A device and method for real-time depth measurement and damage detection of a horizontal borehole in mining

Abstract

The application discloses a kind of mining horizontal drilling real-time depth measurement and damage detection device and method, setting: measurement host computer;Emit probe brush, install at drilling orifice, be connected with measurement host computer by communication cable, coupling measured drill rod with emission wave signal;Receive probe brush, install at drilling orifice, be connected with measurement host computer by communication cable, coupling measured drill rod with echo signal received by measurement host computer;Ground drill, install in coal seam near drilling, be connected with coal seam near drilling by communication cable, form signal loop.The application is suitable for ordinary drill rod, without adding measurement equipment in drilling tool, without reforming drilling tool to save cost, without affecting drilling efficiency;Not only can the total length of drill rod in the process of drilling be measured in real time, but also the damage of each drill rod can be checked.

Description

Technical Field

[0001] This invention relates to the field of underground drilling technology in coal mines, specifically to a device and method for real-time depth measurement and damage detection of horizontal boreholes used in mining. Background Technology

[0002] Gas outbursts and water inrushes are common hazards in coal mines, severely impacting the safe and efficient operation of coal mining enterprises for many years. Currently, the most effective mitigation measure for these hazards is to utilize drilling technology. This involves drilling rigs to create numerous gas extraction and water exploration boreholes within the coal seam, using these boreholes as pathways to completely eliminate potential hazards before mining and tunneling operations, ensuring safe construction. Before drilling, the mine employs various geophysical exploration techniques such as electrical resistivity tomography, seismic surveys, and well logging to conduct advance surveys. Based on the survey results, a corresponding borehole design plan is determined, specifying the drilling location and trajectory for each borehole. Ideally, the boreholes should be constructed strictly according to the design plan to ensure the most efficient extraction or drainage. Therefore, the drilling trajectory is a crucial criterion for evaluating the quality of borehole construction. A satisfactory drilling trajectory ensures the success of subsequent construction operations. Significant deviations in the drilling trajectory not only greatly reduce construction efficiency but also pose significant safety hazards to later stages of construction.

[0003] The drilling trajectory describes the path of the drill string in the coal seam, and can be drawn by combining the attitude information of the drill rod at each depth throughout the drilling process. Therefore, as long as the attitude and depth information can be effectively obtained, the drilling trajectory of the drill rod can be obtained. Among them, the measurement technology of attitude information is relatively mature, and it has been used in coal mine borehole trajectory measurement for a long time with high stability. In contrast, the development of borehole depth information measurement technology applied to horizontal drilling in coal mines has been relatively slow, and there is currently no convenient, efficient, and stable depth measurement equipment that has been widely promoted. In fact, the most widely used depth measurement method in coal mines is still manual counting. During the drilling process, the number of drill rods used is manually counted to calculate the borehole depth. Using this method not only increases the workload of construction workers and reduces construction efficiency, but also often results in misreporting, omissions, and false reporting due to differences in the individual skills and abilities of construction workers, resulting in a high error rate. In addition, this method cannot achieve real-time online detection when calculating depth information, and lacks real-time capability.

[0004] To address the issue of depth measurement, researchers have conducted extensive studies, which can be broadly categorized into the following types: The first type, exemplified by patents CN113008109A (a device for measuring the depth of a pile foundation hole), CN113834410A (a high-precision hole depth measuring device for pile foundation engineering with high stability), and CN114111500A (a hole depth measuring device for rock and soil geological exploration), employs wired measurement methods using tools such as winches, line drills, measuring lines, and rulers. However, this type of method cannot achieve drilling-while-drilling measurements in horizontal drilling in coal mines, requiring re-measurement. Furthermore, the wired method is only suitable for shallow hole measurements, and sending wires to deep horizontal holes is quite difficult. The second category includes patents such as CN102877831B Mining Drilling Depth Monitoring Device, CN 102808610B Real-time Detection Device and Detection Method for Underground Drilling Depth in Coal Mines, CN101338667A Method and Measuring Instrument for Measuring Drilling Depth of Gas Emission in Coal Mines, CN113188465A A Method and Device for Identifying Drilling Depth Based on Video Learning, and CN104612662A A Drill Rod Drilling Depth Measuring Device and Measurement Method Using the Measuring Device. These methods utilize pressure sensors, displacement sensors, slag sensors, and image recognition technology to monitor the movement characteristics of the drilling rig and drilling tools during drilling, thereby calculating the depth of the deep hole. This is an indirect measurement method. The measurement parameters of this type of method vary for different drilling rigs and drilling tools, lacking universality. Furthermore, the calculation methods of this type are relatively complex, requiring operators to strictly follow the design process to ensure accurate measurement, thus limiting the error tolerance. The third category, such as patents CN107476800B (a drilling depth measurement device and method based on radio frequency identification technology) and CN102410013BB (a method for monitoring hole depth during wired drill rod drilling), requires modification of existing drilling tools, resulting in high costs, poor versatility, and difficulty in widespread adoption.

[0005] Meanwhile, drill pipes, being consumable parts, operate under high torque and intense wear conditions in coal seams for extended periods. Regular inspection and replacement are essential to prevent serious economic losses and safety hazards, such as drill bit loss or breakage. However, currently, convenient testing equipment for drill pipes is scarce. Most drill pipe health checks rely on the experience of downhole personnel, which is highly dependent on individual skill and ability. Furthermore, manual inspection often fails to detect internal damage, leading to frequent mass replacements after a certain period. This not only poses serious safety risks but also represents a significant economic waste. Summary of the Invention

[0006] The purpose of this invention is to provide a real-time depth measurement and damage detection device and method for horizontal drilling in coal mines, addressing the needs for borehole depth measurement and drill rod damage detection. This device and method can measure the total length of the drill rod and the damage status of each section of the drill rod in real time during drilling.

[0007] The technical solution adopted in this invention is:

[0008] A real-time depth measurement and damage detection device for horizontal boreholes in mining, comprising:

[0009] Measurement host;

[0010] The transmitting probe is installed at the borehole opening and connected to the measurement host via a communication cable to couple the transmitted wave signal to the drill rod being measured.

