Failure analysis and control measures of deep roadway with composite roof: a case study

There is great variation in the lithology and lamination thickness of composite roof in coal-measure strata; thus, the roof is prone to delamination and falling, and it is difficult to control the surrounding rock when developing roadway in such rock strata. In deep mining, the stress environment of surrounding rock is complex, and the mechanical response of the rock mass is different from that of the shallow rock mass. For composite-roof roadway excavated in deep rock mass, the key to safe and efficient production of the mine is ensuring the stability of the roadway. The present paper obtains typical failure characteristics and deformation and failure mechanisms of composite-roof roadway with a buried depth of 650 m at Zhaozhuang Coal Mine (Shanxi Province, China). On the basis of determining a reasonable cross-section shape of the roadway and according to the failure characteristics of the composite roof in different regions, the roof is divided into an unstable layer, metastable layer, and stable layer. The controlled unstable layer and metastable layer are regarded as a small structure while the stable layer is regarded as a large structure. A superimposed coupling support technology of large and small structures with a multi-level prestressed bearing arch formed by strong rebar bolts and highly prestressed cable bolts is put forward. The support technology provides good application results in the field. The study thus provides theoretical support and technical guidance for ground control under similar geological conditions.