JP6240446B2 - Box Helmholtz Resonator Assembly and Tunnel Blasting Reduction Method - Google Patents

Description

  The present invention relates to an assembly in which a plurality of box-shaped Helmholtz resonators are stacked or arranged in a horizontal direction, and a method for reducing tunnel blasting sound using the assembly of box-shaped Helmholtz resonators.

  In tunnel extension work such as mountain tunnels, tunnel extension work may be carried out while repeating blasting in the tunnel in order from the wellhead side, but the blasting sound generated during this blasting includes broadband frequency sound. It is also known that the sound pressure level is extremely high. When a blasting sound of this nature leaks to the outside, not only the problem of noise to the surrounding environment, but also the problem that the so-called low frequency sound with a frequency of 50 Hz or less included in the blasting sound vibrates the surrounding buildings. Can occur.

  In order to suppress the leakage of such harmful blasting sound, conventionally, countermeasures such as installing soundproof walls that block the tunnel cross section, for example, at two locations in the mine are generally performed. The current situation is that the sound insulation is insufficient, including that the low frequency sound cannot be sufficiently reduced by the resonance phenomenon in the space surrounded by the soundproof wall, and further improvement of the sound insulation is desired.

  Here, Patent Document 1 discloses a muffling technique capable of dealing with a particularly low frequency band sound (low frequency sound) among tunnel blasting sounds.

  In this technique, a tunnel entrance or inside of a tunnel is closed with a predetermined partition, one end is opened into the tunnel tunnel, and the other end is closed, and a plurality of pipes having different path lengths are installed on the face side from the predetermined partition. Is. Here, for each of a plurality of frequency sounds including at least a low frequency sound among the sounds constituting the tunnel blasting sound, a tube having a path length of 1/4 wavelength of the corresponding sound is installed on the face side from the predetermined partition wall. To do.

  In this way, if a tube with a 1/4 wavelength path length is used to reduce the low frequency sound of, for example, 10 Hz, a tube with a length of about 8.5 m is required, for example. When trying to store such a long tube body, there is a possibility that the tube body is forced to be bent from the middle. Note that the technique disclosed in Patent Document 1 intends to actively perform such bending of a tubular body.

  When a plurality of tubular bodies having various lengths and complicated shapes as described above are to be accommodated in the tunnel, a plurality of complicatedly shaped tubular bodies intersect in the tunnel, There may also be a problem that it becomes impossible to secure passages for heavy machinery and workers.

  Also, when each pipe is individually bent into a unique three-dimensional shape, each pipe can be diverted during the extension process in the tunnel construction currently underway, but the cross-sectional dimensions and cross-section Diversion to other tunnels with different shapes and vertical alignments is extremely difficult.

  By the way, although it is not the technique regarding reduction of the blasting sound of a tunnel, the technique regarding the low frequency sound reduction apparatus is disclosed by patent document 2. FIG.

  This technology uses low frequency sound equipment such as vibrating screens, air compressors, and combustion machines in a low frequency sound reduction device surrounded by a panel, and is provided on the sound source side. A Helmholtz resonator composed of a neck and a cavity behind it is provided on the panel so that the resonance frequency of the Helmholtz resonator substantially matches the low frequency of the sound source. It absorbs low frequency sound from the internal sound source.

  Since this device accommodates a device (sound source) that generates low-frequency sound inside it, that is, a device that wraps the sound source and absorbs the sound, this device is temporarily installed in the tunnel. In this case, since there is a blasting point (sound source) outside the device, it is not certain whether or not the low frequency sound generated at the time of blasting can be absorbed effectively.

JP 2011-256609 A Japanese Patent Laid-Open No. 2001-075754

  The present invention has been made in view of the above-described problems, and it is possible to guarantee the passage of heavy machinery and workers in the tunnel without using a complicated and long tubular body. It can be diverted to construction work, and it can effectively reduce the sound pressure of blasting sound that consists of broadband frequency sound generated during tunnel construction, especially the sound pressure of low frequency sound. It is an object of the present invention to provide a box-shaped Helmholtz resonator assembly that can be reduced to a low level and a method for reducing tunnel blasting sound using the assembly.

