Research on simpliffied evaluation method for soil-rock mixed slope stability under dam-break flood impact

Dam-break flood has the characteristics of fast flow speed and large kinetic energy, which can increase the pore water pressure in slope and cause the slope deformation or even destruction. To determine the pore water pressure in slope under impact of dam-break flood, firstly, a novel approach for estimating the impact pressure of dam-break flood under condition of high Froude number is proposed based on equivalent hydrostatic pressure, and the accuracy of this approach is verified by wave flume test; then a simplified calculation method of pore water pressure is put forward based on microwave theory and Darcy's law. Finally, instability mechanism of a soil-rock mixed slope under dam-break flood is investigated, and the instability failure process of this slope is analyzed through field investigation. By constructing its geomechanical model, the slope stability is analyzed under impact of dam-break flood, and the results show that influence of dam break distance on the slope stability is significant in a certain critical range, and the maximum flood pressure distribution pattern changes from triangle to trapezoid with the increase of Froude number. The safety factor diminishes as the flood flow velocity increases, and the safety factors increase with the impact angle and internal friction angle increasing. These results can provide technical reference for landslide hazard risk assessment and emergency decision-making under dam-break flood action.