Antonio Pasculli

SPH modeling of fast muddy debris flow: numerical and experimental comparison of certain commonly utilized approaches

SPH (Smoothed Particle Hydrodynamics) is a particle, purely mesh-free Lagrangian method, proposed by different authors, well suited to the computing of highly transitory free surface flows of complex fluids in complex geometries. Different approaches have been proposed in order to better simulate the mutual interaction between particles and their interactions with boundaries. Therefore, the main target of this article is to discuss and explore the numerical performance of certain commonly utilized SPH approaches, based essentially on mass and momentum balances, in the simulation of a 2D fast mudflow in fast motion, composed of fluid and solid material, assumed to be just one equivalent phase (fluid-solid). The “Herschel-Bulkley”, non Newtonian constitutive equations, describing a viscoplastic material suitable to reproduce the rheological behaviour of mudflows, has been selected. Hence, a laboratory experimental test, already proposed in literature and, after properly scaling, representative of a real fast flow phenomenon, was considered for comparison with numerical outcomes carried out by a research code that has already been tested and discussed in previous papers. A simple but effective statistical approach was developed and applied in order to identify and utilize a numerical index suitable for the quantitative measurement of the degree of matching between numerical results and measurement data affected by experimental errors. More than thirty numerical experiments were performed, of which the most significant eleven simulations are discussed. Satisfactory results were achieved. As outcomes, it was verified that, in particular for the selected experimental test, Rusanov flux addition within the continuity equation with the proper choice of both the viscosity term of momentum and the SPH boundary conditions, is suited to enhancing the performance of this type of numerical simulation of a fast flow.

SPH NUMERICAL APPROACH IN MODELLING 2D MUDDY DEBRIS FLOW

D muddy debris flow has been simulated accord - ing to a dam break like problem along a slope. The two sets of equations related to the fluid and solid phases, as considered by the debris flow mixture theory, have been simplified in only one set of equations, consider - ing just one equivalent material. Then the Herschel- Bulkley fluid constitutive equations have been select - ed. The correct parameters of the HeRsCHel-bulkley model have been chosen in order to correctly simulate the behaviour of mudflows. The final mathematical model, has been solved numerically with the smoothed particle hydrodynamics (SPH) method. SPH is a par- ticle mesh-free Lagrangian method, well suitable for computing highly transitory free surface flows of com - plex fluids in complex geometries. Finally a laboratory experimental test has been selected for comparison. Satisfactory results have been achieved. Nevertheless, further parametric analyses will be carried out and fur- ther considerations about both constitutive equations and numerical improvements will be employed and discussed in future papers.

Geomorphological features of the Montebello sul Sangro large landslide (Abruzzo, Central Italy)

ABSTRACT This work presents the first results of an integrated geomorphological analysis of a large earthflow in Montebello sul Sangro (Abruzzo, Central Italy). The study is based on a multitemporal geomorphological investigation supported by the morphometric analysis of the drainage network and numerical landslide modelling. The multitemporal geomorphological investigation, based on the interpretation of aerial photos, LiDAR data and field geomorphological mapping, outlined the recent geomorphological history and multiple activation phases of the landslides. A 2D Finite Difference Method (FLAC, Fast Lagrangian Analysis of Continua) analysis of the main landslide scarp, affecting the village of Montebello sul Sangro (Italy), was performed. Finally, in order to outline the morphometric features of the landslide area, local slope autocorrelation was used as a morphometric index. The analysis was aimed at studying the evolution of the active current landslide and specifically the possible retreat of the main scarp.

