Monitoring method of fire extinguishing effect of magnetic grouting in coalfield fire area and location method of re-ignition area

Abstract

The present invention relates to the field of geophysical exploration technology, and specifically discloses a method for monitoring the fire extinguishing effect of magnetized grouting in a coalfield fire area and a method for locating a re-ignition area. The monitoring method comprises: fully stirring and mixing magnetizable alloy powder particles with ultrafine bentonite powder, surfactant, and water, drying, magnetizing, crushing, and mixing with original slurry to obtain a mixed grouting slurry; determining a magnetic scanning area based on the projection range of the underground coalfield hidden fire area on the ground, and performing a magnetic scanning to obtain initial magnetic anomaly information; installing a magnetizing coil; injecting mixed grouting slurry into underground burnt areas and cracks, and magnetizing the mixed grouting slurry through a magnetizing coil; performing a magnetic scanning area to obtain magnetic anomaly information after grouting, and then determining the spatial distribution form of the slurry in combination with the initial magnetic anomaly information to judge the grouting fire extinguishing effect. The present invention can clearly identify the distribution form of underground slurry, thereby achieving the purpose of detecting the grouting fire extinguishing effect.

Description

Technical Field

[0001] The invention relates to the technical field of geophysical exploration, in particular to a method for monitoring the fire extinguishing effect of magnetized grouting in a coalfield fire zone and a method for locating a re-ignition zone. Background Art

[0002] Grouting fire extinguishing is a common engineering measure in coalfield fire control projects. Its principle is to inject mud, paste or water-based slurry into the fire area to isolate the high-temperature coal body and reduce the infiltration of oxygen, thereby inhibiting combustion. In grouting projects, due to the complexity of underground burnt areas, cracks and oxygen supply channels, slurry often cannot fill all empty areas, holes and cracks. Therefore, although short-term fire extinguishing projects have achieved certain results, the risk of re-ignition still exists.

[0003] In terms of grouting effect detection and rapid location of fire zone re-ignition area, conventional methods include geological radar, ultrasound, sound wave, electrical method, magnetic method, etc., but their effects are not satisfactory. The main reason is that the underground distribution of coalfield fire areas is very complicated, which makes it impossible to separate the detection signals of various methods from abnormal signals. Therefore, there is an urgent need in this field for a method that can trace the slurry and enhance the abnormal signals induced in the underground fire area to quickly locate the re-ignition area. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for monitoring the fire extinguishing effect of magnetized grouting in coalfield fire areas and a method for locating the re-ignition area. By using the strong residual magnetism of the mixed grouting slurry and the original surrounding rock around the slurry, the distribution morphology of the underground slurry can be clearly identified, thereby achieving the purpose of detecting the grouting fire extinguishing effect. In addition, when a secondary re-ignition occurs, the re-ignition demagnetization area can be quickly located by scanning with the magnetic method, thereby providing accurate location information for the re-ignition fire area management.

[0005] The invention discloses a method for monitoring the fire extinguishing effect of magnetized grouting in a coalfield fire area, comprising:

[0006] S1: fully stirring and mixing the magnetizable alloy powder particles, ultrafine bentonite powder, surfactant and water, and drying to form an alloy powder mixed block; magnetizing and crushing the alloy powder mixed block to obtain alloy powder inclusion particles;

[0007] S2: Determine the magnetic scanning area based on the projection range of the underground coalfield hidden fire area on the ground, and conduct magnetic scanning on the magnetic scanning area to obtain initial magnetic anomaly information;

[0008] S3: mixing the alloy powder inclusion particles with the original slurry to obtain a mixed grouting slurry;

[0009] S4: Determine the position of the magnetizing coil based on the projection range and complete the installation;

[0010] S5: injecting mixed grouting slurry into the underground burnout area and cracks, and magnetizing the mixed grouting slurry through a magnetizing coil;

[0011] S6: After the grouting is completed, the magnetic scanning area is magnetically scanned to obtain the magnetic anomaly information after grouting. The spatial distribution of the mixed grouting slurry is determined by the magnetic anomaly information after grouting and the initial magnetic anomaly information to judge the grouting fire extinguishing effect.

