47 research outputs found
Proprietà dinamiche dei terreni del centro storico di sellano attraverso prove di RCT CLTST e DSDSS
No full textNella presente nota sono riportati i risultati di prove di laboratorio dinamiche (colonna risonante) e cicliche (taglio torsionale e taglio semplice) per la misurazione della rigidezza e dello smorzamento dei campioni di terreno prelevati nel centro abitato di Sellano (Pg), colpito dal terremoto Umbro Marchigiano del 1997. I risultati sperimentali sono espressi in termini di modulo di taglio massimo (Gmax), modulo di taglio normalizzato (Gs/Gmax) e di fattore di smorzamento (D)
Geotechnical seismic hazard evaluation at sellano (Umbria, Italy) using the GIS technique
No full textA tool that has been widely-used in civil engineering in recent years is the geographic information system (GIS) [1]. Geographic Information systems (GIS) are powerful tools for organizing, analyzing, and presenting spatial data. The GIS can be used by geotechnical engineers to aid preliminary assessment through to the final geotechnical design. The aim of this work is to provide some indications for the use of the GIS technique in the field of seismic geotechnical engineering, particularly as regards the problems of seismic hazard zonation maps. The study area is the village of Sellano located in the Umbrian Apennines in central Italy, about 45 km east of Perugia and 120 km north-east of Rome The increasing importance attributed to microzonation derives from the spatial variability of ground motion due to particular local conditions. The use of GIS tools can lead to an early identification of potential barriers to project completion during the design process that may help avoid later costly redesign. © 2008 American Institute of Physics
Geotechnical characterization of ash collected during recent eruptions of Mount Etna: from dangerous waste material to environmental friendly resource
No full textAn exponential increase in the activity of Mount Etna (Catania, Italy) has been observed between the massive eruptions that lasted from 1991 to 1993 and the very significant ones, which occurred between 2012 and 2018. Large amounts of ash repeatedly covered the city of Catania, causing environmental problems for road and air traffic, agriculture and human health. Recent thinking has been to consider volcanic ash as a resource rather than a waste material, thus avoiding damage to both the environment and human health. This goal could be achieved using this material in several fields of geotechnical engineering but first static and dynamic laboratory geotechnical tests must be performed. This paper deals with a static and dynamic geotechnical characterization of volcanic ash collected during recent eruptive activity on Mount Etna. Grading and index properties tests, oedometer tests, direct shear tests and dynamic resonant column tests were performed in the Geotechnical Laboratory at the University of Catania. Particle crushing was also analysed following oedometer tests and direct shear tests. The tested materials are essentially of a gravelly-sandy nature and showed very different strains due to the different grain size distribution curves as well as to the aptitude to crushing of these materials. Cohesion is negligible both at peak state and at the critical state, in line with granular soil behaviour. A light curvature of the failure curves can be observed for some peak envelopes. The results of dynamic tests are in quite good agreement with those of well-known sands. Thus, taking into account crushing, it is possible to appropriately reuse these materials in geotechnical engineering avoiding inhalation and ingestio
Geotechnical seismic risk evaluation in seismic areas
No full textSeismic and geotechnical hazard problems are widespread all over the world and they can cause natural disasters, damaging properties or causing human lives losses. Italian municipalities are not yet organised either to deal with the phenomena consequences, or to plan risk mitigation actions. A clear knowledge of the location and of the space and time evolution of the phenomena is needed for a vulnerability mitigation in the probably involved areas. Geo-hazard can be related with the consequences for exposed people and man made work by a microzonation. GIS technologies could play a crucial role in analysing large areas, but a good geodatabase should be designed and populated with all the available data.
In this work, an approach to detect geotechnical hazard factors and vulnerability elements of urban areas is presented. A geodatabase is designed in terms of conceptual and logical model. A multy-risk analysis is carried out, pointing out geotechnical seismic and hydrogeological risk. Expressly created forms are proposed, that include specific sections regarding buildings, infrastructures and lifelines for vulnerability detection. Some applications in central Sicily (Italy) are shown. From such a analysis, Civil Defence and Local Authorities could obtain a continuous stream of information and integrate them into models for hazard knowledge, vulnerability mitigation and risk prevention
The ground motion grade - 3 microzonation of Sellano
No full textGli eventi sismici che hanno colpito le regioni dell’Umbria e delle Marche nel 1997-1998 rappresentano delle crisi ricorrenti nella storia sismica di quest’area. Tali crisi sono caratterizzate essenzialmente da una magnitudo piuttosto moderata; tuttavia nel 1997-1998 hanno causato notevoli danni in diverse città, così come nella città di Sellano (Umbria). Nel presente articolo, la spiegazione di un tale fenomeno è ricercata nelle caratteristiche geotecniche del terreno coinvolto.
I tre terremoti più significativi accorsi durante la sequenza sismica del 1997-1998 vengono scelti come terremoti “di scenario”. Quindi, sulla base della caratterizzazione geotecnica del territorio di Sellano viene valutata la risposta in supercie. Per ciascuna zona in cui è stato diviso il territorio di Sellano e per i summenzionati terremoti “di scenario” vengono calcolati gli spettri di risposta in superficie. Infine, vengono elaborate le mappe di pericolosità sismica-geotecnica in termini di massimo rapporto di amplificazione e di massima accelerazione orizzontale in superficie.The seismic events that hit the Umbria and Marche Regions in 1997-1998 represent recurrent crises in the seismic history of this area. These crises are mostly characterised by relatively moderate magnitudes; nevertheless in 1997-1998 they caused extensive damage in different towns, such as in the town of Sellano (Umbria Region). In the present paper, the geotechnical characteristics of the soil involved are examined in order to find the explanation for this phenomenon.
