EFFECTS OF TUNNELING ON SURROUNDING STRUCTURES

Abstract

Urban tunneling projects in India have expanded rapidly to support metro and regional transit systems; however, tunneling-induced ground deformations continue to pose critical risks to adjacent structures. This thesis develops and applies an integrated analytical–numerical framework for building risk assessment, focusing on the Delhi Meerut Regional Rapid Transit System (RRTS). Ground deformations were obtained by numerical simulation using PLAXIS 2D under greenfield conditions and validated against established empirical–analytical methods, before being transferred to building’s foundation through the Limiting Tensile Strain Method (LTSM). The research combined systematic numerical modelling, strain-based structural evaluation, and parametric investigations to quantify the effects of tunnel, soil, and structure parameters, with additional emphasis on seismic loading. The baseline numerical model reproduced typical settlement troughs consistent with field behavior, confirming its reliability for Indian soil conditions. Parametric analyses revealed that settlement magnitude and structure response are strongly influenced by tunnel geometry, cover depth, and soil stiffness. Softer ground conditions and larger tunnel dimensions generally resulted in higher ground deformations, while stiffer soils and deeper covers reduced the magnitude of ground movements. Structural characteristics also played a key role in the observed damage outcomes: masonry buildings are more vulnerable to strain concentrations, as compared to framed one. Building damage classification based on LTSM indicated that most structures under baseline conditions fell within slight to moderate categories. However, when seismic loading was introduced, risks increased considerably. Both masonry and framed buildings experienced amplified strains and angular distortions under earthquake conditions, often leading to a shift into higher damage categories. The analysis confirmed that seismic effects represent a critical dimension that is often overlooked in tunneling risk assessments in India. The integrated methodology demonstrated in this research advances beyond traditional greenfield-based assessments by explicitly linking tunneling-induced ground deformations with structural response measures. Key contributions include: (i) development of validated PLAXIS 2D models for Delhi soil conditions; (ii) systematic understanding of the role of tunnel, soil, and structure parameters in influencing building response; (iii) incorporation of seismic scenarios into tunneling-related building risk assessments; and (iv) practical insights for improving safety margins in urban tunneling projects. The results emphasize that damage risk can be effectively reduced through careful design choices such as optimizing tunnel depth, maintaining adequate construction control (i.e. Volume loss), and considering both geotechnical and structural vulnerability during the planning stage. Overall, this thesis establishes a qualitative, transferable framework for Building Risk Assessment (BRA) in Indian tunneling projects. It provides engineers and policymakers with a reliable decision-support tool to ensure safer underground construction in densely populated environments. The findings hold direct applicability for metro, RRTS, and other large-scale tunneling projects in Indian urban regions, underscoring the importance of integrated geotechnical–structural evaluation for sustainable infrastructure development.