JP2022003223A - Blasting sound reduction method and blasting sound reduction device - Google Patents

Abstract

To reduce the blasting sound by structural elements other than a soundproof wall, and to use a lighter soundproof wall.SOLUTION: The present invention comprises: a step of introducing a structure to be used for construction of a tunnel 11, for example, a sheet stretching cart 51, into a pit 13 of the tunnel 11 for blasting and excavating a face 15; a step of preparing a plurality of sound absorbing materials 111 having a porous structure in which board-like sound absorbing material 111, for example, glass wool is hardened in a board-like manner in the step before and after that; and a step of attaching one sound absorbing material 111 and another sound absorbing material 111 to the sheet stretching cart 51 so that the board surfaces arranged along the longitudinal direction of the tunnel 11 face each other with a space S therebetween. Even when a soundproof wall 31 that is thinner and lighter than usual is installed at each site, the sound absorbing material 111 complements the soundproofing effect of the soundproof wall 31 so that the management standard is satisfied as a whole.SELECTED DRAWING: Figure 1

Description

The present invention relates to a blasting sound reducing method and a blasting sound reducing device for reducing blasting sound in a tunnel.

Reducing 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 gives a shock to the listener and is also a loud sound, so that it has a great influence on the surrounding environment. It is important to deal with such blasting sounds at the stage of starting to dig a tunnel. This is because, at the initial stage of digging, the underground distance attenuation of the blasting sound cannot be expected, so that the high sound pressure and wide band frequency components leak out of the tunnel and are easily transmitted to the neighborhood.

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

The soundproofing equipment introduced in Document 1 is a soundproofing wall provided at the front of the equipment trolley (see paragraphs [0019] and [0020] of Document 1). This soundproof wall is a rock wool sound absorbing material that covers almost the entire cross section of the tunnel by sealing the outer peripheral edge with a sealing material, and is excellent in soundproofing. The soundproof wall is provided with an opening / 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 in the upper part of the equipment carriage (see paragraphs [0014] and [0031] of Document 1). The air supply duct is used to supply fresh air to the excavation area in front of the equipment trolley sealed by a noise barrier. Dust generated in the excavation area is collected from the exhaust duct.

Japanese Unexamined Patent Publication No. 2004-204039

In order to reduce the noise generated in the tunnel, it is indispensable to install a soundproof wall as described in Patent Document 1, for example. There are multiple types of soundproof walls that differ in size and soundproof performance, and the type of soundproof wall to be installed is determined according to each site. In other words, management standards are generally set for the noise level outside the tunnel construction. Therefore, a type of soundproof wall that meets the established management standards will be selected and installed for each site.

However, in the actual field, it is rare that any one of the existing soundproof walls exactly meets the established management standards, and usually, a soundproof wall with soundproofing performance that clears the management standards with a margin is available. Be selected. Since the soundproof wall is thick and heavy, the reality is that it has to accept the disadvantages in terms of economy and handling.

One aspect of the blasting sound reduction method is a step of introducing a seat upholstery trolley used for construction of this tunnel into a tunnel for blasting and excavating a face, and a step of attaching a sound absorbing material to the seat upholstery trolley. And, when the sheet tensioning work is started, the step of removing the sound absorbing material from the seat tensioning carriage is provided.
Another aspect of the blasting sound reduction method is a process of introducing a seat upholstery trolley used for the construction of this tunnel into the tunnel where blasting and excavating a face, and a sound absorbing material in the seat upholstery trolley. It has a mounting process.

The unique aspect of the blasting sound reduction device is the seat upholstery trolley used for the construction of this tunnel, which is introduced into the tunnel where blasting and excavating the face, and the sound absorbing material attached to the seat upholstery trolley. To prepare for.

