A cross-hole acoustic wave reflection imaging method

Abstract

This application discloses a cross-hole acoustic wave reflection imaging method, which relates to the field of geotechnical engineering exploration. The method includes: using a coded acoustic wave transmitting assembly to generate a set of coded acoustic wave signals of different frequencies and propagating them to the strata surrounding the transmitting borehole; using a coded acoustic wave receiving assembly to receive all direct transmitted wave signals of the coded acoustic waves propagating through the strata to the receiving borehole, as well as all coded reflected wave signals reflected by geological bodies within the stratum, and sensing corresponding coded electrical signals. The coded acoustic wave transmitting assembly converts these signals into coded acoustic wave digital signals, and data analysis software analyzes the transmitted and reflected acoustic wave signals. If the total number of coded acoustic wave detections reaches a preset number, a three-dimensional formation wave impedance imaging map of the strata beyond the line connecting the transmitting and receiving boreholes is determined based on the time and amplitude of the reflected acoustic wave signals corresponding to any frequency. This application can achieve large-span, high-resolution reflection imaging.

Description

Technical Field

[0001] The present application relates to the field of geotechnical engineering investigation, and in particular to a cross-hole acoustic wave reflection imaging method. Background Art

[0002] Cross-hole acoustic transmission tomography is a technology that reconstructs geological features through acoustic wave data between two boreholes. It is very effective for detecting abnormal bodies such as karst, collapse columns, fissures, cracks, fracture zones, weak interlayers, underground cavities and unknown buried objects in various engineering projects. The principle of cross-hole acoustic transmission tomography is based on the matrix inversion method of ray tracing. It belongs to the category of ray theory tomography methods and is of great significance in rock mechanics research and non-destructive quality testing of concrete components. Specifically, the use of acoustic transmission tomography technology to detect the distribution of physical properties inside concrete components can quantitatively determine the quality or defects of the components, which plays an important role in concrete quality testing of various projects.

[0003] Although cross-hole acoustic transmission tomography has achieved remarkable results, it can only reconstruct geological features using acoustic wave characteristic data from the strata between two boreholes. It cannot reconstruct geological features from strata beyond the line connecting the two boreholes, especially since the area beyond the line connecting the two boreholes is much larger than the area between the two boreholes. Using cross-hole acoustic transmission tomography to achieve large-scale, detailed detection and imaging requires many more geological boreholes, incurring significant drilling costs and consuming significant drilling time. Summary of the Invention

[0004] The purpose of this application is to provide a cross-hole acoustic wave reflection imaging method that can achieve large-span, high-resolution reflection imaging.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] The present application provides a cross-hole acoustic wave reflection imaging method, comprising:

[0007] Sending an imaging instruction to the coded acoustic wave transmitting component through the data analysis and processing software; wherein the coded acoustic wave transmitting component is currently at a first position;

[0008] Based on the imaging instructions, the coded acoustic wave transmitting assembly is used to generate a set of coded acoustic wave signals of different frequencies according to a preset modulation and coding strategy and transmit the signals to the surrounding strata of the transmitting borehole;

[0009] A coded acoustic wave receiving assembly is used to receive all direct transmission wave signals of coded acoustic waves propagating through the stratum to the receiving borehole and all coded reflection wave signals reflected by geological bodies in the stratum, and to induce and generate corresponding coded electrical signals;

[0010] Convert all the coded electrical signals into coded sound wave digital signals through the coded sound wave transmitting component;

[0011] Decoding all the coded acoustic wave digital signals based on the preset modulation and coding strategy by the data analysis and processing software to analyze the transmitted acoustic wave signal and the reflected acoustic wave signal, extract the time and amplitude of the reflected acoustic wave signal, and mark the completion of one coded acoustic wave detection;

[0012] If the total number of coded acoustic wave detections does not reach a preset number, updating the first position to a next position, and then returning to the step of using the coded acoustic wave transmitting component to generate a set of coded acoustic wave signals of different frequencies according to a preset modulation and coding strategy and transmitting them to the surrounding strata of the transmitting borehole;

[0013] If the total number of coded acoustic wave detections reaches a preset number, a three-dimensional formation wave impedance imaging map of the strata outside the line connecting the transmitting borehole and the receiving borehole is determined based on the time and amplitude of the reflected acoustic wave signal corresponding to any frequency.

