drawings are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the present invention, should still fall within the scope of the technical content disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0081] The beneficial effects of this invention are:

[0082] This invention replaces the steel or rubber spring vibration isolators in existing track slabs with a quasi-zero stiffness vibration isolation device. This achieves low or near-zero dynamic stiffness in a static equilibrium state, solving the problem of traditional linear vibration isolation systems when isolating low-frequency or ultra-low-frequency vibrations. It reduces the initial isolation frequency, increases the isolation frequency range, and improves the system's vibration isolation efficiency. Simultaneously, it fully retains the load-bearing capacity and reliability of existing floating slab vibration-damping tracks. Its main advantages are as follows:

[0083] 1. The quasi-zero stiffness vibration isolation device of this invention has a simple structure, is easy to manufacture, and has value for engineering applications. Replacing the steel springs or rubber spring vibration isolators in the existing track bed with the quasi-zero stiffness vibration isolation device of this invention can effectively improve the vibration isolation effect of the floating slab track bed and eliminate noise pollution.

[0084] 2. The negative stiffness assembly of the quasi-zero stiffness vibration isolation device of the present invention uses a rotatable leaf spring instead of a conventional piston rod, disc spring, or linear spring. This eliminates the problem of unstable and uneven force caused by vertical force when the negative stiffness of the piston rod is formed. It also solves the problem of torsional deformation when the negative stiffness of the disc spring is formed, preventing uneven force in various directions and torsional deformation.

[0085] 3. A rotatable node is used to connect the rotatable leaf spring, allowing both ends of the rotatable leaf spring to rotate. This allows the rotatable leaf spring to adjust its air posture during operation, effectively solving the problem of jamming under vertical force that was previously caused by piston-type rod extension and retraction. By adjusting the air posture of the rotatable leaf spring through the rotation of the rotatable node to create negative stiffness, there is no jamming problem during the process. Therefore, it is possible to truly realize the engineering application of quasi-zero stiffness vibration isolation through negative stiffness intervention.

[0086] 4. The rotatable node adopts an elastic compressible structure. When the rotatable leaf spring rotates from the inclined plane to the horizontal plane, the elastic layer of the rotating node can be compressed to compensate for the dimensional changes of the rotatable leaf spring in the horizontal direction, and prevent the rotatable leaf spring from becoming unstable due to excessive horizontal force.

[0087] 5. By adjusting the rotation and compression of the rotatable leaf spring through the elastic rotating node, negative stiffness can be precisely formed, achieving a perfect match with the positive stiffness of the quasi-zero stiffness vibration isolation system, thus truly realizing quasi-zero stiffness vibration isolation.

[0088] 6. The rotatable leaf spring adopts a buckling leaf spring structure. During operation, negative stiffness can also be formed by the directional deformation of the buckling leaf spring. In this way, the required negative stiffness can be formed by the change of the buckling rotatable leaf spring itself or by its combination with the elastic rotating node.

[0089] 7. This negative stiffness device has a simple structure, is stable and reliable during implementation, and can accurately determine the variation law of negative stiffness, thereby finding the accurate negative stiffness and its variation law required for the quasi-zero stiffness vibration isolation of the system, and truly realizing the quasi-zero stiffness vibration isolation of the system.

[0090] 8. Since the negative stiffness composite component adopts a multi-layer negative stiffness unit combination to form a multi-layer structure, the force of the negative stiffness unit can be effectively dispersed. This method can greatly reduce the stress of the elastic material of the negative stiffness unit, thereby improving the performance and service life of the negative stiffness.

