JP6164882B2 - Porosity measuring device and porosity evaluation method - Google Patents

Description

  The present invention relates to a porosity measurement device and a porosity evaluation method for measuring the porosity of porous concrete in a filtration basin based on vibration characteristics of air.

  In the past, treated water that has undergone treatment such as coagulation sedimentation and sand filtration has been chlorinated at water purification plants, but ozone is used to avoid the generation of harmful organochlorine compounds and improve water quality by removing mold odors and pigments. The introduction of advanced treatment, which is the oxidative decomposition treatment of organic matter and the adsorption removal treatment of pollutants by biological activated carbon, is progressing.

  As a typical structural example of a filtration pond represented by a biological activated carbon adsorption pond, a lower water collecting apparatus having a porous concrete layer is installed. The lower water collecting device has a small air outlet for the purpose of supporting filter media using activated carbon, anthracite, etc. arranged in the upper part, equal collection of treated water, and equal dispersion during simultaneous washing with water and air. A porous concrete layer supporting a filter medium is formed on the uppermost layer, which includes air dispersion beams arranged in an array, a slit plate disposed thereon, and a dispersed gravel layer disposed thereon.

  When filtering the inflow water to the filter basin, the filtered treated water passes through the pores of the porous concrete layer of the lower water collecting device and flows out into the lower water collecting basin. The quality of the porous concrete greatly affects the function of the lower water collecting device because the cleaning water and the air discharged from the air dispersion beam are supplied to the filter medium layer from below through the porous concrete layer. Therefore, it is necessary for porous concrete to have both the physical strength that can withstand the filter medium layer and the backwashing pressure, and the equal processing ability and pressure loss performance during filtration and backwashing. It is necessary to manage such that a certain porosity falls within a predetermined range, for example, a range of 25% to 35%.

  Conventionally, in order to measure the porosity of porous concrete, specimens of the same composition as porous concrete placed on-site are manufactured at the same time, and the Archimedes method is used to correlate the mass of the specimen in air and water. A method of calculating the porosity from the relationship is adopted.

  In addition, in order to confirm the air dispersion status of the porous concrete layer after placing the porous concrete on the site implementation site, the air washing blower is operated from a state where water is stretched on the porous concrete layer at a depth of several centimeters. Thus, a method is employed in which air backwashing is actually performed, and the occurrence of bubbles on the water surface is visually confirmed on the porous concrete layer.

  On the other hand, Patent Document 1 proposes a sound wave type high-performance pavement voidage detection device that measures the internal voidage of a high-performance pavement while traveling at high speed in a non-contact, non-destructive manner. The sound wave type high-performance pavement voidage detection device is configured such that a sound insulation box whose one end is opened toward a road surface is attached to a road surface voidage measurement vehicle, and a speaker and a microphone are arranged in the sound insulation box.

  While driving the road surface porosity measurement car at high speed, emit a pulse sound from the speaker, and the pulse sound emitted from the speaker reaches the microphone before it reaches the road surface, and the pulse sound is reflected by the road surface and reflected on the microphone. The reflected wave that has arrived is detected by a microphone, and the internal porosity of the high-performance pavement is determined based on the ratio of the incident wave and the reflected wave.

JP 2003-83943 A

  However, the measurement method using the Archimedes method can accurately measure the porosity of the specimen, but because the placement range and compaction method are different from the actually placed porous concrete, the measured specimen There is concern that the value is different from the porosity.

  In addition, the method for visually confirming the state of bubble generation has a risk that the porosity cannot be quantitatively grasped, and the judgment on the state of bubble generation may vary depending on the measurer. In addition, if the blower equipment that supplies air to the air dispersion beam and the water supply / drainage equipment of the filter basin are not installed after the construction, the plant equipment necessary for the test is temporarily installed and the test is performed. And had to spend time.

  Moreover, since the sound wave type high-performance pavement voidage detection device described in Patent Document 1 measures a vehicle by traveling at a speed of 80 Km / h or more, it detects a rough value even if it is a road porosity. However, since it is not supposed to detect subtle changes in the porosity of details, it is not suitable for applications that accurately detect the distribution of porosity, such as the porous concrete layer of the lower water collector. In addition to the ratio of incident wave and reflected wave to the actual road surface, it is necessary to correct the sound pressure fluctuation of the pulse source based on the ratio of incident wave and reflected wave to the concrete surface as a reference There was a problem.

  The object of the present invention is to provide a porosity measuring device and a porosity evaluation method capable of accurately detecting the distribution of the porosity as in the porous concrete layer of the lower water collecting device in view of the above-described problems. is there.

In order to achieve the above-mentioned object, the first characteristic configuration of the porosity measuring device according to the present invention is that the porosity of the porous concrete in the filter basin is the vibration characteristic of air as described in claim 1 of the claims. A void ratio measuring apparatus for measuring the volume based on the first sound insulation chamber and the second sound insulation chamber each having an opening formed on one end thereof so as to face the porous concrete, and the first sound insulation chamber is provided with air. A vibration source is installed, a first vibration measurement sensor that measures the intensity of the direct vibration output from the air vibration source is installed, and the second sound insulation chamber outputs the air from the air vibration source to the porous concrete. A second vibration measurement sensor for measuring the reflected vibration intensity is installed ,
An evaluation unit that evaluates the porosity of the porous concrete based on the correlation between the output of the first vibration measurement sensor and the output of the second vibration measurement sensor;
It is in the point equipped with .

