The paper presents the results of an experimental research on the effects of weathering on the geotechnical properties and the mechanical behaviour of a stiff blue Pleistocene clay. The properties and mechanics of block samples taken from a quarry face in yellowish clay are compared with those of the unweathered grey clay below it, which is shown to be the original material the upper yellow clay derives from through chemical and mechanical alteration. Weathering processes affect the swelling behaviour, shear strength and shear stiffness of the clay.
This paper discusses some of the results of an experimental research on the effects of weathering on the properties of a Pleistocene Italian stiff clay (Sub- Apennine Blue Clays). In particular the research refers to the weathered blue clays outcropping at Montemesola, near Taranto (Southern Italy, Figure 1) which have a browny-yellowish colour. The original unweathered clay is an overconsolidated stiff grey clay, mainly illitic, deposited during Santernian in the Montemesola Basin (De Marco et al., 1981; Cotecchia and Chandler, 1995). The original sedimentation environment was protected and the deposit has lithologically uniform features (Cafaro et al., 2000). At the end of normal consolidation, the clay was subjected to diagenetic processes, which caused the development of carbonate bonding (Cotecchia and Chandler, 1995 and 1997). The clay later underwent unloading due to erosion. Weathering started as soon as the sediment surfaced, thus the original clay has been gradually transformed starting from the upper levels downwards, with vertical penetration of the weathering process. The change in colour of the clay, from grey to yellow, has been due to oxidation at the establishment of an aerobic environment in the clay. An experimental comparison has been carried out between both the intrinsic and the mechanical properties of the weathered and the unweathered clay.
