JP7266066B2 - Measurement method and device for the dimensions and shape of ground improvement material - Google Patents

Description

The present invention relates to a method and apparatus for measuring the dimensions and shape of a soil improvement body suitable for use in a ground improvement method for creating a cylindrical improvement body by cutting the ground with an ultra-high pressure injection of a cement-based hardening agent.

Soil improvement technology for improving soft ground, etc. to high strength is one of the technologies that are strongly required in order to secure the foundation of people's lives and social activities. As a ground improvement method, the high-pressure jet stirring method has been put into practical use. The high-pressure injection stirring method is a construction method in which the ground is excavated by an ultra-high-pressure injection of a cement-based hardening agent from a rod nozzle inserted into the ground to create a cylindrical improved body.

In the high-pressure injection stirring method, the shear strength of the soil layer to be ground improvement and the so-called hardness such as the N value, which is a standard penetration test value, affect the dimensions of the improved body to be formed. For this reason, when performing ground improvement work, it is necessary to properly set the injection pressure, injection flow rate, etc. of the cement-based hardener in consideration of the soil quality of the soil to be improved. dimensions must be ensured.

In addition, the dimensions of the soil improvement body created by the high-pressure injection agitation method vary depending on various factors, such as the shear strength of the target soil and the non-uniformity of the target soil layer. Therefore, in order to guarantee the dimensions of the ground improvement material, it is necessary to grasp the dimensions of the soil improvement material actually developed.

However, since the soil improvement body is created in the ground, unless the soil improvement body is exposed by excavation, it is impossible to visually check the soil improvement body or directly measure the dimensions of the soil improvement body.

Therefore, several techniques have been proposed for grasping the dimensions of an improved body during construction of the improved body. For example, in Patent Document 1, a built-in pipe is inserted into the ground around the injection pipe, and the sound or vibration of the solidifying material, which is injected at high pressure from the nozzle of the injection pipe, hitting the built-in pipe is detected using an underwater microphone or the like. By doing so, a technique for grasping the dimensions of the improved body is described and is actually used. In addition, in Patent Document 2, the shape of the soil improvement body is measured using the reflection of sound waves at the interface between the ground (also called the original ground, but hereinafter referred to as soil for easy distinction) and the soil improvement body. technology is described.

JP 2012-62626 A JP 2012-172329 A

However, in the technique described in Patent Document 1, although it can be seen that the soil improvement body has been formed up to the place where the plumbing pipe is inserted, there is a drawback that the dimensions of the soil improvement body in other places are not known.

Further, the technique described in Patent Document 2 is a method of oscillating sound waves from inside the improved body and measuring reflected waves from the wall surface of the improved body. Unlike natural ground, it is difficult for sound waves to propagate through an improved body under construction, so it is difficult to receive reflected waves. was not disclosed at all, and was merely an idea.

The present invention was made to solve the above problems, and the purpose is to measure the dimensions and shape of the ground improvement body that can accurately grasp the dimensions of the created soil improvement body in three dimensions immediately after creation. The object is to provide a method and apparatus.

In the present invention, in order to detect the boundary between the soil improvement material and the soil, a directional sound wave transmitter transmits sound waves toward the boundary, and an omnidirectional wave receiver is used to detect the reflected waves from the boundary. We have found that receiving waves is effective, and have completed the present invention.

That is, the gist and configuration of the present invention are as follows.

(1) In a method for measuring the dimensions and shape of a ground improvement body formed by a ground improvement method, a measurement guide pipe is installed in the ground improvement body, and a directional transmitter that transmits a directional sound wave and a sound wave A plurality of omnidirectional wave receivers that receive sound waves independently of the arrival angle are inserted into the ground improvement body, sound waves are transmitted from the directional transmitter, and the ground improvement body and the soil When receiving the reflected wave from the boundary with the omnidirectional wave receiver to obtain a detection signal, the directional transmitter and the plurality of omnidirectional wave receivers are connected to the measurement guide A method for measuring the dimensions and shape of a soil improvement body, wherein the measurement guide tube is rotated about its axis and moved up and down in the pipe to detect the three-dimensional shape of the soil improvement body.

(2) The sound wave to be transmitted is preferably a pseudo-random wave, which is a phase-modulated wave by a binary code string, and its frequency is changed in plurality.

(3) Preferably, the detection signal is obtained from a cross-correlation operation between the received sound wave and the pseudo-random wave.

(4) The plurality of frequencies of the sound waves to be transmitted can be changed according to the design shape of the soil improvement body and/or the time from completion of construction of the soil improvement body. In general, a relatively low frequency wave of 1 kHz to 8 kHz is used until the time after the construction is completed and the sound wave is relatively difficult to propagate, for example, until 2 days later. After that, it is preferable to use relatively high-frequency waves of 2 kHz to 12 kHz or higher.
(5) In addition, when the design size of the ground improvement body is large, the frequencies of the sound waves to be transmitted use lower frequencies than when the design size is small, and the time has elapsed since the construction of the ground improvement body was completed. It is better to use a higher frequency than immediately after construction.

