A multi-probe nuclear magnetic resonance in-situ monitoring system for rock and soil

Abstract

The present application relates to the field of rock and soil detection, and specifically discloses a multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system, which includes a multi-probe assembly, a spectrometer assembly, an industrial computer and a cable, wherein the multi-probe assembly includes a housing and a plurality of nuclear magnetic resonance probes fixedly arranged in the housing, and the plurality of nuclear magnetic resonance probes are respectively located in strata at different depths and have different measurement frequencies; the spectrometer assembly is used to transmit and receive nuclear magnetic resonance measurement radio frequency signals, the industrial computer is used to send measurement instructions and process the measurement data in real time, and the cable is connected to the plurality of nuclear magnetic resonance probes, the spectrometer assembly and the industrial computer for power supply and transmission of measurement data. The present application can simultaneously obtain nuclear magnetic information of in-situ rock and soil of different types and different depths underground, bury the probes in the underground soil for a long time, and can also realize long-term and continuous monitoring of the moisture content of the soil layer and the migration of pollutants in the contaminated site over time.

Description

Technical Field

[0001] The present application relates to the field of rock and soil detection, and in particular to a multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system. Background Art

[0002] Common soil moisture monitoring methods include frequency domain reflectometry, time domain reflectometry, drying method, nuclear magnetic resonance method, etc. Frequency domain reflectometry and time domain reflectometry, which are measured in situ in the soil, indirectly reflect the soil moisture content by measuring the dielectric constant. They are affected by many factors and their accuracy is unstable. Drying method and nuclear magnetic resonance method usually require manual drilling of soil samples, and then obtain soil moisture information through laboratory testing. However, the sampling process of undisturbed soil is difficult to avoid additional disturbances caused by soil collection, transportation, and sample preparation, and experimental tests carried out after sampling are difficult to restore underground conditions.

[0003] On the other hand, the moisture content and distribution of rock and soil have strong temporal and spatial variability, sampling may not be representative, and current related technologies are difficult to obtain information on the changes in moisture content and physical properties of underground rock and soil over time. Therefore, a device for long-term and continuous monitoring of rock and soil is needed to achieve in-situ monitoring of underground rock and soil, especially contaminated sites. Summary of the invention

[0004] In order to carry out long-term and continuous in-situ monitoring of rock and soil, the present application provides a multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system.

[0005] The multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system provided in this application adopts the following technical solution:

[0006] A multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system, comprising:

[0007] A multi-probe assembly comprises a cylindrical housing and a plurality of nuclear magnetic probes fixedly arranged in the housing, wherein the plurality of nuclear magnetic probes are sequentially spaced apart along the axial direction of the housing, and the plurality of nuclear magnetic probes are respectively located in strata at different depths and have different measurement frequencies;

[0008] a spectrometer assembly for transmitting and receiving radio frequency signals for nuclear magnetic resonance measurements;

[0009] Industrial computer, used to send measurement instructions and process measurement data in real time;

[0010] The cable is connected to the plurality of nuclear magnetic probes, the spectrometer assembly and the industrial computer and is used for supplying power and transmitting measurement data.

[0011] The multi-probe assembly is lowered into the borehole, and multiple nuclear magnetic resonance probes are buried in soil layers at different depths. The nuclear magnetic resonance information of the original soil at different depths is measured simultaneously. The data collected by nuclear magnetic resonance probes of different frequencies are uniformly transmitted to the ground spectrometer assembly by cables, which enables the distinction of data from multiple nuclear magnetic resonance probes based on the collected signal frequency.

[0012] The spectrometer component is an acquisition system that controls the signal reception and transmission. It is used to control the radio frequency coil of each nuclear magnetic resonance probe to transmit radio frequency signals of different frequencies, and receive the different frequency signals measured by each probe through a multi-channel receiver. After distinguishing the signal frequencies using spectrum analysis, the nuclear magnetic resonance acquisition signals of the underground soil are transmitted to the industrial computer.

[0013] The industrial computer contains a data processing component for processing NMR data. After executing one acquisition, each NMR probe measures the echo signal of the soil at the corresponding depth. The NMR echo signals collected by multiple probes are inverted by the data processing component to obtain the T2 distribution spectrum of the original soil at different depths. The T2 spectrum at each depth point reflects the water content distribution, microscopic pore structure and oil-water fluid information of the soil to a certain extent. The water content is obtained by integrating the T2 spectrum. The NMR information of soil layers at different depths can be further compared to evaluate the heterogeneity of the soil.

[0014] By burying the multi-probe assembly in the underground soil for a long time, long-term and continuous monitoring of moisture information in the soil and oil pollutants in contaminated sites can be achieved.

