Method for estimating propagation speed, device for estimating propagation speed, program for estimating propagation speed, measuring device for ground improvement bodies, and construction device for ground improvement bodies.

Abstract

This method estimates the propagation speed of elastic waves propagating through a medium without using a guide tube for measuring propagation speed. [Solution] The method includes the steps of acquiring a received waveform obtained by multiple vibration receiving sensors 162 of an array sensor 160 from an elastic wave emitted from an oscillator 154, and setting the propagation speed at which the amplitude value of the output waveform obtained by array signal processing performed on the received waveform by changing the propagation speed to the propagation speed of the elastic wave is the propagation speed of the elastic wave.

Description

Technical Field

[0001] The present invention relates to a propagation speed estimation method, a propagation speed estimation device, a propagation speed estimation program, a measuring device for a ground improvement body, and a ground improvement body forming device.

Background Art

[0002] Patent Document 1 discloses a technique related to a method for measuring the formation shape of a ground improvement body formed by high-pressure injection of a curing material liquid or the like from an injection rod inserted into the ground. In this prior art, a sound wave oscillator and a vibration receiver are inserted into the ground for forming the ground improvement body, and while injecting the curing material liquid into the ground to form the ground improvement body, the sound wave oscillated from the sound wave oscillator is continuously received by the vibration receiver at the interface between the ground and the ground improvement body, thereby measuring the formation shape of the ground improvement body.

[0003] Patent Document 2 discloses a technique related to a measuring device for a ground improvement body and a buried object. In this prior art, the measuring device includes a rotating rod inserted into the ground improvement body before curing, an oscillation unit provided on the rotating rod for simultaneously oscillating ultrasonic waves of different frequencies from the same sound source in the same direction, a vibration receiving unit provided on the rotating rod for receiving reflected waves reflected by the boundary between the ground improvement body and the ground and the buried object buried in the ground due to the interaction of ultrasonic waves of different frequencies oscillated from the oscillation unit, and a detection device for detecting the boundary position between the ground improvement body and the ground and the buried position of the buried object based on the time difference between the oscillation of the ultrasonic waves of the oscillation unit and the reception of the reflected waves of the vibration receiving unit.

[0004] In addition, other related technologies are disclosed in Non-Patent Documents 1 to Non-Patent Documents 6.

Prior Art Documents

Patent Documents

[0005] [[ID=3I]]

Patent Document 1

Patent Document 2

[0006] [Non-Patent Document 1] Soft Ground Improvement Technology: Jet Grout Method (Technology, Design, and Management) (Published by Gijutsudo Publishing) [Non-Patent Document 2] Quality characteristics and control methods for high-pressure injection mixing methods. (Foundation Engineering, March 2022 issue) [Non-Patent Document 3] Verification test of improved shape of high-pressure jet agitation method using acoustic exploration. 73rd Annual Scientific Conference of the Japan Society of Civil Engineers (August 2018) [Non-Patent Document 4] Improved Shape Measurement Test of High-Pressure Jet Mixing Method Using Sonar Exploration: Proceedings of the 14th Ground Improvement Symposium [Non-Patent Document 5] Acoustical Technology Series 16: Array Signal Processing of Sounds - The Acoustical Society of Japan [Non-Patent Document 6] Effects of air voids on ultrasonic wave propagation in early age cement pastes. Cement and Concrete Research, 41, (2011), 872-881. Jinying Zhu, Seong-Hoon Kee, Dongyeop Han, Yi-Te Tsai [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] For example, in the field of civil engineering and construction, there is a need for a technology to efficiently measure the improved diameter of ground improvement bodies created by high-pressure jet agitation, one of the ground improvement technologies, and technological development using acoustic exploration technology is underway. However, in the case of unconsolidated ground improvement bodies constructed by high-pressure jet agitation, the propagation speed of elastic waves changes over time as the ground improvement body itself hardens. When measuring the diameter of such unconsolidated ground improvement bodies, where the propagation speed of elastic waves changes over time, using acoustic exploration, it is necessary to separately install a guide pipe for propagation speed measurement in order to grasp the change in the propagation speed of elastic waves in real time, which is inefficient and impractical.

[0008] Furthermore, in actual ground conditions, soil properties, porosity, and the presence or absence of groundwater vary spatially, so it is conceivable that the propagation speed of elastic waves may change depending on the direction in which they are emitted. For this reason, in cases where the propagation speed differs depending on the direction, it would be necessary to insert guide tubes for measuring the propagation speed in multiple directions, for example, four directions (0°, 90°, 180°, 270°), which would be even more inefficient and impractical.

[0009] In view of the above facts, the present invention aims to estimate the propagation speed of elastic waves propagating through a medium without using a guide tube for measuring propagation speed. [Means for solving the problem]

[0010] The first embodiment is a propagation speed estimation method comprising the steps of: acquiring a received waveform obtained by multiple vibration receiving sensors of an array sensor from an oscillator that emits an elastic wave; and setting the propagation speed at which the amplitude value of the output waveform obtained by performing array signal processing on the received waveform while changing the propagation speed to the propagation speed at which the amplitude value of the output waveform is largest as the propagation speed of the elastic wave.

[0011] In the propagation velocity estimation method of the first embodiment, the propagation velocity at which the amplitude value of the output waveform obtained by performing array signal processing on the received waveform, which is obtained by receiving the elastic wave emitted from the oscillator by multiple receiving sensors of an array sensor, while varying the propagation velocity, is the propagation velocity of the elastic wave is defined as the propagation velocity of the elastic wave. Therefore, the propagation velocity of the elastic wave can be estimated without using a guide tube for propagation velocity measurement.

[0012] The second embodiment is a propagation speed estimation method comprising the steps of: determining the peak frequency by frequency analysis of the received waveform obtained by multiple vibration receiving sensors of an array sensor from an oscillator that has been emitted; and extracting the amplitude value of the frequency component of the peak frequency of the output waveform obtained by array signal processing on the received waveform while changing the propagation speed, and setting the propagation speed at which the amplitude value is largest as the propagation speed of the elastic wave.

[0013] In the propagation velocity estimation method of the second embodiment, the received waveform is frequency-analyzed to identify the peak frequency, and the propagation velocity at which the amplitude value of the frequency component of the identified peak frequency is largest is defined as the propagation velocity of the elastic wave. Therefore, the propagation velocity of the elastic wave can be estimated without using a guide tube for propagation velocity measurement. Furthermore, by combining this with frequency analysis, the accuracy of propagation velocity estimation is improved compared to when frequency analysis is not combined.

[0014] The third embodiment is a propagation speed estimation device having one or more processors, the processors acquiring a received waveform obtained by multiple vibration receiving sensors of an array sensor from an oscillator that emits elastic waves, frequency analyzing the received waveform to identify the peak frequency, performing array signal processing on the received waveform by changing the propagation speed to obtain an output waveform, extracting the amplitude value of the frequency component of the peak frequency, and setting the propagation speed at which the amplitude value is largest as the propagation speed of the elastic wave.

[0015] In the propagation velocity estimation device of the third embodiment, the received waveform is frequency-analyzed to identify the peak frequency, and the propagation velocity at which the amplitude value of the frequency component of the identified peak frequency is largest is defined as the propagation velocity of the elastic wave. Therefore, the propagation velocity of the elastic wave can be estimated without using a guide tube for propagation velocity measurement.

[0016] The fourth aspect is a propagation speed estimation program for causing a computer to execute a process, which includes: obtaining a received waveform in which a plurality of vibration sensors of an array sensor receive an elastic wave oscillated from an oscillator; performing frequency analysis on the received waveform to identify a peak frequency; performing array signal processing on the received waveform while changing a propagation speed, and extracting an amplitude value of a frequency component of the peak frequency of an output waveform obtained thereby; and setting the propagation speed at which the amplitude value becomes the largest as the propagation speed of the elastic wave.

[0017] In the propagation speed estimation program of the fourth aspect, frequency analysis is performed on the received waveform to identify a peak frequency, and the propagation speed at which the amplitude value of the frequency component of the identified peak frequency becomes the largest is set as the propagation speed of the elastic wave. Therefore, the propagation speed of the elastic wave can be estimated without using a guide tube for measuring the propagation speed.

[0018] The fifth aspect is a measuring device for a ground improvement body, which includes: a shaft member inserted into the ground improvement body before curing; an oscillator provided on the shaft member for oscillating an elastic wave; an array sensor provided on the shaft member, in which a plurality of vibration sensors for receiving the elastic wave reflected at the boundary between the ground improvement body and the ground are arranged at intervals in the circumferential direction; a propagation speed estimation device that obtains a received waveform in which the received vibration sensors receive the elastic wave reflected at the boundary, performs frequency analysis on the received waveform to identify a peak frequency, performs array signal processing on the received waveform while changing a propagation speed, and extracts an amplitude value of a frequency component of the peak frequency of an output waveform obtained thereby, and sets the propagation speed at which the amplitude value becomes the largest as the propagation speed of the elastic wave; and a distance estimation device that estimates the distance between the array sensor and the boundary from the propagation speed obtained by the propagation speed estimation device and the time from the oscillation of the elastic wave to the reception of the elastic wave reflected at the boundary.

[0019] In the measuring device for a ground improvement body of the fifth aspect, the distance to the boundary between the ground improvement body and the ground can be estimated by estimating the propagation speed of the ground improvement body.

[0020] The sixth aspect is the measuring device for the ground improvement body according to the fifth aspect, wherein the oscillator oscillates the elastic wave having directivity.

[0021] In the measuring device for the ground improvement body of the sixth aspect, the outer shape of the ground improvement body can be estimated by rotating the shaft member around the axis.

