Geotechnical and geophysical evaluation and remediation of hill road failure: a case study

Purpose The purpose of this study is to investigate the possible causes of slope failure along the Gudalur to Nilambur State Highway (SH-28) in Kerala, India, and to propose effective mitigation measures for restoring the highway to a trafficable condition. Design/methodology/approach Field and laboratory investigations were conducted as per standard methodology including site reconnaissance, geophysical surveys, borehole drilling and soil characterization. Based on the result, slope stability analysis was carried out to assess the causative factors. Systematic forensic analysis approach was adopted considering the field engineers and policymakers to mitigate the similar landslide geohazard-prone area. Findings The slope failure was primarily attributed to excessive rainfall leading to water accumulation in an unlined uphill pond, causing seepage through deep vertical cracks. This resulted in slope instability and road deformation. The study proposed a combination of mitigation measures, including gabion walls with soil nails, a breast wall and an enhanced drainage system to stabilize the slope and prevent future failures. Research limitations/implications The study was limited to typical highway section, and variations in geological and hydrological conditions limited its application. Future research should explore long-term monitoring of implemented measures and assess their effectiveness under extreme weather conditions for general application. Originality/value Paper specifically deals the geophysical, geotechnical and laboratory investigations with slope stability analysis to determine failure causes and propose targeted mitigation strategies. The findings are valuable for practice engineers, researchers and policymakers to mitigate the landslide for road infrastructure.