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The goal of this paper is to simulate the interaction of stress waves and rock fractures in a particle micromechanical model. Stress waves travelling in fractured rock masses are slowed down and attenuated by natural heterogeneities, voids, microcracks and, above all, by faults and fractures. Considerable laboratory and theoretical investigation have uncovered the major aspects of this phenomenon, but models that cover the core mechanisms of the wave propagation in rock masses are necessary to investigate aspects of wave

O método dos elementos discretos adoptando partículas para discretização dodomínio tem sido utilizado no estudo do fenómeno da fractura em meios nãohomogéneos, como o betão e a rocha. Neste artigo, é proposto um modelo de análisepara o betão armado no qual as armaduras são modeladas com elementos rígidosunidimensionais ligados por molas. Os elementos rígidos interagem com o betão,modelado por partículas circulares, através de uma interface de contacto. O modelo évalidado com base em ensaios de flexão em viga a três pontos e a quatro pontos,sem armaduras de esforço transverso. No ensaio de flexão a 3 pontos o modelo dáuma boa aproximação do comportamento real em termos do processo de evolução dafractura e da relação carga-deslocamento. No ensaio de flexão a 4 pontos, verifica-seuma boa correlação com os resultados experimentais, nomeadamente o valor dacarga última, o efeito de escala e a evolução do processo de fractura.

The overcoring method for measuring in situ stresses is frequently used in rock engineering projects. Most models for its interpretation assume that the rock is homogeneous, linear elastic and isotropic. The elastic constants are determined by various methods, namely by biaxial tests on the recovered core.A three-dimensional finite element model was developed, which allows to compute the stress state from the strain measurements obtained during overcoring, assuming a transversely-isotropic behaviour of the rock mass. Different testing methodologies for elastic constants determination of anisotropic rocks are introduced and discussed. Several numerical tests were performed to analyse the influence of the weakness planes that sometimes occur in the rock core owing to the tensile strains that are generated during the biaxial test. To avoid the tensile strains in the biaxial test, a new triaxial testing procedure of the overcored rock sample with the cell was developed. The effect of the degree of rock anisotropy on in situ stress determination and the error involved in neglecting rock anisotropy are analysed. Differences on the principal stresses and principal directions calculated considering the usual isotropic model and the developed numerical model for a real case of anisotropic rock are presented.

The integration of healing capsules into asphalt mixtures has demonstrated promising advancements in their intrinsic self-healing properties. However, the efficacy of this technology still requires further investigation. Rigid particle models, utilizing the discrete element method (DEM), have been adopted to simulate the creep, fracture, and viscoelastic behavior of asphalt mixtures, accounting for their irregular microstructure and particle contacts. This study utilizes the previously developed VirtualPM3DLab, a three-dimensional DEM framework, to numerically assess the impact of rejuvenator-modified mastic particles on the stiffness properties of post-healed asphalt mixtures where the asphalt mixture has undergone healing. Simulations consider different capsule proportions (0.30, 0.75, and 1.20 wt%) incorporated in the specimens. Numerical results reveal that the encapsulated rejuvenator reduces the stiffness modulus of asphalt mixtures, with this impact becoming more pronounced as the capsule amount increases due to the additional rejuvenator representation in the specimen. In addition, the phase angle remains unaffected across all numerical scenarios, suggesting that the viscoelastic behavior of asphalt mixtures is not significantly impacted and indicating the suitability of capsules for pavement applications. The findings also suggest that the percentage of these healing elements can slightly surpass the traditional amounts commonly used in laboratory settings.