[0022] The seventh aspect is the measuring device for the ground improvement body according to the fifth aspect, wherein the oscillator oscillates the elastic wave having no directivity over the entire circumference in the circumferential direction, and the array sensor has the vibration receiving sensors arranged over the entire circumference in the circumferential direction.

[0023] In the measuring device for the ground improvement body of the seventh aspect, the outer shape of the ground improvement body can be estimated without rotating the shaft member around the axis.

[0024] The eighth aspect is a ground improvement body forming device including: a forming unit that forms a ground improvement body by ejecting a curing material from a tip while pulling up a shaft member inserted into the ground; a measuring device for the ground improvement body according to any one of the fifth to seventh aspects inserted into the ground improvement body being formed; and an adjusting unit that adjusts the ejection amount of the curing material according to the distance detected by the measuring device for the ground improvement body.

[0025] In the ground improvement body forming device of the eighth aspect, since the ejection amount of the curing material is adjusted according to the distance to the boundary between the ground improvement body and the ground, the ground improvement body can be formed with higher precision compared to the case where the ejection amount is not adjusted according to the distance.

Advantages of the Invention

[0026] According to the present invention, the propagation speed of the elastic wave can be estimated without using a guide tube for measuring the propagation speed.

Brief Description of the Drawings

[0027] [Figure 1] It is a front view showing a schematic configuration of the forming device. [Figure 2] It is a front view showing a schematic configuration of the measuring device according to the first embodiment of the present invention. [Figure 3] This is a top view showing the schematic configuration of the measuring instrument of the first measuring device. [Figure 4] Figure 3 is a front view showing the schematic configuration of the measuring instrument of the measuring device. [Figure 5] This is a block diagram showing the hardware configuration of the control device of the measuring device according to the first embodiment. [Figure 6] This is a block diagram showing the functional configuration of the control device for the measuring device of the first embodiment. [Figure 7] This flowchart shows an example of the processing flow in the control device of the measuring device according to the first embodiment. [Figure 8] This is the output waveform obtained by processing the received waveform with an array signal. [Figure 9] This is a top view corresponding to Figure 3, which shows the schematic configuration of the measuring instrument of the measuring device of the second embodiment of the present invention. [Figure 10] This is a front view corresponding to Figure 4, showing the schematic configuration of the measuring instrument of the measuring device in Figure 9. [Figure 11] Figure 9 is an explanatory diagram of the array signal processing performed by the measuring instrument of the measuring device. [Figure 12] This flowchart shows an example of the processing flow in the control device of the measuring device according to the second embodiment. [Figure 13] This is an explanatory diagram illustrating the basic principle of an estimation method that uses array signal processing to estimate propagation speed. [Figure 14] This is an explanatory diagram illustrating the steps of a basic estimation method that estimates propagation speed using array signal processing without performing frequency analysis. [Figure 15] (A) is the received waveform of the elastic wave received by the vibration sensor 4 hours after construction, and (B) is the result of the Fourier transform of (A). [Figure 16] (A) is the received waveform of the elastic wave received by the vibration sensor 7 hours after construction, and (B) is the result of the Fourier transform of (A). [Figure 17] This is the waveform of a burst wave with a frequency of 15 kHz. [Figure 18]This is an explanatory diagram illustrating the steps of an estimation method in an embodiment that estimates propagation speed using array signal processing combined with frequency analysis. [Figure 19] This is an explanatory diagram illustrating the conditions for computer simulation. [Figure 20] This is the received waveform of a vibration receiving sensor in an array sensor, as determined by computer simulation. [Figure 21] This is the result of a Fourier transform of the received waveform in Figure 20, obtained through computer simulation. [Figure 22] (A) is the output waveform of the array signal processing at a propagation speed of 20 m / s, (B) is the output waveform of the array signal processing at a propagation speed of 40 m / s, (C) is the output waveform of the array signal processing at a propagation speed of 60 m / s, and (D) is the output waveform of the array signal processing at a propagation speed of 80 m / s. [Figure 23] (A) is the result of the Fourier transform of the output waveform in Figure 22(A), (B) is the result of the Fourier transform of the output waveform in Figure 22(B), (C) is the result of the Fourier transform of the output waveform in Figure 22(A), and (D) is the result of the Fourier transform of the output waveform in Figure 22(D). [Figure 24] These graphs show the estimated propagation speeds at 1 kHz and 5 kHz, respectively. [Figure 25] (A) is a front view showing the internal structure of the simulated experimental apparatus, and (B) is a vertical cross-section. [Figure 26] Figure 24 is a perspective view of the measuring instruments in the simulated experimental setup. [Figure 27] This is the waveform of a 15kHz burst wave generated by the oscillator of the simulation device. [Figure 28] These are the received waveforms from each vibration receiving sensor of the array sensor on the simulated ground improvement body, four hours after construction. [Figure 29] (A) shows the result of the Fourier transform of the received waveform received by the CH4 vibration sensor in the simulated ground improvement body four hours after construction, and (B) shows the result of the Fourier transform of the received waveform received by the CH5 vibration sensor. [Figure 30](A) is the output waveform of the array signal processing at a propagation speed of 150 m / s in the simulated ground improvement body four hours after construction, (B) is the output waveform of the array signal processing at a propagation speed of 200 m / s, and (C) is the output waveform of the array signal processing at a propagation speed of 250 m / s. [Figure 31] (A) is the result of the Fourier transform of the output waveform in Figure 30(A), (B) is the result of the Fourier transform of the output waveform in Figure 30(B), and (C) is the result of the Fourier transform of the output waveform in Figure 30(C). [Figure 32] This graph shows the estimated propagation velocity in a simulated ground improvement structure four hours after construction. [Figure 33] This graph shows the results of estimating the propagation velocity using the basic estimation method shown in Figure 14 for a simulated ground improvement body four hours after construction. [Figure 34] This waveform is obtained by AM modulating a 15kHz burst wave generated by the oscillator of the simulated experimental device to 2kHz. [Figure 35] These are the received waveforms from each vibration receiving sensor of the array sensor on the simulated ground improvement body, 7 hours after construction. [Figure 36] (A) shows the result of the Fourier transform of the received waveform from the CH4 vibration sensor in the simulated ground improvement body 7 hours after construction, and (B) shows the result of the Fourier transform of the received waveform from the CH5 vibration sensor. [Figure 37] (A) is the output waveform of the array signal processing at a propagation speed of 200 m / s in the simulated ground improvement body 7 hours after construction, (B) is the output waveform of the array signal processing at a propagation speed of 300 m / s, and (C) is the output waveform of the array signal processing at a propagation speed of 400 m / s. [Figure 38] (A) is the result of the Fourier transform of the output waveform in Figure 37(A), (B) is the result of the Fourier transform of the output waveform in Figure 37(B), and (C) is the result of the Fourier transform of the output waveform in Figure 37(C). [Figure 39] This graph shows the estimated propagation velocity in a simulated ground improvement structure 7 hours after construction. [Figure 40]This is a spectrogram of the output waveform of the array signal processing in a simulated ground improvement body 7 hours after construction. [Figure 41] Figure 40 is a graph of the amplitude values ​​of the 3kHz component in the spectrogram. [Figure 42] This is a front view showing a schematic configuration of a construction device according to one embodiment of the present invention. [Figure 43] This is a sonar image used to examine the accuracy of the propagation velocity estimation results. [Figure 44] This is a sonar image used to examine the accuracy of the propagation velocity estimation results. [Modes for carrying out the invention]

[0028] This document describes the propagation velocity estimation method, propagation velocity estimation device, propagation velocity estimation program, ground improvement body measurement device, and ground improvement body construction device of this embodiment. Note that the propagation velocity estimated in this embodiment may be referred to as the "estimated propagation velocity."

[0029] [Ground improvement structure construction device] First, I will explain the ground improvement structure construction equipment and the ground improvement structure itself.

[0030] As shown in Figure 1, the construction device 10 is a device for constructing a ground improvement body 50 using a high-pressure injection mixing method. Specifically, the construction device 10 cuts the ground G while mixing the cut ground G with cement milk MK, which is an example of a cement-based hardening agent that has been injected under high pressure, to create the ground improvement body 50. Note that Figure 1 is a schematic illustration, so the size of each device, equipment, and component may differ from the actual ones. Also, the ground improvement body 50 is schematically shown in its completed state.

[0031] The concrete mixer 10 comprises a rotating rod 30 and a device body 20. The device body 20 is installed on the ground G (above ground) and has the function of rotating the rotating rod 30 around its axis (see arrow Q) while spraying cement grout MK laterally from the spray nozzle 32 at its tip, and also raising and lowering the rotating rod 30 (see arrow Z). The device body 20 also has an operating unit 22 that allows a worker (not shown) to operate the rotation speed of the rotating rod 30, the vertical movement of the rotating rod 30, and the amount of cement grout MK sprayed per unit time.

[0032] The ground-building device 10 inserts a rotating rod 30 into the ground G, sprays cement milk MK at high pressure from a nozzle 32 at the tip of the rod, and raises and lowers the rotating rod 30 while it rotates, so that the cement milk MK and soil are mixed together, and a ground-improved body 50 with a horizontal cross-section that is roughly circular or roughly fan-shaped is created.

[0033] [Measuring device of the first embodiment] Next, the measuring apparatus of the first embodiment of the present invention will be described.

[0034] (composition) First, the configuration of the measuring device according to the first embodiment will be described.

[0035] The measuring device 100 of the first embodiment shown in Figure 2 measures the distance R between the boundary K between the ground improvement body 50 and the ground G using a measuring instrument 150 provided on a measuring rod 130 (described later), and visualizes the overall shape of the outer form of the ground improvement body 50. The measuring device 100 is composed of a measuring rod 130, a drive unit 110, a measuring instrument 150, and a control device 120.