[0011] The receiving probe is installed at the borehole opening and connected to the measurement host via a communication cable. It couples the echo signal received by the drill rod under test to the measurement host.

[0012] The ground probe is installed in the coal seam near the borehole and is connected to the coal seam near the borehole via a communication cable to form a signal loop.

[0013] Optionally, the measurement host is equipped with a main control processor, which is connected to a depth data calculator and a damage data calculator.

[0014] The main control processor is connected in two ways to a signal generator, a signal generator driver, a signal splitter, a signal conditioner, a data acquisition unit, and a data storage unit. The data storage unit is connected back to the main control processor.

[0015] The main control processor is connected to a feature encoding generator via three channels, and the feature encoding generator is connected to the transmit signal generation driver.

[0016] After the signal splitter, a transmitting signal coupler and a transmitting probe, a receiving signal coupler and a receiving probe, and a grounding coupler and a grounding rod are connected in parallel in sequence.

[0017] Optionally, the main control processor is the main control unit, used to control each module;

[0018] A signal generator is used to generate standard excitation signals;

[0019] A feature code generator is used to generate random coded signals with distinct characteristics;

[0020] The transmit signal generation driver generates a transmit signal with distinct characteristics by combining a standard excitation signal and a feature-encoded signal, and then amplifies the power of the transmit signal.

[0021] The signal splitter has a built-in multiplexer switch and coupling unit for channel switching of transmitted signals, received signals and loop signals;

[0022] A signal conditioner is used to condition the received signal;

[0023] The data acquisition unit is used to acquire the complete received echo signal;

[0024] Data storage device, used to store the acquired received echo signals;

[0025] The depth data calculator is used to determine the valid reflected wave signal from the complete received signal and to calculate the depth information of the borehole.

[0026] The damage data calculator is used to extract the reflected wave signals at the damage points of each section of the drill pipe from the effective reflected wave signals. After normalization and related calculations, the location and degree of damage of the drill pipe damage points are obtained.

[0027] The transmitter signal coupler, receiver signal coupler, and ground wire coupler are used to connect the transmitter brush, receiver brush, and ground wire to the measurement host. The output port adopts an isolated coupling form.

[0028] A method for real-time depth measurement and damage detection of horizontal boreholes in mining, which is performed using any of the real-time depth measurement and damage detection devices for horizontal boreholes in mining as described in this invention;

[0029] Electrical signals are used as measurement signals, and the drill rod and coal seam are used as signal transmission carriers. The transmitted signal is coupled to the drill rod being measured through a transmitting probe. When the transmitted signal encounters the connection end face of the drill rod or a damaged part of the rod body, the transmitted signal is reflected back. The transmitting probe and the receiving probe are connected to the drill rod, and the ground probe is connected to the ground. The transmitted signal forms a return flow through the drill rod and the ground for signal transmission and signal reception.

[0030] By calculating the consistency of the characteristic waveforms of the transmitted and received signals, a valid signal is identified when the output value of the consistency ratio is at its maximum. At this point, the distance the signal is transmitted can be calculated using the time difference between transmission and reception, which is the drilling depth. Then, the degree of damage to the drill rod is determined by the strength of the received signal. This enables the detection of the total length of the drill rod and the damage status of each drill rod.

[0031] Optionally, the transmitted signal includes:

[0032] The method of adjusting the standard excitation signal using random feature coding makes the standard excitation wave change with the changes in the random coded signal. The main control processor controls the signal generator to generate the standard excitation signal, and at the same time generates the random coded signal through the feature encoder generator. The standard excitation signal and the coded signal are combined by the signal transmission signal generator driver and the power is amplified to generate a transmission excitation signal with obvious characteristics. Since the random coded signal has good characteristic waveform recognition characteristics, the modulated transmission excitation signal also has good recognition characteristics. The transmission excitation signal is sent to the transmission signal coupler through the signal splitter.

[0033] Optionally, the signal reception includes:

[0034] When measuring the drilling depth, the impedance of the drill rod is discontinuous at the joint. When the transmitted signal encounters the joint, a strong reflection waveform will occur. This transmitted waveform will be coupled through the receiving circuit. The data acquisition device will collect the received signal. At the same time, the main control processor starts timing when the transmitted signal is completed. The main control processor will calculate the transmitted and received waveforms through characteristic waveform recognition. When the received signal and the transmitted signal have a high degree of consistency, it is considered to be a reflection process. The reflection distance is calculated and stored using the wave speed transmission formula.

[0035] After the first strongest reflected waveform arrives, the main control processor saves the first received reflected waveform. When subsequent reflected waves are received, the characteristic waveform consistency calculation is performed between the first received waveform and the subsequent received waveforms to determine whether it is a true reflected waveform. This process is repeated to determine the position of the reflected waveform on each joint end face. Then, the received reflected waveform is compared with the transmitted waveform to calculate the waveform propagation distance and realize the determination of the drilling depth.

[0036] Optionally, the signal receiving further includes:

[0037] When determining the damage status of the drill pipe, the impedance at the point of mechanical damage will also change, so the transmitted signal will be reflected when it encounters the mechanical damage point. The reflected wave energy at the damage point is less than the reflected energy at the end face of the joint. The reflected signal inside the reflection interval of the end face can be identified as the reflected signal at the damage point. After signal extraction, the location of the damage point on the drill pipe can be determined by calculating the consistency of the characteristic waveforms of the reflected signal at the end face and the reflected signal at the damage point.

[0038] Optionally, when determining the degree of damage to the drill pipe, the received signal needs to be normalized first to obtain the energy compensation coefficient, and then the degree of damage needs to be determined based on the intensity of the reflected signal. An early warning will be issued after a certain threshold is reached.

[0039] Optionally, the transmitted signal includes:

[0040] The signal generator produces a set of orthogonal sine wave signals with the same amplitude and a 90° phase difference. The pair of orthogonal sine wave signals with a 90° phase difference are sent to the subsequent stage for PN code modulation.

