Abstract: A tunnel in Sanya City will align through a broken quartz fault. The excavation in tunnel indicates that surrounding rock in the fault is completely weathered and it has a poor stability property. The mud rush and severe deformation at the arch were encountered during the excavation and the original construction procedures could not be safely implemented. Based on the comparison of the construction supporting method, the following comprehensive technique is selected to control the deformation of tunnel: grouting with double grouts, middlesized pipe roof presupport and sixpart CRD excavation method with independent closure strong supporting structure in time. Threedimensional numerical method is performed to analyze the deformation of tunnel and the stress of the initial supporting structure and lining. The field monitoring result and construction effects have shown that the selected construction scheme can ensure the tunnel excavation safety.

Key words: Completely Weathered Materials, Fractured Fault, Highway Tunnels, 3D FEM, CRD Cutting Method