[0012] Furthermore, the step S1 includes:

[0013] S101: preparing alloy powder particles from the raw materials of neodymium iron ore alloy by mechanical crushing, grinding and screening, wherein the particle size thereof is 5 to 20 microns;

[0014] S102: Ultrafine bentonite powder, surfactant, alloy powder particles, and water are fully stirred and mixed in a mass ratio of 18:1:3:90, and placed in a container for drying to form an alloy powder mixed block; wherein the particle size of the ultrafine bentonite powder is less than 1 micron, and the surfactant is sodium dodecyl sulfate;

[0015] S103: magnetizing the alloy powder mixed block by a magnetizer device;

[0016] S104: The alloy powder mixed block is mechanically crushed by a crusher, and the alloy powder inclusion particles having a particle size of 6 to 25 microns are screened by a screening machine.

[0017] Furthermore, the step S2 comprises:

[0018] S201: According to the surface burnout, collapse and fissure conditions and abnormal surface temperature, determine the projection range of the underground coalfield hidden fire area on the ground and the longest axis of the projection range;

[0019] S202: Determine the midline point of the longest axis as the geometric center of the magnetic scanning area, and determine the side length of the square magnetic scanning area based on the length of the longest axis;

[0020] S203: using a high-precision proton magnetometer, recording the magnetic field strength at different positions in the magnetic scanning area according to a grid spacing of 0.5 m×0.5 m, and collecting magnetic scanning data;

[0021] S204: After a series of data processing including diurnal variation correction, gradient correction, altitude correction and magnetization pole correction is performed on the collected magnetic scanning data, initial magnetic anomaly information is obtained.

[0022] Furthermore, the step S3 includes:

[0023] The grouting slurry and the alloy powder inclusion particles are uniformly mixed in a mass ratio of 10:1 to obtain a mixed grouting slurry with magnetic response characteristics.

[0024] Furthermore, the step S4 comprises:

[0025] S401: Determine the position of the magnetizing coil: determine the circular coil reference position on the ground with the midline point of the longest axis as the center and the longest axis as the radius, so that the projection range is completely within the coil reference position, and bury a 2m high fixing pile vertically at every 1~2m on the inner edge of the coil reference position to fix the magnetizing coil;

[0026] S402: Installation of magnetizing coil: Wrap the power supply cable around the outer edge of the fixed pile in the form of a vertical spiral coil. The winding height is the height of the fixed pile. The head and tail ends of the power supply cable are respectively connected to the positive and negative poles of the high-power pulse power supply.

[0027] Furthermore, the step S5 also includes:

[0028] Arrange drill holes for injecting mixed grouting slurry;

[0029] Water injection to cool the fire area: High-pressure water injection is performed to cool the borehole and its surrounding areas, so that the temperature of the fire area drops below 100°C.

[0030] Furthermore, the step S5 also includes: determining the solidification time of the mixed grouting slurry;

[0031] The step S5 comprises:

[0032] S501: using grouting equipment to inject the mixed grouting slurry into the underground burnout area and cracks through the drilled hole;

[0033] S502: When the grouting process exceeds T / 2, magnetization work needs to be carried out every 60 minutes of grouting work, and each magnetization lasts 10 minutes; after the grouting is completed, magnetization work is carried out continuously for T time;

[0034] Where T is the consolidation time of the mixed grouting slurry.

