Abstract：Diversion tunnel is a new type tunnel structure. There is not any technical standard of design and construction for the diversion tunnel at present. A large-scale diversion tunnel of highway under construction is studied through the 3D geomechanical model test method in order to understand stress and deformation situations of surrounding rock mass of the diversion tunnel under excavation state. The changing laws of stress and displacement around the tunnel and the failure mechanism for the surrounding rock mass of tunnel have been effectively revealed after test. The design and limit load-bearing safety reliability for the diversion tunnel have also been achieved. According to results of the model test，some useful suggestions and conclusions for the optimization design and construction of the diversion tunnel have been proposed.
