Wetting-Induced Collapse Characteristics of Silty Sand Matrix from the Kodari Landslide, Nepal
DOI:
https://doi.org/10.64862/Keywords:
Wetting-induced collapse, Collapse potential, Silty sand matrix, Landslide debris, Nepal HimalayaAbstract
Wetting-induced collapse is a critical but largely unexplored mechanism in slope stability analysis in Nepal. Highways frequently experience rainfall-induced slope failures, yet the role of collapse behavior in these failures remains poorly understood. This study investigates the wetting-induced collapse behavior of the silty sand matrix derived from surface deposits of the Kodari Landslide along the Araniko Highway, Sindhupalchok, Nepal. The landslide-affected zone consists of heterogeneous, highly permeable materials ranging from silty sand (SM) to well-graded gravel (GW), with SM as the dominant soil type, exhibiting high apparent strength under dry conditions but undergoing volumetric collapse and rapid strength reduction during intense rainfall. One-dimensional consolidation and wetting-induced collapse tests were conducted on four representative samples of the reconstituted matrix fraction (<2 mm). Consolidation results indicated an overconsolidated state (OCR ~7.0–9.5), likely linked to desiccation-induced suction in addition to past loading history. Collapse potential ranged from 0.25–1.40% under natural moisture conditions and increased to 7.88% under air-dried conditions, with fines content also appearing to influence collapse sensitivity. These findings suggest that wetting-induced collapse may act as a potential contributing factor to landslide initiation at Kodari, requiring further investigation, while emphasizing the importance of effective drainage for reducing slope-failure risk.
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