JP7377484B2 - Detection device and detection method - Google Patents

Description

The present disclosure relates to a detection device and a detection method, and particularly relates to a clay mineral detection device and a detection method.

For example, in mountain tunnel construction, etc., if clay minerals are contained in the ground forming the face, the clay minerals absorb water and swell, thereby reducing the diameter of the tunnel.

If such swelling of clay minerals occurs before the lining concrete is placed, it will be necessary to re-excavate the area, which will significantly affect the construction period and cost. Furthermore, if swelling of clay minerals occurs after the lining concrete is placed, there is also the problem of causing cracks in the concrete. For this reason, it is extremely important to properly understand the clay minerals contained in the ground in mountain tunnel construction.

For example, Patent Document 1 discloses a technique for irradiating a sample taken from a target ground with X-rays, capturing fluorescent X-rays, and analyzing the presence or absence and amount of multiple elements contained therein.

Japanese Patent Application Publication No. 2017-197955

By the way, in order to grasp the state of the entire face using the technique described in Patent Document 1, it is necessary to collect and analyze a large amount of samples from the face. For this reason, there is a problem that a lot of labor and time are required for sample collection work and furthermore for analysis work. There is also the issue of prolonging the construction period as it takes time to collect and analyze samples. Furthermore, in order to collect samples, it is necessary to get close to the face, which is at risk of collapsing, which poses the problem of not being able to fully ensure safety.

The technology of the present disclosure aims to effectively detect clay minerals contained in a test object with a simple configuration.

The detection device of the present disclosure includes: an irradiation unit that irradiates an object to be inspected with infrared rays; an imaging unit that images the infrared rays reflected from the object to be inspected as infrared images of at least two different wavelengths; A determination means for calculating the brightness of each image from the above-mentioned infrared images of different wavelengths and determining whether or not the object to be inspected contains clay minerals based on each calculated brightness. do.

Further, the imaging means is configured to provide, as the infrared images, at least an infrared image with a low reflectance in which the infrared reflectance of the clay mineral is lower than or equal to a predetermined reflectance, and an infrared image in which the infrared reflectance of the clay mineral is higher than the predetermined reflectance. the determination means calculates a brightness ratio between the brightness of a predetermined area in the low reflectance infrared image and the brightness of a predetermined area in the high reflectance infrared image. At the same time, it is preferable to determine whether a clay mineral is contained in a portion of the object to be inspected corresponding to the predetermined region based on the calculated brightness ratio.

Further, the imaging means takes at least two or more different low reflectance infrared images in which the infrared reflectance of the clay mineral is equal to or lower than the predetermined reflectance as the low reflectance infrared images, and the determining means includes: Calculate the brightness ratio of each predetermined area in the two or more different infrared images with low reflectance and the brightness of the predetermined area in the high reflectance infrared image, and calculate each of the calculated at least two or more infrared images. It is preferable to specify the type of clay mineral contained in a portion of the object to be inspected corresponding to the predetermined region based on the brightness ratio.

Further, the imaging means may produce an infrared image with a first low reflectance near a wavelength of 1.4 μm, a second low reflectance near a wavelength 1.9 μm, and a third low reflectance near a wavelength 2.2 μm. The determining means captures infrared images of each reflectance, and determines the brightness of each predetermined area within the infrared images of the first low reflectance, the second low reflectance, and the third low reflectance, and the brightness of the high reflectance. The brightness ratio of the reflectance to the brightness of a predetermined area in the infrared image is calculated, and if each of the three calculated brightness ratios is less than or equal to a threshold value, the part of the object to be inspected corresponding to the predetermined area is included. Preferably, the clay mineral is identified as montmorillonite.

Further, it is preferable that the imaging means includes a plurality of bandpass filters that can transmit infrared rays of different wavelengths, and an infrared camera that detects the infrared rays that have passed through the bandpass filters.

The detection method of the present disclosure includes an irradiation step of irradiating an object to be inspected with infrared rays, an imaging step of imaging the infrared rays reflected from the object to be inspected as infrared images of at least two or more different wavelengths, and a step of imaging the infrared rays reflected from the object to be inspected as infrared images of at least two different wavelengths; A determination step of calculating the brightness of each image from the infrared images of different wavelengths, and determining whether or not the object to be inspected contains clay minerals based on each calculated brightness. do.

