1. Characterisation of ground thermal and thermo-mechanical behaviour for shallow geothermal energy applicationsAna Vieira, Maria Alberdi-Pegola, Paul Christodoulides, Saqib Javed, Fleur Loveridge, Frederic Nguyen, Francesco Cecinato, João Maranha, Georgios Florides, Iulia Prodan, Gust Van Lysebetten, Elsa Ramalhosa, Diana Salciarini, Aleksandar Georgiev, Sandrine Rosin-Paumier, Rumen Popov, Stanislav Lenart, Søren Erbs Poulsen, Georgia Radioti, 2017, izvirni znanstveni članek Povzetek: 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. Ključne besede: hallow geotehermal systems, soil thermal behaviour, laboratory testing, in situ testing, thermo-mechanical behaviour Objavljeno v DiRROS: 14.08.2024; Ogledov: 36; Prenosov: 74
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2. Changes of permeability of nonwoven geotextiles due to clogging and cyclic water flow in laboratory conditionsAnna Miszkowska, Stanislav Lenart, Eugeniusz Koda, 2017, izvirni znanstveni članek Povzetek: The use of geotextile filters has been a common application in geo-environmental and geotechnical engineering for decades. The purpose of the present paper is to assess the influence of artificial physical clogging and cyclic water flow on the water permeability characteristics of nonwoven geotextiles used commonly in filter and drainage systems. Despite many studies examining the behavior of soil-geosynthetics, the mechanism of physical clogging is not fully understood yet and remains incompletely defined. Artificial clogging and cyclic water flow tests have been conducted according to a procedure created by the authors. Three nonwoven geotextiles and silty sand were employed in the test series. Hydraulic properties of the tested geosynthetics were determined according to the ISO standard. Filter design criteria are also discussed. The paper also presents the changes of water permeability characteristics due to clogging and cyclic water flow. The results show significant decrease of water permeability coefficients of the tested nonwoven geotextiles after artificial clogging and under cyclic water flow. Furthermore, the clogging mechanism was observed and confirmed by three-dimensional computed tomography. Ključne besede: nonwoven geotextile, clogging, cyclic flow, permeability, soil Objavljeno v DiRROS: 14.08.2024; Ogledov: 41; Prenosov: 59
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3. Reviewing the modeling aspects and practices of shallow geothermal energy systemsPaul Christodoulides, Ana Vieira, Stanislav Lenart, João Maranha, Gregor Vidmar, Rumen Popov, Aleksandar Georgiev, Lazaros Aresti, Georgios Florides, 2020, pregledni znanstveni članek Povzetek: Shallow geothermal energy systems (SGES) may take different forms and have recently taken considerable attention due to energy geo-structures (EGS) resulting from the integration of heat exchange elements in geotechnical structures. Still, there is a lack of systematic design guidelines of SGES. Hence, in order to contribute towards that direction, the current study aims at reviewing the available SGES modeling options along with their various aspects and practices. This is done by first presenting the main analytical and numerical models and methods related to the thermal behavior of SGES. Then, the most important supplementary factors affecting such modeling are discussed. These include: (i) the boundary conditions, in the form of temperature variation or heat flow, that majorly affect the predicted thermal behavior of SGES; (ii) the spatial dimensions that may be crucial when relaxing the infinite length assumption for short heat exchangers such as energy piles (EP); (iii) the determination of SGES parameters that may need employing specific techniques to overcome practical difficulties; (iv) a short-term vs. long-term analysis depending on the thermal storage characteristics of GHE of different sizes; (v) the influence of groundwater that can have a moderating effect on fluid temperatures in both heating and cooling modes. Subsequently, thermo-mechanical interactions modeling issues are addressed that may be crucial in EGS that exhibit a dual functioning of heat exchangers and structural elements. Finally, a quite lengthy overview of the main software tools related to thermal and thermo-hydro-mechanical analysis of SGES that may be useful for practical applications is given. A unified software package incorporating all related features of all SGES may be a future aim. Ključne besede: shalow geothermal energy systems, energy geo-structures, thermal analysis, thermo-hydro-mechanical, modelling, software tools Objavljeno v DiRROS: 05.03.2024; Ogledov: 389; Prenosov: 167
