JPH08136532A - Evaluation method for pavement - Google Patents

Abstract

PURPOSE: To evaluate a pavement without impeding the traffic while protecting the pavement against damage due to sampling of core by installing a microphone in the vicinity of the tire of a vehicle and sampling the noise level at the time of running on the pavement. CONSTITUTION: A commercially available microphone 3 is employed. A filter for taking out the high frequency components includes an octave or 1/3 octave band analyzer and a bandpass filter combined with an indication mechanism or a recording mechanism. Preferably, the microphone is fixed in the rear of the tire. The inventive method is specifically applicable to an asphalt pavement 5. The relationship between the roughness of pavement and the tire noise is such that when the components having wavelength of 20mm or above increases in the roughness of pavement, for example, 250Hz and 500Hz components increase in the octave band. When the component having wavelength of 10mm or below increases, frequency components higher than 2kHz decreases. The surface roughness is evaluated by capturing the variation of respective frequency components.

Description

Detailed Description of the Invention

[0001]

[Industrial application field] The present invention relates to a pavement evaluation method.

[0002]

2. Description of the Related Art Conventional pavements, such as drainage pavements, have the functions of drainage and low noise, but their performance in service depends on the quality of the work and the clogging after the work. Both noise characteristics vary considerably, and appropriate evaluation is required. The following methods are available to evaluate drainage pavement. (1) Method of measuring the thickness of core extracted from the road surface, porosity, and normal incidence sound absorption coefficient (2) Method of evaluating drainage performance by conducting a water permeability test on the road surface.

[0003]

The above-mentioned evaluation method requires traffic restrictions during evaluation or core extraction, and is extremely difficult to carry out on an actual highway or the like. Further, when the core is collected, it is necessary to take measures such as filling back the hole formed by collecting the core.

[0004]

The gist of the present invention is to install a microphone near the tire of a vehicle and collect the noise level of the microphone when the vehicle is running on a pavement. A pavement evaluation method characterized in that the noise level is a high frequency component obtained by using a filter, as defined in claim 2. Still further, according to a third aspect of the present invention, there is provided a pavement evaluation method characterized in that the microphone is installed behind a tire.

[0005]

The pavement evaluation method of the present invention is performed by simply measuring the noise level when the vehicle is mounted on the pavement with a microphone installed near the tire without restricting traffic or collecting cores as in the conventional method. The condition can be evaluated.

[0006]

The present invention will be described in detail below. FIG. 1 is a schematic diagram of the evaluation method of the present invention. Here, 1 is a vehicle, 2 is a rear wheel, 3 is a microphone, 4 is a rear bumper, and 5 is a pavement, so that the input portion of the microphone 3 faces the rear wheel 2 below the rear bumper 4 of the vehicle 1. It is fixed and is set so that the vehicle 1 travels on the pavement 5 and the noise level at that time can be input. The vehicle 1 used for the measurement is not particularly limited, and a commercially available automobile or the like can be used. The microphone 3 is not particularly limited, and a commercially available microphone can be used. Further, as the filter for extracting the high frequency component, in addition to the octave and 1/3 octave band analyzers specified in JIS C-1513, it is possible to use a high bass filter combined with an indicator mechanism or a recording mechanism. it can.

Further, as the pavement 5, generally, there are asphalt pavement and concrete pavement, but the evaluation method of the present invention particularly relates to asphalt pavement. Asphalt pavement, eg classified by the mixture used on the surface,
Examples include open grain size, coarse grain size, fine grain size, and fine grain size (based on "Asphalt Pavement Guidelines" edited by Japan Road Association). In addition, the drainage pavement referred to in the present application uses an asphalt mixture of an open particle size type having a large porosity.

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

The measurement conditions of the examples are as follows. Experimental vehicle: passenger car. Displacement 2000cc Tire: SF322 195 / 65R14 (manufactured by Bridgestone Corporation) Internal pressure 2.0 atm. Microphone: Type 4155 condenser microphone (manufactured by B & K). Number of passengers: 4 Pavement thickness: 4 cm Weather: Sunny Travel speed: 100 km / h

Various measurements were performed based on the above measurement conditions. Figure 2 shows the relationship between the thickness of the surface layer of drainage pavement and the noise reduction effect. The thicker the surface layer, the greater the noise reduction effect. That is, the lower the frequency at which the noise is reduced, the thicker the pavement and the better the noise reduction effect. In addition, as for the drainage performance, if the porosity is the same, the thicker the pavement, the larger the amount of voids in the interior, so that the water retention capacity is increased, and good drainage performance is exhibited.

