| Author | Rai, Niralal |
| Call Number | AIT Thesis no.TE-04-05 |
| Subject(s) | Pavements, Flexible--Bhutan
|
| Note | A thesis submitted in partial fulfillment of the requirements for the
degree of Master of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. TE-04-05 |
| Abstract | Bhutan indeed faces a unique challenge in the upkeep of its road infrastructure owing to her rugged and mountainous terrain, and extreme climatic conditions. Besides, pavement design has not received serious attention due to other teething problems and priorities. The pace of current maintenance practices has not been able to remedy the rapidly deteriorating pavement conditions. It has been realized that the adoption of a mechanistic-empirical design method could provide a solution to this recurrent problem. This research is focused on the determination of design parameters and an optimal design method. As a first step towards pavement design in Bhutan, design parameters were determined for the Tashichhodzong-Babesa Highway by conducting laboratory tests and acquiring the necessary supplementary data from the Department of Roads (DOR), Bhutan and other relevant sources. The key design parameters determined were subgrade resilient modulus of 59 MPa and axle loadings of 1.18 million equivalent single axle loads. Furthermore, the subgrade soil was classified as the well graded silty sand by AASHTO and Unified Soil Classification systems. Two mechanistic-empirical design methods namely the Thai Method of Equivalent Thickness (Thai MET) and the Asphalt Institute were employed in this research to design the required pavement in Bhutan . Comparisons of the design outputs were carried out on the basis of total thickness, economic analysis and mechanistic analysis. The Asphalt Institute method produced the optimal design with a total pavement thickness of 420 mm consisting of 140 mm asphalt concrete layer, 180 mm aggregated base and 100 mm subbase layers. The total thickness designed by the Thai MET was also 420 mm which consisted of 80 mm asphalt concrete layer, 120 mm aggregate base and 220 mm subbase layers. In light of above, the Asphalt Institute method is considered as the most suitable design method for the study area and the design procedure can be replicated to any other sites in Bhutan with appropriate adjustments. Review of the existing DOR design practices revealed that the designed thicknesses by traditional methods are too thin to resist the stresses and strains being experienced by the pavement structure. However, the designs currently being implemented in the study area were found to be adequate in terms of layer thicknesses and strain responses. Parametric study of the designed thickness was also conducted to examine the effects of changes in truck factor, layer equivalency ratio and traffic growth rate. The studies showed that the thickness increases with increase in the magnitudes of truck factor, substitution ratio and traffic growth rate while it decrease with increase in the moduli of materials. The relationship between the total designed thickness and the independent parameters such as truck factor can be described by regression equations. These regression equations can be used to predict the thickness of pavements by using equivalent single axle load repetitions as an input variable. |
| Year | 2005 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. TE-04-05 |
| Type | Thesis |
| School | School of Civil Engineering |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Transportation Engineering (TE) |
| Chairperson(s) | Yordphol Tanaboriboon; |
| Examination Committee(s) | Montri Dechasakulsom;Hanaoka, Shinya; |
| Scholarship Donor(s) | Royal Government of Bhutan; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2005 |