Mineral content measurement method and mineral content measurement device

Abstract

To improve the measurement accuracy of a smectite content.SOLUTION: A mineral content measurement method comprises the steps of: irradiating an objected to be measured with light to spectrum-analyze the object to be measured; acquiring light absorbance of the object to be measured on the basis of first, second and third measurement values being measurement results of spectrum analysis in first, second and third wavelengths determined according to a mineral; and acquiring a mineral content in the object to be measured on the basis of the absorbance. The absorbance is acquired on the basis of a correction value obtained by quantifying the second and third measurement values by the first measurement value.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for measuring mineral content. [Background technology]

[0002] Patent Document 1 discloses a method for quantifying kaolins in a sample by subjecting the sample to infrared absorptiometry analysis, determining peak intensity from the peak height of the absorbance waveform at a predetermined frequency or the integrated value of the waveform. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-315263 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, in mountain tunnel construction, swelling clay minerals contained in the bedrock can absorb water and expand after tunnel excavation, which can lead to problems such as the need to re-excavate the tunnel. In order to deal with such problems appropriately, it is necessary to measure the swelling clay mineral content of the bedrock.

[0005] The method disclosed in Patent Document 1 quantifies the mineral content of a measurement object from the peak intensity of the infrared absorbance waveform. However, even if the mineral content is the same, the peak intensity of the absorbance waveform varies depending on the type of measurement object, the type of light source, the method of applying light, and other analytical conditions. Therefore, it is difficult to sufficiently improve the accuracy of mineral content measurement using the method disclosed in Patent Document 1.

[0006] The present invention aims to improve the accuracy of measuring mineral content. [Means for solving the problem]

[0007] The present invention is a mineral content measurement method for measuring the content of a specific mineral contained in a measurement object, and includes the steps of: irradiating the measurement object with light and performing a spectral analysis of the measurement object; acquiring the light absorbance of the measurement object based on first, second, and third measurement values, which are the measurement results of the spectral analysis at a first wavelength, a second wavelength, and a third wavelength determined according to the mineral; and acquiring the mineral content in the measurement object based on the absorbance, wherein the absorbance is acquired based on correction values ​​that quantify the second and third measurement values ​​using the first measurement value.

[0008] The present invention also provides a mineral content measuring device for measuring the content of a specific mineral contained in a measurement object, comprising: a measurement unit that irradiates the measurement object with light and performs a spectral analysis of the measurement object; and a calculation unit that acquires the mineral content in the measurement object based on the measurement results of the measurement unit, wherein the calculation unit is configured to acquire the light absorbance of the measurement object based on first measurement values, second measurement values, and third measurement values, which are the measurement results of the spectral analysis at first wavelengths, second wavelengths, and third wavelengths determined according to the mineral, and to acquire the mineral content in the measurement object based on the absorbance, and the absorbance is acquired based on correction values ​​that quantify the second measurement values ​​and the third measurement values ​​using the first measurement value. [Effects of the Invention]

[0009] According to the present invention, the accuracy of measuring the mineral content is improved. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing the configuration of a mineral content measuring device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram for explaining a mineral content measurement method according to an embodiment of the present invention, and is a graph showing the relationship between the wavelength of light irradiated onto the measurement object and reflectance. [Figure 3]FIG. 1 is a graph illustrating the relationship between the smectite content and the light absorbance, illustrating a method for measuring the mineral content according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a mineral content measuring device 100 and a mineral content measuring method according to an embodiment of the present invention will be described with reference to the drawings. In the following, an example will be described in which excavated soil obtained by excavating the ground is used as a measurement object (sample), and the content of smectite, a swelling clay mineral contained in the measurement object, is measured.

[0012] First, with reference to FIG. 1, a mineral content measuring device 100 according to this embodiment (hereinafter also simply referred to as "measuring device 100") will be described.

[0013] As shown in FIG. 1, the measuring device 100 includes a measuring unit 10 that irradiates the object to be measured with light and performs spectral analysis (spectroscopic analysis) of the object to be measured, a calculation unit 20 that acquires the smectite content in the object to be measured (content rate within the object to be measured) based on the measurement results of the measuring unit 10, an operation unit 30 that accepts operation inputs from the user, and a display unit 40 that displays information.

[0014] The measurement unit 10 is a spectrometer (spectrometer) that irradiates a measurement object with light and measures the reflection, transmission, or absorption of the light by the measurement object. Since a known configuration can be used for the measurement unit 10, detailed description and illustrations are omitted. For example, the measurement unit 10 includes a light source that irradiates light, a spectrometer that separates the light from the light source according to wavelength and irradiates the light onto the measurement object, and a sensor that detects light reflected, transmitted, or absorbed by the measurement object. In this embodiment, the measurement unit 10 measures the reflectance of light by the measurement object and transmits the result to the calculation unit 20. Note that the measurement unit 10 may also measure the transmittance or absorbance of light as a measurement value.

