JP3668690B2 - Ultrasonic measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
This invention radiates an ultrasonic pulse toward the wall surface of the hole while moving the ultrasonic transducer vertically in the hole where the muddy water is accumulated, receives the reflected wave, and the distance to the wall surface of the hole The present invention relates to an ultrasonic measurement apparatus that records
[0002]
[Prior art]
For example, in order to create a foundation pile for a reinforced concrete building, a concrete pile for the building is made by drilling a hole in the ground, inserting a reinforcing bar, pouring raw concrete. The diameter of this hole is 1m to 2m and the depth is 30m to 50m, and several dozen foundation piles are made for each building.
When drilling a pit, it is necessary to drill vertically, and if it is drilled diagonally, the building is completed, and if the weight of the building is applied to the foundation pile, the foundation pile may not be able to withstand that load. Therefore, when a pothole is being drilled, it is necessary to monitor whether the pothole is being drilled vertically. Furthermore, in order to prevent the collapse of the pit due to the seepage of groundwater, the pit is filled with water to a position higher than the groundwater level.
[0003]
To prevent the water itself from collapsing, this water is mixed with clay (actually fine powder of mineral called bentonite, not clay), and this clay creates an impermeable layer on the wall of the pit and Protect.
Whether the wall surface of the pit is vertical is confirmed by dropping the weight from the vicinity of the center of the pit and measuring the distance between the weight and the wall surface. The distance between the weight and the wall surface is measured by measuring the reciprocation time of the ultrasonic pulse, and the distance is obtained. However, in the water mixed with clay in the pit (called muddy water), the attenuation of the ultrasonic wave is large. Measurement is quite difficult. Moreover, the attenuation of the ultrasonic waves is not uniform from the upper part to the lower part of the pit. This is mainly because soil and sand are mixed in the muddy water during excavation, and this mixing rate is different between the upper part and the lower part.
[0004]
[Problems to be solved by the invention]
Therefore, in order to make the received signal intensity that changes as the weight rises and falls constant during measurement, the measurer needs to adjust the sensitivity adjustment knob to an appropriate value. In order to reduce the burden on the measurer, it is conceivable to incorporate a control function called AGC (automatic gain control) or ALC (automatic level control) that automatically controls sensitivity adjustment in the conventional concept. In reality, however, the attenuation of ultrasonic waves per unit distance varies depending on the muddy water condition, so the received signal strength varies greatly depending on the measurement position in the vertical direction and the distance to the wall surface. Regardless of the distance, it is difficult to correct the wave signal intensity to be almost constant by increasing or decreasing the amplification degree.
[0005]
[Means for Solving the Problems]
According to the present invention, the receiving device is provided with a sensitivity time control unit that lowers the gain at a short distance, that is, a so-called STC (Sensitivity Time Control) unit, and should be recorded by the received pulse whose amplitude is controlled by the STC unit. The recording width is obtained, and the difference between the obtained recording width to be recorded and the target recording width is obtained, and the control characteristic of the STC unit is corrected by the correcting means so that the difference is reduced.
In general, the attenuation in the round trip of ultrasonic waves is
Attenuation amount = diffusion attenuation amount + absorption attenuation amount + reflection loss amount. The attenuation generated in the muddy water is very large in absorption attenuation, and the diffusion attenuation is negligible as a correction amount.
[0006]
In contrast, sounding instruments used in seawater have a large measurement depth (distance), a large diffusion attenuation, and a very small absorption attenuation in seawater. Only the amount is targeted for correction.
Incidentally, the absorption attenuation coefficient of seawater is 250 dB / f ² × 10 ^-17 cm (f is a frequency), and the absorption attenuation coefficient of 100 kHz is only 0.0025 dB / m. However, in the muddy water, the absorption attenuation coefficient differs depending on the concentration, but is roughly different from that of seawater because it is about 20 dB / m.
[0007]
The relationship between the attenuation of ultrasonic waves in water is
Reciprocal attenuation (dB) = 2αR + 20 log2R ²
It becomes. Where α is the absorption attenuation coefficient and R is the distance.
