Long-Term Deformation Analysis and Treatment Measures for Layered Soil Slopes in Dam Reservoirs: A Case Study

During the construction of Jinsha River Wudongde Hydropower Station, we encountered problems affecting the safety and stability of the mountain, such as the development of laminated geological formations, poor integrity of the slope surface rock, and even slippage and large deformation. In order to strengthen the deformation and stability control of the layered rock body of the side slope and ensure the safety of the dam project, we tracked and analyzed the actual measured displacement data. Taking the flood relief tunnel rock body and slope as the main research object, we analyzed the valley deformation and development trend in key areas, and summarized the spatial and temporal distribution law of valley deformation in different areas. At the same time, a three-dimensional geological model is established by numerical simulation method, and the finite difference combined with the reduction method is used to calculate the stability of the slope of the flushing pool. The deformation monitoring and numerical simulation results reveal the deformation characteristics of the valley and the stability of steep slopes in the early stage of water storage, and explain the evolution mechanism of slope deformation based on geological structure characteristics. It is found that: the laminated slopes in the reservoir area of the dam are prone to deformation under the joint action of long-term construction disturbance and fracture water seepage; construction disturbance has a high degree of influence on the artificial excavation area below 1070m in elevation, with the maximum rock deformation and surface displacement reaching 92.2mm and 312.5mm, respectively; however, the mountain above 1070m in elevation is limitedly affected, and the valley deformation of the mountain on the left bank of the reservoir area is higher than that on the right bank, the accumulated deformation on the left and right still does not exceed 20mm; seepage has a more obvious effect on the displacement of the top of the slope, and excavation and other disturbances have a more obvious effect on the displacement of the artificial slope; for the deformation of the valley of the water pad pond behind the dam increases more slowly, the deformation data at the site is basically consistent with the change trend of the numerically calculated data, and generally shows a contraction trend, the maximum contraction of the simulated calculation is close to 20mm, located at an elevation of 990m. On-site slope displacement monitoring, with high precision and real and reliable data, is of great significance for hydropower plant construction and long-term safe operation after completion.