The three most significant shocks which occurred during the 1997-1998 Umbria-Marche seismic sequence are chosen as “scenario” earthquakes. Then, on the basis of the site characterisation of the Sellano area, the soil response is analysed. For each different zone and for the input motions considered as “scenario” earthquakes the response spectra at the surface level are developed. Finally, the seismic, geotechnical hazard maps in terms of maximum amplification ratio and in terms of maximum horizontal acceleration at the soil surface are drawn-u
Dynamic response analysis of earth-retaining walls by means of shaking table tests
No full textThe paper describes the results of some experimental activities performed at the Earthquake Engineering Research Center of Bristol University and related to the seismic response analysis of earth-retaining walls. The activities consist of several shaking table tests performed on a earth-retaining wall system involving a scaled concrete wall model and a Leighton Buzzard sand deposit. The obtained results are presented in terms of amplitude of acceleration and displacement of the wall and are discussed focusing the attention on some aspects of the response generally neglected in the traditional performance-based design approaches. Copyright © (2006) by Earthquake Engineering Research Institute All rights reserved
Geotechnical seismic hazard evaluation at Siracusa (Sicily) using GIS techniques
No full textSiracusa province is prone to seismic risk. Many towns of the Siracusa province were destroyed by the 1693 earthquake; among these, the town of Noto was completely destroyed and rebuilt in a site some kilometres distant from the original one. To evaluate seismic risk at a specific area, it is important to have as much information as possible about many data related to the given area, but there are several problems with detection, collection, and use of spatial data/information for disaster management. Seismic hazard can be related with the consequences for exposed buildings and human life. GIS technologies could play a crucial role in analysing large areas, but a good geodatabase should be designed and populated with all the available data. The research that is being carried out has the aim to obtain an approach to detect seismic hazard factors and vulnerability elements of urban areas. To evaluate seismic vulnerability, a geo-database in terms of conceptual, logical and physical model to collect and store information about multy-risk analyses have been created to point out especially seismic risk evaluation. To evaluate seismic hazard, some scenario earthquake of a studied area should be applied to calculate the site seismic response. In this work the studied area is Siracusa, one of the most beautiful town in Sicily (Italy), with a baroque old town centre built after the great 1693 earthquake that destroyed eastern Sicily. The level 1 “scenario” earthquake is that of 1693 with its synthetic accelerogram, while level 2 “scenario” earthquake is the most significant shock which occurred during the 1990 Sicily earthquake, recorded on rock at the accelerometric station located in the town of Sortino, near Siracusa. Based on the site characterization of Siracusa area, the soil response is analysed. For each different zone and for the input motions considered as “scenario” earthquakes the response spectra at the surface level is developed. Some examples of site response evaluation of Siracusa area is shown in this paper. Finally, a seismic geotechnical hazard map in terms of maximum horizontal acceleration at the soil surface is drawn-up
Caratterizzazione statica e dinamica dei terreni del centro storico di Sellano
No full textGli eventi sismici che hanno colpito le regioni dell’Umbria e delle Marche nel 1997-1998 rappresentano delle crisi ricorrenti nella storia sismica di quest’area. Tali crisi sono caratterizzate essenzialmente da una magnitudo piuttosto moderata; tuttavia nel 1997-1998 hanno causato notevoli danni in diverse città, così come nella città di Sellano (Umbria). In questo lavoro per definire il comportamento dinamico del terreno della città di Sellano, è stata svolta un’ulteriore campagna di indagini geotecniche alla fine di Gennaio 2003, nella zona del paese maggiormente danneggiata. Sono stati realizzati tre sondaggi, ed effettuate prove SPT e downhole; sono stati prelevati altresì campioni indisturbati di terreno, per eseguire prove di laboratorio in campo dinamico con l’apparecchiatura di colonna risonante/taglio torsionale ciclico. In particolare sono stati ricavati le leggi del modulo di taglio (G) e del rapporto di smorzamento (D) al variare della deformazione γThe seismic events that hit the Umbria and Marche Regions in 1997-1998 represent recurrent crises in the seismic history of this area. These crises are mostly characterised by relatively moderate magnitudes; nevertheless in 1997-1998 they caused extensive damage in different towns, such as in the town of Sellano (Umbria Region). In this paper in order to define the seismic behaviour of the Sellano soil, further geotechnical investigations on the most significantly damaged zones in the Sellano built-up area was carried out, at the end of January 2003. Three boreholes were made. During the boring SPT and down-hole tests were also performed and the undisturbed samples were retrieved from the boreholes. On the undisturbed samples the dynamic laboratory tests with the resonant column device were performed. In particular for Sellano soil was determined, the shear modulus (G) and the damping ratio (D) linked to the current shear deformation γ
Seismic displacements of retaining walls: Shaking table test results vs numerical predictions
No full textThe seismic performance of retaining walls is usually evaluated through simplified displacement-based approaches which neglect the change in the soilwall system geometry as displacements develop. In this vein, the paper describes the results of several shaking table tests carried out on a reduced-scale model of a retaining wall placed inside a flexible soil container and subjected to harmonic input motions. In the paper the permanent displacements of the wall and of the retained soil were presented and compared with numerical predictions obtained using a modified Newmark-type model, which encompasses the kinematic compatibility between the wall and the soil
