JP7270700B2 - Blasting noise reduction method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a blasting noise reduction method for reducing blasting noise in the pit of a tunnel.

The reduction of blasting noise has become an issue in tunnel excavation work using the blasting method. This is because the blasting sound is an extraordinary sound that shocks the listener and is also loud, and thus has a great impact on the surrounding environment. It is important to deal with such blasting noise at the stage of starting to dig a tunnel. At the initial stage of excavation, the blasting sound cannot be expected to be attenuated within the tunnel, so large sound pressure and broadband frequency components leak out of the tunnel and are likely to be transmitted to the surrounding area.

In Patent Document 1, in a tunnel, an equipment trolley equipped with soundproofing equipment and air conditioning equipment is moved to an area immediately after excavation to reduce the noise generated in the front area of the equipment trolley, that is, the explosion sound caused by blasting. The invention is described (see paragraphs [0002] [0012] [0020] [0025] [0030] [0031] of Document 1).

The soundproofing equipment introduced in Document 1 is a soundproof wall provided in the front part of the equipment truck (see paragraphs [0019] and [0020] of Document 1). This soundproof wall is a rock wool sound absorbing material that seals the outer periphery with a sealing material and covers almost the entire tunnel cross section, and is excellent in soundproofing. The soundproof wall is provided with an opening and closing door for the purpose of allowing heavy machinery and vehicles to pass through.

The air conditioning equipment introduced in Document 1 is an air supply duct and an exhaust duct provided on the upper part of the equipment truck (see paragraphs [0014] and [0031] of Document 1). The supply air duct is used to supply fresh air to the excavation area in front of the equipment truck which is sealed off by a noise barrier. The exhaust duct collects dust generated in the excavation area.

Japanese Patent Application Laid-Open No. 2004-204539

In order to reduce the noise generated in the pit of a tunnel, it is essential to install a soundproof wall as described in Patent Document 1, for example. There are several types of soundproof walls with different sizes and soundproof performances, and the type of soundproof wall to be installed is determined according to each site. In other words, control standards are generally established for outside noise levels during tunnel construction. Therefore, for each site, a type of soundproof wall that meets the defined management standards is selected and installed.

However, in actual construction sites, it is rare that any one of the existing soundproof walls satisfies the established management standards. selected. Because of the thick and heavy soundproof wall, the reality is that we have to accept the disadvantages in terms of economy and handling.

One aspect of the blasting noise reduction method includes the step of introducing a structure used for construction of the tunnel into the pit of the tunnel in which the face is excavated by blasting, preparing a plurality of board-shaped sound absorbing materials, A step of attaching one sound absorbing material having a board surface arranged along the longitudinal direction of the tunnel and another sound absorbing material to the structure so as to face each other in a direction orthogonal to the longitudinal direction of the tunnel with a space therebetween. and removing the sound absorbing material from the structure when the face is excavated at a predetermined distance or more from the portal of the tunnel.

When the blasting noise is generated on the face side in the tunnel, the blasting noise is reduced by the sound absorbing material, so the effect of reducing the blasting noise can be increased by the portion other than the soundproof wall.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a state in which a sound absorbing material is attached to a sheet-covered carriage (structure) introduced into a tunnel pit, in order to explain the blasting noise reduction method and blasting noise reduction device according to the present embodiment; Front view of the sheet-covered carriage (structure) introduced into the tunnel viewed from the pit side toward the cutting side. A perspective view of a sheet-covered carriage. Its perspective view. Fig. 3 is a perspective view showing a sheet-covered carriage with sound-absorbing material attached along the longitudinal direction of the tunnel; Its perspective view. A perspective view showing a sheet-covered carriage to which a sound absorbing material is further added along the longitudinal direction of the tunnel from the state shown in FIG. Its perspective view. A perspective view showing a sheet-covered truck to which a sound absorbing material is added along a direction orthogonal to the longitudinal direction of the tunnel from the state shown in FIG. Its perspective view. Schematic diagram for explaining experimental equipment using a pipe-shaped member imitating a tunnel. As an experiment using the equipment shown in FIG. 11, (a) is a case where a single sound absorbing material is used, and (b) is a case where a pair of sound absorbing materials facing each other with a space is used. Schematic diagram shown. As an experiment using the equipment shown in FIG. 11, (a) shows a case where a single sound absorbing material is used, and (b) shows a case where a pair of sound absorbing materials facing each other with a space is used from the front direction. Pattern diagram. Graphs plotting the sound pressure levels at the sound receiving points in three modes: without sound absorbing material, installing a single sound absorbing material, and installing a pair of sound absorbing materials facing each other across a space. Graphs showing the amount of reduction in sound pressure level when a single sound absorbing material is installed and when a pair of sound absorbing materials are placed facing each other with a space between them, as compared to the case where no sound absorbing material is used, as experimental results. The amount of attenuation increased at the front and rear positions of the sheet-covered truck with the sound-absorbing material attached as shown in FIGS. Graph of experimental results showing for each frequency.

