Multi-Parameters Approach to Assessment of Soil Liquefaction Vulnerability in Wetland Areas of Lagos, Southwestern, Nigeria

Abstract

Abstract The liquefaction potentials of coastal sands in the Lagos metropolis was investigated in this study using geotechnical and geophysical methods. The study aims to reveal the possible causes of failures in engineering structures around the coastal areas. To achieve this objective, the Seismic Multichannel Analysis of Surface Waves, Cone Penetrometer Test and Standard Penetration Test were used to carry out measurements of soils parameters at three different sites, which were used to characterize the geological units in the areas. The results of the MASW measurements showed that the shear waves velocity (Vs) ranges from 160 and 470 m/s. The very loose to loose sand delineated had Vs in the range from 170–250 m/s. The tip resistance and sleeve resistance values spanned between 4.0–72.0 kg/cm2 and 6.0–94 kg/cm2 respectively. The depth of the liquefiable sands in the study area varied between 2.5 to 18.0 m. At Ikoyi, owing to the prevalence of loose silty sand, corroborated by borehole data and the LPI index, it is classified as having a high-risk liquefaction and could be responsible for the tremendous damages on structural infrastructures. The sediments mapped at Okun-Ajah and Badore sites were mainly saturated loose sand with high likelihood to liquefaction. Hence, the severity was classified as very-high to high risk. The study concludes that the presence of these sediments and other factors that could induce ground motion making the study sites potentially susceptible to liquefaction. Hence, an urgent attention must be given to early monitoring measures to address the trend.