Large-span high-frequency coding sound wave imaging device and method

Abstract

The invention discloses a large-span high-frequency coding sound wave imaging device. A coding sound wave control and receiving processor is used for generating a control instruction of coding sound waves; the coded sound wave transmitter is used for generating a coded driving signal according to a coded sound wave control instruction; the coded sound wave transmitting probe is used for generating a coded sound wave signal according to the coded driving signal and spreading to the stratum around the drill hole; the coded sound wave receiving sensor string is used for receiving coded sound wave signals transmitted by the stratum and sensing and generating corresponding coded electric signals, and the coded sound wave control and receiving processor converts the coded electric signals into corresponding coded sound wave digital signals; the processor is used for analyzing the coded sound wave digital signal into a penetrating sound wave signal according to a corresponding coding interpretation rule; the processor obtains a two-dimensional sound wave velocity profile image and a two-dimensional sound wave amplitude attenuation profile image of the formation between the transmitting borehole and the receiving borehole. The method is high in environmental adaptability, is not afraid of interference of detection sites, and is especially suitable for complex-environment sites such as cities.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical engineering investigation, and in particular to a large-span high-frequency coded acoustic wave imaging device and method. Background Art

[0002] Cross-hole acoustic tomography is a technique that reconstructs geological features using acoustic data between two boreholes.

[0003] Cross-hole acoustic tomography technology has incomparable advantages over single borehole measurement methods. It reflects the geological characteristics of the cross section between two boreholes and realizes area measurement. This technology has a good effect on various engineering detection abnormal bodies such as karst, collapse columns, fissures, cracks, fracture zones, weak interlayers, underground cavities and unknown buried objects. The application field of acoustic tomography technology has been extended from medicine to optics, geophysical exploration, and detection of the internal structure of materials. The field sources used have also expanded from X-rays to light waves, seismic waves, electromagnetic waves, sound waves and ultrasound.

[0004] The principle of cross-hole acoustic tomography technology is based on the matrix inversion method of ray tracing. This is a relatively mature method and belongs to the category of ray theory tomography methods. It is widely used in the engineering field, such as rock mass acoustic cross-hole tomography, concrete internal physical structure tomography, etc. This technology reconstructs the internal information of the object through the ultrasonic data detected outside the object, divides the detected object into tiny units, gives the object image on each unit, and then superimposes this series of images to obtain the image inside the object. This is a reconstruction technology from data to image, which can reflect the internal quality of the material or product being tested through pseudo-color images, and conduct qualitative and quantitative analysis of defects, thereby improving the reliability of detection.

[0005] In addition, cross-hole acoustic tomography technology is of great significance in rock mechanics research and non-destructive quality testing of concrete components. Using acoustic tomography technology to detect the physical property distribution inside concrete components and quantitatively determine the quality or defects of components plays an important role in concrete quality testing of various projects.

[0006] Compared with the great progress made in cross-hole acoustic tomography (CT) calculation methods, acoustic tomography testing technology is relatively backward. The low efficiency of existing tomography testing technology has greatly restricted the development of acoustic tomography. The main problems are:

[0007] 1. The vibration source control is inconvenient and the energy is unstable. Conventional ultrasonic emission vibration sources can only be used for geological tests within a size of 1 to 2 meters. Without a high-precision, high-sensitivity test system, a very large amount of energy is required to generate an excitation vibration signal for the stratum. The current conventional artificial excitation vibration sources include: explosives, electric spark vibration sources, giant magnetostrictive acoustic wave emission vibration sources, etc. Among them, explosives and electric sparks have large energy, but the on-site operation is not convenient enough, the intensity of the excited sound waves is unstable, and the explosion of explosives or electric spark discharge operations will cause secondary hazards such as vibration, impact, and noise to the surrounding environment. The giant magnetostrictive acoustic wave emission vibration source is generally only suitable for acoustic wave testing within a few meters, and cannot be used for geological engineering of tens of meters or even hundreds of meters.

