Method for detecting grouting reinforcement horizon in coal mining subsidence area

Abstract

The invention discloses a method for detecting a grouting reinforcement horizon in a coal mining subsidence area. The coal mining subsidence area grouting reinforcement horizon detection method is composed of data collection and analysis, geological drilling, VSP seismic exploration, well logging and in-hole television. Data collection and analysis are carried out on the basis of previous exploration data analysis, and geological drilling is used for further finding out the occurrence state, the water filling characteristic, the overlying strata fracture development rule, the mining height and the goaf burial depth of the goaf and providing conditions for carrying out VSP seismic exploration, well logging, in-hole television and other work. According to geological drilling coring and in-hole television measurement, crack and cavity development horizon can be visually found out from a television image; in-hole television images and logging curves of drill hole cracks and cavity development layer sections can be obtained, and an important theoretical basis is provided for later grouting.

Description

Technical Field

[0001] The present invention relates to the technical field of mining area detection, and particularly to a method for detecting the grouting reinforcement horizon in a coal mining subsidence area. Background Art

[0002] With the large-scale exploitation of coal resources, the problem of coal mining subsidence areas has become increasingly prominent. In related technologies, gob collapse grouting, as an effective treatment means, can fill the cavities and fissures in the gob, improve the strength and stability of the surrounding rock in the gob, and reduce the occurrence of surface subsidence.

[0003] However, during the grouting construction process, there is a lack of precise detection of the grouting reinforcement horizon in the coal mining subsidence area. Traditional exploration methods can only generally understand the distribution range and basic geological conditions of the gob, and it is difficult to accurately determine the specific horizons that need grouting reinforcement, including the precise positions and characteristics of the caving zone, fissure zone, and bending subsidence zone.

[0004] Due to the inability to accurately master the reinforcement horizon information, the grouting design can only be based on relatively rough geological data. This leads to difficulties in reasonably determining the depth, angle, and spacing of the drill holes, resulting in the situation where the drill holes cannot accurately reach the target reinforcement horizon, and the grouting effect is poor. At the same time, the rock properties, void sizes, and distributions of different reinforcement horizons vary greatly. If the appropriate grouting materials and parameters cannot be selected according to the characteristics of specific horizons, problems such as uneven slurry diffusion and local non-filling are likely to occur. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems in the related technologies to some extent.

[0006] To this end, an embodiment of the present invention provides a method for detecting the grouting reinforcement horizon in a coal mining subsidence area to improve the quality and efficiency of gob collapse grouting and ensure the safety and stability of the project.

[0007] The method for detecting the grouting reinforcement horizon in a coal mining subsidence area according to the embodiment of the present invention includes:

[0008] Collect and analyze data based on previous geological mining data;

[0009] Conduct geological drilling using a two-opening borehole structure to analyze the occurrence state, water filling characteristics, overlying rock fissure development law, mining height, and burial depth of the gob;

[0010] Conduct VSP seismic exploration in the borehole, extract the geophysical parameters of the gob and the caving zone, establish a geological model of the position, shape, and development of the gob, and explore the dominant orientation and density of underground mining-induced fissures in the research area;

[0011] Use electrical logging, sonic logging and radioactive logging methods to obtain data on geophysical parameters, stratigraphic division, stratigraphic integrity and fracture identification;

[0012] Use in-hole television equipment to scan the borehole wall to identify cracks, cavities, lithology, integrity and filling conditions, and analyze the characteristics of hole wall fracture development, the integrity of the goaf roof and the water filling condition;

[0013] The optimal location of the grouting layer is determined by comprehensively analyzing the detection results of geological drilling, well logging, VSP seismic exploration and in-hole television.

[0014] The method for detecting the grouting reinforcement layer in the coal mining subsidence area according to the embodiment of the present invention can intuitively find the layers where cracks and cavities are developed from the television images based on geological drilling core sampling and in-hole television measurement; it can obtain in-hole television images and logging curves of the layers where cracks and cavities are developed in the borehole, providing an important theoretical basis for the subsequent grouting.

