Working Face Of Mine Research Articles

Spontaneous combustion of coal in regenerated roof and its prevention technology

The dangerous zone of spontaneous combustion of coal in regenerated roof cannot be directly identified and the air leakage law is not clear, which makes it difficult to take effective control measures. Aiming at these problems, taking the 5304 working face of Zhoujing coal mine as the research object, the law of air leakage and the law of oxygen concentration change were studied and the dangerous zone of coal spontaneous combustion in the regenerated roof was delineated through experimental test and numerical simulation. The law of temperature rose in the dangerous zone was further analyzed. The hidden danger of spontaneous combustion was eliminated by using composite spraying materials and water injection. The results showed that when the temperature rose to 80℃, the coal sample of 5304 working face started to oxidize rapidly. The air leakage velocity and oxygen concentration of were directly affected by the ventilation rate in the regenerated roof. By superimposing the oxidation zone of air leakage velocity and the oxidation zone of oxygen concentration, the dangerous zone of coal spontaneous combustion was delineated and it was known that reducing air leakage can effectively eliminate the dangerous zone of coal spontaneous combustion. Composite spraying materials were used for the wall of the return airway and water was injected into the dangerous zone of coal spontaneous combustion, the roadway surface temperature and backwater temperature were reduced to 28.5℃ and 30.3℃ respectively. The oxygen concentration was reduced to 3.8–6.2%.

Modeling Approaches to Permeability of Coal Based on a Variable-Order Fractional Derivative

In the past decades, many permeability models have been proposed to characterize the coal permeability evolution in the elastic state. Considering that the coal near the mining working face is often in the plastic or post-peak failure state, it is significant to characterize the coal permeability evolution in the plastic and post-peak failure stages for safe mining. In this study, two permeability models are developed using a variable-order fractional derivative to characterize the coal permeability evolution during the whole process of elastic, plastic, and post-peak failure stages. The results indicate that both models have the ability to better describe the coal permeability evolution during the whole process in areas near the mining working face. In addition, the physical and mechanical interpretation of the variable-order function is given as an indicator of fracture development, indicating the sensitivity of stress variation to coal fracture development. Moreover, the relationships among the effective stress, damage variable, and post-peak permeability of coal are discussed.

Research on the dynamic evolution law of fissures in shallow-buried and short-distance coal seam mining in Lijiahao Coal Mine

Aiming at the problem of spontaneous combustion of coal relics caused by the overburden fracture network penetrating the upper and lower coal seams in the process of shallow-buried and short-distance coal seam mining, the 31114 working face of Lijiahao coal mine was used as the research background to study the characteristics of overburden transport and fracture development in shallow-buried and short-distance coal seam mining by using physical similar simulation test; the fractal dimension and image processing techniques were used to quantify the overburden fractures; the classical mechanical models of "solid support beam" and "masonry beam" were combined to analyze the causes of fracture dynamic evolution. The results show that: (1) Before the key seam fracture, the stress in the upper rock seam only changes in a small amount, and the stress in the lower rock seam evolves similarly to the single coal seam mining; when the key seam fracture is broken, the stress in the upper and lower rock seams will change by jumps. (2) The fractal dimension of the fissures rised from 1.4 to 1.5, the total area of fissures is increased from 16,638 pixels to 17,707 pixels, and the total length is increased from 2217 to 3071 pixels; after the main key layer of the overlying rock is broken, the fractal dimension of the fissures is reduced from 1.56 to 1.5, and the total area of fissures is reduced from 31,451 pixels to 29,089 pixels, the total length has increased from 5657 to 6619 pixels. (3) Before the key layer between the coal seams is broken, it will be suspended to form a "fixed beam". After the first break, the broken rock above it will settle synchronously until the rock blocks form a hinged structure and then collapse. After the fall stops, the key layer periodically breaks to form a "masonry beam" structure, and the overlying stratum settles synchronously.

