Study problems of building tunnels in Shemshak formation

Abstract:
      Shemshak and their equivalents are of the most widespread geological formations in Iran, which their outcrops are visible in Alborz, Central Iran and Sanandaj-Sirjan metamorphic belt. Because of this widespread extension, the construction of a great number of water conveyance tunnels, subways and road tunnels are under way in this formation. Although there are some differences in stratigraphic features of this formation in different parts of Iran, there are some main similarities in its engineering geological characteristics and geomechanical behavior. These similarities especially are visible in tunneling projects, which distinguish this formation from other ones. The scope of this paper is to categorize these characteristics and to study resultant problems in tunneling and then giving approaches to control them according to experiences obtained from some projects under construction in this formation.

General:
     Shemshak and their equivalents are of the most widespread geological formations in Iran, which their outcrops are visible in Alborz, Central Iran and Sanandaj-Sirjan metamorphic belt. Because of this widespread extension, the construction of a great number of water conveyance tunnels, subways and road tunnels are under way in this formation. Although there are some differences in stratigraphic features of this formation in different parts of Iran, there are some main similarities in its engineering geological characteristics and geomechanical behavior. These similarities especially are visible in tunneling projects, which distinguish this formation from other ones. The scope of this paper is to categorize these characteristics and to study resultant problems in tunneling and then giving approaches to control them according to experiences obtained from some projects under construction in this formation.