CN114755729A - Method and device for rapidly detecting geological defects of urban road - Google Patents
Method and device for rapidly detecting geological defects of urban road Download PDFInfo
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- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
- G01V3/10—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils
Abstract
The invention relates to a method and a device for rapidly detecting urban road geological defects, in particular to a method and a device for detecting underground medium electric distribution by a frequency domain electromagnetic induction method, wherein a horizontal magnetic dipole source coded signal electromagnetic emission system inverts direct current power supply current into a coded signal according to a set inverse M sequence pseudo-random signal waveform, outputs the coded signal through an emission coil to generate a coded electromagnetic field, records the emitted current as a time sequence through a current sensor, samples a magnetic field horizontal component Hy into the time sequence by a data recording system for collecting the magnetic field horizontal component Hy under the control of a program, records the time sequence and position information received by a Beidou/GPS positioning system as a file and stores the file, calculates the frequency response of each channel by a cloud data processing system, calculates the apparent resistivity of each channel, calculates the horizontal and vertical gradient changes, and transmits the change back to a mobile phone end for real-time display, the invention can realize the quick detection of urban road geological defects and underground pipe network diseases, and can be applied to other fields such as geological exploration and the like.
Description
Technical Field
The invention relates to the technical field of detecting the electrical distribution of an underground medium by a frequency domain electromagnetic induction method, in particular to a method and a device for quickly detecting urban road geological defects and underground pipeline diseases.
Background
The road and underground pipe network system is the blood vessel of the city and maintains the development and future of the city. However, the early buried pipe network is inconvenient to maintain, and diseases of various urban roads and underground pipe networks are increasingly prominent along with the aging of underground pipe network infrastructures such as water supply and drainage.
In order to find out urban road geological defects and underground pipeline diseases in time, a series of nondestructive testing and rapid exploration technical systems are applied, such as a geological radar detection method, a transient electromagnetic radar detection method, a high-density resistivity method, a transient surface wave method, a micro-motion exploration method, a seismic mapping method, a transient electromagnetic method and the like.
In the prior art, the ground penetrating radar has the advantages of convenience in field implementation, external environment interference resistance, rapidness and convenience in operation, high detection efficiency, low implementation cost and the like, and is widely applied to urban road and underground pipe network detection. But the defects are that the high-frequency electromagnetic wave is attenuated quickly in the stratum, the detection depth is shallow, and the effective detection depth of the conventional instrument is within 3-5m below the ground surface.
In the prior art, the high-density resistivity method cannot be used for laying electrodes under the urban road hardening condition and is difficult to develop.
In the prior art, a micro-motion detection method needs to collect natural source vibration signals for a long time in order to obtain a surface wave frequency dispersion curve, but is limited by road traffic conditions.
In the prior art, the time domain transient electromagnetic method has large detection depth, but is easily interfered by environment electromagnetic waves in an urban area, and has low detection efficiency.
Disclosure of Invention
The invention aims to provide a method and a device for rapidly detecting urban road geological defects, wherein a horizontal magnetic dipole formed by exciting a vertical coil by utilizing coded multi-frequency signal current generates an alternating electromagnetic field, and a frequency domain electromagnetic sounding detection method is carried out by receiving a horizontal component Hy of the magnetic field. And combining the system identification technology of a coded signal cross-correlation method, obtaining magnetic field Hy frequency response by using a magnetic field horizontal component Hy response time sequence and a coded current time sequence circulating cross-correlation method which are synchronously recorded, calculating a whole-area apparent resistivity spectrum, and identifying the position of the underground geological defect through the horizontal and vertical gradient changes of the horizontal magnetic field Hy, thereby realizing the rapid detection of the urban road geological defect and the underground pipeline disease.
In order to solve the technical problem, the method for rapidly detecting the geological defects of the urban road comprises a horizontal magnetic dipole source coded signal electromagnetic emission system, a data recording system for acquiring a horizontal component Hy of a magnetic field, a mobile phone client and a cloud data processing system.