[0035] Furthermore, the step S6 comprises:

[0036] S601: After the grouting is completed and T time has passed, magnetic scanning is performed to obtain magnetic anomaly information after grouting;

[0037] S602: Calculate the magnetic anomaly value caused by the mixed grouting slurry through the post-grouting magnetic anomaly information and the initial magnetic anomaly information before and after grouting. The expression is as follows:

[0038] ΔT 浆 =ΔTn -ΔT0;

[0039] Among them, ΔT0 is the magnetic anomaly value of the initial magnetic anomaly information, ΔT n is the magnetic anomaly value of the magnetic anomaly information after grouting, ΔT 浆 It is the magnetic anomaly value caused by the mixed grouting slurry;

[0040] S603: By ΔT 浆 The three-dimensional forward and inversion of the magnetic source distribution of underground alloy powder inclusions is determined, thereby determining the spatial distribution morphology of the mixed grouting slurry, and judging the grouting fire extinguishing effect based on the spatial distribution morphology.

[0041] The present invention also discloses a method for locating a re-ignition area, which is based on the above-mentioned method for monitoring the fire extinguishing effect of magnetized grouting in a coalfield fire area. The method for locating a re-ignition area includes:

[0042] After the grouting fire extinguishing project is completed, if there are signs of re-ignition in the fire area, the magnetic scanning area is scanned again to obtain the third magnetic anomaly information; and based on the third magnetic anomaly information and the magnetic anomaly information after grouting, the corresponding area where the underground mixed grouting slurry is demagnetized is determined, thereby determining the re-ignition area of ​​the fire area.

[0043] Furthermore, the method for locating the re-ignition area specifically includes:

[0044] After the grouting fire extinguishing project is completed, if there are signs of re-ignition in the fire area causing the surface temperature to rise, the magnetic scanning area will be scanned again to obtain the third magnetic anomaly information;

[0045] The calculation expression of the magnetic anomaly value caused by the re-ignition of the fire area is as follows:

[0046] ΔT 复 =ΔT m -ΔT n ;

[0047] Where, ΔT 复 is the magnetic anomaly value caused by the re-ignition of the fire area; ΔT m is the magnetic anomaly value of the third magnetic anomaly information; ΔT n is the magnetic anomaly value of the magnetic anomaly information after grouting;

[0048] By ΔT 复 The three-dimensional forward and inverse model is used to determine the corresponding area where the alloy powder inclusion particles are demagnetized due to high temperature, thereby determining the re-ignition area of ​​the fire zone.

[0049] The present invention has at least the following beneficial effects:

[0050] The present invention adds saturated magnetized alloy powder particles to the traditional grouting slurry, and drives the alloy powder particles to rotate through the external magnetic field, so that the direction of the magnetic field is consistent with the direction of the external magnetic field. After the slurry is solidified for a period of time, the external magnetic field is withdrawn, and the slurry as a whole has a strong residual magnetism. On the contrary, the residual magnetism of the original surrounding rock around the slurry is very weak, forming a sharp contrast. Therefore, by performing magnetic scanning measurement on the magnetic scanning area, the distribution morphology of the underground slurry can be clearly identified, thereby achieving the purpose of detecting the grouting fire extinguishing effect.

[0051] In addition, after a period of time after the grouting fire extinguishing project is completed, when the grouting area causes a secondary reignition of the fire in a local area due to air leakage, the high temperature in this area will cause the magnetic moment direction of the magnetic domains of the alloy particles in the slurry to rearrange, resulting in demagnetization. Therefore, the magnetic method can be used to scan the surface and quickly locate the re-ignition demagnetization area, thereby providing accurate location information for the re-ignition fire area management.

[0052] Other beneficial effects of the present invention will be described in detail in the specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0054] Figure 1 The invention discloses a flow chart of a method for monitoring the effect of magnetized grouting fire extinguishing in a coalfield fire zone.

[0055] Figure 2 It is a schematic diagram of the installation position of the magnetizing coil disclosed in the present invention.

[0056] Figure 3 It is a comparison diagram of a single particle of the alloy powder inclusion body disclosed in the present invention before and after inclusion.

[0057] Figure 4 It is a schematic diagram of the installation structure of the magnetizing coil disclosed in the present invention.

