Method for determining top coal caving ratio of extra-large mining height extra-thick hard coal

Abstract

The invention discloses a super-large mining height extra-thick hard coal top coal caving mining ratio determination method, which comprises the following steps: S1, carrying out stability analysis on a coal wall of a working surface, and determining a first mechanical mining height range H1 of a coal mining machine according to a strain range of the coal wall; s2, constructing a top coal body cantilever mechanical model, deducing to obtain a relational expression between the top coal thickness and the limit suspended top length, and determining a second machine mining height range H2 of the coal mining machine in combination with the coal caving step pitch parameter; and S3, comparing the first mechanical mining height range H1 with the second mechanical mining height range H2, if an overlapping area exists between the first mechanical mining height range H1 and the second mechanical mining height range H2, selecting the maximum value in the overlapping area as the mechanical mining height of the coal mining machine, and if the overlapping area does not exist between the first mechanical mining height range H1 and the second mechanical mining height range H2, selecting the maximum value in the first mechanical mining height range H1 as the mechanical mining height of the coal mining machine. The method for determining the top coal caving ratio of the extra-large mining height extra-thick hard coal has the advantages of being simple in step, high in safety performance and the like.

Description

Technical Field

[0001] This invention relates to the field of coal mining, specifically to a method for determining the top coal caving ratio in ultra-high mining height, extra-thick hard coal. Background Technology

[0002] Determining a reasonable ratio for top coal caving in extra-thick hard coal is crucial for efficient mining of hard coal faces. This ratio is a core technical parameter in fully mechanized top coal caving mining. Improper selection can easily lead to high stress concentration at the working face, and excessive coal caving height may cause sudden roof collapse. Insufficient top coal fracturing can also create closed fracture zones, leading to gas accumulation and serious safety hazards.

[0003] In related technologies, mining extra-thick hard coal is difficult, and the ratio of mining height to coal release height is not set reasonably, resulting in significant safety hazards. Summary of the Invention

[0004] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0005] In related technologies, extra-thick hard coal has a high coal wall hardness, making top coal caving more difficult than in soft coal, which affects coal release efficiency. Hard coal has a low degree of fracture development and large caving block size. If the mining height is too high, it may cause the top coal to remain suspended or caving to be delayed. It is necessary to adjust the top coal fragmentation by adjusting the ratio of mining height to coal release height. If the ratio of mining height to coal release height is not set properly, it may lead to low top coal recovery rate or the mixing of gangue, affecting coal quality. Excessive coal release height can easily lead to premature mixing of gangue, making the mining of extra-thick hard coal difficult.

[0006] The present invention aims to at least partially solve one of the technical problems in the related art.

[0007] Therefore, embodiments of the present invention propose a method for determining the top coal caving ratio in ultra-high mining height, extra-thick hard coal, which is convenient to mine, has minimal safety hazards, and a reasonable ratio between mining height and caving height.

[0008] The method for determining the top coal caving ratio in ultra-high mining height and extra-thick hard coal according to an embodiment of the present invention includes: S1: performing stability analysis on the coal wall of the working face, and determining the first mining height range H1 of the coal mining machine based on the strain range of the coal wall; S2: constructing a cantilever mechanical model of the top coal body, deriving the relationship between the top coal thickness and the ultimate cantilever length, and determining the second mining height range H2 of the coal mining machine in combination with the coal caving step distance parameter; S3: comparing the first mining height range H1 and the second mining height range H2, if there is an overlapping area between the two, the maximum value in the overlapping area is selected as the mining height of the coal mining machine; if there is no overlapping area between the two, the maximum value in the first mining height range H1 is selected as the mining height of the coal mining machine.

