A method for exploring a large-depth water-filled goaf in an open-pit iron mine based on transient electromagnetic method

Abstract

This invention belongs to the field of open-pit iron ore mining technology, and particularly relates to a method for exploring deep water-filled goaf areas in open-pit iron ore mines based on transient electromagnetic methods. The specific steps are as follows: A transmitting wire frame is deployed at the edge of the open-pit iron ore platform to collect induced voltage signals; the location of the water-filled goaf area is predicted by comparing the induced voltage. The size of the transmitting wire frame is adjusted and deployed in areas suspected of having water-filled goaf areas below, and induced voltage signals are collected again; the top position of the water-filled goaf area is determined by comparing the induced voltage. The transmitting wire frame is moved to the first platform below the top of the water-filled goaf area, and the signal acquisition probe is moved to the first platform below the platform where the transmitting wire frame is located. The transmitting wire frame and the signal acquisition probe are moved down platform by platform, and induced voltage signals are collected again; the bottom position of the water-filled goaf area is determined by comparing the induced voltage. This method determines the extent of the water-filled goaf area by comparing the maximum voltage values ​​collected on different platforms and the corresponding times, thus avoiding safety hazards.

Description

Technical Field

[0001] This invention belongs to the field of open-pit iron ore mining technology, and particularly relates to an exploration method for deep water-filled goaf areas in open-pit iron ore mines based on transient electromagnetic methods. Background Technology

[0002] With the development of large-scale machinery and equipment, my country has established many large iron ore mines using open-pit mining techniques. Before the adoption of large-scale open-pit mining, due to the limitations of large machinery and equipment, many small iron ore mines used underground mining techniques, excavating from the surface along the ore into deeper strata. After the ore was extracted, columnar or olive-shaped goafs with large depths and small cross-sectional dimensions were formed. Due to the depletion of shallow resources in small iron ore mines, or after prolonged periods of consolidation and closure, some goafs may contain water accumulation. Furthermore, the lack of design and blueprints in small iron ore mines means that the location of these water-filled goafs is often unknown. These unidentified water-filled goafs may cause machinery to fall, and even personnel to fall. Water inrush accidents in goafs can damage equipment in the working face, causing economic losses and casualties. To reduce losses caused by unidentified water-filled goafs during open-pit iron ore mining, the location of these goafs should be determined before accidents occur, and reasonable prevention and control measures should be taken.

[0003] There are various exploration methods for water-filled goaf areas. Transient electromagnetic methods (TEMs) are widely used due to their advantages of being less affected by terrain and having high construction efficiency. However, TEMs have significant problems for exploring deep water-filled goaf areas in open-pit iron mines. For example… Figure 1 As shown, the transient electromagnetic method induces eddy currents in the formation by passing a pulsed current through the transmitting frame. During the propagation of the induced eddy currents into the deeper layers of the formation, the propagation speed of the induced eddy currents in the waterlogged goaf is relatively slow, and the induced eddy currents decay continuously over time. As a result, before the induced eddy currents have propagated to the deepest part of the deep waterlogged goaf, the electromagnetic induction signal generated by the induced eddy currents is buried in electromagnetic noise and is difficult to collect by the signal acquisition probe. This makes it difficult to effectively identify the middle and lower parts of the deep waterlogged goaf in open-pit iron mines, resulting in blind spots in exploration, which can easily lead to accidents and pose a great safety hazard. Summary of the Invention

[0004] The purpose of this invention is to provide an exploration method for deep water-filled goaf areas in open-pit iron mines based on transient electromagnetic methods. This method solves the problem that traditional exploration methods are difficult to collect data through signal acquisition probes, resulting in the difficulty in effectively identifying the middle and lower parts of deep water-filled goaf areas in open-pit iron mines and creating blind spots in the exploration.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An exploration method for deep water-filled goaf in open-pit iron mines based on transient electromagnetic methods, the specific steps of which are as follows:

[0007] Step 1: Lay out a transmitting wire frame along the edge of the open-pit iron ore platform. Determine the electrical characteristics of the strata based on the stratigraphic distribution shown in the existing geological data. Determine the transmitting frequency f of the transmitting current in the transmitting wire frame based on the electrical characteristics of the strata, in Hz, to ensure that the induced voltage signal can reflect the geological information within 100m below the platform where the transmitting wire frame is located.

[0008] Step 2: Set up the measuring lines and measuring points on the platform where the transmitting frame is located, adjust the transmitting current I (in A), and use the signal acquisition probe to collect the induced voltage signal at each measuring point; compare the collected voltages, delineate the area where the measuring point with the higher induced voltage is located, and predict that there is a water accumulation mining area below it.

