TITLE:
Modeling the Undrained Shear Strength with Soil Index Properties for Niger Delta Soft Clays
AUTHORS:
Chigozie Dimgba, Ify L. Nwaogazie, Akuro Big-Alabo
KEYWORDS:
Undrained Shear Strength, Inorganic Clay, Escravos, Multiple Regression Modelling
JOURNAL NAME:
Open Journal of Civil Engineering,
Vol.13 No.1,
March
22,
2023
ABSTRACT: The aim of this study was to model the Undrained
Shear Strength (USS) of soil found in the coastal region of the Niger Delta in
Nigeria with some soil properties. The undrained shear strength
(USS) is a key parameter needed for most geotechnical/structural designs.
Accurate determination of the USS of soft clays can be challenging to obtain in
the laboratory due to the difficulty in remoulding the clay to its in-situ conditions before testing and
more accurate test such as Cone Penetration test (CPT) can be quite expensive.
This study was carried out at Escravos site which is located in Delta state,
Nigeria. Three Boreholes were drilled and soil samples were
collected at 0.75 m intervals up to a depth of 45 m. Laboratory tests were used to obtain the moisture
content, bulk unit weight, liquid and plastic limit, while CPT was used in obtaining the undrained shear
strength. Classification of the soil samples was done by adopting the Unified
Soil Classification System and various models relating the USS with the soil
properties were developed. The result showed that most of the soils at Escravos
site were predominately inorganic clay of high plasticity which are problematic
due to the expansion and shrinking nature of this type of soil. The model
developed showed that the soil properties that gave the best fit with the USS
were the moisture content and effective stress of the soil. The coefficient of
determination (R2) and the root mean square error (RMSE) obtained
for this model were 0.805 and 6.37 KN/m2,
respectively.