Recently, the proportion of long tunnel has increased for efficient use of land due to limited land area, driving convenience and high speed. RMR and Q-System of empirical methods has been mainly used for tunnel support design in domestic. Although shotcrete is the key to NATM tunnel, the related studies are insufficient.
So, steel fiber reinforced shotcrete is applied to II∼V grade rocks on domestic and foreign applications. And same amount of shotcrete is equally applied to tunnel roof and wall regardless of the applied rock load. Shotcrete is applied excessively rather than the original proposed value of RMR and Q-System.
Thus, this study is to reevaluate the application part of plain shotcrete and steel fiber reinforced shotcrete of tunnel in Daebo granite, and to propose the reasonable application method of steel fiber reinforced shotcrete. Field test and numerical back analysis using measurements were performed to verify stability. According to results, if RMR values are the upper class in the III grade, it can be designed in accordance with upper grade.
In addition, if rock condition is good as a mountain tunnel in Daebo granite, it can be applied for plain shotcrete to III grade rocks because there is also no stability problems. And although steel fiber reinforced shotcrete is applied only crown of the tunnel in IV grade rocks, it is possible to secure stability for falling rock by key-block.