Universitätsbibliothek
Weimar Open Access

Muhammad Ibrar Khan

• The hydraulic properties of the polymer-enhanced bentonite-sand mixtures (PEBSMs) investigated in this study consisted of the water retention behaviour (or the soil-water characteristic curve (SWCC)) and the saturated and unsaturated coefficients of permeability. The SWCCs of the compacted polymer-enhanced bentonite-sand mixtures were measured using two techniques; namely, axis-translationThe hydraulic properties of the polymer-enhanced bentonite-sand mixtures (PEBSMs) investigated in this study consisted of the water retention behaviour (or the soil-water characteristic curve (SWCC)) and the saturated and unsaturated coefficients of permeability. The SWCCs of the compacted polymer-enhanced bentonite-sand mixtures were measured using two techniques; namely, axis-translation technique and vapour equilibrium technique. The results obtained from both methods were combined to establish a single SWCC for each specimen. The saturated coefficient of permeability of the material was measured using the constant-head flexible wall permeameter method. The unsaturated coefficient of permeability was computed from the SWCCs and the saturated permeability values using the statistical model. The study revealed that the wetting curves for the PEBSM and clay are above the drying curves. The fact is thought be due to the specimens being not saturated before starting the drying tests. Since the specimens are expensive soil such a trend can be expected. The permeability deduced from the oedometer test data over-estimates the actual water flow rate resulting in a higher computed saturated coefficient of permeability compared to the measured values. The nets of polymer and bentonite clusters are thought to retard the flow of water during the direct measurement. However, the net of polymer and bentonite clusters are compressed during loading and rebound during unloading. Hysteresis effect was found for the PEBSMs in the permeability versus degree of saturation curve. This is due to possible difference in the spatial distribution of water in the specimens depending whether the specimens were on drying or wetting path.…