Tunnel blasting vibration control system based on damping hole built-in metamaterial gradient resonators

Abstract

The invention discloses a tunnel blasting vibration control system based on a damping hole built-in metamaterial gradient resonator. The system comprises damping holes distributed on the periphery of a tunnel face peripheral hole, a wave guide panel outside the holes and a metamaterial damping device inside the holes. The damping hole built-in metamaterial gradient resonator is composed of a series of local resonance units with resonance frequencies arranged in an asymmetric gradient mode, and blasting vibration energy of a specified frequency band can be captured and dissipated in a targeted mode. The composite shell of the in-hole damping device provides protection for the resonator and is coupled with the hole wall rock mass to achieve the wave guiding function. The out-hole wave guide panel reflects blasting vibration through the specific angle of the fiber laying layer and restrains the blasting vibration in the triangular arrangement structure of the damping holes, and the vibration energy is secondarily dissipated through the in-hole damping device. Through the synergistic effect that the gradient resonators are used for core filtering and guided waves and the damping hole structures are used for assisting, vibration reduction and energy consumption of tunnel blasting vibration at any specified frequency band are achieved, and the tunnel blasting vibration damping device has the advantages of being high in pertinence and high in reliability.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of blasting vibration hazard control, and particularly relates to a tunnel blasting vibration control system based on a shock-absorbing hole built-in metamaterial gradient resonator. BACKGROUND

[0002] In the construction of railway tunnels and shafts by the drill-and-blast method, stress waves generated by blasting propagate in the rock-soil medium. Although the intensity of the stress waves rapidly decays after passing through the fracture circle, they can still excite the elastic vibration of rock particles. These elastic vibrations propagate outward in the form of elastic waves, forming blasting seismic waves, which can cause damage to the surrounding rock, adjacent engineering and surface buildings and structures, and threaten the stability of the tunnel and the safety of the construction. To control such vibrations, taking vibration reduction measures at the blasting source and its surrounding area is one of the effective ways to block the propagation of blasting seismic waves. A commonly used technical means is to arrange vibration reduction holes in the area of the blasting face. This technique uses the physical interruption effect of the holes to reduce the outward radiation propagation of stress waves and reduce the adverse effects of blasting vibration. However, the joint fissure development of natural rock mass is complex and has significant heterogeneous characteristics. The setting of vibration reduction holes often induces stress distribution in the surrounding rock that does not meet the design requirements of self-bearing capacity, leading to instability or even collapse of the blasting face and posing a risk to construction safety. Therefore, existing technologies propose methods of setting fillers or vibration reduction components in the vibration reduction holes to balance the requirements of surrounding rock stability and vibration control. However, these technologies often encounter the following problems in application:

[0003] 1. Insufficient wave impedance matching: The wave impedance of the fillers or vibration reduction components in the vibration reduction holes does not match the wave impedance of the blasting seismic waves, causing a large amount of blasting seismic waves to be reflected at the interface, and not achieving effective dissipation, thus the vibration control efficiency is not high;

[0004] 2. Lack of blast and impact resistance: If the material properties of the fillers or vibration reduction components in the vibration reduction holes are not properly designed, they lack blast and impact resistance and can be easily damaged under blasting loads, losing their vibration reduction and support functions;

[0005] 3. Lack of frequency-specific attenuation mechanism: The fillers or vibration reduction components in the vibration reduction holes cannot achieve frequency-specific attenuation of different frequency bands of blasting seismic waves and vibrations according to the blasting propagation path and depth.

[0006] The above problems significantly weaken the regulation and dissipation efficiency of blasting seismic waves and vibrations, making it difficult to achieve both safety and good vibration reduction performance.

[0007] For example, the Chinese patent with publication number CN115324586 discloses a "advance support damping system" built before blasting, which is mainly composed of a working chamber-free advance steel pipe shed and an advance small guide pipe applied in the soil layer. This system mainly covers the annular wall surface area of the blasting working face, and cannot form an effective protection distribution at the bottom of the working face. This incompleteness in spatial layout results in a large amount of vibration energy generated by blasting directly acting on and transmitting to the tunnel bottom surrounding rock and structure, and cannot effectively suppress the impact of blasting vibration on the tunnel bottom. The overall damping range has a significant defect. The damping steel pipe and other components relied on by this system have a huge difference in material wave impedance from the surrounding rock-soil layer. This serious wave impedance mismatch will cause strong reflection of blasting seismic waves at the steel pipe interface, rather than effective penetration and attenuation. As a result, only a small part of the vibration energy can be dissipated in the system, and most of the energy is reflected or diffracted and still continues to propagate to the surrounding rock-soil medium, causing damage risk to the rear and surrounding areas.

