Abstract: The bearing capacity of conventional prestressed anchor cable in largespan tunnel is always insufficient. As a result, the methods for improving the bearing capacity of prestressed anchor cable are studied by theoretical analysis and field test; and the methods of increasing anchor joint and high pressure grouting are proposed. The research results show that: (1) The main factors affecting the bearing capacity of prestressed anchor cable are the pullout bearing capacity of grouting body and reinforcement body in anchoring section and that between grouting body and strata. (2) By increasing anchor joint and adopting high pressure grouting technology, the bearing capacity of prestressed anchor cable can be improved significantly, the construction period can be shortened, the construction cost can be reduced, and the cable tension can meet the design requirements with high technoeconomic benefit.

Key words: largespan tunnel, prestressed anchor cable, pullout resistance, field test