Further, in the imaging step, the infrared images include at least an infrared image with a low reflectance in which the infrared reflectance of the clay mineral is less than or equal to a predetermined reflectance, and an infrared image in which the infrared reflectance of the clay mineral is higher than the predetermined reflectance. An infrared image with a high reflectance is captured, and in the determination step, a brightness ratio between the brightness of a predetermined area in the infrared image with a low reflectance and the brightness of a predetermined area in the infrared image with a high reflectance is calculated. At the same time, it is preferable to determine whether a clay mineral is contained in a portion of the object to be inspected corresponding to the predetermined region based on the calculated brightness ratio.

Further, in the imaging step, at least two or more different low reflectance infrared images in which the infrared reflectance of the clay mineral is equal to or lower than the predetermined reflectance are captured as the low reflectance infrared images, and in the determining step, Calculate the brightness ratio of each predetermined area in the two or more different infrared images with low reflectance and the brightness of the predetermined area in the high reflectance infrared image, and calculate each of the calculated at least two or more infrared images. It is preferable to specify the type of clay mineral contained in a portion of the object to be inspected corresponding to the predetermined region based on the brightness ratio.

In addition, in the imaging step, as the infrared images with low reflectance, a first low reflectance around a wavelength of 1.4 μm, a second low reflectance around a wavelength of 1.9 μm, and a third low reflectance around a wavelength of 2.2 μm are obtained. Infrared images of the respective reflectances are taken, and in the determination step, each brightness of a predetermined area in the infrared images of the first low reflectance, the second low reflectance, and the third low reflectance, and the brightness of the high reflectance are determined. The brightness ratio of the reflectance to the brightness of a predetermined area in the infrared image is calculated, and if each of the three calculated brightness ratios is less than or equal to a threshold value, the part of the object to be inspected corresponding to the predetermined area is included. Preferably, the clay mineral is identified as montmorillonite.

According to the technology of the present disclosure, clay minerals contained in an object to be inspected can be effectively detected with a simple configuration.

FIG. 1 is a schematic diagram showing an example in which the detection device according to the present embodiment is applied to a mountain tunnel construction method. It is a graph showing the reflectance characteristics of montmorillonite, kaolinite, and illite as examples of clay minerals. FIG. 2 is a functional block diagram showing a detection device according to the present embodiment. It is a schematic diagram which shows the specific example of each luminance image in this embodiment. It is a schematic diagram which shows an example of the brightness ratio image produced|generated based on each brightness image in this embodiment. It is a flow chart explaining the flow of a clay mineral detection process by a detection device concerning this embodiment. It is a flow chart explaining the flow of a clay mineral detection process concerning other embodiments.

Hereinafter, a detection device and a detection method according to the present embodiment will be described based on the accompanying drawings. Identical parts are given the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

FIG. 1 is a schematic diagram showing an example in which a detection device 10 according to the present embodiment is applied to a mountain tunnel construction method. In the figure, reference numeral G schematically indicates the ground, 1 the tunnel formed by excavation, 2 the face, 3 the shoring, and 4 the concrete lining.

As shown in FIG. 1, the detection device 10 is used, for example, to detect clay minerals contained in the ground G forming the face 2. Specifically, the detection device 10 includes an irradiation section 20, an imaging section 30, a data processing section 50, an input section 60, and a display section 70.

The irradiation unit 20 is an illumination device capable of irradiating infrared rays (hereinafter, in the present embodiment, when referred to as "infrared rays" includes "near infrared rays") to the face 2, and uses, for example, a halogen lamp. It is configured. The irradiation unit 20 is preferably installed inside the tunnel 1 using a tripod or the like. Note that the irradiation unit 20 may be a lamp light source other than a halogen lamp, a light emitting diode, a laser diode, or the like.

The imaging section 30 includes a filter section 31 and an infrared camera 40. The filter section 31 is arranged between the face 2 and the infrared camera 40, and includes a plurality of (for example, four in this embodiment) first to fourth filters 32 to 35 that can be selectively switched. There is. Each of these filters 32 to 35 is a bandpass filter (optical filter) that transmits infrared rays in different specific wavelength bands. Detailed selection of wavelength bands for each of the filters 32 to 35 will be described below.

Figure 2 is a graph showing the reflectance characteristics of montmorillonite, kaolinite, and illite as examples of clay minerals (Source: Castaldi, F., Palombo, A., Pascucci, S., Pignatti, S., Santini , F., Casa, R. (2015) Reducing the influence of soil moisture on the estimation of clay from hyperspectral data: a case study using simulated PRISMA data. Remote Sensing, vol. 7, pp. 15561-15582, Fig. 5 ). Generally, in the infrared reflectance characteristics of clay minerals, there are a plurality of bottoms where the infrared reflectance rapidly decreases (absorption rate rapidly increases) in a predetermined wavelength band.

