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Povzetek: The Mavčiče concrete gravity dam, part of the corresponding hydro-power plant, was built on the Sava River, in Slovenia, in 1986. It has a maximum structural height of 38.5 m, and the dam crest has a length of 149 m. The dam structure consists of an erection bay, a machine hall, and two spillways, followed by an embankment dam. Most of the dam is founded on permeable Quaternary conglomerate bedrock, so that a cut-off grout curtain had to be constructed to a depth of up to 60 m below the ground surface, where a layer of impermeable Oligocene marine clay occurs. However, the erection bay, which is located on the right bank of the dam, is founded on a layer of gravel backfill, up to about 25 m thick, which lies on top of the conglomerate bedrock. Long-term manual technical monitoring of the behaviour of the dam began in 1986, and an automated monitoring system was established between 2003 and 2005. In general, the results of measurements and visual inspections did not show any abnormalities. However, this was not the case for the erection bay located on the top of the backfilled right bank of the dam, where the results of measurements of vertical displacements showed increasing settlements. By 1999, i.e. over a period of 12 years, these settlements had increased to 22 mm. The results of investigations, by drilling three research boreholes in 1993, and another six such boreholes in 1996, indicated that the settlements were the consequence of the secondary consolidation of the backfill, and probable also due to scouring of fine material from the backfill. Due to the resulting differential settlements, the crane rail which connects the erection bay to the machine hall, as well as the crane rail which is located along the crest of the dam, became nonfunctional, and needed height corrections. For this reason rehabilitation works of the backfill and of the substratum of the right bank of the dam were performed between September 1999 and August 2000, using 50 m long grouted boreholes. This grouting was performed using a combination of water reactive polyurethane and a cement-bentonite mixture. Measurements performed since than have shown that the settlement rate has slowed down slightly (by 2017, i.e. over the last 17 years, the settlements had increased by up to 8 mm), but from the point of view of the operation of the two crane rails the settlement process needed to be stopped. Additional investigations, involving the drilling of two research boreholes, as well as appropriate laboratory and field measurements, were performed between November 2015 and March 2016. According to the results of these most recent investigations, the newer settlements were the consequence of additional scouring of fine material from the backfill. In order to achieve a final solution to the problem of the subsidence of the erection bay, additional rehabilitation works of the backfill and substratum of the right bank of the dam, by grouting the permeable zones, would be needed in order to stop both the scouring of fine material from the backfill, as well as any internal erosion of the cavernous conglomerate at the base of the backfill. The latter concerns the long-term stability of the right bank of the dam with potentially serious results.
Ključne besede: concrete dams, gravity dams, Mavčiče Dam, Sava River, technical monitoring, geotechnical investigation, rehabilitation
Objavljeno v DiRROS: 05.04.2024; Ogledov: 65; Prenosov: 36
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Povzetek: The article proposes a procedure for calibration of strain gauge bridge standards with improved relative calibration uncertainty. In contrast to a typical calibration with voltage ratio standards or comparison calibration with other bridge standards, the proposed procedure uses a calibrated reference bridge amplifier, additionally evaluated using combinatorial calibration technique to improve its calibration uncertainty. The resulting uncertainty of ratio steps referenced to zero ratio step is lower than the traditional uncertainty achieved through direct independent traceability to mVV−1 ratio values. The proposed procedure enables direct application of the calibrated bridge standard values with low relative uncertainty for calibration of bridge amplifiers, without the need for additional combinatorial evaluation of each individual bridge amplifier.
Ključne besede: voltage ratio, linearity check, bridge standard, calibration
Objavljeno v DiRROS: 05.04.2024; Ogledov: 60; Prenosov: 49
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Povzetek: A model organic pigment (diketopyrrolopyrrole) is encapsulated by a silica coating in order to improve its photochemical stability. Unlike in previous works where single-layer silica coatings were used for similar purposes, we here propose creation of a multi-layer silica shell synthesized via in-situ sol-gel method, which should significantly improve the homogeneity and thus the protection ability of the coating. This is done by repeating the basic two-step process (pigment surface modification and silica encapsulation) several times, creating the final protective shell in a layer-by-layer fashion. The compositional and structural properties of the prepared coatings is studied using Fourier-transform infrared spectroscopy, differential thermal and thermogravimetric analysis, nitrogen adsorption measurements and transmission electron microscopy. Photochemical stability of non-encapsulated and encapsulated pigment particles is evaluated via the so-called fast-irradiation method. Various correlations between the essential coating properties, such as thickness, porosity, SiO2 content, and the corresponding photochemical stability of the samples are established and discussed in detail. As a whole, our results confirm the basic hypothesis, that multiple-layered silica shells show improved pigment protection ability in comparison to the single-layer coatings.
Ključne besede: organic pigments, silica coating, encapsulation, morphology, photocemical stability
Objavljeno v DiRROS: 27.03.2024; Ogledov: 121; Prenosov: 54
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Povzetek: Traffic load models used for the design of new bridges are based on conservative assumptions and have not been proven efficient for assessing safety of existing bridges. In the case of existing bridges, it is reasonable to use load models that are based on bridge weigh-in-motion data which, in addition to axle loads and spacing of bridge-crossing vehicles, provide information on bridge behaviour under traffic load. This paper provides an overview of traffic load models, as well as guidelines on the use of weigh-in-motion data when assessing condition of existing road bridges.
Ključne besede: prometna obtežba, tehtanje vozil med vožnjo, mostni WIM, ocenjevanje stanja, obstoječi mostovi, traffic load, weigh-in-motion, bridge WIM, condition assessment, existing bridges
Objavljeno v DiRROS: 27.03.2024; Ogledov: 110; Prenosov: 81
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Povzetek: To foster sustainable development in construction sectors, environmental impacts need to be reduced dramatically. The Life Cycle Assessment (LCA) technique is the most firmly established methodology used to quantify these environmental impacts and, therefore, has been applied with increasing frequency to assess the environmental performance of buildings. To effectively improve a building's environmental performance, an integration of LCA in the design process is required. This can be achieved by coupling LCA with digital design tools, e.g., Building Information Modelling (BIM). To identify the pro and cons of streamlining the integration of LCA and BIM, a comprehensive Systematic Literature Review (SLR) was performed. We identified more than 50 relevant BIM-LCA case studies and analysed the applied BIM-LCA workflows in detail. In most of the studies reviewed, the LCA has been applied in an early design stage. The authors primarily used LCA tools and manual or semi-automatic methods to exchange data between BIM models. In most cases, contemporary BIM-LCA workflows utilized conventional spreadsheets (e.g., Excel worksheets). However, the results of the analysis show that an automated link between LCA and BIM can be achieved if certain challenges are overcome. By automating exchange of information between BIM and LCA tools and improving the reliability of this process, the LCA application can be streamlined in design practice and, hence, the necessary improvements of the environmental performance of buildings can be supported.
Ključne besede: building information modelling, life cycle assessment, systematic Literature Review
Objavljeno v DiRROS: 18.03.2024; Ogledov: 92; Prenosov: 73
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