[0014] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a cross-hole acoustic wave reflection imaging method, which detects and images the strata between and outside the two borehole lines. It can achieve large-scale geological exploration through two boreholes and improve the ability of various engineering projects to detect abnormal bodies. In addition, the reflected acoustic wave signal is identified, and the geological body in the stratum is identified and analyzed through the reflected acoustic wave signal to achieve high-resolution reflection imaging, which can further assist in the construction of geological feature imaging of the strata outside and between the two borehole lines. The solution of this application can greatly reduce the number of geological drill holes, drilling costs and detection time, and has great social value and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 A schematic flow chart of a cross-hole acoustic wave reflection imaging method provided in one embodiment of the present application;

[0017] Figure 2 A schematic plan view of a device for executing a method according to an embodiment of the present application;

[0018] Figure 3 A three-dimensional schematic diagram of an apparatus for executing a method provided in one embodiment of the present application;

[0019] Figure 4 Schematic diagram of three-dimensional slice of cross-hole acoustic wave reflection impedance imaging effect.

[0020] Figure numerals: 1-acoustic receiver, 2-acoustic transmitter, 3-computer and processing and analysis software, 4-acoustic receiving sensor string, 5-acoustic transmitting probe, 6-acoustic receiving cable, 7-acoustic transmitting cable, 8-receiving borehole, 9-transmitting borehole, 10-water, 11-cable bracket, 12-transmitted acoustic wave signal, 13-reflected acoustic wave signal, 14-stratum, 15-geological body. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0022] In order to make the purpose, features and advantages of this application more obvious and easy to understand, this application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0023] In an exemplary embodiment, Figure 1 As shown, a cross-hole acoustic wave reflection imaging method is provided. Figure 2 and Figure 3 In the embodiment of the present application, the cross-hole acoustic wave reflection imaging method includes:

[0024] Step 100: Sending an imaging instruction to a coded acoustic wave transmitting component through data analysis and processing software; wherein the coded acoustic wave transmitting component is currently at a first position.

[0025] Specifically, the coded acoustic wave transmitting assembly includes an acoustic wave receiver 1, an acoustic wave transmitter 2, an acoustic wave transmitting probe 5, and an acoustic wave transmitting cable 7; the coded acoustic wave receiving assembly includes an acoustic wave receiving sensor 4. The acoustic wave receiving cable 6 is connected to the acoustic wave receiving sensor string 4, and the acoustic wave receiving sensor string 4 is placed and suspended at the bottom of the receiving borehole 8, ensuring that the sensors on the acoustic wave receiving sensor string 4 are in a suspended state. The acoustic wave receiving cable 6 is connected to the acoustic wave receiver 1 via a cable bracket 11. The acoustic wave transmitting cable 7 is connected to the acoustic wave transmitting probe 5 and placed at the bottom of the transmitting borehole 9. The acoustic wave transmitting cable 7 is connected to the acoustic wave transmitter 2 via a cable bracket 11. The acoustic wave receiver 1 and the acoustic wave transmitter 2 are connected for communication and control via a cable or wireless network connection, and are respectively arranged near the receiving borehole 8 and the transmitting borehole 9. The data analysis and processing software uses a computer and processing analysis software 3, which is used to control the operation of the acoustic wave receiver 1, and sends the data to the acoustic wave receiver 1 via a wired or wireless network. The acoustic wave receiver 1 then transmits the data to the acoustic wave transmitter 2 via a wireless or wired network. This process is not limited by distance. The receiving borehole 8 and the transmitting borehole 9 are filled with a liquid acoustic wave propagation medium (such as water 10). The elevation of the bottom of the receiving borehole 8 and the bottom of the transmitting borehole 9 are as high as possible. The corresponding first position can be the height of the lowest acoustic wave receiving sensor in the acoustic wave receiving sensor string 4, corresponding to the position in the transmitting borehole 9.