[0009] Step 3: Calculate the side length of the small transmitting frame by converting the area of ​​the delineated region, and lay out the small transmitting frame within the delineated area; lay out survey lines and measuring points on the first, second, third, and fourth platforms below the platform where the small transmitting frame is located, and use a signal acquisition probe to collect induced voltage signals, and adjust the transmitting current I and transmitting frequency f in the small transmitting frame in a timely manner to ensure that the induced voltage signal can reflect the geological information between the platform where the transmitting frame is located and the platform where the signal acquisition probe is located;

[0010] Step 4: Compare the acquisition time corresponding to the maximum voltage values ​​collected on the first, second, third, and fourth platforms below the platform where the small transmitting frame is located to determine the top position of the waterlogged mining area;

[0011] Step 5: Deploy the small transmitting frame on the first platform below the top of the waterlogged goaf area determined in Step 4, and place the small transmitting frame in the area where the maximum value of the induced voltage signal is collected. Move the signal acquisition probe to the first platform below the platform where the small transmitting frame is located, and adjust the transmitting current I and the transmitting frequency f to ensure that the induced voltage signal can reflect the geological information between the platform where the small transmitting frame is located and the platform where the signal acquisition probe is located. Keeping the transmitting current I and the transmitting frequency f unchanged, move the small transmitting frame and the signal acquisition probe down platform by platform and collect the induced voltage signal. Compare the maximum voltage value and the collection time corresponding to the maximum value to determine the bottom position of the waterlogged goaf area.

[0012] Preferably, in step one, the electrical conductivity of each rock layer is estimated based on the stratigraphic information reflected in existing geological data, and the weighted average electrical conductivity E of the strata within 100m below the platform where the transmitting frame is located is calculated according to formula (1). 100 .

[0013] E 100 =ΣD i ·E i / ∑D i (1)

[0014] E in formula (1) i D represents the electrical conductivity of the i-th stratum below the platform containing the transmitting wireframe, in units of S / m. i E represents the thickness of the i-th stratum below the platform containing the transmitting wireframe, in meters. 100 The weighted average electrical conductivity of the strata within 100m below the platform where the transmitting frame is located, in S / m, ΣD i ≤100m.

[0015] The velocity of the induced eddy current spreading into the deeper layers of the formation is calculated according to formula (2).

[0016] v = 3.18 / (10 -5 ×Et) 1 / 2 (2)

[0017] In formula (2), v represents the velocity of the induced eddy current propagating into the deep part of the stratum, in m / s, E is the electrical conductivity of the stratum, in S / m, and t is the time, in s.

[0018] Adjust the transmission frequency f according to formulas (3)-(5) to ensure that the induced voltage signal can reflect the geological information within 100m below the platform where the transmission frame is located.

[0019]

[0020] T = (1 / f) > t = t1 + t2 (5)

[0021] In formulas (3)-(5), t, t1, and t2 are all times in seconds, and t0 = 10 seconds. -4 s, E in formula (4) w The conductivity of the water in the goaf is expressed in S / m. In formula (5), T is the induced voltage signal acquisition period, expressed in s, and f is the emission frequency of the emission current in the emission frame, expressed in Hz.

[0022] Preferably, in step two, the transmitting current I is adjusted to ensure that the induced voltage signal acquired near time T is higher than five times the power frequency electromagnetic noise, which is typically 5 × 10⁻⁶. -7 V, that is, the induced voltage signal value acquired by the signal acquisition probe at the approach time T, must be greater than 2.5 × 10⁻⁶. -6 V.

[0023] Preferably, the side length of the small emitting wireframe in step three is calculated according to formula (6).

[0024] l = S 1 / 2 (6)

[0025] In formula (6), l is the side length of the small transmitting frame in meters (m), and S is the area of ​​the region with higher induced voltage signal value delineated in step two in meters (m²). 2 .

[0026] Preferably, in step three, the transmitting current I and the transmitting frequency f are adjusted in a timely manner according to formulas (7)-(10) to ensure that the induced voltage signal can reflect the geological information between the platform where the small transmitting frame is located and the platform where the signal acquisition probe is located, and that the signal is close to T. n The induced voltage signal collected at that time was greater than 2.5 × 10. -6 V.