[0015] In some embodiments, by describing the flushing fluid consumption, core recovery rate, RQD, drilling speed, drill drop, drill sticking, and wind blowing and suction phenomena during the drilling process, the occurrence state, water filling characteristics and development rules of the overburden fractures in the goaf are determined.

[0016] In some embodiments, the depth of the secondary drilling structure is required to enter the target goaf or coal seam floor by 3 to 5 meters. The secondary drilling includes:

[0017] The first stage borehole diameter was φ190 mm, and the hole was drilled to 5 meters into the Quaternary bedrock. φ168 mm casing was run throughout the entire section and cement slurry was used to fix the pipe.

[0018] The second stage of drilling is φ150 mm in diameter, and the hole is drilled to the final depth. φ127 mm casing is lowered into the entire hole section, and the pipe is fixed with cement slurry throughout the hole section.

[0019] In some embodiments, during drilling:

[0020] The plane deviation of the drilling position is less than ±0.20 meters, and the elevation control deviation is less than ±4 centimeters;

[0021] Hole depth correction is carried out every 50 meters. The hole depth error is less than 1‰ in the main goaf, collapse area, weak zone, water gushing area, slurry leakage area, diameter change area and end hole. If the error range is exceeded, the hole depth is re-measured and the report is corrected in time.

[0022] Inclination is measured and corrected every 50 meters, and the hole slope is less than 1° / 100 meters.

[0023] In some embodiments, during the drilling process, mud is used for protecting the borehole wall in the loose layer, and clear water is used for drilling in the bedrock section. The consumption of the flushing fluid is recorded every 2 meters in the bedrock section, and the consumption of the flushing fluid is recorded every 1 meter within 30 meters above the roof of the goaf.

[0024] In some embodiments, during the drilling process, the drilling speed is recorded every 2 meters. Starting from the prediction of entering the fracture zone of the goaf, the development status of the three zones in the goaf of the main coal seam is judged based on the recorded drilling speed, borehole water level, sticking of the drill, burying of the drill, dropping of the drill, fragmentation of the core, and air suction.

[0025] In some embodiments, all-hole continuous coring drilling is adopted for geological drilling. The coring rate of the intact rock stratum is higher than 80%, and that of the strongly weathered and fractured strata is higher than 65%.

[0026] In some embodiments, the footage of each drilling round in geological drilling is less than 2 meters and less than the length of the core barrel, and the core recovery rate is recorded section by section.

[0027] In some embodiments, the pipe is fixed by the grouting method. The annular space between the casing and the borehole wall is densely filled with cement slurry. For the casing with a diameter of φ127 mm, the cement slurry for fixing the borehole returns from the whole section at the orifice, and the bottom is sealed with 2 - 3 meters of cement slurry. The inner diameter of the φ127 mm casing is greater than 115 mm, the inner surface of the casing joint is flat, and the pipe wall is smooth.

[0028] In some embodiments, after the pipe fixing is completed, the mud in the φ127 mm casing is flushed with clear water, and the cleanliness of the inner wall of the casing is detected by a borehole peephole instrument. Description of the Drawings

[0029] Figure 1 is a flow chart of the method for detecting the grouting reinforcement layer position in the coal mining subsidence area according to the embodiment of the present invention.

[0030] Figure 2 is a schematic diagram of the second-opening borehole according to the embodiment of the present invention.

[0031] Figure 3 is a bar chart of the consumption of the flushing fluid, RQD, and core recovery rate according to the embodiment of the present invention.

[0032] Reference Signs:

[0033] 1 - soil layer, 2 - bedrock section, 3 - goaf, 4 - cement slurry. Detailed Embodiments

[0034] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0035] The following describes the method for detecting the grouting reinforcement horizon in the coal mining subsidence area of the embodiments of the present invention in conjunction with the accompanying drawings.

[0036] As Figures 1 to 3 shown, the method for detecting the grouting reinforcement horizon in the coal mining subsidence area of the embodiments of the present invention consists of data collection and analysis, geological drilling, VSP seismic exploration, well logging, and borehole television.

[0037] Data collection and analysis are carried out on the basis of the analysis of previous geological and mining data, focusing on key information such as stratigraphic structure, lithology, attitude of strata, uniaxial compressive strength of rock mass, and integrity index of rock mass. These information are the basis for deeply understanding the geological conditions of the coal mining subsidence area and are crucial for subsequent detection of the grouting reinforcement horizon and design of the grouting plan.