An embodiment will be described with reference to the drawings. The present embodiment is an example of a blasting noise reduction method and a blasting noise reduction device using a sheet-covered carriage as a structure.

Schematically shown in FIG. 1 is a tunnel 11 dug about 100 meters. This tunnel 11 is dug by blasting. In other words, the dynamite charged in the drilled hole is exploded to crush the bedrock, and the resulting muck is carried out of the tunnel 11 . Steel shoring is then installed as required, the walls are blasted with concrete, and rock bolts are installed (all unmarked not shown). At this time, a soundproof wall 31 is installed at the portal 12 of the tunnel 11 in order to reduce the blasting noise.

After that, a sheet-covered carriage 51 is introduced into the pit 13 of the tunnel 11, and a sheet (not shown) is put on the walls of the tunnel 11 sprayed with concrete for waterproofing. FIG. 1 shows the state before the sheet is stretched.

The blasting noise reduction method of the present embodiment is executed by three steps.

The first is a step of introducing a sheet-covered carriage 51 as a structure used for construction of the tunnel 11 into the pit 13 of the tunnel 11 in which the face is excavated by blasting.

The second step is to attach the sound absorbing material 71 to the sheet-covered carriage 51 .

The third step is to remove the sound absorbing material 71 .

(Structure introduction process)
As shown in FIG. 2, the sheet-covered carriage 51 is a structure that is placed on rails 14 laid on the ground G in the tunnel 11 and moves along the rails 14 . After the tunnel 11 has been dug several tens of meters, for example, about fifty meters, the rails 14 are laid, and the sheet-covered carriage 51 is introduced into the pit 13 of the tunnel 11 .

As shown in FIGS. 2 to 4, the sheet-covered carriage 51 has a pair of legs 53 erected vertically on a base 52. The tops of the legs 53 are connected by beams 54, and the corners are reinforced by braces 55. A plurality of structural elements 56 are provided, and a frame structure 57 is provided in which these structural elements 56 are arranged side by side at regular intervals and fixed. The direction in which the structural elements 56 are arranged is the longitudinal direction of the tunnel 11 from the wellhead 12 to the face 15 . The frame structure 57 is rotatably provided with wheels 58 on the base 52 (the wheels 58 are omitted in FIGS. 3 to 10), and the wheels 58 are fitted into the rails 14 so that the vehicle can run.

The frame structure 57 is provided with scaffolds 59a, 59b, and 59c on both left and right sides and on the upper surface. These scaffolds 59a, 59b, and 59c are frame-like structures made by assembling squared timbers made of steel, and some of them also serve to connect and fix the individual structural elements 56 that make up the frame structure 57. ing.

What is indicated by reference numeral 59a is the lower stage scaffold provided on the lower stage on both the left and right sides. The lower scaffolding 59a is reinforced by a reinforcing steel pipe 59aL bent in an L shape.

Reference numeral 59b denotes scaffolds 59 provided on the upper left and right sides.