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

In order to explain the blasting sound reduction method and the blasting sound reduction device of the present embodiment, a schematic diagram showing a state in which a sound absorbing material is attached to a seat tensioning trolley (structure) introduced in a tunnel mine. Front view of the seat bogie (structure) introduced in the tunnel from the wellhead side to the face side. A perspective view of a seat-covered bogie. The perspective view. A perspective view showing a seated trolley with a sound absorbing material attached along the longitudinal direction of the tunnel. The perspective view. From the state shown in FIG. 5, a perspective view showing a seat upholstery bogie to which a sound absorbing material is further added along the longitudinal direction of the tunnel. The perspective view. From the state shown in FIG. 5, a perspective view showing a seat-covered bogie to which a sound absorbing material is added along a direction orthogonal to the longitudinal direction of the tunnel. The 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 across a space are used from diagonal directions. 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 across a space are used from the front direction. Pattern diagram. As an experimental result, a graph plotting the sound pressure level at the sound receiving point in three modes: no sound absorbing material, a single sound absorbing material installed, and a pair of sound absorbing materials facing each other across a space. As an experimental result, a graph showing the amount of reduction in the sound pressure level when a single sound absorbing material is installed and when a pair of sound absorbing materials are installed facing each other across a space, as opposed to the case where there is no sound absorbing material. Attenuation increased at the front and rear positions of the seat upholstery with the sound absorbing material as illustrated in FIGS. 9 and 10 with respect to the amount of acoustic attenuation at the front and rear positions of the seat upholstery without the sound absorbing material. Is a graph of experimental results showing each frequency.

One embodiment will be described with reference to the drawings. This embodiment is an example of a blasting sound reducing method and a blasting sound reducing device using a seat tension carriage as a structure.

Schematically shown in FIG. 1, is a tunnel 11 dug about 100 meters. This tunnel 11 is being dug by blasting. That is, the dynamite charged in the drilled hole is detonated to crush the bedrock, and the resulting debris is carried out of the tunnel 11. After that, steel supports will be installed as needed, concrete will be sprayed on the walls, and lock bolts will be installed (all unsigned ones are not shown). At this time, a soundproof wall 31 is installed at the wellhead 12 of the tunnel 11 in order to reduce the blasting noise.

After that, a sheet upholstery trolley 51 is introduced into the tunnel 13 in the tunnel 11, and a sheet (not shown) is stretched on the wall surface of the tunnel 11 sprayed with concrete to perform waterproof treatment. FIG. 1 shows a state before the sheet is stretched.

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

The first is a step of introducing a seat upholstery trolley 51 as a structure used for the construction of the tunnel 11 into the tunnel 13 of the tunnel 11 for blasting and excavating the face.

The second is the process of attaching the sound absorbing material 71 to the seat tensioning carriage 51.

The third is the step of removing the sound absorbing material 71.

(Structure introduction process)
As shown in FIG. 2, the seat tension carriage 51 is a structure that is placed on a rail 14 laid on the ground G in the tunnel 11 and moves along the rail 14. The rail 14 is laid when the tunnel 11 is dug for several tens of meters, for example, about 50 meters, and the seat tension carriage 51 is introduced into the tunnel 13 in the tunnel 11.

As shown in FIGS. 2 to 4, in the seat tension carriage 51, the upper portions of a pair of legs 53 vertically erected on the base 52 are connected by beams 54, and the corner portions are reinforced by braces 55. A plurality of structural elements 56 are provided, and a frame structure 57 in which these structural elements 56 are arranged and fixed at regular intervals is provided. 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 provided with wheels 58 rotatably on a portion of the base 52 (wheels 58 are omitted in FIGS. 3 to 10), and the wheels 58 are fitted into the rail 14 so that the frame structure 57 can travel.

The frame structure 57 is provided with scaffolding 59a, 59b, 59c on both the left and right sides and the upper surface. These scaffolds 59a, 59b, 59c are frame-shaped structures manufactured by assembling steel square timbers, and a part thereof also plays a role of connecting and fixing individual structural elements 56 forming the frame structure 57. ing.

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

What is indicated by reference numeral 59b is a scaffolding 59 provided on the upper tiers on both the left and right sides.

Reference numeral 59c is an upper surface scaffold provided on the upper surface of the frame structure 57. Scaffolding plates 60 are fitted in these scaffolds 59a, 59b, 59c so that a person can walk.

A pair of left and right lower ladders 61a is provided in a portion rising to the lower scaffold 59a, and a pair of left and right upper ladders 61b are provided in a portion rising from the lower scaffold 59a to the upper scaffold 59b. The installation position of the lower ladder 61a is on the rear side in the traveling direction of the seat tensioning carriage 51, and the installation position of the upper ladder 61b is on the front side in the traveling direction of the seat tensioning carriage 51. A two-step step 62 is provided at a portion rising from the upper surface scaffold 59c to the upper surface scaffold 59c. The step 62 is provided in three steps even when reaching the upper surface scaffold 59c, and gives the seat tensioning carriage 51 a shape along the arch shape of the tunnel 11.