( 6 ) Through continuous Wavelet transformation of the detection signal and Wavelet function, it is possible to improve the distinguishability of the reflected wave from the boundary between the soil improvement body and the soil. Whether to extract high frequency components or low frequency components by continuous Wavelet transformation should be changed according to the hardening condition of the ground improvement material and the purpose of signal processing.

( 7 ) The Wavelet function can be Gabor wavelet or Symlet wavelet.

( 8 ) The directional transmitter and a plurality of omnidirectional receivers may be connected by a fixing member to form a transmitter/receiver.

( 9 ) Phase synthesis using signals received by each of the plurality of omnidirectional wave receivers, or numerical calculation regardless of phase, from the boundary between the soil improvement body and the soil It is also good to improve the discriminability of the reflected wave.

( 10 ) The transducers are connected in a row in the depth direction of the ground improvement body, and a plurality of the omnidirectional transducers are arranged on at least one of the upper side and the lower side of the directional transmitter. A sound absorbing material may be provided between the directional transmitter and the omnidirectional receiver.

( 11 ) A sound absorbing material may be provided on the back surface of the omnidirectional wave receiver.

( 12 ) Put a plurality of wave receivers for receiving sound waves in a transmission guide pipe installed at a different position of the ground improvement body, and transmit sound waves from the sound wave transmitter placed in the measurement guide pipe, The transmitted waves are received by a plurality of wave receivers of the transmission guide tube, the sound velocity in the ground improvement body is obtained from the distance between the measurement guide tube and the transmission guide tube and the transmission time of the transmitted waves, and the sound velocity and , the distance between the directional transmitter and the boundary can be obtained from the propagation time of the reflected wave from the boundary between the soil improvement material and the soil.

( 13 ) A calibration curve is obtained in advance from the relationship between the speed of sound in the soil improvement body and the elapsed time after the creation of the soil improvement body, and the sound velocity value obtained from the calibration curve by the elapsed time from the creation of the soil improvement body The distance between the directional transmitter and the boundary may be obtained from the propagation time of the reflected wave from the boundary between the soil improvement material and the soil.

( 14 ) It is preferable to measure the dimensions and shape of the soil improvement body when the speed of sound in the soil improvement body is 2000 m/s or less.

( 15 ) In a size and shape measuring device that is performed by installing a measurement guide pipe in a ground improvement body immediately after construction formed by a ground improvement method, a sound wave having directivity is transmitted by inserting it into the measurement guide pipe. and a plurality of directional wave transmitters that are inserted into the measurement guide pipe to receive reflected waves from the boundary between the soil improvement body and the soil, and that receive sound waves independently of the arrival angle of the sound waves. An omnidirectional wave receiver, means for obtaining a detection signal from a received wave signal, the directional transmitter and the plurality of omnidirectional wave receivers are rotated within the measurement guide tube around the axis of the measurement guide tube. and means for detecting the three-dimensional shape of the soil improvement body by moving it up and down while moving it up and down .

( 16 ) The sound wave to be transmitted is preferably a pseudo-random wave, which is a phase-modulated wave by a binary code sequence, and has means for changing its frequency in a plurality of ways.

( 17 ) It is preferable that the means for obtaining the detection signal from the received wave signal is cross-correlation calculation means between the received sound wave and the pseudo-random wave.

( 18 ) It is preferable to have means for changing a plurality of frequencies of the sound waves to be transmitted according to the design shape of the soil improvement body and the time from the completion of construction of the soil improvement body.

( 19 ) In order to improve the distinguishability of the reflected wave from the boundary between the ground improvement material and the soil, it is preferable to have means for performing continuous Wavelet transformation between the detection signal and the Wavelet function.

( 20 ) The Wavelet function used by the means for performing continuous Wavelet transformation is preferably Gabor wavelet or Symlet wavelet.

( 21 ) A transducer in which the directional transmitter and a plurality of the omnidirectional receivers are connected by a fixing member in order to measure the shape change due to the orientation of the ground improvement body and / or the three-dimensional shape and means for rotating and raising and lowering the transducer.

( 22 ) In order to improve the distinguishability of the reflected wave from the boundary between the soil improvement material and the soil, a plurality of the omnidirectional wave receivers and a means for phase combining using the signals received by each, or , and means for numerically operating independently of the phase.

( 23 ) One of the directional transmitters connected in a row in the depth direction of the ground improvement body, and a plurality of the directional wave receivers arranged on at least one of the upper side and the lower side of the directional wave receivers It is preferable to provide an omnidirectional wave receiver and a sound absorbing material provided between the directional transmitter and the omnidirectional wave receiver.

( 24 ) It is preferable to have a sound absorbing material provided on the back surface of the omnidirectional wave receiver.

( 25 ) The transmission guide tube containing a plurality of wave receivers for receiving sound waves installed at another position of the ground improvement body, and the sound wave transmitted from the transmitter placed in the measurement guide tube, Means for determining the transmission time from the transmitted wave received by the receiver of the transmission guide pipe, and means for determining the sound velocity in the soil improvement body from the distance between the measurement guide pipe and the transmission guide pipe and the transmission time of the transmitted wave. and means for measuring the propagation time of the reflected wave from the boundary between the soil improvement material and the soil, and the distance between the directional transmitter and the boundary from the measured values of the speed of sound and the propagation time of the reflected wave. It is preferable to further comprise a means for obtaining the

( 26 ) Means for storing a calibration curve obtained in advance from the relationship between the speed of sound in the soil improvement body and the elapsed time after the creation of the soil improvement body, and the progress from the creation of the soil improvement body from the stored calibration curve Means for obtaining a sound velocity value according to time, means for measuring the propagation time of the reflected wave from the boundary between the soil improvement material and the soil, and the directional transmitter from the measured values of the sound velocity and the propagation time and means for determining the distance to said boundary.