[0041] The encoded transmission signal is generated using PN code generation methods based on autocorrelation and cross-correlation.

[0042]

[0043]

[0044]

[0045] In equations (1) and (2), τ represents the coefficients used to generate the code order, which are dynamically provided by the program during testing. After the program provides the coefficients, the resulting sequence of points is the value of N, where N is a natural number and R is a natural number. x (τ) and R y (τ) forms a pair of orthogonal sequences with a phase difference of 90°;

[0046] Equations (1) and (2) are the autocorrelation codes generated by the modulation of the orthogonal sine wave signals respectively. The autocorrelation codes are cross-correlated using equation (3). The codes processed by equation (3) are coupled to the drill rod under test through the transmitting circuit.

[0047] Optionally, the reflected signal may be processed, including:

[0048] The total signal reflected back is:

[0049]

[0050] The first reflected signal of the fault location test signal is r1 = a1x(t-τ), where τ is the signal transmission delay in the drill pipe, n(t) is the signal noise, and a k is the reflection coefficient, where t is the discrete unit of the signal in the time domain, and k is the superposition weight of the sinusoidal signals of the reflected signal in the time domain;

[0051] Perform autocorrelation and cross-correlation operations on a set of reflected quadrature modulated signals:

[0052]

[0053] x(t) is an integral over a time interval, so it can be considered as an energy signal. Therefore, the energy spectral density can be expressed as the square of the absolute value of the Fourier transform of the x(t) signal, where T is the maximum frequency weight of the frequency domain superposition. Assuming X(f) is the Fourier transform of x(t), the energy spectral density is:

[0054] G x(f) =|F{x(t)}| 2 =|X(f)| 2 ;

[0055] Its power spectral density will not be zero within a finite time period, therefore its power spectral density function can be calculated as follows:

[0056]

[0057] The total energy of x(t) can be calculated using Rayleigh's theorem.

[0058]

[0059] in

[0060] n and m represent the time series combination of x(t), f represents the set of frequency points in the frequency domain, and d is the integral symbol;

[0061] We also need to calculate the cross-correlation energy between x(t) and n(t). Calculating the cross-correlation energy requires first calculating the Fourier transform of the cross-correlation.

[0062] F{R xn (t)}=F{x(t)*n(-t)}=X(f)N * (f);

[0063] In the formula N * (f) is the conjugate of the frequency domain sequence N(f);

[0064] The final formula for the cross-correlation energy is:

[0065]

[0066] By continuously calculating the received signal sequence, when the cross-correlation energy exceeds the threshold, it can be considered as a reflected signal with a sudden impedance change. At this time, the time difference from transmission to reflection can be used to calculate the distance between the drill pipe joint or crack and the transmitted signal. By continuously adjusting the threshold range during the detection process, the specific location of each joint and crack on the drill pipe can be obtained.

[0067] The beneficial effects of this invention are:

[0068] 1. This invention is applicable to ordinary drill pipes, eliminating the need to add measuring equipment inside the drill string, saving costs by eliminating the need to modify the drill string, and without affecting drilling efficiency;

[0069] 2. This invention employs wireless detection technology, enabling deep hole measurement;

[0070] 3. This invention relates to the direct measurement of drill pipe depth and is not limited by the parameters of the drilling rig being measured;

[0071] 4. The device of this invention is compact and convenient, highly efficient, has high measurement accuracy, and strong anti-interference and fault tolerance capabilities;

[0072] 5. This invention can not only measure the total length of the drill rod in real time during drilling, but also check the damage of each section of the drill rod. Attached Figure Description

[0073] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0074] Figure 1 This is a schematic diagram of the construction of the mining horizontal borehole real-time depth measurement and damage detection device of the present invention.

[0075] Figure 2 This is a block diagram of the detection system of the real-time depth measurement and damage detection device for horizontal boreholes in mining according to the present invention.

[0076] Figure 3 This is a schematic diagram illustrating the signal generation principle of the mining horizontal borehole real-time depth measurement and damage detection device of the present invention.

[0077] Figure 4 This is a schematic diagram illustrating the drilling depth measurement and damage detection principle of the real-time depth measurement and damage detection device for horizontal boreholes in mining according to the present invention.

[0078] Figure 5 The orthogonal sine wave signal generated by the signal generator of this application. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0080] The detection device mainly consists of a measuring host 1, a transmitting probe 2, a receiving probe 3, a ground probe 4, and a communication cable 5. The measuring host 1 is installed; the transmitting probe 2 is installed at the borehole opening and connected to the measuring host 1 via the communication cable to couple the transmitted wave signal to the drill rod under test; the receiving probe 3 is installed at the borehole opening and connected to the measuring host 1 via the communication cable to couple the echo signal received by the drill rod under test to the measuring host 1; the ground probe 4 is installed in the coal seam near the borehole and connected to the coal seam near the borehole via the communication cable 5 to form a signal loop.

[0081] In this invention, the measurement host is equipped with a main control processor. The main control processor is connected to a depth data calculator and a damage data calculator in one direction. The main control processor is connected to a signal generator, a transmit signal generator driver, a signal splitter, a signal conditioner, a data acquisition unit, and a data storage unit in two directions. The data storage unit is connected back to the main control processor. The main control processor is connected to a feature encoding generator in three directions, and the feature encoding generator is connected to the transmit signal generator driver. After the signal splitter, a transmit signal coupler and a transmit probe, a receive signal coupler and a receive probe, and a ground coupler and a ground probe are connected in parallel in sequence.