  In order to achieve the above object, an assembly of a box-shaped Helmholtz resonator according to the present invention comprises a box and a through pipe disposed inside the box, and the through pipe is provided on one side surface constituting the box. A box-shaped Helmholtz resonator is configured to be fixed to the side surface so as to communicate with the formed hole, and all of the plurality of the box-shaped Helmholtz resonators have the one side surface in the same direction and the end of the through-tube. The through-holes are stacked and / or provided side-by-side so that the opening of the part faces the outside, and the penetrating pipe has a different cross-sectional area and / or pipe length for each box-shaped Helmholtz resonator.

  The box-shaped Helmholtz resonator constituting the assembly of the present invention has a simple box-shaped Helmholtz in which one or a plurality of through tubes are fixed to the side so as to communicate with one or a plurality of holes on the side of the box. It is a resonator. This box-shaped Helmholtz resonator can also be referred to as a “box-shaped resonator”.

  Further, the through-tubes of the box-shaped Helmholtz resonators constituting the assembly have different cross-sectional areas and / or tube lengths for each resonator, so that it is possible to effectively generate broadband frequency sounds of tunnel blasts. The sound pressure can be reduced and the sound pressure of a low frequency sound of 50 Hz or less included in the blasting sound can be effectively reduced.

  Here, “having a different cross-sectional area and / or tube length for each box-shaped Helmholtz resonator” means that, for example, when 10 box-shaped Helmholtz resonators are stacked to form an assembly, Forms in which the cross-sectional areas and pipe lengths of the through pipes that they all have are different, forms in which only the cross-sectional areas are different or only the pipe lengths are different, and five of the ten groups (the former) are the cross-sectional areas and pipe lengths of the through pipes they have The remaining five units (the latter) also include various forms such as those having the same cross-sectional area and length as the through-tubes, but different cross-sectional areas and lengths from the former. Meaning. In addition, the cross-sectional shape of the through tube can be applied in various shapes such as a circle, an ellipse, a polygon including a square and a rectangle.

  In any case, a box-shaped Helmholtz resonator is constructed by providing one or a plurality of through-tubes in a box, and the cross-sectional area or length of this through-tube, or a plurality of box-like shapes in which both the cross-sectional area and the length are different. Since Helmholtz resonators are stacked, installed side by side in the horizontal direction, or assembled in both stacks and side-by-side, an assembly is configured for each box-shaped Helmholtz resonator even in one tunnel application. It is easy to handle and can be installed at a desired position while securing heavy machinery passages and worker passages even for various tunnel cross sections that can vary depending on the construction section, and tunnels with various cross sections For diversion, it is possible to cope by simply adjusting the number of stacked Helmholtz resonators and the number of the box-shaped Helmholtz resonators.

  The box constituting the box-shaped Helmholtz resonator is, for example, a metal plate assembled in a cube or a rectangular parallelepiped, and the dimensions of the box are relatively small, such as a rectangular parallelepiped or a cube with a side of about 1 m. It's okay. For example, of two end openings of a metal or resin through pipe (such as PVC), only one end opening is fixed to one side of the box, and the other end opening is located inside the box. Thus, the length of the through-tube fixed to the box is shorter than the length of the end of the resonator parallel to the extending direction.

  Here, as an arrangement form of the through pipe with respect to the box, a form in which the through pipe is attached to the inside of the box, a form in which the through pipe is attached to the outside of the box, or the through pipe from the inside to the outside of the box The form etc. which are attached can be mentioned. Further, one side surface of the box has a concave portion and a convex portion, and the outer surface of the one side surface is a position of the concave portion. The form which protrudes from the recessed part can also be mentioned.

  In addition, as described above, although the length and cross-sectional area of the through-pipe are changed in order to reduce wideband frequency sound, the box dimensions are the same for all box-shaped Helmholtz resonators constituting the assembly. Is desirable from the viewpoint of manufacturing cost, assembly of the assembly, and the like.

  In addition, the boxes may form a stacking posture or a side-by-side posture while simply abutting against each other, or a convex portion is fitted into one abutting side surface of an adjacent box, and a concave portion into which the convex portion is fitted into the other abutting side surface. There is a variety of necessity of connection between the boxes, connection structure for connecting, etc., such as a form in which the boxes are connected by fitting the concave and convex portions.