By measuring how much the reflected vibration intensity reflected by the porous concrete is attenuated against the intensity of the direct vibration output from the air vibration source, the porosity of the porous concrete to be measured falls within the allowable range. It can be evaluated whether or not it is within. This is because the reflected vibration intensity indicates the degree to which the intensity of the direct vibration incident on the porous concrete is attenuated by the gap. For this reason, an air vibration source and a vibration measurement sensor are installed in the sound insulation chamber to shield external noise. However, in order to evaluate whether or not the porosity of the porous concrete is within the allowable range, it is necessary that the reflected vibration intensity changes appropriately with the porosity inside and outside the allowable range of the porosity. If the change in the reflected vibration intensity is small or does not change on the inside or outside, there is a possibility that it cannot be evaluated correctly. According to the above-described configuration, the reflected vibration intensity detected by the second vibration measurement sensor on the inner side and the outer side of the allowable range of the void ratio through the openings of the first and second sound insulation rooms arranged adjacent to each other. The reflection vibration intensity from the porous concrete can be obtained so as to change appropriately. As a result, the porosity of the porous concrete is appropriately evaluated by the evaluation unit.

  The second characteristic configuration is a porosity measuring device that measures the porosity of the porous concrete based on acoustic characteristics in addition to the first characteristic configuration described above, as described in claim 2, A first sound insulation chamber and a second sound insulation chamber having an opening formed on one end side so as to face the porous concrete are disposed adjacent to each other through a boundary wall, and a sound source is installed in the first sound insulation chamber and the sound source A first acoustic sensor that measures the acoustic intensity of the output direct sound is installed, and is output from the sound source to the second sound insulation chamber and from a gap portion of a predetermined size formed between the boundary wall and the porous concrete. A second acoustic sensor for measuring the reflected acoustic intensity from the propagating porous concrete is provided.

  A sound source is preferably used as the air vibration source. By measuring how much the sound intensity of the reflected sound reflected by the porous concrete is attenuated with respect to the sound pressure or sound intensity of the direct sound output from the sound source, the porosity of the porous concrete to be measured is measured. It can be evaluated whether or not is within an allowable range. This is because the sound intensity of the reflected sound indicates the degree to which the incident sound on the porous concrete is attenuated by the gap. In order to evaluate whether or not the porosity of the porous concrete is within an allowable range, it is preferable to set the gap formed between the boundary wall and the porous concrete to a predetermined size. The reflected acoustic intensity from the porous concrete can be obtained so that the acoustic intensity of the reflected sound detected by the second acoustic sensor on the inside and outside changes appropriately.

In the third feature configuration, in addition to the second feature configuration described above, the boundary among the openings of the first sound insulation chamber and the second sound insulation chamber facing the porous concrete is the boundary. There exists the point in which the obstruction | occlusion member which obstruct | occludes area | regions other than the predetermined width area | region facing the lower end of a wall is installed.

  According to the above configuration, the area where the direct sound output from the sound source is incident on the porous concrete is limited to a predetermined width area facing the lower end of the boundary wall by the closing member, so that the intensity of the sound source is not increased so much. However, the degree of attenuation by the porous concrete can be detected efficiently and accurately, and the reflected sound from the porous concrete can be reliably received by the second acoustic sensor.

In the fourth feature configuration, in addition to the second or third feature configuration described above, in addition to the above-described second or third feature configuration, a close contact member in which the peripheral portion of the opening closely contacts the porous concrete surface is provided. It is in the point provided.

  If there is a gap between the periphery of the opening and the surface of the porous concrete, not only the acoustic energy output from the sound source leaks from the gap, but also external noise enters through the gap, preventing accurate measurement. Although there is a possibility, since such a gap is closed by the close contact member, accurate measurement is possible even when the porous concrete surface has irregularities. Furthermore, since such a gap is closed by the close contact member, accurate measurement is possible even in a place where the surface of the porous concrete has irregularities, while easily changing the measurement place of the porous concrete.

In addition to any one of the second to fourth feature configurations described above, the fifth feature configuration includes a speaker that outputs white noise of a predetermined intensity, as described in claim 5. The first acoustic sensor and the second acoustic sensor include a frequency band selection unit that selectively measures acoustic intensity in a frequency band individually set by the porous concrete among white noise.

  Even if the porosity of the porous concrete to be measured is the same, the frequency range of the sound source to be attenuated differs if the average size or size distribution of each void is different. However, if the sound source is composed of a speaker that outputs white noise of a predetermined intensity, it is not necessary to adjust the frequency of the sound source according to the average size or size distribution of the air gap, and the first acoustic sensor and the second acoustic sensor are provided. A signal in a frequency band adapted to the size of the void in the porous concrete can be obtained via the frequency band selection unit.

In the sixth feature configuration, as described in claim 6, in addition to any of the second to fourth feature configurations described above, the sound source is a sound in a frequency band individually set by the porous concrete. Is composed of a frequency band selection unit that selects the sound and a speaker that outputs sound in the frequency band selected by the frequency band selection unit.

