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The instability of river bank can result in considerable human and land losses. The Po river is the most important in Italy, characterized by main banks of significant and constantly increasing height. This study presents multilayer perceptron of artificial neural network (ANN) to construct prediction models for the stability analysis of river banks along the Po River, under various river and groundwater boundary conditions. For this aim, a number of networks of threshold logic unit are tested using different combinations of the input parameters. Factor of safety (FS), as an index of slope stability, is formulated in terms of several influencing geometrical and geotechnical parameters. In order to obtain a comprehensive geotechnical database, several cone penetration tests from the study site have been interpreted. The proposed models are developed upon stability analyses using finite element code over different representative sections of river embankments. For the validity verification, the ANN models are employed to predict the FS values of a part of the database beyond the calibration data domain. The results indicate that the proposed ANN models are effective tools for evaluating the slope stability. The ANN models notably outperform the derived multiple linear regression models.

The cone penetration test (CPT), together with its recent variation (CPTU), has become the most widely used in-situ testing technique for soil profiling and geotechnical characterization. The knowledge gained over the last decades on the interpretation procedures in sands and clays is certainly wide, whilst very few contributions can be found as regards the analysis of CPT(u) data in intermediate soils. Indeed, it is widely accepted that at the standard rate of penetration (v = 20 mm/s), drained penetration occurs in sands while undrained penetration occurs in clays. However, a problem arise when the available interpretation approaches are applied to cone measurements in silts, sandy silts, silty or clayey sands, since such intermediate geomaterials are often characterized by permeability values within the range in which partial drainage is very likely to occur. Hence, the application of the available and well-established interpretation procedures, developed for ‘standard’ clays and sands, may result in invalid estimates of soil parameters. This study aims at providing a better understanding on the interpretation of CPTU data in natural sand and silt mixtures, by taking into account two main aspects, as specified below: 1)Investigating the effect of penetration rate on piezocone measurements, with the aim of identifying drainage conditions when cone penetration is performed at a standard rate. This part of the thesis has been carried out with reference to a specific CPTU database recently collected in a liquefaction-prone area (Emilia-Romagna Region, Italy). 2)Providing a better insight into the interpretation of piezocone tests in the widely studied silty sediments of the Venetian lagoon (Italy). Research has focused on the calibration and verification of some site-specific correlations, with special reference to the estimate of compressibility parameters for the assessment of long-term settlements of the Venetian coastal defences.

Mountainous areas are prone to natural hazards like rockfalls. Among the many countermeasures, rockfall protection barriers represent an effective solution to mitigate the risk. They are metallic structures designed to intercept rocks falling from unstable slopes, thus dissipating the energy deriving from the impact. This study aims at providing a better understanding of the response of several rockfall barrier types, through the development of rather sophisticated three-dimensional numerical finite elements models which take into account for the highly dynamic and non-linear conditions of such events. The models are built considering the actual geometrical and mechanical properties of real systems. Particular attention is given to the connecting details between the structural components and to their interactions. The importance of the work lies in being able to support a wide experimental activity with appropriate numerical modelling. The data of several full-scale tests carried out on barrier prototypes, as well as on their structural components, are combined with results of numerical simulations. Though the models are designed with relatively simple solutions in order to obtain a low computational cost of the simulations, they are able to reproduce with great accuracy the test results, thus validating the reliability of the numerical strategy proposed for the design of these structures. The developed models have shown to be readily applied to predict the barrier performance under different possible scenarios, by varying the initial configuration of the structures and/or of the impact conditions. Furthermore, the numerical models enable to optimize the design of these structures and to evaluate the benefit of possible solutions. Finally it is shown they can be also used as a valuable supporting tool for the operators within a rockfall risk assessment procedure, to gain crucial understanding of the performance of existing barriers in working conditions.

