Giacomo Russo

Natural sinkholes are among the most critical geological hazards in karst terrains, where surface collapses can occur suddenly and affect infrastructure, cultural heritage, and human safety. Coastal environments are particularly vulnerable due to the combined effect of karst dissolution, structural discontinuities, and wave-induced erosion. This study focuses on the coastal sector of Maratea (Basilicata, Southern Italy), the only Tyrrhenian outlet of the region, which extends over ~32 km and hosts several sinkholes and marine caves at different evolutionary stages. A multidisciplinary methodology was applied, combining hydrogeological, geological and geomechanical measurements with field surveys, and drone-based photogrammetry. Sinkhole sites were documented through high-resolution orthophotos and 3D models, while kinematic analysis supported the identification of instability mechanisms (planar sliding, wedge sliding, direct toppling). The integration of speleological and GIS data confirmed the strong relationship between marine caves and sinkhole collapse. Results highlight the role of tectonic discontinuities, karst processes, and marine erosion in triggering cliff failures, proposing a methodological framework useful for hazard assessment and coastal risk mitigation.

In the present work, an investigation on the influence of the chemical environment on the sedimentation behaviour of bentonite suspensions is performed with particular reference to the effect of lime addition on the clay particle arrangement. The role of lime content, cation valence and source of calcium ions is considered in the experimental work. At the microscale, particle interaction is analysed by means of zeta potential measurements. Soil fabric formation during sedimentation and its physical properties are inferred from dynamic light scattering measurements, sedimentation tests and Atterberg limits. The addition of cations to pore water promotes the flocculation of montmorillonite particles favouring the formation of particle aggregates, whose dimension depends on ion valence and concentration. The final height of sediments reflects the combined effect of the mutual interactions among particles and the development of secondary phases due to pozzolanic reactions. The influence of clay mineralogy and its effects on the physical properties of lime-treated bentonite is highlighted by comparison with experimental evidence on lime-treated kaolin.

Soil-improvement techniques with binders are used in several geotechnical engineering applications as a sustainable solution for the reuse of waste soils. Due to their inherent complexity and their mechanical behaviour, pyroclastic soils are generally considered waste geomaterials in their natural state. Lime treatment of pyroclastic soils can be considered a viable solution for their reuse in geotechnical applications. In this paper, some peculiar features of the chemo-physical evolution and mechanical behaviour of lime-treated pyroclastic soils are evidenced through a multi-scale experimental investigation. While, for clayey soils, the fine fraction is mainly responsible for ion exchange and pozzolanic reactions induced by lime, for pyroclastic soils, pozzolanic reactions are dominant processes due to the low quantity of clay minerals along with the abundance of aluminates and silicates as the main constituents of their amorphous phase. The link between the phenomena detected at the microscale level, the mineralogical composition, and the macroscopic behaviour of two lime treated pyroclastic soils of different origin is explored through a multiscale approach.

Fallout volcanic deposits of Somma- Vesuvius (Campania, southern Italy), characterized by the presence of layers with contrasting textural and hydraulic properties, are frequently affected by shallow landslides during rainwater infiltration. The soils of the stratigraphic sequence present intra- particle pores, originated by the gases escaped during magma decompression in the volcanic conduit, thus are characterized by double porosity (i.e., intraparticle and interparticle pores), which is expected to affect their hydraulic behaviour, and to play a key role in rainwater infiltration through layered deposits. To understand the effect of double porosity on the hydraulic behaviour of the involved soils, controlled experiments have been carried out in an infiltration column. The experimental apparatus is provided with newly designed non-invasive Time Domain Reflectometry (TDR) probes, not buried in the investigated soil layers so as to minimize disturbance to the flow, allowing water content measurement during vertical flow processes. Specifically, transient flow experiments are carried out through reconstituted specimens of black scoriae and grey pumices, both loose pyroclastic granular soils from fallout deposits of Somma-Vesuvius, featuring double porosity with different pore size distributions, that were estimated by X-ray tomography and Mercury Intrusion Porosimetry. The experimental results highlight the effects of the double porosity and clearly indicate the different behaviour of the two soils during wetting and drying processes, mainly related to the different dimensions of intraparticle pores.

The mechanical efficiency of soil stabilization with cement is mainly controlled by various parameters, namely, the amount of binder, the compaction soil state and the curing conditions. The strength of the treated soil is the result of a complex combination of several factors that condition the physicochemical processes involved in cement hydration, which are difficult to monitor. The objective of this study is to identify the relevant parameters governing the bonding in cement-treated soil and suggest a predictive model for strength evolution using these parameters as input. To this purpose, an extensive testing program is presented to assess the impact of the initial water content (11–18%) and dry density (1.6–1.87 Mg/m³) as well as cement dosage (3 and 6%) in sealed curing conditions for 0, 7, 28 and 90 days. The water content variation, the total suction and the compressive strength were measured after different curing durations. The experimental results are first discussed in the parameters’ space, and then through a principal components analysis to overcome the complexity due to the parameters’ interdependency. The PCA revealed that the cement dosage explained 40% of the dataset variance, the remaining 60% being related to a combination of the initial state and curing time. Finally, a predictive model based on an artificial neural network was developed and tested. The predicted results were excellent, with an R² of +0.99 with the training data and +0.93 with the testing data. These results should be improved by extending the dataset to include different soils and additional compaction conditions.