Li Changmin, Ren Shuguang

Hunan Agricultural University

Abstract：

In order to explore the impact of rapid decline in reservoir water level on the seepage field of homogeneous soil dams, a non-steady-state seepage numerical model was established. The water level was set to decrease from 77.60 m to 61.60 m within 48 hours (with a rate of 0.333 m/h). The results show that the elevation drop of the seepage exit point is only 0.30 m, which is strongly controlled by the downstream boundary. The pore pressure near the upstream slope dissipates quickly (t90 = 46.7 h), whereas there is a significant lag inside the dam body (residual 25.26 kPa after 100 h). The hydraulic gradient at the slope toe reaches its peak at 50–60 hours (0.83), lagging behind the end of the water level decline. The study quantitatively revealed the coupling relationship of water level decline, pore pressure hysteresis, and hydraulic gradient peak, providing a basis for identifying the most unfavorable working conditions.

Key Words：

unsteady flow; sudden drop in reservoir water level; pore pressure hysteresis; hydraulic gradient; homogeneous earth dam