[0008] 2. Inconvenient detection. For some larger tomographic detection across obstacles (such as houses, roads, railways, rivers and tunnels), cable communication is needed to achieve synchronization between the transmitter and the receiver. The wiring is complicated and requires a long connecting line, which makes the on-site test operation inconvenient and reduces the overall reliability of the system.

[0009] To sum up, the existing acoustic tomography (CT) test system is only suitable for geological detection with smaller spans, and cannot achieve geological detection with larger spans. If a certain area is to be detected, many geological boreholes need to be added, a lot of drilling costs need to be incurred, and a long drilling time needs to be consumed. At the same time, both the on-site detection layout and the test system have problems such as inconvenient operation and low efficiency. Therefore, a new detection system needs to be developed urgently. Summary of the invention

[0010] The purpose of the present invention is to provide a large-span high-frequency coded acoustic wave imaging device and method, which has strong environmental adaptability, is not afraid of interference from the detection site, and is particularly suitable for complex environmental sites such as cities.

[0011] To achieve this purpose, the present invention is a large-span high-frequency coded acoustic wave imaging device, which is characterized in that it includes a coded acoustic wave control and receiving processor, a coded acoustic wave transmitter, a processor, a coded acoustic wave receiving sensor string and a coded acoustic wave transmitting probe, the coded acoustic wave transmitting probe is used to be set in a transmitting borehole, and the coded acoustic wave receiving sensor string is used to be set in a receiving borehole;

[0012] The coded sound wave control and receiving processor is used to generate control instructions for the coded sound waves;

[0013] The coded sound wave transmitter is used to generate a coded driving signal according to the control instruction of the coded sound wave;

[0014] The coded acoustic wave transmitting probe is used to generate a coded acoustic wave signal according to the coded driving signal and transmit the coded acoustic wave signal to the formation around the borehole;

[0015] The coded acoustic wave receiving sensor string is used to receive the coded acoustic wave signal propagated by the formation and induce the corresponding coded electrical signal. The coded acoustic wave control and receiving processor converts the coded electrical signal into the corresponding coded acoustic wave digital signal.

[0016] The processor is used to resolve the coded sound wave digital signal into a penetrating sound wave signal according to the corresponding coding and decoding rules;

[0017] The processor is used to obtain a two-dimensional acoustic wave velocity profile image and a two-dimensional acoustic wave amplitude attenuation profile image of the stratum between the transmitting borehole and the receiving borehole through coded acoustic wave detection of the full borehole depth of the transmitting borehole and the receiving borehole according to the first wave time and amplitude of the penetrating acoustic wave signal.

[0018] Beneficial effects of the present invention:

[0019] The present invention has the characteristics of coded sound waves, high frequency, multi-frequency, stable energy and convenient operation, so it can realize CT detection with a large span (30 to 300 meters) and high resolution (a span of 100 meters, and a resolution accuracy of 1 meter) (because the coded sound wave is a special signal logic, the reception is processed by this logical relationship, and other signals that do not meet this logical relationship cannot interfere with it, so it can extract very weak signals. The signal extracted by the ordinary method is 3 to 5 times greater than the background noise, while the coded sound wave can extract a signal less than one tenth of the background noise, so it can penetrate a long distance). It can simultaneously obtain a two-dimensional sound wave velocity profile image and a two-dimensional sound wave amplitude attenuation profile image of the stratum between the pair of boreholes to analyze the stratum geological information. Due to the use of coding technology, it is not afraid of interference from the detection site, it has strong adaptability to the environment, and is particularly suitable for sites with complex environments such as cities. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the use state of the present invention;

[0021] Figure 2 It is a schematic diagram of the structure of the coded sound wave receiving sensor string;

[0022] Figure 3 It is a schematic diagram of the process of encoding sound wave signals;

[0023] Figure 4 Extraction of penetrating sound wave schematic diagram for a coded sound wave at a certain emission point;

[0024] Figure 5 This is a schematic diagram of coded acoustic wave CT detecting acoustic wave rays;

[0025] Figure 6 It is a schematic diagram of CT imaging of two-dimensional acoustic wave velocity or two-dimensional acoustic wave amplitude of the stratum between a pair of boreholes.

