A four-quadrant positioning magnetic resonance detection method applicable to urban underground waterlogging warning

Abstract

The present invention belongs to the field of geophysical exploration, and specifically relates to a four-quadrant positioning magnetic resonance detection method for urban underground waterlogging warning. Four signal line sources of equal length are arranged vertically and intersecting at the urban obstacle working surface, and the intersection point of the vertical intersection is located at the center of the area to be measured; the magnetic resonance detection instrument is placed at the center of the area to be measured; the four signal lines divide the area to be measured into four quadrants, where two signal lines extend along the extension line of the x-axis, and the other two signal lines extend along the extension line of the y-axis; the first quadrant and the third quadrant are grouped as one group, and the second quadrant and the fourth quadrant are grouped as one group, and directional focusing detection is carried out in groups, solving the problems that it is impossible to carry out multi-angle directional excitation on the urban obstacle working surface and it is impossible to achieve high-resolution detection of small-range harmful water. The method of the present invention not only provides a four-quadrant magnetic resonance detection method that is convenient for obstacle avoidance laying for urban detection scenarios, but also provides a method for strengthening the excitation magnetic field of underground waterlogging in multiple angles and directions.

Description

Technical Field

[0001] The present invention belongs to the field of geophysical exploration, and specifically relates to a four-quadrant positioning magnetic resonance detection method for urban underground waterlogging warning. Background Art

[0002] Among many geophysical exploration methods, the Magnetic Resonance Sounding (MRS) technology is the only geophysical exploration method that directly uses remote sensing to quantitatively obtain groundwater information, and has absolute advantages such as directional tracking, qualitative analysis, and positioning quantification.

[0003] However, the current urban magnetic resonance water exploration work has the following practical problems: ① It is difficult to lay large loop devices within the building complex; ② The detection depth resolution of traditional small loops is low; ③ A single electrical source cannot be directionally excited, so it is difficult to achieve precise positioning and quantitative survey of underground water accumulation in complex obstacle environments. Therefore, it is necessary to improve the resolution of magnetic resonance detection in complex ground environments to meet the demand for accurate acquisition of non-invasive information on small-scale harmful water sources in urban construction projects, and accordingly conduct subsequent risk analysis of potential road collapse hazards to serve the development and construction of urban geological engineering and geological resources. Summary of the Invention

[0004] Aiming at the problems existing in the above-mentioned prior art, the present invention provides a four-quadrant positioning magnetic resonance detection method suitable for urban underground waterlogging warning, which solves the problems that it is impossible to carry out multi-angle directional excitation on the urban obstacle working surface and it is impossible to achieve high-resolution detection of small-scale harmful water.

[0005] The present invention is implemented as follows:

[0006] A four-quadrant positioning magnetic resonance detection method suitable for urban underground waterlogging warning, the method includes:

[0007] Arrange four signal line sources of equal length to intersect vertically on the urban obstacle working surface, and the intersection of the vertical intersection is located at the center of the area to be measured;

[0008] Place the magnetic resonance detection instrument at the center of the area to be measured;

[0009] One end of each of the four signal lines is used as a connection end and is connected to the magnetic resonance detection instrument;

[0010] The other ends of the four signal lines are used as grounding ends and are connected to the ground;

[0011] The four signal lines divide the area to be measured into four quadrants, where two signal lines extend along the x-axis extension line, and the other two signal lines extend along the y-axis extension line;

[0012] Group the first and third quadrants as one group, and the second and fourth quadrants as another group, and perform directional focusing detection on them separately.

[0013] When performing directional focusing detection on the first and third quadrants, the connection ends of the two signal lines located on the negative x-axis and the positive y-axis are connected to the positive signal emission terminal of the nuclear magnetic resonance detector, and the connection ends of the two signal lines located on the positive x-axis and the negative y-axis are connected to the negative signal emission terminal of the nuclear magnetic resonance detector.

[0014] Start the nuclear magnetic resonance detector; after the excitation is completed, turn off the signal emission system of the nuclear magnetic resonance detector. At the same time, the connection ends of the two signal lines located on the positive x-axis and the positive y-axis are connected to the same communication channel of the signal acquisition system of the nuclear magnetic resonance detector, and the connection ends of the two signal lines located on the negative x-axis and the negative y-axis are connected to another communication channel of the signal acquisition system of the nuclear magnetic resonance detector, and start to collect the nuclear magnetic resonance response signals of the groundwater under the working surfaces of the first and third quadrants; until the signal acquisition is completed, turn off the nuclear magnetic resonance detector.

