Method for optimizing drilling and caving ratio of fully-mechanized face with large mining height and short wall and analyzing end face coal and rock stability

Abstract

The present application relates to the field of coal mining parameter design, in particular to a large mining height short wall drilling and caving fully mechanized face drilling and caving ratio optimization and end face coal rock stability analysis method. The present application changes the traditional "coal cutting" mining method into a new type of "coal cutting-caving" mining method; the mining process can reduce the installed power of the coal mining machine, release the roof pressure, improve the end face roof and coal wall area stress state, and reduce the occurrence of working face coal wall spalling and end face roof falling. The present application establishes a large mining height mining inside caving outside coal mechanics calculation model, and theoretically analyzes the relationship between the mining part width a and the caving part width b , which provides a theoretical basis for optimizing the drilling and caving ratio. The present application establishes a large mining height mining inside caving outside roof falling and coal wall spalling mechanics calculation model, and theoretically analyzes that the mining inside caving outside mining process has the effect of preventing end face roof falling and coal wall spalling.

Description

Technical Field

[0001] This invention relates to the field of coal mining parameter design, specifically to a method for optimizing the drilling-to-explosion ratio in longwall drilling and venting fully mechanized mining faces with high mining heights and analyzing the stability of coal and rock at the end face. Background Technology

[0002] To address the challenges posed by traditional large-scale fully mechanized mining equipment and conventional shortwall mining machines in adapting to small-block corner coal, large coal pillar recovery, and the mining of thick coal seams and dispersed resources in small and medium-sized mines, Jinmei Group Jinding Coal Machinery Company has developed and produced a high-extraction fully mechanized mining face drill-type coal mining machine and its supporting equipment. Based on this, a novel "inside-mining, outside-releasing" high-extraction drill-mining process has been proposed. This mining process and supporting equipment are suitable for working faces exceeding 10m in depth, with a maximum mining height of 6m. It boasts significant advantages such as high mechanization, low power consumption, strong adaptability, and high resource recovery rate. It can be used not only for conventional shortwall mining in small and medium-sized coal mines but also for recovering corner coal blocks and residual coal pillars. This has significant economic and social benefits in promoting safe and efficient production in small and medium-sized mines, accelerating the safe and efficient mining of small working faces and remaining corner coal seams, improving resource recovery rates, and extending mine service life. Currently, determining the drill-to-release ratio relies heavily on experience. Excessive drilling and insufficient release can reduce construction efficiency and lead to dangerous situations such as coal spillage, while insufficient drilling prevents complete coal release.

[0003] High-extraction fully mechanized mining has outstanding advantages such as large production capacity and high resource recovery rate, and is currently the main mining method for thick coal seams. However, as the mining height increases, the stability of the coal wall weakens, and the coal wall and the roof of the working face are prone to spalling and roof collapse. The spalling of the coal wall and the poor stability of the coal and rock at the end face have become the main problems restricting the safe and efficient mining of high-extraction working faces. Therefore, it is necessary to conduct in-depth research on the stability mechanism of the coal wall in high-extraction working faces. At present, experts at home and abroad have carried out a lot of research on the stability of the coal and rock at the end face of high-extraction working faces and proposed many effective measures to control the instability of the coal wall spalling in high-extraction working faces. For example, using the results of slope stability studies and probabilistic analysis, the causes of spalling in coal faces with high mining heights have been investigated, and a mechanical model of the sliding surface of the coal face in high mining heights has been established; or the deflection characteristics and spalling forms of coal faces with high mining heights have been analyzed using the pressure bar theory, and the influence of the initial support force, working resistance, and support shifting technology on spalling control has been analyzed; or a mechanical model of the "wedge-shaped" sliding body of the coal face has been established, and the mechanism and control methods for spalling caused by poor self-stability of the coal face in soft coal fully mechanized caving faces have been studied. However, the end-face coal and rock stability of the new "in-mining, out-of-mining" high mining height drilling and caving technology has not yet been studied.

