Abstract: The stability of tailing dam is of great importance to mine safety production, and the stability calculation of tailing dam under different working conditions is a major work for the stability analysis. The variation of seepage line at a rapidly changing reservoir level and its influence on the stability of dam were studied. Based on the two-dimensional unsteady seepage equation, the variation of unsteady seepage field and seepage line of dam was educed. And the relation between the variation of seepage line and the dam stability was obtained by Bishop simplified method. Combined with a project case of tailing reservoir, the FEA for the seepage of a dam in different time and the calculation of the safety factor of the dam were made. The issues in relation to the safety operation of tailing dam at a rapidly changing reservoir level that should be noticed and their solutions are put forward.

Key words: Seepage, Stability, Reservoir level, Seepage line