JP2006017584A - Three-dimensional survey method using s-wave, s-wave earthquake-generating device, and three-dimensional survey device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a work efficiency, and to reduce cost, while maintaining a survey accuracy similarly or higher, in three-dimensional S-wave reflection method survey. <P>SOLUTION: In this three-dimensional survey device using an S-wave, a belt type geophone group 13 having four receiving lines is used. In the belt type geophone group 13, geophone units 30 are installed at intervals of 0.5m, and the geophones 30 are installed in an approximately grid shape. The number of points for earthquake generation is three. In this S-wave earthquake-generating device 100, symmetrical reverse impact forces are applied to an earthquake-generating plate from two directions on the right and left oblique upsides by two air knockers, and S-wave vibration is transmitted to the ground surface by the earthquake-generating plate. Received data of a reflected wave of the S-wave received by the geophones 30 are collected by a data collection device 11 and analyzed. The device is equipped with a traction device (for example, a small-sized backhoe 40) for developing and moving the belt type geophone group 13. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a three-dimensional exploration method using an S wave, an S wave seismic device, and a three dimensional method for indirectly diagnosing an internal situation such as embankment embankment of a river dike using elastic waves (S waves). Related to exploration equipment.

  Flood control measures such as dykes and dams that protect lives and property from flooding are important social issues, but the role of river dykes is increasing in the social situation where construction of new dams is becoming difficult It is becoming important. In order to respond to such social demands, exploration technology is being developed for grasping the state of the embankment using elastic waves. Among these, the effectiveness of the three-dimensional S-wave reflection method exploration for density anomalies such as cavities is recognized. However, the big problem of the high cost peculiar to 3D exploration remained.

  Applicability of geophysical exploration methods such as high-density electric exploration, EM exploration, surface wave exploration, and two-dimensional reflection exploration have been studied for embankment exploration, but any method can be implemented efficiently and effectively at present. The stage has not been reached.

  High-density electrical exploration and EM exploration are exploration technologies that attempt to grasp the internal structure of embankment and foundation ground, mainly from the difference in specific resistance of the ground due to the water content ratio. Both exploration techniques have problems in the exploration principle that the resolution decreases with depth and is adversely affected by buried objects of good conductors. In particular, high-density electrical exploration still has problems in field work, such as the need to place a large number of electrodes on the ground surface.

  Surface wave exploration is an exploration technique that focuses on surface waves among elastic waves. For embankment exploration, the ability to detect density anomalies such as cavities is low (about half the depth), and the accuracy of depth is not good, so combined use with boring surveys and sounding is indispensable. However, because exploration costs are low, depending on the purpose, it may be effective to grasp the embankment land and the foundation surface. Details of the surface wave exploration will be described later.

  The two-dimensional S-wave reflection method is more accurate than the above survey methods and methods, and the analysis results that accurately reflect the internal structure of the ground can be obtained. Reflection data is also included, which has the disadvantage of acting as noise. However, since a certain level of accuracy can be secured by accumulating interpretation techniques, it can be applied to rough levee exploration.

  The 3D S-wave reflection method is used for the purpose of grasping the soil layer structure inside the levee / foundation ground, the density abnormalities such as the cavities inside the levee, and the loose area. In particular, it has been put into practical use for exploration of cavities in embankments.

  The three-dimensional S-wave reflection method exploration is a kind of physical exploration technique using elastic waves that receives horizontal motion given on the ground surface with a three-dimensional multi-channel and analyzes the structure of an underground reflecting surface by data processing. In the field data acquisition, a survey line is set in the longitudinal direction at the top of the dike and a small step, and a belt in which a large number of geophones are arranged in a three-dimensional manner so that a band-like range having a certain width in the transverse direction is targeted. Towing and generating S waves in the longitudinal and transverse directions at regular intervals. The data acquired in the field is processed and analyzed by the reflection method, and the underground structure is interpreted by 3D visualization.

An example of conventional three-dimensional S-wave reflection method exploration (Non-Patent Document 1) is shown in FIG. As shown in FIG. 16, the three-dimensional exploration device includes a data recording device 11 mounted on the observation vehicle 10, a signal cable 12, a geophone unit 30 that is a three-dimensional S wave vibration device, a vibration device (small backhoe 41, S It comprises a wave generator 100a). The vibration receiving device is composed of two vibration receiving lines in which 24 vibration receiving unit units 30 are arranged and arranged at intervals of 50 cm on two non-stretchable traction belts 20. The seismic device is a small backhoe 41 with a S-wave seismic device 100a attached to the bucket, and performs seismic work by a plate tapping method. 48 channels of data are acquired simultaneously while performing the five points indicated by crosses in the transverse direction at intervals of 0.5 m of deployment movement interval in the dike longitudinal direction. A structure in which a plurality of traction belts 20 each having a geophone unit 30 arranged at a predetermined interval are fixed in parallel is referred to as a belt-type geophone group.
Shuichi Mochimaru, et al., "Development of technology for exploring dyke interior conditions using elastic waves", Construction Management Technology, Foundation of Economic Research Foundation, May 2001, pages 54-57

  The traction belt 20 is connected to a small backhoe 41 by a traction wire 21 and is unfolded and moved (0.5 m intervals) by the small backhoe 41. FIG. 17 shows a state where a conventional three-dimensional S-wave exploration is actually performed on the bank.

  As described above, the three-dimensional S-wave reflection method exploration is an excellent method in terms of accuracy and application range compared to other methods, and its future potential is expected, but the problem is that the work cost is high. There was a point, and the improvement was desired.