Reasonable Support Technology of Full-Stress Anchoring Technology of Advance Roadway: A Case Study

Based on the engineering background of providing advance support for the working face of mining roadways, this paper studies the reasonable support technology of advance roadway roofs by combining theoretical analysis, numerical simulation, and field tests. Based on the geological conditions of the 1304 working face of Yineng Coal Mine, the FLAC3D numerical simulation software was used to compare and analyze the effects of the original single hydraulic prop advance support and the bolt-mesh-cable support without the single hydraulic prop. The results show that although the deformation of the surrounding rock is reduced under the support of the single hydraulic prop, the convergence of the roof and floor of the roadway and the left and right sides are still as high as 288 mm and 308 mm, respectively, which does not meet the requirements for safe production. Based on this problem, this study proposes full-stress anchoring technology. FLAC3D numerical simulation software is used to simulate and analyze the supporting effect of the full-stress anchoring support technology in advanced mining roadways. The results of numerical simulation experiments show that the convergence of the roof and floor and the convergence of the left and right sides of the roadway surrounding rock are 33 mm and 52 mm, respectively, which have a good control effect on the roadway surrounding rock. The field test of bolt full-stress anchoring support technology was carried out in the return air roadway of the 1304 working face. The deformation of the surrounding rock of the roadway was monitored by setting up stations. The measured results show that the maximum roof and floor convergence of the roadway is 42 mm, and the maximum convergence of the two sides of the roadway is 69 mm, which meets the requirements for safe mining on site. In this study, by comparing with the advance support effect of the original single hydraulic prop, the rationality of the full-stress anchoring technology of the mining roadway in the advance section of the working panel is determined. The use of bolt full-stress anchoring instead of the traditional single hydraulic prop for advanced support has a better surrounding rock control effect and a lower support cost. This is a new technology for advanced support of surrounding rock in mining roadways, which enriches the control technology of roadway surrounding rock and also provides technical reference for other similar engineering cases.

Support Control Design of Mining Roadway under Goaf of Close-Distance Coal Seam

Coal resources have always been the focus of attention in the field of sustainable development. Based on the problem of surrounding rock control in close-distance coal seams, first, a mechanical model of floor failure was established based on the 29204 working face in Dongqu Mine; the failure mechanism of the floor was revealed by the zero displacement line, and a method to judge the occurrence state of the roof in the lower coal seam was put forward. Furthermore, by FLAC3D numerical simulation software, the mechanical model is verified, and the optimal support parameters are optimized, and the optimal water–cement ratio and grouting pressure are determined to be 0.6 and 3 MPa respectively. The application shows that the roof displacement is reduced by about 73.48% compared with the control group. Compared with the control group, the cable stress decreased by about 50.68%, and the application effect is remarkable. The research results provide an effective solution to ensure the sustainable development of coal resources and disaster prevention.

Experimental Study on the Properties of Gas Diffusion in Various Rank Coals under Positive Pressure.

A kind of closed mining and nonventilation working face is proposed, which provides a possibility for eliminating coal mine accidents and extracting high-purity gas. During mining, a confined space above normal pressure is formed in the face. Geological conditions cause significant differences in the physicochemical properties of coal and affect the occurrence and migration of gas in coal seams. The pore structures of five coal samples were obtained by mercury injection and low-temperature nitrogen adsorption. The self-made positive pressure desorption experimental device was used to conduct isothermal desorption experiments under different environmental pressures. An extended Langmuir model was proposed to carry out regression analysis on the curve of positive pressure desorption with time. The effect of coal pore structure on gas diffusion properties was discussed. The results indicate that the development degree of micropores in coal determines the amount of gas adsorption. With the increase of coal rank, both the ultimate desorption quantity and desorption rate first decrease and then increase. The positive pressure enhances the concentration of methane outside the coal and inhibits methane diffusion. With an increase of positive pressure, the desorption capacity of the high-rank ZG was significantly inhibited, and the desorption limit and initial desorption rate decreased by 15.80-44.54 and 16.92-47.93%, respectively. The diffusion coefficient of the middle-rank XS has the greatest decrease rate of 1.56-18.05%. The pore structure of coal is the essential reason that affects methane diffusion.

Simulation of narrow coal pillar width in gob-side entry driving

Numerical simulation of coal pillars with different widths in goaf excavation at 1102 working face of Huacaoan Coal Mine is carried out to study the influence of different widths of coal pillars on the stability of surrounding rock in goaf excavation. Finally, the width of coal pillars is determined to be 5m, which ensures the safety of roadway excavation, improves the utilization rate of coal extraction and responds to the call of green mining.