Conceptual and Numerical Models Applied on the River Pellice (North Western Italy)

Modelsareasimplifyingabstractionofreality.Furthermore,theyprovideoneofthecruciallinks between the analysis of processes and the study of the world around us, the two traditional activities of geomorphology. Starting from these considerations, the present research illustrates the reconstruction of spatial variation in channel morphology in the long, medium and shortterm period using the traditional geomorphologic methods of investigation. This reconstruction allows a preliminary comparison with the conceptual model of the Italian rivers but it leaves several doubts on river evolution in the short-term period. As a consequence, the numerical modelhasbeenintroduced inordertoestimateandevaluateasetofevolutionaryscenariosalong the river and to give an answer to its future evolution. In our research activity, we have applied the Conceptual Evolution Model (CEM) proposed by Surian and Rinaldi and its following updating for the Italian rivers and a cellular automaton (CA) model (CAESAR) at the case-study of the River Pellice, left tributary of the River Po in North Western Italy.

First results of morphometric analysis, multitemporal geomorphological investigation and numerical modeling of the Montebello sul Sangro landslide (Abruzzo, Central Italy)

In this work the first results of an integrated geomorphological analysis of a large earth flow in Montebello sul Sangro (Abruzzo, Central Italy) are presented. The study is based on a new morphometric analysis of the drainage network, a multitemporal geomorphological investigation and a numerical landslide modeling. In order to reconstruct the topography of the Montebello area before the landslide and, accordingly, to explore the possible triggering causes of the instability phenomena, autocorrelation of local slope was introduced as a morphometric index. Multitemporal geomorphological investigation is based on the interpretation of aerial photos, LiDAR data and field geomorphological mapping. The analysis allowed for the outline of the recent multiple activation phases of the landslides. Finally, a 2D Finite Difference Method (FLAC) analysis of a slope, particularly representative because close to the village of Montebello sul Sangro (Italy), was performed.

Application of CAESAR for catchment and river evolution

In recent years the application of reduced complexity models (RCM) is proving to be an excellent alternative resource for evaluating the hydrological response of catchments within a period of time up to decades. In addition, the past two decades have seen significant improvements in the study of river morphology, in particular with regard to the analysis of the processes governing the fluvial evolution resulting from the erosion and transport of sediments. Hence, this paper is aimed at the discussion of the employment of the research code CAESAR, based on cellular automaton (CA) approach, in order to evaluate the water and the sediment outputs from an alpine catchment. Then, the output of the model is applied to a river reach in order to forecast the river evolution in the near future.

Water and Sediment Output Evaluation Using Cellular Automata on Alpine Catchment: Soana, Italy - Test Case

In the alpine contest, the estimation of the rainfall (inflow) and the discharge (outflow) data are very important in order to, at least, analyse historical time series at catchment scale; determine the hydrological maximum and minimum estimate flood and drought frequency. Hydrological researches become a precious source of information for various human activities, in particular for land use management and planning. Many rainfall- runoff models have been proposed to reflect steady, gradually-varied flow condition inside a catchment. In these last years, the application of Reduced Complexity Models (RCM) has been representing an excellent alternative resource for evaluating the hydrological response of catchments, within a period of time up to decades. Hence, this paper is aimed at the discussion of the application of the research code CAESAR, based on cellular automaton (CA) approach, in order to evaluate the water and the sediment outputs from an alpine catchment (Soana, Italy), selected as test case. The comparison between the predicted numerical results, developed through parametric analysis, and the available measured data are discussed. Finally, the analysis of a numerical estimate of the sediment budget over ten years is presented. The necessity of a fast, but reliable numerical support when the measured data are not so easily accessible, as in Alpine catchments, is highlighted.

Dynamically Loaded Anchorages

The present work regards the study of soil-structure interaction, in particular during pull-out tests on anchorages. Due to the complexity of the system, numerical analyses carried out by a commercial code, based on the Finite Difference Method (FDM), were performed. In order to calibrate the overall selected approach, first of all, a simple two-dimensional model of the system was firstly study. The preliminary results and suggestions for incoming 3D modeling improvements are discussed. Furthermore attention has been focused on the nature of the impulsive impacting force due to a virtual debris flow or avalanches striking on the structure, including the anchorages, in order to correctly simulate the test of pull out. Accordingly, a simplified, preliminary model of the anchorages-net system, including the effect of the mass deposition, is proposed and discussed.