NATURE OF PROJECT: ENGINEERING GEOLOGY AND ROCK SLOPE STABILITY ASSESSMENT
DURATION: 4 MONTHS
DURATION: AUG 2018
BACKGROUND AND METHODOLOGY
Geomapping Technology Sdn. Bhd. undertook the assessment on engineering geological assessement and rock slope stability mapping at Bukit Lanjan, Selangor. The lithology of the cut slope consists of granitic rock mass with weathering Grade I to Grade III. Due to the nature of the outcrop, engineering geology assessments is conducted to obtain optimal engineering geological data for comprehensive analysis for rock slope stability. The engineering geological survey methods are:
- Discontinuity Survey: Scanline survey and Terrestrial Laser Scanning (TLS)
- Airborne survey using UAV/drone
- Kinematic analysis
- Rock Mass Rating (RMR) and Slope Mass Rating (SMR)
- Modified Geological Strength Index (GSI)
RESULTS AND DISCUSSION
Based on discontinuity mapping, multiple potential failures were identified using kinematic analysis which was represented potential instabilities on site. The demarcated potential failure is depicted as the major potential failure mode. Each major potential failure blocks were labeled with unique ID and analyzed with limit equilibrium method.
Rock masses were assigned RMR and SMR rating based on the parameters acquired from the mapping survey. The orientations of potential failure plane were used in readjustment factor in SMR analysis. Based on SMR classification, the slopes were identified as Class II (Stable), Class III (Partially Stable) and Class IV (Potentially Unstable).
Figure 1: Oblique aerial photograph showing identified potential instabilities and it is given ID.
The rock masses were also analysed using modified GSI method and the results shows good correlation with RMR (Bieniawski,1989).
Figure 2: Results of TLS point cloud data processed in Coltop3D showing characterized discontinuity sets.
CONCLUSION
Empirical method and rating systems such as kinematic analysis, Rock Mass Rating, Slope Mass Rating, and Geological Strength Index are very useful in determine the rock mass rating for mitigation works. However, limit equilibrium analysis will provide more information on slope stability in specific condition.