[0036] The drive unit 110 and the control device 120 are installed on the ground G (above ground). The drive unit 110 has the function of rotating the measuring rod 130 around its axis (see arrow Q) and the function of raising and lowering the rotating rod 30 (see arrow Z). The measuring rod 130, as an example of an axial member, is a hollow rod with a measuring instrument 150 at its tip, and is inserted into the unconsolidated ground improvement body 50 before solidification.

[0037] As shown in Figure 4, the measuring instrument 150 is configured to include a mounting portion 152, an oscillator 154, and an array sensor 160. The mounting portion 152 is a cylindrical member, and the oscillator 154 and the array sensor 160 are attached to its circumferential surface.

[0038] As shown in Figures 2 and 3, the oscillator 154 (see Figure 4) oscillates an elastic wave N1 toward the boundary K. In this embodiment, the oscillator 154 (see Figure 4) oscillates a directional elastic wave N1. In this embodiment, the elastic wave traveling from the oscillator 154 toward the boundary K is denoted as N1, the elastic wave reflected at the boundary K (reflected wave) is denoted as N2, and the case where neither is distinguished is denoted as elastic wave N.

[0039] As shown in Figures 3 and 4, the array sensor 160 is curved in an arc shape along the circumferential surface of the mounting portion 152. The array sensor 160 also has a plurality of vibration receiving sensors 162 that receive elastic waves N2 (see Figures 2 and 3) reflected at the boundary K from elastic waves N1 emitted from the oscillator 154 (see Figure 4). The vibration receiving sensors 162 are arranged at equal intervals in the circumferential direction of the mounting portion 152.

[0040] In addition, although the vibration receiving sensors 162 of the array sensor 160 shown in Figure 4 are arranged in a single row in the circumferential direction, multiple rows may be provided in the vertical direction. Furthermore, a sensor that integrates the oscillation of elastic wave N1 and the reception of elastic wave N2 may be used; in other words, oscillation and reception may be performed by the same sensor. That is, the array sensor may also be configured to perform the oscillation of elastic waves.

[0041] As shown in Figure 2, the control device 120 is installed on the ground G and is electrically connected to the measuring instrument 150 and the drive unit 110 by cables 112 and 114.

[0042] (Control device) Next, the control device 120 will be described.

[0043] Hardware configuration

[0044] First, the hardware configuration of the control device 120 in this embodiment will be described. The control device 120 has a configuration similar to that of a typical computer.

[0045] As shown in Figure 5, the control device 120 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, storage 104, an input unit 105, a display unit 106, and a communication interface 107. Each component is connected to the others via a bus 109 so that they can communicate with each other.

[0046] The CPU 101 is a central processing unit that controls the overall operation of the measuring device 100 (see Figure 2), including the execution of various programs and the control of each component. Specifically, the CPU 101 reads various programs from the ROM 102 or storage 104 and executes the programs using the RAM 103 as a working area. The CPU 101 controls each of the above components and performs various calculations according to the programs recorded in the ROM 102 or storage 104. In this embodiment, various programs are stored in the ROM 102 or storage 104.

[0047] ROM 102 stores various programs and data. RAM 103 temporarily stores programs or data as a working area. Storage 104 consists of an HDD (Hard Disk Drive), SSD (Solid State Drive), and flash memory, and stores various programs and data, including the operating system.

[0048] The input unit 105 includes a pointing device such as a mouse and a keyboard, and is used for various types of input. The display unit 106 is, for example, a display that shows various types of information. The display unit 27 may use a touch panel system to function as the input unit 105.

[0049] The communication interface 107 is an interface for communicating with other devices such as the drive unit 110 and the measuring instrument 150 (see Figure 2) by wire or wireless connection, and standards such as Ethernet®, FDDI, and Wi-Fi® are used.

[0050] • Functional configuration Next, the functional configuration of the control device 120 will be described.

[0051] As shown in Figure 6, the control device 120 is configured to include a drive unit control unit 121, a measuring instrument control unit 122, a propagation speed estimation unit 123, a distance estimation unit 124, and a shape estimation unit 125.

[0052] The drive unit control unit 121 controls the raising, lowering, and rotation of the measuring rod 130 (see Figure 2) by the drive unit 110. The measuring instrument control unit 122 controls the oscillation of the oscillator 154 of the measuring instrument 150 and the vibration reception of the array sensor 160 (see Figure 4).

[0053] The propagation velocity estimation unit 123 acquires the received waveforms received by each vibration receiving sensor 162 of the array sensor 160 and estimates the propagation velocity of the elastic wave N propagating through the ground improvement body 50 (see Figure 2). The "propagation velocity of elastic wave N" is the average velocity from the time the oscillator 154 oscillates the elastic wave N1 until the vibration receiving sensor 162 of the array sensor 160 receives the elastic wave N2 reflected at the boundary K.

[0054] Here, we will specifically explain how to estimate the propagation speed of elastic wave N. Note that Figure 18 shows an overview of the propagation speed estimation method in this embodiment, but Figure 18 will be explained again.

[0055] The propagation velocity estimation unit 123 acquires the received waveform of the elastic wave N2 (see Figures 2 and 3) reflected at boundary K, which is received by the vibration receiving sensor 162 (see Figure 4), and performs frequency analysis on the received waveform to identify the peak frequency (step 18A in Figure 18).

[0056] The elastic wave N2 reflected at boundary K propagates in the opposite direction to the oscillation direction of the oscillator 154. Therefore, in this embodiment, the peak frequency of the elastic wave N2 received by a receiving sensor 162A (Figures 3 and 4) among the multiple receiving sensors 162 of the array sensor 160, whose oscillation direction and receiving direction coincide or are in the vicinity of the oscillation direction of the directional elastic wave N1, is determined by frequency analysis. It is desirable that one of the multiple receiving sensors 162 of the array sensor 160 be arranged so as to coincide with the oscillation direction of the oscillator 154.

[0057] Furthermore, the propagation speed estimation unit 123 changes the propagation speed (step 14E in Figure 18), performs array signal processing on the received waveform using each vibration receiving sensor 162 to acquire an output waveform, performs frequency analysis on the acquired output waveform (step 18B in Figure 18), and obtains the amplitude value of the frequency component of the identified peak frequency (step 18C in Figure 18). To explain from another perspective, the propagation speed estimation unit 123 extracts the amplitude value of the identified peak frequency component in the output waveform for each propagation speed (C1 to Cn).

[0058] Then, the propagation velocity at which the amplitude value is greatest is determined (step 14F in Figure 18), and this is estimated to be the propagation velocity of elastic wave N, i.e., it is the estimated propagation velocity (step 14G in Figure 18).

[0059] The distance estimation unit 124 estimates the distance R (see Figures 2 and 3) between the measuring instrument 150 and the reflection position KT (see Figures 2 and 3) where elastic wave N1 was reflected at boundary K, using the time from the oscillation of elastic wave N1 by the oscillator 154 (see Figure 4) until the receiving sensor 162 receives elastic wave N2 reflected at boundary K, and the estimated propagation speed of elastic wave N. Note that in Figures 2 and 3, the intersection points of elastic waves N1 and N2 with boundary K do not coincide with the reflection position KT for clarity, but in reality, the intersection points of elastic waves N1 and N2 with boundary K and the reflection position KT coincide.

[0060] In this embodiment, the propagation speed V of the elastic wave N is used to perform array signal processing on the received waveforms received by each vibration receiving sensor 162 of the array sensor 160. The time at which the amplitude value of the output waveform obtained by array signal processing (see Figure 8) is maximum is defined as the time T from when the oscillator 154 oscillates the elastic wave N1 until the array sensor 160 receives the elastic wave N2 reflected at boundary K, and the distance R to the reflection position KT where the elastic wave N1 was reflected at boundary K between the unconsolidated ground improvement body 50 and the ground G is estimated.

[0061] Figure 8 shows an example of an output waveform. The estimated propagation speed was assumed to be 63 m / s. The time at point SS where the amplitude of the output waveform is maximum is time T, which in this example is approximately 0.018 s.

[0062] The method for estimating the distance R from the oscillator 154 to the reflection position KT is not limited to the above. For example, the time at point SH where the rate of change of the amplitude value of the output waveform in Figure 8 is maximum may be taken as the time T from when the oscillator 154 oscillates elastic wave N1 until the array sensor 160 receives the elastic wave N2 reflected at boundary K, which in this example is approximately 0.016 s.

[0063] Furthermore, the method for determining time T is not limited to the time when the amplitude value of the output waveform is maximum or the time when the rate of change of the amplitude value of the output waveform is maximum. For example, methods that utilize the cross-correlation between the transmitted and received waveforms, or methods that utilize the phase difference of the received signal waveform, which are used in seabed topography surveys in the field of underwater acoustics, can also be used.

[0064] Furthermore, the distance R(m) can be calculated using the following equation [Equation 1], where T(s) is the time from when the oscillator 154 emits elastic wave N1 until the array sensor 160 receives the elastic wave N2 reflected at boundary K, and V(m / s) is the propagation speed of the elastic wave.

[0065]

number

[0066] The shape estimation unit 125 plots the reflection position KT (see Figures 2 and 3) from the distance R estimated by the distance estimation unit 124. In addition, in cooperation with the drive unit control unit 121 and the measuring instrument control unit 122, the measuring rod 130 is rotated by a preset rotation angle, for example 1° or 5°, and then stopped. Elastic waves N1 are emitted to determine the distance R, and the reflection position KT after rotation is plotted. By performing this 360°, the shape of the boundary K at a certain depth is visualized by the measuring instrument 150 (see Figure 2), that is, the horizontal cross-sectional shape of the ground improvement body 50 (see Figure 3) is visualized and displayed on the display unit 106 (see Figure 5).