[0082] The main control processor, acting as the main control unit, controls various modules including the signal generator, feature encoding generator, data acquisition unit, data storage unit, depth data calculator, and damage data calculator. The signal generator generates standard excitation signals. The feature encoding generator generates random encoded signals with distinct characteristics. The transmit signal generation driver combines the standard excitation signal and the feature encoding signal to generate a transmit signal with distinct characteristics, and amplifies this transmit signal to ensure sufficient energy for reflection back to the orifice after reaching the bottom. The signal splitter, with built-in multiplexed switches and coupling units, switches the transmit, receive, and loop signals. The signal conditioner, with multi-stage amplification, filtering, and shaping units, conditions the received signal to suppress interference noise in the loop, improving the signal-to-noise ratio and facilitating the extraction of effective signals by subsequent modules. The data acquisition unit acquires complete received echo signals. The data storage unit stores the acquired received echo signals for backup and retrieval by the main control processor. The depth data calculator is used to determine the valid reflected wave signal from the complete received signal and calculate the borehole depth information. The damage data calculator extracts the reflected wave signal at the damage point of each drill pipe section from the valid reflected wave signal, and after normalization and related calculations, determines the location and degree of damage. The transmitting signal coupler, receiving signal coupler, and ground wire coupler are used to connect the transmitting brush, receiving brush, and ground wire to the measurement host. The output ports adopt isolated coupling to ensure safety in underground coal mine applications and reduce energy loss during signal transmission. The transmitting brush, installed at the borehole opening, connects to the measurement host via a communication cable, coupling the transmitted wave signal to the drill pipe being measured. It adopts a brush-type structure, has no rigid connection to the drill pipe, requires no manual intervention, and ensures signal coupling effectiveness even during drill pipe movement. The receiving probe, installed at the borehole opening, connects to the measurement host via a communication cable. It couples the echo signal received by the drill rod to the measurement host. Using a brush-type structure, it has no rigid connection to the drill rod and requires no manual intervention, ensuring effective signal coupling even during drill rod movement. The ground probe, installed in the coal seam near the borehole, connects to the nearby coal seam via a communication cable, forming a signal loop.

[0083] The detection method of the detection system of this invention is as follows:

[0084] This invention uses an electrical signal as the measurement signal and the drill rod and coal seam as the signal transmission carriers. The transmitted signal is coupled to the drill rod under test through a transmitting probe. When the transmitted signal encounters an impedance discontinuity point (i.e., a damaged part of the drill rod connection face or body), the transmitted signal is reflected back. By calculating the consistency of the characteristic waveforms of the transmitted and received signals, a valid signal is considered when the consistency ratio is at its maximum. At this point, the signal transmission distance, i.e., the borehole depth, can be calculated using the time difference between transmission and reception. Then, the degree of damage to the drill rod is determined by the strength of the received signal. This allows for the detection of the total length of the drill rod and the damage status of each drill rod. The transmitting and receiving probes are connected to the exposed portion of the drill rod on the ground, and the ground probe is connected to the earth. In this way, the transmitted signal can form a return flow through the drill rod and the earth for signal transmission and reception.

[0085] Launch principle:

[0086] Due to the harsh working environment, numerous interference sources, and strong interference signals in underground coal mines, using a standard signal as the excitation signal is highly susceptible to interference. Therefore, this invention proposes a method for adjusting the standard excitation signal using random feature coding, so that the standard excitation wave changes with the random coding signal. This results in a unique signal that is distinct from the noise source. This excitation signal modulation method is specifically designed for underground coal mine working conditions, thereby enhancing the signal recognition capability.

[0087] The main control processor controls the signal generator to generate a standard excitation signal, and at the same time generates a random coded signal through the feature encoder generator. The standard excitation signal and the coded signal are combined by the signal transmission signal generator driver and the power is amplified to generate a transmission excitation signal with obvious characteristics. Since the random coded signal has good characteristic waveform recognition characteristics, the modulated transmission excitation signal also has good recognition characteristics. The transmission excitation signal is sent to the transmission signal coupler through the signal splitter.

[0088] Receiving principle:

[0089] Because drill rods are connected in multiple stages during horizontal drilling in coal mines, and each section of the drill rod has basically the same specifications, the transmission distance is relatively long. Therefore, as the drilling depth increases, the transmitted signal energy gradually attenuates, and the signal-to-noise ratio continuously decreases. In addition, the coupling effect between each stage of the drill rod and the coal seam is different, which will cause distortion of the reflected signal. Traditional signal extraction methods are difficult to effectively distinguish the reflected signal. Therefore, this invention proposes a signal extraction method suitable for mine horizontal drill rods.

[0090] During borehole depth measurement, the impedance of the drill rod is discontinuous at the joint. When the transmitted signal encounters the joint, a strong reflection waveform will occur. This transmitted waveform will be coupled through the receiving circuit. The data acquisition device will collect the received signal. At the same time, the main control processor starts timing when the transmitted signal is completed. The main control processor will calculate the transmitted and received waveforms through characteristic waveform recognition. When the received signal and the transmitted signal have a high degree of consistency, it is considered to be a reflection process. The reflection distance is calculated and stored using the wave speed transmission formula. Furthermore, since there are multiple drill pipes, this reflection process will occur multiple times, and the subsequent reflected waveforms will become weaker and weaker. If only the transmitted and received waveforms are used for characteristic waveform consistency calculation, it is easy to cause misjudgment. Therefore, this invention proposes that after the first strongest reflected waveform arrives, the main control processor will save the first received reflected waveform. After subsequent reflected waves are received, the characteristic waveform consistency calculation is performed on the first received waveform and the subsequent received waveforms to determine whether it is a true reflected waveform. This process is repeated to determine the position of the reflected waveform at each joint end face. Then, the received reflected waveform is compared with the transmitted waveform to calculate the waveform propagation distance, thereby realizing the determination of the drilling depth and improving the fault tolerance of the system.

[0091] When assessing drill pipe damage, the impedance at the point of mechanical damage also changes, causing the transmitted signal to be reflected. Since the impedance change at the drill pipe joint end face is much greater than that at the damage point, the reflected wave energy at the damage point is less than that at the joint end face. Furthermore, because the drill pipe has a consistent unit length, the intervals of reflected waves formed by the joint end faces are also generally consistent. Since the end face reflected waves have already been extracted during borehole depth measurement, the reflected signal within the end face reflection interval can be identified as the reflected signal at the damage point. After signal extraction, the location of the damage point on the drill pipe can be determined by calculating the consistency of the characteristic waveforms of the end face reflected signal and the reflected signal at the damage point. In addition, because the signal energy attenuates progressively during transmission, the received signal needs to be normalized to obtain an energy compensation coefficient to ensure consistent energy of the reflected signals at each end face level. This achieves a consistent evaluation standard for all drill pipe sections. The degree of damage is then determined based on the intensity of the reflected signal, and an early warning is issued when a certain threshold is reached.