( 27 ) It is preferable to provide means for determining whether the sound velocity in the soil improvement body is 2000 m/s or less, and measure the dimensions and shape of the soil improvement body when the sound velocity is 2000 m/s or less.

The present invention cuts the ground by ultra-high pressure injection of a cement-based hardening agent, in ground improvement to create a columnar improvement body, install a measurement guide pipe to the ground improvement body immediately after creation, and emit sound waves having directivity. A directional transmitter that transmits waves and multiple omnidirectional receivers that receive sound waves independently of the arrival angle of the sound waves are inserted into the ground improvement body, and sound waves are transmitted from the directional transmitters. The reflected waves from the boundary between the ground improvement body and the soil are received using multiple omnidirectional wave receivers to obtain detection signals. The shape of the direction can be accurately grasped three-dimensionally immediately after construction . Therefore, it is possible to greatly contribute to the stable operation and improvement of ground improvement body construction technology.

Sectional view showing the basic configuration of soil improvement body size and shape measurement according to the present invention Perspective view showing dimensional change measurement of soil improvement body dimensions and three-dimensional shape measurement of soil improvement body dimensions according to the present invention Sectional view showing a modification of soil improvement body size and shape measurement according to the present invention Sectional view showing another modification of soil improvement body size and shape measurement according to the present invention A block diagram showing an example of a calculation unit in an embodiment of soil improvement body size and shape measurement according to the present invention Block diagram showing another example of the calculation unit in the embodiment of the measurement of the dimensions and shape of the soil improvement body according to the present invention Figure showing an example of soil improvement material measurement FIG. 2 is a waveform diagram showing a part of the waveform of the pseudo-random wave transmitted from the transmitter of the embodiment according to the present invention; Waveform diagram showing an example of a signal immediately after pulse compression Waveform diagram showing the results of phase synthesis of detection signals (A) Signal after pulse compression and (B) Waveform diagram showing a comparison of the result of performing continuous Wavelet transform using Gabor wavelet function on this signal Waveform diagram showing the result of applying continuous wavelet transform by symlet wavelet function to the signal after pulse compression A diagram showing an example of a calibration curve showing the relationship between the sound velocity of a soil improvement material and the time from the creation of the soil improvement material. A scatter diagram showing an example of measurement results for the dimensions and shape of a ground improvement material Radar chart showing an example of the diameter change due to the orientation of the ground improvement material at a depth of 4m Radar chart showing an example of the diameter change due to the orientation of the ground improvement material at a depth of 6m Radar chart showing an example of the diameter change due to the orientation of the ground improvement material at a depth of 8m Radar chart showing an example of the diameter change due to the orientation of the ground improvement material at a depth of 10m Boundary diagram showing the boundary between the soil improvement body and the ground, which is a three-dimensional representation of Figures 15 to 18 A 3D external view of the shape of the soil improvement structure constructed by interpolating the data A cross-sectional view of a 2D shape at an arbitrary position of the 3D shape of the soil improvement body constructed by interpolation of data Explanatory diagram showing an example of the relationship between the speed of sound and the elapsed time from the formation of the soil improvement body for two soil improvement bodies formed with similar construction specifications on ground (soil) with a similar composition. FIG. 4 is a waveform diagram showing an example of phase synthesis of detection signals obtained in another connection method of the directional transmitter and the omnidirectional receiver shown in FIG. Explanatory diagram showing an example of the relationship between the upper and lower limits of the frequency at which a signal with a good SN ratio can be obtained and the elapsed time from the construction of the soil improvement body

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the present invention is not limited by the contents described in the following embodiments and examples. In addition, the configuration requirements in the embodiments and examples described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Furthermore, the constituent elements disclosed in the embodiments and examples described below may be combined as appropriate, or may be selected and used as appropriate.

FIG. 1 shows the basic configuration for measuring the dimensions and shape of a soil improvement body according to the present invention. A measurement guide pipe 54 is installed in the soil 50 approximately in the center of the ground improvement body 52 after preparation, and a directional transmitter 12 and a plurality of (four in FIG. 1) omnidirectional wave receivers 14- 1 to 14-4 are coupled with a fixing member 16 to insert a wave transmitter/receiver 10, a sound wave 22 is transmitted from the directional wave transmitter 12, and a reflected wave 24- 1 to 24-4 are received by omnidirectional wave receivers 14-1 to 14-4 to obtain detection signals 46-1 to 46-4.

In the figure, 48 is a Wavelet converter for improving the distinguishability of detection signals 46-1 to 46-4, and 49 is a phase synthesizer.

