Geological and geotechnical properties of soil materials at Tannur dam, Wadi Al Hasa, South Jordan

Tannur dam, sited about 150 km south of Amman on Wadi Al Hasa with a reservoir capacity of 17 × 106 m3, forms part of the Southern Ghors project for water supply and irrigation in the Jordan valley. Values obtained for plastic limit (PL) ranged from 9.8 to 30.3 mass %, liquid limit (LL) 20–42 mass % and plasticity index (PI) 7.3–16.3 mass % for alluvium materials, while values obtained for PL ranged from 10 to 32 mass %, LL 28–58 mass % and PI 12–43 mass % for landslide materials. PSD analysis shows that the materials at the dam site falls into the sandy to clayey silt grain size range. XRD analysis revealed that the landslide materials are composed of smectite as major component with minor amounts of calcite and quartz, while the alluvium materials are mostly composed of quartz, calcite and smectite. Based on the plasticity characteristics, the alluvium materials are slightly to moderately plastic, while the landslide materials are classified as moderate to high plasticity. Accordingly, it is evident that the landslide materials reflect high swell potential due to the presence of considerable amount of expansive clays (smectite).