Study on failure mechanism of a plain irrigation reservoir soil bank slope under wind wave erosion

Abstract

The wind wave erosion is one of the main factors of the soil bank slope retreat in plain irrigation reservoirs, which plays an important role in the bank profile evolution and seriously affects the agricultural irrigation. To study the failure mechanism induced by the wind wave erosion, a reservoir soil bank slope is taken as a research object. Through the field investigations, laboratory tests and prototype observations, a mechanical model of the bank slope recession under the wind wave erosion is established and verified by the field observation results. On this basis, the finite element method is utilized to analyze its stability in different erosion periods, and the evolution law of the safety factors with erosion time is revealed quantitatively. The results show that the lateral retreat of the slope foot will lead to local collapse and form vertical surfaces when eroded by wind waves. Based on the monitoring data in April 2019, the calculated lateral erosion distance is 1.29 m after the wind wave erosion lasts for 9 h, and the vertical surface height reaches 3.10 m, resulting in the bank slope failure. After failure, it is reshaped, and the stability is significantly improved. However, the new slope will face the instability risk of the former one when eroded by wind waves again. The stability safety factors generally show cyclical variation with the wave erosion time. The failure and retreat of the bank slope repeat the above cycle annually.