Dynamic factor of safety of rock slopes due to blasting based on critical displacement and critical acceleration

Abstract

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 diminishes. 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 determined from the Rock Mass Rating (RMR). A case study of a highway rock slope excavated using the drill-and-blast method was also carried out to validate the research results. The findings reveal that very good rock (RMR Class I) has FoSdynamic = 11.7, ucrit = 6 mm, and acrit = 0.061g, while very poor rock (RMR V) has FoSdynamic = 1.7, ucrit = 16 mm, and acrit = 0.035g. This result indicates 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 critical displacement and critical acceleration in assessing the dynamic stability of rock slopes due to blasting.