[0004] Therefore, optimizing the drilling-to-releasing ratio and studying the stability of coal and rock at the end face in the "inside mining, outside releasing" drilling and mining process with high mining height are urgent problems that need to be solved to ensure the safe and efficient mining of this working face. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a method for optimizing the drilling-to-discharge ratio in longwall drilling-to-discharge fully mechanized mining faces with high extraction heights, comprising the following steps:

[0006] S1: Construct a coal mechanical calculation model based on a two-dimensional profile along the working face advance direction, with the working face advance direction as the x-axis and the origin of the coordinate as the coal wall, and determine the width of the plastic zone in front of the coal wall.

[0007] S2: Model assumptions: The energy required per unit volume of coal in the coal discharge section is the same; after the coal mining section is drilled out, the overlying pressure moves to both sides on average, and the mine pressure transferred to the coal discharge section is evenly distributed; the velocity of each part of the coal in the coal discharge section is the same, and there is no energy dissipation.

[0008] S3: Determine the vertical pressure distribution in the plastic zone in front of the coal face;

[0009] S4: Determine the resultant force of the overlying pressure transferred to the coal release section after the coal mining section is mined;

[0010] S5: The work done by the mine pressure and the self-weight of the coal body transferred to the coal discharge section completely destroys and releases the plastic coal body in the originally stable coal discharge section, releasing kinetic energy. For the coal discharge section to release all the coal body by relying on the mine pressure and its own weight, the released kinetic energy must be greater than or equal to zero.

[0011] S6: The width of the coal discharge section calculated by setting the released kinetic energy to zero is the upper limit coal discharge width; the width of the coal discharge section calculated when the released kinetic energy is half the sum of the mine pressure transferred to the coal discharge section and the work done by the coal body's own weight is the lower limit coal discharge width.

[0012] Preferably, in step S1, the width of the plastic zone in front of the coal face is determined as follows:

[0013] (1)

[0014] In the formula, X is the width of the plastic zone in front of the coal face, in meters; ; ; m is the coal thickness, in meters; f1 is the friction coefficient between the coal body and the roof and floor; c1 is the cohesion between the coal body and the roof and floor, in MPa; k1 is the proportion of the pressure of the overlying strata transferred from the mining section to the coal release section, assumed to be 0.5; γ is the formation unit weight, in kN / m³; H is the coal body burial depth, in meters; c is the cohesion of the coal body, in MPa. θ is the internal friction angle of the coal body, °; p is the supporting force of the hydraulic support's sidewall plate on the coal wall, kN.

[0015] Preferably, in step S3, the vertical pressure distribution in the plastic zone in front of the coal wall is as follows:

[0016] (2)

[0017] In the formula, σ z ρ is the vertical pressure in the plastic zone in front of the coal face, MPa; x is the distance from the coal face, m.

[0018] Preferably, in step S4, the resultant force of the overlying pressure transferred to the coal release section after the coal mining section is determined is:

[0019] (3)

[0020] In the formula, F (a-b)合 denoted as kN, representing the resultant force of the overlying pressure transferred to the coal release section after the coal mining section is mined; a represents the width of the coal mining section (m); b represents the width of the coal release section (m).

[0021] Preferably, in step S5, according to the law of conservation of energy:

[0022] (4)

[0023] (5)

[0024] (6)

[0025] In the formula, W 矿压 The work done by the mine pressure transferred to the coal discharge section, J;W G Work done by the weight of the coal body, J; W 总 Work done by mine pressure and the weight of the coal body, J, W 总 For W 矿压 With W G The sum of; E b The energy required to crush and release the coal mass is J;E 动 E0 is the kinetic energy released by the complete destruction of the plastic coal body in the coal discharge section, J; E0 is the energy required to crush and discharge the coal body per unit width in the cyclic advance direction of the coal discharge section, J / m.

[0026] Substituting equations (3), (5), and (6) into equation (4), we get:

[0027] (7)

[0028] Therefore, in order for the coal to be discharged completely by means of mine pressure and its own weight, then ,Right now:

[0029] (8).

[0030] Preferably, in step S6, under the upper limit coal discharge width, the mine pressure and the coal body weight are completely used to crush the coal discharge portion, and the instantaneous speed of the crushed coal body is 0; under the lower limit coal discharge width, half of the total work done by the mine pressure and the coal body weight is used to crush the coal discharge portion, and the other half is used to generate the kinetic energy when the crushed coal body is crushed.