Furthermore, the horizontal magnetic dipole source coded signal electromagnetic transmitting system comprises a transmitting controller and a vertical coil transmitting antenna.
Furthermore, the data recording system for acquiring the horizontal component Hy of the magnetic field comprises a receiving antenna, a receiver, a multi-channel signal conditioning module, a multi-channel high-speed A/D converter, an FPGA, an ARM processor and a Beidou/GPS positioning system, wherein the number of the receiving antenna made of the hollow coils is at least 4.
Furthermore, the mobile phone client is wirelessly connected with a transmitting controller of the electromagnetic transmitting system and a receiver of the data recording system for acquiring the horizontal component Hy of the magnetic field, controls and sets the waveform and frequency of the electromagnetic transmitting system and the sampling rate for acquiring the current and the magnetic field, reads the current time sequence recorded by the current recorder and the multi-channel horizontal component Hy time sequence acquired by the magnetic field data recording system and sends the current time sequence and the multi-channel horizontal component Hy time sequence to the cloud-end data processing system for real-time calculation; the cloud data processing system calculates the magnetic field frequency response of each channel and the apparent resistivity of the whole region of each channel in real time, calculates the horizontal and vertical amplitude spectrums or the gradient change of the resistivity spectrums, and transmits the calculation result back to the mobile phone client for real-time display.
Furthermore, the emission current of the electromagnetic emission system is provided by a lithium battery direct current power supply; the transmitting antenna and the receiving antenna are horizontally spaced by more than 1.6m, vertically arranged in a coplanar manner and packaged by adopting a synthetic resin material or a PVC (polyvinyl chloride) pipe.
Furthermore, the transmitting controller is connected with the transmitting coil through an aviation plug interface on the panel through a cable, the receiving data recording system receiver is connected with the plurality of receiving coils through aviation plug interfaces on the panel through cables, and the number of channels of the data acquisition system receiver is not less than 4; at least 3 receiving coils are arranged in a right-angled triangle vertical coplanar manner at a spacing of 0.5m to form a group of horizontal gradient measurement and a group of vertical gradient measurement.
A method for rapidly detecting geological defects of urban roads comprises the following steps:
s1, arranging a received current file and a multi-channel magnetic field data file into a matrix, calculating a circular cross-correlation sequence of each magnetic field and current and a circular auto-correlation sequence of the current by using a circular cross-correlation subprogram, converting the correlation sequences into amplitude spectra by a Fast Fourier Transform (FFT) algorithm, extracting magnetic field current cross-power spectra with the same frequency and dividing the magnetic field current cross-power spectra with the same frequency with current auto-power spectra, and obtaining the frequency response of each channel magnetic field through a stratum;
s2, the cloud data processing system completes the circular cross correlation of the current time sequence and the magnetic field data of each channel, identifies the frequency response of each channel magnetic field, and calculates the apparent resistivity of the whole area according to a formula:
in the formula (I), the compound is shown in the specification,
is the frequency, r is the center distance between the transmitting coil and the receiving coil,
in order to emit magnetic moment, I is current intensity, S is the area of an emitting coil, and n is the number of turns of the coil; hy is the estimated magnetic field strength,
is emptyMagnetic permeability of gas
，
Is a dielectric resistivity of
Uniform half-space horizontal magnetic field response;
the technical formula of (2) is as follows:
in the formula (I), the compound is shown in the specification,
，
，
is a Bessel function;
s3, calculating the horizontal gradient variation of Hy2 and Hy1, the horizontal gradient variation of Hy3 and Hy2, the horizontal gradient variation of Hy3 and Hy1 and the vertical gradient variation of Hy2 and Hy4 according to the amplitude spectrum of each channel obtained in the step S1; or calculating the horizontal gradient change amounts of Hy2 and Hy1, the horizontal gradient change amounts 2 of Hy3 and Hy, the horizontal gradient change amounts of Hy3 and Hy1, and the vertical gradient change amounts of Hy2 and Hy4 according to the all-channel apparent resistivity spectra obtained in step S2;
and S4, transmitting the calculation result back to the mobile phone client for real-time display.
