Sara Amoroso

Overconsolidation and Stiffness of Venice Lagoon Sands and Silts from SDMT and CPTU

AbstractThis study is part of an extensive research program carried out at the Treporti test site (Venice, Italy), where a cylindrical trial embankment was constructed and monitored from the beginning of its construction until complete removal, 4 years later. This paper concentrates mainly on the evaluation of overconsolidation and stiffness of the Venice lagoon sands and silts. The possibility of estimating the overconsolidation ratio (OCR) in sand by the combined use of seismic dilatometer (SDMT) tests and piezocone (CPTU) tests is investigated. A tentative correlation for estimating the OCR in sand from the ratio MDMT/qt is constructed. Field compression curves have been back-figured from 1-m field oedometer curves reconstructed from local vertical strains measured by a sliding deformeter under the embankment center. The SDMT and CPTU soundings performed before embankment application and postremoval have permitted analyzing how the OCR caused by the embankment was reflected by the before/after SDMT and...

The Seismic Microzonation of San Gregorio Through a Multidisciplinary Approach. Seismic Amplification in a Stiff Site

The village of San Gregorio (L’Aquila, Italy) was severely damaged by the April 6, 2009 earthquake. San Gregorio is situated at the base of a carbonate relief bounded by the Aterno river alluvial plain. The geological features of the area are very complex: jointed carbonate bedrock, cemented gravels and alluvial fan crop out in the village. Co-seismic ground fractures were seen along SW dipping active fault segments crossing San Gregorio. We integrated the microzonation studies with new geological, geotechnical and geophysical data for supporting the reconstruction planning of the village. Noise measurements show strong and polarized peaks in the horizontal-to-vertical spectral ratios (H/V) in the 3–7 Hz frequency band. Interestingly, the alluvial fan and the outcropping rock masses show both H/V peaks. To understand the influence of rock mass joint condition on site effect, we performed structural surveys on carbonate bedrock to look for a possible correlation between rock fracturing and ground-motion amplification.

Soil Liquefaction During the Emilia, 2012 Seismic Sequence: Investigation and Analysis

In the framework of a Project issued by the Italian National Institute of Geophysics and Volcanology (INGV) a Research Unit (RU) has been granted with the commitment to provide a link between the seismic shaking and the triggering of ground failures such as liquefaction. The main goals have regarded both the enlargement of the base of observables for a better constrain of the seismic hazard assessments and the analysis of the triggering and causative factors of permanent ground deformations. Nevertheless, when analyzing the non-linear soil response under which liquefaction occur, some insights into site-effects have been also provided, thus contributing to the general task of the site-specific hazard. The paper illustrates the analyses and investigations carried out within the aim of the project, some of them are still provisional due to the huge amount of data produced and the strong effort required to analyze all the matters related to the observed phenomena.

Quaternary geology and paleoseismology in the Fucino and L’Aquila basins

This 2 days-long field trip aims at exploring field evidence of active tectonics, paleoseismology and Quaternary geology in the Fucino and L’Aquila intermountain basins and adjacent areas, within the inner sector of Central Apennines, characterized by extensional tectonics since at least 3 Ma. Each basin is the result of repeated strong earthquakes over a geological time interval, where the 1915 and 2009 earthquakes are only the latest seismic events recorded respectively in the Fucino and L’Aquila areas. Paleoseismic investigations have found clear evidence of several past earthquakes in the Late Quaternary to Holocene period. Active tectonics has strongly imprinted also the long-term landscape evolution, as clearly shown by numerous geomorphic and stratigraphic features. Due to the very rich local historical and seismological database, and to the extensive Quaternary tectonics and earthquake geology research conducted in the last decades by several Italian and international teams, the area visited by this field trip is today one of the best studied paleoseismological field laboratories in the world. The Fucino and L’Aquila basins preserve excellent exposures of earthquake environmental effects (mainly surface faulting), their cumulative effect on the landscape, and their interaction with the urban history and environment. This is therefore a key region for understanding the role played by earthquake environmental effects in the Quaternary evolution of actively deforming regions, also as a major contribution to seismic risk mitigation strategies.

