Geotechnical Properties of Sub-soils in Escravos Estuary, Western Niger Delta, Nigeria.

Abstract

This study evaluates the sub-soil geotechnical characteristics at the onshore pipeline route at Escravos estuary, Western Niger Delta, Nigeria. Acquisition of soil samples for geotechnical studies was done by conventional boring method using light shell and auger hand rig. Samples were analyzed in the laboratory using standard analytical procedures. The samples explored showed a profile of very soft greenish dark grey and reddish brown clay formation. All samples observed confirmed this lithostratigraphy except for some of the grab samples. The entire formation generally, presents a low amount of organic content, low shear strength and high carbonate content. The unit weight showed an increase with high carbonate content. The samples gave a high amount of moisture content, higher than the liquid limit which indicates that on loading the pipeline route, the weight of the pipeline will dissipate a large amount of the pore water with a resultant increase in settlement. The pipeline should be placed on slippers pad at designated locations on the seabed along the survey route to avoid excessive settlement. This would distribute the anticipated pressure from the pipeline over a greater area and thus reduce the excessive settlement which is the characteristics of the very soft marine clay encountered in this investigation. The dimensions and bearing capacity of such slippers pads can easily be determined.