What is indicated by reference numeral 59c is an upper surface scaffold provided on the upper surface of the frame structure 57. As shown in FIG. A scaffold board 60 is fitted to these scaffolds 59a, 59b, and 59c so that a person can walk.

A pair of left and right lower ladders 61a are provided at the portion to climb the lower scaffold 59a, and a pair of left and right upper ladders 61b are provided at the portion to climb from the lower scaffold 59a to the upper scaffold 59b. The installation position of the lower ladder 61a is on the rear side of the carriage 51 on which the sheet is stretched, and the installation position of the upper ladder 61b is on the front side of the carriage 51 on which the sheet is stretched. A two-stage step 62 is provided in a portion ascending from the upper surface scaffolding 59c to the upper surface scaffolding 59c. The steps 62 are also provided in three steps up to the upper scaffolding 59c, giving the sheet-covered carriage 51 a shape that follows the arch shape of the tunnel 11. As shown in FIG.

The sheet-covered carriage 51 has a plurality of types of handrails 63. - 特許庁

A pair of lower handrails 63a provided on the pair of lower scaffoldings 59a are provided so as to surround the lower scaffoldings 59a. These lower handrails 63a are as tall as a human waist.

A pair of upper scaffolding 59b and upper scaffolding 59c are provided with a plurality of upper handrails 63b at the front portion and rear portion of the sheet-covered carriage 51 in the traveling direction. These upper handrails 63b have a structure in which the upper part and the central part of a pair of vertical steel pipes are connected by two horizontal steel pipes, and the pair of vertical steel pipes are arranged side by side in a direction orthogonal to the longitudinal direction of the tunnel 11 and attached. there is The upper handrail 63b has a height about the height of a person's waist, and is arranged not only on the upper scaffolding 59b and the upper scaffolding 59c but also on each step of the step 62. As shown in FIG.

Separately from the handrails 63, the pair of upper scaffoldings 59b are provided with fences 64, respectively. These fences 64 are arranged at the side end portions of the upper scaffolding 59b.

The frame structure 57 further has a duct frame 65 for installing an exhaust duct (not shown) on the upper scaffolding 59c. The step 62 is provided up to the upper portion of the duct frame 65 .

(Installation process of sound absorbing material)
In this step, the sound absorbing material 71 is attached to the sheet-covered carriage 51 configured as described above. As the sound absorbing material 71, for example, a plurality of board-like materials having a porous structure in which glass wool is hardened are prepared.

As shown in FIGS. 5 and 6, the sound absorbing material 71 is attached to the sheet-covered carriage 51 along the longitudinal direction of the tunnel 11 as an example. More specifically, both sides of the frame structure 57, the reinforcing steel pipe 59aL and the lower handrail 63a in the lower scaffolding 59a, the fence 64 in the upper scaffolding 59b, the brace 55, and the step 62 are made of sound absorbing material. 71 mounting points.

By attaching the sound absorbing material 71 to each part in this way, in this example, one sound absorbing material 71 and another sound absorbing material 71 face each other with the board surfaces facing each other with the space S therebetween. That is, the sound absorbing material 71 attached to both sides of the frame structure 57 and the reinforcing steel pipe 59aL, the sound absorbing material 71 attached to the frame structure 57 and the lower handrail 63a, and the sound absorbing material 71 attached to the frame structure 57 and the brace 55 The sound absorbing material 71 attached to the wall, the sound absorbing material 71 attached to the fence 64 and the step 62, and the sound absorbing material 71 attached to the step 62 face each other with the space S therebetween.

As another example, as shown in FIGS. 7 and 8, the sound absorbing material 71 is attached to the upper handrail 63b and the step 62 arranged on the duct frame 65 in addition to the locations illustrated in FIGS. there is The sound absorbing material 71 attached to the fence 64 of the upper scaffolding 59b has a higher height than the sound absorbing material 71 illustrated in FIGS. The added sound absorbing material 71 is mounted in the mounting direction of the sound absorbing material 71 illustrated in FIGS.