[0015] When performing directional focusing detection on the second and fourth quadrants, the connection ends of the two signal lines located on the negative x-axis and the negative y-axis are connected to the positive signal emission terminal of the nuclear magnetic resonance detector, and the connection ends of the two signal lines located on the positive x-axis and the positive y-axis are connected to the negative signal emission terminal of the nuclear magnetic resonance detector.

[0016] Start the nuclear magnetic resonance detector; after the excitation is completed, turn off the signal emission system of the nuclear magnetic resonance detector. At the same time, the connection ends of the two signal lines located on the positive x-axis and the negative y-axis are connected to the same communication channel of the signal acquisition system of the nuclear magnetic resonance detector, and the connection ends of the two signal lines located on the negative x-axis and the positive y-axis are connected to another communication channel of the signal acquisition system of the nuclear magnetic resonance detector, and start to collect the nuclear magnetic resonance response signals of the groundwater under the working surfaces of the second and fourth quadrants; until the signal acquisition is completed, turn off the nuclear magnetic resonance detector.

[0017] Furthermore, obtain the four-quadrant positioning nuclear magnetic resonance response signals according to the collected signals.

[0018] Theoretically calculate the directional excitation magnetic field intensity generated during directional focusing detection.

[0019] Obtain the four-quadrant positioning nuclear magnetic resonance forward modeling data of the underground hydrogen protons according to the directional excitation magnetic field intensity.

[0020] Through inversion, make the forward modeling data approximate the four-quadrant positioning nuclear magnetic resonance response signals collected during detection, and obtain the content and location distribution of the underground accumulated water through inversion.

[0021] Furthermore, theoretically calculating the directional excitation magnetic field intensity generated during directional focusing detection includes:

[0022] When performing directional focusing detection on the first and third quadrants, the three components of the calculated directional excitation magnetic field intensity are respectively:

[0023] Among them, and and are three-dimensional coordinates, is the excitation current intensity, is the length of the signal line, and are the first-order and zero-order Bessel functions respectively, is the integration coefficient, and and are potential functions, calculated based on parameters such as the Larmor frequency and the earth's conductivity, is within the integration differential element;

[0024] In the area to be measured, two signal lines located on the positive x-axis and positive y-axis generate a magnetic field area with the same direction and enhanced intensity in the first quadrant, two signal lines located on the negative x-axis and negative y-axis generate a magnetic field area with the same direction and enhanced intensity in the third quadrant, two signal lines located on the negative x-axis and positive y-axis generate a magnetic field area with the opposite direction and weakened intensity in the second quadrant, and two signal lines located on the positive x-axis and negative y-axis generate a magnetic field area with the opposite direction and weakened intensity in the fourth quadrant.

[0025] Further, the theoretical calculation of the directional excitation magnetic field intensity during directional focusing detection also includes:

[0026] When performing directional detection on the second and fourth quadrants, the three components of the calculated directional excitation magnetic field intensity are respectively:

[0027] Among them, and and are three-dimensional coordinates, is the excitation current intensity, is the length of the signal line, and are the first-order and zero-order Bessel functions respectively, is the integration coefficient, , , is a potential function, calculated based on parameters such as the Larmor frequency and the earth's conductivity. is the integration microelement within the range;

[0028] In the area to be measured, two signal lines on the positive x-axis and the positive y-axis generate a reverse weakening magnetic field area in the first quadrant, two signal lines on the negative x-axis and the negative y-axis generate a reverse weakening magnetic field area in the third quadrant, two signal lines on the negative x-axis and the positive y-axis generate a co-directional strengthening magnetic field area in the second quadrant, and two signal lines on the positive x-axis and the negative y-axis generate a co-directional strengthening magnetic field area in the fourth quadrant.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The method of the present invention not only provides a four-quadrant magnetic resonance detection method for urban detection scenarios that is convenient for obstacle avoidance laying, but also provides a method for strengthening the magnetic field excited by underground water accumulation in multiple directions. On the one hand, compared with traditional small loops, such signal lines have stronger adaptability in urban environments, are easy to bypass obstacles for large-scale layout, generate stronger signal responses to underground water accumulation, and make it easier for detection instruments to capture information on the distribution of harmful water sources. On the other hand, compared with single emission sources, such four-quadrant excitation sources can generate directional focused excitation magnetic fields to achieve high-resolution positioning of target bodies at different angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of a four-quadrant positioning magnetic resonance underground water accumulation detection method in an urban scenario provided by an embodiment of the present invention;

