ASSESSMENT OF ROCKFALL POTENTIAL OF LIMESTONE HILLS IN THE KINTA VALLEY

Abstract

Limestone hills are an astounding natural beauty to the landscape due to their unique features formed by the dissolution of carbonate by water (natural dissolution). However, depending on a hill’s location, it may also pose danger to humans and properties due to the presence of extensive joints and fractures within the limestone hill. This study was conducted to assess the condition of seven limestone hills in Kinta Valley, Perak. They are Gunung Rapat, Gunung Datok, Gunung Lang, Gunung Paniang, Gua Kandu, Gunung Panjang, and Gua Tempurung. The signifcance of studying these hills are their locations that are close to roads, residential areas and the possible development as tourist attractions. A total of twelve assessment stations with two to three stations for each of the hills were set up to assess their stability using the Rock Mass Strength (RMS) system. The geological conditions of the hills were assessed by seven components in the RMS system for rockfall assessment: intact rock strength (using a Schmidt hammer), weathering, spacing of joints, joint orientations, width of joints, continuity of joints, and outflow of groundwater. Subsequently, the hills are classifed into very strong, strong, moderate, weak, or very weak based on the sum of ratings for all the components. The assessment has revealed that the slopes at the assessment stations at Gunung Rapat and Gunung Lang are classifed as weak whilst that at Gunung Datok is classifed as moderate to weak. The main reasons are these hills are heavily jointed with smaller joint spacings (below 300 mm), joints daylighting steeply out of slopes (85-90˚), wider joint opening (larger than 20 mm) and very low Schmidt hammer rebound values (below 35 an average). Based on these factors, these hills were classifed as weak (RMS: below 50) and highly susceptible to the occurrence of rockfalls. The remaining fve hills have moderate susceptibility based on the RMS.