  As described above, even if the porosity of the porous concrete to be measured is the same, if the average size or size distribution of each void is different, the frequency range of the sound source to be attenuated is different. An average size or size distribution of voids in the porous concrete by the first acoustic sensor and the second acoustic sensor by comprising a frequency band selection unit and a speaker that select and output sound in a frequency band adapted to the average size or size distribution. Can be obtained in a frequency band adapted to.

In addition to any one of the second to sixth characteristic configurations described above, the seventh characteristic configuration includes a gap portion formed between the boundary wall and the porous concrete as described in claim 7. In other words, a gap adjusting mechanism for adjusting the gap width is provided.

  Even when the appropriate porosity range of the porous concrete to be measured is different, or when the average size or size distribution of the voids is different, a gap adjustment mechanism is provided for the gap formed between the boundary wall and the porous concrete. By adjusting the gap width, it is possible to balance so as to minimize the influence of the acoustic intensity that is output from the sound source and propagates directly from the gap, and maximize the intensity of the reverberant sound from the porous concrete. This is a general-purpose porosity measurement device capable of measuring the sound absorption characteristics of concrete with high sensitivity.

In the eighth feature configuration, in addition to the seventh feature configuration described above, the length of the gap is set to 15 to 30 mm, and the speaker or the first feature configuration is described. The frequency band selected by the frequency band selector provided in the acoustic sensor and the second acoustic sensor is set in a range of 5 to 8 kHz.

  If the length of the gap and the frequency band selected by the frequency band selector are set in the above numerical range, the porosity of the porous concrete floor placed in the filter basin can be properly evaluated. It becomes a porosity measuring device.

  The first characteristic configuration of the porosity evaluation method according to the present invention is the porosity evaluation using the porosity measuring device having any one of the first to eighth characteristic configurations described above. In the method, the first vibration measurement sensor and the first vibration sensor are installed when a predetermined vibration is output from an air vibration source by installing the porous concrete so that openings of the first sound insulation chamber and the second sound insulation chamber are opposed to each other. A ratio or difference of vibration intensities detected by the second vibration measurement sensor is calculated, and based on the calculated value, it is estimated whether or not the porosity of the porous concrete is within an allowable range.

  Based on the ratio or difference between the vibration intensities detected by the first vibration measurement sensor and the second vibration measurement sensor, it can be estimated whether the porosity of the porous concrete is within an allowable range.

  As described above, according to the present invention, it is possible to provide a porosity measuring device and a porosity evaluation method capable of accurately detecting the distribution of the porosity as in the porous concrete layer of the lower water collecting device. Became.

Explanatory drawing of the lower water collecting device provided in the filter (A) is explanatory drawing of a filtration process, (b) is explanatory drawing of a washing | cleaning process. (A) is a plan view of the porosity measuring device, (b) is the front view, (c) is the back view, and (d) is the side view. (A) is a block diagram of the wall part of the porosity measuring device, (b) is an explanatory diagram of the measurement principle of the porosity measuring device (A) is a characteristic diagram of the porosity with the gap length L of the boundary wall as a parameter and the measured sound volume in the second sound insulation chamber, and (b) is a porous concrete layer in the frequency band of the sound source from 5 k to 8 kHz. Figure of porosity characteristics (A) is explanatory drawing of the porous concrete layer divided into the predetermined size, (b) is explanatory drawing of the measurement position at the time of re-measurement in the division (A) is a chart of volume reduction and judgment result for each category, (b) is a volume reduction distribution characteristic diagram showing the measurement result. Flow chart showing the evaluation procedure for porosity of porous concrete layer (A) is explanatory drawing of the upper limit and lower limit threshold value for evaluating the porosity of a porous concrete layer, (b) is setting explanatory drawing of a lower limit threshold value, (c) is setting explanatory drawing of an upper limit threshold value

Hereinafter, a porosity measuring device and a porosity evaluation method according to the present invention will be described with reference to the drawings.
FIG. 1 shows a lower water collecting apparatus 1 installed in the filtration basin A. In the lower water collecting apparatus 1, a plurality of air dispersion beams 2 in which minute air outlets 2a are arrayed are arranged in parallel in the short direction of the rectangular bottom at the rectangular bottom of each of the plurality of concrete treatment tanks installed adjacent to each other. Slit plates 3 arranged in a posture and having a SUS net 3a formed on the adjacent air dispersion beams 2 are arranged. An air bottle 7 is formed at one end of the air dispersion beam 2, and air can be ejected from the air outlet 2 a formed in each air dispersion beam 2 from the air bottle 7.

  Further, a dispersed gravel layer 4 in which dispersed gravel is spread is formed on the upper portion of the slit plate 3, and a porous concrete layer 5 which is a porous body is formed on the upper portion thereof. The upper part of the porous concrete layer 5 is filled with a filter medium 6 such as activated carbon or anthracite, and treated water Wt is supplied from above.

  FIG. 2A shows a cross-sectional view of the lower water collecting apparatus 1 in the filtration process. Inflow water to the filtration basin A flows into the drainage basin 10 from the inflow basin 8 through the inflow gate G1, and flows into the lower water collecting apparatuses 1 via the troughs 11 provided in the drainage basin 10.

