Master of Engineering in Foundation Engineering & Earth Retaining Systems

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Browsing Master of Engineering in Foundation Engineering & Earth Retaining Systems by Subject "CIVIL ENGINEERING - Dissertation"

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    item: Thesis-Abstract
    Compressibility characteristics of municipal solid waste in meethotamulla waste fill site
    (2021) Galhena GDWN; Kulathilake SAS
    Municipal solid waste (MSW) is defined as solid waste generated from community, commercial and agricultural operations and it includes wastes from households, offices, stores, industries and other non-manufacturing activities. Management of municipal solid waste is a major problem all over the world. Recently, Municipal Solid Waste Management became a growing concern in Sri Lanka with the catastrophic landfill failures occurred at Meethotamulla. The need to ensure the stability of existing landfills which are mostly uncontrolled through appropriate engineering designs is a major task at present. MSW forms the largest portion of the landfill and its strength and stiffness (compressibility) characteristics controls all aspects of landfill designs. In this research compressibility characteristics of MSW at different stages of decomposition were evaluated under both saturated and unsaturated conditions. Considering the highly heterogeneous state of MSW, larger samples were tested using a Rowe Cell of diameter 150mm with loading, unloading and reloading increments. Characteristics such as; Coefficient of volume compressibility, coefficient of consolidation, coefficient of secondary consolidation, compression index, recompression index were determined to assess the applicability of conventional Terzaghi consolidation theory in modelling the MSW behavior. Results were compared with the behavior of residual soil and organic soils. The test results revealed that MSW experienced high primary and secondary consolidation settlements. These could be significantly reduced by preloading. The coefficient of consolidation values were quite high.
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    item: Thesis-Abstract
    Evaluation of correlations between SPT N and undrained shear strength for fine grained soils of Sri Lankan geological conditions
    (2021) Premathilaka KKW; Thilakasiri H S; De Silva LIN
    Undrained shear strength is one of the essential parameters in most of the applications of geotechnical engineering. Unconsolidated undrained (UU) triaxial test is the most commonly practiced method of determining the undrained shear strength which takes a considerable time and effort to produce its results, since the sampling stage. Such correlations seldom exist pertinent to Sri Lankan soils. Hence, it is important to have reliable correlations between easily executable, commonly used test results and undrained shear strength of Sri Lankan soils to easily and promptly predict the soil structure interaction phenomenon, especially in local geotechnical engineering applications. Thus, in this study, an attempt has been made to correlate the standard penetration test (SPT) with experimentally determined unconsolidated undrained triaxial test parameters, and the undrained shear strength estimated from the field vane shear test data. This analysis consists of three main stages, namely analysis of the available correlations, analysis of the available data set based on the soil and sampling properties to develop a correlation and the analysis on a set of reliable data with a defined deviation factor. A correlation between SPT N60 and undrained shear strength has been proposed for Sri Lankan silty soils. Further, possible analysis methods for developing correlations for other different soil types have also been addressed. In addition, existing drawbacks and difficulties associated with developing such correlations related to Sri Lankan context are also described.
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    item: Thesis-Abstract
    A Study of applicability of different facing types in soil nailing
    (2021) Kumarage B I; Kulathilaka S A S
    Soil nailing has been used in Sri Lanka lately, in a wide range of infrastructure projects, as a cost-effective stabilization technique that can be implemented quickly. However, detailed designs with rigor, for nailhead/ facing are not often carried out in the local practice. Full face shotcrete, grid beams connecting nail heads, isolated nail heads (Pillows), and combinations of all these facings types used in the local practice. When the full face shotcreting is not used vegetation is used as a surface protection cover in between the nail heads with the help of a geotextile and nail heads are combined with a wire mesh of specified tensile strength. The mesh is expected to provide stability against any local shallow failures. The versions without full-face shotcrete blend nicely with the natural environment and have gained greater acceptance. In this research design guidelines for different facing types available in published literature are critically reviewed to assess the suitability under high rainfall intensities in local residual soil formations. A number of sites rectified with soil nailing with different types of facing have now experienced few seasons of rainfall and their performance is assessed. The cost-effectiveness and construction difficulties are also reviewed. Based on these factors some guidelines are developed to decide on the most appropriate type of facing depending on the prevailing local conditions.