Underground pipeline detection system and method based on cross-hole seismic wave CT inspection technology

Abstract

The invention provides an underground pipeline detection system based on a cross-hole seismic wave CT (Computed Tomography) inspection technology, which comprises a seismic wave emission source device and a signal detection head combination device which respectively extend into a first drill hole and a second drill hole of an underground pipeline, and further comprises a plurality of detectors, a seismograph and an upper computer, the invention also provides a detection method using the system. The method comprises the following steps: acquiring an actually measured transverse wave speed and an actually measured longitudinal wave speed; obtaining a wave velocity image map; preprocessing the surface wave data acquired on site; acquiring a frequency dispersion curve meeting a resolution requirement; carrying out constraint limitation on the shear wave speed to obtain a speculated shear wave speed; inverting the frequency dispersion curve to obtain a relation graph of the speed and the depth of the transverse wave; a final contour map is obtained, and then the wave velocity image map and the contour map are jointly compared and checked; performing contour map analysis to obtain the position and section size data of the underground pipeline; according to the invention, the ultra-deep underground pipeline can be accurately and efficiently detected.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-deep pipeline detection, and in particular to an underground pipeline detection system and method based on cross-hole seismic wave CT inspection technology. Background Art

[0002] With the in-depth development and utilization of underground space resources, the hidden dangers of underground space construction have attracted more and more attention in the industry. Safety accidents caused by unclear pipeline detection occur frequently every year. According to the China Underground Pipeline Accident Report, the economic losses caused by underground pipeline accidents have increased linearly every year, which has been particularly obvious in recent years. For ultra-deep pipelines, especially difficult non-metallic pipelines with complex physical properties and deep buried pipelines, conventional geophysical exploration methods are stretched to the limit, becoming a pain point and difficult problem in the underground pipeline industry. Because the underground space is invisible and intangible, and the objective factors such as complex stratum composition make detection more difficult. Generally, pipelines below three meters deep are ultra-deep pipelines. There is a lack of effective methods to solve the problem of ultra-deep burial in the existing technology, while shallow metal pipelines can be detected by the clamp method, direct connection method or other electromagnetic wave methods of pipeline detectors. However, there is a lack of effective solutions to the problem for metal pipelines below three meters, and non-metallic pipelines below three meters are more difficult and almost impossible to detect accurately. Currently, direct excavation, ground penetrating radar, acoustic wave detection and other methods are commonly used for non-metallic pipeline detection, but their detection depth is relatively shallow and can occasionally solve the problem of detecting non-metallic pipelines above three meters. For non-metallic pipelines below three meters, it is currently difficult to accurately detect them. The industry urgently needs effective detection methods. Summary of the invention

[0003] In view of this, it is necessary to propose an underground pipeline detection system and method based on cross-hole seismic wave CT inspection technology to address the above-mentioned problems, so as to overcome several shortcomings in the above-mentioned background technology and solve the technical problem of how to accurately and efficiently detect ultra-deep underground pipelines.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides an underground pipeline detection system based on cross-hole seismic wave CT inspection technology, including a seismic wave emission source device and a signal detection head assembly device. The underground pipeline detection system is applied to a surface layer with a first borehole and a second borehole drilled therein and provided with an underground pipeline. The top view projection of the first borehole and the top view projection of the second borehole are respectively located on the left and right sides of the cross-sectional view direction of the underground pipeline. The signal detection head assembly device and the seismic wave emission source device extend into the first borehole and the second borehole respectively. The virtual connecting straight line between the orifice center of the first borehole and the orifice center of the second borehole is a virtual connecting line between the two holes. The underground pipeline detection system also includes:

[0006] A plurality of geophones are arranged in a linear array on the ground of the surface layer, thereby forming a virtual straight line of the geophone array formed by virtually connecting the geophones, and the virtual straight line of the geophone array intersects with the underground pipeline in the direction of the top view projection; the virtual straight line of the geophone array coincides with the virtual line connecting the two holes, or the virtual straight line of the geophone array is parallel to the virtual line connecting the two holes and the virtual straight line of the geophone array is located beside the virtual line connecting the two holes;

[0007] The seismograph is connected to the signal detection head assembly device by communication; the seismograph is connected to the control end of the seismic wave transmitting source device by physical medium;

[0008] The host computer is respectively connected to communicate with a plurality of geophones and seismographs; the host computer is provided with an analysis program for analyzing the signals of the geophones and seismographs to obtain the position and related dimensions of the underground pipelines.

[0009] Furthermore, the seismic wave emission source device is an electric spark source; the signal detection head assembly device is a tubular detection device, which includes a tube body and a plurality of hydrophones arranged in the tube body, and the tube body does not block the detection ends of the hydrophones.

[0010] Furthermore, the length of the virtual straight line of the detector array is greater than the length of the virtual line connecting the two holes; the number of the detectors is 40-60; the center distance between two adjacent detectors is 0.3 meters to 0.6 meters; the angle formed by the virtual line connecting the two holes and the underground pipeline is 90°±α, and the value of α is ≤9°; the verticality of the first borehole and the second borehole is 90°±β, and the value of β is ≤1°; the length of the virtual line connecting the two holes is 19 meters to 21 meters; the distance between the vertex of the underground pipeline and the ground of the surface layer is greater than 3 meters.

[0011] Furthermore, the analysis program includes the following software modules:

[0012] The wave velocity image acquisition module acquires the wave velocity image according to the measured shear wave velocity and the measured longitudinal wave velocity; the wave velocity image is used to express the internal structure and abnormal conditions of the stratum;

[0013] A data preprocessing module is used to preprocess the surface wave data collected on site;

[0014] A dispersion curve acquisition module, used to acquire a dispersion curve that meets the resolution requirements;

[0015] An estimated shear wave velocity acquisition module is used to acquire the estimated shear wave velocity;

[0016] An inversion processing module is used to invert the dispersion curve to obtain a relationship diagram between shear wave velocity and depth;

[0017] The profile drawing processing module is used to obtain the final contour map, and then compare and check the wave velocity image map with the contour map, so as to effectively verify the internal structure and abnormal conditions of the surface layer, distinguish them from the independent abnormalities of the target pipeline, and accurately find the target underground pipeline;

[0018] The contour map analysis module is used to perform contour map analysis and obtain the location and cross-sectional size data of underground pipelines.

[0019] The present invention further proposes a detection method of an underground pipeline detection system based on cross-hole seismic wave CT inspection technology using any one of the above, comprising:

[0020] Step S1, obtaining the measured shear wave velocity and the measured longitudinal wave velocity;

[0021] The process of obtaining the measured shear wave velocity includes steps S111 to S114:

[0022] Step S111, drilling: drilling a first borehole and a second borehole in the surface layer where the underground pipeline is located, wherein the top view projection of the first borehole and the top view projection of the second borehole are respectively located on the left and right sides of the cross-sectional view direction of the underground pipeline;

[0023] Step S112, extending the signal detection head assembly device and the seismic wave transmitting source device into the first borehole and the second borehole respectively;

[0024] Step S113, the seismic wave transmitting source device sequentially transmits multiple seismic wave signals from shallow to deep;

[0025] Step S114, the signal detection head assembly device collects seismic wave signals and transmits the seismic wave signals to the host computer for internal processing;

[0026] The process of obtaining the measured longitudinal wave velocity is:

[0027] Arrange multiple detectors in a linear array on a virtual straight line of the detector array, and use the midpoint of the detector array composed of the detectors arranged in the linear array as a detection positioning point; a plurality of adjacent test points with equal spacing distances are set between the virtual line connecting the two holes, and each test point is tested respectively by aligning the detection positioning point with the test point, and each test point is tested by hammering the ground at different positions multiple times with a standard penetration hammer as a seismic source and collecting data through each detector; the center of the orifice of the first borehole is the first test point on the virtual line connecting the two holes, and the center of the orifice of the second borehole is the last test point on the virtual line connecting the two holes;

[0028] Step S3, obtaining a wave velocity image according to the measured shear wave velocity and the measured longitudinal wave velocity; the wave velocity image is used to express the internal structure and abnormal conditions of the formation;

[0029] Step S4, preprocessing the surface wave data collected on site;

[0030] Step S5, obtaining a dispersion curve that meets the resolution requirement;

[0031] Step S6, constraining the shear wave velocity to obtain an estimated shear wave velocity;

[0032] Step S7, inverting the dispersion curve to obtain a relationship diagram between shear wave velocity and depth;

[0033] Step S8, generating a relationship diagram between shear wave velocity and depth for each group of geophone queues in the detection area, generating a shear wave velocity depth profile, performing moving average smoothing on the profile to obtain a final contour map, and then jointly comparing and checking the velocity image map with the contour map;

[0034] Step S9, performing contour map analysis to obtain the location and cross-sectional size data of the underground pipeline.

