JPH09228785A - Ultra low frequency sound reducing method of buffering work for tunnel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce sound pressure peak and ultra low frequency sound generated by pressure wave generating at the entrance and exit of a tunnel by properly selecting data of buffering work through model tests of tunnel, train and buffering work. SOLUTION: A cover 3 having a specified length and a larger sectional area than that of a tunnel 2 is arranged at an entrance of the tunnel 2, and an opening 4 is arranged on a side surface of the cover 3. Data of this buffering work for the tunnel 2 comprises the area and shape of the opening 4 and the specified length L and the sectional area S2 of the cover 3. Through execution of model tests, the data is properly made to thereby make a first stage compression wave generating at the entrance of the cover 3 and a secondary stage compression wave generating at the entrance of the fennel 2, a synthesized compression wave as a whole close to one pressure gradient. By making the data properly, the distance between two pressure inclinations mixed in the wave front of the synthesized compression wave is specified, threreby reducing generation of ultra low frequency sound at the exit of the tunnel 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing ultra-low frequency sound of a tunnel buffer, which reduces infrasound due to a pressure wave generated at a tunnel exit when a high-speed vehicle such as a Shinkansen enters a tunnel. It is about. In particular, the present invention relates to a method of reducing infrasound of a tunnel buffer, which has an effect of adjusting the rising of the gradient of a pressure wave to reduce infrasound at the tunnel exit.

[0002]

2. Description of the Related Art When a train enters a tunnel at high speed, the air in the tunnel is compressed and a compression wave is generated. This compression wave propagates in the tunnel toward the exit at the speed of sound, and when it reaches the exit, the minus part of the compression wave is emitted from the exit of the tunnel to the outside as a pulsed pressure wave to generate an air pressure sound. In addition, this pneumatic noise secondarily causes vibrations of houses and the like. The magnitude of this air pressure sound is proportional to the pressure gradient on the front surface of the compression wave reaching the tunnel exit, and the pressure gradient on the front surface of the compression wave generated at the tunnel entrance is proportional to the cube of the train entry speed. Is known to be formed. For this reason, at high speeds of 220 km / hr or more like a Shinkansen, the pneumatic noise at the tunnel exit increases exponentially, which may cause serious environmental problems.

In order to reduce the air pressure noise at the tunnel exit, it is necessary to reduce the pressure gradient on the front surface of the wave front of the compression wave. As a concrete method, the method disclosed in Japanese Patent Publication No. 55-31274 is effective and is still used.

This air pressure sound reducing method will be described with reference to FIG. Although FIG. 1 shows a shock absorber used in the method for reducing infrasound of the present invention, the structure is similar to that of the conventional shock absorber. This pneumatic noise reduction method is provided at the entrance of the tunnel 2 and has a cover 3 having a cross section larger than the tunnel cross-sectional area.
And a tunnel buffer 5 including an opening 4 provided on a side surface of the cover 3. In this method, a compression wave generated when a high-speed vehicle 1 such as a Shinkansen plunges into the tunnel 2 is a first-stage compression wave generated at the entrance of the cover 3 and a second-stage compression wave generated at the entrance of the tunnel 2. Divide into next,
By interposing a time course determined by the length of the cover between the first-stage compression wave and the second-stage compression wave to optimize the area of the opening, the first-stage compression wave and the second-stage compression wave Is a method of reducing the pressure gradient in front of the wave front by forming a continuous gentle compression wave.

[0005]

However, although the air pressure sound can be reduced by the above-mentioned method, the house or the like is vibrated by the secondary low frequency sound, particularly the low frequency sound of 20 Hz or less. There is a problem that causes Such a pressure wave in the infra-low frequency band cannot be reduced as much as the air pressure sound in the audible range. Therefore, although the air pressure sound is inaudible, there is a problem of the infra-low frequency vibration that vibration occurs. Therefore, the present invention relates to a method of reducing infrasound of a tunnel buffer, which reduces infrasound caused by a pressure wave generated at a tunnel exit.

[0006]

Means for Solving the Problems The inventors of the present invention observed the actual generation of a compression wave in a tunnel and conducted intensive studies. As a result, the gap between the two pressure gradients in which the first-stage compression wave generated by the entrance of the cover and the second-stage compression wave generated by the tunnel entrance are mixed in the wave front surface in the initial compression wave , The frequency range of the secondary infrasound generated at the tunnel exit is set to 20H by further adjusting the specifications of the buffer and setting it at a predetermined interval.
It has been found that it is possible to reduce the generation of infrasound by making z exceed.

