Anna d’Onofrio

Geotechnical Aspects of the L’Aquila Earthquake

On April 6, 2009 an earthquake (ML = 5.8 and MW = 6.3) stroke the city of L’Aquila with MCS Intensity I = IX and the surrounding villages with I as high as XI. The earthquake was generated by a normal fault with a maximum vertical dislocation of 25 cm and hypocentral depth of about 8.8 km. The deaths were about 300, the injured were about 1,500 and the damage was estimated as high as about 25 billion €. Both maximum horizontal and vertical components of the accelerations recorded in the epicentral area were close to 0.65 g. The paper summarises the activities in the field of earthquake geotechnical engineering aimed to the emergency and reconstruction issues. The ground motion recorded in the epicentral area is analysed; the geotechnical properties measured by in-situ and laboratory tests before and after the earthquake are summarised; site effects are preliminarily evaluated at accelerometric stations locations and damaged villages; the outstanding cases of ground failure are finally shown.

The Influence of Meso-Structure on the Mechanical Behaviour of a Marly Clay from Low to High Strains

On October 31, 2002, a ML=5.5 earthquake struck the Molise region in Southern Italy. The strongly non-uniform damage distribution observed in the town of San Giuliano di Puglia suggested that site amplification significantly affected the seismic response of the Toppo Capuana marly clay formation.

Lessons learned from two case histories of seismic microzonation in Italy

The prediction of the variability of the seismic ground motion in a given built-up area is considered an effective tool to plan appropriate urban development, to undertake actions on seismic risk mitigation and to understand the damage pattern caused by a strong-motion event. The procedures for studying the seismic response and the seismic microzonation of an urban area are well established; nevertheless, some controversial points still exists and are discussed here. In this paper, the selection of a reference input motion, the construction of a subsoil model and the seismic response analysis procedures are discussed in detail, based on the authors’ experience in two Italian case histories: the seismic microzonation of the city of Benevento, which was a predictive study, and the simulation of seismic response and damage distribution in the village of San Giuliano di Puglia, which was a retrospective analysis.

Dependency of the Mechanical Behaviour of Granular Soils on Loading Frequency: Experimental Results and Constitutive Modelling

The paper shows some cyclic torsional shear test results obtained on dense Toyoura sand specimens. The dependency of the mechanical response of this material on both loading amplitude and frequency are discussed, to obtain a framework to analyze the mechanical behaviour of granular soils. The pseudo-elastic shear stiffness and the damping ratio are the variables taken into consideration; their evolution with the number of cycles performed at the different loading amplitudes is analysed to describe the mechanical irreversibility of the material response.

Development of a simplified model for pore water pressure build-up induced by cyclic loading

In this paper the formulation of a simplified model for predicting pore water pressure build-up under seismic loading is updated and applied to different soils. The model is directly based on the results of cyclic laboratory tests and it is based on the damage parameter concept, avoiding any arbitrary equivalence criterion necessary to compare the seismic demand to the cyclic strength of liquefiable soils. The model is suitable to be implemented into non-linear coupled seismic response analyses since it operates in the time domain. The analytical formulation is fully described and the calibration and the physical meaning of the model parameters are analysed in detail. Simple applications show the practical usefulness of the model with respect to other literature approaches.

Liquefaction Triggering, Consequences, and Mitigation

The importance of predicting ground deformation in loose, saturated granular soils has been widely recognized for a reliable evaluation of liquefaction damage. A procedure is proposed in this paper for the evaluation of post-cyclic consolidation settlements, as a result of volumetric strains induced by the dissipation of excess pore pressure. A stress-based model is first adopted for generating the excess pore water pressure in 1D free-field conditions, allowing for an effective stress analysis according to a loosely coupled approach. Then, the post-cyclic settlement is simply calculated integrating the vertical strains. To this aim, by considering a welldocumented case history in which an extremely small settlement was observed upon seismic excitation, soil stiffness is estimated on the basis of either CPT data or shear stiffness decay curve, to show the effect of modelling hypothesis on the results. Both approaches result into a value of the settlement close to the observed one and much lower than that calculated using a well-established empirical procedure.

Reconnaissance of geotechnical aspects of the 2016 Central Italy earthquakes

Between August and November 2016, three major earthquake events occurred in Central Italy. The first event, with M6.1, took place on 24 August 2016, the second (M5.9) on 26 October, and the third (M6.5) on 30 October 2016. Each event was followed by numerous aftershocks. The 24 August event caused massive damages especially to the villages of Arquata del Tronto, Accumoli, Amatrice, and Pescara del Tronto. In total, there were 299 fatalities, generally from collapses of unreinforced masonry dwellings. The October events caused significant new damage in the villages of Visso, Ussita, and Norcia, although not producing fatalities, since the area had largely been evacuated. The Italy–US Geotechnical Extreme Events Reconnaissance team investigated earthquake effects on slopes, villages, and major infrastructures. The approach adopted to carry out post-earthquake reconnaissance surveys was to combine traditional reconnaissance activities of on-ground evidences and mapping of field conditions with advanced imaging and damage detection routines enabled by state-of-the-art geomatics technology. Presented herein are the outcomes of the post-event reconnaissance surveys conducted after both the August main shock and the October events, focusing on geotechnical aspects, such as earthquake-triggered slope failures, mud volcanoes, performance of different geotechnical structures (i.e., dams, retaining walls, rockfall barriers, road embankments) and building damage patterns related to site amplification.

Correction to: Reconnaissance of geotechnical aspects of the 2016 Central Italy earthquakes

Because of an error during the editorial process the first name initial of author Ernesto Ausilio was incorrectly given as A. (A. Ausilio) in the initial online publication. It should obviously be E. Ausilio. The original article has been corrected.

Mechanical Behavior of Florence Clay at the High-speed Train Station

To develop the design of the Florence high-speed train station, Arup’s office in Milan committed to the geotechnical laboratory of the University of Naples the execution of an extensive experimental program.