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Papers by alessandro flora

Bulletin of Earthquake Engineering

CRC Press eBooks, May 25, 2022

Journal of Geotechnical and Geoenvironmental Engineering

Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2020

Incontro Annuale Ricercatori di Geotecnica 2002, 2002

Proceedings of the Institution of Civil Engineers - Ground Improvement, 2022

The paper presents an original application of vacuum preloading, conceived for the reclamation of... more The paper presents an original application of vacuum preloading, conceived for the reclamation of containment facilities hydraulically filled with fine-grained sediments, and the evaluation of its performance. The technique, which consists in the installation of horizontal vacuum layers within the dredged soil mass, with the aim of reducing the soil volume and accelerating the consolidation while filling is underway, was successfully implemented for the first time in the port of Gaeta (Italy). The construction sequence and the numerical models developed to analyse the huge changes of state experienced by the soil – whose prediction is paramount in evaluating the actual storage capacity of the impoundments – are described. Monitoring data and in situ test results are illustrated and compared with numerical predictions (class A, C and back-analyses), confirming the effectiveness of the technique and of the modelling choices. Finally, the lessons learned from the case history to optimi...

This paper describes the small scale centrifuge modelling activities performed at ISMGEO (Istitut... more This paper describes the small scale centrifuge modelling activities performed at ISMGEO (Istituto Sperimentale Modelli Geotecnici, formerly ISMES – Italy) laboratory in the frame of the H2020 LIQUEFACT project (http://www.liquefact.eu/). The main aim of the experimentation was to analyze the seismic behavior of loose, saturated, sandy deposits, homogeneous or stratified, subjected to increasing seismic excitations up to liquefaction and to verify the effectiveness of different liquefaction mitigation techniques. Some tests were carried out under free field condition, in some others a simple structure based on shallow foundations was modelled. Thirty-seven centrifuge tests were carried out to this aim, organized in three series: the first one aimed at investigating the liquefaction triggering conditions, the second and third ones devoted at analyzing the effectiveness of three selected liquefaction mitigation techniques: vertical drains, horizontal drains and "Induced Partial S...

A database of masonry buildings located in a number of municipalities struck by the 2012 Emilia e... more A database of masonry buildings located in a number of municipalities struck by the 2012 Emilia earthquake has been analyzed for this work. Post seismic survey was carried out by the Italian Department of Civil Protection soon after the earthquake. The database included information on building characteristics, level and extent of damage to structural and non-structural components. Additionally, data on ground conditions and the results of in-situ tests (CPT) were collected. The comparative analysis of observed damage has shown evidences of the impact of soil liquefaction on structures. It led to the formation of unusual crack patterns on the structure compared to the typical inertial damage. The correlation between structural damage and soil liquefaction was then investigated with reference to an exemplificative case of study in the hamlet of San Carlo (Sant'Agostino municipality). A simplified procedure for estimating liquefactioninduced building settlement was applied, obtaini...

Numerical Methods in Geotechnical Engineering, 2006

During the first stage of construction historic towers could have been not so far from a bearing ... more During the first stage of construction historic towers could have been not so far from a bearing capacity collapse, due to lack of strength of the soil, and safely survived thanks to some delay or interruption of the building process, that allowed the foundation soil to improve its strength and the tower to be successfully finished. Then, a more subtle and often unforeseen danger was represented by leaning instability, that increases if there is lack of stiffness of the soil. And, because of creep phenomena, a tower, even if initially stable, can attain with time an instability condition (asymptotic leaning instability). There also are aspects of structural nature, linked to the masonry behaviour as a unilateral material (Heyman, 1992), changes of geometry, reduction of cross section and stress concentration on masonry contact points, that deserve special attention, as proved by the collapse of the Campanile in Venice and the Civic Tower in Pavia. And there are aspects related to se...

Experience gained over the years proves the exposure of cultural heritage to a variety of geotech... more Experience gained over the years proves the exposure of cultural heritage to a variety of geotechnical risks. This poses the problem of conceiving and implementing remedial measures preserving that immaterial value represented by the integrity of the single monument or the "diffuse cultural heritage", that is the goal of any conservation intervention. In addition, it must be kept in mind that each monument or historic site is an "unicum" in itself, neither repeatable nor reproducible. This volume "Geotechnics and Heritage. Historic Towers and Geotechnics", moves along this path and collects well documented case histories of towers (i.e. slender structures transmitting high loads to the subsoil) of historic relevance that had or have geotechnical problems. The outcome is an interesting picture of the variety of geotechnical problems that an historic tower may have to face in its life.

Lecture Notes in Civil Engineering, 2019

The main aim of this work is to study the effectiveness of densification as a mitigation techniqu... more The main aim of this work is to study the effectiveness of densification as a mitigation technique against liquefaction, by means of cyclic simple shear tests carried out on specimens reconstituted at several relative densities. The adopted cyclic simple shear apparatus works with a sophisticated control system, which allows to carry out tests in k0 condition without using confining rings. Two different Italian sands were tested, both retrieved at Pieve di Cento (Emilia Romagna Region, affected by 2012 earthquake) at different depths. The results of cyclic simple shear tests show that densification increases the resistance to liquefaction. The expression of Booker et al. (1976) has been also used to simulate the trend of excess pore pressure ratio with the ratio between number of cycles and number of cycles at liquefaction of the experimental undrained cyclic tests.

International Journal of Architectural Heritage, 2021

The Theodosian walls of Constantinople have suffered many partial destructions in their long-last... more The Theodosian walls of Constantinople have suffered many partial destructions in their long-lasting life, often because of strong seismic events, undergoing subsequent reconstructions. With refere...

Proceedings of the Institution of Civil Engineers - Ground Improvement, 2007

A possible approach is shown for the design of jet grouted umbrellas, which are often used as tem... more A possible approach is shown for the design of jet grouted umbrellas, which are often used as temporary supports in tunnelling practice. In the current paper it is argued that such an approach should be probabilistic or semi-probabilistic. Based on published experimental data and statistical analyses of diameter and centroid position along the axis of jet grouted columns, a series of Monte Carlo simulations were carried out to find the influence of possible defects within the column in the umbrella static performance, with reference to two extreme subsoil conditions: clay and sand. Geometrical considerations on the minimum overlapping among columns necessary for continuity on the whole span of the umbrella are drawn. It is shown that, owing to defects, the real shape of jet grouted umbrellas is not that of a regular frustum of cone. It is also shown that overlapping decreases along the span. There is a critical length after which structural continuity is diffi- cult to obtain, depen...

Géotechnique, 1997

Deformation characteristics at strains less than about 0·001% in compacted well-graded sandy grav... more Deformation characteristics at strains less than about 0·001% in compacted well-graded sandy gravel were evaluated by measuring vertical and horizontal strains locally in very small amplitude cyclic tests on square prismatic specimens. The very small strain Young's modulus E&up0; exhibits strong inherent anisotropy and stress-state-induced anisotropy. The very small strain Poisson's ratio v&up0;vh is a function of stress ratio. Effects of ageing on the values of E&up0;v and v&up0;vh are discussed. On a évalué les caractéristiques de déformation d'un gravier sableux compacté et à granulomé trie continue à des contraintes inférieures à 0,001 p. 100 environ, en mesurant les contraintes verticales et horizontales locales dans des essais cycliques à très faible amplitude réalisés sur des éprouvettes prismatiques carrées. Le module de Young pour très faibles contraintes E0 met en évidence une forte anisotropie inhérente et une anisotropie provoquée par l'état de contrainte...