Effect of freeze-thaw cycles on water permeability of sand mixtures with nanoclay

Abstract

The mixtures of sands and nanoclays are used to isolate municipal and industrial solid wastes. Compared with natural clayey soils, these mixtures are characterized by homogeneous composition, workability, and low compressibility. This study investigated the effect of freeze–thaw cycles on their permeability. The mixtures of four sands and a saponite clay suspension generated by diamond ore processing were studied. The mixtures were prepared on the basis of 4 % and 8 % clay from sand weight. The tests were performed using an apparatus consisting of four devices for measuring frost heave and permeability, which were placed in containers with water. The water level was decreased gradually to ensure sample freezing or increased to ensure sample thawing. The frost heave of the mixtures with 4 % clay was 10.0–16.4 % under an external load of 2 kPa, and the five freeze–thaw cycles resulted in an increase in the hydraulic conductivity by 2.0–4.7 times. The mixtures with 8 % clay were tested under a load of 12 kPa, because of their high frost susceptibility. The hydraulic conductivity increased by approximately the same value as in the first case, i.e., by 1.2–2.0 times. The experiments have shown that the examined mixtures are suitable for isolating wastes. However, to eliminate the above effect, a waterproof liner should be covered with inert soil, which would reduce the depth of frost penetration and apply the load on it.