[0067] Furthermore, the shape estimation unit 125 works in conjunction with the drive unit control unit 121 and the measuring instrument control unit 122 to raise the measuring rod 130 by a preset distance, for example, 10 mm at a time, thereby changing the depth of the measuring instrument 150 and visualizing the horizontal cross-sectional shape of the ground improvement body 50. This visualizes the overall three-dimensional shape of the unconsolidated ground improvement body 50 created by the high-pressure jet mixing method and displays it on the display unit 106 (see Figure 5).

[0068] In this example, the measuring instrument 150 was raised from bottom to top to visualize the overall shape of the ground improvement body 50. However, this is not the only method; the measuring instrument 150 could also be lowered from top to bottom to visualize the overall shape of the ground improvement body 50, or the up-and-down movement could be repeated to visualize the shape more accurately.

[0069] Furthermore, in this example, the measuring rod 130 was rotated by a predetermined angle, for example 1° or 5°, and then stopped. While the elastic wave N1 was oscillated in this stopped state to determine the distance R, the method is not limited to this. For example, the measuring rod 130 may be rotated at a constant angular velocity while the elastic wave N1 is oscillated at predetermined rotation angle intervals to continuously determine the distance R. Alternatively, the measuring rod 130 may be rotated at a constant angular velocity while the elastic wave N1 is oscillated at a preset time interval, for example, every 1 ms, to continuously determine the distance R.

[0070] Details on the methods for estimating propagation speed and distance will be described later.

[0071] • Processing flow Next, an example of the process flow for measuring the distance between the boundary K between the ground improvement body 50 and the ground G, measured by the control device 120 in this embodiment, and the measuring instrument 150, and visualizing the overall shape of the ground improvement body 50 will be explained using Figure 7.

[0072] In step S100, the CPU 101 (see Figure 6) inserts the measuring rod 130 (see Figure 2) into the unconsolidated ground improvement body 50 (see Figure 2), and the measuring instrument 150 (see Figures 2 to 4) is positioned at a predetermined depth at the lower end of the ground improvement body 50.

[0073] In step S101, the CPU 101 acquires the received waveform from the vibration receiving sensor 162A (see Figures 2 and 3) of the array sensor 160 of the measuring instrument 150.

[0074] In step S102, the CPU 101 performs frequency analysis on the received waveform to identify the peak frequency (step 18A in Figure 18).

[0075] In step S103, the CPU 101 performs array signal processing on the received waveform by changing the propagation speed and extracts the amplitude value of the frequency component of the peak frequency in the output waveform obtained (step 18B in Figure 18).

[0076] In step S104, the CPU 101 estimates the propagation speed at which the amplitude value is greatest as the propagation speed of elastic wave N.

[0077] In step S105, the CPU 101 uses the time from the oscillation of elastic wave N1 by oscillator 154 (see Figure 4) until the elastic wave N2 reflected at boundary K is received by the receiving sensor 162 (see Figures 3 and 4), and the estimated propagation speed of elastic wave N, to determine the distance R between the measuring instrument 150 and the reflection position KT (see Figures 2 and 3), and plots the reflection position KT.

[0078] In step S106, the CPU 101 checks whether the measuring rod 130 has rotated 360° or more at this depth. If it has rotated 360° or more (Yes), proceed to step S108; if it has rotated less than 360° (No), proceed to step S107.

[0079] In step S107, the CPU 101 rotates the measuring rod 130 to a preset rotation angle and stops, then returns to step S101.

[0080] In step S108, the CPU 101 checks whether the measuring instrument 150 exceeds the pre-set depth of the upper end of the ground improvement body 50. If it exceeds the depth of the upper end (Yes), the process ends; if it is below the depth (No), the process proceeds to step S109.

[0081] In step S109, the CPU 101 raises the measuring instrument 150 by a preset distance and returns to step S101.

[0082] (action) Next, the operation of the measuring device of this embodiment will be described.

[0083] The measuring device 100 of this embodiment performs frequency analysis on the received waveform to identify the peak frequency, and defines the propagation speed at which the amplitude value of the frequency component of the identified peak frequency is largest as the propagation speed of the elastic wave N. Therefore, even if the frequency components of the elastic wave N1 emitted by the oscillator 154 and the frequency components of the elastic wave N2 received by each vibration receiving sensor 162 are different, and the frequency components of the ground improvement body 50 change with hardening time and may have multiple frequency components, the propagation speed of the elastic wave N can be estimated with high accuracy using array signal processing by the array sensor 160.

[0084] From another perspective, it is possible to estimate the propagation speed of an elastic wave even when the oscillation frequency and reception frequency of the elastic wave N propagating through the medium are different.

[0085] Furthermore, as described in Non-Patent Documents 3 and 4, there is no need to install guide tubes for measuring propagation speed, thus enabling more efficient measurements.

[0086] Furthermore, by estimating the propagation speed of the ground improvement body 50, it is possible to estimate the distance R from the measuring instrument 150 to the boundary K between the ground improvement body 50 and the ground G, or more precisely, from the measuring instrument 150 to the reflection position KT.

[0087] Then, by rotating the measuring rod 130 (measuring instrument 150) around its axis, the outer shape of the horizontal cross-section of the ground improvement body 50 can be estimated and visualized.

[0088] Furthermore, by raising and lowering the measuring rod 130 (measuring instrument 150) to estimate and visualize the external shape of the horizontal cross-section of the ground improvement body 50, the overall three-dimensional shape of the ground improvement body 50 can be estimated.

[0089] In this case, the unconsolidated ground improvement body 50 constructed by the high-pressure injection mixing method exhibits significant attenuation of elastic waves N, and the frequency components of the elastic wave N1 emitted by the oscillator 154 of the measuring instrument 150 and the frequency components of the elastic wave N2 received by each vibration receiving sensor 162 may differ.

[0090] Furthermore, the degree of hardening of the unconsolidated ground improvement body 50 varies depending on the elapsed time since its construction, i.e., the hardening time. Therefore, the frequency components of the elastic waves N2 received by each vibration receiving sensor 162 differ depending on the hardening time. Moreover, the elastic waves N2 received by each vibration receiving sensor 162 may contain multiple frequency components.

[0091] Based on these findings, it is impossible or difficult to estimate the propagation velocity of elastic waves N in the unconsolidated ground improvement body 50 using the basic propagation velocity estimation method shown in Figure 14, which will be described later.

[0092] However, as mentioned above, by using a propagation velocity estimation method that combines frequency analysis, as in this embodiment, the propagation velocity of elastic wave N can be estimated. In other words, the propagation velocity can be estimated even if the oscillation frequency and reception frequency of the elastic wave are different in the medium.

[0093] [Measuring device of the second embodiment] Next, a measuring device of the second embodiment of the present invention will be described. Note that the same reference numerals are used for components identical to those in the first embodiment, and redundant explanations will be omitted or simplified.

[0094] (composition) First, the configuration of the measuring device according to the second embodiment will be described.

[0095] The measuring device 200 of the second embodiment shown in Figures 9 and 10 measures the distance between the ground improvement body 50 and the boundary K (see Figure 9) between the ground G and the measuring instrument 250 provided on the measuring rod 130 (see Figure 10), and visualizes the overall shape of the outer form of the ground improvement body 50. The measuring device 200 is composed of a measuring rod 130, a drive unit 110 (see Figure 2), a measuring instrument 250, and a control device 120 (see Figure 2).

[0096] Note that, unlike the first embodiment, the drive unit 110 does not need to rotate the measuring rod 130, as will be described later, but it is still referred to as the same device and given the same reference numerals. Also, the control device 120 has the same basic functional configuration and hardware configuration as the first embodiment, so it is still referred to as the same device and given the same reference numerals.

[0097] As shown in Figure 10, a measuring instrument 250 is attached to the tip of the measuring rod 130 and is inserted into the unconsolidated ground improvement body 50 before solidification.

[0098] As shown in Figures 9 and 10, the measuring instrument 250 is composed of a mounting portion 152, an oscillator 254 (see Figure 10), and an array sensor 260. The mounting portion 152 is a cylindrical member, and the oscillator 254 and the array sensor 160 are mounted around its entire circumference.

[0099] The oscillator 254 (see Figure 10) emits elastic waves M1 toward the boundary K. In this embodiment, the oscillator 254 emits omnidirectional elastic waves M1. Therefore, the oscillator 254 is positioned around the entire circumference of the mounting portion 152. The elastic waves M1 in Figure 9 are an illustrative diagram that makes it easy to understand that elastic waves M1 are being emitted in all directions.

[0100] The array sensor 260 has multiple vibration receiving sensors 162 that receive elastic waves M2 (see Figure 11) reflected at boundary K from elastic wave M1 emitted from oscillator 254 (see Figure 10). The vibration receiving sensors 162 are arranged at equal intervals in the circumferential direction around the entire circumference of the mounting portion 152. Note that the elastic wave M2 in Figure 11 is illustrated as the elastic wave M2 reflected at reflection position KT. However, in reality, elastic wave M2 propagates by being reflected from the entire boundary K.

[0101] In addition, as with the first embodiment, when describing elastic wave M1 and elastic wave M2 without distinguishing between them, we will refer to them simply as elastic wave M.

[0102] Furthermore, although the vibration receiving sensors 162 of the array sensor 260 shown in Figure 10 are arranged in a single row in the circumferential direction, multiple rows may be provided in the vertical direction. Also, a sensor that integrates the oscillation of elastic wave M1 and the reception of elastic wave M2, in other words, the same sensor may perform both oscillation and reception. That is, the array sensor may also be configured to perform elastic wave oscillation.

