Abstract: A method of designing the support parameters of pipe roof is proposed to ensure the safe construction of tunnel in fault fracture zone and the stability of surrounding rock of working face. First, the pipe roof is divided into several segments of which one part is taken as effective calculation length. The load of loose fractured rock mass on the pipe roof is calculated based on Terzaghi's theory. The bending moment, deflection, and end-reaction are obtained by simplifying the pipe roof into a beam with both ends fixed and supported. Furthermore, the calculation formulae for the support parameters of pipe roof are derived according to the failure conditions of rock mass and pipe roof. The method is applied to a tunnel in fault zone which has undergone several collapses of working face due to only small duct bracing. The results of the proposed method indicate that small duct bracing is inadequate, while pipe roof support could generate smaller convergence deformation during excavation. The research findings offer reference for the design of support parameters of pipe roof in tunnels constructed in fault zones.

Key words: tunnel, fault fracture zone, pipe roof, parameter design, tunnel face stability