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Dive into the research topics where Giovanni B. Crosta is active.

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Featured researches published by Giovanni B. Crosta.


Computers & Geosciences | 2002

STONE: a computer program for the three-dimensional simulation of rock-falls

Fausto Guzzetti; Giovanni B. Crosta; Riccardo Detti; Federico Agliardi

Rock-fall poses a continuous hazard in mountain areas worldwide. Despite the fact that rock fall is a simple landslide type to model, only a few attempts have been made to establish rock-fall hazard and the associated risk at regional scales. We developed a three-dimensional simulation program that generates simple maps useful to assess rockfall hazard, using GIS technology to manipulate existing thematic information available in digital format. The program requires as input a digital terrain model, the location of rock-fall detachment areas, the dynamic friction coefficient used to simulate the loss of velocity during rolling, and the coefficients for normal and tangential energy restitution at the impact points. The program allows for the natural variability of the input data by using a random component approach. Raster outputs include the count of rock-fall trajectories, the maximum velocity and the maximum height computed at each grid cell. Vector outputs consist of the planar (two dimensional) and the three-dimensional trajectories of the rock falls. The program outputs proved to be consistent with the results of other rock-fall simulation programs, to be reliable for modelling rock-fall in three-dimensional geomorphological settings, and to help in the quantitative assessment of rock-fall hazard over large areas.


International Journal of Rock Mechanics and Mining Sciences | 2003

High resolution three-dimensional numerical modelling of rockfalls

Federico Agliardi; Giovanni B. Crosta

Abstract Accurate prediction of rockfalls is a major need in mountain areas, both for hazard assessment and the design of countermeasures. In this paper, the performance of an original simulation code, initially developed for regional-scale analysis, is tested at the local scale by using high-resolution input data, in order to show its application to site-specific problems. The code is based on a kinematic algorithm and allows to run detailed, spatially distributed simulations of rockfall on a three-dimensional topography described by a Digital Elevation Model. Two examples from the Central Italian Alps, both characterised by the occurrence of frequent historical events, valuable elements at risk (urban areas, corridors) and countermeasures (barriers and retaining walls) are presented. The suggested approach proves to effectively account for rockfall dynamics when used with high-resolution data. Model calibration issues are discussed and model results are compared to available experimental data. The scale dependency of the results is also discussed.


Journal of Geophysical Research | 2007

Fragmentation in the Val Pola rock avalanche, Italian Alps

Giovanni B. Crosta; Paolo Frattini; Nicoletta Fusi

[1] Grain size data from the deposit of the 1987 Val Pola rock avalanche (central Italian Alps) are compared with data concerning rock avalanching, rock fragmentation, and comminution. The Weibull distribution fits a small part of the entire particle-size distribution of debris samples, with a mean value of the curve shape factor of 0.54 ± 0.28. This is typical of multiple comminution, or fragmentation with much shearing. A fractal distribution fits over a greater size range. Computed fractal dimensions range between 1.3 and 3.2 within the deposit, with average values of about 2.6–2.7. These values cover the range between the theoretical values of the plane-of-weakness model (1.97) and the pillar-of-strength model (2.84) and are close to the theoretical value for the constrained comminution model (2.58). These suggest that both texturally mature and immature deposits are present and that more than a single comminution process acted during the rock avalanche motion. Variation of the grain size distribution within the deposit and grain size segregation show as trends in the fractal dimension and arise from variation in the fragmentation process. A variety of different physical and empirical laws suggest that 1–30% of the energy expended in the rock avalanche was consumed in fragmentation.


Archive | 2015

Engineering Geology for Society and Territory - Volume 1

Giorgio Lollino; Daniele Giordan; Giovanni B. Crosta; Jordi Corominas; Rafig Azzam; Janusz Wasowski; Nicola Sciarra

Dissociation of natural gas hydrate (NGH) in seabed can product amounts of gas. If the soil layer over NGH layer is permeable, gas will escape. Gas escape can on one hand lead to the damage of seabed, on the other hand lead to the decrease of the density of sea water and so threatens the structures nearby. In this paper movement and expansion behavior of gas in water was first studied, then the damage of seabed due to gas escape was studied. Effects of gas pressure, thickness of soil layer were investigated. The expansion angle of gas in the water was obtained. The characteristics of the hole size induced by gas escape with gas pressure and soil thickness were also obtained. These results can be as references of deeper research and practice.


