Application of geological strength index system for slope stability studies of the crocker formation in Kota Kinabalu, Sabah
The main objective of this study is to apply Geological Strength Index (GSI) classification system for slope stability study in Crocker Formation of Kota Kinabalu area. Six slopes were selected based on different type of composition and structure as in the GSI chart. The geological mapping and di...
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| Format: | Thesis |
| Language: | English |
| Published: |
2017
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| Subjects: | |
| Online Access: | https://eprints.ums.edu.my/id/eprint/16860/1/Application%20of%20geological%20strength.pdf |
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| Summary: | The main objective of this study is to apply Geological Strength Index (GSI)
classification system for slope stability study in Crocker Formation of Kota Kinabalu
area. Six slopes were selected based on different type of composition and structure
as in the GSI chart. The geological mapping and discontinuity survey were
conducted to obtain quantitative description of discontinuities as well as rock
sampling based on rock unit and grain sizes. GSI ratings were analysed using three
GSI approaches which are GSI₁₉₉₇, GSI₂₀₀₇ and GSI₂₀₁₃. The results show that GSI₂₀₀₇ was the most suitable GSI approach to be applied at the Crocker Formation.
Parameters of disturbance factor (D), uniaxial compressive strength (UCS) and rock
mass properties were obtained through field observation, laboratory work and
correlation of Hoek-Brown criterion. Based on the results, it was found that, GSI
rating has the greatest influence on rock mass properties followed by UCS and
disturbance factor. These parameters were directly proportional to the rock mass
properties. Intact rock constant however was inversely proportional to cohesion
and tensile strength because of the present of shale and silt material. Numerical
analyses of kinematic, finite element, (FEA) and limit equilibrium (LEA) analyses
were performed to analyse the slope condition. Kinematic analysis showed that only
slope S1 and slope S5 have probability for wedge failure. FEA and LEA results
indicated that all slopes have the safety factor value that can be considered as
stable, with FEA considered to be more suitable method since it can analyse both
elastic and plastiC properties (elasto-plastic), additionally, it also capable of
handling more complex failure plane and geometry. The safety factors obtained in
FEA considered and computed based on rock mass properties which were neglected
by LEA. Besides GSI rating, slope geometry also found to influence the slope
condition, therefore, this parameter must be incorporated for slope stability
analysis. Finally, the rock cut slope design was proposed with focus on mitigating
localised failure and reducing water pressure build up behind the slope face. No
obvious correlation can be made between GSI and rock cut slope design because it
predominantly controlled by geometry, lithology and stability of individual slope
rather than GSI rating. |
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