The Yang Qu dam : Optimization of Zones by Numerical Modelling on this New Type of Dam

China has a huge need of energy and to meet this demand the government invest in hydropower. Large hydropower plants are both constructed and planned. The dams will continuously be constructed larger and higher. A dam type that has demonstrated decent performance is the Concrete Face Rockfill Dam (CFRD), both in terms of safety and costs. Very high CFRD´s, up to 300 meters, are subjected to large stresses in the face slab, which can cause leakage. It can be hard and costly to repair due to large water depths. To approach a solution, China Institute of Water Resources and Hydropower Research (IWHR) have start developing a new type of dam. It is a combination of a CFRD and a Concrete Gravity Dam (CGD). This dam type will reduce the length of the face slab, and thus decrease the stresses, and enable maintenance work through a gallery in the CGD.A dam prototype with a height of 150 meters, Yang Qu dam, will be built in the Yellow River. The goal with this prototype is, besides energy production, to develop the technique and in the future build this new type of dam to the height of 300 meters or more. The critical area is the transition zone between the CFRD and CGD. To minimize the displacements in this zone hardfill will be used. This material consists of gravel and sand mixed with cement, which reduces the compressibility compared to ordinary rockfill. Yang Qu is analysed in three cases with different distributions of the hardfill material. This is performed by numerical modelling based on the finite element method. Each case is varied with three different values of the Young´s modulus of the hardfill. The maximum allowable displacement perpendicular to the slope of the face slab in the transition zone is 5 cm. Without hardfill the displacement reaches 7.7 cm. All three investigated cases give a displacement under 5 cm. One case shows the best results with the least consumption of cemented fill. It consists of hardfill placed in the same slope as the concrete dam with a width of 50 m (in cross section).Maximum total settlement of the dam body is also being investigated. The maximum allowed settlement is 1.5% of the dam height. All cases including the case without hardfill provides a maximum settlement far below this allowed value.Validerat; 20140126 (global_studentproject_submitter