The rocking response of rigid free standing bodies subjected to seismic excitation has been studi... more The rocking response of rigid free standing bodies subjected to seismic excitation has been studied by many researchers interested in different slender elements such as ancient stone columns, tombstones, rigid building structures. The extension of this model to rock mechanics has been proposed by a few authors. The rocking response of rectangular free standing bodies subjected to horizontal accelerations of natural recorded motions showed that the pseudo-static approach, based on Peak Ground Acceleration (PGA), permits only the determination of the uplift conditions and the beginning of rocking. It does not permit to evaluate the overturning of the blocks. The combined effect of vertical and horizontal seismic motions is negligible and, in some cases, beneficial. This paper presents a new mechanical model, called “one-sided rocking”, that takes into account the presence of a rear rigid wall, that is a typical scenario for the rock blocks completely detached from the cliff but close ...
Proceedings of the 5th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2015
Dynamic effects on shallow circular tunnels in soft ground have often been neglected based on the... more Dynamic effects on shallow circular tunnels in soft ground have often been neglected based on the assumption that their response to earthquakes loading is relatively safe as compared to that of surface structures. Nevertheless, several example of recorded damage to underground structures for which seismic forces were not considered in the design can be quoted. In some cases, damage was associated with strong ground shaking and site amplification, which increased the stress level in the tunnel lining. Ovaling or racking deformations are mostly due to shear waves propagating perpendicularly to the tunnel axis, resulting in a distortion of the cross-section of the structure, while axial compression and extension, or longitudinal bending are due to shear waves propagating parallel or obliquely to the tunnel axis. Pseudo-static and simplified dynamic analyses enable to assess transient changes in internal forces during shaking. In the simplified methods, a tunnel structure is generally designed by imposing a displacement field to its boundary, as obtained from a site seismic response under free field conditions, and calculating the forces in the lining in an uncoupled manner. Axial and bending deformations are generated by the components of the seismic waves producing particle motion parallel or perpendicular to the longitudinal axis of the tunnel, respectively. Nevertheless, experimental evidences of permanent changes in internal loads in the tunnel lining would suggest that a full three-dimensional dynamic analysis including plastic soil behavior should be performed when modelling the dynamic interaction between the tunnel and the ground. In the paper three-dimensional numerical analyses were performed to simulate the response of circular tunnels subjected to different seismic loads acting in the transversal and in the longitudinal direction of the tunnel axis. The main purpose of this study was to provide a three-dimensional numerical model, which would allow the tunnel lining behavior and the displacement field surrounding the tunnel to be evaluated for different directions of seismic wave propagation.
The Central Italy earthquake sequence nominally began on 24 August 2016 with a M6.1 event on a no... more The Central Italy earthquake sequence nominally began on 24 August 2016 with a M6.1 event on a normal fault that produced devastating effects in the town of Amatrice and several nearby villages and hamlets. A major international response was undertaken to record the effects of this disaster, including surface faulting, ground motions, landslides, and damage patterns to structures. This work targeted the development of high-value case histories useful to future research. Subsequent events in October 2016 exacerbated the damage in previously affected areas and caused damage to new areas in the north, particularly the relatively large town of Norcia. Additional reconnaissance after a M6.5 event on 30 October 2016 documented and mapped several large landslide features and increased damage states for structures in villages and hamlets throughout the region. This paper provides an overview of the reconnaissance activities undertaken to document and map these and other effects, and highlig...
Landslides and Engineered Slopes. Experience, Theory and Practice, 2016
The optimum desing of slope stabilizing piles is a key point for an effective mitigation of the r... more The optimum desing of slope stabilizing piles is a key point for an effective mitigation of the risk associated to landslides. Such an ambitious result requires efficient and reliable design approaches, allowing the engineer to face both with ultimate (in case of a localized failure mechanism is triggered in the slope) and serviceability limit states (when the focus is on the reduction of the soil displacement rate before the onset of the failure). The paper gives a contribution by presenting in a unified framework such multi-level design approaches, by specifically highlighting the most important geometrical and mechanical issues. The focus of the paper is always performance oriented, and particular importance is given to the precise definition of the soil displacement fiel
This paper outlines the results of an experimental program carried out on centrifuge models of ca... more This paper outlines the results of an experimental program carried out on centrifuge models of cantilevered and propped retaining walls embedded in saturated sand. The main aim of the paper is to investigate the dynamic response of these structures when the foundation soil is saturated by measuring the accelerations and pore pressures in the soil, displacements and bending moment of the walls. A comparison among tests with different geometrical configurations and relative density of the soil is presented. The centrifuge models were subjected to dynamic loading in the form of sinusoidal accelerations applied at the base of the models. This paper also presents data from pressure sensors used to measure total earth pressure on the walls. Furthermore, these results are compared with previous dynamic centrifuge tests on flexible retaining walls in dry sand.