More specifically, montmorillonite has a low reflectance band A1 around a wavelength of 1.4 μm, a low reflectance band A1 around a wavelength of 1.9 μm, and a low reflectance band A1 around a wavelength of 1.9 μm, as wavelength bands where the reflectance of infrared rays rapidly decreases to about 60% or less (an example of a predetermined reflectance). There are approximately three bottoms: a reflectance band A2 and a low reflectance band A3 around a wavelength of 2.2 μm. Kaolinite has a low reflectance band A1 around a wavelength of 1.4 μm, where the reflectance of infrared rays rapidly decreases to about 50% or less, and a low reflectance band A1 of around 2.2 μm, where the reflectance of infrared rays suddenly decreases to about 30% or less. There are approximately two bottoms of rate band A3. These rapid decreases in reflectance occur because electromagnetic waves are absorbed by vibrations of hydroxyl groups (OH) and water molecules contained in clay minerals.

In this embodiment, as the first filter 32, a bandpass filter that can transmit infrared rays in a low reflectance band A1 around a wavelength of 1.4 μm, where the infrared reflectance of all clay minerals including montmorillonite and kaolinite rapidly decreases, is selected. has been done. Furthermore, as the second filter 33, a bandpass filter is selected that can transmit at least infrared rays in a low reflectance band A2 around a wavelength of 1.9 μm, where the infrared reflectance of montmorillonite sharply decreases. Further, as the third filter 34, a bandpass filter is selected that can transmit infrared rays in a low reflectance band A3 around a wavelength of 2.2 μm, where the infrared reflectance rapidly decreases in at least montmorillonite and kaolinite. Further, as the fourth filter 35, a plurality of high reflectance bands B1, B2, and B3 different from these low reflectance bands A1, A2, and A3 (for example, a band where the infrared reflectance is higher than about 70% in montmorillonite) ), a bandpass filter that can transmit infrared rays of any wavelength is selected.

Note that the number of filters 32 to 35 and selection of wavelength bands are not limited to these, and can be set as appropriate depending on the type of clay mineral to be detected, the purpose of detection, etc. Further, the number of filters for the high reflectance bands B1, B2, and B3 is not limited to one in the fourth filter 35, and the number of filters may be added for each of the high reflectance bands B1, B2, and B3 as necessary. may be configured.

Returning to FIG. 1, the infrared camera 40 detects the infrared rays reflected from the face 2 and transmitted through the filter section 31, and inputs the captured infrared image data to the data processing section 50. The infrared camera 40 is preferably installed inside the tunnel 1 using a tripod or the like. The installation distance of the infrared camera 40 from the face 2 is within a range where infrared rays reflected from the face 2 can be imaged, and preferably, the entire image of the face 2 is included in the image acquired by one imaging, or Alternatively, in addition to the entire image of the face 2, it is adjusted appropriately so that a part of the shoring 3 (or the bolt head of an anchor bolt (not shown), etc.) is included.

Note that although the filter section 31 is assumed to be incorporated into a part of the imaging section 30, it may be incorporated into the irradiation section 20. When incorporated into the irradiation section 20 , the filter section 31 may be placed between the light source of the irradiation section 20 and the face 2 . Alternatively, if the irradiation section 20 is a variable wavelength light source, the filter section 31 itself can be omitted.

The data processing unit 50 is configured using an information processing device such as a personal computer or a server. Note that the data processing unit 50 may be configured using an information processing device such as a tablet or a smartphone. The data processing unit 50 acquires infrared image data captured by the imaging unit 30. The data processing unit 50 also determines whether clay minerals are included in the ground G constituting the face 2 and specifies the type of clay mineral contained in the ground G based on the acquired image data. implement.

The input unit 60 is, for example, a keyboard connected to the data processing unit 50, and inputs various information, instructions, etc. to the data processing unit 50. The display unit 70 is, for example, a display connected to the data processing unit 50, and displays the detection results by the detection device 10, the input contents from the input unit 60 to the data processing unit 50, and the like.

In this embodiment, the irradiation unit 20 and the imaging unit 30 are installed inside the tunnel 1 (dark area) that is not easily affected by disturbances such as sunlight. Further, the data processing section 50, the input section 60, and the display section 70 may be installed either inside the tunnel 1 or outside the tunnel (including a remote location). The on/off of the irradiation unit 20, the switching of the filter unit 31, and the operation of the infrared camera 40 may be automatically controlled in accordance with a command outputted via the data processing unit 50 by the operator's operation of the input unit 60. Alternatively, the irradiation section 20, the filter section 31, and the imaging section 40 may be directly operated manually by an operator.

