Prof. Cinicioglu passed by EPFL on November 11th and gave a lecture entitled “Deformation and stress based approaches to the problems of embankment design on soft soils”.
Design and construction of embankments on soft clays are associated with a number of problems which show themselves as excessive deformations or catastrophic failures. Traditionally, design and construction are considered as separate processes and there is a strong desire for certainty of cost and outcome at the design stage before construction starts. However, it is not usually possible to meet these requirements due to unforeseen conditions during field investigation process and design stage. An improved version of observational method can be made use of as the only available technique to overcome the difficulties related to the prediction of soil behaviour. The method uses field measurements as the direct inputs to the framework of the constitutive behavior and analyses the behavior synchronously as measurements are recorded. As a result, it is possible to work with current parameters and time lags between capture of measurements, their interpretation leading to parameter revision and corresponding design adjustments are prevented. The framework provided for the application of the method is basically the idealized stress space of the Critical State Theory, but the constitutive anisotropic elastoplastic soil model is mounted on it to analyze the behavior and to provide direct links between measurements and design parameters. Strain rate dependency of the soft soils is also incorporated to the interpretation of the behavior. To consider the variation in the behavior of foundation soils, a zonation system is applied and stress axis rotation is considered. The application of the method is a continuous process and the behaviour can be followed as a real time process throughout the construction and consolidation stages and afterwards. Considerable savings in terms of time and economy can be gained by the application of this method and moreover such an application improves the understanding related to the real behavior of soils.
From this viewpoint, an attempt was also made to solve the load sharing mechanism between a soil and a pile subjected to soil movements from an approach embankment, by using deformation and stress values obtained from monitoring and applying a continuous process to follow up the variation in the behavior in a timely manner. The method developed for this purpose is capable to produce the soil response curves which reflect real field behavior through free-field measurements. Load sharing mechanism can be solved realistically with the proposed method for any possible case either the piles are constructed before, during and after embankment construction or for any non-failing or failing state in the responding soil zones.
These two methods are real-time methods that discloses the on time behavior during application and enables the implementation of a flexible design process. However, a specific design method that can easily be used in connection with the proposed real time methods could have been useful and in this connection a new embankment design method combining limit state approach with stress path application was also developed. This method is applicable for embankments either constructed in a single stage or multiple stages. Stage construction technique necessitates to add the tool of stress path application to the method, to consider both the undrained and drained behavior. This is a property that is not found in limit state approaches and gives to the method a capacity to follow and interpret changing stress-strain states and their influence on the mobilized strength states.
S. Feyza Cinicioglu received her BSc in civil engineering from Bogazici University, Istanbul in 1974; M.Eng in civil engineering from Sheffield University, UK in 1976. After working as a professional civil engineer between the years of 1976-1983, she joined academia in 1983, received her Ph.D. in the field of geotechnical engineering in 1986 from Bogazici University, Istanbul, Turkey.
Since 1995, she has been working as a full professor of Civil Engineering at Istanbul University. She also served as Head of the Department of Civil Engineering (1998-2013), Dean of Graduate School of Science and Engineering (2004-2005), General Secretary (2005-2011) and meanwhile as the President of the Turkish National Society of Soil Mechanics and Geotechnical Engineering (2011- ).
Her major areas of research are design and construction of embankments on soft clays, macro and micro soil behavior, soil-structure interaction and seismic microzonation. She has directed several application projects such as; seismic risk assessment of Bakirkoy and Omerli Regions of Turkey (these projects have been implemented by the municipalities of these regions and they are currently effective), research projects on the subjects of development of new methodologies for embankment design and construction on soft clays, micro and macro mechanical behavior of soft soils, behavior of piled bridge abutments. Her refereed articles appeared in a variety of journals including ASCE journal of geotechnical and geoenvironmental engineering, Canadian geotechnical journal, engineering geology, ASCE international journal of geomechanics.