WO2023216713A1

WO2023216713A1 - Geological detection system

Info

Publication number: WO2023216713A1
Application number: PCT/CN2023/081457
Authority: WO
Inventors: �龙昊; 李昆
Original assignee: 华为技术有限公司
Priority date: 2022-05-12
Filing date: 2023-03-14
Publication date: 2023-11-16
Also published as: CN117092704A

Abstract

A geological detection system. The geological detection system comprises a detection device and a magnetic field sensor. The magnetic field sensor is used for detecting a magnetic field signal transmitted by a geologic body, and transmitting, to the detection device under the action of the magnetic field signal, a detection signal having a magnetic field intensity corresponding to that of the magnetic field signal. The detection device is used for determining the magnetic field intensity of the magnetic field signal on the basis of the detection signal, and determining, on the basis of the magnetic field intensity of the magnetic field signal, whether the geologic body is a geologic body of a target type. According to the solution, the magnetic field intensity is used for determining a special geologic body, and the magnetic field intensity does not need to be measured by using a coil, such that the problem that a detection result is interfered by an equivalent inductance is avoided, and the accuracy of the detection result can be improved. Moreover, sensors used for measuring the magnetic field intensity can be generally made small, such that normal use thereof in drilling can be guaranteed.

Description

geological detection system

This application claims priority to the Chinese patent application with application number 202210520057.9 and the invention name "Geological Detection System" submitted on May 12, 2022, the entire content of which is incorporated into this application by reference.

Technical field

This application relates to the field of geological detection technology, and in particular to a geological detection system.

Background technique

In the process of coal mining, various special geological bodies will be encountered, such as water bodies, oil and gas, etc. When certain special geological bodies are mined, major safety accidents will occur. Therefore, before coal mining, geological body detection must be carried out in the mine.

Currently, a relatively effective method for geological exploration is the transient electromagnetic method, which generates an instantaneously changing magnetic field signal to stimulate a secondary electromagnetic field at a low-resistance anomaly. By detecting the magnetic flux of this secondary field signal, the earth can be inverted and interpreted. geological conditions at different depths. Since the secondary field signal is small, large coils with a meter length are usually used for signal detection in the tunnels of the excavation face. However, due to problems such as the large number of underground interference signals, complex geological structures, and strong measurement variability, the detection accuracy is low. In order to minimize the impact of various interference factors in the tunnel on signal detection, a transient electromagnetic solution in the hole has been developed, that is, the coil is placed in the borehole for detection.

Due to the limited size of the drill hole, the detection capability of the electromagnetic sensor can only be improved by increasing the number of coil turns. However, although the number of coil turns can increase the magnetic flux, it also brings additional problems such as equivalent inductance that are difficult to eliminate and affect signal reception. These problems lead to limited detection capabilities, affect detection accuracy and detection distance, and ultimately lead to the loss of geological bodies. Detection is inaccurate.

Contents of the invention

Embodiments of the present application provide a geological detection system that can solve the problem of inaccurate geological body detection results in the prior art. The technical solutions are as follows:

In a first aspect, this application provides a geological detection system, which includes detection equipment and a magnetic field sensor. After the magnetic field sensor detects the magnetic field signal emitted by the geological body, under the action of the magnetic field signal, it emits a detection signal corresponding to the magnetic field intensity of the magnetic field signal to the detection equipment.

The magnetic field sensor can be an optical fiber sensor. Under the action of magnetic field signals with different magnetic field strengths, the spectrum of the reflected signal of the optical fiber sensor will be different. The magnetic field sensor can also be a giant magnetoresistive sensor. The giant magnetoresistive sensor changes its own resistance under the action of magnetic field signals of different magnetic field strengths, thereby changing the size of the detection current. The magnetic field sensor can also be a more sensitive magnetic field sensor based on quantum technology. The quantum magnetic field sensor undergoes an energy level transition under the action of the magnetic field signal and radiates an electromagnetic signal. By detecting the electromagnetic signal, magnetic field sensing can be achieved.

The detection equipment receives the detection signal emitted by the magnetic field sensor, and determines the magnetic field intensity of the magnetic field signal based on the detection signal. Then, based on the magnetic field intensity of the magnetic field signal, it determines whether the geological body is a target type of geological body (i.e., a geological body with low resistivity). ), such as water bodies, etc. A simple way to determine the existence of a target geological body can be to determine the strength of the magnetic field Is it greater than the intensity threshold? If it is greater, it means that the target geological body exists within a certain distance. Using this solution, special geological bodies are determined through the detected magnetic field strength. The magnetic field strength does not need to be detected by a detection coil, so there is no problem of equivalent inductance interfering with the detection results, thus improving the accuracy of the detection results. Moreover, the sensors used to detect magnetic field strength can generally be made smaller to ensure normal use in drilling.

In a possible implementation, the geological detection system further includes a magnetic field generator. The magnetic field generator emits a transient magnetic field signal, and the geological body generates a secondary field echo signal under the stimulation of the transient magnetic field signal emitted by the magnetic field generator. The transient magnetic field signal can be an instantaneous changing electromagnetic pulse. The variable magnetic field signal can be formed by switching the magnetic field generator from the on state to the off state, or by switching the magnetic field generator from the off state to the on state. After detecting the secondary field echo signal emitted by the geological body, the magnetic field sensor emits a corresponding detection signal to the detection equipment. The detection equipment determines the corresponding magnetic field strength based on the detection signal, thereby determining whether the geological body is a target type of geological body.

Using this solution, the geological body can generate a secondary field when excited by an external magnetic field signal. The magnetic field signal emitted by the secondary field and the secondary field echo signal will be stronger and more powerful than the magnetic field signal actively emitted by the geological body. It is easily detected by the magnetic field sensor, and the detection results obtained are more accurate.

In a possible implementation, after the detection equipment determines that the geological body is a target type of geological body, it can use the geological body inversion model to determine the geological body based on the magnetic field strength of the magnetic field signal of the geological body and the position information of the magnetic field sensor. location information. Among them, the geological body inversion model can use magnetotelluric linear or nonlinear inversion algorithms, such as fast relaxation inversion, nonlinear conjugate gradient inversion, Occam inversion, etc. The detection equipment determines the distribution of medium properties in the detection area through the geological body inversion model, and further identifies the location information of low-resistance geological bodies (such as water bodies) based on the distribution of medium properties.

Alternatively, the detection equipment may determine the location information of the geological body based on the reception time of the magnetic field signal of the geological body and the location information of the magnetic field sensor.

Technicians can pre-establish an algorithm model based on the distance formula to calculate the magnetic field strength of the secondary field echo signal based on the reception time of the secondary field echo signal and the position information of the magnetic field sensor (the algorithm model can be a machine learning model or based on theory The deduced mathematical formula), it can be approximately considered that the propagation speed of magnetic field (ie electromagnetic wave) in the formation is a unified value. Therefore, the detection equipment can determine the position information of the geological body in the preset coordinate system.

Optionally, after the detection equipment determines the detected target type of geological body, the location information of the geological body can be sent to a designated computer device. The computer device can display the location information of the geological body and can also issue an alarm to technicians. , such as signal light alarm, sound alarm, etc.

Using this solution, it can not only determine whether the geological body is a target type of geological body, but also detect the location information of the geological body. At the same time, an alarm can be sent to technical personnel, and the mining plan can be adjusted in a timely manner to ensure the safety of coal mining operations. .

In a possible implementation, the magnetic field sensor is an optical fiber sensor, and the detection device and the optical fiber sensor are connected through optical fibers. The signal detector of the detection equipment includes a light transmitter and an optical receiver, and the optical fiber sensor and the signal detector of the detection equipment are connected through optical fibers. The signal detector of the detection equipment continues to emit light signals to the optical fiber sensor, and at the same time, continues to receive the reflected light signals emitted by the optical fiber sensor.