In FIG. 1, four omnidirectional wave receivers 14-1 to 14-4 are arranged above the directional wave transmitter 12. In FIG. A sound absorbing material 18 is interposed between the directional transmitter 12 and the omnidirectional receiver 14-1. The sound-absorbing material 18 allows the bore waves generated in the measurement guide tube 54 when the directional transmitter 12 transmits the sound waves 22 to directly reach the omnidirectional wave receivers 14-1 to 14-4 ( (referred to as direct waves).

Connected to the directional transmitter 12 are a digital pseudo-random wave (phase-modulated wave by a binary code string) generator 30, a digital-analog (D/A) converter 32, and a power amplifier 34 in order of separation. be. The digital pseudorandom wave generating device 30 can be configured using a personal computer or the like, generates a digital signal of a pseudorandom wave (a phase-modulated wave by a binary code sequence), and outputs it to a digital-analog converter 32. , the pseudorandom wave converted into an analog signal by the digital-analog converter 32 is amplified to a high voltage signal by the power amplifier 34 and applied to the directional transmitter 12 to transmit the sound wave 22 .

Upon receiving the pseudo-random wave high voltage signal from the power amplifier 34 , the directional transmitter 12 transmits a directional sound wave 22 having a pseudo-random wave waveform into the soil improvement body 52 . The reflected waves 24-1 to 24-4 that reach the boundary between the soil improvement body 52 and the soil 50 and are reflected at the interface propagate in the direction from which they came and reach the omnidirectional wave receivers 14-1 to 14- 4, amplified to an appropriate magnitude by receiving amplifiers 40-1 to 40-4, and converted to digital received signals by analog-to-digital (A/D) converters 42-1 to 42-4. be.

The cross-correlation calculators 44-1 to 44-4 calculate the cross-correlation between the received digital wave signal and the pseudo-random waves used for transmission, and the results are used as detection signals 46-1 to 46-4. .

Since the pseudo-random wave is a wave in which the phase of a sinusoidal carrier wave is modulated by a binary code string, the frequency of the sinusoidal carrier wave can be changed by providing a frequency changing section 70 as shown in FIG. By doing so, it is possible to change the frequency of sound waves.

Immediately after the formation of the soil improvement body 52, the soil forming the ground and the cement-based hardening agent are not bonded, so the scattering attenuation of the sound waves 22 is large. It couples and the sound wave 22 becomes easy to propagate. Therefore, the frequency of the sound wave 22 may be changed according to the elapsed time from the creation of the soil improvement body 52. Specifically, it is preferable to use a low frequency sound wave of about several kHz immediately after construction, and use a high frequency of about 10 kHz at the timing when the soil improvement body 52 is sufficiently solidified. Also, the frequency of the sound wave 22 may be changed according to the design dimensions of the soil improvement body 52 . If the design size of the soil improvement body 52 is large, the sound wave propagation distance becomes long and the attenuation of the sound wave 22 becomes large, so it is advantageous to use a low frequency with a small attenuation coefficient. The directivity (directivity angle) of the sound wave 22 transmitted by the directional transmitter 12 is proportional to the wavelength of the sound wave. Therefore, the higher the frequency, the shorter the wavelength, the better the directivity of the sound wave 22, and the reflected wave from the boundary between the ground improvement body 52 and the soil 50 is increased. It is also a good idea to make measurements using sound waves of several frequencies and compare the results.

In order to improve the discrimination of the reflected waves 24-1 to 24-4 in the detection signals 46-1 to 46-4 (the detection signals may be collectively referred to as detection signals 46 hereinafter), the detection signals 46-1 to Continuous Wavelet transformation can be performed in Wavelet transformer 48 at 46-4. The continuous Wavelet transform that can extract frequency components lower than the frequency of the transmitted sound wave 22 is effective immediately after the ground improvement body 52 is created and when measuring the ground improvement body 52 having a large size. Continuous Wavelet transform, which can extract frequency components higher than the frequency of the sound wave 22 to be transmitted, is effective for emphasizing the short pulse shape of the reflected wave signal. In order to control the height of the frequency component to be extracted, it is effective to use different Wavelet functions for continuous Wavelet transformation. Gabor wavelet, for example, is effective for extracting low-frequency components, and Gabor wavelet and Symlet wavelet, for example, are effective for extracting high-frequency components.

Detection signals 46-1 to 46-4 obtained from waves received by omnidirectional wave receivers 14-1 to 14-4 in FIG. It is possible to improve the discrimination of the reflected waves by matching the phases according to the propagation distance (temporally compensating for the difference in distance) and synthesizing (phase synthesis). It is also possible to perform numerical calculations such as mutual subtraction of -1 to 46-4.

Note that the Wavelet converter 48 and the phase synthesizer 49 can be used together, either one of them can be used, or both can be omitted.

Furthermore, as shown in FIG. 2, the directional transmitter 12 and the omnidirectional wave receiver 14 (hereafter, a set of a plurality of omnidirectional wave receivers will be referred to as the omnidirectional wave receiver 14) are mounted on a fixing member 16. By rotating the transducer 10 coupled by the rotation/elevation mechanism 20 in the measurement guide tube 54, it is possible to measure the dimensional change of the soil improvement body 52 due to the orientation, and similarly rotate/elevate The three-dimensional shape of the ground improvement body 52 can also be measured by combining the elevation of the transducer 10 in the measurement guide pipe 54 by the mechanism 20 . Note that one of the rotation and elevation can be omitted.

