Influence of composite roof structure on the stability of coal roadway

The composite roof structure of coal roadway is rather complex. Its stability is related to lithology, thickness of strata, number of strata, location of strata and cohesive force between layers. Based on mechanics theory of simplified composite roof composite beams, a simplified mechanical test model of composite beams was established, and the effects of the structural characteristics of composite roof on the stability of composite beams were analyzed by experiments. The purpose is to provide a scientific basis for the classification and control of composite roof stability. The results show that the stability of the roof increases with the increase of the lithology, the increase of the thickness of the hard rock, the decrease of the distance between the hard and thick layers and the strengthening of the interlayer bonding force when the thickness of the composite roof of the coal roadway is certain, but it reduce with the manifold of the number of layers, until the number of layers is more than four layers, and the stability of roof is affected by the number of layers. The influence of variation is small, and the influence degree of its influence factors from large to small is:lithology > rock thickness > layer > rock location > interlayer cohesive force. Compared with other rock formations, the weak thin interlayer with lower strength and small thickness is more prone to produce stress concentration anterior to other damages of layers.