  The present invention has been made to solve such problems, and its purpose is to improve work efficiency and reduce costs in the third-order S-wave reflection method while maintaining the search accuracy at the same level or higher. An object of the present invention is to provide a three-dimensional exploration method using an S wave, an S wave generating device, and a three-dimensional exploration device that can be achieved.

The present invention has been made in order to solve the above-mentioned problems. In the three-dimensional exploration method using S waves of the present invention, a geophone for receiving vibration of S waves is arranged on a river dike, and the dike A three-dimensional exploration method using S-waves that generates vibrations due to S-waves and diagnoses the state of the dike by receiving the S-waves by the geophone, and a geophone for detecting S-wave oscillations Are arranged at the same interval on the levee with the same interval, and the four receiving lines of the geophone are arranged in parallel on the levee, and the four receiving vibrations. A point on the extension of the line passing through the middle between the two receiving lines inside the line and parallel to the receiving line, and a predetermined distance away from the receiving line, and the outside of the receiving lines of the four receiving units On the extension line of the two receiving lines and a predetermined distance from the receiving line A procedure for sequentially generating vibrations due to S at two points separated from each other; a procedure for receiving reflected waves of the S waves from the ground by the receiver and recording and analyzing the received data of the reflected waves; It is characterized by including.
Thereby, it is possible to reduce the focal point to 3 points without reducing the measurement accuracy (5 points in the past). Further, when setting the focal point, the position of the belt-type geophone group (the position of the traction belt) can be used as a mark, and the focal position can be easily identified. For this reason, work efficiency increases and as a result, data can be collected efficiently.

In the three-dimensional exploration method using the S wave according to the present invention, the interval between the four traction belts is approximately α [m], and the interval between the geophones on the traction belt is approximately α [m]. And including each step of arranging the geophones in a grid and setting the deployment movement distance of the traction belt in the direction of the line to about 2α [m].
Thereby, combined with the effect of CMP polymerization, the working efficiency can be made almost twice that of the conventional one without degrading the measurement accuracy.

The three-dimensional exploration method using the S wave according to the present invention includes a first procedure for performing a rough exploration by surface wave exploration to identify an area that requires a precise exploration, and an S wave for the identified area. And a second procedure for performing a three-dimensional exploration using.
Thereby, more efficient three-dimensional exploration can be realized.

Further, the three-dimensional exploration method using the S wave of the present invention has two left and right air knockers that are shocked by a piston when the vibration caused by the S wave is generated on the ground surface, and the two air knockers. It includes a procedure of using an S-wave seismic device including a seismic plate that receives a symmetrical impact force from two directions and transmits S-wave vibrations to the ground surface.
As a result, it is possible to generate a stronger impact energy than that of a conventional zelkova or the like, and it is possible to efficiently and automatically generate an S wave stronger than the conventional one at the focal point. For this reason, it is possible to improve work efficiency while maintaining measurement accuracy.

In addition, the S-wave seismic device of the present invention is disposed opposite to the left and right so as to form a predetermined angle with respect to the horizontal plane, two air knockers that push out a piston by supplying air pressure, and an impact on the ground surface. The seismic plate that receives the symmetrical impact force from the two diagonally upper and lower directions by the two air knockers and transmits the S-wave vibration to the ground surface, and suppresses the side slip of the seismic plate For this purpose, a rubber mat provided on the bottom surface of the seismic plate is provided.
As a result, it is possible to generate a stronger impact energy than that of a conventional zelkova or the like, and it is possible to efficiently and automatically generate an S wave stronger than the conventional one at the focal point. For this reason, it is possible to improve work efficiency while maintaining measurement accuracy.

The S-wave vibration device of the present invention is an electromagnetic valve switch that controls the flow of compressed air supplied to the air knocker, and adjusts the opening speed of exhaust from the air knocker to adjust the return speed of the piston. A solenoid valve switch having a function is provided.
Thereby, the influence of the vibration noise generated when the piston of the air knocker returns to the initial position can be suppressed.

In the three-dimensional exploration apparatus using S waves of the present invention, a geophone receiving vibrations of S waves is arranged on a river dike, and vibrations due to S waves are generated on the dike. A three-dimensional exploration device using S waves that receives S waves and diagnoses the situation inside the levee, and a traction belt in which geophones that detect vibrations of S waves are arranged at intervals of approximately α [m]. Are arranged in parallel with an interval of approximately α [m], and a group of belt-type geophones in which the geophones are arranged in a grid, two air knockers that give an impact by a piston, and the two air knockers, An S-wave generator having an oscillating plate that receives symmetric impact forces in opposite directions from two directions on the left and right sides and transmits S-wave vibrations to the ground surface, and S-waves from the ground received by the geophone Data recording device for recording reflected wave received data and belt type geophone Characterized in that it comprises a pulling device for pulling the survey line direction.
As a result, while maintaining the same measurement quality, the number of S wave seismic points can be reduced and the deployment movement interval in the direction of the survey line can be increased, enabling efficient data collection in three-dimensional exploration.

In the three-dimensional exploration method using the S wave according to the present invention, the number of receiving lines of the geophone is 4 (conventionally 2), and the number of S waves is 3 (conventional is 5). In addition, the focal point is one point on the extension of the center line of the four receiving lines (the line passing through the middle of the two inner receiving lines), and the two receiving lines outside the four receiving lines are extended. Two points are provided on the line.
As a result, the number of focal points can be reduced to 3 without degrading measurement accuracy (5 points in the past). Further, when setting the focal point, the position of the belt-type geophone group (the position of the traction belt) can be used as a mark, and the focal position can be easily identified. For this reason, work efficiency increases and as a result, data can be collected efficiently.

