JP7296250B2 - Excavation surface geological evaluation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an excavated surface geological evaluation method used for grasping the geological state of an excavated surface such as a tunnel face in civil engineering works such as tunnel construction.

Generally, in tunnel construction, the seismic velocity distribution of the ground is estimated before tunnel excavation in order to safely and appropriately construct tunnel excavation and support. During tunnel excavation, elastic wave velocity of the tunnel face is measured in order to grasp the geological condition near the face, which is the excavation surface.

Previously, the inventor of the present application proposed this kind of elastic wave velocity measuring method in Patent Document 1.
This elastic wave velocity measuring method sequentially implements an equipment installation step, a sound wave vibration, an elastic wave vibration recording step, and an elastic wave velocity calculation step.

First, in the equipment installation step, a rock bolt is installed at a predetermined distance from the excavation position in civil engineering work, including the tunnel face, and a portable geophone is fixed to the rock bolt, and a communication cable is connected to the geophone. Connect an IC recorder via

In the next step of recording sound wave vibration and elastic wave vibration, vibration is generated at the excavation position, and the vibration of the elastic wave generated by the vibration of the excavation position and propagating through the ground between the excavation position and the geophone installation position is recorded at the excavation position. An IC recorder that receives and measures the sound wave generated by the vibration of the excavation position and propagates in the air between the excavation position and the geophone installation position, and starts the recording operation before the vibration is generated at the excavation position. to record.

In the elastic wave velocity calculation step, the elastic wave velocity is calculated based on the vibration data of the sound waves and the vibration data of the elastic waves recorded in the IC recorder. In the case of this elastic wave velocity calculation step, from the vibration data of the sound wave, the arrival time of the sound wave is calculated from the time when the recording operation of the IC recorder started before the vibration is generated at the excavation position. In addition to extracting the time until the vibration of the generated sound wave that propagates in the air reaches the IC recorder, from the vibration data of the elastic wave, the recording operation is started before the vibration is generated at the excavation position as the arrival time of the elastic wave. Extract the time from the start of the recording operation of the IC recorder to the time when the vibration of the elastic wave generated by the vibration of the excavation position and propagated through the ground reaches the IC recorder, Based on the sound speed and the sound wave arrival time, the vibration generation time from the start of the recording operation of the IC recorder to the time when the vibration is generated at the excavation position is estimated, and the predetermined distance, the elastic wave arrival time, and the vibration Based on the time of occurrence and the time of occurrence, the elastic wave velocity between the drilling position and the geophone installation position is calculated.

In this way, it is possible to reliably and easily measure elastic wave velocities using only a simple general-purpose portable geophone and a simple general-purpose portable IC recorder, and to implement elastic wave velocity measurements at low cost. can be done.

Japanese Patent No. 6420054

By the way, in the mountain tunnel construction work, during the excavation work, the surface may come off from the face. For this reason, the Ministry of Health, Labor and Welfare has issued the "Guidelines for Measures against Falling Skin Accidents in the Face of Mountain Tunnel Construction", and tunnel construction workers are implementing various disaster prevention measures. However, at present, it has not reached the stage of eradicating occupational accidents due to skin falling from the face. Therefore, there is a demand for the development of a method for protecting workers from falling rocks caused by falling skin, as well as a method for reasonably predicting the occurrence of falling skin.

On the other hand, tunnel workers have been taking measures such as strengthening the inspection of the face when they feel that the blasting sound of the tunnel is abnormal. Although there are many studies on this blasting noise from the viewpoint of noise, there are few studies that quantitatively evaluate the relationship between the blasting noise and the face condition. For this reason, the inventors of the present application focused on the frequency characteristics of this blasting sound and tried to study it. The elastic wave measurement method of Patent Document 1 continuously measures elastic waves generated by tunnel excavation blasting as the excavation progresses, grasps the elastic wave velocity distribution in the tunnel, and predicts geological changes in front of the face. This method is originally intended to measure the elastic waves propagating through the ground, but since the geophone is mechanically fixed to the head of the rock bolt on the wall of the tunnel hole, the blasting sound can also be detected by this geophone at the same time. can be measured. Therefore, in a tunnel that has been excavated in recent years, the above-mentioned elastic wave measurement method was used to measure the vibration of the elastic wave generated by the vibration of the face and propagating through the ground between the face and the geophone installation position. Along with the vibration of the sound wave (explosive sound) that is generated and propagates in the air between the face and the geophone installation position, the vibration is received only by the geophone, measured, recorded on a personal computer, and the frequency of the sound wave as well as the frequency of the elastic wave. As a result, we found a new method for evaluating the risk of geological changes in the face immediately after blasting.