  As described above, a group in which a plurality of box-shaped Helmholtz resonators having different lengths and cross-sectional areas (respectively, resonators having the same length and cross-sectional area may exist) are stacked and / or provided side by side. By applying the solid to the blasting of the tunnel, it is possible to effectively reduce (or mute) the sound pressure of the blasting sound including the broadband frequency sound.

  Also, a form in which a breathable sound absorbing material is accommodated inside the through pipe, a form in which a breathable sound absorbing material is disposed outside the end opening of the through pipe, or the through pipe It is desirable that the breathable sound absorbing material be capped outside the end opening.

  For example, a box-shaped Helmholtz resonator having a through hole having a relatively small size as described above by disposing a breathable sound absorbing material in the vicinity of the end opening facing the outside of the through hole. However, it has been proved by the present inventors that it is possible to effectively reduce the sound pressure of a low frequency sound among wideband frequency sounds. Low-frequency sound is absorbed through the through-holes, but sound in the mid-high range can also be absorbed in other parts of the resonator, so that sound can be absorbed in a wider frequency band. Examples of the sound absorbing material include coarse wool felt made of glass wool, wool, and the like, synthetic fibers such as acetate and nylon, urethane materials, and open-cell porous materials.

  In addition, the present invention extends to a method for reducing tunnel blasting sound, which is provided with a soundproof wall on the tunnel entrance side and inside of the tunnel, respectively, and between the two soundproof walls, the box-shaped Helmholtz resonator. Or a soundproof wall provided inside the tunnel's mine shaft, and the box-shaped Helmholtz resonator assembly is disposed on the wellhead side of the soundproof wall, and further on the wellhead side of the assembly. Providing a separate soundproof wall and disposing the assembly between two soundproof walls, a first step, performing a blasting operation inside the mine, and reducing a blasting sound with a box-shaped Helmholtz resonator assembly It consists of two steps.

  In the first step of the tunnel blasting sound reduction method, assembly and assembly of the soundproof wall are not particularly limited, and may be set in consideration of workability.

  The blasting of the tunnel is repeated many times, and the sound pressure of the tunnel blasting sound is reduced in the above two steps for each blasting.

  As a preferred embodiment of the method for reducing tunnel blasting sound according to the present invention, in the first step, a central space of the tunnel cross section perpendicular to the longitudinal direction of the tunnel is secured as a heavy equipment passage, and the tunnel wall surface of the tunnel cross section is secured. The left and right side spaces are secured as worker passages, and the end openings are directed to the respective passages between the heavy machinery passages and the left and right worker passages. The form which arrange | positions an assembly with the attitude | position side by side can be mentioned.

  By arranging an assembly in which a box-shaped Helmholtz resonator having a relatively small size is assembled in a desired manner, such various passages and spaces can be secured freely.

  In this method mode, a plurality of box-shaped Helmholtz resonators are stacked, and the stacked body is provided in the longitudinal direction of the tunnel to form a belt-like assembly. In the tunnel, in order to secure a heavy machinery passage in the center and two worker passages on the left and right, the above-described assemblies are arranged at two line positions that divide the heavy machinery passage and the two worker passages, respectively. The Moreover, at each line position, the two assemblies are arranged back to back, one assembly is arranged so that the end opening of the through pipe faces the heavy machinery passage, and the other assembly is the through pipe. Is arranged so that the opening of the end faces the worker passage. Therefore, a total of four strip-shaped assemblies are arranged in the tunnel.

  As a further preferred embodiment of the method for reducing tunnel blasting sound according to the present invention, the first step further includes a plate-like shape on the ceiling of each of the two rows of box-shaped Helmholtz resonators arranged on the left and right. And a box-shaped Helmholtz resonator assembly is disposed on the plate-shaped sound absorbing material in such a posture that the end opening faces the space on the ceiling side of the tunnel. .

  Two rows arranged on the left and right sides of the tunnel to absorb and reduce the blasting sound propagating through the ceiling space of the tunnel (since each row is composed of two belt-like assemblies as described above) For example, a plate-like sound absorbing material is placed on the ceiling of the assembly, and a support plate material is placed directly on the plate-like sound absorbing material or on the plate-like sound absorbing material. The box-shaped Helmholtz resonator assembly is disposed in a posture in which the end opening is directed to the space on the ceiling side of the tunnel.

