Soil evaluation and discrimination method

Abstract

To provide a soil evaluation and discrimination method capable of comparatively easily and accurately evaluating and discriminating soil without requiring a large-scale device and complicated sample preparation.SOLUTION: This soil evaluation and determination method includes a signal acquisition step, an image data generation step, and an evaluation and determination step. In the image data generation step, an acoustic parameter value of the surface to be measured 61 is calculated based on the reflected wave signal acquired in the signal acquisition step, and ultrasonic image data corresponding to the value is generated. In the evaluation determination step, at least one index selected from the hardness, particle diameter, particle size distribution, and organic matter distribution of particles present in the soil, and the size, shape, and ratio of voids in the soil 51 is obtained based on the acoustic parameter value and the ultrasonic image data of the surface 61 to be measured. Then, the physical property evaluation and / or the kind discrimination of the soil is performed by using the obtained index as a determination material.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a method for assessing soil properties and classifying soil types. [Background technology]

[0002] Conventionally, methods for evaluating the physical properties of soil generally include methods using X-rays or electromagnetic waves, and methods using various microscopes.

[0003] Techniques that use electromagnetic waves (i.e., high-energy waves) such as X-rays are suitable for analyses that primarily involve inorganic substances (e.g., compositional analysis and identification of mineral species, contained elements, and clay minerals). Specific examples include XRF (X-ray fluorescence) analysis and XRD (X-ray diffraction) analysis. Conventional techniques for evaluating soil properties using electromagnetic waves are described, for example, in Patent Documents 1 and 2.

[0004] In the method using optical microscopes such as polarizing microscopes, soil thin sections are prepared and observed optically. Specifically, soil core samples are hardened with resin and sliced ​​to prepare soil thin sections, which are then polished to a thickness that can be observed with an optical microscope (25 μm to 30 μm). The prepared soil thin sections are then observed with a polarizing microscope to observe the soil structure, pore morphology, particle morphology, crystals, minerals, etc.

[0005] The electron microscope technique is an observation method in which an electron beam is irradiated onto the object to obtain a magnified image, and is suitable for observation at higher resolution than an optical microscope, which obtains a magnified image by irradiating it with light. For example, a transmission electron microscope (TEM) is a microscope that magnifies and observes electrons that have passed through the object. In a TEM, the density of the transmitted electrons changes depending on the structure and components of the object, and this becomes the microscopic image. A scanning electron microscope (SEM) is a microscope that observes images obtained from electrons reflected by the object. SEM is suitable for observing the surface shape and texture of an object, as well as the internal structure relatively close to the surface.

[0006] In addition to the above-mentioned methods, a method of evaluating soil physical properties using ultrasound has been conventionally known, and the present inventors have also previously reported on research into evaluating soil physical properties using an ultrasonic transmission method. However, there are fewer reported examples of soil property evaluation methods using ultrasound than the other methods mentioned above. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 63-307339 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-10568 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the above-mentioned conventional soil property evaluation methods have the following problems.

[0009] Methods that use electromagnetic waves such as X-rays not only require a considerable amount of time and effort to prepare samples, but also decompose organic matter during sample preparation, making it impossible to evaluate organic matter in the soil.

[0010] In the case of the method using an optical microscope, not only does it require skilled techniques to prepare extremely thin soil slices, but the process of preparing such slices also requires a considerable amount of time and effort.

[0011] In the case of methods using electron microscopes, high voltage generators and high vacuum generators are required, so the entire equipment is inevitably large-scale and a dedicated room is required to install the equipment.

[0012] In the case of the method using ultrasonic transmission, it is not currently possible to accurately evaluate the physical properties of soil, nor is it possible to evaluate the microstructure of soil.

[0013] The present invention has been made in view of the above-mentioned problems, and its object is to provide a soil evaluation and discrimination method that can evaluate and discriminate soil relatively easily and accurately without requiring large-scale equipment or complicated sample preparation. [Means for solving the problem]

[0014] In order to solve the above-mentioned problems, the invention described in claim 1 is a soil evaluation and discrimination method using an ultrasonic device having an ultrasonic probe capable of transmitting and receiving ultrasonic waves, comprising: a signal acquisition step of irradiating ultrasonic waves toward a measurement surface of the soil to be measured while scanning the measurement surface with the ultrasonic probe two-dimensionally along the measurement surface and acquiring reflected wave signals from the measurement surface; an image data generation step of calculating acoustic parameter values ​​of the measurement surface based on the acquired reflected wave signals and generating ultrasonic image data corresponding to the acoustic parameter values ​​of the measurement surface; and an evaluation and discrimination step of determining at least one index selected from the hardness, particle size, particle size distribution, and organic matter distribution of particles present in the soil, and the size, shape, and ratio of voids in the soil, based on the acoustic parameter values ​​of the measurement surface and the ultrasonic image data, and evaluating the physical properties and / or type of the soil using the determined index as a judgment material.

[0015] According to the invention described in claim 1, acoustic parameter values ​​of the measurement surface are calculated based on reflected wave signals acquired by transmitting and receiving ultrasonic waves while performing two-dimensional scanning, and ultrasonic image data is generated according to the calculated acoustic parameter values. This allows for the acquisition of data in which the calculated acoustic parameter values ​​are two-dimensionally mapped on the measurement surface, and an ultrasonic image of the measurement surface can be acquired based on the obtained mapping data of the acoustic parameter values. Furthermore, based on such acoustic parameter values ​​and ultrasonic image data, various indices for evaluating soil properties and / or identifying soil types can be easily determined. Therefore, using these indices as judgment materials allows for relatively easy and accurate evaluation and identification of soil. Furthermore, because the method of the present invention does not use high-energy waves such as electromagnetic waves such as X-rays, there is no need to decompose organic matter in the soil during sample preparation. Inorganic and organic matter can be directly subjected to the sample and measured. Therefore, it is possible to grasp the distribution of not only inorganic but also organic matter in the soil, which can be used as an indicator for the above-mentioned judgment. Furthermore, the method of the present invention, which uses reflected ultrasonic signals, does not require light or ultrasonic waves to penetrate the soil, so there is no need to form extremely thin soil slices.Furthermore, high voltage or high vacuum is not required, so the equipment does not need to be large-scale.

[0016] The invention described in claim 2 is based on claim 1, and its gist is that in the signal acquisition step, ultrasonic waves are irradiated using an ultrasonic probe of an ultrasonic microscope having an ultrasonic probe capable of transmitting focused ultrasonic waves, and in the image data generation step, ultrasonic image data of an ultrasonic microscope image that allows the microstructure of the soil to be grasped is generated.

