Lorenza Evangelista

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.

Some Limits in the Use of the MASW Technique in Soils with Inclined Layers

Abstract The surface wave method is a characterization technique that allows obtaining the shear wave velocity profiles trough the measurement of the dispersion of surface waves coupled with an inversion procedure. Spectral and multichannel analysis of surface wave techniques are becoming, recently, a common investigation tool for site characterization. For the inversion of the surface wave dispersion curve, homogeneous or horizontally layered soil models are assumed and this hypothesis could represent a limitation on the practical use of the technique. In this paper, the numerical dispersion curves of a subsoil, constituted by two layers of elastic material separated by a horizontal or an inclined interface, are simulated by a finite element commercial code. This allows detecting some limits in the conventional interpretation of the surface wave tests. MASW experiments executed in two different sites in Molise Region (Italy), characterized by simple or complex stratigraphic conditions, are shown as examples to validate the assumption and the analyses made in the paper.

Analysis of the Stability of a Rock Cavern: The Fontanelle Cemetery

The paper reports the study conducted to evaluate the stability condition of one the most suggestive rock cavity located in the city of Naples (Italy), the Fontanelle (little fountains) Cemetery. It is a chamber and pillar cavity, with a rectangular and elongated plan, consisting of three naves. The cavern was excavated in the Neapolitan Yellow Tuff, a soft rocks widespread used as construction material in the city and its origin goes back to the 16th century while its expansion to the 17th century, when the city was quickly battered by popular uprising, famines, earthquakes, eruptions of the Vesuvius and epidemics. The cavity was addresses to different uses; destined to become an ossuary in the 18th century, progressively turned into a Christian worship place, suffering many events during 400 years of life, until it finds, in the modern age, its stability as a place of worship. The paper reports the numerical analyses by means of a 3D finite difference code, carried out to evaluate the stability condition of the cavity and the hill on which was excavated, taking into account the various stages of life. The results obtained show that there are some stability problem for the roof of the cavity; further investigations on the shape of the pillars, partially hidden by the fill, and on the mechanical properties of the tuff are needed for a more satisfactory evaluation.

Influence of Suction on the Behaviour of Retaining Walls in the City of Naples, Italy

The general principles of EUROCODE 2008 prescribe that new constructions are designed, tested and subjected to maintenance during their lifetime. Safety and performance under service conditions are evaluated through the limit states that may occur during the nominal life of the construction. As it is well known, limit states are the conditions beyond which the construction no longer meets the requirements for which the design has been made. In general, during its lifetime, a construction can experience a variation of the external loading. A clear example is the occurrence of a seismic event. Yet, when the soil is in a partially saturated condition, its hydro-mechanical properties can vary with time as a consequence, for example, of rainfall events and subsequent infiltration. A more complex approach is in this case required as a variation of both soil hydro-mechanical properties and external loading can occur. The present work deals with the above issue. In particular, it refers to the city of Naples where unsaturated pyroclastic soils are widespread. Gravity walls, made of tuff masonry, and retaining unsaturated pyroclastic backfills have been analyzed in terms of general behavior and potential damage induced by rainfall events. A Two-Phase Flow module - FLAC2D (Itasca, 2000) has been employed for the numerical analysis.