[0008] In summary, the existing technology still has limitations in dealing with low-frequency destructive vibration, considering spatial restrictions and engineering feasibility, and achieving precise and designable frequency-selective damping. There is still a lack of a systematic solution that can actively guide and efficiently dissipate vibration energy in a specific frequency band. SUMMARY

[0009] In view of the deficiencies of the prior art and the importance of engineering, the present application provides a tunnel blasting vibration control system based on a shock-absorbing hole built-in metamaterial gradient resonator, which can selectively attenuate blasting vibration in a specific frequency range during blasting and improve the filtering ratio, aiming to solve the blasting damping problems involved in the technical background.

[0010] To achieve the above-mentioned purposes, the technical solutions adopted by the present application are as follows:

[0011] A tunnel blasting vibration control system based on a shock-absorbing hole built-in metamaterial gradient resonator, the system comprising two circles of periodic shock-absorbing holes arranged in an equilateral triangle pattern around the periphery of the hole, a metamaterial damping device located in the shock-absorbing hole, and a waveguide panel located outside the shock-absorbing hole, wherein,

[0012] The metamaterial damping device comprises a composite shell, a metamaterial gradient resonator encapsulated in the composite shell, and a hole bottom fixed support;

[0013] The metamaterial gradient resonator is composed of a plurality of columnar local resonance units connected in series along the axis, and each local resonance unit comprises a negative Poisson's ratio foam matrix and n equidistant mass blocks wrapped therein, and n is a natural number between 1 and 5;

[0014] The resonance frequency of each local resonance unit is asymmetrically distributed along the axial direction in a gradient manner, the blasting hole charge is equivalent to a spherical explosive source, the position closest to the center of the preset explosive source along the axis of the damping hole is taken as the peak point of the resonance frequency, and the resonance frequency of the local resonance unit decreases in turn from the peak point to the hole opening direction and the hole bottom direction, wherein the decreasing speed is faster in the hole bottom direction; the gradient distribution of the resonance frequency is realized by adjusting the stiffness of the negative Poisson's ratio foam matrix in each local resonance unit, and the stiffness The target resonance frequency (f) is determined according to the following formula:

[0015]

[0016] Wherein: f is the resonance frequency; k is the stiffness of the negative Poisson's ratio foam matrix; m is the mass of the equidistant mass block;

[0017] A plurality of target filtering frequency points are arranged inside the damping hole, and each target filtering frequency point is placed with a local resonance unit having the same resonance frequency as the point;

[0018] The target resonance frequency (f) of the local resonance unit is designed according to the following formula:

[0019]

[0020] Wherein: α is the frequency attenuation index; r is the straight-line distance from the installation position of the local resonance unit to the center of the explosive source;

[0021] The waveguide panel is installed on the tunnel wall surface and covers the triangularly arranged area of the damping holes, and the waveguide panel, the damping holes and the metamaterial damping device form a combined effect, change the direction of the blasting seismic wave radiating and propagating along the working face to the tunnel wall surface, and reflect and limit the blasting seismic wave in the triangularly arranged spatial structure connected with the waveguide panel.

[0022] Preferably, the two circles of damping holes are arranged based on an equilateral triangle grid to determine the hole positions, any two adjacent holes in the outer circle form the bottom side of an equilateral triangle, and any hole in the inner circle forms the top end of an equilateral triangle, thereby forming a continuous equilateral triangle grid structure; the axis of the damping hole is inclined outward from the tunnel axis by 10-20°, so that the connecting line of any cross section of the damping hole is located on the periphery of the tunnel contour line, and the forming effect of the tunnel blasting contour is ensured.

[0023] Preferably, the hole distance of each adjacent damping hole in a circle is 0.8-1.0 m, and the radial hole distance of the inner and outer circle damping holes is 0.7-0.9 m, so that the damping holes are arranged to form a close grid structure and avoid mutual interference in the damping process;

[0024] Preferably, each shock absorption hole has a diameter of 76-89 mm; the depth of the shock absorption hole is 2 times the depth of the blasting area charge hole, which is beneficial to the advance blocking of the blasting seismic wave.

[0025] Preferably, the waveguide panel is made of fiber reinforced composite material FRP; wherein the internal fibers of the fiber reinforced composite material FRP adopt a symmetric layer structure of [+θ, -θ], and the layering angle θ is consistent with the axial inclination angle of the shock absorption hole, so as to ensure that the blasting seismic wave reflected by the waveguide panel accurately enters the array space formed by the shock absorption hole 1.