The specifications of the buffer for making the interval of two pressure gradients mixed in the wave front surface in the synthesized initial compression wave a predetermined interval are as follows: area of the opening, shape of the opening, predetermined length of the cover, cover There is a cross-sectional area of the body. By making one or more of these specifications more appropriate, the interval between the two pressure gradients mixed in the wave front surface of the synthesized initial compression wave is set to a predetermined interval. As a result, 2 which is going to occur at the tunnel exit
The frequency range of the next sound can be set to exceed 20 Hz, and the generation of infrasound can be reduced. Furthermore, it is preferable to set the frequency range of the infrasound to be higher than 20 Hz by setting the predetermined interval or less.

It is preferable to carry out the method of reducing the infrasound of the tunnel buffer by a train and model test of the buffer. That is, the first step of converting the first-stage compression wave and the second-stage compression wave into a combined compression wave that is close to one pressure gradient as a whole, and the interval between the two pressure gradients mixed in front of the wavefront of the combined compression wave The second step of setting the predetermined intervals is performed by a model test and applied to an actual machine. There are many restrictions on the experiments on the actual machine, and there are also experimental conditions that cannot be carried out. On the other hand, in the model experiment, the experimental conditions can be freely set, and as a result, it is possible to perform the experiment efficiently and effectively and to further reduce the infrasound generated at the tunnel exit. In addition, the pressure gradient interval in the model experiment is set to the first
It is preferable to set an interval of a representative time during which the stage compression wave and the second stage compression wave generated at the tunnel entrance are maintained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to illustrated examples. First, an analysis result of a model test compression wave when a shock absorber is provided at the entrance of a tunnel is shown (Example 1).
FIG. 1 is a side view and a front view showing a state in which a shock absorber is provided at the entrance of the tunnel. FIG. 2 is a diagram in which the timing at which a train passes near the tunnel entrance and the compression wave generated at that time were measured at the tunnel entrance by the experimental apparatus. The measurement conditions are a tunnel length of 75 m, a buffer covering length of 2.65 m,
The ratio of the sectional area of the cover of the shock absorber / the sectional area of the tunnel is 2.5.
A shock absorber will be installed at the entrance of the tunnel and a model car will be run for 500k.
This is the case when entering the tunnel at m / hr. The horizontal axis of FIG. 2 represents time and the vertical axis represents pressure.

As shown in FIG. 2, the compression wave is formed of three parts. That is, (a) the first stage compression wave formed when the train head portion rushes into the shock absorber, (b) the compression wave formed while passing through the shock absorber, and (c) the train front portion from the shock absorber. It is the second-stage compression wave formed when entering the tunnel.

Next, the analysis result of the investigation of the propagation of the pressure waveform of the compression wave will be shown (Example 2). Figure 3 shows how the compression wave propagates in the pressure waveform from the tunnel entrance to the exit,
Furthermore, the pressure waveform of the micro-pressure wave emitted from the tunnel exit is shown. The measurement was performed under the same measurement conditions as in Example 1.

FIG. 3 shows, in order from the top, (a) the pressure waveform of the compression wave at the tunnel entrance, (b) the pressure waveform of the compression wave immediately before the tunnel exit, and (c) the pressure waveform of the micro-pressure wave emitted from the tunnel exit. is there. The pressure waveform immediately after the tunnel entrance of (a) propagates in the tunnel and becomes a pressure waveform like (b) near the exit. At atmospheric pressure, air propagates at a speed of sound of about 340 m / s. Since the compressed air has a pressure higher than the atmospheric pressure, the sound velocity also increases. Therefore, the compression wave at the entrance of the tunnel in (a) reaches the exit of the tunnel faster in the high pressure portion than in the low pressure portion. This is the reason why the pressure gradient rises as the tunnel exits.

As shown in FIG. 3, in the portion (a) where the pressure gradient of the compression wave at the tunnel entrance is steep, the pressure gradient of the compression wave immediately before the tunnel exit in (b) becomes even steeper. (B)
The pressure waveform of (1) is in a form in which the time axis of the pressure waveform of (a) is compressed.