[0009] The method for determining the top coal caving ratio in ultra-thick hard coal with ultra-high mining height according to the present invention includes steps S1-S3: by comparing the ranges of the first machine mining height range H1 and the second machine mining height range H2, the maximum value is taken when they overlap, taking into account both crushing efficiency and coal wall safety; when there is no overlap, safety is given priority. In the end, a multi-objective balance of mining efficiency, resource recovery rate and operational safety is achieved, providing an implementation scheme for the mining of ultra-thick hard coal and reducing the difficulty of mining ultra-thick hard coal.

[0010] In some embodiments, in step S1, the coal wall is divided into a lower region b1 and an upper region b2 in the height direction according to the trend of horizontal strain. The horizontal strain direction of the lower region b1 is inclined upward, and the horizontal strain direction of the upper region b2 is inclined downward. The coal wall is divided into region a1 and region a2 in the height direction according to the trend of vertical strain. The strain of region a1 is less than a preset value, and the strain of region a2 is greater than a preset value. The overlapping part of region a2 and region b1 is selected as the first mining height range H1 of the coal mining machine.

[0011] In some embodiments, in step S2, the construction of the top coal cantilever mechanical model is based on the following assumptions: the top coal is a homogeneous, isotropic elastic body that obeys the mechanical properties of a continuous medium, and is regarded as a rock beam structure with load-bearing capacity.

[0012] In some embodiments, in step S2, the relationship between the top coal thickness and the ultimate overhang length is:

[0013]

[0014] In the formula, L is the ultimate overhang length, h is the thickness of the top coal above the hydraulic support, and q 支 q represents the support density of the hydraulic support for the top coal, q represents the load density of the roof on the top coal, and a represents the length of the top beam of the hydraulic support.

[0015] In some embodiments, in step S2, the coal discharge step distance is not greater than the ultimate overhang length.

[0016] In some embodiments, in step S3, based on the analysis of the relationship between the mining height and the recovery rate of the coal mining machine, the higher the mining height of the coal mining machine, the higher the recovery rate. The maximum value of the overlapping area or the maximum value in the first mining height range H1 is selected as the mining height of the coal mining machine.

[0017] In some embodiments, in step S2, the coal wall is detected using a detection component to detect changes in the vertical and horizontal stresses of the coal wall.

[0018] In some embodiments, the detection component is a resistance strain gauge, and there are multiple resistance strain gauges arranged at intervals along the height direction of the coal wall. Each layer includes a number of resistance strain gauges arranged at intervals along the width direction of the coal wall.

[0019] In some embodiments, the spacing between two adjacent layers of the resistance strain gauges is 0.5m-1.0m, and the spacing between two adjacent resistance strain gauges in each layer is 1.5m-2.0m. Attached Figure Description

[0020] Figure 1 This is a flowchart of a method for determining the top coal caving ratio in ultra-high mining height, extra-thick hard coal, according to an embodiment of the present invention.

[0021] Figure 2 This is a diagram showing the trend range and variation of horizontal strain of the coal wall in the method for determining the top coal caving ratio of ultra-high mining height and extra-thick hard coal according to an embodiment of the present invention.

[0022] Figure 3 This is a diagram showing the trend range and variation of vertical strain of the coal wall in the method for determining the top coal caving ratio in ultra-high mining height and extra-thick hard coal according to an embodiment of the present invention. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0024] The following describes a method for determining the top coal caving ratio in ultra-high mining height, extra-thick hard coal, according to an embodiment of the present invention, with reference to the accompanying drawings.

[0025] like Figures 1-3 As shown, the method for determining the top coal caving ratio in ultra-high mining height, extra-thick hard coal, according to an embodiment of the present invention, includes steps S1-S3:

[0026] S1: Perform stability analysis on the coal face and determine the first mining height range H1 of the coal mining machine based on the strain range of the coal face. Specifically, such as... Figure 1 As shown, due to the high hardness of the coal body and the low degree of fissure development, the extra-thick hard coal wall is prone to coal wall spalling or roof collapse during mining due to stress concentration. By setting strain gauges on the coal wall of the working face, the strain range of the coal wall can be measured to determine the first mining height range H1 of the coal mining machine.