The seat tension carriage 51 includes a plurality of types of handrails 63.

The pair of lower handrails 63a provided on the pair of lower scaffolds 59a are provided so as to surround the lower scaffolds 59a, respectively. These lower handrails 63a have a height similar to that of a human being.

The pair of upper scaffolding 59b and upper surface scaffolding 59c are provided with a plurality of upper handrails 63b at the front portion and the rear portion of the seat tensioning carriage 51 in the traveling direction. These upper handrails 63b have a structure in which the upper part and the central portion of a pair of vertical steel pipes are connected by two horizontal steel pipes, and the pair of vertical steel pipes are attached side by side in a direction orthogonal to the longitudinal direction of the tunnel 11. There is. The upper handrail 63b has a height similar to that of a human waist, and is arranged not only on the upper scaffolding 59b and the upper surface scaffolding 59c but also on each step of step 62.

Apart from the handrail 63, a fence 64 is provided on each of the pair of upper scaffolds 59b. These fences 64 are arranged at the side end portions of the upper scaffolding 59b.

The frame structure 57 is further provided with a duct frame 65 for installing an exhaust duct (not shown) above the upper surface scaffold 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 seat tensioning carriage 51 configured as described above. As an example, as the sound absorbing material 71, a plurality of board-shaped materials having a porous structure made of glass wool are prepared.

As shown in FIGS. 5 and 6, the sound absorbing material 71 is attached to the seat tensioning 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 bracing 55, and the step 62 are sound absorbing materials. It is the mounting location for 71.

Since the sound absorbing material 71 is attached to each part in this way, in this example, one sound absorbing material 71 and the other sound absorbing material 71 face each other with the board surfaces facing each other with the space S separated. That is, it is attached to 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 to the frame structure 57 and the streak 55. The sound absorbing material 71, 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 via the space S.

As shown in FIGS. 7 and 8, as another example, 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. 5 and 6. There is. Further, as the sound absorbing material 71 attached to the fence 64 of the upper scaffold 59b, a material having a higher height than the sound absorbing material 71 exemplified in FIGS. 5 and 6 is used. The added sound absorbing material 71 is attached in the mounting direction of the sound absorbing material 71 exemplified in FIGS. 5 and 6, that is, in the direction along the longitudinal direction of the tunnel 11.

9 and 10 show still another method of attaching the sound absorbing material 71. Similar to the example shown in FIGS. 7 and 8, the example shown in FIGS. 9 and 10 also has a step 62 arranged on the upper handrail 63b and the duct frame 65 in addition to the locations illustrated in FIGS. 5 and 6. An additional sound absorbing material 71 is attached. The difference from the example 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 is attached along the longitudinal direction of the tunnel 11, whereas in the examples shown in FIGS. 9 and 10, the direction orthogonal to the longitudinal direction of the tunnel 11 is attached. The sound absorbing material 71 is attached along the above.
(Sound absorbing material removal process)

The sound absorbing material 71 is removed from the seat tensioning carriage 51 at a predetermined timing. Two types of timing in this case will be introduced.

The first is the timing at which the face 15 is excavated beyond a predetermined distance from the wellhead 12 of the tunnel 11. The predetermined distance referred to here is, for example, an excavation distance at which the noise level outside the mine is below the control standard even without the sound absorbing material 71. At this time, the step of removing the sound absorbing material 71 from the seat tensioning carriage 51 is executed.

If the sound absorbing material 71 is removed from the seat tensioning carriage 51 at this timing, in principle, the step of reattaching the sound absorbing material 71 is not executed.

The second is the timing to start the sheet tensioning work. This is because the sound absorbing material 71 interferes with the sheet tensioning work. After that, when the seat tensioning carriage 51 is further advanced toward the face 15, the sound absorbing material 71 is reattached to the seat tensioning carriage 51 before blasting.

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

As described above, there are a plurality of types of soundproof walls 31 having different sizes and soundproof performances, and which type of soundproof wall 31 to be installed is determined according to each site. That is, a noise barrier 31 of a type that meets the management standard for the noise level outside the tunnel construction is selected and installed for each site.

