Study on the bearing characteristics of random lumpiness gangue from a gob roof

The bearing characteristics of random lumpiness gangue formed by rock fragmentation in gob roofs are important to ensure roadway stability in the new nonpillar mining approach. In this paper, the bearing characteristics of gangue are divided into bulking and compaction characteristics. Bulking characteristics mainly depend on the lumpiness and bulking coefficient of randomly lumpy gangue (K_RAFT). This paper proposes a method to invert K_RAFT of gangue samples with a small amount of lumpiness, and a random subset of 30% of an experimental sample of broken rocks is selected for analysis. The lumpiness distributions of the subset of samples and all the samples are normal, and the average lumpiness error of the subset is 0.54–2.86%. The ratio of average lumpiness to rock before breakage (K_ASB) is introduced as a parameter for analysis. The results show that K_ASB and K_RAFT have a log-normal functional relationship, and K_ASB can be used to infer K_RAFT from laboratory and field monitoring data. Compaction characteristics show that the relationship between K_RAFT and the supporting force of gangue (σ_GB) is a power function, and σ_GB in gangue during different stages of compression in a gob can be obtained from the value of K_RAFT obtained from experiments or field monitoring.