I. Manzella - Academia.edu (original) (raw)

Papers by I. Manzella

Research paper thumbnail of Physical modelling to better understand rock avalanches

Proceedings of the 7th International Conference on Physical Modelling in Geotechnics (ICPMG 2010), 28th June - 1st July, Zurich, Switzerland, 2010

Research paper thumbnail of Numerical modelling of a rock avalanche laboratory experiment in the framework of the ‘‘Rockslidetec’’ alpine project

Proceedings of the 10th International Symposium on Landslides and Engineered Slopes, 30 June - 4 July 2008, Xi'an, China, 2008

Research paper thumbnail of On the characterization of size and shape of irregular particles

Powder Technology, 2015

ABSTRACT http://www.sciencedirect.com/science/article/pii/S0032591014008651

Research paper thumbnail of Dedicated vertical wind tunnel for the study of sedimentation of non-spherical particles

The Review of scientific instruments, 2013

A dedicated 4-m-high vertical wind tunnel has been designed and constructed at the University of ... more A dedicated 4-m-high vertical wind tunnel has been designed and constructed at the University of Geneva in collaboration with the Groupe de compétence en mécanique des fluides et procédés énergétiques. With its diverging test section, the tunnel is designed to study the aero-dynamical behavior of non-spherical particles with terminal velocities between 5 and 27 ms(-1). A particle tracking velocimetry (PTV) code is developed to calculate drag coefficient of particles in standard conditions based on the real projected area of the particles. Results of our wind tunnel and PTV code are validated by comparing drag coefficient of smooth spherical particles and cylindrical particles to existing literature. Experiments are repeatable with average relative standard deviation of 1.7%. Our preliminary experiments on the effect of particle to fluid density ratio on drag coefficient of cylindrical particles show that the drag coefficient of freely suspended particles in air is lower than those m...

Research paper thumbnail of Écoulements Géophysiques Gravitationnelles

Research paper thumbnail of Geophysical gravitational flows

Research paper thumbnail of Volcanic and non-volcanic debris avalanche deposit

Research paper thumbnail of A study of sedimentation and aggregation of volcanic particles based on experiments carried out with a vertical wind tunnel

Research paper thumbnail of Approche expérimentale dans la compréhension des dangers liés aux éruptions volcaniques

Research paper thumbnail of A new model for the prediction of drag of non-spherical volcanic particles

Research paper thumbnail of Sedimentation and aggregation of volcanic particles: lab and field experiments

Research paper thumbnail of New Strategies For The Characterization Of Size, Shape And Terminal Velocity Of Irregular Particles

Research paper thumbnail of Large-Scale Experiments on Volcanic Processes

Eos, Transactions American Geophysical Union, 2011

Research paper thumbnail of The role of gravitational instabilities in deposition of volcanic ash

Geology, 2015

Volcanic ash is a significant hazard for areas close to volcanoes and for aviation. Gravitational... more Volcanic ash is a significant hazard for areas close to volcanoes and for aviation. Gravitational instabilities forming at the bottom of spreading volcanic clouds have been observed in many explosive eruptions. Here we present the first quantitative description of the dynamics of such instabilities, and correlate this with the characteristics of the fall deposit from observations of the 4 May 2010 Eyjafjallajökull (Iceland) eruption. Gravitational instabilities initially took the form of downward-propagating fingers that formed continuously at the base of the cloud, and appeared to be advected passively at the crosswind speed. Measurements of finger propagation are consistent with initial conditions inferred from previous studies of ash cloud dynamics. Dedicated laboratory analogue experiments confirmed that finger downward propagation significantly exceeded the settling speed of individual particles, demonstrating that gravitational instabilities provide a possible mechanism for enhanced sedimentation of fine ash. Our observations challenge the view that aggregation is the primary explanation of proximal fine ash sedimentation, and give direct support for the role of gravitational instabilities in providing regions of high particle concentration that can promote aggregation.