[0058] Among them, 100-underground coalfield hidden fire area, 101-coil reference position, 102-drilling hole, 103-projection range, 200-alloy powder particles, 201-ultrafine bentonite powder, 300-high-power pulse power supply, 301-fixed pile, 302-magnetic scanning area, 303-vertical spiral coil. DETAILED DESCRIPTION

[0059] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0060] like Figure 1 As shown, the present invention discloses a method for monitoring the fire extinguishing effect of magnetized grouting in a coalfield fire area, comprising:

[0061] S1: fully stirring and mixing the magnetizable alloy powder particles 200, the ultrafine bentonite powder 201, the surfactant and water, and drying to form an alloy powder mixed block; magnetizing and crushing the alloy powder mixed block to obtain alloy powder inclusion particles;

[0062] S2: determining a magnetic scanning area 302 based on a projection range 103 of the underground coalfield hidden fire area 100 on the ground, and performing a magnetic scanning on the magnetic scanning area 302 to obtain initial magnetic anomaly information;

[0063] S3: mixing the alloy powder inclusion particles with the original slurry to obtain a mixed grouting slurry;

[0064] S4: Determine the position of the magnetizing coil based on the projection range 103 and complete the installation;

[0065] S5: injecting mixed grouting slurry into the underground burnout area and cracks, and magnetizing the mixed grouting slurry through a magnetizing coil;

[0066] S6: After the grouting is completed, the magnetic scanning area 302 is magnetically scanned to obtain the magnetic anomaly information after grouting. The spatial distribution of the mixed grouting slurry is determined by the magnetic anomaly information after grouting and the initial magnetic anomaly information to judge the grouting fire extinguishing effect.

[0067] To illustrate the technical solution in detail, the present invention discloses the following embodiments.

[0068] Embodiment 1

[0069] A. Preparation of alloy powder inclusions, including:

[0070] A1. Prepare 200 alloy powder particles;

[0071] The NdFeB alloy raw material is made into alloy powder particles 200 by mechanical crushing, grinding and screening, preferably with a particle size of 5 to 20 microns. Smaller powder particles are more sensitive to external magnetic fields, require less magnetic torque to change the direction of the magnetic moment of their internal magnetic domains, and are more susceptible to magnetization.

[0072] In this embodiment, the production process of the neodymium iron ore alloy raw material is to smelt a variety of metals and cool them naturally, and the main metal proportions are: rare earth metal neodymium 29%~32.5%, metal element iron 63.95%~68.65%, non-metallic element boron 1.1%~1.2%, added dysprosium 0.6%~8%, niobium 0.3%~0.5%, aluminum 0.3%~0.5%, copper 0.05%~0.15%.

[0073] A2, alloy powder mixed block production;

[0074] Ultrafine bentonite powder 201 (particle size less than 1 micron), surfactant (sodium dodecyl sulfate), alloy powder particles 200, and water are fully stirred and mixed in a mass ratio of 18:1:3:90, and placed in a container for drying to form an alloy powder mixed block.

[0075] Among them, the ultrafine bentonite powder 201 can keep a certain distance between the alloy powder particles 200, the surfactant can disperse the alloy powder particles 200 in the aqueous solution, and can adsorb the ultrafine bentonite powder 201 on the surface of the alloy powder particles 200 through electrostatic adsorption to form a stable coating layer. When the alloy powder particles 200 are magnetized in the later stage, the attraction and agglomeration between the alloy powder particles 200 can be effectively prevented.

[0076] A3, magnetizing the alloy powder mixed block;

[0077] The alloy powder mixture is magnetized by a magnetizer so that the magnetic moment directions of all magnetic domains in the alloy powder particles 200 in the alloy powder mixture are basically consistent, and the residual magnetism of the magnetized single alloy microparticles is greatly increased. Figure 3 The left part is a schematic diagram of the magnetic moment of the magnetic domains of a single unmagnetized alloy powder particle. The directions of the magnetic moments of different magnetic domains are arranged chaotically and irregularly, and the external magnetism tends to zero. The right part is a schematic diagram of the magnetic moment of the magnetic domains of a single magnetized alloy powder inclusion particle. The directions of the magnetic moments of the magnetic domains tend to be consistent, showing strong magnetism to the outside.