[0038] For example, geological and mining data include geological exploration reports, mine exploitation records, rock mechanics test reports, geological mapping drawings, etc. Geological exploration reports detail the stratigraphic information obtained during regional geological surveys; mine exploitation records contain the geological conditions and engineering problems encountered during actual exploitation; rock mechanics test reports provide mechanical parameters such as the uniaxial compressive strength of rock mass; geological mapping drawings visually display information such as stratigraphic structure and attitude.

[0039] The stratigraphic structure has a significant impact on the stability of the goaf and the grouting effect. Weak interlayers may cause the strata to be more prone to deformation and collapse, which need to be particularly concerned about in grouting design; fault zones may become leakage channels for the grout, affecting the effectiveness of grouting. Accurately grasping the stratigraphic structure helps to reasonably select the grouting reinforcement horizon and determine the grouting process.

[0040] Lithology directly affects the diffusion and consolidation effect of the grout. For example, sandstone has a relatively large porosity, and the grout is easy to diffuse in it, but may require a higher grouting pressure; shale has a relatively low permeability, and the diffusion of the grout is relatively difficult, and it may be necessary to select a grout material with better permeability. Understanding the lithology of the strata helps to select suitable grouting materials and determine grouting parameters.

[0041] The attitude of strata has an important impact on the stress distribution and deformation characteristics of the goaf. Inclined strata may cause uneven settlement of the overlying strata in the goaf, increasing the risk of surface subsidence. In grouting design, it is necessary to consider the factor of the attitude of strata and reasonably adjust the drilling direction and grouting position to ensure the uniformity of the grouting reinforcement effect.

[0042] The uniaxial compressive strength of rock mass is an important index to measure the stability of the surrounding rock in the goaf. Rock masses with relatively low compressive strength are prone to damage and deformation, and stronger grouting reinforcement measures need to be taken. When determining the grouting reinforcement horizon, strata with higher compressive strength should be preferentially selected as the supporting layer for grouting to improve the grouting effect and the stability of the goaf.

[0043] The rock integrity index is crucial for determining the degree of fracture development and permeability of rock masses surrounding goafs. Rock masses with poor integrity may contain more fractures and cavities, allowing for easier diffusion of slurry, but this can also lead to slurry loss and waste. Grouting design requires appropriate adjustments to grouting pressure and slurry concentration based on the rock integrity index to ensure the slurry effectively fills fractures and cavities.

[0044] Geological drilling refers to further clarifying the occurrence state, water filling characteristics, overburden fracture development pattern, mining height and burial depth of the goaf, and providing conditions for carrying out VSP seismic exploration, well logging and in-hole television.

[0045] By describing the flushing fluid consumption, core recovery rate, RQD (rock quality index), drilling speed, drill drop, drill sticking, and wind blowing and suction phenomena during the drilling process, the occurrence state, water filling characteristics and development rules of overburden fractures in the goaf are identified.

[0046] The drilling depth of geological drilling is required to enter the target goaf or coal seam floor 3 to 5 meters. The drilling adopts a two-opening drilling structure, including: the first stage drilling diameter is φ190 mm, drilling to the Quaternary system into the bedrock 5 meters, and φ168 mm casing is lowered into the entire section, and cement slurry is used to fix the pipe; the second stage drilling diameter is φ150 mm, drilling to the final hole depth, φ127 mm casing is lowered into the entire hole section, and cement slurry is used to fix the pipe.

[0047] During the drilling process, the following requirements must be met for construction:

[0048] Drilling position and elevation requirements: During the measurement process, the hole position deviation is ±0.20 meters, and the elevation control deviation is ±4 centimeters. Strictly stake out before construction and re-measure after construction.

[0049] Drilling hole diameter and final hole completion standard requirements: Strictly implement drilling design requirements;

[0050] Hole depth error requirements: Hole depth shall be corrected in the following situations: every 50 meters of drilling, the maximum allowable error of hole depth shall not exceed 1‰ in the main goaf, collapse area, weak zone, water gushing area, slurry leakage area, diameter change area and end hole. If the error range is exceeded, the hole depth shall be remeasured and the report shall be revised in time;

[0051] The hole inclination requirement is 1° / 100m. The inclination measurement is carried out every 50 meters. If the standard is not met, corrective measures will be taken.