[0035] Furthermore, in the process of obtaining the measured longitudinal wave velocity in step S1, when testing a test point, the ground surface layer located on the left side of the underground pipeline is hammered N times with a standard penetration hammer, and the ground surface layer located on the right side of the underground pipeline is hammered N times with a standard penetration hammer.

[0036] Further, step S3 includes the following steps:

[0037] Step S31, performing cross-hole CT data processing: first selecting the first arrival time of the collected cross-hole CT data, using the spacing value of the two cross-holes and a formula (1) and a formula (2) to obtain the P-wave velocity value distribution of the square grid unit with a first fixed size by using an algebraic reconstruction iterative algorithm, and obtaining the high-precision P-wave velocity value distribution of the square grid unit with a second fixed size by using the least squares difference and encryption, so that the P-wave velocity values ​​of the same coordinates in the shear wave velocity image are associated one by one;

[0038] Formula (1) is:

[0039]

[0040] Formula (2) is:

[0041]

[0042] In formula (1), l nm is the path length of the nth ray in the mth unit, S m is the slowness of the mth unit, t n is the travel time of the nth ray;

[0043] In formula (2), Si represents the slowness of the i-th unit, and Vi represents the longitudinal wave velocity of the i-th unit;

[0044] Step S32, combining the P-wave velocity values ​​of the square intervals with the second fixed size within the detection range between the first borehole and the second borehole with the depth data of the corresponding P-wave velocity values, to generate a wave velocity image, using different colors to represent different velocity intervals.

[0045] Further, step S4 includes the following steps:

[0046] Step S41, calibrating the detector;

[0047] Step S42, using a GNSS receiver to collect the coordinates and elevation of each detector, and adding the coordinate and elevation data during data processing.

[0048] Further, step S5 includes the following steps:

[0049] Step S51, when the detector array composed of the detectors arranged in a linear array collects the first set of waveform record data of the first test point, the method of identifying the strongest noise in the record is used to extract and separate the artificial source and natural source waveform record diagrams at the strongest position; the first set of waveform record data includes test data of twice N (2N) times performed by the standard penetration hammer;

[0050] Step S52, the extracted artificial source waveform record is interpolated between seismic traces using wavelet transform;

[0051] Step S53, using a τ-p transformation algorithm to extract a dispersion energy map, and extracting the strongest signal as the dispersion curve of the group of data according to the dispersion energy map;

[0052] Step S54, when the detector queue composed of the detectors arranged in a linear array collects the first test point, the detector queue at this time is the first group of detectors, and the N times (2N) groups of artificial source surface wave data separated from the first group of waveform recording data are processed to obtain an artificial source surface wave dispersion diagram and an artificial source dispersion curve, and the artificial source dispersion curve corresponding to the N times (2N) groups of artificial source surface wave data separated from the first group of waveform recording data are energy-weighted fused, and the artificial source dispersion curves of the N times (2N) groups are weighted fused, thereby completing the weighted fusion of the final dispersion diagram of the artificial source surface wave and the artificial source dispersion curve;

[0053] Simultaneously or in no particular order, the natural source waveform record data separated from the first set of waveform record data are used to extract a natural source surface wave dispersion energy map using an extended spatial autocorrelation (ESPAC) method;

[0054] Step S55, processing the N times (2N) groups of natural source surface wave data separated from the first group of waveform record data to obtain a natural source surface wave dispersion diagram and a natural source dispersion curve, and performing energy equal-weighted fusion on the N times (2N) groups of natural source dispersion curves, thereby completing the energy equal-weighted fusion of the final dispersion diagram of the natural source surface wave and the natural source dispersion curve;

[0055] Step S56, integrating or summing the squares of the amplitudes of the artificial and natural surface wave signals near the frequency f to obtain energy E1(f) and energy E2(f). The dispersion curve of the artificial surface wave is D1(f), and the dispersion curve of the natural surface wave is D2(f). The energy proportions of the artificial and natural surface waves at each frequency are calculated and expressed as weights: Artificial surface wave weight:

[0056]

[0057] Natural source surface wave weight:

[0058]

[0059] The fused dispersion curve:

[0060] D(f)=P1(f)D1(f)+P2(f)D2(f) (5);

[0061] In step S5 , the remaining test points other than the first test point are all executed in the manner of steps S51 to S56 , so as to obtain the fused dispersion curves of the remaining test points other than the first test point in a one-to-one correspondence.

[0062] Further, step S6 includes the following steps:

[0063] Step S61, constraining the range of the Poisson's ratio and the measured longitudinal wave velocity by obtaining the range of the estimated transverse wave velocity through a formula (6); formula (6) is:

[0064]

[0065] In formula (6), V p is the longitudinal wave velocity, V s is the shear wave velocity, v is the Poisson’s ratio, The porosity is calculated by injecting mercury into the cores of the two previous boreholes. Φ is the medium inhomogeneity coefficient. The standard deviation σ of all longitudinal wave velocities inverted by cross-hole CT is obtained. It is calculated based on the amount of mercury that enters the pores of the cores at different pressures after mercury is injected into the cores taken from the two boreholes;

[0066] Step S62, comparing the estimated shear wave velocity range with the measured shear wave velocity, and resampling or correction is performed again when the measured shear wave velocity does not meet the set requirements until the best dispersion curve is obtained;

[0067] Step S63, according to the relationship between the shear wave velocity and the frequency, using λ=V / f and the half-wavelength empirical formula h=0.5λ, and using the damped least squares method to invert the dispersion curve to obtain the relationship between the shear wave velocity and the depth, and obtain the relationship diagram between the shear wave velocity and the depth of the optimal dispersion curve; wherein λ is the wavelength, f is the frequency, and h is the depth;

[0068] In step S6, the remaining test points other than the first test point are all executed according to the method of steps S61 to S63, so as to obtain the relationship diagram between the shear wave velocity and the depth of the best dispersion curves of the remaining test points other than the first test point one by one.

[0069] Furthermore, when the medium of the surface layer being detected is isotropic, the Poisson's ratio formula is set as:

[0070]

[0071] In formula (7), the porosity is 1, the medium inhomogeneity coefficient Φ is 0; K is a constant: its value is between 1.5 and 2.5; v is Poisson's ratio.

[0072] The beneficial effects of the present invention are:

[0073] The present invention can accurately and efficiently detect ultra-deep underground pipelines, thereby quickly obtaining the accurate buried depth, location and pipe diameter of the underground pipeline, solving the problem of effective detection of ultra-deep underground pipelines that cannot be solved in the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The accompanying drawings are included to provide a further understanding of the present invention, and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description, are used to explain the principles of the present invention. These drawings are for illustration only and are not intended to limit the present invention.

