The dissertation was defended at the public meeting of the Dissertation Defence Council of the Scientific Field of Civil Engineering in the Aula Doctoralis Hall of Vilnius Gediminas Technical University at 9 a. m. on 7 February 2025.
The dissertation investigates road construction and subgrade soils reinforced with geogrids. The interaction between the soil and the geogrid is influenced by their physical and mechanical properties. The proposal is to evaluate the soil and geogrid together as a composite material. This approach simplifies the design of geogrid-reinforced structures using finite element or analytical methods. The primary purpose of this dissertation is to develop a model for evaluating the interaction between soil and geogrid, allowing this interaction to be assessed as an equivalent layer (without geogrid) with alternative layer parameters. The dissertation comprises an introduction, three chapters, general conclusions and references. The introduction presents the research problem, the importance of the dissertation and the study object. It describes the dissertation’s purpose and tasks, the research methodology, scientific novelty, the practical significance of the results, and defended statements. The introduction concludes by listing the author’s publications on the subject of the dissertation and presentations at conferences and defining the dissertation’s structure. The first chapter reviews the literature on road construction, methods for strengthening weak soils, using geogrids, laboratory methods for investigating soil reinforced with geogrids, factors influencing the results, and the possibilities of numerical modelling. The chapter closes with conclusions and reconsidered tasks. The second chapter presents the experimental research program on soil reinforced with geogrids and provides the laboratory results for unreinforced soils and soils reinforced with geogrids. The third chapter investigates road construction using numerical modelling. It determines the values of derived parameters used in the finite element method for modelling soil reinforced with geogrids. Analytical methods are used to determine the optimal position of the geogrid in the embankment and the thickness of the equivalent layer for which the evaluation model parameters are applied. A soil-geogrid interaction evaluation model is proposed. Nine articles were published on the subject of the dissertation: three articles in journals listed in the Web of Science database with a citation index, one article in Web of Science conference proceedings, one article in Scopus conference proceedings, three articles in peer-reviewed international conference materials, and one article in conference materials. Six presentations were given on the subject at conferences in Lithuania and abroad.
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