COLLECTIONS

Documents published in Scipedia

• Safety analysis of rockfill dams during overspill phenomena

  A. LARESE, R. Rossi, S. Idelsohn

  (2012). Annual Meeting of ICOLD. "76th Annual Meeting of ICOLD". Sofia: Bulgarian Committee on Large Dams.

  
  

  Abstract

  An increasing interest is rising on the study of rockfill embankment dams during overspilling. Design criteria of earth dams are being reviewed in many countries to guarantee an increasing safety level in front of an exceptional flooding. The possibility of studying the failure process is currently limited by the lack of a precise knowledge and by the absence of a suitable computational method which can predict accurately the onset and evolution of breaching. The analysis of the possible consequences of an accidental overspill is then impossible or very imprecise and the necessary economical measures for solving the problem are then inefficient. An appropriate computational method will help to reduce the economic impact of the investments in dam safety and in emergency plans for embankment dams. The dam failure is mainly due to the hydrodynamic forces acting on the rockfill material in the downstream face. Two failure mechanisms occur in an alternative or combined mode: dragging of rockfill particles with erosive effects, and loss of stability of a part of the downstream region due to the slippage of a bulk mass of the rockfill material. The loss of a relevant part of the rockfill material in the downstream side of the dam, can lead to mechanical failure of the impervious region, either if this is formed by a concrete (or asphalt) face, or by a clay core. In the latter case, erosion of the cohesive material can also influence the failure process, but the scale time of appearance of this erosion phenomenon is so different from the principal erosion of the rockfill part, that this second one is not taken into account. The objectives of the current work is to develop and validate a new computational method of general applicability that allows treating above problems. The method will combine advanced finite element and particle techniques. Fluid-structure interaction effects and non-linear geometrical and mechanical effects in the dam material will be considered. The specific features of the analysis method proposed make it appropriate to treat the rockfill material adjacent to the downstream surface where a transfer of momentum between the water running over the dam surface and that moving through the interior due to seepage occurs

  Abstract
  An increasing interest is rising on the study of rockfill embankment dams during overspilling. Design criteria of earth dams are being reviewed in many countries to guarantee [...]

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• Theme B: simulation of the behavior of prototypes of rockfill dams during overtopping scenarios: seepage evolution and beginning of failure

  A. LARESE, R. Rossi, M. Toledo, R. Morán, H. Campos, A. Lara

  (2011). "XI ICOLD Benchmark Workshop on Numerical Analysis of Dams". València: 2011, p. 1-25.

  
  

  Abstract

  In recent years the technology on embankments dams has developed sensibly due to the advances in soil mechanic, and in all related sciences. Nevertheless their vulnerability to overtopping still remains their weakest point in comparison with concrete structures. The principal aim of this theme is the simulation of the initial stage of failure of the dam when an overtopping or an exceptional flood occurs. A fluid-structure coupled problem has to be considered. The sudden variation of the upstream conditions induces a quick evolution of a seepage line in the downstream shoulder. Non linear Darcy law has to be taken into account. On the other hand the water, emerging from the toe of the dam, induces dragging of particles and possible mass sliding, depending on geometrical and material conditions. UPM and CEDEX have carried out more than 70 experiments during the last two years. They analyzed the influence of a series of parameters on the failure mechanisms. These parameters are, for instance, the dimension of the rocks, the slope of the downstream part of the dam, the type of impermeable element used, and so on. We propose to reproduce numerically three experiments analyzing the evolution of seepage and following initial stage of failure in the case of a homogeneous dam, of a dam with impermeable upstream face and of a dam with internal core. Experimental data, bottom pressure distribution and topographic analysis of the geometry of the dam during the failure can be compared with numerical results.

  Abstract
  In recent years the technology on embankments dams has developed sensibly due to the advances in soil mechanic, and in all related sciences. Nevertheless their vulnerability [...]

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• Simulation of the beginning of failure in rockfill dams caused by overtopping

  A. LARESE, R. Rossi

  (2015). Dam Protections against Overtopping and Accidental Leakage, Ed: CRC Press, 111 p.

  
  

  Abstract

  This paper presents the work carried out during the last years for the creation of a numerical model to simulate transient seepage phenomena in rockfill dams when overtopping occurs. The objective is to analyze the trigger of failure mechanism in the downstream slope due to hydrodynamic forces. The current work aims to give a contribution to this field proposing a new computational method of general applicability for simulating, with a unique formulation, the flow throughout and over the dam while failure occurs together with the dam structural response. The numerical results are validated with experiments on scale models rockfill dams.

  Abstract
  This paper presents the work carried out during the last years for the creation of a numerical model to simulate transient seepage phenomena in rockfill dams when overtopping [...]