[0075] Figure 1 It is a three-dimensional structural schematic diagram of an underground pipeline detection system based on cross-hole seismic wave CT inspection technology in the present invention in conjunction with a first borehole, a second borehole, and a standard penetration hammer;

[0076] Figure 2 A recording diagram of the original waveform collected by a group of detector arrays involved in the present invention

[0077] Figure 3 It is a relationship effect diagram of the artificial source surface wave dispersion energy diagram and the dispersion curve involved in the present invention;

[0078] Figure 4 It is a relationship effect diagram between the natural source surface wave dispersion energy diagram and the dispersion curve involved in the present invention;

[0079] Figure 5 It is a relationship effect diagram of the fusion of high-resolution dispersion energy diagram and dispersion curve involved in the present invention;

[0080] Figure 6 A graph showing the relationship between shear wave velocity and depth involved in the present invention;

[0081] Figure 7 This is a profile diagram of the detection depth and shear wave velocity contour lines of the No. 12 drainage pipeline of the flood control project in Jiangkou Town, Fengkai, Guangdong Province, which the present invention involves;

[0082] Figure 8 This is a profile diagram of the detection depth and transverse wave velocity contour lines of the No. 14 drainage pipeline of the flood control project in Jiangkou Town, Fengkai, Guangdong Province, which the present invention involves;

[0083] Description of reference numerals:

[0084] Seismic wave transmitting source device 1; signal detection head assembly device 2; first borehole 3; second borehole 4; detector 5; seismograph 6; host computer 7; two-hole virtual connection line 9; detector array virtual straight line 8; standard penetration hammer 10. DETAILED DESCRIPTION

[0085] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be further clearly and completely described in combination with the embodiments of the present invention. It should be noted that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0086] The terms "first", "second", "third", "fourth", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the definition of "first", "second", "third", "fourth" features may explicitly or implicitly include one or more of the features.

[0087] The following is a detailed description of an embodiment of the invention depicted in the accompanying drawings. The embodiments are detailed in order to clearly convey the invention. However, the number of details provided is not intended to limit the intended variations of the embodiments; on the contrary, the intention is to cover all modifications, equivalents, and substitutes that fall within the spirit and scope of the invention as defined by the appended claims.

[0088] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.

[0089] Embodiments of the present invention include various steps, which are described below. These steps can be performed by hardware components, or can be contained in machine executable instructions, which can be used for general or special purpose processors programmed with instructions to perform these steps. Alternatively, the steps can be performed by a combination of hardware, software and firmware and / or a human operator.

[0090] The various methods described herein can be practiced by combining one or more machine-readable storage media containing codes according to the present invention with appropriate standard computer hardware to execute the codes contained therein. Apparatus for implementing various embodiments of the present invention may include one or more computers (or one or more processors within a single computer) and a storage system containing or having network access to computer programs encoded according to the various methods described herein, and the method steps of the present invention may be completed by modules, routines, subroutines or sub-parts of a computer program product.

[0091] If the specification states that a component or feature "may," "could," "might," or "might" include or have a feature, that particular component or feature is not required to be included or have that feature.

[0092] As used in the specification herein and the claims that follow, the meanings of “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

[0093] Exemplary embodiments will now be described more fully below with reference to the accompanying drawings, in which exemplary embodiments are shown. These exemplary embodiments are provided for illustrative purposes only, and so that the present invention is thorough and complete, and the scope of the present invention is fully conveyed to those of ordinary skill in the art. However, the disclosed invention can be implemented in many different forms and should not be interpreted as being limited to the embodiments set forth herein. Various modifications are apparent to those skilled in the art. Without departing from the spirit and scope of the present invention, the general principles defined herein can be applied to other embodiments and applications. In addition, all statements of the embodiments of the present invention and their specific examples described herein are intended to cover their structural and functional equivalents. In addition, these equivalents are intended to include currently known equivalents and equivalents developed in the future (i.e., any element developed to perform the same function, regardless of the structure). Moreover, the terms and wording used are for the purpose of describing exemplary embodiments and should not be considered restrictive. Therefore, the present invention will be given the widest scope, including multiple replacements, modifications and equivalents consistent with the disclosed principles and features. For the sake of clarity, the details of the technical materials known in the technical field related to the present invention are not described in detail, so as not to unnecessarily obscure the present invention.

[0094] Therefore, for example, it will be understood by those of ordinary skill in the art that schematic diagrams, schematic diagrams, diagrams, etc. represent conceptual views or processes that embody the systems and methods of the present invention. The functions of the various elements shown in the figures can be provided by using dedicated hardware and hardware capable of executing related software. Similarly, any switches shown in the figures are only conceptual. Their functions can be performed by the operation of program logic, by dedicated logic, by the interaction of program control and dedicated logic, or even manually, and specific techniques can be selected by the entity that implements the present invention. It will be further understood by those of ordinary skill in the art that the exemplary hardware, software, processes, methods and / or operating systems described herein are for illustrative purposes and are therefore not intended to be limited to any specific named elements.

[0095] Embodiments of the present invention may be provided as a computer program product, which may include a machine-readable storage medium on which instructions are tangibly implemented, which may be used to program a computer (or other electronic device) to perform a process. The term "machine-readable storage medium" or "computer-readable storage medium" includes, but is not limited to, fixed (hardware) drives, tapes, floppy disks, optical disks, optical disk read-only memories (CD-ROMs)) and magneto-optical disks, semiconductor memories such as ROMs, PROMs, random access memories (RAMs), programmable read-only memories (PROMs), erasable PROMs (EPROMs), electrically erasable PROMs (EEPROMs), flash memory, magnetic or optical cards, or other types of media / machine-readable media suitable for storing electronic instructions (e.g., computer programming code, such as software or firmware). Machine-readable media may include non-transitory media in which data may be stored and does not include carrier waves and / or transient electronic signals propagated by wireless or wired connections. Examples of non-transitory media may include, but are not limited to, disks or tapes, optical storage media such as compact disks (CDs) or digital versatile disks (DVDs), flash memory, memory or memory devices. A computer program product may include code and / or machine executable instructions, which may represent any combination of a process, function, subprogram, program, routine, subroutine, module, software package, class, or instruction, data structure, or program statement. A code segment may be coupled to another code segment or a hardware circuit by passing and / or receiving information, data, variables, parameters, or memory contents. Information, variables, parameters, data, etc. may be passed, forwarded, or transmitted by any suitable means, including memory sharing, message passing, token passing, network transmission, etc.

[0096] In addition, the embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description language, or any combination thereof. When implemented in software, firmware, middleware, or microcode, the program code or code segments (e.g., computer program products) that perform the necessary tasks may be stored in a machine-readable medium. A processor may perform the necessary tasks.

[0097] The systems depicted in some of the figures may be provided in various configurations. In some embodiments, the system may be configured as a distributed system, where one or more components of the system are distributed over one or more networks in a cloud computing system.

[0098] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer only to certain specific embodiments. In other cases, it should be recognized that references to the "invention" will refer to the subject matter recited in one or more, but not necessarily all, of the claims.

[0099] Unless otherwise specified herein or the context is clearly contradictory, all methods described herein can be performed in any suitable order. The use of any and all examples or exemplary language (e.g., "such as") provided with respect to certain embodiments herein is intended only to better illustrate the present invention, rather than to limit the scope of the claimed invention. Any language in the specification should not be interpreted as indicating any unclaimed element essential to the implementation of the present invention.

[0100] Various terms used herein are listed below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the relevant art have given that term as reflected in printed publications and issued patents at the time of filing the application.

