Identification of structural domains considering the size effect of rock mass discontinuities: A case study of an underground excavation in Baihetan Dam, China

•We prove the significance of size effect in identifying structural domains.•We propose two methods to identify structural domains considering size effect.•We consider multiple parameters to identify more rational structural domains.

This study used a case study of an underground excavation in Baihetan Dam, China to identify structural domains, which are highly affected by size effects. The magnification and reduction methods involving nonparametric hypothesis tests of the KS, T-, and F-tests were proposed for the identification of structural domains. This process considers the fracture properties of orientation, trace length, position, and density. An ideal fractured rock mass model, whose structural domain identification reliability can easily be assessed, was generated and the size effect was proved to be significant. A sampling window with 159 stochastic fractures along an underground excavation was then presented. Calculations showed that different calculation sizes produce apparently different identification results. Given the objective of the analysis and further calculations, reliable results for the magnification and reduction methods were obtained.