[0052] Drilling technology requirements: For unconsolidated strata, mud slurry is used for hole wall protection during drilling; for bedrock, clear water is used for drilling. The consumption of flushing fluid is recorded every 2 meters in the bedrock section, especially every 1 meter within 30 meters above the roof of the goaf area, to enhance the observation effect of the drilling flushing fluid. During the drilling process, the drilling speed is accurately recorded every 2 meters. Starting from the prediction of entering the fissure zone of the goaf area, the drilling speed, borehole water level, sticking of drill, burying of drill, dropping of drill, core breakage, and air suction should be recorded in detail to judge the development status of the three zones in the mined-out area of the main coal seam;

[0053] Requirements for core recovery rate and drilling round-trip. Continuous coring drilling is carried out for the whole hole. The core recovery rate for intact rock strata should not be less than 80%, and for strongly weathered and fractured strata, it should not be less than 65%. The footage of each drilling round-trip should not be greater than 2 meters and should not exceed the length of the core barrel. The core recovery rate should be recorded section by section.

[0054] After the drilling is completed, VSP seismic exploration, logging, and downhole television work are carried out.

[0055] VSP seismic exploration is carried out in the borehole. It utilizes the propagation characteristics of seismic waves in different media and arranges geophones in the borehole to receive seismic wave signals. There are differences in the physical properties between the goaf area and the surrounding normal rock mass. During the propagation of seismic waves, phenomena such as reflection, refraction, and attenuation will occur. By analyzing these signals, geophysical parameters of the goaf area and the caving zone, such as wave velocity and amplitude, can be extracted.

[0056] Based on the extracted geophysical parameters, a geological model of the location, shape, and development of the goaf area can be established to visually display the underground distribution of the goaf area. At the same time, through further analysis of the seismic wave signals, the dominant orientation and density of the development of underground mining-induced fissures in the study area can be explored, which is of great significance for understanding the degree of damage and permeability of the rock mass around the goaf area and provides a basis for predicting the diffusion direction and range of the grouting slurry in the grouting design.

[0057] Electrical logging, acoustic logging, and radioactive logging methods are adopted. Electrical logging utilizes the differences in the electrical properties of rocks and infers the electrical characteristics of strata by measuring the electric field distribution, which can be used to identify different lithologies, judge the water-bearing capacity and fissure development of strata. Acoustic logging measures the propagation speed and amplitude of acoustic waves in rocks to understand the compactness and integrity of rocks and evaluate the mechanical properties of strata. Radioactive logging uses natural radioactive elements or artificial radioactive sources in rocks to measure the ray intensity, which is used to divide strata and determine parameters such as the porosity and density of rocks.

[0058] Through these logging methods, geophysical parameters, formation division, formation integrity, and fracture identification data can be obtained. These data can help further refine the geological model, accurately distinguish different formations and lithologies, determine the integrity and fracture distribution of the formations around the goaf, and provide more accurate information for the selection of grouting reinforcement horizons.

[0059] The borehole wall is scanned using downhole video equipment, which can provide an intuitive image of the borehole wall, clearly identifying fractures, cavities, lithology, integrity, and filling conditions. By observing the size, orientation, and connectivity of fractures, the fracture development characteristics of the rock mass around the goaf can be understood; identifying the location and size of cavities helps to judge the actual shape and spatial distribution of the goaf; determining the lithology can provide a reference for the compatibility between the grouting material and the formation; evaluating the integrity and filling conditions of the borehole wall is of great significance for judging the stability and injectability of the goaf.

[0060] Analyzing the fracture development characteristics of the borehole wall, the integrity of the goaf roof, and the water filling situation can provide a direct basis for grouting design. For example, if the fractures on the borehole wall are well-developed and connected, it may be necessary to adjust the grouting pressure and the fluidity of the grout to ensure that the grout can fully fill the fractures; if the goaf roof is incomplete, special reinforcement measures or adjustment of the grouting horizon may be required.

