Examinando por Materia "Soil liquefaction"

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    Coastal erosion and village relocation: a Colombian case study
    (Elsevier, 2000-01-01) Correa-Arango, Ivan D.; Gonzales, Juan Luis; Universidad EAFIT. Departamento de Geología; Ivan D. Correa-Arango (icorrea@eafit.edu.co); Ciencias del Mar
    Because of its tectonic setting, the Paci"c coast of Colombia is subject to a variety of geological hazards, including earthquakes, tsunamis and associated phenomena such as regional and local coastal subsidence, #ooding and soil liquefaction. Erosional trends are prevalent along much of the 700 km long, low barrier island's shorelines of the Paci"c littoral and land losses are enhanced by factors such as 30 cm regional sea level rises associated to the occurrence of El Nin8o. Marine erosion is threatening more seashore littoral villages and worsening the already di$cult socioeconomic conditions of most part of the inhabitants. Because of diverse and strong motivations to stay near the sea, the responses of barriers island's inhabitants to marine erosion has consisted in most cases of repetitive in-shore and along-shore directed relocations of villages, rather than de"nitive abandonment of the islands. In the long run, this procedure only has postponed the problem and led to repetitive relocations and economical losses. The recent inland relocation of El Choncho village, on the San Juan River delta, illustrates a di!erent response to marine erosion. Although a new along-shore relocation was physically possible, inhabitants decided to abandon the barrier island and migrate to an interior, ancient beach ridge complex, applying a prudent solution which will be the most appropriate for other threatened villages of the Paci"c littoral. A detailed geomorphologic mapping program must be conducted in order to identify appropriate sites for inland relocation of existing villages on the barriers islands of the Colombian Paci"c coast. ( 2000 Elsevier Science Ltd. All rights reserved.
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    Modeling added spatial variability due to soil improvement: Coupling FEM with binary random fields for seismic risk analysis
    (Elsevier Ltd, 2018-01-01) Montoya-Noguera, Silvana; Lopez-Caballero, Fernando; Mecánica Aplicada
    A binary mixture homogenization model is proposed for predicting the effects on liquefaction-induced settlement after soil improvement based on the consideration of the added spatial variability between the natural and the treated soil. A 2D finite element model of an inelastic structure founded on a shallow foundation was coupled with a binary random field. Nonlinear soil behavior is used and the model is tested for different mesh size, model parameters and input motions. Historical evidence as well as physical and numerical modeling indicate that improved sites present less liquefaction and ground deformation. In most cases this improvement is modeled as homogeneous; however, in-situ measurements evidence the high level of heterogeneity in the deposit. Inherent spatial variability in the soil and the application of some soil improvement techniques such as biogrouting and Bentonite permeations will necessary introduce heterogeneity in the soil deposit shown as clusters of the treated material in the natural soil. Hence, in this study, improvement zones are regarded as a two-phase mixture that will present a nonlinear relation due to the level of complexity of seismic liquefaction and the consequent settlement in a structure. This relation is greatly affected by the mechanical behavior of the soils used and the input motion. The effect on the latter can be efficiently related to the equivalent wave period as the proposed homogenization model depends on the stiffness demand of the input motion. © 2017 Elsevier Ltd
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    Numerical simulations toward validating undrained conditions in Geotechnical Earthquake Engineering
    (Universidad EAFIT, 2016) Gómez Zuluaga, Jesús David; Restrepo Sánchez, Doriam Leidin
    Liquefaction denotes the loss of shear resistance of granular materials due to pore pressure build up during cyclic load -- Traditionally, liquefaction is considered as an undrained phenomenon -- Consequently, pore-fluid flow is deemed nonexistent during the cyclic response of sandy soils -- This paper aims to shed light on the validity of this hypothesis by examining the response of natural structures made of saturated porous material subjected to vertically incident plane waves -- The two porous structures, i.e., (i) an alluvial basin, and (ii) a surficial topography, are analyzed under single- and double-drainage regimes -- The results are obtained using a dynamic undrained formulation and compared against an u-p scheme -- This work provides evidence on the impact of drainage conditions, incident wavefront, frequency content, and type of natural structure, on the accuracy of the no volumetric change hypothesis -- On particular, our findings show that the undrained approach exhibits a better agreement for interior topography than for surficial irregularities -- Similarly, P-incident wavefronts tend to be better represented for the undrained hypothesis than SV incident waves -- Finally, our results prove that the undrained approximation provides better estimates for single-drainage conditions than for double-flow regimes