The present invention is an improvement of the elastic wave measurement method of Patent Document 1, and can evaluate changes in the geological conditions of each excavation surface immediately after vibration is generated on the excavation surface of the ground including the tunnel face. In this way, the evaluation level of the change in the geological situation is displayed on a personal computer or the like, and is provided as construction and safety information to the workers engaged in excavating the natural ground. A new excavation surface geological evaluation that can prevent disasters such as falling skin during excavation work of the ground including the tunnel face by issuing warnings and warnings to workers engaged in tunnel excavation. The purpose is to provide a method.

In order to achieve the above object, the excavated surface geological evaluation method of the present invention includes:
A seismometer and a portable geophone as a microphone are installed at a predetermined installation position at a predetermined distance from the excavation surface in civil engineering work , including the tunnel face, via rock bolts, and a communication cable is connected to the geophone . Connect a portable personal computer or IC recorder as a recording device,
Vibration is generated on the excavation surface, an elastic wave generated during the vibration and propagating through the ground between the excavation surface and the installation position of the geophone , and an elastic wave between the excavation surface and the installation position of the geophone . The sound waves propagating in the air between them are respectively received and measured only by the geophone , and recorded on the personal computer or the IC recorder that has started the recording operation before the vibration occurs on the excavation surface,
A personal computer is used as an analysis device, and analysis software for analyzing elastic wave data and sound wave data is installed in the personal computer, and the analysis is performed from the elastic wave data and sound wave data recorded in the personal computer or the IC recorder . The frequency characteristics of the elastic wave and the frequency characteristics of the sound wave are calculated by the personal computer equipped with the software , and based on the excellent frequency characteristics that can be clearly distinguished from the frequency characteristics of the elastic wave and the frequency characteristics of the sound wave. estimating and evaluating the geological condition of the excavation surface by
This is the gist of it.

And this method is embodied as follows.
(1 ) Blasting is used as a source of vibration of the excavation surface, and a blasting hole is provided in the excavation surface to load the explosive and detonate the explosive.
( 2 ) Instead of ( 1 ) above, various equipment used in civil engineering work, including breakers and hammers, are used as vibration sources for the excavated surface, and the excavated surface is hit by the various equipment including breakers and hammers. good too.
( 3 ) Alarm devices shall be installed at appropriate positions on the site of civil engineering work, including near the excavation surface, and an alarm according to the evaluation of the geological condition of the excavation surface shall be issued by the alarm device for each excavation surface.

According to the excavated surface geological evaluation method of the present invention, a portable geophone is installed at a predetermined installation position at a predetermined distance from an excavated surface in civil engineering work via a rock bolt, and a communication cable is connected to the geophone. A portable personal computer or IC recorder is connected to generate vibrations on the excavation surface, and elastic waves generated during this vibration propagate through the ground between the excavation surface and the geophone installation position, and the excavation surface. The sound waves propagating in the air between the and the geophone installation position are respectively received and measured by the geophone alone , and recorded on a personal computer or IC recorder that starts the recording operation before the vibration occurs on the excavation surface. A computer is equipped with analysis software for analyzing elastic wave data and sound wave data, and this personal computer calculates the frequency characteristics of elastic waves and the frequency characteristics of sound waves from the elastic wave data and sound wave data recorded in the personal computer or IC recorder. However, the geological condition of the excavation surface is estimated and evaluated based on the excellent frequency characteristics that can be clearly distinguished from the frequency characteristics of the elastic waves and the frequency characteristics of the sound waves. It is possible to easily and at a low cost evaluate changes in the geological conditions of each excavated surface immediately after vibration is generated on the excavated surface of the ground including the tunnel face , using simple general-purpose equipment such as The evaluation level of the change in the situation is displayed on a personal computer or the like, and is provided as construction and safety information to the workers engaged in excavating the natural ground. The present invention has a unique and special effect that it is possible to prevent disasters such as falling of the skin during excavation of natural ground including a tunnel face by directing it to workers engaged in excavation.