Optical fiber sensors can detect magnetic field signals emitted by geological bodies, and have different optical signal reflection characteristics under the action of magnetic field signals with different magnetic field strengths. For example, the reflectivity of optical signal components of the same frequency changes. Based on the reflected light signal received from the optical fiber sensor, the detection equipment determines the frequency corresponding to the wave peak in the reflection spectrum based on the spectrum characteristics of the reflected light signal (also called the reflection spectrum). This frequency is the reflection frequency. Then, based on the undetected magnetic field The reflection frequency when the signal is detected, the reflection frequency when the magnetic field signal is detected, and the related algorithm model of the optical fiber sensor determine the magnetic field emitted by the geological body. The magnetic field strength of the field signal, thereby determining whether the geological body is a target type of geological body.

Using this solution, the size of the optical fiber sensor is smaller, which can meet the needs of detection in the hole. Moreover, the optical fiber sensor is more sensitive to the detection of magnetic field intensity, which is beneficial to improving the accuracy of geological detection.

In a possible implementation, the optical fiber sensor includes an optical fiber grating and a magnetically sensitive component, the optical fiber grating is in contact with the magnetically sensitive component, and the optical fiber grating is connected to the detection device through an optical fiber. Among them, the magnetic sensitive component is used to detect the magnetic field signal emitted by the geological body, and adjust the reflection characteristics of the fiber grating under the action of magnetic field signals with different magnetic field strengths. The fiber grating is used to detect the received optical signal under the action of the magnetic sensitive component. Reflect according to the adjusted reflection characteristics.

Using this solution, the magnetically sensitive components are very sensitive to the detection of secondary field echoes, that is, the magnetic field strength of the secondary field echoes can be accurately detected, and the reflection frequency of the optical signal by the fiber grating can be adjusted in a timely manner, which is beneficial to improving detection. accuracy of results.

In a possible implementation, the magnetically sensitive component is a magnetostrictive material, and the fiber grating is fixed on the magnetostrictive material. The fixing method can be as follows: the magnetostrictive material has an arc-shaped groove structure, and the fiber grating is parallel to the main optical axis. The side surface (can be called axial) is stuck or stuck in the arc-shaped groove of the magnetostrictive material. When the magnetostrictive material deforms under the action of the secondary field echo signal, an external force will be exerted on the fiber grating, thereby causing the fiber grating to deform.

In one possible implementation, the magnetostrictive material covers at least half of the radial cross-sectional circumference of the fiber grating.

Generally, the larger the contact area between the magnetostrictive material and the fiber grating, the more obvious the deformation of the fiber grating will be under the action of the magnetostrictive material, and the more obvious the change in the reflection frequency of the optical signal will be. In order to better enable the magnetostrictive material to detect secondary field echo signals in all directions, the contact area between the side surface of the fiber grating parallel to the main optical axis and the magnetostrictive material can be greater than or equal to half of the side surface area. .

When the magnetostrictive material detects secondary field echo signals in any direction, it will deform and drive the fiber grating to deform. After the fiber grating is deformed, the reflection spectrum of the optical signal will change compared with when it is not deformed. After the signal detector of the detection equipment receives the reflected light signal emitted by the fiber sensor, it determines the center of the reflection spectrum based on the reflection spectrum of the reflected light signal. The frequency corresponding to the wave crest is the reflection frequency. Then, based on the reflection frequency, the detection equipment uses the relevant algorithm model of the optical fiber sensor to determine the magnetic field strength of the secondary field echo signal corresponding to the reflected light signal, thereby determining whether it is a geological body of the target type.

Using this solution, the fiber grating can undergo relatively obvious deformation under the action of the magnetostrictive material, so that the change in the reflection frequency becomes obvious, which is beneficial to the analysis of the detection results and improves the accuracy of the detection results.

In a possible implementation, the geological detection system includes at least two optical fiber sensors. In this case, the detection device determines the first deformation of each fiber sensor along the radial direction of the fiber grating and the second deformation along the main optical axis of the fiber grating based on the reflected light signals received from at least two fiber sensors, and then, based on The first deformation of each fiber optic sensor, and the second deformation of each fiber optic sensor, determine the magnetic field strength of the magnetic field signal emitted by the geological body using a related mathematical model of the magnetic field strength.

Among them, the main optical axes of at least two fiber optic sensors are parallel or collinear, and the perpendicular line from the equivalent center of the magnetostrictive material in any fiber optic sensor to the main optical axis of the fiber grating is equal to that of the magnetostrictive material in other fiber optic sensors. The vertical line from the effective center to the main optical axis of the fiber grating is not parallel and not collinear. The above-mentioned first deformation is the deformation of the optical fiber sensor along the vertical direction.

Optionally, after the detection equipment determines the first deformation and the second deformation of each optical fiber sensor, it can determine the vector sum of the first deformation and the average value of the second deformation, thereby using the relevant mathematical model of the magnetic field intensity to determine the geological body. The magnetic field strength of the emitted magnetic field signal.

Optionally, when determining the magnetic field strength of the magnetic field signal emitted by the geological body, the detection equipment can also determine the direction of the total deformation of each optical fiber sensor based on the direction of the first deformation and the direction of the second deformation of each optical fiber sensor, thereby ,Sure The direction of the magnetic field at each fiber optic sensor. Then, based on the magnitude and direction of the magnetic field intensity of each optical fiber sensor and the geological body inversion model, the location information of the geological body is determined.

Using this solution, at least two fiber optic sensors are used as a group of fiber optic sensors. By calculating the average value of the axial deformation and the vector sum of the radial deformation of at least two fiber optic sensors, the magnetic field of the secondary field echo signal can be calculated more accurately. Strength, thus accurately calculating the magnitude of the magnetic field generated by the geological body. Moreover, by comparing the time points when the reflection frequencies of at least two fiber optic sensors change or the detected magnetic field strengths, the distances from the geological bodies to each fiber optic sensor can be sorted, thereby determining the approximate orientation of the geological bodies.

In a possible implementation, the optical fiber sensor includes at least two optical fiber gratings, and the at least two optical fiber gratings are respectively connected to the detection device through optical fibers.

In this case, the detection device determines the third deformation of each fiber grating along the radial direction of the fiber grating and/or the fourth deformation along the axial direction of the fiber grating based on the optical signal received from each fiber grating. Then, based on the third deformation and/or the fourth deformation of at least two fiber gratings, the detection device uses a relevant mathematical model of the magnetic field intensity to determine the magnetic field intensity corresponding to the secondary field echo signal.

Wherein, the side surfaces of at least two fiber gratings parallel to the main optical axis are fixed at different positions on the outer surface of the magnetostrictive material, the main optical axes of at least two fiber gratings are parallel to each other, and the equivalent center of the magnetostrictive material is to each The vertical lines of the main optical axes of the two fiber gratings are not collinear, and the third deformation of the fiber grating is the deformation of the fiber grating along the direction of the vertical line.

Optionally, after the detection equipment determines the third deformation and the fourth deformation of each optical fiber sensor, the vector sum of the third deformation and the average value of the fourth deformation can be determined, thereby using the relevant mathematical model of the magnetic field intensity to determine the geological body. The magnetic field strength of the emitted magnetic field signal.

Optionally, when the detection equipment determines the magnetic field intensity of the magnetic field signal emitted by the geological body, in addition to determining the magnitude of the magnetic field intensity, it can also determine the total value of the optical fiber sensor based on the direction of the third deformation and the direction of the fourth deformation of each fiber grating. The direction of the deformation, and thus, determines the direction of the magnetic field strength at the fiber optic sensor. Then, based on the magnitude and direction of the magnetic field intensity detected by the optical fiber sensor and the geological body inversion model, the location information of the geological body is determined.

Using this solution, at least two fiber gratings share the same magnetostrictive material, which can ensure that at least two fiber gratings detect the same secondary field echo signal. By calculating the detection results of at least two fiber gratings, it can Reflecting the actual situation of the secondary field echo signal more accurately will help improve the accuracy of detection.

In a possible implementation, the magnetically sensitive component is magnetic fluid, and the fiber grating is immersed in the magnetic fluid. When the optical fiber sensor detects the secondary field echo signal emitted by the geological body, the molecules of the magnetic fluid will rotate in the direction of the magnetic field. As the distribution pattern of the molecules of the magnetic fluid changes, the dielectric properties of the magnetic fluid change, thus causing the reflection spectrum of the fiber grating to change.

