The paper discusses the geological history, intrinsic properties, structural features and mechanical behaviour of three differently fissured clays outcropping within the Apennine chain in southern Italy. Based on a large experimental database, the mechanical behaviour of the clays is investigated in the light of their different fissuring features, which have been distinguished and characterised by means of a new chart. The study assumed the soil to be a continuum, despite the different fissuring features of the clay fabric. Therefore laboratory tests were carried out on both natural and reconstituted clay samples, and the results were compared with those recognised in the literature to be typical of unfissured sensitive clays. Based on these comparisons, a behavioural framework is proposed for clays possessing certain fissure structures. The results of the analysis show that the mini- to mesostructure of clays of fissuring intensity I5–I6 can be modelled as part of the structure variable controlling the clay behaviour. Where the structure variable refers solely to the micro scale for unfissured homogeneous clays, for fissured clays I5–I6 it spans from the micro to the meso scale. As for the microstructure of unfissured clays, this micro- to mesostructure influences the soil response as an internal state variable in addition to specific volume in controlling the mechanical response. In particular, it appears that for clays of fissuring intensity I5–I6, structure is detrimental to strength, so that the material is even weaker than the reconstituted clay.

In slopes formed by tectonized clayey turbidites, the soil fissuring recurrently influences the hydro-mechanical soil properties, determining an impoverishment in strength and an increase in permeability of the slope that make them predisposing factors of landsliding. This paper presents three case histories of slopes within tectonized clayey turbidites that are representative of several others in the Southern Apennines and, more widely, in the southern Mediterranean. The paper reports a novel attempt to connect tightly the slope geomorphological and hydromechanical features to the slope geological history, through an introductory presentation of the geological setting and history of the chain where the slopes occur. The slopes, location of very slow landslides, have been reconstructed based upon field surveys and investigations, multi-aerial photo-interpretation, laboratory testing, monitoring and numerical modelling. Furthermore, novel is the attempt to present, all together, the behaviour of the soils involved in the three landslide case studies, in the light of the mechanical modelling approach to fissured clays recently presented in the literature.

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This paper reports the results of the first geomechanical laboratory experiments carried out on the polluted submarine clayey sediments of the Mar Piccolo in Taranto (South of Italy). The study had to face with extreme difficulties for the very soft consistency of the sediments and the contaminants. The mineralogy, composition and physical properties of the sediments were analysed, along with their compression and shearing behaviour. The investigation involved sediments up to about 20 m below the seafloor, along three vertical profiles in the most polluted area of the Mar Piccolo, facing the Italian Navy Arsenal. The experimental results were used to derive a preliminary geotechnical model of the site, necessary for the selection and design of the most sustainable in situ mitigation solutions. Moreover, the experimental data reveal that the clayey sediments of the most polluted top layer do not follow the classical geotechnical correlations for normally consolidated deposits. This seems to open interesting perspectives about the effects of pollutants on the geotechnical behaviour of the investigated sediments.

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The paper presents the preliminary results of experimental research into the stabilisation with cement and/or lime of clayey sediments dredged from the Port of Taranto (Italy). First, the physical properties of the natural sediments are briefly described and compared with those of the same sediments when treated with different additives and cured up to four years. In particular, the effect of the treatment on the soil plasticity properties is originally analysed in terms of plasticity paths.Then, the influence of the different stabilising agents on the compression behaviour of the dredged soil is analysed and methods for quickly predicting the admixed-soil behaviour are presented.

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