A Proposed Method of Coal Pillar Design, Goaf Filling, and Grouting of Steeply Inclined Coal Seams Under Water-Filled Strata

Abstract

The key to safely and efficiently mining steeply inclined coal seams under water-filled strata is to size barrier pillars appropriately and to control the structural integrity of the roof. We propose a method for goaf filling and grouting of steeply inclined coal seams and for appropriately sizing barrier and sectional coal pillars for mining in such conditions. Through theoretical analysis, an expression for a reasonable barrier pillar size was derived, based on the time span of mining, the hydraulic characteristics of the coal seam, the permeability characteristic of the grout in the goaf, and the water pressure. Based on the degree of saturation of the overlying strata and the mining conditions of the steeply inclined no. 48 coal seam of the Longhu mine in Qitaihe, China, we determined through theoretical analysis that the barrier pillar should be 80 m, the width of the sectional coal pillar should be 15 m, the length of the goaf filling should be 80 m, and the grouting length should be 40 m, to ensure safe production in that mine without geotechnical failures or injuries. These recommendations are being implemented.