The detection equipment determines the corresponding reflection spectrum (ie, spectrum characteristics) based on the received reflected light signal, thereby determining the reflection frequency corresponding to the wave peak in the reflection spectrum, and further determines the dielectric properties of the magnetic fluid. Finally, based on the dielectric properties of the magnetic fluid, the detection equipment uses the relevant algorithm model of the optical fiber sensor to determine the magnetic field strength of the secondary field echo signal corresponding to the reflected light signal.

In a possible implementation, the optical fiber sensor includes at least three optical fiber gratings, wherein the main optical axes of the at least three optical fiber gratings may be parallel to each other. The detection device can determine the deformation of each fiber grating based on the frequency of the reflected light signal received from each fiber grating before the magnetic field generator emits the transient magnetic field signal. Then, based on the deformation of each fiber grating, the attitude information of the fiber sensor is determined. In addition to determining the attitude information of the optical fiber sensor at the detection position, during the process of sending the optical fiber sensor to the detection position, the detection equipment monitors the deformation of the optical fiber sensor to obtain the information of the optical fiber sensor. Movement trajectory, and based on the reference position information, attitude information, and movement trajectory of the optical fiber sensor, the final position information (that is, the actual position information) when the optical fiber sensor reaches the detection position is determined through geometric operations. Finally, based on the detected position information from the geological body The magnetic field strength information, the attitude information of the optical fiber sensor and the actual position information are used to determine the position information of the geological body using a geological body inversion model (which can be a machine learning model).

Before detection, technicians will drill horizontal holes along the tunnel's excavation direction. Then, insert the optical fiber sensor connected to the detection equipment through the optical fiber into the hole, so that the optical fiber sensor is in a horizontal state when entering the hole, and record this position as the reference position, that is, the reference position information of the above-mentioned optical fiber sensor.

Before the magnetic field generator emits a transient magnetic field signal, the detection device continues to emit light signals to the optical fiber sensor, and the optical fiber sensor continues to reflect the light signal. When the technician inserts the optical fiber sensor into the hole, the position of the optical fiber sensor will shift under the action of external force. At the same time, the external force will cause different deformations of each fiber grating, thus causing the reflection of the optical signal by each fiber grating. The frequencies are changed. For example, when the optical fiber sensor bends upward, the upper optical fiber grating is compressed and the lower optical fiber grating is stretched.

In this case, for each fiber grating, after the detection equipment receives the optical signal reflected by the fiber grating, the axial deformation and radial deformation of the fiber grating are determined based on the reflection frequency and the reference reflection frequency of the optical signal. Then, based on the axial deformation and radial deformation of each fiber grating, the detection equipment can determine the attitude information of the optical fiber sensor through the virtual work equation and Newton iteration method. Among them, it can be approximately considered that the optical fiber sensor has not deformed but has occurred as a whole. offset, the attitude information can be considered as the angle between the connection between the two ends of the optical fiber sensor and the horizontal direction.

Using this solution, the actual position and attitude information of the optical fiber sensor can be accurately determined before detection. Therefore, the position information of the geological body can be determined based on the actual position and attitude information of the optical fiber sensor and the geological body inversion model to ensure Accuracy of geological body detection.

In a possible implementation, the optical fiber sensor includes three optical fiber gratings, and the three optical fiber gratings are distributed in an equilateral triangle. The three optical fiber gratings are fixed on the same magnetostrictive material, or the three optical fiber gratings are immersed in the same magnetostrictive material. in a magnetic fluid.

In a possible implementation manner, the optical fiber is a polarization-maintaining optical fiber. The detection device emits a first optical signal and a second optical signal to the optical fiber sensor, where the first optical signal and the second optical signal are optical signals with different polarization directions. The magnetic sensitive component is used to detect the magnetic field signal emitted by the geological body, and adjust the first reflection characteristics of the fiber grating to the first optical signal under the action of the magnetic field signal of different magnetic field strengths, and adjust the fiber grating to the first optical signal. the second reflection characteristic of the second optical signal. Fiber grating is a grating etched on a polarization-maintaining optical fiber, and the fiber grating is used to reflect the first optical signal and the second optical signal. The detection equipment determines the magnetic field strength of the magnetic field signal emitted by the geological body based on the frequency of the reflected light signals in different polarization directions received from the optical fiber sensor.

Using this solution, the change of reflection spectrum of light in different polarization directions of fiber grating can be used to estimate the magnetic field intensity on the radial plane. At this time, the detection equipment combines the reflection frequencies of light in two polarization directions when determining the magnetic field intensity. The calculations can be mutually verified, making the results more accurate, that is, ensuring the accuracy of the detection results.

In a possible implementation, the geological detection system includes multiple optical fiber sensors, the multiple optical fiber sensors are connected in series through optical fibers, and the optical fiber sensor at one end is connected to the detection equipment through optical fibers.

Using this solution, detection equipment can combine the detection results of multiple optical fiber sensors to more accurately determine the location information of geological bodies, improve the accuracy of detection results, and help provide accurate data reference for mine operations and ensure the safety of mine operations. .

In a possible implementation, the geological detection system includes multiple optical fiber sensors, and the multiple optical fiber sensors are divided into There are at least three groups, each group of optical fiber sensors is connected in series through optical fibers, and the optical fiber sensor at one end of each group of optical fiber sensors is connected to the detection equipment through optical fibers.

Using this solution, the detection equipment can be equipped with multiple sets of optical fiber sensors in different directions. On the one hand, it can improve the accuracy of determining the location of geological bodies. On the other hand, it can expand the detection direction and provide more accurate and richer references for mine operations. Data to ensure the safety of mine operations.

In a second aspect, this application provides an optical fiber sensor. The optical fiber sensor includes an optical fiber grating and a magnetostrictive material. The optical fiber grating is fixed on the magnetostrictive material. The optical fiber grating is a grating etched on a polarization-maintaining optical fiber. Taking the first aspect of the geological detection system as an example, when using the optical fiber sensor, the optical fiber sensor can be connected to the detection equipment through a polarization-maintaining optical fiber. This can ensure that the polarization direction of the optical signal does not change when propagating in the optical fiber. Therefore, Effectively ensure the accuracy of detection results when using this optical fiber sensor for detection.

In a third aspect, the present application provides an optical fiber sensor, which includes a magnetically sensitive component and at least three optical fiber gratings, and the at least three optical fiber gratings are in contact with the magnetically sensitive component. Using this optical fiber sensor, the optical signal reflected by the optical fiber sensor can be continuously detected, and the current position information and attitude information of the optical fiber sensor can be determined by analyzing the reflected optical signal. Therefore, the actual attitude information and attitude information when the optical fiber sensor reaches the designated detection position can be determined. Location information has reasons to improve the accuracy of detection results.

The beneficial effects brought by the technical solutions provided by the embodiments of this application are:

In this embodiment of the present application, the geological detection system includes detection equipment and a magnetic field sensor. The magnetic field sensor detects the magnetic field signal emitted by the geological body and transmits the corresponding detection signal to the detection equipment. The detection equipment determines the magnetic field strength of the corresponding magnetic field signal based on the detection signal, thereby determining whether the geological body is a target type of geological body through the magnetic field strength of the magnetic field signal. In this solution, magnetic field strength is used to determine special geological bodies. The magnetic field strength does not need to be detected by a detection coil, so there is no problem of equivalent inductance interfering with the detection results, thus improving the accuracy of the detection results. Moreover, the sensors used to detect magnetic field strength can generally be made smaller to ensure normal use in drilling.

