Characteristics of Surface Multi-Scale Fracture Network Considering the Fracture Damage Zone: A Case from Xinchang Section of Beishan, China

The study of rock mass fracture characteristics is a fundamental work for geological engineering, however obtaining the characteristics of multi-scale fracture network remains a challenge to this day. This research investigates the geometric characteristics of surface multi-scale fracture network, considering the geometric and mechanical characteristics of the fracture damage zones in Xinchang section of Beishan, Gansu Province -the designated underground research laboratory site for high-level radioactive waste (HLW) geological disposal in China with remote sensing interpretation and site investigation. The study found that the length and quantity of surface multi-scale fractures follow a power-law distribution and with fracture strikes primarily oriented NNE and NE. The fracture set striking NE nearly parallel to the current maximum horizontal principal stress direction (N59°E) in Xinchang section may exhibit an open state, while the fracture set striking NNE obliquely intersecting this stress direction carries a risk of shear slip. The outer boundaries of fracture damage zones were determined based on cumulative discontinuity density curves. And there is a power-law relationship between the fracture length and the width of its damage zone. Based on the relationship, the multi-scale fracture network considering the fracture damage zone has been built, which provide a fundamental support for the engineering design and safety assessment of the rock mass engineering.