[0101] Example 1

[0102] like Figure 1 As shown:

[0103] This embodiment proposes an underground pipeline detection system based on cross-hole seismic wave CT inspection technology, including a seismic wave emission source device 1 and a signal detection head assembly device 2. The underground pipeline detection system is applied to a surface layer with a first borehole 3 and a second borehole 4 drilled therein and provided with an underground pipeline. The top-view projection of the first borehole 3 and the top-view projection of the second borehole 4 are respectively located on the left and right sides of the cross-sectional view of the underground pipeline. The signal detection head assembly device 2 and the seismic wave emission source device 1 extend into the first borehole 3 and the second borehole 4 respectively. The virtual connecting straight line between the orifice center of the first borehole 3 and the orifice center of the second borehole 4 is a two-hole virtual connecting line 9. The underground pipeline detection system also includes:

[0104] A plurality of geophones 5 are arranged in a linear array on the ground of the surface layer, thereby forming a geophone array virtual straight line 8 formed by virtually connecting the geophones 5, and the geophone array virtual straight line 8 intersects with the underground pipeline in the top view projection direction; the geophone array virtual straight line 8 coincides with the two-hole virtual connecting line 9, or the geophone array virtual straight line 8 is parallel to the two-hole virtual connecting line 9 and the geophone array virtual straight line 8 is located beside the two-hole virtual connecting line 9;

[0105] The seismograph 6 is connected to the signal detection head assembly device 2 in communication; the seismograph 6 is connected to the control end of the seismic wave emission source device 1 in physical medium;

[0106] The host computer 7 is connected to communicate with the plurality of geophones 5 and seismographs 6 respectively; the host computer 7 is provided with an analysis program for analyzing the signals of the geophones 5 and seismographs 6 to obtain the position and related dimensions of the underground pipelines.

[0107] The underground pipeline detection system based on the cross-hole seismic wave CT inspection technology of this embodiment can accurately and efficiently detect ultra-deep underground pipelines below three meters.

[0108] Optimally, the seismic wave transmitting source device 1 is an electric spark source; the signal detection head assembly device 2 is a tubular detection device, which includes a tube body and a plurality of hydrophones arranged in the tube body, and the tube body does not block the detection end of each hydrophone.

[0109] Optimally, the length of the detector array virtual straight line 8 is greater than the length of the two-hole virtual line 9; the number of the detectors 5 is 40-60 (preferably 50); the center distance between two adjacent detectors 5 is 0.3 m-0.6 m (preferably 0.5 m); the angle formed by the two-hole virtual line 9 and the underground pipeline is 90°±α, and the value of α is ≤9°; the borehole verticality of the first borehole 3 and the second borehole 4 is 90°±β, and the value of β is ≤1°; the length of the two-hole virtual line 9 is 19 m-21 m (preferably 20 m); the distance between the vertex of the underground pipeline and the ground of the surface layer is greater than 3 meters.

[0110] Optimally, the analysis program includes the following software modules:

[0111] Wave velocity image acquisition module, used to express the internal structure and abnormal conditions of the strata;

[0112] A data preprocessing module is used to preprocess the surface wave data collected on site;

[0113] A dispersion curve acquisition module, used to acquire a dispersion curve that meets the resolution requirements;

[0114] An estimated shear wave velocity acquisition module is used to acquire the estimated shear wave velocity;

[0115] An inversion processing module is used to invert the dispersion curve to obtain a relationship diagram between shear wave velocity and depth;

[0116] The profile drawing processing module is used to obtain the final contour map, and then compare and check the wave velocity image map with the contour map, so as to effectively verify the internal structure and abnormal conditions of the surface layer, distinguish them from the independent abnormalities of the target pipeline, and accurately find the target underground pipeline;

[0117] The contour map analysis module is used to perform contour map analysis and obtain the location and cross-sectional size data of underground pipelines.

[0118] Specifically, the contour map analysis module analyzes the sudden abnormalities in the non-metallic pipeline in combination with the actual environment, thereby obtaining the location of the underground pipeline and the cross-sectional dimension data of the non-metallic pipeline.

[0119] Further optimized, the data preprocessing module is used to resample, calibrate instruments, correct terrain, eliminate interference, remove linear trends, remove averaging and filter the surface wave data collected in the field.

[0120] Further optimized, the dispersion curve acquisition module is used to fuse the received longitudinal wave velocity data by setting the Poisson's ratio, constrain the range of the received shear wave velocity by the received longitudinal wave velocity, perform multiple iterations and converge, and judge the shear wave velocity and depth relationship diagram that meets the best dispersion curve according to the mean square error conversion rate; then repeat the above steps to obtain the shear wave velocity and depth relationship diagram of all groups of detector arrays in the detection area, and finally, according to the relationship between the shear wave velocity and the frequency, use λ=V / f and the half-wavelength empirical formula h=0.5λ, and use the damped least squares method to invert the dispersion curve to obtain the relationship between the shear wave velocity and the depth.

[0121] Further optimized, the profile drawing processing module generates a shear wave velocity depth profile based on the relationship diagram between shear wave velocity and depth for the central exploration point of each group of detector arrays in the detection area, performs moving average smoothing on the shear wave velocity depth profile, generates surfer drawing data, draws the final contour map, and then compares and verifies the wave velocity image map with the contour map;

[0122] Further optimization shows that the non-metallic pipelines show low-speed anomalies. Non-metallic cement pipelines and metal pipelines will form high-speed layered areas due to their hard surface, and the pipes show low-speed anomalies. The contour map analysis module combines the sudden anomalies with the actual environment analysis to find the location and related dimensions of the underground pipelines.

[0123] Example 2

[0124] like Figure 1-Figure 8 As shown:

[0125] Figure 2 The horizontal axis represents the number of detectors, with an interval of 0.5 m, and the vertical axis represents the time of arrival of the surface wave;

[0126] Figure 3 , Figure 4 , Figure 5 , Figure 6 The horizontal axis is the shear wave velocity, and the vertical axis is the frequency;

[0127] Figure 7 It shows that the actual strata in the section area are loose and seriously broken, which is manifested by abnormal low velocity of shear waves. Figure 7 There is a high-speed shear wave anomaly at the location of the red frame, which is judged to be a cement box culvert with a depth of about 3.5m. It was later confirmed to be the target drainage pipeline through drilling.

[0128] Figure 8The cross-section diagram shows that the hard strata are characterized by higher shear wave velocity. Figure 8 There is a low-velocity shear wave anomaly at the red frame, which is in sharp contrast with the surrounding strata. The depth is about 13.5m, which is judged to be the target detection pipeline. After excavation and plugging, it is verified to be a drainage pipeline with a diameter of about 1m.

[0129] This embodiment further proposes a detection method for an underground pipeline detection system based on cross-hole seismic wave CT inspection technology using any one of the technical solutions in Embodiment 1, including steps S1 to S9 performed sequentially:

[0130] Step S1, obtaining the measured shear wave velocity and the measured longitudinal wave velocity;

[0131] The process of obtaining the measured shear wave velocity includes steps S111 to S114 performed sequentially:

[0132] Step S111, drilling: drilling a first borehole 3 and a second borehole 4 in the surface layer where the underground pipeline is located, wherein the top view projection of the first borehole 3 and the top view projection of the second borehole 4 are respectively located on the left and right sides of the cross-sectional view direction of the underground pipeline;

[0133] Step S112, extending the signal detection head assembly device 2 and the seismic wave transmitting source device 1 into the first borehole 3 and the second borehole 4 respectively;

[0134] Step S113, the seismic wave transmitting source device 1 sends out multiple seismic wave signals from shallow to deep in sequence;

[0135] Step S114, the signal detection head assembly device 2 collects seismic wave signals and transmits the seismic wave signals to the host computer 7 for internal processing;

[0136] The process of obtaining the measured longitudinal wave velocity is:

[0137] A plurality of detectors 5 are arranged in a linear array on the virtual straight line 8 of the detector array, and the midpoint of the detector array composed of the detectors 5 arranged in a linear array is used as a detection positioning point; a plurality of adjacent test points with equal spacing distances are set between the two-hole virtual line 9, and each test point is tested respectively by aligning the detection positioning point with the test point, and each test point is tested by hammering the ground multiple times at different positions with a standard penetration hammer 10 as a seismic source, and data is collected through each detector 5; the center of the orifice of the first borehole 3 is the first test point on the virtual line 9 of the two holes, and the center of the orifice of the second borehole 4 is the last test point on the virtual line 9 of the two holes;