[0027] E nH =ΣD i '·E i ' / ΣD i '(7)

[0028]

[0029] T n =(1 / f)>t n =t 1n +t 2n (10)

[0030] In formula (7), E nH The weighted average conductivity of the strata between the platform where the small transmitting frame is located and the platform where the signal acquisition probe is located in step three is expressed in S / m, E. i ' is the conductivity of the i-th stratum below the platform where the transmitting wire frame is located in step three, in units of S / m, D i ' represents the thickness of the i-th stratum below the platform where the transmitting wireframe is located in step three, in meters, ΣD i =nH; In formulas (7)-(9), H is the height of the open-pit iron mine platform in meters, nH < 100m, and n indicates that the signal acquisition probe is located on the nth platform below the platform where the small transmitting frame is located in step three; In formulas (8)-(10), t n , t 1n , t 2n All times are seconds (s).

[0031] Preferably, the specific steps for determining the top location of the waterlogged mining area in step four are as follows: Compare the voltages collected from the first, second, third, and fourth platforms below the platform where the small transmitting frame is located, and compare the maximum voltage V collected from each platform. nm Corresponding collection time t nm V nm This represents the maximum value of the induced voltage signal collected by the nth platform below the platform containing the small transmitting frame, in V. nm For Vnm The corresponding acquisition time is in seconds. Formula (11) is satisfied when n < N, and formula (12) is satisfied when n ≥ N. It is assumed that the top of the waterlogged mining area is located below the horizontal plane of the Nth platform below the platform where the transmitting frame is located, and above the horizontal plane of the (N+1)th platform below the platform where the transmitting frame is located.

[0032] t 1(n+1) -t 1n =t (n+1)m -t nm (11)

[0033] t 1(n+1) -t 1n <t (n+1)m -t nm (12)

[0034] Where t 1n The time required to satisfy formula (8) is in seconds.

[0035] If the top of the waterlogged goaf is not found on the first, second, third, and fourth platforms below the small transmitter frame, move the transmitter frame from step one to the first platform below it, and repeat steps one, two, three, and four in a loop until the top of the waterlogged goaf is determined.

[0036] Preferably, in step five, the transmitting current I and the transmitting frequency f are adjusted in a timely manner according to formulas (13)-(16) to ensure that the induced voltage signal can reflect the geological information between the platform where the small transmitting frame is located and the platform where the signal acquisition probe is located, and that the induced voltage signal acquired near T' is greater than 2.5 × 10 -6 V.

[0037] E 3H2 =∑D i "·E i ” / ∑D i (13)

[0038]

[0039] T'=(1 / f)>t'=t1'+t'2 (16)

[0040] E in formula (13)-(16) 3H / 2 The weighted average conductivity, in S / m, is the stratum between the platform where the small transmitting frame is located and the platform where the signal acquisition probe is located, as well as the stratum within H / 2 below the platform where the signal acquisition probe is located. i "D represents the conductivity of the i-th stratum below the platform where the small transmitting wire frame is located in step five, in units of S / m." i" represents the thickness of the i-th stratum below the platform where the small transmitting frame is located in step five, in meters, ∑D i =3H / 2.

[0041] As the small transmitting frame and signal acquisition probe are moved down platform by platform, the transmitting frequency f is continuously adjusted to make formulas (13)-(16) hold true; and the transmitting current I is adjusted to ensure that the induced voltage signal acquired when approaching T' is greater than 2.5×10 -6 V.

[0042] Comparing the voltages collected at each platform in step five, the following characteristics of the collected voltages can be used to determine the bottom location of the waterlogged mining area: The maximum voltage value collected at the q-th platform below the area defined by the small transmitting frame in step three is V′. qm The unit is V, and the maximum voltage is V′. qm The corresponding time is t' nm The unit is s; when q < Q, all V′ qm Equal, all t′ qm They are also equal; when q = Q, V′ Qm >V′ q ' m , and t' Qm <t' qm It is assumed that the bottom of the waterlogged mining area is located above the horizontal plane of the Qth platform below the area defined by the small launch frame in step three, and below the horizontal plane of the Q-1th platform below the area defined by the small launch frame in step three.

[0043] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0044] (1) By deploying transmitting frames and signal acquisition probes on different platforms of the open-pit iron mine, the deep water-filled goaf area is explored in sections. The closer the transmitting frames and signal acquisition probes are to the water-filled goaf area, the higher the quality of the exploration signal and the more refined the exploration.

[0045] (2) With the change of the position of the transmitting frame and the signal acquisition probe, combined with timely adjustment of the transmitting current and transmitting frequency, more exploration data is obtained while the data quality is improved; and the high-quality exploration data controls the influence of other variables besides geological information on the exploration data to the greatest extent, so that the exploration data can fully reflect the changes in geological information.

