Papers by Gabriela Medero
Computers and Geotechnics, Oct 1, 2023
Significant progress has been made over the last decade in the effective modeling of the failure ... more Significant progress has been made over the last decade in the effective modeling of the failure and transition from continuum to discontinuum of quasi-brittle materials in many defence, mining and geomechanical applications. However, in several problems, the presence of an additional phase, either gaseous, liquid or both, often controls the behaviour of multi-fracturing material systems. Examples of such interaction include fracture induced in rock masses by the presence of fluid flow and the generation of gas pressure fields due to explosive detonation which drives the fracturing process in rock blasting. Although a generic modelling strategy can be developed for a broad range of such problems, nevertheless, some applications require an individual approach to solution. The main objectives of the presentation is to (i) consider the essential issues related to an effective computational implementation of a continuumdiscontinuum formulation of quasi-brittle materials under various loading conditions, particularly involving fluid interaction and (ii) model the subsequent flow of fragments within such a secondary medium.
Vadose Zone Journal, 2019
We investigated soil response to irrigation with slightly brackish water (1200 mg L −1 total diss... more We investigated soil response to irrigation with slightly brackish water (1200 mg L −1 total dissolved solids on average) in a semiarid environment at the microscopic scale using environmental scanning electron microscopy (ESEM) applied in static and dynamic modes, which allowed comparison between nonirrigated and 3-yr-irrigated soil samples to determine the impact of applied brackish water. Results indicate that (i) there was a change in soil hydrophilic behavior by the continuous accumulation of water-borne salt in the soil matrix, (ii) compared with nonirrigated samples, the wetting process occurred more gradually for the 3-yrirrigated sample, (iii) the wetting process started at a lower vapor pressure for the 3-yr-irrigated sample, (iv) water vapor pressure in the chamber at full saturation was lower for the 3-yr-irrigated sample, and (v) the presence of heavy metals in the soil was more frequent in irrigated samples. Our results show that ESEM is a useful technique to determine the impacts on soil of irrigation with slightly brackish water.
Proceedings of the Third International Conference on Railway Technology: Research, Development and Maintenance, Mar 10, 2016
CRC Press eBooks, Sep 13, 2012
The running of high-speed trains on ballasted railway tracks requires excellent track geometry an... more The running of high-speed trains on ballasted railway tracks requires excellent track geometry and reliability. Three-dimensional polyurethane GeoComposites have been used at many sites across the United Kingdom (UK) to help solve traditional ballast maintenance issues that arise at critical track assets like switch and crossings and transition zones. This paper presents work done on the technique and shows the results of laboratory tests and real site application. In particular the paper concentrates on the application of the technology to transition zones. The issues surrounding transition zone dynamics are discussed and the problem is analyzed through the results of advanced 3-dimensional finite element modeling using the DART3D software. The simulations presented in this paper show how the transition fault develops and how the track stiffness is affected by different transition attributes, such as voiding and track stiffness changes. The use of polyurethane GeoComposite technology for high-speed transition zone reinforcement is then presented and the results of simulations shown as to its effectiveness.
Social Science Research Network, 2022
This paper presents a procedure to optimise by unit-cell rotation a linear-to-circular polariser ... more This paper presents a procedure to optimise by unit-cell rotation a linear-to-circular polariser for near-field incidence. The method is illustrated using an example of an offset flat reflector illuminated by a standard gain horn. Breadboards for the uniform unit-cell array and optimised array have been manufactured and measured, showing good agreement with simulations. Improvements up to 8 dB in the measured cross-polarisation levels of the far-field horizontal plane are obtained for the optimised surface.
Soils and Foundations, Jun 1, 2023
Geomechanics for Energy and the Environment, Mar 1, 2023
CRC Press eBooks, Jun 19, 2009
In this paper the application of polymer geocomposite technology to the reduction/elimination of ... more In this paper the application of polymer geocomposite technology to the reduction/elimination of long standing railway track faults is presented. The polymers used are urethane cross linked polymers that are applied directly to the ballast matrix using on site mixing equipment. Application of the urethane cross linked polymers allows a high degree of visco-elasticity and hence polymer damping characteristics. The formed structure cures within seconds to form a resilient and very strong polymer/ballast geocomposite. The paper describes how the polymer improves the engineering properties of the in situ ballast and presents typical laboratory studies on engineering behavior. Finite element simulations of railway track response before and after polymer application are included to show how the polymer geocomposite behaves under actual train loading. A typical application of the technique to a highspeed, high axle load switch and crossing on the UK West Coast Main Line is described.
International Journal of Geomechanics, Apr 1, 2023
Engineering Geology, Jul 1, 2023
Geometrical Optics (GO) and Physical Optics (PO) have been popular methods to analyse reflector a... more Geometrical Optics (GO) and Physical Optics (PO) have been popular methods to analyse reflector antennas. Although both techniques have extensively been used in the literature and are shown to produce overall accurate results, they lead to some differences in the obtained results. Earlier works have focused on the differences in the sidelobe estimation obtained by GO and PO. The present work presents a comparison of both methods in terms of cross-polarised fields prediction. The study includes both front-fed and offset configurations, using both linearly and circularly polarised feeds and exploits in-house GO and PO tools as well as commercial PO software.
GeoJournal, 2022
Smart city approaches have tended to be top-down, techno-centric/corporate and expensive approach... more Smart city approaches have tended to be top-down, techno-centric/corporate and expensive approaches which are promoted by large, global companies. Smart city narratives focus on their expected capacity to improve citizens’ quality of life. However, can technology-driven and municipally-led smart city initiatives address the issues faced by poor and vulnerable communities in urban and peri-urban areas? This paper explores key aspects of the implementation of smart city approaches in the Global South taking as a case study the Colombian city of Medellín, which has been recognized internationally for its social innovation and is considered a smart city by the Inter-American Development Bank. The paper draws on a local, national and international literature review; interviews with key local stakeholders involved in smart city initiatives; and an international workshop on smart cities and community data management organized by the authors in Medellín and bringing together three perspecti...
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Papers by Gabriela Medero