  As can be understood from the above description, according to the box-shaped Helmholtz resonator assembly of the present invention and the method for reducing tunnel blasting sound using the same, a plurality of box-shaped Helmholtz resonators having relatively small dimensions are stacked and / Or an assembly is constructed side by side, and by placing this assembly at a suitable location in the tunnel, the assembly and transportability are improved. It can be installed at a desired position while securing it and can be diverted to a tunnel with various cross sections, while effectively absorbing the wideband frequency sound of the blasting sound of the tunnel and reducing its sound pressure. In addition, the sound pressure of low frequency sound can be effectively reduced.

It is the perspective view which showed embodiment of the box-shaped Helmholtz resonator which comprises the assembly of the box-shaped Helmholtz resonator of this invention. (A) is the enlarged view of the IIa part of FIG. 1, (b) is the enlarged view of the IIb part of FIG. It is the figure which showed other embodiment of the sound-absorbing material. (A)-(d) are all the cross-sectional views which showed embodiment of the box-shaped Helmholtz resonator. (A), (b) is a cross-sectional view showing an embodiment of a box-shaped Helmholtz resonator, and (c), (d) are both cross-sections showing a mounting form of a sound absorbing material. FIG. (A), (b), (c) is the figure explaining embodiment of the assembly of the box-shaped Helmholtz resonator of this invention. It is the figure explaining the reduction method of the tunnel blasting sound of this invention, Comprising: It is the VII-VII arrow line view of FIG. FIG. 8 is a diagram illustrating a method for reducing tunnel blasting sound according to the present invention, and is a view taken along arrows VIII-VIII in FIG. 7. A case in which a box-shaped Helmholtz resonator assembly (no sound absorbing material) exists between the two sound barriers, and a box-shaped Helmholtz resonator assembly between the two sound barriers, relative to the two sound barrier-only cases (A) is a model schematic diagram of an assembly, and (b) is a diagram showing an analysis result regarding a case where (with a sound absorbing material) exists, and an analysis in which each sound pressure reduction effect is verified. It is the figure which showed the analysis model and analysis result which verified the sound pressure reduction effect at the time of arranging 500 box-shaped Helmholtz resonators. It is the figure which showed the analysis result which verified the table | surface which showed the pipe length conditions at the time of changing the length of a penetration pipe (steel pipe), and the sound pressure reduction effect.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a box-shaped Helmholtz resonator assembly of the present invention and a method for reducing tunnel blasting sound using the assembly will be described below with reference to the drawings. The illustrated example is a box-shaped Helmholtz resonator configured by arranging a plurality of through-tubes in one box, but a box-shaped Helmholtz resonance configured by arranging one through-tube in one box. Of course, it may be a container.

(Box Helmholtz Resonator)
1 is a perspective view showing an embodiment of a box-shaped Helmholtz resonator constituting an assembly of a box-shaped Helmholtz resonator according to the present invention, FIG. 2a is an enlarged view of a portion IIa of FIG. 1, and FIG. FIG. 2 is an enlarged view of a portion IIb in FIG. 1.

  A box-shaped Helmholtz resonator 10 (also referred to as a box-shaped resonator) is disposed on a box 1 in which an iron plate having a thickness of 1 to several mm is assembled in a rectangular parallelepiped, and one side 1a of the box 1 and one of the boxes. The end opening 2a is composed of a plurality of PVC penetrating pipes 2 which are fixed facing the outside. In the illustrated example, nine through pipes 2 are disposed inside the box 1, but the number of installation bases of the through pipe 2 is not limited to this, and the face material of the box 1 and the through pipe 2 are not limited thereto. The material is not limited to iron plates or PVC pipes.

  The size of the box-shaped Helmholtz resonator 10 is relatively small. As shown in the figure, the height t1 is 1 to 2 m (for example, 1.2 m), the length t2 of the vertical side of the plane, and the length t3 of the horizontal side are any. Is also set to about 1 m (for example, 0.9 m). It should be noted that the same outer dimensions of all the box-shaped Helmholtz resonators 10 constituting the assembly to be described later are used from the viewpoint of the manufacturing cost of the box-shaped Helmholtz resonator 10 and the assembly of the assembly. preferable.