FIG. 3 is a functional block diagram showing the detection device 10 according to this embodiment. The detection device 10 includes a CPU (Central Processing Unit), a memory, an auxiliary storage device, etc. connected via a bus, and executes a detection program. Furthermore, the detection device 10 functions as a device including a storage section 51, a brightness image generation section 52, and a clay mineral detection section 53 by executing the detection program. The detection program may be recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, a magneto-optical disk, a portable medium such as a USB, a CD-ROM, or a storage device such as a hard disk built into a computer system. The detection program may also be transmitted via a telecommunications line.

The storage unit 51 is configured using a storage device such as a magnetic hard disk device or a semiconductor storage device. The storage unit 51 stores infrared image data acquired by the infrared camera 40.

The brightness image generation unit 52 generates a brightness image (black and white monochrome image) according to the infrared reflectance based on the infrared image data stored in the storage unit 51. The brightness image is generated, for example, by converting the infrared image data into a gray scale of 256 black and white gradations, and then preferably correcting it with a correction coefficient according to the light source characteristics of the irradiation unit 20 and the sensitivity characteristics of the infrared camera 40. . Note that the number of gradations is not limited to 256 gradations, and may be any number of gradations.

FIG. 4 is a schematic diagram showing a specific example of a brightness image in this embodiment. 4(A) is a brightness image generated from the infrared image data of the low reflectance band A1 (see FIG. 2) transmitted through the first filter 32, and FIG. 4(B) is the luminance image generated from the infrared image data transmitted through the second filter 33. The brightness image generated from the infrared image data of the low reflectance band A2 (see FIG. 2), and FIG. 4(C) is the infrared image of the low reflectance band A3 (see FIG. 2) that has passed through the third filter 34. The luminance image generated from the data, FIG. 4(D), is the luminance image generated from the infrared image data in the high reflectance band (any of B1, B2, and B3 shown in FIG. 2) transmitted through the fourth filter 35. Each image is schematically shown. Regarding the shading of each region X, Y in each of these brightness images, the darker the color (darker the brightness), the lower the reflectance of the infrared rays irradiated to the face 2, and the lighter the color (brighter the brightness), the lower the reflectance of the infrared rays irradiated to the face 2. This shows that the reflectance of infrared rays irradiated to the area is high.

Specifically, if the face 2 corresponding to the region The reflectance of infrared rays becomes low, and the reflectance of infrared rays in high reflectance bands B1, B2, and B3 becomes high. Therefore, as shown in FIGS. 4(A), (B), and (C), the brightness images IMG1, IMG2, and IMG3 generated from the infrared image data in the low reflectance bands A1, A2, and A3 contain montmorillonite. The brightness of region X containing montmorillonite becomes darker than the brightness of region Y (rock mainly composed of silicate minerals, etc.) that does not contain montmorillonite. On the other hand, as shown in FIG. 4(D), in the brightness image IMG4 generated from infrared image data in the high reflectance band (any of B1, B2, or B3), the brightness of the entire image becomes brighter, so that the area The difference in brightness between X and area Y is expressed as small.

The brightness image has, as the pixel value of each pixel, a brightness value that corresponds to the reflectance of the infrared rays irradiated onto the face 2. For convenience of explanation, the brightness image IMG1 generated from the infrared image data transmitted through the first filter 32 will be referred to as "first low reflectance brightness image IMG1", and the infrared image data transmitted through the second filter 33 will be referred to as "first low reflectance brightness image IMG1". The brightness image IMG2 generated from the third filter 34 is referred to as a "second low reflectance brightness image IMG2", and the brightness image IMG3 generated from the infrared image data transmitted through the third filter 34 is referred to as a "third low reflectance brightness image IMG3". The brightness image IMG4 generated from the infrared image data that has passed through the four filters 35 is referred to as a "reference brightness image IMG4."

The clay mineral detection unit 53 detects whether the face 2 contains clay minerals based on the brightness image generated by the brightness image generation unit 52. Specifically, the clay mineral detection unit 53 determines the brightness ratio γ1 (=α1) between the brightness α1 of point x in the first low reflectance brightness image IMG1 and the brightness β of point /β), and if the brightness ratio γ1 is less than a predetermined threshold value, it is determined that the corresponding portion of the face 2 contains clay minerals (clay minerals in general including at least montmorillonite or kaolinite). In this way, by using the brightness ratio γ1 between the brightness α1 of the low reflectance brightness image IMG1 with a low infrared reflectance and the brightness β of the reference brightness image IMG4 with a high infrared reflectance, each point on the face 2 and the irradiation area can be adjusted. 20 (light source) is reduced, and it becomes possible to easily detect the presence or absence of clay minerals without making corrections according to these distance differences.

