JP2018168655A - Soil determination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soil quality determination method capable of improving the accuracy of soil quality determination based on friction noise. SOLUTION: A soil quality determination method including the following steps (1) to (4) is provided. (1) The step of inserting a device having a microphone into the soil. (2) A step of measuring the frictional sound between the device and the soil with the microphone. (3) A step of deriving the data of the sound source of the fricative sound by correcting the data of the fricative sound measured by the microphone based on the transfer function of the device. (4) A step of determining the properties of the soil based on the data of the sound source. [Selection diagram] Fig. 5

Description

  The present invention relates to a soil quality determination method, apparatus, and program for determining soil quality based on friction sound between soil and a device inserted into the soil.

  When conducting ground surveys in the fields of civil engineering and architecture, a test called sounding is often performed to measure the hardness (strength) of the ground. Sounding is a test in which a resistor attached to the tip of a rod is inserted into the soil and the resistance is measured when the resistor penetrates into the soil or rotates in the soil. As a sounding method, various methods such as a standard penetration test, a static / dynamic cone penetration test, and a Swedish penetration test are known. In sounding, it is only possible to evaluate the hardness of the ground, and for example, the particle size cannot be determined. Therefore, when analyzing the particle size, it is common to take a soil sample from the local board (sampling) and bring this sample back to the laboratory for analysis (in-house test). However, sampling and laboratory tests are expensive and time consuming. Therefore, techniques for analyzing soil properties such as grain size by in-situ tests have also been proposed (see Patent Document 1, Non-Patent Documents 1 and 2, etc.).

  In Patent Document 1, a microphone is built in the cone attached to the tip of the rod used for the penetration test, the friction sound between the cone and the soil when the rod penetrates into the soil is detected, and this waveform is analyzed. Is disclosed. Patent Document 1 points out that the spectrum of frictional sound is affected by the average particle size of the soil.

  Non-Patent Documents 1 and 2 disclose that a microphone is built in a cone attached to the tip of a rod used for a dynamic cone penetration test, and friction noise between the cone and soil is measured. Non-Patent Documents 1 and 2 discuss the relationship between frictional sound and the content of fine particles or coarse particles.

JP-A 63-279139

Kento Mizuno and 7 others, “Consideration of the relationship between the frictional sound of the penetration cone and the ground by the large dynamic cone penetration test and the physical properties of the ground”, 51st Geotechnical Research Conference Lecture, NO. 92, pp. 183-184, 2016

Takashi Yamada and 5 others, "Trial of particle size evaluation using sound for ground liquefaction judgment by large dynamic cone penetration test", 49th Geotechnical Research Conference Lecture, NO. 107, pp. 213-214, 2014

  However, the methods of Patent Document 1 and Non-Patent Documents 1 and 2 still do not have sufficient accuracy for determining soil quality based on frictional sound. In this regard, the present inventors have considered that one of the causes is that the microphone does not accurately capture the waveform of the frictional sound source. That is, the waveform measured by the microphone is affected by the response characteristics of the microphone, and is not the waveform of the sound source itself. In addition, if the microphone and the device including the microphone are different for each test environment, the response characteristics change, and the results vary. This makes it impossible to accurately determine the soil quality.

  An object of this invention is to provide the soil determination method, apparatus, and program which can improve the precision of the determination of the soil based on a friction sound.

The soil quality determination method according to the first aspect includes the following steps.
(1) Inserting a device having a microphone into the soil (2) Measuring friction sound between the device and the soil with the microphone (3) Data on the friction sound measured by the microphone (4) Determining the property of the soil based on the sound source data by deriving the sound source data of the friction sound by correcting based on the transfer function of

  A soil quality determination method according to a second aspect is a soil quality determination method according to the first aspect, wherein the step (4) includes determining a particle size characteristic value of the soil based on data of the sound source. .

  The soil determination method according to the third aspect is the soil determination method according to the first or second aspect, wherein the step (4) is based on the sound source data and the sound of the friction sound at the sound source is detected. Calculating a pressure, and determining a property of the soil according to the sound pressure.

