Stability of some potential unstable blocks in the left bank slope of Baihetan hydropower station is evaluated in this paper using the three-dimensional (3D) limit equilibrium method. The Baihetan hydropower station is in the downstream of Jinshajiang River, China. The geological condition in the river valley is complex, and many large discontinuities are detected in the slope of the two banks. As a result, much attention should be paid to the stability of the slope in the feasibility study stage. Because the left bank slope is an oblique consequent one, we mainly focus on the slope stability analysis in the left bank. Comprehensive geological exploration is conducted in the studied area and the detected discontinuities are well researched. By building a 3D geological model of the left bank slope, three potential unstable blocks which are close to the dam site are detected. An irregular wedge analysis method is then used to calculate safety factors of the three blocks under three conditions, which are natural condition, rainfall condition, and seismic condition, respectively. It is found that the safety factors of the block 1# and the block 2# are quite low when compared to the suggested values. Extra care must be exercised when excavating the slope near the block 1# and the block 2#. A preliminary reinforcement is also suggested.
The Baihetan hydropower station, which is located in the junction of Ningnan city in Sichuan province and Qiaojia city in Yunnan province, is in the downstream of Jinshajiang River, China. It is about 45 km away from Qiaojia city. As the main power source of west-east electricity transmission project, it is mainly constructed for electricity generation, and also for sediment retention, flood control, and shipping, etc. The total installed capacity is 14004 MW and the average annual power generation is 602 billion KW·h. The guaranteed output is 5100 MW and the normal pool level of is 825 m. The dam is designed to be a double-curvature arch one with the crest level 834 m and the maximum dam height 289 m. The storage capacity of the reservoir is 206 billion m3 (HCHEC, 2010).
The geological condition of river valley in the studied region is complex. The slopes of two banks are high and steep and the river channel is narrow. Large discontinuities including joints, faults, disturbed belts, fractures, and tensile cracks are well developed in the rock mass of the slope. Potential unstable blocks are easily formed by a combination of these discontinuities. Hence, much attention should be paid to the stability of the slope in Baihetan hydropower station. This paper studies stability of the left bank slope by using the three-dimensional (3D) limit equilibrium method.