9 and 10 show yet another mounting method of the sound absorbing material 71. FIG. The example shown in FIGS. 9 and 10 is similar to the example shown in FIGS. 7 and 8. In addition to the locations illustrated in FIGS. An additional sound absorbing material 71 is attached. The difference from the examples shown in FIGS. 7 and 8 is the mounting direction of the additional sound absorbing material 71 .

In the example shown in FIGS. 7 and 8, the additional sound absorbing material 71 was attached along the longitudinal direction of the tunnel 11, whereas in the example shown in FIGS. A sound absorbing material 71 is attached along.
(Removal process of sound absorbing material)

The sound absorbing material 71 is removed from the sheet-covered carriage 51 at a predetermined timing. Two kinds of timings are introduced in this case.

The first is the timing at which the face 15 is excavated at a distance greater than or equal to a predetermined distance from the portal 12 of the tunnel 11 . The predetermined distance referred to here is, for example, an excavation distance at which the underground noise level is equal to or less than the control standard even without the sound absorbing material 71 . At this time, a step of removing the sound absorbing material 71 from the sheet-covered carriage 51 is executed.

When the sound absorbing material 71 is removed from the sheet-covered carriage 51 at this timing, in principle, the step of attaching the sound absorbing material 71 again is not executed.

The second is the timing of starting the sheet tensioning work. This is because the sound absorbing material 71 interferes with the sheet stretching work. Thereafter, when the sheet-covered carriage 51 is further advanced toward the face 15, the sound absorbing material 71 is attached to the sheet-covered carriage 51 again before blasting.

(action/effect)
According to the present embodiment, when blasting noise is generated on the side of the face 15 in the tunnel 11, the blasting noise is attenuated by the soundproof wall 31 installed at the entrance 12 of the tunnel 11, and is transmitted to the space outside the tunnel 11. Noise transmission is suppressed. At this time, the sound absorbing material 71 attached to the sheet-covered carriage 51 also reduces the blasting noise, and complements the effect of damping the blasting noise.

As described above, there are a plurality of types of soundproof walls 31 with different sizes and soundproof performances, and which type of soundproof wall 31 to install is determined according to each site. That is, for each site, a type of soundproof wall 31 that conforms to the control criteria for the outside noise level of tunnel construction is selected and installed.

However, in the actual field, it is rare that any one of the existing soundproof walls 31 exactly conforms to the defined control standards. For this reason, normally, a soundproof wall 31 having a soundproof performance that satisfies the management standards with a margin is selected and installed at the portal 12 .

On the other hand, according to the present embodiment, even if a soundproof wall 31 having a soundproof performance that does not satisfy the management standards is selected and installed in the wellhead 12, the sound absorbing material 71 attached to the sheet-covered carriage 51 does not generate the blasting sound. attenuate and increase its dampening action. Therefore, in the space outside the tunnel 11, it is possible to reduce the blasting noise so as to satisfy the management standards. Therefore, a thinner and lighter sound barrier 31 than usual can be installed in the wellhead 12, yielding economic and handling benefits.

In the present embodiment, a plurality of board-shaped sound absorbing materials 71 are prepared, the board surfaces face each other with a space S therebetween, and one sound absorbing material 71 and the other sound absorbing material 71 are attached to the sheet-covered carriage 51. there is In the pit 13 of the tunnel 11, the sound wave of the blasting sound generated at the face 15 not only advances straight toward the pit 12, but also changes direction in all directions while being reflected on the walls on which concrete is sprayed. For this reason, when passing through the space S between one sound absorbing material 71 and the other sound absorbing material 71 facing each other, sound waves entering the sound absorbing material 71 in a non-parallel direction collide with the sound absorbing material 71 and are absorbed. Or, it reflects the sound absorbing material 71 and collides with the sound absorbing material 71 facing the sound absorbing material 71 to absorb the sound. By repeating such a sound absorbing action, the effect of reducing the blasting noise is enhanced.

