Design of RCC gravity dam and FEM modelling in GeoStudio - Longtan dam

Sammanfattning: China’s rapid economic development has led to a continuously increasing energy demand and the country is the world’s biggest energy user as of today. The country accounts for around 23% of the global energy production, but 70% of the Chinese energy is generated with coal power and China is the biggest emitter of CO2 in the world. The Chinese government has set a couple of goals to reduce the country’s carbon emissions and to increase the share of renewable energy. Hydropower is a renewable energy source and the construction of large dams will likely be one of the strategies to meet the rising energy demand in a more sustainable way. The failure of dams can be devastating, and it is therefore important that they are designed with proper safety measures. In this report, the Longtan dam has been used as a reference to conduct a preliminary design of a large gravity dam and to evaluate its safety. The preliminary design was based on dam site data provided by the College of Water Conservancy and Hydropower Engineering at Hohai University in Nanjing, China. The structural analysis of the dam was conducted with both analytical and numerical methods. The analytical calculations showed that the dam is safe against overturning, but that there is risk for a sliding failure. The analytical stress analysis showed that the stresses in the dam do not exceed the material capacity. The numerical analysis was done in the commercial FEM software suite GeoStudio. The results from the seepage analysis showed that the peak seepage velocities in the foundation are 4,5-5,0·10-7 m/s, and that it is unlikely that the seepage will compromise the structural integrity of the dam. The numerical stress analysis revealed that the stresses are 0-2 MPa in most of the dam body, but that the dam toe is subjected up to 12 MPa compression and that the dam heel is subjected up to 16 MPa tension. This indicates that a tensile failure will occur in the dam heel, which will lead to cracks in the concrete and a redistribution of the stresses. It is therefore advised that the dam heel is reinforced to avoid potential problems with seepage.