[0017] Therefore, according to the invention described in claim 2, by irradiating focused ultrasonic waves from the ultrasonic probe of the ultrasonic microscope and using the reflected wave signals, it is possible to calculate the acoustic parameter values ​​of the measurement surface in a finer range, thereby making it possible to accurately grasp the microstructure of the soil.

[0018] The invention described in claim 3 is characterized in that in claim 1, the evaluation and discrimination step determines the type of mineral present in the soil based on the difference in the calculated acoustic parameter values.

[0019] The invention described in claim 4 is based on claim 1, and is characterized in that in the evaluation and discrimination step, a distribution state of the acoustic parameter values ​​is determined based on the acoustic parameter values ​​of the measurement surface as the index.

[0020] The invention described in claim 5 is characterized in that, in claim 1, when a first range is defined as a range to which the acoustic parameter values ​​of minerals contained in the soil belong, and a second range is defined as a range to which the acoustic parameter values ​​of organic matter contained in the soil belong and which is lower than the first range, the evaluation and discrimination step determines that a location where the calculated acoustic parameter value belongs to the first range is a location where minerals are present, and determines that a location where the calculated acoustic parameter value belongs to the second range is a location where organic matter is present.

[0021] Therefore, according to the invention as set forth in claim 5, it is possible to grasp the distribution states of minerals and organic matter in the soil, and therefore it is possible to more accurately evaluate and distinguish the soil.

[0022] The invention described in claim 6 is characterized in that, in any one of claims 1 to 5, before the signal acquisition step, an impregnation step of impregnating the voids between the soil particles with a liquid filler, and a soil block preparation step of solidifying the impregnated filler to prepare a soil block are carried out.

[0023] Therefore, according to the invention described in claim 6, by filling the voids with the solidified filler, the voids are not crushed and the soil can be maintained in the same state as when it was collected. In addition, since it becomes easier to obtain a measurement surface that is suitable for reflecting ultrasonic waves, the measurement accuracy of the acoustic parameter value can be improved.

[0024] The invention as set forth in claim 7 is characterized in that, in claim 6, a flattening step of flattening the surface to be measured in the soil block is further carried out after the soil block preparation step.

[0025] Therefore, according to the invention described in claim 7, by flattening the measurement surface, ultrasonic waves can be incident on the measurement surface at a right angle. Furthermore, as a result of ultrasonic waves being less likely to be scattered by the measurement surface, the measurement accuracy of acoustic parameter values ​​is improved.

[0026] The invention described in claim 8 is based on claim 6, and its gist is that the filler has acoustic parameter values ​​in a solidified state that are smaller than the acoustic parameter values ​​of the minerals and organic matter contained in the soil and larger than the acoustic parameter values ​​of water.

[0027] Therefore, according to the invention described in claim 8, since a filler having acoustic parameter values ​​different from those of the minerals and organic matter is used, the minerals and organic matter can be distinguished from the filler, and the distribution status of the minerals and organic matter can be grasped more accurately. Furthermore, since the filler fills the voids, the shape, position, size, etc. of the voids can be grasped accurately. [Effects of the Invention]

[0028] As described above in detail, according to the inventions described in claims 1 to 8, it is possible to provide a soil evaluation and discrimination method that can evaluate and discriminate soil relatively easily and accurately without requiring large-scale equipment or complicated sample preparation. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic diagram showing the configuration of an ultrasonic image inspection device used when carrying out a soil evaluation and discrimination method according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the ultrasonic imaging inspection device. [Figure 3] 1 is a schematic diagram for explaining a procedure for preparing a soil sample used in a soil evaluation and discrimination method according to an embodiment. [Figure 4] FIG. 10 is a schematic diagram for explaining the procedure for preparing soil samples. [Figure 5] FIG. 10 is a schematic diagram for explaining the procedure for preparing soil samples. [Figure 6] FIG. 10 is a schematic diagram for explaining the procedure for preparing soil samples. [Figure 7] FIG. 10 is a schematic diagram for explaining the procedure for preparing soil samples. [Figure 8] 10(a) to 10(d) are acoustic impedance images of four different types of soil in an example illustrating the soil evaluation and discrimination method of the embodiment. [Figure 9] Enlarged acoustic impedance images of red-yellow soil collected in Itoman City, Okinawa Prefecture, enlarged for each scan area. [Figure 10] Magnified acoustic impedance image of the red-yellow soil with comments. [Figure 11] Magnified acoustic impedance image of the red-yellow soil with comments. [Figure 12] Magnified acoustic impedance image of the red-yellow soil with comments. [Figure 13] Magnified acoustic impedance image of the red-yellow soil with comments. [Figure 14] A histogram showing the distribution of acoustic impedance values ​​for the red-yellow soil. [Figure 15] Enlarged acoustic impedance images of sandy soil collected in Shimizu Ward, Shizuoka City, Shizuoka Prefecture, enlarged for each scan area. [Figure 16] Enlarged acoustic impedance image of the above sandy soil with comments. [Figure 17] Enlarged acoustic impedance image of the above sandy soil with comments. [Figure 18] A histogram showing the distribution of acoustic impedance values ​​for the above sandy soil. [Figure 19] Enlarged acoustic impedance images of stagnant gleyed soil collected in Furano, Hokkaido, enlarged for each scan area. [Figure 20] Magnified acoustic impedance image of the above stagnant water gley soil with comments. [Figure 21] Magnified acoustic impedance image of the above stagnant water gley soil with comments. [Figure 22] Magnified acoustic impedance image of the above stagnant water gley soil with comments. [Figure 23] 1 is a histogram showing the distribution of acoustic impedance values ​​of the stagnant water gley soil. [Figure 24] Enlarged acoustic impedance images of allophanic andosol collected in Nakai, Hokota City, Ibaraki Prefecture, enlarged for each scan area. [Figure 25] Magnified acoustic impedance image of the above allophanic andosol with comments. [Figure 26] Magnified acoustic impedance image of the above allophanic andosol with comments. [Figure 27] Magnified acoustic impedance image of the above allophanic andosol with comments. [Figure 28] (a) is an optical microscope image of allophanic Andosol, and (b) is an acoustic impedance image of the same area. DETAILED DESCRIPTION OF THE INVENTION

[0030] A soil evaluation and discrimination method according to one embodiment of the present invention will be described in detail below with reference to FIGS.

[0031] First, the device used to carry out this soil evaluation and discrimination method will be described.

