Method for preventing spontaneous combustion of coal pillar in small coal pillar mining

Abstract

The invention belongs to the technical field of coal mine underground fire prevention and extinguishing, and particularly discloses a method for preventing spontaneous combustion of a coal pillar in small coal pillar mining. The parameters comprise the working face mining coal seam shortest spontaneous combustion period, the goaf coal spontaneous combustion oxidation zone on-site measurement air inlet and return side average width, the coal face actual daily propulsion degree and the small coal pillar thickness; based on the parameters, the distance L between the drill hole groups is determined; drilling the adjacent goaf every L in the roadway of the stope face along the mining direction of the stope face to form a plurality of drill hole groups which are distributed at intervals; and a gelling agent is injected into the triangular non-caving area through the drilling hole set, and a plurality of filling isolation bodies distributed at intervals are formed in the triangular non-caving area. The multiple filling isolation bodies distributed at intervals are arranged in the triangular non-caving area, the air leakage channel is blocked through the filling isolation bodies, the spontaneous combustion oxygen supply condition is cut off, and the spontaneous combustion problem is effectively restrained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coal mine underground fire prevention and extinguishing, and particularly relates to a method for preventing spontaneous combustion of a small coal pillar in small coal pillar mining. BACKGROUND

[0002] In order to save coal resources, improve the recovery rate, and promote the efficient development of coal resources, small coal pillar mining technology has gradually become an important supporting technology for the mining of medium-thick coal seams. The small coal pillar is a coal pillar isolated from the goaf during the driving of the roadway. It is generally believed that the width of the small coal pillar is 5-10 m. The mining of the small coal pillar not only improves the coal recovery rate, but also improves the stress environment of the surrounding rock of the roadway along the goaf, and reduces the occurrence of impact accidents such as rock burst and roof fall of the surrounding rock along the goaf.

[0003] However, in the process of roadway driving and working face mining, the small coal pillar is repeatedly disturbed by the superimposed stress of mining and concentrated stress, and the surface and internal pressure of the coal pillar is broken to gradually form a ventilation leakage channel. Influenced by the ventilation pressure difference on both sides of the small coal pillar, the gas in the adjacent goaf and the coal roadway exchanges frequently through the small coal pillar fissure seepage. When the oxygen in the coal roadway seeps into the adjacent goaf through the small coal pillar fissure, it becomes the oxygen source for the oxidation of the broken coal body in the small coal pillar and the loose coal in the adjacent goaf.

[0004] The broken coal body in the small coal pillar and the loose coal in the adjacent goaf are in a ventilation leakage oxygen supply environment for a long time, and continue to oxidize slowly. The loose coal with a good heat storage environment continues to oxidize for a certain period of time, and the oxidation heat will cause the temperature of the broken coal body in the small coal pillar and the loose coal in the goaf to rise continuously, and then spontaneous combustion occurs.

[0005] In order to fundamentally inhibit the spontaneous combustion of the broken coal body in the small coal pillar and the loose coal in the adjacent goaf, the key is to inhibit the leakage of the gas in the coal roadway into the adjacent goaf through the fissure coal pillar, so as to eliminate the small coal pillar leakage source. Therefore, the current method for preventing spontaneous combustion of the small coal pillar in the coal mine is mostly to inject grout into the coal pillar fissure to block the leakage, or to spray on the surface of the coal pillar. However, the above two methods need to process the whole coal pillar, which not only needs to invest a large amount of grouting and spraying materials and manpower. Moreover, with the passage of time, the ungrouted part and the surface sprayed material of the small coal pillar will crack under the disturbance of the mining stress, forming a new leakage source. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a method for preventing spontaneous combustion of a small coal pillar in small coal pillar mining.

[0007] The technical scheme of the present application is: a method for preventing spontaneous combustion of a small coal pillar in small coal pillar mining, comprising: obtaining parameters, the parameters including the shortest spontaneous combustion period of the working face mining coal seam, the average width of the coal spontaneous combustion oxidation zone measured on the air inlet and outlet side of the goaf, the actual daily advance degree of the coal mining face, and the thickness of the small coal pillar; determining the spacing between the groups of drill holes based on the parameters .

[0008] Along the mining direction of the mining face, every interval of the drilling groups is calculated according to the following formula: Drilling holes towards the adjacent goaf to form multiple groups of interval distributed drilling groups; injecting the gelling agent into the triangular uncollapsed area through the drilling groups to form multiple interval distributed filling isolation bodies in the triangular uncollapsed area; the triangular uncollapsed area is a triangular uncollapsed area in the adjacent goaf which is distributed in a strip shape along the small coal pillar.