In the three-dimensional exploration method using S waves of the present invention, the distance between the four traction belts constituting the belt-type geophone group is approximately α [m], and the geophones installed on each traction belt. Is set to approximately α [m], the geophones are arranged in a grid, and the deployment movement distance of the belt-type geophone group in the direction of the line is approximately 2α [m].
Thereby, combined with the effect of CMP polymerization, the working efficiency can be made almost twice that of the conventional one without degrading the measurement accuracy.

Further, in the three-dimensional exploration method using the S wave of the present invention, a rough exploration is performed by surface wave exploration, an area requiring a precise exploration is specified, and the specified area is subjected to a three-dimensional exploration by the S wave. Do it.
Thereby, more efficient three-dimensional exploration can be realized.

Further, in the three-dimensional exploration method using the S wave of the present invention, two air knockers apply opposite and symmetrical impact forces from two diagonally left and right directions to the earthquake generating plate, and the earthquake generating plate generates an S wave. Transmits vibrations of the earth to the ground surface.
As a result, it is possible to generate a stronger impact energy than that of a conventional zelkova or the like, and it is possible to efficiently and automatically generate an S wave stronger than the conventional one at the focal point. For this reason, it is possible to improve work efficiency while maintaining measurement accuracy.

Further, in the S wave vibration device of the present invention, two air knockers apply a reverse and symmetrical impact force to the vibration plate from two diagonally left and right directions, and the vibration plate causes the S wave vibration to be applied to the ground surface. To communicate. In addition, a slip stopper (hard rubber mat) is provided on the bottom surface of the earthquake generating plate.
As a result, it is possible to generate a stronger impact energy than that of a conventional zelkova or the like, and it is possible to efficiently and automatically generate an S wave stronger than the conventional one at the focal point. For this reason, it is possible to improve work efficiency while maintaining measurement accuracy.

Further, in the S-wave vibration device of the present invention, an electromagnetic valve switch having a function of adjusting the return speed of the piston by adjusting the release speed of the compressed air from the cylinder in the air knocker is used to adjust the return speed of the piston. suppress.
Thereby, the influence of the vibration noise generated when the piston of the air knocker returns to the initial position can be suppressed.

Further, in the three-dimensional exploration device using the S wave of the present invention, a belt-type geophone group consisting of four vibration receiving lines (the distance between the belts is approximately α [m] and can be attached to each belt. The geophones are installed in a substantially lattice pattern with the interval of the capacitors being approximately α [m]. The focal point is 3 points. In addition, by two air knockers, a reverse and symmetrical impact force is applied to the seismic plate from two diagonally upper and lower directions, and the vibration of the S wave is transmitted to the ground surface by the seismic plate. In addition, the received data of the reflected wave of the S wave received by the geophone is collected and analyzed by the data recording device. Further, a traction device (for example, a small backhoe) for deploying and moving the belt-type geophone group is provided.
As a result, while maintaining the same measurement quality, the number of S wave seismic points can be reduced and the deployment movement interval in the direction of the survey line can be increased, enabling efficient data collection in three-dimensional exploration.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

[Description of Outline of Three-Dimensional Exploration Device According to the Present Invention]
FIG. 1 is a diagram showing an outline of a three-dimensional exploration apparatus using S waves according to the present invention. As shown in FIG. 1, the three-dimensional exploration device of the present invention includes a data recording device 11, a signal cable 12, a belt-type geophone group 13, and an S-wave seismic device 100 mounted on an observation vehicle 10. The belt-type vibration receiver group 13 is composed of four vibration receiving lines in which 24 vibration receiving unit units 30 are arranged on the four traction belts 20 at intervals of 50 cm. As a result, the geophone unit 30 is arranged in a grid pattern. The S wave generating device 100 generates an S wave toward the ground. Details of the S-wave generator 100 will be described later.

  Further, the belt-type geophone group 13 is connected to the small backhoe 40 by the pulling wire 21, and is unfolded and moved (1.0 m apart) in the direction of the line by the small backhoe 40.

  Data for 96 channels is generated by the belt-type geophone group 13 and the S-wave seismic device 100 while performing the earthquake at three points indicated by crosses in the transverse direction every 1.0 m of the deployment movement interval in the dike longitudinal direction. Are acquired at the same time.

  The specifications of the data recording device 11 are, for example, “the number of simultaneous receiving channels ... 96CH”, “sampling interval ... 0.25 ms”, “recording length ... 1 s”, “A / D conversion resolution / .. 24 bit "," output file format ... SEG-2 "," maximum number of CMP polymerizations ... 12 ", etc. The specification of the geophone unit 30 is, for example, “two diphone configurations”, “diphone: UM2... 10 Hz, one horizontal component”, and the like.

  Compared with the three-dimensional exploration device shown in FIG. 16, the three-dimensional exploration device shown in FIG. 1 has four receiving lines (conventional two), three focal points (conventional five points), and a deployment movement interval. Is 1.0 m (conventional 0.5 m). As a result, analysis accuracy is improved and work efficiency is improved (work cost is reduced).

  FIG. 2 is a conceptual explanatory diagram of a measurement method using the three-dimensional exploration apparatus of the present invention. As described above, the number of receiving lines is four, the receiving line interval is 0.5 m, and the receiving point interval is 0. In this example, the receiving point array is 24 points × 4 rows and the total number of channels is 96. In addition, regarding the focal points in the transverse direction, the number of focal points is 3, and the focal point interval is 0.75 m.

  In this example, there are a total of seven CMP lines from which a vertical section can be obtained by analysis, which will be described later.

  Note that the receiving line interval is 0.5 m, the receiving point interval is 0.5 m, and the unfolding movement interval is 1.0 m. The receiving line interval is approximately α [m], and the receiving point interval is approximately α [m]. m], the expansion movement interval can be approximately 2α [m], and α can be an arbitrary numerical value.