[0032] 1 is a schematic diagram showing an ultrasonic image inspection device 1 as an acoustic parameter measurement device, and FIG. 2 is a block diagram showing the electrical configuration of the ultrasonic image inspection device 1. As shown in FIG.

[0033] 1, the ultrasonic image inspection device 1 of this embodiment includes a pulsed excitation ultrasonic microscope 2 and a personal computer (personal computer) 3. The pulsed excitation ultrasonic microscope 2 includes a microscope main body 5 and an ultrasonic probe 6, which is electrically connected to the personal computer 3. A plate-shaped soil sample 57 (described later) can be placed on a sample stage 4 provided on top of the microscope main body 5 with the measurement surface 61 facing downward and horizontally.

[0034] The ultrasonic probe 6 comprises a probe body 12, an ultrasonic transducer 13, and an XY stage 14. The probe body 12 is mounted on the XY stage 14 and has a reservoir 11 at its tip that can store water W1, an ultrasonic wave transmission medium. The ultrasonic transducer 13 is disposed approximately in the center of the probe body 12. The reservoir 11 of the probe body 12 is open at the top, and the ultrasonic probe 6 is disposed with the open side of the reservoir 11 facing upward. The XY stage 14 scans the probe body 12 two-dimensionally along the horizontal direction (i.e., along the measurement surface 61 of the plate-shaped soil sample 57).

[0035] The ultrasonic transducer 13 (focused ultrasonic vibrator) is pulse-excited to irradiate focused ultrasonic waves onto the measurement surface 61 of the plate-shaped soil sample 57. The focused ultrasonic waves irradiated by the ultrasonic transducer 13 are focused into a cone shape via an ultrasonic transmission medium W1 and are focused on the measurement surface 61. In this embodiment, the ultrasonic transducer 13 has specifications of a diameter of 2.4 mm, a focal length of 3.2 mm, a center frequency of 80 MHz, and a bandwidth of 50 to 105 MHz (-6 dB), but is not limited to these.

[0036] As shown in FIG. 2, the ultrasonic probe 6 includes an ultrasonic transducer 13, an XY stage 14, a pulse generating circuit 21, a receiving circuit 22, a transmitting / receiving wave separating circuit 23, an A / D conversion circuit 25, an encoder 26, and a controller 27.

[0037] The XY stage 14 (two-dimensional scanning means) includes an X stage 14X and a Y stage 14Y for two-dimensionally scanning the irradiation point of the focused ultrasonic waves, and motors 28X and 28Y for driving the respective stages 14X and 14Y. Stepping motors or linear motors are used as these motors 28X and 28Y.

[0038] A controller 27 is connected to each of the motors 28X, 28Y, and the motors 28X, 28Y are driven in response to drive signals from the controller 27. By driving these motors 28X, 28Y, the X stage 14X is continuously scanned (continuously fed) and the Y stage 14Y is controlled to be fed intermittently, thereby enabling high-speed scanning of the XY stage 14.

[0039] In this embodiment, an encoder 26 is provided corresponding to the X stage 14X, and the encoder 26 detects the scanning position of the X stage 14X. Specifically, if the scanning range (e.g., a scanning range of 4.8 mm vertically and horizontally) is divided into 300 × 300 measurement points (pixels), one scan in the X direction (horizontal direction) is divided into 300 parts. The position of each measurement point is detected by the encoder 26 and input to the personal computer 3. The personal computer 3 generates a drive control signal in synchronization with the output of the encoder 26 and supplies the drive control signal to the controller 27. The controller 27 drives the motor 28X based on the drive control signal to move the X stage 14X in the X direction by one pixel (0.016 mm in this case). Furthermore, the controller 27 drives the motor 28Y based on the output signal of the encoder 26 when scanning of one line in the X direction is completed, to move the Y stage 14Y in the Y direction by one pixel (0.016 mm in this case).

[0040] Furthermore, the controller 27 generates a trigger signal in synchronization with the drive control signal and supplies it to the pulse generating circuit 21. As a result, an excitation pulse is generated in the pulse generating circuit 21 at a timing synchronized with the trigger signal. The excitation pulse is supplied to the ultrasonic transducer 13 via the transmission / reception separation circuit 23, and as a result, focused ultrasonic waves are emitted from the ultrasonic transducer 13. In this embodiment, as the XY stage 14 moves, two-dimensional scanning of the focused ultrasonic waves is sequentially performed in the X and Y directions along the measurement surface 61.

[0041] The ultrasonic transducer 13 is an element that can be used for both transmitting and receiving waves, and converts ultrasonic waves (reflected waves) reflected by the measurement surface 61 into electrical signals. The reflected wave signals are then supplied to the receiving circuit 22 via the transmitting and receiving wave separation circuit 23. The receiving circuit 22 is configured to include a signal amplification circuit, and amplifies and outputs the reflected wave signals.

[0042] The reflected wave signal is supplied to the A / D conversion circuit 25 and then transferred to the personal computer 3. The personal computer 3 then extracts the reflected wave signal from the measurement surface 61 of the soil sample 57 and the reflected wave signal from a reference member (not shown) placed on the measurement surface 61. The reference member is not particularly limited, but for example, a resin material having known acoustic properties is used, and in this embodiment, for example, polystyrene resin (acoustic impedance value: 2.34×10 6 kg / m 2 It is of course possible to use a resin material other than polystyrene resin as the reference member.

[0043] The personal computer 3 includes a CPU 31 , an I / F circuit 32 , a memory 33 , a storage device 34 , an input device 35 , and a display device 36 , which are interconnected via a bus 37 .

[0044] The CPU 31 executes control programs using the memory 33 and performs overall control of the entire system. The control programs include a program for controlling two-dimensional scanning by the XY stage 14, a program for calculating acoustic impedance values, a program for displaying an acoustic impedance image of the ultrasonic microscope 2, and the like.

[0045] The I / F circuit 32 is an interface (specifically, a USB interface) for transmitting and receiving signals to and from the ultrasonic probe 6. The I / F circuit 32 outputs a control signal (a drive control signal to the controller 27) to the ultrasonic probe 6, and inputs transfer data from the ultrasonic probe 6 (such as data transferred from the A / D conversion circuit 25).

[0046] The display device 36 is, for example, a color display such as an LCD or CRT, and is used to display an image (acoustic impedance image) of the soil block 56 and an input screen for various settings. The input device 35 is, for example, a keyboard or mouse device, and is used to input requests, instructions, and parameters from the user.