[0138] Step S3, obtaining a wave velocity image according to the measured shear wave velocity and the measured longitudinal wave velocity; the wave velocity image is used to express the internal structure and abnormal conditions of the formation;

[0139] Step S4, preprocessing the surface wave data collected on site;

[0140] Step S5, obtaining a dispersion curve that meets the resolution requirement;

[0141] Step S6, constraining the shear wave velocity to obtain an estimated shear wave velocity;

[0142] Step S7, inverting the dispersion curve to obtain a relationship diagram between shear wave velocity and depth;

[0143] Step S8, generating a shear wave velocity depth profile based on the shear wave velocity and depth relationship diagram for each group of geophone queues in the detection area, performing moving average smoothing processing on the profile to obtain the final contour map, and then jointly comparing and checking the velocity image map with the contour map, so as to make the internal structure of the formation and the abnormal situation appear consistent, reduce interference and misjudgment, and distinguish between formation abnormalities and target pipeline abnormalities;

[0144] Step S9, performing contour map analysis to obtain the location and cross-sectional size data of the underground pipeline.

[0145] The detection method of this embodiment can solve the problem of accurate detection of ultra-deep underground pipelines below 3 meters, accurately obtain the spatial coordinates, depth, material, size and other data of ultra-deep underground pipelines, and provide basic data for design layout and project construction; it also has the following advantages:

[0146] Advantages 1. According to empirical values, conventional ground penetrating radar can detect the location of pipelines, and the ratio of its size to depth should be between 1 / 5 and 1 / 3. In areas with high water content, radar waves are easily absorbed, and it is difficult to detect pipelines below 3 meters. When using the acoustic wave method for detection, it is necessary to first find the leak point of the pipeline. The acoustic wave detection method is easily affected by objective noise sources, and the detection depth is shallow, making it difficult to detect deep pipelines. The detection method of the present invention can accurately detect underground pipelines at ultra-deep depths, is less affected by external objective conditions, and will not damage the detected pipelines, which belongs to non-destructive detection.

[0147] Advantage 2: For the first time, the cross-hole seismic wave CT technology combined with the scientific theory of surface wave exploration of stratum boundaries was applied to the field of precise detection technology for ultra-deep underground pipelines, and it was successfully applied in engineering projects with good results, solving the problem of precise detection of ultra-deep underground pipelines;

[0148] Advantage 3: By constraining the shear wave velocity through the longitudinal wave velocity and Poisson's ratio of the cross-hole seismic wave CT inversion, the range of the shear wave velocity can be estimated, reducing the disadvantages of the traditional method of directly inverting the shear wave velocity, and improving the accuracy of the inverted shear wave velocity;

[0149] Advantage 4: The active source and passive source dispersion curves are superimposed and merged, which not only improves the vertical resolution of the dispersion curve, but also improves the horizontal resolution, thereby improving the overall resolution of the dispersion curve;

[0150] Advantage 5: It adopts a node-type three-component micro-motion acquisition station to collect natural source surface wave data from multiple angles, integrates Beidou satellite synchronous timing and high-precision temperature-compensated voltage-controlled clock functions, and the time error range between multiple devices is 25ns-100ns. The timing error is less than 2μs in 1 hour without satellite signal, and it has a differential capacitance displacement force balance accelerometer function to avoid data distortion.

[0151] Advantage 6: In the inversion process, the mean square error conversion rate mathematical model can be used to intelligently determine the relationship between the shear wave velocity and depth that meets the best dispersion curve, reducing the error of traditional manual visual identification of the best fitting dispersion curve.

[0152] Optimally, in the process of obtaining the measured longitudinal wave velocity in step S1, when testing a test point, the ground surface layer located on the left side of the underground pipeline is hammered N times (preferably 3 times) by the standard penetration hammer 10, and the ground surface layer located on the right side of the underground pipeline is hammered N times (preferably 3 times) by the standard penetration hammer 10.

[0153] Optimally, step S3 comprises the following steps:

[0154] Step S31, cross-hole CT data processing: first select the first arrival time of the collected cross-hole CT data, and use the algebraic reconstruction iterative algorithm to obtain the P-wave velocity value distribution of the 0.5m*0.5m grid unit through the spacing value of the two cross-holes and a formula (1) and a formula (2), and obtain the high-precision P-wave velocity value distribution of the 0.1m*0.1m grid unit through the least squares difference and encryption, so that the P-wave velocity values ​​of the same coordinates in the shear wave velocity image map are one-to-one associated;

[0155] Formula (1) is:

[0156]

[0157] Formula (2) is:

[0158]

[0159] In formula (1), l nm is the path length of the nth ray in the mth unit, S m is the slowness of the mth unit, t n is the travel time of the nth ray;

[0160] In formula (2), Si represents the slowness of the i-th unit, and Vi represents the longitudinal wave velocity of the i-th unit;

[0161] Step S32, combining the longitudinal wave velocity values ​​of the square intervals of the second fixed size (specifically 0.1m*0.1m) within the detection range between the first borehole 3 and the second borehole 4 with the depth data of the corresponding longitudinal wave velocity values, to generate a wave velocity image diagram, using different colors to represent different velocity intervals.

[0162] Optimally, step S4 comprises the following steps:

[0163] Step S41, calibrating the detector 5;

[0164] Step S42, using a GNSS receiver to collect the coordinates and elevation of each detector 5, and adding the coordinate and elevation data during data processing.

[0165] Optimally, step S5 comprises the following steps:

[0166] Step S51, when the detector array composed of the detectors 5 arranged in a linear array collects the first set of waveform record data of the first test point, the method of identifying the strongest noise in the record is used to extract and separate the artificial source and natural source waveform record diagrams at the strongest position; the first set of waveform record data includes test data of the standard penetration hammer 10 performing N times (2N) times;

[0167] Step S52, the extracted artificial source waveform record is interpolated between seismic traces using wavelet transform;

[0168] Step S53, using a τ-p transformation algorithm to extract a dispersion energy map, and extracting the strongest signal as the dispersion curve of the group of data according to the dispersion energy map;

[0169] Step S54, when the detector array composed of the detectors 5 arranged in a linear array collects the first test point, the detector array at this time is the first group of detectors 5, and the N times (2N) groups of artificial source surface wave data separated from the first group of waveform recording data are processed to obtain the artificial source surface wave dispersion diagram and the artificial source dispersion curve, and the artificial source dispersion curve corresponding to the N times (2N) groups of artificial source surface wave data separated from the first group of waveform recording data are energy-weighted fused, and the artificial source dispersion curves of the N times (2N) groups are weighted fused, so as to complete the final dispersion diagram of the artificial source surface wave and the weighted fusion of the artificial source dispersion curve;

[0170] Simultaneously or in no particular order, the natural source waveform record data separated from the first set of waveform record data are used to extract a natural source surface wave dispersion energy map using an extended spatial autocorrelation (ESPAC) method;

[0171] Step S55, processing the N times (2N) groups of natural source surface wave data separated from the first group of waveform record data to obtain a natural source surface wave dispersion diagram and a natural source dispersion curve, and performing energy equal-weighted fusion on the N times (2N) groups of natural source dispersion curves, thereby completing the energy equal-weighted fusion of the final dispersion diagram of the natural source surface wave and the natural source dispersion curve;

[0172] Step S56, integrating or summing the squares of the amplitudes of the artificial and natural surface wave signals near the frequency f to obtain energy E1(f) and energy E2(f). The dispersion curve of the artificial surface wave is D1(f), and the dispersion curve of the natural surface wave is D2(f). The energy proportions of the artificial and natural surface waves at each frequency are calculated and expressed as weights: Artificial surface wave weight:

[0173]

[0174] Natural source surface wave weight:

[0175]

[0176] The fused dispersion curve:

[0177] D(f)=P1(f)D1(f)+P2(f)D2(f) (5);

[0178] In step S5 , the remaining test points other than the first test point are all executed in the manner of steps S51 to S56 , so as to obtain the fused dispersion curves of the remaining test points other than the first test point in a one-to-one correspondence.