[0026] Among them, 1 is a coded acoustic wave control and receiving processor, 2 is a coded acoustic wave transmitter, 3 is a processor, 4 is a coded acoustic wave receiving sensor string, 5 is a coded acoustic wave transmitting probe, 6 is a coded acoustic wave receiving sensor, 7 is an acoustic wave receiving cable, 8 is an acoustic wave transmitting cable, 9 is a receiving borehole, 10 is a transmitting borehole, 11 is water, 12 is a cable bracket, 13 is a coded acoustic wave signal, and 14 is a formation. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0028] like Figure 1 and 2 The large-span high-frequency coded acoustic wave imaging device shown comprises a coded acoustic wave control and receiving processor 1, a coded acoustic wave transmitter 2, a processor 3, a coded acoustic wave receiving sensor string 4 and a coded acoustic wave transmitting probe 5, wherein the coded acoustic wave transmitting probe 5 is used to be arranged in a transmitting borehole 10, and the coded acoustic wave receiving sensor string 4 is used to be arranged in a receiving borehole 9;

[0029] The coded sound wave control and receiving processor 1 is used to generate control instructions for coded sound waves (according to AM, FM, PM modulation coding) and transmit them to the coded sound wave transmitter 2 via a wired network or a wireless network;

[0030] The coded acoustic wave transmitter 2 is used to generate a coded drive signal according to the control instruction of the coded acoustic wave, and transmit the coded drive signal to the coded acoustic wave transmitting probe 5 through the acoustic wave transmitting cable 8. The piezoelectric material or super magnetotropic material of the transmitter has the function of converting the electrical signal into the acoustic signal and the acoustic signal into the electrical signal;

[0031] The coded acoustic wave transmitting probe 5 is used to generate a coded acoustic wave signal 13 according to the coded driving signal and propagate it to the formation 14 around the borehole;

[0032] The coded acoustic wave receiving sensor string 4 is used to receive the coded acoustic wave signal 13 propagated from the formation, and induce the corresponding coded electrical signal (radio wave modulation such as AM, FM or PM modulation coding), and the coded acoustic wave control and receiving processor 1 converts the coded electrical signal into the corresponding coded acoustic wave digital signal. The coded acoustic wave adopts a special signal logic, and the receiving end adopts this logical relationship for processing. Other signals that do not meet this logical relationship cannot interfere with the signal reception of the coded acoustic wave control and receiving processor 1. The coded acoustic wave control and receiving processor 1 can extract very weak signals. Therefore, the coded electrical signal can be coded according to AM, FM or PM modulation.

[0033] The processor 3 is used to parse the coded sound wave digital signal into a penetrating sound wave signal according to the corresponding coding and decoding rules (corresponding AM, FM or PM modulation coding and decoding rules), such as Figure 3 As shown;

[0034] The processor 3 is used to detect the full borehole depth of the transmitting borehole 10 and the receiving borehole 9 through coded acoustic wave detection (such as Figure 5 As shown, the full hole depth has transmitted and received acoustic wave signals, and the results are as follows Figure 6 As shown), a two-dimensional acoustic wave velocity profile image and a two-dimensional acoustic wave amplitude attenuation profile image of the stratum between the transmitting borehole 10 and the receiving borehole 9 are obtained. The acoustic wave CT has velocity and amplitude attenuation characteristics, while the emission energy of the traditional acoustic wave CT is uncontrollable and the energy emission cannot be constant, so the amplitude attenuation cannot be used for imaging. The emission energy of the present invention can be constant, and the acoustic wave velocity and amplitude attenuation characteristics can be used to analyze the information of the stratum.

[0035] In the above technical solution, the receiving borehole 9 and the transmitting borehole 10 are arranged in parallel. To detect the two-dimensional stratigraphic profile between the two boreholes, the two boreholes are required to be parallel. If they are not parallel, the distance between the two boreholes needs to be corrected (if the two boreholes are not parallel, the distance change between the receiving sensor and the transmitting probe cannot be calculated according to the equal span relationship).