  The treated water is subjected to the adsorption treatment of the pollutant in the packed layer of the filter medium 6 of the lower water collecting apparatus 1, and further flows out downward from the pores formed in the porous concrete layer 5, via the flow meter Q and the flow control valve V1. It is taken out as filtered water. In the figure, B is a blower, and M is an opening / closing drive for the inflow gate G1 and the drain gate G2.

  FIG. 2B shows a cross-sectional view of the lower water collecting apparatus 1 in the cleaning process. If a certain amount of pollutant accumulates in the packed bed of the filter medium 6 by continuing the filtration process, the filtration performance will deteriorate. Therefore, a cleaning process for cleaning the filter medium 6 and removing the pollutant is performed.

  First, the inflow gate G1 is closed from the filtration step of FIG. 2 (a), the filtered water is drained from the lower water collecting apparatus 1, and the drainage gate G2 is opened to drain the treated water from the drainage basin 10. The process is executed.

  Thereafter, the flow regulating valve V1 is closed and the backwash valve V2 is opened, and the washing water is injected from the lower surface of the porous concrete layer 5 to the packed layer of the filter medium 6, and the blower B is activated to air from the air tank 7 Air is injected into the dispersion beam 2, and air is ejected from each air outlet 2 a formed in the air dispersion beam 2.

  The water level gradually rises by pouring the washing water, and at this time, the granular filter medium 6 is vigorously stirred by water and air, and the pollutant is separated from the filter medium 6 and floats on the washing water.

  Immediately before the water level reaches the trough 11, the blower B is stopped, and the pollutant floating in the washing water flows out from the trough 11 to the drainage basin 10 together with the washing water, and is drained from the drain gate G2.

  As described above, the porous concrete layer 5 needs to pass filtered water from the upper side to the lower side in the filtration step, and it is necessary to pass the cleaning water from the lower side to the upper side in the cleaning step. Therefore, the porosity needs to be adjusted to a range of 25 to 35%.

  Such a porous concrete layer 5 is constructed by being placed on a dispersed gravel layer 4 with a thickness of 70 mm and compacted. Although the pond size differs depending on the water purification plant, the placement area is generally When the length is about 10-15m, the width is about 3-5m, and the area is very wide, and even if the void ratio deviates from the range of 25-35% even in a part of the area, appropriate filtration process and washing process in that area Cannot be done.

  The porosity measuring device according to the present invention is a portable device that measures the porosity of a porous body based on acoustic characteristics. For example, the porosity of the porous concrete layer 5 as the porous body described above can be determined during construction or It is an apparatus that is used for evaluating whether or not the porosity is within an appropriate range, measured during maintenance.

FIGS. 3A to 3D show an overview of the porosity measuring device 20.
In the porosity measuring device 20, a first sound insulation chamber 21 and a second sound insulation chamber 22 having openings 24 and 25 formed on one end side so as to face the porous body 5 are disposed adjacent to each other via a central boundary wall 23. A sound source 30 made of a speaker is installed in the first sound insulation chamber 21, and a first acoustic sensor 32 made of a microphone that measures the sound intensity of the direct sound output from the sound source 30 is installed, and a sound source is installed in the second sound insulation chamber 22. The second sound composed of a microphone that measures the acoustic intensity directly output from the gap portion 26 of a predetermined size that is output from 30 and formed between the boundary wall 23 and the porous body 5 and the reflected acoustic intensity from the porous body 5. A sensor 34 is installed. The sound source 30 is an air vibration source of the present invention.

  As shown in FIG. 4A, the wall portion and the boundary wall 23 forming the first sound insulation chamber 21 and the second sound insulation chamber 22 are both polyvinyl chloride sheets on both sides of a thick plate-like sound absorbing member. It is made of a plate material with a thickness of about 35 mm and is insulated so that noise from the outside does not enter the first sound insulation chamber 21 and the second sound insulation chamber 22, and the sound output from the sound source 30 is not absorbed. It is configured to be reflected by a sheet made of polyvinyl chloride.

  The first sound insulation chamber 21 and the second sound insulation chamber 22 are configured by a rectangular parallelepiped having a width of 200 mm, a height of 360 mm, and a depth of 230 mm, and the length L of the gap between the surface position of the openings 24 and 25 and the lower end of the boundary wall 23. Is set in a range of 15 to 30 mm.

  A gap adjusting mechanism 40 that adjusts the gap width L of the gap formed between the boundary wall 23 and the porous body 5, that is, the gap between the surface position of the openings 24 and 25 and the lower end of the boundary wall 23 is a boundary. It is provided on the wall 23. The gap adjusting mechanism 40 is configured by a gap adjusting member having a U-shaped cross section that is bolt-fixed at the lower end portion of the boundary wall 23 so as to be vertically adjustable.

  In order to evaluate whether or not the porosity of the porous body 5 is within the allowable range, the sound intensity of the reflected sound is appropriate within the allowable range of the porosity, in this embodiment, inside and outside the porosity of 25 to 35%. If the change in the acoustic intensity of the reflected sound is small or does not change inside or outside the allowable range, there is a possibility that the evaluation cannot be performed correctly.