A diagram showing the flow of an excavated surface geological evaluation method according to an embodiment of the present invention. A diagram showing a specific example of the equipment installation step and the elastic wave vibration / sound wave vibration recording step in the same method A diagram showing an example of waveform data measured in the elastic wave vibration/sound wave vibration recording step in the same method and recorded in a personal computer. A diagram showing an example of spectral distribution of elastic waves by FFT analysis of the frequency characteristic evaluation step in the same method A diagram showing an example of the spectral distribution of sound waves by FFT analysis of the frequency characteristic evaluation step in the same method A diagram showing changes in the power spectrum of elastic waves and sound waves as the face excavation progresses by repeating the elastic wave vibration/sonic vibration recording step, the frequency characteristics evaluation step, and the geological condition estimation evaluation step in the same method.

Next, a mode for carrying out the present invention will be described with reference to the drawings. Figure 1 shows the method for evaluating the geology of the excavated surface. As shown in FIG. 1, this excavated surface geological evaluation method is carried out by sequentially carrying out the following equipment installation step, elastic wave vibration/sound wave vibration recording step, power spectrum frequency calculation step, and geological condition estimation and evaluation step.

(Equipment installation step (ST1 in FIG. 1))
In Fig. 1, in the equipment installation step, the seismometer is installed at a predetermined installation position behind the excavation surface in civil engineering work including the face of the tunnel, and at the same distance behind the excavation surface as the seismometer. A microphone is installed at a predetermined installation position, and a recording device is connected to the seismometer and the microphone through a communication cable. In this case, a portable geophone is adopted as the seismometer (hereafter referred to as a geophone), and the geophone is installed on a rock bolt fixed at a predetermined position on the tunnel wall so that it can detect elastic waves propagating deep in the ground. do. In this case, a portable geophone may be used as a microphone, and the geophone may be used as both a seismometer and a microphone. A portable personal computer is used as the recording device (hereinafter referred to as a personal computer). Recent computers are usually equipped with stereo pin jacks and stereo recording is possible. to connect. In this case, the personal computer is equipped with analysis software (such as SP-WAVE) for analyzing elastic wave data and sound wave data, and is also used as an analysis device. A two-channel IC recorder may be used as the recording device if the simplicity of equipment installation work is emphasized.

FIG. 2 shows a specific example of this equipment installation step. As shown in FIG. 2, in this step, first, a geophone 1 is installed on the wall surface of the tunnel wall at a position behind the tunnel face, and a microphone 2 is placed at a predetermined position close to the geophone at the same distance as the geophone behind the face. to be installed. Although not shown here, the geophone 1 and the microphone 2 are connected to a personal computer 3 (see FIG. 3) via communication cables.

(Elastic wave vibration/sound wave vibration recording step (ST2, 3, 4 in FIG. 1))
In Fig. 1, in the elastic wave vibration/acoustic vibration recording step, vibration is generated on the excavation surface including the face. Waves and sound waves propagating in the air between the excavation surface and the microphone installation position are received and measured by the geophone and microphone, respectively, and recorded in a personal computer that starts recording operation before the vibration occurs on the excavation surface. In this case, blasting is used as a source of vibration on the excavation surface, a blast hole is provided in the excavation surface, an explosive is loaded, the explosive is detonated, and the elastic wave generated when the explosive is detonated is detected by a geophone and a sound wave. are received and measured with a microphone, and recorded on a computer. In this case, instead of blasting, various equipment used in civil engineering work, including breakers and hammers, are used as the vibration source of the excavated surface, and by hitting the excavated surface with various equipment including breakers and hammers, elastic waves are generated. and may generate sound waves. When an IC recorder is used as the recording device, elastic wave data and sound wave data recorded in the IC recorder are input to a personal computer using a communication cable or a recording medium.

FIG. 2 also shows a specific example of this elastic wave vibration/sound wave vibration recording step. As shown in FIG. 2, first, the face in the tunnel is loaded with explosives. In this case, since blasting is performed when excavating the tunnel face, an electric detonator or the like is used to initiate the blasting. Note that the recording operation by the personal computer 3 before the detonation of the explosive, such as while the blast hole is provided in the face, while the blast hole is loaded with the explosive, or immediately before the detonation of the explosive after the explosive is loaded into the blast hole. start (that is, start recording) and leave it in the recording (during) state. Subsequently, the blasting switch is turned on to detonate the explosive in the face, blow up the face, and generate vibration. Due to this explosion, the elastic wave generated from the face propagates through the ground and reaches the geophone 1 behind the face, and the sound wave generated from the face propagates in the tunnel (in the air) and reaches the microphone 2 behind the face. The elastic waves are received and measured by the geophone 1 and the sound waves by the microphone 2, respectively.

