Compression behaviour of structurally complex marine clays

Due to the high degree of tectonic shearing occurred during Apennine orogenesis, the clay units outcropping in the chain areas of Southern Italy are structurally complex and have often a scaly fabric. This fabric is defined by an intricate network of fissures and shear planes which subdivide the clay into centimetric and millimetric fragments or lenses. The present paper deals with the compression behaviour and the microstructural changes of the Senerchia scaly clays, outcropping in a chain area in Southern Italy. The results of the oedometer tests outline a state boundary envelope in compression for the scaly which lies to the left of their intrinsic compression lines. These clays appear either to contract or to dilate with shear after consolidation respectively to low and high yield stress ratios. Their swelling behaviour is characterised by large unload-reload loops and a vertical shift of the swelling loops with compression post-gross-yield.