  As shown in FIG. 5A, when the horizontal axis is the void ratio and the vertical axis is the output Po of the second acoustic sensor 34, the acoustic intensity at the boundary and inside of the allowable range, as indicated by a broken line or a dashed line. In the case where the change of is small or hardly changes, the correlation with the porosity cannot be found properly. Even in such a case, the correlation can be obtained by adjusting the length L of the gap formed between the boundary wall 30 and the porous body 5. In the present embodiment, when the gap length L is set in the range of 15 to 30 mm, preferably in the range of 20 to 30 mm, in the range of the porosity of 25 to 35% and its boundary region, it becomes large as shown by the solid line in the figure. An inclined favorable characteristic can be obtained.

  That is, by adjusting the gap L formed between the boundary wall 30 and the porous body 5, the influence of the directly propagated acoustic intensity is minimized and the reflected acoustic intensity from the porous body 5 is maximized. To be able to balance.

  FIG. 4B shows the measurement principle of the porosity measuring device 20. The acoustic intensity of the direct sound output from the sound source 30 installed in the first sound insulation chamber 21 is detected by the first acoustic sensor 32, enters the porous body 5 through the openings 24 and 25, and is reflected by the porous body 5. The reflected sound and the acoustic intensity of the direct sound that has passed through the gap width L of the boundary wall 23 are detected by the second acoustic sensor 34 installed in the second sound insulation chamber 22.

  There is a correlation between the ratio (Pi / Po, or 10 Log (Pi / Po)) of the output Pi of the first acoustic sensor 32 and the output Po of the second acoustic sensor 34 and the porosity of the porous body 5. Therefore, it can be evaluated whether or not the porosity of the porous body is within an allowable range.

  That is, when the porosity of the porous body 5 is large, the sound output from the sound source 30 is greatly absorbed and attenuated by the porous body 5, so that the acoustic intensity of the reflected sound is reduced and the porosity of the porous body 5 is reduced. When the rate is small, the sound output from the sound source 30 is not so much attenuated and attenuated by the porous body 5, so that the acoustic intensity of the reflected sound becomes relatively large. As a result, it can be evaluated whether or not the porosity of the porous body to be measured is within an allowable range. Note that there is also a correlation between the difference (Pi−Po) between the output Pi of the first acoustic sensor 32 and the output Po of the second acoustic sensor 34 and the porosity of the porous body 5. Any value can be evaluated. Below, the example which uses a difference is demonstrated.

  A non-sound-absorbing blocking member that blocks a region other than the predetermined width region W facing the lower end of the boundary wall 23 among the openings 24 and 25 facing the porous body 5 of the first sound insulating chamber 21 and the second sound insulating chamber 22. (Sheet) 27 and 28 are installed. As the closing member, a sheet made of polyvinyl chloride is used.

  The region where the direct sound output from the sound source 30 is incident on the porous body 5 is limited to a region having a predetermined width W (see FIG. 3C) facing the lower end of the boundary wall 23 by the blocking members 27 and 28. Therefore, even if the intensity of the sound source 30 is not increased so much, the degree of attenuation by the porous body 5 can be detected efficiently and accurately. The predetermined width W includes the thickness of the boundary wall 23 of 35 mm, preferably in the range of 100 to 160 mm, and more preferably in the range of 120 to 140 mm.

  Furthermore, it is preferable that a close contact member is provided in which the peripheral end faces of the openings 24 and 25 are in close contact with the surface of the porous body 5, and even if the surface of the porous body 5 is uneven, the close contact member Since such a gap is closed, it is possible to prevent acoustic energy output from the sound source 30 from leaking out of the gap or external noise from entering the gap, thereby enabling accurate measurement.

  As the close contact member, an elastic member such as urethane foam covered with a polyvinyl chloride sheet can be suitably used. By covering the foamed urethane with the above-described non-sound-absorbing blocking members (sheets) 27 and 28, it is also possible to use the urethane foam as a close contact member.

  Further, the sound source 30 is configured by a speaker connected to a noise generator that outputs white noise of a predetermined intensity, and is individually set by the porous body 5 among the white noise in the first acoustic sensor 32 and the second acoustic sensor 34. A frequency band selection unit capable of selectively measuring the acoustic intensity of the frequency band. Furthermore, the noise generator may be provided with a frequency band selection unit that outputs only the frequency band set individually among the white noise.

  Even if the porosity of the porous body 5 to be measured is the same, the frequency range of the sound source to be attenuated is different if the average size or size distribution of each void is different. However, if the sound source 30 is composed of a speaker that outputs white noise of a predetermined intensity, there is no need to adjust the frequency of the sound source according to the average size or size distribution of the air gaps, and the first acoustic sensor 32 and the second acoustic sensor 34. A frequency band signal adapted to the size of the voids of the porous body 5 can be obtained via the frequency band selector provided in the above. If the measurement frequency band of the acoustic sensor can be adjusted, the apparatus can be generalized. Furthermore, the frequency band of the white noise output from the noise generator may be selected and output by the frequency band selection unit.

  If the frequency band adapted to the size of the gap of the porous body 5 is known, the sound source 30 can be constituted by a speaker that outputs sound in a frequency band individually set by the porous body 5. .

  When the object to be measured is the porous concrete layer 5 described above, in order to obtain an appropriate frequency band, white noise sound was output from the sound source 30 and octave analysis was performed. As a result, as shown in FIG. 5 (b), it was confirmed that the reduced sound volume Pi-Po shows a good correlation in the frequency band of 5k to 8kHz with respect to the range where the porosity is 25 to 35%. At this time, the gap length L of the boundary wall 23 is set to a range of 15 to 30 mm.

