Planning of Alignment & Proposed Actions for Tunnel Collapse in Diverse Ground Conditions on the Steepest Railway Curves in the Eastern Ghats, India

In 1960, the Indian Railway successfully completed the Kothavalasa–Kirandaul (KK) BG line, East Coast Railway (ECoR) primarily built to transport iron ore. Currently, ECoR is planning for doubling line (a new railway line parallel to existing one) in Kothavalasa–Kirandul line section. This 445 km long railway line has more than 58 existing tunnels and 45 tunnels are proposed for second line. The existing railway line passes through one of the steepest vertical gradients of 1 in 60 (uncompensated) upto (8 Degree Curve). This region is thinly populated and has dense forests. Proposed line is planned to increase freight capacity of the section. RITES Limited was assigned the task of conducting the feasibility study, preparing Detailed Project Reports (DPR) and further was awarded with Project management consultancy (PMC) for tunnel construction for the Kothavalasa–Kirandul line section. This paper focuses on a specific 51 km segment between Boddavara-Karakavalasa section of KK line (Andhra Pradesh), which includes methodology, challenges, and recommendations for planning project with similar conditions.

Furthermore, a detailed case study of Cavity formation during tunnel construction in adjacent section ie. Jarati-Malliguda of KK Line in which RITES is PMC for Railways is discussed highlighting unexpected geological conditions that were not initially anticipated during the feasibility stage and how they were treated. The study becomes crucial as the region lies in intense rainfall frequency zone ie.175 days a year that could further potentially impact the nearby construction activities being held at site.