ABSTRACT
Slurry clays are often encountered in mining and reclamation projects. Soil-bentonite slurries are also extensively used for vertical barriers, especially for contaminant containment. This study describes the experimental investigation of the compressibility and hydraulic conductivity of four different types of clay slurries using a large-diameter Rowe cell testing system. The slurries are made from two types of locally available high plastic clays, and two commercially available sodium bentonites from the state of Gujarat, India. The slurries are prepared at an initial water content of 1.5 times their corresponding liquid limits by mixing distilled water thoroughly in a Hobart mixer. After applying an initial effective stress of 2.5 to 3 kPa, the consolidation tests are performed at effective stresses of 25, 50, 100 and 200 kPa. The coefficient of volume compressibility (mv), coefficient of consolidation (cv), and saturated hydraulic conductivity (k) determined from the consolidation tests are compared for the locally available clays and bentonite slurries. The mineralogy and microstructure of the samples are also studied by using X-ray Diffraction (XRD) analysis and Scanning Electron Microscopy (SEM) analysis. The results show that the difference in hydraulic conductivities in natural clay slurries and bentonite slurries are more profound at low effective stresses i.e., 25 kPa. At the highest applied effective stress of 200 kPa, the hydraulic conductivity of all four slurries is found to be within the range of 1.3 x 10-9 m/sec to 8.6 x 10-11 m/sec. Hence, the potential of using natural and locally available clays in slurry wall backfills is assessed by comparing the compressibility, hydraulic conductivity, and microstructural characteristics.