This paper presents an updating of the analysis and interpretation ofthe structural behavior of Covão do Meio dam (in Portugal) which concrete isaffected by an ongoing swelling process.The simulation of dam

Micromechanical modelling through the Discrete Element Method (DEM) is adopted for the study of bituminous materials given its capability to replicate complex microstructures behaviour. Typically, DEM models of bituminous materials consist of an assembly of randomly distributed spherical rigid particles which interact using elastic and/or simple viscoelastic contact models, and individual aggregates are represented by single particles. However, recent years have witnessed a notable surge in research efforts aimed at incorporating true particle morphologies into numerical models.In the context of this research, an existing 3D DEM model for bituminous materials has been refined with the representation of mineral aggregates with realistic particle shapes. To achieve this, a digital library of aggregate shapes was constructed from X-ray computed tomography (CT) scans. An adaptive image-processing technique was employed to isolate the aggregates in the CT images, and the Delaunay method was used to create a 3D surface model of the aggregates. Several virtual aggregates with varying sizes were selected from this library to mirror the gradation of coarse aggregates in the 3D DEM asphalt model. Each virtual aggregate was discretized using smaller spherical particles, with its deformability given by its inner particle contacts.To evaluate the effectiveness of this enhanced approach, numerical assemblies featuring realistic particle shapes were subjected to a cyclic loading protocol. Overall, realistic particles shapes increased the stiffness modulus and decreased the phase angle of numerical specimens, and the effect was greater with a finer discretization of aggregates. The outcomes clearly demonstrate the importance of this numerical improvement to accurately simulate the bituminous mixture behaviour.

A avaliação estrutural das paredes de alvenaria de pedra tradicional é uma tarefa complexa devido à heterogeneidade e incerteza nas propriedades dos materiais constituintes, argamassa e pedra, e à variabilidade do posicionamento e geometria destes elementos na alvenaria. Nesta comunicação, modelos experimentais de alvenaria de pedra (muretes), construídos de acordo com técnicas tradicionais portuguesas, ensaiados experimentalmente sob condições de carregamento em compressão-corte, são avaliados numericamente, adotando uma abordagem de micro-modelação através de um modelo de partículas 2D (2D-MP). Estudos anteriores demonstram que os modelos 2D-MP conseguem prever o comportamento de estruturas de alvenaria antiga, nomeadamente a propagação de fendas, os modos de rotura final, a resistência máxima ao corte e a ductilidade da parede observados experimentalmente em compressão uniaxial e compressão-corte. Neste trabalho apresentam-se os estudos numéricos desenvolvidos que permitem avaliar a influência do nível de pré-compressão na resposta monotónica em compressão-corte e o desempenho do modelo 2D-MP na reprodução de ensaios cíclicos.

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Stone masonry walls are the main structural elements of many historic buildings. Their restoration and preservation are a major concern given the increasing interest in the rehabilitation of built historical heritage and the implementation of preventive measures to mitigate seismic risk. The accurate structural assessment of the existing rubble stone masonry is a very complex and difficult task, due its composite and complex nature. The heterogeneity and uncertainty in material properties of its constituents, mortar and stone, the variability of the stone units positioning and geometry, among others, make its experimental characterization and accurate numerical modeling still nowadays a challenging task. In this context, the research presented aims to contribute to a better understanding of the in-plane shear behaviour of unreinforced two leaf rubble stone masonry walls, typical stone masonry of ancient buildings that are representative in Portugal.Rubble stone masonry specimens, built with traditional Portuguese construction techniques, tested experimentally under monotonic compression-shear loading conditions are here numerically evaluated, adopting a micro-modelling approach using a 2D particle model (2D-PM). In the 2D-PM model the stone and mortar elements are represented as particle assemblies that interact with each other, thus capable of representing their inherent physical and material heterogeneity. The numerical model is generated through a mapping process of the stone units and mortar joints. The experimental campaign conducted on rubble stone masonry wall specimens allowed to collect the data necessary for the calibration of the PM model parameters, namely the stone-stone and mortar-mortar elastic and strength contact properties. The validation of the 2D-PM models of the rubble stone masonry specimens under compression and combined compression-shear loading conditions is performed using the Parmac2D software. The presented results show that 2D-PM models can predict the crack propagation, the final failure modes, the maximum shear strength, and the wall ductility observed experimentally. Parametric studies are also presented that allow a better agreement between the numerical predictions and the experimental response showing the relevance of the stone-mortar interface strength properties in the overall macroscopic behaviour.

