Overconsolidation Ratio of Some Selected Soil Deposits in Nigeria

Abstract

Undisturbed soil samples, collected at between 0.5 and 3.0 m depths, from 16 soil deposits across Nigeria, were subjected to Identification and one-dimensional consolidation tests. Using Casagrande method, preconsolidation pressures and subsequently, Overconsolidation Ratio (OCR) of the respective soil samples were determined. The results generally showed that the investigated soil deposits are overconsolidated. Although, the OCR of the studied soil deposits covers a relatively wide range, soils deposits from the same region shows relatively narrow range of OCR values. The highest OCR values of between 15.8 and 16.9 were observed with soil samples from deposits in the Northeastern part of the country, that is, from deposits of Vertisol (Black cotton soils). The OCR value of the soil deposit from the Northwestern region shows that the soil is under-consolidated.