It appears evident that, along with the increase of n0, the whole scope of roof failure tend to rise, both the widths and height at failure included. Likewise, the parameter R presents the similar change rule of n0. Specifically, the collapsing dimensions are positive to the magnitude of R. Accordingly, the shape of potential collapsing blocks can be described with corresponding parameters, while it is not plotted here for the sake of simplification and the change rule is analogical in circular tunnels.