[0047] The storage device 34 is a magnetic disk device, an optical disk device, or the like, and stores a control program and various data. The storage device 34 may store data such as the acoustic impedance values ​​of various components contained in the soil and the acoustic impedance value of a reference member.

[0048] The CPU 31 transfers programs and data from the storage device 34 to the memory 33 and executes them sequentially in accordance with instructions from the input device 35. The programs executed by the CPU 31 may be programs stored in a storage medium such as a memory card, a flexible disk, or an optical disk, or programs downloaded via a communication medium, and are installed in the storage device 34 for use when executed.

[0049] Next, a method for producing a plate-shaped soil sample 57, which is the object for measuring the acoustic impedance value, will be described with reference to FIGS.

[0050] First, a sample of soil 51 is collected using a conventionally known soil sampler 52 (collection step). The soil sampler 52 shown in Fig. 3 has a structure in which a pair of grippers 53 protrude from the outer periphery of the upper end of a hollow cylindrical main body 54. By holding the grippers 53 of the soil sampler 52 and inserting the lower end of the main body 54 vertically into the soil 51 by about several tens of centimeters, a lump of soil 51a is taken into the main body 54 as a sample (see Fig. 4).

[0051] Next, the collected soil clod 51a is impregnated with liquid filler 55 (impregnation step). Specifically, the liquid filler 55 is supplied from the upper opening side of the main body 54 of the soil sampler 52, and the filler 55 is gradually permeated from the top surface of the collected soil clod 51a toward the bottom surface. The filler 55 may be permeated naturally by the action of gravity, but may also be permeated forcibly, for example, by drawing a vacuum from the bottom side. In this case, the filler 55 can be permeated efficiently in a short time. Note that there are voids of various shapes between the various particles that make up the soil 51, and the filler 55 is impregnated in such a way that it fills these voids.

[0052] The filler 55 may be, for example, a thermosetting resin, such as unsaturated polyester resin, epoxy resin, polyurethane resin, or polyphenol resin. The reason for using a thermosetting resin is that filling voids with the solidified filler 55 allows the soil to maintain its original state at the time of collection without collapsing the voids. Furthermore, the surface of the soil sample 57 hardens and becomes less uneven, making it easier to obtain a measurement surface 61 suitable for reflecting focused ultrasound. Furthermore, the solidified soil mass 51a facilitates cutting and polishing. While the filler 55 may or may not be colored, it is preferable to select an uncolored, transparent, or translucent resin for improved visibility when performing optical microscopy observations. While the curing temperature of the thermosetting resin filler 55 is not particularly limited, it is preferable to select a filler 55 that hardens at a low temperature (e.g., approximately 60°C to 80°C) in order to preserve the state of the organic matter contained in the soil as much as possible.

[0053] As such a filler 55, the acoustic parameter values ​​in a solidified state are those of the minerals and organic matter contained in the soil 51 (1.80×10 6 kg / m 2 s or more) and is smaller than the acoustic parameter value of water (approximately 1.50 × 10 6 kg / m 2 In this embodiment, the acoustic parameter value in the solidified state is selected to be, for example, 1.53×10 6 kg / m 2 s~1.80×10 6 kg / m 2 A thermosetting resin of about s is used as the filler 55.

[0054] Next, the impregnated filler 55 is solidified to produce a soil block 56 (soil block production step). Here, the soil mass 51a is heated in the state shown in FIG. 6 to harden the filler 55, thereby obtaining a solidified, cylindrical soil block 56. FIG. 7 shows the completed soil block 56 removed from the soil sampler 52.

[0055] Next, the cylindrical soil block 56 is cut and sliced ​​along its axis to a predetermined thickness (for example, about 5 mm to 20 mm) to prepare a plate-shaped soil sample 57 (see FIG. 7). The surface revealed by the cutting (i.e., the measurement surface 61) is then polished to flatten the measurement surface 61 (flattening step). Note that R1 in FIG. 7 indicates the measurement area R1 set within the measurement surface 61, 56a indicates the upper end surface close to the ground surface, and 56b indicates the lower end surface close to the underground.

[0056] Next, the soil evaluation and discrimination method of this embodiment will be described step by step.

[0057] First, the plate-shaped soil sample 57 that has been subjected to a flattening process is prepared and set on the sample stage 4 with the surface 61 to be measured facing downward and horizontal (sample preparation step). Next, the ultrasonic probe 6 is scanned two-dimensionally along the surface 61 to be measured of the plate-shaped soil sample 57, while irradiating the surface 61 with focused ultrasonic waves, and a reflected wave signal from the surface 61 to be measured is acquired (signal acquisition step). Specifically, the process is as follows.

[0058] First, as an initial operation of the ultrasonic probe 6, the motors 28X and 28Y are driven by the controller 27 based on instructions from the CPU 31, and the XY stage 14 is moved so that the scanning position is located at the reference member. At this time, when an excitation pulse is supplied to the transducer 13, focused ultrasonic waves So are irradiated onto the reference member, and the reflected waves Sr are amplified by the receiving circuit 22 and converted into digital data by the A / D conversion circuit 25. Then, the CPU 31 acquires the digital data converted by the A / D conversion circuit 25 via the I / F circuit 32, and stores the data in the memory 33 as intensity data of the reflected waves from the reference member.

[0059] Thereafter, motors 28X and 28Y are driven by controller 27 based on instructions from CPU 31, and two-dimensional scanning by XY stage 14 is initiated. CPU 31 acquires coordinate data of the measurement point based on the output of encoder 26. Next, focused ultrasonic waves So are irradiated onto measurement area R1 on measurement surface 61 of soil sample 57, and the reflected waves St are amplified by receiving circuit 22 and converted into digital data by A / D conversion circuit 25. CPU 31 acquires the digital data converted by A / D conversion circuit 25 via I / F circuit 32, and stores the data in memory 33 as intensity data of the reflected waves from measurement surface 61 in association with the coordinate data.

