Clay Minerals (I972) 9, 329. AN ENGINEERING SOIL AT KERMANSHAH, ZAGROS MOUNTAINS, IRAN

ABSTRACT: The soils examined are from alluvial sheet deposits in a high valley where they are subjected to alternate wetting and drying, leading to desiccation. They are principally derived from shale and limestone bedrock in the surrounding mountains which are rapidly eroded and transported down valley mainly when the snow melts. The soils have engineering properties of fairly low density, high permeability, high plasticity with the plasticity index above the A line (CH range). These properties are correlated with the size grading and the clay mineralogical composition-- about 30 ~ ca/cite, 45-50 ~ clay minerals, dominated by Fen+ and Mg-smectites and fine-grained muscovite. The clay mineralogy isexplained in terms of Millot's zone of smectitization affecting biotite from detrital shale fragments, the muscovite remaining substantially unaltered. Calcite solution and redeposition account for the chalky texture and strong bond