Abstract：Bifurcated tunnel is one of the new type tunnels，the excavation way and support style are key factors to the rock stability. A case study of Miaoya bifurcated tunnel is given；based on the character of large-span shallow part of bifurcated structure，the contents，technique，and method of monitoring in large-span shallow section are presented. Based on the measured data，such as the ground settlement，rock deformation，bolt axial force，concrete ling stress and so on，the deformation and stress properties of surrounding rocks and supporting system are analyzed；in addition to the blasting dynamic characteristics of ground vibration for the serious blasting damage of shallow ground vibration，the in-time information is applied to guide tunnel construction and optimize the supporting system，and monitoring results are discussed in detail. The study provides indispensable evidence for the design and construction of the bifurcated tunnel.