[0026] Preferably, each waveguide panel is arranged around the tunnel section, extending from the central vault to the central floor; the first and last panels have an equilateral triangular structure with three through holes, and the remaining panels have a close-angle equilateral triangle structure with two through holes, and the close-angle is shared with the through hole of the previous panel to form a net-like equilateral triangular structure; each through hole is connected and fixed with the metamaterial damping device in the corresponding shock absorption hole;

[0027] Preferably, the gap between the adjacent waveguide panels is 3-5 mm, so as to avoid vibration interference during damping.

[0028] Preferably, the composite shell of the metamaterial damping device is composed of an inner polyurethane waveguide layer and an outer aramid fiber reinforced layer;

[0029] Preferably, the Shore hardness of the inner, middle and outer layers of the polyurethane waveguide layer increases in the range of 70-95, and the loss factor is 0.1-0.3, so as to guarantee the gradient change of the wave impedance of the polyurethane waveguide layer and realize the high-frequency energy dissipation in the process of blasting seismic wave transmission;

[0030] Preferably, the aramid fiber reinforced layer is spirally wrapped around the outer periphery of the polyurethane waveguide layer, with a spiral width of 10-15 mm and a pitch of 15-20 mm, so that the coverage rate of the aramid fiber reinforced layer on the outer periphery of the polyurethane waveguide layer reaches 50%. The wrapping of the aramid fiber reinforced layer can effectively resist the impact damage of blasting to the internal structure, and the coverage rate of 50% is used to leave enough channels for the blasting seismic wave to enter the inside of the composite shell;

[0031] Preferably, in terms of connection mode and connection material selection, in order to achieve the damping effect, the following conditions are met:

[0032] The composite shell of the metamaterial damping device is filled with grouting material between the outer wall of the composite shell and the hole wall of the damping hole to form a grouting layer; and the inner wall of the composite shell is filled with an epoxy resin adhesive layer between the metamaterial gradient resonators;

[0033] A partition plate is arranged between the local resonance units of different frequencies in the metamaterial gradient resonator, and the partition plate is fixed with the series column on the outer periphery of the local resonance unit through a buckle member.

[0034] Preferably, the composite shell is provided with internal threads on the inner wall of the end close to the entrance of the damping hole, and a conical pin column is connected to the end close to the bottom of the damping hole;

[0035] The hole bottom fixed support is an integral structure, the front end is provided with a conical pin hole, and the conical pin column at the bottom end of the composite shell is connected through screwing in, and the rear end is a solid round steel section, and a ring of controllable telescopic structure sections is arranged on the periphery of the bottom of the solid round steel section.

[0036] The application also provides a construction method of the tunnel blasting construction damping system.

[0037] Step 1, accurate measurement and lofting is performed at the designed position outside the blasting area of the tunnel face, and the center point of the damping hole is calibrated; a drill is used to drill to form the periodic drilling array according to the designed inclination angle and depth;

[0038] Step 2, the hole bottom fixed support is placed into the bottom of the damping hole and is initially embedded and fixed with the rock mass by releasing the telescopic structure section at the bottom of the hole bottom fixed support;

[0039] Step 3, the conical pin column at the bottom end of the composite shell is inserted into the conical pin hole of the hole bottom fixed support and is screwed in, the connection and locking of the two are completed, and pressure grouting is performed on the annular gap between the outer wall of the composite shell and the hole wall of the damping hole to form the grouting layer;

[0040] Step 4, the partition plate and the series column are assembled, and the local resonance unit corresponding to different frequency points is placed in the space formed by the series column and the partition plate to form a metamaterial gradient resonator;

[0041] Step 5, the metamaterial gradient resonator is placed into the inner cavity of the composite shell, and epoxy resin is injected between the outer periphery of the metamaterial gradient resonator and the inner wall of the composite shell to form the epoxy resin bonding layer;

[0042] Step 6, the blocking bolt is screwed into the top end of the composite shell, and a pad plate is installed at the connection between the blocking bolt and the composite shell. Then epoxy mortar is applied on the back of the waveguide panel and the corresponding wall surface, and the waveguide panel is fixedly installed on the wall surface of the tunnel face, so as to cover the drilling array area; wherein the blocking bolt passes through the through holes on the edges and corners of the waveguide panel and is fixed by high-strength bolts and the like.

[0043] The application also provides the application of the tunnel blasting vibration control system or the construction method in tunnel vibration control.

[0044] The application has the following beneficial effects:

[0045] 1. The core of the vibration damping device within the borehole lies in a metamaterial gradient resonator composed of axially connected local resonant units. Based on the principle of local resonance and combined with the superior buffering and energy absorption characteristics of negative Poisson's ratio materials, it can achieve efficient attenuation of blast vibration energy. This invention designs the resonant frequency of the metamaterial gradient resonator to an asymmetric bidirectional gradient distribution with the peak resonant frequency closest to the center of the equivalent blast source, achieving active matching with the actual three-dimensional spatial attenuation law of blast seismic waves within the borehole device. This design can efficiently attenuate blast vibration energy from high to low frequencies, expand the vibration damping range, and achieve highly targeted attenuation of the main destructive frequency bands within a certain range, thus achieving a certain degree of advanced vibration damping effect.

