During tunneling in loose grounds, the ground deformation caused by drillings around the tunnel, leads to land subsidence and the adjacent tunnel which would affect tunnel structure and surrounding structures.
Umbrella Arch Method (UAM) or Forepole is a conventional and economical method in tunnel excavation and is in use to increase the excavation front sustainability, minimize the land subsidence, and prevent debris rocks falling, tunnel faces’ breaking and landslides.
In order to acquire tunnel face stability during excavation operations in areas with loose soil fault or areas with lack of adhesion, methods such as umbrella arch method; pre- holding methods must provide safety when drilling and must be affordable, economically. (Rostami et al., 2016).