  That is, when measuring the porosity of the floor surface made of porous concrete placed in the filtration pond, the length L of the gap is set to 15 to 30 mm, and the selected frequency band of the acoustic sensor is 5 k to When it is set in the range of 8 kHz, the porosity can be evaluated satisfactorily.

  As shown in FIG. 4 (b), the porosity evaluation method according to the present invention is a porosity evaluation method using the above-described porosity measurement device 20, and the first sound insulation chamber 21 and the second sound insulation are formed in the porous body 5. Installed so that the openings 24 and 25 of the chamber 22 face each other, and calculates a difference in acoustic intensity detected by the first acoustic sensor 32 and the second acoustic sensor 34 when a predetermined sound is output from the sound source 30; Based on the calculated value, it is estimated whether or not the porosity of the porous body 5 is within an allowable range.

  The allowable range will be described. Among the plurality of calculated values obtained by repeating the measurement process for calculating the difference in acoustic intensity, in this case, the volume reduction Pi-Po, for a plurality of porous bodies having different porosity, the porosity is the upper limit of the allowable range. The calculated value indicating the upper predetermined ratio (rejection rate) of the relative frequency distribution of the calculated value for the porous material is set as the allowable upper limit value, and the calculated relative value of the porous material whose porosity is the lower limit of the allowable range is below The calculated value indicating the predetermined predetermined ratio (rejection rate) is set as the allowable lower limit value, and the allowable upper limit value and the allowable lower limit value are set as the allowable range.

  In FIG. 9 (a), the length L of the gap is variably adjusted in the range of 15 to 30 mm for nine porous concrete samples having a porosity in the range of 25% to 35%. The distribution diagram characteristics of the reduced sound volume Pi-Po measured each time a plurality of times are shown.

  As shown in FIGS. 9B and 9C, the relative frequency for each sample almost shows a normal distribution. Therefore, the upper limit value and the lower limit value were determined with reference to the p value in statistics. The p value refers to the rejection rate of extreme numerical values (left and right end portions in the relative frequency distribution diagram) in the measurement data. Normally, the p value is a constant value between 5% and 10% of the rejection rate, but is set to a rejection rate of 20% in order to ensure the reliability of the measurement data, and an upper limit value and a lower limit value are calculated for each sample.

  As shown in FIGS. 9B and 9C, the highest upper limit value among the nine samples is 15.44 dB with a porosity of 34.5%, and the lowest lower limit value is with a porosity of 25. It was 9%, 10.54 dB. The dashed-dotted line shown in FIG. 9A is a line segment indicating the allowable upper limit value 15.44 dB and the allowable lower limit value 10.54 dB.

Hereinafter, a specific measurement procedure will be described.
As shown in FIG. 6 (a), in the case of a porous concrete layer having a pond area of 15000 mm in length and 3500 mm in width, 30 small areas of 1500 mm × 1170 mm square are divided into 10 equal parts in the vertical direction and 3 equal parts in the horizontal direction. Each of the small areas is numbered 1 to 30 and the porosity measuring device 20 is installed in the center of each small area to calculate the volume reduction Pi-Po multiple times, and the average value is the small value. The representative value of the area. The size of the small region is preferably in the range of 1000 mm × 1000 mm to 2000 mm × 2000 mm.

  When measuring a porous material with a large area, it takes a lot of time to measure it if it is measured many times with a fine measurement pitch. However, the porous material is divided into predetermined sizes and measured at least at one location for each section. Based on the calculated values obtained in this manner, efficient measurement can be performed by estimating whether the porosity of the entire area of the porous body is within the allowable range.

  FIG. 7A shows the volume reduction and the judgment value for the measurement points numbered 1 to 30, and FIG. 7B shows the distribution characteristics of the volume reduction at that time. .

  FIG. 8 shows evaluation procedures and evaluation criteria for determination. For each processing tank, a first evaluation step is executed to determine whether or not the volume reduction in each small region is within the allowable range of the allowable upper limit value of 15.44 dB and the allowable lower limit value of 10.54 dB (S1). When 80% or more of the number of small areas are within the allowable range (S1, Y), whether or not the volume reduction at each measurement point of the adjacent small areas does not deviate from the allowable range. The second evaluation step is executed. When both do not deviate from the permissible range (S2, Y), it is determined that the porous concrete floor portion is in the range of 25 to 35% porosity (S3). .

  In the first evaluation step, when it is determined that more than 20% of the number of small regions are not within the allowable range (S1, N), the porous evaluation is made without waiting for the second evaluation step. The floor is determined to be inappropriate (S5).

  If it is determined in the second evaluation step of step S2 that the volume reductions of the two adjacent small areas are both out of the allowable range, as shown in FIG. The five re-measurement points are set to be evenly spaced on the circumference of a circle with a radius of 500 mm centered on the position, and the volume reduction at each re-measurement point is the above-described allowable upper limit value of 15.44 dB and the allowable lower limit value. It is determined whether or not it is within the range of 10.54 dB, and if it is determined that 80% (that is, four locations) are within the range (S4), step S2 is executed again (S2).

