JP2015098708A - Sound barrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound barrier that has a simple structure, and has a good effect to reduce the noise generated in tunnel construction, in particular the noise of low frequency sound reduction.SOLUTION: This invention provides a sound barrier 10 installed in a tunnel T in construction of a tunnel T, the sound barrier 10 comprising a dynamic vibration absorber 2 at a position corresponding to an antinode P of its vibration mode W.

Description

  The present invention relates to a soundproof wall installed in a tunnel when the tunnel is constructed.

  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 mine entrance side, but the blasting sound generated during this blasting includes sounds with a wide frequency range. It is also known that the sound pressure level is extremely high. When a blasting sound of this nature leaks to the outside, the so-called low frequency sound with a frequency of 50 Hz or less contained in the blasting sound vibrates the surrounding building fixtures as well as the problem of noise to the surrounding environment. Such a problem may also 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 inadequate, including the inability to sufficiently reduce low-frequency sound in the frequency band where the resonance phenomenon occurs 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.

  On the other hand, Patent Document 2 discloses a noise reduction mechanism in which a rectangular and roll-screen sound-absorbing screen formed of a sound-absorbing material is suspended from a ceiling of a tunnel by a suspension member.

  According to this technology, the noise during tunnel construction can be reduced, but the reliability of the noise reduction effect by the screen remains questionable compared to the case where a soundproof wall is applied, and at the time of blasting It is not certain whether or not the generated low frequency sound can be absorbed effectively.

JP 2011-256609 A JP 2010-106610 A

  The present invention has been made in view of the above-described problems, and has an object to provide a sound barrier having a simple structure and having a high effect of reducing noise generated during tunnel construction, particularly low-frequency sound. To do.

  In order to achieve the above object, the soundproof wall according to the present invention is a soundproof wall installed in the tunnel when the tunnel is constructed, and the soundproof wall is located at a position corresponding to the antinode of the vibration mode of the soundproof wall. A dynamic vibration absorber is provided.

  The soundproof wall of the present invention suppresses resonance of the soundproof wall due to propagating noise by providing a dynamic vibration absorber at a position corresponding to the antinode of the vibration mode of the soundproof wall installed in the tunnel. This is an improvement in sound insulation performance degradation at the natural frequency. The soundproof wall targeted by the present invention is not a doorless soundproof wall having the entire cross-sectional area of the tunnel, but a door is provided inside the wall of the entire cross section, and the door can be opened to enter and exit. This includes a form of a so-called soundproof door having a simple structure.

  When installing soundproof walls for tunnel construction, if high sound insulation performance is required, soundproof walls are installed at two locations on the tunnel face side and on the wellhead side. For example, regarding blasting sound in tunnels having various frequencies, the sound of each frequency that constitutes the blasting sound has a unique wavelength, and one wavelength or half wavelength is a distance between two soundproof walls. A resonance occurs between the two sound barriers when the length roughly matches. Due to this resonance, a large vibration is also generated in the soundproof wall.

  Even if the distance between the soundproof walls is adjusted so that the soundproof walls do not resonate due to such resonance between the soundproof walls, similar resonance occurs at another frequency.

  Therefore, the soundproof wall of the present application can suppress vibration of the soundproof wall itself or resonance between the soundproof wall and the air between the soundproof wall by providing a dynamic vibration absorber on the soundproof wall. Low frequency noise can be reduced.

  Here, the dynamic vibration absorber is composed of a mass body, a spring (coil spring, air spring, etc.), a damper (hydraulic damper, rubber damper, friction braking damper, etc.) and the like.

  The dynamic vibration absorber is provided at a position corresponding to the antinode of the vibration mode of the soundproof wall, so that the vibration damping performance of the dynamic vibration absorber against the soundproof wall body is sufficiently exhibited.

  Here, the “position corresponding to the antinode of the vibration mode” includes the center position (h / 2) of the soundproof wall having a height h and the vicinity of the center position.

