Influence of Wind-Generated Wave Action on Mountain Reservoir Bank Collapse: A Case Study at the Lancang River, Western China

Abstract

Abstract Slopes facing reservoir water often collapse, affecting reservoir capacity. It is important to understand the factors affecting such collapses and predict the locations of collapse after impoundment for practical purposes. However, the mechanism of bank collapse in mountainous areas after reservoir impoundment remains unclear. To address this issue, field geotechnical property surveys, laboratory tests, and numerical simulations were employed to evaluate bank collapse susceptibility. The results showed that (i) bank collapse mainly occurs in slopes with a small cohesion and internal friction angle of less than 30°; (ii) the main effects of wave action on bank collapse are scour, erosion, and cyclic impact on the bank slope: wave erosion occurs in the bank slope with a wave height of less than 1.0 m, cohesion of less than 90 kPa, and slope angle of less than 30°, and wave impaction mainly occurs at the area with a wave height of more than 2.0 m and a slope angle of more than 30°; (iii) for valley reservoirs, softening of water on the slope rock and soil mainly reduces cohesion, which commonly occurs within 30 days; the cyclic action of wave impact load mainly damages the structure and reduces the internal friction angle. The influence of waves on bank collapse is mainly related to the wave height and wave velocity. The antiwave impact broken energy of rock and soil is an important index to evaluate whether bank collapse occurs in the long term, which is related to the strength, structure, and impact resistance. The present research is helpful to better understand the mechanism and evolution process of reservoir bank collapse.