[0031] This invention also proposes a method for analyzing the stability of coal and rock at the end face of a longwall mining face with high extraction height and shortwall drilling, including:

[0032] The internal and external extraction process only requires mining V ABEF Coal body, coal discharge section V FECD The coal seam collapses naturally due to mine pressure and its own weight, while the coal discharge section V FECD When the coal is released, the pressure from the roof support does work on it, reducing the force of the roof on the deeper coal wall in front, thus reducing the degree of damage to the coal wall at the working face. This causes the immediate roof's advance crushing point A to move towards the coal wall, becoming point A'. The length L of the beam structure formed by the coal wall, hydraulic support, and the crushing immediate roof is... A＇B The length L of the beam structure formed when the drilling depth is less than one section depth of normal drilling and mining AB Assuming the beam is simply supported, the coal face is a fixed hinged support, the hydraulic support is a movable hinged support, and the beam is formed by the direct roof, a beam structure calculation model is established, and the calculation formula is as follows:

[0033] (9)

[0034] In the formula: q is the uniformly distributed load, which mainly consists of the gravity of the overlying strata, the pressure formed by the rotation of the fractured rock blocks in the old roof, and its own elastic expansion stress; L is the distance from the point of force application of the front beam of the support to the point of force application of the coal body; at this time, x refers to the distance from the coal wall, in meters.

[0035] Because of L A＇B <L AB Therefore, the maximum bending moment in the middle of the direct roof beam formed by the internal and external drilling mining process is less than the maximum bending moment in the middle of the direct roof beam during normal mining. The possibility of the direct roof beam breaking is reduced, which means that the possibility of the direct roof failure and roof collapse at the end face is greatly reduced, and the possibility of coal wall spalling is also greatly reduced.

[0036] The beneficial effects of the present invention are as follows: (1) The present invention proposes a new type of mining process that transforms the traditional “cutting coal” mining method into a new type of “cutting coal-releasing coal” mining method. This mining process can reduce the installed power of the coal mining machine, release the pressure on the roof, improve the stress state of the end face roof and coal wall area, and reduce the occurrence of coal wall spalling and end face roof collapse in the working face.

[0037] (2) This invention establishes a mechanical calculation model for coal release in and out of high mining height, and theoretically analyzes the relationship between the width a of the mining part and the width b of the release part, providing a theoretical basis for optimizing the drilling-to-release ratio.

[0038] (3) The present invention establishes a mechanical calculation model for high mining height with internal release and external prevention of roof collapse and sidewall spalling. Theoretical analysis shows that the internal release and external mining process has the function of preventing end face roof collapse and coal wall spalling. Attached Figure Description

[0039] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0040] Figure 1 This is a schematic diagram of the high-extraction, internal-extraction, external-extraction process of the present invention;

[0041] Figure 2 This invention is a mechanical calculation model for coal release in and out of high mining areas.

[0042] Figure 3 This is a graph showing the relationship between mine pressure, the total work done by the weight of the coal body during coal discharge, and the energy required for the coal body during discharge, as well as the width of the coal discharge.

[0043] Figure 4 This is a schematic diagram of the stress profile of the inner and outer mining sections of the high-extraction mining area;

[0044] Figure 5 This is a schematic diagram of the cross-section of the inner and outer anti-roofing slabs in the high-extraction mining area;

[0045] Figure 6 It is a mechanical calculation model for high-level mining with internal and external anti-roofing panels. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Example 1

[0048] like Figure 1 , Figure 2 and Figure 4 As shown, the fully mechanized mining face is equipped with a drilling and mining machine, a scraper conveyor, and hydraulic supports. The mining process is as follows: the depth of advance in one cycle is set to a+b. Depth a inside the coal face is achieved by breaking the coal with the drilling and mining machine (i.e., "internal mining"), while depth b at the free face of the coal face (near the scraper conveyor) is achieved by utilizing the inherent brittleness of the coal and the combined effects of external disturbances (mining activity, mine pressure, gravity, and the swaying of the cutting wall) to cause it to fall (i.e., "external mining"). Figure 1As shown, its main process flow is as follows: the drilling and mining machine directly feeds into the return airway at the tail track → travels to drill, release, and load coal → sequentially follows the support frame (hydraulic support) → cuts coal to the head of the machine (scraper conveyor) → the unit (drilling and mining machine) returns empty and shovels the remaining coal → pushes the conveyor (scraper conveyor) from the head to the tail of the machine in sequence to complete one cycle.