[0046] 1. The metamaterial gradient resonator is encased in a functionally layered composite shell. The inner layer is a polyurethane waveguide layer with a gradient wave impedance design, which effectively reduces wave impedance mismatch and facilitates the efficient penetration of blast seismic waves into the damping hole. The outer layer is a helically wound aramid fiber reinforcement layer, which provides excellent blast and impact resistance while minimizing interference with wave propagation. Together, they form a crucial guarantee for filtering blast seismic waves and protecting the devices inside the hole.

[0047] 2. The waveguide panel installed on the tunnel wall has an internal fiber layup angle θ that is consistent with the inclination angle of the damping holes. When blasting occurs, the blasting seismic waves radiate along the tunnel face to the waveguide panel, where they can be reflected and confined by the waveguide panel within the triangular arrangement of damping holes connected to the waveguide panel. This helps to dissipate the blasting vibration energy propagating along the tunnel face and improves the overall blasting control efficiency.

[0048] The damping holes are arranged periodically in an equilateral triangular grid in three-dimensional space. This structure itself forms a waveguide, in which blasting seismic waves can be dissipated through multiple scattering and interference, thereby reducing vibration damage caused by blasting seismic waves. This design not only improves vibration reduction efficiency in terms of wave control, but its stable triangular grid configuration also enhances the mechanical stability of the overall support structure. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the overall situation of the tunnel blasting vibration reduction system in a specific embodiment of the present invention.

[0050] Figure 2 This is a cross-sectional schematic diagram of the vibration damping device inside the hole in a specific embodiment of the present invention.

[0051] Figure 3 This is a schematic diagram of the in-hole vibration damping device in a specific embodiment of the present invention.

[0052] Figure 4 This is a schematic diagram of the end metamaterial gradient resonator of the in-hole vibration damping device in a specific embodiment of the present invention.

[0053] Figure 5 Front view of the partition plate in the damping device in the hole in the specific embodiment of the present application.

[0054] Figure 6 Split view of the hole bottom fixing support in the damping device in the hole in the specific embodiment of the present application.

[0055] Figure 7 Schematic view of the negative Poisson's ratio foam matrix structure in the specific embodiment of the present application.

[0056] The reference signs in the figure are: 1 - damping hole; 2 - waveguide panel; 3 - pad plate; 4 - barrier bolt; 5 - high-strength bolt; 6 - grouting layer; 7 - composite shell; 8 - polyurethane waveguide layer; 9 - aramid fiber reinforced layer; 10 - metamaterial gradient resonator; 11 - partition plate; 12 - series column; 13 - local resonance unit; 14 - negative Poisson's ratio foam matrix; 15 - mass block; 16 - hole bottom fixing support; 17 - conical pin column; 18 - conical pin hole; 19 - solid cylindrical steel section; 20 - controllable telescopic structure section; 21 - epoxy resin bonding layer; 22 - buckle member. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present application will be described in detail and completely below in combination with the drawings in the embodiments of the present application. The same reference signs in the drawings represent functionally identical or similar elements. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0058] Example 1 Device structure

[0059] The present embodiment is directed to a tunnel drilling and blasting construction section of a certain mountain railway, the tunnel has been excavated to a Ⅲ grade surrounding rock section with a burial depth of about 120 m, and the current tunnel face mileage is DK158+425. In order to further control the influence of blasting vibration on the initial support of the tunnel and the rear lined section, a tunnel blasting vibration control system is arranged outside the peripheral hole around the tunnel face. As shown in Figure 1 Some waveguide panels 2 have been assembled into an integral structure with the pre-buried damping holes 1 and the damping devices in the damping holes 1 through high-strength bolts 5, pad plates 3, barrier bolts 4 and other connecting members.

[0060] Figures 1 to 3 A tunnel blasting vibration control system based on a metamaterial gradient resonator built-in damping hole is shown, mainly including two circles of damping holes 1 arranged in an equilateral triangle periodic arrangement around the peripheral hole of the tunnel face, a metamaterial damping device in the damping hole 1 and a waveguide panel 2 outside the damping hole 1. Among them, the metamaterial damping device is composed of a composite shell 7, a metamaterial gradient resonator 10 packaged in the shell and a hole bottom fixing support 16.