The arrangement of the directional transmitter 12 and the omnidirectional receiver 14 is such that the transmitter 12 and the receiver 14 shown in FIG. In addition to a configuration in which a plurality of directional wave receivers 14 are arranged above the directional transmitter 12 and a sound absorbing material 18 is provided between the directional transmitter 12 and the omnidirectional wave receiver 14, As shown in FIG. 3, the transmitter 12 and the receiver 14 are connected in a row in the depth direction of the ground improvement body 52, and one or more (two in FIG. 3) are arranged above the directional transmitter 12. ), and one or more (two in FIG. 3) of the omnidirectional wave receivers below the directional transmitter 12 14-3, 14-4 are arranged, and between the directional transmitter 12 and the omnidirectional receivers 14-1, 14-2 and 14-3, 14-4, sound absorbing materials are provided, respectively A configuration in which 18 and 18' are provided is also possible. Also, contrary to FIG. 2, the wave receiver 14 may be provided only below the wave transmitter 12 .

Furthermore, as shown in FIG. 3, the back surface of the omnidirectional wave receiver 14 (a reflected wave 24 that reached the boundary between the ground improvement body 52 and the soil 50 and was reflected at the interface . A reflected wave received by the set of wave receivers 14 is referred to as a reflected wave 24. Sound absorbing materials 19-1 to 19-4 are provided in a direction opposite to the direction in which . . . It is possible to eliminate noise due to the reflection of the sound wave 22 and the reflected wave 24 at the fixed member 16 that couples the acoustic wave receiver 14 .

Propagation time of a reflected wave 24 transmitted from the directional wave transmitter 12, reaching the boundary between the soil improvement body 52 and the soil 50, reflected at the interface, received by the omnidirectional wave receiver 14 and detected. Therefore, in order to find the distance between the directional transmitter 12 or the omnidirectional receiver 14 and the boundary between the soil improvement body 52 and the soil 50, it is necessary to know the sound velocity in the soil improvement body 52.

For the sound velocity measurement, as shown in FIG. It can be implemented by transmitting a sound wave from the wave device 12 and receiving the transmitted wave by the wave receiver 62 of the transmission guide tube 60 .

Specifically, as exemplified in FIG. 5, the transmission time t1 of the transmitted wave is calculated by the transmission time measurement unit 80 from the difference between the wave transmission time at the wave transmitter 12 and the wave reception time at the wave receiver 62. Measure. Next, the sound velocity calculator 82 obtains the sound velocity V in the ground improvement body 52 from the following equation from the distance L1 between the measurement guide tube 54 and the transmission guide tube 60 and the transmission time t1 of the transmitted wave. In this calculation, a correction is made in consideration of the propagation time of sound waves in the water normally filled in the measurement guide tube 54 and the transmission guide tube 60 .

V=L1/t1 (1)

The boundary between the ground improvement body 52 and the soil 50 obtained by the propagation time measuring unit 84 as the sound velocity V obtained in this way and the difference between the wave transmission time of the wave transmitter 12 and the wave reception time of the wave receiver 14 From the propagation time t2 of the reflected wave 24 from the distance calculator 86, the distance between the directional transmitter 12 or the omnidirectional wave receiver 14 and the soil improvement body 52-soil 50 boundary (that is, Soil improvement body size) L2 can be obtained. In this calculation as well, a correction is made taking into account the time it takes for sound waves to propagate through the water normally filled in the measurement guide tube 54, and the propagation time of the reflected wave 24 propagating between the omnidirectional wave receiver 14 and the boundary is A correction is also made to take into account that the distance is slightly different from the propagation distance of the sound wave 22 propagating between the directional transmitter 12 and the boundary.

L2=V×t2/2 (2)

Alternatively, instead of the method of directly obtaining the sound velocity V in the soil improvement body 52 as described above, the sound velocity V in the soil improvement body 52 as illustrated in FIG. (hereinafter referred to as a calibration curve) is obtained in advance and stored in a calibration curve storage unit 88 as illustrated in FIG. From the propagation time t2 of the reflected wave 24 from the boundary between the ground improvement body 52 and the soil 50 measured by the propagation time measurement unit 84, the distance calculation unit 86 uses the above equation (2) to determine the directional transmitter 12 Alternatively, it is possible to obtain the distance L2 between the omnidirectional wave receiver 14 and the soil improvement body 52-soil 50 boundary.

The directivity angle of the sound wave 22 transmitted by the directional transmitter 12 into the soil improvement body 52 is proportional to the wavelength λ of the sound wave 22, and the wavelength λ is proportional to the speed of the sound wave 22. The sound velocity V in the soil improvement body 52 is the lowest immediately after the soil preparation, and increases with the lapse of time. Therefore, it is preferable to measure the dimensions and shape of the soil improvement body 52 when the directivity angle of the sound wave 22 transmitted by the directional transmitter 12 is small and the sound speed is small. When the sound velocity at 52 is 2000 m/s or less, the SN ratio of the reflected wave 24 is good, so the accuracy of the size and shape measurement is good. For this purpose, for example, a sound velocity determination unit 72 as shown in FIG. 1 can be provided.

