Array electrical focusing magnetic resonance detection method for water penetration in coal mines

Abstract

The present invention belongs to the field of geophysical exploration, and specifically is an array electrical focusing magnetic resonance detection method for coal mine old goaf water perspective. A magnetic resonance signal transmitter and a signal collector are placed on the surface of the coal mine goaf area to be tested; a rectangular coordinate system is established with the magnetic resonance instrument as the center, and two parallel long wires are placed overlapping in four directions of the rectangular coordinate system, totaling eight wires; the two long wires on each side serve as a magnetic resonance electrical signal transmitting line and a magnetic resonance electrical signal receiving line, respectively; through the different connection methods of the breakpoints of the two long wires, array electrical focusing detection of underground old goaf water in the coal mine is realized. Compared with traditional coils, this array electrical focusing detection method can stimulate water accumulation in deeper coal mine goaf areas and generate a stronger three-component induced magnetic field.

Description

Technical Field

[0001] The invention belongs to the field of geophysical exploration, and in particular is an array electric focusing magnetic resonance detection method for coal mine old empty water perspective. Background Art

[0002] The hidden danger of water in old coal mines is of great concern to the national economy and people's livelihood. In recent years, with the rapid development of the economy, coal resources have become one of my country's main energy sources. To meet the ever-increasing energy consumption, coal production has continued to rise in recent years, resulting in the creation of a large number of goafs in mining areas. Water accumulation in goaf coal seams poses a potential water seepage hazard to underground coal mine development and construction. During secondary development, the opening of unknown water layers can cause large amounts of high-pressure water to penetrate underground construction tunnels in a short period of time, damaging operating equipment and threatening the lives of construction workers. This seepage water is often accompanied by gravel and harmful gases, sealing off the underground construction environment and increasing the difficulty of rescue. In addition, the accumulated water is complex and corrosive, easily eroding the ground structure, damaging construction tunnels, polluting water sources, and causing ecological damage. Therefore, the significant economic losses and construction safety hazards caused by the hidden dangers of water in old coal mines need to be urgently addressed.

[0003] Magnetic Resonance Sounding (MRS) technology is the only exploration method among many geophysical exploration methods that can directly and quantitatively obtain groundwater content and distribution. It has absolute advantages such as directional tracking, positioning quantification, and strong targeting. However, the current magnetic resonance water exploration work in coal mines has the following difficulties: ① The detection depth of the traditional loop source device is shallow and it is unable to identify deep old empty water; ② The lateral resolution of the single electrical source is insufficient, and it is impossible to implement a large-scale one-time detection. This shows that it is necessary to target coal mine scenarios, while expanding the detection depth, to quickly and efficiently focus on and excite large-scale underground targets, to meet the needs of coal mine development projects for accurate and efficient acquisition of vertically deep and horizontally wide-range hazardous water source perspective information, so as to avoid or reduce the occurrence of coal seam water seepage accidents, ensure coal quality and ecological health, and provide guidance information for subsequent drainage management and construction arrangements. Summary of the Invention

[0004] In response to the problems existing in the above-mentioned prior art, the present invention provides an array electrically focused magnetic resonance detection method for coal mine old water perspective, which solves the problem that it is impossible to carry out one-time large-area and large-depth focused excitation in the coal mining area and to achieve high-resolution detection of deep old water.

[0005] The present invention is achieved in this way:

[0006] An array electric focusing magnetic resonance detection method suitable for coal mine old empty water perspective, the method comprising:

[0007] Place the magnetic resonance signal transmitter and signal collector on the surface of the coal mine area to be tested;

[0008] A rectangular coordinate system is established with the magnetic resonance instrument as the center. Two parallel long wires are placed overlapping in each of the four directions of the rectangular coordinate system, for a total of eight wires. The two long wires on each side serve as the magnetic resonance electrical signal transmission line and the magnetic resonance electrical signal receiving line, respectively.

[0009] The far end of the electrical signal transmission line in the positive direction of x is grounded, and the proximal end is connected to the proximal end of the electrical signal transmission line in the positive direction of coordinate axis y via the magnetic resonance signal transmitter, and the far end of the electrical signal transmission line in the positive direction of y is grounded;

[0010] The far end of the electrical signal transmission line in the negative direction of x is grounded, and the proximal end is connected to the proximal end of the electrical signal transmission line in the negative direction of y via the magnetic resonance signal transmitter, and the far end of the electrical signal transmission line in the negative direction of y is grounded;

[0011] The far ends of the four electrical signal receiving lines are grounded, and the near ends are connected to four independent communication channels of the magnetic resonance signal collector.