[0092] The operation method of the detection system of this invention is as follows:

[0093] Step 1: Fix the transmitting and receiving probes to the borehole opening, connect the ground probe to the coal seam near the borehole, connect the ground probe to the measurement host via a communication cable, and power on the host to input the measurement software.

[0094] Step 2: After drilling two or three drill rods, input the known drill rod length on the measurement host, which is the length of a single drill rod multiplied by the number of drill rods already drilled. Click to perform system calibration. The system will automatically calculate parameters such as signal speed, transmission coefficient, and signal characteristics under the current working conditions and write these parameters into the measurement system.

[0095] Step 3: Disconnect the transmitting and receiving probes and continue drilling.

[0096] Step 4: When measurement is required, connect the transmitting and receiving probes to the drill rod being measured. The measuring host will automatically display the current borehole depth and the damage status of the drill rod.

[0097] Example 1:

[0098] See Figure 1 The present invention provides a real-time borehole depth measurement and damage detection device for horizontal boreholes in mining. It mainly comprises a measuring host 1, a transmitting brush 2, a receiving brush 3, a ground probe 4, and a communication cable 5. During construction, the transmitting brush 2 and the receiving brush 3 are connected to the drill rod being measured via the communication cable 5. The ground probe 4 is connected to the coal seam near the borehole via the communication cable 5. This allows the transmitted signal to flow back through the drill rod and the ground, facilitating signal transmission and reception, thereby enabling the detection of the total length of the drill rod and the damage status of each drill rod.

[0099] See Figure 2The detection system block diagram shows the detection device, which comprises a measurement host 1, a transmitting probe 2, a receiving probe 3, a ground probe 4, and communication cables 5. The measurement host includes a main control processor, a signal generator, a feature encoding generator, a transmit signal generation driver, a signal splitter, a signal conditioner, a data acquisition unit, a data storage unit, a transmit signal coupler, a receive signal coupler, a ground probe coupler, a depth data calculator, and a damage data calculator. The main control processor, as the main control unit, controls the various modules including the signal generator, feature encoding generator, data acquisition unit, data storage unit, depth data calculator, and damage data calculator. The signal generator generates a standard excitation signal. The feature encoding generator generates a random encoded signal with distinct characteristics. The transmit signal generation driver combines the standard excitation signal and the feature encoded signal to generate a transmit signal with distinct characteristics, and amplifies the power of this transmit signal to ensure sufficient energy for reflection back to the borehole opening after reaching the bottom. The signal splitter, with built-in multiplexer switches and coupling units, switches the channels for transmit signals, receive signals, and loop signals. The signal conditioner, with multi-stage amplification, filtering, and shaping units, conditions the received signal to suppress interference noise in the loop, improving the signal-to-noise ratio and facilitating the extraction of valid signals by subsequent modules. The data acquisition unit collects complete received echo signals. The data storage unit stores the collected received echo signals for backup and retrieval by the main control processor. The depth data calculator identifies valid reflected wave signals from the complete received signal and calculates the borehole depth. The damage data calculator extracts reflected wave signals from damage points in each section of the drill pipe from the valid reflected wave signals, and calculates the location and extent of damage after normalization and related calculations. The transmitting signal coupler, receiving signal coupler, and ground wire coupler connect the transmitting probe 2, receiving probe 3, and ground wire 4 to the measurement host 1. The output ports use isolated coupling to ensure safety in underground coal mine applications and reduce energy loss during signal transmission. Transmitting probe 2 is connected to the measuring host 1 via communication cable 5, coupling the transmitted signal to the drill rod under test. Receiving probe 3 is connected to the measuring host 1 via communication cable 5, coupling the echo signal received by the drill rod under test to the measuring host 1. Ground probe 4 is connected to the coal seam near the borehole via communication cable 5, forming a signal loop.

[0100] This invention uses an electrical signal as the measurement signal and the drill rod and coal seam as the signal transmission carriers. The transmitted signal is coupled to the drill rod under test through a transmitting probe. When the transmitted signal encounters an impedance discontinuity point (i.e., a damaged area on the drill rod connection face or body), the transmitted signal is reflected back. By calculating the consistency of the characteristic waveforms of the transmitted and received signals, a valid signal is considered when the consistency ratio is at its maximum. At this point, the transmission distance, i.e., the borehole depth, can be calculated using the time difference between transmission and reception. Then, the degree of damage to the drill rod is determined by the strength of the received signal. This enables the detection of the total length of the drill rod and the damage status of each drill rod.

[0101] When the detection system is working, the main control processor first controls the signal generator to generate a standard excitation signal, and at the same time generates a random coded signal through the feature encoding generator. The standard excitation signal and the coded signal are combined by the transmission signal generation driver to generate a transmission excitation signal with characteristics. This signal is sent to the transmission signal coupler through the signal splitter, and then transmitted to the transmission probe 2 to complete the signal transmission.

[0102] The main control processor starts timing the moment the transmitted signal is completed. The received signal is transmitted to the receiving signal coupler via receiving probe 3, then through the signal splitter to the signal conditioner. After conditioning, the received signal is acquired by the data acquisition unit. The acquired data is stored in the data memory for backup. The main control processor reads the data and sends it to the depth data calculator. Through multiple characteristic waveform consistency algorithms, the accurate reflected wave signal is determined and extracted, and the borehole depth is calculated. The damage data calculator then performs characteristic waveform consistency calculations based on the borehole depth calculation, comparing the reflected signal from the end face with the reflected signal at the damage point to determine the location of the damage point on the drill pipe. After normalization, the energy compensation coefficient is obtained. The degree of damage is determined based on the intensity of the reflected signal, and an early warning is issued when a certain threshold is reached.