Landslides | 2014

Application of a SPH depth-integrated model to landslide run-out analysis

Manuel Pastor; T. Blanc; B. Haddad; S. Petrone; M. Sanchez Morles; V. Drempetic; Dieter Issler; Giovanni B. Crosta; Leonardo Cascini; Giuseppe Sorbino; Sabatino Cuomo

Hazard and risk assessment of landslides with potentially long run-out is becoming more and more important. Numerical tools exploiting different constitutive models, initial data and numerical solution techniques are important for making the expert’s assessment more objective, even though they cannot substitute for the expert’s understanding of the site-specific conditions and the involved processes. This paper presents a depth-integrated model accounting for pore water pressure dissipation and applications both to real events and problems for which analytical solutions exist. The main ingredients are: (i) The mathematical model, which includes pore pressure dissipation as an additional equation. This makes possible to model flowslide problems with a high mobility at the beginning, the landslide mass coming to rest once pore water pressures dissipate. (ii) The rheological models describing basal friction: Bingham, frictional, Voellmy and cohesive-frictional viscous models. (iii) We have implemented simple erosion laws, providing a comparison between the approaches of Egashira, Hungr and Blanc. (iv) We propose a Lagrangian SPH model to discretize the equations, including pore water pressure information associated to the moving SPH nodes.


Physics and Chemistry of The Earth | 2002

How to obtain alert velocity thresholds for large rockslides

Giovanni B. Crosta; Federico Agliardi

Abstract A reliable forecast of the failure stage of large rockslides is difficult, because of non-linear time dependency of displacements and seasonal effects. Aim of this paper is to suggest a practical method to prepare alert thresholds for large rockslides, assessing critical values of velocity for carrying out civil protection actions using monitoring data. Adopted data concern the 20 Mm3 Ruinon rockslide (Valfurva, Central Alps, Italy), still evolving and suitable to originate a fast moving rock avalanche. Multitemporal analysis of aerial photos, LIDAR-ALTM laser topography, field survey and geomechanical analyses allowed to infer the rockslide kinematics and better understand data provided by a monitoring network including distometers, extensometers, GPS benchmarks and inclinometers. The analysis of displacement and rainfall data over five years (1997–2001) allowed to recognise three different evolutionary patterns of displacements, showing a continuously increasing rate since 1997. Data representing large-scale behaviour of the rock mass were fitted by power-law curves, according to the “accelerating creep” model by Voight, in order to evaluate a suitable failure time. This was hampered by the large seasonal deviations, which can significantly delay the occurrence of failure. Data were fitted using the Voight’s equation, expressed in terms of displacement, through non-linear estimation techniques, in order to find values of the controlling parameters (A, α and tf) suitable to represent the mechanical behaviour of the rock mass approaching the failure. This allowed to compute velocity–time theoretical curves and to define different velocity threshold values (pre-alert, alert and emergency) to be used for emergency management.


Transactions of the American Mathematical Society | 1998

Chaotic vibrations of the one-dimensional wave equation due to a self-excitation boundary condition. Part I: Controlled hysteresis

Goong Chen; Sze-Bi Hsu; Jianxin Zhou; Guanrong Chen; Giovanni B. Crosta

The study of nonlinear vibrations/oscillations in mechanical and electronic systems has always been an important research area. While important progress in the development of mathematical chaos theory has been made for finite dimensional second order nonlinear ODEs arising from nonlinear springs and electronic circuits, the state of understanding of chaotic vibrations for analogous infinite dimensional systems is still very incomplete. The 1-dimensional vibrating string satisfying wtt − wxx = 0 on the unit interval x ∈ (0, 1) is an infinite dimensional harmonic oscillator. Consider the boundary conditions: at the left end x = 0, the string is fixed, while at the right end x = 1, a nonlinear boundary condition wx = αwt − βw3 t , α, β > 0, takes effect. This nonlinear boundary condition behaves like a van der Pol oscillator, causing the total energy to rise and fall within certain bounds regularly or irregularly. We formulate the problem into an equivalent first order hyperbolic system, and use the method of characteristics to derive a nonlinear reflection relation caused by the nonlinear boundary condition. Since the solution of the first order hyperbolic system depends completely on this nonlinear relation and its iterates, the problem is reduced to a discrete iteration problem of the type un+1 = F (un), where F is the nonlinear reflection relation. We say that the PDE system is chaotic if the mapping F is chaotic as an interval map. Algebraic, asymptotic and numerical techniques are developed to tackle the cubic nonlinearities. We then define a rotation number, following J.P. Keener [11], and obtain denseness of orbits and periodic points by either directly constructing a shift sequence or by applying results of M.I. Malkin [17] to determine the chaotic regime of α for the nonlinear reflection relation F , thereby rigorously proving chaos. Nonchaotic cases for other values of α are also classified. Such cases correspond to limit cycles in nonlinear second order ODEs. Numerical simulations of chaotic and nonchaotic vibrations are illustrated by computer graphics. Received by the editors July 20, 1995 and, in revised form, October 16, 1996. 1991 Mathematics Subject Classification. Primary 35L05, 35L70, 58F39, 70L05. The first and third authors’ work was supported in part by NSF Grant DMS 9404380, Texas ARP Grant 010366-046, and Texas A&M University Interdisciplinary Research Initiative IRI 96-39. Work completed while the first author was on sabbatical leave at the Institute of Applied Mathematics, National Tsing Hua University, Hsinchu 30043, Taiwan, R.O.C. The second author’s work was supported in part by Grant NSC 83-0208-M-007-003 from the National Council of Science of the Republic of China. c ©1998 American Mathematical Society


