Integrated Geotechnical and Groundwater Characterization, Static and Pseudo-Static Stability Analysis, and Evaluation of Proposed Mitigation Measures at the Kodari Landslide, Nepal

Abstract

Landslide instability along Himalayan highway corridors reflects interactions among geological conditions, groundwater, rainfall infiltration, slope geometry, and human modification. The Kodari landslide at chainage 113+000 of the Araniko Highway (NH34), Sindhupalchok, Nepal, repeatedly disrupts highway access and threatens infrastructure and cross-border connectivity. This study integrates engineering-geological mapping, geotechnical testing and drilling, electrical resistivity tomography (ERT), hydrogeological interpretation, and limit-equilibrium modelling for static and pseudo-static stability analysis. Investigations covered approximately 75,000 m², including two boreholes, 15 portable dynamic cone penetration tests, 12 infiltration tests, laboratory soil testing, and ERT profiles along and across the slope. Deposits comprise coarse gravel and boulder-mixed soil, with gravel content of 80.91–81.66% and fines of 1.87–2.05% in large-particle samples. Direct-shear tests indicate cohesion of 0.00–1.94 kPa and friction angles of 28.09–31.78°. ERT identifies saturated or water-bearing zones and localized comparatively competent materials. Proposed stabilization measures, including soil nails/rock bolts, earth anchors, vertical drainage wells, horizontal drains, and a mechanically stabilized earth (MSE) wall, increase the static factor of safety (FOS) to approximately 1.5. However, pseudo-static FOS remains 1.034–1.04 under a horizontal seismic coefficient of 0.2, indicating reduced stability under seismic loading. The result emphasizes groundwater management and further seismic verification for effective mitigation design.