[0036] In the above technical solution, the coded sound wave control and receiving processor 1 is used to generate control instructions for the coded sound wave signal 13 according to AM, FM or PM modulation coding;

[0037] The coded sound wave signal 13 is a sound wave signal generated by amplitude modulation AM, frequency modulation FM or phase modulation PM of the sound wave signal to be transmitted;

[0038] The penetrating sound wave signal is obtained by parsing the received coded sound wave digital signal according to the decoding sound wave control instruction corresponding to the coded sound wave control instruction.

[0039] In the above technical scheme, the coded acoustic wave transmitting probe 5 is used to transmit coded acoustic wave signals of multiple frequencies, and the transmitting power of the coded acoustic wave transmitting probe 5 at each transmission frequency is constant. The coded acoustic wave transmitting probe 5 and the coded acoustic wave receiving sensor 6 are both made of piezoelectric ceramic tubes. Since piezoelectric ceramics or super magneto-acoustic wave transmitting materials are used, their transmitting power is related to the transmitting voltage. As long as the transmitting voltage remains unchanged, their transmitting power remains unchanged, so that CT imaging can be performed using the amplitude attenuation method. That is, the transmitting power is constant, and the amplitude of the received signal at a certain place is low, indicating that the formation attenuation is large and the formation is poor where the sound wave passes.

[0040] In the above technical solution, the coded acoustic wave receiving sensor string 4 includes a plurality of coded acoustic wave receiving sensors 6, which may be 1 to 100, and all the coded acoustic wave receiving sensors 6 are fixed in a straight line (all sensors are glued and sealed on a cable line, and a weight is hung on the sensor at the bottom to straighten all sensors during operation), and the acoustic wave receiving end of each coded acoustic wave receiving sensor 6 faces the acoustic wave transmitting end of the coded acoustic wave transmitting probe 5. The number of coded acoustic wave receiving sensors 6 is generally 12, 24 or 36, and the spacing between each coded acoustic wave receiving sensor 6 is 0.5 to 5 meters. The distances between adjacent coded acoustic wave receiving sensors 6 on a coded acoustic wave receiving sensor string 4 are the same, which is convenient for calculation and analysis, and the image is evenly distributed. The equal spacing can easily obtain the distance between the sensors.

[0041] In the above technical solution, the signal output end of each coded sound wave receiving sensor 6 is connected to the signal input end of the coded sound wave control and receiving processor 1 through the corresponding core wire of the sound wave receiving cable 7. The sound wave receiving cable 7 and the sound wave transmitting cable 8 are respectively installed through corresponding cable brackets 12.

[0042] In the above technical solution, the processor 3 obtains a two-dimensional acoustic wave velocity profile image of the stratum between the transmitting borehole 10 and the receiving borehole 9 by scanning and detecting the coded acoustic wave of the full borehole depth of the transmitting borehole 10 and the receiving borehole 9 according to the first wave time and amplitude of the penetrating acoustic wave signal. The specific method is:

[0043] Assume that N sound wave propagation paths are measured in the two-dimensional sound wave velocity profile image. According to the ray CT imaging theory, the imaging area is first divided into M units (the calculation requirements of tomography are generally divided according to the spacing between the sensors 6. For example, if the spacing between the sensors is 1 meter, then the vertical and horizontal M are divided according to 1 meter). The imaging method based on the first wave ray theory solves the following equation:

[0044]

[0045] The above formula is a large sparse linear equation system. In formula (1), ij is the path length of the i-th sound wave propagation path (ray) in the j-th unit, S j =1 / V j , S j is the average slowness value of the jth unit, V j is the average speed of the jth unit, T i is the measured travel time value of the path of the i-th sound wave propagation, where i belongs to N and j belongs to M. According to S j A two-dimensional acoustic wave velocity profile image of the stratum between the transmitting borehole 10 and the receiving borehole 9 is obtained.

