Abstract：Based on some triple-line large-span tunnels under complicated geological condition in Neijiang－Kunming railway，the theoretical analysis，numerical simulation and field survey are used to analyse surrounding rock deformation characteristics and structure stability. Consequently，rational construction methods and assistant construction methods are determinated. After comparing different construction projects，optimal initial shoring modes and parameters are proposed in practice. On the base of analyzing the stability characteristics of rock pile body，accordingly，the construction technique，proof-caving and consolidation measure are established，and satisfactory effect obtained in engineering practice.
