Master of Engineering in Geotechnical Engineering

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Browsing Master of Engineering in Geotechnical Engineering by Subject "GEOTECHNICAL ENGINEERING-Thesis"

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    item: Thesis-Abstract
    Improvement of engineering properties of peat by preconsolidation : a comparison of field and laboratory test results
    Karunawardena, WA; Kulathilake, SAS
    Sri Lanka lies in the monsoon region of South- East Asia. Colombo, the Capital city situated on the Western cost of the island experiences a humid tropical climate with an annual rainfall of 2500 mm. In the Colombo region there exists flood plains of Kelani Gaga to the North and in the in the coastal belt there are some water bodies such as the Kotte Lake, Bolgoda Lake etc. The fluctuation of water table due to excessive rainfall provides suitable condition to accumilate peat deposits in the above areas, as these are poorly drained grounds. The above process has been occuring for a long time and as a result of that now there exists around 2500 acres of marshy land underlain with peat in and around Colombo city. These marshy lands consist of peat layers having thickness around 5m-10m. As most of the lands with good subsoil condition around Colombo are already used up with the development of the country, it is now necessary to use these unused marshy lands for housing and infrastructure development.
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    item: Thesis-Abstract
    Probabilistic analysis of shallow translational slides
    Rathnayake, PLW; Kulathllaka, SAS
    Slope instability is a major environmental hazard, which is widely researched by Geotechnical engineers in the world. In general, there is a vast range of different mechanisms of slope failures. Shallow translational mode of slope failure is one such important mode. This thesis concentrates on shallow translational form of slope failures. Analysis of shallow translational form of failure is carried out deterministically as well as probabilistically. The probabilistic analysis gives due consideration to the uncertainty of soil strength parameters and pore water pressures. Analysis are carried out under both saturated soil mechanics theories and unsaturated soil mechanics theories. Two hypothetical examples representative of natural lateritic slopes in Sri Lanka are analysed deterministically and probabilistically. Finally, the influence of rainfall and wetting front propagation are analysed. The corresponding changes of the probability of failure of the previously unsaturated slope is highlighted. The transition of slope from unsaturated situation to saturated situation with the propagation of wetting band thickness, and the resulting changes in the factor of safety and probability of failure are discussed. A method of evaluating the overall probability of failure is suggested for further research.
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    item: Thesis-Abstract
    A Study on the effects of variation of elastic properties of asphalt concrete on the vertical stress distribution in layered road pavements
    (2014-08-07) Seneviratne, HMU; Puswewala, UGA
    107252-1.pdf Often the natural ground or soil is not mechanically strong enough to withstand the repeated applications of wheel loads without significant deformation. Therefore it is necessary to provide a structure between the wheel and natural ground or subgrade to spread the wheel loads within allowable and recoverable deformation limits. Road pavement is the structure, which serves this purpose, by supporting and distributing the applied load. The primary purposes of the pavement are to prevent excessive deformation of the subgrade and to prevent ultimate failure stage. In order to prevent excessive subgrade deformation the vertical stress oz at subgrade level has to be kept below some critical value. The two main types of pavements used in pavement construction are rigid pavements and flexible pavements. Rigid pavements are very rare in Sri Lanka and consists of very stiff reinforced or roller compacted concrete surfacing over comparatively much softer ground. Flexible pavements consist of three main layers from top to bottom, consisting of the bituminous surfacing, road base and sub base. Sometimes the subbase is not laid. The shear strength, stiffness and the quality of the material of the layers decrease in the downward direction of the pavement. The topmost layer of a flexible pavement is an asphalt concrete surfacing or any other bituminous surface dressing like Double Bituminous Surface Treatment (DBST), Single Bituminous Surface Treatment (SBST) or traditional metal and tar application. The most popular bituminous surface treatment in Sri Lanka is asphalt concrete due to its very good riding quality, durability, higher stiffness or stability, resistance to adverse climatic conditions and the ability to maintain consistent quality during manufacturing and laying. As asphalt concrete surfacing is the most modern and popular method used in flexible pavement construction, this work is limited to studies on flexible pavements with asphalt concrete surfacing. Primarily asphalt concrete is a mix of bitumen and a blend of densely graded aggregates. Mix proportions of the asphalt concrete are determined after a process of mix design to achieve the desired strength and durability against expected traffic and adverse climatic conditions by using available aggregate.