[0078] The magnetic domain mentioned here refers to the small magnetized areas with different directions that are differentiated in the process of spontaneous magnetization of ferromagnetic materials in order to reduce static magnetic energy. Each area contains a large number of atoms, and the magnetic moments of these atoms are neatly arranged, but the directions of the magnetic moments between adjacent magnetic domains are different. Macroscopic objects generally always have many magnetic domains. In this way, the directions of the magnetic moments of the magnetic domains are different, and the results cancel each other out. The external magnetism of the entire object tends to zero, and it cannot attract other magnetic materials. Only when the magnetic material is magnetized, the directions of the magnetic moments of most of the magnetic domains tend to be consistent, and it can show strong magnetism to the outside.

[0079] A4, alloy powder inclusion particles;

[0080] The alloy powder mixed block is mechanically crushed by a crusher, and is screened by a screening machine to obtain alloy powder inclusion particles with a particle size of 6 to 25 microns.

[0081] B. Determination of the magnetic scanning area 302 includes:

[0082] B1. According to the surface burnout, collapse and cracks, and the abnormal surface temperature, the projection range of the underground coalfield hidden fire area 100 on the ground is preliminarily determined to be 103 (N), and the maximum long axis distance d of N is measured. max , where the midline point of the longest axis is point O.

[0083] B2. The range of magnetic scanning is the magnetic scanning area 302, which is a square area with point O as the geometric center and a side length L = 4×d max , to ensure that there is sufficient background field and magnetic anomaly field for comparative analysis.

[0084] B3. Use a high-precision proton magnetometer to record the magnetic field strength at different positions in the magnetic scanning area according to a 0.5m×0.5m grid spacing to collect magnetic scanning data.

[0085] B4. After a series of data processing including diurnal variation correction, gradient correction, altitude correction and magnetization pole correction, ΔT0 is obtained for the collected magnetic scanning data, where ΔT0 is the magnetic anomaly value of the initial magnetic anomaly information.

[0086] Through multiple magnetic scans, the status of the fire area can be dynamically monitored, including the grouting effect and re-ignition situation.

[0087] C. Preparation for grouting work, including:

[0088] C1. Determination and construction of drilling holes 102: The fire area (the area to be extinguished in the coalfield fire area) needs to be drilled. The spacing between drilling holes 102 is determined based on the scale and geological conditions of the fire area. Generally, the spacing is within the range of 5 to 10 meters to ensure that the slurry can effectively cover the key areas of the fire area. Construction is carried out after drilling holes 102 are determined.

[0089] C2. Water injection and cooling in the fire zone: In view of the high temperature in the coalfield fire zone, high-pressure water injection and cooling should be first performed on the borehole 102 and its surrounding areas to ensure that the temperature in the fire zone drops below 100°C. Water injection and cooling can prevent the alloy powder inclusion particles in the slurry from demagnetizing and ensure that the physical properties of the slurry will not change in the subsequent grouting project.

[0090] C3. Slurry material preparation: The conventional grouting slurry and the alloy powder inclusion particles are uniformly mixed in a mass ratio of 10:1 to obtain a mixed grouting slurry having magnetic response characteristics.

[0091] C4. Determine the setting time of the mixed grouting slurry, for example, by indoor testing.

[0092] D. Preparation for magnetization, including:

[0093] D1. Determine the position of the magnetizing coil: see Figure 2 , with point O as the center, d max The radius R (that is, twice d max A circle C (coil reference position 101) is drawn on the ground with a diameter of 100 mm. This ensures that the projection range 103 is completely within the circle C. A larger coil helps to make the magnetic field direction within the projection range 103 as uniform as possible and basically upward. A 2m high fixing pile 301 is vertically buried every 1-2m on the inner edge of the circle C. The buried fixing pile helps to fix the magnetization coil.