When the compression wave just before the tunnel exit of (b) is emitted from the tunnel, outside the tunnel exit, (c)
Is observed as a pulsed micro-pressure wave. It can be seen that the magnitude of this pressure is proportional to the magnitude of the pressure gradient at the tunnel exit. The so-called "don't sound" is this pulse wave, and the magnitude of the "don't sound" is determined by the magnitude of the pressure of the pulse wave. That is, the pressure gradient on the front surface of the obtained compression wave determines the loudness of the air pressure sound at the outlet.

On the other hand, the second-order ultra-low frequency sound generated at the tunnel exit is dominated by frequency components whose period is the time interval of the peak of the pulsed micro-pressure wave. If this frequency matches the resonance frequency of a structure such as a house (usually 20 Hz or less), an ultra-low frequency air vibration problem occurs. The longer the time interval between the peaks of the pulsed micro-atmospheric pressure wave, the more the main frequency component of the micro-atmospheric pressure enters the frequency region where the secondary sound is generated, which causes a problem of ultra-low frequency. Especially,
The first-stage compression wave generated at the entrance of the cover of part (a) and (c)
The time interval of the peak of the second-stage compression wave generated at the entrance of the tunnel in the section greatly contributes to the generation of the ultra-low frequency. That is,
The peak time interval becomes long, and an ultra-low frequency of 20 Hz or less is likely to occur. The frequency of the pulsed micro-pressure wave is analyzed and it has been confirmed that the frequency of the secondary ultra-low frequency sound generated at the tunnel exit is controlled by the peak time interval of the micro-pressure wave.

It was found for the first time that the steep pressure gradient portion of the compression wave at the tunnel entrance in FIG. 3 (a) has a great influence on the secondary infrasound generated at the tunnel exit. Until now, there has been almost no analysis of compression waves when such a buffer was installed at the entrance of a tunnel. In particular, how the second-order infrasound generated at the tunnel exit is generated has not been analyzed so far in the examples.

The inventors of the present invention have earnestly studied to reduce the peak of the air sound pressure to be generated at the tunnel exit (first step) and the reduction of infrasound (second step). First
In the process, the first-stage compression wave generated by the entrance of the cover of the shock absorber and the second-stage compression wave generated by the tunnel entrance due to the train rush are combined into a composite compression wave that approaches one pressure gradient as a whole. Is a means to do. The second step is a means for setting the interval of two pressure gradients mixed on the front surface of the wavefront of the composite compression wave to be a predetermined interval.

The method of reducing the peak of the pneumatic noise that is about to occur at the tunnel exit in the first step will be further described. An example in which the specifications of the buffer in the first step are changed is shown (Example 3). The compression wave was measured by changing the opening area of the side surface of the buffer with the same shape, which has the same length and the same cross-sectional area, and plunging the same model vehicle at the same speed.
The result is shown in FIG. The solid line (a) shows the case where the opening area on the side surface is optimized, and the pressure gradient of the compression wave is gentle. In the case of the broken line (b) with a wide opening area, (b)
As the pressure rise in the section decreases, the inclination of the section (c) rises. On the other hand, in the case of the dotted line (c) where the opening area is narrowed, the increase in pressure in (b) increases,
The inclination of part (a) rises.

The opening provided on the side surface of the shock absorber can adjust the compression wave of the portion (b). By this opening,
By smoothly connecting the compression waves of the parts (a) and (c), it has the function of grading the pressure gradient.
That is, the effect of reducing the pneumatic noise can be enhanced by adjusting the opening area of the side surface. In this embodiment,
It only shows an example in which the opening area of the side surface of the shock absorber is changed. The specifications of the shock absorber can be changed by one or more of the area of the opening, the shape of the opening, the predetermined length of the cover, and the cross-sectional area of the cover to synthesize a compression wave approaching one pressure gradient as a whole.

Next, a method of reducing the infrasound to be generated at the tunnel exit in the second step, which is the point of the present invention, will be described. In the second step, the specifications of the shock absorber were further changed. The length of the cover and the opening area of the side surface are the same,
The same model vehicle model was rushed into the shock absorber with the cross-sectional area of the cover changed at the same speed to perform an experiment, and the compression wave at the tunnel entrance was measured (Example 4). The result is shown in FIG. The ratio of the cross-sectional area of the cover to the cross-sectional area of the tunnel is 1.2 to 2.5
Was changed to.