[Explanation of structure and operation of S-wave seismic mount]
Next, the S wave seismic device used in the three-dimensional exploration device of the present invention will be described.
FIG. 3 is a diagram showing a configuration example of the S wave generator used in the three-dimensional exploration device of the present invention, FIG. 3 (a) shows the entire S wave generator, and FIG. 3 (b) The main part of S wave seismic device is shown.

  In FIG. 3, the left and right air knockers 101a and 101b are fixed at an inclination of 30 ° from the horizontal by an air knocker fixing fitting 102 using H-shaped steel. The seismic board 103 is, for example, a hard wooden board having a width of 50 cm, a height of 20 cm, and a depth of 30 cm. The striking plates 104 a and 104 b are attached to the left and right of the seismic plate 103 by striking plate fixing brackets 105 so as to face the striking shafts (pistons) of the air knockers 101 a and 101 b. The striking plates 104a and 104b are, for example, steel plates having a width of 10 cm and a thickness of 10 mm. The air knockers 101a and 101b are pneumatic and have a working pressure of about 0.5 to 0.7 MPa.

  This S-wave generator 100 is an S-wave generator that strikes the diaphragm 103 obliquely from above (inclination of 30 °) for the purpose of suppressing side slip of the diaphragm 103 and improving the coupling with the ground. In addition, since a downward hitting component is generated by hitting from the upper oblique direction, it is effective in suppressing the side slip of the earthquake generating plate 103.

  Further, a hard rubber mat 106 is struck on the bottom surface of the seismic plate 103 in order to suppress the side slip of the seismic plate 103. Thereby, the side slip suppression effect of the earthquake generating plate can be expected even on the asphalt pavement surface. Further, since the P wave is generated by the downward hitting component, the P wave component that becomes noise is eliminated by the double hitting method.

  In order to prevent the skid 103 from slipping, the entire S-wave generator 100 is suppressed by a small backhoe bucket. However, since vibrations are transmitted to the bucket arm and may adversely affect noise, the bucket and the air knocker fixing bracket A hard rubber mat (not shown) for blocking noise is inserted into the space 102.

  FIG. 4 is a diagram illustrating a configuration example of an air pressure control system of the air knocker. As shown in FIG. 4A, the air knocker 101 (101a, 101b) moves the piston 112 back and forth as the compressed air enters and exits the cylinder 111 under the control of the solenoid valve in the solenoid valve switch 110. .

  Before the air knocker 101 is activated, the flow of air from the compressed air into the cylinder 111 (A → B) is blocked, and the head of the piston 112 is in close contact with the cylinder 111 by magnetic force.

  When the electromagnetic valve switch 110 is turned on as shown in FIG. 4B, the electromagnetic valve 110a moves in the direction of the arrow, the air circuit is opened from A to B, and the piston 112 is activated and pushed forward.

  As shown in FIG. 4C, when the solenoid valve switch 110 is turned OFF, the solenoid valve 110a moves in the direction of the arrow, the air circuit opens from B to C, and compressed air enters the atmosphere from the cylinder 111 into the atmosphere. The piston 112 is released and returned to its original position. The air release speed is adjusted by the cock 113.

  Thus, since the air knockers 101a and 101b are long piston types in which the piston protrudes outside the cylinder, the inertial mass of the piston is large and the energy at the time of striking is large. Is big.

  However, the Air Knocker epicenter has one important problem. As shown in the comparison diagram of the received waveform in FIG. 12, when the Air Knocker hypocenter and the Kakeya hypocenter are compared, significant noise enters the Air Knocker hypocenter near 0.4 s and 0.6 s. The cause of this noise is similar to the waveform near the initial motion, and the polarity (+-) of the amplitude is reversed. Therefore, when the air knocker piston 112 returns, the head of the cylinder 111 is hit. It can be seen that the vibration is generated.

  Since it is considered impossible to remove this noise, we devise a method to delay the time of noise generation. That is, in the three-dimensional search, the data acquisition time is at most about 1 s. Therefore, if the return of the piston 112 can be delayed from this time, there is no problem even if noise occurs thereafter. In order to delay the return of the piston 112, a method of suppressing the release of the compressed air remaining in the cylinder 111 after the impact is adopted. That is, the problem of noise generation is solved by extending the return time of the piston 112 by adjusting the cock 113.

  Further, by adopting the electromagnetic valve switch 110 for controlling the air knocker 101, it is possible to start the air knocker 101 on the observation headquarter side. When the solenoid valve switch 110 is not used, it is necessary to start the air knocker 101 on the seismic device side in response to a preparation OK signal for the data recording device from the observation headquarters. When stacking at the same focal point by using the solenoid valve switch 110, the waiting time is only the time required for standby of the data recording device 11, so no OK sign is sent from the observation headquarters side to the focal device side. In addition, the air knocker 101 can be activated directly. As a result, the work efficiency per day can be improved for the on-site work time. For example, shortening of about 30 minutes per day can be achieved.

[Explanation of expanding the expansion movement interval]
In the conventional three-dimensional exploration device shown in FIG. 16, the field data acquisition work was performed by generating earthquakes at a deployment movement interval of 0.5 m in the survey direction. In the three-dimensional exploration device of the present invention, as described above, the distance is expanded to 1.0 m (see FIG. 1). As a result, the number of focal points is halved, and the amount of work on site can be reduced almost in proportion. This improvement is an extremely important key for reducing the cost of shallow reflection surveys.