[0094] D2. Installation of magnetizing coil: see Figure 4 , the power supply cable is wound around the outer edge of the fixed pile 301 in the form of a vertical spiral coil 303, the winding height is the height of the fixed pile 301, and the head and tail ends of the cable are connected to the positive and negative poles of the high-power pulse power supply 300. Specifically, the connection of the positive and negative poles should be based on the principle of Ampere's law so that the magnetic field induced by the magnetizing coil is directed upward. Increasing the coil height helps the magnetic field penetrate deep into the ground and increases the downward penetration depth of the magnetic lines of force.

[0095] It is worth mentioning that the preparatory work disclosed in the above steps C and D is implemented before the grouting and magnetizing construction, but the specific order can be changed as needed without affecting the subsequent implementation and effect.

[0096] E. Grouting and magnetizing construction, including:

[0097] E1. Use grouting equipment to inject the prepared mixed grouting slurry into the underground burnout area and cracks through the borehole 102. During the grouting process, the injection pressure and flow rate of the slurry should be continuously monitored to ensure that the slurry can fully fill the cracks and empty areas.

[0098] E2. First, the consolidation time T of the mixed grouting slurry should be determined, see step C4 above. Then, magnetization is not required for T / 2 time before the grouting project; when the grouting process exceeds T / 2, magnetization is required every 60 minutes of grouting, and each magnetization time is preferably 10 minutes. After the grouting project is completed, magnetization is performed continuously for T time.

[0099] The above magnetization method ensures that there is sufficient external magnetic field to magnetize the alloy powder inclusions during different time periods from the fluid to the consolidation process of the slurry. The magnetization makes the magnetic field direction of the alloy powder inclusion particles in the grouting material tend to be consistent, and the magnetization process does not affect the implementation of the grouting project. After the external magnetic field is removed, the slurry still maintains a strong residual magnetism, which is convenient for subsequent monitoring.

[0100] It is worth mentioning that the magnetization disclosed in the above step A is to change the direction of the magnetic moment of the magnetic domain inside the particle, so that the directions of the magnetic moments of all the magnetic domains inside the particle are consistent, so as to achieve the effect of enhancing the magnetic field of the particle. The magnetization disclosed in the above step E mainly refers to the magnetization of the entire macroscopic slurry, and its implementation method is mainly to make all particles spin or move to make their magnetic field directions consistent through the external magnetic field. Only particles close to the magnetization coil and in the area with a strong magnetic field will undergo the magnetization method of the above step A.

[0101] F. When the grouting project is completed and T time has passed, a magnetic scanning work is carried out (see B3 and B4 for the processing process) to obtain ΔT n , where ΔT n It is the magnetic anomaly value of the magnetic anomaly information after grouting.

[0102] G. Grouting fire extinguishing effect detection, including:

[0103] G1. Calculate the magnetic anomaly value ΔT caused by the slurry through the magnetic anomaly values ​​before and after grouting 浆 :

[0104] ΔT 浆 =ΔT n -ΔT0;

[0105] Among them, ΔT0 is the magnetic anomaly value of the initial magnetic anomaly information, ΔT n is the magnetic anomaly value of the magnetic anomaly information after grouting, ΔT 浆 It is the magnetic anomaly value caused by the mixed grouting slurry.

[0106] G2, through ΔT 浆 The three-dimensional forward and inversion of magnetic anomaly data determines the magnetic source distribution of underground alloy powder inclusions, thereby determining the spatial distribution pattern of the slurry in order to judge the grouting fire extinguishing effect.

[0107] Embodiment 2

[0108] This embodiment discloses a method for locating a re-ignition area, which is implemented based on the method for monitoring the effect of magnetic grouting fire extinguishing in a coalfield fire area disclosed in the first embodiment, and is specifically as follows:

[0109] H1. After the grouting fire extinguishing project is completed, personnel should be organized to inspect the site regularly. When signs of re-ignition are found in the fire area, such as smoke and increased surface temperature, magnetic scanning should be carried out again.