The improvement in the effect of reducing the blasting noise is remarkable when the board-shaped sound absorbing material 71 is arranged along the longitudinal direction of the tunnel 11. However, when it is arranged along the direction orthogonal to the longitudinal direction of the tunnel 11, It can happen even if there is. Further, when the board-shaped sound absorbing material 71 is arranged along the direction perpendicular to the longitudinal direction of the tunnel 11, the sound waves of the blasting sound traveling straight from the face 15 toward the pit 12 are also absorbed by the sound absorbing material 71. , to produce a damping effect.

In any case, as the sound absorbing material 71, a board-like material having a porous structure in which glass wool is hardened is used. Therefore, it is possible to attenuate the blasting sound by using a material that is lightweight, easy to handle, and inexpensive. can.

According to this embodiment, since the sound absorbing material 71 is attached to the sheet-covered carriage 51 used for construction of the tunnel 11, a structure unrelated to the construction of the tunnel 11 is used to attach the sound absorbing material 71 to the tunnel. 11 does not need to be installed. Therefore, blasting noise can be reduced without lowering work efficiency.

According to this embodiment, the sound absorbing material 71 is removed from the sheet-covered carriage 51 when the face 15 is excavated at a distance greater than or equal to a predetermined distance from the portal 12 of the tunnel 11 . The predetermined distance at this time is, for example, an excavation distance at which the underground noise level is equal to or less than the control standard even without the sound absorbing material 71 . Therefore, when the sound absorbing material 71 no longer needs to complement the blasting noise reduction effect of the soundproof wall 31, the sound absorbing material 71 is promptly removed. At this time, since the sound absorbing material 71 is lightweight and excellent in handleability, the removal work can be facilitated.

Further, in the present embodiment, the sound absorbing material 71 is removed from the sheeting carriage 51 when starting the sheeting work so as not to interfere with the sheeting work. When blasting is performed on the face 15, the sound absorbing material 71 is attached again. simplification can be achieved.

Various modifications and variations are permissible in implementation. For example, a structure used for construction of a tunnel is not limited to the sheet-covered cart 51, but may be a center, a temporary scaffold, a construction vehicle, or the like. All other variations and modifications are allowed.

As described above, in this embodiment, the sound absorbing material 71 is attached to the sheet-covered carriage 51 introduced into the tunnel 11 . In addition, a plurality of board-shaped sound absorbing materials 71 are prepared, and the board surfaces arranged along the longitudinal direction of the tunnel 11 across the space S face each other, and one sound absorbing material 71 and another sound absorbing material 71 are sheeted. It is attached to the carriage 51 . Therefore, the effect of reducing the blasting noise by the sound absorbing material 71 was verified.

Verification was performed by two types of experiments (experiment 1 and experiment 2). Experiment 1 is a simulated experiment prepared with a pseudo tunnel. Experiment 2 is a field verification performed in an actual tunnel.

(Experiment 1)
FIG. 11 is a schematic diagram of experimental equipment used for verification. Five PVC pipes 101 made of vinyl chloride are prepared and connected to form a pseudo-tunnel 102, thereby creating an environment imitating the tunnel 11. - 特許庁The PVC pipe 101 has a diameter of 550 mm and a length of 1000 mm.

The pseudo-tunnel 102 has one end surface as an open surface and the opposite end surface as a closed surface. The open face is the pseudo wellhead 103 and the closed face is the pseudo face 104 . A speaker 105 is arranged inside the pseudo face 104 side to generate a sound corresponding to the blasting sound.

As shown in FIGS. 12 and 13, a flat board 106 is arranged inside each PVC pipe 101 to form a structure that imitates the ground G of the tunnel 11 . When connecting the individual PVC pipes 101, the individual boards 106 are positioned in the same plane and adjusted to form a structure that imitates the ground G.

In the experiment, sound absorbing material 111 made of glass wool is placed inside pseudo tunnel 102 , sound is generated from speaker 105 and sound is received at sound receiving point 131 . A microphone is arranged at the sound receiving point 131 so that the sound pressure level can be detected.