  A soil determination method according to a fourth aspect is the soil determination method according to any of the first to third aspects, wherein the device further includes a cone that houses the microphone, and the cone is a rod It is fixed at the tip. Inserting the device into the soil includes applying a force to the rod to penetrate the cone into the soil.

The soil quality determination method according to the fifth aspect is a soil quality determination method according to the fourth aspect, and further includes the following steps.
(5) Step of rotating the rod (6) Step of measuring peripheral friction acting on the rod during rotation of the rod The step of (2) is executed during rotation of the rod.

  A soil determination device according to a sixth aspect is a soil determination device that determines the property of soil into which a device having a microphone is inserted, and includes an acquisition unit, a correction unit, and a determination unit. The acquisition unit acquires measurement data that is data of friction sound between the device and the soil measured by the microphone. The correction unit derives data of the sound source of the frictional sound by correcting the measurement data based on a transfer function of the device. The determination unit determines the property of the soil based on the data of the sound source.

The soil determination program according to the seventh aspect is a soil determination program for determining the property of soil in which a device having a microphone is inserted, and causes the computer to execute the following steps (1) to (3).
(1) Obtaining measurement data that is data of friction sound between the device and the soil measured by the microphone (2) Correcting the measurement data based on a transfer function of the device, thereby obtaining the friction sound (3) Determining the properties of the soil based on the sound source data

  According to the present invention, the friction sound between the device and the soil is measured by the microphone included in the device inserted into the soil. Then, the data of the frictional sound measured by the microphone is corrected based on the transfer function of the device, whereby the data of the sound source of the frictional sound is derived. That is, the response characteristic of the device including the microphone is canceled from the data of the frictional sound measured by the microphone. The soil quality is determined based on the corrected frictional sound data. As described above, since the influence of the response characteristics of the device including the microphone is excluded from the data of the frictional sound measured by the microphone, it is possible to improve the accuracy of the determination of the soil quality based on the frictional sound.

BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram of the testing apparatus for enforcing the soil judgment method concerning one Embodiment of this invention. 1 is an enlarged cross-sectional view of a device including a cone according to an embodiment of the present invention. The block block diagram of the test apparatus which concerns on one Embodiment of this invention. The flowchart which shows the flow of the soil quality determination process based on the friction sound which concerns on one Embodiment of this invention. The figure which illustrates notionally the principle of extraction of sound source waveform data. The graph which shows the transfer function of three types of cones. The graph which shows the measurement waveform at the time of using three types of cones of FIG. The graph which shows the sound source waveform at the time of using 3 types of cones of FIG. The graph which compared the result of the soil quality judgment by a standard penetration test, and the result of the soil quality judgment based on a friction sound.

  Hereinafter, a soil determination method, apparatus, and program according to an embodiment of the present invention will be described with reference to the drawings.

<1. Overall configuration of test equipment>
FIG. 1 is an overall configuration diagram of a test apparatus 100 for carrying out the soil determination method according to the present embodiment. The soil determination method according to the present embodiment includes a normal dynamic cone penetration test, and measures the hardness (strength) of the ground and simultaneously performs a grain size analysis of the ground. As shown in FIG. 1, the test apparatus 100 includes a dynamic cone penetration tester 1 and a control device 2 that controls the operation of the dynamic cone penetration tester 1. The control device 2 measures the N value representing the hardness (strength) of the ground and the peripheral friction, and also based on the friction sound data between the cone 12 and the soil inserted into the soil during the dynamic cone penetration test. To determine the particle size characteristic value. This friction sound is measured by the microphone 3 housed in a cone 12 described later. Hereinafter, the configuration of the testing machine 1 and the control device 2 will be described in detail.