[0032] Figure 2 is for the first and third quadrants of positioning detection provided by an embodiment of the present invention Figure 1 in the connection schematic diagram of the magnetic resonance device;

[0033] Figure 3 is for the second and fourth quadrants of positioning detection provided by an embodiment of the present invention Figure 1 in the connection schematic diagram of the magnetic resonance device. DETAILED DESCRIPTION OF THE INVENTION

[0034] The following further describes the present invention in detail with reference to the drawings and embodiments:

[0035] As Figure 1 shown, a four-quadrant positioning magnetic resonance detection method for urban underground water accumulation warning, the detection equipment used specifically includes:

[0036] A magnetic resonance detector and four signal lines; the magnetic resonance detector 5 is placed on the surface of the urban area to be measured. The first signal line 1, the second signal line 2, the third signal line 3 and the fourth signal line 4 are placed on the surface in a cross shape with the magnetic resonance detector 5 as the plane coordinate center, dividing the area to be measured into area A, area B, area C and area D, corresponding to the first quadrant, the second quadrant, the third quadrant and the fourth quadrant respectively. The first signal line 1 is placed along the positive x-axis, the first grounding end 1a is grounded, and the first connection end 1b is connected to the magnetic resonance detector 5. The second signal line 2 is placed along the positive y-axis, the second grounding end 2a is grounded, and the second connection end 2b is connected to the magnetic resonance detector 5. The third signal line 3 is placed along the negative x-axis, the third grounding end 3a is grounded, and the third connection end 3b is connected to the magnetic resonance detector 5. Finally, the fourth signal line 4 is placed along the negative y-axis, the fourth grounding end 4a is grounded, and the fourth connection end 4b is connected to the magnetic resonance detector 5;

[0037] Group the first quadrant and the third quadrant as one group, and the second quadrant and the fourth quadrant as one group, and perform directional focusing detection in groups.

[0038] As Figure 2 shown, when performing directional focusing detection on the first quadrant and the third quadrant, the second connection end 2b of the second signal line 2 and the third connection end 3b of the third signal line 3 are respectively connected to the positive signal emission terminals P1 and P2 of the magnetic resonance detector 5, and the first connection end 1b of the first signal line 1 and the fourth connection end 4b of the fourth signal line 4 are respectively connected to the negative signal emission terminals N1 and N2 of the magnetic resonance detector;

[0039] Start the magnetic resonance detector 5 to start exciting the groundwater in the first and third quadrants; after the excitation is completed, turn off the signal emission system of the magnetic resonance detector 5. At the same time, the first connection end 1b of the first signal line 1 and the second connection end 2b of the second signal line 2 are connected to the same communication channel of the signal acquisition system of the magnetic resonance detector 5, and the third connection end 3b of the third signal line 3 and the fourth connection end 4b of the fourth signal line 4 are connected to another communication channel of the signal acquisition system of the magnetic resonance detector 5 to start collecting the magnetic resonance response signals of the groundwater below the working surfaces of the first and third quadrants; until the signal collection is completed, turn off the magnetic resonance detector 5;

[0040] As Figure 3 shown, when performing directional focusing detection on the second and fourth quadrants, the third connection end 3b of the third signal line 3 and the fourth connection end 4b of the fourth signal line 4 are respectively connected to the positive signal emission terminals P2 and P1 of the magnetic resonance detector 5, and the first connection end 1b of the first signal line 1 and the second connection end 2b of the second signal line 2 are respectively connected to the negative signal emission terminals N1 and N2 of the magnetic resonance detector;

[0041] Start the nuclear magnetic resonance detector 5 and begin to excite the groundwater in the second and fourth quadrants. After the excitation is completed, turn off the signal emission system of the nuclear magnetic resonance detector 5. Connect the first connection end 1b of the first signal line 1 and the fourth connection end 4b of the fourth signal line 4 to the same communication channel of the signal acquisition system of the nuclear magnetic resonance detector, and connect the second connection end 2b of the second signal line 2 and the third connection end 3b of the third signal line 3 to another communication channel of the signal acquisition system of the nuclear magnetic resonance detector, and start to collect the nuclear magnetic resonance response signals of the groundwater below the working surfaces in the second and fourth quadrants. Until the signal collection is completed, turn off the nuclear magnetic resonance detector 5;

