INVESTIGATION OF THE HYDRAULIC EFFICIENCY OF SAND - NATURAL EXPANSIVE CLAY MIXTURES

Abstract

The aim of this study is to evaluate the hydraulic performance of a sand-natural expansive clay
mixture in comparison with sand-bentonite mixture. Natural expansive clay used in this study was obtained from
Al-Qatif region, Saudi Arabia. The saturated hydraulic conductivity was evaluated for different mixtures of
sand-Al Qatif clay with clay contents ranging from 10% to 60% clay. Similarly, the saturated hydraulic
conductivity of sand-bentonite mixtures with different bentonite contents (0%, 5%, 10% and 20%) was also
evaluated. All hydraulic conductivity tests were performed under different confining pressures. Test results
revealed that sand-Al-Qatif clay mixtures can perform adequately as a hydraulic barrier; however, with Al-Qatif
clay contents greater than that used for sand-bentonite mixtures. This is attributed to difference between clay
mineralogy between Al-Qatif clay and bentonite. In addition a quantitative approach is proposed to assess the
hydraulic conductivity of sand-Al-Qatif clay mixtures in comparison to that for sand-bentonite mixtures. Finally,
soil fabric of mixtures was examined using scanning electron microscope (SEM) technique to observe
differences in fabric between sand-Al-Qatif clay and sand-bentonite mixtures.