[0015] Furthermore, the nuclear magnetic resonance probe includes a sleeve, a magnet fixed in the sleeve, and a radio frequency coil wound outside the sleeve, the radio frequency coil is connected to a radio frequency coil circuit, the cable runs through multiple nuclear magnetic resonance probes and the cable is connected to each of the radio frequency coil circuits.

[0016] Furthermore, the nuclear magnetic resonance probe also includes a sleeve that passes through the sleeve, the sleeve is coaxial with the sleeve and the two are fixedly connected, the axial length of the sleeve is greater than the axial length of the sleeve, two adjacent sleeves are connected by threads, and the cable is installed in the sleeve.

[0017] Furthermore, in each of the nuclear magnetic resonance probes, the magnet includes two hollow cylindrical magnets with opposite polarities, and the two magnets are arranged at intervals along their own axial direction to generate a circular static magnetic field B0 around the axis; the radio frequency coil is located between the two magnets, and the radio frequency magnetic field B1 generated by the radio frequency coil is along the axial direction of the magnet and perpendicular to the static magnetic field B0.

[0018] Furthermore, in different nuclear magnetic resonance probes, the magnetic field strengths of the magnets are different, so that the resonance frequency of each nuclear magnetic resonance probe is different.

[0019] Each nuclear magnetic probe uses a magnet with different magnetic field strengths. According to the relationship between the magnetic field strength B0 and the resonance frequency , the resonant frequency of each probe The data collected by radio frequency coils of different frequencies are uniformly transmitted to the ground spectrometer system by cables, thus realizing the distinction of data from multiple nuclear magnetic probes based on the collected signal frequency.

[0020] Furthermore, a groove for winding the radio frequency coil is provided in the middle of the outer circumference of the sleeve, and the groove facilitates the radio frequency coil to be wound evenly outside the sleeve.

[0021] Furthermore, one end of the shell away from the ground is fixedly connected to a top cover, and a surface of the top cover in contact with the soil is a convex arc surface.

[0022] The convex curved surface helps to smoothly lower the multi-probe assembly into the borehole and prevents the probes from getting stuck in the drill.

[0023] Furthermore, the sleeve is made of non-magnetic material.

[0024] The non-magnetic material enables the main magnetic field and radio frequency magnetic field of the nuclear magnetic probe to penetrate the casing and reach the soil area that needs to be measured.

[0025] Furthermore, the sleeve is made of polytetrafluoroethylene material.

[0026] The PTFE material allows magnetic fields to penetrate and helps reduce background noise interference in the NMR measurement signal.

[0027] Furthermore, the shell is made of non-magnetic and non-conductive material.

[0028] The non-magnetic and non-conductive material enables the main magnetic field and radio frequency magnetic field of the nuclear magnetic probe to penetrate the outer shell to reach the soil area that needs to be measured, while ensuring that the probe has good waterproof and anti-corrosion properties when it is lowered and buried in the underground soil.

[0029] In summary, the present application includes at least one of the following beneficial technical effects:

[0030] 1. Multiple nuclear magnetic resonance probes are buried in soil layers at different depths, and the nuclear magnetic information of the original soil at different depths is measured in real time in situ. The moisture content, moisture distribution and other information of the original soil at different depths can be obtained, and the measurement results of soil layers at different depths can be compared to evaluate the heterogeneity of the soil.

[0031] 2. Each nuclear magnetic probe uses magnets with different magnetic field strengths, so that each nuclear magnetic probe works at a different frequency. The data collected by the radio frequency coils of different frequencies are uniformly transmitted to the ground spectrometer system by cables, realizing the distinction of multi-nuclear magnetic probe data from the frequency of the collected signals;

[0032] 3. By burying the multi-probe assembly in the underground soil for a long time, long-term and continuous monitoring of moisture information in the soil and oil pollutants in contaminated sites can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present application;

[0034] Figure 2 It is a schematic cross-sectional structural diagram of the multi-probe assembly in an embodiment of the present application.

[0035] Figure numerals: 1. MRI probe; 2. magnet; 3. RF coil; 4. sleeve; 5. RF coil circuit; 6. cable; 7. housing; 8. sleeve; 9. top cover. DETAILED DESCRIPTION

[0036] The following is combined with Figure 1-2 This application is described in further detail.

[0037] The present application embodiment discloses a multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system. Figure 1 and Figure 2 The multi-probe nuclear magnetic resonance in-situ monitoring system for rock and soil includes a multi-probe assembly, a spectrometer assembly, an industrial computer and a cable 6. The multi-probe assembly includes a cylindrical shell 7 and a plurality of nuclear magnetic resonance probes 1 fixedly arranged in the shell 7. In this embodiment, the number of nuclear magnetic resonance probes 1 is 4. The plurality of nuclear magnetic resonance probes 1 are arranged in sequence along the axial direction of the shell 7. The plurality of nuclear magnetic resonance probes 1 are respectively located in strata of different depths and have different measurement frequencies. The cable 6 is connected to the plurality of nuclear magnetic resonance probes 1, the spectrometer assembly and the industrial computer for power supply and transmission of measurement data.