As shown in FIG. 5, the relationship between the degree of amplification and the distance R at which a received signal with an appropriate strength is obtained is a curve 11 in fresh water (such as the supernatant of muddy water in the drilling hole), and the diffusion attenuation amount. It is sufficient that the amplification degree is gradually increased as the distance R increases. As bentonite is mixed with fresh water, the attenuation coefficient of muddy water increases, and in order to correct the attenuation due to muddy water, the amplification increases as distance R increases even at a short distance of about 1 m. The ratio to be increased increases as shown by the curves 12, 13, and 14. That is, it is necessary to control the STC control characteristics, that is, the inclination with respect to the horizontal axis in FIG. 5 in accordance with the muddy water attenuation coefficient (muddy water concentration).
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1A, for example, the transducer 24 suspended from the elevator 22 to the rope 23 is lowered into the hole 21 being excavated. The transmitter / receiver 24 is positioned substantially on the center line of the pit hole 21, and usually the two transmitter / receivers 24 radiate ultrasonic pulses toward the wall surface of the pit hole 21 in directions opposite to each other with respect to the center line of the pit hole 21. Alternatively, the four transducers 24 are attached so as to radiate toward the wall surface of the pothole 21 in the direction of the angular interval of 90 degrees with respect to the center line of the pothole 21. Further, the radiation direction of the ultrasonic pulse is generally substantially horizontal. These two or four transducers 24 are integrated into one block.
[0009]
A signal line for transmitting a pulse signal for driving and radiating ultrasonic pulses to these transducers 24 and a signal for receiving a reflected wave of the emitted ultrasonic pulses by the transducer 24. Is provided on the cable 23.
As shown in FIG. 2, an electrical pulse signal having an ultrasonic frequency is periodically supplied from the transmitter 31 to the transmitter / receiver 24 through the signal line 32, and an ultrasonic pulse is emitted from the transmitter / receiver 24. The reflected wave is received by the transducer 24 and converted into an electrical signal, and the reflected signal (received pulse signal) converted into an electrical signal is supplied to the receiver 33 through the signal line 32. Although not shown, the transmitter 31 and the receiver 33 are provided with means for separating the transmission pulse signal and the reflected signal.
[0010]
A sensitivity time control unit, so-called STC unit 34, is provided in the receiver 33. The received pulse signal is passed through the STC unit 34, and after the ultrasonic pulse is transmitted, the time elapses (reflection point) as shown in FIG. The gain increases with increasing distance R). Thereafter, the signal is detected, sampled by the binarization circuit 35, and each sample value is binarized. The reflected signal is sampled, for example, 4000 times for each transmission pulse, and the sampling frequency is selected so that a strong reflected signal from the wall surface of the pit is sampled during 4000 times of sampling.
[0011]
This binarized reflected signal is supplied to the recorder 36. In the recorder 36, the input binary reflected signal sequence is temporarily stored in a memory (not shown) immediately after the transmission of the ultrasonic pulse, and then read out from the memory and recorded on the recording paper 37 (FIG. 1A). Record). For example, the ultrasonic pulse is emitted as shown in FIG. 3A, and the reflected signal is obtained as shown in FIG. 3B, and this becomes a binarized reflected signal string as shown in FIG. 3C. A portion where “1” continues in this binary reflected signal sequence is a portion of a reflected pulse by the wall surface. When the two transducers 24 are attached back to back, it is desirable to record the excavated state of the pit 21 so that it can be intuitively read from the record, that is, the vertical section of the pit 21 can be immediately recognized. From this point, for example, as shown in FIG. 1B, the recording is performed from the transmitter / receiver 24 to the reflection point on the both sides of the center line 38 that bisects the width direction of the recording sheet 37 as the distance from the center line 38 increases. The distance is made large. Recording lines 39a and 39b having widths on both sides of the center line 38 in FIG. 1B indicate received pulse signals from the walls of the ultrasonic pulses emitted from the two transmitters / receivers 24, for example, opposite to each other. The inner distance between the recording lines 39a and 39b corresponds to the diameter of the hole 21. Further, the parallelism of the recording lines 39a and 39b with respect to the center line 38 becomes the perpendicularity of the hole 21.