  Further, by adjusting the cross-sectional area and length of the penetrating tube 2, the frequency sound (frequency band of sound waves) that can reduce the sound pressure by the box-shaped Helmholtz resonator 10 is different.

  Accordingly, the plurality of box-shaped Helmholtz resonators 10 may have the same outer dimensions, t1, t2, and t3. However, for each box-shaped Helmholtz resonator 10, the tube length t4 of the through tube 2 or Those with different tube diameters are prepared.

  When the box 1 has the above dimensions, the tube length t1 can be changed between several tens of cm to 1 m, and the tube diameter can be changed in the range of about 50 to 100 mm.

  Also, as shown in FIGS. 2a and 2b, in the vicinity of the end opening 2a (front surface) inside each through pipe 2, and in the vicinity of the other opening located in the box 1, a breathable sound absorbing material, For example, sound absorbing materials 3 and 3 made of an open-cell porous material are attached.

  Since the breathable sound absorbing material 3 is attached to the inside of the through pipe 2 (inside), the effect of reducing the sound pressure of the low-frequency sound is further enhanced among the blasting sounds of the tunnel including the broadband frequency sound. be able to.

  In addition to the form shown in FIG. 2, the form of the sound absorbing material is such that a plate-like sound absorbing material 3A is disposed on the side surface of the box 1 as shown in FIG. There is a form in which the through pipe 2 is fixed and the sound absorbing material 3 is attached to the outside of the through pipe 2 as described above, and a high low frequency sound pressure reducing effect can be expected.

4 and 5 show still another embodiment of the box-shaped Helmholtz resonator.
The box-shaped Helmholtz resonator 10A shown in FIG. 4a is the box-shaped Helmholtz resonator 1 shown in FIG.
0 has a configuration substantially the same as that of the box-shaped Helmholtz resonator 10, but includes a through-tube 2 that is shorter than the box-shaped Helmholtz resonator 10. 2 is completely accommodated in the box 1, and the end opening 2a of the through pipe 2 is formed flush with the one side surface 1a.

  A box-shaped Helmholtz resonator 10 </ b> B shown in FIG. 4B has a configuration in which the through-tube 2 is attached from the inside to the outside of the box 1.

  A box-shaped Helmholtz resonator 10C shown in FIG. 4c has a configuration in which the through pipe 2 is attached to the outside of one side surface 1a.

  In the box-shaped Helmholtz resonator 10D shown in FIG. 4d, one side surface 1a of the box 1 has a concave portion 1a ', and the length between the concave portion 1a' and the convex portion is the same (or short) from the outside of the concave portion 1a '. This is a form in which a through-tube 2 having a length of length (3) protrudes.

  On the other hand, the box-shaped Helmholtz resonator 10E shown in FIG. 5a is arranged in such a manner that the sound absorbing material 3 protrudes outside the end opening 2a of the through tube 2 of the box-shaped Helmholtz resonator 10 shown in FIG. 4a. It is.

  The box-shaped Helmholtz resonator 10F shown in FIG. 5b is arranged in a posture in which the sound absorbing material 3 protrudes inside the end opening in the box 1 in the through pipe 2 of the box-shaped Helmholtz resonator 10 shown in FIG. 4a. It is a form. As shown in FIG. 5c, a sound absorbing material 3 'processed into a nylon sheet is applied, and its end 3a is placed on the through pipe 2 and fastened with a fastening material 3b such as a string, rubber, or tape, and fixed. There is a method of adhering and fixing with an adhesive (not shown). Further, as shown in FIG. 5d, there is a method in which a metal fitting 3c having a tip projecting outward is provided on the sound absorbing material 3 ″, and the metal fitting 3c is inserted into the through pipe 2 and fixed at the tip of the metal fitting 3c.

  As described above, the box-shaped Helmholtz resonators 10 to 10F having various forms are included in the box-shaped Helmholtz resonator according to the present invention.

