Deformation analysis and mechanism research for stratified rock and soil slope

The slope on the left side of the spillway tunnel at Wudongde Hydropower Station's water cushion pool exhibited significant deformation during excavation. Based on long-term monitoring data, an analysis was conducted on the deformation mechanism of the stratified rock and soil slope. A geological model of a high and very steep slope was established using FLAC^3D to evaluate its stability. It was observed that the left stratified rock and slope at the spillway tunnel is prone to deformation due to long-term construction disturbance and fissure water seepage. Construction disturbance strongly impacts the artificially excavated area below 1070 m, while it has limited influence on the mountain above 1070 m. The maximum rock deformation and surface displacement reached 92.2 mm and 312.5 mm, respectively. After water filling, there will be a significant increase in deformation for the natural mountain on the left bank at the outlet of the spillway tunnel; however, deformations in unexcavated parts of this natural mountain remain below 20 mm. Furthermore, deformation of the left bank was higher compared to those observed in the right bank. Numerical simulation indicates that once the excavation is complete, fundamental safety factor of approximately 1.3 can be achieved for the left bank slope at the exit from the spillway tunnel. The rate of increase in deformation for the water cushion pond behind the dam is slight over time, and the trend of displacement change in-situ monitoring is mostly consistent without numerical calculation, eventually showing a convergence trend.