ABSTRACT
The 10.3km of underground tunnels is being constructed as part of Chennai Metro Rail Phase II Project, which provided an opportunity to evaluate volume loss and trough width parameters in the region’s distinct geological conditions. The Project is using Earth Pressure Balanced Tunnel Boring Machines to bore through various geological formations, such as silty sand, clayey soils and weathered charnockite rocks etc. As the tunnel is being built, the ground settlement mainly happens due to volume loss associated with tunnelling. However, there is limited published data on the actual volume loss experienced during tunnelling in geological formations encountered in Chennai. Ground settlement markers and other instruments have been strategically placed along the tunneling route to track ground response. This study uses PLAXIS 2D to determine volume loss by fitting PLAXIS 2D-simulated settlements with the measured data obtained from settlement markers. Further, empirical Gaussian curve is fitted to the measured settlement to determine the trough width parameter. The findings could provide valuable insights for future tunnelling projects in comparable geological conditions.