[0103] See Figure 3The schematic diagram illustrates the principle of transmitting signal generation. To further improve the measurement accuracy, signal anti-interference capability, and fault tolerance of this invention, the key lies in obtaining a distinctive transmitting excitation signal so as to extract the accurate reflected wave signal from numerous echo signals. To this end, this invention designs a modulation method. The signal generator first generates a set of high-frequency standard signals as the starting marker signal for the transmitting signal, and then emits a standard excitation signal as the excitation (see Figure 3a). Simultaneously, the feature encoding generator generates a random encoding signal (see Figure 3b). This signal is modulated with the standard excitation signal. When the random encoding signal is negative, phase reversal occurs, forming a unique transmitting waveform (see Figure 3c). Because the random encoding signal is unique, it possesses excellent characteristic waveform recognition properties. Therefore, the modulated transmitting excitation signal also possesses excellent recognition properties.

[0104] See Figure 4 Schematic diagram of borehole depth measurement and damage detection principle (see attached image). Figure 4 In Figure a, during borehole depth measurement, the impedance of the drill rod is discontinuous at the joint. When the transmitted signal encounters the joint, a strong reflection waveform occurs. This transmitted waveform is coupled through the receiving circuit, and the received signal is acquired by data acquisition devices 1-8. At the same time, the main control processor starts timing when the transmitted signal is completed. The main control processor will calculate the transmitted and received waveforms through characteristic waveform recognition. When the received and transmitted signals have a high degree of consistency, it is considered a reflection process. The reflection distance is calculated and saved using the wave speed transmission formula. Furthermore, since there are multiple drill pipes, this reflection process will occur multiple times, and the subsequent reflected waveforms will become weaker and weaker. If only the transmitted and received waveforms are used for characteristic waveform consistency calculation, it is easy to cause misjudgment. Therefore, this invention proposes that after the first strongest reflected waveform arrives, the main control processor will save the first received reflected waveform. After subsequent reflected waves are received, the characteristic waveform consistency calculation is performed on the first received waveform and the subsequent received waveforms to determine whether it is a true reflected waveform. This process is repeated to determine the position of the reflected waveform at each joint end face. Then, the received reflected waveform is compared with the transmitted waveform to calculate the waveform propagation distance, thereby realizing the determination of the drilling depth and improving the fault tolerance of the system.

[0105] When assessing drill pipe damage, the impedance at the point of mechanical damage also changes, causing the transmitted signal to be reflected. Since the impedance change at the drill pipe joint end face is much greater than that at the damage point, the reflected wave energy at the damage point is less than that at the joint end face. Furthermore, because the drill pipe has a consistent unit length, the intervals of the reflected waves formed by the joint end face are also generally consistent. Since the end face reflected waves have already been extracted during borehole depth measurement, the reflected signal within the end face reflection interval can be identified as the reflected signal at the damage point. After signal extraction, by calculating the consistency of the characteristic waveforms of the end face reflected signal and the reflected signal at the damage point, the location of the damage point on the drill pipe can be determined. Figure 4 Figure a in the diagram illustrates the principle of borehole depth measurement. Figure 4 Figure b shows a schematic diagram illustrating the damage detection principle. Figure 4 Figure a illustrates that in practical applications, due to energy loss during signal propagation in the drill pipe, the reflected signal gradually attenuates with increasing depth. Specifically, the reflected signal at the end face 1 is greater than the reflected signal at the end face 2, the reflected signal at the end face 2 is greater than the reflected signal at the end face 3, and so on, until the reflected signal at the bottom of the hole, n. Therefore, the closer the joint end face is to the bottom of the hole, the lower the excitation energy received, and the smaller the reflected signal. For damage points of the same specifications, the reflected signal at the hole opening is much greater than the reflected signal at the bottom of the hole. To avoid misjudging the damage condition due to energy attenuation, this invention proposes that the received signal be normalized before determining the degree of drill pipe damage. See [reference needed]. Figure 4 In Figure b, the energy compensation coefficient is obtained to ensure that the energy of the reflected signals from each end face is consistent, thereby achieving a unified evaluation standard for each level of drill pipe. The degree of damage is then determined based on the intensity of the reflected signal, and an early warning is issued when a certain threshold is reached.

[0106] Protection requirements for the signal generation and demodulation sections:

[0107] ① Traditional excitation signals generate a standard sine wave. This invention requires the signal generator to produce a pair of orthogonal sine wave signals with consistent amplitude and a 90° phase difference. These two orthogonal sine wave signals with a 90° phase difference are then fed into a subsequent stage for PN code modulation. This avoids the interference resistance shortcomings of a single sine wave signal from the source. For example... Figure 5 .

[0108] ② Generation of PN codes. Traditional PN code generation only utilizes its balance and run-length properties, and can only achieve autocorrelation or cross-correlation. This invention utilizes a unique PN code generation method, which combines autocorrelation and cross-correlation.

[0109] The mutual characteristics make the correlation of the transmitted signals stronger.

[0110]

[0111]

[0112]

[0113] In equations (1) and (2), τ represents the coefficients used to generate the code sequence, which are dynamically provided by the program during testing. After the program provides the coefficients, for example, if a sequence of 4096 points is taken, then N is 4096, and R... x (τ) and R y (τ) forms a pair of orthogonal sequences with a phase difference of 90°. Equations (1) and (2) are the autocorrelation codes generated by the modulation of the orthogonal sine wave signals respectively. The autocorrelation codes are cross-correlated using equation (3). The codes processed by equation (3) are coupled to the drill pipe under test through the transmitting circuit.