FIG. 3 shows an example of waveform data measured using a geophone as a microphone and recorded in the personal computer 3 in this elastic wave vibration/sound wave vibration recording step. This waveform data is displayed on the display of the personal computer 3 . In this case, the horizontal axis indicates time, the vertical axis indicates amplitude, the sampling frequency is 44.1 kHz, and the number of quantization bits is 24 bits. As for the measurement results, after the blasting ignition, the elastic wave propagating through the ground is first recorded, and then the blasting sound propagating through the air is recorded. The upper row shows the measurement record of the blasting signal (not used in the patent of the present application). From this record, it can be seen that the blasting was initiated 8.685 ms after the start of recording, and elastic waves and sound waves were generated from the face. The bottom row is the measurement record of Geophone 1 and Microphone 2. From this result, it can be seen that the elastic wave reached Geophone 1 at 22.971 ms and the sound wave reached Microphone 2 at 148.367 ms. While the elastic wave is relatively predominant in low-frequency components, the blasting sound is predominant in high-frequency components, which can be clearly distinguished from the measured waveform.

(Power spectrum frequency calculation step (ST5, 6))
In FIG. 1, in the power spectrum frequency calculation step, the power spectrum frequency of the elastic wave and the power spectrum frequency of the sound wave are calculated from the elastic wave data and the sound wave data recorded in the personal computer. Here, FFT analysis is performed on the elastic waves and sound waves recorded in the personal computer using (analysis software of) the personal computer, and respective power spectra are calculated. In this case SP-WAVE is used.

FIG. 4 shows an example of spectral distribution of elastic waves by FFT analysis, and FIG. 5 shows an example of spectral distribution of sound waves by FFT analysis. The analysis result by this FFT analysis is displayed on the display of the personal computer 3. FIG. From this result, as shown in FIG. 4, the power spectrum frequency of elastic waves peaks at 64.600 Hz, which is the predominant frequency, and the power spectrum frequency of sound waves peaks at 1119.727 Hz, which is the predominant frequency. I understand.

この場合、閾値α及びβは、評価開始時点では０とし、記録されたデータから閾値の修正を行うものとする。
そして、切羽などの掘削面の地質状況の変化を次表１の判定マトリックスから判定する。ここで、数式１及び数式２では、数式が成立する場合に一致、不成立の場合に不一致とする。

すなわち、この判定マトリックスから、現地点と前地点の弾性波のパワースペクトル周波数と現地点と前地点の音波のパワースペクトル周波数がどちらも一致する場合は、切羽の地質状況が変化する可能性が小さいと評価し、パソコンのディスプレイにはこれを例えばＡ判定と表示し、現地点と前地点の弾性波のパワースペクトル周波数と現地点と前地点の音波のパワースペクトル周波数が共に不一致の場合は、切羽の地質状況が変化する可能性が大きいと評価し、パソコンのディスプレイにはこれを例えばＣ判定と表示し、現地点と前地点の弾性波のパワースペクトル周波数と現地点と前地点の音波のパワースペクトル周波数のどちらか一方が一致、他方が不一致の場合は、切羽の地質状況が変化する可能性が見込まれると評価し、パソコンのディスプレイにはこれを例えばＢ判定と表示する。なお、弾性波パワースペクトル周波数と音波パワースペクトル周波数の一致、不一致の閾値（つまり、一致の範囲）は、トンネルの掘削に伴い、随時、修正の設定を行うこととする。 (Geological situation estimation evaluation step (ST7, 8))
In the geological condition estimation evaluation step, the geological condition of the excavation surface is estimated and evaluated based on the power spectrum frequency of the elastic wave and the power spectrum frequency of the sound wave. Here, on a personal computer, first, for each of the elastic waves and sound waves generated by vibrations such as blasting on the excavation surface such as the face, one By comparing the elastic wave power spectrum frequency and the acoustic wave power spectrum frequency on the excavation surface of the previous point (hereinafter simply referred to as the previous point), that is, by comparing the data at the time of this blasting and the data at the time of the previous blasting , matching between the elastic wave power spectrum frequency at the local point and the elastic wave power spectrum frequency at the previous point, and matching between the sound wave power spectrum frequency at the current point and the sound wave power spectrum frequency at the previous point. The determination is made by the following equations (1) and (2).