However, in the actual field, it is rare that any one of the existing soundproof walls 31 exactly meets the established management standards. Therefore, normally, a soundproof wall 31 having a soundproofing performance that clears the management standard with a margin is selected, and this is installed at the wellhead 12.

On the other hand, according to the present embodiment, even if the soundproof wall 31 having the soundproofing performance that does not satisfy the management standard is selected and installed at the wellhead 12, the sound absorbing material 71 attached to the seat upholstery trolley 51 emits a bursting sound. It attenuates and increases its reducing effect. Therefore, in the space outside the tunnel 11, it is possible to reduce the blasting sound so as to satisfy the management standard. Therefore, the soundproof wall 31 which is thinner and lighter than usual can be installed at the wellhead 12, and can bring about 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 across a space S, and one sound absorbing material 71 and another sound absorbing material 71 are attached to the seat tensioning carriage 51. There is. In the tunnel 13 inside the tunnel 11, the sound wave of the blasting sound generated at the face 15 not only travels straight toward the wellhead 12, but also turns in all directions while reflecting the wall surface on which the concrete is sprayed. Therefore, when passing through the space S between one sound absorbing material 71 facing each other and the other sound absorbing material 71, sound waves entering from a direction non-parallel to the sound absorbing material 71 collide with the sound absorbing material 71 and are absorbed. Or, the sound absorbing material 71 is reflected and collides with the sound absorbing material 71 facing the sound absorbing material 71 to absorb sound. By repeating such a sound absorbing action, the action of reducing blasting sound is enhanced.

Such an improvement in the effect of reducing blasting sound is remarkable when the board-shaped sound absorbing material 71 is arranged along the longitudinal direction of the tunnel 11, but when it is arranged along the direction orthogonal to the longitudinal direction of the tunnel 11. Even if there is, it can occur. Further, when the board-shaped sound absorbing material 71 is arranged along the direction orthogonal to the longitudinal direction of the tunnel 11, the sound absorbing material 71 is also used for the sound wave of the blasting sound traveling straight from the face 15 toward the wellhead 12. It is possible to cause a damping effect by colliding with.

In any case, as the sound absorbing material 71, a board-shaped material having a porous structure made of glass wool is used, so that it is possible to attenuate the blasting sound by using a material that is lightweight, easy to handle, and inexpensive. can.

According to the present embodiment, since the sound absorbing material 71 is attached to the seat tensioning carriage 51 used for the construction of the tunnel 11, a structure unrelated to the construction of the tunnel 11 is tunneled in order to attach the sound absorbing material 71. There is no need to introduce it in 11. Therefore, the blasting sound can be reduced without lowering the work efficiency.

According to the present embodiment, when the face 15 is excavated from the wellhead 12 of the tunnel 11 by a predetermined distance or more, the sound absorbing material 71 is removed from the seat tensioning carriage 51. The predetermined distance at this time is, for example, an excavation distance at which the noise level outside the mine is equal to or less than the control standard even without the sound absorbing material 71. Therefore, when it is no longer necessary to supplement the blasting sound reduction effect of the soundproof wall 31 with the sound absorbing material 71, the sound absorbing material 71 is promptly removed. At this time, since the sound absorbing material 71 is lightweight and has excellent handleability, the removal work can be facilitated.

Further, in the present embodiment, the sound absorbing material 71 is removed from the seat tensioning carriage 51 even when the seat tensioning work is started so as not to interfere with the seat tensioning work. When blasting with the face 15, the sound absorbing material 71 will be attached again, but even when the sound absorbing material 71 is repeatedly attached and detached, the sound absorbing material 71 is lightweight and has excellent handleability. It can be facilitated.

Various changes and modifications are allowed in the implementation. For example, the structure used for the construction of the tunnel is not limited to the seat tension carriage 51, and may be, for example, a centre, a temporary scaffold, a construction vehicle, or the like. Any other deformations or changes are allowed.

As described above, in the present embodiment, the sound absorbing material 71 is attached to the seat tensioning carriage 51 introduced in the tunnel 11. Moreover, a plurality of board-shaped sound absorbing materials 71 are prepared, and the board surfaces arranged along the longitudinal direction of the tunnel 11 are faced to each other with the space S separated from each other, and one sound absorbing material 71 and the other sound absorbing material 71 are sheeted. It is attached to the trolley 51. Therefore, the effect of reducing the blasting sound 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 in which a pseudo tunnel is prepared. Experiment 2 is a field verification conducted in an actual tunnel.