[0061] AsFigure 1 As shown in the figure, the damping holes 1 are arranged in double circles, and the inner and outer circle hole positions are arranged in staggered equilateral triangles. The distance between adjacent holes in the inner and outer circles is 0.8 m, and any hole in the inner circle is located at the vertex of the equilateral triangle formed by the adjacent two holes in the outer circle, and the radial circle distance is 0.7 m. The diameter of the damping hole 1 is 89 mm, and the hole depth is 2 times the depth of the blasting area charge hole, which is beneficial to the advance blocking of the blasting seismic wave. The axis of all damping holes 1 is inclined outward by 15° relative to the tunnel axis to ensure the forming effect of the tunnel blasting profile.

[0062] As shown in the figure, Figure 1 The waveguide panel 2 corresponds to the equilateral triangle area formed by every three damping holes 1. The waveguide panel extends from the central area of the vault of the tunnel contour to the central area of the tunnel bottom plate, a total of 28 blocks. The first and last waveguide panels 2 are complete equilateral triangle structures, and each corner is provided with a through hole; the waveguide panels 2 in the remaining area are notched equilateral triangle panels provided with two through holes, and the notched corner shares a through hole with the previous panel to form a net-like equilateral triangle structure. A 5 mm deformation joint is reserved between adjacent panels. The waveguide panel 2 is connected and fixed with the device inside the damping hole 1 through the through hole preset at the corner.

[0063] As shown in the figure, Figure 3 The composite shell 7 of the metamaterial damping device is composed of an inner polyurethane waveguide layer 8 and an outer aramid fiber reinforced layer 9, and the composite shell 7 is bonded and fixed with the inner wall of the damping hole 1 by pressure grouting process. The metamaterial gradient resonator 10 is encapsulated inside the composite shell 7 by epoxy resin bonding. The inner wall of the top end of the composite shell 7 is provided with an inner thread section, and the bottom end is connected with a conical pin column 17. The aramid fiber reinforced layer 9 is spirally wound outside the polyurethane waveguide layer 8, and there is a gap between the spiral bands.

[0064] As shown in the figure, Figures 2 to 5 The metamaterial gradient resonator 10 is composed of a plurality of local resonance units 13 with different resonance frequencies axially connected in series. Each local resonance unit 13 includes a columnar negative Poisson's ratio foam matrix 14 and three symmetric metal mass blocks 15 inside at equal intervals, and a multi-frequency point resonance system is formed by gradient arrangement of each local resonance unit 13. In this embodiment, the frequency points in the damping hole 1 are designed according to the formula as 20 target filter frequency points: 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5 Hz. Four circumferentially distributed series columns 12 are arranged on the outer periphery of the local resonance unit 13 as the skeleton of the metamaterial gradient resonator 10, and the local resonance units 13 with different frequencies are isolated by the partition plates 11. The buckle members 22 and the partition plates 11 are locked on the series columns 12 at intervals.

[0065] AsFigure 6 As shown, the hole bottom fixed support 16 is an integrated steel structure, the front end is provided with a tapered pin hole 18, which is threadedly connected with the tapered pin column 17 at the bottom end of the composite shell 7; the rear end is a solid cylindrical steel section 19, the outer edge of the bottom thereof is provided with a ring of controllable expansion structure section 20, which can be expanded and pressed against the hole wall after installation to enhance the impact stability of the device.

[0066] Example 2 Method and process

[0067] The attenuation effect of the device inside and outside the hole in the system on the blasting seismic wave during blasting is achieved by the following steps:

[0068] Step 1, outside the blasting area of the tunnel face, the surveyor uses a total station to accurately measure and lay out at the designed position, marks the center point of each shock absorption hole 1 and sprays paint for marking. After the drilling machine is in place, the operator adjusts the angle of the drill rod according to the design parameters to ensure that it is inclined outward by 15°, and then starts drilling. The drill bit continues to work until the predetermined depth is reached, forming a neat array of drill holes.

[0069] Step 2, the operator carefully places the hole bottom fixed support 16 into the bottom of the shock absorption hole 1. After reaching the bottom of the hole, the controllable expansion structure section 20 at the bottom of the hole bottom fixed support 16 is released by a special tool to make it expand outward and preliminarily fit with the hole wall rock mass, forming a stable bottom anchoring.

[0070] Step 3, align the tapered pin column 17 at the bottom end of the composite shell 7 with the tapered pin hole 18 at the top of the hole bottom fixed support 16, insert it and then screw it in using a torque wrench until they are tightly locked. Then, pressure grouting is carried out through the grouting pipe to the annular gap between the outer wall of the composite shell 7 and the hole wall of the shock absorption hole 1. The slurry fills the gap and forms a dense grouting layer 6 after solidification, firmly bonding the composite shell 7 and the surrounding rock as one.

