| The Bagdad Mine, an open pit mine located in northwestern Arizona, has experienced a slope failure related to a weak weathered tuff bed. The unit has been altered to a clay-like material in areas of the pit. Overburden pressures have caused the tuff to be squeezed out, and blocks of the overlying basalt unit have toppled forward.;The failure has been remedied by reducing the pit slope to about 20°, but this solution is not desirable.;Modelling of the slope is done using a general purpose finite element method program. The Drucker-Prager theory is used to model the tuff bed, while the other units are treated as being linearly elastic.;Material properties for the three rock units are obtained from a variety of sources.;Results suggest that loss of shear strength in the tuff, due to blasting-induced liquefaction, may be the cause of slope failure. Suggestions are made for remedial action. |
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