A Geomechanical Approach to Landslide Hazard Assessment: The Multiscalar Method for Landslide Mitigation

AbstractThe landslide hazard assessment, when based on the deterministic diagnosis of the processes, can be pursued only through the interpretation and the geo-hydro-mechanical modelling of the slope equilibrium. In practice, though, landslide hazard assessment is still seldom dealt with slope modelling, in particular when it addresses vast areas, where either heuristic or statistical methods do not entail any geo-hydro-mechanical knowledge of slope features and stability. The Multiscalar Method for Landslide Mitigation (MMLM) is an original methodological approach for intermediate to regional landslide hazard assessment. It is based on the geo-hydro-mechanical knowledge achieved from the application of a stage-wise diagnostic methodology of the landslide mechanism at the slope scale. The paper discusses the main steps of the MMLM aiming at diagnoses of landslide hazard based on hydro-mechanics, for small scale hazard mapping (at the large area)

Sustainable environmental geotechnics practices for a green economy

The revitalisation of the global economy after the Covid-19 era presents environmental geotechnics with the opportunity to reinforce the need for a change in paradigm towards a green, circular economy and to promote aggressively the use and development of sustainable technologies and management practices. This paper aims to assist in this effort by concentrating on several thematic areas where sustainability solutions and future improvements are sought. These include the re-entry of construction and demolition of wastes, excavated materials, industrial wastes and marine sediments into the production cycle and the reuse of existing foundations. Despite the recent trend in advanced countries towards recycling and waste-to-energy thermal treatment, landfills still constitute the most common municipal solid waste management practice, especially in low-and-middle-income countries, and technological solutions to improve their environmental footprint are hereby presented. At the same time, remediation solutions are required to address the multitude of contaminated sites worldwide. Advanced developments that incorporate environmental, economic and social dimensions are expounded by the authors, together with sustainable ground improvement solutions for infrastructure projects conducted in soft and weak soils. The topic of thermo-active geostructures concludes this paper, where, apart from their infrastructure utility, these structures have the potential to contribute to the renewable energy source.Published versionThe second author would like to acknowledge the support of the Office of the Associate Provost for Research and Academic Development at Abu Dhabi University, UAE through grant19300540

Stabilization and recycling of contaminated marine sediments

The paper deals with the treatment and reuse of submarine sediments, i.e. a relevant environmental issue due to the annual huge quantities of dredged sediments (over half contaminated) in Europe. In a vision of sustainability and circular economy, stabilization and solidification (S/S) treatments represent an interesting solution for both environmental protection and reuse of sediments in engineering works. The investigation involved polluted clayey sediments taken up to depths of about 1.5m from the seafloor of the Gulf of Taranto (South of Italy). The research investigates the effects of a treatment with cement and lime enhanced by the addition of green additives, such as active carbon and biochar, for chemical remediation. The last one is a promising and cheap adsorbent material, that is the by-product of - mainly - agricultural waste pyrolysis. The first results suggest that appropriate mix designs and curing times could allow the reuse of sediments by both improving their geotechnical characteristics and making them environmentally acceptable in accordance to end-of-waste criteria

Strain fields and mechanical response of a high to medium fissured bentonite clay

This article presents the developments of an ongoing research aimed at modelling the influence of fissuring on the behaviour of clays. In particular, it recalls the main results of an extensive laboratory investigation on a fissured bentonite clay from the south of Italy and presents the data of a new investigation on the evolution with shearing of the strain fields developing within the clay, resulting from Digital Image Correlation (DIC). Element test results are analysed in the framework of continuum mechanics and linked to the clay fissuring features, once characterised using the Fissuring IDentity (F-ID) chart. This article compares the bentonite behaviour with that of other fissured clays of different F-IDs, highlighting the common behavioural features. Thereafter, the soil response at the macro level is related to the DIC-derived strain fields evolving within the clay with loading. For this purpose, DIC was successfully used to investigate the deformation processes active in the fissured clay and the sources of the localisation phenomena. DIC is shown to provide indications of the extent to which highly to medium fissured clays element test results can be of use to model the clay behaviour according to continuum mechanics

