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" Geotechnical Hazard Assessment of Road Cuts Stability in Mountainous Areas in Saudi Arabia "
Basahel, Hassan Mabrouk
Mitri, Hani
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Latin Dissertation
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English
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| Record Number
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1107819
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TLpq2457501395
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| Main Entry
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Basahel, Hassan Mabrouk
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Mitri, Hani
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| Title & Author
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Geotechnical Hazard Assessment of Road Cuts Stability in Mountainous Areas in Saudi Arabia\ Basahel, Hassan MabroukMitri, Hani
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| College
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McGill University (Canada)
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| Date
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2019
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| student score
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2019
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| Degree
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Ph.D.
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| Page No
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177
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| Abstract
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The stability of rock slopes is crucial to public safety in highways passing through rock cuts. Slope instability and failures occur due to many factors such as adverse slop geometries, geological discontinuities, weak or weathered slope materials as well as severe weather conditions. External loads like heavy precipitation and earthquakes could play a significant role in slope failure. In this thesis, several rock mass classification systems for rock slope stability assessment were critically evaluated against known rock slope conditions in the south western region of Saudi Arabia. Selected empirical methods were applied to 22 rock cuts, and the stability conditions were identified. The results obtained from these methods were compared to each other and served to highlight the limitations of each empirical classification system. A probabilistic stability analysis approach is then developed. The stability condition of a jointed rock slope in one of the selected rock cuts taken from the previously chosen 22 rock cuts was assessed using deterministic and probabilistic approaches, under both dry and wet conditions. The stability analysis was carried out using FLAC3D to generate a 3-dimensional model, and bedding is simulated with a ubiquitous joint model, to determine the influence of the dominant, unfavorable bedding orientation with respect to the slope face. The deterministic analysis was implemented first using the mean values of the selected random variables, namely the dip, dip direction and friction angle of the dominant discontinuity set, and the stability condition was assessed. A Box-Behnken design (BBD) approach is then adopted to create the surface response function, as a second order polynomial for the factor of safety. To do so, fifteen FLAC3D models were generated in accordance with BBD. Based on this, 10,000 simulations of different slope realizations were carried out using Monte-Carlo simulation technique, and the probability of unsatisfactory of performance of the rock slope was assessed. It is shown that the probabilistic approach provides more insight and confidence in the stability condition of the rock slope, under both dry and steady state heavy rainfall conditions. A new factor, herein defined as the failure intensity factor is introduced to describe the severity of slope failure with respect to the roadway width, to distinguish between rock slopes having the same probability of failure, yet not the same magnitude of failed material. A maximum shear strain criterion is adopted to delineate the volume of sliding material and its effect on the roadway, and 3 levels of the intensity factors – low, moderate and high – are defined. Finally, the intensity factor is used to derive the geotechnical hazard index matrix. A 5-level geotechnical HI matrix is proposed, based on reported recommended levels of low, moderate and high probabilities of failure. The proposed Hazard Index matrix considers both the probability of unsatisfactory of performance of the rock slope and the severity of the slope failure expressed as the intensity factor.
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Geological engineering
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Geology
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Mining
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