Note that the brightness ratio γ1 may be calculated for each pixel or for each predetermined area formed from the average value of a plurality of pixels. The respective brightness images IMG1 and IMG4 may be aligned using, for example, the shoring 3 (or the bolt head of an anchor bolt (not shown), etc.) included in the image as a reference point.

Furthermore, the clay mineral detection unit 53 extracts the distribution area of clay minerals in the face 2 based on the area where the brightness ratio γ1 is equal to or less than the threshold value. FIG. 5 is a schematic diagram showing an example of a brightness ratio image IMG5 generated based on the brightness images IMG1 and IMG4 shown in FIGS. 4(A) and (D). By using the brightness ratio image IMG5 generated based on the brightness ratio γ1 in this way, it is possible to identify a region The brightness difference with the area Y (mainly rocks) where there is no clay mineral can be clearly expressed, and the distribution area of clay minerals can be easily and accurately extracted.

Note that the brightness image used for determination and extraction is not limited to the first low reflectance brightness image IMG1, but may be the second low reflectance brightness image IMG2 shown in FIG. 4(B) or the third low reflectance brightness image IMG2 shown in FIG. 4(C). Any of the low reflectance brightness images IMG3 may be used. When using the second low reflectance brightness image IMG2, the brightness ratio γ2 (= α2/β), and if the brightness ratio γ2 is less than or equal to the threshold value, it may be determined that the corresponding portion contains clay minerals (clay minerals containing at least montmorillonite). Similarly, when using the third low reflectance brightness image IMG3, the brightness ratio between the brightness α3 of point x in the third low reflectance brightness image IMG3 and the brightness β of point x in the corresponding reference brightness image IMG4 γ3 (=α3/β) is calculated, and if the brightness ratio γ3 is less than or equal to a threshold value, it may be determined that a clay mineral (a clay mineral containing at least montmorillonite or kaolinite) is included in the portion. Each threshold value used for determination may be appropriately set according to the type of clay mineral to be detected, the purpose of detection, etc.

Further, the clay mineral detection unit 53 identifies the type of clay mineral included in the region X of the face 2 based on the calculated brightness ratios γ1, γ2, and γ3. As explained based on FIG. 2, in montmorillonite and kaolinite, the infrared reflectance rapidly decreases in the two wavelength bands A1 and A3, around the wavelength of 1.4 μm and around the wavelength of 2.2 μm, while in montmorillonite, Furthermore, the infrared reflectance rapidly decreases even in the wavelength band A2 near the wavelength of 1.9 μm. The clay mineral determination unit 53 identifies the type of clay mineral by using the difference in infrared reflectance depending on the type of clay mineral.

Specifically, (1) the brightness ratio γ1 calculated based on the first low reflectance brightness image IMG1 and the reference brightness image IMG4 is equal to or less than the threshold, and (2) the second low reflectance brightness image IMG2 and the reference brightness The brightness ratio γ2 calculated based on the image IMG4 is below the threshold value, and (3) the brightness ratio γ3 calculated based on the third low reflectance brightness image IMG3 and the reference brightness image IMG4 is below the threshold value (1 ) to (3), it means that the infrared reflectance rapidly decreases in the low reflectance bands A1, A2, and A3 unique to montmorillonite. In this case, the clay mineral detection unit 53 identifies the type of clay mineral contained in region X as montmorillonite. On the other hand, if conditions (1) and (3) hold, but condition (2) does not hold, the infrared reflectance decreases rapidly in the low reflectance bands A1 and A3 common to montmorillonite and kaolinite, and montmorillonite This means that the infrared reflectance does not suddenly decrease in the unique low reflectance band A2. In this case, the clay mineral detection unit 53 identifies the type of clay mineral contained in region X as kaolinite.

Note that the specification of the type of clay mineral is not limited to these montmorillonite and kaolinite, and may be configured to further specify other clay minerals. In this case, first, a bandpass filter that can transmit infrared rays in a wavelength band where the infrared reflectance of other clay minerals sharply decreases is added to the filter section 31. Then, a brightness image is generated from the infrared image data according to the added bandpass filter, the brightness ratio with the reference brightness image IMG4 is calculated, and the type of clay mineral is determined by combining and comparing multiple brightness ratios. What is necessary is to configure it so that it can be specified.