[0060] Next, the CPU 31 calculates acoustic parameter values ​​of the measurement surface 61 based on the acquired reflected wave signal. Specifically, the CPU 31 performs predetermined arithmetic processing based on the above-mentioned data (i.e., intensity data of the reflected wave from the measurement surface 61) stored in association with the coordinate data, and calculates an acoustic impedance value for each piece of coordinate data. The calculated acoustic impedance values ​​are stored in the memory 33. Subsequently, ultrasonic image data (i.e., ultrasonic image data of an ultrasonic microscope image that allows the soil microstructure to be grasped) corresponding to the acoustic parameter values ​​of the measurement surface 61 is generated (image data generation step). Specifically, the CPU 31 first reads the calculated acoustic impedance value for each piece of coordinate data from the memory 33, and performs image processing to generate an acoustic impedance image based on this acoustic impedance value for each piece of coordinate data. More specifically, the CPU 31 performs color modulation processing using the acoustic impedance value to generate ultrasonic image data corresponding to the magnitude of the acoustic impedance value, and stores this ultrasonic image data in the memory 33. Specific examples of this processing include image processing in which the larger the acoustic impedance value, the stronger the reddish color tone, and the smaller the acoustic impedance value, the stronger the blueish color tone. When the CPU 31 determines that processing at all measurement points has been completed and one screen's worth of ultrasound image data has been acquired, it transfers the ultrasound image data to the display device 36 and displays an acoustic impedance image on the screen (image display step).

[0061] Once an acoustic impedance image based on the acoustic parameter values ​​of the measurement surface 61 and the ultrasonic image data has been obtained as described above, the physical properties of the soil 51 are evaluated and the type of soil 51 is identified (evaluation and identification step). Specifically, the following indices are first obtained based on the acoustic parameter values ​​(here, acoustic impedance values) of the measurement surface 61 and ultrasonic image data (here, an acoustic impedance image of the ultrasonic microscope 2 that can grasp the microstructure of the soil 51). Examples of the indices include the hardness, particle size, particle size distribution, and organic matter distribution of particles present in the soil 51, as well as the size, shape, and ratio of voids in the soil 51. The obtained indices are then used as criteria for evaluating the physical properties of the soil 51 and identifying the type of soil 51. Note that, although only one index may be used as criteria for evaluating the physical properties and / or identifying the type of soil, it is preferable to use a combination of multiple indices as criteria for making the judgment.

[0062] For example, the hardness of particles in the soil 51 can be determined to some extent by performing predetermined calculations based on acoustic parameter values ​​such as acoustic impedance. The particle size of particles in the soil 51 can be determined relatively easily by measuring the acoustic impedance image displayed on the screen of the display device 36. Similarly, the shape of particles in the soil 51 can be determined relatively easily by looking at the acoustic impedance image. The particle size distribution of particles in the soil 51 can be determined relatively easily by calculating the variance and coefficient of variation based on the particle size measurement results of multiple particles within a predetermined range. Even if minerals and organic matter are mixed in the soil 51, the organic matter will have different shapes, sizes, and acoustic impedance values ​​from the surrounding mineral particles. Therefore, the distribution of organic matter can be determined based on the acoustic impedance image displayed on the screen of the display device 36 and the acoustic impedance value of the corresponding location.

[0063] It is also believed that the voids in the soil 51 originally contained air and water, but most of this is replaced by the filler 55 after the impregnation step. Therefore, if there is a region in the acoustic impedance image displayed on the screen of the display device 36 that shows an acoustic impedance value corresponding to the filler 55, it can be determined that this is a void. In other words, if the acoustic impedance value is 1.53×10 6 kg / m 2 s~1.80×10 6 kg / m 2 If there is an area of ​​about s, it is concluded that there is a void. The size, shape, and ratio of the voids in the soil 51 can be determined relatively easily by measuring and observing the acoustic impedance image displayed on the screen of the display device 36.

[0064] Here, there are various minerals contained in the soil 51, which can be classified by size into clay with a particle size of 0.005 mm or less, silt with a particle size of 0.005 mm to 0.075 mm, sand with a particle size of 0.075 mm to 2 mm, gravel with a particle size of over 2 mm, etc. Note that silt refers to mud (or fine sand), which is a clastic material that is smaller than sand and coarser than clay. The acoustic impedance value of clay is approximately 2.20 × 10 6 kg / m 2 s~2.60×10 6 kg / m 2 The acoustic impedance value of silt is approximately 2.60 × 10 6 kg / m 2 s~3.00×10 6 kg / m 2 The acoustic impedance of sand is approximately 3.00 × 10 6 kg / m 2 s~7.00×10 6 kg / m 2 s. Here, the range to which the acoustic parameter values ​​of the minerals contained in the soil 51 belong is defined as the first range (2.20 × 10 6 kg / m 2 s~7.00×10 6 kg / m 2 s).

[0065] On the other hand, organic matter contained in the soil 51 can be mainly derived from plants (for example, seeds, etc.), and the acoustic impedance value of the organic matter is approximately 1.80×10 6 kg / m 2 s~2.20×10 6 kg / m 2 Here, the range to which the acoustic parameter values ​​of the organic matter belong and which is lower than the first range is defined as the second range.

[0066] In the evaluation and determination step, a location where the calculated acoustic impedance value falls within the first range may be determined as a "location where minerals are present," and a location where the calculated acoustic impedance value falls within the second range may be determined as a "location where organic matter is present." Furthermore, a range lower than the second range, specifically 1.53×10 corresponding to the acoustic impedance value of the filler 55, may be determined as a "location where organic matter is present." 6 kg / m 2 s~1.80×10 6 kg / m 2 The range in which s is satisfied may be defined as a third range and used to determine the location of a void.

[0067] In addition, in the evaluation and discrimination step, the type of mineral present in the soil 51 may be determined based on the differences in the calculated acoustic impedance values. In this case, the type determination may be performed by taking into account not only the differences in acoustic impedance values ​​but also the differences in particle size and shape of the particles contained in the soil 51. Furthermore, in the evaluation and discrimination step, the distribution of acoustic impedance values ​​may be determined based on the acoustic impedance value of the measurement surface 61 as an index for making the above determination. The distribution of acoustic impedance values ​​determined in this manner may be displayed on a screen, for example, as a histogram. Such a display allows the distribution of acoustic impedance values ​​to be easily understood visually.

[0068] [Example] An example will now be described to explain the evaluation and determination step of this embodiment in more detail.

[0069] In this example, soil samples 51 collected at four different locations were used as measurement targets. For each of these four types of soil 51, plate-shaped soil samples 57 were prepared according to the procedure described above. Specifically, after collecting soil samples 51 at each location (collection step), the collected soil clods 51a were impregnated with a liquid filler 55 (impregnation step). The filler 55 was then solidified by heat treatment to prepare soil blocks 56 (soil block preparation step). The cylindrical soil blocks 56 were then sliced ​​to prepare plate-shaped soil samples 57, and one side of each sample (measurement surface 61) was polished to form a flattened measurement surface 61 (flattening step). For each soil sample 57, a measurement area R1 was set at a depth of approximately 10 cm from the ground surface. The measurement area R1 was a rectangular shape elongated along the depth direction, specifically consisting of five or six 4.8 mm x 4.8 mm scan areas arranged vertically.

