Integration of Geophysical and Engineering Geological Methods for Slope Characterization and Assessment Over Granitic Bedrock Area in Tropical Residual Soil :: A Case study on the cut slope at Km 50.0, Federa route 6, Penang, Malaysia

ISMAIL, Mohd Ashraf Mohamad, Ir. Dwikora Karnawati, M.Sc.,Ph.D

2006 | Tesis | S2 Teknik Geologi

Granitic bedrock cut slope at Km 50.0, Federal Route 6, Penang have been threatened by continuous slope instabilities and failures generation soon after its construction work finished in 1999. The presence of heterogeneous and irregularity weathering sequences associated with the cutting of the slope had exposed numerous core boulders with variety grades of weathering profile. In conjunction with the above condition and continuous intense climatic influence, this kind of slope has been found susceptible and preferable to potential rock fall and shallow type of failures. These failures will keep occur due to the difficulty to obtain the reliable subsurface information and also indistinct understanding for its determining mechanisms. In addressing such problem, this research had been carried out with special consideration given to the slope characteristics and behavior respond to the electrical resistivity parameter used. Field investigations consist of electrical resistivity with the integration of engineering geological method, selective laboratory tests and numerical modeling had been used. The combination of these approaches serves as a tool to get the input. In another way, qualitative approach with acceptable engineering justification and judgment had been used as an analysis and assessment tool. Based on the result, it is proved that the application of electrical resistivity with the integration of engineering geological methods are appropriate to infer the nature of the granitic cut slope at this research area. Thus the effort did indirectly reduce the ambiguity of the subsurface profile characterization and assessment. As a result, slope condition and the materials physical properties inherited are found to be the major controlling factors; while, rainfall, with the role to bring water to the slope have been found as the major triggering factor. Due to the heterogeneous slope stratigraphy condition where the impermeable and permeable layer alternating each others in irregularity sequences within the shallow subsurface profile, it is understood that, the main mechanism involved in facilitating the potential rock fall and shallow types of failures is saturation and loss of negative pore water pressure. However, the combination of the above mechanism with the deeper discontinuities underneath will be another mechanism in facilitating deep types of failure in the future. When the determining factors are clearly investigated and understood, the outcomes used to minimize and mitigate the hazard. At the present time, the focused is to manage the major triggering factors by controlling the excessive water infiltration into the slope and to allow the pore water dissipation in the soils. However, the above actions are only preemptive works. Further detailed investigation is needed in order to propose comprehensive design of sustainable countermeasure works by taking into account also the major controlling factors inherent.

Kata Kunci : Batuan Dasar Granit,Metode Teknik Geologi dan Geofisika