[0049] In this embodiment, taking the 1305 longwall face of the No. 2 shaft of Zhaozhuang Mine as an example, the longwall face adopts a strike-longwall layout with a strike length of 298.6m, an inclination length of 85m, a coal seam thickness of 4.6~5.5m (average 5m), a coal seam dip angle of 1~8° (average 3°), and a coal seam burial depth of 400.8~414.4m. The 1305 longwall face is equipped with three machines: a ZY5500 / 24 / 52 new high-mining-height two-column shield fully mechanized mining support, an MG120 / 181-NWD single-drum AC traction coal mining machine, and an SGZ764 / 315 shortwall face scraper conveyor. The longwall face adopts a 5m high-mining-height fully mechanized mining process with one-pass full-height mining.

[0050] The core idea of ​​the "inside mining, outside release" principle in high-extraction mining is to determine the optimal ratio of the coal mining width and the coal release width (b) of the drilling and mining machine within one cycle of advance, thereby optimizing the economic and technical benefits of the working face. This means ensuring that within one cycle of advance, the mining pressure and self-weight generated by the drilling and mining machine in mining a portion of the coal body cause the coal body to be completely broken and safely released, while simultaneously maintaining a reasonable advance speed for the working face.

[0051] Accordingly, this invention proposes a method for optimizing the drilling-to-displacement ratio in a longwall drilling-to-displacement face with high mining height, comprising the following steps:

[0052] S1: As Figure 2 As shown, a coal mechanics calculation model for internal and external coal release is constructed based on a two-dimensional profile along the cyclic advance direction (working face advancement direction). The horizontal axis x represents the cyclic advance direction, and the origin of the coordinate system is the coal wall. The calculation formula for the width X of the plastic zone in front of the coal wall is determined according to the Lade-Duncan failure criterion under plane strain conditions as follows:

[0053] (1)

[0054] In the formula, X is the width of the plastic zone in front of the coal face, in meters; ; ; m is the coal thickness, in meters; f1 is the friction coefficient between the coal body and the roof and floor; c1 is the cohesion between the coal body and the roof and floor, in MPa; k1 is the proportion of the pressure of the overlying strata transferred from the mining section to the coal release section, assumed to be 0.5; γ is the formation unit weight, in kN / m³; H is the coal body burial depth, in meters; c is the cohesion of the coal body, in MPa. θ is the internal friction angle of the coal body, °; p is the supporting force of the hydraulic support's sidewall plate on the coal wall, kN.

[0055] In this embodiment, the width X of the plastic zone in front of the coal face of the 1305 working face is 5.8m, and the width of the broken zone in the plastic zone in front of the coal face is about 2m. Based on the size of the drilling and mining machine drum, the drilling cycle advance B (B=a+b) is set to 1.2m, which is located in the broken zone in front of the coal face.

[0056] S2: Model Assumptions; Due to the complex and unpredictable redistribution of mine pressure after the coal mining section is extracted, and the inability to calculate the original energy of the plastically fractured coal body in the coal release section, the following assumptions are made for the mechanical calculation model of coal release within and outside the mining section in order to theoretically derive some qualitative laws regarding the width 'a' of the mining section and the width 'b' of the coal release section (a reasonable ratio): The energy required to release a unit volume of coal is the same for the crushed and discharged portion; After the coal mining section is drilled out, the overlying pressure moves to both sides on average. That is, the pressure of the overlying strata is divided into two parts and applied to the coal body in front of the coal wall and the deep coal body in front of the coal body. The mining pressure transferred to the coal mining section is evenly distributed along the direction of the circulating advance (the direction of the working face advance). At the moment the coal is crushed and released, all parts of the coal body in the released section have the same velocity, and energy is dissipated silently and without heat.