[0071] Step 4, in the neat assembly area, the operator first assembles the skeleton by clamping the partition plate 11 and the series column 12. Then, the local resonance units 13 of different frequencies are placed in the grid space formed by the skeleton according to the number, and finally assembled into a complete metamaterial gradient resonator 10.

[0072] Step 5, slowly hoist and place the assembled metamaterial gradient resonator 10 into the inner cavity of the fixed composite shell 7. After accurate positioning, epoxy resin is injected into the gap between the outer periphery of the resonator and the inner wall of the shell through the reserved glue injection hole. The resin slowly flows and fills all the gaps, and after solidification, a uniform epoxy resin bonding layer 21 is formed, realizing the complete coupling of the core structure and the composite shell 7.

[0073] Step 6, finally, the barrier bolt 4 is screwed into the threaded opening at the top end of the composite shell 7, and a pad plate is installed at the connection between the barrier bolt 4 and the composite shell 7. Then, a layer of epoxy mortar is evenly applied on the back of the waveguide panel 2 and the corresponding wall area of the working face, and then the panel is attached in place, so that it completely covers the drilling array area. The barrier bolt passes through the through hole on each corner of the waveguide panel 2 in turn, and is fastened with a high-strength bolt 5, completing the installation of the entire system.

[0074] Example 3

[0075] In this embodiment, the vibration reduction effect of the system will be demonstrated through the comparison of partial structures.

[0076] A tunnel blasting vibration control system based on a shock-absorbing hole inner metamaterial resonator is designed, and all the local resonance units 13 in the metamaterial resonator 10 are set to have a single and consistent resonance frequency, thereby forming a single-frequency metamaterial resonator. After the metamaterial resonator is packaged inside the composite shell 7, the remaining structures are assembled according to the same steps of the system.

[0077] Through field research and analysis, the vibration reduction efficiency of the system is lower than that of the blasting vibration control system in the present invention during the blasting process.

[0078] The blasting stress wave generated under the action of the blasting load rapidly attenuates after passing through the near-zone fracture circle, but still causes elastic vibration of rock particles, which propagates outward in the form of elastic waves, forming blasting seismic waves. The high-frequency component of the blasting seismic wave rapidly attenuates with the propagation distance due to the internal damping and scattering of the rock mass, while the low-frequency component attenuates slowly and propagates farther. Therefore, the dominant frequency band of the blasting seismic wave changes at different positions from the blast source, resulting in different ranges of the main vibration frequency band of rock mass damage.

[0079] Since the metamaterial resonator in the system is designed for a single frequency, the generated local resonance band gap is narrow. This means that the vibration reduction device in the system can only attenuate the blasting seismic wave in a small frequency range. During the blasting process, the seismic wave and the vibration propagate non-uniformly from the blast source to the surrounding rock mass, and the wave of some frequency bands can be effectively attenuated by the resonator, while the wave of the remaining frequency bands continues to propagate to a long distance, resulting in cracks in the local rock wall of the tunnel, and even inducing rock mass instability and other vibration secondary disasters in severe cases.

[0080] If you want to improve the vibration reduction effect to a greater extent, the local resonance band gap of the local resonance units in the metamaterial resonator designed in the system needs to be widened, so as to filter more frequency range of the blasting seismic wave, thereby achieving better vibration reduction effect.

[0081] Example 4

[0082] In the embodiment, the vibration reduction effect of the system is demonstrated by comparing the partial structures.

[0083] A tunnel vibration control system based on a damping hole inner metamaterial gradient resonator is designed, and the composite shell 7 in the damping device in the hole is replaced by a common rigid shell with uniform wave impedance characteristics, and the remaining structures in the system remain consistent with the structures in the application.

[0084] Through field research and analysis, compared with the vibration control system in the application, the damping efficiency of the system is reduced during the blasting process. During the blasting process, when the blasting seismic wave propagates to the damping hole 1 position in the rock mass, due to the significant wave impedance mismatch between the common shell material and the surrounding rock, strong wave reflection effect will occur at the interface. As a result, most of the incident wave energy is reflected, and the reflected energy still propagates in the rock mass and spreads far away, only a small part of the energy can be transmitted into the borehole and captured and dissipated by the metamaterial gradient resonator 10. Therefore, the overall system damping efficiency of the comparative example is limited by the lower wave energy transmission rate, and the vibration generated in the blasting process will still have adverse effects on the surrounding rock mass.

[0085] If you want to improve the damping effect to a greater extent, then for the shell in the hole damping device, a material with wave impedance that can match the blasting seismic wave impedance should be selected as the shell part, and the anti-blast and impact performance should be considered as well, which can improve the proportion of blasting seismic waves entering the damping hole 1 and protect the core metamaterial gradient resonator 10, so as to achieve better damping effect.