[0110] H2, magnetic anomaly ΔT caused by the re-ignition of the fire area 复 Calculation:

[0111] ΔT 复 =ΔT m -ΔT n ;

[0112] Where, ΔT 复 is the magnetic anomaly value caused by the re-ignition of the fire area, ΔT m is the magnetic anomaly value of the third magnetic anomaly information.

[0113] H3, through ΔT 复 The three-dimensional forward inversion of magnetic anomaly data determines the area where the underground alloy powder inclusions are demagnetized due to high temperature, thereby determining the re-ignition area of ​​the fire zone.

[0114] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for monitoring the fire extinguishing effect of magnetized grouting in a coalfield fire area, characterized in that: include: S1: fully stirring and mixing the magnetizable alloy powder particles, ultrafine bentonite powder, surfactant and water, and drying to form an alloy powder mixed block; magnetizing and crushing the alloy powder mixed block to obtain alloy powder inclusion particles; S2: Determine the magnetic scanning area based on the projection range of the underground coalfield hidden fire area on the ground, and conduct magnetic scanning on the magnetic scanning area to obtain initial magnetic anomaly information; S3: mixing the alloy powder inclusion particles with the original slurry to obtain a mixed grouting slurry; S4: Determine the position of the magnetizing coil based on the projection range and complete the installation; S5: injecting mixed grouting slurry into the underground burnout area and cracks, and magnetizing the mixed grouting slurry through a magnetizing coil; S6: After the grouting is completed, the magnetic scanning area is magnetically scanned to obtain the magnetic anomaly information after grouting. The spatial distribution of the mixed grouting slurry is determined by the magnetic anomaly information after grouting and the initial magnetic anomaly information to judge the grouting fire extinguishing effect.

2. The method for monitoring the fire extinguishing effect of magnetized grouting in coalfield fire area according to claim 1 is characterized in that: The step S1 comprises: S101: preparing alloy powder particles from the raw materials of neodymium iron ore alloy by mechanical crushing, grinding and screening, wherein the particle size thereof is 5 to 20 microns; S102: Ultrafine bentonite powder, surfactant, alloy powder particles, and water are fully stirred and mixed in a mass ratio of 18:1:3:90, and placed in a container for drying to form an alloy powder mixed block; wherein the particle size of the ultrafine bentonite powder is less than 1 micron, and the surfactant is sodium dodecyl sulfate; S103: magnetizing the alloy powder mixed block by a magnetizer device; S104: The alloy powder mixed block is mechanically crushed by a crusher, and the alloy powder inclusion particles with a particle size of 6 to 25 microns are screened by a screening machine.

3. The method for monitoring the fire extinguishing effect of magnetized grouting in coalfield fire area according to claim 1 is characterized in that: The step S2 comprises: S201: According to the surface burnout, collapse and fissure conditions and abnormal surface temperature, determine the projection range of the underground coalfield hidden fire area on the ground and the longest axis of the projection range; S202: Determine the midline point of the longest axis as the geometric center of the magnetic scanning area, and determine the side length of the square magnetic scanning area based on the length of the longest axis; S203: using a high-precision proton magnetometer, recording the magnetic field strength at different positions in the magnetic scanning area according to a grid spacing of 0.5 m×0.5 m, and collecting magnetic scanning data; S204: After a series of data processing including diurnal variation correction, gradient correction, altitude correction and magnetization pole correction is performed on the collected magnetic scanning data, initial magnetic anomaly information is obtained.

4. The method for monitoring the fire extinguishing effect of magnetized grouting in coalfield fire area according to claim 1 is characterized in that: The step S3 comprises: The grouting slurry and the alloy powder inclusion particles are uniformly mixed in a mass ratio of 10:1 to obtain a mixed grouting slurry with magnetic response characteristics.