Tectonophysics | 2002

Paleostress analyses in NW Syria: constraints on the Cenozoic evolution of the northwestern margin of the Arabian plate

Andrea Zanchi; Giovanni B. Crosta; Abdul Nasser Darkal

Abstract Fault analysis between the Dead Sea Transform and the Euphrates region in northern Syria shows two main directions of compression connected to the recent evolution of the northwestern wedge of the Arabian plate. E–W open folds due to N–S compression gently deform the Cretaceous to Tortonian successions of the Aleppo Plateau and the eastern termination of the Palmyrides west of the Euphrates. Conjugate sets of strike-slip and normal faults, pre- as well as post-dating folding occur in the plateau and are still consistent with the same stress field. N–S normal faults cross recent deposits and control Quaternary volcanoes along the Euphrates, suggesting the persistence of this stress regime. A NW–SE compression related to the Syrian segment of the Dead Sea Transform (DST) was detected in the western part of the study area. The activation of large N–S left-lateral strike-slip and WNW–ESE right-lateral faults follows in time the growth of in-line folds and thrusts. Permutation of the σ1 and σ2 stress axes is related to activation of NW–SE normal faults, which generally accompany strike-slip faults and post-date E–W folds within the plateau. Recent E–W extension in the Euphrates region is consistent with a horizontal N–S maximum direction of compression and seems to be partially coeval with the stress regime induced by the DST. This stress pattern can be explained by the superposition of the northward push of the Arabian plate to the N–S left-lateral shearing along the DST.


Journal of Geophysical Research | 2011

Modeling the evolution of natural cliffs subject to weathering: 2. Discrete element approach

Stefano Utili; Giovanni B. Crosta

The evolution of slopes subjected to weathering has been modeled by assuming Mohr-Coulomb behavior and by using a numerical approach based on the discrete element method (DEM). According to this method, soil and/or rock are represented by an assembly of bonded particles. Particle bonds are subject to progressive weakening, and so the material weathering and removal processes are modeled. Slope instability and material movement follow the decrease of material strength in space and time with the only assumption concerning the weathering distribution within the slope. First, the case of cliffs subject to strong erosion (weathering-limited conditions) and uniform weathering was studied to compare the results of the DEM approach with the limit analysis approach. Second, transport-limited slopes subject to nonuniform slope weathering were studied. Results have been compared with experimental data and other geomorphologic models from the literature (Fisher-Lehmann and Bakker–Le Heux). The flux of material from the slope is modeled assuming degradation both in space and time.


Rock Mechanics and Rock Engineering | 1997

Evaluating rock mass geometry from photographic images

Giovanni B. Crosta

SummaryThe importance of discontinuities in controlling rock mass behaviour in any engineering project involving excavations calls for a sound and spatial characterization of the discontinuity structure present. Such a characterization necessitates field work that requires sufficient rock exposures in order to obtain an adequate number of data, time and considerable cost. Photoanalysis techniques can help in overcoming the above difficulties equally well or better than other techniques. This paper refers to simple photographic techniques and their implementation for computer aided analyses for the characterization of the rock mass fracturing features. In particular attention is focused on scale problems and on reconstruction of fracture density stereoplots on the basis of data collected from one or two images according to different lithologies and outcropping conditions. The methodology for evaluating the volumetric fracture intensity follows in a slightly modified way a technique previously suggested in the literature. Certain reported examples allow to validate the photoanalytical technique used and the proposed method of analysis. Furthermore, analyses on planar density, spacing, frequency, terminations in solid rock or against other discontinuities and spatial correlation have been implemented in a software to yield a more complete rock mass characterization. At the same time input data and analysis results are produced in data files available as input for numerical analyses.

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Federico Agliardi

University of Milano-Bicocca

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Serena Lari

University of Milano-Bicocca

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R. Castellanza

University of Milano-Bicocca

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Andrea Valagussa

University of Milano-Bicocca

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