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In this work three constitutive contact models that include softening are adopted for particle model fracture studies in both rock and concrete. For a single local contact, the constitutive contact model performance is initially compared in tensile, pure shear and shear tests under constant axial. Additionally, compression, direct tensile, and confined triaxial tests of quasi-britlle material discretized with spherical particles are presented and the predicted macroscopic response is compared. For a single local contact, the three contact models predict a similar behaviour. As shown, it is possible to calibrate each contact model to reproduce complex macroscopic behaviour observed in rock and concrete, but each contact model requires different contact properties or particle generation procedures.

Asphalt mixture faces damage due to vehicle speed, repeated loads, and ultravioletradiation over time, regardless of being a self-healing material. Induced healing mechanismsare necessary to promote autonomous pavement recovery due to adverse in-service conditions,and the capsule-asphalt mixture system incorporating low-viscosity oils (rejuvenators) hasshown to be a possible solution in laboratory tests. This study aims to numerically investigatethe effect of rejuvenator-modified mastic (activated capsules) on the stiffness properties ofasphalt mixtures within the discrete element method. A three-dimensional model previouslyvalidated for rejuvenator-modified mastics with different rejuvenator-to-bitumen ratios (0, 2.5,and 10 wt%) is adopted. A generalised Kelvin contact model represents the time-dependentcontacts, and its contact parameters define the rejuvenator amount in the mastic phase. Theanalysis assesses the impact of the modified mastic amount and the rejuvenator-to-bitumenratio. Results show that the increasing modified mastic content progressively reduces themixture dynamic modulus. When the total mastic phase has rejuvenator-modified properties,the mixture stiffness modulus significantly reduces, and the phase angle performs differentlyfrom the expected (decrease with frequency) at a 10% rejuvenator-to-bitumen ratio due to theexcessively softened state, possibly compromising the pavement mechanical performance. Fora 0.30 wt% modified mastic ratio case adopting a local effect, the embedded elements do notsignificantly influence the mixture rheological properties, especially the stiffness modulus,which may be insufficient for self-healing purposes. Nevertheless, the negligible impact on thephase angle highlights the potential of the rejuvenator-modified asphalt mixture across differenttraffic and temperature conditions.

Masonry is a combination of units such as stones, bricks or blocks usually laid in a cementitious or limemortar. It is probably the oldest material used in construction and has proven to be both simple to buildand durable. Over the years, existing masonry constructions have inevitably suffered damage with time.Earthquakes, soil settlements, material degradation and lack of maintenance are the main reasons forthat. Careful and periodic assessment of such structures is necessary in order to evaluate their structuralcapacity and safety levels. However, performing the structural analysis of masonry construction is notan easy task. A review is presented of the main models based on the discrete element method and the available related numerical techniques that have been proposed for the analysis of masonry. The essential assumptions adopted by these models and numerical implementation issues are discussed. Differences between available models are illustrated by applications to various masonry problems including static and dynamic analysis of masonry arch bridges, walls, vaults, domes and ancient colonnades.This book is composed of 17 chapters authored/co-authored by 25 outstanding researchers from 11countries (Canada, France, Greece, Hungary, Iran,Italy, Mexico, Norway, Portugal, UK, USA), whichwere reviewed by 60 referees.

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This chapter consists of two parts. First a general overview is given: the exact definition of the Discrete Element Method is provided, and the main types of existing models are introduced; then the theoretical fundaments of the most important approaches available today for masonry analysis are given. The second part of the chapter focuses on 3DEC, the most widespread commercial DEM code for masonry analysis. This second part begins with a theoretical overview. Application issues for masonry structures are then considered (block material behaviour, contact representation, structural elements like cables or bars etc.). Among the practical examples arches, barrel vaults, walls, coloumns and complete structures (like houses) are presented, including the issues of quasi-static versus dynamic analysis and of block fracture as well. The readers can find helpful advice on how to simulate their own problems most effectively.