[0012] When conducting array electrical focusing detection on underground old water in coal mines, the magnetic resonance signal transmitter is started, and sinusoidal AC pulses are introduced into the connected x-positive and y-positive electrical signal transmission lines. At the same time, anti-phase sinusoidal AC pulses are introduced into the connected x-negative and y-negative electrical signal transmission lines to start focusing and exciting the underground old water in the entire detection area. After completing the signal transmission, the magnetic resonance signal transmitter is turned off, and the magnetic resonance signal collector is started at the same time to collect the underground old water response information in the entire detection area through 4 electrical signal receiving lines. The magnetic resonance signal collector is turned off after the signal collection is completed.

[0013] Furthermore, it also includes:

[0014] obtaining a magnetic resonance response signal according to the collected signal;

[0015] Calculate the excitation magnetic induction intensity and unilateral receiving magnetic induction intensity generated by the array electric focusing source;

[0016] Based on the excitation magnetic induction intensity and the unilateral receiving magnetic induction intensity, the magnetic resonance forward data of underground hydrogen protons is obtained. The inversion method is used to make the magnetic resonance forward data close to the magnetic resonance response signal, and the content and location distribution of underground old empty water are obtained through inversion.

[0017] Furthermore, the excitation magnetic induction intensity and the unilateral receiving magnetic induction intensity generated by the array-type electric focusing source are calculated, including:

[0018] The x component of the excitation magnetic induction intensity generated by the array electric focusing source is obtained as:

[0019]

[0020] The y component of the excitation magnetic induction intensity generated by the array electric focusing source is obtained as:

[0021]

[0022] The z component of the excitation magnetic induction intensity generated by the array electric focusing source is obtained as:

[0023]

[0024] Where x, y, and z are three-dimensional coordinates, μ0 is the vacuum permeability, q is the excitation pulse, t is the excitation pulse duration, l is the length of the signal line, J1 and J0 are the first-order and zero-order Bessel functions, respectively, λ is the integral coefficient, and F1, F2, and F3 are potential functions calculated based on parameters such as Larmor frequency and earth conductivity. x′ is Integral differential within the range.

[0025] Furthermore, the calculation of the excitation magnetic induction intensity and the unilateral receiving magnetic induction intensity generated by the array-type electric focusing source also includes:

[0026] When the magnetic resonance signal transmitter is turned off, the three components of the received magnetic induction intensity formed by the x-positive electrical signal receiving line are:

[0027]

[0028]

[0029]

[0030] The three components of the received magnetic induction intensity formed by the y positive electrical signal receiving line are:

[0031]

[0032]

[0033]

[0034] The three components of the received magnetic induction intensity formed by the x-negative electrical signal receiving line are:

[0035]

[0036]

[0037]

[0038] The three components of the received magnetic induction intensity formed by the y negative electrical signal receiving line are:

[0039]

[0040]

[0041]

[0042] In the above process, the parameters μ0, l, q and t are set according to actual conditions.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The method of the present invention provides an array-type electrically focused magnetic resonance detection method for coal mine goaf water detection scenarios. On the one hand, compared to traditional coils, this array-type electrically focused detection method can stimulate water accumulation in deeper coal mine goafs, generating a stronger three-component induced magnetic field. On the other hand, compared to a single emission source, this array-type electrically focused source has a wider lateral excitation range, enabling one-time, high-efficiency detection over a larger area, thereby achieving the goal of obtaining underground goaf water information with higher lateral resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A schematic diagram of the detection state of the array-type electrically focused magnetic resonance detection method in the coal mine old water detection scenario provided by an embodiment of the present invention;

[0046] Figure 2 for Figure 1 Schematic diagram of the connection method of the array type electric magnetic resonance signal transmission line;

[0047] Figure 3 for Figure 1 Schematic diagram of the connection method of the array-type electro-magnetic resonance signal receiving line. DETAILED DESCRIPTION

[0048] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0049] like Figure 1 Combine Figure 2 and Figure 3 As shown, an array electric focusing magnetic resonance detection method for coal mine old empty water perspective, the detection equipment used specifically includes:

