Experimental and numerical analysis of single pile foundation behaviour in expansive Ankara clay

Expansive clays can induce heave and uplift forces on pile foundations because of suction changes and moisture-induced volume variations. This study investigates the uplift behaviour of single concrete piles embedded in expansive Ankara clay using laboratory-scale model tests and finite element analyses based on the Barcelona Basic Model (BBM). The experimental programme included geotechnical and mineralogical characterisation, soil-water retention curve development, concrete–clay interface shear testing, and controlled-wetting pile tests. BBM parameters were calibrated from saturated and unsaturated consolidation tests, triaxial tests, an evaporation test, and the soil-water retention curve, and implemented in an axisymmetric RS2 model. The model predicted 4.07 mm pile uplift and 5.41 mm average surface heave, compared with measured values of 4.52 and 5.80 mm. Tests showed that an anchorage depth at least 1.5 times the active-zone depth prevented progressive pile uplift under the tested conditions.