Determination of geo-hydro seismic impact on slope stability at east of Malaysia using limit equilibrium analysis

• Main Author: Mohammad Haziq Rosly
• Format: Thesis
• Language: English; English
• Published: 2023
• Subjects: TA703-712 Engineering geology. Rock mechanics. Soil mechanics. Underground construction
• Online Access: https://eprints.ums.edu.my/id/eprint/40539/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/40539/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/40539/
• Institution: Universiti Malaysia Sabah

Rainfall and earthquake have been identified as the highest contributing factors that lead to landslide occurrence worldwide. This is due to rainwater infiltration have caused the groundwater to increase and decrease creating fluctuation of groundwater level. Whereby earthquake have deteriorated the shear strength of soil due to the dynamic loading. Further to that, Ranau and Kota Belud, Sabah have been selected in this study due to the presence of both contributing factors and located within the same geological formation. GeoStudio was utilized to perform the slope stability analysis by using Slope/W and Seep/W features using soil parameter input obtained from soil investigation works and lab testing. Also, statistical analysis was conducted to develop Intensity Duration Frequency (IDF) graph using existing data for rainfall intensity calculation. The objective of this study is to identify the impact of rainfall and earthquake to factor of safety of slope at RNU1, KB1 & KB2. Based on the IDF graph developed using data obtained has shown that Ranau and Kota Belud are having dense rainfall every year with maximum rainfall intensity is ranging between 175.2 mm/hr to 220.3 mm/hr. As for earthquake, Ranau recorded the highest seismic activity with 1,093 number of events between year 2000 until 2020. While Kota Belud recorded not significant seismic event for the similar window period. From the slope stability without earthquake, and the factor of safety recorded at Kota Belud is ranging between 2.333 to 3.375 while Ranau recorded factor of safety between 2.431 to 2.572. For the slope stability with earthquake, four earthquake values were introduced are 0.03g, 0.06g, 0.09g and 0.12g. Presence of earthquake have dropped the factor of safety for the Kota Belud approximately between -16.8% to -9.6%. while for Ranau the factor of safety dropped roughly within -9.3% to -7.7%. Slope stability analysis has indicated that there is fluctuation of pore pressure during rainfall infiltration into the ground. In conclusion, combination of rainfall and earthquake resulted to catastrophic landslide that impacting the pore pressure and frictional strength respectively.