  FIG. 13 is a diagram showing an example of changes in the analysis cross section depending on the development movement interval. The upper diagram shows a case where the interval is 0.5 m, and the lower diagram shows a case where the interval is 1.0 m. As described above, in the three-dimensional exploration, even when the development movement interval is 1.0 m, a result having almost the same quality as that in the case of 0.5 m is obtained. Since it is determined that no problem will occur, the present invention employs this method for three-dimensional S-wave reflection method exploration.

[Explanation about 3D parallel exploration and CMP line]
In the conventional three-dimensional parallel type exploration shown in FIG. 16, since there are two receiving lines, it is necessary to provide five focal points in the bank crossing direction at the same survey distance. In the three-dimensional exploration method of the present invention, the number of vibration receiving lines is increased to four, and the focal point is reduced to three in return. This makes it possible to acquire data having the same quality while reducing the amount of work on site.

  FIG. 5 is a diagram illustrating a comparative example of the three-dimensional parallel search. FIG. 5 (a) shows an example of conventional parallel exploration. In the conventional three-dimensional exploration, the number of receiving point lines is 2 and the number of seismic points in the transverse direction is 5. ]. Details will be described later.

  FIGS. 5B and 5C are diagrams showing an example of parallel search according to the present invention. The parallel search according to the present invention is basically [4] as shown in FIG. × 3 type] (eight CMP lines, analysis width expanded from [2 × 5 type]). However, there is a problem that the outer focal point must be installed 25 cm outside the receiving line. Therefore, since it is more practical and practical to install the outer focal point according to the receiving point line, [4 × 3 ′ type] shown in FIG. 5C can also be used.

  In the [4 × 3 ′ type], a part having a CMP interval of 12.5 cm is partially generated. However, as in [2 × 5 type], this can be integrated into seven CMP lines with a 25 cm interval. . However, compared with [2 × 5 type], the number of CMP lines having a polymerization number of 2 in the transverse direction is increased from 3 to 5, and the analysis accuracy can be improved. Details will be described later.

  FIG. 6 is an explanatory diagram of a conventional [2 × 5 type] CMP polymerization, and is an example in the case of performing a three-dimensional exploration method in the crossing direction of the bank. In FIG. 6, the S wave generated from the focal point S1 travels from the ground surface into the ground and is reflected by the reflecting surface. The S wave generated from the focal point S1 is received at the receiving point R1 through the path a1 → the reflection point F1 → the path a2. The S wave generated from the focal point S1 is received at the receiving point R2 through the path a3 → the reflection point F3 → the path a4.

  In the same manner, S waves generated at each of the focal points S2 to S5 are observed at the receiving points R1 and R2, and as a result, one observation data is obtained for the reflection points F1, F2, F6, and F7. Thus, two observation data are obtained for the reflection points F3, F4, and F5. Since these observation data are subjected to CMP polymerization, the CMP polymerization number is 1 for the reflection points F1, F2, F6, and F7, and the CMP polymerization number is 2 for the reflection points F3, F4, and F5.

  FIG. 7 is a diagram showing an example of [4 × 3 type] CMP polymerization, and is an example in the case where a three-dimensional exploration method is performed in the transverse direction of the bank. In FIG. 7, the S wave generated from the focal point S1 travels from the ground surface into the ground and is reflected by the reflecting surface. Then, the S wave generated from the focal point S1 is received at the receiving point R1 through the path a1 → the reflection point F1 → the path a2. Further, the path a3 → the reflection point F2 → the path a4 through the receiving point R2, the path a5 → the reflection point F3 → the path a6 through the receiving point R3, and the path a7 → the reflection point F4 → the path a8 through the receiving point. Each is received at R4.

  In the same manner, S waves generated at the respective focal points S2 to S3 are observed at the receiving points R1 to R4. As a result, one observation data is obtained for the reflection points F1, F2, F7, and F8. Thus, two observation data are obtained for the reflection points F3, F4, F5, and F6. Since these observation data are subjected to CMP polymerization, the number of CMP polymerization is 1 for reflection points F1, F2, F7, and F8, and the number of CMP polymerization is 2 for reflection points F3, F4, F5, and F6.

  FIG. 8 is a diagram showing an example of [4 × 3 ′ type] CMP polymerization, and is an example in the case where a three-dimensional exploration method is performed in the transverse direction of the bank. In FIG. 8, the S wave generated from the focal point S1 travels from the ground surface into the ground and is reflected by the reflecting surface. The S wave generated from the focal point S1 passes through the path a1, is reflected by the reflecting surface F1 directly below, and is received at the receiving point R1. The S wave generated from the focal point S1 is received at the receiving point R2 through the path a2 → the reflection point F2 → the path a3. Further, the vibration is received at the receiving point R3 through the route a4 → the reflection point F4 → the route a5 and at the receiving point R4 through the route a6 → the reflection point F6 → the route a7.

  In the same manner, S waves generated at the respective focal points S2 to S3 are observed at the receiving points R1 to R4. As a result, the reflection points F1, F2, F3, F4, F5, F7, F8, F9, One observation data is obtained for F10 and F11, and two observation data are obtained for the reflection point F6. Further, as described in FIG. 5C, the observation data of the reflection surface F3 is integrated with the observation data of the reflection surface F2, the observation data of the reflection surface F5 is integrated with the observation data of the reflection surface F4, and the reflection surface F7. Is integrated with the observation data of the reflection surface F8, and the observation data of the reflection surface F9 is integrated with the observation data of the reflection surface F10.

  Thereby, the CMP polymerization number is 1 for the reflection points F1 and F11, and the CMP polymerization number is 2 for the reflection points F2, F4, F6, F8, and F10.

