Study on Width Optimization of Sectional Coal Pillar for Fully Mechanized Coal Mining Face in Shallow Depth Mine

In order to reduce the width of the sectional pillar in the coal mining section of the mining block and to improve the coal mining recovery rate of the mining block,a site observation method was applied to analyze two mining operations of the up and low coal mining faces when the sectional coal pillar with a width of 20 m.Under the dynamic pressure role,the max roof displacement of the gateway was 56 mm and the convergence between the two sidewalls of the gateway was 45 mm.In order to further reduce the coal pillar width of the gateway,under the conduction of the previous support mode unchanged,a rational coal pillar width was optimized and determined.The numerical calculation method was applied to simulate the deformation features of the gateway with different width coal pillars.The calculation showed that the gateway with a coal pillar width of 12 m could be kept in stable.The project practices showed that the subsidence of the roof during the driving and mining period was 112 mm in total and the convergence between the two sidewalls was 106 mm in total.The deformation of the gateway could be controlled within the allowed scope and the coal pillar could be in stable to meet the requirements of the mine safety production.There were about 70 000 t additional coal mined recovered from the coal pillars.