[0009] Compared with the traditional method of "treating the whole coal pillar", the present application constructs drilling groups at a calculated interval in the roadway of the mining face, prepares the gelling agent, and injects the gelling agent into the triangular uncollapsed area to form the filling isolation body, and the interval between the drilling groups is accurately determined by multiple parameters. This method only arranges the filling isolation body in the core air leakage area, avoids the invalid treatment of the non-risk area, directly cuts off the "oxygen supply channel" of spontaneous combustion, and the fire prevention and extinguishing target is more clear, and the efficiency is significantly improved.

[0010] Further, the interval between the drilling groups is calculated according to the following formula: According to the following formula.

[0011] ; wherein, The interval between the drilling groups is represented by d; The shortest spontaneous combustion period of the coal seam in the working face is represented by t; The average width of the measured air inlet and outlet side of the coal spontaneous combustion oxidation zone in the goaf is represented by b; The actual daily progress of the coal mining face is represented by v; The thickness of the small coal pillar is represented by h; , , and all represent safety correction factors; The comprehensive amplification coefficient is represented by k.

[0012] Further, the ratio of the thickness of the filling isolation body to the thickness of the small coal pillar is in the range of (3.8-4.2):1. This ratio limits the "coverage requirement" of the triangular uncollapsed area and the "small coal pillar working condition adaptability" design, so that the thickness of the filling isolation body can fully wrap the triangular uncollapsed area around the small coal pillar. This ratio is quantitatively limited, and a balance is found between "effective air leakage blocking" and "material consumption control", further reducing the comprehensive cost, and achieving the core goal of "reducing material consumption and reducing cost".

[0013] Still further, the thickness of the small coal pillar is in the range of 5m-10m. By limiting the thickness range of the small coal pillar, a specific and calculable quantitative benchmark is directly provided for the thickness of the filling isolation body, avoiding the design of the filling isolation body out of control due to the lack of clear boundaries of the thickness of the small coal pillar. The disadvantages of the traditional small coal pillar thickness "without quantification" are effectively avoided, and the safety and economic risks are reduced.

[0014] Further, a ratio of the width of the filling isolation body to the thickness of the filling isolation body ranges from 1:(1.8-2.2), and a ratio of the height of the filling isolation body to the mining height ranges from 1:(1.4-1.8). The thickness of the filling isolation body is a core size against radial air leakage of the small coal pillar, the width is calculated according to 1:(1.8-2.2), which can completely cover the triangular air leakage zone along the advancing direction and avoid side air leakage, and the height of the filling isolation body is calculated according to 1:(1.4-1.8), which not only covers the entire mining height, but also extends to the loose rock layer at the top of the goaf, thereby eliminating up and down flow.

[0015] Further, the volume of the filling isolation body is determined according to the following formula.

[0016] , wherein, represents the volume of the filling isolation body; represents the thickness of the small coal pillar; represents the mining height.

[0017] Further, the glue injection amount of each filling isolation body is determined according to the following formula.

[0018] , wherein, represents the glue injection amount of each filling isolation body; represents the porosity value in the air leakage channel; represents the surplus coefficient; represents the gelation proportion of the gelling agent; represents the thickness of the small coal pillar; represents the mining height.

[0019] The core role of the filling isolation body is to "block the air leakage channel", and its performance depends on the "gelling agent filling density": if the glue injection amount is insufficient, there will be hollow or loose areas in the filling isolation body, which cannot effectively isolate oxygen; if the glue injection amount is accurate, the gelling agent can fully fill the pores and stably gel in proportion, forming a dense and continuous isolation structure. The glue injection amount accurately calculated by the above formula can ensure the density of the filling isolation body, effectively block the air leakage and cut off the spontaneous combustion oxygen supply condition, and ultimately achieve stable fire prevention effect, avoiding the risk of fire prevention failure caused by unstable performance of the filling isolation body due to traditional experience grouting.

[0020] Further, the actual daily advancing degree of the coal mining face , the shortest spontaneous combustion period of the coal seam mined in the coal mining face , the average width of the measured oxidation zone of the coal spontaneous combustion in the goaf on the air inlet and outlet sides satisfy the following formula.

[0021] .