  Moreover, the installation form of the dynamic vibration absorber can include a plurality of forms shown below.

  One of the installation forms of the dynamic vibration absorber is a form in which a frame is provided at a position corresponding to the belly of one side of the soundproof wall, and the dynamic vibration absorber is disposed on the frame.

  For example, a pedestal is installed near the center of one of the two side surfaces of the soundproof wall, and a mass body equipped with moving means such as wheels is placed on the cradle. By connecting with a spring and a damper in parallel relationship, a configuration in which a dynamic vibration absorber is disposed on one side of the soundproof wall can be configured. As an example of a specific configuration of the gantry, a member that is directly attached to the soundproof wall, a member that a wheel or the like travels, and a member that supports a member that the wheel or the like travels, a member that the wheel or the like travels is a flat surface. Or the form by which the rail surface is installed horizontally and the whole is comprised can be mentioned. The member that supports the member on which the wheel or the like travels may be provided with a tilt adjusting mechanism so that the plane or the rail surface can be adjusted horizontally with respect to the tilt displacement during use.

  Another one of the installation forms of the dynamic vibration absorber is a form in which a through hole is opened at a position corresponding to the antinode of the soundproof wall, and the dynamic vibration absorber is disposed in the through hole.

  For example, a braking effect by a dynamic vibration absorber can be expected by fixing a box containing a dynamic vibration absorber to a through-hole and connecting the side surface of the box and a mass body with a spring and a damper in a parallel relationship. The box preferably has a sound insulation performance equal to or higher than that of the soundproof wall.

  Further, a plurality of the above-described various forms of dynamic vibration absorbers may be provided near the center of the height of the soundproof wall, for example. For example, two dynamic vibration absorbers are arranged in a vertical or horizontal relationship near the center of the height and width (hence near the center of the noise barrier) against a noise barrier of height h and width t when viewed from the front. Alternatively, two upper and lower dynamic vibration absorbers may be arranged at predetermined intervals in the width direction.

  As described above, there is no example of a technique for applying a soundproof wall provided with a dynamic vibration absorber as a soundproof wall installed in a tunnel, and by applying the soundproof wall of the present invention, it is caused by blasting sound or the like. Vibration of the soundproof wall can be suppressed, and a soundproof wall having excellent sound insulation can be provided by suppressing resonance of the soundproof wall.

  As can be understood from the above description, according to the soundproof wall of the present invention, the vibration absorber is provided at a position corresponding to the antinode of the vibration mode of the soundproof wall installed in the tunnel. The resonance of the wall can be suppressed, or the sound insulation performance degradation can be improved by suppressing the resonance caused by the two soundproof walls and the air between them.

It is the longitudinal cross-sectional view explaining the condition which installed the soundproof wall of this invention in the tunnel. It is the schematic diagram explaining Embodiment 1 of a dynamic vibration absorber. It is the schematic diagram explaining Embodiment 2 of a dynamic vibration absorber. (A), (b), (c) is the figure which showed the arrangement | positioning form of the dynamic vibration absorber by the front view of the tunnel. It is the figure which showed the result of having installed two soundproof walls in the tunnel at intervals of 20 m, and measuring the sound pressure level of the blasting sound at the wellhead side. It is the figure which showed the result of having installed two soundproof walls in the tunnel at intervals of 20 m, and measuring the sound pressure level in the frequency band of 8 Hz at each measurement point between the soundproof walls and outside the soundproof wall. It is the figure which showed the result of having installed two soundproof walls in the tunnel at intervals of 20 m, and measuring the sound pressure level in a frequency band of 20 Hz at each measurement point between the soundproof walls and outside the soundproof wall. It is the figure which showed the result of having measured the vibration acceleration level of the out-of-plane direction in a soundproof wall.

  Hereinafter, embodiments of a soundproof wall of the present invention will be described with reference to the drawings.