[0012]
In order to perform such recording, for example, as shown by an arrow 41 on the recording paper 37, when scanning recording is performed from the left end of the recording paper 37 to the right end in the drawing, the recording of the left portion of the center line 38 corresponds. The binarized reflected signal sequence stored in the memory is read out in the reverse order of the storage order, and the right side portion of the center line 38 is recorded in the binarized reflected signal sequence stored in the corresponding memory. Read in order.
Each line width of the recording lines 39a and 39b corresponds to the number of “1” by the wall surface reflection pulse in the binarized reflection signal sequence. As described above, since the concentration of muddy water at the position where the ultrasonic pulse is radiated is different and the absorption attenuation coefficient is considerably different depending on the concentration, if the intensity of the reflected signal is too small, the recording lines 39a and 39b are generated. If the reflected signal intensity is too high, the recording lines 39a and 39b are not only too thick but also reflected by a minute object in the path of the ultrasonic pulse between the transducer 24 and the wall surface. Occurs in the binarized reflected signal sequence, and a large number of minute spots occur between the recording lines 39a and 39b, making it difficult to see. The appropriate line width is assumed to be about several hundreds of 1 for 4000 samples and about 10% of the maximum recording width. The characteristics of the STC unit 34 are initially set so that a recording width of this level can be obtained in a muddy water that is considered to be representative.
[0013]
However, as described above, since the absorption attenuation coefficient varies considerably depending on the concentration of muddy water, when measuring the state of the wall hole 21 with this ultrasonic measuring device, the measurer first radiates an ultrasonic pulse on a trial basis. Recording the line widths of the recording lines 39a and 39b on the recording paper 37, and seeing these line widths, a density (recording line width) adjustment knob (not shown) of the density setting unit 45 is set so that the line width becomes easy to see. Adjust. That is, for example, the darkness adjustment knob has a dark (thick) display on one side of the reference position and a light (thin) display on the other side, and moves (or rotates) the adjustment knob in the target direction. Depending on the adjustment position of the adjustment knob, the recording width corresponding to the initial setting for the STC unit 34 is increased or decreased and supplied to the deviation calculation unit 46 as a target recording width.
[0014]
The recording width to be recorded is obtained by the received pulse signal, that is, the reflection pulse from the wall surface, the difference between the recording width to be recorded and the target recording width is obtained, and the STC unit 34 Correct the control characteristics. For this reason, in this embodiment, a binarized reflected signal sequence for each ultrasonic pulse radiation from the binarizing circuit 35 is supplied to the data integrating unit 44, and the binarized reflected signal sequence, that is, a series of 0 and 1 is included. The number of 1's is counted. In the binarized reflection signal sequence, a part corresponding to the wall surface reflection pulse has several consecutive 1s, and thus this count value corresponds to each line width of the recording lines 39a and 39b.
[0015]
As described above, the difference between the target recording width E set by the measurer and the number M counted by the data integrating unit 44 is calculated by the deviation calculating unit 46, and this difference M−E is calculated as the STC correction value generating unit 47. The STC correction value generation unit 47 corrects the STC characteristic of the STC unit 34, that is, the slope characteristic in FIG. 5, so that the absolute value of the difference M−E becomes small. Therefore, when the line width of the test recording is adjusted to be too thin and thick (thick), for example, the target recording width E is made larger than the count value M, and the STC characteristic in the STC section 34 is, for example, in FIG. The curve 13 is corrected to the curve 14.
[0016]
In the STC unit 34, for example, as shown in FIG. 4, each time an ultrasonic pulse is transmitted, the switch 52 in parallel with the capacitor 51 is turned on to discharge the electric charge of the capacitor 51, and then the switch 52 is turned off. A constant current is supplied from the source 53 to the capacitor 51, and the gain of the variable gain amplifier is controlled by the voltage across the capacitor 51 so that the gain (amplification degree) increases with time. The output correction value of the STC correction value generation unit 47 is converted into an analog correction signal by the D / A converter 48, and the reference voltage value that determines the constant current value output from the constant current source 53 is corrected by this correction signal. The current value is increased so that the slope of the STC characteristic in the STC unit 34 is increased.
[0017]
If the slope of the STC characteristic, for example, the reference voltage of the constant current source 53 is the STC value, the STC value is STC value = previous STC value− (ME) × F.