Description of the drawings

Figure 1 is a schematic structural diagram of a geological detection system provided by an embodiment of the present application;

Figure 2 is a schematic structural diagram of a detection device provided by an embodiment of the present application;

Figure 3 is a schematic structural diagram of a geological detection system provided by an embodiment of the present application;

Figure 4 is a schematic structural diagram of a geological detection system provided by an embodiment of the present application;

Figure 5 is a schematic structural diagram of an optical fiber sensor provided by an embodiment of the present application;

Figure 6 is a schematic structural diagram of an optical fiber sensor provided by an embodiment of the present application;

Figure 7 is a schematic structural diagram of a geological detection system provided by an embodiment of the present application;

Figure 8 is a schematic structural diagram of a geological detection system provided by an embodiment of the present application;

Figure 9 is a schematic structural diagram of the radial cross-section of the optical fiber sensor of Figure 6 provided by the embodiment of the present application;

Figure 10 is a schematic structural diagram of an optical fiber sensor provided by an embodiment of the present application;

Figure 11 is a schematic structural diagram of an optical fiber sensor provided by an embodiment of the present application;

Figure 12 is a schematic diagram of radial deformation provided by an embodiment of the present application;

Figure 13 is a schematic structural diagram of an optical fiber sensor provided by an embodiment of the present application;

Figure 14 is a schematic diagram of radial deformation provided by an embodiment of the present application;

Figure 15 is a schematic diagram of the actual position and reference position of an optical fiber sensor provided by an embodiment of the present application;

Figure 16 is a schematic structural diagram of an optical fiber sensor provided by an embodiment of the present application.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

Before explaining the embodiments of the present application in detail, the application scenarios of the embodiments of the present application will be described first.

There are various geological bodies contained in the strata, such as water bodies, oil and gas, etc. During the coal mining process, these geological bodies will more or less increase the difficulty of coal mining, and even cause disasters, causing casualties and equipment damage. For example, if dangerous water bodies are encountered during mining, the resulting water disasters can easily cause casualties, etc. Therefore, before coal mining, geological body detection must be carried out along the mining direction of the mine. If dangerous geological bodies are detected, the mining plan can be adjusted in time to ensure the safety of coal mining operations.

In the formation, the above-mentioned dangerous geological bodies are generally low-resistivity geological bodies. Low-resistivity geological bodies (such as water bodies, etc.) can emit magnetic field signals to the outside. The magnetic field intensity of this magnetic field signal is significantly stronger than that of soil, rocks, etc. Magnetic field signals emitted by geological bodies with high resistivity. Therefore, it can be determined whether there is a target geological body (ie, a geological body with low resistivity) in the current detection direction by detecting the magnetic field intensity of the magnetic field signal. The embodiments of this application take the detection of water bodies as an example to illustrate the solution. Other situations are similar and will not be described again in the embodiments of this application.

An embodiment of the present application provides a geological detection system. The corresponding structure is shown in Figure 1. The geological detection system includes detection equipment and a magnetic field sensor. The detection equipment is connected to the magnetic field sensor.

The magnetic field sensor can detect the magnetic field signal emitted by the geological body and transmit the corresponding detection signal to the detection equipment according to the detected magnetic field signal. The magnetic field sensor can be an optical fiber sensor. Under the action of magnetic field signals with different magnetic field strengths, the optical fiber sensor will have different spectra of reflected signals, that is, it can reflect light signals of different frequencies. The magnetic field sensor can also be a giant magnetoresistive sensor. The giant magnetoresistive sensor changes its own resistance under the action of magnetic field signals of different magnetic field strengths, thereby changing the size of the detection current. The magnetic field sensor can also be a more sensitive magnetic field sensor based on quantum technology. There are no restrictions on the type of magnetic field sensor.

The detection equipment can determine the magnetic field strength of the magnetic field signal corresponding to the detection signal based on the received detection signal, thereby determining whether the currently detected geological body is the target geological body based on the magnetic field strength. A simple way to determine the existence of the target geological body can be to determine whether the magnetic field intensity is greater than the intensity threshold. If it is greater, it means that the target geological body exists within a certain distance.

From the perspective of hardware composition, the detection equipment can include a signal detector, a processor and a memory. The corresponding structure is shown in Figure 2.

The signal detector can be used to receive the detection signal (an analog signal) emitted by the magnetic field sensor and convert the received detection signal into a digital signal. The type of signal detector is determined according to the type of magnetic field sensor. For example, when the magnetic field sensor is an optical fiber sensor, the signal detector is a light receiver and a light transmitter, and so on.

The processor can be a central processing unit (CPU) or a system-on-chip (System on Chip, SoC) etc. The processor can be used to determine the magnetic field strength of the secondary field echo signal, and can be used to determine whether the geological body is a target type of geological body, and so on.

The memory can be various volatile memories or non-volatile memories, such as solid state disk (Solid State Disk, SSD), dynamic random access memory (Dynamic Random Access Memory, DRAM) memory, etc. The memory can be used to store pre-stored data, intermediate data and result data during the execution of operation instructions. For example, the magnetic field strength of the secondary field echo signal, the position information of the magnetic field sensor, etc.

In addition to the signal detector, processor and memory, the detection device may also include communication components, display components, etc.

The communication component can be a wired network connector, a Wireless Fidelity (WiFi) module, a Bluetooth module, a cellular network communication module, etc. The communication component can be used for data transmission with other devices, and other devices can be management devices, servers, or other detection devices.

The display component may be a display panel integrated with the detection device, or may be a display device separated from the detection device and established with a communication connection. When the display component is a display panel, it can be a Twisted Nematic (TN) panel, a Vertical Alignment (VA) panel, or an In-Plane Switching (IPS) panel. ,etc. The display component can be used to display detection signals, magnetic field signals, location information of geological bodies, etc.

Since low-resistance geological bodies can generate secondary fields when excited by external magnetic field signals, the magnetic field intensity of the magnetic field signals emitted by this secondary field (called secondary field echo signals) will be stronger than the magnetic field signals actively emitted by geological bodies. Some are more easily detected by magnetic field sensors. By detecting the magnetic field intensity of secondary field echo signals at different times within a period of time after emitting the excitation magnetic field signal, low-resistance geological bodies can be detected. Therefore, embodiments of the present application provide a geological detection system as shown in Figure 3. The geological detection system includes detection equipment, a magnetic field generator and a magnetic field sensor. The magnetic field generator can emit a transient magnetic field signal to excite the geological body to generate a secondary field echo signal. The transient magnetic field signal can be an instantaneously changing electromagnetic pulse. The transient magnetic field signal can be generated by the magnetic field generator. It is formed by switching the on state to the off state, or by switching the magnetic field generator from the off state to the on state. The magnetic field sensor is used to detect the secondary field echo signal emitted by the geological body and transmit the corresponding detection signal to the detection equipment.

The process of using this geological detection system to detect geological bodies can be as follows:

First, technicians need to perform drilling operations in advance along the excavation direction of the mine tunnel and insert the magnetic field sensor into the hole. If the diameter of the hole is too large, it may cause leakage of dangerous geological bodies and pose certain safety risks. Therefore, the diameter of the hole is generally smaller, such as 3 cm.

Then, after the magnetic field sensor is inserted into the hole, the detection device can determine the position information of each magnetic field sensor in the preset coordinate system. At the same time, technicians determine the emission position of the magnetic field generator in the tunnel, and record the position information (i.e., spatial coordinates) of the magnetic field generator in the preset coordinate system in the detection equipment. Next, technicians use a magnetic field generator to emit electromagnetic pulses (i.e., transient magnetic field signals) with specified magnetic field intensity along the excavation direction of the mine tunnel. The detection equipment can record the time when the magnetic field generator emits the transient magnetic field signal and the time of the transient magnetic field signal. The magnetic field strength of the magnetic field signal.

The magnetic field generator can be connected to the detection equipment. In this case, the detection equipment can also be used to supply power to the magnetic field generator. The technician changes the on-off state between the magnetic field generator and the detection equipment, such as changing the on-state to off-state. On state, etc., thus causing the magnetic field generator to emit a transient magnetic field signal. The magnetic field generator can also be independent of the detection equipment, that is, it has an independent power supply. The technician changes the on-off state between the magnetic field generator and the power supply, so that the magnetic field generator emits a transient magnetic field signal.

Afterwards, the magnetic field signal emitted by the magnetic field generator expanded and propagated from the shallow layer to the deep layer in the formation, and encountered a certain After some geological bodies with low resistivity (that is, target type of geological bodies, such as water bodies, etc.), eddy currents will be generated in the geological bodies. This eddy current will further stimulate secondary fields in the geological bodies and send them to The secondary field echo signal is emitted externally.