In this case, the thresholds α and β are set to 0 at the start of evaluation, and the thresholds are corrected from the recorded data.
Then, the change in the geological condition of the excavation surface such as the working face is determined from the determination matrix in Table 1 below. Here, in the formulas 1 and 2, it is determined that they match when the formulas hold, and they do not match when they do not hold.

In other words, from this decision matrix, if both the power spectrum frequencies of the elastic waves at the local point and the previous point and the power spectrum frequencies of the sound waves at the local point and the previous point match, there is little possibility that the geological conditions of the face will change. This is evaluated as, for example, A judgment on the display of the personal computer, and if both the power spectrum frequency of the elastic wave at the local point and the previous point and the power spectrum frequency of the sound wave at the local point and the previous point do not match, the face It is evaluated that there is a high possibility that the geological situation will change, and this is displayed as, for example, a C judgment on the computer display, and the power spectrum frequency of the elastic waves at the local point and the previous point and the power of the sound waves at the local point and the previous point. If one of the spectral frequencies matches and the other does not match, it is evaluated that there is a possibility that the geological condition of the face will change, and this is displayed as B judgment, for example, on the display of the personal computer. The matching and non-matching thresholds (that is, the range of matching) between the elastic wave power spectrum frequency and the acoustic wave power spectrum frequency are set to be corrected as needed as the tunnel is excavated.

Figure 6 shows changes in the power spectrum of elastic waves and sound waves as the face excavation progresses.
FIG. 6(a) shows a section where the face geology changes from granodiorite to fine-grained tuff as the face advances, although the shoring pattern does not change from CII-b. This measurement result is displayed on the display of the personal computer 3 . The horizontal axis represents the distance of each face, and the vertical axis represents the power spectrum frequency. Circle marks indicate the power spectrum frequencies of elastic waves, and diamond marks indicate the power spectrum frequencies of sound waves. The dotted line indicates the moving average value of the power spectrum frequencies of the five facets for reference.
Here, in the same geological sections of granodiorite and fine-grained tuff, the power spectrum frequencies of elastic waves and sound waves at each excavation surface did not change significantly, indicating that the geological conditions have not changed. I understand. On the other hand, along with the geological change from granodiorite to fine-grained tuff, a decrease in the power spectrum frequency of elastic waves and an increase in the power spectrum frequency of sound waves were observed, indicating changes in geological conditions between different geological features. It is understood that In this case, the change in the sound wave is remarkable, and the variation in the sound wave is relatively large compared to the elastic wave.
Fig. 6(b) shows an interval where the geology is the same as granodiorite, but the shoring pattern changes from CI to CII-b to CI. Here, in the section of the support pattern from CI to CII-b, the power spectrum of both the elastic wave and the sound wave is lower in the section CII-b than in the section CI. Also, the TD. In the section after 604 m, many of the sound wave power spectrum frequencies are 1000 Hz or higher. On the other hand, the power spectrum frequency of elastic waves is TD. After 617m, many show 66Hz or more, but TD. There is some deviation from the support pattern change point near 604m. This is thought to be due to the elastic waves propagating through the ground around the tunnel.

