JP2014047582A - Design method for tunnel blasting sound reduction device, tunnel blasting sound reduction device, and construction method for tunnel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tunnel blasting sound reduction device by which a blasting sound reduction effect can be surely obtained without degrading workability in a tunnel and without needing a power or the like separately.SOLUTION: In designing a tunnel blasting sound reduction device, a target frequency of the blasting sound to be reduced by a sound absorbing body of the tunnel blasting sound reduction device is selected. Then, a dimension of the sound absorbing body is set. Moreover, rigidity of each face of the sound absorbing body is set. Furthermore, sound energy loss due to friction of an opening of the sound absorbing body, resonance of air inside the sound absorbing body, and effect of displacement of a wall surface of the sound absorbing body are expressed by applying an equivalent electric circuit theory, and an acoustic absorption coefficient of the sound absorbing body is estimated on the basis of the equivalent electric circuit theory. Then, when the acoustic absorption coefficient becomes a desired acoustic absorption coefficient or more with respect to the target frequency of the blasting sound, the sound absorbing body is formed by using the set rigidity as rigidity of the faces of the sound absorbing body.

Description

  The present invention relates to a method for designing a tunnel blast noise reduction device, a tunnel blast noise reduction device, and a tunnel construction method.

  Conventionally, when performing blasting work in mountain tunnel construction, various measures have been taken to prevent the blasting sound generated at the face part from propagating outside the tunnel. For example, a typical measure is to install a soundproof door near the tunnel entrance. An excellent sound insulation effect can be obtained by closing the tunnel pit with a soundproof door made of steel or concrete and having a large rigidity and mass. In addition, it has also been proposed to form a soundproof wall by arranging a large number of steel pipes in parallel without any gaps, and in this soundproof wall, the rigidity in the longitudinal direction of the steel pipe is significantly improved compared to conventional soundproof panels, and the low noise included in the blast sound is low. It is possible to prevent the soundproof wall from resonating with the frequency sound (for example, see Patent Document 1).

  Furthermore, in addition to closing the tunnel entrance or tunnel with a partition wall (soundproof wall), a plurality of pipes having one end opened in the tunnel tunnel and the other end closed and having different path lengths are installed closer to the face than the partition wall. Countermeasures have also been proposed. Then, by forming a tube with a path length of ¼ wavelength of a plurality of frequency sounds, it is possible to effectively mute blast sounds, particularly low frequency sounds (for example, see Patent Document 2).

JP-A-11-107672 JP 2011-256609 A

  However, in the above-described conventional soundproof wall using steel pipes, the number of steel pipes that can be installed is limited because the steel pipes are arranged in parallel to close the tunnel wellhead. There is a limit.

  In addition, in measures to install multiple pipes with different path lengths closer to the face than the bulkhead (soundproof wall), the tunnel cross-section is covered with a pipe, and it is a large scale. There is a risk that workability in the tunnel mine will be deteriorated. In addition, it uses a side-branch sound absorption mechanism that forms a tube with a 1/4 wavelength path length and cancels the original sound wave with the opposite-phase sound wave generated by this tube, reducing low-frequency sound. In order to make this happen, a long tube is required, and the scale becomes even larger.

  In contrast, the inventor of the present application, as shown in FIG. 1, uses a box-shaped sound absorber 1 having an opening 2 formed using, for example, a structural plywood, as a tunnel blast sound reducing device A, and mine tunnels T The sound-absorbing body 1 was considered to reduce the blasting sound. That is, in the tunnel blasting sound reduction device A in which a plurality of sound absorbers 1 are installed at an arbitrary location in the tunnel mine between the face part and the wellhead, the blasting sound passes near the sound absorber 1 during the blasting operation. A part of the sound energy enters the sound absorber 1 through the opening 2. Then, Helmholtz resonance occurs in the sound absorber 1, and the sound energy that has entered the sound absorber 1 can be absorbed and reduced. Thereby, it is possible to install a plurality of sound absorbers 1 in a lump or disperse and configure the tunnel blast noise reduction device A, without causing deterioration of workability in the mine, and separately providing power. It is possible to obtain a blasting sound reduction effect without the need.

