1,720,974 research outputs found
Soil–Water–Structure Interactions
Full text linkInteractions between soil, fluids (e.g., water), and structures are intrinsic to most geotechnical problems. However, these can be extremely complex and further understanding is needed in this field. Soil–water–structure interactions can be studied on many different scales (micro to macro) and perspectives (experimental, numerical, and theoretical). In any case, the consequences of these interactions control soil behaviour, the stability of civil infrastructure, and, ultimately, the safety of our communities. This Special Issue consists of five papers (three research papers and two literature reviews) that highlight the importance of soil–water–structure interactions in a broad range of different applications. The topics addressed in the research contributions include (a) the performance of shallow footings under oblique loads, (b) the assessment of nonlinear base-isolated building systems under dynamic loading, and (c) the applicability of lightweight materials as fill for retaining wall systems. The other innovative papers, on the other hand, provide comprehensive reviews on (d) the role of the clay content in the interface characteristics between sand–clay mixtures and structures and (e) the latest developments in the understanding and measurements of the Atterberg limits
Evaluating the exceedance probability of the runout distance of rainfall-induced landslides using a two-stage FEM-MPM approach
No full textEvaluating the exceedance probability within a time period (EPT) of the runout distance of rainfall-induced landslides is important for the quantitative risk assessment (QRA) of rainfall-induced landslides. However, assessing the EPT of the runout distance of rainfall-induced landslides using a mechanics-based method remains a challenging problem since it requires considering uncertainties in both soil properties and rainfall. This paper proposes a novel mechanics-based method is to assess the EPT of the runout distance of rainfall-induced landslides with explicit consideration of the above two types of uncertainties. A two-stage numerical approach, which combines the finite element method (FEM) and the material point method (MPM), is first developed for the large deformation analysis to obtain runout distances of landslides under given rainfalls. To further enhance the computational efficiency, a machine learning-based surrogate model is built to predict the exceedance of the runout distance, and the EPT of the runout distance is finally estimated via Monte Carlo simulation. The proposed method is applied to a sandy slope under rainfall. The results show that the EPT increases as the time period becomes longer, and the runout distance of the landslide is controlled by the first failure of the slope caused by rainfall. This study contributes to the development of a general and efficient tool to support the QRA of rainfall-induced landslides
Modelling unsaturated soils with the Material Point Method. A discussion of the state-of-the-art
Full text linkMany natural hazards involve large deformations of unsaturated soils, e.g. rainfall-induced landslides, embankment collapses due to wetting, seepage-induced instabilities of dams and levees, etc. The study of these phenomena requires accounting for the complex hydro-mechanical interactions between solid skeleton and pore fluids and modeling large deformations to predict the post-failure behaviour, which poses significant computational challenges. In recent years, several hydro-mechanical coupled MPM formulations were developed to model saturated and unsaturated soils. These approaches are slightly different in terms of governing equations, integration schemes and have been implemented in different MPM software; thus, they benefit from various computational features. The purpose of this paper is to present an overview of the available MPM approaches to model unsaturated soils discussing differences and similarities of the formulations and their impact on the results under different conditions in a range of geotechnical applications. In addition, the effect of partially saturated conditions on the critical time step in explicit numerical integration schemes is studied for the first time. Different analytical expressions are derived and compared with the numerical results
Modelling deformations in water retention structures with unsaturated material point method
No full textWetting induced instabilities in layered slopes: A Material Point Method analysis
Full text linkThe increase of pore water pressure due to rainfall infiltration or upstream recharge is among the primary
triggers of landslides, and soil layering has a significant effect on the hydromechanical behavior of the slope. The failure and post-failure behavior of heterogeneous layered slopes triggered by these phenomena are investigated in this study. In particular, a low permeability layer is embedded in a reference slope with different inclinations, and the impact of different saturation mechanisms on the post-failure behavior is assessed. To this aim, an unsaturated formulation of the Material Point Method (MPM) is used to reproduce the whole deformation process of a layered slope. The results show different failure and post-failure mechanisms and kinematics for both upstream recharge and rainfall infiltration (i.e., bottom-up and top-down saturation processes, respectively).
Bottom-up saturation mechanism triggers deep failure mechanisms that barely evolve during the instability
process. On the contrary, top-down saturation mechanism induces an anticipated shallow semi-planar failure
limited by the location of the low permeable layer. These failures are characterized by high velocities and by a
deepening of the slip surface during the post-failure process. Final displacements in both wetting mechanisms are of the same order of magnitude. The subsequent reactivation movements are observed as a result of the
continuous injection of water in the system
MPM DEVELOPMENTS IN SOIL-WATER-STRUCTURE INTERACTION IMPLEMENTED IN ANURA3D
Full text linkThe material point method (MPM) showed to be well suited to study geotechnical
applications involving large deformations, non-linear material behaviour, soil-structure
interactions, and multiphase (solid, liquid, gas) interactions. This contribution shows the latest
numerical developments implemented in the software Anura3D. Particular attention is given to
some geotechnical applications, such as the simulation of slope collapse due to earthquake or
water pressure changes, erosion problems, installation problems, underground explosions, and
soil-structure interaction in liquefied soils
Simulating landslides with the material point method: Best practices, potentialities, and challenges
Full text linkAdvances in numerical methods have provided useful tools to investigate the complex behaviour of landslides, which can be a valuable support for landslide hazard assessment, planning, and design of mitigation measures. Among different methodologies, the Material Point Method (MPM) has recently grown in popularity thanks to its ability to simulate large displacements and has been applied to simulate an increasing number of real cases. Despite the success, there are still several challenges to be addressed. This paper aims to present the current state of the art of the modelling of real landslide case histories with MPM. The key numerical features used to capture the evolution of different types of landslides are discussed, such as constitutive models, soil-water interaction, and triggering mechanisms, thus providing insights into the computational aspects of using MPM to serve as guidelines for future applications. Limitations and future perspectives are also mentioned to encourage the development of new solutions for current numerical challenges and further extend the applicability of the methodology in this field
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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