[0179] Optimally, step S6 comprises the following steps:

[0180] Step S61, constraining the range of the Poisson's ratio and the measured longitudinal wave velocity by obtaining the range of the estimated transverse wave velocity through a formula (6); formula (6) is:

[0181]

[0182] In formula (6), V p is the longitudinal wave velocity, V s is the shear wave velocity, v is the Poisson’s ratio, which is usually between 0.2 and 0.4. is the porosity. The cores are taken from the first two boreholes and mercury is injected. The porosity is calculated according to the amount of mercury entering the core pores under different pressures. Φ is the medium heterogeneity coefficient. The standard deviation σ is obtained by using all the longitudinal wave velocities inverted by cross-hole CT. When σ is 0, it means that the medium is uniform and Φ is 0. When 0<σ≤2, Φ takes the value of 0.1. When σ<2, Φ takes the value of 0.3. K is a constant: the value is between 1.5-2.5 (the value is preferably 2); Porosity It is calculated based on the amount of mercury entering the core pores under different pressures after mercury is injected into the cores taken out from the two boreholes; specifically, Φ is defined as the medium inhomogeneity coefficient, and the error σ is calculated by all longitudinal wave velocities inverted by cross-hole CT. When σ is 0, it means that the medium is uniform and Φ is 0. When 0<σ≤2, Φ takes a value of 0.1, and when σ<2, Φ takes a value of 0.3;

[0183] Step S62, comparing the estimated shear wave velocity range with the measured shear wave velocity, and resampling or correction is performed again when the measured shear wave velocity does not meet the set requirements until the best dispersion curve is obtained;

[0184] Step S63, according to the relationship between the shear wave velocity and the frequency, using λ=V / f and the half-wavelength empirical formula h=0.5λ, and using the damped least squares method to invert the dispersion curve to obtain the relationship between the shear wave velocity and the depth, and obtain the relationship diagram between the shear wave velocity and the depth of the optimal dispersion curve; wherein λ is the wavelength, f is the frequency, and h is the depth;

[0185] In step S6, the remaining test points other than the first test point are all executed according to the method of steps S61 to S63, so as to obtain the relationship diagram between the shear wave velocity and the depth of the best dispersion curves of the remaining test points other than the first test point one by one.

[0186] Optimally, when the media of the surface layer being detected are isotropic, the Poisson's ratio formula is set to:

[0187]

[0188] In formula (7), the porosity is 1, the medium inhomogeneity coefficient Φ is 0, and the meanings of the other symbols in formula (7) are the same as those in formula (6).

[0189] Example 3

[0190] Embodiment 3 is an optimized design of any one of the technical solutions in Embodiment 2;

[0191] In step S112, after the drilling is completed, PVC casing is inserted, and then a high-sensitivity multi-channel hydrophone with an interval of 0.5m is placed in each borehole, and the length of the hydrophone is from the ground to the bottom of the hole. An electric spark source is placed in one hole, and the hydrophone is connected to the seismograph on the ground. The electric spark source is connected to an energy box (that is, the control end of the seismic wave emission source device 1 described in Example 1), and the other end of the energy box is connected to the seismograph. The seismograph is connected to a computer, and the data acquisition work is controlled by a workstation; there is a virtual straight line between the centers of the two boreholes, and the two ends are extended by 20m each.

[0192] In step S113, the spark source is fired from the ground downwards every 0.2 m, and the hydrophone receives seismic data until the spark source reaches the bottom of the hole, completing data collection.

[0193] In step S114, after the cross-hole seismic wave CT acquires data, internal processing is performed to invert the distribution of P-wave velocity values ​​between the two holes according to the 0.5m*0.5m grid unit, and the least square difference method is used to obtain the distribution of P-wave velocity values ​​in the 0.1m*0.1m grid unit.

[0194] In the process of obtaining the measured longitudinal wave velocity in step S1, a standard penetration hammer of more than 50 kg is used as a source to hammer the ground on the left side of the linear array geophone. A piece of iron is placed on the ground. The angle between the iron sheet and the first geophone and the straight line where the geophone is located is as 0° as possible, ensuring that it is less than -9° to 9°. The source position of the hammer is on the same straight line as the center of the geophone and the offset is 3 meters. After collecting the first set of hammering data, move the iron sheet with an offset of 5 meters, hammer again for the second time after an interval of about 10 minutes, move the iron sheet again, the distance between the geophones is 8 meters, hammer again for the third time after an interval of about 10 minutes, the sampling interval of the geophone is 0.1ms, the number of sampling points is 200000, the total acquisition time is about 20 minutes, and a total of 3 sets of data are collected. Move the iron sheet to the right side of the geophone, and also ensure that the source position of the hammer is on the same straight line as the center of the geophone and the offset is 3 meters. After collecting the first set of hammering data, move the iron sheet, the shot distance is 5 meters, and hammer for the second time after about 10 minutes. Move the iron sheet again, the detector spacing is 8 meters, and hammer for the third time after about 10 minutes. The detector sampling interval is 0.1ms, the number of sampling points is 200000, the total acquisition time is about 20 minutes, and a total of 3 sets of data are collected. A total of 6 sets of data are collected in the whole process; specifically, arrange the linear array on the straight line, place 50 detectors, set the detector offset distance to 0.5m, arrange them in sequence from left to right, and make the center of the array overlap with the center of the left borehole, so as to ensure that the first set of waveform data collected by the array is on the vertical line of the center of the borehole; specifically, move the first detector on the far left to the far right, and the distance from the far right detector is also 0.5m, repeat step 2, and obtain the data after moving the array. After a set of array arrangement data is collected, continue to roll and move the leftmost detector to the far right until the center of the array overlaps with the center of the right borehole.

[0195] In step S4, the surface wave data collected on site are resampled, instrument calibrated, terrain corrected, interference eliminated, linear trend removed, averaged, and filtered. After a series of data preprocessing, the detection accuracy is effectively improved.

[0196] In step S5, each group of data collected by the first group of detectors is identified and separated from the waveform record of the artificial source and the natural source by the strongest noise, and the self-developed surface wave processing software is used to first use the wavelet transform to realize the interpolation between seismic traces of each group of original collected data, and the interpolation interval is 0.1m. Then, a τ-p transformation algorithm is used to extract the dispersion energy map of each group of interpolated waveform data of the artificial source surface wave, and the dispersion curve with the strongest signal as the group of data is extracted according to the dispersion energy map, and all the dispersion curves of the left source and the right source are merged to obtain the average dispersion curve of the artificial source surface wave; the extended spatial autocorrelation (ESPAC) method is used to extract the dispersion energy map of the natural source surface wave, and the dispersion curve with the strongest signal as the natural source surface wave is extracted according to the dispersion energy map, and the dispersion curves of the artificial source and the natural source surface wave are merged to form a high-resolution dispersion curve.

[0197] In step S9, the wave velocity image of the cross-hole CT generated above is compared and analyzed to more accurately determine the stratum structure, distinguish it from the abnormality of the underground pipeline, and reduce the possibility of misjudgment due to stratum abnormalities; underground pipelines have their own independent abnormalities due to physical properties, which will not interfere with each other and will be different from stratum abnormalities. Non-metallic pipelines will show low-speed abnormalities. Non-metallic cement pipelines and metal pipelines will form high-speed layered areas due to their hard surfaces, which will show low-speed abnormalities inside the pipes. According to the sudden abnormalities of the pipelines combined with the actual environment analysis, the buried depth and size of the underground pipelines can be accurately found.