[0042] Obtain the quadrant-located nuclear magnetic resonance response signals based on the collected signals;

[0043] Theoretically calculate the intensity of the directional excitation magnetic field generated during directional focused detection;

[0044] Obtain the forward modeling data of the quadrant-located nuclear magnetic resonance of the underground hydrogen protons based on the intensity of the directional excitation magnetic field;

[0045] Through inversion, make the forward modeling data approximate the quadrant-located nuclear magnetic resonance response signals collected during detection, and obtain the content and position distribution of the underground accumulated water through inversion. The inversion and forward modeling here are both realized by conventional methods in this field and will not be specifically elaborated.

[0046] When performing directional detection on the first and third quadrants, the three components of the intensity of the directional excitation magnetic field generated are:

[0047] Among them, 、 、 are three-dimensional coordinates, is the excitation current intensity, is the length of the signal line, and are the first-order and zero-order Bessel functions respectively, is the integral coefficient, 、 、 are potential functions, calculated based on parameters such as the Larmor frequency and the earth's conductivity, is the integral microelement within the range;

[0048] At this time, within the area to be measured in the city, the first signal line 1 and the second signal line 2 generate a co-directional enhanced magnetic field area in the first quadrant A area, the third signal line 3 and the fourth signal line 4 generate a co-directional enhanced magnetic field area in the third quadrant C area, the second signal line 2 and the third signal line 3 generate a counter-directional weakened magnetic field area in the second quadrant B area, and the first signal line 1 and the fourth signal line 4 generate a counter-directional weakened magnetic field area in the fourth quadrant D area. Thus, the underground water accumulation in the first and third quadrants (i.e., area A and area C) can be subjected to directional enhanced excitation;

[0049] When performing directional detection on the second and fourth quadrants, the three components of the directional excitation magnetic field intensity generated are:

[0050] Among them, 、 、 are three-dimensional coordinates, is the excitation current intensity, is the length of the signal line, and are the first-order and zero-order Bessel functions respectively, is the integral coefficient, 、 、 are potential functions, calculated based on parameters such as the Larmor frequency and the earth's conductivity, is the integral microelement within the range;

[0051] At this time, within the area to be measured in the city, the first signal line 1 and the second signal line 2 generate a counter-directional weakened magnetic field area in the first quadrant A area, the third signal line 3 and the fourth signal line 4 generate a counter-directional weakened magnetic field area in the third quadrant C area, the second signal line 2 and the third signal line 3 generate a co-directional enhanced magnetic field area in the second quadrant B area, and the first signal line 1 and the fourth signal line 4 generate a co-directional enhanced magnetic field area in the fourth quadrant D area. Thus, the underground water accumulation in the second and fourth quadrants (i.e., area B and area D) can be subjected to directional enhanced excitation.

[0052] The above are only the embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A four - quadrant positioning magnetic resonance detection method applicable to urban underground waterlogging warning, characterized in that, The method includes: Arranging four signal line sources of equal length to intersect vertically on the urban obstacle working surface, and the intersection point of the vertical intersection is located at the center of the area to be measured; Placing the nuclear magnetic resonance detector at the center of the area to be measured; One end of each of the four signal lines is used as a connection end and is connected to the nuclear magnetic resonance detector; The other ends of the four signal lines are used as grounding ends and are connected to the ground; The four signal lines divide the area to be measured into four quadrants, where two signal lines extend along the x-axis extension line and the other two signal lines extend along the y-axis extension line; Taking the first quadrant and the third quadrant as a group, and the second quadrant and the fourth quadrant as a group, and performing directional focusing detection in groups; When performing directional focusing detection on the first quadrant and the third quadrant, the connection ends of the two signal lines located on the negative x-axis and the positive y-axis are connected to the positive signal emission end of the nuclear magnetic resonance detector, and the connection ends of the two signal lines located on the positive x-axis and the negative y-axis are connected to the negative signal emission end of the nuclear magnetic resonance detector; Starting the nuclear magnetic resonance detector; after completion of excitation, turning off the signal emission system of the nuclear magnetic resonance detector, and at the same time, the connection ends of the two signal lines located on the positive x-axis and the positive y-axis are connected to the same communication channel of the signal acquisition system of the nuclear magnetic resonance detector, and the connection ends of the two signal lines located on the negative x-axis and the negative y-axis are connected to another communication channel of the signal acquisition system of the nuclear magnetic resonance detector, and starting to collect the nuclear magnetic resonance response signal of the groundwater below the working surfaces of the first quadrant and the third quadrant; until the signal collection is completed, turning off the nuclear magnetic resonance detector; When performing directional focusing detection on the second quadrant and the fourth quadrant, the connection ends of the two signal lines located on the negative x-axis and the negative y-axis are connected to the positive signal emission end of the nuclear magnetic resonance detector, and the connection ends of the two signal lines located on the positive x-axis and the positive y-axis are connected to the negative signal emission end of the nuclear magnetic resonance detector; Starting the nuclear magnetic resonance detector; after completion of excitation, turning off the signal emission system of the nuclear magnetic resonance detector, and at the same time, the connection ends of the two signal lines located on the positive x-axis and the negative y-axis are connected to the same communication channel of the signal acquisition system of the nuclear magnetic resonance detector, and the connection ends of the two signal lines located on the negative x-axis and the positive y-axis are connected to another communication channel of the signal acquisition system of the nuclear magnetic resonance detector, and starting to collect the nuclear magnetic resonance response signal of the groundwater below the working surfaces of the second quadrant and the fourth quadrant; until the signal collection is completed, turning off the nuclear magnetic resonance detector.