  As will be described later, a plurality of box-shaped Helmholtz resonators are stacked or side by side to form an assembly, and this assembly is applied to a tunnel or the like. All of the through-tubes included in the box-shaped Helmholtz resonator may have a sound-absorbing material, or there may be a box-shaped Helmholtz resonator that does not include any sound-absorbing material. Among the two box-shaped Helmholtz resonators, there may be a box-shaped Helmholtz resonator in which there is a penetrating tube including a sound absorbing material and a penetrating tube including no sound absorbing material.

(Assembly)
6a, 6b, and 6c are respectively views for explaining an embodiment of the box-shaped Helmholtz resonator assembly of the present invention. In describing the assembly, the box-shaped Helmholtz resonator 10 will be described.

  The box-shaped Helmholtz resonator 10 shown in the figure is mainly used for construction that requires blasting among tunnel constructions such as mountain tunnels, as described above. Since it contains broadband frequency sound, a plurality of box-shaped Helmholtz resonators 10 having relatively small dimensions are stacked or provided together, or an assembly is configured by using both stacked and attached, and the like. Applies when blasting in

  As the form of this assembly, a form in which it is provided in the horizontal direction as in the assembly 100 shown in FIG. 6a, a form in which it is stacked as in the assembly 100A shown in FIG. 6b, and an assembly 100B shown in FIG. 6c. There are forms such as stacking and side-by-side.

  Although not shown, the box-shaped Helmholtz resonators 10 and 10 constituting the assembly 100 or the like may form a stacked posture or a side-by-side posture while simply contacting each other, or adjacent box-shaped Helmholtz resonances. A convex portion is formed on one abutting side surface of the vessel 10, 10 and a concave portion is formed on the other abutting side surface, and the box-shaped Helmholtz resonators 10, 10 are connected to each other by fitting the concave portion and the convex portion. There may be a form in which the box-shaped Helmholtz resonators 10 and 10 are connected, and there are various connection structures for connection.

(Method of reducing tunnel blasting sound)
Next, a method for reducing tunnel blasting sound using the box-shaped Helmholtz resonator assembly described above with reference to FIGS. Here, FIG. 7 is a diagram for explaining the method for reducing tunnel blasting sound according to the present invention, and is a view taken along the line VII-VII of FIG. 8, and FIG. 8 is a diagram for explaining the method for reducing tunnel blasting sound according to the present invention. And it is a VIII-VIII arrow line view of FIG.

  In the first method of reducing the tunnel blasting noise, two soundproof walls 4A and 4B are respectively installed on the tunnel mouth side and the inside of the tunnel T, and a space between the soundproof walls 4A and 4B is provided. Then, an assembly of the box-shaped Helmholtz resonator is assembled. The order of the installation of the soundproof walls 4A and 4B and the assembly of the assembly are not limited to this. First, the soundproof wall 4B on the inner side of the mine is installed, and then the soundproof wall 4B is located closer to the wellhead side. A method of assembling the assembly in the space and installing the remaining soundproof wall 4A closer to the wellhead than the assembly may be used.

  In any case, a box-shaped Helmholtz resonator assembly is formed in the space between the two soundproof walls 4A and 4B.

  In the illustrated example, an assembly is formed so that a heavy machinery passage is secured in the center of the tunnel T, worker passages are secured at the left and right ends, and a ceiling space is secured.

  The concrete wall 6 is constructed by spraying concrete onto the wall surface according to the extension of the tunnel T.

  In the cross section of FIG. 8, the blasting sound that propagates propagates through the space for heavy machinery passages, worker passages, ceiling spaces, etc., and effectively absorbs this blasting sound to reduce its sound pressure. Accordingly, the assembly is disposed so that one side surface 1a of the box-shaped Helmholtz resonator 10 constituting the assembly, that is, the end opening 2a of the through pipe 2 faces each space.

  In the illustrated example, two box-shaped Helmholtz resonators 10 are provided at two line positions between the central heavy machinery passage and the left and right worker passages so that one side face 1a faces each space. Are stacked in four stages (see FIG. 8), and seven sets of the stacked bodies are provided side by side in the longitudinal direction of the tunnel T (see FIG. 7) to form one assembly 100C.

  The two assemblies 100C and 100C on the left and right sides ensure a heavy machinery passage and two left and right worker passages, and can ensure good workability in the mine.