[0038] The multi-probe assembly is lowered into the borehole, so that multiple nuclear magnetic resonance probes 1 are buried in soil layers at different depths, and the nuclear magnetic resonance information of the original soil at different depths is measured simultaneously; the data collected by the nuclear magnetic resonance probes 1 of different frequencies are uniformly transmitted to the ground spectrometer assembly by cable 6, so that the data of multiple nuclear magnetic resonance probes 1 can be distinguished from the frequency of the collected signals.

[0039] The spectrometer component is an acquisition system for controlling signal reception and transmission. It is used to control each nuclear magnetic resonance probe 1 to transmit radio frequency signals of different frequencies, and receive the different frequency signals measured by each nuclear magnetic resonance probe 1 through a multi-channel receiver. After distinguishing the signal frequencies by spectrum analysis, the nuclear magnetic resonance acquisition signals of the underground soil are transmitted to the industrial computer.

[0040] The industrial computer is used to send measurement instructions and process the measurement data in real time. After executing one acquisition, each nuclear magnetic resonance probe 1 measures the echo signal of the soil at the corresponding depth. The nuclear magnetic resonance echo signals collected by multiple probes are inverted through the data processing component of the industrial computer to obtain the T2 distribution spectrum of the original soil at different depths. The T2 spectrum at each depth point reflects the water content distribution, microscopic pore structure and oil-water fluid information of the soil to a certain extent. The water content is obtained by integrating the T2 spectrum. The nuclear magnetic resonance information of soil layers at different depths can be further compared to evaluate the heterogeneity of the soil.

[0041] By burying the multi-probe assembly in the underground soil for a long time, long-term and continuous monitoring of moisture information in the soil and oil pollutants in contaminated sites can be achieved.

[0042] Reference Figure 2 Each nuclear magnetic probe 1 includes a sleeve 4 and a sleeve 8 penetrating the sleeve 4. The sleeve 8 is coaxial with the sleeve 4 and the two are fixed by epoxy resin. The outer wall of the sleeve 4 abuts against the inner wall of the shell 7. The axial length of the sleeve 8 is greater than the axial length of the sleeve 4. Two adjacent sleeves 8 are connected by threads, and any number of nuclear magnetic probes 1 can be connected; the cable 6 is installed in the sleeve 8.

[0043] Further, refer to Figure 2 , each sleeve 4 is fixedly provided with a magnet, the magnet includes two hollow cylindrical magnets 2, the two magnets 2 are arranged at intervals along their own axial direction and the polarities of the two are opposite, that is, the directions of the magnetic fields of the two are opposite; the sleeve 8 runs through the magnets 2. The sleeve 4 is wound with a radio frequency coil 3, the radio frequency coil 3 is located between the two magnets 2, and the outer peripheral side of the middle of the sleeve 4 is provided with a groove for the radio frequency coil 3 to be wound. The radio frequency coil 3 is connected to a radio frequency coil circuit 5, and each radio frequency coil circuit 5 is connected to a cable 6.

[0044] In each nuclear magnetic probe 1, two magnets 2 generate a circular static magnetic field B0 around the axis, and the area where the static magnetic field B0 is uniform is the sensitive area; the radio frequency magnetic field B1 generated by the radio frequency coil 3 is along the axis of the magnet and perpendicular to the static magnetic field B0.

[0045] Furthermore, in different nuclear magnetic probes 1, the magnetic field strength of the magnet is different. According to the relationship between the magnetic field strength B0 and the resonance frequency , the resonance frequency of each MRI probe 1 The frequency of the radio frequency coil 3 of each nuclear magnetic probe 1 is tuned to be consistent with the magnetic field strength of the static magnetic field B0 generated by the magnet, so that each nuclear magnetic probe 1 works at a different frequency, and the data collected by the radio frequency coils 3 of different frequencies are uniformly transmitted to the ground spectrometer system by the cable 6, so that the data of multiple nuclear magnetic probes 1 can be distinguished from each other in terms of the collected signal frequency.

[0046] In order to enable the magnetic field of the nuclear magnetic probe 1 to reach the soil area to be measured, the casing 8 is made of non-magnetic stainless steel, the sleeve 4 is made of polytetrafluoroethylene material, and the shell 7 is made of non-magnetic and non-conductive fiberglass material.