Further, FIG. 3 shows spectra of passing noise measured in the drainage pavement and the dense-grained asphalt concrete pavement. The noise reduction effect of the drainage pavement is great at high frequencies. This results from frequencies where the thicker the surface, the lower the noise reduction.

The noise measurement is based on JIS D1024, and the maximum noise level when the vehicle is passing 7.5 m to the left of the vehicle running center line and 1.2 m above the ground from the vehicle running center line of a passenger car that runs steadily at a speed of 80 km / h. And the spectrum at the maximum noise level was obtained. The noise reduction effect is a value subtracted from the value measured in a dense-grained asphalt concrete pavement using crushed stones of the same grain size.

The present invention is intended to measure the noise in the vicinity of tires during steady running in order to evaluate the pavement by grasping the noise reduction effect without hindering traffic. The microphone is preferably attached to the rear of the tire for the following reasons. (1) Fig. 5 shows the spectra of the drainage pavement and the dense-grained pavement measured on the tire rear side and Fig. 6 on the tire side (see Fig. 1 and 4 for the mounting position). ,
The noise reduction effect of drainage pavement is remarkable. (2) If the tire is mounted on the side of the vehicle from the outside of the vehicle, it protrudes out of the vehicle body, which is an obstacle to traffic. (3) It is preferable to use a windscreen to remove low-frequency sounds, but since the microphone is oriented rearward in front of the tire, special means for fixing the windscreen is required.

Although the present invention has been described above as an evaluation means for drainage pavement, it can also be used for evaluation of ordinary pavement, for example, dense-grained asphalt concrete pavement. The relationship between the pavement roughness and tire noise is as follows. If the component of the road surface roughness with a wavelength of 20 mm or more increases, 25
If the octave band components of 0 Hz and 500 Hz increase and the component of the road surface roughness with a wavelength of 10 mm or less increases, 2 k
Frequency components above Hz are reduced. By capturing the change in each frequency component, the surface roughness can be evaluated.

Further, the vehicle was driven on a highway where drainage pavement and density asphalt concrete pavement were repeated. Table 1 shows the distance of each pavement section. There are 6 drainage pavements on the road surface.

[0016]

[Table 1]

FIG. 7 shows the time variation of the noise level of the 1250 octave band of 1250 Hz, FIG. 8 shows the noise level of the 1/3 octave band of 1000 Hz, and FIG. 9 shows the temporal variation of the noise level of the 1/3 octave band of 800 Hz. At 1250 Hz,
All the construction sections show a large noise reduction effect, but 1000Hz
In, the construction section 7, the construction section 9, and the construction section 11 show the noise reduction effect, and at 800 Hz, only the construction section 9, the construction section 11 shows the noise reduction effect. The noise is reduced from the low frequency in the construction zone 7, and is reduced from the lower frequency in the construction zones 9 and 11 as compared with the construction zones 1, 3 and 5. That is, compared to construction zones 1, 3, and 5, construction zone 7
It can be judged that the surface layer is thick and the construction sections 9 and 11 are thicker.
This is consistent with the drainage situation observed during rainfall. In addition, the thickness of the surface layer measured from the core extracted from the pavement showed the same tendency.

The noise level shown here is an equivalent noise level for 5 seconds obtained by dividing the running time into 5 seconds.

[0019]

According to the present invention, since the pavement is evaluated by measuring the sound using a vehicle traveling at a normal speed, the pavement can be collected by collecting the core without disturbing road traffic. Pavement can be evaluated without damaging it.

[Brief description of drawings]

FIG. 1 is an example of a schematic diagram of an evaluation method of the present invention.

FIG. 2 is a relationship diagram showing the noise reduction effect and the thickness of the surface layer of the drainage pavement.

FIG. 3 is a spectrum diagram of passing noise.

FIG. 4 is another example of the schematic diagram of the evaluation method of the present invention.

FIG. 5 is a noise spectrum behind the tire.

FIG. 6 is a noise spectrum on the side of the tire.

FIG. 7 is a diagram showing a noise level change in a 1/3 octave band at 1250 Hz.

FIG. 8 is a diagram showing a noise level change in a 1/3 octave band of 1000 Hz.

FIG. 9 is a diagram showing a noise level change in a 1/3 octave band of 800 Hz.

[Explanation of symbols]

 1 Vehicle 2 Rear Wheel 3 Microphone 4 Rear Bumper 5 Pavement

Claims (3)

[Claims] 1. A pavement evaluation method characterized in that a microphone is installed near a tire of a vehicle, and a noise level is sampled by the microphone when the vehicle travels on the pavement. 2. The noise level is a high frequency component obtained by using a filter.
Pavement evaluation method described. 3. The pavement evaluation method according to claim 1, wherein the microphone is installed at the rear of the tire.