Probabilistic analysis of potential planar-type rock slope failure of selected malaysian rock slopes

Afiq Farhan Abdul Rahim, Norbert Simon, Tuan Rusli Mohamed, Abdul Ghani Md Rafek, Ailie Sofyiana Serasa, Yanlong Chen, Mingwei Zhang, Khai Ern Lee, Thian Lai Goh

Research output: Contribution to journalArticle

Abstract

Quantification of rock slope stability analysis in Malaysia has generally been limited to the traditional methods of Rock Mass Rating (RMR) or Slope Mass Rating (SMR). While these methods represent a means to convey message from geologists to engineers, they can be confusing especially in designing slope stabilization efforts. The limit equilibrium method which is widely used worldwide has only seen limited application for rock slope stability analysis in Malaysia. This paper discusses the limit equilibrium method using Factor of Safety (FOS) from deterministic calculations to probabilistic analysis. Four rock slopes in Klang Valley (L1, L2, L3 and L4) with potential and failed planar failures have been selected for FOS calculation. In this study, Barton’s equation has been selected in favour of the Mohr-Coulomb method due to the availability of Joint Roughness Coefficient (JRC) data. A deterministic calculation in dry conditions shows that FOS values range from 1.08 to 2.34 which indicates stable conditions. However, introduction of water into the discontinuities (50% filling) reduces the FOS value from 0.80 to 1.89 while 100% filling of water inside discontinuities further reduces the FOS value to the range from 0.00 to 0.55. The results indicate the importance of water in influencing the FOS calculations. Probabilistic analysis uses normal distribution of parameters measured at the field except for water content in which an exponential distribution is assumed. The probabilistic FOS analysis shows probability of failure ranging from 4.83% to 44.80% whereby the slope with highest likelihood of failure is at L1. Estimated block weight shows median mass value between 0.07 tonne/m to 1.30 tonne/m. The establishment of FOS and probability of failure values will help the engineers better to design adequate stabilization structures if needed.

Original languageEnglish
Pages (from-to)95-102
Number of pages8
JournalBulletin of the Geological Society of Malaysia
Volume2019
Issue number67
DOIs
Publication statusPublished - 1 Jan 2019

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slope failure
safety
rock
slope stability
stability analysis
discontinuity
slope stabilization
analysis
water
roughness
stabilization
water content
method
valley
calculation

Keywords

  • Factor of safety
  • Planar failure
  • Probability of failure
  • Rock slope

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Probabilistic analysis of potential planar-type rock slope failure of selected malaysian rock slopes. / Rahim, Afiq Farhan Abdul; Simon, Norbert; Mohamed, Tuan Rusli; Rafek, Abdul Ghani Md; Serasa, Ailie Sofyiana; Chen, Yanlong; Zhang, Mingwei; Lee, Khai Ern; Goh, Thian Lai.

In: Bulletin of the Geological Society of Malaysia, Vol. 2019, No. 67, 01.01.2019, p. 95-102.

Research output: Contribution to journalArticle

Rahim, Afiq Farhan Abdul ; Simon, Norbert ; Mohamed, Tuan Rusli ; Rafek, Abdul Ghani Md ; Serasa, Ailie Sofyiana ; Chen, Yanlong ; Zhang, Mingwei ; Lee, Khai Ern ; Goh, Thian Lai. / Probabilistic analysis of potential planar-type rock slope failure of selected malaysian rock slopes. In: Bulletin of the Geological Society of Malaysia. 2019 ; Vol. 2019, No. 67. pp. 95-102.
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AB - Quantification of rock slope stability analysis in Malaysia has generally been limited to the traditional methods of Rock Mass Rating (RMR) or Slope Mass Rating (SMR). While these methods represent a means to convey message from geologists to engineers, they can be confusing especially in designing slope stabilization efforts. The limit equilibrium method which is widely used worldwide has only seen limited application for rock slope stability analysis in Malaysia. This paper discusses the limit equilibrium method using Factor of Safety (FOS) from deterministic calculations to probabilistic analysis. Four rock slopes in Klang Valley (L1, L2, L3 and L4) with potential and failed planar failures have been selected for FOS calculation. In this study, Barton’s equation has been selected in favour of the Mohr-Coulomb method due to the availability of Joint Roughness Coefficient (JRC) data. A deterministic calculation in dry conditions shows that FOS values range from 1.08 to 2.34 which indicates stable conditions. However, introduction of water into the discontinuities (50% filling) reduces the FOS value from 0.80 to 1.89 while 100% filling of water inside discontinuities further reduces the FOS value to the range from 0.00 to 0.55. The results indicate the importance of water in influencing the FOS calculations. Probabilistic analysis uses normal distribution of parameters measured at the field except for water content in which an exponential distribution is assumed. The probabilistic FOS analysis shows probability of failure ranging from 4.83% to 44.80% whereby the slope with highest likelihood of failure is at L1. Estimated block weight shows median mass value between 0.07 tonne/m to 1.30 tonne/m. The establishment of FOS and probability of failure values will help the engineers better to design adequate stabilization structures if needed.

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