Evolution law of mining-induced overburden stratum stress and fracture fields in inclined coal seam

Purpose This study aims to clarify the evolution law of stress field and fracture field during the mining process of inclined coal seam, to prevent the occurrence of roof burst water and impact ground pressure accident during the advancing process of working face. Design/methodology/approach The evolution law of stress-fracture field under different mining conditions of inclined coal seam was studied by using discrete element method and similar material simulation method. Findings The overburden stress at the lower end of the coal seam was mainly transmitted to the deep rock mass on the left side, and the overburden stress at the upper end was mainly transmitted to the floor direction. With the increase of the inclined length of the mining coal seam, the development of the fracture zone gradually evolves from the “irregular arch” form to the “transversely developed trapezoid” form. The development range of the fracture zone was always in the internal area of the stress concentration shell. Originality/value An original element of this paper is based on the condition that the dip angle of coal seam is 35°, and the evolution law of overburden stress-fracture field during the excavation of coal seam with different lengths was analyzed by UDEC numerical simulation software. The coupling relationship between stress shell and fracture field was proposed, and the development range of fracture zone was determined by stress. The value of this paper is to provide technical support and practical basis for the safety production of a mine working face.

Multiple regression method for working face mining pressure prediction based on hydraulic support monitoring dataset

Introduction: In the coal mining process, the intense mining pressure is an important factor hindering the safe and efficient production of the working face. In severe cases, it causes deformations in roadways such as roof breakages and rockbursts, and leads to instability. This can result in the roof falling over a large area and the coal wall, thereby inducing dynamic disasters. These aspects have restricted the economic benefits of coal.Methods: In this study, we set four model limitations based on the limited scope of action of the mining pressure itself and the quantitative relationships between mining pressures in different regions. A multiple linear regression model with these limitations is proposed for predicting the mining pressure for preventing roof breakages and rockbursts. Based on a hydraulic support monitoring dataset from a fully mechanized caving face of coal mining, the mining pressure prediction model is trained by using the first 70% of the dataset. And the linear regression coefficient of the model and the predicted value of the mining pressure are obtained. Then, the last 30% of the dataset was used for the validation of the model.Results: The research results show that the constrained multiple linear regression model can achieve remarkable prediction results. According to predictions of tens of thousands of on-site mining pressure datasets, the predicted data and actual pressure data have the same change trend and maintain a low relative error.Discussion: Therefore, after real-time mining pressure monitoring, the system obtains the roof pressure of the fully mechanized mining face. According to the dataset, the proposed prediction model algorithm quickly predicts the roof pressure value of the next mining section and effectively forewarns roof breakages and other accidents.

Air Leakage Law and Prevention Technology of Coal Spontaneous Combustion in the Goaf of “Isolated Island” Fully Mechanized Caving Face

ABSTRACT The coal pillar along the goaf of the completely mechanized caving face of “Isolated Island” is severely damaged, with complex air leakage and a high risk of coal spontaneous combustion. In order to research the law of goaf air leakage in “Isolated Island” working face and effectively control the hidden threat of coal spontaneous combustion in goaf, it is necessary to investigate the goaf air leakage law. In this work, the 3302 “Isolated Island” entirely mechanized caving face of Jining No. 2 Coal Mine in Shandong province, China, served as an example. SF6 tracer gas air leakage measurement was utilized to identify the air leaking route in the goaf. In conjunction with the numerical modeling, the air leakage route surrounding the goaf was evaluated to establish the coal spontaneous combustion risk region, and the targeted prevention and controlled ways of coal spontaneous combustion were proposed. The results indicated that the primary source of air leakage was the seepage of air flow through the working face to the rear goaf and the diffusion to the adjacent goaf through the broken coal pillar. The risk area for coal spontaneous combustion was 40–80 m behind the rear goaf and 50 m within the coal pillar of the adjacent goaf. Regarding this region, the comprehensive prevention and control strategies of plugging and oxygen reduction, inerting and cooling, monitoring and forecasting were proposed. In addition, the fire prevention and extinguishing system combining slurry spraying, sodium silicate, and liquid CO2 injection was designed at both ends of the 3302 track and haulage roads. Using field measurements during the working face mining process, the corresponding methods for reducing the CO volume fraction in 3302 return air roadway and air return corner effectively prevented and controlled the hidden danger of coal spontaneous combustion in the goaf and ensured the safety of working face mining. This research developed a new technology for the prevention and management of coal spontaneous combustion in the goaf of the “Isolated Island” working face.

