Bearing capacity assessment of shallow foundations on hydraulic fill overlying soft marine clay
1*Awodiya I.S and 2*Dr. Akintayo F
1,2Civil Engineering, University of Ibadan, Oyo State, Nigeria
DOI: 10.36108/laujoces/6202.71.0150
Abstract
Hydraulically reclaimed coastal land is increasingly used for urban development, yet shallow foundation design on hydraulic fill overlying soft marine clay remains geotechnically challenging. This study assesses the bearing capacity of shallow foundations on such a stratified profile at a reclaimed coastal site along the Lagos shoreline, Nigeria. Borehole logs, Standard Penetration Test (SPT) records and Cone Penetration Test with pore pressure measurement (CPT/CPTu) profiles were jointly interpreted to establish the subsurface stratigraphy and derive representative design parameters. The profile comprised clean to silty sand fill from the surface to approximately 6.8 m, a transitional zone to 9.5 m, clay to silty clay between 9.5 m and 12.4 m, and denser sand below 12.4 m. Adopted parameters included a fill friction angle of 35°, fill unit weight of 18.0 kN/m³, fill thickness of 7.0 m, marine clay unit weight of 16.0 kN/m³ and undrained shear strength of 20.0 kPa. Five bearing-capacity frameworks were evaluated: the single-layer methods of Terzaghi, Meyerhof, Hansen and Vesic, and the Meyerhof and Hanna (1978) two-layer punching shear model. For a 1.5 m wide strip footing at 1.0 m depth, single-layer methods yielded allowable capacities of 44.0–49.4 kPa, while the two-layer model gave 367.0 kPa. For a 10 m × 15 m raft, single-layer checks gave 46.3–51.6 kPa and the two-layer model gave 235.2 kPa. Single-layer methods are overly conservative for this stratified profile because they neglect load transfer and punching resistance through the fill. The Meyerhof and Hanna two-layer framework is therefore recommended as the more physically representative model, provided that consolidation settlement of the underlying marine clay is assessed separately.
Keywords: bearing capacity; hydraulic fill; soft marine clay; reclaimed land; Meyerhof and Hanna