1,721,039 research outputs found
Discrete element simulation of wire-mesh retaining systems: An insight into the mechanical behaviour
No full textThis work presents a new study approach for the evaluation of the behaviour of anchored mesh systems with the Discrete Element Method (DEM) in slope stability applications. Firstly, the mesh model is validated against experimental punch test results. Secondly, it is applied to an idealized field condition in which a secured drapery system is loaded by an unstable debris volume. The non-linear force-displacement response of the mesh is characterized by small deformations to the failure conditions. Furthermore, the force transmitted to the anchors and the stress distribution in the steel wires surrounding the anchors are discussed. A local wedge-shaped failure mechanism, associated with each single mesh panel, is identified as typical of the failure process occurring in the debris layer. Finally, the influence of the thickness of the debris layer and of the anchors’ pattern on the mesh mechanical response is investigated
Calibrazione dei parametri di contatto e discretizzazione di particelle non sferiche per analisi con il metodo agli elementi discreti
Full text linkIl Metodo degli Elementi Discreti (DEM) consente di rappresentare i materiali granulari a partire dalla descrizione delle particelle che lo compongono, dalla loro forma, dai modelli e parametri al contatto. Al fine di rappresentare elementi granulari appartenenti a ghiaie, ed in particolar modo volendo replicare con buona approssimazione la loro forma, è possibile adottare una discretizzazione dei corpi tramite aggregati rigidi di sfere (clumps). Eseguendo analisi sui materiali naturali in maniera da ricavarne le curve granulometriche, gli angoli di resistenza al taglio e i coefficienti di restituzione elastica, attraverso questo lavoro ci si propone di investigare la calibrazione numerica delle dimensioni e delle forme degli elementi, e dei parametri al contatto dei materiali
Use of an up-scaled DEM model for analysing the behaviour of a shallow foundation on a model slope
No full textCalibration of rheological properties of materials involved in flow-like landslides
No full textOne of the effects of climate change is an expansion of the areas affected by flow-like landslides and an increase in human loss and economic damage caused by these natural hazards. The risk assessment connected to flow-like landslides utilizes several study approaches, such as the mapping of lands affected in the past, the understanding of triggering and propagation mechanisms through the monitoring of some watershed basins periodically subject to flow-like landslides, and the prediction of flow-like landslide propagation by means of advanced mathematical models. Research has made much progress in the development of advanced mathematical models able to account for various rheological models, 3D morphology of the slope, and engagement of other materials from the boundary, etc. Calibration of the parameters is, however, one of the most problematic phases of numerical modelling; the validation of propagation models is usually carried out on the basis of laboratory flume tests executed in very simple conditions or on the basis of data achieved from field observation, which are very often of low quality. After a brief state-of-art review concerning the most recent developments in flow-like landslide modelling, the present paper examines the techniques adopted for calibrating the models. Particularly, it considers the difficulties linked to the upscaling of rheological properties moving from the physical tests performed in viscometer or artificial flume, and attaining the estimation of average properties of the heterogeneous materials involved in real flow-like landslides
MODELLAZIONE MICROMECCANICA DELL’EFFETTO DELL’EVAPORAZIONE SULLA STABILITÀ DI UN PENDIO GRANULARE
No full textModellazione del collasso arginale indotto da sollevamento al piede con il metodo dei punti materiali
Full text linkIn questo contributo viene indagato un tipico meccanismo di collasso arginale, indotto da sovrapressioni nei terreni di fondazione. Tale meccanismo è caratterizzato dal sollevamento al piede dell’argine e da una perdita di resistenza che può favorire localizzazione di deformazioni e lo scivolamento profondo. Una possibile conseguenza è la propagazione della superficie di rottura con l’interessamento del corpo arginale, e la formazione di una triplice superficie di scorrimento di forma non circolare. Questo fenomeno complesso viene per la prima volta analizzato mediante il Metodo dei Punti Materiali (MPM) che consente l’analisi delle fasi di formazione della superficie di scivolamento e collasso, senza i vincoli degli approcci agli elementi finiti (FEM).
Attraverso la riproduzione di un esperimento in centrifuga geotecnica, il contributo si propone di testare l’abilità dell’MPM come strumento predditivo di questo tipo di fenomeno e di supportare analisi di rischio affidabili, non troppo conservative. Il confronto con approcci numerici convenzionali supporta la tesi e conclude il contributo
Discrete element analysis of the punching behaviour of a secured drapery system: from laboratory characterization to idealized in situ conditions
Full text linkIn this work, the mechanical response of a steel wire mesh panel against a punching load is studied starting from laboratory test conditions and extending the results to field applications. Wire meshes anchored with bolts and steel plates are extensively used in rockfall protection and slope stabilization. Their performances are evaluated through laboratory tests, but the mechanical constraints, the geometry and the loading conditions may strongly differ from the in situ conditions leading to incorrect estimations of the strength of the mesh. In this work, the discrete element method is used to simulate a wire mesh. After validation of the numerical mesh model against experimental data, the punching behaviour of an anchored mesh panel is investigated in order to obtain a more realistic characterization of the mesh mechanical response in field conditions. The dimension of the punching element, its position, the anchor plate size and the anchor spacing are varied, providing analytical relationships able to predict the panel response in different loading conditions. Furthermore, the mesh panel aspect ratio is analysed showing the existence of an optimal value. The results of this study can provide useful information to practitioners for designing secured drapery systems, as well as for the assessment of their safety conditions
DEM Modeling of a Plate Bearing Capacity Test on a Mesh-Soil System
No full textAnchored wire mesh facings are commonly adopted as a countermeasure against shallow instabilities in granular soil slopes. In this work, the interaction between a wire mesh panel and a granular material is investigated by adopting a discrete element approach. The wire mesh is modeled as a set of interconnected nodal particles. The interaction between the nodal particles is ruled by experimentally derived elasto-plastic tensile laws in which a distortion is introduced stochastically to account for the geometrical irregularities of the wires in real mesh panels. The granular layer is described by rolling resistant spherical particles. Experimental results conducted on a special plate bearing test configuration in which a mesh panel was draped over the granular layer are used for the model calibration. The numerical outputs permit investigation of the complex interaction mechanism among the mesh and the granular layer and estimation of the different contribution of the system’s components. Furthermore, the impact of the mesh introduction on the failure mechanism occurring in the granular soil is discussed in light of the numerical findings. Finally, the role of the loading plate geometry and of the mesh mechanical characteristics on the system bearing capacity and on the mesh-soil interaction is addressed
Comparison of two dem strategies for modelling cortical meshes
Full text linkThis work deals with the particle-based modelling of cortical wire meshes. Such meshes are being used in many engineering applications but their modelling is particularly complex because of the common large displacement serviceability conditions, the chance of localized failures, and the intrinsic geometrical and mechanical anisotropies. The discrete element method has proved to be an excellent numerical tool for the investigation of such structures. Here, two modelling strategies are compared using a wire-node description and a wire-cylinder description: In the first the wire mesh is described by a collection of spheres at nodes linked by long-range interaction forces, in the second the wires are represented by means of interconnected cylinders. The force-displacement constitutive model of the interactions is calibrated based on specific tensile tests. The comparison is performed on results of tensile tests and punch tests on a reference mesh panel
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