In this study, for the rapid transit of urban and metropolitan railways, the installation of passing loop tunnel in the underground section of urban railroads in operation is reviewed. Unlike road tunnels, it is difficult to secure working spaces because the railwau tunnel is very narrow, impossible to bypass, and related facilities such as overhead wire exist. In addition, urban railways have limitations that must be carried out without blocking the existing trains or construction within four hours when the trains are not running. Therefore, in this study, the construction plan of passing loop tunnel during railway operation for the rapid transit was reviewed.

Recently, Seismic design criteria for major domestic structures has been being improved constantly, because the importance of seismic design for major public infrastructures is largely recognized. A preliminary assessment of the seismic performance for the existing rapid-transit railway tunnel, a precedent task before conducting a detailed assessment, can be use as the standard of judgement to decide whether to perform a detailed assessment or not. On the other hand, There are no reasonable study in this area. In this study, an assessment method was presented to evaluate a seismic performance of the existing rapid-transit railway tunnels which seismic design are not performed more economically and rationally.