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Povzetek: The present study evaluates the shear strength characteristics, deformation properties, and degradation behavior of limestone-based reused ballast (RB) material by mixing crumbs of waste tire-derived aggregates (TDA), focusing on its suitability for railway infrastructure. Conventional large-scale direct shear tests and novel large-scale cyclic simple shear tests were performed to investigate the effects of tire-derived aggregate (TDA) content, with particle sizes varying between 22.4 mm and 50 mm. The results indicate that adding 5 % by the mass of TDA slightly reduced the friction angle from 46.6° to 44.5°, which is not a significant change compared to RB. However, increasing the TDA content to 10 % led to a notable decrease in the friction angle to 41°, highlighting the significant impact of higher TDA content on the shear strength behavior. Further, incorporating 5 % TDA improved the shear modulus and damping ratio relative to RB, which is attributed mainly to the similar larger particle sizes (22.4–50 mm) of TDA. Conversely, at 10 % TDA content, reductions in both shear modulus and damping ratio were observed. The ballast breakage index (BBI), evaluated through cyclic simple shear tests, showed a significant decrease from 15 % for RB to 9.5 % for the ballast sample containing 5 % TDA. Additionally, increased TDA content enhanced material durability, reducing Los Angeles abrasion (LAA) losses from an initial 33.5 to under 30 % at 5 % TDA. These findings demonstrate that incorporating 5 % by mass of TDA into RB material is optimal for enhancing deformation characteristics and reducing ballast degradation while maintaining adequate shear strength. This sustainable approach facilitates the recycling of waste materials, promotes a circular economy, and helps maintain safe and stable railway track conditions.
Ključne besede: reused ballast, rubber, cyclic simple shear tests, BBI, degradation
Objavljeno v DiRROS: 04.06.2025; Ogledov: 515; Prenosov: 305
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Povzetek: Marginal and recycled fills are increasingly being utilized in geosynthetic reinforced soil (GRS) structures like retaining walls and bridge abutments due to their cost- effectiveness and sustainability. Marginal fills, including locally available soils with less desirable engineering properties, can be used when properly engineered with geosynthetics to enhance strength and stability. Recycled fills, such as recycled concrete, asphalt, various ashes have been proved already as an eco-friendly alternative to conventional aggregates. However, these practices involve thorough characterization and testing of marginal and recycled fills to ensure their suitability for specific applications. Advanced geotechnical analyses, including laboratory tests and numerical modeling, help determine the optimal blend of materials and reinforcement for achieving desired performance criteria. Experiences with the use of residues from deinking paper industry and river debris as backfill material are presented. Time effect on the compaction and deformation characteristics as well as the impact of high basicity of backfill material have been considered.
Ključne besede: soil reinforcement, reinforced fill structures, GRS abutments, residues from paper industry, river debris
Objavljeno v DiRROS: 21.01.2025; Ogledov: 916; Prenosov: 445
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Povzetek: Over the past few decades, flexible pavements across the globe have seen a significant reduction in their service life due to climate changes. The flexible pavements with unsaturated sub- grades undergo volumetric changes during the drying and wetting phases, affecting their long-term deformation behavior. These phases cause significant variations in matric suction and groundwater table depth. This study employs a coupled pore pressure-deformation analysis on flexible pavements to investigate the impact of groundwater table depth and suction variations in unsaturated subgrades. Finite-element simulations using the Abaqus and developed USDFLD code were validated against literature data. Sensitivity analysis was conducted by varying the suctions in subgrades during drying and subsequent wetting to evaluate the groundwater table depth. Furthermore, under heavy cyclic wheel loading, pavement-deformation analysis was conducted to investigate the influence of subgrade suction. The findings demonstrate that, after an initial drying phase at 5000 kPa suction, wetting over 180 days caused the groundwater level to rise from 5.45 m beneath the subgrade to the surface. This led to a 98% increase in surface-vertical deformations due to cyclic wheel loading after 180 days of wetting compared to the deformations during the drying phase at the same suction level. This assessment of groundwater-depth variations and long-term deformation behavior with the impact of suction improves the design and sustainability of flexible pavements.
Ključne besede: flexible pavement, unsaturated soil, suction, finite-element method
Objavljeno v DiRROS: 21.01.2025; Ogledov: 654; Prenosov: 455
Celotno besedilo (8,71 MB)
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