Influence Of Earthquakes

The stabil ity of engineered embankments subjected to earthquakes has received considerable attention in the last 10 years, but most of the effort has been directed toward stability of earth dams. Based upon past performance, earthquake- induced failures on non-impounding mine waste structures will likely correspond to small, local slumps or debris slides, and their stability should be considered as an integral part of mine economic planning. As such, stability considerations should include earthquake hazard, characteristics of earthquake ground motion, dynamic slope stability, and the impact that waste-dump failures have on mine operations. Numerous techniques have been proposed for analyzing the stability of embankments subjected to earthquakes. Before choosing an analysis technique, it is worth noting two important differences between the dynamic response of waste embankments and natural slopes. First, waste embankments respond as structures having unique modes of vibration, which causes embankment motions to differ from nearby ground motion. Second, because of embankment response, accelerations can be different at embankment crests than elsewhere in the structure and occur at frequencies that do not correspond to input ground motion. Because of these factors, embankment response should be calculated prior to slope stability assessment. In this paper several analysis techniques designed to calculate slope stability are evaluated, and conventional pseudostatic techniques are shown to be inappropriate for dynamic considerations. Techniques to calculate dynamic stability should include embankment response, all characteristics of earthquake motion, and roughness along failure planes as input, and should provide a displacement time-history of the slide mass as output. Two techniques satisfy this criterion, and in this paper the LADRS technique is recommended for its versatility and simplicity.