FIG. 11 shows two quasi-tunnels 102 for the purpose of clarifying the length dimension of the quasi-tunnel 102 and the structure in which the PVC pipes 101 are connected, and for the purpose of explaining the contents of the experiment. There is one pseudo-tunnel 102 . After preparing two kinds of sound absorbing materials 111, the sound absorbing materials 111 were set at different times, and different data were acquired for each sound absorbing material 111. FIG. All of the sound absorbing materials 111 are placed on a board 106 imitating the ground G inside the pseudo tunnel 102 .

One of the two types of sound absorbing material 111 is a single sound absorbing material 111a having a thickness of 50 mm, a width of 200 mm, and a height of 225 mm. As shown in FIGS. 12( a ) and 13 ( a ), the sound absorbing material 111 a is arranged on the right side when the direction of the pseudo face 104 is viewed from the pseudo wellhead 103 .

The other of the two types of sound absorbing materials 111 is a pair of sound absorbing materials 111b each having a thickness of 25 mm, a width of 200 mm, and a height of 225 mm. Therefore, when the two sheets are put together, they have the same thickness, width and height as the single sound absorbing material 111a as shown in FIGS. 12(a) and 13(a). As shown in FIGS. 12(b) and 13(b), the sound absorbing material 111b is arranged so as to be bilaterally symmetrical when the direction of the pseudo face 104 is viewed from the pseudo wellhead 103. As shown in FIG.

FIG. 14 shows the blasting sound from the speaker 105 in three modes: a state in which no sound absorbing material 111 is arranged in the pseudo tunnel 102, a state in which only a single sound absorbing material 111a is arranged, and a state in which a pair of sound absorbing materials 111b are arranged facing each other. The sound pressure level (dB) at the sound receiving point 131 for each frequency (Hz) when the sound corresponding to is generated is shown in comparison. Data were obtained for eight frequencies of 125 Hz, 250 Hz, 500 Hz, 1 KHz, 2 KHz, 4 KHz, 8 KHz and 16 KHz. The graph shown in FIG. 14 plots the sound pressure level for each of these frequencies and connects the individual plot points. The solid line shows data when no sound absorbing material 111 is arranged, the dashed line shows data when only a single sound absorbing material 111a is arranged, and the one-dot chain line shows data when a pair of sound absorbing materials 111b are arranged facing each other.

As shown in FIG. 14, between 125 Hz and 500 Hz, there is no significant difference in sound pressure level for any of the three modes. On the other hand, when the frequency band exceeds 500 Hz and reaches 1 KHz or higher, it can be seen that the sound pressure level is lower when the sound absorbing material 111 is arranged than when the sound absorbing material 111 is not arranged.

FIG. 15 shows the amount of reduction (dB) with respect to the sound pressure level when no sound absorbing material 111 is arranged in the pseudo tunnel 102, when only a single sound absorbing material 111a is arranged, and when a pair of sound absorbing materials 111b are arranged facing each other. It is shown in comparison with time. As in the graph of FIG. 14, the dashed line indicates data when only a single sound absorbing member 111a is arranged, and the dashed line indicates data when a pair of sound absorbing members 111b are arranged facing each other.

The amount of reduction when only a single sound absorbing material 111a is arranged is 0.4 dB at 250 Hz, 0.2 dB at 500 Hz, 1.1 dB at 1 KHz, 1.2 dB at 2 KHz, 1.8 dB at 4 KHz, and 3.0 dB at 8 KHz. 7 dB, 1.9 dB at 16 KHz. The amount of reduction when the pair of sound absorbing materials 111b are arranged facing each other is 0.8 dB at 125 Hz, 0.5 dB at 250 Hz, 0.2 dB at 500 Hz, 1.0 dB at 1 KHz, 1.7 dB at 2 KHz, and 1.8 dB at 4 KHz. , 4.7 dB at 8 KHz and 2.5 dB at 16 KHz. Therefore, it can be seen that the sound pressure level is generally lower when the pair of sound absorbing members 111b are arranged facing each other than when only a single sound absorbing member 111a is arranged. This tendency is conspicuous in the high frequency band.

