Hydrogeological Assessment of Hydraulic Conductivity on Gully Formation in Erosion Degraded Residual Soil of an Unstable Slope

• Published in: Indian Geotechnical Journal Vol. 52; no. 3; pp. 519 - 536
• Main Authors: Olabode, Oladunjoye Peter, San, Hwee Lim
• Format: Journal Article
• Language: English
• Published: New Delhi Springer India 2022; Springer Nature B.V
• Subjects: Engineering; Foundations; Friability; Geoengineering; Geology; Gullies; Gully erosion; Hydraulics; Hydrogeology; Instability; Landslides & mudslides; Original Paper; Particle size distribution; Pipes; Rain; Rain water; Rainfall; Residual soils; Size distribution; Slope stability; Soil; Soil degradation; Soil erosion; Soil pipe; Soil stability; Stability analysis; Urbanization; Hydraulic conductivity; Soil piping; Slope instability; Gully erosion; Hydrogeological assessment
• ISSN: 0971-9555; 2277-3347
• DOI: 10.1007/s40098-021-00585-w

Urbanization around the world has led to expansion and building of structures into slope areas that are prone to slope instability caused by gully erosion occasioned from soil piping due to poor drainage of rainwater and low cohesion of friable soils, which needs to be investigated. Hydrogeological assessment of empirically derived hydraulic conductivity (EDHC) from particle size distribution (PSD) analysis of eighteen (18) soil samples collected from residual soil of weathered granitic basement were calibrated with laboratory-determined hydraulic conductivity (LDHC). The results of the investigation revealed that soil pipes were initiated at 0.1–0.45 m depth and developed into gullies of > 2 m which leads to slope instability. Poorly graded soils with low EDHC values within 0.5 m depth were responsible for the initiation of soil pipes, growth and development into gullies during heavy rainfall that cause substantial loss of soil and create potential slope instability in the area. Assessed EDHC values showed that poorly graded soils have fairly medium–low hydraulic conductivity ranging from 5.028 × 10 –5 to 1.178 × 10 –4  m/s compared to the low hydraulic conductivity values of 4.06 × 10 –5 and 5.8 × 10 –5  m/s obtained for LDHC that were well calibrated with the results of the EDHC. Therefore, medium–low-hydraulic-conductivity soils were responsible for the development of gullies that create slope instability in the area.