[0070] Next, these four types of soil samples 57, which are the measurement objects, were set in the ultrasonic image inspection device 1 of Fig. 1, and the signal acquisition step, image data generation step, and image display step were performed according to the procedure of the above embodiment. Then, through these steps, the acoustic impedance value of the measurement surface 61 was calculated, and an acoustic impedance image corresponding to the acoustic impedance value of the measurement surface 61 was generated and displayed. In this case, the range for analyzing the acoustic impedance value was set to 1.5 to 7 x 10 6 kg / m 2 The image was processed so that the larger the acoustic impedance value, the whiter (brighter) the color, and the smaller the acoustic impedance value, the blacker (darker) the color. The results are shown in Figure 8.

[0071] Figures 8(a) to (d) show acoustic impedance images of four types of soil 51. The soil shown in Figure 8(a) is a reddish-yellow soil (SP1) collected in Itoman City, Okinawa Prefecture. The soil shown in Figure 8(b) is a sandy soil (SP2) collected in Shimizu Ward, Shizuoka City, Shizuoka Prefecture. The soil shown in Figure 8(c) is a stagnant water gley soil (SP3) collected in Furano City, Hokkaido. The soil shown in Figure 8(d) is an allophanic andisolated soil (SP4) collected in Nakai, Hokota City, Ibaraki Prefecture.

[0072] Figure 9 shows enlarged acoustic impedance images of red-yellow soil (SP1) collected in Itoman City, Okinawa Prefecture, arranged by scan area. Figures 10 to 13 are enlarged acoustic impedance images of the red-yellow soil, accompanied by comments and acoustic impedance values. The acoustic impedance images in Figures 8(a) and 9 indicate that the soil is composed of fine particles of various types uniformly distributed throughout, and the entire image is dark. Most of the area in the acoustic impedance image is fine and fuzzy, but this area appears to have a fairly dense structure, with clay attached to fine sand or silt. Furthermore, the acoustic impedance image of the red-yellow soil (SP1) reveals the presence of large clay layers and clumps in some places. In addition to very fine voids, several large, elongated voids (cracks) were observed throughout the soil, suggesting that the soil is relatively permeable. Furthermore, the acoustic impedance image of this soil does not contain any organic matter.

[0073] Figure 14 shows a histogram of the acoustic impedance values ​​of red-yellow soil (SP1) collected in Itoman City, Okinawa Prefecture, at each depth. According to this histogram, the average acoustic impedance value of this soil is approximately 2.0 × 10 6 kg / m 2 s~2.5×10 6 kg / m 2 s. The average acoustic impedance value tended to decrease as one went underground. Furthermore, the dispersion of the acoustic impedance values ​​was relatively small.

[0074] Figure 15 shows enlarged acoustic impedance images of sandy soil (SP2) collected in Shimizu Ward, Shizuoka City, Shizuoka Prefecture, arranged by scan area. Figures 16 and 17 are enlarged acoustic impedance images of the same sandy soil, accompanied by comments and acoustic impedance values. The acoustic impedance images in Figures 8(b) and 15 indicate that the soil is composed of many relatively large, light-colored particles, and the entire image is noticeably bright. Based on the acoustic impedance values, these relatively large, light-colored particles were concluded to be sand particles. Furthermore, clay and voids were found to be present around the sand particles. However, while relatively small voids were observed, no large, elongated voids (cracks) were observed overall. Furthermore, the acoustic impedance image of this soil contained areas that were circular in shape and had acoustic impedance values ​​that were clearly different from those of the surrounding particles. These were considered to be organic matter (plant seeds).

[0075] Figure 18 shows a histogram of the acoustic impedance values ​​of sandy soil (SP2) collected in Shimizu Ward, Shizuoka City, Shizuoka Prefecture, plotted at each depth. According to this histogram, the average acoustic impedance value of this soil is approximately 2.6 × 10 6 kg / m 2 s~2.9×10 6 kg / m 2 s. The average acoustic impedance value tended to decrease as one went underground. Furthermore, the dispersion of the acoustic impedance values ​​was relatively large.

[0076] Figure 19 shows enlarged acoustic impedance images of a stagnant gley soil (SP3) collected in Furano City, Hokkaido, arranged by scan area. Figures 20 to 22 are enlarged acoustic impedance images of the stagnant gley soil, accompanied by comments and acoustic impedance values. The acoustic impedance images in Figures 8(c) and 19 indicate that the soil is composed primarily of fine sand and silt, and the overall image is darker than Figure 8(b). Compared to Figure 8(a), the soil particles tend to be slightly larger and the clay content lower. In addition to fine voids, several large, elongated voids (cracks) were observed throughout the soil, suggesting that the soil is relatively permeable. Furthermore, the acoustic impedance image of this soil did not contain any organic matter.

[0077] Figure 23 shows a histogram of the acoustic impedance values ​​of stagnant water gley soil (SP3) collected in Furano City, Hokkaido, plotted at different depths. According to this histogram, the average acoustic impedance value of this soil is approximately 1.8 × 10 6 kg / m 2 s~2.0×10 6 kg / m 2 s. Also, there was no tendency for the average acoustic impedance value to decrease as one goes underground. Furthermore, the dispersion (variance) of the acoustic impedance values ​​was relatively small. Incidentally, when comparing the histogram of the stagnant water gley soil (SP3) shown in Figure 23 with the histogram of the red-yellow soil (SP1) shown in Figure 14, the dispersion of the acoustic impedance values ​​of the former soil was slightly larger. Also, the dispersion of the acoustic impedance values ​​of the former soil was 2.0 x 10 6 kg / m 2 The frequency of occurrence of high acoustic impedance values ​​exceeding s was high. Furthermore, in the former soil, there was little difference in the shape of the histogram depending on the depth position, whereas in the latter soil, there was a difference in the shape of the histogram depending on the depth position.

[0078] Figure 24 shows enlarged acoustic impedance images of an allophanic andosol (SP4) collected in Nakai, Hokota City, arranged side-by-side for each scan area. The acoustic impedance images in Figures 8(d) and 24 indicate that this soil is primarily composed of silt and clay. The overall image is darker than Figure 8(b), but slightly brighter than Figures 8(a) and 8(c). The acoustic impedance image of this soil reveals widespread, fine, fuzzy areas, which indicate that these areas are composed of silt surrounded by clay and almost no sand particles. Furthermore, the proportion of bright areas in the acoustic impedance image tends to increase as one moves deeper underground. In addition to small voids, several large, elongated voids (cracks) were observed throughout the soil, but not as numerous as in Figures 8(a) and 8(c). Furthermore, the acoustic impedance image of this soil contains some areas that may be organic matter.

