Behaviour of tunnel and surrounding strata using 3Dec numerical modelling: Case study of an U/G metro rail project

Abstract

Tunnel serves various purposes including transportation. A case study of an underground metro rail project involving considerable length of the tunnel was taken up for this study. This paper presents the analysis carried out for a stretch of 350m long tunnel being constructed for an underground metro. Modeling was carried out at seven different cross sections of tunnel, using 3DEC software, incorporating the strata characteristics. Study was carried out for the stability of tunnel with and without support. Observations were made about the behaviour of tunnel under given conditions for Vertical Stress, Vertical Displacement, at points like crown of tunnel and at the surface. Minute displacement of 0.05mm was observed particularly at the chainage where the tunnel is completely passing strong rock at Chainage 9345m. Tunnel is passing through Moderately Weathered Rock at Chainage 9295m, and the analysis resulted in a displacement of 4mm without support which has reduced to 0.5mm after placing the lining. Higher displacements were observed at chainages where the tunnel is passing through Silty sand, Highly Weathered Rock and Sandy Silt. Displacement at the tunnel crown increased to 18.6mm where the tunnel is passing through Silty sand (Chainage 9495m). 2012 CAFET-INNOVA TECHNICAL SOCIETY.