  Although the principle of the CMP polymerization polymerization method is well known, only a brief explanation will be given here. Since the signal of the reflected wave from the basement is weak, the signal is often buried in noise and a clear reflection record cannot be obtained simply by providing a single receiving point for one earthquake. Therefore, in the reflection method exploration, the vibration record is recorded simultaneously at a number of points for each occurrence of the earthquake, and the S / N ratio is improved. As described above, the vibration record recorded by the multi-channel method is subjected to data processing using a method called CMP polymerization. An outline of this principle will be described by taking a two-dimensional search as an example.

  As shown in FIG. 15 (a), the seismic points are S1 to S6 and the seismic points are R1 to R6, as shown in FIG. Are reflected points (common intermediate point D), a plurality of reflection records having different propagation velocity paths shown in FIG. 15B are extracted according to the difference in the distance between the focal point and the receiving point (offset distance) (CMP). ensemble). Next, by correcting the travel time due to the difference in the offset distance [NMO correction], it can be replaced with a record on the vertical line connecting the offset distance zero, that is, the common intermediate point D and the ground surface immediately above (Fig. (C) )). Finally, these records are added together, and the reflected waves are collected into one record called a CMP trace (FIG. (D)). At this time, the number of recordings of the CMP ensemble added together to make the CMP trace is called the CMP polymerization number.

  The CMP polymerization method in the case of three-dimensional exploration is also the same as that in the case of two-dimensional exploration in principle, but the one corresponding to the common intermediate point D is called a bin, and a place having a certain area is the one in the two-dimensional exploration. Different from the case. The bins are divided in a lattice pattern at equal intervals, and reflection recordings that enter the same bin constitute a CMP ensemble, and the number of recordings is the number of superposed CMPs.

[Explanation of surface exploration]
In the three-dimensional exploration method of the present invention, by using the conventional surface exploration method, after identifying the rough internal structure of the object to be investigated (such as a levee), the region requiring precise exploration is specified. If the three-dimensional exploration method of the present invention is used, more effective three-dimensional exploration can be performed.
The surface exploration method is a well-known technique. Here, the surface exploration method will be described.

  Surface wave exploration is an exploration technique that focuses on surface waves among elastic waves. For embankment exploration, the ability to detect density anomalies such as cavities is low (about half the depth), and the accuracy of depth is not good, so combined use with boring surveys and sounding is indispensable. However, because exploration costs are low, depending on the purpose, it is effective to gain a rough understanding of the embankment land and foundation surface.

  FIG. 9 is a diagram for explaining the concept of the surface exploration measurement method. The surface wave exploration is used to roughly grasp the soil layer structure inside the levee and the foundation ground, and to estimate the loose area inside the levee. The S-wave velocity, which is excellent in economic efficiency and directly obtains the basic ground constant, can be directly obtained.

Surface wave exploration is a type of elastic wave exploration that analyzes the S wave velocity structure by striking the ground surface with kayak, receiving vertical vibrations applied on the ground surface by multiple channels, and extracting surface waves. As shown in FIG. 9, on-site data acquisition is performed by installing a large number of geophone units 30 at regular intervals on a survey line, and receiving data of vibration waveforms oscillated at regular intervals on a multichannel by the data recording device 11. . The above data is re-edited into the waveform data group for each point, the S wave velocity distribution in the vertical direction is obtained, and finally the vertical section under the survey line is back-analyzed to interpret the underground structure.
FIG. 10 is a diagram showing a data processing procedure in the surface exploration method. Hereinafter, the procedure will be described with reference to FIG.

First, a geometry is created (step S101).
Create information on the location of the seismic point and receiving point of each shot data. A collection of traces (waveform data) in shot data is called shot gather.

Next, a CMP cross correlation gather is created (step S102).
Rather than simply rearranging shot gathers to CMP gathers as in the case of reflection method exploration, CMP editing is performed on a trace that has been subjected to waveform processing called cross-correlation. Note that cross-correlation is a combination of all two traces extracted from all traces in shot gather, and a cross-correlation process is performed on these trace pairs to obtain a trace similar to waveform data. Is. In the case of 24 simultaneous data acquisition channels, the number of combinations “ ₂₄ C ₂ = 276” cross correlations can be obtained from one shot gather. The cross correlation is given as attribute values the interval between the receiving points of the two traces and the coordinates (CMP) of the midpoint between the receiving points.

  Cross correlations are obtained in the same manner for the other shot gathers, and these cross correlations are rearranged into CMP gathers in the same manner as in the reflection method. At this time, cross correlations in which the receiving point intervals are the same in each CMP gather are added and aggregated into one trace. As a result, a collection of cross-correlation traces corresponding one-to-one with the receiving point interval is completed. This is called CMP cross-correlation gather. When the cross-correlation traces are arranged in order from the narrowest receiving point interval, a waveform display called pseudo-common excitation point recording can be obtained.

Next, a variance analysis is performed (step S103).
For CMP cross-correlation gathers, each cross-correlation trace is first converted to the frequency domain. Next, an apparent speed is set, the phase is shifted according to the receiving point interval, and integration is performed in the receiving point interval direction. From this result, a graph of frequency and phase velocity is obtained, and a dispersion curve is obtained. Thus, one dispersion curve is obtained for one CMP cross-correlation gather. For the obtained dispersion curve, noise and higher-order modes are erased, and smoothing is performed in the depth direction and the measurement line direction.

Next, an initial model is constructed (step S104).
The S wave velocity structure is calculated based on the dispersion curve edited by the above procedure. A plot of the obtained S wave velocity distribution is taken as a provisional analysis cross section.