[0114] ③ Reflection signal processing

[0115] The total signal reflected back is:

[0116]

[0117] The first reflected signal of the fault location test signal is r1 = a1x(t-τ), where τ is the signal transmission delay in the drill pipe, n(t) is the signal noise (including other working signals and interference signals in the drill pipe), and a k Let T be the reflection coefficient, t be the discrete unit of the signal in the time domain, and k be the superposition weight of the sinusoidal signals of the reflected signal in the time domain. Noise is considered to act throughout the entire time interval; therefore, its duration of action is much longer than that of the signal x(t). That is, T... n T x , can be seen as: T n +T x ≈T n Utilizing this relationship, the present invention designs a unique received signal processing method, which involves performing autocorrelation and cross-correlation operations on a set of reflected quadrature modulated signals:

[0118]

[0119] x(t) is an integral over a time interval, so it can be considered as an energy signal. Therefore, the energy spectral density can be expressed as the square of the absolute value of the Fourier transform of the x(t) signal, where T is the maximum frequency weight of the frequency domain superposition. Assuming X(f) is the Fourier transform of x(t), the energy spectral density is:

[0120] G x(f) =|F{x(t)}| 2 =|X(f)|2 ;

[0121] Its power spectral density will not be zero within a finite time period, therefore its power spectral density function can be calculated as follows:

[0122]

[0123] The total energy of x(t) can be calculated using Rayleigh's theorem.

[0124]

[0125] in

[0126] n and m represent the time series combination of x(t), f represents the set of frequency points in the frequency domain, and d is the integral symbol;

[0127] We also need to calculate the cross-correlation energy between x(t) and n(t). Calculating the cross-correlation energy requires first calculating the Fourier transform of the cross-correlation.

[0128] F{R xn (t)}=F{x(t)*n(-t)}=X(f)N * (f);

[0129] In the formula N * (f) is the conjugate of the frequency domain sequence N(f);

[0130] The final formula for the cross-correlation energy is:

[0131]

[0132] By continuously calculating the received signal sequence, when the cross-correlation energy exceeds the threshold, it can be considered as a reflected signal with a sudden impedance change. At this time, the time difference from transmission to reflection can be used to calculate the distance between the drill pipe joint or crack and the transmitted signal. By continuously adjusting the threshold range during the detection process, the specific location of each joint and crack on the drill pipe can be obtained. Due to the use of a combination of autocorrelation and cross-correlation technology, the detection accuracy can reach the centimeter level and the stability is very high.

[0133] The operation method of the detection system of this invention is as follows:

[0134] Step 1: Fix the transmitting and receiving probes to the borehole opening, connect the ground probe to the coal seam near the borehole, connect the ground probe to the measurement host via a communication cable, and power on the host to input the measurement software.

[0135] Step 2: After drilling two or three drill rods, input the known drill rod length on the measurement host, which is the length of a single drill rod multiplied by the number of drill rods already drilled. Click to perform system calibration. The system will automatically calculate parameters such as signal speed, transmission coefficient, and signal characteristics under the current working conditions and write these parameters into the measurement system.

[0136] Step 3: Disconnect the transmitting and receiving probes and continue drilling.

[0137] Step 4: When measurement is required, connect the transmitting and receiving probes to the drill rod being measured. The measuring host will automatically display the current borehole depth and the damage status of the drill rod.

[0138] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0139] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0140] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for real-time depth measurement and damage detection of horizontal boreholes used in mining, characterized in that, The method utilizes a real-time depth measurement and damage detection device for horizontal mine boreholes. This device includes: a measurement host; a transmitting probe, installed at the borehole opening and connected to the measurement host via a communication cable, which couples the transmitted wave signal to the drill rod under test; a receiving probe, also installed at the borehole opening and connected to the measurement host via a communication cable, which couples the echo signal received by the drill rod under test to the measurement host; and a ground probe, installed in the coal seam near the borehole and connected to the coal seam near the borehole via a communication cable, forming a signal loop. Electrical signals are used as measurement signals, and the drill rod and coal seam are used as signal transmission carriers. The transmitted signal is coupled to the drill rod being measured through a transmitting probe. When the transmitted signal encounters the connection end face of the drill rod or a damaged part of the rod body, the transmitted signal is reflected back. The transmitting probe and the receiving probe are connected to the drill rod, and the ground probe is connected to the ground. The transmitted signal forms a return flow through the drill rod and the ground for signal transmission and signal reception. By calculating the consistency of the characteristic waveforms of the transmitted and received signals, a valid signal is identified when the output value of the consistency ratio is at its maximum. At this point, the distance the signal is transmitted can be calculated using the time difference between transmission and reception, which is the drilling depth. Then, the degree of damage to the drill rod is determined by the strength of the received signal. This enables the detection of the total length of the drill rod and the damage status of each drill rod. The transmitted signals include: The signal generator produces a set of orthogonal sine wave signals with the same amplitude and a 90° phase difference. The pair of orthogonal sine wave signals with a 90° phase difference are sent to the subsequent stage for PN code modulation. The encoded transmission signal is generated using PN code generation methods based on autocorrelation and cross-correlation. (1)； (2)； （3）； In equations (1) and (2) The coefficients used to generate the code order are dynamically provided by the program during testing; after the program provides the coefficients, the resulting sequence of points is the value of N, where N is a natural number. and This forms a pair of orthogonal sequences with a 90° phase difference; Where x, y, i, N, and The two orthogonal PN code sequences and their related calculation parameters are represented sequentially, where x is the in-phase PN code sequence, y is the orthogonal PN code sequence, i is the code sequence sampling point number, and N is the code sequence length involved in the correlation calculation. and These represent the PN code sequence values ​​of the in-phase branch and the quadrature branch at the corresponding sampling points, respectively. Equations (1) and (2) are the autocorrelation codes generated by the modulation of the orthogonal sine wave signals respectively. The autocorrelation codes are cross-correlated using equation (3). The codes processed by equation (3) are coupled to the drill rod under test through the transmitting circuit.

2. The method for real-time depth measurement and damage detection of horizontal boreholes in mining according to claim 1, characterized in that, The transmitted signals include: The method of adjusting the standard excitation signal using random feature coding makes the standard excitation wave change with the changes in the random coded signal. The main control processor controls the signal generator to generate the standard excitation signal, and at the same time generates the random coded signal through the feature encoder generator. The standard excitation signal and the coded signal are combined by the signal transmission signal generator driver and the power is amplified to generate a transmission excitation signal with obvious characteristics. Since the random coded signal has good characteristic waveform recognition characteristics, the modulated transmission excitation signal also has good recognition characteristics. The transmission excitation signal is sent to the transmission signal coupler through the signal splitter.

