Field and numerical investigation on roof failure and fracture control of thick coal seam roadway

Compared with rock roof roadways, coal roof roadways are more sensitive to changes in the stress field due to excavation and mining. For thick-coal-roof roadways, the roof damage range usually exceeds the length of roof bolts, which brings security risks to roadway support. Taking the thickcoal-roof roadways as the study subject, the failure evolution of a thick coal roof under inefficient support was studied for two important geological conditions, namely the gob effect and variation in the coal roof thickness. The field investigation and numerical simulation were performed. The results showed three severely damaged areas from shallow to deep in the thick coal roof, namely a lower area, upper middle area, and coal-rock interface area. The failure of lower coal roof directly affected the stability of the entire thick coal roof. The residual abutment stress of adjacent gob aggravated damage to the lower coal roof. Roof subsidence and damaged area obviously increase with the thickening of coal roof. A critical failure height in the thick coal roof is found. An improved support was proposed adopting a thick anchorage structure and roof surface reinforcement for thick-coal-roof roadways. A field test showed that the coal roof surface of the roadway remained smooth and intact during excavation and mining period. The deformation of the roadway in mining period was reduced by 50%. The damage height of the thick coal roof was also reduced.