Effect of hydraulic gradient on swell and hydraulic response of desiccated expansive soil – an experimental study

Abstract

ABSTRACT Desiccation cracks in compacted clay liners act as preferential flow paths and affect the hydraulic response during initial stage of wetting. This paper investigates the effect of initial hydraulic gradient on swell, infiltration and hydraulic conductivity during wetting of desiccated expansive soil specimens in oedometric-infiltrometer test set-up. The experimental results on the desiccated specimens demonstrated that the rate of swelling and the infiltration rates in the initial outflow region through the annular gap and permeation outflow region through the swollen soil matrix increased with the increase in hydraulic gradient, whereas the time for reoccurrence of outflow and the establishment of steady state condition decreased. The outflow infiltration rates of the desiccated specimens subjected to initial hydraulic gradients (i) of 2, 5 and 20 reduced from 1.56 × 10−3, 4.83 × 10−3 and 6.57 × 10−2 cm/s, respectively, in the initial outflow region to about 6.65 × 10−6 cm/s (under i= 20) in the permeation outflow region due to the swelling of the desiccated expansive soil. The minimum possible initial hydraulic gradient that can be adopted on desiccated expansive soil specimens during infiltration testing was found to be 2 without considering the infiltration driven by soil suction.