[0022] Further, the working face mining coal seam shortest spontaneous combustion period Determined by coal spontaneous combustion physical simulation experiment. The working face mining coal seam shortest spontaneous combustion period is a key parameter reflecting "the shortest time required for a specific coal seam from oxidation to spontaneous combustion", which is influenced by multiple factors such as coal seam physical and chemical properties, underground environment, etc. Different mines, even different working faces in the same mine There are significant differences. In practice, the characteristics of the coal seam of the target working face and the underground environment parameters can be reduced in the laboratory, and the coal oxidation and temperature rise process can be dynamically monitored to directly determine the From the source, eliminate parameter deviation, and provide accurate basis for subsequent design.

[0023] Further, the safety correction factor related to the coal seam mining method There is a negative correlation between the amount of residual coal in the goaf and the air leakage caused by field mining, that is, the more residual coal in the goaf or the more air leakage caused by field mining, the smaller the safety factor Should take smaller value.

[0024] The core risk source of coal pillar spontaneous combustion is "residual coal + air leakage", and the strength of the two directly determines the spontaneous combustion risk level: the more residual coal, the more coal body can participate in oxidation, the faster the oxidation heat generation rate, and the shorter the spontaneous combustion critical time; the larger the air leakage, the more sufficient the oxygen supply, the more intense the oxidation reaction, and the more accelerated the spontaneous combustion process. The "negative correlation rule" pointed out here is essentially Inversely bound with "risk source strength": the stronger the risk source, that is, more residual coal + more air leakage, by reducing The filling isolation body is directly aimed at the "high fuel + high oxygen supply" scene to strengthen the blockage; the weaker the risk source, that is, less residual coal + less air leakage, by amplifying The sparse filling isolation body does not need excessive protection. This "the higher the risk, the denser the protection" precise matching is more targeted than the traditional "non-discriminatory protection", ensuring that the filling isolation body is "not too much, not too little, just to deal with the risk".

[0025] Compared with the prior art, the present application has the following advantages: This invention utilizes multiple spaced-apart filling isolation bodies within a triangular, uncollapsed zone to block air leakage channels, cut off the oxygen supply for spontaneous combustion, and form a stable protective structure, effectively suppressing the spontaneous combustion of broken coal bodies in small coal pillars and loose coal residues in adjacent goaf areas. Because the filling isolation bodies are spaced apart, there is no need to treat the entire coal pillar, significantly reducing material consumption and manpower. Compared to the traditional method of "treating the entire coal pillar," this invention involves constructing borehole groups at calculated intervals in the longwall face roadway, preparing a gelling agent, and injecting the gelling agent into the triangular, uncollapsed zone to form filling isolation bodies. The spacing between the borehole groups is precisely determined through multiple parameters. This method only targets the core air leakage area with filling isolation bodies, avoiding ineffective treatment of non-risk areas, directly cutting off the "oxygen supply channel" for spontaneous combustion, making fire prevention and extinguishing objectives clearer and significantly improving efficiency.

[0026] Moreover, the spaced filling isolation bodies divide the area between the adjacent goaf and the small coal pillar into multiple independent zones, effectively preventing the problem of continuous oxidation in the adjacent goaf.

[0027] This invention focuses on the core air leakage area, using parameters to determine the precise layout of filling isolation bodies, avoiding ineffective treatment of non-risk areas and improving the targeting of fire prevention and extinguishing; the parameter system determines the range of filling isolation bodies, reducing material consumption, relying on conventional equipment for construction, eliminating the need to widen coal pillars, reducing overall costs and ensuring resource recovery; furthermore, the parameter system can be flexibly adjusted without restructuring the technical framework, adapting to various easily self-igniting coal seam mining scenarios, and construction does not conflict with production schedules. Attached Figure Description

[0028] Figure 1 This is a distribution diagram of the filling separator of the present invention. Detailed Implementation

[0029] The following is in conjunction with the appendix Figure 1 The specific embodiments of the present invention will be described in detail below. In the description of the present invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present 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, and therefore should not be construed as a limitation of the present invention.

[0030] The terms "first", "second", "third", etc. are used only for descriptive purposes and should not be construed as implying or suggesting relative importance or an indicated number of technical features. Thus, features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features; in the description of the present application, the meaning of "a plurality" is two or more, unless otherwise stated.