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Discrete element models have become a major tool for masonry analysis, allowing a suitable representation of its discontinuous nature and marked nonlinear behaviour. The chapter reviews the fundamental assumptions of the main DEM formulations available. It focuses more specifically on the widely used UDEC and 3DEC codes, explaining their relation with the other approaches, and the most relevant issues arising in their application to masonry. Applications to the main types of structures are reviewed, considering both static and dynamic analyses. Recent research providing comparisons of the numerical models with experimental and field data is particularly covered. The discussion of the different examples is aimed at clarifying the key capabilities of DEM and demonstrating the most effective ways of using it in a variety of masonry analysis situations.

This chapter is focused on the Portuguese experience on the developmentand exploration of systems for continuously monitoring dam vibrations, usingaccelerometers. The pioneer system for seismic and structural health monitoring(SSHM) installed in Cabril dam (the highest Portuguese arch dam: 132 m high) isdescribed in detail. The design of this system was the result of a long-term LNECresearch program, still ongoing. These monitoring systems should include softwaredeveloped to automatically perform the analysis of collected data, including theautomatic comparison with numerical results from 3DFE models. In view of thegood results obtained with the system in operation in Cabril dam since 2008, similarsystems have been installed in other large dams in Portugal, particularly in recentlybuilt dams. Finally, Baixo Sabor dam is presented as an example of a new Portuguesedam with a complete SSHM system, in operation since 2015. Themain experimentalresults obtained for both dams are shown, namely the evolution of natural frequenciesover time, mode shapes and the measured seismic response to earthquake events.

Para verificação do cumprimento das exigências de segurança das barragens,tanto relativamente à funcionalidade (cenários correntes), como em relação àsegurança ao colapso (cenários de rotura), é essencial utilizar modelos de simulação oude interpretação (no caso de obras existentes) do seu comportamento. Estes modelossão idealizações (simplificações) da realidade, tanto no que diz respeito às acções(modelos das acções), como no que respeita à componente estrutural (modelos estruturais).A solução destes modelos, através de adequados métodos de análise, quantificaparâmetros da resposta das estruturas que permitem avaliar a sua segurança, utilizandocritérios de segurança previamente definidos.A validação destes modelos pode ser feita, no caso de cenários correntes,através da sua comparação com os resultados da observação do comportamento debarragens. No caso de cenários de rotura, não existe muita experiência de comparaçãodestes resultados com situações reais: é pequeno o número de acidentes ocorrido e,mesmo nestes, o volume de informação é reduzido. Desta forma, o recurso a métodosexperimentais, para o estudo de cenários de rotura, tem uma importância acrescida.Assim o principal objectivo deste trabalho é contribuir para melhorar a capacidade deavaliação da segurança de barragens de betão envolvendo cenários de rotura pela fundação.Neste trabalho desenvolveram-se dois ensaios experimentais em modelosfísicos: um primeiro envolvendo uma barragem abóbada, para o estudo de cenários derotura da fundação para acções estáticas; e um segundo de uma barragem gravidadeensaiado em mesa sísmica, com vista a estudar a rotura pela fundação para acçõesdinâmicas.A previsão e interpretação dos ensaios foram efectuadas com modelosmatemáticos adequados, que permitiram a sua validação e posterior utilização no estudode outros cenários.

Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto DEMRock6m do P2I/LNEC 2013-2020. Os resultados da atividade desenvolvida são analisados e avaliados em face dos objetivos inicialmente previstos.

Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto MEBAD do P2I/LNEC 2013-2020, no período 2016-2023. Os resultados da atividade são analisados e avaliados, em face dos objetivos previstos.

Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto RockGeoStat do P2I/LNEC 2013-2020. Os resultados da atividade desenvolvida são analisados e avaliados em face dos objetivos inicialmente previstos.