(alarm step)
This excavated surface geological evaluation method may have an alarm step of issuing an alarm according to the evaluation of the geological condition of the excavated surface following the geological condition estimation evaluation step. In this warning step, alarm devices are provided in advance at appropriate positions on the site of the civil engineering work including the vicinity of the excavation surface, and an alarm corresponding to the evaluation of the geological condition of the excavation surface is issued by the alarm device for each excavation surface. The alarm system of the alarm shall be alarm sound, voice, warning light, or a combination of these according to the evaluation of the geological condition of the excavation surface. These alarms are then electrically connected to a personal computer and activated based on the evaluation of the geological situation by the personal computer. For example, if the personal computer evaluates that there is little possibility that the geological conditions of the face will change, and an A judgment is displayed on the personal computer display, the warning sound and sound type alarm will not emit a siren or sound, and a warning light will be emitted. The type of alarm turned off, or turned a rotating light in a color that indicated safety, such as blue. In this case, an alarm sound or voice type alarm emits a siren or voice to warn evacuation, and a warning light type alarm turns a rotating light of a color, such as red, to warn evacuation, and the geological condition of the face is displayed on a computer. If it is evaluated that the possibility of change is expected and a B judgment is displayed on the display of the personal computer, the warning sound and voice type alarm emits a siren or voice to call attention, and the warning light type alarm Now turn on a rotating light of a color that calls attention, for example yellow. In this way, the evaluation level of changes in geological conditions is displayed on the display of a personal computer, etc., and is provided as construction and safety information to workers engaged in excavating natural ground. By issuing such alarms and warnings to workers who are engaged in tunnel excavation, it is possible to prevent skin fall disasters in the excavation work of the ground including the tunnel face.

As described above, in this excavated surface geological evaluation method, a geophone is installed at a predetermined installation position at a predetermined distance from an excavated surface in civil engineering work including a tunnel face, and the geophone is placed at the same distance from the excavated surface as the geophone. A microphone is installed at a predetermined installation position, and a personal computer is connected to the geophone and microphone via a communication cable. Elastic waves propagating in the ground between the excavation surface and the location where the geophone is installed, and acoustic waves propagating in the air between the excavation surface and the location where the microphone is installed are received and measured by the geophone and microphone, respectively. Recorded on a personal computer that started the recording operation before the vibration occurred, and from the elastic wave data and sound wave data recorded on the personal computer, the power spectrum frequency of the elastic wave as the frequency characteristic of the elastic wave and the power of the sound wave as the frequency characteristic of the sound wave The spectral frequencies are calculated, and due to the similarity of the power spectral frequencies of the elastic wave and the acoustic wave power spectral frequencies, i.e., the power spectral frequencies of the elastic waves at the local point and the previous point and the power spectral frequencies of the acoustic waves at the local point and the previous point are If they match, the geological condition of the excavation face is estimated and evaluated, and the power spectrum frequency of the elastic waves at the local and previous points and the sound waves at the local and previous points are estimated and evaluated. If the power spectrum frequencies of both do not match, it is likely that the geological condition of the face will change. If one of them matches and the other does not match, the geological condition of the excavated surface is estimated and evaluated if the possibility of changes in the geological condition of the face is expected, so that the excavated surface of the ground including the tunnel face will not vibrate. It is possible to evaluate the change in the geological condition of the excavated surface for each excavated surface immediately after it is generated. Then, the evaluation level of the change in the geological situation is displayed on the display of a personal computer, etc., and is provided as construction and safety information to the workers engaged in excavating the natural ground, or the evaluation level of the change in the geological situation is displayed. By issuing alarms and warnings to workers engaged in tunnel excavation, it is possible to prevent skin fall disasters in the excavation work of the ground including the tunnel face.

In addition, in the elastic wave velocity measurement method of Patent Document 1, since the elastic wave velocity propagating through the ground is calculated from the travel time curve of the propagation distance and the propagation time, in order to calculate the elastic wave velocity near the face, propagation It is necessary to measure multiple blasts at different distances with a single seismometer, which takes a relatively long time. By adding the method of estimating the geological condition of the face from the frequency characteristics of sound waves propagating in the air to the method of estimating the geological condition of the face from the frequency characteristics of waves, we aim to improve the accuracy of estimating the geological condition of the face. Since it is possible to evaluate the change in the geological condition of the excavated surface for each excavated surface immediately after vibration is generated on the excavated surface of the ground including the tunnel face, in this respect, the elastic wave velocity measurement method of Patent Document 1 is greatly improved. be able to.

In addition, in this method, a portable geophone is used for receiving and measuring elastic waves, a microphone is used for receiving and measuring sound waves, a personal computer or a two-channel stereo IC recorder is used for recording elastic waves and sound waves, and a general method is used for analyzing elastic wave data and sound wave data. Since elastic waves and sound waves are measured and analyzed using simple general-purpose measurement equipment, such as a personal computer equipped with specialized analysis software, geological evaluation of the excavated surface can be performed reliably, easily, and at low cost. . As a result, many civil engineers can easily measure the geological evaluation of the excavated surface in civil engineering work such as the face of a tunnel pit. In the conventional seismic survey method conducted inside the tunnel, there is a method of measuring one blast with multiple seismometers, but this method requires the installation of multiple seismometers inside the tunnel. , it takes a lot of time to install the seismometer, and the measurement is done by a specialized company using an expensive multi-channel data logger, which increases the cost. Since the geological evaluation of the excavated surface can be performed easily and at low cost, the conventional seismic survey method can be significantly improved in this respect.

