Structural mapping of coastal plain sands using engineering geophysical technique: Lagos Nigeria case study

摘要

An engineering geological survey using the cone penetrometer and finite element method was carried out to characterize sand-fill thick- nesses in a reclaimed area of Lagos, SW Nigeria. A previously developed finite element program was modified in order to allow for predicting the sand-fill thicknesses, and have an unders- tanding of the geomorphic shallow structures existing pre-sand-fill. The program was tested using the obtained cone penetrometer test re-sults from the Lekki-Peninsula area. The finite element predicted thicknesses show good cor-relation with the penetrometer obtained thicknesses. Six zones with thick sand-fill thick-nesses varying from 1.25 to 6.0m were identified from the isopach maps, these zones correlate with major/minor depression associated with river/stream channels and creeks. These are the main shallow geomorphic structural features present in the area pre-sand fill. The structural trends of the depressions are largely influenced by the oceanic fracture pattern.