This paper introduces the successful experience of over roadway extraction in complex geology that has roof step,face roof collapse with cavity,passing through fault etc.

Using the initial post-buckling theory and the cusp catastrophic model,the bifurcation buckling mechanism and unstability of roof strata were studied to derive the formulae of the main roof breaking convergence during the first weighting,to build the criterion of step convergence after the main roof breaking and to determine the final step convergence value.

Energy consumption in different patterns of ascending and descending the stairs;