[0046] (3) Based on a large amount of high-quality exploration data, by comparing the maximum voltage values ​​collected on different platforms and the time corresponding to the maximum values, the extent of the open-pit iron mine waterlogged goaf area is jointly determined. This adds a basis for determining the waterlogged goaf area in addition to the induced voltage signal itself, greatly improving the exploration accuracy of the open-pit iron mine waterlogged goaf area, realizing the effective identification of different platforms, eliminating blind spots in exploration, and avoiding safety hazards. Attached Figure Description

[0047] Figure 1 This is a schematic diagram illustrating the principle of transient electromagnetic method and the propagation of induced eddy currents in the background technology of this invention;

[0048] Figure 2 This is a schematic diagram of the open-pit iron mine mining morphology and the waterlogged goaf in an embodiment of the present invention;

[0049] Figure 3 This is a schematic diagram of a pilot exploration of a goaf area by setting up a transmitting wire frame on a platform in an embodiment of the present invention.

[0050] Figure 4 This is a schematic diagram of the stratigraphic distribution within 100 meters below platform one in an embodiment of the present invention;

[0051] Figure 5 This is a schematic diagram of a suspected goaf area discovered after exploration on platform one, as described in an embodiment of the present invention.

[0052] Figure 6 This is a schematic diagram illustrating the acquisition of induced voltage signals by setting up a small transmitting wire frame on platform one and setting up measuring points on platform two in an embodiment of the present invention.

[0053] Figure 7 This is a schematic diagram illustrating the acquisition of induced voltage signals by setting up a small transmitting wire frame on platform one and setting up measuring points on platform three in an embodiment of the present invention.

[0054] Figure 8 This is a schematic diagram illustrating the acquisition of induced voltage signals by setting up a small transmitting wire frame on platform one and setting up measuring points on platform four in an embodiment of the present invention.

[0055] Figure 9 This is a schematic diagram illustrating the acquisition of induced voltage signals by setting up a small transmitting wire frame on platform one and setting up measuring points on platform five in an embodiment of the present invention.

[0056] Figure 10 This is a schematic diagram illustrating the acquisition of induced voltage signals by setting up a small transmitting wire frame on platform four and setting up measuring points on platform five in an embodiment of the present invention.

[0057] Figure 11 This is a schematic diagram illustrating the acquisition of induced voltage signals by setting up a small transmitting wire frame on platform five and setting up measuring points on platform six in an embodiment of the present invention.

[0058] Figure 12 This is a schematic diagram illustrating the acquisition of induced voltage signals by setting up a small transmitting wire frame on platform six and setting up measuring points on platform seven in an embodiment of the present invention.

[0059] Explanation of reference numerals in the attached diagram: 1. Transmitting frame; 2. Induced eddy current; 3. Waterlogged goaf area; 4. Platform 1; 5. First connecting line; 6. Generator; 7. Second connecting line; 8. Transmitting controller; 9. Signal acquisition probe; 10. Deployed measuring points; 11. Iron-bearing quartzite; 12. Conglomerate iron ore; 13. Quartzite; 14. Area where measuring points with higher induced voltage values ​​are located; 15. Small transmitting frame; 16. Platform 2; 17. Platform 3; 18. Platform 4; 19. Platform 5; 20. Platform 6; 21. Platform 7. Detailed Implementation

[0060] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0061] An exploration method for deep water-filled goaf in open-pit iron mines based on transient electromagnetic methods, the specific steps of which are as follows:

[0062] Step 1: As Figure 2-3 As shown, the height of the open-pit iron mine mining platform H = 15m. A transmitting frame 1 is installed along the edge of platform 4. The transmitting frame 1 and generator 6 are connected via a first connecting line 5, and the generator 6 and transmitting controller 8 are connected via a second connecting line 7. Figure 4 As shown, according to existing geological data, the strata distribution within 100m below Platform 4 is as follows: 0m-42m is iron-bearing quartzite 11, thickness D1 = 42m; 42m-75m is conglomerate iron ore 12, thickness D2 = 33m; 75m-100m is quartzite 13, thickness D3 = 25m. The electrical conductivity of the rock samples from each stratum, measured by an electrical conductivity meter, is: E1 = 2 × 10⁻⁶ for iron-bearing quartzite 11. - 3 S / m; E2 of conglomerate iron ore 12 = 4 × 10 -3 S / m; E3 = 10 for quartzite 13 -3 S / m; Calculate the weighted average conductivity E of the strata within 100m below the platform where the transmitting frame 1 is located according to formula (1). 100 .