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4. Real-time monitoring and analyses of sensory data integrated into the bim platformStanislav Lenart, Veljko Janjić, Uros Jovanovic, Rok Vezočnik, 2021, objavljeni znanstveni prispevek na konferenci Povzetek: Bridges and tunnels, crucial elements of the railway infrastructure, are exposed to various types of deterioration processes. Their condition is a subject of monitoring, as it is important to collect as much as possible information in every life cycle phase to reliably predict their future performance. An enormous quantity of monitoring data is generated during the whole life cycle of these assets. EU funded Shift2Rail research project Assets4Rail which is focusing on measuring, monitoring, and data handling for railway assets, as data management is as important as their generation. This paper presents the major outcomes of the Assets4Rail project and its application to infrastructure projects. Ključne besede: monitoring, information management, BIM, information management, bridge, tunnel, Assets4Rail Objavljeno v DiRROS: 23.02.2024; Ogledov: 410; Prenosov: 310
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5. Corrosion monitoring of steel structure coating degradationBojan Zajec, Mirjam Bajt Leban, Tadeja Kosec, Viljem Kuhar, Andraž Legat, Stanislav Lenart, Karmen Fifer Bizjak, Gavin Kenneth, 2018, izvirni znanstveni članek Povzetek: An important aspect regarding the sustainability of steel structures is to ensure the structure is protected from corrosion. A number of surface coatings are availablethat play an important role in protecting these structures. An important part of the management of these structures is reliable and regular inspection along with methods forearly detection of corrosion processes. In this paper, a development and application of sensors for monitoring the steel coating degradation and corrosion damage to steelsubstrate are presented. An encapsulated corrosion kit with integrated EIS sensors and ER probes was developed. To test its efficiency, steel probes were coated withselected coatings in the laboratory and their performance was assessed under various aggressive atmospheres, including; salt, industrial and humid atmosphere. Ključne besede: coatings, corrosion, electrochemical impedance spectroscopy, electrical resistance probes, railways, steel structures Objavljeno v DiRROS: 13.12.2023; Ogledov: 353; Prenosov: 185
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6. Parametarska studija kolničke konstrukcije ojačane geoćelijamaSamo Peter Medved, Bojan Žlender, Stanislav Lenart, 2018, izvirni znanstveni članek Povzetek: U radu je prikazano parametarsko ispitivanje kolničke konstrukcije ojačane geoćelijama. Analiza temeljena na metodi konačnih elemenata uključuje model neojačane kolničke konstrukcije te model kolničke konstrukcije ojačane geoćelijama, pri čemu se analiziraju razni položaji, debljine i čvrstoća geoćelija. U okviru modela određen je i očekivani vijek trajanja kolničke konstrukcije. Rezultati parametarskog proučavanja u skladu su s rezultatima analitičkih rješenja, laboratorijskih i terenskih ispitivanja. Dobiveni rezultati upućuju na bitno poboljšanje nosivosti, smanjenje debljine asfaltnih slojeva i povećanje trajnosti kolničke konstrukcije kada je ona ojačana geoćelijama. Objavljeno v DiRROS: 12.12.2023; Ogledov: 369; Prenosov: 251
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7. Atmosphere - vegetation - soil interactions in a climate change context; impact of changing conditions on engineered transport infrastructure slopes in EuropeAnh Minh Tang, P. N. Hughes, T. A. Dijkstra, Amin Askarinejad, Mihael Brenčič, Yu Jun Cui, J. J. Diez, T. Firgi, Beata Gajewska, F. Gentile, G. Grossi, C. Jommi, F. Kehagia, E. Koda, H. W. ter Maat, Stanislav Lenart, S. Lourenco, M. Oliveira, P. Osinski, Sarah Springman, Ross Stirling, D. G. Toll, Ursula J. Van Beek, 2018, izvirni znanstveni članek Povzetek: In assessing the impact of climate change on infrastructure, it is essential to consider the interactions between the atmosphere, vegetation and the near-surface soil. This paper presents an overview of these processes, focusing on recent advances from the literature and those made by members of COST Action TU1202 - Impacts of climate change on engineered slopes for infrastructure. Climate- and vegetation-driven processes (suction generation, erosion, desiccation cracking, freeze-thaw effects) are expected to change in incidence and severity, which will affect the stability of new and existing infrastructure slopes. This paper identifies the climate- and vegetation-driven processes that are of greatest concern, the suite of known unknowns that require further research, and lists key aspect that should be considered for the design of engineered transport infrastructure slopes in the context of climate change. Objavljeno v DiRROS: 12.12.2023; Ogledov: 301; Prenosov: 176