(Sound barrier implementation)
FIG. 1 is a longitudinal cross-sectional view of a situation where a soundproof wall of the present invention is installed in a tunnel, and FIGS. 2 and 3 are schematic diagrams illustrating first and second embodiments of a dynamic vibration absorber, respectively. FIGS. 4A, 4B, and 4C are diagrams showing the arrangement of the dynamic vibration absorber as viewed from the front of the tunnel.

  As shown in FIG. 1, when constructing the tunnel T, when the excavation is repeated while blasting on the face K side, a predetermined separation length is set at two positions on the face K side and the wellhead M side in the tunnel T. The soundproof wall 10 is installed.

  Here, the soundproof wall 10 is roughly constituted by a soundproof wall body 1 made of steel or concrete and a dynamic vibration absorber 2 provided on one side surface of the soundproof wall body 1. In the illustrated example, the dynamic vibration absorber 2 is attached to the soundproof wall 1 on both the face K side and the wellhead M side, but the dynamic vibration absorber 2 is attached only to the soundproof wall 1 on the wellhead M side. Form may be sufficient.

  As shown in FIG. 4, the soundproof wall body 1 has a form having only a semicircular cross section wall and a form in which a door (soundproof door) (not shown) that can enter and exit the central region of the wall is provided. In general, the latter is adopted.

  As shown in FIG. 1, a dynamic vibration absorber 2 is attached to a central level (height h / 2) of a soundproof wall 1 having a height h. This center level is the position of the antinode P of the vibration wave W (vibration mode) when the soundproof wall 1 vibrates, as shown in FIG.

  By providing the dynamic vibration absorber 2 at or near the position of the antinode P of the vibration mode of the soundproof wall 1, vibration of the soundproof wall 1 due to the blasting sound can be effectively suppressed.

  A dynamic vibration absorber 2 according to the first embodiment shown in FIG. 2 includes a mass body 3, a spring 4 and a damper 5 that are in parallel relation, and a gantry attached to one side surface of the soundproof wall body 1. A mass body 3 having wheels is placed on 6, and the entire side surface of the soundproof wall body 1 and the mass body 3 are connected by a spring 4 and a damper 5 in a parallel relationship. Here, the gantry 6 is formed of a member that is directly attached to the soundproof wall, a member that the wheel or the like travels, and a member that supports the member that the wheel or the like travels. Are installed horizontally to constitute the entire gantry 6. The member that supports the member on which the wheel or the like travels may be provided with a tilt adjusting mechanism so that the plane or the rail surface can be adjusted horizontally with respect to the tilt displacement during use.

  On the other hand, in the dynamic vibration absorber 2A according to the second embodiment shown in FIG. 3, a through hole 1a is opened in the soundproof wall 1, and a box 7 containing the dynamic vibration absorber 2A is fixed to the through hole 1a such as an angle. It is fixed by the member 8, and the inside of the box 7 is configured such that the side surface of the box 7 and the mass body 3 are connected by a spring 4 and a damper 5 in a parallel relationship.

  Next, with reference to FIG. 4, the arrangement | positioning form of a dynamic vibration absorber is demonstrated. Here, the dynamic vibration absorber 2 will be described.

  As shown in FIG. 4a, the arrangement of the dynamic vibration absorber 2 with respect to the soundproof wall 1 is the center position of the soundproof wall 1 (the center position t / 2 of the width t and the center position h / 2 of the height h). A mode in which one dynamic vibration absorber 2 is provided on the top, or a mode in which two dynamic vibration absorbers 2 are provided at two positions above and below the central position of the height at the central position of the width of the soundproof wall 1, as shown in FIG. Furthermore, as shown in FIG. 4 c, there is a mode in which two dynamic vibration absorbers 2 are provided at two positions on the left and right of the central position of the width of the soundproof wall 1. In addition, although illustration is omitted, a configuration in which a total of four units in the top and bottom in FIG. 4c are further provided, or a configuration in which three in the top and bottom are provided in FIG. What is necessary is just to arrange | position a dynamic vibration absorber suitably in the corresponding position (a center position, a center vicinity position).

