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

Author : Afiq Farhan Abdul Rahim, Norbert Simon, Tuan Rusli Mohamed, Abdul Ghani Md Rafek, Ailie Sofyiana Serasa, Yanlong Chen, Mingwei Zhang, Lee Khai Ern, Goh Thian Lai
Publication : Bulletin of the Geological Society of Malaysia
Page : 83-90
Volume Number : 67
Year : 2019

Bulletin of the Geological Society of Malaysia, Volume 67, June 2019, pp. 83 – 89

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

Afiq Farhan Abdul Rahim1, Norbert Simon1, Tuan Rusli Mohamed2, Abdul Ghani Md Rafek3, Ailie Sofyiana Serasa4, Yanlong Chen5, Mingwei Zhang5, Lee Khai Ern6, Goh Thian Lai1,*

1School of Environmental and Natural Resource Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia
2Dept. of Mineral and Geoscience Malaysia Perak, Jalan Sultan Azlan Shah, 31400 Ipoh, Perak, Malaysia
3Dept. of Geosciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak, Malaysia
4School of Engineering (Petroleum), Asia Pacific University of Technology & Innovation (APU), Technology Park Malaysia, Bukit Jalil, 57000, Kuala Lumpur, Malaysia
5State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, No.1, Daxue Road, Xuzhou, Jiangsu, 221116, P.R. China
6Institute for Environment and Development (LESTARI), Universiti Kebangsaan Malaysia, 43600, UKM Bangi, Selangor, Malaysia
*Corresponding author email address:

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.

Keywords: Factor of safety, probability of failure, planar failure, rock slope