DYNAMIC FACTOR OF SAFETY OF ROCK SLOPES DUE TO BLASTING BASED ON CRITICAL DISPLACEMENT AND CRITICAL ACCELERATION

• Main Author: Nasrullah
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69888
• Institution: Institut Teknologi Bandung

Blasting activities, not all of the energy produced is used to form rock fragmentation. Some of the energy is transmitted to the rock mass in the form of waves which are known as seismic waves. Seismic waves generated by the explosion are felt as ground vibrations. This vibration can cause deformation in the rock to cause instability on the slope if it exceeds a certain limit. If the ground vibration resulting from blasting activities is too large and exceeds the rock mass strength limit to withstand it, it will result in slope instability.Analysis of slope stability due to blasting based on the pseudostatic principle is considered too conservative because the slope receives a constant maximum seismic load and hence constant acceleration, without considering the duration of the blast. In reality, the acceleration fluctuates with time and eventually dies off. One method to analyze the stability of rock slopes due to blasting is to conduct dynamic simulations using Newmark displacement analysis to obtain the dynamic Factor of Safety (FoS) based on the magnitude of critical displacement (ucrit) and critical acceleration (acrit). This study was carried out using hypothetical slopes of various rock mass strengths that are determined from its Rock Mass Rating (RMR). A case study of highway rock slope excavated using drill-and-blast method was also carried out to validate the research results. It is found that very good rock (RMR Class I) has FoSdynamic = 11.7, ucrit = 6 mm, and acrit = 0.061g while very poor rocks (RMR Class V) has FoSdynamic = 1.7, ucrit = 16 mm, and acrit = 0.035g. This result that indicate that the smaller the strength of the rock mass, the smaller the critical acceleration and the greater the value of the critical displacement will be. This study reinforces the significance of the critical displacement and critical acceleration in assessing the dynamic stability of rock slopes due to blasting.