Retracement Ground Pressure Appearance and Control of the Working Face under the Overlying Residual Pillar: A Case Study

On the working face below shallow and close coal seams, there are residual pillars. The mine’s ability to operate safely is constrained by the coal pillars’ vulnerability to sudden instability and powerful ground pressure disasters during withdrawal. This paper uses the 31,106 working face of the Huoluowan coal mine as its research backdrop and employs field observation, theoretical analysis, and numerical simulation to examine the strong dynamic load mechanism of the overlying coal pillars. According to the analysis, the residual pillar’s stress diffusion angle is 29 degrees after mining the working face above it, which has an impact on the main roof’s stability above the working face’s retracement roadway. The main roof is impacted by the excavation disturbance and the remaining pillars during the working face’s final mining phase, displaying a complex stress superposition state. The retracement roadway is significantly deformed as a result of the plastic zone of the surrounding rock changing from small-scale damage to extensive damage. The proposed “hydraulic roof cutting + reinforcement support” prevention technology is based on the prevention idea of weakening important rock strata, changing the stress transmission path, and strengthening adjacent rock. Field testing shows how hydraulic fracturing reinforces the roof structure, lessens the heavy dynamic load on the supporting pillars of overlying residual coal, reduces rock deformation in the retracement roadway, and ensures the stability of the working face during withdrawal. The study’s findings are significant for the secure removal of a working face under similar circumstances.

Surrounding rock activity law and support optimization of double flexible formwork wall gob-side entry retention in stratified mining coal seams

To ensure gas control in the layered mining of extra-thick coal seams in Baijigou Coal Mine—in addition to reducing the loss of coal resources and amount of roadway driving—this article proposes the gob-side entry retention technology of flexible formwork concrete, and retains the 010202 working face four-layered return air roadway as the 010203 working face gas drainage lane. By combining theory and field practice, a flexible formwork concrete wall + anchor cable joint support scheme is proposed to strengthen small coal pillars. Further, the design scheme for the aforementioned framework at the bottom of the layered mining region of an extra-thick coal seam is proposed. Then, field tests are carried out, and the surrounding rock activity law of the double flexible formwork wall entry retention in a layered mining coal seam is obtained. The results show that (i) 010202 the whole process of overburden collapse to stability at the stratified mining face is completed 60--200 m behind the face and (ii) the roadway deformation of the extra-thick coal seam in the Baijigou Coal mine can be divided into four stages, and the mining pressure of the gas drainage roadway basically presents a dynamic change of “pressurized stage – peak stage – stabilized pressure stage”. Based on this, three mechanical stages of roadway deformation are derived: (1) δz< Nmz<< Nwz; (2) Nmz < δz << Nwz; and (3) Nmz < δz< Nwz. Three repeated mining support optimization schemes are provided, one for each stage. Finally, the deformation and damage of the surrounding rock are effectively controlled, and the requirement that the gas drainage roadway is still intact under the influence of the 010203 working face mining is realized. This study has certain reference significance for gob-side entry retention in the bottom layer of stratified mining in extra-thick coal seams.

Study on Source Identification of Mixed Gas Emission and Law of Gas Emission Based on Isotope Method

It is of great significance to obtain the source of mixed gas emission from the working face and the law of gas emission from each coal seam for the targeted implementation of gas control measures. Based on the principle that the hydrocarbon isotope values of gas in different coal seams have significant variability, a hydrocarbon isotope method for identifying the source of gas emission is proposed. Taking Pingmei No. 6 Coal Mine as the study area, the distribution characteristics of each value were obtained by testing the values of carbon and hydrogen isotopes in the gas of mined coal seams and adjacent coal seams; by testing the hydrocarbon isotope value of CH4 in the mixed gas of coal seam, the proportion of gas emission in each coal seam is determined and the law of gas emission in each coal seam is studied. The results show that the variation law of the proportion of gas emission in each coal seam can be divided into three stages: the dominant stage of gas emission in the mining layer (stage I), the stage of gas emission in the long-distance adjacent coal seam (stage II), and the dynamic equilibrium stage of gas emission in each coal seam (stage III). In the process of working face mining, the amount of gas emission in the mining layer remains in a small fluctuation state, and the proportion of gas emission decreases rapidly in stage I and stage II, and remains stable in stage III; the amount of gas emission and the proportion of gas emission in adjacent coal seams increase rapidly in stage I and stage II, and remain stable in stage III; the mixed gas emission of the working face increases rapidly in stage I and stage II, and remains stable in stage III. The calculation formula of the gas emission rate of the adjacent coal seam is established; during the development of the height of the mining fractured zone, the gas emission rate of the adjacent coal seam increases exponentially, and the gas emission ratio and gas emission amount of the adjacent coal seam increase; after the height of mining fracture zone tends to be stable, the gas emission rate, the proportion of gas emission, and the amount of gas emission remain of adjacent coal seams remain in a small fluctuation state.

