Analysis of Arching Mechanism and Evolution Characteristics of Tunnel Pressure Arch

Key and difficult problems are the arching mechanism and the evolution characteristics of the pressure arch in the surrounding rock after the tunnel excavation. Regarding a practical engineering as background, the definition of pressure arch of a highway tunnel was given and the boundary parameters of the pressure arch were determined by using the combination methods of theoretical analysis and numerical calculation. Considering the size of the highway tunnel excavation, the strength variation of the surrounding rock, the stress state of the highway tunnel, the geometry of the pressure arch and its mechanical evolution characteristics were revealed. Then, the engineering mechanical models were built through fitting the pressure arch centroid lines, and the mechanical stability of the pressure arch and the instability failure modes were also analyzed. The results provide a theoretical basis for the construction and reinforcing design of highway tunnels.