[0063] E 100 =ΣD i ·E i / ∑D i (1)

[0064] E in formula (1) i D represents the electrical conductivity of the i-th stratum below the platform containing the transmitting wireframe, in units of S / m. iE represents the thickness of the i-th stratum below the platform containing the transmitting wireframe, in meters. 100 The weighted average conductivity of the strata within 100m below the platform where the launch frame is located, in units of S / m, ∑D i ≤100m, E is calculated according to formula (1) 100 =2.41×10 -3 S / m.

[0065] The velocity of the induced eddy current 2 diffusing into the deeper layers of the stratum is calculated according to formula (2).

[0066] v = 3.18 / (10 -5 ×Et) 1 / 2 (2)

[0067] In formula (2), v represents the velocity of the induced eddy current 2 propagating into the deep part of the stratum, in m / s, E is the electrical conductivity of the stratum, in S / m, and t is the time, in s.

[0068] Adjust the transmission frequency f according to formulas (3)-(5), with the unit being Hz, to ensure that the induced voltage signal can reflect the geological information within 100m below the platform where the transmission frame is located.

[0069]

[0070] T = (1 / f) > t = t1 + t2 (5)

[0071] In formulas (3)-(4), t, t1, and t2 are time units in seconds, and t0 = 10 seconds. -4 s, E in formula (4) w E represents the electrical conductivity of the water accumulated in the goaf, measured in S / m. w =39S / m, T is the induced voltage signal acquisition period in seconds, and f is the transmission frequency of the transmitting current in the transmitting frame in Hz. The calculated value is: t1 = 1.55 × 10⁻⁶. -4 s,t2=1.03×10 -1 s, set the transmission frequency f to 8Hz, T = 1.25 × 10 -1 S.

[0072] Step Two: As Figure 3 As shown, the open-pit iron mine platform 1 is 1800m long and 35m wide. A network of 10m × 10m measuring points 10 is laid out on platform 4. The transmission frequency f = 8Hz. Trial signal acquisition is performed using signal acquisition probe 9. When the transmission current I = 12A, the signal acquisition time is 1.25 × 10... -1 At time s, the induced voltage signal is 5 × 10 -6V is greater than five times the power frequency electromagnetic noise. The transmitting current I is set to 12A, and the induced voltage signal is collected at each measuring point. The area 14 where the measuring point with the higher induced voltage value is located is delineated.

[0073] Step 3: As Figure 5-6 As shown, the area of ​​region 14, where the induced voltage value is relatively high, is 405m². 2 According to formula (6), the side length l of the small transmitting frame 15 is calculated to be 20m.

[0074] l = S 1 / 2 (6)

[0075] In formula (6), l is the side length of the small transmitting frame 15, in meters, and S is the area of ​​the region where the measured point with the higher induced voltage signal value is located, as defined in step two, in meters. 2 .

[0076] like Figures 6-9 As shown, the small transmitting frame 15 is set up within the defined area of ​​platform 14, and a 10m×10m measuring point network is set up on platform 2 16, platform 3 17, platform 4 18, and platform 5 19. The induced voltage signal is collected using the signal acquisition probe 9. The transmitting frequency f is adjusted in a timely manner according to formulas (7)-(10) to ensure that the induced voltage signal can reflect the geological information between the platform where the transmitting frame is located and the platform where the signal acquisition probe is located. The transmitting current I is also adjusted to ensure that the signal is close to T. n The induced voltage signal collected at that time was greater than 2.5 × 10. -6 V.

[0077] E nH =∑D i '·E i ' / ∑D i (7)

[0078]

[0079] T n =(1 / f)>t n =t 1n +t 2n (10)

[0080] In formula (7), E nH The weighted average conductivity of the strata between the platform where the small transmitting frame is located and the platform where the signal acquisition probe is located, in S / m, E i ' is the electrical conductivity of the i-th stratum below the platform where the small transmitting frame is located, in S / m, D i ' represents the thickness of the i-th stratum below the platform where the small transmitting frame is located, in meters, ∑D i=nH; In formulas (7)-(9), H is the height of the open-pit iron mine bench, H = 15m, nH < 100m, and n indicates that the signal acquisition probe is located on the nth platform below the platform where the small transmitting frame is located; In formulas (8)-(10), t n , t 1n , t 2n All times are seconds (s).

