Abstract:

Controlling the rock mass's state to relieve mine pressure on the haulage roadway in the longwallpressure zone is the most important and complex technological stage in the combination of supportand maintenance solutions for reusing the haulage roadway under non-pillar mining schemes.Directional roof-cutting blasting has been widely applied in China and the Russian Federation. Dueto the wide variability in physico-mechanical properties and structural characteristics of roof strata, itis difficult to form an ideal fracture surface (weakly connected surface) that allows the roof to caveand break as expected. In practice, combined methods are commonly employed: combining themethod of concentrated blasting to cut the rock face with the method of blasting to break up the rockmass; combining the method of directional hydraulic blasting with the method of blasting to break upthe rock mass. These approaches result in a very large volume of drilling and blasting work, especiallyin the case of mining thick seams accordingto the method by mining lower coal layer and cavingupper layer to retrieve coaland theroof rock is stable and unlikely to collapse. Based on theoreticalresearch and practical application of methods to weaken the rock mass, the authors propose atechnology for roof cutting using a combined hydraulic-directional blasting method applied to theconditions of mining thick seams and someexperimental results of the technology at the IV-9-17longwall haulage roadway of Ha Long Coal Company.