Giovanni Vannucchi

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.

Influence of uncorrected accelerogram processing techniques on Newmark's rigid block displacement evaluation

Design seismic motion represents a fundamental issue of many geotechnical applications. In more complex numerical procedures, input motion is required in the complete form of an accelerogram, whereas in simplified prediction methods it is generally expressed by means of synthetic parameters such as peak ground acceleration, peak ground velocity, Arias intensity, etc. The aim of this paper is to show the sensitiveness of these parameters to small changes in the characteristics of the accelerogram associated with the filtering procedures used for reducing digitisation errors, instrument distortions, etc. and the influence of the consequent uncertainties on geotechnical applications. More specifically this paper examines the incidence of processing techniques of uncorrected records from Italian accelerograph network on slope displacement evaluation based on Newmarks rigid block model.

CPT-Based Liquefaction Case History from the 2012 Emilia Earthquake in Italy

AbstractSignificant and widespread liquefaction phenomena were observed after the main shock of the Emilia earthquake (Italy) on May 20, 2012. A considerable number of surveys were subsequently performed to accurately test the susceptibility to liquefaction of soil deposits affected by the most severe liquefaction-induced effects and damage. Ground surface morphology was defined in detail by means of LIDAR survey results; subsoil stratigraphy and water table level were inferred from CPT tests and soundings; physical properties and mechanical parameters of soils were obtained from laboratory tests or indirectly inferred from the results of a large number of CPT tests carried out in the area. Two main sandy layers susceptible to liquefaction were identified and appropriately characterized. Seismic loading induced by the main shocks of the sequence was carefully estimated from the peak ground acceleration map produced by the National Institute of Geophysics and Volcanology. More than 90 sites were examined i...

A Methodology for Advanced Seismic Microzoning Using 2D Analyses: The Case Study of Barberino di Mugello, Florence, Italy

The here presented study was developed in the frame of the VEL/DOCUP projects promoted by the Regional Government of Tuscany (Central Italy) in order to mitigate the risk from earthquake. It concerns the assessment of local seismic effects aimed at drawing up a detailed seismic microzoning map for an area including some villages, industrial and commercial settlements close to the most important town of western Mugello, one of the highest seismicity zones of the Northern Apennine Chain. Geological subsoil modelling and geotechnical characterization of the area under study were performed by using the results of an in-depth survey including in situ and laboratory tests. On the basis of geomorphologic and lithostratigraphic data, a first level of seismic zoning map was prepared aimed to recognize areas involved in different kinds of geotechnical phenomena (amplification, slope-instability, liquefaction, etc.) and several representative cross sections were then identified for the whole area under study. Numerical 2D analyses were implemented on the selected cross sections to quantify the local seismic response on ground surface. The performed analyses allowed to recognize zones with different seismic response in term of a suitable selected amplification factor and to draw a Level 3 seismic microzonation map according to the procedure recommended by the Italian guidelines for microzoning. In this paper the results of two-dimensional local seismic response analyses and advanced seismic microzonation mapping for the area under study are presented and discussed.

Soil Liquefaction Analyses in a Test-Area Affected by the 2012 Emilia-Romagna Earthquake (Italy)

Significant and widespread liquefaction effects were observed in the area of San Carlo and Mirabello villages during the Emilia-Romagna earthquake of May 20 and 29, 2012. After the earthquake, an intensive program of laboratory and in situ (mostly CPT’s) tests was carried out in the affected area. The stratigraphic and geotechnical conditions have been found to predispose the soil deposits to liquefaction phenomena. The triggering conditions, i.e. the design earthquake parameters, have been evaluated according to the most recent seismic hazard analyses and local seismic response analyses. The liquefaction risk, expressed in term of liquefaction potential index (LPI), was determined by using the CPT-based simplified method of Robertson and Wride. The obtained results are not consistent with the observed liquefaction effects and the liquefaction risk seems to be systematically underestimated. In the present paper the reason of this underestimation is investigated and a possible correction for applying the simplified cyclic stress approaches is proposed.

Influence of Soil Dynamic Parameters on Seismic Response of a Site at Fabriano, Italy

1 Dipartimento di Ingegneria Civile, Universita di Firenze, Italy – teresa@dicea.unifi.it 2 Dipartimento di Ingegneria Strutturale e Geotecnica, Politecnico di Torino, Italy diego@geohp.polito.it 3 Dipartimento di Ingegneria Civile, Universita di Firenze, Italy 4 Dipartimento di Ingegneria Civile, Universita di Firenze, Italy INFLUENCE OF SOIL DYNAMIC PARAMETERS ON SEISMIC RESPONSE OF A SITE AT FABRIANO, ITALY

Seismic Stability Analyses of the Po River Banks

The Po River is the major Italian watercourse. Over half its length is controlled with embankments as protection measures against heavy floodings. Recently, the Italian Government has funded a project for the evaluation of the seismic stability of about 90 km of embankments of the Po River. The project mainly aims at the seismic stability analyses of the river banks, with assessment of local site response and evaluation of the liquefaction potential. Hundreds of geotechnical investigations within the study area were performed and the water level variations in the embankment and subsoil were investigated using piezometers. This paper describes the methodology and the main results of the analyses. The safety of 43 significant sections in static and seismic conditions was investigated using limit equilibrium analyses. Dynamic effects in the seismic condition were considered using the pseudostatic method. Local seismic hazard and effects of site conditions on the ground motion are taken into account in the definition of the expected seismic action. Eventually, the analysis results are summarized in a static and seismic stability map of the investigated area, a useful tool for the local Authority in the prevention and mitigation.

Geotechnical Aspects in Seismic Soil–Structure Interaction of San Gimignano Towers: Probabilistic Approach

AbstractThis paper summarizes the main aspects of geotechnical modeling and soil–structure interaction analyses performed for the seismic risk assessment of the San Gimignano towers. Morphological,...

Liquefaction Hazard Maps of the Harbour Area of Gioia Tauro (Italy) by Geo-Statistical Methods

This paper reports the results of a case study of liquefaction assessment and mapping carried out in the harbour area of Gioia Tauro, in the southern part of Italy. The area, lying on a flat plain prevalently constituted in the first 20 meters below the ground level by cohesionless loose soils, struck by several historical earthquakes with intensity superior to VIII MCS, was the object of extensive seismological, geological and geotechnical surveys. The cyclic resistance ratio and the liquefaction potential index were estimated from numerous but not equispatially distributed in the area CPT and SPT profiles. Therefore geo-statistical method were applied to draw up reliable liquefaction hazard maps including uncertainties of estimated risk.

Seismic Response and Soil-Structure Dynamic Interaction for a Large Building in Florence

The New Law Court in Florence, the construction of which is under way, consists of buildings of different heights, up to a maximum of 77 m from g.l. It covers an area of about 30,000 m, and has a total volume of 750,000 m, approximately 550,000 m of which are above ground level. Figure 1 reproduces a photograph of the plastic model of the building in progress. The foundation soil is part of a very thick recent alluvial deposit (more than 80 m) consisting mostly of consistent and overconsolidated silts and clays, with local inclusions of pebbles, gravel and calcareous nodules with dimensions that are even centimetric, more frequently in the first 20 m of depth. Thorough geotechnical studies were carried out (Vannucchi, 1997; 1999) in view of the importance of the work. In particular, the local seismic response in a free field was evaluated, and an analysis of the soil structure dynamic interaction was made. The results of these analyses are discussed synthetically here as follows. 2 CHARACTERISTICS OF THE DESIGN MOTION