[0081] Based on existing geological data, the following calculations were performed: t 11 =1.1×10 -4 s,t 21 =6.38×10 -3 s;t 12 =1.17×10 -4 s,t 22 =1.6×10 -2 s;t 13 =1.26×10 -4 s,t 23 =2.99×10 -2 s;t 14 =1.37×10 -4 s,t 24 =4.82×10 -2 When signal acquisition probe 9 performs signal acquisition on platform 16, the transmission frequency f is set to 128Hz, and T = 7.81 × 10⁻⁶. -3 When signal acquisition probe 9 is performing signal acquisition on platform 3.17, the transmission frequency f is set to 55Hz, and T = 1.82 × 10⁻⁶. -2 When signal acquisition probe 9 is performing signal acquisition on platform 418, the transmission frequency f is set to 30Hz, and T = 3.33 × 10⁻⁶. -2 When signal acquisition probe 9 is performing signal acquisition on platform 519, the transmission frequency f is set to 20Hz, and T = 5.0 × 10⁻⁶. -2 After trial signal acquisition, when the transmitting current I = 10A, the induced voltage signals acquired on platforms 2 (16), 3 (17), 4 (18), and 5 (19) all exceeded 2.5 × 10⁻⁶ when approaching the T value of their respective platforms. -6 V, so the emission current I is set to 10A.

[0082] Step 4: Compare the voltages collected at Platform 2 (16), Platform 3 (17), Platform 4 (18), and Platform 5 (19), and compare the maximum voltage value V. nm Corresponding collection time t nm Determine the top location of waterlogged goaf 3; V nm This represents the maximum value of the induced voltage signal collected by the nth platform below platform 4, where the small transmitting frame is located, in V, t. nm For Vnm The corresponding acquisition time, in seconds, is the maximum voltage value and the corresponding acquisition time data acquired on Platform 2 (16), Platform 3 (17), Platform 4 (18), and Platform 5 (19): t 1m =1.08×10 -4 s, t 2m =1.15×10 -4 s, t 3m =2.36×10 -3 s, t 4m =1.19×10 - 2 s;V 1m =1.47×10 -2 V, V 2m =1.39×10 -2 V, V 3m =1.27×10 -2 V, V 4m =1.09×10 -2 V, when n<2, satisfies formula (11), and when n≥2, satisfies formula (12). It is assumed that the top of the waterlogged mining area 3 is located below the horizontal plane of platform 317 and above the horizontal plane of platform 418.

[0083] t 1(n+1) -t 1n =t (n+1)m -t nm (11)

[0084] t 1(n+1) -t 1n <t (n+1)m -t nm (12)

[0085] Where t 1n The time required to satisfy formula (8) is in seconds.

[0086] Step 5: As Figure 10 As shown, the small transmitting frame 15 is deployed on platform four 18, and the small transmitting frame 15 is deployed on the V acquisition point. 3m At the measurement point, the signal acquisition probe 9 is moved to platform 19. According to formulas (13)-(16), the transmission frequency f of the transmission current in the small transmitting frame 15 is adjusted in time, and the transmission frequency is set to 128Hz, T'=7.81×10 -3 When the transmitting current I = 10A, the induced voltage signal collected on each platform is close to 7.81 × 10⁻⁶. -3 At time s, the induced voltage signal is greater than 2.5 × 10 - 6 V, so the emission current I is set to 10A.

[0087] E 3H2 =ΣD i "·E i ” / ΣD i (13)

[0088]

[0089] T'=(1 / f)>t'=t1'+t'2 (16)

[0090] E in formula (13)-(15) 3H / 2 The weighted average electrical conductivity is given for the strata between Platform 418 and Platform 519, and for the strata within H / 2 below Platform 519, in units of S / m and E. i "D represents the electrical conductivity of the i-th stratum below platform 418, in units of S / m." i ” The thickness of the i-th stratum below platform 418 is given by ∑D. i =3H / 2.

[0091] like Figures 11-12 As shown, the small transmitting frame 15 and the signal acquisition probe 9 are moved down to platform 7 21 one platform at a time. During the implementation, the change in the conductivity of the strata between adjacent platforms has little effect on the transmission frequency. During the downward movement, the transmission frequency f = 128Hz is kept constant, and the transmission current I = 10A is kept constant.