(Experiment 1)
FIG. 11 is a schematic diagram of the experimental equipment used for verification. Five vinyl chloride pipes 101 made of vinyl chloride are prepared and connected to form a pseudo tunnel 102, creating an environment imitating the tunnel 11. The PVC pipe 101 has a diameter of 550 mm and a length of 1000 mm, and is formed into a pseudo tunnel 102 having a total length of 5000 mm by connecting five pipes.

In the pseudo tunnel 102, one end face side is an open surface and the other end face side is a closed surface. The open surface is a pseudo wellhead 103, and the closed surface is a pseudo face 104. A speaker 105 was placed inside the pseudo-face 104 side to generate sound corresponding to blasting sound.

As shown in FIGS. 12 and 13, a flat plate-shaped board 106 is arranged inside each PVC pipe 101 to have a structure imitating 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 so as to form a structure imitating the ground G.

In the experiment, a sound absorbing material 111 made of glass wool is placed inside the pseudo tunnel 102, sound is generated from the speaker 105, and sound is received at the 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 pseudo tunnels 102 for the purpose of clarifying the length dimension of the pseudo tunnel 102 and the structure in which the PVC pipes 101 are connected, and for the purpose of explaining the contents of the experiment, but the two pseudo tunnels 102 are prepared in an actual experiment. There is only one pseudo tunnel 102. After preparing two types 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. Each of the sound absorbing materials 111 is 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 111a was arranged closer to the right side when the direction of the pseudo face 104 was 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 having a thickness of 25 mm, a width of 200 mm and a height of 225 mm. Therefore, when the two sheets are combined, 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 symmetrical when the direction of the pseudo face 104 is viewed from the pseudo wellhead 103.

FIG. 14 shows a state in which the sound absorbing material 111 is not 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 face-to-face. The sound pressure level (dB) at the sound receiving point 131 for each frequency (Hz) when the sound corresponding to the above is generated is shown in comparison. As for the frequency, data were acquired for eight ways of 125Hz, 250Hz, 500Hz, 1KHz, 2KHz, 4KHz, 8KHz, and 16KHz. The graph shown in FIG. 14 plots the sound pressure levels for each of these frequencies and connects the individual plot points. The solid line shows the data when the sound absorbing material 111 is not arranged, the broken line shows the data when only the sound absorbing material 111a is arranged, and the alternate long and short dash line shows the data when the pair of sound absorbing materials 111b are arranged face-to-face.

As shown in FIG. 14, there is no significant difference in sound pressure level between 125 Hz and 500 Hz in any of the three embodiments. 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 reduction amount (dB) with respect to the sound pressure level when the sound absorbing material 111 is not 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 face-to-face. It is shown in comparison with the time. Similar to the graph of FIG. 14, the broken line shows the data when only a single sound absorbing material 111a is arranged, and the alternate long and short dash line shows the data when the pair of sound absorbing materials 111b are arranged face-to-face.

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. It is 1.9 dB at 7 dB and 16 KHz. When the pair of sound absorbing materials 111b are arranged face-to-face, the amount of reduction 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, in general, the sound pressure level is lower when the pair of sound absorbing materials 111b are arranged face-to-face than when only the single sound absorbing material 111a is arranged. This tendency is remarkable in the high frequency band.

From the above experimental results, a higher acoustic attenuation effect was obtained when the sound absorbing material 111 was provided than when it was not provided, and a pair of sound absorbing materials 111b were faced to each other as compared with the case where the single sound absorbing material 111a was provided. It was verified that the sound reduction effect was higher in the case.

(Experiment 2)
Experiment 2 was performed inside an actual tunnel 11 as illustrated in FIG. In this experiment, as illustrated in FIGS. 9 and 10, a seat tension carriage 51 to which the sound absorbing material 111 is attached is arranged near the wellhead 12, and a sound corresponding to blasting sound is emitted from a speaker 105 arranged near the face 15. generate. Then, the sound pressure level (dB) for each frequency (Hz) was acquired at each of the sound receiving points at the points P1 and P2 (see FIG. 1) 10 meters before and after the seat tensioning carriage 51.

