Due to the flat arched structure usually adopted in singlearch fourlane highway tunnels, the distribution of the

secondary stresses in the surrounding rock mass after tunnel excavation is nonuniform and the reinforcement effect of the primary

reinforcement elements is poor. In order to study the mechanical characteristics of the primary reinforcement elements under

different construction methods, the dynamic construction processes of singlearch fourlane highway tunnels in different

surrounding rock mass are simulated by finite difference software FLAC3D and the stress and displacement characteristics of the

primary reinforcement elements under different construction methods are obtained. By comparing these mechanical characteristics,

construction methods under which the optimum reinforcement effect of the primary reinforcement elements can be reached are proposed.