Claims

1. A quasi-zero stiffness vibration isolation method for a floating slab track bed in an urban rail transit tunnel, comprising setting a concrete floating slab on the floating slab track bed of the urban rail transit, wherein a quasi-zero stiffness vibration isolation device is installed in the concrete floating slab, the quasi-zero stiffness vibration isolation device comprising a positive stiffness component, a negative stiffness combination component, and a height adjustment pad, thereby enabling the concrete floating slab to be in a floating state on the floating slab track bed through the quasi-zero stiffness vibration isolation device; characterized in that: The aforementioned negative stiffness assembly is a negative stiffness device formed by rotatable spring combinations. The negative stiffness assembly is a negative stiffness mechanism formed by the vertical stacking of multiple rotatable leaf spring units. This mechanism is positioned above the positive stiffness assembly and floats with the upper support platform of the positive stiffness assembly. During the floating process, negative stiffness is generated through the up-and-down movement, rotation, and compression of the rotatable leaf springs, achieving vibration isolation with near-zero stiffness of the floating concrete slab. The negative stiffness generated by the up-and-down movement, rotation, and compression of the rotatable leaf springs is achieved using long strip-shaped leaf springs with a width less than their length. The two ends of the long strip-shaped leaf springs are respectively mounted on the upper and lower support blocks of the negative stiffness assembly via rotating nodes. As the upper and lower support blocks move up and down relative to each other, and the springs rotate around the rotating nodes during this movement, the rotatable leaf springs are compressed. The vertical component of the rotatable leaf spring's force is changed through its up-and-down movement, rotation, and compression, thus generating negative stiffness.

2. The quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels as described in claim 1, characterized in that: The negative stiffness mechanism arranged on top of the positive stiffness component refers to assembling multiple individual rotatable leaf springs into a ring-shaped negative stiffness unit combination, then vertically stacking multiple negative stiffness unit combinations together to form a negative stiffness mechanism, installing the negative stiffness mechanism in a closed annular cylinder to form a negative stiffness assembly, and then placing the negative stiffness assembly on top of the positive stiffness component.

3. The quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels as described in claim 1, characterized in that: The aforementioned method of changing the vertical component of the rotatable leaf spring through its up-and-down movement, rotation, and compression refers to the use of a buckling leaf spring installed between the upper and lower support blocks of the negative stiffness unit. As the buckling leaf spring moves up and down with the upper and lower support blocks, the buckling deformation of the leaf spring changes the vertical component of the rotatable leaf spring, creating negative stiffness that matches the positive stiffness, thus forming quasi-zero stiffness vibration isolation.

4. The quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels as described in claim 1, characterized in that: The aforementioned method of changing the vertical component of the rotatable leaf spring through its up-and-down movement, rotation, and compression refers to the use of elastic rotatable nodes. Both ends of the rotatable leaf spring are connected to the upper and lower support blocks of the negative stiffness unit through rotatable nodes, and at least one end of the rotatable node is an elastic rotatable node. As the rotatable leaf spring moves up and down with the upper and lower support blocks, the compression of the elastic rotatable node by the leaf spring changes the vertical component of the rotatable leaf spring, forming negative stiffness, which matches the positive stiffness, thus forming quasi-zero stiffness vibration isolation.

5. The quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels as described in claim 1, characterized in that: The method of changing the vertical component of the rotatable leaf spring by moving up and down, rotating, and compressing it employs a buckling leaf spring in conjunction with an elastic rotatable node to form negative stiffness. The rotatable leaf spring is a buckling leaf spring, with both ends connected to the upper and lower support blocks of the negative stiffness unit via rotatable nodes, and at least one end of the rotatable node is an elastic rotatable node. As the rotatable buckling leaf spring moves up and down with the upper and lower support blocks, it undergoes buckling deformation on one side and compression of the elastic rotatable node on the other, causing deformation of the elastic rotatable node. The combined effect of these two factors changes the vertical component of the buckling leaf spring, forming negative stiffness that matches the positive stiffness, thus achieving quasi-zero stiffness vibration isolation.

6. The quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels as described in claim 3 or 5, characterized in that: The aforementioned flexible leaf spring is a flat spring sheet, which is rectangular in shape. Its width is 1 / 3 to 1 / 2 of its length, and it is slightly bent downward along the middle of the length direction. At both ends of the length direction, there are cylindrical surfaces with the width direction as the axis. The radius of the cylindrical surface is 1.3 to 1.8 times the thickness of the spring sheet. The cylindrical surface at the end is connected to the upper and lower surfaces of the spring sheet in the thickness direction by a rounded transition.