[0027] S2: Construct a cantilever mechanical model of the top coal seam, derive the relationship between the top coal thickness and the ultimate cantilever length, and determine the second mining height range H2 of the coal mining machine by combining the coal release step distance parameters. Specifically, such as... Figure 1As shown, in a fully mechanized longwall mining face with an extra-thick hard coal face, the top coal body is in a cantilever state under the support of the support frame. Based on the cantilever beam theory in mechanics of materials, the top coal body is simplified as an elastic cantilever beam structure subjected to a uniformly distributed load. The difference between the pressure of the overlying strata and the support force is used as the net load acting on the top coal surface. The top beam of the support frame is considered as a fixed end constraint, and the coal wall side is the free end. By establishing the mechanical equilibrium equation of the top coal body, a quantitative relationship between the top coal thickness h and the ultimate cantilever length L is derived. Combined with the field coal release process parameters and the influence of the coal release step distance s on the spatiotemporal effect of top coal caving, a multi-parameter coupling equation of the second mining height H2, the top coal thickness h, and the coal release step distance s is established, thereby determining the range of the second mining height H2 of the coal mining machine.

[0028] S3: Compare the first mining height range H1 with the second mining height range H2. If there is an overlap, the maximum value within that overlap range is selected as the mining height of the coal mining machine. If there is no overlap, the maximum value within the first mining height range H1 is selected as the mining height of the coal mining machine. Specifically, as follows... Figure 1 As shown, comparing the first mechanized mining height range H1 and the second mechanized mining height range H2, when H1 and H2 overlap, it indicates that under the current geological conditions, reasonable technological conditions can simultaneously achieve coal face stability control and efficient top coal release. The maximum value of the overlapping area is selected as the final mechanized mining height, thus improving the top coal release capability and promoting sufficient top coal crushing, while avoiding increased coal face spalling risk due to excessive height. If H1 and H2 do not overlap, it means that the set technological conditions cannot simultaneously achieve top coal release efficiency and coal face stability. To ensure the safety of the working face, the maximum value within the H1 range is selected as the mechanized mining height, ensuring sufficient bearing capacity of the coal face at the selected cutting height, achieving a dynamic balance between mining efficiency and safety.

[0029] The method for determining the top coal caving ratio in ultra-thick hard coal with ultra-high mining height according to this invention includes steps S1-S3. Step S1 determines the first mechanized mining height range H1 through actual measurement of coal wall strain, which can accurately quantify the correlation between coal wall stability and mining height. Coal is caved in areas with well-developed top coal fractures, maximizing the effective release of top coal and particle crushing while avoiding the risks of roof collapse or caving. Second, step S2 establishes a quantitative relationship between top coal thickness and overhang length based on a cantilever mechanics model, and derives the second mechanized mining height range H2 by combining the coal caving step distance parameter, achieving synergistic optimization of efficient top coal release and the spatiotemporal effect of caving. Finally, step S3 dynamically selects the mechanized mining height by comparing the overlap between H1 and H2. When there is overlap, the maximum value is taken to balance crushing efficiency and coal wall safety, while safety is prioritized when there is no overlap. Ultimately, a multi-objective balance of mining efficiency, resource recovery rate, and operational safety is achieved, providing an implementation solution for the mining of ultra-thick hard coal and reducing the difficulty of mining ultra-thick hard coal.

[0030] In some embodiments, in step S1, the coal wall is divided into a lower region b1 and an upper region b2 in the height direction according to the trend of horizontal strain. The horizontal strain direction of the lower region b1 is inclined upward, and the horizontal strain direction of the upper region b2 is inclined downward. The coal wall is divided into region a1 and region a2 in the height direction according to the trend of vertical strain. The strain of region a1 is less than a preset value, and the strain of region a2 is greater than a preset value. The overlapping part of the upper vertical strain region a2 and the lower horizontal strain upward region b1 is selected as the first mining height range H1 of the coal mining machine.