In questa nota viene presentato un nuovo modello costitutivo sviluppato nell\u2019ambito della me... more In questa nota viene presentato un nuovo modello costitutivo sviluppato nell\u2019ambito della meccanica dello stato critico in grado di riprodurre i principali aspetti caratteristici del comportamento meccanico delle rocce tenere. Il modello \ue8 stato usato per simulare una serie di prove di carico su piastra condotte sul Tufo Giallo Napoletano negli anni \u201970, che, grazie alla realizzazione di cicli di carico, scarico e ricarico con piastre di diametro diverso, avevano messo in evidenza il ruolo dei fenomeni di destrutturazione nella risposta osservata. La calibrazione dei parametri e delle variabili di stato del modello \ue8 stata condotta con riferimento ad una serie di prove di laboratorio condotte sullo stesso materiale ed utilizzando il primo ciclo di carico e scarico di due delle prove di carico su piastra. Il confronto tra la simulazione numerica e le successive fasi di ricarico, fino ad elevati livelli di tensione, e scarico \ue8 risultato piuttosto soddisfacente ed ha quindi permesso di validare la formulazione costitutiva messa a punto
A novel numerical procedure for defining failure envelopes of pile groups under inclined and ecce... more A novel numerical procedure for defining failure envelopes of pile groups under inclined and eccentric load is proposed. The starting point is a closed form exact solution for interaction diagram o...
This paper deals with geogrid-reinforced artificial barriers used as mitigation works against deb... more This paper deals with geogrid-reinforced artificial barriers used as mitigation works against debris avalanches. Deformable Geosynthetic-Reinforced Barriers (DGRB) can be made of coarse-grained mat...
A research programme on the stabilityof the vertical cliff overhanging via Krupp in Capri is desc... more A research programme on the stabilityof the vertical cliff overhanging via Krupp in Capri is described in the paper. The research is finalised to the proposition of intervention techniques able to guarantee a "safe" use of the pedestrian road and to be respectful of the archiectural, historic and environmental values of the site.
The rocking response of rigid free standing bodies subjected to seismic excitation has been studi... more The rocking response of rigid free standing bodies subjected to seismic excitation has been studied by many researchers interested in different slender elements such as ancient stone columns, tombstones, rigid building structures. The extension of this model to rock mechanics has been proposed by a few authors. The rocking response of rectangular free standing bodies subjected to horizontal accelerations of natural recorded motions showed that the pseudo-static approach, based on Peak Ground Acceleration (PGA), permits only the determination of the uplift conditions and the beginning of rocking. It does not permit to evaluate the overturning of the blocks. The combined effect of vertical and horizontal seismic motions is negligible and, in some cases, beneficial. This paper presents a new mechanical model, called “one-sided rocking”, that takes into account the presence of a rear rigid wall, that is a typical scenario for the rock blocks completely detached from the cliff but close ...
Proceedings of the 5th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2015
Dynamic effects on shallow circular tunnels in soft ground have often been neglected based on the... more Dynamic effects on shallow circular tunnels in soft ground have often been neglected based on the assumption that their response to earthquakes loading is relatively safe as compared to that of surface structures. Nevertheless, several example of recorded damage to underground structures for which seismic forces were not considered in the design can be quoted. In some cases, damage was associated with strong ground shaking and site amplification, which increased the stress level in the tunnel lining. Ovaling or racking deformations are mostly due to shear waves propagating perpendicularly to the tunnel axis, resulting in a distortion of the cross-section of the structure, while axial compression and extension, or longitudinal bending are due to shear waves propagating parallel or obliquely to the tunnel axis. Pseudo-static and simplified dynamic analyses enable to assess transient changes in internal forces during shaking. In the simplified methods, a tunnel structure is generally designed by imposing a displacement field to its boundary, as obtained from a site seismic response under free field conditions, and calculating the forces in the lining in an uncoupled manner. Axial and bending deformations are generated by the components of the seismic waves producing particle motion parallel or perpendicular to the longitudinal axis of the tunnel, respectively. Nevertheless, experimental evidences of permanent changes in internal loads in the tunnel lining would suggest that a full three-dimensional dynamic analysis including plastic soil behavior should be performed when modelling the dynamic interaction between the tunnel and the ground. In the paper three-dimensional numerical analyses were performed to simulate the response of circular tunnels subjected to different seismic loads acting in the transversal and in the longitudinal direction of the tunnel axis. The main purpose of this study was to provide a three-dimensional numerical model, which would allow the tunnel lining behavior and the displacement field surrounding the tunnel to be evaluated for different directions of seismic wave propagation.
