Vertical and horizontal displacements of a reservoir slope due to slope aging effect, rainfall, and reservoir water

Landslides are common hazards in reservoir areas and significantly affect dam operation and human lives. For the prevention and management of landslides, accurate assessment of the factors influencing their generation is essential. This study evaluated the key external factors influencing horizontal and vertical displacements of Luobogang Reservoir Slope in Hanyuan County, China. Displacements had been monitored by a surface-displacement-monitoring system consisting of 118 GPS stations during 2012–2015. To identify the external driving factors, their influence zones, and slope responses, we analyzed 32 months of displacement measurements and other multi-source datasets using the empirical orthogonal function. Overall, the results show that slope aging effect, rainfall, and reservoir water levels are three main driving factors. For horizontal displacement, aging effect is the most critical factor and predominantly affects the edges of landslides, the gob cave, and the public building zones. The secondary factor is the reservoir water level, which mainly acts on the boundary between the slope and reservoir water surface. The closer the slope zone is to the reservoir water, the more significant the impact is. Regarding vertical displacement, the most important factor is rainfall. The vertical displacement caused by rainfall accounts for 56.76% of the total vertical displacements. However, rainfall induces elastic displacements that generally cause less damage to the slope. The secondary factor is aging effect, and the vertical displacement caused by aging effect accounts for 9.42%. However, seven individual zones are highly affected by slope aging effect, which is consistent with the distribution of public buildings.