Research paper thumbnail of Influence of initial block packing on rock avalanche flow and emplacement mechanisms through FEM/DEM simulations

The importance of the initial packing of a rock cumulus on its flow process and emplacement mecha... more The importance of the initial packing of a rock cumulus on its flow process and emplacement mechanism has been highlighted by several small-scale experiments where thousands of terracotta bricks were either randomly settled as a loose material or orderly piled one on top of the other before releasing them on an inclined slope. When bricks were piled, longer runout were observed compared to tests run with loose bricks. The reason of this difference has been highlighted using a 2D Finite Element-Discrete Element code by explicitly accounting for the shape of the blocks and the interactions between them. When bricks are piled, the mass has originally an ordinate structure that tends to be preserved during the downhill motion and only after the slope break it shatters, whereas in the case of bricks randomly settled into the box, the mass behaves as a loose material from the start and more energy is lost from the beginning through both friction and collisions at the base and within the granular mass. When the slope break is smoother, the relatively-coherent structure of the block cumulus is even less disaggregated, as a consequence less energy is dissipated at the toe, the mass can travel further and it preserves the inherited geometries. Simulations confirm the experimental results, giving a better insight on the understanding of the effect of the initial block packing on the longitudinal spreading and on the mechanisms underneath the process of rock avalanche propagation.

Research paper thumbnail of Extension of the Fringe Projection Method to Measure Shape and Position of the Centre of Mass of Granular Flow Deposit

this paper illustrates the application of a new optical measuring technique, the fringe projectio... more this paper illustrates the application of a new optical measuring technique, the fringe projection method, to obtain the final deposit thickness of unconstrained granular flow experiments. This allows retrieving the position of the centre of mass, important information for the study of rock avalanche propagation. The fringe projection method consists in projecting alternate lines of dark and light (fringes) on the deposit surface. When fringes are projected on a planar surface, they are straight and equally spaced, whereas on a rough surface they are distorted and this distortion is related to the thickness of the object. This information is contained in the object optical print (phase map) which can be computed using different algorithms; in the present study a formula which implies the use of three different images has been chosen. The obtained phase is directly proportional to the height of the object by a factor which has been computed as the ratio of the maximum height of the d...

Research paper thumbnail of Qualitative Analysis of Rock Avalanches Propagation by Means of Physical Modelling of Non-Constrained Gravel Flows

Rock Mechanics and Rock Engineering, 2008

This paper presents an experimental study of rock avalanches run-out and propagation carried out ... more This paper presents an experimental study of rock avalanches run-out and propagation carried out with a small-scale physical model at the EPFL Rock Mechanics Laboratory. Fall height, volume, releasing geometry and materials used for testing have been varied and their influence on deposit characteristics (such as length, width, height and morphology) and run-out has been studied. The experiments have shown that deposit morphology is dependent on the type of material used: sand or gravel. Sand deposit shape, regular and compact, is in accordance with many tests described in the literature, while Aquarium gravel deposit is closer to real cases such as the Six des Eaux Froides event (Switzerland). There is also a considerable difference in deposit morphology and dimensions when the event is the consequence of one large volume released at once or when the same volume is released at different times. In this latter case the final deposit characteristics do not depend on the entire failed volume but on the individual smaller ones. This behaviour is in agreement with the Randa event (Swiss Alps) which occurred over several hours. For all-in-once releases, run-out distance depends primarily on the volume. Fall height and releasing geometry have a small influence on run-out, but on the other hand a higher fall height leads to a different lateral spreading and to the development of two different propagation mechanisms of the sliding mass.

Research paper thumbnail of Empirical and analytical analyses of laboratory granular flows to investigate rock avalanche propagation

Landslides, 2013

The rights are held by Springer-Verlag Wien.

Research paper thumbnail of Flow experiments with gravel and blocks at small scale to investigate parameters and mechanisms involved in rock avalanches

Engineering Geology, 2009

Laboratory experiments play an important role in improving the modelling of rock avalanches since... more Laboratory experiments play an important role in improving the modelling of rock avalanches since they contribute to a better understanding of the mechanisms that characterise propagation and to identifying parameters influencing velocity and deposit characteristics. Tests analysed in this paper consist of unconstrained flows of gravel and small blocks down an inclined board, which ends with a horizontal part where

Research paper thumbnail of Vulnerability Assessment and Risk Mitigation: The Case of Vulcano Island, Italy

This paper reports on a comprehensive vulnerability analysis based on a research work developed w... more This paper reports on a comprehensive vulnerability analysis based on a research work developed within the EC ENSURE Project (7FP) dealing with the assessment of different volcanic phenomena and induced mass-movements on Vulcano Island (S Italy) as a key tool for proactive efforts for multi-risk mitigation. The work is mainly focused on tephra sedimentation and lahar hazards and related physical, systemic and mitigation capacities.