[0057] S3: Determine the vertical pressure distribution in the plastic zone in front of the coal face; within one cycle of drilling and mining, the width of the mining section is a, the width of the coal release section is b, and the proportion of the pressure transferred from the overlying strata in the mining section to the coal release section is k1 (taken as 0.5 according to model assumptions). The energy required to break and release the coal body per unit width in the cycle of drilling and mining (working face advance direction) of the coal release section is E0. When determining the width of the plastic zone in front of the coal face in a high mining height based on the Lade-Duncan failure criterion under plane strain conditions, the vertical pressure σ in the plastic zone in front of the coal face can be obtained. z The distribution is as follows:

[0058] (2)

[0059] In the formula, σ z ρ is the vertical pressure in the plastic zone in front of the coal face, MPa; x is the distance from the coal face, m.

[0060] S4: Determine the resultant force F of the overlying pressure transferred to the coal release section after the coal mining section is mined. (a-b)合 :

[0061] (3)

[0062] In the formula, F (a-b)合denoted as kN, representing the resultant force of the overlying pressure transferred to the coal release section after the coal mining section is mined; a represents the width of the coal mining section (m); b represents the width of the coal release section (m).

[0063] S5: The work done by the mine pressure and the coal's own weight in the coal discharge section causes the previously stable plastic coal in the discharge section to be completely broken up and released, releasing kinetic energy. Let the released momentum be E. 动 According to the law of conservation of energy:

[0064] (4)

[0065] (5)

[0066] (6)

[0067] In the formula, W 矿压 The work done by the mine pressure transferred to the coal discharge section, J;W G Work done by the weight of the coal body, J; W 总 The work done by the mine pressure and the weight of the coal body, J, is W. 矿压 With W G The sum of; E b The energy required to crush and release the coal mass is J;E 动 E0 is the kinetic energy released by the complete destruction of the plastic coal body in the coal discharge section, J; E0 is the energy required to crush and discharge the coal body per unit width in the cyclic advance direction of the coal discharge section, J / m.

[0068] Substituting equations (3), (5), and (6) into equation (4), we get:

[0069] (7)

[0070] Therefore, in order for the coal to be discharged completely by means of mine pressure and its own weight, then ,Right now:

[0071] (8)

[0072] S6: When At that time, the maximum value of the width b of the coal discharge section can be obtained based on formula (8). max That is, the upper limit coal discharge width b max At the upper limit coal discharge width b max Under these conditions, the mine pressure and the coal's own weight are entirely used to crush the coal in the discharge section, and the instantaneous crushing velocity of the coal is 0; the lower limit discharge width b is set. min For E 动 =bE0=0.5W 总The width of the coal discharge at that time, that is, half of the total work done by the mine pressure and the coal body's own weight is used to crush the coal body during the discharge, and the other half is used to generate the kinetic energy during the crushing of the coal body. When the coal discharge width b is located in the dangerous coal discharge width [0, b], min At that time, E 动 When the coal is relatively large, and the coal body is crushed and discharged too quickly, it is easy for it to jump out and damage the scraper, support, or injure workers, making production at the working face unsafe; when b∈[b min b max At that time, E 动 The coal discharge width is relatively small, resulting in a slow and safe discharge speed, which facilitates coal loading; when the coal discharge width b is within the insufficient coal discharge width [b max When the coal seam width *b* increases, the total work done by the mine pressure and the coal's own weight is insufficient to completely break down and release the coal in the release section. This results in incomplete release of the coal, and the effect worsens with increasing release width *b*, leading to failure of the "inside-mining, outside-releasing" drilling and mining method. Therefore, the release width *b* in "inside-mining, outside-releasing" high-mining drilling and mining must be at a reasonable release width. min b max This not only allows for the safe and efficient release of the coal body, but also makes full use of mine pressure mining, saving the mining power of drilling and mining machines and reducing the damage range in front of the coal face.

[0073] The range of the coal discharge section width b determined in this embodiment is shown in the figure. Figure 3 .