Next, inversion using the N value (step S105) is performed.
Find the correlation (Vs = b · N ^a ) between the converted N-value data obtained by the Swedish sounding test and the S-wave velocity from the surface wave search results at that point. This correlation is interpolated in the direction of the survey line and inversion is performed. A plot of the obtained S wave velocity distribution is taken as a final analysis sectional view.

[Explanation of processing procedure in 3D exploration device]
1 and 2, the outline of the three-dimensional exploration method by the three-dimensional exploration apparatus of the present invention has been described, and in FIG. 7 and FIG. 8, the CMP polymerization and the vibration receiving line have been described. A data processing method and procedure in the exploration device will be described.

  FIG. 11 is a diagram showing a data processing procedure in the three-dimensional exploration device of the present invention. Hereinafter, the processing procedure will be described with reference to FIG.

First, format conversion of the received data collected by the data recording device 11 is performed (step S201).
Since the field acquisition data is recorded in the SEG-2 format, it is converted into a standard format dedicated to software for subsequent processing.

  Next, a geometry is created (step S202). The waveform data obtained for each earthquake is edited into CMP waveform data to create a CMP gather. Information by this operation is recorded in the header part of each trace and is referred to in later data processing.

Next, trace editing is performed (step S203).
All earthquake records are displayed, and defective traces that are thought to adversely affect the subsequent processing are deleted.

An initial mute is performed (step S204).
Cut (mute) the direct wave that appears at the beginning of the trace. In particular, the direct wave recorded on the geophone trace close to the focal point has the largest amplitude in the raw data, which may adversely affect the amplitude compensation described later, so the mute operation is an important step. .

A band pass filter is operated (step S205).
In order to extract significant high frequency components from the data and to remove low frequency components for noise removal, band pass filter operation is performed on all traces. Appropriate frequencies for low cut, low pass, high pass, and high cut are selected in the entire data processing. For example, 15 Hz, 20 Hz, 70 Hz, and 80 Hz are used, respectively.

Amplitude compensation is performed (step S206).
The amplitude of the elastic wave emitted from the hypocenter decreases due to various causes (geometric divergence effect, multiple reflection effect, inelastic dissipation, etc.). Amplitude compensation is applied to compensate for these effects and restore the uniformity (steadiness) of the recording amplitude. There are several methods for amplitude compensation. For example, AGC (Automatic Gain Control) for obtaining a gain function from trace data is used.

  Velocity analysis is performed (step S207). In the speed analysis, polymerization is first performed at an approximate speed, and after an overview of the whole is grasped, a CMP gather is selected at a substantially constant interval (for example, 12.5 m) in the measurement direction to determine the polymerization speed.

NMO correction and mute (Normal Movement Correction, Mute) are performed (steps S208 and S209).
NMO correction is performed using the polymerization rate obtained by the rate analysis (step S208). At the same time, the over-extension waveform is muted (step S209). The speed analysis (step S207) to NMO correction / mute (step S209) are steps for analyzing the most appropriate cross section by repetition and correspond to the heart of the CMP polymerization method.

CMP polymerization (CMP Stack) is performed (step S210).
Polymerize CMP ensemble traces per bin. The amplitude after polymerization is normalized by dividing it by the square root of the number of polymerization traces. At this stage, a velocity analysis cross section is obtained.

  Amplitude adjustment (Trace Balancing) is performed (step S211). Amplitude adjustment by AGC is performed. For example, if the influence of the diffracted wave is strong, migration is also performed (step S212). At this stage, a time cross section is obtained.

Depth conversion is performed (step S213).
Depth conversion is performed using the conversion rate estimated from the polymerization rate, and the time sectional view is converted into the depth sectional view. The conversion rate is generally said to be about 80% of the polymerization rate.

Three-dimensional visualization analysis is performed (step S214).
In order to interpret the 3D exploration results and display them in an easy-to-understand manner, 3D visualization analysis is performed. In this step, for example, Seis Vision (registered trademark) manufactured by Landmark and e-GeoVR (registered trademark) manufactured by CRC Solutions are used as dedicated software for three-dimensional visualization analysis. From this result, a final analysis result such as a transmission method analysis chart can be obtained.

  As projection methods for visualizing the three-dimensional analysis results, there are an orthographic projection and a projection projection. Orthographic projection is to look at the object with the viewpoint at infinity, and the line of sight is all parallel and the dimensional scale of each part of the object is equally divided. On the other hand, the projection projection places a viewpoint within a finite range to reproduce an image seen by a person, so that a near object is large and a distant object is small and a sense of perspective can be expressed. In the analysis result of the three-dimensional exploration method, even if it is said to be three-dimensional, since the depth (analysis width in the bank embankment direction) is small, the stereoscopic projection does not appear in the orthographic projection, so it is better to apply the projection projection.

  FIG. 14 shows an example of a transmission method analysis diagram by projection projection among the three-dimensional visualization analysis diagrams obtained from the data processing / analysis results. The transmission method analysis is a transmission processing technique in which a waveform whose amplitude value is smaller than a certain value is cut off and the back of the waveform is seen through, and only positive amplitude is shown in FIG. In FIG. 14, the position of the viewpoint is set slightly above the top of the left bank side embankment near a survey distance of 130 m.

  As described above, in the three-dimensional exploration device and the three-dimensional exploration method of the present invention, the work efficiency can be improved as compared with the conventional three-dimensional exploration method, and the analysis accuracy is also improved by the conventional three-dimensional exploration method. Compared to, it is equivalent or better.

  As mentioned above, although embodiment of this invention was described, the three-dimensional exploration apparatus of this invention is not limited only to the above-mentioned illustration example, A various change can be added within the range which does not deviate from the summary of this invention. Of course.