Research paper thumbnail of Physical modelling to better understand rock avalanches

Proceedings of the 7th International Conference on Physical Modelling in Geotechnics (ICPMG 2010), 28th June - 1st July, Zurich, Switzerland, 2010

Research paper thumbnail of Numerical modelling of a rock avalanche laboratory experiment in the framework of the ‘‘Rockslidetec’’ alpine project

Proceedings of the 10th International Symposium on Landslides and Engineered Slopes, 30 June - 4 July 2008, Xi'an, China, 2008

Research paper thumbnail of On the characterization of size and shape of irregular particles

Powder Technology, 2015

ABSTRACT http://www.sciencedirect.com/science/article/pii/S0032591014008651

Research paper thumbnail of Dedicated vertical wind tunnel for the study of sedimentation of non-spherical particles

The Review of scientific instruments, 2013

A dedicated 4-m-high vertical wind tunnel has been designed and constructed at the University of ... more A dedicated 4-m-high vertical wind tunnel has been designed and constructed at the University of Geneva in collaboration with the Groupe de compétence en mécanique des fluides et procédés énergétiques. With its diverging test section, the tunnel is designed to study the aero-dynamical behavior of non-spherical particles with terminal velocities between 5 and 27 ms(-1). A particle tracking velocimetry (PTV) code is developed to calculate drag coefficient of particles in standard conditions based on the real projected area of the particles. Results of our wind tunnel and PTV code are validated by comparing drag coefficient of smooth spherical particles and cylindrical particles to existing literature. Experiments are repeatable with average relative standard deviation of 1.7%. Our preliminary experiments on the effect of particle to fluid density ratio on drag coefficient of cylindrical particles show that the drag coefficient of freely suspended particles in air is lower than those m...

Research paper thumbnail of Écoulements Géophysiques Gravitationnelles

Research paper thumbnail of Geophysical gravitational flows

Research paper thumbnail of Volcanic and non-volcanic debris avalanche deposit

Research paper thumbnail of A study of sedimentation and aggregation of volcanic particles based on experiments carried out with a vertical wind tunnel

Research paper thumbnail of Approche expérimentale dans la compréhension des dangers liés aux éruptions volcaniques

Research paper thumbnail of A new model for the prediction of drag of non-spherical volcanic particles

Research paper thumbnail of Sedimentation and aggregation of volcanic particles: lab and field experiments

Research paper thumbnail of New Strategies For The Characterization Of Size, Shape And Terminal Velocity Of Irregular Particles

Research paper thumbnail of Large-Scale Experiments on Volcanic Processes

Eos, Transactions American Geophysical Union, 2011

Research paper thumbnail of The role of gravitational instabilities in deposition of volcanic ash

Geology, 2015

Volcanic ash is a significant hazard for areas close to volcanoes and for aviation. Gravitational... more Volcanic ash is a significant hazard for areas close to volcanoes and for aviation. Gravitational instabilities forming at the bottom of spreading volcanic clouds have been observed in many explosive eruptions. Here we present the first quantitative description of the dynamics of such instabilities, and correlate this with the characteristics of the fall deposit from observations of the 4 May 2010 Eyjafjallajökull (Iceland) eruption. Gravitational instabilities initially took the form of downward-propagating fingers that formed continuously at the base of the cloud, and appeared to be advected passively at the crosswind speed. Measurements of finger propagation are consistent with initial conditions inferred from previous studies of ash cloud dynamics. Dedicated laboratory analogue experiments confirmed that finger downward propagation significantly exceeded the settling speed of individual particles, demonstrating that gravitational instabilities provide a possible mechanism for enhanced sedimentation of fine ash. Our observations challenge the view that aggregation is the primary explanation of proximal fine ash sedimentation, and give direct support for the role of gravitational instabilities in providing regions of high particle concentration that can promote aggregation.

