No beded and fractured roof can be treated as an elastic continuous beam,when it consists of rock blocks formed by cross joints and fractures.In fact,it,as a mechan-ic structure , is an arch.

• 受采动裂隙和节理切割的层状破裂顶板不能视为弹性连续梁，其力学结构应为岩块相互挤压而成的压力拱。