The main goal of this report is to present DamDamage3D1.0, a 3D finite element-based program for non-linear static analysis of arch dams, developed using MATLAB. The non-linear simulations are performed using a damage law and an iterative numerical method based on the stress-transfer technique, considering the redistribution of unbalanced forces in each iteration due to material damage. The concrete

The main goal of this report is to present DamDamage3D1.0, a 3D finite element-based program for non-linear static analysis of arch dams, developed using MATLAB. The non-linear simulations are performed using a damage law and an iterative numerical method based on the stress-transfer technique, considering the redistribution of unbalanced forces in each iteration due to material damage. The concrete

In this work we present the version 1.0 of the GDams2D 1.0 program developed for 2D analysis of gravity dams using the finite element method. This initial version of the program is prepared to analyze the structural behavior of gravity dams for static loads, considering linear-elastic behavior, and using Lagrange finite elements of 4 sides, with 9 nodal points. The GDams2D 1.0 program, developed in MATLAB, includes a module for automatic generation of meshes with a great level of refinement (generated from coarse meshes of quadrilaterals, with 4 nodal points at the vertices) and is designed for easy adaptation to non-linear analyzes, using stress-transfer modules such as those recently developed for the DamSlide3D and DamDamage3D programs. After a brief reference to the fundamentals of solid mechanics and to the simplified hypotheses of plane elasticity, the Fundamentals of the Finite Element Method (FEM) are presented, referring in particular the formulation of the four-node, linear and isoparametric, finite element (FE4nos), with two translation d.o.f per node, and the quadrangular FEs of 9 nodes (FE9nos) used in GDams2D 1.0. Based on some examples of application to simple 2D structures whose response is knownanalytically, the advantages of FEs are emphasized in relation to FE4nos and the verification and operability of GDams2D 1.0 is made using various discretizations. Finally, the case of a gravity dam (25 m high) is presented. The dam

The main objective of this work is the development and presentation of a three-dimensional finite element program, DamSlide3D, to study the behavior of gravity dams for scenarios of sliding through the dam-foundation interface. The DamSlide3D, developed using MATLAB, includes cube-type finite elements with 20 nodal points ("serendipity") and finite interface elements with 16 nodal points (joint elements). Initially, we present the fundamental equations of Solid Mechanics, referring to the main simplified hypotheses considered in the computationally implemented formulation, which is presented mathematically as a problem of boundary values using a displacement formulation. For the structure body and for the foundation, the hypothesis of isotropic materials with linear elastic behavior is assumed and for the interfaces the hypothesis of non-linear behavior is considered using the Mohr- Coulomb criterion. The DamSlide3D input data is provided in an excel file and includes structure geometry data, material properties, support conditions and load parameters. As output, the program graphically displays the stress field (principal stresses) and the displacement field (deformed structure). The program was verified throughout three numerical tests with known theoretical solutions. In these tests a simple structure was used, composed by a column discretized in 3DFE. At the contact surface between the column and the base (horizontal surface) it was considered an interface discretized using joint finite elements. A plane surface that crosses the column with a given slope is also considered, discretized using the same type of joint finite elements. In the first test, the field of elastic stresses at the base, due to self-weight (SW) and hydrostatic pressure (HP), was compared with the theoretical results. In the second test the nonlinear column response was studied for different values of thefriction angle at the inclined interface (in this test the structure is only submitted to SW). In the third test, for the main SW + HP loads, the stability of the column is studied for a variation of the friction angle, and for a variation of the water level. In these three numerical tests the results were always consistent with the theoretical solutions. Finally, as an example of application, a gravity dam structural behavior was analyzed considering the non-linear behavior in the dam-foundation interface. The dam was subjected to self-weight and hydrostatic pressure. A parametric study was developed in order to study the dam stability for differentvalues of water level and friction angle.

Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto CoMatFail até ao final de 2017. É feita a apreciação da atividade desenvolvida, nomeadamente quanto ao grau de cumprimento do plano de trabalhos, bem como dos objetivos específicos e dos indicadores de desempenho propostos na ficha de projeto. São ainda referidas as aplicações dos resultados da investigação em trabalhos contratados ao LNEC e as candidaturas a financiamento externo desenvolvidas no âmbito do projeto. Inclui-se em anexo a ficha do projeto atualizada, que contempla a revisão do plano de trabalhos.

Neste relatório apresenta-se de forma sucinta a descrição da atividade de investigação realizada no âmbito do projeto DEMRock6m no período 2016-2017. Os resultados da atividade são analisados e avaliados em face dos objetivos inicialmente previstos, sendo proposta uma revisão do plano de atividades para os próximos três anos.

Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto RockGeoStat no período 2016-2017. Os resultados da atividade são analisados e avaliados em face dos objetivos inicialmente previstos, sendo proposto um prolongamento do projeto até ao final de 2018.

This document presents a back analysis procedure for identification of the elastic parameters of transversely isotropic rock cores, containing an overcoring triaxial strain probe, from the strains measured during a biaxial test. A three-dimensional finite element model was developed to simulate the biaxial test on the overcored rock specimen and to compute the strains at the location of the strain gauges. Different optimisation algorithms were tested and the most suitable one was selected. The back analysis procedure was tested for identification of the five elastic parameters and the two orientation angles that characterise a transversely isotropic rock core. In spite that, with the developed methodology, convergence was reached and all those parameters could be identified, sensitivity analyses demonstrated that the results obtained were not stable and therefore they were not reliable. By introducing constrains based on common practice and previous experience, a stable and robust methodology was achieved: the three elastic parameters, E1, E2 and ?2, are reliably identified using the value of G2 calculated with Saint-Venant’s expression and a fixed value of ?1, while the orientation parameters are obtained from observation of overcored rock. Analysis of the results shows that application of this methodology represents an enormous step forward when compared with the traditional use of isotropy. Besides, the methodology is general and can also be used with other types of overcoring equipment. The five elastic parameters and the two orientation angles obtained can then be used, together with the overcoring strains, to compute the complete in situ state of stress.

This document presents the work developed by the PhD student Margarida Espada in the scope of the course unit Risk Analysis in Geotechnical Works of the Doctoral Program in Civil Engineering of the Faculty of Engineering of the University of Porto (FEUP). This work presents a reliability analysis, using the response surface method (RSM), for the case study of the left bank excavation slopes of the Baihetan arch dam foundation, which is one of the case studies of Margarida Espada's PhD thesis. The aim was to approximate an implicit limit state function by computing safety factors, using a discrete element model of the Baihetan left bank developed in 3DEC software, where the shear strength parameters of two important rock discontinuities were considered as random variables. The probability of failure was then obtained through an iterative process, using approximation methods. This work presents the 3DEC model developed to analyse the stability conditions in the Baihetan left bank and the results of the reliability analysis.

O problema da solução das equações de Navier Stokes é abordado neste trabalhopropondo-se uma técnica de representação das incógnitas deslocamentos e pressõesvariáveis no espaço e no tempo em série de Delta de Dirac e suas derivadas no tempocujos coeficientes se determinam com base na solução de sistemas de equaçõesdiferenciais definidos no espaço (problema com três variáveis espaciais independentesque pode ser estudado pelo método de Monge).

Neste relatório apresentam-se as equações básicas da elastodinâmica linear, as soluçõesfundamentais e o teorema da representação no domínio de tempo e de frequência.Para movimentos finitos de casca formula-se o teorema dos trabalhos virtuais e a suaimplementação pelo método dos elementos finitos.

Neste relatório apresentam-se os principais aspectos da modelação sísmica de barragensabóbada. Assim propõe-se: modelos numéricos de geração de sismos por uma falha; aforma como o sismo actua na barragem; modelos para estudar a influência da albufeirana vibração do conjunto; métodos para solução das equações do movimento; e novasformulações de elementos finitos para o problema estrutural.

In pressure tunnels and shafts, in addition to the mechanical effect that excavation has on the rock mass and the disturbance that it introduces in the water flow, also the contained water can interact from the mechanical and hydraulic points of view with the rock mass. Seepage in fractured rock masses is dominated by the flow that takes place through the joints, and this is highly d(;pendent on their properties, namely aperture and roughness. Joint aperture, in tum, i::; very sensitive to stress changes. Special attention must therefore be paid to the joints in hydromechanical analyses. In this report are presented some studies that were carried out for the hydromechanical characterization of joints of the Alto Lindoso rock mass and numerical simulations of the hydromechanical behaviour of two selected sections of the high pressure circuit.