[0031] Specifically, such as Figure 2 and Figure 3 As shown, the coal wall is first divided into sections along its height. Based on strain monitoring data, the coal wall is divided into a lower region b1 and an upper region b2. The lower region b1 is affected by the hysteresis effect of the roof pressure transmission, and its strain shows a clear upward expansion trend, that is, the coal body tends to be squeezed towards the goaf. The upper region b2, on the other hand, directly bears the load of the overlying strata, and its strain direction turns downward contraction, that is, the coal body is squeezed into the working face. Meanwhile, through vertical strain monitoring, the coal wall can be divided into region a1 and region a2 in the height direction according to the vertical strain. Based on the coal body damage threshold, the coal wall is divided into shallow strain region a1 and deep strain region a2. Region a1 is in the stress reduction zone, and its horizontal strain value is less than the preset value, which is the elastic limit strain of the coal body and is taken as 0.002-0.003. Region a2 is in the plastic failure zone, and its strain value exceeds the preset value and is accompanied by obvious crack expansion. The spatial overlap area between the upper vertical strain significant region a2 and the lower horizontal strain increasing region b1 is selected. The vertical projection height range of this overlap area is defined as the first mining height range H1 of the coal mining machine. This range can ensure that the lower coal body has sufficient bearing capacity to prevent spalling. The vertical and horizontal cracks in the region are well intersected, forming a "network-tree" composite crack structure, which significantly improves the connectivity of the crack network, thereby effectively improving the difficulty of top coal falling in extra-thick hard coal seams and the problem of large coal blocks.

[0032] In some embodiments, in step S2, the construction of the cantilever mechanical model of the top coal body is based on the following assumptions: the top coal is a homogeneous, isotropic elastic body that obeys the mechanical properties of a continuous medium, and is regarded as a rock beam structure with load-bearing capacity. Specifically, in step S2, the cantilever mechanical model of the top coal body is based on the following core assumptions: First, the top coal body is considered as a homogeneous and isotropic elastic body, that is, it is assumed that the material composition and mechanical properties inside the coal body are uniformly distributed in space, and the elastic parameters in all directions are exactly the same. The elastic parameters can be elastic modulus, Poisson's ratio, etc. This assumption ignores the local influence of non-homogeneous features such as joints and cracks in the coal body on the mechanical response. Second, it is assumed that the top coal body completely obeys the mechanical properties of a continuum, that is, it is considered that the coal material is continuously distributed in space, and there is no mass discontinuity caused by voids or fracture surfaces. Therefore, it can be described by stress-strain relationship and equilibrium equation in continuum mechanics. Finally, from the perspective of structural mechanics, the top coal body is abstracted as a rock beam structure with a clear load-bearing capacity. That is, it is considered that the top coal forms a cantilever beam shape under the support of hydraulic supports. Its upper surface bears the uniformly distributed load transmitted by the overlying rock strata through the direct roof, and its lower surface is subjected to the elastic support reaction force of the support top beam. The two ends are respectively constrained by the coal wall and the free boundary conditions at the coal discharge port at the rear of the support. Based on the above assumptions, the model simplifies the complex deformation and failure process of top coal into a quantifiable elastic cantilever beam bending problem, laying the foundation for the subsequent derivation of the theoretical relationship between top coal thickness and ultimate cantilever length.

[0033] In some embodiments, the relationship between the top coal thickness and the ultimate overhang length in step S2 is as follows:

[0034]

[0035] In the formula, L is the ultimate overhang length, h is the thickness of the top coal above the hydraulic support, and q 支 Let q be the support density of the hydraulic support on the top coal, q be the load density of the roof on the top coal, and a be the length of the top beam of the hydraulic support. Therefore, L is the ultimate overhang length calculated using the top coal thickness, load density, support density, and the length of the top beam of the hydraulic support.

