Abstract
In view of the fact that the face‐end roof fall under repeated mining of close‐distance coal seams seriously affects the normal production of the working face, this paper takes working face 17101 as the background, different influencing factors of face‐end roof caving exposed to repeated mining are analyzed through field observation of mine pressure data, different calculation schemes are obtained by using the orthogonal experiment, the subsidence of the face‐end roof is taken as the judgment index, UDEC simulation software is used to calculate the subsidence of the face‐end roof when different influencing factors change, and the application of SPSS statistical software is used for various parameters of multivariate linear regression analysis. The research results show that the influence degree of different factors from large to small is, respectively, mining height > tip‐to‐face distance > advancing speed > distance of coal seams > surrounding rock strength > support setting load. It is necessary to strengthen the coordination of all influencing factors and comprehensively control the stability of the face‐end roof exposed to repeated mining. Through the analysis of the regression model, it is found that there is no collinearity among the influencing factors, which has a significant influence on the regression equation and regression coefficient, and the multiple linear regression equation has a good fitting effect. The model can predict the stability of the face‐end roof exposed to repeated mining, which provides a basis for controlling the face‐end roof exposed to repeated mining.
Highlights
In the process of repeated mining of close-distance coal seams, the roof bearing capacity will be greatly reduced, and the roof area exposed in the mining process between the hydraulic support and the coal wall is easy to produce leakage, forming a large range of empty roof, known as faceend roof leaks, which pose a great threat to the safe mining of the working face. e stability of the face-end roof exposed to repeated mining has an important influence on the mining of the close-distance coal seams, which is one of the main factors restricting the safe and efficient mining of the close-distance coal seams
SPSS software performs the F-test on the model, and the significant value of 0.000b is less than 0.05, showing that mining height, tip-to-face distance, distance of coal seams, surrounding rock strength, support setting load, and advancing speed as a whole have a significant influence on the dependent variable, the subsidence of the face-end roof, the regression equation is significant, and there is a linear relationship, which is statistically significant, but it cannot reflect the effects of each independent variable on the overall strength. e statistical significance of the model does not mean that all the variables in the model are statistically significant, and the respective variables need to be further tested
(1) e orthogonality analysis of six factors of the stability of the face-end roof exposed to repeated mining is carried out by means of mathematical statistics, the subsidence of the face-end roof is taken as the test index, UDEC numerical simulation software is used to simulate 25 groups of orthogonal experiments, and the subsidence of the face-end roof is obtained when there are 6 influencing factors and 5 horizontal interactions, which overcomes the defect of neglecting the interaction of control factors in previous experiments
Summary
In the process of repeated mining of close-distance coal seams, the roof bearing capacity will be greatly reduced, and the roof area exposed in the mining process between the hydraulic support and the coal wall is easy to produce leakage, forming a large range of empty roof, known as faceend roof leaks, which pose a great threat to the safe mining of the working face. e stability of the face-end roof exposed to repeated mining has an important influence on the mining of the close-distance coal seams, which is one of the main factors restricting the safe and efficient mining of the close-distance coal seams. In view of different mining conditions, scholars have analyzed and studied the mechanism of roof caving and rib spalling exposed to repeated mining in close-distance coal seams from the aspects of overburden structure movement, supporting pressure distribution, and working face support parameters and obtained some research results [1, 2]. In order to analyze the basic situation of face-end roof caving, 5 measuring stations were evenly arranged along the fully mechanized mining face 17101, respectively, located at the supports of no. In order to determine the key influencing factors and degree of face-end roof leaks at the working face, it is necessary to further analyze and find out the correlation between them
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