[0047] In this way, the main magnetic field and radio frequency magnetic field of the nuclear magnetic resonance probe 1 can penetrate the casing 8, sleeve 4 and shell 7 to reach the soil area that needs to be measured; further, the sleeve 4 is made of polytetrafluoroethylene material, which helps to reduce the background noise interference in the nuclear magnetic resonance measurement signal; the shell 7 is made of non-magnetic and non-conductive material, which also ensures that the multi-probe assembly has good waterproof and anti-corrosion properties when it is lowered and buried in the underground soil.

[0048] Reference Figure 2 The end of the housing 7 away from the ground is fixedly connected with a top cover 9 made of non-magnetic stainless steel, and the side of the top cover 9 in contact with the soil is a convex arc surface. The convex arc surface helps to smoothly lower the multi-probe assembly into the borehole to prevent the probe from getting stuck in the drill.

[0049] The implementation principle of a multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system in the embodiment of the present application is as follows: the multi-probe assembly is lowered into the borehole, so that multiple nuclear magnetic resonance probes 1 are buried in soil layers of different depths, and the nuclear magnetic information of the original soil at different depths is measured simultaneously; the data collected by the nuclear magnetic resonance probes 1 of different frequencies are uniformly transmitted to the ground spectrometer assembly by cable 6, and the nuclear magnetic resonance acquisition signal of the underground soil is transmitted to the industrial computer after the signal frequency is distinguished by spectrum analysis, and the nuclear magnetic resonance echo signal collected by the multi-probe is inverted by the data processing assembly to obtain the T2 distribution spectrum of the original soil at different depths. The T2 spectrum at each depth point reflects the water distribution, microscopic pore structure and oil-water fluid information of the soil to a certain extent, and the water content is obtained by integrating the T2 spectrum. The nuclear magnetic resonance information of soil layers of different depths can be further compared to evaluate the heterogeneity of the soil. The multi-probe assembly is buried in the underground soil for a long time, which can realize the long-term and continuous monitoring of the moisture information in the soil and the oil pollutants in the contaminated site.

[0050] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system, characterized by: include: A multi-probe assembly comprises a cylindrical shell and a plurality of nuclear magnetic probes fixedly arranged in the shell, wherein the plurality of nuclear magnetic probes are arranged in sequence and spaced apart along the axial direction of the shell, and the plurality of nuclear magnetic probes are respectively located in strata at different depths and have different measurement frequencies; the nuclear magnetic probe comprises a magnet, and the magnetic field strength of the magnet in different nuclear magnetic probes is different, so that the resonance frequency of each nuclear magnetic probe is different; a spectrometer assembly for transmitting and receiving radio frequency signals for nuclear magnetic resonance measurements; Industrial computer, used to send measurement instructions and process measurement data in real time; The cable is connected to the plurality of nuclear magnetic probes, the spectrometer assembly and the industrial computer and is used for supplying power and transmitting measurement data.

2. A multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system according to claim 1, characterized in that: The nuclear magnetic resonance probe includes a sleeve and a radio frequency coil wound outside the sleeve, the radio frequency coil is connected to a radio frequency coil circuit, the cable runs through multiple nuclear magnetic resonance probes and the cable is connected to each radio frequency coil circuit, and the magnet is fixedly arranged in the sleeve.

3. A multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system according to claim 2, characterized in that: The nuclear magnetic resonance probe also includes a sleeve that passes through the sleeve, the sleeve is coaxial with the sleeve and the two are fixedly connected, the axial length of the sleeve is greater than the axial length of the sleeve, two adjacent sleeves are connected by threads, and the cable is installed in the sleeve.

4. A multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system according to claim 3, characterized in that: In each of the nuclear magnetic resonance probes, the magnet includes two hollow cylindrical magnets with opposite polarities, and the two magnets are arranged at intervals along their own axial direction to generate a circular static magnetic field B0 around the axis; the radio frequency coil is located between the two magnets, and the radio frequency magnetic field B1 generated by the radio frequency coil is along the axial direction of the magnet and perpendicular to the static magnetic field B0.

5. A multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system according to claim 4, characterized in that: A groove for winding the radio frequency coil is provided in the middle of the outer circumference of the sleeve.

6. The multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system according to claim 3, characterized in that: One end of the shell away from the ground is fixedly connected with a top cover, and a surface of the top cover in contact with the soil is a convex arc surface.

7. The multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system according to claim 3, characterized in that: The sleeve is made of non-magnetic material.

8. The multi-probe nuclear magnetic resonance rock and soil in-situ monitoring system according to claim 2, characterized in that: The sleeve is made of polytetrafluoroethylene material.

9. The multi-probe nuclear magnetic resonance in-situ rock and soil monitoring system according to claim 1, characterized in that: The shell is made of non-magnetic and non-conductive material.

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