[0026] The acoustic wave transmitting probe 5 is a piezoelectric ceramic probe, a giant magnetostrictive probe, an electric spark probe, or an explosive source. The acoustic wave receiving sensor string 4 comprises sensors made of piezoelectric ceramic tubes, which receive all information about the transmitted acoustic wave signals 12 and reflected acoustic wave signals 13 around the borehole by receiving water 10 in the borehole 8.

[0027] Step 200: Based on the imaging instruction, the coded acoustic wave transmitting assembly is used to generate a set of coded acoustic wave signals of different frequencies according to a preset modulation and coding strategy, and propagate the signals to the surrounding strata of the transmitting borehole; wherein the coded acoustic wave signals generated by the coded acoustic wave transmitting assembly are spherical point source acoustic waves, which propagate in all directions to the surrounding strata through the liquid acoustic wave propagation medium contained in the transmitting borehole.

[0028] Specifically, the acoustic wave receiver 1 starts working according to the imaging instruction and generates an acoustic wave emission control instruction; the acoustic wave transmitter 2 generates a driving signal according to the acoustic wave emission control instruction; the acoustic wave transmitting probe 5 generates an acoustic wave signal according to the driving signal and transmits it to the strata around the borehole through the water 10 in the transmitting borehole 9; when there is a geological body 15 with different wave impedance in the stratum 14 outside the line between the receiving borehole 8 and the transmitting borehole 9, a reflected acoustic wave signal 13 will be generated when the transmitted acoustic wave signal 12 propagates to the geological body 15, and the reflected acoustic wave signal 13 will propagate to the receiving borehole 8.

[0029] In step 300, a coded acoustic wave receiving assembly receives all directly transmitted acoustic wave signals propagating through the stratum to the receiving borehole, as well as all coded reflected acoustic wave signals reflected by geological bodies within the stratum, and generates corresponding coded electrical signals. Specifically, the transmitted acoustic wave signals 12 and reflected acoustic wave signals 13 are transmitted to the water 10 in the receiving borehole 8 and sensed by the acoustic wave receiving sensor string 4, generating corresponding coded electrical signals.

[0030] Step 400: convert all the coded electrical signals into coded acoustic digital signals by the coded acoustic wave transmitting component, specifically by converting all the coded electrical signals into coded acoustic digital signals by the acoustic wave receiver 1.

[0031] Step 500: All the coded acoustic wave digital signals are interpreted by the data analysis and processing software based on the preset modulation and coding strategy to identify the transmitted acoustic wave signal and the reflected acoustic wave signal, and the time and amplitude of the reflected acoustic wave signal are extracted, and a coded acoustic wave detection is marked as completed.

[0032] In an application example, all the coded sound wave digital signals are interpreted by the data analysis and processing software based on the preset modulation and coding strategy to analyze the transmitted sound wave signal and the reflected sound wave signal, including: all the coded sound wave digital signals are interpreted by the data analysis and processing software based on the preset modulation and coding strategy to obtain transmitted sound wave signals corresponding to different frequencies; the first wave time in the transmitted sound wave signal is extracted; and the wave signal received after a preset time interval with the first wave time as the starting moment is marked as a reflected sound wave signal.

[0033] In step 600, if the total number of coded acoustic wave detections does not reach the preset number, the first position is updated to the next position, and then the process returns to the step of using the coded acoustic wave transmitting component to generate a set of coded acoustic wave signals of different frequencies according to a preset modulation coding strategy and propagate them to the surrounding strata of the transmitting borehole.

[0034] In an application example, the coded sound wave receiving component includes multiple coded sound wave receiving sensors; all the coded sound wave receiving sensors are arranged at equal intervals on a straight line; the coded sound wave transmitting component includes a sound wave transmitting probe 5; the step of updating the first position to the next position includes: lifting the sound wave transmitting probe 5 upward by a displacement value to reach the next position; the displacement value is equal to the value of the distance between two adjacent coded sound wave receiving sensors, that is, when the position is updated, the sound wave transmitting probe 5 is raised by a transmitting point distance.

