Browsing by Author "Bekele, Matewos"

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    Engineering Geological Charaaterization, Suitability Analysis and Possible Remedial Measuras for Sebeta-Ambo Railway Project Central Ethiopia
    (Addis Ababa University, 2012-06-06) Bekele, Matewos; Kumar, Tarun (PhD)
    Adequate knowledge and proper investigation of the sub-structure condition is important for effective assessment and control of deterioration of train track geometry. The present research study was conducted to characterize and assess the general suitability of the proposed route alignment of Sebeta–Ambo railway corridor. The present research was mainly focused on analyzing the engineering geological suitability of the railway alignment and to evolve possible remedial measures for the likely engineering geological problems along the general alignment. Besides, the construction material proposed to be used as embankment fill, blanketing and to be used as replacement material for sub-grade has also been characterized for its general suitability. In order to meet out the general objectives of the present research study attempts were made to characterize the natural sub-grade and embankment fill materials including blanketing layer. For this field observation, investigation, sampling and laboratory tests for physical and strength properties assessment were performed on representative samples from natural sub-grade and fill materials. Besides, settlement potential of the natural sub-grade, in particular was evaluated. The dynamic property of the embankment material was also assessed by reviewing relevant literatures. Different manuals and specifications were used to evaluate the suitability of the materials as well as to characterize and interpret the topography of the area. Further, attempts were also made to identify and characterize the hydrology and hydro-geological setup of the area by reviewing the relevant literatures and previous works carried out in the area. Based on the characterization, the natural sub-grade was found to be unsuitable based on its low bearing capacity, settlement potential and high potential for volume change under moisture variation. In order to improve the foundation condition it has been suggested to remove the top natural undesirable soil and replace it with improved material. Besides, stage construction of fill materials can also be implemented. In addition to this it has been assessed that most of the identified fill material is granular in nature and can be designated as silty gravel (GM). This problem can be addressed by blending it with fine soil in appropriate proportion with the fill material. Blanketing materials, coarse, granular and well graded, was also used to improve the bearing capacity of the formation and hence similar materials as that of the embankment fill were used to characterize them. Based on the standard practices followed in other leading railway systems, it is evident that multi-layer formation system– layers with adequate strength and stiffness has to be adopted. Hence, according to Indian Railways Research Designs & Standards Organization, Two Layer System (Blanket & Prepared Sub-grade on Embankment Fill) of sub-structure formation design thickness has been suggested. Finally, this research project will provide an additional input for consultants participating in construction; will be the platform for future academic researcher and similar type of project.