[0031] It should be noted that: in order to completely eliminate the coal spontaneous combustion hidden danger and air leakage source, the pressure difference between the two sides of the coal pillar must be reduced or eliminated. According to the "O" ring theory formed by the overburden strata of the coal mining face after mining, there is a triangular uncollapsed area at the root of the coal pillar adjacent to the goaf. This triangular uncollapsed area along the small coal pillar in the adjacent goaf is a main air leakage channel. Under the condition of full negative pressure ventilation of the working face, this air leakage channel leaks air for a long time under the action of the pressure difference at both ends, so the present application is to fill and block this air leakage channel to reduce the pressure difference of the air leakage channel.

[0032] Embodiment A method for preventing spontaneous combustion of small coal pillars during mining, comprising: obtaining parameters, the parameters including the shortest spontaneous combustion period of the coal seam in the working face, the average width of the coal spontaneous combustion oxidation zone measured on the air inlet and outlet sides of the goaf, the actual daily advance degree of the coal mining face, and the thickness of the small coal pillar; determining the spacing between the drill hole groups based on the parameters .

[0033] Every interval Drilling holes into the adjacent goaf to form a plurality of groups of spaced drill holes; preparing a gelling agent; injecting the gelling agent into the triangular uncollapsed area through the drill hole groups to form a plurality of spaced filling isolation bodies in the triangular uncollapsed area; the triangular uncollapsed area is a triangular uncollapsed area along the small coal pillar in the adjacent goaf.

[0034] Compared with the traditional method of "treating the entire coal pillar", the present embodiment constructs drill hole groups at a calculated interval in the roadway of the mining face, prepares a gelling agent, and injects the gelling agent into the triangular uncollapsed area to form filling isolation bodies, and the spacing between the drill hole groups is accurately determined by multiple parameters. This method only arranges filling isolation bodies in the core air leakage area, avoids ineffective treatment of non-risk areas, directly cuts off the "oxygen supply channel" of spontaneous combustion, and the fire prevention and extinguishing target is more clear, and the efficiency is significantly improved.

[0035] By arranging multiple spaced-apart filling isolation bodies within the triangular non-collapsed zone, these bodies block air leakage channels, cut off spontaneous combustion oxygen supply, and form a stable protective structure, thus avoiding hazards such as excessive carbon monoxide and ensuring safe production. Because the filling isolation bodies are spaced out, there is no need to treat the entire coal pillar, greatly reducing material consumption and manpower. Furthermore, the spaced-apart filling isolation bodies divide the area between adjacent goafs and small coal pillars into multiple independent zones, effectively preventing gas exchange between adjacent goafs and coal roadways. Even if there is an air leakage source in the small coal pillar, this leakage source can only exchange gas with the area within the adjacent goaf between two adjacent filling isolation bodies. This area cannot exchange gas with other areas within the adjacent goaf due to the blocking effect of the filling isolation bodies, thus effectively preventing continuous oxidation within the adjacent goaf.

[0036] The spacing between borehole groups is determined by the following factors: the shortest spontaneous combustion period of the coal seam being mined at the working face, the average width of the coal spontaneous combustion oxidation zone on the intake and return air sides measured on-site, the actual daily advance of the coal mining face, and the thickness of the small coal pillar. The core is based on the three-dimensional risk logic of "time-space-dynamic mining" of coal pillar spontaneous combustion. The essence of coal pillar spontaneous combustion is "the continuous oxidation of broken coal body in a leaky environment, with heat accumulation to the critical temperature." These four parameters correspond to the "time boundary, spatial range, dynamic change, and basic carrier characteristics" of spontaneous combustion risk, and together they constitute the scientific basis for spacing design.

[0037] Shortest spontaneous combustion period in coal seams during working face mining This refers to the shortest time it takes for a specific coal seam to reach its auto-ignition critical temperature in an underground environment, from the onset of oxidation. It is a core indicator of the coal's inherent oxidation characteristics. The spacing between borehole groups must ensure that... Before the expiration date, the newly deployed infill isolation structures should be able to completely block air leakage. —If the spacing is too large, the construction interval between two adjacent sets of isolation structures should exceed [a certain limit]. This could lead to a situation where "coal outside the protection range of the previous isolation barrier has already entered the spontaneous combustion stage before the construction of the next isolation barrier," resulting in protection failure; if the spacing is not combined... Designing based solely on experience may result in missing the optimal protection opportunity due to a failure to match the spontaneous combustion rate of the coal seam.

[0038] The oxidation zone is the core area within the goaf where "oxygen concentration is suitable and coal is easily and continuously oxidized." The average width of the spontaneous combustion oxidation zone on the intake and return air sides of the goaf is measured on-site. This directly reflects "the area of ​​space where air leakage needs to be blocked." Only by using spatial reference can we ensure that the isolation body completely covers the oxidation zone without any blind spots.