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8. Influence of structural parameters of nonwoven geotextiles on separation and filtration in road constructionŠpela Bezgovšek, Dunja Šajn Gorjanc, Boštjan Pulko, Stanislav Lenart, 2020, izvirni znanstveni članek Povzetek: Nonwoven geotextiles are often used in road construction as a separation layer. They consist of the web of fibers with different orientations. The orientation of fibers has an important influence on physical and mechanical properties of nonwoven geotextiles. The production of nonwoven geotextiles is cheaper in comparison to woven or knitted fabrics which can also be used as separation geotextiles. The purpose of this research was to study the influence of structural properties of nonwoven geotextiles, namely the diameter of fibers and mass and thickness of nonwoven geotextiles, on their mechanical and hydraulic properties. Six types of nonwoven geotextiles were used in the research. They were produced by the drylaid process (carded) using mechanical bonding technique and also with the combination of mechanical and thermal bonding technique. The research confirmed that the bonding technique and structural properties significantly influence the separation and filtration properties of nonwoven geotextiles, such as opening size and water permeability. It was also found that there are no significant differences in mechanical properties, such as viscoelastic properties and compression creep, between the samples in the dry and wet conditions. Ključne besede: nonwoven geotextiles, bonding techniques, opening size, water permeability Objavljeno v DiRROS: 16.11.2023; Ogledov: 583; Prenosov: 243
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9. Dynamic properties of lightweight foamed glass and their effect on railway vibrationStanislav Lenart, Amir M. Kaynia, 2019, izvirni znanstveni članek Povzetek: Deformation properties of lightweight coarse grained material from recycled foamed glass have been determined from large-scale triaxial tests on prismatic specimens with dimensions 40 cm x 40 cm x 80 cm. Deformations were measured locally using vertical and horizontal local deformation transducers. Monotonic and cyclic loading at small to medium strain range were conducted. Three load sequences representing the expected conditions of use of lightweight material as vibration-reducing material in railway geotechnics have been used. Results indicate strong effect of brittle cellular structure of tested material as well as confining pressure dependency of elastic threshold shear strain and damping ratio. The results were used to assess the applicability of empirical formulas for shear modulus of granular materials to lightweight foamed glass. The parameters determined from the laboratory tests were further used in numerical analysis of railway dynamic response. The results of the numerical simulations show that replacement of fill in track embankment by lightweight material could improve the dynamic response of the track in reducing the vibration. Ključne besede: lightweight material, recycled foamed glass, railway vibration, shear modulus, damping Objavljeno v DiRROS: 16.11.2023; Ogledov: 492; Prenosov: 350
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10. Digital twins and road construction using secondary raw materialsSebastjan Meža, Alenka Mauko Pranjić, Rok Vezočnik, Igor Osmokrović, Stanislav Lenart, 2021, izvirni znanstveni članek Povzetek: Secondary raw materials (SRMs) tend to be a valuable replacement for finite virgin materials especially since construction works (i.e., building and civil engineering work such as road construction) require vast quantities of raw materials. Using SRM originating from recycling a broad range of inorganic waste materials (e.g., mining waste, different industrial wastes, construction, and demolition waste) has been recognized as a promising, generally more cost-efficient, and environmentally friendly alternative to the exploitation of natural resources. Despite the benefits of using SRM, several challenges need to be addressed before using SRM even more. One of them is the long-term durability and little-known response of construction works built using such alternative materials. In this paper, we present the activities to establish a fully functioning digital twin (DT) of a road constructed using SRM. The first part of the paper is devoted to the theoretical justification of efforts and ways of establishing the monitoring systems, followed by a DT case study where an integrated data environment synthesizing a Building Information Model and monitored data is presented. Although the paper builds upon a small scale, the case study is methodologically designed to allow parallels to be drawn with much larger construction projects. Ključne besede: digital twins, road construction, circular economy Objavljeno v DiRROS: 19.07.2023; Ogledov: 557; Prenosov: 291
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