A combined initial support system of high in -situ stress and soft rock tunnel
After excavation, the surrounding rock of the high in-situ stress and soft rock tunnel will produce large deformation, resulting in the yield, crack, and even collapse of the initial support. This study was guided by the flexible support concept based on the energy principle, proposed a combined initial support system suitable for high in-situ stress and soft rock tunnel. The combined initial support system mainly includes radial dampers, circular dampers, steel arch, and shotcrete. The radial damper is arranged between the steel arch and surrounding rock and is mainly used to absorb the radial deformation of surrounding rock; The circular damper is installed on the steel arch directly and is mainly used to absorb the circular deformation of the steel arch. The structural parameters and mechanical properties of radial damper and circular damper were determined by laboratory tests. The combined initial support system has been applied in the Changping tunnel in China and achieved a good supporting effect. These findings can provide some technical references for similar projects.