[0039] Actual daily progress of coal mining face The distance of the working face advancing forward per day determines the dynamic change speed of the "goaf range and the oxidation zone position". The spacing between the drill hole groups needs to be combined with synchronization - if the spacing is too large, the working face advancing speed is faster than the isolation body laying pace, and the lag problem of "newly formed goaf oxidation zone has appeared, but the isolation body has not been laid in time" will occur; if the spacing is not combined with the advancing speed, it may lead to the dislocation of the isolation body and the dynamically changing oxidation zone, the originally protected area is separated from the oxidation zone with the advancing, and the new oxidation zone has no protection, losing the blocking effect.

[0040] The small coal pillar is the "isolation carrier" of the goaf and the roadway, and the thickness of the small coal pillar directly determines the degree of crushing, the distribution and scale of the air leakage channel. The thickness of the small coal pillar determines the "width of the triangular uncollapsed area" - the greater the thickness, the wider the triangular uncollapsed area, and a larger isolation body coverage range is needed, which corresponds to the spacing between the drill hole groups. If it is ignored , and only the spacing is designed according to other parameters, the isolation body may not be able to adapt to the air leakage scale of the small coal pillar, resulting in the existence of local air leakage.

[0041] The spacing between the drill hole groups is determined by the above four parameters, and the essence is "to replace the traditional experience estimation with scientific quantification", which solves the pain points of "blind spacing design and unstable protection effect" in the traditional fire prevention and extinguishing method.

[0042] Preferably, the spacing between each group of drill holes is determined according to the following formula.

[0043] ; wherein, represents the spacing between the drill hole groups, unit: m; represents the shortest spontaneous combustion period of the working face mining coal seam, unit: days; represents the average width of the goaf coal spontaneous combustion oxidation zone measured on the air inlet and outlet sides, unit: m; represents the actual daily advancing degree of the coal mining face, unit: m / day; represents the thickness of the small coal pillar, unit: m; represents a safety correction coefficient related to the coal seam mining method, with a value range of 0.6-0.9; represents a safety correction coefficient related to the natural tendency of the mined coal seam, surrounding rock temperature, etc., with a value range of 0.8-0.9; represents a comprehensive amplification coefficient related to the complex geological conditions on site and the safety margin requirement, with a value range of 6.3-7.8.

[0044] The quantitative calculation logic of the spacing between the drill hole groups is determined in combination with "the shortest spontaneous combustion period of the coal seam in the working face, the average width of the coal spontaneous combustion oxidation zone measured on the air inlet and outlet sides, the actual daily advance degree of the coal mining face, the thickness of the small coal pillar, and two safety correction coefficients", effectively ensuring that the layout density of the filling isolation body matches the coal seam spontaneous combustion speed and the mining progress, and avoiding the incomplete blocking of the air leakage channel due to too large spacing, or resource waste due to too small spacing.

[0045] The construction process relies on conventional coal mine equipment, and focuses on local operation of the "triangular non-caving area", without occupying the core recovery space of the working face, and without needing to suspend coal mining operations.

[0046] Preferably, the ratio of the thickness of the filling isolation body to the thickness of the small coal pillar is in the range of (3.8-4.2):1. This ratio limits the design of the "coverage requirement of the triangular non-caving area" and the "adaptability of the small coal pillar working condition", so that the thickness of the filling isolation body can fully wrap the triangular non-caving area around the small coal pillar. This ratio is quantitatively limited to find a balance between "effective blocking of air leakage" and "control of material consumption", further reducing the overall cost, and achieving the core goal of "reducing material consumption and cost".

[0047] Preferably, the thickness of the small coal pillar is in the range of 5m-10m. If the thickness of the small coal pillar is 5m, the thickness of the filling isolation body is 19m-21m, which can cover the air leakage channel extending on both sides of the small coal pillar; if the thickness of the small coal pillar is 10m, the thickness of the filling isolation body is 38m-42m, which can also completely cover a wider strip-shaped air leakage area. Compared with the traditional "non-quantitative thickness design", this ratio ensures that the filling isolation body "precisely covers the risk area", completely blocks the air leakage from space, and cuts off the oxygen supply channel of spontaneous combustion.

