Extraction and statistics of discontinuity orientation and trace length from typical fractured rock mass: A case study of the Xinchang underground research laboratory site, China

The geological parameters of rock discontinuities are of great significance for the evaluation of high-level radioactive waste repository and underground research laboratory (URL) site characteristics. To provide sufficient basis for the construction of the Xinchang URL site, this paper presents a comprehensive set of methods for acquisition of discontinuity parameters. In this set of methods, a high precision three-dimensional point cloud model of an outcrop with real geographic information is established based on close-range photogrammetry technology, from which not only planar discontinuities but also linear discontinuities can be identified and extracted by a semi-automatic method. A new fast-fuzzy clustering method is proposed to cluster discontinuity sets. The statistics method based on topographic window projection is improved to increase the rationality of estimating the geometric characteristics of fracture traces. As a preliminary validation, the results of this case study reveal that these methods have good applicability in acquiring discontinuity parameters, which is also conducive to the establishment of a deterministic-stochastic discrete fracture network (DSDFN) model to further analyze the properties of fractured rock mass. In addition, it is preliminarily found that some outcrops different locations have structures with similar geological features to a certain extent; moreover, the fractures exposed on the outcrop surface have distribution characteristics similar to those in the granite body obtained by drilling. Above all, the presented multidisciplinary methods could provide an alternative and practical approach for low-cost and accurate acquisition of discontinuity parameters, and thus, to study the properties of fractured rock mass effectively.