Then, the secondary field echo signal emitted by the geological body expands and propagates outward. When the magnetic field sensor detects the secondary field echo signal, under the action of the secondary field echo signal, it will transmit a signal related to the secondary field echo signal to the detection equipment. The detection signal corresponding to the magnetic field strength of the secondary field echo signal. For example, when the magnetic field sensor is an optical fiber sensor, under the action of secondary field echo signals of different magnetic field strengths, the spectrum of the reflected signal will be different, that is, it can reflect light signals of different frequencies; when the magnetic field sensor is a giant magnetoresistance sensor, Under the action of secondary field echo signals of different magnetic field strengths, it changes its own resistance, thereby changing the size of the detection current, and so on. At the same time, the detection equipment can record the reception time of receiving the secondary field echo signal. Specifically, the detection device continues to detect within a period of time and records a set of received detection signals and the time corresponding to the detection signals.

Finally, when the detection device determines the magnitude of the magnetic field intensity at each optical fiber sensor, it can also determine the direction of the magnetic field intensity at each optical fiber sensor. Then, based on the magnitude and direction of the magnetic field intensity detected by each optical fiber sensor and the geological body inversion model, the location information of the geological body is determined. Specifically, the detection equipment can be based on the magnetic field strength of the transient magnetic field signal emitted by the magnetic field generator, the size and direction of the secondary field echo signal detected by each magnetic field sensor at different times within a period of time after emitting the transient magnetic field, and the magnetic field. The position information of the generator and the position information of each magnetic field sensor determine the position information of the geological body in the preset coordinate system. Since there are usually multiple low-resistance medium bodies in the target area, the signal detected by the detection equipment may be the superposition signal of multiple secondary field echoes in the target area. The detection equipment uses magnetotelluric linear or nonlinear inversion algorithms, for example, Fast relaxation inversion, nonlinear conjugate gradient inversion, Occam inversion, etc. determine the distribution of medium characteristics in the detection area, and further identify the location information of low-resistivity geological bodies (such as water bodies) in the target area based on the distribution of medium characteristics.

Optionally, the detection device determines the magnetic field strength of the secondary field echo signal corresponding to the detection signal based on the received detection signal. If the magnetic field intensity is greater than the intensity threshold, the detection equipment can further determine the relevant information of the geological body. Technicians can pre-establish an algorithm based on the distance formula to calculate the magnetic field strength of the secondary field echo signal based on the emission time of the magnetic field signal, the reception time of the secondary field echo signal, the position information of the magnetic field generator and the position information of the magnetic field sensor. Model (the algorithm model can be a machine learning model or a mathematical formula derived based on theory).

Fiber optic sensors are smaller than other sensors and are more suitable for detection operations in small spaces. Moreover, the optical fiber sensor uses light as the carrier of sensitive information and optical fiber as the medium to transmit sensitive information, making it more sensitive.

The embodiment of the present application provides a geological detection system. The magnetic field sensor adopts an optical fiber sensor. The corresponding structure is shown in Figure 4. The signal detector of the detection equipment includes an optical transmitter and an optical receiver. The optical fiber sensor and the signal detector of the detection equipment pass through Fiber optic connection. The signal detector of the detection equipment continues to emit light signals to the optical fiber sensor, and at the same time, continues to receive the reflected light signals emitted by the optical fiber sensor.

Optionally, since fiber gratings have different reflection frequencies for optical signals with different polarization directions, in order to ensure that the polarization direction does not change when the optical signal propagates in the optical fiber, polarization-maintaining optical fiber can be used in the geological detection system to connect the detection equipment and Fiber optic sensor connection.

Fiber optic sensors can include fiber gratings (such as fiber Bragg gratings, weak gratings with low reflectivity, etc.) and magnetic sensitive parts. components, fiber gratings and magnetically sensitive components are in contact.

Fiber grating is an optical fiber etched with a grating structure. Fiber grating is connected to the detection equipment through optical fibers and is used to reflect the optical signal of a certain frequency (generally called the reflection frequency) in the optical signal emitted by the detection equipment.

Magnetic sensitive components refer to components whose characteristics change under the action of a magnetic field (that is, when a magnetic field signal is detected), such as magnetostrictive materials, magnetic fluids, etc. The magnetically sensitive component is used to detect the secondary field echo signal and adjust the reflection characteristics of the fiber grating under the action of the secondary field echo signal with different magnetic field strengths. The fiber grating will strongly reflect light signals of certain frequencies. Two common magnetically sensitive components are introduced below:

(1) The magnetically sensitive component can be magnetic fluid, and the fiber grating is immersed in the magnetic fluid. The corresponding structure is shown in Figure 5. The molecules of the magnetic fluid are distributed in the internal gaps of the fiber grating. When no magnetic field signal is detected, the molecules of the magnetic fluid are randomly distributed, and the dielectric properties of the magnetic fluid (such as dielectric constant, refractive index, etc.) are a certain fixed value. Usually, when a magnetic fluid detects a magnetic field signal, the molecules of the magnetic fluid will be distributed along the direction of the magnetic field (that is, rotate in the direction of the magnetic field). The direction of molecular rotation is related to the direction of the magnetic field, and the rotation speed and amount of rotation of the molecules are related to the strength of the magnetic field. Changes in the distribution of molecules in the magnetic fluid will change the dielectric properties of the magnetic fluid, which will lead to corresponding changes in the reflection properties of optical signals by fiber gratings.

(2) The magnetically sensitive component can be a magnetostrictive material. The side surface of the fiber grating parallel to the main optical axis is fixed on the magnetostrictive material. The corresponding structure is shown in Figure 6. The magnetostrictive material is exposed to magnetic fields of different magnetic field strengths. Different deformations will occur under the influence of signals. Since the fiber grating is fixed on the magnetostrictive material, the deformation of the magnetostrictive material will produce corresponding forces (such as pressure, tension, etc.) on the fiber grating, causing the fiber grating to deform accordingly, thereby making the fiber grating affect the optical signal. Reflective properties change.

When the geological detection system includes an optical fiber sensor, it can be applied to determine whether the formation contains water. When the geological exploration system includes multiple optical fiber sensors, the detection results of each optical fiber sensor can be jointly calculated, so that the location information of the water body in the formation can be determined.

A geological exploration system can include multiple fiber optic sensors, and accordingly, there are a variety of possible connection structures:

Connection structure one

Multiple sensors can be connected in series through optical fibers. The magnetic field sensor at one end is connected to the detection equipment through optical fibers. The corresponding structure is shown in Figure 7.

Connection structure two

Multiple optical fiber sensors can also be divided into multiple groups. Each group of optical fiber sensors is connected in series through optical fibers, and the optical fiber sensor at one end of each group of optical fiber sensors is connected to the detection equipment through optical fibers. The corresponding structure is shown in Figure 8, etc.

For example, technicians can divide multiple fiber optic sensors into three groups, and each group of fiber optic sensors is placed in a different hole. The holes where the three groups of fiber optic sensors are located are distributed in an equilateral triangle. For each group of optical fiber sensors, each optical fiber sensor is connected in series through an optical fiber, and the optical fiber sensor at one end is connected to the detection equipment through an optical fiber. For the same secondary field echo signal, all three groups of optical fiber sensors can detect it, and the detection equipment can perform joint calculations based on the detection results of the three groups of optical fiber sensors, thereby improving the accuracy of the detection results and accurately determining the location of the geological body. location information. The number of groups of optical fiber sensors can also be greater than three groups, and the number of groups is not limited here.

The geological body generates secondary field echo signals under the action of the transient magnetic field signal emitted by the magnetic field generator. After the optical fiber sensor detects the secondary field echo signal, the reflection spectrum will change, and the optical signal with a frequency corresponding to the magnetic field strength of the secondary field echo signal will be reflected. After the signal detector of the detection equipment receives the reflected light signal emitted by the optical fiber sensor, it determines the frequency corresponding to the wave peak in the reflection spectrum based on the reflection spectrum of the reflected light signal. This frequency is the reflection frequency. Then, the detection device uses the relevant algorithm model of the optical fiber sensor according to the reflection frequency (the algorithm model can be a machine learning model or Based on mathematical formulas derived from theory), the magnetic field strength of the secondary field echo signal corresponding to the reflected light signal and the position information of the geological body can be determined.

