Thesis supervisor: János Szendefy
Location of studies (in Hungarian): BME, Geotechnika és Mérnökgeológia Tanszék Abbreviation of location of studies: BMEGM
Description of the research topic:
At the alternative design approach of pavements, bearing capacity of the subgrade may be characterized by its resilient modulus and Poisson ratio. The resilient modulus is an elastic modulus, which can be calculated from the elastic strain originating from traffic-induced dynamic actions. The resilient modulus may be determined in the laboratory using dynamic triaxial device. Such equipment only became available in the last few years in the country, therefore such tests haven’t been performed in Hungary before. A dynamic triaxial device is available in the Geotechnical Laboratory of BUTE Department of Engineering Geology and Geotechnics, with which laboratory testing of resilient modulus becomes possible. The first series of these tests have already been conducted and their results have already been published in Hungarian journals. With the appearance of these modern devices, testing of strain characteristics of soils due to dynamic loading has become actively researched and published in international journals.
According to international publications, resilient modulus of the soil is extremely sensitive to the change of moisture content. This sensitivity is particularly important because of its effect on bearing capacity of subgrades below pavements. The effect of suction on shear strength in unsaturated soils was only recognized recently in soil mechanics; studies addressing this issue were only started in the last few years in Hungary.
In this research, our goal is to use these novel test and design methods and develop correlation between suction and the resilient modulus.
The following steps has to be carried out during the research work:
• Overview of previous international research results and methods.
• Laboratory tests to measure the suction curves of clay, loess and sand soils and binder-stabilized soils.
• Laboratory tests to measure the resilient modulus with a dynamic triaxial apparatus at the characteristic water content of the suction curves using different types of binders and dosages.
• Laboratory tests to measure CBR bearing capacity at the characteristic water content of the suction curves using different types of binders and dosages.
• Determine correlation between the suction and the bearing capacity characterized with resilient modulus and CBR In case of soils and stabilized soils.