DETERMINATION OF THE APPROPRIATE SEISMIC LOAD TO GET THE DYNAMIC SAFETY FACTOR OF SLOPE DUE TO BLASTING AND EARTHQUAKE

• Main Author: Choirul Viqri Mubarok, Muhammad
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/66077
• Institution: Institut Teknologi Bandung

Excavation of slopes can be carried out by direct excavation method with mechanical digging tools or drilling and blasting methods. Drilling and blasting methods in making slopes can cause vibrations that can affect slope stability. Analysis of slope stability due to blasting can be done by calculating the dynamic factor of safety (FoS) of the slope. Dynamic FoS values can be calculated using two principles, namely pseudostatically and fully dynamically. Dynamic FoS which is calculated based on the pseudostatic principle is hereinafter referred to as pseudostatic FoS. This pseudostatic FoS calculation is still considered too conservative because the slope is assumed to receive the maximum load/ acceleration without considering the duration of the blast. While the full dynamic FK calculation is still rarely done because this method is too difficult to do where the dynamic input uses an acceleration value that varies with time. Therefore, this study was conducted with the aim of determining the seismic load/ acceleration limit dynamic FoS calculation in the pseudostatic principle so that the value obtained by full dynamic is equivalent to dynamic FoS in the duration of one detonation. Dynamic FoS is fully dynamically calculated by dynamic simulation method that uses displacement values in its calculations. This research was conducted using 2D numerical modeling on Slide2 software with the Newmark method to generate displacement. Then a dynamic simulation is carried out by reducing the shear strength of the slope material until the resulting displacement reaches the predetermined criteria, namely 5 mm or 50 mm. The principle of decreasing the shear strength parameter is commonly called the strength reduction factor (SRF). The SRF value when the displacement reaches the specified criteria can be expressed as the dynamic FoS of the slope. The results showed that the appropriate seismic load for pseudostatic FoS calculations was 55% of PPA due to blasting and 70% of PPA due to earthquake. In addition, the rock mass, and the type of seismic load input into the model also affect the calculation of the slope dynamics FoS. Pseudostatic FoS is more appropriate when the rock mass class is very poor, and the dynamic load used is in the form of earthquake waves.