Further, the transmitting coding current comprises 3-order, 4-order, 5-order or 6-order inverse M sequence and is generated by modulating a pseudorandom sequence with the length of 126 bits, a clock frequency of 25.2MHz constant temperature crystal oscillator is used for dividing the pseudorandom sequence with the length of 126 bits to output the pseudorandom sequence with the length of 12.6 kHz, 25.2kHz, 31.5kHz, 50.4kHz or 63kHz, the period of a coding signal is generated for 0.004s, and the frequency range of an electromagnetic field signal is generated from 250Hz to 87.25 kHz.
Further, the frequency band of the emission coil is 10Hz to 100 kHz; the sensor for receiving the horizontal component Hy of the magnetic field is a coil or a superconducting quantum magnetometer, and the frequency bandwidth is 10Hz to 150 kHz.
The invention has the beneficial effects that:
1. the invention adopts a horizontal magnetic dipole formed by vertical coils to establish an electromagnetic field, receives the horizontal magnetic field component Hy, calculates the apparent resistivity of the whole area, and detects the gradient change of the horizontal direction and the vertical direction.
2. The invention adopts the coded source signal to continuously excite the electromagnetic field in a multi-period way, can obtain the resistivity response of a very wide frequency band, has rich frequency and has higher longitudinal resolution on the stratum.
3. The invention adopts the correlation identification technology, obtains frequency response by a recorded emission current signal and a magnetic field signal circulation cross-correlation method received by each channel, and has stronger interference suppression capability on various types of random noise.
4. According to the invention, the plurality of magnetic field sensors are adopted to synchronously acquire the horizontal component Hy of the magnetic field, so that the gradient change (amplitude or resistivity) of the horizontal component Hy of the magnetic field in the horizontal direction and the vertical direction can be obtained, and more information is provided for abnormality identification.
5. The invention has various combined observation modes: the transmitting coil and the receiving system can be synchronously moved and observed at a fixed interval, the transmitting coil can also be fixed for fixed-point transmission, and the receiving system can move and detect along the section.
6. The observation system can be carried on a non-metal wheel type platform, and is convenient for mobile observation.
Drawings
FIG. 1 is a schematic diagram of the present invention;
fig. 2 is a schematic view of a cloud data processing flow according to the present invention.
Detailed Description
As shown in fig. 1 and fig. 2, the method for rapidly detecting geological defects of urban roads comprises a horizontal magnetic dipole source coded signal electromagnetic emission system, a data recording system for collecting a horizontal component Hy of a magnetic field, a mobile phone client and a cloud data processing system.
Furthermore, the horizontal magnetic dipole source coded signal electromagnetic transmitting system comprises a transmitting controller and a vertical coil transmitting antenna.
Furthermore, the data recording system for acquiring the horizontal component Hy of the magnetic field comprises a receiving antenna, a receiver, a multi-channel signal conditioning module, a multi-channel high-speed A/D converter, an FPGA, an ARM processor and a Beidou/GPS positioning system, wherein the number of the receiving antenna made of the hollow coils is at least 4.
Furthermore, the mobile phone client is wirelessly connected with a transmitting controller of the electromagnetic transmitting system and a receiver of the data recording system for acquiring the horizontal component Hy of the magnetic field, the mobile phone client controls and sets the waveform and frequency of the electromagnetic transmitting system and the sampling rate of current and magnetic field acquisition, and the mobile phone client reads the current time sequence recorded by the current recorder and the multi-channel horizontal component Hy time sequence acquired by the magnetic field data recording system and sends the current time sequence and the multi-channel horizontal component Hy time sequence to the cloud-end data processing system for real-time calculation; the cloud data processing system calculates the magnetic field frequency response of each channel and the apparent resistivity of the whole region of each channel in real time, calculates the horizontal and vertical amplitude spectrums or the gradient change of the resistivity spectrums, and transmits the calculation result back to the mobile phone client for real-time display.