  On the other hand, the energy of the blasting sound is large, and a large force is applied to each surface of the sound absorber 1 having a box-type structure installed in the tunnel T tunnel during the blasting work. At this time, if the deformation or bending of each surface of the sound absorber 1 increases, the sound absorption characteristics of the sound absorber 1 change, and sufficient sound absorption performance cannot be obtained for the sound of the target frequency. More specifically, for example, as shown in FIG. 9, the inventor of the present application targets the frequency range near 30 Hz, and changes the sound absorption rate when the rigidity of the surface of the sound absorber 1 in which the opening 2 is formed is changed. As shown in FIG. 9, it was confirmed that the sound absorption performance greatly changes depending on the rigidity of the surface of the sound absorber 1. From this, in the tunnel blast noise reducing device A including the box-shaped structure sound absorber 1 having the opening 2, as shown in FIG. 10, due to insufficient rigidity of each surface of the sound absorber 1, There was a possibility that the reduction effect could not be obtained for the target low frequency sound (in the vicinity of 30 Hz / 16 to 31.5 Hz in FIG. 10), and the designed sound absorption performance might not be exhibited.

  The design method of the tunnel blast sound reducing device of the present invention is a design method of a tunnel blast sound reducing device comprising a sound absorber for reducing blast sound generated by blasting work of tunnel construction, wherein the sound absorber is In addition, it is formed with a box structure having an opening, and a partition wall is provided inside, and a plurality of small chambers communicating with each other are formed, and a target frequency of blasting sound to be reduced by the sound absorber is selected. A target frequency selection step, a sound absorber size setting step for setting the dimensions of the sound absorber, a sound absorber rigidity setting step for setting the rigidity of each surface of the sound absorber, and sound energy due to friction of the opening of the sound absorber The effect of loss, resonance of the air inside the sound absorber, and displacement of the wall surface of the sound absorber is expressed by applying an equivalent electric circuit theory, and the sound absorption rate of the sound absorber is estimated based on the equivalent electric circuit theory The sound absorption coefficient when the sound absorption coefficient obtained in the sound absorption coefficient estimation step is equal to or higher than a desired sound absorption coefficient with respect to the target frequency of the blasting sound selected in the target frequency selection process. The rigidity set in the body rigidity setting step is defined as the rigidity of the surface of the sound absorber.

  A tunnel blast noise reducing device of the present invention is a tunnel blast noise reducing device comprising a sound absorber for reducing blast noise generated by blasting work of tunnel construction, and a method for designing the above tunnel blast noise reducing device The sound absorber is formed based on the above.

  A tunnel construction method according to the present invention is a tunnel construction method involving a blasting operation, wherein a plurality of the above tunnel blasting sound reduction devices are arranged at a location closer to the tunnel entrance side than a location where the blasting operation is performed. Blasting sound is reduced.

  In the tunnel blast noise reducing device design method, the tunnel blast noise reducing device and the tunnel construction method of the present invention, the sound absorption coefficient obtained in the sound absorption coefficient estimation step with respect to the target frequency of the blast sound selected in the target frequency selection step. Is equal to or higher than a desired sound absorption rate (for example, 50%), the sound absorber is formed with the rigidity set in the sound absorber rigidity setting step on each surface. As a result, even during the blasting operation, even if the energy of the blasting sound acts on each surface of the sound absorber, the surface of the sound absorber is not deformed or bent more than expected, and the sound of the target frequency is not affected. Sufficient sound absorbing performance can be obtained.

  Therefore, according to the design method of the tunnel blast noise reduction device, the tunnel blast noise reduction device, and the tunnel construction method of the present invention, the sound absorber exhibits the sound absorption performance as designed and is preferably generated by the blast work of tunnel construction. Blasting sound can be reduced. In addition, when constructing a tunnel that involves blasting work, multiple tunnel blast noise reduction devices (sound absorbers) are placed closer to the tunnel entrance side than where blasting work is performed, so that tunnel blasting sound can be effectively reduced. Reduction can be achieved and propagation of blasting sound to the outside of the tunnel can be effectively prevented.

