Twin tunnelling caused distortions and its effect on a hospital building on mixed ground conditions

An extensive geotechnical assessment of a hospital building under-crossed by twin tunnels is presented in this paper. The case study considered in the study is Phase III of Delhi Metro Gray line, which has been built recently using Tunnel Boring Machine. Finite element analysis was carried out to simulate the construction of two tunnels underneath the building, and the soil is simulated using an advanced constitutive model. The numerical model was validated against the field monitoring data, and the effect of tunnelling on the building deformation is also studied. Also, the comparison of building settlements with greenfield conditions is carried out. The study showed that the building influences the pattern of the settlement trough. Quantitative study of the settlement showed that there was no undue distress to the building due to the construction of twin tunnels, suggesting the safe crossing of twin tunnel below hospital building.