[0015] The calculation unit 20 is configured by a computer including a CPU (Central Processing Unit) that executes a control program and the like, a ROM (Read-Only Memory) that stores the control program executed by the CPU, a RAM (Random Access Memory) that stores the results of CPU calculations and the like, a communication device, etc. The calculation unit 20 executes various functions of the calculation unit 20 described in this specification by loading the control program stored in the ROM into the RAM and executing it on the RAM by the CPU. The calculation unit 20 may be configured by one computer, or may be configured by multiple microcomputers and configured to distribute the various controls among the multiple computers.

[0016] A command signal for performing a predetermined process is input to the calculation unit 20 via the operation unit 30. The calculation unit 20 also stores in advance the relationship between the absorbance D of the measurement object and the smectite content, which will be described later.

[0017] The display unit 40 is connected to the calculation unit 20 and serves as a user interface for operating the measuring device 100 via the operation unit 30, and as a monitor for displaying the results of calculations by the calculation unit 20, etc.

[0018] Next, the mineral content measurement method of this embodiment (hereinafter also simply referred to as "measurement method") will be described. The calculation unit 20 is pre-programmed so as to be able to execute the following measurement method.

[0019] The measurement method includes a step of irradiating the object to be measured with light and performing a spectral analysis of the object to be measured (measurement step), a step of acquiring the light absorbance D of the object to be measured (absorbance acquisition step), and a step of acquiring the smectite content in the object to be measured based on the absorbance D (content acquisition step).

[0020] [Measurement process] In the measurement process, first, the measurement object and measurement unit 10 are set so that light from the light source of measurement unit 10 is irradiated onto the measurement object. In this state, when the user operates the operation unit 30 to start measurement, a command signal is sent from the calculation unit 20 to the measurement unit 10, and the measurement unit 10 measures the reflectance. As a result, the measurement results shown in FIG. 2 are obtained. The measurement results from measurement unit 10 are input to the calculation unit 20.

[0021] [Absorbance acquisition process] In this embodiment, absorbance D is set as an index representing the degree of absorption of light in a predetermined wavelength range. In the absorbance acquisition step, the calculation unit 20 acquires the absorbance D of light in the measurement object based on the measurement results of the measurement unit 10. The absorbance D is calculated using three values, namely, a first reflectance R1 (first measured value), a second reflectance R2 (second measured value), and a third reflectance R3 (third measured value), which are reflectances at the first wavelength, the second wavelength, and the third wavelength.

[0022] The first, second, and third wavelengths are determined according to the type of mineral so that the characteristics of the mineral to be measured can be observed. Smectite, whose content is measured in this embodiment, is known to have a large light absorption band in the near-infrared region (wavelengths of 2.5 μm or less), particularly in the 1.9 to 2.0 μm wavelength region. Therefore, it is desirable that the first wavelength be set within the range of 1.90 μm to 1.98 μm, the second wavelength be set within the range of 1.80 μm to 1.88 μm, and the third wavelength be set within the range of 2.02 μm to 2.10 μm. In this embodiment, the first wavelength is set to 1.94 μm, the second wavelength to 1.84 μm, and the third wavelength to 2.06 μm. The first wavelength is a wavelength near the extreme value of reflectance in the 1.9 to 2.0 μm wavelength region. The second wavelength is set to a value smaller than the first wavelength, and the third wavelength is set to a value larger than the first wavelength.

[0023] The absorbance D is calculated using correction values ​​obtained by quantifying the second reflectance R2 and the third reflectance R3 using the first reflectance R1. In this embodiment, the value obtained by dividing the value of the second reflectance R2 by the value of the first reflectance R1 is defined as a first correction value C1 (=R2 / R1), and the value obtained by dividing the value of the third reflectance R3 by the value of the first reflectance R1 is defined as a second correction value C2 (=R3 / R1), and these values ​​are quantified. The absorbance D is then obtained as the product of the first correction value C1 and the second correction value C2 using the following formula (1):

[0024]

number

[0025] As described above, the calculation unit 20 obtains the values ​​of the first reflectance R1, the second reflectance R2, and the third reflectance R3 from the measurement results by the measurement unit 10, and calculates the absorbance D of the object to be measured based on the above formula (1).

[0026] [Content acquisition process] In the content acquisition step, the smectite content (content rate) in the measurement target is acquired based on the relationship between absorbance D and smectite stored in advance in the calculation unit 20. The relationship between absorbance D and smectite is acquired, for example, by acquiring absorbance D for multiple samples with known smectite contents using a method similar to the measurement method of this embodiment, and then determining an approximate equation (approximate curve) from a graph plotting the relationship between the acquired absorbance D and the content. In this embodiment, absorbance D is acquired for two types of samples: a mixed sample of smectite and anorthite, and a mixed sample of smectite and kaolinite, and all results are plotted on a graph to obtain the approximate equation shown in FIG. 3. The calculation unit 20 acquires the content corresponding to the absorbance D acquired in the absorbance acquisition step from the approximate equation, thereby acquiring the smectite content in the measurement target.