It is a perspective view which shows the tunnel blasting sound reduction apparatus which concerns on one Embodiment of this invention. It is a perspective view which shows the sound-absorbing body of the tunnel blasting sound reduction apparatus which concerns on one Embodiment of this invention. FIG. 3 is a view taken along line X1-X1 in FIG. 2 and is a diagram illustrating a sound absorber of a tunnel blast sound reducing device according to an embodiment of the present invention. FIG. 3 is a view taken along line X2-X2 in FIG. 2 and is a diagram illustrating a sound absorber of a tunnel blast sound reducing device according to an embodiment of the present invention. FIG. 3 is a view taken in the direction of arrows X3-X3 in FIG. 2 and is a diagram illustrating a sound absorber of a tunnel blast reduction device according to an embodiment of the present invention. It is a flowchart which shows the design method of the tunnel blasting sound reduction apparatus which concerns on one Embodiment of this invention. In the design method of a tunnel blast noise reduction device according to an embodiment of the present invention, the effects of sound energy loss due to friction of the sound absorber opening, resonance of air inside the sound absorber, and displacement of the wall surface of the sound absorber are equivalent. It is the figure expressed applying electric circuit theory. It is a figure which shows the sound absorption performance of the sound absorber formed based on the design method of the tunnel blasting sound reduction apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the relationship between the rigidity of the surface of a sound absorber, and sound absorption performance. It is a figure which shows an example of the sound absorption performance of the conventional sound absorber.

  Hereinafter, a method for designing a tunnel blast noise reduction device, a tunnel blast noise reduction device, and a tunnel construction method according to an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the tunnel blast noise reduction device A of the present embodiment is installed between the face part of the tunnel T and the wellhead, and absorbs the blast sound generated by blasting work such as mountain tunnel construction. It is an apparatus for reducing.

  Moreover, the tunnel blast sound reduction device A according to the present embodiment includes a plurality of sound absorbers 1. And the sound-absorbing body 1 of this embodiment is 2-4 m in length, 1 m in width, 0.5 m in height, for example using comparatively lightweight materials, such as a structural plywood, as shown in FIGS. It is formed with a rectangular box-type structure. When constructing the tunnel T with blasting work, it is preferable to place a plurality of tunnel blasting sound reduction devices A (sound absorbers 1) closer to the tunnel entrance side (wellhead side) than the part to be blasted.

  Further, the sound absorber 1 is provided with a partition wall 3 therein. This partition wall 3 has one end 3a connected to one of the pair of side walls 4, 5 of the sound absorber 1 extending along the width direction S1, and a pair of side walls 6 extending along the length direction S2. , 7 and parallel to the second side wall 5. Moreover, the partition wall 3 is arrange | positioned in the width direction S1 substantially center, and is arrange | positioned at predetermined intervals between the other end 3b and the 2nd side wall 5. As shown in FIG.

  Furthermore, the partition wall 3 is disposed with its upper end and lower end connected to the upper plate 8 and the lower plate 9 of the sound absorber 1, respectively. Thus, a plurality of small chambers 10 and 11 communicating with each other by the partition wall 3 are formed inside the sound absorber 1.

  As shown in FIGS. 2 to 4, the first side wall 4 is formed with an opening 2 through which the small chamber 10 between the partition wall 3 and the third side wall 6 communicates with the outside. Then, the opening 2 is formed with a width of 25 cm and a height of 10 cm, for example.

  In this embodiment, in addition to the first side wall 4, the second side wall 5, the third side wall 6, the fourth side wall 7, the upper plate 8, and the lower plate 9 constituting the sound absorber 1, the partition wall 3 and the opening 2. Thus, a Helmholtz resonance mechanism 12 is formed through which the blasting sound (sound energy) generated during the blasting operation enters through the opening 2 and generates Helmholtz resonance. Moreover, in this embodiment, this Helmholtz resonance mechanism 12 is comprised so that it may resonate with the low frequency sound (low frequency band) of 20-80 Hz of blasting sound, for example. The sound absorber 1 according to the present invention is not necessarily limited to the shape and the number and arrangement of the partition walls as in the present embodiment, and may be appropriately determined according to the required sound absorbing performance.

  Furthermore, the sound absorber 1 of the tunnel blast noise reduction device A of the present embodiment includes a first side wall 4, a second side wall 5, a third side wall 6, a fourth side wall 7, an upper plate 8, a lower plate 9, and a partition wall 3. As appropriate, it can be folded and disassembled (removable), and is formed in an assembly-type structure.

  And in the tunnel blast noise reduction apparatus A of this embodiment which consists of the said structure, as shown in FIG. 1, the sound absorber 1 is placed in the arbitrary places in the tunnel mine between a face part and a wellhead. Can be installed together, such as stacked, or distributed. Further, for example, the sound absorber 1 is installed while appropriately adjusting the position of the opening 2 such that the opening 2 is directed to the face portion on the generation source side of the blasting sound. When a plurality of sound absorbers 1 are installed in this way, during the blasting operation, the blast sound passes through the vicinity of the sound absorber 1 and part of the sound energy enters the sound absorber 1 through the opening 2 and is absorbed. The At this time, in the present embodiment, since the Helmholtz resonance mechanism 12 is formed inside the sound absorber 1, sound energy enters the sound absorber 1 and Helmholtz resonance occurs, thereby ensuring reliable and effective effects. Blast sound is absorbed and reduced.