[0103] In this embodiment as well, the measuring instrument 250 is electrically connected to the control device 120 by a cable 112, as shown in Figure 2.

[0104] (Control device) Next, the control device 120 (see Figure 2) will be described.

[0105] Hardware configuration The hardware configuration of the control device 120 is the same as in Figure 5, so the explanation is omitted.

[0106] • Functional configuration The basic functional configuration of the control device 120 is the same as in Figure 6. However, the specific functions of each component are different, so they will be explained below.

[0107] The drive unit control unit 121 controls the raising and lowering and rotation of the measuring rod 130 (see Figure 10). The measuring instrument control unit 122 controls the oscillation of the oscillator 254 of the measuring instrument 250 and the vibration reception of the array sensor 260 (see Figure 10).

[0108] The propagation velocity estimation unit 123 acquires the received waveforms received by each receiving sensor 162 of the array sensor 260 and estimates the propagation velocity of the elastic wave M propagating through the ground improvement body 50 (see Figure 2, etc.). The "propagation velocity of the elastic wave M" is the average velocity from the time the oscillator 254 oscillates the elastic wave M1 until the receiving sensor 162 of the array sensor 260 receives the elastic wave M2 reflected at the boundary K.

[0109] Here, we will specifically explain how to estimate the propagation speed of elastic wave M. As with the first embodiment, Figure 18 shows an overview of the propagation speed estimation method of this embodiment, but Figure 18 will be explained again.

[0110] The propagation velocity estimation unit 123 acquires the received waveform of the elastic wave M2 (see Figure 11) reflected at boundary K and received by the vibration receiving sensor 162 (see Figures 9 to 11), and performs frequency analysis on the received waveform to identify the peak frequency (step 18A in Figure 18).

[0111] In this embodiment, when determining the peak frequency of the elastic wave M2 from boundary K, the peak frequency is determined by performing frequency analysis on the received waveform of any of the vibration receiving sensors 162 of the array sensor 260. For example, in this embodiment, as shown in Figure 11, vibration receiving sensor 162A is used as the reference vibration receiving sensor for determining the peak frequency. The direction of reception of the elastic wave M2 by vibration receiving sensor 162A is defined as JA.

[0112] Furthermore, the propagation speed estimation unit 123 changes the propagation speed (step 14E in Figure 18), performs array signal processing on the received waveform using each vibration receiving sensor 162 to acquire an output waveform, performs frequency analysis on the acquired output waveform (step 18B in Figure 18), and obtains the amplitude value of the frequency component of the identified peak frequency (step 18C in Figure 18). To explain from another perspective, the propagation speed estimation unit 123 extracts the amplitude value of the identified peak frequency component in the output waveform for each propagation speed (C1 to Cn).

[0113] In this embodiment, as shown in Figure 11, a vibration receiving sensor 162 located within the range JH of ±α° with respect to the vibration receiving direction JA is used, and, similar to the first embodiment, array signal processing is performed on the received waveform to obtain the amplitude values ​​of the frequency components of the identified peak frequencies in the output waveform for each propagation speed. The propagation speed at which the amplitude value is largest is then estimated to be the propagation speed of the elastic wave M.

[0114] The distance estimation unit 124 uses the time from the oscillation of the elastic wave M1 of the oscillator 254 (see Figure 10) until the elastic wave M2 reflected at boundary K is received by the vibration receiving sensor 162, and the estimated propagation speed of the elastic wave M, to estimate the distance between the measuring instrument 250 and boundary K, and in this embodiment, the distance R between the vibration receiving sensor 162A of the measuring instrument 250 and the reflection position KT. Note that the sign R of the distance R is not shown in Figure 11 because it would be difficult to see.

[0115] Specifically, in this embodiment, the propagation speed V of the elastic wave M is used to perform array signal processing on the received waveforms received by each receiving sensor 162 within the range JH of the array sensor 260. The time at which the amplitude value of the output waveform obtained from the array signal processing is maximum is defined as the time T from when the oscillator 254 oscillates the elastic wave M1 until the array sensor 260 receives the elastic wave M2 reflected at the boundary K, and the distance R from the unconsolidated ground improvement body 50 to the reflection position KT at the boundary K is estimated.

[0116] The time T is the same as in the first embodiment, which is the time at point SS where the amplitude value of the output waveform in Figure 8 is maximum, or the time at which the rate of change of the amplitude value of the output waveform is maximum. However, as mentioned above, the method is not limited to these methods.

[0117] The shape estimation unit 125 plots the reflection position KT from the distance R estimated by the distance estimation unit 124. In addition, in cooperation with the measuring instrument control unit 122, the propagation speed is measured over the entire circumferential area by sequentially changing the vibration receiving sensor 162A and determining the distance, thereby visualizing the shape of the boundary K at the depth where the measuring instrument 250 is located, that is, the horizontal cross-sectional shape of the ground improvement body 50 (see Figure 3).

[0118] Furthermore, the shape estimation unit 125 works in conjunction with the drive unit control unit 121 and the measuring instrument control unit 122 to raise the measuring rod 130 by a preset distance, for example 10 mm, thereby changing the depth of the measuring instrument 250 and visualizing the horizontal cross-sectional shape of the ground improvement body 50. This visualizes the overall three-dimensional shape of the unconsolidated ground improvement body 50 created by the high-pressure jet mixing method.

[0119] Next, an example of the process flow for measuring the distance between the boundary K between the ground improvement body 50 and the ground G, measured by the control device 120 in this embodiment, and the measuring instrument 250, and visualizing the overall shape of the outer form of the ground improvement body 50 will be explained using Figure 12.

[0120] In step S200, the CPU 101 (see Figure 6) inserts the measuring rod 130 (see Figure 2) into the unconsolidated ground improvement body 50 (see Figure 2, etc.), and the measuring instrument 150 is positioned at a predetermined depth at the lower end of the ground improvement body 50.

[0121] In step S201, the CPU 101 acquires the received waveform from the vibration receiving sensor 162A (see Figure 11), which is used as the reference for the array sensor 160 of the measuring instrument 250.

[0122] In step S202, the CPU 101 performs a frequency analysis on the received waveform to identify the peak frequency.

[0123] In step S203, the CPU 101 changes the propagation speed and performs array signal processing on the received waveform to obtain the amplitude value of the frequency component of the identified peak frequency in the output waveform.

[0124] In step S204, the CPU 101 estimates the propagation speed at which the amplitude value is greatest as the propagation speed of the elastic wave M.

[0125] In step S205, the CPU 101 uses the time from the oscillation of elastic wave M1 by oscillator 254 (see Figure 4) until the elastic wave M2 reflected at boundary K is received by the receiving sensor 162 (see Figures 9 and 10), and the estimated propagation speed of elastic wave M, to determine the distance R between the measuring instrument 250 and the reflection position KT (see Figure 9), and plots the reflection position KT.

[0126] In step S206, the CPU 101 checks whether it has estimated the distance R based on all the vibration sensors 162 at this depth. If it has estimated the distance R using all the vibration sensors 162 (Yes), it proceeds to step S208; if it has not calculated the distance R using all the vibration sensors 162 (No), it proceeds to step S207.

[0127] In step S207, the CPU 101 sets the adjacent vibration receiving sensor 162A as the reference vibration receiving sensor 162, and returns to step S201.

[0128] In step S208, the CPU 101 checks whether the measuring instrument 250 has exceeded the pre-set depth of the upper end of the ground improvement body 50. If it has exceeded the depth of the upper end (Yes), the process ends; if it is below the depth (No), the process proceeds to step S209.

[0129] In step S209, the CPU 101 raises the measuring instrument 250 by a preset distance and returns to step S201.

[0130] (action) Next, the operation of the measuring device of this embodiment will be described.

[0131] Similar to the first embodiment, the measuring device 200 of this embodiment performs frequency analysis on the received waveform to identify the peak frequency, and defines the propagation speed at which the amplitude value of the frequency component of the identified peak frequency is largest as the propagation speed of the elastic wave M. Therefore, the propagation speed of the elastic wave M can be estimated using array signal processing by the array sensor 260.

[0132] Furthermore, as described in Non-Patent Documents 3 and 4, there is no need to install guide tubes for measuring propagation speed, thus enabling more efficient measurements.

[0133] Furthermore, by estimating the propagation speed of the ground improvement body, it is possible to estimate the distance R from the measuring instrument 250 to the boundary K between the ground improvement body 50 and the ground G, or more precisely, from the measuring instrument 250 to the reflection position KT.

[0134] Then, by sequentially changing the reference vibration receiving sensor 162, the external shape of the horizontal cross-section of the ground improvement body 50 can be estimated and visualized without rotating the measuring rod 130 (measuring instrument 250) around its axis.

[0135] Furthermore, by raising and lowering the measuring rod 130 (measuring instrument 250) to estimate and visualize the external shape of the horizontal cross-section of the ground improvement body 50, the overall three-dimensional shape of the ground improvement body 50 can be estimated.

[0136] <Ground improvement structure construction device> Next, we will describe a ground improvement body construction device as an example of the present invention.

[0137] As shown in Figure 42, the ground preparation device 700 is configured to include a ground preparation device 10 (see Figure 1) and a measuring device 100 (see Figure 2) according to the first embodiment. The control device 120 is electrically connected to the ground preparation device 10 by a cable 116. The control device 120 also controls the preparation of the ground improvement body 50 by the ground preparation device 10.