The Central Italy earthquake sequence nominally began on 24 August 2016 with a M6.1 event on a no... more The Central Italy earthquake sequence nominally began on 24 August 2016 with a M6.1 event on a normal fault that produced devastating effects in the town of Amatrice and several nearby villages and hamlets. A major international response was undertaken to record the effects of this disaster, including surface faulting, ground motions, landslides, and damage patterns to structures. This work targeted the development of high-value case histories useful to future research. Subsequent events in October 2016 exacerbated the damage in previously affected areas and caused damage to new areas in the north, particularly the relatively large town of Norcia. Additional reconnaissance after a M6.5 event on 30 October 2016 documented and mapped several large landslide features and increased damage states for structures in villages and hamlets throughout the region. This paper provides an overview of the reconnaissance activities undertaken to document and map these and other effects, and highlig...
Landslides and Engineered Slopes. Experience, Theory and Practice, 2016
The optimum desing of slope stabilizing piles is a key point for an effective mitigation of the r... more The optimum desing of slope stabilizing piles is a key point for an effective mitigation of the risk associated to landslides. Such an ambitious result requires efficient and reliable design approaches, allowing the engineer to face both with ultimate (in case of a localized failure mechanism is triggered in the slope) and serviceability limit states (when the focus is on the reduction of the soil displacement rate before the onset of the failure). The paper gives a contribution by presenting in a unified framework such multi-level design approaches, by specifically highlighting the most important geometrical and mechanical issues. The focus of the paper is always performance oriented, and particular importance is given to the precise definition of the soil displacement fiel
This paper outlines the results of an experimental program carried out on centrifuge models of ca... more This paper outlines the results of an experimental program carried out on centrifuge models of cantilevered and propped retaining walls embedded in saturated sand. The main aim of the paper is to investigate the dynamic response of these structures when the foundation soil is saturated by measuring the accelerations and pore pressures in the soil, displacements and bending moment of the walls. A comparison among tests with different geometrical configurations and relative density of the soil is presented. The centrifuge models were subjected to dynamic loading in the form of sinusoidal accelerations applied at the base of the models. This paper also presents data from pressure sensors used to measure total earth pressure on the walls. Furthermore, these results are compared with previous dynamic centrifuge tests on flexible retaining walls in dry sand.
In questa nota viene presentato un nuovo modello costitutivo sviluppato nell\u2019ambito della me... more In questa nota viene presentato un nuovo modello costitutivo sviluppato nell\u2019ambito della meccanica dello stato critico in grado di riprodurre i principali aspetti caratteristici del comportamento meccanico delle rocce tenere. Il modello \ue8 stato usato per simulare una serie di prove di carico su piastra condotte sul Tufo Giallo Napoletano negli anni \u201970, che, grazie alla realizzazione di cicli di carico, scarico e ricarico con piastre di diametro diverso, avevano messo in evidenza il ruolo dei fenomeni di destrutturazione nella risposta osservata. La calibrazione dei parametri e delle variabili di stato del modello \ue8 stata condotta con riferimento ad una serie di prove di laboratorio condotte sullo stesso materiale ed utilizzando il primo ciclo di carico e scarico di due delle prove di carico su piastra. Il confronto tra la simulazione numerica e le successive fasi di ricarico, fino ad elevati livelli di tensione, e scarico \ue8 risultato piuttosto soddisfacente ed ha quindi permesso di validare la formulazione costitutiva messa a punto
A novel numerical procedure for defining failure envelopes of pile groups under inclined and ecce... more A novel numerical procedure for defining failure envelopes of pile groups under inclined and eccentric load is proposed. The starting point is a closed form exact solution for interaction diagram o...
This paper deals with geogrid-reinforced artificial barriers used as mitigation works against deb... more This paper deals with geogrid-reinforced artificial barriers used as mitigation works against debris avalanches. Deformable Geosynthetic-Reinforced Barriers (DGRB) can be made of coarse-grained mat...
A research programme on the stabilityof the vertical cliff overhanging via Krupp in Capri is desc... more A research programme on the stabilityof the vertical cliff overhanging via Krupp in Capri is described in the paper. The research is finalised to the proposition of intervention techniques able to guarantee a "safe" use of the pedestrian road and to be respectful of the archiectural, historic and environmental values of the site.
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Papers by S. Aversa
The research is finalised to the proposition of intervention techniques able to guarantee a "safe" use of the pedestrian road and to be respectful of the archiectural, historic and environmental values of the site.
The research is finalised to the proposition of intervention techniques able to guarantee a "safe" use of the pedestrian road and to be respectful of the archiectural, historic and environmental values of the site.