FIG. 6 is a flowchart illustrating the flow of clay mineral detection processing by the detection device 10 according to the present embodiment. The clay mineral detection process using the detection device 10 is preferably carried out by being incorporated into the face observation process that is part of the mountain tunnel construction process.

In step S110, infrared rays are irradiated from the irradiation unit 20 toward the face 2.

Next, in step S120, image data of infrared rays reflected from the face 2 is captured by the infrared camera 40 while appropriately switching each of the filters 32 to 35 of the filter section 31. The number of times of imaging can be set as appropriate depending on the purpose of detection. Specifically, when only determining whether or not clay minerals are included in the face 2, it is necessary to perform at least two consecutive imaging operations using the first filter 32 and the fourth filter 35. good. Furthermore, if the type of clay mineral is also to be specified, imaging may be performed at least four times in total using the first to fourth filters 32 to 35. The order of imaging using each of these filters 32 to 35 is random.

In step S130, the infrared image data acquired in step S120 is input into the storage unit 51, and in step S140, a brightness image according to the reflectance of infrared rays is created based on the infrared image data stored in the storage unit 51. generate.

In step S150, the brightness ratio γ1 (=α1/β) between the brightness α1 of the first low reflectance brightness image IMG1 and the brightness β of the reference brightness image IMG4 is calculated, and then in step S160, the brightness ratio γ1 is set to a predetermined value. Determine whether it is below a threshold value. If the brightness ratio γ1 is below the threshold value (affirmative), it means that the infrared reflectance decreases rapidly in the low reflectance band A1 around the wavelength of 1.4 μm, which is common to many clay minerals. In this case, in step S170, it is determined that clay minerals (general clay minerals including at least montmorillonite or kaolinite) are contained (present) in the part of the face 2. On the other hand, if the brightness ratio γ1 is higher than the threshold (no), it is determined in step S300 that clay minerals are not included in the part of the face 2 (absent).

In step S180, a region X where the brightness ratio γ1 is equal to or less than a threshold is specified from the brightness ratio image IMG5 generated based on each brightness image IMG1, IMG4, and the distribution area of clay minerals in the entire face 2 is extracted.

Next, in step S200, a brightness ratio γ3 (=α3/β) between the brightness α3 of the third low reflectance brightness image IMG3 and the brightness β of the reference brightness image IMG4 is calculated, and in step S210, the brightness ratio γ3 is determined to be a predetermined value. Determine whether it is below a threshold value. If the brightness ratio γ3 is higher than the threshold value (negative), it means that the infrared reflectance has not sharply decreased in the third low reflectance band A3 around the wavelength of 2.2 μm, which is specific to montmorillonite and kaolinite. In this case, the process proceeds to step S270, and the clay mineral is identified as another clay mineral that does not fall under either montmorillonite or kaolinite.

On the other hand, if the brightness ratio γ3 is equal to or less than the threshold in step S210 (affirmative), the process proceeds to step S220, where the brightness ratio between the brightness α2 of the second low reflectance brightness image IMG2 and the brightness β of the reference brightness image IMG4 is determined. Calculate γ2 (=α2/β).

In step S230, it is determined whether the brightness ratio γ2 is less than or equal to a predetermined threshold value. If the brightness ratio γ2 is higher than the threshold (negative), the infrared reflectance sharply decreases in two low reflectance bands A1 and A3, around a wavelength of 1.4 μm and around a wavelength of 2.2 μm, which are common to montmorillonite and kaolinite. However, in the second low reflectance band A2 around the wavelength of 1.9 μm, which is unique to montmorillonite, the infrared reflectance does not decrease sharply. In this case, the process proceeds to step S280, and the type of clay mineral is identified as kaolinite.

On the other hand, in step S230, if the brightness ratio γ2 is less than the threshold value (affirmative), a total of three low reflectance bands of around 1.4 μm wavelength, around 1.9 μm wavelength, and around 2.2 μm wavelength, which are unique to montmorillonite, are detected. This means that the infrared reflectance rapidly decreases at A1, A2, and A3. In this case, the process proceeds to step S240, where the clay mineral is identified as montmorillonite, and the detection of the clay mineral is ended. Thereafter, each of the above-mentioned steps is preferably repeated in the next face observation process in mountain tunnel construction.

According to the present embodiment described in detail above, the irradiation unit 20 irradiates the face 2 with infrared rays, and the infrared camera 40 captures infrared images of at least the low reflectance band and the high reflectance band, and By comparing the brightness ratio of each infrared image in the reflectance band and the high reflectance band, the presence or absence of clay minerals in the face 2 and further the type of clay minerals can be determined.