[0048] If the thickness of the small coal pillar exceeds 10m, a large amount of coal resources will be left as coal pillars and cannot be mined, which goes against the original intention of "small coal pillar mining to improve recovery rate"; if the thickness of the small coal pillar is less than 5m, the coal pillar is prone to serious crushing under the superimposed disturbance of mining stress and concentrated stress, that is, the "small coal pillar repeatedly disturbed by mining stress to form an air leakage channel" mentioned in the background technology, which instead aggravates the risk of air leakage and spontaneous combustion, and may also cause roof falling and rock burst in the gob-side entry, etc. The range of 5m-10m not only ensures that the small coal pillar has sufficient bearing capacity to maintain the stability of the surrounding rock, but also reduces the broken air leakage and maximizes the reduction of coal resource waste, perfectly matching the technical positioning of small coal pillar mining.

[0049] By limiting the thickness range of the small coal pillar, a specific and calculable quantitative benchmark is directly provided for the thickness of the filling isolation body, avoiding the design out of control of the filling isolation body due to the lack of clear boundaries of the small coal pillar thickness. This effectively avoids the disadvantages of the traditional non-quantitative small coal pillar thickness, and reduces safety and economic risks.

[0050] Preferably, the ratio of the width of the filling isolation body to the thickness of the filling isolation body ranges from 1:(1.8-2.2), and the ratio of the height of the filling isolation body to the mining height ranges from 1:(1.4-1.8). The thickness of the filling isolation body is the core size against radial air leakage of the small coal pillar, the width is calculated according to 1:(1.8-2.2) to completely cover the triangular air leakage zone along the advancing direction and avoid side air leakage, and the height of the filling isolation body is calculated according to 1:(1.4-1.8) to not only cover the entire mining height but also extend to the loose rock layer at the top of the goaf to eliminate up and down flow.

[0051] Preferably, the volume of the filling isolation body is determined according to the following formula.

[0052] , wherein, represents the volume of the filling isolation body, unit: m 3 ; represents the thickness of the small coal pillar, unit: m; represents the mining height, unit: m. The formula is a quantitative landing of the foregoing "size ratio of the filling isolation body" and solves the problem of "empirical estimation of the volume of the filling isolation body and disconnection from the amount of glue injection" in the traditional fire prevention and extinguishing method.

[0053] Preferably, the amount of glue injection of each filling isolation body is determined according to the following formula.

[0054] , wherein, represents the amount of glue injection of each filling isolation body; represents the porosity value in the air leakage channel; represents the surplus coefficient; represents the proportion of gelation of the gelling agent; represents the thickness of the small coal pillar, unit: m; represents the mining height, unit: m.

[0055] The core role of the filling isolation body is to "block the air leakage channel", and its performance depends on the "filling density of the gelling agent": if the amount of glue injection is insufficient, there will be cavities or loose areas in the filling isolation body, which cannot effectively isolate oxygen; if the amount of glue injection is accurate, the gelling agent can fully fill the pores and stably gel in proportion to form a dense and continuous isolation structure. The amount of glue injection accurately calculated by the foregoing formula can ensure the density of the filling isolation body, effectively block the air leakage and cut off the self-ignition oxygen supply condition, and finally realize stable fire prevention and extinguishing effect and avoid the risk of fire prevention and extinguishing failure caused by unstable performance of the filling isolation body in the traditional experience grouting.

[0056] Preferably, the actual daily advancing degree of the coal mining face , the shortest self-ignition period of the coal seam mined in the coal mining face , the average width of the site measured on the return air side of the coal spontaneous combustion oxidation zone in the goaf The following expression is satisfied.

[0057] .

[0058] Ensuring the working face advances at a speed sufficient to remove residual coal from the oxidation zone "before spontaneous combustion" cuts off the "continuous oxidation conditions" for spontaneous combustion of residual coal from a "time-space dimension." This quantitative matching is more precise than the traditional "adjusting the advance speed based on experience": it avoids residual coal remaining in the oxidation zone due to insufficient actual daily advance of the coal mining face, and it also avoids blindly increasing the actual daily advance of the coal mining face to excessively avoid risks, thus achieving a balance between "safety and efficiency."

[0059] Traditional methods lack this prior verification, potentially leading to blind construction in scenarios where the "progress speed is mismatched with the risk of spontaneous combustion," resulting in wasted material, manpower, and time costs without addressing the spontaneous combustion hazard. This formula, however, pre-screens applicable scenarios where the "progress speed can cover the risk of oxidation," avoiding ineffective investment from the outset and ensuring that subsequent construction has actual fire prevention and extinguishing value.