<2. Configuration of each part>
<2-1. Dynamic cone penetration testing machine>
As shown in FIG. 1, the dynamic cone penetration tester 1 includes a rod 11 and a device 10 having a cone 12 fixed to the tip of the rod 11. The rod 11 extends in the vertical direction. The cone 12 is a member whose tip is pointed in a conical shape, and is connected to the lower end of the rod 11 so that the apex of the cone faces downward.

  The testing machine 1 also includes a hammer 14 and a hammer guide 15 for allowing the hammer 14 to freely fall along the vertical direction. The hammer 14 is a striking device for applying a downward force to the upper end portion of the rod 11 when freely falling along the hammer guide 15 and penetrating the cone 12 into the soil by the force. The hammer 14 is a columnar member having a central axis extending in the vertical direction, and has a central opening along the central axis. The hammer guide 15 is a bar-like member extending in the vertical direction, and is inserted into the central opening of the hammer 14. The surface defining the central opening of the hammer 14 and the outer peripheral surface of the hammer guide 15 are configured to slide substantially without friction. The testing machine 1 also includes an anvil 13 that receives the upper end of the rod 11 and the lower end of the hammer guide 15. Therefore, the free-falling hammer 14 collides with the anvil 13, and the impact force at this time is transmitted to the rod 11 through the anvil 13. Note that the hammer 14 is lifted by a lifting device (not shown), and then freely dropped. The operation of the lifting device is controlled by the control device 2. The testing machine 1 includes a counter 20 that measures the number of drops of the hammer 14.

  Further, the testing machine 1 includes a torque measuring device 16. The torque measuring device 16 rotates the rod 11 and measures torque generated when the rod 11 rotates. In this embodiment, the torque measuring device 16 includes a swivel head configured to be able to grip the rod 11 and a hydraulic motor that rotates the swivel head in a state where the rod 11 is gripped. The operations of the swivel head and the hydraulic motor are controlled by the control device 2. The control device 2 converts the oil pressure when the rod 11 is rotated by the hydraulic motor into torque, and derives the peripheral friction acting on the rod 11 based on this torque.

  The cone 12, the rod 11, the anvil 13, the hammer 14, and the hammer guide 15 are aligned coaxially, and are arranged from the bottom to the top in this order. Further, the torque measuring device 16 is arranged so as to surround the rod 11 under the anvil 13. These elements 11 to 16 are supported on the ground by a support base 17 installed on the ground, a frame 18 extending upward from the support base, and a support column 19 that supports the support base 17 and the frame 18 so as not to fall down. Supported. The support column 19 is a rod-like member that extends obliquely from the frame 18 toward the ground, and the tip on the ground side is driven into the ground.

  FIG. 2 is an enlarged cross-sectional view of the device 10 including the cone 12. As shown in the figure, an internal space is formed in the cone 12, and the device 10 has a microphone 3 accommodated in the internal space. The microphone chamber in which the microphone 3 is installed is aligned with the central axis of the cone 12. The cone 12 is made of metal, and is made of stainless steel in the present embodiment. The microphone 3 is a sound collector for measuring the frictional sound between the cone 12 in the soil and the soil, and is a condenser microphone in this embodiment. In the present embodiment, the microphone 3 is fixed in the microphone chamber, and the gap in the microphone chamber in which the microphone 3 is accommodated is filled with epoxy resin so that the microphone 3 does not fall off due to the impact of the hammer 14 being hit. ing. Furthermore, in the present embodiment, the cover 31 is fixed to the inner wall surface of the cone 12 with screws 32 so as to cover the entrance of the microphone chamber in which the microphone 3 is accommodated. Further, the cover 31 is biased toward the microphone chamber side by the spring 33 with respect to the inner wall surface of the cone 12.

  FIG. 2 also shows the lower end of the rod 11. The rod 11 has a hollow shape as shown in FIG. A cable 3 a extends from the microphone 3 to the control device 2 through this central opening of the rod 11. The cable 3 a is a communication line that connects the microphone 3 and the control device 2, and transmits frictional sound data measured by the microphone 3 to the control device 2. The testing machine 1 includes a microphone amplifier 4, and a cable 3 a connects the microphone 3 and the microphone amplifier 4 and connects the microphone amplifier 4 and the control device 2. The microphone amplifier 4 amplifies the frictional sound data measured by the microphone 3 and then outputs the amplified data to the control device 2.

