Granular material being used at road and railway embankments are subjected to specific stress conditions with confining stresses much lower than stresses applied in vertical direction. To im-prove strength characteristics geosynthetic reinforcement is often applied. A series of large-scale triaxial tests on dense gravel, prismatic specimens with dimensions of 50 cm in height and 23 cm times 23 cm in cross-section was conducted to investigate the contribution of confining effect of reinforcement to the strength and particularly the impact upon the deformation properties of reinforced gravel from very small to large strain range. Two kinds of geosynthetics have been used as a reinforcement: geogrid and geo-composite. Deformations were measured locally using vertical and horizontal local deformation transduc-ers. Unsaturated specimen were tested in drained triaxial compression, using monotonic loading. Confin-ing pressure of 25 kPa has been applied by vacuum. Besides strength characteristics, particularly the stiff-ness properties were subject of research interests. Stiffness at different stress states was evaluated by using very small strain load cycles.
COBISS.SI-ID: 2426215
In the paper, bending problem of a transversely cracked beam resting on elastic foundations is addressed by means of the finite element method. The paper covers the derivation of a new finite element, where the soil is modelled by classical Winkler soil model, and the cracked beam is represented by the simplified computational. The presented approach is ideal for the effortless modelling of cracked beams in conditions where neither information about the crack's growth nor the stresses at the crack's tip is required.
COBISS.SI-ID: 21969430
On the railway infrastructure in Slovenia, especially in the karst terrain, we face the phenomenon of so called floating sleepers. In order to improve the situation, we are conducting a research, within the CRP project, that enables us to better understand related phenomena. This paper presents the results of research already carried out. Through field measurements and mathematical simulations, we have found that a dynamic mathematical model is required for an effective mathematical description of a phenomenon. Dynamic effects have a markedly unfavorable effect on the degradation of the track ballast, which sooner or later leads to a floating sleeper. Improving the behavior of the concrete sleeper is possible by using new modern materials (binders and fillers) with adequate quantification of the phenomenon. To this end, we have also developed an empirical model of ballast degradation, based on visual expert judgment, which can be linked to the results of the micro-Deval test with the proposed empirical expression.
COBISS.SI-ID: 22789142
Several various examples of anomalies on ballast railway tracks resulting in accelerated degradation of railway sleepers and ballast layer are described in the paper. Initially, some locations on the Slovenian railway network (SRN) where the degradation occurs were identified. Afterwards, various experimental field investigations (georadar, geometry measurements, measurements of displacements and accelerations on the track, visual assessment of ballast degradation) have been used to measure the characteristics of the railway track and the parameters of its behavior. Based on the experimentally obtained data a simplified numerical model which interconnects the individual measured and estimated parameters of the railway track and also the processes of further degradation has been developed using the artificial neural network. Influential factors for the model’s individual parameters influencing the degradation were identified. The proposed model is able to assist in the evaluation of critical areas on the railway infrastructure and further enables a better understanding of the process and prediction/estimation of degradation of railway sleepers and ballast.
COBISS.SI-ID: 26786051