  Moreover, in the construction of the assembly 100C, the box-shaped Helmholtz resonators 10 that are relatively small and light in weight need only be sequentially installed, so that the assembly of the assembly 100C is very good. This means that good workability can be assured in the subsequent disassembly work and transfer work, and also in the refilling work after stretching.

  When the two-row assemblies 100C and 100C are constructed, a plate-like sound absorbing material 5 is bridged on the ceiling, and a plurality of box-shaped Helmholtz resonances are arranged with the end opening 2a facing the ceiling space of the tunnel. The container 10 is provided side by side in the horizontal direction (see FIGS. 7 and 8), and a separate assembly 100D is constructed.

  As shown in the figure, by the assemblies 100C and 100D formed so that the end openings 2a face the respective spaces, the wideband frequency sound constituting the blasting sound of the tunnel is effectively absorbed by these assemblies. Thus, the sound pressure can be reduced. In particular, the sound pressure of low frequency sound of 50 Hz or less of the blasting sound can be reduced more effectively.

  Since the box-shaped Helmholtz resonator 10 having a relatively small size can be assembled as desired to construct an assembly having a desired shape, even if the tunnel T shown in the figure changes in cross-section during its extension process, It is possible to effectively absorb the blasting sound and reduce the sound pressure while always securing the worker passage. In addition, since it can be used for other tunnels with different cross-sectional dimensions, cross-sectional shapes, and even vertical alignments, it can be said to be an epoch-making blast sound reduction method for tunnel construction that requires future blasting.

[For a case with only two soundproof walls, a case in which a box-shaped Helmholtz resonator assembly (no sound absorbing material) exists between the two soundproof walls, and a set of box-shaped Helmholtz resonators between the two soundproof walls. Cases where three-dimensional (with sound absorbing material) exists, analysis and results of verifying each sound pressure reduction effect]
The inventors of the present invention installed a model outline assembly shown in FIG. 9a in a case (case 1) in which only two soundproof walls are installed at intervals in a tunnel, and in a space between the two soundproof walls. For the case (case 2) and the case (case 3) in which the penetrating pipe provided in the box-shaped Helmholtz resonator is provided with a sound absorbing material with respect to the case 2, the sound pressure for each frequency sound of the blast sound The results of case 1 were subtracted from the results of case 2 and case 3, and the analysis was performed to determine the amount of sound pressure reduction for each of case 2 and case 3 with respect to case 1. However, the analysis range is the heavy machinery path shown in FIG. 8, and only the low frequency sound transmitted through the heavy machinery path is the analysis target. The analysis result is shown in FIG. 9b.

  From this figure, it is demonstrated that both cases 2 and 3 can achieve a sound pressure reduction effect in a low frequency sound region of 50 Hz or less.

  To analyze in more detail, in Case 2, the frequency range where the sound pressure reduction effect is obtained is limited to a range of about 15 to 20 Hz, whereas in Case 3, the sound is almost in the entire range of 5 to 50 Hz and low frequency sounds. It was found that a pressure reduction effect can be obtained.

  From this analysis result, in the assembly of the box-shaped Helmholtz resonator of the present invention, it is possible to obtain a sound pressure reducing effect particularly in a low-frequency sound region, and the through pipe included in the box-shaped Helmholtz resonator includes a sound absorbing material. In some cases, it has been proved that the frequency sound range in which the sound pressure reduction effect is obtained covers a wider range.

[Analysis and results of verifying the sound pressure reduction effect when 500 box-shaped Helmholtz resonators are placed]
The present inventors conducted an analysis to verify the sound pressure reduction effect when 500 box-shaped Helmholtz resonators are arranged. FIG. 10 is a diagram showing an analysis model and an analysis result. Note that this analysis is not limited to the analysis range shown in FIG. 8, and the entire tunnel was analyzed.

  As a result of this analysis, when an assembly consisting of 500 box-shaped Helmholtz resonators is installed in the double soundproof door, compared to the case with only the double soundproof door, the double soundproof door is located at the wellhead side. It has been demonstrated that a sound pressure reduction effect of about 15 dB can be obtained.