Furthermore, the emission current of the electromagnetic emission system is provided by a lithium battery direct current power supply; the transmitting antenna and the receiving antenna are horizontally spaced by more than 1.6m, vertically arranged in a coplanar manner and packaged by adopting a synthetic resin material or a PVC (polyvinyl chloride) pipe.
Furthermore, the transmitting controller is connected with the transmitting coil through an aviation plug interface on the panel through a cable, the receiving data recording system receiver is connected with the plurality of receiving coils through aviation plug interfaces on the panel through cables, and the number of channels of the data acquisition system receiver is not less than 4; at least 3 receiving coils are arranged in a right-angled triangle vertical coplanar manner at a spacing of 0.5m to form a group of horizontal gradient measurement and a group of vertical gradient measurement.
A method for rapidly detecting geological defects of urban roads comprises the following steps:
s1, arranging a received current file and a multi-channel magnetic field data file into a matrix, calculating a circular cross-correlation sequence of each magnetic field and current and a circular auto-correlation sequence of the current by using a circular cross-correlation subprogram, converting the correlation sequences into amplitude spectra by a Fast Fourier Transform (FFT) algorithm, extracting magnetic field current cross-power spectra with the same frequency and dividing the magnetic field current cross-power spectra with the same frequency with current auto-power spectra, and obtaining the frequency response of each channel magnetic field through a stratum;
s2, the cloud data processing system completes the circular cross correlation of the current time sequence and the magnetic field data of each channel, identifies the frequency response of each channel magnetic field, and calculates the apparent resistivity of the whole area according to a formula:
in the formula (I), the compound is shown in the specification,
is the frequency, r is the center distance between the transmitting coil and the receiving coil,
the magnetic moment is transmitted, I is the current intensity, S is the area of the transmitting coil, and n is the number of turns of the coil; hy is the estimated magnetic field strength,
is magnetic permeability of air
，
Is a dielectric resistivity of
Uniform half-space horizontal magnetic field response;
the technical formula of (2) is as follows:
in the formula (I), the compound is shown in the specification,
，
，
is a Bessel function;
s3, calculating the horizontal gradient variation of Hy2 and Hy1, the horizontal gradient variation of Hy3 and Hy2, the horizontal gradient variation of Hy3 and Hy1 and the vertical gradient variation of Hy2 and Hy4 according to the amplitude spectrum of each channel obtained in the step S1; or the horizontal gradient change amounts of Hy2 and Hy1, the horizontal gradient change amounts 2 of Hy3 and Hy, the horizontal gradient change amounts of Hy3 and Hy1, and the vertical gradient change amounts of Hy2 and Hy4 are calculated according to the apparent resistivity spectra of all the channels obtained in step S2.
S4, transmitting the calculation result back to the mobile phone client for real-time display;
further, the transmitting coding current comprises 3-order, 4-order, 5-order or 6-order inverse M sequence and is generated by modulating a pseudorandom sequence with the length of 126 bits, a clock frequency of 25.2MHz constant temperature crystal oscillator is used for dividing the pseudorandom sequence with the length of 126 bits to output the pseudorandom sequence with the length of 12.6 kHz, 25.2kHz, 31.5kHz, 50.4kHz or 63kHz, the period of a coding signal is generated for 0.004s, and the frequency range of an electromagnetic field signal is generated from 250Hz to 87.25 kHz.
Further, the frequency band of the emission coil is 10Hz to 100 kHz; the sensor for receiving the horizontal component Hy of the magnetic field is a coil or a superconducting quantum magnetometer, and the frequency bandwidth is 10Hz to 150 kHz.
The invention can obtain the whole-region apparent resistivity response of the horizontal component Hy of the magnetic field with dozens of frequencies by one-time excitation, and the vertical or horizontal gradient change of the response, and has high detection efficiency and longitudinal resolution. Due to the adoption of the system identification technology, the interference of power frequency and random electromagnetic noise can be suppressed, and the anti-interference capability is strong.
The transmitting system and the receiving system can be arranged on a non-metal wheel type moving vehicle, can be combined into a whole for synchronous moving detection, and can also be separated from each other, the fixed position of the transmitting system is fixed, the fixed-point transmitting is carried out, and the receiving system is movable for detecting along the section.
