Major infrastructure projects require significant amount of natural materials, often followed by the soft soil stabilization using hydraulic binders. This paper presents the results of a laboratory study of alternative waste materials (fly ash and slag) that can be used for earthworks. Results of high plasticity clay stabilization using fly ash from Serbian power plants are presented in the first part. In the second part of the paper, engineering properties of ash and ash-slag mixtures are discussed with the emphasis on the application in road subgrade and embankment construction. Physical and mechanical properties were determined via following laboratory tests: Specific gravity, grain size distribution, the moisture–density relationship (Proctor compaction test), unconfined compressive strength (UCS), oedometer and swell tests, direct shear and the California bearing ratio (CBR). The results indicate the positive effects of the clay stabilization using fly ash, in terms of increasing strength and stiffness and reducing expansivity. Fly ashes and ash-slag mixtures have also comparable mechanical properties with sands, which in combination with multiple other benefits (lower energy consumption and CO₂ emission, saving of natural materials and smaller waste landfill areas), make them suitable fill materials for embankments, especially considering the necessity for sustainable development.

Monitoring data provide valuable information on embankment dam behavior but are typically not integrated into a classical probabilistic safety assessment. This paper introduces a Bayesian-inspired methodology to directly integrate actual dam monitoring records into a Monte Carlo probabilistic safety assessment using a finite element framework, without recalibrating the original input parameters ‘distributions. After the baseline (unweighted) set of simulations is generated, the method assigns a weight coefficient to each simulation outcome based on the likelihood of matching monitoring data, effectively updating the baseline probabilistic analysis results. Therefore, such “weighted” analysis produces an updated probability distribution of the dam’s factor of safety (FS) that reflects both prior uncertainty of model parameters and actual monitoring data. To illustrate the approach, a case study of a rockfill triaxial test specimen is analyzed: a baseline probabilistic analysis yields a mean FS ~1.7, whereas the weighted analysis incorporating monitoring data reduces the mean FS to ~1.5 and narrows the variability. The weighted analysis suggests less favorable conditions than the baseline projections. This methodology offers a transparent, computationally tractable route for embedding monitoring evidence into reliability calculations, producing more reflective safety estimates of actual dam behavior.

The soil-vegetation-atmosphere interaction is a dynamic process, which governs the continuous change of soil hydrological conditions. These changes directly affect the seasonal and long-term performance of infrastructure cut and embankment slopes. It has been established that the combined effect of vegetation and precipitation induces seasonal cycles of shrinkage and swelling, which give rise to serviceability issues. Previous numerical studies regarding the effect of the soil-vegetation-atmosphere system interaction on the behaviour of infrastructure embankments, were unable to quantitatively reproduce the observed hydraulic behaviour. They were either based on pure hydraulic approach or in case of fully coupled analyses were employing saturated mechanical models. The framework presented in this paper is based on the fully coupled flow-deformation analysis, combined with unsaturated soil mechanics theory and sophisticated climatic boundary conditions, implemented within the ICFEP numerical code. The instrumented railway embankment located in the UK, suffering from poor track ride quality related to the presence of vegetation on the slopes, is used as a case study for this investigation. <!----> <!----> <!----> <!---->