[0092] Comparing the maximum voltage values ​​and corresponding times collected on platforms 5.19, 6.20, and 7.21, V4' m =0.92×10 -2 V, V5' m =0.92×10 -2 V, V6' m =1.24×10 -2 V;t' 4m =4.05×10 -3 s、t' 5m =4.05×10 -3 s、t' 6m =1.94×10 -3 s, V′ qm This refers to the maximum value of the induced voltage signal t' collected on the q-th platform below platform 4 during the process of setting up the small transmitting frame 15 on platform 4, moving the signal acquisition probe 9 to platform 5, and moving the small transmitting frame 15 and the signal acquisition probe 9 down platform by platform. qm For V′ qmThe corresponding time. The induced voltage signals collected from each platform have the following characteristics, which can be used to determine the bottom location of the waterlogged mining area 3: V′ 4m =V′ 5m <V′ 6m , and t′ 4m =t′ 5m >t′ 6m It is believed that the bottom of the waterlogged mining area 3 is located above the level of platform 721 and below the level of platform 620.

Claims

1. A method for exploring deep, waterlogged goaf areas in open-pit iron mines based on transient electromagnetic methods, characterized in that, The specific steps are as follows: Step 1: Lay out transmitting wire frames along the edge of the open-pit iron ore platform. Determine the electrical characteristics of the strata based on the existing geological data showing the stratigraphic distribution. Determine the transmission frequency of the transmitting current in the transmitting wire frames based on the electrical characteristics of the strata. The unit is This ensures that the induced voltage signal can reflect the geological information within a 100m range below the platform where the transmitting frame is located; Step 2: Set up the measuring lines and measuring points on the platform where the transmitting frame is located, adjust the transmitting current I (in A), and use the signal acquisition probe to collect the induced voltage signal at each measuring point; compare the collected voltage, delineate the area where the measuring point with the higher induced voltage signal is located, and predict that there is a water accumulation mining area below it. Step 3: Calculate the side length of the small transmitting frame by converting the area of ​​the demarcated region, and lay out the small transmitting frame within the demarcated area; lay out the measurement lines and measurement points on the first, second, third, and fourth platforms below the platform where the small transmitting frame is located, and use a signal acquisition probe to collect the induced voltage signal, adjusting the transmitting current I and the transmitting frequency in the small transmitting frame in a timely manner. This ensures that the induced voltage signal can reflect the geological information between the platform where the transmitting frame is located and the platform where the signal acquisition probe is located; Step 4: Compare the acquisition time corresponding to the maximum voltage values ​​collected on the first, second, third, and fourth platforms below the platform where the small transmitting frame is located to determine the top position of the waterlogged mining area; Step 5: Set up the small transmitting frame on the first platform below the top of the waterlogged goaf area determined in Step 4, and place the small transmitting frame in the area where the maximum value of the induced voltage signal is collected. Move the signal acquisition probe to the first platform below the platform where the small transmitting frame is located, and adjust the transmitting current I and the transmitting frequency. Ensure that the induced voltage signal can reflect the geological information between the platform where the small transmitting frame is located and the platform where the signal acquisition probe is located; maintain the transmitting current I and the transmitting frequency. Without changing the position, the small transmitting frame and the signal acquisition probe are moved down platform by platform to collect the induced voltage signal. The maximum voltage value and the acquisition time corresponding to the maximum value are compared to determine the bottom position of the waterlogged mining area. In step one, the electrical conductivity of each rock layer is estimated based on the stratigraphic information reflected in the existing geological data, and the weighted average electrical conductivity of the strata within 100m below the platform where the transmitting frame is located is calculated according to formula (1). , (1) In formula (1) The first one below the platform where the launch wireframe is located The electrical conductivity of the strata, in units of , The first one below the platform where the launch wireframe is located The thickness of each stratum, in units of , The weighted average electrical conductivity of the strata within 100m below the platform where the launch frame is located, in units of , , The velocity of the induced eddy current diffusing into the deeper layers of the formation is calculated according to formula (2). (2) In formula (2) This represents the speed at which induced eddies propagate into deeper layers of the earth, measured in units of... , The electrical conductivity of the formation, in units of , For time, the unit is , Adjust the transmission frequency according to formulas (3)-(5) This ensures that the induced voltage signal can reflect geological information within a 100m radius below the platform where the transmitting frame is located. (3) (4) (5) In formula (3)-(5) , , All times are time, in units of , , in formula (4) The electrical conductivity of the water accumulated in the goaf, in units of , in formula (5) The induced voltage signal acquisition period is expressed in units of 1. , The transmitting frequency of the transmitting current in the transmitting frame, in units of .