5. The method for monitoring the fire extinguishing effect of magnetized grouting in coalfield fire area according to claim 1 is characterized in that: The step S4 comprises: S401: Determine the position of the magnetizing coil: determine the circular coil reference position on the ground with the midline point of the longest axis as the center and the longest axis as the radius, so that the projection range is completely within the coil reference position, and bury a 2m high fixing pile vertically at every 1~2m on the inner edge of the coil reference position to fix the magnetizing coil; S402: Installation of magnetizing coil: Wrap the power supply cable around the outer edge of the fixed pile in the form of a vertical spiral coil. The winding height is the height of the fixed pile. The head and tail ends of the power supply cable are respectively connected to the positive and negative poles of the high-power pulse power supply.

6. The method for monitoring the fire extinguishing effect of magnetized grouting in coalfield fire area according to claim 1 is characterized in that: The step S5 also includes: Arrange drill holes for injecting mixed grouting slurry; Water injection to cool the fire area: High-pressure water injection is performed to cool the borehole and its surrounding areas, so that the temperature of the fire area drops below 100°C.

7. The method for monitoring the fire extinguishing effect of magnetized grouting in coalfield fire area according to claim 6 is characterized in that: The step S5 also includes: determining the solidification time of the mixed grouting slurry; The step S5 comprises: S501: using grouting equipment to inject the mixed grouting slurry into the underground burnout area and cracks through the drilled hole; S502: When the grouting process exceeds T / 2, magnetization work needs to be carried out every 60 minutes of grouting work, and each magnetization lasts 10 minutes; after the grouting is completed, magnetization work is carried out continuously for T time; Where T is the consolidation time of the mixed grouting slurry.

8. The method for monitoring the fire extinguishing effect of magnetized grouting in coalfield fire area according to claim 7 is characterized in that: The step S6 comprises: S601: After the grouting is completed and T time has passed, magnetic scanning is performed to obtain magnetic anomaly information after grouting; S602: Calculate the magnetic anomaly value caused by the mixed grouting slurry through the post-grouting magnetic anomaly information and the initial magnetic anomaly information before and after grouting. The expression is as follows: ΔT 浆 =ΔT n -ΔT0; Among them, ΔT0 is the magnetic anomaly value of the initial magnetic anomaly information, ΔT n is the magnetic anomaly value of the magnetic anomaly information after grouting, ΔT 浆 It is the magnetic anomaly value caused by the mixed grouting slurry; S603: Through ΔT 浆 The three-dimensional forward and inversion of the magnetic source distribution of underground alloy powder inclusions is determined, thereby determining the spatial distribution morphology of the mixed grouting slurry, and judging the grouting fire extinguishing effect based on the spatial distribution morphology.

9. A method for locating a re-ignition area, characterized in that: The method is implemented based on the method for monitoring the fire extinguishing effect of magnetized grouting in a coalfield fire area according to any one of claims 1 to 8, and the method for locating the re-ignition area includes: After the grouting fire extinguishing project is completed, if there are signs of re-ignition in the fire area, the magnetic scanning area is scanned again to obtain the third magnetic anomaly information; and based on the third magnetic anomaly information and the magnetic anomaly information after grouting, the corresponding area where the underground mixed grouting slurry is demagnetized is determined, thereby determining the re-ignition area of ​​the fire area.

10. A method for locating a re-ignition area according to claim 9, characterized in that: The method specifically includes: After the grouting fire extinguishing project is completed, if there are signs of re-ignition in the fire area causing the surface temperature to rise, the magnetic scanning area will be scanned again to obtain the third magnetic anomaly information; The calculation expression of the magnetic anomaly value caused by the re-ignition of the fire area is as follows: ΔT 复 =ΔT m -ΔT n ; Where, ΔT 复 is the magnetic anomaly value caused by the re-ignition of the fire area; ΔT m is the magnetic anomaly value of the third magnetic anomaly information; ΔT n is the magnetic anomaly value of the magnetic anomaly information after grouting; By ΔT 复 The three-dimensional forward and inverse model is used to determine the corresponding area where the alloy powder inclusion particles are demagnetized due to high temperature, thereby determining the re-ignition area of ​​the fire zone.

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