  When the second evaluation step is executed in step S2 to determine whether or not the volume reduction at each measurement point of the adjacent small area does not deviate from the allowable range, and both do not deviate from the allowable range. (S2, Y), the porosity is in the range of 25 to 35%, and it is determined that the floor portion made of porous concrete is appropriate (S3).

  If the range of the small region is in the range of 1000 mm × 1000 mm to 2000 mm × 2000 mm, the five remeasurement points are evenly distributed within the small region and separated from each other by about 500 mm, so that sufficient measurement accuracy can be obtained. . In other words, the measurement points for remeasurement need to be a plurality of measurement points that are evenly distributed within the small area with respect to the first measurement point.

  According to this procedure, the porous concrete layer showing the volume reduction distribution characteristic of FIG. 7B deviates from the allowable range in the small region of number 20, but is within the allowable range in the other small regions. The above evaluation criteria are satisfied and it is determined that the construction state is appropriate.

  If there is a problem in the pouring method or compacting method of porous concrete, it will have a great influence on water treatment in a wide range. Therefore, a broad definition is defined as two or more adjacent small regions. The adjacent direction of the region is a concept including not only the front-rear direction and the up-down direction but also the oblique direction.

  That is, the porosity evaluation method according to the present invention divides a porous body having a large area into a predetermined size, calculates a ratio or difference in acoustic intensity at at least one location for each section, and based on the calculated value, calculates the porosity. Estimate whether the porosity of the whole body is within the allowable range, and calculate the ratio or difference of the sound intensity at multiple positions separated by a predetermined distance from the measurement location for the category where the calculated value deviates from the allowable range When the ratio of the number of measurement positions whose calculated values are within the allowable range is equal to or greater than a predetermined ratio, it is estimated that the category is within the allowable range.

  In the above-described embodiment, the porosity measuring device that mainly measures the porosity of the floor surface made of porous concrete placed in the filtration pond has been described. However, the measurement target of the porosity measuring device according to the present invention is porous concrete. It is not limited to the floor surface made of a product, and the porosity of an arbitrary porous body can also be measured.

  When evaluating the porosity of the porous concrete layer, it is preferable that the length L of the gap is set to 15 to 30 mm and the selection frequency band of the acoustic sensor is set to a range of 5 to 8 kHz. The length L of the part and the selected frequency band of the acoustic sensor are values that are appropriately set according to the measurement target.

  In the above-described embodiment, the gap adjusting mechanism 40 is provided in the boundary wall 23 and the porosity measuring device having versatility has been described. However, the boundary wall 23 and the porous body 5 are not provided without the gap adjusting mechanism 40. The length of the gap formed between the two may be set to an appropriate value in advance according to the measurement target.

  In the above-described embodiment, the case where the sound insulation chambers 21 and 22 have a rectangular parallelepiped shape has been described. However, the sound insulation chambers 21 and 22 may be partitioned by the boundary wall 23, and the shape is not particularly limited. For example, the sound insulation chambers 21 and 22 may be formed of a cylindrical body having a curved peripheral wall.

  In the embodiment described above, the first sound insulation chamber and the second sound insulation chamber having an opening formed on one end side so as to face the porous body are disposed adjacent to each other through the boundary wall, and the sound source is installed in the first sound insulation chamber. And a first acoustic sensor for measuring the acoustic intensity of the direct sound output from the sound source, and a gap of a predetermined size formed between the boundary wall and the porous body output from the sound source in the second sound insulation chamber. The porosity evaluation method using the porosity measuring device in which the second acoustic sensor for measuring the reflected acoustic intensity from the porous body propagating from the part has been described. However, the porosity evaluation method itself has the above-described configuration. If it is a porosity measuring device that can be employed when using a porosity measuring device other than the porosity measuring device equipped with, and obtain the porosity of the porous body by measuring the reflected acoustic intensity from the porous body Using a porosity measuring device of any configuration It is possible to evaluate the porosity.

  That is, as a porosity evaluation method using a porosity measuring device that measures the reflected acoustic intensity from a porous body to determine the porosity of the porous body, the acoustic strength is applied to a plurality of porous bodies having different porosity in advance. Among the plurality of calculated values obtained by repeating the measurement process for calculating the ratio or difference of the ratio, the calculated value indicating the upper predetermined ratio of the relative frequency distribution of the calculated value with respect to the porous body whose porosity is the upper limit of the allowable range is the allowable upper limit Set the calculated value indicating the lower predetermined ratio of the relative frequency distribution of the calculated value to the porous body whose porosity is the lower limit of the allowable range, and set the calculated value of the porous body to be measured as the allowable lower limit value. Can be estimated whether or not the porosity of the porous body is within the allowable range based on whether or not is between the allowable upper limit value and the allowable lower limit value.

  Also, the planar porous body is divided into predetermined sizes, and the ratio or difference of the acoustic intensity is calculated at least at one location for each section, and the porosity of the entire area of the porous body is within an allowable range based on the calculated value. The ratio or difference of the sound intensity is calculated at a plurality of positions separated by a predetermined distance from the measurement location for the category where the calculated value deviates from the allowable range, and the calculated value falls within the allowable range. When the ratio of the number of certain measurement positions is equal to or greater than a predetermined ratio, it can be estimated that the division is within the allowable range.

