Experimental evaluation of time effect on swelling pressure in high plasticity clay

Søvind Marl, a high plasticity overconsolidated Danish Paleogene clay, is a stiff clay known to exhibit swelling potential. The dependency of its swelling pressure on time is investigated by performing constant volume (CV) tests. Long periods of swelling are applied to the samples. Two samples are allowed to swell for 19 weeks, the other two only for 24 hours. The long-lasting tests show that the swelling pressure reaches the maximum value (σ'cv) after 13 weeks of testing, and the change between the σ'cv and the swelling pressure after 24 hours reaches 38%. In order to correct the underestimation of σ'cv due to the sampling, a graphical correction of the consolidation curve is made. Due to the characteristic smooth yielding of the Søvind Marl, the graphical correction can be affected by personal interpretation.