Investigation for Influence of Pressure on Face Stability of Mega Tunnel

Abstract

Urbanization in Developing countries raise the demand of smart and efficient infrastructure facility. Due to faster growth rate, urban area meets many challenges like traffic congestion and thereby increased travel time. To cope with these, effective utilization of underground spaces is a need of time. Mega tunnel plays an important role to satisfy this need, as it is large diameter tunnel whose diameter is greater than 10 m. Mega Tunnel may facilitate with multi operating transport to prove its benefit for society. Tunnel excavation using Tunnel Boring Machine (TBM), is frequently performed to avoid surface traffic disturbance and to minimize construction time during project execution period. Face Stability of such type of tunnels has been emerging topic for researchers, as this issue get more critical with the increase in tunnel diameter. This increment of Critical cover to Diameter (C/D) ratio leads to increase in indirect construction cost. This paper focuses on the investigation of adequate pressures to be applied on Mega Tunnel to ascertain the ground induced settlement at various C/D ratios. Three-dimensional finite element analysis was performed by using Midas Gtx Nx software with different C/D ratios and pressure parameters for soft soil. Parametric study had been done on 15 m diameter tunnel. The conclusions were drawn based on 95 analytical models with five different cases. This study concluded that adequate application of pressure minimizes the C/D ratio to stabilize the face of Mega Tunnel, which can be proven to minimize the construction cost in practical use.