Influence of deep excavation and foundation loading on the response of the existing tunnel in sand

The interaction between new construction activities and neighboring existing tunnels was analyzed through model testing and numerical analysis in cohesionless soil. The site conditions of the Delhi Metro were adopted for the present study. Model tests were conducted in Yamuna sand in dry and submerged conditions with variations in parameters like basement depth, number of storeys, groundwater level, and horizontal offset distance between the tunnel and the new construction area. The experimental results were measured at the crown, invert, and spring levels in the form of strains. The results obtained from the experimental tests were used to validate the numerical FEM analysis, and after the validation, a detailed numerical analysis was conducted using PLAXIS 2D with different parameters. Based on several parametric analyses, it can be concluded that the critical distance between the tunnel and footing is 2.5 times the tunnel diameter, after which there is no significant influence.