Comparative Analysis of the Effect of Circular and Horseshoe Underground Tunnel Shapes on the Required Support Pressure in the General Geological Context of Kandy City

Rapidly expanding cities like Kandy in Sri Lanka frequently encounter obstacles linked to traffic congestion, sustainability concerns, and constraints on infrastructure expansion when it comes to urban development. Subway systems can be proposed as a sustainable remedy to tackle these issues. This research employs a multidisciplinary approach, encompassing geotechnical engineering, environmental science, urban planning, and transportation engineering methods to explore the correlation between the required support pressure to maintain the structural integrity of the tunnel shapes of circular and horseshoe in the general geological context of Kandy city with PLAXIS-3D. At this point, Tunnel Boring Machine (TBM) and New Austrian Tunneling Method (NATM) are used to investigate these circular and horseshoe-shaped tunnel designs respectively. In the field of underground construction, PLAXIS-3D software can be called a successful tool for its ability to simulate complex soil-structure interactions. The data collected geologically for this purpose includes information on soil types, groundwater levels, soil properties, and other relevant material and equipment parameters. Then using finite element analysis software PLAXIS-3D, the detailed 3D models of the common geological strata of Kandy city were constructed to facilitate the tunnel geometry, stress and deformation analysis, visual representation, and to run the tunnel performance analysis. Based on stress distribution and deformation pattern analysis of these 3D models, it was possible to evaluate how tunnel shapes affect the surrounding soil and subsurface environment. Circular and horseshoe-shaped tunnels exhibit distinct support pressure patterns and stress distributions, affecting structural responses and displacement values in Plaxis-3D analysis under fed Kandy geological context. Finally, these findings contribute to optimizing the design and construction of appropriate tunnel shapes by exploring the correlation between the required support pressure based on tunnel shapes as an effective solution to promote sustainable development of Kandy city, improving the safety and cost-effectiveness of underground infrastructure projects.