The embodiment of the present application provides an optical fiber sensor. The magnetostrictive material has an arc-shaped groove structure. The side surface of the fiber grating parallel to the main optical axis (which can be called the axial direction) is pasted or stuck in the arc-shaped groove of the magnetostrictive material. , the corresponding structure is shown in Figure 6.

In the optical fiber sensor, the optical fiber grating is fixed on the magnetostrictive material. When the magnetostrictive material deforms under the action of the secondary field echo signal, an external force will be exerted on the optical fiber grating, thus causing the optical fiber grating to deform. Generally, the larger the contact area between the magnetostrictive material and the fiber grating, the more obvious the deformation of the fiber grating will be under the action of the magnetostrictive material, and the more obvious the change in the reflection frequency of the optical signal will be. In order to better enable the magnetostrictive material to detect secondary field echo signals in all directions, the contact area between the magnetostrictive material and the fiber grating can be greater than or equal to half of the side surface area of the fiber grating, that is, the magnetostrictive material covers At least half of the radial cross-sectional circumference of the fiber grating. For example, the magnetostrictive material half wraps the fiber grating, that is, the arc-shaped groove of the magnetostrictive material is a semicircular groove. The corresponding structure is shown in Figure 9. At this time, the contact area between the magnetostrictive material and the fiber grating is equal to the fiber grating. Half of the side surface area; the magnetostrictive material completely wraps the fiber grating, and the corresponding structure is shown in Figure 10. At this time, the contact area between the magnetostrictive material and the fiber grating is equal to the side surface area of the fiber grating, and so on.

With the above structure, when the magnetostrictive material detects the secondary field echo signal in any direction, it will deform and drive the fiber grating to deform. After the fiber grating is deformed, the reflection characteristics will change compared to when the fiber grating is not deformed, that is, the reflection spectrum (also called spectrum characteristics) of the optical signal will change. After the signal detector of the detection equipment receives the reflected light signal emitted by the fiber sensor, , according to the reflection spectrum of the reflected light signal, determine the frequency corresponding to the wave peak in the reflection spectrum, and this frequency is the reflection frequency. Then, based on the reflection frequency, the detection equipment uses the relevant algorithm model of the optical fiber sensor to determine the magnetic field strength of the secondary field echo signal corresponding to the reflected light signal, thereby determining whether there is water.

Optionally, embodiments of the present application may also adopt other forms of sensor structures. For example, multiple magnetostrictive materials are fixed at different positions on the side of the fiber grating to realize the perception of secondary field echo signals from different directions. There are no specific restrictions here.

In order to improve the accuracy of the geological detection system, the geological detection system can use polarization-maintaining optical fiber. In this case, the fiber grating can be a grating etched on the polarization-maintaining optical fiber. The detection equipment can emit two optical signals with different polarization directions (called the third optical signal). First optical signal and second optical signal), and based on the reflection of the two polarized lights by the fiber grating, the relevant information of the geological body is determined.

For the case where magnetostrictive materials are used for magnetically sensitive components, combined with the use of polarization-maintaining optical fibers, several possible structures of optical fiber sensors are given below, and the method of determining the magnetic field strength is explained based on the structure. The corresponding optical fiber sensor combined with polarization-maintaining optical fiber can better improve the detection accuracy of magnetic field intensity.

Structure one

The embodiment of the present application provides an optical fiber sensor. The magnetostrictive material has an arc-shaped groove structure. The side surface of the fiber grating parallel to the main optical axis (which can be called the axial direction) is pasted or stuck in the arc-shaped groove of the magnetostrictive material. , the corresponding structure is shown in Figure 6. The specific structure is the same as the structure mentioned above and will not be described again here.

With this structure, when the magnetostrictive material detects the secondary field echo signal in any direction, it will undergo obvious deformation. The deformation has an axial component and a radial component (that is, the equivalent center of the magnetostrictive material and The vertical direction component of the main optical axis of the fiber grating. The deformation component of the magnetostrictive material in the axial direction drives the fiber grating to undergo the same deformation along the axial direction. For example, when the magnetostrictive material stretches along the axial direction, it will exert a tensile force on the fiber grating along the axial direction, causing the fiber grating to move along the axial direction. axial elongation, etc. The deformation component of the magnetostrictive material in the radial direction drives the fiber grating to undergo opposite deformation in the radial direction. For example, when the magnetostrictive material expands in the radial direction, it will exert a pressure on the fiber grating in the radial direction, causing the fiber grating to deform in the radial direction. Shrinkage occurs, etc. After the fiber grating is deformed, the reflection frequency of the optical signal changes compared with when it is not deformed.

The reflection characteristics (ie, reflection frequency) of the first optical signal and the second optical signal of the optical fiber grating are different. When the optical fiber sensor does not detect the secondary field echo signal, the optical fiber grating does not deform. At this time, the optical fiber grating reflects the first optical signal. The reflection frequency of the signal and the second optical signal remains unchanged, which can be called the reference reflection frequency. The reference reflection frequency of the fiber grating to the first optical signal can be recorded as f ₁ , and the reference reflection frequency of the fiber grating to the second optical signal can be recorded as f 1 . Denote it as f ₂ . When the optical fiber sensor detects the secondary field echo signal, the optical fiber grating deforms. At this time, the reflection frequency of the first optical signal and the second optical signal by the optical fiber grating changes. The reflection frequency of the first optical signal by the optical fiber grating at this time can be The reflection frequency of the fiber grating is recorded as f ₁ ', and the reflection frequency of the second optical signal by the fiber grating at this time is recorded as f ₂ '.

After receiving the reflected light signal, the detection device can determine the reflection frequencies of the first light signal and the second light signal respectively. Then, based on the reflection frequency and the reference reflection frequency of the first optical signal and the reflection frequency and the reference reflection frequency of the second optical signal, the axial deformation P ₌ and the radial deformation P _⊥ of the fiber grating are calculated.

For axial deformation P ₌ , it is necessary to first determine the reference center reflection frequency (f ₂ +f ₁ )/2 of the fiber grating before deformation, and the center reflection frequency (f ₂ '+f ₁ ')/2 of the fiber grating after deformation; Then, calculate the absolute value of the difference between the reference center reflection frequency and the center reflection frequency |(f ₂ '+f ₁ ')/2-(f ₂ +f ₁ )/2|; finally, determine based on the absolute value of the difference Axial deformation P ₌ , axial deformation P ₌ is positively related to the absolute value of the difference, recorded as P ₌ ∝|(f ₂ '+f ₁ ')/2-(f ₂ +f ₁ )/2|.

For the radial deformation P _⊥ , it is necessary to first determine the difference in the reflection frequency of the first optical signal and the second optical signal (f ₂ '-f ₁ '), and the difference in the reference reflection frequency of the first optical signal and the second optical signal. (f ₂ -f ₁ ); Then, determine the difference between the difference between the reflection frequency and the reference reflection frequency, and take the absolute value, that is, |(f ₂ '-f ₁ ')-(f ₂ -f ₁ )| ; Finally, the radial deformation P _⊥ is determined based on the absolute value. The radial deformation P _⊥ is positively related to the absolute value, recorded as P _⊥ ∝|(f ₂ '-f ₁ ')-(f ₂ -f ₁ )| .

Next, the detection equipment uses the relevant mathematical model of magnetic field intensity to determine the magnetic field intensity corresponding to the secondary field echo signal based on the axial deformation P ₌ and radial deformation P _⊥ of the fiber grating.

Optionally, for an optical fiber sensor, when the detection device determines the magnetic field strength at the optical fiber sensor, it can also determine the direction of the radial deformation P _⊥ and the direction of the axial deformation P ₌ of the optical fiber sensor. The direction of the total deformation, and thus, determines the direction of the magnetic field at the fiber optic sensor. Then, the location information of the geological body is determined based on the magnitude and direction of the magnetic field intensity of multiple optical fiber sensors and the geological body inversion model.

