On March 11, 2008 Mr. Cheevin Limsiri successfully defended his PhD thesis and propositions on Very soft organic clay applied for road embankment: modelling and optimisation approach.
Very soft organic clay poses serious problems for embankment construction in deltaic areas. This clay has very poor engineering properties; therefore it cannot be used as embankment fill material without improvement.
Dewatering by evaporative drying, dewatering by horizontal sand drainage (clay-sand layers in a sandwich construction) and pre-loading (surcharging) are considered to be the simplest, most practical and most cost-effective methods for the improvement of the properties. During his PhD study Cheevin Limsiri has developed strategies for using such very soft organic clay as a fill material for road embankment construction.
Computer programs for simulation of evaporative drying, of consolidation, and for slope stability calculation were used to analyse clay behaviour. Field and laboratory testing programs for a trial embankment were set up in order to study the relations of parameters, to examine suitability and workability of the clay, and to verify the improvement methods.
An optimisation technique was applied as a rational method for using very soft organic clay for road embankments leading to an economic construction. Optimisation models were developed for this particular problem, consisting of an equipment selection model and a multi-objective optimisation model for clay-sand layered embankment constructions.
The equipment selection model provides an optimum selection of the size and number of the earthmoving equipment fleet, which yields minimum equipment costs. The obtained equipment costs were used as parameters in the development of cost models that are part of the multi-objective optimisation of clay-sand layered embankments.
A special computer program was developed to integrate the embankment design to the optimisation process. The calculation in the design part is performed using Artificial Neural Network (ANN) models. These models were developed from the results of the simulations in order to cope with complexity of the problem and to reduce computation time of the optimisation process.
A clay-sand layered trial embankment was constructed by the Port of Rotterdam Authority at the dredging sludge disposal site, The Slufter, to investigate the behaviour of such an embankment and to evaluate the potential of the reuse of very soft organic clay. Therefore unpolluted Slufter clay was used as a fill material.
Before the material was used in the construction evaporative drying in ripening fields and conditioning by mechanical equipment reduced the water content in the clay. The monitoring data were used to verify the evaporative drying simulation program and the ANN models.
The results from the optimisation analysis and the trial embankment investigation were used together to develop a rational method for using very soft organic clay in road embankment constructions.
Cheevin Limsiri was born in Bangkok, Thailand on October 20, 1960. He obtained his B.Eng. in Civil Engineering in 1982 from Kasetsart University. In the same year, he joined the Port Authority of Thailand where he took responsibility in planning and design of port infrastructure.
In 1987, he was awarded the Master of Engineering Degree in Civil Engineering from Chulalongkorn University. In 1991, he acquired his Postgraduate Diploma with distinction in Hydraulic Engineering from IHE in Delft, the Netherlands.
In 1995, he joined Vongchavalitkul University as Head of the Civil Engineering Branch. During the period 2000-2007, he has undertaken the PhD research supervised by UNESCO-IHE and Delft University of Technology, the Netherlands. During this period, the first four years were spent at GeoDelft and UNESCO-IHE, and the last three years were spent at Vongchavalitkul University where he was the vice president for research affairs.
Since graduation, he has spent 25 years working and researching in the civil engineering field including subject such as hydraulic engineering, highway engineering, geotechnical engineering and optimisation for civil engineering. Cheevin Limsiri published two journal and seven symposium papers, most of which were related to his PhD topics.