[0198] In step S41, a site with relatively uniform geological structure is found, all detectors for collecting data are arranged into a circle, and a standard penetration hammer is used to excite the source at the center of the circle. According to theory, the distance from the source to each detector is consistent, and the amplitude and phase of the wave received by each detector should be consistent. The detectors with inconsistent phases or amplitudes are corrected, and the correction values ​​are added to the data collected by the detector for preprocessing.

[0199] In step S42, a GNSS receiver is used to collect the coordinates and elevation of each detector. When processing the data, the coordinate and elevation data are added instead of treating the elevations of all detectors as the same, so that the recorded point position is more accurate and more in line with the actual situation, and accurate basic data is prepared for the next steps.

[0200] In step S52 , the interpolation interval is 0.1 m.

[0201] Step S5 also includes step S57 executed after step S56: on the basis of energy-weighted fusion, an adaptive mechanism is introduced to dynamically adjust the weight according to the characteristics and quality of the data, and a weight adjustment function based on indicators such as data signal-to-noise ratio and bandwidth is used. When the signal-to-noise ratio of a certain frequency band is high and the frequency band is wide, its weight in this frequency band is automatically increased, and vice versa, the weight is reduced, thereby achieving high-precision fusion of dispersion curves.

[0202] In step S5, after the remaining test points other than the first test point are executed in the manner of steps S51 to S56, the following is executed: on the basis of energy weighted fusion, an adaptive mechanism is introduced to dynamically adjust the weight according to the characteristics and quality of the data, and a weight adjustment function based on indicators such as data signal-to-noise ratio and bandwidth is automatically increased when the signal-to-noise ratio of a certain frequency band is high and the frequency band is wide, and vice versa, the weight is reduced to achieve high-precision fusion of dispersion curves (such as Figure 4 shown).

[0203] In formula (6) of step S6, the range of the shear wave velocity value is obtained by substituting the range value of the Poisson's ratio and the longitudinal wave velocity value; in step S62, after repeated calculations for many times, when there is no unreasonable and obvious difference between the inverted shear wave velocity and the inferred shear wave velocity, the inversion result gradually approaches a fixed value, and a repeated calculation will produce a mean square error change rate. The end of the inversion is determined by continuously observing the mean square error transformation rate of the calculation result. The mean square error change rate represents the overlap between the inverted measured dispersion curve and the original theoretical dispersion curve. When the mean square error change rate approaches 0, it can be found that the original dispersion curve is infinitely close to the measured dispersion curve, and the best dispersion curve can be obtained.

[0204] Example 4

[0205] Embodiment 4 is a further optimized design of Embodiment 1;

[0206] The analysis procedure performs the following control steps:

[0207] According to the measured shear wave velocity and the measured longitudinal wave velocity, a wave velocity image is obtained; the wave velocity image is used to express the internal structure and abnormal conditions of the stratum;

[0208] Preprocess the surface wave data collected on site;

[0209] Obtain a dispersion curve that meets the resolution requirements;

[0210] Constraining the shear wave velocity to obtain the estimated shear wave velocity;

[0211] Invert the dispersion curve to obtain a plot of shear wave velocity versus depth;

[0212] Generate a shear wave velocity depth profile based on the shear wave velocity and depth relationship diagram for each group of geophone queues in the detection area, perform moving average smoothing on the profile to obtain the final contour map, and then compare and verify the velocity image map with the contour map;

[0213] Conduct contour map analysis to obtain the location and cross-sectional size data of underground pipelines.

[0214] Further optimized, the specific implementation process of the above steps is the same as the corresponding steps of the method in Example 2.

[0215] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An underground pipeline detection system based on cross-hole seismic wave CT inspection technology, comprising a seismic wave emission source device and a signal detection head assembly device, the underground pipeline detection system is applied to a surface layer with a first borehole and a second borehole drilled therein and provided with an underground pipeline, the top-view projection of the first borehole and the top-view projection of the second borehole are respectively located on the left and right sides of the cross-sectional viewing direction of the underground pipeline, the signal detection head assembly device and the seismic wave emission source device are respectively extended into the first borehole and the second borehole, the virtual connecting straight line between the orifice center of the first borehole and the orifice center of the second borehole is a virtual connecting line between the two holes, characterized in that: The underground pipeline detection system also includes: A plurality of geophones are arranged in a linear array on the ground of the surface layer, thereby forming a virtual straight line of the geophone array formed by virtually connecting the geophones, and the virtual straight line of the geophone array intersects with the underground pipeline in the direction of the top view projection; the virtual straight line of the geophone array coincides with the virtual line connecting the two holes, or the virtual straight line of the geophone array is parallel to the virtual line connecting the two holes and the virtual straight line of the geophone array is located beside the virtual line connecting the two holes; The seismograph is connected to the signal detection head assembly device by communication; the seismograph is connected to the control end of the seismic wave transmitting source device by physical medium; The host computer is respectively connected to communicate with a plurality of geophones and seismographs; the host computer is provided with an analysis program for analyzing the signals of the geophones and seismographs to obtain the position and related dimensions of the underground pipelines.

2. The underground pipeline detection system based on cross-hole seismic wave CT inspection technology according to claim 1 is characterized in that: The seismic wave transmitting source device is an electric spark source; the signal detection head assembly device is a tubular detection device, which includes a tube body and a plurality of hydrophones arranged in the tube body, and the tube body does not block the detection ends of the hydrophones.

3. The underground pipeline detection system based on cross-hole seismic wave CT inspection technology according to claim 1 is characterized in that: The length of the virtual straight line of the detector array is greater than the length of the virtual line connecting the two holes; the number of the detectors is 40-60; the center distance between two adjacent detectors is 0.3 meters to 0.6 meters; the angle formed by the virtual line connecting the two holes and the underground pipeline is 90°±α, and the value of α is ≤9°; the verticality of the first borehole and the second borehole is 90°±β, and the value of β is ≤1°; the length of the virtual line connecting the two holes is 19 meters to 21 meters; the distance between the vertex of the underground pipeline and the ground of the surface layer is greater than 3 meters.

4. The underground pipeline detection system based on cross-hole seismic wave CT inspection technology according to claim 1 is characterized in that: The analysis program includes the following software modules: The wave velocity image acquisition module acquires the wave velocity image according to the measured shear wave velocity and the measured longitudinal wave velocity; the wave velocity image is used to express the internal structure and abnormal conditions of the stratum; A data preprocessing module is used to preprocess the surface wave data collected on site; A dispersion curve acquisition module, used to acquire a dispersion curve that meets the resolution requirements; An estimated shear wave velocity acquisition module is used to acquire the estimated shear wave velocity; An inversion processing module is used to invert the dispersion curve to obtain a relationship diagram between shear wave velocity and depth; The profile drawing processing module is used to obtain the final contour map, and then compare and check the wave velocity image map with the contour map, so as to effectively verify the internal structure and abnormal conditions of the surface layer, distinguish them from the independent abnormalities of the target pipeline, and accurately find the target underground pipeline; The contour map analysis module is used to perform contour map analysis and obtain the location and cross-sectional size data of underground pipelines.

