RELATIONSHIP BETWEEN CLAYSTONE CHARACTERISTIC, WEATHERING GRADE AND SLOPE STABILITY OF BOBONARO FORMATION; CASE STUDY IN THE SITE PLAN OF TIMAU NATIONAL OBSERVATORIUM AT KUPANG REGENCY, EAST NUSA TENGGARA

• Main Author: Setiawan, Arie
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/41556
• Institution: Institut Teknologi Bandung

The study presents influence of claystone characteristic and weathering grade to slope stability. The research was located at Amfoang Tengah hills, Nusa Tenggara Timur and consists of the claystone of Bobonaro Formation. In this study, the claystone of Bobonaro Formation can be classified into four classes of weathering grade. The basic parameters of slope stability analysis which consist of unit weight, cohesion, and friction angle show decreasing value to increasing the weathering grade. The value of unit weight in weathering grade II ranging from 2 to 2.1 g/cm3, weathering grade III ranging from 1.90 to 2.01 g/cm3, weathering grade IV ranging from 1.88 to 1.98 g/cm3, and weathering grade V ranging from 1.53 to 1.89 g/cm3. The cohesion in weathering grade II ranging from 1.51 to 1.96 kg/cm2, weathering grade III ranging from 0.22 to 0.35 kg/cm2, weathering grade IV ranging from 0.195 to 0.23 kg/cm2, and weathering grade V ranging from 0.14 to 0.23 kg/cm2. The friction angle in weathering grade II ranging from 25.57 o to 29.82o, weathering grade III ranging from 11.8 o to 20.6o, weathering grade IV ranging from 10.64 o to 18.64o, and weathering grade V ranging from 8.34o to 14.49o. The analysis shows that the claystone of Bobonaro Formation was susceptible to weathering process with slake durability index low to very low and the swelling potential was low to moderate. Slope stability analysis is based on the assumes that the slope consists of non-homogeneous material with the value of the engineering properties varied in the weathering grade and homogeneous material, which is valued in weathering grade V. The results of slope stability analysis show significant differences in the value of a safety factor between slopes consisting of materials with varying degrees of weathering and slopes consisting of homogeneous material. It shows that the more expansion of the weathering grade in claystone will reduce the shear strength along with slope stability which is reflected in the value of the lower safety factor.