  In the above description, in the porosity measuring device of the present invention, the first sound insulation chamber and the second sound insulation chamber in which an opening is formed on one end side so as to face the porous concrete are disposed adjacent to each other through the boundary wall. A sound source is installed in the sound insulation room and a first acoustic sensor is installed to measure the sound intensity of the direct sound output from the sound source, and is formed between the boundary wall and the porous concrete output from the sound source in the second sound insulation room. Although the description has focused on the optimum example in which the second acoustic sensor for measuring the reflected acoustic intensity from the porous body propagating from the gap portion of the predetermined size is provided, the porosity measuring device of the present invention is The frequency is not limited as long as the porosity is measured based on the vibration characteristics of air, not limited to the one that measures the porosity based on the acoustic intensity of the frequency.

  That is, the first sound insulation chamber and the second sound insulation chamber having an opening formed on one end side so as to face the porous concrete are disposed adjacent to each other, and an air vibration source is installed in the first sound insulation chamber and output from the air vibration source. The first vibration measurement sensor that measures the intensity of the direct vibration is installed, and the second vibration measurement sensor that measures the reflected vibration intensity from the porous concrete that is output from the air vibration source is installed in the second sound insulation chamber. If it is.

  Specifically, the porosity measuring device may be configured such that the boundary wall extends to the surface of the porous concrete and no gap is formed. Moreover, the porosity measuring apparatus should just have the 1st sound insulation room and the 2nd sound insulation room which the opening part was formed in the one end side adjacently arranged, and the 1st sound insulation room and the 2nd sound insulation room have a common boundary wall. It does not need to be adjacently arranged.

  The above-described embodiment is one aspect of the present invention, and the present invention is not limited by the description. Specific configurations and control aspects of each part can be appropriately changed and designed within the scope of the effects of the present invention. Needless to say.

5: Porous body 20: Porosity measuring device 21: first sound insulation chamber 22: second sound insulation chamber 23: boundary wall 30: sound source 32: first acoustic sensor 34: second acoustic sensor

Claims (9)

A porosity measuring device for measuring porosity of porous concrete in a filtration basin based on vibration characteristics of air,
A first sound insulation chamber and a second sound insulation chamber having an opening formed on one end side so as to face the porous concrete are disposed adjacent to each other,
An air vibration source is installed in the first sound insulation chamber, and a first vibration measurement sensor for measuring the intensity of the direct vibration output from the air vibration source is installed,
A second vibration measurement sensor that is output from the air vibration source and measures the reflected vibration intensity from the porous concrete is installed in the second sound insulation chamber ;
An evaluation unit that evaluates the porosity of the porous concrete based on the correlation between the output of the first vibration measurement sensor and the output of the second vibration measurement sensor;
And has porosity measurement device includes a. A porosity measuring device for measuring the porosity of the porous concrete based on acoustic characteristics,
A first sound insulation chamber and a second sound insulation chamber having an opening formed on one end side so as to face the porous concrete are disposed adjacent to each other through a boundary wall,
A sound source is installed in the first sound insulation chamber, and a first acoustic sensor that measures the acoustic intensity of the direct sound output from the sound source is installed,
A second acoustic sensor that measures the reflected acoustic intensity from the porous concrete that is output from the sound source and propagates through a gap of a predetermined size formed between the boundary wall and the porous concrete is installed in the second sound insulation chamber. The porosity measuring device according to claim 1. The space | gap of Claim 2 in which the obstruction | occlusion member which obstruct | occludes area | regions other than the predetermined width area | region which opposes the lower end of the said boundary wall among the opening parts which face the said porous concrete of a 1st sound insulation room and a 2nd sound insulation room is installed. Rate measuring device. The porosity measuring device according to claim 2 or 3, wherein a close contact member is provided in which a peripheral portion of the opening closely contacts the surface of the porous concrete. The sound source is configured with a speaker that outputs white noise of a predetermined intensity, and the first acoustic sensor and the second acoustic sensor are selectively configured to have acoustic intensity in a frequency band individually set by the porous concrete among white noise. The porosity measuring device according to any one of claims 2 to 4, further comprising a frequency band selection unit for measurement. They claim 2, wherein the instrument is configured by a speaker for outputting a sound of a frequency band selected by its frequency band selection unit frequency band selection unit for selecting a sound of a frequency band set individually by the porous concrete 5. The porosity measuring device according to any one of 4 above. The porosity measuring device according to claim 2, further comprising a gap adjusting mechanism that adjusts a gap width of a gap formed between the boundary wall and the porous concrete. The length of the gap is set to 15 to 30 mm, and the selection frequency band by the frequency band selection unit provided in the speaker or the first and second acoustic sensors is set to a range of 5 to 8 kHz. The porosity measuring device according to claim 7 . A porosity evaluation method using the porosity measuring device according to any one of claims 1 to 8,
The first vibration measurement sensor and the second vibration measurement sensor are installed when the porous concrete is installed so that the openings of the first sound insulation chamber and the second sound insulation chamber face each other and a predetermined vibration is output from an air vibration source. The porosity evaluation method of calculating the ratio or difference of the vibration intensity detected in step (a) and estimating whether the porosity of the porous concrete is within an allowable range based on the calculated value.