From the above experimental results, when the sound absorbing material 111 is provided, a higher sound attenuation effect is obtained than when not provided, and the pair of sound absorbing materials 111b facing each other is more effective than when a single sound absorbing material 111a is provided. It was verified that the sound reduction effect is higher when the

(Experiment 2)
Experiment 2 was conducted inside an actual tunnel 11 as illustrated in FIG. In this experiment, as illustrated in FIGS. 9 and 10, a sheet-covered carriage 51 fitted with a sound absorbing material 111 was placed near the pit 12, and sound corresponding to the blasting sound was emitted from a speaker 105 placed near the face 15. generate. Points P1 and P2 (see FIG. 1) 10 meters in front and behind the sheet-covered carriage 51 were used as sound receiving points, and the sound pressure level (dB) for each frequency (Hz) was obtained at each sound receiving point.

As the sound absorbing material 111, a board-like material made of glass wool and having a thickness of 50 mm was used, and this was arranged in an area of 320 m ² . It has a density of 2.4 Kg per ^m2 .

The graph shown in FIG. 16 shows the amount of sound attenuation from the point P1 to the point P2 obtained in the state where the sound absorbing material 111 is not attached to the sheet covered truck 51, and the sound attenuation amount obtained by attaching the sound absorbing material 111 to the sheet covered truck 51. The amount of attenuation from point P1 to point P2, which is increased due to the increase in frequency, is shown for each frequency. From this graph, it can be seen that there is a reduction effect of about 6 dB in the middle range (around 250 Hz) and about 3 dB in the high range (500 Hz or higher).

Therefore, it was verified from the results of practical experiments that a higher sound damping effect can be obtained when the sound absorbing material 111 is provided than when it is not provided.

11 Tunnel 12 Wellhead 13 Underground 14 Rail 15 Face 31 Soundproof wall 51 Sheet covered truck 52 Base 53 Leg 54 Beam 55 Brace 56 Structural element 57 Frame structure 58 Wheel 59 Scaffolding 59a Lower scaffolding 59aL Reinforcing steel pipe 59b Upper scaffolding 59c Upper scaffolding 60 Scaffold board 61a Lower ladder 61b Upper ladder 62 Step 63 Handrail 63a Lower handrail 63b Upper handrail 64 Fence 65 Duct frame 71 Sound absorbing material 101 PVC pipe 102 Pseudo tunnel 103 Pseudo tunnel entrance 104 Pseudo face 105 Speaker 106 Board 111 Sound absorbing material 111a Sound absorbing material 111b Sound absorbing material 131 Sound receiving point S Space

Claims (6)

A step of introducing a structure used for construction of the tunnel into the tunnel pit in which the face is excavated by blasting;
A plurality of board-shaped sound absorbing materials are prepared, and one sound absorbing material having a board surface arranged along the longitudinal direction of the tunnel and another sound absorbing material are arranged perpendicular to the longitudinal direction of the tunnel with a space. attaching to the structure facing the direction;
removing the sound absorbing material from the structure when the face is excavated at a predetermined distance or more from the entrance of the tunnel;
A blasting noise reduction method comprising: The space is a space with an open top,
The method for reducing blasting noise according to claim 1, characterized in that: A part of the board-shaped sound absorbing material is attached to the structure along a direction orthogonal to the longitudinal direction of the tunnel.
The method for reducing blasting noise according to claim 1 or 2, characterized in that: The predetermined distance is an excavation distance at which the underground noise level is below the control standard even without the sound absorbing material.
4. The method for reducing blasting noise according to any one of claims 1 to 3, characterized in that: The sound absorbing material has a porous structure,
5. The method for reducing blasting noise according to any one of claims 1 to 4 , characterized in that: The sound absorbing material having a porous structure is glass wool,
The method for reducing blasting noise according to claim 5 , characterized in that:

Images