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Rock masses are highly characterized by size effect due to the existence of complex discontinuities, which could be reflected by representative volume element (RVE). This study exemplified calculation of RVE in Datengxia sluice rock mass analysis with consideration of anisotropy, which extends the application of traditional RVE featured by three-dimensional (3-D) equal sizes. Specifically, fracture network modeling was conducted to generate fractures in 3-D space. Fracture frequency values, which can comprehensively reflect the fracture density, size and occurrence in different lengths, were used to represent size effect of one-dimensional (1-D) parameters. Subsequently, geostatistic theory was introduced to synthesize substantial fracture frequency data and analyze their relationships in different regions and educe convergence size by analyzing the significant sub-theory of variogram. Linear representative volume elements (LRVE) in different directions were proved to be varied; thus, a modified RVE with orthogonal directions corresponding to individual LRVE values were applied. As RVE takes account on linear anisotropy features of rock masses, size effect can better guide parameter selection and numerical modeling of rock masses. [ABSTRACT FROM AUTHOR]

The failure mechanism analysis of dam foundations is key for designing hydropower stations. This study analyses the rock masses in a sluice section, which is an important part of the main dam of the Datengxia Hydropower Station currently built in China. The stability of the sluice rock masses is predominantly affected by gentle through-going soft interlayers and steep structural fractures. Its foundation failure mechanism is investigated by means of a numerical method, i.e., Universal Distinct Element Code (UDEC) and the geomechanical model method. The modeling principle and process, and results for the rock dam foundation are introduced and generated by using the abovementioned two methods. The results indicate that the failure mechanism of the foundation rock masses, as characterized by gentle through-going and steep structural discontinuities, is not a conventional type of shear failure mechanism but a buckling one. This type of failure mechanism is verified by analyzing the deformation features resulting from the overloading of both methods and strength reduction of the numerical method. [ABSTRACT FROM AUTHOR]

The discontinuity persistence is an important parameter that affects the strength of rock masses and stability in rock engineering. However, determining the 3D discontinuity persistence in practical field projects remains difficult. This study proposes an approach to determine the 3D discontinuity persistence (percentage of total discontinuity area to the area of the potential failure surface) on the basis of Dijkstra's shortest-path algorithm and Bayesian bootstrap method. First, Dijkstra's shortest-path algorithm is used to determine the linear discontinuity persistence (percentage of total discontinuity trace length to the length of 2D potential failure surface), which is essential to determining 3D discontinuity persistence. Second, geological analysis is performed to deduce 3D discontinuity persistence as a function related to two linear discontinuity persistence in two vertical directions. Lastly, Bayesian bootstrap method is used to analyze the linear and 3D discontinuity persistence. This approach can substantially simplify the process of determining discontinuity persistence and comprehensively considers the uncertainty of the fracture network. The mean, standard deviation, and p-value (i.e., value at the 95% confidence limit) are used as the statistical parameters of the linear and 3D discontinuity persistence. [ABSTRACT FROM AUTHOR]