Deformation and failure of floor in mine with soft coal, soft floor, hard roof and varying thicknesses of coal seam

Abstract

In this study, the characteristics of the deformation and failure of the mine floor and the influence of the thickness of the mined seam on mine floor deformation are examined in the context of a mine with soft coal, soft mine floor, hard mine roof and varying thickness of the coal seam. The geological and mining conditions at the Working Face 23,301 of the Yungaishan No. 2 Coal Mine are taken into consideration when using the strain induction method to determine the depth of the failure zone which is found to be between 11.6 and 15.5 m based on strain measurements at different depths of the mine floor. The strain increments show that the distance before periodic weighting occurs is between 13.3 and 14.2 m, which is basically in agreement with the observed ground pressure from mining. On this basis, the geological profile of the working face is used in the development of a 3D numerical model. This numerical model is used to determine the depth of the failure zone which is at a depth of about 15 m, which is basically in agreement with the field measurements. It is found that the failure of the floor has obvious zonation. At the same time, the effect of different thicknesses of the mined coal seams on the degree of deformation of the mine floor is discussed with the other conditions unchanged. The results show that the thickness of the mined seam has little effect. That is also consistent with the results of multivariate regression equations and correlation analysis which show that the depth of the failure zone is less impact correlated with the thickness of the mined seam based on 65 sets of measurements of the depth of the failure zone. The research findings are an important practical reference source for preventing water inrush through the mine floor, and determining support strategies for mines.