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Abstract: Seepage during the first filling of a reservoir is a critical aspect for earth dams and embankments safety, which requires precise monitoring. The thermometric method has demonstrated significant potential for detecting seepage anomalies through continuous temperature measurements using optical fiber distributed temperature sensing (DTS). However, most previous research has primarily focused on thermal monitoring when seepage flow reached a steady-state condition, which highlights the need for more research on seepage and heat transfer in transient state, particularly in unsaturated soils during the reservoir’s first filling. This paper addresses the transient seepage flow and heat transfer during the first filling of a laboratory sand model. Temperature variations within the sand were recorded using an optical fiber DTS, while seepage progression was tracked through digital imaging at regular intervals, followed by image processing. A coupled hydrothermal numerical model was also developed to simulate transient seepage flow and heat transfer within the unsaturated and variably saturated sand. In numerical modeling, heat dispersion and the thermal conductivity of sand were investigated through parameter calibration. Results indicate that thermal monitoring using optical fiber DTS is an effective method for estimating the development of the phreatic line during the first filling of the reservoir. Numerical simulations further revealed that seepage velocity plays a key role in the heat transfer process during transient seepage. Additionally, the results highlight that heat dispersion significantly influences heat transfer, particularly during transient seepage flow, whereas the effect of thermal conductivity is relatively minor as seepage progresses.
Keywords: seepage, phreatic line, temperature, heat dispersion, optical fiber DTS
Published in DiRROS: 09.05.2025; Views: 202; Downloads: 95
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Abstract: In the past couple years, the region of South-East Europe is subjected to gust rainfall events activating many landslides which cause significant material and human losses. To revaluate the existing risk maps and set new standards some old case histories are revaluated. This paper presents two case histories of landslide instabilities subjected to excess climatic perturbations, gust rainfall, namely the «Stanjevci» cut-slope near the railway line in North-East of Slovenia; and the «Ramina» a natural landslide in urban area near the city of Veles in Central Macedonia. They are briefly described later to be analysed using coupled thermo-mechanical calculations. They are subjected to specific short and gusting rainfall considered as possible trigger. Hence, van Genuchten's hydraulic model is used in combination with elastoplastic material models. The results are summarized with critical comments regarding the mathematical formulation used to describe atmospheric-soil interaction and the influence of different aspects on the accuracy is discussed briefly.
Keywords: numerical, unsaturated soil, slope stability analysis, climate effect
Published in DiRROS: 04.03.2025; Views: 221; Downloads: 125
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Abstract: Insufficient effective confining pressure within the ballast layer can lead to the permanent rotation of grains, causing increased wear and abrasion. Augmenting confinement may not only mitigate ballast degradation but also enhance the overall performance of the track. The increased confining pressure causes the increase of ballasted track stiffness and reduction of resilient and permanent deformation. This paper outlines developing a cost-effective ballast wall arrangement (BWA) to boost ballast layer confinement without disrupting maintenance procedures. It involves incorporating specific secondary raw material elements along the track shoulder, combined with a horizontal geosynthetic reinforcing layer at the base of the ballast layer. These shoulder elements not only impact the track's geometry but also facilitate a reduction in required ballast volume. The efficacy of the ballast confinement mechanism has undergone small-scale testing to prove the concept of reinforcement. Numerical modeling has been developed, which plays a crucial role in supporting the optimal design of this solution.
Keywords: ballast, railway track, geosynthetics, confining pressure, small-scale test
Published in DiRROS: 30.01.2025; Views: 280; Downloads: 169
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Abstract: Energy-efficient homes are constructed with a continuous and uniform thermal envelope and are commonly built on top of a thermal insulation (TI) layer that encloses the entire building. Lightweight aggregates such as foamed glass aggregate, expanded clay aggregate, and extruded polystyrene (XPS) insulation boards are commonly used as materials for the TI layer to prevent thermal bridging at the ground floor slab. However, the reinforced concrete slab foundation above the TI layer is susceptible to horizontal sliding during seismic loading. To improve the seismic behavior of buildings founded on TI layers, this study discussed the shear stiffness and damping characteristics of lightweight aggregates and three types of XPS boards through laboratory tests available in the literature. A 2-dimensional numerical analysis is performed, and the corresponding validation results of the simulations are presented. The effect of TI layers on the seismic performance of buildings constructed with TI layers made from these materials is assessed. A comparative analysis of various interface conditions of the TI materials under seismic loading is also conducted. Overall, this research aims to enhance the resilience and sustainability of energy-efficient homes by investigating the impact of TI layers on their seismic performance. The findings provide valuable insights for designing more robust structures that can withstand seismic events.
Keywords: energy-efficient buildings, thermal insulation, extruded polystyrene (XPS), finite element analysis, foamed glass aggregate, seismic response
Published in DiRROS: 21.01.2025; Views: 288; Downloads: 165
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Abstract: Increasing use of the ground as a thermal reservoir is expected in the near future. Shallow geothermal energy (SGE) systems have proved to be sustainable alternative solutions for buildings and infrastructure conditioning in many areas across the globe in the past decades. Recently novel solutions, including energy geostructures, where SGE systems are coupled with foundation heat exchangers, have also been developed. The performance of these systems is dependent on a series of factors, among which the thermal properties of the soil play a major role. The purpose of this paper is to present, in an integrated manner, the main methods and procedures to assess ground thermal properties for SGE systems and to carry out a critical review of the methods. In particular, laboratory testing through either steady-state or transient methods are discussed and a new synthesis comparing results for different techniques is presented. In situ testing including all variations of the thermal response test is presented in detail, including a first comparison between new and traditional approaches. The issue of different scales between laboratory and in situ measurements is then analysed in detail. Finally, the thermo-hydro-mechanical behaviour of soil is introduced and discussed. These coupled processes are important for confirming the structural integrity of energy geostructures, but routine methods for parameter determination are still lacking.
Keywords: hallow geotehermal systems, soil thermal behaviour, laboratory testing, in situ testing, thermo-mechanical behaviour
Published in DiRROS: 14.08.2024; Views: 663; Downloads: 404
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