[0036] In some embodiments, in step S2, the coal release step distance is not greater than the ultimate overhang length. Specifically, the coal release step distance is the horizontal advance distance between two adjacent coal release operations and should not exceed the ultimate overhang length of the roof coal body under the support condition. This can prevent the exposed area of ​​the roof coal from exceeding its bearing limit, prevent tensile fracture or shear slip damage caused by excessive overhang, eliminate major safety hazards such as local roof falls and support collapse at the source, and improve the safety of coal mining.

[0037] In some embodiments, in step S2, the second mining height range H2 can be calculated from the coal release step distance range based on the relationship between the top coal thickness and the ultimate overhang length.

[0038] In some embodiments, in step S3, based on the analysis of the relationship between the mining height and the recovery rate of the coal mining machine, the higher the mining height, the higher the recovery rate. Therefore, the maximum value of the overlapping area or the maximum value within the first mining height range H1 is selected as the mining height of the coal mining machine. Specifically, since the coal resource recovery rate of the cutting section of the coal mining machine can generally reach 98%, while the top coal release rate is generally only 75%-85%, increasing the mining height can improve the resource recovery rate of the top coal seam. Therefore, to increase the recovery rate, the maximum value of the overlapping area or the maximum value within the first mining height range H1 is selected as the mining height of the coal mining machine.

[0039] In some embodiments, in step S2, a detection component is used to detect changes in the vertical and horizontal stresses of the coal wall. Thus, by detecting changes in the vertical and horizontal stresses of the coal wall in both the horizontal and vertical directions using the detection component, changes in the vertical and horizontal stresses of the coal wall are detected.

[0040] In some embodiments, the detection component is a resistance strain gauge, and there are multiple resistance strain gauges arranged at intervals along the height direction of the coal wall. Each layer includes several resistance strain gauges arranged at intervals along the width direction of the coal wall. Specifically, there are multiple resistance strain gauges, and all of them are located inside the coal wall. In the height direction of the coal wall, 3 to 6 layers of strain gauge groups are arranged in layers along the vertical mining height range to ensure coverage of the top coal caving zone and the plastic zone of the coal wall. Each strain gauge group contains 4 to 8 strain gauges arranged at intervals along the width direction of the coal wall, which is the working face advancing direction, to capture changes in horizontal stress gradient. Thus, changes in vertical and horizontal stress in the coal wall are detected by multiple resistance strain gauges.

[0041] In some embodiments, the spacing between two adjacent layers of resistance strain gauges is 0.5m-1.0m. Specifically, the spacing between two adjacent layers of resistance strain gauges can be any one of 0.5m, 0.6m, 0.7m, 0.8m, 0.9m, and 1m. If the layer spacing is less than 0.5m, the stress fields monitored by adjacent layers will highly overlap, causing data redundancy and signal noise superposition. At the same time, it will significantly increase the number of boreholes and wiring complexity, pushing up installation and maintenance costs. If the layer spacing is greater than 1m, it will miss the key stress concentration layers in the vertical direction of the coal wall and the development process of dynamic collapse arches, creating monitoring blind spots, causing stress gradient analysis to be distorted, and becoming disconnected from the cutting depth of the coal mining machine and the support shifting cycle, making it impossible to capture stress changes in time, ultimately leading to the failure of early warning for accidents such as collapse.

[0042] In some embodiments, the spacing between two adjacent resistance strain gauges in each layer is 1.5m-2.0m. Specifically, the spacing between two adjacent resistance strain gauges in each layer is any one of 1.5m, 1.6m, 1.7m, 1.8m, 1.9m, and 2m. When the spacing between two resistance strain gauges is less than 1.5m, the monitored stress field areas will highly overlap, the data correlation will be enhanced while the independence will be reduced, making it difficult to accurately capture the characteristics of local stress abrupt changes. At the same time, signal crosstalk may be caused by the non-homogeneity of the coal wall, reducing the monitoring accuracy. If the spacing is greater than 2m, stress monitoring blind spots will appear, missing key stress concentration zones or stress transmission paths in the dynamic deformation process, resulting in distortion of stress gradient analysis and failure to reflect changes in coal wall stability in a timely manner.

