Browsing by Author "Rifkhan, M.N.M."

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    Analysis of Slope Stability on Road Cut Slopes; a Case Study at Badulla- Bibile Road and a Cost-Effective Proposal for Future Road Cut Slope Studies
    (Uva Wellassa University of Sri Lanka, 2018) Rifkhan, M.N.M.; Jayasinghe, P.; Christopher, W.A.P.
    Sri Lanka is frequently affected by hydro meteorological disasters, one of which is slope failure triggered by unusual intense rainfall. Post-disaster inspections reveal the lack of preliminary investigations being carried out on cut slope failures. The first objective, which was a slope stability analysis on proposed cut slopes of Badulla-Bibile road was designed in a three-fold methodology including Preliminary Study, Field Investigation and Laboratory Investigations. Laboratory investigation consisted of Sieve analysis, Liquid limit, Direct Shear and simple pour pile method. The data were interpreted with reference to slope geometry and soil strength. Geometrical interpretation identified that 32.5% of natural and 73.3% of cut slope failures were possible. The soil analysis interpreted using Unified Soil Classification System reveals that silty gravel, Lean Clay, Silt, Silty Sand, Clayey Sand soil types were present. All these soils were known to be cohesion-less and changing the slope angle was identified to be the ideal mitigation. The second objective was to understand the importance of preliminary study in future road cut slope. This proposed method includes geometrical and soil study. Geometrical study is done with three criteria considering the slope angle, slip angle, friction angle, strike of slip and strike slope. The soil analyses are performed using Unified soil classification system considering the Sieve analysis and Liquid limit test. Identified properties of the soil were modeled in Slope W software to check the factor of safety. This method to find the soil properties is cost effective and less time consuming than direct Shear method. This study has considered direct shear as a conventional method and interpreted for a location. Both results were coinciding, and a conclusion can be drawn that the proposed cost effective basic method is economical which can be used as a preliminary study in future road projects in Sri Lanka.
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    Preliminary Investigation on the Occurrence of Reddish Brown Colour in Zircon from Kolonna, Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2020) Rifkhan, M.N.M.; Wewegedara, W.G.C.N.; Jayasinghe, R.M.N.P.K.; Dharmaratne, T.S.; Malaviarachchi, M.A.S.P.K.; Rohana, C.
    Sri Lanka is famous for various types of gem minerals. From among these minerals, gemquality zircon is found in both primary and secondary deposits. Kolonna is a location where zircon is found in primary deposits with a reddish-brown colour. The main objective of this study was to investigate the occurrence of reddish-brown colour in zircon from Kolonna area. Although many factors could cause the colour of gem minerals, the colour of zircons is known to be produced by trace elements (transition metals, lanthanides, actinides, and REEs), radiation damage (radiation-induced color centers) and charge transfer. Five randomly selected reddish-brown zircon samples were selected for this study. All samples were translucent, highly fractured, sub-adamantine, and with euhedral to subhedral crystal form. Samples were analyzed with EDXRF, UV-Vis Spectrophotometer, and FTIR methods. The UV-Vis spectrum of these samples showed an increase in absorption towards the UV region and declines towards the NIR region with a shoulder at around 500 nm. This can be identified as a structurally defected colour center that may occur due to the radiation damage caused by radioactive elements such as U and Th. This was further confirmed by the U4+ peak at 654 and 690 nm. The U5+ peak at 6663 cm-1 in the FTIR spectrum further confirmed the presence of U in samples. This was confirmed by the EDXRF analyses that showed a trace amount of radioactive elements. The average weight percentage of U and Th were 0.06 and 0.02, respectively. It was also noted an occurrence of an OH- group indicated at 3196 cm-1 on FTIR spectra. This may be probably due to slight radiation damage caused by radioactive elements in zircon samples. This study revealed the presence of U which accounts for structural defects that form colour centers in reddish-brown zircon from the Kolonna region. Keywords: Absorption, Colour center, Cause of color, Zircon, Radiation