Influences of antecedent rainfall and change of reservoir water level on seepage and stability characteristics of earth rock dams
摘要
The climate change has brought unprecedented challenges to the safe operation and management of reservoir dams. The antecedent rainfall and change of reservoir water level are the key factors affecting the instability of reservoir dam slopes, and the impact of rainfall on the stability of dam slopes or shallow dam slopes is not considered in the existing design code for rolled earth-rock fill dams. The landslide or dam break of reservoir dams seriously threatens human lives and causes huge economic losses. Taking the core wall dam of a reservoir as the research object, a finite element model is established, the influences of the antecedent rainfall and change of reservoir water level on the seepage and stability characteristics of the core wall dam are investigated, the variation rules of pore water pressure, hydraulic gradient and safety factor of anti-sliding stability of the dam slope are released, and the accuracy of the model is verified by using the high-density electrical method and the safety monitoring data. The research results show that the antecedent rainfall has a great impact on the pore water pressure and safety factor of anti-sliding stability in the shallow depth of the dam slope. The influence degree of the antecedent rainfall on the pore water pressure of the downstream dam slope has the descending order: slope top, slope shoulder and slope toe. With the increase of the antecedent rainfall, the pore water pressure within 10 m of the downstream dam slope gradually increases, and the surface soil of the downstream dam slope reaches the saturated state. After the main rainfall, the safety factor of anti-sliding stability of the downstream dam slope greatly decreases. The phreatic line elevation of the proposed model is consistent with the measured water level using the high-density electrical method and the piezometric tube, which verifies its accuracy. The reservoir water level is the main factor affecting the pore water pressure and safety factor o