Abstract:Concept of limit displacements of primary support system of railway tunnel are presented,and the method for determining the limit displacements is introduced systematically. The continuum model is adopted,and the cross section pattern and the material properties are used according to the design standard for railway tunnel lining. The limit displacements of the primary support system of railway tunnels are simulated and calculated for the tunnels of different depths in surrounding rocks of different classification. The calculation results are further treated in a statistical manner and compared with the allowable displacements. The limit displacements for single track tunnels and for double track tunnels are discriminated. Criteria are established respectively for crown settlement,horizontal convergence at arch springer and at wall foot. The depth ranges in the original codes are adopted,and the displacement range values are determined by combining the two sets of limit values. A series of limit displacement data are finally determined synthetically,which are consistent with the current displacement criterion for railway tunnel stability.