[0074] Example 2

[0075] This invention also proposes a method for analyzing the stability of coal and rock at the end face of a longwall mining face with high extraction height and shortwall drilling, including:

[0076] like Figure 4 As shown, the "mining inside and releasing outside" process only requires mining V ABEF Coal body, coal discharge section V FECD The coal seam collapses naturally due to mine pressure and its own weight, which is more efficient than directly mining with drilling and mining machines by advancing one cut depth (V). ABEF Compared to coal seams, this reduces the cutting power of drilling and mining machines, while also increasing the V-shaped output of the coal discharge section. FECD The work done on the coal seam by the roof support pressure when the coal is released is the W calculated in the previous theoretical analysis. 矿压 The work done released part of the pressure on the overlying slab, which is the F calculated in the previous theoretical analysis. (a-b)合 This reduces the force exerted by the roof on the deeper coal face, thus decreasing the degree of coal face damage. Consequently, the direct roof pre-break point A shifts towards the coal face, becoming point A'. Figure 5 As shown, the length L of the beam structure formed by the coal face, hydraulic support, and crushed direct roof is... A＇B The length L of the beam structure formed when the drilling depth is less than one section depth of normal drilling and miningAB Assume the beam is approximately a simply supported beam, the coal face is a fixed hinged support, the support is a movable hinged support, and the beam is formed by the direct roof. Establish the following... Figure 6 The calculation model for the beam structure shown is illustrated, and the calculation formulas are as follows:

[0077] (9)

[0078] In the formula: q is the uniformly distributed load, which is mainly composed of the gravity of the overlying rock strata, the pressure formed by the rotation of the fractured rock block in the old roof, and its own elastic expansion stress; L is the distance from the point of force application of the front beam of the support to the point of force application of the coal body; at this time, x refers to the distance from the coal wall, in meters.

[0079] M(x) changes with x as follows Figure 6 As shown, when x= At that time, M max = That is, the bending moment reaches its maximum value at the middle of the beam, and the middle of the beam is also the most vulnerable to failure; from M max = It can be seen that M max It is directly proportional to the square of L; as L decreases, M... max The value is greatly reduced, which greatly reduces the chance of direct collapse due to L. A＇B <L AB Therefore, the maximum bending moment in the middle of the direct roof beam formed by the "inside-outside" drilling and mining process is less than the maximum bending moment in the middle of the direct roof beam during normal mining. This significantly reduces the likelihood of the direct roof beam fracturing, meaning the possibility of roof collapse at the end face is greatly reduced. Based on the linkage between coal wall spalling and roof fall in high-mining faces, the significantly reduced possibility of end-face roof fall also greatly reduces the possibility of coal wall spalling. Therefore, the coal and rock stability at the end face of the "inside-outside" drilling and mining face is much more stable than that of a normal drilling and mining face, greatly improving the stability of the surrounding rock at the end face of high-mining faces.

[0080] The above description of the disclosed embodiments is presented in a progressive manner to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for optimizing the drilling-to-expansion ratio in a longwall mining face with high extraction height, characterized in that, Includes the following steps: S1: Construct a coal mechanical calculation model based on a two-dimensional profile along the working face advance direction, with the working face advance direction as the x-axis and the origin of the coordinate as the coal wall, and determine the width of the plastic zone in front of the coal wall. S2: Model assumptions: The energy required per unit volume of coal in the coal discharge section is the same; after the coal mining section is drilled out, the overlying pressure moves to both sides on average, and the mine pressure transferred to the coal discharge section is evenly distributed; the velocity of each part of the coal in the coal discharge section is the same, and there is no energy dissipation. S3: Determine the vertical pressure distribution in the plastic zone in front of the coal face; S4: Determine the resultant force of the overlying pressure transferred to the coal release section after the coal mining section is mined; S5: The work done by the mine pressure and the self-weight of the coal body transferred to the coal discharge section completely destroys and releases the plastic coal body in the originally stable coal discharge section, releasing kinetic energy. For the coal discharge section to release all the coal body by relying on the mine pressure and its own weight, the released kinetic energy must be greater than or equal to zero. S6: The width of the coal discharge section calculated by setting the released kinetic energy to zero is the upper limit coal discharge width; the width of the coal discharge section calculated when the released kinetic energy is half the sum of the mine pressure transferred to the coal discharge section and the work done by the coal body's own weight is the lower limit coal discharge width.