[0138] The control device 120 constructs the ground improvement body 50 with the construction machine 10, while the measuring device 100 estimates the external shape and overall shape of the horizontal cross-section of the ground improvement body 50.

[0139] Then, the shaping device 10 is controlled to adjust the rotation speed of the rotating rod 30, the lifting speed of the rotating rod 30, and the amount of cement milk MK ejected per unit time, etc., so that the shape of the ground improvement body 50 approaches the design value. In other words, the lifting speed of the rotating rod 30 and the amount of cement milk MK ejected per unit time, etc., are automatically adjusted based on the external shape of the horizontal cross-section and the overall shape of the ground improvement body 50 estimated by the measuring device 100.

[0140] <Method for estimating propagation speed> Next, the propagation velocity estimation method using array signal processing of this embodiment to which the present invention is applied will be described in detail.

[0141] [Basic principle] First, we will explain the basic principles of the propagation speed estimation method using array signal processing.

[0142] Figure 13 is a schematic diagram of an array sensor in which M vibration receiving sensors CH1 to CHM, each with the same specifications as vibration receiving sensor 162 (see Figure 2, etc.), are arranged linearly at equal intervals. Note that the M vibration receiving sensors CH1 to CHM are sometimes simply referred to as vibration receiving sensors CH.

[0143] Since the spacing between each vibration receiving sensor CH of the array sensor is constant, the elastic wave S propagating at an angle θ is received by each vibration receiving sensor CH of the array sensor with a time difference T. Let T1 be the time difference for vibration receiving sensor CH1, and T2, T3, ... TM be the time differences for vibration receiving sensors CH2 and beyond, respectively.

[0144] Here, the time differences T1 to TM are obtained from the interval between the vibration receiving sensors CH and the propagation speed C of the elastic wave S, respectively, by the following equation [Equation 2].

[0145]

number

[0146] Note that i is the number of each vibration receiving sensor CH, ranging from 1 to M. Di is the distance between the reference point and each vibration receiving sensor CH. If the reference point is vibration receiving sensor CH1, then D1 is 0, D2 is d, D3 is 2×d, and DM is (M-1)×d.

[0147] The elastic waves received by each vibration receiving sensor CH are recorded with a time difference of Ti, which is calculated by [Equation 2] above. Therefore, if the received waveforms recorded by each vibration receiving sensor CH are shifted by the time difference Ti, the phases of the elastic waves S propagating from the θ direction will be aligned. In other words, phase alignment is performed. Then, the output waveform Y(t) obtained by summing and averaging the received waveforms from each vibration receiving sensor CH after phase alignment shows that the elastic waves from the θ direction are emphasized because their phases are aligned, while signals from other directions (noise components) are suppressed because their phases are not aligned.

[0148] Next, we consider the basic propagation speed estimation method shown in Figure 14 by performing array signal processing while varying the propagation speed C within an arbitrary range. This basic propagation speed estimation method is also an example of the present invention.

[0149] The vibration receiving sensors CH1 to CHM receive data from the received waveform (step 14A), the propagation speed is changed (step 14E), array signal processing is performed on the received waveform (step 14A), and the amplitude value (Ai) in the resulting output waveform (step 14C) is obtained (step 14D).

[0150] In this case, when the time difference Ti obtained in [Equation 2] matches the actual time difference Ttrue, the phase of the received elastic wave S is aligned and amplified; when Ti and Ttrue do not match, the phase is not aligned and is suppressed. Therefore, the amplitude of the received waveform takes its maximum value when Ti and Ttrue match.

[0151] Then, the propagation speed (Ci_Max) when the amplitude of the received waveform (Ai_Max) is at its maximum is determined (step 14F), and the determined propagation speed (Ci_Max) is estimated to be the propagation speed (step 14G).

[0152] In this way, by applying array signal processing to data measured by an array sensor while varying the propagation speed within an arbitrary range, the propagation speed (Ci_Max) at which the amplitude of the received waveform (Ai_Max) is maximized can be used to estimate the propagation speed.

[0153] [Method for estimating the propagation velocity of ground improvement in an unconsolidated state] Next, a method for estimating the propagation velocity of an unconsolidated ground improvement body 50 (see Figures 1 and 2, etc.) that has not solidified after construction will be explained. Note that the unconsolidated ground improvement body 50 is an example of a medium in which the oscillation frequency and reception frequency of elastic waves are different. Furthermore, the method for estimating the propagation velocity of unconsolidated ground improvement is an example of a method for estimating the propagation velocity when the oscillation frequency and reception frequency of elastic waves differ due to the characteristics of the medium (for example, elastic wave attenuation).

[0154] As mentioned above, in the unconsolidated ground improvement body 50, which has not hardened after construction, the elastic wave N is greatly attenuated, and the frequency components of the elastic wave N1 emitted by the oscillator 154 of the measuring instrument 150 and the frequency components of the elastic wave N2 received by each vibration receiving sensor 162 are different. To explain in more detail, in the ground improvement body 50 constructed by the high-pressure jet mixing method, the elastic wave is greatly attenuated, and the peak frequency of the received waveform is lower than the peak frequency of the emitted elastic wave. In addition, the propagation speed and frequency characteristics of the elastic wave change depending on the degree of hardening progress over time. In other words, the frequency components of the received elastic wave N2 change depending on the hardening state of the ground improvement body 50, and therefore change with the time elapsed since construction. It should be noted that this phenomenon in ground improvement bodies is already known and has been reported, for example, in the aforementioned Non-Patent Document 6.

[0155] (Confirmation of the peak frequency of the ground improvement structure) Next, we will describe the verification experiment conducted by the inventors to confirm the peak frequency of the ground improvement body.

[0156] Figure 15(A) shows the received waveform of elastic waves received by a vibration receiving sensor 162 (see Figure 3, etc.) four hours after the construction of a simulated ground improvement body 500 (see Figure 25, etc.), which is equivalent to the ground improvement body 50 (see Figures 1 and 2, etc.). The elastic waves are burst waves with a frequency of 15 kHz, as shown in Figure 17, generated by an oscillator equivalent to the oscillator 154 (see Figure 10).

[0157] Figure 15(A) shows the received waveform of the elastic wave received by the vibration sensor 162 in range 15A, and Figure 15(B) shows the Fourier transform result of the received waveform in range 15A. From the Fourier transform result, the received waveform after 4 hours has an amplitude peak at 2 kHz, which is a lower frequency compared to the 15 kHz of the transmitted elastic wave waveform.

[0158] Figure 16(A) shows the received waveform of the elastic wave received by the vibration receiving sensor 162 7 hours after the construction of the same simulated ground improvement body.

[0159] Figure 16(A) shows the received waveform of the elastic wave received by the vibration sensor 162 in range 16A, and Figure 16(B) shows the Fourier transform result of the received waveform in range 16A. From the Fourier transform result, the received waveform after 7 hours has an amplitude peak at 2.5 kHz, which is a lower frequency compared to the 15 kHz of the transmitted elastic wave waveform, and has changed from the peak frequency of 2 kHz after 4 hours. Furthermore, after 7 hours, there are amplitude peaks at 8 kHz in addition to 2.5 kHz.

[0160] In a ground improvement body 50 with such characteristics and high elastic wave attenuation, the estimation method that estimates the propagation velocity of elastic waves using the basic method or processing shown in Figure 14 makes it impossible or difficult to measure the propagation velocity with high accuracy.

[0161] Specifically, because elastic waves attenuate, the frequency components of the elastic wave and the frequency components of the received waveform differ. Furthermore, the frequency components of the received waveform change over time after construction. Therefore, in the basic propagation speed estimation method, the signal-to-noise ratio (SNR) of the received signal becomes small, making it difficult to detect the received waveform, and thus it is impossible or difficult to measure the propagation speed with high accuracy.

[0162] Furthermore, when multiple frequency components are present, the basic propagation speed estimation method cannot accurately measure the propagation speed due to factors such as the overlapping of waveforms of multiple frequencies causing a shift in the propagation speed at which the amplitude value is maximum.

[0163] The reason the signal-to-noise ratio (SNR) becomes small is that the oscillating elastic wave is a burst wave of a specific frequency, such as 15 kHz. Therefore, the signal level of the burst wave naturally has the strongest signal at a specific frequency component. However, as the oscillating burst wave propagates through the unconsolidated ground improvement body 50, the strongest frequency component of the burst wave is attenuated, and only the frequency components that were hardly present in the burst wave in the first place remain and are received by the array sensor. In such a case, the basic estimation method in Figure 14 is affected by noise, making it difficult to detect a clear peak and thus difficult to estimate the propagation speed.

[0164] (Outline of the method for estimating the propagation velocity of ground improvement in an unconsolidated state) Next, an overview of the propagation speed estimation method in this embodiment will be described. Note that the same steps as those shown in Figure 14 will be omitted or simplified in the explanation.

[0165] As shown in Figure 18, frequency analysis is performed on the output waveform obtained by array signal processing to identify specific frequency components, specifically peak frequency components, and then propagation velocity estimation is performed on these peak frequency components to estimate the propagation velocity.

[0166] For details, as shown in step 18A of Figure 18, the peak frequency (fr) is identified by frequency analysis (step 18AA of Figure 18) of one or more received waveforms of the vibration receiving sensor CH of the array sensor (step 18AB of Figure 18).

[0167] Furthermore, frequency analysis is performed on the output waveform obtained by array signal processing (step 18B in Figure 18) to obtain the amplitude value of the frequency component of the identified peak frequency (fr) (step 18C in Figure 18). Then, the propagation speed is varied from C1 to Cn, and the propagation speed at which the amplitude value is largest is taken as the estimated propagation speed of the elastic wave (step 14F in Figure 18).

