ABSTRACT
Conventional excavation for tunnels requires the determination of each round length in consideration of the ground condition, support capacity, construction cost and time, etc. (Baudendistel 1997). Presently most of the decisions in the design and construction stage are based on personal experience. Although the round length has a considerable influence on the stability of excavation and construction cost, most of research has focused on the stability of face itself and the influence of round length has not been thoroughly investigated.