That is, on-site work is limited to infrared ray irradiation and imaging, making it possible to omit sample collection work that requires time and labor, and making it possible to significantly shorten work time.

Further, since infrared ray irradiation and imaging do not require getting close to the face 2, which is at risk of collapse, work safety can also be effectively ensured.

Furthermore, since infrared irradiation and imaging can be incorporated into a part of the face observation process in mountain tunnel construction, it is possible to effectively prevent delays in the entire tunnel construction process.

In addition, by using the brightness ratio of an infrared image in a low reflectance band and an infrared image in a high reflectance band to detect and identify clay minerals, the influence of the distance difference between each point on Face 2 and the light source can be effectively ignored. It will be reduced to That is, by eliminating the need for correction according to the distance difference, it becomes possible to realize highly accurate detection and identification of clay minerals while effectively shortening the analysis time.

In addition, the distribution area of clay minerals over the entire face 2 can be appropriately understood by simply comparing the brightness ratio obtained from the captured infrared images, so the analysis results can be used to select auxiliary methods for ground G in mountain tunnel construction and It also becomes possible to effectively utilize this method for strength selection of work 3.

Note that the present disclosure is not limited to the above-described embodiments, and can be modified and implemented as appropriate without departing from the spirit of the present disclosure.

In the above embodiment, the explanation was given using a mountain tunnel construction site as an example, but for example, even if it is an outdoor dam construction site, it is carried out at night, in an environment that is not easily affected by disturbances such as sunlight (dark area). If implemented, it can be widely applied to other sites.

Furthermore, the detection target is not limited to the clay minerals contained in the face 2, but can be widely applied to the detection of other minerals and rocks that can be detected based on the brightness ratio of the infrared image.

Further, the type of clay mineral is not limited to montmorillonite or kaolinite, and for example, illite may be further specified. Unlike montmorillonite and kaolinite, in the reflectance characteristics shown in Figure 2, illite has a relatively small decrease in infrared reflectance in band A1 near the wavelength 1.4 μm, and in band A2 near the wavelength 1.9 μm. There is a characteristic that the infrared reflectance decreases the most, and then the infrared reflectance decreases greatly in the band A3 near the wavelength of 2.2 μm.

That is, by changing the steps after step S300 in the flowchart shown in FIG. 6 to the flow shown in FIG. 7, illite can be further specified. Specifically, as shown in FIG. 7, if it is determined in step S160 that the brightness ratio γ1 is higher than the threshold (the reflectance has hardly decreased), the brightness ratio γ2 is calculated in step S300. Furthermore, in step S310, the brightness ratio γ3 is calculated. Note that the processing in steps S300 and S310 is performed in random order. Next, in step S320, if the relationship of brightness ratio γ2<brightness ratio γ3≦threshold holds true (affirmative), the clay mineral may be identified as illite in step S330.

G... Earth, 1... Tunnel, 2... Face, 3... Shoring, 4... Lining concrete, 10... Detection device, 20... Irradiation section, 30... Imaging section, 31... Filter section, 32... First filter, 33...Second filter, 34...Third filter, 35...Fourth filter, 40...Infrared camera, 50...Data processing section, 51...Storage section, 52...Brightness image generation section, 53...Clay mineral detection section, 60... Input section, 70...display section

Claims (4)