[0168] (Verification through numerical simulation) Next, numerical simulations will verify that the propagation speed can be estimated using the estimation method shown in Figure 18, even when the received waveform contains multiple frequency components.

[0169] Figure 19 shows the simulation conditions. The array sensor 710 was assumed to consist of eight vibration receiving sensors CH1 to CH8 arranged in a fan shape with a diameter of 20 cm. The spacing between each vibration receiving sensor CH was 15°. The oscillator 720 oscillates elastic waves at two frequencies: 1 kHz and 5 kHz. The propagation speed of the elastic wave at 1 kHz was assumed to be 59 m / s, and the propagation speed of the elastic wave at 5 kHz was assumed to be 63 m / s. The distance between the oscillator 720 and the array sensor 710 was assumed to be 1 m.

[0170] Figure 20 shows the received waveforms from each vibration receiving sensor CH of the array sensor 710 in Figure 19.

[0171] First, to identify the peak frequency, a frequency analysis, specifically a Fourier transform, was performed on the waveform received by the vibration sensor CH4. The reason for using the waveform received by vibration sensor CH4 was twofold, based on the simulation conditions: the vibration sensor CH4 is oriented towards the oscillator, and the amplitude of the received waveform is large.

[0172] Figure 21 shows the results of the Fourier transform. From Figure 21, it can be seen that the frequency components of the received waveform have two peaks, at 1 kHz and 5 kHz, similar to the simulation conditions. Furthermore, it can be seen that the heights of the 1 kHz and 5 kHz peaks, i.e., the magnitudes of the Fourier amplitudes, are approximately the same. Then, the propagation speeds of the 1 kHz and 5 kHz frequency components were estimated using the propagation speed estimation method shown in Figure 18.

[0173] In the simulation, array signal processing was performed while varying the propagation speed (Ci) from 10 m / s to 100 m / s in 1 m / s increments. Figure 22 shows, as an example, the output waveforms of the array signal processing when the propagation speed Ci is 20 m / s (Figure 22(A)), 40 m / s (Figure 22(B)), 60 m / s (Figure 22(C)), and 80 m / s (Figure 22(D)).

[0174] Figure 23 shows the results of frequency analysis, specifically the Fourier transform, of the output waveforms at each velocity in Figure 22.

[0175] As shown in Figure 23, the frequency analysis results of the output waveform differ depending on the propagation speed. In Figure 23(A), at a propagation speed of 20 m / s, the amplitude is larger at 5 kHz than at 1 kHz. However, in Figures 23(B), 23(C), and 23(D), at propagation speeds of 40 m / s, 60 m / s, and 80 m / s, the amplitude is larger at 1 kHz than at 5 kHz.

[0176] Figure 24 shows the propagation velocity results obtained by performing frequency analysis on the output waveform of an array signal processing array with propagation velocities varied from 10 m / s to 100 m / s, and extracting the amplitude values ​​at 1 kHz and 5 kHz from the frequency analysis results. As can be seen from Figure 24, the propagation velocity at which the amplitude value is maximum differs between 1 kHz and 5 kHz. The propagation velocity at which the amplitude value is maximum is 59 m / s at 1 kHz (see arrow 24A in the figure) and 63 m / s at 5 kHz (see arrow 24B in the figure). In other words, it is consistent with the simulation conditions and can be seen that the propagation velocity has been estimated accurately.

[0177] Furthermore, it can be seen that the propagation speed can be estimated even when the received waveform contains multiple frequency components.

[0178] Furthermore, when numerical simulations were performed using the basic propagation velocity estimation method shown in Figure 14, although not shown in the illustration, the maximum propagation velocity was 63 m / s, which matched the simulation condition of 63 m / s at 5 kHz, but the 59 m / s at 1 kHz could not be estimated.

[0179] (Model experiment) Next, we will describe a specific example demonstrating, using a model experimental apparatus, that the propagation speed estimation method of this embodiment can estimate the propagation speed with high accuracy.

[0180] As shown in Figure 25, in the model experimental apparatus 501, a simulated ground improvement body 500 was fabricated by filling a model formwork 502 with a mixture of silica sand No. 6, cement, and water in a weight ratio of 3:1:1. The dimensions of the model formwork 502 are 1000 mm in width, 1200 mm in length, and 600 mm in depth. The distance between the oscillator 504 and the array sensor 510 is 1000 mm.

[0181] An oscillator 504 was placed on one end of the simulated ground improvement body 500, and an array sensor 510 was placed on the other end. The array sensor 510 is curved in an arc along the circumferential surface of the mounting portion 506 (see also Figure 26) of a PVC pipe with a diameter of 216 mm.

[0182] As shown in Figure 26, the array sensor 510 consists of eight identical vibration receiving sensors 512 arranged in a staggered pattern around the circumference. For convenience, when distinguishing between the vibration receiving sensors 512, they are designated CH1, CH2, CH3, CH4, CH5, CH6, CH7, and CH8 from right to left in Figure 26.

[0183] • Estimation of propagation speed after 4 hours First, we will explain the estimation of the propagation speed of the simulated ground improvement body 500 four hours after filling. The transmitted waveform oscillated by the oscillator 504 was a 15kHz burst wave as shown in Figure 27.

[0184] Figure 28 shows the received waveforms (measured data) from each vibration receiving sensor 512 (see Figures 25 and 26) of the array sensor 510 of the simulated ground improvement body 500 after 4 hours have elapsed since filling. Frequency analysis, specifically a Fourier transform, is performed on the received waveforms (measured data) from the CH4 and CH5 vibration receiving sensors 512 in Figure 28 to identify the frequencies to be used for propagation velocity estimation. In this embodiment, this analysis is performed on the CH4 and CH5 vibration receiving sensors 512 because their vibration receiving direction is close to that of the oscillator 504.

[0185] Figure 29 shows the Fourier transform results of the received waveforms from the vibration sensors 512 of CH4 and CH5. The peak frequency of the received waveforms was approximately the same for both CH4 and CH5, at 1 kHz. Therefore, the propagation speed after 4 hours is estimated using a frequency component of 1 kHz.

[0186] Then, for the received waveform measured by the array sensor 510, the propagation speed C is changed from 100 m / s to 300 m / s in 1 m / s increments for a 1 kHz frequency component. The amplitude value is extracted for each propagation speed C, and the propagation speed at which the amplitude is largest is estimated to be the propagation speed of the elastic wave.

[0187] Figure 30 shows examples of output waveforms from array signal processing at propagation speeds of 150 m / s (Figure 30(A)), 200 m / s (Figure 30(B)), and 250 m / s (Figure 30(C)). Figure 31 shows the results of frequency analysis at propagation speeds of 150 m / s (Figure 31(A)), 200 m / s (Figure 31(B)), and 250 m / s (Figure 31(C)).

[0188] In the output waveform of the array signal processing shown in Figure 30, it is difficult to capture the change in amplitude due to differences in propagation speed. However, the results of the frequency analysis shown in Figure 31 show that the amplitude value of the 1kHz component is larger when the propagation speed is 200m / s compared to when the propagation speeds are 150m / s and 250m / s.

[0189] Figure 32 is a graph showing the relationship between propagation velocity and amplitude value for a 1 kHz frequency component. As shown in Figure 32, the amplitude value of the 1 kHz frequency component is maximum at a propagation velocity of 201 m / s. Therefore, it can be estimated that the propagation velocity at 1 kHz for the simulated ground improvement body 500 after 4 hours is 201 m / s.

[0190] Furthermore, Figure 43 shows the results of creating a sonar image by performing array signal processing on a fan-shaped range from -45° to 45° at a propagation speed of 201 m / s, in order to examine the accuracy of the propagation speed estimation results. As shown in Figure 43, a strong echo response was observed at a position slightly delayed from the position of oscillator 504, confirming that the propagation speed estimation results were valid.

[0191] Furthermore, Figure 33 shows the results of estimating the propagation speed using the basic propagation speed estimation method shown in Figure 14. The estimated propagation speed was 175 m / s.

[0192] Furthermore, although not shown in the diagram, when a sonar image was created with a propagation speed of 175 m / s, a strong echo response was observed at a position shifted from the oscillator 504, and there were multiple strong echo responses. Therefore, it was confirmed that the initial propagation speed estimation result was inaccurate.

[0193] Furthermore, the multiple strong echo reactions are thought to be reflections of elastic waves from the walls and bottom of the model formwork 502 (see Figure 25), or the top surface of the simulated ground improvement body 500, etc., so-called multipath effects.

[0194] • Propagation speed of the simulated ground improvement material 7 hours after filling Next, we will explain the estimation of the propagation speed of the simulated ground improvement body 500 (see Figure 25) 7 hours after filling. The transmitted waveform oscillated by the oscillator 504 (see Figure 25) was a 15 kHz burst wave AM-modulated at 2 kHz, as shown in Figure 34.

[0195] Figure 35 shows the received waveforms (measured data) from each vibration receiving sensor 512 (see Figures 25 and 26) of the array sensor 510 of the simulated ground improvement body 500 after 7 hours of filling. Similar to the 4-hour period, the received waveforms (measured data) from the vibration receiving sensors 512 of CH4 and CH5 in Figure 35 are subjected to a Fourier transform to identify the frequencies used for propagation velocity estimation.

[0196] Figure 36 shows the Fourier transform results of the received waveforms from the CH4 and CH5 vibration sensors 512. In Figure 36(A), for the CH4 vibration sensor 512, the peak frequency component with the largest amplitude is 17 kHz, followed by the next largest amplitude component at 3 kHz. In Figure 36(B), for the CH5 vibration sensor 512, the peak frequency component with the largest amplitude is 13 kHz, followed by the next largest amplitude component at 3 kHz. Therefore, in this frequency analysis, we decided to estimate the propagation speed using the 3 kHz frequency component, which had a common peak.

