General geology and slope failure assessment of soil cut-slope at Kuala Balah, Jeli district, Kelantan, Malaysia

Slope failure assessment in this research included the study of characteristics of the slope and the factor of safety of the slope. The properties of the slope forming materials are significant in the slope stability analysis. The study area is located at Kuala Balah, Jeli, Kelantan. The total area of the study are is 25km2 and bounded within the coordinate of 5° 26’ 10.80” N, 101° 54’ 15.00” E and 5° 23’ 28.8” N, 101° 56’ 56.40” E. The objectives of this study are to update the geological map of the Kuala Balah, Jeli, Kelantan with scale of 1:25 000, to produce slope failure inventory of the study area with slope geometry, mode/ type of failure, failure geometry, origin of soil/ rock, cause of failure, type of slope stabilization protection and vegetation cover of failure and to construct slope stability analysis for soil cut-slope at study area by using Slope/ W software. Geological mapping and engineering mapping were carried out to identify the geological features and the soil-cut-slope. Geological map of Kuala Balah, Jeli, Kelantan has been updated. The lithology consists of fine-grained granite, granodiorite, fine-grained biotite granite, quartzite, fine-grained gneiss, coarse-grained quartz-plagioclase gneiss, shale, mudstone and metasandstone. There are a total eight cut-slope failure observed in the study area. The inventory of slope failure is constructed. Most of the weathering grade of soil cut-slope is five and originated from shale. The mode of failure of all slope is rotational slide and protected by vegetation or Gabion retaining wall. Major causes of the failure are weathering process and rainfall. Laboratory analysis for properties of soil had been done for the slope stability analysis. Based on the laboratory tests of soil, the classification of soil is done and the results are used in the determination of factor of safety of slope. The soil samples are categorized into three groups which area sandy silty clay, sandy lean clay and sandy high plasticity clay. The factor of safety of the selected slopes are range in 0.339 to 2.548 which indicated there has stable slope and unstable slopes.