<2-2. Control device>
The control device 2 is a device that controls the operation of each part of the dynamic cone penetration testing machine 1, acquires various measurement data from each part of the dynamic cone penetration testing machine 1, and determines the soil quality based on this measurement data. is there. FIG. 3 shows a block configuration diagram of the test apparatus 100. As illustrated in FIG. 3, the control device 2 includes a display unit 21, an input unit 22, a storage unit 23, a control unit 24, and a communication unit 25. These parts 21 to 25 are connected to each other via a bus line 26.

  The display unit 21 is configured by a liquid crystal display or the like, and is a user interface that displays various screens to the operator. The input unit 22 includes an operation button, a touch panel, and the like, and is a user interface that receives operations from the operator for the control device 2 and the dynamic cone penetration tester 1. The communication unit 25 is a communication interface that enables communication with each unit of the dynamic cone penetration testing machine 1. The microphone 3 and the microphone amplifier 4 described above are connected to the communication unit 25 via the cable 3a. In addition, the lifting mechanism of the hammer 14, the counter 20, and the torque measuring device 16 are also connected to the communication unit 25. The storage unit 23 includes a nonvolatile storage device such as a hard disk or a flash memory. Stored in the storage unit 23 is a program 6 for causing the control device 2 and the dynamic cone penetration tester 1 to perform an operation described later.

  The control unit 24 includes a CPU, a ROM, a RAM, and the like, and reads and executes the program 6 stored in the storage unit 23, thereby virtually hitting the control unit 24a, the torque measurement unit 24b, and the sound. It operates as a measurement unit 24c, a correction unit 24d, and a soil determination unit 24e. The operation of each unit 24a to 24e will be described later.

<3. Soil determination method>
Next, a soil determination method performed by the test apparatus 100 will be described. First, the dynamic cone penetration testing machine 1 is installed on the ground to be subjected to soil quality determination as shown in FIG. 1, and the cone 12 is inserted into the soil.

  Subsequently, when the operator performs a predetermined operation on the input unit 22, the hitting control unit 24 a drives the above-described lifting mechanism and causes the hammer 14 to freely fall from the predetermined height position toward the anvil 13. The striking control unit 24a applies a downward force to the cone 12 by repeating the striking with the hammer 14, and gradually penetrates the cone 12 deeply into the soil. Then, every time the cone 12 enters deeper into the soil by a predetermined distance (for example, 20 cm), the hit with the hammer 14 is stopped. At this time, the hitting control unit 24 a reads the number of drops of the hammer 14 required for inserting the cone 12 deeper by a predetermined distance from the counter 20 and stores it in the storage unit 23. It is assumed that the insertion depth of the cone 12 is measured by a measuring device (not shown), and measurement data by the measuring device is transmitted to the hitting control unit 24a. The measuring device can have various configurations. For example, it can be realized as a winding displacement meter fixed to a jig fixed to the anvil 13, or a sensor that reads a scale attached to the rod 11. Etc. can be configured.

  The torque measuring unit 24b drives the torque measuring device 16 to rotate the rod 11 during the striking pause period. Further, the torque measuring unit 24b measures the torque (maximum rotational torque or the like) generated at this time via the torque measuring device 16, and based on this torque, the peripheral surface friction (friction force, frictional resistance, etc.) of the rod 11 with respect to the ground. ). The values of torque and circumferential friction are stored in the storage unit 23. When the torque measurement is finished, the hammer 14 is restarted. When the cone 12 is further inserted into the soil by a predetermined depth, the same torque is measured again.