2. A four-quadrant positioning nuclear magnetic resonance detection method applicable to urban underground waterlogging warning according to claim 1, characterized in that Obtaining the four-quadrant positioning nuclear magnetic resonance response signal according to the collected signal; Theoretically calculating the directional excitation magnetic field intensity generated during directional focusing detection; Obtaining the four-quadrant positioning nuclear magnetic resonance forward data of underground hydrogen protons according to the directional excitation magnetic field intensity; Through inversion, making the forward data approximate the four-quadrant positioning nuclear magnetic resonance response signal collected during detection, and obtaining the content and position distribution of underground waterlogging through inversion.

3. A four - quadrant positioning magnetic resonance detection method applicable to urban underground waterlogging early warning according to claim 2, characterized in that, Theoretically calculating the directional excitation magnetic field intensity generated during directional focusing detection, including: When performing directional focusing detection on the first quadrant and the third quadrant, the three components of the calculated directional excitation magnetic field intensity are respectively: where x, y, and z are three-dimensional coordinates, I is the excitation current intensity, l is the length of the signal line, J1 and J0 are the first-order and zero-order Bessel functions respectively, λ is the integration coefficient, F1, F2, and F3 are potential functions calculated based on the Larmor frequency and the earth's conductivity, and x′ is the integration differential element within the range; Within the area to be measured, two signal lines located on the positive x-axis and the positive y-axis generate a co-directional enhanced magnetic field region in the first quadrant, two signal lines located on the negative x-axis and the negative y-axis generate a co-directional enhanced magnetic field region in the third quadrant, two signal lines located on the negative x-axis and the positive y-axis generate an anti-directional weakened magnetic field region in the second quadrant, and two signal lines located on the positive x-axis and the negative y-axis generate an anti-directional weakened magnetic field region in the fourth quadrant.

4. A four - quadrant positioning magnetic resonance detection method applicable to urban underground waterlogging early warning according to claim 3, characterized in that, The theoretical calculation of the directional excitation magnetic field intensity generated during directional focusing detection also includes: When performing directional detection on the second and fourth quadrants, the three components of the directional excitation magnetic field intensity generated are respectively: where x, y, and z are three-dimensional coordinates, I is the excitation current intensity, l is the length of the signal line, J1 and J0 are the first-order and zero-order Bessel functions respectively, λ is the integration coefficient, and F1, F2, and F3 are potential functions calculated based on the Larmor frequency and the earth's conductivity. x′ is the integration differential element within the range; Within the area to be measured, two signal lines located on the positive x-axis and the positive y-axis generate an anti-directional weakened magnetic field region in the first quadrant, two signal lines located on the negative x-axis and the negative y-axis generate an anti-directional weakened magnetic field region in the third quadrant, two signal lines located on the negative x-axis and the positive y-axis generate a co-directional enhanced magnetic field region in the second quadrant, and two signal lines located on the positive x-axis and the negative y-axis generate a co-directional enhanced magnetic field region in the fourth quadrant.

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