Structure 2

The geological detection system includes at least two optical fiber sensors. Each optical fiber sensor includes a magnetostrictive material and an optical fiber grating. The following is an example of including two optical fiber sensors.

The geological detection system may include two optical fiber sensors, called a first optical fiber sensor and a second optical fiber sensor. The corresponding structure is shown in Figure 11. The main optical axes of the first fiber optic sensor and the second fiber optic sensor are collinear, the first fiber optic sensor includes a first magnetostrictive material and a first fiber grating, the second fiber optic sensor includes a second magnetostrictive material and two fiber gratings, The first magnetostrictive material and the second magnetostrictive material may have a flat plate structure. The perpendicular line from the equivalent center of the first magnetostrictive material to the main optical axis of the first fiber grating is called the first perpendicular line. The second magnetostrictive material may have a flat plate structure. The perpendicular line from the equivalent center of the stretch material to the main optical axis of the second fiber grating is called the second perpendicular line. The first perpendicular line and the second perpendicular line have different directions on the same radial plane, such as the first perpendicular line and the second perpendicular line. The angle between the second vertical lines is 120°, etc., and the corresponding structure is shown in Figure 12.

For the first optical fiber sensor and the second optical fiber sensor, after detecting the secondary field echo signal emitted by the same geological body, At this time, the overall deformation of the optical fiber sensor is approximately the same. For the first optical fiber sensor, after detecting the secondary field echo signal emitted by the geological body, the corresponding axial deformation of the first optical fiber grating and the deformation in the first vertical direction can be determined. For the first optical fiber sensor, after detecting the secondary field echo signal emitted by the geological body, the corresponding axial deformation and the deformation in the second vertical direction of the second optical fiber grating can be determined. The calculation process of the deformation in the above directions is the same as that in Structure 1, and will not be described again here.

Further, the detection device can calculate the average value of the axial deformation of the first fiber grating and the axial deformation of the second fiber grating, and the vector sum of the deformation in the first vertical direction and the deformation in the second vertical direction (as shown in the figure) shown in 12). Then, based on the above average value and vector sum, the magnetic field strength of the secondary field echo signal emitted by the water body perpendicular to the main optical axis is determined.

Using the above geological detection system, the first optical fiber sensor and the second optical fiber sensor are used as a group of optical fiber sensors, and the secondary field is calculated more accurately by calculating the average value of the axial deformation and the vector sum of the radial deformation of multiple optical fiber sensors. The magnetic field strength of the echo signal can be used to accurately calculate the magnitude of the magnetic field generated by the water body. In the geological detection system, multiple groups of optical fiber sensors are placed, and the multiple groups of optical fiber sensors are connected in series through optical fibers. Based on the detection results of the multiple groups of optical fiber sensors, the location information of the water body can be determined.

Structure three

The optical fiber sensor may include a magnetostrictive material and at least two fiber gratings. The at least two fiber gratings are respectively connected to the detection device through optical fibers. The side surfaces of the at least two fiber gratings parallel to the main optical axis are fixed outside the magnetostrictive material. At different positions on the surface, the main optical axes of at least two fiber gratings are parallel to each other, and the vertical line from the equivalent center of the magnetostrictive material to the main optical axis of each fiber grating is not collinear, that is, the radial direction of each fiber grating The directions of deformation are different. The following is an example of an optical fiber sensor including three fiber gratings.

The optical fiber sensor includes three fiber gratings, which are distributed in an equilateral triangle. The corresponding structure is shown in Figure 13. When the optical fiber sensor detects the secondary field echo signal, the magnetostrictive material deforms, driving each fiber grating to undergo axial deformation and radial deformation. The detection equipment will determine the axial deformation and radial deformation of each fiber grating based on the optical signal of each fiber grating. The process of determining the deformation is the same as the process of determining the deformation in Structure 1, and will not be described again here. Then, the detection equipment will calculate the average of the axial deformations of the three fiber gratings (as shown in Figure 14, the fourth deformation of the first fiber grating, the fourth deformation of the second fiber grating, and the fourth deformation of the third fiber grating) value, and the vector sum of the radial deformations of these three fiber gratings (as shown in Figure 14, the third deformation of the first fiber grating, the third deformation of the second fiber grating, and the third deformation of the third fiber grating), according to The average value of axial deformation and the vector sum of radial deformation are used to determine the magnetic field intensity corresponding to the secondary field echo signal using the relevant mathematical model of magnetic field intensity.

This embodiment takes the magnetically sensitive component as a magnetic fluid material as an example to explain the structure of the optical fiber sensor and the process of determining water-related information.

When the magnetically sensitive component is magnetic fluid, the fiber grating is immersed in the magnetic fluid, and the corresponding structure is shown in Figure 5. When the optical fiber sensor detects the secondary field echo signal emitted by the water body, the molecules of the magnetic fluid will rotate in the direction of the magnetic field. As the distribution pattern of the molecules of the magnetic fluid changes, the dielectric properties of the magnetic fluid change, which causes the reflection spectrum of the fiber grating to change, that is, the frequency of the optical signal that the fiber grating can reflect changes.

The detection equipment determines the corresponding reflection spectrum based on the received reflected light signal, thereby determining the reflection frequency corresponding to the wave peak in the reflection spectrum. Finally, based on the reflection frequency of the reflected light signal, the detection equipment uses the relevant algorithm model of the optical fiber sensor to determine the magnetic field strength of the secondary field echo signal corresponding to the reflected light signal.

Before detection, technicians will establish a spatial coordinate system and drill horizontal holes along the tunnel's excavation direction. Then, insert the optical fiber sensor connected to the detection equipment through optical fiber into the hole to ensure that the optical fiber sensor is in a horizontal state, which is called the reference position. However, due to various reasons, such as not ensuring that the hole is in a horizontal state when drilling, the position of the fiber optic sensor being displaced due to external force when inserted into the hole, etc., the actual position of the fiber optic sensor will deviate from the reference position, as shown in As shown in Figure 15. For fiber optic sensors, if the position information is not determined, the calculation results of the detection equipment will deviate greatly from the actual situation, eventually leading to inaccurate water body position information. Therefore, the actual position of the fiber optic sensor needs to be determined before detection.

In response to the above requirements, embodiments of the present application provide an optical fiber sensor, which includes a magnetically sensitive component and at least three optical fiber gratings. The following takes a magnetostrictive material and three optical fiber gratings as an example to determine the actual position of the optical fiber sensor. The process is explained.

When the optical fiber sensor includes a magnetostrictive material and three fiber gratings, the corresponding structure is the same as the above-mentioned structure three. The corresponding structure is shown in Figure 13, and the structure will not be described in detail here.

Before the magnetic field generator emits a transient magnetic field signal, the detection device continues to emit light signals to the optical fiber sensor, and the optical fiber sensor continues to reflect the light signal. When the technician inserts the optical fiber sensor into the hole, the position of the optical fiber sensor will shift under the action of external force. At the same time, the external force will cause different deformations of each fiber grating, thus causing the reflection of the optical signal by each fiber grating. The frequencies are changed. Under normal circumstances, the position and shape of the fiber optic sensor will change as shown in Figure 15. The fiber optic sensor bends upward, the fiber grating located above is compressed, the fiber grating located below is stretched, and so on.

For each fiber grating, after the detection equipment receives the optical signal reflected by the fiber grating, it determines the axial deformation and radial deformation of the fiber grating through the reflection frequency and reference reflection frequency of the optical signal. The determination process of the deformation is the same as above. are the same and will not be described again here. Then, based on the axial deformation and vertical deformation of each fiber grating, the detection equipment can determine the attitude information of the optical fiber sensor through the virtual work equation and Newton iteration method. In addition to determining the attitude information of the optical fiber sensor at the detection position, during the process of sending the optical fiber sensor to the detection position, the detection equipment monitors the deformation of the optical fiber sensor to obtain the movement trajectory of the optical fiber sensor, and based on the reference position information and attitude information of the optical fiber sensor , and the motion trajectory, the final position information (ie, the actual position information) of the optical fiber sensor when it reaches the detection position is determined through geometric operations. For each optical fiber sensor, after detecting the secondary field echo signal, the detection equipment can detect the magnetic field intensity information from the geological body (such as the magnitude and direction of the magnetic field intensity, etc.), and the optical fiber sensor can detect the magnetic field for a period of time after the magnetic field is emitted. The geological body inversion model is used to determine the position information of the water body based on the secondary field echo signals emitted by the water body detected at different times in the geology, the position information of the magnetic field generator, and the attitude information and actual position information of the optical fiber sensor.