  During the striking stop period, not only the torque is measured, but also the friction sound between the cone 12 and the soil is measured. The measurement of the frictional sound is performed while the rod 11 and the device 10 are rotating. FIG. 4 is a flowchart showing the flow of the soil quality determination process based on the friction sound. First, the sound measuring unit 24c drives the microphone 3 to cause the microphone 3 to measure the frictional sound between the rotating cone 12 and the surrounding soil, and the waveform of the frictional sound measured by the microphone 3 (hereinafter referred to as a measurement waveform). ) (Hereinafter referred to as measurement waveform data) is acquired (step S1). The measured waveform data is amplified by the microphone amplifier 4 and then collected by the sound measuring unit 24c. In the following, the measurement waveform data after amplification is also simply referred to as measurement waveform data. The measurement waveform data is time-series data, and is collected at a sampling period of 44.1 KHz in this embodiment. The measured waveform data is stored in the storage unit 23.

  Next, the correction unit 24d corrects the measurement waveform data so that the response characteristics of the device 10, that is, the response characteristics of the microphone 3 and the cone 12 are canceled from the measurement waveform data (step S2). Thereby, data (hereinafter referred to as sound source waveform data) representing a waveform (hereinafter referred to as sound source waveform) of the frictional sound source is extracted from the measured waveform data.

FIG. 5 is a diagram conceptually illustrating the principle of extraction of sound source waveform data. That is, the measurement waveform b (t) collected by the microphone 3 and recorded in the control device 2 is not the sound source waveform a (t) itself but a wave including the response characteristics of the device 10. When this relationship is formulated, the measurement waveform b (t) is expressed by a convolution integral of the sound source waveform a (t) and the impulse response function h (t) of the device 10 as shown in the following equation. Note that t represents time.

Here, the Fourier transform of the measured waveform b (t) is B (f), the Fourier transform of the sound source waveform a (t) is A (f), and the Fourier transform of the impulse response function h (t) is H (f). Then, the following equation holds.
B (f) = A (f) × H (f)

  H (f) is the transfer function of the device 10. Note that h (t) is a notation in the time domain of the transfer function of the device 10, and H (f) is a notation in the frequency domain of the transfer function of the device 10. The transfer function H (f) is a pair of spectra of a frequency response function (amplitude spectrum) and a phase spectrum. Note that f represents a frequency.

  In view of the above principle, in this embodiment, the transfer function H (f) as a parameter representing the response characteristic of the device 10 is measured in advance and stored in the storage unit 23. In step S2, the correction unit 24d performs frequency analysis on the measurement waveform data, and measures the frequency f while changing the frequency f from a lower limit frequency (for example, about 0 kHz to 20 Hz) to 22.1 kHz. A Fourier transform B (f) of the waveform b (t) is derived. Next, the correction unit 24d refers to the transfer function H (f) in the storage unit 23 and derives the Fourier transform A (f) of the sound source waveform a (t) based on the above equation. Subsequently, the correcting unit 24d derives the sound source waveform a (t) by performing inverse Fourier transform on A (f).

  In the present embodiment, the measured waveform data is analyzed in consideration of the response characteristics of the wave propagation system including the microphone 3 and the cone 12. Therefore, the sound source waveform data can be acquired by only determining the transfer function H (f) of the device 10 without considering the material and shape of the cone 12, the type of the microphone 3, and the like.

  In subsequent step S3, the soil determination unit 24e determines the soil based on the sound source waveform data. In the present embodiment, the soil grain size characteristic value is determined as an index for determining the soil quality. The particle size characteristic value includes the coarse particle content, the fine particle content, and the average particle size, and the soil determination unit 24e derives these depth distributions from the sound source waveform data.

  Here, the principle that the soil quality can be determined from the sound source waveform data will be described while showing the result of the verification experiment actually performed by the present inventors. First, the present inventors prepared three types of cones, each containing a condenser microphone, and created three devices (hereinafter, these devices were referred to as cone No. 1, cone No. 2, cone No. 3). And cone no. 1-No. When the transfer function H (f) of 3 was measured, the result of FIG. 6 was obtained.