The emission current is sampled by a high-precision current sensor and recorded as a time sequence, and the sampling rate is the same as that of the receiving system.
Sampling and recording horizontal magnetic field components Hy received by a plurality of coils as a time sequence by adopting a multi-channel A/D converter;
the type selection of the transmitted signal, the selection of the excitation frequency and the selection of the sampling rate can be controlled and operated by the mobile phone client. And receiving channel selection of a system, and controlling the sampling rate selection through a mobile phone client. The mobile phone client can receive the current and the multi-channel magnetic field data, display the data in real time and send the data to the cloud-end data processing system.
The cloud data processing result can be transmitted to the mobile client to display the calculation result in real time, and an operator can judge the abnormal position according to the display result.
As shown in FIG. 1, the coordinate system is from left to right in the x direction of the paper, vertically upward in the z direction, and vertically in the y direction. The transmitting coil can be round or square, and in an x-z plane, the direction of a magnetic field generated by the central point of the coil is vertical to the paper surface and changes along the y direction; the four magnetic field receivers can be air coils, in an x-z plane, magnetic rods or a superconducting quantum magnetometer, Hy components are measured along the y direction, the transmitting coil and the four magnetic field receivers are in the same x-z plane, and when the integrated detection is carried out, the horizontal distance between the transmitting coil and the receiving coil 1 along the x direction is more than 3 m, the receiving coil 1, the receiving coil 2 and the receiving coil 3 are arranged at equal intervals along the x direction, the distance is 0.5m, and the receiving coil 4 is vertically above the receiving coil 2 and is 0.5 m.
The transmitting controller inverts the direct-current power supply according to the 6-order inverse M sequence waveform, outputs the inverted direct-current power supply through the transmitting coil to generate a coded electromagnetic signal, and records output current as a time sequence by using the current sensor; the receiver has at least 4 sampling channels, and the magnetic field signals are synchronously acquired and recorded as a time sequence. And recording the Beidou/GPS position information and the collected data as files.
The mobile phone end can set the working parameters of the transmitting controller and the receiver. And uploading the acquired data file to a cloud-end data processing system. And displaying a cloud processing result.
The data recording system for acquiring the horizontal component Hy of the magnetic field consists of at least 4 receiving antenna arrays made of air coils or superconducting quantum magnetometers, a multi-channel signal conditioning module, a multi-channel high-speed A/D converter, an FPGA (field programmable gate array), an ARM (advanced RISC machine) processor and a Beidou/GPS (global positioning system); under the control of a program, the horizontal component Hy of the magnetic field is sampled into a time sequence, and the time sequence and the position information received by the Beidou/GPS positioning system are recorded as files and stored.
The mobile phone client can be wirelessly connected with the electromagnetic emission system controller and the data recording system receiver of the magnetic field horizontal component Hy, can control and set the waveform and frequency of the emission system and the sampling rate of current and magnetic field acquisition, reads the current time sequence recorded by the current recorder and the multi-channel magnetic field horizontal component Hy time sequence file acquired by the magnetic field data recording system and sends the current time sequence and the multi-channel magnetic field horizontal component Hy time sequence file to the cloud data processing system for real-time calculation, and the cloud data processing calculation result can be displayed in real time through the mobile phone client.
The transmitting encoding current is generated by modulating a pseudorandom sequence with the length of 126 bits by a 6-order inverse M sequence, a 25.2MHz constant-temperature crystal oscillator is used for dividing a pseudorandom sequence with the length of 126 bits by a 63kHz clock excitation time sequence and outputting the pseudorandom sequence, the period of a generated encoding signal is 0.004s, and the frequency range of the generated electromagnetic field signal is 250Hz to 87.25 kHz. Optionally, the order of the inverse M sequence may also be set to 3, 4, 5 orders, and the clock frequency may also be set to 12.6 kHz, 25.2kHz, 31.5kHz, and 50.4 kHz.