[0043] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0047] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0048] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for determining the top coal caving ratio in ultra-high, extra-thick, hard coal mines, characterized in that, include: S1: Perform stability analysis on the coal face and determine the first mining height range H1 of the coal mining machine based on the strain range of the coal face; S2: Construct a cantilever mechanical model of the top coal body, derive the relationship between the top coal thickness and the ultimate cantilever length, and determine the second mining height range H2 of the coal mining machine by combining the coal release step distance parameter; S3: Compare the first mining height range H1 with the second mining height range H2. If there is an overlapping area between the two, the maximum value in the overlapping area shall be selected as the mining height of the coal mining machine. If there is no overlapping area between the two, the maximum value in the first mining height range H1 shall be selected as the mining height of the coal mining machine.

2. The method for determining the top coal caving ratio in ultra-high mining height and extra-thick hard coal as described in claim 1, characterized in that, In step S1, the coal wall is divided into a lower region b1 and an upper region b2 in the height direction according to the trend of horizontal strain. The horizontal strain direction of the lower region b1 is inclined upward, and the horizontal strain direction of the upper region b2 is inclined downward. The coal wall is divided into region a1 and region a2 in the height direction according to the trend of vertical strain. The strain of region a1 is less than a preset value, and the strain of region a2 is greater than a preset value. The overlapping part of region a2 and region b1 is selected as the first mining height range H1 of the coal mining machine.

3. The method for determining the top coal caving ratio in ultra-high mining height, extra-thick hard coal as described in claim 1, is characterized in that... In step S2, the construction of the top coal cantilever mechanical model is based on the following assumptions: the top coal is a uniform, isotropic elastic body that obeys the mechanical properties of a continuous medium, and is regarded as a rock beam structure with load-bearing capacity.

4. The method for determining the top coal caving ratio in ultra-high mining height and extra-thick hard coal as described in claim 1, characterized in that, In step S2, the relationship between the top coal thickness and the ultimate overhang length is as follows: In the formula, L is the ultimate overhang length, h is the thickness of the top coal above the hydraulic support, and q 支 q represents the support density of the hydraulic support for the top coal, q represents the load density of the roof on the top coal, and a represents the length of the top beam of the hydraulic support.

5. The method for determining the top coal caving ratio in ultra-high mining height, extra-thick hard coal, according to claim 4, is characterized in that... In step S2, the coal discharge step distance is not greater than the maximum overhang length.

6. The method for determining the top coal caving ratio in ultra-high mining height, extra-thick hard coal as described in claim 1, is characterized in that... In step S3, based on the analysis of the relationship between the mining height and the recovery rate of the coal mining machine, the higher the mining height of the coal mining machine, the higher the recovery rate. The maximum value of the overlapping area or the maximum value in the first mining height range H1 is selected as the mining height of the coal mining machine.

7. The method for determining the top coal caving ratio in ultra-high mining height, extra-thick hard coal as described in claim 1, is characterized in that... In step S2, the coal wall is detected using a detection component to detect changes in the vertical and horizontal stresses of the coal wall.

8. The method for determining the top coal caving ratio in ultra-high mining height, extra-thick hard coal as described in claim 7, is characterized in that... The detection component is a resistance strain gauge, and there are multiple resistance strain gauges. The multiple resistance strain gauges are arranged at intervals along the height direction of the coal wall, and each layer includes several resistance strain gauges arranged at intervals along the width direction of the coal wall.

9. The method for determining the top coal caving ratio in ultra-high mining height, extra-thick hard coal, according to claim 8, is characterized in that... The spacing between two adjacent layers of the resistance strain gauges is 0.5m-1.0m, and the spacing between two adjacent resistance strain gauges in each layer is 1.5m-2.0m.

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