1,720,955 research outputs found
MPM hydro-mechanical modelling of flows impacting rigid walls
Full text linkThe study on impact mechanisms of flow-like landslides against structures is still an open issue in the scientific literature. Many researchers have employed so far either experiments or numerical methods, but the evaluation of the impact forces on mitigation obstacles remains difficult especially if the solid-fluid interaction within the flow is considered. This study shows how advanced numerical tools, such as Material Point Method, may be used in simulating those complex processes. The simulations are carried out for two well documented laboratory tests: a dry granular flow impacting a rigid wall under different geometries and testing conditions in a small-scaled flume and a saturated flow with complex propagation pattern in a centrifuge apparatus. The numerical modelling is validated against the observations and then used to explore the response of different flows impacting rigid structures in other conditions than in the experiments. The soil-fluid interaction influences the type of impact mechanism, the kinematics of the flow, and the space-time trend of the impact pressure against the structure.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Coupled hydro-mechanical modelling of a 1995 Hong Kong landslide
No full textThe paper deals with the modelling of the instability mechanism induced by rainfall in an unsaturated cut-slope. A large-sized landslide occurred in 1995 in Hong Kong (the so-called “Fei Tsui Road landslide”). It was here analysed because it was characterized by unusual dimensions and very large runout distance for the study area. The slope failure was attributed to a decrease in soil shear strength due to the rise of a perched water table above a weak kaolin-rich layer, together with the loss of suction caused by water infiltration during a heavy rainfall event. The hydro-mechanical coupled analyses made through the commercial software Plaxis 2D aimed to investigate the relations between the hydrological variables (i.e., rainfall infiltration, suction, saturation) and the slope response in terms of changes in soil resistance and soil plastic deformations. The study demonstrates that the evaluation of the hydro-mechanical coupling effects on the hydraulic slope response as well as on the stability of the whole slope is a crucial issue to well capture the mechanical behaviour of the unsaturated cut-slope. Different failure scenarios have been also considered in order to match the field observations and to back-analyse the initial condition of the slope before landslide
Analytical and numerical models of debris flow impact
No full textA full understanding of the interaction mechanisms among flow-like landslides and impacted protection structures is still an open issue. Although several approaches, from experimental to numerical, have been used so far, a thoroughly assessment of the hydromechanical behaviour of the landslide body is achievable only through a multiphase and large deformation approach. This paper firstly proposes a conceptual model for a specific type of protection structure, namely a Deformable Geosynthetics-Reinforced Barrier (DGRB), i.e., an embankment made of coarse-grained soil layers reinforced by geogrids. In such a case, the sliding of the barrier along its base, under the impulsive action of a flow-type landslide, is an important landslide energy dissipation mechanism, and a key issue for the design. Then, two different approaches are proposed: i) an advanced hydro-mechanical numerical model based on Material Point Method is tested in simulating the whole complex landslide-structure interaction mechanisms, ii) an analytical model is set up to deal with the landslide energy dissipation and the kinematics of both the landslide and barrier. The calibration of the proposed analytical model is pursued based on the numerical results. Finally, the analytical model is successfully validated to interpret a large dataset of landslide impact field evidence, for whose interpretation also five empirical methods available in the literature are tested.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Dynamics of Structure
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Multi-phase large deformation modelling of flow- like landslide interaction with protection structures
No full text2020 - 2021The study on impact mechanisms of flow-like landslides against structures is still an open issue in the scientific
literature. Many researchers have employed so far either experiments or numerical methods, but the evaluation
of the impact forces on mitigation obstacles remains difficult especially if the solid-fluid interaction within the
flow is considered. In addition, flow-like landslides are often characterized by large deformations, which
depend on slope geometry, soil type and triggering mechanisms.
Throughout the past decades many numerical methods aiming to simulate large deformations have been
introduced, as for example Discrete Element Method (DEM), Smooth Particle Hydrodynamics (SPH), Updated
Lagrangian Finite Element Method (UL-FEM) and Material Point Method (MPM). All of them are based on
different theories, capabilities, and accuracy, but the complexity is their common feature. In fact, the response
of landslide body under large deformations is still unclear, especially for Landslide-Structure-Interaction (LSI)
problems, due to: i) the hydro-mechanical features of the impacting flow, ii) the geometry and stress-strain
response of the structure, and iii) initial and boundary conditions for the specific LSI problem. Numerical
methods greatly contribute to a safer and more cost-effective design of landslide mitigation works. However,
most of these approaches are very recent, and still need comprehensive validation.
The advanced numerical technique of the Material Point Method (MPM) is used in this thesis to provide a
novel contribution in investigating the dynamics and the impact mechanisms of flow-like landslides against
protection structures, thanks to its capability of considering both the coupled hydro-mechanical behaviour of
the propagating mass and large deformations of the approaching flow. The MPM numerical method is
validated against observations coming from famous landslide benchmarks (like the Fei Tsui Road landslide or
the Wenjia gully debris flow) or from well documented laboratory experiments investigating the impacts of
granular flows against rigid obstacles. Then, the model is used to explore the response of different flows
impacting rigid barriers, focusing the attention on the potential efficiency of different types of barriers in
intercepting the propagation of the flow under several impact conditions. The study principally highlighted
that the soil-fluid interaction within the flow and the barrier geometry influence the type of impact mechanism,
the kinematics of the flow, and the space-time trend of the impact forces against the structure.
The satisfactory validation of MPM also allows to derive simplified analytical and empirical models for
estimating the temporal trend of the impact force on a rigid structure and the kinetic energy reduction of the
flow during impact. However, the assumption of rigid body used for the design of these barriers must be
analysed. For this reason, additional stress-strain analyses on two different mitigation options (such as
Reinforced-Concrete walls and Deformable Geosynthetics-Reinforced Barriers) were conducted for
examining the extent of internal deformations and the possible ultimate limit states of the structure under
impact.
As a conclusion, the research shows how multi-phase, hydro-mechanical coupled and large deformations
numerical methods are of primary importance for modelling flow-like landslides dynamics and for studying
the interaction mechanisms between the landslide and the structure. [edited by Author]XXXIV cicl
Empirical formulation for debris flow impact and energy release
No full textFull understanding the interaction mechanisms between flow-like landslides and the impacted protection structures is an open issue. While several approaches, from experimental to numerical, have been used so far, it is clear that the adequate assessment of the hydromechanical behaviour of the landslide body requires both a multiphase and large deformation approach. This paper refers to a specific type of protection structure, namely a rigid barrier, fixed to the base ground. Firstly, a framework for the Landslide-Structure-Interaction (LSI) is outlined with special reference to the potential barrier overtopping (nil, moderate, large) depending on the features of both the flow and the barrier. Then, a novel empirical method is casted to estimate the impact force on the barrier and the time evolution of the flow kinetic energy. The new method is calibrated by using an advanced hydro-mechanical numerical model based on the Material Point Method. The validation of the empirical formulation is pursued referring to a large dataset of field evidence for the peak impact pressure. Both numerical and empirical methods can appropriately simulate the physical phenomena. The performance of the newly proposed empirical method is compared to the literature methods and its advantages are outlined.Dynamics of Structure
- …
