Page - 852 - in Book of Full Papers - Symposium Hydro Engineering

Uncertainties in shear strength parameters will cause uncertainties in the sliding stability of the dam body. Similarly, uncertainties in the rock deformation modulus will cause the stress values in the dam body and foundation to experience variations. Exerting the “minimum” shear strength parameters is a conservative and costly design approach on one hand, and exerting the “mean” values may not be safe on the other. Therefore, studying the stability and stresses in the dam body and foundation would require a huge amount of rigid body stability and finite element analysis, making the final decision-making difficult. This is where applying the probabilistic method comes as a great advantage. In the following, utilizing this method to calculate the sliding stability is described, and its application to determine the modulus of deformation is explained in the next section. Initially, consider the shear strength parameters of Dasht-e-Palang dam. An evaluation of the rock mechanics parameters based on a vast range of studies is presented in the table shown in Fig. 6 (left). The first step is to perform a stability analysis on different optional pairs of cohesion and friction angle, which will result in a calculable sliding safety factors. Obtaining this data matrix and performing a probabilistic analysis (finding the interpolation of SFs between each node of cohesion and the friction angle), the distribution of SFs can be plotted. In addition, by selecting the minimum desired safety factor, the probability of failure and the adequacy of the dam body geometry will be yielded according to Fig. 6 (right). Fig. 6 Safety factors against sliding (left), the distribution of safety factors (right) 4. CONSTRUCTION SIMPLICITY Even though the construction simplicity of CMDs is a key asset, it could also cause a number of challenges to the prediction of the material behavior, the highly layered dam body amongst them. The bonding between the Hardfill layers is generally less than the RCC layers due to the following reasons: - The total cement content is low. - Treatment between successive layers is not necessary. - There is no need to bedding mortars between layers. - More segregation occurs compared to RCC. 852