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• Simulation of two and three-dimensional viscoplastic flows using adaptive mesh refinement

  J. Cotela, R. Rossi, A. LARESE

  International Journal for Numerical Methods in Engineering (2017). Vol. 112 (11), pp. 1636-1658

  
  

  Abstract

  This paper presents a finite element solver for the simulation of steady non‐Newtonian flow problems, using a regularized Bingham model, with adaptive mesh refinement capabilities. The solver is based on a stabilized formulation derived from the variational multiscale framework. This choice allows the introduction of an a posteriori error indicator based on the small scale part of the solution, which is used to drive a mesh refinement procedure based on element subdivision. This approach applied to the solution of a series of benchmark examples, which allow us to validate the formulation and assess its capabilities to model 2D and 3D non‐Newtonian flows.

  Abstract
  This paper presents a finite element solver for the simulation of steady non‐Newtonian flow problems, using a regularized Bingham model, with adaptive mesh refinement capabilities. [...]

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• Comparison of a Material Point Method and a Galerkin Meshfree Method for the Simulation of Cohesive-Frictional Materials

  I. Iaconeta, A. LARESE, R. Rossi, Z. Guo

  Materials (2017). Vol. 10 (10), pp. 1150

  
  

  Abstract

  The simulation of large deformation problems, involving complex history-dependent constitutive laws, is of paramount importance in several engineering fields. Particular attention has to be paid to the choice of a suitable numerical technique such that reliable results can be obtained. In this paper, a Material Point Method (MPM) and a Galerkin Meshfree Method (GMM) are presented and verified against classical benchmarks in solid mechanics. The aim is to demonstrate the good behavior of the methods in the simulation of cohesive-frictional materials, both in static and dynamic regimes and in problems dealing with large deformations. The vast majority of MPM techniques in the literatrue are based on some sort of explicit time integration. The techniques proposed in the current work, on the contrary, are based on implicit approaches, which can also be easily adapted to the simulation of static cases. The two methods are presented so as to highlight the similarities to rather than the differences from "standard" Updated Lagrangian (UL) approaches commonly employed by the Finite Elements (FE) community. Although both methods are able to give a good prediction, it is observed that, under very large deformation of the medium, GMM lacks robustness due to its meshfree natrue, which makes the definition of the meshless shape functions more difficult and expensive than in MPM. On the other hand, the mesh-based MPM is demonstrated to be more robust and reliable for extremely large deformation cases.

  Abstract
  The simulation of large deformation problems, involving complex history-dependent constitutive laws, is of paramount importance in several engineering fields. Particular attention [...]

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• A Finite Element Implementation for the Three Variable Biot Model and an Introduction to its Application to Sugar Cane Milling Processes

  R. Rossi, J. Amaya, A. Larese, M. Pohl

  IEEE 38th Central America and Panama Convention (CONCAPAN XXXVIII)

  
  

  Abstract

  This document presents a step-by-step derivation for the formulation of a Biot model for saturated porous media, this formulation is apt to be implemented both in two and three dimensions. Afterwards, the spatial and temporal discretization for the model is also presented, focusing on a symbolic representation around the Gauss points for a particular element in an implementation. Lastly, the results for a couple of test cases are shown, and of special interest, the test case that constitutes the first approximation towards an implementation of this model for the simulation of sugar cane milling processes.

  Abstract
  This document presents a step-by-step derivation for the formulation of a Biot model for saturated porous media, this formulation is apt to be implemented both in two and [...]

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• Soil-structure interaction simulation of landslides impacting a structure using an implicit material point method

  B. Chandra, A. Larese, I. Iaconeta, R. Rossi, R. Wüchner

  2nd International Conference on the Material Point Method for Modelling Soil-Water-Structure Interaction

  
  

  Abstract

  Global warming and climate changes have been one of the many causes that triggered numerous catastrophic landslide and mudflow disasters in the past twenty years. The increase of earth temperature has contributed to the increase of precipitation and undisputedly affected the soil slope stability, which by further may cause landslides in various scale and speed. This large soil deformation phenomenon carries along huge rocks and heavy materials that often results in extensive damage in civil infrastructures both directly or indirectly. Coming with this motivation, a soil-structure interaction simulation based on the implicit material point method (MPM) has been implemented within the Kratos Multiphysics framework for the objective of predicting structural deformation and, furthermore, structural failure caused by environmental flow problems such as landslides. In the current study, the soil is modeled using a non-associated Mohr-Coulomb-based elastoplastic law, while the structure is modeled as elastic and Neo-Hookean hyperelastic materials. In the numerical tests conducted, the equivalent stress and displacement measured on both rigid and flexible structures show a good qualitative agreement. In the future works, a more adequate consideration of the soil and structural model will be investigated before conducting a real-scale landslide simulation.