2. The drilling-to-discharge ratio optimization method according to claim 1, characterized in that, In step S1, the width of the plastic zone in front of the coal face is determined as follows: （1）； In the formula, X is the width of the plastic zone in front of the coal face, in meters; ; ; m represents the coal thickness, in meters. f1 is the friction coefficient between the coal body and the roof and floor; c1 is the cohesion between the coal body and the roof and floor, MPa; k1 is the proportion of the pressure of the overlying strata transferred to the coal release section in the mining section, which is assumed to be 0.5; γ is the unit weight of the formation, kN / m³; H is the burial depth of the coal body, m; c is the cohesion of the coal body, MPa. θ is the internal friction angle of the coal body, °; p is the supporting force of the hydraulic support's sidewall plate on the coal wall, kN.

3. The drilling-to-discharge ratio optimization method according to claim 2, characterized in that, In step S3, the vertical pressure distribution in the plastic zone in front of the coal wall is as follows: （2）； In the formula, σ z ρ is the vertical pressure in the plastic zone in front of the coal face, MPa; x is the distance from the coal face, m.

4. The drilling-to-discharge ratio optimization method according to claim 3, characterized in that, In step S4, the resultant force of the overlying pressure transferred to the coal release section after the coal mining section is determined to be: （3）； In the formula, F (a-b)合 denoted as kN, representing the resultant force transferred from the overlying pressure after the coal mining section is mined to the coal discharge section; a represents the width of the coal mining section (m); b represents the width of the coal discharge section (m).

5. The drilling-to-discharge ratio optimization method according to claim 4, characterized in that, In step S5, according to the law of conservation of energy: （4）； （5）； （6）； In the formula, W 矿压 The work done by the mine pressure transferred to the coal discharge section, J;W G Work done by the weight of the coal body, J; W 总 Work done by mine pressure and the weight of the coal body, J, W 总 For W 矿压 With W G The sum of; E b The energy required to crush and release the coal mass is J;E 动 E0 is the kinetic energy released by the complete destruction of the plastic coal body in the coal discharge section, J; E0 is the energy required to crush and discharge the coal body per unit width in the cyclic advance direction of the coal discharge section, J / m; Substituting equations (3), (5), and (6) into equation (4), we get: （7） Therefore, in order for the coal to be discharged completely by means of mine pressure and its own weight, then ,Right now: （8）。 6. The drilling-to-discharge ratio optimization method according to claim 5, characterized in that, In step S6, under the upper limit coal discharge width, the mine pressure and the coal body weight are used entirely to crush the coal discharge portion, and the instantaneous velocity of the crushed coal body is 0; under the lower limit coal discharge width, half of the total work done by the mine pressure and the coal body weight is used to crush the coal discharge portion, and the other half is used to generate the kinetic energy when the crushed coal body is crushed.

7. A method for analyzing the stability of coal and rock at the end face of a longwall mining face with high extraction height and shortwall drilling, characterized in that, include: The internal and external extraction process only requires mining V ABEF Coal body, coal discharge section V FECD The coal seam collapses naturally due to mine pressure and its own weight, while the coal discharge section V FECD When the coal is released, the pressure from the roof support does work on it, reducing the force of the roof on the deeper coal wall in front, thus reducing the degree of damage to the coal wall at the working face. This causes the direct roof's advanced crushing point A to move towards the coal wall and become point A'. The length L of the beam structure formed by the coal wall, hydraulic support, and crushing direct roof is... A＇B The length L of the beam structure formed when the drilling depth is less than one section depth of normal drilling and mining AB Assuming the beam is simply supported, the coal face is fixed hinged, the hydraulic support is movable hinged, and the beam is formed by the direct roof, a beam structure calculation model is established, and the calculation formula is as follows: (9)； In the formula: q is the uniformly distributed load, mainly composed of the gravity of the overlying strata, the pressure formed by the rotation of the fractured rock blocks in the old roof, and its own elastic expansion stress; L is the distance from the point of contact of the front beam of the support to the point of contact of the coal body; at this time, x refers to the distance from the coal wall, in meters; since L A＇B <L AB Therefore, the maximum bending moment in the middle of the direct roof beam formed by the internal and external drilling mining process is less than the maximum bending moment in the middle of the direct roof beam during normal mining. The possibility of the direct roof beam breaking is reduced, which means that the possibility of the direct roof failure and roof collapse at the end face is greatly reduced, and the possibility of coal wall spalling is also greatly reduced.

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