Abstract：The multiplicity and randomness of fractures distribution in rock mass are key issues in research on engineering properties of fractured rock mass. The randomness of fractures geometrical shapes(orientation，dip，trace length，spacing，and width) of fractures is considered；and Monte Carlo simulation technique is adopted to develop a new code RFNM(including RFNM2D and RFNM3D). By RFNM，not only the virtual fractured rock mass，in which the structure information of fractures is described and the real engineering rock mass is represented，can be generated；but also the digital fractured rock mass can be discretized and then be combined with numerical methods(such as FEM，DEM，and so on) to solve practical engineering problems. Therefore，the virtual fractured rock mass with random fracture networks is a digital fractured rock mass model actually. In addition，based on seepage theory of porous media，FEM is adopted to develop the software GeoCAAS (geo-engineering computer aided analysis system). The hydraulic properties of fractured rock mass are studied；and the effects of fracture geometrical shapes on the seepage properties are discussed.
