Modelling on earthwork feasibility analyses of geotechnical and georesistivity fingerprints of subsoils: Application to tank farm, road and building developments in part of the Niger Delta

The western Niger Delta has been challenged with rampant incidents of building collapse, road failures and syn-constructional failures, which have been attributed to poor ground conditions in recent times. This study examines the foundation competence of subsurface soils in the Delta for sustainable building, tank farm and road developments based on their geotechnical and geo-resistivity signatures. Investigations involved walk-over surveys, Vertical Electrical Soundings (VES), Horizontal Resistivity Profiling (HRP), drilling of five geotechnical boreholes and several geotechnical testing programmes such as Cone Penetration Tests (CPT), Standard Penetration Test (CPT), sieve analysis, consistency tests and California Bearing Ratio (CBR), consolidation, shear box and unconsolidated undrained triaxial tests. The investigations unveil a predominantly homogeneous soil profile that is stratified as (i) upper sands (~ 3 m thick) and (ii) lower sands (~ 27mthick). Bearing capacity and settlement analyses indicated that the upper sand is a competent foundation horizon for medium-size structures. The lower sand constitutes the best foundation substratum for medium to heavy structures as it reflects the highest SPT "N" value of over 30 blows with an allowable pile bearing capacity of 854-4940Kpa at depths of 18-22 m. California Bearing Ratio (CBR) of superficial soils confirmed that the soils are competent subgrade materials but incompetent sub-base and base courses for road development. Stone dust stabilisation improved the superficial soils to sub-base quality at 30% stone dust. The study provides a model georesistivity and geotechnical database for sustainable earthworks and also confirms that stone dust stabilisation is a viable solution to pavement deficiency in superficial soils of the Western Niger Delta.