Furthermore, according to this method, the geophone, microphone and personal computer or IC recorder can be installed at a position sufficiently distant from the vibration source (blasting point) on the excavation surface, so the measurement work itself is safe and damage to the measurement equipment is minimized. Very unlikely.

In this embodiment, a geophone and a microphone are installed at a predetermined position behind the excavation surface (vibration source) such as the face of the tunnel shaft at the same distance, and when vibration is generated on the excavation surface by blasting or the like. At the same time, we measured the elastic waves propagating through the ground with a geophone and the sound waves propagating in the air with a microphone, and recorded them on a personal computer. All of the propagating sound waves may be received and measured only by the geophone. Even in this case, the sound wave measurement accuracy is slightly inferior to that of the microphone, but substantially the same effects as those of the above embodiment can be obtained. can be done.

Further, in this embodiment, blasting is used as a vibration source of the excavation surface in order to generate vibrations on the excavation surface such as the tunnel face, and the excavation surface is blasted by the blasting. Using various equipment used in civil engineering work, including breakers and hammers, as vibration sources, the excavated surface is hit with a breaker, hammer, etc., and the elastic waves generated by the impact on the excavated surface are received and measured by a geophone, and the excavated surface is measured. A microphone may be used to receive and measure the sound waves generated by the impact of the ball, and the results may be recorded in a personal computer.

Furthermore, in this embodiment, the tunnel face was exemplified as an excavation position in civil engineering work, but the excavated surface geological evaluation method according to the present invention can be applied not only to the tunnel face but also to so-called open excavation work such as dam and land development work. It is possible to quantitatively grasp the bedrock properties and stability of the excavation slope by this evaluation method. Also in this case, general-purpose equipment can be used as the equipment, which is inexpensive and can contribute to cost reduction.

1 Seismometer (geophone)
2 microphone 3 recording device (personal computer)

Claims (4)

A seismometer and a portable geophone as a microphone are installed at a predetermined installation position at a predetermined distance from the excavation surface in civil engineering work , including the tunnel face, via rock bolts, and a communication cable is connected to the geophone . Connect a portable personal computer or IC recorder as a recording device,
Vibration is generated on the excavation surface, an elastic wave generated during the vibration and propagating through the ground between the excavation surface and the installation position of the geophone , and an elastic wave between the excavation surface and the installation position of the geophone . The sound waves propagating in the air between them are respectively received and measured only by the geophone , and recorded on the personal computer or the IC recorder that has started the recording operation before the vibration occurs on the excavation surface,
A personal computer is used as an analysis device, and analysis software for analyzing elastic wave data and sound wave data is installed in the personal computer, and the analysis is performed from the elastic wave data and sound wave data recorded in the personal computer or the IC recorder . The frequency characteristics of the elastic wave and the frequency characteristics of the sound wave are calculated by the personal computer equipped with the software , and based on the excellent frequency characteristics that can be clearly distinguished from the frequency characteristics of the elastic wave and the frequency characteristics of the sound wave. estimating and evaluating the geological condition of the excavation surface by
An excavated surface geological evaluation method characterized by: 2. The excavated surface geological evaluation method according to claim 1, wherein blasting is used as a source of vibration of the excavated surface, a blast hole is provided in the excavated surface, an explosive is charged, and the explosive is detonated. 2. The excavated surface geological evaluation method according to claim 1 , wherein various equipment used in civil engineering work, including breakers and hammers, are used as vibration sources for the excavated surface, and the excavated surface is hit by the various equipment including breakers and hammers. 4. Any one of claims 1 to 3, wherein an alarm device is provided at an appropriate position of the civil engineering work site including the vicinity of the excavated surface, and an alarm corresponding to the evaluation of the geological condition of the excavated surface is issued by the alarm device for each excavated surface. The excavated surface geological evaluation method described.

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