LAUSR

A high-level radioactive waste repository requires a rock mass to have good retardation properties. However, because a fault zone can be a potential seepage conduit for nuclides, its influence on the hydraulic conductivity of that fault zone must be assessed. Key sets of fractures were found based on an assessment of the statistical characteristics of fracture orientations and the tectonic analysis of a representative north–east fault in the Jijicao rock block in the Beishan region of Gansu Province, China. The trace midpoint density of each set was calculated using ArcGIS, a geographic information system, and a model of the hydraulic conductivity in the fault zone was developed based on a water pressure test and calculations, such that the respect distance and margin for excavation of this fault could also be determined. The calculated results show that the fault core and host rock are less conductive when the damage zone is 10- to 100-fold more conductive due to its greater density of fractures. The density is stable at 100 m, while the key set is stable until 65 m, and the calculated hydraulic conductivity is stable until 25 m; these results are consistent with the results of water pressure analysis.