The uncertainties in the determination of the stratigraphic profile of natural soils is one of the main problems in geotechnics, in particular for landslide characterization and modeling. The study deals with a new approach in geotechnical modeling which relays on a stochastic generation of different soil layers distributions, following a boolean logic – the method has been thus called BoSG (Boolean Stochastic Generation). In this way, it is possible to randomize the presence of a specific material interdigitated in a uniform matrix. In the building of a geotechnical model it is generally common to discard some stratigraphic data in order to simplify the model itself, assuming that the significance of the results of the modeling procedure would not be affected. With the proposed technique it is possible to quantify the error associated with this simplification. Moreover, it could be used to determine the most significant zones where eventual further investigations and surveys would be more effective to build the geotechnical model of the slope. The commercial software FLAC was used for the 2D and 3D geotechnical model. The distribution of the materials was randomized through a specifically coded MatLab program that automatically generates text files, each of them representing a specific soil configuration. Besides, a routine was designed to automate the computation of FLAC with the different data files in order to maximize the sample number. The methodology is applied with reference to a simplified slope in 2D, a simplified slope in 3D and an actual landslide, namely the Mortisa mudslide (Cortina d’Ampezzo, BL, Italy). However, it could be extended to numerous different cases, especially for hydrogeological analysis and landslide stability assessment, in different geological and geomorphological contexts. / L’incertezza nella determinazione del profilo stratigrafico e dei parametri meccanici dei singoli terreni è tra i principali problemi dell’ingegneria geotecnica, in particolare per l’analisi dei fenomeni franosi. Lo studio presenta un nuovo approccio nella modellazione geotecnica che si basa sulla generazione stocastica di diverse distribuzioni di strati di terreno, seguendo una logica booleana - il metodo è stato perciò chiamato BoSG (Boolean Stochastic Generation – Generazione Stocastica Booleana). Con questo metodo è possibile randomizzare la presenza di uno specifico materiale interdigitato in una matrice uniforme. Nell’impostare un modello geotecnico, infatti, generalmente si eliminano alcuni dati stratigrafici per semplificare il modello stesso, assumendo che la significatività dei risultati non ne risenta. La metodologia proposta permette di quantificare l'errore associato a questa semplificazione. Inoltre, può essere utilizzata per determinare le zone più significativi nelle quali possibili ulteriori indagini geotecniche sarebbero più efficaci per la definizione del modello geotecnico. Per la modellizzazione bidimensionale e tridimensionale è stato utilizzato il software commerciale alle differenze finite FLAC. La distribuzione dei materiali è stata randomizzata attraverso un programma in MatLab specificamente codificato che genera automaticamente dei file di testo con le configurazioni del terreno. E’ stata inoltre programmata una routine per automatizzare il calcolo FLAC con diverse file di dati al fine di massimizzare la numerosità campionaria. In questa tesi la metodologia è stata applicata ad un pendio semplice in 2D, un pendio semplice in 3D e una frana reale: la frana di colata di Mortisa (Cortina d'Ampezzo, BL). Il metodo, tuttavia, potrebbe essere applicato ad altri casi, in particolare per studi di idrologia sotterranea, per l’analisi di stabilità di altre frane e in diversi contesti geologici e geomorfologici

Sheet pile walls are one of the oldest earth retention systems utilized in civil engineering projects. They are used for various purposes; such as excavation support system, cofferdams, cut-off walls under dams, slope stabilization, waterfront structures, and flood walls. Sheet pile walls are one of the most common types of quay walls used in port construction. The worldwide increases in utilization of large ships for transportation have created an urgent need of deepening the seabed within port areas and consequently the rehabilitation of its wharfs. Several methods can be used to increase the load-carrying capacity of sheet-piling walls. The use of additional anchored tie rods grouted into the backfill soil and arranged along the exposed wall height is one of the most practical and appropriate solutions adopted for stabilization and rehabilitation of the existing quay wall. The Ravenna Port Authority initiated a project to deepen the harbor bottom at selected wharves. An extensive parametric study through the finite element program, PLAXIS 2D, version 2012 was carried out to investigate the enhancement of using submerged grouted anchors technique on the load response of sheet-piling quay wall. The influence of grout-ties area, length of grouted body, anchor inclination and anchor location were considered and evaluated due to the effect of different system parameters. Also a comparative study was conducted by Plaxis 2D and 3D program to investigate the behavior of these sheet pile quay walls in terms of horizontal displacements induced along the sheet pile wall and ground surface settlements as well as the anchor force and calculated factor of safety. Finally, a comprehensive study was carried out by using different constitutive models to simulate the mechanical behavior of the soil to investigate the effect of these two models (Mohr-Coulomb and Hardening Soil) on the behavior of these sheet pile quay walls.

