Integrated Geotechnical and Geomorphological Implication of Urbanization on Slope Stability in the Vicinity of GRA Hills Nsukka Southeastern Nigeria

This study evaluates the impact of indiscriminate construction on slope stability in Nsukka, Enugu State, Nigeria, through geotechnical analysis and slope stability simulations. Ten soil samples were collected and tested for grain size, Atterberg limits, compaction, shear strength, and permeability. The results showed that the soils were composed of 13.29–20.41% gravel, 67.61–89.61% sand, and 6.00–12.17% fines, indicating sandy soil with medium plasticity (liquid limit: 30.5–38.6%, plasticity index: 11.9–16.2%). Compaction tests revealed an optimum moisture content of 1.64–1.75 kg/m³ and maximum dry density of 13.1–16.5%, suggesting moderate water retention and low compaction. The shear strength tests indicated weak soils with cohesion values between 10.3–16 kPa and internal friction angles ranging from 23° to 31°, prone to shear failure. Permeability results ranged from 1.79 × 10⁻⁵ to 2.95 × 10⁻⁴ m/s, indicating poor to moderate drainage capacity. Slope stability analysis revealed potential slide masses of 45.93–130.63 m³ and 44.93–132.63 m³ under unsaturated and saturated conditions, respectively. The factor of safety ranged from 0.80 to 1.30 (unsaturated) and 0.77 to 1.26 (saturated), indicating areas of instability with values < 1. Principal component analysis identified key geotechnical factors as the main contributors to slope failure. Satellite imagery analysis from 2010 to 2022 highlighted significant urbanization, which has exacerbated slope instability. The study concludes that anthropogenic activities, particularly unplanned construction, are the primary cause of landslides in Nsukka. It recommends better urban planning, improved construction practices, and slope stabilization measures to reduce future landslide risks.