Below, an example of measuring a soil improvement body 52 having a horizontal cross section such as the Yamagata bread shown in FIG. The measurement guide tube 54 had an outer diameter of 250 mm and was inserted at the end of the soil improvement body 52, and the permeation guide tube 60 was inserted at a position separated from the measurement guide tube 54 by 1 m. The distance between the center of the measurement guide pipe 54 and the curved boundary (the boundary between the soil improvement body 52 and the soil 50) was 1800 mm, and the distance between the center of the measurement guide pipe 54 and the straight portion of the side surface was 900 mm.

In the measurement, a sound wave with a frequency of 1 kHz to 12 kHz is transmitted from the directional transmitter 12 shown in FIG. Received.

FIG. 8 shows an example waveform of the sound wave 22 (pseudo-random wave) transmitted from the directional transmitter 12 . FIG. 8 shows a portion of a pseudo-random wave with a frequency of 2 kHz, which is actually a signal having a pulse width of 1000 cycles or more. A signal such as that shown in FIG. 8 is amplified to an amplitude of 420 V _PP and applied to the transducer of the sound wave 22 built in the directional transmitter 12 to transmit a sound wave having an equivalent waveform. Sound waves with frequencies between 1 kHz and 12 kHz were transmitted by varying the frequency of the phase-carrying sine wave.

Detection obtained by converting the signal received by the omnidirectional wave receiver 14-1 into a digital received wave signal by the analog-digital converter 42 and calculating the cross-correlation between the signal and the pseudo-random wave used for transmission. An example signal is shown in FIG. The detection signal is a raw signal (signal immediately after pulse compression) detected when the frequency of the pseudo-random wave is 2 kHz and is not subjected to continuous Wavelet transform or the like. A reflected wave (echo) 24 from the boundary between the soil improvement body 52 and the soil 50 (in FIGS. 9 to 12 and 23, the distance between the directional transmitter 12 and the boundary is 1710 mm) is captured.

Further, the signals received by the omnidirectional wave receivers 14-1 to 14-4 are similarly processed to obtain detection signals 46-1 to 46-4, and the results of phase synthesis of these signals are shown in FIG. shown in A reflected wave 24 from the boundary between the soil improvement body 52 and the soil 50 is more clearly captured.

FIG. 11 shows an example of the result of performing continuous Wavelet transform on the detected signal 46-1 obtained from the signal received by the omnidirectional wave receiver 14-1. A Gabor wavelet was used as the Wavelet function, and the wavelength of the Gabor wavelet was twice the wavelength of the sound wave transmitted by the directional transmitter 12 . FIG. 11(A) shows the pulse-compressed signal obtained by transmitting the sound wave 22 with a pseudo-random wave frequency of 4 kHz and detecting the received wave signal. , the frequency is 1/2) is the result of extracting the 2 kHz signal using continuous Wavelet transform, and in FIG. S/N ratio is captured well.

FIG. 12 shows the result of performing a similar continuous Wavelet transform using the Symlet wavelet as a Wavelet function. A signal with a frequency higher than the transmitted sound wave (frequency of 2 kHz) was extracted. A reflected wave 24-1 from the boundary between the ground improvement body 52 and the soil 50 is captured as in the case of the Gabor wavelet.

In FIG. 13, as shown in FIG. 4, a wave receiver 62 for receiving sound waves is placed in the transmission guide tube 60, and a sound wave is transmitted from a wave transmitter placed in the measurement guide tube 54. The transmitted wave is received by the wave receiver 62 of the tube 60, and the sound velocity V in the soil improvement body 52 is obtained from the distance L1 between the measurement guide tube 54 and the transmission guide tube 60 and the transmission time t1 of the transmitted wave. showing. The horizontal axis is the elapsed time from the construction of the soil improvement body 52 . The speed of sound V in the soil improvement body 52 increases rapidly immediately after construction, and hardly changes after a certain period of time. The sound velocity obtained here was used for the shape measurement of the soil improvement body 52 whose results are shown below.

FIG. 14 shows the transducer 10 in which the directional transmitter 12 and the omnidirectional receiver 14 are coupled with the fixing member 16 using the rotation/elevating mechanism 20 as shown in FIG. An example of measuring the dimensions and shape of a soil improvement body 52 having a horizontal cross-sectional shape like the mountain-shaped bread shown in FIG. 7 is shown. there is In this measurement, the surface that reflects the ultrasonic waves was limited, so the comparison between the measured dimension and the actual dimension is shown instead of the three-dimensional shape. Both agree well with an error of about 2%, and it can be seen that according to the present invention, the dimensions of the soil improvement body 52 can be measured satisfactorily. Therefore, usually, a measurement guide pipe 54 is provided at the center of the ground improvement body having a cylindrical shape, and sound waves are transmitted and received in all directions from the transducer 10 arranged in the middle, and / or It can be seen that the three-dimensional shape of the ground improvement body 52 can also be measured by changing the depth at which the transducer 10 is arranged and transmitting and receiving sound waves.