A new constitutive model is proposed to describe the stress-strain-time behaviour of clays and organic soils. This approach is based on the framework of overstress viscoplastic theory and can be applied to any elastoplastic (inviscid) model.The most innovative idea of the proposed model is the identification of two components of strain for each deformation mechanism. In particular, in both the elastic and the plastic regimes a fast and a slow strain mechanism are assumed to be present. To this aim the constitutive model is based on two yield surfaces based on overstress viscoplasticity theory: one is quasi-instantaneous (for the fast part of plastic deformations) and the other is viscous (for the slow part of plastic deformations). This assumption permits the reliable simulation of the mechanical behaviour of a wide range of clayey soils: from inorganic clay (a.e. kaolinite and bentonite), to organic clays and peats. A further interesting aspect of the proposed model is the capability of simulate both the normally consolidated and the overconsolidated regime within a unique constitutive approach. An extensive experimental program on three different peaty soils has been performed to validate the constitutive model. The experimental tests include a wide range of oedometric tests (with very different loading conditions), and a series of triaxial tests conducted on NC and OC peats. The model has been validated also by simulating the settlements of a real embankment founded on a thick layer of organic clay.

The research focuses on the implementation and validation of advanced direct and indirect methods of investigation for the structural and mechanical characterisation of bimrocks. In particular, a non conventional in situ shear test has been develop in order to evaluate the strength parameters of bimrocks by properly taking into account the influence of blocks. Also, a geostatistical approach has been introduced for the investigation of block morphological and spatial properties from digital images, by means of a variographic analysis of the block Indicator Variable.

This research tries to fill a gap between two very different scales of enquiry: the local (i.e. hillslope) scale, where detailed investigations are possible but difficult to generalize over large areas, and the landscape (i.e., catchment) scale, where representation of the physics is minimised, the resolution in space and time is maximised, and the focus is upon predicting emergent properties rather than system details. Specifically, this Thesis focused on an aspect of the geosciences that is of critical current concern: the representation of the interface between hydrological response and geomorphic processes, notable mass movements. At present there remains a great difficulty at this interface: detailed geotechnical and hydrological studies of mass movements reveal exceptionally complex interlinkages between water and the surface sediment mass, notably dynamically at the onset and during mass release; but these kinds of studies are only possible with a very detailed description of the three-dimensional structure of the porous media and its hydrological and mechanical response during (and after) rainfall events. Such analyses are feasible but tend to result in analyses that are restricted in terms of geographical generalisation. On the other hand, approaches that apply to larger spatial scales tend to over-simplify the representation of critical failure processes, such as in the assumptions that infinite slope stability analysis can be applied to failures that are finite in their slope length, or that upslope contributing area can always act as a surrogate for the hydrologic response at a point in the watershed. The innovative element in this research lies on the assessment of rainfall-induced shallow landslide occurrence over large spatial scales, whilst accepting that shallow landslides triggering may be influenced by processes that operate over much smaller scales. Specifically, this Thesis focuses upon connection by subsurface flow pathways. New model approaches that incorporate connectivity are required to address the findings of field hydrologists. Thus, this Thesis starts from the understanding of small-scale hydrological processes to develop a large-scale topographic index-based shallow landslide model that includes the concept of subsurface hydrological connectivity. The research aims to provide a tool for more realistic assessments of when shallow landslides may occur and where landsliding may occur at the catchment scale to support decision makers in developing more accurate land-use maps and landslide hazard mitigation plans and procedures.