Study on the failure law of surrounding rock in inclined coal seam with gob side entry

Aiming at the problem of stability control of surrounding rock in the process of upward mining of inclined coal seam gob-side entry retaining, the gob-side entry retaining of 5449 working face in Beipingdong coal mine is taken as the research background. Based on the study of theoretical model of gob-side entry retaining, the law of overburden movement and surrounding rock deformation in the process of gob-side entry retaining is obtained through similar simulation experiment and numerical simulation analysis, and the optimal optimization scheme of supporting structure is put forward. The main research results are as follows: in the process of coal seam mining, the center of gravity of the overlying strata on the whole working face will shift to the side of the goaf, and the supporting structure composed of roadside filling body and bolt effectively inhibits the deformation of the roadway, in which the roadside filling body plays a key role; the top bolt bears greater stress than the side bolt in the process of mining, so the top bolt mainly maintains the stability of the roadway, and the side bolt plays the role of strengthening the side and preventing the extrusion. The width of the roadside filling body should be about 2.5 m, and the plastic failure range can be well controlled under this width.

Stability mechanism and control technology of large inclined working face roof in large-scale caving area

Abstract Based on the compound roof in the 211 112 working face of mine no. 2 in the Xinji area and various newly emerging geological conditions such as crack development in coal seams and major slopes, the roof of the severely sloped working face was studied focusing on the stress, strain and fracture features, along with the mechanism of rib spalling in the coal wall and the grouting strengthening technology. According to the analysis, the pre-loaded pressure on the working face tended to be redistributed with the development of the coal roof caving zone, which resulted in new stress concentration in the coal wall before the caving zone. Compared with the stress before rib spalling, stress decreased with the increased depth of rib spalling, which caused a slightly lower risk of rib spalling. Based on the analysis, an inorganic grouting reinforcement with a water-solid ratio of 3:1 was adopted to meet the needs of filling-body strength, which reduced operation time and increased economic benefits. The work ensures the safe and efficient mining of the composite roof face with a large inclination angle of Xinji No. 2 Mine and offers a reference for the mining coal seams under similar conditions.

Influence of Coal Mining on Historical Buildings: Case Study in Shanxi

Numerous historical buildings exist in Shanxi Province, a major coal producing area in China, so there exist many overlapping areas between ancient wooden buildings and coal mining. Coal mining in overlapping areas will lead to surface subsidence, which will have an impact on historical buildings. Based on the distribution of historical buildings and the distribution and mining of coal resources in Shanxi Province, this paper concludes that the overlapping areas of coal mining and ancient wooden buildings in Shanxi Province are mainly concentrated in Changzhi City, and the Lu'an mining area in Changzhi City is selected as the research object. In addition, using the gray correlation analysis method, the surface subsidence coefficient, which characterizes the intensity of mining subsidence, is used as the reference sequence. Seven factors selected from the geological conditions and mining conditions of the Lu'an mining area are used as the comparison sequence to calculate the gray correlation between each influencing factor and the surface subsidence coefficient, and to obtain that geological factors such as the nature of the overlying rock layer, bedrock thickness and dip angle of the coal seam, and mining factors such as mining height, average mining depth and working face size largely determine the surface subsidence coefficient. The surface subsidence in the overlap area could largely be influenced by geological factors such as the nature of the overlying rock layer, bedrock thickness and coal seam inclination, and mining factors such as mining height, average mining depth and working face size. Finally, we investigate the possible effects of surface subsidence on ancient wooden buildings in the overlapping area with the surface subsidence and formation mechanism and propose technical measures to reduce the effects of surface subsidence due to coal mining on historical buildings in the overlapping area.

Research on Water-Conducting Fractured Zone Height under the Condition of Large Mining Height in Yushen Mining Area, China

Abstract Accurately predicting the development height of the water-conducting fracture zone (HW) is imperative for safe mining in coal mines, in addition to the protection of water resources and the environment. At present, there are relatively few fine-scale zoning studies that specifically focus on predicting the HW under high-intensity mining conditions in western China. In view of this, this paper takes the Yushen mining area as an example, studies the relationship between the water-conducting fissure zone and coal seam mining height, coal seam mining depth, hard rock scale factor, and working face slope length, finally proposing a method to determine the development height of the HW based on multiple nonlinear regression models optimized using the entropy weight method (EWM-MNR). To compare the reliability of this model, random forest regression (RFR) and support vector machine regression (SVR) models were constructed for prediction. The findings of this study showed that the results of the EWM-MNR model were in better agreement with the measured values. Finally, the model was used to accurately predict the development height of the hydraulic conductivity fracture zone in the 112201 working face of the Xiaobaodang coal mine. The research results provide a theoretical reference for water damage control and mine ecological protection in the Yushen mine and other similar high-intensity mining areas.