From FIG. 4, it has been clarified that the position of the portion of the compression wave where the pressure gradient is steep and the pressure gradient are changed by changing the ratio of the cross-sectional areas. In particular, the position of the steep portion of the pressure gradient of the compression wave is important for reducing the secondary infrasound that is about to occur at the tunnel exit. The position of the representative time at which the steep portion of the pressure gradient is maintained is the center of each gradient.

In order to reduce the second-order infrasound to be generated at the tunnel exit, the time interval of the steep portion of the pressure gradient between the first-stage compression wave and the second-stage compression wave at the tunnel entrance is predetermined. Must be spaced. It is preferable to set the time interval to be the predetermined interval or less and to further increase the frequency of the infrasound.

The predetermined interval is determined by the time interval of the peak of the pressure waveform of the micro atmospheric pressure wave emitted from the tunnel exit. Further, the predetermined interval is determined by adding conditions such as tunnel length and train speed. The tunnel length affects the propagation distance of the compression wave. The longer the tunnel, the steeper the pressure gradient of the compression wave at the tunnel exit. As a result, the frequency characteristics of the second-order infrasound are affected. The train speed also affects the frequency characteristics of the secondary infrasound. Details will be described later.

In FIG. 4, the time interval between the steep pressure gradient portions of the first-stage compression wave and the second-stage compression wave was short, and the ratio of the cross-sectional area of the covering body / the cross-sectional area of the tunnel was 1.2. Regarding the shock absorber, the state of propagation of the pressure waveform of the compression wave was further investigated by a model test (Example 5). The result of this analysis is shown in FIG. Compared to the second embodiment (FIG. 3), the time interval of the peak of the pressure waveform of the micro atmospheric pressure wave at the tunnel exit is narrower, and as a result, the frequency of the generated ultra-low frequency sound is higher. FIG.
As shown in, the time interval of the peak of the pressure waveform of the micro atmospheric pressure wave at the tunnel exit is 1.20 msec. The main frequency of the super low frequency sound generated at this time is 833 Hz. This frequency is 24.5 Hz when converted to an actual machine.

Furthermore, the influence of the length of the cover of the buffer and the train speed on the frequency of the secondary infrasound emitted from the tunnel exit was examined. The maximum value t of the time interval between the first-stage compression wave and the second-stage compression wave of the pressure waveform at the tunnel entrance is determined by the length of the cushion cover and the train speed.
The maximum value t of the time interval between the first-stage compression wave and the second-stage compression wave of the pressure waveform at the tunnel inlet is t = L / V-L / C, where L is the length of the cover of the shock absorber. , V is the train speed, and C is the speed of sound. The frequency f at this time is represented by f = 1 / t. As a result, the minimum frequency of infrasound generated at the tunnel exit is determined. This is due to the fact that when propagating from the tunnel entrance to the exit, the time interval is shortened, and the interval between the two pressure gradients at the entrance is not larger than t.

In the adjustment of the frequency characteristic of the super low frequency sound of the present invention, the minimum frequency is the lower limit. In order to reduce the above-mentioned super low frequency sound, the length of the cover of the shock absorber may be shortened. However, in order to reduce the air pressure noise at the tunnel exit, the length of the cover of the shock absorber needs to be a predetermined length.

As previously described in the second embodiment (FIG. 3), by adjusting the opening area of the side surface of the shock absorber,
The rising waveform of the compression wave can be adjusted. Therefore,
It is possible to adjust the frequency characteristics of the infrasound of the pneumatic sound emitted from the tunnel exit. The specifications of the shock absorber,
By changing one or more of the area of the opening, the shape of the opening, the predetermined length of the cover, and the cross-sectional area of the cover, and by setting the interval of the two pressure gradients mixed in the wave front surface of the composite compression wave to be the predetermined interval,
It is possible to reduce the infrasound that is generated at the tunnel exit.