  On the other hand, during the blasting operation, blasting energy is applied to each surface of the first side wall 4, the second side wall 5, the third side wall 6, the fourth side wall 7, the upper plate 8, and the lower plate 9 of the sound absorber 1, and the sound absorber 1. There is a possibility that deformation and deflection of each surface of the above will occur, and sufficient sound absorption performance for the sound of the target frequency may not be obtained.

  On the other hand, in the present embodiment, during the blasting operation, the sound absorber 1 is suppressed so that the deformation and bending of each surface of the sound absorber 1 are suppressed and sufficient sound absorbing performance is exhibited with respect to the target frequency sound. Form. Specifically, in the design method of the tunnel blast sound reducing device according to the present embodiment, as shown in FIG. 6, first, the blast sound to be reduced by the sound absorber 1 based on the frequency analysis result of the blast sound measurement data, etc. Select the frequency (target frequency selection process). Moreover, the dimension (length, width, height) of the sound absorber 1 is set (sound absorber dimension setting step).

  Next, the material of the sound absorber 1 is selected, and the rigidity of each surface of the sound absorber 1 is set (sound absorber rigidity setting step). At this time, sufficient rigidity is set so as not to cause excessive deformation on each surface of the sound absorber 1 due to the pressure of the blasting sound while considering the density, Young's modulus, Poisson's ratio, and the like.

  In this way, at the stage where the target frequency, the size and rigidity of the sound absorber 1 are set, the sound absorption performance of the sound absorber 1 with respect to the blasting sound of the target frequency is confirmed by simulation. At this time, in this embodiment, as shown in FIG. 7, the effects of sound energy loss due to friction of the opening 2 of the sound absorber 1, resonance of air inside the sound absorber 1, and displacement of the wall surface of the sound absorber 1, An equivalent electric circuit theory is applied and expressed, and the sound absorption coefficient of the sound absorber 1 is estimated based on the equivalent electric circuit theory (sound absorption coefficient estimation step). That is, the blasting energy of the target frequency is input, the resistance of air when propagating through the atmosphere, the influence of the internal air of the sound absorber 1 (resistance, resonance), the sound energy when entering and exiting the opening 2 of the sound absorber 1 The sound energy loss concerning the loss and the mass and rigidity of the wall surface of the sound absorber 1 is obtained, and the sound absorption rate by the sound absorber 1 is calculated.

  When the obtained sound absorption coefficient is equal to or higher than a predetermined desired sound absorption coefficient (for example, 50%) with respect to the selected target frequency of the blasting sound, the rigidity set in the sound absorber rigidity setting step is The rigidity of the surface.

  On the other hand, when it is determined that the calculated sound absorption rate is lower than a desired sound absorption rate (for example, 50%) and the sound absorber 1 is not sufficiently rigid, the sound absorber 1 is returned to the sound absorber dimension setting step. The size of the sound absorber 1 is reset by changing the size and aspect ratio of each surface, and the rigidity of each surface of the sound absorber 1 is set again in the sound absorber rigidity setting step, and the sound absorption rate by the sound absorber 1 is set. Calculate. Then, the above operation is performed until a desired sound absorption rate is obtained, and the rigidity of the surface of the sound absorber 1 is determined.

  Here, FIG. 8 shows the result of modeling the sound absorber 1 based on the equivalent electric circuit theory and simulating the sound absorption characteristics according to the design method of the tunnel blast sound reducing device of the present embodiment. In FIG. 8, the relationship between the frequency of the blasting sound and the average sound absorption rate of the blasting sound by the sound absorber 1 is shown. As shown in this figure, in the sound absorber 1 of the tunnel blast sound reduction device A of the present embodiment, the sound absorption rate of 50% or more is obtained by the Helmholtz resonance mechanism 12 in the low frequency band of 20 to 80 Hz of the blast sound. It was confirmed that Further, at 40 to 63 Hz, the sound absorption rate exceeded 80%, and it was confirmed that a particularly excellent sound absorption effect was exhibited.