[0050] Magnetic resonance signal transmitter, magnetic resonance signal collector, 4 electrical signal transmitting lines and 4 electrical signal receiving lines; the magnetic resonance signal transmitter 9 and the magnetic resonance signal collector 10 are placed together on the surface of the coal mine to be tested area, the electrical signal transmitting line 1, the electrical signal transmitting line 2, the electrical signal transmitting line 3 and the electrical signal transmitting line 4 are respectively placed in the x positive direction, y positive direction, x negative direction and y negative direction of the coordinate axis, the first electrical signal receiving line 5, the second electrical signal receiving line 6, the third electrical signal receiving line 7 and the fourth electrical signal receiving line 8 are respectively placed overlapping with the first electrical signal transmitting line 1, the second electrical signal transmitting line 2, the third electrical signal transmitting line 3 and the fourth electrical signal transmitting line 4, the distal end 1a of the first electrical signal transmitting line 1 is grounded, and the proximal end 1b is connected to the proximal end 2b of the second electrical signal transmitting line 2 via the magnetic resonance signal transmitter 9. The distal end 2a of the second electrical signal transmitting line 2 is grounded, the distal end 3a of the third electrical signal transmitting line 3 is grounded, and the proximal end 3b is connected to the proximal end 4b of the fourth electrical signal transmitting line 4 via the magnetic resonance signal transmitter 9. The distal end 4a of the fourth electrical signal transmitting line 4 is grounded, and the distal ends 5a, 6a, 7a and 8a of the first electrical signal receiving line 5, the second electrical signal receiving line 6, the third electrical signal receiving line 7 and the fourth electrical signal receiving line 8 are grounded, and the proximal ends 5b, 6b, 7b and 8b are connected to the four independent communication channels S1, S2, S3 and S4 of the magnetic resonance signal collector 10. The four independent communication channel grounding terminals S1g, S2g, S3g and S4g of the magnetic resonance signal collector 10 are grounded nearby;

[0051] The specific detection method using the above device includes:

[0052] Place the magnetic resonance signal transmitter 9 and the signal collector 10 on the surface of the coal mine area to be tested;

[0053] With the magnetic resonance instrument as the center, two long wires are placed overlapping in each of the four perpendicular directions of the rectangular coordinate system, for a total of eight wires; the two long wires on each side serve as the magnetic resonance electrical signal transmission line and the magnetic resonance electrical signal receiving line respectively;

[0054] like Figure 2 As shown, the distal end 1a of the first electrical signal transmission line 1 is grounded, and the proximal end 1b is connected to the proximal end 2b of the second electrical signal transmission line 2 via the magnetic resonance signal transmitter 9, and the distal end 2a of the second electrical signal transmission line 2 is grounded; the distal end 3a of the third electrical signal transmission line 3 is grounded, and the proximal end 3b is connected to the proximal end 4b of the fourth electrical signal transmission line 4 via the magnetic resonance signal transmitter 9, and the distal end 4a of the electrical signal transmission line 4 is grounded;

[0055] like Figure 3As shown, the distal ends 5a, 6a, 7a, and 8a of the four electrical signal receiving lines are grounded, and the proximal ends 5b, 6b, 7b, and 8b are connected to the four independent communication channels S1, S2, S3, and S4 of the magnetic resonance signal collector 10. The four independent communication channel grounding terminals S1g, S2g, S3g, and S4g of the magnetic resonance signal collector 10 are grounded nearby.

[0056] When performing array electrical focusing detection on underground old water in coal mines, the magnetic resonance signal transmitter 9 is started, such as Figure 2 As shown, a sinusoidal AC pulse q is introduced into the first electrical signal transmission line 1 and the second electrical signal transmission line 2. 1-2 At the same time, an anti-phase sinusoidal AC pulse q is introduced into the connected third electrical signal transmission line 3 and the fourth electrical signal transmission line 4. 3-4 , start focusing and exciting the underground old empty water in the entire detection area; after completing the signal transmission, turn off the magnetic resonance signal transmitter 9, and start the magnetic resonance signal collector 10 at the same time, and collect the underground old empty water response information in the entire detection area through the four electrical signal receiving lines; until the signal collection is completed, turn off the magnetic resonance signal collector 10;

[0057] When exciting large-scale underground old empty water, four electrical signal transmission lines form an array-type electrical focusing source. Every two electrical signal transmission lines will generate a same-direction excitation magnetic field in the area sandwiched between them. The same-direction excitation magnetic field can achieve focused and enhanced excitation of the underground old empty water in the corresponding area due to the superposition effect.

[0058] obtaining a magnetic resonance response signal according to the collected signal;

[0059] Calculate the excitation magnetic induction intensity and unilateral receiving magnetic induction intensity generated by the array electric focusing source;

[0060] Based on the excitation magnetic induction intensity and the unilateral receiving magnetic induction intensity, the magnetic resonance forward data of underground hydrogen protons is obtained. The inversion method is used to make the magnetic resonance forward data close to the magnetic resonance response signal, and the content and location distribution of underground old empty water are obtained through inversion.

