Kolkata Metro Rail Corporation
Online published on 5 October, 2017.
Twin tunnels of Kolkata East West Metro Corridor passes below the river Hooghly at a depth of approximately 13 m below river bed. The 5.55 m internal diameter tunnels with RCC segmental liner has been constructed using Earth pressure balancing tunnel boring machines. This is the first transportation tunnel project in India under any mighty river. The river crossing width is 520 m and the depth of water at average tide is about 13 m. This ambitious initiative involved meticulous planning of the alignment and investigation as well as proper choice of tunneling method. The field instrumentation and monitoring of tunneling parameters were well orchestrated through an organized protocol. Sufficient and full proof precautionary measures were taken before launching of the TBMs inside the river. The parameters achieved during this uninterrupted successful tunneling without any requirement of intervention below the river is compared with desirable parameters. This paper covers the following:
Geomorphology of Kolkata, Geotechnical investigation, hydrological data collection & its impact on alignment of the tunnel under river
Details of Tunneling below the river
Water proofing of tunnel
Precautions taken during tunneling below river.
Comparison of theoretical and actual tunneling parameters.