  In the present embodiment, the belt-type geophone group 13 has four traction belts 20 including a plurality of geophone units 30, and the S wave seismic point at that time is three. This example is effective in practical use, but is not limited thereto. For example, the number of the traction belts 20 may be more than four, and an appropriate number / position of the S wave seismic point may be determined based on the relationship between the number of the traction belts 20 and the CMP polymerization.

  In the third-order S-wave reflection method exploration, since the work cost can be reduced while maintaining the exploration accuracy at the same level or higher, the present invention relates to a three-dimensional exploration method using S-waves, S-waves. It is useful for a seismic device and a three-dimensional exploration device.

It is a figure which shows the outline | summary of the three-dimensional exploration apparatus using S wave by this invention. It is a conceptual explanatory drawing of the measuring method by the three-dimensional exploration apparatus of this invention. It is a figure which shows the structural example of the S wave seismic device by this invention. It is a figure which shows the structural example of the air pressure control system of an air knocker. It is a figure which shows the comparative example of a three-dimensional parallel search. It is explanatory drawing of conventional [2x5 type] CMP superposition | polymerization. It is explanatory drawing of CMP polymerization of [4x3 type]. It is explanatory drawing of CMP superposition | polymerization of [4x3 'type]. It is a figure for demonstrating the concept of a surface exploration measuring method. It is a figure which shows the data processing procedure in the surface exploration method. It is a figure which shows the data processing procedure in the three-dimensional search apparatus of this invention. It is a comparison figure of a receiving waveform. It is a figure which shows the example of the change of the analysis cross section by an expansion movement space | interval. It is a figure which shows the example of the transmission method analysis figure obtained by the three-dimensional exploration apparatus. It is a principle explanatory view of CMP polymerization. It is a figure which shows the example of the conventional three-dimensional S wave reflection method search. It is a figure which shows a mode that the conventional three-dimensional S wave exploration is performed on a dike.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Observation vehicle 11 Data recording device 12 Signal cable 13 Belt type geophone group 20 Traction belt 21 Traction wire 30 Vibrator unit 40 Small backhoe 100 S wave seismic device 101a, 101b Air knocker 102 Air knocker fixing bracket 103 Seismic plate 104a, 104b Impact plate 105 Strike plate fixing bracket 106 Hard rubber mat 110 Solenoid valve switch 110a Solenoid valve 111 Cylinder 112 Piston 113 Cock

Claims (7)

Place a geophone to receive S-wave vibration on a river dike, oscillate S-wave vibration on the dike, and receive the S-wave by the geophone to diagnose the internal situation of the dike A three-dimensional exploration method using
Four traction belts, which are equipped with geophones that detect S-wave vibrations, are arranged on the levee at the same interval, and four geophone lines are arranged on the levee in parallel. And the steps to
A point on the extension of a line parallel to the receiving line passing through the middle between the two receiving lines inside the four receiving lines and a predetermined distance away from the receiving line; and the four receiving units A procedure of sequentially generating vibrations by S waves at two points on the extension line of the two receiving lines outside the receiving line and at a predetermined distance from the receiving line;
A method of receiving a reflected wave of the S wave from the ground by the geophone, and recording and analyzing the received data of the reflected wave. The arrangement interval of the four traction belts is approximately α [m], the arrangement interval of the geophones on the traction belt is substantially α [m], the geophones are arranged in a lattice shape, The three-dimensional exploration method using the S wave according to claim 1, further comprising a step of setting a deployment movement distance in a survey line direction to approximately 2α [m]. A first procedure for performing a rough exploration by surface wave exploration and identifying an area requiring a fine exploration;
3. A three-dimensional exploration method using S waves according to claim 1, comprising: a second procedure for performing three-dimensional exploration using S waves for the specified region. When generating vibrations from the S wave on the ground surface,
S-waves with two air knockers that give impact by pistons, and a seismic plate that receives symmetric impact forces in opposite directions from two diagonally upper and lower directions and transmits S-wave vibrations to the ground surface by the two air knockers The three-dimensional exploration method using the S wave according to any one of claims 1 to 3, further comprising a procedure of using the seismic device. Two air knockers that are arranged opposite to the left and right so as to form a predetermined angle with respect to the horizontal plane, and that pushes out the impact by supplying air pressure to give an impact;
A seismic plate that is horizontally disposed on the ground surface, receives a symmetrical impact force in two opposite directions from two diagonally upper and lower directions by the two air knockers, and transmits S-wave vibrations to the ground surface;
An S-wave generating device, comprising: a rubber mat provided on a bottom surface of the seismic plate to suppress a side slip of the seismic plate. An electromagnetic valve switch for controlling a flow of compressed air supplied to the air knocker, the electromagnetic valve switch having a function of adjusting a return speed of a piston by adjusting an opening speed of exhaust from the air knocker. The S-wave seismic device according to claim 5. Place a geophone to receive S-wave vibration on a river dike, oscillate S-wave vibration on the dike, and receive the S-wave by the geophone to diagnose the internal situation of the dike A three-dimensional exploration device using
Four traction belts in which the geophones for detecting the vibration of the S wave are arranged at intervals of about α [m] are arranged in parallel at intervals of about α [m], and the geophones are arranged in a lattice shape. A belt-type geophone group;
S-wave seismicity having two air knockers that give impacts by pistons, and a seismic plate that receives symmetric impact forces in opposite directions from two diagonally upper and lower directions and transmits S-wave vibrations to the ground surface by the two air knockers. Equipment,
A data recording device for recording received data of reflected S waves from the ground received by the geophone;
A three-dimensional exploration device using S waves, comprising: a pulling device that pulls the belt-type geophone group in a direction of a line.

Images