[0060] Preferably, the shortest spontaneous combustion period for coal seams during working face mining. The shortest spontaneous combustion period of a coal seam was determined through physical simulation experiments on coal spontaneous combustion. This is a key parameter reflecting the shortest time required for a specific coal seam to spontaneously combust from oxidation. It is influenced by multiple factors, including the physicochemical properties of the coal seam itself and the underground environment, and varies between different mines, and even between different working faces within the same mine. The differences are significant. In practice, the coal seam characteristics and underground environmental parameters of the target working face can be reproduced in the laboratory, the coal oxidation and heating process can be dynamically monitored, and the coal seam can be directly measured. This eliminates parameter deviations from the source, providing a precise foundation for subsequent design.

[0061] Preferred safety correction factor related to coal seam mining method There is a negative correlation between the amount of residual coal and the amount of air leakage in the goaf caused by on-site mining, meaning that the greater the amount of residual coal and the amount of air leakage in the goaf caused by on-site mining, the lower the safety factor. The smaller the phase should be.

[0062] The core risk sources of spontaneous combustion in coal pillars are "residual coal + air leakage," and the intensity of these two factors directly determines the risk level of spontaneous combustion: The more residual coal, the more coal can participate in oxidation, the faster the oxidation heat generation rate, and the shorter the critical time for spontaneous combustion; the greater the air leakage, the more abundant the oxygen supply, the more intense the oxidation reaction, and the faster the spontaneous combustion process. The "negative correlation rule" mentioned here is essentially... It is inversely linked to the "risk source intensity": the stronger the risk source, i.e., more residual coal + greater air leakage, the more effective it is in mitigating risks. The encrypted filling of the isolation chamber directly strengthens the blocking effect in "high fuel + high oxygen supply" scenarios; the weaker the risk source, i.e., less residual coal and less air leakage, the more effective the blocking. Sparse filling isolation body, no need for excessive protection. This "the higher the risk, the more protection" precise match, more targeted than the traditional "no difference protection", to ensure that the filling isolation body is "not too much, just right to deal with the risk".

[0063] Application example The method proposed in the above embodiment is applied to the prevention of coal pillar spontaneous combustion in a certain coal mine.

[0064] A coal mine 2205 working face mining 3# coal seam, mining height is 3m, along the empty small coal pillar thickness is 3.0m, through the site measurement, the shortest spontaneous combustion period of working face mining coal seam is 35 days, the average width of the site measurement of coal spontaneous combustion oxidation zone in the air return side is 15m, the actual working face daily advance degree of coal mining working face is 1.0m / day.

[0065] S1. Verify process applicability According to the formula Verification, the verification result meets the construction premise.

[0066] S2. Determine key parameters based on engineering examples The air leakage of the working face is moderate, and the "dense shallow hole grouting" process is adopted. The safety correction coefficient related to the coal seam mining method is 0.75, and the safety correction coefficient is 0.8.

[0067] Core parameters of glue injection: the porosity value in the air leakage channel is 0.35, the glue injection surplus coefficient is 1.1, and the glue forming ratio of the gelling agent is 1.0 (gelling agent stone rate).

[0068] S2. Core parameter calculation The distance between the drill hole groups is calculated according to the formula The calculation result is 69.1m.

[0069] The volume of the filling isolation body is calculated according to the formula The calculation result is 324m 3 .

[0070] The glue injection amount of the gelling agent is calculated according to the formula The calculation result is 124.74m 3 , according to every group of drill holes is 4 drill holes, the single hole glue injection amount is 31.185m 3 .

[0071] S3. Preliminary preparation Air leakage channel positioning: through the beam tube monitoring system, lock the triangular air leakage area (oxygen concentration> 18%) in the small coal pillar 2m~3m.

[0072] Material preparation of gelling agent: put A component: B component: water = 1:1:4 into the blender, stirring time 3min-5min, control the slurry slump 180±20mm; wherein, A component adopts JDAQ-4 type inorganic filling and reinforcing material, B component adopts high water setting gel resistance agent.

[0073] S4. Drilling ZYWL-6000D type directional drilling machine is used to construct a group of drillings in the roadway of the recovery working face every 69.1m interval to the adjacent goaf. Among them, each group of drillings includes four drillings in square distribution.

[0074] Bore diameter: φ94mm opening, φ75mm final hole; angle: 25° with the horizontal plane, depth 8m needs to penetrate the coal pillar straight to the air leakage area.