[0046] In the above technical solution, the processor 3 obtains the two-dimensional acoustic wave amplitude attenuation profile image by scanning and detecting the coded acoustic wave of the full borehole depth of the transmitting borehole 10 and the receiving borehole 9 according to the first wave time and amplitude of the penetrating acoustic wave signal as follows:

[0047] The imaging area is divided into M units. According to the attenuation CT theory, for the N sound wave propagation paths in the measurement area, the attenuation coefficient ray CT equations are obtained;

[0048]

[0049] In the above formula (2), ij is the path length of the i-th sound wave propagation path in the j-th unit, a 0j is the average absorption coefficient of the jth unit, P i is the measured projection of the i-th ray, where i belongs to N and j belongs to M. According to a 0j A two-dimensional acoustic wave amplitude attenuation profile image of the stratum between the transmitting borehole 10 and the receiving borehole 9 is obtained.

[0050] A large-span high-frequency coded acoustic wave imaging method based on the above device is characterized in that it comprises the following steps:

[0051] Step 1: connect the sound wave receiving cable 7 with the coded sound wave receiving sensor string 4, place and hang at the bottom of the hole of the sound wave receiving borehole 9, ensure that each coded sound wave receiving sensor 6 on the coded sound wave receiving sensor string 4 is in a suspended state, the sound wave receiving cable 7 is connected to the coded sound wave control and receiving processor 1 through the cable bracket 12, the sound wave transmitting cable 8 is connected to the coded sound wave transmitting probe 5, and is placed at the bottom of the hole of the sound wave transmitting borehole 10, the sound wave transmitting cable 8 is connected to the coded sound wave transmitter 2 through the cable bracket, the sound wave receiving borehole 9 and the sound wave transmitting borehole 10 are filled with water 11, and the elevation of the bottom of the sound wave receiving borehole 9 and the bottom of the sound wave transmitting borehole 10 is required to be as high as possible, because the angle between the connecting line between the transmitting probe and the receiving sensor during the acoustic wave CT detection and the borehole cannot be too small, and the angle range is 60 ° ~ 90 °, if the elevation of the bottom of the borehole is different, it is easy to cause the angle to be less than 60 degrees, so that the detection effect is not good, and the angle range ensures the energy consistency of the transmitting direction;

[0052] Step 2: The coded acoustic wave control and receiving processor 1 generates a control instruction for the coded acoustic wave, starts the coded signal command of 1 to 5 (or even more) coded acoustic waves of different frequencies, transmits a group of 1 to 5 coded acoustic wave signals 13 of different frequencies, and simultaneously collects and processes a group of 1 to 5 coded acoustic wave signals 13 of different frequencies propagated through the stratum 14 to the acoustic wave receiving borehole 9, and completes the test of a group of 1 to 5 coded acoustic wave signals 12 of different frequencies of the first test. The frequency is low and the resolution is poor, but it is better for regional analysis. The frequency is high and the resolution is high, and it is good for fine analysis. In this way, the multi-frequency combined analysis can analyze the stratum information in more detail and accurately, such as Figure 4 As shown, Figure 4 It can be seen that the signal of sound waves penetrating the stratum is strong, the test signal is good, and the test effect is good;

[0053] Step 3: The coded sound wave transmitter 2 generates a coded driving signal according to the control instruction of the coded sound wave;

[0054] Step 4: The coded acoustic wave transmitting probe 5 generates a coded acoustic wave signal 13 according to the coded driving signal and transmits the coded acoustic wave signal 13 to the formation around the borehole through the water 11 in the transmitting borehole 10;

[0055] Step 5: The coded acoustic wave signal 13 is sensed by the coded acoustic wave receiving sensor string 4 through the water 11 in the receiving borehole 9, and a corresponding coded electrical signal is generated. The coded acoustic wave control and receiving processor 1 converts the coded electrical signal into a corresponding coded acoustic wave digital signal (if there is no water coupling, the acoustic wave cannot be emitted into the rock formation around the borehole, and the acoustic wave signal transmitted from the rock formation cannot be received). The receiving sensor is suspended in the borehole, and the sensor and the hole wall cannot be tightly coupled. If there is no water, the acoustic wave signal transmitted from the stratum cannot be transmitted to the receiving sensor, and the acoustic wave signal cannot be received;

[0056] Step 6: The processor 3 parses the coded sound wave digital signal into a penetrating sound wave signal according to the corresponding coding interpretation rule; and completes the test of a group of 1 to 5 coded sound wave signals 13 of different frequencies in the first test;