[0061] By comprehensively analyzing the test results of geological drilling, logging, VSP seismic exploration, and downhole video, the information obtained by different methods is integrated and mutually verified. Geological drilling provides direct geological information about the goaf, logging and VSP seismic exploration obtain geophysical parameters and formation structure information, and downhole video provides intuitive image information of the borehole wall. Fusing and analyzing these multi-source data can provide a more comprehensive and accurate understanding of the geological conditions and goaf characteristics in the coal mining subsidence area.

[0062] Determining the optimal position of the grouting horizon based on the comprehensive analysis results can achieve the best grouting reinforcement effect. Selecting an appropriate grouting horizon can ensure that the grout can effectively fill the cavities and fractures in the goaf, improve the strength and stability of the surrounding rock mass of the goaf, and reduce the risk of surface subsidence. At the same time, grouting in unnecessary areas is avoided, reducing the grouting cost and construction difficulty.

[0063] The grouting reinforcement layer position detection method for coal mining subsidence areas in the embodiments of the present invention covers multiple key links from data collection to finally determining the optimal position of the grouting layer. Data collection and analysis provide basic information for subsequent detection; geological drilling can directly obtain key information such as the occurrence state of the goaf; VSP seismic exploration is used to establish a geological model and explore the development of fractures; logging obtains data such as geophysical parameters; downhole television equipment visually identifies relevant features of the hole wall; finally, the optimal grouting layer is determined through comprehensive analysis of the detection results of each link, and each link is closely connected to form a complete detection system.

[0064] Through different detection methods, relevant information of the goaf is obtained from multiple dimensions. For example, geological drilling analyzes water filling characteristics, the development law of overlying rock fractures, etc.; VSP seismic exploration extracts geophysical parameters and establishes a geological model; logging obtains data such as stratigraphic division; downhole television identifies cracks, cavities, etc., ensuring the comprehensiveness of the collection of grouting reinforcement layer position information and helping to accurately determine the optimal grouting layer.

[0065] The grouting reinforcement layer position detection method for coal mining subsidence areas in the embodiments of the present invention can provide accurate grouting layer position information for the grouting construction of goaf collapse, which helps to optimize the grouting design, including reasonably determining the depth, angle and spacing of the boreholes, selecting appropriate grouting materials and parameters, thereby improving the grouting effect and reducing ineffective grouting and construction costs.

[0066] In some embodiments, the two-opening borehole structure uses the grout sitting method to fix the pipe, and the cement slurry densely fills the annular space between the casing and the hole wall. For the section passing through the coal mine goaf, thick cement slurry can be adopted, and a certain amount of clay or bentonite can be added if necessary. The cement slurry for fixing the hole with a φ127 mm casing returns from the hole mouth in the whole section, and the bottom is sealed with 2 - 3 m of cement slurry to ensure the stability of the groundwater level in the hole and reduce noise.

[0067] After the pipe fixing is completed, the slurry in the φ127 mm casing is repeatedly flushed with clean water, and the cleanliness of the inner wall of the casing is detected by a borehole peephole. Only after the detection is qualified can the geophone for VSP seismic exploration be lowered.

[0068] Optionally, the inner diameter of the φ127 mm casing is greater than 115 mm, the casing interface is flush inside, and the pipe wall is smooth to ensure that the geophone for VSP seismic exploration can be lowered normally and pushed against smoothly.

[0069] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the present invention.

[0070] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0071] In the present invention, unless otherwise clearly specified and defined, terms such as "mounted", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or communicable with each other; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0072] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0073] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0074] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions, and variations made by those of ordinary skill in the art to the above embodiments are within the scope of protection of the present invention.

