Different Toppling Bank Slope Failures under Hydrodynamic Action during Impoundment of the Miaowei Hydropower Station Reservoir

Abstract

Toppling is a common deformation and failure phenomenon in the reservoir bank slopes of hydropower projects. This paper studies the genesis and evolution of different toppling bodies during water impoundment at the Miaowei Hydropower Station Reservoir on the Lancang River in southwest China. Toppling properties were determined and second failure characteristics analyzed in different reservoir impoundment stages. Different degrees of toppling deformation were primarily affected by the transverse bending stress, while the regional tectonic stress has been shown to have a significant effect on the transverse bending of the rock layers. Combined with the on-site investigation and monitoring results, the failure mechanisms of the different toppling deformation bodies were analyzed. The second failure of the toppling rock mass caused by the reservoir impoundment process is mainly the hydrodynamic splitting along fractures, wave impaction and softening on the slope foot. The transverse bending effect of gravity is transmitted upward through joint misalignment, rotation and slip, accelerating the speed of secondary toppling failure and forming a compression-shear failure along the toppling tension crack. A model to predict the scope and time of failure in the toppling deformation banks under the action of reservoir hydrodynamics was proposed.

Development Pattern of Toppling Deformation Slopes in Western China

“…Owing to diverse causes, geological engineering concerns about toppling deformations have gradually become major issues in the field. Until now, most studies on toppling deformations, especially in hydropower projects, have focused on the evolutionary process [13][14][15][16], deformation mechanisms [17][18][19][20][21][22][23][24][25][26][27][28] and development characteristics [29][30][31][32] of single toppling deformation slopes. The development regularity and susceptibility of toppling deformations are rarely studied from the angle of regional geological conditions and geographic position.…”

Stability Analysis of Strongly Weathered Muddy Slate Slopes Considering Softening Conditions of Water Immersion

“…Among them, with their natural layered structure, the strongly weathered bedding slate slopes are prone to destabilization accidents under extreme climatic conditions such as heavy rainfall and water inundation. This results in significant safety hazards and economic losses [4,5]. The shear strength parameter of the structural or laminar surface plays a significant role in controlling the stability of strongly weathered bedding slate slopes [6].…”