[0057] Step 7: The coded acoustic wave transmitting probe 5 is lifted to the spacing height of the coded acoustic wave receiving sensor 6 of the coded acoustic wave receiving sensor string 4, and the operations of steps 2 to 6 are repeated until the test of lifting the coded acoustic wave transmitting probe 5 to the height of the top coded acoustic wave receiving sensor 6 of the coded acoustic wave receiving sensor string 4 is completed. Figure 5 As shown, the ultrasonic CT imaging effect is guaranteed and a complete imaging picture can be obtained;

[0058] The processor 3 (computer or tablet) reads the first wave time and amplitude of the penetrating sound wave signal from the test data of the coded sound wave signal 13 of each frequency, and obtains a two-dimensional sound wave velocity profile image and a two-dimensional sound wave amplitude attenuation profile image of the stratum between the transmitting borehole 10 and the receiving borehole 9 by coded sound wave detection of the full borehole depth of the transmitting borehole 10 and the receiving borehole 9 (at each preset depth interval, the stratum between the transmitting borehole 10 and the receiving borehole 9 is detected), such as Figure 6 As shown in the figure, analyzing the changes in the formation from the two parameters of the formation's acoustic wave velocity and amplitude attenuation can more accurately analyze the formation's information. Figure 6 In the data, we can see the changes in the strata. The parts with high acoustic wave velocity and small amplitude attenuation are good strata, while the parts with low acoustic wave velocity and large amplitude attenuation are bad strata.

[0059] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A large-span high-frequency coded acoustic imaging device, Features: It comprises a coded acoustic wave control and receiving processor (1), a coded acoustic wave transmitter (2), a processor (3), a coded acoustic wave receiving sensor string (4) and a coded acoustic wave transmitting probe (5); the coded acoustic wave transmitting probe (5) is used to be arranged in a transmitting borehole (10), and the coded acoustic wave receiving sensor string (4) is used to be arranged in a receiving borehole (9); The coded sound wave control and receiving processor (1) is used to generate control instructions for the coded sound wave; The coded sound wave transmitter (2) is used to generate a coded driving signal according to the control instruction of the coded sound wave; The coded acoustic wave transmitting probe (5) is used to generate a coded acoustic wave signal (13) according to the coded driving signal and transmit the coded acoustic wave signal to the formation around the borehole; The coded acoustic wave receiving sensor string (4) is used to receive the coded acoustic wave signal (13) propagated in the formation and induce the generation of a corresponding coded electrical signal, and the coded acoustic wave control and receiving processor (1) converts the coded electrical signal into a corresponding coded acoustic wave digital signal; The processor (3) is used to resolve the coded sound wave digital signal into a penetrating sound wave signal according to the corresponding coding and decoding rules; The processor (3) is used to obtain a two-dimensional acoustic wave velocity profile image and a two-dimensional acoustic wave amplitude attenuation profile image of the stratum between the transmitting borehole (10) and the receiving borehole (9) based on the first wave time and amplitude of the penetrating acoustic wave signal by coded acoustic wave detection of the full borehole depth of the transmitting borehole (10) and the receiving borehole (9).

2. The large-span high-frequency coded acoustic imaging device according to claim 1: It is characterized in that The receiving borehole (9) and the transmitting borehole (10) are arranged in parallel.

3. The large-span high-frequency coded acoustic wave imaging device according to claim 1: It is characterized in that The coded sound wave control and receiving processor (1) is used to generate control instructions for a coded sound wave signal (13) according to AM, FM or PM modulation coding; The coded sound wave signal (13) is a sound wave signal generated by amplitude modulation, frequency modulation or phase modulation of the sound wave signal to be transmitted; The penetrating sound wave signal is obtained by parsing the received coded sound wave digital signal according to the decoding sound wave control instruction corresponding to the coded sound wave control instruction.

4. The large-span high-frequency coded acoustic imaging device according to claim 1: Features: The coded sound wave transmitting probe (5) is used to transmit coded sound wave signals of multiple frequencies, and the coded sound wave transmitting probe (5) has a constant transmission power at each transmission frequency.