[0079] Incidentally, Figure 28(a) is an optical microscope image of allophanic andosol (SP4) collected in Nakai, Hokota City, and Figure 28(b) is an ultrasonic microscope image (acoustic impedance image) of the same area. By comparing these two images side by side, it was confirmed that cracks of the same shape were present in the same locations in the two images, and that there was a correspondence between the two images. However, areas that appeared uniform in the optical microscope image appeared non-uniform in the acoustic impedance image. In other words, the acoustic impedance values ​​within areas that appeared uniform in the optical microscope image were not consistent. Therefore, it was found that it was possible to determine the type and distribution of each particle in this area as well.

[0080] By comparing the acoustic impedance images obtained for each soil, it is possible to easily distinguish between, for example, the red-yellow soil (SP1) collected in Itoman City, Okinawa Prefecture and the sandy soil (SP2) collected in Shimizu Ward, Shizuoka City, Shizuoka Prefecture, based on differences in particle size. It is also possible to easily distinguish between, for example, the red-yellow soil (SP1) collected in Itoman City, Okinawa Prefecture and the stagnant gley soil (SP3) collected in Furano City, Hokkaido, based on differences in porosity. It is also possible to easily distinguish between, for example, the red-yellow soil (SP1) collected in Itoman City, Okinawa Prefecture and the allophanic andosol (SP4) collected in Nakai, Hokota City, Ibaraki Prefecture, based on differences in structural density.

[0081] The data of the results obtained by the above embodiment (such as acoustic impedance images and histograms for the four types of soil 51) may be stored in the memory 33 of the personal computer 3 and compiled into a database. Then, when an unknown soil sample is to be used as a measurement object in the future, the data stored in the database may be used to evaluate the physical properties and identify the type of the unknown soil 51.

[0082] Therefore, according to the above-described embodiment, the following effects can be obtained.

[0083] (1) According to the soil evaluation and discrimination method of this embodiment, the acoustic impedance value of the measurement surface 61 is calculated based on the reflected wave signal acquired by transmitting and receiving ultrasonic waves while performing two-dimensional scanning, and ultrasonic image data is generated according to the calculation result of the acoustic impedance value. Therefore, it is possible to acquire data in which the calculated acoustic impedance value of the measurement surface 61 is mapped two-dimensionally. Therefore, it is possible to acquire an acoustic impedance image of the measurement surface 61 based on the obtained mapping data of the acoustic impedance value. Furthermore, based on such acoustic impedance values ​​and acoustic impedance image, it is possible to easily obtain various indices for evaluating the physical properties of the soil 51 and / or for discriminating the type of the soil 51. Therefore, by using these indices as judgment materials, it is possible to relatively easily and accurately evaluate and discriminate the soil 51.

[0084] (2) The soil evaluation and discrimination method of this embodiment also has the advantage of not using high-energy waves such as electromagnetic waves, such as X-rays. Therefore, there is no need to decompose the organic matter in the soil 51 during sample preparation; inorganic and organic matter can be directly used in the sample for measurement. Therefore, it is possible to grasp the distribution of not only inorganic matter but also organic matter in the soil 51, which can be effectively used as an indicator for the above-mentioned judgment. In contrast, conventional ultrasonic transmission methods have been unable to grasp the presence or distribution of organic matter. Incidentally, by performing a process to extract organic matter from a bulk soil sample, it is possible to measure the amount of organic matter contained in the bulk soil sample. However, it was impossible to grasp the presence or distribution of organic matter on a specific surface of the soil 51.

[0085] (3) In the soil evaluation and discrimination method of this embodiment, because reflected ultrasonic signals are used, there is no need to transmit light or ultrasonic waves through the soil. Therefore, it is not necessary to use an extremely thin soil slice as the measurement object. In other words, this soil evaluation and discrimination method requires only one flat measurement surface 61, so there are no particular restrictions on the shape of the soil sample 57 itself. Therefore, unlike, for example, methods using optical microscopes, there is no need to prepare extremely thin soil slices, which require time, labor, and skilled techniques, and this avoids the need for complex and costly sample preparation work.

[0086] (4) The soil evaluation and discrimination method of this embodiment is implemented using an ultrasonic image inspection device 1 equipped with a pulsed-excitation ultrasonic microscope 2. In the signal acquisition step of this method, ultrasonic waves are irradiated using an ultrasonic probe 6 capable of transmitting focused ultrasonic waves. In the image data generation step, ultrasonic image data of an ultrasonic microscope image that allows the microstructure of the soil 51 to be grasped is generated based on the reflected wave signal of the ultrasonic waves. Therefore, the acoustic parameter values ​​of the measurement surface 61 can be calculated over a finer range. This makes it possible to accurately grasp the microstructure of the soil 51. Furthermore, the soil evaluation and discrimination method of this embodiment, which is implemented using the above-mentioned device, does not require a high-voltage generator or a high-vacuum generator, unlike methods that use electron microscopes. Therefore, the entire device does not become large-scale, and a dedicated room for installing the device is not required. Therefore, there are no restrictions on the installation location of the device, and high device costs can be avoided.

[0087] (5) In the soil evaluation and discrimination method of this embodiment, the distribution of acoustic parameter values ​​is determined based on the acoustic parameter values ​​of the measurement surface 61, and this distribution is used as one of the judgment indices for evaluating the physical properties and discriminating the type of soil 51. More specifically, the distribution of acoustic impedance values ​​is determined for each different depth position on the measurement surface 61, and the determined distribution of acoustic impedance values ​​is displayed on the screen as multiple histograms (see FIGS. 14, 18, and 23). Displaying the distribution in this manner makes it easy to visually understand the distribution of acoustic impedance values. Furthermore, knowing the distribution of acoustic impedance values ​​makes it easier to compare the physical properties of each type of soil 51, making it possible to easily and accurately evaluate the physical properties and discriminate the type. In particular, in this embodiment, the distribution of acoustic impedance values ​​at each different depth can be grasped, which has the advantage of conveniently increasing the amount of information available when comparing the physical properties of each type of soil 51.