Law of strata pressure behavior of surrounding rock in nearby goaf roadway for extra-thick coal seams of Datong mine area

The nearby goaf road in the extra-thick coal seam of the Datong mining area exhibits intense strata pressure behavior, which affects the working face mining. Herein, we study the laws of the strata pressure behavior of this road in detail using various methods, including laboratory tests, theoretical analyses, numerical simulation, and field monitoring. Considering the mine pressure characteristics of the nearby goaf road, namely, roof cracking, two-side deformation, and floor heaving, the mechanical tests and theoretical failure analyses of the surrounding rock in the mining-induced non-uniform stress field were carried out. The circular-oval-butterfly failure trend of the surrounding rock in the nearby goaf road under the influence of mining was obtained. The steady failure evolution lateral pressure coefficient (λ=0.5∼1.8) and butterfly mutation lateral pressure coefficient (λ<0.35 or λ>2.1) of the surrounding rock in the nearby goaf road were analyzed. We performed numerical simulation to study the stress field and the plastic zone shape-size characteristics of the surrounding rock during excavation and mining (with or without the top extraction road), and the theoretical law of the mine pressure was obtained for the Tong Xin coal mine. Finally, field monitoring indicates that the mine pressure behavior of the nearby goaf road exhibits spatial differences, namely, the difference between the stresses of the two sides and roof, and the stress characteristics of the deep and shallow surrounding rock. The findings of this study on the mine pressure behavior in the nearby goaf road have great practical significance for targeted measures to control the surrounding rock stability.

Hazardous Area Reconstruction and Law Analysis of Coal Spontaneous Combustion and Gas Coupling Disasters in Goaf Based on DEM-CFD.

Coal spontaneous combustion and gas coupling disasters are the highest percentage of serious accidents in coal mines, causing the most serious disasters. China is one of the countries with the most serious coal spontaneous combustion and gas coupling disasters in goaf, and it is of great significance to explore the evolution law of coal spontaneous combustion and gas coupling disasters in goaf for disaster prevention and control. To study the three-dimensional spatial characteristics of the hazardous area of the coupling coal spontaneous combustion and gas disaster in goaf, a discrete element method-computational fluid dynamics (DEM-CFD)-based hazardous area reconstruction method was proposed. Taking a fully mechanized caving face of a coal mine in Shandong, China, as an example, first, the working face mining model was established by PFC3D, and the porosity of different horizontal and vertical positions of goaf after mining was extracted. Second, the porosity extracted was imported into computational fluid simulation software FLUENT by UDF. Finally, the distribution laws of oxygen and gas concentration during the real goaf mining process were simulated and analyzed. The results showed that the oxygen concentration in the intake roadway at a depth of 50.7 m in goaf decreased to 12%, and the gas concentration at a depth of 42.0 m in goaf increased to 16%. The oxygen concentration in the return airway roadway was reduced to 12% at 17.3 m depth in goaf, and the gas concentration increased to 16% at 6 m in the direction of goaf. The gas concentration was higher at the return air corner. The three-dimensional shapes of the hazardous area in goaf were constructed to satisfy the coupling of O2 concentration field, CH4 explosion limit concentration field, and fracture field and so were the laws of hazardous area analyzed qualitatively and quantitatively. It has important research significance for the rapid identification and determination of the coal spontaneous combustion and gas coupling disasters hazardous area.

Overburden and surface subsidence with slicing paste filling mining in thick coal seams

To overcome the difficulties of overburden failure and surface subsidence induced by the slicing mining of extra-thick coal seams, slicing filler paste is typically utilized. In this paper, a continuous curved beam mechanical model of paste filling mining was established by theoretical analysis against the background of the 3305 working face of Yangcheng Coal Mine, the main controlling factors of surface subsidence were analyzed using an orthogonal experiment method (OEM) and an analytic network process (ANP) coupled comprehensive assignment, and the vertical displacement distribution of the overlying rock under different filling intensity was simulated using numerical simulation software. The following main findings were obtained. First, the elastic modulus of the backfill is the primary regulating factor, as demonstrated by the results. Second, the greater the filling body’s elastic modulus, the more efficiently it carries the overburden load and minimizes the maximum surface subsidence. Third, the distance from the open-cut mine likewise reflects the degree of surface subsidence, with the amount of subsidence increasing as the distance from the mine increases.