A comparative example of the test results of the actual machine and the model is shown in FIG. 7 (Example 6). In the actual machine test, Shinkinmei road tunnel (tunnel length: 7 km) equipped with shock absorbers, train 57 m / s
Then, the compression wave generated was measured at the tunnel entrance (east pit entrance 80m point). Model experiment is 1/34
Using a model tunnel, a model train was rushed into the tunnel at a speed of 58 m / s, and the generated compression wave was measured at the tunnel entrance (pit 2.3 m point). As shown in FIG. 7, the rising of the compression wave was not significantly different between the actual machine and the model test. The first-stage compression wave generated by the entrance of the cover of the present invention and the second-stage compression wave generated by the tunnel entrance correspond to the rising portion of FIG. 7. As a result, it was confirmed that the correlation between the actual machine and the model test was considerably high. The difference between the two is the latter half of the compression wave, but this is due to the difference in the vehicle length of the actual machine and the vehicle length of the model, and is not related to the pressure gradient that determines the micro-pressure wave.

[0029]

According to the first and second aspects of the present invention, the area of the opening, the shape of the opening, and
By making one or more of the predetermined length of the cover and the cross-sectional area of the cover more appropriate, the first-stage compression wave generated by the entrance of the cover and the second-stage compression wave generated by the tunnel entrance Can be set to a predetermined interval between the two pressure gradients mixed in the front surface of the wave in the synthesized initial compression wave.
As a result, there is an effect that it is possible to reduce the generation of secondary infrasound generated at the tunnel exit.

Further, the invention according to claims 3 and 4 of the present invention is a super low frequency sound reduction method which is attempted to be more efficiently generated at a tunnel exit by performing a model test of trains and buffers. It has an effect that low frequency sound can be further reduced. According to the present invention, since the frequency characteristic of the pressure wave generated from the tunnel exit can be adjusted, it is possible to design the shock absorber so as to avoid the problematic frequency and reduce the infrasound. .

[Brief description of drawings]

FIG. 1 is a side view and a front view showing a state in which a shock absorber of the present invention is provided at an entrance of a tunnel.

FIG. 2 is a diagram showing a process of forming a compression wave in a tunnel.

FIG. 3 is a diagram showing a relationship between a compression wave in a tunnel and a pressure wave generated from an outlet. (Ratio of cross-sectional area of cover / cross-sectional area of tunnel: 2.5)

FIG. 4 is a diagram showing an effect of an opening area on a side surface of a cover of a shock absorber.

FIG. 5 is a diagram showing a change in a compression wave due to a change in a cross-sectional area of a cover of a shock absorber.

FIG. 6 is a diagram showing a relationship between a compression wave in a tunnel and a pressure wave generated from an outlet. (Ratio of cross-sectional area of cover / cross-sectional area of tunnel: 2.5)

FIG. 7 is a diagram showing a comparison between an actual machine and a model of a shock absorber.

[Explanation of symbols]

 1 Train 2 Tunnel 3 Cover 4 Opening 5 Buffer L Length of Cover S1 Cross Section of Tunnel S2 Cross Section of Cover

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Nagura 1-4-1, Mei Station, Nakamura-ku, Nagoya-shi, Aichi Tokai Passenger Railroad Co., Ltd. (72) Mineo Oishi, Mei Station, Nakamura-ku, Nagoya-shi, Aichi 1-4-1 Tokai Passenger Railway Co., Ltd.

Claims (4)

[Claims] 1. A train bumper is provided by using a tunnel buffer, which is provided at a tunnel entrance and has a cover of a predetermined length having a cross section larger than the tunnel cross section, and an opening provided on a side surface of the cover. The first generated by the inlet of the cover
The stage compression wave and the second stage compression wave generated by the tunnel entrance are generated at the tunnel exit by appropriately adjusting the specifications of the buffer and forming a composite compression wave that approaches one pressure gradient as a whole. The first step of reducing the peak of the air sound pressure to be attempted, and the interval between the two pressure gradients mixed on the front surface of the composite compression wave are set to predetermined intervals by further adjusting the specifications of the shock absorber. And a second step of reducing the infrasound that is about to occur at the tunnel exit, thereby reducing the infrasound of the tunnel buffer. 2. The tunnel according to claim 1, wherein the specifications of the buffer are one or more of an area of the opening, a shape of the opening, a predetermined length of the cover, and a cross-sectional area of the cover. Ultra low frequency sound reduction method of shock absorber. 3. The method for reducing infrasound of a tunnel buffer according to claim 2, wherein the first step and the second step are performed in a model test of the tunnel, the train and the buffer. 4. The method according to claim 3, wherein the interval between the pressure gradients is a representative time interval during which each of the two pressure gradients is maintained.