FIGS. 15 to 18 show that, as shown in FIG. 2, the directional transmitter 12 and the omnidirectional receiver 14 are connected by the fixing member 16, and the transducer 10 is rotated in the measurement guide tube 54. Furthermore, it ascends and descends in the measurement guide tube 54 to measure the diameter change of the soil improvement body 52 (a columnar soil improvement body different from FIGS. 7 and 14) and the three-dimensional shape of the soil improvement body 52 depending on the orientation. It shows an example obtained when 15 shows an example of a position of 4 m depth, FIG. 16 shows an example of a position of 6 m depth, FIG. 17 shows an example of a position of 8 m depth, and FIG. 18 shows an example of a position of 10 m depth. If measurements are taken every 22.5° in azimuth, there will be 16 measurements for one depth position. The diameter of the ground improvement body 52 varies slightly depending on the orientation and also varies depending on the depth.

FIG. 19 is a boundary diagram showing the boundary between the soil improvement body 52 and the soil 50, which is a three-dimensional representation of FIGS. 15 to 18, and FIG. FIG. 21 is a cross-sectional view of a two-dimensional shape at an arbitrary position of the three-dimensional shape of the soil improvement body 52 constructed by data interpolation. In FIG. 20, the shape of the soil improvement body 52 is three-dimensionally displayed using dot configurations with different densities. In FIG. 21, the soil improvement body 52 in the center is shown with a dark dot configuration, the boundary between the soil improvement body 52 and the soil 50 is shown with a bright dot configuration, and the soil 50 is shown with an intermediate density dot configuration. The reason why the boundary between the ground improvement material 52 and the soil 50 is expressed with thickness is to make the boundary easier to see. Practically, if each is displayed in color, the structure of the boundary between the ground improvement material 52 and the soil 50 becomes easier to understand. Any display diagram is suitable for grasping the three-dimensional shape of the soil improvement body 52, and it is possible to obtain meaningful information about the construction of the soil improvement body.

FIG. 22 shows the relationship between the sound velocity V and the elapsed time for two soil improvement bodies P and Q formed with similar construction specifications on ground (soil) with similar compositions. Since the sound velocity values are almost the same, if the relationship between the sound velocity V and the elapsed time for the soil improvement body P is obtained, it is found that it is not necessary to measure the sound velocity for the soil improvement body Q. Therefore, when making a number of soil improvement bodies at the same site, the relationship between the sound speed and the elapsed time is obtained for one soil improvement body, and the sound speed is obtained using that relationship for the other soil improvement bodies, and the sound speed and The dimensions of the soil improvement body can be obtained from the propagation time of the reflected wave from the soil improvement body-soil boundary.

In FIG. 23, the transducers 10 are connected in a row in the depth direction of the ground improvement body 52, and two omnidirectional transducers 14-1 and 14-2 are placed above the directional transmitter 12. , two omnidirectional wave receivers 14-3 and 14-4 are placed below the directional transmitter 12, and four omnidirectional wave receivers 14 obtain from the signals received. An example is shown in which phase synthesis is performed using the four detection signals 46-1 to 46-4 obtained. Between the directional transmitter 12 and the omnidirectional wave receivers 14-1, 14-2 and between the directional transmitter 12 and the omnidirectional wave receivers 14-3, 14-4, materials A cork sound absorbing material 18, 18' is provided. This is an example of a case where the boundary echo is detected with the frequency of the transmitted sound wave set to 2 kHz, and the soil improvement body 52 obtained with the result of FIG. 10 is measured at substantially the same timing.

FIG. 24 shows the upper and lower limits of the frequency at which a signal with a good SN ratio is obtained and the elapsed time from the creation of the soil improvement body 52 in the dimension measurement experiment of the soil improvement body 52 that obtained the results of FIGS. It shows the relationship with It can be seen that the frequency of the sound wave 22 to be transmitted should be changed according to the elapsed time. Also, since many frequencies are included between the upper and lower limits, reliability is improved by performing measurements at several frequencies and comparing the results.

DESCRIPTION OF SYMBOLS 10... Transducer 12... Directional transmitter 14, 14-1, 14-2, 14-3, 14-4... Omnidirectional wave receiver 16... Fixed member 18, 18', 19-1, 19 -2, 19-3, 19-4... Sound absorbing material 20... Rotation/lifting mechanism 22... (Directive) sound wave 24, 24-1, 24-2, 24-3, 24-4... Reflected wave (echo)
30... (Digital) pseudo-random wave (phase modulated wave by binary code sequence) generator 32... Digital-analog (D/A) converter 34... Power amplifier 40-1, 40-2, 40-3, 40- 4 Receiving amplifier 42, 42-1, 42-2, 42-3, 42-4 Analog-digital (A/D) converter 44-1, 44-2, 44-3, 44-4 Cross-correlation Calculator 46, 46-1, 46-2, 46-3, 46-4... Detection signal 48... Wavelet converter 49... Phase synthesizer 50... Soil 52, P, Q... Ground improvement material 54... Measurement guide tube 60 Transmission guide tube 62 Wave receiver 70 Frequency changing unit 72 Sound velocity determination unit 80 Transmission time measurement unit 82 Sound velocity calculation unit 84 Propagation time measurement unit 86 Distance calculation unit 88 Calibration curve storage unit

Claims (15)

