Forensic Geotechnical Evaluation of Challenges in Constructing the Flood Protection Infrastructure (Wall) at Kadana Powerhouse, Gujarat, India

Abstract

This paper presents a forensic geotechnical evaluation of the construction challenges and long-term stability of a 34-meter-high flood protection (FP) infrastructure (wall) at the Kadana Powerhouse, Gujarat, India, built within a geologically complex terrain. Following a critical design shift from underground draft tube tunnels to a cut-and-cover system necessitated by construction delays and adverse rock mass conditions previously confined slopes were exposed, revealing weak fault and foliation planes dipping unfavorably toward the excavation face. Emergency stabilization measures, including pre-stressed anchors and Perfo-bolts, were deployed to arrest progressive instability during construction. Nearly four decades later, a back-analysis incorporating 2D stability modeling, based on historical performance data was conducted to evaluate the long-term efficacy of these interventions. The analysis confirmed a notable improvement in the Factor of Safety (FOS) from 1.099 to 1.578 for sliding and from 3.053 to 4.048 for overturning, validating the adequacy of the original design response. The novelty of this study lies in its integration of retrospective analysis and performance monitoring to assess legacy infrastructure a rarely documented forensic geotechnical case of FP wall from India. The findings underscore the importance of integrating geological insight with adaptive engineering during both the design and construction phases and offer valuable guidance for future infrastructure development in weak or structurally disturbed rock masses.