  Abstract
  Global warming and climate changes have been one of the many causes that triggered numerous catastrophic landslide and mudflow disasters in the past twenty years. The increase [...]

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• Corrigendum to “Modelling of Bingham and Herschel-Bulkley flows with mixed P1/P1 finite elements stabilized with Orthogonal Subgrid Scale” [J. Nonnewt Fluid Mech, 228, 2016, p. 1–16]

  E. Moreno, A. LARESE, M. Cervera

  Journal of Non-Newtonian Fluid Mechanics (2019). Vol. 267, pp. 100

  
  

  Abstract

  This corrigendum provides some missing data and a reference for the paper Modelling of Bingham and Herschel-Bulkley flows with mixed P1/P1 finite elements stabilized with Orthogonal Subgrid Scale, as well as it corrects a mistaken unit of measure in the caption of a figure. The authors apologise for the inconveniences caused. Corrigendum – The caption of Figure 14 should read: Cylinder in an Herschel-Bulkley fluid. Drag force coefficient in terms of the relation L:R for Bn∗ = 10. – The flow index n in the sub-captions of Figure 17(a)-17(l) is nondimensional. – The following Reference should be added: [71] E. Moreno, M. Cervera "Elementos finitos mixtos estabilizados para flujos confinados de Bingham y de Herschel-Bulkley Parte II: soluciones numéricas" Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería, 2016; 32(3); 131-138. – The captions of Figures 2, 4-7, 22-25 should include the following text at the end:   (Reproduced with permission from [71]).

  Abstract
  This corrigendum provides some missing data and a reference for the paper Modelling of Bingham and Herschel-Bulkley flows with mixed P1/P1 finite elements stabilized with [...]

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• Coupled Soil-Structure Interaction Modeling and Simulation of Landslide Protective Structures

  B. Chandra, A. LARESE, P. Bucher, R. Wüchner

  (2019). VIII International Conferenceon Computational Methods for Coupled Problems in Science and Engineering

  
  

  Abstract

  Within the past two decades, mass movements hazards involving fast and large soil deformation have increased significantly in frequency and magnitude due to their strong relation to climate changes and global warming. These phenomena often bring along rocks, debris, and heavy materials that can extensively damage and destroy the landscape and infrastructures, causing devastating economic loss, and often, human casualties. The risk of future disasters continues to escalate with the increase of real estate development in suburban areas, including mountainous regions. Further assessment and prediction on such disasters and their countermeasures are, therefore, in high economic demands. One of the most intuitive ways is to install protective structures in mountain slopes and valleys that can hold the materials brought by the moving landslides. While the current state of the art of landslide prediction using numerical methods has been mainly dominated by the development of advanced geomechanical models suited for different types of soil materials, e.g. multi-phase unsaturated soil model, this study focuses more on the interaction of such phenomena with the installed protective structures. Here, an implicit formulation of material point method (MPM) is implemented to model the landslides considering finite strain assumption. Furthermore, a staggered coupling scheme with traditional Finite Element Method (FEM) is proposed to simulate accurately and robustly the dynamic force and displacement coupling of soil-structure interaction (SSI). All developments of the method are implemented within the Kratos-Multiphysics framework and available under the BSD license (https://github.com/KratosMultiphysics/Kratos/wiki). In the future works, more adequate consideration of coupling scheme and material models considering damage and fracture will be investigated before conducting a real-scale landslide simulation.

  Abstract
  Within the past two decades, mass movements hazards involving fast and large soil deformation have increased significantly in frequency and magnitude due to their strong relation [...]

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• A procedure to design toe protections for rockfill dams against extreme through-flows

  R. Morán Moya, M. Toledo, A. LARESE, R. Monteiro-Alves

  Engineering Structures (2019). Vol. 195, pp. 400-412

  
  

  Abstract

  This article presents a procedure for designing rockfill toe protections with a highly permeable downstream shoulder to avoid mass sliding in dams during extremely high through-flow episodes. This accidental through-flow may be caused by reasons such as overtopping or leakage flow due to the loss of sealing at the impervious element of the dam or its foundation. The proposed protection is located at the downstream toe of the dam, and it is composed of highly permeable material, typically compacted rockfill. This material can be different from the rockfill forming the downstream shoulder of the main dam. The work is a result of a combination of numerical and experimental research carried out to analyze the influence of the geometry of the toe protection for given material properties of both dam shoulder and protection, when they can be considered highly isotropic. As a result of these studies, a design methodology is obtained. A series of validation tests are presented to support the reliability of the method.

  Abstract
  This article presents a procedure for designing rockfill toe protections with a highly permeable downstream shoulder to avoid mass sliding in dams during extremely high through-flow [...]

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