  Therefore, in the tunnel blast noise reducing device design method and the tunnel blast noise reducing device of the present embodiment, the sound absorption rate obtained in the sound absorption rate estimation step is desired for the target frequency of the blast sound selected in the target frequency selection step. The sound absorbing body 1 is formed with the rigidity set in the sound absorbing body rigidity setting step provided on each surface when the sound absorbing ratio becomes 50% or more (for example, 50%). Thereby, even if the energy of the blasting sound acts on each surface of the sound absorber 1 at the time of the blasting work, the surface of the sound absorber 1 is not deformed or bent more than expected, and the sound of the target frequency is generated. In contrast, sufficient sound absorption performance can be obtained. Therefore, the sound absorber 1 exhibits the sound absorbing performance as designed, and it is possible to suitably reduce the blasting sound generated by the blasting work of the tunnel construction. Further, when the tunnel T with blasting work is constructed, it is effective by arranging a plurality of tunnel blasting sound reducing devices A (sound absorbers 1) nearer to the tunnel entrance side (wellhead side) than the blasting work place. In addition, it is possible to reduce the tunnel blast noise and effectively prevent the blast noise from propagating to the outside of the tunnel T.

  Moreover, in the tunnel blasting sound reduction device A of the present embodiment, when a plurality of sound absorbers 1 are installed at any place in the tunnel T pit between the face part and the wellhead, the blasting sound is generated by the sound absorber 1 during the blasting operation. While passing through the vicinity, part of the sound energy enters the sound absorber 1 through the opening 2. At this time, since the Helmholtz resonance mechanism 12 is formed inside the sound absorber 1, it is possible to absorb and reduce sound energy that has entered the sound absorber.

  Thereby, in the tunnel blasting sound reduction device A of the present embodiment, a plurality of sound absorbers 1 are collectively installed or dispersedly installed in an arbitrary place in the tunnel T between the face part and the wellhead. It is possible to obtain the effect of reducing the blasting sound without causing deterioration of workability in the mine and without requiring additional power.

  Furthermore, since the sound absorber 1 is formed in a foldable and / or disassembled assembly structure, it can be easily installed, moved, and removed, and does not hinder underground work. In addition, it can be reused and the cost can be reduced.

  As mentioned above, although the design method of the tunnel blasting sound reducing device and the embodiment of the tunnel blasting sound reducing device according to the present invention have been described, the present invention is not limited to the above embodiment, and does not depart from the gist thereof. It can be changed as appropriate.

DESCRIPTION OF SYMBOLS 1 Sound absorber 2 Opening part 3 Partition wall 3a One end 3b Other end 4 1st side wall 5 2nd side wall 6 3rd side wall 7 4th side wall 8 Upper plate 9 Lower plate 10 Small chamber 11 Small chamber 12 Helmholtz resonance mechanism A Tunnel blast sound reduction device S1 Width direction S2 Length direction T Tunnel

Claims (3)

A design method of a tunnel blasting sound reduction device comprising a sound absorber for reducing blasting sound generated by blasting work of tunnel construction,
The sound absorber is formed with a box-type structure having an opening, and is provided with a partition wall in the interior and includes a plurality of small chambers communicating with each other.
A target frequency selection step of selecting a target frequency of blasting sound to be reduced by the sound absorber;
A sound absorber size setting step for setting the dimensions of the sound absorber;
A sound absorber rigidity setting step for setting the rigidity of each surface of the sound absorber;
Representing the effects of sound energy loss due to friction at the opening of the sound absorber, resonance of the air inside the sound absorber, and displacement of the wall surface of the sound absorber by applying an equivalent electric circuit theory, the equivalent electric circuit theory And a sound absorption coefficient estimation step for estimating the sound absorption coefficient of the sound absorber based on
When the sound absorption coefficient obtained in the sound absorption coefficient estimation step is equal to or higher than a desired sound absorption coefficient with respect to the target frequency of the blasting sound selected in the target frequency selection step, the rigidity set in the sound absorber rigidity setting step is set. A design method of a tunnel blasting sound reducing device, characterized in that the sound absorbing body has a rigid surface. A tunnel blasting sound reduction device comprising a sound absorber for reducing blasting sound generated by blasting work of tunnel construction,
The tunnel blast sound reducing device according to claim 1, wherein the sound absorber is formed based on the design method of the tunnel blast sound reducing device according to claim 1. A tunnel construction method involving blasting work,
A tunnel construction method characterized in that a tunnel blast noise is reduced by arranging a plurality of tunnel blast noise reduction devices according to claim 2 at a location closer to the tunnel entrance side than a location where a blast operation is performed.

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