Next, the ground with the same conditions was created three times, and cone no. 1-No. 3 was used to measure the frictional noise between the cone and the soil. More specifically, a model experiment was conducted on the ground with the same conditions of soil quality, density, and overlay pressure (soil cover pressure). For the soil sample, commercially available silica sand No. 5 (produced by Toki City, Gifu Prefecture) was used. As for soil layer conditions, a ground having a relative density of 50% was prepared by an air drop method, and the experiment was performed under dry conditions. The upper loading pressure was 50 kN / m ² , and the cone rotation speed was 45 deg / sec. The experimental results at this time are shown in FIGS. FIG. 7 (A) shows cone no. 1-No. 3 is a graph of the measured waveform b (t) when 3 is used, and FIG. 7B is a graph of the spectrum thereof. On the other hand, FIG. 8 shows sound source waveform data derived from the measured waveform data of FIG. 7 by the same calculation formula as in step S2, using the transfer function H (f) of FIG. FIG. 8 (A) shows cone no. 1-No. 3 is a graph of the sound source waveform a (t) when 3 is used, and FIG. 8B is a graph of the spectrum thereof.

  As can be seen from a comparison of FIGS. 7 and 8, the sound source waveform has a louder sound than the measurement waveform, and it can be seen that a peak not seen in the measurement waveform appears in the vicinity of 1000 kHz. Further, in the measurement waveform, the sound pressure level and the frequency at which the peak appears are different for each cone, whereas in the sound source waveform, the coincidence rate of the spectrum obtained from the three cones is high particularly in the frequency region of 300 Hz or higher. . Therefore, cone no. 1-No. It was found that according to the sound source waveform considering the response characteristic No. 3, the soil properties can be determined more accurately.

  In addition, the inventors of the present invention have a corn no. 2 was used to perform a dynamic cone penetration test on the ground in Suwa City, Nagano Prefecture, and the friction noise between the cone and the soil was measured at the time of torque measurement performed every 20 cm of penetration depth of the cone. Then, the sound source waveform a (t) of the friction sound was derived by the above-described method, and the depth distribution of the effective value of the sound pressure of the sound source waveform a (t) was derived. In addition, standard penetration tests are performed on the same ground, N value is obtained, soil samples are collected and analyzed, and depth distribution of particle size characteristic values (coarse grain content, fine grain content and average grain size) Was measured. The results of the above two experiments are shown in FIG. In addition, the graph of the dark dot in the graph of N value, a coarse particle content rate, and an average particle diameter is a graph of the effective value of the sound pressure of the sound source waveform a (t). Moreover, the graph of the thin dot in the graph of these graphs and the fine particle content rate has shown the result of the standard penetration test.

  As can be seen from FIG. 9, the shape of the effective value depth distribution of the sound pressure waveform a (t) is in good agreement with the N value, the coarse particle content, and the average particle size depth distribution. That is, when the N value, the coarse particle content, and the average particle size increase, the effective value of the sound source waveform a (t) also increases, and when the N value, the coarse particle content, and the average particle size decrease, the sound source waveform a. The effective value of (t) is also reduced. In addition, since the fine particle content is expressed by 1-coarse particle content, when the fine particle content increases, the effective value of the sound source waveform a (t) decreases, and the fine particle content becomes smaller. As the value decreases, the effective value of the sound source waveform a (t) increases. From the above, it has been found that the soil particle size characteristic values such as the N value and the fine particle content, the coarse particle content, and the average particle size can be determined according to the effective value of the sound source waveform a (t).

  In response to the above knowledge, in step S3, the soil determination unit 24e determines the effective value of the sound pressure of the sound source waveform a (t). And the soil quality determination part 24e determines the particle size characteristic values of soil, such as a fine particle content rate, a coarse particle content rate, and an average particle size, according to the effective value of the sound pressure of the sound source waveform a (t). It is assumed that parameters for converting the effective value of the sound pressure of the sound source waveform a (t) into various granularity characteristic values are obtained in advance through a number of experiments and stored in the storage unit 23.