5. A detection method for underground pipeline detection system based on cross-hole seismic wave CT inspection technology using any one of claims 1 to 4, characterized in that: include: Step S1, obtaining the measured shear wave velocity and the measured longitudinal wave velocity; The process of obtaining the measured shear wave velocity includes steps S111 to S114: Step S111, drilling: drilling a first borehole and a second borehole in the surface layer where the underground pipeline is located, wherein the top view projection of the first borehole and the top view projection of the second borehole are respectively located on the left and right sides of the cross-sectional view direction of the underground pipeline; Step S112, extending the signal detection head assembly device and the seismic wave transmitting source device into the first borehole and the second borehole respectively; Step S113, the seismic wave transmitting source device sequentially transmits multiple seismic wave signals from shallow to deep; Step S114, the signal detection head assembly device collects seismic wave signals and transmits the seismic wave signals to a host computer for internal processing; The process of obtaining the measured longitudinal wave velocity is: Arrange multiple detectors in a linear array on a virtual straight line of the detector array, and use the midpoint of the detector array composed of the detectors arranged in the linear array as a detection positioning point; a plurality of adjacent test points with equal spacing distances are set between the virtual line connecting the two holes, and each test point is tested respectively by aligning the detection positioning point with the test point, and each test point is tested by hammering the ground at different positions multiple times with a standard penetration hammer as a seismic source and collecting data through each detector; the center of the orifice of the first borehole is the first test point on the virtual line connecting the two holes, and the center of the orifice of the second borehole is the last test point on the virtual line connecting the two holes; Step S3, obtaining a wave velocity image according to the measured shear wave velocity and the measured longitudinal wave velocity; the wave velocity image is used to express the internal structure and abnormal conditions of the formation; Step S4, preprocessing the surface wave data collected on site; Step S5, obtaining a dispersion curve that meets the resolution requirement; Step S6, constraining the shear wave velocity to obtain an estimated shear wave velocity; Step S7, inverting the dispersion curve to obtain a relationship diagram between shear wave velocity and depth; Step S8, generating a relationship diagram between shear wave velocity and depth for each group of geophone queues in the detection area, generating a shear wave velocity depth profile, performing moving average smoothing on the profile to obtain a final contour map, and then jointly comparing and checking the velocity image map with the contour map; Step S9, performing contour map analysis to obtain the location and cross-sectional size data of the underground pipeline.

6. The detection method according to claim 5, characterized in that: In the process of obtaining the measured longitudinal wave velocity in step S1, when testing a test point, the ground surface layer located on the left side of the underground pipeline is hammered N times with a standard penetration hammer, and the ground surface layer located on the right side of the underground pipeline is hammered N times with a standard penetration hammer.

7. The detection method according to claim 5, characterized in that: Step S3 includes the following steps: Step S31, performing cross-hole CT data processing: first selecting the first arrival time of the collected cross-hole CT data, using the spacing value of the two cross-holes and a formula (1) and a formula (2) to use an algebraic reconstruction iterative algorithm to obtain the P-wave velocity value distribution of the square grid unit with a first fixed size, and using the least squares method to obtain the high-precision P-wave velocity value distribution of the square grid unit with a second fixed size by interpolation and encryption, so that the P-wave velocity values ​​of the same coordinates in the shear wave velocity image are one-to-one associated; Formula (1) is: Formula (2) is: In formula (1), l nm is the path length of the nth ray in the mth unit, S m is the slowness of the mth unit, t n is the travel time of the nth ray; In formula (2), Si represents the slowness of the i-th unit, and Vi represents the longitudinal wave velocity of the i-th unit; Step S32, combining the P-wave velocity values ​​of the square intervals with the second fixed size within the detection range between the first borehole and the second borehole with the depth data of the corresponding P-wave velocity values, to generate a wave velocity image, using different colors to represent different velocity intervals.

8. The detection method according to claim 5, characterized in that: Step S4 includes the following steps: Step S41, calibrating the detector; Step S42, using a GNSS receiver to collect the coordinates and elevation of each detector, and adding the coordinate and elevation data during data processing.

9. The detection method according to claim 6, characterized in that: Step S5 includes the following steps: Step S51, when the detector array composed of the detectors arranged in a linear array collects the first set of waveform record data of the first test point, the method of identifying the strongest noise in the record is used to extract and separate the artificial source and natural source waveform record diagrams at the strongest position; the first set of waveform record data includes test data of twice N (2N) times performed by the standard penetration hammer; Step S52, the extracted artificial source waveform record is interpolated between seismic traces using wavelet transform; Step S53, using a τ-p transformation algorithm to extract a dispersion energy map, and extracting the strongest signal as the dispersion curve of the group of data according to the dispersion energy map; Step S54, when the detector queue composed of the detectors arranged in a linear array collects the first test point, the detector queue at this time is the first group of detectors, and the N times (2N) groups of artificial source surface wave data separated from the first group of waveform recording data are processed to obtain an artificial source surface wave dispersion diagram and an artificial source dispersion curve, and the artificial source dispersion curve corresponding to the N times (2N) groups of artificial source surface wave data separated from the first group of waveform recording data are energy-weighted fused, and the artificial source dispersion curves of the N times (2N) groups are weighted fused, thereby completing the weighted fusion of the final dispersion diagram of the artificial source surface wave and the artificial source dispersion curve; Simultaneously or in no particular order, the natural source waveform record data separated from the first set of waveform record data are used to extract a natural source surface wave dispersion energy map using an extended spatial autocorrelation (ESPAC) method; Step S55, processing the N times (2N) groups of natural source surface wave data separated from the first group of waveform record data to obtain a natural source surface wave dispersion diagram and a natural source dispersion curve, and performing energy equal-weighted fusion on the N times (2N) groups of natural source dispersion curves, thereby completing the energy equal-weighted fusion of the final dispersion diagram of the natural source surface wave and the natural source dispersion curve; Step S56, integrating or summing the squares of the amplitudes of the artificial and natural surface wave signals near the frequency f to obtain energy E1(f) and energy E2(f). The dispersion curve of the artificial surface wave is D1(f), and the dispersion curve of the natural surface wave is D2(f). The energy proportions of the artificial and natural surface waves at each frequency are calculated and expressed as weights: Artificial surface wave weight: Natural source surface wave weight: The fused dispersion curve: D(f)=P1(f)D1(f)+P2(f)D2(f) (5); In step S5 , the remaining test points other than the first test point are all executed in the manner of steps S51 to S56 , so as to obtain the fused dispersion curves of the remaining test points other than the first test point in a one-to-one correspondence.

10. The detection method according to claim 5, characterized in that: Step S6 includes the following steps: Step S61, constraining the range of the Poisson's ratio and the measured longitudinal wave velocity by obtaining the range of the estimated transverse wave velocity through a formula (6); formula (6) is: In formula (6), V p is the longitudinal wave velocity, V s is the shear wave velocity, v is the Poisson’s ratio, The porosity is calculated by injecting mercury into the cores of the two previous boreholes. Φ is the medium inhomogeneity coefficient. The standard deviation σ of all longitudinal wave velocities inverted by cross-hole CT is obtained. It is calculated based on the amount of mercury that enters the pores of the cores at different pressures after mercury is injected into the cores taken from the two boreholes; Step S62, comparing the estimated shear wave velocity range with the measured shear wave velocity, and resampling or correction is performed again when the measured shear wave velocity does not meet the set requirements until the best dispersion curve is obtained; Step S63, according to the relationship between the shear wave velocity and the frequency, using λ=V / f and the half-wavelength empirical formula h=0.5λ, and using the damped least squares method to invert the dispersion curve to obtain the relationship between the shear wave velocity and the depth, and obtain the relationship diagram between the shear wave velocity and the depth of the optimal dispersion curve; wherein λ is the wavelength, f is the frequency, and h is the depth; In step S6, the remaining test points other than the first test point are all executed according to the method of steps S61 to S63, so as to obtain the relationship diagram between the shear wave velocity and the depth of the best dispersion curves of the remaining test points other than the first test point one by one.

11. The detection method according to claim 10, characterized in that: When the media of the surface layer being detected are isotropic, the Poisson's ratio formula is set as: In formula (7), the porosity is 1, the medium inhomogeneity coefficient Φ is 0; K is a constant: its value is between 1.5 and 2.5; v is Poisson's ratio.

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