[0086] The above description is only a few embodiments of the application, and does not limit the implementation and protection scope of the application. For those skilled in the art, any equivalent conversion or obvious change obtained by using the content of the application specification and drawings is within the protection scope of the application.

Claims

1. A tunnel blasting vibration control system based on a metamaterial gradient resonator with an embedded damping hole, characterized in that, The system includes two rings of periodic damping holes (1) arranged in an equilateral triangle around the perimeter of the tunnel face, a metamaterial damping device inside the damping holes (1), and a waveguide panel (2) outside the damping holes (1). The metamaterial vibration damping device includes a composite shell (7), a metamaterial gradient resonator (10) encapsulated in the composite shell (7), and a hole bottom fixing support (16). The metamaterial gradient resonator (10) is composed of multiple columnar local resonant units (13) connected in series axially. Each local resonant unit (13) includes a negative Poisson's ratio foam matrix (14) and n equidistant mass blocks (15) enclosed therein, where n is a natural number between 1 and 5. The resonance frequencies of each local resonance unit (13) exhibit an asymmetric gradient distribution along the axial direction. Based on the assumption that the explosive charge inside the borehole can be equivalent to a spherical blast source, the peak value of the resonance frequency is determined by the position closest to the preset blast source center on the axis of the damping hole (1). From the peak value towards the borehole opening and bottom, the resonance frequencies of the local resonance units (13) decrease sequentially, with a faster decrease towards the bottom. The gradient distribution of the resonance frequencies is achieved by adjusting the stiffness of the negative Poisson's ratio foam matrix (14) of each local resonance unit (13). The stiffness k is determined based on the target resonance frequency (f). Where: f—resonance frequency; k—stiffness of the negative Poisson's ratio foam matrix; m—mass of equidistant mass blocks; Multiple target filtering frequency points are set inside the damping hole (1), and a local resonance unit (13) with the same resonance frequency as the point is placed at each target filtering frequency point. The target resonance frequency (f) of the local resonance unit (13) is designed according to the following formula: Where: α—frequency attenuation index; r—straight-line distance from the installation location of the local resonance unit to the center of the explosion source; The waveguide panel (2) is installed on the tunnel wall and covers the area of ​​the triangular arrangement of the shock-absorbing holes (1). The waveguide panel (2), the shock-absorbing holes (1) and the metamaterial vibration reduction device form a combined effect, which changes the direction of the blasting seismic wave radiating and propagating along the tunnel face to the tunnel wall, and reflects and confines the blasting seismic wave within the triangular arrangement of the shock-absorbing holes (1) connected to the waveguide panel (2).

2. The tunnel blasting vibration control system according to claim 1, characterized in that, The two rings of shock-absorbing holes (1) are arranged based on an equilateral triangle grid to determine the hole positions. Any two adjacent holes in the outer ring form the base of an equilateral triangle, and any hole in the inner ring forms the apex of an equilateral triangle, thus forming a continuous equilateral triangle grid structure. The axis of the shock-absorbing hole (1) is inclined 10-20° outward from the tunnel axis so that the line connecting any cross section of the shock-absorbing hole (1) is outside the tunnel outline, ensuring the forming effect of the tunnel blasting outline.

3. The tunnel blasting vibration control system according to claim 2, characterized in that, The spacing between adjacent damping holes (1) in each ring is 0.8-1.0 m, and the radial spacing between the inner and outer ring damping holes (1) is 0.7-0.9 m, so that the damping holes (1) are arranged to form a tight grid structure and avoid mutual interference during the vibration reduction process. Each damping hole (1) has a diameter of 76-89 mm; the depth of the damping hole (1) is twice the depth of the charge hole in the blasting area, so as to facilitate the advance blocking of blasting seismic waves.

4. The tunnel blasting vibration control system according to claim 1, characterized in that, The waveguide panel (2) is made of fiber-reinforced composite material (FRP); wherein the internal fibers of the fiber-reinforced composite material (FRP) adopt a symmetrical layup structure of [+θ, -θ], and the layup angle θ is consistent with the axial tilt angle of the damping hole (1), so as to ensure that the explosive vibration reflected by the waveguide panel accurately enters the array space formed by the damping hole (1).

5. The tunnel blasting vibration control system according to claim 1, characterized in that, The waveguide panels (2) are arranged around the tunnel cross section, extending from the center of the arch to the center of the bottom plate; the first and last panels are equilateral triangles with three through holes, and the remaining panels are adjacent equilateral triangles with missing corners, each with two through holes. The missing corners share through holes with the previous panel, forming a mesh equilateral triangle structure; each through hole is connected and fixed to the corresponding shock-absorbing hole (1) with the supermaterial vibration damping device. The gap between adjacent waveguide panels (2) is 3-5mm to avoid vibration interference during the vibration reduction process.

