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Probabilistic Stability Analysis of a Railway Embankment on Dispersive Strata Subjected to Periodic Rainfall Conditions with Various Patterns

Kaheh, Shadnaz | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54086 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ahmadi, Mohammad Mehdi
  7. Abstract:
  8. The importance of rainfall pattern in assessing embankment stability and deformation is widely known. However, many studies have examined an embankment with simple rainfall patterns or used average and maximum ones. The importance of diverse rainfall patterns has also been overlooked in the study of divergent soil stability in the previous study. Therefore, the hydraulic properties of a natural soil with and without salinity potential and the stability analysis of the railway embankment located on this type of soil under various rainfall patterns are investigated. The study area is part of the Zahedan Chabahar National Railway Project, which is located on divergent soil and has high variability in climate. In recent years, natural precipitation with non-uniform random patterns has caused instabilities of the final limit state type in the railway embankment, which doubles the priority of studying this lesser-known phenomenon. In this study, in the laboratory to study the water-soil retention curve, the drying branch of the retention curves of two types of natural and desalinated soils, both natural density and standard density were measured using a filter paper method. The ripening curves of the previous study were examined. Also, the possibility of embankment rupture under precipitation patterns was investigated using reliability methods and to estimate various rainfall patterns, meteorological precipitation data and space satellite during 4 years were obtained. In modeling, three rainfall patterns were applied to the embankment on a bed with salinity potential and in two cases with and without considering the effects of hysteresis. It should be noted that the purpose of measuring wet and dry curves was to study the effects of hydraulic hysteresis along with the precipitation pattern on the embankment of the railway in order to further verify the simulation conditions to reality. The results of the laboratory section show that the retention capacity in total suction is reduced by salt removal due to osmotic suction and in denser samples is increased due to the elimination of particle cavities, while the effects of hysteresis in saline materials are shown more. Regarding precipitation, due to the small difference between station and satellite, satellite data, in addition to greater accuracy, has led to a lower reliability, which is more important than the uniform precipitation pattern. Although more changes in reliability coefficients occurred in rainfall cycles in terms of the hysteresis phenomenon, but the probability of conditional rupture in terms of hysteresis phenomenon with precipitation has increased, which indicates the importance of probabilistic studies of precipitation compared to the unique reliability study
  9. Keywords:
  10. Embankments ; Railway ; Dispersive Strata ; Random Pattern ; Rainfall Pattern ; Two-Phase Transient State Current

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