[0197] Then, for the received waveform measured by the array sensor 510, the propagation speed C is changed from 100 m / s to 500 m / s in 1 m / s increments for a 3 kHz frequency component. The amplitude value is extracted for each propagation speed C, and the propagation speed at which it is largest is taken as the propagation speed of the elastic wave (estimated propagation speed).

[0198] Figure 37 shows examples of output waveforms from array signal processing at propagation speeds of 200 m / s (Figure 37(A)), 300 m / s (Figure 37(B)), and 400 m / s (Figure 37(C)). Figure 38 shows the results of frequency analysis for propagation speeds of 200 m / s (Figure 38(A)), 300 m / s (Figure 38(B)), and 400 m / s (Figure 38(C)).

[0199] In the output waveform of the array signal processing shown in Figure 37, the amplitude value at a propagation speed of 300 m / s is lower than that at propagation speeds of 200 m / s and 400 m / s. From the frequency analysis results shown in Figure 38, the amplitude value of the 3 kHz component is lowest at a propagation speed of 200 m / s, and is approximately the same for propagation speeds of 300 m / s and 400 m / s.

[0200] Figure 39 is a graph showing the relationship between propagation velocity and amplitude value for a 3kHz frequency component. As shown in Figure 39, the amplitude value of the 3kHz frequency component is maximum at a propagation velocity of 325 m / s. Therefore, it can be estimated that the propagation velocity at 3kHz for the simulated ground improvement body 500 after 7 hours is 325 m / s.

[0201] Figure 44 shows the results of creating a sonar image by performing array signal processing on a fan-shaped range from -45° to 45° at a propagation speed of 325 m / s, in order to examine the accuracy of the propagation speed estimation. As shown in Figure 44, there is a strong echo response at approximately the same position as the oscillator 504, indicating that the propagation speed estimation result is valid.

[0202] • Frequency analysis (Fourier transform) in estimating propagation speed Next, we will describe an example of a method for obtaining the amplitude value of the frequency component of the identified peak frequency in step 18C of the propagation velocity estimation shown in Figure 18.

[0203] In numerical simulations and model experiments, propagation speeds were estimated by creating a spectrogram using the Short-Time Fourier Transform (STFT), and then obtaining the amplitude values ​​of the frequency components of the identified peak frequencies from the spectrogram results. Therefore, a brief explanation will be given of the method for extracting the amplitude values ​​of the frequency components of the identified peak frequencies using the Short-Time Fourier Transform (STFT).

[0204] First, Figure 40 shows an example of a spectrogram created using the Short-Time Fourier Transform (STFT). Figure 40 is an example of data analysis after 7 hours in the aforementioned model experiment, and is a spectrogram of the output waveform of the array signal processing when the propagation speed is 300 m / s and the receiving direction is 0°, i.e., the direction of the oscillator 504. The dashed line in the figure indicates the position of the oscillator 504 at a propagation speed of 300 m / s. From Figure 40, it can be seen that the received signal has the maximum amplitude of the 3 kHz component around 0.003 s. Then, Figure 41 is obtained by extracting the amplitude value of the 3 kHz component from the spectrogram in Figure 40, and the propagation speed was estimated by obtaining the maximum value in Figure 41.

[0205] In this study, we used a spectrogram created using the Short-Time Fourier Transform (STFT) to obtain the results of the frequency analysis. However, frequency analysis in estimating propagation speed is not limited to the Short-Time Fourier Transform (STFT), and any method may be used.

[0206] For example, the amplitude values ​​of the frequency components at the peak frequency may be obtained using filtering processes such as high-pass filters, low-pass filters, and band-pass filters.

[0207] Alternatively, the frequency components of the peak frequencies identified by Fourier transforms other than the Short-Time Fourier Transform (STFT) and wavelet transforms may be extracted.

[0208] Furthermore, short-time Fourier transform (STFT) and wavelet transform can be appropriately applied to determine the peak frequency of the received waveform in step 18A of Figure 18.

[0209] <Other> The present invention is not limited to the embodiments described above.

[0210] For example, the propagation velocity estimation method of the above embodiment estimated the propagation velocity of the ground improvement body (determined the estimated propagation velocity), but it is not limited to this. The present invention can be applied, for example, to a medium in which the propagation velocity of elastic waves changes over time, or to a case in which the oscillation frequency and the reception frequency differ due to the characteristics of the medium that affect the propagation of elastic waves (e.g., attenuation).

[0211] An example of an object to which this method could be applied, other than ground improvement bodies, is the detection of buried objects in the ground.

[0212] In the ground, there are spatial variations in the quantity and distribution of soil type, voids, and groundwater. Therefore, the propagation speed of elastic waves in the ground is thought to vary depending on the direction and depth from which the elastic waves are transmitted. For this reason, when detecting buried objects in the ground (for example, foundation piles of a building), the present invention can be applied to reflected waves from the buried objects to estimate the propagation speed and detect the buried objects.

[0213] In this case, the method of implementing the present invention involves inserting an array sensor into the ground as shown in Figure 2, emitting elastic waves laterally, and receiving reflected waves from buried objects such as foundation piles. If there are buried objects in multiple directions around the insertion point of the array sensor, and the propagation speed of elastic waves differs depending on the direction, applying the present invention will allow for the accurate detection of the location of the buried objects. If the present invention is not applied, it would be necessary to insert guide pipes to measure the propagation speed in each direction where there are buried objects, which is not practical in terms of cost and efficiency.

[0214] Furthermore, the present invention can be implemented in various forms without departing from the spirit of the invention. Multiple embodiments and modifications can be combined as appropriate. [Explanation of Symbols]

[0215] 10 Creator 30 Rotating Rod 32 spray nozzles 50 Ground Improvement Unit 100 measuring devices 120 Control device 130 Measuring Rod 150 measuring instruments 154 Oscillator 160 Array Sensors 162 Vibration sensor 200 measuring devices 250 measuring instruments 254 Oscillators 260 Array Sensors 504 Oscillator 510 Array Sensor 512 Vibration sensor 700 Creation equipment 710 Array Sensor 720 Oscillator K boundary

Claims

1. A process to acquire a received waveform obtained by multiple vibration receiving sensors of an array sensor that receive elastic waves emitted from an oscillator, A step of setting the propagation speed of the elastic wave to the propagation speed at which the amplitude value of the output waveform obtained by performing array signal processing on the received waveform while changing the propagation speed is largest, A propagation speed estimation method comprising the following:

2. A process of determining the peak frequency by frequency analysis of the received waveform, which is obtained by multiple receiving sensors of an array sensor from an elastic wave emitted from an oscillator, and A step of performing array signal processing on the received waveform while changing the propagation speed to obtain the output waveform, extracting the amplitude value of the frequency component of the peak frequency, and setting the propagation speed at which the amplitude value is largest as the propagation speed of the elastic wave, A propagation speed estimation method comprising the following:

3. Having one or more processors, The aforementioned processor, The elastic wave emitted from the oscillator is received by multiple vibration receiving sensors in an array sensor, and the received waveform is acquired. The peak frequency is identified by frequency analysis of the received waveform. The propagation speed is varied and array signal processing is performed on the received waveform to obtain the output waveform. The amplitude value of the frequency component of the peak frequency of the output waveform is extracted, and the propagation speed at which the amplitude value is largest is defined as the propagation speed of the elastic wave. Propagation velocity estimation device.

4. The elastic wave emitted from the oscillator is received by multiple vibration receiving sensors in an array sensor, and the received waveform is acquired. The peak frequency is identified by frequency analysis of the received waveform. The propagation speed is varied and array signal processing is performed on the received waveform to obtain the output waveform. The amplitude value of the frequency component of the peak frequency of the output waveform is extracted, and the propagation speed at which the amplitude value is largest is defined as the propagation speed of the elastic wave. A propagation speed estimation program that allows a computer to perform the processing.

5. A shaft member inserted into the ground improvement body before hardening, An oscillator that emits elastic waves is provided on the aforementioned shaft member, An array sensor is provided on the shaft member, and a plurality of vibration receiving sensors are arranged at circumferential intervals to receive the elastic waves that are reflected at the boundary between the ground improvement body and the ground, which are emitted from the oscillator. A propagation speed estimation device that acquires a received waveform from the elastic wave reflected at the boundary, identifies the peak frequency by frequency analysis of the received waveform, extracts the amplitude value of the frequency component of the peak frequency of the output waveform obtained by array signal processing on the received waveform while changing the propagation speed, and sets the propagation speed at which the amplitude value is largest as the propagation speed of the elastic wave. A distance estimation device that estimates the distance between the array sensor and the boundary from the propagation speed obtained by the propagation speed estimation device and the time from the oscillation of the elastic wave to the reception of the elastic wave reflected at the boundary, A measuring device for ground improvement bodies equipped with the following features.

6. The oscillator emits the directional elastic wave. A measuring device for a ground improvement body according to claim 5.

7. The oscillator oscillates the non-directional elastic wave over the entire circumference. The aforementioned array sensor has the vibration receiving sensors arranged around the entire circumference. A measuring device for a ground improvement body according to claim 5.

8. A construction section that creates a ground improvement body by ejecting a hardening agent from its tip while pulling up a shaft member inserted into the ground, A measuring device for a ground improvement body according to any one of claims 4 to 6, inserted into the ground improvement body during construction, An adjustment unit that adjusts the amount of hardening material ejected according to the distance detected by the measuring device for the ground improvement body, A ground improvement body construction device equipped with the following features.

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