In the method for measuring the dimensions and shape of the ground improvement body formed by the ground improvement method,
Install a measurement guide pipe to the ground improvement body,
Inserting a directional transmitter that transmits directional sound waves and a plurality of non-directional wave receivers that receive sound waves independently of the arrival angle of the sound waves into the ground improvement body,
When transmitting a sound wave from the directional transmitter and receiving a reflected wave from the boundary between the soil improvement body and the soil using the omnidirectional wave receiver to obtain a detection signal,
The directional transmitter and the plurality of omnidirectional wave receivers are rotated around the axis of the measurement guide tube and moved up and down in the measurement guide tube to detect the three-dimensional shape of the ground improvement body. A method for measuring the dimensions and shape of a ground improvement body, characterized by: 2. The method for measuring the dimensions and shape of a ground improvement body according to claim 1, wherein the transmitted sound wave is a pseudo-random wave, which is a phase-modulated wave by a binary code sequence, and the frequency of the wave is changed in a plurality of ways. 3. The method for measuring the size and shape of a ground improvement body according to claim 2, wherein the detection signal is obtained from a cross-correlation calculation between the received sound wave and the pseudo-random wave. 4. The ground according to claim 2 or 3, wherein the plurality of frequencies of the sound waves to be transmitted are changed according to the design shape of the soil improvement body and/or the time from completion of construction of the ground improvement body. A method for measuring the dimensions and shape of the improved body. For the plurality of frequencies of the sound waves to be transmitted, when the design size of the ground improvement body is large, use a lower frequency than when the design size is small, and when the time has passed since the construction of the ground improvement body is completed. 5. The method for measuring the dimensions and shape of a soil improvement body according to claim 4, wherein a frequency higher than immediately after construction is used. The ground improvement according to any one of claims 1 to 5 , characterized in that the discrimination of the reflected wave from the boundary between the ground improvement body and the soil is improved by continuous Wavelet transformation of the detection signal and the Wavelet function. A method of measuring body dimensions and shapes. 7. The method for measuring the dimensions and shape of a ground improvement body according to claim 6 , wherein the Wavelet function is Gabor wavelet or Symlet wavelet. The ground improvement body according to any one of claims 1 to 7 , wherein the directional transmitter and the plurality of omnidirectional receivers are connected by a fixing member to form a transmitter/receiver. Dimensional shape measurement method. The signals received by each of the plurality of omnidirectional wave receivers are phase-synthesized, or the reflected waves from the boundary between the soil improvement body and the soil are calculated numerically regardless of the phase. 9. The method for measuring the dimensions and shape of the soil improvement body according to any one of claims 1 to 8, wherein the identification is improved. The transducers are connected in a row in the depth direction of the ground improvement body, and a plurality of the omnidirectional transducers are arranged on at least one of the upper side and the lower side of the directional transmitter, and the directional 10. The method for measuring the size and shape of a soil improvement body according to any one of claims 1 to 9, wherein a sound absorbing material is provided between the omnidirectional wave receiver and the omnidirectional wave receiver. 11. The method for measuring the dimensions and shape of a ground improvement body according to any one of claims 1 to 10 , wherein a sound absorbing material is provided on the back surface of said omnidirectional wave receiver. Putting a plurality of wave receivers for receiving sound waves in a transmission guide pipe installed at another position of the ground improvement body,
transmitting sound waves from a sound wave transmitter placed in the measurement guide tube;
receiving transmitted waves by a plurality of wave receivers of the transmission guide tube;
From the distance between the measurement guide pipe and the transmission guide pipe and the transmission time of the transmitted wave, the sound speed in the soil improvement body is obtained, and the sound speed and the propagation time of the reflected wave from the boundary between the soil improvement body and the soil. 12. The method for measuring the size and shape of a ground improvement body according to any one of claims 1 to 11 , wherein the distance between the directional transmitter and the boundary is obtained from the above. A calibration curve is obtained in advance from the relationship between the speed of sound in the soil improvement body and the elapsed time after the construction of the soil improvement body,
The distance between the directional transmitter and the boundary is obtained from the sound velocity value obtained from the calibration curve based on the elapsed time from the construction of the soil improvement body and the propagation time of the reflected wave from the boundary between the soil improvement body and the soil. The method for measuring the dimensions and shape of the soil improvement body according to any one of claims 1 to 11 , characterized in that: The method for measuring the dimensions and shape of the soil improvement material according to any one of claims 1 to 13 , wherein the measurement of the dimensions and shape of the soil improvement material is performed when the speed of sound in the soil improvement material is 2000 m / s or less. . In the dimensional and shape measuring device that installs the measurement guide pipe to the ground improvement body immediately after the ground improvement is formed by the ground improvement method,
a directional transmitter that is inserted into the measurement guide tube and transmits a directional sound wave;
a plurality of omnidirectional wave receivers that are inserted into the measurement guide pipe to receive reflected waves from the boundary between the soil improvement body and the soil, and that receive sound waves independently of the arrival angle of the sound waves; ,
means for obtaining a detected signal from the received signal;
The directional transmitter and the plurality of omnidirectional wave receivers are rotated around the axis of the measurement guide tube and moved up and down in the measurement guide tube to detect the three-dimensional shape of the ground improvement body. means and
A measurement device for the dimensions and shape of a ground improvement body, comprising:

Images