[0035] In step 700, if the total number of coded acoustic wave detections reaches a preset number, a three-dimensional formation impedance imaging map of the strata beyond the line connecting the transmitting borehole and the receiving borehole is determined based on the time and amplitude of the reflected acoustic wave signal corresponding to any frequency. Corresponding to the above application example, when the total number of coded acoustic wave detections reaches the preset number, the acoustic wave transmitting probe 5 is raised to the height of the topmost acoustic wave receiving sensor in the acoustic wave receiving sensor string 4.

[0036] In one application example, the cross-hole acoustic wave reflection imaging method further includes: analyzing the three-dimensional stratum wave impedance imaging map by the data analysis and processing software to determine the state of the geological body in the stratum; the state of the geological body is whether the geological body exists or does not exist. That is, the computer and processing analysis software 3 analyze the time and amplitude of the reflected acoustic wave signal 3, analyze whether there is a geological body 15 in the stratum 14 outside the line connecting the transmitting borehole 9 and the receiving borehole 8, and finally generate a three-dimensional imaging map of the stratum 14 outside the line connecting the two boreholes. The geological information of the geological body 15 can be analyzed through three-dimensional slicing, such as Figure 4 When a geological body 15 with varying wave impedance exists in the stratum 14, a reflected acoustic wave signal 13 is generated. The analysis method is to perform calculation and analysis based on the principle of acoustic wave reflection, i.e., to analyze the three-dimensional stratum wave impedance imaging map using the data analysis and processing software, using the following formula:

[0037] A R =A0R.

[0038]

[0039] z1=ρ1v1;z2=ρ2v2.

[0040] Among them, A R is the amplitude of the reflected sound wave generated by the geological body, A0 is the amplitude of the coded sound wave signal emitted by the coded sound wave transmitting component when it propagates to the surface of the geological body, R is the reflection wave coefficient of the geological body; z1 is the wave impedance of the formation; Z2 is the wave impedance of the geological body; v1 is the sound wave velocity of the formation, v2 is the sound wave velocity of the geological body, ρ1 is the rock density of the formation, and ρ2 is the rock density of the geological body.

[0041] In another application example, the cross-hole acoustic wave reflection imaging method further includes: displaying the three-dimensional formation wave impedance imaging map by the data analysis and processing software.

[0042] In another application example, the present application also uses a computer and processing and analysis software to read the first wave time and amplitude of the transmitted acoustic wave signal, calculate a two-dimensional acoustic wave velocity profile image and a two-dimensional acoustic wave amplitude attenuation profile image of the stratum 14 between the transmitting borehole 9 and the receiving borehole 8, and analyze the changes in the stratum based on the two parameters of acoustic wave velocity and amplitude attenuation, thereby more accurately analyzing the stratum information. Furthermore, through cross-hole acoustic wave detection between two boreholes, it is possible to simultaneously complete the detection of acoustic wave reflection strata beyond the connecting line between the two boreholes and the tomographic detection of acoustic wave transmission strata between the two boreholes.

[0043] In summary, the present invention has the ability to detect and image the strata between and outside the line connecting the two boreholes, thereby increasing the detection range of the two holes and improving the ability of various engineering projects to detect abnormal bodies (such as karst, sinkholes, fissures, cracks, fracture zones, weak interlayers, underground cavities and unidentified buried objects), greatly reducing the number of geological boreholes, drilling costs and detection time, and has great social value and economic benefits.

