Assessment of road structure strengthening with geogrid

Aurimas Šiukščius

Doctoral dissertation

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In order to ensure sustainable and long-term functioning of the road pavement structure over the subgrade with organic soil layers, it is necessary to use additional materials to improve earth subgrade strength. Geosynthetic materials are used worldwide for soil reinforcement for more than 40 years, when in Lithuania for 20 years. To solve road subgrade strengthening problems over soft soils, geogrids in Lithuania are used over the last decade. The dissertation examines the influence of geogrid reinforced pavement and (or) subgrade on the road structure degradation.

The aim of the dissertation is to develop the geogrid usage demand assessment and selection scheme by determining the effect of pavement structure and (or) earth subgrade reinforcement with geogrids on the degradation of a road structure through the experimental investigations. The dissertation consists of an introduction, three chapters, general conclusions and recommendations, references and a list of scientific publications by the author on the topic of the thesis, summary in English and six annexes.

The introduction reveals the investigated problem, relevance of the thesis, describes the object of thesis, formulates the aim and tasks of the paper, research methodology, scientific novelty of the thesis, the practical value of the research findings, defended statements and the structure of the dissertation. Chapter 1 revises used scientific literature and provides an analysis of soil reinforcement principles and geogrid characteristics, analysis of geogrid properties and their variation influence on the permanence of the road structure, analysis of weak subgrade strengthening methods, geogrid selection principles, an analysis of the documents regulating the use of geogrids for earthworks in Lithuania and other countries. At the end of the chapter, conclusions are drawn and the tasks of the dissertation are reconsidered. Chapter 2 provides the experimental research of road pavement structures. It describes the experimental research plan and methodology, identifies the tested pavement structure types, geological structure, the results of road pavement loading, roughness and road structure layer elasticity modulus. Chapter 3 provides the statistical analysis of the results of the experimental study. Indicates the rational geogrid reinforced subgrade option using the multi-criteria SAW method, evaluates the purposefulness and the most important properties of geogrid. Provides the geogrid usage demand assessment and selection scheme.

On the topic of the thesis, 6 scientific articles were published: three – in scientific journals included in the Clarivate Analytics Web of Science data base, three – in the international conferences Clarivate Analytics Proceedings data base. 3 presentations on the subject have been given in conferences at international level.

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160 p.
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