[Analysis of the sound pressure reduction effect when the length of the penetration pipe (steel pipe) is changed and its result]
The present inventors conducted an analysis to verify the sound pressure reduction effect when the length of the through pipe (steel pipe) was changed. FIG. 11 is a table showing pipe length conditions and an analysis result. The analysis results show that the sound pressure in the case of only the double soundproof door and the box-shaped Helmholtz resonator assembly with pipes (penetration pipes) of different lengths are arranged in the double soundproof door. The sound pressure is analyzed and the increase in the sound insulation performance of the latter with respect to the former is obtained.

  As a result of the analysis, in any case, the greatest sound pressure reduction effect is obtained in the vicinity of 16 Hz where the low frequency sound is easily amplified by resonance between the two sound barriers.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Box, 1a ... One side surface, 1a '... Recess, 2 ... Through pipe, 2a ... End part opening, 3, 3A, 3', 3 "... Sound absorption material, 3a ... Film edge part, 3b ... Fastening material, 3c: metal fittings, 4A: soundproof wall (soundproof wall on the wellhead side), 4B: soundproof wall (soundproof wall on the inside of the mine), 5 ... ceiling sound insulation material, 6: concrete wall, 10, 10A, 10B, 10C, 10D, 10E , 10F ... Box-shaped Helmholtz resonator, 100, 100A, 100B, 100C, 100D ... Assembly (assembly of box-shaped Helmholtz resonator), T ... Tunnel

Claims (8)

A box-shaped Helmholtz resonator is composed of a box and a through pipe disposed in the box, and the through pipe is fixed to the side surface so as to communicate with a hole provided on one side surface constituting the box. All of the plurality of box-shaped Helmholtz resonators are stacked and / or provided side by side so that each of the one side faces in the same direction and the end opening of the through pipe faces the outside,
An assembly of box-shaped Helmholtz resonators, wherein the penetrating tube has a different cross-sectional area and / or tube length for each box-shaped Helmholtz resonator.   The assembly of the box-shaped Helmholtz resonator according to claim 1, wherein a through pipe is attached inside the box, outside the box, or from the inside to the outside of the box.   The breathable sound absorbing material is accommodated in the inside of the through pipe, or the breathable sound absorbing material is disposed outside an end opening of the through pipe. Box-shaped Helmholtz resonator assembly.   The box-shaped Helmholtz resonator assembly according to claim 1 or 2, wherein a breathable sound absorbing material is capped outside an end opening of the through pipe.   The one side surface of the box has a concave portion and a convex portion. When the outer side surface of the one side surface is a concave portion, a projecting through-tube having a length equal to or shorter than the length between the concave portion and the convex portion is the concave portion. The resonance type sound absorber according to claim 2 or claim 3 depending on claim 2, which protrudes from the above. A soundproof wall is provided on each of the tunnel well side and the inside of the tunnel, and the box-shaped Helmholtz resonator assembly according to any one of claims 1 to 5 is disposed between the two soundproof walls. A soundproof wall is provided on the inner side, and the assembly of the box-shaped Helmholtz resonator according to claim 1 or 2 is disposed closer to the wellhead side than the soundproof wall, and a separate soundproof wall is provided closer to the wellhead side than the assembly. A first step of disposing the assembly between two sound barriers,
A method for reducing tunnel blasting sound, comprising a second step of performing blasting work inside a mine and reducing the blasting sound with a box-shaped Helmholtz resonator assembly.   In the first step, a central space of the tunnel cross section perpendicular to the longitudinal direction of the tunnel is secured as a heavy equipment passage, and left and right side spaces on the tunnel wall surface side of the tunnel cross section are secured as worker passages. The tunnel blasting according to claim 6, wherein two rows of box-shaped Helmholtz resonator assemblies are arranged side by side so that the end openings are directed to the respective passages between the left and right worker passages. Sound reduction method. The method for reducing a tunnel blast sound according to claim 7,
In the second step, a plate-like sound absorbing material is bridged on the ceiling of each of the two rows of box-shaped Helmholtz resonators arranged on the left and right, and the end portion is placed on the plate-like sound absorbing material. A method for reducing tunnel blasting sound, in which an assembly of box-shaped Helmholtz resonators is arranged in a posture in which the opening is directed to the space on the ceiling side of the tunnel.

Images