3. The method for real-time depth measurement and damage detection of horizontal boreholes in mining according to claim 1, characterized in that, The signal reception includes: When measuring the drilling depth, the impedance of the drill rod is discontinuous at the joint. When the transmitted signal encounters the joint, a strong reflection waveform will occur. This transmitted waveform will be coupled through the receiving circuit. The data acquisition device will collect the received signal. At the same time, the main control processor starts timing when the transmitted signal is completed. The main control processor will calculate the transmitted and received waveforms through characteristic waveform recognition. When the received signal and the transmitted signal have a high degree of consistency, it is considered to be a reflection process. The reflection distance is calculated and stored using the wave speed transmission formula. After the first strongest reflected waveform arrives, the main control processor saves the first received reflected waveform. When subsequent reflected waves are received, the characteristic waveform consistency calculation is performed between the first received waveform and the subsequent received waveforms to determine whether it is a true reflected waveform. This process is repeated to determine the position of the reflected waveform on each joint end face. Then, the received reflected waveform is compared with the transmitted waveform to calculate the waveform propagation distance and realize the determination of the drilling depth.

4. The method for real-time depth measurement and damage detection of horizontal boreholes in mining according to claim 1, characterized in that, The signal reception also includes: When determining the damage status of the drill pipe, the impedance at the point of mechanical damage will also change, so the transmitted signal will be reflected when it encounters the mechanical damage point. The reflected wave energy at the damage point is less than the reflected energy at the end face of the joint. The reflected signal inside the reflection interval of the end face can be identified as the reflected signal at the damage point. After signal extraction, the location of the damage point on the drill pipe can be determined by calculating the consistency of the characteristic waveforms of the reflected signal at the end face and the reflected signal at the damage point.

5. The method for real-time depth measurement and damage detection of horizontal boreholes in mining according to claim 4, characterized in that, When determining the degree of damage to the drill pipe, the received signal needs to be normalized first to obtain the energy compensation coefficient, and then the degree of damage needs to be determined based on the intensity of the reflected signal. An early warning is issued when a certain threshold is reached.

6. The method for real-time depth measurement and damage detection of horizontal boreholes in mining according to claim 1, characterized in that, Processing the reflected signal includes: The total signal reflected back is: ； The first reflected signal of the fault location test signal is: , The signal transmission delay in the drill pipe, For signal noise, is the reflection coefficient, where t is the discrete time variable in the time domain, and k is the reflection path number or reflection component number; Perform autocorrelation and cross-correlation operations on a set of reflected quadrature modulated signals: ； Where x(t) is the transmitted coded signal sequence, y(t) is the received echo signal sequence participating in the correlation operation, d is the integral element, and t i This corresponds to the propagation delay of the reflection path; Since it is an integral over a time period, it can be considered as an energy signal. Therefore, the spectral density of the energy can be expressed as... The square of the absolute value of the Fourier transform of the signal, where T is the maximum frequency weight of the frequency domain superposition; assuming yes The Fourier transform of the energy spectral density is: ； Where f is the frequency point in the frequency domain and F{} is the Fourier transform operator; Its power spectral density will not be zero within a finite time period, therefore its power spectral density function can be calculated as follows: ； Among them, T x The length of the finite observation time window used to calculate the power spectral density of the signal; According to Rayleigh's theorem, we can find... Total energy: ； in ; n and m represent The time series combination, f represents the set of frequency points in the frequency domain, and d is the integral symbol; We still need to find and The cross-correlation energy needs to be calculated first, which requires calculating the Fourier transform of the cross-correlation: ； In the formula Frequency domain sequence Conjugate; The final formula for the cross-correlation energy is: ； in, The cross-correlation function of signal and noise and It is a frequency domain integral infinitesimal element; By continuously calculating the received signal sequence, when the cross-correlation energy exceeds the threshold, it can be considered as a reflected signal with a sudden impedance change. At this time, the time difference from transmission to reflection can be used to calculate the distance between the drill pipe joint or crack and the transmitted signal. By continuously adjusting the threshold range during the detection process, the specific location of each joint and crack on the drill pipe can be obtained.

7. The method for real-time depth measurement and damage detection of horizontal boreholes in mining according to any one of claims 1 to 6, characterized in that, The measurement host is equipped with a main control processor, which is connected to a depth data calculator and a damage data calculator. The main control processor is connected in two ways to a signal generator, a signal generator driver, a signal splitter, a signal conditioner, a data acquisition unit, and a data storage unit. The data storage unit is connected back to the main control processor. The main control processor is connected to a feature encoding generator via three channels, and the feature encoding generator is connected to the transmit signal generation driver. After the signal splitter, a transmitting signal coupler and a transmitting probe, a receiving signal coupler and a receiving probe, and a grounding coupler and a grounding rod are connected in parallel in sequence.

8. The method for real-time depth measurement and damage detection of horizontal boreholes in mining according to claim 7, characterized in that, The main control processor is the main control unit, used to control each module; A signal generator is used to generate standard excitation signals; A feature code generator is used to generate random coded signals with distinct characteristics; The transmit signal generation driver generates a transmit signal with distinct characteristics by combining a standard excitation signal and a feature-encoded signal, and then amplifies the power of the transmit signal. The signal splitter has a built-in multiplexer switch and coupling unit for channel switching of transmitted signals, received signals and loop signals; A signal conditioner is used to condition the received signal; The data acquisition unit is used to acquire the complete received echo signal; Data storage device, used to store the acquired received echo signals; The depth data calculator is used to determine the valid reflected wave signal from the complete received signal and to calculate the depth information of the borehole. The damage data calculator is used to extract the reflected wave signals at the damage points of each section of the drill pipe from the effective reflected wave signals. After normalization and related calculations, the location and degree of damage of the drill pipe damage points are obtained. The transmitter signal coupler, receiver signal coupler, and ground wire coupler are used to connect the transmitter brush, receiver brush, and ground wire to the measurement host. The output ports adopt isolated coupling.

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