As the sound absorbing material 111, a board-shaped material having a thickness of 50 mm made of glass wool was used, and this was arranged in an area of ^{320 m 2.} The density is 2.4 kg per 1 m ^2.

In the graph shown in FIG. 16, the sound absorbing material 111 is attached to the seat upholstery trolley 51 with respect to the amount of sound attenuation between the P1 point and the P2 point acquired in the state where the sound absorbing material 111 is not attached to the seat upholstery trolley 51. The amount of attenuation from the P1 point to the P2 point, which has increased due to this, is shown for each frequency. From this graph, it can be seen that there is a reduction effect of about 6 dB in the midrange (around 250 Hz) and about 3 dB in the high range (500 Hz or higher).

Therefore, even in the results of the conducted experiment, it was verified that a higher acoustic attenuation effect can be obtained when the sound absorbing material 111 is provided than when it is not provided.

11 Tunnel 12 Wellhead 13 Inside 14 Rail 15 Face 31 Soundproof wall 51 Seat tension trolley 52 Base 53 Leg 54 Beam 55 Brace 56 Structural element 57 Frame structure 58 Wheel 59 Scaffold 59a Lower scaffold 59aL Reinforced steel pipe 59b Upper scaffold 59c Top scaffold 60 Scaffolding board 61a Lower ladder 61b Upper beam 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 wellhead 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 (15)

The process of introducing a seat upholstery trolley used for the construction of this tunnel in the tunnel where blasting and excavating the face, and
The process of attaching the sound absorbing material to the seat upholstery trolley and
When starting the seat tensioning work, the step of removing the sound absorbing material from the seat tensioning bogie, and
A method for reducing blasting sound, which is characterized by being provided with. The process of introducing a seat upholstery trolley used for the construction of this tunnel in the tunnel where blasting and excavating the face, and
The process of attaching the sound absorbing material to the seat upholstery trolley and
A method for reducing blasting sound, which is characterized by being provided with. Further comprising a step of removing the sound absorbing material from the seat upholstery bogie when the face is excavated more than a predetermined distance from the wellhead of the tunnel.
The method for reducing blasting sound according to claim 2. The predetermined distance is an excavation distance at which the noise level outside the mine is below the control standard even without the sound absorbing material.
The method for reducing blasting sound according to claim 3. A plurality of the board-shaped sound absorbing materials are prepared, and the board surfaces are faced to each other across a space, and one sound absorbing material and the other sound absorbing material are attached to the seat upholstery trolley.
The method for reducing blasting sound according to any one of claims 1 to 4, wherein the method is characterized by the above. The board-shaped sound absorbing material is attached to the seat tension carriage along the longitudinal direction of the tunnel.
The method for reducing blasting sound according to any one of claims 1 to 5, wherein the method is characterized by the above. The board-shaped sound absorbing material is attached to the seat upholstery trolley along a direction orthogonal to the longitudinal direction of the tunnel.
The method for reducing blasting sound according to any one of claims 1 to 6, wherein the method is characterized by the above. The sound absorbing material has a porous structure.
The method for reducing blasting sound according to any one of claims 1 to 7, wherein the method is characterized by the above. The sound absorbing material having a porous structure is glass wool.
The method for reducing blasting sound according to claim 8. The seat upholstery trolley used for the construction of this tunnel, which will be introduced into the tunnel where blasting and excavating the face,
The sound absorbing material attached to the seat upholstery trolley and
A blasting sound reduction device characterized by being equipped with. A plurality of board-shaped sound absorbing materials are provided, and the board surfaces face each other across a space, and one sound absorbing material and another sound absorbing material are attached to the seat upholstery trolley.
The blasting sound reducing device according to claim 10. The board-shaped sound absorbing material is attached to the seat tension carriage along the longitudinal direction of the tunnel.
The blasting sound reducing device according to claim 10 or 11. The board-shaped sound absorbing material is attached to the seat upholstery trolley along a direction orthogonal to the longitudinal direction of the tunnel.
The blasting sound reducing device according to any one of claims 10 to 12, characterized in that. The sound absorbing material has a porous structure.
The blasting sound reducing device according to any one of claims 10 to 13. The sound absorbing material having a porous structure is glass wool.
The blasting sound reducing device according to claim 14.

Images