[0061] The x component of the excitation magnetic induction intensity generated by the array electric focusing source is calculated by the following formula:

[0062]

[0063] The y component of the excitation magnetic induction intensity generated by the array-type electric focusing source is:

[0064]

[0065] The z component of the excitation magnetic induction intensity generated by the array-type electric focusing source is:

[0066]

[0067] Where x, y, and z are three-dimensional coordinates, μ0 is the vacuum permeability, q is the excitation pulse, and q = |q 1-2 |=|q 3-4 |, t is the duration of the excitation pulse, 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, F3 are potential functions, which can be calculated based on parameters such as Larmor frequency and earth conductivity. x′ is Integral differential within the range;

[0068] When the magnetic resonance signal transmitter 9 is turned off, the three components of the received magnetic induction intensity formed by the first electrical signal receiving line 5 are calculated as:

[0069]

[0070]

[0071]

[0072] The three components of the received magnetic induction intensity formed by the second electrical signal receiving line 6 are:

[0073]

[0074]

[0075]

[0076] The three components of the received magnetic induction intensity formed by the third electrical signal receiving line 7 are:

[0077]

[0078]

[0079]

[0080] The three components of the received magnetic induction intensity formed by the fourth electrical signal receiving line 8 are:

[0081]

[0082]

[0083]

[0084] In the above process, the parameters μ0, l, q and t are set according to actual conditions.

[0085] The above descriptions are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An array electric focusing magnetic resonance detection method suitable for coal mine old empty water perspective, characterized in that: The method includes: Place the magnetic resonance signal transmitter and signal collector on the surface of the coal mine area to be tested; A rectangular coordinate system is established with the magnetic resonance instrument as the center. Two parallel long wires are placed overlapping in each of the four directions of the rectangular coordinate system, for a total of eight wires. The two long wires on each side serve as the magnetic resonance electrical signal transmission line and the magnetic resonance electrical signal receiving line, respectively. The far end of the electrical signal transmission line in the positive direction of x is grounded, and the proximal end is connected to the proximal end of the electrical signal transmission line in the positive direction of coordinate axis y via the magnetic resonance signal transmitter, and the far end of the electrical signal transmission line in the positive direction of y is grounded; The far end of the electrical signal transmission line in the negative direction of x is grounded, and the proximal end is connected to the proximal end of the electrical signal transmission line in the negative direction of y via the magnetic resonance signal transmitter, and the far end of the electrical signal transmission line in the negative direction of y is grounded; The far ends of the four electrical signal receiving lines are grounded, and the near ends are connected to four independent communication channels of the magnetic resonance signal collector; When conducting array electrical focusing detection on underground old water in coal mines, the magnetic resonance signal transmitter is started, and sinusoidal AC pulses are introduced into the connected x-positive and y-positive electrical signal transmission lines. At the same time, anti-phase sinusoidal AC pulses are introduced into the connected x-negative and y-negative electrical signal transmission lines to start focusing and exciting the underground old water in the entire detection area. After completing the signal transmission, the magnetic resonance signal transmitter is turned off, and the magnetic resonance signal collector is started at the same time to collect the underground old water response information in the entire detection area through 4 electrical signal receiving lines. The magnetic resonance signal collector is turned off after the signal collection is completed.

2. The array electric focusing magnetic resonance detection method for coal mine old empty water perspective according to claim 1 is characterized in that: Also includes: obtaining a magnetic resonance response signal according to the collected signal; Calculate the excitation magnetic induction intensity and unilateral receiving magnetic induction intensity generated by the array electric focusing source; Based on the excitation magnetic induction intensity and the unilateral receiving magnetic induction intensity, the magnetic resonance forward data of underground hydrogen protons is obtained. The inversion method is used to make the magnetic resonance forward data close to the magnetic resonance response signal, and the content and location distribution of underground old empty water are obtained through inversion.

3. The array electric focusing magnetic resonance detection method for coal mine old empty water perspective according to claim 2 is characterized in that: Calculate the excitation magnetic induction intensity and unilateral receiving magnetic induction intensity generated by the array electric focusing source, including: The x component of the excitation magnetic induction intensity generated by the array electric focusing source is obtained as: The y component of the excitation magnetic induction intensity generated by the array electric focusing source is obtained as: The z component of the excitation magnetic induction intensity generated by the array electric focusing source is obtained as: Where x, y, and z are three-dimensional coordinates, μ0 is the vacuum permeability, q is the excitation pulse, t is the excitation pulse duration, l is the length of the signal line, J1 and J0 are the first-order and zero-order Bessel functions, respectively, λ is the integral coefficient, and F1, F2, and F3 are potential functions calculated based on parameters such as Larmor frequency and earth conductivity. x′ is Integral differential within the range.

4. The array electric focusing magnetic resonance detection method for coal mine old empty water fluoroscopy according to claim 3, wherein the excitation magnetic induction intensity and the unilateral receiving magnetic induction intensity generated by the array electric focusing source are calculated, further comprising: When the magnetic resonance signal transmitter is turned off, the three components of the received magnetic induction intensity formed by the x-positive electrical signal receiving line are: The three components of the received magnetic induction intensity formed by the y positive electrical signal receiving line are: The three components of the received magnetic induction intensity formed by the x-negative electrical signal receiving line are: The three components of the received magnetic induction intensity formed by the y negative electrical signal receiving line are: In the above process, the parameters μ0, l, q and t are set according to actual conditions.

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