[0088] (6) In the soil evaluation and discrimination method of this embodiment, the voids between the soil particles 51 in the soil sample 57 are impregnated with a liquid filler 55, the filler 55 is solidified, and a soil block is prepared. Then, ultrasonic reflected wave signals are acquired. By filling the voids with the solidified filler as described above, the soil can be measured without crushing the voids. Furthermore, since a measurement surface 61 suitable for reflecting ultrasonic waves is easily obtained, the measurement accuracy of the acoustic parameter values ​​can be improved. Furthermore, in this embodiment, after the soil block preparation step, a plate-shaped soil sample 57 is cut out from the soil block 56, and the exposed measurement surface 61 is flattened. Therefore, ultrasonic waves can be incident perpendicularly on the measurement surface 61 and are less likely to be scattered by the measurement surface 61, resulting in improved measurement accuracy of the acoustic parameter values.

[0089] (7) In the soil evaluation and discrimination method of this embodiment, the soil block 56 is prepared using a filler 55 whose acoustic impedance in a solidified state is smaller than that of the minerals and organic matter contained in the soil 51 and larger than that of water. In other words, because the filler 55 has acoustic impedance values ​​different from those of the minerals and organic matter, the minerals and organic matter can be distinguished from the filler 55, allowing for a more accurate understanding of the distribution of each mineral and organic matter. Furthermore, because the filler 55 fills voids, the shape, position, size, etc. of the voids can be accurately understood. Therefore, for example, in this embodiment, the condition of cracks in the soil 51 can also be understood. Furthermore, if the size, directionality, distribution, etc. of the cracks are known, it becomes possible to predict the flow pattern in the soil 51, as well as predict the permeability and water retention properties.

[0090] (8) In the soil evaluation and discrimination method of this embodiment, soil sample 57 is prepared by impregnating soil 51 with filler 55, which is a transparent thermosetting resin. Therefore, optical microscope images and ultrasonic microscope images (acoustic impedance images) can be acquired for the same area of ​​a common measurement object (common measurement surface 61), and these images can be compared and observed side by side. Based on both the optical microscope image and the ultrasonic microscope image (acoustic impedance image), it becomes possible to more easily and accurately evaluate the physical properties of soil 51 and discriminate the type of soil 51.

[0091] The above embodiment may be modified as follows.

[0092] In the above embodiment, the ultrasonic image inspection device 1 including the pulsed excitation ultrasonic microscope 2 is used, and the ultrasonic probe 6 is used to transmit and receive focused ultrasonic waves to generate ultrasonic image data of an ultrasonic microscope image that can grasp the microstructure of the soil 51. However, the present invention is not limited to this. For example, in another embodiment, ultrasonic image data of an ultrasonic image may be generated by transmitting and receiving ultrasonic waves using an ultrasonic image inspection device that does not include the ultrasonic microscope 2.

[0093] In the above embodiment, the soil block preparation step is followed by a flattening step for flattening the measurement surface 61 of the soil block 56, but this is not limiting. For example, if the measurement surface 61 is flat to a certain extent without any further effort, the flattening step may be omitted.

[0094] In the above embodiment, the signal acquisition step is preceded by an impregnation step in which liquid filler 55 is impregnated into voids between particles of soil 51, and a soil block preparation step in which the impregnated filler 55 is solidified to prepare a soil block, but this is not limiting. For example, if the collected soil mass 51a is sufficiently hard and can maintain its shape, the signal acquisition step may be performed without performing the impregnation step or the soil block preparation step. [Explanation of symbols]

[0095] 1: Ultrasound imaging inspection equipment as an ultrasound device 2: Ultrasound microscope 6: Ultrasound probe 51: Soil 55: Filling material 56: Soil Block 61: Surface to be measured

Claims

1. A soil evaluation and discrimination method using an ultrasonic device having an ultrasonic probe capable of transmitting and receiving ultrasonic waves, a signal acquisition step of irradiating ultrasonic waves toward a measurement surface of the soil to be measured while scanning the ultrasonic probe two-dimensionally along the measurement surface, and acquiring a reflected wave signal from the measurement surface; an image data generating step of calculating acoustic parameter values ​​of the measurement target surface based on the acquired reflected wave signals and generating ultrasound image data according to the acoustic parameter values ​​of the measurement target surface; an evaluation and discrimination step of determining at least one index selected from the hardness, particle size, particle size distribution, and organic matter distribution of particles present in the soil, and the size, shape, and ratio of voids in the soil, based on the acoustic parameter values ​​of the measurement surface and the ultrasonic image data, and evaluating the physical properties and / or discriminating the type of the soil using the determined index as a judgment material; A soil evaluation and discrimination method, including:

2. In the signal acquisition step, ultrasonic waves are irradiated using an ultrasonic probe of an ultrasonic microscope that has an ultrasonic probe capable of transmitting focused ultrasonic waves, In the image data generating step, the ultrasonic image data of the ultrasonic microscope image that can grasp the microstructure of the soil is generated.

2. The soil evaluation and discrimination method according to claim 1.

3. 2. The soil evaluation and discrimination method according to claim 1, wherein the evaluation and discrimination step determines the type of minerals present in the soil based on the difference between the calculated acoustic parameter values.

4. 2. The soil evaluation and discrimination method according to claim 1, wherein the evaluation and discrimination step determines, as the index, a distribution state of the acoustic parameter values ​​based on the acoustic parameter values ​​of the measurement surface.

5. When a range to which the acoustic parameter values ​​of the minerals contained in the soil belong is defined as a first range, and a range to which the acoustic parameter values ​​of the organic matter contained in the soil belong and which is lower than the first range is defined as a second range, In the evaluation and discrimination step, a location where the calculated acoustic parameter value falls within the first range is determined to be a location where minerals are present, and a location where the calculated acoustic parameter value falls within the second range is determined to be a location where organic matter is present.

2. The soil evaluation and discrimination method according to claim 1.

6. before the signal acquisition step, an impregnation step of impregnating voids of the soil particles with a liquid filler; a soil block preparation step of solidifying the impregnated filler to prepare a soil block; 6. The soil evaluation and discrimination method according to claim 1, wherein the following steps are carried out:

7. 7. The soil evaluation and discrimination method according to claim 6, further comprising the step of flattening the surface to be measured in the soil block after the soil block preparation step.

8. 7. The soil evaluation and discrimination method according to claim 6, wherein the filler has acoustic parameter values ​​in a solidified state that are smaller than the acoustic parameter values ​​of the minerals and organic matter contained in the soil and larger than the acoustic parameter value of water.

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