  The above steps S1 to S3 are executed each time the cone 12 enters deeper into the soil by a predetermined depth. That is, the particle size characteristic value at each depth is calculated, and thereby the depth distribution of the particle size characteristic value is calculated. The depth distribution of the particle size characteristic value is stored in the storage unit 23.

  The results of the above various measurements are displayed on the display unit 21. Specifically, the depth distribution of the N value measured by the counter 20 and the depth distribution of the torque (circumferential friction) are displayed on the display unit 21 in addition to the depth distribution of the particle size characteristic value calculated in step S3. The The operator can determine the soil quality based on these pieces of information.

<4. Modification>
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the meaning. For example, the following changes can be made. Moreover, the gist of the following modifications can be combined as appropriate.

<4-1>
In the above embodiment, the soil determination processing based on the frictional sound is performed together with the dynamic cone penetration test, but can be combined with tests such as a standard penetration test, a static cone penetration test, and a Swedish penetration test. Alternatively, only the soil determination process based on the friction sound can be performed independently.

<4-2>
In the above embodiment, the soil determination process based on the frictional sound shown in FIG. 4 is executed by the control device 2 that controls the dynamic cone penetration test, but may be executed by another computer. In addition, a computer that executes soil quality determination processing based on frictional sound can be incorporated in the cone 12.

<4-3>
In the above embodiment, the transfer function H (f) in the frequency domain is measured in advance as a parameter representing the response characteristic of the device 10 and stored in the storage unit 23. h (t) can also be stored in advance.

<4-4>
In the above embodiment, the frictional sound is measured while the cone 12 is rotating, but the timing of the frictional sound measurement is not limited to this mode. For example, in the stage where the dynamic cone penetration test is completed and cleaned up, it is possible to measure the frictional sound when the rod 11 is pulled out from the ground.

DESCRIPTION OF SYMBOLS 1 Dynamic cone penetration test machine 10 Device 100 Test apparatus 11 Rod 12 Cone 2 Control apparatus 24c Sound measurement part (acquisition part)
24d Correction unit 24e Soil determination unit (determination unit)
3 Microphone a (t) Sound source waveform b (t) Measurement waveform H (f) Transfer function

Claims (7)

A soil judgment method,
Inserting a device with a microphone into the soil;
Measuring the friction sound between the device and the soil with the microphone;
Deriving the data of the sound source of the frictional sound by correcting the data of the frictional sound measured by the microphone based on a transfer function of the device;
Determining a property of the soil based on data of the sound source. The step of determining the property of the soil includes determining a particle size characteristic value of the soil based on data of the sound source.
The soil judgment method according to claim 1. The step of determining the property of the soil includes calculating a sound pressure of the friction sound based on the data of the sound source, and determining the property of the soil according to the sound pressure.
The soil quality determination method according to claim 1 or 2. The device further includes a cone that houses the microphone, and the cone is fixed to a tip of a rod;
Inserting the device into the soil includes applying a force to the rod to penetrate the cone into the soil;
The soil quality determination method according to any one of claims 1 to 3. Rotating the rod;
Measuring circumferential friction acting on the rod during rotation of the rod,
The step of measuring the frictional sound with the microphone is performed during rotation of the rod.
The soil quality determination method according to claim 4. A soil judgment device for judging the nature of soil into which a device having a microphone is inserted,
An acquisition unit that acquires measurement data that is data of friction sound between the device and the soil measured by the microphone;
A correction unit for deriving data of the sound source of the frictional sound by correcting the measurement data based on a transfer function of the device;
A soil determination device comprising: a determination unit that determines the property of the soil based on the data of the sound source. A soil determination program for determining the nature of soil into which a device having a microphone is inserted,
Obtaining measurement data that is data of friction sound between the device and the soil measured by the microphone;
Deriving data of the frictional sound source by correcting the measurement data based on the transfer function of the device;
Making the computer execute the step of determining the property of the soil based on the data of the sound source;
Soil judgment program.