Research paper thumbnail of Influence of initial block packing on rock avalanche flow and emplacement mechanisms through FEM/DEM simulations

The importance of the initial packing of a rock cumulus on its flow process and emplacement mecha... more The importance of the initial packing of a rock cumulus on its flow process and emplacement mechanism has been highlighted by several small-scale experiments where thousands of terracotta bricks were either randomly settled as a loose material or orderly piled one on top of the other before releasing them on an inclined slope. When bricks were piled, longer runout were observed compared to tests run with loose bricks. The reason of this difference has been highlighted using a 2D Finite Element-Discrete Element code by explicitly accounting for the shape of the blocks and the interactions between them. When bricks are piled, the mass has originally an ordinate structure that tends to be preserved during the downhill motion and only after the slope break it shatters, whereas in the case of bricks randomly settled into the box, the mass behaves as a loose material from the start and more energy is lost from the beginning through both friction and collisions at the base and within the granular mass. When the slope break is smoother, the relatively-coherent structure of the block cumulus is even less disaggregated, as a consequence less energy is dissipated at the toe, the mass can travel further and it preserves the inherited geometries. Simulations confirm the experimental results, giving a better insight on the understanding of the effect of the initial block packing on the longitudinal spreading and on the mechanisms underneath the process of rock avalanche propagation.

Research paper thumbnail of Extension of the Fringe Projection Method to Measure Shape and Position of the Centre of Mass of Granular Flow Deposit

this paper illustrates the application of a new optical measuring technique, the fringe projectio... more this paper illustrates the application of a new optical measuring technique, the fringe projection method, to obtain the final deposit thickness of unconstrained granular flow experiments. This allows retrieving the position of the centre of mass, important information for the study of rock avalanche propagation. The fringe projection method consists in projecting alternate lines of dark and light (fringes) on the deposit surface. When fringes are projected on a planar surface, they are straight and equally spaced, whereas on a rough surface they are distorted and this distortion is related to the thickness of the object. This information is contained in the object optical print (phase map) which can be computed using different algorithms; in the present study a formula which implies the use of three different images has been chosen. The obtained phase is directly proportional to the height of the object by a factor which has been computed as the ratio of the maximum height of the d...

Research paper thumbnail of Qualitative Analysis of Rock Avalanches Propagation by Means of Physical Modelling of Non-Constrained Gravel Flows

Rock Mechanics and Rock Engineering, 2008

This paper presents an experimental study of rock avalanches run-out and propagation carried out ... more This paper presents an experimental study of rock avalanches run-out and propagation carried out with a small-scale physical model at the EPFL Rock Mechanics Laboratory. Fall height, volume, releasing geometry and materials used for testing have been varied and their influence on deposit characteristics (such as length, width, height and morphology) and run-out has been studied. The experiments have shown that deposit morphology is dependent on the type of material used: sand or gravel. Sand deposit shape, regular and compact, is in accordance with many tests described in the literature, while Aquarium gravel deposit is closer to real cases such as the Six des Eaux Froides event (Switzerland). There is also a considerable difference in deposit morphology and dimensions when the event is the consequence of one large volume released at once or when the same volume is released at different times. In this latter case the final deposit characteristics do not depend on the entire failed volume but on the individual smaller ones. This behaviour is in agreement with the Randa event (Swiss Alps) which occurred over several hours. For all-in-once releases, run-out distance depends primarily on the volume. Fall height and releasing geometry have a small influence on run-out, but on the other hand a higher fall height leads to a different lateral spreading and to the development of two different propagation mechanisms of the sliding mass.

Research paper thumbnail of Empirical and analytical analyses of laboratory granular flows to investigate rock avalanche propagation

Landslides, 2013

The rights are held by Springer-Verlag Wien.

Research paper thumbnail of Flow experiments with gravel and blocks at small scale to investigate parameters and mechanisms involved in rock avalanches

Engineering Geology, 2009

Laboratory experiments play an important role in improving the modelling of rock avalanches since... more Laboratory experiments play an important role in improving the modelling of rock avalanches since they contribute to a better understanding of the mechanisms that characterise propagation and to identifying parameters influencing velocity and deposit characteristics. Tests analysed in this paper consist of unconstrained flows of gravel and small blocks down an inclined board, which ends with a horizontal part where

Research paper thumbnail of Vulnerability Assessment and Risk Mitigation: The Case of Vulcano Island, Italy

This paper reports on a comprehensive vulnerability analysis based on a research work developed w... more This paper reports on a comprehensive vulnerability analysis based on a research work developed within the EC ENSURE Project (7FP) dealing with the assessment of different volcanic phenomena and induced mass-movements on Vulcano Island (S Italy) as a key tool for proactive efforts for multi-risk mitigation. The work is mainly focused on tephra sedimentation and lahar hazards and related physical, systemic and mitigation capacities.