[0044] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0045] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A cross-hole acoustic wave reflection imaging method, characterized in that: The cross-hole acoustic wave reflection imaging method comprises: Sending an imaging instruction to the coded acoustic wave transmitting component through the data analysis and processing software; wherein the coded acoustic wave transmitting component is currently at a first position; Based on the imaging instructions, the coded acoustic wave transmitting assembly is used to generate a set of coded acoustic wave signals of different frequencies according to a preset modulation and coding strategy and transmit the signals to the surrounding strata of the transmitting borehole; A coded acoustic wave receiving assembly is used to receive all direct transmission wave signals of coded acoustic waves propagating through the stratum to the receiving borehole and all coded reflection wave signals reflected by geological bodies in the stratum, and to induce and generate corresponding coded electrical signals; Convert all the coded electrical signals into coded sound wave digital signals through the coded sound wave transmitting component; Decoding all the coded acoustic wave digital signals based on the preset modulation and coding strategy by the data analysis and processing software to analyze the transmitted acoustic wave signal and the reflected acoustic wave signal, extract the time and amplitude of the reflected acoustic wave signal, and mark the completion of one coded acoustic wave detection; If the total number of coded acoustic wave detections does not reach a preset number, updating the first position to a next position, and then returning to the step of using the coded acoustic wave transmitting component to generate a set of coded acoustic wave signals of different frequencies according to a preset modulation and coding strategy and transmitting them to the surrounding strata of the transmitting borehole; If the total number of coded acoustic wave detections reaches a preset number, a three-dimensional formation wave impedance imaging map of the strata outside the line connecting the transmitting borehole and the receiving borehole is determined based on the time and amplitude of the reflected acoustic wave signal corresponding to any frequency.

2. The cross-hole acoustic wave reflection imaging method according to claim 1, characterized in that: Decoding all the coded acoustic wave digital signals based on the preset modulation and coding strategy by the data analysis and processing software to analyze the transmitted acoustic wave signals and the reflected acoustic wave signals, including: Decoding all the coded acoustic wave digital signals based on the preset modulation and coding strategy by the data analysis and processing software to obtain transmitted acoustic wave signals corresponding to different frequencies; Extracting the first wave time in the transmitted acoustic wave signal; Taking the first wave time as the starting moment, the wave signal received after a preset time interval is marked as a reflected sound wave signal.

3. The cross-hole acoustic wave reflection imaging method according to claim 1, characterized in that: The cross-hole acoustic wave reflection imaging method further comprises: The three-dimensional stratum wave impedance imaging diagram is analyzed by the data analysis and processing software to determine the state of the geological body in the stratum; the state of the geological body is whether the geological body exists or does not exist.

4. The cross-hole acoustic wave reflection imaging method according to claim 3, characterized in that: The step of analyzing the three-dimensional formation wave impedance imaging map by the data analysis and processing software is implemented using the following formula: A R =A0R; z1=ρ1v1;z2=ρ2v2; Among them, A R is the amplitude of the reflected sound wave generated by the geological body, A0 is the amplitude of the sound wave when the coded sound wave signal emitted by the coded sound wave transmitting component propagates to the surface of the geological body, R is the reflection wave coefficient of the geological body; z1 is the wave impedance of the formation; z2 is the wave impedance of the geological body; v1 is the sound wave velocity of the formation, v2 is the sound wave velocity of the geological body, ρ1 is the rock density of the formation, and ρ2 is the rock density of the geological body.

5. The cross-hole acoustic wave reflection imaging method according to claim 1, characterized in that: The cross-hole acoustic wave reflection imaging method further includes: displaying the three-dimensional formation wave impedance imaging map by the data analysis and processing software.

6. The cross-hole acoustic wave reflection imaging method according to claim 1, characterized in that: The coded acoustic wave signal generated by the coded acoustic wave transmitting assembly is a spherical point source acoustic wave, which propagates in all directions to the surrounding strata through the liquid acoustic wave propagation medium contained in the transmitting borehole.

7. The cross-hole acoustic wave reflection imaging method according to claim 1, characterized in that: The coded sound wave receiving component includes a plurality of coded sound wave receiving sensors; all the coded sound wave receiving sensors are arranged in a straight line with equal spacing; the coded sound wave transmitting component includes a sound wave transmitting probe; The step of updating the first position to the next position includes: lifting the acoustic wave transmitting probe upward by a displacement value to reach the next position; the displacement value is equal to the distance between two adjacent coded acoustic wave receiving sensors.

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