Local Seismic Response in the Southern Part of the Historic Centre of L’Aquila

This paper illustrates the results of the numerical modeling carried out to investigate the local seismic response in the Southern part of the city centre of L’Aquila (Italy), namely in the area of Via XX Settembre, harshly damaged by the April 6, 2009 earthquake. The upper portion of the subsoil in this area is irregularly affected by peculiar local conditions that may have originated major amplification of the ground motion during the main shock. The geotechnical model of the subsoil and related parameters, defined based on accurate site investigations, were used for a seismic response analysis. The results of this analysis indicated that the site effects due to local subsoil conditions played an important role in the observed damage distribution.

Characterization of soil deformation due to blast-induced liquefaction by UAV-based photogrammetry and terrestrial laser scanning

ABSTRACT Soil liquefaction due to an earthquake can lead to permanent soil deformation and reduction of load-bearing capacity that in turn could act on building stability. Since a quantitative evaluation of post-liquefaction settlements is often very difficult, field scale liquefaction tests, carried out under controlled conditions, such as blast tests, are used to perform a correct quantitative analysis of the liquefaction phenomena. Among the significant parameters related to a blast test, there are the geometric ones, i.e. the extension of the area affected by the blast-induced liquefaction and the corresponding vertical displacements. This article shows the results of a blast test carried out at a trial site located in Mirabello (Ferrara, Italy) from a remote-sensing perspective. Data provided by aerial Structure-from-Motion photogrammetry, supported by terrestrial laser scanning measurements, were used to evaluate the soil deformation that, in the specific case study, aided a geological/geotechnical interpretation of the blast test results. In general, the proposed method can be used to characterize areas affected by blast-induced liquefaction, including those cases where blasting is used as ground improvement technique aimed at mitigating the seismic hazard.

Marchetti flat dilatometer tests in a virtual calibration chamber

Calibration chambers are frequently used to verify, adapt, or both verify and adapt empirical relations between different state variables and in situ test results. Virtual calibration chambers (VCC) built with 3D discrete element models may be used to extend and partially substitute costly physical testing series. VCC are used here to explore the mechanics of flat dilatometer penetration and expansion. Results obtained for a simulation of physical tests in Ticino sand are presented. Blade tip resistance during penetration is in good agreement with the experiments. A piston-like design is used for the blade so that larger displacements may be applied than it is possible with a membrane. Initial piston pressures in the expansion curves are very low, strongly affected by the scaled-up grain sizes. Despite that difficulty, expansion curves may be easily interpreted to recover dilatometer moduli ED close to those observed in the physical experiments. Particle-scale examination of the results allows a firmer understanding of the current limitations and future potential of the technique.

2D site response analysis of a cultural heritage: the case study of the site of Santa Maria di Collemaggio Basilica (L’Aquila, Italy)

The Santa Maria di Collemaggio Basilica is an important cultural heritage site and exemplifies Romanesque-Gothic art in the Abruzzo region (central Italy). Erected in the second half of the XII century, the Basilica was severely damaged during the April 6, 2009 L’Aquila earthquake (MW 6.1). In particular, the area of the transept collapsed causing the dome to fall. A refined two-dimensional (2D) geotechnical model was built representing a section that includes the Basilica, in order to better understand the soil response of the Basilica site. The subsoil model was constrained using the geophysical and geotechnical data collected from the seismic microzonation studies, the reconstruction of private damaged buildings and other technical and scientific studies realized in the L’Aquila basin and in the area of the Basilica before and after L’Aquila earthquake. 2D site response analyses were performed to verify the presence of local site effects by comparing simulated versus experimental transfer functions. Moreover, a frequency–wavenumber (f–k) analysis was executed with the aim of evaluating the occurrence of surface waves generated within the basin. 2D seismic effects involve significant amplification in the period range of engineering interest, therein providing an appropriate elastic response spectrum for the restoration of the Basilica.

The Seismic Site Characterization of Palazzo Centi in L’Aquila City Centre: The Case Study of a Historical Building Damaged by the April 6th 2009 Earthquake

An extensive geological, geotechnical and geophysical investigation was performed in L’Aquila city centre to restore Palazzo Centi, a historical building, damaged by the April 6, 2009 L’Aquila earthquake. This site investigation consisted of punctual and linear tests that allowed to define a detailed 3D model of the subsoil, irregularly affected by some peculiar conditions and characterized by low and variable values of the shear wave velocity V S in the near surface volume. In particular, the variable thickness of the upper fine-grained residual soils probably determined different ground motion amplifications during the main shock.