161 Dynamics of Natural and Built Environments

Our communities, economies and infrastructure depend on interactions between the natural and built environments. Engineered systems (e.g. earthworks, structures, utilities) must be resilient to evolving natural forcings, and similarly engineered systems must also minimize negative effects on the natural environment.

Tuesday, 21 October 2025
8:00 AM - 12:00 PM
HBGCC, 214A

Geotechnical and Groundwater Assessment for Helipad Construction on Southwestern Nigerian Coastline

Paper number: 161-12
Program: Technical Sessions
Time: 11:00 AM – 11:15 AM

Authors

Abstract

Coastal environments in southwestern Nigeria present significant geotechnical challenges for infrastructure development, particularly for helipads. The problem arises from the inherent characteristics of coastal soils due to their high water content, low shear strength, significant settlement potential, and high groundwater tables, which collectively threaten the long-term stability and durability of engineering constructions. This study aims to evaluate the suitability of these coastal soils for helipad foundations designs and construction through a detailed engineering geologic investigation. The objectives include characterizing the geotechnical properties of the subsurface soils, analyzing the groundwater conditions, and providing information for foundation design and material selection. To achieve these aims, field investigations involving soil sampling and borehole drilling were done, including laboratory testing to determine key geotechnical parameters such as water content, density, plasticity index, and shear strength (friction angle). Groundwater samples were also collected and analyzed for chloride content and total dissolved solids (TDS). The results revealed a wide range in soil properties: water content (20.50% - 80.50%), density (1.50 - 3.05 g/cm³), and plasticity index (12.50% - 35.50%). Shear strength, indicated by friction angles, varied considerably (4.9° - 25.50°). Groundwater analysis showed elevated chloride levels (335.00 - 355.00 mg/L) and high TDS concentrations (up to 22,806 mg/L), suggesting a corrosive environment. Based on these findings, the study concludes that shallow foundations are unsuitable due to the weak nature of the near-surface soils. Pile foundations are recommended to transfer structural loads to deeper, more competent strata. Furthermore, the use of corrosion-resistant materials is crucial to mitigate the aggressive effects of the groundwater. This investigation highlights the critical need for thorough engineering geologic assessments to ensure the safe and durable construction of infrastructure in challenging coastal environments. Keywords: Corrosion risk, foundation, soil density, water content and settlement potentials.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412031

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