ABSTRACT
Construction of a NATM tunnel in soft ground usually calls for a supplementary method or methods to secure the stability of its working face and minimize its effect on the structures on surface. Especially face bolts prevent collapse of the face and settlement of ground during excavation. Therefore, they are frequently used in soft ground. (Geofronte research Association, 2002). As the main characteristic, the face bolts are installed in the excavation area and cut off during excavation process. (Geofronte research Association, 2002). Geofronte research Association (2002) reported that the face bolts has been used with other supplementary methods in 84% tunnel construction sites out of 29 tunnels where the bolts are employed. The reason of this is thought that the vertical settlement, such as surface settlement, as well as the axial displacement of the face is needed to be controlled.