[0027] Anorthite and kaolinite have large differences in their absorption spectra in the near-infrared region. Therefore, by obtaining an approximate equation using two types of mixed samples of anorthite and kaolinite, it is possible to obtain a more versatile result (approximate equation) that is less affected by the types of minerals other than smectite contained in the natural ground than when using only one of them. The mixed sample used to obtain the approximate equation may be one type, or three or more types.

[0028] In this way, the content of smectite in the measurement object is obtained. Note that each step in the measurement method may be automatically executed by a program stored in the calculation unit 20 from the start of the measurement step by a user's operation input until the completion of the content acquisition step, or may be executed manually in response to a user's operation input via the operation unit 30.

[0029] According to the above embodiment, the following advantageous effects are achieved.

[0030] A mineral content measurement method for measuring the smectite content contained in a measurement object includes the steps of irradiating the measurement object with light and performing a spectral analysis of the measurement object, obtaining the light absorbance D of the measurement object based on a first reflectance R1, a second reflectance R2, and a third reflectance R3, which are measurement results of the spectral analysis at a first wavelength, a second wavelength, and a third wavelength, and obtaining the smectite content of the measurement object based on the absorbance D, where the absorbance D is obtained based on corrected values ​​obtained by quantifying the second reflectance R2 and the third reflectance R3 using the first reflectance R1.

[0031] A mineral content measuring device 100 for measuring the smectite content in a measurement object comprises a measurement unit 10 that irradiates the measurement object with light and performs spectral analysis of the measurement object, and a calculation unit 20 that acquires the smectite content in the measurement object based on the measurement results of the measurement unit 10. The calculation unit 20 is configured to acquire the light absorbance D of the measurement object based on a first reflectance R1, a second reflectance R2, and a third reflectance R3, which are measurement results of the spectral analysis at a first wavelength, a second wavelength, and a third wavelength determined according to the mineral, and to acquire the smectite content in the measurement object based on the absorbance D, and the absorbance D is acquired based on corrected values ​​that quantify the second reflectance R2 and the third reflectance R3 using the first reflectance R1.

[0032] In this embodiment, the absorbance D is obtained based on a corrected value obtained by quantifying the second reflectance R2 and the third reflectance R3 using the first reflectance R1, and therefore does not change even if the peak value (absolute value) of the reflectance in the spectral analysis changes. Therefore, the smectite content can be measured accurately without being affected by fluctuations in the peak value of the reflectance due to the type of rock or the analytical environment of the spectral analysis.

[0033] Furthermore, in this embodiment, when the value of the second reflectance R2 divided by the value of the first reflectance R1 is defined as the first correction value C1, and the value of the third reflectance R3 divided by the value of the first reflectance R1 is defined as the second correction value C2, the absorbance D is obtained as the product of the first correction value C1 and the second correction value C2.

[0034] In this embodiment, the mineral whose content is to be measured is smectite, and the first wavelength is set within the range of 1.90 to 1.98 μm, the second wavelength is set within the range of 1.80 to 1.88 μm, and the third wavelength is set within the range of 2.02 to 2.10 μm.

[0035] Smectite is known to have an absorption band in the vicinity of 1.4 to 1.5 μm, but this wavelength range may overlap with the absorption bands of other minerals. Therefore, by setting the first, second, and third wavelengths as in this embodiment, the smectite content can be obtained more accurately.

[0036] The methylene blue adsorption method is also known as a method for measuring smectite content. For example, in the spot method, 1 ml of methylene blue solution is added to a smectite dispersion in solution, stirring each time and dropping the solution onto filter paper to create a spot. A halo (a smudge) appears around the spot when the amount of methylene blue exceeds the maximum amount adsorbed by bentonite. Measuring the width of the halo indicates the amount of methylene blue adsorbed, and thus the bentonite content. This methylene blue adsorption method requires steps such as solution preparation and stirring, making it difficult to perform at tunnel construction sites.

[0037] In contrast, in this embodiment, the smectite content can be easily and accurately measured using the measurement unit 10, which is a spectrometer, and the calculation unit 20, which is a computer. Therefore, the smectite content can be measured at a tunnel construction site by using excavated soil as a measurement target. By easily measuring the content of excavated soil on site, it is also possible to evaluate the natural ground (ground) during tunnel excavation. Specifically, one of the evaluation items for natural ground is swelling, and the smectite content is one index that represents swelling. Therefore, the smectite content measured by this embodiment can be used to evaluate the swelling of the natural ground.