The size of the transmitting coil and the frequency band capable of transmitting by winding turns are 10Hz to 100 kHz.
The sensor receiving the horizontal component Hy of the magnetic field may be a coil or a superconducting quantum magnetometer with a frequency bandwidth of 10Hz to 150 kHz.
The emission current is provided by a plurality of lithium batteries; the transmitting antenna and the receiving antenna are horizontally spaced by more than 1.6m and are vertically arranged in a coplanar manner, and the transmitting antenna is packaged by adopting a synthetic resin material or a PVC (polyvinyl chloride) pipe; the magnetic field receiving antenna is installed through a non-metal support, the receiving coil 1, the receiving coil 2 and the receiving coil 3 are arranged at equal intervals along the horizontal x direction, the interval is 0.5m, and the receiving coil 4 is arranged right above the receiving coil 2 at the interval of 0.5 m. The magnetic field response signals of the 4 magnetic field receivers are synchronously recorded as a time sequence by a receiver multi-channel sampler and stored.
And the mobile phone client reads the current file of the transmitting controller and the multi-channel magnetic field response file recorded by the receiver and sends the multi-channel magnetic field response file to the cloud-end data processing system.
The invention adopts a horizontal magnetic dipole formed by vertical coils to establish an electromagnetic field, receives the horizontal magnetic field component Hy, calculates the apparent resistivity of the whole area, and detects the gradient change of the horizontal direction and the vertical direction. By adopting the multi-period continuous excitation electromagnetic field of the encoding source signal, the resistivity response of a very wide frequency band can be obtained, the frequency is rich, and the longitudinal resolution on the stratum is higher. By adopting a correlation identification technology, frequency response is obtained by a recorded transmitting current signal and a magnetic field signal received by each channel through a circular cross-correlation method, and the interference suppression method has strong interference suppression capability on various types of random noise. The magnetic field horizontal component Hy is synchronously collected by adopting a plurality of magnetic field sensors, so that the gradient change (amplitude or resistivity) of the magnetic field horizontal component Hy in the horizontal direction and the vertical direction can be obtained, and more information is provided for abnormality identification. There are many combined observation modes, the transmitting coil and the receiving system can be kept in fixed distance for synchronous moving observation, the transmitting coil can also be fixed for fixed-point transmission, and the receiving system can move along the section for detection. Can be carried on a non-metal wheel type platform, and is convenient for mobile observation.
Claims (9)
1. The utility model provides a quick detection device of urban road geological defect which characterized in that: the system comprises a horizontal magnetic dipole source coded signal electromagnetic emission system, a data recording system for collecting a magnetic field horizontal component Hy, a mobile phone client and a cloud data processing system.
2. The urban road geological defect rapid detection device according to claim 1, characterized in that: the horizontal magnetic dipole source coded signal electromagnetic transmitting system comprises a transmitting controller and a vertical coil transmitting antenna.
3. The urban road geological defect rapid detection device according to claim 2, characterized in that: the data recording system for acquiring the horizontal component Hy of the magnetic field comprises at least 4 receiving antennas made of a plurality of hollow coils, a receiver, a multi-channel signal conditioning module, a multi-channel high-speed A/D converter, an FPGA (field programmable gate array), an ARM (advanced RISC machine) processor and a Beidou/GPS (global positioning system).
4. The urban road geological defect rapid detection device according to claim 3, characterized in that: the mobile phone client is wirelessly connected with a transmitting controller of the electromagnetic transmitting system and a receiver of the data recording system for acquiring the horizontal component Hy of the magnetic field, controls and sets the waveform and frequency of the electromagnetic transmitting system and the sampling rate of current and magnetic field acquisition, reads a current time sequence recorded by the current recorder and a multi-channel horizontal component Hy time sequence acquired by the magnetic field data recording system and sends the current time sequence and the multi-channel horizontal component Hy time sequence to the cloud-end data processing system for real-time calculation; the cloud data processing system calculates the magnetic field frequency response of each channel and the apparent resistivity of the whole region in real time, calculates the horizontal and vertical amplitude spectrums or the gradient change of the resistivity spectrums, and transmits the calculation results back to the mobile phone client for real-time display.