6. The tunnel blasting vibration control system according to claim 1, characterized in that, The composite shell (7) of the metamaterial vibration damping device is composed of an inner polyurethane waveguide layer (8) and an outer aramid fiber reinforcement layer (9); The inner, middle and outer layers of the polyurethane waveguide layer (8) have an increasing Shore hardness in the range of 70-95 and a loss factor of 0.1-0.3, which ensures the gradient change of the wave impedance of the polyurethane waveguide layer (8) and realizes the high-frequency energy dissipation in the process of blasting seismic wave propagation. The aramid fiber reinforcement layer (9) is wrapped around the outer periphery of the polyurethane waveguide layer (8) in a spiral winding manner. The spiral width is 10-15 mm and the pitch is 15-20 mm, so that the coverage of the aramid fiber reinforcement layer (9) on the outer periphery of the polyurethane waveguide layer (8) is 50%. The coverage of the aramid fiber reinforcement layer (9) can effectively resist the impact damage of the explosion to the internal structure. The 50% coverage is used to leave enough channels for the explosion seismic waves to enter the interior of the composite shell (7).

7. The tunnel blasting vibration control system according to claim 1, characterized in that, Regarding the selection of connection methods and materials for the in-hole metamaterial vibration damping device, in order to achieve the vibration damping effect, the following should be considered: The outer wall of the composite shell (7) of the metamaterial vibration damping device is filled with grout between the outer wall of the composite shell (7) and the wall of the vibration damping hole (1) to form a grouting layer (6); the inner wall of the composite shell (7) is filled with an epoxy resin adhesive layer (20) between the inner wall of the composite shell (7) and the metamaterial gradient resonator (10). A partition (11) is provided between local resonant units (13) of different frequencies in the metamaterial gradient resonator (10). The partition (11) is fixed to the series column (12) on the outer periphery of the local resonant unit (13) by a snap-fit ​​component (22).

8. The tunnel blasting vibration control system according to claim 1, characterized in that, The inner wall of the composite shell (7) near the inlet of the shock-absorbing hole (1) is provided with an internal thread, and the end near the bottom of the shock-absorbing hole (1) is connected with a tapered pin (17). The hole bottom fixing support (16) is an integral structure with a tapered pin hole (18) at the front end, which is connected to the tapered pin (17) at the bottom of the composite shell (7) by screwing in. The rear end is a solid round steel section (19), and a controllable telescopic structure section (20) is provided around the bottom of the solid round steel section (19).

9. A construction method for installing the tunnel blasting vibration control system according to any one of claims 1-8, characterized in that, Includes the following steps: S1, accurately measure and lay out the design position outside the blasting area of ​​the tunnel face, and mark the center point of the shock-absorbing hole (1); use a drilling rig to drill according to the designed outward inclination angle and depth to form the periodic drill array; S2, the hole bottom fixing support (16) is placed into the bottom of the shock absorption hole (1) and the retractable structural section (20) at the bottom of the hole bottom fixing support (16) is released to initially embed and fix it with the rock mass; S3, insert the tapered pin (17) at the bottom of the composite shell (7) into the tapered pin hole (18) of the hole bottom fixing support (16) and screw it in to complete the connection and locking of the two; perform pressure grouting on the annular gap between the outer wall of the composite shell (7) and the hole wall of the shock absorption hole (1) to form the grouting layer (6). S4, assemble the partition (11) and the series column (12), and then place the local resonant units (13) corresponding to different frequency points into the space formed by the series column (12) and the partition (11) to form a metamaterial gradient resonator (10). S5, the metamaterial gradient resonator (10) is placed into the inner cavity of the composite shell (7), and epoxy resin is injected between the outer periphery of the metamaterial gradient resonator (10) and the inner wall of the composite shell (7) to form the epoxy resin adhesive layer (21). S6, screw the barrier bolt (4) into the top of the composite shell (7) and install a pad at the connection between the barrier bolt (4) and the composite shell (7); then apply epoxy mortar to the back of the waveguide panel (2) and the corresponding wall surface, and then fix the waveguide panel (2) to the tunnel wall so that it covers the drilling array area; wherein the barrier bolt (4) passes through the through holes on each corner of the waveguide panel (2) and is fixed with high-strength bolts (5) and other components.

10. The application of the tunnel blasting vibration control system according to any one of claims 1-8 or the construction method according to claim 9 in tunnel blasting vibration control.

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