  In any form of the soundproof wall shown in the figure, for example, the air between the two soundproof walls 10 and 10 installed in the tunnel T and the resonance of each soundproof wall 10 are the dynamic vibration absorbers 2 and 2A which are constituent elements thereof. The soundproof wall 10 having excellent sound insulation can be provided by suppressing resonance of the soundproof wall 10.

[Experiments and results of installing two sound barriers in the tunnel, measuring the sound pressure of the blasting sound, and measuring the out-of-plane acceleration of the sound barrier]
The present inventors installed two soundproof walls (conventional soundproof walls) 20 m apart in the tunnel, at a height of 1.8 m, at a position closer to the wellhead than the soundproof wall, and between the two soundproof walls. The sound pressure at the time of blasting was measured at each of the positions and the positions on the face side of the sound barrier.

  Here, FIG. 5 is the figure which showed the result of having measured the sound pressure level of the blasting sound on the wellhead side. It can be seen from the figure that the sound pressure level is high at 8 Hz and 20 Hz.

  As for the sound in the frequency band of 8 Hz, the wavelength is about 43 m, and therefore the half wavelength is almost coincident with the sound barrier separation distance 20 m.

  Here, FIG. 6 is a diagram showing the result of measuring the sound pressure level of the sound in the frequency band of 8 Hz at each measurement point between the sound barriers and outside the sound barrier. From this figure, it can be seen that resonance occurs between the soundproof walls.

  On the other hand, the sound with a frequency band of 20 Hz has a wavelength of about 17 m, and therefore the wavelength substantially coincides with the separation wall 20 m.

  Here, FIG. 7 is a diagram showing the results of measuring the sound pressure level of the sound in the frequency band of 20 Hz at each measurement point between the sound barriers and outside the sound barrier. From this figure, it can be seen that resonance also occurs between the soundproof walls in this frequency band.

  As described above, a large vibration can occur in the soundproof wall in a frequency band where the distance between the soundproof walls coincides with one wavelength or half wavelength. Here, FIG. 8 is a diagram showing the result of measuring the vibration acceleration level in the out-of-plane direction on the soundproof wall.

  From the figure, it can be seen that the vibration acceleration level is high in the 10 Hz (near 8 Hz) and 20 Hz bands as well as the sound pressure level of the sound in each frequency band.

  Based on the above experimental results, the present inventors installed the soundproof wall of the present invention shown in FIGS. 1 and 2 in the tunnel, thereby suppressing the resonance between the soundproof wall and the air due to the propagating noise, or soundproofing. It was decided to improve the sound insulation performance degradation at the natural frequency of the wall itself, and effectively reduce the low frequency sound.

  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 ... Soundproof wall body, 1a ... Through-hole, 2 and 2A ... Dynamic vibration absorber, 3 ... Mass body, 4 ... Spring, 5 ... Damper, 6 ... Mount, 7 ... Box, 8 ... Fixing member, 10 ... Soundproof wall, T ... tunnel, K ... face, M ... wellhead, W ... vibration wave (vibration mode), P ... belly

Claims (4)

A soundproof wall installed in the tunnel when the tunnel is constructed,
The soundproof wall is provided with a dynamic vibration absorber at a position corresponding to the antinode of the vibration mode of the soundproof wall.   The soundproof wall according to claim 1, wherein a stand is provided at a position corresponding to the belly on one side of the soundproof wall, and a dynamic vibration absorber is disposed on the stand.   The soundproof wall according to claim 1, wherein a through hole is opened at a position corresponding to the antinode of the soundproof wall, and a dynamic vibration absorber is disposed in the through hole.   The soundproof wall according to any one of claims 1 to 3, wherein a plurality of dynamic vibration absorbers are disposed at positions corresponding to the antinodes on one side of the soundproof wall.

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