5. The urban road geological defect rapid detection device according to claim 4, characterized in that: the emission current of the electromagnetic emission system is provided by a lithium battery direct current power supply; the transmitting antenna and the receiving antenna are horizontally spaced by more than 1.6m, vertically arranged in a coplanar manner and packaged by adopting a synthetic resin material or a PVC (polyvinyl chloride) pipe.
6. The urban road geological defect rapid detection device according to claim 5, characterized in that: the transmitting controller is connected with the transmitting coil through an aviation plug interface on the panel through a cable, the receiving data recording system receiver is connected with the plurality of receiving coils through aviation plug interfaces on the panel through cables, and the number of channels of the data acquisition system receiver is not less than 4; at least 3 receiving coils are arranged in a right-angled triangle vertical coplanar manner at a spacing of 0.5m to form a group of horizontal gradient measurement and a group of vertical gradient measurement.
7. A method for rapidly detecting geological defects of urban roads, comprising the device for rapidly detecting geological defects of urban roads according to claim 7, wherein: the method comprises the following steps:
s1, sorting the received current file and the multi-channel magnetic field data file into a matrix, calculating a circular cross-correlation sequence of each magnetic field and current and a circular auto-correlation sequence of the current by using a circular cross-correlation subprogram, converting the correlation sequences into a magnitude spectrum by a Fast Fourier Transform (FFT) algorithm, extracting a magnetic field current cross-power spectrum with the same frequency and dividing the magnetic field current cross-power spectrum with the same frequency with a current auto-power spectrum to obtain the frequency response of each channel magnetic field through a stratum;
s2, the cloud data processing system completes the circular cross correlation of the current time sequence and the magnetic field data of each channel, identifies the frequency response of each channel magnetic field, and calculates the apparent resistivity of the whole area according to a formula:
in the formula (I), the compound is shown in the specification,
is the frequency, r is the center distance between the transmitting coil and the receiving coil,
in order to emit magnetic moment, I is current intensity, S is the area of an emitting coil, and n is the number of turns of the coil; hy is the estimated magnetic field strength,
is magnetic permeability of air
，
Is a dielectric resistivity of
Uniform half-space horizontal magnetic field response;
the technical formula of (2) is as follows:
in the formula (I), the compound is shown in the specification,
，
，
is a Bessel function;
s3, calculating the horizontal gradient change amount of Hy2 and Hy1, the horizontal gradient change amount of Hy3 and Hy2, the horizontal gradient change amount of Hy3 and Hy1 and the vertical gradient change amount of Hy2 and Hy4 according to the amplitude spectrum of each channel obtained in the step S1; or calculating the horizontal gradient change amount of Hy2 and Hy1, the horizontal gradient change amount 2 of Hy3 and Hy, the horizontal gradient change amount of Hy3 and Hy1, and the vertical gradient change amount of Hy2 and Hy4 according to the apparent resistivity spectra of all the channels obtained in step S2;
and S4, transmitting the calculation result back to the mobile phone client for real-time display.
8. The urban road geological defect rapid detection method according to claim 7, characterized in that: the transmitting coding current comprises 3-order, 4-order, 5-order or 6-order inverse M sequences and is generated by modulating a pseudorandom sequence with the length of 126 bits, a 25.2MHz constant-temperature crystal oscillator is used for dividing a clock frequency of 12.6 kHz, 25.2kHz, 31.5kHz, 50.4kHz or 63kHz to excite the pseudorandom sequence with the length of 126 bits to output in a time sequence manner, the period of a coding signal is 0.004s, and the frequency range of an electromagnetic field signal is 250Hz to 87.25 kHz.
9. The urban road geological defect rapid detection method according to claim 8, characterized in that: the frequency band of the transmission of the transmitting coil is 10Hz to 100 kHz; the sensor for receiving the horizontal component Hy of the magnetic field is a coil or a superconducting quantum magnetometer, and the frequency bandwidth is 10Hz to 150 kHz.
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