7. The quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels as described in claim 6, characterized in that: The bending leaf spring is inclined at an angle to the horizontal plane along its length direction, and the cylindrical surfaces at both ends of the spring form the upper and lower joint support surfaces of the upper support block and the lower support block, respectively.

8. The quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels as described in claim 6, characterized in that: The length (L) of the bent leaf spring is 14-25 mm; the thickness is 0.6-1 mm; and the initial angle (A) of the bent leaf spring is between 15-25 degrees.

9. The quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels as described in claim 4 or 5, characterized in that: The elastic rotatable node includes a rubber layer and a supporting spring sheet; the rubber layer and the supporting spring sheet are vulcanized together, and the rubber layer is vulcanized at the joint position of the upper support block and the lower support block respectively. The two ends of the rotatable spring sheet are inserted into the supporting spring sheet to form an elastic rotatable node.

10. The quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels as described in claim 9, characterized in that: The supporting spring plate is a spring plate with a width consistent with the width of the leaf spring, but bent into an arc-like shape in the length direction. The cylindrical concave surface in the middle part forms a friction pair connection with the supporting copper tile of the leaf spring.

11. The quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels as described in claim 1, characterized in that: The upper support block and the lower support block are each a single load-bearing component that allows vertical movement. They have an arc-shaped concave surface in opposite directions, which corresponds to the arc-shaped convex surface of the support spring plate. The gap between the arc-shaped concave surface of the support block and the arc-shaped convex surface of the support spring plate is filled with a support rubber component and bonded and vulcanized together to form an elastic layer.

12. A system apparatus for implementing the quasi-zero stiffness vibration isolation method for floating slab track beds in urban rail transit tunnels as described in claim 1, comprising a base track bed, a floating slab track bed laid on the base track bed, concrete floating slabs disposed on the floating slab track bed, tracks disposed on the floating slabs, and a floating vibration isolation device disposed between the floating slab track bed and the floating slabs; characterized in that: The floating vibration isolation device is a quasi-zero stiffness vibration isolation device. It includes a positive stiffness component, a negative stiffness assembly, and a height adjustment plate. The negative stiffness assembly is a rotatable spring-type negative stiffness mechanism. This mechanism is formed by vertically stacking multiple rotatable leaf springs forming negative stiffness units. The negative stiffness mechanism is positioned above the positive stiffness component and floats with the upper support platform of the positive stiffness component. During this floating process, negative stiffness is generated through the up-and-down movement, rotation, and compression of the rotatable leaf springs. The negative stiffness assembly includes an outer support component, an inner support component, a negative stiffness mechanism, and a top cover plate. The outer support component is a stepped cylindrical structure with a larger upper end and a smaller lower end along its axial direction. Its upper inner cavity has a stepped hole structure and an internal thread near the end. The top cover plate screws onto the internal thread at the port of the outer support component, forming a closed cavity. The inner support component, the negative stiffness mechanism, and the top cover plate are coaxially mounted within this cavity. The lower end of the outer cylinder is provided with an external thread, which forms an assembly relationship with the internal thread at the upper end of the stepped hole in the center of the upper cover bearing cylinder in the positive stiffness component; the inner bearing component is a cylindrical structure, the outer diameter of the bottom of the barrel is larger than the outer diameter of the barrel and forms a shoulder, and a central circular hole is opened at the bottom of the barrel. The central circular hole and the end face of the hole form an assembly relationship with the top stepped shaft of the central shaft pin provided on the base plate in the positive stiffness component; the inner bearing component is coaxially installed at the bottom of the upper inner cavity of the outer bearing component; the negative stiffness mechanism is coaxially installed between the upper inner cavity of the outer bearing component and the cylindrical part of the inner bearing component; the negative stiffness mechanism is a negative stiffness mechanism formed by the combination of multiple negative stiffness units stacked along the plumb line; the negative stiffness unit combination is a negative stiffness unit formed by multiple rotatable leaf springs, which are arranged in a ring in the same plane to form a ring combination; then the multiple negative stiffness unit combinations are vertically stacked together to form a negative stiffness mechanism, and the negative stiffness mechanism is installed in the negative stiffness combination component.

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