Geo-chemo-mechanical characterization of a polluted marine basin

The work shows the first results of the characterization of the heavily polluted sediments in the Mar Piccolo basin (Taranto, south of Italy), obtained thanks to an integrated investigation method. In the field of the actions promoted by the Italian Government to select the most sustainable remediation strategies, a multidisciplinary investigation of the site has been carried out involving the reconstruction of the geological set-up of the basin, the analysis of the chemical contamination and the geo-mechanical properties of the sediments collected up to 30 m below the sea floor. The devices and methodologies used for the off-shore sampling, storage and transport of the sediments and for the laboratory testing were specifically designed to obtain the best possible picture of the site. The quality of the soil sampling resulted to be high enough for chemical, geochemical and geotechnical characterization and to develop integrated analyses. With this purpose, the paper discusses preliminary correlations of data, focusing on the geotechnical properties of plasticity that have been interpreted in the light of soil composition and chemical and geological facets of the sediments

A microstructural insight into the compression behaviour of scaly clays

Scaly clays are intensely fissured clays with lens shaped elements of millimetre size and show a complex compression behaviour that poses challenges to the design and construction of geostructures (excavations, retaining diaphragms, and tunnels). Scaly clays show a Normal Compression Line (NCL) where plastic deformation accumulates as typically observed in non-scaly clays. Yet the response observed upon unloading and subsequent reloading is very peculiar, i) the unloading-reloading cycle is typically a close-loop with relatively large hysteresis; ii) the compressibility recorded at high OCR ratio of the unloading or reloading branches is close to the NCL compressibility. This paper presents a microstructural study on an Italian scaly clay where SEM observations are integrated with Mercury Intrusion Porosimetry (MIP) analyses and X-ray Computed Tomography (XCT) images. The mechanism associated with the closing of inter-scale porosity and the generation of new intra-scale porosity was identified as the process responsible for the plastic deformation. Experimental observation of reconstituted clay showed a “quasi-reversible” behaviour upon loading and unloading and a pore size distribution characterized only by interparticle porosity. The observation that unloading and reloading curves are parallel in natural and reconstituted clays, led to postulate that the interparticle porosity is controlling the elastic response

An interdisciplinary approach to landslide damage assessment in urban areas

This paper presents some results of a multidisciplinary research about the assessment of damages to ordinary buildings at the urban scale in landslide areas. The methodology represents part of a multi-level approach for landslide vulnerability assessment that has been recently developed. It is based on rapid visual inspections of the buildings, the application of ‘simple models’ to interpret the structural response, the geological and geotechnical knowledge of the site. The end-product is the landslide damage geotechnical chart, including: i) the damage grade of the buildings, ii) the geomorphological and geotechnical map of the area, iii) the direction of the settlements causing damages. The application of the methodology to an historical site in southern Italy is also outlined. Finally, the contribution of innovative non-invasive spaceborne remote sensing techniques to monitor landslide-affected urban areas is highlighted

The influence of meso-structure on the mechanical behaviour of marly clays from low to high strains.

On the 31st of October 2002, a ML=5.5 earthquake struck the Molise region in Southern Italy. The earthquake was followed by a comparable aftershock (ML=5.4) nearby on the day after, and by a series of seismic events of lower energy in the following month (Fig. 1). In the town of San Giuliano di Puglia, the distribution of the damage consequent to the mainshocks was strongly non-uniform: the old part, which was less damaged, lies on outcropping rock, while the most severe damages were surprisingly concentrated in the new part of the town, lying on fine-grained soils. This evidence suggested that differential site amplification significantly affected the seismic response in the town. This hypothesis has been confirmed by aftershock records logged by two temporary accelerometric stations, located both in the ancient and in the new portions of the town (Puglia, 2005). In order to develop a seismic microzonation of the area (Baranello et al., 2003), the Department of Civil Protection of the Italian Government committed a comprehensive investigation on the subsoil properties. The experimental programme included: boreholes, in situ piezometric measurements, CPT, cross-hole and down-hole tests and laboratory investigations on undisturbed samples, namely oedometer, triaxial and cyclic/dynamic torsional shear tests. The geotechnical laboratories of both the University of Naples and the Technical University of Bari were entrusted by the Department of Civil Protection with the laboratory investigations, aiming at the characterisation of the mechanical behaviour of the fine-grained soils. The present paper discusses the main experimental results of such laboratory investigations, as well as a comparison with seismic in-situ tests, giving evidence to the dependency of both the soil strength properties and stress-strain behaviour on the soil structural features