Alternatively, it can be approximately considered that the optical fiber sensor is deformed but shifted as a whole, and the attitude information can be considered as the angle between the line connecting the two ends of the optical fiber sensor and the horizontal direction. Further, the detection equipment can determine the actual position information of the optical fiber sensor based on the reference position information and attitude information of the optical fiber sensor through geometric calculation. The reference position information can be the center point of the main optical axis when the optical fiber sensor does not deflect. The coordinates in the preset spatial coordinate system. The actual position information can be the coordinates of the center point of the line connecting the two ends of the optical fiber sensor in the preset spatial coordinate system after the offset.

Optionally, this structure can also be used when the magnetically sensitive component is magnetic fluid. That is, the optical fiber sensor includes a magnetic fluid and at least three fiber gratings. The corresponding structure is shown in Figure 16. At least three fiber gratings are immersed in the magnetic fluid. , and the main optical axes of at least three fiber gratings are parallel to each other. In this case, the process of determining the actual position information of the optical fiber sensor is the same as above and will not be described again here.

The above is only an embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present application shall be included in the protection scope of the present application.

Claims

A geological detection system, characterized in that the geological detection system includes detection equipment and a magnetic field sensor;

The magnetic field sensor is used to detect the magnetic field signal emitted by the geological body, and under the action of the magnetic field signal, transmits to the detection equipment a detection signal corresponding to the magnetic field intensity of the magnetic field signal;

The detection device is configured to receive the detection signal, determine the magnetic field strength of the magnetic field signal based on the detection signal, and determine whether the geological body is a target type of geological body based on the magnetic field strength of the magnetic field signal.
The geological detection system according to claim 1, characterized in that the geological detection system further includes a magnetic field generator;

The magnetic field generator is used to emit transient magnetic field signals;

The magnetic field signal emitted by the geological body is a secondary field echo signal generated by the geological body under the stimulation of the transient magnetic field signal emitted by the magnetic field generator.
The geological detection system according to claim 1, characterized in that the detection equipment is also used for:

After it is determined that the geological body is a geological body of the target type, the position information of the geological body is determined based on the magnetic field strength of the magnetic field signal of the geological body and the position information of the magnetic field sensor.
The geological detection system according to any one of claims 1 to 3, characterized in that the magnetic field sensor is an optical fiber sensor, and the detection equipment and the optical fiber sensor are connected through optical fibers;

The detection device is also used to emit optical signals to the optical fiber sensor;

The optical fiber sensor is used to detect the magnetic field signal emitted by the geological body, and has different optical signal reflection characteristics under the action of magnetic field signals of different magnetic field strengths;

The detection device is configured to determine the magnetic field strength of the magnetic field signal emitted by the geological body based on the spectral characteristics of the reflected light signal received from the optical fiber sensor.
The geological detection system according to claim 4, wherein the optical fiber sensor includes an optical fiber grating and a magnetically sensitive component, the optical fiber grating is in contact with the magnetically sensitive component, and the optical fiber grating passes through the detection equipment. fiber optic connections;

The magnetic sensitive component is used to detect the magnetic field signal emitted by the geological body, and adjust the reflection characteristics of the fiber grating under the action of magnetic field signals of different magnetic field strengths;

The fiber grating is used to reflect the received optical signal.
The geological exploration system according to claim 5, wherein the magnetically sensitive component is a magnetostrictive material, and the fiber grating is fixed on the magnetostrictive material.
The geological exploration system of claim 6, wherein the magnetostrictive material covers at least half of the radial cross-sectional circumference of the fiber grating.
The geological detection system according to claim 6, characterized in that the geological detection system includes at least two optical fiber sensors;

The detection equipment is used for:

Based on the reflected light signals received from the at least two optical fiber sensors, determine a first deformation of each optical fiber sensor along the radial direction of the fiber grating and a second deformation along the main optical axis of the fiber grating;

Based on the first deformation and the second deformation of each optical fiber sensor, the magnetic field strength of the magnetic field signal emitted by the geological body is determined.
The geological detection system according to claim 6, wherein the optical fiber sensor includes at least two optical fiber gratings, and the at least two optical fiber gratings are respectively connected to the detection equipment through optical fibers;

The detection equipment is used for:

Based on the optical signal received from each fiber grating, determine a third deformation of each fiber grating along the radial direction of the fiber grating and a fourth deformation along the main optical axis direction of the fiber grating;

Based on the third deformation and the fourth deformation of each fiber grating, the magnetic field strength of the magnetic field signal emitted by the geological body is determined.
The geological detection system according to claim 5, characterized in that the magnetically sensitive component is magnetic fluid, and the fiber grating is immersed in the magnetic fluid;

The detection device is configured to determine the dielectric properties of the magnetic fluid based on the spectral characteristics of the reflected light signal, and determine the magnetic field strength of the magnetic field signal emitted by the geological body based on the dielectric properties of the magnetic fluid.
The geological detection system according to claim 6 or 10, characterized in that the optical fiber sensor includes at least three fiber gratings, and the detection equipment is also used for:

Before the magnetic field generator emits a transient magnetic field signal, the deformation of each optical fiber grating is determined based on the frequency of the reflected light signal received from each optical fiber grating, and the deformation of the optical fiber sensor is determined based on the deformation of each optical fiber grating. Attitude information, based on the attitude information and the reference position information of the optical fiber sensor, determine the actual position information of the optical fiber sensor;

The position information of the geological body is determined based on the magnetic field strength of the magnetic field signal emitted by the geological body, the attitude information and the actual position information of the optical fiber sensor.
The geological detection system according to claim 11, wherein the optical fiber sensor includes three optical fiber gratings, and the three optical fiber gratings are distributed in an equilateral triangle.
The geological detection system according to claims 5-12, characterized in that the optical fiber is a polarization-maintaining optical fiber;

The detection device is configured to transmit a first optical signal and a second optical signal to the optical fiber sensor, wherein the first optical signal and the second optical signal are optical signals with different polarization directions;

The magnetic sensitive component is used to detect the magnetic field signal emitted by the geological body, adjust the first reflection characteristic of the fiber grating to the first optical signal under the action of magnetic field signals with different magnetic field strengths, and adjust the first reflection characteristic of the first optical signal. The fiber grating is suitable for the Second reflection characteristics of the second optical signal;

The fiber grating is a grating etched on a polarization-maintaining optical fiber, used to reflect the first optical signal and the second optical signal;

The detection device is used to determine the magnetic field strength of the magnetic field signal emitted by the geological body based on the spectral characteristics of the reflected light signals in different polarization directions received from the optical fiber sensor.
The geological detection system according to any one of claims 4 to 13, characterized in that the geological detection system includes a plurality of optical fiber sensors, the plurality of optical fiber sensors are connected in series through optical fibers, and the optical fiber sensor located at one end is connected to the optical fiber sensor. Detection equipment is connected via fiber optics.
The geological detection system according to any one of claims 4 to 13, characterized in that the geological detection system includes a plurality of optical fiber sensors, the plurality of optical fiber sensors are divided into at least three groups, and each group of optical fiber sensors are connected in series through optical fibers. , and the optical fiber sensor located at one end of each group of optical fiber sensors is connected to the detection equipment through an optical fiber.
An optical fiber sensor, characterized in that the optical fiber sensor includes an optical fiber grating and a magnetostrictive material, the optical fiber grating is fixed on the magnetostrictive material, and the optical fiber grating is a grating etched on a polarization-maintaining optical fiber.
An optical fiber sensor, characterized in that the optical fiber sensor includes a magnetically sensitive component and at least three optical fiber gratings, and the at least three optical fiber gratings are in contact with the magnetically sensitive component.