And correct. F in the correction value (ME) × F is a coefficient for converting (ME) into a value corresponding to the STC value. For example, the reference voltage of the constant current source 53 is corrected according to the correction value (ME) × F. The initial value of the previous STC value, that is, the value when the output of the deviation calculating unit 46 is zero when the adjustment knob is set to the reference position, is a value that is considered reasonable (default value). When the absolute value of the correction value (ME) × F is equal to or greater than a predetermined value (abnormal data), correction processing is not performed in order to avoid an abrupt change in the STC value, or the correction value corresponds to the correction direction of the correction value. It is preferable to correct a predetermined constant value.
[0018]
After adjusting so as to obtain a desired recording line width as described above, actual measurement is started. Even during this actual measurement, as the transducer 24 descends, as the muddy water concentration increases, the attenuation coefficient increases. Since the change of the attenuation coefficient with respect to this concentration change is large, as described above, the normal automatic gain adjustment ( With the AGC function, the intensity of the reflected signal cannot be kept constant. However, in the configuration of FIG. 2, when the intensity of the reflected signal decreases and the wall surface reflected pulse width decreases, the coefficient value M of the data integrating unit 44 becomes smaller than the target recording width E, and this difference becomes zero. A correction signal is generated from the STC correction value generation unit 47, the STC value of the STC unit 34 is corrected in the same manner as described above, the inclination of the STC characteristic is increased, and the reflected signal intensity becomes predetermined. In this way, the recording line 39a having a substantially predetermined line width can be obtained without the trouble of sequentially adjusting the sensitivity adjustment of the transducer 24 while observing the recording line width in which the measurement amount is recorded in the actual measurement. 39b is obtained to the bottom of the vertical hole 21. As described above, the setting display for the adjustment knob of the density setting unit 45 is, for example, darker and lighter than the reference position, and is converted into a target line width E having a value corresponding to the direction and distance from the reference position of the indicated position. It is supplied to the deviation calculation unit 46. The data integration unit 44, the deviation calculation unit 46, and the STC correction value generation unit 47 can be caused to function by a microcomputer, for example.
[0019]
For the fluctuation of the reflection coefficient of the wall surface, the position of the reference amplification degree, the value of the amplification degree As at the distance R = 0 in FIG. 5 may be changed, and the STC characteristic may be translated along the vertical axis.
In general, the measurement is performed while lowering the transducer 24. For example, the measurement is performed while lowering two transducers 24 back to back, and when reaching the bottom during excavation, the transmission / reception direction of the transducer 24 is set to the horizontal plane. You may make it measure by rotating 90 degree within and pulling up the transmitter / receiver 24. In this way, the diameter and inclination of the hole 21 can be measured. Moreover, it is applicable not only to the measurement of the verticality of the hole for the foundation pile but also to the measurement of other hole.
[0020]
【The invention's effect】
As described above, according to the present invention, measurement is performed while moving the ultrasonic transducer vertically in the hole in which muddy water has accumulated, and the distance to the wall surface is correctly adjusted even if the concentration of muddy water fluctuates in the middle. Can be measured.
[Brief description of the drawings]
FIG. 1A is a diagram showing an example of a transducer, its elevator, and a recorder, and B is a diagram showing an example of a recording state.
FIG. 2 is a diagram showing a functional configuration example of an embodiment of the inventive device.
FIG. 3 is a diagram showing an example of a radiation ultrasonic pulse, its reflected received signal, and a binarized received signal.
FIG. 4 is a diagram showing a configuration example of generation of an STC control signal.
FIG. 5 is a diagram showing STC characteristics according to the magnitude of mud attenuation.

Claims (1)

While moving the ultrasonic transducer vertically in the muddy water hole, the ultrasonic pulse is emitted toward the wall of the hole, the reflected wave is received, and the amplitude of the received signal is controlled by the sensitivity time controller. In the ultrasonic measurement apparatus that records the distance to the wall surface of the hole using the controlled received signal,
Means for determining a recording line width to be recorded by a received ultrasonic pulse;
Means for determining the difference between the recorded recording line width and the target recording line width to be,
Means for correcting the control characteristics of the sensitivity time control unit so that the difference is reduced;
An ultrasonic measurement apparatus comprising:

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