Low-Cost Landslide Mitigation Measures for Roadside Slopes: A Case Study of Jamunedanda, Pyuthan, Nepal

Abstract

Roadside landslides are a recurrent problem along mountain highways in Nepal, where weak geological materials, steep terrain, rainfall infiltration and concentrated runoff can interact to reduce slope stability. This paper presents a field-based case study of the Jamunedanda landslide at Ch. 27+800 of the Bhaluwang–Chakchake–Liwang–Darebot Road (NH-53), Pyuthan, Nepal. The investigation combined desk study, topographic survey, engineering-geological mapping, field geotechnical testing, laboratory testing, infiltration assessment and numerical slope-stability analysis. The site is characterized by highly weathered and fragmented black shale with colluvial and gravelly slope materials, erosional gullies, tension cracks and tilted trees. Laboratory results showed natural moisture contents of 4.88–14.88%, specific gravity of 2.64–2.74 and bulk density of 1.51–2.00 g/cm³, while grain-size analysis indicated predominantly SP, SW and GP-type materials. Preliminary PLAXIS 2D analysis indicated marginal natural-condition stability. The mitigation concept combines slope trimming, 12 m soil nails/anchors, gabion or masonry retaining structures, horizontal drains, check dams, surface drainage and bioengineering. The case demonstrates the value of combining structural reinforcement, water management and erosion control for stabilization of constrained Himalayan roadside slopes.