Identification of the main mechanism of shallow landslides in bukit fraser, Pahang

Abstract

Slope stability problems in Bukit Fraser are raising concern where 22 shallow landslides were recorded as of 6 August 2017. Identification of main shallow slope failure mechanisms were done on the basis of structural geology analysis, soil engineering and geophysics from 6 selected slopes along ascending and descending route of Bukit Fraser. Based on the information of the regional lineament, Bukit Fraser consists of 3 lineament sets with North-South, North East-South West and North West-South East orientation. One minor lineament set was oriented to East-West. Fluvial system patterns are parallel to sub-dendritic and flowing mostly to the North West, North East and South direction. According to the engineering geology evaluation of the slope, all slopes angled at about 70º with slope materials consist of sandy soils (SM). The existence of silt of low plasticity (ML) is high as compared to clay for most slopes indicating existence of high organic content. According to the electrical resistivity survey and induced polarization method, the existence of materials with high water content consists of silt and sand with value lower than 100 Ωm can be seen at almost all sub-surface area. The existence of clayey materials is showing higher chargeability values of about 10 milisecond and vice versa for sandy materials. The main mechanisms for shallow slope landslides as a whole are caused by dynamic imbalance of the slopes including steep cut-slope angle, slope materials completely weathered to residual soils of grade VI, high water content existence inside sandy and silty slope materials and also low plasticity slope material with high compressibility indices.