[0075] Verification: using compressed air test pressure drop, the drilling is qualified.

[0076] S5. Glue injection Two grouting pumps are used, the pressure is 1.5MPa-2MPa; the single hole is injected with gelling agent for three times, each time interval is 5 minutes, and the pump is stopped after 31.185m³ is injected in total.

[0077] S6. Effect monitoring After the gelling agent is injected, the oxygen concentration difference between the two sides of the coal pillar is reduced from 4% to 0.5% in 24 hours; the coal body temperature is stable at 26℃-29℃ within 30 days.

[0078] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and does not limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application is included in the protection scope of the present application.

Claims

1. A method of preventing spontaneous combustion of a coal pillar in a coal pillar mining operation, characterised by, The application relates to a method for injecting a gelling agent into a triangular non-caving area through a borehole group to form a plurality of interval distributed filling isolation bodies in the triangular non-caving area; the triangular non-caving area is a triangular non-caving area in a strip shape along a small coal pillar in a goaf. Obtaining parameters, the parameters including the shortest spontaneous combustion period of the coal seam in the working face, the average width of the coal spontaneous combustion oxidation zone measured on the return air side, the actual daily advance degree of the coal mining face, and the small coal pillar thickness; determining the spacing between the groups of drilling holes based on the parameters ; Each interval of the drilling groups is formed by drilling in the mining direction of the mining face and in the roadway of the mining face The adjacent goaf is drilled to form a plurality of groups of drilling holes which are spaced apart. The ratio of the thickness of the filling isolation body to the thickness of the small coal pillar ranges from 3.8 to 4.2:

1.

2. A method of preventing spontaneous combustion of a coal pillar in a coal pillar mining operation as claimed in claim 1 wherein, the spacing between the drill hole sets L is determined according to the following formula; ; wherein, represents the interval between the drill hole groups; represents the shortest spontaneous combustion period of the coal seam in the working face; represents the average width of the coal spontaneous combustion oxidation zone measured on the air inlet and outlet sides of the goaf; represents the actual daily advance rate of the coal mining face; represents the small coal pillar thickness; , , all represent safety correction factors; represents the comprehensive amplification factor.

3. A method of preventing spontaneous combustion of a coal pillar in a coal pillar mining operation as claimed in claim 1 wherein, The thickness of the small coal pillar ranges from 5m to 10m.

4. A method of preventing spontaneous combustion of a coal pillar in a coal pillar mining operation as claimed in claim 3 wherein, The ratio of the width of the filling isolation body to the thickness of the filling isolation body ranges from 1:1.8 to 1:2.2, and the ratio of the height of the filling isolation body to the mining height ranges from 1:1.4 to 1:1.

8.

5. A method of preventing spontaneous combustion of a coal pillar in a coal pillar mining operation as claimed in claim 3 wherein, The volume of the filling isolation body is determined according to the following formula:

6. A method of preventing spontaneous combustion of a coal pillar in a coal pillar mining operation as claimed in claim 5 wherein, The glue injection amount of each filling isolation body is determined according to the following formula: wherein, V represents the volume of the filled spacer; h represents the small pillar thickness; H represents the mining height.

7. A method of preventing spontaneous combustion of a coal pillar in a coal pillar mining operation as claimed in claim 6 wherein, ​ ; wherein, represents the glue injection amount of each filling spacer; represents the porosity value of the air leakage channel inner hole; represents the surplus coefficient; represents the gelation proportion of the gelling agent; represents the small coal column thickness; represents the mining height.

8. A method of preventing spontaneous combustion of a coal pillar in a coal pillar mining operation as claimed in claim 2 wherein, The actual daily advancing degree of the coal mining face , the shortest spontaneous combustion period of the coal seam mined by the coal mining face , the average width of the coal spontaneous combustion oxidation zone on the air inlet side and the air outlet side measured on site satisfies the following formula; 。 9. A method of preventing spontaneous combustion of a coal pillar in a coal pillar mining operation as claimed in claim 2 wherein, The working face mines the coal seam with the shortest spontaneous combustion period Determined by physical simulation experiment of coal spontaneous combustion.

10. A method of preventing spontaneous combustion of a coal pillar in a coal pillar mining operation as claimed in claim 2 wherein, The safety correction factor related to the coal seam mining method There is a negative correlation between the amount of residual coal and the amount of air leakage caused by on-site mining.

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