Daiva Žilionienė

Comparison study of spherical and multi-spherical particles under cyclic uniaxial compression

Abstract Numerical simulation of cyclic compression of granular material by performing oedometric test has been performed. Discrete Element Method (DEM) has been employed for simulation. A comparison study has aimed to examine the differences in macroscopic behaviour of material discretized by spherical (S) and non-spherical shape models of a particle. During the study, microscopic data of sand from Klaipėda were used for modelling the shape of particles. The nonspherical particles were described by multi-spherical (MS) models retaining distributions for size and aspect ratios. Two DE models of tested specimens were developed and the deformation behaviour under cyclic uniaxial compression was simulated numerically by applying the commercial EDEM code. The variation of the oedometric elasticity modulus was investigated and influence of particle shape on void ratio changes was demonstrated. It was clearly shown that application of S particles is much more sensitive to rearrangement of particles during densi...

Correspondence of horizontal and vertical alignment with safe driving conditions on low-volume roads

Since 1998, when the Gravel Roads Paving Program was started on the regional roads of the Republic of Lithuania, the length of gravel roads has shortened by 13.4% after reconstruction. It was discovered, however, that after reconstruction, 4.7% of gravel road sections became potentially dangerous. A disadvantage that was noted during implementation of the Gravel Roads Paving Program was a slightly changed or entirely unchanged horizontal alignment of the roads. In addition, after a gravel road is paved, the speed limit increases from 70 km/h to 90 km/h, as is allowed by traffic regulations, although the design speed of regional roads is 70 km/h and the road alignment was planned for that design speed. The horizontal alignment of 30 regional roads was investigated to assess the compatibility of horizontal alignment elements and their correspondence with traffic safety and to study the sight distance in vertical alignments. It was determined that compatibility of the horizontal alignment elements of regional roads was sufficient, but the estimated flow speed on these elements was 10 to 20 km/h higher than the design speed. Analysis of the sight distance, the stopping sight distance, and the passing sight distance in the vertical alignment of roads showed that in 90% of the cases, the sight distance was shorter than the stopping sight distance on a tangent.

DESIGN SOLUTIONS FOR LITHUANIAN GRAVEL ROAD PAVEMENTS

Abstract This article deals with the design problems of gravel road pavements. Mathematical models related to geological and hydrological conditions of a location, thickness of gravel pavement and characteristics of the gravel contained in this pavement are proposed to be used for pavements. For the selection of gravel pavements for reconstruction we recommend the models developed by the method of experimental planning to calculate the equivalent deformation modulus of the gravel pavements change depending on the deformation modulus of the subgrade, thickness of the gravel pavement and the materials used for its layers. Practical applications of these models will eliminate the mistakes that are still found in road pavement design.

Using artificial neural network and multivariate analysis techniques to evaluate road operating conditions

Regional paved roads are low volume roads with a prevalence of heavy traffic. In the world, these roads concern about 80% of the total road network; however, the traffic that affects these roads is about 20%. Since regional roads are characterized by weak demand, budget for their management/maintenance is very low. This produces considerable difficulties in the choice of strategies for maintenance planning and scheduling. For this reason, the recurring topics of research in this field deal with typical roads issues and aim to develop low cost tools and methods. The study proposes a decision support system to evaluate regional paved roads operating condition in relation to the hydrogeological situation. In particular, the system allows to evaluate in a quick and easy manner, the operating conditions of the road, through low-cost tools (i.e. using low economic resources). This is very useful in the case of LVRs because administrations for these roads have a limited budget. The procedure is developed on a regional paved roads network based on more than 80 roads located in Southern Italy. Data is collected by direct surveys in the field and is integrated with cartography and information available in road agency records. From data analysis, obtained using two different techniques, an easy and quick use procedure is made. In particular, Model 1 is built through multivariate analysis and Model 2 using the artificial neural network (ANN) technique. The results show the validity of the two models in Regional paved roads operating conditions estimation in relation to hydrogeological situations of sites. Both models show good reliability. In particular, the first model (Model 1) is characterized by a high level of significance (p < 0.01) and by a coefficient of determination equal to 0.82. Comparative tests between the second model (Model 2) on which standard tests cannot be performed for obvious reasons, and the first model (Model 1). The results show that the ANN model (model 2), characterized by lower residual, simulates more accurately than the second (Model 1).