Investigating the effect of earthquakes on open pit mine slopes

This paper develops a database for studying the circumstances under which dynamic loading of earthquake can cause slope failure in deep open pit mines with a long lifetime. The database includes 177 open pit mines hit by earthquake and 95 natural slopes and 37 tailing dams which have been failed by earthquakes. Both earthquake parameters and geomechanical characteristics involved in each case-study are investigated. From this information, the elements playing role in the earthquake-triggered failures in natural slopes and tailing dams are identified and used to indicate conditions that may result in earthquake-induced failures in open pit mines. The result shows that even though the valley shape geometry and absence of the top weathered layer make open pit mines less prone to earthquake-induced failures, excessive pore pressure in pit slopes still carries the risk of earthquake-triggered failures in open pit slopes. Only limited numbers of open pit mines have been so far exposed to earthquakes with the same parameters as those causing failure in natural slopes and tailing dams. That is, the response of open pit mines to higher magnitude, shallower, and closer earthquakes is still unknown. Studying the earthquakes that have caused failure in other slopes, it is concluded that open pit mines may still experience reportable failures if struck by earthquakes with local depth of less than 40 km, epicentral distance of less than 100 km, and magnitude of greater than 6.0. The necessity of accounting for seismic loading in slope stability analyses and active dewatering for open pit mines located in seismically active areas are also discussed.