5. The large-span high-frequency coded acoustic imaging device according to claim 1: Features: The coded sound wave receiving sensor string (4) comprises a plurality of coded sound wave receiving sensors (6), all of which are fixed in a straight line, and the sound wave receiving end of each coded sound wave receiving sensor (6) faces the sound wave transmitting end of the coded sound wave transmitting probe (5).

6. The large-span high-frequency coded acoustic wave imaging device according to claim 1: Features: The signal output end of each coded sound wave receiving sensor (6) is connected to the signal input end of the coded sound wave control and receiving processor (1) through the corresponding core wire of the sound wave receiving cable (7).

7. The large-span high-frequency coded acoustic wave imaging device according to claim 1: Features: The spacing between adjacent coded sound wave receiving sensors (6) in the coded sound wave receiving sensor string (4) is equal.

8. The large-span high-frequency coded acoustic imaging device according to claim 1: Features: The processor (3) obtains a two-dimensional acoustic wave velocity profile image of the stratum between the transmitting borehole (10) and the receiving borehole (9) by scanning and detecting the coded acoustic wave at the full borehole depth of the transmitting borehole (10) and the receiving borehole (9) according to the first wave time and amplitude of the penetrating acoustic wave signal. The specific method is: Assume that N sound wave propagation paths are measured in the two-dimensional sound wave velocity profile image. According to the ray CT imaging theory, the imaging area is first divided into M units, and the imaging method based on the first wave ray theory is used to solve the following equation: In the above formula (1), ij is the path length of the i-th sound wave propagation path in the j-th unit, S j =1 / V j , S j is the average slowness value of the jth unit, V j is the average speed of the jth unit, T i is the measured travel time value of the path of the i-th sound wave propagation, where i belongs to N and j belongs to M. According to S j A two-dimensional acoustic wave velocity profile image of the stratum between the transmitting borehole (10) and the receiving borehole (9) is obtained.

9. The large-span high-frequency coded acoustic wave imaging device according to claim 1: Features: The processor (3) obtains a two-dimensional acoustic wave amplitude attenuation profile image by scanning and detecting the coded acoustic wave at the full borehole depth of the transmitting borehole (10) and the receiving borehole (9) according to the first wave time and amplitude of the penetrating acoustic wave signal. The specific method is: The imaging area is divided into M units. According to the attenuation CT theory, for the N sound wave propagation paths in the measurement area, the attenuation coefficient ray CT equations are obtained; In the above formula (2), ij is the path length of the i-th sound wave propagation path in the j-th unit, a 0j is the average absorption coefficient of the jth unit, P i is the measured projection of the i-th ray, where i belongs to N and j belongs to M. According to a 0j A two-dimensional acoustic wave amplitude attenuation profile image of the stratum between the transmitting borehole (10) and the receiving borehole (9) is obtained.

10. A method for long-span high-frequency coded acoustic wave imaging based on the device of claim 1, It is characterized in that It includes the following steps: The coded sound wave control and receiving processor (1) generates control instructions for the coded sound wave; The coded sound wave transmitter (2) generates a coded driving signal according to the control instruction of the coded sound wave; The coded acoustic wave transmitting probe (5) generates a coded acoustic wave signal (13) according to the coded driving signal and transmits the coded acoustic wave signal to the formation around the borehole through the water (11) in the transmitting borehole (10); The coded acoustic wave signal (13) is sensed by the coded acoustic wave receiving sensor string (4) through the water (11) in the receiving borehole (9), and generates a corresponding coded electrical signal, and the coded acoustic wave control and receiving processor (1) converts the coded electrical signal into a corresponding coded acoustic wave digital signal; The processor (3) parses the coded sound wave digital signal into a penetrating sound wave signal according to the corresponding coding and decoding rules; The processor (3) obtains a two-dimensional acoustic wave velocity profile image and a two-dimensional acoustic wave amplitude attenuation profile image of the stratum between the transmitting borehole (10) and the receiving borehole (9) by coded acoustic wave detection of the full borehole depth of the transmitting borehole (10) and the receiving borehole (9) based on the first wave time and amplitude of the penetrating acoustic wave signal.

Images