N soil exploration and foundations in the recent coastal areas of Nigeria

TLDR: In the coastal region of Nigeria consisting of meander belt, fresh water and backswamp deposits, mangrove swamps, beach ridge bars and estuaries are underlain by a complex stratigraphical succession of soft silty clay, sand and gravels.

Abstract: The sub-environnements in the coastal region of Nigeria consisting of meander belt, fresh water and backswamp deposits, mangrove swamps, beach ridge bars and estuaries are underlain by a complex stratigraphical succession of soft silty clay, sand and gravels. The unpredictable stratigraphical succession is complicated by the prevalence of soft and thinly bedded strata which are hardly detected during soil exploration. These thin soft beds introduce inaccuracies on settlement computation and create difficulty in foundation design which frequently lead to unsatisfactory performance. Although some heavy structures can be founded within the sandy formation, occurring on the top layers the stresses induced by such structures can result in indesirable and large total consolidation settlement of the underlying compressible layers. Sensitive structures need therefore be founded on piles, driven to lepths where either sufficient shaft or end-point resistance can be mobilized to ensure satisfactory performance. Strip or raft foundations can easily support structures like bungalows and one storey buildings within the coastal plain sand-and-beach-ridge sub-environments. Ground improvement is generally required in mangrove swamp, meander belt and within the Sombreiro-Warri-deltaic sediments, even for simple structures.