Irradiation means for irradiating infrared rays onto a tunnel construction face ;
an imaging means for imaging infrared rays reflected from the face as infrared images of at least two or more different wavelengths;
A determining means for calculating the brightness of each image from the captured infrared images of two or more different wavelengths, and determining whether or not the face contains clay minerals based on each calculated brightness,
The imaging means is configured to produce a first low reflectance infrared image at a wavelength of around 1.4 μm, and a first low reflectance infrared image at a wavelength around 1.9 μm, as a low reflectance infrared image in which the infrared reflectance of the clay mineral is equal to or lower than a predetermined reflectance. A second low-reflectance infrared image and a third low-reflectance infrared image at a wavelength of around 2.2 μm are respectively captured, and a high-reflectance infrared ray that causes the infrared reflectance of the clay mineral to be higher than the predetermined reflectance. As an image, an infrared image is taken in a wavelength band where the infrared reflectance of montmorillonite is higher than 70% ,
The determining means includes a first brightness ratio that is a ratio between the brightness of a predetermined area in the first low reflectance infrared image and the brightness of a predetermined area in the high reflectance infrared image, and the second low reflectance. a second brightness ratio that is the ratio of the brightness of a predetermined area in the infrared image with the high reflectance to the brightness of the predetermined area in the infrared image with the third low reflectance; Calculating a third brightness ratio that is a ratio to the brightness of a predetermined area in the high reflectance infrared image ,
The determining means is further configured to convert clay minerals contained in a portion of the face corresponding to the predetermined region into montmorillonite when the first brightness ratio, the second brightness ratio, and the third brightness ratio are below a predetermined threshold. If it is determined that the first brightness ratio and the third brightness ratio are less than or equal to the threshold value, and the second brightness ratio is higher than the threshold value, the part of the face corresponding to the predetermined area includes is determined to be kaolinite, the first brightness ratio is higher than the threshold, the second brightness ratio is lower than the third brightness ratio, and the third brightness ratio is lower than the third brightness ratio. If the relationship is equal to or less than the threshold value, the clay mineral contained in the part corresponding to the predetermined area of the face is determined to be illite, and if the first brightness ratio is higher than the threshold value, the relationship is determined to be illite. If this is not true, it is determined that there is no clay mineral in a portion of the face corresponding to the predetermined region, and if the first brightness ratio is less than or equal to the threshold value and the third brightness ratio is higher than the threshold value, A detection device characterized in that a clay mineral contained in a portion of the face corresponding to the predetermined region is determined to be a clay mineral other than montmorillonite, kaolinite, and illite. The detection device according to claim 1 , wherein the imaging means includes a plurality of bandpass filters that can transmit infrared rays of different wavelengths, and an infrared camera that detects the infrared rays that have passed through the bandpass filters. The imaging means is installed in a tunnel, and the installation distance of the imaging means from the face is within a range where infrared rays reflected from the face can be imaged, and within an image obtained by one imaging. Set at a distance that includes the entire image of the face and also includes a part of the shoring ,
The determination means is included in each of the first low reflectance infrared image, the second low reflectance infrared image, the third low reflectance infrared image, and the high reflectance infrared image. Align each image using the support as a reference point.
The detection device according to claim 1 or 2 . an irradiation step of irradiating infrared rays onto the tunnel construction face ;
an imaging step of imaging infrared rays reflected from the face as infrared images of at least two or more different wavelengths;
a determination step of calculating the brightness of each image from the captured infrared images of two or more different wavelengths, and determining whether or not the face contains clay minerals based on each calculated brightness. ,
In the imaging step , a first low reflectance infrared image with a wavelength of about 1.4 μm and a first low reflectance infrared image with a wavelength of about 1.9 μm are used as low reflectance infrared images in which the infrared reflectance of the clay mineral is less than or equal to a predetermined reflectance. A second low-reflectance infrared image and a third low-reflectance infrared image at a wavelength of around 2.2 μm are respectively captured, and a high-reflectance infrared ray that causes the infrared reflectance of the clay mineral to be higher than the predetermined reflectance. As an image, an infrared image is taken in a wavelength band where the infrared reflectance of montmorillonite is higher than 70% ,
In the determination step, a first brightness ratio, which is a ratio between the brightness of a predetermined area in the first low reflectance infrared image and the brightness of a predetermined area in the high reflectance infrared image, and the second low reflectance a second brightness ratio that is the ratio of the brightness of a predetermined area in the infrared image with the high reflectance to the brightness of the predetermined area in the infrared image with the third low reflectance; Calculating a third brightness ratio that is a ratio to the brightness of a predetermined area in the high reflectance infrared image ,
In the determination step, if the first brightness ratio, the second brightness ratio, and the third brightness ratio are less than or equal to a predetermined threshold, the clay mineral contained in the portion corresponding to the predetermined area of the face is converted into montmorillonite. If it is determined that the first brightness ratio and the third brightness ratio are less than or equal to the threshold value, and the second brightness ratio is higher than the threshold value, the part of the face corresponding to the predetermined area includes is determined to be kaolinite, the first brightness ratio is higher than the threshold, the second brightness ratio is lower than the third brightness ratio, and the third brightness ratio is lower than the third brightness ratio. If the relationship is equal to or less than the threshold value, the clay mineral contained in the part corresponding to the predetermined area of the face is determined to be illite, and if the first brightness ratio is higher than the threshold value, the relationship is determined to be illite. If this is not true, it is determined that there is no clay mineral in a portion of the face corresponding to the predetermined region, and if the first brightness ratio is less than or equal to the threshold value and the third brightness ratio is higher than the threshold value, A detection method characterized in that a clay mineral contained in a portion of the face corresponding to the predetermined region is determined to be a clay mineral other than montmorillonite, kaolinite, and illite.

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