Geological Engineering investigations in situ and Geotechnical Engineering solutions to support the realization of the third lot of the Water Treatment Plant in Calabar, Nigeria

This paper shows the results of the Geological-Engineering investigations in situ and the Geotechnical-Engineering solutions to support the building of the third lot of the Water Treatment Plant, located in Calabar, Cross River State, Republic of Nigeria. In order to characterize the litho-stratigraphic succession and a geotechnical profile of the subsoil in Calabar, three different geognostic investigations have been carried out: surface, subsurface and laboratory investigations. The aim of the paper is to validate the use of the 3D subsurface geological-geotechnical modeling to optimize the design and the Engineering structures of the Water Treatment Plant. The results of the four Bore Holes, drilled for a total length of 64 m and of the five Cone Penetration Tests, set up to a depth of 22,40 m from the surface, were analyzed to develop a geological/geotechnical model. Approximately twenty-two soil samples have been obtained. The variability of qc (cone resistance in kPa); e0 (initial void ratio); Eeod (compressibility modulus in kPa); Dr (relative density);  (friction angle); cu (undrained shear strength in kPa); for the clayey sand and gravelly sand were spatially described and the influence of these parameters on the immediate and consolidation settlements of the treatment plant was also highlighted.