ABSTRACT
Demand on tunneling through soft ground has been increasing in parallel to urbanization, since most of the urban areas are on soft ground and most of the infrastructure systems are constructed in shallow depths where soft grounds/soils below underground water are dominant. Very weak and weathered rocks are also considered as soft ground in addition to soils. Therefore, the most important tunneling problems arise in stability of the excavated environment such as roof or face collapse and surface settlement. Accordingly, the shielded and face pressurized soft ground tunnel boring machines (TBMs) have been developed to minimize the stability and safety problems for the last 3-4 decades (Maidl et al. 1996).