2. The exploration method for deep water-filled goaf areas in open-pit iron mines based on transient electromagnetic methods according to claim 1, characterized in that, In step two, the emission current is adjusted. Guarantee at close The induced voltage signal collected at that time was more than five times higher than the power frequency electromagnetic noise, which is typically 5 × 10⁻⁶. -7 V, which is the re-approach time of the signal acquisition probe. The induced voltage signal value collected at that time must be greater than 2.5 × 10⁻⁶. -6 V; In step three, the side length of the small emitting wireframe is calculated according to formula (6). (6) In formula (6), The side length of the small emitting wireframe, in units of , The area of ​​the region with higher induced voltage signal values ​​identified in step two, in units of .

3. The exploration method for deep water-filled goaf areas in open-pit iron mines based on transient electromagnetic methods according to claim 1, characterized in that, In step three, the emission current and transmission frequency Adjustments should be made promptly according to formulas (7)-(10) to ensure that the induced voltage signal can reflect the geological information between the platform where the small transmitting frame is located and the platform where the signal acquisition probe is located, and to ensure that the signal is close to the geological information between the platform where the small transmitting frame is located and the platform where the signal acquisition probe is located. The induced voltage signal collected at that time was greater than 2.5 × 10. -6 V, (7) (8) (9) (10) In formula (7), This represents the weighted average conductivity of the strata between the platform containing the small transmitting frame and the platform containing the signal acquisition probe in step three, in units of... , The first one below the platform where the transmitting wire frame is located in step three. The electrical conductivity of the strata, in units of , The first one below the platform where the transmitting wire frame is located in step three. The thickness of each stratum, in units of , ;In formula (7)-(9) This refers to the height of the open-pit iron mine bench, in units of... , , This indicates that the signal acquisition probe is located below the platform where the small transmitting wire frame is located in step three. Each platform; in formulas (8)-(10) , , All times are time, in units of .

4. The exploration method for deep water-filled goaf areas in open-pit iron mines based on transient electromagnetic methods according to claim 1, characterized in that, The specific steps for determining the top location of the waterlogged mining area in step four are as follows: Compare the voltages collected from the first, second, third, and fourth platforms below the platform where the small transmitting frame is located, and compare the maximum voltage values ​​collected from each platform. Corresponding collection time , This represents the maximum value of the induced voltage signal collected by the nth platform below the platform containing the small transmitting frame, in units of... , for The corresponding data collection time, in units of ,when When it satisfies formula (11), and When the condition satisfies formula (12), it is assumed that the top of the waterlogged goaf area is located below the platform where the launch frame is located. Below the horizontal plane of the platform, located below the platform where the transmitting wireframe is situated. Above the horizontal plane of each platform, (11) (12) in The time required to satisfy formula (8) is in units of , If the top of the waterlogged goaf is not found on the first, second, third, and fourth platforms below the small transmitter frame, move the transmitter frame from step one to the first platform below it, and repeat steps one, two, three, and four in a loop until the top of the waterlogged goaf is determined.

5. The exploration method for deep water-filled goaf areas in open-pit iron mines based on transient electromagnetic methods according to claim 1, characterized in that, In step five, the transmitting current I and the transmitting frequency Adjustments should be made promptly according to formulas (13)-(16) to ensure that the induced voltage signal can reflect the geological information between the platform where the small transmitting frame is located and the platform where the signal acquisition probe is located, and in close proximity to... The induced voltage signal collected at that time was greater than 2.5 × 10. -6 V, (13) (14) (15) (16) In formula (13)-(16) The stratum between the platform where the small transmitting frame is located and the platform where the signal acquisition probe is located, and the stratum below the platform where the signal acquisition probe is located. Weighted average electrical conductivity of the inner strata, in units of , The platform below the small transmitting wireframe in step five. The electrical conductivity of the strata, in units of , The platform below the small transmitting wireframe in step five. The thickness of each stratum, in units of , , The transmission frequency was continuously adjusted as the small transmitter frame and signal acquisition probe were moved down platform by platform. This makes formulas (13)-(16) true; and the emission current I is adjusted to ensure it is close to... The induced voltage signal collected at that time was greater than 2.5 × 10. -6 V, Comparing the voltages collected from each platform in step five, the following characteristics of the collected voltages can be used to determine the bottom location of the waterlogged mining area: the area below the small transmitting frame in step three. The maximum value of the induced voltage signal collected by each platform is The unit is Maximum value of induced voltage signal The corresponding time is The unit is ;when All Equal, all They are equally equal; when hour, ,and It is believed that the bottom of the waterlogged mining area is located below the area defined by the small emission frame in step three. Above the horizontal plane of the platform, below the area defined by the small transmitting frame in step three, the [number]th [section / section] Below the horizontal plane of each platform.

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