Abstract: The load sharing ratio of gravity anchor pier foundation of Xiushan bridge is complicated as the foundation is separated from anchor block. In this article, a 3-D finite difference model of the interaction among anchorage, pile foundation of support pier, and ground is established to research the load sharing ratios and failure modes of different parts of the anchorage system of Xiushan bridge. The simulation load increases by 0.5P (P is the design cable load) until limit state appears. Results reveal that when cable load is between 1P and 2P, the load sharing ratio of anchor block bottom, rock mass in front of anchor block, support pier foundation, and anchor block side is 64%, 23%, 6%, 7%, respectively; when cable load reaches 2.5P, tensile failure of rock on the bottom of anchor block appears due to non-uniform shear force on the interface between anchor and rock. The limit cable load of support pier foundation is 3.5P, approximated to uniaxial compressive failure. As load increases continuously, the contact surface of anchor block bottom gradually detaches, and the horizontal load moves toward the rock mass in front
of anchor block. The research achievements offer reference for the structural design, foundation reinforcement, and limit bearing capacity of gravity anchorage system.

Key words: Xiushan bridge, gravity anchor, pile foundation of support pier, load sharing ratio, bearing capacity