[0038] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0039] The absorbance D, the first correction value C1, and the second correction value C2 are not limited to those in the above embodiment and can be obtained using any formula. The correction value can be obtained using any definition (formula) as long as it is calculated using a reference value (first reflectance R1) and a value to be corrected (second reflectance R2 or third reflectance R3). For example, the correction value may be any of the sum, difference, product, and quotient of the reference value and the value to be corrected, or a combination thereof. Similarly, the absorbance D may be any of the sum, difference, product, and quotient of correction values, or a combination thereof. For example, a correction value based on the difference between the reference value and the value to be corrected and a correction value based on the product may be obtained separately, and the absorbance D may be obtained by combining these. In other words, the correction values ​​may be obtained using multiple definitions (formulas), and the absorbance D may be obtained by combining correction values ​​of different definitions.

[0040] Furthermore, in the above embodiment, three measurement values ​​are obtained from the measurement results to obtain the absorbance D, but this is not limited to this. Four or more measurement values ​​may be obtained from the measurement results, and a correction value may be obtained by quantifying the remaining measurement values ​​using one of the measurement values ​​as a reference, and the absorbance D may be obtained from the correction value. In this case, it is not necessary to use all of the correction values ​​to obtain the absorbance D. For example, the absorbance D may be obtained using some correction values ​​extracted from the multiple correction values, such as the two largest values ​​among the multiple correction values.

[0041] In addition, in the above embodiment, the measurement object is the ground (excavated soil and sand from the ground) and the smectite content in the measurement object is measured as an example, but the measurement object and the mineral whose content is measured are not limited to those in the above embodiment.

[0042] In the above embodiment, the first, second, and third wavelengths are set in the wavelength range of approximately 1.9 to 2.0 μm. In contrast, smectite also exhibits a light absorption band in the wavelength range of approximately 1.4 to 1.5 μm. Because the wavelength range of approximately 1.4 to 1.5 μm overlaps with the absorption bands of other minerals, it is desirable to set the first to third wavelengths in the wavelength range of approximately 1.9 to 2.0 μm to further improve the accuracy of measuring the smectite content. However, if accuracy can be ensured, the first to third wavelengths may be set in other wavelength ranges, such as approximately 1.4 to 1.5 μm.

[0043] In the above embodiment, the wavelength having the middle wavelength length among the first to third wavelengths is designated as the first wavelength, and the reflectances of the other two wavelengths are corrected based on the first reflectance R1 of the first wavelength. Alternatively, the shortest wavelength of the three may be designated as the first wavelength and the reflectances of the other two wavelengths may be corrected, or the longest wavelength may be designated as the first wavelength and the reflectances of the other two wavelengths may be corrected. [Explanation of symbols]

[0044] 100 Mineral content measuring device 10 Measuring part 20 Arithmetic section C1 First correction value (correction value) C2 Second correction value (correction value) D. Absorbency R1 First reflectance (first measurement value) R2 Second reflectance (second measurement value) R3 Third reflectance (third measurement value)

Claims

1. A mineral content measurement method for measuring the content of a specific mineral contained in a measurement object, comprising: irradiating the measurement object with light and performing a spectral analysis of the measurement object; a step of acquiring the light absorbance of the measurement object based on first, second, and third measurement values ​​that are measurement results of the spectral analysis at first, second, and third wavelengths determined according to the mineral; and acquiring the content of the mineral in the measurement object based on the absorbance, The absorbance is obtained based on a corrected value obtained by quantifying the second measurement value and the third measurement value using the first measurement value. Methods for determining mineral content.

2. The method for measuring mineral content according to claim 1, a first correction value obtained by dividing the value of the second measurement value by the value of the first measurement value, and a second correction value obtained by dividing the value of the third measurement value by the value of the first measurement value, the absorbance is obtained as the product of the first correction value and the second correction value. Methods for determining mineral content.

3. The mineral content measurement method according to claim 2, the mineral is smectite, the first wavelength is set in a range of 1.90 μm or more and 1.98 μm or less, the second wavelength is set in a range of 1.80 μm or more and 1.88 μm or less, the third wavelength is set in the range of 2.02 μm or more and 2.10 μm or less; Methods for determining mineral content.

4. A mineral content measuring device for measuring the content of a specific mineral contained in a measurement object, a measurement unit that irradiates the measurement object with light and performs a spectral analysis of the measurement object; a calculation unit that acquires the content of the mineral in the measurement object based on the measurement result of the measurement unit, The calculation unit acquiring the light absorbance of the measurement object based on a first measurement value, a second measurement value, and a third measurement value, which are measurement results of the spectral analysis at a first wavelength, a second wavelength, and a third wavelength determined according to the mineral; The content of the mineral in the measurement object is obtained based on the absorbance, The absorbance is obtained based on a corrected value obtained by quantifying the second measurement value and the third measurement value using the first measurement value. Mineral content measuring device.

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