Claims

1. A method for detecting the grouting reinforcement horizon in a coal mining subsidence area, characterized in that, include: Collect and analyze data based on previous geological and mining data; Use a two-hole drilling structure to conduct geological drilling to analyze the occurrence state of the goaf, water filling characteristics, overburden fracture development patterns, mining height and burial depth; Conduct VSP seismic exploration in boreholes to extract geophysical parameters of goafs and collapse zones, establish a geological model of goaf location, morphology, and development, and explore the dominant orientation and density of underground mining-induced fractures in the study area. Use electrical logging, sonic logging and radioactive logging methods to obtain data on geophysical parameters, stratigraphic division, stratigraphic integrity and fracture identification; Use in-hole television equipment to scan the borehole wall to identify cracks, voids, lithology, integrity and filling conditions, and analyze the characteristics of hole wall crack development, the integrity of the goaf roof and the water filling condition; The optimal location of the grouting layer is determined by comprehensively analyzing the detection results of geological drilling, well logging, VSP seismic exploration and in-hole television.

2. The grouting reinforcement layer position detection method for coal mining subsidence areas according to claim 1, characterized in that By describing the flushing fluid consumption, core recovery rate, RQD, drilling speed, drill drop, drill sticking, and wind blowing and suction phenomena during the drilling process, the occurrence state, water filling characteristics and development rules of overburden fractures in the goaf are identified.

3. The grouting reinforcement layer position detection method for coal mining subsidence areas according to claim 2, characterized in that The depth of the secondary drilling structure is required to enter the target goaf or coal seam floor 3 to 5 meters. The secondary drilling includes: The first stage borehole diameter was φ190 mm, and the hole was drilled to 5 meters into the Quaternary bedrock. φ168 mm casing was run throughout the entire section and cement slurry was used to fix the pipe. The second stage of drilling is φ150 mm in diameter, and the hole is drilled to the final depth. φ127 mm casing is lowered into the entire hole section, and the pipe is fixed with cement slurry throughout the hole section.

4. The grouting reinforcement horizon detection method for coal mining subsidence areas according to claim 3, characterized in that During drilling: The plane deviation of the drilling position is less than ±0.20 meters, and the elevation control deviation is less than ±4 centimeters; Hole depth correction is carried out every 50 meters. The hole depth error is less than 1‰ in the main goaf, collapse area, weak zone, water gushing area, slurry leakage area, diameter change area and end hole. If the error range is exceeded, the hole depth is re-measured and the report is corrected in time. Inclination is measured and corrected every 50 meters, and the hole slope is less than 1° / 100 meters.

5. The method for detecting the grouting reinforcement horizon in the coal mining subsidence area according to claim 4, wherein During the drilling process, mud wall drilling is used in the loose layer, and clean water drilling is used in the bedrock section. The flushing fluid consumption is recorded every 2 meters in the bedrock section, and the flushing fluid consumption is recorded every 1 meter within 30 meters above the top of the goaf.

6. The method for detecting the grouting reinforcement horizon in a coal mining subsidence area according to claim 5, characterized in that, During the drilling process, the drilling speed is recorded every 2 meters, and the start of the fracture zone in the goaf is predicted. The development status of the three zones in the goaf of the main coal seam is judged by recording the drilling speed, borehole water level, drill sticking, drill burial, drill drop, core breakage and air suction.

7. The method for detecting the grouting reinforcement horizon in coal mining subsidence areas according to claim 6, characterized in that, The geological drilling adopts full-hole continuous coring drilling, with the coring rate of intact rock formations exceeding 80% and that of strongly weathered and broken formations exceeding 65%.

8. The method for detecting grouting reinforcement layers in coal mining subsidence areas according to claim 7, wherein the drilling footage of each geological drilling pass is less than 2 meters and less than the length of the core tube, and the core recovery rate is recorded section by section.

9. The method for detecting the grouting reinforcement horizon in a coal mining subsidence area according to any one of claims 3-8, characterized in that The slurry method is used to fix the pipe. The cement slurry densely fills the annular space between the casing and the hole wall. The entire section of the φ127 mm casing hole fixing cement slurry is returned from the hole mouth. The bottom is sealed with 2 to 3 meters of cement slurry. The inner diameter of the φ127 mm casing is greater than 115 mm, the casing interface is flat inside, and the pipe wall is smooth.

10. The method for detecting the grouting reinforcement horizon in a coal mining subsidence area according to claim 9, characterized in that, After the casing pipe is fixed, flush the mud in the φ127-mm casing pipe with clean water, and use a borehole peephole instrument to detect the cleanliness of the inner wall of the casing pipe.

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