Tunnel-Induced Ground Settlement: A Case Study Showing the Importance of Dynamic Analysis

The implementation of Smart City Missions in India has been instrumental in enhancing urban infrastructure, including transportation and communication networks, primarily in densely populated and highly urbanized cities such as Delhi, Mumbai, Bengaluru, Hyderabad, and Kolkata. In the near future, situations will arise where underground tunneling work will be necessary in many parts of the country. In this context, an incident is mentioned here which took place in Kolkata in 2019 during such tunneling work. As a fall out of this incidence, several houses collapsed and many more were severely damaged. This happened due to the ground movements, which had occurred during tunneling work for the undergoing metro project. This incident highlights the need for effective analysis of tunnel-induced ground settlement before as well as after the construction. In this manuscript, a holistic approach is made to investigate the 2019 Kolkata tunneling incident by means of numerical and analytical methods. Tunnel-induced ground settlement is obtained by means of numerical static and dynamic analyses using PLAXIS 2D. Total vertical settlement (U_y), surface settlement (U_{y (z=0)}), and surface lateral displacement (U_{x (z=0)}) obtained from the numerical static analysis have been compared with the analytical results to validate the PLAXIS 2D finite element model (FEM). These settlement values are used for the damage assessment of the existing superstructures, based on the critical tensile strain ( \({\varepsilon }_{\text{crit}}\) ${\epsilon }_{\text{crit}}$ ) and tilt ( \(\delta )\) $\delta )$ of the superstructure. The results obtained from the dynamic analysis are 87 to 287% more than the static numerical analysis, as incorporating TBM wheel rotation into the analysis further enhances the reliability of the approach. This suggests that by incorporating dynamic analysis into the design process, engineers can mitigate the risks of ground settlement and ensure the overall safety of the public.